Extrusion process for the preparation of alkali metal carbonate, bicarbonate and sesquicarbonate formulations using a dissolved functionalizing agent

A process for preparing a formulation for foaming plastics, the formulation consisting of an alkali metal salt a functionalizing agent, and optionally water, wherein the alkali metal salt is selected from the group consisting of alkali metal bicarbonate salts, alkali metal sesquicarbonate salts and combinations thereof, wherein said process comprises:

• (a) dissolving the functionalizing agent in water to obtain a solution comprising the functionalizing agent in an amount of 20 to 40 g per 100 g water;
• (b) mixing the alkali metal salt with the solution comprising the functionalizing agent in a weight ratio of at least 1/1 to at most 3/1 of alkali metal salt to the solution comprising the functionalizing agent so that a paste-like composition comprising the alkali metal salt and the functionalizing agent is formed;
• (c) extruding the paste-like composition to obtain a powder, filaments or granules comprising water, the alkali metal salt and the functionalizing agent, wherein the alkali metal salt is present in the paste-like composition undergoing extrusion in an amount of at least 75% by weight;
• and
• (d) at least partially removing the water from the powder, filaments or granules to obtain a powder, filaments or granules comprising the alkali metal salt and the functionalizing agent,
• wherein the functionalizing agent is polyvinylalcohol (PVOH).

A process for preparing a formulation for foaming plastics, the formulation comprising sodium bicarbonate, a functionalizing agent, and optionally water, wherein the functionalizing agent increases the CO2 release beginning temperature and/or the CO2 release maximum temperature of the sodium bicarbonate when used for foaming plastics, and wherein said process comprises:

• (a) dissolving the functionalizing agent in water to obtain a solution comprising the functionalizing agent in an amount of at least 20 g per 100 g water;
• (b) mixing the sodium bicarbonate with the solution comprising the functionalizing agent in a weight ratio so that a paste-like composition comprising the sodium bicarbonate and the functionalizing agent is formed;
• (c) extruding the paste-like composition to obtain a powder, filaments or granules comprising water, the sodium bicarbonate and the functionalizing agent, wherein the sodium bicarbonate is present in the paste-like composition undergoing extrusion in an amount of at least 75% by weight;
• and
• (d) at least partially removing the water from the powder, filaments or granules to obtain a powder, filaments or granules comprising the sodium bicarbonate and the functionalizing agent,
• wherein the functionalizing agent is polyvinylalcohol (PVOH), wherein the solution at step a) comprises 20 to 40 g of PVOH per 100 g of water, and wherein the mixing of the alkali metal salt with the solution of PVOH at step b) is at a weight ratio of at least 1/1 to at most 3/1 of alkali metal salt to the solution.