Patent GB-510942-A (GB)
Title: Improvements in composite films and methods of making the same
IPC: C09J7/35
Filed: 1937-12-07
Abstract: 510,942. Adhesives. SCOTT, C. Dec., 7, 1937, No. 33913. [Class 121] [Also in Groups IV and VIII] A thin composite sheet of film capable of being attached to a fibrous base material solely by the action of heat and pressure is obtained by forming on a casting surface, from a solution in a volatile solvent, a water-repellent, heat-resistant, non-tacky, translucid, non- fibrous base lamina containing a plasticiser or non-volatile solvent; and then while the base lamina is still on the casting surface, depositing on the lamina and autogenously bonding thereto, from a solution containing a solvent for the base lamina, at least one water-repellent, heat and pressure sensitive lamina comprising a plasticiser and as major constituent a thermoadhesive compound. This compound may be a resin such as shellac, or a synthetic resin such as phenol-formaldehyde resin, glycerol-phthalate resin, methyl methacrylate resin, polyvinyl acetate or polyvinyl chlor-acetate. The film is impervious to water, mild acids and alkalis, and highly repellent to oils and greases. The film is normally not tacky or adhesive, becoming so only by the action of heat and pressure. It may be applied to paper, fabrics, leather, wood, or metal, or it may be used alone for wrapping foodstuffs, cigars, or other materials. When attached to printed or ornamented paper, it may take up the ink or dye and if desired a printed transparent film may be obtained by soaking and scraping off the paper fibres. The base layer may comprise cellulose acetate together with dimethyl phthalate, triphenyl phosphate, and a glycerol phthalate resin, or with triphenyl or tricresyl phosphate, or with diethyl phthalate, diethylene-glycol mono-ethyl ether, and triphenyl phosphate. It may comprise ethyl cellulose, diethyl phthalate, diethyleneglycol ethyl ether, and triphenyl phosphate, or polyvinyl chloride and tricresyl phosphate, or chlorinated rubber and triphenyl phosphate. Volatile solvents used include acetone, coal tar hydrocarbons with alcohol, and ethylene dichloride. The thermo-adhesive layer may comprise shellac, polyvinyl acetate, diethyl phthalate, diethylene-glycol ethyl ether, and triphenyl phosphate, or bleached bone-dry wax-free shellac, ethyl cellulose, and tricresyl phosphate, or glycerol phthalate resin, ethyl cellulose and tricresyl phosphate, or polyvinyl chlor-acetate, diethyl phthalate, diethylene glycol ethyl ether, and tricresyl phosphate. The solution forming the adhesive layer may be cast on to the base layer while the latter still contains residual volatile solvent. The composite film may be provided with one or more thin coatings of wax, wax and resin, rubber, rubber and wax, natural or synthetic resins or gums, e.g., phenol-formaldehyde resin, drying oils, or cellulose derivatives, e.g., ethyl cellulose. These coatings ensure against selfadhesion of the composite film when it is stored in a roll and help to prevent cracking. Provided it is sufficiently thin the coating layer may be applied to the thermo-adhesive surface without affecting the welding properties of the film. The composite film may be made very thin and both basic and adhesive layers may be so thin that individually they would not be self-supporting. Specification 431,560 is referred to.