US2917805A

US2917805A - Method for curling highly crystalline synthetic fibers and filaments

Info

Publication number: US2917805A
Application number: US567291A
Authority: US
Inventors: Leo F Rokosz
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1956-02-23
Filing date: 1956-02-23
Publication date: 1959-12-22
Anticipated expiration: 1976-12-22

Description

Dec. Z2, 1959 L. F. RoKosZ METHOD FOR CURLING HIGHLY CRYSTALLINE SYNTHETIC FIBERS AND FILAMENTS Filed Feb. 23. 195e TTNEYS United States Patent IVIETHOD FOR CURLING HIGHLY CRYSTALLINE SYNTHETIC FIBERS AND FILAMENTS Leo F. Rokosz, Linwood, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Application February 23, 1956, Serial No. 567,291

Claims. (Cl. 2S-72) This invention relates to an improved method for producing a curliness or crinkle in synthetic fibers and filaments comprised of highly crystalline polymeric or resin ous thermoplastic materials.

In order to facilitate their being more advantageously processed into spun yarns and the like, and for other purposes, it is desirable to provide a wool-resembling curliness or crinkle for synthetic fibers and filaments. Pinching gears, opposed tinted or serrated roller or belt systems and various types of stuffing box crimpers are employed frequently for this purpose. Their utilization, however, may tend to have a deleterious inuence on the physical properties of the fiber. The also involve additional mechanical processing operations in the manufacture of the fiber. It would be beneficial, therefore, to avoid mechanical crimping operations for purposes of curling or crinkling synthetic fibers and filaments.

Advantageously, this may be accomplished with certain types of highly crystalline synthetic fibers and filaments, particularly with those which may be obtained when coagulable latex emulsions of highly crystalline, fiberforming, synthetic polymeric materials, such as saran copolymers containing copolymerized vinylidene chloride, are employed for forming the filamentary material.

According to the invention, a highly crystalline synthetic fiber and the like may be provided with a permanent, wool-resembling crimp by directionally heating the fiber while it is in a relaxed condition to unilaterally differentially amorphize it cross-sectionally; tensioning the differentially amorphized, relaxed ber so as to preferentially elongate it in its more amorphous cross-sectional regions, stretching said fiber to a completely oriented condition; and relaxing said oriented fiber.

After its orientation, the relaxing fiber assumes a permanent curliness or crinkled condition due to the differential amounts or degrees of relaxation which are experienced by its opposing, differentially amorphized sides or cross-sectional regions. The curliness which may thus be imparted to the fiber equals or exceeds the crimp that is obtainable for many fibers for conventional mechanical crimping means. The pitch of the crimp or degree of curliness which may be imparted to a fiber having a given thickness by practice of the invention is advantageously variable with changes in the conditions of operation. A more drastic differential amorphization, for example, or more pronounced preferential elongation or attenuation of the differentially amorphized fiber or greater degrees of orientation, or any combination of these infiuences, usually effect a greater degree of curliness or a finer crimp in the fiber.

Advantageously, as is schematically illustrated in the accompanying drawing, the method of the invention may be practiced by placing the fiber in a relaxed condition on a heated, non-adherescent surface to unilaterally differentially amorphize it cross-sectionally; drawing the heated, differentially amorphized, relaxed fiber from said surface so as to preferentially elongate it in its more amorphous cross-sectional regions; and subsequently orienting and relaxing said liber to produce the desired curliness therein.

Beneficially, uninterrupted or endless lengths of the fiber may be employed and the fiber may be curled and the method may be practiced in a continuous manner by employing a traveling, heated, non-adherescent surface, which conveniently may be in the form of an endless belt or the like, upon and from which an uninterrupted length of fiber is continuously placed and withdrawn to subsequently be continuously oriented and relaxed. The curled fiber product may be stapled for subsequent mechanical spinning operations or it may be otherwise treated and employed as a permanently crimped filamentary article.

Various materials which are not susceptible to sticking or coalescence with the amorphized fiber may be ernployed for providing the heated, non-adherescent surface. Advantageously, a silicone rubber material or a surface treated with a repellent silicone material may be utilized, although in some cases polytetrafiuoroethylene and like materials may form satisfactory surfaces. The surface may be heated by any desired means and in any desired manner. It may frequently be convenient and desirable to employ infra-red heating means for the purpose of heating the non-adherescent surface.

It is usually advantageous to curl a freshly formed filamentary material by the method of the invention. ln certain instances, a partial or complete drying of a freshly formed, wet fiber may be accomplished simultaneously with its differential amorphization on the heated surface. If it is desired, however, the ber may be obtained from any suitable supply of oriented material. Hollow fibers, such as those which may be obtained by spinning through annular orifices and by other known procedures, are often especially well suited for being effectively curled according to the method of the invention. This is due to their usually more pronounced capability for being more drastically cross-sectionally, differentially amor phized when they are unilaterally directionally heated.

While fibers from any highly crystalline polymeric or resinous fiber-forming material may ordinarily be curled by the present method, the invention is particularly adapted to be practiced with fibers which are comprised of the normally highly crystalline satan copolymers. It is especially advantageous to employ bers prepared from the highly crystalline saran copolymers of vinylidene chloride and acrylonitrile, particularly those which contain at least about percent by weight of vinylidene chloride polymerized in the copolymer molecule. When saran fibers are curled, it is advantageous for their differential amorphization to be accomplished on a non-adherescent surface which is heated to a temperature between about and 175 C. and, more advantageously, particularly when Saran copolymers of vinylidene chloride and acrylonitrile are employed, between about and 175 C. The formation of such fibers as well as their orientation and relaxation in the practice of the invention may advantageously be accomplished according to conventional techniques for such purposes.

Extremely effective crimping results may be obtained when the method of the invention is utilized to curl fibers from saran copolymers of vinylidene chloride and acrylonitrile which contain about 97 percent by weight of vinylidene chloride polymerized in the copolymer molecule. Fine fibers of such copolymers may', for example, be readily obtained by practice of the invention having a 2O to 35 percent permanent crimp induced with from 4 to 12 curls and more per inch in the fiber product.

What is claimed is:

l. Method for curling highly crystalline synthetic fibers of a normally highly crystalline saran copolymer to provide them with a permanent crimp which comprises directionally heating the ber while it is in a relaxed condition to unilaterally differentially amorphize it Crosssectionally; tensioning the differentially amorphized, relaxed ber so as to preferentially elongate it in its more amorphous cross-sectional regions without substantially orienting said fiber; stretching said fiber to a completely oriented condition; and relaxing said oriented fiber.

2. Method for curling highly crystalline synthetic bers of a normally highly crystalline saran copolymer to provide them with a permanent crimp which comprises placing the iiber in a relaxed condition on a heated, nonadherescent surface to unilaterally diierentially a'morphize it cross-sectionally; drawing the heated, diiferentially arnorphized, relaxed ber from said surface so as to preferentially elongate it in its more amorphous crosssectional regions without substantially orienting said fiber; stretching said fiber to a completely oriented condition; and relaxing said oriented fiber.

3. The method of claim 2 wherein said fiber is in the form of an uninterrupted, endless length which is continuously placed on a traveling non-adherescent surface and wherein the steps of drawing said liber from the surface to preferentially elongate it; stretching said liber t orient it and relaxing the oriented ber are continuously performed.

4. The method of claim 2 wherein the non-adherescent surface is comprised of a silicone material.

5. The method of claim 2 wherein the non-adherescent surface is heated by infra-red heating means.

6. The method of claim 2 wherein said liber is a hollow fiber.

7. The method of claim 2 wherein the non-adherescerit surface is heated to a temperature between about 160 and 175 C. to dilerentially amorphize said fiber.

8. The method of claim 2 wherein said fiber is comprised of a saran copolymer of vinylidene chloride and acrylonitrile containing at least about percent by weight of vinyiidene chloride polymerized in the copolymer molecule and wherein the non-adherescent surface is heated to a temperature between about and 175 C. to differentially amorphize said ber.

9. The method of claim 2 wherein said fiber is comprised of a Saran copolymer of vinylidene chloride and acrylonitrile containing about 97 percent by weight of vinylidene chloride polymerized in the copolymer molecule and wherein the nonadherescent surface is heated to a temperature between about and 175 C. to differentially amorphize said fiber.

10. A method in accordance with the method of claim 9 wherein said iiber is a hollow ber.

References Cited in the file of this patent UNITED STATES PATENTS 2,242,988 Averns May 20, 1941 2,333,279 Truesdail Nov. 2, 1943 2,338,978 Shepherd Jan. l1, 1944 2,344,511 Harder Mar. 2l, 1944 2,377,810 Robbins June 5, 1945 2,399,259 Taylor Apr. 30, 1946 2,542,973 Abernethy Feb. 27, 1951 2,543,027 Jones Feb. 27, 1951 2,602,964 Sisson July 15, 1952 2,708,813 Bourgeaux May 24, 1955 2,730,758 Morrell et al. Jan. 17, 1956 2,758,908 Kolb Aug. 14, 1956 2,764,468 Hare Sept. 25, 1956

Claims

1. METHOD FOR CURLING HIGHLY CRYSTALLINE SYNTHETIC FIBERS OF A NORMALLY HIGH CRYSTALLINE SARAN COPOLYMER TO PROVIDE THEM WITH A PERMANENT CRIMP WHICH COMPRISES DIRECTIONALLY HEATING THE FIBER WHILE IT IS IN A RELAXED CONDITION TO UNILATERALLY DIFFERENTIALLY AMORPHIZE IT CROSSSECTIONALLY; TENSIONING THE DIFFERENTIALLY AMORPHIZED, RELAXED FIBER SO AS TO PREFERENTIALLY ELONGATE IT IN ITS MORE