JP7749606B2 - Method for producing bicomponent fibers and articles containing same - Google Patents

Description

This disclosure relates generally to bicomponent fibers, and more particularly to methods of making bicomponent fibers and articles including the same.

Bicomponent fibers, produced by side-by-side spinning of two polyesters, are widely used in the textile industry and primarily impart stretch to the final garment or article. The level of stretch can be manipulated by the relative shrinkage of the two polyesters, which can depend in part on the intrinsic viscosities (I.V.) of the two polymers. Ideally, in the bicomponent fiber manufacturing process, the polyester starting material used has the desired I.V., is readily available, and is inexpensive. Otherwise, compromises must often be made in the fiber manufacturing process, the physical properties of the bicomponent fiber, or both, to achieve the desired performance of the bicomponent fiber.

In a first embodiment, disclosed herein is a method for producing a bicomponent fiber, comprising: a) extruding a first and second component in a spinning machine capable of producing two or more independent melt streams; b) combining the melt streams in a spinneret adapted to produce a bicomponent fiber; c) quenching in air the bicomponent fiber produced in step (b); d) drawing and heat setting the quenched bicomponent fiber; and e) winding up the bicomponent fiber of step (d) by any suitable means; wherein the first extruded component has a lower moisture level than the second extruded component.

All cited patents, patent applications, and publications are incorporated herein by reference in their entirety.

Ranges and Variations Where present, all ranges are inclusive and combinable. For example, if a range of "1 to 5" is recited, the recited range should be interpreted as including ranges such as "1 to 4,""1 to 3,""1 to 2,""1 to 2 and 4 to 5,""1 to 3 and 5," etc. When used herein in connection with numerical values, the term "about" refers to a range of +/- 0.5 of the numerical value unless the context clearly defines otherwise. For example, the phrase "a pH value of about 6" refers to a pH value of 5.5 to 6.5 unless the pH value is clearly defined otherwise.

Every maximum numerical limit given throughout this specification is intended to include every lower numerical limit, as if such lower numerical limit were expressly written herein. Every minimum numerical limit given throughout this specification will include every higher numerical limit, as if such higher numerical limit were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical range were expressly written herein.

DEFINITIONS As used herein, the terms "embodiments" or "disclosure" are not intended to be limiting and apply generally to any of the embodiments defined in the claims or described herein. These terms are used interchangeably herein. In this disclosure, several terms and abbreviations are used. Unless otherwise specified, the following definitions apply:

The articles "a," "an," and "the" preceding an element or component are intended to be open-ended regarding the number of instances (i.e., occurrences) of the element or component. Thus, "a," "an," and "the" should be read to include one or at least one, and the singular form of a word for an element or component also includes the plural, unless the number is clearly intended to be singular.

The term "comprising" refers to the presence of stated features, components, steps, or ingredients recited in a claim, but does not exclude the presence or addition of one or more other features, components, steps, ingredients, or groups thereof. The term "comprising" is intended to include embodiments encompassed by the terms "consisting essentially of" and "consisting of." Similarly, the term "consisting essentially of" is intended to include embodiments encompassed by the term "consisting of."

The term "bicomponent fiber," as used herein, refers to a fiber containing two different polymer components, which may be different polymer types, the same polymer type but with different intrinsic viscosities, or a blend of two or more polymers. Bicomponent fibers may also be referred to as composite fibers, and the terms may be used interchangeably.

The term "BCF" refers to bulky or high-loft continuous bicomponent filament, which is essentially one long continuous strand of fiber used to make carpet. The terms "bulky" and "high-loft" are used interchangeably herein.

The term "carpet," as used herein, refers to a floor covering composed of pile yarns or fibers and a backing system. It may be tufted or woven. As used herein, the term "carpet" includes wall-to-wall carpets, carpet tiles, rugs, and vehicle and building entrance mats, such as those designed to trap dirt from feet.

The term "face" refers to the side of the carpet containing the tufted or woven yarns.

The term "surface fibers," as used herein, refers to the fiber content of the carpet, including those visible to the observer. Surface fibers are primarily composed of yarns, which may be cut, looped, cut and looped, or styled in several styles known to those skilled in the art.

The term "copolymer" refers to a polymer composed of a combination of more than one type of monomer. Copolymers may form the basis of some man-made fibers.

The term "crimp" refers to the waviness of a fiber, expressed in crimps per unit length. "Crimping" is the process of imparting crimp to filament yarns.

The term "crimp contraction" is a measure of fiber crimp and refers to the contraction of yarn length from a fully extended state (i.e., a state in which the filaments are substantially straight). This is due to the formation of crimps in individual filaments under specific crimp-generating conditions. It is expressed as a percentage of the extended length. Crimp contraction can be measured before and/or after treating the fiber to partially or fully generate crimp, for example, by heating; typically, post-heat crimp contraction is more interesting and informative because it includes crimps generated by heating. Unless otherwise specified, crimp contraction values disclosed herein are post-heat crimp contraction values (Cca).

The term "denier" is a measure of the weight per unit length of any linear material.

The term "fiber" refers to a unit of material, either natural or synthetic, that forms the building block of fabrics and other textile structures. It is characterized by having a length at least 1000 times its diameter or width. Typically, a textile fiber is a unit from which yarn can be spun or fabrics can be made by various processes, including weaving, knitting, braiding, felting, and twisting. Fibers are characterized by their denier (weight in grams per 9000 meters of fiber) and the number of filaments they contain.

"Filament" refers to a thin thread or continuous strand of fiber. There are two types of filament: monofilament and multifilament. Filaments are characterized by their denier per filament ("dpf").

The term "homofilament" means that the filament is made from one polymer type.

"Staple" refers to either natural fiber or lengths cut from filament.

The term "intrinsic viscosity" ("IV") refers to the ratio of the specific viscosity of a solution of known concentration to the concentration of the solute, extrapolated to zero concentration.

The term "tufting" refers to the process of creating fabrics, such as carpets, on specialized multi-needle machines. "Tufts" are loose threads threaded through the fabric and protruding from the surface in the form of cut threads or loops. The cut or uncut loops form the surface of a tufted or woven carpet.

The term "yarn" refers to a collection of individual filaments, either alone or twisted together with a collection of other filaments. The terms "fiber" and "yarn" are used interchangeably herein.

The term "quench" refers to rapid cooling in water, oil, or air to achieve certain physical or material properties.

The term "poly(ethylene terephthalate)" or PET refers to a polymer derived substantially exclusively from ethylene glycol and terephthalic acid (or equivalents, e.g., dimethyl terephthalate), also known as poly(ethylene terephthalate) homopolymer. As used herein, the term "poly(ethylene terephthalate) copolymer" or "co-PET" refers to a polymer comprising repeat units derived from ethylene glycol and terephthalic acid (or equivalents) and also containing at least one additional unit derived from an additional monomer, e.g., isophthalic acid (IPA) or cyclohexanedimethanol (CHDM). Poly(ethylene terephthalate) copolymers can contain from about 1 mol % to about 30 mol % of the additional monomer, e.g., from about 1 mol % to about 15 mol % of the additional monomer.

The term "poly(butylene terephthalate)" or PBT refers to a polymer derived substantially exclusively from 1,4-butanediol and terephthalic acid, also known as poly(butylene terephthalate) homopolymer. As used herein, the term "poly(butylene terephthalate) copolymer" refers to a polymer comprising repeat units derived from 1,4-butanediol and terephthalic acid and also containing at least one additional unit derived from an additional monomer, such as a comonomer for the PTT copolymer disclosed herein.

The term "poly(trimethylene terephthalate)" or PTT refers to a polyester made by polymerizing 1,3-propanediol and terephthalic acid. It is known for its high elastic recovery and resilience. PPT is known to provide stain resistance, static resistance, and improved dyeability. The term "poly(trimethylene terephthalate) homopolymer" refers to a polymer of essentially only 1,3-propanediol and terephthalic acid (or equivalent). The term "poly(trimethylene terephthalate)" also includes PTT copolymers, which refer to polymers containing repeat units derived from 1,3-propanediol and terephthalic acid (or equivalent) and at least one additional unit derived from an additional monomer.

Examples of PTT copolymers include copolyesters made using three or more reactants, each having two ester-forming groups. For example, copoly(trimethylene terephthalate) can be used, where the comonomers used to make the copolyester are linear, cyclic, and branched aliphatic dicarboxylic acids having 4 to 12 carbon atoms (e.g., butanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioic acid, and 1,4-cyclohexanedicarboxylic acid); aromatic dicarboxylic acids having 8 to 12 carbon atoms other than terephthalic acid (e.g., isophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched aliphatic diols having 2 to 8 carbon atoms (e.g., 1,3-propanol); Other than ethanediols, such as ethanediol, 1,2-propanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-cyclohexanediol; and aliphatic and aromatic ether glycols having 4 to 10 carbon atoms (e.g., hydroquinone bis(2-hydroxyethyl) ether, or poly(ethylene ether) glycols having a molecular weight of less than about 460, including diethylene ether glycol). The comonomer is typically present in the copolyester at a level ranging from about 0.5 mol % to about 15 mol %, and can be present in an amount up to about 30 mol %.

The term "Triexta" refers to the generic name for PTT, a subclass of polyester. The terms Triexta and PTT may be used interchangeably herein.

Poly(trimethylene terephthalate) typically has an intrinsic viscosity of about 0.5 deciliters per gram (dl/g) or greater, typically about 2 dl/g or less. Poly(trimethylene terephthalate) preferably has an intrinsic viscosity of about 0.7 dl/g or greater, more preferably 0.8 dl/g or greater, even more preferably 0.9 dl/g or greater, typically about 1.5 dl/g or less, preferably 1.4 dl/g or less, with currently available commercial products having an intrinsic viscosity of 1.2 dl/g or less. Poly(trimethylene terephthalate) is commercially available under the trademark "Sorona®" from E. I. du Pont de Nemours and Company, Wilmington, Delaware.

Carpets made using poly(trimethylene terephthalate) homofibers and the production thereof, as well as the production of such homofibers, are described in U.S. Pat. Nos. 5,645,782 to Howell et al., 6,109,015 to Roark et al., and 6,113,825 to Chuah; U.S. Pat. Nos. 6,740,276, 6,576,340, and 6,723,799; WO 99/19557 to Scott et al.; H. Modlich, "Experience with Polyesters Fibers in Tufted Articles of Heat-Set Yarns," Chemiefasern/Textilind. 41/93, pp. 786-94 (1991); and H. Chuah, "Corterra Poly(trimethylene terephthalate) - New Polymeric Fiber for Carpets," The Textile Institute Tifcon '96 (1996), all of which are incorporated herein by reference. Staple fibers are primarily used to manufacture residential carpets. BCF yarns are used to manufacture all types of carpets and are generally preferred for carpets.

Typically, PTT-containing bicomponent fibers are used to manufacture fabrics and garments that have durable and stretchable properties. In contrast, such stretchable properties are not required in carpet manufacturing. Rather, fibers for use in carpet manufacturing are typically mechanically bulked to provide a high level of bulk; such fibers are typically referred to as "BCF" fibers.

General Applicants have advantageously discovered a method for producing bicomponent fibers that allows for on-line control of the I.V. of the starting polymer; the potential use of less expensive polymers in the fiber manufacturing process; and optimization of bulk fiber properties without being limited by polymer I.V.

Applicant has also advantageously discovered a method for producing bicomponent fibers by controlling the I.V. of the starting polymers off-line.

A method for producing bicomponent fibers is disclosed herein.

The method includes: a) extruding the first and second components in a spinning machine capable of producing two or more independent melt streams; b) combining the melt streams in a spinneret adapted to produce bicomponent fibers; c) quenching in air the bicomponent fibers produced in step (b); d) drawing and heat setting the quenched bicomponent fibers; and e) winding up the bicomponent fibers of step (d) by any suitable means; wherein the first extruded component has a lower moisture level than the second extruded component.

The first and second components of the methods disclosed herein may independently comprise polyester and nylon, and combinations thereof.

The first and second components of the bicomponent fiber may be present in a weight percent ratio ranging from 20:80 to 80:20. The weight percent ratio may be selected from the group consisting of 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, and 80:20.

The first and second components may independently comprise polyester and nylon homopolymers, copolymers, blends, and combinations thereof.

In one embodiment, the first and second components may independently comprise a polyester selected from the group consisting of: poly(trimethylene terephthalate), poly(ethylene terephthalate), poly(butylene terephthalate), and combinations thereof.

In one embodiment, the polyester in the bicomponent fiber can be a copolyester, which is included within the meaning of poly(ethylene terephthalate) and poly(trimethylene terephthalate), provided that such variations do not adversely affect the amount of crimp in the interlaced yarn or the processing characteristics of the fiber. For example, copoly(ethylene terephthalate) can be used, where the comonomers used to prepare the copolyester are linear, cyclic, and branched aliphatic dicarboxylic acids having 4 to 12 carbon atoms (e.g., butanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioic acid, and 1,4-cyclohexanedicarboxylic acid); aromatic dicarboxylic acids having 8 to 12 carbon atoms other than terephthalic acid (e.g., isophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched aliphatic diols having 3 to 8 carbon atoms (e.g., , 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-cyclohexanediol); and aliphatic and araliphatic ether glycols having 4 to 10 carbon atoms (e.g., hydroquinone bis(2-hydroxyethyl) ether, or poly(ethylene ether) glycols having a molecular weight less than about 460, including diethylene ether glycol). The comonomer may be present in the copolyester at a level of about 0.5 to about 15 mole percent. Isophthalic acid, pentanedioic acid, hexanedioic acid, 1,3-propanediol, and 1,4-butanediol are typically used because they are readily available and inexpensive commercially. The copolyester may also contain small amounts of other comonomers. Such other comonomers include, but are not limited to, sodium 5-sulfoisophthalate at levels of about 0.2 to about 5 mole percent. Minor amounts of trifunctional comonomers, such as trimellitic acid, may also be incorporated for viscosity control.

In one embodiment, the first and second components may independently comprise poly(ethylene terephthalate) (PET) homopolymer or poly(ethylene terephthalate) copolymer (co-PET), poly(trimethylene) terephthalate (PTT) polymer, or a blend of PTT and PET homopolymer or PET copolymer (co-PET).

In one embodiment of the bicomponent fiber, the first component may comprise PTT and the second component may comprise PET, and the bicomponent fiber is self-stretching due to differential shrinkage. The first component may comprise PTT having a pellet intrinsic viscosity ranging from about 0.9 dL/g to about 1.25 dL/g, and the second component may comprise a mixture of PET pellets having an intrinsic viscosity of about 0.50 dL/g to about 0.80 dL/g, where the PET pellets comprise a blend of dried pellets (moisture level of about 50 ppm) and wet pellets (moisture level of about 2500 ppm).

In one embodiment, the moisture level of the undried PET pellets described herein can range from 300 ppm to about 5000 ppm. Examples of pellet moisture levels include, but are not limited to: 300 ppm, 310 ppm, 320 ppm, 330 ppm, 340 ppm, 350 ppm, 360 ppm, 370 ppm, 380 ppm, 390 ppm, 400 ppm, 410 ppm, 420 ppm, 430 ppm, 440 ppm, 450 ppm, 460 ppm, 470 ppm, 480 ppm, 490 ppm, 500 ppm, 510 ppm, 520 ppm, 530 ppm, 540 ppm, 550 ppm, 560 ppm, 570 ppm, 580 ppm, 590ppm, 600ppm, 610ppm, 620ppm, 630ppm, 640ppm, 650ppm, 660ppm, 67 0ppm, 680ppm, 690ppm, 700ppm, 710ppm, 720ppm, 730ppm, 740ppm, 750ppm m, 760ppm, 770ppm, 780ppm, 790ppm, 800ppm, 810ppm, 820ppm, 830ppm, 840ppm, 850ppm, 860ppm, 870ppm, 880ppm, 890ppm, 900ppm, 910ppm, 920 ppm, 930ppm, 940ppm, 950ppm, 960ppm, 970ppm, 980ppm, 990ppm, 1000p pm, 1010ppm, 1020ppm, 1030ppm, 1040ppm, 1050ppm, 1060ppm, 1070ppm , 1080ppm, 1090ppm, 1100ppm, 1110ppm, 1120ppm, 1130ppm, 1140ppm, 1 150ppm, 1160ppm, 1170ppm, 1180ppm, 1190ppm, 1200ppm, 1210ppm, 1220 ppm, 1230ppm, 1240ppm, 1250ppm, 1260ppm, 1270ppm, 1280ppm, 1290ppm m, 1300ppm, 1310ppm, 1320ppm, 1330ppm, 1340ppm, 1350ppm, 1360ppm, 1 370ppm, 1380ppm, 1390ppm, 1400ppm, 1410ppm, 1420ppm, 1430ppm, 144 0ppm, 1450ppm, 1460ppm, 1470ppm, 1480ppm, 1490ppm, 1500ppm, 1510ppm m, 1520ppm, 1530ppm, 1540ppm, 1550ppm, 1560ppm, 1570ppm, 1580ppm, 1590ppm, 1600ppm, 1610ppm, 1620ppm, 1630ppm, 1640ppm, 1650ppm, 16 60ppm, 1670ppm, 1680ppm, 1690ppm, 1700ppm, 1710ppm, 1720ppm, 1730 ppm, 1740ppm, 1750ppm, 1760ppm, 1770ppm, 1780ppm, 1790ppm, 1800ppm , 1810ppm, 1820ppm, 1830ppm, 1840ppm, 1850ppm, 1860ppm, 1870ppm, 1 880ppm, 1890ppm, 1900ppm, 1910ppm, 1920ppm, 1930ppm, 1940ppm, 1950 ppm, 1960ppm, 1970ppm, 1980ppm, 1990ppm, 2000ppm, 2010ppm, 2020ppm m, 2030ppm, 2040ppm, 2050ppm, 2060ppm, 2070ppm, 2080ppm, 2090ppm, 2 100ppm, 2110ppm, 2120ppm, 2130ppm, 2140ppm, 2150ppm, 2160ppm, 217 0ppm, 2180ppm, 2190ppm, 2200ppm, 2210ppm, 2220ppm, 2230ppm, 2240p pm, 2250ppm, 2260ppm, 2270ppm, 2280ppm, 2290ppm, 2300ppm, 2310ppm , 2320ppm, 2330ppm, 2340ppm, 2350ppm, 2360ppm, 2370ppm, 2380ppm, 23 90ppm, 2400ppm, 2410ppm, 2420ppm, 2430ppm, 2440ppm, 2450ppm, 2460 ppm, 2470ppm, 2480ppm, 2490ppm, 2500ppm, 2510ppm, 2520ppm, 2530ppm , 2540ppm, 2550ppm, 2560ppm, 2570ppm, 2580ppm, 2590ppm, 2600ppm, 2 610ppm, 2620ppm, 2630ppm, 2640ppm, 2650ppm, 2660ppm, 2670ppm, 2680 ppm, 2690ppm, 2700ppm, 2710ppm, 2720ppm, 2730ppm, 2740ppm, 2750ppm m, 2760ppm, 2770ppm, 2780ppm, 2790ppm, 2800ppm, 2810ppm, 2820ppm, 2830ppm, 2840ppm, 2850ppm, 2860ppm, 2870ppm, 2880ppm, 2890ppm, 29 00ppm, 2910ppm, 2920ppm, 2930ppm, 2940ppm, 2950ppm, 2960ppm, 2970p pm, 2980ppm, 2990ppm, 3000ppm, 3010ppm, 3020ppm, 3030ppm, 3040ppm , 3050ppm, 3060ppm, 3070ppm, 3080ppm, 3090ppm, 3100ppm, 3110ppm, 31 20ppm, 3130ppm, 3140ppm, 3150ppm, 3160ppm, 3170ppm, 3180ppm, 3190 ppm, 3200ppm, 3210ppm, 3220ppm, 3230ppm, 3240ppm, 3250ppm, 3260ppm , 3270ppm, 3280ppm, 3290ppm, 3300ppm, 3310ppm, 3320ppm, 3330ppm, 3 340ppm, 3350ppm, 3360ppm, 3370ppm, 3380ppm, 3390ppm, 3400ppm, 341 0ppm, 3420ppm, 3430ppm, 3440ppm, 3450ppm, 3460ppm, 3470ppm, 3480p pm, 3490ppm, 3500ppm, 3510ppm, 3520ppm, 3530ppm, 3540ppm, 3550ppm, 3560ppm, 3570ppm, 3580ppm, 3590ppm, 3600ppm, 3610ppm, 3620ppm, 36 30ppm, 3640ppm, 3650ppm, 3660ppm, 3670ppm, 3680ppm, 3690ppm, 3700p pm, 3710ppm, 3720ppm, 3730ppm, 3740ppm, 3750ppm, 3760ppm, 3770ppm , 3780ppm, 3790ppm, 3800ppm, 3810ppm, 3820ppm, 3830ppm, 3840ppm, 38 50ppm, 3860ppm, 3870ppm, 3880ppm, 3890ppm, 3900ppm, 3910ppm, 3920 ppm, 3930ppm, 3940ppm, 3950ppm, 3960ppm, 3970ppm, 3980ppm, 3990ppm m, 4000ppm, 4010ppm, 4020ppm, 4030ppm, 4040ppm, 4050ppm, 4060ppm, 4070ppm, 4080ppm, 4090ppm, 4100ppm, 4110ppm, 4120ppm, 4130ppm, 414 0ppm, 4150ppm, 4160ppm, 4170ppm, 4180ppm, 4190ppm, 4200ppm, 4210p pm, 4220ppm, 4230ppm, 4240ppm, 4250ppm, 4260ppm, 4270ppm, 4280ppm, 4290ppm, 4300ppm, 4310ppm, 4320ppm, 4330ppm, 4340ppm, 4350ppm, 43 60ppm, 4370ppm, 4380ppm, 4390ppm, 4400ppm, 4410ppm, 4420ppm, 4430p pm, 4440ppm, 4450ppm, 4460ppm, 4470ppm, 4480ppm, 4490ppm, 4500ppm , 4510ppm, 4520ppm, 4530ppm, 4540ppm, 4550ppm, 4560ppm, 4570ppm, 45 80ppm, 4590ppm, 4600ppm, 4610ppm, 4620ppm, 4630ppm, 4640ppm, 4650 ppm, 4660ppm, 4670ppm, 4680ppm, 4690ppm, 4700ppm, 4710ppm, 4720ppm , 4730 ppm, 4740 ppm, 4750 ppm, 4760 ppm, 4770 ppm, 4780 ppm, 4790 ppm, 4800 ppm, 4810 ppm, 4820 ppm, 4830 ppm, 4840 ppm, 4850 ppm, 4860 ppm, 4870 ppm, 4880 ppm, 4890 ppm, 4900 ppm, 4910 ppm, 4920 ppm, 4930 ppm, 4940 ppm, 4950 ppm, 4960 ppm, 4970 ppm, 4980 ppm, 4990 ppm, and 5000 ppm.

The weight ratio of dry pellets to wet pellets may vary from 0 to 100%. Examples of weight percent ratios of dry pellets to wet pellets include, but are not limited to, 0:100, 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10, 95:5, and 100:0.

In one embodiment, the moisture level of the wet PET pellets (described above) can be varied in combination with varying the weight percent ratio of dry to wet pellets (described above) to control the final bulk measurement (crimp %) of the subsequently formed bicomponent fiber.

In another embodiment of the bicomponent fiber, the first component may comprise PTT and the second component may comprise PET, wherein the first component may have a PTT pellet intrinsic viscosity ranging from about 0.9 dL/g to about 1.25 dL/g, the PTT pellets may be extruded at about 245°C to 265°C, the second component may have a PET pellet intrinsic viscosity of about 0.50 dL/g to about 0.80 dL/g, and the PET pellets may be wet (moisture level of about 2500 ppm) and may be extruded at a temperature of about 250°C to 280°C.

In one embodiment, the moisture level of the undried PET pellets can range from 300 ppm to about 5000 ppm.

Extrusion temperatures used for undried PET pellets may include, but are not limited to, 250°C, 255°C, 260°C, 265°C, 270°C, and 280°C.

In one embodiment, the moisture level (described above) of the wet PET pellets can be varied in combination with varying the extrusion temperature (described above) of the wet PET pellets to control the final bulk measurement (% crimp) of the subsequently formed bicomponent fiber.

In one embodiment of the method described herein, a PET extruder may be fed with a feed of dry PET pellets and a feed of non-dried PET pellets in a desired ratio as described herein, except that the non-dried and dried PET pellets are added to the extruder separately rather than being premixed.

In one embodiment of the method described herein, the drying conditions in the PET pellet feed hopper can be adjusted to provide the moisture necessary for hydrolysis. For example, PET pellets are typically dried to 50 ppm moisture during bicomponent production. By "under-drying" the PET pellets (e.g., to 300 ppm moisture), the maintained pellet moisture can promote hydrolysis in the extruder to achieve the desired lower IV. In this way, the desired PET IV can be "dialed in" for the spinning process.

In one embodiment of the method described herein, the PET extruder may be equipped with a vacuum system to control the PET I.V. In this manner, high-IV PET wet pellets with little or no drying can be "trimmed" by the amount of vacuum applied to achieve the desired I.V.

In one embodiment of the method described herein, PET pellets may be dried (approximately 50 ppm) in the manner described herein, and a small amount of water may be injected into the heated extruder to affect the desired level of hydrolysis and subsequent I.V. value.

The on-line hydrolysis process described herein is an efficient method for controlling I.V. However, it may be desirable to use the techniques described herein off-line. For example, the hydrolysis process described herein can be performed off-line in an extruder not associated with fiber spinning. The hydrolyzed PET exiting the extruder may have a desired I.V. and then be re-pelletized. The re-pelletized pellets, having the desired I.V., can then be dried in a conventional manner without the need for on-line I.V. control.

The stretchability measurement (% crimp) of bicomponent fibers produced by the methods disclosed herein may increase by about 10% to about 85%. Examples of increased stretchability measurements include, but are not limited to, 10%, 12%, 17%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, and 85%.

In another embodiment of the bicomponent fiber, the first component may comprise PTT and the second component may comprise PET, where the first component may have a PTT pellet intrinsic viscosity ranging from about 0.9 dL/g to about 1.25 dL/g, the PTT pellets may be extruded at 260°C, the second component may have a PET pellet intrinsic viscosity of about 0.50 dL/g, and the PET pellets may comprise a blend of dry pellets (about 50 ppm moisture) and wet pellets (about 2500 ppm moisture). The weight ratio of dry pellets to wet pellets may vary from 0 to 20%.

The first and second components may independently be PET or co-PET, and PTT or a blend of PTT and PET or coPET, and may be present in the bicomponent fiber in a weight ratio ranging from about 80:20 to about 20:80. For example, the weight ratio of the first component to the second component may be 80:20, 75:25, 70:30, 65:35, 60:40, 55:45, 50:50, 45:55, 40:60, 35:65, 30:70, 25:75, 20:80, or any ratio within this range.

In one embodiment, the stretch measurement (% crimp) of bicomponent fibers produced by the methods disclosed herein need not be increased, but may be controlled by varying the moisture level of the wet components; the ratio of dry to wet pellets of the components; and/or the extrusion temperature of a particular component. Increasing and controlling the stretch measurement depends on the type of polymer used to produce a particular bicomponent fiber.

Various additives may be added to one or both of the polymers of the first and second components. Additives include, but are not limited to, lubricants, nucleating agents, antioxidants, UV stabilizers, pigments, dyes, antistatic agents, soil and stain resistant agents, antimicrobial agents, and flame retardants.

Bicomponent fibers may be produced by delivering the polymers to a spinneret in the desired volume or weight ratio. While any conventional multicomponent spinning technique may be used, an exemplary spinning apparatus and method for producing bicomponent fibers is described in U.S. Patent No. 5,162,074 to Hills, which is incorporated herein by reference in its entirety.

The bicomponent fibers described herein can be in a side-by-side ("S/S") or eccentric sheath-core ("S/C") configuration. Bicomponent fibers can be produced in a variety of cross-sectional shapes, such as round, delta, trilobal, scalloped, or other shapes, by using specific spinnerets for each shape, as disclosed, for example, in U.S. Pat. No. 6,803,102, which is incorporated herein by reference in its entirety.

Also disclosed herein are articles comprising the bicomponent fibers produced by the methods described herein. Articles include, but are not limited to, apparel, fabrics, fully oriented yarns (FDY), partially oriented yarns (POY), staple fibers, nonwoven fibers, nonwoven fabrics, and carpets.

Disclosed herein, in one embodiment, is a carpet, the face fibers of which comprise bicomponent fibers produced by the methods disclosed herein.

For use in carpets, the bicomponent fibers disclosed herein can have a denier ranging from about 300 to about 1400 grams per denier. Useful denier per filament can range from about 2 to about 20.

The bicomponent fibers disclosed herein may be used with all other types of fibers, both synthetic and natural, used in carpet manufacturing. Carpets can be produced by mechanical or manual tufting, weaving, and hand knotting. Examples include: 1) broadloom carpets (also known as wall-to-wall carpets), where tufted carpets are produced in long continuous lengths several meters wide for home or commercial use; 2) carpet tiles, which are made in squares of various sizes for ease of installation; 3) rugs for home use; or 4) mats for vehicles and building entrances designed to clean feet before entering a building.

In manufacturing the carpets described herein, any method known to those skilled in the art for manufacturing carpet from fibers may be used. Typically, the bicomponent fibers disclosed herein can be used in the same carpet manufacturing process in which other synthetic and natural fibers are used. The bicomponent fibers may be used alone in carpet construction (i.e., as "single" yarns) or may be plied with similar bicomponent fibers or other fiber types (e.g., nylon, polypropylene, polyester) to increase denier. Optionally, the single and plied fibers may be entangled using an air jet prior to plying, and may be heat set using a machine specifically designed to thermally set the physical properties of the single and tufted yarns.

One example of a heat-setting machine suitable for this purpose is manufactured by Superba® (Mulhouse, France). After the bicomponent fibers have been optionally air-entangled, twisted, or heat-set, the fibers may then be tufted into a standard nonwoven or woven backing sheet typical of the carpet industry. The face fiber loops of the tufted carpet may be cut to produce a cut-loop carpet. After tufting, adhesive is often applied to the backside of the carpet (i.e., the side opposite the face fibers) to hold the tufts in place. An additional backing layer may also be added to the backside of the carpet. The adhesive layer may contain fillers or flame retardants, depending on the end use of the particular carpet. The carpet may then be subjected to dyeing by standard processes common to the carpet-making industry; alternatively, pigments may be added to the bicomponent fibers and/or entrained fibers during fiber extrusion to impart color to the finished fabric. Additionally, the face yarns may be treated with materials designed to impart fire resistance, antistatic properties, or stain and soil resistance. The finished carpet is often dried to remove any water remaining from the dyeing process.

The manufacturing process described above is typical for broadloom tufted carpet. Variations of this process known in the industry may also be used in making rugs, carpet tiles, and vehicle mats.

Surface fibers, including bicomponent fibers, may have circular or non-circular cross-sections, e.g., trilobal.

The present disclosure is further defined in the following examples. It should be understood that the examples, while illustrating certain specific embodiments, are given for illustrative purposes only. From the above discussion and examples, one skilled in the art will be able to ascertain the essential characteristics of the present disclosure and can make various changes and modifications to adapt it to various uses and conditions without departing from its spirit and scope.

As used herein, "Comp. Ex." means comparative example; "Ex." means example; "No." means number; "%" means percent or percentage; "wt%" means percent by weight; "IV" means intrinsic viscosity; "dL/g" means deciliters per gram; "g" means grams; "mg" means milligrams; "°C" means degrees Celsius; "°F" means degrees Fahrenheit; "temp" means temperature; "min" means minutes; "h" means hours; "sec" means seconds; "lb" means pounds; and "kg" means kilograms. "mm" is millimeter; "m" is meter; "gpl" is grams per liter; "m/min" is meters per minute; "mol" is mole; "kg" is kilogram; "ppm" is parts per million; "wt" is weight; "dpf" is denier per filament; "gpd" or "g/d" is grams per denier; "dtex" means decitex; "dN/tex" means deciNewtons per tex; "mL" means milliliter; "IV" means intrinsic viscosity.

All materials were used as received unless otherwise noted.

Test Methods Measurement of crimp shrinkage after heating (CCa%) - Crimp shrinkage method:
The crimp contraction after heating (CCa%, also known as stretch value) was measured according to the method described herein. Each example and comparative fiber was individually formed into a skein of approximately 5000 +/- 5 total denier (5550 dtex) using a skein frame at a tension of approximately 0.1 gpd (0.09 dN/tex). The skeins were then folded in half to fit inside the oven used for heat setting. The folded skeins were hung from a hook by their center and conditioned for a minimum of 16 hours at 70 +/- 1°F (21 +/- 1°C) and 65 +/- 2% relative humidity. The folded skein was then hung from a hook at its center, substantially vertically on a rack, and a 1.5 mg/denier (1.35 mg/dtex) weight was hung at the bottom of the skein through two loops in the folded skein. The loaded skein was then heated in an oven at 250°F (121°C) for 5 minutes, after which the rack and skein were removed and allowed to cool for 5 minutes, and then conditioned for a minimum of 2 hours at 70°F +/- 1°F (21 +/- 1°C) and 65% +/- 2% relative humidity, with the 1.5 mg/denier weight remaining on the skein for the remainder of the test. The length of the skein was measured to within 1 mm and recorded as "Ca." A 1000 g weight was then hung from the bottom of the skein, allowed to reach equilibrium, and the length of the skein was measured to within 1 mm and recorded as "La." The crimp shrinkage "CCa" value (%) after heating is calculated using the formula:
CCa%=100×(La-Ca)/La
was calculated according to

Intrinsic Viscosity Measurement: Intrinsic viscosity (IV) was measured using a Viscoteck Y501C Forced Flow Viscometer (Malvern Corporation, Houston, Texas, USA). 0.15 g of sample was weighed into a 40 mL glass vial containing 30 mL of solvent (phenol/1,1,2,2-tetrachloroethane (60/40 weight percent)) and a stir bar. The sample was then placed in a heat block preheated to 100°C, heated and stirred for 30 minutes, removed from the block, and allowed to cool for 30-45 minutes before being placed in the viscometer's autosampler rack. The sample was then analyzed according to ASTM Method D5225-92 (Standard Test Method for Measuring Solution Viscosity of Polymers Using a Differential Viscometer).

Polymer Preparation Two grades of PTT homopolymer pellets were obtained from E. I. du Pont de Nemours and Company, Wilmington, Delaware, USA. One grade had an IV of 1.02 dL/g, and the second grade had an IV of 0.92 dL/g. PET homopolymer pellets were obtained from Sinopec Shanghai Petrochemical Company, Ltd., Shanghai, People's Republic of China, and had an IV of 0.50 dL/g. PET copolymer (containing 1.9 mol% isophthalic acid) pellets with an IV of 0.80 dL/g were obtained from NanYa Plastics Corporation, Livingston, New Jersey, USA.

In preparation for melt spinning, the PET and PTT pellets were dried under nitrogen in a vacuum oven at 25 inches of mercury and 120°C for 15 hours. Under these conditions, the moisture content of both the PET and PTT pellets was reduced to approximately 50 ppm. The dried pellets were transferred directly to the nitrogen-purged feed hopper of the spinner. In examples using a mixture of dried and undried PET pellets, the undried pellets were taken directly from the bag and had a residual moisture content of approximately 2500 ppm.

Fiber Manufacturing The first and second components of the bicomponent fibers are melt spun using processes and equipment generally applicable to spinning side-by-side and eccentric sheath/core bicomponent fibers, for example, as disclosed in U.S. Pat. Nos. 6,641,916 B1, 6,803,102, and 7,615,173 B2, which are incorporated herein by reference in their entireties.

In spinning the bicomponent fibers of the examples, polymers were melted in a pair of Werner & Pfleiderer co-rotating 28 mm twin-screw extruders with capacities of 0.5 to 40 lbs/hr (0.23 to 18.1 kg/hr). One extruder (referred to herein as the East extruder) was used to melt either 1) PET pellets dried to approximately 50 ppm or 2) a mixture of PET pellets, some of which were dried to a residual moisture level of approximately 50 ppm and the remaining pellets were undried, resulting in a residual moisture level of approximately 2500 ppm. A second extruder (referred to herein as the West extruder) was used to melt PTT pellets dried to a residual moisture level of approximately 50 ppm. The temperatures of the West extruder, spin block, and East extruder are described in the examples. Each extruder fed into a spin block containing an embedded spinneret. The spinneret used was a post-merged side-by-side bicomponent spinneret with 34 pairs of capillaries arranged in a circle (30° interior angle between each pair of capillaries, 0.64 mm capillary diameter, and 4.24 mm capillary length).

The bicomponent filaments exiting the spinneret were cooled by cross-flow quench air at a nominal temperature of 20°C and a face velocity of 0.5 mm/s. The filaments were then fed to dual feed rolls operating at approximately 800-1200 meters/min, depending on the draw ratio. A finish applicator was used to apply lubricant to the filament bundle between the spinneret and the feed rolls. The feed rolls were typically heated to 70°C to affect the draw ratio. The filament bundle was then accelerated to an anneal roll operating at a speed of approximately 3000-3600 meters/min, depending on the desired draw ratio; the anneal roll temperature was typically 170°C. The annealed bicomponent fibers were then fed to two sets of dual letdown rolls operating at room temperature and subsequently wound on a Barmag SW6 600 winder. The fibers had a snowman-shaped (oval) cross-sectional shape. The bicomponent fibers in all examples were 75 denier, 34 filaments.

Comparative Example A and Examples 1-3: Differences in Pellet Moisture Content Comparative Example A illustrates a typical manufacturing process for producing PET/PTT bicomponent fibers, in which 0.50 I.V. PET pellets are dried to about 50 ppm residual moisture and then extruded through the East extruder at 270°C, and 1.02 I.V. PTT pellets are dried to about 50 ppm residual moisture and then extruded through the West extruder at 260°C. The ratio of PET to PTT in the bicomponent fiber is 50/50. The measured stretch value of 48% is in the typical range for commercially available bicomponent fibers.

Examples 1-3 demonstrate the use of on-line hydrolysis to control the amount of fiber stretch produced in bicomponent fibers using 0.80 I.V. PET. In Examples 1-3, 1.02 IV PTT was dried to approximately 50 ppm and extruded at the temperatures indicated. The only variable in these examples was the amount of wet PET (approximately 2500 ppm residual moisture) blended with the dried PET. As evidenced in Example 1, drying 0.80 IV to the same level as PTT (e.g., 50 ppm moisture) results in a fiber with little stretch. The relatively small difference in pellet I.V. between PET and PTT does not promote differential fiber shrinkage or stretch. In Example 2, the ratio of wet PET pellets to dry PET pellets was 10/90 weight percent. Under these process conditions, residual moisture in the wet polymer promotes hydrolysis of 0.80 I.V. PET in the heated extruder. The effect of hydrolysis can be seen in the reduction in pack pressure from 950 psi to 370 psi. This reduction in pack pressure is associated with a decrease in polymer melt viscosity, a decrease in polymer molecular weight, an increase in differential shrinkage, and an increase in fiber stretchability. The examples show the effect of increasing the ratio of wet PET to dry PET to 20/80 weight percent, where the additional residual moisture further promotes a decrease in pack pressure and melt viscosity, and an increase in differential shrinkage and stretchability.

Examples 4-7: Extrusion Temperature Variations. Examples 4-7 demonstrate the use of on-line hydrolysis to control the amount of fiber stretch produced in bicomponent fibers by varying the temperature at which hydrolysis occurs in the PET extruder. In Examples 4-7, the 0.92 IV PTT was dried to approximately 50 ppm, and the 0.80 IV PET was 100% wet (i.e., approximately 2500 ppm residual moisture). The polymer ratio of PET to PTT in the fiber was 70/30 weight percent. Rather than affecting hydrolysis through wet pellet concentration, the extent of hydrolysis was controlled through the PET extruder temperature. Hydrolysis is a chemical reaction between polyester and residual moisture, and the extent of the reaction increases with increasing extrusion temperature. In Example 4, the PET extruder was set at 250°C. At this relatively low temperature, little hydrolysis occurred, pack pressures remained high, molecular weight remained high, little differential fiber shrinkage occurred, and fiber shrinkage levels were low (10.8%). In Example 5, the PET extruder temperature was increased by 10°C to 260°C. At this higher extrusion temperature, hydrolysis increased, pack pressure decreased, molecular weight decreased, differential fiber shrinkage increased, and fiber stretch increased to 22%. Comparing Examples 4 and 5 shows that a 10°C increase in PET more than doubles fiber shrinkage. Examples 6 and 7 show that increasing the PET extruder temperature to 270°C and 280°C increases measured stretch to 27.2% and 50.5%, respectively. These examples demonstrate the important role of extrusion temperature on the extent of hydrolysis and fiber properties.

Examples 8-10: Stretch Formation. Examples 8-10 illustrate the use of on-line hydrolysis to produce bicomponent fibers with higher stretch values than can be obtained by conventional means. Because low-IV PET is difficult to pelletize, 0.50 I.V. PET, preferred in the production of PET/PTT bicomponent fibers, is typically the lowest IV PET that can be commercially produced. Lowering the PET IV through hydrolysis is an option because it is desired to increase stretch to levels higher than can typically be obtained with 0.50 IV PET. Example 8 demonstrates the process and results of a 50/50 weight ratio PET/PTT bicomponent fiber made with fully dried (approximately 50 ppm residual moisture) 0.50 I.V. PET and 1.02 IV PTT. Examples 9 and 10 demonstrate the process and results of 50/50 weight ratio PET/PTT bicomponent fibers made with 5% and 10% undried 0.50 I.V. PET, respectively. Figure 1 shows the stretch results for fibers made by blending dry PET with PET (residual moisture of approximately 2500 ppm). The stretch values of 65.8% and 69.3% are significantly higher than commercially available fibers. In these examples, the additional residual moisture further promotes a decrease in pack pressure and melt viscosity, and an increase in differential shrinkage and stretch percentage.

Claims (7)

1. A method for making a bicomponent fiber, comprising:
a) extruding first and second components in a spinner capable of producing two or more independent melt streams;
b) combining the molten streams in a spinneret adapted to produce bicomponent fibers;
c) quenching the bicomponent fibers produced in step (b) in air;
d) drawing and heat setting the quenched bicomponent fibers;
and e) winding the bicomponent fiber of step (d) by any suitable means; wherein the first extruded component has a lower moisture level than the second extruded component; the first extruded component has a moisture level of 50 ppm or less and the second component has a moisture level of greater than 50 ppm;
the first and second components are polyesters independently selected from the group consisting of: poly(trimethylene terephthalate), poly(ethylene terephthalate), poly(butylene terephthalate), and copolymers thereof;
The second component is a polyester selected from the group consisting of: poly(trimethylene terephthalate), poly(ethylene terephthalate), poly(butylene terephthalate), and copolymers thereof;
method. 10. The method of claim 1 , wherein the first component is poly(ethylene terephthalate) and the second component is poly(trimethylene terephthalate). The method of claim 1, wherein the first and second components of the bicomponent fiber are present in a weight percent ratio ranging from 20:80 to 80:20. The method of claim 1, wherein the bicomponent fibers are in a configuration selected from the group consisting of: side-by-side, eccentric sheath-core configuration, and trilobal. The crimp shrinkage of the bicomponent fiber after heating in step (e) is 1.0 or less when measured according to the crimp shrinkage method.
The method of claim 1, wherein the range is from 0% to 85%. The method of claim 1, wherein the extruder temperature of one of the components in step (a) is in the range of 240°C to 320°C. 7. The method of claim 6, wherein the extruder temperature of one of the two extrusion components in step (a) is selected from the group consisting of: 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, and 320 °C.