United States Patent (19) (11) 4,347,203 Mimura et al. 45) Aug. 31, 1982 54 PROCESS FOR PRODUCING ACRYLIC FIBER FOREIGN PATENT DOCUMENTS 40-13698 7/1965 Japan ................................... 264/182 (75) Inventors: Koji Mimura, Hiroshima; Yasunori 51-149922 12/1976 Japan. Kawachi, Ohtake; Atsushi Kawai, 51-149923 12/1976 Japan. Hiroshima, all of Japan 1532668 11/1978 United Kingdom . 73) Assignee: Mitsubishi Rayon Company, Ltd., 1532770 11/1978 United Kingdom. Tokyo, Japan OTHER PUBLICATIONS 21) Appl. No.: 152,172 "Studies on Acrylic Fibers', by Takeda, Kogyo Kagaku Zasshi 67, 630-632, (1964). 22 Filed: May 22, 1980 Primary Examiner-Jay H. Woo (30) Foreign Application Priority Data Attorney, Agent, or Firm-Oblon, Fisher, Spivak, May 30, 1979 JP Japan .................................. 54-671.85 McClelland & Maier Jun. 5, 1979 JP Japan .................................. 54.70415 57 ABSTRACT 51) Int. Cl. ......................... B29D 27/00; B29F 3/10 An acrylic fiber having linen- or cotton-like feeling, dry 52 U.S. Cl. ...................................... 264/41; 264/171; feeling, a high hygroscopicity and a high water reten 264/182; 428/374; 428/398 tivity, which is characterized in that said fiber is cov 58 Field of Search ................ 428/374; 264/171, 182, ered on the outside with creases running along the fiber 264/41 axis, adjacent creases being 0.1 to 5u apart on the aver age; has in any of its cross-sections two or more mac (56) References Cited rovoids, 2 or more in major diameter, which extend in U.S. PATENT DOCUMENTS the direction of fiber axis; and said fiber has 30 to 150 3,639,204 2/1972 Ohki et al. .......................... 264/171. microcrimps per 25 mm of fiber length. A method for 3,885,013 5/1975 Sato ..................................... 264/182 producing such a fiber is also disclosed. 3,975,486 8/1976 Sekiguchi et al. .................. 264/182 3,976,737 8/1976 Sekiguchi et al. .................. 264/182 4 Claims, 5 Drawing Figures U.S. Patent Aug. 31, 1982 Sheet 1 of 3 4,347,203 U.S. Patent Aug. 31, 1982 Sheet 2 of 3 4,347,203 U.S. Patent Aug. 31, 1982 Sheet 3 of 3 4,347,203 4,347,203 1. 2 tion caused by the large number of microvoids within PROCESS FOR PRODUCING ACRYLIC FIBER the fiber. Efforts have also been made to improve the method This invention relates to acrylonitrile-based fiber for producing hygroscopic acrylic fibers having a large having a novel feeling. More particularly, it relates to number of internal microvoids, as disclosed in British acrylonitrile-based fiber having linen- or cotton-like Pat. Nos. 1,532,770 and 1,532,668 and Japanese Patent feeling, water absorptive property, water retentive Application Kokai (Laid-open) Nos. 149,922/76 and property, and dry feeling. 149,923/76. The inventions disclosed in said British The fiber of this invention has in any of its cross-sec patents relate to a method for producing acrylic fiber by tions two or more macrovoids, 2 or more in cross-sec 10 the dry spinning of a spinning solution comprising a tional major diameter, which extend in the direction of uniform mixture of an acrylonitrile polymer, a good fiber axis; is covered on the outside with a great number solvent for the polymer, and a poor solvent for the of creases running along the fiber axis, adjacent creases polymer, which has a boiling point higher than that of being 0.1 to 5u apart on the average; and has 35 to 150 Said good solvent, such as, for example, a polyhydric crimps per 25 mm of fiber length. The fiber of this in 15 alcohol. The acrylic fiber produced according to the vention is produced by the wet spinning process, partic disclosure has a core-jacket (sheath) structure, the mi ularly by the side-by-side conjugate spinning process, croporous core being capable of adsorbing water while under such conditions that the ratio of spinning draft to the jacket being insensible to water. Although such a maximum spinning draft is 0.5 to 0.9. structure improves the fiber having microporous core Acrylic fiber having internal microvoids, 1 u, or less in 20 pore diameter and prolonged in the direction of fiber structure in the resistance against fibrillation, the fiber axis has been known as a fiber possessing favorable produced still retains wool-like feeling characteristic of hygroscopicity, as described in patent documents such an acrylic fiber. as, for example, British Pat. Nos. 1,345,266, 1,532,668 Disclosed in Japanese Patent Application Kokai and 1,532,770; Japanese Patent Application Kokai 25 (Laid-open) Nos. 149,922/76 and 149,923/76 are meth (Laid-open) Nos. 149,922/76 and 149,923/76. The ods for producing a microporous acrylic fiber by the cross-sectional structures of the fibers produced by the wet spinning of a spinning solution comprising a co methods described in the above documents are as polymer of acrylonitrile with a vinyl monomer of the shown in the drawings attached to British Pat. Nos. general formula (1) 1,532,668 and 1,532,770. These fibers have good hygro scopicity but feel wool-like to the touch. U.S. Pat. No. (1) 3,639,204 has disclosed conjugate acrylic fiber of the side-by-side type having 48 crimps per 25 mm of fiber CH2=C-COO-(-CH-CHOH length. This solid fiber is very harsh to the touch and a solvent, and a blowing agent insoluble in water and does not suit for the apparel. The raw material for this 35 fiber is a copolymer of acrylonitrile and a higher-alkyl boiling at 95 C. or lower temperatures, such as, for acrylate having 5 to 14 carbon atoms in the alkyl group. example, carbon tetrachloride. The resultant fiber also Such a copolymer is tacky and the filaments tend to fuse has smooth surface and feels wool-like. together during spinning and cause end breakage. An acrylic fiber having an improved crimpability has Moreover, the fiber does not show linen- or cotton-like 40 been described in U.S. Pat. No. 3,639,204. This fiber is feeling, desirable hygroscopicity and water retentivity, made from an acrylonitrile copolymer comprising 65 to or dry feeling. 95% by weight of acrylonitrile and 35 to 5% by weight Acrylonitrile fibers having wool-like feeling and ex of a higher-alkyl acrylate having 5 to 14 carbon atoms in cellent physical and chemical properties have been well the alkyl group and has 10 to 48 crimps per 25 mm fiber known and used in the field of winter clothing and 45 length. This fiber has a high bulkiness and a highly underwear which require warmth. Because of their wool-like feeling. However, because a higher-alkyl warm feeling and insufficient dry feeling, these acrylic acrylate is used as the comonomer of acrylonitrile, the fibers are not suitable for spring and summer clothing extruded filaments tend to fuse together and cause end which require cool feeling and hygroscopicity. Such breakage during the high ratio drawing treatment re characteristics have limited the use range of acrylic 50 quired to produce a highly crimped fiber. This fiber is fibers. It is generally considered, therefore, that if the tacky and feels wool-like. It is difficult to produce a acrylic fiber is imparted with linen- or cotton-like feel fiber predominant in macrovoids. ing, dry feeling, hygroscopicity and water retentivity Under the circumstances the present inventors ad which are lacking in conventional acrylic fibers, the vanced the research and have accomplished the present acrylic fiber will acquire those characteristics which are 55 invention. The fiber of this invention is an acrylonitrile required for the spring and summer clothing, resulting based fiber which has in any of its cross-sections two or in enlargement of the use field of the acrylic fiber. For more macrovoids, 2 or more in cross-sectional major this reason, researches are under way in the fiber circles diameter, which extend in the direction of fiber axes; is to develop hygroscopic fibers having a large number of covered on the outside with a great number of creases internal fine pores. For instance, British Pat. No. 60 running along the fiber axis, the adjacent creases being 1,345,266 has disclosed a fiber having a porosity of 4.0 0.1 to 5p, apart; and has 35 to 150 microcrimps per 25 to 63.2%, a free surface area of 1.0x10 to 1.7 x 106 mm of fiber length. This acrylic fiber is produced by the cm2/g, and an angle of contact with water of 45" or less. wet spinning of a spinning solution having a viscosity of Because of its large free surface area, this acrylic fiber 200 poises or less, as measured at 50 C., preferably has an excellent hygroscopicity. Since the pore formed 65 under such conditions that the ratio of spinning draft to within the fiber is very fine and the exterior surface is maximum spinning draft is in the range of 0.5 to 0.9. The comparatively smooth, the said fiber feels wool-like. A structure as specified in this invention can be especially disadvantage of this fiber is its susceptibility to fibrilla efficiently embodied in a conjugate fiber of the side-by 4,347,203 3 4. side type made from two acryl copolymers different in other hand, in case of the fiber of the present invention, the copolymer composition. because of the effects due to the surface structure and The fiber of the present invention is illustrated below the inner specific structure, it is possible to improve the with reference to the drawings attached hereto.