Patent GB-882359-A (GB)
Title: Process for the manufacture of non-woven fibrous sheet materials
IPC: D04H1/4309
Filed: 1958-02-13
Abstract: 882,359. Agglutinated fibrous materials; paper &c. made from synthetic filaments. FARBWERKE HOECHST A.G. Feb. 13, 1958 [Feb. 13, 1957], No. 4819/58. Classes 96 and 140. Non-woven fibrous sheet material is made by bringing into sheet form a mass of fibres consisting wholly or partly of fibres of polyvinyl alcohol or a water-soluble derivative or copolymer thereof or fibres obtained from a mixture of polyvinyl alcohol with up to 20%, based on the weight of the polyvinyl alcohol, of another water-soluble linear polymer, said fibres being capable of swelling in water at temperatures from 40 to 90 C. with retention of fibrous structure, then heating the sheet material in the presence of water at a temperature such that the said fibres swell with retention of their fibrous structure and finally drying the resulting sheet material. Specified derivatives of polyvinyl alcohol are the partial acetates with formaldehyde, acetaldehyde, pyridine aldehyde or glyoxylic acid whereas the copolymers specified are those obtained from vinyl acetate and other hydrophilic monomers such as acrylic acid, acrylamide, methacrylamide and vinyl pyrrolidone. Fibres obtained from spinning solutions containing polyvinyl alcohol and up to 20% of polyacrylamide, polyacrylic acid, polyvinyl pyrrolidone or partly hydrolysed polyacrylonitrile are also specified. The fibres may be pretreated by stretching, heat treatment or shrinking; they may also be crimped. A stable length of between 0.1 and 10 cms. is usually used. Up to 90% of the mass of fibres may be non-swellable fibres, e.g. fibres of acetalized polyvinyl alcohol, of polymers and copolymers of acrylonitrile, vinyl chloride, ethylene or propylene; of polyamides, polyurethanes or polyesters; of cellulose hydrate, cellulose acetate or cotton; and of natural or synthetic protein compounds. A dry or wet method of sheeting may be used; in the former a fleece or sliver is produced by means of a scribbling or carding machine and the moisture can be sprayed on to the mass after moulding, whereas in the latter method a suspension of fibres in water is poured on to a sieve and the excess water removed by suction. The subsequent heat treatment may be effected by indirect heating, infra-red radiation, highfrequency electric current, saturated steam or hot water. The sheet material may be made resistant to hot water by acetalizing with an aldehyde such as formaldehyde, butyraldehyde, nonyl aldehyde, glyoxal or terephthalaldehyde. A filler such as baryta, kaolin, talcum, an aluminium salt or cork meal, a pigment dye or a wax may be incorporated into the fibrous mass and, if necessary, casein, glue or starch may be used as a binder for the additive. The bonding action of the polyvinyl alcohol fibres may be supplemented by adding known binders such as resins or vinyl polymers. The sheet material may also be dyed. Uses. Filling material, absorptive linings, blotting paper, protective covers, hygienic articles, shock-absorbing felts and, when acetalized, paper including wall-paper, table linen, sterilizable medical articles, fleeces fast to boiling, wiping cloths, inner soles or durable felt articles.