Molding sand comprising biodegradable polymeric binder

Abstract

Molding sand containing (i) 100 parts by weight of refractory quartz or olivine matrix and (ii) 1 to 5 parts by weight of organic binder. The organic binder contains a mixture of (a) 40-50% w/w aqueous solution of sodium poly(acrylate) in the amount of 30-70% by weight and (b) 40-50% w/w aqueous solution of dextrin in the amount of 30-70% by weight.

The invention claimed is: 
     
         1 . Molding sand, comprising:
 (i) 100 parts by weight of refractory quartz or olivine matrix, and   (ii) between 1 and 5 parts by weight of an organic binder, wherein   the organic binder comprises a mixture of:   (ii-a) 30-70% by weight with respect to the weight of the organic binder of a 40-50% w/w aqueous solution of sodium poly(acrylate), and   (ii-b) 30-70% by weight with respect to the weight of the organic binder of a 40-50% w/w aqueous solution of dextrin.   
     
     
         2 . The molding sand of  claim 1 , wherein the sodium poly(acrylate) has a weight average molecular weight Mw of 4,000-250,000 g/mol, pH of 7-9, and Brookfield viscosity of 400-5000 mPas. 
     
     
         3 . The molding sand of  claim 1 , wherein the dextrin has a molar mass Mw of 4,000-8,000 g/mol, pH of 6.5-7.5, and a Brookfield viscosity of 4000 mPas.