GB1309038A - Process for producing acrylic composite fibres having woolly crimp characteristics - Google Patents

Abstract

1309038 Composite acrylic filaments AMERICAN CYANAMID CO 29 July 1971 [26 Aug 1970] 35802/71 Heading B5B Side-by-side type bicomponent filaments are wet-spun from two polymers each containing at least 88 wt. per cent acrylonitrile, one having an "irreversible swelling index" at least 0À05 higher than, and a Young's Modulus at least equal to that of the other. The wet-gel filaments are washed, stretched and relaxed at 60-130‹ C. in water or steam while maintaining at least 40% water content, and are thereafter dehydrated, collapsed and finally stretched 1À02 to 1À20 x at 90-135‹ C., and crimped, whereby the said one polymer forms the inside component of the crimps. The second stretch is conducted at the temperature at which the filaments exhibit maximum shrinking force. The first stretch may be partially combined with the washing. Between stretchings the filaments may be heated tensionless at 80-130‹ C. in steam or water. The "irreversible swelling index" is W G /W D where W G and W D are the respective filament weights after wet heat-stretching and after drying. The required 0À05 differential in this factor may be obtained by the following alternatives: (a) providing an acrylonitrile content differential between the polymers of at least 2%; (b) by providing a strong acid group content of up to 30 meq./kg. higher in the high shrinking component than in the other component; (c) by providing up to 10% more hydrophilic groups in the higher shrinking component than the other component; (d) by using spinning solutions of different concentrations (e.g. 0À3-5À0% difference) ; or (e) by using a polymer of lower M.W. for the high shrinking component. In examples, 97/3 and 92/8 acrylonitrile/methyl acrylate copolymers are used as high and low shrinking components respectively, each containing 50 meq./kg. of sulphonate (as Na methallylsulphonate) and are spun from 11% and 13% solutions in NaCNS into 10% aqueous NaCNS at 0‹ C.