APPLICATION OF A FLUOROCHEMICAL SOLUTION TO A FINISHED FIBER

Abstract: A method and apparatus for applying fluorochemical solution to a finished fiber to avoid housekeeping and fiber breakage problems normally encountered during the fiber manufacture process. The present invention uses preferably two finishing rolls to apply the fluorochemical solution to the finished fiber. The method and apparatus improve soil resistance, stain resistance, and water repellency of the finished fiber.

Description: TITLE APPLICATION OF A FLUOROCHEMICAL SOLUTION TO A FINISHED FIBER FIELD OF THE INVENTION The invention relates to an application of finish solution to yarn, and more particularly, to applying a fluorochemical solution to a fiber or yarn after the fiber manufacture or spinning process. The yarn can be twisted, heat set or treated with any other type of conventional fiber finishing treatment prior to applying the fluorochemical solution using a roller application . BACKGROUND OF THE INVENTION Flooring a-rticles, such as carpets, that provide good soil resistance, stain resistance and water repellency are desired by designers and consumers. It is known to use fluorochemical solutions to improve the soil resistance, stain resistance and water repellant features of flooring articles made from yarn. However, conventional methods of applying fluorochemical solutions to the yarn have normally taken place during the process of manufacturing the fiber. For example, in one method of manufacturing a fiber, the fluorochemical finish or solution is applied to the polymer during fiber spinning: after the quench zone and prior to the feed-draw zone; or before winding the yarn. Applying the fluorochemical at these locations in the fiber manufacturing process created or compounded fiber breakage or housekeeping problems in the process. At the location between the quench zone and the feed- draw zone, fiber breakage occurs because of the finish deposits that accumulate on the spinning rolls. At the location prior to winding in the fiber manufacturing process, dripping of the finish solution occurs when the fluorochemical solution is added at this location leaving residue on the spinning process equipment creating a housekeeping problem. The equipment must be shut down for cleaning of the housekeeping problems and thus affects productivity. Because of these problems, the present methods of applying fluorochemicals in the fiber manufacturing process are undesirable. A method that avoids the housekeeping and fiber breakage problems described above is desirable. The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows: JP62 62-85080 to Ochi et al. discloses the application of a fluorine-containing lubricant to short fibers or filaments, especially to undrawn fibers, of polyamide systems by well-known methods such as roller coating, dipping, sprinkling, and is ideally for use as the spinning lubricant when drawing. JP-60-126375 to Toun et al discloses a readily dyeable stain-proofing fiber. The readily dyeable fiber is coated with a film of fluorine-based stain-proofing agent containing a fluorine-based wetting agent. The fluorine based stain-proofing agent was applied to the finished product rather than to the finished fiber. While it is known that finishes such as a tint solution can be applied by spraying the solution through spray nozzles onto a heat-set yarn, it was found that fluorochemical solutions do not adhere to the yarn or fiber surface when applied using a spraying method. Furthermore, it is believed that an adequate level of fluorochemical solution is not provided to the fibers by spraying. It is desired to have a method for applying fluorochemical solution to a multifilament yarn or fiber so that the housekeeping concerns associated with applying fluorochemical solution during spinning are eliminated and the soil resistance, stain resistance and water repellency of the ultimate flooring article or other finished article is optimized . SUMMARY OF THE INVENTION Briefly stated and in accordance with one aspect of the present invention, there is provided a method of treating a finished fiber comprising the steps of: a) manufacturing the finished fiber; and b) applying a fluorochemical solution to the finished fiber. Pursuant to another aspect of the present invention, there is provided an apparatus for treating a finished fiber comprising: means for manufacturing a finished fiber; and at least one roll that carries a fluorochemical solution and contacts the finished fiber having a fiber surface, the at least one roll being rotatable applies the fluorochemical solution onto the fiber surface as the at least one roll rotates. BRIEF DESCRIPTION OF THE DRAWINGS Other features of the present invention will become apparent as the following description and example proceeds and upon reference to the drawing, in which : Figure 1 is a schematic illustration of an embodiment of the present invention for application of a fluorochemical finish to a heat set and twisted yarn on heat setting equipment. While the present invention will be described in connection with an embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims . DETAILED DESCRIPTION OF THE INVENTION As used herein the following terms may be used for interpretation of the claims and the specification: The terms "yarn" and "fiber" refer interchangably to a cohesive bundle of multiple filaments produced and processed as one. The terms "finished multifilament yarn," "finished fiber", and "finished yarn" are used interchangably to refer to a synthetic single or multifilament yarn upon completion of manufacture by a fiber manufacturer (e.g., DuPont or BASF) and otherwise ready to be incorporated into a finished article such as a carpet (e.g. by tufting, weaving or other means) or other flooring article and apparel. The term "mill" refers to the entity that creates a finished article such as a flooring article (e.g. carpet or rug) and apparel (e.g. socks, swimwear, etc.) from the finished yarn. The term "fluorochemical solution" or "fluorochemical finish" refers to a fluorine based solution (e.g. polymer containing perfluoro akyl chains ) . Reference is now made to the drawings, where the showing is for the purpose of describing a preferred embodiment of the invention and not for limiting same. Figure 1 illustrates a process of the invention using preferably dual finishing rolls to apply the fluorochemical solution to the surface of the finished fiber subsequent to the heat setting process. It is believed that one roll can also be used to cover the entire surface area of the finished fiber with fluorochemical solution in the present invention. The finished fiber is typically twisted and heat set prior to the application of the fluorochemical solution thereto, when the finished article is, for example, a carpet, since these steps impart the necessary body to be useful in carpet forming and the ultimate use of the carpet. Additionally, since the most common means of forming a carpet is by tufting, and the most common type of multifilament fiber used is white dyeable nylon, the finished yarn typically has already been subjected to twisting and heat setting by conventional means well known to fiber processors. The following example describes an embodiment of the present invention shown by Figure 1. Example Process Apparatus: Twisted yarn bundles 10 of 1245 denier DuPont Antron" nylon fibers, having twelve ends, were sent through a Superba Tunnel 20 (Superba™ Model SUTBP) at a speed of 500 meters/minute. The yarn bundles were coiled on a perforated Superba™ belt moving at a speed of 15 meters/minute. The Superba™ Tunnel operated at a temperature of 265°F. The twisted bundles of nylon yarn 10 were heat set as they passed through the Superba™ Tunnel 20. The heat set twisted nylon yarn bundles, upon exit from the Superba™ Tunnel 20, were straightened by passing over a series of rods (not shown) . The straightened fiber 11 was then transported over two rollers 31, 32 en route to the winding area 55. The finish rolls, 40 and 50, had a diameter of about 4.5 inches and a width of about 6.25 inches. The straightened fiber bundles 11 traveled past roller 33 and onto dual rolls 40, 50 rotating in the direction of arrows 41, and 51, respectively. In this test, the dual rolls 40, 50 were located a distance of about 10 inches, center to center, from each other on either side of the straightened fiber bundles 11. The dual rolls 40, 50 contacted opposite sides of the fibers covering the entire surface area of the straightened fiber bundles 11. The rotational speed of the dual rolls 40, 50 was varied from 20 rpm (revolutions per minute) , 35 rpm, 45 rpm, 48 rpm, 55 rpm, 58 rpm and 84 rpm as shown by the attached tables. The fluorochemical used was an anionic polyfluoronitrogen- containing soil resist agent prepared according to US Patent No. 5,580,645 using sodium alkyl sulfonates as the surfactant to stabilize the emulsion, e.g., N130, made by E. I. Du Pont de Nemours and Company, Inc. (A detailed description of N130 is provided in US Patent No. 5,948,980 and is incorporated herein by reference.) The N130 fluorochemical was diluted with water at 5:1, 15:1 and 20:1 ratios to form the fluorochemical solution used. (See Table I) . (Note: By 5:1 concentration, it is meant five parts water to one part of 100% N130; for 15:1 concentration, it is meant 15 parts water to one part of 100% N130 and so for other concentration ratios used herein.) The fluorochemical solution was applied via the finish rolls 40, 50. The rolls 40, 50, are made of a ceramic material. The fluorochemical solution was pumped from a finish tank (not shown) into the finish pans 42 and 52 located just under the finish rolls 40, 50, respectively. The finish rolls 40,50 were lubricated with fluorochemical solution from these pans by rolling the finish rolls through the pans 42, 52 containing the fluorochemical solution. The level of fluorochemical solution in the pans 42, 52 was kept constant by allowing a small amount of fluorochemical solution to overflow over the edge of the pan and be caught and transferred back to the finish tank. The straightened yarn bundles 11 were run over the rolls 40, 50 as shown in the Figure 1, allowing application of the fluorochemical solution or finish on both sides of the yarn bundles 11. The yarn bundles 11, now having fluorochemical solution applied thereto, were transferred to a winding machine after passing over roller 34, located about twenty (20) meters from the rolls 40, 50 for adequate air drying. Each bundle was separately wound on a tube (not shown) . The fluorine level (in ppm) was determined using the DuPont Fluorine Analysis/Combustion Method. Briefly described, this method involves measuring fluorine on yarn. A weighed sample is burned in a flask containing NaOH (sodium hydroxide) solution and the gases are dissolved in the NaOH solution to form sodium fluoride. The amount of fluorine in sodium fluoride solution is measured using a pre-calibrated Fluoride Ion Activity Electrode. Further details of the method are available from DuPont, in Seaford, De under the Du Pont Test Method - TM 0371-86 called Fluorine Analysis/Combustion Method. Process Results: The above process was used to determine the amount of fluorine (ppm) that could be applied by the dual rolls on the finished fibers. The results are shown in Tables I-IV. Each of the Samples in Table I, represent a fiber bundle lot (meaning more than one fiber bundle with fluorochemical solution applied after fiber manufacture) . The average fluorine level values of the bundled finished fibers shown in the Tables reflect the combined tubes or samples used in manufacturing a finished product. Tables I - III, show that by varying the roll speed of the dual rolls from 45 to 84 rpm at a concentration of 20:1, the average fluorine values ranged from 186 ppm to 537 ppm. Table I, Sample C, showed an average fluorine value of 300 ppm at a concentration of 15:1 with a roll speed of 45 rpm. The roll speed and the fluorine concentration were varied to determine if the process of the present invention could provide desired fluorine concentration on the finished fibers. For example, it is known that the application of fluorochemical solution to fibers provides desirable characteristics such as good soil resistance, good stain resistance, and water repellency. In order to achieve these desirable characteristics, an average fluorine value of about 400 ppm (parts per million) to about 800 ppm is required on the finished fibers. This desired average fluorine value range was based upon the average fluorine ppm range that achieved the best soil resistance, stain resistance, and water repellency results when the fluorochemical solution was applied during the spinning operation. The results shown in Table IV show that increasing the fluorine concentration to 5:1 and using a roll speed of 35 rpm provides an average fluorine value of 510 which is in the range desired (i .e. ~400ppm- -800 ppm). As shown in Table IV, and Tables I-III, the present invention contains flexibility to achieve a variety of fluorine amounts on the finished fibers. The process of applying the fluorochemical solution to the finished fiber avoids the housekeeping and fiber breakage problems that occur when the fluorochemical is applied during the fiber spinning operation. Twisting the finished fiber prior to the fluorochemical solution application is preferred, but not required, because the twisting of the fiber strengthens the fiber reducing fiber breakage problems. Additionally, the roll application, preferably dual roll application, is capable of supplying desired amounts of fluorine to the finished fibers as shown by Tables I-IV. TABLE I: TABLE II Concentration of N-130 = 20:1 Roll speed = 48 rpm Avg = 186 ppm Fluorine (F) EXAMPLE III Concentration of N-130 = 20:1 Speed = 58 rpm Avg. = 285 ppm Fluorine Example IV Concentration of N130 = 5:1 The amount of fluorine applied to the fiber or yarn bundles by the rolls was increased by increasing the rotational speed of the finish rolls. It is believed that a rotational speed of a single finish roll in combination with the appropriate amount of fluorochemical solution applied to the finish roll, would enable the entire surface area of the finished fiber to be covered using a single finish roll. Thus, eliminating the need for two finish rolls to apply the fluorochemical solution. In another embodiment of the present invention, it is not required that any heat setting or other treating of the finished fiber occur for the enhanced properties of the finished fiber to occur in the ultimate product. These ' enhanced properties include improved soil resistance, stain resistance, and water repellency. These improvements are of importance to manufacturers and consumers of the finished product (e.g. carpets, rugs, and apparel) . A novel element of the present invention is when the application of the fluorochemical solution to the finished fiber occurs. The fluorochemical solution is applied after fiber manufacture, typically at a fiber processor or carpet mill, and prior to the manufacture of the finished article, (e.g. the carpet, socks, swimwear) , thereby avoiding the housekeeping and fiber breakage problems of other methods. Additionally, the present invention uses finishing rolls to apply the fluorochemical solution rather than spraying the finished fiber or finished article. The present invention provides sufficient fluorine based solution to the fiber for better soil resistance, stain resistance, and water repellency of the finished article that spraying the fluorine based solution does not accomplish due to lack of adherence of the fluorine solution to the fiber. It is believed that any polymers containing perfluoro akyl chains are applicable to the finished fiber of the present invention as a fluorochemical solution. Examples of applicable fluorine based solutions are described in US Patent Nos. 5,414,111, 5,411,766 and 4,517,376. It is therefore apparent that there has been provided in accordance with the present invention a process for applying fluorochemical solution to a finished fiber after manufacture of the fiber but prior to manufacture of the finished product, e.g. a tufted or woven carpet, socks, swimwear and other articles made from the finished fiber. While this invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims: IT IS CLAIMED: 1. A method of treating a finished fiber comprising the steps of: a) manufacturing the finished fiber; and b) applying a fluorochemical solution to the finished fiber. 2. The method of claim 1, further comprising between step a) and b) the step of twisting the finished fiber. 3. The method of claim 2, further comprising after the twisting step and before step b) the steps of: heat-setting the finished fiber and straightening the heat-set finished fiber. 4. The method of claim 1, wherein the applying step comprises contacting the finished fiber, having a fiber surface, with at least one roll, the at least one roll containing the fluorochemical solution. 5. The method of claim 4, wherein the fluorochemical solution is applied to the finished fiber using two rolls contacting the fiber surface at different locations thereon. 6. The method of claim 5, wherein the two rolls contact opposing sides of the surface of the finished fiber. 7. The method of claim 3, wherein the applying step comprises contacting the finished fiber, having a fiber surface, with at least one roll, the at least one roll containing the fluorochemical solution. 8. The method of claim 7, wherein the fluorochemical solution is applied to the finished fiber using two rolls contacting the fiber surface at different locations thereon. 9. The method of claim 8, wherein the two rolls contact opposing sides of the surface of the finished fiber. 10. The method of claim 1, wherein the fluorochemical solution is a polymer containing perfluoro akyl chains. 11. The method of claim 1, wherein the fluorochemical solution is an anionic polyfluoronitrogen-containing soil resist agent using sodium alkyl sulfonates as a surfactant. 12. The method of claim 1, wherein the finished fiber is selected from the group consisting of polyamide, polyester, and polypropylene. 13. The method of claim 1, further comprising: a) manufacturing a finished article from the finished fiber having the fluorochemical solution applied thereto; and b) dyeing the finished article. 14. An apparatus for treating a finished fiber comprising : means for manufacturing a finished fiber; and at least one roll that carries a fluorochemical solution and contacts the finished fiber having a fiber surface, the at least one roll being rotatable applies the fluorochemical solution onto the fiber surface as the at least one roll rotates. 15. The apparatus of claim 14 , further comprising means for twisting, heat-setting and straightening the finished fiber prior to applying the fluorochemical solution to the finished fiber. 16. The apparatus of claim 14, wherein two rolls carry the fluorochemical solution, the two rolls contact the fiber surface of the finished fiber at different locations along the fiber surface. 17. The apparatus of claim 16, wherein the two rolls contact the fiber surface at locations opposite one another along the fiber surface. 18. The apparatus of claim 14, wherein the fluorochemical solution is a polymer containing perfluoro akyl chains. 19. The apparatus of claim 14, wherein the fluorochemical solution is an anionic polyfluoronitrogen-containing soil resist agent using sodium alkyl sulfonates as a surfactant. 20. The apparatus of claim 14, wherein the finished fiber is selected from the group consisting of polyamide, polyester, and polypropylene .

Inventors: BANKAR VILAS, LIN PERRY, BANKAR, VILAS, LIN, PERRY
Applicants: DU PONT, E. I. DU PONT DE NEMOURS AND COMPANY
Application year: 2001
Main classification: D06M15
IPC codes: D06B1, D06M15, D06M23