GB1098874A - Polyamide-based artificial leather and polyamide products used therein - Google Patents

Abstract

A polyamide containing hydrophilic groups is crosslinked using an acid crosslinking agent to render it water insoluble, but water absorbent up to 35% and flexible. The polyamide may be polyamide-6 or -66. The hydrophilic groups may be alkoxyalkyl or hydroxyalkyl groups dependant from 15-50% of the nitrogen atoms. They may, for example, be introduced by treatment with HCHO. The alkyl and alkylene groups in the hydrolytic groups may contain up to 6 carbon atoms, e.g. methyl, ethyl, methylene, and ethylene. The crosslinking may be effected by heating to 50-150 DEG C. in the presence of a polycarboxylic acid, e.g. citric, tartaric or 0.7-1.2% of maleic. 10-50% of a plasticizer, e.g. benzene N-butyl-sulphonamide, o- or p-toluene N-ethylsulphonamide or a 2-ethylhexanol/p-hydroxybenzoic acid condensate, pigments, e.g. carbon black and black iron oxide, matting agents and fillers, e.g. SiO2. A 40% solution of the polyamide in aqueous alcohol may be applied to a fibrous substrate to give a leather substitute. The substrate may comprise 50% or more of cellulose, e.g. cotton fibres, interwoven with rayon fibres. 20-100% of polyamide may be coated on to this and heated after application to crosslink it. The leather substitute may be used to make footwear uppers.ALSO:A leather substitute comprises a web of fibrous material carrying a flexible layer of cross-linked polyamide containing pendant hydrophilic groups and having a water absorption capacity up to 35%. The web may be a double rib hosiery material, one ply of which is a cellulosic material, e.g. rayon, and the other ply of which is a synthetic resin fibre, e.g. nylon. It may weigh 350g./sq. metre and may be roughened and prestretched before use. 20-100 wt.% of the polyamide in 40% aq. alcohol solution may be applied to the nylon side of the fabric in 1 or more layers. It may contain N-hydroxyalkyl and/or N-alkoxyalkyl hydrophilic groups or up to 50% of its nitrogen atoms and may be cross-linked with 0.7 - 1.2% of a polycarboxylic acid after application. A plasticizer, filler and/or pigment may be present. In typical Example 1 a fabric of nylon and rayon is dyed black, shrunk during dying, dried, roughened and calendered hot. Several coatings of a primer, comprising hydroxymethylated methoxymethylated nylon 6, benzene sulphonic acid butyl amide as plasticizer, ivory black, maleic acid, water and ethanol, are applied to a total weight of 240, g/sq. cm. Several layers of finish, comprising hydroxymethylated methoxymethylated nylon 6, ivory black, SiO2, maleic acid and water, are applied to a weight of 60 g./sq. cm. The product is heated to cross-link it, embossed and 100 g./sq. cm. of dressing applied. In other p Examples materials specified are methoxymethylated nylon 66, ethoxyethylated nylon 66 and hydroxyethylated ethoxyethylated nylon 6 as polyamides, black iron oxide as a pigment, and tartaric and citric acids a cross-linking agents.