The present invention aims to provide a means by which a cured product to be obtained has a low dielectric loss tangent and higher heat resistance. Specifically, provided is an active ester resin that is a reaction product of a first aromatic compound having two or more phenolic hydroxy groups, a second aromatic compound having a phenolic hydroxy group, and a third aromatic compound having two or more carboxy groups and/or an acid halide thereof or an esterified compound thereof, in which at least one of the first aromatic compound, the second aromatic compound, and the third aromatic compound and/or the acid halide thereof or the esterified compound thereof has an unsaturated bond-containing substituent.

A plasticizer for a vinyl chloride resin with excellent balance of non-transfer properties, fogging resistance, flexibility, heat resistance, and cold resistance is provided. Specifically, a plasticizer for a vinyl chloride resin is a polyester made from a glycol having 2 to 18 carbon atoms, an aliphatic dicarboxylic acid having 4 to 14 carbon atoms, and a monoalcohol having 4 to 18 carbon atoms and/or a monocarboxylic acid having 2 to 21 carbon atoms, as reaction raw materials, in which the polyester has a number average molecular weight in a range of 500 to 6,000 and contains components with a molecular weight of 600 or less in a range of 0.5 to 3.0% by mass in terms of area ratio in gel permeation chromatography measurement.

A plasticizer for a vinyl chloride resin with excellent balance of non-transfer properties, fogging resistance, flexibility, heat resistance, and cold resistance is provided. Specifically, a plasticizer for a vinyl chloride resin is a polyester made from a glycol having 2 to 18 carbon atoms, an aliphatic dicarboxylic acid having 4 to 14 carbon atoms, and a monoalcohol having 4 to 18 carbon atoms and/or a monocarboxylic acid having 2 to 21 carbon atoms, as reaction raw materials, in which the polyester has a number average molecular weight in a range of 500 to 6,000 and contains components with a molecular weight of 600 or less in a range of 0.5 to 3.0% by mass in terms of area ratio in gel permeation chromatography measurement.

A plasticizer and a method for producing the same are provided. The method for producing the plasticizer includes: reacting a reaction mixture at each of a plurality of temperature holding stages in a heating process to form a semi-finished product; and purifying the semi-finished product at each of a plurality of low pressure stages of a decompression process to obtain a plasticizer. A temperature range of the heating process is from 140° C. to 220° C., a pressure range of the decompression process is from 750 Torr to 20 Torr, and the reaction mixture contains dibasic acid, diol, monohydric alcohol, and catalyst.

Provided are a monofunctional phenolic compound used for producing an active ester resin capable of forming a cured product having excellent dielectric properties and excellent heat resistance, an active ester resin and a method for producing the active ester resin, and a thermosetting resin composition and a cured product of the thermosetting resin composition. Specifically, provided are a monofunctional phenolic compound including one or more vinylbenzyl groups and an active ester resin including a vinylbenzyl structure attached to a terminal group of the molecular chain and derived from the monofunctional phenolic compound. The vinylbenzyl structure preferably includes a vinylbenzyl-modified aryloxycarbonyl group.

Provided are a monofunctional phenolic compound used for producing an active ester resin capable of forming a cured product having excellent dielectric properties and excellent heat resistance, an active ester resin and a method for producing the active ester resin, and a thermosetting resin composition and a cured product of the thermosetting resin composition. Specifically, provided are a monofunctional phenolic compound including one or more vinylbenzyl groups and an active ester resin including a vinylbenzyl structure attached to a terminal group of the molecular chain and derived from the monofunctional phenolic compound. The vinylbenzyl structure preferably includes a vinylbenzyl-modified aryloxycarbonyl group.

An unsaturated polyester resin composition with low styrene volatility and a molding article thereof are provided. The unsaturated polyester resin composition of includes: 30 to 60 parts by weight of unsaturated polyester resin and 2 to 30 parts by weight of comonomer, and the comonomer includes: (a) methyl styrene, (b) hydroxy acrylate monomer and (c) diallyl phthalate monomer, and the weight ratio of the content (a), (b), and (c) is 6:3:1 in the comonomer.

An unsaturated polyester resin composition with low styrene volatility and a molding article thereof are provided. The unsaturated polyester resin composition of includes: 30 to 60 parts by weight of unsaturated polyester resin and 2 to 30 parts by weight of comonomer, and the comonomer includes: (a) methyl styrene, (b) hydroxy acrylate monomer and (c) diallyl phthalate monomer, and the weight ratio of the content (a), (b), and (c) is 6:3:1 in the comonomer.

An object is to provide a crosslinked polyester resin that has high strength at room temperature but is capable of reprocessing, adhesion between films, and self-repair at a softening temperature thereof or higher, due to dynamic covalent crosslinks allowing bond exchange at high temperatures, that exhibits softening behavior due to bond exchange by a transesterification reaction even without containing any transesterification catalyst, and that exhibits self-adhesiveness, remoldability, and scratch repair properties. A crosslinked polyester resin in which a polyester resin having a carboxy group on a side chain is crosslinked by an epoxy-based crosslinking agent having a plurality of epoxy groups, wherein the epoxy-based crosslinking agent includes an epoxy amine compound having two or more tertiary amino groups and two or more epoxy groups in a molecule, and an amount of the epoxy amine compound is 3 to 30 parts by mole per 100 parts by mole of the carboxy group of the polyester resin.

An object is to provide a crosslinked polyester resin that has high strength at room temperature but is capable of reprocessing, adhesion between films, and self-repair at a softening temperature thereof or higher, due to dynamic covalent crosslinks allowing bond exchange at high temperatures, that exhibits softening behavior due to bond exchange by a transesterification reaction even without containing any transesterification catalyst, and that exhibits self-adhesiveness, remoldability, and scratch repair properties. A crosslinked polyester resin in which a polyester resin having a carboxy group on a side chain is crosslinked by an epoxy-based crosslinking agent having a plurality of epoxy groups, wherein the epoxy-based crosslinking agent includes an epoxy amine compound having two or more tertiary amino groups and two or more epoxy groups in a molecule, and an amount of the epoxy amine compound is 3 to 30 parts by mole per 100 parts by mole of the carboxy group of the polyester resin.