GB1001526A - Cellulose-based films - Google Patents

Abstract

A reaction product of 1 mol. propylene glycol and 2.5 mol ethylene oxide is made by charging a stainless steel batch reactor, equipped with a rotary stirrer and steam heating and cooling facilities, and previously purged with nitrogen, with 76 parts propylene glycol. 0.15% by weight of potassium carbonate as catalyst, based on the glycol, is added and the temperature raised to 100 DEG C. After solution of the catalyst, the nitrogen is vented and 100 parts ethylene oxide added in such a manner that the temperature is kept at 115 DEG to 120 DEG C., allowing a maximum pressure of 3.5 kg./cm2. Stirring of the reaction mixture is continued at this temperature until the pressure drops to about 0.35 kg./cm.2, and the resulting product is cooled, neutralized with ortho-phosphoric acid and filtered. It is found to have a molecular weight of 187, specific gravity 1.087 and viscosity 59.1 cs. at 20 DEG C. Reaction products of propylene glycol with alkylene oxides in general are also mentioned, propylene and butylene oxides being specifically mentioned. From 1 to 5 mols. of alkylene oxide per mol. of propylene glycol may be used.ALSO:A regenerated cellulose film is impregnated with a propylene glycol-ethylene oxide reaction product and a urea formaldehyde anchoring resin and is then coated on both sides with a nitrocellulose based coating. In general, cellulose-based films comprising cellulose, regenerated cellulose or esters thereof, and a humectant which is a reaction product of propylene glycol and an alkylene oxide may be so treated. The humectant may be a reaction product of 1-5 mol. alkylene oxide, especially 2,5 mol. alkylene oxide, per mol. propylene glycol, and a reaction product of propylene glycol and ethylene oxide is preferred, suitably in a proportion of 1-25% by weight of the film, especially 5-15%. Propylene oxide and butylene oxide are also specified. In addition to the humectant, the film may comprise glycerine, urea, dyes, anchoring resins, fillers and/or extenders. Specified cellulose derivatives are cellulose nitrate, acetate, propionate, butyrate, acetate-propionate, acetate-butyrate and acetate-nitrate. Incorporation of the humectant in the film may be carried out following washing, desulphurization and bleaching of the film in the casting machine, by passing the film through a tank containing a dilute solution of the humectant.