JPH01201384A - Epoxy resin adhesive composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an epoxy resin adhesive composition,
More specifically, it relates to a preheated adhesive that gels in a short time when heated at a relatively low temperature, and which hardens the epoxy resin and develops excellent adhesive strength when subsequently heated at a high temperature. .

(Prior Art) In the automobile industry, one-component thermosetting epoxy adhesives have been widely used in the joints of panels for purposes such as bonding and rust prevention.

For example, when using these adhesives for the hemming part of a car door, etc., after applying the adhesive to the outer periphery of the panel,
After assembling and hemming the panels to be joined,
An undercoat coating called an electrodeposition coating process is performed. However, in this conventional method, the adhesive passes through the electrodeposition coating process without being cured, which can cause the panel to shift or the uncured adhesive to be eluted into various processing solutions during the electrodeposition coating process. , there are problems such as the processing liquid being contaminated with adhesive.

This problem can be solved by immediately applying preheating to gel the adhesive after applying the adhesive and assembling the panels. The present inventors previously proposed a material suitable for such purposes in Japanese Patent Application Laid-Open No. 62-297377.
No. 61-297919 discloses that by blending powdered acrylic resin with a specific structure and properties into liquid epoxy resin, the adhesive gels when heated at a relatively low temperature for a short period of time. It shows what can be done.

(Problem to be Solved by the Invention) Such adhesives are fully cured in a post-electrodeposition baking oven and exhibit their adhesive strength, but adhesives used for such parts have poor shear strength and peelability. It is required to have excellent strength. Therefore, an object of the present invention is to obtain an adhesive that gels immediately after being preheated at a relatively low temperature for a short time, and exhibits adhesive strength with excellent both shear strength and peel strength when further heated at a high temperature.

(Means for Solving the Problems) The present inventors conducted various studies on the composition in order to obtain a composition that can exhibit excellent adhesive strength when the powdered acrylic resin is used in combination with a liquid epoxy resin. By using a liquid epoxy resin composition containing as an essential component an epoxy resin derived from liquid butadiene-acrylonitrile copolymer (hereinafter referred to as NBR-modified epoxy resin), it has excellent adhesive strength and improved adhesive strength. It was confirmed that an adhesive composition could be obtained, and the present invention was achieved.

Therefore, in the adhesive composition of the present invention, 1 part by weight of the powdered acrylic resin is mixed with 100 parts by weight of the NBR-modified epoxy resin composition.
It contains 0 to 100 parts by weight and a heat-activated curing agent for epoxy resin.

The NBR-modified epoxy resin used in the present invention is commercially available as a liquid NBR that reacts with an epoxy group such as a carboxyl group or an amino group at the terminal or side chain, and can be easily obtained by reacting it with a bisphenol A type epoxy resin. It will be done. Basically, it is sufficient to use the NBR-modified epoxy resin obtained in this way together with a powdered acrylic resin and a heat-activated curing agent, but since the NBR-modified epoxy resin has a high viscosity, Liquid epoxy resins, such as bisphenol A type epoxy resins and bisphenol F type epoxy resins, as well as aliphatic diglycidyl ethers called reactive diluents, aromatic monoepoxies, etc., are used to lower the viscosity of liquid epoxy resins. used as a thing. In this case, the NBR component contained in the epoxy resin needs to be 3% by weight or more. NBR
When the component is less than 3% by weight in the epoxy resin composition,
The peel strength decreases, making it impractical.

Furthermore, if an NBR-modified epoxy resin is used as the epoxy resin component, other modified epoxy resins with high viscosity, such as urethane-modified epoxy resins, can also be used.

The powdered acrylic resin blended into the liquid epoxy resin is an important component that causes gelation during preheating.
(meth)acrylate polymers, epoxy group-containing (meth)acrylate polymers, carboxyl group-containing (meth)acrylate polymers, hydroxyl group-containing ( There are meth)acrylate polymers, amino group-containing (meth)acrylate polymers, amide group-containing (meth)acrylate polymers, nitrile group-containing (meth)acrylate polymers, etc., all of which are in powder form, and the NBR-modified 10 to 100 parts by weight of liquid epoxy resin containing epoxy resin
They are mixed and used in a proportion of 100 parts by weight.

These powdered acrylic resins are insoluble in epoxy resins at room temperature, but when preheated, for example to 100° C. or higher, they swell and absorb liquid epoxy resins to form a gel. If the amount of powdered acrylic resin is less than 10% by weight based on the epoxy resin, gelation will be insufficient and the object of the present invention will not be achieved. In addition, containing more than 100 ffiχ,
On the contrary, the adhesive strength decreases and the viscosity becomes high, making it difficult to actually manufacture the adhesive.

When heated at a high temperature (140 to 200°C) after the above-mentioned gelation, it reacts and hardens due to the action of a heat-activated curing agent to which an epoxy resin is added, and exhibits adhesive strength.

Heat-activated curing agents include conventionally known dicyandiamide, dibasic acid dihydrazides such as adipic acid dihydrazide and dodecanoic acid dihydrazide, guanidines such as tetramethylguanidine, and 2-
Examples include imidazoles such as undecylimidazole and 2-phenyl-4-methylimidazole. This is appropriately blended into the composition depending on the equivalent weight of the epoxy resin used and the curing conditions, but it is usually desirable to use 1 to 35 parts by weight per 100 parts by weight of the epoxy resin.

Imidazole derivative, N,N'-dialkyl urea BR
4, alkylaminophenol derivatives, etc. can also be used as accelerators. The amount of the curing agent and accelerator necessary and sufficient for curing can be easily determined by conducting a preliminary test.

The epoxy adhesive composition of the present invention may also contain other components such as viscosity modifiers, fillers, pigments, etc., if necessary.

As the viscosity modifier, thickeners such as anhydrous silicic acid, hydrated silicic acid, asbestos, finely divided calcium carbonate, and bentonite, and reactive diluents such as monoepoxide can be used in the same way as in normal applications, if necessary.

As the filler, calcium carbonate, talc, clay, etc. can be added according to the usual method.

Colorants such as carbon can be used as pigments in the same way as in normal applications.

Plasticizers such as phthalate esters and phosphate esters can also be added to give the adhesive flexibility after pseudo-curing and main curing. If a large amount of plasticizer is used, it may cause a decrease in adhesive strength or cause bleeding, so it is preferable to use a plasticizer that is compatible with the epoxy resin.
A range of 0 to 80 parts by weight is suitable for 0 parts by weight.

(Function) The adhesive obtained as above is applied to the panel,
After the panels to be joined are assembled, they are immediately gelled by preheating (for example, 120° C., about 1 minute). Next, through the electrodeposition coating process, baked open (140~2
00"C/about 30 minutes). During this time,
Due to the adhesive strength of the gelled adhesive, the panel will not shift, and since the adhesive is gelled, it will not be eluted during the electrodeposition coating process.

Moreover, due to its excellent adhesive strength, the durability of the member is improved and excellent quality can be obtained.

(Example) Next, the present invention will be explained with reference to Examples and Comparative Examples.

The powdered acrylic resin and NBR-modified epoxy resin used in Examples and Comparative Examples were manufactured by the method shown below.

'Acrylic resin 12-U Powdered acrylic resin was obtained by emulsion polymerizing the following four types of polymers with each monomer component in a predetermined ratio, followed by spray drying. The basic particle size of each was 0.2μ and the average molecular weight was about 1 million.

Acrylic resin (1) Copolymer of methyl methacrylate/glycidyl methacrylate 9515 (weight ratio) (2) Polymer of methyl methacrylate (3) Copolymer of methyl methacrylate/acrylonitrile 90/10 (4) Methyl methacrylate/2 - Hydroxyethyl methacrylate 9515 copolymer 1, 100 parts by weight of DN601 (manufactured by Nippon Zeon ■, trade name) as NBR, 182B (as epoxy resin)
150 parts by weight (manufactured by Yuka Shell Epoxy ■) was charged into a 4-tube flask and reacted at 160° C. for 2 hours under a nitrogen atmosphere to obtain an NBR-modified epoxy resin (A). The epoxy equivalent weight was 420. It also contained 40% by weight of NBR component.

2. 100 parts by weight of CTBN1300X8 (manufactured by Ube Industries ■, trade name) as NBR, 11 parts as epoxy resin
828,100 parts by weight was reacted in the same manner as in 1 above, and N
BR-modified modified elaxi resin) was obtained. Epoxy equivalent is 4
30 and contained 50% by weight of NBR component.

1-9, 6 1-5 Using the above acrylic resins (1) to (4) and NBR modified epoxy resins (A) and (B), each epoxy resin was prepared using a three-roll mill with the material composition shown in the table. A sample of the resin composition was produced. Thereafter, the gelling properties and adhesive strength of each sample were measured using the following evaluation methods, and the results are also listed in the table.

a Yuta (b) Gelability Each sample was applied onto a bead with a diameter of 3 mm on a steel plate, and 1
Baking is performed at 50°C for 4 minutes. Thereafter, after being left at room temperature for 30 minutes, the dry state was checked by touching with a finger.

○: Dry ×: Sticky and undried (b) Adhesive strength Tensile shear strength and T-shaped failure strength were determined based on JIS K6850 and JIS K6854.

Test piece Material: Mild steel plate (JIS 3141 dull steel plate) Thickness Shear test piece t・1゜mm T-shaped peel test piece t=0.8 mm (Effects of the invention) As explained above, the adhesive of the present invention The composition contains an NBR-modified epoxy resin as an essential component in a liquid epoxy resin, and combines a powdered acrylic resin and a curing agent for epoxy resin, so as to be able to withstand tensile shear as is clear from the results shown in the table. It exhibits high adhesive strength with an excellent balance of strength and T-peel strength.

Patent applicant: Nissan Motor Co., Ltd. Representative Patent Attorney: Hide Sugimura

Claims (1)

[Claims] 1. 10 to 100 parts by weight of a powdered acrylic resin and a heat-activated curing agent for epoxy resin per 100 parts by weight of a liquid epoxy resin containing an epoxy resin derived from a liquid butadiene-acrylonitrile copolymer as an essential component. An epoxy resin adhesive composition comprising: