| 摘要 |
513,266. Polyvinyl acetal resins. KODAK, Ltd. March 7, 1938, No. 7159. Convention date, March 5, 1937. [Class 2 (iii)] Stable polyvinyl acetal resins are'prepared by subjecting a polyvinyl acetal resin before it has been heat-dried, or a polyvinyl body used as an intermediate in the manufacture of the polyvinyl acetal resin, to a reducing action. The reducing action may be effected on the acetal resin or on a polyvinyl alcohol or ester used in preparing the acetal, either in the reaction mixture in which it is prepared or in solution (e.g. in alcohol, acetic acid, and alcohol respectively) after separation therefrom. The preparation of the acetal may be carried out in the presence of a reducing agent. Reduction may be carried out with a non- metallic agent such as hydroquinone, pyrogallol, a reducing amine, hydroxylamine, or hydrazine, or with hydrogen in the presence of a catalyst or in an electrolytic process. The process may be applied to acetals prepared from esters such as the acetate, propionate, butyrate, acetatepropionate, acetate-butyrate, acetate-chloride, and mixtures of esters, partially or completely hydrolyzed and reacted with formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, or mixtures' thereof. After heat-drying the products may be used, mixed if desired with cellulose esters or ethers, gums, natural or synthetic resins, waxes or oils, for making films (e.g. photographic films), artificial yarn, lacquers, moulding compositions, impregnated textiles, wrapping material, electrical insulation, waterproofing, and laminated materials e.g. glass, wood, metal, or paper. In examples (1)-(3) polyvinyl acetate is (1) hydrogenated in the presence of platinum oxide or platinum black ; (2) electrolytically reduced ; (3) treated with hydroxylamine, then condensed with paraldehyde ; (4) vinyl acetate is polymerized in benzene solution, platinum oxide added, and the polyvinyl acetate hydrogenated, being then converted to acetal ; (5) polyvinyl acetate is Hydrolyzed and simultaneously reacted with paraldehyde and butyraldehyde in the presence of hydroxylamine hydrochloride ; (6), (7) polyvinyl acetaldehyde acetal is hydrogenated in the presence of platinum oxide or Raney nickel catalyst ; (8) polyvinyl acetaldehydebutyraldehyde acetal is hydrogenated in the presence of platinum oxide; (9) polyvinyl acetaldehyde acetal is electrolytically reduced ; (10) a partial polyvinyl butyraldehyde acetal prepared according to Specification 459,878 was hydrogenated in the presence of platinum. U.S.A. Specification 1,583,803 also is referred to. The Specification as open to inspection under Sect. 91 refers also to stabilizing, preferably before heat-drying, polyvinyl resins in general, including polyvinyl organic esters, polyvinyl alcohol, polyvinyl halides and polystyrenes. It includes an example in which polyvinyl acetate is hydrogenated in the presence of platinum oxide. This subject-matter does not appear in the Specification as accepted. |
