JPH0488077A - Spot-weldable adhesive composition - Google Patents

Abstract

PURPOSE:To provide the title composition capable of spot welding at lower temperatures, prevented from scattering due to heated shower, comprising an epoxy resin liquid at temperatures at or higher than a specified level, partially crosslinked rubber, potentially curing agent, filler and additive. CONSTITUTION:The objective composition comprising (A) an epoxy resin liquid at >=0 deg.C such as bisphenol A-type liquid epoxy resin, (B) a partially crosslinked rubber such as acrylic rubber, (C) a potentially curing agent such as dicyandiamide or Lewis acid complex, (D) a filter such as calcium carbonate or aluminum powder, and (E) additive(s) such as thixotropy-imparting agent and/or coupling agent. The present composition is used for mutual bonding of steel plates, enabling their integral bonding by its curing during the coating film drying process following an interim fixation process by spot welding, washing process using a heated shower, and coating process.

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.

[Conventional technology] For example, on an automobile production line, a paste adhesive mainly composed of epoxy resin is applied to join steel plates, they are joined together, and then temporarily fixed by caulking or welding to the subbutton 1, and then when the paint is baked. At the same time, the adhesive is cured by heating.

However, the painting process requires hot water shower cleaning as a pretreatment, and low-viscosity paste adhesives scatter and are removed.
Other parts may be contaminated, and the adhesive must be made to have a high viscosity that can withstand hot showers. These methods include adding a solid epoxy resin, increasing the viscosity by modifying an epoxy resin with rubber or ex-mers, or adding rubber or elastomers. . However, if a solid epoxy resin is used, the viscosity at low temperatures will be too high, making spot welding impossible, and if it is modified or blended with rubber or elastomer, the cured product will soften when the bonded area is exposed to high temperatures. Due to problems such as a decrease in strength, we had no choice but to limit the areas in which it could be used.

Therefore, Japanese Patent Application Laid-Open No. 64-81878 discloses an adhesive composition containing a blend of thermoplastic elastomers and a high polymer content.

[Problem to be solved by the invention] JP-A-6/1. Although the adhesive composition disclosed in Japanese Patent No. 81878 has some effects, it lacks strength in hot conditions and does not have sufficient fatigue resistance, and there is still room for improvement.

The present invention was made in view of these circumstances, and
While achieving both low temperature spot weldability and hot water shower resistance,
The purpose is to improve strength and fatigue resistance when hot.

[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 forms an integral bond at temperatures above 0°C, and is characterized by consisting of an epoxy resin that is liquid at temperatures above 0°C, partially crosslinked rubber, a latent curing agent, fillers, and additives. shall be.

Epoxy resins are used in liquid form at temperatures above 0°C, including bisphenol A type, bisphenol F type, novolac 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 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 that a partially crosslinked rubber is used in combination with an epoxy resin. Partially crosslinked rubber here refers to something between unvulcanized rubber and fully vulcanized rubber, and when the entire crosslinkable part of unvulcanized rubber is taken as 100, 1 to 99% of the part is crosslinked. refers to something that exists. This partially crosslinked rubber may be one that is compatible with the epoxy resin, and partially crosslinked rubbers such as NBR, SBR, CR, and acrylic rubber are preferred. Vulcanized rubber has poor compatibility with epoxy resins, and unvulcanized rubber is not used because its strength during hot heating is greatly reduced.

This partially crosslinked rubber is used, for example, in an amount of 10 to 50 parts by weight per 100 parts by weight of the epoxy resin. Although it varies depending on the type, if there is little partially crosslinked rubber, the viscosity will be low and scattering will occur during hot showers. In addition, if the amount is too large, it becomes difficult to form a paste, making it difficult to blow out and spot welding at low temperatures. The practical range is 10~
It is optimal to mix 20 parts by weight.

Various conventionally known latent curing agents can be used, such as dicyandiamide, 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 such as calcium carbonate, quartz powder, 6 blue, kaolin, clay, mica, tar, dolomite, alumina, zircon, titanium compounds, molybdenum compounds, andandimon compounds can be used. 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 fiber, etc. can also be used. If such a conductive filler is used, the weldability will be further improved.

As additives, a chicken property imparting agent, a coupling agent, a stabilizer, etc. can be added depending on the purpose.

[Function] The adhesive composition of the present invention is first heated to a predetermined temperature to lower its viscosity and then 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 partially crosslinked rubber hinders contact between functional groups, the reaction is slow even when heated to the coating temperature. Therefore, it has excellent storage stability.

The steel plates are then stacked together using an adhesive.

Next, the steel plates are temporarily fixed together by spora 1 and welding.

In the composition of the present invention, the epoxy resin maintains a liquid state even at OoC, and the presence of the partially crosslinked rubber makes the applied composition flexible, making spot welding possible even at low temperatures. ing. Then, they are washed with a hot shower. At this time, the adhesive composition is warmed by the heat of the hot water shower and its viscosity decreases, but the degree of decrease is smaller than in the case of only epoxy resin. Therefore, it has a viscosity that can withstand the force of a hot shower.
Splashing of the composition is prevented.

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. It also has good adhesion to curved steel plates. Furthermore, since the adhesive composition of the present invention has excellent storage stability, hot application is possible and automation can be achieved.

The cured product formed from the adhesive composition of the present invention is
Due to the restraining effect of the molecular chains of partially crosslinked rubber, it has high strength when hot and has excellent fatigue resistance.

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

(Example 1) As the epoxy resin, bisphenol A type liquid epoxy resin (rEP-4-100", epoxy weight @ 180.
~200, manufactured by Asahi Denka Co., Ltd.) 50 parts by weight, NBR modified epoxy resin (rR-1309j, epoxy equivalent: 300.
ACR Co., Ltd.) 10 parts by weight, reactive diluent (rED-
503j, aliphatic diglycidyl ether, manufactured by Asahi Denka Co., Ltd.) 10 parts by weight, partially crosslinked rubber as NBR type (Krajinak XL389J manufactured by Polycer Co., Ltd. > 10 parts by weight, dicyandiamide as a curing agent, 6 parts by weight, as a filler) The adhesive composition of Example 1 was prepared by thoroughly stirring and mixing 80 parts by weight of aluminum powder (1-A (2500j, manufactured by Toyo Aluminum Co., Ltd.)).

The following characteristic values and performance were measured for the obtained adhesive composition.

(1) Oil surface adhesion cleaning rust preventive oil (“Metal Guard 831TJ Manufactured by Mobil Co., Ltd.”)
SCl”D steel plate (25x100
x 1.6 mm) is prepared and bonded with the above adhesive composition with a margin of 1 Q mm.

And 180'C
Adhesive strength was measured in an atmosphere of 00'C at a tensile rate of 5 mm/min.

(2) Prepare fatigue-resistant 5CP-D steel plates (25 x 100 x 1.6 mm) and bond with the above adhesive composition with a 15 mm margin. After baking at 180'CX for 30 minutes, use a fatigue tester (
(manufactured by Shimadzu Corporation), 20'C and 100'
In the atmosphere of C, frequency 50H7, maximum and minimum load ratio 3
The number of breaks was measured under the conditions of 50 kq/70 kg.

(3) Hot water shower resistance Hold a 15 x 150 x 0.8 mm steel plate over the center of a 70 x 150 x 0.8 mrn steel plate with an adhesive composition of 1 mm thickness in between, and spray the exposed side surface of the adhesive composition. is pressure 4kC]/cm2, distance 25cm, angle 45
Warm water at 50'C was sprayed for 1 minute at 50°C. Then, the degree of scattering of the composition was visually determined, and those with no scattering were graded Q, those with some scattering were graded △, and those with a lot of scattering were graded X.

(4) Low-temperature spot weldability SP (made of -D cold rolled steel plate, 25X100X1゜Om)
The adhesive composition is applied in the form of a bead with a diameter of 3 mm to a steel plate having a size of m, and the same steel plates are stacked on top of each other. And under the condition of 5℃,
Initial pressurization 200kg-4Q cycle, energization 10KA-1
Spot welding was performed in two cycles and the degree of welding was determined. A mark of ○ means that the weld is completely welded, a mark of △ means that there is some welding problem, and a mark of × means that the joint strength is weak or the weld is not welded.

(5) The high temperature stable adhesive composition was held at 60'C for 72 hours, and changes in viscosity before and after acceleration were examined. O for those that have not thickened at all
1 A sample with a slight increase in viscosity is rated △, and a sample with severe viscosity increase is rated ×.

These results are shown in Table 1.

(Other Examples and Comparative Examples) As shown in Table 1, the types and amounts of epoxy resin, vulcanized rubber, partially crosslinked rubber, and thermoplastic Ex-1 to M were variously changed to create adhesive compositions. A sample was prepared and the performance was measured in the same manner as in Example 1.

In addition, as unvulcanized rubber, high nitrile NBR (manufactured by Flynac 50F 5J Polyzer Co., Ltd.) and low nitrile NB are used.
Using R (r flynac 2f 50j manufactured by Polycer),
FTP-29C has a low melting point as a thermoplastic elastomer)
J (manufactured by Nippon Gosei Kagaku Co., Ltd.) and high melting point [Vylon 300J (manufactured by Toyobo Co., Ltd.) were used. In addition, in Example 3.4, SBR-based l'-Nip was used as the partially crosslinked rubber.
ol-1009'' (manufactured by Nippon Zeon Co., Ltd.) was used.

The same raw material as in Example 1 was used as the raw material.

(Evaluation) From Table 1, it is clear that the adhesive compositions of each example were excellent in all performances.

The composition of Comparative Example 4, which has a small amount of partially crosslinked rubber, has poor hot water shower resistance. On the other hand, the composition of Comparative Example 3, which contains a large amount of partially crosslinked rubber, does not form a paste 1 or more and does not function as an adhesive. Therefore, it can be seen that within the range of the raw materials used, the optimum blending amount of the partially crosslinked rubber is 10 to 20 parts by weight per 100 parts by weight of the epoxy resin.

In addition, the compositions of Comparative Examples 5 and 6, in which the dil to lyle content was changed with non-hl sulfurized NBR, had low oil surface adhesion at high temperatures and poor fatigue resistance at high temperatures.

Among the compositions of Comparative Example 7 and Comparative Example 8 using a thermoplastic elastomer with a low melting point, the composition of Comparative Example 8, which contains a particularly large amount, is excellent in hot water shower resistance and low-temperature spot weldability. However, it has low adhesion to oil surfaces at high temperatures and poor fatigue resistance at high temperatures.

This tendency becomes more pronounced as the amount of thermoplastic elastomer added increases. Furthermore, the composition of Comparative Example 9 containing a thermoplastic elastomer with a high melting point has low oil surface adhesion at high temperatures, poor fatigue resistance at high temperatures, and is difficult to spot weld at low temperatures.

That is, according to the adhesive composition of this example, by using an epoxy resin that is liquid at temperatures above ○°C and a partially crosslinked rubber, both low temperature spora 1 - weldability and hot water shower resistance are achieved. It is clear that it has excellent strength and fatigue resistance when hot.

Patent applicant: Aisin Kako Co., Ltd. Agent: Patent attorney: Hiroshi Okawa

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, An adhesive composition capable of spot welding, comprising an epoxy resin that is liquid at a temperature of 0° C. or higher, a partially crosslinked rubber, a latent curing agent, a filler, and an additive.