Patent GB-709995-A (GB)
Title: Improvements relating to the manufacture of textile materials
Inventor: HAMPSON NOEL ARTHUR
IPC: B29C48/05
Filed: 1951-04-11
Abstract: Artificial filaments are made by extruding and solidifying by the removal of solvent an acetone solution of a vinylidene chlorideacrylonitrile copolymer containing 20-50, and especially 40-48 per cent., by weight of acrylonitrile, stretching the filaments by 300-2,000 per cent. of their original length at over 120 DEG C., heating them to 150 DEG C. or over while preventing shrinkage and then heating them to 150 DEG C. or over while allowing them to shrink freely or to a controlled degree.  The copolymer may be made by copolymerizing the monomers in an aqueous medium, the initial amount of water present being 2-10 times the total weight of the two monomers as described in Specification 643,198.  The acetone used may be pure or may contain up to 7.5 per cent. of water and/or an alcohol boiling below 120 DEG C., especially methyl, ethyl or isopropyl alcohol.  The solution may contain about 18-32 per cent. of the copolymer and may be extruded into a current of an evaporative medium at 20-27 DEG  C. but preferably 60-80 DEG  C.  After leaving the spinning cell the filaments may be quickly washed with water before being wound up or stretched.  The stretching of the filaments is preferably carried out at about 150 DEG -200 DEG  C., and especially about 175 DEG -195 DEG  C., and they are preferably stretched to 500-1,000 per cent. of the initial length.  The setting or annealing stage following the stretching may be carried out at about 150 DEG -190 DEG  C., especially 165 DEG -190 DEG  C. for 2-5 minutes.  The heating in both stages may be carried out by means of an inert fluid such as air, steam or water under pressure, a mineral oil or a glycol or glycerol, or by radiation.  The heating of the set filaments under little or no tension may be carried out for about 2 minutes or more at the setting temperature or at a higher temperature up to about 195 DEG -200 DEG  C., or at a temperature not more than about 25 DEG  C. below the setting temperature, preferably for about 3-7 minutes.  The filaments are preferably dry-spun, but may be wet-spun, e.g. by extruding the spinning solution into an aqueous coagulating bath containing a swelling agent for the copolymer such as acetone or another lower aliphatic ketone. Alternatively the bath may contain water-soluble metal thiocyanates.  The freshly coagulated material may be stretched during the spinning.  The copolymers may be colourstabilized by the addition of 0.1-2 per cent. of lead orthosilicate, phthalate, stearate or naphthenate, zinc stearate or naphthenate, dibutyl tin laurate, stearate or naphthenate, di-alkyl di-alkoxy compounds of tin such as dibutyl dibutoxy tin, calcium acetoacetate and stearate, cadmium 2-ethyl-hexoate, barium stearate, strontium naphthenate; epoxides such as epoxy-propyl ethers of bis-phenols, e.g. 4, 41-bis-(2, 3-epoxypropoxy)-diphenyl, endomethylene tetrahydrophthalic acid, 1, 11-diphenyl-diethyl ether, maleic acid and derivatives thereof, butyro-lactone, 2, 3, 5-trichloro21-hydroxy-benzophenone, 2, 21-dihydroxybenzophenone, alkaline earth metal salts of chlorinated hydroxy-benzophenones, phenyl salicylate and alkyl-phenyl salicylates such as t-butyl-salol. In an example 22 parts (by weight) of a copolymer of 45 per cent. by weight of acrylonitrile and 55 per cent. of vinylidene chloride (prepared in a described manner) are dissolved in 71.5 parts of acetone, 3.7 parts of methylated spirit and 2.8 parts of water, and the solution is heated to about 75 DEG  C. and extruded downwardly into an upwardly flowing air stream at room temperature.  The filaments produced are formed into a yarn with a low degree of twist which is stretched at 180 DEG  C. by 600 per cent. of its length, heated at p  constant length for 3 minutes at 185 DEG  C. and heated without tension at 185 DEG  C. for 5 minutes.  In all the examples one per cent. of stabilizer such as dibutyl tin laurate may be incorporated in the copolymer.  Specification 674,323 also is referred to.  The Provisional Specification states that the copolymer may contain 30-60 per cent. of acrylonitrile.