| Title of Invention | "POLYETHYLENE GLYCOL MODIFIED POLYESTER FIBERS AND METHOD FOR MAKING THE SAME" |
|---|---|
| Abstract | The present invention discloses a method of copolymerizing polyethylene glycol (PEG) and branching agent into polyethylene terephthalate (PET) to achieve a polyethylene glycol-modified polyester composition that can be spun into filaments. Fabrics made from fibers formed from the copolyester composition possess wicking (Figure 5), drying (Figure 6), flame-retardancy (Figure 7), static-dissipation (Figure 8), stretching, abrasion-resistance (Figure 9), dyeability, and tactility properties that are superior to those of fabrics formed from conventional polyethylene terephthalate fibers of the same yarn and fabric construction. Also disclosed are polyethylene glycol modified copolyester compositions, fibers, yarns, and fabrics. |
| Full Text | 1 POLYETHYLENE GLYCOL MODIFIED POLYESTER FIBERS AND METHOD FOR MAKING THE SAME CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of pending U. S. Application Serial No: 09/444,192, filed November 19, 1999, for a Method of Preparing Polyethylene Glycol Modified Polyester Filaments, which is commonly 5 assigned with this application. FIELD OF THE INVENTION The present invention relates to the production of polyethylene glycol modified polyester fibers. The present invention also relates to the . manufacture of yams and fabrics from these copolyester fibers. 10 BACKGROUND QFTHE INVENTION Polyester filament is strong, yet lightweight, and has excellent elastic memory characteristics. Polyester fabric resists wrinkles and creases,:retains its shape in garments, resists abrasions, dries quickly, and requires minimal care. Because it is synthetic, however, polyester is often considered to have 15 an unacceptable appearance for garment purposes when initially formed as a filament. Accordingly, polyesteir filaments require texturing to produce acceptable characteristics of appearance, hand, and comfort in yams and fabrics. Even then, polyester is often viewed unfavorably in garments. In pursuit of improved polyesters, various chemical modifications have 20 been attempted to obtain desirable textile features, Unfortunately, some such treatments can produce unexpected or unwanted characteristics in the modified polyester. For example, polyethylene glycol enhances certain polyester properties, such as dye uptake, but diminishes other properties, especially those melt phase characteristics that are critical to filament 25 spinning. Consequently, manufacturers have found that significant fractions of polyethylene glycol In copolyester can complicate—and even preclude—the commercial production of acceptable copolyester filaments. To gain REPLACEMENT PAGE 2 commercial production of acceptable copolyester filaments. To gain commercial acceptance, modified polyesters must be compatible with commercial equipment with respect to melt-spinning, texturing, yarn spinning, fabric forming (e.g., weaving and knitting), and fabric finishing. This need for 5 processing compatibility through conventional equipment has constrained the development of innovative polyester compositions. To overcome the limitations of polyester compositions, polyester fibers are often blended with other kinds of fibers, both synthetic and natural. Perhaps most widely used in clothing are blended yarns and fabrics made of 10 polyester and cotton. In general, blended fabrics-of polyester and cotton are formed by spinning blended yarn from cotton fibers and polyester staple fibers. The blended yarns can then be woven or knitted into fabrics. Cotton, like polyester, has certain advantages and disadvantages. Cotton is formed almost entirely of pure cellulose. Cotton fibers are typically 15 about one inch long, but can vary from about one half inch to more than two inches. Mature cotton fibers are characterized by their convolutions. Under a microscope, cotton appears as a twisted ribbon with thickened edges. Cotton is lightweight,.absorbs moisture quickly and easily, and has a generally favorable texture (I.e., hand) when woven into fabrics. Cotton, however, lacks 20 strength characteristics and elastic memory. Consequently, garments formed entirely of cotton require frequent laundering and pressing. Blends of cotton and polyester fibers have found wide-ranging acceptance as they combine the desirable characteristics of each. Even so, there are continuing efforts to develop polyester filament, yarns, and fabrics 25 that more closely resemble those of cotton, silk, rayon, or other natural fibers. One example is polyester microfibers, which are characterized by extremely fine filaments that offer exceptionally good aesthetics and hand, while retaining the benefits of polyester. Polyester microfibers, however, have proved to be difficult to dye because of their high degree of molecular 30 orientation and crystallinity. 3 fibers, while retaining the advantagesof polyester. One such composition and method for producing the same is disclosed by Nichols and Humelsine in commonly-assigned, pending U.S. patent application Serial No. 09/141,665, filed August 28,1998, for polyester. Modified. witjLPoIyethylene.GIycoI and 5 Pentaerythritol. U.S. patent application Serial No', 09/141,665, discloses a polyester, composition that includes polyethylene terephthalate, polyethylene glycol in„an amount sufficient to increase the wetting and wicking properties of a fiber made from the composition to a level substantially similar to the properties of cotton, but [ess than the amount that would reduce the favorable 10 elastic memory properties of the polyester composition, and chain branching agent in an amount that raises the melt viscosity of thejaolyester composition to a level that permits filament manufacture under substantially normal spinning conditions. Including significant concentrations of branching agents to increase melt viscosity, however, is sometimes undesirable because 15 branching agents promote cross-linking. This reduces filament strength, which can lead to processing failures. Moreover, a method for achieving enhanced polyester fibers is described by Branum' in commonly-assigned, pending U.S. patent application Serial No. 09/444,192, filed November 19,1999, for a Method of Preparing 20 Polyethylene Glycol Modified Polyester Filaments. U.S. patent application Serial No. 09/444.192 describes copolymerlzlng poiyethylene^glycol, which typically makes up between about 4 percent and 20 percent by weight:0f the resulting copolyester, into polyethylene terephthalate in the melt-phase to a relatively low intrinsic viscosity (/.e.,-a viscosity that will not support filament 25 spinning). The resulting PEG-rnodified polyester is then further polymerized in the solid phase until the copolyester is capable of achieving a melt viscosity sufficient to spin filaments. By. introducing a solid state polymerization (SSP) step, this REPLACEMENT PAGE 4 method reduces the need to add branching agents, such as pentaerythritol, to increase the melt-phase polymerization rate and thereby achieve an intrinsic viscosity that facilitatesihe spjrjning of filaments. U.S. patent application Serial No. 09/444,192 explains that branching agents promote cross-linkinc; 5 which can lead to relatively weaker textiles. OBJECT AND SUMMARY OF THE INVENTION Therefore, it is an object of this invention to provide polyethylene glycol modified polyester fibers that possess favorable characteristics similar to natural fibers, yet retain the.advantag:esToI,p.oLyesiex, and that can be formed, 10 into exceptionally comfortable fabrics. It is a further objectof the.present invention to provide a method of copolymerizing polyethylene glycol (PEG) into polyethylene terephthalate (PET) in the melt phase to achieve a PEG-modified polyester composition that is readily spun into filaments. As is understood by those of ordinary skill in the art, modifying 15 conventional polyesters with polyethylene glycol can improve certain polyester characteristics, yet can adversely affect others. For example, adding polyethylene glycol to polyethylene terephthalate improves wetting and wicking, but slows melt-phase polymerization kinetics. It also depresses melt viscosity and renders the processing of such PEG-modified polyesters 20 somewhat impractical in commercial polyester spinning operations. Accordingly, in one aspect,, the Invention is a method of copolymerizing polyethylene glycol into polyethylene terephthalate in a way that retains the favorable properties of polyethylene glycol while attaining a high intrinsic viscosity. This facilitates the commercial spinning of the PEG-modified 25 polyester using conventional spinning equipment. As will be understood by those having ordinary skill in the artt copolymerizing polyethylene glycol and branching agent into polyethylene terephthalate is conventionally achieved by reacting ethylene glycol and either terephthalic acid or dimethyl terephthalate in the presence of polyethylene glycol and branching agent. In'one aspect, the invention is a method of copolymerizing polyethylene glycol and a chain branching agent into polyethylene terephthalate in the melt phase to form a copolyaster composition having an intrinsic viscosity of at least about 0.67 dl/g. In this regard, the polyethylene 5 terephthalate is present in the copolyester composition in an amount sufficient for a fiber made from the copolyester composition to possess dimensional stability properties substantially similar to those of conventional, unmodified polyethylene terephthalate fibers.. The polyethylene glycol has an average molecular weight of less than about 50QO g/mol and is present in an amount 10 sufficient for a fiber made from the copolyester composition to possess wicking, drying, and static-dissipation properties that are superior to those of conventional, unmodified polyethylene terephthalate fibers. The chain branching agent is present in the copolyester composition in an. amount hetween about 0.0003 and 0.0014 mole-equivalent branches per mole of 15 standardized polymer, the standardized polymer being unmodified polyethylene terephthalate. Finally, the copolyester composition Is spun into a filament. In another aspect, the invention is a method of spinning the modified polyester composition to form partially oriented yarns (POY). The resulting 20 copolyester POY is particularly suitable for yarns and fabrics, either alone or in a blend with one or more other kinds of fibers. In yet another aspect, the invention is a method of spinning the modified polyester composition to form sfapfa filaments, which can be drawn (and perhaps crimped), and cut into staple fiber. Staple fiber, in turn, can be farmed into polyester yams by 25 employing conventional spinning techniques (e.g., ring, open-end, air-jet, or vortex spinning). In addition, continuous filament and spun yarns can then be formed into fabrics, preferably by knitting or weaving, either alone or in a blend with one or more other kinds of fibers, In yet another aspect, the invention is a method of dyeing the copolyester fibers at or below a 30 temperature of 116flC (240° F), and preferably below the temperature defined by the boiling point of water at atmospheric pressure. REPLACEMENT PAGE 6 A distinct advantage of the present method Is that it produces a copolyester fiber that, while possessing wicking, drying, flame-retardancy, abrasion-resistance, soft hand, dye uptake, and static-dissipation properties that are superior to those of conventional polyethylene terephthalate fibers, 5 can be processed using conventional melt spinning equipment (e.g., spun into partially oriented yarns or formed into staple fibers). The foregoing, as well as other objectives and advantages of the invention and the manner In which the same are accomplished, is further specified within the following detailed description and its accompanying 10 drawings. BRIEF DESCRIPTION OF THE DRAWINGS: Figure 1 describes the melt-polymorizGd intrinsic viscosity of PEG-modified copolyester versus the weight fraction of polyethylene glycol when branching agent is employed in an amount of less than about 0.0014 mole-15 equivalent branches per mole of standardized polymer. Figure 2 describes effective model for batch dyeing the copolyester fibers produced according to the present invention. Figure 3 describes the effect of temperature on uptake of low-energy, medium-energy, and high-energy dyes at a pH of about 5. 20 Figure 4 describes the effect of pH upon low-energy, medium-energy, and high-energy disperse dyeing at'99°C (210aF). Figure 5 describes the wicking properties of fabrics formed from copolyester fibers produced according to the invention as compared to the wicking properties of fabrics formed from conventional, unmodffied 25 polyethylene terephthalate fibers. Figure 6 describes the drying properties of fabrics formed from copolyester fibers produced according to the present invention as compared to the drying properties of fabrics formed from conventional, unmodified polyethylene terephthalate fibers. REPLACEMENT PAGE vpmzr 7 Figure 7 describes the flame-retardancy properties of fabrics formed from copolyester fibers produced according to the invention as compared to the flame-retardancy properties of fabrics formed from conventional, unmodified polyethylene terephthalate fibers. 5 Figure 8 describes the static-dissipation properties of fabrics formed from copolyester fibers produced according to the invention as compared to the static-dissipation properties of fabrics formed from conventional, unmodified polyethylene terephthalate fibers. Figure 9 describes the abrasion resistance properties of fabrics formed 10 from copolyester fibers produced according to the invention as compared to the abrasion resistance properties of fabrics formed from conventional, unmodified polyethylene terephthalate fibers. Figure 10 describes the strength properties of fabrics woven from copolyester fibers produced according to the present invention as compared 15 to the strength properties of fabrics woven from conventional, unmodified polyethylene terephthalate fibers. Figure 11 describes the improved properties of fabrics formed from copolyester fibers produced according to the invention as compared to the properties of fabrics formed from conventional, unmodified polyethylene 20 terephthalate fibers. DETAILED DESCRIPTION Parent U.S. patent application Serial No. 09/444,192 discloses a method of preparing PEG-modified copolyester fibers by copolymerizing polyethylene glycol into polyethylene terephthalate in the melt phase to form a 25 copolyester composition, then polymerizing the copolyester composition in the solid phase until the copolyester is capable of achieving a melt viscosity that facilitates the spinning of filaments, and thereafter spinning filaments from the copolyester. 8 The present invention is an alternative method of preparing PEG-modified copoiyester fibers that can be formed into exceptionally comfortable fabrics. In a broad aspect, the method includes copolymerizing polyethylene glycol and a chain branching agent into polyethylene terephthalate in the melt 5 phase to form a copoiyester composition having an intrinsic viscosity of at least about 0.67 dl/g. Preferably, this copoiyester composition achieves a zero-shear melt viscosity of between about 2000 and 3500 poise when heated to 260°C. The polyethylene terephthalate is present in the copoiyester 10 composition in an amount sufficient for a fiber made from the copoiyester composition to possess dimensional stability properties substantially similar to those of conventional, unmodified polyethylene terephthalate fibers. The polyethylene glycol has an average molecular weight of less than about 5000 g/mol and is present in an amount sufficient for a fiber made from the 15 copoiyester composition to possess wicking, drying, and static-dissipation properties that are superior to those of conventional, unmodified polyethylene terephthalate fibers. The chain branching agent is present in the copoiyester composition in an amount less than about 0.0014 mole-equivalent branches per mole of standardized polymer, and more preferably in an amount between 20 about 0.0003 and 0.0014 mole-equivalent branches per mole of standardized polymer, the standardized polymer being unmodified polyethylene terephthalate. (As discussed herein, to describe the molar fraction of branching agent consistently, mole-equivalent branches are referenced to unmodified polyethylene terephthalate.) Finally, the copoiyester composition1 25 is spun into a filament. The present invention incorporates into polyester the favorable properties of polyethylene glycol, such as its outstanding wetting and wicking properties, by employing a higher intrinsic viscosity to compensate for the tendency of higher fractions of polyethylene glycol to lower the melt viscosity 30 of the copoiyester. Consequently, the present method need not employ significant amounts of branching agent. As will be understood by those of skill 9 in the art, a low melt viscosity hinders the processing of copolyester through conventional spinning equipment. The present invention differs from the method disclosed by the aforementioned U.S. patent application Serial No. 09/444,192 in that the melt 5 polymerization is continued until an intrinsic viscosity of at least 0.67 dl/g, whereupon the copolyester is spun into a filament. In contrast, the parent application employs a solid state polymerization step to achieve high intrinsic viscosities. The invention is also a polyethylene glycol modified copolyester fiber 10 that includes polyethylene terephthalate in amount sufficient for the copolyester fiber to possess dimensional stability properties substantially similar to those of conventional, unmodified polyethylene terephthalate fibers, polyethylene glycol having an average molecular weight of less than about 5000 g/mol in an amount sufficient for the copolyester fiber to possess 15 wicking, drying, and static-dissipation properties that are superior to those of conventional, unmodified polyethylene terephthalate fibers, and chain branching agent in an amount less than about 0.0014 mole-equivalent branches per mole of standardized polymer, the standardized polymer being unmodified polyethylene terephthalate. The copolyester fiber has an intrinsic 20 viscosity of at least about 0.67 dl/g. As used herein, the term "copolyester fiber" broadly refers to uncut filament (e.g., POY, flat-drawn yarn, or textured yarn) and cut fiber (e.g., staple fiber). Although the term "copolyester filament" may include fibers, such as staple, that are subsequently cut from spun filament, it is generally 25 used to refer to an extruded fiber of indefinite length. The meaning of the terms "copolyester fiber" and "copolyester filament" will be easily understood by those of ordinary skill in the art based on the contextual use of these terms. . The terms "melt viscosity" and "intrinsic viscosity" are used herein in their conventional sense. As used herein, the term "melt viscosity" refers to 30 "zero-shear melt viscosity" unless indicated otherwise. 10 Melt viscosity represents the resistance of molten polymer to shear deformation or flow as measured at specified conditions. Melt viscosity is primarily a factor of intrinsic viscosity, shear, and temperature. The zero-shear melt viscosity at a particular temperature can be calculated by 5 employing ASTM Test Method D-3835-93Ato determine melt viscosities at several shear rates between about 35 sec"1 and 4000 sec"1, and thereafter extrapolating these melt viscosities to zero. In calculating zero-shear viscosity, it is recommended that several low shear rates (e.g., less than 100 sec"1) be included to ensure that the extrapolation to zero is accurate.. 10 Intrinsic viscosity is the ratio of the specific viscosity of a polymer solution of known concentration to the concentration of solute, extrapolated to zero concentration. Intrinsic viscosity is directly proportional to average polymer molecular weight. See, e.g., Dictionary of Fiber and Textile Technology, Hoechst Celanese Corporation (1990); Tortora & Merkel, 15 Fairchild's Dictionary of Textiles (7th Edition 1996). As used herein, average molecular weight refers to number-average molecular weight, rather than weight-average molecular weight. Both melt viscosity and intrinsic viscosity, which are widely recognized as standard measurements of polymer characteristics, can be measured and 20 determined without undue experimentation by those of ordinary skill in this art. For the intrinsic viscosity values described herein, the intrinsic viscosity is determined by dissolving the copolyester in orthochlorophenol (OCP), measuring the relative viscosity of the solution using a Schott Autoviscometer (AVS Schott and AVS 500 Viscosystem), and then calculating the intrinsic 25 viscosity based on the relative viscosity. See, e.g., Dictionary of Fiber and Textile Technology ("intrinsic viscosity"). In particular, a 0.6-gram sample (+/- 0.005 g) of dried polymer sample is dissolved in about 50 ml (61.0 - 63.5 grams) of orthochlorophenol at a temperature of about 105°C. Fiber and yarn samples are typically cut into 30 small pieces, whereas chip samples are ground. After cooling to room 11 temperature, the solution is placed in the viscometer and the relative viscosity is measured. As noted, intrinsic viscosity is calculated from relative viscosity. As will be understood by those having ordinary skill in the art, copolymerizing polyethylene glycol and branching agent into polyethylene 5 terephthalate is conventionally achieved by reacting ethylene glycol and either terephthalic acid or dimethyl terephthalate in the presence of polyethylene glycol and branching agent. Consequently, it is preferred that the copolymerization of polyethylene glycol and chain branching agent into polyethylene terephthalate yield a copolyester composition that is comprised 10 of polymer chains formed from structural units consisting essentially of diol monomers, aromatic non-substituted diacid monomers, and branching agent monomers. As herein described, such copolyester compositions are preferably formed into copolyester fibers. The term "diol monomer" as herein used refers to diols, such as 15 ethylene glycol, propylene glycol, and butane diol, as well as ethers that possess terminal alcohols, such as diethylene glycol (DEG). In this regard, -polyethylene glycol (PEG) is formed from such ethylene glycol monomers and is therefore embraced by the term "diol monomer." The term "aromatic non-substituted diacid monomers" as herein used refers to aromatic carboxylic 20 diacids and diesters, especially terephthalic acid (TA) and its diaikyl ester,. dimethyl terephthalate (DMT), whose functional groups are limited to those that facilitate polymer chain growth and that can be used to prepare modified polyethylene terephthalate. Accordingly, "aromatic non-substituted diacid monomers" include single-ringed compounds, such as isophthalic acid and its 25 diaikyl ester (i.e., dimethyl isophthalate), and polycyclic compounds, such as 2,8 naphthalene dicarboxylic acid or its diaikyl ester (i.e., dimethyl 2,6 naphthalene dicarboxylate). Finally, the term "branching agent" refers to a multifunctional monomer that promotes the formation of side branches of linked monomer molecules along the main polymer chain. See Odian, 30 Principles of Polymerization, pp„ 18-20 (Second Edition 1981). Moreover, it will be understood by those of ordinary skill in the art that the terminal ends of 12 the copoiyester chains may be structural units characterized by a lone, chain-propagating reactive site. Such chain terminating groups are within the scope of the phrase "consisting essentially of dio! monomers, aromatic non-substituted diacid monomers, and branching agent monomers." 5 In accordance with the invention, copoiyester characteristics can be tailored for specific applications by altering the polyethylene glycol content. This permits choice in designing fabrics made with copoiyester or copoiyester blends according to the present invention. In this sense, the invention establishes a technology family. For example, the weight fraction and the 10 molecular weight of the polyethylene glycol can be adjusted to produce specific effects, such as wicking, drying, dye rates, stretch, and softness. Similarly, such modifications can improve the dye strike rate and reduce the dye usage. In particular, higher polyethylene glycol fractions (e.g., greater than about 4 weight percent) result in softer fabrics that wick faster, dry 15 quicker, and dye darker as compared to conventional polyesters. The present copoiyester shows as much as 30 percent more dye uptake of non-exhaustive polyester dye formulations as compared to conventional polyesters. In practicing the present invention, It is preferred that the polyethylene glycol formulations include sufficient concentrations of antioxidants to prevent 20 formaldehyde generation during spinning operations. For example, the polyethylene glycol used in the development of the present invention includes about 1.36 weight percent of Irganox 245, an antioxidant that is available from Ciba-Gelgy. The inclusion of this or similar antioxidants will not adversely affect the methods herein described. 25 In preferred embodiments, the polyethylene glycol is present in the, copoiyester composition in an amount between about 4 weight percent and 20 weight percent. When amounts of polyethylene glycol greater than about 20 weight percent are present, the resulting copoiyester does not polymerize efficiently. Moreover, at such elevated polyethylene glycol fractions, the 30 copoiyester composition is difficult to store and transport for it tends to crystallize, which causes undesirable sticking and clumping. Consequently, 13 polyethylene glycol amounts between about 8 weight percent and 14 weight percent are more preferred, and amounts between about 10 weight percent and 12 weight percent are most preferred. Furthermore, while polyethylene glycol with an average molecular weight of IBSS than about 5000 g/mol may 5 be effectively employed, the preferred average molecular weight for polyethylene glycol is between about 300 and 1000 g/mol, most preferably 400 g/mol. For consistency in discussing composition and fiber properties, the data herein disclosed refer to copolyestor of the present invention that is 10 modified between about 10 and 12 weight percent polyethylene glycol having a molecular weight of about 400 g/mol, unless indicated otherwise. As known to those familiar with the manufacture of polyester, the equipment used to spin polyester into filaments is designed, built, and adjusted to process polymers whose zero-shear melt viscosity falls within a 15 certain range, typically between about 1600 and 4000 poise. Thus, such equipment runs most satisfactorily whon the melt viscosity of the copolyester, which is directly proportional to the Intrinsic viscosity as discussed herein, is within this viscosity range. If polyethylene glycol Is Included in relatively significant amounts [he.t more than about 4 weight percent), a number of 20 spinning failures are likely to occur when conventional polymerization methods are followed (e.g„ the intrinsic viscosity is not increased). In other words, high polyethylene glycol fractions can suppress melt viscosity, which in turn can hinder spinning productivity. Thus, the melt polymerization of polyethylene glycol and branching 25 agent into polyethylene terephthalate continues until the PEG-modified polyester has a melt viscosity sufficient for practical processing, and sufficient spinning tensions for a stable and high-throughput commercial process, This is so despite the presence of only insignificant amounts of branching agent (i.e., between about 0.0003 and 0.0014 mole-equivalent branches per mole of 30 standardized polymer). REPLACEMENT PAGE 14 According to the present method, copolyester filaments are preferably spun at a temperature between about 260°C and 300°C. This temperature range comports with that employed in conventional spinning equipment using Dowtherm A vapor heat transfer media, which is available from Dow Chemtca 5 Co. Accordingly, in one preferred embodiment, the method includes copoiymerizing between about 10 and 12 weight percent polyethylene glycol and a chain branching agent in an amount between about 0.0003 and 0.0014 mole-equivalent branches per mole of standardized polymer into polyethylene 10 terephthalate in the melt phase to form a copolyester composition that achieves a zero-shear melt viscosity of between about 2000 and 3500 poise when heated to 260°C. In another embodiment, the copolyester composition is spun into filaments having a mean tenacity of less than 3 grams per denier. - A tenacity of less than 3 grams per denier accentuates the superior tactifity 15 (i.e., soft hand) of the copolyester filament and staple fiber, and reduces the tendency of staple fiber to pill.. - As will be understood by those having ordinary skill in this art, the copolyester need not be spun immediately after undergoing melt polymerization, in one embodiment, the copolyester is formed into chips after 20 the step of copoiymerizing polyethylene glycol and a chain branching agent into polyethylene terephthalafe in the melt phase and before the step of spinning the copolyester composition into a filament. - ¦ As discussed previously, in its broadest aspects, the method includes copoiymerizing polyethylene glycol and a chain branching agent into 25 polyethylene terephthalate in the melt phase to form a copolyester composition having an intrinsic viscosity of at least about 0.67 dl/g. Thereafter, the copolyester composition is spun into a filament. Figure 1 defines the preferred intrinsic viscosity of the copolyester after melt -polymerization as a function of the weight fraction of polyethylene glycol when 30 chain branching agent is present in the copolyester composition in an amount between about 0.0003 and 0.0014 mole-equivalent branches per mole of 15 standardized polymer (e.g., between .about 110 ppm and 500 ppm of pentaerythritol). In particular, when the weight fraction of polyethylene glycol in the copolyester composition is about 5 percent, the copolyester composition is 5 preferably polymerized \n the melt phasB to an Intrinsic viscosity of between about 0.67 and 0.78 dl/g. Similarly, when the weight fraction of polyethylene glycol in the copolyester composition is between about 10 and 12 percent, the copolyester composition is preferably polymerized in the melt phase to an intrinsic viscosity of between about 0,73 and 0.88 dl/g. Finally, when the 10 weight fraction of polyethylene glycol in the copolyester composition Is about 15 percent, the copolyester composition is preferably polymerized in the melt phase to an intrinsic viscosity of between about 0.80 and 0.93 di/g. It will be understood to those of skill in the art that the polyethylene glycol reduces melt temperature (Tm) and glass transition temperature (Ta). 15 For example, at a 10 weight percent substitution of polyethylene glycol having a molecular weight of about 400 g/moi, Tm is approximately 238°C andTg is approximately 48°C. Consequently, the temperature at which dyes will penetrate the modified polyester structure is lowered. Accordingly, the present method further comprises dyeing the 20 copolyester filaments at a temperature of less than about 116°C (240°F). Above 116oC(240aF), fastness may somewhat decrease using certain dyes at high concentrations. In one preferred embodiment, the method includes dyeing the copolyester filaments at a temperature of iess than about 110aC (230aF).. In yet another prefen-ed embodiment, the method includes dyeing 25 the copolyester filaments at a temperature of less than about 104°C (220°F). In fact, the copolyester filaments can be dyed at or below the temperature defined by the boiling point of water at atmospheric pressure [i.e., 212°F or 100°C). More specifically, the copolyester fibers can achieve excellent color 30 depth even when dyed at 93DC (200°F). In this regard, when high-energy disperse dyes (e.g., Color Index Disperse Blue 79) are employed, the REPLACEMENT PAGE i 15a copolyester fibers are most preferably dyed between about 104DC (200°F) and 100aC(212T). Similarly, ' %UL- U^J^ ^h^ts^ M^^ REPLACEMENT PAGE m 16 when low-energy disperse dyes (e.g., Color Index Disperse Blue 56) are employed, the copolyester fibers are preferably dyed between about 82°c (180?F) and 93°C (200DF), and most preferably dyed between about 82°C {18Q°F) and 88°C (1G0°F). As will be understood by those of ordinary skill in 5 the dyeing arts, with respect to the present copolyester fibers, high-energy dyes typically have better wash fastness and poorer light fastness as compared to low-energy dyes. A particular advantage of the present invention is that the disclosed copolyester fibers may be dyed at atmospheric pressure without a carrier (i.e., 10 a dye bath additive that promotes the dyeing of hydrophobic fibers), although leveling and dispersing agents are recommended. Moreover, unlike conventional polyester fibers, which typically require an acidic dye bath adjustment to a pH of about 4-5, the present copolyester fibers do not require any pH modification. In this regard, the copolyester can be effectively 15 disperse dyed in an alkaline dye bath having a pH as high as 10, limited only by the stability of the disperse dyes at such alkaline conditions and B9°C (210T) rather than the properties of the present copolyester. Furthermore, the copolyester fibers of the present invention have comparable hand to polyester microfibers (/.e.( fibers The copolyester fiber of the present invention also possesses a high exhaustion rate, which translates to reduced dye costs and fewer environmental issues. In fact, dye uptake Is maximized near the normal boiling point of water (/.©., 100°C or212°F). In preferred embodiments, the 25 dyeing of the copolyester fibers employs a relatively high ramp rate of about 2.8°C (5°F) per minute below 38°C (100T), as the fibers absorb little dye at such temperatures. Above 38aC (100°F), however, the fibers do absorb dye and so the ramp rate should be reduced to about 1.1 °C (2°F) per minute to achieve level dyeing; Optionally, a holding period between about 5 and 10 30 minutes may be employed between about 49°C (120QF) and 88QC (190°F) to promote level dyeing. REPLACEMENT PAGE 16a An effective ramp technique for batch dyeing, especially for jet or beck dyeing, is illustrated as Figure 2. Minor adjustments to Figure 2 may be appropriate for package and beam dyeings. Because the copolyester fibers of the present invention begin to dye at 38°C (100aF), fabrics formed from the ^ tfjljjL. ^^ J^U REPLACEMENT PAGE V" 17 copolyester fibers should be home laundered in cold to warm water (i.e., less than 41 "C (105°F)) to ensure that dyes from other fabrics do not stain the copolyester fabrics. As used herein, the concept of dyeing copolyester filaments broadly 5 includes dyeing not only uncut filaments (e.g., partially oriented yarns or textured yams), but also cut filaments (e.g., staple fibers). Moreover, this concept further includes dyeing copolyester fibers that are formed into yarns or fabrics, either alone or in blends with one or more other Kinds of fiber (e.g., cotton or spandex fibers). 10 To evaluate the dyeing characteristic, the disperse dyeability of the PEG-modified copolyester was studied using Color Index Disperse Blue 56, 73, and 79, See Example 1 (below). These kinds of generic dyes, which are readily available, are representative low, medium and high energy disperse dyes, respectively* 15 Example 1 The copolyester fabric used in the testing was a 2 x 2 twill fabric using a 150 denier 100 filament count textured continuous filament yarn formed from copolyester fibers including between about 10 and 12 weight percent polyethylene glycol having a molecular weight of about 400 g/mol. A 20 comparison fabric made of conventional polyester was also employed. This fabric was plain woven, 38 x 58 grc-ige count with crimped polyethylene terephthalate filament yam, and a fabric weight of 146 g/m2 (4.3 oz/sq.yd.) The copolyester fabric was washed according to AATCC Test Method 124-1996, on normal cycle, at41°C'(l05°F) for 8 minutes, to remove spin 25 finishes and size materials. A pot dyeing method was used, wherein the liquor ratio was 10:1 and the fabric size was about 13 cm x 9.5 cm (5 inches x 12 Inches). Dyeing temperature was raised from ambient to 100DC (2129F) at a rate of 1.7°C'/mn (3°F/minute) and held at 100°C (212°F) for 30 minutes with a dye concentration of 3 percent on weight of fabric (owf), unless otherwise 30 stated. The conventional PET fabric was dyed at 130°C (265T) for 30 REPLACEMENT PAGE 17a minutes. Dyeing pH was adjusted by acetic acid and Na2C03/NaHC03 buffer REPLACEMENT PAGE mm 18 for the acidic and alkaline dyeing conditions, respectively. After dyeing, the fabrics were washed in a wash machine according to MTCC Test Method 124-1998, on normal cycle, at41°C (1G5°F) for8 minutes, then tumble dried. After dyeing, the dye uptake was evaluated and compared by K/S values at 5 the wavelength with maximum absorbency. This describes shade depth and is directly proportional to dye concentration on the fiber, provided the shade depth is not too high, Wash fastness was examined according to AATCC Test Method 61-2A(1996). Crock fastness was examined according to AATCC Test Method 8-1996. 10 To evaluate temperature effectsupon dyeing, fabrics were held at various temperatures for 60 minutes at a pH of 5. Thereafter, K/S values were measured. Figure 3 describes.the results. For the low-energy Disperse Blue 56, the optimal K/S value was achieved at 82DC (180flF). For the high-energy Disperse Blue 79, 200e,F provides excellent dye uptake. With respect 15 to medium-energy Disperse Blue 73, dye uptake increased from 93"C (200°F) to 129°C (265 °F), although the subsequent gain in dye uptake was minimal. For comparison, a conventional polyethylene terephthalate fabric was dyed at 129*0(265^). Figure 3 shows that the copolyester fibers begin to dye at about 43°C 20 (110°F). At49°C (120DF). 8 percent of the low-energy Disperse Blue 56 and 3 percent of the high-energy Disperse Blue 79 were sorbed. As disperse dyeing is a reversible sorption process, dyes being sorbed can also be de-sorbed if the temperature is high enough to open the fiber structure. Figure 4 depicts the pH effects upon disperse dyeing at 99gC (210°F). 25 This.suggests that no pH adjustment is necessary when disperse dyeing the copolyester fibers at the aforementioned preferred temperatures (/.a, less than 100°C (212°F)). interestingly, Disperse Blue 79, a dye that is sensitive to alkaline conditions, showed high stability at about a 10 pH. Table 1 (below) describes laundering colorfastness of copolyester 30 fabric dyed with low-energy, medium-energy, and hIgh-Bnergy disperse dyes at different shade depths {/.a, 0.5%, 1.2%, and 3.0% dye owf). As might be REPLACEMENT PAGE 19 expected by one having ordinary skill in the art, wash fastness decreased with increasing shade depth and the high-energy dyes had better wash fastness than low-energy dyes. In Tables 1 and 2 (below), AATCC Method 61-2A (1996), commonly 5 referred to as a 2A wash test, was used to evaluate washfastness. As will be known by those having ordinary skill in the art, Tables 1 and 2 refer to a 1-5 visual rating system, wherein 5 is best and 1 is worst. Table 1 Disperse Dye Dye Cone (%) K/S Color Change Multifiber Acetate Cotton Nylon Polyester Acrylic Wool Blue 56 0.5 9.36 4.5 3 4.5 2.5 4.5 5 4 1.2 19.95 4.5 2 4.5 1.5 4 5 3.5 3 28.31 4.5 2 4 ' 1.5 4 5 3 ¦ Blue 73 0.5 10.59 4.5 4 5 3 5 5 4.5 1.2 21.02 4.5 3 4.5 2.5 4.5 5 4 3 28.62 4.5 2.5 4.5 2 4 5 3.5 Blue 79 0.5 7.17 4.5 5 5 4.5 5 5 4.5 1.2 18.89 4.5 4.5 5 4- ' 4.5 5 4.5 3 32.84 4.5 3.5 4.5 3.5 3.5 5 4 10 Table 2 (below) describes colorfastness of laundered fabrics dyed at different temperatures. In general, higher dyeing temperatures do not improve wash fastness. 20 TABLE 2 Pisperse Dye Dyeing Tamp. CC (°F) K/S Color Change MultiflDer Crocking Acetate Cotton Nylon polyester Acrylic Wool Dry Wet Blue 56 PET 129 (265) 25.45 4-5 3 4-5 2 4-5 5 4 4-5 4-5 79(175) 28.95 4-5 2 4 1-2 4 5 3 5 5 93 (200) 29.35 4-5 2 4 1-2 4 5 3 5 5 104(220) 29.16 4-5 2 4 1-2 4 5 3 5 5 116(240) 28.70 4-5 2 4 1-2 4 5 3 5 5 129 (265) 29.20 4-5 2 4 1-2 4 5 3 5 5 Blue 73 PET 129 (265) 24.02 4-5 3 4-5 2-3 4-5 5 4 4-5 4-5 79(175) 20.97 5 4-5 93 (200) 27.81 4^5 2-3 4-5 2 4 5 3-4 4-5 4-5 104(220) 2S.62 4-5 2-3 4-5 2 4 5 3-4 4-5 4-5 116(240) 29.10 4-5 2-3 4-5 1-2 4 5 3-4 4-5 4-5 129(265) 29.46 4-5 2 4 1-2 4 5 3-4 4-5 4-5 Blue 79 PET 129 (265) 26.63 4-5 2 4 3 3 5 3-4 4 4 79 (175) 23.26 5 5 93 (200) 32.94 4-5 3-4 4-5 3-4 3-4 5 4 5 5 104 (220) 32.70 4-5 3-4 4-5 3-4 3^ 5 4 5 5 116(240) 32.41 4-5 3-4 4-5 3-4 3-4 5 4 5 5 129(265) 31.14 4-5 3-4 4-5 3-4 3-4 s 4 § 5 The copoiyester fiber produced according to the present invention had comparable wash fastness to that of conventional polyester fiber (/.e„ PET 5 265). Note, however, that the low-energy disperse dye resulted in poorer wash fastness as compared to the results using the high-energy disperse dye. REPLACEMENT PAGE e m 20a Accordingly, lower-anergy dyas might be better employed where good light fastness is required, but wash festness is not required (e.g., automotive REPLACEMENT PAGE 21 fabrics). The copolyester fiber had better crock fastness and the conventional polyester fiber in most cases, The copolyester also had better washfastness than the conventional polyester when using the high-energy dye Color Index Blue 79 5 In one particular embodiment, the method of preparing PEG-modified copolyester fibers includes reacting in the melt phase ethylene glycol and a reactant selected from the group consisting of terephthalic acid and dimethyl terephthalate in the presence of polyethylene glycol and a branching agent to form a low molecular weight prepolymer. The prepolymer is then polymerized 10 in the melt phase to form a copolyester composition that has an intrinsic viscosity of at least about 0,73 dl/g and that achieves a zero-shear melt viscosity of at least about 2000 poise when heated to 260°C. In this -embodiment, the polyethylene glycol has an average molecular weight of less than about 5000 g/mol and is present in the resulting copolyester composition 15 between about 10 percent and 12 weight percent and the chain branching agent is present in the resulting copolyester composition in an amount between about 0.0003 and 0.0014 male-equivalent branches per mole of standardized polymer. Thereafter, the copolyester composition is spun into fibers having a mean tenacity of less than 3 grams per denier. The 20 copolyester fibers are then dyed at a temperature of less than about 116QC (24Q°F), preferably at or below a temperature defined by the boiling point of water at atmospheric pressure (i.e., 100°C or 212°F). As noted, in one aspect the method of preparing PEG-modifled copolyester fibers includes copolymerizing polyethylene glycol arid chain 25 branching agent into polyethylene terephthalate in the melt phase to form a copolyester composition. The polyethylene terephthalate is present in an amount sufficient for a fiber made from the copolyester composition to possess dimensional stability properties (e.g., shrinkage during home laundering) substantially similar to those of conventional polyethylene 30 terephthalate fibers. The polyethylene glycol, which has an average molecular weight less than about 5000 g/mol, is present in an amount REPLACEMENT PAGE 22 sufficient for fibers made from the copofyester composition to possess wetting, wicking, drying, flame-retardancy, static-dissipation, stretch, and dye , uptake properties that are superior to those of conventional polyethylene tereph'thalata fibers. Open fabric constructions, such as pique knits and low 5 greige yam density wovens, tend to accentuate moisture movement and stretch performance. Moreover, it has been further observed that fabrics formed according to the present invention possess significantly improved hand {i.e., tactile qualities) as compared to conventional poiyesterfabrics mada of fibers having 10 similar denier per filament (dpf). In this regard, 1,5 dpf copolyester fibers of the present invention are comparable to 0.6-0.75 dpf conventional polyester fibers. Figure 5 describes the wicking properties of fabrics formed from copolyester fibers produced according to the invention as compared ia the 15 wicking properties of fabrics formed from conventional, unmodified polyethylene terephthalate fibers. As noted, the copolyester fibers included between about 10 and 12 weight percent polyethylene glycol having a molecular weight of about 400 g/mol. Wicking properties were measured using 2.5 cm x 15 cm (1 inch x 7 inches) strips that were suspended vertically 20 above water-filled beakers and then submersed one inch below the water surface. After one minute, the water migration up the test strips was measured. The fabrics were tested in both fabric directions and averaged. The test strip fabrics were laundered once before testing. The room conditions were ASTM standard 21 aC and 65 percent relative humidity. 25 Figure 6 describes the drying properties of fabrics formed from copolyester fibers produced according to the present invention as compared to the drying properties of fabrics formed from conventional, unmodified polyethylene terephthalate fibers. As noted, the copolyester fibers included between about 10 and 12 weight percent polyethylene glycol having a 30 molecular weight of about 400 g/mol. Drying rate was determined using a Sartorius MA30-0D0V3 at 40°C. Two or three drops of water were placed on REPLACEMENT PAGE m 23 the fabrics. Then, the evaporation time was measured and an evaporation rate was calculated. The room conditions were ASTM standard 21°C and 65 percent relative humidity. Figure 7 describes the flame-retardancy properties of fabrics formed 5 from copolyester fibers produced according to the invention as compared to the flame-retardancy properties of fabrics formed from conventional; unmodified polyethylene terephthaiate fibers. As noted, the copolyester fibers included between about 10 and 12 weight percent polyethylene glycol having a molecular weight of about 400 g/mol. The testing was performed in 10 accordance with the NFPA 701 Method small-scale-after-flame test. Figure 7 merely shows that fabrics formed from copolyester fibers produced according to the invention have better flame-retardancy properties as compared to those of fabrics formed from conventional, unmodified polyethylene terephthaiate fibers. Figure 7 is not intended to imply that fabrics formed from copolyester 15" fibers produced according to the invention will meet any particular government flammability standards. Figure 8 describes the static-dissipation properties of fabrics formed from copolyester fibers produced according to the invention as compared to the static-dissipation properties of fabrics formed from conventional, 20 unmodified polyethylene terephthaiate fibers. As noted, the copolyester fibers included between about 10 and 12 weight percent polyethylene glycol having a molecular weight of about 400 g/mol. Static dissipation was determined using a Rothschild Static-Voltmeter R-4021. In brief, fabric was mounted between the electrodes, and then the time for the voltage across the fabric to 25 reduce from 150 volts to 75 volts was measured. The room conditions were ASTM standard 21 °C and 65 percent relative humidity. As will be understood by those having ordinary skill in the art, a shorter charge half-life is desirable in fabrics because it means fabric static is dissipated faster. . Figure 9 describes the abrasion resistance properties of fabrics formed 30 from copolyester fibers produced according to the invention as compared to the abrasion resistance properties of fabrics formed from conventional, 24 unmodified polyethylene terephthalate fibers. As noted, the copolyester fibers included between about 10 and 12 weight percent polyethylene glycol having a molecular weight of about 400 g/mot. The fabrics each had a Ti02 level of 3000 ppm. Abrasion resistance was determined using Stoll flat (knits) ASTM 5 D 3886 method and Taber (wovens) ASTM D 3884 method. Figure 10 describes the strength properties of fabrics woven from copolyester fibers produced according to the present invention as compared to the strength properties of fabrics woven from conventional, unmodified polyethylene terephthalate fibers. As noted, the copolyester fibers included 10 between about 10 and 12 weight percent polyethylene glycol having a molecular weight of about 400 g/mol. The somewhat weaker strength of fabrics formed from the fibers prepared according to the invention reduces undesirable pilling. Fabric strength was determined by strip test (wovens) ASTM D 1682-64 method or by Bail Burst (knits) ASTM D3787-80A. 15 Figure 11 summarizes on a percentage basis the improved properties of fabrics formed from copolyester fibers produced according to the invention as compared to the properties of fabrics formed from conventional, unmodified polyethylene terephthalate fibers. As noted, the. copolyester fibers included between about 10 and 12 weight percent polyethylene glycol having 20 a molecular weight of about 400 g/mol. With respect to dye uptake, the 30 percent improvement is based on darker shades. With respect to fabric hand, fabric formed from 1.5 dpf copolyester fibers according to the present invention subjectively feels like fabric formed from 0.75 dpf conventional polyester microfibers. 25 Preparing PEG-modified copolyester fibers according to the invention not only yields certain improved textile characteristics, but also retains the -desirable dimensional stability of ordinary polyester. Despite the significant concentration of polyethylene glycol, copolyester fibers prepared according to the invention have dimensional stability properties, especially shrinkage 30 during home laundering, that are substantially similar to those of conventional polyethylene terephthalate fibers. For example, conventional polyester fabric mm €¦4 25 exhibits less than about five percent shrinkage In home laundering if finished at a temperature at or above 177°C (350°F). Similarly, copolyester fabric of the invention exhibits less than about five percent shrinKage in home laundering if finished (i.e., heat set) at a fabric temperature at or above 166°C 5 (33Q°F). This is about the expected home laundering shrinkage of conventional polyester fabrics. Moreover, fabrics formed from the filaments spun according to the invention will possess better elastic-memory properties (;.eM stretch and recovery) as.compared .to fabrics formed.from, conventional polyethylene, 10 terephthalate filaments. The commonly-assigned patent application Serial No. 09/141,665 discloses that chain branching agents can raise the melt viscosity of PEG-modified copolymer melt to within the range of normal, unmodified polyethylene terephthalate. In contrast, the present invention introduces an 15 alternative method of producing fibers from PEG-modified copolyester without resorting to significant fractions of branching agent. In accordance with this aspect of the invention, chain branching agent is present in the copolyester composition in an amount less than about 0,0014 mole-equivalent branches per mole of standardized polymer, and preferably 20 between about 0.0003 and 0.0014 mole-equivalent branches per mole of standardized polymer. As used herein, the term "mole-equivalent branches" refers to the reactive sites available for chain branching on a molar basis (/.e.( the number of reactive sites in excess of the two required to form a linear molecule). For 25 example, pentaerythritoi is a tetrafunctional branching agent, so it possesses two available chain branching reactive sites. In addition, as used herein, the term "standardized polymer" refers to the repeat unit of unmodified polyethylene terephthalate, which has a molecular weight of 192 g/mol. In this regard, it will be understood by those of 30 skill in the art that, for a given total weight of polyethylene terephthalate, REPLACEMENT PAGE 26 polyethylene glycol, and branching agent, increasing the relative weight fraction of polyethylene glycol, which preferably has a molecular weight of less than 5000 g/mol, will decrease total moles. (This is so because the molecular weight of polyethylene terephthalate is less than the molecular 5 weight of the polyethylene glycol.) Consequently, to maintain uniformity across various concentrations and molecular weights of polyethylene glycol, the chain branching agent concentration of between about 0.003 and 0.0014 mofe-equivafent branches per mole of standardized polymer is based on the repeat unit of unmodified polyethylene terephthalate. 10 In other words, the weight fraction of branching agent should be calculated as if the polymer is made of only unmodified polyethylene terephthalate. Consequently, the weight fraction of polyethylene glycol (e.g., preferably between about 4 weight percent and 20 weight percent) and the molecular weight of the polyethylene glycol (e.g., preferably less than about 15 5000 g/mol) can be disregarded In calcuiating mole-equivalent branches per mole of standardized polymer. For example, an amount of pentaerythritol between about 0.0003 and 0.0014 mole-equivalent branches per mole of the copolyester composition is equivalent to a weight fraction of between about 110 and 500 ppm when 20 based on the standardized polymer of unmodified polyethylene terephthalate, whose repeat unit has a molecular weight of about 192 g/mol. To further illustrate this relationship, assume 1000 grams of starting materials—500 ppm pentaerythritol, which has a molecular weight of 136.15 g/mol, and the remainder polyethylene terephthalate. This is equivalent to 0^5 25 gram pentaerythritol, or 0.00367 moles of pentaerythritol, and 999.5 grams polyethylene terephthalate, or 5.21 moles polyethylene terephthalate repeat units. The mole fraction of pentaerythritol relative to the polyethylene terephthalate is, therefore, 0.0705 mole percent (i.e., 0.00367 moles of pentaerythritol-^ 5.21 moles polyethylene terephthalate). As noted, 30 pentaerythritol has two available chain branching reactive sites. Thus, the mole-equivalent branches per mole of unmodified polyethylene terephthalate 27 is 0.14 percent (i.e., 0.0014 mole-equivalent branches per mole of standardized polymer.) The weight fraction corresponding to mole-equivalent branches per mole of standardized polymer can be estimated for any branching agent using 5 the following equation: branching agent (ppm) = (MEB * CBRS) * (BAMW - SPMW) • 106, wherein MEB ~ mole-equivalent branches per mole of standardized polymer CBRS = number of available chain branching reactive sites 10 BAMW ~ molecular weight of the branching agent (g/mol) SPMW= 192 g/moi—molecular weight of the standardized polymer (i.e., unmodified polyethylene terephthalate) It will be appreciated by those of skill in the chemical arts that if the mole-equivalent branches were not referenced to a mole of standardized 15 polymer, a branching agent concentration of 0.0014 mole-equivalent branches per mole of polymer (i.e., the copolyester composition) would translate to a slightly lower weight fraction (i.e., ppm) when a greater polyethylene glycol weight fraction is used, or when polyethylene glycol having a higher average molecular weight is employed. 20 For example, if mole-equivalent branches per mole of polymer were not related to a common standard, but rather to the actual components of the copolyester composition, an amount of pentaerythritol less than about 0.0014 mole-equivalent branches per mole of the copolyester composition would be equivalent to a weight fraction of less than about 450 ppm when,based on 25 polyethylene terephthalate that is modified by 20 weight percent polyethylene glycol having an average molecular weight of about 400 g/mol. Likewise, an amount of pentaerythritol less than about 0.0014 mole-equivalent branches per mole of the copolyester composition would be equivalent to a weight fraction of less than about 400 ppm when based on polyethylene 30 terephthalate that is modified by 20 weight percent polyethylene glycol having an average molecular weight of about 5000 g/mol. By employing unmodified 28 polyethylene terephthalate as the standardized polymer, however, an amount of pentaerythrito! less than about 0.0014 mole-equivalent branches per mole of standardized polymer is equivalent to a weight fraction of less than about 500 ppm regardless of the weight fraction or molecular weight of the 5 polyethylene glycol. The chain branching agent is preferably a Afunctional or tetrafunctional alcohol or acid that will copolymerize with polyethylene terephthalate. AS-will be understood by those skilled in the art, a trifunctional branching agent has one reactive site available for branching and a tetrafunctional branching agent 10 has two reactive sites available for branching. Acceptable chain branching agents include, but are not limited to, trimesic acid (C6H3(COOH)3), pyromellitic acid (C6H2(COOH)4), pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, trimethylol propane (C2H5C(CH2OH)3), ditrimethylol propane (C2H5C(CH2OH)2G2H40C(CH20H)2C2H5), dipentaerythritol 15 {CH20HC(CH2QH)2C2H40C(CH20H)2CH2OH), and preferably pentaerythrito! (C(CH2OH)4). If the total number of reactive sites exceeds four per branching agent molecule, steric hindrance can sometimes prevent full polymerization at the available reactive sites such, that more branching agent may be required to achieve the desired mole-equivalent branches. See, e.g., U.S. Patent Nos.' 20 4,092,299 and 4,113,704 by MacLean and Estes. in another aspect, the invention is a polyethylene glycol modified copoiyester composition that is particularly suitable for fibers. The copolyester composition includes polyethylene terephthalate in amount sufficient for a fiber made from the composition to possess dimensional 25 stability properties substantially similar to those of conventional, unmodified polyethylene terephthalate fibers. The polyethylene glycol in an amount sufficient for a fiber made from the composition to possess wicking, drying, and static-dissipation properties that are superior to those of conventional, unmodified polyethylene terephthalate fibers, wherein the polyethylene glycol 30 has an average molecular weight of less than about 5000 g/mol. The chain branching agent selected from the group consisting of trifunctional alcohols, 29 trifunctional acids, tetrafunctional alcohols, tetrafunctional acids, pentafunctional alcohols, pentafunctional acids, hexafunctiona! alcohols, and hexafunctional acids that will copolymerize with polyethylene terephthalate, wherein the chain branching agent is present in said composition in an 5 amount less than about 0.0014 mole-equivalent branches per mole of standardized polymer, the standardized polymer being unmodified polyethylene terephthalate. The weight fraction of polyethylene glycol in said composition and the intrinsic viscosity of said composition are defined by the shaded region of Figure 1. 10 In a preferred embodiment, the weight fraction of polyethylene glycol in the composition is between about 10 and 12 percent, and the composition has an intrinsic viscosity of between about 0.73 and 0.88 dl/g. To facilitate spinning, the copolyester composition is preferably achieves a zero-shear melt viscosity of between about 2000 and 3500 poise when heated to 260°C. 15 As previously disclosed, in another embodiment, the copolyester composition is comprised of polymer chains formed from structural units consisting essentially of dio! monomers, aromatic non-substituted diacid monomers, and branching agent monomers. A distinct advantage of the present method is that it produces a 20 copolyester fiber that, while possessing wetting, wicktng, drying, soft hand, dye uptake, fiame-retardancy, abrasion-resistance, stretch, and static-dissipation properties that are superior to those of conventional polyethylene terephthalate fibers, can be processed using conventional textile equipment. For example, in one broad aspect, the PET-modified copolyester can be spun 25 into partially, oriented yarns (POY). As will be understood by those having ordinary skill in the art, POY is often comprised of from tens to hundreds of intermingled filaments (e.g., between 30 and 200) that are extruded from a spinneret at speeds typically between about 2000 and 4000 meters per minute. "The POY is then typically drawn to form a drawn yarn (e.g., by draw 30 texturing, fiat drawing, or warp drawing). Thereafter, the drawn yarn is formed into fabric, which is typically finished as well. As will be known by those 30 skilled in the art, texturing POY can be effected in numerous ways, such as air jet texturing, gear crimping, and false-twist texturing. More generally, copolyester fibers of the present invention (i.e., staple or POY) may be textured according to various techniques, such as air jet, edge crimping, false--5 twist, gear crimping, knit-de-knit, and stuffer box methods. Table 3 (below) discloses an exemplary set point and preferred set point ranges for texturing the copolyester POY using a contact false-twist texturing machine. Table 3 Contact Heater False-Twist Texturing Set Points Range Models Barmag L-80; Barmag RPR 3SD90 Draw Ratio 1.55 1.3-2.0 Primary Heat (C) 130 100-190 Speed (m/min) 500 300 - 800 Secondary Heat (°C) 160°C Off-190 D/Y ratio 1.7 1.3-2.0 PU Disk stacking (S-PU-S) PU=polyurethane, S=stainless steel 2-5-1 3-4-1 % Takeup Overfeed 6 2-14 Pre-aggregate tension (g) 63 30-80 Post-aggregate tension (g) 36 20-70 Twist SorZ all S and Z combinations . Takeup Tension (g) Denier 60 - 525 Tenacity (g/denier) 1.65 .1.4-3.0 % Elongation 30-35 .15-75 % Shrinkage 4 - 4.5 set or -7 stretch 2-20 % Crimp 3 - 5 set or -16 stretch 2-30 %Bulk 7-10 set or-24 stretch 5-40 31 Table 4 (below) discloses an exemplary set point and preferred set point ranges for texturing the copofyester POY using a non-contact false-twist texturing machine. TABLE 4 Non-Contact Heater False-Twist Texturing Set Points Range Models Barmag AFK; Rieter Scragg Draw Ratio 1.58 1.3-2.0 Primary Heat (1sl/2na)(°C) 300/220 100-190 Speed (m/min) 500 300-800 Secondary Heat for set yarn (°C) 160 Off-190 D/Y 1.7 1.3-2.0 PU Disk stacking (S-PU-S) PU=polyurethane, S=stainless steel 1-7-1 % Takeup Overfeed 4.5 2-14 Pre-aggregate tension (g) 65 30-80 Post-aggregate tension (g) 42 20-70 Takeup Tension (g) 10 4-20 Denier 60-525 Tenacity (g/denier) 2.3 1.2-3.0 % Elongation 63 15-75 % Shrinkage 4.3 set or -7 stretch 2-20 % Crimp 3-6 set or-16 stretch 2-30 % Bulk 7-10 set or-24 stretch 5-40 Table 5 (below) discloses an exemplary set point and preferred set point ranges for draw-winding the copolyester POY using a draw-winding machine with heated godet rolls. 32 TABLE 5 Draw-Winding Set Points Range Models Barmag Draw Ratio 1.85 1.5-2.2 Primary Heat ( C) 60 100- 190 Speed (m/min) 500 300 - 800 Secondary Heat for set yarn (°C) 140 Off-190 Denier 60-1100 Tenacity (g/denier) 2.9 1.2-3.0 % Elongation 60 i 15-75 % Shrinkage 3.2 set or -7 stretch 2-20 As will be understood by those having ordinary skill in the art, in Tables 3-5 (above) "denier" depends on the POY denier and number of plies, and "secondary heat" applies to set yarns. Moreover, "D/Y" is the ratio of disk speed to yarn speed, wherein the disk speed the linear speed of a point on the circumference of the disk. It is re-emphasized that the disclosed settings (above) are exemplary rather than limiting, and that when the filament of the present invention is textured on another kind of machinery, those of ordinary skill in the art will be able to replicate the results described herein without undue experimentation. It should be noted that flat drawn POY produced according to the invention results in yarns having dyeing characteristics similar to those of cellulose acetate yams. These copolyester yarns are especially suitable for producing suit linings. As will be known to those having ordinary skill in the art, suit linings are conventionally jig dyed using low-energy dyes, which have poor fastness properties. The yarns and fabric formed according to the invention, however, can be dyed on conventional jig dyeing equipment using high-energy dyes. Such yarns and fabrics are machine washable, which is not possible with acetate products. 33 Because of the characteristic advantages that the invention brings to the polyester compositions described herein, the resulting polyester fibers are particularly useful in blended yarns and blended fabrics. Accordingly, copolyester POY can be blended with at least one other kind of fiber (i.e., a 5 fiber having a different chemical composition or having been differently processed) to form a blended yarn. As will be understood by those familiar with textile processes, the copolyester POY is typically either draw textured to form a draw-textured yarn (DTYJ or flat drawn to form a flat-drawn yarn (i.e., a hard yarn) before blending. The drawn copolyester yarn is especially suitable 10 for blending with cotton fibers, rayon fibers, polypropylene fibers, acetate fibers, nylon fibers, spandex fibers, and conventional polyester fibers. Furthermore, the drawn copolyester yarn (e.g., DTY or hard yarn) can also be blended with a least one other kind of fiber to form blended fabric. In this regard, the drawn copolyester yarn is especially suitable for blending with 15 cotton fibers, rayon fibers, polypropylene fibers, acetate fibers, nylon fibers, spandex fibers, conventional polyester fibers, and even copolyester staple fibers of the present invention. It will be understood that, as used herein, the concept of forming a blended fabric from the drawn copolyester yarn and at least one other kind of fiber not only includes directly forming a fabric from the 20 drawn copolyester yarn and a second kind of fiber, but also includes first forming a blended yarn before forming the blended fabric, in either case, however, the blended fabric is formed from a drawn copolyester yarn and a second kind of fiber. As will be known to those skilled in the art, two different kinds of 25 filaments are not usually textured together unless they can use the same temperature and draw ratio. Consequently, it is desirable to form a blended fabric without first forming a blended yarn when the second kind of fiber has different texturing requirements than those of the copolyester POY. It has been observed, however, that the copolyester POY and nylon 30 yarn require similar texturing temperatures. Accordingly, in a preferred embodiment, the copolyester POY and a nylon yarn are formed into a blended 34 yarn. Thereafter, the blended yarn is textured. Interestingly, because of dye selectivity, the resulting blended yarn may be dyed with disperse dyet which preferentially dyes the copoiyester component, and acid-based dye, which preferentially dyes the nylon component. In this way, a heather yam (or a 5 two-colored yarn) can be produced, which may then be formed into an attractive, heather fabric (or a two-colored fabric). In another broad aspect, the invention further includes cutting the copoiyester filaments into staple fibers. As wil! be understood by those having ordinary skill in the art, perhaps thousands of filaments can be spun from a 10 single spinneret, typically at speeds of between about 500 and 2000 meters per minute. The filaments, often from numerous spinneret positions, are combined into a tow. The tow is often crimped before the filaments are cut into staple fibers. The staple fibers can be formed into yarn using any conventional spinning technique, such as ring spinning, open-end spinning, 15 and air jet spinning. In this regard, open end and air jet spinning are becoming increasingly more preferred for polyester yarns, as well as for blended yarns containing polyester. The yarns formed from the copoiyester filaments of the invention, in turn, can be woven or knitted into fabrics that have the advantageous characteristics referred to herein. Alternativeiy, the 20 staple fibers can be formed directly into a non-woven fabric. As used herein, the concept of forming staple fibers into fabric includes first forming a yarn (e.g., knitting and weaving), in addition to forming the staple fibers directly into fabric (e.g., non-woven fabric). In another aspect, the method includes bfendtng the staple copoiyester 25 fibers with at least a second kind of fiber, such as cotton fibers, rayon fibers, polypropylene fibers, acetate fibers, nylon fibers, spandex fibers, an6 conventional unmodified polyester fibers. In this regard, acetate fibers and spandex fibers are usually in filament form. Thereafter, the staple fibers and the second kind of fiber can be spun into yarn, and the yam formed into fabric 30 using conventional techniques. Alternatively, the staple fibers and the second kind of fiber can be formed directly into a non-woven fabric. 35 In yet another aspect, the invention includes forming copolyester fibers from the copoiyester composition as previously disclosed, and then blending the copolyester fibers with spandex fibers. As described previously, the term "copolyester fiber" broadly refers to uncut filament (e.g., POY, fiat-drawn yarn, 5 or textured yarn) and cut fiber (e.g., staple fiber). For example, the copolyester fibers and the spandex fibers can be blended into yarn. In one preferred embodiment, this comprises core spinning copolyester staple fibers around a care of spandex filaments. Likewise, in anotherprafe/red embqdimenMha cqpq^ 10 form of POY—are wrapped around spandex filaments. The copolyester fibers and the spandex fibers may also be formed into fabric using conventional techniques. For example, the fabric may be formed (B.g., woven or knitted) from a blended yam that is spun from the copolyester fibers and the spandex fibers. Alternatively, the copolyester fibers and 15 spandex fibers may be directly formed into a fabric, preferably a knit fabric. To accomplish this, the spandex is laid into a copolyestar knit by employing an appropriate knitting machine attachment. As noted previously, the invention can include dyeing the copolyester fibers at a temperature of less than about 116°C (240°F). In particular, this 20 reduction in dyeing temperature not only reduces energy usage, but also permits copolyester fibers that are produced according to this embodiment of the invention to be more effectively combined with spandex filaments. Blended yarns and fabrics that are made from PEG-modified copolyester fibers—preferably staple fibers or POY—and spandex fibers can be dyed at 25 temperatures of less than about 1160C (240°F), and yet can achieve excellent fastness and depth of color. In one preferred embodiment, the spandex fibers and the copolyester fibers may be dyed at a temperature of less than about 110DC (230°F). In another preferred embodiment, the spandex fibers and the copolyester fibers may be dyed at a temperature of less than about 104°C 30 (220°F). In yet another preferred embodiment, the spandex fibers and the REPLACEMENT PAGE Ml 130 11200, ***** pmnf,nB*7i>it in.Nnv..99:37 -»»** 35a copoiyester fibers may be dyed &t or below a temperature of less than the boiling point of \il^ bL*-*^ OAO^CJL^ REPLACEMENT PAGE 36 water at atmospheric pressure (/.e., 212T or 100°C). In this regard, it should be understood that the concept of dyeing copolyester fibers and spandex fibers includes dyeing the blend in the form of blended yams and blended fabrics. It is emphasized that, as used herein, the term "copolyester fibers" 5 broadly refers to cut copolyester fibers (e.g., staple fibers) and uncut copolyester filaments (e.g., POY). Dyeing copolyester fibers and spandex fibers at reduced temperatures prevents the degradation of the stretch properties possessed by spandex. In conventional polyester-spandex blended textiles, dyeing temperatures of 10 about 129°C (265°F) are required to adequately dye the conventional polyester fibers. Unfortunately, such high temperatures weaken such high-power stretch polyurethane filaments. Consequently, dyeing blends of copolyester and spandex at lower temperatures is advantageous. In other embodiments of the method, copolyester fibers, whether staple 15 fibers or POY, are blended with cotton fibers. The preferred copolyester/cotton blends include between about 5 percent and 95 weight percent cotton fibers with the remainder comprising the copolyester fibers. Most preferably, the blend includes between about 30 weight percent and 70 weight percent cotton fibers with the remainder comprising the polyester 20 fibers. In this regard, the Invention provides the opportunity to increase the synthetic content of blended cotton and polyester yarns to take advantage of the desirable characteristics of the copolyester in the resulting yarns and fabrics. For example, unlike conventional unmodified polyester fibers, the copolyester fibers formed according to the present method possess statfc-25 dissipation properties that are closer to that of cotton, Moreover, the present copolyester fibers retain the desirable dimensional stability characteristics of conventional polyesters. A particular advantage of the present invention is that copolyester fibers and cotton fibers can be dyed in one step, which is expected to reduce 30 dyeing and energy expenditures by 30 percent or more. As will be understood by those of ordinary skill in the art, cotton is typically dyed using REPLACEMENT PAGE 37 cotton dyes (e.g., reactive dyes) in alkaline dye baths and polyester is typically dyed at high temperatures (e.g. 129°C or 265°F) In acidic dye baths. Accordingly, dyeing blended cotton and polyester yarns and fabrics requires a two-step dyeing process. Such blends are usually dyed in an alkaline pH 5 using suitable cotton dyes to selectively dye the cotton fibers and are thereafter dyed in an acidic pH using disperse dyes to selectively dye the polyester fibers. As described previously, however, the present copolyester fibers da not require any pH adjustment and can be dyed effectively In an alkaline dye bath having a pH as high as 10. Consequently, blended yams 10 and fabrics that are made from PEG-modifled copolyester fibers and cotton fibers can be dyed simultaneously in an alkaline dye bath that includes both reactive and disperse dyes. Preferably, dyeing such cotton/copofyester blends fs carried out in a dye bath having a pH of about 10 or less and a temperature at or below the boiling point of water at atmospheric pressure 15 (i.e., 212"F or 1008C). It should be understood that the concept of dyeing copolyester fibers and cotton fibers includes dyeing the blend in the form of blended yams and blended fabrics. It is re-emphasized that, as used herein, tho term "copolyester fibers" broadly refers to cut copolyester fibers (e.g., staple fibers) and uncut 20 copolyester filaments (e.g., POY). It is further emphasized that this one-step dyeing technique can be employed effectively with other blends of copolyester fibers and celfulosic fibers, such as rayon and acetates Those familiar with textile terminology will understand that "spinning" refers to two different processes. In one sense, the term "spinning" refers to 25 the production of synthetic polymer filaments from a polymer melt. In its older, conventional use, the term "spinning" refers to the process of twisting a plurality of individual fibers into yarns. The use of both of thesB terms Is widespread and well understood in this art such that the particular use herein should be easily recognized by those of ordinary skill In the art. 30 Conventional techniques of polymerizing polyester and spinning filaments are well known by those having ordinary skill in the art. Accordingly, REPLACEMENT PAGE 38 the following examples highlight the modifications to conventional process steps to achieve an especially desirable fabric. Example 2 Melt Polymerization—The copolyester composition was polymerized 5 like standard polyethylene terephthalate, except that the polymerization temperature was 10°C lower than normal. Polyethylene glycol, having an average molecular weight of 400 g/mole, was injected into the process before the initiation of the polymerization at a rate sufficient to yield 10 weight percent polyethylene glycol in the copolyester composition: Likewise, 10 pentaerythyritol was added before polymerization at a rate that would yield about 400 ppm in the copolyestercomposition. The copolyester was then extruded, quenched, and cut The quench water was 10"C colder than normal- The copolyester was crystallized 10QC lower than normal. The copolyester was melt polymerized to an intrinsic viscosity of 0.78 dl/g. 15 Filament Spinning—The copolyester formed POYIike a conventional polyethylene terephthalate product having the same filament count, except that the spinning temperature was reduced by 10°C, Texturing—The POY was textured on a non-contact heater Barmag AFK false twist texturing machine with poiyurethane disks. The POY 20 processed like standard polyethylene terephthalate POY Bxcept that the temperature was between about 50°C and 1G0°C befow normal primary-heater temperatures. Finally, the secondary heater was not used, yielding a stretch textured yarn. Fabric Formation—Fabric formation was identical to conventional 25 weaving and knitting techniques. Dyeing—Dyeing was the same as conventional techniques except that no carrier was used and the batch was held at a dye temperature of 99flC (210aF) for 30 minutes. The heat-up rate was held to 1.1°C (2°F) per minute between 43°C (110°F).and 99flC (210flF)to ensure level dyeing. REPLACEMENT PAGE B x ,n ..... «*.„ ISllISI^ , 39 Finishing—Finishing was the same as conventional techniques except that the zone temperature was reduced 10°C and no finish was used in the pad. Example _3 5 The copolyester composition was processed in accordance with Example 1, except for the following texturing modification. Texturing—The POY was textured on a non-contact heater Barmag AFK false twist texturing machine with polyurethane disks. The POY processed like standard polyethylene terephthalate POY except that the 10 temperature was between about 50°C and 100°C below normal primary-heater temperatures. Finally, the secondary heater at 160DC was used to yield a set textured yarn. Fabric Formation—Fabric formation was identical to conventional knitting techniques. 15 In the drawings and the specification, typical embodiments of the invention have been disclosed. Specific terms have been used only in a generic and descriptive sense, and not for purposes of limitation. The scope of the invention is set forth in the following claims. ^i^ yu^- s^^ szkzv&n 40 WE CLAIM : 1. A method of preparing polyethylene glycol modified copoiyester fibers that can be formed into exceptionally comfortable fabrics, comprising: copolymerizing polyethylene glycol and a chain branching agent into polyethylene terephthalate in the melt phase to form a copoiyester composition having an intrinsic viscosity of at least 0.67 dl/g; wherein the polyethylene glycol has an average molecular weight of less than 5000 g/mol and is present in the copoiyester composition in an amount between 4 weight percent and 20 weight percent; and wherein the chain branching agent is present in the copoiyester composition in an amount less than 0,0014 mole-equivalent branches per mole of standardized polymer, the standardized polymer being unmodified polyethylene terephthalate; and thereafter spinning the copoiyester composition into a filament. 2. A method of preparing copoiyester fibers as claimed in Claim 1, wherein the step of copolymerizing polyethylene glycol and a chain branching agent into polyethylene terephthalate yields a copoiyester composition that is comprised of polymer chains formed from structural units consisting essentially of dioi monomers, aromatic non-substituted diacid monomers, and branching agent monomers. 3. A method of preparing copoiyester fibers as claimed in Claim 1, wherein the polyethylene glycol has an average molecular weight of between 300 g/mol and 1000 g/mol. 4. A method of preparing copoiyester fibers as claimed in Claim 1, wherein the step of spinning filaments from the copoiyester comprises spinning copoiyester filaments at a temperature between 280°C and 300°C, 5. A method of preparing copoiyester fibers as claimed in Claim 1, comprising the step of forming the copoiyester into chips after the step of copolymerizing polyethylene glycol and a chain branching agent into polyethylene terephthalate in the 41 melt phase and before the step of spinning the copolyester composition into a filament. 6. A method of preparing copolyester fibers as claimed in Claim 1, wherein the step of spinning the copolyester composition into a filament comprises spinning filaments having a mean tenacity of less than 3 grams per denier. 7. A method of preparing copolyester fibers as claimed in Claim 1, wherein the chain branching agent is present in the copolyester composition in an amount between 0.0003 and 0.0014 mole-equivalent branches per mole of standardized polymer, the standardized polymer being unmodified polyethylene terephthalate. 8. A method of preparing copolyester fibers as claimed in Claim 1, wherein the chain branching agent selected from the group consisting of trifunctional alcohols, trifunctional acids, tetrafunctional alcohols, tetrafunctional acids, pentafunctional alcohols, pentafunctional acids, hexafunctional alcohols, and hexafunctional acids that will copolymerize with polyethylene terephthalate. 9. A method of preparing copolyester fibers as claimed in Claim 1, wherein the chain branching agent is selected from the group consisting of pentaerythritol, dipentaerythritol, trimesic acid, pyromellitic acid, pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, trimethylol propane, and ditrimethylol propane. 10. A method of preparing copolyester fibers as claimed in Claim 1, wherein: the chain branching agent is pentaerythritol; and the pentaerythritol is present in the copolyester composition in an amount between 110 and 500 ppm. 11. A method of preparing copolyester fibers as claimed in any of Claims 1-10, wherein the weight fraction of polyethylene glycol in the copolyester composition is between 8 percent and 14 percent. 42 12. A method of preparing copolyester fibers as claimed in Claim 11, wherein the weight fraction of polyethylene glycol in the copolyester composition is between 10 percent and 12 percent. 13. A method of preparing copolyester fibers as claimed in Claims 1-10, wherein the step of copolymerizing polyethylene glycol and a chain branching agent into polyethylene terephthalate comprises copolymerizing polyethylene glycol and a chain branching agent into polyethylene terephthalate in the melt phase to form a copolyester composition that achieves a zero-shear melt viscosity of between about 2000 and 3500 poise when heated to 260°C. 14. A method for producing copolyester fibers as claimed in any of Claims 1-10, wherein the step of spinning a filament from the copolyester comprises spinning POY from the copolyester. 15. A method for producing copolyester fibers as claimed in Claim 14, comprising drawing the POY to form drawn yarn. 16. A method for producing copolyester fibers as claimed in Claim 15, wherein the step of drawing the POY comprises draw-texturing the POY to form textured yarn. 17. A method for producing copolyester fibers as claimed in Claim 15, comprising: forming the drawn yarn into a fabric; and finishing the fabric. 18. A method for producing copolyester fibers as claimed in Claim 15, comprising forming the drawn yarn and a second kind of fiber into a blended yarn. 19. A method for producing copolyester fibers as claimed in Claim 18, wherein i the step of forming the blended yarn comprises wrapping the copolyester drawn yarn 43 around spandex filaments. 20. A method for producing copolyester fibers as claimed in Claim 15, comprising forming the drawn yarn and a second kind of fiber into a fabric. 21. A method for producing copolyester fibers as claimed in Claim 14, comprising: forming the POY and a nylon yarn into a blended yarn; texturing the blended yarn; and dyeing the blended yarn with a disperse dye, which selectively dyes the copolyester component, and an acid-based dye, which selectively dyes the nylon component. 22. A method of preparing copolyester fibers as claimed in any of Claims 1-10, comprising cutting the copolyester filament into staple fibers. 23. A method for producing copolyester fibers as claimed in Claim 22, comprising forming the staple fibers into yarn. 24. A method for producing copolyester fibers as claimed in Claim 22, comprising forming the staple fibers into fabric. 25. A method for producing copolyester fibers as claimed in Claim 22, comprising forming the copolyester staple fibers and a second kind of fiber into a blended yarn. 26. A method for producing copolyester fibers as claimed in Claim 25, wherein the step of forming the blended yarn comprises core spinning copolyester staple fibers around a core of spandex filaments. 44 27. A method for producing copolyester fibers as claimed in Claim 22, comprising forming the copolyester staple fibers and a second kind of fiber into a fabric. 28. A method for producing copolyester fibers as claimed in Claim 18, wherein the second kind of fiber is selected from the group consisting of cotton fibers, rayon fibers, polypropylene fibers, acetate fibers, nylon fibers, spandex fibers, and conventional polyester fibers. 29. A method for producing copolyester fibers as claimed in any of Claims 1-10, comprising forming the copolyester filaments and spandex fibers into fabric. 30. A method for producing copolyester fibers as claimed in any of Claims 1-10, comprising dyeing the copolyester filament at a temperature of less than 116°C (240°F). 31. A method for producing copolyester fibers as claimed in Claim 30, wherein the step of dyeing the copolyester filament at a temperature of less than 116°C (240°F) comprises dyeing the copolyester filament at a temperature of less than 104°C (220°F). 32. A method for producing copolyester fibers as claimed in Claim 31, wherein the step of dyeing the copolyester filament at a temperature of less than 104°C (220°F) comprises dyeing the copolyester filament at or below a temperature defined by the boiling point of water at atmospheric pressure. 33. A method for producing copolyester fibers as claimed in Claim 32, wherein the step of dyeing the copolyester filament at or below a temperature defined by the boiling point of water at atmospheric pressure comprises dyeing the copolyester filament using a high-energy dye between 93°C (200°F) and 100°C (212°F). 34. A method for producing copolyester fibers as claimed in Claim 32, wherein the step of dyeing the copolyester filaments at or below a temperature defined by the 45 boiling point of water at atmospheric pressure comprises dyeing the copolyester filament using a low-energy dye between 82°C (180°F) and 100°C (200°F). 35. A polyethylene glycol modified copolyester fiber that can be formed into exceptionally comfortable fabrics, comprising: polyethylene terephthalate; polyethylene glycol having an average molecular weight of less than 5000 g/mol and present.in an amount between 4 percent and 20 percent by weight; and chain branching agent in an amount less than 0.0014 mole-equivalent branches per mole of standardized polymer, the standardized polymer being unmodified polyethylene terephthalate; and wherein said copolyester fiber has an intrinsic viscosity of at least 0.67 dl/g. 36. A copolyester fiber as claimed in Claim 35, wherein said copolyester fiber is comprised of polymer chains formed from structural units consisting essentially of diol monomers, aromatic non-substituted diacid monomers, and branching agent monomers. 37. A copolyester fiber as claimed in Claim 35, wherein the polyethylene glycol has an average molecular weight of between 300 g/mol and 1000 g/mol. 38. A copolyester fiber as claimed in Claim 35, wherein said copolyester fiber has a mean tenacity of less than 3 grams per denier. 39. A copolyester fiber as claimed in Claim 35, wherein the chain branching agent selected from the group consisting of trifunctional alcohols, Afunctional acids, tetrafunotional alcohols, tetrafunctional acids, pentafunctional alcohols, pentafunctional acids, hexafunctional alcohols, and hexafunctional acids that will copolymerize with polyethylene terephthalate. 40. A copolyester fiber as claimed in Claim 35, wherein the chain branching 46 agent is selected from the group consisting of pentaerythritol, dipentaerythritol, trimesic acid, pyromellitic acid, pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, trimethylol propane, and ditrimethylol propane. 41. A polyethylene glycol modified copolyester defined by the composition of the fiber as claimed in any of Claims 35-40. 42. A copolyester fiber as claimed in any of Claims 35-40, wherein the weight fraction of the polyethylene glycol in said copolyester fiber is between 8 percent and 14 percent. 43. A copolyester fiber as claimed in any of Claims 35-40, wherein the weight fraction of the polyethylene glycol in said copolyester fiber is between 10 percent and 12 percent. 44. A yam formed from copolyester fibers as claimed in any of Claims 35-40. 45. A yarn as claimed in Claim 44, wherein the yarn comprises a blend of copolyester fibers and a second kind of fiber. 48. A fabric formed from copolyester fibers as claimed in any of Claims 35-40. 47. A fabric as claimed in Claim 46, wherein the fabric comprises a blend of copolyester fibers and a second kind of fiber. 48. A yarn or fabric as claimed in either Claim 45 or Claim 47, wherein the second kind of fiber is selected from the group consisting of cotton fibers, rayon fibers, polypropylene libers, acetate fibers, nylon fibers, spandex fibers, and conventional polyester fibers 47 49. A yarn or fabric as claimed in either Claim 45 or Claim 47, wherein the second kind of fiber is in the form of a nylon yarn. 50. A yarn or fabric as claimed in either Claim 45 or Claim 47, wherein the second kind of fiber is spandex fibers. 51. A yarn or fabric as claimed in either Claim 45 or Claim 47, wherein the second kind of fiber is cotton fibers. The present invention discloses a method of copolymerizing polyethylene glycol (PEG) and branching agent into polyethylene terephthalate (PET) to achieve a polyethylene glycol-modified polyester composition that can be spun into filaments. Fabrics made from fibers formed from the copolyester composition possess wicking (Figure 5), drying (Figure 6), flame-retardancy (Figure 7), static-dissipation (Figure 8), stretching, abrasion-resistance (Figure 9), dyeability, and tactility properties that are superior to those of fabrics formed from conventional polyethylene terephthalate fibers of the same yarn and fabric construction. Also disclosed are polyethylene glycol modified copolyester compositions, fibers, yarns, and fabrics. |
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| Patent Number | 200699 | ||||||||||||
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| Indian Patent Application Number | IN/PCT/2002/00677/KOL | ||||||||||||
| PG Journal Number | N/A | ||||||||||||
| Publication Date | 19-Jan-2007 | ||||||||||||
| Grant Date | 19-Jan-2007 | ||||||||||||
| Date of Filing | 20-May-2002 | ||||||||||||
| Name of Patentee | WELLMAN, INC. | ||||||||||||
| Applicant Address | 1040 BROAD STREET, # 302 SHREWSBURY, NJ 07702- 4318, UNITED STATES OF AMERICA, A UNITED STATES COPORATION. | ||||||||||||
Inventors:
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| PCT International Classification Number | D01F6/86 | ||||||||||||
| PCT International Application Number | PCT/US00/31255 | ||||||||||||
| PCT International Filing date | 2000-11-14 | ||||||||||||
PCT Conventions:
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