Patent GB-570840-A (GB)
Title: Improvements in or relating to the manufacture of compound sheet materials
IPC: C09J5/02
Filed: 1943-01-04
Abstract: 570,840. Compound sheet material. McGILL, J. H., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Jan. 4, 1943, No. 123. [Class 140] In the production of compound sheet material comprising at least two sheets of paper, fabric, or the like bonded together with the assistance of heat and pressure by means of at least one interlayer of a flexible waterproof thermoplastic material, a coating of ungelatinized polyvinyl chloride paste is applied to at least one of the surfaces to be united, the coating is heated to an extent sufficient only to set the coating to a condition of low mechanical strength, a coating of an easily thermoplastic polymerized unsaturated compound that can be rendered plastic at a substantially lower temperature than polyvinyl chloride is applied to at least one of the surfaces to be united, the sheets are assembled with the coatings interposed between the materials to be united and are subjected to heat and pressure to an extent sufficient to cement them together, and the polyvinyl chloride is gelatinized and the sheets firmly bonded together by heating the assembly to an elevated temperature insufficient to damage the sheets. The sheets may have external coatings of compositions not easily thermoplastic. The thermoplastic coating is preferably thin, and may be deposited on one or both of the set polyvinyl chloride coatings by evaporation of a solution in a volatile solvent. A plasticizer may be applied to at least one of every two set polyvinyl chloride surfaces to be assembled in juxtaposition. The assembly may be cemented in a plate press or calender at temperatures below 100‹C, and subsequently stoved while festooned or wound under tension on a drum at temperatures from 120-140‹C. The thermoplastic compound may be a polymerized alkyl acrylate or methacrylate, a polymerized vinyl fatty acid ester, or an interpolymer of one unsaturated ester with another or with a polymerizable unsaturated compound other than an ester. The thermoplastic cement may comprise polymethyl methacrylate and a plasticizer, or an interpolymer of vinyl acetate and vinyl chloride and a plasticizer, e.g. tricresyl phosphate or dibutyl phthalate. The same plasticizer may be used in the polyvinyl chloride paste. Fabrics may have a polyvinyl chloride coating on one or both outer surfaces as well as in the interlayer, and these outer layers may be gelatinized by radiant heat. These outer polyvinyl chloride coatings may be applied and gelatinized first. In example 1, dyed cotton sheets are each spread with polyvinyl chloride paste formed by mixing polyvinyl chloride powder, tricresyl phosphate, and yellow ochre, two spreads being applied to each sheet, and after each application the fabric is passed through a heated chest at 93-105‹C. On the set polyvinyl chloride surface is spread a solution comprising polymethyl methacrylate, tricresyl phosphate, benzene, and methylated spirits. After drying, the fabrics are assembled with their coated faces together and joined in a hydraulic plate press at 66‹C. The compound fabric is festooned in a stove for one hour at 132‹C. In example 2, similarly coated sheets assembled together as above are wound under tension on to a cylindrical hollow drum and heated for one hour at 130‹C. Treatments comprising the coating of cellulosic sheets with polyvinyl chloride paste, heating to a moderate temperature, and subsequently exposing the coating but not the sheet to radiant heat to gelatinize the coating and comprising the cementing of polyvinyl chloride coated surfaces with other cements rendered tacky by a volatile solvent or by exposure to moderate temperatures are referred to.