Patent GB-904003-A (GB)
Title: Method and apparatus for the production of cellular synthetic rubber
Inventor: MERRIMAN PETER
IPC: B29B7/40
Filed: 1958-02-06
Abstract: In a continuous process for preparing cellular synthetic rubber from a liquid composition containing a polymer and a compound capable of reacting therewith to form a synthetic elastomer, an inert gas which is in the liquefied state and which is soluble in the polymer is incorporated under pressure into the liquid composition at a temperature at which substantially no reaction between the polymer and the compound takes place, the composition is foamed by reducing the pressure thereon, and the temperature of the foam is raised to convert the composition into an elastomer before substantial breakdown of the foam takes place. The process is applicable to the production of polyurethane foams from polymers derived from the reaction of polyols with polyisocyanates or polyisothiocyanates.  In a modification the inert gas is incorporated into the polymer prior to the addition of the compound capable of reacting therewith. Specified inert gases are carbon dioxide, sulphur dioxide, nitrous oxide, ethylene oxide, and lower hydrocarbons and halogenated methanes.  The reacting compound (i.e. cross-linking agent) may be water or a polyol.  The composition may also include a cross-linking catalyst.  In the example, a mixture was made by successively adding trimethylol propane, benzoyl chloride, toluene diisocyanate and polydimethyl siloxane to polypropylene glycol; the resulting polymer was mixed with liquid carbon dioxide, N,N-dimethylbenzylamine and N-methyl morpholine (catalysts), pressure in the mixing chamber being maintained at 300 p.s.i.; the material was foamed by running it into an open mould; and the foam was set, compressed by passing it through rollers, and finally matured by heating.  A suitable mixing apparatus is that disclosed in Specification 804,004.ALSO:In a continuous process for preparing cellular synthetic rubber from a liquid composition containing a polymer and a compound capable of reacting therewith to form a synthetic elastomer, an inert gas which is in the liquefied state and which is soluble in the polymer is incorporated under pressure into the liquid composition at a temperature at which substantially no reaction between the polymer and the compound takes place, the composition is foamed by reducing the pressure thereon, and the temperature of the foam is raised to convert the composition into an elastomer before substantial breakdown of the foam takes place.  The process is applicable to the production of polyurethane foams from polymers derived from the reaction of polyols with polyisocyanates or polyisothiocyanates.  In a modification, the inert gas is incorporated into the polymer prior to the addition of the compound capable of reacting therewith.  Specified inert gases are carbon dioxide, sulphur dioxide, nitrous oxide, ethylene oxide, and lower hydrocarbons and halogenated methanes.  The reacting compound (i.e. crosslinking agent) may be water or a polyol.  The composition may also include a cross-linking catalyst.  In the example, a mixture was made by successively adding trimethylol propane, benzoyl chloride, toluene diisocyanate and polydimethyl siloxane to polypropylene glycol; the resulting polymer was mixed with liquid carbon dioxide, N1N-dimethylbenzgylamine and N-methyl morpholine (catalysts), pressure in the mixing chamber being maintained at 300 p.s.i.; the material was foamed by running it into an open mould, and the foam was set, compressed by passing it through rollers, and finally matured by heating.  A suitable mixing apparatus is that disclosed in Specification 804,004.