Patent GB-329704-A (GB)
Title: Manufacture of cellulose esters
IPC: C08B3/24
Filed: 1929-02-25
Abstract: 329,704. Ellis, G. B., (Soc. des Usines Chimiques Rh¶ne-Poulenc). Feb. 25, 1929. Cellulose crotonates. - Cellulose crotonates, particularly those prepared by the process described in Specification 328,588, are subjected to a partial saponification in solution in a solvent or mixture of solvents containing water and preferably in the presence of saponification catalysts to give cellulose crotonates of different solubility. The process can either be applied to a solution of a cellulose crotonate prepared from an already isolated tricrotonate or to the primary solution obtained by the crotonylation of cellulose. Suitable catalysts comprise those employed in the saponification of cellulose acetate or other cellulose esters, for example mineral acids, fatty or aromatic sulphonic acids, acid salts such as bisulphates, or zinc chloride. The catalyst employed for esterification may be used for saponificution or this may be either partly or completely neutralized and another catalyst added. Suitable solvents comprise, for example, acetic acid or its homologues, or crotonic acid or mixtures thereof. Alcohol may if desired be added to obtain an homogenous medium. The solubilities of the saponified crotonates depend upon the degree to which saponification has been effected, for example in the case of a slightly saponified tricrotonate, its solubility properties are akin to those of cellulose tricrotonate, whilst crotonic esters near to cellulose dicrotonate are insoluble at ordinary temperatures in benzene in which the initial tricrotonate was perfectly soluble but are still soluble in acetone, chloroform, and a mixture of benzene and alcohol. If the tricronate is saponified further, esters are obtained which are soluble in mixture of acetone and water. The cellulose crotonate obtained may be used, for example, for the manufacture of artificial silk, films, or plastic masses analogous to celluloid or varnishes. Moreover, the double bonds in the crotonyl radicals can be saturated by fixation with various radicals. In examples cellulose tricrotonate prepared in any suitable manner is dissolved in 50 per cent acetic acid, and then treated with a mixture of 90 per cent acetic acid and sulphuric acid until a product is obtained approximately to cellulose dicrotonate, whereupon the mass is precipitated bv water or other suitable liquid, washed, and dried to give a product soluble in acetone, chloroform, alcohol-benzene, and acetone-water to give solutions from which transparent films can be obtained by evaporation and insoluble in water, ether, ligroin, or benzene; a cellulose tricrotonate prepared as described in Specification 328,588 is treated in its primary solution with a mixture of 80 per cent acetic acid and ethyl alcohol and the saponified crotonate, after being precipitated, washed, and dried is soluble in pure acetone, acetone-alcohol, benzenealcohol, or acetic acid and insoluble in water, ether, acetone-water, or methyl or ethyl alcohols; a cellulose tricrotonate prepared as described in Specification 328,588 is treated in its primary solution with a mixture of crotonic acid, water, and alcohol and then precipitated with 85 per cent alcohol or other suitable liquid to give a cellulose crotonate which after washing and drying is soluble in acetone, chloroform, benzene alcohol or benzylic-alcohol and insoluble in water, alcohol, ether, or ligroin.