JP2010070725A - Adhesive member, method for producing the same and adhesion structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive technique by which high adhesive strength against hot water and steam can be obtained, excellent in durability against strong alkalis and strong acids, and which uses a plastic substrate firmly adhered to an adherend in advance, in bonding the plastic substrate to which good adhesiveness can not be obtained even with an epoxy-based adhesive to the adherend. <P>SOLUTION: An adhesive member 1 includes a plastic substrate 2 and an uncured epoxy-based adhesive layer 3. The plastic substrate 2 has chemical bonds between nitrogen functional groups introduced by surface treatment on the interface contacting the epoxy-based adhesive layer 3 and epoxy groups of the epoxy-based adhesive. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a plastic substrate for bonding various plastic substrates such as a polymer electrolyte membrane that can be bonded to an epoxy adhesive to a plastic substrate that is difficult to obtain good adhesion even with an epoxy adhesive. The present invention relates to an adhesive member firmly bonded in advance, a manufacturing method thereof, and an adhesive structure in which an epoxy adhesive is cured by adhering the adhesive member to an adherend.

Epoxy adhesives have high adhesive strength, water resistance and heat resistance, and have a wide range of applicable targets, and are therefore used for fixing and laminating various members and substrates. However, adhesiveness may not be sufficient for plastic substrates, particularly plastic substrates that do not have polar groups.
For example, when a polymer electrolyte membrane made of a fluorine-based resin or an aromatic resin of a fuel cell is bonded to a plastic substrate having no polar group, the resin forming the polymer electrolyte membrane is generally a sulfonic acid group. In the side chain, it is excellent in adhesiveness with an epoxy adhesive, but a plastic substrate having no polar group may not have high adhesive strength even when an epoxy adhesive is used.
In addition, the plastic substrate bonded to such a polymer electrolyte membrane is exposed to a strongly acidic aqueous solution due to the sulfonic acid group of the polymer electrolyte membrane at the bonding interface of the plastic substrate. Furthermore, it may be exposed to the aqueous solution which became high temperature with power generation.
For this reason, there is a need for a technology for bonding a plastic base material that is not easily lowered in adhesive strength even when exposed to a strong acidic or high-temperature aqueous solution and has excellent durability.

  In general, not only epoxy adhesives but also adhesive methods that can provide high adhesive strength include chemical surface treatment using primer and anchoring agents and other surface treatments, surface cleaning of substrates to be bonded, and formation of fine irregularities. And physical surface treatment such as irradiation of ultraviolet rays or plasma for introducing functional groups. As a physical surface treatment, for example, corona discharge treatment in the air has been used for a long time to improve the wettability of various resin films including polyolefin and improve the adhesion. Corona discharge treatment uses a high-frequency voltage to generate corona discharge in the atmosphere, irradiates the surface of the resin film with electrons generated along with it, and adds functional groups due to oxygen atoms to the surface of the resin film. The surface of the film is modified.

In addition, in order to clean the surface of the base material to be bonded and to form fine irregularities, the surface is treated by bringing oxygen atom plasma into contact with the substrate to improve the adhesion. For example, Patent Document 1 discloses a method in which when a plastic molded body made of polyethylene is bonded via an epoxy adhesive, the plastic molded body contains polyphenylene sulfide (PPS) and is plasma-treated in a low-pressure air atmosphere. Proposed. According to this method, a part of the carbon-sulfur bond of PPS is broken, oxygen atoms are bonded to the sulfur, and the oxygen atoms are bonded to molecules of the epoxy adhesive to increase the adhesive strength.
However, as is apparent from the example of Patent Document 1, this method requires a high PPS content in order to obtain high adhesive strength. Therefore, the original properties of the resin forming the adherend may be impaired. Moreover, even if the initial adhesive strength is high, this method has a poor durability in hot water or a strongly acidic environment because the introduced functional group has a sulfur-oxygen bond. Moreover, since the low pressure plasma treatment is discharged in a vacuum state, a vacuum facility is required, so that the apparatus is large and the operation is complicated.

As for the problems that require a large amount of equipment, a glow discharge state that can only be generated in a vacuum state is normally used, and a rare gas such as helium or argon or an inert gas such as nitrogen is used as the atmosphere gas to stably perform a glow discharge. An apparatus for generating and performing plasma processing (atmospheric pressure plasma processing) near atmospheric pressure has been developed. Atmospheric pressure plasma treatment, in which surface modification is performed using reaction radicals, electrons, and the like generated thereby, has come to be easily used for cleaning the surface of wafers and the like and improving the adhesion of electronic components. For example, in Patent Document 2, a monomer is applied to a surface on which a metal material is deposited, and a mixed gas of an inert gas such as a rare gas or nitrogen gas and an oxygen-containing gas, or a processing gas such as nitrogen gas or hydrogen gas is used. Has been proposed to form a thick hydrophilic radical polymerized film on the surface of the metal material to be adhered with an epoxy adhesive.
However, although a thick hydrophilic film is expected to have a high anchoring effect, there is a concern that it is inferior in durability in a hot water, strongly acidic or strongly alkaline environment.

In Patent Document 3, both surfaces of stretched polyethylene terephthalate (PET) are treated with an atmospheric pressure plasma in an inert gas such as a rare gas or nitrogen gas or an oxygen gas, and an epoxy adhesive or a urethane adhesive is used. It has been proposed to laminate a thermoplastic resin such as vinyl chloride by extrusion.
However, this method also has a high initial adhesive strength, but since the introduced functional group is based on oxygen atoms, there is a concern that the durability is inferior in a hot water, strongly acidic or strongly alkaline environment.

Furthermore, in Patent Document 4, a nitrogen functional group is generated on the treated surface of the first resin film that has been surface-treated with nitrogen atoms by discharge in a nitrogen atmosphere that does not substantially contain oxygen, and oxygen gas and / Alternatively, the treated surface of the second resin film in which oxygen functional groups are generated on the treated surface by performing surface treatment with oxygen atoms and / or nitrogen atoms by discharge in an atmosphere containing nitrogen gas is passed through the adhesive layer. There has been proposed a laminated film having a laminated structure that is crimped without any problems.
Japanese Patent Laid-Open No. 07-216105 Japanese Patent Laid-Open No. 08-259902 JP 2007-268798 A JP 2007-307771 A

  In any of the methods described in Patent Documents 1 to 3, oxygen functional groups are introduced into the adhesion surface of the adherend, so that high initial adhesive strength is obtained, but high adhesive strength against hot water and water vapor is obtained. It is not something that can be done. On the other hand, the method described in Patent Document 4 can obtain a high initial adhesive force and a high adhesive strength against hot water or water vapor, but the adhesive strength under strongly alkaline or strongly acidic conditions. In order to prevent the decrease, there was still a problem.

  The present invention has been made in view of the above circumstances, and when a plastic substrate that is difficult to obtain good adhesion even with an epoxy adhesive is adhered to an adherend, the plastic substrate is firmly adhered in advance. In addition, an adhesive member having high adhesive strength to hot water and water vapor and having excellent durability against strong alkali and strong acid, its manufacturing method, and an epoxy adhesive by adhering it to an adherend It is an object of the present invention to provide an adhesive structure obtained by curing the material.

In order to solve the above-mentioned problems, the inventors of the present invention have intensively studied. As a result, by introducing a nitrogen functional group to the surface to which the plastic base material is bonded, the nitrogen functional group is similar to the curing agent of the epoxy adhesive. The present invention was made based on the knowledge that a strong bond can be obtained by chemically bonding with the epoxy group of the epoxy adhesive.
That is, the present invention is an adhesive member having a plastic substrate and an uncured epoxy adhesive layer, and is introduced by surface treatment at an interface in contact with the epoxy adhesive layer in the plastic substrate. There is provided an adhesive member having a chemical bond between a nitrogen functional group and an epoxy group of the epoxy adhesive.
The nitrogen functional group is preferably at least one nitrogen functional group selected from a primary amine, a secondary amine, and an amide.
The epoxy adhesive constituting the epoxy adhesive layer is preferably a one-pack type containing a curing agent.
It is preferable that the plastic substrate is a film or a sheet.
It is preferable that release paper is laminated on the epoxy adhesive layer.
The adherend to be bonded to the epoxy adhesive is preferably a polymer electrolyte membrane made of a polymer electrolyte having a sulfonic acid group.

The present invention is also a method for producing the adhesive member of the present invention, wherein a nitrogen functional group introducing step of introducing a nitrogen functional group to the surface of the plastic substrate by surface treatment of the plastic substrate, and the nitrogen functional group And an epoxy-based adhesive layer forming step of forming an epoxy-based adhesive layer on the surface of the plastic substrate into which is introduced.
The nitrogen functional group introduction step is preferably a surface treatment step by discharge treatment under a nitrogen atmosphere in which the oxygen concentration is 1000 ppm or less by volume ratio.
The nitrogen functional group introduction step is preferably performed under atmospheric pressure.
The nitrogen functional group introduction step is preferably a corona discharge treatment.
It is preferable that the plastic substrate is a film or a sheet, and the nitrogen functional group introduction step is continuously performed by roll-to-roll.

The present invention also provides an adhesive structure in which the above-mentioned adhesive member of the present invention is bonded to an adherend to cure the epoxy adhesive.
It is preferable that the glass transition temperature of the epoxy adhesive and the plastic constituting the plastic substrate is 80 ° C. or higher.
The adherend is preferably a plastic material having an acid functional group at the bonding interface.
The adherend is preferably a plastic material having a nitrogen functional group by surface treatment at the bonding interface.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is an epoxy-type adhesive agent, the plastic base material and adherend which cannot obtain high adhesive strength can be adhere | attached with high adhesive strength. Moreover, high adhesion strength to hot water and water vapor is obtained, and even when the adhesion interface is exposed to a strong alkali, strong acidity or high temperature environment, a durable plastic base material adhesion structure is obtained. be able to.

The present invention will be described below based on the best mode.
The adhesive member having the plastic base material and the epoxy adhesive layer of the present invention has a nitrogen functional group introduced into at least one surface of the plastic base material by surface treatment, and is in contact with the surface into which the nitrogen functional group has been introduced. It can be manufactured by forming an epoxy adhesive layer.

Resin which comprises the plastic base material used by this invention is not specifically limited, According to the use of an adhesive member, it can select suitably. For example, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyamides (PA) such as 6-nylon and 66-nylon, polyolefins such as polyethylene (PE) and polypropylene (PP), and ethylene-vinyl alcohol Polymers, thermoplastic resins such as polyvinylidene chloride, polystyrene, polyvinyl chloride; polyphenylene sulfide (PPS), polyether ether ketone (PPEK), polyether sulfone (PES), polyphenylene ether (PPE) and polystyrene (PS) Resins called super engineering plastics such as alloys (hereinafter sometimes referred to as PPE-PS alloys); curable resins made of polyimide, epoxy resin, and the like. Among these, a plastic substrate having no polar group such as polyolefin is a suitable target because the effect of the present invention is remarkable.
The form of the plastic substrate used in the present invention is not particularly limited, and examples thereof include films and sheets (hereinafter collectively referred to as films).
In order to improve heat resistance, the glass transition temperature of the plastic constituting the plastic substrate is preferably 80 ° C. or higher.

The surface treatment of the plastic substrate used in the surface treatment step of introducing a nitrogen functional group into the surface of the plastic substrate by the surface treatment of the plastic substrate of the present invention is performed by using a primary amine (—NH ₂ ) as a nitrogen functional group, A technique capable of introducing at least one nitrogen functional group selected from a secondary amine (—NH—) and an amide (—CONH—) onto the surface of the plastic substrate is preferable.
And the surface which adhere | attaches an epoxy-type adhesive bond layer to a plastic base material should be surface-treated, and the said nitrogen functional group should just be introduce | transduced. That is, for example, when the epoxy adhesive layer is laminated on both surfaces of a film-like plastic substrate, the nitrogen functional group is introduced by performing surface treatment on both surfaces. The introduced nitrogen functional group reacts with the epoxy group of the epoxy adhesive to form a chemical bond, thereby obtaining a strong adhesive force.

(Nitrogen functional group introduction process)
As a surface treatment method for introducing a nitrogen functional group, it can be performed by a discharge treatment in a nitrogen atmosphere containing nitrogen gas and substantially free of oxygen gas. Such a surface treatment method is preferable because nitrogen functional groups can be introduced on the surfaces of the various plastics described above.
When the oxygen concentration is high, the amount of nitrogen functional groups introduced into the plastic surface is reduced, and when the oxygen concentration is low, the amount of nitrogen functional groups is increased and adhesion is enhanced. The oxygen concentration in the nitrogen atmosphere is preferably 1000 ppm or less by volume ratio. Whether or not the nitrogen functional group is introduced on the surface of the plastic can be confirmed by the chemical bond energy in 1 s of N (nitrogen atom) in XPS (X-ray photoelectron spectroscopy) as described later.

The discharge treatment under the nitrogen atmosphere may be a plasma treatment or a corona discharge treatment. The plasma treatment may be a low-pressure (vacuum) plasma treatment or an atmospheric pressure plasma treatment. Among these discharge treatments, in this nitrogen functional group introduction step, the apparatus is simple, and when the plastic substrate is a film, the nitrogen functional group introduction step is continuously performed by roll-to-roll. Therefore, corona discharge treatment is preferable. In addition, when performing a surface treatment under a nitrogen atmosphere suitable for the present invention described later in a roll-to-roll manner, the corona discharge treatment device is covered with a housing provided with a narrow inlet and outlet through which the film can pass, A positive pressure can be maintained with a treatment gas such as nitrogen gas, and the discharge treatment can be performed continuously.
And in the epoxy-based adhesive layer forming step described later, when applying continuously with a roll-to-roll using a known film coating device, it is upstream from the adhesive coating portion of this film coating device. If a corona discharge treatment apparatus covered with a housing is installed, the surface treatment step and the epoxy-based adhesive layer forming step can be successively performed.

By the way, in the corona discharge surface treatment performed in a normal air atmosphere, active oxygen atoms (oxygen radicals) are generated. Although the content of oxygen gas in air is much smaller than that of nitrogen gas, the surface of the plastic substrate treated with corona discharge is surface-treated with this active oxygen atom. That is, the surface of the plastic substrate is oxidized, and oxygen functional groups such as a carbonyl group (> CO) and a carboxyl group (—COOH) are mainly formed on the main chain and side chain of the polymer on the surface of the plastic substrate. The
And although these functional groups contribute to the adhesive performance with an epoxy-type adhesive agent, high adhesive strength is not obtained with respect to hot water or water vapor | steam. In addition, it is impossible to prevent a decrease in adhesive strength under strongly acidic conditions. The reason for this is not clear, but since this active oxygen atom has a strong action of cutting a polymer to lower the molecular weight when generating a functional group, a low molecular compound containing an oxygen atom is formed on the surface of a plastic substrate. Produced in a very thin layer. This low molecular weight compound layer has a relatively small molecular weight, and thus is likely to be hydrophilic and has a low physical strength such as cohesive force.

On the other hand, the corona discharge treatment in a nitrogen atmosphere substantially free of oxygen gas, which is preferably used in the surface treatment process of the present invention, is caused by nitrogen atoms in the polymer main chain or side chain on the substrate surface. Nitrogen functional groups such as amino groups (—NH ₂ ) are mainly produced. And this corona discharge treatment in the nitrogen atmosphere is different from the corona discharge treatment in the normal air atmosphere, so that the discharge occurs in the nitrogen atmosphere substantially not containing oxygen gas, so the generation amount of active oxygen atoms is small, In addition, since the active nitrogen atom generates a functional group, the action of cutting the polymer to lower the molecular weight is weak, so the occurrence of low molecular weight compounds that occur when corona discharge treatment is performed in an air atmosphere can be suppressed. it is conceivable that.
In other words, the low molecular weight compound produced during corona discharge treatment in a nitrogen atmosphere with a low oxygen concentration has a higher molecular weight than the low molecular weight compound produced during corona discharge treatment in an air atmosphere. The mechanical strength is also increased. From this, it is considered that the effect of improving the adhesiveness with the epoxy adhesive layer can be obtained by applying the surface treatment process of the present invention to the plastic substrate.

In the present invention, from the viewpoint of water resistance and acid resistance, it is desirable to introduce more amino groups than amide groups. Therefore, it is preferable that the nitrogen atmosphere of the corona discharge treatment contains as little oxygen gas as possible. Although depending on the plastic substrate to be subjected to corona discharge treatment and processing conditions, the oxygen concentration is controlled to 1000 ppm or less, more preferably 50 ppm or less, and still more preferably 20 ppm or less in terms of volume ratio. At the same time, it is preferable not to mix a material that supplies oxygen atoms (for example, CO ₂ or NO ₂ ) other than the plastic substrate into the nitrogen atmosphere. In order to introduce amino groups more actively, a material that absorbs oxygen atoms (for example, H ₂ , NH ₃ , CH _4, etc.) may be added to the nitrogen atmosphere.

In the present invention, CO ₂ can be intentionally mixed in the nitrogen atmosphere of the corona discharge treatment to form an amide group (—NHCO—) instead of an amino group. In the nitrogen atmosphere, CO ₂ becomes a radical, and a CO radical and an oxygen radical are generated, so that an amide group is preferentially generated over an amino group.
In the surface treatment process of the present invention, atmospheric pressure plasma treatment in a nitrogen atmosphere can also be used. In this case, a rare gas may be mixed for stable glow discharge. And the ratio of a noble gas can also exceed half.

(Epoxy adhesive layer forming process)
An epoxy adhesive is applied to the surface of the plastic substrate into which the nitrogen functional group has been introduced to form an epoxy adhesive layer. For application, dipping, spray coating, spin coating, brush coating, or the like can be employed. When the plastic substrate is a film, a known film coating method such as gravure coating or doctor coating can be adopted, and it is continuously applied with a roll-to-roll using a known film coating apparatus. be able to.
As an epoxy adhesive to be applied, it contains a main agent and a curing agent, and is not cured when applied, or has a viscosity that can be applied to an adherend even if partially cured, etc. Is mentioned. The epoxy adhesive can be used in a one-pack type in which a curing agent is blended in advance or a two-pack type in which a curing agent is blended in use. Of these, the one-pack type is preferred because it eliminates the trouble of blending the curing agent. In particular, when the plastic substrate is a film, the curing agent is preferably a one-component type.

The applied epoxy adhesive is preferably laminated with release paper in order to protect the surface from contact with other articles and adhesion of dust and the like. The release paper may be peel-treated with a release agent such as silicone, but the release agent may move to the epoxy adhesive layer and affect the adhesive force. It is preferable to use a film made of a resin. Since these films do not have good adhesion to an epoxy adhesive, they can function as release paper.
When using release paper, an epoxy adhesive may be applied to the release paper to match the plastic substrate.

As the main agent, a compound containing an epoxy group is used. For example, glycidyl ether type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolak type epoxy resin, brominated epoxy resin; epoxidized double bond of alicyclic olefin Cycloaliphatic epoxy resins; polyglycidyl compounds obtained by reaction of polyols, hydroxyl group-containing silicone resins and epihalohydrins; glycidylamines such as N, N-diglycidylaniline, tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol Resin: glycidyl such as phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, diglycidyl-p-oxybenzoic acid And ester resins.
The epoxy adhesive may contain two or more kinds of main agents. As the main agent, glycidyl ether epoxy resin and glycidyl amine resin are preferable, and bisphenol A type epoxy resin is particularly preferable.

Examples of the curing agent blended in the epoxy adhesive include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine, diethylaminopropylamine, piperidine, N-aminoethylpiperazine, mensendiamine, and m-xylenediamine. Aliphatic polyamines such as; dimethylaminoalkylphenols such as 2- (dimethylaminomethyl) phenol, bis (dimethylaminoethyl) phenol, 2,4,6-tris (dimethylaminomethyl) phenol; methanephenylenediamine, diaminodiphenylmethane, Aromatic amines such as diaminodiphenylsulfone; trimetic anhydride, ethylene glycol bis (anhydro trimellitate), glycerol tris (anhydro trimellitate) Acid anhydrides such as pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, etc .; polyaminopolyamides that react diamine with polyamines; 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, etc. Examples thereof include imidazoles; boron trifluoride-amine complexes; dicyandiamide; aromatic diazonium salts; polysulfides. It is also possible to use a thermosetting one-component epoxy adhesive using an aromatic amine or the like as the curing agent. A thermosetting one-component epoxy adhesive is preferable because the curing device is simple and the effect operation is easy.
The epoxy adhesive may contain two or more kinds of curing agents. As the curing agent, polyamine-based curing agents, dimethylaminoalkylphenols, polyaminopolyamides and the like are particularly preferable.

Epoxy adhesives include other resins, inorganic fillers such as calcium carbonate, organic fillers, anti-sagging agents, dyes, pigments, thickeners, antifoaming agents, dispersants, as long as adhesion is not impaired. You may contain compounding agents, such as surface modifiers, such as a flame retardant, a brightener, a thixotropy imparting agent, adhesion imparting agent, and surfactant, a ultraviolet absorber, antioxidant, and an antistatic agent.
Here, other resins that may be contained include polymerizable double bond-containing monomers such as unsaturated polyesters and prepolymers thereof; polybutadiene, maleated butadiene, epoxidized butadiene, maleated butadiene, and butadiene-acrylonitrile. Copolymer and its carboxyl group-containing resin, polychloroprene, maleated butadiene, butadiene-acrylonitrile copolymer and its carboxyl group-containing resin, polychloroprene, butadiene-styrene copolymer, polyisoprene, butyl rubber, fluororubber, natural rubber Low molecular weight liquid or high molecular weight elastomers such as polyethylene, polypropylene, polybutene, poly-4-methylpentene, polystyrene, AS resin, MBS resin, ABS resin, polyethylene-propylene Polymers, tetrafluoroethylene-hexafluoropropylene copolymers, etc .; high molecular weight polymers such as polycarbonate, polyphenylene ether, polysulfone, polyester, polyimide, polyphenylene sulfide and their low molecular weight prepolymers or oligomers; polyurethanes, multifunctional maleimides, etc. Is exemplified.

(Adhesion with adherend)
The adhesive member of the present invention can be used as it is when the epoxy adhesive is a one-pack type, or in the case of a two-pack type, with a curing agent, and the epoxy adhesive layer can be used for bonding to an adherend. . The adhesion method to the adherend is the same as the adhesion using a normal pressure-sensitive adhesive. However, when both the plastic substrate to be adhered and the adherend are films, the epoxy adhesive layer of the adhesive member and A thermal laminate in which adherends are superposed and thermocompression bonded is preferable.
The thermal lamination is performed by heating and thermocompression bonding with the adhesive member and the adherend overlapped. The conditions for thermocompression bonding may be appropriately selected as long as the target adhesive strength can be obtained. The adhesive strength is improved by increasing the thermocompression bonding temperature, time, and pressure.
When the adherend is a plastic material, the glass transition temperature Tg of the plastic material is preferably 80 ° C. or higher from the viewpoint of heat resistance.
And the epoxy-type adhesive agent adhere | attached on the to-be-adhered body can be hardened, and the adhesive structure of this invention can be formed. When the epoxy adhesive is a thermosetting type, the curing treatment may be performed simultaneously with the thermocompression bonding.
The glass transition temperature Tg of the cured epoxy adhesive is preferably 80 ° C. or higher. This is because the battery itself may generate heat during power generation, and the atmosphere in the place where the battery is installed may exceed 60 ° C. In this case, battery performance may be deteriorated due to a decrease in sealing performance. Therefore, the glass transition temperature is preferably 80 ° C. or higher in view of heat resistance of the epoxy adhesive.

The adherend to which the adhesive member of the present invention is preferably applied is not particularly limited. However, when the adherend is a plastic material, the plastic material containing an acid functional group may be used as an epoxy adhesive. It is preferable because of its excellent adhesiveness.
Plastic materials containing acid functional groups include plastic materials made of carboxylic acid-modified resins such as sulfonic acid groups and carboxyl groups, carboxylic acid-modified polyolefin resins, and discharge treatment in an atmosphere containing oxygen gas. A plastic material into which an acid functional group has been introduced can be mentioned.
Specific examples of the plastic material containing a resin having a sulfonic acid group include a polymer electrolyte membrane made of a polymer electrolyte having a sulfonic acid group.
The polymer electrolyte membrane used for the solid polymer electrolyte membrane of a fuel cell can be preferably applied to the present invention. For example, a perfluoroalkylenesulfonic acid polymer compound (for example, Nafion (trade name) manufactured by DuPont) or sulfone can be used. Solid polymer electrolytes such as modified polyarylene compounds.

Carboxylic acid-modified polyolefin resin is a resin in which a polyolefin is modified by introducing a carboxyl group and / or a derivative thereof (ester, acid anhydride, salt, etc.) by graft polymerization or the like, a copolymer of an olefin and a monomer having a carboxyl group And their derivatives. Since the carboxylic acid-modified polyolefin resin is not hydrolyzable, it is not decomposed by moisture and is chemically stable, so that it is preferable as an application target of the present invention.
Specific examples of resins suitable as the carboxylic acid-modified polyolefin resin include ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), and ethylene-ethyl acrylate copolymer (EEA). Examples thereof include ethylene unsaturated carboxylic acid copolymers; polyethylene and polypropylene (adhesive resin) modified by graft polymerization of maleic anhydride; ionomers obtained by neutralizing EMAA and EAA with metal ions such as sodium and zinc.

In the present invention, when the plastic adherend is inferior in adhesion to the epoxy adhesive, the adhesion is improved by using a plastic material having an oxygen functional group introduced by surface treatment at the interface in contact with the adhesive layer. can do.
Furthermore, in the present invention, when the adhesion structure with the plastic adherend is inferior in durability due to a decrease in adhesion strength at the adhesion interface in a hot water or strongly acidic environment, the surface treatment is performed on the interface in contact with the adhesive layer. Adhesiveness can be improved by using a plastic material in which a nitrogen functional group is introduced. That is, in this case, a laminated structure in which an epoxy adhesive layer is interposed between two plastic base materials having nitrogen functional groups introduced by surface treatment at the interface is obtained.
The surface treatment method when the adherend is a plastic material is the same as the surface treatment method of the plastic substrate of the adhesive member described above.
The plastic material of the adherend may be the same as or different from the plastic base material of the adhesive member in terms of material, thickness, shape, and the like.

  The adhesive structure of the present invention is not limited to a structure in which the adhesive member of the present invention is bonded to one side of an adherend (for example, a three-layer structure of a plastic substrate / epoxy adhesive layer / adherend). The adhesive member of the present invention is bonded to both surfaces of an adherend (for example, a plastic base / epoxy adhesive layer / adherent / epoxy adhesive layer / plastic base five-layer structure), plastic base A material in which an adherend is adhered to both surfaces of an adhesive member of the present invention in which an epoxy adhesive layer is provided on both surfaces of the material (for example, adherend / epoxy adhesive layer / plastic substrate / epoxy adhesive layer / There are no particular limitations, and examples include a five-layer structure of the adherend and a structure having a larger number of layers.

The adhesive structure of the present invention using the adhesive member of the present invention can be used as various members. According to the adhesive member of the present invention, since the plastic substrate has a nitrogen functional group by surface treatment at the interface contacting the epoxy adhesive layer, the nitrogen functional group reacts with the epoxy group of the epoxy adhesive layer and is strong. Adhesive strength is obtained.
By using surface treatment by discharge treatment in a nitrogen atmosphere that does not substantially contain oxygen, it becomes possible to introduce nitrogen functional groups only at the interface where the plastic substrate contacts the adhesive layer, and does not contact the adhesive layer. The structure has no nitrogen functional group inside. For this reason, even if the adhesive member of the present invention or an adhesive structure formed by adhering the adhesive member to an adherend is in contact with a strongly acidic substance, the nitrogen functional group of the plastic substrate does not react with the strongly acidic substance as a base. Therefore, when used as a member in contact with a strongly acidic medium such as a fuel cell in which a strongly acidic substance is generated, there is no possibility of altering the contents or medium.

Therefore, the adhesive member of the present invention can be suitably used for a polymer electrolyte fuel cell electrolyte membrane.
As shown in FIG. 1, the adhesive member 1 is obtained by introducing a nitrogen functional group onto the surface 4 of a frame-shaped plastic substrate 2 having an opening 5 and forming an epoxy adhesive layer 3 thereon. . The bonding body having the bonding structure of the present invention shown in FIG. 2 is obtained by bonding the adhesive member 1 of FIG. 1 to the peripheral edge of the adherend 6 from both the front and back surfaces and curing the epoxy adhesive. In FIG. 2, by using the polymer electrolyte membrane as the adherend 6, the present invention can be applied to the polymer electrolyte fuel cell electrolyte membrane.

  Examples of the polymer electrolyte membrane to be the adherend 6 include a polymer electrolyte membrane made of a polymer electrolyte containing a sulfonic acid group. Examples of the polymer electrolyte include polymer electrolytes such as perfluoroalkylenesulfonic acid polymer compounds (for example, Nafion (trade name) manufactured by DuPont) and sulfonated polyarylene compounds. The surface of the polymer electrolyte membrane 6 is preferably formed with irregularities (referred to as “wrinkles”) having a maximum surface roughness height Rmax in the range of 3 to 20 μm. The irregularities can be formed by pressing a mold having a maximum surface roughness Rmax in the range of 5 to 50 μm under heating and transferring the surface shape of the mold.

  When a fuel cell is produced using the polymer electrolyte fuel cell electrolyte membrane of this embodiment, catalyst layers are laminated on both the front and back surfaces of the polymer electrolyte membrane, and a porous diffusion layer is laminated on both catalyst layers. It is preferable to constitute the formed membrane-electrode structure. Such a membrane-electrode structure has a configuration in which the electrodes formed by the catalyst layer and the porous diffusion layer are disposed on both sides of the polymer electrolyte membrane.

  The catalyst layer is stacked so as to be positioned on the inner peripheral side of the outer peripheral edge of the polymer electrolyte membrane, and a porous diffusion layer is stacked on the catalyst layer. The porous diffusion layer can be composed of, for example, carbon paper (made of carbon fiber) and a base layer (not shown) formed on the carbon paper. The underlayer is made of, for example, a 4: 6 (weight ratio) mixture of carbon black and polytetrafluoroethylene (PTFE) particles. Examples of a method for forming the underlayer include a method in which a slurry in which a mixture of carbon black and PTFE particles is uniformly dispersed in ethylene glycol is applied to one side of carbon paper and dried.

  The catalyst layer is composed of, for example, catalyst particles and an ion conductive binder. Examples of the method for forming the catalyst layer include a method of forming the catalyst layer by applying and drying a catalyst paste prepared by uniformly dispersing catalyst particles in an ion conductive binder made of a polymer electrolyte solution. As the catalyst particles, for example, carbon black (furnace black) on which platinum particles are supported so that platinum: carbon particles = 1: 1 (weight ratio) can be used. In addition, as the ion conductive binder, a polymer electrolyte similar to the polymer electrolyte membrane can be used.

  Examples of the method of forming the electrode by the catalyst layer and the porous diffusion layer include a method of forming a base layer on one side of carbon paper and further forming a catalyst layer on the base layer. The membrane-electrode structure can be manufactured by sandwiching and laminating the polymer electrolyte membrane with two electrodes with the catalyst layer facing the polymer electrolyte membrane side. As shown in FIG. 1, if the adhesive member 1 has a frame shape having an opening 5 inside, the catalyst layer can be brought into contact with the surface of the polymer electrolyte membrane 6 through the opening 5. The porous diffusion layer may be laminated so that the outer peripheral edge thereof overlaps with the adhesive member 1.

  In the membrane-electrode structure, one electrode is used as a fuel electrode (anode), and a reducing gas such as hydrogen or methanol is introduced into a catalyst layer through a porous diffusion layer on the anode side, while the other electrode is used as an oxygen electrode. As the (cathode), an oxidizing gas such as air or oxygen is introduced into the catalyst layer through the porous diffusion layer on the cathode side. In this way, on the fuel electrode (anode) side, protons and electrons are generated from the reducing gas by the action of the catalyst contained in the catalyst layer, and the protons pass through the solid polymer electrolyte membrane and the oxygen electrode. It moves to the catalyst layer on the (cathode) side. The protons react with the oxidizing gas and electrons introduced into the catalyst layer by the action of the catalyst contained in the catalyst layer to generate water. Therefore, by connecting the fuel electrode and the oxygen electrode via a conducting wire, a circuit for sending electrons generated at the fuel electrode to the oxygen electrode is formed, and a current can be taken out. In this way, a fuel cell can be constructed using the membrane-electrode structure.

Hereinafter, the present invention will be specifically described with reference to examples.
(Reference Example 1: Measurement of nitrogen abundance by XPS)
The surface of the PPS film (thickness 12 μm) is subjected to corona discharge treatment in a nitrogen atmosphere using a batch corona discharge treatment device manufactured in-house as a surface treatment step, and the surface is subjected to XPS (X-ray photoelectron spectroscopy). Nitrogen (N), carbon (C) and sulfur (S) element abundances (atomic%) were measured. The oxygen concentration (volume ratio) of the corona treatment in a nitrogen atmosphere was set to three types of 0.2%, 0.09%, and 0.075% (2000 ppm, 900 ppm, 750 ppm). The results are shown in Table 1.

In Table 1, “N (%)” is the N abundance on the surface, “N / C” is the ratio of the N abundance / C abundance on the surface, and “N / S” is the N abundance on the surface. / S abundance ratio.
For comparison, the amount of nitrogen (N) on the surface of the PPS that was corona-treated in the atmosphere and the untreated PPS was also measured by XPS, but the amount of N was 0.
From Table 1, the nitrogen functional group is not introduced by the surface treatment under an air atmosphere, but is introduced by the surface treatment under a nitrogen atmosphere with a low oxygen concentration, and with a decrease in the oxygen concentration in the nitrogen atmosphere. It can be seen that the amount of nitrogen functional group introduced increases.

3 and 4 show XPS analysis charts when corona treatment is performed in a nitrogen atmosphere with an oxygen concentration of 900 ppm.
FIG. 3 is a chart including peaks corresponding to F (1s), O (1s), N (1s), C (1s), and S (2p).
FIG. 4 shows an analysis of the ratio of the peak of amine (NH ₂ ) and the peak of amide (NHCO) by enlarging the N (1s) peak. Of the N abundance, NHCO nitrogen was about 65% and NH ₂ nitrogen was about 35%.

(Reference Example 2: Observation of epoxy resin by XPS)
In order to use elemental bromine as an index, only the main component of brominated epoxy adhesive in which bromine atoms are introduced into bisphenol A is corona-treated in a nitrogen atmosphere with an oxygen concentration of 900 ppm and applied to a PPS film into which nitrogen functional groups have been introduced. And heat treatment at 150 ° C. for 20 minutes. Then, the heat-treated PPS film was immersed in MEK (methyl ethyl ketone) capable of dissolving the main component of the brominated epoxy adhesive, and ultrasonically cleaned for 2 hours. Then, it was immersed in MEK for 2 days as it was, and ultrasonically washed again for 2 hours immediately before taking out. The sample taken out by completely removing the unreacted brominated epoxy adhesive from the surface of the PPS film was dried, and the surface of the PPS film in contact with the brominated epoxy adhesive was subjected to surface analysis by XPS. The results are shown in FIG.

From FIG. 5, the expression of the chemical bond by the bromine atom which existed in brominated epoxy adhesive was confirmed.
This shows that the brominated epoxy resin is present on the surface of the PPS film. That is, it is presumed that the nitrogen functional group introduced on the surface of the PPS film and the epoxy group of the brominated epoxy adhesive were chemically bonded and bonded to the surface of the PPS film. Therefore, the nitrogen functional group introduced into the PPS functions in the same manner as the curing agent of the brominated epoxy adhesive, and a part of the epoxy group reacts with this to become insoluble in MEK and is fixed to the PPS film. It is guessed.

6 shows the N abundance after the treatment with the brominated epoxy adhesive, and FIG. 4 shows the N abundance before the treatment, and the reduction in the ratio of the bonding amount of nitrogen atoms introduced to the PPS film surface. From FIG. 5 and FIG. 5, it was confirmed that the bond amount ratio of sulfur atoms was decreased.
This means that the majority of nitrogen and sulfur atoms are no longer exposed on the surface of the PPS film. Therefore, it is estimated that the brominated epoxy resin fixed to the PPS film that does not dissolve in a very small amount of MEK covers the surface of the PPS film like a film.
In the adhesive member of the present invention, the epoxy group of the epoxy adhesive and the nitrogen functional group are bonded so as to cover the surface of the plastic substrate, and the epoxy resin is cured by bonding to the adherend. At that time, it is presumed that the unreacted epoxy group remaining in the immobilized epoxy resin reacts with the curing agent to form an adhesive interface highly resistant to hot water, acid and alkali.

Example 1
Nitrogen atmosphere in which two 12 μm-thick PPS base materials were prepared, and each side was filled with nitrogen gas and maintained at an oxygen concentration of 900 ppm as a surface treatment process using a batch corona discharge treatment device manufactured in-house. Under the corona discharge treatment, nitrogen functional groups were introduced. In addition, when the amount of nitrogen on the surface of this substrate was measured by XPS, it was found that 6.5% was introduced.
An epoxy adhesive (manufactured by Nagase ChemteX Corp., T812 / R001) containing a bisphenol A type epoxy resin containing 15% by weight of a polyamine curing agent on the surface of each base material into which nitrogen functional groups have been introduced. After coating with a thickness of 20 μm and forming an adhesive layer between two surface-treated substrates, the epoxy adhesive was cured by heating at 150 ° C. for 10 minutes, and the substrate / adhesive layer / A bonded body having a three-layer adhesive structure of the substrate was produced.
The glass transition temperature after curing of the epoxy adhesive was 105 ° C.

A part of the bonded body of this example was cut to a width of 15 mm, and the initial adhesive strength was measured by 180 ° peeling (according to JIS Z 0238, the same shall apply hereinafter), and it was 9.0 N / 15 mm.
Moreover, when another part of the bonded body of this example was cut to a width of 15 mm, immersed in 100 ° C. hot water in a pressure cooker, and heated for 1000 hours, the adhesive strength was measured by 180 ° peeling,
It was 9.0 N / 15 mm.
Similarly, another part of the bonded body of this example was cut to a width of 15 mm, immersed in a sulfuric acid aqueous solution of pH 1.0 (95 ° C.) for 1000 hours, and then measured for adhesive strength by 180 ° peeling. 0.0 N / 15 mm.
In the three peel tests of Example 1, the peel between the PPS base material and the epoxy adhesive layer is a cohesive failure of the base material peculiar to PPS in which the surface on the base material side peels thinly. The adhesive strength at the interface between the material and the epoxy adhesive layer is considered to be higher than 9.0 N / 15 mm.
Further, another part of the bonded body of this example was cut to a width of 15 mm and immersed in a 1N sodium hydroxide solution (25 ° C.) to completely remove the unreacted brominated epoxy adhesive from the surface of the PPS film described above. Ultrasonic cleaning similar to the removal was performed for 10 minutes, but no peeling occurred and there was no change in appearance.
From this, it can be seen that in Example 1, a bonded body was obtained in which the adhesive strength hardly deteriorates even under hot water, strong acidity or strong alkali conditions.

(Comparative Example 1)
Surface treatment was performed in the same manner as in Example 1 except that the corona discharge treatment was performed in the air. When the surface of the substrate was analyzed by XPS, no chemical bonds due to nitrogen atoms were found, and no introduction of nitrogen functional groups was observed.
As in Example 1, a bonded body having a three-layer adhesive structure of base material / adhesive layer / base material was prepared, and the initial adhesive strength was measured. As a result, it was 9.0 N / 15 mm.
However, when the adhesive strength after immersion in hot water was measured in the same manner as in Example 1, the adhesive strength was reduced to 1.5 N / 15 mm.
Moreover, when it immersed in the sulfuric acid aqueous solution similarly to Example 1, it peeled during immersion.
In the peel test of Comparative Example 1, the peel between the base material and the adhesive layer was a cohesive failure of the base material at the time of measuring the initial adhesive strength, but the peel after immersion in hot water was bonded to the base material. It was adhesive peeling at the interface with the agent layer.
From this, it can be seen that the adhesive strength at the interface deteriorated under hot water or strongly acidic conditions.

(Comparative Example 2)
A bonded body having a three-layer adhesive structure of base material / adhesive layer / base material was produced in the same manner as in Example 1 except that the surface treatment was not performed.
As in Example 1, the initial adhesive strength was measured and found to be 3.0 N / 15 mm.
Moreover, when it immersed in hot water like Example 1, it peeled during immersion.
Moreover, when it immersed in the sulfuric acid aqueous solution similarly to Example 1, it peeled during immersion.
From this, it is understood that a sufficient adhesive strength cannot be obtained with an untreated substrate.

(Example 2)
About the combination of the following plastic base material and a to-be-adhered body, the adhesive body was created by interposing an epoxy-type adhesive agent, and 180 degree peeling adhesive strength in width 15mm was measured.
Five types of PPS (thickness: 12 μm), PEEK (thickness: 100 μm), maleic anhydride-modified PP (thickness: 100 μm), PEN (thickness: 100 μm), and PPE / PS (thickness: 100 μm) are prepared as plastic substrates. What was corona-treated in a nitrogen atmosphere having a concentration of 1000 ppm was used.
As an adherend, Nafion (thickness 50.8 μm), PPS (thickness 12 μm), PEEK (thickness 100 μm), maleic anhydride modified PP (manufactured by Mitsui Chemicals, Inc., Admer QE060) is formed into a single layer by a T-die cast film machine. 6 types of PEN (thickness 100 μm) and PPE-PS alloy (thickness 100 μm) were prepared. For Nafion and acid-modified PP, two types were used: an untreated product that was not surface-treated and a treated product that was corona-treated in a nitrogen atmosphere, and the other adherends were those that were corona-treated in a nitrogen atmosphere.

For the surface treatment of the substrate and the adherend, the corona discharge treatment apparatus of Example 1 was used, and the corona discharge treatment was performed in a nitrogen atmosphere filled with nitrogen gas and maintained at an oxygen concentration of 1000 ppm. Was introduced.
An epoxy adhesive (manufactured by Nagase Chemtex Co., Ltd., two-pack type epoxy adhesive; XNR3305 / XNH3305) is applied to the surface of the plastic substrate with the nitrogen functional group introduced thereto to a thickness of 20 μm, and the adherend is adhered. The sample of each bonding body was produced by heating at 120 degreeC for 1 hour, and hardening an adhesive agent. The 180 ° peel adhesion strength was measured by using a sample after being cured and stored at 40 ° C. for 3 days, then immersed in hot water at 100 ° C. in a pressure cooker and heated for 100 hours.
The glass transition temperature after curing of the epoxy adhesive was 105 ° C.

  As shown in Table 2 and Table 3, it can be seen that, for various combinations of substrates and adherends, bonded bodies having excellent adhesive strength after a pressure cooker test (100 ° C., 100 hours) were obtained. In Tables 2 and 3, maleic anhydride-modified PP is simply referred to as “acid-modified PP”.

  The present invention adheres to an adherend that is difficult to bond with an adhesive, for example, an electrolyte membrane of a polymer electrolyte fuel cell (PEFC) made of a fluorine resin or an aromatic resin, or a separation membrane used for electrolysis of water. It can be suitably used as an adhesive member.

It is drawing which shows an example of the adhesive member of this invention, (a) is a top view, (b) is sectional drawing which follows the AA line of (a). It is drawing which shows an example of the bonding body formed by adhere | attaching the adhesive member of this invention to a to-be-adhered body, (a) is a top view, (b) is sectional drawing which follows the BB line of (a). It is a chart which shows an example of the XPS analysis result of PPS which carried out the corona treatment in nitrogen atmosphere. FIG. 4 is a partially enlarged chart showing an N (1s) peak in the chart of FIG. 3. Sulfur comparing the XPS analysis results of a sample of PPS treated with corona under a nitrogen atmosphere and a sample where only the main component of brominated epoxy adhesive was applied to PPS into which nitrogen functional groups were introduced and heat-treated to clean the surface with MEK It is a partial expansion chart which shows the peak of (S) and bromine (Br). It is the elements on larger scale which show the N (1s) peak in the XPS analysis result of the sample which apply | coated only the main ingredient of the brominated epoxy adhesive to PPS which introduce | transduced the nitrogen functional group, heat-processed, and wash | cleaned the surface with MEK.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Adhesive member, 2 ... Plastic base material, 3 ... Epoxy adhesive layer, 4 ... Interface (surface of plastic base material), 5 ... Opening part, 6 ... Adhering body (polymer electrolyte membrane etc.).

Claims (15)

A bonding member having a plastic substrate and an uncured epoxy adhesive layer,
An adhesive member having a chemical bond between a nitrogen functional group introduced by surface treatment at an interface in contact with the epoxy adhesive layer in the plastic substrate and an epoxy group of the epoxy adhesive.   The adhesive member according to claim 1, wherein the nitrogen functional group is at least one nitrogen functional group selected from a primary amine, a secondary amine, and an amide.   The adhesive member according to claim 1 or 2, wherein the epoxy adhesive constituting the epoxy adhesive layer is a one-pack type containing a curing agent.   The adhesive member according to claim 1, wherein the plastic substrate is a film or a sheet.   The adhesive member according to claim 1, wherein release paper is laminated on the epoxy adhesive layer.   6. The adhesive member according to claim 1, wherein the adherend bonded to the epoxy adhesive is a polymer electrolyte membrane made of a polymer electrolyte having a sulfonic acid group. A method for producing an adhesive member according to any one of claims 1 to 6,
Nitrogen functional group introduction step for introducing nitrogen functional group into the surface of plastic base material by surface treatment of plastic base material, and epoxy system for forming epoxy adhesive layer on the surface of plastic base material into which said nitrogen functional group has been introduced A method for producing an adhesive member, comprising: an adhesive layer forming step.   8. The method for manufacturing an adhesive member according to claim 7, wherein the nitrogen functional group introduction step is a surface treatment step by a discharge treatment in a nitrogen atmosphere having an oxygen concentration of 1000 ppm or less by volume ratio.   The method for manufacturing an adhesive member according to claim 7 or 8, wherein the nitrogen functional group introduction step is performed under atmospheric pressure.   The method for producing an adhesive member according to claim 7, wherein the nitrogen functional group introduction step is a corona discharge treatment.   The plastic base material is a film or a sheet, and the nitrogen functional group introduction step is continuously performed by a roll-to-roll method. Method.   An adhesive structure, wherein the adhesive member according to any one of claims 1 to 6 is adhered to an adherend to cure an epoxy adhesive.   The adhesive structure according to claim 12, wherein the glass transition temperature of the epoxy adhesive and the plastic constituting the plastic substrate are both 80 ° C or higher.   The adhesion structure according to claim 12 or 13, wherein the adherend is a plastic material having an acid functional group at an adhesion interface.   The adhesion structure according to claim 12 or 13, wherein the adherend is a plastic material having a nitrogen functional group by surface treatment at an adhesion interface.

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