GB340436A - Improvements in the production of artificial materials by wet spinning processes - Google Patents

Abstract

The wet-coagulation process of the parent Specification for the manufacture of filaments, threads. films &c. from solutions of cellulose acetate or other organic esters of cellulose or of cellulose ethers in which process the solutions are extruded into coagulation baths containing a relatively high proportion of solvent for the cellulose derivative so that the coagulated products emerge in a plastic state, is modified in that there is incorporated in the spinning solution itself, wholly or in part for the solvent of the coagulation bath, solvents which are less p volatile than the non-solvent medium of that bath, for example, diacetone-alcohol, diethyl tartrate, mono- or di-acetin, and ethyl lactate if the non-solvent is water or alcohol, these solvents being preferably employed in the spinning solution in conjunction with a volatile solvent such as acetone. Other non-solvents that may be employed are,-methyl alcohol and its other homologues; hydrocarbons such as benzene, toluene, gasoline and kerosene. The quantities of solvent employed may be such that the emerging filaments &c. may be in such a state of plasticity that if brought together they will coalesce. Before collecting the products excess of solvent should be washed out or otherwise removed to prevent coalescence, for example, by washing with water, salt solutions or solvent solutions of lower concentration, conveniently by using solutions of decreasing concentrations. The washing may be effected by spraying or in a centrifugal spinning box. The solvents employed in the spinning solutions and coagulation baths are preferably such that by reason of their innocuous properties a residue of solvent may be permitted to remain in the washed products. During coagulation, a stretch may be applied so as to produce filaments of one denier or less even with the use of relatively large jet orifices. By adjusting the proportion of solvents, products of various degrees of lustre may be obtained, generally the lustre being higher as the proportion of solvent is greater. By the present process very strong filaments &c. may be obtained directly from primary or secondary acetylation or other esterification solutions preferably after destroying any acetic anhydride or other esterifying agent, and particularly such solutions as do not contain a deleterious catalyst, for example, the solutions obtained according to the processes of Specifications 308,322, 308,323, 309,201, 312,095 and 312,096, [all in Class 2 (ii), Cellulose &c.]. Instead of destroying any excess of anhydride the latter may be arranged to combine with the alcohol &c. of the coagulation bath to produce a substance capable of exerting or assisting the solvent action on the filaments &c. Non-solvent media may be added to the spinning solutions; and the coagulation baths may include a lubricant such as an oil, present in the form of an emulsion or as a layer on the bath. The products obtained are distinctive in that although wet-spun their lustre is reduced by moist steam or hot or boiling aqueous media, and in that ironing or treatment with solvents does not increase the lustre of the non-lustrous products. The finished products may be subjected, while under tension or not, to treatment with solvents still further to improve their qualities. In the Provisional Specification, Specification 311,790, [Class 2 (ii), Cellulose &c.], also is referred to.