Improvements in or relating to the production of moisture-proof regenerated cellulose sheets and films

摘要

545,523. Films; resinous condensation products. BRITISH CELLOPHANE, Ltd. Aug. 27, 1940, No. 13490. Convention date, Sept. 1, 1939. [Classes 2 (ii) and 2 (iii)] [Also in Group VIII] A moistureproof regenerated cellulose sheet or film comprises a moisture-proofing surface coating and an intermediate anchoring layer comprising a urea- or thiourea-formaldehyde monohydric alcohol resin in the hardened insoluble form. The resin layer may be formed by applying aqueous or organic solvent solutions, e.g. in acetone, ethanol, butanol, iso-butanol, ethyl or amyl acetate, benzene or toluene, of methylol-urea or thiourea ethers in the monomeric or partially polymerized form and subsequently heating. Examples of such ethers are the methyl and ethyl ethers of monomethylol- and dimethylol-urea or thiourea and the dimethylol urea ether of ethylene glycol monomethyl ether. Their preparation is described in Specifications 522,643, 522,644, 535,378 and 538,280. The ethers may be applied by dissolving them in the softening bath for the gelregenerated cellulose film. Modifying agents such as rosin, hydrogenated rosin, polystyrene, oils and oil acids, fats, waxes, rubber derivatives and dyes may be added to the ether solution. Polymerization catalysts such as phosphoric, maleic, citric, lactic, acetic, trichloracetic, tartaric, oxalic or phthalic acid, mono-iso-butyl phosphate, dibutyl phosphate, mono-phenyl phosphate, mono-butyl phosphate, mono-ethyl succinate, rosin, shellac and alkyd resins may be used. Cellulose nitrate or acetate or ethyl cellulose may be added to the composition in such proportions as to exude on drying to form a superficial layer. Of the incompletely polymerized' urea-formaldehyde monohydric alcohol resins soluble in organic solvents, those formed from propyl, iso- and n-butyl, hexyl and lauryl alcohols are preferred. The preparation of such resins is described in Specification 483,399. A suitable moisture-proofing coating composition comprises nitrocellulose, paraffin wax, dibutyl phthalate and gum dammar.