JP3197587B2 - Epoxy resin adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a novel epoxy resin-based adhesive composition, and more particularly, to an excellent epoxy resin-based adhesive composition comprising a core-shell type powdery polymer in which the core and the shell are (meth) acrylate-based polymers. And an epoxy resin-based adhesive composition having both impact resistance and pseudo-curability.

[0002]

2. Description of the Related Art Conventionally, since epoxy resins have various excellent properties, for example, adhesives, adhesive films, base resin, casting resins, powder molding resins, paints, electronic circuit sealants, Widely used for various applications such as base resin for composite materials. However, this epoxy resin has a disadvantage of insufficient impact resistance, and various improvements have been made so far. Methods for improving the impact resistance can be broadly classified into a method of improving the chemical structure of the epoxy resin itself and a method of adding a separately prepared impact modifier to the epoxy resin. By itself, an epoxy resin that can sufficiently satisfy impact resistance cannot be obtained. on the other hand,
As the latter method, (1) a method in which a soluble elastomer monomer is added to an uncured epoxy resin and both are polymerized simultaneously, (2) a method in which a compatible elastomer polymer is added, (3) fine particles There is known a method of dispersing a polymer for improving impact resistance in the form of a ball. In the method (1), n-butyl acrylate is converted into SIPN (Simultaneous interpee) in an epoxy resin.
netting networks) as 0.
Attempts have been made to produce rubber domains of 1-0.2 μm [see Journal of Polymer Science Symposium (JPolymer Sci. Sy).
mposium), Vol. 46, pp. 175-190 (1974)], and this method generally has disadvantages such as lowering the softening point of the product and varying the mechanical strength. Regarding the method (2), various examples of modifying the rubber by adding an elastomer component such as a butadiene-acrylonitrile copolymer rubber having a carboxyl group and an amino group as a terminal group have been proposed, some of which have been put into practical use. However, those obtained by this method are not yet sufficiently satisfactory in terms of impact resistance and toughness for use as a structural adhesive. Further, regarding the method (3), many impact modifiers have been proposed, including polyamide resin-based ones, but all of them have a drawback that pseudo-curability is insufficient. By the way, it is generally known that when a rubber component having a glass transition temperature of −30 ° C. or less is added as a plastic impact resistance improver, it acts to absorb external stress and greatly improves the impact resistance. ing. However, when many of such rubber components are mixed with a liquid epoxy resin as a matrix, the dispersibility thereof is easily affected by the mixing conditions, and the obtained composition has unstable storage properties, It is not practical as an automotive adhesive that requires stability. Furthermore, it is also important for the epoxy resin-based adhesive to have pseudo-curability, and in order to impart pseudo-curability to the epoxy resin composition, a core-shell type modifier made of a (meth) acrylate-based polymer is required. Is known to be effective (Japanese Patent Laid-Open No. 2-80483). The term “pseudo-curing” as used herein refers to a property in which a liquid or a paste adhesive is solidified into a non-adhesive or tacky state at a heating temperature lower than the temperature at which the adhesive is thermally cured, and such pseudo-curing properties are as shown below. Has advantages. That is, in the automotive industry, after a heat-curable adhesive composition based on an epoxy resin is applied to a metal substrate, bending, cutting, degreasing, and washing may be performed. In addition, there is a problem that the working environment is deteriorated due to the dropping or scattering of the adhesive or the removal of the excess adhesive protruding from the bonding portion, and the contamination of the coating pretreatment liquid due to the elution of the adhesive easily occurs. On the other hand, after applying the adhesive to the base material, heating is performed in a short time to form a pseudo-cured material, which makes it easy to remove the excess adhesive from the base material and contaminates the pretreatment liquid for coating. Can also be solved.

[0003]

Under these circumstances, the present invention provides an epoxy resin having excellent adhesion properties such as impact resistance, tensile shear strength and T-peel strength, and pseudo-curability. The purpose of the present invention is to provide a resin-based adhesive composition.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to develop an epoxy resin-based adhesive composition having the above-mentioned preferable properties. It has been found that a core-shell type powdery polymer composed of a (meth) acrylate-based polymer is combined at a predetermined ratio, and a composition containing these and a latent curing agent for an epoxy resin can achieve the object, Based on this finding, the present invention has been completed.

That is, the present invention relates to (1) (A) a liquid epoxy resin, (B) a glass transition temperature containing a crosslinkable monomer having a weight average particle diameter of 0.1 to 3.0 μm. Shells of 20 to 80% by weight of a (meth) acrylate polymer having a glass transition temperature of 70 ° C. or more containing a core of 20 to 80% by weight of a (meth) acrylate polymer having a temperature of not higher than −30 ° C. % Of the core-shell type powdery polymer and (C) a latent curing agent for epoxy resin, and the content of the component (B) is 10 to 100% by weight per 100 parts by weight of the component (A). And (2) a (meth) acrylate-based polymer having a glass transition temperature of -30 ° C or lower. (Core) ) Graft copolymerization using 0.01 to 10% by weight of a crosslinkable monomer based on the total weight of the acrylate monomer and the monomer, contains a crosslinkable monomer unit and has a glass transition temperature of 70 ° C or higher. 2. The epoxy resin-based adhesive composition according to claim 1, wherein a shell made of the (meth) acrylate polymer having an average thickness of 50 ° or more is formed.

Hereinafter, the present invention will be described in detail. In the composition of the present invention, the epoxy resin used as the component (A) includes, for example, glycidyl ethers such as bisphenol A, bisphenol F, resorcin, hydrogenated bisphenol A, and glycidyl ethers such as phenol novolak resin and polyglycidyl ether of cresol novolak resin. Examples include a glycidyl ester type such as a silyl ether type, phthalic acid, hexahydrophthalic acid, and tetrahydrophthalic acid, a glycidylamine type, a linear aliphatic epoxide type, a hydantoin type, a dimer acid type, and an epoxy-modified NBR. These epoxy resins may be used alone or in combination of two or more.

In the composition of the present invention, a core-shell type powdery polymer whose core and shell are made of a (meth) acrylate polymer is used as the impact modifier of the component (B). In this core-shell type powdery polymer,
The (meth) acrylate polymer forming the core is made of a rubber-like polymer having a glass transition temperature of -30 ° C or lower,
On the other hand, the (meth) acrylate-based polymer forming the shell is made of a glassy polymer having a glass transition temperature of 70 ° C. or higher, and can be produced by a continuous multi-stage seed emulsion polymerization method of at least two stages. Also,
The seed latex prepared in the first step may be partially aggregated by solvent coagulation or the like, and then graft-polymerized thereon to form a shell.

First, in the first-stage polymerization, a (meth) acrylate monomer having 2 to 8 carbon atoms in the alkyl group is preferably used, and the (meth) acrylate monomer and the crosslinkable monomer are preferably used. Are polymerized to have a glass transition temperature of -30 ° C.
The following rubbery seed polymer is prepared. Examples of the (meth) acrylate monomer having 2 to 8 carbon atoms in the alkyl group include n-propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and n-decyl methacrylate. Species may be used, or two or more may be used in combination.

The crosslinkable monomers having two or more double bonds having substantially the same reactivity, for example, ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, butylene glycol dimethacrylate , Trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,
Hexanediol diacrylate, hexanediol methacrylate, oligoethylene diacrylate, oligoethylene dimethacrylate, aromatic divinyl monomers such as divinylbenzene, triallyl trimellitate, triallyl isocyanurate and the like can be used. Each of these crosslinkable monomers may be used alone, or two or more kinds may be used in combination.
The amount used is usually from 0.01 to 0.01 based on the total weight of the monomers.
It is selected in the range of 5% by weight, preferably 0.1 to 2% by weight.

[0010] In addition to the (meth) acrylate-based monomer and the crosslinkable monomer, other copolymerizable monomers can be used if desired. As other copolymerizable monomers used as desired, for example, styrene, vinyl toluene, aromatic vinyl compounds such as α-methylstyrene, acrylonitrile, vinyl cyanide compounds such as methacrylonitrile, Further, vinylidene cyanide, 2-hydroxyethyl acrylate, 2
-Hydroxyethyl methacrylate, 3-hydroxybutyl acrylate, 2-hydroxyethyl fumarate,
Examples thereof include hydroxybutyl vinyl ether, monobutyl maleate, glycidyl methacrylate, and butoxyethyl methacrylate. These may be used alone or in combination of two or more, and the amount used is usually selected within a range of 50% by weight or less based on the total weight of the monomers.

Next, the (meth) acrylate polymer particles thus obtained are used as a core, and the (meth) acrylate monomer having an alkyl group having 1 to 4 carbon atoms is crosslinked with a crosslinkable monomer. The second stage of emulsion polymerization in which a shell is formed by graft copolymerization with the polymer is performed. At this time, a (meth) acrylate monomer having an alkyl group having 1 to 4 carbon atoms includes For example, ethyl acrylate, n-butyl acrylate, methyl methacrylate, butyl methacrylate and the like can be mentioned, and these may be used alone or in combination of two or more. Among them, methyl methacrylate is particularly preferable. It is.

As the crosslinkable monomer, one or more of those exemplified in the description of the (meth) acrylate polymer forming the core can be used. The amount of the crosslinkable monomer to be used is generally selected in the range of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the monomer. Furthermore, together with the (meth) acrylate-based monomer and the crosslinkable monomer,
Other copolymerizable monomers can be used as desired. As the other copolymerizable monomer used as desired, one or more kinds selected from those exemplified in the description of the (meth) acrylate polymer forming the core may be used. it can. The amount used is usually selected within the range of 50% by weight or less based on the total weight of the monomers.

The transition temperature of the (meth) acrylate-based polymer forming the shell must be 70 ° C. or higher. When the transition temperature is lower than 70 ° C., when the adhesive composition is mixed with an epoxy resin, the storage stability is poor. When the temperature is lower than 40 ° C., the polymer has high tackiness, and may cause clogging of nozzles during spray drying. The latex containing the core-shell type polymer obtained by such multi-stage emulsion polymerization is usually directly spray-dried to obtain a core-shell type powdery polymer excellent in dispersibility in an epoxy resin. This core-shell type powdery polymer can be obtained by a multi-stage seed emulsion polymerization method of at least two stages as described above. In some cases, the seed latex prepared in the first stage is partially coagulated, and It may be prepared by graft polymerization, and further, after emulsion polymerization, latex particles are coagulated and separated by a salting method or a freezing method, and a wet cake prepared by dehydration is dried with a fluidized bed or the like to obtain aggregated particles. It can also be obtained as a form.

In the core-shell type powdery polymer thus obtained, it is necessary that the content of the core component is in the range of 20 to 80% by weight and the content of the shell component is in the range of 80 to 20% by weight. It is. When the content of the core component is less than 20% by weight, the effect of improving impact resistance is not sufficiently exhibited,
If the content exceeds 80% by weight, the core cannot be completely covered with the shell, and when mixed with the epoxy resin, the change in viscosity of the entire system with the lapse of time or the variation in the impact resistance improving effect may occur. Become.

Further, the weight average particle diameter of the core of the core-shell type powdery polymer needs to be in the range of 0.1 to 3.0 μm. The components may be polymerized, or the core particles may be agglomerated by solvent coagulation or salting out coagulation and then polymerized for coating the shell component. There are many known methods for secondary aggregation, and any of them can be used. The particle size of the core particles is 0.1 μm
When the weight is less than the above, the dispersibility is inferior because the surface area is increased with the same weight, and the mechanical strength and storage stability of the epoxy resin adhesive composition containing the core-shell type powder polymer are significantly reduced. When the particle diameter of the core particles exceeds 3.0 μm, the shear strength and the peel strength tend to decrease. The average thickness of the shell of the core-shell type powder polymer is 5
It is preferably 0 ° or more, and if it is less than 50 °, the coatability of the shell component is not sufficient, which causes a decrease in storage stability. In the composition of the present invention, the core-shell type powdery polymer (B) is used in an amount of 10 to 100 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the epoxy resin (A). It is necessary to mix. If the amount is less than 10 parts by weight, the effect of improving the impact resistance is not sufficiently exhibited, and if it exceeds 100 parts by weight, the viscosity becomes extremely high and the handling becomes difficult.

In the composition of the present invention, the latent curing agent for the epoxy resin used as the component (C) includes, for example, imidazole derivatives such as dicyandiamide, 4,4'-diaminodiphenylsulfone, and 2-n-heptadecylimidazole. , Isophthalic dihydrazide, N, N-
Dialkyl urea derivatives, N, N-dialkyl thiourea derivatives, acid anhydrides such as tetrahydrophthalic anhydride, isophorone diamine, m-phenylenediamine, N-aminoethylpiperazine, melamine, guanamine, boron trifluoride complex compound, tris Examples thereof include dimethylaminomethylphenol. These may be used alone or in combination of two or more. Among them, dicyandiamide is particularly preferable.

In the composition of the present invention, various additives may be added, if desired, for the purpose of adjusting workability, viscosity and other application properties, stability, and reducing costs, as long as the object of the present invention is not impaired. , For example, curing accelerators, fillers,
Pigments, thixotropic agents, flame retardants, antioxidants, release agents, surfactants, foaming agents and the like can be added.
Examples of the curing accelerator include alcohols, phenols, mercaptans, dimethylureas, alicyclics,
Furthermore, imidazole etc. are mentioned. In addition, for cost reduction, fillers that are commonly blended include, for example, calcium carbonate, silica, talc, mica, kaolin clay, celite, asbestos, perlite, barite, silica sand, flaky graphite, dolomite limestone, Gypsum, aluminum fine powder and the like. Examples of the pigment include titanium dioxide, litharge, lithobon, zinc oxide, and carbon black. Examples of the thixotropic agent include silicic acid (colloidal silica) such as silicic anhydride and hydrous silicic acid, and organic bentonite and the like. And the like. The amount of the thixotropic agent to be added is usually selected in the range of 1 to 15 parts by weight per 100 parts by weight of the epoxy resin (A).

The epoxy resin adhesive composition of the present invention comprises:
It can be prepared by homogeneously kneading the component (A), the component (B), the component (C), and various additives used as needed at room temperature. Examples of the kneaders used in this case include commonly used change-can mixers, planetary mixers, dispersers, Henschel mixers, kneaders, ink rolls, and extruders.

The epoxy resin-based adhesive composition of the present invention prepared as described above has a lower content than the core-shell type powdery polymer composed of the (meth) acrylate polymer (B). The impact peeling strength and T-shaped peeling strength are remarkably improved, and pseudo-curability is also provided. The epoxy resin-based adhesive composition is applied to a substrate to be adhered by a usual method, for example, a method such as spraying, a sealer gun, or brushing. The substrate to be bonded is usually a metal,
Even if rust-preventive oil is attached, the composition of the present invention does not impair the adhesiveness.

[0020]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. In addition, the performance of the adhesive composition was evaluated as follows. (1) Pseudo-curing property Heating was performed at 110 ° C. for 5 minutes to cause gelation, and peeling-removability was determined, and evaluated according to the following criteria. ：: The gelled adhesive composition was easily peeled and removed. ：: The gelled adhesive composition was weak in strength and was broken at the removal stage. X: Pseudo-cure was not obtained by heating at 110 ° C. for 5 minutes. (2) Storage stability The ratio of the viscosity over time when stored at 40 ° C. for 7 days to the initial viscosity was determined and evaluated according to the following criteria. ：: The ratio is 1.5 or less Δ: The ratio is greater than 1.5 and 5 or less ×: The ratio is greater than 5 (3) Adhesion strength It evaluated according to. The curing was performed at 180 ° C. for 30 minutes. Impact peel strength: JIS K-6855 Tensile shear strength: JIS K-6850, test piece 0.8 × 25 × 200 mm T-shaped peel strength: JIS K-6850, test piece 0.8 × 25 × 200 mm

Example 1 Bisphenol A type epoxy resin [Epicoat # 82]
8, manufactured by Yuka Shell Epoxy Co.] 50 parts by weight of core-shell type polymer B-1 and 8 parts by weight of dicyandiamide shown in Table 1 were added to 100 parts by weight, kneaded with a planetary mixer for 5 minutes, and vacuumed. Defoaming treatment with a defoaming machine,
An epoxy resin-based adhesive composition was prepared, and pseudo-curability and storage stability were determined. Next, the composition was applied to a predetermined steel plate with a doctor knife and heat-treated to prepare an evaluation sample, and the adhesive strength was determined. Table 2 shows the results.

Example 2 In Example 1, B-1 was used as the core-shell type polymer.
Was carried out in the same manner as in Example 1 except that B-2 was used instead of. Table 2 shows the results.

Example 3 In Example 1, B-1 was used as the core-shell type polymer.
Was performed in the same manner as in Example 1 except that B-3 was used instead of. Table 2 shows the results.

Example 4 In Example 1, B-1 was used as the core-shell type polymer.
Was carried out in the same manner as in Example 1 except that B-4 was used instead of Table 2 shows the results.

Comparative Example 1 In Example 1, B-1 was used as the core-shell type polymer.
Was carried out in the same manner as in Example 1 except that B-5 was used instead of. Table 2 shows the results. The core-shell type polymer used had a high glass transition temperature of the core component of 25 ° C., and as a result, the impact peel strength and the T-shaped peel strength decreased, and the effect of adding the core-shell polymer was not exhibited.

Comparative Example 2 In Example 1, B-1 was used as the core-shell type polymer.
Was carried out in the same manner as in Example 1 except that B-7 was used instead of. Table 2 shows the results. Since the core-shell type polymer B-7 used has a large average particle size of 12 μm, the effect of improving the impact peel strength and the T-shaped peel strength is not sufficiently exhibited, and the tensile shear strength is low.

Comparative Example 3 The procedure of Example 1 was repeated, except that the core-shell polymer was not used. Table 2 shows the results. In this case, the T-shaped peel strength is particularly low,
There was no pseudo-curability.

Comparative Example 4 The procedure of Example 1 was repeated, except that a liquid terminal carboxyl-modified acronitrile-butadiene rubber was used instead of the core-shell polymer B-1. Table 2 shows the results. In this case, although the impact peel strength and T-shaped peel strength were improved, they were inferior to those obtained when the core-shell polymer was used, and had no pseudo-curability.

Comparative Example 5 In Example 1, B-1 was used as the core-shell type polymer.
Was carried out in the same manner as in Example 1 except that B-6 was used instead of Table 2 shows the results. The core-shell polymer used did not use a crosslinkable monomer for forming the shell, and although the adhesive strength was good, the pseudo-curability was somewhat inferior, and particularly the storage stability was inferior.

Comparative Example 6 In Example 1, B-1 was used as the core-shell type polymer.
Was carried out in the same manner as in Example 1 except that B-8 was used instead of B-8. Table 2 shows the results. The core-shell polymer used has a shell component having a glass transition temperature of 25 ° C.
And the tensile shear strength, pseudo-curability, and storage stability were all inferior.

Comparative Example 7 In Example 1, B-1 was used as the core-shell type polymer.
Was carried out in the same manner as in Example 1 except that B-9 was used instead of B-9. Table 2 shows the results. The core-shell polymer used had a large content of the core component of about 91% by weight, and was inferior in adhesive strength, pseudo-curability and storage stability.

Comparative Example 8 The procedure of Example 1 was repeated, except that B-10 was used instead of B-1 as the core-shell polymer. Table 2 shows the results. The core-shell type polymer used had a low content of the core component of about 17% by weight, and although the pseudo-curability and the storage stability were good,
The effect of improving the adhesive strength was hardly observed.

[0033]

[Table 1]

(Note) Both the core component and the shell component were formed by emulsion polymerization at a reaction temperature of 70 ° C. Also,
All polymerized latexes were spray dried.

[0035]

[Table 2]

Note 1) Carboxyl-terminated acrylonitrile-rubutaciene rubber

[0037]

The epoxy resin-based adhesive composition of the present invention contains a core-shell (meth) acrylate-based powdery polymer as an impact resistance improver, and has an impact resistance and a tensile shear strength. It has characteristics such as excellent adhesive performance such as T-peel strength and good pseudo-curability.

Continuing on the front page (72) Inventor Akira Nakayama 1-2-1 Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa Japan Zeon Co., Ltd. No. 1 Nippon Zeon Co., Ltd. Research and Development Center (56) References JP-A-61-222152 (JP, A) JP-A-2-80483 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C08L 63/00-63/10 C09J 163/00-163/10

Claims (2)

(57) [Claims] (1) a liquid epoxy resin, (B) a weight ratio
The average particle size is 0.1 to 3.0 μm, and the crosslinkable monomer is
20 to 80% by weight of a core comprising a (meth) acrylate polymer having a glass transition temperature of -30 ° C or lower and a crosslinkability
A core-shell type powdery polymer comprising a monomer unit and comprising 80 to 20% by weight of a shell made of a (meth) acrylate polymer having a glass transition temperature of 70 ° C. or more; and (C) latent type curing for an epoxy resin And the content of the component (B) is 1 per 100 parts by weight of the component (A).
An epoxy resin-based adhesive composition characterized by being in the range of 0 to 100 parts by weight. 2. The core-shell type powdery polymer as the component (B) comprises a (meth) acrylate-based polymer having a glass transition temperature of -30 ° C. or lower, and a (meth) acrylate-based monomer and all monomers. Graft copolymerization using 0.01 to 10% by weight of a crosslinkable monomer based on the weight of the crosslinkable monomer;
2. The epoxy resin-based adhesive composition according to claim 1, wherein a shell comprising units and comprising a (meth) acrylate-based polymer having a glass transition temperature of 70 ° C. or more and an average thickness of 50 ° or more is formed.