| 摘要 |
Delayed action setting of a composition comprising an amonic latex of a film forming polymer is effected by the addition of a delayed action setting agent which is a mixture of: (1) a compound containing a multivalent metal cation, which compound has a solubility in the range 0.1 g to 150 g per 100 g of water at 20 DEG C. and which has a dissolution time greater than 1 minute, and (11) and alkali metal silico fluoride Other film forming materials such as bitumen may be present in the composition. The process is particularly useful for mixtures of polychloroprene latex and bitumen emulsion. The compound (1) can be either one which gives or one which does not give exudation (or 'sweating') of water from the latex. A preferred compound of the former type is calcium sulphate hemihydrate. The preferred fluoride (11) is sodium silico fluoride. The composition may also contain inert non-hydraulic particulate filler which can be a hard filler, e.g. sand or a deformable filler, e.g. tire crumbs, or a mixture of the two. |
