PRODUCTION OF FOAM

PURPOSE:To obtain a foam, containing uniform and fine cells at a high expansion ratio and useful for heat insulating and cushioning materials, etc., by melt kneading a specific expandable composition, dissolving a specific amount of an inorganic gas in the resultant molding and thermally expanding the prepared molding at a specified temperature. CONSTITUTION:This method for producing a foam is to melt knead an expandable composition comprising (A) a polyolefin and (B) a thermal decomposition type foaming agent such as azodicarbonamide or N,N'- dinitrosopentamethylenetetramine at a lower temperature than the decomposition temperature of the component (B), then dissolve (C) an inorganic gas such as carbon dioxide or nitrogen in an amount of >=1cm based on 1g molding before or after cross-linking the molding, heat the resultant molding at a temperature above the decomposition temperature of the component (B) and expand the resultant molding.