Coating compositions for inorganic casting molds and cores, comprising formic acid esters, and use thereof

Abstract

The subject matter of the invention relates to coating compositions comprising formic acid esters, an aqueous carrier liquid and pulverulent refractory material, and to the use thereof for casting molds, in particular those produced using water glass as a binder.

1 . A sizing composition comprising:
 (A) esters of formic acid;   (B) a carrier fluid comprising or consisting of water, and   (C) refractory materials.   
     
     
         2 . The sizing composition according to  claim 1 , wherein the alcohol group(s) of the formic acid ester(s) in each case contain fewer than 10 carbon atoms. 
     
     
         3 . The sizing composition according to  claim 2 , wherein the concentration of the formic acid esters in the sizing composition amounts to 1 to 8% by weight. 
     
     
         4 . The sizing composition according to  claim 1 , wherein the carrier fluid comprises of more than 50% by weight of water. 
     
     
         5 . The sizing composition according to  claim 1 , wherein the solids content of the sizing composition amounts to 30 to 70% by weight. 
     
     
         6 . The sizing Sizing composition according to  claim 1 , wherein the sizing composition comprises 10 to 85% by weight of refractory material, based on the solids content of the sizing composition. 
     
     
         7 . The sizing composition according to  claim 1 , wherein the refractory materials are selected from the group consisting of: quartz, aluminum oxide, zirconium dioxide, aluminum silicates, zirconium sands, zirconium silicates, olivine, talc, mica, coke, feldspar, diatomite, kaolins, calcined kaolins, kaolinite, metakaolinite, iron oxide, bauxite and mixtures thereof. 
     
     
         8 . The sizing composition according to  claim 1 , in which the refractory materials have particle sizes of 0.1 to 500 μm, measured by light scattering according to DIN/ISO 13320. 
     
     
         9 . The sizing composition according to  claim 1 , wherein the sizing composition comprises 0.1 to 20% by weight, of at least one binder, based on the solids content of the sizing composition. 
     
     
         10 . The sizing composition according to  claim 1 , wherein the sizing composition comprises a lustrous coal forming agent or graphite. 
     
     
         11 - 14 . (canceled) 
     
     
         15 . The sizing composition according to  claim 1 , wherein the alcohol group(s) of the formic acid ester(s) in each case contain fewer than 6 carbon atoms. 
     
     
         16 . The sizing composition according to  claim 1 , wherein the alcohol group(s) of the formic acid ester(s) in each case contain fewer than 3 carbon atoms. 
     
     
         17 . The sizing composition according to  claim 2 , wherein the concentration of the formic acid esters in the sizing composition amounts to 2 to 8% by weight. 
     
     
         18 . The sizing composition according to  claim 2 , wherein the concentration of the formic acid esters in the sizing composition amounts to 3 to 6% by weight. 
     
     
         19 . The sizing composition according to  claim 4 , wherein the carrier fluid further comprises alcohols, including polyalcohols and polyether alcohols. 
     
     
         20 . The sizing composition according to  claim 19 , wherein the carrier fluid can be fully evaporated at up to 160° C. and 1013 mbar. 
     
     
         21 . The sizing composition according to  claim 1 , in which the refractory materials have particle sizes of 1 to 200 μm, measured by light scattering according to DIN/ISO 13320. 
     
     
         22 . The sizing composition according to  claim 1 , wherein the sizing composition comprises 0.5 to 5-% by weight of at least one binder, based on the solids content of the sizing composition. 
     
     
         23 . The sizing composition according to  claim 10 , wherein the lustrous coal forming agent or graphite is present in the amount of 0.1 to 10% by weight. 
     
     
         24 . The sizing composition according to  claim 10 , wherein the lustrous coal forming agent or graphite is present in the amount of 0.5 to 3% by weight. 
     
     
         25 . A mold or core for casting, comprising:
 a molding material mixture, coated with a sizing composition according to  claim 1 ; and   a binder comprising water glass.   
     
     
         26 . The mold or core of  claim 25 , wherein:
 the molding material mixture comprises at least one member selected from the group consisting of: silicon dioxide, aluminum oxide, titanium oxide and zinc oxide.   
     
     
         27 . The mold or core of  claim 25 , wherein:
 the sizing composition is diluted with at least water before coating the molding material mixture.   
     
     
         28 . A method for sizing a mold or core for casting, comprising the steps of:
 providing a mold or core for casting, the mold or core comprising a molding material mixture and a binder comprising water glass; and   coating the mold or core with a sizing composition comprising:
 esters of formic acid; 
 a carrier fluid comprising water, and 
 refractory materials. 
   
     
     
         29 . The method of  claim 29 , wherein:
 the molding material mixture comprises at least one member selected from the group consisting of: silicon dioxide, aluminum oxide, titanium oxide and zinc oxide.   
     
     
         30 . The method of  claim 29 , wherein:
 the sizing composition is diluted with at least water before the coating step.