[0001] This patent application claims the benefit of priority from U.S. Provisional Application Serial No. 63/253,625 filed October 8, 2021, teachings of which are herein incorporated by reference in their entirety.

FIELD

[0002] This disclosure relates to a stable segmented polyurethane for making spandex fiber that is useful in apparel and hygiene applications and which can affordably and efficiently be reprocessed into spandex fiber with similar properties when recovered via recycling from finished articles such as, but not limited to, apparel and hygiene applications in which it is used.

BACKGROUND

[0003] Polyurethane for making spandex fibers is a segmented copolymer with phase separated domains of both hard and soft segments that enable the fibers to stretch and recover. Spandex fibers are widely used in apparel and hygiene applications to provide recoverable stretch to fabrics as well as improve their overall stretch properties by changing the modulus of extension relative to non-spandex containing fabrics (referred to here as ‘rigid’ fabrics). The properties of spandex that enable the consumer benefits of recoverable stretch in garments are dependent on both the monomers used to make the polymer of the fiber, as well as the precise morphology of the polymer in the fiber (viz. configurations of the domains in the copolymer), and any additives. [0004] The use of polyurethane spandex fibers in textile and hygiene processes often involves the spandex fiber being blended in fabric form with another fiber (cotton, nylon, polyester, acrylic, wool) and then subjecting the fabric to a high temperature dye process (commonly from 90°C to 135°C in an aqueous environment, which may also be pressurized). Further, garments containing spandex may be worn for years by consumers during which time the garment is typically subjected to numerous wash and dry-cleaning processes, the majority of which are done above room temperature as well as time-induced aging of the product. Through all of these processes, the molecular weight of typical polyurethane spandex has been known to increase over time. [0005] It is therefore difficult to recycle polyurethane spandex fibers from waste materials into new materials and objects because the complicated polymer structure makes depolymerizing the polymer and separating the components difficult and expensive. It is also difficult to recycle spandex for reuse without depolymerizing, because the polymer molecular weight is materially changed by textile processing and consumer use of the fiber during its life. Spandex fibers recovered from fabrics and garments generally have a more variable and higher molecular weight after consumer use compared to the molecular weight when it was initially manufactured. This variation in molecular weight presents difficulties for dissolution and reprocessing.

[0006] A method to avoid the challenges of spandex recycling is detailed in CN112726009A where a recyclable four-sided elastic lace fabric is disclosed and fabric construction is modified to eliminate the use of spandex in the fabric.

[0007] WO 2013/032408 Al discloses a method for controlled thermal degradation followed by a washing treatment for the destructive removal of spandex from garments. Since this method is destructive to the spandex, it is not suitable for a circular process in which the spandex from the garment can be reprocessed into useful spandex fiber.

[0008] US 2021/0246581A1 describes a general method to make a textile fiber in which the degree of polymerization in the recycled polymer is lower than it was before the recycling process.

[0009] WO 2021/060292 Al has been proposed to partially overcome the problem by redissolving spandex and blending it with virgin spandex to make a spandex fiber. This method, by definition however, does not enable a fully circular process as it requires addition of new non recycled materials into the process.

[00010] The ability to fully reprocess spandex is a requirement to enable a complete circular textile process so that the spandex component in garments does not become a waste product for the landfill, and that the spandex fiber can be remade in a way that does not require blending with virgin polymeric materials. In this manner the consumer can continue to gain the benefits of shape retention and recoverable stretch in garments with a fiber that participates in a fully circular process.

[00011] A reprocessible spandex fiber chemistry and method for reuse as a recycled spandex fiber is therefore needed. SUMMARY

[00012] An aspect of this disclosure relates to a reprocessible segmented polyurethane polymer useful in production of spandex fiber which, when recycled from a finished article, exhibits similar characteristics to the original segmented polyurethane polymer and/or spandex. The reprocessible polymer comprises polyurethane or polyurethane-urea with permanent or partial termination which exhibits a weight average molecular weight (Mw) about 180,000 or lower, a polydispersity (PD) calculated as PD = Mw/Mn of about 4.0 or lower and a hard segment melting temperature of about 250°C or lower which maintains these characteristics when removed from a finished article.

[00013] Another aspect this disclosure relates to spandex fiber comprising this reprocessible segmented polyurethane polymer.

[00014] Another aspect of this disclosure relate to yarn comprising the spandex fiber comprising this reprocessible segmented polyurethane polymer.

[00015] Another aspect of this disclosure relates to stretch fabrics and garments comprising these stretch fabrics which comprise spandex fiber or yarn comprising spandex fiber comprising this reprocessible segmented polyurethane polymer.

[00016] Another aspect of this disclosure relates to an article comprising recycled spandex produced from a segmented polyurethane polymer with permanent or partial termination which exhibits a weight average molecular weight (Mw) about 180,000 or lower, a polydispersity (PD) calculated as PD = Mw/Mn about 4.0 or lower and a hard segment melting temperature of about 250°C or lower which has been removed from a finished article.

[00017] Another aspect of this disclosure relates to a method for production of a recyclable spandex containing article, said method comprising incorporating into the article spandex fiber or yarn comprising spandex fiber comprising a segmented polyurethane polymer with permanent or partial termination which exhibits a weight average molecular weight (Mw) about 180,000 or lower, a polydispersity (PD) calculated as PD = Mw/Mn about 4.0 or lower and a hard segment melting temperature of about 250°C or lower, wherein the spandex maintains these characteristics when removed from the article.

DETAILED DESCRIPTION [00018] “Spandex” is a manufactured filament in which the filament-forming substance is a long chain synthetic polymer comprised of at least 85% by weight of segmented polyurethane or polyurethane-urea. A polyurethane, polyurethane-urea, and a segmented polyurethane or polyurethane-urea polymer are used interchangeably in this disclosure and use of any of these terms is meant to encompass each of these polymers. A polyurethane with high stability means that the weight average polymer molecular weight of the fiber is relatively stable under storage and process conditions, within a range of ±25% and preferably within ±20%, after the fiber is formed. It also means the polymer has a low and stable polydispersity.

[00019] As described above, there is a need for a stretch spandex fiber that is stable to the demands of the textile (fabrics and garments for apparel) and hygiene (e.g. recoverable elastics in diaper side panels and adult incontinence products) production processes and those placed on the fiber by the consumer during the life of a garment made with that fiber during consumer use, that can be recovered at end of life in a form that enables it to be reprocessed back into a spandex fiber.

[00020] In this disclosure, a segmented polyurethane polymer with properties rendering it stable for production of spandex and use of such spandex in finished articles and reprocessing when removed from such finished articles has been identified.

[00021] For purposes of this disclosure, by “greige fiber, yarn or fabric”, it is meant any un-bleached, un-dyed or un-treated fiber, yarn or fabric which may or may not be modified by mechanical processes such as drafting, twisting, plating with other fibers, co-mingling, and/or rewinding.

[00022] For purposes of this disclosure, by “finished article” it is meant to include any spandex containing fiber, fabric, garment or hygiene article wherein the greige fiber, yarn or fabric from which the article originated has been modified from its un-bleached, un-dyed and/or un-treated form.

[00023] In one nonlimiting embodiment, by “finished article” it is meant to include any spandex containing fibers or yarns, or fabrics, garments or article thereof that are knitted, woven or nonwoven and processed by a thermal treatment at any temperature or combination of temperatures in the range 100°C to 210°C.

[00024] In one nonlimiting embodiment, by “finished article”, it is meant to include spandex containing fibers, yarns or fabrics and articles produced therefrom which are dyed by any known dye process, such as, but not limited to, disperse, acid, anionic, cationic, and reactive textile dyes following standard methods. The dye process can also be done in a waterless fashion using, for example, carbon dioxide as the dye carrier.

[00025] In some nonlimiting embodiments, the finished article goes through both thermal treatment and dyeing processes.

[00026] In other nonlimiting embodiments, by “finished article” it is meant a fabric, garment or other article made from fibers or yarns that are knitted, woven or nonwoven, processed by a thermal treatment at any temperature or combination of temperatures in the range 100°C to 210°C, but do not go through a dye process or alternatively, a fabric, garment or other article made from fibers or yarns that is knitted, woven or nonwoven and is dyed by any known dye process, such as disperse, acid, anionic, cationic, and reactive textile dyes following standard methods but does not go through a thermal treatment above 100°C after or before the dye process step.

[00027] Examples of finished articles of this disclosure include, but are in no way limited to, any scoured and/or bleached and/or dyed and/or heat treated spandex containing fiber or yarn or fabric or garments prepared from treated spandex containing fiber or yarn or fabric, denim fabric and garments prepared therefrom, ready-to wear garments, hosiery, leggings, sportswear, underwear, bras, socks and disposable hygiene articles including, but not limited to disposable diapers, training pants, adult incontinence devices and products, catamenial devices, garments and products, bandages; wound dressings, surgical drapes, surgical gowns, surgical or other hygienic protective masks, hygienic gloves, head coverings, head bands, ostomy bags, bed pads, bed sheets, and the like.

[00028] The reprocessible segmented polyurethane polymer of this disclosure is comprised of a polyether-based glycol, a diisocyanate, a chain extender and a terminator. Any of these ingredients can be a single component by its chemical identity or a mixture of two or more chemicals. The chain extender can be a diol or a diamine, and the terminator can be a monofunctional alcohol or amine. The reprocessible segmented polyurethane polymer can be produced in a batch or a continuous process.

[00029] The reprocessible segmented polyurethane polymer of this disclosure has reduced secondary chain extension in order to provide at least partial permanent termination to provide molecular weight stability to the polymer after fiber formation. Further, the polyurethane of the polymer has sufficiently high molecular weight that it can be made into a spandex fiber that is capable of being knit or woven into fabrics that are subjected to dye processes such as those used to dye cotton, polyester, nylon, wool or blends thereof. It is stable to the high temperature processes used for heat setting of fabrics, and it is stable to the effects of long term aging of the product during the life of a garment by the consumer. This includes garment care such as washing and tumble drying or drying in sunlight in the open air. The reprocessible segmented polyurethane polymer of this disclosure has a unique combination of properties that keeps the molecular weight of the polymer sufficiently high enough to allow fiber making but not too high so as to have too much viscosity when dissolved in a solvent for dry spinning. In addition to being in the right molecular weight range, the reprocessible segmented polyurethane polymer must be consistently in that range by having a low polydispersity through fiber making, fabric production, and consumer use in garment form, such that the polyurethane chemistry of the invention can be re-processed cost effectively into fiber with similar characteristics after collection from a waste stream or as part of a circular recycling process.

[00030] In one nonlimiting embodiment, the reprocessible segmented polyurethane polymer of this disclosure exhibits a weight average molecular weight (Mw) about 180,000 or lower, a polydispersity (PD) calculated as PD = Mw/Mn of 4.0 or lower, and a hard segment melting temperature of 250°C or lower and maintains these characteristics when removed from a finished article.

[00031] In one nonlimiting embodiment, the reprocessible segmented polyurethane polymer of this disclosure exhibits a weight average molecular weight (Mw) between about 70,000 to about 180,000, a polydispersity (PD) calculated as PD = Mw/Mn of about 1.5 to about 4.0 , and a hard segment melting temperature of about 180° to about 250°C, and maintains these characteristics when removed from the finished article.

[00032] The reprocessible segmented polyurethane polymer of this disclosure can be used to produce a polyurethane spandex fiber with a unique set of properties that includes at least partial termination, a hard segment with the melting temperature not higher than 250°C, a polyether based glycol with a molecular weight between 1000 and 3000, a % NCO of isocyanate terminated prepolymer between 5.0 and 7.5, and a denier per filament of 8 to 20. The spandex of the invention can be melt-spun, dry-spun or wet-spun to form the fiber. Additives can also be added to the spandex of the invention. These may include delustrants such as titanium dioxide, carbon black, chlorine resist agents, dye assist agents, UV screeners, anti-tack agents, hindered amine light stabilizers, and the like. The spandex may also have a finish applied to the fiber surface or incorporated into the fiber that is based on silicone, mineral oil, aliphatic ethoxylates, or combinations thereof.

[00033] Further, as demonstrated herein, the reprocessible segmented polyurethane polymer is useful in production of spandex fiber which, when recycled from waste materials into new materials and objects, exhibits similar characteristics to the original polymer and/or spandex.

[00034] Thus, this disclosure also relates to spandex fiber comprising this reprocessible segmented polyurethane polymer, yams comprising the spandex fiber comprising this reprocessible segmented polyurethane polymer, and to stretch fabrics and garments comprising these stretch fabrics which comprise the spandex fiber and/or yams comprising this reprocessible segmented polyurethane polymer. Preferred is that the spandex fiber can be remade in a way that does not require blending with virgin polymeric materials.

[00035] Yarns of this disclosure may be prepared by various methods including, but not limited to, core spinning, co-mingling or twisting of the spandex fiber with one or more additional fibers or yarns. Nonlimiting examples of additional fibers or yarns are those comprising cotton, polyester or nylon or combinations thereof.

[00036] As demonstrated herein, knitted or woven fabric comprising this spandex exhibits characteristics which will meet consumer expectations with respect to stretch and recovery behavior of spandex containing articles.

[00037] In one nonlimiting embodiment, the fabric is a woven fabric comprising 0.5 to 18% of the spandex fiber comprising this reprocessible segmented polyurethane polymer. In one nonlimiting embodiment, the fabric is a denim fabric.

[00038] In another nonlimiting embodiment, the fabric is a knit fabric comprising 1 to 50% spandex fiber comprising this reprocessible segmented polyurethane polymer.

[00039] The spandex fiber is also expected to be useful in hygiene applications in which spandex is routinely used. Nonlimiting examples of such hygiene applications include disposable diapers, training pants, adult incontinence devices and products, catamenial devices, garments and products, bandages; wound dressings, surgical drapes, surgical gowns, surgical or other hygienic protective masks, hygienic gloves, head coverings, head bands, ostomy bags, bed pads, bed sheets, and the like.

[00040] In addition, this disclosure relates to recycled spandex and articles comprising recycled spandex produced from the reprocessible segmented polyurethane polymer which has been removed from a finished article. In one nonlimiting embodiment, the reprocessible segmented polyurethane polymer is removed from a fabric or garment or article used in hygiene applications by processing with a solvent in which the segmented polyurethane polymer dissolves and then reprocessed using conventional dry spinning or melt spinning to make a spandex fiber that has a polydispersity of 4.0 or lower, a Mw below 180,000, and a hard segment melting temperature of 250°C or lower.

[00041] In one nonlimiting embodiment, the recycled article comprises at least 20% of the recycled spandex.

[00042] In one nonlimiting embodiment, the recycled article comprises at least 50% of the recycled spandex.

[00043] Further, this disclosure relates to methods for production of a recyclable spandex containing article via incorporating into the article spandex fiber comprising this reprocessible segmented polyurethane polymer.

[00044] The following test methods were used to characterize fabrics of this disclosure.

Fabric Recovery Force and elongation

[00045] Fabric tensile testing for knitted fabrics is performed according to ASTM D4964- 96. The samples were conditioned for 16 hours at 70° F and 65% relative humidity. Fabric tensile tests were performed by cycling to 50% elongation at 200% per minute. The fabric recovery force at 30% elongation on the third cycle is recorded as fabric recovery force. Fabrics were evaluated for % elongation under 7 kg load force in the fabric weft and warp directions. [00046] Fabric tensile testing and shrinkage for woven and denim fabrics is performed according to methods described in US 7637091B2.

Polyurethane Test Methods

[00047] Polyurethane samples were tested for %NCO according to US 6,472,494B2. The polymer molecular weights are measured by a gel permeation chromatography (GPC), and the hard segment melting temperature or HSTm (peak position) of the polymer is measured by a differential scanning calorimetry (DSC) method at a heating rate of 10°C per minute. Mw is the weight average molecular weight calculated as the sum of the weight fractions of polymer chains of differing chain length. Mn is the number average molecular weight calculated as the sum of the mole fractions of the polymer chains of differing chain length. The polydispersity (PD) is calculated as PD = Mw/Mn.

[00048] The features and advantages of the polymer compositions and articles prepared therefrom of this disclosure are more fully shown by the following examples which are provided for purposes of illustration, and are not to be construed as limiting the invention in any way.

EXAMPLE 1 High stability polyurethane preparation

[00049] The segmented polyurethane of this disclosure suitable for spinning into spandex fibers was made through a polymerization process by reacting poly(tetramethylene ether) glycol (PTMEG), methylene bis(4-phenyl isocyanate) (MDI) and ethylene glycol (EG) in dimethyl acetamide (DMAc), optionally with a catalyst. In a typical polymer batch, 600 grams of PTMEG with a number average molecular weight of 2000 Daltons and 216.49 grams of MDI were added into a reaction kettle equipped with a mixer, followed by 614.08 grams of DMAc and a solution consisting of 680 grams of DMAc, 33.88 grams of EG and 35 microliters of phosphoric acid (H3PO4). These ingredients were mixed well with an agitator running at 50 rpm and heated at 70°C for 180 minutes when the viscosity of the mixture was increased. The reaction mixture was continued at 70°C for another 90 minutes while the agitator speed was reduced to 20 rpm for managing the increased polymer solution viscosity. A solution containing 5.00 grams of butanol dissolved in 25.00 grams of DMAc, combined with a solution of 15 grams with 40% Irganox® 245 by BASF (chemically, which is ethylene bis (oxyethylene) bis-(3-(5-tert-butyl-4-hydroxy-m- tolyl)-propionate)) in DMAc, were then added to the above polymer solution which was mixed for additional 45 minutes. The formed viscous polymer solution was added to 0.50 grams of cyclohexylamine (CHA) in 2.00 grams of DMAc and mixed for 30 minutes before cooling down to room temperatures. The formed polyurethane solution had a measured percentage of solids of 39.33%, a measured viscosity by falling-ball method at 40°C of 6105 poise, and an intrinsic viscosity of 1.06 dL/g for the dried films cast from this solution. The %NCO is 5.75 based on the combined weight of PTMEG and MDI for the completed reaction. This solution was used to spin into spandex fibers by a conventional dry-spinning process.

EXAMPLE 2 High stability polyurethane comparative

[00050] Stability of the polymer molecular weight of the polyurethane fiber of this disclosure was evaluated by knitting the spandex fiber on single tube FAK knitting machine (Lawson-Hemphill - US). Comparison types of polyurethane-urea spandex used are listed in Table- 1 as items IL, 2B, 3B, 4B, HX, UX all of which are available commercially either from The LYCRA Corporation or other global spandex suppliers. After the knitting process, the fabrics were scoured at 80°C for 15 minutes. They were then heat set on a conventional stenter at 180°C for 60 seconds. They were then dyed in polyester disperse conditions in a pressurized vessel at 130°C for 60 minutes at a pH of 4-5. The heat-set, then dyed samples are referred to as dyed fabrics. Samples of the dyed fabrics where then dissolved in DMAc at 80°C to form a solution with 20% solids by weight. This solution was then dry-spun into a film. The film samples of each item are referred to as recycled polymer. The polymer molecular weights of the dyed and recycled polymer were measured by GPC. The Polydispersity (Mw/Mn) referred to as PD was also calculated. Results are depicted in Table 1.

[00051] As the shown in the Table 1, the fiber prepared from the polymer of this disclosure has high stability as compared to the other commercially available polyurethane-urea spandex because for both the dyed and recycled polymer form, the polymer composition exhibited the unique combination a Mw below 180,000, a poly dispersity (PD) below 4.0, and a hard segment melting point below 250°C. This unexpected combination of polymer molecular weight properties and hard segment melting behavior enables the polymer to be reprocessed back into a fiber when it has removed from a finished article.

EXAMPLE 3 Denim Fabric

[00052] The polyurethane of Example 1 was made into a 78 decitex - 4 filament spandex fiber by a conventional dry-spinning process. The spandex fiber was core spun (Manufactured by Pinter - Spain) at 3.5X draft with cotton roving to make a 14/1 covered yarn with 40 picks per inch and 14 twists per inch. The yarn was used as the filling yam in a 2x1 twill denim fabric construction (Dornier rapier loom - Germany). The 14S covered yarn was used in weft direction and the warp was an 8/1 indigo dyed cotton yarn with 64 ends per inch. The denim fabric was desized and scoured in a dye machine and then relaxed in 80°C water for 10 minutes. After relaxing, fabric was air-dried on a rack. Properties of the fabrics are disclosed in Table 2.

[00053] As shown by Table 2, a stretch denim fabric meeting industry standards for stretch and low shrinkage can be made from this polymer composition.

EXAMPLE 4 Knit Fabric with Polyester

[00054] The polyurethane polymer of Example 1 was made into a 78 decitex - 4 filament spandex fiber by a conventional dry-spinning process. It was then knitted on a 28 gg CK machine (Monarch - England) at a 3. OX draft and it was plaited with 78dtex polyester yarn at every course to make a single jersey construction fabric. The fabric was scoured at 80 °C for 30 minutes and then heat set at 185 °C for 60 seconds. Fabric was dyed at 130°C for 60 minutes and then air dried. A control fabric was made identically except a polyurethane-urea spandex fiber was used (The LYCRA Company type 78dtex type 582L) and the fabric was heat set at 192°C for 60 seconds. The stretch properties of the fabrics when stretched in the width direction, measured according ASTM D4964-96 are provided in Table 3. Table 3

[00055] This example indicates the method of the invention has similar stretch and recovery properties to a standard polyurethane-urea spandex.

EXAMPLE 5 Recycled Example of a processed fabric

[00056] A circular knit fabric made from a spandex fiber made from the polymer of Example 1 was prepared, treated by scouring at 80°C for 15 minutes. It was then heat set at 180°C for 60 seconds and processed in a conventional disperse dye process conditions of 130°C pressurized aqueous conditions for 60 minutes at a pH of 4-5. The treated fabric was then dissolved in DMAc at 80°C to form a solution with 39% solids. The polymer molecular weights were monitored by GPC in this recycling process as shown in Table 4.

Table 4

[00057] The solution of recycled polymer was spun by conventional dry spinning to make a 28dtex spandex fiber. The fiber had an elongation to break of 411% and a % set of 32.

EXAMPLE 6 Knit Fabric with Cotton

[00058] The polyurethane of Example 1 was made into a 78 decitex - 4 filament spandex fiber by a conventional dry-spinning process. It was then knitted on a 28 gg CK machine at 1.5X draft, and plaited with 60s cotton yarn at every course to make a single jersey construction circular knit fabric. Fabric was scoured at 80 °C for 30 minutes then heat set at 185 °C for 60 seconds. Fabric was dyed at 130°C for 60 minutes and air dried. The fabric had a desirable high power in the weft direction. This fabric, 1000 grams in total weight, was cut into pieces about 25 x 25 centimeters, and placed in 4000 grams of DMAc to dissolve the spandex fibers. The mixture of cotton fabrics and spandex solution was processed through a mechanical press to extract and separate the polymer solution from the undissolved cotton. The collected polyurethane polymer solution was then precipitated in water, and then dried at about 70°C for 2 days. A total of 330 grams of dried polyurethane polymer was collected. This dried polymer was dissolved in DMAc to prepare a solution of 39% solids. Polymer films were prepared from a solution of the polymer in example- 1 have a number average molecular weight (Mn) at 29838 Daltons and a weight average molecular weight at 88253 Daltons measured by gel permeation chromatography (GPC) method. The precipitated and dried polymer solids of example-5 have a Mn and Mw at 34523 and 92073 Daltons respectively. This example demonstrates the stability of the molecular weight to the conditions of the textile processing route.