GB1038028A - Process for producing artificial fibres - Google Patents

Abstract

A spinning dope I containing a polymer A consisting of acrylonitrile, acrylate and/or methacrylate and a monomer containing sulphonic acid groups, and a spinning dope II containing a mixture of polymer A and a polymer B consisting of acrylonitrile, or of acrylonitrile, acrylate and/or methacrylate and a monomer containing sulphonic acid groups, are simultaneously extruded into a congulating bath to form conjugate filaments. Polymer A satisfies the equations 6.0<XA+YA<11.0 and 0.5\sE=YA<1.0 where XA is wt. per cent of acrylate and/or methacrylate in polymer A and YA is wt per cent of sulphonic monomer; polymer B satisfies the equations <FORM:1038028/C3/1> where XA is wt. per cent of acrylate and/or methacrylate in polymer B and YB is wt. per cent of sulphonic monomer; and the mixed polymer of dope II satisfies the equations <FORM:1038028/C3/2> where m is the proportion of polymer B in the mixed polymer of dope II. Concentrated aqueous nitric acid which is substantially free from nitrous acid is preferred as the solvent for the polymers. The acrylate and/or methacrylate component may be esters of methyl, ethyl, propyl and butyl alcohols. The monomer containing sulphonic acid groups may be methallyl sulphonic acid, a -methyl vinyl sulphonic acid, p-styrene sulphonic acid, a -sodium sulphoacrylonitrile, allyl sulphonic acid or 3-sodium sulphopropyl acrylate. In examples, dope II consists of (1) a 60-40 mixture of a 91.5% acrylonitrile-8.0% methyl acrylate-0.5% methallyl sulphonic acid copolymer (polymer A) and polyacrylonitrile (polymer B); (2) a 40-60 mixture of the above polymers; (3) a 60-40 mixture of a 89.5% acrylonitrile-9.8% methyl acrylate-0.7% methallyl sulphonic acid copolymer (polymer A) and a 95.8% acrylonitrile-4.6% methyl acrylate-0.3% methallyl sulphonic acid copolymer (polymer B); (4) a 60-40 mixture of 93% acrylonitrile-6.4% methyl acrylate-0.6% p-styrene sulphonic acid copolymer (polymer A) and a 98.5% acrylonitrile-1.2% methyl acrylate-0.3% methallyl sulphonic acid copolymer (polymer B).ALSO:Conjugate acrylic fibres having a latent helical crimp are made by extruding through one orifice, two spinning dopes of specified constitution into a coagulating bath. A helical crimp of at least 3 crimps per 10 mm. of extended length is developed by heat-treating the fibres, which may also be mechanically crimped. In an Example, a tow of fibres spun from two dopes consisting of (1) a copolymer of acrylonitrile, methylacrylate and methalkyl sulphonic acid (polymer A) and (2) a mixture of polymer A and polyacrylonitrile, are treated, after drying, with steam at 120 DEG C. to develop the crimps and are then mechanically crimped.