JP2024080951A - Block copolymer, epoxy resin modifier, and epoxy resin composition containing the same - Google Patents

Abstract

[Problem] To provide a novel block copolymer useful as an epoxy resin modifier, and an epoxy resin composition containing the same. [Solution] The block copolymer of the present invention is an A-B type block copolymer having an A block and a B block, wherein the A block has a structural unit derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle, the B block has a structural unit derived from at least one vinyl monomer selected from the group consisting of (meth)acrylates having a chain alkyl group and (meth)acrylates having a cyclic alkyl group, one of the A block or the B block further has a structural unit (c) derived from a vinyl monomer having a polymerization initiation group bonded to one of the vinyl-bonded carbons, and the block having the structural unit (c) has a branched structure. [Selected Figure] None

Description

The present invention relates to a block copolymer, an epoxy resin modifier, and an epoxy resin composition containing the same, as well as an adhesive and an underfill material made of the epoxy resin composition, and a resin cured product obtained by curing the epoxy resin composition.

Epoxy resin is a general term for thermosetting resins obtained by mixing epoxy resins (main agent) with epoxy groups and amines, acid anhydrides, etc. (hardeners) and then subjecting them to a heat curing process. In addition to their high elastic modulus, epoxy resins also have excellent tensile strength, solvent resistance, and electrical properties, and are therefore used in automotive structural adhesives, construction and civil engineering paints, sealing materials for electronic materials such as semiconductors (potting materials, underfill materials), composite materials for aircraft, and composite materials for sporting goods. For example, when a semiconductor circuit is subjected to a heat cycle test, excessive mechanical stress is applied to the solder bumps, etc. due to the difference in linear expansion coefficient between the circuit board and the semiconductor chip, causing cracks in the solder bumps, etc., and sometimes compromising the connection reliability of the semiconductor circuit. To solve this problem, an underfill material made of epoxy resin is filled into the gap between the circuit board and the semiconductor chip.

However, because epoxy resins are highly elastic, they also have the characteristic that microcracks in the resin tend to grow easily. As a result, their fracture toughness and peel adhesion are weak, and there is a need to improve these. Therefore, many attempts have been made to improve the toughness and peel adhesion of epoxy resins by adding epoxy resin modifiers such as block copolymers and core-shell particles to the epoxy resins.

For example, Patent Document 1 discloses that toughness is improved by blending an epoxy resin with a block copolymer having an A block having structural units derived from a (meth)acrylate having a 4- to 6-membered cyclic ether group or cyclic thioether group, and a B block having structural units derived from a (meth)acrylate having a chain alkyl group or cyclic alkyl group.

Patent Document 2 discloses that toughness (impact resistance) is improved by blending an epoxy resin with core/shell particles whose main component is polybutadiene or polybutyl acrylate and whose main component is an acrylate or methacrylate polymer.

Patent Document 3 discloses that toughness and rigidity are improved by blending an epoxy resin with a block copolymer consisting of a polymer block (a) made of a (meth)acrylic polymer and a polymer block (b) made of an acrylic polymer different from the polymer block (a).

Patent Document 4 discloses that by blending an epoxy resin with a block copolymer having one or more polymer blocks A mainly made up of structural units derived from an alkyl methacrylate ester and one or more polymer blocks B mainly made up of structural units derived from an alkyl acrylate ester, the fracture toughness and peel adhesion strength can be improved.

Hyperbranched polymers are being considered as new materials. Hyperbranched polymers are polymers with numerous branched structures, such as dendrons (tree-like) and dendrimers. Hyperbranched polymers have a smaller hydrodynamic radius than linear polymers, and therefore have characteristics such as greatly improved solubility, greatly reduced viscosity, and large changes in glass transition temperature. For this reason, their uses are being widely investigated in the medical and chemical industries.

As a method for synthesizing hyperbranched polymers, there is a dendrimer synthesis method. The dendrimer synthesis method is a method of reacting AB ₂ type monomers (A and B are organic groups having different functional groups a and b, and the functional groups a and b are capable of chemically undergoing condensation reaction or addition reaction with each other) stepwise (see Scheme 1 below). This produces a polymer having a dendritic structure centered on a core molecule, but the monomers, oligomers, and polymers react with each other to produce a polymer with a non-uniform branched structure and a polydispersed structure. There is also a known method for producing a monodispersed polymer having a regularly and completely dendritic structure, but the manufacturing process is very complicated. For this reason, there have been no examples of dendrimers being put to practical use.

Scheme 1: Method using _AB2 type monomer

Patent Document 5 discloses a method for synthesizing a hyperbranched polymer using a monomer called an inimer, which has a polymerizable functional group and a polymerization initiator group in the same molecule (see Scheme 2 below. In Scheme 2, B* represents a polymerization initiator group).

Scheme 2: Method using Inimer

Patent Document 6 discloses a method for producing a hyperbranched polymer using a vinyl monomer (also called a "brancher") in which a polymerization initiator group is directly bonded to a polymerizable double bond. In Scheme 3, B* represents the polymerization initiator group.

Scheme 3: Method using Brammer

JP 2018-35266 A Japanese Patent Application Laid-Open No. 9-25393 Publication No. 2014-142024 Publication No. 2009-101961 JP 2013-148798 A International Publication No. WO2017/191766

In recent years, automotive structural adhesives, electronic materials such as semiconductors, and aviation materials have become increasingly high-performance. Therefore, the epoxy resins used in these materials are also required to have higher performance. However, when using the above-mentioned method to sufficiently improve toughness and peel adhesion, it is necessary to increase the proportion of the modifier (block copolymer or core/shell particles) contained in the epoxy resin. However, epoxy resins with a high proportion of the modifier weaken the inherent characteristics of epoxy resins, such as tensile strength and solvent resistance, and cannot be applied to materials that require such characteristics.

The present invention has been made in view of the above circumstances, and aims to provide a novel block copolymer useful as an epoxy resin modifier, an epoxy resin composition containing the same, an adhesive made of the epoxy resin composition, an underfill material made of the epoxy resin, and a cured product obtained by curing the epoxy resin composition. The present invention includes a method for producing the block copolymer of the present invention.

The present inventors discovered that when one of the blocks of a block copolymer used as an epoxy resin modifier has a branched structure, the affinity of the block copolymer for epoxy resins changes, and thus completed the present invention.

The block copolymer of the present invention, which has been able to solve the above problems, is an A-B type block copolymer having an A block and a B block, wherein the A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle, and the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of a (meth)acrylate having a chain alkyl group and a (meth)acrylate having a cyclic alkyl group,
One of the A block or the B block further has a structural unit (c) derived from a vinyl monomer having a polymerization initiation group bonded to one of the vinyl-bonded carbons, and the block having the structural unit (c) has a branched structure.

The A-B type block copolymer of the present invention includes a first embodiment in which the A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle, and a structural unit (c), and the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of a (meth)acrylate having a chain-like alkyl group and a (meth)acrylate having a cyclic alkyl group, and a second embodiment in which the A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle, and the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of a (meth)acrylate having a chain-like alkyl group and a (meth)acrylate having a cyclic alkyl group, and a structural unit (c).

The block copolymer of the present invention has a structural unit (a-1) in the A block that has high affinity with epoxy resins. The B block has a lower affinity with epoxy resins than the A block.

When the block copolymer of the present invention is blended with an epoxy resin, a state in which the low-affinity B block is not compatible with the epoxy resin and is dispersed therein, i.e., a sea-island structure, is formed. When a crack propagates in the epoxy resin, the island portion causes cavitation, and the resulting cavities are used by the surrounding resin to relieve stress, which is thought to disperse the energy of the crack propagation and improve fracture toughness. The degree to which the energy of the crack propagation can be dispersed is affected by the size and shape of the island portion.

Block copolymers with an A block that has a high affinity for epoxy resin and a B block that has a low affinity for epoxy resin are dispersed in the epoxy resin in the form of micelles with the low affinity block B as the core and the high affinity block A as the shell. The micelle shape is governed by the critical packing parameter (CPP). CPP is expressed as v/a l for a cone made of a single polymer chain in a micelle, where v is the volume, l is the length of the generating line, and a is the area of the base. The smaller the CPP, the smaller the diameter of the micelle.

(Shell branch type)
In the first embodiment in which the A block has the structural unit (c), the block copolymer has a structure in which the main chain is branched in the shell portion, so that the hydrodynamic radius of the polymer chain is small, and the shear viscosity of the resin composition is small. This makes it possible to easily form nanoworm-like micelles in the resin composition that can efficiently disperse crack extension energy, and the effect of imparting fracture toughness to the cured resin is increased. In addition, it is presumed that the structure in which the main chain is branched in the shell portion increases the area a of the base of the cone consisting of one polymer chain in the micelle, resulting in a cured resin with a smaller micelle diameter and higher transparency than a linear block copolymer of the same composition.

(Core branch type)
In the epoxy resin composition, the shear viscosity increases rapidly during the transition process (crosslinking reaction) from the resin composition to the cured resin. Since the increase in shear viscosity restricts the movement of the block copolymer, not all block copolymers necessarily form the most energetically stable micelles under high shear viscosity. Since the most energetically stable micelle formation state is considered to have a higher fracture toughness imparting effect, it is considered important how the movement of the block copolymer is not hindered during the transition process from the resin composition to the cured resin. In the second embodiment in which the B block has the structural unit (c), the main chain has a structure in which the main chain is branched at the site (core site) corresponding to the micelle core, so that the entanglement of the copolymer chains is reduced and the obstruction of movement is reduced compared to that of a straight-chain copolymer. Therefore, it is presumed that the increase in the shear viscosity of the resin composition is suppressed and the effect of imparting fracture toughness to the cured resin is increased. Furthermore, since the main chain has a structure in which the core site is branched, the arrangement that the side chain can take is restricted and the crystallization of the side chain is suppressed. It is presumed that by suppressing the crystallization of the side chains, the decrease in anchor effect due to crystallization can be suppressed, resulting in high shear adhesive strength.

The present invention includes an epoxy resin composition containing an epoxy resin, a curing agent, and the epoxy resin modifier. The present invention also includes an adhesive comprising the epoxy resin composition, an underfill material comprising the epoxy resin composition, and a cured resin obtained by curing the epoxy resin composition. The present invention also includes a method for producing the block copolymer of the present invention.

The present invention provides a novel block copolymer that is useful as an epoxy resin modifier. When blended with an epoxy resin to form a cured product, the epoxy resin modifier of the present invention can impart excellent fracture toughness.

The block copolymer of the present invention is an A-B type block copolymer having an A block and a B block, wherein the A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle, and the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of a (meth)acrylate having a chain alkyl group and a (meth)acrylate having a cyclic alkyl group,
One of the A block or the B block further has a structural unit (c) derived from a vinyl monomer having a polymerization initiation group bonded to one of the vinyl-bonded carbons, and the block having the structural unit (c) has a branched structure.

The block copolymer is preferably a (meth)acrylate copolymer. A (meth)acrylate copolymer is any copolymer that contains structural units derived from (meth)acrylate as the main component (50% by mass or more), and may contain structural units derived from vinyl monomers other than (meth)acrylate. The content of structural units derived from (meth)acrylate in the copolymer is preferably 80% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of the entire copolymer.

In the present invention, the "A block" can be rephrased as the "A segment", and the "B block" can be rephrased as the "B segment". In the present invention, the "vinyl monomer" refers to a monomer having a radically polymerizable carbon-carbon double bond in the molecule. The "structural unit derived from the vinyl monomer" refers to a structural unit in which the radically polymerizable carbon-carbon double bond of the vinyl monomer is polymerized to a carbon-carbon single bond. "(Meth)acrylic" refers to "at least one of acrylic and methacrylic", and "(meth)acrylate" refers to "at least one of acrylate and methacrylate". In addition, a (meth)acrylate having a chain alkyl group is a (meth)acrylate having a non-cyclic alkyl group. In the present invention, a "(meth)acrylate having a chain alkyl group" can be rephrased as "(meth)acrylic acid chain alkyl ester" or "(meth)acrylic acid chain alkyl", and a "(meth)acrylate having a cyclic alkyl group" can be rephrased as "(meth)acrylic acid cyclic alkyl ester" or "(meth)acrylic acid cyclic alkyl".

The various components of the block copolymer of the present invention are described below.

(Block A)
First, the block A will be described. The block A has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle.

The oxygen-containing heterocycle or sulfur-containing heterocycle has a structure in which at least one of the carbon atoms constituting the hydrocarbon ring is replaced with an oxygen atom or a sulfur atom. The oxygen-containing heterocycle or sulfur-containing heterocycle is preferably a three-membered or larger ring, and preferably a six-membered or smaller ring. From the viewpoint of the shear viscosity of the resin composition, a three-membered ring is preferable, and from the viewpoint of the shear adhesive strength of the cured product of the resin composition, a four-membered to six-membered ring is preferable.

The carbon atoms constituting the ring may be further replaced by other atoms. A specific example of the other atom is a nitrogen atom. In addition, two or more of the carbon atoms constituting the three- to six-membered hydrocarbon ring may be replaced by an atom other than a carbon atom. Furthermore, the bonds constituting the three- to six-membered ring may be saturated or unsaturated. In addition, in the oxygen-containing heterocycle or sulfur-containing heterocycle, the hydrogen atom directly bonded to the atom constituting the ring may be replaced by a substituent. Examples of the substituent include a hydrocarbon group.

〔一般式（１）において、Ｒ^１２は、水素原子またはメチル基を表す。Ｘ^１１は、単結合または酸素原子を表す。Ｒ^１１は、単結合、炭素数が１～１８のアルキレン基または炭素数が１～１８のオキシアルキレン基を表す。Ｑ^１１は、３員環～６員環の環状エーテル基または環状チオエーテル基を表す。〕 The structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle preferably has a structure represented by the following formula (1):

[In the general formula (1), R ¹² represents a hydrogen atom or a methyl group. X ¹¹ represents a single bond or an oxygen atom. R ¹¹ represents a single bond, an alkylene group having 1 to 18 carbon atoms, or an oxyalkylene group having 1 to 18 carbon atoms. ^{Q 11} represents a 3- to 6-membered cyclic ether group or a cyclic thioether group.]

Specific examples of the 3- to 6-membered cyclic ether group represented by ^Q11 include, for example, an epoxy group, an oxetanyl group (4), a furanyl group (furyl group, 5), a tetrahydrofurfuryl group (6), a pyranyl group (7a, 7b), a dihydropyranyl group (8a, 8b), a tetrahydropyranyl group (9), a dioxolanyl group (10), and a dioxanyl group (11); and examples of the 3- to 6-membered cyclic ether group in which a carbon atom constituting a 3- to 6-membered ring is substituted with an oxygen atom and a nitrogen atom include an oxolanyl group (12), an oxolanyl group (13), and an oxolanyl group (14). Examples of the cyclic thioether group in which the carbon atoms constituting the 3- to 6-membered ring are replaced with sulfur atoms include the thietanyl group (15) and the thienyl group (16); the cyclic thioether group in which the carbon atoms constituting the 3- to 6-membered ring are replaced with sulfur atoms and nitrogen atoms includes the thiazolyl group (17); and the cyclic ether group (or cyclic thioether group) in which the carbon atoms constituting the 3- to 6-membered ring are replaced with oxygen atoms and sulfur atoms includes the oxathiolanyl group (18). The chemical formulas of the functional groups are shown below. The numbers in parentheses of the functional group name correspond to the numbers in the chemical formula.

In the chemical formula, the position where the (meth)acrylic acid skeleton is bonded to the ring structure of ^Q11 is shown as a representative example, but is not limited thereto. That is, the (meth)acrylic acid skeleton can be bonded to any atom constituting the ring structure of ^Q11 .

Q ¹¹ is preferably one having no unsaturated bond, and examples thereof include an epoxy group, an oxetanyl group (4), a tetrahydrofurfuryl group (6), a thietanyl group (15), a tetrahydropyranyl group (9), a dioxolanyl group (10), a dioxanyl group (11), an oxathiolanyl group (18), and a morpholino group (14).

Specific examples of vinyl monomers forming the structural unit (a-1) represented by general formula (1) include 4-hydroxybutyl (meth)acrylate glycidyl ether, tetrahydrofurfuryl (meth)acrylate, morpholino (meth)acrylate, morpholinoethyl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, 2-[(2-tetrahydropyranyl)oxy]ethyl (meth)acrylate, 1,3-dioxanyl (meth)acrylate, and the like.

The A block may have only one type of structural unit (a-1) represented by general formula (1), or may have two or more types of structural units (a-1) represented by general formula (1).

The structural unit (a-1) represented by general formula (1) has an oxygen-containing heterocycle or sulfur-containing heterocycle that has a high affinity for epoxy resins, and increases the affinity of the A block for epoxy resins.

The content of the structural unit (a-1) represented by general formula (1) in the A block is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 65 mol% or more, and preferably 100 mol% or less, based on 100 mol% of the structural units constituting the A block. By setting the content of the structural unit (a-1) within the above range, the compatibility of the A block with the epoxy resin is improved, and the B block can be dispersed in the epoxy resin at the nanoscale. If it is a shell branched type, the cured product of the obtained epoxy resin composition exhibits high transparency, and if it is a core branched type, the cured product of the obtained epoxy resin composition exhibits high shear adhesive strength.

The A block may further have a structural unit (a-2) derived from a (meth)acrylate having a chain alkyl group in addition to the structural unit (a-1) represented by the general formula (1) described above. The structural unit (a-2) has a lower affinity with epoxy resins than the structural unit (a-1).

Examples of the chain alkyl group contained in the (meth)acrylate having a chain alkyl group constituting the structural unit (a-2) include a linear alkyl group and a branched alkyl group. Examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. Examples of the branched alkyl group include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, a 2-ethylhexyl group, an isoheptyl group, an isooctyl group, an isononyl group, and an isodecyl group. Among these, linear alkyl groups having 1 to 10 carbon atoms are preferred, linear alkyl groups having 1 to 10 carbon atoms and/or branched alkyl groups having 3 to 10 carbon atoms are more preferred, and branched alkyl groups having 3 to 10 carbon atoms are even more preferred. By using a (meth)acrylate having such a linear alkyl group, the A block has good compatibility with the epoxy resin, while the affinity of the A block with the epoxy resin is likely to be in an appropriate range.

The A block may have only one type of structural unit (a-2), or may have two or more types of structural unit (a-2).

The content of the structural unit (a-2) in the A block is preferably 1 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less, based on 100 mol% of the structural units constituting the A block. By setting the content of the structural unit (a-2) within the above range, the affinity of the A block with the epoxy resin becomes appropriate, and the B block can be dispersed in the epoxy resin in the form of nanoworm-like micelles, so that the cured product of the obtained epoxy resin composition can be given excellent fracture toughness. Furthermore, if it is a shell-branched type, the cured product of the obtained epoxy resin composition exhibits high transparency, and if it is a core-branched type, the cured product of the obtained epoxy resin composition exhibits high shear adhesive strength.

The A block may be composed only of the structural units (a-1) and (a-2) described above, or may contain other structural units (a-3) to the extent that the A block maintains an appropriate affinity for the epoxy resin.

The other structural unit (a-3) that can be included in the A block is not particularly limited as long as it is formed from a vinyl monomer that forms the structural unit (a-1) represented by general formula (1), a (meth)acrylate having a chain alkyl group that forms the structural unit (a-2), and a vinyl monomer that can be copolymerized with the vinyl monomer that forms the B block described below. Specific examples of vinyl monomers that can form the other structural unit (a-3) in the A block include aromatic vinyl monomers, vinyl monomers having a hydroxyl group, vinyl monomers having a carboxyl group, vinyl monomers having a sulfonic acid group, vinyl monomers having a phosphoric acid group, vinyl monomers containing a tertiary amine, vinyl monomers containing a quaternary ammonium base, vinyl monomers containing a heterocycle, vinyl amides, vinyl carboxylates, α-olefins, dienes, (meth)acrylic monomers, etc.

Examples of aromatic vinyl monomers include styrene, α-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 2-hydroxymethylstyrene, and 1-vinylnaphthalene.

Examples of vinyl monomers having a hydroxy group include hydroxyalkyl (meth)acrylates.

Examples of vinyl monomers having a carboxy group include monomers obtained by reacting the vinyl monomers having a hydroxy group with acid anhydrides such as maleic anhydride, succinic anhydride, and phthalic anhydride, as well as crotonic acid, maleic acid, itaconic acid, and (meth)acrylic acid.

Examples of vinyl monomers having a sulfonic acid group include vinyl sulfonic acid, styrene sulfonic acid, ethyl disulfonate (meth)acrylate, methylpropylsulfonic acid (meth)acrylamide, and ethyl sulfonate (meth)acrylamide.

Examples of vinyl monomers having a phosphate group include methacryloxyethyl phosphate ester.

Examples of vinyl monomers containing a tertiary amine include N,N-dimethylaminopropyl (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylamide, 2-(dimethylamino)ethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

Examples of vinyl monomers containing a quaternary ammonium base include N-2-hydroxy-3-acryloyloxypropyl-N,N,N-trimethylammonium chloride, N-methacryloylaminoethyl-N,N,N-dimethylbenzylammonium chloride, etc.

Examples of vinyl monomers containing a heterocycle include 2-vinylthiophene, N-methyl-2-vinylpyrrole, 1-vinyl-2-pyrrolidone, 2-vinylpyridine, and 4-vinylpyridine. Note that vinyl monomers containing a heterocycle that can form the structural unit (a-3) do not include (meth)acrylates having an oxygen-containing heterocycle or sulfur-containing heterocycle that forms the structural unit (a-1).

Examples of vinyl amides include N-vinylformamide, N-vinylacetamide, and N-vinyl-ε-caprolactam.

Examples of vinyl carboxylates include vinyl acetate, vinyl pivalate, and vinyl benzoate. Examples of α-olefins include 1-hexene, 1-octene, and 1-decene. Examples of dienes include butadiene, isoprene, 4-methyl-1,4-hexadiene, and 7-methyl-1,6-octadiene.

(Meth)acrylic monomers include (meth)acrylates having a cyclic alkyl group, (meth)acrylates having a hydroxy group, (meth)acrylates having an alkoxy group, (meth)acrylates having a sulfonic acid group, (meth)acrylates containing a tertiary amine, (meth)acrylates having a polyethylene glycol structural unit, (meth)acrylates having an aromatic ring group, and (meth)acrylamides.

Examples of (meth)acrylates having a cyclic alkyl group include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, and cyclododecyl (meth)acrylate.

Examples of (meth)acrylates having a hydroxy group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

Examples of (meth)acrylates having an alkoxy group include methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate.

Examples of (meth)acrylates having sulfonic acid groups include ethyl disulfonate (meth)acrylate.

Tertiary amine-containing (meth)acrylates include 2-(dimethylamino)ethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, etc.

Examples of (meth)acrylates having a polyethylene glycol structural unit include diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, tetraethylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate.

Examples of (meth)acrylates having an aromatic ring group include benzyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

(Meth)acrylamides include (meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, etc.

The vinyl monomer capable of forming the structural unit (a-3) may be used alone or in combination of two or more kinds.

When the A block has the structural unit (a-3), the content of the structural unit (a-3) in the A block is preferably 10 mol% or less, more preferably 8 mol% or less, even more preferably 6 mol% or less, and particularly preferably 5 mol% or less, based on 100 mol% of the structural units constituting the A block. The lower limit of the content of the structural unit (a-3) is 0 mol%.

It is also preferred that the A block does not substantially contain the structural unit (b-1) contained in the B block. That is, in the A block, the content of the structural unit (b-1) contained in the B block is preferably 10 mol% or less, more preferably 8 mol% or less, even more preferably 5 mol% or less, and particularly preferably 2 mol% or less, based on 100 mol% of the structural units constituting the A block. The lower limit of the content is 0 mol%.

When two or more types of structural units are contained in the A block, the various structural units contained in the A block may be contained in the A block in any form, such as random copolymerization or block copolymerization, and from the viewpoint of uniformity, it is preferable that they are contained in the A block in the form of random copolymerization. For example, the A block may be formed of a copolymer of a block consisting of the (a-1) structural unit and a block consisting of the (a-2) structural unit.

(Block B)
Next, the B block will be described. The B block is a polymer block having a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of (meth)acrylates having a chain alkyl group and (meth)acrylates having a cyclic alkyl group. Since the B block does not substantially contain the structural unit (a-1) derived from the vinyl monomer, it is considered to have lower compatibility with epoxy resins than the A block.

Examples of (meth)acrylates having a chain alkyl group include dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate (stearyl (meth)acrylate), nonadecyl (meth)acrylate, etc. Among these, (meth)acrylates having a chain alkyl group with 11 to 20 carbon atoms are preferred. The chain alkyl group may be either a straight-chain alkyl group or a branched-chain alkyl group, but a straight-chain alkyl group is preferred.

Examples of (meth)acrylates having a cyclic alkyl group include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, ethylcyclohexyl (meth)acrylate, butylcyclohexyl (meth)acrylate, pentylcyclohexyl (meth)acrylate, and cyclododecyl (meth)acrylate. Among these, (meth)acrylates having a cyclic alkyl group (particularly a monocyclic alkyl group) with 6 to 15 carbon atoms are preferred.

The vinyl monomers may be used alone or in combination of two or more.

As the vinyl monomer forming the structural unit (b-1), it is particularly preferable to use a (meth)acrylate having a chain alkyl group, more preferably a (meth)acrylate having a chain alkyl group having 11 to 20 carbon atoms, even more preferably a (meth)acrylate having a linear alkyl group having 11 to 20 carbon atoms, and particularly preferably a (meth)acrylate having a linear alkyl group having 11 to 15 carbon atoms. By using a (meth)acrylate having a chain alkyl group having 11 to 20 carbon atoms as the vinyl monomer forming the structural unit (b-1), the B block becomes flexible, the energy dispersion effect during crack extension is improved, and a cured product of the epoxy resin composition having improved fracture toughness can be obtained.

The content of the structural unit (b-1) is preferably 50 mol% or more, more preferably 80 mol% or more, and even more preferably 93 mol% or more, out of 100 mol% of the structural units constituting the B block. The upper limit of the content of the structural unit (b-1) is preferably 100 mol%. By setting the content of the structural unit (b-1) within the above range, a cured product of the epoxy resin composition having improved fracture toughness can be obtained.

The B block may be composed of only the structural unit (b-1), or may contain other structural units as long as the B block maintains low compatibility with the epoxy resin. It is also preferable that the B block does not substantially contain the structural units (a-1) and (a-2) contained in the A block. That is, in the B block, the content of each of the structural units (a-1) and (a-2) contained in the A block is preferably 10 mol% or less, more preferably 8 mol% or less, even more preferably 5 mol% or less, and particularly preferably 2 mol% or less, based on 100 mol% of the structural units constituting the B block. The lower limit of the content is 0 mol%.

Specific examples of vinyl monomers that can form other structural units of the B block include aromatic vinyl monomers, vinyl monomers having a hydroxy group, vinyl monomers having a carboxy group, vinyl monomers having a sulfonic acid group, vinyl monomers having a phosphoric acid group, vinyl monomers containing a tertiary amine, vinyl monomers containing a quaternary ammonium base, vinyl monomers containing a heterocycle, vinyl amides, vinyl carboxylates, α-olefins, dienes, (meth)acrylic monomers, etc.

(Meth)acrylic monomers include (meth)acrylates having a hydroxy group, (meth)acrylates having an alkoxy group, (meth)acrylates having a sulfonic acid group, (meth)acrylates containing a tertiary amine, (meth)acrylates having a polyethylene glycol structural unit, (meth)acrylates having an aromatic ring group, and (meth)acrylamides.

Specific examples of the vinyl monomer include the same ones as those given as specific examples of the vinyl monomer that can form the other structural unit (a-3) of the A block.

The vinyl monomers used in the B block may each be one or more of each type.

The content of other structural units in the B block is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less, based on 100 mol% of the structural units constituting the B block. The lower limit of the content of other structural units in the B block is 0 mol%.

When two or more types of structural units are contained in the B block, the various structural units contained in the B block may be contained in the B block in any form, such as random copolymerization or block copolymerization, and from the viewpoint of uniformity, it is preferable that they are contained in the form of random copolymerization.

In the block copolymer of the present invention, one of the A block and the B block further has a structural unit (c) derived from a vinyl monomer having a polymerization initiator group bonded to one of the vinyl-bonded carbons.

［一般式（２）において、Ｚはリビングラジカル重合開始基を表す。Ｒ^２２～Ｒ^２４は、それぞれ独立に水素原子、炭素数１～８のアルキル基、アリール基、芳香族へテロ環基、アルコキシ基、アシル基、アミド基、オキシカルボニル基、シアノ基、シリル基またはフッ素原子を表す。］ The structural unit (c) is derived from a vinyl monomer having a polymerization initiation group bonded to one of the vinyl bond carbons. The vinyl monomer having a polymerization initiation group bonded to one of the vinyl bond carbons is preferably a vinyl monomer represented by the following general formula (2):

[In formula (2), Z represents a living radical polymerization initiating group. R ²² to R ²⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group, or a fluorine atom.]

［一般式（３）において、Ｒ^２２～Ｒ^２４は、それぞれ独立に水素原子、炭素数１～８のアルキル基、アリール基、芳香族へテロ環基、アルコキシ基、アシル基、アミド基、オキシカルボニル基、シアノ基、シリル基またはフッ素原子を表す。］ Furthermore, a structural unit derived from a vinyl monomer having a polymerization initiation group bonded to one of the vinyl bond carbons can be represented by the following formula (3).

[In formula (3), R ²² to R ²⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group, or a fluorine atom.]

As described above, the groups represented by R ²² to R ²⁴ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group, or a fluorine atom, and are specifically as follows:

Examples of alkyl groups having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclohexyl. The alkyl groups may be substituted with a heteroelement functional group. A linear or branched alkyl group having 1 to 8 carbon atoms is preferred.

Examples of aryl groups include phenyl and naphthyl groups.

Examples of aromatic heterocyclic groups include pyridyl groups, furyl groups, and thienyl groups.

The alkoxy group is preferably a group in which an alkyl group having 1 to 8 carbon atoms is bonded to an oxygen atom, and examples of such groups include methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, sec-butoxy, tet-butoxy, pentyloxy, hexyloxy, heptyloxy, and octyloxy groups.

Examples of acyl groups include acetyl, propionyl, and benzoyl groups.

Examples of the amide group include --CONR ²²¹ R ²²² (R ²²¹ and R ²²² each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group).

The oxycarbonyl group is preferably a group represented by -COOR ²²³ (R ²²³ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group), such as a carboxyl group, a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a n-butoxycarbonyl group, a sec-butoxycarbonyl group, a tert-butoxycarbonyl group, a n-pentoxycarbonyl group, a phenoxycarbonyl group, etc. Preferred oxycarbonyl groups are methoxycarbonyl and ethoxycarbonyl groups.

Examples of silyl groups include trimethylsilyl and triethylsilyl groups.

The group represented by Z is a living radical polymerization initiating group, and is not particularly limited as long as it is a functional group (polymerization initiating group) that functions as a polymerization initiating site for living radical polymerization. Examples of the living radical polymerization initiating group include -Te-R ²¹ , -Cl, -Br, -I, -SC(=S)R ²¹ , -SC(=S)OR ²¹ , and -S(C=S)NR ²¹ _2. Among these, -Te-R ²¹ is preferred as the polymerization initiating group from the viewpoint of the diversity of monomers that can be used.

The group represented by R ²¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group, and specifically includes the following.

Examples of alkyl groups having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclohexyl. Linear or branched alkyl groups having 1 to 4 carbon atoms are preferred, and linear alkyl groups having 1 to 4 carbon atoms are even more preferred.

Examples of aryl groups include phenyl and naphthyl groups.

Examples of aromatic heterocyclic groups include pyridyl groups, furyl groups, and thienyl groups.

(Block Copolymer)
The block copolymer of the present invention has the A block and the B block. The structure of the block copolymer is preferably at least one selected from the group consisting of (A-B) type, (A-B)-A type, and (B-A)-B type (m is an integer of 1 or more, for example, an integer of 1 to 3). Among these, the block copolymer of the present invention is preferably an A-B type diblock copolymer from the viewpoints of handling during processing and physical properties of the composition. The block copolymer may have a block other than the A block and the B block.

In the A-B type block copolymer of the present invention, one of the A block or the B block further has a structural unit (c) derived from a vinyl monomer having a polymerization initiator group bonded to one of the vinyl-bonded carbons, and the block having the structural unit (c) has a branched structure.

That is, the A-B type block copolymer of the present invention includes a first embodiment in which the A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle and a structural unit (c), and the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of a (meth)acrylate having a chain-like alkyl group and a (meth)acrylate having a cyclic alkyl group, and a second embodiment in which the A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle, and the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of a (meth)acrylate having a chain-like alkyl group and a (meth)acrylate having a cyclic alkyl group and a structural unit (c).

In the first embodiment in which the A block has the structural unit (c), the content of the structural unit (c) in the A block is more than 0 mol, preferably 1.0 mol or more, more preferably 2.0 mol or more, preferably 10 mol or less, more preferably 8 mol or less, and even more preferably 5 mol or less, relative to 1 mol of the entire B block. The content of the structural unit (c) is indicated by the degree of branching. If the content of the structural unit (c) is within the above range, the A block has a moderate branched structure, and high fracture toughness and transparency are obtained. The content of the structural unit (c) in the A block can be calculated by (the number of moles of the structural unit (c) in the A block / the number of moles of the chain transfer agent used in the synthesis of the B block). For example, in the TERP method described below, it can be calculated by (mol number of structural units (c) in A block / mol number of chain transfer agent (BTEE: ethyl 2-methyl-2-n-butyltellanyl-propionate) used in the synthesis of B block).

In the second embodiment in which the B block has the structural unit (c), the content of the structural unit (c) in the B block is more than 0 mol, preferably 0.5 mol or more, more preferably 1.5 mol or more, even more preferably 3.5 mol or more, preferably 10 mol or less, more preferably 9 mol or less, and even more preferably 8 mol or less, relative to 1 mol of the entire A block. The content of the structural unit (c) is indicated by the degree of branching. If the content of the structural unit (c) is within the above range, the B block has a moderate branched structure, and high fracture toughness and shear adhesive strength are obtained. The content of the structural unit (c) in the B block can be calculated by (mol number of structural unit (c) in the B block / mol number of chain transfer agent used in the synthesis of the A block). For example, in the TERP method described below, it can be calculated by (mol number of structural units (c) in B block / mol number of chain transfer agent (BTEE: ethyl 2-methyl-2-n-butyltellanyl-propionate) used in the synthesis of A block).

The content of the A block is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 65 mol% or less, out of 100 mol% of the structural units constituting the block copolymer. By adjusting the content of the A block within the above range, a block copolymer having the desired function can be prepared.

The content of the B block is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 35 mol% or more, preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 60 mol% or less, out of 100 mol% of the structural units constituting the block copolymer. By adjusting the content of the B block within the above range, a block copolymer having the desired function can be prepared.

The number average molecular weight (Mn) of the block copolymer of the present invention is preferably 10,000 or more, more preferably 15,000 or more, and preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. If the number average molecular weight is below the lower limit, the ability to impart fracture toughness is insufficient, and if it is above the upper limit, the solubility in epoxy resins decreases. If the number average molecular weight of the block copolymer of the present invention is within the above range, a cured product of an epoxy resin composition having improved fracture toughness can be obtained.

The molecular weight distribution (Mw/Mn) of the block copolymer is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.1 or less. In the present invention, the molecular weight distribution (Mw/Mn) is calculated by (weight average molecular weight (Mw) of the block copolymer)/(number average molecular weight (Mn) of the block copolymer). The smaller the Mw/Mn, the narrower the molecular weight distribution width, and the copolymer has a uniform molecular weight, and when the value is 1.0, the molecular weight distribution width is the narrowest. When the molecular weight distribution (Mw/Mn) of the block copolymer exceeds 3.0, it includes those with small molecular weights and those with large molecular weights. If the molecular weight is small, the fracture toughness imparting ability is insufficient, and if the molecular weight is large, the solubility in epoxy resin decreases, so there is a risk of mechanical strength decreasing.

The weight average molecular weight and number average molecular weight are measured by gel permeation chromatography (hereinafter referred to as "GPC").

(Method for Producing Block Copolymer)
The block copolymer of the present invention is preferably produced by living radical polymerization. That is, the block copolymer is preferably one polymerized by living radical polymerization. In conventional radical polymerization methods, not only initiation reactions and propagation reactions but also termination reactions and chain transfer reactions cause deactivation of the growing end, which tends to result in a mixture of polymers with various molecular weights and non-uniform compositions. The living radical polymerization method is preferable in that it maintains the simplicity and versatility of conventional radical polymerization methods, but is less likely to cause termination reactions or chain transfer reactions, and grows without deactivating the growing end, making it easy to precisely control the molecular weight distribution and produce polymers with uniform composition.

Living radical polymerization methods include a method using a compound capable of generating nitroxide radicals (nitroxide method (NMP method)) depending on the method of stabilizing the polymerization growth end; a method using a metal complex such as copper or ruthenium to polymerize a halogenated compound as a polymerization initiator compound in a living manner from the polymerization initiator compound (ATRP method); a method using a dithiocarboxylic acid ester or a xanthate compound (RAFT method); a method using an organic tellurium compound (TERP method); a method using an organic iodine compound (ITP method); a method using an iodine compound as a polymerization initiator compound and an organic compound such as a phosphorus compound, a nitrogen compound, an oxygen compound, or a hydrocarbon as a catalyst (reversible transfer catalyst polymerization (RTCP method), reversible catalyst-mediated polymerization (RCMP method)), etc. Among these methods, the TERP method is preferable from the viewpoint of the diversity of monomers that can be used, molecular weight control in the polymer region, uniform composition, or coloring.

Living radical polymerization, especially the TERP method, is preferred because the polymer chains react uniformly with the monomers while polymerizing, so the composition of all polymers approaches uniformity and the probability of forming pseudo-crosslinks increases.

The TERP method is a method of polymerizing a radically polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent, and is a method described, for example, in WO 2004/14848, WO 2004/14962, WO 2004/072126, and WO 2004/096870.

(Polymerization method (TERP method))
The method using an organic tellurium compound (TERP method) is a living radical polymerization using an organic tellurium compound represented by the following general formula (4) as a chain transfer agent, or a macro chain transfer agent obtained from the organic tellurium compound (hereinafter, these are collectively referred to simply as an organic tellurium compound), etc. In the TERP method, the chain transfer agent may be one selected from organic tellurium compounds, or two or more may be used in combination.

The macro chain transfer agent is a vinyl polymer obtained by living radical polymerization of a vinyl monomer using an organotellurium compound represented by the following general formula (4). The macro chain transfer agent preferably has a living radical polymerization initiator group represented by the following general formula (5) at one end of the polymer.

[In the general formula (4), R ⁴¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group. R ⁴² and R ⁴³ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ⁴⁴ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, an allyl group, or a propargyl group.]

-Te-R ⁴¹ (5)
[In formula (5), R ⁴¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.]

As described above, the group represented by R ⁴¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group, and specifically, is as follows.

Examples of alkyl groups having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclohexyl. Linear or branched alkyl groups having 1 to 4 carbon atoms are preferred, and linear alkyl groups having 1 to 4 carbon atoms are even more preferred.

Examples of aryl groups include phenyl and naphthyl groups.

Examples of aromatic heterocyclic groups include pyridyl groups, furyl groups, and thienyl groups.

The groups represented by R ⁴² and R ⁴³ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and specific examples are as follows.

Examples of alkyl groups having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclohexyl. Straight or branched alkyl groups having 1 to 4 carbon atoms are preferred, and methyl or ethyl groups are even more preferred.

The group represented by R ⁴⁴ is an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, an allyl group or a propargyl group, and specific examples are as follows.

Examples of alkyl groups having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclohexyl. Straight or branched alkyl groups having 1 to 4 carbon atoms are preferred, and methyl or ethyl groups are even more preferred.

Examples of aryl groups include phenyl and naphthyl groups. Phenyl groups are preferred.

Examples of the substituted aryl group include a phenyl group having a substituent, a naphthyl group having a substituent, etc. Examples of the substituent of the aryl group having a substituent include a halogen atom, a hydroxyl group, an alkoxy group, an amino group, a nitro group, a cyano group, a carbonyl-containing group represented by -COR ⁴⁴¹ (R ⁴⁴¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group, an alkoxy group having 1 to 8 carbon atoms, or an aryloxy group), a sulfonyl group, a trifluoromethyl group, etc. It is preferable that one or two of these substituents are substituted.

Examples of aromatic heterocyclic groups include pyridyl groups, furyl groups, and thienyl groups.

As the alkoxy group, a group in which an alkyl group having 1 to 8 carbon atoms is bonded to an oxygen atom is preferable, and examples thereof include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a n-butoxy group, a sec-butoxy group, a tet-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group.

Examples of acyl groups include acetyl, propionyl, and benzoyl groups.

Examples of the amide group include --CONR ⁴⁴²¹ R ⁴⁴²² (R ⁴⁴²¹ and R ⁴⁴²² each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group).

The oxycarbonyl group is preferably a group represented by -COOR ⁴⁴³ (R ⁴⁴³ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group), such as a carboxyl group, a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a n-butoxycarbonyl group, a sec-butoxycarbonyl group, a tert-butoxycarbonyl group, a n-pentoxycarbonyl group, a phenoxycarbonyl group, etc. Preferred oxycarbonyl groups are methoxycarbonyl and ethoxycarbonyl groups.

Examples of the allyl group include -CR ⁴⁴⁴¹ R ⁴⁴⁴² -CR ⁴⁴⁴³ ═CR ⁴⁴⁴⁴ R ⁴⁴⁴⁵ (R ⁴⁴⁴¹ and R ⁴⁴⁴² each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ⁴⁴⁴³ , R ⁴⁴⁴⁴ and R ⁴⁴⁴⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an aryl group, and each of the substituents may be connected in a cyclic structure).

Examples of the propargyl group include --CR ⁴⁴⁵¹ R ⁴⁴⁵² --C≡CR ⁴⁴⁵³ (R ⁴⁴⁵¹ and R ⁴⁴⁵² are hydrogen atoms or alkyl groups having 1 to 8 carbon atoms, and R ⁴⁴⁵³ is hydrogen atoms, alkyl groups having 1 to 8 carbon atoms, aryl groups or silyl groups).

Specific examples of the organotellurium compound represented by the general formula (4) include (methyltellanylmethyl)benzene, (methyltellanylmethyl)naphthalene, ethyl = 2-methyl-2-methyltellanyl-propionate, ethyl = 2-methyl-2-n-butyltellanyl-propionate, (2-trimethylsiloxyethyl) = 2-methyl-2-methyltellanyl-propionate, (2-hydroxyethyl) = 2-methyl-2-methyltellanyl-propionate, (3-trimethylsilylpropargyl) = 2-methyl-2-methyltellanyl-propionate, etc.

The method for producing the A-B type block copolymer of the present invention is preferably a method of living radical polymerization using a macro chain transfer agent having a block of the A block or B block that does not contain the structural unit (c).

As described above, the A-B type block copolymer of the present invention includes a first embodiment in which the A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle and a structural unit (c) derived from a vinyl monomer having a polymerization initiator group bonded to one of the vinyl-bonded carbons, and the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of a (meth)acrylate having a chain-like alkyl group and a (meth)acrylate having a cyclic alkyl group, and a second embodiment in which the A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle, and the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of a (meth)acrylate having a chain-like alkyl group and a (meth)acrylate having a cyclic alkyl group, and a structural unit (c) derived from a vinyl monomer having a polymerization initiator group bonded to one of the vinyl-bonded carbons.

The method for producing the A-B type block copolymer of the present invention includes a first step of preparing a block that does not contain the structural unit (c) among the A block or the B block,
and a second step of preparing a block having the structural unit (c) using the obtained macro chain transfer agent having a block not containing the structural unit (c).

For example, in the first embodiment in which the A block has the structural unit (c), the method for producing the A-B block copolymer of the present invention includes a first step of producing a B block having a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of (meth)acrylates having a chain alkyl group and (meth)acrylates having a cyclic alkyl group, and a second step of using the B block as a macro chain transfer agent to prepare an A block having a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle and a structural unit (c) derived from a vinyl monomer having a polymerization initiator group bonded to one of the vinyl-bonded carbons.

Regarding the second embodiment in which the B block has the structural unit (c), the method for producing the A-B block copolymer of the present invention includes a first step of preparing an A block having a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle;
and a second step of preparing a B block using the A block as a macro chain transfer agent, the B block having a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of (meth)acrylates having a cyclic alkyl group, and a structural unit (c) derived from a vinyl monomer having a polymerization initiation group bonded to one of the vinyl-bonded carbons.

When the living radical polymerization is the TERP method, the vinyl monomer having a polymerization initiation group bonded to one of the vinyl bond carbons is preferably a vinyl monomer represented by general formula (6).

[In the general formula (6), R ⁶² represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group, or a fluorine atom. R ⁶¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.]

As described above, the group represented by R ⁶² is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group or a fluorine atom, and specifically, is as follows:

Examples of alkyl groups having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclohexyl. Straight or branched alkyl groups having 1 to 4 carbon atoms are preferred, and methyl or ethyl groups are even more preferred.

Examples of aryl groups include phenyl and naphthyl groups.

Examples of aromatic heterocyclic groups include pyridyl groups, furyl groups, and thienyl groups.

The alkoxy group is preferably a group in which an alkyl group having 1 to 8 carbon atoms is bonded to an oxygen atom, and examples of such groups include methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, sec-butoxy, tet-butoxy, pentyloxy, hexyloxy, heptyloxy, and octyloxy groups.

Examples of acyl groups include acetyl, propionyl, and benzoyl groups.

Examples of the amide group include --CONR ⁶²¹ R ⁶²² (R ⁶²¹ and R ⁶²² each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group).

The oxycarbonyl group is preferably a group represented by -COOR ⁶²³ (R ⁶²³ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group), such as a carboxyl group, a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a n-butoxycarbonyl group, a sec-butoxycarbonyl group, a tert-butoxycarbonyl group, a n-pentoxycarbonyl group, a phenoxycarbonyl group, etc. Preferred oxycarbonyl groups are methoxycarbonyl and ethoxycarbonyl groups.

Examples of silyl groups include trimethylsilyl and triethylsilyl groups.

The group represented by R ⁶¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group or an aromatic heterocyclic group, and specific examples are as follows.

Examples of alkyl groups having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclohexyl. Straight or branched alkyl groups having 1 to 4 carbon atoms are preferred, and straight alkyl groups having 1 to 4 carbon atoms are more preferred.

Examples of aryl groups include phenyl and naphthyl groups.

Examples of aromatic heterocyclic groups include pyridyl groups, furyl groups, and thienyl groups.

Specific examples of vinyl monomers represented by general formula (6) include 2-methyltellanylpropene, 2-butyltellanylpropene, 2-phenyltellanylpropene, 2-methyltellanylbutene, and 2-butyltellanylbutene.

In the TERP method, polymerization may be carried out by further adding an azo polymerization initiator and/or an organic ditellurium compound represented by general formula (7) for the purpose of promoting the reaction and controlling the molecular weight depending on the type of vinyl monomer.

Specifically, a vinyl monomer is polymerized using any one of the following (a) to (d) to produce a vinyl polymer.
(a) Organotellurium compounds.
(b) A mixture of an organotellurium compound and an azo polymerization initiator.
(c) Mixtures of organotellurium compounds and organoditellurium compounds.
(d) A mixture of an organotellurium compound, an azo polymerization initiator and an organoditellurium compound.

( ^R41Te ) ₂ (7)

[In the general formula (7), R ⁴¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.]

Specific examples of the organic ditellurium compounds represented by the general formula (7) include dimethyl ditelluride, diethyl ditelluride, di-n-propyl ditelluride, diisopropyl ditelluride, dicyclopropyl ditelluride, di-n-butyl ditelluride, di-s-butyl ditelluride, di-t-butyl ditelluride, dicyclobutyl ditelluride, diphenyl ditelluride, bis-(p-methoxyphenyl) ditelluride, bis-(p-aminophenyl) ditelluride, bis-(p-nitrophenyl) ditelluride, bis-(p-cyanophenyl) ditelluride, bis-(p-sulfonylphenyl) ditelluride, dinaphthyl ditelluride, and dipyridyl ditelluride.

The azo polymerization initiator can be any azo polymerization initiator used in normal radical polymerization without any particular restrictions. For example, 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2-methylbutyronitrile) (AMBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), dimethyl-2,2'-azobisisobutyrate (MAIB), 4,4'-azobis(4-cyanovaleric acid) (ACVA), 1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobis(2-methylbutyramide), 2,2'-azobis(4-methoxyphenyl)-2,2'-azobis(4-methoxyphenyl)-1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobis(2-methylbutyramide), 2,2'-azobis(4-methoxyphenyl)-1,1'-azobis(1-acetoxy-1-phenylethane ...4-methoxyphenyl)-1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobis(4-methoxyphenyl)-1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobis(4-methoxyphenyl)- -2,4-dimethylvaleronitrile) (V-70), 2,2'-azobis(2-methylamidinopropane) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2,4,4-trimethylpentane), 2-cyano-2-propylazoformamide, 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), etc. can be mentioned.

In the polymerization process, a vinyl monomer and an organotellurium compound are mixed with an azo-based polymerization initiator and/or an organotellurium compound in a vessel purged with an inert gas for the purpose of promoting the reaction and controlling the molecular weight depending on the type of vinyl monomer. Examples of the inert gas include nitrogen, argon, and helium. Argon and nitrogen are preferred. Nitrogen is particularly preferred.

The amount of vinyl monomer used can be adjusted appropriately depending on the structure of the desired vinyl polymer. For example, the amount of vinyl monomer used can be 10 mol to 50,000 mol, preferably 25 mol to 10,000 mol, more preferably 50 mol to 5,000 mol, and even more preferably 75 mol to 1,000 mol, per 1 mol of organotellurium compound.

When an organic tellurium compound and an azo polymerization initiator are used in combination, the amount of the azo polymerization initiator used is usually 0.01 mol to 1 mol per 1 mol of the organic tellurium compound.

When an organic tellurium compound and an organic ditellurium compound are used in combination, the amount of the organic ditellurium compound used can usually be 0.1 mol to 10 mol per 1 mol of the organic tellurium compound.

When an organic tellurium compound, an organic ditellurium compound, and an azo polymerization initiator are used in combination, the amount of the azo polymerization initiator used can usually be 0.01 mol to 10 mol per 1 mol of the total of the organic tellurium compound and the organic ditellurium compound.

The polymerization process can be carried out without a solvent, but is usually carried out using a solvent (aprotic or protic solvent) commonly used in radical polymerization, and by stirring the mixture.

Aprotic solvents that can be used are not particularly limited, and examples include benzene, toluene, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, 2-butanone (methyl ethyl ketone), dioxane, hexafluoroisopropanol, chloroform, carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, trifluoromethylbenzene, and propylene glycol monomethyl ether acetate.

Examples of protic solvents that can be used include water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, diacetone alcohol, etc.

The amount of solvent used may be adjusted as appropriate. For example, it is usually in the range of 0.001 ml to 50 ml, preferably 0.01 ml to 10 ml, and more preferably 0.02 ml to 3 ml per gram of vinyl monomer.

The reaction temperature and reaction time may be adjusted as appropriate depending on the molecular weight or molecular weight distribution of the desired vinyl polymer, and the reaction is usually carried out at a temperature in the range of 0°C to 150°C for 1 minute to 150 hours. The reaction is usually carried out at normal pressure, but it may be increased or decreased.

Since the growing ends of the vinyl polymer obtained by the polymerization step are in the form of -TeR ⁴¹ (wherein R ⁴¹ is the same as above) and -TeR ⁶¹ (wherein R ⁶¹ is the same as above) derived from the organotellurium compound, it is possible to introduce various substituents and functional groups into the growing ends to improve the performance of the vinyl polymer. Also, it can be used as a macro chain transfer agent.

After the polymerization process is completed, the solvent and remaining monomers are removed from the polymerization solution under reduced pressure to obtain the desired vinyl polymer, or the desired vinyl polymer can be isolated by reprecipitation using an insoluble solvent. By operating in air after the polymerization process, the growing end of the obtained vinyl polymer is deactivated, but tellurium atoms may remain. Since vinyl polymers with tellurium atoms remaining at the end are colored and have poor thermal stability, the following purification methods can be used: radical reduction using tributylstannane or thiol compounds, adsorption using activated carbon, silica gel, activated alumina, activated clay, molecular sieves, polymer adsorbents, etc., metal adsorption using ion exchange resins, etc., or adding peroxides such as hydrogen peroxide or benzoyl peroxide, or blowing air or oxygen into the system to oxidize and decompose the tellurium atoms at the end of the vinyl polymer, and then removing the remaining tellurium compounds by washing with water or combining with an appropriate solvent. These methods can also be combined to purify the solution.

(Polymerization method (ATRP method))
The method using a transition metal catalyst (ATRP method) is a living radical polymerization method using an organic halogen compound or a macro chain transfer agent obtained from the organic halogen compound (hereinafter, these are collectively referred to as an ATRP initiator) as a chain transfer agent in the presence of a redox catalyst consisting of a transition metal complex. In the ATRP method, the chain transfer agent may be one selected from organic halogen compounds or two or more may be used in combination.

The transition metal complex used as the redox catalyst is a complex of a metal element selected from Groups 8 to 11 of the periodic table. The transition metal complex is composed of a transition metal and an organic ligand. Specific examples of the transition metal are copper, nickel, ruthenium, and iron. Among these, copper complexes are preferred from the viewpoints of reaction control and cost. Examples of monovalent copper compounds include cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide, cuprous oxide, and cuprous perchlorate. Among these, cuprous chloride and cuprous bromide are preferred from the viewpoint of polymerization control. Polymerization can also be performed by adding a reducing agent to cupric chloride and cupric bromide, which are more stable and easier to handle, to generate cuprous chloride and cuprous bromide in the polymerization system.

As organic ligands that form complexes with transition metals, bidentate or higher nitrogen ligands are preferred, such as 2,2'-bipyridyl, 4,4'-bipyridyl, ethylenediamine, tetramethylethylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, tris[2-(dimethylamino)ethyl]amine, and tris[2-(pyridyl)methyl]amine.

The transition metal salt and organic ligand may be added separately to form a transition metal complex in the polymerization system, or a transition metal complex previously prepared from a transition metal salt and an organic ligand may be added to the polymerization system. When the transition metal is copper, the former method is preferred, and when the transition metal is ruthenium, iron, or nickel, the latter method is preferred.

As organic halogen compounds, various organic compounds having one or more carbon-halogen bonds (wherein the halogen is other than fluorine) in the molecule can be used, including aliphatic hydrocarbon halides and aromatic hydrocarbon halides.

Specific examples of aliphatic hydrocarbon halides include 2-chloropropionamide, 2-bromopropionamide, 2-chloroacetamide, ethyl 2-bromoisobutyrate, methyl 2-bromopropionate, t-butyl 2-bromopropionate, methyl 2-bromoisobutyrate, and 2-hydroxyethyl 2-bromoisobutyrate.

Specific examples of aromatic hydrocarbon halides include benzal chloride, benzyl bromide, 4-bromobenzyl bromide, and benzenesulfonyl chloride.

When the living radical polymerization is the ATRP method, the vinyl monomer is preferably a vinyl monomer represented by general formula (8).

[In the general formula (8), R ⁸¹ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group, or a fluorine atom. Z ² represents a living radical polymerization initiating group, such as chlorine or iodine.]

As described above, the group represented by R ⁸¹ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group or a fluorine atom, and specifically, is as follows:

Examples of alkyl groups having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, and cyclic alkyl groups such as cyclohexyl. Straight or branched alkyl groups having 1 to 4 carbon atoms are preferred, and methyl or ethyl are more preferred.

Examples of aryl groups include phenyl and naphthyl groups.

Examples of aromatic heterocyclic groups include pyridyl groups, furyl groups, and thienyl groups.

As the alkoxy group, a group in which an alkyl group having 1 to 8 carbon atoms is bonded to an oxygen atom is preferable, and examples thereof include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a n-butoxy group, a sec-butoxy group, a tet-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group.

Examples of acyl groups include acetyl, propionyl, and benzoyl groups.

The amide group may be --CONR ⁸¹¹ R ⁸¹² (R ⁸¹¹ and R ⁸¹² each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group).

The oxycarbonyl group is preferably a group represented by -COOR ⁸¹³ (R ⁸¹³ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group), such as a carboxyl group, a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a n-butoxycarbonyl group, a sec-butoxycarbonyl group, a tert-butoxycarbonyl group, a n-pentoxycarbonyl group, a phenoxycarbonyl group, etc. Preferred oxycarbonyl groups include a methoxycarbonyl group and an ethoxycarbonyl group.

Examples of silyl groups include trimethylsilyl and triethylsilyl groups.

In the polymerization process, a vinyl monomer, a transition metal complex, and an ATRP initiator are mixed in a container. During and after mixing, the reaction is preferably carried out under an inert gas atmosphere such as nitrogen, argon, or helium to suppress side reactions.

The amount of the transition metal complex used is 0.03 mol to 3 mol, preferably 0.1 mol to 2 mol, per 1 mol of the ATRP initiator. The amount of the organic ligand used is usually 1 mol to 5 mol, preferably 1 mol to 3 mol, per 1 mol of the transition metal.

The polymerization process can be carried out without a solvent, but it can also be carried out by using a solvent used in the ATRP method and stirring the mixture.

The reaction temperature and reaction time may be adjusted as appropriate depending on the molecular weight or molecular weight distribution of the desired vinyl polymer, and the reaction is usually carried out at a temperature in the range of 0°C to 150°C for 1 minute to 150 hours. The reaction is usually carried out at normal pressure, but it may be increased or decreased.

Since the growing end of the vinyl polymer obtained by the polymerization process has a polymerization initiation group, it is possible to improve the functionality of the vinyl polymer by introducing various substituents and functional groups to the growing end. It can also be used as a macro chain transfer agent.

After the polymerization process is completed, the solvent and residual monomers can be removed from the polymerization solution under reduced pressure to obtain the desired vinyl polymer, or the desired vinyl polymer can be isolated by reprecipitation using an insoluble solvent.

As described above, the manufacturing method of the present invention can be carried out in one pot, and is a simple manufacturing method that can produce hyperbranched polymers with narrow molecular weight distributions, making it an industrially advantageous method. Furthermore, the hyperbranched polymers obtained by the manufacturing method of the present invention have highly controlled branching, and it is also possible to introduce suitable substituents and functional groups to the polymer terminals.

<Epoxy resin modifier>
The epoxy resin modifier of the present invention contains the above-mentioned block copolymer and is used by being blended with an epoxy resin.

The epoxy resin modifier of the present invention may contain only the block copolymer, or may further contain other components. Examples of other components that may be contained in the epoxy resin modifier of the present invention include various known additives such as organic solvents, stabilizers, plasticizers, flame retardants, flame retardant assistants, antioxidants, and antistatic agents. Examples of the organic solvent include, but are not limited to, xylene, toluene, butanol, ethyl acetate, butyl acetate, N,N-dimethylformamide, methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, ethyl ethoxypropionate, and cyclohexanone.

<Epoxy resin composition>
The epoxy resin composition of the present invention contains an epoxy resin, a curing agent, and the above-mentioned epoxy resin modifier of the present invention.

As the epoxy resin used in the present invention, any of the conventionally known epoxy resins can be used. Specific examples thereof include bisphenol type epoxy resins, phenol novolac type epoxy resins, orthocresol novolac type epoxy resins, biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, diphenylfluorene type epoxy resins, and their halogen, amino group or alkyl substitution products, glycidyl ester type epoxy resins, naphthalene type epoxy resins, aromatic ring/aliphatic ring-containing epoxy resins such as heterocyclic epoxy resins, isocyanate-modified epoxy resins, diarylsulfone type epoxy resins, hydroquinone type epoxy resins, hydantoin type epoxy resins, resorcinol diglycidyl ether, triglycidyl-p-aminophenol, m-aminophenol triglycidyl ether, tetraglycidylmethylenedianiline, (trihydroxyphenyl)methane triglycidyl ether, tetraphenylethane tetraglycidyl ether, and other epoxy resins (polyepoxy compounds) containing two or more epoxy groups in the molecule. One or more of the above epoxy resins can be used.

From the viewpoints of handling and composition adjustment, the epoxy resin is preferably liquid even at room temperature (25°C). Epoxy resins that are liquid at room temperature usually have a weight average molecular weight of 300 to 1000 and an epoxy equivalent of 150 g/eq to 600 g/eq, preferably 150 g/eq to 200 g/eq. Among the epoxy resins, bisphenol-type epoxy resins are preferably used from the viewpoints of handling of the resin composition, processability, heat resistance, fracture toughness, peel adhesion strength, etc. of the resin cured product. Specific examples of bisphenol-type epoxy resins include bisphenol A-type epoxy resins obtained by reacting bisphenol A with epichlorohydrin, bisphenol F-type epoxy resins obtained by reacting bisphenol F with epichlorohydrin, bisphenol S-type epoxy resins obtained by reacting bisphenol S with epichlorohydrin, bisphenol AD-type epoxy resins obtained by reacting bisphenol AD with epichlorohydrin, and halogen or alkyl-substituted versions of these. Among these, bisphenol A type epoxy resins are more preferably used, and bisphenol A type diglycidyl ether is even more preferably used, because they provide better handling and processability of the resin composition and better heat resistance of the cured resin.

The type of curing agent used in the present invention is not particularly limited, and any of the conventionally used curing agents for epoxy resins can be used. Examples of the curing agent include acid anhydride curing agents, amine curing agents, and phenol curing agents. Among these, acid anhydride curing agents and amine curing agents are preferred, and acid anhydride curing agents are more preferred. An acid anhydride curing agent is a curing agent having one or more carboxylic acid anhydride groups per molecule, and the epoxy resin composition is cured by a polycondensation reaction between an epoxy group of an epoxy resin or the like and a carboxylic acid anhydride group. Examples of acid anhydride curing agents include cyclic aliphatic acid anhydrides, aromatic acid anhydrides, and aliphatic acid anhydrides, and more specifically, maleic anhydride, succinic anhydride, phthalic anhydride, 4-methylphthalic anhydride, 4-methylcyclohexanedicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, and tetrahydrophthalic anhydride. The amine-based curing agent is a curing agent having one or more amino groups per molecule, and the epoxy resin composition is cured by a polycondensation reaction between the epoxy group of the epoxy resin or the like and the amino group. Examples of the amine-based curing agent include cyclic aliphatic amines, aromatic amines, and aliphatic amines, and specific examples thereof include diethylenetriamine, triethylenetetramine, metaxylylenediamine, diaminodiphenylmethane, methanephenylenediamine, and diaminodiphenylsulfone. Examples of the phenol-based curing agent include phenol novolac resins. These curing agents may be used alone or in combination of two or more.

The content of the curing agent is not particularly limited, but is preferably 5 parts by mass or more, more preferably 25 parts by mass or more, even more preferably 50 parts by mass or more, particularly preferably 70 parts by mass or more, and is preferably 250 parts by mass or less, more preferably 200 parts by mass or less, and even more preferably 150 parts by mass or less, relative to 100 parts by mass of the epoxy resin. In addition, the curing agent is preferably 0.5 equivalents or more, preferably 2.5 equivalents or less, and more preferably 1.5 equivalents or less, relative to the epoxy groups in the epoxy resin composition. This is because if the content of the curing agent is within the above range, the mechanical properties of the cured product of the epoxy resin composition are improved.

The epoxy resin composition of the present invention preferably further contains a curing accelerator. Specific examples of the curing accelerator include tertiary amine compounds such as benzyldimethylamine, cyclohexyldimethylamine, pyridine, triethanolamine, 2-(dimethylaminomethyl)phenol, dimethylpiperazine, 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,4-diazabicyclo[2.2.2]octane (DABCO), and 2,4,6-tris(dimethylaminomethyl)phenol; 2-methylimidazole, 2-ethylimidazole, 2-n-heptylimidazole, 2-n-undecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-(2-cyanoethyl)-2-methylimidazole, 1-(2-cyanoethyl)-2-n-undecylimidazole, 1-(2-cyanoethyl)-2-phenylimidazole, 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2 -phenyl-4,5-di(hydroxymethyl)imidazole, 1-(2-cyanoethyl)-2-phenyl-4,5-di((2'-cyanoethoxy)methyl)imidazole, 1-(2-cyanoethyl)-2-n-undecylimidazolium trimellitate, 1-(2-cyanoethyl)-2-phenylimidazolium trimellitate, 1-(2-cyanoethyl)-2-ethyl-4-methylimidazolium trimellitate, 2,4-diamino-6-(2'-methylimidazolyl-(1'))ethyl-s-triazine, 2,4-diamino-6-(2'-n-undecylimidazolyl)ethyl- Examples of the imidazole compounds include s-triazine, 2,4-diamino-6-(2'-ethyl-4'-methylimidazolyl-(1'))ethyl-s-triazine, isocyanuric acid adduct of 2-methylimidazole, isocyanuric acid adduct of 2-phenylimidazole, and isocyanuric acid adduct of 2,4-diamino-6-(2'-methylimidazolyl-(1'))ethyl-s-triazine; phosphine compounds such as triphenylphosphine, phosphonium salts such as tetraphenylphosphonium and tetraphenylborate; metal compounds such as tin octylate, and microcapsule-type curing accelerators. These may be used alone or in combination of two or more.

The content of the curing accelerator is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 5 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1.5 parts by mass or less, relative to 100 parts by mass of the epoxy resin. This is because if the content of the curing accelerator is within the above range, the mechanical properties of the cured product of the epoxy resin composition are improved.

In the epoxy resin composition of the present invention, the content of the epoxy resin modifier of the present invention is, in terms of the amount of A-B type block copolymer, preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, preferably 25 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less, per 100 parts by mass of the total amount of the epoxy resin and the curing agent. If the content of the epoxy resin modifier is 1 part by mass or more, a cured product of the epoxy resin composition having excellent fracture toughness can be obtained. Also, if the content of the epoxy resin modifier is 25 parts by mass or less, the deterioration of the function of the epoxy resin (tensile strength, solvent resistance, etc.) due to the addition of a large amount of the epoxy resin modifier can be suppressed.

In addition to the epoxy resin, the curing agent, the curing accelerator, and the epoxy resin modifier of the present invention, the epoxy resin composition of the present invention may contain other additives as necessary within the range that does not impair the effects of the present invention. For example, n-butanol glycidyl ether, butyl glycidyl ether, butylphenyl glycidyl ether, hexyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, tetrahydrofurfuryl glycidyl ether, furfuryl glycidyl ether, trimethoxysilyl glycidyl ether, other higher alcohol glycidyl ethers, methacrylic acid glycidyl esters, etc., reactive diluents such as polyfunctional 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, and dimer acid diglycidyl ester; carbon black such as Ketjen black, silica, fine calcium carbonate, thixotropic agents such as sepiolite ( Thixotropic agents); calcium carbonate, talc, magnesia, calcium silicate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, alumina, zircon, graphite, barium sulfate, clay, mica, kaolin, wollastonite, mica, feldspar, syenite, chlorite, bentonite, montmorillonite, barite, cristobalite, dolomite, quartz, diatomaceous earth, aluminum silicate, barium carbonate, magnesium carbonate, zinc carbonate, mineral fibers, textile fibers, glass fibers, aramid pulp, boron fibers, carbon fibers, phosphates, crystalline silica, amorphous silica, fused silica, fumed silica, calcined silica, precipitated silica, pulverized (fine powder) Examples of such fillers include silica such as silica, wax stone, silica sand, cellulose, cement, resin powders such as polyethylene, calcium oxide, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, titanium dioxide, hollow ceramic beads, hollow glass beads, and other hollow inorganic beads, hollow organic beads made of polyester resins, glass beads, metal powders, and bituminous substances; reaction retarders; anti-aging agents; antioxidants; plasticizers; adhesion promoters; flame retardants; antistatic agents; ultraviolet absorbers; surfactants; dispersants; defoamers; rheology adjusters; polymerization inhibitors; pigments; dyes; coupling agents; ion scavengers; release agents; thermosetting resins other than epoxy resins; and thermoplastic resins.

The epoxy resin composition of the present invention preferably contains a reactive diluent. As the reactive diluent, 1,6-hexanediol diglycidyl ether and butyl glycidyl ether are preferred. The content of the reactive diluent in the epoxy resin composition is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 10% by mass or less, and more preferably 7% by mass or less. If the content of the reactive diluent is within the above range, the shear viscosity of the epoxy resin composition can be reduced while maintaining excellent fracture toughness.

The method for producing the epoxy resin composition of the present invention is not particularly limited, and any method capable of uniformly mixing the epoxy resin, the curing agent, the epoxy resin modifier of the present invention, and, if necessary, the curing accelerator and other additives can be adopted. For example, the epoxy resin composition of the present invention can be produced by adopting a method in which (1) the epoxy resin is introduced into a reactor, and if the epoxy resin is solid, it is heated at an appropriate temperature to make it liquid, and the epoxy resin modifier is added thereto to dissolve it, and the curing agent and the curing accelerator are added thereto to uniformly mix in the liquid state, and further degassing treatment is performed as necessary. (2) The epoxy resin, the curing agent and the curing accelerator, and the epoxy resin modifier are uniformly mixed using a mixer or the like, and then the mixture is melt-kneaded using a heat roll, a twin-screw extruder, a kneader, or the like to produce an epoxy resin composition. (3) The epoxy resin, the curing agent and the curing accelerator, and the epoxy resin modifier are dissolved in a solvent such as methyl ethyl ketone, acetone, toluene, or the like to produce a varnish-like epoxy resin composition.

<Adhesive>
The epoxy resin composition of the present invention is useful as an adhesive since it can provide excellent shear adhesive strength. Applications of the adhesive of the present invention include, for example, vehicle structures such as automobiles, civil engineering and construction, electronic materials, general office use, medical use, industrial use, etc.

<Underfill material>
In the manufacture of electronic devices such as semiconductor devices, semiconductor chip mounting is performed in which components such as a substrate and a semiconductor chip, or a semiconductor chip and a semiconductor chip are connected to each other by solder bumps or the like. In this semiconductor chip mounting, a sealing material (underfill material) is used to fill the gaps between the components. The epoxy resin composition of the present invention can provide excellent shear adhesive strength and fracture toughness, and is therefore also useful as an underfill material such as a capillary underfill material and a mold underfill material. Applications of the underfill material of the present invention include semiconductor chip mounting, etc. More specifically, it can be suitably used for filling the gaps between a semiconductor chip and a substrate connected by solder bumps or the like, or the gaps between semiconductor chips.

The underfill material of the present invention is preferably liquid at room temperature (25°C). The shear viscosity of the underfill material of the present invention at room temperature (25°C) is preferably 500 mPa·s or more, more preferably 1500 mPa·s or more, even more preferably 2500 mPa·s or more, preferably 6000 mPa·s or less, more preferably 4500 mPa·s or less, and even more preferably 3000 mPa·s or less. If the shear viscosity of the underfill material is within the above range, it is suitable for use as a capillary underfill material. That is, the underfill material makes it easier for the resin to penetrate quickly and without gaps between the substrate and the semiconductor chip by utilizing the capillary phenomenon, and can prevent the resin from diffusing between the penetration and curing. The shear viscosity is measured by the method described below.

<Cured Resin>
The cured resin product of the present invention is obtained by curing the above-mentioned epoxy resin composition of the present invention.

When producing a resin cured product using the epoxy resin composition, any of the conventional methods for curing epoxy resin compositions can be used. For example, any of the heat curing method, energy ray curing method (electron beam curing method, ultraviolet ray curing method, etc.), and moisture curing method can be used, and among these, the heat curing method is preferred from the viewpoint of dispersion of the block copolymer.

When the epoxy resin composition of the present invention is solid at room temperature (25°C), it can be, for example, crushed, tableted, and then cured and molded by a conventional molding method such as transfer molding, compression molding, or injection molding to produce a resin cured product (cured molded product).

In addition, when the epoxy resin composition of the present invention is in a liquid or varnish state at room temperature (25°C), it can be applied in an appropriate manner, such as pouring into a mold (molding), pouring into a container (potting, etc.), applying onto a substrate (lamination), impregnating fibers (filaments) or the like (filament winding, etc.), and then heating and curing to obtain a resin cured product suitable for each application, etc.

The curing temperature and curing time when curing the epoxy resin composition of the present invention may vary depending on the type of epoxy resin and curing agent, but for example, conditions such as a curing temperature of 20°C to 250°C and a curing time of 1 hour to 24 hours are used.

The light transmittance of the cured resin of the present invention is preferably 30% or more, more preferably 35% or more, and even more preferably 40% or more, when the light transmittance of the cured epoxy resin composition not containing the epoxy resin modifier of the present invention is taken as 100%. By making the light transmittance 30% or more, a cured resin with excellent transparency is obtained.

The shear adhesive strength of the cured resin of the present invention is preferably 5.2 MPa or more, and more preferably 5.5 MPa or more. By making the shear adhesive strength 5.2 MPa or more, the cured resin has excellent shear adhesive strength.

The fracture toughness of the cured resin of the present invention is preferably 0.7 MPa·m ^1/2 or more, more preferably 0.8 MPa·m ^1/2 or more, and even more preferably 0.9 MPa·m ^1/2 or more. By setting the fracture toughness to 0.7 MPa·m ^1/2 or more, a cured resin having excellent fracture toughness is obtained.

The optical transmittance, shear adhesive strength, fracture toughness, etc. of the cured resin of the present invention are measured by the methods described below.

The resin cured product of the present invention can be used in a wide variety of applications in which conventional cured products of epoxy resins are used. For example, when a shell-branched type epoxy modifier is used, it can be used in optical adhesive applications because of its high fracture toughness and transparency. Furthermore, when a core-branched type epoxy modifier is used, it can be used in adhesive applications such as structural adhesives for automobiles and underfill materials for semiconductor chip mounting because of its excellent fracture toughness and shear adhesive strength.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these specific examples.

The meanings of the abbreviations are as follows:
BTEE: Ethyl 2-methyl-2-n-butyltellanyl-propionate VT: 2-butyltellanylpropene AIBN: 2,2'-azobis(isobutyronitrile)
THFA: tetrahydrofurfuryl acrylate iBA: isobutyl acrylate LA: dodecyl acrylate 4HBAGE: 4-hydroxybutyl acrylate glycidyl ether THF: tetrahydrofuran TMS: tetramethylsilane CDCl ₃ : deuterated chloroform

[Evaluation method]
(Polymerization rate)
^1H -NMR was measured (solvent: _CDCl3 , internal standard: TMS) using a nuclear magnetic resonance (NMR) measurement device (manufactured by Bruker Biospin, model: AVANCE500 (frequency 500 MHz)). From the obtained NMR spectrum, the integral ratio of the peaks of the vinyl group derived from the monomer and the ester side chain derived from the polymer was obtained, and the polymerization rate of the monomer was calculated.

(Weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn))
The measurement was carried out by gel permeation chromatography (GPC) using a high performance liquid chromatograph (Tosoh Corporation, model: HLC-8320GPC). Two TSKgel SuperMultipore HZ-H (Φ4.6 mm×150 mm) (Tosoh Corporation) columns were directly connected, THF was used as the mobile phase, and a differential refractive index detector was used as the detector. The measurement conditions were as follows: column temperature 40° C., sample concentration 5 mg/mL, sample injection amount 10 μL, and flow rate 0.35 mL/min. A calibration curve was prepared using polystyrene (molecular weights: 2,890,000, 1,090,000, 706,000, 427,000, 190,000, 96,400, 37,900, 10,200, 2,630, and 440) as a standard substance, and the weight average molecular weight (Mw) and number average molecular weight (Mn) were measured. The molecular weight distribution (Mw/Mn) was calculated from these measured values.

(Particle size in dilute THF solution)
Using a dynamic light scattering device (Otsuka Electronics Co., Ltd., model ELSZ-2000), the particle size in a dilute THF solution was determined by dynamic light scattering (photon correlation method). The prepared block copolymer was dissolved in THF at a concentration of 0.5 mg/mL, and the solution was irradiated with a semiconductor laser. The particle size in the dilute THF solution was calculated by analyzing the scattered light obtained by the photon correlation method using the Einstein-Stokes equation. A polymer in which a branched structure is formed has a smaller particle size in a dilute THF solution than a linear polymer. The larger the number of branched chains, the smaller the particle size in a dilute THF solution. Therefore, by measuring the particle size in a dilute THF solution, it is possible to confirm whether a branched structure is formed in the polymer chain.

(Shear Viscosity of Epoxy Resin Composition)
The shear viscosity of the epoxy resin composition (before curing) was measured at room temperature (25°C) using an E-type viscometer (product name: TVE-22L, manufactured by Toki Sangyo Co., Ltd.) The cone rotor used was one that matched the viscosity to be measured (1°34'xR24 for less than 1500 mPa·s, 3°xR14 for 1500 mPa·s or more), the rotor rotation speed was 5 rpm, and the measurement range was 5.

(Transparency of Cured Product of Epoxy Resin Composition)
The 600 nm light transmittance per 6 mm of the cured product obtained by heat curing the epoxy resin composition at 120°C for 90 minutes was measured using a spectrophotometer U-3900 (manufactured by Hitachi High-Tech Science Corporation). The measurement was performed 10 times, and the average of the 10 measurements was taken as the light transmittance value. The light transmittance of the cured product of each epoxy resin composition in Table 3 is an indexed value, with the light transmittance of the cured product of epoxy resin composition No. 8, which did not contain a block copolymer, taken as 100%. A larger indexed value indicates that the cured product of the epoxy resin composition has better transparency.
[Transparency evaluation criteria]
Cloudy: Light transmittance of 15% or less Slightly cloudy: Light transmittance of 15% or more, but less than 30% Transparent: Light transmittance of 30% or more

(Shear adhesive strength of epoxy resin composition)
The epoxy resin composition was applied to an aluminum plate (A1050P, 1.6x25x100mm) with an area of 12.5mmx25mm, and then bonded to another aluminum plate. A 0.2mm spacer was sandwiched between the adhesive layer. The aluminum plate was heated at 120°C for 90 minutes to cure the epoxy resin composition. After returning to room temperature, the two aluminum plates were pulled in the shear direction at a head speed of 10mm/min using a Shimadzu Corporation mechanical testing machine Autograph AGS-J until they separated. The stress at the time of separation was taken as the shear adhesive strength. The measurement was carried out five times, and the average value of the five measurements was used.

(Fracture toughness of cured epoxy resin composition)
The epoxy resin composition was poured into a mold with dimensions of 6 mm x 12 mm x 60 mm, and heat cured at 120°C for 90 minutes. The resulting cured product was subjected to a fracture toughness test using a Shimadzu Corporation mechanical testing machine Autograph AGS-J in accordance with ASTM D5045-93. The measurement was performed 10 times, and the average of the 10 measurements was taken as the fracture toughness value. Fracture toughness K1c indicates resistance to crack progression, and the higher the value, the higher the fracture toughness.

1. <Production of a block copolymer (shell type) in which the A block has a branched structure>
(Synthesis Example 1): Synthesis of Block Copolymer No. 1 by Living Radical Polymerization In a nitrogen-substituted Φ25mm x L200mm test tube, 10.02g of nitrogen-substituted LA, 0.15g of BTEE, 0.0167g of AIBN, and 10.03g of toluene were placed and reacted at 60°C for 21.67 hours to produce a B block. The polymerization rate was 92.6%. Using this B block as a macro chain transfer agent, 8.03g of nitrogen-substituted THFA, 2.02g of iBA, 10.00g of toluene, and 0.0166g of AIBN were added to the reaction solution and reacted at 60°C for 23.00 hours. The polymerization rate was 95.1%.
The reaction solution was diluted with THF and poured into stirred methanol. After pressure filtration, it was dried at 70°C and 2 kPa to obtain block copolymer No. 1. Block copolymer No. 1 had an Mn of 30,973, an Mw/Mn of 1.33, and a particle size in the THF dilute solution of 27.7 nm.

Table 1 shows the raw material monomers, organotellurium compounds, organoditellurium compounds, azo-based polymerization initiators, solvents, reaction conditions, and polymerization rates used. Table 2 shows the block copolymer composition, Mn, Mw/Mn, and particle size in a dilute THF solution. The content of each structural unit in the block copolymer was calculated from the charge ratio of the monomers used in the polymerization reaction and the polymerization rate.

(Synthesis Examples 2 to 7): Synthesis of Block Copolymers No. 2 to 7 by Living Radical Polymerization Block copolymers No. 2 to 7 were synthesized in the same manner as block copolymer No. 1, except that the blending amounts of each raw material and the reaction time were changed as shown in Table 1. The Mn, Mw/Mn, and particle size in a dilute THF solution of block copolymers No. 2 to 7 are shown in Table 2.

<Production of Epoxy Resin Composition>
(Epoxy resin compositions No. 1 to 7)
49.65% by mass of bisphenol A type epoxy resin (product name: jER (registered trademark) 828, epoxy equivalent 194 g/eq, weight average molecular weight 370, manufactured by Mitsubishi Chemical Corporation), 45.17% by mass of 4-methylcyclohexane-1,2-dicarboxylic anhydride as a curing agent (2.0 equivalents relative to the epoxy resin), 0.47% by mass of 2-ethyl-4-methylimidazole as a curing accelerator, and 4.71% by mass of the block copolymer obtained above as an epoxy resin modifier were mixed, and the mixture was stirred and defoamed for 22 minutes in a stirring defoamer (AR-250, manufactured by Thinky Corporation) to obtain epoxy resin compositions No. 1 to 7.

(Epoxy resin composition No. 8)
52.23 mass% of bisphenol A type epoxy resin (product name: jER (registered trademark) 828, epoxy equivalent 194 g/eq, weight average molecular weight 370, manufactured by Mitsubishi Chemical Corporation), 47.27 mass% of 4-methylcyclohexane-1,2-dicarboxylic anhydride as a curing agent (2.1 equivalents relative to the epoxy resin), and 0.49 mass% of 2-ethyl-4-methylimidazole as a curing accelerator were mixed, and the mixture was stirred and defoamed for 22 minutes in a stirring defoamer (AR-250, manufactured by Thinky Corporation) to obtain epoxy resin composition No. 8.

The evaluation results for the obtained epoxy resin compositions No. 1 to No. 8 and their cured products are shown in Table 3.

The epoxy resin composition using a block copolymer in which the A block contains the structural unit (c) as a modifier has a reduced shear viscosity at 25°C compared to the epoxy resin composition using a block copolymer in which the A block does not contain the structural unit (c) as a modifier. This is thought to be because the introduction of the structural unit (c) shortens the polymer chain length of the block copolymer, reducing entanglement between the polymer chains. The fact that the polymer chain length of the block copolymer is shortened is also suggested by the fact that the particle size in the THF dilute solution shown in Table 2 is reduced by the introduction of the structural unit (c).

By using a block copolymer in which the A block contains the structural unit (c) as a modifier for epoxy resin, both the light transmittance and fracture toughness of the cured product of the epoxy resin composition are increased. This is thought to be because the introduction of the structural unit (c) makes it easier for the B block of the block copolymer to diffuse into the epoxy resin, making it less likely to form aggregates compared to when a block copolymer that does not contain the structural unit (c) is used as a modifier, and because the change in CPP results in a micellar form that can efficiently disperse crack extension energy.

2. <Production of block copolymer (core type) in which B block has a branched structure>
(Synthesis Example 9): Synthesis of Block Copolymer No. 9 by Living Radical Polymerization In a nitrogen-purged test tube with a diameter of 25 mm x length of 200 mm, 6.35 g of nitrogen-purged THFA, 0.34 g of 4HBAGE, 0.11 g of BTEE, 0.0112 g of AIBN, and 6.68 g of toluene were placed and reacted at 60° C. for 41.00 hours to produce block A. The polymerization rate was 98.8%.

Using this A block as a macro chain transfer agent, 13.35 g of nitrogen-substituted LA, 10.02 g of toluene, and 0.0114 g of AIBN were added to the reaction solution and reacted at 60°C for 39.67 hours. The polymerization rate was 95.8%. The reaction solution was diluted with THF and poured into methanol under stirring. After pressure filtration, the mixture was dried at 70°C and 2 kPa to obtain block copolymer No. 9. The Mn of block copolymer No. 9 was 35,458, the Mw/Mn was 1.30, and the particle size in the THF dilute solution was 34.2 nm.

Table 4 shows the raw material monomers, organotellurium compounds, organoditellurium compounds, azo-based polymerization initiators, solvents, reaction conditions, and polymerization rates used. Table 5 shows the block copolymer composition, Mn, Mw/Mn, and particle size in a dilute THF solution. The content of each structural unit in the block copolymer was calculated from the charge ratio of the monomers used in the polymerization reaction and the polymerization rate.

(Synthesis Examples 10 to 13): Block Copolymers No. 10 to 13 by Living Radical Polymerization
Block copolymers No. 10 to 13 were synthesized in the same manner as for block copolymer No. 9, except that the amounts of each raw material and the reaction time were changed as shown in Table 4. The Mn, Mw/Mn, and particle size in a dilute THF solution of block copolymers No. 10 to 13 are shown in Table 5.

<Production of Epoxy Resin Composition>
(Epoxy resin compositions Nos. 9 to 13)
[0113] 49.65% by mass of bisphenol A type epoxy resin (product name: jER (registered trademark) 828, epoxy equivalent 194 g/eq, weight average molecular weight 370, manufactured by Mitsubishi Chemical Corporation), 45.17% by mass of 4-methylcyclohexane-1,2-dicarboxylic anhydride as a curing agent (2.0 equivalents relative to the epoxy resin), 0.47% by mass of 2-ethyl-4-methylimidazole as a curing accelerator, and 4.71% by mass of the block copolymer obtained above as an epoxy resin modifier were mixed, and the mixture was stirred and defoamed for 22 minutes in a stirring defoamer (AR-250, manufactured by Thinky Corporation) to obtain epoxy resin compositions Nos. 9 to 13.

The evaluation results for the obtained epoxy resin compositions No. 9 to No. 13 and their cured products are shown in Table 6.

The epoxy resin composition using a block copolymer in which the B block contains the structural unit (c) as a modifier has a reduced shear viscosity at 25°C compared to the epoxy resin composition using a block copolymer in which the B block does not contain the structural unit (c) as a modifier. This is thought to be because the introduction of the structural unit (c) shortens the polymer chain length of the block copolymer, reducing entanglement between the polymer chains. The fact that the polymer chain length of the block copolymer is shortened is also suggested by the fact that the particle size in the THF dilute solution shown in Table 5 is reduced by the introduction of the structural unit (c).

By using a block copolymer in which the B block contains the structural unit (c) as an epoxy resin modifier, the fracture toughness of the cured product of the epoxy resin composition is increased. This is thought to be because the introduction of the structural unit (c) increases the mobility of the block copolymer in the epoxy resin, making it more difficult for aggregates to form compared to when a block copolymer that does not contain the structural unit (c) is used, and because the change in CPP results in a micellar form that can efficiently disperse crack extension energy.

The results in Tables 1 to 6 show that the block copolymer of the present invention is useful as an epoxy resin modifier. It is clear that the cured product of the epoxy resin composition containing the epoxy resin modifier of the present invention has excellent fracture toughness.

The block copolymer of the present invention is useful as an epoxy resin modifier. In addition, an epoxy resin composition containing the epoxy resin modifier of the present invention can be used in a wide variety of applications in which conventional epoxy resins are used. In addition, since it has high transparency, it can be used in applications where transparency is required. Furthermore, since it has high shear adhesive strength, it can be used in adhesive applications such as structural adhesives for automobiles and underfill materials such as semiconductor chip mounting, and since it has excellent fracture toughness, it can also be applied to aviation materials and sports applications that are easily subjected to impact.

A preferred embodiment 1 of the present invention is an A-B type block copolymer having an A block and a B block,
The A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle,
the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of (meth)acrylates having a chain alkyl group and (meth)acrylates having a cyclic alkyl group,
One of the A block or the B block further has a structural unit (c) derived from a vinyl monomer having a polymerization initiation group bonded to one of the vinyl-bonded carbons, and the block having the structural unit (c) has a branched structure.

A preferred embodiment 2 of the present invention is the block copolymer according to embodiment 1, in which the A block has the structural unit (c), and the content of the structural unit (c) in the A block is more than 0 mol and 10 mol or less per 1 mol of the entire B block.

A preferred embodiment 3 of the present invention is the block copolymer according to embodiment 1, in which the B block has the structural unit (c) and the content of the structural unit (c) in the B block is more than 0 mol and 10 mol or less per 1 mol of the total A block.

［一般式（２）において、Ｚはリビングラジカル重合開始基である。Ｒ^２２～Ｒ^２４は、それぞれ独立に水素原子、炭素数１～８のアルキル基、アリール基、芳香族へテロ環基、アルコキシ基、アシル基、アミド基、オキシカルボニル基、シアノ基、シリル基またはフッ素原子を表す。］ A preferred embodiment 4 of the present invention is the block copolymer according to any one of embodiments 1 to 3, in which the vinyl monomer having a polymerization initiating group bonded to one of the vinyl-bonded carbons is a vinyl monomer represented by the following general formula (2):

[In general formula (2), Z is a living radical polymerization initiating group. R ²² to R ²⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group, or a fluorine atom.]

A preferred embodiment 5 of the present invention is a block copolymer according to any one of embodiments 1 to 4, in which the A block further has a structural unit (a-2) derived from a (meth)acrylate having a chain alkyl group.

A preferred embodiment 6 of the present invention is the block copolymer according to any one of embodiments 1 to 5, in which the content of the structural unit (a-1) in the A block is 50 mol % or more and 100 mol % or less, based on 100 mol % of the structural units constituting the A block.

A preferred embodiment 7 of the present invention is the block copolymer according to any one of embodiments 1 to 6, in which the content of the structural unit (b-1) in the B block is 50 mol % or more and 100 mol % or less, based on 100 mol % of the structural units constituting the B block.

A preferred embodiment 8 of the present invention is the block copolymer according to any one of embodiments 1 to 7, in which the content of the A block is 20 mol % or more and 80 mol % or less, based on 100 mol % of the structural units constituting the block copolymer.

A preferred embodiment 9 of the present invention is the block copolymer according to any one of embodiments 1 to 8, in which the number average molecular weight (Mn) of the block copolymer measured by gel permeation chromatography is 10,000 or more and 100,000 or less, and the molecular weight distribution (Mw/Mn) is 3.0 or less.

A preferred embodiment 10 of the present invention is an epoxy resin modifier containing the block copolymer described in any one of embodiments 1 to 9.

A preferred embodiment 11 of the present invention is an epoxy resin composition containing an epoxy resin, a curing agent, and the epoxy resin modifier described in embodiment 10.

A preferred embodiment 12 of the present invention is the epoxy resin composition according to embodiment 11, in which the content of the epoxy resin modifier is 1 part by mass to 25 parts by mass per 100 parts by mass of the epoxy resin and the curing agent in terms of the amount of the A-B type block copolymer.

A preferred embodiment 13 of the present invention is an adhesive comprising the epoxy resin composition according to embodiment 11 or 12.

A preferred embodiment 14 of the present invention is an underfill material comprising the epoxy resin composition according to embodiment 11 or 12.

A preferred embodiment 15 of the present invention is a resin cured product obtained by curing the epoxy resin composition described in embodiment 11 or 12.

A preferred embodiment 16 of the present invention is a method for producing a block copolymer according to any one of embodiments 1 to 9, characterized in that living radical polymerization is carried out using a macro chain transfer agent having a block of the A block or the B block that does not contain the structural unit (c).

A preferred embodiment 17 of the present invention is the method for producing a block copolymer according to embodiment 16, wherein the macro chain transfer agent is a macro chain transfer agent having a living radical polymerization initiating group represented by the following general formula (5) at one end of the polymer:
-Te-R ⁴¹ (5)
[In formula (5), R ⁴¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.]

Claims (17)

An A-B type block copolymer having an A block and a B block,
The A block has a structural unit (a-1) derived from a (meth)acrylate having an oxygen-containing heterocycle or a sulfur-containing heterocycle,
the B block has a structural unit (b-1) derived from at least one vinyl monomer selected from the group consisting of (meth)acrylates having a chain alkyl group and (meth)acrylates having a cyclic alkyl group,
A block copolymer characterized in that one of the A block or the B block further has a structural unit (c) derived from a vinyl monomer having a polymerization initiation group bonded to one of the vinyl-bonded carbons, and the block having the structural unit (c) has a branched structure. The block copolymer according to claim 1, wherein the A block has the structural unit (c), and the content of the structural unit (c) in the A block is more than 0 mol and 10 mol or less per 1 mol of the entire B block. The block copolymer according to claim 1, wherein the B block has the structural unit (c), and the content of the structural unit (c) in the B block is more than 0 mol and 10 mol or less per 1 mol of the total A block. 2. The block copolymer according to claim 1, wherein the vinyl monomer having a polymerization initiating group bonded to one of the vinyl bond carbons is a vinyl monomer represented by the following general formula (2):

[In formula (2), Z represents a living radical polymerization initiating group. R ²² to R ²⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, a silyl group, or a fluorine atom.] The block copolymer according to claim 1, wherein the A block further comprises a structural unit (a-2) derived from a (meth)acrylate having a chain alkyl group. The block copolymer according to claim 1, wherein the content of the structural unit (a-1) in the A block is 50 mol % or more and 100 mol % or less, based on 100 mol % of the structural units constituting the A block. The block copolymer according to claim 1, wherein the content of the structural unit (b-1) in the B block is 50 mol % or more and 100 mol % or less, based on 100 mol % of the structural units constituting the B block. The block copolymer according to claim 1, wherein the content of the A block is 20 mol% or more and 80 mol% or less out of 100 mol% of the structural units constituting the block copolymer. The block copolymer according to claim 1, wherein the number average molecular weight (Mn) of the block copolymer measured by gel permeation chromatography is 10,000 or more and 100,000 or less, and the molecular weight distribution (Mw/Mn) is 3.0 or less. An epoxy resin modifier containing the block copolymer according to any one of claims 1 to 9. An epoxy resin composition containing an epoxy resin, a curing agent, and the epoxy resin modifier according to claim 10. The epoxy resin composition according to claim 11, wherein the content of the epoxy resin modifier is 1 to 25 parts by mass per 100 parts by mass of the epoxy resin and the curing agent in terms of the amount of the A-B type block copolymer. An adhesive comprising the epoxy resin composition according to claim 11. An underfill material comprising the epoxy resin composition according to claim 11. A resin cured product obtained by curing the epoxy resin composition according to claim 11. The method for producing the block copolymer according to claim 1, characterized in that living radical polymerization is carried out using a macro chain transfer agent having a block of the A block or the B block that does not contain the structural unit (c). The method for producing a block copolymer according to claim 16, wherein the macro chain transfer agent is a macro chain transfer agent having a living radical polymerization initiating group represented by the following general formula (5) at one end of the polymer:
-Te-R ⁴¹ (5)
[In formula (5), R ⁴¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.]