PURPOSE: To improve the hot strength and collapsing properties of a mold by a titled composition by compounding an unsaturated polyester resin contg. a copolymerizable unsaturated prepolymer or monomer and a bismaleinimide at specific ratios.
CONSTITUTION: A copolymerizable unsaturated prepolymer or monomer is compounded as a crosslinkable monomer at 0W50pts.wt. to 100pts.wt. crystallinne unsaturated polyester which is solid at ordinary temp. and has practically no tackiness. 100Pts.wt. the unsaturated polyester resin obtained in this way and 5W100pts.wt. a bismaleinimide compound expressed by the formula I (R1 denotes a bivalent org. group having C=C, and R2 denotes an aromatic or alicyclic org. group) are compounded. If a core or mold is formed by using this resin composition as a molding sand binder, the core or mold of excellent hot bending strength and good collapsing properties after casting is obtained.
KONNAI NOBUO
SUYAMA ISAO
OOKAWA HIROE
OYAMADA AKIRA
JINBOU YOSHIO
NISSAN MOTOR