KR101799924B1 - High strength fabrics consisting of thin gauge constant compression elastic fibers - Google Patents

Abstract

The present invention relates to elastic fibers having relatively flat modulus curves at 100% to 200% elongation. The fibers can be made into garments having a very comfortable feel. The preferred resilient fibers are made of a thermoplastic polyurethane polymer and are produced by a unique melt spinning process wherein the fibers are wound onto the bobbins at a rate slightly higher than the melting rate of the polymer exiting the spinneret.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to high strength fabrics composed of elastic fibers of a certain compressive force of a coarse gauge.

The present invention relates to a high strength fabric made of elastic fibers of constant gauge compressive strength. Garments made of elastic fibers of constant compressive strength make the wearer feel very comfortable. The garment is also not punctured because it is a high strength fabric made of elastic fibers.

Recently, due to changes in lifestyles around the world, there is a growing demand for greater functionality of fabrics, beyond basic insulation. What we pursue after functionality is a spun gauge fabric that does not detract from the strength and completeness of the fabric. Such a coarse gauge fabric can result in reduced packing volume, reduced "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 having a hard and soft segment is typically a poly (ether-amide) is, for example, Pebax ^® or co-polyester, such as Hytrel ^® or thermoplastic polyurethane, such as Estane ^®. However, SEF typically utilizes a hard and soft segment, a polymer, such as dry spinning polyurethane (Lycra ^®) or melt-spinning a thermoplastic polyurethane (Estane ^®) of a very high elongation (elongation). These SEFs vary in low or very high breakage elongation, but all of them can be generally described as having a modulus (strain) that increases exponentially with increasing elongation (stress).

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

Melt-spun TPU fibers are prepared by melt spinning a TPU polymer. The TPU polymer comprises the following three components: (a) a hydroxyl-terminated intermediate, typically a polyether or polyester end-capped with a hydroxyl group; (b) polyisocyanates such as diisocyanate; And (c) reaction of a short chain hydroxyl end chain extender. The hydroxyl end intermediate forms a soft segment of the TPU polymer while the polyisocyanate and chain extender forms a hard segment of the TPU polymer. The combination of soft and hard segments provides elastic properties to the TPU polymer. TPU polymers also provide improved properties by often slightly crosslinking using prepolymer 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 to 250% elongation and to produce garments and / or fabrics of constant compressive strength containing such TPU fibers. It would also be desirable for the fabric of constant compressive force to have a coarse gauge and high puncture strength. Clothes made from such fabrics will provide greater comfort and confidence to the wearer.

It is an object of the present invention to provide an improved high strength fiber.

It is a further object of the present invention to produce fabrics from the improved high strength fibers.

Summary of the Invention

It is an object of the present invention to provide a high compressive strength high strength fiber having a coarse gauge having a relatively uniform and / or constant modulus in loading and unloading cycles of 100% to 200% elongation with a final elongation of at least 400%. The uniform and / or constant modulus is in gram-force less than 0.023 grams per denier at 100% elongation at loading cycles, gram-force less than 0.023 grams per denier at 150% elongation, less than 0.053 grams per denier at 200% elongation Evidenced by stress; In the unloading cycle, it is evidenced by a stress of less than 0.027 grams per denier at 200% elongation, a gram-force less than 0.018 per denier at 150% elongation, and a gram-force of less than 0.015 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 the cross-linking agent to the polymer melt during the melt spinning process, preferably from 5 to 20% by weight.

The process for producing fibers includes a melt spinning process whereby the fibers are formed by passing the polymer melt through a spinnerette. The speed of the fibers coming out of the spinneret and the speed at which the fibers are wound onto the bobbins are relatively similar. That is, the fibers must be wound onto the bobbins at a rate that is greater than the speed at which the fibers exit the spinnerette, but not more than 50%, preferably 20%, and more preferably not more than 10%.

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

Clothes, for example undergarments, are made of elastic fibers. Such garments provide very good comfort to the wearer.

INDUSTRIAL APPLICABILITY The present invention provides an improved high strength fiber and a method of producing the same.

1 is a photomicrograph of a 70 denier multi-filament of commercially available dry-spun polyurethane fibers.
2 is a photomicrograph of a 70 denier melt-spun, constant compressive strength thermoplastic polyurethane fiber according to the present invention.
3 is a graph showing the Y axis of the X axis versus fiber width squared (square micron) as denier. The fibers of the present invention are compared with commercially available dry spinning fibers.

DETAILED DESCRIPTION OF THE INVENTION

The fibers of the present invention are made of a thermoplastic elastomer. A preferred thermoplastic elastomer is a thermoplastic polyurethane polymer (TPU). The present invention will be described using TPU, but it should be understood that this is just one example, and 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 literature as long as the TPU polymer has an appropriate molecular weight. TPU polymers are generally prepared by reacting a polyisocyanate with an intermediate, such as a hydroxyl terminated polyester, a hydroxyl terminated polyether, a hydroxyl terminated polycarbonate, or a mixture thereof, with at least one chain extender, Are well known to those skilled in the art.

Hydroxyl-terminated polyester intermediates generally have a number average molecular weight (Mn) of from about 500 to about 10,000, preferably from about 700 to about 5,000, and preferably from about 700 to about 4,000, wherein the acid number is generally Is 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 prepared by (1) esterifying one or more glycols with one or more dicarboxylic acids or anhydrides, or (2) by transesterification, i.e., reacting one or more glycols with an ester of a dicarboxylic acid Lt; / RTI > In order to obtain a linear chain having a plurality of terminal hydroxyl groups, it is generally preferred that the molar ratio of glycol to acid is in excess of 1 mole or more. Suitable polyester intermediates also typically include bifunctional initiators such as di-ethylene glycol and various lactones such as polycaprolactone prepared from epsilon -caprolactone. The dicarboxylic acid of the desired polyester may be aliphatic, cycloaliphatic, aromatic, or a combination thereof. Suitable dicarboxylic acids which may be used alone or in admixture generally have a total carbon number of 4 to 15 and are selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, Isophthalic acid, terephthalic acid, and cyclohexanedicarboxylic acid. The anhydrides of the dicarboxylic acids, such as phthalic anhydride and tetrahydrophthalic anhydride, may also be used. Adipic acid is the preferred acid. The glycols to be reacted to form the preferred polyester intermediates may be aliphatic, aromatic or combinations thereof and have a total carbon number of 2 to 12 and may be selected from 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 preferable glycol.

The hydroxyl-terminated polyether intermediate is a diol or polyol having a total carbon atom of 2 to 15 carbon atoms, preferably an alkylene oxide having from 2 to 6 carbon atoms, typically an alkyl ether having reacted with an ether comprising ethylene oxide or propylene oxide, Diols or polyether polyols derived from polyols. For example, the hydroxyl functional polyether can be produced by first reacting propylene glycol with propylene oxide followed by reaction with ethylene oxide. The primary hydroxyl groups of ethylene oxide origin are preferred because they are more reactive than secondary hydroxyl groups. Useful commercial polyether polyols include, but are not limited to, poly (ethylene glycols) comprising ethylene oxide reacted with ethylene glycol, poly (propylene glycol) including propylene oxide reacted with propylene glycol, water reacted with tetrahydrofuran, (Tetramethylglycol) (PTMG). Polytetramethylene ether glycol (PTMEG) is the preferred polyether intermediate. The polyether polyols further comprise polyamine adducts of alkylene oxides and include, for example, ethylenediamine adducts comprising reaction products of ethylene diamine and propylene oxide, reaction products of diethylene triamine with propylene oxide Diethylenetriamine adducts and polyether polyols of similar polyamide type. Copolyethers may also be used in the present invention. Typical copolyethers include the reaction product of THF and ethylene oxide or the reaction product 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. The various polyether intermediates have an average molecular weight of at least about 700, such as from about 700 to about 10,000, preferably from about 1000 to about 5000, and preferably from about 1000 to about 2500, as measured by analysis of the terminal functionality Number average molecular weight (Mn). A preferred specific polyether intermediate is a blend of two or more different molecular weight polyethers, such as a blend of 2000 M _n and 1000 M _n PTMEG.

A most preferred embodiment of the present invention employs polyester intermediates prepared from the reaction of adipic acid with a 50/50 blend of 1,4-butanediol and 1,6-hexanediol.

The polycarbonate-based polyurethane resin of the present invention is prepared by reacting a diisocyanate with a blend of a hydroxyl-terminated polycarbonate and a chain extender. Hydroxyl-terminated polycarbonates can be prepared by reacting a glycol with a carbonate.

U.S. Pat. No. 4,131,731 discloses hydroxyl-terminated polycarbonates and methods for their preparation and is incorporated herein by reference. Such polycarbonates are linear and have terminal hydroxyl groups essentially excluding other terminal groups. The requisite reactants are glycol and carbonate. Suitable glycols include alicyclic and aliphatic diols having from 4 to 40 carbon atoms and preferably from 4 to 12 carbon atoms and polyoxyalkylene having from 2 to 20 alkoxy groups per molecule wherein each alkoxy group has from 2 to 4 carbon atoms Alkylene glycols. Diols suitable for use in the present invention include aliphatic diols having 4 to 12 carbon atoms such as butanediol-1,4, pentanediol-1,4, neopentyl glycol, hexanediol-1,6, 2,2, 4-trimethylhexanediol-1,6, decanediol-1,10, hydrogenated dirinoleate 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-hydroxymethylcyclohexane, and polyalkylene glycol. The diol used in the reaction may be either a single diol or a mixture 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 comprising 5 to 7 membered rings of the formula:

Wherein R is a saturated divalent radical having from 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- Tylenecarbonate.

Also suitable herein are dialkyl carbonates, alicyclic carbonate and diaryl carbonates. The dialkyl carbonate may contain from 2 to 5 carbon atoms in each alkyl group, specific examples of which are diethyl carbonate and dipropyl carbonate. Alicyclic carbonates, especially dicycloaliphatic carbonates, may contain from 4 to 7 carbon atoms in each cyclic structure, and one or two such structures may be present. When one group is an alicyclic, the other may be alkyl or aryl. On the other hand, when one group is aryl, the other group 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.

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

More particularly, the hydroxyl-terminated polycarbonate is prepared in two stages. In the first step, the glycol is reacted with an alkylene carbonate to form a low molecular weight hydroxyl-terminated polycarbonate. Distillation is carried out at a temperature of 100 to 300 DEG C, preferably 150 to 250 DEG C under a reduced pressure of 10 to 30 mmHg, preferably 50 to 200 mmHg to remove lower boiling point glycol. A fractionation column is used to separate the glycol by-product from the reaction mixture. Glycol byproducts are removed from the top of the column and unreacted alkylene carbonate and glycol reactants return to the reaction vessel as reflux. An inert gas or stream of inert solvent may be used to facilitate removal of the formed glycol byproduct. If the amount of glycol by-products obtained indicates that the degree of polymerization of the hydroxyl-terminated polycarbonate is in the range of 2 to 10, the pressure is gradually reduced to 0.1 to 10 mm Hg and the unreacted glycol and alkylene carbonate . This initiates the second step of the reaction, at a pressure of from 0.1 to 10 mm Hg and a temperature of from 100 to 300 캜, preferably from 150 to 250 캜, until the hydroxyl- The low molecular weight hydroxyl-terminated polycarbonate is condensed by distilling the formed glycol at < RTI ID = 0.0 > 0 C. < / RTI > The molecular weight (Mn) of the hydroxyl terminated polycarbonate may vary from about 500 to about 10,000, but in a preferred embodiment will range from 500 to 2500.

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

In general, the polyisocyanates of the present invention have the formula R (NCO) _n , wherein n is generally from 2 to 4 and the formula is highly 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, Because. R may be aromatic, alicyclic, aliphatic, or combinations thereof, generally having from 2 to about 20 carbon atoms. Examples of suitable aromatic diisocyanates include diphenylmethane-4,4'-diisocyanate (MDI), H ₁₂ MDI, m-xylylene diisocyanate (XDI), m-tetramethylxylylene 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 - tetramethylhexane (TMDI), 1,10-decane diisocyanate and trans-dicyclohexylmethane diisocyanate (HMDI). A highly preferred diisocyanate is MDI containing less than about 3% by weight of ortho-para (2,4) isomers.

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 from about 2 to about 10 carbon atoms and are, for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, triethylene glycol, cyclohexyldimethylol 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 xylenene glycols are suitable chain extenders for the preparation of the TPU of the present invention. The xyleneglycol is a mixture of 1,4-di (hydroxymethyl) benzene and 1,2-di (hydroxymethyl) benzene. Benzene glycols are preferred aromatic chain extenders and, in particular, hydroquinone, i.e., bis (beta -hydroxyethyl) ether (also known as 1,4-di (2-hydroxyethoxy) benzene); Resorcinol, i. E. Bis (beta -hydroxyethyl) ether (also known as 1,3-di (2-hydroxyethyl) benzene); Catechol, i.e., bis (beta -hydroxyethyl) ether (also known as 1,2-di (2-hydroxyethoxy) benzene) and combinations thereof. A preferred chain extender is 1,4-butanediol.

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

In general, any conventional catalyst can be used to react diisocyanates with hydroxyl end intermediates or chain extenders, and these 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. 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 as small as about 20 to about 200 parts per million, 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 in the literature.

The thermoplastic polyurethanes of the present invention are preferably prepared via a " one shot "process wherein all components are added together and simultaneously to a heated extruder simultaneously and substantially simultaneously to form a polyurethane. The equivalent ratio of diisocyanate to the total equivalents of hydroxyl end intermediate and diol chain extender is generally from about 0.95 to about 1.10, preferably from about 0.97 to about 1.03, and more preferably from about 0.97 to about 1.00. The Shore A hardness of the formed TPU should be from 65A to 95A, and preferably from about 75A to about 85A, to achieve the most desirable properties of the finished product. The reaction temperature using a urethane catalyst is generally from about 175 ° C to about 245 ° C, preferably from 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 polystyrene standards.

Thermoplastic polyurethanes can also be prepared using prepolymer processes. In the prepolymer pathway, the hydroxyl-terminated polyether intermediate is generally reacted with an over-equivalent amount of at least one polyisocyanate to form a prepolymer solution having a polyisocyanate that is free or unreacted therein. The reaction is generally carried out in the presence of a suitable urethane catalyst at a temperature of from about 80 째 C to about 220 째 C and preferably at a temperature of from about 150 째 C to about 200 째 C. An optional type of chain extender as described above is then generally added in any equivalent of the free or unreacted diisocyanate compound as well as the isocyanate terminal group, generally equivalent. Thus, the total equivalent ratio of total diisocyanate to total equivalents of hydroxyl end intermediate and chain extender is from about 0.95 to about 1.10, preferably from about 0.98 to about 1.05, and more preferably from about 0.99 to about 1.03. The equivalent ratio of hydroxyl end intermediate to chain extender is adjusted to provide a Shore strength of 65A to 95A, preferably 75A to 85A. The temperature of the chain extension reaction is generally from about 180 캜 to about 250 캜, preferably from about 200 캜 to about 240 캜. Typically, the prepolymer path can be performed in any conventional apparatus and an extruder is preferred. Thus, the hydroxyl end intermediate is reacted with an excess of diisocyanate in a first portion of the extruder to form a prepolymer solution and then a chain extender is added to the downstream portion 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 greater, preferably 25 or greater.

Useful additives may be used in suitable amounts, including opacifying pigments, colorants, inorganic fillers, stabilizers, lubricants, UV absorbers, processing aids and other additives as desired. Useful opacifying pigments include titanium dioxide, zinc oxide and titanate yellow, while useful tinting pigments include carbon black, yellow oxides, brown oxides, raw and burnt sienna or umbellate umber, chromium oxide green, cadmium pigments, chromium pigments and other mixed metal oxides and organic pigments. Useful fillers include diatomaceous earth (superfloss) clay, silica, talc, mica, wollastonite, barium sulphate and calcium carbonate. If desired, useful stabilizers such as antioxidants may be used, which include phenolic antioxidants, while useful photostabilizers include organic phosphates and organotin thiolates (mercaptides). Useful lubricants include metal stearate, paraffin oil and amide wax. Useful UV absorbers include 2- (2'-hydroxyphenol) benzotriazole and 2-hydroxybenzophenone.

In addition, the plasticizer additive can be advantageously used to reduce hardness without affecting the properties.

During the melt spinning process, the TPU polymer described above may be weakly crosslinked with a crosslinking agent. The crosslinking agent is a prepolymer of a hydroxyl end intermediate which is a polyether, polyester, polycarbonate, polycaprolactone, or a mixture thereof, reacted with a polyisocyanate. Polyesters or polyethers are preferred hydroxyl end intermediates for preparing crosslinking agents, and when used with polyester TPU, polyethers are most preferred. The crosslinking agent, which is a prepolymer, will have an 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 end intermediate are capped with isocyanate so that the isocyanate functionality is 2.0.

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

The crosslinking agent has a number average molecular weight (Mn) of from about 1,000 to about 10,000 daltons, preferably from about 1,200 to about 4,000, more preferably from about 1,500 to about 2,800 daltons. Crosslinkers having 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% crosslinking agent used is% by weight based on the total weight of the TPU polymer and the crosslinking agent.

A preferred melt spinning process for preparing the TPU fibers of the present invention comprises feeding the preformed TPU polymer to an extruder to melt the TPU polymer, wherein the cross-linking agent is present near the point where the TPU melt is discharged from the extruder, or the TPU melt is discharged from the extruder And is continuously added downstream after being discharged. The crosslinking agent may be added to the extruder before the melt is discharged from the extruder or after the melt is discharged from the extruder. If the melt is added after being discharged from the extruder, it is necessary to ensure that the cross-linking agent can be properly mixed with the TPU polymer melt by mixing it with the TPU melt using a static or dynamic mixer. After exiting the extruder, the TPU polymer melted together with the crosslinking agent flows into the manifold. The manifold divides the molten stream into different streams, where each stream is fed to a plurality of spinnerets. Typically, there is a melt pump for each different stream flowing from the manifold, and each melt pump provides multiple spinnerets. The spinnerette has a small hole through which the melt is pushed 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 exits the spin pack assembly used as a fiber. The preferred spin pack assembly used is an assembly that provides a plug flow of the TPU polymer through the assembly. The most preferred radiation pack assembly is disclosed in PCT patent application WO 2007/076380, the full text of which is incorporated herein by reference.

Once the fibers are out of the spinnerette, cool the fibers before winding them on the bobbin. The fibers are passed over a first godet, a finish oil is applied, and the fibers are advanced to the second core. An important aspect of the process of making the fibers of the present invention is the relative speed at which the fibers are wound onto the bobbin. The relative speed means the speed (melt speed) of the melt discharged from the spinneret in relation to the winding speed. Usually, in the prior art TPU melt spinning process, the fibers are crimped at a rate four to six times faster than the melt rate. Thereby stretching and stretching the fibers. In the case of the unique fibers of the present invention, such extensive drawing is not desirable. The fibers must be crimped at least at the same rate as the melt rate to perform the process. In the case of the fibers according to the invention, it is necessary to wind the fibers at a higher speed than the melting rate of 50% or less, preferably 20% or less, and more preferably 10% or less, and a speed of 5% Results. Winding speeds, such as melt speed, would be ideal, but a slightly higher winding speed would be required to carry out the process. For example, fibers discharged at a speed of 300 meters per minute at the spinning mill would most preferably be wound at a speed of 300 to 315 meters per minute.

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

An antisticking agent such as a finish oil, for example silicon oil, is generally added to the surface of the fibers during the production of the fibers by the process of the present invention, after cooling or cooling, and immediately before being wound on the bobbins.

An important aspect of the melt spinning process is the mixing of the cross-linking 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 cross-linking agent should be a method of achieving plug-flow, i.e. first-in-first-out. Suitable mixing can be achieved using a dynamic mixer or a static mixer. A static mixer is more difficult to clean, so a dynamic mixer is preferred. A dynamic mixer with feed screw and mixing pin is the preferred mixer. U.S. Patent No. 6,709,147, which is incorporated herein by reference, describes such a mixer, which has a rotatable mixing pin. Also, 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 mixed 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 must be designed to move the polymer melt in an incremental manner with very little backmixing to achieve the plug-flow of the melt. The L / D of the mixing screw should be from 3 or more to less than 30, preferably from about 7 to about 20, more preferably from about 10 to about 12.

The temperature in the mixing zone in which the TPU polymer melt and the crosslinking agent are mixed is from about 200 캜 to about 240 캜, preferably from about 210 캜 to about 225 캜. These temperatures are needed to cause the reaction without degrading the polymer.

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

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

The unique fibers of the present invention have a relatively uniform and / or constant modulus in loading and unloading cycles of 100% to 200% elongation. The uniform modulus is due to the stress of less than 0.023 grams per denier at 100% elongation in the loading cycle, gram-force less than 0.036 grams per denier at 150% elongation and gram-force less than 0.053 per denier at 200% elongation Proved; In the unloading cycle, it is evidenced by a stress of less than 0.027 grams per denier at 200% elongation, a gram-force less than 0.018 per denier at 150% elongation, and a gram-force of less than 0.015 per denier at 100% elongation, All these data were collected from 360 denier fibers.

The homogeneous modulus can also be attributed to stresses of less than 0.158 grams per denier at 100% elongation in the loading cycle, gram-force less than 0.207 denier at 150% elongation, less than 0.265 grams force per denier at 200% elongation Proved by; A gram-force of less than 0.021 per denier at 200% elongation in the unloading cycle, a gram-force of less than 0.012 per denier at 150% elongation, and a gram-force of less than 0.008 per denier at 100% elongation, All these data were collected from 70 denier fibers.

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

The fibers of the present invention have a breaking elongation of at least 400%, and preferably from about 450 to 500%. The fibers are monofilaments of rounded shape. Referring to FIG. 2, it can be confirmed that the 70 denier monofilament fiber is actually round in cross-sectional shape. Figure 1 shows a 70 denier monofilament dry spinning fiber with a larger cross sectional width.

3 shows a graph comparing the dry spinning fiber with the melt spinning fiber of the present invention. The graph plots the denier (X axis) versus fiber width squared (square micron). The graph shows that the melt-spun fibers of the present invention have a constant slope on the graph, whereas dry-spun fibers have an exponentially increasing slope. The result is that fabrics can be made from the fibers of this invention which are thinner and more comfortable for 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.

The above characteristics 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 surprising that the fibers of the present invention exhibited about 50 to 75% improvement in burst strength compared to dry-spun polyurethane fibers. Even so, even if the tensile strength of the fibers is approximately the same, there is such an improved burst strength.

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

Fabrics made using the fibers of the present invention can be made by knitting or weaving. Often it is desirable to make fabrics using other fibers 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 snag resistance of fabrics compared to 100% elastic fiber fabrics. A preferred fabric is a fabric having a denier of 140 denier TPU / 70 denier nylon after alternating with a strand of 140 denier TPU (referred to as 1-1 fabric) or a strand of 140 denier TPU / 70 denier nylon, 2 fabric ") < / RTI >

The garment can be made from the fabric of the present invention. The most preferred use of fabrics is in the manufacture of underwear or tight fit apparels due to the comfort provided by the fibers. Sportswear used in activities such as running, skating, cycling or other sports as well as underwear and T-shirts such as bras can benefit from the characteristics of these fibers. Since the modulus is lowered as the fiber reaches body temperature, the garments worn next to the body will benefit from the uniform modulus of these fibers. Clothes that feel tight will become more comfortable after about 30 seconds to 5 minutes of fiber reaching body temperature. It will be understood by those skilled in the art that any garment may be made from the fabrics and fibers of the present invention. An exemplary embodiment is a wing of a brassier made of a brassiered shoulder strap and a knitted fabric made of a woven fabric, both of which are woven and knit fabrics containing the melt-spun TPU fibers of the present invention. The bra strap will not require 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 a polyester hydroxyl end intermediate (polyol) with a 1,4-butanediol chain extender and MDI. The polyester polyol was prepared by reacting adipic acid with a 50/50 mixture of 1,4-butanediol and 1,6-hexanediol. The Mn of the polyol is 2,500. TPU was prepared by a one - shot process. The crosslinking agent added to the TPU during the spinning process was a polyether prepolymer prepared by reacting 1000 Mn PTMEG with MDI to produce an isocyanate terminated capped polyether. The crosslinking agent was used at a level of 10% by weight of the combined weight of TPU and crosslinking agent. The fibers were melt spinned to produce the 40, 70, 140 and 360 denier fibers used in the examples.

Example  One

This example has been provided to demonstrate a relatively uniform modulus curve of the inventive fibers (70 denier) compared to existing conventional melt spinning TPU fibers (40 denier) and commercial dry spinning fibers (70 denier).

The test procedure used was as described above to test the elastic properties. An Instron Model 5564 tensiometer with Merlin software was used. The test conditions were 23 캜 2 캜 and 50% 5% humidity. The fiber length of the test specimen was 50.0 mm. Four specimens were tested and the results are the average of the four specimens tested. The results are shown in Table 1.

Table I

All of the data is an average for the four samples tested.

From the data it can be seen that the melt-spun fibers of the present invention have a relatively uniform modulus curve over five test cycles. The first cycle is usually ignored because it relaxes the stresses in the fibers.

Example  2

This example has been provided to illustrate the width of the melt-spun fibers of the present invention compared to commercially available dry spun fibers. The width was measured by SEM. The results are shown in Table II below.

Table II

As can be seen, the dry spinning fibers have much higher widths and the larger the denier, the greater the difference.

Example 3

This example has been provided to demonstrate improved burst strength of the melt-spun TPU fibers of the present invention compared to commercially available dry-spun polyurethane fibers. 70 denier fibers were used to make signel jersey knit fabrics from each type of fiber. The fabrics were tested for burst puncture strength according to ASTM D751. The results are shown in Table III below. The following results are the average of the five samples tested.

Table III

Although the melt-spun fibers of the present invention did not have a higher tensile strength than the dry spun fibers, it was surprising that the rupture strength of the melt-spun fibers was higher.

While the best mode and the preferred embodiment have been described in accordance with the Patent Act, the scope of the present invention is not limited thereto but is limited by the appended claims.

Claims (22)

Made from a polyester thermoplastic polyurethane made from a reaction mixture comprising a polyisocyanate, a polyester intermediate terminated with a linear hydroxyl group, at least one chain extender, and a crosslinking agent and having a melt elongation at break of at least 400% As fibers,
Wherein the polyisocyanate comprises diphenylmethane-4,4'-diisocyanate,
Wherein the linear hydroxyl group-terminated polyester intermediate comprises the reaction product of adipic acid with a 50/50 blend of 1,4-butanediol and 1,6-hexanediol,
The intermediate has a number average molecular weight (Mn) of 500 to 10,000 and an acid number of less than 1.3,
Wherein the one or more chain extenders comprise 1,4-butanediol,
Wherein the crosslinking agent comprises a polyether crosslinking agent. The melt-spun elastomeric fiber according to claim 1, wherein the polyester thermoplastic polyurethane has a weight average molecular weight of 200,000 to 700,000 daltons. The melt-spun elastic fiber according to claim 1, wherein the cross-linking agent is 5 to 20% by weight of the combined weight of the polyester thermoplastic polyurethane and the cross-linking agent. The melt-spun elastic fiber according to claim 1, wherein the crosslinking agent is 8 to 12% by weight 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 fiber according to claim 1, at least one of the fibers being a hard fiber. 6. The fabric of claim 5, wherein the fabric is made of two strands of hard fibers and fibers according to claim 1, respectively. 6. The fabric of claim 5, wherein the fibers of claim 1 have a denier of from 20 to 600 denier. 6. The fabric of claim 5, wherein the hard fibers are selected from the group consisting of nylon and polyester. 9. The fabric of claim 8, wherein the hard fibers have 70 denier and the thermoplastic polyurethane fibers have 140 denier. A garment product comprising the fabric of claim 5. The article of claim 10, wherein the article is an undergarment or a tight fitting garment. delete delete delete delete delete delete delete delete delete delete delete

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