WASTE

TECHNICAL FIELD

[0001] The present disclosure generally relates to the field of recycling of plastic waste including, but not limited to flakes, polymers and post-consumer recycled plastic. More specifically, the present disclosure relates to a method of manufacturing recycled polyester yarn from polyester wastes.

BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior-art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Millions of tons of plastic waste are produced every year in manufacturing of various products. A significant proportion of the plastic waste is accounted for by polyester waste such as PET bottles, polyester fiber and yarn waste and the likes. Hence, rigorous research has been done, at least in the last 2 decades, in the area of polyester recycling to effectively make use of such recycled polyester in various applications.

[0004] US4003880A discloses a method of recovering polyester from mixed collections of fibers in the form of fibers, filaments, or fabrics (including dyed or undyed fibers other than polyester fibers as well as dyed polyester fibers) and using them in the production of new undyed fibers, films and other polymer products through the process of stripping the dye from the polyester fibers by contacting the fabrics with a dye stripping solvent for polyester polymer, which is preferably not a solvent for fibers other than polyester fibers at a temperature below which the polyester fibers dissolve and above which the crystalline lattice of the polyester fibers swell so as to release the dye; then removing essentially all of the dye- containing dye-stripping solvent which is not absorbed by the fibers; then contacting the solvent-laden fibers (which may contain residual dye) with sufficient additional solvent under selective dissolution conditions for polyester fibers; then removing the undissolved fibers and any other undissolved impurities from the solution; thereafter precipitating the polyester out of; and, separating the polyester from the solution. US3937675A discloses a method of recycling of textile wastes formed of blended cellulose and polyester fibers by treated them with a mineral acid agent, such as sulfuric acid, under conditions which serve to hydrolyze the cellulose and convert it to a form which is readily removed from the polyester fibers while leaving the polyester fiber substantially unaffected. The cellulosic material is recovered in the form of "fibrets" adapted for use as such or for treatment in producing other cellulosic compounds whereas the polyester fiber recovered may be garnetted for reuse in either spun yarn manufacture or in nonwoven processes. However, these processes are environmentally hazardous and are very expensive.

[0005] Still further method which finds limited industrial utility in recycling of plastic waste, particularly, polyester waste is conversion thereof into monomers by deglycol reaction (also known as deglycolization reaction) i.e. reacting the polymer at a temperature of about 250°C or more and at a pressure of 1 mmHg or less in presence of deglycol catalyst such as a metal compound catalyst to form the monomers and then converting them into polymers to produce different kind of yarns. However, this method also suffers from several-fold disadvantages, for example, requirement of high temperature and highly reduced pressure conditions, requirement of precious metal catalysts and the likes that have thwarted utility of this method in selected industrial setups.

[0006] There is, therefore, a need in the art to develop a simple, safe, environmentally benign (or environment friendly) and cost-effective method of manufacturing recycled polyester yarn from variety of polyester wastes that can alleviate or preclude one or more shortcomings of the conventional methods.

BRIEF DESCRIPTION OF DRAWINGS

[0007] FIG. 1 illustrates an exemplary process flow showing various steps (including one or more optional steps) involved in the method of manufacturing recycled polyester yam from polyester wastes, in accordance with embodiments of the present disclosure.

[0008] FIG. 2A and 2B illustrate exemplary schematic diagram showing a method of manufacturing recycled polyester yarn from polyester wastes, in accordance with embodiments of the present disclosure.

[0009] FIG. 3 illustrates an exemplary setup for producing a draw textured yam (DTY), in accordance with an embodiment of the present disclosure.

SUMMARY

[0010] An aspect of the present disclosure relates to a method of manufacturing a polyester yarn from a polyester waste, the method comprising the steps of: (a) taking the polyester waste; (b) effecting crystallization of the polyester waste by exposing the polyester waste to a hot air having a temperature ranging from 130°C to 200°C; (c) drying the polyester waste obtained from step (b) to obtain a dried polyester waste having a moisture content below 150 PPM; (d) obtaining a molten polymer mixture by feeding the dried polyester waste to an extruder, said extruder defining at least one heating zone having a temperature ranging from 250°C to 320°C; (e) feeding the molten polymer mixture to a spinneret to obtain at least one stream of viscous polymer; and (f) quenching the at least one stream of viscous polymer to obtain the polyester yam.

[0011] In an embodiment, the method does not make use of any of a solvent and a deglycolization catalyst. In an embodiment, the polyester waste comprises polyethylene terephthalate (PET) waste having a size ranging from 1 mm to 25 mm, bulk density ranging from 50 Kg/M ³ to 500 Kg/M ³ , and polyvinyl chloride content below 400 PPM. In an embodiment, the step of effecting crystallization of the polyester waste comprises exposing the polyester waste to a hot air having a temperature ranging from 150°C to 180°C. In an embodiment, the step of drying the polyester waste obtained from step (b) comprises exposing the polyester waste obtained from step (b) to a hot air having a temperature ranging from 130°C to 200°C and a dew point below -30°C (minus 30°C) for a time period ranging from 4 hours to 10 hours. In an embodiment, the step of obtaining the molten polymer mixture comprises: feeding the dried polyester waste to the extruder; and feeding a virgin polymer in an amount ranging from 0.1% to 80% by weight of the dried polyester waste, optionally with one or more excipients, to the extruder to obtain the molten polymer mixture. In an embodiment, the virgin polymer comprises polyethylene terephthalate (PET) chips having a size ranging from 1 mm to 25 mm and intrinsic viscosity ranging from 0.500 to 0.900 dl/g. In an embodiment, the polyethylene terephthalate (PET) chips are fed to the extruder in an amount of 25% by weight of the dried polyester waste. In an embodiment, the method comprises the step of subjecting the molten polymer mixture to filtration before feeding the molten polymer mixture to the spinneret. In an embodiment, the quenching of the at least one stream of viscous polymer is effected at a temperature ranging from 5°C to 35°C.

DETAILED DESCRIPTION

[0012] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0013] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0014] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0015] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0016] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0017] The terms “flakes” and “chips” as used herein throughout the present disclosure synonymously and interchangeably denotes the meaning of pieces, particles or particulate matters, either in the solid form or in semi-solid/viscous form, of any size that may serve as a source of the polymeric material.

[0018] The present disclosure generally relates to the field of recycling of plastic waste including, but not limited to flakes, polymers and post-consumer recycled plastic. More specifically, the present disclosure relates to a method of manufacturing recycled polyester yarn from polyester wastes.

[0019] An aspect of the present disclosure relates to a method of manufacturing a polyester yarn from a polyester waste, the method comprising the steps of: (a) taking the polyester waste; (b) effecting crystallization of the polyester waste by exposing the polyester waste to a hot air having a temperature ranging from 130°C to 200°C; (c) drying the polyester waste obtained from step (b) to obtain a dried polyester waste having a moisture content below 150 PPM; (d) obtaining a molten polymer mixture by feeding the dried polyester waste to an extruder, said extruder defining at least one heating zone having a temperature ranging from 250°C to 320°C; (e) feeding the molten polymer mixture to a spinneret to obtain at least one stream of viscous polymer; and (f) quenching the at least one stream of viscous polymer to obtain the polyester yam.

[0020] In an embodiment, the method does not make use of any of a solvent and a deglycolization catalyst. In an embodiment, the polyester waste comprises polyethylene terephthalate (PET) waste having a size ranging from 1 mm to 25 mm, bulk density ranging from 50 Kg/M ³ to 500 Kg/M ³ , and polyvinyl chloride content below 400 PPM. In an embodiment, the step of effecting crystallization of the polyester waste comprises exposing the polyester waste to a hot air having a temperature ranging from 150°C to 180°C. In an embodiment, the step of drying the polyester waste obtained from step (b) comprises exposing the polyester waste obtained from step (b) to a hot air having a temperature ranging from 130°C to 200°C and a dew point below -30°C (minus 30°C) for a time period ranging from 4 hours to 10 hours. In an embodiment, the step of obtaining the molten polymer mixture comprises: feeding the dried polyester waste to the extruder; and feeding a virgin polymer in an amount ranging from 0.1% to 80% by weight of the dried polyester waste, optionally with one or more excipients, to the extruder to obtain the molten polymer mixture. In an embodiment, the virgin polymer comprises polyethylene terephthalate (PET) chips having a size ranging from 1 mm to 25 mm and intrinsic viscosity ranging from 0.500 to 0.900 dl/g. In an embodiment, the virgin polymer comprises polyethylene terephthalate (PET) chips having a size ranging from 1 mm to 25 mm and intrinsic viscosity of about 0.8 dl/g. In an embodiment, the polyethylene terephthalate (PET) chips are fed to the extruder in an amount of 25% by weight of the dried polyester waste. In an embodiment, the method comprises the step of subjecting the molten polymer mixture to filtration before feeding the molten polymer mixture to the spinneret. In an embodiment, the quenching of the at least one stream of viscous polymer is effected at a temperature ranging from 5°C to 35°C.

[0021] FIG. 1 illustrates an exemplary process flow showing various steps (including one or more optional steps) involved in the method of manufacturing recycled polyester yam from polyester wastes in accordance with embodiments of the present disclosure.

[0022] FIG. 2A and FIG. 2B illustrates an exemplary schematic diagram showing the method of manufacturing recycled polyester yarn from polyester wastes. A person skilled in the art should appreciate that although one or more embodiments of the present disclosure are described using the term “polyester flakes”, any other type or form of polyester waste such as polyester chips, polyester fibers, polyester yams or mixture thereof can be subjected to the advantageous recycling process as detailed in embodiments of the present disclosure to produce the recycled polyester yarn without departing from the scope and spirit of the present disclosure.

[0023] Polyester Flakes

[0024] In an embodiment, polyester bottles are collected and sorted to remove PVC contents such as caps and name wrappers. Separated PET bottles are cleaned with water wash and dried, and then cut into small flakes with the help of cutter. Such polyester flakes can find utility as one of the source material for producing polyester yarn(s) in accordance with embodiments of the present disclosure. Table 1 below illustrates exemplary characteristics of the polyester flakes:

Table 1: Exemplary physical properties of the polyester flakes

[0025] PET Flakes received from market may further be sorted for removal of foreign contamination. Then it is washed through washing line. Water is separated and excess/un bound moisture is removed through dryer. Dried PET flakes are packed and sent for crystallization and removing excess/unbound moisture through drying PET flakes.

[0026] Crystallization and Drying Phase

[0027] In an embodiment, the polyester flakes are charged into a crystallizer. In an embodiment, the polyester flakes are charged into a charging hopper to be transported to a hopper above the crystallizer through a rotary valve by means of compressed air (i.e. pneumatic conveying). In crystallizer, hot air is fed that makes fluidization of the flakes, and un-bound moisture is removed. The temperature of the hot air may be between about 130°C to about 200°C, preferably between about 150°C to about 180°C. In crystallizer top surface of flakes become harder as molecules on top surface makes defined lattice structure. [0028] The flakes are then conveyed to a dryer column, wherein hot air is fed to ensure uniform drying of the flakes to remove Excess/unbound moisture. The temperature of hot air in the dryer column may range between about 130°C to about 200°C. In an embodiment, air having a dew point level ranging from about -10°C to about -50°C is heated by a heater to a temperature ranging from 130°C to 200°C and then fed to the dryer column from the bottom. In an embodiment, residence time of flakes for drying in dryer column ranges from about 4 hours to about 10 hours. The dried flakes may have a moisture level below 150 PPM, preferably between 30 - 40 PPM. This is controlled by outlet temperature of hot air coming out from dryer.

[0029] Extrusion Phase

[0030] In an embodiment, the dried flakes are transported to a hopper above the extruder. The dried flakes may be fed to extruder by gravity. However, any other means or modes of conveyance, as known to or appreciated by a person skilled in the art, can be used without departing from scope and spirit of the present disclosure. In an embodiment, virgin polymer(s) is/are also fed to the extruder. For example, the virgin polymer(s) may be mixed with the polyester flakes in the drier itself. Alternatively, the virgin polymer(s) may be directly fed to extruder. In an embodiment, virgin polymer(s) include(s) any or a combination of polyethylene terephthalate (PET) and polybutylene terephthalate. In an embodiment, one or more excipients such as master batch, optical brightener and the likes are also fed to the extruder. In an embodiment, other excipient(s)/ingredient(s) such as virgin PET chips ranging from 0.1% to 80% by weight of the dried polyester waste are fed with the help of Hopper/K- tron that transfers exact quantity of PET chips to extruder defined in SOP. In case of manufacturing dope dyed yarn, master batch and/or optical brightener may be fed to the extruder using suitable dosing system. In an embodiment, Hopper/K-Tron master batch dosing system is employed for addition of excipient(s)/ingredient(s). A person skilled in the art would appreciate that the dosing ratio is governed by the type of yam to be produced. [0031] Table 2 below provides exemplary characteristics of virgin PET chips that may be mixed with the polyester waste (polyester flakes) in accordance with embodiments of the present disclosure

Table 2: Exemplary physical properties of the virgin PET chips

[0032] In an embodiment, flakes and other ingredient(s)/excipient(s) are fed to the extruder. The extruder may include different heating zones and conveyer(s) or other displacement mechanism(s). In an embodiment, the heating zone temperature(s) is kept within a range of about 250°C to about 320°C, preferably between about 285°C to about 295°C. In an embodiment, the conveyer(s)/displacement mechanism(s) includes screw/barrel. Flakes melt in the extruder and screw/barrel can push it further. The molten polymer may then pass through filter (such as Continuous Polymerisation Filter) and then be fed to the spinning beam. In an embodiment, the spinning beam includes one or more static mixtures to aid in homogenizing the polymer. As would be appreciated by a person skilled in the art, process optimization of temperature, and kneading of polymer in extruder leads to the consistent quality of yarn.

[0033] Spinning / Winding Phase

[0034] In an embodiment, molten polymer coming from the extruder is fed to a spin pack where it is subjected to filtration and then spun into yarn(s) through spinneret. One or more metering units/valves can be employed for controlling the rate of molten polymer fed to the spin pack. The spun filament yarn can then be quenched/solidified using a cold air blowing from a quench screen. In an embodiment, spun filament yarn is quenched at a temperature ranging from about 5°C to about 35°C, preferably between the temperature ranging from about 22°C to about 24°C. The Spin finish oil can then optionally be applied to the yarn at an Oil Pickup rate ranging from about 0.10% to about 1.50%. Finished yarns can then be supplied to migration jet(s), Godet(s), or intermingling unit(s) and wound into POY/FDY bobbins of required bobbin weight.

[0035] Table 3 below illustrates exemplary characteristics of a 250/48 POY yarn produced in accordance with embodiments of the present disclosure.

Table 3: Exemplary characteristics of a 250/48 POY yarn

[0036] Texturising

[0037] Texturising or texturizing is a process by which texture (physical appearance)of synthetic fibers are modified. Any conventional texturizing method, as known to or appreciated by a person skilled in the art can be employed to serve its intended purpose without departing from the scope and spirit of the present disclosure. In an embodiment, any or a combination of bulking (where thermoplastic fibers are twisted, heat set and untwisted), crimping and coiling can be used for texturing the yarns. In an embodiment, texturization is done at a temperature ranging from 15°C to about 240°C. FIG. 3 illustrates an exemplary setup for producing a draw textured yarn (DTY) in accordance with an embodiment of the present disclosure.

[0038] In an embodiment, a polyester yarn is made from 100% polymer waste and /or blended with virgin PET / PBT chips in a ratio ranging from 0.1% to 99% using the method as detailed in embodiments of the present disclosure.

[0039] In an embodiment, the method of present disclosure is amenable to production of polyester yarns with deniers ranging from 10 to 1500. In an embodiment, the method of present disclosure is amenable to production of polyester yams with filaments ranging from 8 to 1152. In an embodiment, the method of present disclosure is amenable to production of polyester yarns with cross-sections of circular, trilobal, plus, hollow C, octolobal, pentalobal, Slit and Dog Bone. In an embodiment, the method of present disclosure is amenable to production of polyester yarns of types - POY, FDY and DTY including Parallel, Ply and twists thereof. In an embodiment, the method of present disclosure is amenable to production of polyester yarns with lusters - Clear, Transparent, Bright, Semi-Dull, Full Dull, Dope Dyed, FR and Anti Bacterial.

[0040] In an embodiment, PET Flakes and PET chips in a ratio of 80:20 are converted in to a yam. PET flakes are conveyed through pneumatic conveyer to crystallizer. After crystallizing, drying of flakes takes place to reduce moisture below 100 PPM. This is done by blowing hot dry air of Dew Point below -30 Deg C. Dried flakes are conveyed through hot conveying into flakes hopper. Alongside PET flakes, PET High IV chips are dried in a small drier. Full dull T1O2 master batch or color master batch with specified quantity of optical brightener (to maintain color of yam) is mixed with dried PET chips. Dried PET flakes and PET chips with additive are mixed through K-Tron mixer and fed to extruder which is maintained at constant temperature and pressure throughout the process. At constant pressure flakes and additives melts and kneaded in different zones of extruder and high pressure melt is passed through low micron filter. Filtered polymer is then passed through static mixer to maintain homogeneity to give consistent quality of yarn. Molten polymer is spun, quenched and spin finish oil is applied on POY yarn. Each spool is marked according to its type and category and sent to DTY unit to convert POY in to DTY. In DTY, POY yarn is heated to a desired temperature and stretched to maintain its desired properties, suitable for knitting and weaving.

[0041] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

[0042] EXAMPLE 1 - Production of 130/36 POY [0043] Crystallization and Drying

[0044] Transparent Flakes of used PET bottles of bulk density 0.3 gram/CC having less than 100 PPM PVC, and Intrinsic Viscosity (IV) of 0.78 were charged into a charging hopper, which then transports the flakes to the hopper above the crystallizer. These flakes were crystallized up to 25% crystallization in the crystallizer at a temperature of about 180°C. [0045] The flakes were then moved from the crystallizer to the dryer column by fluidization. In the dryer column, the air from air drying unit with dew point level of about -40°C was heated by heater to around 185°C. Residence time of flakes in the dryer was about 8 hrs for drying, after which the flakes were transported to a hopper above the extruder. The dried flakes were having moisture level at around 40 ppm. Along with the recycled PET flakes, virgin PET chips with high IV of about 0.8 was added in an amount of about 30% of the mix, together with black masterbatch for color. Ktron master batch dosing system was used for the same.

[0046] Extrusion

[0047] The charge comprising recycled PET Flakes, virgin PET chips and master batch were fed to the Extruder, which has heating zones and screw/barrel. The mixture was molten in the extruder, maintained at a temperature of about 288°C, and the charge was pushed further by the screw at pressure of 110 Kg/cm such that it passed through the candles filter (Continuous Polymerisation Filter (CPF) of 40 micron size). Molten polymer then moved to the spinning beam with static mixers to help the polymer to be homogenous. Temperature of spin beam was maintained at 289 °C, with high IV of 0.8.

[0048] Spinning/Winding

[0049] Molten Polymer from the extruder coming to the spin beam was passed through metering polymer pump into the spin pack where it was further filtered and then spun into yarn as per the requirement of 130/36 filaments through spinneret.

[0050] The spun filament yam was then quenched/solidified by cold air blowing from the quench screen at 500 pascal pressure, 0.55 m/sec air flow, maintaining quench temp at 23°C and Relative Humidity of 75%. Spin finish oil was applied to the yarn at an Oil Pickup rate of about 0.35%, after which the yam was passed through migration jet/Godets/Intermingling and was finally wound into POY/FDY bobbins of 14 Kg bobbin weight at winder speed of about 3000 meter/minute.

[0051] The 130/36 POY produced from the process above was tested for properties, results whereof are presented below:

• Denier - 125D

• Elongation - 130 %

• Tenacity - 2.50 gpd

• Draw Force - 44 cN

• Spin Finish Oil - 0.35%

• Uster - below 1.20%

• Intermingling point - 12 to 14/meter

[0052] After testing the POY, bobbins were inspected for physical faults like winding defects, cross winding, bulging, damage, dirty, breakage etc. The bobbins were then transported to DTY facility for making textured yam (DTY). Following parameters were set for production of DTY :

• Speed of machine: 600 MPM

• Temperature 175°C,

• Draw ratio 1.68 ,

• T2/T1 0.8

• doff weight: 5 Kg each with OPU 2.5%. ADVANTAGES OF THE INVENTION

[0053] The present disclosure provides a method of manufacturing recycled polyester yarn from polyester waste that overcomes one or more deficiencies associated with the prior art reported methods.

[0054] The present disclosure provides a method of manufacturing recycled polyester yarn from polyester waste that is simple, safe and environmentally benign (or environment friendly).

[0055] The present disclosure provides a method of manufacturing recycled polyester yarn from polyester waste that is economical as compared to the conventional methods.