Polyester composition with improved dyeing properties

Abstract

A copolymer composition is disclosed with advantages for textile fibers, yarns, blended yarns, fabrics, and garments. The composition includes polyester copolymer, between about 9.5 and 10.5 percent adipic acid based on the amount of copolymer, between about 630 and 770 parts per million (ppm) of pentaerythritol based on the amount of copolymer, and between about 3.4 and 4.2 percent polyethylene glycol based on the amount of copolymer.

Claims

1. A polyester copolymer filament comprising: a composition of between about 9.5 and 10.5 percent adipic acid based on the total weight amount of polyester copolymer, between about 630 and 770 parts per million (ppm) of pentaerythritol based on the total weight amount of polyester copolymer, between about 3.4 and 4.2 percent polyethylene glycol based on the total weight amount of polyester copolymer, and between about 2 and 3 percent diethylene glycol based on the total weight amount of polyester copolymer.

2. A textured filament made from the filament of claim 1.

3. A yarn formed from the filament of claim 1.

4. A textured filament according to claim 2 that receives and retains disperse dye at atmospheric pressure and at temperatures below 212.degree. F. (100.degree. C.).

5. Staple fibers cut from the textured filament of claim 2.

6. A blend of cotton fibers and the staple fibers of claim 5.

7. A fabric formed from the yarn of claim 3 and selected from the group consisting of woven fabrics and knitted fabrics.

8. A blended yarn consisting essentially of: between about 20 percent and 80 percent by weight cotton; and textured polyester copolymer staple fibers consisting essentially of, between about 9.5 and 10.5 percent adipic acid based on the amount of polyester copolymer, between about 630 and 770 parts per million (ppm) of pentaerythritol based on the amount of polyester copolymer, between about 3.4 and 4.2 percent polyethylene glycol based on the amount of polyester copolymer, and between about 2 and 3 percent diethylene glycol based on the amount of polyester copolymer.

9. A blended yarn according to claim 8 dyed with a dye selected from the group consisting of reactive dye, disperse dye, and combinations thereof.

10. A fabric formed from the yarn of claim 8.

11. A fabric according to claim 10 selected from the group consisting of woven fabrics and knitted fabrics.

12. A fabric formed from the blended yarn of claim 9.

13. A fabric according to claim 12 selected from the group consisting of woven fabrics and knitted fabrics.

14. A garment formed from the blended yarn of claim 8.

15. A dyed fabric formed from a blended yarn that consists essentially of: between about 20 percent and 80 percent by weight cotton; with the remainder being textured polyester copolymer staple fibers composed of between about 9.5 and 10.5 percent adipic acid based on the amount of polyester copolymer, between about 630 and 770 parts per million (ppm) of pentaerythritol based on the amount of polyester copolymer, between about 3.4 and 4.2 percent polyethylene glycol based on the amount of polyester copolymer, and between about 2 and 3 percent diethylene glycol based on the amount of polyester copolymer; and a dye selected from the group consisting of reactive dye, disperse dye, and combinations thereof.

16. A dyed fabric according to claim 15 selected from the group consisting of woven fabrics and knitted fabrics.

17. A garment formed from the dyed fabric of claim 16.

Description

DETAILED DESCRIPTION

(1) As set forth herein, the goal of the invention is to produce a fiber that is based upon polyester (polyethylene terephthalate) that, if desired, can be dyed with cotton in a single bath or single vessel.

(2) In one aspect the invention is a composition with advantages for textile fibers. In this aspect, the invention is a melt of polyester precursors selected from the group consisting of terephthalic acid, dimethyl terephthalate, and ethylene glycol; adipic acid in an amount sufficient to give filaments and fibers made from the melt a dye receptively similar to cotton at atmospheric pressure; pentaerythritol in an amount sufficient to give pill resistance to yarns blended of cotton with fibers made from the melt; and polyethylene glycol in an amount sufficient to give the melt the elasticity necessary to produce extruded filament from the melt. The melt is maintained at a temperature of between about 265° C. and 295° C., and at an intrinsic viscosity of between about 0.58 and 0.82.

(3) As well understood in the art, cotton is typically dyed with reactive or direct dyes at temperatures of about 65° C. (about 150° F.; i.e., well below the boiling point of water) and atmospheric pressure. Polyester is typically, and necessarily, dyed with dispersed dyes which require much higher temperatures (above 120° C. in most cases) and thus also may require pressurized equipment (above atmospheric pressure conditions) in order for the dye dispersion to penetrate the polyester. Cotton dying tends to be sensitive to pH, while polyester typically requires additives referred to as carriers or leveling agents (such as fatty acid derivatives) which function to help the dye migrate throughout the substrate material.

(4) In the textile art, terms such as “texturing” and “crimping,” are used both broadly and specifically. In the broadest sense, texturing and crimping are used as synonyms to refer to steps in which synthetic filament, staple fiber, or yarn is mechanically treated, thermally treated, or both, to have a greater volume then the untreated filament, staple, or yarn. In a narrower sense, the term crimping is used to describe the production of a two dimensional saw tooth orientation in a filament, fiber or yarn, while the term texturing is used to refer to treatments that produce looping and curling. The meaning is generally clear in context. In the specification and claims, the word “texture” is used in a broad sense to include all possibilities for producing the desired effect in a filament, staple fiber, or yarn.

(5) Thus, according to the invention, it has been unexpectedly determined that the presence of diethylene glycol in percentages above about 3% lead to problems dyeing cotton polyester blends with certain dye colors under cotton-favorable conditions.

(6) Based on additional trial compositions and then dyeing and color fastness testing, the invention provides a polyester copolymer that will dye with cotton with much better results over a wider range of colors than many comparative attempts. The improved copolymer can be produced by incorporating adipic acid in an amount of between about 9.5 and 10.5%; pentaerythritol in an amount of between about 630 and 770 ppm; between about 3.4 and 4.2% of polyethylene glycol; and while maintaining the amount of diethylene glycol, (a constant byproduct of the esterification of terephthalic acid and ethylene glycol) at between about 2% and 3%. These respective amounts are all based on their proportions in the finished copolymer.

(7) The range of 2%-3% diethylene glycol (DEG) helps the resulting polyester to hold dye better than polyesters with higher DEG levels. In some cases, the DEG is maintained at a range of between about 1.4% and 3%.

(8) In the most helpful composition to date, the adipic acid is present at about 10%, the pentaerythritol at about 700 ppm, and the polyethylene glycol at about 3.8%.

(9) The high level (relativity) of pentaerythritol increases the reactivity of the polymerization reaction. Thus, the conventional expectation is that a lower temperature melt is required to moderate this reactivity. In the invention, however, the pentaerythritol and the increased reactivity are allowed to increase the intrinsic viscosity of the polymer and the overall viscosity of the melt. Conventionally the intrinsic viscosity of polyester used for the filament and then staple fiber is kept at about 0.52-0.65. A less viscous melt tends to be too “watery” and an overly viscous melt tends to separate during extrusion from the spinneret (spinning).

(10) In the invention, the intrinsic viscosity is allowed to significantly increase, and in particular to reach between about 0.58 and 0.82, with about 0.72 being exemplary. Given that conventional copolymers tend to run at lower intrinsic viscosities, the higher intrinsic viscosity of the invention is counterintuitive.

(11) In comparison to conventional polyester melts, the spinning step is more favorably carried out at lower temperatures; i.e., below about 270° C.

(12) Several options exist for spinning the melt at these lower temperatures.

(13) As one option, the melt can be made using a continuous polymerizer (“CP”) at the lower temperatures (e.g. 268° C.) and then spun at (or near) that lower temperature. The lower temperature of the continuous polymerizer, however, somewhat lowers throughput. This is an acceptable trade-off in many circumstances.

(14) As another option, the continuous polymerizer can be run at more conventional temperatures (e.g., 285° C.) following which the melt can be forwarded to a heat exchanger to lower the temperature of the melt to below 270° C. (again, about 268° C. is acceptable), following which the melt is spun at the lower temperature. A heat exchanger of the necessary type is relatively expensive, however, and thus will be the best option in some, but not necessarily all, circumstances.

(15) As a third option (“batch”), the polyester can be polymerized at more conventional temperatures (again, 285° C. is exemplary, but not limiting), then extruded at about (e.g.) 265° C.−268° C. and quenched into chip, after which the chip can be remelted and spun into filament at below 270° C. (again, 268° C. is exemplary).

(16) The added pentaerythritol reduces the tenacity of the resulting filament, but in the invention this characteristic advantageous because it tends to reduce pilling when staple made from the filament is blended with cotton.

(17) As known to those familiar with textiles in general and polyester fibers and blends of polyester and cotton in particular, the term “pilling” is used to describe small undesired entanglements of fibers (“pills”) that can result when the surface of a fabric is abraded (including normal wear and tear). In cotton-polyester blends, pilling can be more noticeable because the strength of the polyester tends to preclude pills formed from the polyester fibers from breaking off of the fabric as easily as do pills of cotton fibers. Pilling can be tested using ASTM D3512 (“Standard Test Method for Pilling Resistance and Other Related Surface Changes of Textile Fabrics”) e.g., random tumble testing; or AATCC Test Method 124-2014 (“Smoothness Appearance of Fabrics after Repeated Home Laundering”).

(18) Table 1640 illustrates a number of comparative compositions developed for the purpose of identifying the most advantageous compositions for the invention. Table 1640 includes a series of 4 experiments and 2 predictive formulations each of which was designed to produce a 1000 gram (1 Kg) batch of polymer. These batches were produced in a one kilogram NCCATT reactor, following which the filament was spun on a laboratory scale extrusion machine.

(19) The stoichiometric relationship between organic acid and organic glycol (e.g. terephthalic or adipic acid, and ethylene glycol or methyl ethylene glycol or polyethylene glycol) is always one to one in forming polyester. Thus, the amount of terephthalic acid will be moderated as compared to U.S. Ser. No. 10/174,454 to maintain this relationship.

(20) Table 1640 is exemplary:

(21) TABLE-US-00001 TABLE 1640 Sample Sample Sample Sample Predictive Predictive Units 1641 1642 1643 1644 1645 1646 TA Grams 772 772 772 772 811 733 EG ml 391 391 391 391 411 371 Sb.sub.2O.sub.3 Grams 0.3 0.3 0.3 0.3 0.3 0.3 Cobalt Grams 0.09 0.09 0.09 0.09 0.09 0.09 Acetate TiO.sub.2 Grams 2.0 2.0 2.0 2.0 2.0 2.0 OB Grams 0.2 0.2 0.2 0.2 0.2 0.2 PEG ml 38.0 38.0 38.0 30.0 34.0 42.0 (MW = 400) Note 1 Adipic Grams 100 100 100 100 95 105 Acid Penta- Grams 1.0 0.7 0.5 0.7 0.63 0.77 erythritol Total of Grams 1305 1305 1304 1296 1354 1254 Raw Materials TA = Terephthalic acid; EG = ethylene glycol; PEG = polyethylene glycol; OB = optical brightener Note 1: add after esterification & before polymerization

(22) As Table 1640 indicates, the starting materials included appropriate catalysts and at least one optical brightener (fluorescent whitening agent). Optical brighteners are generally well understood in the art, and function by absorbing UV radiation (e.g., in the region from 360 to 380 nanometers) and re-emitting longer-wavelength, visible blue-violet light in the visible portion of the spectrum. Such compositions can be selected by the skilled person without undue experimentation, and provided that the selected brightener does not undesirably affect the desired properties of the finished copolymer, fiber, or fabrics. The starting materials also included small amounts of antimony trioxide oxide (catalyst; 0.35 g), 0.02 g of 10% phosphoric acid (thermal stabilizer), and tetramethyl ammonium hydroxide (0.160 g of a 5% solution in water; pH buffer).

(23) TABLE-US-00002 TABLE 1617 Terasil Blue Terasil Blue Terasil Blue Terasil Blue WW-2GS WW-2GS WW-2GS WW-2GS 5 ml ALPHA 10 ml BETA 15 ml CHARLIE 20 ml ECHO 99° C. 99° C. 99° C. 99° C. Standard Standard Standard Standard Polyester Polyester Polyester Polyester Exp. 50/50 OE Exp. 50/50 OE Exp. 50/50 OE Exp. 50/50 OE Exp. 100% RS Exp. 100% RS Exp. 100% RS Exp. 100% RS U.S. Pat. No. U.S. Pat. No. U.S. Pat. No. U.S. Pat. No. 10,174,454 10,174,454 10,174,454 10,174,454 Terasil Blue Terasil Blue Terasil Blue Terasil Blue WW-2GS WW-2GS WW-2GS WW-2GS 5 ml FOXTROT 10 ml GOLF 15 ml HOTEL 20 ml INDIA 90° C. 90° C. 90° C. 90° C. Standard Standard Standard Standard Polyester Polyester Polyester Polyester Exp. 50/50 OE Exp. 50/50 OE Exp. 50/50 OE Exp. 50/50 OE Exp. 100% RS Exp. 100% RS Exp. 100% RS Exp. 100% RS U.S. Pat. No. U.S. Pat. No. U.S. Pat. No. U.S. Pat. No. 10,174,454 10,174,454 10,174,454 10,174,454 Terasil Blue Terasil Blue Terasil Blue Terasil Blue WW-2GS WW-2GS WW-2GS WW-2GS 5 ml JERICHO 10 ml KILO 15 ml LIMA 20 ml MIKE 85° C. 85° C. 85° C. 85° C. Standard Standard Standard Standard Polyester Polyester Polyester Polyester Exp. 50/50 OE Exp. 50/50 OE Exp. 50/50 OE Exp. 50/50 OE Exp. 100% RS Exp. 100% RS Exp. 100% RS Exp. 100% RS U.S. Pat. No. U.S. Pat. No. U.S. Pat. No. U.S. Pat. No. 10,174,454 10,174,454 10,174,454 10,174,454

(24) Table 1617 summarizes test data on the fabric according to the invention and in comparison to other polyester compositions. Table 1617 is arranged so that moving across a horizontal row, all conditions are the same, but with an increasing amount of dye solution added to the can (5 mL, 10 mL, 15 mL, 20 mL). In each case the dye i.

(25) Terasil Blue WW-2GS from Huntsman (https://www.huntsman.com/textile_effects/a/Solutions/Product %20Highlights/Dyes/TER ASIL %20Cyan %20Blue %20WW-GS; accessed Oct. 25, 2019).

(26) The horizontal columns are arranged for identical conditions other than temperature, which decreases from trial to trial moving downward (99° C., 90° C., 85° C.).

(27) The dye was mixed as a 1% solution in water. This 1% solution was added in the indicated amounts (5 mL, 10, 15, 20) along with knitted tubes (socks) weighing 10 g each (+0.05 g) and the dye solution in a laboratory dye can large enough to hold at 100 mL of liquid and the sock.

(28) 2 mL of a leveling agent (e.g. https://www.huntsman.com/textile_effects/a/Products/Dyeing %20Auxiliaries/Polyester; accessed Oct. 31, 2019) were added to the dye bath, along with 1 mL of acetic acid, 2 mL of buffer (http://www.huntsman.com/textile_effects/Media%20Library/global/files/213001e_BRO_T ERASIL_TC_LR.pdf; accessed Oct. 31, 2019) and sufficient water to bring the total volume of liquid in the dye can to 100 mL.

(29) The dye bath was ramped at a rate of 2° C. per minute until it reached the indicated temperature at which it was held for about 25 minutes, followed by a 2° per minute ramp return to ambient temperature.

(30) The results are categorized in Tables Alpha through Mike showing Aa*, Ab*, AL, and related information familiar to the skilled person. The comparisons were carried out on the Datacolor 800 spectrophotometer (https://www.datacolor.comibusiness-solutions/product-overview/datacolor-800-spectrophotometer/; accessed Oct. 31, 2019) with the comparison being made between socks made according to U.S. Ser. No. 10/174,454 and those made according to the present invention.

(31) TABLE-US-00003 TABLE Alpha Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −1.78 0.18 −2.24 1.07 0.56 2.15 FO.sub.2 10° −2.03 1.75 −4.26 1.81 1.66 3.18 A 10° −2.07 −0.39 −3.64 1.57 0.74 2.70

(32) TABLE-US-00004 TABLE Beta Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −2.24 −0.25 0.46 −0.21 −0.24 2.26 FO.sub.2 10° −2.39 1.24 −0.79 0.33 0.94 2.59 A 10° −2.45 0.23 −0.47 0.16 0.25 2.47

(33) TABLE-US-00005 TABLE Charlie Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −3.41 0.71 1.88 −0.98 0.47 3.58 FO.sub.2 10° −3.49 1.76 1.25 −0.59 1.30 3.77 A 10° −3.54 1.67 1.56 −0.92 0.79 3.74

(34) TABLE-US-00006 TABLE Echo Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −3.27 0.94 2.30 −1.18 0.80 3.57 FO.sub.2 10° −3.25 1.86 1.91 −0.85 1.48 3.67 A 10° −3.32 2.09 2.21 −1.26 1.06 3.70

(35) TABLE-US-00007 TABLE Foxtrot Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° 0.90 0.72 −7.20 3.52 1.67 4.00 FO.sub.2 10° 0.59 2.66 −10.58 4.81 2.73 5.56 A 10° 0.47 −2.14 −9.29 4.31 1.07 4.47

(36) TABLE-US-00008 TABLE Golf Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −1.08 2.32 −5.66 2.67 2.42 3.76 FO.sub.2 10° −1.37 3.86 −8.65 3.82 3.17 5.15 A 10° −1.49 −0.38 −7.14 3.10 1.45 3.73

(37) TABLE-US-00009 TABLE Hotel Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −0.14 1.87 −5.61 2.74 1.95 3.37 FO.sub.2 10° −0.37 3.44 −8.51 3.85 2.76 4.76 A 10° −0.53 −0.87 −7.12 3.23 1.06 3.44

(38) TABLE-US-00010 TABLE India Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −1.72 2.56 −4.44 2.15 2.35 3.62 FO.sub.2 10° −1.96 3.92 −6.91 3.15 3.01 4.77 A 10° −2.11 0.09 −5.62 2.44 1.30 3.48

(39) TABLE-US-00011 TABLE Jericho Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −0.33 1.37 −8.11 3.92 2.43 4.63 FO.sub.2 10° −0.69 3.16 −11.94 5.37 3.30 6.34 A 10° −0.80 −1.95 −10.23 4.72 1.45 5.01

(40) TABLE-US-00012 TABLE Kilo Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −0.68 2.20 −6.88 3.31 2.58 4.25 FO.sub.2 10° −0.97 3.77 −10.25 4.61 3.31 5.75 A 10° −1.10 −0.93 −8.56 3.85 1.49 4.27

(41) TABLE-US-00013 TABLE Lima Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −2.29 2.89 −5.51 2.61 2.84 4.49 FO.sub.2 10° −2.57 4.32 −8.39 3.78 3.50 5.76 A 10° −2.71 −0.15 −6.81 2.98 1.51 4.30

(42) TABLE-US-00014 TABLE Mike Illum/Obs ΔL*/ISL Δa* Δb* ΔC*/cSC ΔH*/SH ΔEcmc Δ65 10° −0.72 2.21 −6.63 3.28 2.35 4.10 FO.sub.2 10° −1.03 3.69 −9.91 4.56 3.04 5.58 A 10° −1.17 −0.97 −8.24 3.78 1.28 4.16

(43) Although the invention is not limited by any particular theory, it can be hypothesized that the adipic acid provides the dye receptivity, the pentaerythritol provides the pill resistance, and the polyethylene glycol provides the elasticity to spin the melt into filament.

(44) Accordingly, it will be understood that in one aspect the invention is the composition: polyester, adipic acid, pentaerythritol, polyethylene glycol, or low amounts of diethylene glycol. In turn, the composition can be understood as a polymerized melt, as a polyester copolymer filament made from the melt, or as a textured filament made from the composition.

(45) Texturing is well understood in the art and will not be otherwise described in detail, other than to point out that to date, the composition of the invention produces filament that can be textured using conventional steps (e.g., heat setting while in a twisted position).

(46) The composition aspects of the invention also include the manufacture of staple fibers cut from the filament (typically from a textured filament), yarns, particularly blends of cotton and the polyester copolymer of the invention, dyed yarns, fabrics, dyed fabrics, and garments.

(47) It will further be understood that the dying step can be carried out on the blended yarn, on a fabric formed from the blended yard, or even on a garment formed from the blended yarn.

(48) In the method context, the invention includes the steps of polymerizing a charge of terephthalic acid, ethylene glycol, adipic acid in an amount of between about 9.5 and 10.5%, pentaerythritol in an amount of between about 630 and 770 ppm, polyethylene glycol in an amount of between about 3.4 and 4.2%, and between about 2% and 3% diethylene glycol. These amounts are expressed as the weight percentage of the component as compared to the total weight of the finished copolymer.

(49) The charge is run at (or until it reaches) an intrinsic viscosity of between about 0.68 and 0.82 and at a temperature of between about 265° C. and 295° C. The melt is spun into filament in an otherwise conventional process.

(50) The filament produced by the method can be textured and cut into staple fiber, spun into a blended yarn with cotton (typically with cotton in the range of 5-95% by weight) and dyed as yarn. Alternatively, the blended yarn can be woven or knitted into fabric and then dyed and then formed into a garment. In some circumstances, the dyeing step will be carried out on the garment, but dyeing the yarn is probably most common.

(51) Those skilled in the art will also appreciate, however, that the filament can be used as a yarn (“filament yarn”); i.e., without being cut into staple or without being blended with another fiber (e.g., cotton). Such filament yarns are particularly advantageous in the active wear industry. In particular, filament yarn according to the invention provides the opportunity to use spandex that can be dyed at the inventive dyeing temperatures (about 80° C. to 95° C.) while maintaining all of the desired spandex properties. As set forth in the background, variations of spandex that can be dyed at high temperature are available, but at higher cost, and without any corresponding stretch or recovery advantages for active wear purposes.

(52) Because poly-cotton blends are manufactured, sold, and used in a variety of proportions, a potentially wide range (5-95% cotton) is expressed herein. Nevertheless, it will be understood that although the invention certainly offers advantages for high cotton blends, the invention provide particular advantages for poly-cotton blends with a larger proportion (50% or more) of polyester.

(53) As noted previously, with respect to the composition, in the method steps, the best results to date have been obtained with about 10% adipic acid, about 700 ppm pentaerythritol and about 3.8% polyethylene glycol, all based on the total weight of the copolymer composition.

(54) In another aspect, the invention can be considered as the method of dying a blended yard formed from cotton and textured polyester staple that starts with the composition described herein. Thus, the dyeing step is carried out on a yarn that includes between about 5 and 95 percent by weight cotton, along with the polyester that includes the amounts of adipic acid, pentaerythritol, polyethylene glycol, and diethylene glycol recited with respect to the composition and the method of making the filament.

(55) In another aspect, the invention is the blended yarn itself containing about 5-95% by weight cotton, with the textured polyester as the remainder. The textured polyester has the composition described with respect to the other embodiments. For the sake of completeness these are about 9.5-10.5% adipic acid (10% exemplary), between 630 and 770 ppm of pentaerythritol (700 ppm exemplary), between about 3.4 and 4.2% polyethylene glycol (3.8% exemplary) and between about 2% and 3% of the diethylene glycol byproduct. Again, these amounts are based on the weight of the finished copolymer.

(56) As with the other embodiments, the yarn can be dyed, and formed into fabric and garments with the dyeing being carried out on the blend as opposed to the conventional steps of dyeing cotton separately from polyester.

(57) Thus, using the invention, a blended fabric can be successfully dyed using a single dye; i.e., reactive dye for the cotton or disperse dye for the polyester. Alternatively, if two dyes are preferred—reactive dye for the cotton and disperse dye for the polyester—the invention allows both dyestuffs to be maintained in a single vessel, thus eliminating the conventional rinsing or scouring step between a disperse dyeing step for the polyester and a direct dyeing step for the cotton. In particular, the polyester can be dyed first with the disperse dye at an acidic pH, while at a temperature that avoids degrading the reactive dye. After the polyester is dyed, the pH can be increased to the basic side using a combination of sodium hydroxide (NaOH) and sodium chloride (NaCl) to dye the cotton. In turn, the invention provides the advantages of less water used and less effluent produced.

(58) On a production or continuous scale, the invention is expected to be formed and used in steps with which the skilled person is quite familiar. Thus, as a predictive example, the terephthalic acid and ethylene glycol are mixed into a paste (or slurry) at a mole ratio of between about 1:1 and 1.2:1 (TA to EG). The paste is then transferred to a primary esterifier (“PE”) under above-atmospheric pressure (i.e., a pressurized vessel) and temperatures above 250° C. The composition forms the esterified monomer (usually representing about 90 percent esterification). This product is then transferred to a secondary esterifier, at which point the pentaerythritol and adipic acid can be added. Pressures in the secondary esterifier are lower than the primary esterifier, but temperatures are slightly higher. Esterification reaches (for example) about 94% in the secondary esterifier.

(59) The esterified composition is then transferred to the low polymerizer, and if desired the pentaerythritol and adipic acid alternately can be added between the secondary esterifier and the low polymerizer. The low polymerizer operates at a temperature of about 265-280° C., and under a vacuum to remove the water vapor (the polymerization is a condensation reaction) and the monomers reach a degree of polymerization of about 75-100. The composition is then transferred to a high polymerizer where polymerization reaches much higher numbers, typically on the order of 20,000 units.

(60) Intrinsic viscosity is typically measured in a capillary viscometer using a sample of the polymer dissolved in an appropriate solvent. As an alternative, instruments are available that can measure the intrinsic viscosity directly and without the step of dissolving the polymer in a solvent. The intrinsic viscosities described herein can be measured or confirmed using, for example ASTM D5225 (“Standard Test Method for Measuring Solution Viscosity of Polymers with a Differential Viscometer”) or any test or instrument that gives the same results within an acceptable tolerance or margin of error.

(61) With respect to the invention (and in many cases in general) color fastness represents the resistance of a dyed color to fading or bleeding under various types of influences on the yarn, fabric, or garment. Exposure to water, light, rubbing, washing, and perspiration are typical. Color fastness testing seeks to identify the properties of the material in a manner that is helpful and reproducible.

(62) In a typical test, (AATCC Test Method 61-2013; Colorfastness to Laundering: Accelerated) the fabric color loss and surface changes resulting from detergent solution and abrasive action of five typical hand or home launderings, with or without chlorine, are roughly approximated by one 45 minute test. Samples are exposed to conditions of temperature, detergent solution, bleaching and abrasive action that are expected to produce a color change representative of five hand or home launderings. Standard tests have also been developed by the Society of Dyers and Colorists (SDC; www.sdc.org.uk; accessed Jul. 24, 2015) and the International Organization for Standardization (ISO; www.iso.org; accessed Jul. 24, 2015).

(63) Light fastness (i.e., color fastness under exposure to light) can also be carried out using a high energy xenon fadometers under defined conditions of radiation intensity cycle time (light and dark) and temperature. AATCC Test Method 169-2009, “Weather Resistance of Textiles: Xenon Lamp Exposure,” is an appropriate test.

(64) The resulting color differences can be evaluated using standardized gray scale and gray scale testing methods (e.g., ASTM D2616-12; “Standard Test Method for Evaluation of Visual Color Difference With a Gray Scale”).

(65) This one vessel two-step process avoids of the need to empty the dye vessel (“pot”) after the polyester dying step and to refill it for the cotton dying step. At a minimum this provides a significant time savings which becomes cumulatively advantageous for repeated dyeing steps. Secondly, because the temperature of the bath can be the same for both the cotton and polyester dyeing steps, less heating is required, as is the time required for re-heating. The result is a fully dyed blended fabric from the single dye bath.

(66) Other tests used or useable to identify and compare the properties of the invention include one or more of the following.

(67) AATCC 61 is a test developed by the American Association of Textile Chemists and Colorists (Research Triangle Park North Carolina USA). The details of the test are available from the association at AATCC.org/test/methods/test-method-61/; accessed Mar. 3, 2016.

(68) The test evaluates the colorfastness with respect to laundering of textiles that are expected to withstand frequent laundering. Specimens are tested “under appropriate conditions of temperature, detergent solution, bleaching and abrasive action such that the color change is similar to that occurring in five hand or home launderings.

(69) The shrinkage test is AATCC 135. Again this is proprietary in its details, but generally consists of marking a sample section of the fabric at selected measured distances, laundering the fabric in a predetermined manner, including drying, and then re-measuring the position of the marks to determine the amount of shrinkage.

(70) Crocking (AATCC 8) is used to determine the amount of color that transfers from one sample fabric to another fabric by rubbing. The sample fabric to be tested is fastened to a crock meter and then rubbed against a white test cloth. The test is carried out both with a dry test cloth and then a wet test cloth. The amount of color transferred to the test cloth is assessed by comparison with the AATCC chromatic transference scale. The details of the test are proprietary to AATCC, but are publicly available and well understood by the skilled person.

(71) The fabrics were also tested under AATCC skewing (skew, skewness) test method 179 which again is proprietary to AATCC, but publicly available and well understood in the art. The test determines the change in skewness in woven and knitted fabrics, or twisting garments when subjected to testing that mimics repeated automatic laundering procedures commonly used in home laundering. The test defines particular washing and drying procedures for obtaining the measured results. To some extent skewness testing gives an indication of the degree to which the yarns or courses in a fabric will be distorted from their intended and manufacture design.

(72) Colorfastness with respect to commercial and domestic hot laundering can also be determined using ISO test number 105-006. The exact test apparatus, materials and reagents and procedures are proprietary to the International Standards Organization (web address), but again are publicly available (subscription or individual purchase cost) and well understood by the skilled person.

(73) Related tests deal with perspiration fastness (ISO 105-E04) water fastness (ISO 105-E01); and light fastness (ISO 105-B02).

(74) In general, perspiration testing is carried out using two standard solutions that mimic perspiration, but with one being slightly acidic (e.g., pH 5.5) and one being slightly basic (e.g. pH 8.0).

(75) In the specification there has been set forth a preferred embodiment of the invention, and although specific terms have been employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.