(19)
(11)EP 3 501 785 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
26.06.2019 Bulletin 2019/26

(21)Application number: 19154277.8

(22)Date of filing:  17.11.2015
(51)International Patent Classification (IPC): 
B29C 48/42(2019.01)
B29B 17/00(2006.01)
B29C 48/60(2019.01)
B29K 67/00(2006.01)
B29C 48/76(2019.01)
B29C 48/00(2019.01)
B29L 31/00(2006.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 18.11.2014 US 201414546819

(62)Application number of the earlier application in accordance with Art. 76 EPC:
15860981.8 / 3221119

(71)Applicant: Mohawk Industries Inc.
Marietta, GA 30062 (US)

(72)Inventor:
  • CLARK, Thomas R.
    Chattanooga, TN 37415 (US)

(74)Representative: Van Steenlandt, Wim August Maria 
Mohawk International Services, BVBA Patent department Ooigemstraat 3
8710 Wielsbeke
8710 Wielsbeke (BE)

 
Remarks:
This application was filed on 29-01-2019 as a divisional application to the application mentioned under INID code 62.
 


(54)SYSTEMS AND METHODS FOR MANUFACTURING BULKED CONTINUOUS FILAMENT


(57) A method of manufacturing bulked continuous carpet filament which, in various embodiments, comprises: (A) grinding recycled PET bottles into a group of flakes; (B) washing the flakes; (C) identifying and removing impurities, including impure flakes, from the group of flakes; (D) passing the group of flakes through an expanded surface area extruder while maintaining a pressure within the expanded surface area extruder below about 25 millibars; (E) passing the resulting polymer melt through at least one filter having a micron rating of less than about 50 microns; and (F) forming the recycled polymer into bulked continuous carpet filament that consists essentially of recycled PET.




Description

BACKGROUND



[0001] Because pure virgin PET polymer is more expensive than recycled PET polymer, and because of the environmental benefits associated with using recycled polymer, it would be desirable to be able to produce bulked continuous carpet filament from 100% recycled PET polymer (e.g., PET polymer from post-consumer PET bottles).

SUMMARY



[0002] A method of manufacturing bulked continuous carpet filament, according to various embodiments, comprises: (A) providing a first extruder comprising a first extruder inlet, a first extruder outlet and a pressure regulation system that is adapted to maintain a pressure within the first extruder below about 18 millibars; (B) using the pressure regulation system to reduce a pressure within the first extruder to below about 18 millibars; (C) while maintaining the pressure within the first extruder below about 18 millibars, passing a plurality of flakes of recycled PET through the first extruder via the first extruder inlet to at least partially melt the plurality of flakes into a polymer melt; (D) providing at least one spinning machine comprising at least one spinning machine inlet, wherein the at least one spinning machine inlet is substantially directly coupled to the first extruder outlet; (E) after the step of passing the polymer melt through the first extruder, substantially immediately forming the polymer melt into bulked continuous carpet filament using the at least one spinning machine.

[0003] A method of manufacturing bulked continuous carpet filament, according to various embodiments: (A) providing an expanded surface area extruder, wherein the expanded surface area extruder defines an expanded surface area extruder inlet and an expanded surface area extruder outlet; (B) providing a pressure regulation system configured to reduce a pressure within at least a portion of the expanded surface area extruder below about 12 mbar; (C) providing a spinning machine defining a spinning machine inlet, wherein the spinning machine inlet is operatively coupled to the expanded surface area extruder outlet; (D) using the pressure regulation system to reduce the pressure within the at least a portion of the expanded surface area extruder below about 12 mbar; (E) passing a plurality of flakes consisting essentially of PET flakes through the expanded surface area extruder via the expanded surface area extruder inlet to at least partially melt the plurality of flakes to form a polymer melt; and (F) substantially immediately after passing the plurality of flakes through the expanded surface area extruder, using the spinning machine to form the polymer melt into bulked continuous carpet filament.

[0004] A method of manufacturing carpet filament, in particular embodiments, comprises the steps of: (A) grinding a plurality of recycled PET bottles into a group of polymer flakes; (B) washing the group of polymer flakes to remove at least a portion of one or more contaminants from a surface of the flakes, the group of flakes comprising a first plurality of flakes that consist essentially of PET and a second plurality of flakes that do not consist essentially of PET; (C) after the step of washing the first plurality of flakes: (i) scanning the washed group of flakes to identify the second plurality of flakes, and(ii) separating the second plurality of flakes from the first plurality of flakes; (D) providing an expanded surface area extruder having an extruder inlet and an extruder outlet; (E) providing a pressure regulation system configured to reduce a pressure within the expanded surface area extruder between about 0 mbar and about 5 mbar; (F) providing a spinning machine having a spinning machine inlet, wherein the spinning machine inlet is directly coupled to the extruder outlet; (G) using the pressure regulation system to reduce the pressure within the expanded surface area extruder between about 0 mbar and about 5 mbar; (H) while maintaining the pressure within the expanded surface area extruder between about 0 mbar about 5 mbar, passing the second plurality of flakes through the expanded surface area extruder via the fist inlet; (I) melting the second plurality of flakes using the expanded surface area extruder to produce a polymer melt; and (J) substantially immediately after passing the second plurality of flakes through the expanded surface area extruder, spinning the polymer melt into bulked continuous carpet filament using the spinning machine.

BRIEF DESCRIPTION OF THE DRAWINGS



[0005] Having described various embodiments in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

FIG. 1 depicts a process flow, according to a particular embodiment, for manufacturing bulked continuous carpet filament.

FIG. 2 is a perspective view of an MRS extruder that is suitable for use in the process of FIG. 1.

FIG. 3 is a cross-sectional view of an exemplary MRS section of the MRS extruder of FIG. 2.

FIG. 4 depicts a process flow depicting the flow of polymer through an MRS extruder and filtration system according to a particular embodiment.

FIG. 5 is a high-level flow chart of a method, according to various embodiments, of manufacturing bulked continuous carpet filament.


DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS



[0006] Various embodiments will now be described in greater detail. It should be understood that the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

I. Overview



[0007] New processes for making fiber from recycled polymer (e.g., recycled PET polymer) are described below. In various embodiments, this new process: (1) is more effective than earlier processes in removing contaminates and water from the recycled polymer; and/or (2) does not require the polymer to be melted and cooled as many times as in earlier processes. In at least one embodiment, the improved process results in a recycled PET polymer having a polymer quality that is high enough that the PET polymer may be used in producing bulked continuous carpet filament from 100% recycled PET content (e.g., 100% from PET obtained from previously used PET bottles). In particular embodiments, the recycled PET polymer has an intrinsic viscosity of at least about 0.79 dL/g (e.g., of between about 0.79 dL/g and about 1.00 dL/g).

II. More Detailed Discussion



[0008] A BCF (bulked continuous filament) manufacturing process, according to a particular embodiment, may generally be broken down into three steps: (1) preparing flakes of PET polymer from post-consumer bottles for use in the process; (2) passing the flakes through an extruder that melts the flakes and purifies the resulting PET polymer; and (3) feeding the purified polymer into a spinning machine that turns the polymer into filament for use in manufacturing carpets. These three steps are described in greater detail below.

STEP 1: Preparing Flakes of PET Polymer from Post-Consumer Bottles



[0009] In a particular embodiment, the step of preparing flakes of PET polymer from post-consumer bottles comprises: (A) sorting post-consumer PET bottles and grinding the bottles into flakes; (B) washing the flakes; and (C) identifying and removing any impurities or impure flakes.

A. Sorting Post-Consumer PET bottles and Grinding the Bottles into Flakes



[0010] In particular embodiments, bales of clear and mixed colored recycled post-consumer (e.g., "curbside") PET bottles (or other containers) obtained from various recycling facilities make-up the post-consumer PET containers for use in the process. In other embodiments, the source of the post-consumer PET containers may be returned 'deposit' bottles (e.g., PET bottles whose price includes a deposit that is returned to a customer when the customer returns the bottle after consuming the bottle's contents). The curbside or returned "post-consumer" or "recycled" containers may contain a small level of non-PET contaminates. The contaminants in the containers may include, for example, non-PET polymeric contaminants (e.g., PVC, PLA, PP, PE, PS, PA, etc.), metal (e.g., ferrous and non-ferrous metal), paper, cardboard, sand, glass or other unwanted materials that may find their way into the collection of recycled PET. The non-PET contaminants may be removed from the desired PET components, for example, through one or more of the various processes described below.

[0011] In particular embodiments, smaller components and debris (e.g., components and debris greater than 2 inches in size) are removed from the whole bottles via a rotating trammel. Various metal removal magnets and eddy current systems may be incorporated into the process to remove any metal contaminants. Near Infra-Red optical sorting equipment such as the NRT Multi Sort IR machine from Bulk Handling Systems Company of Eugene, Oregon, or the Spyder IR machine from National Recovery Technologies of Nashville, Tennessee, may be utilized to remove any loose polymeric contaminants that may be mixed in with the PET flakes (e.g., PVC, PLA, PP, PE, PS, and PA). Additionally, automated X-ray sorting equipment such as a VINYLCYCLE machine from National Recovery Technologies of Nashville, Tennessee may be utilized to remove remaining PVC contaminants.

[0012] In particular embodiments, a binary segregation of the clear materials from the colored materials is achieved using automated color sorting equipment equipped with a camera detection system (e.g., an Multisort ES machine from National Recovery Technologies of Nashville, Tennessee). In various embodiments, manual sorters are stationed at various points on the line to remove contaminants not removed by the sorter and any colored bottles. In particular embodiments, the sorted material is taken through a granulation step (e.g., using a 50B Granulator machine from Cumberland Engineering Corporation of New Berlin, Wisconsin) to size reduce (e.g., grind) the bottles down to a size of less than one half of an inch. In various embodiments, the bottle labels are removed from the resultant "dirty flake" (e.g., the PET flakes formed during the granulation step) via an air separation system prior to entering the wash process.

B. Washing the Flakes



[0013] In particular embodiments, the "dirty flake" is then mixed into a series of wash tanks. As part of the wash process, in various embodiments, an aqueous density separation is utilized to separate the olefin bottle caps (which may, for example, be present in the "dirty flake" as remnants from recycled PET bottles) from the higher specific gravity PET flakes. In particular embodiments, the flakes are washed in a heated caustic bath to about 190 degrees Fahrenheit. In particular embodiments, the caustic bath is maintained at a concentration of between about 0.6% and about 1.2% sodium hydroxide. In various embodiments, soap surfactants as well as defoaming agents are added to the caustic bath, for example, to further increase the separation and cleaning of the flakes. A double rinse system then washes the caustic from the flakes.

[0014] In various embodiments, the flake is centrifugally dewatered and then dried with hot air to at least substantially remove any surface moisture. The resultant "clean flake" is then processed through an electrostatic separation system (e.g., an electrostatic separator from Carpco, Inc. of Jacksonville, Florida) and a flake metal detection system (e.g., an MSS Metal Sorting System) to further remove any metal contaminants that remain in the flake. In particular embodiments, an air separation step removes any remaining label from the clean flake. In various embodiments, the flake is then taken through a flake color sorting step (e.g., using an OPTIMIX machine from TSM Control Systems of Dundalk, Ireland) to remove any remaining color contaminants remaining in the flake. In various embodiments, an electro-optical flake sorter based at least in part on Raman technology (e.g., a Powersort 200 from Unisensor Sensorsysteme GmbH of Karlsruhe, Germany) performs the final polymer separation to remove any non-PET polymers remaining in the flake. This step may also further remove any remaining metal contaminants and color contaminants.

[0015] In various embodiments, the combination of these steps delivers substantially clean (e.g., clean) PET bottle flake comprising less than about 50 parts per million PVC (e.g., 25 ppm PVC) and less than about 15 parts per million metals for use in the downstream extrusion process described below.

C. Identifying and Removing Impurities and Impure Flakes



[0016] In particular embodiments, after the flakes are washed, they are fed down a conveyor and scanned with a high-speed laser system 300. In various embodiments, particular lasers that make up the high-speed laser system 300 are configured to detect the presence of particular contaminates (e.g., PVC or Aluminum). Flakes that are identified as not consisting essentially of PET may be blown from the main stream of flakes with air jets. In various embodiments, the resulting level of non-PET flakes is less than 25 ppm.

[0017] In various embodiments, the system is adapted to ensure that the PET polymer being processed into filament is substantially free of water (e.g., entirely free of water). In a particular embodiment, the flakes are placed into a pre-conditioner for between about 20 and about 40 minutes (e.g., about 30 minutes) during which the pre-conditioner blows the surface water off of the flakes. In particular embodiments, interstitial water remains within the flakes. In various embodiments, these "wet" flakes (e.g., flakes comprising interstitial water) may then be fed into an extruder (e.g., as described in Step 2 below), which includes a vacuum setup designed to remove - among other things - the interstitial water that remains present in the flakes following the quick-drying process described above.

STEP 2: Using an Extrusion System to Melt and Purify PET Flakes



[0018] In particular embodiments, an extruder is used to turn the wet flakes described above into a molten recycled PET polymer and to perform a number of purification processes to prepare the polymer to be turned into BCF for carpet. As noted above, in various embodiments, after STEP 1 is complete, the recycled PET polymer flakes are wet (e.g., surface water is substantially removed (e.g., fully removed) from the flakes, but interstitial water remains in the flakes). In particular embodiments, these wet flakes are fed into a Multiple Rotating Screw ("MRS") extruder 400. In other embodiments, the wet flakes are fed into any other suitable extruder (e.g., a twin screw extruder, a multiple screw extruder, a planetary extruder, or any other suitable extrusion system). An exemplary MRS Extruder 400 is shown in Figures 2 and 3. A particular example of such an MRS extruder is described in U.S. Published Patent Application 2005/0047267, entitled "Extruder for Producing Molten Plastic Materials", which was published on March 3, 2005, and which is hereby incorporated herein by reference.

[0019] As may be understood from this figure, in particular embodiments, the MRS extruder includes a first single-screw extruder section 410 for feeding material into an MRS section 420 and a second single-screw extruder section 440 for transporting material away from the MRS section.

[0020] In various embodiments, the wet flakes are fed directly into the MRS extruder 400 substantially immediately (e.g., immediately) following the washing step described above (e.g., without drying the flakes or allowing the flakes to dry). In particular embodiments, a system that feeds the wet flakes directly into the MRS Extruder 400 substantially immediately (e.g., immediately) following the washing step described above may consume about 20% less energy than a system that substantially fully pre-dries the flakes before extrusion (e.g., a system that pre-dries the flakes by passing hot air over the wet flakes for a prolonged period of time). In various embodiments, a system that feeds the wet flakes directly into the MRS Extruder 400 substantially immediately (e.g., immediately) following the washing step described above avoids the need to wait a period of time (e.g., up to eight hours) generally required to fully dry the flakes (e.g., remove all of the surface and interstitial water from the flakes).

[0021] Figure 4 depicts a process flow that illustrates the various processes performed by the MRS Extruder 400 in a particular embodiment. In the embodiment shown in this figure, the wet flakes are first fed through the MRS extruder's first single-screw extruder section 410, which may, for example, generate sufficient heat (e.g., via shearing) to at least substantially melt (e.g., melt) the wet flakes.

[0022] The resultant polymer melt (e.g., comprising the melted flakes), in various embodiments, is then fed into the extruder's MRS section 420, in which the extruder separates the melt flow into a plurality of different streams (e.g., 4, 6, 8, or more streams) through a plurality of open chambers. Figure 3 shows a detailed cutaway view of an MRS Section 420 according to a particular embodiment. In particular embodiments, such as the embodiment shown in this figure, the MRS Section 420 separates the melt flow into eight different streams, which are subsequently fed through eight satellite screws 425A-H. As may be understood from Figure 2, in particular embodiments, these satellite screws are substantially parallel (e.g., parallel) to one other and to a primary screw axis of the MRS Machine 400.

[0023] In the MRS section 420, in various embodiments, the satellite screws 425A-H may, for example, rotate faster than (e.g., about four times faster than) in previous systems. As shown in Figure 3, in particular embodiments: (1) the satellite screws 425A-H are arranged within a single screw drum 428 that is mounted to rotate about its central axis; and (2) the satellite screws 425A-H are configured to rotate in a direction that is opposite to the direction in which the single screw drum rotates 428. In various other embodiments, the satellite screws 425A-H and the single screw drum 428 rotate in the same direction. In particular embodiments, the rotation of the satellite screws 425A-H is driven by a ring gear. Also, in various embodiments, the single screw drum 428 rotates about four times faster than each individual satellite screw 425A-H. In certain embodiments, the satellite screws 425A-H rotate at substantially similar (e.g., the same) speeds.

[0024] In various embodiments, as may be understood from Figure 4, the satellite screws 425A-H are housed within respective extruder barrels, which may, for example be about 30% open to the outer chamber of the MRS section 420. In particular embodiments, the rotation of the satellite screws 425A-H and single screw drum 428 increases the surface exchange of the polymer melt (e.g., exposes more surface area of the melted polymer to the open chamber than in previous systems). In various embodiments, the MRS section 420 creates a melt surface area that is, for example, between about twenty and about thirty times greater than the melt surface area created by a co-rotating twin screw extruder. In a particular embodiment, the MRS section 420 creates a melt surface area that is, for example, about twenty five times greater than the melt surface area created by a co-rotating twin screw extruder

[0025] In various embodiments, the MRS extruder's MRS Section 420 is fitted with a Vacuum Pump 430 that is attached to a vacuum attachment portion 422 of the MRS section 420 so that the Vacuum Pump 430 is in communication with the interior of the MRS section via a suitable opening 424 in the MRS section's housing. In still other embodiments, the MRS Section 420 is fitted with a series of Vacuum Pumps. In particular embodiments, the Vacuum Pump 430 is configured to reduce the pressure within the interior of the MRS Section 420 to a pressure that is between about 0.5 millibars and about 5 millibars. In particular embodiments, the Vacuum Pump 430 is configured to reduce the pressure in the MRS Section 420 to less than about 1.5 millibars (e.g., about 1 millibar or less). The low-pressure vacuum created by the Vacuum Pump 430 in the MRS Section 420 may remove, for example: (1) volatile organics present in the melted polymer as the melted polymer passes through the MRS Section 420; and/or (2) at least a portion of any interstitial water that was present in the wet flakes when the wet flakes entered the MRS Extruder 400. In various embodiments, the low-pressure vacuum removes substantially all (e.g., all) of the water and contaminants from the polymer stream.

[0026] In a particular example, the Vacuum Pump 430 comprises three mechanical lobe vacuum pumps (e.g., arranged in series) to reduce the pressure in the chamber to a suitable level (e.g., to a pressure of about 1.0 millibar). In other embodiments, rather than the three mechanical lobe vacuum pump arrangement discussed above, the Vacuum Pump 430 includes a jet vacuum pump fit to the MRS extruder. In various embodiments, the jet vacuum pump is configured to achieve about 1 millibar of pressure in the interior of the MRS section 420 and about the same results described above regarding a resulting intrinsic viscosity of the polymer melt. In various embodiments, using a jet vacuum pump can be advantageous because jet vacuum pumps are steam powered and therefore substantially self-cleaning (e.g., self-cleaning), thereby reducing the maintenance required in comparison to mechanical lobe pumps (which may, for example, require repeated cleaning due to volatiles coming off and condensing on the lobes of the pump). In a particular embodiment, the Vacuum Pump 430 is a jet vacuum pump is made by Arpuma GmbH of Bergheim, Germany.

[0027] In particular embodiments, after the molten polymer is run the through the multi-stream MRS Section 420, the streams of molten polymer are recombined and flow into the MRS extruder's second single screw section 440. In various embodiments, the single stream of molten polymer is next run through a filtration system 450 that includes at least one filter.

[0028] In a particular embodiment, the filtration system 450 includes two levels of filtration (e.g., a 40 micron screen filter followed by a 25 micron screen filter). Although, in various embodiments, water and volatile organic impurities are removed during the vacuum process as discussed above, particulate contaminates such as, for example, aluminum particles, sand, dirt, and other contaminants may remain in the polymer melt. Thus, this filtration step may be advantageous in removing particulate contaminates (e.g., particulate contaminates that were not removed in the MRS Section 420).

[0029] In particular embodiments, a viscosity sensor 460 (see Figure 4) is used to sense the melt viscosity of the molten polymer stream following its passage through the filtration system 450. In various embodiments, the viscosity sensor 460, measures the melt viscosity of the stream, for example, by measuring the stream's pressure drop across a known area. In particular embodiments, in response to measuring an intrinsic viscosity of the stream that is below a predetermined level (e.g., below about 0.8 g/dL), the system may: (1) discard the portion of the stream with low intrinsic viscosity; and/or (2) lower the pressure in the MRS Section 420 in order to achieve a higher intrinsic viscosity in the polymer melt. In particular embodiments, decreasing the pressure in the MRS Section 420 is executed in a substantially automated manner (e.g., automatically) using the viscosity sensor in a computer-controlled feedback control loop with the vacuum section 430.

[0030] In particular embodiments, removing the water and contaminates from the polymer improves the intrinsic viscosity of the recycled PET polymer by allowing polymer chains in the polymer to reconnect and extend the chain length. In particular embodiments, following its passage through the MRS Section 420 with its attached Vacuum Pump 430, the recycled polymer melt has an intrinsic viscosity of at least about 0.79 dL/g (e.g., of between about 0.79 dL/g and about 1.00 dL/g). In particular embodiments, passage through the low pressure MRS Section 420 purifies the recycled polymer melt (e.g., by removing the contaminants and interstitial water) and makes the recycled polymer substantially structurally similar to (e.g., structurally the same as) pure virgin PET polymer. In particular embodiments, the water removed by the vacuum includes both water from the wash water used to clean the recycled PET bottles as described above, as well as from unreacted water generated by the melting of the PET polymer in the single screw heater 410 (e.g., interstitial water). In particular embodiments, the majority of water present in the polymer is wash water, but some percentage may be unreacted water.

[0031] In particular embodiments, the resulting polymer is a recycled PET polymer (e.g., obtained 100% from post-consumer PET products, such as PET bottles or containers) having a polymer quality that is suitable for use in producing PET carpet filament using substantially only (e.g., only) PET from recycled PET products.

Step 3: Purified PET Polymer Fed into Spinning Machine to be Turned into Carpet Yarn



[0032] In particular embodiments, after the recycled PET polymer has been extruded and purified by the above-described extrusion process, the resulting molten recycled PET polymer is fed directly into a BCF (or "spinning") machine 500 that is configured to turn the molten polymer into bulked continuous filament. For example, in various embodiments, the output of the MRS extruder 400 is connected substantially directly (e.g., directly) to the input of the spinning machine 500 so that molten polymer from the extruder is fed directly into the spinning machine 500. This process may be advantageous because molten polymer may, in certain embodiments, not need to be cooled into pellets after extrusion (as it would need to be if the recycled polymer were being mixed with virgin PET polymer). In particular embodiments, not cooling the recycled molten polymer into pellets serves to avoid potential chain scission in the polymer that might lower the polymer's intrinsic viscosity.

[0033] In particular embodiments, the spinning machine 500 extrudes molten polymer through small holes in a spinneret in order to produce carpet yarn filament from the polymer. In particular embodiments, the molten recycled PET polymer cools after leaving the spinneret. The carpet yarn is then taken up by rollers and ultimately turned into filaments that are used to produce carpet. In various embodiments, the carpet yarn produced by the spinning machine 500 may have a tenacity between about 3 gram-force per unit denier (gf/den) and about 9 gf/den. In particular embodiments, the resulting carpet yarn has a tenacity of at least about 3 gf/den.

[0034] In particular embodiments, the spinning machine 500 used in the process described above is the Sytec One spinning machine manufactured by Oerlika Neumag of Neumuenster, Germany. The Sytec One machine may be especially adapted for hard-to-run fibers, such as nylon or solution-dyed fibers, where the filaments are prone to breakage during processing. In various embodiments, the Sytec One machine keeps the runs downstream of the spinneret as straight as possible, uses only one threadline, and is designed to be quick to rethread when there are filament breaks.

[0035] Although the example described above describes using the Sytec One spinning machine to produce carpet yarn filament from the polymer, it should be understood that any other suitable spinning machine maybe used. Such spinning machines may include, for example, any suitable one-threadline or three-threadline spinning machine made by Oerlika Neumag of Neumuenster, Germany or any other company.

[0036] In various embodiments, the improved strength of the recycled PET polymer generated using the process above allows it to be run at higher speeds through the spinning machine 500 than would be possible using pure virgin PET polymer. This may allow for higher processing speeds than are possible when using virgin PET polymer.

Summary of Exemplary Process



[0037] Figure 5 provides a high-level summary of the method of manufacturing bulked continuous filament described above. As shown in the figure, the method begins at Step 602, where recycled PET bottles are ground into a group of flakes. Next, at Step 604, the group of flakes is washed to remove contaminants from the flakes' respective outer surfaces. Next, at Step 606, the group of flakes is scanned (e.g., using one or more of the methods discussed above) to identify impurities, including impure flakes. These impurities, and impure flakes, are then removed from the group of flakes.

[0038] Next, at Step 608, the group of flakes is passed through an MRS extruder while maintaining the pressure within an MRS portion of the extruder below about 1.5 millibars. At Step 610, the resulting polymer melt is passed through at least one filter having a micron rating of less than about 50 microns. Finally, at Step 612, the recycled polymer is formed into bulked continuous carpet filament, which may be used in producing carpet. The method then ends at Step 614.

Alternative Embodiments



[0039] In particular embodiments, the system may comprise alternative components or perform alternative processes in order to produce substantially continuous BCF from 100% recycled PET, or other recycled polymer. Exemplary alternatives are discussed below.

Non-MRS Extrusion System



[0040] In particular embodiments, the process may utilize a polymer flow extrusion system other than the MRS Extruder described above. The alternative extrusion system may include for example, a twin screw extruder, a multiple screw extruder, a planetary extruder, or any other suitable extrusion system. In a particular embodiment, the process may include a plurality of any combination of any suitable conical screw extruders (e.g., four twin screw extruders, three multiple screw extruders, etc.).

Making Carpet Yarn from 100% Recycled Carpet



[0041] In particular embodiments, the process described above may be adapted for processing and preparing old carpet (or any other suitable post-consumer product) to produce new carpet yarn comprising 100% recycled carpet. In such embodiments, the process would begin by grinding and washing recycled carpet rather than recycled PET bottles. In various embodiments where old carpet is converted into new carpet yarn comprising 100% recycled carpet, the process may comprise additional steps to remove additional materials or impurities that may be present in recycled carpet that may not be present in recycled PET bottles (e.g., carpet backing, adhesive, etc.).

Other Sources of Recycled PET



[0042] In various embodiments, the process described above is adapted for processing recycled PET from any suitable source (e.g., sources other than recycled bottles or carpet) to produce new carpet yarn comprising 100% recycled PET.

The Use of a Crystallizer as Part of BCF Process



[0043] In various embodiments, the process for producing recycled BCF may further include a crystallizing step that utilizes one or more PET crystallizers. In particular embodiments, the system is configured to perform the crystallization step on the ground flakes prior to running the flakes through the one or more extruders (e.g., single screw extruder, MRS extruder, etc.). In particular embodiments, the PET crystallizer comprises a housing, a hopper screw (e.g., an auger) disposed at least partially within the housing, a stirring apparatus, one or more heating elements, and one or more blowers.

Hopper Screw



[0044] In particular embodiments, the hopper screw comprises any suitable screw conveyor (e.g., such as an Archimedes' screw) for moving liquid or granular materials (e.g., such as PET flakes). In various embodiments, the hopper screw comprises a substantially cylindrical shaft and a helical screw blade disposed along at least a portion of the cylindrical shaft. In particular embodiments, the substantially cylindrical shaft is configured to rotate the screw blade, causing that hopper screw to move material (e.g., the PET flakes) along the cylindrical shaft and into the crystallizer housing. In other embodiments, the hopper screw comprises any other suitable screw conveyer such as, for example, a shaftless spiral. In embodiments in which the hopper screw comprises a shaftless spiral, the shaftless spiral may be substantially fixed at one end and free at the other end and configured to be driven at the fixed end. In various embodiments, the hopper screw is disposed at least partially within the crystallizer housing.

[0045] In various embodiments, the hopper screw is configured to feed PET flakes into the crystallizer. In various embodiments, the PET crystallizer is configured to feed the PET flakes into the crystallizer using the hopper screw relatively slowly.

One or More Heating Elements



[0046] In various embodiments, the crystallizer comprises one or more heating elements for raising a temperature within the crystallizer. In particular embodiments, the one or more heating elements comprise one or more electric heating elements, one or more gas-fired heating elements, or any other suitable heating elements. In some embodiments, the one or more heating elements may be substantially electrically powered. In various embodiments, the one or more heating elements comprise one or more infra-red heating elements. In other embodiments, the one or more heating elements may utilize natural gas such, for example, propane. In particular embodiments, the one or more heating elements are configured to raise a temperature within the crystallizer to between about 100 degrees Fahrenheit and about 180 degrees Fahrenheit. In still other embodiments, the one or more heating elements are configured to raise a temperature within the crystallizer to between about 100 degrees Celsius and 180 degrees Celsius. In some embodiments, the one or more heating elements are configured to maintain a temperature within the crystallizer that is substantially about a maximum crystallization temperature of PET. In particular embodiments, the maximum crystallization temperature of PET is between about 140 degrees Celsius and about 230 degrees Celsius.

One or More Blowers



[0047] In various embodiments, the crystallizer further comprises one or more blowers configured to blow air over the flakes as the flakes passes through the crystallizer. In particular embodiments, the one or more blowers comprise any suitable blowers for moving air substantially across a surface area of the flakes as the flakes pass through the crystallizer. For example, in some embodiments, the one or more blowers comprise one or more suitable fans or other suitable mechanisms for moving air. In various embodiments, the one or more blowers are configured to blow air that has been at least partially heated by the one or more heating elements. In particular embodiments, the one or more blowers are configured to blow air having a temperature of at least about 140 degree Fahrenheit. In another particular embodiments, the one or more blowers are configured to blow air having a temperature of at least about 140 degree Celsius. In other embodiments, the one or more blowers are configured to maintain the temperature in the crystallizer between about 140 degrees Fahrenheit and about 180 degrees Fahrenheit. In some embodiments, the one or more blowers are configured to blow hot air from a bottom portion of the crystallizer and draw air from an upper portion of the crystallizer.

Stirring Apparatus



[0048] In various embodiments, the crystallizer comprises a stirring apparatus that comprises any suitable apparatus for stirring the PET flakes while the PET flakes are passing through the crystallizer. In various embodiments, the stirring apparatus may be operated, for example, by any suitable gear motor. In a particular embodiment, the stirring apparatus comprises a suitable rod or other suitable mechanism mounted to rotate, or otherwise stir the PET flakes as the PET flakes are passing through the crystallizer. In other embodiments, the stirring apparatus may comprise any suitable tumbler, which may, for example, comprise a drum mounted to rotate via the gear mother such that the PET flakes are at least partially stirred and/or agitated while the PET flakes are within the drum. In still other embodiments, the stirring apparatus comprises one or more screws and/or augers configured to rotate and stir the PET flakes. In particular embodiments, the stirring apparatus comprises the hopper screw.

[0049] As may be understood from this disclosure, the stirring apparatus is configured to agitate or stir the PET flakes as the one or more blowers blow air heated by the one or more heating elements across the PET flakes. In particular embodiments, the stirring apparatus is configured to at least partially reduce agglomeration (e.g., sticking or clumping of the flake) while the flake is at least partially crystallizing in the crystallizer.

[0050] In particular embodiments, the crystallizer at least partially dries the surface of the PET flakes. In various embodiments, the PET crystallizer is configured to reduce a moisture content of the PET flakes to about 50 ppm. In other embodiments the PET crystallizer is configured to reduce a moisture content of the PET flakes to between about 30 and about 50 ppm.

[0051] In various embodiments, the use of drier flakes may enable the system to run the flakes through the MRS extruder more slowly, which may allow for higher pressure within the MRS extruder during extrusion (e.g., may enable the system to maintain a higher pressure within the MRS extruder, rather than very low pressure). In various embodiments of the process, the pressure regulation system may be configured to maintain a pressure within the MRS extruder of between about 0 millibars and about 25 millibars. In particular embodiments, such as embodiments in which the PET flakes have been run through a crystallizer before being extruded in the MRS extruder, the pressure regulation system may be configured to maintain a pressure within the MRS extruder of between about 0 and about 18 millibars. In other embodiments, the pressure regulation system may be configured to maintain a pressure within the MRS extruder between about 0 and about 12 millibars. In still other embodiments, the pressure regulation system may be configured to maintain a pressure within the MRS extruder between about 0 and about 8 millibars. In still other embodiments, the pressure regulation system may be configured to maintain a pressure within the MRS extruder between about 5 millibars and about 10 millibars. In particular embodiments, the pressure regulation system may be configured to maintain a pressure within the MRS extruder at about 5 millibars, about 6 millibars, about 7 millibars, about 8 millibars, about 9 millibars, or about any suitable pressure between about 0 millibars and about 25 millibars.

[0052] In particular embodiments, the crystallizer causes the flakes to at least partially reduce in size, which may, for example, reduce a potential for the flakes to stick together. In particular embodiments, the crystallizer may particularly reduce stickiness of larger flakes, which may, for example, include flakes comprising portions of the ground PET bottles which may be thicker than other portions of the PET bottles (e.g., flakes ground from a threaded portion of the PET bottle on which a cap would typically be screwed).

Use of Curbside Recycling v. Deposit Bottles in Process



[0053] In various embodiments, the system is configured to utilize recycled PET of varying quality in the process described above. For example, in various embodiments, the system is configured to produce bulked continuous carpet filament from PET derived from PET bottles sourced from curbside recycling sources (e.g., PET bottles that were collected as part of a general bulk recycling program or other recycling source) as well as deposit PET bottles (e.g., bottles returned as part of a deposit program). In various embodiments, Curbside recycled bottles may require more thorough processing in order to produce bulked continuous filament, as curbside recycled PET bottles may be mixed in with and otherwise include contaminants such as, for example: other recyclable goods (e.g., paper, other plastics, etc.), garbage, and other non-PET bottle items due to imperfect sorting of recycled goods or for any other reason. Deposit PET bottles may include PET bottles with fewer unwanted contaminants due in part because deposit PET bottles may be collected separately from other recyclable or disposable goods.

[0054] In various embodiments, curbside recycled PET bottles acquired during particular times of year may include more impurities and other contaminants than at other times of the year. For example, curbside recycled PET bottles collected during summer months may comprise a higher percentage of clear PET bottles (e.g., water bottles) at least in part due to additional water consumption during summer months.

[0055] In various embodiments, the system described above may be configured to adjust particular components of the process based at least in part on the source of recycled PET being used to produce the bulked continuous carpet filament. For example, because deposit PET bottles include fewer impurities that need to be removed during the initial cleaning and sorting phases of the process, the pressure regulation system may be configured to maintain a pressure within the MRS extruder that is higher than a pressure that it would be configured to maintain for PET flake derived from curbside recycled PET bottles. In a particular embodiment, the pressure regulation system may be configured to maintain a pressure within the MRS extruder of between about 0 millibars and about 12 millibars when flakes derived from deposit PET bottles are passing through the MRS extruder. In still other embodiments, the pressure regulation system may be configured to maintain a pressure within the MRS extruder of between about 5 millibars and about 10 millibars in such instances.

[0056] In various embodiments, the system is configured to determine a suitable pressure at which to maintain the pressure within the MRS extruder based at least in part on the source of the recycled PET. In other embodiments, the system is configured to omit one or more of the steps above or include one or more additional steps to the steps described above based at least in part on the source of the recycled PET.

Direct Coupling of Various Process Components


Direct Coupling of MRS Extruder to Spinning Machine



[0057] In particular embodiments, the output of the MRS machine may be substantially directly coupled (e.g., directly coupled) to a spinning machine for forming the resulting molten polymer into bulked continuous filament. In such embodiments, after the recycled PET polymer has been extruded and purified by the above-described extrusion process, the resulting molten recycled PET polymer is fed substantially directly (e.g., directly) into the spinning machine. This process may be advantageous because molten polymer may, in certain embodiments, not need to be cooled into pellets after extrusion (as it would need to be if the recycled polymer were being mixed with virgin PET polymer) prior to spinning the molten polymer into filament. In particular embodiments, not cooling the recycled molten polymer into pellets serves to avoid potential chain scission in the polymer that might lower the polymer's intrinsic viscosity.

Direct Coupling of Non-MRS Extruder to Spinning Machine



[0058] In various embodiments of the process for recycling PET (e.g., or other polymers) into BCF, the recycled PET flakes are passed through an extruder other than an MRS extruder (e.g., a "first extruder") prior to spinning the resultant molten polymer into BCF. In particular embodiments, the first extruder is substantially directly coupled (e.g., directly coupled) to the spinning machine (e.g., an outlet of the first extruder is substantially directly coupled to an inlet of the spinning machine). For example, in various embodiments, an outlet of the first extruder is substantially directly coupled (e.g., via a suitable pipe, connector, etc.) to one or more inlets of one or more spinning machines. In particular embodiments, the first extruder may include any suitable expanded surface area extruder. In various embodiments, the first extruder may include, for example, a twin screw extruder, a multiple screw extruder, a planetary extruder, or any other suitable extrusion system (e.g., any other suitable expanded surface area extruder). In various embodiments, the first extruder is any suitable extruder for increasing an amount of surface area of a polymer melt being extruded by the first extruder that is exposed to a low pressure within the first extruder (e.g., a low pressure caused by a pressure regulation system, such as any suitable pressure regulation system described above). In a particular embodiment, the first extruder is an MAS extruder manufactured by Maschinen und Anlagenbau Schulz GmbH of Pucking, Austria.

[0059] In various embodiments, the first extruder is a conical co-rotating twin screw extruder. In such embodiments, the first extruder comprises an extruder housing in which two, co-rotating conical screws are disposed (e.g., a first conical screw and a second conical screw). In various embodiments, each conical screw is substantially conical (e.g., conical) such that the screw narrows from a first diameter at a base end of each respective conical screw to a second diameter at a vertex end of each respective conical screw that is less than the first diameter. In various embodiments, each particular conical screw may have any suitable thread or threading. In some embodiments, each conical screw has a substantially uniform (e.g., uniform) thread pitch and thread crest along at least a portion of the conical screw. In other embodiments, thread pitch and crest may at least partially vary along a length of the particular conical screw. In still other embodiments, a difference between a major and minor diameter of the conical screw may vary along a length of the conical screw (e.g., the screw thread may be larger or smaller along particular portions of the conical screw). In a particular embodiment, the pitch of thread of a particular conical screw may decrease along the conical screw from the base portion to the vertex portion. In particular embodiments, the first and second conical screws are substantially structurally identical (e.g., structurally identical).

[0060] In particular embodiments, the two conical screws are oriented within the conical twin screw extruder such that the base portion of each screw is disposed adjacent an intake (e.g., inlet) of the conical twin screw extruder, and the vertex portion of each screw is disposed adjacent an outlet of the conical twin extruder. In particular embodiments, a central axis of the first conical screw forms an acute angle with the central axis of the second conical screw. In various embodiments, the first and second conical screws are disposed such that at least a portion of the thread of the first conical screw at least partially mates with (e.g., mates with) at least a portion of the thread of the second conical screw. In other embodiments, at least a portion of the thread of the first conical screw at least partially engages with (e.g., engages with) at least a portion of the thread of the second conical screw

[0061] In particular embodiments, the conical twin screw extruder may be configured to at least partially melt the plurality of flakes into a polymer melt. In such embodiments, the conical twin screw extruder may, for example, generate sufficient heat (e.g., via shearing) to at least substantially melt (e.g., melt) the flakes. In particular embodiments, the first extruder is configured to increase a surface area of the polymer melt. In various embodiments, the conical design of the conical twin screw extruder may result in an intake volume that is substantially greater (e.g., greater) than a discharge volume of the conical twin screw extruder. This higher intake volume, in various embodiments, may result in a high volume throughput per revolution of the twin conical screws. In various embodiments, the first extruder is configured to receive a plurality of polymer flakes (e.g., PET flakes) via a first extruder inlet, melt the plurality of flakes into a polymer melt while extruding the plurality of flakes, and pass the resulting polymer melt though an extruder outlet.

[0062] In various embodiments, the first extruder comprises a pressure regulation system configured to reduce a pressure within the first extruder. In a particular embodiment, the first extruder is fitted with a suitable vacuum pump such that the vacuum pump is in communication with an interior of the first extruder's housing via a suitable opening in the first extruder's housing. In still other embodiments, the first extruder is fitted with a series of vacuum pumps. In particular embodiments, the vacuum pump is configured to reduce the pressure within the interior of the first extruder to a pressure that is between about Omillibars and about 25 millibars. In other embodiments, the vacuum pump is configured to reduce a pressure within the first extruder to between about 5 millibars and about 18 millibars. In still other embodiments, the vacuum pump is configured to reduce a pressure within the first extruder to any particular suitable pressure between about 0 millibars and about 25 millibars. In various embodiments, the low-pressure vacuum created by the vacuum pump in the first extruder may remove, for example: (1) volatile organics present in the melted polymer as the melted polymer passes through the first extruder; and/or (2) at least a portion of any interstitial water that was present in the wet flakes when the wet flakes entered the first extruder. In various embodiments, the low-pressure vacuum removes substantially all (e.g., all) of the water and contaminants from the polymer stream. In various embodiments, the vacuum pump may include any suitable vacuum pump, such as any vacuum pump described above or any other suitable vacuum pump.

[0063] In embodiments in which the system includes a first extruder directly coupled to the spinning machine, the process may include passing the plurality of flakes (e.g., a plurality of wet flakes after a washing step) through the first extruder to at least partially melt the plurality of flakes into a polymer melt and remove at least a portion of the impurities from the polymer melt. The polymer melt is then fed substantially directly (e.g., directly) into the spinning machine for spinning into bulked continuous carpet filament.

Conclusion



[0064] Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, although the vacuum system discussed above is described as being configured to maintain the pressure in the open chambers of the MRS extruder to about 1 mbar, in other embodiments, the vacuum system may be adapted to maintain the pressure in the open chambers of the MRS extruder at pressures greater than, or less than, 1 mbar. For example, the vacuum system may be adapted to maintain this pressure at between about 0.5 mbar and about 12 mbar.

[0065] Similarly, although various embodiments of the systems described above may be adapted to produce carpet filament from substantially only recycled PET (so the resulting carpet filament would comprise, consist of, and/or consist essentially of recycled PET), in other embodiments, the system may be adapted to produce carpet filament from a combination of recycled PET and virgin PET. The resulting carpet filament may, for example, comprise, consist of, and/or consist essentially of between about 80% and about 100% recycled PET, and between about 0% and about 20% virgin PET.

[0066] Also, while various embodiments are discussed above in regard to producing carpet filament from PET, similar techniques may be used to produce carpet filament from other polymers. Similarly, while various embodiments are discussed above in regard to producing carpet filament from PET, similar techniques may be used to produce other products from PET or other polymers.

[0067] In addition, it should be understood that various embodiments may omit any of the steps described above or add additional steps.

[0068] In light of the above, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for the purposes of limitation.

[0069] Clause 1. A method of manufacturing bulked continuous carpet filament, said method comprising:
  1. (A) providing a first extruder, said first extruder comprising:

    a first extruder inlet and a first extruder outlet; and

    a pressure regulation system that is adapted to maintain a pressure within said first extruder below about 18 millibars;

  2. (B) using said pressure regulation system to reduce a pressure within said first extruder to below about 18 millibars;
  3. (C) while maintaining said pressure within said first extruder below about 18 millibars, passing a plurality of flakes of recycled PET through said first extruder via said first extruder inlet to at least partially melt said plurality of flakes into a polymer melt;
  4. (D) providing at least one spinning machine comprising at least one spinning machine inlet, wherein said at least one spinning machine inlet is substantially directly coupled to said first extruder outlet;
  5. (E) after said step of passing said polymer melt through said first extruder, substantially immediately forming said polymer melt into bulked continuous carpet filament using said at least one spinning machine.


[0070] Clause 2. The method of Clause 1, wherein said first extruder is a conical co-rotating twin screw extruder.

[0071] Clause 3. The method of Clause 2, wherein said first extruder comprises a first conical screw and a second conical screw.

[0072] Clause 4. The method of Clause 3, wherein said first conical screw and said second conical screw are configured to at least partially melt said plurality of flakes into said polymer melt through shearing.

[0073] Clause 5. The method of Clause 4, wherein a central axis of said first conical screw forms an acute angle with a central axis of said second conical screw.

[0074] Clause 6. The method of Clause 5, wherein a vertex end of said first conical screw is disposed adjacent a vertex end of said second conical screw.

[0075] Clause 7. The method of Clause 6, wherein said vertex end of said first conical screw and said vertex end of said second conical screw are disposed adjacent said first extruder output.

[0076] Clause 8. The method of Clause 7, wherein at least a portion of a thread of said first conical screw at least partially mates with and at least partially engages at least a portion of a thread of said second conical screw.

[0077] Clause 9. The method of Clause 1, wherein:
said first extruder comprises a multi-rotating screw extruder comprising:

a first satellite screw extruder, said first satellite screw extruder comprising a first satellite screw that is mounted to rotate about a central axis of said first satellite screw;

a second satellite screw extruder, said second satellite screw extruder comprising a second satellite screw that is mounted to rotate about a central axis of said second satellite screw;

a third satellite screw extruder, said third satellite screw extruder comprising a third satellite screw that is mounted to rotate about a central axis of said third satellite screw; and

a fourth satellite screw extruder, said fourth satellite screw extruder comprising a fourth satellite screw that is mounted to rotate about a central axis of said fourth satellite screw; and

passing said polymer melt through said first extruder comprises passing said polymer melt through said multi-rotating screw extruder so that: (1) a first portion of said melt passes through said first satellite screw extruder, (2) a second portion of said melt passes through said second satellite screw extruder, (3) a third portion of said melt passes through said third satellite screw extruder, and (4) a fourth portion of said melt passes through said fourth satellite screw extruder.



[0078] Clause 10. The method of Clause 9, wherein:
said multi-rotating screw extruder comprises a satellite screw extruder support system that is adapted to rotate said first, second, third, and fourth satellite screws about a main axis, said main axis being substantially parallel to: (a) said central axis of said first satellite screw; (b) said central axis of said second satellite screw; (c) said central axis of said third satellite screw; and (d) said central axis of said fourth satellite screw.

[0079] Clause 11. The method of Clause 10, wherein:

said pressure regulation system is adapted to maintain said pressure within said first extruder below about 5 millibars; and

said method further comprises using said pressure regulation system to reduce a pressure within said first extruder to below about 5 millibars.




Claims

1. A method of manufacturing carpet filament comprising the steps of:

(A) grinding a plurality of recycled PET bottles into a group of polymer flakes;

(B) washing said group of polymer flakes to remove at least a portion of one or more contaminants from a surface of said flakes, said group of flakes comprising a first plurality of flakes that consist essentially of PET and a second plurality of flakes that do not consist essentially of PET;

(C) after said step of washing said first plurality of flakes:

(i) scanning said washed group of flakes to identify said second plurality of flakes,

(ii) separating said second plurality of flakes from said first plurality of flakes;

(D) providing an expanded surface area extruder having an extruder inlet and an extruder outlet;

(E) providing a pressure regulation system configured to reduce a pressure within said expanded surface area extruder between about 0 mbar and about 5 mbar;

(F) providing a spinning machine having a spinning machine inlet, wherein said spinning machine inlet is directly coupled to said extruder outlet;

(G) using said pressure regulation system to reduce said pressure within said expanded surface area extruder between about 0 mbar and about 5 mbar;

(H) while maintaining said pressure within said expanded surface area extruder between about 0 mbar about 5 mbar, passing said second plurality of flakes through said expanded surface area extruder via said fist inlet;

(I) melting said second plurality of flakes using said expanded surface area extruder to produce a polymer melt; and

(J) substantially immediately after passing said second plurality of flakes through said expanded surface area extruder, spinning said polymer melt into bulked continuous carpet filament using said spinning machine.


 
2. The method of Claim 1, wherein said expanded surface area extruder is an extruder selected from a group consisting of:

i. a conical, co-rotating twin screw extruder; and

ii. a multi-rotating screw extruder.


 
3. The method according to any one of the preceding claims, wherein smaller components and debris are removed from the plurality of recycled PET bottles via a rotating trammel, prior to the grinding step.
 
4. The method according to any one of the preceding claims, wherein, prior to the grinding step, metals contaminants are removed from the plurality of recycled PET bottles using metal removing magnets or eddy current systems.
 
5. The method according to any one of the preceding claims, wherein, prior to the grinding step, loose polymeric contaminants are removed from the plurality of recycled PET bottles using Near Infra-red optical sorting equipment
 
6. The method according to any one of the preceding claims, wherein, prior to the grinding step, remaining PVC is removed from the plurality of recycled PET bottles using automated X-ray sorting equipment.
 
7. The method according to any one of the preceding claims, wherein, after to the grinding step but before the washing step, bottle labels are removed from the flakes via an air separation system.
 
8. The method according to any one of the preceding claims, wherein, during the washing step, an aqueous density separation is utilized to separate the olefin bottle caps from the higher specific gravity PET flakes.
 
9. The method according to any one of the preceding claims, wherein, during the washing step, the flakes are washed in a heated caustic bath at about 190°F.
 
10. the method according to claim 9, wherein, during the washing step, the flakes are washed in a caustic bath with maintained concentration of sodium hydroxide between 0.6% and 1.2%.
 
11. The method according to any one of the preceding claims, wherein the plurality of recycled PET bottles are sourced from curbside recycling sources.
 
12. The method according to any one of the preceding claims, wherein the plurality of recycled PET bottles are sourced from returned deposit bottle sources.
 




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Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description