Adhesive composition and bonded body

Abstract

To provide an adhesive composition that is favorably applicable to bonding of metals such as silver.SOLUTION: An adhesive composition contains a polymerizable monomer having a methacryloyl group, a radical polymerization initiator, and an elastomer. The adhesive composition contains a sulfur atom. The sulfur atom density in a cured body of the adhesive composition is 100 ppm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition and a bonded body. [Background technology]

[0002] Due to their industrial importance, adhesive compositions have been the subject of extensive investigation.

[0003] Patent Document 1 describes a curable composition containing a vinyl polymer (I) having on average at least one crosslinkable silyl group, a compound (II) containing an S atom in the molecule, and a curing catalyst (III) for the vinyl polymer (I). Patent Document 1 also describes that this curable composition is particularly useful as a sealant or adhesive. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-154009 Summary of the Invention [Problem to be solved by the invention]

[0005] In the course of research into improving adhesive compositions, the present inventors have found that conventional adhesive compositions can corrode metals such as silver.

[0006] The present invention has been made in view of the above circumstances, and one of the objects of the present invention is to provide an adhesive composition that is preferably applicable to bonding metals such as silver. [Means for solving the problem]

[0007] The present inventors have completed the invention provided below and solved the above problems.

[0008] According to the present invention, An adhesive composition comprising a polymerizable monomer having a (meth)acryloyl group, a radical polymerization initiator, and an elastomer, The adhesive composition contains sulfur atoms, and the concentration of sulfur atoms in a cured product of the adhesive composition is 100 ppm or less. is provided.

[0009] Further, according to the present invention, a first structural member; a second structural member; and a bonded body comprising a cured product of the adhesive composition for bonding the first structural member and the second structural member together; is provided. [Effects of the Invention]

[0010] The adhesive composition of the present invention is preferably applicable to bonding metals such as silver. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail.

[0012] In the description of groups (atomic groups) in this specification, when a notation does not specify whether the group is substituted or unsubstituted, it encompasses both groups having no substituents and groups having a substituent. For example, the term "alkyl group" encompasses not only alkyl groups having no substituents (unsubstituted alkyl groups) but also alkyl groups having a substituent (substituted alkyl groups). In this specification, the term "(meth)acrylic" represents a concept that encompasses both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate." Unless otherwise specified, the term "organic group" as used herein means an atomic group obtained by removing one or more hydrogen atoms from an organic compound. For example, a "monovalent organic group" refers to an atomic group obtained by removing one hydrogen atom from any organic compound. In this specification, when the adhesive composition is a two-component type consisting of a first component and a second component, the amount or ratio of each component preferably represents the amount or ratio relative to the total of the first component and the second component.

[0013] <Adhesive composition> The adhesive composition of the present embodiment contains a polymerizable monomer having a (meth)acryloyl group, a radical polymerization initiator, and an elastomer. The adhesive composition of the present embodiment contains sulfur atoms. The sulfur atom concentration in the cured product of the adhesive composition of this embodiment is 100 ppm or less.

[0014] The present inventors have investigated from every possible perspective the reasons why conventional adhesive compositions can corrode metals such as silver. As a result of their investigation, the present inventors have discovered that conventional adhesive compositions contain sulfur atoms that are contained as impurities in raw materials (e.g., polymerizable monomers), and that these sulfur atoms appear to cause corrosion of metals. Based on this finding, the inventors decided to select raw materials such as polymerizable monomers that contain a low content of sulfur atoms, thereby enabling the creation of an adhesive composition that contains sulfur atoms but has a sulfur atom concentration of 100 ppm or less when cured, and thus suppressing corrosion of metals. The sulfur atom concentration in the cured product of the adhesive composition may be 100 ppm or less, preferably less than 100 ppm, more preferably 50 ppm or less, and most preferably 25 ppm or less. The lower limit of the sulfur atom concentration in the cured product of the adhesive composition is not particularly limited, but in practice it is, for example, 0.1 ppm or more, specifically 1 ppm or more. The sulfur atom concentration in the cured adhesive composition can be measured by a combination of oxygen flask combustion method and ion chromatography (see the Examples section below for details).

[0015] The components contained in the adhesive composition, as well as the properties and physical characteristics of the adhesive composition, will be described below.

[0016] (polymerizable monomer) The adhesive composition of the present embodiment contains a polymerizable monomer having a (meth)acryloyl group. In this specification, the polymerizable monomer having a (meth)acryloyl group is also referred to simply as a "polymerizable monomer." At least a part of the polymerizable monomers is preferably a polymerizable monomer having a polar functional group and a polymerizable carbon-carbon double bond (highly polar monomer). The polymerizable monomers may also include other monomers, such as monofunctional monomers and polyfunctional monomers described below. Each monomer will be described below.

[0017] Polymerizable monomers having polar functional groups and polymerizable carbon-carbon double bonds (highly polar monomers) The adhesive composition of this embodiment preferably contains a polymerizable monomer having a polar functional group and a polymerizable carbon-carbon double bond. In this specification, this polymerizable monomer is also referred to as a "highly polar monomer." The highly polar monomer may be monofunctional (having only one polymerizable carbon-carbon double bond) or polyfunctional (having two or more polymerizable carbon-carbon double bonds), but the former is preferred in terms of the ease with which the polar group interacts with the adherend.

[0018] The polar functional group of the highly polar monomer is preferably a carboxy group, a hydroxy group, or a phosphate group, more preferably a carboxy group or a phosphate group, and even more preferably a carboxy group, in terms of interaction with components used in automobile manufacturing.

[0019] The polymerizable monomer preferably contains, as a highly polar monomer, at least one selected from the group consisting of (meth)acrylic acid, (meth)acrylic anhydride, fumaric acid, maleic acid, fumaric anhydride, maleic anhydride, and dimers and trimers thereof. Other examples of highly polar monomers include compounds having a phosphate group and a (meth)acryloyl group, and hydroxyalkyl (meth)acrylates.

[0020] Polymerizable monomers with only one polymerizable carbon-carbon double bond (monofunctional monomers) The adhesive composition of this embodiment preferably contains, as the polymerizable monomer, a polymerizable monomer having only one polymerizable carbon-carbon double bond (monofunctional monomer). Incidentally, in this specification, monofunctional monomers having a polar group are classified as the above-mentioned highly polar monomers.

[0021] The polymerizable monomer preferably contains a monomer represented by the following general formula (I) as a monofunctional monomer. CH2=CHR 1 -COO-R 2 (I) In general formula (I), R 1 is a hydrogen atom or a methyl group, R 2 R is a group containing a cyclic hydrocarbon skeleton, preferably a group containing a polycyclic hydrocarbon skeleton. 2 The cyclic hydrocarbon skeleton contained in is preferably an alicyclic skeleton containing no aromatic ring.

[0022] Examples of the monomer represented by general formula (I) include dicyclopentenyloxyethyl (meth)acrylate, norbornene (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, etc. Among them, at least one selected from the group consisting of isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate is preferred, and isobornyl (meth)acrylate is more preferred. When the polymerizable monomer contains a monomer having a cyclic hydrocarbon skeleton, the glass transition temperature of the cured product of the adhesive composition tends to be higher, and for example, the heat resistance of the cured product tends to be improved.

[0023] Furthermore, examples of monofunctional monomers include linear or branched alkyl (meth)acrylates, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate. The monofunctional monomer may contain a (meth)acrylate skeleton having a heterocycle, such as (meth)acryloylmorpholine.

[0024] Polymerizable monomers with two or more polymerizable carbon-carbon double bonds (multifunctional monomers) The adhesive composition of this embodiment may contain, as the polymerizable monomer, a polymerizable monomer having two or more polymerizable carbon-carbon double bonds (a polyfunctional monomer). From the viewpoint of good elongation after curing, the polyfunctional monomer is typically di- to hexa-functional, preferably di- to tetra-functional, more preferably di- or tri-functional, and even more preferably di-functional. Incidentally, in this specification, polyfunctional monomers having polar groups are classified as the above-mentioned highly polar monomers.

[0025] Examples of the polyfunctional monomer include polyfunctional (meth)acrylates having an alicyclic structure such as dimethylol-tricyclodecane di(meth)acrylate and dimethylol-cyclohexane di(meth)acrylate; polyfunctional (meth)acrylates having an aromatic ring structure such as ethylene oxide-added bisphenol A di(meth)acrylate, ethylene oxide-added bisphenol F di(meth)acrylate, propylene oxide-added bisphenol A di(meth)acrylate and propylene oxide-added bisphenol F di(meth)acrylate; and polyfunctional (meth)acrylates having an aliphatic branched structure such as trimethylolpropane tri(meth)acrylate.

[0026] The amount of the polymerizable monomer is, for example, 10% by mass or more and 80% by mass or less, and preferably 20% by mass or more and 70% by mass or less, based on the total non-volatile components of the adhesive composition. When multiple types of polymerizable monomers are used in combination, the ratio of each polymerizable monomer when the total amount of polymerizable monomers is 100 parts by mass is as follows. By appropriately adjusting the ratio, it may be possible to further improve the curability and elongation of the cured product. Highly polar monomer: preferably 50 parts by mass or more and 95 parts by mass or less, more preferably 60 parts by mass or more and 90 parts by mass or less Monofunctional monomer: preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 10 parts by mass or more and 40 parts by mass or less Polyfunctional monomer: for example, 0 parts by mass or more and 30 parts by mass or less, preferably 5 parts by mass or more and 20 parts by mass or less

[0027] Commercially available polymerizable monomers can be used as the polymerizable monomer. However, since some commercially available polymerizable monomers contain a large amount of sulfur atoms as impurities, it is desirable to select and use a polymerizable monomer with a low sulfur atom content.

[0028] Furthermore, the proportion of the monomer represented by general formula (I) (containing a cyclic hydrocarbon skeleton) in the total amount of monofunctional monomers is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0029] (Radical polymerization initiator) The adhesive composition of this embodiment contains a radical polymerization initiator, which polymerizes the polymerizable carbon-carbon double bonds of the polymerizable monomer, thereby enabling adhesion of articles.

[0030] The radical polymerization initiator is preferably a thermal radical polymerization initiator. Preferred examples of the thermal radical polymerization initiator include organic peroxides. Examples of organic peroxides include cumene hydroperoxide, paramenthane hydroperoxide, tertiary butyl hydroperoxide, diisopropylbenzene dihydroperoxide, methyl ethyl ketone peroxide, tertiary butyl peroxybenzoate, and benzoyl peroxide. Among these, cumene hydroperoxide is preferred from the viewpoint of stability. Incidentally, by using a radical polymerization initiator in combination with a reducing agent, which will be described later, it is possible to further enhance the curability and achieve room temperature curing.

[0031] The amount of radical polymerization initiator is preferably 0.1 to 20 parts by mass, more preferably 0.4 to 10 parts by mass, per 100 parts by mass of polymerizable monomer. By using a moderately large amount of radical polymerization initiator, the curing rate can be sufficiently increased. On the other hand, by not using too much radical polymerization initiator, storage stability can be further improved.

[0032] (Elastomer) The adhesive composition of the present embodiment contains an elastomer. The action of the elastomer gives the cured product of the adhesive composition appropriate viscoelasticity, which can further improve adhesive strength.

[0033] The elastomer preferably has a radically polymerizable group. It is presumed that the use of an elastomer having a radically polymerizable group allows the polymerizable monomer to participate in the curing process together with the elastomer, resulting in the formation of a more uniform cured film. This can further improve the adhesive strength. The radically polymerizable group is preferably a carbon-carbon double bond-containing group such as a (meth)acryloyl group.

[0034] The elastomer preferably contains a urethane (meth)acrylate, more preferably an aromatic urethane (meth)acrylate. A "urethane (meth)acrylate" is generally a compound having a urethane bond formed by reacting an isocyanate group with a hydroxyl group, and a (meth)acryloyl group. The polymerizable monomer having a (meth)acryloyl group is preferably excluding a urethane (meth)acrylate. It is believed that the moderate flexibility of the urethane (meth)acrylate gives the cured product of the adhesive composition moderate viscoelasticity, which can further improve the adhesive strength.

[0035] As the urethane poly(meth)acrylate, commercially available products can be used, including the following: Shin-Nakamura Chemical Co., Ltd.'s U-200PA, UA-W2, UA-W2A, UA-122P, UA-160TM, UA-2235PE, UA-4200, UA-4400, UA-7000, UA-31F, UA-7100, U-2HA, U-2PPA, U-6LPA, U-10PA, U-10HA, UA-33H, UA-53H, UA-32P, UA-1100H, etc. Negami Kogyo's UN-350, UN-352, UN353, UN-1255, UN-2600, UN-2700, UN-5500, UN-5590, UN-5507, UN-6060PTM, UN-6060S, UN6200, UN-6202, UN-6303, U N-6304, UN-6305, UN-7600, UN-7700, UN-9000PEP, UN-9200A, UN-3320HA, UN-3320HC, UN-3320HS, UN-904, UN-906S, UN-901T, UN-905, UN-952, etc. Kyoeisha's AH-600, UA-306H, UA-306T, UA-306I, UA-510H, UF-8001G, DAUA-167, BPZA-66, etc. Miramer PU210, Miramer PU256, Miramer PU2050, Miramer PU2100, Miramer PU2300C, Miramer PU2560, Miramer PU320, Miramer PU340, Miramer PU3000, Miramer PU3200, Miramer PU3450, Miramer PU5000, Miramer PU610, Miramer PU6510, Miramer PU9500, Miramer PU9800, Miramer UA5216, Miramer SC2100, Miramer SC2152, Miramer SC2404, Miramer SC2565, Miramer MU3603, Miramer PU370, Miramer PU640, Miramer PU2421NT, etc. manufactured by MIWON EBECRYL 210, EBECRYL 220, EBECRYL 4500, EBECRYL 230, EBECRYL 270, EBECRYL 280 / 15IB, EBECRYL 284, EBECRYL 4491, EBECRYL 4683, EBECRYL 4858, EBECRYL 8307, EBECRYL 8402, EBECRYL 8411, EBECRYL 8413, EBECRYL 8804, EBECRYL 8807, EBECRYL 9270, EBECRYL 7735, KRM8961, EBECRYL 8800, EBECRYL 1259, 294 / 25HD, EBECRYL 4100, EBECRYL 4220, EBECRYL 4513, EBECRYL 4740, EBECRYL 4820, EBECRYL 8311, EBECRYL 8465, EBECRYL 9260, EBECRYL 8701, EBECRYL 8667, EBECRYL 8701, KRM 8667, KRM 8296, EBECRYL 4587, EBECRYL 4200, EBECRYL 4666, EBECRYL 4680, EBECRYL 8210, EBECRYL 8405, KRT 8528, EBECRYL 1290, EBECRYL 5129, EBECRYL 8254, EBECRYL 8301R, KRM 8200, KRM 8200AE, KRM 8530, KRM 8904, KRM 8531BA, KRM 8452, etc. manufactured by Daicel Ornex Co., Ltd. Sartomer CN910, CN959, CN963, CN964, CN965, CN966, CN969 NS, CN980 NS, CN981 NS, CN982, CN983 NS, CN985, CN991 NS, CN996 NS, CN2920, CN8881 NS, CN8883 NS, CN9001 NS, CN9004, CN9005, CN9009, CN9011, CN9021 NS, CN9023, CN9028, CN9030, CN9178 NS, CN9290, CN9893 NS, CN929, CN989 NS, CN968 NS, CN9006 NS, CN9010 NS, CN9025, CN9026, CN9039, CN9062, CN9110 NS, CN9029, CN8885 NS, CN9013 NS, CN973, CN978 NS, CN992, CN9167, CN9782, Cn9783, CN970, CN971, CN972, CN975 NS, CN9165 etc.

[0036] The amount of elastomer is, for example, 50 to 300 parts by mass, preferably 100 to 300 parts by mass, more preferably 100 to 250 parts by mass, per 100 parts by mass of polymerizable monomer.

[0037] (reducing agent) The adhesive composition of this embodiment preferably contains one or more reducing agents. By using a radical polymerization initiator and a reducing agent in combination, the curability can be further improved and room temperature curing can be achieved. The reducing agent may be any known reducing agent that reacts with the polymerization initiator to generate radicals. The reducing agent is preferably at least one selected from the group consisting of tertiary amines, thiourea derivatives, and transition metal salts, and more preferably transition metal salts. Examples of thiourea derivatives include acetylthiourea and ethylenethiourea. Examples of transition metal salts include cobalt naphthenate, cobalt octoate, copper naphthenate, and vanadyl acetylacetonate. Among the transition metal salts, vanadyl acetylacetonate is preferred.

[0038] When a reducing agent is used, the amount used is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of polymerizable monomer. Using 0.01 part by mass or more will sufficiently increase the curing rate, and using 10 parts by mass or less will improve storage stability.

[0039] (Other ingredients) The curable composition of the present embodiment may or may not contain optional components other than those described above. For example, the curable composition of the present embodiment may contain spacers (particles) for adjusting the film thickness during use. The spacers are typically spherical particles made of a resin such as polyolefin.

[0040] As another example, the adhesive composition of this embodiment may contain various stabilizers to improve storage stability (suppress deterioration during storage). Examples of stabilizers include (i) compounds known as phenolic antioxidants, (ii) quinone compounds such as p-benzoquinone and hydroquinone monomethyl ether, (iii) compounds known as polymerization inhibitors such as amine-based polymerization inhibitors such as phenothiazine, and (iv) stable radical-type compounds having stable radicals. Among these, stable radical-type compounds are preferred because they improve storage stability without impairing adhesive performance (tensile shear adhesive strength and storage modulus).

[0041] The stable radical is preferably a nitroxide radical. Specific examples of the stable radical compound include 1-oxyl-2,2,6,6-tetramethylpiperidine, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, and 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine 1-oxyl. When a stable radical compound is used, it is preferable to use one or more of these.

[0042] When a stabilizer such as a stable radical compound is used, the content thereof is, for example, 0.001 part by mass or more and 1 part by mass or less, preferably 0.001 part by mass or more and 0.5 parts by mass or less, more preferably 0.01 part by mass or more and 0.3 parts by mass or less, and even more preferably 0.02 part by mass or more and 0.1 part by mass or less, relative to 100 parts by mass of polymerizable monomer, in order to improve storage stability without impairing performance as an adhesive.

[0043] Incidentally, from the viewpoint of reducing the sulfur atom concentration, the adhesive composition of this embodiment preferably does not contain nitrile rubber (e.g., NBR: nitrile butadiene rubber), which is often contained in adhesive compositions, or if it does contain it, it contains only a very small amount. Specifically, the content of nitrile rubber in the adhesive composition of this embodiment is preferably 0% by mass or more and 0.1% by mass or less.

[0044] (single-dose / two-dose) The adhesive composition of this embodiment may be a so-called one-component type, or may be a two-component type (an adhesive composition in which two components filled in separate containers are mixed immediately before use). In the case of a two-component system, the radical polymerization initiator is preferably contained in the first component and the reducing agent is preferably contained in the second component. However, the tertiary amine is preferably contained in the first component, and the thiourea derivative and transition metal salt are preferably contained in the second component. Other components can be mixed into the two components as appropriate. The first and second components can be mixed immediately before use. Incidentally, when the adhesive composition of the present embodiment is a two-component type, it is preferable to adjust the amount of each component in the first and second components so that the adhesive composition after mixing the first and second components contains each component within the above-mentioned preferred content ranges.

[0045] (Applications, characteristics) As already mentioned, the adhesive composition of this embodiment has a low sulfur atom concentration, and therefore when used to bond metal members such as silver, it can suppress corrosion of the metal members. In other words, the adhesive composition of this embodiment is preferably used for bonding metal members, particularly metal members containing silver.

[0046] The corrosion inhibition of metal members can be quantitatively evaluated, for example, by the following procedure. [procedure] (1) The adhesive composition (in the case of a two-component adhesive, the adhesive composition is used immediately after mixing the first and second components) is cured for 24 hours in an environment of 23°C and 50% relative humidity to prepare a cured sample. (2) The obtained hardened sample is processed into a size of 10 mm x 10 mm, placed on pure silver foil, placed in a 150 mL magnetic crucible, and heated at 260°C for 30 minutes in an air atmosphere. (3) After heating, observe whether there is any corrosion on the pure silver foil.

[0047] In the above step (3), if there is no corrosion on the pure silver foil, it can be said that the adhesive composition of this embodiment is particularly suitable for use in bonding metals such as silver. Note that the presence or absence of corrosion is carefully observed visually.

[0048] (Manufacturing method) The adhesive composition of this embodiment can be produced by thoroughly mixing the above-mentioned components (preferably those with a low sulfur atom content). A stirring device equipped with stirring blades can be used for mixing. As a precaution, it is preferable to pay attention to the material of the production equipment so that sulfur atoms do not escape from the inner walls of the production equipment.

[0049] <zygote> A bonded body including a cured product of the adhesive composition can be obtained by applying the adhesive composition of this embodiment to an article and curing it. Specifically, by using the adhesive composition of this embodiment, a bonded body including a first structural member, a second structural member, and a cured product of the adhesive composition that bonds the first structural member and the second structural member can be obtained. The adhesive composition of the present embodiment, particularly when it contains a reducing agent, preferably cures without heating (at room temperature) and can bond articles together, although heating is not necessarily required to obtain a bonded structure.

[0050] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0051] The embodiments of the present invention will be described in detail based on Examples and Comparative Examples. However, it should be noted that the present invention is not limited to the Examples.

[0052] <Production of Adhesive Composition> The raw materials shown in Table 1 below were thoroughly mixed in the amounts (unit: parts by mass) shown in Table 1 using a stirring device equipped with stirring blades, thereby producing adhesive compositions (agents A and B) for each example and comparative example. Raw materials (especially polymerizable monomers) with low sulfur content were selected from commercially available materials. For reference, the sulfur content of each raw material is also shown in Table 1. For reference, sources for the polymerization initiator and elastomer are listed below. ·PH-80: Made by NOF MU3603: Bifunctional urethane acrylate with aromatic ring, manufactured by MIWON Co., Ltd., Korea, purchased from Toyo Chemicals Co., Ltd. N220SH: JSR DN612P: Zeon Corporation BL-20: Manufactured by Denka Co., Ltd.

[0053] <Measurement of sulfur concentration in hardened material> The sulfur concentration in the cured body (sulfur concentration of the cured material) was measured by combining the oxygen flask combustion method and ion chromatography. The details are as follows. First, an adhesive composition was prepared by mixing equal amounts of the first and second agents in an environment of 23°C and 50% relative humidity, and sandwiched between PET films (manufactured by Toray Industries, Inc.). The thickness was adjusted to 1 mm and the film was left to cure for 24 hours in the same environment to prepare a cured sample. Approximately 20 mg of the cured sample was collected on filter paper. This was burned in a combustion flask containing 5 mL of approximately 0.5% H2O2 (Fujifilm Wako Pure Chemical Industries, Ltd.), and then immediately shaken for 2 minutes. After leaving it for 30 minutes, ultrapure water (Fujifilm Wako Pure Chemical Industries, Ltd.) was added to make a 20 mL volume and used as a sample. And the SO4 in the sample 2- The concentration was measured using an ion chromatograph (Thermo Fisher: ICS-1500). 2- Based on the concentration, the sulfur atom concentration in the cured product of the adhesive composition was calculated.

[0054] <Evaluation of tensile shear adhesive strength> In an environment of 23°C and 50% relative humidity, an adhesive composition containing equal amounts of the first and second agents was applied to one side of a test piece (200 mm x 25 mm x 1.6 mm, SPCC steel plate) in accordance with JIS K 6850. Immediately after that, the other test piece (200 mm x 25 mm x 1.6 mm, SPCC steel plate) was attached to the adhesive surface with a bonding area of ​​312.5 mm. 2 After laminating the pieces so that the thickness was such ... The above samples were used to measure the tensile shear adhesive strength (unit: MPa) using a universal testing machine in an environment of a temperature of 23°C and a relative humidity of 50% at a tensile speed of 10 mm / min.

[0055] <Evaluation of metal (silver) corrosion> The corrosion test was evaluated according to the following procedure. (1) An adhesive composition was prepared by mixing equal amounts of the first and second agents in an environment of 23°C and 50% relative humidity. The adhesive composition was sandwiched between PET films (manufactured by Toray Industries, Inc.), adjusted to a thickness of 1 mm, and cured for 24 hours in the same environment to prepare a cured sample. (2) The cured sample was cut into a size of 10 mm x 10 mm and placed on a 30 mm x 30 mm pure silver foil (pure silver foil manufactured by Hakuza Co., Ltd.). This was placed in a 150 mL magnetic crucible and heated. The heating conditions were 260 °C x 30 minutes in an air atmosphere. (3) After heating, the pure silver foil was visually inspected for corrosion.

[0056] The above information is summarized in Tables 1 and 2.

[0057] [Table 1]

[0058] [Table 2]

[0059] As shown in Tables 1 and 2, the cured product of the adhesive composition of the example (containing a low amount of sulfur) did not corrode the thin silver film (pure silver foil) and did not corrode the metal (silver). On the other hand, the cured products of the adhesive compositions of Comparative Examples 1 and 2, which contained a large amount of sulfur, corroded metal (silver).

[0060] Incidentally, Examples 1 to 7, in which a relatively large amount of elastomer was used, had a higher tensile shear adhesive strength than Examples 8 and 9, in which a relatively small amount of elastomer was used.

Claims

1. An adhesive composition comprising a polymerizable monomer having a (meth)acryloyl group, a radical polymerization initiator, and an elastomer, the polymerizable monomer includes a highly polar monomer having a carboxy group and a polymerizable carbon-carbon double bond; the adhesive composition contains sulfur atoms, and a sulfur atom concentration in a cured product of the adhesive composition is 100 ppm or less; An adhesive composition used for bonding metal members containing silver.

2. 2. The adhesive composition of claim 1, The adhesive composition wherein the elastomer has a radical polymerizable group.

3. The adhesive composition according to claim 1 or 2, The adhesive composition, wherein the elastomer comprises a urethane (meth)acrylate.

4. The adhesive composition according to any one of claims 1 to 3, The adhesive composition, wherein the elastomer comprises an aromatic urethane (meth)acrylate.

5. The adhesive composition according to claim 1 or 2, The adhesive composition further comprises a reducing agent.

6. The adhesive composition according to claim 5, The adhesive composition is a two-part adhesive composition consisting of a first part and a second part that are mixed together immediately before use, An adhesive composition wherein the first part contains the radical polymerization initiator and the second part contains the reducing agent.

7. The adhesive composition according to any one of claims 1 to 6. An adhesive composition having a nitrile rubber content of 0% by mass or more and 0.1% by mass or less.

8. The adhesive composition according to any one of claims 1 to 7, The adhesive composition further comprises a stable radical type compound having a stable radical.

9. 9. The adhesive composition according to claim 8, An adhesive composition wherein the stable radical is a nitroxide radical.

10. The adhesive composition according to claim 8 or 9, The adhesive composition wherein the stable radical compound comprises at least one compound selected from the group consisting of 1-oxyl-2,2,6,6-tetramethylpiperidine, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, and 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine 1-oxyl.

11. The adhesive composition according to any one of claims 8 to 10, The adhesive composition has a stable radical compound content of 0.001 parts by mass or more and 0.5 parts by mass or less relative to 100 parts by mass of the polymerizable monomer.

12. The adhesive composition according to any one of claims 1 to 11, An adhesive composition in which no corrosion of the silver thin film is observed in a corrosion test performed according to the following procedure. [procedure] (1) The adhesive composition is cured for 24 hours in an environment of a temperature of 23°C and a relative humidity of 50% to prepare a cured sample. (2) The obtained cured sample is processed into a size of 10 mm x 10 mm, placed on pure silver foil, placed in a 150 mL porcelain crucible, and heated at 260°C for 30 minutes in an air atmosphere. (3) After heating, observe whether there is any corrosion on the pure silver foil.

13. a first structural member; a second structural member; and A bonded body comprising a cured product of the adhesive composition according to any one of claims 1 to 12, which bonds the first structural member and the second structural member.

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