GB605305A - Improvements in the production of regenerated cellulose or sheet material - Google Patents

Abstract

Films of regenerated cellulose in which the variation of tenacity and extension with the direction of stressing is substantially eliminated are obtained by treating a film of cellulose acetate or other organic ester of cellulose in the dry condition, first with a swelling agent and then, while still in a swollen condition, with a saponifying agent, the film being free to contract during swelling and saponification. Suitable swelling agents are acetone diluted with fusel oil or with water, ethyl alcohol diluted with water and acetone vapour. Organic or inorganic saponifying agents such as methylamine, ethylamine, ethanolamine, ethylene diamine, cyclohexylamine, trimethyl - ammonium hydroxide; sodium, potassium or ammonium hydroxide and sodium or potassium carbonate may be employed. The films are treated with the swelling agent preferably at room temperature, excess liquid being removed by, for example, squeeze rolls. Saponification is effected preferably at 65 DEG to 150 DEG F. and the treated films are washed and treated with a softening agent, e.g. glycerol, ethylene glycol or propylene glycol. Examples are given, in one of which cellulose acetate film is treated in a bath of aqueous acetone at 72 DEG F., excess liquid being removed and the film saponified in an aqueous bath containing sodium hydroxide, sodium sulphate and sodium acetate at 116 DEG F. The saponified film is then washed, softened in aqueous glycerol at 72 DEG F. and dried. In another example, the swelling agent comprises a mixture of fusel oil and acetone.