Patent GB-548807-A (GB)
Title: Improvements in or relating to the treatment of cellulose derivatives and articles made thereof for modifying the properties thereof
IPC: C08B15/06
Filed: 1941-04-21
Abstract: 548,807. Cellulose derivatives ; artificial silk, films &c.: proofing permeable materials. DU PONT DE NEMOURS & CO., E. 1., COFFMAN, D. D., and REESE, J. S. April 21, 1941, No. 5114. [Class 2 (ii)] [Also in Group VIII] The chemical and physical properties of cellulose derivatives which are soluble in organic solvents and which possess esterifiable hydroxyl groups are modified by subjecting the cellulose derivatives to treatment with an organic polyisocyanate. The reaction may be assisted if desired by heating. The treatment increases the softening point and resistance of the cellulose derivatives to the action of solvents. It increases the water-repellency of cellulose derivative materials. The cellulose derivatives may be treated in solution, e.g. as coating compositions, or in solid form, e.g. as flake, film, fibre, or moulded or similarly shaped articles. The esterifiable hydroxyl groups may be in substituent radicals, but preferably the cellulose derivative is one having less than three substituent groups per glucose unit. A solution of cellulose acetate in acetone becomes more and more viscous when a little hexamethylene diisocyanate is added and finally sets to a gel. When freed from acetone the cellulose derivative becomes hard, insoluble, and infusible. Other di-isocyanates specified are decamethylene, m- and p-phenylene, ethylene, tri-, tetra-, and penta-methylene, and higher paraffin di-isocyanates, and di-isocyanates derived from aromatic amines such as o-phenylene diamine, 4:4<SP>1</SP>-diaminobenzophenone, and diamino-stilbene. The di-isocyanate may be applied as a solution, emulsion, or vapour. It may be incorporated in a spinning solution from which fibres are obtained by dry spinning or by an electrical method. The fibres are subsequently baked, e.g. at 155‹C. Cellulose acetate yarn, fibre or fabric, may be impregnated with a benzene solution of the reagent, dried, and then baked. The treated material has increased elastic recovery and reduced elongation as well as a higher softening point and resistance to solvents. The reaction alters the composition of the cellulose derivatives by the introduction of nitrogen. In an example, a solution of cellulose acetate in acetone containing hexamethylene di-isocyanate is allowed to stand for several hours and is then cast into a film on a glass plate. The dried film is aged and then heated to 150‹C. Where the di-isocyanate is applied to the material as a solution, the solvent used mav be gasoline, kerosene, benzene, toluene, ether, benzine, carbon tetrachloride, dichlorodiethyl ether, or ethyl propionate. Instead of a separate baking treatment, the materials may be impregnated in a hot solution of the reagent in a high boiling mineral oil such as kerosene. In another example a film is made by casting on to a rapidly spinning tin disc a solution of cellulose nitrate in butyl acetate containing butyl phthalate, hexamethylene di-isocyanate, and a little cobalt naphthenate. The film is dried and then heated. Other cellulose derivatives specified are the formate and butyrate esters, and ethyl, butyl, benzyl, and phenyl ethers. Specification 521,116 is referred to.