GB1011250A - Improvements relating to the production of latex foam rubber - Google Patents

Abstract

<PICT:1011250/C3/1> Latex foam rubber is manufactured by a process comprising the steps of preparing a stable fluid foam of latex compound of a density higher than the foam rubber density ultimately required, introducing a metered amount of the fluid foam into a mould, causing the foam to expand in the mould and freezing, gelling and vulcanizing the foam, characterized in that the flow of air from the mould during expansion of the foam is arrested automatically as soon as the foam fills the mould, the expanded foam being then rapidly frozen before being gelled. The expansion of the foam in the mould is preferably effected by applying a vacuum to the mould, a suitable mould for which is shown in Fig. 1. A prefoamed latex compound is metered to the mould cavity formed by the walls 1 and 2 which contain elongated passages 3. A vacuum is then applied to the enclosure 14 to evacuate the mould cavity through the semi-permeable inner gasket 3 and the prefoamed mix expands until contact is made with the gasket whereupon the foam coagulates to prevent air and foam escaping from the cavity, and forms a seal isolated from atmospheric pressure by the enclosure 14. Brine at -30 DEG F. is then circulated through the passages 3 to freeze the foam which may then be gelled by breaking the vacuum with carbon dioxide or by cold sensitizing for a sufficient time at a low temperature. Brine at room temperature is then circulated to warm the mould and its contents and then at 230 DEG F. to vulcanize the foam. A butadiene-styrene copolymer latex is mentioned as being suitable for the process. Instead of applying a vacuum to expand the foam, the same effect can be achieved by supplying the prefoamed latex to a pressurized mould which after isolation from the supply source is coupled to the outside atmosphere whereupon the foam expands and fills the mould. Specifications 455,138 and 619,619 are referred to.