JPH0431427A - Curing agent for spherical epoxy resin - Google Patents

Abstract

PURPOSE: To obtain the subject curing agent providing a curing compsn. high in bulk specific gravity, excellent in the dispensability to an epoxy resin and excellent in storage stability, composed of an adduct synthesized from and amine compd. and an epoxy compd. and having a spherical shape.

CONSTITUTION: The subject curing agent to be selected is an adduct synthesized from an amine compd. (e.g.; 2-methylimidazole) and an epoxy compd. (e.g.; bisphenol A diglycidyl ether) and has a spherical shape and is pref. obtained by reacting the amine compd. and the epoxy compd. in the presence of a dispersant (e.g.; methyl methacrylate/methacrylic acid copolymer obtained by the graft polymn. of methyl methacrylate) in an org. solvent (e.g.; methyl isobutyl ketone) dissolving both compds. but out dissolving the adduct.

COPYRIGHT: (C)1992,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a curing agent for epoxy resins. More specifically, it is an anionic polymerization curing agent that is synthesized from an amine compound and an epoxy compound and is solid at room temperature.
In powder form, it is not bulky, easily dispersible, and has little increase in viscosity.
The invention also relates to spherical curing agent particles for epoxy resins that provide a cured composition with excellent storage stability.

[Prior art] Cured epoxy resin has adhesive properties, mechanical properties, thermal properties,
Due to its excellent chemical resistance and electrical properties, it is widely used industrially as paints, adhesives, and electrical/electronic insulating materials. Epoxy resin formulations used for these purposes are broadly divided into one-component systems and two-component systems.

A two-component system consists of an epoxy resin compound and a curing agent or a compound thereof. They are stored separately, and the user weighs and mixes both as needed, but it is important to avoid measuring errors. However, it is often difficult in practice to always obtain a homogeneous cured composition. The reaction between the epoxy resin and the curing agent begins upon mixing. The general form of a cured epoxy resin composition is liquid, and when it comes to a cured composition in this form, the viscosity of the system gradually increases, and it undergoes gelation and hardening. The time until it gels and becomes unusable is called pot life. Pot life is determined by the chemical structure and formulation of the epoxy resin and hardener. - If a system is used for boat fishing with a fast curing speed, the pot life will be shortened. If a curing agent that focuses on curing speed is used, it is possible to cure at room temperature or at a low temperature, but this inevitably shortens the pot life and requires frequent compounding in small amounts, resulting in a significant decrease in work efficiency. It's hard to escape.

On the other hand, in one-component systems, the curing agent is pre-blended with the epoxy resin, thereby eliminating all the problems associated with two-component systems. A curing agent used for this purpose is called a latent curing agent. The simplest one-component system is obtained by incorporating a high temperature curing agent such as dicyandiamide, phenol novolak, adipic dihydrazide, diallylmelamine, diaminomaleonitrile, BF3-amine complex, amine salt, modified imidazole compound, etc. These high-temperature curing agents have a slow curing rate and the reaction at room temperature does not proceed slowly, so they can be stored stably at room temperature or lower for a certain period of time, and they cannot be cured by high-temperature heating. Enables one-component formulation that hardens.

If this is a high-temperature hardening agent that does not dissolve in the epoxy resin at room temperature and is dispersed in the form of particles, the storage stability will be significantly improved. This is obviously because the contact area with the epoxy resin becomes extremely small. In this case, the size of the curing agent particles is important; the smaller the size, the faster the curing speed, and the more uniform the cured structure of the cured product, as described in the literature [J, Appl, Polymer Sci,
32.5095 (198B)).

Such a dispersion type curing agent can also be said to be a type of latent curing agent.

A full-fledged one-component epoxy resin curing composition requires the inclusion of a latent curing agent that essentially does not react with the epoxy resin as it is, but is activated by stimulation.

Aminimide compounds activated by thermal decomposition, ketimine compounds activated by contact with moisture, aromatic diazonium salt compounds, diallyliodonium salt compounds, triallylsulfonium salts or selenium salt compounds activated by light irradiation, mechanical Examples include curing agents that are microencapsulated with materials that can be destroyed by physical pressure or heat, but due to performance and cost issues, they have not yet been widely used, and are currently being used as a bridge until they become mainstream. The dispersed latent curing agent mentioned earlier is important.

Practically superior curing agents of this type are adducts obtained by the reaction of amine compounds and epoxy compounds, so-called modified amine curing agents. Modification by adding an epoxy compound not only significantly improves the shortcomings of amine compound curing agents, such as volatility, which causes problems in handling, and hygroscopicity, which has a large effect on curing properties, but also compatibility with epoxy resins. It also becomes possible to control the melting point. Epoxy resins are cured by polyaddition reaction with a curing agent or ionic polymerization, but in such secondary processing type curing agents, which inevitably increase costs, it is possible to add a small amount without worrying about the equivalent ratio of addition. However, an ionic polymerizable curing agent that can be cured is advantageous. In terms of performance, anionic polymerization type curing agents (tertiary amine adducts) that are free from metal corrosion are preferred. Practical-F An imidazole/epoxy resin adduct is suitable for this purpose, and its technology is disclosed in detail in Pr#J 13623-1982 and JP-A-81-268721.

The solid adduct synthesized from the amine compound and the epoxy resin is conventionally obtained in the form of a lump by reacting the amine compound and the epoxy resin in a solvent and then removing the solvent from the system. Next, it is crushed and further classified to take out curing agent particles of the desired size. There are limits to crushing,
Industrially, it is extremely difficult to produce fine particles with a Stokes diameter of 3 or less.

[Problems to be Solved by the Present Invention] The above-mentioned manufacturing method has long and complicated steps, which not only results in extremely high manufacturing costs, but also limits the ability of the hardening agent particles to be made into particles by pulverization. Due to its fractured form, it has the following disadvantages.

a. It is bulky and is inconvenient for packaging and transportation.

b0 It tends to solidify, and it takes a lot of effort to disperse it into an epoxy resin during use.

A large increase in viscosity occurs when compounded into epoxy resins.

There is a limit to the improvement in curing speed by reducing the d3 particle size.

e. The stable storage period of the blended cured composition is relatively short.

For this reason, although amine compound/epoxy compound adduct particles have various excellent advantages as a curing agent, these are not fully utilized in one-component curing compositions.

[Means for Solving the Problems] The present inventors have overcome the problems associated with amine compound/epoxy compound adduct particles in the conventional technology and have developed a curing agent that can fully utilize the advantages of a one-component epoxy resin curing composition. After extensive research and development, we have finally achieved the present invention.

That is, the present invention is as follows: In the conventional addition reaction between an amine compound and an epoxy compound in an organic solvent, an organic solvent in which the amine compound and the epoxy compound are dissolved but the adduct is not dissolved is selected, and an appropriate dispersion is further carried out. coexist with a stabilizer,
By stably dispersing the produced spherical adduct particles without aggregating them, controlled spherical amine compound/epoxy compound adduct particles can be obtained in one step.

Spherical adduct particles are separated from the dispersion thus produced and dried to obtain a powder. The method of the present invention not only significantly simplifies the manufacturing process of amine compound/epoxy compound adduct particles according to the prior art, but also reduces the concentration of the amine compound and epoxy compound raw materials as raw materials.
Depending on the type and concentration of the dispersion stabilizer, reaction temperature, stirring conditions, and reaction rate, the adduct particles produced may have a diameter of 0.1 to
The desired size can be easily controlled within the range of 2°. This is probably due to the fact that fine particles of 3 ta or less, which were previously difficult to achieve, can be easily obtained, and a part of the dispersion stabilizer used is probably fixed to the particles, but the curing reactivity decreases. It is possible to obtain curing agent particles that provide a cured composition with outstanding storage stability without any
This is a major feature of the present invention over the prior art. Further, while the adduct particles of the prior art have a crushed shape as shown in the photograph of FIG. 1, those of the present invention have a nearly perfect spherical shape as shown in the photograph of FIG. All the above-mentioned drawbacks associated with adduct particles of the prior art are thereby improved.

Embodiments of the invention are as follows.

1. A curing agent for epoxy resin that is an adduct synthesized from an amine compound and an epoxy compound and has a spherical shape.

2. The curing agent for epoxy resins according to item 1 above, which has a melting point of 50°C or higher.

3. The curing agent for epoxy resins according to item 1 or 2 above, wherein the amine compound is an amine≠ compound containing at least one secondary amino group in the molecule.

4. The curing agent for epoxy resins according to any one of the above items 1 to 3, wherein the epoxy compound has an epoxy equivalent of 1000 or less.

5, 0.1~20! The first term ~ having a particle size of in.
The curing agent for epoxy resin according to any one of Item 4.

6. The amine compound and the epoxy compound are reacted in the presence of a dispersant in an organic solvent that dissolves both the amine compound and the epoxy compound, but does not dissolve the adduct formed from both, and A method of producing the spherical curing agent for epoxy resin described above.

7. The method according to item 2, item 6, wherein the produced curing agent for epoxy resin has a melting point of 50° C. or higher.

8. The method according to item 6 or 7 above, wherein the amine compound is an amino compound containing at least one secondary amine≠ group in the molecule.

9. The method according to any one of the above items 6 to 8, wherein the epoxy compound has an epoxy equivalent of 1000 or less.

10. The curing agent for epoxy resin produced is 0.1-20I
Any one of the above items 6 to 9 having a particle size of in
The method described in section.

11. The method according to any one of the above items 6 to 10, wherein the dispersant is an amphiphilic compound having a molecular weight of 1000 or more.

12. The method according to any one of items 6 to 11 above, wherein the organic solvent is a single or mixed organic solvent having a solubility parameter in the range of 8 to 11.

13. A thermosetting composition comprising the curing agent for spherical epoxy resin according to any one of items 1 to 5 above and an epoxy resin as main components.

14. A thermosetting composition comprising as main components a curing agent for spherical epoxy resin and an epoxy resin produced by the method according to any one of items 6 to 12 above.

15. A thermosetting product comprising an epoxy resin and a high-temperature curing type curing agent as the main constituents, to which the curing agent for spherical epoxy resins according to any one of items 1 to 5 above is added as an accelerator. Composition.

16. An epoxy resin and a high-temperature curing curing agent are the main components, and a curing agent for spherical epoxy resin produced by the method described in any one of items 6 to 12 above is added as an accelerator. A thermosetting composition.

The present invention will be explained in more detail below. First, an amine compound and an epoxy compound are used as raw materials, and these are selected in consideration of the properties of the adduct as a curing agent.

What is important is the chemical structure that promotes anionic polymerization curing, melting point, excellent compatibility in the molten state with the compounded epoxy resin to be cured, fast curing property, and addition effect (high curing reactivity with small addition amount). However, it is defined as the melting point here.

All types of amine compounds can be used for this purpose, but are subject to restrictions depending on the type of epoxy compound to be combined with them. This is because, in the present invention, it is necessary to avoid polymerization and limit the reaction to addition. It is possible to combine all kinds of amine compounds with monofunctional epoxy compounds, but only those with one active hydrogen that contributes to the reaction with the epoxy group can be combined with polyfunctional epoxy compounds. The only amine compounds that are not present. In either case, there is no problem at all that a tertiary amino group having no active hydrogen may be included. Rather, its presence is preferable in order to increase the concentration of amino groups that contribute to the curing reaction of the adduct, that is, to enhance the effect of addition as a curing agent. As will be described later, the most common epoxy compound is bifunctional bisphenol A diglycidyl ether. Taking this compound as an example, an example of an amine compound suitable for combination with it is 2-methyl. imidazole compounds, typified by imidazole and 2,4-dimethylimidazole;
Piperazine compounds such as N-methylpiperazine and N-hydroxyethylpiperazine, anabasine compounds such as anabasine, pyrazole compounds such as 3,5-dimethylpyrazole, purine compounds such as tetramethylguanidine and purine, These include pyrazole compounds, typified by pyrazole, and triazole compounds, typified by 1.2.4-triazole.

All kinds of epoxy compounds can be used as the other raw material. For example, monofunctional compounds include n-butyl glycidyl ether, styrene oxide, phenylglycidyl ether, and bifunctional compounds include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, and phthalic acid. diglycidyl ester, triglycidyl isocyanurate as a trifunctional compound,
Triglycidyl balaminophenol, tetrafunctional compounds such as tetraglycidyl metaxylene diamine and tetraglycidyl diaminodiphenylmethane, and compounds with higher functional groups such as cresol novolac polyglycidyl ether and phenol novolac polyglycidyl ether. However, the same restrictions as described for amine compounds are imposed depending on the type of amine compound to be combined. In other words, all types of epoxy compounds can be combined with amine compounds that have only one active hydrogen, but only monofunctional epoxy compounds can be combined with amine compounds that have two or more active hydrogens. be.

The epoxy compound is selected in consideration of the melting point of the adduct to be produced and its compatibility in the molten state (with the epoxy resin to be cured). Since the overwhelming amount of the epoxy resin to be cured is bisphenol A diglycidyl ether, this compound, which has excellent compatibility with it and is cost-effective, is suitable as an epoxy compound as a raw material for the adduct. can be commonly used. In epoxy compounds, the concentration of epoxy groups is expressed in epoxy equivalents. The lower the epoxy concentration, the higher the epoxy group concentration, but a high epoxy group concentration is desirable in order to prevent the tertiary amino group concentration of the f4 adduct from decreasing as much as possible.

Therefore, it is desired that the epoxy equivalent of the epoxy compound be as small as possible. Usually, an epoxy compound having a molecular weight of 1,000 or less, preferably 500 or less is used.

The melting point of the amine compound/epoxy compound adduct is determined by the chemical structure of the amine compound and the epoxy resin, as well as the mode of addition, the structure of the adduct, and the addition ratio of the epoxy resin to the amine compound. By appropriately selecting them, it becomes possible to synthesize adducts with a low melting point to a high melting point depending on the purpose. The higher the zero melting point, the easier it is to handle, but on the contrary, the curing reaction initiation temperature of the formulation becomes higher.

Therefore, from the viewpoint of curability, the melting point is not bad, but when considering ease of handling, especially in the summer, a melting point of at least 50° C. is required.

It is important to select a solvent that dissolves the amine compound and epoxy compound as raw materials, but does not dissolve the addition product and precipitates it as particles. - When going fishing on a boat, substances dissolve in solvents with similar polarities.

The polarity of a solvent is determined by its solubility parameter (unit = (ca
1, /ca) 1/2), but if the general solubility range is shown according to this display method, the epoxy compound: 8 to 11. Ami≠compound: 8 or more, amine compound/
Epoxy compound adduct=11 to 16. Therefore, in order to carry out the intended precipitation reaction of the present invention, a solvent having a solubility parameter of 8 to 11 is suitable. Examples of solvents used in the practice of the present invention include methyl isobutyl ketone, methyl isopropyl ketone, methyl ethyl ketone, acetone, acetic acid, n-butyl acetate, isobutyl acetate, ethyl acetate, methyl acetate, tetrahydrofuran, 1,4-dioxane, Examples include cellosolve, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, anisole, toluene, p-xylene, benzene, methylene chloride, chloroform, trichloroethylene, chlorobenzene, and pyridine. They can be used alone or in combination of two or more. Even if the solvent has a solubility parameter outside the range of 8 to 11, it is possible to adjust the solubility parameter to within the specified range by combining two or more kinds of solvents and use them. However, since the exact solubility parameters of a compatible solvent naturally vary somewhat depending on the chemical structure of the amine compound and the epoxy compound, it is important to select them strictly depending on the individual case. If the selection is not strict, even if the precipitation reaction proceeds smoothly, the resulting adduct may have a high solubility in the solvent, resulting in a low yield.

A dispersion stabilizer stably disperses adduct particles precipitated in a precipitation reaction in a solvent. If it is not present, the produced adduct particles will solidify during the reaction, making it impossible to obtain the desired spherical particles. As a dispersion stabilizer for this purpose, an amphiphilic polymer compound having high affinity for both the produced adduct and the organic solvent is suitable. In terms of chemical structure, graft copolymers, block copolymers, random copolymers, and other polymers all meet the qualification requirements. Examples of graft copolymers:
Methyl methacrylate graft copolymerized with styrene/
Methacrylic acid copolymer, methyl methacrylate/2-hydroxyethyl methacrylate copolymer, poly 2-hydroxy methacrylate, poly 2,3-dihydroxypropyl methacrylate, polyacrylamide-2-methylpropanesulfonic acid, polyvinyl alcohol, polyvinyl acetate, Methyl methacrylate/methacrylic acid copolymer obtained by graft copolymerizing polymethacrylic acid, polyacrylamide, polyethylene oxide, poly4-vinyl ethylpyridium bromide, and methyl methacrylate,
Glycidyl methacrylate/styrene copolymer and methyl methacrylate/fluoroalkyl acrylate copolymer, polybutadiene and methyl methacrylate/glycidyl methacrylate copolymer grafted with methacrylic acid, polymethyl methacrylate grafted with N-methylol acrylamide, and 2 -Hydroxyethyl methacrylate copolymer, 12-Polymethyl methacrylate graft copolymerized with hydroxystearic acid, ethyl acrylate/methacrylic acid copolymer, methyl acrylate/methacrylic acid copolymer, and styrene/methacrylic acid copolymer, 2- Examples include polymethyl methacrylate, which is a graft copolymer of hydroxyethyl methacrylate, and polyvinyl chloride, which is a graft copolymer of ethylene oxide.

Examples of block copolymers are: polylauryl methacrylate/polymethacrylic acid block copolymers, polystyrene/polymethacrylic acid block copolymers, polyethylene oxide/polystyrene/polyethylene oxide block copolymers and poly12-hydroxystearic acid. /polyethylene glycol/poly12-hydroxystearic acid, etc. Examples of random copolymers include: vinyl acetate/vinyl alcohol copolymer, vinyl acetate/N-vinylpyrrolidone copolymer, and N-vinylpyrrolidone/methyl methacrylate.

Examples of other polymers include cationized amine-modified polyesters. The stabilizing effect increases as the molecular weight of the dispersion stabilizer increases; however, if the molecular weight is increased beyond the limit, the aggregation effect gradually becomes stronger, resulting in the opposite effect.

Therefore, the molecular weight of the dispersion stabilizer that meets the purpose of the present invention is from i,ooo to 200,000, preferably 2.0.
A range of 00 to 1.00,000 is suitable. As mentioned above, there are many types of dispersion stabilizers, but their effects naturally vary depending on the chemical structure of the amine compound/epoxy compound. In practice, trial-and-error selection is required.

When the selected amine compound and epoxy compound are dissolved in the selected solvent and the selected dispersion stabilizer is further dissolved and heated with stirring, the initially transparent solution becomes opaque as adducts form. become.

As the reaction progresses, the opacity of the system gradually increases, and the system begins to exhibit a cloudy white appearance characteristic of dispersions. The reaction stops when stirring is stopped at an appropriate point and the mixture is cooled. By filtering only the particles from the obtained amine compound/epoxy compound adduct particle dispersion, washing off unreacted raw materials adhering to the particles with fresh solvent, and drying, the desired spherical curing agent particles can be obtained. .

In the reaction for producing adduct particles, what is important is the smooth progression of the reaction without producing coagulation and control of the size of the particles produced. First, the reaction is stable, and this is controlled by the raw material concentration, reaction temperature, dispersion stabilizer concentration, stirring conditions, and reaction rate.

What is important is the dispersion stabilizer, and in order to produce a stable dispersion, the amount added is usually 5 to 40%, preferably 10% to the total of the amine compound and epoxy compound.
~30% is required. Even if sufficient dispersion stabilizer is present, coagulation tends to occur as the reaction temperature and raw material concentration increase. Therefore, the reaction temperature is usually 40 to 9
0°C, preferably 50-70°C is used. In addition, the raw material concentration in the solvent is usually 2 to 40%, preferably 5 to 30%.
shall be.

The formation of coagulated material is further related to stirring conditions and reaction rate.

Appropriate stirring speeds vary depending on the formulation, reaction conditions, and shape of the stirring blade, so it cannot be generalized, but stirring that is too fast will promote the formation of agglomerates, and stirring that is too slow is not suitable for obtaining spherical particles. . Trial-and-error decisions are required for each individual system. Depending on the reaction conditions,
In general, the higher the reaction rate, the less likely a coagulated substance is to be formed. As mentioned above, as the reaction temperature and raw material concentration become higher, as the concentration of the dispersion stabilizer becomes lower, and as the size of the adduct particles to be produced becomes smaller, a coagulated product starts to be produced at a lower reaction rate.

Although it is possible to achieve a 100% reaction rate by adjusting the conditions, it is generally more efficient to stop the reaction at a lower reaction rate.

The ratio of the amine compound to the epoxy compound is basically the equivalent ratio of the active hydrogen concentration of the amine compound to the epoxy group concentration, but in the case of a system where the reaction rate does not reach 100%, it is necessary to stick to the equivalent ratio. There isn't. This is because the raw materials recovered from the reaction system can be reused as they are. Combine the filtrate and washing liquid, accurately measure the concentrations of amine compounds, epoxy compounds, and dispersion stabilizers contained therein, remove excess solvent, and fill in the missing raw materials for the initial formulation. Almost the same reaction results are obtained. Therefore, if the raw materials are recovered and reused, it is possible to use an excessive amount of either raw material depending on the structure of the adduct.

The size of the adduct particles produced is determined by the type of raw materials, reaction conditions, and type and amount of dispersion stabilizer added. Of these factors, the type of dispersion stabilizer is decisive. For example, in the precipitation reaction of 2-methylimidazole and bisphenol A diglycidyl ether in methyl isobutyl ketone, a methyl acrylate/methacrylic acid copolymer dispersant graft-copolymerized with styrene or methyl methacrylate gives a micron-sized particle size. In contrast, cationized amine-modified polyester gives submicron fine particles. The next major influence is the reaction conditions; generally speaking, the higher the raw material concentration, dispersion stabilizer concentration, reaction temperature, and reaction rate, and the slower the stirring speed, the larger the particles produced.

Compared to these factors, the influence of the type of raw material is relatively small.

A more detailed explanation will be given below using comparative examples and examples.

Comparative Example 1 600 g of xylene and 300 g of 2-methylimidazole were charged into a 3,000 m1 round-bottomed three-bottle flask equipped with a thermometer, a reflux condenser, and a stainless steel propeller-type stirrer, and heated to 120° C. with stirring. The mixture was heated to completely dissolve 2-methylimidazole (2Mz). Next, while continuing to stir, a solution of 680 g of epoxy J118B bisphenol A diglycidyl ether (Epicote 828, manufactured by Yuka Shell Co., Ltd.) dissolved in 300 g of xylene was added over 90 minutes while maintaining the temperature at 120°C. . Since the adduct produced was insoluble in xylene, it precipitated as a viscous candy as the reaction progressed. The reaction was continued for another 2 hours, and after confirming that the reaction rate had reached 98% or more using the epoxy group analysis method described in Example 4, the temperature was lowered to room temperature.

After stopping the stirring and decanting the upper layer of xylene, the contents of the flask were heated to 140°C and the residual xylene was distilled off under reduced pressure of 110 mm1. It was poured into a dish and cooled to obtain a reddish-brown adduct mass. This was repeatedly ground with a jet mill and finally classified to obtain particles with a Stokes diameter of 2.9. The particle shape is shown in Figure 1. Shown as an electron micrograph.

In this way, the 2Mz/epoxy resin adduct curing agent particles produced by the conventional method (pulverization method) were blended into Epikote 828,
The properties of the cured composition were measured. The curing composition was prepared according to the following procedure: 100 parts by weight of Epikote 828 and 1 part by weight.
0 parts by weight (10 phr) of 2Mz/Epikote 828 adduct particles were added and briefly milled, followed by a three roll mill to completely disperse the curing agent particles. As is well known, fine particles require considerable mechanical grinding for complete dispersion because, in a dry state, original primary particles coagulate to form secondary particles. The dispersion state was checked with a crush gauge each time it passed through the three-roll mill. It was passed through a roll mill at a rate of 120 g/min, but three passes were required to completely disperse the curative particles under these milling conditions.

For the cured compositions prepared, gelation time (measured by stroke cure method) as a guide to viscosity and curing speed.
was measured. Separately, a cured product was created by curing at 120°C for 30 minutes, and the Tg, tensile properties, and water resistance (water absorption rate when immersed in boiling water for 6 hours) as a guide for heat resistance.
was measured. The results are shown in Table 1 in comparison with Examples.

Example 1 In a 5,000 m1 round-bottom three-bottle flask equipped with a thermometer, reflux condenser, and glass half-moon stirrer, two
．． 750 g of methyl isobutyl ketone (MIBK) was charged, 160 g of 2Mz (1,94 equivalents) was added thereto, and the temperature was raised to 60° C. to completely dissolve it. Next, as a dispersion stabilizer, a 30% MIBK solution of a methyl methacrylate/methacrylic acid copolymer dispersion stabilizer prepared by graft copolymerizing methyl methacrylate (manufactured by Toagosei Co., Ltd., GC-
Add 425g of 10M) and then add 5 of Epicoat 828.
700 g (1.88 eq.) of 0% MIBK solution was added. Adduct raw material concentration 812.6%, total raw material concentration: 15.
8%, amount of dispersion stabilizer added to adduct raw material = 25%.

The contents were reacted at 60° C. for 8 hours while stirring at a speed of 40 rpm. The initially transparent reaction system gradually became bluish and translucent, but at the end of the reaction it turned milky and opaque. After reaction for a predetermined period of time, the mixture was cooled to room temperature and left to stand day and night to precipitate the generated particles.

- decanting the supernatant and then filtering off the particles;
Thoroughly washed with MIBK. Further, vacuum drying was performed at 40° C. for 24 hours to obtain 268 g of white curing agent particles. The particle size was measured for the MIBK dispersion immediately after the reaction was completed using a laser particle size analyzer manufactured by Jinu Denshi, LPA 3000/
Measured at 3100. The average particle diameter was 2.5 μs.

As clarified in the example of recovery and reuse of unreacted raw materials described in Example 4, a part of the dispersion stabilizer used for particle generation is fixed to the particles and is not recovered. Some of it probably reacts with the epoxy groups and is chemically fixed to the particles, and some of it is fixed by adsorption, but when the amount was determined for the four particle generation experiments in Example 4, it was found that it was consumed. On average, it is 40% based on the adduct raw material. Based on this value, of the 268 g of curing agent particles obtained in this example, the generated adduct was 190 g and the fixed dispersion stabilizer was 78 g. Therefore, the reaction rate is 37%
If the dispersion stabilizer is also considered as a raw material for the produced particles, the particle yield will be 42%.

In this example, the reaction was stopped at a reaction rate of 37%, but it was preliminarily confirmed that if the reaction was allowed to proceed any further, a coagulated product would be formed. Also used here is 40
The stirring speed of 0 rpm was determined in preliminary experiments; if the stirring speed was higher than this, a coagulate would form before the reaction rate reached 37%, and if the stirring speed was lower than this, completely spherical adduct particles would be formed. It has been confirmed that it does not occur.

The shape of the particles is shown in FIG. 2 as an electron micrograph, and they are almost perfectly spherical. Table 1 compares the bulk density with that of crushed particles of approximately the same size produced by the conventional method.Since spherical particles can be packed compactly, the bulk density is almost twice that of crushed particles. has reached. This promises compact packaging and transport convenience.

The thus produced spherical particle curing agent was blended with Epicote 828 in exactly the same manner as described in the comparative example to prepare a cured composition. However, the dispersion of curing agent particles by a three-roll mill is much easier than in the comparative example, with only one pass compared to the three passes required in the comparative example.
Complete dispersion was achieved in one pass. The properties of the cured composition are shown in Table 1.

Even with only 1 Ophr of the outgoing particles, the temperature at 20°C is 13
．． The viscosity of 800 cps Epicote 828 was 42.00.
0 cps, whereas the spherical curing agent particles of Example 1 only provide an increase of 27,000 cps. Differences are also seen in gelation rate and storage stability. Although the curing speed of the curing agent particles of the present invention is somewhat slower than that of the curing agent particles of the conventional method, the storage stability is much superior, and the stable storage period of Comparative Example 1 is 8 weeks compared to 1 week. It's so long that it doesn't.

Whereas the curing agent particles of conventional methods are chemically pure,
In the curing agent particles of the present invention, a dispersion stabilizer is probably fixed at the interface thereof, and the above-mentioned difference probably occurs due to its function. No particular difference was observed in the color, physical properties, and water resistance (water absorption) of the cured products.

Although it is presumed that the fixation of the dispersion stabilizer contributes to improving storage stability, there is a concern that in return, the curability and the physical properties, heat resistance, and water resistance of the cured product may deteriorate. However, this embodiment completely eliminates such concerns.

Example 2 Into the same reactor as in Example 1, 3.400 g of M
IBK was charged, 115 g of 2Mz (lJg equivalent) was added thereto, and the temperature was raised to 50°C to completely dissolve.

Next, methyl methacrylate was graft copolymerized as a dispersion stabilizer. 25 g of methyl ethyl ketone/butyl acetate solution (Toagosei Co., Ltd., GC-10) 146 g of methyl methacrylate/methacrylic acid copolymer dispersion stabilizer was added, and then 50 g of Epicote 828 was added. % MIBK solution 5
00g (4 equivalents of IJ) was added.

Adduct raw material concentration = 8.8%, total raw material concentration [: 9.7%, amount of dispersion stabilizer added to adduct raw material: 10.0%.

This was reacted at 50° C. for 24 hours with stirring. After the reaction was completed, 81 g of white dry curing agent particles were obtained in the same manner as in Example 1. The resulting particles were completely spherical and had a diameter of 0.21
It was μm. When calculated using the same criteria as in Example], the reaction rate is 16% and the particle yield is 20%.

The obtained curing agent particles had a small size (the bulk density was significantly reduced as shown in Table 1), but the dispersibility was particularly high in the preparation of a curing composition in which 10 phr was blended with Epikote 828. There was no tendency for the dispersion to decrease, and a complete dispersion state was obtained after passing through the three-roll mill once.

Properties of the cured composition are shown in Table 1 in comparison with Comparative Examples and other Examples. Compared to Example 1, the reduced particle size increases the viscosity of the cured composition and significantly increases the cure rate. On the other hand, the storage stability is lowered by the increased curing speed, but the level is much higher than that of the comparative example. Furthermore, the properties of the cured product are also affected by the reduction in the size of the curing agent particles. The color of the cured product was the same as in Example 1 (reddish brown and translucent), but the heat resistance, tensile strength and elongation, and water resistance were slightly improved.

Example 3 Into the reactor described in Example 1, 2.750 g of MIBK was added.
195g of N-methylbiperazine (N
MPz) (1,94 eq.) was added and the temperature was raised to 60° C. to completely dissolve. Next, G C-1 was used as a dispersion stabilizer.
Add 425g of 0M, then 50g of Epicote 828
700 g of % MIBK solution (1,88 equifIk) was added. Adduct raw material concentration: 13.4%, total raw material concentration: 16
．． 5%, amount of dispersion stabilizer added to adduct raw material: 23
．． 4%. This was reacted at 60° C. for 14 hours while stirring at 400 rpm. After the reaction was completed, the spherical curing agent particles produced in the same manner as in Example 1 were collected and obtained as white dry particles. The obtained particles weighed 174 g and had a particle size of 0.
551Xn, and the bulk specific gravity was 0.26. Calculated using the same criteria as Example 1, reaction rate: 23%, particle yield:
This will be 26%.

A cured composition was prepared by blending 10 phr of the curing agent particles obtained here with Epikote 828 in the same manner as in the comparative example. The dispersibility was the same as in Examples 1 and 2;
Complete dispersion was obtained after three passes through the three-roll mill.

The properties of the cured composition are shown in Table 1 in comparison with Comparative Examples and other Examples.

Compared to 2Mz/Epicote 828 adduct curing agent, 1
Curing speed at 20°C is fast < Curing speed at 140°C is slow. On the other hand, storage stability is 2Mz/Epicote 828
Considerably superior to adduct hardeners.

When comparing the properties of the cured product with the 2Mz/Epicote 828 adduct curing agent, the most significant difference is seen in its appearance. Unlike the reddish-brown translucent color of the latter, the NMPz/Epicote 828 adduct hardener particles gave a pale yellow transparent cured product. Although there are no major differences in heat resistance, tensile strength, elongation, and water absorption, the NMPz/Epicote 828 adduct curing agent particles have slightly lower tensile strength but higher elongation, and are slightly better in heat resistance and water resistance. It gave an inferior cured product.

Example 4 In Examples 1 to 3, the reactions were all interrupted at a low reaction rate of 50% or less. From an industrial standpoint, it is naturally desirable to recover and reuse unreacted raw materials. To do this, the concentration of the raw materials in the recovered filtrate and washing solution must be accurately quantified, unnecessary solvents removed, and the original reaction composition readjusted, and then the same adduct as in the first reaction produced. It is desirable to obtain particles. If this is possible, the raw material can be converted into adduct particles without waste by repeating the process. Examples thereof are shown below.

Into the reactor described in Example 1, 2,750 g of MIBK was added.
160 g of 22Mz was added thereto, and the temperature was raised to 60°C to completely dissolve it. Next, 425 g of GC-10M was added as a dispersion stabilizer, and then 700 g of a 50% MIBK solution of Epicote 828 was added. Adduct raw material concentration: 12.6%, total raw material concentration: 15.8%,
Addition of dispersion stabilizer ffl to adduct raw material: 25%.

This was reacted at 60° C. for 8 hours while stirring with 400 rl In.

After the reaction was completed, the particles produced were collected in the same manner as in Example 1 to obtain white dry particles.

The filtrate and washing solution after removing the particles were combined, and the concentrations of 2Mz, Epicote 828, and dispersion stabilizer contained therein were measured. The measurement method was as follows. 2Mz concentration in the presence of epoxy resin: After adding glacial acetic acid and crystal violet to the sample solution, 0.1N perchloric acid/
Determined by titration with acetic acid solution. Epoxy resin concentration in the presence of 2Mz: Determined by opening the epoxy group with hydrochloric acid and titrating the excess hydrochloric acid potentiometrically with a silver nitrate solution. Dispersion stabilizer concentration: Measured by GPC. Determined from the peak area ratio using standard polystyrene as an internal standard and a proportionality constant determined in advance. The measurement results are shown in Table 2 as recovery rates for the raw materials. Unfortunately, because the measurement accuracy is not high enough, it is not possible to obtain the recovery rate as expected in theory. However, as will be described later, even this level of accuracy can be used without any practical problems.

The combined filtrate and washing liquid were concentrated in vacuo to 2.500 g and subjected to the second reaction. 2Mz, Epicote 8
28 and GC-], OM was added, the initial formulation was readjusted, and the mixture was reacted under the same conditions for 6 hours.

This reaction time was different from the first time because the course of the reaction was somewhat different and signs of coagulation were observed in appearance at this reaction time. A third reaction and then a fourth reaction was performed using the same procedure. The results are summarized in Table 2. As the reaction progresses, some differences occur in the course of the reaction, but adduct particles of approximately the same size are obtained without any problems.

/ Table 2 Reaction temperature Reaction time Particle yield Reaction rate Particle yield Particle diameter ('C) (hr) (g) (%) (%) 0 lessons) Unreacted recovered raw material Mz Epicote 828 GC-C-1 O% )61°9 72.5 55.8 71.6
(%) 50.9 57.6 43.2 6
0.3(%) 23.6 30.3 37.9
39.2 Curability and storage stability Gel time (see, 120°C) In Table 2, the recovery rate of Epikote 828 was always 2Mz
It has reached only about 80% of the total. The amount of preparation is 9 of 2Mz
7%, but this relative recovery is considerably lower. On the other hand, the recovery rate of the dispersion stabilizer would have to reach nearly 100% if it were not fixed to the particles. These clearly suggest consumption of some epoxy groups by the dispersion stabilizer and possibly resulting chemical fixation of the dispersion stabilizer onto the particles. Others may be fixed by adsorption. A trial calculation of the amount of dispersion stabilizer immobilized on the particles shows considerable variation, but on average it reaches 40% of the adduct produced.

One ophr of the adduct particles obtained in the same manner as in Example 1 was added to Epikote 828 to prepare a cured composition.

The properties are shown in Table 2, and there is no major difference in curability and storage stability. The above results indicate that the recovered unreacted raw materials can be recovered and reused without any problem.

[Effects of the Invention] By the precipitation reaction method of the present invention, amine compound/epoxy compound adduct particles as a curing agent for epoxy resin can be produced with significantly fewer steps than the conventional pulverization method. . In addition, the particles produced are spherical, which is highly suitable as a curing agent, and the size reaches submicrons, which is impossible with conventional methods. In addition to this, due to the amphiphilic compound added for the purpose of imparting dispersion stability, the latent curability of the resulting curing agent particles is much superior to that of conventional methods.

The spherical morphology offers a variety of advantages to the curing agent itself or to the curing composition in which it is incorporated, including:

a. Large bulk specific gravity. This property reduces packaging volume and contributes to lower packaging and transportation costs.

b. Easier dispersion when blending into epoxy resin.

This greatly simplifies the manufacturing process of the cured composition.

C. The increase in viscosity of the compound is small when blended with epoxy resin. In blending epoxy resins with relatively high viscosity, blending raw materials with a small tendency to increase viscosity are highly desirable, and greatly contribute to expanding the degree of freedom in blending design.

The fine curing agent particles also provide the following advantages to the curing compositions in which they are incorporated.

d. Faster curing speed, giving a more homogeneous cured structure.

e. Expanding the range of application of the cured composition. In conventional cured compositions containing large curing agent particles, the curing agent particles are often filtered out when injected through a narrow slit, resulting in poor curing of the cured composition. Concerns are dispelled.

Finally, the improved latent curability naturally provides a cured composition that can be stored stably for a long time.

In a one-component cured composition, it goes without saying that it is important to extend the shelf life without impairing curability.

The spherical curing agent particles of the present invention function as a latent anionic polymerization type curing agent when used alone, and when used in combination with other high temperature curable polyaddition type curing agents, such as dicyandiamide and acid anhydride, they can be used to harden them. It acts effectively as a potential accelerator to effectively lower the temperature. Taking advantage of this property, the spherical curing agent particles of the present invention can be used in a wide range of fields to provide component epoxy resin curing compositions. Examples include structural adhesives: adhesives for heavy vehicle assembly, optical machinery assembly adhesives, electronic/electrical equipment assembly adhesives, etc., paints: powder coatings, baking paints, etc., electronics: niblint wiring boards, etc. Glass cloth impregnated materials, IC chip encapsulants, conductive paints, solder resists, die bonding adhesives, printed circuit board adhesives, conductive adhesives, etc. Electrical field: electrical insulation materials, coil impregnated materials, battery case adhesives , tape head adhesive etc.

[Brief explanation of the drawing]

FIG. 1 is an electron micrograph showing the structure of amine compound/epoxy compound adduct particles produced by a conventional pulverization method. FIG. 2 is an electron micrograph showing the structure of amine compound/epoxy compound adduct particles produced by the method of the present invention. (4 other people) 1st figure

Claims (1)

[Claims] 1. A curing agent for epoxy resin which is an adduct synthesized from an amine compound and an epoxy compound and has a spherical shape. 2. The amine compound and the epoxy compound are reacted in the presence of a dispersant in an organic solvent that dissolves both the amine compound and the epoxy compound, but does not dissolve the adduct formed from both, according to claim 1. A method for producing a spherical curing agent for epoxy resin. 3. A thermosetting composition comprising the curing agent for spherical epoxy resin according to claim 1 and an epoxy resin as main components. 4. A thermosetting composition comprising an epoxy resin and a high-temperature curing agent as main components, to which the curing agent for spherical epoxy resin according to claim 1 is added as an accelerator.