GB282789A - Process of manufacturing cellulose esters - Google Patents

Abstract

282,789. Ruth-Aldo Co., Inc., (Assignees of Barthelemy, H. L.). Dec. 28, 1926, [Convention date]. Cellulose acetates. - Sulpho-acetates formed during the manufacture of cellulose acetates while using sulphuric acid as the catalyst, are decomposed by carrying out the after-treatment in the following manner :-to the acetylation mixture is added sufficient aqueous formic or acetic acid to decompose the excess of acetic anhydride while at the same time preventing incipient precipitation of the acetate, then, after cooling, adding a further quantity of an aqueous solution of formic or acetic acid containing an amount of hydrochloric acid which is at least chemically equivalent to the amount of sulphuric acid used as catalyst in the acetylation, that is to say, the ratio of the amounts of hydrochloric and sulphuric acid must not be less than 36.5- 49. The relative proportions in the solutions may be so computed that the total quantity of water in the mass is 5 to 10 per cent of the total of the acids present after the last bath has been introduced. The cellulose acetate may, for example, be prepared as described in Specifications 19330/05 and 282,788. In an example, 18 kg. of boiled cotton is acetylated in a bath comprising acetic acid, acetic anhydride, and 0.13 kg. of sulphuric acid (density 1.84). The solution is heated to 42‹ C. and a bath of aqueous acetic acid is then added. The temperature rises by about 12‹ C. and then, after cooling to 41‹ C., an aqueous solution of acetic acid containing 0.739 kg. of dry hydrochloric acid is added and the temperature is maintained constant until a cellulose acetate is obtained having an acetyl value between 38 and 43 per cent and possessing complete solubility in acetone. The product is precipitated by adding water and is afterwards washed in the usual manner. Specification 20977/11 also is referred to.