JPH08109362A - Bonding epoxy resin composition - Google Patents

Abstract

PURPOSE: To obtain a bonding epoxy resin composition used as a principal component resin of a structural adhesive having both pseudocurability (pregelation properties) and high adhesion. CONSTITUTION: This bonding epoxy resin composition contains (a) 10-90 pts.wt. liquid epoxy resin derived from bisphenol A or bisphenol F, (b) 10-90 pts.wt. epoxy resin containing an acrylate-based or a methacrylate-based polymer, having a glass transition temperature within the range of -70 to -30 deg.C and dispersed therein, (c) 10-100 pts.wt. dried powdery acrylate or methacrylate polymer, having a basic particle diameter within the range of 0.1-50μm, a number-average molecular weight within the range of 300000-2000000 and a glass transition temperature within the range of 70-140 deg.C and (d) a heat- activating type curing agent for the epoxy resin as principal components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive epoxy resin composition, and more particularly, an adhesive epoxy used as a main component resin of a structural adhesive having both pseudo-curability and high adhesiveness. It relates to a resin composition.

[0002]

2. Description of the Related Art Conventionally, assembling of an automobile, particularly a joint between an outer panel and an inner panel of a door or a hood has a caulking structure called hemming, and this joint has a rust preventive performance. Epoxy adhesives are often used.

Among these adhesives, a pseudo-curing type epoxy adhesive may be used from the viewpoint of workability. This pseudo-curable adhesive has the following advantages. That is, in the case of an automobile, it is common to apply an adhesive to a steel plate, align the panels, perform spot welding or mechanical joining, and then put the coating process.
If a pseudo-curable adhesive is used, apply the adhesive, align the panels to be joined, and then heat the adhesive-applied part on the panels for a short time to pseudo-cure the adhesive. Then, the shape of the component can be frozen. By using this pseudo-curing adhesive, spot welding can be omitted when fixing the panel with the adhesive, and since the adhesive is in a gel state, it can be applied to the pretreatment liquid for coating. It has an advantage that it is possible to solve the problem that the adhesive melts and the adhesive scatters in the shower of washing with water.

Therefore, a pseudo-curable adhesive has been proposed in which acrylic particles obtained by emulsion polymerization, suspension polymerization or a method similar thereto are dispersed in a liquid epoxy resin (Japanese Patent Laid-Open No. 62-297377). Gazette).

[0005]

However, in the pseudo-curing type adhesive described in the above-mentioned publication, in which acrylic particles are simply dispersed in the liquid epoxy resin, although it is excellent in pseudo-curing property, When used as a structural adhesive that requires adhesive strength such as shear strength and peel strength, it is usually modified epoxy resin such as rubber-modified epoxy resin or urethane-modified epoxy resin in order to improve the adhesiveness. The amount of these modified epoxy resins is increased in order to obtain higher adhesive strength, but the viscosity of the adhesive composition is Becomes higher,
When applying the adhesive to the panel, the adhesiveness of the adhesive to the panel deteriorates and the adhesive cannot be applied to the panel well, or the applied adhesive falls off from the panel due to its high viscosity. There was a drawback to do.

Further, even if a rubber-modified epoxy resin or a urethane-modified epoxy resin is used together to improve the adhesive strength, the modified epoxy resin having a high viscosity is also used together, so that the compounding amount is also limited. was there. Particularly, in the case of automobiles, since it is applied to a steel plate coated with rust preventive oil or press oil, the fixing property of the adhesive to the panel becomes a very important problem, and the adhesive needs to have appropriate fluidity.

Under these circumstances, the workability of coating is prioritized at present, so that an epoxy adhesive in which acrylic particles are dispersed is more likely to be used than an ordinary epoxy adhesive for structure which does not contain acrylic particles. The adhesive strength tends to be slightly inferior. Therefore, in order to expand the use of the pseudo-curable adhesive, it is necessary to increase the strength of the epoxy resin adhesive in which the acrylic particles are dispersed.

Therefore, an object of the present invention is to find a modified epoxy resin as an active ingredient necessary for increasing the strength of an epoxy resin adhesive in which acrylic particles are dispersed,
By using this together, it is intended to provide a novel adhesive epoxy resin composition having excellent adhesive performance without impairing the pseudo-curability and adhesiveness.

[0009]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have replaced the rubber-modified epoxy resin and urethane-modified epoxy resin used together in the past with epoxy as a modified epoxy resin. An epoxy resin in which rubbery acrylic particles having a glass transition temperature (Tg) in the range of −70 to −30 ° C. are dispersed in the resin (hereinafter referred to as an acrylic rubber-dispersed epoxy resin) is used as an acrylic particle-dispersed epoxy resin. The present invention has been achieved by finding that a composition used as a single component exhibits extremely excellent adhesive performance.

The above objects of the present invention are: (a) 10 to 90 parts by weight of a liquid epoxy resin derived from bisphenol A or bisphenol F, and (b) a glass transition temperature in the range of -70 to -30 ° C. Epoxy resin 10-90 in which certain acrylate or methacrylate polymer is dispersed
Parts by weight and (c) a dry powdery acrylate having a basic particle size of 0.1 to 50 μm, a number average molecular weight of 300 to 2,000,000, and a glass transition temperature of 70 to 140 ° C. Or methacrylate polymer 10 to 100
It was achieved by an adhesive epoxy resin composition characterized by containing parts by weight and (d) a heat-activatable curing agent for epoxy resin as main components.

The present invention will be described in more detail below.

The composition of the present invention contains 10 to 90 parts by weight of a liquid epoxy resin derived from bisphenol A or bisphenol F as a main component. This resin is a so-called general-purpose epoxy resin, and is typically a bisphenol A type epoxy resin or a bisphenol F type epoxy resin. As the resin, bisphenol A or bisphenol F to which propylene oxide, ethylene oxide or the like is added can be used. Furthermore, mixtures of the abovementioned epoxy resins can also be used. If the amount of the liquid epoxy resin is less than 10 parts by weight, the elastic modulus of the composition after curing is lowered and the tensile shear strength is lowered. On the other hand, if it exceeds 90 parts by weight, the curing system tends to be hard and brittle, and the adhesive performance is deteriorated.

Further, the composition of the present invention contains epoxy resins 10 to 90 in which an acrylate or methacrylate polymer having a glass transition temperature in the range of -70 to -30 ° C is dispersed.
Contains parts by weight. In reality, it is difficult and difficult to obtain an acrylate or methacrylate polymer having a glass transition temperature of lower than -70 ° C. On the contrary, the epoxy resin in which the glass transition temperature of which exceeds −30 ° C. is dispersed will reduce the adhesiveness. Glass transition temperature is -70
Examples of the acrylate or methacrylate polymer in the range of to -30 ° C include n-butyl acrylate, cyclohexyl acrylate, butyl methacrylate and the like. A modified epoxy resin obtained by dispersing these polymers in an epoxy resin is commercially available as an acrylic rubber-dispersed epoxy resin and is available.

When the epoxy resin is less than 10 parts by weight,
It is not possible to improve the adhesive strength, especially the peel strength.
On the other hand, if it exceeds 90 parts by weight, the cured product becomes soft and the shear strength decreases, and the viscosity of the adhesive composition also increases, so that the ejection performance deteriorates, making it practically difficult to use.

Further, in the present invention, 10 to 100 parts by weight of a powdery acrylate or methacrylate polymer is blended to obtain an acrylic particle-dispersed adhesive epoxy resin composition. The particle size of the acrylic particles is 0.1 to 50 μm
In the range, the number average molecular weight is in the range of 300 to 2,000,000, and the glass transition temperature is required to be dry particles in the range of 70 to 140 ° C. When the particle size of the acrylic particles is less than 0.1 μm, the stability of the composition containing the acrylic particles, in other words, the storage stability as a one-component thermosetting adhesive decreases, which is a practical problem. On the other hand, if the particle size exceeds 50 μm, the pseudo-curing speed when the composition is heated, that is, the swelling speed of the acrylic particles and the liquid epoxy resin becomes extremely slow, and the gelling speed that can be used in the production line is increased. Cannot be obtained, which is a practical problem.

The number average molecular weight of the acrylic particles is 30.
If it is less than 10,000, the film-forming property after pseudo-curing is poor, and the adhesive that has run off and the shower resistance are insufficient. On the contrary, if the number average molecular weight exceeds 2,000,000, the pseudo-curability will be deteriorated.

Further, the glass transition temperature of the adhesive composition is stable during storage and pseudo-curability when heated.
That is, it relates to the pregel property. When the glass transition temperature is lower than 70 ° C., the acrylic particles and the epoxy resin are gradually swollen at room temperature, the coagulation curability during use and the stability during storage are deteriorated, and there is a problem that they cannot be put to practical use. Conversely, 14
If it exceeds 0 ° C, the temperature for pseudo-curing becomes high, and the temperature is close to the curing temperature of a conventional adhesive (usually 140 to 200 ° C), and the pseudo-curing property is lost.

Specific examples of the powdery acrylate or methacrylate include alkyl methacrylate such as methyl acrylate, methyl methacrylate and stearyl methacrylate. The acrylic particles may be a copolymer, and may be copolymerized with the above-mentioned monomer using, for example, glycidyl methacrylate. Further, in the production of acrylic particles, as the crosslinkable monomer, those having two or more reactive double bonds, such as ethylene glycol diacrylate and trimethylolpropane trimethacrylate can be used.

In the composition of the present invention, a heat-activatable curing agent for epoxy resin is used as a main component together with the above resin. Examples of this curing agent include dicyandiamide,
Examples include imidazole derivatives such as 4,4′-diaminodiphenyl sulfone, 2-n-heptadecylimidazole, adipic acid dihydrazide, and N, N′-dialkylurea derivatives, with dicyandiamide being particularly preferred.

These hardeners are basically derived from the epoxy equivalent of the epoxy resin used and the active hydrogen equivalent of the hardener, but in order to obtain good adhesive performance, 100 weight parts of the epoxy resin is usually used. 1 to 20
The range is parts by weight. If the curing agent is less than 1 part by weight,
If the amount of the curing agent exceeds 20 parts by weight, the curing agent remains in the cured product in an unreacted form, which adversely affects the performance such as durability.

In the present invention, although not particularly required, for example, a plasticizer, a diluent, a stabilizer, a filler, a coloring agent and the like may be added if necessary. The epoxy resin composition of the present invention thus obtained can be used not only as an adhesive, but also as a paint, a sealing material, a foamed product, and the like, particularly at room temperature for 1 month before being heat-molded. ~ 2
It is preferably used for processing applications that may be stored for about a year.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

The composition was evaluated by the following methods. (1) Fixability to oil surface steel plate A nozzle of a cartridge containing an adhesive was pressed against a steel plate coated with rust preventive oil to apply the adhesive in a bead shape. The diameter of the nozzle was 3 mm. The following criteria were followed. ◯: The adhesive can be applied without any problem, and even after the application, the steel sheet is stood upright and fixed without being dropped from the steel sheet. X: Even if the adhesive is discharged from the nozzle, it is not well fixed on the steel plate, and the adhesive cannot be applied to a predetermined position.
Alternatively, even if the adhesive is discharged onto the steel plate, the adhesive will fall off when the steel plate is leaned.

(2) Pseudo-curability The adhesive applied to the steel sheet was heated at 110 ° C. for 5 minutes to cause it to gel, and then it was peeled off by hand, and the following judgment criteria were followed. ◯: The gelled adhesive composition can be peeled off relatively easily like rubber. X: The composition does not gel, or even if it gels, the strength of the composition is weak and it cannot be peeled by hand.

(3) Tensile shear strength, peel strength Tensile shear strength is JIS, K6850, peel strength is J
According to IS, K6854, an adhesion test was conducted using a mild steel plate coated with rust preventive oil. 1.6m for tensile shear test
For the peeling test, a plate having a thickness of 0.8 mm was used. Also,
The baking conditions were 180 ° C. and 20 minutes.

Example 1 85 parts by weight of Epicoat # 828 (trade name of Yuka Shell Epoxy Co., Ltd.) derived from bisphenol A as a liquid epoxy resin, acrylic rubber dispersed epoxy resin CX-MN77 (manufactured by Nippon Shokubai Co., Ltd.) 15 parts by weight, 8 parts by weight of dicyandiamide (H3636S, manufactured by AC R Co., Ltd.) as a curing agent, acrylic particles (F301, manufactured by Nippon Zeon Co., Ltd.) to impart pseudo-curability.
40 parts by weight were mixed to obtain a homogenized epoxy resin-based adhesive composition. With respect to the obtained adhesive composition, the fixability to an oil surface steel plate, pseudo-curability and adhesive strength were determined. Table 1 shows the results.

Examples 2 to 8 Adhesive compositions having the formulations shown in Table 1 were prepared and evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Examples 1 to 6 Adhesive compositions having the formulations shown in Table 1 were prepared and evaluated in the same manner as in Example 1. Table 1 shows the results.

[0029]

[Table 1]

[0030]

INDUSTRIAL APPLICABILITY The present invention impairs pseudo-curability and adhesiveness by using a modified epoxy resin as an active ingredient necessary for increasing the strength of an epoxy resin adhesive in which acrylic particles are dispersed. It is a novel adhesive epoxy resin composition which has excellent adhesive performance without any trouble. Therefore, the epoxy resin composition of the present invention can be used not only as an adhesive, but also as a paint, a sealing material, a foamed product, etc., and especially at room temperature for about 1 month to 2 years before being heat-molded. It can be suitably used for processing applications that may be stored.

Claims (1)

[Claims] 1. (a) 10 to 90 parts by weight of a liquid epoxy resin derived from bisphenol A or bisphenol F, and (b) an acrylate or methacrylate-based polymer having a glass transition temperature in the range of -70 to -30 ° C. 10 to 90 parts by weight of the epoxy resin having the coalesced dispersed therein, (c) a basic particle size of 0.1 to 50 μm, and a number average molecular weight of 30
~ 2 million, glass transition temperature 70 ~ 14
An adhesive epoxy resin composition comprising 10 to 100 parts by weight of a dry powdery acrylate or methacrylate polymer in the range of 0 ° C. and (d) a heat-activatable curing agent for an epoxy resin as main components. .