| 摘要 |
Polystyrene foam is prepared by mixing a polystyrene resin, a salt capable of liberating carbon dioxide on reaction with an organic acid, and an organic acid mixture comprising an organic acid hydrate and an anhydrous organic acid, heating to a temperature sufficient to melt the admixture, injecting a liquid blowing agent and mixing with the molten mixture and cooling to a temperature at which it can be extruded as a polystyrene foam having fine cell size. Examples of suitable salts capable of forming carbon dioxide are alkali and alkaline-earth metal carbonates and bicarbonates, particularly sodium bicarbonate. Examples of organic acids which may be used in the acid component are oxalic, succinic, itaconic, malonic, citraconic, adipic, malic, tartaric, phthalic, chloroacetic, diglycollic and, particularly, citric acids. The per cent by weight ratio of organic acid hydrate to anyhydrous organic acid is from 10:90 to 90:10. The blowing agent is preferably a volatile organic liquid, such as butane, propane, hexane or petroleum ether. |
