JP2011225666A - Epoxy resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition, by which a uniformly-cured cured product having high reliability can be formed.SOLUTION: The epoxy resin composition comprises an epoxy resin and a curing accelerator microcapsule. The difference in specific gravity between the epoxy resin and the curing accelerator microcapsule is 0.3 or smaller.

Description

The present invention relates to an epoxy resin composition that can form a uniformly cured product with high reliability.

Epoxy resins are used in various applications such as adhesives, sealants, and coating agents. Generally, a curing agent is added to the epoxy resin as a component for causing the curing reaction to proceed, and a curing accelerator is added as a component for improving the curability. In particular, in order to make the curing agent or the curing accelerator and the epoxy resin into one liquid, a latent curing agent or curing accelerator is frequently used.

The latent curing agent or curing accelerator must have both sufficient latency that does not decrease the storage stability of the epoxy resin composition and curability that can be cured at a low temperature in a short time. Desired.
As such a latent curing agent or curing accelerator, for example, Patent Document 1 discloses a microcapsule type curing catalyst in which a material containing a curing catalyst is covered and encapsulated with an inorganic layer composed of polysilazane-derived SiO _2. Are listed. Patent Document 1 discloses that the microcapsule-type curing catalyst described in the same document can realize high storage stability regardless of the type of curing agent used, utilizing the chemical resistance, water resistance, and heat resistance of the shell. Is described.

Patent Document 2 discloses an uncured adhesive composed of a resin component, a curing agent component, and a microencapsulated accelerator component, and the microencapsulated accelerator component includes an infrared absorber, an accelerator, And uncured adhesives that consist of wall surfaces that substantially cover the entire surface of the accelerator. In Patent Document 2, the uncured adhesive described in the document can be latent at ambient temperature until it is exposed to IR energy for a short time and polymerization starts, and the necessity of two-pack type and the necessity of freezing It is described that there is no.

However, with the microcapsule-type curing catalyst described in Patent Document 1 or the microencapsulated accelerator component described in Patent Document 2, uneven curing may occur in the cured product, and the cured material is highly cured with high reliability. The problem is that things cannot be obtained.

JP 2000-186132 A JP 2004-277701 A

An object of this invention is to provide the epoxy resin composition which can form the hardened | cured material highly cured uniformly.

The present invention is an epoxy resin composition containing an epoxy resin and a curing accelerator microcapsule, wherein the specific gravity difference between the epoxy resin and the curing accelerator microcapsule is 0.3 or less It is a thing.
The present invention is described in detail below.

Conventionally, many of the curing accelerator microcapsules have a shell made of only an organic material, and when a curing accelerator having a small specific gravity is encapsulated, the specific gravity is smaller than that of the epoxy resin, and the shell is uniform in the epoxy resin composition. It was difficult to disperse. Further, due to the low dispersibility of the curing accelerator microcapsules, curing unevenness occurred in the cured product. On the other hand, the specific gravity of the curing accelerator microcapsule whose shell is made of only an inorganic material is too large compared to the epoxy resin.
In contrast, in the epoxy resin composition containing an epoxy resin and a curing accelerator microcapsule, the inventors set the specific gravity difference between the epoxy resin and the curing accelerator microcapsule to a predetermined range, It has been found that curing unevenness can be suppressed and a highly reliable cured product that is uniformly cured can be obtained, and the present invention has been completed.

The epoxy resin composition of the present invention contains an epoxy resin and a curing accelerator microcapsule.
The upper limit of the specific gravity difference between the epoxy resin and the curing accelerator microcapsule is 0.3. By setting the specific gravity difference between the epoxy resin and the curing accelerator microcapsule in such a range, the epoxy resin composition of the present invention can uniformly disperse the curing accelerator microcapsule, Curing unevenness can be suppressed, and a highly reliable cured product that is uniformly cured can be formed.

When the specific gravity difference between the epoxy resin and the curing accelerator microcapsule exceeds 0.3, the resulting epoxy resin composition cannot uniformly disperse the curing accelerator microcapsule, and is uniform. A cured product with high reliability cannot be formed.
The upper limit with a preferable specific gravity difference between the said epoxy resin and the said hardening accelerator microcapsule is 0.2, and a more preferable upper limit is 0.1.

In the epoxy resin composition of the present invention, the specific gravity between the epoxy resin and the curing accelerator microcapsule is appropriately selected by adjusting the specific gravity difference between the epoxy resin and the curing accelerator microcapsule. The difference can be in the range described above.
At this time, for example, the specific gravity of the curing accelerator microcapsule can be adjusted by appropriately selecting the material constituting the shell of the curing accelerator microcapsule and the core agent.

Although the specific gravity of the said epoxy resin is not specifically limited, A preferable minimum is 0.9 and a preferable upper limit is 1.5. If the specific gravity of the epoxy resin is less than 0.9 or exceeds 1.5, the specific gravity difference between the epoxy resin and the curing accelerator microcapsule cannot be in the above range, The obtained epoxy resin composition may not be able to form a uniformly cured product with high reliability.
The more preferable lower limit of the specific gravity of the epoxy resin is 1.1, and the more preferable upper limit is 1.3.

More specifically, examples of the epoxy resin include bisphenol A type epoxy resin, dicyclopentadiene type epoxy resin, naphthalene type epoxy resin, CTBN-modified epoxy resin, tetrahydroxyphenylethane type epoxy resin, and epoxy-containing acrylic polymer. Can be mentioned. Of these, bisphenol A type epoxy resins are preferred.

Among the above epoxy resins, commercially available products include, for example, bisphenol A type epoxy resin (specific gravity 1.17, JER828, manufactured by Japan Epoxy Resin Co., Ltd.), dicyclopentadiene type epoxy resin (specific gravity 1.19, HP-7200HH, DIC Corporation). Product), naphthalene type epoxy resin (specific gravity 1.26, EXA-4710, manufactured by DIC), CTBN-modified epoxy resin (specific gravity 1.05, EPR-4023, manufactured by ADEKA), and the like.

Although the specific gravity of the said hardening accelerator microcapsule is not specifically limited, A preferable minimum is 1.2 and a preferable upper limit is 1.5. When the specific gravity of the curing accelerator microcapsule is less than 1.2 or exceeds 1.5, the specific gravity difference between the epoxy resin and the curing accelerator microcapsule may be within the above-described range. The resulting epoxy resin composition may not be able to form a uniform cured product with high reliability.
The minimum with more preferable specific gravity of the said hardening accelerator microcapsule is 1.25, the more preferable upper limit is 1.4, Furthermore, a preferable upper limit is 1.35.

In addition, the specific gravity of the said hardening accelerator microcapsule can be calculated | required with a specific gravity measuring apparatus (AUW220D, Shimadzu Corporation Corp.) etc., for example.

Although the said hardening accelerator microcapsule is not specifically limited, The hardening accelerator microcapsule which encloses a core agent in the shell which consists of polymers is preferable.
Although the said polymer is not specifically limited, It is preferable to contain a thermoplastic polymer and an inorganic polymer.
For example, when the polymer consists only of the thermoplastic polymer, the specific gravity of the resulting curing accelerator microcapsules becomes too small, and the specific gravity difference between the epoxy resin and the curing accelerator microcapsules is within the above-described range. It may not be possible. On the other hand, the specific gravity of the obtained curing accelerator microcapsule can be adjusted by using the inorganic polymer and the thermoplastic polymer in combination, whereby the epoxy resin and the curing accelerator microcapsule can be adjusted. The specific gravity difference between them can be adjusted.

Furthermore, when the said polymer contains the said inorganic polymer, the hardening accelerator microcapsule obtained improves a solvent resistance, and even when it is a case where it mixes with a solvent, the storage stability of an epoxy resin composition improves.

The inorganic polymer is not particularly limited, and has at least one metal element selected from the group consisting of Si, Al, Zr, and Ti, having two or more alkoxy groups having 1 to 6 carbon atoms in the molecule. The polymer of the organometallic compound containing is preferable. Examples of such a polymer of an organometallic compound include silicone resins, polyborosiloxane resins, polycarbosilane resins, polysilastyrene resins, polysilazane resins, and polytitanocarbosilane resins. Among these, a silicone resin is preferable, and a silicone resin having a glycidyl group is more preferable.

The thermoplastic polymer is not particularly limited, but preferably has a hydrophilic group and a hydrophobic group. By using a thermoplastic polymer having such a hydrophilic group and a hydrophobic group, a curing accelerator microcapsule having a core-shell structure and a small aspect ratio can be obtained.
In addition, the shell ratio of the curing accelerator microcapsule becomes almost constant because the aspect ratio of the curing accelerator microcapsule is small, and in the resulting epoxy resin composition, the core agent partially oozes out during storage. Problems such as reduced storage stability and non-uniform curing and reduced reliability of the cured product can be reduced.

The said hydrophilic group is not specifically limited, For example, when using a hydrophobic imidazole compound as a core agent, a glycidyl group, a hydroxyl group, a carboxyl group, a sulfone group etc. are mentioned.

The hydrophobic group is not particularly limited, and examples thereof include a phenyl group, a methyl group, an ethyl group, a propyl group, and a methacryl group. Of these, a phenyl group is preferred.

Specific examples of the thermoplastic polymer having a hydrophilic group and a hydrophobic group include a polystyrene derivative, a polymethacrylic acid derivative, a polyacrylic acid derivative, and polyacrylonitrile. Of these, polystyrene derivatives are preferred.
The polystyrene derivative is not particularly limited as long as it has the hydrophilic group and the hydrophobic group. For example, phenyl derivative having a glycidyl group as the hydrophilic group and derived from a polystyrene skeleton as the hydrophobic group. A polystyrene derivative having a group is preferred.

When the thermoplastic polymer has a hydrophilic group and a hydrophobic group as described above, the ratio of the number of hydrophilic groups to the number of hydrophobic groups in the molecule is 0.5: 9.5-3. .5: 6.5 is preferred. If the number of hydrophilic groups in the molecule is less than the above range, the thermoplastic polymer becomes too hydrophobic, and the resulting curing accelerator microcapsules may not have a core-shell structure. When the number of hydrophilic groups in the molecule is larger than the above range, the hydrophilicity of the thermoplastic polymer becomes too large, and the aspect ratio of the resulting curing accelerator microcapsules may increase.
In the thermoplastic polymer, the ratio of the number of hydrophilic groups to the number of hydrophobic groups in the molecule is more preferably 2.0: 8.0 to 3.1: 6.9.

Further, when the thermoplastic polymer has a hydrophilic group and a hydrophobic group as described above, a curing accelerator microcapsule having a hydrophilic group on the surface can be obtained.
The curing accelerator microcapsule preferably has a hydrophilic group on the surface.

Although the weight average molecular weight of the said thermoplastic polymer is not specifically limited, A preferable minimum is 5000 and a preferable upper limit is 100,000. When the weight average molecular weight of the thermoplastic polymer is less than 5000, the heat resistance of the resulting curing accelerator microcapsule is lowered, and the epoxy resin composition starts to be cured before reaching the desired curing temperature. In addition, the solvent resistance of the resulting curing accelerator microcapsules may be reduced, and the long-term storage stability of the epoxy resin composition may be reduced. When the weight average molecular weight of the thermoplastic polymer exceeds 100,000, the precipitation rate of the thermoplastic polymer is too high when producing the curing accelerator microcapsule, and the resulting curing accelerator microcapsule has a core-shell structure. May not be possible, and the aspect ratio may increase.

When the said polymer contains the said thermoplastic polymer and the said inorganic polymer, it is preferable that the weight ratio of the compounding quantity of the said thermoplastic polymer and the compounding quantity of the said inorganic polymer is 4: 6-7: 3. If the amount of the thermoplastic polymer blended is less than the above range, the specific gravity of the resulting curing accelerator microcapsules becomes too large, and the resulting epoxy resin composition forms a uniformly cured highly reliable cured product. There are times when you can't. If the amount of the thermoplastic polymer blended is greater than the above range, the specific gravity of the resulting curing accelerator microcapsules will be too small, and the resulting epoxy resin composition will form a uniform cured product with high reliability. There are times when you can't.
As for the weight ratio of the compounding quantity of the said thermoplastic polymer, and the compounding quantity of the said inorganic polymer, it is more preferable that it is 5: 5-6: 4.

Although the said core agent will not be specifically limited if it is a hardening accelerator of the epoxy resin normally used, It is preferable that it is a hydrophobic imidazole compound.
In the present specification, the hydrophobic imidazole compound means an imidazole compound having a concentration of less than 5% by weight when dissolved in water to the maximum.

Although the said hydrophobic imidazole compound will not be specifically limited if the density | concentration when dissolved in water to the maximum is less than 5 weight%, The imidazole compound which has a C11 or more hydrocarbon group is preferable. Examples of the imidazole compound having a hydrocarbon group having 11 or more carbon atoms include 2-undecylimidazole, 2-heptadecylimidazole, 1-cyanoethylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4 -Diamino-6- [2'-undecylimidazolyl- (1 ')-ethyl-s-triazine and the like. Of these, 2-undecylimidazole is preferable.

The encapsulation rate of the core agent of the curing accelerator microcapsule is not particularly limited, but a preferred lower limit is 30% by weight and a preferred upper limit is 50% by weight. When the encapsulation rate of the core agent of the curing accelerator microcapsule is less than 30% by weight, the specific gravity of the resulting curing accelerator microcapsule becomes too large, and the resulting epoxy resin composition has a uniform cured reliability. A high cured product may not be formed. When the encapsulation rate of the core agent of the curing accelerator microcapsule exceeds 50% by weight, the specific gravity of the resulting curing accelerator microcapsule becomes too small, and the resulting epoxy resin composition is highly reliable and uniformly cured. A cured product may not be formed.
The more preferable lower limit of the encapsulation rate of the core agent of the curing accelerator microcapsule is 35% by weight, and the more preferable upper limit is 40% by weight.

Although the shell thickness of the said hardening accelerator microcapsule is not specifically limited, A preferable minimum is 0.05 micrometer and a preferable upper limit is 1.0 micrometer. If the shell thickness of the curing accelerator microcapsule is less than 0.05 μm, the retainability of the shell may be lowered. When the shell thickness of the curing accelerator microcapsule exceeds 1.0 μm, the resulting epoxy resin composition may not release the core agent even when heated depending on the temperature.
The minimum with more preferable shell thickness of the said hardening accelerator microcapsule is 0.1 micrometer, and a more preferable upper limit is 0.5 micrometer.

Although the average particle diameter of the said hardening accelerator microcapsule is not specifically limited, A preferable minimum is 0.1 micrometer and a preferable upper limit is 5.0 micrometers. When the average particle size is less than 0.1 μm, the shell thickness of the curing accelerator microcapsules may be reduced and the retention of the shell may be lowered when maintaining the inclusion ratio in the above-described range. When the average particle diameter exceeds 5.0 μm, in the obtained epoxy resin composition, after the core agent is released by heating, a large void may be generated and the reliability of the cured product may be lowered.
The more preferable lower limit of the average particle diameter of the curing accelerator microcapsules is 0.5 μm, the more preferable upper limit is 3.0 μm, and the still more preferable upper limit is 1.0 μm.

Although the aspect ratio of the said hardening accelerator microcapsule is not specifically limited, A preferable upper limit is 1.1. When the aspect ratio of the curing accelerator microcapsule exceeds 1.1, the shell thickness of the curing accelerator microcapsule is not constant, and the core agent partially oozes during storage, so that the storage stability of the epoxy resin composition is stable. In some cases, the reliability of the cured product may be reduced due to a decrease in the properties, or the curing may be uneven.
A more preferable upper limit of the aspect ratio of the curing accelerator microcapsule is 1.05.

The CV value of the particle diameter of the curing accelerator microcapsule is not particularly limited, but a preferable upper limit is 50%. When the CV value of the particle size of the curing accelerator microcapsule exceeds 50%, the core agent partially oozes during storage and the storage stability of the epoxy resin composition is lowered, or the curing becomes uneven. As a result, the reliability of the cured product may decrease.
The upper limit with more preferable CV value of the particle diameter of the said hardening accelerator microcapsule is 30%.

In the present specification, the average particle diameter, aspect ratio, and CV value of the particle diameter of the curing accelerator microcapsule mean values obtained as follows.
The curing accelerator microcapsules are observed with a scanning electron microscope at a magnification at which about 100 curing accelerator microcapsules can be observed in one field of view. The arbitrarily selected longest diameter of 50 curing accelerator microcapsules and The shortest diameter is measured using calipers. Using the longest diameter as the particle diameter, the number average value of the particle diameters is obtained, and this is used as the average particle diameter. . The aspect ratio means that the closer to 1, the closer to a true sphere. Further, the CV value of the particle diameter is represented by the following formula.
CV value (%) = (standard deviation σ of particle diameter / number average particle diameter Dn) × 100

The method for producing the curing accelerator microcapsule is not particularly limited, for example, a step of dissolving the polymer and the core agent in a solvent to prepare a mixed solution containing the polymer and the core agent; By carrying out a step of emulsifying and dispersing the mixed solution in an aqueous medium and a step of removing the solvent in the aqueous medium, a curing accelerator microcapsule encapsulating the core agent in a shell made of the polymer. The manufacturing method is preferred.

The solvent is not particularly limited as long as it can dissolve both the polymer and the core agent, and is appropriately selected according to the polymer and the core agent to be used. For example, methyl isobutyl ketone, cyclohexane and isopropyl alcohol And a mixed solvent of ethyl acetate and isopropyl alcohol, a mixed solvent of methyl ethyl ketone and isopropyl alcohol, and the like.

The aqueous medium is not particularly limited. For example, water or a mixture of water and a water-soluble organic solvent such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, 1-butanol, 2-butanol, or t-butyl alcohol. Etc.
Moreover, the said aqueous medium may contain an emulsifier as needed. The emulsifier is not particularly limited, and examples thereof include alkyl sulfate sulfonate, alkyl benzene sulfonate, alkyl sulfate triethanolamine, and polyoxyethylene alkyl ether.

The method of emulsifying and dispersing is not particularly limited. For example, the aqueous medium is dropped into the mixed solution and stirred using a homogenizer, the method of emulsifying by ultrasonic irradiation, the microchannel or the SPG membrane is used for emulsification. For example, a spraying method, and a phase inversion emulsification method.
The addition amount of the aqueous medium is not particularly limited, but a preferable lower limit with respect to 100 parts by weight of the mixed solution is 300 parts by weight, and a preferable upper limit is 1000 parts by weight.

The method for removing the solvent is not particularly limited, and examples thereof include a method for reducing pressure while heating, a method for adding a poor solvent for the polymer, and the like.
By performing the step of removing the solvent in the aqueous medium, the polymer and the core agent are phase-separated, the polymer is precipitated to form a core-shell structure, and a curing accelerator microcapsule dispersion is obtained. . Further, the curing accelerator microcapsules in the obtained curing accelerator microcapsule dispersion may be repeatedly washed with pure water and then dried by vacuum drying or the like. When the curing accelerator microcapsules thus obtained are heated to a temperature of 100 to 200 ° C. or higher, the shell is dissolved or disintegrated and the core agent can be released.

A method for producing the epoxy resin composition of the present invention is not particularly limited, and examples thereof include a method of stirring and mixing the epoxy resin and the curing accelerator microcapsule using a homodisper or the like.
At this time, for example, by appropriately selecting the epoxy resin and the curing accelerator microcapsule and adjusting the specific gravity difference between them, the specific gravity difference between the epoxy resin and the curing accelerator microcapsule is within the above-described range. It can be.

The epoxy resin composition of the present invention can uniformly disperse the above-mentioned curing accelerator microcapsules, can suppress curing unevenness, and can form uniformly cured highly reliable cured products. It is suitably used for applications. As an application of the epoxy resin composition of the present invention, for example, an adhesive or the like for joining electronic components such as a semiconductor chip or a substrate can be mentioned.

ADVANTAGE OF THE INVENTION According to this invention, the epoxy resin composition which can form the highly reliable hardened | cured material hardened | cured uniformly can be provided.

Examples of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
(1) Production of curing accelerator microcapsule 3 parts by weight of proof (G-0130S, polystyrene partially epoxy-substituted, manufactured by NOF Corporation) as a thermoplastic polymer having a hydrophilic group and a hydrophobic group, and a hydrophobic imidazole As a compound, 3.2 parts by weight of 2-undecylimidazole, and 3 parts by weight of a silicone resin (X-41-1053, alkoxy oligomer partially epoxy-substituted, manufactured by Shin-Etsu Chemical Co., Ltd.) as an inorganic polymer, ethyl acetate and isopropyl alcohol (IPA) and a mixed solvent (ethyl acetate: isopropyl alcohol (IPA) = 3: 2) were dissolved in 250 parts by weight to obtain a mixed solution. To this mixed solution, 1000 parts by weight of water containing 3% by weight of polyoxyethylene lauryl ether as an emulsifier was dropped, and the mixture was emulsified and dispersed by stirring at 3000 rpm using a homogenizer. Thereafter, the obtained dispersion was depressurized while being heated in a reactor equipped with a decompression device, and the solvent was removed to obtain a curing accelerator microcapsule dispersion. The curing accelerator microcapsules in the obtained curing accelerator microcapsule dispersion were repeatedly washed with pure water and then vacuum dried.
About the obtained hardening accelerator microcapsule, specific gravity calculated | required by measuring with a specific gravity measuring apparatus (AUW220D, Shimadzu Corporation Corp.) was 1.26.

(2) Production of Epoxy Resin Composition The obtained curing accelerator microcapsules (specific gravity 1.26) and bisphenol A type epoxy resin (specific gravity 1.17, JER828, manufactured by Japan Epoxy Resin Co., Ltd.) have a weight of 5:10. The mixture was mixed at a ratio to prepare 300 g of an epoxy resin composition.

(Example 2)
(1) Production of curing accelerator microcapsule 3 parts by weight of proof (G-0130S, polystyrene partially epoxy-substituted, manufactured by NOF Corporation) as a thermoplastic polymer having a hydrophilic group and a hydrophobic group, and a hydrophobic imidazole 1.6 parts by weight of 2-undecylimidazole as a compound, 3 parts by weight of a silicone resin (X-41-1053, alkoxy oligomer partially epoxy-substituted, manufactured by Shin-Etsu Chemical Co., Ltd.) as an inorganic polymer, ethyl acetate and isopropyl alcohol (IPA) and a mixed solvent (ethyl acetate: isopropyl alcohol (IPA) = 3: 2) were dissolved in 250 parts by weight to obtain a mixed solution. To this mixed solution, 1000 parts by weight of water containing 3% by weight of polyoxyethylene lauryl ether as an emulsifier was dropped, and the mixture was emulsified and dispersed by stirring at 3000 rpm using a homogenizer. Thereafter, the obtained dispersion was depressurized while being heated in a reactor equipped with a decompression device, and the solvent was removed to obtain a curing accelerator microcapsule dispersion. The curing accelerator microcapsules in the obtained curing accelerator microcapsule dispersion were repeatedly washed with pure water and then vacuum dried.
About the obtained hardening accelerator microcapsule, specific gravity calculated | required by measuring with a specific gravity measuring apparatus (AUW220D, Shimadzu Corporation Corp.) was 1.33.

(2) Production of Epoxy Resin Composition The obtained curing accelerator microcapsules (specific gravity 1.33) and bisphenol A type epoxy resin (specific gravity 1.17, JER828, manufactured by Japan Epoxy Resin Co., Ltd.) have a weight of 5:10. The mixture was mixed at a ratio to prepare 300 g of an epoxy resin composition.

(Comparative Example 1)
(1) Production of curing accelerator microcapsule As a thermoplastic polymer having a hydrophilic group and a hydrophobic group, 1.2 parts by weight of Marproof (G-0130S, polystyrene partially epoxy-substituted, manufactured by NOF Corporation), hydrophobic Acetic acid containing 3.2 parts by weight of 2-undecylimidazole as a reactive imidazole compound and 4.8 parts by weight of a silicone resin (X-41-1053, alkoxy oligomer partially epoxy-substituted, manufactured by Shin-Etsu Chemical Co., Ltd.) as an inorganic polymer. It was dissolved in 250 parts by weight of a mixed solvent of ethyl and isopropyl alcohol (IPA) (ethyl acetate: isopropyl alcohol (IPA) = 3: 2) to obtain a mixed solution. To this mixed solution, 1000 parts by weight of water containing 3% by weight of polyoxyethylene lauryl ether as an emulsifier was dropped, and the mixture was emulsified and dispersed by stirring at 3000 rpm using a homogenizer. Thereafter, the obtained dispersion was depressurized while being heated in a reactor equipped with a decompression device, and the solvent was removed to obtain a curing accelerator microcapsule dispersion. The curing accelerator microcapsules in the obtained curing accelerator microcapsule dispersion were repeatedly washed with pure water and then vacuum dried.
About the obtained hardening accelerator microcapsule, specific gravity calculated | required by measuring with a specific gravity measuring apparatus (AUW220D, Shimadzu Corporation Corp.) was 1.49.

(2) Production of epoxy resin composition 5:10 weight of the obtained curing accelerator microcapsule (specific gravity 1.49) and bisphenol A type epoxy resin (specific gravity 1.17, JER828, manufactured by Japan Epoxy Resin Co., Ltd.) The mixture was mixed at a ratio to prepare 300 g of an epoxy resin composition.

(Comparative Example 2)
(1) Production of curing accelerator microcapsule As a thermoplastic polymer having a hydrophilic group and a hydrophobic group, Marproof (G-0130S, polystyrene partially epoxy-substituted, manufactured by NOF Corporation), 6.0 parts by weight, hydrophobic As a functional imidazole compound, 3.2 parts by weight of 2-undecylimidazole was dissolved in 250 parts by weight of a mixed solvent of ethyl acetate and isopropyl alcohol (IPA) (ethyl acetate: isopropyl alcohol (IPA) = 3: 2). A mixed solution was obtained. To this mixed solution, 1000 parts by weight of water containing 3% by weight of polyoxyethylene lauryl ether as an emulsifier was dropped, and the mixture was emulsified and dispersed by stirring at 3000 rpm using a homogenizer. Thereafter, the obtained dispersion was depressurized while being heated in a reactor equipped with a decompression device, and the solvent was removed to obtain a curing accelerator microcapsule dispersion. The curing accelerator microcapsules in the obtained curing accelerator microcapsule dispersion were repeatedly washed with pure water and then vacuum dried.
About the obtained hardening accelerator microcapsule, specific gravity calculated | required by measuring with a specific gravity measuring apparatus (AUW220D, Shimadzu Corporation Corp.) was 0.86.

(2) Production of epoxy resin composition 5:10 weight of the obtained curing accelerator microcapsule (specific gravity 0.86) and bisphenol A type epoxy resin (specific gravity 1.17, JER828, manufactured by Japan Epoxy Resin Co., Ltd.) The mixture was mixed at a ratio to prepare 300 g of an epoxy resin composition.

(Evaluation)
The following evaluation was performed about the epoxy resin composition obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Dispersibility test of curing accelerator microcapsules After the obtained epoxy resin composition was cast on a polypropylene film, it was heated at 150 ° C. for 30 minutes and cured to obtain a film having a thickness of 10 μm. The cross section of the obtained film was divided into an upper layer of 0 to 1 μm, an intermediate layer of 5 to 6 μm, and a lower layer of 9 to 10 μm from the upper surface of the film and observed with a TEM (transmission electron microscope) at a magnification of 30,000 times.
The dispersibility of the obtained images of each layer was evaluated by counting the number of softening accelerator microcapsules.

(2) Storage Stability Test The viscosity (Pa · s) at 25 ° C. of the obtained epoxy resin composition was measured with a B-type viscometer (BM, manufactured by Haake). Thereafter, the viscosity (Pa · s) after leaving the epoxy resin composition at 40 ° C. for 10 days was measured.
The storage stability was evaluated by calculating the difference in viscosity before and after storage (40 ° C., before and after standing for 10 days).

(3) Curability test After applying the obtained epoxy resin composition to a release-treated surface of a PET film subjected to a release treatment using a bar coater and curing at 140 ° C. for 30 minutes, the PET film was peeled off and thickened. A 200 μm-thick film-shaped measurement sample was produced.
The tensile strength (kgf / cm ² ) of the obtained measurement sample is measured at a tensile speed of 5 mm / min according to JIS K-6911 using a Tensilon tester (RTC-1310A, manufactured by Orientec). Thus, curability was evaluated.

ADVANTAGE OF THE INVENTION According to this invention, the epoxy resin composition which can form the highly reliable hardened | cured material hardened | cured uniformly can be provided.

Claims (6)

An epoxy resin composition containing an epoxy resin and a curing accelerator microcapsule,
An epoxy resin composition, wherein a specific gravity difference between the epoxy resin and the curing accelerator microcapsule is 0.3 or less. The epoxy resin composition according to claim 1, wherein the specific gravity of the curing accelerator microcapsule is 1.2 to 1.5. The epoxy resin composition according to claim 1, wherein the specific gravity of the epoxy resin is 0.9 to 1.5. The epoxy resin composition according to claim 1, 2, or 3, wherein the curing accelerator microcapsule has an average particle size of 0.1 to 5.0 µm. The epoxy resin composition according to claim 1, 2, 3, or 4, wherein the curing accelerator microcapsule has a core agent encapsulation rate of 30% by weight or more. 6. The epoxy resin composition according to claim 1, wherein the curing accelerator microcapsule has a hydrophilic group on the surface.