GB964855A - A process for the production of sheet materials from polyamide fibres - Google Patents

Abstract

Sheet materials are made from polyamide fibres by treating the fibres with natural tanning agents containing hydroxyl groups, partial ethers or esters thereof or synthetic polyhydroxy compounds having a tanning action, dispersing the treated fibres in water, casting the dispersion to form a web, dehydrating, drying and consolidating the product. Polyamides referred to are those from caprolactam and from the salt of adipic acid and hexamethylene diamine. Tanning agents referred to are gallotannins, oak bark tanning substances, catechol tanning substances, partially etherified and esterified tannins, polyhydroxy-benzophenones, polyhydroxyanthraquinones; polyhydroxynaphthoquinones and condensation products thereof with agents such as formaldehyde, and digallic acid. The fibres can be treated by conducting a tow through the tanning solution, and then stretching and washing, or they can be treated with tanning solutions after stretching or cutting to length. The fibres are preferably not dried after treatment with the tanning agent, but merely separated from the treatment liquor by centrifuging. The products can be calendered hot or cold, or sprayed in a dry condition with impregnating agents or binding resins, or drawn through solutions or emulsions of such materials, e.g. a copolyamide. They can be consolidated by heat and pressure, when they contain a proportion of polyamide fibres which have a lower melting point than the other fibres, using a temperature slightly above the melting point of the fibres of lower melting point. In one example untreated fibres are added to an aqueous suspension of treated fibres, this suspension made into paper, and the paper is calendered at the melting point of the untreated fibres. Specification 868,651 is referred to.