Provided is a heat-curable maleimide resin composition exhibiting no turbidity and separation when in the form of a varnish, and yielding a cured product that not only has excellent dielectric properties but also has a strong adhesive force to organic resins such as LCP and MPI and copper. The composition contains: (A) a styrene-based elastomer having a reactive functional group at both ends; (B) a maleimide compound represented by the following formula (1)

##STR00001##

wherein R.sup.1 represents a dimer acid skeleton-derived divalent hydrocarbon group; (C) an epoxy resin having at least two epoxy groups per molecule; and (D) an anionic polymerization initiating catalyst,
wherein a ratio between the components (A) and (B) (mass ratio (A)/(B)) is 2 to 20.

Provided is a heat-curable maleimide resin composition exhibiting no turbidity and separation when in the form of a varnish, and yielding a cured product that not only has excellent dielectric properties but also has a strong adhesive force to organic resins such as LCP and MPI and copper. The composition contains: (A) a styrene-based elastomer having a reactive functional group at both ends; (B) a maleimide compound represented by the following formula (1)

##STR00001##

wherein R.sup.1 represents a dimer acid skeleton-derived divalent hydrocarbon group; (C) an epoxy resin having at least two epoxy groups per molecule; and (D) an anionic polymerization initiating catalyst,
wherein a ratio between the components (A) and (B) (mass ratio (A)/(B)) is 2 to 20.

First embodiment of a (meth)acrylic copolymer in the present invention includes following: a (meth)acrylic copolymer having at least one kind of constitutional unit selected from the group consisting of a constitutional unit (A1) having at least one kind of structure (I) selected from the group consisting of structures represented by the following formula (1), formula (2), or formula (3) and a constitutional unit (A2) having a triorganosilyloxycarbonyl group and a constitutional unit (B) derived from a macromonomer (b): ##STR00001## (where, X represents —O—, —S—, or —NR.sup.14—, R.sup.14 represents a hydrogen atom or an alkyl group, R.sup.1 and R.sup.2 each represent a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms, R.sup.3 and R.sup.5 each represent an alkyl group having from 1 to 20 carbon atoms, a cycloalkyl group, or an aryl group, and R.sup.4 and R.sup.6 each represent an alkylene group having from 1 to 10 carbon atoms).

First embodiment of a (meth)acrylic copolymer in the present invention includes following: a (meth)acrylic copolymer having at least one kind of constitutional unit selected from the group consisting of a constitutional unit (A1) having at least one kind of structure (I) selected from the group consisting of structures represented by the following formula (1), formula (2), or formula (3) and a constitutional unit (A2) having a triorganosilyloxycarbonyl group and a constitutional unit (B) derived from a macromonomer (b): ##STR00001## (where, X represents —O—, —S—, or —NR.sup.14—, R.sup.14 represents a hydrogen atom or an alkyl group, R.sup.1 and R.sup.2 each represent a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms, R.sup.3 and R.sup.5 each represent an alkyl group having from 1 to 20 carbon atoms, a cycloalkyl group, or an aryl group, and R.sup.4 and R.sup.6 each represent an alkylene group having from 1 to 10 carbon atoms).

A process for preparing an aqueous polymer dispersion, wherein the process comprising free-radically initiated emulsion polymerization in an aqueous medium, in the presence of at least one vinyl polymer A, to obtain a polymer B comprising a vinyl polymer phase B1 with a glass transition temperature of from −20 to +15° C. and a vinyl polymer phase B2 with a glass transition temperature of from +50 to +110° C., with the proviso that the difference in glass transition temperature between polymer B1 and polymer B2 is at least 40° C., wherein the weight ratio of polymer B1 to polymer B2 is from 80:10 to 10:20, wherein the at least one polymer A is obtained by a process comprising: free-radically initiated bulk or solution polymerizing of: from 5 to 25 wt. % of at least one carboxylic acid functional ethylenically unsaturated monomer A1, and from 75 to 95 wt. % of at least one ethylenically unsaturated monomer A2 different than monomer A1, where the amounts are given relative to the total weight of monomers charged in the polymerization to prepare the vinyl polymer A, wherein the weight average molecular weight of the polymer A is lower than the weight average molecular weight of the polymer B, and wherein the weight ratio of polymer A to polymer B is from 10:90 to 40:60.

A process for preparing an aqueous polymer dispersion, wherein the process comprising free-radically initiated emulsion polymerization in an aqueous medium, in the presence of at least one vinyl polymer A, to obtain a polymer B comprising a vinyl polymer phase B1 with a glass transition temperature of from −20 to +15° C. and a vinyl polymer phase B2 with a glass transition temperature of from +50 to +110° C., with the proviso that the difference in glass transition temperature between polymer B1 and polymer B2 is at least 40° C., wherein the weight ratio of polymer B1 to polymer B2 is from 80:10 to 10:20, wherein the at least one polymer A is obtained by a process comprising: free-radically initiated bulk or solution polymerizing of: from 5 to 25 wt. % of at least one carboxylic acid functional ethylenically unsaturated monomer A1, and from 75 to 95 wt. % of at least one ethylenically unsaturated monomer A2 different than monomer A1, where the amounts are given relative to the total weight of monomers charged in the polymerization to prepare the vinyl polymer A, wherein the weight average molecular weight of the polymer A is lower than the weight average molecular weight of the polymer B, and wherein the weight ratio of polymer A to polymer B is from 10:90 to 40:60.

There is provided an adhesive capable of improving the visibility and controlling gaps with high accuracy. The adhesive according to the present invention is an adhesive containing a curable component and a gap material, in which the 10% K value of the gap material is 10000 N/mm.sup.2 or less, and the absolute value of the difference between the refractive index of a cured product obtained by curing the curable component at 23° C. for 1 hour and the refractive index of the gap material is 0.1 or less.

There is provided an adhesive capable of improving the visibility and controlling gaps with high accuracy. The adhesive according to the present invention is an adhesive containing a curable component and a gap material, in which the 10% K value of the gap material is 10000 N/mm.sup.2 or less, and the absolute value of the difference between the refractive index of a cured product obtained by curing the curable component at 23° C. for 1 hour and the refractive index of the gap material is 0.1 or less.

There is provided an adhesive capable of improving the visibility and controlling gaps with high accuracy. The adhesive according to the present invention is an adhesive containing a curable component and a gap material, in which the 10% K value of the gap material is 10000 N/mm.sup.2 or less, and the absolute value of the difference between the refractive index of a cured product obtained by curing the curable component at 23° C. for 1 hour and the refractive index of the gap material is 0.1 or less.

The present invention relates to a multistage polymer in form of polymeric particles, its composition and its process of preparation. The invention also relates to a multistage polymer in form of polymeric particles made by a multistage process while the last stage comprises a polymer with a low molecular weight. The invention further relates to polymer compositions in form of polymeric particles made by a multistage process comprising at least three stages while the last stage comprises a polymer with a low molecular weight, its method of preparation, its use as impact modifier in polymer compositions for composites comprising thermosetting resins or thermoplastic polymers and compositions and articles comprising it.