JPH02252779A - Thermosetting adhesive tape - Google Patents

Abstract

PURPOSE:To obtain a thermosetting adhesive tape excellent in the adhesiveness, releasability, and spot-welding properties by forming outer layers comprising a highly viscous resin compsn. mainly contg. an epoxy resin on both surfaces of an inner layer comprising a lowly viscous resin compsn. mainly contg. the epoxy resin. CONSTITUTION:On both surfaces of an inner layer comprising a lowly viscous resin compsn. which has a viscosity at 25 deg.C of pref. 1X10<4>-4X10<5>P and contains an epoxy resin pref. having at least two epoxy groups in the molecule (e.g. a bisphenol A epoxy resin) and a thermoplastic resin (e.g. a phenoxy resin), outer layers comprising a highly viscous resin compsn. which has a viscosity at 25 deg.C of pref. 5X10<5>-5X10<6>P and contains the epoxy resin pref. having at least two epoxy groups in the molecule an the thermoplastic resin are formed to give a thermosetting adhesive tape with a three-layered structure and mainly comprising the epoxy resin.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has adhesiveness at room temperature and excellent separator releasability, has good spot weldability, and has excellent adhesive strength by heating and curing. The present invention relates to the resulting spot-weldable thermosetting adhesive tape.

[Prior Art and Problems to be Solved by the Invention] Various types of thermosetting adhesive tapes mainly made of epoxy resins are known depending on their purposes and uses.

However, when bonding is performed using spot welding, conventional thermosetting adhesive tapes require a high viscosity of the resin composition layer to improve separator removability.
There is a problem in that adhesion to an adherend makes subsequent spot welding difficult, and conversely, when the viscosity of the resin composition layer is lowered to improve spot weldability, it becomes difficult to peel off the separator.

Therefore, there is currently no thermosetting adhesive tape that satisfies both of the contradictory properties of separator releasability and spot weldability.

[Means to solve the problem]

The present invention has been made to solve these problems, and has adhesiveness at room temperature and excellent separator removability, good spot weldability, and excellent adhesive strength by heating and curing. Provided is a thermosetting adhesive tape that can be spot welded.

That is, the present invention is a thermosetting adhesive tape mainly made of epoxy resin, which has a three-layer structure in which an outer layer made of a high viscosity resin composition is formed on both sides of an inner layer made of a low viscosity resin composition. Thermosetting adhesive tape.

By adopting such a three-layer structure, the outer layer of both the electrodes has a high viscosity, so the separator peelability is good, and the inner layer has a low viscosity, so when the electrodes are pressurized during spot welding, the resin between the electrodes can be easily removed. It becomes easier to conduct electricity and improves weldability.
It is possible to achieve both separator removability and spot weldability, which are contradictory.

In the present invention, the inner layer is made of a low viscosity resin composition, and its viscosity is preferably 1 x 104 to 4 x 105 poise at 25°C, and the outer layer is made of a high viscosity resin composition, and its viscosity is preferably 5 x 10' to 4 x 10' poise at 25°C. 5×106 bores is preferred.
By setting the viscosity of the inner layer within the above range, the shape retention and spot weldability of the sheet can be satisfied.

Furthermore, by setting the viscosity of the outer layer within the above range, spot weldability and separator releasability can be satisfied.

The viscosity of each layer can be adjusted mainly by adjusting the amount of the epoxy resin and thermoplastic resin to be described later, but it can also be adjusted by changing the amount of the liquid epoxy resin and solid epoxy resin. Note that the viscosity here was measured using a Koka type flow tester.

The resin composition used in each layer of the present invention is not particularly limited as long as it has an epoxy resin as its main component and satisfies the above viscosity range, and the inner layer and outer layer may be the same or different. good.

From the viewpoint of adhesive strength, heat resistance, etc., such epoxy resins preferably have an average of two or more epoxy groups in one molecule, and specifically include bisphenol A type, bisphenol F type, cycloaliphatic , hydantoin type, novolak type, dimer acid glycidyl ester type, glycidyl amine type, polyalkylene glycol diglycidyl ether, polynuclear phenyl glycidyl ether, amine-modified epoxy resin, rubber-modified epoxy resin, etc. Mixtures of more than one species can be used.

In the present invention, for each resin composition layer, the above-mentioned epoxy resin and a thermoplastic resin such as phenoxy resin, butyral resin, polyamide resin, ethylene-vinyl acetate copolymer resin, etc. are used together to improve compatibility with the epoxy resin. , preferred from the viewpoint of dispersibility.

In particular, in order to improve shape retention as a thermosetting adhesive tape, it is preferable to use phenoxy resin in combination, and furthermore, butyl rubber, isoprene rubber, butadiene rubber,
A rubber component such as butadiene acrylonitrile copolymer rubber can also be included.

The blending amount of these thermoplastic resins or rubber components can be appropriately set so that the viscosity of each resin composition layer falls within the above range, but it is usually 60% by weight or less in the composition, preferably 50f.
Fiit% or less.

Furthermore, the curing agent for the epoxy resin contained in each resin composition layer is not particularly limited, and may be dicyandiamide, hydrazide, phenol, mercaptan, amine, polyamide, boron, imidazole, or acid anhydride. system,
Examples include amine imide-based curing agents, and dicyandiamide-based, hydrazide-based, and phenol-based curing agents are particularly preferably used from the viewpoint of storage stability.

Moreover, a curing accelerator can also be used together with the above curing agent. Such curing accelerators are not particularly limited, but for example, imidazole-based, guanidine-based, amine-imide-based, urea-based, etc. are preferably used.

Further, in the present invention, it is preferable to incorporate a conductive filler into each resin composition layer, especially when the outer layer or inner layer with high viscosity is thick, to improve spot weldability. Such conductive fillers include silver, palladium, copper,
Examples include metal powders such as aluminum, iron, nickel, and zinc, and inorganic fillers such as carbon black and graphite, and the amount added is determined by the epoxy resin component or a mixture of epoxy resin and thermoplastic resin, etc. It is used in an amount of 10 to 300 parts by weight, preferably 30 to 100 parts by weight, per 100 parts by weight of the resin component.

Furthermore, in the thermosetting adhesive tape of the present invention, various commonly used additive components such as pigments, anti-aging agents, coupling agents, and blowing agents, which have been conventionally used in epoxy resin compositions, are added. It can be blended as appropriate depending on the purpose and use.

The thickness of the thermosetting adhesive tape of the present invention is not particularly limited, but the high viscosity outer layer is preferably thinner from the point of view of spot weldability, and is usually preferably 50 μm or less. The low viscosity inner layer is usually less than 1 mm thick.

FIG. 1 is a sectional view showing an example of the thermosetting adhesive tape of the present invention, in which an outer layer 2 is formed on both sides of the inner layer N1.
Further, a separator 3 made of release treated paper, polypropylene, etc. is usually provided on the outside of the outer layer 2.

Such a thermosetting adhesive tape can be manufactured by a conventional method, in which the resin compositions for the inner and outer layers are formed into sheets by uniformly mixing each component, and then each sheet is heated using a press or a roll. A three-layer thermosetting adhesive tape can be obtained by fusing. Each resin composition can also be obtained by three-layer extrusion.

〔Effect of the invention〕

The thermosetting adhesive tape of the present invention has a three-layer structure as described above; 1) it has tackiness at room temperature and excellent separator removability; it also has good spot weldability, and has excellent properties when cured by heating; This has the effect of providing adhesive strength.

〔Example〕

Examples of the present invention will be shown below. Here, part and % are
Means parts by weight and % by weight, respectively.

■Resin composition layer for inner layer 75 parts of bisphenol A type epoxy resin (average molecular weight 380, epoxy equivalent weight 190) having an average of two or more epoxy groups per molecule and 25 parts of phenoxy resin with number average molecular weight 30,000, 150 parts Heat and melt mix at ~200°C for 4 to 6 hours.

After cooling this resin component to 80 to 100°C, 100 parts of aluminum powder, 5 parts of dicyandiamide, and 1.5 parts of 3-(3,4 dichlorophenyl)-1,1-dimethylurea were added and mixed to form an epoxy resin composition. This was formed into a sheet (thickness 10100p to form a resin composition layer for the inner layer) by hot pressing.The viscosity of the inner layer was 3X1 at 25°C.
It was 0' poise.

(2) Resin composition layer for outer layer 60 parts of the same bisphenol A type epoxy resin and 30 parts of phenoxy resin are heated and melt-mixed at 150 to 200°C for 4 to 6 hours.

After cooling this resin component to 80 to 100°C, the number average molecule i
t 25000 hydrogenated isoprene rubber (hydrogenation rate 90%) 10 parts, aluminum powder 50 parts, copper powder 50 parts,
5 parts of dicyandiamide and 1.5 parts of 3-(3,4-dichlorophenyl)-1,1-dimethylurea were added and mixed to obtain an epoxy resin composition, which was formed into a sheet (30 μm thick) by hot pressing. ) to obtain a resin composition layer for the outer layer.

The viscosity of the outer layer was 7 x 10' poise at 25°C.

■ Adhesive tape production The resin composition layer for the outer layer is pasted on both sides of the resin composition layer for the inner layer obtained above, and the resin composition layer for the outer layer is fused and integrated using a hot press, resulting in a final three-layer structure with a thickness of 150 μm. A thermosetting adhesive tape was obtained.

Comparative Example Comparative Example 1 is a case in which a single-layer type adhesive tape is prepared using the above resin composition for the inner layer alone, and Comparative Example 2 is a case in which a single-layer type adhesive tape is similarly prepared using only the resin composition for the outer layer. did.

The separator releasability, tensile shear adhesive strength, and spot weldability of the thermosetting adhesive tapes obtained in these Examples and Comparative Examples were evaluated by the following methods, and the results are shown in the table.

(1) Separator peelability An adhesive tape with a width of 12.5 mm was attached to a steel plate, and the strength was measured when the separator was peeled off at room temperature at a rate of 50 per sin.

(2) Tensile shear adhesive strength As shown in Figure 2, the thermosetting adhesive tape
C-SD, 100 x 25 x 1.6' mi) and heat cured at 180°C for 20 minutes.
Measured according to JIS-6850.

(3) The spot weldable thermosetting adhesive tape was attached to the steel plate in the same manner as in (2) above, and then spot welding was carried out under the following conditions as shown in Fig. 3. Thereafter, in the same manner as in (2) above. It was heated and cured.

Pressure force squeeze (pressure) time Current supply time Current value 250 kg/cA 90 cycles (1,55 ec) 8 cycles (0,1255 ec) 000 A As is clear from the table, the thermosetting adhesive tape of the present invention has the following properties:
It can be seen that the separator has excellent removability, spot weldability is good, and excellent adhesive strength can be obtained by heat curing.

(Margin below)

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an example of the thermosetting adhesive tape of the present invention, Fig. 2 is a sectional view showing the state of use of the thermosetting adhesive tape of the invention before heat curing, and Fig. 3 is Fig. 2. FIG. 3 is a cross-sectional view showing a state when spot welding is subsequently performed. 1 ・・・・・・Inner layer, 2 ・・・・・・Outer layer, 3
−−−−−−Separator 4−・−・・・・Metal plate

Claims (6)

[Claims] (1) A thermosetting adhesive tape mainly made of epoxy resin, with a three-layer structure in which an outer layer made of a high viscosity resin composition is formed on both sides of an inner layer made of a low viscosity resin composition. adhesive tape. (2) The viscosity of the inner layer made of a low-viscosity resin composition is 1 x 10^4 to 4 x 10^5 poise at 25°C, and the viscosity of the outer layer made of a high-viscosity resin composition is 5 x 10^ at 25°C. 5-5
The thermosetting adhesive tape according to claim 1, which has a diameter of 10^6 poise. (3) The resin composition of the inner layer and outer layer contains an average of 2 in 1 molecule.
2. The thermosetting adhesive tape according to claim 1, comprising an epoxy resin having at least one epoxy group and a thermoplastic resin. (4) Claim (3) wherein the thermoplastic resin is a phenoxy resin.
Thermosetting adhesive tape described in ). (5) The thermosetting adhesive tape according to claim (3), wherein the resin compositions of the inner layer and the outer layer further contain a rubber component. (6) The thermosetting adhesive tape according to claim (3), wherein the resin compositions of the inner layer and the outer layer further contain a conductive filler.