JP2006225544A - Epoxy resin adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin adhesive suitable for a structural application that requires advanced mechanical properties, having excellent adhesive strength properties and heat resistance, and capable of easily dismounting a bonded structure after use of an adhesion/joint component. <P>SOLUTION: This epoxy resin adhesive has an ≥80°C glass transition temperature after hardening, ≤20 MPa dynamic modulus of a rubbery flat part of dynamic viscoelasticity and ≤20 MPa dynamic modulus at 170°C, contains a 10-45 wt% monofunctional epoxy compound with an imide backbone based on the epoxy compound and can heat-soften the hardened adhesive to dismount at 120-250°C. The bonded structure is provided using the adhesive. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an epoxy resin adhesive and an adhesive body. In particular, the present invention relates to an adhesive and an adhesive that have an adhesive performance that can be suitably used for bonding a structural material, and that can easily disassemble the adhesive after use.

  Recycling of materials and parts is required in various industrial fields. For example, in the automobile industry and the building materials industry, a joining member is formed by bonding different materials and used for the structure. However, there is a strong social need to dismantle the joining member after use and promote member recycling. However, there is no bonding technique that can be easily disassembled after use while ensuring a strong bonding structure that supports the structure during use of the member.

  In other words, the existing adhesive system using thermoplastic resin adhesive has a heat melting property, so it can be disassembled when a load is applied in a state exposed to high temperatures, but it has poor adhesive performance in the first place and is reliable It does not become an adhesive for structural materials that are required. On the other hand, an adhesive system using a thermosetting resin adhesive such as an epoxy resin adhesive has a high adhesive force, but since the degree of thermal softening is small, thermal decomposition is not performed and the recyclability of the adherend is poor. .

  Against this backdrop, the concept / needs of “dismantling adhesiveness” has arisen, and studies have been made assuming applications that do not require a large load, such as interior decorative boards and home appliances. For example, an emulsion-type dismantling adhesive (see, for example, Patent Document 1, Patent Document 2, Patent Document 3, Non-Patent Document 1, and Non-Patent Document 2), an elastic disintegrating adhesive, and the like (for example, Non-Patent Document 3). Non-Patent Document 4). Both are based on a relatively soft adhesive with poor heat resistance and to which thermally expandable microcapsules are added. Although these studies have yielded certain results in terms of dismantling, these technologies have a low bond strength of 4 MPa or less in the first place and lack heat resistance. It is difficult to apply to bonding for structural materials.

  On the other hand, Patent Document 4 discloses a technique for thermally decomposing by adding thermally expandable graphite to an existing epoxy resin adhesive. However, although this technique uses an existing epoxy resin adhesive, the adhesive strength itself is relatively high, but it is assumed that it is dismantled by being exposed to a high temperature of 400 ° C. or higher, and a great deal of heat energy is required. In addition, when a plastic material is used as the adherend, the adherend itself is thermally decomposed during disassembly, so that it is difficult to reuse the adherend.

As described above, high adhesive strength, heat resistance that can also be used for structural materials, and decomposable adhesive systems that can be applied to plastic materials, for example, with dismantling / recyclability at temperatures of 250 ° C. or lower. Yes, not yet realized.
JP 2002-127290 A JP 2002-127292 A JP 2002-129134 A JP 2004-189856 A `` Materials '' Vol. 53, No. 10, pp. 1143-1148, 2004 "Journal of the Adhesion Society of Japan" Vol.40, No.4, pp.146-151,2004 `` Materials '' Vol. 53, No. 10, pp. 1143-1148, 2004 "Journal of the Adhesion Society of Japan" Vol.40, No.5, pp.184-191, 2004

  In view of the above-mentioned present situation, the present invention is an adhesive suitable for structural material applications requiring high mechanical properties, and has excellent adhesive strength characteristics and heat resistance, and also uses an adhesive / joining member. An object of the present invention is to provide an epoxy resin adhesive and an adhesive that can be easily disassembled later.

  As a result of intensive studies, the present inventors have found that the glass transition temperature Tg (hereinafter abbreviated as Tg) of the cured product is higher than a specific temperature, and the dynamic elastic modulus of the rubber-like flat portion in dynamic viscoelasticity. By using an epoxy resin adhesive made of a resin composition in which E′r (the dynamic elastic modulus of the rubber-like flat portion is hereinafter also simply referred to as E′r) is a specific value or less, the above-mentioned problems are solved. The present invention has been completed. That is, the present invention is an epoxy resin adhesive having a Tg after curing of 80 ° C. or more and an E′r in dynamic viscoelasticity of 20 MPa or less.

  The present invention is also an adhesive body in which an adherend is bonded with an epoxy resin adhesive, and the adhesive cured product can be disassembled by heat softening at 120 to 250 ° C. It is also an adhesive body using a resin adhesive.

(1) Since the epoxy resin adhesive of the present invention has the above-described configuration, it is possible to obtain an adhesive that exhibits high adhesion performance, and the adhesive can be obtained in a short time even at a relatively low temperature of 250 ° C. or less. It can be dismantled.
(2) Since the epoxy resin adhesive of the present invention has the above-described structure, an adhesive body having sufficient adhesive strength as a structural material and disassembly / recyclability after use can be obtained.
(3) Since the epoxy resin adhesive of the present invention has the above-described configuration, it is easy to reuse even when a plastic material is used as an adherend, and the epoxy resin adhesive and adhesive that are practical in cost. The body and its disassembly method are obtained.
(4) Since the adhesive body of the present invention has the above-described configuration, it exhibits a high tensile shear adhesive strength applicable to structural material applications in an environment of at least 80 ° C. and a relatively low temperature of 120 to 250 ° C. By being exposed to the ambient temperature, the cured adhesive can be softened and easily disassembled.

  The epoxy resin adhesive of the present invention has a Tg after curing of 80 ° C. or higher. Tg in the present invention is defined by the following measured value by dynamic viscoelasticity measurement (DMA) or differential scanning calorimeter (DSC). Preferably it is 90 degreeC or more, More preferably, it is 100 degreeC or more. If it is less than 80 ° C., the adhesive heat resistance of the adhesive member as the structural material is insufficient.

Dynamic Viscoelasticity Measurement (DMA) Method In this measurement method, Tg and dynamic elastic modulus of the cured adhesive resin (in this specification, dynamic elastic modulus represents storage elastic modulus E ′. Hereinafter, simply referred to as E ′ (E'r, glassy dynamic elastic modulus E'g at 25 ° C (glassy dynamic elastic modulus is also simply referred to as E'g) and E 'at 170 ° C) Use. The shape of the cured resin specimen is 50 mm long × 10 mm wide × 2 mm thick, and the temperature rising rate is 2 ° C./min in a temperature range of 0 ° C. to 200 ° C. in a double-sided bending sine wave mode with a chuck distance of 20 mm. And measured at a frequency of 1 Hz. This measurement reads E'r, E'g at 25 ° C, and E 'at 170 ° C. Moreover, as shown in FIG. 1, the intersection of the tangent from the point where the gradient of the curve of the glass region straight line extrapolated tangent and the glass transition region is maximized is defined as Tg. This method is the same as the method for determining the glass transition temperature of JIS K7121.

Differential Scanning Calorimeter (DSC) Measurement Method This measurement method is used for evaluating the Tg of the cured resin in the adhesive. About 10 mg of a sample of the cured resin portion scraped from the adhesive is placed in an aluminum pan (sample pan), placed in the same electric furnace as the reference pan (aluminum pan only), and heated at a heating rate of 2 ° C./min. Measure the temperature difference between them. As shown in FIG. 1, the slope of the extrapolated tangent to the high temperature side of the base line on the low temperature side and the curve of the step-like change portion of the glass transition region is maximized in the region where the curve moves away from the base line to the endothermic side due to the resin glass transition. The intersection of tangents from such a point is read and defined as Tg. This method is the same as the method for determining the glass transition temperature of JIS K7121.

  Further, the epoxy resin adhesive of the present invention has an E′r in dynamic viscoelasticity of 20 MPa or less. As described above, this value can be obtained from the chart showing the temperature dependence of the elastic modulus in the dynamic viscoelasticity measurement (DMA). That is, when the measurement results are plotted with the elastic modulus on the vertical axis and the temperature on the horizontal axis, in general, as shown in FIG. 1, the epoxy resin changes its elastic modulus in a temperature-dependent manner. As the temperature rises, the dynamic elastic modulus at the flat part of the rubber region in the chart changes from a glass region with a high elastic modulus to a rubber region with a low elastic modulus through a glass transition region. Is E'r.

  By the way, generally, in the existing thermosetting resin, when Tg is increased, E'r also tends to increase at the same time. However, the epoxy resin adhesive of the present invention makes it possible to decrease E′r while keeping Tg high at 80 ° C. or higher, whereby the Tg of the cured product is 80 ° C. or higher and E ′ r is 20 MPa or less.

  E'r is preferably 10 MPa or less, more preferably 5 MPa or less, from the viewpoint of imparting cost and practical advantages to disassembly.

  Moreover, the epoxy resin adhesive of the present invention preferably has a dynamic elastic modulus E ′ at 170 ° C. of 20 MPa or less, more preferably 10 MPa or less, from the viewpoint of imparting cost for disassembly and practical disassembly. Preferably, 5 MPa or less is more preferable.

  That is, even when an existing epoxy resin adhesive is used, as described above, an adhesive body that can be disassembled by being exposed to a high temperature of 400 ° C. can be obtained. However, a great deal of heat energy or time is required for disassembly, which is not practical as an adhesive disassembly system. In particular, when a plastic material such as fiber reinforced plastic is used as the adherend, not only the thermal decomposition of the adhesive, but also the thermal decomposition of the adherend itself occurs at the same time, so the adherend is reused after disassembly. It becomes difficult. On the other hand, according to the present invention, E′r is 20 MPa or less, and preferably the dynamic elastic modulus E ′ at 170 ° C. is 20 MPa or less. Therefore, even at a relatively low temperature, for example, 250 ° C. or less, it is short. The dismantling system can be dismantled in time, and even when a plastic material is used as an adherend, it can be easily reused, and the dismantling system is practical in terms of cost.

  The adhesive that becomes the cured resin having the above viscoelastic behavior is rigid at room temperature (25 ° C.) to about 80 ° C. and has high mechanical properties and adhesiveness, but contrasts with room temperature elasticity at 120 to 250 ° C. Thus, it can be heat softened to give thermal dismantling at an appropriate temperature within a range of 120 to 250 ° C.

  Furthermore, in order to improve the thermal disassembly property of the adhesive of the present invention, it is preferable to contain particles that expand at a temperature of 100 ° C. or higher to a volume of 5 times or more the volume at 25 ° C. From the viewpoint of improving dismantling properties, those that expand to a volume of 20 times or more of the volume at 25 ° C. are more preferable.

  The particles that expand may be inorganic particles or organic particles as long as they expand to a volume that is 5 times or more the volume at 25 ° C. when heated to 100 ° C. or higher. Examples of such a material include thermally expandable graphite as inorganic particles and thermally expandable fine hollow bodies (also referred to as thermally expandable microcapsules) as organic particles. Thermally expandable graphite generally refers to graphite having the property of expanding from several times its original volume to several hundred times when heated. The thermally expandable fine hollow body is a fine particle enclosing a liquid gas in a polymer film (shell), and when heated, the gas pressure inside the shell increases and the polymer film softens, Particles that expand dramatically in volume. As the particles that expand, it is also preferable to use thermally expandable graphite. However, a thermally expandable fine particle hollow body is preferable because it can impart excellent dismantling properties while suppressing a decrease in adhesiveness.

  The expansion start temperature of the above expanding particles (in the case of a thermally expandable fine particle hollow body, the foam start temperature) is preferably 90 to 170 ° C. in consideration of the heat resistance of adhesion and the dismantling property. If it is less than 90 degreeC, it may be necessary to set the hardening temperature of an adhesive agent low, As a result, the heat resistance of an adhesive agent may fall. Moreover, when it exceeds 170 degreeC, there is a case where there is little effect for provision of disassembly property at comparatively low temperature, for example, 250 degrees C or less.

  The particle size of the expanding particles is preferably an average particle size of 0.1 to 50 μm before expansion. When the average particle size is less than 0.1 μm, disassembly may be insufficient, and when it exceeds 50 μm, workability as an adhesive may be inferior. In addition, the particle size in this case means a volume average particle size obtained by a centrifugal sedimentation rate method or the like.

  Specific examples of the expandable fine hollow body include, for example, EXPANCEL 053DU (manufactured by EXPANCEL, foaming ratio of about 35 times, foaming start temperature of about 100 ° C.), EXPANCEL 092DU (manufactured by EXPANCEL, foaming ratio of 50 times, foaming start temperature of about 120). ℃), Matsumoto Microsphere F-50 (Matsumoto Yushi Seiyaku Co., Ltd., foaming ratio 50-100 times, foaming start temperature about 110 ° C), Matsumoto Microsphere F-85 (Matsumoto Yushi Seiyaku Co., Ltd., foaming ratio) 50 to 100 times, a foaming start temperature of about 140 ° C.) and the like can be used.

  The expanding particles are preferably contained in the total resin component in an amount of 5 to 50% by weight. When the amount is less than 5% by weight, the disassembling property of the adhesive may not be sufficient, and when it exceeds 50% by weight, the adhesive performance may be deteriorated. More preferably, it is 10-40 weight%, More preferably, it is 15-35 weight%.

  In the present invention, a compound having an epoxy group in the molecule is called an epoxy compound, a compound having one epoxy group in one molecule is a monofunctional epoxy compound, and an epoxy compound having two or more epoxy groups is a multifunctional epoxy. Called resin. In the present invention, a monofunctional epoxy compound, a polyfunctional epoxy resin, or a combination of both can be used, but it is preferable to use the monofunctional epoxy compound by blending it into the adhesive composition. Mixing an appropriate amount of the monofunctional epoxy compound is an effective method for reducing the E′r of the cured resin to a preferable range. By lowering the E'r after curing of the adhesive, dismantling is imparted, while maintaining the 80 ° C heat resistance at a certain level or more, while maintaining the adhesiveness and heat resistance of the adhesive and ease of disassembly. In order to achieve both, it is preferable to use a monofunctional epoxy compound and a polyfunctional epoxy resin in combination, and to contain the monofunctional epoxy compound in an amount of 10 to 45% by weight in 100% by weight of the epoxy compound. When the amount is less than 10% by weight, the effect may be small in imparting disassembly. On the other hand, when it is more than 45% by weight, the adhesive strength may be lowered or the heat resistance may be insufficient.

  Examples of the monofunctional epoxy compound include phenyl glycidyl ether, phenol poly (n = 2-8) ethylene oxide glycidyl ether, para-t-butylphenyl glycidyl ether, N-glycidyl phthalimide, and dibromophenyl glycidyl ether. Among these, para-t-butylphenyl glycidyl ether and N-glycidyl phthalimide are preferable because they provide dismantling properties while suppressing a decrease in heat resistance. In particular, the addition of a monofunctional epoxy compound having an imide skeleton such as N-glycidyl phthalimide is particularly preferable because it provides disassembly while providing good adhesion and heat resistance.

  As the polyfunctional epoxy resin, it is preferable to blend a bifunctional epoxy resin in order to satisfy both required properties of heat resistance and ease of disassembly. In particular, it is preferable to contain 55 to 90% by weight of a bifunctional epoxy resin in 100% by weight of the epoxy compound.

  The E′g at 25 ° C. of the cured adhesive obtained by blending the above bifunctional epoxy resin is preferably 2.5 GPa or more in order to provide excellent shear bond strength of the bonded body.

  Examples of the bifunctional epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin that gives a rigid resin with good moisture and heat resistance, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, oxazolidone ring An epoxy resin having a skeleton, a diphenylfluorene type epoxy resin, or the like, or a mixture thereof can be used.

  Specific examples of the bisphenol A type epoxy resin include, for example, Epicoat 827 (epoxy equivalent: 180 to 190), Epicoat 828 (epoxy equivalent: 184 to 194), Epicoat 1001 (epoxy equivalent: 450 to 500), Epicoat 1004 (epoxy) Equivalent: 875-975) (Registered trademark, manufactured by Yuka Shell Epoxy Co., Ltd.); YD128 (Epoxy Equivalent: 184-194) (manufactured by Tohto Kasei Co., Ltd.); Epicron 840 (Epoxy Equivalent: 180-190) , Epicron 850 (Epoxy equivalent: 184 to 194), Epicron 855 (Epoxy equivalent: 183 to 193), Epicron 860 (Epoxy equivalent: 230 to 270), Epicron 1050 (Epoxy equivalent: 450 to 500) (Registered trademark, Dainippon Ink & Chemicals, Inc.); EL 128 (epoxy equivalent: 184 to 194) (manufactured by Sumitomo Chemical (Co.)); DER 331 (epoxy equivalent: 184 to 194) (manufactured by Dow Chemical Co.), and the like can be used.

  Specific examples of the bisphenol F type epoxy resin include Epicron 830 (epoxy equivalent: 165 to 185) (registered trademark, manufactured by Dainippon Ink & Chemicals, Inc.), Epicoat 807 (epoxy equivalent: 160 to 175) (registered trademark, Yuka Shell Epoxy Co., Ltd.) can be used.

  Specific examples of the biphenyl type epoxy resin include YX4000 (epoxy equivalent: 180 to 192, manufactured by Yuka Shell Epoxy Co., Ltd.); specific examples of the naphthalene type epoxy resin include HP-4032 (epoxy equivalent: 140 to 150, large Nippon Ink Chemical Co., Ltd.); As a specific example of the dicyclopentadiene type epoxy resin, EXA-7200 (epoxy equivalent: 260-285, manufactured by Dainippon Ink & Chemicals, Inc.); epoxy resin having an oxazolidone ring skeleton Specific examples of AER4152 (average epoxy equivalent: 330, manufactured by Asahi Kasei Chemicals Corporation), XAC4151 (average epoxy equivalent: 420, manufactured by Asahi Kasei Chemicals Corporation); specific examples of diphenylfluorene type epoxy resins include EPON HPT1079 (epoxy Equivalent: 250-260) (Trademark, Shell Company) ) Or the like can be preferably used.

  Among these, it is preferable to contain a bifunctional epoxy resin having a dicyclopentadiene skeleton, an oxazolidone ring skeleton, or a bisphenol S skeleton in order to achieve both adhesion at 80 ° C. and disassembly at 250 ° C. or less.

  The bifunctional epoxy resin having a dicyclopentadiene skeleton, an oxazolidone ring skeleton or a bisphenol S skeleton is preferably blended in an amount of 10 to 60% by weight in 100% by weight of the epoxy compound. More preferably, it is 15 to 50% by weight.

  In the present invention, a trifunctional or higher functional epoxy resin having three or more epoxy groups in one molecule can be used within a range not sacrificing the dismantling property in order to give a rigid cured product with good heat and moisture resistance.

  Examples of the trifunctional epoxy resin or the tetrafunctional epoxy resin include, for example, a phenol novolac type epoxy resin, a cresol novolac type epoxy resin; a glycidylamine type epoxy resin such as tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, and triglycidylaminocresol; A glycidyl ether type epoxy resin such as (glycidyloxyphenyl) ethane or tris (glycidyloxy) methane, or a mixture thereof can be used.

Specific examples of the phenol novolac type epoxy resin include Epicoat 152 (epoxy equivalent: 172 to 179), Epicoat 154 (epoxy equivalent: 176 to 181) (registered trademark, manufactured by Yuka Shell Epoxy Co., Ltd.); DER438 ( Epoxy equivalent: 176-181) (manufactured by Dow Chemical Co.); EPN1138 (epoxy equivalent: 176-181), EPN1139 (epoxy equivalent: 172-179) (above, trade name, manufactured by Ciba Geigy) and the like can be used.
Specific examples of the cresol novolac type epoxy resin include ESCN220L (epoxy equivalent: 200 to 230) (manufactured by Sumitomo Chemical Co., Ltd.), Epicoat 180S65 (epoxy equivalent: 205 to 220) (registered trademark, Yuka Shell Epoxy Co., Ltd.) )), ECN1273 (epoxy equivalent 225) (manufactured by Ciba Geigy Co., Ltd.) and the like can be used.
Specific examples of tetraglycidyldiaminodiphenylmethane include ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Tohto Kasei Co., Ltd.), Epicoat 604 (registered trademark, manufactured by Yuka Shell Epoxy Co., Ltd.), and the like. .
Specific examples of triglycidylaminophenol or triglycidylaminocresol include ELM100 (manufactured by Sumitomo Chemical Co., Ltd.), MY0510 (manufactured by Ciba Geigy), Epicoat 630 (registered trademark, manufactured by Yuka Shell Epoxy Co., Ltd.), and the like. Can be used.

  The curing agent for epoxy resin used in the present invention is not particularly limited as long as it is a compound having an active group capable of reacting with an epoxy group. Specifically, aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, aliphatic amines, polyamidoamines, imidazole derivatives, dicyandiamide, tetramethylguanidine, thiourea addition amines, and carboxyls such as methylhexahydrophthalic anhydride. Examples include acid anhydrides, carboxylic acid hydrazides, carboxylic acid amides, polyphenol compounds, novolak resins, and polymercaptans. Of these, dicyandiamide is preferable because a resin excellent in adhesiveness and storage stability can be easily obtained.

  These curing agents can be combined with a curing accelerator in order to increase the curing activity. As the curing accelerator, a compound containing a nitrogen atom is preferable because of its high reaction acceleration. Specifically, examples in which dicyandiamide is combined with a urea derivative such as 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU) or an imidazole derivative as a curing accelerator, carboxylic acid anhydride or novolak Examples include a combination of a resin with a tertiary amine, an imidazole derivative or the like as a curing accelerator.

  Moreover, as a curing catalyst used together with a curing agent, for example, a so-called Lewis acid complex such as boron trifluoride ethylamine complex can be used.

  In addition, in order to adjust the viscosity of the resin composition or improve the storage stability, a compound obtained by pre-reacting an epoxy resin and a curing agent can be blended in the resin composition. From this point of view, it is particularly preferable to use dicyandiamide as a curing agent and use the above-described compound containing a nitrogen atom as a curing accelerator in order to achieve both adhesiveness, storage stability, and fast curability. Particularly when heat-expanding particles are added to the adhesive, it is preferable to cure the adhesive at a temperature not higher than the expansion start temperature of the particles, and in that sense, the epoxy resin is cured at a temperature of 120 ° C. or lower. It is preferable to mix a curing agent / curing accelerator.

  In the present invention, the bisphenol compound is used as an extender of the chain length between cross-linking points, and it is added in an amount of 1 to 20% by weight, preferably 2 to 10% by weight based on 100% by weight of the total epoxy compound. If it is less than 1% by weight, the effect of improving disassembly may be insufficient, and if it exceeds 20% by weight, the storage stability of the adhesive may be lowered.

  Examples of the bisphenol compound include bisphenol A, bisphenol F, bisphenol S, bisphenol AD, bisphenol Z, bisphenol fluorene, dihydroxybiphenyl, and the like, and alkyl-substituted products and halides thereof can also be suitably used. Furthermore, dihydroxynaphthalene, dihydroxyanthracene, or the like can be used as the bisphenol compound. Among them, bisphenol S is preferable because it has excellent effects of improving peel adhesion and heat resistance and adhesiveness of a cured product obtained by heating a resin composition.

  In the present invention, in order to improve adhesive resin toughness and peel adhesion properties and control fluidity during resin curing, it is preferable to add a thermoplastic resin that can be dissolved in an epoxy resin to the resin composition. Thermoplastic resins include carbon-carbon bonds, amide bonds, imide bonds (polyetherimide, etc.), ester bonds, ether bonds, siloxane bonds, carbonate bonds, urethane bonds, urea bonds, thioether bonds, sulfone bonds, imidazoles in the main chain. Examples thereof include a thermoplastic resin having a bond and a bond selected from carbonyl bonds. Among these, a thermoplastic resin having a sulfone bond such as polyethersulfone is preferable from the viewpoint of improving the heat and moisture resistance, impact resistance, and adhesion of the cured resin.

  Note that the thermoplastic resin may be a so-called oligomer. In this case, from the viewpoint of preventing the resin viscosity at the time of molding from becoming excessive and impairing the fluidity of the resin, the number average molecular weight of the oligomer should be 10,000 or less, preferably 7000 or less, From the viewpoint of maintaining the modification effect by the thermoplastic resin and the impact resistance of the resulting composite material, the number average molecular weight of the oligomer should be 3000 or more, preferably 4000 or more.

  Moreover, it is preferable that the oligomer has the functional group which reacts with a thermosetting resin in the terminal or a molecular chain.

  Examples of the thermoplastic resin oligomer include polysulfone, polyethersulfone, polyetherimide, polyimide, polyamide, polyamideimide, and polyphenylene ether.

  These thermoplastic resins may be blended in an amount of 5 to 20% by weight, preferably 8 to 15% by weight, based on 100% by weight of the total epoxy compound. If it is less than 5% by weight, the toughness of the cured product may be insufficient, and if it exceeds 20% by weight, the fluidity of the resin may be impaired.

  In the present invention, it is also preferable to add a rubber compound to the adhesive composition in order to improve adhesive resin toughness and peel adhesive properties and control fluidity during resin curing. In particular, a liquid rubber having reactivity with an epoxy resin is preferable. As a basic skeleton of the liquid rubber, butadiene acrylonitrile rubber, styrene butadiene rubber, butyl acrylate, or the like can be used. Similarly, blending rubber fine particles having an average particle diameter of 0.01 to 5 [mu] m in the adhesive composition as a rubber compound is preferable because it has a great effect on improving the peel adhesion characteristics.

  In the present invention, various resin fine particles and inorganic fillers that are usually used in an adhesive composition can also be blended in order to improve peel adhesion and impact resistance of the resulting bonded body.

  If the adhesive of the present invention is used, the adherend is bonded with an epoxy resin adhesive and is not thermally disassembled at a temperature of 80 ° C. or lower, but the adhesive is cured at a temperature of 120 to 250 ° C. The adhesive body of the present invention that can be softened and disassembled can be obtained. Since the said adhesive body expresses the heat resistance as a structural member, it is preferable. Further, even when the adherend includes a plastic material such as fiber reinforced plastic, it has both sufficient adhesive strength as a structural material and disassembly / recyclability after use.

  The adhesive body of the present invention gives a tensile shear bond strength of at least 7 MPa, more preferably 10 MPa or more, and even more preferably 15 MPa or more in the temperature region of 80 ° C. or less as an index of adhesive strength.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the following description is exclusively for explanation, and the present invention is not limited to these examples.

The meanings of the abbreviations in Table 1 are as follows.
Ep828: Bisphenol A type epoxy resin, Epicoat 828 (manufactured by Yuka Shell Epoxy Co., Ltd., registered trademark)
Ep1001: Bisphenol A type epoxy resin, Epicoat 1001 (manufactured by Yuka Shell Epoxy Co., Ltd., registered trademark)
EX146: Monofunctional epoxy compound, para-t-butylphenylglycidyl ether (manufactured by Nagase ChemteX Corporation, registered trademark)
EX145: monofunctional epoxy compound, phenol polyethylene oxide glycidyl ether (manufactured by Nagase ChemteX Corporation, registered trademark)
EX731: Monofunctional epoxy compound, N-glycidylphthalimide (manufactured by Nagase ChemteX Corporation, registered trademark)
2-MZ: curing agent, 2-methyl-imidazole (manufactured by Shikoku Kasei Co., Ltd., model number)
DICY: Curing agent, dicyandiamide (Oilized Shell Epoxy Co., Ltd., model number)
DCMU: curing accelerator, 3- (3,4-dichlorophenyl) -1,1-dimethylurea (manufactured by Hodogaya Chemical Co., Ltd., model number)
Expanded graphite: SYZR501 (manufactured by Sanyo Trading Co., Ltd., model number)
F-100D: Expandable fine hollow particle, Matsumoto Microsphere (manufactured by Matsumoto Yushi Seiyaku Co., Ltd., model number)

Examples 1-7, Comparative Examples 1-2
About each Example and the comparative example, resin cured board preparation, dynamic viscoelasticity measurement (DMA) of cured resin, tensile shear bond strength measurement, and disassembly evaluation were performed by the following method.

Preparation of cured resin plate In accordance with each resin composition shown in Table 1, first all epoxy resin components were sufficiently mixed at 120 ° C, and then at 80 to 100 ° C, a curing agent, a curing accelerator component and expanded graphite or an expandable fine particle hollow body. Were mixed. The resin composition is vacuum degassed at 80 ° C., poured into an aluminum mold that has been pre-molded and kept at 110 ° C., and then cured by holding the mold in an oven at 120 ° C. for 1 hour. A resin plate was prepared.

Dynamic viscoelasticity measurement (DMA)
Measurement was performed by the method described above.
Tensile shear bond strength measurement and disassembly evaluation This evaluation method was used for evaluating the adhesive at room temperature (25 ° C.), 80 ° C. heat resistance, and 170 ° C. disassembly. Cold-rolled steel plate SPCC-D was used as the adherend for the adhesion test. As pretreatment of the adherend, it was degreased with acetone. The steel plate dimensions are length, width and thickness of 125 mm x 25 mm x 1.6 mm, the lap length of the bonded part is 10 mm (bonded area 250 mm ² ), and the adhesive resin is applied on one side to the bonded part of one steel sheet, The adhesive wrap portion of the other steel plate was overlapped and fixed with a clip, and the adhesive resin was heat cured (1 hour in an oven at 120 ° C.). After completion of curing, a tensile load was applied at a displacement rate of 10 mm / min in the tensile mode of the material strength tester, and the shear bond strength was measured at each of the material strength tester chamber temperatures of 25 ° C. and 80 ° C. Five specimens were evaluated and the average value was taken.
Moreover, the dismantling property was evaluated by whether or not it peeled off when stress was applied at 170 ° C. The evaluation criteria were as follows.
A: Peeled off with a stress of 1 MPa or less B: Peeled off with a stress of 2 MPa or less X: Peeled only with a stress of 4 MPa or more The evaluation results for each resin composition of Examples and Comparative Examples are summarized in Table 1.

  The composition of Examples 1-7 had adhesiveness (25 degreeC, 80 degreeC) and dismantling property (170 degreeC). However, the composition of Comparative Example 1 had good adhesiveness but lacked disassembly, and the composition of Comparative Example 2 had disintegration but lacked adhesiveness at 80 ° C.

  The epoxy resin adhesive of the present invention can be applied to the recycling of structural adherends (target materials to be joined) in building materials / residential buildings, vehicles (automobile industry, etc.) and electrical / electronic industries, etc. Enables advanced resource recycling.

The figure which shows the method of calculating | requiring Tg by DMA method or DSC method.

Claims (8)

An epoxy resin adhesive having a glass transition temperature after curing of 80 ° C. or more and a dynamic elastic modulus E′r of a rubber-like flat portion in dynamic viscoelasticity of 20 MPa or less. The epoxy resin adhesive according to claim 1, wherein the dynamic elastic modulus E ′ at 170 ° C. is 20 MPa or less. 3. The epoxy resin adhesive according to claim 1, comprising particles that expand at a temperature of 100 ° C. or higher to a volume that is 5 times or more the volume at 25 ° C. of the total resin component. The epoxy resin adhesive according to claim 3, wherein the expanding particles are a thermally expandable fine particle hollow body or a thermally expandable graphite. The epoxy resin adhesive according to any one of claims 1 to 4, comprising a monofunctional epoxy compound in an amount of 10 to 45% by weight in 100% by weight of the epoxy compound. The epoxy resin adhesive according to claim 5, wherein the monofunctional epoxy compound is a compound having an imide skeleton. An adherend formed by bonding an adherend with an epoxy resin adhesive, and capable of being thermally softened and disassembled at 120 to 250 ° C. An adhesive body comprising the epoxy resin adhesive according to any one of the above. The adhesive body according to claim 7, comprising a plastic material as the adherend.

Images