JPH04266922A - Epoxy resin composition and semicured material prepared from the same composition - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin composition by dissolving an epoxy resin and a specific curing agent in a solvent in the presence of an organic carboxylic acid, preservable and transportable in B-stage state prepared by removing solvent. CONSTITUTION:(A) An epoxy resin consisting essentially of a solid epoxy resin having preferably 130-4,000 epoxy equivalent as a main agent component and (B) 2-phenyl-4-benzyl-5-hydroxymethylimidazole as a curing agent component are dissolved in a solvent which is preferably methyl cellosolve, N,N- dimethylformamide and/or dimethyl sulfoxide in the presence of (C) an organic carboxylic acid to give an epoxy resin composition providing a cured material by heating. The solvent is removed from this composition to give a semicured material in B-stage.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to a latent curing epoxy resin composition having 2-phenyl-4-benzyl-5-hydroxymethylimidazole as a curing agent component, and in particular,
Either as a solution or impregnated into prepreg, etc.
The present invention relates to an epoxy resin composition that can be stored and transported in a B-stage state after removing the solvent and that can be cured by heating, and a semi-cured material using the same.

0002

[Background technology] Epoxy resin has excellent electrical properties, adhesive properties, chemical resistance, water resistance, and heat resistance, and is also easy to handle before curing, so it is used in paints, adhesives, sealants, insulating varnishes, potting It is used as a thermosetting resin in a wide range of fields, including materials, sealants, composite materials, and printed circuit boards.

Epoxy resin can be used as a thermosetting resin for the first time by mixing it with a curing agent and reacting it.
Furthermore, since the reaction rate and the physical properties of the cured product change depending on the type of curing agent used, the development of curing agents has been actively conducted.

Among the curing agents, anionic polymerization type curing agents are:
Tertiary amines have been known for some time and have been commonly used because they exhibit good adhesion to epoxy resins in relatively small amounts, but they have the disadvantage of poor heat resistance. Subsequently, imidazole derivatives were developed as compounds that cure using the same mechanism as above, and their heat resistance was also significantly improved.

[0005] Imidazole is a 5-membered heterocyclic compound having two nitrogen atoms, one nitrogen atom being a secondary amine and the other being a tertiary amine, but it is possible to introduce a substituent into the ring. A large number of derivatives can be synthesized.

Although imidazole derivatives can generally cure epoxy resins at relatively low temperatures and in a short time compared to other curing agents, the pot life after mixing with epoxy resins is relatively short. It has the characteristic of being long. If this property is greatly enhanced, a so-called one-component epoxy resin composition can be obtained. That is, even if an epoxy resin and a curing agent are mixed, it is possible to create a system that hardly reacts and is stable at room temperature, but rapidly hardens when heated.

[0007] Curing agents used for this purpose are called latent curing agents, and some imidazole derivatives satisfy the conditions as latent curing agents.
Phenyl-4-benzyl-5-hydroxymethylimidazole is a typical example. This compound was added to a general liquid bisphenol A type epoxy resin (epoxy equivalent: 185
~195), although the one-component composition containing 5 to 15 PHR has a pot life of over 1 year at room temperature.
It is said that gelation can be achieved in 4 to 10 minutes when heated to 150°C.

[0008]

Problems to be Solved by the Invention Depending on the intended use, epoxy resin compositions are often used with a solvent added thereto. For example, there are film or sheet adhesives produced by coating or impregnating an adherend or base material and then volatilizing a solvent, prepregs for printed circuit boards, prepregs for composite materials, and the like. These need to be transported and worked in a so-called B-stage state in which the solvent has been volatilized, and it is naturally desirable that they can be stored in a B-stage state for a long period of time.

However, 2-phenyl-4-benzyl-
Even though 5-hydroxymethylimidazole was intended to be used as a curing agent for epoxy resins for the above-mentioned purpose due to its excellent latent curability, it could not be used until now because it hardly dissolves in a suitable solvent.

[0010] That is, the solvents used in epoxy resin compositions containing solvents are those that have a high dissolving power, are inexpensive, and have a relatively low boiling point. Specifically, hydrocarbon solvents such as benzene, toluene and xylene, alcohol solvents such as methanol, ethanol, propanol and butanol, methyl ethyl ketone, isobutyl ketone,
Ketone solvents such as cyclohexanone, ester solvents such as ethyl acetate and isoamyl acetate, cellosolve solvents such as methyl cellosolve and ethyl cellosolve, and other N,N-
Examples include solvents such as dimethylformamide and dioxane.

However, 2-phenyl-4-benzyl-5
-Hydroxymethylimidazole is included in the above solvent system.
It was not possible to prepare an epoxy resin composition containing a solvent because it essentially did not dissolve at all or only slightly dissolved at room temperature.

0012

[Means for Solving the Problems] As a result of intensive studies to eliminate such drawbacks, the inventors have discovered that 2-phenyl-4-benzyl-5-hydroxymethylimidazole, in coexistence with a certain organic carboxylic acid, We discovered that 2-phenyl-4-benzyl-5-hydroxymethylimidazole dissolves in solvents, and applied this to dissolve 2-phenyl-4-benzyl-5-hydroxymethylimidazole in epoxy resin compositions containing solvents, making it a latent curing type. The present invention was realized based on the finding that the method can be applied as a method.

That is, the present invention contains an epoxy resin as a main component, 2-phenyl-4-benzyl-5-hydroxymethylimidazole as a curing agent component, and the curing agent component is dissolved in a solvent in the presence of an organic carboxylic acid. An epoxy resin composition is provided.

[0014] Here, the epoxy resin is mainly composed of a solid epoxy resin having an epoxy equivalent of 130 to 4000 (g/eq), and the solvent is methyl cellosolve, ethyl cellosolve, N,N-dimethylformamide. The epoxy resin composition is preferably at least one selected from the group consisting of and dimethyl sulfoxide.

[0015] Furthermore, the above-mentioned 2-phenyl-4-benzyl-
An epoxy resin composition in which 5-hydroxymethylimidazole is 300/E to 3800/E per 100 g of the epoxy resin in relation to the epoxy equivalent E (g/eq) of the epoxy resin, the compatibilizer is 2-phenyl-
An epoxy resin composition containing 0.5 to 3 moles per mole of 4-benzyl-5-hydroxymethylimidazole is preferred.

The present invention provides a semi-cured material in which an epoxy resin composition is used as it is or is impregnated with a reinforcing material, and at least a portion of the solvent is removed to bring the composition into a B-stage state.

The present invention will be explained in detail below. In the composition of the present invention, the epoxy resin used is a compound containing two or more epoxy groups in one molecule. As such epoxy resins, for example, the following are used.

Bisphenol A, 2,2-bis(4-hydroxyphenylbutane) (bisphenol B), 1,
1'-bis(4-hydroxyphenyl)ethane (sometimes abbreviated as bisphenol AD), bis(4-hydroxyphenyl)methane (bisphenol F), 1,1
, 2,2-tetrakis(4-hydroxyphenyl)ethane, 4-hydroxyphenyl ether, and glycidyl ether-based epoxy resins of polyphenol compounds such as P-(4-hydroxy)phenol. A glycidyl ether-based epoxy resin of a nuclear hydride of the polyphenol compound.

Catechol, resorcinol, hydroquinone,
Glycidyl ether-based epoxy resin of polyhydric phenols such as phloroglucin. Glycidyl ether-based epoxy resin of polyhydric alcohols such as ethylene glycol, butanediol, glycerol, erythritol, and polyoxyalkylene glycol. Novolac type epoxy resin. Vinyl cyclohexene dioxide, limonene dioxide,
Alicyclic epoxy resins such as dicyclopentadiene oxide.

[0020] A polyglycidyl ester type epoxy resin which is an ester condensation product of polycarboxylic acids such as phthalic acid and cyclohexane-1,2-dicarboxylic acid. Polyglycidylamine-based epoxy resin. Methyl epicro type epoxy resin.

In the present invention, the above-mentioned epoxy resins are used alone or in combination, but it is usually preferable that the epoxy resin be in a tack-free or tacky solid state in the B-stage state. Contains mainly mold epoxy resin. The solid epoxy resin preferably has an epoxy equivalent of 130 to 4000 (g/eq).

Furthermore, the main component is not only an epoxy resin, but also an oligomer other than an epoxy resin that is soluble in a solvent in order to improve the fluidity of the B-stage state and the flexibility, adhesiveness, and impact resistance of the cured product. It can also be used in combination with polymers. Specifically, acrylic rubber, acrylic elastomer, nitrile rubber, carboxylated nitrile rubber or oligomer, butyral resin, phenoxy resin,
Examples include silicone oligomers, nylon, and polyester.

[0023] In addition, adjustment of fluidity and tackiness in the B-stage state, reduction of linear expansion coefficient of cured product, thermal conductivity,
Fillers can be added for the purpose of improving flame retardancy, adhesiveness, electrical properties, etc. Fillers used include silica, alumina, aluminum hydroxide, talc, calcium carbonate, barium sulfate, aluminum silicate, glass powder, iron powder, aluminum powder, zinc white, asbestos, antimony trioxide, and titanium dioxide, depending on the purpose. etc. can be mentioned.

The solvent used in the composition of the present invention is not particularly limited as long as it can dissolve 2-phenyl-4-benzyl-5-hydroxymethylimidazole in coexistence with a certain organic carboxylic acid. The solvent is preferably one with relatively high polarity, specifically a protic solvent such as methyl cellosolve, ethyl cellosolve, or N,N-
Mention may be made of aprotic solvents such as dimethylformamide and dimethylsulfoxide. These solvents can be used alone or in combination of two or more.

Preferred solvents include methyl cellosolve, ethyl cellosolve, and N,N-dimethylformamide. Energy required for heating when dissolving 2-phenyl-4-benzyl-5-hydroxymethylimidazole in a solvent together with an epoxy resin in the presence of an organic carboxylic acid and scattering the solvent in a drying oven when B-staged. It is preferable that the boiling point of the solvent be relatively low in order to minimize the amount of water, remove the solvent as fully as possible, suppress the curing reaction of the epoxy resin as much as possible, and prevent heat damage to the base material.

The curing agent used in the composition of the present invention is 2-phenyl-4-benzyl-5-hydroxymethylimidazole, and 2-phenyl-4-benzyl-5-hydroxymethylimidazole accelerates the curing of dicyandiamide. When preparing an epoxy resin composition containing a solvent using dicyandiamide as a curing agent, it is necessary to use a solvent containing dicyandiamide/2-phenyl-4-benzyl-5-hydroxymethylimidazole/organic carboxylic acid. It is also possible to use compositions as curing agent components.

The structural factors of the organic carboxylic acid present in the composition of the present invention in order to dissolve 2-phenyl-4-benzyl-5-hydroxymethylimidazole in a solvent are quite complex. 2-phenyl-4-benzyl-5-hydroxymethylimidazole is a basic compound,
Since organic carboxylic acids are acids, it is certain that they form salts and act as compatibilizers, but due to slight differences in the structure of carboxylic acids, 2-phenyl-4-benzyl-5-
The ability to dissolve hydroxymethylimidazole is so different that it cannot simply be argued.

[0028] The inventors investigated organic monocarboxylic acids, which are relatively easily available, and organic pentacarboxylic acids, and found an organic carboxylic acid that can dissolve 2-phenyl-4-benzyl-5-hydroxymethylimidazole in a solvent. confirmed. Differences in solubility based on structural differences of organic carboxylic acids when N,N-dimethylformamide is used as a solvent will be outlined below.

(1) Organic monocarboxylic acids: a) Among aliphatic organic carboxylic acids, pyruvic acid, 2-ketobutanoic acid,
Cyanoacetic acid, trifluoroacetic acid, etc. are 2-phenyl-4
Although effective in dissolving 2-phenyl-4-benzyl-5-hydroxymethylimidazole, acetic acid, butyric acid, acrylic acid, etc. did not dissolve 2-phenyl-4-benzyl-5-hydroxymethylimidazole.

b) Among aromatic organic carboxylic acids, salicylic acid, o-nitrobenzoic acid, o-cyanobenzoic acid, etc.
2-phenyl-4-benzyl-5-hydroxymethylimidazole was sufficiently dissolved, but benzoic acid, o-toluic acid, gallic acid, p-hydroxybenzoic acid, picolinic acid, etc. were not dissolved.

(2) Organic dicarboxylic acids a) Among the aliphatic organic dicarboxylic acids, oxalic acid, malonic acid, ±-tartaric acid, etc. are 2-phenyl-4-benzyl-5-
Hydroxymethylimidazole was dissolved, but succinic acid and glutaric acid were not dissolved. Furthermore, although both maleic acid and fumaric acid were dissolved, maleic acid was superior as a compatibilizer.

b) Among aromatic organic dicarboxylic acids, when comparing the structural isomers phthalic acid, isophthalic acid, and terephthalic acid, phthalic acid is particularly superior. Terephthalic acid was also dissolved, but not isophthalic acid. Incidentally, cyclohexyl phthalic acid (cis, trans mixture), which is a hydrogenated product of phthalic acid, was not dissolved. Also 2,6
- Dicarboxynaphthalic acid was also not dissolved.

(3) Organic tricarboxylic acid Among aliphatic organic carboxylic acids, citric acid is 2-phenyl-4-benzyl-
It had the effect of dissolving 5-hydroxymethylimidazole. On the other hand, structural isomers of aromatic organic tricarboxylic acids, trimellitic acid, trimesic acid, and hemimellitic acid, each had the effect of dissolving 2-phenyl-4-benzyl-5-hydroxymethylimidazole;
Trimellitic acid was particularly good.

(4) As other tetracarboxylic acids, pyromellitic acid and as pentacarboxylic acids, benzenepentacarboxylic acid were investigated, but neither of them had the effect of dissolving 2-phenyl-4-benzyl-5-hydroxymethylimidazole. there were.

From the above experimental facts, the following organic carboxylic acids can be used in the present invention. As the aliphatic monovalent carboxylic acid, a carboxylic acid represented by the following formula (a) or (b) can be used.

[0036]

[Chemical formula 14] However, R1 is a hydrogen atom, a straight chain or branched alkyl group having 1 to 6 carbon atoms, an aryl group, an alkoxy group having a straight chain or branched alkyl group having 1 to 4 carbon atoms, or an acetyl group. represents. Formula (b) CX3 COOH However, X represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a cyano group, or a nitro group, and out of three X, at most two hydrogen atoms are present. As the aromatic monovalent carboxylic acid, a carboxylic acid represented by the following formula (c) can be used.

[0037]

[Chemical formula 15] However, Y is a nitro group, a hydroxyl group, a sulfonic acid group, or a cyano group, and one or two of R2 and R3 are a hydrogen atom, a halogen atom, or a linear or branched chain having 1 to 3 carbon atoms. Represents an alkyl group.

For organic dicarboxylic acids, the following formulas (d) to
Dicarboxylic acids represented by (k) and compound group (p) can be used.

[0039]

embedded image However, one or two of R4 and R5 represent a hydrogen atom, a linear or branched alkyl group having 1 to 3 carbon atoms, an aryl group, or a halogen atom.

[0040]

embedded image However, one or two of R6 and R7 represent a hydrogen atom, a halogen atom, a methyl group or an ethyl group.

[0041]

embedded image However, one or two of R8 and R9 represent a hydrogen atom, an aryl group, a straight or branched alkyl group having 1 to 6 carbon atoms, an allyl group, or a benzyl group.

[0042]

embedded image However, R10, R11, R12 and R13 are the same or different and each independently represents a hydrogen atom, a halogen atom, an aryl group, a hydroxyl group, a nitro group, a cyano group, or a linear or Represents a branched alkyl group.

[0043]

embedded image However, one or two of R14 and R15 represent a hydrogen atom, a halogen atom, a nitro group or a cyano group.

[0044]

embedded image where n represents an integer of 1 to 4, R16 and R17
One or two of them represent a hydrogen atom, a methyl group, an ethyl group or an aryl group.

[0045]

embedded image However, R18, R19 and R20 are the same or different and each independently represents a hydrogen atom, a methyl group, an ethyl group or an aryl group.

[0046]

embedded image However, one or two of R21 and R22 represent a hydrogen atom, a methyl group, an ethyl group, or an aryl group. It may also be an optical isomer of formula (k) or a mixture thereof. (p) oxalic acid, acetylene dicarboxylic acid and 2,3
-Dicarboxynaphthalic acid.

As the organic trivalent carboxylic acid, carboxylic acids represented by the following formulas (q) and (r) can be used.

[0048]

embedded image However, R23, R24 and R25 are the same or different and each independently represents a hydrogen atom, a halogen atom, a straight or branched alkyl group having 1 to 3 carbon atoms, an aryl group, a cyano group, a hydroxyl group, or Represents an ester group having a straight chain or branched alkyl group having 1 to 6 carbon atoms.

[0049]

embedded image However, R26, R27, R28 and R29 are the same or different and each independently represents a hydrogen atom, a hydroxyl group, a straight or branched alkyl group having 1 to 3 carbon atoms, or an aryl group.

As other polyhydric carboxylic acids, carboxylic acids represented by formula (s) and compound group (t) can be used.

[0051]

embedded image However, one or two of R30 and R31 are a hydrogen atom, a carboxyl group, a halogen atom, a straight chain or branched alkyl group having 1 to 3 carbon atoms, or a straight chain or branched alkyl group having 1 to 6 carbon atoms. Represents an ester group with a chain or branched alkyl group. (t) Cis- or trans-aconitic acid, 5,5'-carbonylbistrimellitic acid, 3,3',4,4'-benzophenonetetracarboxylic acid and 2',3,4-benzophenonetricarboxylic acid.

The effect of the organic carboxylic acid in dissolving 2-phenyl-4-benzyl-5-hydroxymethylimidazole in a solvent differs slightly depending on the solvent used. For example, when the solvent is methyl cellosolve, the organic carboxylic acids that particularly effectively dissolve 2-phenyl-4-benzyl-5-hydroxymethylimidazole are acetylene dicarboxylic acid, maleic acid, trimellitic acid,
2-ketobutanoic acid, pyruvic acid, etc. The solvent is N,
In the case of N-dimethylformamide, in addition to the above-mentioned carboxylic acids, phthalic acid, salicylic acid, oxalic acid, etc. are particularly effective. Furthermore, when the solvent is dimethyl sulfoxide, pyromellitic acid is particularly effective in addition to the above-mentioned carboxylic acids, excluding 2-ketobutanoic acid.

The mixing ratio of 2-phenyl-4-benzyl-5-hydroxymethylimidazole and organic carboxylic acid during dissolution is as follows: Effective from about 0.5 mol, 1.0 to 2
．． At 0 mol, 2-phenyl-4-benzyl-5-hydroxymethylimidazole becomes sufficiently soluble in the solvent. The purpose of adding organic carboxylic acid is to dissolve 2-phenyl-4-benzyl-5-hydroxymethylimidazole in the solvent, so there is no point in adding a large amount, and adding a large amount will cause the cured product to deteriorate. Since it may impair physical properties, 2-phenyl-4-benzyl-
The amount of organic carboxylic acid added as a compatibilizer per 1.0 mol of 5-hydroxymethylimidazole is 0.5 to 3.
It is used in an amount of 0 mol, preferably in a range of 0.75 to 2.2 mol.

[0054] The method for preparing the epoxy resin composition of the present invention involves mixing the above-described main component, curing agent component, organic carboxylic acid, and solvent by any method.

The semi-cured material of the present invention can be obtained in a B-stage (semi-cured) state by heating the epoxy resin composition prepared as described above, preferably at 80° C. or higher and 150° C. or lower. The shape of the semi-cured material can be made into any shape, and these shapes include film, plate,
Examples include a block shape, a curved shape, and an irregularly shaped shape.

The semi-cured material can be formed directly on the surface of the object to be adhered, but it may also be formed on release paper, release film, release sheet material, etc.

To prepare a prepreg, the epoxy resin composition of the present invention is impregnated into glass fiber, carbon fiber, Kevlar (trade name), polyester fiber, etc., and heated at 80°C or higher for 15 minutes.
It is dried at 0° C. or lower to obtain a B-stage state.

The semi-cured material obtained in the B-stage state is suitable for transportation and storage, and when used it is brought into contact with the adherend, preferably at 100°C.
Pressure bonding is carried out at the above temperature and under pressure of 1 to 50 kg/cm2.

[0059]

[Examples] The present invention will be explained in detail with reference to Examples below, but the present invention is not limited thereto. (Preliminary experiment) In a 100cm3 Erlenmeyer flask with a stopper, N
, 30.00 g of N-dimethylformamide and a rotor were added, and while stirring at 25 to 26°C, 2-phenyl-4-benzyl-5-hydroxymethylimidazole (Shikoku Kasei Product Curazol 2P4BHz, hereinafter referred to as 2P4BHz) was added.
) was added in 0.10 g portions to examine the solubility. The total amount up to 0.80 g was completely dissolved, but when the amount was 0.90 g, it was not completely dissolved even after stirring for more than 1 hour.

(Experimental Examples 1 to 7) Based on the results of preliminary experiments, monovalent organic carboxylic acids were added in the amounts shown in Table 1 under the same conditions, and the amount of 2P4BHZ dissolved was investigated. 2P
4BHZ 1.00g or more was judged to be effective, but effective monovalent organic carboxylic acid
I found a type. The results are shown in Table 1.

[0061]

[Table 1]

(Comparative Experimental Examples 1 to 19) In the same manner as Experimental Examples 1 to 7, 1.00 g of 2P4BHZ was
Table 2 shows the monovalent organic carboxylic acids that could not be dissolved even when added at a molar ratio of 2.00 to 2.0.

[0063]

[Table 2]

(Experimental Examples 8 to 29) In the same manner as Experimental Examples 1 to 7, divalent organic carboxylic acids that were able to dissolve 1.00 g or more of 2P4BHZ are shown in Table 3 together with the amount of 2P4BHZ dissolved.

[0065]

[Table 3]

[Table 4]

(Comparative Experimental Examples 20 to 27) Table 4 shows divalent organic carboxylic acids that could not dissolve 1.00 g of 2P4BHZ in the same manner as in Experimental Examples 1 to 7.

[0067]

[Table 5]

(Experimental Examples 30 to 35) Table 5 shows trivalent or higher organic carboxylic acids that were able to dissolve 1.00 g or more of 2P4BHZ and their amounts added in the same manner as in Experimental Examples 1 to 7. .

[0069]

[Table 6]

Examples of epoxy resin compositions using these compatibilizers are shown below. (Example 1, adhesive) Tertiary copolymer rubber (butadiene/
A solid bis A type epoxy resin (epoxy equivalent: 450-500, softening point: 6) is added to a solution in which 340.0 g of acrylonitrile/acrylic acid = 68/28/4, Mooney viscosity: 46) is dissolved in 1,660.0 g of methyl ethyl ketone.
4-74℃) 600.0g, orthocresol novolak type epoxy resin (epoxy equivalent 210-230, softening point 80-90℃) 125.0g, liquid bis A-type epoxy resin (epoxy equivalent 185-190, viscosity 130-14
5p (25°C)) 75.0g and 20g of fine fused silica
0.0g was added and dissolved. Subsequently, this solution was thoroughly stirred with a homomixer to obtain a main ingredient.

[0071] 30.0 g of the curing agent component shown in Table 6 was mixed with 300.0 g of this main component to prepare an adhesive solution. Apply the adhesive solution prepared by the above method onto a Teflon sheet using a film applicator until the thickness of the adhesive is 40 μm.
It was applied so that the thickness was m. This was dried in a 130° C. oven for 4 minutes to prepare a B-stage adhesive film material.

[0072] Aluminum manufactured by Japan Test Panel Industry Co., Ltd. (JIS H4000 (A1050p), 0.5 m
mt x 25 mm x 300 mm) with #240 sandpaper and degreased with acetone, the adhesive film cut into strips with a width of 25 mm was sandwiched between the two aluminum plates. 10 heated to 150℃
Cured for 1 hour using a ton press (press pressure 20Kgf/c)
m2), after preparing a test piece, the T-peel adhesive strength was measured according to JIS6854-1979. Further, for the purpose of examining storage stability, the adhesive film was left at 40° C. for 20 days, and then test beads were prepared again, and the T-peel strength was measured. The results are shown in Table 6.

(Example 2, electrical laminate) Brominated epoxy resin having bisphenol and tetrabromobisphenol skeletons (epoxy equivalent: 438, bromine content: 19.1w)
t%) 500.0g, methyl ethyl ketone 173.0
A solution (viscosity: 630 cps (25° C.)) was prepared by dissolving it in g and used as a main ingredient. Subsequently, the curing agent components shown in Table 7 were prepared and mixed with the main component to prepare an impregnating varnish.

[0074] Electrical glass cloth treated with epoxy silane was impregnated with the above varnish and dried in an oven at 140°C for 4 minutes to obtain a B-stage prepreg. 9 sheets of this prepreg are stacked on top of each other, and the top and bottom are further 35 μm thick.
Layer electrolytic copper foil and heat at 170℃ for 40~ with a 37 ton press.
After pressing for 45 seconds, it was cured for 30 minutes at a press pressure of 10 kg/cm2. The resin impregnation rate of the completed laminate was 35 wt%,
The thickness was 1.6 mm. This laminate is JIS C
6484-1976, and the results are shown in Table 8.

[0075]

[0076]

[0077]

Effects of the Invention The epoxy resin composition of the present invention is prepared as a solution containing an epoxy resin and 2-phenyl-4-benzyl-5-hydroxymethylimidazole as a latent curing agent in the presence of an organic carboxylic acid. As a result, it can be stored as it is or impregnated with a reinforcing material, the solvent is volatilized to make it B-stage, and it can be stored or transported for a long period of time as a semi-cured material.

The obtained semi-cured material has strong adhesion to metal substrates and other resin substrates as a film or prepreg, and has high heat resistance. The composition of the present invention can be widely used in adhesives, prepregs for electrical circuit laminates, prepregs for C/C composites, and the like.

Claims (7)

[Claims] Claim 1: An epoxy resin comprising an epoxy resin as a base component and 2-phenyl-4-benzyl-5-hydroxymethylimidazole as a curing agent component dissolved in a solvent in the presence of an organic carboxylic acid. Composition. 2. The organic carboxylic acid is as shown below (
The epoxy resin composition according to claim 1, which is at least one organic carboxylic acid selected from the group consisting of 1) to (3). (1) Organic monovalent carboxylic acids represented by the following formulas (a) to (c). [Formula 1] However, R1 is a hydrogen atom, a straight chain or branched alkyl group having 1 to 6 carbon atoms, an aryl group, an alkoxy group having a straight chain or branched alkyl group having 1 to 4 carbon atoms, or an acetyl group. represents. Formula (b) CX3 COOH However, X represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a cyano group, or a nitro group, and out of three X, at most two hydrogen atoms are present. [Formula 2] However, Y is a nitro group, a hydroxyl group, a sulfonic acid group, or a cyano group, and one or two of R2 and R3 are hydrogen atoms, halogen atoms, or linear or branched chains having 1 to 3 carbon atoms. represents an alkyl group. (2) Organic divalent carboxylic acids represented by the following formulas (d) to (k) and compound group (p). embedded image However, one or two of R4 and R5 represent a hydrogen atom, a linear or branched alkyl group having 1 to 3 carbon atoms, an aryl group, or a halogen atom. embedded image However, one or two of R6 and R7 represent a hydrogen atom, a halogen atom, a methyl group or an ethyl group. embedded image However, one or two of R8 and R9 represent a hydrogen atom, an aryl group, a linear or branched alkyl group having 1 to 6 carbon atoms, an allyl group, or a benzyl group. embedded image However, R10, R11, R12 and R13 are the same or different and each independently represents a hydrogen atom, a halogen atom, an aryl group, a hydroxyl group, a nitro group, a cyano group, or a linear or Represents a branched alkyl group. embedded image However, one or two of R14 and R15 represent a hydrogen atom, a halogen atom, a nitro group or a cyano group. [Image Omitted] However, n represents an integer of 1 to 4, and R16 and R17
One or two of them represent a hydrogen atom, a methyl group, an ethyl group or an aryl group. embedded image However, R18, R19 and R20 are the same or different and each independently represents a hydrogen atom, a methyl group, an ethyl group or an aryl group. embedded image However, one or two of R21 and R22 represent a hydrogen atom, a methyl group, an ethyl group, or an aryl group. It may also be an optical isomer of formula (k) or a mixture thereof. (p) oxalic acid, acetylene dicarboxylic acid and 2,3
-Dicarboxynaphthalic acid. (3) Trivalent or higher organic polyhydric carboxylic acids represented by the following formulas (q) to (s) and compound group (t). embedded image However, R23, R24 and R25 are the same or different and each independently represents a hydrogen atom, a halogen atom, a straight or branched alkyl group having 1 to 3 carbon atoms, an aryl group, a cyano group, a hydroxyl group, or Represents an ester group having a straight chain or branched alkyl group having 1 to 6 carbon atoms. embedded image However, R26, R27, R28 and R29 are the same or different and each independently represents a hydrogen atom, a hydroxyl group, a straight or branched alkyl group having 1 to 3 carbon atoms, or an aryl group. embedded image However, one or two of R30 and R31 is a hydrogen atom, a carboxyl group, a halogen atom, a straight or branched alkyl group having 1 to 3 carbon atoms, or a straight chain or branched alkyl group having 1 to 6 carbon atoms. Represents an ester group with a chain or branched alkyl group. (t) cis- or trans-aconitic acid, 5,5'-carbonylbistrimellitic acid, 3,3',4,4'-benzophenonetetracarboxylic acid and 2',3,4-benzophenonetricarboxylic acid. 3. The epoxy resin has an epoxy equivalent of 1
The epoxy resin composition according to claim 1 or 2, which has a solid epoxy resin of 30 to 4000 (g/eq) as a main component. 4. The epoxy resin composition according to claim 1, wherein the solvent is at least one selected from the group consisting of methyl cellosolve, ethyl cellosolve, N,N-dimethylformamide, and dimethyl sulfoxide. . 5. The 2-phenyl-4-benzyl-5
The epoxy according to any one of claims 1 to 4, wherein -hydroxymethylimidazole is 300/E to 3800/E per 100 g of the epoxy resin in relation to the epoxy equivalent E (g/eq) of the epoxy resin. Resin composition. 6. The compatibilizer is 2-phenyl-4-
The epoxy resin composition according to any one of claims 1 to 5, wherein the amount is 0.5 to 3 mol per mol of benzyl-5-hydroxymethylimidazole. 7. The epoxy resin composition according to any one of claims 1 to 6 is used as it is or is impregnated into a reinforcing material, and at least a part of the solvent is removed to make the composition B.
- A semi-cured material characterized by being in a staged state.