GB338201A - Improvements in or relating to the manufacture of cellulose esters - Google Patents

Abstract

338,201. Kodak, Ltd., (Assignees of Staud, C. J. and Webber, C. S.). Feb. 18, 1928, [Convention date]. Cellulose carboxylates.-Mixed cellulose esters, other than cellulose lacto-formate, are prepared by digesting an acyl ester of cellulose, such as cellulose acetate, with an aliphatic or aromaticaliphatic mono- or di-basic carboxylic acid containing a hydroxyl group in the alpha position. Suitable hydroxy acids mentioned are lactic, tartaric, racemic, glycollic, glyceric, mandelic, and malic acids. The reaction is preferably carried out by digesting a solution of the acyl ester of cellulose in the desired hydroxy acid in a flask fitted with a reflux condenser, at a temperature of about 100‹ C. and at atmospheric pressure. The use of higher pressures is referred to. It is essential that the acyl cellulose ester be soluble in the acid employed, and for this purpose it may be necessary to add a small quantity of water; thus for example, cellulose acetate is soluble in a 75-85 per cent aqueous solution of lactic acid, and in a 77 per cent aqueous solution of tartaric acid. The composition of the mixed ester obtained depends on the extent of the digestion and the amount of water present, the longer the digestion the more does the solubility of the product pass over from solubility in acetone, to solubility in alcohol-water mixtures and finally to solubility in water. The initial acyl ester may or may not be partially hydrolyzed to the acetone soluble stage. In examples, (1) cellulose acetate, hydrolyzed or not, is dissolved in 75-85 per cent lactic acid and heated at 100‹ C. The product is precipitated with acetone, and is soluble in water. (2) Cellulose acetate containing 33 per cent acetyl is dissolved in glycollic acid and heated to 100‹ C. )3) Cellulose acetate containing 33 per cent acetvl is dissolved in tartaric acid containing water and is heated to 100‹ C. (4) Cellulose acetate containing 34.1 per cent acetyl is mixed with glyceric acid and heated to 100‹ C. (5) Cellulose acetate containing 34.1 per cent acetyl is digested with mandelic acid at 120-130‹ C. The product is soluble in an ethylene chloride, methanol mixture. (6) Partially hydrolyzed cellulose acetate is dissolved in a mixture of racemic acid and water, and heated by steam. (7) Cellulose acetomalate is prepared by dissolving cellulose acetate in a saturated aqueous solution of d-l malic acid, or in pure l-malic acid, and heating to 100‹ C. A progressive change is observed from solubility in acetone, in 75 per cent aqueous ethanol, in 50 per cent aqueous ethanol, and finally to solubility in water. Specification 8313/11 is referred to.