| 摘要 |
Artificial materials are manufactured by condensing polyvinyl alcohols with aldehydes in an anhydrous or practically anhydrous medium, if desired in the presence of small amounts of acid reacting substances, while rendering innocuous or removing the water formed during the reaction. Alternatively, polyvinyl carboxylates, e.g. polyvinyl acetate, formate or butyrate, and alcohols are employed instead of polyvinyl alcohols. The water may be rendered innocuous or removed by absorbing it during the reaction by means of neutral substances having a strong water-absorbing action, e.g. anhydrous calcium chloride, dehydrated sodium sulphate, anhydrous copper sulphate, anhydrous sodium acetate, dehydrated magnesium or calcium sulphate, or advantageously by carrying out the reaction in a diluent which is insoluble in water, e.g. benzene, ethylene chloride, methylene chloride, chloroform, carbon tetrachloride, trichorethylene, dichlorethylene, benzine fractions, cyclohexane, monochlorbenzene, dichlorbenzene or nitrobenzene, the water formed being distilled off together with the diluent during the reaction. If the reaction is carried out in the presence both of a diluent and of a waterabsorbing substance the working temperature may be below the boiling point of the diluent. The amount of diluent is usually 1 to 10 times the weight of the reaction mixture. After separating the water the diluent may be returned to the reaction vessel. The amount of water separated gives an indication of how far the reaction has proceeded and when it is completed, which is of special importance when using impure industrial mixtures containing aldehydes, e.g. crude commercial butyraldehyde, or mixtures of aldehydes obtainable by catalytic dehydrogenation of mixtures of alcohols prepared by catalytic hydrogenation of fatty oils and fats, e.g. coconut oil, sperm oil, rape seed oil or cotton seed oil. The reaction may be stopped when only a part of the hydroxy groups has reacted with the aldehyde. Suitable aldehydes are aliphatic aldehydes, e.g. formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, dodecylaldehyde, octodecylaldehyde, crotonaldehyde, oleylaldehyde or 2 - ethyl-capronicaldehyde, cyclic aldehydes such as cycloaliphatic aldehydes, e.g. hyxahydrobenzaldehyde, aromatic aldehydes, e.g. benzaldehyde, chlorobenzaldehyde, cinnamic aldehyde or a -or b -naphthaldehyde, or heterocyclic aldehydes, e.g. furfurol. Acid reacting substances suitable as accelerators are substantially anhydrous non-oxidizing acids, e.g. sulphuric, phosphoric, hydrochloric, chloracetic, p-toluenesulphonic or methyl sulphuric acids, which may be employed in an amount between .01 and 10 per cent, preferably .1 to 1 per cent, by weight of the polyvinyl alcohol. If the polyvinyl alcohol has been prepared by acid saponification of a polyvinyl ester, addition of an acid accelerator is unnecessary, but if the saponification has been carried out by means of alkali, sufficient of the acid accelerator should be added to neutralize any alkali still present and to produce a slightly acid reaction. In examples: (1) polyvinyl alcohol (obtained by saponification of polyvinyl acetate) is mixed with methylene chloride, acetaldehyde and phosphoric acid and the mixture boiled, the water formed passing over with the methylene chloride; (2) polyvinyl acetate (obtained by a polymerization with the aid of benzoyl peroxide) is similarly reacted with butyraldehyde and a solution of phosphoric acid in n-butyl alcohol; the products of (1) and (2) may be employed as a substitute for celluloid for the preparation of films or lacquers; (3) polyvinyl alcohol is reacted with lauric aldehyde in the presence of ethylene chloride and sulphuric acid, the water formed being distilled off with the ethylene chloride; (4) polyvinyl alcohol is similarly reacted with butyraldehyde and lauric aldehyde in the presence of sulphuric acid and methylene chloride; (5) polyvinyl acetate is reacted with butyraldehyde and anhydrous ethyl alcohol in the presence of sulphuric acid and dehydrated sodium sulphate; (6) polyvinyl alcohol (obtained by saponification of polyvinyl chloracetate) is reacted with butyraldehyde in the presence of sulphuric acid and methylene chloride; (7) polyvinyl alcohol (obtained by saponification of polyvinyl acetate) is reacted with 2-ethylcapronic aldehyde in the presence of phosphoric acid and of chloroform which is distilled off with the water formed; the product may be employed as an insulating material for electric devices. Specification 378,608 is referred to. |
