An addition reaction type polyimide resin molded body having a thickness of 5 mm or more, with a number of defects having a size of 0.5 mm or more present on the entire surface of the molded body being 1 per 100 cm.sup.2 or less. The addition reaction type polyimide resin molded body is formed by: holding a prepolymer of an addition reaction type polyimide resin at a temperature equal to or higher than a viscosity increase starting temperature of the addition reaction type polyimide resin and increasing a melt viscosity at a temperature lower by 10° C. than the viscosity increase starting temperature to 70 to 900 kPa.Math.s; grinding and mixing the addition reaction type polyimide resin to form a molding precursor; and shaping the molding precursor at a temperature equal to or higher than a heat-curing temperature of the addition reaction type polyimide resin.

An addition reaction type polyimide resin molded body having a thickness of 5 mm or more, with a number of defects having a size of 0.5 mm or more present on the entire surface of the molded body being 1 per 100 cm.sup.2 or less. The addition reaction type polyimide resin molded body is formed by: holding a prepolymer of an addition reaction type polyimide resin at a temperature equal to or higher than a viscosity increase starting temperature of the addition reaction type polyimide resin and increasing a melt viscosity at a temperature lower by 10° C. than the viscosity increase starting temperature to 70 to 900 kPa.Math.s; grinding and mixing the addition reaction type polyimide resin to form a molding precursor; and shaping the molding precursor at a temperature equal to or higher than a heat-curing temperature of the addition reaction type polyimide resin.

There is provided an aromatic hydrocarbon formaldehyde resin obtained by reacting an aromatic hydrocarbon compound (A) represented by the following formula (1) with formaldehyde (B) in the presence of an acidic catalyst. ##STR00001##
wherein R represents an organic group having 1 to 10 carbon atoms; l represents an integer of 0 to 2, and m and n represent integers satisfying 1≦m+n≦10, m≧0 and n≧1.

There is provided an aromatic hydrocarbon formaldehyde resin obtained by reacting an aromatic hydrocarbon compound (A) represented by the following formula (1) with formaldehyde (B) in the presence of an acidic catalyst. ##STR00001##
wherein R represents an organic group having 1 to 10 carbon atoms; l represents an integer of 0 to 2, and m and n represent integers satisfying 1≦m+n≦10, m≧0 and n≧1.

An addition reaction type polyimide resin molded body having a thickness of 5 mm or more, with a number of defects having a size of 0.5 mm or more present on the entire surface of the molded body being 1 per 100 cm.sup.2 or less. The addition reaction type polyimide resin molded body is formed by: holding a prepolymer of an addition reaction type polyimide resin at a temperature equal to or higher than a viscosity increase starting temperature of the addition reaction type polyimide resin and increasing a melt viscosity at a temperature lower by 10 C. than the viscosity increase starting temperature to 70 to 900 kPa.Math.s; grinding and mixing the addition reaction type polyimide resin to form a molding precursor; and shaping the molding precursor at a temperature equal to or higher than a heat-curing temperature of the addition reaction type polyimide resin.

An addition reaction type polyimide resin molded body having a thickness of 5 mm or more, with a number of defects having a size of 0.5 mm or more present on the entire surface of the molded body being 1 per 100 cm.sup.2 or less. The addition reaction type polyimide resin molded body is formed by: holding a prepolymer of an addition reaction type polyimide resin at a temperature equal to or higher than a viscosity increase starting temperature of the addition reaction type polyimide resin and increasing a melt viscosity at a temperature lower by 10 C. than the viscosity increase starting temperature to 70 to 900 kPa.Math.s; grinding and mixing the addition reaction type polyimide resin to form a molding precursor; and shaping the molding precursor at a temperature equal to or higher than a heat-curing temperature of the addition reaction type polyimide resin.