JP2013014697A - Microcapsule-type latent curing agent, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microcapsule-type latent curing agent whose curing temperature is set high irrespective of thermal characteristics of the curing agent itself, and to provide a method for producing the same.SOLUTION: The microcapsule-type latent curing agent includes a porous inorganic microparticle, a curing agent for an epoxy resin impregnated inside the porous inorganic microparticle, and a cured film of the epoxy resin formed on the surface of the porous inorganic microparticle by reaction of the curing agent with an epoxy resin prepolymer. The microcapsule-type latent curing agent is preferably used for a single-component epoxy resin composition and the like.

Description

  The present invention relates to a microcapsule type latent curing agent.

  Epoxy resins have cured materials with excellent mechanical properties, electrical properties, thermal properties, chemical resistance, adhesiveness, etc., paints, electrical and electronic insulation materials, civil engineering and building materials, adhesion It is widely used for agents and sealants. Currently, the epoxy resin composition generally used is a so-called two-component type in which two components of an epoxy resin and a curing agent are mixed at the time of use.

  Since the two-pack type epoxy resin composition stores the epoxy resin and the curing agent separately, it is difficult to cure during storage and has excellent storage stability. However, since the epoxy resin and the curing agent are stored separately, it is necessary to weigh and mix both the epoxy resin and the curing agent each time they are used, and handling is very complicated. Furthermore, when an epoxy resin and a curing agent are mixed, the epoxy resin is easily cured, so that the usable time is limited and it is necessary to use it quickly. Therefore, even if it is a necessary amount, if the amount is large, it takes time to use up and cannot be mixed in advance. Thus, the two-pack type epoxy resin composition must frequently mix the two liquids, and the working efficiency is also lowered.

Since a two-pack type epoxy resin composition has the above problems, a one-pack type epoxy resin composition has been proposed in recent years. This one-pack type epoxy resin composition is obtained by adding a curing agent such as dicyandiamide, BF ₃ -amine complex, amine salt, and modified imidazole compound to the epoxy resin. However, this one-pack type epoxy resin composition has poor storage stability, and the epoxy resin may be cured even at about room temperature. For this reason, for example, it must be stored in a low temperature environment of −20 ° C. or lower.

  From the viewpoint of enhancing the storage stability of a one-pack type epoxy resin composition, a so-called latent curing agent has been proposed that suppresses the curing of the epoxy resin in a room temperature environment by increasing the curing temperature of the epoxy resin. ing. For example, Patent Document 1 contains an epoxy resin, a novolac-type phenol resin curing agent, and a microcapsule in which a curing accelerator is enclosed in a shell made of a cured epoxy resin having an elution temperature of 100 to 150 ° C. An epoxy resin composition for semiconductor encapsulation is disclosed. In Patent Document 2, as a method for producing a microcapsule-type epoxy resin curing agent, an amine-based curing agent and an epoxy resin are reacted on the surface of the core made of the epoxy resin curing agent. A method for forming a shell is described. In Non-Patent Document 1, an S / O (solid in oil) dispersion is prepared by pulverizing and stirring a curing accelerator in an epoxy resin solution, and then an interfacial reaction with the epoxy resin is performed on the imidazole particle surface. A method for microencapsulating a cure accelerator by performing is described.

JP-A-1-242616 JP 2007-204669 A

“Microencapsulation of epoxy resin curing accelerator by interfacial curing reaction method”, “Journal of the Adhesion Society of Japan”, 2006, Vol. 42, no. 7, pages 272-279

  The latent curing agents described in Patent Documents 1 and 2 and Non-Patent Document 1 have good storage stability at room temperature. However, the epoxy resin is cured by heating to about 100 to 140 ° C. For this reason, it is not suitable for uses that require a higher curing temperature for the epoxy resin. For example, in the solder paste flux, the epoxy resin cures faster than the solder metal powder melts, so that the solder metal powder is sufficiently melted before the epoxy resin begins to cure. Designed not to be too much. Accordingly, the curing agent used for the solder paste flux may require a high curing temperature exceeding 180 ° C., for example.

  In addition, as a conventional latent curing agent, one having a curing temperature in a high temperature region of 170 ° C. or higher, such as dicyandiamide, is known. However, the physical properties of the epoxy resin after curing are greatly affected by the combination of the epoxy resin main agent used and the curing agent. Therefore, rather than relying on the thermal properties of the curing agent itself, the curing temperature of the latent curing agent is a combination of the epoxy resin main agent and the curing agent by setting the curing temperature high regardless of the type of curing agent. There is a need to increase the degree of freedom.

  An object of the present invention is to provide a microcapsule-type latent curing agent having a high curing temperature regardless of the thermal characteristics of the curing agent itself used, and a method for producing the same. Another object of the present invention is to provide an epoxy resin composition having excellent storage stability and a high curing temperature regardless of the thermal characteristics of the curing agent used.

As a result of intensive studies to solve the above problems, the present inventors have found a solution means having the following configuration, and have completed the present invention.
(1) porous inorganic fine particles;
A curing agent for epoxy resin impregnated inside the porous inorganic fine particles;
A cured film of an epoxy resin formed on the surface of the porous inorganic fine particles by a reaction between the curing agent and the epoxy resin prepolymer;
A microcapsule type latent curing agent comprising:
(2) impregnating the inside of the porous inorganic fine particles with a curing agent for epoxy resin;
The porous inorganic fine particles impregnated with the curing agent are brought into contact with the epoxy resin prepolymer, and the curing agent and the epoxy resin prepolymer are bonded at the interface between the porous inorganic fine particles and the epoxy resin prepolymer. Forming a cured film of an epoxy resin on the surface of the porous inorganic fine particles by reacting; and
A process for producing a microcapsule type latent curing agent, comprising:
(3) A one-pack type epoxy resin composition containing the microcapsule-type latent curing agent according to (1) above.

  According to the present invention, the curing agent for epoxy resin is impregnated inside the porous inorganic fine particles, and the surface of the porous inorganic fine particles is covered with a cured film of an epoxy resin. Therefore, the microcapsule-type latent curing agent of the present invention is added in advance to the epoxy resin main component as a curing agent for the epoxy resin, so that the contact between the epoxy resin main component and the curing agent is achieved even as a one-pack type epoxy resin composition. And the progress of curing of the epoxy resin main agent can be delayed.

  Further, in the one-pack type epoxy resin composition of the present invention, the curing of the epoxy resin main agent is such that the cured epoxy resin film formed on the surface of the porous inorganic fine particles is softened by heating and impregnated with the porous inorganic fine particles. The process proceeds after the curing agent for the epoxy resin comes into contact with the epoxy resin main agent. That is, according to the microcapsule-type latent curing agent of the present invention, the temperature at which the epoxy resin main component is cured is not a curing temperature of the curing agent impregnated with the porous inorganic fine particles, but a high temperature corresponding to the softening temperature of the cured film. Can be set to temperature. Furthermore, the selection of the curing agent to be used can be determined according to the suitability of the combination with the epoxy resin main agent without determining based on the curing temperature of the curing agent itself.

  Moreover, since the microcapsule-type latent curing agent of the present invention is impregnated and held in porous inorganic fine particles, compared with a case where the curing agent is simply contained in a shell made of a cured film of an epoxy resin. Thus, microencapsulation can be easily performed. In addition, the microcapsule type latent curing agent of the present invention has a degree of direct contact between the curing agent and the cured film inside the microcapsule when the curing agent is simply contained in a shell made of a cured film of an epoxy resin. Since it is lower than the above, the storage stability of the microcapsules can be improved.

It is a conceptual diagram which shows typically the cross section of the microcapsule type | mold latent hardening | curing agent which concerns on one embodiment of this invention.

(Microcapsule type latent curing agent)
The microcapsule type latent curing agent of the present invention includes porous inorganic fine particles, a curing agent for epoxy resin impregnated inside the porous inorganic fine particles, and curing of the epoxy resin formed on the surface of the porous inorganic fine particles. And a membrane. Hereinafter, the microcapsule-type latent curing agent of the present invention will be described with reference to FIG.

  FIG. 1 is a conceptual diagram schematically showing a cross section of a microcapsule-type latent curing agent according to an embodiment of the present invention. For example, as shown in FIG. 1, the microcapsule-type latent curing agent 10 includes porous inorganic fine particles 11 serving as a core and a cured film 12 of an epoxy resin formed on the surface thereof. The porous inorganic fine particles 11 have a large number of micropores 13 opened on the surface of the porous inorganic fine particles 11 inside, and the micropores 13 are filled with a curing agent (not shown) for epoxy resin. Has been.

  The porous inorganic fine particles are not particularly limited as long as they are inorganic fine particles having a large number of fine pores. Specifically, calcium silicate, precipitated silica, calcium carbonate / silica composite particles, basic magnesium carbonate, silica gel, colloidal silica Etc. Among these, calcium silicate, precipitated silica, calcium carbonate / silica composite particles, basic magnesium carbonate from the viewpoint of poor reactivity with curing agents and curing accelerators for epoxy resins and high porosity inside the fine particles Silica fine particles formed by a wet method such as the above are preferred.

The average particle diameter d ₅₀ of the porous inorganic fine particles is preferably 0.5 to 150 μm, more preferably 1 to 20 μm, and particularly preferably 1 to 10 μm. When the average particle diameter d ₅₀ is less than 0.5 μm, there is a tendency that a sufficient amount of the curing agent cannot be impregnated inside the porous inorganic fine particles. Since the porous inorganic fine particles remain in the cured epoxy resin, the average particle diameter d ₅₀ of the porous inorganic fine particles is preferably as small as possible within the above range. Depending on the use of the epoxy resin, when the average particle size d ₅₀ of the porous inorganic fine particles exceeds 150 μm, the cured epoxy resin has irregularities due to the porous inorganic fine particles, or the porous inorganic fine particles May hinder the curing of the epoxy resin.

Oil absorption of the porous inorganic fine particles are not particularly limited, as oil absorption of linseed oil, preferably from 100~500cm ³ / 100g, more preferably 150~300cm ³ / 100g. When oil amount is 100 cm ^3/100 g or more, it may be impregnated with a sufficient amount of curing agent in the interior of the porous inorganic particles. Incidentally, the porous inorganic particles such as oil absorption exceeds 500 cm ^3/100 g, it is difficult to obtain.

  The hardening | curing agent for epoxy resins used for this invention is not specifically limited, The various hardening agent used conventionally is mentioned. The curing agent includes a curing accelerator. Specific examples of the curing agent include oxazines, imidazoles, polyamines, acid anhydrides and the like. Among these, oxazines or imidazoles are preferable. A hardening | curing agent may be used independently and may use 2 or more types together.

  Examples of oxazines include various known oxazine compounds as curing agents or curing accelerators for epoxy resins. Specifically, bisphenol F-aniline (Fa) type benzoxazine, phenol-diaminodiphenylmethane (Pd) type benzoxazine, bisphenol S-aniline type benzoxazine, bisphenol A-aniline (Ba) type benzo And oxazine.

  Examples of the F-a type benzoxazine include a commercial product of Shikoku Kasei Co., Ltd. and a trade name “BF-BXZ” manufactured by Konishi Chemical Co., Ltd. As Pd type benzoxazine, the commercial item of Shikoku Kasei Co., Ltd. is mentioned. Examples of the bisphenol S-aniline type benzoxazine include trade name “BS-BXZ” manufactured by Konishi Chemical Co., Ltd. Examples of the Ba type benzoxazine include trade name “BA-BXZ” manufactured by Konishi Chemical Co., Ltd.

  Examples of imidazoles include various known imidazole compounds as curing agents or curing accelerators for epoxy resins. Specifically, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, epoxy-imidazole adduct, Examples include epoxy-phenol-boric acid ester blends, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-heptadecylimidazole, and the like.

  Examples of the polyamine include aliphatic amines such as diethylenetriamine, triethylenetetramine, and metaxylylenediamine, alicyclic amines such as isophoronediamine and 1,3-bisaminomethylcyclohexane, diaminodiphenylmethane, m-phenylenediamine, and diaminodiphenyl. Examples include aromatic amines such as sulfone, dicyandiamide, and organic acid dihydrazides. The polyamine type curing agent may be various modified products such as dimer acid modified polyamide, ketone modified ketimine, epoxide modified epoxy adduct, thiourea modified, Mannich modified, Michael addition modified. .

  Examples of the acid anhydride include aromatic acid anhydrides such as phthalic anhydride, trimellitic anhydride, and pyromellitic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methylendomethylenetetrahydrophthalic anhydride. And cyclic aliphatic acid anhydrides such as acid, dodecenyl succinic anhydride, and trialkyltetrahydrophthalic anhydride.

Commercially available curing agents include the following trade names in addition to those described above.
Trade names CURAZOLE (registered trademark) 2PHZ-PW (2-phenyl-4,5-dihydroxymethylimidazole), CURAZOLE 2P4MHZ-PW (2-phenyl-4-methyl-5-hydroxymethylimidazole) manufactured by Shikoku Kasei Kogyo Co., Ltd. , Trade name C11Z-CNS (1-cyanoethyl-2-undecylimidazolium trimellitate), cure duct P-050 (epoxy-imidazole adduct), cure duct L-07N (epoxy-phenol-borate compound) ;
Trade names Fujicure (registered trademark) FXR-1020, Fujicure FXR-1030, Fujicure FXR-1050, Fujicure FXR-1080 (above, aliphatic polyamines) manufactured by Fuji Chemical Industry Co., Ltd .;
Ajinomoto Fine Techno Co., Ltd. trade names Amicure PN-23, Amicure MY-24, Amicure PN-31, Amicure PN-40 (above, amine adducts), A trade name Amicure VDH (hydrazides);
Product name HE-100 series (phenol aralkyl resin) manufactured by Air Water Co., Ltd .;
Trade names TIC-188, NIPA-2E4MZ, NIPA-2P4MZ, HIPA-2E4MZ, HIPA-2E4MHZ, NIPA-2MZ, HIPA-2MZ and TEP-2MZ manufactured by Nippon Soda Co., Ltd.

  The cured film of the epoxy resin constituting the microcapsule type latent curing agent of the present invention is formed on the surface of the porous inorganic fine particles impregnated with the curing agent. This cured film is formed by a reaction between the curing agent exposed to the fine pore openings of the porous inorganic fine particles or adhering to the surface of the porous inorganic fine particles and the epoxy resin prepolymer.

  The thickness of the cured film is not particularly limited, and can be appropriately set in consideration of, for example, the size of the porous inorganic fine particles, the use of the epoxy resin curing microcapsules, and the like. The film thickness of the cured film can be adjusted by the reaction time and reaction temperature between the curing agent in the porous inorganic fine particles and the epoxy resin prepolymer. Usually, the thicker the cured film, the more difficult it is to collapse and the higher the storage stability.

  Examples of the epoxy resin prepolymer used for forming the cured film include various epoxy resin prepolymers. Specifically, various glycidyl ether type epoxies such as bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AF type, biphenyl type, naphthalene type, fluorene type, etc. Examples thereof include prepolymers, glycidyl ester type epoxy prepolymers, glycidylamine type epoxy prepolymers, and alicyclic epoxy prepolymers. Among these, bisphenol A type, bisphenol F type, bisphenol S type or naphthalene type is preferable. An epoxy resin prepolymer may be used independently and may use 2 or more types together.

  The softening temperature of the cured film varies depending on the type and molecular weight of the epoxy resin prepolymer. What is necessary is just to set suitably the softening temperature of the cured film in the microcapsule type | mold latent hardener of this invention according to the hardening temperature calculated | required by the use of a microcapsule type | mold latent hardener.

(Method for producing microcapsules for epoxy resin curing)
The microcapsule-type latent curing agent of the present invention is produced, for example, through the following steps.
(I) a step of impregnating the inside of the porous inorganic fine particles with a curing agent for epoxy resin, and (ii) a porous inorganic fine particle impregnated with the curing agent in the step (i), an epoxy resin prepolymer, And a cured film of epoxy resin on the surface of the porous inorganic fine particles by reacting the curing agent with the epoxy resin prepolymer at the interface between the porous inorganic fine particles and the epoxy resin prepolymer. Forming.

  In the step (i), in order to impregnate the inside of the porous inorganic fine particles with the curing agent, first, the curing agent is dissolved in a solvent. The solvent is not particularly limited as long as it dissolves the curing agent, but a volatile solvent is preferable. In this case, the solvent can be easily removed from the porous inorganic fine particles after the impregnation treatment with the curing agent. An example of such a solvent is toluene.

  Next, the porous inorganic fine particles are introduced into a solution containing the curing agent, and the pores of the porous inorganic fine particles are impregnated with the curing agent. The content ratio of the curing agent and the porous inorganic fine particles in the solvent can be appropriately set according to, for example, the amount of the porous inorganic fine particles impregnated with the curing agent and the viscosity of the solution containing the curing agent. it can.

  It is preferable that the porous inorganic fine particles are impregnated with the curing agent after the porous inorganic fine particles are left under reduced pressure. By leaving the porous inorganic fine particles under reduced pressure, the air in the fine pores of the porous inorganic fine particles is removed. Thereafter, the pores can be efficiently impregnated in the pores by returning to normal pressure while the porous inorganic fine particles are in contact with the curing agent.

  In the step (i), after impregnating the porous inorganic fine particles with the curing agent, the porous inorganic fine particles are usually taken out from the solution containing the curing agent and dried to obtain the porous inorganic fine particles. The solvent contained in the fine particles is removed. Thus, porous inorganic fine particles having fine pores impregnated with a curing agent can be obtained.

It can be confirmed that the porous inorganic fine particles are impregnated with the curing agent by, for example, heat flux differential scanning calorimetry (heat flux DSC). The content (%) of the curing agent in the porous inorganic fine particles can be determined based on the following formula. Q ₁ represents the heat amount (J / g) of the porous inorganic fine particles, and Q ₂ represents the heat amount (J / g) of the porous inorganic fine particles impregnated with the curing agent inside, for example, the heat amount is the heat flux. Measured with DSC. The content (%) of the curing agent in the porous inorganic fine particles is not particularly limited. Generally, the epoxy resin main component does not necessarily have a high content because the curing reaction proceeds with a small amount of the curing agent. For example, it may be about 2 to 10% at all.
Content rate (%) = (Q ₂ / Q ₁ ) × 100

  In addition, when the curing agent itself is colored, it is possible to confirm whether the porous inorganic fine particles are impregnated with the curing agent by visually observing the color of the porous inorganic fine particles.

  Next, the porous inorganic fine particles impregnated with the curing agent in the step (i) form a cured film of the epoxy resin by reacting the curing agent with the epoxy resin prepolymer on the surface of the porous inorganic fine particles. Provided to step (ii).

  In step (ii), first, the epoxy resin prepolymer is dissolved in a diluent. The diluent is not particularly limited as long as it is a solvent that can dissolve the epoxy resin prepolymer. From the viewpoint of avoiding residual diluent in the microcapsule-type latent curing agent, a solvent that easily volatilizes is preferable. Further, from the viewpoint of preventing the curing agent for epoxy resin from escaping from the inside of the porous inorganic fine particles, a solvent having poor compatibility with the curing agent is preferable.

  Next, porous inorganic fine particles impregnated with a curing agent are put into a diluent containing an epoxy resin prepolymer and heated. As a result, the curing agent exposed to the fine pore openings of the porous inorganic fine particles or adhering to the surface of the porous inorganic fine particles reacts with the epoxy resin prepolymer dissolved in the diluent, and the epoxy resin A cured film is formed.

  In step (ii), the reaction time and reaction temperature between the epoxy resin prepolymer and the epoxy resin curing agent are not particularly limited. For example, it is appropriately set according to the combination of the epoxy resin prepolymer and the curing agent, the speed of the curing reaction, etc., and it is usually preferably set to 1 to 30 minutes. As the reaction time becomes longer, the curing agent impregnated in the porous inorganic fine particles is consumed for forming the cured film, and the content in the porous inorganic fine particles tends to be lowered.

  After forming the cured film of the epoxy resin, the product is separated from the diluent, recovered, and dried to obtain the microcapsule-type latent curing agent of the present invention. The formation of a cured film of epoxy resin on the surface of the porous inorganic fine particles can be confirmed, for example, by observing the surface of the fine particles with a scanning electron microscope (SEM).

(One-pack type epoxy resin composition)
The one-pack type epoxy resin composition of the present invention contains the microcapsule-type latent curing agent. Specifically, the one-pack type epoxy resin composition of the present invention includes an epoxy resin main component and the above-described microcapsule-type latent curing agent, and further, if necessary, a dispersion medium, an activator, an antioxidant, an antioxidant. Contains other components such as rusting agents and chelating agents.

  The microcapsule-type latent curing agent according to the present invention described above is preliminarily added to the epoxy resin main agent and stored because the curing agent is impregnated inside the porous inorganic fine particles and the surface of the fine particles is coated with a cured film. Even if it does, a hardening | curing agent and an epoxy resin main ingredient do not contact. Therefore, the one-pack type epoxy resin composition of the present invention containing this microcapsule type latent curing agent is superior in storage stability as compared with the conventional one-pack type epoxy resin composition.

  The “epoxy resin main component” in the one-pack type epoxy resin composition is used in the same meaning as the “epoxy resin prepolymer” used for forming the cured film of the epoxy resin in the microcapsule type latent curing agent of the present invention. Examples of the epoxy resin main agent include an epoxy resin prepolymer exemplified as a material for forming a cured film of an epoxy resin.

  It does not specifically limit as a dispersion medium used for a one-pack type epoxy resin composition, The various dispersion medium generally used for an epoxy resin composition can be used. Specifically, for example, alcohols such as terpineol, hexylene glycol, butyl carbitol, benzyl alcohol, isopalmityl alcohol, isostearyl alcohol, lauryl alcohol; esters such as diisobutyl adipate, diethyl phthalate, dibutyl phthalate; hexadecane And organic solvents such as hydrocarbons such as dodecylbenzene.

  It does not specifically limit as an activator used for a one-pack type epoxy resin composition, The various activators generally used for an epoxy resin composition can be used. Specific examples include hydrohalic acid salts of amines such as ethylamine and propylamine; and organic carboxylic acids such as lactic acid, citric acid and benzoic acid.

  The one-pack type epoxy resin composition of the present invention can be suitably used in various applications such as adhesives and sealants. As a specific use, the example used as a hardening | curing agent in a solder paste is mentioned, for example. The solder paste is not particularly limited with respect to compounding components and the amount thereof, except that the solder paste includes a solder metal powder, an epoxy resin main component, a microcapsule type latent curing agent of the present invention, an activator, and a dispersion medium. It is not something. As components other than the microcapsule type latent curing agent, various components usually used in solder paste can be used.

  Since the one-pack type epoxy resin composition of the present invention uses the microcapsule-type latent curing agent as a curing agent, the curing temperature of the epoxy resin can be set high.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited to these Examples.

<Preparation of microcapsule type latent curing agent>
As the porous inorganic fine particles used for the microcapsule type latent curing agent, calcium silicate manufactured by Tokuyama Corporation, trade name “FLORITE (registered trademark)” was used. This porous inorganic fine particle was a petal-like crystal powder of calcium silicate and had many fine pores inside and many fine pore openings on the surface. Further, the porous inorganic particles have an average particle size d ₅₀ of 10 to 20 [mu] m, oil absorption amount of linseed oil was 350~500cm ³ / 100g.

  The epoxy resin curing agent impregnated inside the porous inorganic fine particles includes Fa (bisphenol F-aniline) type benzoxazine (manufactured by Shikoku Kasei Co., Ltd.) and 2-phenyl-4 which is an imidazole curing agent. , 5-dihydroxymethylimidazole (trade name Curesol (registered trademark) 2PHZ-PW, manufactured by Shikoku Kasei Co., Ltd.) was used.

Example 1
(1) Preparation of porous inorganic fine particles impregnated with curing agent A toluene solution of a curing agent was prepared by adding Fa-type benzoxazine and an imidazole-based curing agent to toluene, and heating and stirring. The Fa type benzoxazine and the imidazole curing agent are mixed at a mass ratio of 4: 1, and the content ratio in the toluene solution is 45% by mass in the total amount of the Fa type benzoxazine and the imidazole curing agent. It adjusted so that it might become.

  Next, porous inorganic fine particles were introduced into the vacuum chamber, and the inside of the vacuum chamber was decompressed. While maintaining the reduced pressure state in the vacuum chamber, a toluene solution of a curing agent was added and left at room temperature. The input amount of the porous inorganic fine particles was adjusted to 5% by mass with respect to toluene. After leaving, the inside of the vacuum chamber was returned to normal pressure to obtain porous inorganic fine particles impregnated with a curing agent.

(2) Preparation of cured epoxy resin film Biochemical corn oil manufactured by Wako Pure Chemical Industries, Ltd. was used as a dispersion medium for dispersing porous inorganic fine particles impregnated with a curing agent. A polyfunctional type epoxy resin “jER (registered trademark) 152” manufactured by Mitsubishi Chemical Corporation was used as an epoxy resin prepolymer for forming a cured film of the epoxy resin.

  An epoxy resin prepolymer solution was obtained by adding 5 parts by mass of an epoxy resin prepolymer to 70 parts by mass of corn oil and stirring while heating to 160 ° C. Next, while maintaining the temperature of the solution at 160 ° C., 1 part by mass of porous inorganic fine particles impregnated with the curing agent obtained in the above (1) was added and stirred for 5 minutes. As a result, the curing agent exposed on the surface of the porous inorganic fine particles and the epoxy resin prepolymer react at the interface between the porous inorganic fine particles and corn oil, and the cured film of the epoxy resin is formed on the surface of the porous inorganic fine particles. Been formed. After forming the cured film, the product was separated from the epoxy resin prepolymer solution by suction filtration, recovered, and air dried. As a result, a microcapsule type latent curing agent comprising porous inorganic fine particles impregnated with a curing agent and an epoxy resin cured film formed on the surface thereof was obtained.

(Example 2)
In the same manner as in Example 1 except that the time for stirring the porous inorganic fine particles impregnated with the curing agent in the epoxy resin prepolymer solution was changed to 30 minutes when forming the cured epoxy resin film, A capsule-type latent curing agent was obtained.

(Example 3)
A microcapsule-type latent curing agent was obtained in the same manner as in Example 1 except that the content ratio of the Fa type benzoxazine and the imidazole curing agent was 30% by mass.

Example 4
A microcapsule-type latent curing agent was obtained in the same manner as in Example 1 except that the content ratio of the F-a type benzoxazine and the imidazole curing agent was 60% by mass.

<Evaluation of microcapsule type latent curing agent>
(1) Observation of the surface state of a capsule About the microcapsule type | mold latent hardening | curing agent obtained in Examples 1-4, the surface state and the shape were observed with the scanning electron micrograph (SEM). In any of the examples, a cured film of an epoxy resin could be confirmed on the particle surface of the microcapsule type latent curing agent.

(2) Evaluation of thermal characteristics of capsules For a mixture in which Fa type benzoxazine and imidazole curing agent are mixed at a mass ratio of 4: 1, the calorific value thereof is a heat flux differential scanning calorific value manufactured by Shimadzu Corporation. Measurement (heat flux DSC), measured using model DSC-60 (control). Next, the amount of heat of the microcapsule-type latent curing agent obtained in Examples 1 to 4 was measured by a heat flux DSC, and compared with the measurement result (control) for the above mixture. For all of the microcapsule-type latent curing agents obtained in Examples 1 to 4, observe the exothermic peak around 150 ° C. observed for the mixture of Fa type benzoxazine and imidazole curing agent. I was able to. Therefore, in any of the examples, it was found that the mixture of the Fa type benzoxazine and the imidazole curing agent was impregnated inside the porous inorganic fine particles.

(3) Measurement of curing agent content rate Measurement result Q ₂ (J / g) of heat quantity by heat flux DSC obtained in “(2) Evaluation of thermal properties of capsule” and impregnation with curing agent. The content (%) of the curing agent in the porous inorganic fine particles was determined from the measurement result Q ₁ (J / g) of the calorific value of the porous inorganic fine particles not used, using the following formula. Table 1 shows the calculation results of the content rate.
Content rate (%) = (Q ₂ / Q ₁ ) × 100

  In any of Examples 1 to 4, it can be seen that the curing agent remains in the porous inorganic fine particles without using all of the curing agent in forming the cured film. As described above, the content ratio is not necessarily high, and even the content ratios in Examples 2 and 3 can be used in practice.

<Preparation of one-pack type epoxy resin composition>
As the epoxy resin prepolymer for the one-pack type epoxy resin composition, a polyfunctional type epoxy resin “jER (registered trademark) 152” manufactured by Mitsubishi Chemical Corporation was used.

(Example 5)
73 parts by mass of the microcapsule-type latent curing agent obtained in Example 1 was added to 100 parts by mass of the epoxy resin prepolymer, stirred at room temperature, and dispersed to obtain a one-pack type epoxy resin composition. . The content ratio of the curing agent with respect to 100 parts by mass of the epoxy resin prepolymer was 20 parts by mass for the Fa-type benzoxazine and 5 parts by mass for the imidazole-based curing agent.

(Comparative Example 1)
35 parts by mass of porous inorganic fine particles impregnated with a curing agent prepared in Example 1 (1) (without forming a cured film of an epoxy resin) were added to 100 parts by mass of an epoxy resin prepolymer. The mixture was stirred and dispersed at room temperature to obtain a one-pack type epoxy resin composition. The content ratio of the curing agent with respect to 100 parts by mass of the epoxy resin prepolymer was 20 parts by mass for the Fa-type benzoxazine and 5 parts by mass for the imidazole-based curing agent.

(Comparative Example 2)
One-part epoxy resin by adding 20 parts by mass of Fa type benzoxazine and 5 parts by mass of imidazole curing agent to 100 parts by mass of the epoxy resin prepolymer, stirring, dissolving and dispersing at room temperature A composition was obtained.

<Evaluation of curing characteristics of one-pack type epoxy resin composition>
A small amount of each of the one-component epoxy resin compositions obtained in Example 5 and Comparative Examples 1 and 2 was applied onto a glass plate to prepare a sample. The sample was then heated to 100 ° C., 140 ° C., or 180 ° C., and the curing of the epoxy resin was visually observed. The sample was heated for 20 minutes at any heating temperature. The results of the curing experiment are shown in Table 2.

  As shown in Table 2, in the one-pack type epoxy resin composition obtained in Example 5, when the heating temperature was 100 ° C. or 140 ° C., no curing of the epoxy resin was observed. When the heating temperature was 180 ° C., curing was partially confirmed. Among the curing agents contained in the microcapsule-type latent curing agent, the Fa-type benzoxazine has a curing temperature of about 200 ° C. when used alone, but the other imidazole-based curing agent (Curazole ( (Registered trademark) 2PHZ-PW) has a curing start temperature of about 145 ° C. and an active region of about 160 to 170 ° C. when used alone. For this reason, when the Fa type benzoxazine and the imidazole curing agent are mixed and used, curing of the epoxy resin starts at about 140 ° C.

  In Example 5, when heating temperature was 140 degreeC, it turned out that hardening of an epoxy resin can be suppressed and an epoxy resin can be hardened by setting heating temperature to 180 degreeC or more. From this result, according to the one-pack type epoxy resin composition obtained in Example 5, when the curing agent is a combined system of Fa type benzoxazine and an imidazole type curing agent, It was found that the temperature at which the curing of the epoxy resin is initiated can be set to a temperature higher than the curing temperature.

  On the other hand, as the curing agent, Comparative Example 1 using a porous inorganic fine particle impregnated with a curing agent but not forming an epoxy cured film on the surface of the porous inorganic fine particle, and Fa type benzoxazine In Comparative Example 2 in which the imidazole-based curing agent was directly added to the epoxy resin main component, curing of the epoxy resin had already started when the heating temperature was 140 ° C., and when the heating temperature was 180 ° C., the entire epoxy resin Cured. That is, when the curing agent is a combined system of Fa type benzoxazine and an imidazole-based curing agent, curing of the epoxy resin started at the original curing temperature of this combined system.

DESCRIPTION OF SYMBOLS 10 Microcapsule type latent hardening agent 11 Porous inorganic fine particle 12 Cured film of epoxy resin 13 Micropore

Claims (3)

Porous inorganic fine particles;
A curing agent for epoxy resin impregnated inside the porous inorganic fine particles;
A cured film of an epoxy resin formed on the surface of the porous inorganic fine particles by a reaction between the curing agent and the epoxy resin prepolymer;
A microcapsule type latent curing agent comprising: A step of impregnating a curing agent for epoxy resin inside the porous inorganic fine particles;
The porous inorganic fine particles impregnated with the curing agent are brought into contact with the epoxy resin prepolymer, and the curing agent and the epoxy resin prepolymer are bonded at the interface between the porous inorganic fine particles and the epoxy resin prepolymer. Forming a cured film of an epoxy resin on the surface of the porous inorganic fine particles by reacting; and
A process for producing a microcapsule type latent curing agent, comprising:   A one-pack type epoxy resin composition containing the microcapsule-type latent curing agent according to claim 1.

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