JPS60235877A - Epoxy resin adhesive for automobile - Google Patents

Abstract

PURPOSE:To provide the titled adhesive which has excellent coatability with an electrodeposit and an excellent rust-inhibiting effect after coating, by blending a specified glycidyl ether type epoxy resin, a modified epoxy resin, a latent curving agent and an electrically conductive material. CONSTITUTION:100pts.wt. glycidyl ether type epoxy resin (A) which has an epoxy equivalent of 500 or below and is a liquid at room temp., 20-200pts.wt. modified epoxy resin (B) obtd. by reacting a urethane polymer (a) contg. isocyanate groups at its terminals obtd. by reacting polytetramethylene ether glycol having an MW of 500-5,000 with a diisocyanate in a nitrogen atmosphere at 60-120 deg.C for 1-6hr, with an epoxy resin (b) contg. at least one hydroxyl group per molecule at 80-110 deg.C until the reaction of the isocyanate group with the hydroxyl group is completed, 1-30pts.wt. latent curing agent (C) activating at 100-200 deg.C (e.g. dicyandiamide), 2-200pts.wt. electrically conductive material (D) (e.g. carbon powder and/or graphite powder) and optionally a rust inhibitor (E) are blended together.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an epoxy resin adhesive for automobiles 5.
A one-component heat-curing adhesive useful for adhering coated steel sheets for electrodeposition coating, and by imparting electrical conductivity, the electrodeposition film adheres well to the adhesive layer. Regarding epoxy resin adhesive for automobiles.

Epoxy resins have traditionally been widely used in adhesives, paints, etc. because they have excellent mechanical properties, electrical properties, chemical resistance, etc., and also have good adhesive strength to various materials. However, when using epoxy resin adhesives for special purposes, such as when performing electrodeposition coating in the next step after bonding steel plate bases with the adhesive, adhesive components may be present in the electrodeposition coating liquid. Accidents such as elution causing contamination and deterioration of the coating solution occur frequently, which causes problems such as the uniformity of the electrodeposited coating film being formed and the formation of crater-shaped spots on the coating film. .

As a result of intensive research to resolve such pollution and deterioration, the present inventors have found that:
■ A modified epoxy resin made by reacting a urethane prepolymer containing terminal incyanate groups with polytetramethylene ether glycol and diisocyanate, and an epoxy resin having at least one hydroxyl group in one molecule, and ■ A latent curing agent. We have developed a one-component heat-curable epoxy resin adhesive, and have already applied for a patent for this. However, when performing performance tests on this adhesive, it was newly discovered that rusting occurs because the electrodeposited film is not uniformly applied to the adhesive layer during electrodeposition coating. Therefore, the present inventor discovered that if a conductive material is added to the epoxy resin adhesive, the adhesion of the electrodeposited film becomes better.
The present invention has now been completed.

That is, the present invention provides an epoxy resin adhesive for automobiles, which is a one-component heat-curable epoxy resin adhesive consisting of the above-mentioned components (1) to (4), which is characterized in that it contains a conductive material.

In the present invention, what is the epoxy resin as component (1) above?

Refers to the normal glycidyl ether type. Specifically, reaction products of polyhydric phenol and epichlorohydrin (for example, diglycidyl ether of 2,2-bis(4-hydroxyphenyl)propane [hereinafter referred to as bisphenol 8]), alkylene oxide adducts of polyhydric phenol and epichlorohydrin reactants (e.g. bisphenol A
ethylene oxide and optionally propylene oxide adducts), reactants of aliphatic polyhydric alcohols with epichlorohydrin (e.g. triglycidyl ether of glycerin, diglycidyl ether of 1,6-hexanediol), Hydrogenated products of the reaction products of hydrohydric phenol or its alkylene oxide adduct with epichlorohydrin (for example, polyglycidyl ether of hydrogenated bisphenol A), and in particular diglycidyl ether of bisphenol A, which is a polyhydric phenol derivative.

- Chill is preferred. It is desirable that the epoxy equivalent is 500 or less and is liquid at room temperature.

In the present invention, the modified epoxy resin of component (1) above is obtained by reacting polytetramethylene ether glycol with an excess of diisocyanate to obtain a urethane prepolymer containing free incyanate groups at the terminals (hereinafter referred to as terminal NGO prepolymer). is produced by reacting this with an epoxy resin having at least one hydroxyl group in one molecule (hereinafter referred to as OH epoxy resin).

As the above polytetramethylene ether glycol,
Molecular weight 500-5000, preferably 1000-250
0 may be used.

Examples of the diisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, inphorone diisocyanate, hexamethylene diisocyanate, and tolylene diisocyanate and diphenylmethane diisocyanate are particularly preferred.

When reacting the above-mentioned polytetramethylene ether glyco-)V with diisocyanate, the ratio between the two is usually set so that the incyanate group of the latter is 1.2 to 3 equivalents to the hydroxyl group of the former, and the temperature is 60 to 120°C1
The reaction may be carried out for 1 to 6 hours. In addition, when reacting the above-mentioned terminal NCO prepolymer with an OH epoxy resin (for example, the above-mentioned diglycidyl ether of bisphenol A, diglycidyl ether of aliphatic polyhydric alcohol, etc.), the ratio of the two is usually adjusted to the incyanate group of the former to the incyanate group of the latter. The amount of hydroxyl group is equal to or more (preferably 2 to 5 equivalents)
The reaction is continued at a temperature of 80 to 110''C until the reaction between the incyanate group and the hydroxyl group is completed.

If unreacted polytetramethylene ether glycol remains after the reaction, it is desirable to remove it by means such as distillation in order to avoid elution into the electrodeposition coating solution.

The amount of the modified epoxy resin obtained in this way is usually 20 to 200 parts, preferably 30 to 100 parts (1 part by weight, hereinafter the same) of the epoxy resin of component (1) above.
It may be selected within the range of OO section. If it is less than 20 copies,
Flexibility, which is one of the effects of a urethane-modified epoxy resin, is undesirable, and if the amount exceeds 200 parts, the viscosity of the adhesive tends to become high, resulting in poor workability.

In the present invention, the latent curing agent of component (1) above includes 1
Those activated in the temperature range of 00 to 200°C may be used, such as dicyandiamide, 4,4-diaminodiphenylsulfone, imidazole derivatives (such as 2-n-heptanedecyl imidazole), isophthalic acid dihydrazide, N,N - dialkyl urea derivatives %N, N-dialkyl thiourea XM conductors, melamine derivatives, etc.
One or a mixture of two or more of these may be used.

The amount of the latent curing agent is usually selected in the range of 1 to 30 parts, preferably 5 to 20 parts, based on 100 parts of the epoxy resin of component (1) above, depending on the desired curing state of the adhesive. . If it is less than 1 part, the curing conditions are 140-120°
C/If it does not completely cure in 30 minutes and exceeds 30 parts,
Cured products tend to become brittle.

In the present invention, the conductive material of the component (2) has the general formula; MeO.Fe 203 (Me is Mn, B
a.

Sintered metal oxide-iron oxide composite ferrite or α-Fe203 particle powder represented by divalent metals such as Go, Sr, Pb, Zn, Mg, and Cd, silver, copper,
Metal powders such as palladium, aluminum, and nickel, oxidized metal powders such as ruthenium oxide, bismuth oxide, and iridium oxide, carbon powder, graphite powder, and silver-coated glass powder may be used. In particular, carbon powder or graphite powder is desirable because by adding a small amount, it is possible to obtain a four-electrity property sufficient to coat an electrodeposition paint.

The amount of such conductive material to be blended is usually 2 to 200 parts relative to the epoxy resin Bl&lOO part I of component (1) above, preferably 2 to 3 parts when carbon powder or graphite powder is used.
The amount may be selected in the range of 0 parts, especially in the range of 5 to io parts, and in the case of other conductive materials, in the range of 35 to 150 parts. The above normal combination! If the amount is less than 2 parts, the desired conductivity cannot be achieved, and if it exceeds 200 parts, the viscosity tends to increase and workability tends to deteriorate.

The automotive epoxy resin adhesive according to the present invention has the above-mentioned
~＠Constructed by blending the ingredients in a predetermined ratio, but if necessary, ordinary additives such as rust preventives, fillers (
Calcium subacid, clay, silica, talc, etc.), some plasticizers, solvents, etc. may be blended as appropriate. In addition, in order to impart flexibility to the epoxy resin, it is possible to mix or react a flexible epoxy resin with nitrifle butadiene rubber, etc., and further disperse fine particles of vulcanized rubber to form a seabird structure. It is also possible to provide a so-called matrix structure. The above-mentioned rust preventive material may be a white powder of phosphate having water of crystallization that is harmless to humans or animals (for example, aluminum dihydrogen tripolyphosphate [AeH2P301O
-nH2O, n=2-4] or zinc phosphate [Zo3(
Fe4)2] etc.) are preferred, and it is recognized that by blending these, the effects of the conductive materials are mutually beneficial. Of course, rust preventive materials such as zinc chromate may also be used.

The adhesive of the present invention having the above-mentioned structure is a wave-type thermosetting adhesive and is mainly used for bonding coated steel sheets in the automobile assembly industry. Specifically, for example, when the peripheral edges of the outer pile and the inner panel are overlapped, bent, and fixed by hemming, the adhesive of the present invention is applied to the peripheral edge, and the steel plate panels are fixed after spot explosion welding. The surface is treated by degreasing, etc., then immersed in an electrodeposition coating liquid to perform electrodeposition coating, and then the electrodeposition formed film and the adhesive layer are cured by PA, and then surface coating is performed. According to the adhesive of the present invention, compared to conventional one-component heat-curing epoxy resin adhesives, the problem of elution of the adhesive component into the electrostatic coating liquid and its deterioration is greatly reduced or eliminated. This prevents undesirable defects in the electrodeposited coating film and allows continuous electrodeposition coating of the white body of an automobile assembly.Furthermore, since the adhesive layer is electrically conductive, The adhesion of the deposited film becomes better,
The rust prevention effect after painting can be effectively achieved.

Next, the present invention will be explained in more detail with reference to Production Examples, Examples, and Comparative Examples.

Production Example 1 Polytetramethylene ether glyco-/l/ (molecule 1
looo) looo31 and tolylene diisocyanate 3
5 parts were mixed in a flask purged with nitrogen, heated to 80°C after the end of heat generation, and stirred for 3 hours to obtain a terminal NCO prepolymer.

Diglycidyl ether to bisphenol (11,215 parts per epoxy group, 119 parts per hydroxyl group) was added to 45 parts of this prepolymer.
00) was added and stirred at 95'C for 7 hours to obtain a modified epoxy resin having an epoxy weight of I260.

Production Example 2 Polytetramethylene ether glyco-/I/(molecule 11
500) 100 parts and inphorone diisocyanate 4
6 parts were mixed in a flask purged with nitrogen, and
Stir for 6 hours to obtain terminal NGO prepolymer.

50 parts of this prepolymer was added to bispheno-/l/A diglycidyl ether (1230 parts per epoxy group and 1230 parts per hydroxyl group)
150 parts of propylene oxide adduct of bisphenol/l/A)
Add 100 parts of (11,400 parts per epoxy, 750 parts per hydroxyl group) and stir at 11O"c for 8 hours to obtain @33 parts per epoxy.
0 modified epoxy resin is obtained.

Production Example 3 Polytetramethylene ether glyfur (molecule 1200
0) and 30 parts of diphenylmethane diincyanate are mixed in a nitrogen-substituted flask, and after the exotherm has ended, the temperature is raised to 80°C and stirred for 3 hours to obtain a terminal N 2 CO prepolymer.

50 parts of this prepolymer, 150 parts of diglycidyl ether/L/(epoxy equivalent: 11,270, hydroxyl equivalent: 750) of +vA, were added, and the mixture was stirred at 90'C for 6 hours to form a modified epoxy resin with an epoxy equivalent of 370. obtain.

Examples 1 to 4 Each component in the number shown in Table 1 was kneaded in a kneader, passed through three rolls twice, and then defoamed and stirred in the kneader again.
Prepare epoxy resin adhesive.

Comparative example 1.

An epoxy resin adhesive is prepared in the same manner as in Examples 1 to 4 using each component in Table 1.

Electrodeposition coating property evaluation Each adhesive of Examples 1 to 4 and Comparative Example 1 was applied to a toluene-degreased steel plate (7oXl 00x0.8m) in a width of 30111mm and a thickness of 5mm. Gradually thinner from n to 2MM (apply at an angle, then electrodeposit while applying electricity at 200 volts and 0.5 amperes (as an electrodeposition paint, use a cationic electrodeposition coating made by Kansai Paint Co., Ltd.) use).

After that, it was washed with water, heated and cured at 180°C for 30 minutes,
Evaluate the state of application of electrodeposition paint. The results are shown in Table 1.

Table 1 Note ■) The modified resins of Production Examples 1 to 3 shown in the table were used.

■) ○: Electrodeposition paint adheres to the surface of the adhesive.

×: Electrodeposition paint does not adhere to the surface of the adhesive.

Patent applicant: Sunstar Giken Co., Ltd. Representative patent attorney: 1 person named above

Claims (1)

[Claims] 1. 1. A glycidyl ether type epoxy resin, 2. A urethane prepolymer containing a terminal incyanate group obtained by reacting polytetramethylene ether glycol with a diisocyanate, and having at least one hydroxyl group in each molecule. An epoxy resin adhesive for automobiles, which is a one-component heat-curable epoxy resin adhesive consisting of a modified epoxy resin reacted with an epoxy resin, and a latent curing agent, and which contains a conductive material. 2. The blending ratio of the ■ component, ■ component, ■ component, and @ component is
Weight ratio: 100:20-200:l-30:2-2
00. The adhesive according to item 1 above. 3. The component (■) is carbon powder and/or graphite powder, and the mixing ratio with the component (■) is 100:2 to 100:2 by weight.
The adhesive 4 according to item 1 above, which is No. 30, and the adhesive according to item @ 1, which contains a rust preventive material as another component.