Abstract: A toner binder for electrophotography is provided whose minimum fixing temperature is low, image offsetting temperature to the heat-roll is high, and whose stability upon storage is good.The toner binder comprises a thermoplastic resin (I) of 10 to 50% by weight, i.e., a copolymer having a structural unit consisting of a styrene series monomer and a (meth)acrylic monomer, having a molecular weight of more than 30,000 when fractionated by gel permeation chromatography, having a glass transition temperature of -20.degree. to +40.degree. C.; and a thermoplastic resin (II) of 10 to 50% by weight, i.e., a polymer selected from a copolymer (II-a) of a vinyl monomer selected from group consisting of styrene and substituted styrenes, a copolymer (II-b) having a structural unit consisting of styrene series monomers and (meth)acrylic monomers, polyester resin (II-c), and a copolymer (II-d) including a moiety of a copolymer (II-b) and a moiety of a polyester resin (II-c).

Abstract: High-density polyisocyanurate resins having improved rigidity, heat resistance and/or impact resistance can be obtained by reacting a polyisocyanate with a polymer polyol derived from a polyol having a molecular weight of at least 4500, and optionally a crosslinker, in the presence of trimerization catalyst, using isocyanate index of 200-5000.