Method of producing polyurethane-based composite material, polyurethane-based composite material, and material for dental cutting work

A method of producing a polyurethane-based composite material, comprising:

• a polyaddition reaction step of subjecting a diol compound (a1) having one or more radically polymerizable groups and a diisocyanate compound (a2) to a polyaddition reaction in a polyaddition-reactive raw material composition containing the diol compound (a1), the diisocyanate compound (a2), and a polymerizable monomer (B) having one or more radically polymerizable groups in a molecule, and being free from causing a polyaddition reaction with any of the diol compound (a1) and the diisocyanate compound (a2), and free of a catalyst for accelerating the polyaddition reaction, at a temperature of 30° C. to 100° C., to thereby form a polyurethane component (A) having a number average molecular weight of from 1,500 to 5,000 and having a radically polymerizable group in side chains;
• a radically polymerizable raw material composition-preparing step of preparing a paste-like radically polymerizable raw material composition containing the polyurethane component (A), the polymerizable monomer (B), a radical polymerization initiator (C), and a filler (D);
• and
• a radical polymerization step of performing radical polymerization using the paste-like radically polymerizable raw material composition after completion of the polyaddition reaction step and the radically polymerizable raw material composition-preparing step, to thereby form a polyurethane-based composite material, wherein a content ratio of the filler (D) in the paste-like radically polymerizable raw material composition is from 71 mass % to 85 mass %,
• a polymerizable monomer blending ratio Rr represented by the following equation (1) is from 20 mass % to 80 mass %:
• Rr=100×Br/[a1r+a2r+Ar+Br], and Equation (1)
• in the equation (1), a1r represents a content (parts by mass) of the diol compound (a1) remaining unreacted in the paste-like radically polymerizable raw material composition, a2r represents a content (parts by mass) of the diisocyanate compound (a2) remaining unreacted in the paste-like radically polymerizable raw material composition, Ar represents a content (parts by mass) of the polyurethane component (A) in the paste-like radically polymerizable raw material composition, and Br represents a content (parts by mass) of the polymerizable monomer (B) in the paste-like radically polymerizable raw material composition.