WO2013181274A2 - Controlling melt fracture in bimodal resin pipe - Google Patents
Controlling melt fracture in bimodal resin pipe Download PDFInfo
- Publication number
- WO2013181274A2 WO2013181274A2 PCT/US2013/043154 US2013043154W WO2013181274A2 WO 2013181274 A2 WO2013181274 A2 WO 2013181274A2 US 2013043154 W US2013043154 W US 2013043154W WO 2013181274 A2 WO2013181274 A2 WO 2013181274A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- smooth
- stress
- matte transition
- molecular weight
- catalyzed polyethylene
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F110/02—Ethene
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N11/02—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material
- G01N11/04—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by measuring flow of the material through a restricted passage, e.g. tube, aperture
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/06—Polyethene
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L9/00—Rigid pipes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
-
- G—PHYSICS
- G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
- G16C—COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE
- G16C20/00—Chemoinformatics, i.e. ICT specially adapted for the handling of physicochemical or structural data of chemical particles, elements, compounds or mixtures
- G16C20/20—Identification of molecular entities, parts thereof or of chemical compositions
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L9/00—Rigid pipes
- F16L9/12—Rigid pipes of plastics with or without reinforcement
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
- Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
- Y10T428/139—Open-ended, self-supporting conduit, cylinder, or tube-type article
Definitions
- the present disclosure relates to polyethylene compositions and pipe made from same, more specifically to multimodal polyethylene compositions having improved processing characteristics.
- Polymeric pipes have replaced metal pipes in many applications such as high-pressure fluid transportation.
- Polymeric pipes have several advantages over metal pipes including being of relatively lighter weight, more corrosion resistant, inexpensive, more thermally and electrically insulative, tougher, more durable and more easily shaped during manufacture.
- Such pipes are exposed to numerous stresses during their lifetime that may result in cracks or breaks that are expensive to repair, especially in situations where the pipe is buried in a structure or underground.
- As such polymeric pipes may be required to meet industry-defined standards depending on their intended use.
- Polymeric material used in the fabrication of pipe has often been optimized to provide a more durable end-use article.
- One such optimization may involve the use of a multimodal polymer composition as the polymeric material.
- a challenge to the use of a multimodal polymer composition as the polymeric material in the fabrication of pipe is that these compositions, when melted to form a polymer melt, may display poor processing characteristics such as melt fractures, which are surface irregularities that occur during the extrusion process when the production rate is increased. The poor processing characteristics of these materials may result in a reduced production rate and/or product having undesirable physical properties and/or appearance.
- melt fractures which are surface irregularities that occur during the extrusion process when the production rate is increased.
- the poor processing characteristics of these materials may result in a reduced production rate and/or product having undesirable physical properties and/or appearance.
- a method of improving processing of polyethylene resins comprising obtaining a plurality of multimodal metallocene-catalyzed polyethylene samples; measuring the shear stress as a function of shear rate for the plurality of multimodal metallocene-catalyzed polyethylene samples using capillary rheometry wherein the measuring yields values for a magnitude of slip-stick, a stress for smooth to matte transition, and a shear rate for smooth to matte transition; and identifying from the plurality of multimodal metallocene-catalyzed polyethylene samples individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture characterized by a magnitude of slip-stick greater than about 300 psi, a stress for smooth to matte transition greater than about 90 kPa, and a shear rate for smooth to matte transition greater than about 10 s "1 .
- Also disclosed herein is a method of improving processing of polyethylene resins comprising obtaining a known molecular weight distribution, a known magnitude of slip-stick, a known stress for smooth to matte transition, and a known shear rate for smooth to matte transition, for each of a plurality of polyethylene resins; performing chemometric analysis to determine an analytical relationship between the known molecular weight distribution, the known magnitude of slip-stick, the known stress for smooth to matte transition, and the known shear rate for smooth to matte transition for the plurality of polyethylene resins; obtaining a plurality of multimodal metallocene-catalyzed polyethylene resins, each having a known molecular weight distribution, an unknown magnitude of slip-stick, an unknown stress for smooth to matte transition, and an unknown shear rate for smooth to matte transition; utilizing the analytical relationship to determine a value for the unknown magnitude of slip-stick, a value for the unknown stress for smooth to matte transition, and the unknown shear rate for smooth to matte transition for each of the plurality of multimodal metallocen
- a system for improving processing of polyethylene resins comprising a processor; a memory; an output device; and an analysis component stored in the memory, that when executed on the processor, configures the processor to receive a shear stress as a function of shear rate for a plurality of multimodal metallocene-catalyzed polyethylene samples, wherein the determination of the shear stress as a function of the shear rate comprises using capillary rheometry determine values for a magnitude of slip-stick, a stress for smooth to matte transition, and a shear rate for smooth to matte transition for each of the plurality of multimodal metallocene-catalyzed polyethylene samples based on the shear stress and the shear rate measured from capillary rheometry; identify individual multimodal metallocene-catalyzed polyethylene resins from the plurality of multimodal metallocene-catalyzed polyethylene samples having a reduced tendency to melt fracture characterized by a magnitude of slip-stick greater than about
- a system for improving processing of polyethylene resins comprising a processor; a memory; an output device; and an analysis component stored in the memory, that when executed on the processor, configures the processor to receive a known molecular weight distribution, a known magnitude of slip-stick, a known stress for smooth to matte transition, and a known shear rate for smooth to matte transition for each of a plurality of polyethylene resins; determine, using chemometric analysis, an analytical relationship between the known molecular weight distribution, the known magnitude of slip-stick, the known stress for smooth to matte transition, and the known shear rate for smooth to matte transition for the plurality of polyethylene resins; receiving a known molecular weight distribution for each of a plurality of multimodal metallocene-catalyzed polyethylene samples; determine, using the analytical relationship, a value for an unknown magnitude of slip-stick, a value for an unknown stress for smooth to matte transition, and a value for an unknown shear rate for smooth to matte transition for each of the plurality of
- Also disclosed herein is a computer implemented method for improving processing of polyethylene resins, comprising receiving by a processor, a shear stress as a function of shear rate for a plurality of multimodal metallocene-catalyzed polyethylene samples, wherein the determination of the shear stress as a function of the shear rate comprises using capillary rheometry; determining, by the processor, values for a slip-stick, a stress for smooth to matte transition, and a shear rate for smooth to matte transition for each of the plurality of multimodal metallocene-catalyzed polyethylene samples based on the shear stress and the shear rate; identifying, by the processor, individual multimodal metallocene-catalyzed polyethylene resins from the plurality of multimodal metallocene-catalyzed polyethylene samples having a reduced tendency to melt fracture characterized by a magnitude of slip-stick greater than about 300 psi, a stress for smooth to matte transition greater than about 90 kPa of stress,
- Also disclosed herein is a computer implemented method for improving processing of polyethylene resins
- an analysis component stored in the memory that when executed on the processor, configures the processor to receiving, by an analysis component stored in a memory and executed on a processor, a known molecular weight distribution, a known magnitude of slip-stick, a known stress for smooth to matte transition, and a known shear rate for each of a plurality of polyethylene resins; determining, by the analysis component, an analytical relationship between the known molecular weight distribution, the known magnitude of slip-stick, the known stress for smooth to matte transition, and the known shear rate for smooth to matte transition for the plurality of polyethylene resins using chemometric analysis; receiving a known molecular weight distribution for each of a plurality of multimodal metallocene- catalyzed polyethylene samples; determining, by the analysis component, a value for an unknown magnitude of slip-stick, a value for an unknown stress for smooth to matte transition, and a value for an unknown shear rate for smooth to matte transition
- Also disclosed herein is a method of preparing a medium-density polyethylene pipe comprising melting a multimodal metallocene-catalyzed polyethylene resin to form a molten polyethylene, wherein the multimodal metallocene-catalyzed polyethylene resin has a density of from about 0.925 g/ml to about 0.942 g/ml, a magnitude of slip-stick greater than about 300 psi, a stress for smooth to matte transition of greater than about 90 kPa, and a shear rate for smooth to matte transition greater than about 10 s "1 , wherein the magnitude of slip-stick, stress for smooth to matte transition, and shear rate for smooth to matte transition are determined by a capillary rheology test; and forming the molten polyethylene resin into pipe.
- a pipe prepared from a multimodal metallocene-catalyzed polyethylene resin having a density of from about 0.925 g/ml to about 0.942 g/ml, a magnitude of slip-stick greater than about 300 psi; a stress for smooth to matte transition of greater than about 90 kPa, and a shear rate for smooth to matte transition greater than about 10 s "1 , wherein the magnitude of slip-stick, stress for smooth to matte transition, and shear rate for smooth to matte transition are determined by a capillary rheology test.
- Figure 1A is a schematic of the melt fracture behavior of a conventional unimodal polyethylene composition.
- Figure IB is a schematic of the melt fracture behavior of a multimodal polyethylene base resin of the type disclosed herein.
- Figure 2 is a plot of the predicted slip-stick values as a function of the measured slip-stick values for the calibration samples from Example 1.
- Figure 3 is a plot of the predicted slip-stick values as a function of the measured slip-stick values for the calibration and validation samples from Example 1.
- Figure 4 is a plot of the predicted onset for smooth to matte transition as a function of the measured onset for smooth to matte transition for the calibration samples from Example 1.
- Figure 5 is a plot of the predicted onset for smooth to matte transition as a function of the measured onset for smooth to matte transition for the calibration and validation samples from Example 1.
- Figure 6 is a plot of the predicted onset for the matte to wavy transition as a function of the measured onset for the matte to wavy transition for the calibration samples from Example 1.
- Figure 7 is a depiction of the molecular weight distribution of a bimodal polymer sample.
- Figure 8 is a Figure 8 is a plot of the magnitude of slip-stick as a function of the weight fraction of the lower molecular weight (LMW) component and the peak molecular weight.
- LMW lower molecular weight
- Figure 9 is a plot of the stress for the smooth to matte transition as a function of the peak molecular weights of components PI and P2.
- Figure 10 is a schematic illustration of an embodiment of a computer program product for implementing the disclosed functionalities.
- the method comprises obtaining a plurality of multimodal metallocene-catalyzed polyethylene resins and subjecting these resins to capillary rheometry in order to measure the shear stress as a function of shear rate.
- the rheometric measurements may be used to identify multimodal metallocene-catalyzed polyethylene resins having one or more desired processing characteristics.
- metallocene-catalyzed polyethylene resins also termed a PE base resin
- general features of said metallocene-catalyzed polyethylene resins methods for identifying metallocene-catalyzed polyethylene resins having desired processing characteristics, methods of modifying metallocene-catalyzed polyethylene resins to provide desired processing characteristics, and methods of preparing articles from metallocene-catalyzed polyethylene resins having desired processing characteristics.
- a PE base resin of the present disclosure is produced by any olefin polymerization method, using various types of polymerization reactors and catalyst systems.
- a “base resin” refers to a resin that has not undergone a modification to improve processability of the type described herein.
- base resin refers to the PE starting material that is accessed and modified according to the present disclosure.
- the base resin may include virgin PE resin or "fluff as recovered from a polymerization process and prior to the addition of any additives or modifiers and/or includes PE resin recovered from a polymerization process that has undergone further processing such as pelletization, which may include the addition of a base additive package of the type commonly added to commercial PE resins (e.g., antioxidants, stabilizer).
- the PE base resin has not undergone any modification (e.g., inclusion of processing aids.) to improve the melt fracture characteristics of the material.
- the PE base resin does not include any polymer processing aids (PPAs) of the type known to those skilled in the art.
- the catalyst system for preparation of the PE base resin comprises at least two metallocene complexes.
- metallocene describes a compound comprising at least one ⁇ 3 to r
- substituted derivatives thereof in this disclosure comprises partially saturated ligands such as tetrahydroindenyl, tetrahydrofluorenyl, octahydrofluorenyl, partially saturated indenyl, partially saturated fluorenyl, substituted partially saturated indenyl, substituted partially saturated fluorenyl, and the like.
- the metallocenes may be combined with a solid activator, an aluminum alkyl compound, an olefin monomer, and an olefin comonomer to produce the desired bimodal polyolefin.
- the activity and the productivity of the catalyst may be relatively high.
- the activity refers to the grams of polymer produced per gram of solid catalyst charged per hour
- productivity refers to the grams of polymer produced per gram of solid catalyst charged.
- Examples of such catalyst systems are disclosed in U.S. Patent Application Serial No. 11/209,006, filed August 22, 2005 and entitled “Polymerization Catalysts And Process For Producing Bimodal Polymers In A Single Reactor," and U.S. Patent Application Serial No. 11/208,077, filed August 19, 2005 and entitled “Polymerization Catalysts and Process for Producing Bimodal Polymers in a Single Reactor,” each of which is incorporated herein in its entirety.
- polymerization reactor includes any reactor capable of polymerizing olefin monomers (e.g., ethylene) to produce homopolymers and/or copolymers (e.g., PE homopolymers and/or copolymers). Homopolymers and/or copolymers produced in the reactor may be referred to as resin and/or polymers.
- the various types of reactors include, but are not limited to those that may be referred to as batch, slurry, gas-phase, solution, high pressure, tubular, autoclave, or other reactor and/or reactors.
- Gas phase reactors may comprise fluidized bed reactors or staged horizontal reactors.
- Slurry reactors may comprise vertical and/or horizontal loops.
- High pressure reactors may comprise autoclave and/or tubular reactors.
- Reactor types may include batch and/or continuous processes. Continuous processes may use intermittent and/or continuous product discharge or transfer. Processes may also include partial or full direct recycle of un-reacted monomer, un-reacted comonomer, catalyst and/or co-catalysts, diluents, and/or other materials of the polymerization process.
- Polymerization reactor systems of the present disclosure may comprise one type of reactor in a system or multiple reactors of the same or different type, operated in any suitable configuration.
- Production of polymers in multiple reactors may include several stages in at least two separate polymerization reactors interconnected by a transfer system making it possible to transfer the polymers resulting from the first polymerization reactor into the second reactor.
- polymerization in multiple reactors may include the transfer, either manual or automatic, of polymer from one reactor to subsequent reactor or reactors for additional polymerization.
- multi-stage or multi-step polymerization may take place in a single reactor, wherein the conditions are changed such that a different polymerization reaction takes place.
- the desired polymerization conditions in one of the reactors may be the same as or different from the operating conditions of any other reactors involved in the overall process of producing the polymer of the present disclosure.
- Multiple reactor systems may include any combination including, but not limited to multiple loop reactors, multiple gas phase reactors, a combination of loop and gas phase reactors, multiple high pressure reactors or a combination of high pressure with loop and/or gas reactors.
- the multiple reactors may be operated in series or in parallel. In an embodiment, any arrangement and/or any combination of reactors may be employed to produce the polymer of the present disclosure.
- the polymerization reactor system may comprise at least one loop slurry reactor. Such reactors are commonplace, and may comprise vertical or horizontal loops. Monomer, diluent, catalyst system, and optionally any comonomer may be continuously fed to a loop slurry reactor, where polymerization occurs.
- continuous processes may comprise the continuous introduction of a monomer, a catalyst, and/or a diluent into a polymerization reactor and the continuous removal from this reactor of a suspension comprising polymer particles and the diluent.
- Reactor effluent may be flashed to remove the liquids that comprise the diluent from the solid polymer, monomer and/or comonomer.
- Various technologies may be used for this separation step including but not limited to, flashing that may include any combination of heat addition and pressure reduction; separation by cyclonic action in either a cyclone or hydrocyclone; separation by centrifugation; or other appropriate method of separation.
- Typical slurry polymerization processes are disclosed in U.S. Patent Nos. 3,248,179, 4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191 and 6,833,415, for example; each of which are herein incorporated by reference in their entirety.
- Suitable diluents used in slurry polymerization include, but are not limited to, the monomer being polymerized and hydrocarbons that are liquids under reaction conditions.
- suitable diluents include, but are not limited to, hydrocarbons such as propane, cyclohexane, isobutane, n-butane, n- pentane, isopentane, neopentane, and n-hexane.
- Some loop polymerization reactions can occur under bulk conditions where no diluent is used.
- An example is polymerization of propylene monomer as disclosed in U.S. Patent No. 5,455,314, which is incorporated by reference herein in its entirety.
- the polymerization reactor may comprise at least one gas phase reactor.
- Such systems may employ a continuous recycle stream containing one or more monomers continuously cycled through a fluidized bed in the presence of the catalyst under polymerization conditions.
- a recycle stream may be withdrawn from the fluidized bed and recycled back into the reactor.
- polymer product may be withdrawn from the reactor and new or fresh monomer may be added to replace the polymerized monomer.
- Such gas phase reactors may comprise a process for multi-step gas-phase polymerization of olefins, in which olefins are polymerized in the gaseous phase in at least two independent gas-phase polymerization zones while feeding a catalyst-containing polymer formed in a first polymerization zone to a second polymerization zone.
- One type of gas phase reactor is disclosed in U.S. Patent Nos. 4,588,790, 5,352,749, and 5,436,304, each of which is incorporated by reference in its entirety herein.
- a high pressure polymerization reactor may comprise a tubular reactor or an autoclave reactor.
- Tubular reactors may have several zones where fresh monomer, initiators, or catalysts are added.
- Monomer may be entrained in an inert gaseous stream and introduced at one zone of the reactor.
- Initiators, catalysts, and/or catalyst components may be entrained in a gaseous stream and introduced at another zone of the reactor.
- the gas streams may be intermixed for polymerization. Heat and pressure may be employed appropriately to obtain optimal polymerization reaction conditions.
- the polymerization reactor may comprise a solution polymerization reactor wherein the monomer is contacted with the catalyst composition by suitable stirring or other means.
- a carrier comprising an organic diluent or excess monomer may be employed.
- the monomer may be brought in the vapor phase into contact with the catalytic reaction product, in the presence or absence of liquid material.
- the polymerization zone is maintained at temperatures and pressures that will result in the formation of a solution of the polymer in a reaction medium. Agitation may be employed to obtain better temperature control and to maintain uniform polymerization mixtures throughout the polymerization zone. Adequate means are utilized for dissipating the exothermic heat of polymerization.
- Polymerization reactors suitable for the present disclosure may further comprise any combination of at least one raw material feed system, at least one feed system for catalyst or catalyst components, and/or at least one polymer recovery system.
- Suitable reactor systems for the present invention may further comprise systems for feedstock purification, catalyst storage and preparation, extrusion, reactor cooling, polymer recovery, fractionation, recycle, storage, loadout, laboratory analysis, and process control.
- Conditions that are controlled for polymerization efficiency and to provide polymer properties include, but are not limited to temperature, pressure, type and quantity of catalyst or co-catalyst, and the concentrations of various reactants.
- Polymerization temperature can affect catalyst productivity, polymer molecular weight and molecular weight distribution.
- Suitable polymerization temperatures may be any temperature below the de-polymerization temperature, according to the Gibbs Free Energy Equation. Typically, this includes from about 60°C to about 280°C, for example, and/or from about 70°C to about 110°C, depending upon the type of polymerization reactor and/or polymerization process.
- Suitable pressures will also vary according to the reactor and polymerization process.
- the pressure for liquid phase polymerization in a loop reactor is typically less than 1000 psig.
- Pressure for gas phase polymerization is usually at about 200 - 500 psig.
- High pressure polymerization in tubular or autoclave reactors is generally run at about 20,000 to 75,000 psig.
- Polymerization reactors can also be operated in a supercritical region occurring at generally higher temperatures and pressures. Operation above the critical point of a pressure/temperature diagram (supercritical phase) may offer advantages.
- the concentration of various reactants can be controlled to produce polymers with certain physical and mechanical properties.
- the proposed end-use product that will be formed by the polymer and the method of forming that product may be varied to determine the desired final product properties.
- Mechanical properties include, but are not limited to tensile strength, flexural modulus, impact resistance, creep, stress relaxation and hardness tests.
- Physical properties include, but are not limited to density, molecular weight, molecular weight distribution, melting temperature, glass transition temperature, temperature melt of crystallization, density, stereoregularity, crack growth, short chain branching, long chain branching and rheological measurements.
- the concentrations of monomer, co-monomer, hydrogen, co-catalyst, modifiers, and electron donors are generally important in producing specific polymer properties.
- Comonomer may be used to control product density.
- Hydrogen may be used to control product molecular weight.
- Co-catalysts may be used to alkylate, scavenge poisons and/or control molecular weight.
- the concentration of poisons may be minimized, as poisons may impact the reactions and/or otherwise affect polymer product properties.
- Modifiers may be used to control product properties and electron donors may affect stereoregularity.
- a PE base resin of the type described herein comprises a polymer blend, e.g., a blend of two or more component polymers such as a higher molecular weight (HMW) component and a lower molecular weight (LMW) component.
- the polymer blend may be of any type compatible with and able to produce a PE base resin of the type described herein.
- the PE base resin may be a physical or mechanical blend of polymers, alternatively the PE base resin may be a reactor blend of polymers.
- a process for the preparation of a PE base resin of the type disclosed herein comprises the preparation of each component of the PE base resin independent of the other components.
- the process may comprise polymerization of an alpha-olefin monomer in the presence of a catalyst system under a first set of reaction conditions to form a first component of the PE base resin.
- the process may further comprise polymerization of an alpha-olefin in the presence of a catalyst system under a second set of reaction conditions to form a second component of the PE base resin.
- the formation of the second component may be carried out in the presence of the first component (e.g., a reactor blend) or in the absence of the first component (and the two components subsequently blended, for example via mechanical blending, co-extrusion, etc.). It is to be understood adjustments of the reaction conditions to which the catalyst system is subjected during polymerization may substantively alter the resultant product.
- a process for preparation of a PE base resin may further comprise contacting the first and second components utilizing any appropriate methodology (e.g., mechanical mixing).
- the resultant PE base resin comprises a physical blend of the first and second component.
- a process for the preparation of a PE base resin of the type disclosed herein comprises polymerization of an alpha-olefin monomer in the presence of at least two different catalytic materials or catalysts, for example a catalyst system comprising at least two transition metal complexes.
- the catalyst system may comprise a first and a second transition metal complex wherein the first and second transition metal complexes are different.
- the catalyst system comprises at least two metallocene complexes and results in the simultaneous formation of the two components of the PE base resin when both catalysts are employed in a single reactor.
- a first catalyst system comprising a first metallocene complex that may be associated with a first reactor.
- Alpha-olefin monomer may be contacted with the first catalyst system and reactor and conditions adjusted such that polymerization of the alpha-olefin monomer results and a first component of the PE base resin is produced.
- the first component may then be contacted with a second catalyst system and alpha-olefin monomer under conditions to result in the polymerization of the alpha-olefin monomer and formation of the second component of the PE base resin.
- the components of the PE base resin are produced sequentially.
- the PE base resin formed may be described as a reactor blend of the two components.
- the PE base resin comprises a multimodal PE resin.
- the "modality" of a polymer resin refers to the form of its molecular weight distribution curve, i.e., the appearance of the graph of the polymer weight fraction as a function of its molecular weight.
- the polymer weight fraction refers to the weight fraction of molecules of a given size.
- a polymer having a molecular weight distribution curve showing a single peak may be referred to as a unimodal polymer
- a polymer having curve showing two distinct peaks may be referred to as bimodal polymer
- a polymer having a curve showing three distinct peaks may be referred to as trimodal polymer, etc.
- references to a PE base resin is understood to include a multimodal PE base resin, including but not limited to a resin having a HMW component and a LMW component that is produced from a catalyst system comprising at least two metallocene complexes (e.g., a dual-metallocene catalyst).
- the PE base resin is a metallocene-catalyzed, multimodal (e.g., bimodal) polyethylene copolymer with 1-hexene.
- the PE base resin is a dual-metallocene- catalyzed, multimodal (e.g., bimodal) polyethylene copolymer.
- suitable comonomers include without limitation unsaturated hydrocarbons having from 3 to 20 carbon atoms such as propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-l-butene, 4-methyl-l-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, and mixtures thereof.
- the comonomer is 1 -hexene.
- a polymer resin may have two or more components that may be distinguishable from one another, for example based upon their individual composition and/or molecular weight distribution.
- a molecular weight distribution curve may be prepared for each individual component of the polymer resin.
- the molecular weight distribution curve for the individual components of the polymer resin may display a single peak and thus be unimodal.
- the molecular weight distribution curves for the individual components may be superimposed onto a common chart to form the weight distribution curve for the polymer resin as a whole. Upon such superimposition, the resultant curve for the polymer resin as a whole may be multimodal or show n distinct peaks corresponding to n polymer components of differing molecular weight distributions.
- a bimodal polymer resin may show two distinct peaks corresponding to two individual components.
- a bimodal polymer resin may have a first component that may be generally characterized as a higher molecular weight polymer component and a second component that may be generally characterized as a lower molecular weight polymer component.
- a trimodal polymer composition may show three distinct peaks corresponding to three individual polymer components.
- superimposition of the molecular weight distribution curves from the individual components may show a single peak that is broadened in comparison with the curves for the individual components corresponding to polymer fractions having different but overlapping molecular weight distributions.
- Such compositions while appearing unimodal may be deconvoluted into their individual component peaks and can thus be shown to be a multimodal composition.
- the individual components of the PE base resin may comprise a homopolymer, a copolymer, or blends thereof.
- the components of the PE base resin may be a copolymer comprised of a polymer of ethylene with one or more comonomers such as alpha olefins.
- the PE base resin comprises a higher molecular weight (HMW) component and a lower molecular weight (LMW) component, for example a HMW copolymer component (e.g., a copolymer of ethylene and 1-hexene) and a LMW copolymer component (e.g., a copolymer of ethylene and 1-hexane).
- the PE base resin is a dual-metallocene polyethylene having a HMW component comprised of polyethylene copolymer with 1- hexene and a LMW component comprised of polyethylene copolymer with 1-hexene.
- the PE base resin comprises a LMW component and a HMW component, wherein the LMW component is present in the PE base resin in a weight fraction of from about 0.3 to about 0.7, alternatively from about 0.4 to about 0.7 or alternatively from about 0.5 to about 0.65 based on total weight of the PE base resin, and the HMW component makes up the balance of the PE base resin.
- PE base resins of the type disclosed herein may be characterized by a LMW component having a peak molecular weight (M p ) ranging from about 25 kg/mol to about 65 kg/mol, alternatively from about 35 kg/mol to about 60 kg/mol, or alternatively from about 40 kg/mol to about 50 kg/mol and a HMW component having a M p ranging from about 67 kg/mol to about 600 kg/mol, alternatively from about 200 kg/mol to about 600 kg/mol, or alternatively from about 400 kg/mol to about 500 kg/mol.
- M p peak molecular weight
- the molecular weight distribution (MWD) of the PE base resin may be characterized by the ratio of the weight average molecular weight to the number average molecular weight, which is also referred to as the polydispersity index (PDI) or more simply as polydispersity.
- the number average molecular weight is the common average of the molecular weights of the individual polymers calculated by measuring the molecular weight of n polymer molecules, summing the weights, and dividing by n.
- the weight average molecular weight describes the molecular weight distribution of a polymer composition and is calculated according to equation 1 :
- the individual components of the PE base resin e.g., the LMW component and the HMW component
- the HMW component may have a PDI of from about 2 to about 5, alternatively from about 2 to about 4, or alternatively from about 2 to about 3.
- the LMW component may have a PDI of from about 2 to about 5, alternatively from about 2 to about 4, or alternatively from about 2 to about 3.
- the resultant PE base resin i.e., including both the LMW and HMW components
- a PE base resin prepared as described herein may display one or more types of melt fracture during polymer melt formation and processing such as extrusion molding.
- the type, extent, and conditions under which the polymer melt experiences melt fracture may vary depending on the polymer microstructure.
- a method of identifying a PE base resin having desirable processing characteristics comprises obtaining a plurality of PE base resins of the type disclosed herein and measuring the shear stress as a function of shear rate for the plurality of base resins using capillary rheometry.
- Capillary rheometry is a technique whereby a sample undergoes extrusion through a die of defined dimensions and the shear pressure drop across the die is recorded at set volumetric flow rates.
- a PE base resin of the type disclosed herein is the subject of a capillary extrusion experiment to characterize the melt fracture behavior of the resin.
- the capillary extrusion experiment may be carried out using any suitable methodology.
- the capillary extrusion experiments may be carried out at 190 °C, using a dual-bore capillary rheometer (Rosand RH-7, Malvern) operated in constant speed mode.
- a capillary die with 1 mm diameter and of 16 mm length and an orifice die with 1 mm diameter may be used.
- the entrance angle for the dies can be 180°, and the contraction ratio from the reservoir barrel to the die may be about 15.
- a step shear rate test can be performed for a given sample to obtain the apparent wall shear rate ( ⁇ A ) and apparent wall shear stress ( ⁇ ⁇ ) according to equation 2:
- PE base resins of the type disclosed herein display a surface melt fracture (SMF) that occurs at a critical stress of less than about 200 kiloPascals (kPa), alternatively from about 30 kPa to about 180 kPa.
- SMF surface melt fracture
- the critical stress refers to the wall shear stresses that serves as the trigger for the onset of a particular extrudate distortion or melt fracture.
- SMF may also be referred to as the smooth to matte transition or the sharkskin melt fracture (SSMF).
- SSMF sharkskin melt fracture
- the onset of SMF is a polymer instability in the PE base resin that originates at the exit of a die during extrusion of melted resin (i.e., melt) through the die.
- the SMF may be attributable to the acceleration (high stretching rate) of the melt as it exits the die.
- sharkskin which is a visible surface defect present in the product being produced from the die (e.g., pipe).
- the critical stress is related to the onset of SMF.
- the PE base resins of this disclosure display a reduced amount of slip-stick fracture (SSF) when compared to a unimodal PE base resin or a PE that is not made using a dual- metallocene catalyst.
- SSF slip-stick fracture
- the melt jerks forward as a plug, relieving the pressure behind it and allowing the oriented chain segments to recoil somewhat. Once the pressure is relieved, the rate of movement of the polymer slows and it re-establishes the non-slip boundary condition.
- SSF slip-stick fracture
- a PE base resin of the type disclosed herein displays a tendency to SSF pressure oscillation that is less than a unimodal PE base resin or a PE that is not made using a dual-metallocene catalyst.
- a PE base resin of the type disclosed herein is characterized by a magnitude of slip-stick of from about 300 psi to about 1500 psi, alternatively from about 500 psi to about 1500 psi, alternatively from about 500 psi to about 900 psi, or alternatively from about 600 psi to about 800 psi .
- a PE base resin of the type disclosed herein may display surface melt fracture that occurs at a critical shear rate of from about 10 s "1 to about 100 s "1 , alternatively from about 10 s “ 1 to about 50 s “1 , or alternatively from about 20 s “1 to about 40 s “1 .
- the shear rate refers to the extrusion speed that serves as the trigger for the onset of a particular extrudate distortion or melt fracture. This relates to the critical stress discussed previously and the melt flow index/viscosity of a PE base resin.
- FIG. 1A The melt fracture behavior of a conventional unimodal PE base resin and a PE base resin of the type disclosed herein is schematized in Figures 1A and IB, respectively.
- Figure 1 show plots of the log of shear rate in MegaPascals (MPa) units with the log of shear stress in inverse seconds (1/s) units, each of which were determined as described in more detail herein.
- a PE base resin displaying melt fracture behavior consistent with Figure IB may be referred to as having an about smooth curve of the log of shear stress as a function of the log of shear rate.
- Figure 1A shows four regions associated with characteristics of the melt, namely smooth, sharkskin, slip- stick, and gross melt fracture (GMF).
- Figure IB shows four regions associated with characteristics of the melt, namely smooth, matte, wavy, and gross melt fracture (GMF).
- a plurality of PE base resins of the type disclosed herein are subjected to capillary rheometry.
- a method of identifying a PE base resin having a reduced tendency to melt fracture comprises identifying a PE base resin having a magnitude of slip-stick of greater than about 300 psi, a smooth to matte transition of greater than about 90 kPa of stress and a shear rate of greater than about 10 s "1 .
- Such resins having a magnitude of slip-stick of greater than about 300 psi, a smooth to matte transition of greater than about 90 kPa of stress and a shear rate of greater than about 10 s "1 and thus a reduced tendency to melt fracture, are termed polymers with a reduced melt fracture tendency (PRMT).
- PRMT reduced melt fracture tendency
- the PRMTs may be selected and further processed into articles (e.g., pipes) as described in more detail herein.
- capillary extrusion experiments are carried out and identify PE base resins characterized by at least one of the following conditions a magnitude of slip-stick less than about 300 psi; a smooth to matte transition of less than about 90 kPa of stress and a shear rate less than about 10 s "1 .
- Such resins may display an increased tendency to melt fracture and are herein termed resins with increased melt fracture (RIM).
- a PRMT e.g, metallocene-catalyzed multimodal PE base resin
- a PRMT having a reduced tendency to melt fracture
- a magnitude of slip-stick greater than about 300 psi e.g., metallocene-catalyzed multimodal PE base resin
- a smooth to matte transition of greater than about 90 kPa of stress e.g., a shear rate greater than about 10 s "1 .
- measurement of the magnitude of slip-stick pressure oscillation and the stress and shear rate for the smooth to matte transition may be made by capillary extrusion experiments. As will be understood by one of ordinary skill in the art, capillary extrusion experiments are both time and labor intensive.
- an alternative methodology for identifying PE base resins having a reduced tendency to melt fracture comprises relating one or more processing characteristics of a PE base resin of the type disclosed herein (e.g., melt fracture behavior) to measurements carried out using techniques that inform on polymer microstructure such as Gel Permeation Chromatography (GPC).
- GPC Gel Permeation Chromatography
- an analytical relationship between the polymer microstructure and processing characteristic is defined by chemometric analysis.
- the analytical relationship may be in the form of a mathematical equation.
- Chemometric analysis refers to the application of statistical and pattern recognition techniques to data provided by chemical analysis such as GPC data.
- a method comprises relating the MWD profile of a polymer to the melt fracture properties as determined by capillary rheometry.
- chemometric analysis is performed on data obtained from a series of at least two training samples of PE base resins of the type disclosed herein having different, known compositions, which are studied to ascertain interrelationships between the data and one or more known sample characteristics.
- the data comprises information on the polymer microstructure (e.g., data as determined by GPC) and the one or more sample characteristics comprise melt fracture behavior (e.g., melt fracture behavior of the type alternatively provided via capillary analysis as described herein, that is the characteristics used to identify a RIM or a PRMT).
- At least 5 training samples, or at least 10 training samples, or at least 20 training samples, or at least 30 training samples, or at least 40 training samples, or at least 50 training samples can be analyzed.
- the limit to the number of training samples that can be analyzed together usually is dictated by limitations of the software and computer hardware employed, and no specific upper limit to the number of samples to be used is contemplated.
- Training samples optionally can be samples characterized in prior work, the literature, by interpolation or extrapolation from other training samples, or other sources, as opposed to samples that are made physically available.
- Training samples normally will closely resemble the desired test samples, so the properties of the test samples and the training samples can readily be compared.
- the set of training samples should include members having a range of properties that goes beyond the expected properties of the test samples. Selecting a broad range of training samples will allow a more robust model to be developed, so the data obtained from the training samples can be used for samples that may have properties somewhat different from the expected ones.
- the training samples can, but need not be made by separating fractions of a test sample.
- materials other than those of the test samples can be used as training samples or constituents of training samples.
- Analytical data for the training samples can be measured, obtained from literature values, derived from prior work, or obtained from a combination of sources.
- the polymer microstructure data results (e.g., as provided by GPC) or other polymer microstructure information for the training samples are analyzed to find correlations between polymer microstructure and the predicted melt fracture behavior of the polymer.
- Analysis of the relationship between the polymer microstructure (e.g., as provided by GPC data) and the predicted melt fracture behavior may be carried out using any suitable chemometric software.
- the chemometric software compares the polymer microstructure results from the training samples and finds correlations between the polymer microstructure results (e.g., GPC data) of the polymer and the melt fracture behavior.
- chemometric analysis of the relevant data is carried out using any suitable chemometric technique.
- suitable chemometric techniques include but are not limited to Partial Least Squares Regression (PLS), Multilinear Regression Analysis (MLR), Principal Components Regression (PCR), Principal Component Analysis (PCA) and Discriminant Analysis, as well as Design of Experiment (DOE) and Response Surface Methodologies.
- PLS Partial Least Squares Regression
- MLR Multilinear Regression Analysis
- PCR Principal Components Regression
- PCA Principal Component Analysis
- Discriminant Analysis as well as Design of Experiment (DOE) and Response Surface Methodologies.
- the chemometric analysis is carried out using PLS2.
- PLS refers to a wide class of methods for modeling relations between sets of observed variables by means of latent variables. The underlying assumption of all PLS methods is that the observed data is generated by a system or process which is driven by a small number of latent variables.
- a methodology for evaluating the melt fracture characteristics of a polymer sample comprises identifying at least two polymer training samples having different but known melt fracture characteristics.
- the training samples may be subjected to GPC to determine various characteristics of the polymer sample such as the molecular weight distribution, amount of each constituent present in the polymer sample, weight average molecular weight and the like.
- the results of the GPC analysis are determined using standard computer software to plot and/or analyze the results of the chromatographic separation.
- GPC data for the training samples may be obtained from any suitable source (e.g., literature values). Analysis of the GPC data may then be carried out to determine at least one parameter that correlates with the known difference in melt fracture characteristics among the training samples.
- Chemometric analysis may be carried out to define the number of polymer microstructure data, type of polymer microstructure data and relationship between the polymer microstructure data that would serve as a proxy for the observed melt fracture characteristics of the PE base resins. It is to be understood that establishing that a relationship exists between the proxy data (e.g., GPC) and the actual characteristic being observed (e.g., melt fracture) and analytically defining that relationship will be dependent on the nature of the training samples chosen as discussed previously herein.
- the proxy data e.g., GPC
- melt fracture e.g., melt fracture
- GPC data for polymer samples having unknown melt fracture characteristics are provided.
- the values of the parameters determined to be correlated to melt fracture characteristics in the training samples are identified for the test samples.
- the analytical relationship found by analysis of the training samples is applied to these parameter values identified in the test samples and as a result the melt fracture characteristics of the test samples are predicted. From such predicted characteristics, the sample may be identified as a RIM or a PRMT.
- DOE of the GPC data for a set of training samples may define a relationship between a melt fracture characteristic (Y) and the polymer microstructure as an equation having measurable variables (e.g., M p ) and constants determined by chemometric analysis of the training sample.
- Mp measurable variables
- a method of identifying PE base resins having one or more desired processing characteristics comprises obtaining a plurality of PE base resins of the type disclosed herein having a known molecular weight distribution, a known magnitude of slip-stick, a known stress for a smooth to matte transition, and a known shear rate (i.e., training samples).
- the method may further comprise performing chemometric analysis to determine an analytical relationship between the known molecular weight distribution, the known magnitude of slip-stick, the known stress for a smooth to matte transition, and the known shear rate for the plurality of PE resins (i.e., training samples).
- the method may further comprise obtaining a plurality of samples of multimodal metallocene-catalyzed PE resins, each having a known molecular weight distribution, an unknown magnitude of slip-stick, an unknown stress for a smooth to matte transition, and an unknown shear rate (i.e., test samples) and utilizing the analytical relationship to determine a value for the unknown magnitude of slip-stick, a value for the unknown stress for a smooth to matte transition, and a value for the unknown shear rate for each of the plurality of multimodal metallocene-catalyzed PE samples (i.e., test samples).
- the method may further comprise identifying multimodal metallocene-catalyzed PE resins (e.g., PRMPs) having a reduced tendency to melt fracture characterized by samples having a magnitude of slip-stick greater than about 300 psi, a smooth to matte transition of greater than about 90 kPa of stress and a shear rate greater than about 10 s "1 .
- the method may further comprise forming the PRMPs into articles such as pipe.
- the method may further comprise identifying multimodal metallocene-catalyzed PE resins (e.g., RIMs) having an increased tendency to melt fracture characterized by samples having a magnitude of slip-stick less than about 300 psi, a smooth to matte transition of less than about 90 kPa of stress and a shear rate less than about 10 s 1 .
- the method may further comprise modifying the identified RIM to decrease the tendency of the material to melt fracture.
- the modified RIM may be analyzed (e.g., via GPC) to determine molecular weight distribution, and thereby predict melt fracture behavior (as described herein) of the modified RIM, e.g., to determine whether the RIM has been modified to yield a PRMP.
- the method may further comprise forming the PRMT into articles such as pipe.
- the flow properties determined by capillary rheometry may be related to the entire MWD profile of the polymer.
- the MWD is the metric used to inform on the polymer microstructure.
- the MWD of the polymer is dependent on several factors.
- a method comprises performing chemometric analysis in order to establish the relationship between one or more factors contributing to the MWD and the melt fracture behavior of the polymer. For example, using statistical design of experiment (DOE) and response surface methodology, the MWD profile of a polymer in terms of its molecular weight components and their subsequent effect on the capillary results may be determined.
- DOE statistical design of experiment
- the MWD profile of a particular polymer is described as the linear combination of n factors where n is equal to or greater than 2, alternatively equal to or greater than about 3, or alternatively equal to or greater than about 4.
- n is 2 and the components are designated PI and P2.
- PI and P2 can each be assigned a M p , PDI, and weight fraction composition. Using a combination of these two components (i.e., PI and P2), the effects of various MWD profiles on the melt fracture characteristics of the polymer (i.e, capillary response) can be explored in a systematic manner.
- the components of the MWD can be represented using any suitable peak shape such as Gaussian or Schluz-Flory.
- the components of the MWD i.e., PI and P2 are represented using log normal (i.e., Gaussian) shaped peaks.
- the polymer is a physical blend or mixture of polymers where the exact number of components is known as well as the nature of these components in terms of M w and M n .
- the MWD of a polymer having been described initially as the linear combination of two components can be further characterized by the peak molecular weight of each component (M p PI and M p P2), the PDI of each component, and the weight fraction of each component.
- the method further comprises digitally generating MWD profiles by varying the individual parameters that characterize the MWD (i.e., M p , PDI and weight fraction of each component).
- M p the individual parameters that characterize the MWD
- PDI weight fraction of each component
- the MWD profile generated for each variation of parameters may be utilized to predict a melt fracture characteristic (e.g., magnitude of slip- stick).
- Digitally varying the parameters and identifying the relative contribution of each parameter and/or combination of parameters to the particular melt fracture characteristic may aid in elucidating the analytical relationship between a particular parameter and/or combination of parameters and the resultant melt fracture characteristic (e.g., magnitude of slip-stick).
- the relationship between one or more of the varied parameters and the result (e.g., magnitude of slip-stick) may be codified in the form of a mathematical algorithm of the type previously disclosed herein and exemplified below.
- the algorithm includes all of the parameters of the MWD identified to contribute to the resultant melt fracture characteristic (e.g., magnitude of slip-stick).
- the method further comprises statistical analysis of the results of the chemometric determinations to identify parameters that significantly contribute to the resultant melt fracture characteristic (e.g., magnitude of slip-stick).
- "significant” refers to statistical significance which is defined as the likelihood that the result obtained has occurred by chance.
- the statistical significance of the analysis can determined using any suitable methodology.
- the method may further comprise analysis of the variance in the results of the chemometric determinations. Analysis of Variance (ANOVA) methods are used in data analysis to determine differential expressions under different experimental conditions. In a one-way ANOVA, there is one experimental factor under investigation. For example, the factor may be the effect of the peak molecular weight on the magnitude of slip-stick.
- ANOVA Analysis of Variance
- ANOVA In a two-way ANOVA, there are two factors under investigation, for example, the effect of the amount of the LMW component and PDI of the LMW component on the magnitude of the slip-stick. Each factor may have multiple levels. Interaction between the two factors is also included in the ANOVA analysis. ANOVA may also be carried out in order to determine whether there are statistical differences among the means of measurements in different measurement groups.
- the different measurement groups may contain measurements of the magnitude of slip-stick at different weight fractions of a particular component. In each group, there may be several replicate measurements under the same conditions. First, one finds the within- group variance and the between-group variance.
- the within-group variance is the measurement variance of measurements within a set of experiments carried out under the same conditions.
- the between-group variance is the measurement variance of the means of experiments carried out under different conditions.
- the within-group variance reflects the measurement error of the measurement technology, and the between- group variance includes both the measurement error of the measurement technology and changes caused by different conditions.
- the between-group variance is compared to the within-group variance. If the between-group variance is significantly larger than the within-group variance, it may be concluded that the different conditions have produced statistically significant changes in the determinations of the melt fracture characteristics (e.g., magnitude of slip-stick).
- ANOVA analysis the underlying null-hypothesis is that all conditions have the same mean. With the estimated mean squares and degrees of freedom, a p-value of F- statistics can be calculated.
- the p-value is the probability that the null-hypothesis may be accepted.
- a given threshold for example p-value ⁇ 0.01
- the null-hypothesis can be rejected and the alternative hypothesis, which means that some of the experimental conditions have different means, can be accepted. In other words, some experimental conditions have produced changes in the melt fracture characteristics.
- the algorithm describing the relationship between one or more of the varied parameters and the result is modified to reflect only those parameters found to contribute significantly to the result.
- statistical models may be constructed and extrapolated to produce values of parameters that lie outside of the range observable or probable for actual samples. For example, utilizing the methodologies disclosed herein, models may be constructed which predict a negative value for the magnitude of slip-stick. In such instances, the limitations of the model are realized and the negative values obtained can be assumed to have a value of zero.
- a PMRT is prepared by blending n components having one or more parameters (e.g., wt fraction of each component, PDI of each component) determined to provide a polymer blend having one or more desirable melt fracture characteristics.
- parameters e.g., wt fraction of each component, PDI of each component
- the results of the chemometric analysis may indicate that one of the significant factors in the stress for the smooth to matte transition is peak molecular weight of the LMW component. Consequently, adjusting the peak molecular weight of the LMW component to within a range indicated by the results of the chemometric analysis (e.g., adjustments responsive to the chemometric analysis results) would be expected to produce a resin having a stress for the smooth to matte transition within some user and/or process desired range. Consequently there can be numerous polymer designs which display a reduced tendency to melt fracture as such solutions to the problem of melt fracture are dependent on a variety of parameters but may be understood and employed in view of the disclosure herein (e.g., responsive to chemometric analysis).
- a method for reducing or eliminating melt fracture (e.g., SMF) in a RIM of the type disclosed herein comprises increasing the molecular weight of the LMW component.
- a method for reducing or eliminating melt fracture (e.g., SMF) in a RIM of the type disclosed herein comprises decreasing both the amount of the LMW component and the M w of the HMW component.
- a method for reducing or eliminating melt fracture (e.g., SMF) in a RIM of the type disclosed herein comprises introducing a polymer component having a MWD peak mode that is disposed between the MWD peak modes of the LMW component and HMW component.
- Such modifications may be carried out by altering one or more process conditions during polymerization of the LMW component and/or the HMW component (e.g., during formation of a reactor blend) and/or by replacing and/or adding one or more components during formation of a mechanical blend such as selecting an alternative LMW component and/or HMW component than that present in the RIM and/or by adding an additional component having a MWD peak mode between those of the LMW and HMW components.
- modifications of the RIM are effective to convert the RIM to a PRMT.
- the methodologies disclosed herein are intended to provide modifications to components that are constituents of a multimodal polymeric material. Further, it is to be understood that in the case of a polymer blend it may be difficult or impossible to independently act upon or characterize a single component of the multicomponent blend without the influence and/or presence of the other components of the blend. Thus, the methods disclosed herein when referring to a component of a polymer blend (e.g., HMW component) refer to the ability to act upon or modify a portion of the polymer designated as the particular component with the understanding that these components may not be independent entities and/or that some impact may occur on another component of the polymer.
- a component of a polymer blend e.g., HMW component
- RIMs of the type disclosed herein may exhibit the aforementioned melt fracture characteristics such as shown in Figure IB as a result of the composition having components that behave as discrete entities.
- the LMW component may result in migration toward the surface that is not impeded by molecular entanglements to the HMW component.
- the unique melt fracture and slip behaviors of RIMs of the type disclosed herein are attributable to the fact that the MWD peaks of the two components are considerably separated and the low mode has a significant amount of LMW component such that entanglements are limited within this mode.
- various embodiments for modifying the melt fracture characteristics of the RIM include holding constant the MWD peak associated with the HMW component and modifying the MWD of the LMW component (e.g., moving the location of and/or adjusting the size of the MWD peak associated with the LWM component).
- the PRMT is a multimodal metallocene-catalyzed resin. Further, such resins displaying a magnitude of slip-stick greater than about 300 psi, a smooth to matte transition of greater than about 90 kPa of stress, and a shear rate greater than about 10 s "1 are characterized by a reduced tendency to melt fracture.
- PRMTs as described herein may be formed into various articles, including but not limited to, household containers, utensils, film products, drums, fuel tanks, pipes, geomembranes, and liners.
- the PRMT of this disclosure is fabricated into a pipe by a plastics shaping process such as extrusion.
- a method of making a polymeric pipe comprises extruding the polymer or copolymer in a molten state through a die to form the polymeric pipe and cooling the pipe.
- Pipe extrusion in the simplest terms is performed by melting, conveying polyethylene pellets into a particular shape (generally an annular shape), and solidifying that shape during a cooling process. There are numerous steps to pipe extrusion as provided below.
- the polymer feedstock can either be a pre- pigmented polyethylene resin or it can be a mixture of natural polyethylene and color concentrate (referred to as "Salt and Pepper blends"). In North America, the most common feedstock for pipe extrusion is “Salt and Pepper blends.” In Europe and other areas of the world, the most common feedstock for pipe extrusion is pre-pigmented polyethylene resin. Feedstock is rigidly controlled to obtain the proper finished product (pipe) and ultimate consumer specifications.
- the feedstock is then fed into an extruder.
- the most common extruder system for pipe production is a single-screw extruder.
- the purpose of the extruder is to melt, convey, and homogenize the polyethylene pellets. Extrusion temperatures typically range from 178°C to 250°C depending upon the extruder screw design and flow properties of the polyethylene.
- the molten polymer is then passed through a die.
- the die distributes the homogenous polyethylene polymer melt around a solid mandrel, which forms it into an annular shape. Adjustments can be made at the die exit to try to compensate for polymer sag through the rest of the process.
- the pipe is then sized. There are two methods for sizing: vacuum or pressure. Both employ different techniques and different equipment.
- the pipe is cooled and solidified in the desired dimensions. Cooling is accomplished by the use of several water tanks where the outside pipe is either submerged or water is sprayed on the pipe exterior. The pipe is cooled from the outside surface to the inside surface. The interior wall and inside surfaces of the pipe can stay very hot for a long period of time, as polyethylene is a poor conductor of heat. Finally, the pipe is printed and either coiled or cut to length.
- the PRMT is used to prepare the pipe has a density of greater than about 0.925 g/ml to about 0.942 g/ml, alternatively from about 0.928 to about 0.940 g/ml or alternatively from about 0.930 g/ml to about 0.940 g/ml as determined in accordance with ASTM D1505.
- a majority of the field failures in pressure pipe (gas transport) applications are attributable to a brittle fracture mode referred to as slow crack growth (SCG).
- SCG slow crack growth
- PENT Pennsylvania Notch Tensile Test
- FNCT Full Notch Creep Test
- a pipe prepared from the PRMTs disclosed herein may display PENT values of from about 500 hours to about 20,000 hours, alternatively from about 550 hours to about 20,000 hours, or alternatively from about 600 hours to about 20,000 hours.
- a modified Charpy impact test referred to as the Razor-Notched Charpy Impact Test, has emerged as a useful indicator of the resistance to RCP fractures.
- This modified Charpy test is described in detail in ASTM F2231. This test involves measuring the impact energy when a thin molded rectangular plaque (with a razor notch) is impacted by a swinging pendulum. This test can be performed at multiple temperatures; enabling one to determine the temperature at which the failure mode changes from ductile to brittle.
- a pipe prepared from the PRMTs disclosed herein may have a Charpy T db less than about - 25°C; alternatively, the Charpy T db is less than about -15°C, or alternatively, the Charpy T db may be less than about -10°C.
- Charpy impact energy is a measure of an article's impact toughness.
- Test articles of polymer produced in accordance with the present disclosure may have a Charpy impact energy of from about 1.0 J to about 3.0 J, or alternatively from about 1.0 J to about 2.58J as determined in accordance with ASTM F2231 razor-notched Charpy impact test at room temperature.
- a pipe prepared from a PRMT of the type disclosed herein is characterized by the flexural modulus.
- the flexural modulus may be defined as the ratio, within the elastic limit, of the applied stress on a test specimen in flexure, to the corresponding strain in the outermost fibers of the specimen.
- a pipe prepared from a PRMT of the type disclosed herein has a flexural modulus, 2% secant of from about 80 kpsi to about 110 kpsi, alternatively from about 85 kpsi to about 105 kpsi, or alternatively from about 90 kpsi to about 100 kpsi as determined in accordance with ASTM D790 using an injection molded test specimen having a 16.1 inch span depth at a rate of 0.5 in/min.
- a pipe prepared from a PRMT of the type described herein exhibits an elongation at break of greater than about 400%, alternatively greater than about 450% or alternatively greater than about 500% as determined in accordance with ASTM D638.
- the elongation at break refers to the elongation which corresponds to the tensile breaking strength.
- a pipe prepared from a PRMT of the type described herein displays an increased Young's modulus.
- Young's modulus is a measure of the stiffness of a material and is defined as the ratio of the rate of change of stress with strain. Young's modulus can be determined experimentally from the slope of a stress-strain curve created during tensile tests conducted on a sample of a material, as determined in accordance with ASTM D638.
- the PRMT is used to make a Type IV bar and exhibits a Young' s modulus ranging from about 120 kpsi to about 190 kpsi, alternatively from about 120 kpsi to about 185 kpsi, or alternatively from about 120 kpsi to about 180 kpsi when determined in accordance with ASTM D638 at a speed of 2in/min.
- a pipe prepared from a PRMT of the type described herein exhibits a tensile strength at yield of from about 2600 psi to less than about 3,000 psi, alternatively from 2600 psi to about 2950 psi, or alternatively 2600 psi to about 2,900 psi as determined in accordance with ASTM D638.
- the tensile strength at yield refers to the tensile stress where an increase in expansion is admitted without an increase in gaining the weight on stress-strain curve.
- a pipe prepared from a PRMT of the type described herein exhibits a tensile strength at break of greater than about 4000 psi, alternatively greater than about 4500 psi, or alternatively greater than about 5000 psi as determined in accordance with ASTM D638.
- the tensile strength at break refers to the tensile stress at the moment the material is destroyed.
- the pipe prepared from the PRMT was a Type IV bar which was tested at 2 in/min.
- a pipe prepared from a PRMT of the type described herein displays a thermal stability of greater than about 220°C as determined in accordance with ASTM D3350.
- a pipe prepared from a PRMT of the type disclosed herein is characterized by the extent to which it can resist rapid crack propagation (RCP).
- RCP rapid crack propagation
- the Small-Scale Steady-State (S4) test is the current standard for measuring the RCP resistance of polyethylene pipes.
- the pipe specimens are seven diameters long and are sealed at both ends and pressurized with air.
- pipe specimens are conditioned externally at the test temperature, and then moved to the S4 rig for testing.
- a sharp chisel-edged striker impacts the pipe at one end and drives a fast-running crack through the main section of the pipe.
- T c critical temperature
- Another method of evaluating the SCG resistance is by determining the tensile natural draw ratio (tensile NDR) of the resin.
- tensile NDR tensile natural draw ratio
- the tensile NDR is directly related to the SCG resistance of HDPE such that the lower the tensile NDR the higher the resistance to SCG.
- a description of the correlation of SCG to tensile NDR may be found in: E. Laurent, Comprehensive Evaluation of the Long- Term Mechanical Properties ofPElOO Resin Meeting the Requirements of Modern Installation Techniques, Plastic Pipes XI Proceedings of the International Conference, Woodhead Publishing Limited (2001); and in an article by L.
- a pipe prepared from a PRMT of the type disclosed herein has a NDR of less than about 500% as determined in accordance with ASTM D 638 for a Type IV bar at a rate of 2 in/min.
- a PRMT of the type disclosed herein displays a melt flow rate (MFR) of less than about 0.4 g/10 min.
- MFR melt flow rate
- a pipe prepared from a PRMT of the type disclosed herein is characterized by a hydrostatic design basis (HDB) at 23°C of from about 1200 psi to less than about 1530 psi and a HDB at 60°C of from about 960 psi to less than about 1200 psi.
- the HDB test is used for the purpose of determining the long-term strength characteristic of a plastic pipe and may be determined in accordance with ASTM D2837.
- LTHS long-term hydrostatic strength
- MRS minimum required strength
- a method of assessing melt fracture potential comprises obtaining at least one metallocene-catalyzed polymer sample and performing a capillary extrusion test on the at least one metallocene-catalyzed polymer sample.
- the method may further comprise identifying a metallocene- catalyzed polymer sample having a magnitude of slip-stick greater than about 300 psi; a smooth to matte transition greater than about 90 kPa and a shear rate of greater than about 10 s "1 wherein said identified polymer sample has an increased melt fracture potential when compared to a conventional resin.
- a method of assessing melt fracture potential comprises obtaining at least one metallocene-catalyzed polymer sample.
- the method may further comprise performing a capillary extrusion test on the at least one metallocene-catalyzed polymer sample.
- the method may further comprise identifying a metallocene-catalyzed polymer sample having a magnitude of slip- stick less than about 300 psi; a smooth to matte transition less than about 90 kPa and a shear rate of less than about 10 s "1 wherein said identified polymer sample has an increased melt fracture potential when compared to a conventional resin not having a magnitude of slip-stick greater than about 300 psi; a smooth to matte transition greater than about 90 kPa and a shear rate of greater than about 10 s "1 .
- a method of assessing melt fracture potential comprises performing capillary rheometry on a polymer sample to obtain measurements of the shear stress as a function of the shear rate.
- the method may further comprise plotting the shear stress as a function of shear rate to obtain a plot of the melt fracture behavior.
- the method may further comprise comparing the plot of melt fracture behavior of the polymer sample to a plot of the melt fracture behavior of a conventional resin.
- the method further comprises identifying polymer samples having melt fracture behavior characterized by a magnitude of slip- stick greater than about 300 psi; a smooth to matte transition of greater than about 90 kPa and a shear rate greater than about 10 s "1 .
- a method of identifying polymer samples having poor processing characteristics comprises obtaining a plurality of metallocene-catalyzed multimodal polyethylene polymer samples.
- the method may further comprise measuring the shear stress as a function of shear rate for the plurality of dual metallocene-catalyzed polyethylene polymer samples.
- the method may further comprises identifying dual metallocene-catalyzed polyethylene polymer samples having melt fracture behavior characterized by a magnitude of slip-stick greater than about 300 psi; a smooth to matte transition greater than about 90 kPa and a shear rate greater than about 10 s "1 .
- a method of assessing melt fracture characteristics of one or more multimodal metallocene-catalyzed polyethylene resins comprises for a training set comprising a plurality of multimodal metallocene-catalyst polyethylene resins, determining melt fracture characteristics comprising a magnitude of slip-stick, a stress for a smooth to matte transition and a shear rate.
- the method may further comprise measuring a molecular weight distribution for each resin in the training set.
- the method may further comprise determining a relationship between the melt fracture characteristics and the molecular weight distribution of the training set.
- the method may further comprise providing one or more validation samples of multimodal metallocene-catalyzed resin having a known molecular weight distribution and an unknown melt fracture characteristic.
- the method may further comprise predicting the melt fracture characteristics of the validation samples via the relationship.
- a method of predicting melt fracture behavior of a multimodal metallocene- catalyzed polyethylene resin comprises determining the melt fracture behavior of at least two polyethylene resins by capillary rheometry. The method may further comprise determining the molecular weight distribution of the at least two polyethylene resins. The method may further comprise performing chemometric analysis to establish a mathematical relationship between the melt fracture behavior and the molecular weight distribution for the at least two polyethylene resins. The method may further comprise obtaining the molecular weight distribution of the multimodal metallocene-catalyzed polyethylene resin. The method may further comprise utilizing the mathematical relationship to predict the melt fracture behavior of the multimodal metallocene-catalyzed polyethylene resin.
- a method of identifying polyethylene (PE) resins having one or more desired processing characteristics comprises obtaining a plurality of PE resins each having a known molecular weight distribution, a known magnitude of slip-stick, a known stress for a smooth to matte transition, and a known shear rate.
- the method may further comprise performing chemometric analysis to determine a mathematical relationship between the known molecular weight distribution, the known magnitude of slip- stick, the known stress for a smooth to matte transition, and the known shear rate for the plurality of PE resins.
- the method may further comprise obtaining a plurality of samples of the multimodal metallocene- catalyzed PE resins, each having a known molecular weight distribution, an unknown magnitude of slip- stick, an unknown stress for a smooth to matte transition, and an unknown shear rate.
- the method may further comprise utilizing the mathematical relationship to determine a value for the unknown magnitude of slip-stick, a value for the unknown stress for a smooth to matte transition, and a value for the unknown shear rate for each of the plurality of multimodal metallocene-catalyzed PE samples.
- the method may further comprise identifying the multimodal metallocene-catalyzed PE resins having a reduced tendency to melt fracture characterized by samples having a magnitude of slip-stick greater than about 300 psi; a smooth to matte transition of greater than about 90 kPa of stress and a shear rate greater than about 10 s "1 .
- a method of preparing pipe comprises identifying a multimodal metallocene-catalyzed PE resin having a reduced tendency to melt fracture characterized a magnitude of slip-stick greater than about 300 psi; a smooth to matte transition of greater than about 90 kPa of stress, and a shear rate greater than about 10 s 1 .
- the method may further comprise forming the multimodal metallocene-catalyzed PE resin into the pipe.
- a pipe formed from a multimodal metallocene-catalyzed PE resin having a reduced tendency to melt fracture is characterized by a magnitude of slip-stick greater than about 300 psi; a smooth to matte transition of greater than about 90 kPa of stress and a shear rate greater than about 10 s "1 .
- a method of preparing a medium-density polyethylene pipe comprise identifying a multimodal metallocene-catalyzed PE resin having a density of greater than about 0.925 g/ml to about 0.940 g/ml, a magnitude of slip-stick greater than about 300 psi; a smooth to matte transition of greater than about 90 kPa of stress, and a shear rate greater than about 10 s 1 .
- the method may further comprise forming the multimodal multimodal metallocene-catalyzed PE resin into pipe.
- a method comprises identifying a multimodal metallocene-catalyzed PE resin a higher molecular weight (HMW) component and a lower molecular weight (LMW) component; and characterized by at least one of the following conditions a magnitude of slip-stick less than about 300 psi; a smooth to matte transition of greater than about 90 kPa of stress and a shear rate less than about 10 s "1 .
- the method may further comprise treating the multimodal metallocene-catalyzed PE resin to provide a modified polymer wherein the treatment comprises at least one of the following (i) increasing the weight average molecular weight of the LMW component; (ii) introducing a bridging polymer; (iii) decreasing the amount of LMW component and decreasing a weight average molecular weight of the HMW component; and (iv) introducing a polymer processing aid to the multimodal metallocene-catalyzed PE resin wherein the modified polymer is characterized by a magnitude of slip-stick greater than about 300 psi; a smooth to matte transition of greater than about 90 kPa of stress, and a shear rate greater than about 10 s 1 .
- FIG. 10 illustrates a computer system 780 suitable for implementing one or more embodiments disclosed herein.
- the computer system 780 includes a processor 782 (which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage 784, read only memory (ROM) 786, random access memory (RAM) 788, input/output (I/O) devices 790, and network connectivity devices 792.
- the processor 782 may be implemented as one or more CPU chips.
- a design that is still subject to frequent change may be preferred to be implemented in software, because re-spinning a hardware implementation is more expensive than re-spinning a software design.
- a design that is stable that will be produced in large volume may be preferred to be implemented in hardware, for example in an application specific integrated circuit (ASIC), because for large production runs the hardware implementation may be less expensive than the software implementation.
- ASIC application specific integrated circuit
- a design may be developed and tested in a software form and later transformed, by well known design rules, to an equivalent hardware implementation in an application specific integrated circuit that hardwires the instructions of the software.
- a machine controlled by a new ASIC is a particular machine or apparatus, likewise a computer that has been programmed and/or loaded with executable instructions may be viewed as a particular machine or apparatus.
- the secondary storage 784 is typically comprised of one or more disk drives or tape drives and is used for non- volatile storage of data and as an over-flow data storage device if RAM 788 is not large enough to hold all working data. Secondary storage 784 may be used to store programs which are loaded into RAM 788 when such programs are selected for execution.
- the ROM 786 is used to store instructions and perhaps data which are read during program execution. ROM 786 is a non-volatile memory device which typically has a small memory capacity relative to the larger memory capacity of secondary storage 784.
- the RAM 788 is used to store volatile data and perhaps to store instructions. Access to both ROM 786 and RAM 788 is typically faster than to secondary storage 784.
- the secondary storage 784, the RAM 788, and/or the ROM 786 may be referred to in some contexts as computer readable storage media and/or non-transitory computer readable media.
- I/O devices 790 may include printers, video monitors, liquid crystal displays (LCDs), touch screen displays, keyboards, keypads, switches, dials, mice, track balls, voice recognizers, card readers, paper tape readers, or other well-known input devices.
- LCDs liquid crystal displays
- touch screen displays keyboards, keypads, switches, dials, mice, track balls, voice recognizers, card readers, paper tape readers, or other well-known input devices.
- the network connectivity devices 792 may take the form of modems, modem banks, Ethernet cards, universal serial bus (USB) interface cards, serial interfaces, token ring cards, fiber distributed data interface (FDDI) cards, wireless local area network (WLAN) cards, radio transceiver cards such as code division multiple access (CDMA), global system for mobile communications (GSM), long-term evolution (LTE), worldwide interoperability for microwave access (WiMAX), and/or other air interface protocol radio transceiver cards, and other well-known network devices.
- FDDI fiber distributed data interface
- WLAN wireless local area network
- radio transceiver cards such as code division multiple access (CDMA), global system for mobile communications (GSM), long-term evolution (LTE), worldwide interoperability for microwave access (WiMAX), and/or other air interface protocol radio transceiver cards, and other well-known network devices.
- CDMA code division multiple access
- GSM global system for mobile communications
- LTE long-term evolution
- WiMAX worldwide interoperability for
- the processor 782 might receive information from the network, or might output information to the network in the course of performing the above -described method steps. Such information, which is often represented as a sequence of instructions to be executed using processor 782, may be received from and outputted to the network, for example, in the form of a computer data signal embodied in a carrier wave. [00116] Such information, which may include data or instructions to be executed using processor 782 for example, may be received from and outputted to the network, for example, in the form of a computer data baseband signal or signal embodied in a carrier wave.
- the baseband signal or signal embodied in the carrier wave generated by the network connectivity devices 792 may propagate in or on the surface of electrical conductors, in coaxial cables, in waveguides, in an optical conduit, for example an optical fiber, or in the air or free space.
- the information contained in the baseband signal or signal embedded in the carrier wave may be ordered according to different sequences, as may be desirable for either processing or generating the information or transmitting or receiving the information.
- the baseband signal or signal embedded in the carrier wave, or other types of signals currently used or hereafter developed, may be generated according to several methods well known to one skilled in the art.
- the baseband signal and/or signal embedded in the carrier wave may be referred to in some contexts as a transitory signal.
- the processor 782 executes instructions, codes, computer programs, scripts which it accesses from hard disk, floppy disk, optical disk (these various disk based systems may all be considered secondary storage 784), ROM 786, RAM 788, or the network connectivity devices 792. While only one processor 782 is shown, multiple processors may be present. Thus, while instructions may be discussed as executed by a processor, the instructions may be executed simultaneously, serially, or otherwise executed by one or multiple processors.
- the computer system 780 may comprise two or more computers in communication with each other that collaborate to perform a task.
- an application may be partitioned in such a way as to permit concurrent and/or parallel processing of the instructions of the application.
- the data processed by the application may be partitioned in such a way as to permit concurrent and/or parallel processing of different portions of a data set by the two or more computers.
- virtualization software may be employed by the computer system 780 to provide the functionality of a number of servers that is not directly bound to the number of computers in the computer system 780. For example, virtualization software may provide twenty virtual servers on four physical computers.
- Cloud computing may comprise providing computing services via a network connection using dynamically scalable computing resources.
- Cloud computing may be supported, at least in part, by virtualization software.
- a cloud computing environment may be established by an enterprise and/or may be hired on an as-needed basis from a third party provider.
- Some cloud computing environments may comprise cloud computing resources owned and operated by the enterprise as well as cloud computing resources hired and/or leased from a third party provider.
- the computer program product may comprise one or more computer readable storage medium having computer usable program code embodied therein to implement the functionality disclosed above.
- the computer program product may comprise data structures, executable instructions, and other computer usable program code.
- the computer program product may be embodied in removable computer storage media and/or non-removable computer storage media.
- the removable computer readable storage medium may comprise, without limitation, a paper tape, a magnetic tape, magnetic disk, an optical disk, a solid state memory chip, for example analog magnetic tape, compact disk read only memory (CD- ROM) disks, floppy disks, jump drives, digital cards, multimedia cards, and others.
- the computer program product may be suitable for loading, by the computer system 780, at least portions of the contents of the computer program product to the secondary storage 784, to the ROM 786, to the RAM 788, and/or to other non-volatile memory and volatile memory of the computer system 780.
- the processor 782 may process the executable instructions and/or data structures in part by directly accessing the computer program product, for example by reading from a CD-ROM disk inserted into a disk drive peripheral of the computer system 780.
- the processor 782 may process the executable instructions and/or data structures by remotely accessing the computer program product, for example by downloading the executable instructions and/or data structures from a remote server through the network connectivity devices 792.
- the computer program product may comprise instructions that promote the loading and/or copying of data, data structures, files, and/or executable instructions to the secondary storage 784, to the ROM 786, to the RAM 788, and/or to other non-volatile memory and volatile memory of the computer system 780.
- a baseband signal and/or a signal embodied in a carrier wave may be referred to as a transitory signal.
- the secondary storage 784, the ROM 786, and the RAM 788 may be referred to as a non-transitory computer readable medium or a computer readable storage media.
- a dynamic RAM embodiment of the RAM 788 likewise, may be referred to as a non- transitory computer readable medium in that while the dynamic RAM receives electrical power and is operated in accordance with its design, for example during a period of time during which the computer 780 is turned on and operational, the dynamic RAM stores information that is written to it.
- the processor 782 may comprise an internal RAM, an internal ROM, a cache memory, and/or other internal non-transitory storage blocks, sections, or components that may be referred to in some contexts as non- transitory computer readable media or computer readable storage media.
- the computer system 780 is utilized to improve the processing of polymers of the type disclosed herein (e.g., PE base resin).
- information obtained as described herein may serve as input to an analysis component of the computer stored in memory that when executed on the processor, configures the processor to receive a shear stress as a function of shear rate for a plurality of multimodal metallocene- catalyzed polyethylene samples, wherein the determination of the shear stress as a function of the shear rate comprises using capillary rheometry determine values for a slip-stick, a smooth to matte transition, and a shear rate for each of the plurality of multimodal metallocene-catalyzed polyethylene samples based on the shear stress and the shear rate identify individual multimodal metallocene-catalyzed polyethylene resins from the plurality of multimodal metallocene-catalyzed polyethylene samples having a reduced tendency to melt fracture characterized by a magnitude of slip-stick greater than about 300 psi, a smooth to matte transition of greater than about 90 kPa of stress, and a shear rate greater than about 10 s 1 ;
- a first embodiment which is a method of improving processing of polyethylene resins comprising obtaining a plurality of multimodal metallocene-catalyzed polyethylene samples; measuring the shear stress as a function of shear rate for the plurality of multimodal metallocene-catalyzed polyethylene samples using capillary rheometry wherein the measuring yields values for a magnitude of slip-stick, a stress for smooth to matte transition, and a shear rate for smooth to matte transition; and identifying from the plurality of multimodal metallocene-catalyzed polyethylene samples individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture characterized by a magnitude of slip-stick greater than about 300 psi, a stress for smooth to matte transition greater than about 90 kPa, and a shear rate for smooth to matte transition greater than about 10 s "1 .
- a second embodiment which is the method of the first embodiment wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples comprises a polymer blend.
- a third embodiment which is the method of any of the first through second embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples comprises a higher molecular weight component and a lower molecular weight component.
- a fourth embodiment which is the method of the third embodiment wherein the higher molecular weight component has a peak molecular weight ranging from about 67 kg/mol to about 600 kg/mol and the lower molecular weight component has a peak molecular weight ranging from about 25 kg/mol to about 65 kg/mol.
- a fifth embodiment which is the method of any of the first through fourth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a molecular weight distribution of from about 5 to about 30.
- a sixth embodiment which is the method of any of the first through fifth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a magnitude of stick- slip of from greater than about 300 psi to about 1500 psi.
- a seventh embodiment which is the method of any of the first through sixth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a shear rate for smooth to matte transition of from greater than about 10 s "1 to about 100 s "1 .
- An eighth embodiment which is the method of any of the first through seventh embodiments wherein the melt fracture is sharkskin melt fracture, slip-stick fracture or gross melt fracture.
- a ninth embodiment which is a method of improving processing of polyethylene resins comprising obtaining a known molecular weight distribution, a known magnitude of slip-stick, a known stress for smooth to matte transition, and a known shear rate for smooth to matte transition, for each of a plurality of polyethylene resins; performing chemometric analysis to determine an analytical relationship between the known molecular weight distribution, the known magnitude of slip-stick, the known stress for smooth to matte transition, and the known shear rate for smooth to matte transition for the plurality of polyethylene resins; obtaining a plurality of multimodal metallocene-catalyzed polyethylene resins, each having a known molecular weight distribution, an unknown magnitude of slip-stick, an unknown stress for smooth to matte transition, and an unknown shear rate for smooth to matte transition; utilizing the analytical relationship to determine a value for the unknown magnitude of slip-stick, a value for the unknown stress for smooth to matte transition, and the unknown shear rate for smooth to matte transition for each of the plurality of multimodal metallocen
- a tenth embodiment which the method of the ninth embodiment wherein the analytical relationship is a mathematical equation.
- An eleventh embodiment which is the method of any of the ninth through tenth embodiment wherein the analytical relationship is established using at least one chemometric technique selected from the group consisting of Partial Least Squares Regression, Multilinear Regression Analysis, Principal Components Regression, Principal Component Analysis, Discriminant Analysis, Design of Experiment, and Response Surface Methodologies.
- a twelfth embodiment which is the method of any of the ninth through eleventh embodiments wherein the plurality of polyethylene resins comprises equal to or greater than about 10 samples.
- a thirteenth embodiment which is the method of any of the ninth through twelfth embodiments wherein the known molecular weight distribution is from about 5 to about 30.
- a fourteenth embodiment which is the method of any of the ninth through thirteenth embodiments wherein the known magnitude of slip-stick is from about 300 psi to about 1500 psi.
- a fifteenth embodiment which is the method of any of the ninth through fourteenth embodiments wherein the known stress for a smooth to matte transition is less than about 200 kPa.
- a sixteenth embodiment which is the method of any of the ninth through fifteenth embodiments wherein the known shear rate for smooth to matte transition is from greater than about 10 s "1 to about 100 s _1 .
- a seventeenth embodiment which is the method of any of the ninth through sixteenth embodiments wherein the individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture comprise a higher molecular weight component and a lower molecular weight component.
- An eighteenth embodiment which is the method of the seventeenth embodiment wherein the higher molecular weight component has a peak molecular weight ranging from about 67 kg/mol to about 600 kg/mol and the lower molecular weight component has a peak molecular weight ranging from about 25 kg/mol to about 65 kg/mol.
- a nineteenth embodiment which is the method of any of the ninth through eighteenth embodiments wherein the individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture comprise a comonomer.
- a twentieth embodiment which the method of any of the ninth through nineteenth embodiments further comprising identifying individual multimodal metallocene-catalyzed polyethylene resins having an increased tendency to melt fracture.
- a twenty-first embodiment which is the method of any of the first through eight embodiments further comprising forming one or more of the individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture into an article.
- a twenty-second embodiment which is the method of any of the ninth through twentieth embodiments further comprising forming one or more of the individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture into an article.
- a twenty-third embodiment which is the method of any of the first through eight embodiments further comprising providing one or more of the individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture to a user in need thereof.
- a twenty-fourth embodiment which is the method of any of the ninth through twentieth embodiments further comprising providing one or more of the individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture to a user in need thereof.
- a twenty-fifth embodiment which is a system for improving processing of polyethylene resins, comprising a processor; a memory; an output device; and an analysis component stored in the memory, that when executed on the processor, configures the processor to receive a shear stress as a function of shear rate for a plurality of multimodal metallocene-catalyzed polyethylene samples, wherein the determination of the shear stress as a function of the shear rate comprises using capillary rheometry; determine values for a magnitude of slip-stick, a stress for smooth to matte transition, and a shear rate for smooth to matte transition for each of the plurality of multimodal metallocene-catalyzed polyethylene samples based on the shear stress and the shear rate measured from capillary rheometry; identify individual multimodal metallocene-catalyzed polyethylene resins from the plurality of multimodal metallocene-catalyzed polyethylene samples having a reduced tendency to melt fracture characterized by a magnitude of slip
- a twenty-six embodiment which is the system of the twenty-fifth embodiment wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples comprises a polymer blend.
- a twenty-seventh embodiment which is the system of any of the twenty-fifth through twenty- sixth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples comprises a higher molecular weight component and a lower molecular weight component, and wherein the values for the slip-stick, the stress for smooth to matte transition, and the shear rate for smooth to matte transition are further determined based on at least one property of the higher molecular weight component and at least one property of the lower molecular weight components.
- a twenty-eighth embodiment which is the system of the twenty-seventh embodiment wherein the at least one property of the higher molecular weight component comprises a peak molecular weight, wherein the peak molecular weight of the higher molecular weight component ranges from about 67 kg/mol to about 600 kg/mol, wherein the at least one property of the lower molecular weight component comprises a peak molecular weight, and wherein the peak molecular weight of the lower molecular weight component ranges from about 25 kg/mol to about 65 kg/mol.
- a twenty-ninth embodiment which is the system of any of the twenty-fifth through twenty- eighth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a molecular weight distribution of from about 5 to about 30.
- a thirtieth embodiment which is the system of any of the twenty-fifth through twenty-ninth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a magnitude of stick-slip of greater than about 300 psi to about 1500 psi.
- a thirty-first embodiment which is the system of any of the twenty-fifth through thirtieth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a shear rate for smooth to matte transition of from greater than about 10 s "1 to about 100 s "1 .
- a thirty-second embodiment which is the system of any of the twenty-fifth through thirty-first embodiments wherein the melt fracture is a sharkskin melt fracture, a slip-stick fracture, or a gross melt fracture.
- a thirty-third embodiment which is a system for improving processing of polyethylene (PE) resins comprising a processor; a memory; an output device; and an analysis component stored in the memory, that when executed on the processor, configures the processor to receive a known molecular weight distribution, a known magnitude of slip-stick, a known stress for smooth to matte transition and a known shear rate for smooth to matte transition for each of a plurality of polyethylene resins; determine, using chemometric analysis, an analytical relationship between the known molecular weight distribution, the known magnitude of slip-stick, the known stress for smooth to matte transition and known shear rate for smooth to matte transition for the plurality of polyethylene resins; receiving a known molecular weight distribution for each of a plurality of multimodal metallocene-catalyzed polyethylene samples; determine, using the analytical relationship, a value for an unknown magnitude of slip-stick, a value for an unknown stress for smooth to matte transition and unknown shear rate for smooth to matte transition for each of the plurality of multimodal metalloc
- a thirty-fourth embodiment which is the system of the thirty-third embodiment wherein the analytical relationship is a mathematical equation.
- a thirty-fifth embodiment which is the system of any of the thirty-third through thirty-fourth embodiments wherein the analytical relationship is determined using at least one chemometric technique selected from the group consisting of; Partial Least Squares Regression (PLS), Multilinear Regression Analysis (MLR), Principal Components Regression (PCR), Principal Component Analysis (PC A) and
- PLS Partial Least Squares Regression
- MLR Multilinear Regression Analysis
- PCR Principal Components Regression
- PC A Principal Component Analysis
- a thirty-sixth embodiment which is the system of any of the thirty-third through thirty-fifth embodiments wherein the plurality of polyethylene resins comprises equal to or greater than about 10 samples.
- a thirty-seventh embodiment which is the system of any of the thirty-third through thirty-sixth embodiments wherein the known molecular weight distribution is from about 5 to about 30.
- a thirty-eighth embodiment which is the system of any of the thirty-third through thirty-seventh embodiments wherein the known magnitude of slip-stick is from about 300 psi to about 1500 psi.
- a thirty-ninth embodiment which is the system of any of the thirty-third though thirty-eighth embodiments wherein the known stress for smooth to matte transition is less than about 200 kPa.
- a fortieth embodiment which is the system of any of the thirty-third through thirty-ninth embodiments wherein the known shear rate for smooth to matte transition is from greater than about 10 s "1 to about 100 s 1 .
- a forty-first embodiment which is the system of any of the thirty-third through fortieth embodiments wherein the individual multimodal metallocene-catalyzed polyethylene samples having a reduced tendency to melt fracture comprise a higher molecular weight component and a lower molecular weight component.
- a forty-second embodiment which is the system of the forty-first embodiment wherein the higher molecular weight component has a peak molecular weight ranging from about 67 kg/mol to about 600 kg/mol and the lower molecular weight component has a peak molecular weight ranging from about 25 kg/mol to about 65 kg/mol.
- a forty-third embodiment which is the system of any of the thirty-third through forty-second embodiments wherein the individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture comprise a comonomer.
- a forty-fourth embodiment which is the system of any of the thirty-third through forty-third embodiments wherein the analysis component further configures the processor identify individual multimodal metallocene-catalyzed polyethylene samples having an increased tendency to melt fracture.
- a forty-fifth embodiment which is a computer implemented method for improving processing of polyethylene resins, comprising receiving by a processor, a shear stress for smooth to matte transition as a function of shear rate for smooth to matte transition for a plurality of multimodal metallocene-catalyzed polyethylene samples, wherein the determination of the shear stress for smooth to matte transition as a function of the shear rate for smooth to matte transition comprises using capillary rheometry; determining, by the processor, values for a slip-stick pressure oscillation, a stress for smooth to matte transition and a shear rate for smooth to matte transition for each of the plurality of multimodal metallocene-catalyzed polyethylene samples based on the shear stress for smooth to matte transition and the shear rate for smooth to matte transition; identifying, by the processor, individual multimodal metallocene-catalyzed polyethylene resins from the plurality of multimodal metallocene-catalyzed polyethylene samples having a reduced tendency to melt fracture characterized
- a forty-sixth embodiment which is the method of the forty-fifth embodiment wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples comprises a polymer blend.
- a forty-seventh embodiment which is the method of any of the forty-fifth through forty-sixth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples comprises a higher molecular weight component and a lower molecular weight component, and wherein the values for the magnitude of slip-stick, the stress for smooth to matte transition and the shear rate for smooth to matte transition are further determined based on at least one property of the higher molecular weight component and at least one property of the lower molecular weight components
- a forty-eighth embodiment which is the method of any of the forty-fifth through forty-seventh embodiments wherein the at least one property of the higher molecular weight component comprises a peak molecular weight, wherein the peak molecular weight of the higher molecular weight component ranges from about 67 kg/mol to about 600 kg/mol, wherein the at least one property of the lower molecular weight component comprises a peak molecular weight, and wherein the peak molecular weight of the lower molecular weight component ranges from about 25 kg/mol to about 65 kg/mol.
- a forty-ninth embodiment which is the method of any of the forty-fifth through forty-eighth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a molecular weight distribution of from about 5 to about 30.
- a fiftieth embodiment which the method of any of the forty-fifth through forty-ninth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a magnitude of stick-slip of greater than about 300 psi to about 1500 psi.
- a fifty-first embodiment which is the method of any of the forty-fifth through fiftieth embodiments wherein each of the plurality of multimodal metallocene-catalyzed polyethylene samples has a shear rate for smooth to matte transition from greater than about 10 s "1 to about 100 s 1 .
- a fifty-second embodiment which is the method of any of the forty-fifth through fifty-first embodiments wherein the melt fracture is a sharkskin melt fracture, a slip-stick fracture, or a gross melt fracture.
- a fifty-third embodiment which is a computer implemented method for improving processing of polyethylene resins comprising an analysis component stored in the memory, that when executed on the processor, configures the processor to receiving, by an analysis component stored in a memory and executed on a processor, a known molecular weight distribution, a known magnitude of slip-stick, a known stress for a smooth to matte transition, and a known shear rate for smooth to matte transition for each of a plurality of polyethylene resins; determining, by the analysis component, an analytical relationship between the known molecular weight distribution, the known magnitude of slip-stick, the known stress for smooth to matte transition and shear rate for smooth to matte transition for the plurality of polyethylene resins using chemometric analysis; receiving a known molecular weight distribution for each of a plurality of multimodal metallocene-catalyzed polyethylene samples; determining, by the analysis component, a value for an unknown magnitude of slip-stick, a value for an unknown stress for a smooth to matte transition, and a value for an unknown
- a fifty-fourth embodiment which is the method of the fifty-third embodiment wherein the analytical relationship is a mathematical equation.
- a fifty-fifth embodiment which is the method of any of the fifty-third through fifty-fourth embodiments wherein the analytical relationship is determined using at least one chemometric technique selected from the group consisting of; Partial Least Squares Regression (PLS), Multilinear Regression Analysis (MLR), Principal Components Regression (PCR), Principal Component Analysis (PC A) and Discriminant Analysis, Design of Experiment (DOE), and Response Surface Methodologies.
- PLS Partial Least Squares Regression
- MLR Multilinear Regression Analysis
- PCR Principal Components Regression
- PC A Principal Component Analysis
- DOE Design of Experiment
- a fifty-sixth embodiment which is the method of any of the fifty-third through fifty-fifth embodiments wherein the plurality of polyethylene resins comprises equal to or greater than about 10 samples.
- a fifty-seventh embodiment which is the method of any of the fifty-third through fifty-sixth embodiments wherein the known molecular weight distribution is from about 5 to about 30.
- a fifty-eighth embodiment which is the method of any of the fifty-third through fifty-seventh embodiments wherein the known magnitude of slip-stick is from about 300 psi to about 1500 psi.
- a fifty-ninth embodiment which is the method of any of the fifty-third through fifty-eighth embodiments wherein the known stress for smooth to matte transition is less than about 200 kPa.
- a sixtieth embodiment which is the method of any of the fifty-third through fifty-ninth embodiments wherein the known shear rate for smooth to matte transition is from greater than about 10 s "1 to about 100 s 1 .
- a sixty-first embodiment which is the method of any of the fifty-third through sixtieth embodiments wherein the individual multimodal metallocene-catalyzed polyethylene samples having a reduced tendency to melt fracture comprise a higher molecular weight component and a lower molecular weight component.
- a sixty-second embodiment which is the method of any of the fifty-third through sixty-first embodiments wherein the higher molecular weight component has a peak molecular weight ranging from about 67 kg/mol to about 600 kg/mol and the lower molecular weight component has a peak molecular weight ranging from about 25 kg/mol to about 65 kg/mol.
- a sixty-third embodiment which is the method of any of the fifty-third through sixty-second embodiments wherein the individual multimodal metallocene-catalyzed polyethylene resins having a reduced tendency to melt fracture comprise a comonomer.
- a sixty-fourth embodiment which is the method of any of the fifty-third through sixty-third embodiments further comprising identifying, by the analysis component, individual multimodal metallocene-catalyzed polyethylene samples having an increased tendency to melt fracture.
- a sixty-fifth embodiment which is a method of preparing a medium-density polyethylene pipe comprising melting a multimodal metallocene-catalyzed polyethylene resin to form a molten polyethylene, wherein the multimodal metallocene-catalyzed polyethylene resin has a density of from about 0.925 g/ml to about 0.942 g/ml, a magnitude of slip-stick greater than about 300 psi, a stress for smooth to matte transition of greater than about 90 kPa of stress, and a shear rate for smooth to matte transition greater than about 10 s "1 , wherein the magnitude of slip-stick, stress for smooth to matte transition, and shear rate for smooth to matte transition are determined by a capillary rheology test; and forming the molten polyethylene resin into pipe.
- a sixty-sixth embodiment which is the method of the sixty-fifth embodiment wherein the polyethylene resin has a density of from about 0.928 g/ml to about 0.940 g/ml.
- a sixty-seventh embodiment which is the method of any of the sixty-fifth through sixty-sixth embodiments wherein the polyethylene resin has a melt flow rate of less than about 0.4 g/10 min.
- a sixty-eighth embodiment which is the method of any of the sixty-fifth through sixty-seventh embodiments wherein the pipe has a PENT value of from about 500 hours to about 20,000 hours.
- a sixty-ninth embodiment which is the method of any of the sixty-fifth through sixty-eighth embodiments wherein the pipe has a Charpy T db of less than about -25°C.
- a seventieth embodiment which is the method of any of the sixty-fifth through sixty-ninth embodiments wherein the pipe has a Charpy impact energy of from about 1.0 J to about 3.0 J.
- a seventy-first embodiment which is the method of any of the sixty-fifth through seventieth embodiments wherein the pipe has a flexural modulus, 2% secant of from about 80 kpsi to about 110 kpsi.
- a seventy-second embodiment which is the method of any of the sixty-fifth through seventy- first embodiments wherein the pipe has an elongation at break of greater than about 450%.
- a seventy-third embodiment which is the method of any of the sixty-fifth through seventy- second embodiments wherein the pipe has a Young's modulus of from about 120 kpsi to about 190 kpsi.
- a seventy-fourth embodiment which is the method of any of the sixty-fifth through seventy- third embodiments wherein the pipe has a tensile strength at yield of from about 2600 psi to less than about 3,000 psi.
- a seventy-fifth embodiment which is the method of any of the sixty-fifth through seventy- fourth embodiments wherein the pipe has a tensile strength at break of greater than about 3000 psi.
- a seventy-sixth embodiment which is the method of any of the sixty-fifth through seventy-fifth embodiments wherein the pipe has a thermal stability of greater than about 220°C.
- a seventy-seventh embodiment which is the method of any of the sixty-fifth through seventy- sixth embodiments wherein the pipe has a critical temperature value (T c ) of equal to or less than about 0°C.
- a seventy-eighth embodiment which is the method of any of the sixty-fifth through seventy- seventh embodiments wherein the pipe has a critical pressure value (P c ) of greater than about 12 bar.
- a seventy-ninth embodiment which is the method of any of the sixty-fifth through seventy- eighth embodiments wherein the pipe has a tensile natural draw ratio of less than about 500%.
- An eightieth embodiment which is the method of any of the sixty-fifth through seventy-ninth embodiments wherein the pipe has a hydrostatic design basis at 23°C of from about 1200 psi to less than about 1530 psi and at 60°C of from about 960 psi to less than about 1200 psi.
- An eighty-first embodiment which is the method of any of the sixty-fifth through eightieth embodiments wherein the pipe has a minimum required strength of from about 8 ⁇ oLPL ⁇ 10 MPa.
- An eighty-second embodiment which is a pipe prepared from a multimodal metallocene- catalyzed polyethylene resin having a density of from about 0.925 g/ml to about 0.942 g/ml, a magnitude of slip-stick greater than about 300 psi; a stress for smooth to matte transition of greater than about 90 kPa, and a shear rate for smooth to matte transition greater than about 10 s "1 , wherein the magnitude of slip-stick, stress for smooth to matte transition, and shear rate for smooth to matte transition are determined by a capillary rheology test.
- An eighty-third embodiment which is the pipe of the eighty-second embodiment having a PENT value of from about 500 hours to about 20,000 hours.
- An eighty-fourth embodiment which is the pipe of any of the eighty-second through eighty- third embodiments having a Charpy T db of less than about -25 °C.
- Dissolution of the sample in stabilized TCB was carried out by heating at 150°C for about 5 hours with occasional, gentle agitation.
- the columns used were three PLgel 20 m Mixed A LS columns (7.5x300mm) and were calibrated with the integral method using a broad linear polyethylene standard (Chevron Phillips Chemical Company Marlex® BHB 5003 polyethylene) for which the molecular weight distribution had been determined.
- An IR4 detector (Polymer Char, Spain) was used for the concentration detection.
- a PLS2 calibration curve was generated using Pirouette chemometric software (Infometrix) to correlate the polymer microstructure obtained by GPC] to the melt fracture behavior as determined by capillary rheometry.
- Pirouette chemometric software Infometrix
- a four component calibration model was calculated and optimized using the process of cross validation. The calibration model was verified using a cross-validation approach.
- Figure 4 is plot of the predicted magnitude values (kPa) for the smooth to matte transition as a function of the measured magnitude values (kPa) for the smooth to matte transition for the calibration samples.
- Figure 5 is a plot of the predicted magnitude values (kPa) for smooth to matte transition as a function of the measured magnitude values (kPa) for the smooth to matte transition for both the calibration samples and validation samples.
- Figure 6 is a plot of the predicted magnitude values (kPa) for the onset of wavy transition as a function of the measured magnitude values (kPa) for the onset of wavy transition for the calibration samples.
- the Model F- value of 36.92 implies the model is significant. There is only a 0.01% chance that a "Model F-Value” this large could occur due to noise. Further, the values of "Prob > F” less than 0.0500 indicate model terms are significant. The results demonstrate that in this case A, B, C, E, AC, AE, BD, BE, DE are significant model terms as values greater than 0.1000 indicate the model terms are not significant. A better model can be obtained by removing insignificant model terms (not counting those required to support hierarchy), in order to demonstrate the influence of all the terms.
- the "Lack of Fit F- value” of 2.59 implies the Lack of Fit is not significant relative to the pure error. There is a 12.78% chance that a "Lack of Fit F-value” this large could occur due to noise. Further statistical evaluation provided the following:
- the sign of the coefficient estimate indicated the magnitude of influence and direction of effect for the particular parameter or combination of parameters. For example increasing the M p PI, increased the slip-stick magnitude while increasing the M p of P2 decreased the slip-stick magnitude (greater MW difference between components, therefore less overlap).
- the Model F- value of 41.75 implies the model is significant. There is onlya 0.01% chance that a "Model F-Value” this large could occur due to noise. Values of "Prob > F” less than 0.0500 indicate model terms are significant. In this case A, B, E, AC, AE, BD, BE are significant model terms. Values greater than 0.1000 indicate the model terms are not significant.
- the "Lack of Fit F- value” of 2.18 implies the Lack of Fit is not significant relative to the pure error. There is a 20.35% chance that a "Lack of Fit F- value” this large could occur due to noise.
- the Model F-value of 39.88 implies the model is significant. There is only a 0.01% chance that a "Model F-Value” this large could occur due to noise. Values of "Prob > F” less than 0.0500 indicate model terms are significant. In this case A, B, BD, BE, CE are significant model terms. Values greater than 0.1000 indicate the model terms are not significant.
- the "Lack of Fit F-value” of 0.80 implies the Lack of Fit is not significant relative to the pure error. There is a 61.91% chance that a "Lack value” this large could occur due to noise.
- Tables 17a-24a provide the optimization constraints for chemometric analysis while tables 17b-27b provide the solutions determined based on the constraints.
- Figure 8 is a plot of the magnitude of slip-stick as a function of the weight fraction of the lower molecular weight (LMW) component and the peak molecular weight for the based on the results of chemometric analysis while
- Figure 9 is a plot of the stress for the smooth to matte transition as a function of the peak molecular weights of components PI and P2.
Abstract
Description
Claims
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IN10132DEN2014 IN2014DN10132A (en) | 2012-05-31 | 2013-05-29 | |
SG11201407968RA SG11201407968RA (en) | 2012-05-31 | 2013-05-29 | Controlling melt fracture in bimodal resin pipe |
CA2874630A CA2874630C (en) | 2012-05-31 | 2013-05-29 | Controlling melt fracture in bimodal resin pipe |
BR112014029866-1A BR112014029866B1 (en) | 2012-05-31 | 2013-05-29 | method of preparing a medium density polyethylene pipe and pipe prepared from a multimodal metallocene catalyzed polyethylene resin |
KR1020147033497A KR102145077B1 (en) | 2012-05-31 | 2013-05-29 | Controlling melt fracture in bimodal resin pipe |
MX2014014496A MX2014014496A (en) | 2012-05-31 | 2013-05-29 | Controlling melt fracture in bimodal resin pipe. |
CN201380028242.5A CN104508453A (en) | 2012-05-31 | 2013-05-29 | Controlling melt fracture in bimodal resin pipe |
EP13728893.2A EP2856105A2 (en) | 2012-05-31 | 2013-05-29 | Controlling melt fracture in bimodal resin pipe |
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US13/660,750 US20130325363A1 (en) | 2012-05-31 | 2012-10-25 | Controlling Melt Fracture in Bimodal Resin Pipe |
US13/660,747 | 2012-10-25 | ||
US13/660,777 US8771816B2 (en) | 2012-05-31 | 2012-10-25 | Controlling melt fracture in bimodal resin pipe |
US13/660,750 | 2012-10-25 | ||
US13/660,747 US20130319131A1 (en) | 2012-05-31 | 2012-10-25 | Controlling Melt Fracture in Bimodal Resin Pipe |
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US8912285B2 (en) | 2012-12-06 | 2014-12-16 | Chevron Phillips Chemical Company Lp | Catalyst system with three metallocenes for producing broad molecular weight distribution polymers |
US9346897B2 (en) | 2013-05-14 | 2016-05-24 | Chevron Phillips Chemical Company Lp | Peroxide treated metallocene-based polyolefins with improved melt strength |
EP2860200B1 (en) * | 2013-10-10 | 2017-08-02 | Borealis AG | Polyethylene composition for pipe and pipe coating applications |
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US10550252B2 (en) | 2017-04-20 | 2020-02-04 | Chevron Phillips Chemical Company Lp | Bimodal PE resins with improved melt strength |
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CN108388761B (en) * | 2018-02-27 | 2021-12-28 | 华东理工大学 | High-precision rapid prediction model construction method for polyethylene molecular weight distribution and application thereof |
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SG11201407968RA (en) | 2014-12-30 |
CA2874630C (en) | 2020-09-22 |
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BR112014029866A2 (en) | 2017-06-27 |
WO2013181274A3 (en) | 2014-05-15 |
US20130323450A1 (en) | 2013-12-05 |
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CN104508453A (en) | 2015-04-08 |
US20130325363A1 (en) | 2013-12-05 |
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KR20150024322A (en) | 2015-03-06 |
US8771816B2 (en) | 2014-07-08 |
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US20130319131A1 (en) | 2013-12-05 |
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