| 摘要 |
1,125,046. Starch ethers; polyurethane foams. OLIN MATHIESON CHEMICAL CORP. 2 March, 1966 [26 March, 1965], No. 9146/66. Headings C3C and C3U. A starch-based polyhydroxy-polyoxyalkylene ether is prepared by reacting starch and polyol in the presence of an acid catalyst at elevated temperature and oxyalkylating the mixture with an alkylene oxide, using at least 0À5% by weight of acid catalyst based on the combined polyol and starch, and at least 0À5 mole each of polyol and alkylene oxide per glucose unit weight of starch, after which the oxyalkylated product is reacted with additional starch, acid catalyst and alkylene oxide, using sufficient starch to increase the total molar ratio of glucose unit weight of starch to polyol to at least 2: 1, the proportion of catalyst being at least 0À5% of the combined weight of starch and polyol, and the proportion of alkylene oxide being at least 0À5 mole per glucose unit weight of starch in the additional starch. The starch is suitably corn or potato starch. Specified polyols are glycerol, ethylene glycol, propylene glycol, sorbitol and many other di-ols; specified alkylene oxides have 2-6 carbon atoms; epichlorohydrin and cyclic oxides are also mentioned. A Lewis acid, e.g. BF 3 , is best used as catalyst, but inorganic acids, e.g. HCl, H 2 SO 4 or acids such as fluorosulphonic and p-toluene sulphonic are also mentioned. It is stated that the initial step of the reaction, prior to oxyalkylation, causes degradation of the starch molecule by hydrolysis. In the initial reaction the temperature is suitably 30-200‹ C., and in the second suitably 100- 200‹ C. Polyurethanes are prepared from the above ethers by reaction of the ether with a polyisocyanate, using at least 0À7 NCO groups per available OH group, and a foaming agent and in the presence of a reaction catalyst. One-shot or " prepolymer " methods may be used. It is desirable to have a hydroxyl number between 80-300 in the starch ether when used for this process. The foaming agent may be water or a volatile halohydrocarbon. |
