JPS5863773A - Bonding layer for composite material - Google Patents

Abstract

PURPOSE:The titled bonding layer, prepared by crosslinking the bonding layer under irradiation with electron rays in forming a composite material having the bonding layer consisting of a resin material on the surface of a metallic foil, etc., and having improved bonding strength and heat, solvent, and stress cracking resistance. CONSTITUTION:A bonding layer prepared by irradiating a bonding layer prepared by extruding a silane-modified polyolefin (copolymer) film on the surface of a metallic foil, e.g. a copper foil, or a metallic filament, e.g. a copper filament, and fusing the resultant bonding layer at the same temperature as the extrusion temperature or a preheating temperature above the extrusion temperature to form a composite material with electron rays, preferably at >=10 Mrad absorbed dose. EFFECT:Improved bonding strength at high temperatures.

Description

[Detailed description of the invention] The present invention relates to improvements in adhesive layers for composite materials.

It is well known that composite materials, traditionally referred to as laminate materials, were first developed by applying adhesives.

However, as the flammability and pollution of the solvent used to dissolve adhesives become a problem, adhesives are gradually shifting to hot-melt and film-type adhesives. However, hot melts have various differences in melting point and M (melt viscosity index), and although they are easy to handle, they have advantages and disadvantages in heat resistance and other aspects. Furthermore, although film types are easy to use, they have limited thickness, and in the case of thermoplastic polymers, there are problems with heat resistance.

In addition, in some thermosetting films, the problem of curing (curing and adhesion time) is a bottleneck in production.

The present invention was made in view of the above situation, and an object of the present invention is to provide an adhesive layer for composite materials that can improve adhesive strength, heat resistance, solvent resistance, and stress cracking resistance.

The adhesive layer for a composite material of the present invention is obtained by interposing an adhesive layer made of a resin material on the surface of a metal foil or metal strip to form a composite material, and then crosslinking the adhesive layer by irradiating it with an electron beam. It is something.

Examples of the adhesive layer for composite materials of the present invention will be described below.

Copper foil or copper strip or other metal foil or metal strip is bonded with silane-modified polyolefin or silane-modified polyolefin copolymer film at the same time as extrusion at a preheating temperature that is the same as or higher than the extrusion temperature. When the body is formed, this adhesive layer is free of condensing agents. Therefore, it is a thermoplastic resin, and when modified, the melt viscosity index decreases to 115 to 1/7 and the molecular weight increases, but it also has problems with heat resistance, chemical resistance, oil resistance, and solvent resistance. In order to do this, it is possible to create a cross-linked structure.

Radiation increases the viscosity, average molecular weight, and branching of many polymers. These changes are based on the binding of two molecules to each other. That is, crosslinking is a reaction in which side chain bonds are cleaved by radiation and new bonds are formed between adjacent molecules through the resulting radicals. in general,
In vinyl polymers whose main chain is C--C bonded, there is a certain relationship between the radiation effect and the chemical structure. If the polymer has the structure (-cH, -0HR-)n, it will be crosslinked, and C-OH, -c (OH,) R
-) It is generally said that if it has a structure n, it will collapse.

Here, R represents a substituent such as H, CHs, C6H, etc., but this relationship does not necessarily hold true for non-vinyl polymers.

Polymers gelled by radiation become macromolecules with a three-dimensional structure, so they become insoluble in solvents, but this depends on the degree of crosslinking. For example, when polyethylene is irradiated, crosslinking occurs between molecules, so those that are sufficiently irradiated will have improved heat resistance, solvent resistance, stress cracking resistance, etc. Most of the irradiation is performed using electron beams generated by high-capacity electron accelerators. A fairly large absorbed dose of 10 Mra or more is required to sufficiently crosslink the material to provide heat resistance.

When radiation with a high dose rate such as an electron beam is used, crosslinking can be efficiently achieved even during aerial irradiation. Crosslinking of polyolefins such as polyethylene can also be carried out by non-chemical methods. However, since chemical methods generally use high temperatures, they are difficult to apply to thin, already bonded plates or thin films, so radiation treatment may be considered more advantageous than other methods.

A sample, a copper foil of about 100 fflll square and 45 μm thick, was irradiated from the adhesive layer side of the copper foil with 100 μm of the above silane-modified polyolefin adhesive layer fused at an irradiation voltage of 7.35 MV at an irradiation dose as shown in the figure.

The dose at this time is calculated as follows.

Dose calculation 1, 35 MVX2 mA=2.7 X I D”W=
=2.7 X 10" joule 2.7X10" joule = 2.7
2+5 seconds)=3,575×10sMrad/gr Since the utilization efficiency is empirically known to be 0.05 to 0.15, if it is set to 0.01, it becomes about 34 Mrad.

As shown in Tables 1 to 3 of the adhesive strength test results of the above samples, there is a significant difference in peel loads at 23°C and 110°C. 2 for each sample.
Among the numerical values, the smaller number is the value at the start of peeling, and the larger number is the value at the time the peeling is completed. Also,
If there is one number, the peeling starts and ends at the same time.

As described above, the adhesive layer for composite materials of this example is crosslinked by electron beam irradiation, which improves adhesive strength compared to untreated products at various temperatures, and shows remarkable improvement in solvent resistance and resistance at relatively high temperatures. Stress cracking properties can also be improved.

As described above, the adhesive layer for composite materials of the present invention has the effect of improving adhesive strength, heat resistance, solvent resistance, and stress cracking resistance.

[Brief explanation of the drawing]

The figure is an explanatory diagram of the amount of electron beam irradiation in an example of the adhesive layer for composite materials of the present invention. (Runnin” - 4 Denmusume Gakuun 1 Torture -

Claims (1)

[Claims] 1. An adhesive layer for a composite material in which a composite material is formed by interposing an adhesive layer made of a resin material on the surface of a metal foil or metal strip, characterized in that the adhesive layer is crosslinked by irradiation with an electron beam. Adhesive layer for composite materials.