Resin composition, prepreg, metal foil with resin, laminate, printed wiring board, and method for producing resin composition

1. A prepreg, which is prepared by impregnating a base material with a resin composition comprising an acrylic polymer (A) and a thermosetting resin (B), wherein a phase separation structure of a first phase containing the acrylic polymer (A) and a second phase containing the thermosetting resin (B) is formed, and an average domain size of the second phase is 20 μm or less,

wherein in case that ten sheets of the prepreg which were processed into a size of 250 mm×250 mm are superimposed and put into a hermetically sealable bag, which is then charged in a constant-temperature and constant-humidity environment at a temperature of 25° C. and a humidity of 70% for 48 hours, the prepreg arranged in the bottom and the prepreg adjacent thereto are separated from each other,

wherein a solubility parameter (SP value) of the acrylic polymer (A) is from 9.0 to 12.0, and

wherein an absolute value of a difference between the solubility parameter (SP value) of the acrylic polymer (A) and a solubility parameter (SP value) of the thermosetting resin (B) is from 0.1 to 5.0.

2. The prepreg according to claim 1 , wherein the acrylic polymer (A) is an acrylic polymer containing a (meth)acrylic acid ester-derived structural unit represented by the following general formula (A1):

wherein R 2 represents an alkyl group, a cycloalkyl group, a cycloalkylalkyl group, an aryl group, or an aralkyl group; and R 1 represents a hydrogen atom or a methyl group.

3. The prepreg according to claim 1 , wherein the solubility parameter (SP value) of the acrylic polymer (A) is from 9.4 to 11.6.

4. The prepreg according to claim 1 , wherein a weight average molecular weight of the acrylic polymer (A) is from 100,000 to 1,500,000.

5. The prepreg according to claim 1 , wherein the content of the acrylic polymer (A) is from 10 to 50 parts by mass based on 100 parts by mass of the total solid content of the resin composition.

6. The prepreg according to claim 1 , wherein the thermosetting resin (B) is at least one selected from the group consisting of an epoxy resin, a cyanate resin, a bismaleimide, an addition polymer of a bismaleimide and a diamine, a phenol resin, a resole resin, an isocyanate resin, triallyl isocyanurate, triallyl cyanurate, and a vinyl group-containing polyolefin compound.

7. The prepreg according to claim 1 , wherein the phase separation structure is a sea-island structure, a sea phase is constituted of the first phase, and an island phase is constituted of the second phase.

8. The prepreg according to claim 1 , wherein the solubility parameter (SP value) of the thermosetting resin (B) is from 9.0 to 15.0, provided that the absolute value of a difference between the solubility parameter (SP value) of the acrylic polymer (A) and the solubility parameter (SP value) of the thermosetting resin (B) is from 0.1 to 5.0.

9. The prepreg according to claim 1 , wherein the absolute value of a difference between the solubility parameter (SP value) of the acrylic polymer (A) and the solubility parameter (SP value) of the thermosetting resin (B) is from 0.11 to 4.9.

10. The prepreg according to claim 1 , wherein the absolute value of a difference between the solubility parameter (SP value) of the acrylic polymer (A) and the solubility parameter (SP value) of the thermosetting resin (B) is from 0.12 to 4.8.

11. The prepreg according to claim 1 , wherein the absolute value of a difference between the solubility parameter (SP value) of the acrylic polymer (A) and the solubility parameter (SP value) of the thermosetting resin (B) is from 0.13 to 4.7.

12. A laminate plate, which is prepared by laminating the prepreg according to claim 1 , and then heating and pressurizing.

13. A printed wiring board, which is prepared by subjecting the laminate plate according to claim 12 to circuit processing.