Patent GB-582522-A (GB)
Title: Modification of the properties of filaments, bristles, yarns, fabrics, films and like shaped articles derived from nylon
Filed: 1944-09-29
Abstract: Filaments, bristles, yarns, fabrics, films and like shaped articles of nylon consisting of or comprising structures which have been completely or partially oriented by drawing and thereafter disoriented, for example, by means of a shrinking treatment, are made elastic by heating them in the presence of an alcohol, formaldehyde vapour and an acidic catalyst.  Suitable alcohols which may contain other substituents and which may be used in admixture are aliphatic monohydric alcohols such as methyl-, ethyl-, propyl-, n-propyl-, iso-propyl-, n-butyl-, iso-butyl-, 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 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 solultions 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 pressures.  The shrunk 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.  The drawn nylon materials are subjected to shrinkage treatment in hot aqueous liquid or steam or in aqueous solutions of monohydric phenols such as phenol, cresols, xylenols, thymol and parabutyl phenol; polyhydric phenols such as resorcinol, catechol and pyrogallol; or acids such as formic, acetic, hydrochloric and sulphuric acids.  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 vapours 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.  In the examples: (1) a fabric woven from cold drawn polyhexamethylene adipamide filament yarn is immersed in an aqueous solution of phenol at 40 DEG  C. whereby it is shrunk.  It is removed, water-rinsed, dried and then heated in a mixture of formaldehyde and methanol vapours using glycollic acid as catalyst.  (2) Cold-drawn polyhexamethylene adipamide yarn is immersed in an aqueous solution of phenol at 70 DEG C. whereby it is shrunk.  It is then removed, washed, dried, and steeped in a solution of oxalic acid in aqueous methyl alcohol.  It is then squeezed, dried, heated to 100 DEG  C. and exposed to the vapours of formaldehyde and methyl alcohol at this temperature.  The shrinking treatment may be effected in a solution of formic acid at 20 DEG  C.  Specifications 534,698, 582,518 and 582,520 also are referred to.