Method for preparing articles from recyclable fabrics

Abstract

The present invention relates to a method for preparing an article by recycling a disperse-dyed fabric. The fabric is made of melt-spun thermoplastic polyurethane fibers, and the melt-spun thermoplastic polyurethane fibers contain copolymer diols derived from ε-caprolactone monomers and polyether polyols. The fabric is shredded and then heat-treated to form particles, and the particles can be melted in an extruder to form an article.

Description

BACKGROUND OF THE INVENTION

[0001] In the apparel market, there is an increasing interest in fabrics that are stretchable but maintain their shape and fit. Thermoplastic polyurethane ("TPU") fibers show great potential for providing stretch and fit characteristics, but have some drawbacks. Many polyurethane fibers are prepared by a dry spinning method that involves dissolving reactive components in a solvent. Such fibers generally have good heat resistance, but the dry spinning method is expensive, time-consuming, and involves the use of volatile solvents, creating environmental problems. Fiber melt spinning has manufacturing advantages, but not all TPUs are suitable for forming fibers under melt spinning conditions. In addition, prior art TPUs that can be melt spun into fibers do not have the heat resistance that would allow them to withstand certain dyeing conditions. This makes it difficult to combine melt spun TPU fibers with other common synthetic or natural fibers, because the TPU fibers may lose their stretch and recovery characteristics after exposure to dyeing conditions.

[0002] Accordingly, there is a desire to have melt spun TPU fibers that have good stretch and recovery characteristics, but can be dyed under disperse dyeing conditions (e.g., at a temperature of about 130°C to 135°C). There is also a desire to have fabrics made from TPU fibers alone or in combination with other fiber materials to provide fabrics that can be dyed and have the desired characteristics.

[0003] In addition, the recycling of waste or used fabrics is an area of increasing concern. There is a desire to have methods for recycling fabric materials to prepare other articles. SUMMARY OF THE INVENTION

[0004] In one embodiment, the present invention is a melt spun fiber, wherein the fiber comprises a thermoplastic polyurethane composition and an isocyanate functional crosslinking agent. The thermoplastic polyurethane composition used in the fiber comprises the reaction product of: (i) a polyol component that comprises or consists of a copolymer diol derived from ε-caprolactone monomer and poly(tetramethylene ether glycol), (ii) a hydroxyl terminated chain extender component, and (iii) a first diisocyanate component.

[0005] In another embodiment, the present invention includes a method for preparing a thermoplastic polyurethane, the method having the following steps: (a) preparing a reactive thermoplastic polyurethane composition, which is a reaction product of: (a) a polyol component, wherein the polyol component comprises a copolymer diol derived from ε-caprolactone monomer and poly(tetramethylene ether glycol); (b) a chain extender component comprising 1,4-bis(β-hydroxyethoxy)benzene; and (c) a diisocyanate; (2) drying the reactive thermoplastic polyurethane composition; (3) melting the reactive thermoplastic polyurethane composition in an extruder; (4) adding an isocyanate-functional prepolymer to the extruder; (5) mixing the reactive thermoplastic polyurethane composition and the isocyanate-functional prepolymer in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) feeding the crosslinked thermoplastic polyurethane polymer to at least one spinneret to produce melt-spun fibers; (7) cooling the melt-spun fibers; and (8) winding the melt-spun fibers onto a bobbin.

[0006] In yet another embodiment, the present invention provides a fabric comprising a first fiber component and a second fiber component, the first fiber component comprising a hard yarn having an ultimate elongation of 10% to 75% measured according to ASTM D2256, such as a polyester fiber, and the second fiber component comprising melt-spun thermoplastic polyurethane filaments having an ultimate elongation of at least 300% measured according to ASTM D2731, wherein the first fiber component and the second fiber component are knitted together to form the fabric, and wherein the fabric is dyed using disperse dyeing conditions.

[0007] In another embodiment, the present invention provides a method for recycling the fabric prepared herein to prepare other articles.

[0008] These various embodiments are described in more detail below. Detailed Description

[0009] The features and embodiments of the present invention will be described below by the following non-limiting description.

[0010] The disclosed technology includes a melt-spun fiber comprising a thermoplastic polyurethane (“TPU”) composition and an isocyanate-functional crosslinker. The TPU composition useful for preparing the melt-spun fibers of the present invention is a reaction product of a polyol component, a hydroxyl-terminated chain extender component, and a diisocyanate component. The isocyanate-functional crosslinker is a reaction product of a polyol and an excess of isocyanate. Each of these components will be described in more detail below.

[0011] As used herein, the weight-average molecular weight (Mw) is measured by gel permeation chromatography using polystyrene standards, and the number-average molecular weight (Mn) is measured by end-group analysis.

[0012] Thermoplastic polyurethane composition

[0013] The TPU composition useful for preparing the melt-spun fibers of the present invention comprises a polyol component, which can also be described as a hydroxyl-terminated intermediate. In the present invention, the polyol component comprises a copolymer diol derived from caprolactone monomers and a hydroxyl-functional polyether intermediate or consists of such copolymer diol.

[0014] Caprolactone monomers useful for preparing the copolymer polyol for the present invention include ε-caprolactone and 2-oxepanone. In one embodiment, the caprolactone monomer reacts with a polyether diol to form a copolymer diol. In another embodiment, ε-caprolactone can react with another bifunctional initiator such as diethylene glycol, 1,4-butanediol, neopentyl glycol or any other diol and / or diol known to those skilled in the art.

[0015] In embodiments where ε-caprolactone reacts with a polyether polyol intermediate, suitable hydroxyl-functional polyether intermediates include polyether polyols derived from diols or polyols having a total of 2 to 15 carbon atoms, including in some embodiments alkyl diols or diols that react with ethers containing alkylene oxides having 2 to 6 carbon atoms (usually ethylene oxide or propylene oxide or mixtures thereof). For example, a hydroxyl-functional polyether can be prepared by first reacting propylene glycol with propylene oxide and then with ethylene oxide. The primary hydroxyl groups produced by ethylene oxide are more reactive than secondary hydroxyl groups and may thus be preferred. Commercially available polyether polyols include poly(ethylene glycol) containing ethylene oxide reacted with ethylene glycol, poly(propylene glycol) containing propylene oxide reacted with propylene glycol, poly(tetramethylene ether glycol) containing water reacted with tetrahydrofuran, which can also be described as polytetrahydrofuran and is commonly referred to as PTMEG. In some embodiments, the hydroxyl-functional polyether intermediate used in the present invention comprises PTMEG or consists of PTMEG.

[0016] In one embodiment, the polyol component comprises a copolymer diol that is the reaction product of caprolactone monomers and poly(tetramethylene ether glycol) or consists of such copolymer diol. In another embodiment, the polyol component comprises or consists of the reaction product of about 50 wt% ε-caprolactone monomers and about 50 wt% poly(tetramethylene ether glycol).

[0017] In one embodiment of the present invention, the reaction mixture for forming the TPU composition used herein comprises about 50 wt% to about 80 wt% of the polyol component, such as about 60 wt% to about 75 wt% or even about 65 wt% to about 70 wt%.

[0018] Chain extender component

[0019] Prepare the TPU compositions described herein using a chain extender component. Suitable chain extenders include diols, diamines, and combinations thereof.

[0020] Suitable chain extenders include relatively small polyhydroxy compounds, such as lower aliphatic or short-chain diols having 2 to 20, or 2 to 12, or 2 to 10 carbon atoms. Suitable examples include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol (BDO), 1,6-hexanediol (HDO), 1,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol (CHDM), 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane (HEPP), 1,4-bis(β-hydroxyethoxy)benzene (HQEE), hexamethylene glycol, heptanediol, nonanediol, dodecanediol, 3-methyl-1,5-pentanediol, ethylenediamine, butanediamine, hexamethylenediamine, and hydroxyethylresorcinol (HER), among others, and mixtures thereof. In one embodiment, the chain extender comprises or consists of 1,4-bis(β-hydroxyethoxy)benzene (HQEE).

[0021] In one embodiment of the present invention, the reaction mixture for forming the TPU compositions used herein comprises from about 5 wt% to about 25 wt% of a chain extender component, such as from about 5 wt% to about 15 wt% or even from about 8 wt% to 10 wt%.

[0022] Isocyanate component

[0023] Prepare the TPU of the present invention using an isocyanate component. The isocyanate component can include one or more polyisocyanates, or more particularly, one or more diisocyanates. Suitable polyisocyanates include aromatic diisocyanates, aliphatic diisocyanates, or combinations thereof. In some embodiments, the polyisocyanate component includes one or more aromatic diisocyanates. In some embodiments, the polyisocyanate component is substantially free or even completely free of aliphatic diisocyanates. In other embodiments, the polyisocyanate component includes one or more aliphatic diisocyanates. In some embodiments, the polyisocyanate component is substantially free or even completely free of aromatic diisocyanates. In some embodiments, a mixture of aliphatic and aromatic diisocyanates may be useful.

[0024] Examples of useful polyisocyanates include aromatic diisocyanates such as 4,4′-methylenebis(phenyl isocyanate) (MDI), 3,3'-dimethyl-4,4'-biphenyl diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), m-xylene diisocyanate (XDI), phenylene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, and toluene diisocyanate (TDI); and aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 1,4-cyclohexane diisocyanate (CHDI), decane-1,10-diisocyanate, lysine diisocyanate (LDI), 1,4-butane diisocyanate (BDI), isophorone diisocyanate (PDI), and dicyclohexylmethane-4,4′-diisocyanate (H12MDI). Isomers of these diisocyanates may also be useful. Mixtures of two or more polyisocyanates may be used. In some embodiments, the isocyanate component comprises or consists of an aromatic diisocyanate. In some embodiments, the isocyanate component comprises or consists of MDI.

[0025] In one embodiment of the present invention, the reaction mixture for forming the TPU composition used herein comprises from about 15 wt% to about 30 wt% of an isocyanate component, such as from about 15 wt% to about 25 wt% or even from about 18 wt% to about 20 wt%.

[0026] Optionally, one or more polymerization catalysts may be present during the polymerization of the TPU. Generally, any conventional catalyst can be utilized to react the diisocyanate with the polyol intermediate or chain extender. In particular, examples of suitable catalysts that accelerate the reaction between the NCO groups of the diisocyanate and the hydroxyl groups of the polyol and chain extender are conventional tertiary amines known from the prior art, such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N′-dimethylpiperazine, 2-(dimethylaminoethoxy)ethanol, diazabicyclo[2.2.2]octane, etc., and also in particular organometallic compounds such as titanates, iron compounds such as iron acetylacetonate, tin compounds such as stannous diacetate, stannous octoate, stannous dilaurate, bismuth compounds such as bismuth trisneodecanoate, or dialkyltin salts of aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate, etc. The usual amount of catalyst is from 0.001 to 0.1 parts by weight per 100 parts by weight of the polyol component. In some embodiments, the reaction for forming the TPU of the present invention is substantially free or completely free of catalyst.

[0027] The TPU compositions for the present invention can be prepared via a "one-step" method, in which all components are added together simultaneously or substantially simultaneously to a heated extruder and reacted to form the TPU. The equivalent ratio of the total equivalents of the diisocyanate to the hydroxyl-terminated intermediate and the chain extender is typically from about 0.95 to about 1.10, such as from about 0.97 to about 1.03 or even from about 0.98 to about 1.0. In one embodiment, the equivalent ratio can be less than 1.0 such that the TPU has terminal hydroxyl groups to enhance the reaction with the crosslinker during the fiber spinning process. The weight average molecular weight (MW) of the TPU is typically from about 25,000 to about 300,000, such as from about 50,000 to about 200,000, and even further such as from about 75,000 to about 150,000.

[0028] In another embodiment, the TPU can be prepared using a prepolymer method. In the prepolymer method, the hydroxyl-terminated intermediate is reacted with one or more diisocyanates in a generally equivalent excess to form a prepolymer solution having free or unreacted isocyanate therein. Subsequently, the chain extender as described herein is added in an amount generally equal to the equivalents of the isocyanate end groups and any free or unreacted diisocyanate compounds. Thus, the total equivalent ratio of the total equivalents of the diisocyanate to the hydroxyl-terminated intermediate and the chain extender is from about 0.95 to about 1.10, such as from about 0.97 to about 1.03 or even from about 0.98 to about 1.0. In one embodiment, the equivalent ratio can be less than 1.0 such that the TPU has terminal hydroxyl groups to enhance the reaction with the crosslinker during the fiber spinning process. Generally, the prepolymer method can be carried out in any conventional apparatus such as an extruder.

[0029] Optional additive components can be present during the polymerization reaction, and / or the optional additive components can be incorporated into the above TPU elastomers to improve processing and other properties. These additives include but are not limited to antioxidants, organic phosphites, phosphines and phosphonates, hindered amines, organic amines, organic sulfur compounds, lactones and hydroxylamine compounds, biocides, fungicides, antimicrobials, compatibilizers, electrical dissipation or antistatic additives, fillers and reinforcing agents such as titanium dioxide, alumina, clay and carbon black, flame retardants such as phosphate esters, halogenated materials and metal salts of alkylbenzenesulfonic acid, impact modifiers such as methyl methacrylate-butadiene-styrene ("MBS") and methyl methacrylate-butyl acrylate ("MBA"), mold release agents such as waxes, greases, pigments and colorants, plasticizers, polymers, rheology modifiers such as monoamines, polyamide waxes, silicones and polysiloxanes, slip additives such as paraffin wax, hydrocarbon polyolefins and / or fluorinated polyolefins, and UV stabilizers, which can be of the hindered amine light stabilizer (HALS) and / or UV light absorber (UVA) type. Other additives can be used to enhance the properties of the TPU compositions or blend products. All of the above additives can be used in effective amounts commonly used for these substances.

[0030] These additional additives can be incorporated into the components used to prepare the TPU resin or into the reaction mixture used for the preparation of the TPU resin, or incorporated after the TPU resin is prepared. In another method, all the materials can be mixed with the TPU resin and then melted, or they can be directly incorporated into the melt of the TPU resin.

[0031] Isocyanate-functional crosslinking agent

[0032] The above TPU composition is combined with an isocyanate-functional crosslinking agent. The crosslinking agent is the reaction product of a hydroxyl-terminated polyol selected from polyethers, polyesters, polycaprolactones, polycarbonates, and mixtures thereof with an excess of diisocyanate. In one embodiment, the hydroxyl-terminated polyol used in the crosslinking agent is a polyether polyol. For example, the hydroxyl-terminated polyether may comprise or consist of poly(tetramethylene ether glycol). In another embodiment, the hydroxyl-terminated polyol used in the crosslinking agent is a polyester. For example, the hydroxyl-terminated polyester may comprise or consist of neopentyl glycol adipate. In one embodiment, the polyisocyanate component is an aromatic diisocyanate, such as MDI. In another embodiment, the polyisocyanate component is an aliphatic diisocyanate, such as H12MDI. The crosslinking agent has an isocyanate functionality greater than 1.0, for example about 1.5 to 2.5, further for example about 1.8 to 2.2. The isocyanate-functional crosslinking agent can be prepared using the prepolymer method as described herein, wherein a hydroxyl-terminated intermediate is reacted with an equivalent excess of one or more diisocyanates to form a prepolymer solution having free or unreacted isocyanates.

[0033] The weight percentage of the crosslinking agent used with the TPU polymer is from about 5.0 wt% to about 20 wt%, for example from about 8.0 wt% to about 15 wt%. The percentage of the crosslinking agent used is a weight percentage based on the total weight of the TPU and the crosslinking agent.

[0034] Thermoplastic polyurethane fiber

[0035] Melt-spun TPU fibers are prepared by melting a TPU composition in an extruder and adding a crosslinking agent to the molten TPU. The TPU melt and the crosslinking agent are fed to a spinneret. The melt exits the spinneret to form fibers, and the fibers are cooled and wound onto a bobbin. The method comprises the steps of: (1) preparing a reactive thermoplastic polyurethane composition which is a reaction product of: (a) a polyol component, wherein the polyol component comprises or consists of a copolymer diol derived from ε-caprolactone monomer and poly(tetramethylene ether glycol); (b) a chain extender component, the chain extender component comprising or consisting of 1,4-bis(β-hydroxyethoxy)benzene; and (c) a diisocyanate; (2) drying the reactive thermoplastic polyurethane composition; (3) melting the reactive thermoplastic polyurethane composition in an extruder; (4) adding an isocyanate-functional prepolymer to the extruder; (5) mixing the reactive thermoplastic polyurethane composition and the isocyanate-functional prepolymer in the extruder to form a crosslinked thermoplastic polyurethane polymer; (6) feeding the crosslinked thermoplastic polyurethane polymer to at least one spinneret to produce melt-spun fibers; (7) cooling the melt-spun fibers; and (8) winding the melt-spun fibers onto a bobbin core. The steps of the method will be described in more detail below.

[0036] The melt-spinning method starts with feeding a preformed TPU polymer into an extruder. The TPU is melted in the extruder, and the crosslinking agent is continuously added downstream near or after the point where the TPU melt exits the extruder. If the crosslinking agent is added after the melt exits the extruder, a static or dynamic mixer is required to mix the crosslinking agent with the TPU melt to ensure proper incorporation of the crosslinking agent into the TPU polymer melt. After leaving the extruder and the mixer, the molten TPU polymer and the crosslinking agent flow into a manifold. The manifold divides the melt stream into different streams, and each stream is fed to a plurality of spinnerets. Typically, there is a melt pump for each different stream flowing out of the manifold, and each melt pump feeds a number of spinnerets. The spinneret will have small holes through which the melt is forced and exits the spinneret in the form of fibers. The size of the holes in the spinneret will depend on the desired size (denier) of the fiber. The fibers are drawn or stretched as they leave the spinneret and are cooled before being wound onto a bobbin. The fibers are stretched by winding the bobbin at a speed higher than the speed at which the fibers leave the spinneret. For melt-spun TPU fibers, the bobbin is typically wound at a rate greater than the speed at which the fibers leave the spinneret, for example, at a rate 4 to 8 times the speed at which the fibers leave the spinneret in some embodiments, but may be wound slower or faster depending on the particular equipment. Typical bobbin winding speeds can range from 100 meters per minute to 3000 meters per minute, but more typical speeds for TPU melt-spun fibers are from 300 meters per minute to 1200 meters per minute. A finish oil (such as silicone oil) is typically added to the surface of the fibers after cooling and just before winding onto the bobbin.

[0037] An important aspect of the melt spinning process is the mixing of the TPU polymer melt with the crosslinking agent. Proper homogeneous mixing is important for achieving uniform fiber properties and enabling long run times without experiencing fiber breakage. The mixing of the TPU melt and the crosslinking agent should be a method that achieves plug flow (i.e., first in, first out). Appropriate mixing can be achieved using a dynamic mixer or a static mixer. For example, a dynamic mixer with a feed screw and mixing pins can be used. U.S. Patent 6,709,147 describes such a mixer and has rotatable mixing pins.

[0038] During the fiber spinning process, the TPU reacts with the crosslinking agent, resulting in a fiber-form TPU having a weight average molecular weight (MW) of about 200,000 to about 800,000, preferably about 250,000 to about 500,000, and more preferably about 300,000 to about 450,000. At the point where the TPU exits the spinneret, the reaction between the TPU and the crosslinking agent in the fiber spinning process should be higher than 20%, preferably about 30% to about 60%, and more preferably about 40% to about 50%. The typical prior art TPU melt spinning reaction between the TPU polymer and the crosslinking agent is less than 20%, and usually about 10% to 15% reacts. The reaction is determined by the disappearance of the NCO groups. The higher reaction % of the present invention improves the melt strength, thus allowing a higher spinning temperature, which improves the spinnability of the TPU. The fibers are typically aged on a spool in an oven until the molecular weight reaches a stable level.

[0039] The spinning temperature (the temperature of the polymer melt in the spinneret) should be higher than the melting point of the polymer, and preferably about 10 °C to about 20 °C higher than the melting point of the polymer. The higher the spinning temperature that can be used, the better the spinning. However, if the spinning temperature is too high, the polymer may degrade. Therefore, being about 10 °C to about 20 °C higher than the melting point of the TPU polymer is the optimal temperature for achieving a balance of good spinning without polymer degradation. If the spinning temperature is too low, the polymer may solidify in the spinneret and cause fiber breakage. The spinning temperature of the fibers produced by the present invention is greater than 190 °C, and preferably about 190 °C to about 220 °C, or even about 190 °C to about 200 °C.

[0040] An important aspect of preparing melt - spun TPU fibers is the length of time the process can be run continuously. The need to stop the process is typically the result of fiber breakage. Fiber breakage occurs when the pressure at the spinneret increases to an unacceptable level. Fiber breakage typically occurs when the pressure reaches about 140 to 200 kgf / cm². Pressure buildup can occur for several reasons, such as improper mixing. This leads to the formation of products due to the self - reaction of cross - linkers, which can partially block the small exit holes in the spinneret with fibers. The present invention allows for a much longer run time before the harmful pressure buildup that causes fiber breakage.

[0041] Melt - spun TPU fibers can be made in a variety of deniers. The term "denier" is defined as the mass in grams of 9000 meters of fiber, filament, or yarn. It describes the linear density, the mass per unit length, of the fiber, filament, or yarn and is measured according to ASTM D1577 Option B. Typical melt - spun TPU fibers are made in sizes less than 240 denier, more typically in the range of 10 to less than 240 denier, with 20 and 40 denier being commonly used sizes.

[0042] Due to the high temperatures required for polyester dyeing, prior art melt - spun TPU fibers are not typically used in combination with polyester fibers. Due to the lack of polarity and the highly crystalline nature of polyester polymers and fibers, disperse dyes are commonly used for dyeing. Such fibers are typically dyed at 120 °C to 135 °C (e.g., about 130 °C) for 60 minutes, and the pressure is 1 to 1.5 kg / cm 2 . This pressure dyeing "opens" the polyester polymer, allowing the dye molecules to penetrate. When the dyeing is complete and the fabric is removed from the pressure - dyeing vessel (called a dyeing machine), the polyester polymer system "closes" again, thus "trapping" the disperse dye molecules inside. Prior art melt - spun TPU fibers cannot withstand this type of temperature for 60 minutes without losing their physical properties, such as tenacity and percentage of setting measured according to ASTM D2731. In addition, when exposed to the aforementioned elevated temperatures and pressures, prior art melt - spun TPU fibers also tend to fuse with adjacent fibers, which is harmful to the tensile properties of the fabric.

[0043] The high heat resistance of the melt - spun TPU fibers of the present invention can withstand the dyeing operation of polyester fibers while retaining sufficient physical properties to maintain elasticity.

[0044] Another feature of the high - heat - resistant melt - spun TPU fibers of the present invention is their ability to absorb disperse dyes. The method of disperse dyeing involves exposure to a temperature of about 130 °C for about 60 minutes (the dyeing conditions for polyester fibers). Many TPU fibers do not exhibit dye absorption, color fastness (after washing), and bleach resistance after exposure to these temperatures.

[0045] The melt-spun fibers prepared according to the present invention have unique physical properties not exhibited by prior art TPU fibers. First, the fibers exhibit unique elastic properties. For example, the fibers prepared according to the present invention exhibit a hysteresis of less than 30% or even less than 20% at 100% elongation after the 5th loading and unloading cycle; less than 30% or even less than 18% at 150% elongation; and less than 30% or even less than 18% at 200% elongation; The term "hysteresis" is defined as the residual physical effect after the external stimulus is removed, and in the fiber, it is observed as the dimensional change after stretching and recovery. Expressed as the percentage of hysteresis at the corresponding elongation (or strain). Hysteresis is measured according to ASTM D2731. The calculation of hysteresis can be calculated by using the following information and equations:

[0046] Modulus at 100% elongation during the load cycle = m1

[0047] Modulus at 100% elongation during the unloading cycle = m2

[0048] % Hysteresis at 100% elongation = (m1 - m2) / m1 × 100. Hysteresis can be calculated similarly at 150% and 200% elongation.

[0049] The melt-spun TPU fibers prepared according to the present invention also have an ultimate elongation of at least 300% (e.g., 300% to 650%) as measured by ASTM D2731. Generally, elastic materials are characterized by ductility and elasticity: when the external force is released, these materials almost completely return to their original dimensions. For an ideal elastic material, on the stress-strain graph, only one curve traces the loading and unloading cycles. However, for most materials, due to energy loss (in the form of heat), most materials show different loading and unloading curves, also known as "hysteresis". A lower % hysteresis value means excellent elasticity. The use of elastic fibers with extremely low % hysteresis can be used to obtain fabrics with less deformation in clothing.

[0050] In addition, the melt-spun TPU fibers prepared according to the present invention may also have a melt onset of 140°C to 170°C, such as 150°C to 170°C, further such as about 155°C to 166°C as measured by ASTM D3418, and an elastic modulus of 3.5E+05 to 12E+05 Pa at 130°C as measured by DMA (dynamic mechanical analysis). DMA measurements are performed using a parallel plate configuration with a heating rate of 2°C / min from -100°C to 250°C at a frequency of 1 Hz and a strain of 0.1%.

[0051] Fabric

[0052] The TPU fibers of the present invention can be used alone or in combination with other natural or synthetic fibers by knitting or weaving the fibers to prepare fabrics that can be used in a variety of articles. It is desirable to dye such fabrics in a variety of colors.

[0053] In one embodiment, the melt-spun TPU fibers of the present invention can be woven to prepare a fabric. In another embodiment, the melt-spun TPU fibers of the present invention can be combined with one or more different TPU fibers to prepare a fabric. In yet another embodiment, the melt-spun TPU fibers of the present invention can be combined with other fibers such as cotton, nylon, or polyester to prepare various end-use articles, including apparel.

[0054] For example, a fabric according to the present invention can combine the melt-spun TPU fibers of the present invention with a yarn having a lower elasticity than the TPU fibers of the present invention (also referred to herein as a "stiff yarn"). The stiff yarn can include, for example, polyester, nylon, cotton, wool, acrylic, polypropylene, or viscose rayon. The stiff yarn can also include, for example, other TPU fibers (not the TPU fibers of the present invention) having a smaller elasticity than the TPU fibers of the present invention. In one embodiment, the stiff yarn has an ultimate elongation of 10% to 200%, such as 10% to 75%, or 10% to 60%, or even 10% to 50%, or even 10% to 30%, and the melt-spun TPU fibers of the present invention have an ultimate elongation of at least 300%, such as 300% to 650%. Each fiber component can be included in the composition in an amount of 1 wt% to 99 wt%. The weight% of the melt-spun TPU fibers in the end-use application can vary depending on the desired elasticity. For example, a woven fabric has 1 wt% to 8 wt% of melt-spun TPU fibers, an undergarment has 2 wt% to 5 wt% of melt-spun TPU fibers, a swimsuit and sportswear have 8 wt% to 30 wt% of melt-spun TPU fibers, a corset has 10 wt% to 45 wt% of melt-spun TPU fibers, and a medical hose has 35 wt% to 60 wt% of melt-spun TPU fibers, with the remaining amount being stiff non-elastic fibers. Fabrics made from these two fiber materials can be constructed by various methods, including but not limited to circular knitting, warp knitting, weaving, braiding, non-woven fabrics, or combinations thereof. In one embodiment, a fabric made from the fibers of the present invention will have a stretch rate greater than 100% measured by ASTM D4964. The fibers can be dyed at elevated temperatures of at least 130°C.

[0055] Recycled fabric

[0056] The present invention also includes a method for preparing an article by recycling the fabrics disclosed herein. In this method, a disperse-dyed fabric made of the thermoplastic polyurethane fibers described herein can be shredded and then heat-treated to form particles. The heat treatment method for forming the particles will be understood by those skilled in the art. The particles can then be melted and sheared in an extruder to form an article, as is commonly understood in the art.

[0057] Fabrics that can be recycled in the present invention include those made of the melt-spun thermoplastic polyurethane fibers prepared herein. Such fabrics may also contain other fibers, including fibers of polyester, nylon, acrylic, polypropylene, or mixtures thereof. In one embodiment, in addition to the melt-spun thermoplastic polyurethane fibers, the fabric will further contain up to 70% polyester fibers.

[0058] In another embodiment, a second polymeric material can be added to the extruder together with the particles made from the recycled fabric. Examples of the second polymer that can be used include polyester or other thermoplastic polyurethanes or mixtures thereof.

[0059] In the present application and the following examples, the following properties and methods for measuring such properties are mentioned:

[0060] · Denier is a measure of linear density and is measured according to ASTM D1577 Option B;

[0061] · The tenacity of the elastic filament (which is the tensile strength normalized by denier) is also measured and reported according to ASTM D2731;

[0062] · The ultimate elongation of the elastic filament (which is the elongation at break) is also measured and reported according to ASTM D2731;

[0063] · Hysteresis, which is defined and calculated at the corresponding elongation as previously mentioned herein and is reported according to ASTM D2731 for elastic filaments;

[0064] · For inelastic hard yarns such as polyester, tenacity and elongation are measured and the ASTM D2256 standard is used;

[0065] · The content of individual components in the fabric is measured according to ASTM D629

[0066] · The fabric stretch and fabric modulus are measured according to ASTM D4964.

[0067] · Fabric washing is carried out according to the American Association of Textile Chemists and Colorists (“AATCC”) Test Method 135

[0068] ·

[0069] The present invention will be better understood by reference to the following examples.

[0070] Example

[0071] Table 1 lists the TPU compositions prepared for making the fibers in the present invention. The TPU hard segment is the total amount by weight of the isocyanate and chain extender in the TPU composition.

[0072] Table 1

[0073]

[0074] The TPU polymers of Examples A to G were pre-dried in a vacuum batch dryer at 80 °C for 12 hours. After drying, the TPU polymers were melted in a 1.25-inch single-screw extruder with an L / D ratio of 24. The extruder had four heating zones maintained between 180 °C and 225 °C throughout the process. As it exited the extruder, the TPU polymer melt was mixed with 10 wt% of a prepolymer crosslinker (90 wt% TPU polymer melt / 10 wt% crosslinker). The combination of TPU and crosslinker is summarized in Table 2.

[0075] Table 2

[0076]

[0077] The crosslinker was mixed with the TPU polymer melt in a dynamic mixer and then pumped through a manifold to a spinneret. Each spinneret had a spinneret hole size of 0.65 mm. The polymer stream exiting the spinneret was air-cooled, a silicone finish oil was applied, and the formed fibers were wound onto a bobbin. Before testing the physical properties of the fibers, the fibers on the bobbin were heat-aged at 80 °C for 24 hours. Table 3 summarizes the key properties of the fibers.

[0078] Table 3

[0079]

[0080] The fibers of Example 1 were used to prepare a single-sided knitted fabric on a Vanguard circular knitting machine. A 70D (68 filaments) multifilament texturized polyester yarn (as the hard yarn) was combined with the examples in Table 3. The knitting tension on the machine was adjusted to knit a balanced ratio throughout the fabric such that it contained 25% of the elastic yarn in Table 3 and 75% polyester yarn (which was confirmed by mechanically separating the elastic yarn and hard yarn by weight in a fabric sample according to ASTM D629-15). The fiber of Example 1 in Table 2 was successfully converted into a fabric. The fibers of Examples 2 to 7 were too sticky and kept breaking during the knitting process and could not be converted into a fabric.

[0081] The knitted fabric using the fiber of Example 1 was dyed as described below.

[0082] Scouring, dyeing, and reduction clearing solutions: 1000 ml of the scouring solution contains 2 g of Na2CO3, 6 g of NaOH, and the balance is deionized water. 1000 ml of the dye solution contains 2 g of Foron Navy S-2GRL200 from Archroma U.S., 6 g of Na2CO3, and the balance is deionized water. The pH of the dye bath was adjusted to 4.5 using acetic acid. 1000 ml of the reduction clearing solution contains 6 g of NaOH, and the balance is deionized water.

[0083] A 10-meter long and 1-kg fabric was placed in a Thies dyeing machine. The dyeing machine was programmed to perform scouring, dyeing, and reduction clearing temperature cycles.

[0084] Scouring was carried out for 30 minutes at 65 °C using one liter of the scouring solution prepared above, followed by rinsing with warm tap water. Then the dye container was filled with one liter of the dye solution. The dyeing process was started at 50 °C, and then the bath temperature was slowly increased at a rate of 2 °C / min to 130 °C and held at this temperature for 60 minutes. Then the temperature was lowered to 80 °C, after which the dye solution was drained from the dye container, followed by two cycles of rinsing with tap water.

[0085] After rinsing, one liter of the reduction clearing solution prepared above was introduced into the dyeing container at 75 °C to 80 °C and held for 30 minutes. Then, the fabric sample was rinsed with warm tap water until no more dye leaked out. Finally, the fabric was soaked in a 1% acetic acid neutralizing solution for 30 seconds.

[0086] The wet fabric sample was air-dried overnight. Once dry, the fabric was heat-set in a stenter, and the fabric was pre-stretched 20% larger than the initial width. The fabric was then passed through the stenter twice.

[0087] Next, the fabric sample was washed using the American Association of Textile Chemists and Colorists (“AATCC”) Test Method 135-2018. After washing, the tensile properties of the fabric sample were evaluated according to the following table:

[0088] Table 4

[0089]

[0090]

[0091] *At a constant load of 10 lb-f in both the warp (fabric length) and weft (fabric width) directions according to ASTM D4964.

[0092] The fabrics made from the fibers of the present invention can also be recycled. In one embodiment, the fabrics prepared according to the present invention are recycled to prepare extruded or molded articles. Accordingly, the present invention provides a method for preparing articles, which method comprises providing a disperse-dyed fabric prepared according to the present invention, shredding such fabric, heat-treating such shredded fabric to form particles, and then melting and shearing these particles in an extruder to form an article.

[0093] Each of the documents mentioned above is incorporated herein by reference, including any prior applications claiming priority therefrom, whether specifically listed above or not. The mention of any document is not an admission that such document is eligible as prior art or constitutes common general knowledge of a person skilled in the art in any jurisdiction. Unless otherwise specified in the examples or explicitly indicated otherwise, all numerical quantities specifying amounts of substances, reaction conditions, molecular weights, numbers of carbon atoms, etc. in this specification should be understood to be modified by the word "about". It should be understood that the upper and lower limits of the amounts, ranges and ratios described herein can be combined independently. Similarly, the ranges and amounts of each element of the present invention can be used in conjunction with the ranges or amounts of any other element.

[0094] As used herein, the transitional term "comprising", which is synonymous with "including", "containing" or "characterized by", is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. However, in each use of the term "comprising" herein, it is intended that the term also cover, as alternative embodiments, the phrases "consisting essentially of" and "consisting of", where "consisting of" excludes any element or step not specified, and "consisting essentially of" permits the inclusion of additional unrecited elements or steps that do not substantially affect the basic and novel characteristics of the composition or method under consideration.

[0095] Although certain representative embodiments and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the present invention. In this regard, the scope of the present invention is defined only by the following claims.

Claims

1. A method for preparing an article, the method comprising: (1) providing a disperse-dyed fabric comprising melt-spun thermoplastic polyurethane fibers and second fibers, wherein the melt-spun thermoplastic polyurethane fibers comprise the reaction product of: (a) a reactive thermoplastic polyurethane composition, the reactive thermoplastic polyurethane composition comprising (i) a polyol component, wherein the polyol component comprises a copolymer diol derived from ε-caprolactone monomers and a polyether polyol, (ii) a hydroxyl-terminated chain extender component, and (iii) a first diisocyanate component; and (b) an isocyanate-functional prepolymer crosslinker; wherein the second fibers are selected from thermoplastic polyurethane fibers, polyester fibers, nylon fibers, acrylic fibers, polypropylene fibers, or mixtures thereof; (2) chopping the fabric; (3) heat-treating the chopped fabric to form pellets; (4) melting and shearing the pellets in an extruder to form an article.

2. The method according to claim 1, wherein the fabric comprises up to 99% polyester fibers.

3. The method according to claim 1, wherein the fabric comprises up to 70% polyester fibers.

4. The method according to claim 1, wherein the copolymer comprises the reaction product of ε-caprolactone monomer polyol and poly(tetramethylene ether glycol).

5. The method according to claim 2, wherein the copolymer comprises the reaction product of ε-caprolactone monomer polyol and poly(tetramethylene ether glycol).

6. The method according to claim 4, wherein the copolymer comprises the reaction product of 50 wt% ε-caprolactone monomer polyol and 50 wt% poly(tetramethylene ether glycol).

7. The method according to any one of claims 1 to 6, wherein the copolymer has a number average molecular weight of 2000 daltons.

8. The method according to any one of claims 1 to 6, wherein the chain extender component consists of 1,4-bis(β-hydroxyethoxy)benzene.

9. The method according to claim 8, wherein the chain extender component further comprises a co-chain extender.

10. The method according to claim 9, wherein the co-chain extender is selected from ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, hexamethylene glycol, heptanediol, nonanediol, dodecanediol, 3-methyl-1,5-pentanediol, ethylenediamine, butanediamine, hexamethylenediamine, hydroxyethylresorcinol, and mixtures thereof.

11. The method according to any one of claims 1 to 6, wherein the first diisocyanate component comprises an aromatic diisocyanate or consists of an aromatic diisocyanate.

12. The method according to claim 11, wherein the first diisocyanate component comprises 4,4'-diphenylmethane diisocyanate or consists of 4,4'-diphenylmethane diisocyanate.

13. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 50% to 80% by weight of the polyol component.

14. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 60% to 80% by weight of the polyol component.

15. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 70% to 80% by weight of the polyol component.

16. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 5% to 25% by weight of the chain extender component.

17. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 5% to 15% by weight of the chain extender component.

18. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 5% to 10% by weight of the chain extender component.

19. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 15% to 30% by weight of the first diisocyanate.

20. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 15% to 25% by weight of the first diisocyanate.

21. The method according to any one of claims 1 to 6, wherein the reactive thermoplastic polyurethane composition contains 15% to 20% by weight of the first diisocyanate.

22. The method according to any one of claims 1 to 6, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of a reaction product of poly(tetramethylene ether glycol) and a second diisocyanate component.

23. The method according to any one of claims 1 to 6, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of a reaction product of neopentyl glycol adipate and a second diisocyanate component.

24. The method according to claim 22, wherein the second diisocyanate component comprises an aromatic diisocyanate.

25. The method according to claim 23, wherein the second diisocyanate component comprises an aromatic diisocyanate.

26. The method according to claim 24 or 25, wherein the second diisocyanate component comprises or consists of 4,4′-methylenebis(phenyl isocyanate).

27. The method according to claim 22, wherein the second diisocyanate component comprises an aliphatic diisocyanate.

28. The method according to claim 23, wherein the second diisocyanate component comprises an aliphatic diisocyanate.

29. The method according to claim 27 or 28, wherein the second diisocyanate component comprises or consists of dicyclohexylmethane - 4,4'-diisocyanate.

30. The method according to any one of claims 1 to 6, the method further comprising the steps of providing a second polymer material and adding the second polymer together with the particles to the extruder.

31. The method according to claim 30, wherein the second polymer is selected from polyesters or thermoplastic polyurethanes.

32. A method of manufacturing an article, the method comprising the steps of: (1) providing a disperse-dyed fabric, the disperse-dyed fabric comprising (i) a first fiber component, the first fiber component being a thermoplastic hard yarn having an ultimate elongation of 10% to 200% measured according to ASTM D2256, and (ii) a second fiber component, the second fiber component comprising melt-spun thermoplastic polyurethane fibers having an ultimate elongation of at least 300% measured according to ASTM D2731, wherein the first fiber component and the second fiber component are knitted together to form the fabric, and wherein the fabric is dyed at a temperature of at least 130°C, wherein the second fiber component is a melt-spun thermoplastic fiber, the melt-spun thermoplastic fiber comprising the reaction product of: a polyol component, wherein the polyol component comprises a copolymer diol derived from ε-caprolactone monomer and poly(tetramethylene ether glycol); a hydroxyl-terminated chain extender component; and a first diisocyanate component; and an isocyanate-functional prepolymer crosslinker; (2) chopping the fabric; (3) heat-treating the chopped fabric to form particles; and (4) melting and shearing the particles in an extruder to form an article.

33. The method according to claim 32, wherein the first fiber component is a thermoplastic hard yarn having an ultimate elongation of 10% to 75% measured according to ASTM D2256.

34. The method according to claim 32, wherein the first fiber component is a thermoplastic hard yarn having an ultimate elongation of 10% to 60% measured according to ASTM D2256.

35. The method according to claim 32, wherein the melt-spun thermoplastic polyurethane fibers exhibit the following hysteresis after the 5th loading and unloading cycle: (a) having a hysteresis of less than 30% at 100% elongation (b) having a hysteresis of less than 30% at 150% elongation (c) having a hysteresis of less than 30% at 200% elongation wherein the hysteresis is measured according to ASTM D2731.

36. The method according to claim 32, wherein the copolymer diol comprises the reaction product of 50 wt% ε-caprolactone monomer polyol and 50 wt% poly(tetramethylene ether glycol).

37. The method according to claim 32, wherein the melt-spun thermoplastic polyurethane fibers have a weight-average molecular weight of 300,000 to 450,000 measured by gel permeation chromatography.

38. The method according to claim 36, wherein the melt-spun thermoplastic polyurethane fiber has a weight-average molecular weight of 300,000 to 450,000 as measured by gel permeation chromatography.

39. The method according to any one of claims 32 to 38, wherein the first diisocyanate component comprises or consists of an aromatic diisocyanate.

40. The method according to claim 39, wherein the first diisocyanate component comprises or consists of 4,4'-diphenylmethane diisocyanate.

41. The method according to any one of claims 32 to 38, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of a reaction product of poly(tetramethylene ether glycol) and a second diisocyanate component.

42. The method according to any one of claims 32 to 38, wherein the isocyanate-functional prepolymer crosslinker comprises or consists of a reaction product of neopentyl glycol adipate and a second diisocyanate component.

43. The method according to claim 41, wherein the second diisocyanate component comprises an aromatic diisocyanate.

44. The method according to claim 42, wherein the second diisocyanate component comprises an aromatic diisocyanate.

45. The method according to claim 43 or 44, wherein the second diisocyanate component comprises or consists of 4,4′-methylenebis(phenyl isocyanate).

46. The method according to claim 41, wherein the second diisocyanate component comprises an aliphatic diisocyanate.

47. The method according to claim 42, wherein the second diisocyanate component comprises an aliphatic diisocyanate.

48. The method according to claim 46 or 47, wherein the second diisocyanate component comprises or consists of dicyclohexylmethane-4,4′-diisocyanate.

49. The method according to any one of claims 32 to 35, wherein the first fiber is selected from thermoplastic polyurethane fibers, polyester fibers, nylon fibers, cotton fibers, wool fibers, acrylic fibers, polypropylene fibers, viscose rayon fibers, or mixtures thereof.

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