GB847081A - Improvements in and relating to gas-expanded cellular articles - Google Patents

Abstract

Compositions of cellular rubber or plastic material ('plastic' being defined as a normally solid synthetic organic polymer) are produced by mixing the material with a finely divided solid molecular sieve-type adsorbent charged with an adsorbate which is released as a gas at or just below the curing temperature of the material, the mixture being heated to at least the curing temperature. Adsorbents specified are zeolites, naturally occurring such as chabasite, or synthetic of formula <FORM:0847081/IV(a)/1> where "n" is the valency of the cation "M" and "X" and "Y" indicate numbers of molecules. Synthetic zeolites designated A and X in which "M" is preferably sodium in the above formula but can be at least one of the group hydrogen. ammonium, metals in Group I and II and the transition metals of the Periodic Table, are described in Specification 777,232. Such zeolites blow adsorbates such as water, carbon dioxide, ethane and "Freon"-12 (Registered Trade Mark) at temperatures up to 200 DEG C. and can also be used for blowing polymers such as polyfluoroethylenes and polyamides at higher temperatures. In examples, sodium zeolites A and X saturated with water or carbon dioxide are employed to blow compositions comprising (1) a thermosetting methyl- and phenylcontaining silicone resin; (2) a dimethyl silicone gumstock, silica and dibenzyl peroxide; (3) a butadiene styrene rubber stock, a plasticizer composed of a mixture of an oil-soluble sulphonic acid and a paraffin oil, silica and zinc oxide. In Example 3, different curing agents, viz. sulphur, benzothiazyl disulphide, zinc hexyl xanthate, or dibenzylamine are included in the composition.ALSO:Cellular rubber or plastic material ('plastic' being defined as a normally solid synthetic organic polymer) is produced by mixing the material with a finely divided solid molecular sieve-type adsorbent charged with an adsorbate which is released as a gas at or just below the curing temperature of the material, the mixture being heated to at least the curing temperature. Adsorbents specified are zeolites, naturally occurring such as chabasite, or synthetic of formula M2-nO : Al2O3 : XSiO2 : YH2O where "n" is the valency of the cation "M" and "X" and "Y" indicate numbers of molecules. Synthetic zeolites designated A and X in which "M" is preferably sodium in the above formula but can be at least one of the group hydrogen, ammonium, metals in Group I and II and the transition metals of the Periodic Table, are described in Specification 777,232. Such zeolites blow adsorbates such as water, carbon dioxide, ethane and "Freon"-12 (Registered Trade Mark) as temperatures up to 200 DEG C and can also be used for blowing polymers such as polyfluoroethylenes and polyamides at higher temperatures. In Examples sodium zeolites A and X saturated with water or carbon dioxide are employed to blow compositions comprising (1) a thermosetting methyl- and phenylcontaining silicone resin; (2) a dimethyl silicone gumstock, silica and dibenzyl peroxide; (3) a butadiene styrene rubber stock, a plasticizer composed of a mixture of an oil-soluble sulphonic acid and a paraffin oil, silica and zinc oxide. In Example 3 the effect is illustrated of using different curing agents viz.: sulphur, benzothiazyl p disulphide, zinc hexyl xanthate or dibenzylamine, for obtaining a high or low temperature cure.