Thermosetting resin composition and its production method, prepreg, laminate, and printed wiring board

1. A method for producing a thermosetting resin composition that comprises:

(A) a maleimide compound having an acidic substituent and an N-substituted maleimide group, which is obtained by reacting (a1) a maleimide compound having at least two N-substituted maleimide groups in one molecule, (a2) a monoamine compound having an acidic substituent, and (a3) a diamine compound,

(B) an epoxy resin having at least two epoxy groups in one molecule,

(C) a copolymer resin having a structural unit derived from an aromatic vinyl compound and a structural unit derived from a maleic anhydride,

(D) a silica treated with an aminosilane coupling agent, and

(E) a flame retardant dispersion,

the method comprising the following steps 1 and 2:

step 1: a step of dispersing a flame retardant in a dispersion medium to prepare (E) a flame retardant dispersion, wherein the flame retardant has a mean particle size of 0.1 to 8 μm; and

step 2: a step of mixing (A) a maleimide compound, (B) an epoxy resin having at least two epoxy groups in one molecule, (C) a copolymer resin having a structural unit derived from an aromatic vinyl compound and a structural unit derived from a maleic anhydride, (D) a silica treated with an aminosilane coupling agent, and (E) the flame retardant dispersion prepared in the step 1.

2. The method for producing a thermosetting resin composition according to claim 1 , wherein the component (E) is a dispersion of a flame retardant dispersed in an organic solvent, and the content of the organic solvent in the component (E) is from 25 to 55 parts by mass relative to 100 parts by mass of the flame retardant.

3. The method for producing a thermosetting resin composition according to claim 1 , wherein the component (E) comprises a metal salt of a di-substituted phosphinic acid as a flame retardant.

4. The method for producing a thermosetting resin composition according to claim 1 , wherein the component (E) comprises a ketone solvent as an organic solvent.

5. The method for producing a thermosetting resin composition according to claim 1 , wherein the component (a2) is a monoamine compound having an acidic substituent represented by the following general formula (a2-1), and the component (a3) is a diamine compound represented by the following general formula (a3-1):

wherein R A4 represents an acidic substituent selected from a hydroxy group, a carboxy group and a sulfonic acid group, R A5 represents an alkyl group having 1 to 5 carbon atoms, or a halogen atom, t represents an integer of 1 to 5, u represents an integer of 0 to 4, and t and u satisfy 1≤t+u≤5, provided that when t is an integer of 2 to 5, plural R A4 'S may be the same or different, and when u is an integer of 2 to 4, plural R A5 's may be the same or different,

wherein X A2 represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or —O—, R A6 and R A7 each independently represent an alkyl group having 1 to 5 carbon atoms, a halogen atom, a hydroxy group, a carboxy group or a sulfonic acid group, and v and w each independently represent an integer of 0 to 4.

6. The method for producing a thermosetting resin composition according to claim 1 , wherein the component (C) is a copolymer resin having a structural unit represented by the following general formula (C-i) and a structural unit represented by the following formula (C-ii):

wherein R C1 represents a hydrogen atom, or an alkyl group having 1 to 5 carbon atoms, R C2 represents an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 6 to 20 carbon atoms, a hydroxy group, or a (meth)acryloyl group, and x represents an integer of 0 to 3, provided that when x is 2 or 3, plural R C2 's may be the same or different.

7. The method for producing a thermosetting resin composition according to claim 1 , wherein in the component (C), the content ratio of the structural unit derived from an aromatic vinyl compound to the structural unit derived from a maleic anhydride [aromatic vinyl compound-derived structural unit/maleic anhydride-derived structural unit] (molar ratio) is from 1 to 9.

8. The method for producing a thermosetting resin composition according to claim 1 , wherein the weight average molecular weight of the component (C) is from 4,500 to 18,000.

9. The method for producing a thermosetting resin composition according to claim 1 , wherein the component (B) is one or more selected from the group consisting of a bisphenol F-type epoxy resin, a phenol-novolak-type epoxy resin, a cresol-novolak-type epoxy resin, a naphthalene-type epoxy resin, an anthracene-type epoxy resin, a biphenyl-type epoxy resin, a biphenylaralkyl-type epoxy resin, and a dicyclopentadiene-type epoxy resin.

10. The method for producing a thermosetting resin composition according to claim 1 , wherein (F) a curing agent is mixed with (A) the maleimide compound, (B) the epoxy resin having at least two epoxy groups in one molecule, (C) the copolymer resin having a structural unit derived from an aromatic vinyl compound and a structural unit derived from a maleic anhydride, (D) the silica treated with an aminosilane coupling agent, and (E) the flame retardant dispersion.

11. A method for producing a prepreg comprising impregnating or applying the thermosetting resin composition produced by the method of claim 1 to a sheet-like reinforcing substrate.

12. A method for producing a laminate comprising laminating the prepreg produced by the method of claim 11 and a metal foil.

13. A method for producing a printed wiring board comprising forming electric circuits on the prepreg produced by the method of claim 11 .

14. The method for producing a thermosetting resin composition according to claim 1 , wherein the flame retardant has a mean particle size of 0.5 to 6 μm.

15. The method for producing a thermosetting resin composition according to claim 1 , wherein the flame retardant has a mean particle size of 1 to 5 μm.