Epoxy adhesive composition containing block copolymer, method for producing same, and cured epoxy adhesive containing block copolymer

Abstract

The obdurability can be improved. An epoxy adhesive composition containing a block copolymer contains an epoxy resin, a curing agent, and a block copolymer comprising a hydrocarbon rubbery polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25 DEG C or less, and a polymer compatible with the epoxy resin.

Description

Technical Field

[0001] The present invention relates to an epoxy adhesive composition containing a block copolymer, a method for producing the same, and a cured product of an epoxy adhesive containing a block copolymer, which can be applied to uses such as structural adhesives for automobiles, and particularly relates to an epoxy adhesive composition containing a block copolymer, a method for producing the same, and a cured product of an epoxy adhesive containing a block copolymer, which can improve toughness. Background Art

[0002] In recent years, for the purpose of reducing environmental load substances and the like, the trend of low fuel consumption and low exhaust gas has accelerated for vehicles such as automobiles, and the development of vehicle lightweight technologies has been promoted. For example, for automobile body panels and the like, attempts have been made to reduce the weight by thinning the thickness of steel plates or by using materials with lower specific gravities such as aluminum and resin, that is, so-called multi-materialization.

[0003] However, in order to reduce the weight, if the steel plates used in body panels and the like are thinned, there is a problem of reduced strength. Therefore, as a technology for achieving both vehicle lightweight and strength improvement, for example, a technology has been developed in which, instead of using only spot welding for joining steel plates, surface bonding using an adhesive is employed.

[0004] In addition, spot welding used in the joining of conventional steel plates is not suitable for bonding to materials other than steel plates, and for bonding to different materials such as aluminum and resin, attempts have been made to use adhesives for joining.

[0005] Moreover, as bonding for use in combination with such spot welding and in parts where spot welding is not possible, a thermosetting epoxy adhesive using a thermosetting resin such as epoxy resin, which is excellent in shear strength, tensile strength, etc., as a main agent is used.

[0006] However, the cured product of epoxy resin lacks flexibility, is hard and brittle. In particular, in the case of one-component epoxy resin, although it shows high shear adhesive strength, its ductility is insufficient and it is not easily bent, so generally it shows low peel adhesive strength and impact adhesive strength.

[0007] Therefore, in order to improve the low toughness of such epoxy resin, for example, a modification technique using core-shell rubber particles as shown in Patent Document 1 is known.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Patent Laid-Open No. 5-065491 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] However, in the case of modifying with such core-shell rubber particles, during the curing of the epoxy resin, due to phase separation, domains of the rubber component are formed, and the size of the domains depends on the curing conditions, so it is sometimes difficult to obtain stable quality characteristics. In addition, since the rubber-like polymer as the core is coated with a shell such as an acrylic copolymer, if the content of the rubber-like polymer is at a level that does not impair coatability, etc., there are also limitations in improving toughness. Furthermore, in the case of core-shell rubber particles, there are efforts and high costs in their manufacture.

[0013] Therefore, the present invention provides an epoxy-based adhesive composition containing a block copolymer capable of improving toughness, a method for manufacturing the same, and a cured product of the epoxy-based adhesive containing the block copolymer.

[0014] Means for Solving the Problem

[0015] The epoxy-based adhesive composition containing a block copolymer according to the invention of claim 1 contains an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon-based rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin.

[0016] As the above epoxy resin, general epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, urethane-modified epoxy resin, rubber-modified epoxy resin, etc. can be used, and general epoxy resins such as bisphenol A type epoxy resin are preferred.

[0017] As the above curing agent, any curing agent having an active group that reacts with an epoxy group can be used. For example, a latent curing agent such as a dicyandiamide-based imidazole compound with excellent storage stability is preferably used.

[0018] The above block copolymer (block polymer) is a copolymer formed by chemically bonding different polymer chains of a hydrocarbon-based rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature (T g ) of 25°C or lower and a polymer that is compatible with the epoxy resin.

[0019] Among them, the hydrocarbon-based rubber-like polymer having a glass transition temperature (T g ) of 25°C or lower in the above block copolymer is a polymer composed of carbon atoms C and hydrogen atoms H and having a glass transition temperature (T g ) lower than room temperature, which is equivalent to a soft segment at room temperature. The lower limit value of the glass transition temperature (T g ) is a finite value determined according to the type of the rubber-like polymer. For example, the minimum value is about -120°C.

[0020] The term "rubbery" in the above hydrocarbon-based rubbery polymer means that due to the glass transition temperature (T g ) of the polymer being 25°C or lower, the segments in the polymer act as soft segments at room temperature. It should be noted that a soft segment is a segment where segmental motion (microscopic Brownian motion of segments) occurs actively, and a hard segment is a segment where segmental motion has basically stopped. Incidentally, a segment is a unit related to the motion of the polymer chain and is a unit that aggregates several to a dozen monomer units.

[0021] In addition, the polymer in the above block copolymer that is compatible with the epoxy resin is a block having a glass transition temperature (T g ) higher than room temperature and is equivalent to a hard segment at room temperature.

[0022] The above glass transition temperature (glass transition temperature: T g ) can be determined by differential scanning calorimetry (DSC) according to JIS K 6240 (2011).

[0023] As the above block copolymer, for example, (hydrogenated) styrene-based thermoplastic elastomers such as polystyrene-polyisoprene-polystyrene block copolymer (SIS), its hydride polystyrene-polyethylene-propylene-polystyrene block copolymer (SEPS), polystyrene-polybutadiene-polystyrene block copolymer (SBS), its hydride polystyrene-polyethylene-butene-polystyrene block copolymer (SEBS), etc., and styrene-based thermoplastic elastomers containing polyisobutylene such as polystyrene-polyisobutylene-polystyrene block copolymer (SIBS) can be used.

[0024] In the block copolymer in the epoxy-based adhesive composition containing the block copolymer of the invention of claim 2, the hydrocarbon-based rubbery polymer contains monomer units of isoprene, butadiene, hydrogenated isoprene, or hydrogenated butadiene, and the polymer in the block copolymer that is compatible with the epoxy resin contains monomer units having a styrene skeleton, a methacrylic acid-based skeleton, an acrylic acid-based skeleton, or an ether skeleton.

[0025] Here, the monomer unit of the above isoprene is a monomer unit obtained by polymerizing CH2=C(CH3)-CH=CH2 and is represented, for example, by the chemical structural formula of -CH2-C(CH3)=CH-CH2-.

[0026] The monomer unit of the above hydrogenated isoprene is a monomer unit obtained by hydrogenating the double bond part of the isoprene monomer unit and is represented, for example, by the chemical structural formula of -CH2-CH(CH3)-CH2-CH2-.

[0027] The monomer unit of the above-mentioned butadiene is a monomer unit formed by polymerizing CH2=CH-CH=CH2, and is represented by chemical structural formulas such as -CH2-CH=CH-CH2- and -CH2-CH(CH=CH2)-, for example.

[0028] The monomer unit of the above-mentioned hydrogenated butadiene is a monomer unit obtained by hydrogenating the double bond part of butadiene in the butadiene monomer unit, and is represented by chemical structural formulas such as -CH2-CH2-CH2-CH2- and -CH2-CH(CH2-CH3)-, for example.

[0029] In addition, the above-mentioned styrene skeleton is represented by the chemical structural formula of -CH2-CH(C6H4R)- [R is H or an organic functional group], the above-mentioned methacrylic acid-based skeleton is represented by the chemical structural formula of -CH2-C(CH3)(COOR)- [R is H or an organic functional group], the above-mentioned acrylic acid-based skeleton is represented by the chemical structural formula of -CH2-CH(COOR)- [R is H or an organic functional group], and the above-mentioned ether skeleton is represented by - (CH2) n -O- [n is a natural number from 1 to 8] in the chemical structural formula.

[0030] In the block copolymer contained in the epoxy adhesive composition of the invention according to claim 3, the hydrocarbon rubber-like polymer in the block copolymer preferably contains 0.5 parts by mass or more and 3000 parts by mass or less, more preferably 0.7 parts by mass or more and 2800 parts by mass or less, further preferably 2.0 parts by mass or more and 2600 parts by mass or less, and particularly preferably 3.0 parts by mass or more and 2500 parts by mass or less, based on 100 parts by mass of the epoxy resin.

[0031] In the block copolymer contained in the epoxy adhesive composition of the invention according to claim 4, the content of the polymer compatible with the epoxy resin is preferably 3% by mass or more and 80% by mass or less, more preferably 5% by mass or more and 70% by mass or less, and further preferably 10% by mass or more and 50% by mass or less.

[0032] In the block copolymer contained in the epoxy adhesive composition of the invention according to claim 5, the number average molecular weight (Mn) of the polymer compatible with the epoxy resin is preferably 1000 or more and 50000 or less, more preferably 1000 or more and 40000 or less, and further preferably 1500 or more and 30000 or less. It should be noted that this molecular weight corresponds to the molecular weight of the polymer of the block unit. In addition, the number average molecular weight (Mn) is determined by gel permeation chromatography (GPC) using standard polystyrene.

[0033] In the epoxy adhesive composition containing a block copolymer according to the invention of claim 6, the block copolymer is preferably in the range of 0.5 parts by mass or more and 3500 parts by mass or less, more preferably 0.8 parts by mass or more and 3400 parts by mass or less, still more preferably 2 parts by mass or more and 3200 parts by mass or less, and particularly preferably 5 parts by mass or more and 3000 parts by mass or less, based on 100 parts by mass of the epoxy resin.

[0034] The block copolymer in the epoxy adhesive composition containing a block copolymer according to the invention of claim 7 is a styrenic thermoplastic elastomer or a hydrogenated styrenic thermoplastic elastomer.

[0035] As the above-mentioned thermoplastic styrenic elastomer (TPS), a polystyrene-polyisoprene-polystyrene block copolymer (SIS) or a polystyrene-polybutadiene-polystyrene block copolymer (SBS) can be used.

[0036] As the above-mentioned hydrogenated styrenic thermoplastic elastomer, a polystyrene-polyethylene-propylene-polystyrene block copolymer (SEPS) or a polystyrene-polyethylene-butene-polystyrene block copolymer (SEBS) can be used.

[0037] An example of the chemical structural formula of the polystyrene-polyisoprene-polystyrene block copolymer (SIS) is shown in [Chemical Formula 1], an example of the chemical structural formula of the polystyrene-polybutadiene-polystyrene block copolymer (SBS) is shown in [Chemical Formula 2], an example of the chemical structural formula of the polystyrene-polyethylene-propylene-polystyrene block copolymer (SEPS) is shown in [Chemical Formula 3], and an example of the chemical structural formula of the polystyrene-polyethylene-butene-polystyrene block copolymer (SEBS) is shown in [Chemical Formula 4].

[0038] [Chemical Formula 1]

[0039]

[0040] [Chemical Formula 2]

[0041]

[0042] [Chemical Formula 3]

[0043]

[0044] [Chemical Formula 4]

[0045]

[0046] The epoxy adhesive composition containing a block copolymer according to the invention of claim 8 contains an epoxy resin, a curing agent, and a polystyrene-polyisoprene-polystyrene block copolymer or a hydrogenated product thereof.

[0047] The above-mentioned polystyrene-polyisoprene-polystyrene block copolymer (SIS) is a block copolymer having polystyrene blocks acting as hard segments at both ends and a polyisoprene block acting as a soft segment at the center at room temperature.

[0048] The so-called hydrogenated product of the above-mentioned polystyrene-polyisoprene-polystyrene block copolymer (hydrogenated SIS) is a product obtained by hydrogenating the polyisoprene part of the polystyrene-polyisoprene-polystyrene block copolymer (SIS), and is a polystyrene-polyethylene-propylene-polystyrene block copolymer (SEPS).

[0049] The epoxy adhesive composition containing a block copolymer according to the invention of claim 9 contains an epoxy resin, a curing agent, and a polystyrene-polybutadiene-polystyrene block copolymer or a hydrogenated product thereof.

[0050] The above-mentioned polystyrene-polybutadiene-polystyrene block copolymer (SBS) is a block copolymer having polystyrene blocks acting as hard segments at both ends and a polybutadiene block acting as a soft segment at the center at room temperature.

[0051] The so-called hydrogenated product of the above-mentioned polystyrene-polybutadiene-polystyrene block copolymer (hydrogenated SBS) is a product obtained by hydrogenating the polybutadiene part of the polystyrene-polybutadiene-polystyrene block copolymer (SBS), and is a polystyrene-polyethylene-butene-polystyrene block copolymer (SEBS).

[0052] The manufacturing method of the epoxy adhesive composition containing a block copolymer according to the invention of claim 10 is a manufacturing method of an epoxy adhesive composition containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin. In the mixing step, at least the epoxy resin and the block copolymer are mixed with a solvent, and then the solvent is removed in the solvent removal step.

[0053] The so-called "at least" in the above-mentioned mixing step means that a curing agent and other additives can be mixed in the mixing step. However, the curing agent and other additives can also be mixed not in the mixing step but after the solvent removal step.

[0054] Examples of the above solvents include tetrahydrofuran (THF), 2-methyltetrahydrofuran, toluene, acetone, cyclohexane, n-hexane, ethyl acetate, methanol, dichloromethane, methyl ethyl ketone (MEK), butyl acetate, methylcyclohexane (MCH), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and the like.

[0055] The epoxy-based adhesive cured product containing the block copolymer according to the invention of claim 11 is a substance obtained by heat-curing an epoxy-based adhesive composition containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin.

[0056] Effects of the Invention

[0057] According to the epoxy-based adhesive composition containing a block copolymer of the invention of claim 1, by containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin, the polymer compatible with the epoxy resin in the block copolymer is compatible with the epoxy resin while the hydrocarbon rubber-like polymer is incompatible. Therefore, the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer are exhibited. Thus, toughness can be improved.

[0058] According to the epoxy-based adhesive composition containing a block copolymer of the invention of claim 2, since the hydrocarbon rubber-like polymer in the block copolymer contains monomer units of isoprene, butadiene, hydrogenated isoprene, or hydrogenated butadiene, and the polymer compatible with the epoxy resin in the block copolymer contains monomer units having a styrene backbone, a methacrylic acid backbone, an acrylic acid backbone, or an ether backbone, in addition to the effects described in claim 1, properties such as rubber elasticity, heat aging resistance, and weather resistance can be improved.

[0059] According to the epoxy-based adhesive composition containing a block copolymer of the invention of claim 3, the hydrocarbon rubber-like polymer in the block copolymer is contained in the range of 0.5 parts by mass or more and 3000 parts by mass or less with respect to 100 parts by mass of the epoxy resin. Therefore, toughness can be improved and durability can also be improved. Thus, in addition to the effects described in claim 1, even when applied to the bonding of different types of materials, a highly reliable bonding strength can be obtained.

[0060] The epoxy adhesive composition containing a block copolymer according to the invention of claim 4 can improve the compatibility with the epoxy resin and can be uniformly mixed because the content of the polymer compatible with the epoxy resin in the block copolymer is in the range of 3% by mass or more and 80% by mass or less. Therefore, in addition to the effects described in claim 1, stable properties of the cured adhesive are obtained.

[0061] The epoxy adhesive composition containing a block copolymer according to the invention of claim 5 can improve the compatibility with the epoxy resin and can be uniformly mixed because the number-average molecular weight of the polymer compatible with the epoxy resin in the block copolymer is in the range of 1000 or more and 50000 or less. Therefore, in addition to the effects described in claim 1, stable properties of the cured adhesive are obtained.

[0062] The epoxy adhesive composition containing a block copolymer according to the invention of claim 6 is formulated in the range of 1 part by mass or more and 3000 parts by mass or less with respect to 100 parts by mass of the epoxy resin. Therefore, in addition to the effects described in claim 1, good coatability and improved toughness can be achieved simultaneously.

[0063] The epoxy adhesive composition containing a block copolymer according to the invention of claim 7 is a styrene-based thermoplastic elastomer or a hydrogenated styrene-based thermoplastic elastomer. Therefore, it is inexpensive and has excellent ductility, flexibility, and elastic modulus. Thus, in addition to the effects described in claim 1, the cost is low and the toughness can be improved.

[0064] The epoxy adhesive composition containing a block copolymer according to the invention of claim 8 contains an epoxy resin, a curing agent, and a polystyrene-polyisoprene-polystyrene block copolymer or its hydride. Thus, the polystyrene part of the polystyrene-polyisoprene-polystyrene block copolymer or its hydride is compatible with the epoxy resin, while the polyisoprene part and the hydrogenated isoprene part are incompatible. Therefore, the ductility, flexibility, and elastic modulus generated by the polyisoprene part and the hydrogenated isoprene part are exhibited. Thus, the toughness can be improved.

[0065] The epoxy adhesive composition containing a block copolymer according to the invention of claim 9 contains an epoxy resin, a curing agent, and a polystyrene-polybutadiene-polystyrene block copolymer or its hydride. Thus, the polystyrene part of the polystyrene-polybutadiene-polystyrene block copolymer or its hydride is compatible with the epoxy resin, while the polybutadiene part and the hydrogenated butadiene part are incompatible. Therefore, the ductility, flexibility, and elastic modulus generated by the polybutadiene part and the hydrogenated butadiene part are exhibited. Thus, the toughness can be improved.

[0066] The manufacturing method of an epoxy adhesive composition containing a block copolymer according to the invention of claim 10 is a manufacturing method of an epoxy adhesive composition containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin. By mixing at least the epoxy resin and the block copolymer with a solvent in a mixing step and removing the solvent in a solvent removal step, an epoxy adhesive composition is obtained. In the obtained epoxy adhesive composition, the polymer compatible with the epoxy resin in the block copolymer is compatible with the epoxy resin, while the hydrocarbon rubber-like polymer is incompatible. Therefore, the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer are exhibited. Therefore, the toughness can be improved.

[0067] The cured product of an epoxy adhesive containing a block copolymer according to the invention of claim 11 is a substance obtained by curing an epoxy adhesive composition containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin. The polymer compatible with the epoxy resin in the block copolymer is compatible with the epoxy resin, while the hydrocarbon rubber-like polymer is incompatible. Therefore, the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer are exhibited. Therefore, the toughness is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 (a) is a conceptual diagram showing the molecular structure of an example of a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with an epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, namely, a polystyrene-polyisoprene-polystyrene block copolymer (SIS). Figure 1 (b) is a conceptual diagram showing the phase separation structure of an example of a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with an epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, namely, a polystyrene-polyisoprene-polystyrene block copolymer (SIS). Figure 1 (c) is a conceptual diagram showing the structure of a polystyrene-polyisoprene-polystyrene block copolymer (SIS) in an epoxy resin when an example of a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with an epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, namely, a polystyrene-polyisoprene-polystyrene block copolymer (SIS), is mixed with the epoxy resin.

[0069] Figure 2 For the liquid epoxy adhesive composition containing a block copolymer according to Example 10 of the embodiment of the present invention1 1H-NMR spectrum.

[0070] Figure 3 Optical microscope photograph showing the phase separation state of polyisoprene and epoxy resin.

[0071] Figure 4 (a) FT-IR spectra of the cured product of the epoxy adhesive composition containing a block copolymer according to Example 36 of the embodiment of the present invention, the cured product of the epoxy adhesive composition according to Comparative Example 3, and polystyrene-polyisoprene-polystyrene block copolymer (SIS). Figure 4 (b) Coordinate graph of the loss tangent (tanδ) data in the dynamic viscoelasticity measurement of the cured product of the epoxy adhesive composition containing a block copolymer according to Example 36 of the embodiment of the present invention, the cured product of the epoxy adhesive composition according to Comparative Example 3, and polystyrene-polyisoprene-polystyrene block copolymer (SIS).

[0072] Figure 5 (a) TEM image of the cured product of the epoxy adhesive composition according to Example 36. Figure 5 (b) TEM image of polystyrene-polyisoprene-polystyrene block copolymer (SIS).

[0073] Figure 6 DSC thermogram of the cured product of the epoxy adhesive composition containing a block copolymer according to Example 36 of the embodiment of the present invention, the cured product of the epoxy adhesive composition according to Comparative Example 3, and polystyrene-polyisoprene-polystyrene block copolymer (SIS). Detailed implementation mode

[0074] The following describes the embodiments of the present invention.

[0075] The epoxy adhesive composition containing a block copolymer according to the embodiment of the present invention (hereinafter sometimes simply referred to as "epoxy adhesive composition") is a thermosetting epoxy resin composition having an epoxy resin and a curing agent for the epoxy resin as the basic components, that is, an epoxy resin having two or more epoxy groups (ethylene oxide rings) in the molecule and a curing agent component having active hydrogen and catalytic action, and a block copolymer (hereinafter sometimes simply referred to as "block copolymer") composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin is blended.

[0076] Epoxy resins generally refer to compounds that have two or more epoxy groups (oxirane rings) in one molecule and form a three-dimensional cured product using a curing agent. For example, there are bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AD type, bisphenol AF type, epoxy compounds with biphenyl groups such as biphenyl type, polyalkylene glycol type, alkylene glycol type epoxy compounds, epoxy compounds with naphthalene rings, epoxy compounds with fluorenyl groups, etc., difunctional glycidyl ether type epoxy resins, novolak type epoxy resins such as phenol novolak type and o-cresol novolak type, polyfunctional glycidyl ethers, polyfunctional glycidyl ether type epoxy resins such as tetraphenylol ethane type, glycidyl esters of synthetic fatty acids such as dimer acid, aromatic epoxy resins with glycidylamino groups such as N, N, N′, N′-tetraglycidyl diaminodiphenylmethane (TGDDM), tetraglycidyl metaxylylenediamine, triglycidyl -p-aminophenol, N, N-diglycidylaniline, etc., tris(hydroxyphenyl)methane type epoxy resins, epoxy compounds with tricyclodecane rings (for example, epoxy compounds obtained by a manufacturing method in which dicyclopentadiene and cresols or phenols such as m-cresol are polymerized and then epichlorohydrin is reacted), tris(hydroxyphenyl)methane type epoxy resins, sorbitol type epoxy resins, polyglycerol type epoxy resins, glycidyl ester type epoxy resins, heterocyclic epoxy resins, diaryl sulfone type epoxy resins, pentaerythritol type epoxy resins, trimethylolpropane type epoxy resins, etc. Furthermore, as epoxy resins, modified epoxy resins such as urethane-modified epoxy resins, dimer acid modification, and rubber modification can also be used. As urethane-modified epoxy resins, as long as the resin has a urethane bond and two or more epoxy groups in the molecule, its structure is not particularly limited. From the aspect of being able to effectively introduce a urethane bond and an epoxy group in one molecule, resins obtained by reacting a urethane bond-containing compound having an isocyanate group with a hydroxyl group-containing epoxy compound are preferred. Rubber-modified epoxy resins have two or more epoxy groups. Examples of the rubber as the backbone include polybutadiene, acrylonitrile-butadiene rubber (NBR), butadiene-acrylonitrile rubber (CTBN), etc. Two or more of such epoxy resins can also be used in combination.

[0077] Since the curing reaction of such epoxy resins is ring-opening polymerization, the curing shrinkage is small compared to other thermosetting resins. In addition, due to the presence of hydrophilic groups and hydrophobic groups in the molecule, the adhesiveness to various adherends is also high.

[0078] Among these, from the viewpoint of high compatibility with block copolymers composed of a hydrocarbon-based rubbery polymer incompatible with epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with epoxy resin, such as styrenic thermoplastic elastomers like polystyrene-polyisoprene-polystyrene block copolymer, bisphenol A type and bisphenol F type are preferred as general-purpose epoxy resins. In particular, bisphenol A diglycidyl ether (DGEBA) produced by the reaction of bisphenol A and epichlorohydrin is generally used. In the case of bisphenol A type, its benzene ring imparts preferred properties such as adhesiveness, heat resistance, and chemical resistance.

[0079] Epoxy resins such as bisphenol A type epoxy resin can use liquid to solid epoxy resins according to the molecular weight. From the viewpoint of compatibility with styrenic thermoplastic elastomers such as polystyrene-polyisoprene-polystyrene block copolymer, it is preferred to use high molecular weight epoxy resins that are solid at room temperature or low molecular weight epoxy resins that are liquid to semi-solid at room temperature. General-purpose epoxy resins that are solid at room temperature usually have a number average molecular weight of about 900 to 3000, preferably in the range of epoxy equivalent of 400 to 2500 g / eq, and more preferably in the range of 450 to 2200 g / eq. General-purpose epoxy resins that are liquid at room temperature usually have a number average molecular weight of about 300 to 500, preferably in the range of epoxy equivalent of 150 to 400 g / eq, and more preferably in the range of 180 to 300 g / eq. It should be noted that the epoxy equivalent means the number of grams of resin containing 1 gram equivalent of epoxy groups (unit: g / eq). If it is a liquid epoxy resin, the viscosity is preferably in the range of 5000 to 30000 mPa·s / 25°C, and more preferably in the range of 10000 to 20000 mPa·s / 25°C.

[0080] As the curing agent, any curing agent that is usually used for curing epoxy resin, that is, a curing agent having an active group that reacts with epoxy groups can be used. For example, there are dicyandiamide, polyaminoamide, 4,4'-diaminodiphenyl sulfone, imidazole compounds such as 2-n-heptadecylimidazole, adipic dihydrazide, stearic dihydrazide, isophthalic dihydrazide, organic acid hydrazide compounds of dibasic acid hydrazide, urea compounds such as N,N-dialkylurea derivatives, N,N-dialkylthiourea derivatives, acid anhydrides such as tetrahydrophthalic anhydride, semicarbazide, cyanoacetamide, diaminodiphenyl methane, aliphatic and aromatic tertiary amines, polyamines, isophorone diamine, m-phenylenediamine and other amine compounds, aminotriazoles such as 3-amino-1,2,4-triazole, N-aminoethylpiperazine, melamine compounds, guanamine compounds such as acetylguanamine and benzoguanamine, guanidine compounds, dimethylurea compounds, boron trifluoride complexes, boron trichloride complexes, Lewis acid complexes, polythiols, liquid phenols such as tris(dimethylaminomethyl)phenol, polythiols, triphenylphosphine, ketimine compounds, sulfonium salts, ammonium salts, phenol novolac resins, etc. These can be used alone or in combination of two or more.

[0081] Among them, from the viewpoints of workability of the combination, etc., latent curing agents of the heat-activated dispersion type such as dicyandiamide, imidazole compounds, and organic acid hydrazides that do not undergo chemical reactions with epoxy resins at room temperature are preferred. More preferably, from the viewpoints of adhesive strength, storage stability of being dispersed in a fine powder state in the epoxy resin, etc., dicyandiamide of the heat-dissolution reaction type (also including derivatives such as polyepoxide addition-modified products, amidation-modified products, Mannich-modified products, Michael addition-modified products, etc.) is used. If it is dicyandiamide, due to heat, the curing agent component dissolves and activates, and the epoxy resin can be cured under the temperature condition of 160 to 180°C.

[0082] It should be noted that regarding the blending amount of the curing agent, for example, if it is an amine such as dicyandiamide, it is set based on its amine equivalent and epoxy equivalent. Curing agents such as dicyandiamide are blended in an amount of 1 to 20 parts by mass, preferably 2 to 15 parts by mass, and more preferably 5 to 10 parts by mass, relative to 100 parts by mass of the epoxy resin.

[0083] Furthermore, in the case of implementing the present invention, a curing accelerator that shortens the curing time and lowers the curing temperature to promote the chemical reaction between the epoxy resin and the curing agent can be blended. As the curing accelerator (curing accelerator), for example, urea-based (dimethylurea, etc.), imidazole-based, amine-based, triphenylphosphine, etc. can be used.

[0084] When the curing accelerator is blended, it is preferably in the range of 0.5 to 10 parts by mass, more preferably 0.7 to 8 parts by mass, and further preferably 1 to 5 parts by mass, relative to 100 parts by mass of the epoxy resin. If it is within this range, the curing acceleration effect can be obtained without impairing coatability, viscosity characteristics, adhesiveness, etc.

[0085] A block copolymer composed of a hydrocarbon-based rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin is a diblock copolymer of a polymer block that is incompatible with the epoxy resin and a polymer block that is compatible with the epoxy resin, or a triblock polymer, and preferably a triblock polymer having polymer blocks compatible with the epoxy resin at both ends and a polymer block incompatible with the epoxy resin inside.

[0086] As a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with epoxy resin, for example, (hydrogenated) styrene-based thermoplastic elastomers such as polystyrene-polyisoprene-polystyrene block copolymer (SIS), its hydride polystyrene-polyethylene-propylene-polystyrene block copolymer (SEPS), polystyrene-polybutadiene-polystyrene block copolymer (SBS), its hydride polystyrene-polyethylene-butene-polystyrene block copolymer (SEBS), etc., and styrene-based thermoplastic elastomers containing polyisobutylene such as polystyrene-polyisobutylene-polystyrene block copolymer (SIBS) can be used. These have a block with a glass transition temperature (T g ) exceeding 25°C and compatible with epoxy resin at both ends, and a hydrocarbon block with a rubber structure having a glass transition temperature (T g ) of 25°C or lower and incompatible with epoxy resin inside.

[0087] Polystyrene-polyisoprene-polystyrene block copolymer (SIS) is a kind of styrene-based thermoplastic elastomer (TPS) in thermoplastic elastomers (TPE). It is a triblock copolymer composed of incompatible styrene (S) and isoprene (I), and has a block (hard segment) composed of polystyrene with a glass transition temperature (T g ) of about 100°C and a block (soft segment) composed of isoprene with a glass transition temperature (T g ) of about -20 to -80°C in the basic structural unit.

[0088] Styrene-isoprene-styrene block copolymer (SIS) can be made from substances manufactured by known methods such as solution polymerization (batch), for example, it can use Quintack (registered trademark) of Zeon Corporation, VECTOR (registered trademark) of TSRC Corporation, Hybrar of Kuraray Co., Ltd., Kraton D of Kraton Polymer Japan Co., Ltd., etc. It should be noted that as a method for manufacturing styrene-isoprene-styrene block copolymer, generally, first, a refined solvent such as cyclohexane (e.g., hexane, cyclohexane, etc.) is charged into a polymerization reactor, and then refined styrene is added. As a polymerization initiator, a lithium catalyst such as butyllithium is put in, and the styrene block polymerization is carried out under nitrogen to generate polystyryllithium. Next, isoprene is added to generate styrene-isoprene-lithium, and then styrene is added to generate styrene-isoprene-styrene-lithium. After the polymerization is completed, water, acid, alcohol, etc. are used to deactivate the active terminal (lithium). Thus, styrene-isoprene-styrene block copolymer (SIS) is manufactured. In particular, in such a manufacturing method using living anionic polymerization, the monomer arrangement such as the content, molecular weight, molecular weight distribution, the chain and branched structure of styrene and isoprene, and the isomer composition of the polyisoprene part can be controlled, and the degree of freedom in polymer structure design is high. Usually, the molecular weights of the two terminal polystyrene blocks are made symmetric, but a block with different molecular weights of the two terminal polystyrene blocks can also be used to make it asymmetric.

[0089] Styrene-butadiene-styrene block copolymer (SBS) is also a kind of styrene-based thermoplastic elastomer (TPS) in thermoplastic elastomers (TPE). It is a triblock copolymer composed of mutually incompatible styrene (S) and butadiene (B), and has a block (hard segment) composed of polystyrene with a glass transition temperature (T g ) of about 100 °C and a block (soft segment) composed of butadiene with a glass transition temperature (T g ) of about -20 to -80 °C in the basic structural unit. Regarding styrene-butadiene-styrene block copolymer, similar to styrene-isoprene-styrene block copolymer (SIS), substances manufactured by using butadiene instead of isoprene in the above manufacturing method can be used. For example, it can use Tufprene (registered trademark), Asaprene (registered trademark) of Asahi Kasei Chemicals Corporation, Epofreind of Daicel Chemical Industries, Ltd.

[0090] In addition, it is also possible to use a polystyrene-polyethylene-propylene-polystyrene block copolymer (SEPS) of a saturated TPS (hydrogenated TPS) obtained by hydrogenating the soft segment (polyisoprene portion) of a polystyrene-polyisoprene-polystyrene block copolymer (SIS) of such an unsaturated TPS, and a polystyrene-polyethylene-butene-polystyrene block copolymer (SEBS) of a saturated TPS (hydrogenated TPS) obtained by hydrogenating the soft segment (polybutadiene portion) of a polystyrene-polybutadiene-polystyrene block copolymer (SBS) of an unsaturated TPS. As the polystyrene-polyethylene-propylene-polystyrene block copolymer (SEPS), for example, Septon of Kuraray Co., Ltd., TAIPOL (registered trademark) of TSRC Co., Ltd., etc. can be used. As the polystyrene-polyethylene-butene-polystyrene block copolymer (SEBS), for example, Taftec of Asahi Kasei Chemicals Corporation, Rabalon of Mitsubishi Chemical Corporation, Actymer of RIKEN TECHNOS Corporation, Elastomer AR of Aron Kasei Co., Ltd., Kraton G of Kraton Polymer Japan Co., Ltd., etc. can be used.

[0091] The polystyrene-polyisobutylene-polystyrene block copolymer (SIBS) is a kind of isobutylene-based thermoplastic elastomer (TPE) in thermoplastic elastomers, and is a triblock copolymer composed of styrene (S) and isobutylene (IB), and is a thermoplastic block copolymer having a block (hard segment) composed of polystyrene with a glass transition temperature (T g ) of about 100 °C and a block (soft segment) composed of polyisobutylene with a glass transition temperature (T g ) of about -80 °C.

[0092] The polystyrene-polyisobutylene-polystyrene block copolymer (SIBS) can be, for example, a substance manufactured by living cationic polymerization, and for example, SIBSTAR (registered trademark) of Kaneka Corporation can be used.

[0093] By incorporating such a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin into the epoxy-based adhesive composition, the polymer compatible with the epoxy resin is compatible with the epoxy resin, so that the hydrocarbon rubber-like polymer incompatible with the epoxy resin is dispersed in the epoxy resin, imparting the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer and toughening it. Therefore, the peel strength and impact resistance of the epoxy resin cured product can be improved. Moreover, due to the toughening effect of the block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, the internal stress caused by the curing shrinkage and thermal shrinkage during the curing of the adhesive composition and the stress generated at these interfaces due to the difference in the coefficient of thermal expansion between the bonded material and the adherend after bonding can be alleviated, thereby improving the durability of the epoxy resin cured product, i.e., the adhesive cured product.

[0094] Among them, preferably, if the content of the polymer compatible with the epoxy resin in the block copolymer is in the range of 3% by mass or more and 80% by mass or less, the compatibility with the epoxy resin can be improved, enabling uniform mixing, and thus more stable properties of the adhesive cured product can be obtained. More preferably, it is in the range of 5% by mass or more and 70% by mass or less, and further preferably, it is in the range of 10% by mass or more and 50% by mass or less. Incidentally, for chemical manufacturers dealing with TPS, products with a polystyrene weight fraction of 10 - 50 wt% are generally sold. Therefore, if it is within this range, it is easy to obtain, and more stable properties of the adhesive cured product can be confirmed.

[0095] Regarding the content of the hydrocarbon rubber-like polymer, if the content of the hydrocarbon rubber-like polymer is in the range of 20% by mass or more and 97% by mass or less, the ductility, flexibility, and elastic modulus can be improved, thereby improving the peel strength and impact resistance. More preferably, it is in the range of 30% by mass or more and 95% by mass or less, and further preferably, it is in the range of 50% by mass or more and 90% by mass or less.

[0096] In addition, regarding the block copolymer, preferably, if it is in the range of 1 part by mass or more and 3000 parts by mass or less relative to 100 parts by mass of the epoxy resin, the coatability will not be impaired, and the epoxy resin cured product can be effectively toughened. More preferably, it is in the range of 0.5 part by mass or more and 3500 parts by mass or less, further preferably, it is in the range of 0.8 part by mass or more and 3400 parts by mass or less, and particularly preferably, it is in the range of 2.0 parts by mass or more and 3200 parts by mass or less.

[0097] Furthermore, when the hydrocarbon rubbery polymer in the block copolymer is in the range of preferably 0.5 parts by mass or more and 3,000 parts by mass or less with respect to 100 parts by mass of the epoxy resin, the ductility, flexibility, and elastic modulus can be improved, and thus the peel strength and impact resistance can be improved. More preferably, it is in the range of 0.7 parts by mass or more and 2,800 parts by mass or less, further preferably, it is in the range of 2 parts by mass or more and 2,600 parts by mass or less, and particularly preferably, it is in the range of 3.0 parts by mass or more and 2,500 parts by mass or less.

[0098] In addition, when the content of the polymer compatible with the epoxy resin in the block copolymer is in the range of preferably 0.1 parts by mass or more and 650 parts by mass or less with respect to 100 parts by mass of the epoxy resin, the compatibility with the epoxy resin can be improved, and they can be uniformly mixed, and thus more stable properties of the cured adhesive can be obtained. More preferably, it is in the range of 0.15 parts by mass or more and 620 parts by mass or less, and further preferably, it is in the range of 0.2 parts by mass or more and 600 parts by mass or less.

[0099] In particular, the hydrocarbon rubbery polymer in the block copolymer preferably contains monomer units of isoprene, butadiene, hydrogenated isoprene, or hydrogenated butadiene, and the content of these monomer units is preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably 90 mol% or more.

[0100] In addition, the polymer compatible with the epoxy resin preferably contains monomer units having a styrene skeleton, a methacrylic acid-based skeleton, an acrylic acid-based skeleton, or an ether skeleton, and the content of these monomer units is preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably 90 mol% or more.

[0101] Thereby, properties such as rubber elasticity, heat aging resistance, and weather resistance can be improved.

[0102] More preferably, the block copolymer is a styrenic thermoplastic elastomer (TPS). As described above, as the styrenic thermoplastic elastomer (TPS), there are polystyrene - polyisoprene - polystyrene block copolymer (SIS), its hydride, polystyrene - polyethylene - propylene - polystyrene block copolymer (SEPS), polystyrene - polybutadiene - polystyrene block copolymer (SBS), its hydride, polystyrene - polyethylene - butene - polystyrene block copolymer (SEBS), etc. Such styrenic thermoplastic elastomers (TPS) have low costs, can be obtained, and have a high elastic modulus, and thus the peel strength and impact resistance of the epoxy resin cured product can be improved at low cost.

[0103] In the present embodiment, the method for producing the epoxy-based adhesive composition is not particularly limited. For example, by performing a mixing step of mixing an epoxy resin, a block copolymer, and a solvent, and a solvent removal step of evaporating and removing the solvent by heating or the like, an epoxy-based adhesive composition in the form of a masterbatch is produced. At this time, the curing agent can be mixed with the epoxy resin, the block copolymer, and the solvent in the mixing step, or can be mixed after the solvent removal step. Furthermore, depending on the object to be bonded, by mixing the epoxy-based adhesive composition in the form of a masterbatch with other additives, an adhesive composition having target properties can also be formulated.

[0104] As the mixer (including kneader) when mixing (including kneading) the epoxy resin, the block copolymer, and the solvent, for example, a planetary mixer, a DISPER (dissolver), a Henschel mixer, a kneader, a roll mill, a homogenizer, an internal mixer, a kneader, a roll, etc. can be used. By adding at least the epoxy resin and the block copolymer to the solvent and mixing (including kneading), uniform mixing and dispersion of the materials can be achieved.

[0105] In addition, examples of the solvent at this time include tetrahydrofuran (THF), 2-methyltetrahydrofuran, toluene, acetone, cyclohexane, n-hexane, ethyl acetate, methanol, dichloromethane, methyl ethyl ketone (MEK), butyl acetate, methylcyclohexane (MCH), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and the like.

[0106] The epoxy-based adhesive composition of the present embodiment thus produced is in a liquid, paste, or film (sheet) form. As long as it is a liquid or paste composition, it can be applied to the object to be bonded (adherend) by a known method, such as spraying, gun coating, brush coating, etc. using a pump or the like. For example, when the object to be bonded is a vehicle body, it is applied to the joint part of the vehicle body by spraying, gun coating, etc. using a pump or the like in the vehicle body process or the like. If it is a film (sheet) composition, the solution obtained by mixing the resin and the block copolymer in the solvent is applied to the adherend, dried, and thus the adherend can be processed and can also be pasted to the adherend.

[0107] If 0.5 parts by mass or more and 60 parts by mass or less of the block copolymer is formulated with respect to 100 parts by mass of the epoxy resin, a liquid or paste epoxy-based adhesive composition can be obtained.

[0108] For example, by volatilizing and removing the solvent from a liquid or paste-like mixture prepared by mixing a block copolymer, a solvent, and an epoxy resin, a liquid or paste-like epoxy adhesive composition can be obtained. In the liquid or paste-like epoxy adhesive composition, preferably 2.0 parts by mass or more and 56 parts by mass or less, more preferably 4.0 parts by mass or more and 55 parts by mass or less of the block copolymer are blended with respect to 100 parts by mass of the epoxy resin.

[0109] In addition, when 60 parts by mass or more and 3000 parts by mass or less of the block copolymer are blended with respect to 100 parts by mass of the epoxy resin, a film-like epoxy adhesive composition can be obtained.

[0110] For example, by spreading a solution prepared by mixing a block copolymer, a solvent, and an epoxy resin on a sheet (substrate) such as a plate or a mat on which a sheet is laid, and volatilizing and removing the solvent, a film-like epoxy adhesive composition can be obtained. In the film-like epoxy adhesive composition, preferably 80 parts by mass or more and 3000 parts by mass or less, more preferably 100 parts by mass or more and 2500 parts by mass or less of the block copolymer are blended with respect to 100 parts by mass of the epoxy resin.

[0111] In the case of implementing the present invention, if necessary, that is, according to the bonding object (adherend), the environment of the bonding part, the desired properties, etc., additives can also be blended. For example, reactive diluents (epoxy-based reactive diluents having an epoxy group, etc.) for reducing viscosity and improving fluidity, filling materials such as heavy calcium carbonate and talc, carbon black such as silica micropowder and Ketjen black, thixotropy imparting agents (thixotropy imparting agents, thixotropic agents) such as colloidal calcium carbonate (fine particle calcium carbonate), sepiolite, and colloidal hydrated aluminum silicate / organic complex, viscosity regulators (thickeners), heat resistance imparting agents such as polyfunctional epoxy resins (e.g., novolak type epoxy resins), glycidylamine resins, and glycidyl ether resins, acrylic resins as adhesion improvers for improving adhesion, coupling agents, etc. In addition, various additives can also be blended, such as pigments, dyes, colorants, defoaming agents, leveling agents, adhesion imparting agents (bonding imparting agents), flame retardants, catalysts, plasticizers, reaction retardants, anti-aging agents, antioxidants, antistatic agents, conductivity imparting agents, lubricants, sliding property imparting agents, ultraviolet absorbers, surfactants, dispersants, dispersion stabilizers, dehydrating agents, crosslinking agents, rust preventives, solvents, etc.

[0112] Thus, in the epoxy-based adhesive composition according to the present embodiment, by containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon-based rubbery polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, the low toughness of the epoxy resin, such as lack of flexibility, hardness, and brittleness, is improved by the block copolymer composed of a hydrocarbon-based rubbery polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, and a tough adhesive cured product is obtained.

[0113] It is considered that this is because the polymer compatible with the epoxy resin in the block copolymer is compatible with the epoxy resin, and the polymer compatible with the epoxy resin in the block copolymer is chemically bonded to the hydrocarbon-based rubbery polymer incompatible with the epoxy resin in the block copolymer. Thus, even at room temperature, the hydrocarbon-based rubbery polymer is dispersed and exists, exerting the ductility, flexibility, and elastic modulus generated by the hydrocarbon-based rubbery polymer.

[0114] Moreover, by imparting toughness by adopting such a block copolymer, the stress of curing shrinkage generated during curing and the stress of thermal shrinkage generated when cooling from the curing temperature to room temperature can be alleviated. In addition, the stress generated at the interface between the layer of the adhesive cured product and the adherend after bonding due to the difference in the coefficient of thermal expansion can be alleviated. In particular, in the case of bonding different types of materials having a difference in the coefficient of thermal expansion, the stress generated between the different types of materials increases, and such stress can also be effectively alleviated. Therefore, the peel strength is improved. In addition, by exerting the ductility, flexibility, and elastic modulus of the hydrocarbon-based rubbery polymer of the block copolymer, the impact energy is easily absorbed, and thus the impact resistance of the obtained adhesive cured product is improved.

[0115] Therefore, by adopting the blending of the block copolymer, these stresses and impact energy can be alleviated, and thus the durability of the adhesive cured product can be improved.

[0116] In particular, when the epoxy resin is thermosetting and the block copolymer composed of a hydrocarbon-based rubbery polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin is a thermoplastic elastomer, it becomes a mixture of materials with opposite thermal properties. Since the polymer compatible with the epoxy resin in the block copolymer is compatible with the epoxy resin, the epoxy resin and the block copolymer can be mixed without separation. At this time, as described above, by mixing in a specified solvent, the epoxy resin and the block copolymer can be more easily and uniformly mixed.

[0117] Regarding the toughening of epoxy resins, there have been methods in the past to impart flexibility by introducing rubber-based structures, linear polymer structures on the main chain, side chain, or end of epoxy resins. However, according to such methods, the material becomes highly viscous, resulting in impaired coatability, or due to a decrease in crosslink density, the original properties of epoxy resins such as heat resistance and adhesiveness deteriorate.

[0118] In addition, for the modification of epoxy resins, liquid rubbers (such as butadiene acrylonitrile copolymers) are sometimes used as flexibility imparting agents. However, in the case of such liquid rubbers, the compatibility with epoxy resins is poor and difficult to mix, so their mixing reaction requires time and effort. Moreover, they do not show compatibility during the curing of epoxy resins, resulting in poor dispersibility and limited effectiveness in achieving toughening. Furthermore, phase separation occurs during curing, forming large domains (dispersed rubber particle phases) of several to dozens of microns or more. The formation of these domains also strongly depends on the curing conditions, making it difficult to obtain stable properties. That is, in order to effectively modify and obtain stable quality, it is necessary to take time and precision in controlling the appearance of the microphase separation structure, such as the addition amount of liquid rubber and curing conditions. In addition, sometimes a part of the uncrosslinked rubber remains partially dissolved in the cured product of epoxy resin, thus lowering the glass transition temperature (T g ) of epoxy resin, accompanied by a decrease in elastic modulus, and sometimes also causing changes in the original physical properties of epoxy resin.

[0119] To improve such problems of liquid rubbers, it is also known to use core-shell rubber particles. However, for thermosetting resins, it is difficult to uniformly mix and disperse the core-shell rubber particles without destroying the powder. In addition, due to the presence of the shell part, the toughening effect with respect to the addition amount of the rubber component becomes smaller, and it is also limited in improving the flexibility and ductility of the adhesive composition without impairing coatability to achieve toughening. Furthermore, such core-shell rubber particles require time and cost in their production.

[0120] The epoxy-based adhesive composition of the present embodiment is imparted with toughness by incorporating a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin. That is, as will be described in detail later, since the polymer compatible with the epoxy resin of the block copolymer is compatible with the epoxy resin, domains are not formed even at room temperature, and the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer are exhibited. Depending on the content of the hydrocarbon rubber-like polymer, the toughness can be effectively increased. Thereby, the peel strength and impact resistance of the cured product of the adhesive containing the epoxy resin can be improved. That is, if it is a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin, since the polymer compatible with the epoxy resin of the block copolymer is compatible with the epoxy resin, the dispersion of the hydrocarbon rubber-like polymer in the epoxy resin is good, and the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer are significantly exhibited, and toughness with improved peel strength and impact resistance is obtained. In addition, for a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin, its synthesis is easy, it is inexpensive, and it can be obtained simply.

[0121] Moreover, by incorporating such a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin, flexibility, ductility, and elastic modulus are imparted to toughen it, thereby enabling the reduction of internal stress generated during the curing process and cooling process of the epoxy-based adhesive composition and internal stress generated at the interface due to the difference in the thermal expansion coefficients of the adhesive and the adherend, and enabling the impartation of resistance to the growth of cracks and defects. Therefore, the generation of cracks can also be suppressed.

[0122] Furthermore, if it is a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin, the coatability is not impaired. In addition, the toughness can be improved while maintaining the original properties (heat resistance, high adhesiveness, mechanical properties, durability, etc.) of the epoxy resin. Since the low stressing of the residual strain associated with the shrinkage caused by curing and heat can be absorbed, the crack resistance, fatigue resistance, and durability can be improved.

[0123] In addition, in a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with an epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin, the hydrocarbon rubber-like polymer and the polymer compatible with the epoxy resin are incompatible with each other, and it is easy to manufacture a block copolymer with a changed ratio thereof. By controlling the ratio of the hydrocarbon rubber-like polymer and the polymer compatible with the epoxy resin, the control of the physical properties of the cured adhesive can also be easily performed. Furthermore, due to the improvement of flexibility, ductility, and elastic modulus, a vibration damping effect can also be expected.

[0124] Hereinafter, examples of the epoxy adhesive composition containing a block copolymer according to an embodiment of the present invention will be described.

[0125] [Example 1]

[0126] In Example 1, a film-like (sheet-like) adhesive composition (hereinafter referred to as "adhesive") containing Quintac (registered trademark) 3440 (manufactured by Zeon Corporation, polystyrene-polyisoprene-polystyrene block copolymer composition, hereinafter also referred to as "SIS") 19 and a general-purpose epoxy resin that is liquid at room temperature, bisphenol A type epoxy resin (bisphenol A diglycidyl ether as a bifunctional epoxy resin: DGEBA, hereinafter also referred to as "EP resin") and dicyandiamide (hereinafter also referred to as "DICY") as a latent curing agent was produced. Among them, the polystyrene content of SIS 19 is 19 wt%, and the polystyrene block (hereinafter also referred to as "S block") of SIS 19 is a polymer compatible with the EP resin. In addition, the polyisoprene block (hereinafter also referred to as "I block") of SIS 19 is a hydrocarbon rubber-like polymer with a glass transition temperature of about -60°C and is a polymer incompatible (insoluble) with the EP resin.

[0127] In Example 1, 13.3 g, 6.67 g, and 0.467 g of SIS 19 , EP resin, and DICY were weighed in this order and dissolved in 133 g of a mixed solvent of THF and methanol (weight ratio 8:2). Then, the obtained solution was transferred to a 20×16.5 cm mat lined with a Teflon (registered trademark) sheet, and solvent casting was performed at 35°C for 1 day. Then, it was vacuum dried at room temperature for 2 days or more to evaporate the volatile solvents (THF and methanol), thereby obtaining a mixture (adhesive composition). The obtained mixture was a relatively uniform film-like (sheet-like) and was a one-component heat-curing type epoxy adhesive composition. In Example 1, 200 parts by mass of SIS 19 (162 parts by mass of the I block) and 7 parts by mass of DICY were blended with respect to 100 parts by mass of the EP resin.

[0128] [Example 2]

[0129] In Example 2, except that 400 parts by mass of SIS 19 (324 parts by mass of the I block) was compounded relative to 100 parts by mass of the EP resin, a mixed film containing SIS 19 and the EP resin and DICY was produced in the same manner as in Example 1 and used as an adhesive.

[0130] [Example 3]

[0131] In Example 3, except that 600 parts by mass of SIS 19 (486 parts by mass of the I block) was compounded relative to 100 parts by mass of the EP resin, a mixed film containing SIS 19 and the EP resin and DICY was produced in the same manner as in Example 1 and used as an adhesive.

[0132] [Example 4]

[0133] In Example 4, except that 1 part by mass of an amine adduct accelerator (Amicure TMMY-24, hereinafter also referred to as "AA") was added as an additive relative to 100 parts by mass of the EP resin, a mixed film containing SIS 19 and the EP resin and DICY and AA was produced in the same manner as in Example 1 and used as an adhesive. It should be noted that AA was mixed when SIS 19 and the EP resin and DICY and the solvent were mixed. The same applies to the following examples.

[0134] [Example 5]

[0135] In Example 5, except that 300 parts by mass of SIS 19 (243 parts by mass of the I block at this time) was used relative to 100 parts by mass of the EP resin and 1 part by mass of AA was added, a mixed film containing SIS 19 and the EP resin and DICY and AA was produced in the same manner as in Example 1 and used as an adhesive.

[0136] [Example 6]

[0137] In Example 6, except that 600 parts by mass of SIS 19 (486 parts by mass of the I block at this time) was used relative to 100 parts by mass of the EP resin and 1 part by mass of AA was added, a mixed film containing SIS 19 and DICY and AA was produced in the same manner as in Example 1 and used as an adhesive.

[0138] [Example 7]

[0139] In Example 7, except that 1000 parts by mass of SIS 19 (810 parts by mass of the I block) was used relative to 100 parts by mass of the EP resin, and 1 part by mass of AA was additionally added, a mixed film containing SIS 19 and EP resin and DICY and AA was produced in the same manner as in Example 1 and used as an adhesive.

[0140] [Example 8]

[0141] In Example 8, except that 1900 parts by mass of SIS 19 (1539 parts by mass of the I block) was used relative to 100 parts by mass of the EP resin, and 1 part by mass of AA was additionally added, a mixed film containing SIS 19 and EP resin and DICY and AA was produced in the same manner as in Example 1 and used as an adhesive.

[0142] [Example 9]

[0143] In Example 9, except that 3000 parts by mass of SIS 19 (2430 parts by mass of the I block) was used relative to 100 parts by mass of the EP resin, and 1 part by mass of AA was additionally added, a mixed film containing SIS 19 and EP resin and DICY and AA was produced in the same manner as in Example 1 and used as an adhesive.

[0144] [Example 10]

[0145] In Example 10, first, a relatively uniform liquid mixture containing 23 parts by mass of SIS 19 (18.6 parts by mass of the I block) relative to 100 parts by mass of the EP resin was prepared. 7 parts by mass of DICY and 1 part by mass of AA were added to 100 parts by mass of the EP resin in the obtained liquid mixture, and the mixture was stirred well. The obtained liquid mixture was used as an adhesive.

[0146] In Example 10, 100 g of SIS 19 and 500 g of THF were added to a round-bottom flask and stirred well using a mechanical stirrer at room temperature. Then, 500 g of EP resin was added and stirred well using a mechanical stirrer at room temperature. Subsequently, the obtained mixed solution was rotary evaporated to evaporate THF. Further, it was stirred using a mechanical stirrer at 55 °C for 18 hours and vacuum dried to evaporate almost all of the THF. The obtained mixture containing SIS 19 and EP resin was relatively uniform and liquid.

[0147] Among them, in order to confirm the composition of the obtained liquid mixture, proton nuclear magnetic resonance spectroscopy ( 1 1H-NMR) was used to obtain a spectrum. As the solvent, deuterated chloroform was used. The obtained 1 1H-NMR spectrum is shown in Figure 2 . From the integral ratios of the signals of the protons of the I block from SIS 19 , the signal of the protons of the epoxy ring of the EP resin (a), and the signal of the protons of THF (g), the molar ratios of the respective components were calculated, and the weight ratios were estimated. As a result, it was found that in the liquid mixture, 23 parts by mass of SIS 19 was contained relative to 100 parts by mass of the EP resin, and 0.12 part by mass of THF was also contained, and almost all of it was removed.

[0148] Furthermore, 7 parts by mass of DICY and 1 part by mass of AA were added to 100 parts by mass of the EP resin in the obtained liquid mixture, and they were thoroughly mixed to obtain a mixture (adhesive composition). The obtained mixture was a relatively uniform liquid and was a one-component heat-curable epoxy-based adhesive composition.

[0149] [Example 11]

[0150] In Example 11, in the same manner as in Example 10, a relatively uniform paste-like mixture containing 56 parts by mass of SIS 19 (at this time, the I block was 45.4 parts by mass) relative to 100 parts by mass of the EP resin was prepared, 7 parts by mass of DICY and 1 part by mass of AA were added, and they were thoroughly mixed, so that the obtained paste-like mixture was used as an adhesive. It should be noted that in order to confirm the amount of THF remaining in the obtained paste-like mixture, 1H-NMR measurement was carried out in the same manner as in Example 10, and as a result, it was found that 1.7 parts by mass of THF was contained relative to 100 parts by mass of the EP resin, and almost all of it was removed. 1 1H-NMR measurement, and as a result, it was found that 1.7 parts by mass of THF was contained relative to 100 parts by mass of the EP resin, and almost all of it was removed.

[0151] [Example 12]

[0152] In Example 12, in the same manner as in Example 10, a relatively uniform liquid mixture containing 12 parts by mass of SIS 19 (at this time, the I block was 9.7 parts by mass) relative to 100 parts by mass of the EP resin was prepared, 7 parts by mass of DICY and 1 part by mass of AA were added, and they were thoroughly mixed, so that the obtained liquid mixture was used as an adhesive. It should be noted that in order to confirm the amount of THF remaining in the obtained liquid mixture, 1H-NMR measurement was carried out in the same manner as in Example 10, and as a result, it was found that 0.15 part by mass of THF was contained relative to 100 parts by mass of the EP resin, and almost all of it was removed. 1 1H-NMR measurement, and as a result, it was found that 0.15 part by mass of THF was contained relative to 100 parts by mass of the EP resin, and almost all of it was removed.

[0153] [Example 13]

[0154] In Example 13, in the same manner as in Example 10, a relatively homogeneous liquid mixture containing 5.6 parts by mass of SIS (where the I-block is 4.5 parts by mass at this time) with respect to 100 parts by mass of the EP resin was prepared, 7 parts by mass of DICY and 1 part by mass of AA were added, and they were thoroughly mixed, whereby the resulting liquid mixture was used as an adhesive. It should be noted that in order to confirm the amount of THF remaining in the resulting liquid mixture, H-NMR measurement was carried out in the same manner as in Example 10, and as a result, it was found that 0.50 part by mass of THF was contained with respect to 100 parts by mass of the EP resin, and almost all of it was removed. 19 (At this time, the I-block is 4.5 parts by mass), and a relatively homogeneous liquid mixture was obtained. 7 parts by mass of DICY and 1 part by mass of AA were added and thoroughly mixed, and the resulting liquid mixture was used as an adhesive. It should be noted that in order to confirm the amount of THF remaining in the resulting liquid mixture, H-NMR measurement was carried out in the same manner as in Example 10, and as a result, it was found that 0.50 part by mass of THF was contained with respect to 100 parts by mass of the EP resin, and almost all of it was removed. 1 H-NMR measurement was carried out, and as a result, it was found that 0.50 part by mass of THF was contained with respect to 100 parts by mass of the EP resin, and almost all of it was removed.

[0155] [Example 14]

[0156] In Example 14, in the same manner as in Example 10, a relatively homogeneous liquid mixture containing 0.87 part by mass of SIS (where the I-block is 0.71 part by mass at this time) with respect to 100 parts by mass of the EP resin was prepared, 7 parts by mass of DICY and 1 part by mass of AA were added, and they were thoroughly mixed, whereby the resulting liquid mixture was used as an adhesive. It should be noted that in order to confirm the amount of THF remaining in the resulting liquid mixture, H-NMR measurement was carried out in the same manner as in Example 10, and as a result, it was found that 0.69 part by mass of THF was contained with respect to 100 parts by mass of the EP resin, and almost all of it was removed. 19 (At this time, the I-block is 0.71 part by mass), and a relatively homogeneous liquid mixture was obtained. 7 parts by mass of DICY and 1 part by mass of AA were added and thoroughly mixed, and the resulting liquid mixture was used as an adhesive. It should be noted that in order to confirm the amount of THF remaining in the resulting liquid mixture, H-NMR measurement was carried out in the same manner as in Example 10, and as a result, it was found that 0.69 part by mass of THF was contained with respect to 100 parts by mass of the EP resin, and almost all of it was removed. 1 H-NMR measurement was carried out, and as a result, it was found that 0.69 part by mass of THF was contained with respect to 100 parts by mass of the EP resin, and almost all of it was removed.

[0157] [Example 15]

[0158] In Example 15, except that 200 parts by mass of Quintac 3290 (manufactured by Zeon Corporation, polystyrene-polyisoprene block-polystyrene block copolymer composition, hereinafter Quintac 3290 will also be referred to as "SIS") was used instead of SIS with respect to 100 parts by mass of the EP resin, in the same manner as in Example 1, a mixed film containing SIS, EP resin, and DICY was produced and used as an adhesive. It should be noted that the polystyrene content of Quintac 3290 is 35 wt%, the S-block of SIS is also a polymer compatible with the EP resin, and the I-block is also a hydrocarbon-based rubber-like polymer with a glass transition temperature of about -60°C and is a polymer incompatible (insoluble) with the EP resin. In Example 15, the I-block with respect to 100 parts by mass of the EP resin in the mixed film is 130 parts by mass. 19 and EP resin and DICY was produced and used as an adhesive. It should be noted that the polystyrene content of Quintac 3290 is 35 wt%, the S-block of SIS is also a polymer compatible with the EP resin, and the I-block is also a hydrocarbon-based rubber-like polymer with a glass transition temperature of about -60°C and is a polymer incompatible (insoluble) with the EP resin. In Example 15, the I-block with respect to 100 parts by mass of the EP resin in the mixed film is 130 parts by mass. 35 ”) was used, in the same manner as in Example 1, a mixed film containing SIS 35 and EP resin and DICY was produced and used as an adhesive. It should be noted that the polystyrene content of Quintac 3290 is 35 wt%, the S-block of SIS is also a polymer compatible with the EP resin, and the I-block is also a hydrocarbon-based rubber-like polymer with a glass transition temperature of about -60°C and is a polymer incompatible (insoluble) with the EP resin. In Example 15, the I-block with respect to 100 parts by mass of the EP resin in the mixed film is 130 parts by mass. 35 and the S-block of SIS is also a polymer compatible with the EP resin, and the I-block is also a hydrocarbon-based rubber-like polymer with a glass transition temperature of about -60°C and is a polymer incompatible (insoluble) with the EP resin. In Example 15, the I-block with respect to 100 parts by mass of the EP resin in the mixed film is 130 parts by mass.

[0159] [Example 16]

[0160] In Example 16, except that 100 parts by mass of SIS 35 (65 parts by mass of the I block) was compounded with respect to 100 parts by mass of the EP resin, a mixed film containing SIS 35 and EP resin and DICY was produced in the same manner as in Example 1 and used as an adhesive.

[0161] [Example 17]

[0162] In Example 17, except that 100 parts by mass of Quintac 3390 (manufactured by Zeon Corporation, polystyrene-polyisoprene block-polystyrene block copolymer composition, hereinafter also referred to as "SIS" 19 ) was used instead of SIS with respect to 100 parts by mass of the EP resin, a mixed film containing SIS 48 and EP resin and DICY was produced in the same manner as in Example 1 and used as an adhesive. It should be noted that the polystyrene content of Quintac 3390 is 48 wt%, and the S block of SIS 48 is also a polymer compatible with the EP resin, and the I block is also a hydrocarbon rubber-like polymer having a glass transition temperature of about -60°C and is a polymer incompatible (insoluble) with the EP resin. In Example 17, the I block with respect to 100 parts by mass of the EP resin in the mixed film is 52 parts by mass. 48

[0163] [Example 18]

[0164] In Example 18, except that 75 parts by mass of SIS 48 (39 parts by mass of the I block) was used with respect to 100 parts by mass of the EP resin, a mixed film containing SIS 48 and EP resin and DICY was produced in the same manner as in Example 1 and used as an adhesive.

[0165] [Example 19]

[0166] In Example 19, except that 100 parts by mass of the EP resin, instead of SIS 19 ​Using 200 parts by mass of a polystyrene-polybutadiene-polystyrene block copolymer (a polystyrene-polybutadiene block copolymer composition with a polystyrene content of 30 wt% purchased from Aldrich (product number 432490), hereinafter also referred to as "SBS"), and in addition to AA, in the same manner as in Example 1, a mixed film containing SBS, EP resin, DICY, and AA was prepared and used as an adhesive. It should be noted that the S block of SBS is a polymer compatible (soluble) with the EP resin, and the polybutadiene block (hereinafter also referred to as the "B block") is a hydrocarbon rubber-like polymer with a glass transition temperature of approximately -60°C and is a polymer insoluble in the EP resin. In Example 20, relative to 100 parts by mass of the EP resin, 200 parts by mass of SBS (140 parts by mass of the B block), 7 parts by mass of DICY, and 1 part by mass of AA were compounded.

[0167] [Example 20]

[0168] In Example 20, except that 400 parts by mass of SBS (280 parts by mass of the B block) was used relative to 100 parts by mass of the EP resin, a mixed film containing SBS, EP resin, DICY, and AA was prepared in the same manner as in Example 19 and used as an adhesive.

[0169] [Example 21]

[0170] In Example 21, in the same manner as in Example 10, a relatively uniform liquid mixture containing 18.5 parts by mass of SBS (13 parts by mass of the B block) relative to 100 parts by mass of the EP resin was prepared, 7 parts by mass of DICY and 1 part by mass of AA were added, and the mixture was thoroughly mixed. Then, the resulting liquid mixture was used as an adhesive. It should be noted that in order to confirm the amount of THF remaining in the resulting liquid mixture, the same 1 1H-NMR measurement was carried out as in Example 10. The results showed that relative to 100 parts by mass of the EP resin, 0.25 parts by mass of THF was contained and almost all of it was removed.

[0171] [Example 22]

[0172] In Example 22, in the same manner as in Example 10, a relatively uniform liquid mixture was prepared which contained 5.6 parts by mass of a polystyrene-poly(ethylene-r-butylene)-polystyrene block copolymer (a polystyrene-poly(ethylene-r-butylene) block copolymer composition having a polystyrene content of 29 wt% purchased from Aldrich, hereinafter also referred to as "SEBS") with respect to 100 parts by mass of an EP resin. 7 parts by mass of DICY and 1 part by mass of AA were added and thoroughly mixed, and the resulting liquid mixture was used as an adhesive. It should be noted that the poly(ethylene-r-butylene) block (hereinafter also referred to as "EB block") of the SEBS copolymer is a hydrocarbon rubber-like polymer having a glass transition temperature of 25°C or lower and is a polymer incompatible (insoluble) with the EP resin, and its content was 4.0 parts by mass. In addition, in order to confirm the amount of THF remaining in the resulting liquid mixture, 1 1 1H-NMR measurement was carried out in the same manner as in Example 10, and as a result, it was found that 0.30 part by mass of THF was contained with respect to 100 parts by mass of the EP resin, and almost all of it was removed.

[0173] [Example 23]

[0174] In Example 23, hydrogenation reaction was carried out on SIS 19 to synthesize a polystyrene-poly(ethylene-alt-propylene)-polystyrene block copolymer (a polystyrene-poly(ethylene-alt-propylene) block copolymer composition having a polystyrene content of 17.5 wt%, hereinafter also referred to as "SEPS"). In the same manner as in Example 10, a relatively uniform liquid mixture was prepared which contained 6.6 parts by mass of SEPS with respect to 100 parts by mass of the EP resin. 7 parts by mass of DICY and 1 part by mass of AA were added and thoroughly mixed, and the resulting liquid mixture was used as an adhesive. It should be noted that the poly(ethylene-alt-propylene) block (hereinafter also referred to as "EP block") of the SEPS copolymer is a hydrocarbon rubber-like polymer having a glass transition temperature of 25°C or lower and is a polymer incompatible (insoluble) with the EP resin, and its content was 5.4 parts by mass.

[0175] Among them, SEPS was synthesized by the following method. First, 10.0 g of SIS 19 was dissolved in 163 g of p-xylene, and then 101 g of p-toluenesulfonylhydrazide was added. A Dimroth condenser was installed in the flask, and the mixture was stirred in an oil bath at 145°C for 9 hours. The reaction solution was dropped into about 3000 mL of methanol to precipitate the polymer. The resulting polymer was separated by suction filtration, thoroughly dried by vacuum drying, dissolved in THF, and then dropped into methanol again to precipitate the polymer. This purification operation was repeated 3 times to remove unreacted p-toluenesulfonylhydrazide, its by-products, solvents, etc., to obtain SEPS.

[0176] The obtained SEPS was dissolved in deuterated chloroform to prepare a solution of about 2% by mass, and 1 1H-NMR measurement was carried out. As a result, the peak at 4.5 to 5.3 ppm from the protons carried by the C═C double bond became quite small. From the integration ratio with the peak at 6.2 to 7.2 ppm from the phenyl group of polystyrene, it was found that 99.6% of the C═C double bonds became single bonds.

[0177] Then, in the same manner as in Example 10, a relatively homogeneous liquid mixture containing 6.6 parts by mass of SEPS (5.4 parts by mass of the EP block at this time) with respect to 100 parts by mass of the EP resin was prepared. 7 parts by mass of DICY and 1 part by mass of AA were added and thoroughly mixed, and thus the obtained liquid mixture was used as an adhesive. It should be noted that in order to confirm the amount of THF remaining in the obtained liquid mixture, 1 1H-NMR measurement was carried out in the same manner as in Example 10. As a result, it was found that with respect to 100 parts by mass of EP, 0.59 part by mass of THF was contained and almost all of it was removed.

[0178] [Example 24]

[0179] In Example 24, except that 5 parts by mass of silica particles (manufactured by Tokuyama Corporation, REOLOSIL (registered trademark) QS-40, the same applies to the following examples) were added with respect to 100 parts by mass of the EP resin, in the same manner as in Example 1, a mixed film containing SIS 19 and EP resin and DICY and silica particles was prepared and used as an adhesive. It should be noted that the silica particles were mixed when SIS 19 and EP resin and DICY and the solvent were mixed. The same applies to the following examples.

[0180] [Example 25]

[0181] In Example 25, except that 1 part by mass of AA and 5 parts by mass of silica particles were added with respect to 100 parts by mass of the EP resin, in the same manner as in Example 1, a mixed film containing SIS 19 and EP resin and DICY and AA and silica particles was prepared and used as an adhesive.

[0182] [Example 26]

[0183] In Example 26, except that 600 parts by mass of SIS 19 (486 parts by mass of the I block) were used with respect to 100 parts by mass of the EP resin and 5 parts by mass of silica particles were added, in the same manner as in Example 1, a mixed film containing SIS 19A mixed film of EP resin, DICY, and silica particles is used as an adhesive.

[0184] [Example 27]

[0185] In Example 27, except that 5 parts by mass of colloidal calcium carbonate particles (manufactured by Shiraishi Kogyo Co., Ltd., Viscoexcel (registered trademark) 30HV, the same applies to the following examples) were added relative to 100 parts by mass of EP resin, a mixed film containing SIS 19 and EP, DICY, and colloidal calcium carbonate particles was produced in the same manner as in Example 1 and used as an adhesive. It should be noted that the colloidal calcium carbonate particles were also mixed during the mixing of SIS 19 and EP resin, DICY, and solvent. The same applies to the following examples.

[0186] [Example 28]

[0187] In Example 28, except that 600 parts by mass of SIS 19 (486 parts by mass of the I-block) were used relative to 100 parts by mass of EP resin and 5 parts by mass of colloidal calcium carbonate particles were added, a mixed film containing SIS 19 and EP resin, DICY, and colloidal calcium carbonate particles was produced in the same manner as in Example 1 and used as an adhesive.

[0188] In addition, as a comparative example, an adhesive composition without a block copolymer was also produced.

[0189] [Comparative Example 1]

[0190] In Comparative Example 1, a liquid mixture obtained by stirring without using a polymer other than EP resin, with 7 parts by mass of DICY and 1 part by mass of AA added relative to 100 parts by mass of EP resin, was used as an adhesive.

[0191] For each of the epoxy-based adhesive compositions of the examples and comparative examples prepared with these respective formulations, a shear tensile test, a T-peel test, and a dumbbell tensile test were performed on the cured adhesives.

[0192] (Shear Tensile Test)

[0193] For the film-like adhesive compositions (Examples 1 to 9, Examples 15 to 20, Examples 24 to 28), a piece with a size of about 25 mm × 12.5 mm was cut out and sandwiched between two SPC270 substrates with a thickness of 1.6 mm, a width of 25 mm, and a length of 100 mm together with the glass beads (about 0.2 mm) of the spacer, and fixed with a clip (the bonding area was about 25 mm × 12.5 mm). Then, the prepared specimen was transferred to an oven heated to 170 °C and taken out of the oven after 50 minutes, thus obtaining a test piece in which the film-like adhesive composition was heat-cured to bond between the substrates. Then, a shear tensile test was performed on the obtained test piece. As the measuring device at this time, AGS-X, a 10 kN load cell, and an air-type flat fixture manufactured by Shimadzu Corporation were used, and the shear tensile test was performed under the conditions of an air pressure of 0.40 MPa for the fixture, room temperature, and a tensile speed of 50 mm / min. The average values of three tests for each specimen are shown in Table 1 below.

[0194] For the liquid or paste-like adhesives (Examples 10 to 14, Examples 21 to 23, Comparative Example 1), it was coated and sandwiched between two SPC270 substrates with a thickness of 1.6 mm, a width of 25 mm, and a length of 100 mm together with the glass beads (about 0.2 mm) of the spacer, and fixed with a clip. At this time, the bonding area was made about 25 mm × 12.5 mm. Then, in the same manner as above, the prepared specimen was transferred to an oven heated to 170 °C and taken out of the oven after 50 minutes, thus obtaining a test piece in which the adhesive composition was heat-cured to bond between the substrates. Then, a shear tensile test was performed on the obtained test piece. In the same manner as above, as the measuring device, AGS-X, a 10 kN load cell, and an air-type flat fixture manufactured by Shimadzu Corporation were used, and the shear tensile test was performed under the conditions of an air pressure of 0.40 MPa for the fixture, room temperature, and a tensile speed of 50 mm / min. The average values of two tests for each specimen are shown in Table 1.

[0195] (T-peel test)

[0196] The T-peel test was measured according to the T-peel bonding strength test method of JIS K6854-3 (1999).

[0197] For the film-like adhesive compositions (Examples 1 to 9, Examples 15 to 20, Examples 24 to 28), a piece with a size of about 25 mm × 150 mm was cut out and clamped between two T-shaped peel test substrates made of SPC270 with an adhesive surface, each 0.8 mm thick, 25 mm wide, and 150 mm long, together with glass beads (about 0.2 mm) of the spacer, and fixed with a clip. Then, the prepared specimen was transferred to an oven heated to 170 °C, taken out of the oven after 50 minutes, so as to obtain a test piece in which the film-like adhesive composition was heat-cured to bond the substrates. Then, a T-shaped peel test was performed on the obtained test piece. As the measuring device at this time, AGS-X, a 500 N load cell, and an air-type flat fixture manufactured by Shimadzu Corporation were used, and the T-shaped peel test was carried out under the conditions of an air pressure of 0.40 MPa of the fixture, room temperature, and a tensile speed of 200 mm / min. The average values when each test was performed three times for each specimen are shown in Table 1.

[0198] For the liquid or paste-like adhesives (Examples 10 to 14, Examples 21 to 23, Comparative Example 1), it was coated and clamped together with glass beads (about 0.2 mm) of the spacer between two T-shaped peel test substrates made of SPC270 with an adhesive surface, each 0.8 mm thick, 25 mm wide, and 150 mm long, and fixed with a clip. Then, in the same manner as above, the prepared specimen was transferred to an oven heated to 170 °C, taken out of the oven after 50 minutes, so as to obtain a test piece in which the adhesive composition was heat-cured to bond the substrates. Then, a T-shaped peel test was performed on the obtained test piece. In the same manner as above, as the measuring device, AGS-X, a 500 N load cell, and a screw-type flat fixture manufactured by Shimadzu Corporation were used, and the T-shaped peel test was carried out under the conditions of room temperature and a tensile speed of 50 mm / min. The average values when each test was performed twice for each specimen are shown in Table 1.

[0199] (Dumbbell tensile test)

[0200] Furthermore, for the film-like adhesive compositions (Examples 1 to 9, Examples 15 to 20, Examples 24 to 28), they were transferred to an oven heated to 170°C and taken out of the oven after 50 minutes to obtain heat-cured film specimens. Then, the heat-cured film specimens (0.5 mm thick) were punched with a punching die corresponding to No. 6 or No. 7 dumbbell shape described in Japanese Industrial Standard JIS K6251:2017 to obtain test pieces. Then, a dumbbell tensile test was conducted on the obtained test pieces. As the measuring device, AGS-X, a 500N load cell, and an air-type flat fixture manufactured by Shimadzu Corporation were used to conduct the tensile test. It should be noted that in the case of the test piece of No. 6 dumbbell shape, the tensile test was conducted under the conditions of an air pressure of 0.40 MPa in the fixture, room temperature, a distance between the fixtures of about 50 mm, and an initial strain rate of about 0.033 / s (tensile speed of 100 mm / min). In the case of the test of No. 7 dumbbell shape, the tensile test was conducted under the conditions of an air pressure of 0.40 MPa in the fixture, room temperature, a distance between the fixtures of about 10 mm, and an initial strain rate of about 0.017 / s (tensile speed of 10 mm / min). The average values when each test was conducted twice for each specimen are shown in Table 1. It should be noted that the Young's modulus was obtained from the initial gradient of the stress-strain curve (the slope when the strain was 0 to 10%), the tensile strength was obtained from the maximum value of the stress, and the elongation at break was obtained from the elongation at the time of fracture.

[0201] For the liquid adhesives of Example 10 and Comparative Example 1, defoaming was carried out at 60°C under vacuum for 30 minutes, and then transferred to a Teflon (registered trademark) mold corresponding to No. 6 or No. 7 dumbbell shape described in Japanese Industrial Standard JIS K6251:2017. Then, it was transferred to an oven heated to 170°C and taken out of the oven after 50 minutes to obtain a heat-cured test piece. The thickness of the test piece was about 2 mm. As the measuring device, AGS-X, a 10kN load cell, and an air-type flat fixture manufactured by Shimadzu Corporation were used to conduct the tensile test under the conditions of an air pressure of 0.40 MPa in the fixture, room temperature, a distance between the fixtures of about 50 mm, and an initial strain rate of about 0.017 / s (tensile speed of 50 mm / min). The average values when each test was conducted twice for each specimen are shown in Table 1. It should be noted that the Young's modulus was obtained from the initial gradient of the stress-strain curve (the slope when the strain was 0 to 0.3%), the tensile strength was obtained from the maximum value of the stress, and the elongation at break was obtained from the elongation at the time of fracture.

[0202] The composition ratios of these Examples and Comparative Examples and the results of various tests are summarized in Table 1 below.

[0203] [Table 1]

[0204]

[0205] As shown in Table 1, in Comparative Example 1 containing only EP resin, latent curing agent DICY, and amine adduct curing accelerator (AA) without blending block copolymer, the shear tensile strength in the shear test was 16.5 Mpa, the peel strength in the T-peel test was 26.7 N / 25 mm, and the Young's modulus, tensile strength, and elongation at break in the dumbbell tensile test were 2410 MPa, 12.0 MPa, and 0.61%, respectively. It should be noted that the Young's modulus was obtained from the initial gradient of the stress-strain curve (the slope when the strain was 0 to 0.3%).

[0206] In Examples 1 to 9 and Examples 24 to 28 of the film-like adhesive blended with SIS 19 the peel strength was excellent. It is considered that this is because, since the elongation at break of the dumbbell physical properties is extremely high, the S block in SIS is compatible with the EP resin, and the rubber-like polymer in SIS, that is, the I block, is incompatible with the EP resin. By the compatibility of the S block in SIS with the EP resin, the I block is dispersed in the EP resin, and the I block also functions as rubber after the heat curing of the EP resin. By imparting ductility, softness, and elastic modulus generated by the I block, the epoxy resin is toughened.

[0207] That is, in a single body of a polystyrene-polyisoprene-polystyrene block copolymer in which polystyrene blocks are polymerized at both ends of a chain-linked polyisoprene block, as Figure 1 (b) shows, at room temperature (normal temperature), the polystyrene block (hard segment) and the polyisoprene block (soft segment) are thermodynamically incompatible (do not mix independently), the polystyrene part condenses, forming polystyrene domains, forming a microphase separation structure. That is, since the glass transition temperature (T g ) of the polystyrene part is a temperature higher than room temperature, it is in a glassy state, and this hard polystyrene part aggregates and condenses to form domains, thereby forming pseudo-crosslinking points that physically crosslink the polyisoprene part.

[0208] In the cured adhesive formed from an epoxy adhesive composition obtained by mixing an epoxy resin, a curing agent, a polystyrene-polyisoprene-polystyrene block copolymer, etc., as Figure 1 (c) shows, it is considered that since the polystyrene part of the polystyrene-polyisoprene-polystyrene block copolymer is compatible with the epoxy resin at room temperature (normal temperature), the polystyrene part does not aggregate and condense to form pseudo-crosslinking points, and the polyisoprene part is dispersed in the epoxy resin. Due to the action of the rubber-like polyisoprene part, softness, ductility, and elastic modulus are imparted. It is speculated that this toughens the cured epoxy resin and improves the peel strength.

[0209] This can also be confirmed from the comparison between the examples. For example, from the comparison of Examples 1 to 3, it can be seen that if the content of isoprene relative to the epoxy resin increases, the peel strength increases. It is considered that due to the polyisoprene part, flexibility, ductility, and elastic modulus are imparted.

[0210] In addition, in Examples 1 to 9 of the film-like adhesive containing SIS 19 and in the comparison with Examples 15 to 18 of the film-like adhesive containing SIS 35 and SIS 48 in Examples 15 to 18 of the film-like adhesive containing SIS 35 and SIS 48 the elongation at break of the dumbbell physical properties in Examples 15 to 18 is higher than that of Comparative Example 1. Compared with Examples 1 to 9 with a high content of polyisoprene, the peel strength increases in Examples 15 to 18.

[0211] Incidentally, the failure state in the shear tensile test and T-peel test is cohesive failure (CF) in Comparative Example 1, while in Example 1, due to the improvement of toughness, a large number of interfacial failures (AF) and thin-layer cohesive failures (TCF) are found.

[0212] It should be noted that the reason for the lower shear strength in Examples 1 to 9 and Examples 15 to 18 compared with Comparative Example 1 is that in these examples, the amount of epoxy resin is less than that in Comparative Example 1.

[0213] In addition, in Examples 24 to 28 containing silica and colloidal calcium carbonate, due to the addition of silica and colloidal calcium carbonate, a tendency of increasing peel strength and shear strength is found, and an increase in mechanical strength due to the addition of silica and colloidal calcium carbonate is found.

[0214] Furthermore, in Examples 10 to 14 of the paste-like and film-like adhesives containing SIS 19 an increase in peel strength and shear strength is also found compared with Comparative Example 1.

[0215] In addition, in Examples 19 to 21 containing SBS, an increase in any of the elongation at break, tensile strength, peel strength, and shear strength of the dumbbell physical properties is found. In the examples containing SBS, it is considered that the S block in SBS is compatible with the EP resin, and the rubber-like polymer in SBS, i.e., the B block, is incompatible with the EP resin. Since the S block in SBS is compatible with the EP resin, the B block is dispersed in the EP resin. After the heat curing of the EP resin, the B block also functions as rubber, and the epoxy resin is toughened by the imparting of ductility, flexibility, and elastic modulus generated by the B block.

[0216] Similarly, in Example 22 containing SEBS and Example 23 containing SEPS, an increase in peel strength and shear strength was also found. In the example containing SEBS, it is considered that the S block in SEBS is compatible with the EP resin, and the rubber-like polymer in SEBS, namely the EB block, is incompatible with the EP resin. Since the S block in SEBS is compatible with the EP resin, the EB block is dispersed in the EP resin. After the EP resin is heat-cured, the EB block also functions as rubber. By imparting ductility, flexibility, and elastic modulus generated by the EB block, the epoxy resin is toughened. In addition, in the example containing SEPS, it is considered that the S block in SEPS is compatible with the EP resin, and the rubber-like polymer in SEPS, namely the EP block, is incompatible with the EP resin. Since the S block in SBS is compatible with the EP resin, the EP block is dispersed in the EP resin. After the EP resin is heat-cured, the EP block also functions as rubber. By imparting ductility, flexibility, and elastic modulus generated by the EB block, the epoxy resin is toughened.

[0217] It should be noted that, as described above, the higher the content ratio of the hydrocarbon-based rubber-like polymer in the block copolymer such as polyisoprene block (I block), polybutadiene block (B block), poly(ethylene-r-butene) block (EB block), and poly(ethylene-alt-propylene) block (EP block), in other words, the smaller the content ratio of the polymer compatible with the epoxy resin, namely the polystyrene block (S block), the more the tensile strength, elongation at break, etc. of the dumbbell physical properties are improved.

[0218] Among them, the present inventors further conducted impact resistance tests on the above Examples 1 to 3, Examples 15 to 18, and Comparative Example 1.

[0219] (Impact Resistance Test)

[0220] The impact resistance test was measured by a dynamic fracture resistance test (wedge impact method) under the impact conditions according to JIS K6865.

[0221] For the film-like adhesive compositions (Examples 1 to 3 and Examples 15 to 18), a piece of about 25 mm × 150 mm in size was cut out and clamped together with the glass beads (about 0.2 mm) of the spacer between two cold-rolled steel sheets made of SPC270 with an adhesive surface, 0.8 mm thick, 25 mm wide, and 150 mm long, and fixed with a clip (the adhesive area was about 25 mm × 12.5 mm). Then, the prepared specimen was transferred to an oven heated to 170 °C, taken out of the oven after 60 minutes, and thus a symmetric wedge test piece with the substrates bonded by a heat-cured mixed film was obtained. Then, using a high-speed tensile testing machine (manufactured by Shimadzu Corporation), an impact test was carried out on the symmetric wedge test piece at room temperature (about 20 °C) and a test speed of 2 m / s, applying a load with a test wedge (made of quenched steel) to cause it to break, and measuring the test force (strength) (KN) in the range of 25 to 90% of the total displacement (stroke) during the test. The average strength (KN) was divided by the width (mm) of the test piece to calculate the impact strength.

[0222] For the liquid adhesive (Comparative Example 1), it was coated and clamped together with the glass beads (about 0.2 mm) of the spacer between two cold-rolled steel sheets made of SPC270 with an adhesive surface, 0.8 mm thick, 25 mm wide, and 150 mm long, and fixed with a clip. Then, in the same manner as above, a test piece was made and an impact test was carried out.

[0223] The results of the impact resistance test are shown in Table 2 below. It should be noted that the values shown in Table 2 are the averages when each test was carried out twice for each specimen.

[0224] [Table 2]

[0225]

[0226] As shown in Table 2, in Comparative Example 1 without the addition of block copolymer and only containing epoxy resin (EP resin), latent curing agent DICY, and amine adduct-based curing accelerator (AA), the impact strength was 1.6 KN / m, while in Examples 1 to 3 and Examples 15 to 18 with the addition of SIS, the impact strength was 5.7 KN / m or more, and the impact strength was improved. It is considered that this is because, as described above, the elongation at break of the dumbbell physical properties and others were improved compared to Comparative Example 1. Therefore, the S block in SIS is compatible with the EP resin, and the rubber-like polymer, i.e., the I block in SIS, is incompatible with the EP resin. Since the S block in SIS is compatible with the EP resin, the I block is dispersed in the EP resin. After the heat curing of the EP resin, the I block also functions as rubber, and through the imparting of ductility, softness, and elastic modulus generated by the I block, the epoxy resin is toughened.

[0227] Furthermore, the present inventors conducted a T-peel test and an impact resistance test on the adhesive compositions of the examples and comparative examples of the compounding compositions shown in Table 3 below.

[0228] [Table 3]

[0229]

[0230] [Example 29]

[0231] In Example 29, for the liquid mixture prepared by the same steps as in Example 10 above and containing 10 parts by mass of SIS relative to 100 parts by mass of the EP resin 19 6 parts by mass of DICY, 1 part by mass of phenyl-1,1-dimethylurea A (hereinafter also referred to as "DCMU") as a curing accelerator, 38 parts by mass of colloidal calcium carbonate particles (manufactured by Shiraishi Kogyo Co., Ltd., Viscoexcel (registered trademark) 30HV, the same applies to the following examples), and 2 parts by mass of calcium oxide were added and thoroughly mixed to prepare a liquid mixture containing 10 parts by mass of SIS relative to 100 parts by mass of the EP resin 19 (8 parts by mass of the I-block), 6 parts by mass of DICY, 1 part by mass of DCMU, 38 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide, and this was used as the adhesive.

[0232] [Example 30]

[0233] In Example 30, for the liquid mixture prepared by the same steps as in Example 10 above and containing 15 parts by mass of SIS relative to 100 parts by mass of the EP resin 19 6 parts by mass of DICY, 1 part by mass of DCMU, 39 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide were added and thoroughly mixed to prepare a liquid mixture containing 15 parts by mass of SIS relative to 100 parts by mass of the EP resin 19 (12 parts by mass of the I-block), 6 parts by mass of DICY, 1 part by mass of DCMU, 39 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide, and this was used as the adhesive.

[0234] [Example 31]

[0235] In Example 31, for the liquid mixture prepared by the same steps as in Example 10 above and containing 20 parts by mass of SIS relative to 100 parts by mass of the EP resin 19 6 parts by mass of DICY, 1 part by mass of DCMU, 41 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide were added and thoroughly mixed to prepare a liquid mixture containing 20 parts by mass of SIS relative to 100 parts by mass of the EP resin19 (The I block is 16 parts by mass), 6 parts by mass of DICY, 1 part by mass of DCMU, 41 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide are used as a liquid mixture and used as an adhesive.

[0236] [Example 32]

[0237] In Example 32, for a liquid mixture prepared by the same steps as in Example 10 above and containing 30 parts by mass of SIS relative to 100 parts by mass of EP resin 19 6 parts by mass of DICY, 1 part by mass of DCMU, 45 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide are added and thoroughly mixed to prepare a liquid mixture containing 30 parts by mass of SIS relative to 100 parts by mass of EP resin 19 (The I block is 24 parts by mass), 6 parts by mass of DICY, 1 part by mass of DCMU, 45 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide are used as a liquid mixture and used as an adhesive.

[0238] [Example 33]

[0239] In Example 33, for a liquid mixture prepared by the same steps as in Example 10 above and containing 40 parts by mass of SIS relative to 100 parts by mass of EP resin 19 6 parts by mass of DICY, 1 part by mass of DCMU, 48 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide are added and thoroughly mixed to prepare a liquid mixture containing 40 parts by mass of SIS relative to 100 parts by mass of EP resin 19 (The I block is 32 parts by mass), 6 parts by mass of DICY, 1 part by mass of DCMU, 48 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide are used as a liquid mixture and used as an adhesive.

[0240] [Example 34]

[0241] In Example 34, for a liquid mixture prepared by the same steps as in Example 10 above and containing 50 parts by mass of SIS relative to 100 parts by mass of EP resin 19 6 parts by mass of DICY, 1 part by mass of DCMU, 52 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide are added and thoroughly mixed to prepare a liquid mixture containing 50 parts by mass of SIS relative to 100 parts by mass of EP resin 19 (The I block is 40 parts by mass), 6 parts by mass of DICY, 1 part by mass of DCMU, 52 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide are used as a liquid mixture and used as an adhesive.

[0242] [Example 35]

[0243] In Example 35, for a liquid mixture prepared by the same steps as in Example 10 above and containing 5 parts by mass of SIS relative to 100 parts by mass of the EP resin 19 6 parts by mass of DICY, 1 part by mass of DCMU, 36 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide were added, and thoroughly mixed to prepare a liquid mixture containing 5 parts by mass of SIS relative to 100 parts by mass of the EP resin 19 (4 parts by mass of the I-block), 6 parts by mass of DICY, 1 part by mass of DCMU, 36 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide, and this was used as an adhesive.

[0244] [Comparative Example 2]

[0245] In Comparative Example 2, no polymer other than the EP resin was used. Relative to 100 parts by mass of the EP resin, 6 parts by mass of DICY, 1 part by mass of DCMU, 34 parts by mass of colloidal calcium carbonate particles, and 2 parts by mass of calcium oxide were blended, stirred, and the resulting liquid mixture was used as an adhesive.

[0246] For these Examples 29 to 35 and Comparative Example 2, the above T-peel test and impact test were also carried out. The test results of the T-peel test and impact test are shown in Table 3.

[0247] As shown in Table 3, in Comparative Example 2 which did not contain a block copolymer and was composed of an epoxy resin (EP resin), latent curing agent DICY, and urea-based curing accelerator (DCMU), colloidal calcium carbonate particles, and calcium oxide, the impact strength was 1.1 KN / m and the peel strength was 48.5 N / 25 mm. In Examples 29 to 35 in which SIS was blended, the impact strength was 1.3 KN / m or more, and the impact strength was improved. It is considered that this is because, as described above, the S-block in SIS is compatible with the EP resin, and the rubber-like polymer in SIS, that is, the I-block, is not compatible with the EP resin. Since the S-block in SIS is compatible with the EP resin, the I-block is dispersed in the EP resin, and the I-block also functions as rubber after the heat curing of the EP resin. By imparting ductility, softness, and elastic modulus generated by the I-block, the epoxy resin is toughened. In particular, in Comparative Example 2, the peel strength was 48.5 N / 25 mm, while in Examples 30 to 34 in which 12 parts by mass or more of polyisoprene was blended relative to 100 parts by mass of the epoxy resin, the peel strength was 50 N / 25 mm or more, and the peel strength was extremely excellent.

[0248] It should be noted that such a liquid adhesive composition is also applicable to uses such as structural adhesives for automobiles.

[0249] In addition, the present inventors prepared the adhesive compositions of Examples 36 to 40 and Comparative Example 3 shown in Table 4 below, and conducted T-peel tests, impact resistance tests, shear tensile tests, measurements by Fourier transform infrared spectroscopy (FT-IR), dynamic viscoelasticity measurements, observations of nanostructures using a transmission electron microscope (TEM), and differential scanning calorimetry (DSC).

[0250] [Table 4]

[0251]

[0252] In Example 36, for a liquid mixture prepared in the same manner as in Example 10 above and containing 5.6 parts by mass of SIS per 100 parts by mass of the EP resin 19 (4.5 parts by mass of the I block), 7 parts by mass of DICY, 1 part by mass of an amine adduct-based curing accelerator (AA), and 20.0 parts by mass of colloidal calcium carbonate particles (manufactured by Shiraishi Kogyo Co., Ltd., Viscoexcel (registered trademark) 30HV, the same applies hereinafter) were blended and stirred, and the resulting liquid mixture was used as the adhesive.

[0253] In Example 37, for a liquid mixture prepared in the same manner as in Example 10 above and containing 9.6 parts by mass of SIS per 100 parts by mass of the EP resin 19 (7.8 parts by mass of the I block), 7 parts by mass of DICY, 1 part by mass of AA, and 20.8 parts by mass of colloidal calcium carbonate particles were blended and stirred, and the resulting liquid mixture was used as the adhesive.

[0254] In Example 38, for a liquid mixture prepared in the same manner as in Example 10 above and containing 16 parts by mass of SIS per 100 parts by mass of the EP resin 19 (13.0 parts by mass of the I block), 7 parts by mass of DICY, 1 part by mass of AA, and 21.9 parts by mass of colloidal calcium carbonate particles were blended and stirred, and the resulting liquid mixture was used as the adhesive.

[0255] In Example 39, for a liquid mixture prepared in the same manner as in Example 10 above and containing 19 parts by mass of SIS per 100 parts by mass of the EP resin 19 (15.4 parts by mass of the I block), 7 parts by mass of DICY, 1 part by mass of AA, and 22.4 parts by mass of colloidal calcium carbonate particles were blended and stirred, and the resulting liquid mixture was used as the adhesive.

[0256] In Example 40, for a liquid mixture prepared in the same manner as in Example 10 above and containing 26 parts by mass of SIS per 100 parts by mass of the EP resin19 (The I block is 21.1 parts by mass) of the liquid mixture, compounded with 7 parts by mass of DICY, 1 part by mass of AA, and 23.6 parts by mass of colloidal calcium carbonate particles, stirred, and the resulting liquid mixture is used as an adhesive.

[0257] In Comparative Example 3, no polymer other than the EP resin was used. Relative to 100 parts by mass of the EP resin, 7 parts by mass of DICY, 1 part by mass of AA, and 19.1 parts by mass of colloidal calcium carbonate particles were compounded, stirred, and the resulting liquid mixture was used as an adhesive.

[0258] For these Examples 36 to 40 and Comparative Example 3, the impact resistance test, T-peel test, and shear tensile test were carried out in the same manner as above. Their test results are shown in Table 4.

[0259] In addition, for Example 39 as an example of an epoxy-based adhesive composition containing SIS and Comparative Example 3 as an example of an epoxy-based adhesive composition without SIS and without using a polymer other than the EP resin, Fourier transform infrared spectroscopy (FT-IR) measurement and dynamic viscoelasticity measurement were carried out. Furthermore, for Example 39, observation of the nanostructure using a transmission electron microscope (TEM) was carried out. In addition, for Examples 36 to 40 and Comparative Example 3, differential scanning calorimetry (DSC) was carried out.

[0260] (FT-IR measurement)

[0261] The liquid adhesives of Example 39 and Comparative Example 3 were sandwiched between potassium bromide (KBr) plates, transferred to an oven heated to 170 °C, and taken out of the oven after 50 minutes, thereby obtaining specimens for FT-IR measurement of heat-cured products. In addition, as a control specimen, SIS 19 film was prepared on a KBr plate using THF solvent. For the FT-IR measurement, FT / IR-6100 (manufactured by JASCO) was used, measured at room temperature, and the number of accumulations was set to 1024 times. The FT-IR spectra of the heat-cured specimen of Example 39, the heat-cured specimen of Comparative Example 3, and the SIS specimen obtained are shown in Figure 4 (a).

[0262] (Dynamic viscoelasticity measurement)

[0263] The liquid adhesives of Example 39 and Comparative Example 3 were transferred to a silicone mold (width about 4.5 m × length about 350 mm × thickness about 2 mm), degassed at 60 °C, and then transferred to an oven heated to 170 °C and taken out of the oven after 50 minutes, thereby obtaining heat-cured test pieces. In addition, as a control specimen, SIS 19film. Using the obtained test piece, tensile dynamic viscoelasticity measurement was carried out using Rheogel E4000 (manufactured by UBM) under the conditions of a frequency of 10 Hz, a strain of 0.1%, a distance between clamps of 20 mm, a temperature range of -100 to 300 °C, and a heating rate of 10 °C / min. The data of the loss tangent (tanδ) obtained were shown in Figure 4 (b). In the sample of Example 39 containing SIS, a relatively large peak was found around -50 °C. Since a large peak was found around -50 °C in SIS, it was considered that this peak was the T g peak from the I block of SIS. It should be noted that in the sample of Comparative Example 3 where no polymer other than the EP resin was used, a very broad peak and a large peak were found around -50 °C and 170 °C, respectively, and they were considered to be the β relaxation and T g peak from the EP resin, respectively. Moreover, the value of tanδ at 26 °C near room temperature was 0.022 in the sample of Comparative Example 3, while in the sample of Example 39, it increased to 0.029, suggesting that due to the presence of the I block as a soft rubbery component, the stress relaxation ability was improved.

[0264] (TEM Observation)

[0265] The liquid adhesive of Example 39 was transferred to an oven heated to 170 °C and taken out of the oven after 50 minutes to obtain a heat-cured test piece. In addition, as a control sample, a film of SIS was prepared by a solution casting method using a THF solvent and embedded in an epoxy resin. For these samples, ultra-thin sections with a thickness of about 80 nm were prepared by a slicing method. To enhance the contrast of the TEM image, osmium tetroxide vapor was used for overnight staining. TEM observation was carried out using JEM-1400 Flash (manufactured by JEOL) at an accelerating voltage of 100 kV. 19 The TEM images of the cured product of the adhesive of Example 39 and the sample of SIS were shown in

[0266] (a) and Figure 5 (b), respectively. Since staining with osmium tetroxide vapor was carried out, the phase of the I block looked dark and the phases of the S block and the EP resin looked bright. In Figure 5 (b), spheres or columnar bright fine phases (about 10 - 20 nm) were seen on the dark continuous phase, and it was found that SIS formed a nano-phase separation structure in which isolated microdomains (columns or spheres) of the S block existed in the matrix of the I block. In Figure 5 (a), in addition to the dark continuous phase and the bright island-like fine phases, a large number of spherical domains in the range of dozens to hundreds of nm were found. Compared with Figure 5 (a), in addition to the dark continuous phase and the bright island-like fine phases, a large number of spherical domains in the range of dozens to hundreds of nm were found. Compared with Figure 5The bright island-like fine phase appears larger than the bright fine phase in (b). It is considered that since polystyrene is compatible with the EP resin, the fine phase in which the S block is mixed with the EP resin has become a structure floating in the matrix of the I block. On the other hand, since a large amount of EP resin is present relative to SIS, there should also be EP resin that is not completely mixed with the S block, and it is considered that it appears as spherical domains in the order of dozens to hundreds of nm.

[0267] (Differential Scanning Calorimetry (DSC))

[0268] Regarding the adhesive cured products of Examples 36 to 40, the adhesive cured product of Comparative Example 3, and SIS, in order to evaluate T g , DSC measurements were carried out. For Examples 36 to 40 and Comparative Example 3, each sample was transferred to an oven heated to 170 °C and taken out of the oven after 50 minutes to obtain the adhesive cured product. Each specimen was placed in an aluminum pan, and DSC measurements were carried out using DSC Q2000 (manufactured by TA Instruments) under the conditions of a nitrogen flow rate of 50 min / mL, a heating rate of 10 °C / min, and a temperature range of -80 to 230 °C.

[0269] The DSC thermograms of the adhesive cured products of Examples 36 to 40 containing SIS, the adhesive cured product of Comparative Example 3 without SIS, and SIS are shown in Figure 6 . The white arrow (▽) in the thermogram indicates the position of T g from the rubbery component, and the black arrow (▼) indicates the position of T g from the EP resin. The values of T g are summarized in Table 4. In the specimens of the adhesive cured products containing 15 parts by mass or more of SIS, T g from the I block was found near -60 to -50 °C. It is considered that this is because the I block is incompatible with the EP resin. In the specimens containing less than 15 parts by mass of SIS, T g from the I block was not found, and it is considered that this is because the proportion of the I block in the specimen is small and the step in the thermogram could not be detected, which is well observed in the DSC measurement of the block copolymer specimen. In addition, it was found that as the content of SIS increased, T g from the I block slightly increased. It is considered that this is because the molecular mobility slightly decreased due to slightly dissolving or reacting at the interface between the I block and the EP resin, but the effect is small. T g near 150 °C from the EP resin hardly changed regardless of the content of SIS. Therefore, it is considered that the heat resistance of the adhesive due to the inclusion of SIS hardly decreases. It is considered that this is because the I block is incompatible with the EP resin, and the S block (Tg The amount (about 100 °C) is small relative to the whole, and the influence on the T of the EP resin is small. g has little impact.

[0270] As shown in Table 4, compared with Comparative Example 3 without SIS, in Examples 36 to 40 with SIS, both the impact strength and the peel strength are improved. It is considered that this is because, as described above, the S block in SIS is compatible with the EP resin, and the rubber-like polymer in SIS, that is, the I block, is incompatible with the EP resin. Since the S block in SIS is compatible with the EP resin, the I block is dispersed in the EP resin. After the EP resin is heated and cured, the I block also functions as a rubber, and the epoxy resin is toughened by the ductility, softness, and elastic modulus imparted by the I block. In addition, as seen in the TEM image of Figure 5 (a), the spherical domains of the EP resin not mixed with the S block are relatively uniformly dispersed at the level of dozens to hundreds of nm below microns, from which it is speculated that the toughening of the epoxy resin is achieved.

[0271] Here, for reference, the present inventors conducted the following experiments on the compatibility with epoxy resin.

[0272] [Reference Example 1]

[0273] In Reference Example 1, the compatibility of a hydrocarbon-based rubber-like polymer, polyisoprene (rich in 1,4 structure, number-average molecular weight 150,000, hereinafter also referred to as "PI") with a glass transition temperature of 25 °C or lower and a bisphenol A-type epoxy resin (prepolymer) (hereinafter also referred to as "EP resin") was confirmed.

[0274] PI and EP resin were weighed so that PI became 11, 43, 100, 233, and 900 parts by mass relative to 100 parts by mass of the EP resin, and a common good solvent for PI and EP resin, tetrahydrofuran (THF), was added to prepare a solution of about 10 wt%. About 1 to 2 drops of the obtained solution were dropped on a glass cover slip. The glass cover slip with the dropped solution was left standing on a hot plate at 40 °C to evaporate THF. Optical microscopy of the obtained specimen was performed (refer to Figure 3 ), and as a result, microscopic phase separation of about dozens to hundreds of μm was found in all cases, and it was confirmed that PI and EP resin are incompatible.

[0275] [Reference Example 2]

[0276] In Reference Example 2, the compatibility of polystyrene (manufactured by Polymer Source Inc., product number P41847-S, number-average molecular weight 11,000, hereinafter also referred to as "PS1") and EP resin was confirmed.

[0277] In the same manner as in Reference Example 1, mixtures were prepared such that, with respect to 100 parts by mass of the EP resin, the amounts of PS1 were 11, 43, 100, 233, and 900 parts by mass, respectively. Optical microscope observations were carried out, and the results showed uniformity in all cases, with no phase separation being found. Therefore, it was confirmed that PS1 was compatible with the EP resin.

[0278] [Reference Example 3]

[0279] In Reference Example 3, the compatibility of polystyrene (manufactured by Polymer Source Inc., product number P40440-S, number-average molecular weight 17,000, hereinafter also referred to as "PS2") and the EP resin was confirmed.

[0280] In the same manner as in Reference Example 1, mixtures were prepared such that, with respect to 100 parts by mass of the EP resin, the amounts of PS2 were 11, 43, 100, 233, and 900 parts by mass, respectively. Optical microscope observations were carried out, and the results showed uniformity in all cases, with no phase separation being found. Therefore, it was confirmed that PS2 was also compatible with the EP resin.

[0281] [Reference Example 4]

[0282] In Reference Example 4, the compatibility of polystyrene (manufactured by Polymer Source Inc., product number P1507-S, number-average molecular weight 24,000, hereinafter also referred to as "PS3") and the EP resin was confirmed.

[0283] In the same manner as in Reference Example 1, mixtures were prepared such that, with respect to 100 parts by mass of the EP resin, the amounts of PS3 were 11, 43, 100, 233, and 900 parts by mass, respectively. Optical microscope observations were carried out, and the results showed uniformity in all cases, with no phase separation being found. Therefore, it was confirmed that PS3 was also compatible with the EP resin.

[0284] [Reference Example 5]

[0285] In Reference Example 5, the compatibility of polystyrene (manufactured by Polymer Source Inc., product number P40382-S, number-average molecular weight 34,000, hereinafter also referred to as "PS4") and the EP resin was confirmed.

[0286] In the same manner as in Reference Example 1, mixtures were prepared such that, with respect to 100 parts by mass of the EP resin, the amounts of PS4 were 11, 43, 100, 233, and 900 parts by mass, respectively. Optical microscope observations were carried out, and the results showed uniformity in all cases, with no phase separation being found. Therefore, it was confirmed that PS4 was also compatible with the EP resin.

[0287] [Reference Example 6]

[0288] In Reference Example 6, the compatibility of polybutadiene (number-average molecular weight 3,000, hereinafter also referred to as "PB") and the EP resin was confirmed.

[0289] In the same manner as in Reference Example 1, mixtures were prepared such that the amount of PB was 11, 100, and 900 parts by mass relative to 100 parts by mass of the EP resin, and optical microscope observations were carried out. As a result, microphase separation of about several tens of μm was found in all cases, and it was confirmed that PB and the EP resin were incompatible.

[0290] That is, in the present embodiment, the polymer compatible with the epoxy resin in the block copolymer refers to a substance having a high affinity for the epoxy resin and being mixed without phase separation, and the hydrocarbon rubber-like polymer incompatible with the epoxy resin refers to a substance that is not mixed with the epoxy resin and undergoes phase separation.

[0291] Thus, according to a one-component thermosetting epoxy adhesive composition containing an epoxy resin, a latent curing agent, and a styrenic thermoplastic elastomer such as a polystyrene-polyisoprene-polystyrene block copolymer (SIS), a polystyrene-polyethylene-propylene-polystyrene block copolymer (SPES), a polystyrene-polybutadiene-polystyrene block copolymer (SBS), or a polystyrene-polyethylene-butene-polystyrene block copolymer (SEBS) which is a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, since the compatibility between the polystyrene part of the block copolymer and the epoxy resin is good at room temperature (ordinary temperature), the formation of false crosslinking points due to the aggregation of the polystyrene part does not occur. Thus, by utilizing the softening, ductility, and elastic modulus imparting effects generated by the isoprene part, polyethylene-propylene part, butene part, or polyethylene-butene part of the hydrocarbon rubber-like polymer, the adhesive cured product as an epoxy resin cured product is toughened. As a result, the peel strength and impact resistance are improved. Moreover, the internal stress caused by the curing shrinkage and thermal shrinkage during the curing of the adhesive can be alleviated, and in addition, the stress generated at the interface between the adhesive layer and the adherend after adhesion due to the difference in the coefficient of thermal expansion between the two can be alleviated. Therefore, the durability of the adhesive cured product can be improved.

[0292] It should be noted that the above-described examples are one-component thermosetting epoxy resin systems. If they are one-component, they do not have the problems of metering, mixing operation work, and pot life limitations of two-component mixing types, and the quality is more stable. Furthermore, they do not occupy storage and storage space.

[0293] In addition, in the above-described examples, examples of general styrenic thermoplastic elastomers were used for illustration. However, in the case of implementing the present invention, even a thermoplastic elastomer containing polyisobutylene, such as a polystyrene-polyisobutylene-polystyrene block copolymer (SIBS), can similarly toughen the epoxy resin cured product.

[0294] As described above, the epoxy adhesive composition containing a block copolymer of the above-described embodiment contains: an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin.

[0295] Therefore, according to the epoxy adhesive composition containing a block copolymer of the above-described embodiment, the high adhesiveness generated by the epoxy resin is exhibited. In addition, since the polymer compatible with the epoxy resin of the block copolymer has good compatibility with the epoxy resin, the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer are exhibited. Therefore, the toughness of the adhesive cured product can be improved, and an adhesive cured product having high peel strength, high impact resistance, and high durability can be obtained.

[0296] In particular, in the epoxy adhesive composition containing a block copolymer of the above-described embodiment, if the hydrocarbon rubber-like polymer of the block copolymer contains monomer units of isoprene, butadiene, hydrogenated isoprene, or hydrogenated butadiene, and the polymer compatible with the epoxy resin of the block copolymer contains monomer units having a styrene skeleton, a methacrylic acid skeleton, an acrylic acid skeleton, or an ether skeleton, then properties such as rubber elasticity, heat aging resistance, and weather resistance can be improved.

[0297] The styrene skeleton is represented by the chemical structural formula of -CH2-CH(C6H4R)- [R is H or an organic functional group]. For example, there are polystyrene, polystyrene-based polymers having an alkyl group with 1 to 12 carbon atoms as a substituent, polystyrene-based polymers having an ether group or an ester group as a substituent, etc. More specifically, for example, polystyrene, polyacetylstyrene, polymethylstyrene, polydimethylstyrene, polybiphenylstyrene, polyphenylacetylstyrene, polyphenylstyrene, polybromoethoxystyrene, polybromomethoxystyrene, polybromostyrene, polybutoxymethylstyrene, polytert-butylstyrene, polybutyrylstyrene, polychlorofluorostyrene, polychloromethylstyrene, polychlorostyrene, polydichlorostyrene, polyfluorostyrene, polyethoxymethylstyrene, polycyanostyrene, polyethoxystyrene, polyfluoromethylstyrene, polyfluorostyrene, polyiodostyrene, polymethoxycarbonylstyrene, polymethoxymethylstyrene, polyanisoylstyrene, polybenzoylstyrene, polymethoxystyrene, polyperfluorostyrene, polyphenoxystyrene, polypropoxystyrene, polytoluoylstyrene, polytrimethylstyrene, etc. Polystyrene is preferred.

[0298] The methacrylic acid-based backbone is represented by the chemical structural formula of -CH2-C(CH3)(COOR)- [where R is H or an organic functional group]. Examples thereof include polymethyl methacrylate, polyethyl methacrylate, polymethacrylonitrile, polyadamantyl methacrylate, polybenzyl methacrylate, poly-tert-butyl methacrylate, poly-tert-butylphenyl methacrylate, polycycloethyl methacrylate, polycyanoethyl methacrylate, polycyanomethylphenyl methacrylate, polycyanophenyl methacrylate, polycyclodecyl methacrylate, polycyclododecyl methacrylate, polycyclobutyl methacrylate, polycyclohexyl methacrylate, polycyclooctyl methacrylate, polyfluoroalkyl methacrylate, polyglycidyl methacrylate, polyisobornyl methacrylate, polyisobutyl methacrylate, poly phenyl methacrylate, polytrimethylsilyl methacrylate, polydimethylphenyl methacrylate and other polymethacrylates.

[0299] The acrylic acid-based backbone is represented by the chemical structural formula of -CH2-CH(COOR)- [where R is H or an organic functional group]. Examples thereof include polyadamantyl acrylate, poly-tert-butyl acrylate, poly-tert-butylphenyl acrylate, polycyanoheptyl acrylate, polycyanohexyl acrylate, polycyanomethyl acrylate, polycyanophenyl acrylate, polyfluoromethyl acrylate, poly(methoxycarbonylphenyl) acrylate, poly(methoxyphenyl) acrylate, polynaphthyl acrylate, pentafluorophenyl acrylate, phenyl acrylate and other polyacrylates.

[0300] The ether backbone is represented by -(CH2) n -O- [where n is a natural number from 1 to 8]. Examples thereof include poly(butoxyethylene), poly(decoxyethylene), poly(ethoxyethylene), poly(isobutoxyethylene), poly(methoxyethylene), poly(propoxyethylene) and other polyvinyl ethers.

[0301] In the polymers compatible with epoxy resin in the block copolymer having such a styrene backbone, methacrylic acid-based backbone, acrylic acid-based backbone, or ether backbone, it is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably substantially 100% by mass or more. If the styrene backbone, methacrylic acid-based backbone, acrylic acid-based backbone, or ether backbone is the main repeating unit, other monomer units may be included.

[0302] Among them, if the block copolymer is a styrene-based thermoplastic elastomer or a hydrogenated styrene-based thermoplastic elastomer, it has a low price and excellent ductility, flexibility, and elastic modulus, so that the toughness can be improved at low cost. Therefore, the peel strength and impact strength can be improved at low cost.

[0303] In addition, in the epoxy-based adhesive composition containing a block copolymer in the above-described embodiment, if the hydrocarbon rubber-like polymer of the block copolymer is contained in an amount of 0.5 parts by mass or more and 3000 parts by mass or less with respect to 100 parts by mass of the epoxy resin, the toughness can be further improved and the durability can be further enhanced. Therefore, even when applied to the bonding of different types of materials, a highly reliable bonding strength can be obtained.

[0304] Furthermore, in the epoxy-based adhesive composition containing a block copolymer in the above-described embodiment, if the content of the polymer compatible with the epoxy resin in the block copolymer is in the range of 3% by mass or more and 80% by mass or less, the compatibility with the epoxy resin can be improved and they can be uniformly mixed, and thus stable properties of the cured adhesive can be obtained.

[0305] In addition, in the epoxy-based adhesive composition containing a block copolymer in the above-described embodiment, when the number average molecular weight of the polymer compatible with the epoxy resin in the block copolymer is in the range of 1000 or more and 50000 or less, the compatibility with the epoxy resin can also be improved and they can be uniformly mixed, thereby obtaining stable properties of the cured adhesive.

[0306] In addition, in the epoxy-based adhesive composition containing a block copolymer in the above-described embodiment, if the block copolymer is blended in an amount of 0.5 parts by mass or more and 3500 parts by mass or less with respect to 100 parts by mass of the epoxy resin, good coatability and improved toughness can be achieved simultaneously.

[0307] Moreover, in the epoxy-based adhesive composition in the above-described embodiment, if the blending amount of a latent curing agent such as dicyandiamide is preferably in the range of 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the epoxy resin, the epoxy resin can be cured without impairing the coatability and water resistance.

[0308] In addition, the epoxy-based adhesive composition containing a block copolymer in the above-described embodiment contains an epoxy resin, a curing agent, and a polystyrene-polyisoprene-polystyrene block copolymer (hereinafter also referred to as "SIS") or a hydrogenated product thereof (hereinafter also referred to as "SEPS"). Therefore, according to the epoxy-based adhesive composition in the above-described embodiment, the high adhesiveness generated by the epoxy resin is exhibited, and in addition, the ductility, flexibility, and elastic modulus generated by SIS or SEPS are imparted. Therefore, the toughness of the cured adhesive can be improved, and a cured adhesive with high durability can be obtained.

[0309] That is, since the polystyrene part of SIS or SEPS is compatible with the epoxy resin, through the compatibilization of SIS or SEPS with the epoxy resin, SIS or SEPS is microdispersed in the epoxy resin. In addition, the ductility, flexibility, and elastic modulus generated by the polyisoprene part or hydrogenated polyisoprene (ethylene-propylene) part of SIS or SEPS endow toughness. Therefore, it is possible to relieve the internal stress during curing shrinkage and thermal shrinkage, and the stress generated at the interface between the adhesive layer and the adherend after bonding due to the difference in thermal expansion coefficients between the two. That is, due to the improvement in toughness caused by the addition of SIS or SEPS, the stress is dispersed, thereby increasing the bonding strength such as peel adhesion strength and impact adhesion strength. Therefore, it becomes an adhesive cured product with high toughness and durability.

[0310] In particular, if it is such SIS or SEPS, the original properties of the epoxy resin (such as adhesiveness, heat resistance, temperature characteristics, etc.) will not be impaired, and the effect of improving toughness due to the blending amount of isoprene is high. In addition, since the original heat resistance of the epoxy resin is maintained, the service temperature range is also wide. Furthermore, if it is such SIS or SEPS, its polymerization control can be achieved, and by controlling the contents of styrene and (hydrogenated) isoprene, the desired properties of ductility, flexibility, and elastic modulus can be obtained.

[0311] In addition, the epoxy-based adhesive composition containing a block copolymer in the above embodiment contains an epoxy resin, a curing agent, and a polystyrene-polybutadiene-polystyrene block copolymer (hereinafter also referred to as "SBS") or its hydride (hereinafter also referred to as "SEBS"). Therefore, according to the epoxy-based adhesive composition of the above embodiment, the high adhesiveness generated by the epoxy resin is exhibited, and in addition, the ductility, flexibility, and elastic modulus generated by SBS or SEBS are imparted. Therefore, the toughness of the adhesive cured product can be improved, and an adhesive cured product with high durability can be obtained.

[0312] That is, since the polystyrene part of SBS or SEBS is compatible with the epoxy resin, through the compatibilization of SBS or SEBS with the epoxy resin, SBS or SEBS is microdispersed in the epoxy resin. In addition, the ductility, flexibility, and elastic modulus generated by the polybutadiene part or hydrogenated polybutadiene (ethylene-butene) part of SBS or SEBS endow toughness. Therefore, it is possible to relieve the internal stress during curing shrinkage and thermal shrinkage, and the stress generated at the interface between the adhesive layer and the adherend after bonding due to the difference in thermal expansion coefficients between the two. That is, due to the improvement in toughness caused by the addition of SBS or SEBS, the stress is dispersed, thereby increasing the bonding strength such as peel adhesion strength and impact adhesion strength. Therefore, it becomes an adhesive cured product with high toughness and durability.

[0313] In particular, in the case of such SBS or SEBS, the original properties of the epoxy resin (such as adhesiveness, heat resistance, temperature characteristics, etc.) are not impaired, and the effect of improving the toughness due to the blending amount of butadiene is high. In addition, since the original heat resistance of the epoxy resin is maintained, the service temperature range is also wide. Furthermore, in the case of such SBS or SEBS, its polymerization control can be achieved, and by controlling the contents of styrene and (hydrogenated) butadiene, the desired properties of ductility, flexibility, and elastic modulus can be obtained.

[0314] The above description can also be understood as an invention of a method for manufacturing an epoxy-based adhesive composition containing a block copolymer, which is a method for manufacturing an adhesive composition containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, and includes: a mixing step of adding at least the epoxy resin and the block copolymer to a solvent for mixing; and a solvent removing step of removing the solvent.

[0315] According to the method for manufacturing an epoxy-based adhesive composition containing a block copolymer according to the above embodiment, the obtained adhesive composition contains an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, thereby exhibiting the high adhesiveness generated by the epoxy resin. In addition, the polymer of the block copolymer compatible with the epoxy resin has good compatibility with the epoxy resin, thereby exhibiting the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer. Therefore, the toughness of the adhesive cured product can be improved, and an adhesive cured product with high peel strength, high impact resistance, and high durability can be obtained. In particular, according to the method for manufacturing an epoxy-based adhesive composition according to the above embodiment, the epoxy resin and the block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin can be easily and uniformly mixed and dispersed in a short time without material deterioration, and are easy to handle.

[0316] Furthermore, the above description can also be understood as an invention of an epoxy-based adhesive cured product containing a block copolymer, which is cured from an epoxy-based adhesive composition containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin.

[0317] The cured epoxy adhesive containing a block copolymer according to the above-described embodiment contains an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, thereby exhibiting the high adhesiveness generated by the epoxy resin. In addition, the polymer compatible with the epoxy resin in the block copolymer has good compatibility with the epoxy resin, thereby exhibiting the ductility, flexibility, and elastic modulus generated by the hydrocarbon rubber-like polymer. Therefore, the toughness of the cured adhesive can be improved, resulting in a material with high peel strength, high impact resistance, and high durability.

[0318] Such an epoxy adhesive composition containing a block copolymer of the present invention can be used not only as an adhesive for structural members (e.g., organic-polymer materials such as metal materials and plastics, inorganic materials such as concrete, etc.) in the automotive, vehicle (Shinkansen, trains), civil engineering, construction, electronics, aircraft, space industry fields, etc., but also as an adhesive for medical, general office, and electronic material uses (e.g., an interlayer adhesive for substrates of electronic devices such as build-up substrates, a chip bonding agent, a semiconductor adhesive such as underfill, a bottom filler for BGA reinforcement, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), etc. for mounting). It can be applied to a wide range of fields. In addition, not limited to the use as an adhesive, as an epoxy resin composition, it can also be applied to general-purpose articles such as coatings, coating agents, molding materials (including sheets, films, FRP, etc.), insulating materials (including printed circuit boards, wire coatings, etc.), sealants (e.g., potting, impregnation, transfer molding sealing for capacitors, transistors, diodes, light-emitting diodes, ICs, LSIs, etc., encapsulation for ICs, LSIs for COB, COF, TAB, etc., bottom fillers for flip chips, sealing during installation of IC packages such as QFP, BGA, CSP, etc.).

[0319] Among them, the toughening effect generated by the incorporation of a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin makes it suitable for hemming adhesives and structural adhesives used in the hemming parts of doors, hoods, etc. of automobiles, aircraft, etc. In particular, the epoxy resin has high material strength and adhesiveness, and due to the toughening effect generated by the incorporation of the block copolymer, the cured adhesive also has high durability and impact resistance. Therefore, it is also suitable for structural adhesives that require high adhesive strength such as high peel strength. In addition, due to the improved impact resistance, an improvement in safety and a fatigue resistance effect can also be expected. Furthermore, it can also be applied to uses of composite materials used in electronic materials such as wind power generation blades, laminated plates, sealing materials, insulating materials, for industrial use, bicycles, etc.

[0320] In the case of implementing the present invention, the composition, components, compounding amounts, manufacturing methods, etc. of other parts of the epoxy-based adhesive composition are not limited to the above-described embodiments. Furthermore, regarding the numerical values listed in the embodiments and examples of the present invention, not all of them represent critical values, and a certain numerical value represents a preferred value suitable for implementation. Therefore, even if the above numerical values are changed to some extent, the implementation thereof is not denied.

Claims

1. An epoxy adhesive composition containing a block copolymer, characterized in that, It contains an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin.

2. The epoxy adhesive composition containing a block copolymer according to claim 1, characterized in that, The hydrocarbon rubber-like polymer in the block copolymer contains monomer units of isoprene, butadiene, hydrogenated isoprene, or hydrogenated butadiene. The polymer compatible with the epoxy resin in the block copolymer contains monomer units having a styrene backbone, a methacrylic acid backbone, an acrylic acid backbone, or an ether backbone.

3. The epoxy adhesive composition containing a block copolymer according to claim 1, characterized in that, The hydrocarbon rubber-like polymer in the block copolymer is contained in the range of 0.5 parts by mass or more and 3000 parts by mass or less with respect to 100 parts by mass of the epoxy resin.

4. The epoxy adhesive composition containing a block copolymer according to claim 1, characterized in that, The content of the polymer compatible with the epoxy resin in the block copolymer is in the range of 3% by mass or more and 80% by mass or less.

5. The epoxy adhesive composition containing a block copolymer according to claim 1, characterized in that The number average molecular weight of the polymer compatible with the epoxy resin in the block copolymer is in the range of 1000 or more and 50000 or less.

6. The epoxy adhesive composition containing a block copolymer according to claim 1, characterized in that, The block copolymer is compounded in the range of 0.5 parts by mass or more and 3500 parts by mass or less with respect to 100 parts by mass of the epoxy resin.

7. The epoxy adhesive composition containing a block copolymer according to claim 1, characterized in that The block copolymer is a styrene-based thermoplastic elastomer or a hydrogenated styrene-based thermoplastic elastomer.

8. An epoxy adhesive composition containing a block copolymer, characterized in that, It contains an epoxy resin, a curing agent, and a polystyrene-polyisoprene-polystyrene block copolymer or its hydride.

9. An epoxy adhesive composition containing a block copolymer, characterized in that, It contains an epoxy resin, a curing agent, and a polystyrene-polybutadiene-polystyrene block copolymer or its hydride.

10. A method for manufacturing an epoxy adhesive composition containing a block copolymer, which is a method for manufacturing an epoxy adhesive composition containing a block copolymer, the epoxy adhesive composition containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer incompatible with the epoxy resin and having a glass transition temperature of 25°C or lower and a polymer compatible with the epoxy resin, characterized in that It includes: A mixing step of at least mixing the epoxy resin and the block copolymer with a solvent; and A solvent removal step of removing the solvent.

11. The cured epoxy adhesive containing a block copolymer, characterized in that, It is cured from an epoxy-based adhesive composition containing an epoxy resin, a curing agent, and a block copolymer composed of a hydrocarbon rubber-like polymer that is incompatible with the epoxy resin and has a glass transition temperature of 25°C or lower and a polymer that is compatible with the epoxy resin.

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