Binder composition for foundry sand molds

#This invention relates to binder compositions having self-hardening properties at room temperature for foundry (or molding) sands for metal-casting molds.

#In the foundry industry, binder compositions for producing sand molds are extremely useful and important.

#Heretofore, inorganic and organic binders (bonding materials) have been used in sand molds for metal casting. In all of these binders, however, there are advantages and drawbacks, and a fully satisfactory binder has not yet been found.

#In order to indicate more fully the nature and utility of this invention, the following specific examples or practice thereof are set forth, it being understood that these examples are presented as illustrative only and that they are not intended to limit the scope of the invention.

#Throughout these examples, quantities expressed in "part(s)" and "percent" are by weight.

#3,500 parts of "Ayaragi" silica sand No. 6 and a mixture of 15.5 parts of dipropylene glycol, 7.8 parts of nonyl phenol, and 15.5 parts of a distillation residue produced in the production of ethylbenzene were homogeneously mixed in a mixer, and, thereafter, into the resulting mixture, 31.1 parts of polymethylene polyisocyanate which is a mixture of diphenylmethane diisocyanate and triphenylmethane triisocyanate, NCO group content being 31.5% was further blended. The resulting mixture was thoroughly mixed by agitation. This mixture was poured into a cylindrical metal mold of 5-cm inner diameter and 13-cm height and was tamped by means of a standard compaction testing machine. The strength of the tamped mixture after one day was measured. The bench life was amply long, being approximately one hour, and the compressive strength after one day was 34.3 kg/cm.sup.2.