JPH06108028A - Epoxy resin-based adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the adhesive compsn. which is excellent in storage stability, firmly adheres to various adherends, and is suitable for an automotive structural adhesive. CONSTITUTION:This epoxy resin-based adhesive compsn. for an automotive structural adhesive contains crosslinked resin particles obtd. by crosslinking, with a mono- or divalent metal cation, copolymer resin particles comprising a core component consisting of a (meth)acrylate polymer having a Tg of -30 deg.C or lower and a shell component consisting of a copolymer of a (meth)acrylate with a 3-8C unsatd. carboxylic acid having a Tg of 70 deg.C or higher in a wt. ratio of the core component to the shell component of (10:1)-(1:4), a phosphoric triester, a bisphenol A epoxy resin, and a thermally active curing agent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel epoxy resin adhesive composition for structural adhesion of automobiles, and more particularly, to an ionically crosslinked acrylic reinforcing agent for imparting toughness and pseudo-curability. Epoxy resin-based structural adhesive composition for automobiles, which has a long-term storage stability and is effective for a wide range of materials to be adhered, which is blended with a phosphoric acid ester-based modifier to obtain good workability. It is about things.

[0002]

2. Description of the Related Art Conventionally, since epoxy resins have various excellent properties, for example, adhesives, adhesive films, base resins, casting resins, powder molding resins, paints, electronic circuit sealing agents, Widely used for various applications such as base resin for composite materials. However, this epoxy resin has a drawback that its impact resistance is insufficient, and various improvements have been made so far. The method of improving the impact resistance can be roughly divided into a method of improving the chemical structure of the epoxy resin itself and a method of adding a separately prepared impact resistance improver to the epoxy resin, but the former method. By itself, an epoxy resin which can sufficiently satisfy the impact resistance cannot be obtained. on the other hand,
As the latter method, (1) a method of adding a soluble elastomer monomer to an uncured epoxy resin and simultaneously polymerizing the two, (2) a method of adding a compatible elastomer polymer, (3) fine particles There is known a method of dispersing a polymer for improving impact resistance in a shape. Regarding the method (1), n-butyl acrylate is mixed with SIPN (Simultaneous interface) in an epoxy resin.
As netrating networks),
A method for producing a rubber domain having a size of 1 to 0.2 μm has been attempted [see “Journal of Polymer Science Symposium (J Polymer Sci. S.
ymposium) ", Vol. 46, pp. 175-190 (1974)], this method generally has drawbacks such as a decrease in the softening point of the product and variations in mechanical strength. Regarding the method (2), various examples have been proposed in which an elastomer component such as a butadiene-acrylonitrile copolymer rubber having carboxyl groups and amino groups as terminal groups is added to modify the rubber, and some of them are put into practical use. However, the product obtained by this method is still not sufficiently satisfactory in terms of impact resistance and toughness for use as a structural adhesive. Regarding the method (3), many impact resistance improvers including polyamide resin-based ones have been proposed, but all of them have the drawback of insufficient pseudo-curability. 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 an impact resistance improver for plastics, it acts to absorb external stress and the impact strength is significantly improved. 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 resulting composition has unstable storage properties, and thus has long-term storage properties. Is not practical as an adhesive that requires stability. Further, it is also important for the epoxy resin adhesive to have a pseudo-curing property, and in order to impart a pseudo-curing property to the epoxy resin while maintaining the impact resistance improving effect, the (meth) acrylate-based adhesive is used. It is known that a core-shell type modifier composed of a coalesced is effective (JP-A-2-
No. 80483). Pseudo-curability here refers to the property of solidifying to a non-adhesive or tacky state at a heating temperature lower than the temperature at which a liquid or paste adhesive is thermoset, and such pseudo-curability is as shown below. Have advantages.
That is, in the automobile industry, after applying a heat-curable adhesive composition based on an epoxy resin to a metal substrate, bending, cutting, degreasing cleaning, acid treatment and the like may be performed. However, there is a problem in that the work environment is deteriorated due to the dropping or scattering of the adhesive, or the removal of the excess adhesive protruding from the bonded portion, and the pretreatment liquid for coating is easily contaminated due to the elution of the adhesive. On the other hand, after applying the adhesive to the base material, heating it in a short time to form a pseudo-cured product makes it easier to remove the excess adhesive from the base material and also to prevent contamination of the pretreatment liquid. The problem of can be solved. However, since the pseudo-curable and impact resistance imparting agent particles using the (meth) acrylate resin as described above have high compatibility with the epoxy resin which is a medium of the adhesive composition, storage before heat curing is performed. In many cases, a remarkable increase in viscosity occurs, making it impossible to coat. In this case, the storage stability can be improved by cross-linking the (meth) acrylate layer serving as the shell component, but the original purpose is to lower the impact resistance, which is a contradictory result. Further, conventionally, an ion-crosslinked polymer is widely known as a so-called ionomer (trade name). This ionomer utilizes thermoreversible ionic cross-linking, which is a heat resistance, which is a drawback of polymers with a two-dimensional structure.
The ionic cross-linking structure improves mechanical properties such as solvent resistance or creep resistance at high temperatures, and moreover,
It is characterized by maintaining processability as a thermoplastic polymer, unlike ordinary three-dimensionally cross-linked polymers by covalent bonds. Ion-crosslinked polymers have been developed for a wide range of applications by utilizing this characteristic. On the other hand, in the processing technology for heat-curable adhesives, resin fine particles such as an impact resistance improver may be suspended and dispersed in a plasticizer, a liquid monomer, or a liquid polymer. In this case, these dispersions are applied or shaped before heating and then reacted by heat treatment to cure the medium and the resin fine particles into an integral substance. In view of mechanical properties, it is preferable that the compatibility parameter values of the substances of both the dispersion medium and the resin particles are close to each other. However, if such compatibility parameter values are used, the polymer particles are likely to swell due to the medium substance during storage of the resin fine particles as a dispersion, the viscosity of the entire dispersion is changed, and the storage stability thereof is improved. Is deteriorated, which hinders shaping operation and coating operation before heating, resulting in an unfavorable situation. By the way, in manufacturing an automobile, a predetermined mounting component is incorporated into a frame of the automobile, and then an outer plate of the body is attached. Generally, the attachment of the outer plate is simplified by spot welding instead of linear welding between the outer plate and a required portion of the frame, and by adhering the spots with an adhesive. ing. Also, many automobiles are manufactured by a monocoque body method in which a frame is eliminated and the body itself can withstand an external force. In this case, an adhesive is used between the spots in the joining between the units as in the above. As the adhesive used for such structural adhesion, cold rolled steel, which is a metal material for automobile manufacturing, hot rolled steel,
Furthermore, it must be capable of adhering an aluminum plate or the like with a large adhesive force. That is, for various kinds of materials to be adhered made of the above metal materials,
It must always exhibit a T-shaped peel strength of 0 kgf / 25 mm or more. Further, since the steel sheet is generally coated with rust preventive oil for rust prevention, it must have a large adhesive force even against oil drops. Conventional structural adhesives have not shown stable and high adhesive strength to such various adherend materials.

[0003]

Under the circumstances, the present invention provides an adhesive composition in which acrylate or methacrylate polymer resin fine particles are dispersed in an epoxy resin uncured medium having a close compatibility parameter, Provided is an epoxy resin-based structural adhesive composition for automobiles, which prevents the resin fine particles from swelling by a medium, has excellent long-term storage stability, and has high adhesive strength to a wide range of adherend materials. It was made for the purpose.

[0004]

Means for Solving the Problems As a result of intensive studies to develop an epoxy resin-based adhesive composition having the above-mentioned preferable properties, the present inventors have found that the ionic crosslinked structure is a crosslinked structure but is thermoplastic. Paying attention to the unique phenomenon of maintaining the above, by ion-crosslinking the core-shell type acrylate or methacrylate-based copolymer resin particles, the swelling phenomenon of the particles by the epoxy resin medium can be prevented. The epoxy resin-based adhesive composition containing resin particles of, while excellent in storage stability for a long period of time, also has good mechanical strength of the thermosetting product, and by adding a specific additive thereto,
It has been found that an equally high bond strength is obtained for a wide range of automotive structural materials. The present invention has been made based on such findings.

That is, the present invention comprises (A) (a) a core component composed of an acrylate or methacrylate polymer having a glass transition point of -30 ° C. or lower, and (b) (a) an acrylate or methacrylate monomer. (B) A core component comprising a carboxyl group-containing radically polymerizable unsaturated carboxylic acid monomer having 3 to 8 carbon atoms and a shell component composed of a copolymer having a glass transition point of 70 ° C. or higher, and a core. Resin powder particles obtained by ion-crosslinking copolymer resin particles having a component / shell component weight ratio in the range of 10/1 to 1/4 by addition of monovalent or divalent metal cations, (B) molecular weight 1
Epoxy containing 80 to 460 aliphatic and / or aromatic phosphoric acid triester, (C) epoxy resin derived from bisphenol A, and (D) heat-activatable curing agent for epoxy resin as essential components The present invention provides a resin-based structural adhesive composition for automobiles. Hereinafter, the present invention will be described in detail. In the composition of the present invention, the resin powder particles used as the component (A) are core-shell type acrylate or methacrylate copolymer resin particles to which a monovalent or divalent metal cation is added and ionically crosslinked. . In the production of the resin powder particles of the component (A),
First, (a) the glass transition temperature (Tg) of the core component is −
A rubber-like seed polymer composed of an acrylate or methacrylate polymer at 30 ° C. or lower is prepared. Tg is-
Examples of the (meth) acrylate-based monomer that gives a polymer at 30 ° C. or lower include ethyl acrylate, propyl acrylate, n-butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, butyl methacrylate, and the like. You may use 1 type and may use it in combination of 2 or more type.

If desired, a crosslinkable monomer may be added to the above (meth) acrylate-based monomer to further enhance the rubber property. As a crosslinkable monomer for this,
Having two or more double bonds with substantially equal reactivity, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, butylene glycol dimethacrylate,
Aroma such as trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, hexanediol diacrylate, hexanediol methacrylate, oligoethylene diacrylate, oligoethylene dimethacrylate, and divinylbenzene. Group divinyl monomers, triallyl trimellitate, triallyl isocyanurate and the like can be used. These crosslinkable monomers may be used alone in the range where the Tg of the obtained polymer is −30 ° C. or lower, or may be used in combination of two or more kinds.
The amount used is usually 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. In addition to the (meth) acrylate-based monomer and the crosslinkable monomer, other copolymerizable monomers can be used if desired. As the other copolymerizable monomer used as desired, for example, styrene, vinyltoluene, aromatic vinyl compounds such as α-methylstyrene, acrylonitrile, vinyl cyanide compounds such as methacrylonitrile, Furthermore, vinylidene cyanide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxybutyl acrylate, 2-hydroxyethyl fumarate, hydroxybutyl vinyl ether, monobutyl maleate, glycidyl methacrylate, butoxyethyl methacrylate and the like can be mentioned. To be These may be used alone or in combination of two or more, and the amount to be used needs to be selected within the range where the Tg of the obtained polymer is -30 ° C or less, but usually a single amount is used. It is selected in the range of 50% by weight or less based on the total body weight.

Next, the (meth) acrylate polymer particles thus obtained are used as a core, and the (a) (meth) acrylate monomer and (b) a carboxyl group-containing C3-8 monomer are used. Graft copolymerization with a radically polymerizable unsaturated carboxylic acid monomer gives (b) a glass transition temperature of 70.
A second stage emulsion polymerization is performed to form a shell made of a copolymer having a temperature of ℃ or higher. Examples of the (meth) acrylate-based monomer as the raw material component (a) used in this case include (meth) having an alkyl group having 1 to 4 carbon atoms such as ethyl acrylate, n-butyl acrylate, methyl methacrylate, and butyl methacrylate. Acrylate may be mentioned, and these may be used alone or in combination of two or more, and among these, methyl methacrylate is particularly preferable. Examples of the radically polymerizable unsaturated carboxylic acid monomer having a carboxyl group and having 3 to 8 carbon atoms used as the raw material component (b) include acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, cinnamic acid, etc. Unsaturated dicarboxylic acids such as unsaturated monocarboxylic acids, maleic acid, itaconic acid, fumaric acid, citraconic acid, chloromaleic acid and their anhydrides, monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, fumarate Examples thereof include monoesters of unsaturated dicarboxylic acids such as monoethyl acid acid, monomethyl itaconate, monoethyl itaconate, and monobutyl itaconate, and their derivatives. These may be used alone or in combination of two or more, and among these, acrylic acid, methacrylic acid, maleic acid, maleic anhydride and fumaric acid are particularly preferable.

At this time, if desired, a crosslinkable monomer may be added as a raw material component (C). As the crosslinkable monomer, one kind or two or more kinds can be selected and used from those exemplified in the description of the (meth) acrylate polymer forming the core. The amount of the crosslinkable monomer used is usually 0.01 to 1 based on the total weight of the monomers.
It is selected in the range of 0% by weight, preferably 0.1 to 5% by weight. Furthermore, if desired, other copolymerizable monomers can be used together with the raw material components (a), (b) and (c). The other copolymerizable monomer used as desired forms the core (meta).
It is possible to select and use one kind or two or more kinds from those exemplified in the description of the acrylate polymer. The amount used is usually selected in the range of 50% by weight or less based on the total weight of the monomers. The resin particles thus obtained have a carboxyl group-containing copolymer at least in the shell part, and the copolymer has an average of monomer units containing a carboxyl group per copolymer molecule. And one or more of them are combined, and the carboxyl group is present in a proportion of 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight, and more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the copolymer. Those containing a monomer unit having The content of this monomer unit is 0.0
If it is less than 1 part by weight, the effect of modifying the surface of the particle by ionic crosslinking is hardly exhibited, and if it exceeds 20 parts by weight, the improvement of the effect of modifying the surface of the particle is not recognized for the amount, but rather the original effect of the base resin. The mechanical properties are deteriorated, which is not preferable.

In the resin particles, the entire shell portion can be a copolymer having a carboxyl group,
The outermost layer of the shell part may be a copolymer having a carboxyl group. To make only the outermost layer of the shell part a copolymer containing a carboxyl group, the carboxyl group-containing monomer may be added continuously or intermittently in the latter stage of the entire polymerization reaction. By this method, the proportion of the monomer unit having a carboxyl group in the entire resin particles can be reduced and the original resin physical properties can be maintained. In the case of producing resin particles in which a copolymer having a carboxyl group is present only in the shell portion, for example, first, the monomer having a carboxyl group is removed, and only the required monomer components are emulsion polymerized. After producing a latex of polymer particles to be the core part, the required monomer component containing a monomer having a carboxyl group is added to the latex to continue the polymerization, and the surface of the core part polymer particles is added. It is possible to use a so-called core / shell emulsion polymerization method in which a shell portion made of a copolymer having a carboxyl group is formed. Also, if desired, the main monomer used for the shell copolymer may be of a different type from the monomer used for the core polymer particles.

The transition temperature of the (meth) acrylate-based copolymer forming the shell must be 70 ° C. or higher, and if it is lower than 70 ° C., the storage stability will be low when it is mixed with an epoxy resin to form an adhesive composition. Is insufficient, the polymer has a high heat fusion property, and may cause a nozzle clogging during spray drying. Latex containing a core-shell type polymer obtained by such a multi-stage emulsion polymerization,
Usually, direct spray drying gives a core-shell type powdery polymer having excellent dispersibility in an epoxy resin. This core-shell type powdery polymer can be obtained by the multistage 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 aggregated, and then the seed latex is formed thereon. It may be prepared by graft polymerization, and further, after emulsion polymerization, latex particles are coagulated and separated by a salt folding method or a freezing method, and a wet cake prepared by dehydration is dried in a fluidized bed or the like,
It can also be obtained in the form of agglomerated particles. The weight of the shell portion of the core-shell type resin particles thus obtained is
(A) component (meth) acrylate-based monomer, (B) component carboxyl group-containing radically polymerizable unsaturated monomer, (C) component crosslinkable monomer used as desired, and others The weight ratio of the core component / shell component in the present invention is 10/1 to 1 in the present invention.
It is necessary to be in the range of / 4. If the weight ratio deviates from the above range, the object of the present invention cannot be sufficiently achieved.

Next, a monovalent or divalent metal cation is added to the core-shell type resin particles to cause ionic crosslinking. Examples of the monovalent or divalent metal cations include monovalent metal ions such as potassium, sodium, lithium and cesium, and divalent metal ions such as calcium, zinc, tin, chromium and lead, especially I in the periodic table. Monovalent or divalent ions of metals belonging to Group III are preferred. As the cation supplier, the monovalent or divalent metal ion oxides, hydroxides, phosphates, carbonates, nitrates, sulfates,
Chlorides, nitrites, sulfites, and further octylic acid, stearic acid, oleic acid, capric acid, formic acid, succinic acid, erucic acid, linolenic acid, palmitic acid, propionic acid, acetic acid, adipic acid, butyric acid, naphthenic acid, Examples thereof include salts of organic acids such as thiocarboxylic acid, acetylacetone salts, and alcoholates such as ethoxide and methoxide. In the case of an acid salt, it is desirable that the acid dissociation constant pKa is 4 or more. Among these cation suppliers, monovalent metal hydroxides and carboxylates are particularly effective from the viewpoints of the reaction efficiency of ionic crosslinking and the mechanical strength of the heat-molded article. The monovalent and divalent cation donors, unlike trivalent or higher cation donors, do not require heating for a relatively long time in performing an ionic crosslinking reaction, and at room temperature in a solution. The feature is that the ionic cross-linking reaction can be performed within a few minutes.

When a carboxyl-containing monomer is copolymerized in an aqueous polymerization solution, most of the carboxyl groups are accumulated on the surface layer of the fine particles due to its hydrophilic property. Therefore, a cation supplier is added to the aqueous layer. In this case, since it is a reaction between ions, the probability of encountering the cation dissociated in the aqueous layer with the highly dissociative carboxyl group is extremely high, and the ionic crosslinking reaction is completed in a short time. Since the ionic crosslinking reaction in the present invention occurs on the surface of the shell portion, the resin constituting the core portion does not need to be a copolymer with a carboxyl group-containing monomer, but a copolymer having a carboxyl group It can also be united. In addition, the temperature dependence of the ionic crosslinking rate of the resin particles is small, and the amount of metal ions present in the copolymer after ionic crosslinking remains unchanged in the temperature range of 0 to 50 ° C. Does not require any particular temperature control, and a certain ionic crosslinking can be easily obtained. In the above ionic crosslinked product, a part or all of the carboxyl groups are ionized to form carboxyl anions, and monovalent or divalent metal ions are used as counter cations to form an ionic bond. It can be easily adjusted according to the amount of body. The above-mentioned ionic crosslinking reaction generally proceeds quantitatively, but it is possible to use an excessive amount of the cation donor as compared with the theoretical amount. The presence of this ionic cross-link can be easily analyzed by measuring the absorption of the carboxylate group by infrared absorption spectrum, quantifying the metal ion, and measuring the degree of swelling in a solvent. The dissociation property of ionic crosslinks can be confirmed by differential thermal analysis, and the density can be confirmed by measuring the degree of swelling.

In order to efficiently obtain the ionic crosslinked product used in the present invention, the molar ratio of the metal atom of the cation donor per the carboxyl group contained in the copolymer is selected according to the desired degree of crosslinking. The addition amount of the cation supplier is 0.1 to 1 with respect to the amount of carboxyl groups in the copolymer.
A suitable range is 3 times by mole, and at this molar ratio, the ionic crosslinked product has particularly excellent mechanical properties. When the above molar ratio is less than 0.1 times, the surface modification effect is remarkably poor,
When it exceeds 3 times by mole, mechanical properties tend to deteriorate, which is not preferable. Further, as described above, even if the structure of the ionic crosslinked product is used, the above-mentioned pseudo-curability is not deteriorated. As a method of obtaining the ionic crosslinked product, for example, a method of dissolving the copolymer in a suitable solvent and adding a cation supplier or a solution thereof to the polymer solution to cause an ionic crosslinking reaction, after the polymerization step There is a method of adding a cation supplier or a solution thereof to the latex, a method of adding a cation supplier in the process of adding a powder of a copolymer to an unreacted epoxy resin and mixing and preparing an adhesive. Any of these methods can be used as a method for obtaining the ionic crosslinked product of the present invention, but the latex addition method is simple and useful from the viewpoint of handleability and dispersion efficiency. The ionic cross-linked product of the component (A) thus obtained differs from a cross-linked structure of a covalent bond such as a sulfur cross-link or a peroxide cross-link, because the formation of the cross-linked structure changes reversibly thermo-reversibly. The surface of the modified resin particles exhibits a property of a crosslinked structure at room temperature, while it exhibits a property of a structure in which the crosslinks are dissociated under the molding condition of heat curing, and as a result, the composition of the present invention is storage stable. And the mechanical strength of the molded product.

That is, in the present invention, the cation as a cross-linking agent forms an ionic cross-link between the carboxyl groups present as the side chains of the copolymer constituting the shell portion of the resin particle, and the shell of the resin particle is formed. The three-dimensional polymer structure formed in the part reduces the swelling property at room temperature by the epoxy resin medium, and the heat-cured product of the base polymer and the dispersion medium does not impair the original physical properties and the storage stability of the composition is improved. It has improved sex. Further, in order to reduce the swelling property of the resin particles, the object can be achieved by providing an ionic cross-linking structure in at least the polymer of the shell portion, but if desired, the core portion of the resin particles may also have ions. Providing a crosslinked structure can also be appropriately adopted depending on the physical properties of the molded product. In the composition of the present invention,
The core-shell type resin particles used as the component (A) are
For example, it can be produced by an emulsion polymerization method, a fine suspension polymerization method and a suspension polymerization method. Further, in order to effectively modify the surface of fine particles having a size of about 0.1 to 5 μm by graft polymerization, particles obtained by mainly emulsion polymerization method or fine suspension polymerization method are aggregated, As described above, it is effective to copolymerize a required monomer including a carboxyl group-containing monomer so that the shell portion contains a carboxyl group and ionically crosslink. Carboxyl group-containing monomers are used in the case where they are charged in a reactor at the same time as the base polymer monomers for polymerization, when they are added later in the reaction of the base monomer, and when the base monomer is reacted. In some cases, they may be added dividedly in some cases, and depending on the combination of the monomers to be used, suitable methods can be appropriately adopted according to their specific reactivity ratios.

In the composition of the present invention, the fatty acid group and / or aromatic phosphate triester having a molecular weight of 180 to 460 used as the component (B) is, for example, tricresyl phosphate or tri-2-ethylhexyl phosphate. , Tributyl phosphate, triphenyl phosphate, trixylyl phosphate, cresyl diphenyl phosphate, tributoxyethyl phosphate, triethyl phosphate, diphenyl-2
-Methacryloyloxyethyl phosphate, octyldiphenyl phosphate, dioctyl-2-methacryloyloxyethyl phosphate, trisdichloropropyl phosphate, trisdichloroethyl phosphate, etc., among which tricresyl phosphate is particularly preferred. Fates are preferred. These phosphate triesters may be used alone or in combination of two or more, and the addition amount thereof is usually 1 to 30 parts by weight with respect to 100 parts by weight of the epoxy resin as the component (C). Parts, preferably 5 to 20 parts by weight. Bisphenol A used as the component (C) in the composition of the present invention
Examples of epoxy resins derived from

[0016]

[Chemical 1]

Those represented by can be mentioned. Although n in the general formula [1] is a number of 0 or more, those having an average value of less than 1 are suitable because they are liquid at room temperature. Further, an epoxy resin derived from a compound obtained by adding 2 to 20 mol of ethylene oxide or propylene oxide to bisphenol A can also be used. In the composition of the present invention, the heat-activatable curing agent for epoxy resin used as the component (D) is, for example, dicyandiamide, 4,4′-diaminodiphenylsulfone,
Imidazole derivatives such as 2-n-heptadecyl imidazole, isophthalic acid dihydrazide, N, N-dialkylurea derivatives, N, N-dialkylthiourea derivatives,
Examples thereof include acid anhydrides such as tetrahydrophthalic anhydride, isophoronediamine, m-phenylenediamine, N-aminoethylpiperazine, melamine, guanamine, boron trifluoride complex compounds, and trisdimethylaminomethylphenol. These are one kind. They may be used, or two or more kinds may be used in combination, and among these, dicyandiamide is particularly preferable.

The amount of the heat-activatable curing agent as the component (D) is not particularly limited, but is usually 3 to 30 parts by weight, preferably 100 parts by weight of the epoxy resin as the component (C). It is a ratio of 5 to 20 parts by weight. If this amount is less than 3 parts by weight, curing failure will occur, causing a significant decrease in each adhesive strength, and if it exceeds 30 parts by weight, partial decomposition or thermal deterioration will occur due to excessive exothermic reaction during molding.
As a result, each adhesive strength is significantly reduced or discolored. The epoxy resin-based adhesive composition of the present invention comprises an epoxy resin as the component (C), ion-crosslinked resin powder particles as the component (A), a phosphoric acid triester as the component (B), and thermal activity as the component (D). It can be prepared by blending the mold curing agent and optional components used as desired and mixing them homogeneously. Examples of the additive component to be added to the adhesive composition as desired include, for example, plasticizers, diluents, stabilizers, emulsifiers, fillers, reinforcing agents, colorants, foaming agents, antioxidants, and UV inhibitors. Lubricants and the like can be mentioned. The epoxy resin-based adhesive composition of the present invention is used as a structural adhesive for automobiles,
It is suitably used for bonding a wide range of materials to be adhered, such as cold rolled steel, hot rolled steel, cold rolled stainless steel, and aluminum.

[0019]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. The physical properties of the composition were evaluated by the methods described below. (1) T-shaped peel strength According to JIS K 6850, it was carried out using a test piece of 0.8 × 25 × 20 cm. (2) Viscosity storage stability After standing at 40 ° C for 7 days, the viscosity was measured with a Brookfield H type viscometer. The value obtained by dividing the viscosity after 7 days by the initial viscosity was evaluated according to the following criteria. ◯: The value is less than 1.5 Δ: The value is 1.5 to 5.0 x: The value is more than 5.0 (3) Pseudo-curability After heating at 110 ° C. for 5 minutes After gelling, peeling removability was obtained and evaluated according to the following criteria. ◯: The gelled adhesive composition could be easily peeled off Δ: The gelled adhesive composition was weak in strength and was torn at the removal stage x: Those which were not pseudo-cured by heating at 110 ° C. for 5 minutes

Example 1, Comparative Example 1 48 parts by weight of n-butyl acrylate and 1 part by weight of tetraethylene glycol dimethacrylate were used, and the carbon number was 1
Using 1 part by weight of 2 to 18 sodium alkylsulfate as an emulsifier, 0.1 part by weight of a potassium persulfate catalyst was added, and emulsion polymerization was carried out by stirring in 150 parts by weight of water at a polymerization temperature of 70 ° C. for 180 minutes. . Then, using the latex obtained by this polymerization as a seed, graft polymerization is carried out with 48 parts by weight of methyl methacrylate, and further 3 parts by weight of methacrylic acid and 1 part by weight of tetraethylene glycol methacrylate are continuously added at the end of this polymerization. A polymer for an acrylic reinforcing agent was produced by To the latex after polymerization, as a counter cation for ionic crosslinking, an aqueous potassium hydroxide solution was added at room temperature so as to be equimolar to methacrylic acid, and the pH was adjusted to 7 to 8. Then, this latex was heated at an inlet hot air temperature of 160 ° C. and at an outlet gas. Spray drying was carried out at a temperature of 55 ° C. to obtain an acrylic reinforcing agent. next,
Epoxy resin (Epicoat 828, manufactured by Shell Yuka Epoxy Co., Ltd.) 100 parts by weight, latent curing agent (dicyandiamide) 8 parts by weight, the reinforcing agent 50 parts by weight and modifier 1
The basic formulation was 0 parts by weight [3 parts by weight of the surfactant in (14) and (15) of Comparative Example 1]. The compounding is carried out in a planetary mixer with vacuum degassing, and it is applied as a sample for T-peel test to three types of steel plates of [1], [2] and [3] of a predetermined size, and at 180 ° C for 30 minutes. It was heat-cured to obtain a sample. [1] and [2] are cold rolled steel sheets (JIS G 3141 SPCC) manufactured by different manufacturers, and [3] is a rolled material for general structure (JIS G 3101 SS55). The evaluation results of each physical property are shown in Table 1.

[0021]

[Table 1]

Note 1) Rust-proof oil was wiped off with gauze. Therefore, it is a test in the oil level state.

Example 2 and Comparative Example 2 An example in which polished 5000 series aluminum alloys (JIS H 4000) were used as the materials to be adhered, and the same acrylic reinforcing agent as that used in Table 1 was used. . The compounding conditions of the adhesive, the preparation and measurement conditions of the T-peel strength test sample, and the storage stability and pseudo-curability measurement conditions were the same as in Example 1. As a comparative example, a terminal carboxyl-modified acrylonitrile-butadiene rubber which is most commonly used as a reinforcing agent at present is used. When a generally used general-purpose reinforcing agent is used, the T-shaped peel strength of the aluminum alloy is 3 to 5 as compared with the cold rolled steel sheet.
Although it is said that the result of Example 2 is almost the same, the result of Example 2 is almost the same as the result of Example 1 of Table 1, and it can be seen that the adhesive strength of the present invention is excellent.

[0024]

[Table 2]

Note 1) Terminal carboxyl modified acrylonitrile-butadiene rubber 2) Unit is kgf / 25mm

[0026]

The epoxy resin-based adhesive composition of the present invention comprises an ionically cross-linked acrylic reinforcing agent for imparting toughness and pseudo-curability and a phosphate ester-based modification for obtaining good workability. It is a compounding agent, has excellent long-term storage stability, has high adhesive strength to a wide range of materials to be adhered, and is suitably used as a structural adhesive for automobiles.

Claims (1)

[Claims] 1. A core component comprising (A) (a) an acrylate or methacrylate polymer having a glass transition point of -30 ° C. or lower, (b) (a) acrylate or methacrylate monomer and (b) carboxyl. Group having 3 to 3 carbon atoms
And a shell component composed of a copolymer having a glass transition point of 70 ° C. or higher obtained from the radically polymerizable unsaturated carboxylic acid monomer of 8 and having a core component / shell component weight ratio of 10/1 to Resin powder particles obtained by adding a monovalent or divalent metal cation to the ion-crosslinked copolymer resin particles in the range of 1/4, and (B) an aliphatic and / or aromatic phosphorus having a molecular weight of 180 to 460. An epoxy resin-based structural adhesive composition for an automobile, comprising an acid triester, (C) an epoxy resin derived from bisphenol A, and (D) a heat-activatable curing agent for an epoxy resin as essential components.