GB353978A - Manufacture of cellulose esters - Google Patents

Abstract

Cellulose fibres, fabrics, or other articles, for example of cotton or regenerated artificial silk, are esterified, while maintaining their structure, by treatment with an aliphatic acid anhydride in the presence of a potassium salt of a weak acid and in the absence of an acid catalyst. The process may be applied also to fibres &c. of cellulose esters or ethers still containing free hydroxyl groups. The fibres, which may be swollen with suitable swelling agents, are preferably impregnated with the potassium salt, dried, and thereafter esterified. The esterification is advantageously carried out in the presence of a tertiary organic base, and according to the conditions selected, the products may have a completely matt, voluminous, woolly, or highly lustrous appearance. The treated fibres or fabrics have changed dyeing properties; they become for example completely reserved to substantive and vat dyestuffs and acquire the properties of ester silk. The process may be applied to the printing of fabrics, particularly of regenerated artificial silk, in which case the fabric, which may be dyed or not, is printed by means of a paste consisting of a thickened solution of a suitable potassium salt, and then subjected to the action of an aliphatic anhydride whereupon esterification occurs at the printed portions only. The esterified portions appear as a matt pattern on an unchanged ground. In examples, (1) cotton yarn is steeped in a solution of potassium acetate, dried, and esterified by means of acetic anhydride containing potassium acetate. (2) Cotton is swollen by means of potash lye, nitric acid, or calcium sulphocyanide solution, immersed in a saturated solution of potassium acetate, centrifuged, dried at 70-80 DEG C., and then esterified with acetic anhydride. The cotton, which now contains more than two acetyl groups is suitable as a parent material for the manufacture of further conversion products of cellulose. (3) Viscose or cuprammonium silk is immersed in potassium acetate solution of 60 per cent strength, freed from excess liquid by centrifuging, dried, and esterified by means of a boiling solution of acetic anhydride in benzene, toluene, xylene, carbon tetrachloride or the like. The silk, which has become delustred in the process, may be relustred by treatment with acetic acid. In the following example, a lustrous material is obtained directly-viscose silk which has been impregnated with potassium acetate and dried is esterified with acetic anhydride, the excess of which is subsequently removed by washing with glacial acetic acid. (4) Viscose silk is impregnated with potassium carbonate, and further treated with a boiling solution of acetic anhydride in toluene. (5) Viscose silk is esterified directly in a mixture of acetic anhydride, potassium acetate or potassium palmitate and xylene. In other examples, viscose silk is impregnated with potassium acetate and esterified with (6) butyric anhydride in xylene, (7) butyric anhydride, pyridine and carbon tetrachloride, (8) the mixed anhydride of stearic and acetic acids. The product in the latter case has a matt appearance resembling wool. (9) Cotton yarn is mercerized, washed free from alkali, impregnated with potassium acetate and finally esterified by means of chloracetic anhydride dissolved in xylene. Artificial silk is impregnated with potassium acetate and treated with (10) a benzene solution of chloracetic anhydride, or (11) a solution of chloracetic anhydride in acetic anhydride. (12) A silk of cellulose acetate containing free hydroxyl groups is immersed in potassium acetate solution, pressed, dried, and esterified by chloracetic anhydride in toluene. (13) Cuprammonium silk which has been printed with a thickened solution of potassium acetate is acetylated by means of acetic anhydride in toluene solution, with or without a tertiary organic base. The printed portions appear as a matt pattern and a two-colour effect may be obtained by dyeing with a dye-bath containing both Cibacet Violet 2R and Chlorantine Fast Green BL; the esterified portions appear as a violet pattern on a green ground. (14) Cuprammonium silk is printed with a thickened paste containing Flavanthrene, potassium carbonate, potassium acetate and Hydrosulphite R concentrated. The material is steamed and then esterified as in the previous example, when the printed portions appear as a yellow pattern; the fabric may be further dyed with a substantive dyestuff to give a two-colour effect. (15) Cotton or cellulose artificial silk yarn, esterified in the manner of the preceding examples is dyed by means of a dyestuff for acetate silk. (16) A mixed fabric of acetate silk and viscose which has been treated as in Examples 3 to 6 is treated with a boiling soap solution; the acetate silk becomes delustred, whilst the esterified viscose remains unchanged.