| 摘要 |
Vulcanizable compositions comprise rubber, a free sulphur vulcanizing system and a rubber reinforcing composition comprising a formaldehyde donor and a reactive phenolic composition comprising a resin obtained by reacting phenol with sulphur or a sulphur chloride, the proportion of phenol/sulphur resin being 1 to 15% by weight of the rubber. The rubber may be natural rubber, polyisoprene, polybutadiene, polychloroprene, butadiene/styrene copolymer, butadiene/acrylonitrile copolymer, isobutylene/isoprene copolymer or ethylene/propylene/diene terpolymer. The formaldehyde donor may be hexamethylene tetramine, paraform, anhydroformaldehyde aniline resoles or melamine/formaldehyde resins. The reactive phenolic composition is essentially not heat advancing or self hardening, but reacts with the formaldehyde donor to form a thermoset product. If the phenol/sulphur resin does not so react a novolak must also be added, or the resin co-condensed through formaldehyde with a trifunctional phenol. The resin may be prepared by reacting phenols containing at least two free o or p positions with sulphur or a sulphur chloride under alkaline conditions. The reactive phenolic compositions preferably also contain a novolak resin. In examples styrene/butadiene, acrylonitrile/ butadiene and natural rubbers are vulcanized with reactive phenolic compositions comprising hexamethylene tetramine and (1) a phenol/sulphur resin, (2) a cresol/sulphur resin, (3) a phenol/sulphur resin and a cashew nut shell oil modified phenolic novolak, (4) a cresol/sulphur resin and a phenol/formaldehyde novolak, (5) a phenol/sulphur resin reacted with formaldehyde, (6) a phenol/sulphur resin reacted with formaldehyde and modified with partially polymerized cashew nut shell oil, (7) a cyclopentenyl phenol/sulphur resin reacted with formaldehyde, and then with phenol and formaldehyde, and (8) a resorcinol/sulphur resin. |
