GB165439A - Improvements in cellulose ester compositions - Google Patents

Abstract

As softening-agent in the manufacture of pyroxylin compositions and solutions, a mixture of diacetin and triacetin substantially free from monoacetin is employed; the acetin should contain at least 50 per cent of triacetin, and preferably 60-70 per cent., the remainder being dioacetin. Such an acetin is prepared by treating one molecule of glycerol with 5-6 molecules of glacial acetic acid in the presence of 0.1 per cent of sulphuric acid as catalyzer, distilling off the water formed until an acid of 90 per cent or more comes over, neutralizing the catalyzer by the addition of sodium acetate and finally fractionating in vacuo. In the preparation of plastics the procedure is as usual employing a volatile solvent such as alcohol or acetone and optionally an addition of camphor or camphor substitute, and a stabilizer such as urea and pigments, and colours may be added. The proportion of pyroxylin to acetin is preferably from 3 : 1 to 4 : 1. For liquid compositions, a solvent such as methyl alcohol and ethyl, methyl or other alkyl acetate is added. Specifications 13131/00, 27201/08, [Class 70, India-rubber &c.], 16940/13, and 127,678 are referred to. The Specification as open to inspection under Sect. 91 (3) (a) refers to the use of the softening-agent with cellulose esters generally. This subject-matter does not appear in the Specification as accepted.ALSO:A mixture of diacetin and triacetin is prepared by treating one molecule of glycerol with 5-6 molecules of acetic acid in the presence of 0.1 per cent of sulphuric acid as catalyzer, distilling the mixture until an acid of 90 per cent or greater strength comes over, then neutralizing the catalyzer by the addition of sodium acetate, and finally fractionating in vacuo. The final product contains more than 60 per cent of triacetin. Specification 13131/00 is referred to.