Endothermic blowing agents compositions and applications

Abstract

A stabilized powdered endothermic blowing agent [which] is a mixture or a polycarboxylic acid and an inorganic carbonate, [and] the polycarboxylic acid and inorganic carbonate each having been surface treated with a component which prevents water from being absorbed thereby. The blowing agent is incorporated into a polymeric concentrate used for producing foamed products.

What is claimed: 
     
       1. An endothermic blowing agent which comprises a mixture of a polycarboxylic acid and an inorganic carbonate, wherein said polycarboxylic acid and said inorganic carbonate have been surface treated with a component selected from the group consisting of mono gylcerides, stearic acid, silane coupling agents and mixtures thereof which prevents water from being absorbed by said polycarboxylic acid and said inorganic carbonate.Iadd., said inorganic carbonate comprising sodium aluminum hydroxy carbonate..Iaddend. 
     
     
       2. An endothermic blowing agent according to claim 1, wherein said polycarboxylic acid is selected from the group consisting of those of the formula HOOC--R--COOH and alkali metal salts thereof, wherein R is alkylene of 1 to 8 carbon atoms which may contain one or more hydroxy substituents and may also contain unsaturation. 
     
     
       3. An endothermic blowing agent according to claim 2, wherein said polycarboxylic acid is citric acid, selected from the group consisting of fumaric acid, tartaric acid, sodium hydrogen citrate, monosodium citrate, and mixtures thereof. .[.4. An endothermic blowing agent according to claim 1, wherein said inorganic carbonate is an alkali metal or alkaline 
     
     
        earth metal carbonate..]. 5. An endothermic blowing agent according to claim 1, wherein said .[.inorganic carbonate is selected from the group consisting of sodium aluminum hydroxy carbonate, sodium bicarbonate and 
     
     
        mixtures thereof, and said.]. polycarboxylic acid is citric acid. 6. An endothermic blowing agent according to claim 1, wherein said surface 
     
     
        treating component comprises glyceryl monostearate. 7. An endothermic blowing agent according to claim 1, wherein the level of surface treatment of said polycarboxylic acid and said inorganic carbonate is between about 
     
     
        0.1 and 10.0 percent weight. 8. An endothermic blowing agent according to claim 7, wherein said level of surface treatment of said polycarboxylic 
     
     
        acid is about 1.0 percent by weight. 9. An endothermic blowing agent according to claim 7, wherein said level of surface treatment of said 
     
     
        inorganic carbonate is about 3.0 percent by weight. 10. An endothermic blowing agent according to claim 1, wherein the weight ratio of said surface treated polycarboxylic acid to said surface treated inorganic 
     
     
        carbonate is between about 0.10 and about 99.00. 11. An endothermic blowing agent according to claim 10, wherein said weight ratio of said surface treated polycarboxylic acid to said surface treated inorganic carbonate is between about 1.00 and about 5.00.