| 摘要 |
1,139,519. Cellulose ethers; alkali cellulose. DOW CHEMICAL CO. 28 Oct., 1966 [1 Nov., 1965], No. 48510/66. Headings C3A and C3F. A novel hydroxypropyl methyl cellulose having a methoxy D.S. of 0À4-1À3, a hydroxypropoxyl D.S. of 0À2-1À4 and an average total D.S. of at least 1.0 is made by etherifying, in the presence of a non-reactive reaction control agent, with the appropriate proportions of methyl chloride and propylene oxide, an alkali cellulose which has been obtained by reacting cellulose with less than the stoichiometric equivalent of alkali. The reaction control agent serves to prevent temperature rise during etherification, and is suitably a non-solvent such as dimethyl ether, or ethyl chloride, which boils at the etherification temperature, which is suitably 35-60‹ C. External cooling may also be applied. Alkali cellulose containing 1À2-2À8 mole of base/mole of cellulose is made by contacting cellulose with 0À3-0À7 parts of NaOH by wt./ part of cellulose. Compositions for painting comprise cellulose ether as identified above, together with water, TiO 2 , Mica, CaCO 3 , clay, polypropylene glycol, an acrylic latex, a defoamer and a preservative. |
