Patent GB-583014-A (GB)
Title: Modification of the properties of filaments, bristles, yarns, fabrics, films and like shaped articles derived from nylon
Filed: 1944-10-04
Abstract: Filaments, bristles, yarns, fabrics, films and like shaped articles of nylon consisting of or comprising structures which have been completely or substantially completely oriented by drawing, are made elastic by heating them in the presence of an alcohol, formaldehyde vapour and an acidic catalyst.  Suitable alcohols which may contain other substitutents and which may be used in admixture, are aliphatic monohydric alcohols such as methyl-, ethyl-, propyl-, n-propyl-, iso-propyl-, n-butyl-, isobutyl-, octyl-, dodecyl-, methallyl alcohol, castor oil fatty acids and cyclohexanol; polyhydric alcohols such as ethylene glycol, diethylene glycol and b  : b 1-dihydroxydiethyl sulphide-, ethers of polyhydric alcohols containing free hydroxyl groups such as ethylene glycol monomethyl ether and ethylene p  glycol monoethyl ether; and aromatic-aliphatic alcohols such as benzyl alcohol.  Suitable catalysts are acids or acid-reacting salts or mixtures thereof such as phosphoric acid, ammonium dihydrogen phosphate, oxalic acid, maleic acid, glycollic acid, lactic acid and citric acid, and they are usually employed as solutions in, e.g. water and/or alcohols or inert volatile organic liquids such as ethylene dichloride and dioxan.  The process may be effected at atmospheric, reduced or elevated pressure.  The nylon materials may first be impregnated with the acidic catalyst and then heated in the presence of the alcohol and formaldehyde both in the form of vapour, or the materials may be impregnated with a volatile monohydric alcohol or a non-volatile monohydric alcohol or a mixture thereof containing the acidic catalyst and subsequently heated in formaldehyde vapour in the presence or absence of a volatile monohydric alcohol also in vapour form.  The heating is effected under substantially anhydrous conditions so that if the materials are first impregnated with an aqueous solution of the catalyst they are dried before heating.  The temperature of heating may vary from 80 DEG  to 150 DEG  C.  Formaldehyde vapour may be obtained by, e.g. heating a polymeride of formaldehyde such as paraformaldehyde trioxymethylene or trioxane in the presence of a trace of alkali, and the vapour may be diluted by inert vapours such as nitrogen or carbon dioxide, or the vapours of volatile organic liquids such as benzene or xylene. Suitable nylons are those obtained as described in Specifications 461,236, 461,237, 474,999 and 495,790, and the articles may be derived wholly or in part from nylon, e.g. in a fabric the weft may comprise nylon and the warp some other material. The materials may be pretreated with wetting, dispersing or swelling agents such as cetyl pyridinium bromide and sodium cetyl sulphate, or these reagents may be incorporated with the liquid reagents used in the process of the invention.  The treated materials may be finally stretched as by cold drawing.  Examples are given in which (1) cold-drawn polyhexamethylene adipamide yarn is stepped in an aqueous solution of glycollic acid at 60 DEG  C., squeezed, dried, heated to 120 DEG  C. and exposed to the mixed vapours of formaldehyde and methanol at 110 DEG  C.; (2) a solution of oxalic acid in aqueous methanol is used as the catalyst and treatment with the mixed vapours of (1) is effected at 100 DEG  C.; (3) a woven fabric composed of cold-drawn nylon filaments is treated as in (2); (4) a colddrawn monofil of the interpolyamide obtained by heating together hexamethylene diammonium adipate, hexamethylene diammonium sebacate and caprolactam is treated with the same reagents as employed in (2). Specifications 534,698, 582,517, 582,518 and 582,520 also are referred to.