CA2290493C - Method of recycling polyester foam - Google Patents
Method of recycling polyester foam Download PDFInfo
- Publication number
- CA2290493C CA2290493C CA 2290493 CA2290493A CA2290493C CA 2290493 C CA2290493 C CA 2290493C CA 2290493 CA2290493 CA 2290493 CA 2290493 A CA2290493 A CA 2290493A CA 2290493 C CA2290493 C CA 2290493C
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- Canada
- Prior art keywords
- foam
- polyester foam
- pellets
- polyester
- drying
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000006260 foam Substances 0.000 title claims abstract description 96
- 229920000728 polyester Polymers 0.000 title claims description 56
- 238000000034 method Methods 0.000 title claims description 53
- 238000004064 recycling Methods 0.000 title claims description 12
- 239000008188 pellet Substances 0.000 claims abstract description 57
- 239000002274 desiccant Substances 0.000 claims abstract description 7
- 238000001035 drying Methods 0.000 claims description 24
- 239000007787 solid Substances 0.000 claims description 11
- 238000012545 processing Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 abstract description 13
- 229920000139 polyethylene terephthalate Polymers 0.000 description 30
- 239000005020 polyethylene terephthalate Substances 0.000 description 29
- 239000000203 mixture Substances 0.000 description 18
- 239000004604 Blowing Agent Substances 0.000 description 14
- 238000001125 extrusion Methods 0.000 description 14
- 238000010586 diagram Methods 0.000 description 10
- 239000002994 raw material Substances 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 9
- 229920000642 polymer Polymers 0.000 description 9
- 238000005453 pelletization Methods 0.000 description 6
- 229920005989 resin Polymers 0.000 description 6
- 239000011347 resin Substances 0.000 description 6
- 229920001225 polyester resin Polymers 0.000 description 5
- 239000004645 polyester resin Substances 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 238000005187 foaming Methods 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- 238000000280 densification Methods 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 229920006327 polystyrene foam Polymers 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 239000004793 Polystyrene Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 210000004027 cell Anatomy 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- -1 for example Polymers 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229920002223 polystyrene Polymers 0.000 description 2
- 238000004513 sizing Methods 0.000 description 2
- 238000003856 thermoforming Methods 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 210000002421 cell wall Anatomy 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000002817 coal dust Substances 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010981 drying operation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 150000005826 halohydrocarbons Chemical class 0.000 description 1
- 239000008240 homogeneous mixture Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000004620 low density foam Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 238000012667 polymer degradation Methods 0.000 description 1
- 238000005381 potential energy Methods 0.000 description 1
- 230000000135 prohibitive effect Effects 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000032258 transport Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING 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
- B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING 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
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
-
- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
-
- 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
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
- Y10S264/71—Processes of shaping by shrinking
Abstract
PET foam is processed (24) into flakes. The flakes are densified (26) in a pellet mill at between about 300 ~F and about 350 ~F to produce pellets. The pellets are then dried (28) in a desiccant dryer at about 350 ~F for about 6 hours, so that the dew point of the pellets reaches about - 40 ~F. The dried pellets have an intrinsic viscosity about equal to virgin PET and a crystallinity greater than 20 %. This material can be reused (30) as if it were virgin PET.
Description
METHOD OF RECYCLING POLYESTER FOAM
BACKGROUND OF THE INVENTION
Technical Field The present invention generally relates to recycling. More particularly, the present invention relates to a method of recycling foamed polyester.
Background Information In the past, low density polystyrene foam has been found useful in insulation, packaging, beverage cups and food containers. However, polystyrene foam and the extrusion process for making it have been associated with undesirable environmental concerns, regardless of whether those concerns have their origin in fact. In addition, polystyrene products generally have a service temperature limit of about 200° F. Above the service temperature limit, the product will warp and distort. Therefore, there is a general desire for other types of low density foam that are not associated with such concerns. Polyester resins, such as PET (poly(ethylene terephthalate)), exist that could be used without such associated concerns. PET is currently widely used to make many recyclable plastic items, such - as soda bottles.
In the production of polyester foam articles, such as, far example, food service containers, the first step is typically to produce a polyester foam sheet, e.g., by extrusion. This sheet is then thermoformed into the desired article. In doing so, the excess material around the parts (the "skeleton"), scrap sheet and scrap parts are reprocessed and fed back into the extrusion process so that no raw materials are lost.
Early attempts to incorporate the polystyrene foam scrap directly back into the sheet extrusion process had very limited success. Due to the very low bulk density of the scrap, the extruder had to be either very large relative to throughput, or run at very high speeds. Both scenarios resulted in high shear rates leading to excessive polymer degradation and unstable process conditions. This direct incorporation approach, if taken with PET foam regrind, would be fatal.
The high shear rates would so degrade the polymer that the intrinsic viscosity would no longer be sufficient to support foam production.
To solve the problem in conventional foam processes, a separate repelletization line has been incorporated into the overall process. The repelletization line is designed to produce a pellet of high density from scrap, and operates at relatively low throughputs and low shear rates to minimize product degradation. Unfortunately, this operation is not well suited to polyester foam regrind. Polyester is generally more shear sensitive than other foam polymers, such as, for example, polystyrene. However, the greater challenge is drying the regrind before processing.
In PET processing, for example, the polymer must be dried to a dew point of about -40° F. Even ..._ small amounts of water cause excessive ' degradation. The problem is that with the low bulk density of the regrind, the size of the dryer becomes cost prohibitive and in fact is so large that it is difficult to ensure even drying and/or even flow through the dryer.
Thus, a need exists for an improved method of recycling polyester foam.
SU1~IARY OF THE INVENTION
Briefly, the present invention satisfies the need for an improved method of recycling polyester foam by increasing the density of the foam, e.g., by mechanically compressing it. The increased density is accompanied by a molecular surface area greater than that of equal weight unfoamed polyester. The increased surface area results in a significant increase in intrinsic viscosity during subsequent drying, prior to re-use in sheet manufacture.
In accordance with the above, it is an object of the present invention to provide a method of recycling polyester foam.
It is another object of the present invention to provide a method of recycling polyester foam - 25 that requires little or no drying time of the foam before densifying.
It is still another object of the present invention to provide a method of recycling polyester foam that increases the intrinsic viscosity of the polyester foam.
The present invention provides a method of recycling polyester foam.
The method comprises steps of densifying a given type of polyester foam such that when in densified foam, the polyester foam has a molecular surface area greater than that of equal weight densified unfoamed solid polyester of the given type;
and drying the densified polyester foam such that the intrinsic viscosity thereof increases such that the stable foam from dried densified polyester foam is obtainable.
These, and other objects, features and advantages of this invention will become apparent from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified diagram of a pellet mill useful with the present invention.
FIG. 2 is a partial cross-section view of the pellet mill of FIG. 1.
FIG. 3 is a block diagram of the recycling process of the present invention.
FIG. 4 is a block diagram of a production line incorporating the present invention.
FIG. 5 is a block diagram of extrusion equipment useful in the production line of FIG. 4.
BACKGROUND OF THE INVENTION
Technical Field The present invention generally relates to recycling. More particularly, the present invention relates to a method of recycling foamed polyester.
Background Information In the past, low density polystyrene foam has been found useful in insulation, packaging, beverage cups and food containers. However, polystyrene foam and the extrusion process for making it have been associated with undesirable environmental concerns, regardless of whether those concerns have their origin in fact. In addition, polystyrene products generally have a service temperature limit of about 200° F. Above the service temperature limit, the product will warp and distort. Therefore, there is a general desire for other types of low density foam that are not associated with such concerns. Polyester resins, such as PET (poly(ethylene terephthalate)), exist that could be used without such associated concerns. PET is currently widely used to make many recyclable plastic items, such - as soda bottles.
In the production of polyester foam articles, such as, far example, food service containers, the first step is typically to produce a polyester foam sheet, e.g., by extrusion. This sheet is then thermoformed into the desired article. In doing so, the excess material around the parts (the "skeleton"), scrap sheet and scrap parts are reprocessed and fed back into the extrusion process so that no raw materials are lost.
Early attempts to incorporate the polystyrene foam scrap directly back into the sheet extrusion process had very limited success. Due to the very low bulk density of the scrap, the extruder had to be either very large relative to throughput, or run at very high speeds. Both scenarios resulted in high shear rates leading to excessive polymer degradation and unstable process conditions. This direct incorporation approach, if taken with PET foam regrind, would be fatal.
The high shear rates would so degrade the polymer that the intrinsic viscosity would no longer be sufficient to support foam production.
To solve the problem in conventional foam processes, a separate repelletization line has been incorporated into the overall process. The repelletization line is designed to produce a pellet of high density from scrap, and operates at relatively low throughputs and low shear rates to minimize product degradation. Unfortunately, this operation is not well suited to polyester foam regrind. Polyester is generally more shear sensitive than other foam polymers, such as, for example, polystyrene. However, the greater challenge is drying the regrind before processing.
In PET processing, for example, the polymer must be dried to a dew point of about -40° F. Even ..._ small amounts of water cause excessive ' degradation. The problem is that with the low bulk density of the regrind, the size of the dryer becomes cost prohibitive and in fact is so large that it is difficult to ensure even drying and/or even flow through the dryer.
Thus, a need exists for an improved method of recycling polyester foam.
SU1~IARY OF THE INVENTION
Briefly, the present invention satisfies the need for an improved method of recycling polyester foam by increasing the density of the foam, e.g., by mechanically compressing it. The increased density is accompanied by a molecular surface area greater than that of equal weight unfoamed polyester. The increased surface area results in a significant increase in intrinsic viscosity during subsequent drying, prior to re-use in sheet manufacture.
In accordance with the above, it is an object of the present invention to provide a method of recycling polyester foam.
It is another object of the present invention to provide a method of recycling polyester foam - 25 that requires little or no drying time of the foam before densifying.
It is still another object of the present invention to provide a method of recycling polyester foam that increases the intrinsic viscosity of the polyester foam.
The present invention provides a method of recycling polyester foam.
The method comprises steps of densifying a given type of polyester foam such that when in densified foam, the polyester foam has a molecular surface area greater than that of equal weight densified unfoamed solid polyester of the given type;
and drying the densified polyester foam such that the intrinsic viscosity thereof increases such that the stable foam from dried densified polyester foam is obtainable.
These, and other objects, features and advantages of this invention will become apparent from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified diagram of a pellet mill useful with the present invention.
FIG. 2 is a partial cross-section view of the pellet mill of FIG. 1.
FIG. 3 is a block diagram of the recycling process of the present invention.
FIG. 4 is a block diagram of a production line incorporating the present invention.
FIG. 5 is a block diagram of extrusion equipment useful in the production line of FIG. 4.
FIG. 6 is a flow diagram for the operation of the extrusion equipment of FIG. 5.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a simplified diagram of a pellet mill 10 useful with the present invention, and FIG. 2 is a partial cross-sectional view thereof.
Such pellet mills are commercially available in many shapes and sizes from various companies.
Pelletizing machines are used for a number of different purposes, such as, for example, to produce animal feed and to produce coal pellets from coal dust. Pellet mills have also been used in the carpet industry to press polyester fibers together without destroying them.
Pellet mill 10 includes an infeed conveyor 12, chute 13, die 14, rollers 16 and 18, and sizing knife 20. The pellet mill used in conjunction with experiments for the present invention had a die with 1/8 inch diameter holes by 1.5 inches deep. However, it will be understood that other pellet mills, as well as other types of densifying machines could be used.
However, the densifying machine used is preferably able to densify the polyester foam without melting it, such that the densified polyester foam has a molecular surface area greater than that of equal weight unfoamed polyester (e. g., virgin polyester). The polyester foam used was scrap PET
foam from a thermoforming process, however, it will be appreciated that other types of polyester foam could be used, and the foam need not be scrap. The foam to be recycled could also be, for example, used polyester foam containers that have been suitably cleaned or imperfect polyester foam containers rejected during manufacturing. A
general description of the basic operation of pellet mill 10 will now be given.
Infeed conveyor 12 transports ground material (in this case, foam) to a chute 13. In the chute, gravity causes the material to fall into the mill interior. Die 14 compresses the material by the rotation of rollers 16 and 18. That is, the die 24 rotates about its axis as the rollers 16 and 18 rotate about their axes. No other motion occurs.
This action forces the material into holes 22 in the die. Sizing knife 20 is used to cut the compressed material that is forced out, forming pellets.
Prior to the pelletizing investigation, it was expected that the density of the PET foam would increase, at the expense of some intrinsic viscosity. As one skilled in the art will know, "intrinsic viscosity" refers to an indirect measurement of molecular weight. However, the investigation revealed that no loss in intrinsic viscosity was realized due to densification. More surprising was the result that, when the densified PET foam was dried, the intrinsic viscosity increased dramatically.
It has been the experience of various PET
manufacturers that while typical PET resins are incapable of forming a stable foam structure, high molecular weight PET, typified by higher intrinsic viscosities, can produce stable medium and low _7_ density foam products. In the manufacture of PET, it is known that intrinsic viscosity can be increased by a process known as "solid stating."
In the solid stating process, virgin PET pellets are held at temperatures of about 400° F for a period of about 24 hours. Trace amounts of unreacted sites in the PET undergo reaction, yielding an increase in intrinsic viscosity from values of, for example, about 0.7 to 0.8 dl/g to about 1.1 to 1.3 dl/g. Solid stating is a slow process and accounts for the extra cost of producing high intrinsic viscosity polyester. A
drawback to the solid stating process is that an increased intrinsic viscosity is related to particle surface area, which is relatively small for commonly available solid PET pellets.
As will be shown from the example data below, the bulk density of the PET foam scrap was increased from typical values of between about 6 to 10 lb/ft3 to values of between about 30 to 40 lb/ft3. The intrinsic viscosity of the scrap PET
foam was between about 0.8 to 0.85 dl/g, with the densified PET foam showing no loss in intrinsic viscosity. When the PET pellets were dried in a desiccant dryer at 350° F, the intrinsic viscosity increased to about 1.2 dl/g within only six hours time. As one skilled in the art will know, a "desiccant dryer" removes moisture, allowing the material to be dried to a dew point of -40° F or less.
' A detailed description of the preferred embodiment of the present invention will now be given with reference to the block diagram of FIG.
_g_ 3. The following description will be given with respect to scrap PET foam, and using a pellet mill, such as that in FIGS. 1 and 2. However, it will be appreciated that other types of polyester foam could be used, though mixing different types is not preferred, and other densifying machines could be used.
The scrap PET foam is first processed into flakes, by, for example, using a sheet grinder.
Step 24, "PROCESS PET FOAM INTO FLAKES." At this point the flakes could be stored until needed.
The PET foam flakes are then densified into pellets, for example, by using the pellet mill 10 of FIGs. 1 and 2. While the densification of PET
foam can take place at temperatures of between about 200° F and about 400° F, greater densifies with better cohesion of the pellets is achieved at temperatures of between about 275° F and about 375° F, and preferably between about 300° F and about 350° F. In any case, the densification must take place at a temperature below the melting point of the polyester foam used. Step 26, "DENSIFY PET FOAM FLAKES INTO PELLETS." At this point, the pellets could be classified by size, and undersized particles (called "fines") can be removed and run back through the densifying process again such that no material is lost. One way to densify is to compress the flakes, preferably to a bulk density of greater than about 0.3 g/cm3, and most preferably greater than about 0.5 g/cm3. The PET foam pellets are then dried, preferably in a desiccant dryer, at less than about 375° F and preferably about 350° F, for less than about 6 hours and preferably about 4 hours, ~.~. r. ..__._ _ _.
so that the dew point of the pellets reaches about -40° F. After drying, the pellets preferably have an intrinsic viscosity of greater than about 0.95 ' g/dl. Step 28, "DRY PELLETS." Optionally, the dried pellets may then be reused in a thermoforming process, such as, for example, an extrusion process. Step 30, "REUSE PELLETS IN
EXTRUSION PROCESS."
FIG. 4 is a block diagram of an exemplary manufacturing line 32 that the present invention is incorporated into. Grinders 34 and 36 are sheet grinders used to turn reject or off-grade parts (grinder 34) and scrap foam sheet or skeletons (grinder 36) into foam flakes. The flakes are then transferred to a fluff bin 38.
The flakes are then sent via conveyer belt 40 to pellet mill 42 for pelletization. The pellets produced are then sorted by a size classifier 44 according to size, and dried by desiccant dryer 46. After drying, the pellets are ready to be used in, for example, an extrusion process using extruder machinery 48.
Example data will now be presented. Although specific polyester resins are noted, it will be understood that other polyester resins could be used with the present invention.
Example 1 Foam sheet was produced using Shell "TRAYTUF
~ 2928" polyester resin with a hydrocarbon blowing agent. The sheet was ground into a flake form and pelletized by the process disclosed, using a California Pellet Mill with a 12" diameter die.
The die had holes of 1/8" diameter and was 1.5"
thick. The temperature of the die during the pelletization operation ranged from 320°F to 340°F. The pellets were subsequently dried at 350°F for six hours. The following data was collected:
I.V. Crystallinity Density (dl/g) (%) (g/cm3,bulk) Foam Flake 0.834 11.0 Approx. 0.12 Pellets 0.828 30.6 Approx. 0.61 Pellets 1.16 (after drying) Virgin Resin 1.20 (typical) 0.7 (typical) In this example, the pellets produced had a bulk density nearly that of virgin resin and required no additional density increase for subsequent processing into foam sheet. The I.V.
(intrinsic viscosity) of the pellets produced (before drying) was within experimental error of being identical to the I.V. of the flake before processing. In addition, the crystallinity of the pellets was 30.6%, showing a dramatic increase over the flake and therefore eliminating the further need to re-crystallize the pellets before drying. The drying operation yielded an increase in I.V. of over 0.3 dl/g, which is not expected with solid pellets dried for this duration at the stated temperature. The repel (i.e., repelletized polyester foam) produced was further processed back into foam sheet without any apparent negative product affects.
WO 98/52730 PCTlUS98I10213 Example 2 Foam sheet was produced using Shell "TRAYTUF
2928" polyester with a hydrocarbon blowing agent.
The sheet was ground into a flake form and pelletized by the process disclosed, using a California Pellet Mill with a 16" diameter die.
The die had holes of 1/8" diameter and was 1.5°
thick. The temperature of the die during the pelletization operation ranged from 240°F to 270°F.
I.V. Crystallinity Density (dl/g) (%) (g/cm3,bulk) Foam Flake 0.894 9.7 Approx. 0.12 Pellets 0.900 29.2 Approx. 0.32 Foam Sheet (100% Virgin) 0.898 Foam Sheet (50 o Repel) 0. 875 This example again illustrates the increase in crystallinity achieved by the method of pelletizing and again shows that the I.V. of the pellets was, in essence, identical to the starting foam flakes. In this example, a lower operating temperature yielded less density increase, but the pellets could still be adequately extruded without adverse process affects. In addition, the I.V. of the final sheet, produced from 48% repelletized polyester, was compared to sheet produced from 96%
virgin resin (the balance being blowing agent and nucleant). The results indicate that the I.V. of both materials to again be identical, that is, the repelletized polyester showed no deterioration in performance due to previous processing history.
WO 9$/52730 PCT/US98/10213 Example 3 Polyester foam flake was dried using a desiccant dryer and processed on a twin screw extruder at a melt temperature of approximately 520°F. The following data was collected:
I.V. Crystallinity Density (dl/g) ( o ) (g/cm3, bulk) Foam Flake 0.834 11.0 Approx. 0.12 Pellets 0.738 Approx. 0.7 Although the density by this method increased to the value of virgin resin, a substantial drop in I.V. was observed. Although I.V. was not measured after subsequent drying, the material would not support stable foam formation and collapse was observed when extruded with 500 virgin polyester resin. This example is used to illustrate the failure of conventional technology to produce a usable pellet from foam flakes.
It can be seen from the above that the present inventive method increased the intrinsic viscosity of the PET pellets much faster and at lower temperatures than solid stating. A
plausible explanation for this phenomenon is that although the scrap PET foam (after flaking) was compressed to a high bulk density, the individual flakes, while their cell structure was destroyed, still existed. As a result, the pellets at a molecular level have a very large surface area.
This large surface area allows the intrinsic viscosity to rapidly increase at a relatively low temperature. The practical value of this phenomenon is that the intrinsic viscosity of the scrap PET foam can be increased to that of virgin PET resin using the normal drying process. No additional equipment or processing is required and ~ the final product will not deteriorate in performance due to degradation of the scrap or the amount incorporated. An additional benefit is that the material exiting the pellet mill was found to be crystallized, whether or not the material fed to the pellet mill was crystallized.
20 This eliminates the need to crystallize before drying.
With reference to FIGS. 5 and 6, a general tandem extrusion process will now be described that is useful with the present invention. It will be understood, however, that other extrusion processes exist that could also be used, and this is merely one example given in order to put the invention in context.
FIG. 5 is a block diagram of the major portions of extrusion machinery 48 used in a tandem extrusion process beyond dryer 46 in FIG.
4. The major portions include a primary extruder 50, secondary extruder 52 and die 54. One of ordinary skill in the art will understand the operation of the major portions. Generally, melting of the solids from dryer 46 to be extruded (a polymer) and mixing with the blowing agent 56 are accomplished in primary extruder 50. Cooling of the mixture is performed in secondary extruder 52. Finally, the cooled mixture is fed to die 54 for foaming.
FIG. 6 is a flow diagram for the extrusion process of FIG. 5. The dried raw materials, including any additives, are first fed to primary extruder 50 (STEP 58, "FEED RAW MATERIALS"). The raw materials will generally comprise a mixture of virgin polymer, reclaim polymer generated in manufacturing, colorants, stabilizers, nucleators, flame retardants, plasticisers, and possibly other additives. Although ratios of the additives may vary greatly, generally the virgin polymer and reclaim polymer constitute about 900 or more of the solid feed by weight. The raw materials may be fed to primary extruder 50 by volumetric or gravimetric feeders and may or may not use a blender to homogenize the mixture before being fed. Often, the primary extruder is flood fed;
that is, there is a constant supply of raw material directly on the extruder inlet or feed throat, although other types of feeding are practiced.
After the raw materials are fed to primary extruder 50, they are compressed and heated to melt them (STEP 60, "COMPRESS AND HEAT"). After melting the raw materials, the melt is pressurized (STEP 62, "PRESSURIZE MELT"). Typical pressures range from about 150 atm to about 350 atm. After pressurizing the melt, a blowing agent or agents (e. g., hydrocarbons, halohydrocarbons and/or inert gases) is injected into primary extruder 50. The pressure may temporarily be reduced to aid in the injection. The melted raw materials and blowing agent are then mixed to create a homogeneous mixture prior to exiting primary extruder 50 (STEP
64, "MIX WITH BLOWING AGENT"). The mixing can be distributive or dispersive, depending on the solubility of the selected blowing agent.
After injecting the blowing agent and combining with the melted raw materials, the mixture is generally too hot to foam. When the mixture is .too hot, viscosity is low, and if foaming were attempted, the blowing agent would expand the cells within the foam too rapidly, leading to cell wall rupture and foam collapse.
If, on the other hand, the mixture were too cold, the blowing agent would have insufficient potential energy to expand the mixture into a foam. Precise control of the foaming temperature is thus needed to ensure good quality foam.
Cooling of the mixture is accomplished in secondary extruder 52 (STEP 66, "COOL MIXTURE").
The secondary extruder is usually larger than the primary extruder to maximize the amount of surface area for heat transfer. Shear heating of the mixture is minimized through various designs for the secondary extruder screw, which provides continuous surface renewal. Without this renewal, the mixture at the surface of the extruder barrel would freeze and insulate the rest of the mass, which would pass through the secondary extruder without being cooled. Usually, the extruder barrel in the secondary extruder operates at much lower revolutions than that of the primary extruder, to reduce shear heating. The particular screw design used may affect the pressure of the mixture.
The cooled mixture is then delivered to die 54 for foaming iSTEP 68, "FOAM MIXTURE"). The principle purpose of the die is to shape the polymer into a form, while maintaining the pressure to ensure that the blowing agent does not separate from the mixture prematurely. Ideally, the blowing agent remains in the mixture until exiting the die. The design of the die determines the shape/thickness of the extruded foam. After the foam is extruded, any number of finishing equipment technologies may be used to produce the final product.
While several aspects of the present invention have been described and depicted herein, alternative aspects may be effected by those skilled in the art to accomplish the same objectives. Accordingly, it is intended by the appended claims to cover all such alternative aspects as fall within the true spirit and scope of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a simplified diagram of a pellet mill 10 useful with the present invention, and FIG. 2 is a partial cross-sectional view thereof.
Such pellet mills are commercially available in many shapes and sizes from various companies.
Pelletizing machines are used for a number of different purposes, such as, for example, to produce animal feed and to produce coal pellets from coal dust. Pellet mills have also been used in the carpet industry to press polyester fibers together without destroying them.
Pellet mill 10 includes an infeed conveyor 12, chute 13, die 14, rollers 16 and 18, and sizing knife 20. The pellet mill used in conjunction with experiments for the present invention had a die with 1/8 inch diameter holes by 1.5 inches deep. However, it will be understood that other pellet mills, as well as other types of densifying machines could be used.
However, the densifying machine used is preferably able to densify the polyester foam without melting it, such that the densified polyester foam has a molecular surface area greater than that of equal weight unfoamed polyester (e. g., virgin polyester). The polyester foam used was scrap PET
foam from a thermoforming process, however, it will be appreciated that other types of polyester foam could be used, and the foam need not be scrap. The foam to be recycled could also be, for example, used polyester foam containers that have been suitably cleaned or imperfect polyester foam containers rejected during manufacturing. A
general description of the basic operation of pellet mill 10 will now be given.
Infeed conveyor 12 transports ground material (in this case, foam) to a chute 13. In the chute, gravity causes the material to fall into the mill interior. Die 14 compresses the material by the rotation of rollers 16 and 18. That is, the die 24 rotates about its axis as the rollers 16 and 18 rotate about their axes. No other motion occurs.
This action forces the material into holes 22 in the die. Sizing knife 20 is used to cut the compressed material that is forced out, forming pellets.
Prior to the pelletizing investigation, it was expected that the density of the PET foam would increase, at the expense of some intrinsic viscosity. As one skilled in the art will know, "intrinsic viscosity" refers to an indirect measurement of molecular weight. However, the investigation revealed that no loss in intrinsic viscosity was realized due to densification. More surprising was the result that, when the densified PET foam was dried, the intrinsic viscosity increased dramatically.
It has been the experience of various PET
manufacturers that while typical PET resins are incapable of forming a stable foam structure, high molecular weight PET, typified by higher intrinsic viscosities, can produce stable medium and low _7_ density foam products. In the manufacture of PET, it is known that intrinsic viscosity can be increased by a process known as "solid stating."
In the solid stating process, virgin PET pellets are held at temperatures of about 400° F for a period of about 24 hours. Trace amounts of unreacted sites in the PET undergo reaction, yielding an increase in intrinsic viscosity from values of, for example, about 0.7 to 0.8 dl/g to about 1.1 to 1.3 dl/g. Solid stating is a slow process and accounts for the extra cost of producing high intrinsic viscosity polyester. A
drawback to the solid stating process is that an increased intrinsic viscosity is related to particle surface area, which is relatively small for commonly available solid PET pellets.
As will be shown from the example data below, the bulk density of the PET foam scrap was increased from typical values of between about 6 to 10 lb/ft3 to values of between about 30 to 40 lb/ft3. The intrinsic viscosity of the scrap PET
foam was between about 0.8 to 0.85 dl/g, with the densified PET foam showing no loss in intrinsic viscosity. When the PET pellets were dried in a desiccant dryer at 350° F, the intrinsic viscosity increased to about 1.2 dl/g within only six hours time. As one skilled in the art will know, a "desiccant dryer" removes moisture, allowing the material to be dried to a dew point of -40° F or less.
' A detailed description of the preferred embodiment of the present invention will now be given with reference to the block diagram of FIG.
_g_ 3. The following description will be given with respect to scrap PET foam, and using a pellet mill, such as that in FIGS. 1 and 2. However, it will be appreciated that other types of polyester foam could be used, though mixing different types is not preferred, and other densifying machines could be used.
The scrap PET foam is first processed into flakes, by, for example, using a sheet grinder.
Step 24, "PROCESS PET FOAM INTO FLAKES." At this point the flakes could be stored until needed.
The PET foam flakes are then densified into pellets, for example, by using the pellet mill 10 of FIGs. 1 and 2. While the densification of PET
foam can take place at temperatures of between about 200° F and about 400° F, greater densifies with better cohesion of the pellets is achieved at temperatures of between about 275° F and about 375° F, and preferably between about 300° F and about 350° F. In any case, the densification must take place at a temperature below the melting point of the polyester foam used. Step 26, "DENSIFY PET FOAM FLAKES INTO PELLETS." At this point, the pellets could be classified by size, and undersized particles (called "fines") can be removed and run back through the densifying process again such that no material is lost. One way to densify is to compress the flakes, preferably to a bulk density of greater than about 0.3 g/cm3, and most preferably greater than about 0.5 g/cm3. The PET foam pellets are then dried, preferably in a desiccant dryer, at less than about 375° F and preferably about 350° F, for less than about 6 hours and preferably about 4 hours, ~.~. r. ..__._ _ _.
so that the dew point of the pellets reaches about -40° F. After drying, the pellets preferably have an intrinsic viscosity of greater than about 0.95 ' g/dl. Step 28, "DRY PELLETS." Optionally, the dried pellets may then be reused in a thermoforming process, such as, for example, an extrusion process. Step 30, "REUSE PELLETS IN
EXTRUSION PROCESS."
FIG. 4 is a block diagram of an exemplary manufacturing line 32 that the present invention is incorporated into. Grinders 34 and 36 are sheet grinders used to turn reject or off-grade parts (grinder 34) and scrap foam sheet or skeletons (grinder 36) into foam flakes. The flakes are then transferred to a fluff bin 38.
The flakes are then sent via conveyer belt 40 to pellet mill 42 for pelletization. The pellets produced are then sorted by a size classifier 44 according to size, and dried by desiccant dryer 46. After drying, the pellets are ready to be used in, for example, an extrusion process using extruder machinery 48.
Example data will now be presented. Although specific polyester resins are noted, it will be understood that other polyester resins could be used with the present invention.
Example 1 Foam sheet was produced using Shell "TRAYTUF
~ 2928" polyester resin with a hydrocarbon blowing agent. The sheet was ground into a flake form and pelletized by the process disclosed, using a California Pellet Mill with a 12" diameter die.
The die had holes of 1/8" diameter and was 1.5"
thick. The temperature of the die during the pelletization operation ranged from 320°F to 340°F. The pellets were subsequently dried at 350°F for six hours. The following data was collected:
I.V. Crystallinity Density (dl/g) (%) (g/cm3,bulk) Foam Flake 0.834 11.0 Approx. 0.12 Pellets 0.828 30.6 Approx. 0.61 Pellets 1.16 (after drying) Virgin Resin 1.20 (typical) 0.7 (typical) In this example, the pellets produced had a bulk density nearly that of virgin resin and required no additional density increase for subsequent processing into foam sheet. The I.V.
(intrinsic viscosity) of the pellets produced (before drying) was within experimental error of being identical to the I.V. of the flake before processing. In addition, the crystallinity of the pellets was 30.6%, showing a dramatic increase over the flake and therefore eliminating the further need to re-crystallize the pellets before drying. The drying operation yielded an increase in I.V. of over 0.3 dl/g, which is not expected with solid pellets dried for this duration at the stated temperature. The repel (i.e., repelletized polyester foam) produced was further processed back into foam sheet without any apparent negative product affects.
WO 98/52730 PCTlUS98I10213 Example 2 Foam sheet was produced using Shell "TRAYTUF
2928" polyester with a hydrocarbon blowing agent.
The sheet was ground into a flake form and pelletized by the process disclosed, using a California Pellet Mill with a 16" diameter die.
The die had holes of 1/8" diameter and was 1.5°
thick. The temperature of the die during the pelletization operation ranged from 240°F to 270°F.
I.V. Crystallinity Density (dl/g) (%) (g/cm3,bulk) Foam Flake 0.894 9.7 Approx. 0.12 Pellets 0.900 29.2 Approx. 0.32 Foam Sheet (100% Virgin) 0.898 Foam Sheet (50 o Repel) 0. 875 This example again illustrates the increase in crystallinity achieved by the method of pelletizing and again shows that the I.V. of the pellets was, in essence, identical to the starting foam flakes. In this example, a lower operating temperature yielded less density increase, but the pellets could still be adequately extruded without adverse process affects. In addition, the I.V. of the final sheet, produced from 48% repelletized polyester, was compared to sheet produced from 96%
virgin resin (the balance being blowing agent and nucleant). The results indicate that the I.V. of both materials to again be identical, that is, the repelletized polyester showed no deterioration in performance due to previous processing history.
WO 9$/52730 PCT/US98/10213 Example 3 Polyester foam flake was dried using a desiccant dryer and processed on a twin screw extruder at a melt temperature of approximately 520°F. The following data was collected:
I.V. Crystallinity Density (dl/g) ( o ) (g/cm3, bulk) Foam Flake 0.834 11.0 Approx. 0.12 Pellets 0.738 Approx. 0.7 Although the density by this method increased to the value of virgin resin, a substantial drop in I.V. was observed. Although I.V. was not measured after subsequent drying, the material would not support stable foam formation and collapse was observed when extruded with 500 virgin polyester resin. This example is used to illustrate the failure of conventional technology to produce a usable pellet from foam flakes.
It can be seen from the above that the present inventive method increased the intrinsic viscosity of the PET pellets much faster and at lower temperatures than solid stating. A
plausible explanation for this phenomenon is that although the scrap PET foam (after flaking) was compressed to a high bulk density, the individual flakes, while their cell structure was destroyed, still existed. As a result, the pellets at a molecular level have a very large surface area.
This large surface area allows the intrinsic viscosity to rapidly increase at a relatively low temperature. The practical value of this phenomenon is that the intrinsic viscosity of the scrap PET foam can be increased to that of virgin PET resin using the normal drying process. No additional equipment or processing is required and ~ the final product will not deteriorate in performance due to degradation of the scrap or the amount incorporated. An additional benefit is that the material exiting the pellet mill was found to be crystallized, whether or not the material fed to the pellet mill was crystallized.
20 This eliminates the need to crystallize before drying.
With reference to FIGS. 5 and 6, a general tandem extrusion process will now be described that is useful with the present invention. It will be understood, however, that other extrusion processes exist that could also be used, and this is merely one example given in order to put the invention in context.
FIG. 5 is a block diagram of the major portions of extrusion machinery 48 used in a tandem extrusion process beyond dryer 46 in FIG.
4. The major portions include a primary extruder 50, secondary extruder 52 and die 54. One of ordinary skill in the art will understand the operation of the major portions. Generally, melting of the solids from dryer 46 to be extruded (a polymer) and mixing with the blowing agent 56 are accomplished in primary extruder 50. Cooling of the mixture is performed in secondary extruder 52. Finally, the cooled mixture is fed to die 54 for foaming.
FIG. 6 is a flow diagram for the extrusion process of FIG. 5. The dried raw materials, including any additives, are first fed to primary extruder 50 (STEP 58, "FEED RAW MATERIALS"). The raw materials will generally comprise a mixture of virgin polymer, reclaim polymer generated in manufacturing, colorants, stabilizers, nucleators, flame retardants, plasticisers, and possibly other additives. Although ratios of the additives may vary greatly, generally the virgin polymer and reclaim polymer constitute about 900 or more of the solid feed by weight. The raw materials may be fed to primary extruder 50 by volumetric or gravimetric feeders and may or may not use a blender to homogenize the mixture before being fed. Often, the primary extruder is flood fed;
that is, there is a constant supply of raw material directly on the extruder inlet or feed throat, although other types of feeding are practiced.
After the raw materials are fed to primary extruder 50, they are compressed and heated to melt them (STEP 60, "COMPRESS AND HEAT"). After melting the raw materials, the melt is pressurized (STEP 62, "PRESSURIZE MELT"). Typical pressures range from about 150 atm to about 350 atm. After pressurizing the melt, a blowing agent or agents (e. g., hydrocarbons, halohydrocarbons and/or inert gases) is injected into primary extruder 50. The pressure may temporarily be reduced to aid in the injection. The melted raw materials and blowing agent are then mixed to create a homogeneous mixture prior to exiting primary extruder 50 (STEP
64, "MIX WITH BLOWING AGENT"). The mixing can be distributive or dispersive, depending on the solubility of the selected blowing agent.
After injecting the blowing agent and combining with the melted raw materials, the mixture is generally too hot to foam. When the mixture is .too hot, viscosity is low, and if foaming were attempted, the blowing agent would expand the cells within the foam too rapidly, leading to cell wall rupture and foam collapse.
If, on the other hand, the mixture were too cold, the blowing agent would have insufficient potential energy to expand the mixture into a foam. Precise control of the foaming temperature is thus needed to ensure good quality foam.
Cooling of the mixture is accomplished in secondary extruder 52 (STEP 66, "COOL MIXTURE").
The secondary extruder is usually larger than the primary extruder to maximize the amount of surface area for heat transfer. Shear heating of the mixture is minimized through various designs for the secondary extruder screw, which provides continuous surface renewal. Without this renewal, the mixture at the surface of the extruder barrel would freeze and insulate the rest of the mass, which would pass through the secondary extruder without being cooled. Usually, the extruder barrel in the secondary extruder operates at much lower revolutions than that of the primary extruder, to reduce shear heating. The particular screw design used may affect the pressure of the mixture.
The cooled mixture is then delivered to die 54 for foaming iSTEP 68, "FOAM MIXTURE"). The principle purpose of the die is to shape the polymer into a form, while maintaining the pressure to ensure that the blowing agent does not separate from the mixture prematurely. Ideally, the blowing agent remains in the mixture until exiting the die. The design of the die determines the shape/thickness of the extruded foam. After the foam is extruded, any number of finishing equipment technologies may be used to produce the final product.
While several aspects of the present invention have been described and depicted herein, alternative aspects may be effected by those skilled in the art to accomplish the same objectives. Accordingly, it is intended by the appended claims to cover all such alternative aspects as fall within the true spirit and scope of the invention.
Claims (17)
1. A method of recycling polyester foam, comprising steps of:
densifying (26) a given type of polyester foam such that when in densified form, the polyester foam has a molecular surface area greater than that of equal weight densified unfoamed solid polyester of the given type; and drying (28) the densified polyester foam such that the intrinsic viscosity thereof increases such that the stable foam from dried densified polyester foam is obtainable.
densifying (26) a given type of polyester foam such that when in densified form, the polyester foam has a molecular surface area greater than that of equal weight densified unfoamed solid polyester of the given type; and drying (28) the densified polyester foam such that the intrinsic viscosity thereof increases such that the stable foam from dried densified polyester foam is obtainable.
2. The method of claim 1 further comprising, prior to the step of densifying, the step of processing (24) the polyester foam to create a plurality of polyester foam flakes.
3. The method of claim 2, wherein the plurality of polyester foam flakes and the densified polyester foam have about the same intrinsic viscosity.
4. The method of claim 2, wherein the step of densifying comprises densifying the plurality of polyester foam flakes at a temperature of between 200° F
and about 400°F.
and about 400°F.
5. The method of claim 4, wherein the temperature is between about 275°F and about 375°F.
6. The method of claim 5, wherein the temperature is between about 300° F and about 350°
F.
F.
7. The method of claim 2, wherein the step of densifying comprises compressing the plurality of polyester foam flakes into a plurality of pellets, and wherein the step of drying comprises drying the plurality of pellets.
8. The method of claim 7, wherein the step of drying comprises drying the plurality of pellets to a dew point of about -40° F.
9. The method of claim 8, wherein the step of drying comprises drying the plurality of pellets at a temperature of less than about 375° F
for less than about 6 hours.
for less than about 6 hours.
10. The method of claim 9, wherein the step of drying comprises drying the plurality of pellets in a desiccant dryer.
11. The method of claim 9, wherein the temperature is about 350° F.
12. The method of claim 1 further comprising the step of extruding (30) polyester foam sheet from the dried densified polyester foam, whereby the polyester foam is recycled.
13. The method of claim 1, wherein the step of densifying comprises compressing the polyester foam to a bulk density greater than about 0.3 g/cm3.
14. The method of claims 13, wherein the bulk density is greater than about 0.5 g/cm3.
15. The method of claim 1, wherein the polyester foam comprises PET, wherein the step of densifying comprises densifying the PET, and wherein the step of drying comprises drying the densified PET.
16. The method of claim 1, wherein the densified polyester foam has a crystallinity of at least 20%.
17. The method of claim 1, wherein the dried densified polyester foam has an intrinsic viscosity of greater than 0.95 g/d1.
* * * * *
* * * * *
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/859,202 US6130261A (en) | 1997-05-20 | 1997-05-20 | Method of recycling polyester foam |
US08/859,202 | 1997-05-20 | ||
PCT/US1998/010213 WO1998052730A1 (en) | 1997-05-20 | 1998-05-19 | Method of recycling polyester foam |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2290493A1 CA2290493A1 (en) | 1998-11-26 |
CA2290493C true CA2290493C (en) | 2001-08-14 |
Family
ID=25330334
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA 2290493 Expired - Fee Related CA2290493C (en) | 1997-05-20 | 1998-05-19 | Method of recycling polyester foam |
Country Status (5)
Country | Link |
---|---|
US (1) | US6130261A (en) |
EP (1) | EP1066140A1 (en) |
AU (1) | AU7497598A (en) |
CA (1) | CA2290493C (en) |
WO (1) | WO1998052730A1 (en) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6284808B1 (en) * | 1997-02-03 | 2001-09-04 | Illinois Tool Works Inc. | Inline solid state polymerization of PET flakes for manufacturing plastic strap by removing non-crystalline materials from recycled PET |
US7951449B2 (en) | 2002-06-27 | 2011-05-31 | Wenguang Ma | Polyester core materials and structural sandwich composites thereof |
EP1636009A4 (en) | 2003-05-17 | 2010-12-22 | Gregory L Branch | Method of producing thermoformed articles from gas impregnated polymer |
US9410026B1 (en) | 2009-05-22 | 2016-08-09 | Columbia Insurance Company | Rebond polyurethane foam comprising reclaimed carpet material and methods for the manufacture of same |
US9724852B1 (en) | 2009-05-22 | 2017-08-08 | Columbia Insurance Company | High density composites comprising reclaimed carpet material |
EP2383309B2 (en) | 2010-04-29 | 2019-11-20 | Armacell Enterprise GmbH & Co. KG | Cellular polyester made of post-consumer flakes and the use of products made thereof |
US11111350B2 (en) | 2017-10-26 | 2021-09-07 | Wrh Technology, Llc | Method for production of low density polyester foam and articles made thereof utilizing low I.V. polyester feedstock |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3607999A (en) * | 1969-06-19 | 1971-09-21 | Dow Chemical Co | Foam scrap recovery and apparatus |
US3746610A (en) * | 1971-01-29 | 1973-07-17 | Du Pont | Composite boards prepared from foam sheeting |
DE3037011C2 (en) * | 1980-10-01 | 1983-12-01 | Dynamit Nobel Ag, 5210 Troisdorf | Method and device for the continuous production of a sheet-like layer material from foam particles |
CH678184A5 (en) * | 1989-03-09 | 1991-08-15 | Tisslan S A | |
DE3923054A1 (en) * | 1989-07-13 | 1991-01-24 | Huels Troisdorf | METHOD FOR PRODUCING A PANEL OR SHEET-SHAPED LAYER MATERIAL FROM THERMOPLASTIC FOAM |
US5286321A (en) * | 1990-12-21 | 1994-02-15 | Free-Flow Packaging Corporation | System and method for densifying expanded plastic foam materials |
US5695133A (en) * | 1996-06-19 | 1997-12-09 | Nova Chemicals (International) S.A. | Thermoplastic washer/recycler |
-
1997
- 1997-05-20 US US08/859,202 patent/US6130261A/en not_active Expired - Fee Related
-
1998
- 1998-05-19 EP EP19980922423 patent/EP1066140A1/en not_active Withdrawn
- 1998-05-19 WO PCT/US1998/010213 patent/WO1998052730A1/en not_active Application Discontinuation
- 1998-05-19 AU AU74975/98A patent/AU7497598A/en not_active Abandoned
- 1998-05-19 CA CA 2290493 patent/CA2290493C/en not_active Expired - Fee Related
Also Published As
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EP1066140A1 (en) | 2001-01-10 |
US6130261A (en) | 2000-10-10 |
CA2290493A1 (en) | 1998-11-26 |
AU7497598A (en) | 1998-12-11 |
WO1998052730A1 (en) | 1998-11-26 |
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