GB608335A - A process for improving the properties of nylon fibres - Google Patents

Abstract

Nylon filaments are given a softer hand, an increased resiliency and resistance to solvents, a higher melting point and a better dye receptivity by reacting the undrawn filaments with a solution having a pH below 3 of formaldehyde and an oxygen-containing acid catalyst in an alcohol at a temperature of from 40 DEG to 130 DEG C., cold drawing the so-treated filaments and insolubilizing them by, for example, a baking treatment. The polyamide to be treated must possess hydrogen-bearing amide groups, and the formaldehyde treatment is stopped when from 1 to 20 per cent of the total amide groups in the molecule is converted into N-alkoxymethyl groups. Formaldehyde is preferably employed in the form of paraformaldehyde, but a formalin solution or polyoxymethylene can also be used. Suitable alcohols are methanol, ethanol, propyl, butyl, amyl and benzyl alcohol, cyclohexanol, ethylene glycol, diethylene glycol, propylene glycol, allyl, methallyl and crotyl alcohol and substituted alcohols such as hydroxy-acetic or lactic acids. Suitable acid catalysts are oxalic, maleic, mono-, di- or tri-chloroacetic, fumaric, formic, p-toluenesulphonic, phosphoric and phosphorous acid. Numerous suitable polyamides and interpolyamides are specified. The insolubilizing treatment may be effected by heat alone, but is preferably carried out by baking in the presence of an acid such as maleic, oxalic, succinic, adipic, glutaric, p-toluenesulphonic, acetic, formic, hydroxy-acetic, lactic, sulphuric and hydrochloric acid. Alternatively, insolubilization may be effected by impregnating the filaments with a solution of a peroxy compound, e.g. benzoyl peroxide, diacetyl peroxide, lauroyl peroxide, diethyl peroxide, zinc peroxide and hydrogen peroxide, and then baking or exposing to a source of concentrated ultra-violet light. If desired, the acid catalyst or the peroxy compound may be applied to the filaments prior to cold drawing. Fibres may be woven or knitted into fabric prior to the insolubilizing treatment, any impregnation with acid or peroxide being done either before or after weaving. In an example, polyhexamethylene adipamide yarn is immersed in a methanol solution of paraformaldehyde and anhydrous oxalic acid at 64 DEG C. The yarn is removed, rinsed with aqueous ammonium hydroxide, dried, cold drawn to a ratio of 3.51 : 1, soaked in an aqueous oxalic acid solution, dried and baked for 5 minutes at 110 DEG C. Specifications 461,236, 461,237, 534,698, 573,482 and 582,517 are referred to.