KR20120102578A - High strength fabrics consisting of thin gauge constant compression elastic fibers - Google Patents

Abstract

The present invention relates to elastic fibers having a relatively flat modulus curve at 100% to 200% elongation. The fibers can be made into garments that have a very comfortable feeling. Preferred elastic fibers are made of thermoplastic polyurethane polymers and are produced by a unique melt spinning process in which the fibers are wound into bobbins at a rate only slightly higher than the melt rate of the polymer exiting the spinneret.

Description

HIGH STRENGTH FABRICS CONSISTING OF THIN GAUGE CONSTANT COMPRESSION ELASTIC FIBERS}

FIELD OF THE INVENTION The present invention relates to high strength fabrics made from elastic fibers of constant compressive force of thin gauges. Garments made of elastic fibers of constant compression force the wearer to feel very comfortable. The garment is also not punctured because it is a high strength fabric made of elastic fibers.

Recently, due to lifestyle changes around the world, there is a growing demand for greater functionality of fabrics beyond basic insulation. The pursuit after functionality is a loose gauge fabric that does not degrade the strength and integrity of the fabric. Such coarse gauge fabric can reduce the packing volume, reduce the "bulk" feel and, in the case of underwear, no external visibility through the garment.

Synthetic elastic fibers (SEF) are usually made from polymers having soft and hard segments to provide elasticity. Polymers with hard and soft segments are typically poly (ether-amides) such as Pebax® or copolyesters such as Hytrel® or thermoplastic polyurethanes such as Estane®. However, very high elongation SEFs typically use hard and soft segmented polymers such as dry spun polyurethane (Lycra®) or melt spun thermoplastic polyurethane (Estane®). These SEFs change low or very high in break elongation, but all of them can generally be described as having modulus (strain) which increases exponentially with increasing elongation (stress).

Melt spinning TPU fibers provide some advantages over dry spinning polyurethane fibers in that no solvent is used in the melt spinning process, while in the dry spinning process, the polymer is dissolved in the solvent and spun. Thereafter, the solvent is partially evaporated out of the fiber. All solvents are very difficult to remove completely from dry spun fibers. To facilitate the removal of the solvent from the dry spun fibers, the fibers are typically made in small sizes and brought together to produce multi-filament (ribbon-like) fibers. This results in a larger physical size than the melt spun fibers for a given denier. These physical features cause more bulk in the fabric and the properties of the multi-filament bundles cause a loss of comfort.

Melt Spinning TPU fibers are made by melt spinning the TPU polymer. TPU polymers include the following three components: (a) hydroxyl terminal intermediates, which are typically polyethers or polyesters end capped with hydroxyl groups; (b) polyisocyanates such as diisocyanates; And (c) reaction of short-chain hydroxyl end chain extenders. The hydroxyl terminal intermediate forms the soft segment of the TPU polymer, while the polyisocyanate and chain extender forms the hard segment of the TPU polymer. The combination of soft and hard segments provides elastic properties to the TPU polymer. TPU polymers also often provide slightly improved crosslinking, using prepolymers end-capped with polyisocyanates. The crosslinking material is added to the molten TPU polymer during melt spinning of the fibers.

It would be desirable to obtain TPU elastic fibers having a relatively constant compressive force at 0-250% elongation and to produce garments and / or fabrics of constant compressive force containing such TPU fibers. It would also be desirable for the fabric of constant compressive force to be coarse gauge and to have high puncture strength. Garments made of such fabrics will give the wearer greater comfort and confidence.

1 is a micrograph of 70 denier multi-filaments of commercially available dry spun polyurethane fibers.
Figure 2 is a micrograph of a 70 denier melt spun constant compressive thermoplastic polyurethane fiber according to the present invention.
3 is a graph depicting the X axis as denier versus the Y axis of fiber width squared (square microns). The fiber of the present invention is compared with the commercially available dry spun fiber.

Summary of the Invention

It is an object of the present invention to provide a high strength fiber of constant compressive force of a coarse gauge having a final elongation of 400% or more and a relatively uniform and / or constant modulus in the loading and unloading cycles of 100% to 200% elongation. The uniform and / or constant modulus is less than 0.023 gram-force per denier at 100% elongation in loading cycles, less than 0.023 gram-force per denier at 150% elongation, and less than 0.053 gram-force per denier at 200% elongation. Evidenced by stress; Unloading cycles are evidenced by stresses of less than 0.027 grams-force per denier at 200% elongation, less than 0.018 grams-force per denier at 150% elongation, and less than 0.015 gram-forces per denier at 100% elongation.

Exemplary fibers are made by melt spinning a thermoplastic polyurethane polymer, preferably a polyester polyurethane polymer. The fibers are slightly crosslinked by adding a crosslinking agent, preferably 5-20% by weight, to the polymer melt during the melt spinning process.

The process of producing the fiber includes a melt spinning process whereby the fiber is formed by passing the polymer melt through the spinneret. The speed of the fiber exiting the spinneret and the rate at which the fiber is wound into bobbins are relatively similar. That is, the fibers should be wound into the bobbin at a rate that is greater than the rate at which the fibers exit the spinneret, but no more than 50%, preferably no more than 20%, and more preferably no more than 10%.

Another object of the present invention is to produce a fabric from fibers of constant compressive force of a coarse gauge. In an exemplary embodiment, the fabric is made by combining, for example, knitting or weaving elastic fibers with hard fibers, such as nylon and / or polyester fibers. Fabrics made from the novel fibers also have high burst strength.

Garments, for example underwear, are made of elastic fibers. Such clothing provides the wearer with very good comfort.

DETAILED DESCRIPTION OF THE INVENTION

The fibers of the present invention are made of thermoplastic elastomers. Preferred thermoplastic elastomers are thermoplastic polyurethane polymers (TPUs). The present invention will be described using a TPU, but it is only one embodiment and it should be understood that other thermoplastic elastomers may be used by those skilled in the art.

The TPU polymer type used in the present invention may be any conventional TPU polymer known in the art and in the literature as long as the TPU polymer has a suitable molecular weight. TPU polymers are generally prepared by reacting polyisocyanates with intermediates such as hydroxyl terminated polyesters, hydroxyl terminated polyethers, hydroxyl terminated polycarbonates or mixtures thereof, one or more chain extenders, all of which are Are well known to those skilled in the art.

The hydroxyl terminated polyester intermediates generally have a number average molecular weight (Mn) of about 500 to about 10,000, preferably about 700 to about 5,000, and preferably about 700 to about 4,000, and acid numbers generally. Linear polyesters less than 1.3 and preferably less than 0.8. The molecular weight is determined by analysis of the terminal functional groups and is related to the number average molecular weight. The polymer may be reacted by (1) esterifying one or more glycols with one or more dicarboxylic acids or anhydrides or (2) by transesterification reactions, ie, reacting one or more glycols with esters of dicarboxylic acids Is produced by. In order to obtain linear chains having a large number of terminal hydroxyl groups, it is preferred that the molar ratio of glycol to acid is generally in excess of 1 mole. Suitable polyester intermediates also include a variety of lactones such as polycaprolactone, typically made from ε-caprolactone, and difunctional initiators such as diethylene glycol. The dicarboxylic acids of the desired polyesters can be aliphatic, cycloaliphatic, aromatic or combinations thereof. Suitable dicarboxylic acids that can be used alone or in combination generally have 4 to 15 carbon atoms in total, and include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, Isophthalic acid, terephthalic acid, cyclohexane dicarboxylic acid and the like. Anhydrides of the above dicarboxylic acids, such as phthalic anhydride and tetrahydrophthalic anhydride, may also be used. Adipic acid is the preferred acid. The glycols reacted to form the preferred polyester intermediates may be aliphatic, aromatic or combinations thereof, having 2 to 12 carbon atoms in total, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1 , 3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, decamethylene glycol , Dodecamethylene glycol, and the like, and 1,4-butanediol is a preferred glycol.

The hydroxyl terminated polyether intermediates are alkyl reacted with diols or polyols having 2 to 15 carbon atoms in total, preferably alkylene oxides having 2 to 6 carbon atoms, typically ethers comprising ethylene oxide or propylene oxide or mixtures thereof. Polyether polyols derived from diols or polyols. For example, hydroxyl functional polyethers can be produced by first reacting propylene glycol with propylene oxide and then with ethylene oxide. Primary hydroxyl groups of ethylene oxide origin are preferred because they are more reactive than secondary hydroxyl groups. Useful commercial polyether polyols include poly (ethylene glycol) comprising ethylene oxide reacted with ethylene glycol, poly (propylene glycol) comprising propylene oxide reacted with propylene glycol, poly containing water reacted with tetrahydrofuran (Tetramethyl glycol) (PTMG). Polytetramethylene ether glycol (PTMEG) is the preferred polyether intermediate. Polyether polyols further comprise polyamide adducts of alkylene oxides and include, for example, ethylenediamine adducts comprising reaction products of ethylenediamine and propylene oxide, reaction products of diethylenetriamine and propylene oxide Diethylenetriamine adducts and polyether polyols of similar polyamide type. Copolyethers can also be used in the present invention. Typical copolyethers include reaction products of THF and ethylene oxide or reaction products of THF and propylene oxide. These are commercially available as poly THF B, a block copolymer from BASF, and poly THF R, a random copolymer. Various polyether intermediates have an average molecular weight of about 700 or more, such as about 700 to about 10,000, preferably about 1000 to about 5000, and preferably about 1000 to about 2500, as measured by analysis of terminal functional groups. It has a number average molecular weight (Mn). Preferred specific polyether intermediates are blends of two or more different molecular weight polyethers, such as blends of 2000 M _n and 1000 M _n PTMEG.

Most preferred embodiments of the invention use polyester intermediates prepared from the reaction of a 50/50 blend of adipic acid with 1,4-butanediol and 1,6-hexanediol.

The polycarbonate-based polyurethane resins of the present invention are prepared by reacting diisocyanates with blends of hydroxyl terminated polycarbonates and chain extenders. Hydroxyl terminated polycarbonates can be prepared by reacting glycols with carbonates.

US Pat. No. 4,131,731 describes hydroxyl terminated polycarbonates and methods for their preparation and is incorporated herein by reference. Such polycarbonates are linear and have terminal hydroxyl groups essentially free of other terminal groups. Essential reactants are glycols and carbonates. Suitable glycols are aliphatic and aliphatic diols having 4 to 40 carbon atoms and preferably 4 to 12 carbon atoms, and polyoxys having 2 to 20 alkoxy groups per molecule of each alkoxy group having 2 to 4 carbon atoms Alkylene glycols. Suitable diols for use in the present invention are aliphatic diols having 4 to 12 carbon atoms, for example butanediol-1,4, pentanediol-1,4, neopentyl glycol, hexanediol-1,6, 2,2, 4-trimethylhexanediol-1,6, decanediol-1,10, hydrogenated dilinoleyl glycol, hydrogenated dioleyl glycol; And cycloaliphatic diols, such as cyclohexanediol-1,3-dimethylolcyclohexane-1,4, cyclohexanediol-1,4, dimethylolcyclohexane-1,3, 1,4-endomethylene- 2-hydroxy-5-hydroxymethyl cyclohexane, and polyalkylene glycols. The diols used in this reaction may be single diols or mixtures of diols depending on the properties required in the final product.

Hydroxyl terminated polycarbonate intermediates are generally those known in the art and literature. Suitable carbonates are selected from alkylene carbonates consisting of 5 to 7 membered rings of the formula:

Wherein R is a saturated divalent radical having 2 to 6 linear carbon atoms. Suitable carbonates for use herein include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 2,3- Butylene carbonate, 1,2-ethylene carbonate, 1,3-pentylene carbonate, 1,4-pentylene carbonate, 2,3-pentylene carbonate and 2,4-phene Styrene carbonate.

Also suitable herein are dialkylcarbonates, cycloaliphatic carbonates and diarylcarbonates. Dialkylcarbonates may contain 2 to 5 carbon atoms in each alkyl group, specific examples of which are diethylcarbonate and dipropylcarbonate. Alicyclic carbonates, in particular dicycloaliphatic carbonates, may contain 4 to 7 carbon atoms in each cyclic structure, and one or two such structures may be present. If one group is alicyclic, the other can be alkyl or aryl. On the other hand, when one group is aryl, the other may be alkyl or cycloaliphatic. Preferred examples of diaryl carbonates which may contain 6 to 20 carbon atoms in each aryl group are diphenyl carbonate, ditolyl carbonate and dinaphthyl carbonate.

Glycol glycol at a temperature of 100 ° C. to 300 ° C. in the presence or absence of an ester interchange catalyst and a molar range of 10: 1 to 1:10, preferably 3: 1 to 1: 3 at a pressure range of 0.1 to 300 mm of mercury. The reaction is carried out by reacting with a carbonate, preferably an alkylene carbonate and distilling off the low boiling glycol.

More particularly, hydroxyl terminated polycarbonates are prepared in two steps. In the first step, glycol is reacted with alkylene carbonate to form a low molecular weight hydroxyl terminated polycarbonate. Lower boiling glycols are removed by distillation at 100 ° C to 300 ° C, preferably 150 ° C to 250 ° C under reduced pressure of 10 to 30 mmHg, preferably 50 to 200 mmHg. A fractionation column is used to separate the glycol byproducts from the reaction mixture. Glycol byproducts are removed from the top of the column and unreacted alkylene carbonate and glycol reactant are returned to the reaction vessel as reflux. A stream of inert gas or inert solvent can be used to facilitate removal of the formed glycol byproduct. When the amount of glycol byproduct obtained indicates that the degree of polymerization of hydroxyl terminated polycarbonate is in the range of 2 to 10, the pressure is gradually reduced to 0.1 to 10 mmHg and unreacted glycol and alkylene carbonate Remove it. This initiates the second stage of the reaction, during which a pressure of 0.1 to 10 mmHg and a temperature of 100 ° C. to 300 ° C., preferably 150 ° C. to 250, are obtained until a hydroxyl terminated polycarbonate of the desired molecular weight is obtained. Low molecular weight hydroxyl terminated polycarbonates are condensed by distilling off the glycol formed at < RTI ID = 0.0 > The molecular weight (Mn) of the hydroxyl terminated polycarbonate may vary from about 500 to about 10,000, but in preferred embodiments it will range from 500 to 2500.

The second essential component for preparing the TPU polymer of the present invention is polyisocyanate.

In general, polyisocyanates of the present invention have the formula R (NCO) _n , where n is generally 2-4 and 2 is very preferred since the composition is thermoplastic. Thus, polyisocyanates having a functionality of 3 or 4 are used in very small amounts, for example less than 5% by weight, preferably less than 2% by weight, based on the total weight of all polyisocyanates, which leads to crosslinking. Because. R may generally be an aromatic, alicyclic, aliphatic or combination thereof having from 2 to about 20 carbon atoms. Examples of suitable aromatic diisocyanates include diphenyl methane-4,4'-diisocyanate (MDI), H ₁₂ MDI, m-xylylene diisocyanate (XDI), m-tetramethyl xylylene diisocyanate (TMXDI), Phenylene-1,4-diisocyanate (PPDI), 1,5-naphthalene diisocyanate (NDI) and diphenylmethane-3,3'-dimethoxy-4,4'-diisocyanate (TODI). Examples of suitable aliphatic diisocyanates include isophorone diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (CHDI), hexamethylene diisocyanate (HDI), 1,6-diisocyanato-2,2,4,4 -Tetramethyl hexane (TMDI), 1,10-decane diisocyanate and trans-dicyclohexylmethane diisocyanate (HMDI). Highly preferred diisocyanates are MDIs containing less than about 3% by weight of the ortho-para (2,4) isomer.

The third component required to prepare the TPU polymer of the present invention is a chain extender. Suitable chain extenders are lower aliphatic or short chain glycols having about 2 to about 10 carbon atoms and are for example ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, triethylene glycol, cyclohexyl dimethylol Cis-trans-isomer, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butanediol and 1,5-pentanediol. Aromatic glycols can also be used as chain extenders and are a preferred choice for high temperature applications. Benzene glycol (HQEE) and xyleneene glycol are suitable chain extenders for the production of TPUs of the present invention. Xyleneene glycol is a mixture of 1,4-di (hydroxymethyl) benzene and 1,2-di (hydroxymethyl) benzene. Benzene glycol is the preferred aromatic chain extender and in particular, hydroquinone, ie bis (beta-hydroxyethyl) ether (also known as 1,4-di (2-hydroxyethoxy) benzene); Resorcinol, ie bis (beta-hydroxyethyl) ether (also known as 1,3-di (2-hydroxyethyl) benzene); Catechols, ie bis (beta-hydroxyethyl) ether (also known as 1,2-di (2-hydroxyethoxy) benzene) and combinations thereof. Preferred chain extenders are 1,4-butanediol.

The three essential components (hydroxyl terminal intermediate, polyisocyanate and chain extender) are preferably reacted in the presence of a catalyst.

In general, any conventional catalyst may be used to react diisocyanates with hydroxyl terminal intermediates or chain extenders and they are well known in the art and in the literature. Examples of suitable catalysts include various alkyl ethers or alkyl thiol ethers of bismuth or tin, wherein the alkyl moiety has from 1 to about 20 carbon atoms and specific examples thereof include bismuth octoate and bismuth laurate and the like. Preferred catalysts include various tin catalysts such as tin octoate, dibutyltin dioctoate and dibutyltin dilaurate and the like. The amount of such catalyst is generally small, such as from about 20 to about 200 parts per million (ppm) based on the total weight of the polyurethane forming monomer.

The TPU polymers of the present invention can be prepared by any conventional polymerization method well known in the art and literature.

The thermoplastic polyurethanes of the present invention are preferably prepared through a "one shot" process in which all the components are added together and reacted simultaneously or substantially simultaneously to a heated extruder to form the polyurethane. The equivalent ratio of diisocyanate to the total equivalent of hydroxyl terminal intermediate and diol chain extender is generally about 0.95 to about 1.10, preferably about 0.97 to about 1.03, and more preferably about 0.97 to about 1.00. Shore A hardness of the formed TPU should be between 65A and 95A, and preferably between about 75A and about 85A to achieve the most desirable properties of the finished product. The reaction temperature using the urethane catalyst is generally about 175 ° C to about 245 ° C, preferably about 180 ° C to about 220 ° C. The molecular weight (Mw) of the thermoplastic polyurethane is generally from about 100,000 to about 800,000, preferably from about 150,000 to about 400,000, and preferably from about 150,000 to about 350,000 as measured by GPC compared to the polystyrene standard.

Thermoplastic polyurethanes can also be prepared using prepolymer processes. In the prepolymer route, the hydroxyl terminated polyether intermediate is generally reacted with an excess equivalent of one or more polyisocyanates to form a prepolymer solution with free or unreacted polyisocyanate therein. The reaction is generally carried out at a temperature of about 80 ° C. to about 220 ° C. and preferably at a temperature of about 150 ° C. to about 200 ° C. in the presence of a suitable urethane catalyst. Subsequently, an optional type of chain extender as described above is generally added in generally equivalent equivalents to any free or unreacted diisocyanate compounds as well as isocyanate end groups. Thus the total equivalent ratio of total diisocyanate to the total equivalent of hydroxyl terminal intermediates and chain extenders is from about 0.95 to about 1.10, preferably from about 0.98 to about 1.05, more preferably from about 0.99 to about 1.03. The equivalent ratio of hydroxyl terminal intermediate to chain extender is adjusted to provide 65A to 95A, preferably 75A to 85A Shore strength. The temperature of the chain extension reaction is generally about 180 ° C to about 250 ° C, preferably about 200 ° C to about 240 ° C. Typically, the prepolymer route can be carried out in any conventional apparatus and extruders are preferred. Thus, the hydroxyl terminal intermediate reacts with the excess equivalent of diisocyanate in the first part of the extruder to form a prepolymer solution, and then adds a chain extender to the downstream part to react with the prepolymer solution. Any conventional extruder may be used, and the extruder is equipped with a barrier screw having a length to diameter ratio of 20 or more and preferably 25 or more.

Useful additives may be used in appropriate amounts, including opaque pigments, colorants, inorganic fillers, stabilizers, lubricants, UV absorbers, processing aids and other additives as desired. Useful opaque pigments include titanium dioxide, zinc oxide and titanate yellow, while useful tinting pigments are carbon black, yellow oxide, brown oxide, raw and burnt sienna or umber ( umber), chromium green oxide, cadmium pigments, chromium pigments and other mixed metal oxides and organic pigments. Useful fillers include diatomaceous earth (superfloss) clay, silica, talc, mica, wurostonite, barium sulfate and calcium carbonate. If desired, useful stabilizers such as antioxidants can be used, which include phenolic antioxidants, while useful light stabilizers include organic phosphates and organotin thiolates (mercaptide). Useful lubricants include metal stearates, paraffin oils and amide waxes. Useful UV absorbers include 2- (2'-hydroxyphenol) benzotriazole and 2-hydroxybenzophenone.

Plasticizer additives may also be advantageously used to reduce hardness without affecting properties.

During the melt spinning process, the TPU polymers described above may be lightly crosslinked with a crosslinking agent. The crosslinker is a prepolymer of a hydroxyl terminal intermediate which is a polyether, polyester, polycarbonate, polycaprolactone, or mixtures thereof reacted with polyisocyanate. Polyesters or polyethers are preferred hydroxyl terminal intermediates for preparing crosslinking agents, and polyethers are most preferred when used with polyester TPUs. The prepolymer crosslinker will have isocyanate functionality of at least about 1.0, preferably from about 1.0 to 3.0 and more preferably from about 1.8 to about 2.2. In particular, it is preferred that both ends of the hydroxyl terminal intermediate are capped with isocyanates so that isocyanate functionality is 2.0.

The polyisocyanate used to prepare the crosslinking agent is as described above in preparing the TPU polymer. Diisocyanates such as MDI are preferred diisocyanates.

The crosslinker has a number average molecular weight (Mn) of about 1,000 to about 10,000 Daltons, preferably about 1,200 to about 4,000, more preferably about 1,500 to about 2,800 Daltons. Crosslinkers with M _n of about 1500 or more provide better set properties.

The weight percent of crosslinking agent used with the TPU polymer is from about 2.0% to about 20%, preferably from about 8.0% to about 15%, and more preferably from about 10% to about 13%. The percentage of crosslinker used is% by weight based on the total weight of the TPU polymer and the crosslinker.

Preferred melt spinning processes for producing the TPU fibers of the present invention include supplying a preformed TPU polymer to the extruder to melt the TPU polymer, the crosslinker being near the point where the TPU melt is discharged from the extruder or the TPU melt from the extruder After draining it is added continuously downstream. The crosslinking agent may be added to the extruder before the melt is discharged from the extruder or may be added after the melt is discharged from the extruder. If the melt is added after exiting the extruder, it is necessary to mix the crosslinker with the TPU melt using a static or dynamic mixer to ensure that the crosslinker can be properly mixed into the TPU polymer melt. After exiting the extruder, the molten TPU polymer with the crosslinker flows into the manifold. The manifold splits the melt stream into different streams, where each stream is fed to a plurality of spinnerets. Usually there is a melt pump for each different stream flowing from the manifold and each melt pump supplies several spinnerets. The spinneret has small holes through which the melt is pressed and discharged in the form of monofilament fibers from the spinneret. The size of the hole in the spinneret will depend on the desired size (denier) of the fiber.

The TPU polymer melt can pass through a spin pack assembly and exit the used spin pack assembly as a fiber. The preferred spin pack assembly used is an assembly that provides a plug flow of the TPU polymer through the assembly. Most preferred spin pack assemblies are those disclosed in PCT patent application WO 2007/076380, which is incorporated herein by reference in its entirety.

Once the fiber exits the spinneret, cool the fiber before winding it to the bobbin. The fiber is passed on a first godet, a finish oil is applied and the fiber is advanced to a second gode. An important aspect of the process for making the fibers of the present invention is the relative speed at which the fibers are wound into bobbins. Relative velocity refers to the rate (melt rate) of the melt exiting the spinneret in relation to the winding rate. Usually in the prior art TPU melt spinning process, fibers are wound at speeds four to six times faster than the melt rate. This stretches and stretches the fibers. In the case of the unique fibers of the invention, such extensive stretching is undesirable. The fibers must be wound at a speed at least equal to the melt rate to carry out the process. In the case of the fibers according to the invention, it is necessary to wind the fibers at a faster rate of 50% or less, preferably 20% or less, and more preferably 10% or less, and a speed of 5% or less is good. Give results. Winding rates such as melt rates would be ideal, but it is believed that slightly higher winding speeds are required to perform the process. For example, the fibers exiting the spinneret at a speed of 300 meters per minute would most preferably be wound at a speed of 300 to 315 meters per minute.

The fibers of the invention can be made from a variety of denier. Denier is a term in the art that specifies fiber size. Denier is the gram weight of a 9000 meter fiber length. The fibers of the present invention are typically produced in denier sizes of 20 to 600, preferably 40 to 400 denier sizes, and more preferably 70 to 360 denier sizes.

When preparing fibers by the process of the present invention, anti-sticking agents, such as finish oils, such as silicon oils, are generally added to the surface of the fibers after cooling or during cooling and just before winding onto the bobbin.

An important aspect of the melt spinning process is to mix the crosslinking agent with the TPU polymer melt. Proper and uniform mixing is important to achieve uniform fiber properties and to achieve long run times without the occurrence of fiber breakage. The mixing of the TPU melt and the crosslinker should be a method of achieving plug-flow, ie first-in first-out. Proper mixing can be achieved using a dynamic mixer or a static mixer. Since static mixers are more difficult to clean, dynamic mixers are preferred. Dynamic mixers with feed screws and mixing pins are preferred mixers. U. S. Patent No. 6,709, 147, incorporated herein by reference, describes such a mixer, which has a rotatable mixing pin. In addition, the mixing pin may be in a fixed position, for example attached to the barrel of the mixer and extending towards the centerline of the feed screw. The mixing feed screw can be attached to the end of the extruder screw by a thread and the housing of the mixer can be bolted to the extruder machine. The feed screw of the dynamic mixer should be designed to move the polymer melt in a gradual manner with very little backmixing to achieve plug-flow of the melt. The L / D of the mixing screw should be at least 3 and less than 30, preferably from about 7 to about 20, more preferably from about 10 to about 12.

The temperature in the mixing zone where the TPU polymer melt and crosslinker are mixed is from about 200 ° C to about 240 ° C, preferably from about 210 ° C to about 225 ° C. These temperatures are necessary to cause the reaction without degrading the polymer.

The formed TPU reacts with the crosslinking agent during the melt spinning process to provide a TPU in the form of final fibers of molecular weight (Mw) of about 200,000 to about 800,000, preferably about 250,000 to about 500,000, more preferably about 300,000 to about 450,000.

The spinning temperature (temperature of the polymer melt at the spinneret) should be higher than the melting point of the polymer and preferably about 10 ° C. to about 20 ° C. above the melting point of the polymer. Higher spinning temperatures can be used for better spinning. However, if the spinning temperature is too high, the polymer may decompose. Thus, about 10 ° C. to about 20 ° C. higher than the melting point of the TPU polymer is optimal to achieve a good spinning balance without degradation of the polymer. If the spinning temperature is too low, the polymer may solidify in the spinneret and cause fiber breakage.

The unique fibers of the present invention have a relatively uniform and / or constant modulus in the loading and unloading cycles of 100% to 200% elongation. The uniform modulus is caused by a stress of less than 0.023 grams-force per denier at 100% elongation at load loading cycles, less than 0.036 grams-force per denier at 150% elongation, and less than 0.053 gram-forces per denier at 200% elongation. Proven; Unloading cycles are demonstrated by stresses of less than 0.027 grams-force per denier at 200% elongation, less than 0.018 grams-force per denier at 150% elongation, and less than 0.015 gram-forces per denier at 100% elongation, All this data was collected from 360 denier fibers.

The homogeneous modulus also provides for stresses of less than 0.158 gram-force per denier at 100% elongation in loading cycles, less than 0.207 gram-force per denier at 150% elongation, and less than 0.265 gram-force per denier at 200% elongation. Proven by; Evidenced by a stress of less than 0.021 grams-force per denier at 200% elongation at unloading cycles, less than 0.012 grams-force per denier at 150% elongation, and less than 0.008 gram-forces per denier at 100% elongation, All this data was collected from 70 denier fibers.

The standard test procedure performed to obtain the modulus value was that developed by DuPont for elastic yarns. This test applies the fiber to a series of five cycles. In each cycle, the fibers were stretched to an elongation of 300% and relaxed using a constant elongation (between the original gauge length and 300% elongation). The% set was measured after the fifth cycle. The fiber swatch was then passed through a sixth cycle and stretched to break. The device records the failure elongation and elongation at maximum load as well as the failure load in units of gram-force per denier and rod at each elongation (highest load before failure). The test was usually performed at room temperature (23 ° C. ± 2 ° C .; and 50% ± 5% humidity).

The fibers of the present invention have a break elongation of at least 400%, and preferably about 450 to 500%. The fiber is a monofilament of round shape. 2, it can be seen that the 70 denier monofilament fibers are actually round in cross-sectional shape. 1 shows a 70 denier monofilament dry spun fiber with a larger cross sectional width.

3 shows a graph comparing dry spun fibers to melt spun fibers of the present invention. The graph plots denier (X axis) versus fiber width squared (square microns). The graph shows that the melt spun fiber of the present invention has a constant slope on the graph, while the dry spun fiber has an exponentially increasing slope. The result is that fabrics can be made from the fibers of the present invention that are thinner and more comfortable to the wearer.

Another important feature of the fibers of the present invention is that they exhibit improved burst strength in fabrics compared to dry spun fibers.

This feature can be presented by performing a Ball Burst puncture strength test using a 1 inch diameter ball according to ASTM D751. The test will stimulate finger pushing through the fabric to form a hole. It was very surprising that the fibers of the present invention showed about 50-75% improvement in the burst strength over the dry spun polyurethane fibers. Even when the tensile strength of the fibers is about the same, this improved burst strength is present.

The fibers of the present invention also have higher heat capacity. The combination of uniform modulus curves, higher heat capacity, and coarse gauge produces a fabric made from the fibers of the present invention that gives a garment wearer a comfortable feel.

Fabrics made using the fibers of the invention can be produced by knitting or weaving. It is often desirable to make fabrics using other fibers along with TPU fibers. It is particularly preferable to use hard fibers together with the elastic fibers of the present invention. Hard fibers such as nylon and / or polyester are preferred. Hard fibers improve the fabric's snag resistance compared to 100% elastic fiber fabrics. Preferred fabrics are two strands of 140 denier TPU (1- 1) after alternating strands of 140 denier TPU / 70 denier nylon with strands of 140 denier TPU (referred to as 1-1 fabric) or strands of 140 denier TPU / 70 denier nylon. 2) as knitted using alternating fibers.

Garments can be made from the fabrics of the invention. The most preferred use of the fabric is in the manufacture of underwear or tight fitting garments due to the comfort provided by the fibers. Underwear and T-shirts, such as bras, as well as sportswear used for activities such as running, skiing, cycling or other sports, can benefit from the properties of these fibers. The modulus is further lowered when the fibers reach body temperature, so the next garment worn on the body benefits from the uniform modulus of these fibers. Clothing that feels tight will be more comfortable about 30 seconds to 5 minutes after the fiber reaches body temperature. It will be understood by those skilled in the art that any garment can be made from the fabrics and fibers of the present invention. An exemplary embodiment would be a bra shoulder strap made of woven fabric and a wing of a bra made of knitted fabric, both of which are woven and knitted fabrics containing the melt spun TPU fibers of the present invention. The bra strap will not need an adjustable buckle because the fabric is elastic.

The invention will be better understood with reference to the following examples.

Example

The TPU polymer used in the examples was prepared by reacting polyester hydroxyl terminal intermediates (polyols) with 1,4-butanediol chain extenders and MDI. Polyester polyols were prepared by reacting adipic acid with a 50/50 mixture of 1,4-butanediol and 1,6-hexanediol. Mn of the polyol is 2500. TPU was prepared by a one-shot process. The crosslinker added to the TPU during the spinning process was a polyether prepolymer prepared by reacting 1000 Mn PTMEG with MDI to produce a polyether end capped with isocyanate. The crosslinker was used at a level of 10% by weight of the combined weight of the TPU and the crosslinker. The fibers were melt spun to produce the 40, 70, 140 and 360 denier fibers used in the examples.

Example  One

This example was provided to show a relatively uniform modulus curve of the fiber (70 denier) of the present invention as compared to existing conventional melt spun TPU fibers (40 denier) and commercially available dry spun fiber (70 denier).

The test procedure used was as described above to test the elastic properties. An Instron model 5564 tension meter with Merlin software was used. Test conditions were 23 ° C. ± 2 ° C. and 50% ± 5% humidity. The fiber length of the test specimen was 50.0 mm. Four specimens were tested and the result is the average of the four specimens tested. The results are shown in Table 1.

Table I

All of the above data are averages for the four specimens tested.

From the data, it can be seen that the melt spun fiber of the present invention has a relatively uniform modulus curve for five test cycles. The first cycle is usually ignored because it relieves stress in the fiber.

Example  2

This example was provided to show the width of the melt spun fiber of the present invention as compared to the dry spun fiber on the market. The width was measured by SEM. The results are shown in Table II below.

table II

As can be seen, the dry spun fibers have a much higher width and the difference increases with increasing denier.

Example  3

This example was provided to demonstrate the improved burst strength of the melt spun TPU fibers of the present invention over commercial dry spun polyurethane fibers. 70 denier fibers were used to make a Signel Jersey knit fabric from each type of fiber. The fabric was tested for burst puncture strength according to ASTM D751. The results are shown in Table III below. The following results are the average of five samples tested.

table III

Although the melt spun fiber of the present invention did not have a higher tensile strength than the dry spun fiber, it was very surprising that the burst strength of the melt spun fiber was higher.

In accordance with patent legislation, the best mode and preferred embodiments have been described, but the scope of the invention is not limited thereto but by the appended claims.

Claims (22)

High burst strength of constant compression of a coarse gauge with a final elongation of 400% or more and a relatively uniform modulus in the loading and unloading cycles of 100% to 200% elongation. Elastic fibers. The fiber of claim 1, wherein the 40 denier monofilament fibers have a width of less than 100 microns. The fabric of claim 1, wherein 70 fibers of the fiber are made of a fabric, the fabric is tested for puncture strenth according to ASTM D751, and the fabric has a load at failure of more than 6 pounds. Genie, fiber. The fiber of claim 1 wherein the fiber is a thermoplastic polyurethane fiber. The fiber of claim 4 wherein the fiber is a polyester thermoplastic polyurethane. 6. The fiber of claim 5 wherein the fiber is crosslinked with a polyether crosslinker. 6. The fiber of claim 5 wherein the polyester thermoplastic polyurethane has a weight average molecular weight of 200,000 to 700,000 Daltons. The fiber of claim 6, wherein the crosslinking agent is 5 to 20% by weight of the combined weight of the polyester thermoplastic polyurethane and the crosslinking agent. The fiber of claim 8, wherein the crosslinking agent is 8 to 12 wt% of the combined weight of the polyester thermoplastic polyurethane and the crosslinking agent. A fabric comprising at least two different fibers, wherein at least one of the fibers is a thermoplastic polyurethane fiber, at least one of the fibers is a rigid fiber, and the thermoplastic polyurethane fiber is relatively flat stress-strain at 100 to 200% elongation. (stress-strain) A fabric with a curve. 11. The fabric of claim 10 wherein said fabric is made of two strands of thermoplastic polyurethane fibers for each strand of hard fiber. The fabric of claim 10 wherein said thermoplastic polyurethane fibers are from 20 to 600 denier. 13. The fabric of claim 12 wherein said thermoplastic polyurethane fibers are from 70 to 360 denier. The fabric of claim 10 wherein said hard fibers are selected from the group consisting of nylon and polyester. 15. The fabric of claim 14 wherein said hard fibers are about 70 denier and said thermoplastic polyurethane fibers are about 140 denier. An article of clothing comprising the fabric of claim 10. The product of claim 16, wherein the product is underwear. 18. The article of claim 17, wherein the article is a bra. (a) melt spinning the thermoplastic elastomer polymer through the spinneret;
(b) a relatively uniform modulus in the loading and unloading cycles of 100% to 200% elongation, including winding the elastic fibers to the bobbin at a winding speed no greater than 50% faster than the polymer melt rate exiting the spinneret. Genie how to produce elastic fibers. 20. The method of claim 19, wherein the winding speed is 20% or less faster than the polymer melting rate exiting the spinneret. 21. The method of claim 20, wherein the winding speed is 10% or less faster than the polymer melting rate exiting the spinneret. 20. The method of claim 19, wherein the thermoplastic elastomeric polymer is a thermoplastic polyurethane.

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