Composite particles

Abstract

The present invention relates to: composite particles having a polymer graft chain on the surface of inorganic particles, the inorganic particles being hollow and having an average particle diameter greater than 200 nm and at most 3,000 nm; and a resin composition containing the composite particles. The present invention provides inorganic particles having excellent dispersibility in a resin, and a resin composition containing such inorganic particles.

Description

composite particles

[0001] The present invention relates to composite particles.

[0002] In recent years, there has been a demand for smaller electronic devices, faster signal speeds, and higher wiring density. To meet these demands, build-up substrates are required to have a low dielectric constant, a low dielectric loss tangent, a low thermal expansion coefficient, and multi-layer construction. To meet these demands, Patent Document 1 considers blending hollow particles into a low dielectric loss tangent resin to achieve a low dielectric loss tangent and a low thermal expansion coefficient.

[0003] Japanese Patent Application Laid-Open No. 2008-031409

[0004] The present invention relates to the following items [1] to

[10] . [1] Composite particles having polymer graft chains on the surfaces of inorganic particles, wherein the inorganic particles are hollow particles, and the average particle size of the inorganic particles is greater than 200 nm and not greater than 3,000 nm. [2] The composite particles according to item [1], wherein the porosity of the inorganic particles is 50% by volume or more and 80% by volume or less. [3] The graft density of the polymer graft chains in the composite particles is 0.01 chains / nm. ２ or more. [4] The composite particle according to any one of [1] to [3], wherein the polymer graft chain is a polymer composed of one or more monomers selected from the group consisting of styrene-based monomers, nitrile-based monomers, (meth)acrylic-based monomers, fluorine-based monomers, unsaturated olefin-based monomers, conjugated diene-based monomers, and monomers having an amino group, a hydroxy group, or a glycidyl group. [5] The composite particle according to any one of [1] to [4], wherein the inorganic particle is silica. [6] The composite particle according to any one of [1] to [5], wherein the inorganic particle is silica, and the total content of alkali metals and alkaline earth metals relative to the content of silica in the inorganic particle is 50 ppm by mass or less. [7] The composite particle according to any one of [1] to [6], wherein the polymer graft chain is provided via a structure represented by the following formula (A): (polymer graft chain)-X-(CH ２ ) ｍ -Si-(R １ ) (R２ ) (R ３ ) Formula (A) (In formula (A), -X- is a divalent group, one of which is -(CH ２ ) ｍ The other bonded to the polymer graft chain. m is an integer of 0 to 12. R １ , R ２ and R ３ At least one of the groups bonded to the particles by forming a metalloxane bond, and those not bonded to the particles are each independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, a hydrogen atom, a hydroxy group, or a halogen atom.) [8] A resin composition containing the composite particle according to any one of [1] to [7] above and a resin. [9] A resin composition for low dielectric materials containing the composite particle according to any one of [1] to [7] above and a resin.

[10] A low dielectric resin composition containing the composite particle according to any one of [1] to [7] above and a resin.

[0005] Fig. 1 is a schematic diagram showing an example of bonding between inorganic particles and polymer graft chains in a composite particle. １ , R ２ and R ３ It is assumed that all of the above forms a siloxane bond with the silica of the inorganic particle. In Figure 1, the area surrounded by the dashed line between the inorganic particle and the polymer graft chain corresponds to X in formula (A). Detailed Description of the Invention

[0006] However, since the dispersibility of inorganic particles in organic resins is low, even when the two are mixed, the inorganic particles often settle over time or aggregate between the inorganic particles, and the performance improvement expected by blending the particles tends not to be achieved. Furthermore, curable resins or resins that do not have a melting point or glass transition point of 230°C or less are difficult to melt-knead, making it difficult to disperse inorganic particles.

[0007] The present invention has been made in view of the above circumstances, and relates to providing inorganic particles that are highly dispersible in resins, and resin compositions containing such particles.

[0008] According to the present invention, it is possible to provide inorganic particles that are highly dispersible in resins, and resin compositions containing such particles.

[0009] As a result of investigations, the present inventors have found that the use of composite particles having polymer graft chains on the surface of hollow inorganic particles can improve the dispersibility of the particles in resin. While the mechanism by which this effect is achieved is unclear, it is presumed that the entanglement and interaction of the polymer graft chains, which have high affinity with the matrix resin, improves the dispersibility of the composite particles. Therefore, the use of composite particles having such polymer graft chains on the surface of inorganic particles can be expected to improve the dielectric properties, surface smoothness, low thermal expansion, high rigidity, vibration damping, adhesion, and viscosity reduction of resin compositions and their cured products (resin molded articles).

[0010] <Composite Particles> The composite particles of the present invention are composite particles having polymer graft chains on the surfaces of inorganic particles, wherein the inorganic particles are hollow particles and have an average particle size of more than 200 nm and not more than 3,000 nm.

[0011] [Inorganic particles] Composite particles have polymer graft chains on the surface of inorganic particles.As inorganic particles, inorganic particles known as fillers can be used, and include inorganic particles such as metal oxides, metal oxide salts, metal hydroxides, and metal carbonates, and preferably one or more selected from the group consisting of metal oxides, metal oxide salts, metal hydroxides, and metal carbonates, more preferably one or more selected from the group consisting of silicon oxides such as silica, and silicates such as mica and talc, and even more preferably silica.The shape of the particles is not particularly limited, and can be plate-like, granular, needle-like, fibrous, etc.

[0012] The average particle size of the inorganic particles is greater than 200 nm, preferably 300 nm or more, more preferably 400 nm or more, even more preferably 500 nm or more, and even more preferably 1000 nm or more, from the viewpoint of obtaining a molded product of the resin composition exhibiting the desired dielectric properties. On the other hand, from the viewpoint of improving the appearance of the resin composition, the average particle size of the particles is 3,000 nm or less, preferably 2,500 nm or less, more preferably 2,000 nm or less, and even more preferably 1200 nm or less. The reason why the average particle size of the inorganic particles is greater than 200 nm is that a smaller average particle size increases the specific surface area, and in the case of silica, the amount of surface SiOH increases, which increases the dielectric loss tangent, presumably making it unsuitable for use in low-dielectric materials. Furthermore, a smaller particle size is thought to increase viscosity and deteriorate processability. Furthermore, as the particle size decreases, particles tend to approach and contact each other more easily, which may result in increased aggregation. It is also presumed that stronger interactions between particles due to inertial forces and gravity are also one of the causes of increased aggregation. For this reason, even if polymer graft chains are attached, if the average particle size is smaller than a predetermined range, it is expected that dispersibility will decrease, and special improvements to the graft chains will be necessary to improve the dispersibility of such particles. In the present invention, the average particle size of inorganic particles refers to the average particle size on a volume basis. The average particle size of inorganic particles is measured by the method described in the Examples below.

[0013] The inorganic particles are particles having a predetermined porosity, i.e., hollow particles. From the viewpoint of obtaining a molded article of the resin composition exhibiting the desired dielectric properties, the porosity of the inorganic particles is preferably 50% by volume or more, more preferably 55% by volume or more, and even more preferably 60% by volume or more. On the other hand, from the viewpoint of the mechanical strength of the particles, the porosity of the inorganic particles is preferably 80% by volume or less, more preferably 77% by volume or less, even more preferably 74% by volume or less, and even more preferably 70% by volume or less. The porosity of the inorganic particles is measured by the method described in the Examples below.

[0014] When the inorganic particles are silica, the total content of alkali metals and alkaline earth metals relative to the content of silica in the inorganic particles is preferably small from the viewpoint of exhibiting desired dielectric properties. Specifically, the total content is preferably 50 ppm by mass or less, more preferably 30 ppm by mass or less, and even more preferably 10 ppm by mass or less. The total content is measured by the method described in the Examples below.

[0015] Commercially available inorganic particles can be used, and when hollow silica particles are used as the inorganic particles, they can be produced by a known method, for example, the method described below.

[0016] [Method for producing hollow silica particles] Hollow silica particles can be produced by a method including, for example, the following steps: Step A: A step of preparing an aqueous emulsion of a hydrophobic liquid using a cationic surfactant A; Step B: A step of adding a silanol precursor, an alkaline substance, and a cationic surfactant B to the aqueous emulsion obtained in Step A to produce a hollow silica particle precursor; Step C: A step of heat-treating the hollow silica particle precursor obtained in Step B at a temperature higher than 1000°C and not higher than 1200°C for 1 hour or longer.

[0017] In step A, cationic surfactant A and a hydrophobic liquid are mixed with and stirred in a liquid A containing water to prepare an aqueous emulsion of the hydrophobic liquid in which droplets of the hydrophobic liquid are dispersed. The preparation of the aqueous emulsion of the hydrophobic liquid can be carried out by a general method.

[0018] Examples of water contained in liquid A include distilled water, ion-exchanged water, and ultrapure water. Liquid A may also contain a water-compatible organic solvent, from the viewpoint of more uniform and stable emulsification of the hydrophobic liquid. Examples of water-compatible organic solvents include lower alcohols such as methanol, ethanol, and isopropyl alcohol, and acetone. The water content in liquid A is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 98% by mass or more, and even more preferably 100% by mass, from the viewpoint of instantly reducing the solubility of the hydrophobic liquid in liquid A.

[0019] Cationic Surfactant A From the viewpoint of facilitating the formation of a complex with the condensed silanol in Step B described below, and from the viewpoint of decomposition and volatilization in Step C described below, the cationic surfactant A is preferably a quaternary ammonium salt, more preferably at least one selected from alkyltrimethylammonium salts and dialkyldimethylammonium salts, and even more preferably at least one selected from the group consisting of quaternary ammonium salts represented by the following general formula (1) or general formula (2): [R １ R ３ ３ N] ＋ X － (1) [R １ R ２ R ３ ２ N] ＋ X － (2)

[0020] In the general formula (1) and the general formula (2), R １ and R ２ each independently represents a linear or branched alkyl group having 4 to 22 carbon atoms; R ３ represents an alkyl group having 1 to 3 carbon atoms, and a plurality of R ３ may be different groups, and X － represents a monovalent anion. Examples of alkyl groups having 4 to 22 carbon atoms include various butyl groups, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, various tetradecyl groups, various hexadecyl groups, various octadecyl groups, and various eicosyl groups. Examples of alkyl groups having 1 to 3 carbon atoms include methyl groups, ethyl groups, n-propyl groups, and isopropyl groups. In general formula (1) and general formula (2), R ３ is preferably a methyl group.

[0021] X in general formulas (1) and (2) － is preferably at least one monovalent anion selected from halogen ions, hydroxide ions, nitrate ions, etc., from the viewpoint of easy decomposition and volatilization during firing. －The cation is more preferably a halide ion, and even more preferably a chloride ion.

[0022] Examples of the alkyltrimethylammonium salt represented by general formula (1) include butyltrimethylammonium chloride, hexyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, lauryltrimethylammonium chloride (dodecyltrimethylammonium chloride), tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, butyltrimethylammonium bromide, hexyltrimethylammonium bromide, octyltrimethylammonium bromide, decyltrimethylammonium bromide, lauryltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, stearyltrimethylammonium bromide, and behenyltrimethylammonium bromide.

[0023] Examples of the dialkyldimethylammonium salt represented by the general formula (2) include dibutyldimethylammonium chloride, dihexyldimethylammonium chloride, dioctyldimethylammonium chloride, dihexyldimethylammonium bromide, dioctyldimethylammonium bromide, dilauryldimethylammonium bromide, and ditetradecyldimethylammonium bromide.

[0024] From the viewpoint of facilitating the formation of a complex with the condensed silanol in step B and facilitating decomposition and volatilization in step C, the quaternary ammonium salt is preferably lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, or behenyltrimethylammonium chloride, and more preferably stearyltrimethylammonium chloride or behenyltrimethylammonium chloride.

[0025] Hydrophobic Liquid The hydrophobic liquid is preferably one that can form emulsified droplets (emulsified oil droplets) in water. Furthermore, in view of using liquid A containing water as the dispersion medium and improving the utilization efficiency of the hydrophobic liquid, the temperature range in the liquid state is preferably 0 to 100°C, and more preferably 20 to 90°C. Specific examples of hydrophobic liquids include those described in paragraphs

[0015] to

[0023] of JP 2016-121060 A. Among these, hydrocarbons having 6 to 18 carbon atoms are preferred, hydrocarbons having 8 to 14 carbon atoms are more preferred, and dodecane is more preferred.

[0026] In step A, the mass ratio of the hydrophobic liquid to water [hydrophobic liquid / water] is preferably 0.3 or more, more preferably 0.35 or more, even more preferably 0.4 or more, from the viewpoint of keeping the particle size of the resulting droplets of the hydrophobic liquid within an appropriate range, and is preferably 0.8 or less, more preferably 0.75 or less, even more preferably 0.7 or less.

[0027] In step A, the mass ratio of cationic surfactant A to the hydrophobic liquid [cationic surfactant A / hydrophobic liquid] is, from the viewpoint of dispersing the hydrophobic liquid in liquid A, preferably 0.0005 or more, more preferably 0.001 or more, even more preferably 0.0015 or more, and is preferably 0.05 or less, more preferably 0.04 or less, even more preferably 0.035 or less.

[0028] In step A, the particle size of the resulting droplets containing the hydrophobic liquid can be adjusted to an appropriate range by appropriately adjusting the stirring speed, temperature, etc. Step A is preferably carried out at a temperature of 15° C. to 80° C. From the viewpoint of adjusting the average particle size of the hollow silica particles to the above range, the volume average particle size of the droplets containing the hydrophobic liquid is preferably 0.1 μm or more, more preferably 0.3 μm or more, even more preferably 0.4 μm or more, and is preferably 2.5 μm or less, more preferably 2.0 μm or less, even more preferably 1.5 μm or less.

[0029] Step B In step B, a silanol precursor, an alkaline substance, and a cationic surfactant B are added to the aqueous emulsion obtained in step A to produce hollow silica particle precursors. Specifically, the silanol precursor present on the surface of the hydrophobic liquid droplets is first hydrolyzed in the presence of an alkaline substance to obtain silanols. The obtained silanols are then condensed in the presence of the alkaline substance to form hollow silica particle precursors having an outer shell containing silica and the cationic surfactant B on the surface of the hydrophobic liquid droplets and containing the hydrophobic liquid inside.

[0030] The silanol precursor, the alkaline substance, and the cationic surfactant B may be added to the aqueous emulsion by adding the silanol precursor and the cationic surfactant B to the aqueous emulsion simultaneously or separately, or by adding the aqueous emulsion to either the silanol precursor or the cationic surfactant B and then adding the other.

[0031] Step B may include, after the formation of the hollow silica particle precursor and before Step C, a step of isolating the hollow silica particle precursor and a step of drying the hollow silica particle precursor. The hollow silica particles can be isolated by, for example, filtration. Furthermore, if the boiling point of the hydrophobic liquid contained in the hollow silica particle precursor is higher than 100°C, the hollow silica particle precursor can be dried by, for example, heating to a temperature of 100°C or higher and lower than the boiling point of the hydrophobic liquid. If the boiling point of the hydrophobic liquid contained in the hollow silica particle precursor is 100°C or lower, the hollow silica particle precursor can be dried by, for example, freeze-drying or the like.

[0032] Silanol Precursor The silanol precursor is a compound that generates a silanol compound by hydrolysis of an alkoxysilane or the like, and is preferably selected from alkyl orthosilicate esters and alkyl pyrosilicate esters. Specific examples include compounds represented by the following general formulas (3) to (7), or combinations thereof. SiY ４ (3) R ３ SiY ３ (4) R ３ ２ SiY ２(5) R ３ ３ SiY (6) Y ３ Si—O—SiY ３ (7)

[0033] In general formulas (3) to (7), R ３ each independently represents an organic group in which a carbon atom is directly bonded to a silicon atom, and Y represents a monovalent hydrolyzable group that becomes a hydroxy group upon hydrolysis.

[0034] In the general formulas (4) to (6), R ３ are each independently a hydrocarbon group preferably having 1 to 22 carbon atoms in which some of the hydrogen atoms may be substituted with fluorine atoms, and from the viewpoint of improving the utilization efficiency of the hydrophobic organic substance, are preferably an alkyl group, a phenyl group, or a benzyl group having 1 to 22 carbon atoms, more preferably 4 to 18 carbon atoms, and even more preferably 8 to 16 carbon atoms.

[0035] In the general formulas (3) to (7), Y is preferably an alkoxy group having 1 to 8 carbon atoms or a halogen group excluding fluorine, and more preferably an alkoxy group having 2 to 4 carbon atoms. When Y is an alkoxy group having 1 carbon atom or a halogen group excluding fluorine, the hydrolysis reaction rate is too fast, making it difficult for the outer shell of the hollow silica precursor to become dense, and shrinkage during firing increases, which tends to increase the relative dielectric constant and dielectric loss tangent of the hollow silica particles. Conversely, an alkoxy group having 5 or more carbon atoms slows the hydrolysis rate.

[0036] The silanol precursor is preferably selected from compounds represented by general formula (3) and general formula (7). From the viewpoint of suppressing the generation of metal-corrosive acids and from the viewpoint of hydrolysis reactivity, the silanol precursor is preferably selected from compounds represented by general formula (3) and general formula (7) in which Y is an alkoxy group having 2 to 4 carbon atoms, and more preferably selected from compounds represented by general formula (3) and general formula (7) in which Y is an ethoxy group. The silanol precursors can be used alone or in combination of two or more.

[0037] The mass ratio of the silanol precursor to the hydrophobic liquid [silanol precursor / hydrophobic liquid] is preferably 10 or more, more preferably 20 or more, even more preferably 25 or more, from the viewpoint of keeping the porosity of the hollow silica particles within an appropriate range, and is preferably 90 or less, more preferably 80 or less, even more preferably 75 or less.

[0038] Cationic Surfactant B As the cationic surfactant B, the same cationic surfactant B as the cationic surfactant A shown in step A can be used. As the cationic surfactant B, from the viewpoint of facilitating the formation of a complex with the condensed silanol and facilitating decomposition and volatilization in step C, a quaternary ammonium salt is preferred, more preferably lauryltrimethylammonium chloride (dodecyltrimethylammonium chloride), stearyltrimethylammonium chloride, and behenyltrimethylammonium chloride, and even more preferably lauryltrimethylammonium chloride. The cationic surfactant B used in this step may be the same as or different from the cationic surfactant A used in step A. Furthermore, the cationic surfactant B can be used alone or in combination of two or more types.

[0039] From the viewpoint of dispersibility of the hollow silica particle precursor, the mass ratio of the silanol precursor to the cationic surfactant B [silanol precursor / cationic surfactant B] is preferably 3 or more, more preferably 5 or more, even more preferably 6 or more, and is preferably 25 or less, more preferably 20 or less, even more preferably 18 or less.

[0040] Alkaline Substance The silanol precursor is hydrolyzed to silanol by the alkaline substance, and then undergoes dehydration condensation to form silica. Specific examples of the alkaline substance include those described in paragraph

[0014] of JP 2016-121060 A. Among these, quaternary ammonium hydroxide salts are preferred. Specific examples of quaternary ammonium hydroxide salts include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tributylmethylammonium hydroxide, trimethylhydroxyethylammonium hydroxide (choline), tetraethanolammonium hydroxide, methyltriethanolammonium hydroxide, and dimethylbis(2-hydroxyethyl)ammonium hydroxide. From the viewpoint of densifying the outer shell of the hollow silica particle precursor, preferred are tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, methyltriethanolammonium hydroxide, and dimethylbis(2-hydroxyethyl)ammonium hydroxide, and more preferred are tetramethylammonium hydroxide and dimethylbis(2-hydroxyethyl)ammonium hydroxide.

[0041] The mass ratio of the silanol precursor to the alkaline substance [silanol precursor / alkaline substance] is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more, from the viewpoint of making the outer shell of the hollow silica particle precursor dense, and is preferably 100 or less, more preferably 80 or less, and even more preferably 70 or less, from the viewpoint of efficiently carrying out the condensation reaction of the silanol precursor.

[0042] The alkaline substance may contain, in addition to the hydroxide salt of the quaternary ammonium, for example, an alkali metal salt, an alkaline earth metal salt, etc., but in order to reduce the content of alkali metals and alkaline earth metals in the obtained hollow silica particles, the total content of alkali metals and alkaline earth metals relative to the silanol precursor is set to be less than the content of silica (SiO ２Furthermore, the content is preferably 30 ppm by mass or less, and more preferably 10 ppm by mass or less.

[0043] By mixing an alkaline substance with a cationic surfactant B and contacting the mixture with a silanol precursor, hollow silica particles having a small maximum particle size and an appropriate coefficient of variation can be obtained. The contact of the mixture of the alkaline substance and the cationic surfactant B with the silanol precursor may be carried out by adding the mixture of the alkaline substance and the cationic surfactant B to a reaction system containing the silanol precursor, or by adding the silanol precursor to a reaction system containing the mixture of the alkaline substance and the cationic surfactant B. However, from the viewpoints of increasing the porosity and the synthesis concentration to increase productivity, it is preferable to add the mixture of the alkaline substance and the cationic surfactant B to a reaction system containing the silanol precursor.

[0044] The temperature at which step B is carried out can be appropriately adjusted depending on the type and amount of the silanol precursor and alkaline substance used, and is preferably 0° C. or higher and 100° C. or lower from the viewpoint of densifying the outer shell of the hollow silica particle precursor. For example, when orthosilicate ethyl ester or pyrosilicate ethyl ester is used as the silanol precursor, the temperature is preferably 20° C. or higher and 45° C. or lower, and when orthosilicate methyl ester or pyrosilicate methyl ester is used, the temperature is preferably 0° C. or higher and 20° C. or lower. Of these, it is preferable to use orthosilicate ethyl ester or pyrosilicate ethyl ester from the viewpoint of reaction control.

[0045] The time for carrying out step B is preferably 30 minutes or more, more preferably 1 hour or more, and even more preferably 2 hours or more from the viewpoint of densifying the outer shell of the hollow silica particle precursor, and is preferably 24 hours or less, more preferably 20 hours or less, and even more preferably 16 hours or less from the viewpoint of production efficiency.

[0046] Hollow silica particle precursor The hollow silica particle precursor is a composite silica particle having a silica-containing shell and a hydrophobic liquid inside the shell. The shell has pores formed radially toward the particle center using a cationic surfactant as a template.

[0047] Step C In step C, the hollow silica particle precursor obtained in step B is heat-treated at a temperature higher than 1000°C and not higher than 1200°C for 1 hour or longer to decompose and volatilize the cationic surfactant present in the outer shell of the hollow silica particle precursor and volatilize the hydrophobic liquid inside, and then the pores present in the outer shell are closed by firing to obtain hollow silica particles having a uniform outer shell.

[0048] The heat treatment temperature in step C is preferably 1,010°C or higher, more preferably 1,030°C or higher, and even more preferably 1,050°C or higher, from the viewpoint of reducing silanol groups on the surfaces of the hollow silica particles, and is 1,200°C or lower, preferably 1,190°C or lower, more preferably 1,180°C or lower, and even more preferably 1,160°C or lower, from the viewpoint of avoiding aggregation of the hollow silica particles.

[0049] The heat treatment time in step C is preferably 15 minutes or longer, more preferably 30 minutes or longer, and even more preferably 45 minutes or longer, from the viewpoint of reducing silanol groups on the surface of the hollow silica particles, and is preferably 3 hours or shorter, more preferably 2 hours or shorter, and even more preferably 1.5 hours or shorter, from the viewpoint of avoiding aggregation of the hollow silica particles.

[0050] [Polymer graft chain] Examples of the polymer graft chain include a polymer composed of one or more monomers selected from the group consisting of styrene-based monomers, nitrile-based monomers, (meth)acrylic monomers, fluorine-based monomers, unsaturated olefin-based monomers, conjugated diene-based monomers, and monomers having an amino group, a hydroxy group, or a glycidyl group. Here, the polymer constituting the polymer graft chain may be a homopolymer or a copolymer. From the viewpoint of exhibiting desired dielectric properties and from the viewpoint of dispersibility of composite particles in the resin composition, a polymer composed of a styrene-based monomer and / or a conjugated diene-based monomer is preferred.

[0051] Specific examples of monomers used as raw materials for polymer graft chains include butyl methacrylate, butyl acrylate, ethyl methacrylate, ethyl acrylate, methyl methacrylate, methyl acrylate, acrylamide, acrylonitrile, 4-benzoylphenyl acrylate, benzyl methacrylate, allyl methacrylate, cyclohexyl methacrylate, N,N-dimethylmethacrylamide, dodecyl acrylate, dodecyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, n-hexyl methacrylate, methacrylamide, and methacryl. Examples of suitable vinyl acrylates include acrylic acid, octadecyl acrylate, phenyl acrylate, propyl methacrylate, vinyl acetate, methoxypolyethylene glycol acrylate, methoxypolyalkylene glycol methacrylate, styrene, p-bromostyrene, 4-tert-butylstyrene, p-chlorostyrene, 4-iodostyrene, p-methoxystyrene, p-methylstyrene, α-methylstyrene, divinylbenzene (o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene), p-ethylstyrene, sodium p-styrenesulfonate, and vinylbenzyl chloride.

[0052] From the viewpoint of dispersibility of the composite particles, it is preferable that the polymer graft chain contains 10% by mass or more of one or more monomer units selected from the group consisting of styrene, divinylbenzene, glycidyl methacrylate, allyl methacrylate, and cyclohexyl methacrylate.

[0053] From the viewpoint of dispersibility of the composite particles and reactivity with the resin, the content of such monomer units in the polymer graft chain is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and still more preferably 100% by mass.

[0054] Here, the content of the monomer unit in the polymer graft chain is determined as follows: The content of the above-mentioned monomer in the polymerization solution is measured by NMR. The difference between the content of the monomer before polymerization and the content of the monomer after polymerization is the amount of monomer used in the polymerization reaction. Assuming that all of the amount used is formed as a polymer graft chain, the amount of monomer used in the polymerization reaction is calculated as the content of the monomer unit in the polymer graft chain.

[0055] [Method for producing composite particles] Composite particles can be obtained by bonding polymer graft chains to the surfaces of inorganic particles. The method for bonding polymer graft chains to the particle surfaces is not particularly limited as long as it is a method that can perform graft polymerization of polymer chains, but a grafting from method in which polymer graft chains are polymerized from polymerization initiation points on the particle surfaces is preferred.

[0056] The polymerization method is not particularly limited, and examples thereof include radical polymerization, anionic polymerization, cationic polymerization, etc. Among these, living radical polymerization, living anionic polymerization, and living cationic polymerization are preferred from the viewpoint of ease of control of the molecular weight and molecular weight distribution of the polymer chain and ease of grafting various copolymers, and living radical polymerization is more preferred from the viewpoint of applicability to a wide range of monomers.

[0057] As the living radical polymerization method, atom transfer radical polymerization method (ATRP method), reversible addition-fragmentation chain transfer polymerization method (RAFT method), and nitroxide-mediated living radical polymerization method (NMP method) can be used, and from the same viewpoint, atom transfer radical polymerization method (ATRP method) is preferred.

[0058] More specifically, an example of a production method for composite particles includes the following step 2, and if necessary, the following step 1 may also be carried out. The following steps 1 and 2 can be carried out under known conditions for living radical polymerization. Step 1: A step of bonding a polymerization initiating group to the particle surface. Step 2: A step of contacting particles having polymerization initiating groups on their surface with a monomer under living radical polymerization conditions.

[0059] Step 1 is a step in which the particles are reacted with, for example, a coupling agent, thereby bonding the polymerization initiation groups of the coupling agent to the particle surface. Specifically, the particles and the coupling agent, and optionally a catalyst, a solvent, etc., are mixed to cause a reaction between them. The reaction temperature during the reaction between the particles and the coupling agent is preferably 25°C to 250°C. The amount of coupling agent used per 100 parts by mass of the particles is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 part by mass or more. On the other hand, from the viewpoint of suppressing reaction between the coupling agents, the amount is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less.

[0060] Step 1 preferably includes a step of introducing an amino group or a hydroxy group onto the particle surface and a step of introducing a polymerization initiating group. In this case, it is preferable to use, as a component having the same effect as a coupling agent, a "compound having a group that bonds to the particle surface and an amino group or a hydroxyl group" or a "compound having a polymerization initiating group and a functional group that reacts with an amino group or a hydroxyl group." From the viewpoint of bonding a polymer graft chain to the particle surface, it is more preferable to include a step of introducing a polymerization initiating group onto the particle surface after the step of introducing an amino group or a hydroxyl group onto the particle surface.

[0061] The compound used in the step of introducing an amino group or a hydroxyl group onto the particle surface is a compound having a group that bonds to the particle surface and an amino group or a hydroxyl group, and from the viewpoint of easy availability, is preferably a silane compound, more preferably an aminoalkylsilane compound, and even more preferably 3-aminopropyltrimethoxysilane.

[0062] The compound used in the step of introducing a polymerization initiating group is a compound having a polymerization initiating group and a functional group reactive with an amino group or a hydroxy group, and from the viewpoint of bonding a polymer graft chain to the particle surface, is preferably a haloalkanoic acid derivative, more preferably a bromoalkanoic acid derivative, even more preferably a 2-bromo-2-methylpropionic acid derivative, and even more preferably 2-bromoisobutyl bromide.

[0063] In this way, when the step of introducing a polymerization initiating group is carried out after the step of introducing an amino group or a hydroxy group onto the particle surface, the resulting composite particles have a polymer graft chain via a structure represented by the following formula (A): (polymer graft chain)-X-(CH ２ ) ｍ -Si-(R １ ) (R ２ ) (R ３ ) Formula (A) (In formula (A), -X- is a divalent group, one of which is -(CH ２ ) ｍ The other bonded to the polymer graft chain. m is an integer of 0 to 12. R １ , R ２ and R ３ At least one of the groups is bonded to the particles by forming a metalloxane bond, and the groups not bonded to the particles are each independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, a hydrogen atom, a hydroxy group, or a halogen atom.

[0064] In formula (A), -X- is preferably an alkylene group having 2 to 12 carbon atoms, which may have one or more substituents (e.g., a carbonyl group, an alkyl group, or a phenyl group), and which may further be substituted with an oxygen atom or -NH-. Specific examples of suitable -X- include the following structures:

[0065]

[0066] Of these, the following structures are more preferred:

[0067]

[0068] -(CH ２ ) ｍ In the formula (A), m is an integer of 0 to 12. When m is 0, -(CH ２ ) ｍ - is a single bond, and the formula (A) is (polymer graft chain)-X-Si-(R １ ) (R ２ ) (R ３ ) When m is 1 to 12, -(CH ２ )ｍ One or more -CH ２ - may be substituted with a phenylene group and / or -NH-.

[0069] R in formula (A) １ , R ２ and R ３ At least one of the above bonds to the particles by forming a metalloxane bond. For example, if the particles are silica, it bonds to the particles by forming a siloxane bond.

[0070] For example, when the particles originally have a polymerization initiation site or are formed as a result of surface treatment by plasma treatment or the like, they have a polymerization initiation group, so step 1 is not necessary, but when silica, mica, talc, glass filler, etc. that do not have a polymerization initiation group are used, step 1 may be performed. Note that, from the viewpoint of adjusting the graft density, a silane coupling agent that does not contain a polymerization initiation group may be added to a silane coupling agent containing a polymerization initiation group in step 1. In the step of bonding the polymerization initiation group to the particle surface in step 1, a method of dispersing the particles in a dispersion medium is preferred from the viewpoint of preventing the particles from agglomerating.

[0071] The coupling agent that can be used in step 1 is a compound used to bond the inorganic particles and the polymer graft chains. This coupling agent is not particularly limited as long as it is a compound having a polymerization initiation group and a functional group that reacts with the inorganic particle surface to form a bond. The inorganic particle surface in this case may be formed from the inorganic compound itself, or may be surface-treated. The surface treatment referred to here means modifying the inorganic particle surface with a functional group by chemical reaction, heat treatment, light irradiation, plasma irradiation, radiation irradiation, or the like.

[0072] The method for bonding a coupling agent to the surface of inorganic particles is not particularly limited, but includes, for example, a method of reacting a hydroxy group on the surface of inorganic particles with a coupling agent, or a method of reacting a functional group introduced by surface treatment of the surface of inorganic particles with a coupling agent. It is also possible to further react a coupling agent with the coupling agent bonded to the inorganic particles to link multiple coupling agents. Depending on the type of coupling agent, water or a catalyst may be used in combination.

[0073] The functional group of the coupling agent is not particularly limited, but for example, when a bond is formed by reaction with a hydroxy group on the surface of an inorganic particle, examples of the functional group include a phosphate group, a carboxy group, an acid halide group, an acid anhydride group, an isocyanate group, a glycidyl group, a chlorosilyl group, an alkoxysilyl group, a silanol group, an amino group, a phosphonium group, and a sulfonium group. Among these, from the viewpoint of the balance between reactivity, the amount of residual acid, and coloration, preferred are an isocyanate group, a chlorosilyl group, an alkoxysilyl group, and a silanol group, and more preferred are a chlorosilyl group and an alkoxysilyl group.

[0074] The polymerization initiating group of the coupling agent is not particularly limited as long as it is a functional group having polymerization initiation ability, and examples thereof include polymerization initiating groups used in nitroxide-mediated radical polymerization, atom transfer radical polymerization, and reversible addition-fragmentation chain transfer polymerization.

[0075] The polymerization initiating group in the NMP method is not particularly limited as long as it is a group to which a nitroxide group is bonded. The polymerization initiating group in the ATRP method is typically a group containing a halogen atom. It is preferable that the bond dissociation energy of the halogen atom is low. Examples of preferred structures include a halogen atom bonded to a tertiary carbon atom, a halogen atom bonded to a carbon atom adjacent to an unsaturated carbon-carbon bond such as a vinyl group, a vinylidene group, or a phenyl group, and a group having a halogen atom bonded directly to a heteroatom-containing conjugated group such as a carbonyl group, a cyano group, or a sulfonyl group or to an atom adjacent to such a heteroatom-containing conjugated group. More specifically, an organic halide group represented by the following general formula (1) and a halogenated sulfonyl group represented by the following general formula (2) are suitable.

[0076]

[0077] In the above formulas (1) and (2), R １ and R ２ each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may have a substituent, an allyl group which may have a substituent, an aryl group having 6 to 20 carbon atoms which may have a substituent, an alkylaryl group, or an alkylaryl group which may have a substituent, and Z represents a halogen atom.

[0078] The polymerization initiating group of formula (1) may have a carbonyl group, as shown in the following general formula (3): １ , R ２ and Z is R in formula (1). １ , R ２ and Z.

[0079]

[0080] Specific examples of the polymerization initiating group of formula (3) are shown in the following chemical formula.

[0081]

[0082] The polymerization initiator group in the RAFT method is not particularly limited as long as it is a general radical polymerization initiator group. A group containing a sulfur atom that functions as a RAFT agent can also be used as the polymerization initiator group. Examples of the polymerization initiator group include trithiocarbonate, dithioester, thioamide, thiocarbamate, dithiocarbamate, thiouranium, thiourea, dithiooxamide, thioketone, and trisulfide.

[0083] Specific examples of suitable coupling agents include 3-(2-bromoisobutyrylamino)propyltrimethoxysilane and 3-(2-bromoisobutyryloxy)propyltrimethoxysilane.

[0084] Step 2 is a step of contacting particles having polymerization initiating groups on their surfaces with a monomer under living radical polymerization conditions. In step 2, the particles having polymerization initiating groups on their surfaces with a monomer are preferably dispersed in a dispersion medium and polymerized, from the viewpoint of preventing aggregation of the particles, monomer, and composite particles.

[0085] The particles having polymerization initiating groups on their surfaces in step 2 are not particularly limited as long as they have a binding group that bonds the particle surface to a polymer chain. From the viewpoint of bonding a polymer graft chain to the particle surface, the polymerization initiating group is a living radical polymerization initiating group, preferably an atom transfer radical polymerization initiating group, more preferably a haloacyl group, even more preferably an α-haloacyl group, even more preferably an α-bromoacyl group, and even more preferably a 2-bromoisobutyryl group. Compounds that serve as raw materials for the binding group include compounds having a group that bonds to the particle surface and a polymerization initiating group, and compounds having a group that bonds to the particle surface or a polymerization initiating group. In the present invention, the particles having polymerization initiating groups on their surfaces in step 2 are preferably the particles obtained in step 1 above.

[0086] The amount of particles having polymerization initiation groups on their surfaces to be charged in step 2 is preferably 0.02 parts by mass or more and preferably 0.3 parts by mass or less per part by mass of the dispersion medium.

[0087] Examples of the monomer in step 2 include styrene-based monomers, nitrile-based monomers, (meth)acrylic monomers, fluorine-based monomers, unsaturated olefin-based monomers, conjugated diene-based monomers, etc., and also include monomers having specific groups in their side chains (for example, monomers having an amino group, a hydroxy group, or a glycidyl group). Specific examples of the monomers preferably used in step 2 include those described above in "Specific examples of monomers as raw materials for polymer graft chains."

[0088] The amount of the monomer charged in step 2 is preferably 1 part by mass or more and preferably 10 parts by mass or less per part by mass of the particles having polymerization initiation groups on the surface thereof.

[0089] In step 2, a known catalyst used in living radical polymerization is used. Preferred examples of the catalyst include copper complex catalysts (e.g., Cu(I)Br / pentamethyldiethylenetriamine, Cu(I)Br / 2,2′-bipyridyl, Cu(II)Br ２ / Pentamethyldiethylenetriamine, Cu(II)Br ２ / 2,2'-bipyridyl).

[0090] The amount of the catalyst used in step 2 is preferably 0.001 part by mass or more and preferably 0.05 part by mass or less per part by mass of the dispersion medium.

[0091] The dispersion medium used in step 2 may be a known dispersion medium used in living radical polymerization, such as anisole, acetonitrile, propionitrile, benzonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ether, methanol, ethanol, propanol, isopropanol, n-butyl alcohol, tert-butyl alcohol, dimethyl sulfoxide, dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, ethylene carbonate, propylene carbonate, tetrahydrofuran, ethyl acetate, butyl acetate, pentane, hexane, cyclohexane, octane, decane, benzene, toluene, methylene chloride, chloroform, an ionic liquid, or water.

[0092] Regarding the reaction conditions in step 2, for example, the reaction temperature is preferably 40° C. or higher and 90° C. or lower, and the reaction time is preferably 1 minute or higher and 120 minutes or lower.

[0093] After polymerization, the composite particles may be optionally purified. In the purification step of the composite particles, it is preferable to disperse the composite particles in a dispersion medium in the polymer from the viewpoint of preventing aggregation of the composite particles. Although the solvent may be optionally removed, it is preferable to leave a portion of the dispersion medium and keep the polymer in a wet state. Furthermore, a method of removing the metal catalyst used in the polymerization step is preferable.

[0094] [Properties of Composite Particles] The graft density of the polymer graft chains in the composite particles is preferably 0.01 chains / nm from the viewpoint of dispersibility of the composite particles in the resin composition. ２ More preferably, 0.05 chains / nm ２ More preferably, 0.1 chains / nm ２ On the other hand, from the viewpoint of ease of grafting of polymer chains, it is preferable that the number of chains is 2 chains / nm. ２ or less, more preferably 1.5 chains / nm ２ More preferably, 1 chain / nm ２ Even more preferably 0.5 chains / nm or less ２ The graft density of the composite particles is measured by the method described in the Examples below.

[0095] From the viewpoint of dispersibility of the composite particles in the resin composition, the film thickness of the polymer graft chain in the composite particle is preferably 0.1 nm or more, more preferably 0.5 nm or more, and even more preferably 1 nm or more. From the same viewpoint, it is preferably 1 μm or less, more preferably 500 nm or less, even more preferably 100 nm or less, still more preferably 50 nm or less, even more preferably 25 nm or less, and even more preferably 10 nm or less. The film thickness of the polymer graft chain is calculated by the method described in the Examples below.

[0096] From the viewpoint of dispersibility of the composite particles in the resin composition, the number average molecular weight of the polymer graft chains in the composite particles is preferably 1,000 or more, more preferably 1,500 or more. From the same viewpoint, the number average molecular weight is preferably 1,000,000 or less, more preferably 500,000 or less, even more preferably 200,000 or less, still more preferably 100,000 or less, still more preferably 50,000 or less, still more preferably 30,000 or less, still more preferably 20,000 or less, still more preferably 12,000 or less, still more preferably 8,000 or less, and still more preferably 4,500 or less. The number average molecular weight of the polymer graft chains is measured by the method described in the Examples below.

[0097] From the viewpoint of dispersibility of the composite particles, the content of the polymer graft chains in the composite particles is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and is preferably 6.0% by mass or less, more preferably 4.0% by mass or less, even more preferably 2.0% by mass or less.

[0098] The number average molecular weight of the side chain of the polymer graft chain is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more, from the viewpoint of improving dispersibility. Furthermore, from the viewpoint of reactivity with the particle surface, the number average molecular weight of the side chain is preferably 1,000 or less, more preferably 800 or less, and even more preferably 500 or less. The number average molecular weight of the side chain of the polymer graft chain can be determined from the molecular weight of the compound used as the monomer unit. For example, when glycidyl methacrylate is used as the monomer, the formed polymer graft chain, polyglycidyl methacrylate, has a structure shown in the following formula, and the main chain and side chain in the polymer graft chain according to the present invention also have the relationship shown in the following formula.

[0099]

[0100] As described above, if the portion of polyglycidyl methacrylate outside the carbonyl bond is considered to be the side chain, the molecular weight of the side chain is 101. In other words, when the polymer graft chain is polyglycidyl methacrylate (PGMA), the number average molecular weight of the side chain is 101. Similarly, when the polymer graft chain is polystyrene (PSt), the number average molecular weight of the side chain is 77, and when the polymer graft chain is polydivinylbenzene (PDVB), the number average molecular weight of the side chain is 103.

[0101] From the viewpoint of obtaining a molded article of the resin composition exhibiting the desired dielectric properties, the average particle size of the composite particles is preferably greater than 250 nm, more preferably 300 nm or more, and even more preferably 400 nm or more. On the other hand, from the viewpoint of improving the appearance of the resin composition, the average particle size of the composite particles is preferably 3,000 nm or less, more preferably 2,500 nm or less, and even more preferably 2,000 nm or less. The average particle size of the inorganic particles in the composite particles is measured by the same method as the average particle size of the inorganic particles, i.e., the method described in the Examples below.

[0102] The smaller the dielectric constant and dielectric loss tangent of the composite particles, the better. For example, the dielectric constant ε of the composite particles at a frequency of 10 GHz and a temperature of 25°C is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. For example, the dielectric loss tangent tanδ of the composite particles at a frequency of 10 GHz and a temperature of 25°C is preferably less than 0.01, more preferably 0.007 or less, and even more preferably 0.005 or less. Such dielectric properties can be determined by the method described in the Examples.

[0103] <Resin Composition> The resin composition of the present invention is a composition containing the composite particles of the present invention and a resin. The resin composition of the present invention may be a resin composition or a semi-cured product of the resin composition. The semi-cured product of the present invention refers to a resin composition that has been partially cured to the extent that it can be further cured. For example, when a resin composition is heated, the viscosity initially gradually decreases as it melts, and then curing begins, and the viscosity gradually increases. In such a case, semi-curing can refer to a state between when the viscosity starts to gradually decrease and when it is not completely cured.

[0104] Resins used in the resin composition of the present invention include thermosetting resins and thermoplastic resins. Thermosetting resins include polyurethane resins, urea resins, phenolic resin foams, unsaturated polyester resins, alkyd resins, melamine resins, epoxy resins, silicone resins, and modified polyphenylene ether resins. Among these, modified polyphenylene ether resins are preferred from the viewpoint of exhibiting excellent low dielectric properties. Specific examples of modified polyphenylene ether resins include resins obtained using modified polyphenylene ether compounds described in WO2019 / 065941 and crosslinking curing agents having carbon-carbon unsaturated double bonds in the molecule. Examples of thermoplastic resins include polyolefin resins, cycloolefin resins, polystyrene resins, polyphenylene ether resins, 5-methylpentene resins, polyphenylene sulfide resins, fluorinated polyimide resins, fluorine-based resins, aromatic polyester resins, aromatic polycarbonate resins, thermotropic liquid crystal polymer resins, aromatic polysulfone resins, aromatic polyether resins, polyimide resins, polytetrafluoroethylene resins, polychlorotrifluoroethylene resins, and polyvinylidene fluoride resins.

[0105] The resin content in the resin composition of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more from the viewpoint of obtaining a molded article of the resin composition, while it is preferably 99% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less from the viewpoint of exhibiting desired dielectric properties.

[0106] The content of the composite particles in the resin composition of the present invention is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more from the viewpoint of exhibiting desired dielectric properties, while it is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less from the viewpoint of obtaining a molded article of the resin composition exhibiting desired dielectric properties.

[0107] A preferred embodiment of the resin composition of the present invention is the above-described resin composition, wherein the resin is an epoxy resin and the polymer graft chain contains 10 mass % or more of a monomer unit having an SP value of 10 to 12. From the viewpoints of dispersibility of the composite particles and reduction in viscosity, such a resin composition is another preferred embodiment of the resin composition of the present invention.

[0108] In the above aspect, from the viewpoint of dispersibility of the composite particles, the monomer unit in the polymer graft chain is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and still more preferably 100% by mass.

[0109] Another preferred embodiment of the resin composition of the present invention is the above-described resin composition, wherein the resin is a modified polyphenylene ether resin, and the polymer graft chain contains 10 mass % or more of a monomer unit having an SP value of 8 to 10. From the viewpoint of dispersibility of the composite particles, such a resin composition is another preferred embodiment of the resin composition of the present invention.

[0110] In the above aspect, from the viewpoints of dispersibility of the composite particles and reactivity with the resin, the monomer unit in the polymer graft chain is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, still more preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and still more preferably 100% by mass.

[0111] The SP value in this specification refers to the solubility parameter calculated by the Fedors method (unit: (cal / cm 3 ) 1 / 2 ) and are described in, for example, references such as "SP Value Basics, Applications and Calculation Methods" (Johokikansha, 2005) and Polymer Handbook Third Edition (A Wiley-Interscience publication, 1989).

[0112] The main monomers used as the monomer units and their SP values ​​are as follows: styrene (SP value: 9.0), divinylbenzene (SP value: 9.3), glycidyl methacrylate (SP value: 10.7), and allyl methacrylate (SP value: 9.7).

[0113] [Method for Producing Resin Composition] The resin composition of the present invention can be produced by a production method including a step of mixing or kneading the composite particles of the present invention with a resin. For example, a production method including a step of melt-kneading the resin and the composite particles can be used. For melt-kneading, a known kneader such as an internal kneader, a single-screw or twin-screw extruder, or an open-roll kneader can be used. After melt-kneading, the melt-kneaded mixture may be dried or cooled according to a known method. Alternatively, the raw materials may be uniformly mixed in advance using a Henschel mixer, a super mixer, or the like, before being subjected to melt-kneading. The melt-kneading temperature and melt-kneading time are not necessarily determined depending on the type of raw materials used, but are preferably 170 to 300°C and 15 to 900 seconds.

[0114] As an example of a production method, a method of kneading the components without thermal melting will be described below. First, the components soluble in organic solvents are added to the organic solvent and dissolved. Heating may be performed as necessary. Subsequently, components that are insoluble in organic solvents, if necessary, are added and dispersed until a predetermined dispersion state is achieved using a ball mill, bead mill, planetary mixer, roll mill, rotary mixer, planetary mixer, high-pressure homogenizer, ultrasonic homogenizer, or the like, to prepare a varnish-like composition. It is also preferable to pre-disperse the components that are insoluble in organic solvents in organic solvents. Examples of pre-dispersion methods include ball mills, bead mills, planetary mixers, roll mills, rotary mixers, planetary mixers, roll mills, rotary mixers, planetary mixers, high-pressure homogenizers, ultrasonic homogenizers, and the like. The organic solvent used here is not particularly limited, as long as it dissolves the modified polyphenylene ether compound and the cross-linked curing agent and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

[0115] [Dielectric Properties of Resin Composition] The smaller the relative dielectric constant and dielectric loss tangent of the cured product of the resin composition of the present invention, the better. For example, the relative dielectric constant ε of the cured product at a frequency of 10 GHz and a temperature of 25°C is preferably 2.8 or less, more preferably 2.5 or less, even more preferably 2.3 or less, even more preferably 2.0 or less, and even more preferably 1.8 or less. For example, the dielectric loss tangent tanδ of the cured product at a frequency of 10 GHz and a temperature of 25°C is preferably 0.008 or less, more preferably 0.007 or less, even more preferably 0.006 or less, even more preferably 0.005 or less, and even more preferably 0.004 or less. Such dielectric properties can be determined by the method described in the examples.

[0116] <Resin composition for low dielectric materials and low dielectric resin composition> The resin composition for low dielectric materials of the present invention contains the composite particles of the present invention described above and a resin. Furthermore, the low dielectric resin composition of the present invention contains the composite particles of the present invention described above and a resin. Since the resin composition of the present invention can achieve such dielectric properties, the resin composition of the present invention can be used as a resin composition for low dielectric materials, a low dielectric resin composition, a resin composition for copper-clad laminates, a resin composition for primary mounting underfill materials, or a resin composition for interlayer insulation materials. Therefore, the resin composition for low dielectric materials and the low dielectric resin composition of the present invention are compositions containing the composite particles of the present invention described above and a resin.

[0117] The resin composition, resin composition for low dielectric material, low dielectric resin composition, resin composition for copper-clad laminate, resin composition for primary mounting underfill material or resin composition for interlayer insulating material of the present invention may contain, as necessary, other components in addition to those described above, such as a flame retardant, an initiator, an antifoaming agent, an antioxidant, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a pigment or dye, a lubricant, an inorganic filler, a crosslinking agent, a toughness improver, an impact absorber or the like.

[0118] The applications of the resin composition of the present invention, the resin composition for low dielectric materials, the low dielectric resin composition, the resin composition for copper-clad laminates, the resin composition for primary mounting underfill materials, or the resin composition for interlayer insulating materials are not particularly limited, and they can be used in a wide range of applications requiring resin compositions, such as adhesive films, sheet-like laminate materials such as prepregs, solder resists, underfill materials, die bonding materials, semiconductor encapsulants, hole filling resins, component embedding resins, circuit boards (laminates, multilayer printed wiring boards, etc.), and semiconductor devices.

[0119] The present invention also includes the following aspects.

[0120] <1> Composite particles having polymer graft chains on the surfaces of inorganic particles, wherein the inorganic particles are hollow particles, and the average particle size of the inorganic particles is greater than 200 nm and not greater than 3,000 nm.

[0121] <2> The composite particle according to <1>, wherein the inorganic particle has a porosity of 50% by volume or more and 80% by volume or less. <3> The composite particle according to <1>, wherein the graft density of the polymer graft chains in the composite particle is 0.01 chains / nm ２ <4> The composite particle according to any one of <1> to <3>, wherein the polymer graft chain is a polymer composed of one or more monomers selected from the group consisting of styrene-based monomers, nitrile-based monomers, (meth)acrylic monomers, fluorine-based monomers, unsaturated olefin-based monomers, conjugated diene-based monomers, and monomers having an amino group, a hydroxy group, or a glycidyl group. <5> The composite particle according to any one of <1> to <4>, wherein the inorganic particle is silica. <6> The composite particle according to any one of <1> to <5>, wherein the inorganic particle is silica, and the total content of alkali metals and alkaline earth metals relative to the content of silica in the inorganic particle is 50 ppm by mass or less. <7> The composite particle according to any one of <1> to <6>, wherein the polymer graft chain is present via a structure represented by the following formula (A): (polymer graft chain)-X-(CH ２ ) ｍ -Si-(R １ ) (R ２ ) (R３ ) Formula (A) (In formula (A), -X- is a divalent group, one of which is -(CH ２ ) ｍ The other bonded to the polymer graft chain. m is an integer of 0 to 12. R １ , R ２ and R ３ at least one of the groups bonded to the particles by forming a metalloxane bond, and the groups not bonded to the particles are each independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, a hydrogen atom, a hydroxyl group, or a halogen atom.) <8> The inorganic particles are hollow silica, have an average particle diameter of 1500 nm or more and 2500 nm or less, a porosity of 60 vol% or more and 70 vol% or less, the graft chains are a polymer made of styrene, have a number average molecular weight of 5000 or more and 8000 or less, and a graft chain density of 0.1 chains / nm ２ 1 chain / nm ２ <9> The composite particle according to any one of <1> to <7>, wherein the inorganic particles are hollow silica particles, the average particle diameter is 1500 nm or more and 2500 nm or less, the porosity is 60 vol % or more and 70 vol % or less, the graft chains are polymers made of divinylbenzene, the number average molecular weight is 15,000 or more and 30,000 or less, and the graft chain density is 0.1 chains / nm ２ 1 chain / nm ２ <10> The composite particle according to any one of <1> to <8>, wherein the inorganic particles are hollow silica particles, the average particle diameter is 400 nm or more and 800 nm or less, the porosity is 60 vol% or more and 70 vol% or less, the graft chains are polymers made of methacrylic glycidylates, the number average molecular weight is 1500 or more and 4500 or less, and the graft chain density is 0.1 chains / nm ２ 1 chain / nm ２ or less, and the film thickness of the graft chain is 1 nm or more and 10 nm or less.

[0122] <11> A resin composition containing the composite particles according to any one of <1> to <10> and a resin. <12> A resin composition for low dielectric materials containing the composite particles according to any one of <1> to <10> and a resin. <13> The inorganic particles are hollow silica, have an average particle diameter of 1500 nm or more and 2500 nm or less, a porosity of 60% by volume or more and 70% by volume or less, the graft chains are polymers made of styrene, have a number average molecular weight of 5000 or more and 8000 or less, and a graft chain density of 0.1 chains / nm ２ 1 chain / nm ２ <14> The resin composition for low dielectric materials according to <11> or <12>, comprising composite particles having an average particle diameter of 1,500 nm or more and 2,500 nm or less, and a graft chain film thickness of 1 nm or more and 10 nm or less, and a modified polyphenylene ether compound. <15> The inorganic particles are hollow silica, have an average particle diameter of 1,500 nm or more and 2,500 nm or less, have a porosity of 60 volume % or more and 70 volume % or less, the graft chains are polymers made of divinylbenzene, have a number average molecular weight of 15,000 or more and 30,000 or less, and have a graft chain density of 0.1 chains / nm ２ 1 chain / nm ２ <15> The resin composition for low dielectric materials according to <11> or <12>, comprising composite particles having an average particle diameter of 400 nm or more and an average particle size of 800 nm or less, and a porosity of 60% by volume or more and 70% by volume or less, the graft chains being a polymer made of methacrylic glycidylates, and having a number average molecular weight of 1500 or more and an average particle size of 4500 or less, and a graft chain density of 0.1 chains / nm ２ 1 chain / nm ２<16> Use of the composite particles according to any one of <1> to <10> for use in a low dielectric material. <17> Use of a resin composition comprising the composite particles according to any one of <1> to <10> and a resin, as a low dielectric material. <18> The inorganic particles are hollow silica, have an average particle diameter of 1500 nm or more and 2500 nm or less, and a porosity of 60 vol% or more and 70 vol% or less, the graft chains are a polymer made of styrene, and have a number average molecular weight of 5000 or more and 8000 or less, and a graft chain density of 0.1 chains / nm ２ 1 chain / nm ２ <19> Use of composite particles as a low dielectric material according to <16> or <17>, wherein the inorganic particles are hollow silica, the average particle diameter is 1500 nm or more and 2500 nm or less, the porosity is 60 vol% or more and 70 vol% or less, the graft chains are polymers made of divinylbenzene, the number average molecular weight is 15,000 or more and 30,000 or less, and the graft chain density is 0.1 chains / nm ２ 1 chain / nm ２ <20> Use of composite particles as a low dielectric material according to <16> or <17>, wherein the inorganic particles are hollow silica, the average particle diameter is 400 nm or more and 800 nm or less, the porosity is 60 vol% or more and 70 vol% or less, the graft chains are polymers made of methacrylic glycidylate, the number average molecular weight is 1500 or more and 4500 or less, and the graft chain density is 0.1 chains / nm ２ 1 chain / nm ２ or less, and the film thickness of the graft chain is 1 nm or more and 10 nm or less. Use of the composite particles for a low dielectric material according to <16> or <17>.

[0123] <21> The inorganic particles are hollow silica, have an average particle diameter of 1500 nm or more and 2500 nm or less, have a porosity of 60 vol% or more and 70 vol% or less, the graft chains are polymers made of styrene, have a number average molecular weight of 5000 or more and 8000 or less, and have a graft chain density of 0.1 chains / nm ２ 1 chain / nm ２ <22> Use of a composition containing composite particles and a modified polyphenylene ether compound as a low dielectric material according to <17>, wherein the inorganic particles are hollow silica, have an average particle diameter of 1,500 nm or more and 2,500 nm or less, have a porosity of 60% by volume or more and 70% by volume or less, the graft chains are polymers made of divinylbenzene, have a number average molecular weight of 15,000 or more and 30,000 or less, and have a graft chain density of 0.1 chains / nm ２ 1 chain / nm ２ <23> Use of a composition containing composite particles and a modified polyphenylene ether compound as a low dielectric material according to <17>, wherein the inorganic particles are hollow silica, have an average particle diameter of 400 nm or more and 800 nm or less, and have a porosity of 60% by volume or more and 70% by volume or less, the graft chains are polymers made of methacrylic glycidylate, and have a number average molecular weight of 1500 or more and 4500 or less, and a graft chain density of 0.1 chains / nm ２ 1 chain / nm ２ or less, and the film thickness of the graft chain is 1 nm or more and 10 nm or less, and the composition contains an epoxy resin, and the composite particles. Use of the composition as a low dielectric material according to <17>.

[0124] The present invention will be specifically explained below by showing examples, but the present invention is not limited to the following examples.

[0125] [Average particle size of inorganic particles and composite particles] The average particle size of inorganic particles and composite particles was measured by the Coulter counter method using a Multisizer 3 (manufactured by Beckman Coulter, Inc., using a 20 μm aperture tube). That is, the average particle size and standard deviation of particle size were determined on a volume basis, and the coefficient of variation was calculated using the following formula: Coefficient of variation (%) = [(standard deviation of particle size) / (average particle size)] × 100. The maximum particle size was defined as the particle size at 99% of the cumulative frequency distribution on a volume basis.

[0126] [Porosity of inorganic particles] The porosity (volume %) of inorganic particles was calculated according to the following formula using the density measured using a true density measuring device with nitrogen as the measurement gas. The true density measuring device used was an ULTRAPYCNOMETER 1000 manufactured by QUANTACHROME. The material density of silica was 2.2 (g / cm ３ For particles other than silica, the material density value of the material that makes up the particle is used. Porosity (volume %) of inorganic particles = [1 - (measured density / material density of silica particles)] x 100

[0127] [Metal Content of Inorganic Particles] The metal content of inorganic particles was measured as the total content of alkali metals and alkaline earth metals in the particles as follows. 100 mg of particles were placed in a platinum crucible, and 3 mL of concentrated nitric acid, 1 mL of concentrated hydrofluoric acid, and 1 mL of concentrated hydrochloric acid were added thereto, and the mixture was heated to evaporate to dryness. The residue in the crucible was then diluted with hydrochloric acid and measured using an inductively coupled plasma mass spectrometer (Agilent Technologies, product name: Agilent 8900).

[0128] [Specific surface area of ​​particles used in composite particles] The specific surface area of ​​the particles used in the composite particles was measured using the BET specific surface area. Specifically, the BET specific surface area of ​​the particles was measured using a specific surface area measuring device (Shimadzu Corporation, product name "Flowsorb III 2305"). The sample was pretreated by heating at 200°C for 15 minutes.

[0129] [Content of polymer graft chains in composite particles] The content of polymer graft chains in the composite particles was determined by the weight loss rate determined by the thermal weight loss measurement shown below. Then, the content (mass%) of polymer graft chains in the composite particles was calculated using the following formula: Content (mass%) of polymer graft chains = "Weight loss rate (mass%) when heating from 40°C to 500°C at a rate of 10°C / min"

[0130] [Graft Density of Polymer Graft Chains in Composite Particles] The graft density of polymer graft chains in composite particles (chains / nm ２ ) is the mass per unit area of ​​the graft chains on the surface of the composite particle (g / nm ２ The graft density (chains / nm) was calculated by the following formula: ２ ) = [mass of grafted chains per unit area (g / nm ２ ) / number average molecular weight of grafted chains × (Avogadro's number)

[0131] Here, the mass of the grafted chains was determined by thermal gravitational loss (TG) measurements. Specifically, the composite particles to be measured were heated in air from 40°C to 500°C at a rate of 10°C / min, and the weight loss rate was measured. Furthermore, the "mass of grafted chains per unit area" was calculated from the specific surface area of ​​the inorganic particles that were the raw material for the composite particles to be measured. The number-average molecular weight of the grafted chains was determined by gel permeation chromatography (GPC) as shown below.

[0132] [Number-Average Molecular Weight of Polymer Graft Chains in Composite Particles] The number-average molecular weight of the polymer graft chains in the composite particles was determined by extracting only the polymer graft chains from the composite particles. Specifically, 200 mg of composite particles were stirred for 12 hours in 2 mL of a tetrabutylammonium fluoride solution (approximately 1 mol / L) in tetrahydrofuran (Tokyo Chemical Industry Co., Ltd.) to detach the polymer graft chains from the composite particles. The resulting tetrahydrofuran solution containing the dissolved polymer graft chains was reprecipitated with a large amount of methanol, and the solvent was removed and dried to isolate the detached polymer graft chains. This was dissolved in chloroform and used as the solution for the GPC measurement described below. The number-average molecular weight was measured by gel permeation chromatography (GPC) using a TSKgel GMHHR-H + GMHHR-H (cation) (Tosoh Corporation) column, chloroform as the solvent, at a flow rate of 1.0 mL / min and a column temperature of 40°C, using polystyrene as a molecular weight standard.

[0133] [Film Thickness of Polymer Graft Chains in Composite Particles] The film thickness was calculated using the following formula. The polymer density in the formula was defined as the polymer density of the polymer graft chains that were not bonded to the composite particles and were simultaneously produced in the process of producing the composite particles. The polymer density was measured by a pycnometer method in accordance with JIS K 7112.

[0134]

[0135] Production Example 1 [Production of Silica Microparticles] 388.6 g of ion-exchanged water, 200 g of dodecane (Kishida Chemical Co., Ltd.: primary n-dodecane), and 11.4 g of QUARTAMINE 86W (Kao Corporation: containing 28% by mass of stearyl trimethyl ammonium chloride) were mixed and stirred to obtain Emulsion A. The volume average particle size of the particles in the obtained Emulsion A was 0.9 μm. A reaction vessel was charged with 13,192.5 g of ion-exchanged water, 138.1 g of Emulsion A, 125.6 g of QUARTAMINE 24P (Kao Corporation: containing 27.5% by mass of lauryl trimethyl ammonium chloride), and 3,120.8 g of ethyl orthosilicate (Wacker Asahi Kasei Silicones: TEOS999), and the mixture was heated to 40° C. with stirring and then stirred for 10 minutes to obtain Preparation Solution B. Next, 221.5 g of AH212-CS (manufactured by Yokkaichi Synthetic Co., Ltd.: containing 50% by mass of dimethylbis(2-hydroxyethyl)ammonium hydroxide) and 711.6 g of Kotamine 24P were uniformly mixed to obtain Preparation C. The entire amount of Preparation C was added to the entire amount of Preparation B at a constant rate, and then the mixture was stirred at 40°C for 3 hours to obtain a cloudy liquid D. The obtained cloudy liquid D was then filtered using 5C filter paper (manufactured by Advantec Toyo Co., Ltd.), washed with water, and dried at 110°C to obtain white hollow silica particle precursors. The obtained hollow silica particle precursor was calcined at 1100°C for 1 hour to obtain hollow silica particles (average particle size 1.9 μm, coefficient of variation 27%, BET specific surface area 9.6 m ２ The hollow silica particles were designated as silica fine particles 1.

[0136] Production Example 2 [Production of Silica Microparticles] 91 g of Catiogen TML (Dai-ichi Kogyo Seiyaku Co., Ltd.: containing 30% by weight of dodecyltrimethylammonium chloride), 17 g of a 25% aqueous solution of tetramethylammonium hydroxide (Seichem Asia Co., Ltd.: pH 14), and 20 g of hexane (Fujifilm Wako Pure Chemical Industries Co., Ltd., special grade) were added to 2,000 g of methanol (Fujifilm Wako Pure Chemical Industries Co., Ltd.) and stirred to prepare a solution phase containing a hydrophobic organic substance and a hydrophilic organic solvent. The resulting solution phase was simultaneously mixed with 1 part by volume of ion-exchanged water at a ratio of 1 part by volume to 1 part by volume to obtain an emulsion. 1,500 g of ion-exchanged water was added to the resulting emulsion. 18 g of orthosilicate methyl ester (tetramethoxysilane) (Tama Chemicals Co., Ltd.) was added to the emulsion after the addition of ion-exchanged water, and the mixture was stirred at 25°C for 10 minutes to obtain a cloudy white solution. The resulting cloudy solution was filtered using No. 5C filter paper (manufactured by Advantec Toyo Co., Ltd.) and dried at 100°C to obtain composite silica particles. The resulting composite silica particles were calcined at 1000°C for 38 hours to obtain hollow silica particles (average particle size 1.9 μm, coefficient of variation 17%, BET specific surface area 8.0 m). ２ The hollow silica particles were designated as silica fine particles 2.

[0137] Example 1 [Preparation of Composite Particle 1] a) Step of Bonding Polymerization Initiator Groups to the Particle Surface a-1) Introduction of Amino Groups onto the Surface of Silica Particles 40 g of the silica particles obtained in Production Example 1 above and 2 g of 3-aminopropyltrimethoxysilane (KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to 200 mL of ethanol. The mixture was stirred at room temperature for 12 hours. After washing with ethanol, the silica particles were recovered using a centrifuge and then heated at 110°C for 1 hour to obtain amino-group-introduced silica particles.

[0138] a-2) Introduction of polymerization initiator groups onto the surface of amino group-introduced silica microparticles 40 g of the above amino group-introduced silica microparticles, 200 mL of anhydrous THF, 1 mL of anhydrous triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 1 mL of 2-bromoisobutyl bromide (BIBB) (manufactured by Tokyo Chemical Industry Co., Ltd.) were placed in a 500 mL eggplant-shaped flask and stirred at room temperature for 2 hours. After that, the mixture was washed with THF and anisole, and the polymerization initiator group-introduced silica microparticles into which 2-bromoisobutyryl groups had been introduced as polymerization initiator groups were recovered using a centrifuge and then stored as an anisole-wet product of polymerization initiator group-introduced silica microparticles.

[0139] b) A step of contacting particles having polymerization initiator groups on their surfaces with a monomer under living radical polymerization conditions. A 500 mL separable flask was charged with 12 g of the above-prepared silica microparticles having polymerization initiator groups, 60 g of anisole, and 180 g of styrene as a monomer. The mixture was thoroughly stirred and then subjected to reduced pressure and nitrogen substitution. The temperature was then raised to 90 °C, and an acetonitrile solution prepared by stirring 860 mg of Cu(I)Br (Tokyo Chemical Industry Co., Ltd.) and 2080 mg of pentamethyldiethylenetriamine (Tokyo Chemical Industry Co., Ltd.) in 5 mL of acetonitrile under nitrogen was added to initiate polymerization. The mixture was then stirred for 30 minutes, followed by ice-water cooling and air bubbling. An excess of methanol was then added to quench the reaction. The mixture was then washed with methanol and filtered to remove the solution three times, followed by washing with toluene and filtering to remove the solution once, yielding polystyrene-grafted silica microparticles (i.e., composite particles 1). The resulting solid was then added to toluene without drying and stored as a toluene solution. The content of the polymer graft chains in the obtained composite particle 1 was 2.7% by mass, the number average molecular weight of the polymer graft chains was 8,000, and the graft density of the polymer graft chains was 0.19 chains / nm ２ The film thickness of the polymer graft chain was 2 nm, and the content of the monomer unit (styrene) in the polymer graft chain was 100% by mass. A schematic diagram of the structure of the obtained composite particle is shown in Figure 1.

[0140] Example 2 [Preparation of Composite Particles 2] Step b) Contacting Particles Having Polymerization Initiator Groups on Their Surfaces with a Monomer Under Living Radical Polymerization Conditions A 500 mL separable flask was charged with an anisole-wet mixture containing 12 g of silica microparticles having polymerization initiator groups prepared in step a) of Example 1 above, 60 g of anisole, and 180 g of divinylbenzene as a monomer. After thorough stirring, the mixture was subjected to reduced pressure and nitrogen substitution. The temperature was then raised to 90°C, and an acetonitrile solution prepared by stirring 860 mg of Cu(I)Br (Tokyo Chemical Industry Co., Ltd.) and 2080 mg of pentamethyldiethylenetriamine (Tokyo Chemical Industry Co., Ltd.) in 5 mL of acetonitrile under nitrogen was added to initiate polymerization. The mixture was then washed with methanol and filtered three times to remove the solution, followed by washing with toluene and filtering once to remove the solution, yielding silica microparticles grafted with polydivinylbenzene (i.e., composite particles 2). The resulting solid was then added to toluene without drying, and stored as a toluene solution. The content of the polymer graft chains in the obtained composite particle 2 was 2.1% by mass, the number average molecular weight of the polymer graft chains was 6,300, and the graft density of the polymer graft chains was 0.19 chains / nm ２ The film thickness of the polymer graft chains was 2 nm, and the content of the monomer unit (divinylbenzene) in the polymer graft chains was 100% by mass.

[0141] Example 3 [Preparation of Composite Particles 3] Step b) A step of contacting particles having polymerization initiator groups on their surfaces with a monomer under living radical polymerization conditions. A 500 mL separable flask was charged with an anisole-wet solution containing 12 g of silica microparticles having polymerization initiator groups prepared in step a) of Example 1 above, and 240 g of styrene as a monomer. After thorough stirring, the mixture was subjected to reduced pressure and nitrogen substitution. The temperature was then raised to 90 ° C., and an acetonitrile solution prepared by stirring 860 mg of Cu(I)Br (manufactured by Tokyo Chemical Industry Co., Ltd.) and 2080 mg of pentamethyldiethylenetriamine (manufactured by Tokyo Chemical Industry Co., Ltd.) in 5 mL of acetonitrile under nitrogen was poured into the flask to initiate polymerization. The mixture was then washed with methanol and filtered three times to remove the solution, followed by washing with toluene and filtering once to remove the solution, yielding polystyrene-grafted silica microparticles (i.e., Composite Particles 3). The resulting solid was then added with toluene without drying, and stored as a toluene solution. The content of the polymer graft chains in the obtained composite particle 3 was 5.9% by mass, the number average molecular weight of the polymer graft chains was 24,000, and the graft density of the polymer graft chains was 0.14 chains / nm ２ The film thickness of the polymer graft chains was 5 nm, and the content of the monomer unit (styrene) in the polymer graft chains was 100% by mass.

[0142] Example 4 [Preparation of Composite Particles 4] Polystyrene-grafted silica microparticles (i.e., Composite Particles 4) were produced in the same manner as in Example 1, except that 40 g of the silica microparticles obtained in Production Example 2 were used as the silica microparticles. The content of polymer graft chains in the obtained Composite Particles 4 was 2.7 mass %, the number average molecular weight of the polymer graft chains was 8,000, and the graft density of the polymer graft chains was 0.19 chains / nm ２ The film thickness of the polymer graft chains was 2 nm, and the content of the monomer unit (styrene) in the polymer graft chains was 100% by mass.

[0143] Comparative Example 1 [Preparation of Particles 5] (Introduction of Vinyl Groups onto the Surface of Silica Particles) 40 g of the silica particles obtained in Production Example 1 above and 2 g of vinyltrimethoxysilane (manufactured by Kanto Chemical Co., Inc.) were added to 200 mL of ethanol. The mixture was stirred at room temperature for 12 hours. After that, the silica particles were washed with ethanol, and recovered using a centrifuge. The recovered silica particles were then heated at 110°C for 1 hour to obtain vinyl group-introduced silica particles (i.e., composite particles 5).

[0144] Test Example 1 [Dielectric Properties of Composite Particles] The dielectric properties of the composite particles were evaluated as follows. The relative permittivity and dielectric loss tangent of the composite particles were determined by measurement at a temperature of 25°C and a measurement frequency of 10 GHz using a device comprising a network analyzer (manufactured by Agilent Technologies, product name: N5221A) connected to a perturbation method cavity resonator (CP-580) manufactured by Kanto Electronics Application Development Co., Ltd., using a cavity resonator perturbation method (CP-MA dielectric constant measurement software, manufactured by Kanto Electronics Application Development Co., Ltd.). Specifically, a measurement sample was prepared by filling a Teflon (registered trademark) tube (manufactured by Chukoh Chemical Industry Co., Ltd.: PTFE tube, inner diameter 1.5 mm, outer diameter 2.5 mm) with the composite particles so that all of them were within the measurement range (6.75 mm to 36.35 mm from the bottom). The weight of the composite particles was calculated from the weight measurements before and after filling, and the volume of the composite particles filled in the Teflon tube was determined from the filling weight and specific gravity of the composite particles. The relative permittivity and dielectric loss tangent were determined from the difference between the measured values ​​of an empty Teflon tube not filled with composite particles and the measured values ​​of the Teflon tube filled with composite particles.

[0145]

[0146] The abbreviations in the table are as follows: PSt: polystyrene; PDVB: polydivinylbenzene; VTMS: vinyltrimethoxysilane.

[0147] Table 1 demonstrates that the composite particles of the present invention (Examples 1 to 4) are hollow particles because they have a high porosity. Furthermore, with regard to dielectric properties, it was found that the composite particles of Examples 1 to 4 had smaller relative permittivity values ​​and smaller dielectric loss tangent values ​​than the particles of Comparative Example 1. This is thought to be because the particles of Comparative Example 1 did not have polymer craft chains bonded to them.

[0148] Examples 11-14 and Comparative Example 11 [Preparation of Resin Composition] First, each component other than the composite particles was added to toluene at the blending ratio (parts by mass) shown in Table 2 so that the solids concentration was 60% by mass, and mixed. The mixture was stirred at room temperature for 24 hours. Thereafter, a toluene solution of the composite particles was added to the resulting liquid, and the inorganic filler was dispersed using a planetary mixer. This resulted in a varnish-like resin composition (varnish). Next, the resulting varnish was heated and dried at 80°C for approximately 2-3 hours to produce a precursor of a resin molded body. The resulting precursors of the resin molded body were then stacked and heated and pressurized at a temperature of 200°C for 2 hours at a pressure of 3 MPa to obtain an evaluation substrate (resin molded body).

[0149] Test Example 2 [Dielectric Properties of Resin Molded Article] The dielectric properties of the resin molded article were evaluated as follows: The relative permittivity and dielectric loss tangent of the resin molded article were measured at a temperature of 25°C and a measurement frequency of 10 GHz using an apparatus in which a perturbation method cavity resonator (CP-580) manufactured by Kanto Electronics Application Development Co., Ltd. was connected to a network analyzer (manufactured by Agilent Technologies, product name: N5221A) by a cavity resonator perturbation method (CP-MA, dielectric constant measurement software, manufactured by Kanto Electronics Application Development Co., Ltd.).

[0150] Test Example 3 [Dispersibility of Composite Particles] The dispersibility of the composite particles in the resin molding was evaluated by observing the machined surface of the resin molding with a scanning electron microscope (SEM). From the image observed with the SEM, cross sections of 50 composite particles were selected, and the major axis of each was visually read and the average value was taken as the dispersed particle size. Composite particles with a dispersed particle size of 10 μm or more were judged to have poor dispersibility.

[0151] Table 2 shows the compounding ratios of the resin molded body and the evaluation results.

[0152]

[0153] As described above, Examples 11 to 14 used the composite particles of the present invention (Examples 1 to 4), and therefore the dispersibility of the composite particles was excellent and the dielectric properties were also excellent. On the other hand, the dispersibility of the particles in Comparative Example 11 was significantly inferior to that of the Examples. The reason for the large dispersed particle size in Comparative Example 11 is presumed to be that the particles in Comparative Example 1 did not have organic polymer graft chains, and therefore agglomerates formed in the resin, making them unable to be dispersed.

[0154] The components other than the composite particles are as follows. (Resin) The resin used was a curable resin obtained by crosslinking the following modified polyphenylene ether with TAIC, which will be described later. Modified polyphenylene ether compound (modified PPE): Noryl SA9000 resin, manufactured by SABIC Innovative Plastics, weight average molecular weight = 2,000; this is a modified polyphenylene ether in which the terminal hydroxyl groups of polyphenylene ether are modified with methacrylic groups. The specific structure is shown in the following formula (2), and R in formula (2) ９ , R １０ , R １５ and R １６ is a methyl group, and R １１ ~R １４ is a hydrogen atom, X is a methacryl group, and Y is a dimethylmethylene group (i.e., represented by the following formula (3), R １７ and R １８ is a methyl group).

[0155]

[0156] (Cross-linking curing agent) TAIC: triallyl isocyanurate (TAIC manufactured by Nippon Kasei Chemical Industry Co., Ltd., molecular weight 249, number of terminal double bonds 3) (Reaction initiator) Initiator: 1,3-bis(butylperoxyisopropyl)benzene (Perbutyl P (PBP) manufactured by NOF Corporation) (Toughness improver) SBS: styrene-based thermoplastic elastomer (Tufprene A manufactured by Asahi Kasei Corporation)

[0157] Synthesis Example 1 [Synthesis of a silane compound having a polymerization initiator group other than a halosulfonyl group] 17.9 g of 3-aminopropyltrimethoxysilane (KBM-903, Shin-Etsu Chemical Co., Ltd.), 100 mL of anhydrous tetrahydrofuran (THF), and 16.8 mL of anhydrous triethylamine (Tokyo Chemical Industry Co., Ltd.) were added to a 500 mL eggplant-shaped flask. This mixture was ice-cooled, and when it reached 0°C, 14.8 mL of 2-bromoisobutyl bromide (BiBB) (Tokyo Chemical Industry Co., Ltd.) was added dropwise while maintaining the ice cooling, and the mixture was stirred for 4 hours. The solvent was then removed from the liquid phase obtained after filtration using an evaporator. The residue was dried at 50°C for 5 hours to obtain a silane compound having a bromoacyl group as a polymerization initiator group (this compound will be abbreviated as "APTMS-Br"). This silane compound was used as a silane coupling agent. The synthesis scheme for the above-mentioned APTMS-Br is shown below.

[0158]

[0159] Example 24 [Preparation of Composite Particles 24] Step a) Step of Bonding Polymerization Initiator Groups to the Particle Surface 15.6 g of silica microparticles 1 (hollow silica microparticles obtained in Production Example 1) and 0.23 g of anhydrous triethylamine as a catalyst were added to a plastic bag and mixed by hand from the outside of the bag at room temperature for 5 minutes. 0.74 g of the above-mentioned APTMS-Br and 0.74 g of ethanol were added thereto and mixed by hand from the outside of the bag at room temperature for 5 minutes. These were mixed at room temperature for 5 minutes using a crusher (manufactured by Iwatani Corporation) and then allowed to stand for 12 hours. The silica microparticles were then washed with ethanol, and subsequently recovered by suction filtration. They were then heated at 110°C for 1 hour to obtain silica microparticles to which bromoacyl groups, which are polymerization initiator groups, were bonded.

[0160] Step b) A step of contacting particles having a polymerization initiator group on the surface with a monomer under living radical polymerization conditions. 3.7 g of the silica microparticles having a polymerization initiator group prepared above, 180 g of anisole, and 60 g of glycidyl methacrylate as a monomer were placed in a 500 mL separable flask, and after thorough stirring, the mixture was subjected to reduced pressure nitrogen substitution. Then, the temperature was raised to 50 ° C., and an acetonitrile solution prepared by previously stirring 860 mg of Cu (I) Br (manufactured by Tokyo Chemical Industry Co., Ltd.) and 2080 mg of pentamethyldiethylenetriamine (manufactured by Tokyo Chemical Industry Co., Ltd.) in 5 mL of acetonitrile under nitrogen was poured into the flask, and polymerization was initiated. Then, the mixture was stirred for 2 minutes, and then cooled with ice water and air was bubbled, and an excess of methanol was added to quench the reaction.

[0161] Thereafter, washing with methanol and removal of the solution by filtration were repeated three times, followed by washing with toluene and removal of the solution by filtration once, followed by vacuum drying at 60° C. for 12 hours, and the resulting solid was crushed in a mortar to obtain a powder. The obtained powder was silica fine particles grafted with polyglycidyl methacrylate, and these fine particles were designated as composite particles 24.

[0162] The content of the polymer graft chains in the obtained composite particles 24 was 1.0 mass %, the number average molecular weight of the polymer graft chains was 3,000, and the graft density of the polymer graft chains was 0.19 / nm ２ The film thickness of the polymer graft chains was 1 nm, and the content of the monomer unit (glycidyl methacrylate) in the polymer graft chains was 100% by mass.

[0163] Example 25 [Preparation of Composite Particle 25] Composite particle 25 was obtained in the same manner as in Example 24, except that in step b), the mixture was vacuum dried at 60°C for 12 hours, the resulting solid was crushed in a mortar to obtain a powder, and then further crushed in a jet mill.

[0164] Example 26 [Preparation of Composite Particles 26] [Preparation of Silica Fine Particles] In Preparation Example 1, the stirring speed and temperature were adjusted to obtain Emulsion A having a volume average particle size of 0.3 μm. Next, hollow silica particles (average particle size 0.6 μm, coefficient of variation 27%, BET specific surface area 21.0 m) were prepared under reaction conditions similar to those in Preparation Example 1. ２The hollow silica particles were designated as silica fine particles 3.

[0165] [Preparation of Composite Particles] Silica microparticles grafted with polyglycidyl methacrylate (i.e., composite particles 26) were obtained in the same manner as in Example 24, except that the hollow silica microparticles 3 were used instead of the silica microparticles having polymerization initiating groups prepared in step a) of Example 1.

[0166] The content of the polymer graft chains in the obtained composite particles 26 was 1.4% by mass, the number average molecular weight of the polymer graft chains was 2,800, and the graft density of the polymer graft chains was 0.15 chains / nm ２ The film thickness of the polymer graft chain was 6 nm, and the content of the monomer unit (glycidyl methacrylate) in the polymer graft chain was 100% by mass.

[0167] The main characteristics of Examples 24 to 26 are summarized in Table 3.

[0168]

[0169] The abbreviations in the table are as follows: PGMA: polyglycidyl methacrylate.

[0170] Examples 27 to 29 [Preparation of Resin Compositions] First, an epoxy resin, an amine curing agent, and each composite particle were mixed in the blending ratios shown in Table 4. The mixture was used in a planetary mixer to disperse the composite particles, thereby preparing resin compositions (before curing).

[0171] Example 30 [Preparation of Resin Composition] An epoxy resin, a phenolic curing agent, and Composite Particles 26 were mixed in the blending ratios shown in Table 4. The mixture was dispersed in a planetary mixer to prepare a resin composition (before curing).

[0172] The compounding ratios of the resin molded bodies and the evaluation results are shown in Table 4. In Table 4, the dispersed particle size of the composite particles that was 10 times or less the average particle size of the inorganic particles used was marked with "+", and the dispersed particle size that was more than 10 times was marked with "-".

[0173]

[0174] The machined surfaces of the resin molded articles obtained in Examples 27 to 30 were observed and the dispersibility of the composite particles was evaluated in the same manner as in Test Example 3. As a result, it was found that the dispersed particle size of the composite particles in all Examples was 1 to 5 μm, which was 10 times or less the average particle size of the inorganic particles.

[0175] In Example 29, the shear viscosity of the resin composition (before curing) and the CTE of the resin molded article (after curing) were evaluated by the following methods. As a result, the shear viscosity was 0.17 Pa s and the CTE was 30.5 ppm. This indicates that the resin composition of Example 29 has a sufficiently low viscosity and that the resin molded article of Example 29 has excellent dimensional stability.

[0176] [Measurement of Shear Viscosity] The shear viscosity (unit: Pa s) of the resin composition (before curing) was measured using a rheometer (MCR300, manufactured by Anton Paar). A 40 mm parallel plate was used as the spindle, and the temperature inside the measurement chamber was set to 110°C. The resin composition to be measured was heated to 110°C in advance and placed on a jig in a uniformly dissolved state.

[0177] The shear viscosity of the resin composition was measured by sweeping the shear rate from low to high within the range of 0.1 (1 / s) to 100 (1 / s), and the shear viscosity value at a shear rate of 32.9 (1 / s) is shown in Table 1. The shear viscosity at a shear rate of 32.9 (1 / s) is an evaluation value of "ease of flow," and the smaller the value, the easier the resin composition is to inject.

[0178] [Coefficient of Linear Thermal Expansion (CTE)] The resin molded body (after curing) was cut into strips of 5 mm width and 40 mm length to prepare samples. Using a thermomechanical analyzer (Hitachi High-Tech Corporation, TMA7100), the temperature of the strip samples was increased at a rate of 5°C per minute under a nitrogen atmosphere, and measurements were performed in tensile mode with a load of 20 mN and a span distance of 10 mm. The coefficient of linear thermal expansion was calculated by calculating the average coefficient of linear thermal expansion over a temperature range of 10°C to 30°C. A lower coefficient of linear thermal expansion indicates better dimensional stability.

[0179] Details of the main components other than the composite particles in the above examples are as follows: (Resin) Bisphenol F type epoxy resin (Mitsubishi Chemical Corporation, JER807, epoxy equivalent: 160-175 g / eq) Bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, JER828, epoxy equivalent: 184-194 g / eq)

[0180] (Curing agent) Aromatic amine curing agent (KAYAHARD AA, manufactured by Nippon Kayaku Co., Ltd., amine equivalent: 64 g / eq) Triazine-containing phenolic resin (LA7052, manufactured by DIC Corporation, hydroxyl group equivalent: 120 g / eq)

[0181] The resin composition containing the composite particles obtained by the production method of the present invention can be used in fields such as adhesive films, sheet-like laminate materials such as prepregs, solder resists, underfill materials, die bonding materials, semiconductor encapsulants, hole-filling resins, component-embedding resins, circuit boards (laminates, multilayer printed wiring boards, etc.), and semiconductor devices.

Claims

1. Composite particles having polymer graft chains on the surface of inorganic particles, wherein the inorganic particles are hollow particles, and the average particle size of the inorganic particles is greater than 200 nm and not greater than 3,000 nm.

2. The composite particles according to claim 1, wherein the porosity of the inorganic particles is 50% by volume or more and 80% by volume or less.

3. The graft density of the polymer graft chains in the composite particles is 0.01 chains / nm ２ The composite particle according to claim 1 or 2, wherein the above-mentioned 4. Composite particles according to any one of claims 1 to 3, wherein the polymer graft chain is a polymer comprising one or more monomers selected from the group consisting of styrene-based monomers, nitrile-based monomers, (meth)acrylic-based monomers, fluorine-based monomers, unsaturated olefin-based monomers, conjugated diene-based monomers, and monomers having an amino group, a hydroxy group, or a glycidyl group.

5. The composite particles according to any one of claims 1 to 4, wherein the inorganic particles are silica.

6. Composite particles according to any one of claims 1 to 5, wherein the inorganic particles are silica, and the total content of alkali metals and alkaline earth metals relative to the content of silica in the inorganic particles is 50 mass ppm or less.

7. The composite particle according to any one of claims 1 to 6, wherein the polymer graft chain is provided via a structure represented by the following formula (A): (polymer graft chain)-X-(CH ２ ) ｍ -Si-(R １ ) (R ２ ) (R ３ ) Formula (A) (In formula (A), -X- is a divalent group, one of which is -(CH ２ ) ｍ The other bonded to the polymer graft chain. m is an integer of 0 to 12. R １ , R ２ and R ３ At least one of the groups is bonded to the particles by forming a metalloxane bond, and the groups not bonded to the particles are each independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 9 carbon atoms, a hydrogen atom, a hydroxy group, or a halogen atom.

8. A resin composition containing the composite particles according to any one of claims 1 to 7 and a resin.

9. A resin composition for low dielectric materials containing the composite particles according to any one of claims 1 to 7 and a resin.

10. A low dielectric resin composition containing the composite particles according to any one of claims 1 to 7 and a resin.

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