Molding sand mixture for the manufacture of molds and cores

摘要

A molding sand mixture containing a filler, a binder in the form of a solution of hydrolyzed ethylsilicate and a curing agent; as the latter use is made of an organic solution of a polyorganosilazane of the formula: {(R2SiNH)n [R'Si(NH)1,5]m}k, wherein R is CH3, R' is CH3 or C6H5, n=1, k=4-10, m=1-3. The components are taken in the following proportions in percent by weight: solution of hydrolyzed ethylsilicate 10 to 35 organic solution of polyorganosilazane 0.2 to 2.0 filler the balance. The curing agent according to the present invention gives a high quality of the surface finish of the final castings.