JPH06240222A - Adhesive resin composition - Google Patents

Abstract

PURPOSE:To obtain an adhesive resin compsn. waxy or solid at room temp. but susceptible to rapid lowering in viscosity above the softening temp. thereof to become pasty, by blending a specific epoxy resin with polycaprolactone and a latent curing agent as the indispensable components. CONSTITUTION:An adhesive resin compsn. comprises as the indispensable components (a) 100 pts.wt. epoxy resin which is liq. at room temp. and has at least one epoxy group in the molecule thereof; (b) 10-50 pts.wt. crystalline polycaprolactone having hydroxyl groups in the molecular terminals thereof and a number average mol.wt. of 800 to 10,000 in terms or polystyrene and an m.p. of 30 to 60 deg.C; and (c) 2-30 pts.wt. latent curing agent. The polycaprolactone (b) can be obtained by reacting a diol with an excessive amt. of epsilon-caprolactone monomer. Examples of the epoxy resin (a) include a bisphenol A epoxy resin and a bisphenol F epoxy resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel adhesive resin composition, and more specifically, a one-pack type which can be used for bonding metal members and metal structural materials together in automobile assembly. The present invention relates to a structural adhesive, particularly a structural adhesive applicable to the weld bond method.

[0002]

2. Description of the Related Art In an automobile assembly process, for example, a vehicle structure is made by welding a preformed metal member or metal structural material.
It is assembled by joining. In general, spot welding is widely used for joining a hemming portion of a door, a hood, a trunk lid, or a center pillar, a front pillar, a side sill, an outer sill, or the like. In this case, a weld bond method in which a hemming portion and a flange portion to be joined are coated and filled with an adhesive and then spot welding is performed is widely used. The adhesive used here is mainly an epoxy resin-based adhesive having excellent adhesive strength, durability, moisture resistance, heat resistance, mechanical strength and other properties. A paste-like material, or a sheet-like or tape-like material, which is mainly used at room temperature, has been proposed and used. Also known as hot-melt type, hot-apply type, and warm-apply type, it has high viscosity at room temperature and is waxy or solid.
Epoxy resin adhesives, which become paste when heated at ~ 80 ° C, have also been proposed and started to be used.

However, the paste-like adhesive at room temperature sticks out from the hemming portion or the seam portion when spot welding is performed in the hemming process or the panel assembly process after coating, so that the desired bonding and other than the bonding portion are contaminated. To do. The work of wiping off the protruding adhesive with a waste cloth is a complicated work because it is in a paste form. If it is not completely wiped off, the adhesive will scatter due to the washing shower in the chemical conversion treatment process of the car body or the electrodeposition process, and it will stick to the outer panel of the car body and harden in the oven, so it is easy to cause poor appearance after painting. .

On the other hand, the sheet-like and tape-like adhesives have good workability, do not contaminate the parts other than the desired joining and bonding parts, and have a high viscosity, so that the adhesive will not be scattered by the shower when washing the vehicle body. There is no. However, since it has a high viscosity at room temperature, the adhesive does not flow from the electrode pressure part when spot welding pressure is applied,
In many cases, power failure occurs. Especially in winter, when the temperature drops and the desired bonding site becomes 10 ° C or less, spot welding may become impossible.

Hot-melt, hot-apply, and warm-apply adhesives rapidly increase in viscosity or solidify when they are cooled after being heated and applied, and like the sheet-like and tape-like adhesives, there is a lack of electrical conduction during spot welding. Easy to wake up.
Similar to the sheet-shaped and tape-shaped adhesives, these adhesives may not be spot-welded when the temperature drops in the winter and the desired bonding site becomes 10 ° C. or less.

[0006]

Therefore, although the object of the present invention is to be waxy or solid at room temperature,
An adhesive that rapidly decreases in viscosity at a temperature equal to or higher than the softening point of the composition to form a paste, and does not rapidly increase in viscosity or become solid after being applied by heating, and easily flows from the spot welding pressurization part to prevent defective conduction. Adhesives that do not occur, especially in winter, when the room temperature decreases and the desired adhesion site becomes 10 ° C or less and the adhesive is completely solidified, the adhesive is crushed by the electrode pressing force during spot welding and current can be applied. An adhesive that can be welded, and the body to which this adhesive has been applied is completely wax-like or solid in the chemical conversion treatment step and the electrodeposition step, and does not scatter with a washing shower, and the desired joining, An object of the present invention is to provide an adhesive that can be applied to a weld bond method that does not contaminate parts other than the bonded part.

[0007]

The adhesive resin composition of the present invention satisfying the above object has 100 parts by weight of an epoxy resin which is liquid at room temperature and has crystallinity and has at least one epoxy group in the molecule. Polystyrene equivalent number average molecular weight is 800
It is characterized by containing as an essential component 10 to 50 parts by weight, a melting point of 30 to 60 ° C., polycaprolactone having a terminal hydroxyl group, and 2 to 30 parts by weight of a latent curing agent.

The room temperature liquid epoxy resin having at least one epoxy group in the molecule used in the present invention may be a bisphenol A type epoxy resin or a bisphenol F type epoxy resin. The polystyrene equivalent number average molecular weight is 300-1000, and the epoxy equivalent is
It is between 150 and 600. The epoxy resin which is liquid at room temperature mentioned here may be mixed with a solid epoxy resin, and there is no problem as long as the mixture is liquid at room temperature and the epoxy equivalent of the mixture is within the above range. Particularly preferably, a bisphenol A type epoxy resin having an epoxy equivalent of 170 to 220 is used because of its excellent workability and curability.

The above-mentioned epoxy resin is used as the essential component of polycaprolactone having crystallinity, a polystyrene-equivalent number average molecular weight of 800 to 10,000, a melting point of 30 to 60 ° C., and a terminal hydroxyl group, which is used in the present invention. The amount is 10 to 50 parts by weight, particularly preferably 20 to 40 parts by weight, based on 100 parts by weight. When the blending amount is less than 10 parts by weight, the adhesive resin composition of the present invention does not crystallize at room temperature and remains a highly viscous liquid, and when the blending amount exceeds 50 parts by weight, the epoxy resin has Not only the excellent properties are lost, but also desired bonding of such an adhesive resin composition, rapid crystallization occurs in a process in which the composition is cooled immediately after being heated and applied to an adhesive portion, and becomes a completely solid state. Does not exhibit the effect described by. The polycaprolactone having crystallinity and a terminal hydroxyl group used in the present invention can be obtained by reacting a diol with an excess of ε-caprolactone monomer by a known method. Examples of such diols include polymethylene glycols such as trimethylene glycol, pentamethylene glycol and hexamethylene glycol, polyethylene glycols such as diethylene glycol and triethylene glycol, propylene glycol, butylene glycol, neopentyl glycol and hexylene. Examples include alkylene glycols such as glycol and octylene glycol. Further, glycols having an aromatic group between two hydroxyl groups are also included.

Next, as the latent curing agent used in the present invention, those which are excellent in stability during heating and application at 30 to 80 ° C. and stability during storage are used. From this viewpoint, dicyandiamide, dibasic acid dihydrazides, and their derivatives, imidazole derivatives, N, N-dialkylurea derivatives, N, N-dialkylthiourea derivatives, and boron trifluoride compounds are mentioned. If necessary, two or more kinds may be used in combination. These latent curing agents are added in an amount of 2 to 30 parts by weight based on 100 parts by weight of the epoxy resin. If the compounding amount of such a curing agent is less than 2 parts by weight, the curability of the resulting resin composition will be poor and the adhesive strength will be insufficient, and if the compounding amount exceeds 30 parts by weight, it will be unclear in the composition after curing. Excessive amount of the curing agent remains in the reaction, resulting in a decrease in moisture resistance, a decrease in adhesive strength, and the like, which deteriorates the excellent properties of the epoxy resin.

In the adhesive resin composition of the present invention containing the three essential components thus obtained, if necessary, a filler such as calcium carbonate, titanium oxide, talc, silica, and carbon black may be added. Such as pigments, anti-sagging agents,
It is also possible to add a diluent or the like.

In the adhesive resin composition of the present invention, the above components are mixed and stirred at a temperature not lower than the melting point of polycaprolactone having crystallinity and having a hydroxyl group at the terminal, and then various kneaders,
A resin composition is prepared by uniformly melt-mixing with a three-roll or the like. The thus obtained adhesive resin composition of the present invention gradually crystallizes in the process of cooling after preparation and becomes a wax or solid at room temperature. Solid adhesive is sandwiched on release paper or film and pressed,
It is also possible to process between rolls into a sheet or tape having a desired thickness. These have the same workability and characteristics as those of conventional sheet-shaped or film-shaped adhesives. In addition, it is possible to apply it to a place where the paste adhesive cannot be applied. Alternatively, the adhesive resin composition of the present invention can be pulverized into pellets and applied as an uncured solid adhesive by low-pressure transfer molding, injection molding, or the like.
As described above, it is possible to heat the resin composition into a paste state as described above, and provide the same characteristics as when applied.

[0013]

The adhesive resin composition of the present invention is characterized in that the viscosity does not increase rapidly during the process of heating and coating the desired adhesion site and then cooling, but gradually increases while crystallization occurs. That is, the adhesive resin composition of the present invention is characterized in that its viscosity has hysteresis. Further, after the resin composition becomes completely wax-like or solid between the steel sheet panels to be joined, when performing spot welding to the adhesive filling portion, that is, when performing weld bonding, the wax-like state is applied from the electrode pressing portion. Alternatively, the solidified adhesive is characterized in that it is easily crushed and flows due to pressure so as not to cause a current failure. Particularly in the winter, the temperature of the desired bonding site becomes 10 ° C. or lower, and the feature is that spot welding can be performed even if the applied adhesive rapidly increases in viscosity and becomes solid. In order to gradually crystallize the adhesive applied in this manner, the composition of the present invention, which is applied and applied to a steel plate seam or a hem portion, is squeezed out during the crystallization process or completely crystallized. It can be easily scraped off with a spatula made of resin or bamboo after it is finished into a waxy or solid form, and the work will be complicated without the adhesion of the adhesive to other than the desired adhesion site. There is no. In addition, since the resin composition of the present invention is in a waxy or solid state after being heated and applied, the adhesion of the adhesive to the spot gun electrode during spot welding is completely eliminated. Thus, by using the adhesive resin composition of the present invention, it is possible to enhance the reliability at the joint portion between the metal members or the metal structural materials.

[0014]

The present invention will be described with reference to the following examples and comparative examples. Examples and Comparative Examples (Preparation of Sample) Polycaprolactone having a bisphenol A type epoxy resin (epoxy equivalent 190: manufactured by Epicoat 828 Yuka Shell Epoxy Co., Ltd.) and having a hydroxyl group at the end (number average molecular weight 800- 10,000, melting point 30-60
℃, Praxel 200 series Daicel Chemical Industries, Ltd.
, Hardener dicyandiamide (manufactured by Hanai Chemical Co., Ltd.),
Sample Nos. 1 to 9 of the composition of Example 1 in which calcium carbonate (average particle size 1 micron: manufactured by Shiroishi A Shiraishi Kogyo Co., Ltd.) as an inorganic filler was blended at a ratio shown in Table 1 were each heated to 80 ° C. And kneaded with a three-roll three times to obtain a paste adhesive composition. The composition gradually increased in viscosity after being left at room temperature and became completely waxy or solid 30 minutes after the completion of kneading. Further, in the same manner, by mixing in the proportions shown in Table 2, adhesive compositions of sample numbers 10 to 15 of Comparative Examples were obtained.

(Evaluation of Characteristics) Each sample of the composition thus obtained was heated to 50 ° C. to form a paste, and a diameter of 3 was applied to the flange portion of the center pillar outer panel of the automobile.
It was applied in the form of beads of mm. After the application is completed, the specified time (10
After assembling, the center pillar inner panel, which is the other member, is assembled and the welding current is immediately set to 8k.
A, spot welding was performed on the flange under the conditions of a pressure of 200 kg / cm ² and an energization time of 0.1 seconds. At this time, the ambient temperature at the time of spot welding was set to 25 ° C, 15 ° C and 5 ° C (therefore, the panel temperature and the composition temperature applied were 25 ° C, 15 ° C and 15 ° C, respectively).
℃ and 5 ℃).

At this time, the properties of the composition protruding from the flange portion were observed. In addition, spot weldability, shower resistance, and wipeability of the protruding composition were evaluated by the following methods, and the obtained results are shown in Tables 1 and 2.

The evaluation of the spot weldability is "good" when a nugget having a diameter of 5 mm or more is formed under the above welding conditions and respective atmospheric temperatures, and when a nugget having a diameter of less than 5 mm is formed or spot welding cannot be performed. The case was defined as “poor”.

The shower resistance is evaluated by the oil surface steel plate (SPC
C-SD) A test piece size (0.8 × 100 × 50 mm) was coated with the obtained composition in a bead shape having a diameter of 3 mm to a length of 70 to 80 mm, and allowed to stand for 10 minutes to prepare a test piece. This test piece was fixed at an angle of 90 degrees with respect to the shower nozzle, and the water temperature was 50 to 55 ° C and the water pressure was 3
Shower is sprayed for 1 minute at a distance of 80 cm from the nozzle and the test piece at kgf / cm ² , and the state where the applied composition remains in its original state is “good”, and if it scatters, “scatters”
And

The evaluation of the wiping property of the protruding composition is as follows.
10 minutes after applying by heating, scrape off the composition protruding from the flange part using a spatula made of bamboo, "good" if easily scraped, sticky, stick to other than the joint part, The case where the thread was pulled was defined as "poor".

[0020]

[Table 1]

[0021]

[Table 2]

As is clear from the examples of Table 1, the samples within the scope of the present invention show excellent spot weldability not only at room temperature but also at low temperature (especially 5 ° C.) and also have shower resistance. It is good. Also, the wiping-off property of the composition protruding from the joint portion is easy since it gradually becomes solid after the heating application is completed. Therefore, it does not contaminate the parts other than the desired joining and bonding parts.

On the other hand, in the comparative example of Table 2, the sample number
In Nos. 10 and 11, since the molecular weight of polycaprolactone having a hydroxyl group at the end is outside the range of the present invention, it remains in a paste state and does not become a solid state after being heated and applied. Therefore, the spot weldability at 5 ° C. is also good, but due to these properties, the shower resistance and the wiping property become problems. In Sample No. 12, the amount of polycaprolactone having a hydroxyl group at the end is outside the range of the present invention, so that it does not solidify and the shower resistance becomes a problem. Similarly, in Sample No. 13, since the amount of the polycaprolactone having a hydroxyl group at the end was outside the range of the present invention, crystallization, that is, viscosity increase occurred rapidly after heating application, and spot weldability at 15 ° C. and 5 ° C. It becomes a problem. In Sample Nos. 14 and 15, the molecular weight of polycaprolactone having a hydroxyl group at the terminal is out of the range of the present invention. Like Sample No. 13, the viscosity rapidly increases after heat coating, and there is a problem in spot weldability at 5 ° C. There is.

[0024]

As described above, the novel adhesive resin composition of the present invention contains a liquid epoxy resin, polycaprolactone having crystallinity and a terminal hydroxyl group, and a latent curing agent in a specific amount ratio. It has excellent spot weldability even in a low temperature atmosphere after heat application, has excellent shower resistance, and has excellent wiping-off property for the protruding portion. Due to these actions, in the joining method of metal members or metal structural materials (weld bond method), stable spot welding can be performed regardless of the ambient temperature, and contamination outside the bonded area due to the protruding adhesive can be reduced. Is. In addition, since it gradually becomes solid after being applied by heating, the adhesive does not scatter due to the washing shower, and there is no coating failure due to the adhesive.

Claims (3)

[Claims] 1. 100 parts by weight of an epoxy resin which is liquid at room temperature and has at least one epoxy group in the molecule, has crystallinity and has a polystyrene reduced number average molecular weight of 800 to 10,000,
And 10 to 50 parts by weight of polycaprolactone having a melting point of 30 to 60 ° C. and a terminal hydroxyl group, and a latent curing agent 2.
An adhesive resin composition, characterized by containing -30 parts by weight as an essential component. 2. The adhesive resin composition according to claim 1, wherein the polycaprolactone having a hydroxyl group at the terminal is obtained by reacting a diol with an excess of ε-caprolactone monomer. 3. The adhesive resin composition according to claim 1 or 2, wherein the epoxy resin component is a bisphenol A type epoxy resin or a bisphenol F type epoxy resin.