Patent GB-637867-A (GB)
Title: Improvements in or relating to the production of fibres of synthetic linear hydroxylated polymers having improved water insensitivity
IPC: D06M13/127
Filed: 1947-03-21
Abstract: A filament or fibre of a synthetic polymer, having at least one alcoholic hydroxyl group per six carbon atoms but not more than one hydroxyl for two carbon atoms, is subjected to molecular orientation by drawing in a medium heated to a temperature of 200-250 DEG  C., is then heated in relaxed condition to a temperature of 25-225 DEG  C. until it has shrunk 8-40 per cent of its oriented length, is then preferably swollen and saturated with a liquid aqueous medium while preventing further shrinking, and is then subjected to the action of a reagent which reacts chemically with the hydroxylated polymer to render it resistant to the solvent or swelling action of hot or cold water.  The hydroxyl-containing polymer may be a polyvinyl alcohol or a hydrolysed polyvinyl ester, e.g. hydrolysed polyvinyl acetate or hydrolysed copolymer of a vinyl ester with ethylene, vinyl chloride, vinyl fluoride, vinylidene fluoride, or vinylidene chloride.  In such copolymers the molar ratio of vinyl ester (hydrolysed to vinyl alcohol) to the other polymerizable compound must be at least 1 : 2. The fibres may be drawn in oil or air.  Shrinking may be effected by heating with water, steam, or hot air, while the fibres are in relaxed condition.  Prior to the insolubilizing treatment, the shrunk fibre may be saturated with a swelling agent such as water or alcohol and water while it is held against further shrinkage. The fibre may be insolubilized by treatment with formaldehyde, titanium compounds, or partially condensed phenolformaldehyde resins.  The fibre is preferably treated while held at fixed length.  In an example, yarn of a hydrolysed interpolymer of ethylene and vinyl acetate oriented by drawing at 200-250 DEG  C. is formed into a skein which is immersed in water at 25 DEG  C. and allowed to shrink.  The relaxed yarn is wound on a cylindrical holder and the ends are secured to prevent shrinkage.  The package is contacted with hot water and then with a hot aqueous solution of titanyl sulphate.  The treated yarn is rinsed in alcohol, then in aqueous ammonia and finally in boiling water.  In another example, the oriented yarn is passed over a feed-roll and through a chamber containing a steam-air mixture at 90 DEG  C. and then over a second roll having a lower surface speed than that of the first roll.  The shrunk yarn is wrapped on a holder and soaked in hot water.  It is treated with formaldehyde solution containing oxalic acid, then rinsed, heated to 80 DEG  C. for one hour, and again rinsed.  The treated yarn is resistant to shrinking in hot water. The safe-ironing temperature may be raised above 230 DEG  C. by heating the yarn in oil at 235 DEG  C. while held to prevent shrinkage.  The treated fibres have high dry and wet strength. Insolubilization may be effected by treating the fibres with polyfunctional substances such as methylol and alkoxymethyl derivatives of uron, melamine, urea, dimethylolurea, or N-methoxymethyl polyamides; polybasic acids or their halides, e.g. adipic acid or adipyl chloride; dichlorodioxane; di-isocyanates or related compounds; aldehydes such as acrolein or butyraldehyde; ethanedithiol; heavy metal salts, e.g. chromic, ferric, or titanyl salts.  Specified titanium salts are titanyl sulphate, titanium tetrachloride, titanyl chloride, titanium lactate and glycolate. After treatment with a titanium salt, the yarn is preferably rinsed with an aqueous or alcoholic solution of alkali to remove acid. Polyvinyl alcohol or hydrolysed vinyl ester polymer fibres may be obtained by extruding aqueous solution of the polymer into a saturated aqueous solution of sodium di-hydrogen phosphate.  To avoid weakening of the fibres during removal of the salts, the salt-laden fibres may be drawn in air or at raised temperature until sufficient water-resistance is imparted by the orientation of the molecules. The fibres are then washed while held at fixed length. Specifications 634,140, 6015/48 (as open to inspection under Sect. 91) and U.S.A. Specification 2,169,250, are referred to.