Catalysts comprising methane sulfonic acid for the acid hardening method
A method for producing cores and molds for the foundry industry utilizing a flowable fire-resistant primary molding material. The method includes an acid applied to the flowable fire resistant primary molding material to obtain an acid-coated fire-resistant primary molding material. A binder that can be cured by acid is applied to the acid-coated fire resistant primary molding material to obtain a fire-resistant primary molding material coated with a binder. The fire-resistant primary molding material coated with a binder is then molded into a molded body, and-the molded body is cured. The acid used is a mixture of methane sulfonic acid and at least one sulfur-free acid. The casting molds can be produced having reduced emission of harmful compounds during casting.
1. A method for producing cores and moulds for the foundry industry, comprising:
providing a flowable, fire-resistant primary moulding material;
applying an acid to the flowable, fire-resistant primary moulding material, to obtain an acid-coated primary moulding material;
applying a binder that is curable with an acid to the acid coated fire-resistant primary moulding material, to obtain a fire-resistant primary moulding material coated with a binder;
shaping the fire-resistant primary moulding material coated with a binder to form a moulded body; and
curing the moulded body;
wherein the acid is a mixture of methane sulfonic acid and at least one further, sulphur-free acid, wherein the fraction of methane sulfonic acid in the acid is selected to be less than 70% by weight, the sulphur-free acid is an organic acid having a carboxyl group and at least one more group selected from the group consisting of carboxyl group, hydroxy group, and aldehyde group, and the organic acid has a pK a of less than 4, measured at 25° C., and the acid-binder comprises a furan-no-bake binder or a phenol-no-bake binder.
2. The method according to claim 1 , wherein the organic acid is selected from the group of citric acid, glycolic acid and glyoxylic acid.
3. The method according to claim 1 , wherein the acid is added in the form of an aqueous solution and the concentration of the acid in the aqueous solution is at least 30% by weight.
4. The method according to claim 1 , wherein curing of the moulded body is carried out at a temperature of less than 40° C.