Patent GB-1325719-A (GB)
Title: Fibrous structures bonded by temporarily potentially adhesive component
IPC: D04H1/542
Filed: 1970-12-23
Abstract: 1325719 Fibrous structures; conjugate filaments IMPERIAL CHEMICAL INDUSTRIES Ltd 8 Dec 1971 [23 Dec 1970] 61169/70 Heading B5B [Also in Division D1] An adherent fibrous structure is made by a process comprising forming a fibrous structure, web or fabric comprising fibres of which at least a proportion of the surface is comprised of a potentially adhesive polymer, activating at least a proportion of the potentially adhesive polymer temporarily with formation of bonds between fibres, and then chemically treating the potentially adhesive polymer to render it no longer potentially adhesive. Activation of the potentially adhesive polymer may be affected by raising its temperature to that at which it becomes adhesive, or with the aid of a volatile liquid which softens the polymer rendering it adhesive; the chemical treatment may be a hydrolytic treatment. The potentially adhesive polymer may be a polymer having an ester side chain on at least a proportion, desirably at least 50%, of the structural units, as for example a cellulose ester or a polyvinyl ester. Preferred cellulose esters are cellulose acetate/butyrate, in which the ratio of butyrate radicals to acetate radicals is from 6 : 1 to 0À4 : 1, and cellulose propionate. Where cellulose esters or polyvinyl esters are so used, hydrolytic treatment is desirably such that at least 15% of the weight of the potentially adhesive polymer is lost. The potentially adhesive polymer may be present in the form of fibres which are entirely composed of potentially adhesive polymer, or in the form of conjugate fibres of which at least a proportion of the surface is of a potentially adhesive polymer; in either case, in addition to fibres comprised of potentially adhesive polymer, there may be present fibres not comprised of potentially adhesive polymer. In Example 1, sheath/core filaments having a polyethylene terephthalate core and a cellulose acetatebutyrate copolymer sheath are made by melt spinning, the melt temperature of the cellulose acetate-butyrate being 255 C. and that of the polyethylene terephthalate being 280 C., the combined streams being extruded at 280 C., and from the spun yarn a non-woven fabric is made by laying down two interlaced layers to form a web, which is pressed and heated at 200 C. to give a highly-bonded fabric. The fabric is then saponified with a mixture of aqueous sodium hydroxide and ethanol. Example 2 is similar, except that the meltspun filaments are stretched to a draw ratio of 3 : 1 by passage through a bath of 60 : 40 by volume dioxan and water at 65 C. before preparing the non-woven fabric. In Example 3, cellulose acetate butyrate fibres are randomly laid, pressed between plates and the product heated at 200 C. to give a melded fabric, which is saponified as in the previous example. Example 4 is similar to Example 3, but the fibres are first drawn. In Example 5, spun or drawn fibres of cellulose tripropionate are treated as in Example 3. In Example 6, drawn cellulose triacetate fibres are randomly laid on a plate, sprinkled with acetone, and pressed between plates to yield a melded fabric, which is then saponified as above. In Example 7, spun polyvinyl acetate fibres are randomly laid on a plate, pressed between plates and heated at 40 C. in an oven to yield melded fabric melting below 100 C. The fabric is saponified with a nitric acid/sodium sulphate mixture to yield unaffected by heat at 150 C. Cross-linking of the resulting polyvinyl alcohol fabric with formaldehyde and sulphuric acid renders it less water soluble.