| 摘要 |
<p>The casting of metal articles in sand moulds is effected by breaking the moulded sand material away from the article after casting and cooling. The sand moulds are generally manufactured by mixing the sand with an argillaceous or resinous binder, shaping the mould material around a pattern of wood, plastic or metal to form the mould and then separating the pattern from the mould. The bonded sand, however, tends to stick to the pattern, to the detriment of the pattern and the mould, resulting in about 20 % rejects, a problem which has been identified with a wide variety of known binders thus far. In order to overcome the problem, a release agent in the form of a dispersion or solution of room temperature vulcanisable silicone rubber in a volatile organic solvent is prepared for the purposes of applying it by brush, spray or other appropriate means as a coating to the pattern. Various solvents, such as trichlorethane, benzene, toluene, xylene, solvent naphtha, mineral spirits and mineral turpentine may be used, with a preference for toluene, based on a weight of 96/4 to 50/50 for toluene to silicone rubber. The solution or dispersion allows for a coating application of 0.01 to 1.00 mm thick of silicone rubber, firmly bonded to the pattern after a curing period of about 16 hours at 25 °C and a substantial reduction in the rejection rate. Maintenance of the cured coating is relatively simple and requires no more than touching up at wear spots, when and where they occur.</p> |
