| 摘要 |
1,131,549. Rubber modified novolaks. B.P. CHEMICALS (U.K.) Ltd. 13 Sept., 1967 [5 Oct., 1966], No. 44518/66. Headings C3P and C3R. Rubber modified novolak resins are prepared by allowing an aldehyde to react with a molar excess of phenol under novolak-forming conditions and in the presence of a latex of an acrylonitrile-butadiene rubber. The aldehyde may be paraformaldehyde or formalin and the phenol may be phenol. The rubber may contain 10-55% acrylonitrile units and optionally styrene or methyl methacrylate units and carboxyl groups. The phenol and aldehyde may be reacted at 50‹ to 200‹ C. and a pH between 1 and 7, a catalyst, e.g. aqueous oxalic acid, HCI, H 3 PO 4 , HNO 3 , formic acid or acetic acid, being present. When about 2% of free formaldehyde remains 5 to 150 parts of the latex may then be added per 100 parts of formaldehyde and the liquid media distilled off. The product may be cured by addition of hexamethylene tetramine or paraformaldehyde optionally together with a rubber curing agent. The cured products may be made into brake linings and clutch facings. |
