| 摘要 |
<p>Prepn. of 4,4'-dihydoxy 3,3',5,5'-tetraalkyl diphenylmethanes (I) 2 in which R1 and R2 = alkyl gp.) comprises condensing a 2,6-dialkylphenol with formaldehyde in the presence of an acid catalyst water and >=1. Process gives high yiels of (I) and avoids use of HCl as catalyst, which is corrosive and may give rise to bis chloromethyl ether, a potent carcinogen. The presence of water and an alcohol lowers the vapour pressure of formaldehyde in the system, even at elevated temps., so that formaldehyde losses are reduced and the blockage of apparatus by deposits of low formaldehyde polymers is avoided. Prods. (I) are useful raw materials in the prodn. of polymeric materials. In an example 3050g 2,6-dimethylphenol, 750g 35% aq. formaldehyde soln. and 5850 g isobutanol were pumped continuously to an acid ion exchange resin bed, with an average residence time of 4 hours. Formaldehyde conversion was 82% and the yield more than 98%.</p> |
