JP2600536B2 - Method for producing adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an adhesive composition having excellent storage stability and curability.

[0002]

2. Description of the Related Art A method using a latent curing agent is known as a means for achieving both the preservability and the rapid curing property of a thermosetting adhesive. A latent curing agent refers to a compound that is incorporated into an adhesive and is stable in a storage environment at room temperature or lower, but immediately starts a curing reaction under the action of heat, light, moisture, and pressure. As means for releasing the potential of such a curing agent, for example, dissolution or decomposition of insoluble curing agent particles, elution of the curing agent from the encapsulated molecular sieve, reaching the reaction initiation temperature such as ionic polymerization, curing agent And the like, and destruction of inert microcapsule membranes, and latent curing agents utilizing these are known. As for the microcapsule type curing agent, for example, JP-A-60-99179 and JP-A-64-7052
An epoxy resin and an imidazole derivative as shown in No. 3 are reacted, and the surface of the product is inactivated by an isocyanate compound, or the surface of an amine compound is inactivated by reacting with an epoxy resin. Things are known.

[0003]

A problem common to the above-mentioned microcapsule-type curing agents is that when the thickness of the coating layer is increased, the preservability is improved, but the curability is remarkably reduced. When the thickness is reduced, the curability is improved, but the preservability is reduced, and it has been extremely difficult to obtain a balance between these two properties.
Both of these properties are becoming more demanding due to the recent remarkable progress in automation of the bonding operation. For example, in the case of a thermosetting one-pack type epoxy adhesive, the storage stability is three months or more from the conventional refrigerated or frozen storage to the room temperature storage under the bonding work atmosphere. For high temperature and long time at 170 ° C or more and tens of minutes or more, the curing time at 170 ° C or lower and as low as tens of seconds or less has recently been targeted. Strict compatibility is required more than ever. The present invention has been made in view of the above circumstances, and provides a method for producing an adhesive composition capable of satisfying both storage stability and rapid curing property.

[0004]

According to the present invention, an epoxy resin containing a latent curing agent (hereinafter referred to as a masterbatch) is used.
A heat treatment is performed at a temperature higher than 0 ° C. and lower than the activation temperature indicated by the DSC peak temperature, and the activation temperature is set to 0.
The present invention relates to a method for producing an adhesive composition, which comprises mixing at least 2 ° C. or more with another adhesive component. The latent curing agent referred to in the present invention is 30 ° C. in the presence of an epoxy resin.
In the following, it means that it has a storage stability of 2 months or more and rapidly cures under heating. Although there is no limitation on the means of latentization,
For example, it does not dissolve in an epoxy resin at room temperature, but dissolves when heated to around the melting point and rapidly cures (eg, boron complex salt, hydrazide, tertiary amine, imidazole, dicyandiamide, and derivatives thereof, and amine imides). There are a thermal decomposition type curing agent, a molecular sieve enclosing type, a microcapsule type, and the like, and these can be applied alone or as a mixture of two or more types.

[0005] Among them, a microcapsule type curing agent can be preferably applied. The microcapsule type curing agent is obtained by substantially covering the entire surface of a core material made of the curing agent with a coating layer. The hardening agent which is the core material of the microcapsule type hardening agent includes aliphatic amine, aromatic amine, carboxylic anhydride, thiol, alcohol, phenol, isocyanate, tertiary amine, boron complex salt, inorganic acid, hydrazide compound and imidazole Compounds and the like and modified products thereof can be employed. Among these, tertiary amines, boron complex salts, which require less consideration of chemical equivalents because they are fast-curing and excellent in adhesive workability and also act as a catalyst in an ionic polymerization type,
Hydrazide compounds and imidazole compounds are preferred,
Among them, an imidazole compound whose activation temperature is easily controlled in a wide range depending on the type of the derivative and a modified product thereof are more preferably used. These are used alone or as a mixture of two or more.

As an example of an imidazole compound,
Imidazole, 2-methylimidazole, 2-ethyl-
4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2- Undecylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 2-phenylimidazolium isocyanurate, 2,4-diamino-6- [2-undecylimidazolyl- (1)]-ethyl-s- There are triazines and the like.

The coating layer is not particularly limited, but is composed of a polymer substance such as polystyrene, gelatin and polyisocyanate, an inorganic substance such as calcium silicate, and a metal thin film such as nickel and copper. It is practically preferable that the activation temperature of these latent curing agents is in the range of 50 to 200 ° C., since it is easy to achieve both storage stability and rapid curing property.
More preferably, the temperature is set to 50 ° C.

The activation temperature of the latent curing agent used in the present invention is determined by DSC (Differen) using 3 mg of a sample obtained by mixing a curing agent powder or a microcapsule type curing agent with an epoxy resin.
tialScanning Calorimeter (differential scanning calorimeter) at normal temperature (30 ° C) to high temperature (250 ° C) at 10 ° C / min.
The peak temperature indicates the maximum calorific value when the temperature is raised up to the maximum.

The master batch referred to in the present invention is typically a liquid bisphenol type epoxy resin in which a curing agent is dispersed, and the epoxy resin at this time has two or more epoxy groups in one molecule. All known epoxy resins which are compounds can be applied. Typical examples are polyglycidyl ethers of polyhydric phenols such as bisphenol-type epoxy resins derived from epichlorohydrin and bisphenol A or bisphenol F, and epoxy novolak resins derived from epichlorohydrin and phenol novolak or cresol novolak. Other examples include polyglycidyl esters of polycarboxylic acids, alicyclic epoxies, polyglycidyl ethers of polyhydric alcohols, and polyglycidyl compounds of polyvalent amines, and these can be used alone or in combination of two or more.

These are preferably liquid at ordinary temperature, but even in solid form, a masterbatch can be obtained, for example, by using a solvent or by mixing under heating. Also,
The mixing ratio of the latent curing agent and the epoxy resin in the masterbatch may be determined in consideration of workability at the time of mixing, storage stability of the masterbatch, and the like, so as not to cause gelation under heat treatment. In order to obtain these balances, the polymerization ratio of the curing agent is generally 60% or less, and preferably about 50 to 5%. The masterbatch may also contain a reaction catalyst between the latent curing agent and the epoxy resin, for example, benzyldimethylamine, imidazole and modified products thereof, and may also contain, for example, methyl ethyl ketone or toluene as a solvent. it can.

In the present invention, it is necessary to heat the above-mentioned masterbatch at a temperature higher than 30 ° C. and below the activation temperature, and to increase the activation temperature indicated by the DSC peak temperature before and after the heating by 0.2 ° C. or more. . As a heating method, for example, a simple method such as heating a container containing a master batch in a medium such as air, water, or oil may be used. The heating time is appropriately selected depending on the processing temperature, but the higher the temperature, the shorter the processing time tends to be. The heating temperature is close to the actually conceivable storage temperature of the final adhesive composition.
The temperature is preferably about 5 to 80C, more preferably 40 to 70C. At this time, depending on the properties of the masterbatch, oxygen can be cut off, for example, under nitrogen reflux, or heat treatment can be performed under high humidity. When the activation temperature is increased by the heat treatment, the storage stability can be improved at 0.2 ° C. or higher.
As the temperature rises, curability decreases, but mechanical damage such as roll dispersion and solvent resistance improve.
From these facts, it is preferable to raise the activation temperature to 0.2 to 20 ° C, and more preferably to 0.2 to 10 ° C. Obtainable.

The adhesive composition of the present invention can be obtained by mixing and dispersing the above-mentioned master batch of a curing agent in a reactive adhesive component. As the reactive adhesive component, various substances having reactivity with the curing agent can be applied. In addition to the same epoxy resin used for the master batch, urea resin, melamine resin, guanamine resin, phenol resin,
So-called thermosetting adhesives composed of resins such as xylene resin, furan resin and diallyl phthalate resin, and resins such as polyester, polyurethane, polyvinyl butyral, phenoxy resin, polyamide, polyimide, polycyanoacrylate, carboxyl group and hydroxyl There are rubbers and elastomers containing functional groups such as groups, and these can be used alone or as a mixture of two or more.
These may be further added with a curing accelerator or a curing catalyst. In the adhesive composition, for example, a flexibility imparting agent such as a thermoplastic resin or rubber, a tackifier such as a tackifier or a plasticizer, a filler such as silica or conductive particles, and a crosslinking agent such as isocyanate or melamine. An agent, a solvent, a polymerization inhibitor, a coupling agent and the like can be contained as required.

[0013]

According to the present invention, a master batch of a latent curing agent and an epoxy resin is blended after heating to form an adhesive composition, so that the concentration of the curing agent is high and the adhesive as a final product is obtained. It can promote a reaction that can proceed at a temperature close to the maximum temperature considered as the storage temperature of the composition. In addition, the masterbatch after the heat treatment contributes to the improvement of the preservability because the rise of the heat generation of the DSC curve at the time of temperature rise shifts to a high temperature side, and the fluctuation of the peak temperature is relatively small, so that the curability decreases. There is almost no.

The mechanism of the present invention can be considered as follows. Surface of latent hardener particles due to heating (in the case of microcapsule type, defect due to pinholes in coating, etc.)
The reaction with high activity proceeds preferentially at the contact interface between the epoxy resin and the epoxy resin.However, this reaction has a considerably lower temperature than the curing temperature, so that the reaction becomes a rate-determining state. The interface is passivated. By making the adhesive composition in this state, the preservability of the adhesive composition is improved because the concentration of the curing agent may be diluted. Further, by deactivating the contact interface, solvent resistance and mechanical damage resistance are also improved, and roll workability and the like are improved. . On the other hand, since the fluctuation in the peak temperature is slight, the curability at a high temperature during the curing operation (generally at or above the DSC peak temperature) does not substantially decrease.

[0015]

【Example】

Examples 1 to 3 and Comparative Examples HX-3748 which is a master batch of a latent curing agent
100 g (described later) was collected in a glass bottle and treated in a thermostat at 50 ° C. for a predetermined time to obtain a heat-treated curing agent master batch. Heat treatment conditions and DS of this masterbatch
The activation temperature by C is shown in Table 1. A case without heat treatment is also shown as a comparative example. Here HX-37
Numeral 48 is a trade name of Asahi Kasei Kogyo Co., Ltd., in which a microcapsule type curing agent whose core material surface is covered with a urethane-based coating layer of about 500 ° C. is a liquid bisphenol-based epoxy resin (epoxy equivalent: 185). Inside by weight ratio 1:
This is a master batch dispersed at a ratio of 2. The activation temperature was determined by the DSC method (910 type DSC manufactured by DuPont, sample 3 mg, temperature rise at 10 ° C./min).

Next, as a reactive adhesive component, Epicoat 807 (bisphenol type epoxy resin, trade name of Yuka Shell Epoxy Co., Ltd.) and Epitan E-195 (epoxy terminal modified urethane resin, manufactured by Dainippon Ink and Chemicals, Inc.) (Trade name) was mixed at a weight ratio of 80:20 to obtain a reactive adhesive. This adhesive and the masterbatch were mixed at a mixing ratio of 70:30 by weight to obtain a liquid, solventless adhesive composition. Table 1 shows the results of these evaluations. The storage stability in Table 1 was determined by comparing the adhesive composition to 5
The viscosity (measured with an E-type viscometer) when sealed in a 0 ml screw tube and allowed to stand at 30 ° C. was measured, and the result was indicated by the time at which the viscosity before treatment doubled.

In Examples 1 to 3, the activation temperature was slightly increased by heat treatment as compared with the comparative example, and the preservability of the adhesive composition containing these was remarkably improved. Since the rise in the DSC peak temperature was as small as 0.3 ° C. (Example 1) to 3.9 ° C. (Example 3), the actual curability was hardly changed.

[0018]

[Table 1]

[0019]

As described in detail above, according to the present invention, it has become possible to provide an adhesive composition capable of improving storage stability while maintaining curability.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor: Yutaka Yamaguchi 1500, Oji, Shimodate-shi, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. Goshonomiya Factory Co., Ltd.

Claims (2)

(57) [Claims] 1. An epoxy resin containing a latent curing agent,
Heat treatment at a temperature higher than 0 ° C. and lower than the activation temperature indicated by the DSC peak temperature, and setting the activation temperature to 0.2
A method for producing an adhesive composition, which comprises mixing the composition with another adhesive component after the temperature has been increased by at least ° C. 2. The adhesive composition according to claim 1, wherein the latent curing agent is a heat-activated microcapsule-type curing agent having a curing agent as a nucleus and the entire surface substantially having a coating layer. Method of manufacturing a product.