Patent GB-559520-A (GB)
Title: Improvements in or relating to the production of moistureproof sheet or film
IPC: C08J7/052
Filed: 1942-05-22
Abstract: 559,520. Cellulose-derivative and syntheticresin compositions ; films. BRITISH CELLOPHANE, Ltd. May 22, 1942, No. 7030. Convention date, May 24, 1941. [Classes 2 (ii) and 2 (iii)] [Also in Group VIII] Organic non-fibrous sheets or films are moisture-proofed by coating with a composition comprising a film-forming substance, a wax, and a resinous material obtained by condensing formaldehyde with a urea derivative having the formula RHNC(:A)NH 2 , wherein A represents oxygen or sulphur, R represents a hydrocarbon residue, and one of the hydrogen atoms attached to nitrogen may be replaced by a further hydrocarbon residue. The urea derivative-formaldehyde condensation product is applied in a partly condensed or polymerized form, or in the form of the dimethylol compound of the urea derivative, and is polymerized or condensed to the hardened, insoluble form by heating the coated film or sheet. A suitable resin may be obtained by heating up to 125 C. a solution of mono-n-butyl urea in formalin in the presence of acetic acid. Other resins, obtainable by heating formalin solutions of mono-butyl thiourea, mono-amyl urea, unsymmetrical di-amylurea, mono-allyl thiourea, N: N<SP>1</SP>-di-n-butyl urea, mono-cyclohexyl urea, mono-cyclohexyl thiourea, N : N<SP>1</SP>-di-cyclohexyl urea, mono-phenyl urea, mono-benzyl urea, a mixture of N : N<SP>1</SP>-di-butyl urea with urea, or a mixture of such derivatives may be used. The urea derivative may be dissolved in methanol before adding to the formalin. The resin may be modified by refluxing in toluene. The film-forming substance may be a cellulose ester such as cellulose nitrate, an ether such as ethyl cellulose, a natural or synthetic resin, e.g. shellac, polybutyl methacrylate or oil- or acid-modified glycerol-phthalate resin, or a rubber derivative such as chlorinated rubber or the product obtained by reacting rubber with #-naphthol. The wax may be paraffin, with a melting point over 50 C., or a natural ester wax. A resin or gum such as dammar, ester gum modified with maleic anhydride, or a modified rosin obtained by treating rosin with sulphuric acid to increase its molecular weight may be added, to increase the compatibility of the wax and the film-forming agent. Plasticizers such as butyl benzoyl benzoate, diphenyl lauramide, N-butyl toluene sulphonamide, toluene-sulphonic acid, dibutyl, dicyclohexyl or dimethylcyclohexyl phthalate, or mono-lauryl phthalate may be added and also, if desired, an acid condensing agent such as phosphoric acid or phosphorus pentoxide, maleic, citric, lactic, acetic, trichloracetic, tartaric, oxalic, or phthalic acid, acid esters and half esters such as mono-isobutyl, mono-phenyl or dibutyl phosphate, monobutyl phthalate and mono-ethyl succinate, and acid resins such as rosin, modified rosin, shellac or a glycerol phthalate resin. The coating may be applied as a solution, e.g. in a mixture of ethyl acetate, toluene and isobutyl alcohol, and may' be chilled rapidly after evaporation of the solvent by heat. The film or sheet may be of regenerated cellulose, lowly substituted cellulose esters and ethers such as glycol cellulose, cellulose glycollic acid or methyl or ethyl cellulose, or of polyvinyl alcohol containing not more than 10 per cent. acetyl groups. A polyvinyl alcohol film, cast from an aqueous solution of polyvinyl alcohol containing glycerol and lauryl sodium sulphate, may be precoated with a composition containing 0.1 per cent. polyvinyl butyral, or 0.1 per cent. of lauryl sodium sulphate in 99.8 per cent. methyl or ethyl alcohol to prevent adhesion of adjacent layers during storage. Specification 211,446, [Class 2 (ii)], and U.S.A. Specifications 2,017,866 and 2,158,530 are referred to. The Specification as open to inspection under Sect. 91 describes also the use of urea derivative-formaldehyde resins which have been modified by refluxing in a mixture of toluene and isobutyl alcohol.. This subjectmatter does not appear in the Specification as accepted.