JPH03215582A - Adhesive composition suitable for use in spot welding - Google Patents

Abstract

PURPOSE:To improve the low-temperature spot weldability, hot shower resistance and storage stability of an adhesive composition which is employed for steel-to- steel bonding and is hardened after passing through prescribed steps by compounding specific ingredients. CONSTITUTION:An adhesive composition employed for steel-to steel bonding, which is hardened in a drying step, after passing through a tack welding step in which spot welding is performed, a washing step in which hot shower is employed, and a coating step, thus enabling steel plates to adhere to each other to form an integral body. This adhesive composition consists of 100 parts by weight of an epoxy resin which is liquid at 0 deg.C or higher (e.g. a liquid bisphenol A epoxy resin), 5 to 100 parts by weight of a thermoplastic elastomer (e.g. a polyester elastomer), a latent hardener (e.g. dicyandiamide), a filler (e.g. Al powder) and an additive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an epoxy adhesive composition, which is used in fields where spot welding and adhesion are used in combination for joining steel plates, such as automobiles, aircraft, and electrical equipment.

[Prior Art] For example, in automobile production lines, paste-like adhesives containing epoxy resin as a main component are often used to bond steel plates. Since this adhesive is in an uncured state until the coating film dries, the steel plates are spot welded together in advance with the adhesive interposed to temporarily hold them together, and all steps up to painting are carried out.

By the way, before painting, it is necessary to clean the surface of the steel plate, and this is usually done by showering with hot water at 50 to 70°C. However, with conventional paste adhesives, the viscosity decreases due to the heat of hot water, resulting in the problem that they scatter under the force of the shower and stain the surrounding area. In order to solve this problem, it is possible to increase the viscosity of the adhesive. However, there is a problem in that increasing the viscosity makes coating and spot welding difficult. This problem is particularly likely to occur in cold conditions such as winter.

Therefore, JP-A-54-160456 discloses an adhesive composition whose surface is partially cured by moisture in the air. With such an adhesive, the surface is hardened by the time you take a hot shower, so scattering can be prevented. In addition, since it is not hardened immediately after application, spot welding at low temperatures is possible by appropriately adjusting the viscosity.

Further, Japanese Patent Laid-Open No. 1-104681 discloses a tape-shaped adhesive that can be spot welded. If it is in tape form, there will be almost no scattering due to hot showers.

[Problems to be Solved by the Invention] In the adhesive composition disclosed in JP-A-51-160456, once the surface is hardened, moisture cannot penetrate into the interior, so the adhesive composition is partially hardened. is a very thin layer on the surface. Therefore, if the force of the hot water shower is too strong, the hardened layer may tear and the adhesive inside may scatter.

It also needs to be stored away from contact with moisture.
There was a problem with storage stability. Also, JP-A-1-1046
In a tape-shaped adhesive as disclosed in Publication No. 81,
Since it is a solid material, there is little possibility of automating the application.

The present invention was made in view of these circumstances, and
The purpose is to enable spot welding even at low temperatures, prevent scattering in hot showers, and enable hot application.

[Means for Solving the Problems] The adhesive composition of the present invention is used for joining steel plates together, and undergoes a temporary fixing process by spot welding, a cleaning process using a hot water shower, and a painting process, and then a drying process of the coating film. An adhesive that cures and joins together in one piece, and includes 100 parts by weight of an epoxy resin that is liquid at a temperature of O'C or higher, 5 to 100 parts by weight of a thermoplastic elastomer, a latent curing agent, and a filler. and an additive.

Eboxy resins are used in the form of liquids at temperatures above 0°C, including bisphenol A type, bisphenol F type, noporak type, alicyclic type, glycidylamine type, and hydrogenated bisphenol A.
An epoxy resin such as a mold, or an epoxy resin modified with a flexible component such as NBR or urethane resin can be used. Further, a reactive diluent such as a glycidyl ether such as polyethylene glycol, polypropylene glycol, neopentyl glycol, 1,6 hexanediol, or trimethylolpropane may be mixed with the above-mentioned epoxy resin. Solid epoxy resin is
This is undesirable because it adversely affects spot welding at low temperatures.

The greatest feature of the present invention is the use of a mixture of epoxy resin and thermoplastic elastomer.

The thermoplastic elastomer used is one that is compatible with the epoxy resin, and can be selected from various types such as polyester, polyurethane, polystyrene, polybutadiene, and polyamide.

This thermoplastic elastomer is mixed in an amount of 5 to 100 parts by weight with respect to 100 parts by weight of the epoxy resin. If the thermoplastic elastomer is less than 5 parts by weight, spot welding at low temperatures becomes difficult and scattering occurs during hot showers. Moreover, if the amount exceeds 100 parts by weight, the strength as an adhesive decreases, and the adhesive force on the oil surface also decreases. 20-6
It is optimal to mix 0 parts by weight.

In addition to dicyandiamide, various known latent curing agents can be used, such as Lewis acid complexes, imidazole compounds, organic acid hydrazides, diaminomaleonitrile, melamine and its derivatives, polyamine salts, amine imide compounds, and microencapsulated curing agents. It can be used selectively. The mixing amount is determined depending on the amount of epoxy resin and its reaction equivalent.

As the filler, various known fillers can be used, such as calcium carbonate, quartz powder, gypsum, kaolin, clay, miryoku, talc, dolomite, alumina, zircon, titanium compounds, molybdenum compounds, and antimony compounds. Further, as the conductive filler, iron powder, aluminum powder, silver powder, gold powder, copper powder, carbon powder, stainless steel powder, aluminum fiber, carbon fiber, stainless steel W&fiber, etc. can also be used. If such a conductive filler is used, spot weldability will be further improved.

As additives, thixotropic agents, coupling agents, stabilizers, etc. can be added depending on the purpose.

[Function] The adhesive composition of the present invention is first heated to a predetermined temperature to be thermally softened and applied to the adhesive surface of a steel plate. In the composition of the present invention, a latent curing agent is used, and since the thermoplastic elastomer hinders contact between functional groups, the reaction is slow even when heated.

Therefore, it has excellent storage stability. The steel plates are then stacked together using an adhesive.

Next, the steel plates are temporarily joined together by spot welding. In the composition of the present invention, the epoxy resin maintains a liquid state even at 0°C, and the applied composition has flexibility due to the presence of the thermoplastic elastomer, so spot welding is possible even at low temperatures. It has become. Then, they are washed with a hot shower. At this time, the composition is warmed by the heat of the hot water shower and its viscosity decreases, but as shown in FIG. 1, the degree of decrease is smaller than in the case of only epoxy resin. Therefore, the composition has a viscosity sufficient to withstand the force of a hot shower, thereby preventing the composition from scattering.

After the oil has been removed, the steel plates are coated with electrodeposition coating, intermediate coating, etc. During each drying process, the latent hardener reacts with the epoxy resin, hardens the adhesive, and joins the steel plates together. do.

"Effects of the Invention" Therefore, according to the adhesive composition of the present invention, spot welding at low temperatures is possible, and scattering due to hot showers is also prevented.Furthermore, it has excellent storage stability, so hot application is possible. becomes possible and automation can be achieved.

[Example] Hereinafter, this will be explained in detail using examples.

(Example 1) As the epoxy resin, hisphenol A type liquid epoxy resin (rE P-4 100J, epoxy equivalent 180-200, manufactured by Asahi Denka Co., Ltd.) 30 heavy camellia parts, bisphenol F type low viscosity epoxy resin (rEP-4900J
, epoxy equivalent: 170-190, manufactured by Asahi Denka Co., Ltd.}3
0 parts by weight, reactive diluent (rED-503J, aliphatic diglycidyl ether, manufactured by Asahi Denka Co., Ltd.) 10 parts by weight, polyester "Vylon 300J (softening point 123°C, Toyobo Co., Ltd.) as a thermoplastic elastomer" Co., Ltd.), 6 parts by weight of dicyandiamide as a hardening agent, and 79.5 parts by weight of aluminum powder (rAc-2500J Toyo Aluminum Co., Ltd.) as a filler were thoroughly stirred and mixed to prepare the adhesive of Example 1. A composition was prepared.The following characteristic values and performance of the obtained adhesive composition were measured.A temperature-viscosity curve was also measured and is shown in FIG.

(1) “Metal Guard 831” as oil for adhesion to oil surfaces (manufactured by Mobil)
SCP-D steel plate (25X
100 x 1.6 mm> is prepared and bonded with the above adhesive composition with a margin of 1 Q mm.

After baking 180'CX for 30 minutes, 5mm at room temperature,
The adhesive strength was measured at a pulling rate of /min.

(2) Hot water shower resistance A 15 x 150 x 0.8 mm steel plate is stacked and held in the center of a 70 x 150 x 0.8 mm steel plate via an adhesive composition with a 1 mm abrasion, and the adhesive composition is sprayed onto the exposed side surface. Hot water at 50° C. was sprayed for 1 minute at a C pressure of 4 kg/cm 2 , a distance of 25 cm, and an angle of 45 degrees. Then, visually judge the degree of scattering of the composition, and Q indicates that there is no scattering at all, △ indicates that there is some scattering, and X indicates that there is a lot of scattering.
shall be.

(3) Low temperature spot weldability JIS-G3141 Made of SPCD cold rolled copper plate 25
X100X1. The adhesive composition is applied in the form of a bead with a diameter of 5 mm to a steel plate having a size of 0 mm, and the same steel plates are stacked on top of each other. Then, spot welding was performed under conditions of 5° C. with an initial pressure of 200 kg for 40 cycles and an electric current of 10 KA-1 for 2 cycles, and the degree of welding was determined. If the weld is completely broken, mark it as ○, if there is some problem with welding, mark Δ, and if the joint strength is weak or there is no weld break, mark it as X.

(4) The high temperature stable adhesive composition was maintained at 70° C. for 48 hours, and changes in viscosity before and after acceleration were examined. ○ for those that have hardly thickened;
A sample with a slight increase in viscosity is indicated as Δ, and a case with severe increase in viscosity is indicated as ×.

(5) Dischargeability The adhesive composition was placed in a cartridge, kept warm at 70°C, and dischargeability was examined. A sample that is smoothly discharged is marked as ○, a sample that is slightly difficult to discharge is marked as △, and a sample that is extremely difficult to discharge is marked as X.

These results are shown in Table 1.

(Example 2) As the epoxy resin, NBR modified epoxy resin (rR-1309j, epoxy equivalent 300, A
An adhesive composition of Example 2 was prepared in the same manner as in Example 1 except that 30 parts by weight of CR Co., Ltd. was used and no reactive diluent was used. The results are shown in Table 1.

(Example 3) As the epoxy resin, a bisphenol A type liquid epoxy resin and a bisphenol F type low viscosity epoxy resin (rEP-4900, manufactured by Asahi Denka Co., Ltd. with an epoxy equivalent of 170 to 1901) were used without using a reactive diluent. An adhesive composition of Example 3 was prepared in the same manner as in Example 1 except that 60 parts by weight of 60 parts by weight was used.The characteristic values and performance were measured in the same manner, and the results are shown in Table 1.

(Comparative Example 1) As the epoxy resin, bisphenol A type solid epoxy resin (rEP-5100J, epoxy equivalent: 450
~500, softening point 64~75℃, manufactured by Asahi Denka Co., Ltd.) 60
Weight parts and bisphenol A liquid epoxy resin rEP
An adhesive composition of Comparative Example 1 was prepared in the same manner as in Example 1 except that 10 parts by weight of -4100J was used and no thermoplastic elastomer was used. Then, the characteristic values and performance were measured in the same manner, and the results are shown in Table 1. Further, the temperature-viscosity curve was measured and shown in FIG.

(Comparative Example 2) As epoxy resins, 10 parts by weight of bisphenol A type solid epoxy resin rEP'-5100J, 50 parts by weight of bisphenol A type liquid epoxy resin rEP-4100J, and 10 parts by weight of reactive diluent rED-503J were used. An adhesive composition of Comparative Example 2 was prepared in the same manner as in Example 1 except that 20 parts by weight of the plastic elastomer [Vylon 300J] was used. Then, the characteristic values and performance were measured in the same manner, and the results are shown in Table 1.

(Comparative Example 3) Adhesive composition of Comparative Example 3 was made in the same manner as in Example 1 except that 60 parts by weight of bisphenol F type low viscosity epoxy resin rEP-4900J was used as the epoxy resin and no thermoplastic elastomer was used. I prepared something. Then, the characteristic values and performance were measured in the same manner, and the results are shown in Table 1.

(Evaluation) Although the adhesive compositions of each example were excellent in all performances,
The adhesive compositions of Comparative Examples 1 and 2 are inferior in low temperature spot weldability and hot water shower resistance. Because it contains solid resin, as is clear from the graph in Figure 1, the viscosity and hardness increase at low temperatures.
This is due to the rapid drop in viscosity during hot showers. The adhesive composition of Example 1 has a gentler slope of the curve than Comparative Example 1, and the viscosity during spot welding is lower than that of Comparative Example 1.
The viscosity during hot showering is higher than that of Comparative Example 1.

In addition, the adhesive composition of Comparative Example 3 uses only a low-viscosity epoxy resin, so it has excellent low-temperature spot welding properties, but since it does not contain a thermoplastic elastomer, the viscosity decreases rapidly during hot showers, causing scattering. It is occurring.

Furthermore, the higher the amount of thermoplastic elastomer, the better the high-temperature stability is, which is presumed to be because the thermoplastic elastomer prevents contact between the epoxy resin and the curing agent.

That is, according to the adhesive composition of this example, by using an epoxy resin that is liquid at 0° C. or higher and a thermoplastic elastomer in combination, it is possible to achieve both low-temperature spot weldability and hot water shower resistance. is clear. Moreover, since it has high temperature stability for 48 hours or more, automation by hot application can also be achieved.

[Brief explanation of drawings]

FIG. 1 is a graph showing the temperature-viscosity curves of the adhesive compositions of Example 1 and Comparative Example 1.

Claims (1)

[Claims] (1) An adhesive used to join steel plates together, which undergoes a temporary fixing process using spot welding, a cleaning process using a hot water shower, and a painting process, and then hardens during the drying process of the coating film and joins them together, A spot weldable adhesive comprising 100 parts by weight of an epoxy resin that is liquid at a temperature of 0°C or higher, 5 to 100 parts by weight of a thermoplastic elastomer, a latent curing agent, a filler, and an additive. agent composition.