JPH0813955B2 - Method for producing film-like adhesive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a film adhesive, and more particularly to a method for producing a film adhesive by a solvent dilution method of an epoxy resin / polyvinyl butyral adhesive. .

[Conventional technology]

Since the film adhesive can be easily obtained as an adhesive of uniform thickness and long length, it is possible to improve the accuracy and automation of the bonding work, and it is widely used in various applications such as electricity, electronics, construction, automobiles and aircraft. There is. These film-like adhesives are often used as high-performance curable adhesives by containing an epoxy resin in the compounding system.

On the other hand, polyvinyl butyral (hereinafter PV
Abbreviated as B. ) Is added to obtain flexibility, and as an attempt to obtain the viscosity stability of this system, for example, according to JP-B-61-38947, fine powder PVB is dispersed in an epoxy resin. A solid-liquid dispersion type liquid epoxy composition is proposed.

Attempts have also been made to obtain higher performance adhesives by adding other components to epoxy / PVB / solvent adhesives, such as aziridine compounds (Japanese Patent Publication No. 55-30555) and amino resins (special KAISHO No. 62-116682) and isocyanates and organic acids (JP-A No. 62-132987) are known, and the solvent in these cases is, for example, a ketone solvent such as methyl ethyl ketone, toluene, xylene or the like. Aromatic solvents and alcoholic solvents such as methanol are used alone or as a mixture, and these are used by being directly applied to an adherend as a paste-like or solvent-containing adhesive.

As a method for producing a film adhesive containing a solid component at room temperature, it is common to obtain a thin film-like product having a low viscosity by a method such as heating by roll rolling or dilution with a solvent. It is possible to obtain a more accurate thickness with the solvent method than with the rolling method.

[Problems to be Solved by the Invention]

The composition disclosed in JP-B-61-38947 improves the dispersibility of PVB in an epoxy resin, but it has the following problems when it is used as a film adhesive. In other words, when a liquid epoxy resin is used, it is difficult to control the B stage state when a general curing agent is used, and this has the disadvantage that the physical properties change significantly during storage. When a latent curing agent is used as the curing agent, Since PVB is present in the form of fine powder, the liquid epoxy resin has a low molecular weight and also has no film forming ability, so that a support such as glass or synthetic fiber is required. On the other hand, when dissolving a solid epoxy resin in a solvent at room temperature to form a film, PVB
It is necessary to use a solvent with a relatively low SP value, such as methyl isobutyl ketone (MIBK, SP value 8.5) or n-hexane (SP value 7.30), which is an insoluble solvent for PVB, in order to maintain the powder in the form of fine powder. It is difficult to apply the above solvent to the solvent because the higher the molecular weight grade of the epoxy resin, that is, the higher the softening point of the solid epoxy, the less the solubility.

Methanol (SP value 14.5), methyl ethyl ketone (SP value 9.30), etc., which are general-purpose solvents for epoxy resins, as disclosed in JP-B-55-30555, JP-A-62-116682 and JP-A-62-132987. In the case of the solvent containing alcohol or ketone, the PVB is dissolved in these solvents, so that the dispersion system of granular PVB as shown in JP-B-61-38947 cannot be obtained. Further, when PVB is dissolved in these polar solvents and used, it is difficult to produce a film due to a large change in viscosity of the composition, and these polar solvents also contain many latent curing agents. Since it dissolves, the adhesive gels and cannot be applied. Furthermore, when a hydrocarbon solvent with a low SP value typified by toluene is used alone, the solubility of PVB or high molecular weight epoxy resin is little, or even if it is slightly soluble, the solution viscosity changes. Was difficult to apply.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a method for producing a film adhesive having excellent stability during film production.

It is another object of the present invention to provide a method for producing a film-like adhesive which can be stably stored for a long period of time and can be rapidly cured, and which has excellent adhesive performance.

[Means for solving the problem]

The present invention is an epoxy resin, vinyl acetate component is 2.0 wt% or more and vinyl alcohol component is 15 wt% or less polyvinyl butyral with an average degree of polymerization of 500 or more SP value is not more than 9.20 and boiling point is 150 ℃ or less. A layer of an adhesive solution which is dissolved in a non-chlorine-based solvent and is dispersed in the solution with a latent curing agent which is insoluble in the solvent and has an activation temperature represented by a DSC peak temperature which is equal to or higher than the boiling point of the solvent. Alternatively, the present invention relates to a method for producing a film adhesive, which comprises forming a layer containing the adhesive solution on a peelable substrate and then drying the layer at a boiling point of the solvent or lower.

Typical examples of the epoxy resin used in the present invention include bisphenol-type epoxy resins derived from epichlorohydrin and bisphenol A or bisphenol F, epoxy novolac resins derived from epichlorohydrin and phenol novolac, and cresol novolac, and other glycidyl amine, Glycidyl ester,
Various epoxy compounds having two or more oxirane groups in one molecule such as a fat-reducing type and a complex-reducing type can be applied. These can be used alone or in combination of two or more. Further, the combined use of liquid and solid epoxy resins is a preferable use form from the viewpoint of controlling the film forming property and the fluidity of the adhesive at the time of connection. These epoxy resins, impurity ions ^{(Na +, K +, C1} -, SO 4 2- , etc.) be used and high purity products such as hydrolyzable chlorine is reduced each 300PPm below, connection circuit It is preferable because it prevents corrosion.

PVB is a terpolymer of butyraldehyde, vinyl acetate, and vinyl alcohol obtained by reacting (acetalizing) butyraldehyde with polyvinyl alcohol obtained by saponifying polyvinyl acetate (generally some polyvinyl acetate remains). Is. The PVB used in the present invention has a vinyl acetate component of 2.0% due to the limitation of the solvent described later among these.
A vinyl alcohol content of 15% or less and a vinyl alcohol content of 15% or less is used, which has a higher vinyl acetate content and a lower vinyl alcohol content than ordinary PVB.
0 or more is used. The analysis of these components and the average degree of polymerization of the present invention are based on JIS K-6728. If the vinyl acetate component and the vinyl alcohol component are out of the above range, the solubility in the solvent used in the present invention is decreased, and if the average degree of polymerization is less than 500, the film forming ability is insufficient and a large amount of PVB should be added. Since it is necessary, the heat resistance of the film adhesive becomes insufficient, making it difficult to apply to the present invention. For these reasons, the preferred range is PVB having a vinyl acetate component of 2.0 to 10.0% by weight and a vinyl alcohol component of 8.0 to 14.0% by weight.

The solvent used in the present invention has an SP value of 9.20 or less and a boiling point of
A chlorine-free solvent with a temperature below 150 ° C can be applied. The SP value in the present invention is the adhesive handbook No. 2 published by Nikkan Kogyo Shimbun.
Version (published on December 10, 1982), pages 107-109, the boiling point is the solvent handbook published by Kodansha Co., Ltd.
(Published July 1, 1987) The values listed are used. When the SP value exceeds 9.20, the erodibility of the latent curing agent increases, and when the boiling point exceeds 150 ° C, it is necessary to set higher drying conditions for forming a film, so the latent curing agent's potential is The chlorine-based solvent decreases, and hydrolyzable chlorine in the film remains, so that both are not preferable. In the range of the above solvent, the higher the SP value is, the more the solubility of the epoxy resin or PVB is improved, and the boiling point is preferably 60 to 140 ° C. in consideration of prevention of deterioration of working environment due to volatilization and drying efficiency.

Examples of typical solvents that satisfy this range are pentane (SP value 7.05, boiling point 36.1 ° C) for hydrocarbon-based aliphatic compounds,
Similarly, hexane (7.30,68.7), cyclohexane (8.20,80.72), heptane (7.45,98.4), octane (7.55,125.67), hydrocarbon aromatics such as benzene (9.15,80.1) and toluene (8.90,110.63). ), Xylene (8.80,138.35), and in the ester system ethyl acetate (9.10,77.11), propyl acetate (8.75,101.55), ethyl propionate (8.90,99.1), amyl formate (8.65,130.
4), butyl acetate (8.46,126.11), ethyl butyrate (8.15,1
21.3) etc. A preferred combination among these is when used as a mixed solvent of a hydrocarbon solvent and an ester solvent, and the solubility and viscosity stability of the epoxy resin and PVB solvent are extremely good. The mixing ratio in this case can be arbitrarily determined according to the desired boiling point and solubility. Further, when a mixed solvent of a hydrocarbon aromatic and an ester is used, the water content in the adhesive solution can be reduced, and therefore it is more preferable from the viewpoint of preventing foaming during film production and erosion of the latent curing agent.

Examples of the latent curing agent include imidazole-based, organic acid hydrazide-based, boron trifluoride-amine complex, diaminomaleonitrile, amine imide, polyamine salt, ginandamide, and modified products thereof, and these may be used alone or It can be used as a mixture of two or more kinds. As a preferred form of the present invention, which requires compatibility of contradictory characteristics of long-term storage property and rapid curing property, polyurethane, polystyrene or other polymer substance having these curing agents as cores, or Ni, Cu or other metal thin film is preferable. Use as a coated microcapsule type curing agent, or by the molecular sieve method,
It is preferably used in a form in which the chance of contact between the curing agent and the reactive component such as epoxy resin is reduced. The compounding ratio of the epoxy resin and the latent curing agent can be set arbitrarily.

A point to be noted when using a microcapsule type curing agent applicable as a preferred embodiment of the present invention is to prevent capsule destruction during storage by making the particle size of the capsule smaller than the thickness of the film adhesive. Also, be careful not to lose the potential of the curing agent, for example, by selecting a solvent that does not easily corrode the wall material or paying attention to the drying temperature during manufacturing.

Epoxy resin 10 for manufacturing film adhesive
The amount of PVB added to 0 parts by weight can be arbitrarily selected according to the properties of the epoxy resin, but is preferably 1.0 to 100 parts by weight. If it is less than 1.0 part by weight, it is difficult to form a film, and if it exceeds 100 parts by weight, the heat resistance of the adhesive becomes insufficient. For this reason, the more preferable range is 3.0 to 50 parts by weight. A predetermined amount of the above-mentioned epoxy resin and PVB is mixed and dissolved in a solvent to obtain an adhesive solution in which a predetermined amount of a latent curing agent which is insoluble in the solvent and has an activation temperature higher than the boiling point of the solvent is mixed. At this time, the activation temperature of the latent curing agent is DSC.
The exothermic peak temperature is shown when the mixture of the epoxy resin and the latent curing agent is sampled using a (differential calorimeter) and the temperature is raised from room temperature at 5 ° C./min.

The adhesive solution comprising the above is formed on a releasable base material such as a release paper by film formation and drying using a normal means such as a roll coater, or a base material impregnated with the adhesive solution is laminated. Then, this is dried to obtain a film adhesive. For drying, it is necessary to dry at a temperature not higher than the boiling point of the solvent, preferably 10 ° C or more lower than the boiling point, from the viewpoint of preventing curing of the film, and when using a mixed solvent, the highest boiling point solvent in the system may be considered. .

In the film-like adhesive described above, commonly used additives such as fillers, softening agents, curing accelerators, ultraviolet absorbers, antiaging agents, metal deactivators, colorants, and drying agents. A thixotropic agent, a silane-based or titanium-based coupling agent, a curing agent such as a phenol resin, a melamine resin, or an isocyanate can be contained.

The film adhesive of the present invention obtained as described above is produced as an adhesive layer alone or as an integral body with a substrate such as a fiber or a nonwoven fabric. The thickness of these film adhesives may be determined in consideration of the drying property at the time of film formation and the desired adhesive strength, but is 1 to 100 μm.
Degrees can generally be used.

[Action]

In the present invention, the SP value of the epoxy resin / PVB-based blend by specifying the properties of PVB has a SP value of 9.20 or less and a boiling point of 15
Since it can be dissolved in a non-chlorine solvent at 0 ° C or less and the viscosity stability of this system is remarkably good, the problems in film production by the solvent method can be solved.

Hydrocarbon-based or ester-based solvents have a lower SP value than alcohol-based or ketone-based solvents and have a low water content, so that latent curing agents can exist without being eroded.

The activation temperature of the latent curing agent is above the boiling point of these solvents, and the drying temperature during film production is set below the boiling point of these solvents, so that the latent curing agent retains its latent potential stably. You can

The film adhesive obtained as described above can be stably stored below the activation temperature of the latent curing agent, and can be rapidly cured above the activation temperature during adhesion.

〔Example〕

Example 1 Quartrex 1410 (solid having a melting point of 80 ° C., bisphenol type epoxy resin, hydrolyzable chlorine 48 ppm, trade name of Dow Chemical Co., Ltd.) and Quartrex 2010 (liquid phenol novolac type epoxy resin, hydrolyzable chlorine 64 ppm) , Dow Chemical Co., Ltd.) and 80:20
Butyral 3000K with 100 parts by weight of epoxy resin mixed in
(Polyvinyl bral, 5.1% by weight of vinyl acetate component, 9.5% by weight of vinyl alcohol component, average degree of polymerization of 800, trade name of Denki Kagaku Kogyo Co., Ltd.) 40 parts by weight of a mixed solvent of xylene / butyl acetate = 80/20 It was dissolved so that the concentration became 40%. In this solution, Novacure HX-3612 (a microcapsule type curing agent with an average particle diameter of 5 μm, which has a modified imidazole core as a core and whose surface is coated with polyurethane, activation temperature 134 ° C., trade name of Asahi Kasei Corporation) 40 parts was added to obtain an adhesive solution. This adhesive solution was stable with no increase in viscosity even after standing at room temperature at 25 ° C. for 10 days. A biaxially oriented polypropylene film (hereinafter OP
P, thickness 60 μm) and then 120 using a roll coater
The thickness of the adhesive layer is 30 μm by drying with hot air for 30 minutes at ℃
A film adhesive of

This film has sufficient flexibility at room temperature,
It was possible to wind continuously. With this film,
Copper foil 35μm smooth surface and glass 1.1mm smooth surface connection at 200 ℃
It was performed by the -2kg / cm ² -30 seconds, peel strength (JIS
C-6481) is 1.2 at each at 25 ℃ and 100 ℃.
And 1.kg/cm are good, and the same peeling strength at 25 ° C is obtained after treating this connected product with a pressure cooker at 121 ° C for 100 hours. It is 0.8kg / cm, and corrosion of the copper surface does not occur. There wasn't. In addition, the film is kept at 40 ° C to check its storage stability.
When the same peeling strength at 25 ° C was obtained after storage for -30 days, it was 1.2 kg / cm and was found to have sufficient storability.

From the above, in this example, it is possible to bond with heat resistance by the combined use of a polyfunctional phenol novolac type epoxy resin, and because the content of hydrolyzable chlorine of the material is low, good high temperature resistance By using a microcapsule type curing agent that has wettability, long-term storage and short-time connection were possible.

Example 2 Epicoat 1007 (solid bisphenol type epoxy resin having a melting point of 128 ° C., trade name of Yuka Shell Epoxy Co., Ltd.)
And Epicoat 832 (a liquid bisphenol type epoxy resin, a trade name of Yuka Shell Cepoxy Co., Ltd.) at a solid content ratio of 50:50, and 100 parts by weight of butyral 3000K (above) and 15 parts by weight. It was dissolved in a mixed solvent of toluene / ethyl acetate = 90/10. To this solution, 20 parts by weight of Novacure HX3721 (described above, but activation temperature 119 ° C.) was added to obtain an adhesive solution.

The viscosity of this solution did not increase even after standing at room temperature at 25 ° C for 10 days. Using this solution, a film adhesive was prepared in the same manner as in Example 1. The drying condition was 90 ° C. for 10 minutes.
Since this film has sufficient flexibility at room temperature,
It was possible to slit into a tape with a width of mm. This tape was treated in the same manner as in Example 1 after a storage test at 40 ° C. for 30 days.
When the peeling strength at 25 ° C was examined, the connection conditions
150 ℃ -5kg / cm despite a relatively low temperature short time connected to the ² -30 seconds, it was capable of high strength connection and 1.5 kg / cm.

From this, it can be seen that a film-like adhesive capable of being processed, storable, and capable of being connected at a low temperature for a short time was obtained.

Comparative Example A film-like adhesive was obtained in the same manner as in Example 1 except that a mixed solvent of toluene / methanol = 50/50 which was a general solvent was used.

In this case, the adhesive solution showed a tendency to increase in viscosity after 1 hour of compounding, and the film-like adhesive after drying proceeded to cure and could not be used as an adhesive. This is probably because the coating of the microcapsules was destroyed by methanol (SP value 14.8), the viscosity stability was lost, and the microcapsules were further destroyed during drying and the curing of the epoxy resin proceeded.

〔The invention's effect〕

According to the present invention, a film-like adhesive can be stably produced, and the obtained film-like adhesive can be stored for a long time at a temperature below the activation temperature of the latent curing agent.
In addition, it has excellent adhesive properties such that it can be rapidly cured at an activation temperature or higher during adhesion.

Claims (3)

[Claims] 1. An epoxy resin and polyvinyl butyral having an average degree of polymerization of 500 or more and having a vinyl acetate component of 2.0% by weight or more and a vinyl alcohol component of 15% by weight or less.
Dissolve in a non-chlorine solvent having a value of 9.20 or less and a boiling point of 150 ° C. or less, and dissolve the latent curing agent that is insoluble in the solvent and has an activation temperature represented by a DSC peak temperature of the boiling point of the solvent or more. A layer of a film-like adhesive characterized in that a layer of an adhesive solution dispersed in a liquid or a layer containing the adhesive solution is formed on a peelable substrate, and then dried at a boiling point of the solvent or lower. Production method. 2. The method for producing a film adhesive according to claim 1, wherein the latent curing agent is a microcapsule type curing agent having a curing agent component as a core and the surface thereof covered with a wall material. 3. The method for producing a film adhesive according to claim 1, wherein the solvent is a mixed solvent of hydrocarbon type and ester type.