JP5114923B2 - Adhesive composition - Google Patents

Description

  The present invention relates to an adhesive composition that exhibits a balanced performance with excellent tensile shear adhesive strength, water resistance, heat resistance, and the like.

  Acrylic resins are excellent in transparency and light resistance, and demand is steadily increasing as adhesives. On the other hand, there are still many problems in terms of heat resistance, moist heat resistance, adhesive strength, and adhesive strength retention.

A so-called acrylic-epoxy hybrid adhesive that combines the excellent performance of an epoxy resin as an adhesive and the function of an acrylic resin as a pressure-sensitive adhesive has been proposed (see Patent Document 1). The present proposal provides a curable (meth) acrylate-modified epoxy resin composition containing an epoxy resin, a (meth) acrylate compound and a diamine compound or bis (amino) alkylpiperazine as a curing agent. According to Patent Document 1, the mechanical toughness of the epoxy resin adhesive is improved as it is, and the impact resistance is improved, and it is said that the epoxy resin adhesive is suitable for use as an adhesive for an automobile bumper or the like. The aim of this proposal is
(1) Dilute a high viscosity epoxy resin with a low viscosity (meth) acrylate and reduce the viscosity to improve the adhesive application workability.
(2) In the curing process, the epoxy resin is cured and crosslinked with the diamine compound and the like, and the polymerization of (meth) acrylate is advanced to form an epoxy-acrylic interpenetrating network structure (hereinafter also referred to as IPN). It is considered that an adhesive having excellent impact resistance is to be obtained. The aim of Patent Document 1 is very interesting,
(1) When the viscosity of the adhesive is simply lowered, the adhesive viscosity tends to be Newtonian, the adhesive tends to flow, and there is a tendency that a sufficient thickness of the adhesive layer cannot be obtained. There is a concern that the wettability of the adhesive will deteriorate and the adhesive strength will be insufficient.
(2) As is well known, in the presence of basic compounds (or N-containing compounds) such as diamine compounds and bis (amino) alkylpiperazines, (meth) acrylates are extremely poorly polymerizable and are sufficient for curing. Even if a long time is taken, it is predicted that (meth) acrylate will not be able to dispel the concern that it remains unreacted, and that the adhesive strength will vary significantly. Furthermore, (meth) acrylates are strongly anaerobic, and if deaeration (deoxygenation) is insufficient, there will be similar concerns regarding the development of adhesive strength.

  A curable adhesive containing a polyacrylate component, an epoxy component, and a cationic initiator has been proposed (see Patent Document 2). This proposal is useful for forming structural supports on fragile optical elements. The proposed technique is applied to optical coatings.

  In the adhesive described in Patent Document 2, the polyacrylate exists independently without self-crosslinking. Therefore, it is easily guessed that the entanglement of the epoxy with the polyacrylate, the restraint of the epoxy, and the binder force of the network structure with the epoxy are limited to some extent and are not so strong. In other words, if the polyacrylate slips, it is predicted that the IPN effect that should originally be expected will be dilute simply by dragging and moving.

The polyacrylate may be bonded with a specific functional group, carboxylic acid, or hydroxyl group that the epoxy and the polyacrylate have. When the functional group possessed by the polyacrylate is a carboxylic acid, a reaction with the epoxy group possessed by the epoxy resin occurs, the gelation that does not depend on the original cationic polymerization reaction of the adhesive proceeds, and the storage stability of the adhesive is improved. In addition to the deterioration, there is a concern that mechanical strength and adhesive strength are lowered because sufficient polymerization is inhibited. When the functional group of the polyacrylate is a hydroxyl group, when the adhesive is cured by cationic polymerization, it acts as a chain transfer agent and the apparent curing rate and cross-linking are promoted, but the degree of polymerization is reduced and the adhesive There is a concern that the material becomes brittle and does not function as a structural adhesive.
JP-A-63-215716 JP-T-2005-508435

  Adhesion between plastics such as polyamide, polyphenylene sulfide, ABS resin, and epoxy resin reinforced with carbon fiber and glass fiber, Plastics such as polyamide, polyphenylene sulfide, ABS resin, and epoxy resin reinforced with carbon fiber and glass fiber Provided is an adhesive composition that is suitable for bonding different materials such as metal and other metals and exhibits balanced performance with excellent tensile shear adhesive strength, water resistance, heat resistance, and the like.

The present invention has (1) a unit represented by the following general formula in a molecular chain,

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
Furthermore, it has a unit represented by the following general formula

(Here, R3 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10.)
Acrylic copolymer (A) as a backbone polymer,
(2) An acrylic copolymer (B) having a unit represented by the following general formula in the molecular chain is used as a branched polymer.

(Here, R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl group having 1 to 12 carbon atoms.)
Provided is an adhesive composition comprising an acrylic resin (C) having a number average molecular weight of 2 to 500,000 , an epoxy resin, and either an imidazole compound or a sulfonium salt compound .

  The adhesive composition of the present invention comprises thermoplastic or thermosetting plastics such as polyphenylene sulfide, polyphenylene oxide, nylon, polycarbonate, polyester resin, and epoxy resin reinforced with fillers and fibers, aluminum, copper, iron, titanium, and the like. It exhibits excellent adhesion to metals and provides a well-balanced structural adhesive with excellent water resistance, alkali resistance, and heat resistance.

  In particular, the adhesive composition of the present invention is used to bond a thermoplastic or thermosetting plastic reinforced with carbon fiber reinforcement, and a thermoplastic or thermosetting plastic reinforced with carbon fiber reinforcement and aluminum, iron, titanium, etc. It is an adhesive composition suitable for adhesion to metal.

  The adhesive composition of the present invention is excellent in adhesiveness in a normal state, but even when it is placed in a harsh environment such as high temperature and high humidity, the appearance change of the adhesive, the appearance change of the adherend, Good adhesiveness is maintained and exhibited without deterioration and unchanged from the initial stage.

  The present invention has (1) a unit represented by the following general formula in a molecular chain,

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
Furthermore, it has a unit represented by the following general formula

(Here, R3 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10.)
Acrylic copolymer (A) as a backbone polymer,
(2) An acrylic copolymer (B) having a unit represented by the following general formula in the molecular chain is used as a branched polymer.

(Here, R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl group having 1 to 12 carbon atoms.)
It is an adhesive composition containing an acrylic resin (C) having a number average molecular weight of 2 to 500,000 , an epoxy resin, and either an imidazole compound or a sulfonium salt compound .

  In the adhesive composition of the present invention, the acrylic resin (C) includes the acrylic copolymer (A) as a trunk polymer (hereinafter also referred to as a matrix) and the acrylic copolymer (B) as a branched polymer (hereinafter also referred to as a branch). ) And a graft copolymer.

  The acrylic resin (C) (graft copolymer) of the present invention is preferably an acidic functional group-containing monomer mixture represented by the following structural formula:

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
And a glycidyl ether group-containing monomer (hereinafter also referred to as VBGE)

(Here, R3 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10)
And a copolymerizable acrylic monomer (hereinafter referred to as a matrix) and a (meth) acrylic acid ester macromonomer (hereinafter also referred to as MM) (hereinafter referred to as a branch). References for methods for producing graft copolymers by the macromonomer method; “Radical Polymerization Handbook”, supervised by Mikiharu Tsunoike, Takeshi Endo, published by NTS (1999), p156-p158, p191-p194).

  The acidic functional group-containing monomer mixture represented by the following structural formula is a mixture of two or more monomers in which m is arbitrarily selected from 0 or an integer of 1 to 5.

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
As the acidic functional group-containing monomer mixture, two or more monomers arbitrarily selected from acrylic acid, β-carboxyethyl acrylate, acrylic acid trimer, methacrylic acid, β-carboxyethyl methacrylate, methacrylic acid trimer, and the like Mixtures are exemplified.

  An acidic functional group-containing monomer mixture is, for example, copolymerized by mixing 20% of m = 0 monomer, 40% of m = 1 monomer, and 40% of m = 2-5 monomer. When this is done, for example, the tendency of exhibiting excellent functions is stronger than when a monomer of m = 0 (for example, acrylic acid) is used alone. When the acidic functional group-containing monomer mixture is copolymerized, there is a tendency that the tackiness and adhesiveness of the acrylic resin to the adherend are dramatically improved. Most importantly, for example, when a monomer of m = 0 (for example, acrylic acid) is used alone, the water resistance and heat-and-moisture resistance of the adhesive tend to be extremely poor. For example, in the case of copolymerization as a mixture as described above (m = 0 20%, m = 1 40%, m = 2 to 540%) (acidic functional group-containing monomer mixture), to the adherend Adhesive and tackiness of the adhesive are not only very good, but the transparency, adhesion and tackiness of the adhesive are the same as before the test without any change in the long-term water resistance test and moist heat resistance test. Maintained and demonstrated above.

  The acidic functional group-containing monomer mixture is copolymerized so that the acid value of the acrylic resin (C) is preferably 1 to 50 mgKOH, more preferably 1.2 to 35 mgKOH, and even more preferably 1.5 to 20 mgKOH. Is desirable. When the acid value of the acrylic resin (C) is less than 1 mgKOH, the adhesion to the adherend and the tackiness may be deteriorated, and the water resistance and moist heat resistance tend to be deteriorated. When the acid value of the acrylic resin (C) exceeds 50 mgKOH, the moist heat resistance and water resistance deteriorate, and the adhesive layer tends to swell, whiten and peel easily.

  Examples of the glycidyl ether group-containing monomer (VBGE) monomer include m-vinyl benzyl glycidyl ether, p-vinyl benzyl glycidyl ether, p-vinyl benzyl butyl glycidyl ether and the like. These monomers may be used alone or as a mixture of two or more.

  The glycidyl ether group-containing monomer (VBGE) is preferably 0.02 to 50% by weight, more preferably 0.2 to 30% by weight, further preferably 0.2 to 25% in the acrylic copolymer (A). It is desirable to copolymerize by weight. When the copolymerization amount of the glycidyl ether group-containing monomer (VBGE) is less than 0.02% by weight, there is a tendency that the network between the acrylic polymers and grafting with the epoxy resin tend to be reduced. There are cases where the mechanical strength and adhesive strength are slightly insufficient. When the glycidyl ether group-containing monomer (VBGE) is copolymerized in an amount exceeding 50% by weight, there is a tendency that curing strain tends to remain in the adhesive when the adhesive is cured, and the adhesive cracks. There may be a sink.

  Examples of the acrylic monomer that can be copolymerized with the acidic functional group-containing monomer mixture and the glycidyl ether group-containing monomer (VBGE) include methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, Cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, p-hydroxymethylcyclohexylmethyl acrylate, 2,2,2-trifluoroacrylate Ethyl, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, 2-hydroxy methacrylate Chill, 4-hydroxybutyl methacrylate, p-hydroxymethylcyclohexylmethyl methacrylate, 2,2,2-trifluoroethyl methacrylate, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacrylate Examples include roxypropyltriethoxysilane. These acrylic monomers may be used alone or as a mixture of two or more. Among these acrylic monomers, those having 4 to 12 carbon atoms in the ester group tend to be desirable, and adhesiveness, tackiness, and water resistance may be improved.

  In the present invention, the acrylic monomer preferably contains 60 to 98% by weight of an acrylic acid alkyl ester having an ester group having 4 to 12 carbon atoms. In this case, there is a tendency that the adhesive becomes tougher and impact resistance, shear adhesion, and peel strength are improved.

  When the copolymerization amount of the alkyl ester having 4 to 12 carbon atoms in the ester group is less than 60% by weight, the adhesive tends to become brittle. For example, the crank that the adhesive transmits power When it is used in such cases, adhesion failure may be caused by an impact when transmitting a large applied torque. When the copolymerization amount of the alkyl ester having 4 to 12 carbon atoms in the ester group exceeds 98% by weight, it may be difficult to exhibit the function as an adhesive, resulting in a soft pressure-sensitive adhesive. There is a tendency for the adhesive surface to easily shift and peel off.

  In the adhesive composition of the present invention, the acrylic resin (C) is preferably an acidic functional group-containing monomer mixture and a glycidyl ether group-containing monomer (VBGE), an acrylic monomer copolymerizable therewith, More preferably, it can be produced by copolymerization with a (meth) acrylic acid ester macromonomer (hereinafter also referred to as MM).

  As the (meth) acrylic ester macromonomer (MM) preferably used in the adhesive composition of the present invention, polymethyl methacrylate macromonomer (for example, Aron Macromer AA-6 manufactured by Toagosei Co., Ltd.), polyacrylic acid Butyl macromonomer (for example, Aron Macromer AB-6 manufactured by Toagosei Co., Ltd.), 2-ethylhexyl polyacrylate (for example, Aron Macromer AJ-7 manufactured by Toagosei Co., Ltd.), polymethyl methacrylate / methacrylic acid 2-hydroxyethyl) macromonomer (for example, Aron Macromer AA-714 manufactured by Toagosei Co., Ltd.) and the like. These (meth) acrylic acid ester macromonomers (MM) may be used alone or as a mixture of two or more.

  The macromonomer used in radical polymerization refers to a radical polymerizable oligomer or polymer having a (meth) acryloyl group at one end of a molecular chain. In general, the number average molecular weight is about several thousand to several tens of thousands (references; (1) “Radical Polymerization Handbook”, Mikiharu Tsunoike, supervised by Tsuyoshi Endo, published by NTS (1999), p189-p194, ( 2) “Reactive polymer and its application development”, published by Toray Research Center, Inc. (1998), p48-p56, p231-232).

In the present invention, the (meth) acrylic acid ester macromonomer refers to a polymer or oligomer having a radically polymerizable (meth) acryloyl group at one molecular chain end, and the molecular chain (oligomer or polymer) is
(1) an oligomer obtained by copolymerizing a poly (meth) acrylic acid ester and (2) a radical polymerizable monomer copolymerizable with (meth) acrylic acid ester, such as styrene or acrylonitrile, Refers to a copolymer.

  The adhesive composition containing the acrylic resin (C) of the present invention has a controlled polymer viscosity (rheology) and, in combination with the self-structuring function inherent to the graft copolymer, is compatible with the adherend, wettability, and permeability. There is a strong tendency to improve and improve. Further, preferably, the mechanical properties inherent in the (meth) acrylic acid ester macromonomer (MM) are reflected, and the toughness of the adhesive tends to be improved. As a result, the adhesion of the adherend is improved, and even when the adherend has an uneven surface or has a complicated shape, the adhesion of the adherend is improved and at the same time the impact resistance is improved. The energy transmission efficiency tends to be improved when used in a drive unit such as a crank. Furthermore, good conformability, wettability, and permeability tend to eliminate an air layer at the interface between the adhesive and the adherend and give an adhesive article having good transparency and low haze.

  Further surprisingly, preferably, the acrylic resin (C) is graft-copolymerized by copolymerization of a (meth) acrylic ester macromonomer (MM), so that a polyisocyanate compound further blended in a normal state. Inadvertent reactivity between the epoxy resin or the like and the acidic functional group-containing monomer mixture is controlled, and an adhesive having sufficiently excellent storage stability is produced. In addition, under appropriate curing reaction conditions, the reactivity of the polyisocyanate compound, epoxy resin, and the like with the monomer mixture containing acidic functional groups is remarkably accelerated, and it is tough, heat resistant, moist heat resistant, and impact resistant. There is a tendency to obtain adhesive products with excellent properties.

  The (meth) acrylic acid ester macromonomer (MM) is preferably 0.2 with respect to 100 parts by weight of an acrylic resin matrix having a chain derived from an acidic functional group-containing monomer mixture and a glycidyl ether group-containing monomer (VBGE). It is desirable to introduce -20% by weight, more preferably 0.5-12% by weight, and still more preferably 0.5-8% by weight. When the amount of (meth) acrylic acid ester macromonomer (MM) introduced is less than 0.2% by weight, the polymer viscosity tends to be insufficiently controlled. The adhesiveness may decrease and the adhesive strength may decrease slightly. When the amount of (meth) acrylic acid ester macromonomer (MM) introduced exceeds 20% by weight, the adhesive force tends to decrease, and the tendency to easily peel off is observed.

  In the present invention, an acrylic copolymer (A) having a unit represented by the following general formula in the molecular chain:

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)

(Here, R3 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10).
The glass transition temperature (hereinafter also referred to as Tg) is preferably −80 to 30 ° C., more preferably −55 to 10 ° C., and still more preferably −55 to 0 ° C. When the Tg of the acrylic copolymer (A) is less than −80 ° C., the polymer cohesive force tends to be too small, and the adhesive tends to easily cause cohesive failure, leading to a decrease in adhesive strength. When the Tg of the acrylic copolymer (A) exceeds 30 ° C., the toughness of the adhesive is impaired and the impact resistance tends to deteriorate.

Here, in the present invention, the glass transition temperature (Tg) is determined by the method described in “Mechanical properties of polymer” (translated by JENielsen, translated by Shigeharu Onoki) (published by Kagaku Dojin, 1975) (p15-p27). It calculated according to. That is,
1 / Tg = Σ (wi / Tgi)
(Here, Tg represents the Tg of the acrylic resin (absolute temperature K), Wi represents the copolymerization amount (weight fraction) of the i monomer, and Tgi represents the glass transition temperature of the homopolymer prepared from the i monomer. .)
Calculated by Further, the Tg of the homopolymer prepared from the monomer to be copolymerized is the value described in the above-mentioned document “Mechanical properties of polymer”, and acrylic monomer sales companies (for example, Mitsubishi Rayon, Toagosei, (Nippon Catalyst Industries, Nippon Oil & Fat etc.) The values listed in the catalog were adopted and used.

  The number average molecular weight (hereinafter also referred to as Mn) of the acrylic resin (C) is 2 to 500,000. The number average molecular weight of the acrylic resin (C) is preferably 3 to 350,000, more preferably 5 to 300,000. When the Mn of the acrylic resin (C) is less than 20,000, the polymer cohesive force is weak, resulting in a decrease in adhesive force and deterioration in impact resistance. When the Mn of the acrylic resin (C) exceeds 500,000, the viscosity of the adhesive becomes too strong, the wettability to the adherend and the familiarity are deteriorated, and the adhesive force is reduced.

  Here, in the present invention, the number average molecular weight of the acrylic resin is a polystyrene standard whose molecular weight is determined using gel permeation chromatography (GPC) (for example, “HLC-8220 GPC” system manufactured by Tosoh Corporation). (For example, standard POLYSTYRENE manufactured by GL Sciences Inc.) was measured as a molecular weight standard.

  The acrylic resin (C) of the present invention is preferably produced by radical copolymerization, and can be used for any polymerization method such as bulk polymerization, suspension polymerization, dispersion polymerization, precipitation polymerization, solution polymerization, and emulsion polymerization. Can be achieved.

  In consideration of the post-process using the produced polymer, it is desirable to carry out in a solvent-free or non-aqueous solvent system such as bulk polymerization, dispersion polymerization, precipitation polymerization, and solution polymerization.

  The production of the acrylic resin (C) is preferably carried out in a polymerization system substituted with an inert gas such as nitrogen gas, argon gas or helium gas. At this time, the oxygen concentration of the polymerization system is preferably 5 vol% or less, more preferably 2 vol% or less, and still more preferably 0.5 vol% or less. When the oxygen concentration in the polymerization system exceeds 5 vol%, the radical polymerization reaction is influenced by the oxygen in the system and may not proceed sufficiently. That is, the polymerization rate is remarkably slow, and a large amount of low-polymerization polymer may be generated due to telomerization by oxygen, which tends to cause coloration of the adhesive and a decrease in water resistance.

  The acrylic resin (C) is produced preferably at a polymerization temperature of 50 to 150 ° C, more preferably 60 to 140 ° C. When the polymerization temperature is less than 50 ° C., the polymerization rate is difficult to increase, and the production may take a very long time. A further concern is that the heat resistance of the produced polymer may be degraded. When the polymerization is carried out at a temperature exceeding 150 ° C., the stability of the polymer terminal radical tends to be lowered, and it may be difficult to produce a polymer having a desired molecular weight and molecular weight distribution.

  Examples of the organic solvent that can be used as a solvent in the solution polymerization include toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n- Butyl alcohol, t-butyl alcohol, cyclohexanone, cyclohexane, hexane, heptane, methylcyclohexane, ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, Examples include tripropylene glycol and 1,4-butanediol. These organic solvents may be used alone or as a mixture of two or more.

  Among these solvents, chain transfer such as ethyl acetate and n-propyl acetate is necessary in order to prevent coloration of the polymer and deterioration of heat resistance, and when solvent removal is required when producing an adhesive. Small constants are recommended.

  In the present invention, the acrylic resin (C) preferably contains an acrylic monomer containing an acidic functional group-containing monomer mixture in the presence of a hindered amine compound and an organic peroxide, and a (meth) acrylic acid ester macromonomer (MM It is recommended to be produced by radical copolymerization. More preferably, in the presence of a reaction product of a hindered amine compound and an organic peroxide, an acrylic monomer containing an acidic functional group-containing monomer mixture and a (meth) acrylic ester macromonomer (MM) are radicalized. It is desirable to produce by copolymerization.

  The radical copolymerization reaction proceeds by a living radical polymerization mechanism, and despite the copolymerization of (meth) acrylate macromonomer (MM), the molecular weight distribution is narrow and a high molecular weight acrylic resin (C) can be produced. When the acrylic resin (C) produced by this production method is used, the rheology control of the adhesive is easy and optimized, and not only the coating workability is improved, but also the wettability and permeability to the adherend. There is a strong tendency to improve the toughness, mechanical strength, heat resistance, and adhesive strength of the adhesive.

  Examples of hindered amine compounds include 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, and bis (1,2,2,6). , 6-pentamethyl-4-piperidyl) sebacate, 3-dodecyl-1- (2,2,6,6-tetramethyl-4-piperidinyl) pyrrolidine-2,5-dione, N-methyl-3-dodecyl-1 -(2,2,6,6-tetramethyl-4-piperidinyl) pyrrolidine-2,5-dione, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, N-methyl-4-benzoyloxy Examples include -2,2,6,6-tetramethylpiperidine. The hindered amine compound may be used alone or as a mixture of two or more.

  Examples of organic peroxides include benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, cumene hydroperoxide, t-butyl hydroperoxide, and dicumyl peroxide. Is done. The organic peroxide may be used alone or as a mixture of two or more.

The hindered amine compound and the organic peroxide are preferably 1 × 10 ⁻⁴ mol to 2.5 mol, more preferably 5 × 10 ⁻⁴ mol to 2.0 mol per mol of the hindered amine compound. Used in mole ratios.

When the amount of the organic peroxide used is less than 1 × 10 ⁻⁴ mol relative to 1 mol of the hindered amine compound, the polymerization rate is hardly increased, the polymerization efficiency tends to be poor, and only a small molecular weight tends to be produced. is there.

  When the amount of the organic peroxide used exceeds 2.5 moles with respect to 1 mole of the hindered amine compound, the living property of the polymerization is lost, and a low molecular weight polymer tends to be produced in a large proportion. There is a tendency that the molecular weight distribution of the acrylic resin (C) is widened.

  The hindered amine compound is based on 100 parts by weight of the total amount of the acidic functional group-containing monomer mixture, the acrylic monomer containing the glycidyl ether group-containing monomer (VBGE), and the (meth) acrylic acid ester macromonomer (MM). Thus, it is desirable to use 0.002 to 20.0% by weight, more preferably 0.005 to 15.0% by weight, and still more preferably 0.02 to 12.0% by weight.

  The amount of hindered amine compound used is a total amount of 100 weights of an acidic functional group-containing monomer mixture, an acrylic monomer containing a glycidyl ether group-containing monomer (VBGE), and a (meth) acrylate macromonomer (MM). When the amount is less than 0.002% by weight, the polymerization rate is difficult to increase, and it takes a long time for the polymerization, and the utility tends to be lost.

  The amount of hindered amine compound used is a total amount of 100 weights of an acidic functional group-containing monomer mixture, an acrylic monomer containing a glycidyl ether group-containing monomer (VBGE), and a (meth) acrylate macromonomer (MM). When it is used in an amount exceeding 20.0% by weight, the polymer may be colored, which may cause a practical problem.

  A reaction product of a hindered amine compound and an organic peroxide can be produced, for example, by simply mixing the hindered amine compound and the organic peroxide in a container substituted with an inert gas such as nitrogen gas or helium gas. it can.

  Below, an example of the preferable aspect of acrylic resin (C) manufacture is shown. Of course, the present invention is not limited to this.

  A polymerization solvent (for example, a mixed solvent of ethyl acetate / n-propyl acetate (80/20 weight ratio)) is charged into a flask equipped with a nitrogen gas blowing tube, a temperature sensor, a condenser, and a stirring device. Nitrogen gas is introduced into the bottom of the flask and held for 30 minutes while bubbling. Thereafter, the oxygen concentration in the flask is measured with an oxygen concentration meter “XO-326ALA” (oxygen concentration meter of Shin Cosmos Electric Co., Ltd.), and it is confirmed that the oxygen concentration is less than 0.5 vol%.

  While continuing the bubbling of nitrogen gas, a predetermined amount of a hindered amine compound such as 4-benzoyloxy-2,2,6,6-tetramethylpiperidine is charged into a flask and dissolved uniformly. If dissolution is possible, an organic peroxide such as benzoyl peroxide is charged in an equimolar amount with the hindered amine compound and stirring is continued. The temperature rise is started, the temperature is raised to 80 ° C. in 30 minutes, and the temperature is kept at 80 ° C.

  Monomer, for example, 2-ethylhexyl methacrylate / n-butyl acrylate / acid-containing monomer mixture (for example, m = 0 20%, m = 1 40%, m = 2 and 3 40% in the following structural formula) A mixture of)

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
Glycidyl ether group-containing monomer (VBGE) (for example, vinylbenzyl glycidyl ether), “Aron Macromer AA-6” (methyl methacrylate macromonomer manufactured by Toagosei Co., Ltd.) (= 5/86/1/5/3) ; Weight ratio) of the mixed monomer is dropped into the flask in 2 hours, sampling is performed immediately after completion of the dropping, and the molecular weight and the polymerization rate are measured. When the polymerization rate reaches 100%, the polymerization is terminated and cooling is started.

  The acrylic resin (C) can be manufactured by the above.

A acrylic resin (C) can be used individually, or may be used by blending and curing agent in the acrylic resin (C).

  Examples are described below.

  (1) After the acrylic resin (C) is directly applied to one of the adherends, the organic solvent is removed by drying at a temperature of about room temperature to 150 ° C. The other adherend is pressure-bonded to this by hot pressing or the like, and if necessary, heated at 50 to 150 ° C. to produce an adhesive article.

  (2) To the acrylic resin (C), for example, a radical polymerizable diluent such as 2-ethylhexyl acrylate and epoxy diacrylate oligomer, and a crosslinking agent are added and mixed uniformly. Further, as a polymerization initiator, for example, a redox initiator such as cumene hydroperoxide or cobalt octylate is added to produce a radical curable adhesive. If a photopolymerization initiator such as Michler's ketone is added instead of the redox initiator, a photocurable adhesive can be produced.

  (3) A two-component curable adhesive is produced by adding a curing catalyst such as 3-aminopropyltrimethoxysilane and bisphenol A type epoxy resin and a curing agent to the acrylic resin (C).

  In addition to the acrylic resin (C), the adhesive composition of the present invention includes talc, bentonite, montmorillonite, calcium carbonate, zinc oxide, quartzite powder, glass powder, mica, potassium titanate whisker, glass wool, carbon fiber, etc. Reinforcing and filling fillers, silane coupling agents such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and 3,4-epoxycyclohexylpropyltriethoxysilane can be blended. .

  The adhesive composition of the present invention can be applied to an adherend, and another adherend is pressure-bonded or bonded in a sheet form, and preferably subjected to heat treatment to obtain an adhesive article. . In addition, the adhesive is applied on a peelable protective film, heated at an appropriate temperature, preferably 60 to 120 ° C. for an appropriate time, preferably 30 seconds to 10 minutes, and after passing through the B stage, Can be heat-cured and then bonded to the adherend.

The adhesive composition of the present invention comprises A acrylic resin (C), epoxy resins, and, at least one one imidazole compound or a sulfonium salt compound. The adhesive composition of the present invention tends to be excellent in curability and excellent in adhesive strength. The adhesive composition of the present invention preferably contains either an imidazole compound or a sulfonium salt compound, but does not contain an imidazole compound and a sulfonium salt compound at the same time.

  When the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, the glycidyl ether group-containing monomer (VBGE) has an important and useful function and function. Is expressed.

  That is, it acts as a cross-linking point between acrylic resin chains (hereinafter also referred to as an acrylic polymer network), and the acrylic polymer and epoxy resin form an interpenetrating polymer network structure (hereinafter also referred to as IPN) upon curing. There is a strong tendency to promote strong entanglement between the chain and the epoxy polymer chain, and to improve the mechanical strength, toughness and impact resistance of the adhesive, increasing the usefulness as an adhesive, particularly as a structural adhesive.

  Furthermore, in the glycidyl ether group-containing monomer (VBGE), when the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, the adhesive is cured. It acts as a grafting point between the acrylic resin and the epoxy resin, providing moderate compatibility and incompatibility between the acrylic resin and the epoxy resin, thereby integrating the acrylic resin and the epoxy resin, and mechanically. A structural adhesive having high strength and high adhesive strength is provided. Furthermore, moderate compatibility enhances the transparency of the adhesive and enables applicability to optical coatings.

  Furthermore, when the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, a chain represented by the following general formula in the acrylic copolymer (A): When

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
Chain represented by the following general formula

(Here, R3 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10).
Coexisting at the same time increases the deep curability of the adhesive, improves the mechanical strength of the adhesive, and tends to exhibit a stronger adhesive force.

  On the other hand, when the adhesive composition contains at least one of an acrylic resin (C), an epoxy resin, and an imidazole compound or a sulfonium salt compound, the following general formula (A) The chain shown in the formula does not exist,

(Here, R3 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10).
When it consists only of the chain represented by the following general formula:

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
The adhesive's deep curability is impaired, and the adhesive interface in contact with the adherend is sufficiently cured and exhibits strong adhesive strength, but the adhesive inner surface remains in a semi-cured state (so-called B stage) or uncured state Thus, the adhesive is liable to cause cohesive failure. Furthermore, when the thickness of the adhesive layer is thin (for example, 100 μm or less), it becomes prominent when metals are bonded as adherends. As described above, when the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, the above two general formulas are contained in the acrylic copolymer (A). It is extremely important that the chains shown in FIG.

  When the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, the dispersibility and dispersion stability of the filler are greatly improved, such as montmorillonite. The nano-size functional filler can be nano-dispersed, and has an effect of improving the mechanical strength, heat resistance, moist heat resistance, water resistance, and the like of the adhesive.

  When the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, the epoxy resin includes a bisphenol A type epoxy resin, a novolac type epoxy resin, and an alicyclic type. Examples include compounds having at least one epoxy group in the molecule such as epoxy resins, heterocyclic epoxy resins, brominated epoxy resins, and aliphatic epoxy resins. These epoxy resins may be used alone or as a mixture of two or more. (Reference: “Chemical products of 14705 (issued in 2005)” (Chemical Industry Daily, p1126 to p1135).

  Among these epoxy resins, aromatic epoxy resins such as bisphenol A type epoxy resins and alicyclic epoxy resins are desirable and recommended in terms of storage stability, curability and adhesive strength of the adhesive. When an aromatic epoxy resin such as a bisphenol A type epoxy resin is used, the curing temperature tends to be slightly higher (about 80 to 150 ° C.), and the curing time tends to be slightly longer (about 10 to 120 minutes). However, the storage stability of the adhesive is excellent, and it is often possible to design a one-component adhesive. When an alicyclic epoxy resin is used, it is possible to design an adhesive that exhibits fast curability (about 1 minute to 120 minutes) at a relatively low temperature (about 60 to 120 ° C.). (Pot life is about 1 week at 23 ° C./200 g scale of adhesive), it is desirable to design as a two-component type. In either case, shrinkage (linear expansion coefficient, volume expansion coefficient) when the adhesive is cured is small, and problems such as sink marks and poor adhesion can be avoided to a minimum.

  When the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, the epoxy resin has a total amount of 100 parts by weight of the epoxy resin and the acrylic resin (C). The epoxy resin is preferably blended in an amount of 5 to 98% by weight, more preferably 10 to 85% by weight, and still more preferably 20 to 80% by weight. When the blending amount of the epoxy resin is less than 5% by weight, there are cases where the crosslinking ratio of the adhesive with the epoxy resin is low, and the adhesive strength and the mechanical properties of the adhesive cannot be obtained. When the compounding amount of the epoxy resin exceeds 98% by weight, the acrylic resin (C) has a high molecular weight, high toughness, and the acrylic polymer network function for IPN is not fully utilized, and the adhesive is not used. There is a tendency to become brittle and mechanical strength, adhesive strength, etc. may be insufficient.

  When the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, the acrylic resin (C) and the epoxy resin are blended at a predetermined ratio, and then crosslinked. A curing agent is added.

  When the adhesive composition contains an acrylic resin (C), an epoxy resin, and either an imidazole compound or a sulfonium salt compound, the curing agent is selected from an imidazole compound or an aromatic sulfonium salt.

  These curing agents tend to function functionally in balancing the storage stability of the adhesive, pot life and curing properties. As a result, as a one-pack type, it exhibits long-term storage stability in a low to medium temperature range (about -20 to 40 ° C), and exhibits stable and good curing characteristics in a medium to high temperature range (about 80 to 150 ° C). There is a trend.

  These curing agents are preferably added in an amount of 0.2 to 30 phr, more preferably 0.5 to 20 phr, and still more preferably 1 to 15 phr with respect to the total amount of the acrylic resin and the epoxy resin. . When the amount of the curing agent is less than 0.2 phr, the storage stability is drastically improved, but the curability tends to be extremely deteriorated, and the mechanical strength and adhesive strength of the adhesive are lowered. The case is seen. When the blending amount of the curing agent exceeds 30 phr, the storage stability tends to be deteriorated and the pot life adjustment may be difficult. Furthermore, since hardening progresses rapidly at the time of hardening, the big distortion is produced in an adhesive agent and the tendency for adhesiveness to deteriorate is seen.

  Examples of the imidazole compound used as a curing agent in the present invention include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4. -Methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole and the like are exemplified. These imidazole compounds may be used alone or as a mixture of two or more.

  Examples of the sulfonium salt compound used as a curing agent in the present invention include those represented by the following structural formula.

(Here, R3, R4, and R5 represent an alkyl group having 1 to 12 carbon atoms.)

  Examples of the sulfonium salt compounds include methylphenyl-dimethyl-sulfonium hexafluoroantimony salt, ethylphenyl-dimethyl-sulfonium hexafluoroantimony salt, methylphenyl-dimethyl-sulfonium hexafluorophosphate salt, and the like. These sulfonium salts may be used alone or as a mixture of two or more.

  When the crosslinking reaction is carried out using these curing agents, the adhesive forms a crosslinked structure mainly by ether bonds, and therefore tends to be excellent in water resistance and chemical resistance.

  The adhesive composition containing the acrylic resin (C) of the present invention, an epoxy resin, and either an imidazole compound or a sulfonium salt compound has an acidic functional group-containing monomer mixture and vinylbenzyl glycidyl ether (VBGE) in the molecular chain. ) Can be produced by mixing an acrylic resin (C) having an unit derived from the above, an epoxy resin, and a curing agent.

  For example, the acrylic resin (C) having both an acidic functional group-containing monomer mixture and a unit derived from vinylbenzyl glycidyl ether (VBGE) in the molecular chain produced by solution polymerization can be desolvated in a vacuum. A suitable planetary mixer is charged, and a predetermined amount of epoxy resin is charged into this and stirred and mixed. Thereafter, vacuum desolvation is performed to make the adhesive solvent-free. A predetermined amount of a curing agent is charged into this, and further stirred and mixed to produce an adhesive.

  In the adhesive composition containing the acrylic resin (C) of the present invention, an epoxy resin, and at least one of an imidazole compound or a sulfonium salt compound, an acidic functional group-containing monomer mixture and vinylbenzylglycidyl in the molecular chain The acrylic resin (C) having both units derived from ether (VBGE) is a chain represented by the following structural formula in the molecular chain,

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
Chain shown by the following structural formula

(Here, R3 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10).
It is a graft copolymer having an acrylic copolymer (A) having a backbone polymer as a backbone polymer, and preferably a poly (meth) acrylate ester derived from a (meth) acrylate macromonomer (MM) as a branch polymer. The graft copolymer is known to have a disperse structure in which the trunk polymer and the branch polymer are separated and independent from each other due to the effect of the incompatible structure of the trunk polymer and the branch polymer (references; “polymer alloy”, Edited by the Society of Polymer Science, Tokyo Kagaku Dojin (1985), p196-p220). For this reason, an acrylic resin (C) having both an acidic functional group-containing monomer mixture and a unit derived from vinyl benzyl glycidyl ether (VBGE) in a molecular chain having moderate incompatibility of the backbone polymer / branched polymer is high. An adhesive composition that exhibits thixotropic rheological properties in combination with molecular weight, and therefore includes an acrylic resin (C) of the present invention, an epoxy resin, and at least one of an imidazole compound or a sulfonium salt compound. It exhibits moderate thixotropy. At the same time, as described above, the acrylic resin (C) also has a self-structuring action. Thixotropy (also called thixotropy) is related to changes between sol and gel, but the decrease in liquid viscosity due to stirring, vibration, and increase in shear rate is called thixotropic flow (references: “World of Rheology” Ozaki). Kunihiro, Industrial Research Committee (2004), p114).

  Since the adhesive has appropriate thixotropy and self-structuring action, even if the adherend is a material with a complicated shape and fine irregularities, the adhesive penetrates every corner and has a uniform film thickness. The adhesive composition containing the acrylic resin (C) of the present invention, the epoxy resin, and at least one of the imidazole compound or the sulfonium salt compound, combined with the tendency to become, the strong adhesive strength in terms of not the point Demonstrate.

  The adhesive composition of the present invention is an adhesive for automobiles, motorcycles, bicycle parts, leisure for golf clubs, fishing rods, etc., as an adhesive for sports equipment, as a structural adhesive for ships, aircraft, etc. It is suitably applied to applications that require chemical resistance such as strength, adhesive mechanical properties, toughness, and water resistance. In particular, when used as an adhesive to bond carbon fiber reinforced plastic (CFRP) and base metals such as aluminum, it provides a long-lasting, strong and strong adhesive member that suppresses adhesive failure derived from metal electrical corrosion. To do.

  Hereinafter, the present invention will be described in detail with examples.

  In the examples and comparative examples, the composition ratio represents a weight ratio unless otherwise specified.

  (1) The number average molecular weight of the acrylic resin is determined by using gel permeation chromatography (GPC) (for example, “HLC-8220 GPC” system manufactured by Tosoh Corporation), and a polystyrene standard (for example, GL) having a defined molecular weight. Science standard POLYSTYRENE) was measured as a molecular weight standard.

  (2) The heating residue was measured according to JIS K 5400-1997.

[Evaluation method as structural adhesive]
(3) The tensile test of the adhesive was performed according to JIS K 7113 (1995) (plastic tensile test method). The pulling speed is 300 mm / min. It was.
(4) Adhesion test 1) Initial adhesion test a) Preparation of test piece Adhesive was uniformly applied to an aluminum plate (film thickness 50 μm, application area 25 mm × 25 mm), and another aluminum plate was pressure-bonded to the adhesive surface. Unless otherwise specified, heat curing was performed at 120 ° C. for 1 hour. The shear adhesion force was measured using this test piece.

  b) Test method A-2017P aluminum plate (size: length 50 mm, width 25 mm, thickness 2 mm) is used, and conforms to JIS K 6850 (1999) (Test method for tensile shear bond strength of rigid substrates). I went. The pulling speed is 1.0 mm / min. The test temperature was 23 ° C. unless otherwise specified.

  2) Water resistance test The test piece prepared in (4) -1 (a) was immersed in warm water at 80 ° C. for 72 hours. Then, the adhesiveness test was done according to (4) -1 (b).

[Production example of acrylic resin]
[Manufacture of acrylic resin (1)]
400 g of ethyl acetate / n-propyl acetate (= 50/50) was charged as a polymerization solvent into a 1-liter four-necked flask equipped with a nitrogen gas blowing tube, a temperature sensor, a condenser, and a stirring device. Nitrogen gas was introduced into the bottom of the flask and held for 30 minutes while bubbling. Thereafter, the oxygen concentration in the flask was measured with an oxygen concentration meter “XO-326ALA” (oxygen concentration meter of Shin Cosmos Electric Co., Ltd.), and it was confirmed that the oxygen concentration was less than 0.2 vol%.

  While the bubbling of nitrogen gas was continued, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine was charged to the flask in an amount of 0.4% by weight of the mixed monomer, and dissolved uniformly. If dissolution is possible, benzoyl peroxide is charged in an equimolar amount with 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, and the temperature rise is started. The temperature was raised to 80 ° C. in 30 minutes, and then the temperature was maintained at 80 ° C.

  2-ethylhexyl methacrylate / n-butyl acrylate / “β-CEA” (acidic functional group-containing monomer mixture, monomer from Rhône-Poulenc) (in the following structural formula, R1 = H, m = 0 ( 20%), m = 1 (40%), m = 2 and m = 3 (40%) monomer mixture)

/ P-vinylbenzylglycidyl ether (VBGE) / "Aron Macromer AA-6" (polymethyl methacrylate macromonomer manufactured by Toagosei Co., Ltd.) (= 5/90/1/3/1) mixed monomer ("Aron 400 g of Tg excluding “Macromer AA-6” was −45 ° C.) was dropped into the flask in 2 hours. After completion of dropping, polymerization was performed for 4 hours, and then cooled to room temperature to obtain acrylic resin (1). Manufactured.

  The acrylic resin (1) has a polymer composed of 2-ethylhexyl methacrylate / n-butyl acrylate / “β-CEA” / VBGE as a backbone polymer, and a polymer part (polymethyl methacrylate) of “Aron Macromer AA-6”. It is a graft copolymer as a branched polymer. The polymerization behavior of the acrylic resin (1) is shown in FIG.

  It can be seen that the acrylic resin (1) is produced by living radical polymerization. The acrylic resin (1) had a heating residue of 50.3%, an acid value of 4.0 mgKOH, and a number average molecular weight of 150,000.

[Manufacture of acrylic resin (2)]
400 g of ethyl acetate / n-propyl acetate (= 50/50) was charged as a polymerization solvent into a 1-liter four-necked flask equipped with a nitrogen gas blowing tube, a temperature sensor, a condenser, and a stirring device. Nitrogen gas was introduced into the bottom of the flask and held for 30 minutes while bubbling. Thereafter, the oxygen concentration in the flask was measured with an oxygen concentration meter “XO-326ALA” (oxygen concentration meter of Shin Cosmos Electric Co., Ltd.), and it was confirmed that the oxygen concentration was less than 0.2 vol%.

  The temperature increase was started, and when it reached 80 ° C., it was kept at 80 ° C. during the polymerization.

  Mixed monomer of 2-ethylhexyl methacrylate / n-butyl acrylate / “β-CEA” / p-vinylbenzylglycidyl ether (VBGE) / “Aron Macromer AA-6” (= 5/90/1/3/1) (Tg excluding “Aron Macromer AA-6” was −45 ° C.) 400 g of normal dodecyl mercaptan (hereinafter also referred to as MDM) (chain transfer agent) 1.2 g, α, α-azobisisobutyro 6 g of nitrile (hereinafter also referred to as AIBN) (polymerization initiator) was added and stirred and dissolved until uniform. This mixture was dropped into the flask in 3 hours, and after completion of the dropwise addition, polymerization was further performed for 8 hours, and then cooled to room temperature to produce an acrylic resin (2).

  The acrylic resin (2) is composed of 2-ethylhexyl methacrylate / n-butyl acrylate / “β-CEA” / p-vinylbenzyl glycidyl ether (VBGE) as a backbone polymer, and “Aron Macromer AA-6” A graft copolymer having a polymer portion (polymethyl methacrylate) as a branch polymer.

  The acrylic resin (2) had a heating residue of 50.3%, an acid value of 4.0 mgKOH, and a number average molecular weight of 25,000.

[Manufacture of acrylic resin (3)]
400 g of ethyl acetate / n-propyl acetate (= 50/50) was charged as a polymerization solvent into a 1-liter four-necked flask equipped with a nitrogen gas blowing tube, a temperature sensor, a condenser, and a stirring device. Nitrogen gas was introduced into the bottom of the flask and held for 30 minutes while bubbling. Thereafter, the oxygen concentration in the flask was measured with an oxygen concentration meter “XO-326ALA” (oxygen concentration meter of Shin Cosmos Electric Co., Ltd.), and it was confirmed that the oxygen concentration was less than 0.2 vol%.

  While the bubbling of nitrogen gas was continued, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine was charged to the flask in an amount of 0.4% by weight of the mixed monomer, and dissolved uniformly. If dissolution is possible, benzoyl peroxide is charged in an equimolar amount with 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, and the temperature rise is started. The temperature was raised to 80 ° C. in 30 minutes, and then the temperature was maintained at 80 ° C.

  400 g of a mixed monomer (Tg = −45 ° C.) of 2-ethylhexyl methacrylate / n-butyl acrylate / p-vinylbenzylglycidyl ether (VBGE) (= 5/94/1) was dropped into the flask over 2 hours. After completion of the dropwise addition, polymerization was carried out for 4 hours, and then cooled to room temperature to produce an acrylic resin (3). The acrylic resin (3) is not copolymerized with an acidic functional group-containing monomer mixture and is not a graft copolymer. The acrylic resin (3) showed the same polymerization behavior as the acrylic resin (1).

  It can be seen that the acrylic resin (3) is produced by living radical polymerization. The heating residue of the acrylic resin (3) was 50.3%, and the number average molecular weight was 150,000.

Example 1
A 5 liter planetary mixer connected to a vacuum line provided with a solvent recovery trap, 400 g of acrylic resin (1) and 200 g of “jER 828” (bisphenol A type epoxy resin from Japan Epoxy Resin), γ-glycidoxypropyltrimethoxy 40 g of silane was charged and stirred. (Acrylic resin / epoxy resin = 50/50) While stirring, the pressure was reduced to 1300 Pa, and the solvent contained in the adhesive was recovered in the trap. The evacuation was stopped when the adhesive in the planetary mixer reached a heating residue of 98% or more. To this was added 1 phr of “Sun-Aid SI-80L” (a sulfonium salt compound of Sanshin Chemical Co., Ltd.), and stirring was further continued for 30 minutes to produce an adhesive (1).

(Adhesive tensile test)
The adhesive (1) was spread out in a sheet shape so as to have a film thickness of 2 mm, and was cured by heating at 120 ° C. for 1 hour. This cured adhesive film was cut with a No. 3 dumbbell and subjected to a tensile test.
The test results are shown in Table 1.

(Adhesive strength evaluation)
(1) Evaluation of initial adhesive strength Adhesive (1) was evenly applied to an aluminum plate (film thickness 50 μm, application area 25 mm × 25 mm), and another aluminum plate was pressure-bonded to the adhesive surface, and 1 at 120 ° C. Heat cured for hours. The shear adhesion force was measured using this test piece. The test results are shown in Table 2.

(2) Evaluation of adhesive strength after water resistance test The test piece prepared in (1) was immersed in warm water at 80 ° C. for 72 hours. Thereafter, the adhesion test was conducted in the same manner as in (1), and the results are shown in Table 1.

Example 2
A 5L planetary mixer connected to a vacuum line provided with a solvent recovery trap, 1.2 kg of acrylic resin (2) and 400 g of “jER 828” (bisphenol A type epoxy resin from Japan Epoxy Resin), γ-glycidoxypropyl 100 g of trimethoxysilane was charged and stirred. (Acrylic resin / epoxy resin = 60/40) While stirring, the pressure was reduced to 1300 Pa, and the solvent contained in the adhesive was recovered in the trap. The evacuation was stopped when the adhesive in the planetary mixer reached a heating residue of 98% or more. To this was added 1 phr of “Sun-Aid SI-80L” (a sulfonium salt compound of Sanshin Chemical Co., Ltd.), and stirring was further continued for 30 minutes to produce an adhesive (2).

  To this was added 3 phr of “Curazole 2E4MZ” (an imidazole compound of Shikoku Kasei Co., Ltd.), and stirring was further continued for 30 minutes to produce an adhesive (3).

(Adhesive tensile test)
The adhesive (2) was spread in a sheet shape so as to have a film thickness of 2 mm, and was heated and cured at 120 ° C. for 1 hour. This cured adhesive film was cut with a No. 3 dumbbell and subjected to a tensile test.
The test results are shown in Table 1.

(Adhesive strength evaluation)
(1) Evaluation of initial adhesive strength Adhesive agent (2) was uniformly applied to an aluminum plate (film thickness 50 μm, application area 25 mm × 25 mm), and another aluminum plate was pressure-bonded to the adhesive surface, and 1 at 120 ° C. Heat cured for hours. The shear adhesion force was measured using this test piece. The test results are shown in Table 1.

(2) Evaluation of adhesive strength after water resistance test The test piece prepared in (1) was immersed in warm water at 80 ° C. for 72 hours. Thereafter, the adhesion test was conducted in the same manner as in (1), and the results are shown in Table 1.

Example 3
A 5L planetary mixer connected to a vacuum line provided with a solvent recovery trap, 1.2 kg of acrylic resin (2) and 400 g of “jER 828” (bisphenol A type epoxy resin from Japan Epoxy Resin), γ-glycidoxypropyl 100 g of trimethoxysilane was charged and stirred. (Acrylic resin / epoxy resin = 60/40) While stirring, the pressure was reduced to 1300 Pa, and the solvent contained in the adhesive was recovered in the trap. The evacuation was stopped when the adhesive in the planetary mixer reached a heating residue of 98% or more. To this was added 3 phr of “Curazole 2E4MZ” (an imidazole compound of Shikoku Kasei Co., Ltd.), and stirring was further continued for 30 minutes to produce an adhesive (3).

(Adhesive tensile test)
The adhesive (2) was spread in a sheet shape so as to have a film thickness of 2 mm, and was heated and cured at 120 ° C. for 1 hour. This cured adhesive film was cut with a No. 3 dumbbell and subjected to a tensile test.
The test results are shown in Table 1.

(Adhesive strength evaluation)
(1) Evaluation of initial adhesive strength Adhesive (3) was evenly applied to an aluminum plate (film thickness 50 μm, application area 25 mm × 25 mm), and another aluminum plate was pressure-bonded to the adhesive surface, and 1 at 120 ° C. Heat cured for hours. The shear adhesion force was measured using this test piece. The test results are shown in Table 1.

(2) Evaluation of adhesive strength after water resistance test The test piece prepared in (1) was immersed in warm water at 80 ° C. for 72 hours. Thereafter, the adhesion test was conducted in the same manner as in (1), and the results are shown in Table 1.

Example 4
A 5 L planetary mixer connected to a vacuum line provided with a solvent recovery trap was charged with 1.4 kg of acrylic resin (2) and 300 g of “ERL-4221” (an alicyclic epoxy resin from Union Carbide) and stirred. . (Acrylic resin / epoxy resin = 70/30) While stirring, the pressure was reduced to 1300 Pa, and the solvent contained in the adhesive was recovered in the trap. The evacuation was stopped when the adhesive in the planetary mixer reached a heating residue of 98% or more. To this was added 1 phr of “Sun-Aid SI-80L” (a sulfonium salt compound of Sanshin Chemical Co., Ltd.), and stirring was further continued for 30 minutes to produce an adhesive (4).

(Adhesive tensile test)
The adhesive (4) was spread out in a sheet shape so as to have a film thickness of 2 mm, and was heated and cured at 120 ° C. for 1 hour. This cured adhesive film was cut with a No. 3 dumbbell and subjected to a tensile test.
The test results are shown in Table 1.

(Adhesive strength evaluation)
(1) Evaluation of initial adhesive strength Adhesive (4) was uniformly applied to an aluminum plate (film thickness 50 μm, application area 25 mm × 25 mm), and another aluminum plate was pressure-bonded to the adhesive surface, and the temperature was 1 at 120 ° C. Heat cured for hours. The shear adhesion force was measured using this test piece. The test results are shown in Table 1.

(2) Evaluation of adhesive strength after water resistance test The test piece prepared in (1) was immersed in warm water at 80 ° C. for 72 hours. Thereafter, the adhesion test was conducted in the same manner as in (1), and the results are shown in Table 1.

  From Table 2, the adhesive (1), the adhesive (2), the adhesive (3), and the adhesive (4) are excellent in the mechanical strength of the adhesive, and further, the adhesive (1) and the adhesive (2). It was revealed that the adhesive (3) and the adhesive (4) were excellent in adhesion and adhesive strength retention after the water resistance test. From the above results, the remarkable effects of the acrylic resin (C), which is a graft copolymer, on the improvement of mechanical strength, adhesion, and water resistance were clarified.

Comparative Example 1
A 5 L planetary mixer connected to a vacuum line provided with a solvent recovery trap was charged with 1.4 kg of acrylic resin (3) and 300 g of “jER 828” (bisphenol A type epoxy resin from Japan Epoxy Resin) and stirred. . (Acrylic resin / epoxy resin = 70/30) While stirring, the pressure was reduced to 1300 Pa, and the solvent contained in the adhesive was recovered in the trap. The evacuation was stopped when the adhesive in the planetary mixer reached a heating residue of 98% or more. 1 phr of “Sun-Aid SI-80L” was added thereto, and stirring was further continued for 30 minutes to produce an adhesive (6).

(Adhesive tensile test)
The adhesive (6) was spread out in a sheet shape so as to have a film thickness of 2 mm and cured by heating at 120 ° C. for 1 hour. This cured adhesive film was cut with a No. 3 dumbbell and subjected to a tensile test.
The test results are shown in Table 2.

(Adhesive strength evaluation)
(1) Evaluation of initial adhesive force Adhesive (5) was uniformly applied to an aluminum plate (film thickness 50 μm, application area 25 mm × 25 mm), and another aluminum plate was pressure-bonded to the adhesive surface, and the temperature was 1 at 120 ° C. Heat cured for hours. The shear adhesion force was measured using this test piece. The test results are shown in Table 2.

(2) Evaluation of adhesive strength after water resistance test The test piece prepared in (1) was immersed in warm water at 80 ° C. for 72 hours. Thereafter, the adhesion test was conducted in the same manner as in (1), and the results are shown in Table 2.

FIG. 1 is a diagram showing the polymerization behavior of the acrylic resin (1).

Claims (2)

(1) having a unit represented by the following general formula in the molecular chain;

(Here, R1 is a hydrogen atom or a methyl group, and m is two or more different values selected from 0 or an integer of 1 to 5.)
Furthermore, it has a unit represented by the following general formula

(Here, R3 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 10.)
Acrylic copolymer (A) as a backbone polymer,
(2) An acrylic copolymer (B) having a unit represented by the following general formula in the molecular chain is used as a branched polymer.

(Here, R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl group having 1 to 12 carbon atoms.)
An adhesive composition comprising an acrylic resin (C) having a number average molecular weight of 2 to 500,000 , an epoxy resin, and either an imidazole compound or a sulfonium salt compound . The acrylic copolymer (A) contains 60 to 98% by weight of an alkyl acrylate ester having 4 to 12 carbon atoms in the molecular chain, and the acid value of the acrylic (C) is 1 to 50 mgKOH. The adhesive composition according to claim 1.

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