MXPA01002129A - Polyester modified with polyethylene glycol and pentaerythritol - Google Patents

Abstract

A polyester composition is disclosed that is particularly suitable for filament. The composition is formed of polyethylene terephthalate;polyethylene glycol in an amount sufficient to increase the wetting and wicking properties of a filament made from the composition to a level substantially similar to the wetting and wicking properties of cotton and other cellulosic fibers (natural or synthetic) but less than the amount that would reduce the favorable elastic memory properties of the polyester composition;and a chain branching agent selected from the group consisting of trifunctional alcohols and acids and tetrafunctional alcohols and acids that will copolymerize with polyethylene terephthalate, the chain branching agent being present in an amount sufficient to raise the melt viscosity of the polyester composition to a level that permits filament manufacture under conditions that are substantially the same as those under which filament can be formed from unmodified polyethylene terephthalate.

Description

POL1ESTER MODIFIED WITH POLYET-LENGLICOL AND PENTAERITRITOL FIELD OF THE INVENTION The present invention relates to the manufacture of yarns and fabrics and in particular it relates to an improved modified polyester composition which is particularly useful for forming mixed yarns from polyester and cotton.

BACKGROUND OF THE INVENTION The mixed fabrics formed of polyester and cotton have found great acceptance for fabrics, in particular for garments. Generally speaking, a "mixed" polyester and cotton fabric is formed by spinning a yarn blended from cotton fibers and short polyester fibers. The mixed yarns are then woven or knitted by the appropriate fabrics. Each of these materials provides certain advantages and disadvantages to a fabric. The cotton is formed, of course, almost completely of pure cellulose with a typical length of approximately 2.54 cm, but with variations in length from approximately 1.27 cm to more than 5.08 cm. The mature cotton fibers are characterized by their curls so that under a microscope, the cotton looks like a twisted ribbon with thickened edges. Cotton is lightweight, absorbs moisture fast and easily, and generally has a favorable texture ("quality to the touch") when it is woven into fabrics. However, cotton lacks certain strength characteristics and elastic memory, and therefore garments formed entirely of cotton require washing, ironing, and in many cases regular starch, between sets of the ordinary user. The polyester is durable, light in weight, and has excellent elastic memory characteristics. Polyester is wrinkle resistant, dries quickly, retains its shape in garments, is resistant to abrasion, and requires minimal care. However, due to its synthetic nature, polyester has a generally unacceptable appearance (at least for most garment purposes) when initially formed as a filament. Accordingly, polyester filaments require some texturing in order to produce acceptable characteristics of appearance, confection, and comfort in yarns and fabrics. Consequently, cotton and polyester blends have found great acceptance due to their combination of the desirable characteristics of cotton with those of polyester. However, the characteristic advantages of polyester are such that efforts to develop filament, threads and polyester fabrics that resemble those of cotton, silk, rayon, or other natural fibers continue. The use of polyester microfibers is an example of this, being the filaments of such a small diameter that they offer aesthetics and quality to the touch Exceptionally good, while retaining all the benefits of polyester. A number of chemical modifications have been made to the polyester to try to obtain the desired properties, but such treatments can produce undesired or unexpected characteristics in the modified polyester. For example, polyethylene glycol can improve certain polyester properties such as dye uptake, but other properties, in particular the melting phase characteristics of the polymer, can be diminished, which make it difficult to form in acceptable filaments in a continuous commercial base. In this regard, it will be understood that the polyester filament is manufactured in significantly large quantities in the world, and that if the modified polyesters are to gain commercial acceptance, they should be essentially compatible with commercial techniques for melt spinning, texturing, spinning and fabric forming techniques; that is, knitting and knitting. Accordingly, the need continues for improved polyester compositions having properties as close as possible to those of cotton and other natural fibers while retaining the advantages of polyester.

OBJECT AND BRIEF DESCRIPTION OF THE INVENTION Accordingly, an object of the present invention is to provide a polyester composition having certain properties substantially similar to those of cotton, while retaining the favorable properties of polyester. The invention accomplishes this object with a polyester composition comprising polyethylene terephthalate, polyethylene glycol in an amount sufficient to increase the wetting and wicking properties of a filament made from the composition at a level substantially similar to the properties of cotton. , but less than the amount that would reduce the favorable elastic memory properties of the polyester composition, and a branching agent in an amount that raises the viscosity of the molten material of the polyester composition to a level that allows the manufacture of the low filament substantially normal spinning conditions. In another aspect, the invention comprises a polyester filament formed from the composition. In another aspect, the invention comprises yarns formed either entirely of polyester or of polyester and cotton blends. In another aspect, the invention comprises woven, non-woven or knitted fabrics formed from polyester yarns or blended according to the present invention.

The above and other objects and advantages of the invention and the manner in which they are carried out will be clarified on the basis of the following detailed description taken together with the accompanying drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of wetting characteristics of a fabric formed in accordance with the present invention; Figure 2 is a graph of the staining characteristics of the polyester filament according to the present invention; and Figure 3 is a graph of certain tension characteristics for several filaments according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention is a polyester composition that is particularly suitable for, but not necessarily limited to, filaments, yarns and fabrics. The composition comprises polyethylene terephthalate, polyethylene glycol in an amount sufficient to increase the wetting and wicking properties of a filament made from the composition at a level substantially similar to the wetting and wicking properties of cotton or other fibers. cellulose (natural or synthetic), but less than the amount that would reduce the favorable elastic memory properties of the polyester composition, and a chain branching agent selected from the group consisting of trifunctional and tetrafunctional alcohols and acids which will be copolymerized with the polyethylene terephthalate. The chain branching agent is present in an amount sufficient to raise the viscosity of the molten material of the polyester composition to a level that allows the manufacture of the filament under conditions that are substantially the same as those under which the filament can be formed. from unmodified polyethylene terephthalate. In preferred embodiments, the polyethylene glycol is present in the polyester composition in an amount greater than about 4% to about 20% by weight based on the weight of the composition, and even more preferred amounts of 6% to 16%. The chain branching agent is preferably selected from the group consisting of pentaerythritol (C (CH2OH)), trimesic acid (C6H3 (COOH) 3), pyromellitic acid (C6H2 (COOH) 4), pyromellitic dianhydride, trimellitic acid, anhydride trimellitic, and trimethylolpropane (C2H5C (CH2OH) 3). In most preferred embodiments, the chain branching agent comprises pentaerythritol, but more recent work indicates that the important factor seems to be the equivalent number of branches; see, for example, patents of E.U.A. 4,092,299 and 4,113,704. The chain branching agent is present in amounts of between about 500 and 4,000 parts per million (ppm) by weight based on the weight of the composition, and when the chain branching agent comprises pentaerythritol, it is most preferably present in amounts of between about 1, 300 and 1, 800 ppm. These amounts are sufficient to provide the polyester composition of the invention with an intrinsic viscosity of between about 0.80 and 0.50 dl / g. As used herein, the favorable elastic memory properties of the polyester include, among others, its heat setting characteristics ("permanent ironing"), and sufficient elongation to be processable under reasonable conditions. Accordingly, when amounts of polyethylene glycol greater than about 20% are present, the resulting compositions exhibit a less useful processing temperature scale. As is known to those who are familiar with the manufacture of polyester, the equipment used for spinning polyester filament is designed, constructed, and adjusted to handle polymers whose viscosity of molten material falls within a certain scale, typically between about 500 and 4000. poises. Therefore, such equipment operates more satisfactorily when the viscosity of the molten material of the polymer (which is directly proportional to the intrinsic viscosity in a manner discussed herein), falls within this scale. The invention provides a technique for including the favorable properties of polyethylene glycol in polyester, particularly the wetting and wicking properties which are similar to those of cotton, but which otherwise they would reduce the viscosity of the molten polymer material to a lower point than can be handled satisfactorily by normal equipment. As a result, if polyethylene glycol is added only in relatively significant amounts, it is possible that a number of spinning failures will occur that impede the efficiency and productivity of the entire process. However, in the present invention, the chain branching agent raises the viscosity of the polymer melt material within the scale of unmodified polyethylene terephthalate, and, therefore, within a scale that typical equipment can handle at a high productivity normally expected. The terms viscosity of the molten material and intrinsic viscosity are used herein in their conventional and usual sense; that is, the viscosity of the molten material represents the resistance of the molten polymer to shear deformation or flow as measured under specified conditions. The viscosity of the molten material is mainly a factor of intrinsic viscosity and temperature. In turn, the intrinsic viscosity is the ratio of the specific viscosity of a polymer solution of known concentration to the concentration of extrapolated solute at zero concentration. The intrinsic viscosity is directly proportional to the average polymer molecular weight, see, for example, Dictionary of Fiber and Textile Technology, Hoechst Celanese Corporation (1990) and Tortora, Fairchild's Dictionary of Textiles, 7th Edition (1996). Both the The viscosity of the molten material as the intrinsic viscosity can be measured and determined by those skilled in the art and without undue experimentation, and indeed are widely recognized as fundamental and conventional measurements of polymer characteristics. For the values of V.l. given in the present, V.l. is determined by dissolving the polymer in orthochlorophenol ("OCP"), measuring the relative viscosity (V.R.) of the solution using a Schott autoviscometer (AVS Schott and AVS 500 Viscosystem), and then calculating the V.l. based on the V.R. (for example, Dictionary of Fiber and Textile Technology, supra, on page 82). In particular, a sample of 0.6 grams (+/- 0.005 g) of dry polymer sample (samples of fiber and yarn are typically cut into small pieces; the flake samples are milled) is dissolved in approximately 50 ml (61.0-63.5 grams) of OCP at a temperature of about 105 ° C. After cooling to room temperature, the solution is placed in the viscometer in which the relative viscosity is measured, and from which the intrinsic viscosity is calculated. In another aspect, the invention comprises a polyester filament. The filament comprises polyethylene terephthalate, polyethylene glycol in an amount sufficient to increase the wetting and wicking properties of a filament made from the composition at a level substantially similar to the wetting and wicking properties of cotton but less than the amount that would reduce the favorable elastic memory properties of the composition of polyester, and a branching agent selected from the aforementioned group and most preferably pentaerythritol, in an amount that raises the viscosity of the molten material of the polyester composition to a level that allows manufacture of the filament under conditions that are substantially the same as those under which the filament can be formed from unmodified polyethylene terephthalate. In preferred embodiments the filament comprises a copolymer of polyethylene terephthalate and polyethylene glycol and contains polyethylene glycol in an amount of between more than about 4% to about 20% by weight based on the weight of the composition, with even more amounts of polyethylene glycol being preferred. between approximately 6% and 16%. As in the above embodiment, pentaerythritol is present in an amount of between about 500 and 4,000 ppm by weight based on the weight of the composition, with even more pentaerythritol amounts being preferred between about 1, 300 and 1, 800 ppm. The polyester filament according to this embodiment of the invention can also be cut into a short fiber which in turn can be formed into polyester yarns using any conventional spinning technique including ring spinning, open end spinning and spinning. of air jet, increasingly preferring open-end spinning and air-jet spinning for polyester yarns and mixed yarns containing polyester.

Those familiar with the textile terminology will understand that the term "spinning" is used to refer to two different procedures. In a sense, the term "spinning" refers to the production of synthetic polymer filaments from a polymer melt material. In its older conventional use, the term "spinning" refers to the process of interlocking a plurality of individual fibers into yarns. The use of both terms is very widespread and well understood in this technique, and the particular use will be recognized quickly and easily by those skilled in the art based on the context of said use. Accordingly, the yarns formed from the filaments of the invention may in turn be woven or knitted per knit in fabrics having the favorable characteristics referred to herein. Due to the characteristic advantages that the invention provides to the polyester compositions described herein, the resultant polyester filaments are particularly useful for mixed yarns including fiber according to the invention mixed with another yarn, the most common of which which includes (but is not limited to) cotton, rayon, polypropylene and conventional polyester. Accordingly, in another embodiment the invention comprises a mixed yarn that includes short fibers according to the present invention. The polyester short fibers comprise polyethylene terephthalate, polyethylene glycol in the amounts described herein sufficient to increase wetting and absorption properties by capillary action of a filament made from the composition at a level substantially similar to the wetting and capillary wicking properties of the cotton fibers but less than the amount that would reduce the favorable elastic memory properties of the polyester short fibers. The polyester also includes pentaerythritol in an amount that raises the viscosity of the molten material of the polyester from which the short fibers are formed to a level that allows the manufacture of the filament under conditions that are substantially the same as those under which the filament is formed. It can form from unmodified polyethylene terephthalate. In preferred embodiments, the polyester short fibers comprise a copolymer of polyethylene terephthalate and polyethylene glycol. As used herein, the term "copolymer" refers to polymers that include monomers in addition to terephthalic acid (or dimethyl terephthalate) and ethylene glycol monomers. Preferred blends include between about 5% and 95% by weight of the cotton fibers with the remainder comprising the short polyester fibers. In this regard, the invention provides the opportunity to increase the synthetic content of mixed cotton and polyester yarns in order to take advantage of increasing certain characteristics of the polyester in the resulting yarns and fabrics. As in the above embodiments, polyethylene glycol is present in the polyester short fibers in an amount of between about 4% and 20% by weight based on the weight of the composition with the amounts of between about 6% and 16% being preferred. .

Similarly, pentaerythritol is present in the polyester short fibers in an amount of between about 1, 000 and 4,000 ppm by weight based on the weight of the composition, with even more preferred amounts of between about 1, 300 and 1, 800 ppm. In another embodiment, the invention comprises a knitted or woven fabric formed from mixed yarns including fibers according to the present invention, and typically from cotton fibers and polyesters. As described above, the polyester comprises polyethylene terephthalate with polyethylene glycol present in amounts sufficient to increase the wetting and wicking properties of the fabric at a level substantially similar to the properties of a fully cotton fabric, but less than an amount which would reduce the favorable elastic memory properties of the polyester in the fabric, with pentaerythritol in an amount that raises the viscosity amount of the polyester into short fibers to a level that allows manufacture of the filament under conditions that are substantially the same as those under the which the filament can be formed from unmodified polyethylene terephthalate. As in the above embodiments, polyester short fibers preferably comprise a copolymer of polyethylene terephthalate and polyethylene glycol, and cotton fibers are present in the fabric in amounts of between about 5 and 95% by weight, with an amount of about 30-70% by weight, and the rest being polyester.

As in the above embodiments, the polyethylene glycol is preferably present in the short fibers in an amount of about 4 and 20% by weight based on the weight of the composition, and most preferably present in an amount of about 6 and 16%. Similarly, pentaerythritol is preferably present in an amount of about 1000 and 4000 ppm by weight based on the weight of the composition with even more preferred amounts of about 1300 and 1800 ppm. However, based on the results to date, it appears that the advantages of the invention may begin to appear in amounts of pentaerythritol as low as 500 ppm. Figures 1-3 help illustrate the features and advantages of the invention. Figure 1 is a graph of the wetted area over a period of 4 minutes at a mean woven per point per 0.5 ml of water, plotted against the percentage of polyethylene glycol in the polyester composition. As shown in Figure 1, some improvement begins when 4% polyethylene glycol is included, with the significant improvement appearing when increasing amounts are included (eg, 6% and 8%). Figure 2 is a graph of the Kubelka-Munk reflectance value (K / S) against the polyethylene glycol present in filaments according to the present invention. As is known to those skilled in the art, K / S is proportional to the concentration of colorant in a material. The K / S value can be calculated from the reflectance factor and provides a technique important and generally well understood for color matching. Figure 2 graphs the K / S value against the percentage of polyethylene glycol in polyester yarns formed according to the present invention at various levels of pentaerythritol. Figure 2 shows the K / S value for control yarns in FORTREL® polyester otherwise conventionally from Wellman, Inc. Figure 2 illustrates that when the level of pentaerythritol is raised to the preferred amounts of 1300 or 1800 ppm, the value K / S increases significantly, thus illustrating the considerably improved staining characteristics of filaments according to the present invention. Figure 3 demonstrates that the tension characteristics of the filament according to the present invention are markedly different from those of conventional polyesters, as well as different from conventional polyesters modified with lower amounts of polyethylene glycol. In particular, Figure 3 graphs the TE value on a gram per denier (gpd) basis against the stretch ratio for the filament formed according to the present invention, and shows that the results for the preferred scale of polyethylene glycol are superior to those that contain a more conventional amount of about 2% polyethylene glycol; for example, Blaeser et al, U.S. Patent Nos. 4,975,233 and 5,091, 504. The information presented illustrated in Figure 1-3 demonstrates the excellent responses based on the amount of additive against tension properties. Although the invention makes it possible to give a 100% match for cotton in these tensile properties, under most circumstances, it is preferable to equal the toughness while leaving sufficient elongation for good processing in the manufacture of fibers and yarns. The additional amount of pentaerythritol or other branching agent also improves the staining characteristics. In summary, the invention provides a technique for incorporating cotton-like characteristics into a polyester filament by modifying polyethylene terephthalate with copolymers to impart specific characteristics. The use of the branching agent produces a viscosity of the melted material sufficient for practical processing and sufficient spinning tensions for a stable commercial process. The degree of wetting / absorption by capillarity and the level of linting yield can be adjusted for specific applications by altering the polyester copolymer content. This allows a choice of cost and benefit when designing fabrics made of polyester or polyester / cotton blends according to the present invention. In this regard, the invention establishes a product technology family. It is also expected that the amount and molecular weight of polyethylene glycol can be altered to produce specific effects such as wetting, drying, staining regimes, dye fixation, and the type of staining chemistry required, while improving the fixing speed of the colorant. , reducing the use of dye, and increasing the selection of availability to include ionic colorants. The data reported herein reflects the use of polyethylene glycol with an average molecular weight of about 400 grams per mole, and polyethylene glycols with other molecular weights seem to work as well, at least at molecular weights below 8000 g / mole as observed at date. The invention allows the compolymers to be added to any container during the process except finishing in the polymerization process. Finally, in a fundamental sense, the use of the branching agent improves the overall productivity of the spinning process. In the drawings and specification, typical embodiments of the invention have been described, and, although specific terms have been employed, they have been used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in following claims.

Claims (17)

NOVELTY OF THE INVENTION CLAIMS

1. - A polyester copolymer composition that is particularly suitable for filament, said composition comprising: polyethylene terephthalate; polyethylene glycol in an amount sufficient to increase the wetting and wicking properties of a filament made from the composition at a level substantially similar to the wetting and wicking properties of cotton but less than the amount that would reduce the properties of favorable elastic memory of said polyester composition; and a chain branching agent selected from the group consisting of alcohols and trifunctional acids and alcohols and tetrafunctional acids which will be copolymerized with polyethylene terephthalate, said chain branching agent being present in an amount sufficient to raise the viscosity of the molten material of said polyester composition at a level that allows the manufacture of the filament under conditions that are substantially the same as those under which the filament can be formed from unmodified polyethylene terephthalate, said amount of branching agent being between about 500 and 4000 ppm by weight based on the weight of the composition.

2. - The polyester composition according to claim 1, further characterized in that said chain branching agent is present in an amount that provides said polyester composition with an intrinsic viscosity of between about 0.5 and 0.8 dl / g.

3. The polyester composition according to claim 1, further characterized in that said chain branching agent is selected from the group consisting of pentaerythritol, trimesic acid, pyromellitic acid, pyromellitic dianhydride, trimellitic acid, trimellitic anhydride, and trimethylolpropane.

4. The polyester composition according to claim 1, further characterized in that said polyethylene glycol is present in an amount of between greater than about 4 percent to about 20 percent by weight, based on the weight of the composition.

5. The polyester filament according to claim 1, further characterized in that said chain branching agent comprises pentaerythritol.

6. A cut short fiber formed from the polyester filament of claim 5.

7. A polyester yarn formed from the short fibers according to claim 6.

8. A woven, knitted, or non-woven fabric comprising the polyester yarn according to claim 7.

9. A polyester filament formed from the composition of claim 1, characterized in that said polyethylene glycol is present in an amount between about 6 and 16 percent.

10. The polyester filament according to claim 9, further characterized in that said chain branching agent is pentaerythritol present in an amount of between about 1300 and 1800 ppm by weight based on the weight of the filament.

11. A mixed yarn comprising: a first series of fibers selected from the group consisting of conventional cotton, rayon, polypropylene and polyester; and polyester short fibers formed from the composition of claim 1.

12. The mixed yarn according to claim 11, further characterized in that said short polyester fibers comprise a copolymer of said polyethylene terephthalate and said polyethylene glycol.

13. The mixed yarn according to claim 11, further characterized in that said cotton fibers are present in an amount between about 5 and 95 weight percent the remainder comprising said polyester fibers.

14. The mixed yarn according to claim 11, further characterized in that said polyethylene glycol is present in said short polyester fibers in an amount of greater than about 4 percent to about 20 weight percent, based on the weight of the composition.

15. The mixed yarn according to claim 11, further characterized in that said chain branching agent is pentaerythritol present in said polyester short fibers in an amount of between about 500 and 4000 ppm by weight based on the weight of the composition.

16. The mixed yarn according to claim 15, further characterized in that said pentaerythritol is present in an amount of between about 1300 and 1800 ppm.

17. A woven, knitted, or non-woven fabric comprising the mixed yarn according to claim 15.