GB1065911A - Improvements in or relating to material comprising collagen fibres and the manufacture thereof - Google Patents

Abstract

Two modifications of the invention of the parent Specification are described and claimed. In the first, the suspension of collagenous fibres is applied to the fibre mass at a pH above that at which no substantial swelling of the fibres occurs, and reaggregated by removing water. In the second modification, the suspension, when applied to the fibrous mass, has a pH above or below the range at which no substantial swelling of the collagenous fibres occurs, and contains short textile fibres as well as collagen fibres. The impregnated sheet may be treated to deswell and reaggregate the collagen fibres and then reimpregnated with a suspension of collagen fibres alone. In addition the suspension may include small fibrous or film-like particles, known as 'fibrids', of some thermoplastic material having a lower melting point than the fibres of the mat; in this case the leather-like products are usually subjected to a heat treatment to fuse the particles in order to improve the bonding of the fibres. The collagen fibres are preferably obtained from lightly tanned hides, the degree of swelling of the fibres and thus also their ability to penetrate and to be retained in the intermeshed fibrous sheets being related to the degree of tanning. Suspensions of relatively highly tanned fibres, e.g. having a formaldehyde content of about 1.1% which would not penetrate well may be blended with suspensions of fibres which are less tanned e.g. having a formaldehyde content of 0.1 to 0.4%. The fibres of the latter type appear to display a carrier action and to improve the penetration of the highly tanned fibres. Addition of gelatine or of a cationic or anionic surface-active agent may be employed to improve the penetration, which is also improved by a highly acidic or highly alkaline pH, by low solids content of the suspension and by an open texture of the fibrous sheet to be impregnated. Textile fibres which are included in the suspension of collagen fibres normally penetrate only to a limited depth from the surface of the fibrous sheet. Suction or pressure may be employed to assist impregnation. Removal of the water and/or adjustment of the pH to deswell and reaggregate the collagen fibres may be achieved by the application of distilled water or of a water-miscible volatile organic solvent such as acetone and other ketones or lower alcohols such as methanol, ethanol and ispropanol, or an aqueous solution of a buffer salt such as an acetate or phosphate or a 10% aqueous ammonium sulphate solution or a vegetable or mineral tanning agent. The leather-like sheet may be further tanned, softened, e.g. by treatment with a 4% solution in acetone of oleic acid, and buffed or needled to improve the porosity. Needling may also be carried out at an earlier stage e.g. between successive impregnation treatments. The collagen fibres used in the suspension are .01 mm to 4 mm in length and comprise 5 to 90% by weight of the finished leather-like sheet. The fibres used in the non-woven sheets may be of nylon, polyacrylic ester, polyester, polypropylene, wool, regenerated cellulose or cellulose acetate. Collagen fibres treated to decrease their affinity for water may also be used. The added textile fibres may be of nylon, polyester, wool, glass, protein fibres such as zein, casein or special collagen fibres such as chrometanned fibres, and cellulosic fibres such as cotton or rayon. Such added fibres are normally from 1 to 3 denier and of length from 0.1 mm to 7 mm. The fibrid particles may be of regenerated cellulose, polyamides, polystyrene or other thermoplastic material.ALSO:Two modifications of the invention of the parent Specification are described and claimed. In the first, the suspension of collagenous fibres is applied to the fibre mass at a pH above that at which no substantial swelling of the fibres occurs, and reaggregated by removing water. In the second modification, the suspension, when applied to the fibrous mass, has a pH above or below the range at which no substantial swelling of the collagenous fibres occurs, and contains short textile fibres as well as collagen fibres. The impregnated sheet may be treated to deswell and reaggregate the collagen fibres and then reimpregnated with a suspension of collagen fibres alone. In addition the suspension may include small fibrous or film-like particles, known as "fibrids", of some thermoplastic material having a lower melting point than the fibres of the mat; in this case the leather-like products are usually subjected to a heat treatment to fuse the particles in order to improve the bonding of the fibres. The collagen fibres are preferably obtained from lightly tanned hides, the degree of swelling of the fibres and thus also their ability to penetrate and to be retained in the intermeshed fibrous sheets being related to the degree of tanning. Suspensions of relatively highly tanned fibres, e.g. having a formaldehyde content of about 1.1% which would not penetrate well may be blended with suspensions of fibres which are less tanned e.g. having a formaldehyde content of 0.1 to 0.4%. The fibres of the latter type appear to display a carrier action and to improve the penetration of the highly tanned fibres. Addition of gelatin or of a cationic or anionic surface-active agent may be employed to improve the penetration, which is also improved by a highly acidic or highly alkaline pH, by low solids content of the suspension and by an open texture of the fibrous sheet to be impregnated. Textile fibres which are included in the suspension of collagen fibres normally penetrate only to a limited depth from the surface of the fibrous sheet. Suction or pressure may be employed to assist impregnation. Removal of the water and/or adjustment of the pH to deswell and reaggregate the collagen fibres may be achieved by the application of distilled water or of a water-miscible volatile organic solvent such as acetone and other ketones or lower alcohols such as methanol, ethanol and isopropanol, or an aqueous solution of a buffer salt such as an acetate or phosphate or a 10% aqueous ammonium sulphate solution or a vegetable or mineral tanning agent. The leather-like sheet may be further tanned, softened, e.g. by treatment with a 4% solution in acetone of oleic acid, and buffed or needled to improve the porosity. Needling may also be carried out at an earlier stage e.g. between successive impregnation treatments. The collagen fibres used in the suspension are .01 mm to 4 mm in length and comprise 5 to 90% by weight of the finished leather-like sheet. The fibres used in the non-woven sheets may be of nylon, polyacrylic ester, polyester, polypropylene, wool, regenerated cellulose or cellulose acetate. Collagen fibres treated to decrease their affinity for water may also be used. The added textile fibres may be of nylon, polyester, wool, glass, protein fibres such as zein, casein or special collagen fibres such as chrome-tanned fibres, and cellulosic fibres such as cotton or rayon. Such added fibres are normally from 1 to 3 denier and of length from 0.1 mm to 7 mm. The fibrid particles may be of regenerated cellulose, polyamides, polystyrene or other themoplastic material.ALSO:Sheet material which can be used as a substitute for leather and which is prepared by impregnating an intermeshed mass of textile fibres with a suspension of collagen fibres which fibres are reaggregated into a larger collagen fibre structure interspersed with the textile fibres (see Division D1) may be coated with leather finishes or resinous and/or waxy material. A preferred finishing treatment involves spraying the sheet with a 70% solution in isopropanol of certain nylons, i.e. alkoxy derivatives of type 6 nylon. The sheet is dried, needled and embossed leaving a soft, strong flexible film closely adherent to the sheet.