Epoxy resin composition, semi-cured epoxy resin composition, cured epoxy resin composition, molded article, and cured molded article

1. An epoxy resin composition, comprising:

an epoxy resin; and

a curing agent, wherein:

the epoxy resin comprises a multimeric compound having at least one selected from the group consisting of a structural unit represented by the following Formula (IA) and a structural unit represented by the following Formula (IB),

the multimeric compound comprises a dimeric compound containing two structural units represented by the following Formula (II) in one molecule,

a ratio of the dimeric compound is from 15% by mass to 28% by mass with respect to the epoxy resin as a whole, and

the epoxy resin comprises a reaction product obtained by reacting an epoxy resin monomer represented by the following Formula (I″) and a divalent phenol compound having two hydroxyl groups as substituents on a single benzene ring, with a ratio (Ep/Ph) of a number of equivalents of the epoxy groups of the epoxy resin monomer represented by the following Formula (I″) (Eh) and a number of equivalents of the phenolic hydroxyl groups of the divalent phenol compound having two hydroxyl groups as substituents on a single benzene ring (Ph) being set in a range of from 100/18 to 100/10:

wherein, in Formula (IA) and Formula (IB), each of R 1 to R 4 independently represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms; each R 5 independently represents an alkyl group having from 1 to 8 carbon atoms; and n represents an integer from 0 to 4;

wherein, in Formula (II), each of R 1 to R 4 independently represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms; and

wherein, in Formula (I″), each of R 1 to R 4 independently represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms.

2. The epoxy resin composition according to claim 1 , wherein:

the dimeric compound comprises at least one selected from the group consisting of a compound represented by the following Formula (II-A), a compound represented by the following Formula (II-B) and a compound represented by the following Formula (II-C), and

a total ratio of the compound represented by the following Formula (II-A), the compound represented by the following Formula (II-B) and the compound represented by the following Formula (II-C) is from 15% by mass to 28% by mass with respect to the epoxy resin as a whole:

wherein, in Formula (II-A), to Formula (II-C), each of R 1 to R 4 independently represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms; each R 5 independently represents an alkyl group having from 1 to 8 carbon atoms; and n represents an integer from 0 to 4.

3. The epoxy resin composition according to claim 1 , wherein the structural unit represented by Formula (IA) is a structural unit represented by the following Formula (IA′), and the structural unit represented by Formula (IB) is a structural unit represented by the following Formula (IB′):

wherein, in Formula (IA′) and Formula (IB′), each of R 1 to R 4 independently represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms; each R 5 independently represents an alkyl group having from 1 to 8 carbon atoms; and n represents an integer from 0 to 4.

4. The epoxy resin composition according to claim 3 , wherein:

the dimeric compound comprises at least one selected from the group consisting of a compound represented by the following Formula (II-A′), a compound represented by the following Formula (II-B′) and a compound represented by the following Formula (II-C′), and

a total ratio of the compound represented by the following Formula (II-A′), the compound represented by the following Formula (II-B′) and the compound represented by the following Formula (II-C′) is from 15% by mass to 28% by mass with respect to the epoxy resin as a whole:

wherein, in Formula (II-A′) to Formula (II-C), each of R 1 to R 4 independently represents a hydrogen atom or an alkyl group having from 1 to 3 carbon atoms; each R 5 independently represents an alkyl group having from 1 to 8 carton atoms; and n represents an integer from 0 to 4.

5. The epoxy resin composition according to claim 1 , wherein:

the epoxy resin comprises the epoxy resin monomer represented by the Formula (I″), and

a ratio of the epoxy resin monomer is from 57% by mass to 80% by mass with respect to the epoxy resin as a whole.

6. The epoxy resin composition according to claim 1 ,

wherein the curing agent comprises a novolac resin that contains a compound having a structural unit represented by at least one selected from the group consisting of the following Formula (II-1) and Formula (II-2):

wherein, in Formula (II-1) and Formula (II-2), each of R 21 and R 24 independently represents an alkyl group, an aryl group, or an aralkyl group; each of R 22 , R 23 , R 25 and R 26 independently represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group; each of m21 and m22 independently represents an integer from 0 to 2; and each of n21 and n22 independently represents an integer from 1 to 7.

7. The epoxy resin composition according to claim 6 , wherein, in the curing agent, a content ratio of a monomer, which is the same as a phenol compound constituting the novolac resin, is from 10% by mass to 50% by mass.

8. The epoxy resin composition according to claim 1 , wherein the curing agent comprises a novolac resin that contains a compound having a structure represented by at least one selected from the group consisting of the following Formula (III-1) to Formula (III-4):

wherein, in Formula (III-1) to Formula (III-4), each of m31 to m34 and n31 to n34 independently represents a positive integer; and each of Ar 31 to Ar 34 independently represents a group represented by the following Formula (III-a) or a group represented by the following Formula (III-b):

wherein, in Formula (III-a) and Formula (III-b), each of R 31 and R 34 independently represents a hydrogen atom or a hydroxyl group; and each of R 32 and R 33 independently represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms.

9. The epoxy resin composition according to claim 8 , wherein, in the curing agent, a content ratio of a monomer, which is the same as a phenol compound constituting the novolac resin, is from 10% by mass to 50% by mass.

10. The epoxy resin composition according to claim 1 , further comprising an inorganic filler.

11. The epoxy resin composition according to claim 10 , wherein the inorganic filler comprises at least one selected from the group consisting of alumina, boron nitride, aluminum nitride, silica, and magnesium oxide.

12. The epoxy resin composition according to claim 10 , wherein a content ratio of the inorganic filler is from 60% by volume to 90% by volume with respect to solid content.

13. The epoxy resin composition according to claim 1 , further comprising a silane coupling agent.

14. The epoxy resin composition according to claim 13 , wherein the silane coupling agent comprises a phenyl group-containing silane coupling agent.

15. A semi-cured epoxy resin composition, which is a semi-cured product of the epoxy resin composition according to claim 1 .

16. A cured epoxy resin composition, which is a cured product of the epoxy resin composition according to claim 1 .

17. A molded article produced by press-molding the epoxy resin composition according to claim 1 .

18. A cured molded article produced by post-curing the molded article according to claim 17 by heating.