Patent GB-1194490-A (GB)
Title: Method of Chemical Embossing Thermoplastic Sheet Material
IPC: B29C44/24
Filed: 1968-10-07
Abstract: 1,194,490. Embossing. ARMSTRONG CORK CO. 7 Oct., 1968 [6 Oct., 1967], No. 47397/68. Heading B6J. [Also in Division B2] A chemically embossed thermoplastic sheet is produced by blending a vinyl chloride resin with a plasticizer, forming the blend into a sheet, applying to the sheet in a pattern a liquid composition which is capable of penetrating into the sheet and which comprises a blowing agent which decomposes when heated to a temperature within the range of from the glass transition temperature of the plasticized vinyl resin to the decomposition temperature of the resin, and heating the resulting sheet to 300‹ to 450‹ F. to fuse the plasticized resin and decompose the blowing agent. The thermoplastic resin may be polyvinyl chloride, copolymers of vinyl chloride with vinyl acetate, vinylidene chloride, vinyl propionate, butyrate, alkyl substituted vinyl esters, acrylic acid and esters thereof and methacrylates. Pigments, dyes, fillers, e.g. clay, ground limestone, silicates, divided silicon dioxide may be added to the resin and the plasticizer as well as heat and light stabilizers, examples of which are given. The mixture may be applied as a plastisol by doctor or roll coating to a backing or to a strippable carrier which may be a steel belt, a rubber belt, paper or a felt having a release coat thereon, or the plastisol may be applied directly on to a backing which is to become a permenant part of a surface covering, e.g. a felt preferably a rubber-bonded asbestos backing, a vinyl sheet backing, or a cellulosic felt. An organosol may be used instead of a plastisol, or a dry blend of resinplasticizer mixture. The blowing agents may be liquid, e.g. azoesters and additives such as dyes, pigments, binders, fillers may be incorporated. Solutions and slurries of solid-heatdecomposable blowing agents such as substituted hydrazides, substituted azo compounds and substituted nitroso compounds, examples of which are given, may also be used. The blowing agent composition may also contain an accelerator such as a metallic soap, e.g. lead, zinc octoate, zinc, lead and dadnium salts of naphthenic acid and/or plithalic acid. The blowing agent accelerator may be incorporated into the vinyl resin-plasticizer before the composition is formed into a sheet. The blowing agent composition may be applied by, e.g. printing with rotogravure cylinders, block printing, silk screen printing. Alternatively, the blowing agent composition may be applied by spraying or wiping through a stencil positioned against the surface of the sheet, or barriers, e.g. metallic foils having a desired figuration or pattern may be applied to the surface of the gelled sheet to become a permanent part of the sheet if desired, and the blowing agent composition then wiped, doctored, sprayed, knife coated, roll coated over the entire surface of the sheet. The barrier may also be in the form of a printed decorative pattern impervious to penetration by the blowing agent composition, the binder in such barriers being, say, vinyl resins, acrylic resins. A barrier film having a binder of the same resin as that used in the gelled sheet may also be used. After application of the blowing agent composition, the sheet may be aged before heating to fuse the resin plasticizer and to decompose the blowing agent. Heating may be achieved by radiation or by hot air. An additional wearing surface may be applied to the decorative sheet prior to the final heating step, e.g. a clear or coloured coating of a thermoplastic resin may be sprayed, doctored, or roll applied to produce a decorative sheet suitable for use as a floor covering.