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AssigneeJ.M. Huber Corporation
InventorsSatish K. Wason, Gerry Mooney, Claude R. Andrews, Michael E. Tarquini, John A. Kosin, Rod A. Garcia
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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.
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 , said inorganic carbonate comprising sodium aluminum hydroxy carbonate.
[4. An endothermic blowing agent according to claim 1, wherein said inorganic carbonate is an alkali metal or alkaline
Dependencies are inferred from the claim text.
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The present invention relates to endothermic blowing agents for use in making foamed products such as cellular structured plastics or rubbers. In particular, the present invention relates to endothermic blowing agents which have been chemically stabilized to prevent premature reaction with water.
The term "foaming agent" or "blowing agent" is used to describe any substance which alone or in combination with other substances is capable of producing a cellular structure in a plastic or rubber mass. Thus, the term includes gases which expand when pressure is released, soluble solids that leave pores when leached out, liquids which develop cells when they change to gases, and chemical agents that decompose or react under the influence of heat to form a gas.
Known liquid foaming agents include certain aliphatic and halogenated hydrocarbons, low boiling alcohol ethers, ketones, and aromatic hydrocarbons. Chemical foaming agents range from simple salts such as ammonium or sodium bicarbonate to complex nitrogen releasing agents, of which azobisformamide is an important example.
The following examples are presented to illustrate the invention which is not intended to be considered as being limited thereto. In the examples and throughout percentages are by weight unless otherwise indicated.
A 25% concentrate of endothermic blowing agent was prepared in ethylene-vinyl acetate using a 30 millimeter twin screw extruder. The concentrates were let down to 0.5% active blowing agent in polypropylene. Plaques (4".times.4".times.1/4") were then foamed in a 50 ton Newbury injection molder at 200.degree. C. Table I sets forth the excellent weight loss and impact properties. Comparisons are made with other commercially available blowing agents.
The procedure used in Example I was repeated, except 1% active blowing agent was used in the final blend of polypropylene. Table II summarizes the weight reduction property as the weight ratio of inorganic carbonate to polycarboxylic acid varied from 0.25 to 1.30.