WO2013127850A1 - 2-k pultrusion formulation and process - Google Patents

2-k pultrusion formulation and process Download PDF

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Publication number
WO2013127850A1
WO2013127850A1 PCT/EP2013/053930 EP2013053930W WO2013127850A1 WO 2013127850 A1 WO2013127850 A1 WO 2013127850A1 EP 2013053930 W EP2013053930 W EP 2013053930W WO 2013127850 A1 WO2013127850 A1 WO 2013127850A1
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Prior art keywords
isocyanate
polyols
diisocyanate
reaction system
mpas
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PCT/EP2013/053930
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French (fr)
Inventor
Stephan Schleiermacher
Dirk Wegener
Harald Rasselnberg
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Bayer Intellectual Property Gmbh
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Publication of WO2013127850A1 publication Critical patent/WO2013127850A1/en

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    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00Polymeric products of isocyanates or isothiocyanates
    • C08G18/06Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72Polyisocyanates or polyisothiocyanates
    • C08G18/74Polyisocyanates or polyisothiocyanates cyclic
    • C08G18/76Polyisocyanates or polyisothiocyanates cyclic aromatic
    • C08G18/7657Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings
    • C08G18/7664Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/04Reinforcing macromolecular compounds with loose or coherent fibrous material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/04Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
    • B29C70/28Shaping operations therefor
    • B29C70/40Shaping or impregnating by compression not applied
    • B29C70/50Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
    • B29C70/52Pultrusion, i.e. forming and compressing by continuously pulling through a die
    • B29C70/521Pultrusion, i.e. forming and compressing by continuously pulling through a die and impregnating the reinforcement before the die
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00Polymeric products of isocyanates or isothiocyanates
    • C08G18/06Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40High-molecular-weight compounds
    • C08G18/48Polyethers
    • C08G18/4804Two or more polyethers of different physical or chemical nature
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/04Reinforcing macromolecular compounds with loose or coherent fibrous material
    • C08J5/0405Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres
    • C08J5/043Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres with glass fibres
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2075/00Use of PU, i.e. polyureas or polyurethanes or derivatives thereof, as moulding material
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2375/00Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
    • C08J2375/04Polyurethanes
    • C08J2375/08Polyurethanes from polyethers

Definitions

  • the present invention relates to a reaction system for the preparation of a fiber reinforced composite, comprising a continuous fiber reinforcing material and a polyurethane formulation comprising a polyisocyanate component containing at least one polyisocyanate and an isocyanate- reactive component containing a blend of at least three polyols.
  • the invention further relates to a fiber reinforced composite which comprises a reaction system of the before mentioned type as well as a pultrusion process for the preparation of a fiber reinforced composite using the reaction system.
  • Pultrusion is a manufacturing process for producing continuous lengths of fiber reinforced plastic ("FRP") structural shapes.
  • Raw materials include a liquid resin mixture (containing resin, fillers and specialized additives) and reinforcing fibers.
  • the process involves pulling these raw materials, rather than pushing as is the case in extrusion, through a heated steel forming die using a continuous pulling device.
  • the reinforcement materials are in continuous forms such as rolls of fiberglass mat or doffs of fiberglass roving.
  • the two ways to impregnate, or "wet out", the glass are open bath process and resin injection.
  • Typical commercial resins include polyester, vinyl esters, phenolics, and epoxy compounds.
  • the resin injection process is used.
  • the reinforcement materials are passed through a small closed box which is usually attached to the die or may be part of the die.
  • the resin is injected under pressure through ports in the box to impregnate the reinforcement materials.
  • Resin injection boxes are designed to minimize resin volume and resin residence time inside the box.
  • There are a number of different resin injection box designs in the literature all of which have the common features of an angled or tapered design and the exit profile matching the shape of the die entrance.
  • the patent art provides a number of teachings with respect to polyurethane pultrusion.
  • US 6,420,493 B discloses a two component chemically thermoset composite resin matrix for use in composite manufacturing processes.
  • the polyisocyanate component and the polyol component are in relative proportions in accordance with an OH/NCO equivalent ratio of 1 : 1 to 1 :2. Further, the presence of 10%-40% of a polyester polyol with the use of 5 to 20 wt % of a - - hydroxyl terminated vegetable oil is required.
  • the isocyanate component it is stated that it is preferred to have at least 15 wt % of an aliphatic polyisocyanate.
  • US 6,793,855 B teaches polyisocyanurate systems, pultrusion of those systems to produce reinforced polyisocyanurate matrix composites and the composites produced by that pultrusion.
  • the polyisocyanurate systems include a polyol component, an optional chain extender, and an isocyanate.
  • the polyisocyanurate systems are said to have extended initiation times of 5 minutes to 30 minutes at room temperature and to be capable of snap curing.
  • the teaching is that substantial polymerization of the polyurethane takes place in the impregnation die.
  • US 7,056,976 B also discloses polyisocyanate-based reaction systems, a pultrusion process using those systems to produce reinforced matrix composites and composites produced by that pultrusion process.
  • the polyisocyanate-based systems are mixed activated reaction systems that include a polyol composition, an optional chain extender or crosslinker and a polyisocyanate.
  • the polyisocyanate-based systems are said to exhibit improved processing characteristics in the manufacture of fiber reinforced thermoset composites via reactive pultrusion.
  • US 7,056,976 B describes that gel times are the key parameter in polyurethane pultrusion.
  • US 2004/0094859 Al describes polyisocyanurate systems, pultrusion of those systems to produce reinforced polyisocyanurate matrix composites and composites produced by that pultrusion process.
  • the polyisocyanurate systems include a polyol component, an optional chain extender and an isocyanate.
  • the polyisocyanurate systems are said to have extended initiation times of 5 minutes to 30 minutes at room temperature, and to be capable of snap curing. It is further mentioned that gel times are the key parameter in polyurethane pultrusion processes.
  • fillers are oftentimes added to pultrusion formulations to improve the surface finish and reduce glass content, such as clays or low profile additives ("LPA"s).
  • LPA low profile additives
  • the use of fillers and LP As is disadvantageous in that such compounds do not form stable suspensions, are prone to settling or floating in the resin mixture and therefore require constant mixing. Also, fillers are prone to absorbing water which can interfere with the urethane reaction.
  • most fillers have a high density and therefore high levels on a weight percent basis are required to effect small changes on a volume percent. Such high levels can lead to extremely high viscosities of the resin mix which can make processing difficult or impossible.
  • US2008/0090966 Al suggests a reaction system for the preparation of a fiber reinforced composite material with a polyurethane formulation comprising a polyisocyanate component and an isocyanate-reactive component.
  • the polyurethane formulation used for the impregnation of the fiber reinforcing material allows better processing and may yield improved reinforced composites.
  • reaction system for the preparation of fiber reinforced composite materials.
  • the reaction system comprises a polyurethane formulation containing a polyisocyanate component and a polyol component, which comprises at least one double metal cyanide (DMC)-catalyzed polyol.
  • DMC double metal cyanide
  • WO 2011/067246 describes a pultrusion resin system comprising inter alia higher functioning acids having a functionality of greater than or equal to 2.
  • the machinery in particular mixing and metering devices for delivery, will become corroded in the long run.
  • the object of the present invention is to provide an improved reaction system of the before mentioned type which allows higher production speeds in a pultrusion process for the preparation of fiber reinforced composites.
  • This object is solved by a reaction system for the preparation of a fiber reinforced composite, comprising a continuous fiber reinforcing material and a polyurethane formulation comprising
  • At least one low viscous polyol is used in the isocyanate-reactive component.
  • the viscosity of the isocyanate-reactive component should be kept in a range from 300 mPas to 900 mPas at 25°C according to DIN EN ISO 3219 at a shear rate of 1/s, more preferably in the range of 350 mPas to 850 mPas at 25 °C determined according to DIN EN ISO 3219 at a shear rate of 1/s.
  • the reaction system of the present invention comprises at least one of said polyols with a viscosity at 25°C in the range of 40 mPas to 90 mPas, more preferably in the range of 40 mPas to 70 mPas determined according to DIN EN ISO 3219.
  • the reaction system is characterized in that the isocyanate-reactive component has a hydroxyl number of 200 to 1000 meq/g, in particular of 300 to 900 meq/g, preferably of 400 to 650 meq/g.
  • the isocyanate-reactive component contains a blend of at least three polyols. Although a larger number of polyols could be used.
  • the isocyanate-reactive component contains four, five, six or seven polyols. More preferably the isocyanate-reactive component contains four, five or six polyols. Most preferably the isocyanate-reactive component contains four or five polyols. - -
  • the isocyanate-reactive component comprises at least three polyols having the following characteristics:
  • a first polyol having a hydroxyl number from 20 to 100 meq/g and a viscosity at 25°C from 700 to 2000 mPas determined according to DIN EN ISO 3219 , ⁇ a second polyol having a hydroxyl number from 800 to 1300 meq/g and a viscosity at
  • a reaction system comprising at least three polyols as defined above lead to particularly readily processable polyurethane compositions and also provide fiber reinforcing composite materials having good mechanical properties.
  • the isocyanate-reactive component comprises the polyols in the following amounts:
  • the isocyanate-reactive component comprises at least three polyols having the following characteristics: ⁇ a first polyol having a hydroxyl number from 200 to 500 meq/g and a viscosity at 25 °C from 200 to 600 mPas determined according to DIN EN ISO 3219,
  • the isocyanate-reactive component comprises the polyols in the following amounts:
  • the isocyanate-reactive component comprises at least four polyols having the following characteristics:
  • a second polyol having a hydroxyl number from 800 to 1300 meq/g and a viscosity at 25°C from 800 to 2000 mPas determined according to DIN EN ISO 3219 ⁇ a third polyol having a hydroxyl number from 350 to 700 meq/g and a viscosity at 25°C from 20 to 100 mPas determined according to DIN EN ISO 3219 and
  • the polyols used for the isocyanate-reactive component may be chosen from a wide variety of different polyols used for polyurethane compositions.
  • Preferred polyols are polyether-polyols. It is preferred that the polyether- polyols are free from polymer polyols like styrene-acrylonitrile polymer polyols, polyuria suspension polymer modified polyols and polyisocyanate polyaddition polymer modified polyols.
  • polymer polyols typically increase the overall viscosity of the isocyanate-reactive component and thus of the polyurethane formulation, which may diminish or compensate the effect of using lower viscous isocyanate-reactive components for the reactive system.
  • the individual polyols used for the isocyanate-reactive component differ principally in regard to hydroxyl group functionality, structure and/ or molecular weight.
  • Suitable polyether polyols that can be employed in the reaction systems of the invention include those that are prepared by reacting an alkylene oxide, a halogen substituted or aromatic substituted alkylene oxide or mixtures thereof, with an active hydrogen containing initiator compound.
  • Suitable oxides include for example ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, epichlorohydrin, epibromohydrin, mixtures thereof, and the like.
  • Propylene oxide and ethylene oxide are particularly preferred alkylene oxides. - -
  • the active hydrogen containing initiator compound is selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, butane diols, butene diol, hexanediols, glycerine, trimethylolpropane, trimethylolethane, pentaerythritol, hexanetriols, sucrose, hydroquinone, resorcinol, catechol, bisphenols, novolac resins and phosphoric acid.
  • the polyol having a viscosity at 25°C in the range of 20 mPas to 100 mPas determined according to DIN EN ISO 3219 is a polyether polyol prepared by reacting an alkylene oxide with an active hydrogen containing initiator compound selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, butane diols, butene diol, hexanediols and glycerine.
  • isocyanate-reactive component minor amounts of other types of isocyanate reactive species that may not conform to the types described hereinabove.
  • the benefits of the inventive formulations are that the pultruded parts have a smooth surface in some embodiments, which prevents defects from arising on the finished surface, especially those parts having complex profiles.
  • the polyisocyanate component or the isocyanate-reactive component may be premixed with any optional additives.
  • the optional additives that are not themselves polyfunctional isocyanate-reactive materials are to be considered (counted) as entities separate from the isocyanate-reactive component, even when mixed therewith.
  • the optional additives, or any part thereof, are premixed with the polyisocyanate component, these are to be considered as entities separate from the polyisocyanate component, except in the case where they are themselves polyfunctional isocyanate species.
  • the pultrusion apparatus preferably has at least one impregnation unit and at least one curing die. Because no polymerization is to take place in the impregnation die, the curing die necessarily will operate at a higher temperature than the impregnation unit.
  • the pultrusion apparatus may optionally contain a plurality of curing dies, or zones. Different curing zones may be set at different temperatures, if desired, but all the zones of the curing die will be higher in temperature than the impregnation unit. - -
  • the pultrusion apparatus may optionally contain a plurality of impregnation units. Preferably, there is just one impregnation unit, and this preferably is situated immediately prior to the first curing die (or zone). As mentioned hereinabove, the impregnation unit is set at a temperature that provides for substantially no reaction (polymerization) between the polyisocyanate component and the polyisocyanate-reactive component in the polyurethane-forming formulation before the fibrous reinforcing structure, which has been at least partially impregnated with the polyurethane-forming formulation, enters the first curing die (or zone).
  • the fiber reinforcing material may be chosen from any materials known for this purpose, whereas the following specification is not to be understood as limiting.
  • An endless fiber based reinforcing material is useful to provide mechanical strength to the pultruded composite, and to allow the transmission of the pulling force in the process. Fibers should preferably be at least long enough to pass though both the impregnation and curing dies and attach to a source of tension.
  • the fibrous reinforcing material may be made of any fibrous material or materials that can provide endless fibers capable of being at least partially wetted by the polyurethane formulation during impregnation.
  • the fibrous reinforcing material may be single strands, braided strands, woven or non-woven mat structures and combinations thereof. Mats or veils made of endless fibers may be used, in single ply or multi-ply structures.
  • Suitable fibrous materials are known in the pultrusion art, include, but are not limited to, glass fibers, glass mats, carbon fibers, polyester fibers, natural fibers, aramid fibers, nylon fibers, basalt fibers, and combinations thereof. Particularly preferred in the present invention are endless glass fibers.
  • the fibers and/or fibrous reinforcing structures may be formed continuously from one or more reels feeding into the pultrusion apparatus and attached to a source of pulling force at the outlet side of the curing die.
  • the reinforcing fibers may optionally be pre-treated with sizing agents or adhesion promoters known to those skilled in the art.
  • the weight percentage of the endless fiber reinforcement in the pultruded composite s of the present invention may vary considerably, depending on the end use application intended for the composite articles. Reinforcement loadings may be from 30 to 95% by weight, preferably from 40 to 90% by weight of the final composite, more preferably from 60 to 90%> by weight, and most preferably from 70 to 90%> by weight, based on the weight of the final composite.
  • the endless fiber reinforcement may be present in the pultruded composites of the present invention in an amount ranging between any combination of these values, inclusive of the recited values.
  • suitable polyisocyanates are known to those skilled in the art and include unmodified isocyanates, modified polyisocyanates, and isocyanate prepolymers.
  • organic polyisocyanates include aliphatic, cycloaliphatic, araliphatic, aromatic, and heterocyclic polyisocyanates of the type described, for example, by W. Siefken in Justus - -
  • n is a number from 2-5, preferably 2-3, and Q is an aliphatic hydrocarbon group containing 2-18, preferably 6-10, carbon atoms; a cycloaliphatic hydrocarbon group containing 4-
  • polyisocyanates examples include ethylene diisocyanate; 1 ,4-tetramethylene diisocyanate; 1,6-hexamethylene diisocyanate; 1,12-dodecane diisocyanate; cyclobutane-1,3- diisocyanate; cyclohexane-1,3- and -1,4-diisocyanate, and mixtures of these isomers; 1- isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; e.g. German Auslegeschrift 1,202,785 and U.S. Pat. No.
  • At least one polyisocyanate is selected from the group consisting of 2,4- and 2,6- hexahydrotoluene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate ("hydrogenated MDI", or "HMDI”), diphenylmethane-2,4'- and/or -4,4'-diisocyanate (“MDI”) and polyphenyl- polymethylene-polyisocyanates (“crude MDI”).
  • hydrogenated MDI dicyclohexylmethane-4,4'-diisocyanate
  • MDI diphenylmethane-2,4'- and/or -4,4'-diisocyanate
  • CAde MDI polyphenyl- polymethylene-polyisocyanates
  • Isocyanate-terminated prepolymers may also be employed in the present invention.
  • Prepolymers may be prepared by reacting an excess of organic polyisocyanate or mixtures thereof with a minor amount of an active hydrogen-containing compound as determined by the well-known Zerewitinoff test, as described by Kohler in "Journal of the American Chemical Society," 49, 3181 (1927). These compounds and their methods of preparation are well known to those skilled in the art. The use of any one specific active hydrogen compound is not critical; any such compound can be employed in the practice of the present invention.
  • the polyisocyanate component preferably contains organic polyisocyanates having a number averaged isocyanate (NCO) functionality of from at least 1.8 to 4.0, more preferably from 2.0 to 3.0, most preferably from 2.3 to 2.9.
  • the NCO functionality of the polyisocyanate component may be in an amount ranging between any combination of these values, inclusive of the recited values.
  • the polyisocyanate component preferably has a free isocyanate group content (NCO content) in the range of from 5% to 50% by weight, more preferably from 8% to 40%, most preferably from 9% to 35%) by weight.
  • the NCO content of the polyisocyanate component may be in an amount ranging between any combination of these values, inclusive of the recited values.
  • reaction mixture does not contain any higher functioning acid having a functionality of greater than or equal to 2.
  • the reaction mixture may optionally contain a catalyst for one or more of the polymer forming reactions of polyisocyanates.
  • Catalyst(s), where used, is/are preferably introduced into the reaction mixture by pre-mixing with the isocyanate-reactive component.
  • Catalysts for the polymer forming reactions of organic polyisocyanates are well known to those skilled in the art.
  • Preferred catalysts include, but are not limited to, tertiary amines, tertiary amine acid salts, organic metal salts, covalently bound organometallic compounds, and combinations thereof.
  • the levels of the preferred catalysts required to achieve the needed reactivity profile for pultrusion processing will - - vary with the composition of the formulation and must be optimized for each reaction system (formulation).
  • the catalysts preferably have at least some degree of solubility in the isocyanate-reactive component used, and are most preferably fully soluble in that component at the use levels required.
  • the inventive formulation may contain other optional additives, if desired. Examples of additional optional additives include particulate or short fiber filler, internal mold release agents, fire retardants, smoke suppressants, dyes, pigments, antistatic agents, antioxidants, UV stabilizers, minor amounts of viscosity reducing inert diluents, combinations of these, and any other known additives from the art.
  • the additives or portions thereof may be provided to the fibers, such as by coating the fibers with the additive.
  • Suitable internal mold release additives are highly preferred in pultrusion of mixing activated isocyanate- based resins systems to prevent sticking or buildup in the die.
  • Suitable internal mold release agents may include, for example, fatty amides such as erucamide or stearamide, fatty acids such a oleic acid, oleic acid amides, fatty esters such as LOXIOL G71 S inert polyester (from Henkel), carnauba wax, beeswax (natural esters), butyl stearate, octyl stearate, ethylene glycol monostearate, ethylene glycol distearate, glycerin di-oleate, glycerin tri-oleate, and esters of polycarboxylic acids with long chain aliphatic monovalent alcohols such as dioctyl sebacate, mixtures of (a) mixed esters of aliphatic polyols, dicarboxylic acids and long-chaine
  • moisture scavengers such as molecular sieves
  • defoamers such as polydimethylsiloxanes
  • coupling agents such as the mono- oxirane or organo-amine functional trialkoxysilanes; combinations of these and the like.
  • the coupling agents are particularly preferred for improving the bonding of the matrix resin to the fiber - - reinforcement.
  • Fine particulate fillers such as clays and fine silicas, are often used at thixotropic additives. Such particulate fillers may also serve as extenders to reduce resin usage. Fire retardants are sometimes desirable as additives in pultruded composites.
  • Examples of preferred fire retardant types include, but are not limited to, triaryl phosphates; trialkyl phosphates, especially those bearing halogens; ammonium polyphosphate; red phosphorous; aluminium trihydroxides; halogenated paraffins and combinations thereof.
  • the stoichiometry of mixing isocyanate-based polymer forming formulations, containing an organic polyisocyanate and a polyfunctional isocyanate reactive resin is often expressed by a quantity known in the art as the isocyanate index.
  • the index of such a mixing activated formulation is simply the ratio of the total number of reactive isocyanate (-NCO) groups present to the total number of isocyanate-reactive groups (that can react with the isocyanate under the conditions employed in the process). This quantity is often multiplied by 100 and expressed as a percent.
  • Preferred isocyanate index values in the mixing activated formulations, which are suitable for use in the invention range from 70 to 150%. A more preferred range of index values is from 90 to 125%.
  • the isocyanate-reactive component comprises at 25°C a non-homogeneous mixture of polyols, more preferably the isocyanate-reactive component comprises at 25 °C a non-homogeneous mixture of polyether-polyols.
  • Homogeneous miscibility is determined by that no phase separation is visible after thoroughly mixing the components. Accordingly, a non-homogeneous mixture is determined by the presence of phase separation after thoroughly mixing the components.
  • pultrusion of polyurethane systems with fiber reinforced composites is performed by supplying the isocyanate and polyol components to a mix/metering machine for delivery in a desired ratio to a mixing apparatus, preferably a static mixer, to produce a reaction mixture.
  • the reaction mixture is supplied to an injection die where it can be used to impregnate fibers being pulled concurrently into the injection die.
  • the resulting uncured composite is pulled through a zoned heating die, attached directly to the injection die, having a desired cross- section where it is shaped and cured.
  • the curing die has two to three heated zones equipped with electrical heating coils individually controlled to maintain the desired temperatures.
  • the entrance to the die is cooled to prevent premature polymerization.
  • the temperature at the hottest zone generally ranges from 175°C to 230°C.
  • the dynamic forces needed to pull the composite through the forming die are supplied by the pulling machine.
  • This machine typically has gripping devices that contact the cured composite profile (or the glass fibers therein) and give the traction necessary to pull the composite profile through the die.
  • the machine also has a device that develops a force in the desired direction of pull - - that gives the impetus necessary to pull the composite profile continuously through the die.
  • the resulting composite profile upon exiting the pulling machine is then cut to the desired length typically by an abrasive cut off saw.
  • a further object of the present invention is directed to a pultrusion process for preparing a fiber reinforced polyurethane composite, the process comprising:
  • the present invention is also directed to a fiber reinforced composite comprising a reaction system according to this invention.
  • Isocyanate Liquid polymeric MDI product having a free isocyanate group content of
  • a reactive system AA without low viscous polyols and inventive reactive systems BB, CC and DD were prepared as follows.
  • the table below represents the isocyanate- reactive components of both reactive systems: - -
  • the isocyanate reactive component for the reactive systems AA was represented by 119 wt. -parts of MDI and the isocyanate reactive component for the reactive systems BB was presented by 133, for CC was presented by 121 and for DD was represented by 154 wt. -parts of MDI.
  • the ingredients of the isocyanate-reactive component were mixed.
  • the MDI was added, mixed for 25 seconds with a wooden spatula and poured into a Geltimer (Gardener).
  • the gelling time was determined until complete curing from the moment the mixture was introduced into the Geltimer. Further, the curing speed at 204 °C was determined on a heated spot plate. . .
  • the viscosity of the isocyanate reactive component was determined according to DIN EN ISO 3219.
  • Pultrusion equipment comprising a closed injection box and a heatable moulding tool was used.
  • the interior diameter of the profile in the moulding tool was 3x115 mm.
  • Standard glass fibers (Advantex® DR399A-AE 4800 provided by 3B, Belgium) were pulled through the injection box and the moulding tool. Glas fiber mats were not used.
  • the amount of glass fibre in relation to the total weight of the pultrudate was 80 % by weight.
  • the components of the reactive systems as outlined above were mixed at room temperature in a low-pressure apparatus with a static mixer at the given isocyanate index. Subsequently, the reactive mixtures were injected into the injection box so that the glass fibers were wetted. The wetted glass fibers were continuously pulled through the moulding tool and cured. . .
  • the production speed was measured as follows:

Abstract

A reaction system for the preparation of a fiber reinforced composite, comprising a continuous fiber reinforcing material and a polyurethane formulation comprising a polyisocyanate component containing at least one polyisocyanate and an isocyanate-reactivecomponent containing a blend of at least threepolyols.The invention further relates to a fiber reinforced composite which comprises a reaction system of the before mentioned type as well as a pultrusion process for the preparation of a fiberreinforced composite using the reaction system.

Description

2-K Pultrusion Formulation and Process
The present invention relates to a reaction system for the preparation of a fiber reinforced composite, comprising a continuous fiber reinforcing material and a polyurethane formulation comprising a polyisocyanate component containing at least one polyisocyanate and an isocyanate- reactive component containing a blend of at least three polyols. The invention further relates to a fiber reinforced composite which comprises a reaction system of the before mentioned type as well as a pultrusion process for the preparation of a fiber reinforced composite using the reaction system.
Pultrusion is a manufacturing process for producing continuous lengths of fiber reinforced plastic ("FRP") structural shapes. Raw materials include a liquid resin mixture (containing resin, fillers and specialized additives) and reinforcing fibers. The process involves pulling these raw materials, rather than pushing as is the case in extrusion, through a heated steel forming die using a continuous pulling device. The reinforcement materials are in continuous forms such as rolls of fiberglass mat or doffs of fiberglass roving. The two ways to impregnate, or "wet out", the glass are open bath process and resin injection. Typical commercial resins include polyester, vinyl esters, phenolics, and epoxy compounds. These resins usually have very long gel times and can be run in an open bath process wherein the reinforcing fibers are soaked in a bath of resin and the excess resin is scraped off by a series of preform plates at the die entrance. As the wetted fibers enter the die, the excess resin is squeezed through and off the reinforcing fibers. The pressure rise in the die inlet helps to enhance fiber wet-out and suppresses void formation. As the saturated reinforcements are pulled through the die, the gelation (or hardening) of the resin is initiated by the heat from the die and a rigid, cured profile is formed that corresponds to the shape of the die.
For resin systems like polyurethanes, which have a fast gel time and a short pot life the resin injection process is used. In the injection process, the reinforcement materials are passed through a small closed box which is usually attached to the die or may be part of the die. The resin is injected under pressure through ports in the box to impregnate the reinforcement materials. Resin injection boxes are designed to minimize resin volume and resin residence time inside the box. There are a number of different resin injection box designs in the literature all of which have the common features of an angled or tapered design and the exit profile matching the shape of the die entrance. The patent art provides a number of teachings with respect to polyurethane pultrusion. For example, US 6,420,493 B discloses a two component chemically thermoset composite resin matrix for use in composite manufacturing processes. The polyisocyanate component and the polyol component are in relative proportions in accordance with an OH/NCO equivalent ratio of 1 : 1 to 1 :2. Further, the presence of 10%-40% of a polyester polyol with the use of 5 to 20 wt % of a - - hydroxyl terminated vegetable oil is required. For the isocyanate component, it is stated that it is preferred to have at least 15 wt % of an aliphatic polyisocyanate.
US 6,793,855 B teaches polyisocyanurate systems, pultrusion of those systems to produce reinforced polyisocyanurate matrix composites and the composites produced by that pultrusion. The polyisocyanurate systems include a polyol component, an optional chain extender, and an isocyanate. The polyisocyanurate systems are said to have extended initiation times of 5 minutes to 30 minutes at room temperature and to be capable of snap curing. The teaching is that substantial polymerization of the polyurethane takes place in the impregnation die.
US 7,056,976 B also discloses polyisocyanate-based reaction systems, a pultrusion process using those systems to produce reinforced matrix composites and composites produced by that pultrusion process. The polyisocyanate-based systems are mixed activated reaction systems that include a polyol composition, an optional chain extender or crosslinker and a polyisocyanate. The polyisocyanate-based systems are said to exhibit improved processing characteristics in the manufacture of fiber reinforced thermoset composites via reactive pultrusion. US 7,056,976 B describes that gel times are the key parameter in polyurethane pultrusion.
US 2004/0094859 Al describes polyisocyanurate systems, pultrusion of those systems to produce reinforced polyisocyanurate matrix composites and composites produced by that pultrusion process. The polyisocyanurate systems include a polyol component, an optional chain extender and an isocyanate. The polyisocyanurate systems are said to have extended initiation times of 5 minutes to 30 minutes at room temperature, and to be capable of snap curing. It is further mentioned that gel times are the key parameter in polyurethane pultrusion processes.
In practice fillers are oftentimes added to pultrusion formulations to improve the surface finish and reduce glass content, such as clays or low profile additives ("LPA"s). However, the use of fillers and LP As is disadvantageous in that such compounds do not form stable suspensions, are prone to settling or floating in the resin mixture and therefore require constant mixing. Also, fillers are prone to absorbing water which can interfere with the urethane reaction. Furthermore, most fillers have a high density and therefore high levels on a weight percent basis are required to effect small changes on a volume percent. Such high levels can lead to extremely high viscosities of the resin mix which can make processing difficult or impossible. US2008/0090966 Al suggests a reaction system for the preparation of a fiber reinforced composite material with a polyurethane formulation comprising a polyisocyanate component and an isocyanate-reactive component. The polyurethane formulation used for the impregnation of the fiber reinforcing material allows better processing and may yield improved reinforced composites. - -
In US2008/0087373 Al a reaction system for the preparation of a fiber reinforced composite according to the pultrusion process is described which contains a polyurethane formulation comprising a polymer polyol, like a styrene-acrylonitrile polymer polyol.
From US2008/0090921 Al, another reaction system for the preparation of fiber reinforced composite materials are known. The reaction system comprises a polyurethane formulation containing a polyisocyanate component and a polyol component, which comprises at least one double metal cyanide (DMC)-catalyzed polyol.
WO 2011/067246 describes a pultrusion resin system comprising inter alia higher functioning acids having a functionality of greater than or equal to 2. However, when using these reaction systems the machinery, in particular mixing and metering devices for delivery, will become corroded in the long run.
Although the prior art already suggests a diversity of polyurethane formulations for use in pultrusion processes, these formulations do not fulfill the production requirements in every aspect. In particular, the polyurethane formulations used so far limit the pulling velocity of the fiber reinforcements through the impregnation chamber and the die of the pultrusion apparatus, thus limiting the production speed.
The object of the present invention is to provide an improved reaction system of the before mentioned type which allows higher production speeds in a pultrusion process for the preparation of fiber reinforced composites. This object is solved by a reaction system for the preparation of a fiber reinforced composite, comprising a continuous fiber reinforcing material and a polyurethane formulation comprising
• a polyisocyanate component containing at least one polyisocyanate and
• an isocyanate-reactive component containing a blend of at least three polyols, whereas at least one of said polyols has a viscosity at 25°C in the range of 20 mPas to 100 mPas determined according to DIN EN ISO 3219
It has surprisingly been found that using a blend of at least three polyols from which at least one is a low viscous polyol having a viscosity at 25°C of in the range of 20 mPas to l OO mPas determined according to DIN EN ISO 3219 allows for increasing the wetting velocity in the impregnation chamber, for example by increasing the pulling speed of the fiber reinforcement material. - -
In other words, according to this invention at least one low viscous polyol is used in the isocyanate-reactive component. This implies that also two or more of such low viscous polyols can be used. Limiting amounts depend however on other ingredients and also on the viscosity of the polyisocyanate component. Preferably, the viscosity of the isocyanate-reactive component should be kept in a range from 300 mPas to 900 mPas at 25°C according to DIN EN ISO 3219 at a shear rate of 1/s, more preferably in the range of 350 mPas to 850 mPas at 25 °C determined according to DIN EN ISO 3219 at a shear rate of 1/s.
All viscosity values given in the present invention are measured with a rotational viscosimeter according to DIN EN ISO 3219. The inventively used polyols are Newtonian fluids. Therefore, the value of the viscosity can be determined without having to take into account the shear rate that is used for determining the viscosity.
The hydroxyl numbers mentioned in the present application are analyzed by acetylating the hydroxyl groups and titration of the resulting acid against KOH. The value is defined as (56.1 x 1,000)/ polymer equivalent weight having the unit "meq/g" . It is preferred that the reaction system of the present invention comprises at least one of said polyols with a viscosity at 25°C in the range of 40 mPas to 90 mPas, more preferably in the range of 40 mPas to 70 mPas determined according to DIN EN ISO 3219.
Experiments have shown that using such a low viscous polyol or polyols in the polyol blend for the polyurethane component strongly reduces the overall viscosity of the polyurethane component after mixing the polyisocyanate component with the isocyanate-reactive component. This has the advantage that the polyurethane component may better penetrate the fiber reinforcing material, like fiber strands or fiber mats. At the same time, the lower viscous polyurethane component has a lower tendency of film break during the impregnation, even at high production speeds compared to higher viscous polyurethane compositions. Hence, the overall process speed is enhanced using such low viscous polyols.
According to another preferred embodiment of the present invention, the reaction system is characterized in that the isocyanate-reactive component has a hydroxyl number of 200 to 1000 meq/g, in particular of 300 to 900 meq/g, preferably of 400 to 650 meq/g.
As set out above, the isocyanate-reactive component contains a blend of at least three polyols. Although a larger number of polyols could be used. Preferably, the isocyanate-reactive component contains four, five, six or seven polyols. More preferably the isocyanate-reactive component contains four, five or six polyols. Most preferably the isocyanate-reactive component contains four or five polyols. - -
In a particular preferred embodiment of the present invention, the isocyanate-reactive component comprises at least three polyols having the following characteristics:
• a first polyol having a hydroxyl number from 20 to 100 meq/g and a viscosity at 25°C from 700 to 2000 mPas determined according to DIN EN ISO 3219 , · a second polyol having a hydroxyl number from 800 to 1300 meq/g and a viscosity at
25°C from 800 to 2000 mPas determined according to DIN EN ISO 3219 and
• a third polyol having a hydroxyl number from 350 to 700 meq/g and a viscosity at 25°C from 20 to 100 mPas determined according to DIN EN ISO 3219 .
A reaction system comprising at least three polyols as defined above lead to particularly readily processable polyurethane compositions and also provide fiber reinforcing composite materials having good mechanical properties.
In that context, it is further preferred that the isocyanate-reactive component comprises the polyols in the following amounts:
• 5 to 25 wt.-% of the first polyol, · 15 to 45 wt.-% of the second polyol,
• 5 to 50 wt.-% of the third polyol, related to the total weight of the isocyanate-reactive component.
In another particular preferred embodiment of the present invention, the isocyanate-reactive component comprises at least three polyols having the following characteristics: · a first polyol having a hydroxyl number from 200 to 500 meq/g and a viscosity at 25 °C from 200 to 600 mPas determined according to DIN EN ISO 3219,
• a second polyol having a hydroxyl number from 800 to 1300 meq/g and a viscosity at 25°C from 800 to 2000 mPas determined according to DIN EN ISO 3219 and
• a third polyol having a hydroxyl number from 350 to 700 meq/g and a viscosity at 25°C from 20 to 100 mPas determined according to DIN EN ISO 3219.
In that context, it is further preferred that the isocyanate-reactive component comprises the polyols in the following amounts:
• 30 to 65 wt.-% of the first polyol, - -
• 15 to 45 wt.-% of the second polyol,
• 15 to 25 wt.-% of the third polyol, related to the total weight of the isocyanate-reactive component.
In another particular preferred embodiment of the present invention, the isocyanate-reactive component comprises at least four polyols having the following characteristics:
• a first polyol having a hydroxyl number from 20 to 100 meq/g and a viscosity at 25°C from 700 to 2000 mPas determined according to DIN EN ISO 3219 ,
• a second polyol having a hydroxyl number from 800 to 1300 meq/g and a viscosity at 25°C from 800 to 2000 mPas determined according to DIN EN ISO 3219 · a third polyol having a hydroxyl number from 350 to 700 meq/g and a viscosity at 25°C from 20 to 100 mPas determined according to DIN EN ISO 3219 and
• a fourth polyol having a hydroxyl number from 200 to 500 meq/g and a viscosity at 25 °C from 200 to 600 mPas determined according to DIN EN ISO 3219 .
The polyols used for the isocyanate-reactive component may be chosen from a wide variety of different polyols used for polyurethane compositions. Preferred polyols are polyether-polyols. It is preferred that the polyether- polyols are free from polymer polyols like styrene-acrylonitrile polymer polyols, polyuria suspension polymer modified polyols and polyisocyanate polyaddition polymer modified polyols. The advantage of avoiding polymer polyols is that polymer polyols typically increase the overall viscosity of the isocyanate-reactive component and thus of the polyurethane formulation, which may diminish or compensate the effect of using lower viscous isocyanate-reactive components for the reactive system.
The individual polyols used for the isocyanate-reactive component differ principally in regard to hydroxyl group functionality, structure and/ or molecular weight.
Suitable polyether polyols that can be employed in the reaction systems of the invention include those that are prepared by reacting an alkylene oxide, a halogen substituted or aromatic substituted alkylene oxide or mixtures thereof, with an active hydrogen containing initiator compound.
Suitable oxides include for example ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, epichlorohydrin, epibromohydrin, mixtures thereof, and the like. Propylene oxide and ethylene oxide are particularly preferred alkylene oxides. - -
Preferably the active hydrogen containing initiator compound is selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, butane diols, butene diol, hexanediols, glycerine, trimethylolpropane, trimethylolethane, pentaerythritol, hexanetriols, sucrose, hydroquinone, resorcinol, catechol, bisphenols, novolac resins and phosphoric acid. Preferably the polyol having a viscosity at 25°C in the range of 20 mPas to 100 mPas determined according to DIN EN ISO 3219 is a polyether polyol prepared by reacting an alkylene oxide with an active hydrogen containing initiator compound selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, butane diols, butene diol, hexanediols and glycerine.
It is also within the scope of the present invention, albeit less preferred, to include within the isocyanate-reactive component minor amounts of other types of isocyanate reactive species that may not conform to the types described hereinabove.
Besides the advantages regarding easier and faster processing, the benefits of the inventive formulations are that the pultruded parts have a smooth surface in some embodiments, which prevents defects from arising on the finished surface, especially those parts having complex profiles.
Further, in contradistinction to the teaching in the art, exemplified by the patents mentioned hereinabove that require a high degree of polymerization occur within the impregnation die, the present inventors find it desirable to have essentially no reaction occur inside of the impregnation die. The polyisocyanate component or the isocyanate-reactive component may be premixed with any optional additives. However, it is to be understood that the optional additives that are not themselves polyfunctional isocyanate-reactive materials are to be considered (counted) as entities separate from the isocyanate-reactive component, even when mixed therewith. Likewise, if the optional additives, or any part thereof, are premixed with the polyisocyanate component, these are to be considered as entities separate from the polyisocyanate component, except in the case where they are themselves polyfunctional isocyanate species.
The pultrusion apparatus preferably has at least one impregnation unit and at least one curing die. Because no polymerization is to take place in the impregnation die, the curing die necessarily will operate at a higher temperature than the impregnation unit. The pultrusion apparatus may optionally contain a plurality of curing dies, or zones. Different curing zones may be set at different temperatures, if desired, but all the zones of the curing die will be higher in temperature than the impregnation unit. - -
The pultrusion apparatus may optionally contain a plurality of impregnation units. Preferably, there is just one impregnation unit, and this preferably is situated immediately prior to the first curing die (or zone). As mentioned hereinabove, the impregnation unit is set at a temperature that provides for substantially no reaction (polymerization) between the polyisocyanate component and the polyisocyanate-reactive component in the polyurethane-forming formulation before the fibrous reinforcing structure, which has been at least partially impregnated with the polyurethane-forming formulation, enters the first curing die (or zone).
The fiber reinforcing material may be chosen from any materials known for this purpose, whereas the following specification is not to be understood as limiting. An endless fiber based reinforcing material is useful to provide mechanical strength to the pultruded composite, and to allow the transmission of the pulling force in the process. Fibers should preferably be at least long enough to pass though both the impregnation and curing dies and attach to a source of tension. In the present invention, the fibrous reinforcing material may be made of any fibrous material or materials that can provide endless fibers capable of being at least partially wetted by the polyurethane formulation during impregnation. The fibrous reinforcing material may be single strands, braided strands, woven or non-woven mat structures and combinations thereof. Mats or veils made of endless fibers may be used, in single ply or multi-ply structures.
Suitable fibrous materials are known in the pultrusion art, include, but are not limited to, glass fibers, glass mats, carbon fibers, polyester fibers, natural fibers, aramid fibers, nylon fibers, basalt fibers, and combinations thereof. Particularly preferred in the present invention are endless glass fibers. The fibers and/or fibrous reinforcing structures may be formed continuously from one or more reels feeding into the pultrusion apparatus and attached to a source of pulling force at the outlet side of the curing die. The reinforcing fibers may optionally be pre-treated with sizing agents or adhesion promoters known to those skilled in the art. The weight percentage of the endless fiber reinforcement in the pultruded composite s of the present invention may vary considerably, depending on the end use application intended for the composite articles. Reinforcement loadings may be from 30 to 95% by weight, preferably from 40 to 90% by weight of the final composite, more preferably from 60 to 90%> by weight, and most preferably from 70 to 90%> by weight, based on the weight of the final composite. The endless fiber reinforcement may be present in the pultruded composites of the present invention in an amount ranging between any combination of these values, inclusive of the recited values.
Regarding the polyisocyanate component, suitable polyisocyanates are known to those skilled in the art and include unmodified isocyanates, modified polyisocyanates, and isocyanate prepolymers. Such organic polyisocyanates include aliphatic, cycloaliphatic, araliphatic, aromatic, and heterocyclic polyisocyanates of the type described, for example, by W. Siefken in Justus - -
Liebigs Annalen der Chemie, 562, pages 75 to 136. Examples of such isocyanates include those represented by the formula,
Q(NCO)n in which n is a number from 2-5, preferably 2-3, and Q is an aliphatic hydrocarbon group containing 2-18, preferably 6-10, carbon atoms; a cycloaliphatic hydrocarbon group containing 4-
15, preferably 5-10, carbon atoms; an araliphatic hydrocarbon group containing 8-15, preferably 8- 13, carbon atoms; or an aromatic hydrocarbon group containing 6-15, preferably 6-13, carbon atoms.
Examples of suitable polyisocyanates include ethylene diisocyanate; 1 ,4-tetramethylene diisocyanate; 1,6-hexamethylene diisocyanate; 1,12-dodecane diisocyanate; cyclobutane-1,3- diisocyanate; cyclohexane-1,3- and -1,4-diisocyanate, and mixtures of these isomers; 1- isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; e.g. German Auslegeschrift 1,202,785 and U.S. Pat. No. 3,401,190); 2,4- and 2,6-hexahydrotoluene diisocyanate and mixtures of these isomers; dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI, or HMDI); 1,3- and 1 ,4-phenylene diisocyanate; 2,4- and 2,6-toluene diisocyanate and mixtures of these isomers (TDI); diphenylmethane-2,4'- and/or -4,4'-diisocyanate (MDI); naphthylene- 1 ,5-diisocyanate; triphenylmethane-4,4',4"-triisocyanate; polyphenyl-polymethylene- polyisocyanates of the type which may be obtained by condensing aniline with formaldehyde, followed by phosgenation (crude MDI), which are described, for example, in GB 878,430 and GB 848,671; norbornane diisocyanates, such as described in U.S. Pat. No. 3,492,330; m- and p- isocyanatophenyl sulfonylisocyanates of the type described in U. S. Pat. No. 3 ,454,606; perchlorinated aryl polyisocyanates of the type described, for example, in U.S. Pat. No. 3,227,138; modified polyisocyanates containing carbodiimide groups of the type described in U.S. Pat. No. 3,152,162; modified polyisocyanates containing urethane groups of the type described, for example, in U.S. Pat. Nos. 3,394,164 and 3,644,457; modified polyisocyanates containing allophanate groups of the type described, for example, in GB 994,890, BE 761 ,616, and NL 7,102,524; modified polyisocyanates containing isocyanurate groups of the type described, for example, in U.S. Pat. No. 3,002,973, German Patentschriften 1,022,789, 1,222,067 and 1,027,394, and German Offenlegungsschriften 1,919,034 and 2,004,048; modified polyisocyanates containing urea groups of the type described in German Patentschrift 1,230,778; polyisocyanates containing biuret groups of the type described, for example, in German Patentschrift 1,101,394, U.S. Pat. Nos. 3,124,605 and 3,201,372, and in GB 889,050; polyisocyanates obtained by telomerization reactions of the type described, for example, in U.S. Pat. No. 3,654, 106; polyisocyanates containing ester groups of the type described, for example, in GB 965,474 and GB 1,072,956, in U.S. Pat. No. 3,567,763, and in German Patentschrift 1,231,688; reaction products of the above- - - mentioned isocyanates with acetals as described in German Patentschrift 1 ,072,385 ; and polyisocyanates containing polymeric fatty acid groups of the type described in U.S. Pat. No. 3,455,883. It is also possible to use the isocyanate-containing distillation residues accumulating in the production of isocyanates on a commercial scale, optionally in solution in one or more of the polyisocyanates mentioned above. Those skilled in the art will recognize that it is also possible to use mixtures of the polyisocyanates described above.
More preferably at least one polyisocyanate is selected from the group consisting of 2,4- and 2,6- hexahydrotoluene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate ("hydrogenated MDI", or "HMDI"), diphenylmethane-2,4'- and/or -4,4'-diisocyanate ("MDI") and polyphenyl- polymethylene-polyisocyanates ("crude MDI").
Isocyanate-terminated prepolymers may also be employed in the present invention. Prepolymers may be prepared by reacting an excess of organic polyisocyanate or mixtures thereof with a minor amount of an active hydrogen-containing compound as determined by the well-known Zerewitinoff test, as described by Kohler in "Journal of the American Chemical Society," 49, 3181 (1927). These compounds and their methods of preparation are well known to those skilled in the art. The use of any one specific active hydrogen compound is not critical; any such compound can be employed in the practice of the present invention.
The polyisocyanate component preferably contains organic polyisocyanates having a number averaged isocyanate (NCO) functionality of from at least 1.8 to 4.0, more preferably from 2.0 to 3.0, most preferably from 2.3 to 2.9. The NCO functionality of the polyisocyanate component may be in an amount ranging between any combination of these values, inclusive of the recited values. The polyisocyanate component preferably has a free isocyanate group content (NCO content) in the range of from 5% to 50% by weight, more preferably from 8% to 40%, most preferably from 9% to 35%) by weight. The NCO content of the polyisocyanate component may be in an amount ranging between any combination of these values, inclusive of the recited values.
Preferably the reaction mixture does not contain any higher functioning acid having a functionality of greater than or equal to 2.
The reaction mixture may optionally contain a catalyst for one or more of the polymer forming reactions of polyisocyanates. Catalyst(s), where used, is/are preferably introduced into the reaction mixture by pre-mixing with the isocyanate-reactive component. Catalysts for the polymer forming reactions of organic polyisocyanates are well known to those skilled in the art. Preferred catalysts include, but are not limited to, tertiary amines, tertiary amine acid salts, organic metal salts, covalently bound organometallic compounds, and combinations thereof. The levels of the preferred catalysts required to achieve the needed reactivity profile for pultrusion processing will - - vary with the composition of the formulation and must be optimized for each reaction system (formulation). Such optimization would be well understood by persons of ordinary skill in the art. The catalysts preferably have at least some degree of solubility in the isocyanate-reactive component used, and are most preferably fully soluble in that component at the use levels required. The inventive formulation may contain other optional additives, if desired. Examples of additional optional additives include particulate or short fiber filler, internal mold release agents, fire retardants, smoke suppressants, dyes, pigments, antistatic agents, antioxidants, UV stabilizers, minor amounts of viscosity reducing inert diluents, combinations of these, and any other known additives from the art. In some embodiments of the present invention, the additives or portions thereof may be provided to the fibers, such as by coating the fibers with the additive.
Internal mold release additives are highly preferred in pultrusion of mixing activated isocyanate- based resins systems to prevent sticking or buildup in the die. Suitable internal mold release agents may include, for example, fatty amides such as erucamide or stearamide, fatty acids such a oleic acid, oleic acid amides, fatty esters such as LOXIOL G71 S inert polyester (from Henkel), carnauba wax, beeswax (natural esters), butyl stearate, octyl stearate, ethylene glycol monostearate, ethylene glycol distearate, glycerin di-oleate, glycerin tri-oleate, and esters of polycarboxylic acids with long chain aliphatic monovalent alcohols such as dioctyl sebacate, mixtures of (a) mixed esters of aliphatic polyols, dicarboxylic acids and long-chained aliphatic monocarboxylic acids, and (b) esters of the groups: (1) esters of dicarboxylic acids and long- chained aliphatic monofunctional alcohols, (2) esters of long-chained aliphatic monofunctional alcohols and long-chained aliphatic monofunctional carboxylic acids, (3) complete or partial esters of aliphatic polyols and long-chained aliphatic monocarboxylic acids, silicones such as TEGO IMR 412T silicone (fromEvonik), KEMESTER 5721 ester (a fatty acid ester product from Witco Corporation), fatty acid metal carboxylates such as zinc stearate and calcium stearate, waxes such as montan wax and chlorinated waxes , fluorine c ontaining c omp ounds such as polytetrafluoroethylene, fatty alkyl phosphates (both acidic and non-acidic types such as ZELEC UN, ZELEC AN, ZELEC MR, ZELEC VM-, ZELEC UN, ZELECLA-1, and ZELEC LA-2 phosphates, which are all commercially available from Stepan Chemical Company), chlorinated- alkyl phosphates; hydrocarbon oils, combinations of these, and the like. Especially preferred internal mold release agents are TECHLUBE 550HB available from Technic Products and 1948MCH available from Axel Plastics.
Other preferred optional additives for use in pultrusion include moisture scavengers, such as molecular sieves; defoamers, such as polydimethylsiloxanes; coupling agents, such as the mono- oxirane or organo-amine functional trialkoxysilanes; combinations of these and the like. The coupling agents are particularly preferred for improving the bonding of the matrix resin to the fiber - - reinforcement. Fine particulate fillers, such as clays and fine silicas, are often used at thixotropic additives. Such particulate fillers may also serve as extenders to reduce resin usage. Fire retardants are sometimes desirable as additives in pultruded composites. Examples of preferred fire retardant types include, but are not limited to, triaryl phosphates; trialkyl phosphates, especially those bearing halogens; ammonium polyphosphate; red phosphorous; aluminium trihydroxides; halogenated paraffins and combinations thereof.
The stoichiometry of mixing isocyanate-based polymer forming formulations, containing an organic polyisocyanate and a polyfunctional isocyanate reactive resin is often expressed by a quantity known in the art as the isocyanate index. The index of such a mixing activated formulation is simply the ratio of the total number of reactive isocyanate (-NCO) groups present to the total number of isocyanate-reactive groups (that can react with the isocyanate under the conditions employed in the process). This quantity is often multiplied by 100 and expressed as a percent. Preferred isocyanate index values in the mixing activated formulations, which are suitable for use in the invention range from 70 to 150%. A more preferred range of index values is from 90 to 125%.
In the context of the present invention, the isocyanate-reactive component comprises at 25°C a non-homogeneous mixture of polyols, more preferably the isocyanate-reactive component comprises at 25 °C a non-homogeneous mixture of polyether-polyols. Homogeneous miscibility is determined by that no phase separation is visible after thoroughly mixing the components. Accordingly, a non-homogeneous mixture is determined by the presence of phase separation after thoroughly mixing the components.
As those skilled in the art are aware, pultrusion of polyurethane systems with fiber reinforced composites is performed by supplying the isocyanate and polyol components to a mix/metering machine for delivery in a desired ratio to a mixing apparatus, preferably a static mixer, to produce a reaction mixture. The reaction mixture is supplied to an injection die where it can be used to impregnate fibers being pulled concurrently into the injection die. The resulting uncured composite is pulled through a zoned heating die, attached directly to the injection die, having a desired cross- section where it is shaped and cured.
The curing die has two to three heated zones equipped with electrical heating coils individually controlled to maintain the desired temperatures. The entrance to the die is cooled to prevent premature polymerization. The temperature at the hottest zone generally ranges from 175°C to 230°C. The dynamic forces needed to pull the composite through the forming die are supplied by the pulling machine. This machine typically has gripping devices that contact the cured composite profile (or the glass fibers therein) and give the traction necessary to pull the composite profile through the die. The machine also has a device that develops a force in the desired direction of pull - - that gives the impetus necessary to pull the composite profile continuously through the die. The resulting composite profile upon exiting the pulling machine is then cut to the desired length typically by an abrasive cut off saw.
Hence, a further object of the present invention is directed to a pultrusion process for preparing a fiber reinforced polyurethane composite, the process comprising:
• continuously pulling a roving or tow of continuous fiber reinforcing material successively through an impregnation chamber and a die;
• continuously feeding a polyurethane formulation comprising a polyisocyanate component containing at least one polyisocyanate, and an isocyanate-reactive component containing a blend of at least three polyols to the impregnation chamber;
• contacting the fiber reinforcing material with the mixture in the impregnation chamber such that substantially complete wetting of the material by the mixture occurs;
• continuously directing the fiber reinforcing material through a die heated to reaction temperature to form a solid composite; and
• drawing the composite from the die, wherein at least one of said polyols has a viscosity at 25°C in the range of 20 mPas to 100 mPas determined according to DIN EN ISO 3219.
The present invention is also directed to a fiber reinforced composite comprising a reaction system according to this invention.
- -
Examples:
The present invention is further illustrated by the following examples. The following materials were used in the formulations:
Figure imgf000015_0001
Molecular Sieve: Molsiv® L Powder, available from UOP M.S. S.r.L; Viale Milanofiori,
Strada 1, Palazzo El, 1-20090 AS SAGO MI, Milan, Italy
Catalyst: Tin catalyst available as FORMREZ UL 29 from GE Silicones
Internal Mold Release (IMR): Tech-Lube HB-550-D (available from Technick Products Inc.,
238 St. Nicholas Ave., South Plainfield, NJ 07080)
Isocyanate: Liquid polymeric MDI product having a free isocyanate group content of
31.4 % by weight and a number averaged isocyanate group functionality of 2.8
From these ingredients, a reactive system AA without low viscous polyols and inventive reactive systems BB, CC and DD were prepared as follows. The table below represents the isocyanate- reactive components of both reactive systems: - -
Figure imgf000016_0001
The isocyanate reactive component for the reactive systems AA was represented by 119 wt. -parts of MDI and the isocyanate reactive component for the reactive systems BB was presented by 133, for CC was presented by 121 and for DD was represented by 154 wt. -parts of MDI. For the preparation of the polyurethane component, the ingredients of the isocyanate-reactive component were mixed.
Then, the MDI was added, mixed for 25 seconds with a wooden spatula and poured into a Geltimer (Gardener). The gelling time was determined until complete curing from the moment the mixture was introduced into the Geltimer. Further, the curing speed at 204 °C was determined on a heated spot plate. . .
The viscosity of the isocyanate reactive component was determined according to DIN EN ISO 3219.
The results are summarized in the following table:
Figure imgf000017_0001
The results show that the inventive reactive systems BB, CC and DD have in spite of a lower viscosity in uncured state comparable curing speeds to the comparative reactive system AA.
Pultrusion equipment comprising a closed injection box and a heatable moulding tool was used. The interior diameter of the profile in the moulding tool was 3x115 mm. Thus, pultrudates of that size were prepared. Standard glass fibers (Advantex® DR399A-AE 4800 provided by 3B, Belgium) were pulled through the injection box and the moulding tool. Glas fiber mats were not used. The amount of glass fibre in relation to the total weight of the pultrudate was 80 % by weight. The components of the reactive systems as outlined above were mixed at room temperature in a low-pressure apparatus with a static mixer at the given isocyanate index. Subsequently, the reactive mixtures were injected into the injection box so that the glass fibers were wetted. The wetted glass fibers were continuously pulled through the moulding tool and cured. . .
The production speed was measured as follows:
Reactive system Production speed [m/min]
AA 1,30
BB 2,00
CC 2,60
DD 1,80

Claims

Claims:
1. A reaction system for the preparation of a fiber reinforced composite, comprising a continuous fiber reinforcing material and a polyurethane formulation comprising
• a polyisocyanate component containing at least one polyisocyanate and
• an isocyanate-reactive component containing a blend of at least three polyols, characterized in that at least one of said polyols has a viscosity at 25°C in the range of 20 mPas to 100 mPas determined according to DIN EN ISO 3219.
2. The reaction system according to claim 1, characterized in that at least one of said polyols has a viscosity at 25°C in the range of 40 mPas to 90 mPas determined according to DIN EN ISO 3219.
3. The reaction system according to any of the preceding claims, characterized in that the isocyanate-reactive component has a hydroxyl number of 200 to 1000 meq/g.
4. The reaction system according to any of the preceding claims, characterized in that the isocyanate-reactive component contains four, five, six or seven polyols.
5. The reaction system according to any of the preceding claims, characterized in that the viscosity of the isocyanate-reactive component is in a range from 300 mPas to 900 mPas at 25°C according to DIN EN ISO 3219.
6. The reaction system according to any of the preceding claims, characterized in that the isocyanate-reactive component comprises at least three polyols having the following characteristics:
• a first polyol having a hydroxyl number from 20 to 100 meq/g and a viscosity at 25°C from 700 to 2000 mPas determined according to DIN EN ISO 3219,
• a second polyol having a hydroxyl number from 800 to 1300 meq/g and a viscosity at 25°C from 800 to 2000 mPas determined according to DIN EN ISO 3219 and
• a third polyol having a hydroxyl number from 350 to 700 meq/g and a viscosity at 25°C from 20 to 100 mPas determined according to DIN EN ISO 3219.
7. The reaction system according to claim 5, characterized in that the isocyanate-reactive component comprises the polyols in the following amounts: • 5 to 25 wt.-% of the first polyol,
• 15 to 45 wt.-% of the second polyol, 5 to 50 wt.-% of the third polyol, related to the total weight of the isocyanate-reactive component.
8. The reaction system according to any of the preceding claims, characterized in that the polyols are polyether-polyols.
The reaction system according to any of the preceding claims, characterized in that the fiber reinforcing material is selected from the group consisting of single strands, braided strands, woven mat structures, non- woven mat structures and combinations thereof.
The reaction system according to any of the preceding claims, characterized in that the fiber reinforcing material comprises one or more of glass fibers, glass mats, carbon fibers, polyester fibers, natural fibers, aramid fibers, basalt fibers and nylon fibers.
11. The reaction system according to any of the preceding claims, characterized in that at least one polyisocyanate is selected from the group consisting of ethylene diisocyanate, 1,4- tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane-l,3-diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate, l-isocyanato-3,3,5- trimethyl-5-isocyanatomethyl-cyclohexane ("isophorone diisocyanate"), 2,4- and 2,6- hexahydrotoluene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate ("hydrogenated MDI", or "HMDI"), 1,3- and 1 ,4-phenylene diisocyanate, 2,4- and 2,6-toluene diisocyanate ("TDI"), diphenylmethane-2,4'- and/or -4,4'-diisocyanate ("MDI"), naphthylene-1,5- diisocyanate, triphenyl-methane-4,4',4"-triisocyanate, polyphenyl-polymethylene- polyisocyanates ("crude MDI"), norbornane diisocyanates, m- and p-isocyanatophenyl sulfonylisocyanates, perchlorinated aryl polyisocyanates, carbodiimide-modified polyisocyanates, urethane-modified polyisocyanates, allophanate-modified polyisocyanates, isocyanurate-modified polyisocyanates, urea-modified polyisocyanates, biuret-containing polyisocyanates, isocyanate-terminated prepolymers and mixtures thereof.
12. The reaction system according to claim 11, characterized in that at least one polyisocyanate is selected from the group consisting of 2,4- and 2,6-hexahydrotoluene diisocyanate, dicyclohexylmethane-4,4'-di i s o c y an at e ( " hy dr o g e n at e d M D I " , o r " H M D I " ) , diphenylmethane-2,4'- and/or -4,4'-diisocyanate ("MDI") and polyphenyl-polymethylene- polyisocyanates ("crude MDI").
13. The reaction system according to any of the preceding claims, characterized in that the isocyanate-reactive component comprises at 25 °C a non-homogeneous mixture of polyols.
14. A fiber reinforced composite comprising a reaction system according to any of the claims 1 to 13.
15. A pultrusion process for preparing a fiber reinforced polyurethane composite, the process comprising:
• continuously pulling a roving or tow of continuous fiber reinforcing material successively through an impregnation chamber and a die;
• continuously feeding a polyurethane formulation comprising a polyisocyanate component containing at least one polyisocyanate, and an isocyanate-reactive component containing a blend of at least three polyols to the impregnation chamber;
• contacting the fiber reinforcing material with the mixture in the impregnation chamber such that substantially complete wetting of the material by the mixture occurs;
• directing the fiber reinforcing material through a die heated to reaction temperature to form a solid composite; and
• continuously pulling the composite from the die, characterized in that at least one of said polyols has a viscosity at 25°C in the range of 20 mPas to 100 mPas determined according to DIN EN ISO 3219.
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CN105881935A (en) * 2016-05-20 2016-08-24 河南东海复合材料有限公司 Process production method of polyurethane section
CN106700015A (en) * 2015-11-18 2017-05-24 万华化学集团股份有限公司 Polyurethane resin system and method for preparation of pultrusion fiber composite material
CN110546181A (en) * 2017-04-18 2019-12-06 科思创德国股份有限公司 Pultruded part, production and use thereof
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CN106700015B (en) * 2015-11-18 2020-04-10 万华化学集团股份有限公司 Polyurethane resin system and method for preparing pultrusion fiber composite material by using same
CN105881935A (en) * 2016-05-20 2016-08-24 河南东海复合材料有限公司 Process production method of polyurethane section
CN110546181A (en) * 2017-04-18 2019-12-06 科思创德国股份有限公司 Pultruded part, production and use thereof
CN110546181B (en) * 2017-04-18 2022-03-22 科思创德国股份有限公司 Pultruded part, production and use thereof
WO2021021859A1 (en) 2019-08-01 2021-02-04 Dow Global Technologies Llc Polyurethane-based composition
WO2022013182A1 (en) * 2020-07-15 2022-01-20 Covestro Deutschland Ag Polyurethane-reactive system for pultrusion

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