JPH03292378A - Microcapsule, adhesive composition using same, and curing method therefor - Google Patents

Abstract

PURPOSE:To permit foaming of an organic foaming agent with heat, thereby breaking capsules and releasing a curing agent by covering a core material comprising the foaming agent and the curing agent with a hard wall material comprising a thermoplastic resin to form the capsules. CONSTITUTION:A core material (A) is prepared by blending 1 pt.wt. organic foaming agent having a softening point higher than that of the following wall material (e.g. azodicarbonamide), 1-100 pts.wt. curing agent (e.g. 2- undecylimidazole) and, if necessary, auxiliaries, curing accelerator, etc. Then, microcapsules with an average particles size of 100mum or less are provided by covering 1 pt.wt. component A with 0.01-10 pts.wt. wall material comprising a thermoplastic resin having a softening point of 70-200 deg.C (e.g. PS). The above microcapsules are blended with an epoxy, urethane or polysulfide resin to form an adhesive composition.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to microorganisms that are mechanically stable at room temperature (usually below 40°C), and in which the foaming agent foams upon heating, destroys the capsule, and releases the curing agent. The present invention relates to a capsule, an adhesive composition containing the same, and a method for curing the same. This adhesive composition has excellent storage stability, high reactivity, and excellent adhesion, heat resistance, chemical resistance, etc., and is therefore used for adhesives, sealants, paints, and the like.

[Prior art] Epoxy-based, urethane-based, polysulfide-based resins, etc. are used for adhesives, sealants, etc., and with the diversification of their uses, adhesives with low liquid volume and good storage stability are becoming available. In response to this demand, attempts have been made to microencapsulate curing agents (for example, Japanese Patent Laid-Open No. 76935/1983).

[Problems to be Solved by the Invention] Such microcapsules are easily destroyed by the external pressure exerted by the wall material and release the curing agent, resulting in poor storage stability when used as an adhesive, and furthermore, the interfacial polymerization method is difficult. There was a problem in that the workability during manufacturing was poor because it was encapsulated.

In addition, if the wall material is made stiffer (thicker) to improve storage stability, it is difficult to strike a balance because it cannot be broken and the curing agent is not released.

[Means to solve the problem]

The present invention was made to solve this problem, and by encapsulating a foaming agent and a hardening agent at the same time, the foaming agent foams when heated, even if the wall material is hardened (thickened). Provided are microcapsules that are mechanically stable and capable of releasing a curing agent smoothly, an adhesive composition containing the microcapsules, and a method for curing the same.

That is, the present invention first of all relates to microcapsules comprising an organic blowing agent and a curing agent as a core material and a thermoplastic resin as a wall material.

Second, it relates to adhesive compositions containing such microcapsules.

Thirdly, the adhesive composition is heated to a temperature higher than the foaming temperature of the foaming agent to destroy the microcapsule walls by foaming the foaming agent, and then react with the curing agent. Concerning a curing method.

Fourth, it relates to an epoxy resin composition whose main components are (a) an epoxy resin, and (b) microcapsules made of an organic blowing agent and a curing agent as a core material and a thermoplastic resin as a wall material.

The blowing agent used as a core material in the present invention is preferably an organic blowing agent because the rate of gas generation by thermal decomposition is appropriate and the decomposition temperature can be easily adjusted using an auxiliary agent or the like.

Specifically, single or mixed systems such as azodicarposamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, 4,4-oxybisbenisosulfonylhydrazide, and paratoluenesulfonylhydrazide are used. . If the decomposition temperature is too high, it may be adjusted with inorganic salts such as zinc white or tribasic lead sulfate, metal soaps such as zinc stearate or lead stearate, and auxiliary agents such as urea compounds. .

The decomposition temperature of the blowing agent is not particularly limited, but it is preferably higher than the softening point of the wall material described below. For example, in the case of a wall material with a softening point of 100°C, one that decomposes at 100 to 120''C is preferable.

The curing agent used as a core material together with the foaming agent is not particularly limited, and those generally used as curing agents or curing accelerators can be used as appropriate. Therefore, in the present invention, the curing agent includes those used as curing accelerators in -i. Examples include aliphatic amines, aromatic amines, various modified amines, acid anhydrides, polyamides, imidazoles, boric acid esters, Lewis acids, vulcanizing agents, isocyanates, thiol compounds, vulcanization accelerators, and the like.

Specifically, for example, diethylenetriamine, triethylenetetramine, polymethylenediamine, polyetherdiamine, menzendiamine, isophoronediamine,
Bis(4-amino-3-methylcyclohexyl)methane, N-aminoethylpiperazine, metaxylylenediamine, metaphenylenediamine, diaminodiphenylmethane, 39-bis(3-aminopropyl)-2,4,8
,10-tetraspiro15,5] undecane (AT
U), amine adduct, ketimine, tetramethylguanidine, triethylenedeamine, piperidine, trisdimethylaminomethylphenol, polyamide adduct,
2-methylimidazole, 2-undecylimidazole, 2-ethyl-4-methylimidazole, 2-heptadecyl imidazole, azine compound, BF3 amine complex,
3-(3,4-dichlorophenyl)-Ll-dimethylurea, 3-phenyl-1,1-dimethylurea, 3-(4dichlorophenyl)-Ll-dimethylurea, organotin compound, titanium compound, zinc compound, Examples include lead compounds, polyisocyanates, sulfur, selenium, tellurium, peroxides, metal oxides, quinone dioximes, stock price resins, thiazole series, thiuram series, and dithiocarbamates.

The weight ratio of the foaming agent, which is the core material, and the curing agent is 1:1 to 1:
100, preferably 1:10 to 1:50. Too little blowing agent is not preferred because the blowing agent inhibits the reaction of the curing agent.

The wall material used in the present invention has a softening point of 70 to 200°C.
1. Preferably, it is a thermoplastic resin having a temperature of 100 to 150°C. Here, the softening point is measured by the VICAT method. If the softening point is less than 70°C, it will lack stability during storage, and if it exceeds 200°C, it will be difficult to break the capsule, which is not preferred.

Specifically, for example, polyvinyl alcohol, polyvinyl butyral, polyamide, polysulfone, polycarbonate, cellulose acetate, polyvinyl chloride, polyethylene, ethyl cellulose, cellulose propionate, cellulose butyrate, polybutadiene, polyvinyl formal, polystyrene, polymethyl methacrylate. , butyl methacrylate, polyester, polyether sulfone, phenoxy resin, ethylene-vinyl acetate copolymer, hydroxypropylmethylcellulose phthalate, vinyl chloride-propylene-vinyl acetate copolymer, styrene-butyl methacrylate copolymer, and the like.

In the microcapsule of the present invention, the wall material encapsulates a core material made of the foaming agent and the hardening agent, and the weight ratio of the core material and the wall material is 1:0.01 to 1:10, Preferably 1
:1 to 1:5. If there is too little wall material, the core material may not be covered completely, and if there is too much wall material, even if the foaming agent foams, the capsule may not be destroyed.

In addition, the average particle diameter of microcapsules is 100 μm or less,
Preferably it is 10 to 50 μm, and if there are many coarse particles exceeding 1100 μm, the properties of the cured product may deteriorate.
Here, the average particle diameter was obtained by dryly observing a sample using a microscope (optical microscope and electron microscope) and measuring the particle size distribution using Feret diameter.

Such microcapsules are mechanically stable at normal atmospheric temperatures, for example, below 40° C., and when heated, the foaming agent foams, ruptures the capsules, and releases the curing agent or curing accelerator.

The microcapsules of the present invention can be produced by a conventional method such as a solvent evaporation method, a spray drying method, a coacelhesion method,
It can be obtained by encapsulation using an interfacial polymerization method.

By blending the microcapsules of the present invention with resins such as epoxy, urethane, and polysulfide, compositions such as adhesives and sealants that have a low liquid volume and good storage stability can be obtained. Furthermore, since a slight increase in volume occurs due to foaming, it is also used as a filling sealing material and a foamable adhesive.

In the present invention, an epoxy resin composition containing the above-mentioned microcapsules and epoxy resin as main components can be obtained.

As the epoxy resin used in the present invention, bisphenol A type epoxy resin is suitable, but bisphenol F type epoxy resin, cycloaliphatic epoxy resin, tris(2,
(3) epoxypropyl) isocyanurate, hydantoin type epoxy resin, phenol or cresol novolak type epoxy resin, phthalate glycidyl ester type epoxy resin, β-methylepichlorohydrin type epoxy resin, etc. may be used alone or in combination of two or more types. You can also do it.

In addition, to such an epoxy resin, a reactive diluent such as phenyl glycidyl ether cidyl ether or a phenoxy resin is added to the epoxy resin for the purpose of viscosity adjustment, etc., and usually 50 parts by weight or less, preferably 30 parts by weight, per 100 parts by weight of the epoxy resin. The following can also be added.

If too much is added, it is undesirable because the characteristics peculiar to the epoxy resin may be impaired, and the epoxy resin may be partially modified with rubber and used for the purpose of alleviating the residual stress during curing. In this case, the rubber component usually has an average molecular weight of 1000 to 5.
000 and the number of carboxyl groups contained per molecule is 1.5 to 2.5 on average, preferably 1.8 to 2.4, and a linear one having carboxyl groups at both ends of the molecule is preferable. In particular, from the viewpoint of compatibility with the epoxy resin, 10 to 30 parts by weight of acrylonitrile, preferably 15 to 25 parts by weight,
Parts by weight of liquid butadiene-acrylonitrile copolymer rubber is preferred. In the case of rubber modification, the content of the rubbery polymer is preferably 5 to 30% by weight of the entire resin component in order to bring out the rubber properties while maintaining the properties of the epoxy resin.

After the wall material of the capsule is broken by heating, the core material flows out, but not all of it reacts with the epoxy resin, and some remains unreacted.

Therefore, if the amount added is too large, this unreacted portion will lead to a decrease in the properties (especially water resistance) of the cured product.

Therefore, when blending the above-mentioned microcapsules into an epoxy resin, the amount added varies depending on the epoxy resin and curing agent (curing accelerator) used, but is usually 0.1 to 50 parts by weight, preferably 0.1 to 50 parts by weight per 100 parts by weight of the epoxy resin. 1 to 10 parts by weight is preferable. In addition, if it is too small, it cannot function as a curing agent (curing accelerator).

If the curing time becomes longer, in addition to the above-mentioned microcapsules, hydrazide-based, amine-imide-based, imidazole-based, imidacillin-based, tertiary amine-based, monoaminopyridine-based, dicyandiamide, etc. A generally latent curing agent or curing accelerator that is not encapsulated may be used in combination.

In the present invention, a silane coupling agent may be further added for the purpose of improving water resistance, chemical resistance, adhesion, etc. As such a silane coupling agent, for example, XS.

Y, represented by Suitable silane compounds include T-aminopropyltriethoxysilane, vinyltriacetoxysilane, and the like.

In addition, fillers such as silica, clay gypsum, calcium carbonate, barium sulfate, quartz powder, glass fiber, kaolin, mica, alumina, hydrated alumina, aluminum hydroxide, talc, dolomite, zircon, and titanium compounds are added to the epoxy resin composition. , pigments, anti-aging agents, etc. may be added as appropriate depending on the purpose.

Further, for the purpose of imparting weldability, granular powder or acicular powder of aluminum, zinc, stainless steel, copper, etc. can be added as conductive powder.

When the microcapsules of the present invention are dispersed in various resins, such as epoxy resins, it is usually done at room temperature, but if the resin has a high viscosity, it may be heated to 50 to 60°C. Mechanical dispersion may also be performed using a mixer, disperser, or the like.

〔Effect of the invention〕

The microcapsules of the present invention are mechanically stable, and after being blended with a resin component such as an epoxy resin, the microcapsules of the present invention can be used at room temperature (usually 40°C).
In addition, the foaming agent foams when heated, destroys the capsule, releases the curing agent (curing accelerator), and produces a composition with excellent storage stability. It is possible to obtain a cured product with excellent adhesiveness, solvent resistance, etc. by reacting with the resin component.

〔Example〕

The formulations of the capsule compositions of Examples and Comparative Examples and their properties are shown in Table 1. Here, each component is as follows, and parts indicate parts by weight.

A-1: Polysulfone (softening point 160°C) A-2:
Ethyl cellulose (softening point 95°C) A-3 = polystyrene (softening point 220°C) B-1:2-undecylimidazole (melting point 70-74"C) B-2:3- (
3,4 dichlorophenyl)-11 dimethylurea (melting point 1
20-130°C) B-3: 1-hensyl-2-methylimidazole (melting point 40-50°C) C-1: Azodiluposamide system (decomposition temperature 150°C)
) C-2 = oxybisbenzesosulfonyl hydrazide system (decomposition temperature 150°C) C-3 = azodicarbosoamide system (decomposition temperature 220°C
) C-4: Oxybishenisosulfonyl hydrazide system (decomposition temperature 110°C) Properties were evaluated by the following method.

[Average particle size] Obtained by observing a sample dry using a microscope (optical microscope and electron microscope) and measuring particle size distribution based on Feret diameter.

〔exterior] It was observed under a microscope whether the particles were uniform or not.

〔Stability〕

It was dispersed in liquid epoxy resin and its stability was checked after storage at 40°C for one month.

○: No change in viscosity △: Viscosity 2 times or less ×: Viscosity 2 times or more [foamed state] Capsules containing an amount of curing agent that normally causes epoxy to completely react are dispersed in liquid epoxy resin, and heated to 200″C. Then, I looked at the foaming state.

○: Excellent foaming (a small amount of gas is generated) No foaming at all ×: Excessive foaming and curing with generation of a large amount of gas and bubbles, followed by formulation of an epoxy resin composition using the microcapsules shown in Table 1 , and its characteristics are shown in Table 2. Here, each component is as follows, and parts indicate parts by weight.

(A) Rubber-modified epoxy resin (10 parts of butadiene-acrylonitrile copolymer and 90 parts of bisphenol A type epoxy resin (epoxy equivalent: 190) were reacted at 160°C for 1 hour in a melting and mixing pot to obtain a rubber-modified epoxy resin.

(b) Phenoxy resin (average molecular weight 20,000) (c) Propylene glycol diglycidyl ether (epoxy equivalent weight 215, viscosity (25°C) 35 centipoise) (d) Dicyandiamide (e) T-aminopropyltriethoxysilane (f) Aluminum The properties of the powder and the obtained epoxy resin composition were evaluated by the following methods.

[Gel time]

Gelation time of epoxy resin composition at 160''C [Storage Stability] The epoxy resin composition was stored at 40°C, and the viscosity after 3 weeks was evaluated by the following criteria to see how much it had increased from the initial value.

○: No change ×: Viscosity increased by 2 times or more. Viscosity was measured using a Koka type flow tester at 20°C, 1 kg load, and 1 die diameter.

[Shear adhesive strength]

In accordance with JIS K-6850, two 5 pcc-sp steel plates (100 x 25 x 1.6 t am) were bonded together using the above composition to create a test piece. This example 5.7.8
, Comparative Examples 7 and 8 were heat-cured at 160° C. for 1 hour, and Example 6 and Comparative Example 9 were heat-cured at 100° C. for 1 hour, and then measured at room temperature.

[Water Resistance] The samples prepared in the shear adhesive strength test described above were immersed in 40°C warm water for 10 days, and then the adhesive strength was measured at room temperature in the same manner as above.

Claims (4)

[Claims] (1) Microcapsules made of an organic blowing agent and a curing agent as core materials and a thermoplastic resin as a wall material. (2) An adhesive composition containing microcapsules having an organic foaming agent and a curing agent as core materials and a thermoplastic resin as a wall material. (3) The adhesive composition according to claim (2) is heated to a temperature higher than the foaming temperature of the foaming agent to destroy the microcapsule walls by foaming the foaming agent, and then the curing agent is reacted. Method of curing adhesive composition. (4) An epoxy resin composition containing (a) an epoxy resin, and (b) microcapsules having an organic blowing agent and a curing agent as a core material and a thermoplastic resin as a wall material.