A METHOD TO MAKE BICOMPONENT FIBERS AND ARTICLES COMPRISING THE SAME

Field of the Invention

The present disclosure generally relates to bicomponent fibers, and more particularly, methods to make bicomponent fibers and articles comprising them.

Background of the Invention

Bicomponent fibers made from the side-by-side spinning of two polyesters are widely used in the textile industry, mainly to impart stretch in the final garment or article. Stretch level can be manipulated through the relative shrinkage of the two polyesters, which can depend in part on the intrinsic viscosity (I.V.) of the two polymers. In the manufacturing process of bicomponent fibers, ideally, polyester starting materials to be used have a desired I.V., and are readily available and inexpensive. When this is not the case, often compromises must be made in the fiber manufacturing process, physical properties of the bicomponent fibers, or both to achieve desired performance characteristics of the bicomponent fibers.

Summary of the Invention

In a first embodiment, disclosed herein is a method to make bicomponent fibers comprising: a) extruding a first and second component on a spinning machine capable of producing two or more independent melt streams; b) combining the melt streams in a spinneret suited for making 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 in step (d) by any suitable means; wherein the first extruded component has a moisture level less than the second extruded component.

Detailed Description of the Invention All patents, patent applications, and publications cited are incorporated herein by reference in their entirety. Ranges and Variants

Where present, all ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, and the like.

As used herein in connection with a numerical value, the term “about” refers to a range of +/- 0.5 of the numerical value, unless the term is otherwise specifically defined in context. For instance, the phrase a “pH value of about 6” refers to pH values of from 5.5 to 6.5, unless the pH value is specifically defined otherwise.

It is intended that every maximum numerical limitation given throughout this Specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations 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 ranges were all expressly written herein.

Definitions

As used herein, the term “embodiment” or “disclosure” is not meant to be limiting but applies generally to any of the embodiments defined in the claims or described herein. These terms are used interchangeably herein. In this disclosure, a number of terms and abbreviations are used. The following definitions apply unless specifically stated otherwise.

The articles “a”, “an”, and “the” preceding an element or component are intended to be nonrestrictive regarding the number of instances (i.e. , occurrences) of the element or component. Therefore “a”, “an”, and “the” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

The term “comprising” means the presence of the stated features, integers, steps, or components as referred to in the claims, but that it does not preclude the presence or addition of one or more other features, integers, steps, components 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 being comprised of two different polymer components which may be composed of different polymer types, the same polymer type but having different intrinsic viscosities, or blends of two or more polymers. Bicomponent fibers may also be referred to as composite fibers and the terms can be used interchangeably.

The term “BCF” refers to bulk or bulked continuous bicomponent filament. It is essentially one long continuous strand of fiber that is used to make carpet. The terms “bulk” and “bulked” are used interchangeably herein.

The term "carpet" as used herein refers to floor coverings consisting of pile yarns or fibers and a backing system. The may be tufted or woven. As used herein, the term “carpet” encompasses wall-to-wall carpet, carpet tiles, rugs, and mats for vehicles and building entrances, for example those designed to capture foot soil.

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

The term “face fiber” as used herein refers to the fiber content of the carpet including that which is visible to the observer. The face fiber is primarily made up of yarns, and those yarns may be styled as cut, loop, cut and loop or any number of styles known to those skilled in the art.

The term “copolymer” refers to a polymer composed of a combination of more than one monomer. Copolymers can form the basis of some manufactured fibers.

The term “crimp” refers to the waviness of a fiber expressed as crimps per unit length. “Crimping” is the process of imparting crimp to filament yarn.

The term “crimp contraction” is a measure of fiber crimp and refers to the contraction in length of a yarn from the fully extended state (i.e., where the filaments are substantially straightened). This is due to the formation of crimp in individual filaments under specified conditions of crimp development. It is expressed as a percentage of the extended length. Crimp contraction can be measured before and/or after treatment of a fiber, for example by heating, to partially or fully develop the crimp; typically the crimp contraction after heating is of more interest and provides more information as it includes the crimp developed by heating. Unless specified otherwise, crimp contraction values disclosed herein are crimp contraction values after heating (Cca).

The term “denier” is a weight-per-unit-length measure of any linear material.

The term “fiber” refers to unit of matter, either natural or synthetic, that forms the basic element of fabrics and other textile structures. It is characterized by having a length at least 1000 times its diameter or width. Typically, textile fibers are units that can be spun into a yarn or made into a fabric by various methods including weaving, knitting, braiding, felting and twisting.

Fiber is characterized by its denier (weight in grams per 9000 meters of fiber) and the number of filaments contained in the fiber.

The “filament” refers to a fine thread or continuous strand of fiber. There are two types of filaments: mono-filament and multi-filament. 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 fibers or cut lengths from filaments.

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

The term “tufting” refers to a process of creating textiles, such as carpet, on specialized multi-needle machines. A “tuft” is a cluster of soft yarns drawn through a fabric and projecting from the surface in the form of cut yarns or loops. The cut or uncut loops form the face of a tufted or woven carpet.

The term “yarn” refers to a collection of individual filaments, either singly, or plied together with another collection of filaments. The terms “fibers” and “yarns” are used interchangeably herein.

The term “quenching” refers to rapid cooling in water, oil or air to obtain certain physical or material properties. The term “polyethylene terephthalate)” or PET means polymer derived from substantially only ethylene glycol and terephthalic acid (or equivalent, such as dimethyl terephthalate), and is also referred to as polyethylene terephthalate) homopolymer. As used herein, the term “poly(ethylene terephthalate) copolymer” or “co-PET” refers to polymer comprising repeat units derived from ethylene glycol and terephthalic acid (or equivalent) and also containing at least one additional unit derived from an additional monomer, such as isophthalic acid (I PA) or cyclohexanedimethanol (CHDM). Polyethylene terephthalate) copolymer can contain from about 1 mole% to about 30 mole% additional monomer, for example from about 1 mole% to about 15 mole% additional monomer.

The term “poly(butylene terephthalate)” or PBT means polymer derived from substantially only 1 ,4-butanediol and terephthalic acid, and is also referred to as poly(butylene terephthalate) homopolymer. As used herein, the term “poly(butylene terephthalate) copolymer refers to 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, for example a comonomer for PTT copolymers as disclosed herein.

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

Examples of PTT copolymers include copolyesters made using 3 or more reactants, each having two ester forming groups. For example, a copoly(trimethylene terephthalate) can be used in which the comonomer used to make the copolyester is selected from the group consisting of linear, cyclic, and branched aliphatic dicarboxylic acids having 4-12 carbon atoms (for example butanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioic acid, and 1 ,4-cyclo-hexanedicarboxylic acid); aromatic dicarboxylic acids other than terephthalic acid and having 8-12 carbon atoms (for example isophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched aliphatic diols having 2-8 carbon atoms (other than 1 ,3-propanediol, for example, 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 4-10 carbon atoms (for example, hydroquinone bis(2-hydroxyethyl) ether, or a polyethylene ether) glycol having a molecular weight below about 460, including diethylene ether glycol). The comonomer typically is present in the copolyester at a level in the range of about 0.5 mole % to about 15 mole %, and can be present in amounts up to about 30 mole %.

The term “Triexta” refers to a generic name for PTT, a subclass of polyester. The terms Triexta and PTT can be used interchangeably herein.

Poly(trimethylene terephthalate) has an intrinsic viscosity that typically is about 0.5 deciliters/gram (dl/g) or higher, and typically is about 2 dl/g or less.

The poly(trimethylene terephthalate) preferably has an intrinsic viscosity that is about 0.7 dl/g or higher, more preferably 0.8 dl/g or higher, even more preferably 0.9 dl/g or higher, and typically it is about 1 .5 dl/g or less, preferably 1.4 dl/g or less, and commercial products presently available have intrinsic viscosities of 1.2 dl/g or less. Poly(trimethylene terephthalates) is commercially available from E. I. du Pont de Nemours and Company, Wilmington, DE under the trademark “Sorona®”.

Carpets made with poly(trimethylene terephthalate) homofibers and manufacture thereof, as well as the fibers and manufacture of the fibers, are described in U.S. Patent Nos. 5,645,782 Howell et al., 6,109,015 Roark et al. and 6,113,825 Chuah; U.S. Patent Nos. 6,740,276, 6,576,340, and 6,723,799; WO 99/19557 Scott et al.; H. Modlich, "Experience with Polyesters Fibers in Tufted Articles of Heat-Set Yarns, Chemiefasern/Textilind. 41/93, 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 prepare residential carpets. BCF yarns are used to prepare all types of carpets and are usually preferred for carpets.

Typically, PTT-containing bicomponent fiber is used to make fabrics and apparel having durable stretch attributes. In contrast, such stretch attributes are not needed in the manufacture of carpet. Rather, fibers for use in making carpet are typically mechanically bulked to provide high levels of bulk; such fibers are typically referred to as “BCF” fibers.

Generally

The Applicant has advantageously discovered a method to manufacture bicomponent fibers by controlling the on-line I.V. of the starting polymers which allows one to: optionally use inexpensive polymers in the fiber manufacturing process; and optimize bulk fiber properties while not being limited to the polymer I.V.

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

A method to make bicomponent fibers is disclosed herein.

The method comprises: a) extruding a first and second component on a spinning machine capable of producing two or more independent melt streams; b) combining the melt streams in a spinneret suited for making 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 in step (d) by any suitable means; wherein the first extruded component has a moisture level less than the second extruded component.

The first and second components of the method disclosed herein may independently comprise a 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 homopolymers, copolymers, blends, and combinations thereof of polyesters and nylon.

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

In an embodiment, the polyesters in the bicomponent fibers can be copolyesters, and such copolyesters are included in the meanings of polyethylene terephthalate) and poly(trimethylene terephthalate), provided such variants do not have an adverse effect on the amount of crimp in the entangled yarn or on the fibers’ processing characteristics. For example, a copolyethylene terephthalate) can be used in which the comonomer used to make the copolyester is selected from the group consisting of linear, cyclic, and branched aliphatic dicarboxylic acids having 4 to 12 carbon atoms (for example butanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioic acid, and 1 ,4- cyclohexanedicarboxylic acid); aromatic dicarboxylic acids other than terephthalic acid and having 8 to 12 carbon atoms (for example isophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched aliphatic diols having 3 to 8 carbon atoms (for example 1 ,3-propane diol, 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 (for example, hydroquinone bis(2- hydroxyethyl)ether, or a poly(ethyleneether) glycol having a molecular Weight below about 460, including diethyleneether glycol). The comonomer may be present in the copolyester at levels of about 0.5 to about 15 mole percent. Isophthalic acid, pentanedioic acid, hexanedioic acid, 1 ,3-propane diol, and 1 ,4- butanediol are typically used because they are readily commercially available and inexpensive. The copolyester(s) may also contain minor amounts of other comonomers. Such other comonomers include but are not limited to 5-sodium- sulfoisophthalate, at a level of about 0.2 to about 5 mole percent. Very small amounts of trifunctional comonomers, for example trimellitic acid, may also be incorporated for viscosity control. In an embodiment, the first and second components may independently comprise polyethylene terephthalate) (PET) homopolymer or polyethylene terephthalate) copolymer (co-PET), poly(trimethylene) terephthalate (PTT) polymer or a blend of PTT with PET homopolymer or PET copolymer (co-PET).

In an embodiment of the bicomponent fiber, the first component may comprise PTT and the second component may comprise PET, wherein the bicomponent fiber is self-stretching due to differential shrinkage. The first component may comprise PTT having a pellet intrinsic viscosity in the range of 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, wherein the PET pellets comprise a blend of dried pellets (about 50 ppm moisture level) and undried pellets (about 2500 ppm moisture level).

In an embodiment the moisture level of the undried PET pellets described herein can be in a range from 300 ppm to about 5000 ppm. Examples of the moisture levels of pellets include but are not limited to: 300ppm, 310ppm, 320ppm, 330ppm,

340ppm,350ppm,360ppm,370ppm,380ppm,390ppm,400ppm,410ppm,4 20ppm,4

30ppm,440ppm,450ppm,460ppm,470ppm,480ppm,490ppm500ppm,510 ppm,520 ppm,530ppm,540ppm,550ppm,560ppm,570ppm,580ppm,590ppm600ppm,6 10pp m,620ppm,630ppm,640ppm,650ppm,660ppm,670ppm,680ppm,690ppm700 ppm,

710ppm,720ppm,730ppm,740ppm,750ppm,760ppm,770ppm,780ppm,7 90ppm80

0ppm,810ppm,820ppm,830ppm,840ppm,850ppm,860ppm,870ppm,880 ppm,890 ppm900ppm,910ppm,920ppm,930ppm,940ppm,950ppm,960ppm,970ppm,9 80pp m,990ppm1000ppm,1010ppm,1020ppm,1030ppm,1040ppm,1050ppm,1060 ppm,

1070ppm,1080ppm,1090ppm1100ppm,1110ppm,1120ppm,1130ppm,11 40ppm,1

150ppm,1160ppm,1170ppm,1180ppm,1190ppm,1200ppm,1210ppm,12 20ppm,1

230ppm, 1240ppm, 1250ppm, 1260ppm, 1270ppm, 1280ppm, 1290ppm1300ppm, 13

10ppm,1320ppm,1330ppm,1340ppm,1350ppm,1360ppm,1370ppm,138 0ppm,13

90ppm1400ppm,1410ppm,1420ppm,1430ppm,1440ppm,1450ppm,1460 ppm,147

Oppm, 1480ppm, 1490ppm1500ppm, 151 Oppm, 1520ppm, 1530ppm, 1540ppm, 1550 ppm, 1560ppm, 1570ppm, 1580ppm, 1590ppm1600ppm, 161 Oppm, 1620ppm, 1630p pm,1640ppm,1650ppm,1660ppm,1670ppm,1680ppm,1690ppm1700ppm,17 10pp m,1720ppm,1730ppm,1740ppm,1750ppm,1760ppm,1770ppm,1780ppm,17 90pp m1800ppm,1810ppm,1820ppm,1830ppm,1840ppm,1850ppm,1860ppm,187 0pp m,1880ppm,1890ppm1900ppm,1910ppm,1920ppm,1930ppm,1940ppm,195 0pp m,1960ppm,1970ppm,1980ppm,1990ppm2000ppm,2010ppm,2020ppm,203 0pp m,2040ppm,2050ppm,2060ppm,2070ppm,2080ppm,2090ppm2100ppm,211 0pp m,2120ppm,2130ppm,2140ppm,2150ppm,2160ppm,2170ppm,2180ppm,21 90pp m2200ppm,2210ppm,2220ppm,2230ppm,2240ppm,2250ppm,2260ppm,227 0pp m,2280ppm,2290ppm2300ppm,2310ppm,2320ppm,2330ppm,2340ppm,235 0pp m,2360ppm,2370ppm,2380ppm,2390ppm2400ppm,2410ppm,2420ppm,243 0pp m,2440ppm,2450ppm,2460ppm,2470ppm,2480ppm,2490ppm2500ppm,251 0pp m,2520ppm,2530ppm,2540ppm,2550ppm,2560ppm,2570ppm,2580ppm,25 90pp m2600ppm,2610ppm,2620ppm,2630ppm,2640ppm,2650ppm,2660ppm,267 0pp m,2680ppm,2690ppm2700ppm,2710ppm,2720ppm,2730ppm,2740ppm,275 0pp m,2760ppm,2770ppm,2780ppm,2790ppm2800ppm,2810ppm,2820ppm,283 0pp m,2840ppm,2850ppm,2860ppm,2870ppm,2880ppm,2890ppm2900ppm,291 0pp m,2920ppm,2930ppm,2940ppm,2950ppm,2960ppm,2970ppm,2980ppm,29 90pp m3000ppm,3010ppm,3020ppm,3030ppm,3040ppm,3050ppm,3060ppm,307 0pp m,3080ppm,3090ppm3100ppm,3110ppm,3120ppm,3130ppm,3140ppm,315 0pp m,3160ppm,3170ppm,3180ppm,3190ppm3200ppm,3210ppm,3220ppm,323 0pp m,3240ppm,3250ppm,3260ppm,3270ppm,3280ppm,3290ppm3300ppm,331 0pp m,3320ppm,3330ppm,3340ppm,3350ppm,3360ppm,3370ppm,3380ppm,33 90pp m3400ppm,3410ppm,3420ppm,3430ppm,3440ppm,3450ppm,3460ppm,347 0pp m,3480ppm,3490ppm3500ppm,3510ppm,3520ppm,3530ppm,3540ppm,355 0pp m,3560ppm,3570ppm,3580ppm,3590ppm3600ppm,3610ppm,3620ppm,363 0pp m,3640ppm,3650ppm,3660ppm,3670ppm,3680ppm,3690ppm3700ppm,371 0pp m,3720ppm,3730ppm,3740ppm,3750ppm,3760ppm,3770ppm,3780ppm,37 90pp m3800ppm,3810ppm,3820ppm,3830ppm,3840ppm,3850ppm,3860ppm,387 0pp m,3880ppm,3890ppm3900ppm,3910ppm,3920ppm,3930ppm,3940ppm,395 0pp m,3960ppm,3970ppm,3980ppm,3990ppm4000ppm,4010ppm,4020ppm,403 0pp m,4040ppm,4050ppm,4060ppm,4070ppm,4080ppm,4090ppm4100ppm,411 0pp m,4120ppm,4130ppm,4140ppm,4150ppm,4160ppm,4170ppm,4180ppm,41 90pp m4200ppm,4210ppm,4220ppm,4230ppm,4240ppm,4250ppm,4260ppm,427 0pp m,4280ppm,4290ppm4300ppm,4310ppm,4320ppm,4330ppm,4340ppm,435 0pp m,4360ppm,4370ppm,4380ppm,4390ppm4400ppm,4410ppm,4420ppm,443 0pp m,4440ppm,4450ppm,4460ppm,4470ppm,4480ppm,4490ppm4500ppm,451 0pp m,4520ppm,4530ppm,4540ppm,4550ppm,4560ppm,4570ppm,4580ppm,45 90pp m4600ppm,4610ppm,4620ppm,4630ppm,4640ppm,4650ppm,4660ppm,467 0pp m,4680ppm,4690ppm4700ppm,4710ppm,4720ppm,4730ppm,4740ppm,475 0pp m,4760ppm,4770ppm,4780ppm,4790ppm4800ppm,4810ppm,4820ppm,483 0pp m,4840ppm,4850ppm,4860ppm,4870ppm,4880ppm,4890ppm4900ppm,491 0pp m,4920ppm,4930ppm,4940ppm,4950ppm,4960ppm,4970ppm,4980ppm,49 90pp m, and 5000ppm.

The weight ratio between dried and undried pellets may vary between 0 and 100%. Examples of % weight ratios of dried to undried 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 an embodiment, one can vary the moisture levels of the undried PET pellets (as described above) in combination with varying the % weight ratios of the dried and undried pellets (as described above) to control the final bulk measurement values (% crimp) of the subsequently formed bicomponent fibers.

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 in the range of about 0.9 dL/g to about 1.25 dL/g and the PTT pellets may be extruded at about 245°C to 265°C and 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 undried (about 2500 ppm moisture level), and extruded at a temperature between about 250° C and 280° C.

In an embodiment the moisture level of the undried PET pellets can be in a range from 300 ppm to about 5000 ppm.

The extrusion temperature used for the undried PET pellets may include but is not limited to 250° C, 255° C, 260° C, 265° C, 270° C, and 280° C.

In an embodiment, one can vary the moisture levels of the undried PET pellets (as described above) in combination with varying the extrusion temperature of the undried PET pellets (as described above) to control the final bulk measurement values (% crimp) of the subsequently formed bicomponent fibers.

In an embodiment of the methods described herein, the PET extruder may be fed with a dried PET pellet supply and with an undried PET pellet supply in a desired ratio as described herein with a difference being that the undried and dried PET pellets are added individually to the extruder rather than pre-mixed.

In an embodiment of the methods described herein, drying conditions of the PET pellet supply hopper can be adjusted to provide the necessary moisture for hydrolysis. For example, PET pellets are typically dried to 50 ppm of moisture during bicomponent manufacturing. By “under-drying” the PET pellets (for examples to 300 ppm moisture), the retained pellet moisture may promote hydrolysis in the extruder to attain a desired lower I.V. In this way, the desired PET IV may be “dialed in” to the spinning process.

In an embodiment of the methods described herein, the PET extruder may be supplied with a vacuum system to control PET I.V. In this way, high IV PET moist pellets with little or no drying can be “trimmed” by the amount of supplied vacuum to achieve a desired I.V.

In an embodiment of the methods described herein, the PET pellets may be dried (ca. 50 ppm) in the manners described herein and small quantities of water can be injected into the heated extruder to affect the desired level of hydrolysis and subsequent I.V. values.

The on-line hydrolysis methods described herein are efficient ways to control I.V. It may be desirable to use the techniques described herein off-line. For example, the hydrolysis methods described herein can be practiced off-line on an extruder not associated with fiber spinning. The hydrolyzed PET exiting the extruder mau have the desired I.V. and then may be re-pelletized. The re-pelletized pellets with the desired I.V. and can then be dried in the usual manner, without the need to control I.V. on-line.

Stretch measurement (% crimp) values of the bicomponent fibers made by the methods disclosed herein may be increased a range from about 10% to about 85%. Examples of increased stretch measurement values 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 a second component may comprise PET, wherein the first component may have a PTT pellet intrinsic viscosity in the range of about 0.9 dL/g to about 1.25 dL/g and the PTT pellets may be extruded at 260°C and a second component may have a PET pellet intrinsic viscosity of about 0.50 dL/g wherein the PET pellets may comprise a blend of dried pellets (about 50 ppm moisture) and undried pellets (about 2500 ppm moisture). The weight ratio between dried and undried pellets may vary between 0 and 20%.

The first and second components may independently be PET or co-PET, and PTT or a blend of PTT with PET or coPET, 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 and second components 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 an embodiment, Stretch measurement (% crimp) values of the bicomponent fibers made by the methods disclosed herein may not need to be increase but controlled by varying: the moisture levels of an undried component; the ratio of the dried and undried pellets of a component, and/or the extrusion temperature of a particular component. Increasing stretch measurement values as well as controlling them is dependent on the type of polymer(s) used to make a particular bicomponent fiber.

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

Bicomponent fibers may be made 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 making 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 fiber described herein can be in a side-by-side (“S/S”) or an eccentric sheath core (“S/C”) arrangement. The bicomponent fiber can be made in a variety of cross-sectional shapes, for example round, delta, trilobal, scalloped, or other shapes, by using spinnerets specific for each shape, for example as disclosed in U.S. Patent No. 6,803,102, which is incorporated herein by reference in its entirety.

Also disclosed herein are articles comprising the bicomponent fibers made by the methods described herein. The articles include but are not limited to clothing, fabric, fully drawn yarn (FDY), partially oriented yarn (POY), staple fiber, non-woven fiber, a non-woven fabric, and a carpet.

In an embodiment, a carpet is disclosed herein whose face fiber comprises bicomponent fibers made from the processes disclosed herein.

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

The bicomponent fibers disclosed herein may be used in conjunction with all other types of fibers, synthetic and natural, used in making carpets. Carpets can be made through mechanical or hand tufting, weaving and hand knotting. Examples include 1) broadloom carpets (also known as wall-to-wall carpets) where a tufted carpet is made in long continuous lengths that are several meters wide for home and commercial applications 2) carpet tiles produced in squares of various sizes for ease of installation 3) rugs for home use or 4) mats for vehicles and building entrances, designed to capture foot soil prior to building entry.

Any method known in the art of preparing carpet from a fiber may be used in preparing the carpets described herein. Typically, the bicomponent fibers disclosed herein can be used in the same carpet manufacturing processes where other synthetic and natural fibers are employed. The bicomponent fiber may be used by itself in carpet fabrication (i.e. as a “singles” yarn) or plied together with more of the same bicomponent fiber or other fiber types (e.g. nylon, polypropylene, polyester) to increase denier. Optionally, the singles and plied fiber may be entangled with an air jet prior to plying and may also be subjected to heat setting by machines specifically designed to thermally set the singles and tufted yarn physical properties.

One example of a heat setting machines suited for this purpose is manufactured by Superba® (Muhouse, France). Whether the bicomponent fibers are optionally air entangled, plied or heat set, the fibers may then be tufted into standard nonwoven or woven backing sheets typical of the carpet industry. The face fiber loops in the tufted carpet may be severed to provide a cut loop carpet. After tufting, adhesive is often applied to the backside of the carpet (i.e. opposite side from the face fiber) to hold the tufts in place. An additional backing layer may also be added to the carpet back side. The adhesive layer may contain fillers or flame retardants, depending on the specific carpet end use. The carpet may then be subjected to dyeing by standard processes common to the carpet fabrication industry; alternatively, pigments may be added during fiber extrusion to the bicomponent fiber and/or to the companion fibers to impart color to the finished fabrics. In addition, the face yarns may be treated with materials designed to impart fire resistance, anti-static properties or stain and soil resistance. The finished carpet is often dried to remove water remaining from the dyeing process.

The manufacturing process described above is typical for broadloom tufted carpets. Variations to this process known in the industry may be employed in the production of rugs, carpet tiles and vehicle mats.

The face fiber comprising bicomponent fiber may have circular or non circular cross-section, such as trilobal.

Examples

The disclosure is further defined in the following Examples. It should be understood that Examples, while indicating certain embodiments, are given by way of illustration only. From the above discussion and the Examples, one skilled in the art can ascertain essential characteristics of this disclosure, and without departing from the spirit and scope thereof, can make various changes and modifications to adapt to various uses and conditions.

As used herein, “Comp. Ex.” Means Comparative Example; “Ex.” means Example; “No.” means number; “%” means percent or percentage; “wt%” means weight percent; “IV” means intrinsic viscosity; “dL/g” is deciliters per gram; “g” is gram(s); “mg” is millligram(s); “°C” means degrees Celsius; “°F” means degrees Fahrenheit; “temp” means temperature; “min” is minute(s); “h” is hour(s); “sec” is second(s); “lb” is pound(s); “kg” is kilogram(s); “mm” is millimeter(s); “m” is meter(s); “gpl” is grams per liter; “m/min” is meters per minute; “mol” is mole; “kg” is kilogram(s); “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 “deciNewton(s) pertex; “mL” means milliliter(s); “IV” means intrinsic viscosity;

Unless otherwise noted, all materials were used as received.

Test Methods

Measurement of Crimp Contraction After Heating (% CCa) - Crimp Contraction Method:

Crimp contraction after heating (%CCa, also known as stretch value) was determined according to the method described herein. The fiber of each Example and Comparative Example was independently formed into a skein of about 5000 +/- 5 total denier (5550 dtex) with a skein reel at a tension of about 0.1 gpd (0.09 dN/tex). The skein was then halved in length by folding the skein in two to accommodate the interior of the oven used for heat setting. The folded skein was hung at its mid-section from a hook and was conditioned at 70 +/- 1 °F (21 +/- 1 °C) and 65 +/- 2 % relative humidity for a minimum of 16 hours. The folded skein was then hung substantially vertically on a rack from a hook at its mid-section and a 1.5 mg/den (1.35 mg/dtex) weight was hung through the two loops of the folded skein at the bottom of the skein. The weighted skein was then heated in an oven for 5 min at 250 °F (121 °C) after which the rack and skein were removed and allowed to cool for 5 minutes, then allowed conditioned at 70°F +/- 1 °F (21 +/- 1 °C) and 65% +/- 2 % relative humidity for a minimum of 2 hours with the 1.5 mg/denier weight left on the skein for the remainder of the test. The length of the skein was measured to within 1mm and recorded as “Ca”.

Next, a 1000 g weight was hung from the bottom of the skein, allowed to reach equilibrium and the length of the skein measured within 1 mm and recorded as “La”. Crimp contraction after heating “CCa” value (%) was calculated according to the formula:

%CCa=100x (La-Ca)/La Determination of Intrinsic Viscosity

The intrinsic viscosity (IV) was determined using a Viscoteck Y 501 C Forced Flow Viscometer (Malvern Corporation, Houston Texas, USA). A 0.15 g sample was weighed into a 40 ml_ glass vial containing 30 ml_ solvent (phenol/1 ,1 , 2, 2-Tetrachloroethane (60/40 weight percent)) and a stir bar. Sample was then placed into 100°C preheated heat block, heated and stirred for 30 minutes, removed from the block and cooled for 30-45 minutes before placing into the auto sampler rack of the viscometer. Samples were then analyzed by ASTM method D5225-92 (Standard Test Method for Measuring Solution Viscosity of Polymer with 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, a second grade had an IV of 0.92 dL/g. PET homopolymer pellets were obtained from Sinopec Shanghai Petrochemical Company, Ltd. Shanghai, PRC and had an IV of 0.50 dl/g. PET copolymer (containing 1.9 mole % isophthalic acid) pellets with an IV of 0.80 dl/g was 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 for 15 hours at 25 inches mercury vacuum and a temperature of 120 °C. Under these conditions, both PET and PTT pellet moisture is reduced to about 50 ppm. The dried pellets were transferred directly to the nitrogen-purged feed hopper of the spinning machine. In the examples where a mixture of dried and undried PET pellets are used, the undried pellets were taken directly from the bag and had a residual moisture content of about 2500 ppm.

Fiber Preparation

The first and second components of a bicomponent fiber were melt spun using processes and equipment generally applicable to spinning side-by-side and eccentric sheath/core bicomponent fibers, for example as disclosed in US Pat. No. 6,641 ,916 B1 , US Pat. No. 6,803,102, and US Pat. No. 7,615,173 B2, which are incorporated herein by reference in their entirety.

In spinning the bicomponent fibers of the Examples, the polymers were melted in a pair of Werner & Pfleiderer co-rotating 28-mm twin screw extruders having 0.5-40 pound/hour (0.23-18.1 kg/hour) capacities. One extruder, referred to herein as the East extruder, was used to melt 1) PET pellets dried to about 50 ppm or 2) mixtures of PET pellets wherein some of the pellets were dried to a residual moisture level of about 50 ppm and the remaining pellets were undried and had a residual moisture level of about 2500 ppm. A second extruder, referred to herein as the West extruder, was used to melt PTT pellets dried to about 50 ppm residual moisture. The temperatures of the West extruder, spinning block and East extruder are cited in the Examples. Each extruder fed the spinning block containing a recessed spinneret. The spinneret used was a post-coalescence, side by side, bicomponent spinneret having thirty-four pairs of capillaries arranged in a circle, an internal angle between each pair of capillaries of 30 degrees, a capillary diameter of 0.64 mm, and a capillary length of 4.24 mm.

The bicomponent filaments exiting the spinneret were subjected to cooling by cross-flow quench air nominally at 20°C and 0.5 mm/sec face velocity. The filaments were then advanced to dual feed rolls operating at about 800-1200 meters/minute, depending on the draw ratio. Between the spinneret and feed rolls, a finish applicator was used to apply lubricant to the filament bundle. The feed rolls were typically heated to 70 °C to affect draw. The filament bundle was then accelerated to the anneal rolls operating at speeds of about 3000-3600 m/min, depending on the desired draw ratio, and the anneal roll temperature was typically 170° C. The annealed bicomponent fiber was then advanced to two sets of dual letdown rolls operating at room temperature, before being wound on a Barmag SW6 600 winder. The fibers had snowman (oblong) cross-sectional shape. The bicomponent fiber in all examples was 75 denier, 34 filament.

Comparative Example A and Examples 1-3 Variation of Pellet Moisture Content Comparative Example A illustrates a typical manufacturing process for making a PET/PTT bicomponent fiber, wherein 0.50 I.V. PET pellets are dried to about 50 ppm residual moisture and then extruded by the East extruder at 270°

C, and 1.02 I.V. PTT pellets are dried to about 50 ppm residual moisture and extruded by the West extruder at 260° C. The ratio of the PET to PTT in the bicomponent fiber is 50/50. The measured stretch value of 48% is in the typical range of commercial bicomponent fibers.

Examples 1 to 3 illustrate 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 to 3, 1.02 IV PTT was dried to about 50 ppm and extruded at the temperatures indicated. The only variable in these examples was the amount of undried PET (ca. 2500 ppm residual moisture) mixed in with the dried PET. As is evident in Example 1 , drying 0.80 IV to the same level as PTT (e.g. 50 ppm moisture) results in a fiber with almost no stretch. The relatively small difference in pellet I.V. between the PET and PTT does not promote fiber differential shrinkage or percent stretch. In Example 2, the ratio of undried to dried PET pellets was 10/90 weight percent. Under these process condition, the residual moisture in the undried polymer promotes hydrolysis of the 0.80 I.V. PET in the heated extruder. The effect of hydrolysis can be seen by the decrease in pack pressure from 950 psi to 370 psi. This decrease in pack pressure correlates with decreased polymer melt viscosity, decreased polymer molecular weight, increased differential shrinkage and increased fiber stretch. Examples shows the effect of increasing the undried to dried PET ratio to 20/80 weight percent, where the additional residual moisture further promotes decreased pack pressure and melt viscosity and increased differential shrinkage and percent stretch.

Table 1. Process Conditions and Stretch Values for Comparative Example A and Examples 1 to 3 Examples 4-7 Variation of Extrusion Temperature

Examples 4-7 illustrate 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, 0.92 IV PTT was dried to about 50 ppm and 0.80 IV PET was 100% undried (i.e. ca. 2500 ppm residual moisture). The polymer ratio between PET and PTT in the fiber was 70/30 weight percent. Rather than affect hydrolysis by the concentration of undried pellets, the extent of hydrolysis was controlled by PET extruder temperature. Hydrolysis is a chemical reaction between the polyester and residual moisture and the extent of reaction increases as extrusion temperature increases. In Example 4, the PET extruder was set at 250 C. At this relatively low temperature, little hydrolysis occurs, pack pressure is high, molecular weight remains high, little fiber differential shrinkage occurs and fiber stretch level is low (10.8%). In Example 5, the PET extruder temperature is increased 10° C to 260° C. At this higher extruder temperature hydrolysis increases, the pack pressure decreases, molecular weight is reduced, fiber differential stretch increases and fiber stretch increased to 22%. Comparison of Examples 4 and 5 shows that increasing the PET 10° C more than doubles fiber stretch. Examples 6 and 7 show that increasing the PET extruder to 270° C and 280° C increases the stretch measurement to 27.2% and 50.5%, respectively. These examples show the important role of extrusion temperature on extent of hydrolysis and fiber properties.

Table 2. Process Conditions and Stretch Values for Examples 4 to 7 Example 8-10 Stretch Formation

Examples 8-10 illustrate the use of on-line hydrolysis to produce bicomponent fibers with higher stretch values than obtainable by traditional means. The 0.50 I.V. PET preferred by PET/PTT bicomponent fiber manufactures is typically the lowest IV PET that can be commercially produced, due to difficultly in pelletizing low IV PET. As there is a desire to increase stretch to levels greater than typically available with 0.50 IV PET, lowering the PET IV by hydrolysis is an option. Example 8 shows the process and results for a 50/50 weight ratio PET/PTT bicomponent fiber made with fully dried (ca. 50 ppm residual moisture) 0.50 I.V. PET and 1.02 IV PTT. Examples 9 and 10 show the stretch results for fibers made by mixing the dried PET with 5% and 10% undried 0.50 I.V. PET (ca. 2500 ppm residual moisture), respectively. The stretch values of 65.8% and 69.3% are considerably higher than commercially available fibers. In these Examples, the additional residual moisture further promotes decreased pack pressure and melt viscosity and increased differential shrinkage and percent stretch. Table 3. Process Conditions and Stretch Values for Examples 9 to 11