JPH07224268A - Adhesive epoxy resin composition - Google Patents

Abstract

PURPOSE:To obtain a resin composition which exhibits improved adhesiveness and rust-preventing effect to metal panels for a long period of time by using as main components a mononuclear polyhydric phenol/urethane-modified epoxy resin and a latent curing agent thereof. CONSTITUTION:An adhesive epoxy resin composition containing as main components at least a mononuclear polyhydric phenol/urethane-modified epoxy resin and a latent curing agent for the epoxy resin. The modified epoxy resin to be used is prepared reacting a polyhydroxy compound with an isocyanate compound to obtain a urethane prepolymer, reacting the obtained prepolymer with a mononuclear polyhydric phenol to form a mononuclear polyhydric phenol- modified urethane prepolymer, and reacting the obtained prepolymer with an epoxy resin. It is preferred that the number-average molecular weight of the polyhydroxy compound be in the range of 600 to 20,000 and that the number of hydroxy groups contained in the epoxy resin be 0.1 to 2.0 per molecule on the average.

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, it is a one-pack type thermosetting resin and is extremely suitable for various steel plates and various aluminum alloys to which press oil or rust preventive oil is attached. The present invention relates to an adhesive epoxy resin composition which has excellent adhesiveness and rust preventive properties and is therefore used as a main component resin of a structural adhesive particularly in automobile assembly.

[0002]

2. Description of the Related Art In recent years, improvement in corrosion resistance of automobile bodies has been demanded, and accordingly, various surface-treated steel sheets such as steel sheets, galvanized steel sheets and zinc-nickel plated steel sheets, and steel sheets obtained by coating an organic film on a plated steel sheet have been demanded. It is used. Corrosion resistance is ensured by assembling a car body by using spot welding or MIG welding by using these steel plates and then performing chemical conversion treatment or electrodeposition coating.

However, in the case of a closure panel such as a hood or a door, the above processing is performed after the outer panel and the inner panel are hemmed, but the hemming portion is poorly covered by electrodeposition. ,
It becomes a problem in terms of rust prevention. Therefore, in the case of a closure panel, it is generally practiced to apply a one-pack type thermosetting epoxy adhesive or the like to the panel in advance and then perform hemming to ensure rust prevention. In this case, the adhesive is required to have excellent adhesiveness and rust prevention.

On the other hand, recently, in addition to the above-mentioned hemming portion, a so-called weld bond method has also been adopted in which an adhesive and spot welding are used together in order to improve the rigidity of the vehicle body. It becomes important. Therefore, in any case, the anticorrosive property of the adhesive is extremely important in terms of the adhesive life.

However, epoxy type adhesives are generally excellent in initial adhesiveness because they have high polarity, but in the long term, there is a problem that water penetrates to cause a decrease in strength and rust is easily generated around the adhesive. Therefore, it has been desired to develop an epoxy resin for adhesives having excellent durability against these.

In order to solve the above problems, as an adhesive having improved rust prevention, a urethane-modified epoxy resin and a latent curing agent are mixed with a rust prevention pigment or metal powder (Japanese Patent Laid-Open No. Sho 60).
No. 206882), a specific rubber-modified epoxy resin or aromatic epoxy resin and a latent curing agent are mixed with conductive carbon black (JP-A-62-5338).
7), a mixture of a urethane-modified epoxy resin and a rubber-modified epoxy resin, and a latent curing agent mixed with a specific rust preventive pigment (JP-A-1-1411971). .

[0007]

The adhesives described in the above publications do not impart a high rust preventive ability to the epoxy resin itself, but incorporate a filler to prevent the rust preventive ability as an adhesive. Is to improve. However, these adhesives depend on the kneading state of the adhesive, that is, the distribution state of the rust preventive pigment in the resin, and it is difficult to obtain stable rust preventive property. However, there is a problem in that it is difficult to secure rust resistance for a long period of time.

Therefore, an object of the present invention is to use it as a coating material such as an adhesive or a paint having a high adhesiveness and an extremely excellent rust preventive property for a long time with respect to a metal panel such as a steel plate or aluminum. It is to provide a novel adhesive epoxy resin composition that can be used.

[0009]

Means and Actions for Solving the Problems The present inventors have
As a result of extensive studies to solve the above problems, by using an adhesive composition containing a mononuclear polyhydric phenol / urethane modified epoxy resin obtained under predetermined conditions and a latent curing agent as main components, The present invention has been accomplished by finding that an adhesive epoxy resin composition having excellent adhesiveness to steel plates, aluminum, etc. and rust prevention can be obtained.

The above object of the present invention is achieved by an adhesive epoxy resin composition containing at least a mononuclear polyhydric phenol / urethane-modified epoxy resin as a main component and a latent curing agent for the epoxy resin. Was done. Hereinafter, the present invention will be described in more detail.

The mononuclear polyphenol / urethane-modified epoxy resin used in the present invention is a monoprecipitate obtained by reacting a urethane prepolymer obtained by reacting a polyhydroxy compound with an isocyanate compound with a mononuclear polyphenol. It is obtained by reacting a nuclear polyhydric phenol-modified urethane prepolymer with an epoxy resin.

In the present invention, the polyhydroxy compound is not particularly limited, but may be one usually used as a raw material for urethane prepolymer generally called polyether polyol. The polyol component has a number average molecular weight of 60.
It is preferably in the range of 0 to 20,000. If the number average molecular weight is less than 600, the flexible component of the modified epoxy resin is insufficient, and sufficient adhesive strength cannot be obtained.
If it exceeds 50,000, the viscosity of the modified epoxy resin becomes high and it becomes difficult to put it into practical use as an adhesive.

In the present invention, a polyhydroxy compound derived from propylene oxide, ethylene oxide or the like is reacted with an isocyanate compound to give a urethane prepolymer in order to impart flexibility.
It is necessary to adjust the equivalent ratio of the isocyanate group to the hydroxyl group in the range of 1.1 to 1.5. By imparting flexibility in this way, since a rigid molecule is introduced by subsequent modification with mononuclear polyhydric phenol, the adhesive cured product tends to become hard and brittle, preventing the cause of deterioration of the adhesive performance. can do. By adjusting the equivalent ratio of the isocyanate group to the hydroxyl group in the range of 1.1 to 1.5, a urethane prepolymer having isocyanate groups at both ends which is excellent in flexibility is obtained, and the urethane modification of the epoxy resin to be performed later is performed. It will be possible. When the equivalent ratio of both is less than 1.1, it becomes difficult to introduce an isocyanate group into both terminals, and when it exceeds 1.5, a urethane prepolymer having a small molecular weight is obtained and flexibility is insufficient.

In synthesizing the urethane polymer,
The isocyanate compound used as the raw material may be one having two or more isocyanate groups in the molecule,
Specific examples thereof include toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

Examples of mononuclear polyhydric phenols include catechol, 4-t-butylcatechol, and pyrogallol, and catechol is preferably used because of its ease of reaction. The amount of the mononuclear polyhydric phenol used is not particularly limited, but it is preferably adjusted to 0.1 to 5% by weight in the mononuclear polyhydric phenol / urethane modified epoxy resin. The amount of mononuclear polyhydric phenol used is 0.1
If it is less than 5% by weight, the rust preventive property cannot be improved. On the contrary, if it exceeds 5% by weight, the amount of mononuclear polyhydric phenol used becomes too much, and on the contrary, the reactivity decreases and the unreacted amount increases, which is actually , It becomes difficult to obtain a modified epoxy resin, and even if it is obtained, when the modified epoxy resin is cured,
It becomes hard and causes a decrease in adhesiveness. Under these conditions, the urethane polymer synthesized above is reacted with a mononuclear polyhydric phenol to obtain a mononuclear polyphenol-modified urethane prepolymer.

Next, the obtained mononuclear polyhydric phenol-modified urethane prepolymer is reacted with an epoxy resin to obtain a mononuclear polyhydric phenol / urethane-modified epoxy resin. The amount of the mononuclear polyphenol-modified urethane prepolymer used is not particularly limited, but generally, the content of the mononuclear polyphenol in the resin is 100 parts by weight of the epoxy resin.
It may be prepared so as to be 1 to 5% by weight. When the amount of the mononuclear polyphenol-modified urethane prepolymer used is less than 0.1% in the content of the mononuclear polyphenol in the resin, the cured adhesive composition lacks flexibility, and conversely exceeds 5% by weight. The viscosity of the cured product of the adhesive increases, and the workability when applying the adhesive is extremely reduced. From this perspective,
In the present invention, it is preferable to react the mononuclear polyhydric phenol-modified urethane prepolymer in the range of 5 to 40 parts by weight with respect to 100 parts by weight of the epoxy resin.

As the epoxy resin used in the present invention, an epoxy resin derived from bisphenol A or bisphenol F and epichlorohydrin or a mixture thereof is used. At this time, the number of hydroxyl groups contained in the epoxy resin is preferably in the range of 0.1 to 2.0 on average in one molecule. The number of hydroxyl groups contained in the epoxy resin is 1
When the average number is less than 0.1 in the molecule, it becomes difficult to modify with a urethane prepolymer, and a predetermined modified epoxy resin cannot be obtained. On the other hand, when the number of hydroxyl groups is more than 2.0 on average, the epoxy resin becomes solid, which makes it practically difficult to apply the adhesive of the present invention based on a liquid adhesive.

In the present invention, mononuclear polyhydric phenol /
Upon curing the urethane-modified epoxy resin, for example, dicyandiamine may be added as a latent curing agent, and if necessary, a curing accelerator or a filler may be added.

[0019]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

Example 1. Polyether diol P2000 (manufactured by Asahi Denka Co., Ltd., number average molecular weight) as a polyhydroxy compound derived from propylene oxide
About 2000) 100 g was charged into a reactor, and 10 g of toluene diisocyanate was added dropwise to react at 70 ° C. for 2 hours to obtain a urethane prepolymer. In this reaction, the equivalent ratio between the isocyanate group and the hydroxyl group was 1.15.

Then, the obtained urethane prepolymer 1
4g of catechol was added to 00g and reacted at 80 ° C for about 1 hour, 20g of which was taken out and reacted with 80g of bisphenol A type epoxy resin Epicoat 828 (trade name of Yuka Shell Epoxy Co., Ltd.) for 2 hours. Let Then, the temperature was raised to 120 ° C. and the volatile matter was removed while reducing the pressure. Furthermore, based on 100 parts by weight of the obtained mononuclear polyphenol / urethane modified epoxy resin,
8 parts by weight of dicyandiamide as a latent curing agent, 4 parts by weight of H3366S (product number manufactured by ACR Co., Ltd.) as a curing accelerator, and 40 parts by weight of calcium carbonate as a filler are added, mixed, and then defoamed to bond. The epoxy resin composition was obtained.

The adhesive epoxy resin composition thus obtained was subjected to an adhesion test using a mild steel plate and an aluminum plate coated with rust preventive oil. In the adhesion test, shear strength was measured according to JISK6850. As the test piece, SPCC (thickness: 1.6 mm) was used as a mild steel plate, and JIS5182 (pressure: 2 mm) was used as an aluminum plate. As the rust preventive oil, P1420B (product number manufactured by Nippon Oil Co., Ltd.) was used.

The test piece was subjected to electrodeposition coating with the adhesive uncured, and then cured together with the coating material under baking conditions of 170 ° C. for 20 minutes in an oven. Further, salt water spray was carried out for 500 hours in order to check the rust prevention property, and the shear strength retention rate was obtained.

Examples 2 to 7 and Comparative Examples 1 to 5 Based on Table 1, mononuclear polyhydric phenol / urethane prepolymers were prepared in exactly the same manner as in Example 1, and then mononuclear polyhydric phenol / urethane modified. Make epoxy resin,
Further, a curing agent and a filler were blended to obtain an epoxy adhesive composition. The obtained epoxy adhesive composition was used in Example 1.
Tested in exactly the same way as.

[0025]

[Table 1]

Table 2 shows the composition and performance of the epoxy adhesive composition.

[Table 2]

As is clear from Table 2, Examples 1 to 7 show excellent shear strength of 18 MPa or more against steel plates and aluminum plates and have a strength retention rate of 90% or more, which is excellent in rust prevention. showed that. On the other hand, Comparative Examples 1-5
In many cases, the shear strength is inferior to that in the examples, and the strength retention rate is low in many cases because rust has occurred in the test piece.

[0028]

INDUSTRIAL APPLICABILITY The present invention is a novel adhesive epoxy which can be used as a coating material such as an adhesive or a paint having high adhesiveness and extremely excellent anticorrosion property to a metal panel such as a steel plate or aluminum. It is a resin composition. Therefore, the adhesive epoxy resin composition of the present invention can be suitably used as a main component resin of a structural adhesive in automobile assembly using various steel plates or various aluminum alloys to which press oil or rust preventive oil is attached.

Claims (5)

[Claims] 1. An adhesive epoxy resin composition comprising at least a mononuclear polyhydric phenol / urethane-modified epoxy resin as a main component and a latent curing agent for the epoxy resin. 2. A urethane prepolymer obtained by reacting a mononuclear polyhydric phenol / urethane modified epoxy resin with a polyhydroxy compound and an isocyanate compound,
The adhesive epoxy resin composition according to claim 1, which is a resin obtained by reacting a mononuclear polyhydric phenol-modified urethane prepolymer obtained by reacting a mononuclear polyhydric phenol with an epoxy resin. object. 3. The adhesive epoxy resin composition according to claim 2, wherein the number average molecular weight of the polyhydroxy compound is in the range of 600 to 20,000. 4. The urethane prepolymer is obtained by reacting a polyhydroxy compound and an isocyanate so that the equivalent ratio of isocyanate group / hydroxyl group is in the range of 1.1 to 1.5. The adhesive epoxy resin composition according to claim 2. 5. The epoxy resin has an average of 0.1 to 0.1 in the molecule.
The adhesive epoxy resin composition according to claim 2, which has a hydroxyl group in the range of 2.0.