JPS6037837B2 - Foam adhesive sheet - Google Patents

Description

[Detailed description of the invention] The present invention relates to a foamable thermal adhesive sheet.

Conventionally, the foamable resin compositions used for foamable thermal adhesive sheets include those made by blending a foaming agent into a thermoplastic resin such as polyethylene, and those made by blending a foaming agent into a thermosetting resin such as epoxy resin. It is known that it is made by combining them.

These compositions can be formed into a sheet and then heated and foamed to form foamed sheets that have various uses such as heat insulation materials, insulation materials, cooling materials, lightweight materials, sealing materials, etc. can.

In particular, when thermosetting resin is used, it is possible to improve the lack of heat resistance, which is a drawback when using thermoplastic resin, that is, dimensional changes, deformation, foamed structure, and deterioration of appearance that occur at high temperatures. can. Furthermore, when forming a foam adhesive layer using a thermoplastic resin, the adhesive strength is not sufficient and the adhesive strength decreases when exposed to high temperatures. During molding, it is necessary to use a foaming agent with a high decomposition temperature to prevent the foaming agent from decomposing and foaming, and for this reason, the heating and foaming conditions must also be harsh, which has the disadvantage of poor workability. Ta. When a thermosetting resin is used, these drawbacks can be improved. Furthermore, using a foamable heat-adhesive sheet made of a thermosetting resin composition, a surface with an essentially non-smooth rough surface such as an uneven surface, a distorted surface, a porous surface, etc. (hereinafter abbreviated as a assembled surface) ), when bonding
Foaming allows the resin to penetrate into the details of rough surfaces, allowing for uniform adhesion. However, foaming lowers the strength of the foaming agent, which has the disadvantage of lowering adhesive strength. In addition, when a normal thermal adhesive sheet is used to maintain the strength of the adhesive layer, the adhesive area with the rough surface is reduced, making it impossible to obtain a uniform and stable adhesive force, and the adhesive strength also decreases. . In light of the above circumstances, this invention was developed as a result of intensive studies to obtain a new and useful foamable resin composition that has good adhesive strength to rough surfaces and also enables uniform and stable adhesion. The present invention has been discovered, and the object is to provide a foamable thermally adhesive sheet obtained from such a composition.

That is, this invention relates to a foamable adhesive sheet that contains an epoxy resin, a rubbery component, a curing agent, and an appropriate amount of a foaming agent, and has a foaming ratio of 1.1 to 1.9 after being heated and cured. It is. The foamable adhesive sheet obtained by the present invention is suitable for adhering adherends having a rough surface on at least one side. The difference in the bottom part is generally not more than 3 times the thickness of the foamable adhesive sheet before heating and foaming, preferably 0.5 to 1.
It is best to have around 3 notes.

The epoxy resin used in the foamable thermally adhesive sheet of the present invention has an average of one or more reactive epoxy groups per molecule, and includes bisphenol type,
These include various types such as ether ester type, novolacepoxy type, ester type, cycloaliphatic type, and nitrogen-containing glycidyl ethers.

Commercially available products include, for example, Ebicoat #828, #1002, #1004, #1007, manufactured by Shell Chemical Co., Ltd.
Manufactured by Ciba Corporation, product name ECN1280, TGIC, manufactured by Dow Chemical Company, product name DER730DEN438, 439
Manufactured by Dainippon Ink & Chemicals Co., Ltd., product name DIC-EPICL
Examples include ON200, 400, 1030, 4030, manufactured by Chisso Corporation, and product names CX-221 and CX-289.

Above d. In order to prevent the possibility that if the poxy resin is used alone, the foam adhesive sheet and foam adhesive layer will become too hard and cause rigid fracture during processing and handling, making it impossible to fully demonstrate their functions, it is preferable to use a resin composition. It has been proposed to use epoxy resin by reacting it with a rubbery component in advance for the purpose of imparting flexibility to objects. The rubbery component used in this case is a rubbery component mainly composed of a carboxyl group-containing rubbery polymer that is liquid at room temperature. This polymer usually has a molecular weight of 1000 to 500, preferably 3
The average number of carboxyl groups contained per molecule is usually 1.5 to 2.5, preferably 1.8 to 4000.
2.4, and those having carboxyl groups at both ends of the molecule are preferably used. A typical example of such a polymer is a carboxyl group-containing acrylonitrile-butadiene copolymer.
manufactured by ical: liquid nitrile rubber containing about 20% by weight of acrylonitrile and having an acid equivalent of 0.07 per 100g, number average molecular weight 3600).

Such a polymer that is liquid at room temperature may be used alone as a rubbery component in the present invention, or may be used together with a similar polymer that is solid at room temperature, such as Nipole 1072 manufactured by Nippon Zeon Co., Ltd., or a special polymer. In some cases, a small amount of general natural or synthetic rubber such as neorene, ethylene-pyrene-dicyclobentadiene, etc. may be used in combination.

The blending ratio of such rubbery components should be such that the rubbery component accounts for 20 to 70% by weight, preferably 35 to 6% by weight, based on the total amount with the epoxy resin.

If the amount is more than 70% by weight, the heat resistance and adhesiveness after heating and foaming may be poor, and if it is less than 2% by weight, flexibility is likely to be impaired.

In this invention, the above-mentioned epoxy resin and the rubbery component are melt-mixed, and a relatively high temperature is applied during this mixing to form the carboxyl group-containing rubber, which is liquid at room temperature and forms the main component of the rubbery component. It is desirable to react some or all of the polymer with the epoxy resin.

In this reaction, the compatibility between the two is improved, the molecular weight is increased, and the overall viscosity is lowered.
The aim is to improve sheet formability, flexibility, heat resistance, and post-adherence. After this reaction and mixing, it is once cooled to room temperature, and if necessary, the same or different rubber components are blended, and a curing agent and a foaming agent are mixed therein to form a foamable resin composition for obtaining the adhesive sheet of the present invention. can get.

The curing agent used here is preferably one that is stable at room temperature and exhibits activity at high temperatures in order to preserve the resin composition for a long period of time. Nitrogen-containing compounds that decompose to yield at least one active hydrogen-containing amine are preferably used.

Typical degradable curing agents include monourea, polyurea, hydrazide, thiourea, etc. Preferred specific examples include 3-(P-c.lofenyl)-1,1-dimethylurea, 2,4-bis(N,N -dimethylcarbamide) toluene, dicyandiamide, etc., and these may be used alone or in combination of two or more. Of course, it is also possible to use other curing agents, such as acid anhydrides, imidazoles, imidazolines, etc.

Specific examples include phthalic anhydride, maleic anhydride, dodecylsuccinic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, penzophenonetetracarboxylic anhydride, dichlorosuccinic anhydride, and chlorene anhydride. Dick's acid, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-windecylimidazole, 2-hebutadecylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2,4 -dimethylimidazole,
2-phenyl-4-methylimidazole, 2-methylimidazoline, 2-ethyl-4-methylimidazoline, 2
Examples include monophenylimidazoline, 2-undecylimidazoline, 2-hebutadecylimidazoline, 2-ethylimidazoline, 2-isopropylimidazoline, 2,4-dimethylimidazoline, and 2-phenyl-4-methylimidazoline. The usage ratio of the curing agent used in this invention varies depending on the type of epoxy resin and rubbery component and their blending ratio, but usually the resin component is 100%
It may be used at a ratio of 0.5 to 13 parts by weight. In addition, as a foaming agent, one is selected that decomposes at a temperature equal to or higher than the softening temperature of the resin and does not foam during molding (as long as the amount is small), but the aforementioned resin component used in this invention has a relatively low softening temperature. Therefore, there is no need to use a blowing agent with a particularly high decomposition temperature, and general azo compounds, nitroso compounds, hydrazide compounds, etc. can be widely used.

Specific examples include azodicarbonamide, azobisisobutyronitrile, dinitrosobentamethylenetetramine, /latluenesulfonylhydrazide, and 4,4-oxybisbenzenesulfonylhydrazide. These may be used alone or in combination, optionally with foaming aids such as urea and metal salts of carboxylic acids. The usage ratio of such a blowing agent (or this and a blowing aid) is:
Generally, it is about 4 parts by weight or less per 100 parts by weight of the resin content, and it is important that the foaming ratio after heating is 1.1 to 1.93.

This is because when the expansion ratio is 1.95 times or more, the strength of the foamed resin layer decreases and the expected sufficient adhesive strength cannot be obtained. In addition, when the foaming ratio becomes 1.1 times or less, in practice,
The effect of foaming is not observed, and a sufficient bonding area cannot be obtained on a rough surface, making it impossible to bond uniformly, and the adhesive force is also reduced. In addition to the above-mentioned components, various compounding agents can be added to the foamable resin composition used in the present invention, if necessary.

For example, phenyl-8-
naphthylamine, diphenyl-P-phenylene diane,
Stabilizers and anti-aging agents such as diterciabutyl-4-methylphenol, gravhenylphenol, calcium stearate, dilaurylthiodipropionate, etc.
For the purpose of further improving adhesion and flexibility, esters, ester gum, alkyd resin, coumaron resin, flexible epoxy resin, epoxy resin diluent, etc. are cured for the purpose of accelerating or complete curing during heat foaming. Accelerators, rubber vulcanizing agents, etc., and fillers such as clay, talc, calcium carbonate, silica, barium carbonate, etc. can be added for the purpose of improving sheet formability and reducing costs.
Other coloring agents and the like may also be added. In the present invention, the foamable resin composition thus produced is molded into a sheet and used as a foamable adhesive sheet.

For sheet forming, for example, the above-mentioned foamable resin composition is generally kneaded using a mixing roll or presser, and if necessary, pelletized using a pelletizer, and then formed into a sheet using an extrusion molding machine. good.

The extrusion conditions at this time should be such that the composition does not harden and the blowing agent does not decompose (it may decompose if only slightly), but the resin component has a relatively low softening temperature. Therefore, selection of such conditions is easy. Alternatively, the mixed wire material may be coated on a reinforcing material serving as a sheet-like support.

This may be appropriately selected depending on the shape, viscosity, workability, etc. of the resin. In addition, the foamable adhesive sheet obtained by extrusion sheeting may shrink in the extrusion direction during the initial stage of hardening and foaming, and due to this dimensional change, the resin component that has softened and flowed during extrusion molding may undergo molecular orientation. This may reduce the adhesion area and product value.

In such cases, it is usually best to use the foamable adhesive sheet of the present invention by integrally adhering it to the reinforcing material. The reinforcing material has the function of preventing shrinkage at the initial stage of curing and foaming, and also has the function of directing the three-dimensional expansion force caused by foaming only in the thickness direction, so it improves the dimensional stability of the adhesive layer after curing and foaming. It has very good sexual results. There are reinforcing materials for coating, and reinforcing materials used during extrusion molding are made of cheesecloth, coarse sheets of various materials, silk-like materials such as wire mesh, and porous materials such as woven and non-woven fabrics of various materials. is suitable.

With such a porous material, even if the adhesive sheet is placed on only one side of the material, the adhesive sheet will be impregnated from one side to the other when the adhesive is integrated or when it is cured and foamed during use. Because it can be migrated,
The bond between the reinforcing material and the bushing sheet becomes strong, so that the reinforcing material can perform its functions more effectively. From this point of view, the size of the mesh when using the above-mentioned mesh material or cheesecloth is generally 0.5 ribs or more, preferably in the range of 1 to 10 ribs both in the vertical direction and in the horizontal direction.

For those made of other porous materials such as non-woven fabrics and woven fabrics, those having an appropriate thickness or density depending on the material may be used from the same point of view as above and also taking into account its mechanical strength. In addition to such porous materials, materials made of materials substantially free of pores, such as metal sheets such as copper foil and aluminum foil, and plastic sheets, can also be used as reinforcing materials.

In this case, it is generally sufficient to arrange foam adhesive sheets on both sides of these reinforcing materials. The method of bonding and integrating the foam adhesive sheet with the reinforcing material in extrusion molding is as follows:
For example, a foam adhesive sheet may be laminated by pressure while retaining its softened state immediately after melt extrusion, or a pre-manufactured foam adhesive sheet and a reinforcing material may be bonded together using a thermocompression laminator to adjust the curing temperature or the decomposition temperature of the foaming agent. Methods such as lamination and integration at lower temperatures can be adopted. In the foamable adhesive sheet of the present invention obtained by the above sheet molding, the thickness of the resin layer is usually 0.05 to 5, preferably 0.05.
One to three skins is good.

In use, this sheet may be placed between adherends and heated by any means such as press heating, far infrared heating, hot air heating, etc. to harden and foam. This foamed adhesive layer exhibits little decrease in the strength of the resin layer due to foaming, has excellent adhesive strength or adhesion to the adhesive body, and has excellent heat resistance.

Also, those containing rubbery components have good flexibility before curing and foaming and retain their integrity. In addition, in the present invention, since the rubber component mainly consisting of a carboxyl-based polymer IJmer is blended in the above ratio, it foams uniformly during heating and foaming to form a good adhesive layer, and the resulting foamed layer is rigid. It does not cause breakage, and it does not have inferior heat resistance or adhesive properties.

Furthermore, since the adhesive sheet of the present invention contains the rubber component, there is no risk of rigid fracture even when handled before heating and foaming.

Any adherend that can be applied here may be used as long as it does not undergo thermal deformation during curing and foaming, such as metal plates such as aluminum plates, stainless steel plates, and steel plates, inorganic boards such as slate plates and magnesium carbonate plates, and synthetic resins. A wide range of materials include board, paperboard, plywood, etc., but in particular, in the present invention, adherends having a target surface that is not essentially smooth, such as an uneven surface, a distorted surface, a porous surface such as a wire mesh, etc. Particularly suitable for gluing.

Examples of this invention will be described below.

In the following, parts shall mean parts by weight. In addition, the peel adhesion strength in Examples was measured as follows. An aluminum plate (25 x 100 x 0.2
skin), 80 mesh steel wire mesh (25 x 10
The adhesion strength between the aluminum plates and between the aluminum plates and the wire mesh was measured using a bonding plate (0 ribs).

The method involves sandwiching and fixing a foam adhesive sheet between the attached bodies.
Heat bonding was performed for 20 minutes under an atmosphere of 140:00 during the opening. Thereafter, it was left to stand at room temperature for 2 hours or more, and the peel strength was measured using an Instron type tensile tester at a temperature of 2300 and a tensile speed of 5 m/min. Examples 1 and 2, Comparative Examples 1 to 3 Epicoat #1004 (epoxy resin manufactured by Yuka Shell Co., Ltd.)
100 and CTBN (carboxyl group-containing rubbery polymer, B.T.G℃odrich Chemical
(manufactured by AL) 6 triphenylphosphine as the base and catalyst. The reaction mixture was mixed in a heated reaction vessel at 150 o for 4 hours to complete the reaction and the reaction was cooled to room temperature to form a mass.

*Next, a mixture having the composition shown in recipe m below was mixed on a mixing roll.

Mixture table [B] *5. Manufactured by Asahi Kasei *6. Manufactured by Eiwa Kasei Co., Ltd. (decomposition temperature 155°C) Next, Example 1
and 2. The resin compositions of Comparative Examples 1 to 3 were extruded into a sheet using an extruder at a die temperature of 80 pm or less to a thickness of 0.
A molded sheet with 15 ribs was made.

This molded sheet had excellent flexibility and was free from rigid fracture during handling, and was used as it was as an adhesive sheet of the present invention. Next, these adhesive sheets were subjected to peel adhesion strength measurement and expansion ratio measurement in the same manner as described above.

The results are shown in Table 1. As shown in Table 1, by using a foamable thermal adhesive sheet made of a low-foaming thermosetting resin with an expansion ratio of 1.1 to 2 times to adhere to an adherend having a rough surface, the foamed resin can be applied to a rough surface. Since the contact area is large because the contact area is large, and the magnification is low, there is little loss of strength of the foamed resin layer, and the result is a uniform, stable, and good bonding strength that is comparable to bonding on smooth surfaces. Gluing is done.

Note that up to 5% by weight of the epoxy resin in the present invention can be replaced with a thermoplastic resin, and such resins are also included within the scope of the epoxy resin in the present invention.

Comparative Example 4 Formulation A Epicoat #1004 (manufactured by Yuka Shell Co., Ltd. 3 Togekuni Epicoat #828 epoxy resin) 7 Base part curing agent Dicyandiamide 1 Anchor part Foaming agent Azodicarbonamide 0.1 part Solvent Xylene 0.3 part Blend Bepicote #1004 (manufactured by Yuka Shell Co., Ltd. 8 Togeto Epicoat #828 epoxy resin) 2 Anchor filler RG-144 1 Ikari hardening agent Dicyandiamide 6 parts Dippy hardener 3 parts Foaming agent Vinyhole AK #2
1.5 parts of these formulations were mixed using a common mixing roll to obtain thermosetting resin compositions A and B.

Composition A was liquid and could not be formed into a sheet. Therefore, this composition A was applied to the adherend and cured by heating at 200 oo for 24 hours, and then the peel adhesion strength was measured using the method described above. The results are shown in Table 2. Further, the above composition B was made into a molded sheet B having a thickness of 0.3 using an extruder in the same manner as in the examples.

This molded sheet was extremely brittle and prone to rigid fracture, making it inconvenient to handle. Next, an adhesive test piece was prepared using this sheet B, and the peel adhesion force was measured using the method described above. The results are shown in Table 2. Table 2 Peel strength The viscosity decreased and then foaming started, resulting in a coarse and non-uniform cell structure.

Claims (1)

[Scope of Claims] 1. A resin composition sheet containing an epoxy resin, a rubbery component, a curing agent, and a foaming agent, which has an expansion ratio of 1.1 to 1 after heating.
．． 95 times the foaming adhesive sheet, the rubbery component is mainly composed of a carboxyl group-containing rubbery polymer that is liquid at room temperature, and the rubbery polymer accounts for 95 times the total amount of the epoxy resin and the rubbery polymer. A foamable adhesive sheet containing an epoxy resin and a rubbery polymer in a reacted state, in an amount of 20 to 70% by weight. 2. A foamable adhesive sheet according to claim 1, which is integrally bonded to one side of a porous reinforcing material. 3. The foamable adhesive sheet according to claim 2, wherein the porous reinforcing material is a net-like material or cheesecloth.