Adhesive composition, bonded structure, and method for manufacturing the adhesive composition

Abstract

To provide an adhesive composition that offers good storage stability and high adhesion strength.SOLUTION: There is provided an adhesive composition including: a polymerizable monomer having a (meth)acryloyl group; a radical polymerization initiator; and a polymer particle having the property of being swollen by an organic solvent. In a particle size distribution of secondary particles, which are aggregates of the polymer particles, in the adhesive composition, as determined by the laser diffraction-scattering technique, the proportion of secondary particles with a diameter of 1 μm or more and 200 μm or less is 30 vol.% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition, a bonded structure, and a method for producing the adhesive composition. [Background technology]

[0002] Well-known adhesive compositions include epoxy adhesives, acrylic adhesives, and urethane adhesives. Among these, acrylic adhesives are generally superior in terms of oily surface adhesion and ease of application.

[0003] As an example of an acrylic adhesive, Patent Document 1 can be cited. Patent Document 1 describes an acrylic adhesive composition containing (1) a (meth)acrylic acid derivative monomer, (2) a polymerization initiator, (3) a reducing agent, and (4) a diene-based core-shell polymer. In this composition, the diene-based core-shell polymer is an MBS resin (methyl methacrylate-acrylonitrile-butadiene-styrene copolymer) that is swollen in the (meth)acrylic acid derivative monomer and has a swelling degree of 9.5 or higher in toluene at 25°C. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 4707320 [Overview of the project] [Problems that the invention aims to solve]

[0005] As a result of their research, the inventors have completed an adhesive composition that shows improvement over the adhesive composition described in Patent Document 1 in terms of storage stability. Specifically, the present invention has completed an adhesive composition that can obtain the desired adhesive strength even after a period of time has elapsed since manufacturing. [Means for solving the problem]

[0006] The inventors have completed the invention described below.

[0007] According to the present invention, A polymerizable monomer having a (meth)acryloyl group, Radical polymerization initiator, An adhesive composition comprising polymer particles having the property of swelling in an organic solvent, An adhesive composition in which, as determined by laser diffraction and scattering, the particle size distribution of secondary particles which are aggregates of polymer particles in the adhesive composition, shows that the proportion of secondary particles with a diameter of 1 μm or more and 200 μm or less is 30% by volume or more. It will be provided.

[0008] Furthermore, according to the present invention, The first structural member and The second structural member, A joint comprising a cured body of the adhesive composition described above, which joins the first structural member and the second structural member. It will be provided.

[0009] Furthermore, according to the present invention, A method for producing the above-mentioned adhesive composition, The process includes a dispersion step in which polymer particles are added to a container containing the polymerizable monomer and stirred to disperse the polymer particles in the polymerizable monomer. The temperature of the polymerizable monomer at the time of addition is 0°C or higher and 40°C or lower, in the method for producing an adhesive composition. It will be provided. [Effects of the Invention]

[0010] The present invention provides an adhesive composition that exhibits good storage stability and high adhesive strength. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below.

[0012] In this specification, the notation "X to Y" in the description of a numerical range represents X or more and Y or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less". In this specification, it is preferable that the amount used represents the amount with respect to the total of the first agent and the second agent.

[0013] In the notation of a group (atomic group) in this specification, a notation that does not indicate whether it is substituted or unsubstituted includes both those having no substituent and those having a substituent. For example, the "alkyl group" includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group). The notation "(meth)acryl" in this specification represents a concept that includes both acryl and methacryl. The same applies to similar notations such as "(meth)acrylate". In this specification, the term "organic group" means, unless otherwise specified, an atomic group obtained by removing one or more hydrogen atoms from an organic compound. For example, a "monovalent organic group" represents an atomic group obtained by removing one hydrogen atom from an arbitrary organic compound.

[0014] <Adhesive composition> The adhesive composition of this embodiment includes a polymerizable monomer having a (meth)acryloyl group, a radical polymerization initiator, and polymer particles having the property of swelling in an organic solvent. In the particle size distribution of secondary particles, which are aggregates of the above polymer particles, in the adhesive composition of this embodiment determined by the laser diffraction / scattering method, the ratio of secondary particles having a diameter of 1 μm or more and 200 μm or less is 30% by volume or more, preferably 40% by volume or more, more preferably 50% by volume or more. This value may be 100% by volume or may be 99.5% by volume or less.

[0015] The present inventors have conducted various studies to improve the storage stability of the adhesive composition. As described above, the present inventors have set the ratio of secondary particles having a diameter of 1 μm or more and 200 μm or less to 30% by volume or more in the particle size distribution of the secondary particles which are aggregates of polymer particles. Thereby, it was possible to provide an adhesive composition having good storage stability and high adhesive strength.

[0016] The method for producing the adhesive composition of the present embodiment is not limited, but from the viewpoint of appropriately controlling the particle size distribution of the secondary particles which are aggregates of polymer particles, it is preferable to adopt an appropriate production method and production conditions. As points of the production method and production conditions, for example, it is possible to appropriately control the temperature at the time of mixing the polymerizable monomer and the polymer particles, the stirring speed (peripheral stirring speed) at the time of mixing, and the like. Details of the production method and production conditions will be described later.

[0017] Hereinafter, the components that the adhesive composition of the present embodiment can contain, the physical properties of the adhesive composition of the present embodiment, and other matters related to the adhesive composition of the present embodiment will be continued to be described.

[0018] (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 simply referred to as "polymerizable monomer".

[0019] Specific examples of the polymerizable monomer include the following. (i) General formula Z-O-R1 The monomer represented by. In the general formula, Z represents a (meth)acryloyl group, a CH2=CHCOOCH2CH2- group, a CH2=C(CH3)COOCH2-CH2CH2- group, a CH2=CHCOOCH2-CH(OH)- group, a CH2=C(CH3)COOCH2-CH(OH)- group, a CH2=CHCOOCH2-CH(OH)CH2- group, or a CH2=C(CH3)COOCH2-CH(OH)CH2- group, and R1 represents hydrogen, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, a benzyl group, a phenyl group, a tetrahydrofurfuryl group, a glycidyl group, a dicyclopentyl group, a dicyclopentenyl group, a (meth)acryloyl group, and an isobornyl group.

[0020] Examples of such monomers include methyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, glycerol (meth)acrylate, glycerol di(meth)acrylate, isobornyl (meth)acrylate, and (meth)acrylic acid.

[0021] (ii) General formula ZO-(R2O) p -R1 A monomer represented by [this symbol]. In the general formula, Z and R1 are as described above. R2 is -C2H4-, -C3H6-, -CH2CH(CH3)-, -C4H8-, or -C6H 12 - indicates a negative sign, and p represents an integer between 1 and 25 (inclusive).

[0022] Examples of such monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, ethoxyethyl (meth)acrylate, polyethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate.

[0023] (iii) General formula [ka] A monomer represented by [this symbol]. In the general formula, Z and R2 are as described above. R3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and q represents an integer between 0 and 8. Z, R2, R3, and q may be the same or different.

[0024] Examples of such monomers include 2,2-bis(4-(meth)acryloxyphenyl)propane, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypropoxyphenyl)propane, and 2,2-bis(4-(meth)acryloxytetraethoxyphenyl)propane, and ethoxylated bisphenol A di(meth)acrylate.

[0025] (iv) (meth)acrylic acid esters of polyhydric alcohols not included in (i), (ii), or (iii) above.

[0026] Examples of such monomers include trimethylolpropane tri(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate and dipentaerythritol hexa(meth)acrylate, tripropylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate.

[0027] (v) Urethane prepolymer having (meth)acryloyloxy groups. Such monomers can be obtained, for example, by reacting (meth)acrylic acid esters having hydroxyl groups, organic polyisocyanates, and polyhydric alcohols.

[0028] Examples of (meth)acrylic acid esters having a hydroxyl group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[0029] Examples of organic polyisocyanates include toluene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Examples of polyhydric alcohols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyester polyols.

[0030] (vi) Acidic phosphoric acid compounds represented by general formula (I).

[0031] [ka]

[0032] In the above general formula, R is CH2=CR4CO(OR5) m -group (where R4 is hydrogen or methyl group, and R5 is -C2H4-, -C3H6-, -CH2CH(CH3)-, -C4H8-, -C6H 12 -or-C2H4-OCO-C5H 10 - indicates that m is an integer between 1 and 10 (inclusive). ) indicates that n is an integer of 1 or 2.

[0033] Examples of acidic phosphoric acid compounds represented by general formula (I) include acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, bis(2-(meth)acryloyloxyethyl) phosphate, and 2-(meth)acryloyloxyethyl acid phosphate.

[0034] Particularly preferred polymerizable monomers (monofunctional and polyfunctional) are as follows: Monofunctional Methyl (meth)acrylate, ethylhexyl (meth)acrylate, lauryl (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and (meth)acrylic acid ·Multifunctional Ethylene oxide-modified di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, and ethoxylated pentaerythritol tetra(meth)acrylate

[0035] The adhesive composition of this embodiment may contain only one of the monomers (i) to (vi), or it may contain two or more. Among these, one or two or more of (i), (ii), and (vi) are preferred in terms of high adhesiveness and low adhesive distortion of the adherend after bonding, and a combination of (i), (ii), and (vi) is more preferred. When (i) and (ii) are used in combination, the composition ratio is preferably (i):(ii) = 50-95:5-50 by mass ratio, and more preferably 60-80:20-40. When (vi) is used, the amount used is preferably 0.05 parts by mass or more and 10 parts by mass or less, and more preferably 0.1 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the total of (i) and (ii).

[0036] (Radical polymerization initiator) The adhesive composition of this embodiment contains a radical polymerization initiator. The radical polymerization initiator polymerizes the polymerizable carbon-carbon double bond of the polymerizable monomer, enabling adhesion of articles.

[0037] As a radical polymerization initiator, a thermal radical polymerization initiator is preferred. Organic peroxides are preferred as thermal radical polymerization initiators. Examples of organic peroxides include cumene hydroperoxide, paramentane hydroperoxide, tert-butyl hydroperoxide, diisopropylbenzene dihydroperoxide, methyl ethyl ketone peroxide, tert-butyl peroxybenzoate, and benzoyl peroxide. Among these, cumene hydroperoxide is preferred in terms of stability. Incidentally, by using a radical polymerization initiator in combination with a reducing agent (described later), it is possible to further enhance curability or achieve room-temperature curing.

[0038] The amount of radical polymerization initiator is preferably 0.1 parts by mass to 20 parts by mass, and more preferably 0.4 parts by mass 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 speed can be made sufficiently fast. On the other hand, by not using too much radical polymerization initiator, storage stability can be further improved.

[0039] (Polymer particles) The adhesive composition of this embodiment contains polymer particles that swell when exposed to an organic solvent. "Swelling when exposed to an organic solvent" means that when the polymer particles come into contact with a liquid such as an organic solvent, the polymer particles absorb the liquid and swell. Specifically, the degree of swelling is preferably 5 times or more, more preferably 7 times or more, even more preferably 9.5 times or more, and particularly preferably 10 times or more. The upper limit of the degree of swelling is, for example, 15 times.

[0040] The degree of swelling can be measured as described in paragraph 0049 of the aforementioned Patent Document 1. Specifically, 1 g of the sample is left to stand in 100 mL of toluene at 25°C for 24 hours, and then the gel that has swollen in toluene is filtered through a 100-mesh wire mesh (mass A). After 1 minute, the mass B of the swollen gel and wire mesh is measured, and after air-drying at room temperature overnight, vacuum drying is performed, and the mass C of the dried gel and wire mesh is measured. The degree of swelling can then be calculated using the formula: degree of swelling (times) = (BA) / (CA).

[0041] Because the polymer particles are swellable, polymerizable monomers can enter the polymer particles, causing polymerization to occur within the polymer particles, which is expected to further increase adhesive strength and other properties. In this specification, polymer particles that swell when exposed to organic solvents are also simply referred to as "polymer particles."

[0042] For the sake of clarity, unless otherwise specified, the numerical values ​​relating to various particle sizes and particle size distributions of polymer particles in this specification represent the numerical values ​​of polymer particles in the adhesive composition (such as the particle size in the swollen state if the polymer particles are swollen).

[0043] From one perspective, the polymer particles preferably include core-shell type polymer particles. Core-shell type polymer particles can be obtained by methods described in International Publication No. 2005 / 028546 and Japanese Patent Publication No. 2016-104834, etc. From another perspective, the polymer particles preferably include a diene polymer, and more preferably, the polymer constituting the polymer particles includes a (meth)acrylonitrile-butadiene-styrene copolymer and / or a methyl (meth)acrylate-(meth)acrylonitrile-butadiene-styrene copolymer.

[0044] The median diameter D of secondary particles can be determined from the particle size distribution of secondary particles. 50 Preferably, the particle size is 1 μm to 200 μm, more preferably 5 μm to 180 μm, and even more preferably 10 μm to 150 μm. The cumulative 90% diameter D of the secondary particles determined from the particle size distribution of the secondary particles 90 is preferably 10 μm or more and 500 μm or less, more preferably 20 μm or more and 400 μm or less, and even more preferably 30 μm or more and 300 μm or less. These numerical values define that relatively few coarse secondary particles exist from a different perspective from the ratio of the secondary particles having a diameter of 1 μm or more and 200 μm or less described above. By adjusting these numerical values, the performance of the adhesive composition can be further enhanced. The median diameter D of the secondary particles 50 and the cumulative 90% diameter D of the secondary particles 90 can be adjusted, for example, by appropriately controlling the temperature when mixing the polymerizable monomer and the polymer particles, the shear force during mixing, etc. The shear force can be adjusted by appropriately selecting, for example, the rotation speed of the stirring blade, the diameter of the stirring blade, and the stirring speed (stirring peripheral speed).

[0045] Incidentally, the volume average particle diameter of the "primary particles" of the polymer particles is preferably 0.01 μm or more and 1 μm or less, more preferably 0.02 μm or more and 0.8 μm or less, and even more preferably 0.03 μm or more and 0.6 μm or less. By appropriately selecting the volume average particle diameter of the primary particles, the performance of the adhesive composition can also be further enhanced. For example, the volume average particle diameter of the "primary particles" can be adjusted by performing a pulverization process and a sieving classification process after the pulverization process on the polymer particles. The volume average particle diameter of the "primary particles" can also be adjusted by using polymer particles having an appropriate particle size distribution.

[0046] Polymer particles that can be preferably used are available, for example, from Denka Co., Ltd. and Kaneka Corporation.

[0047] The amount of polymer particles is preferably 0.1 parts by mass to 30 parts by mass, and more preferably 1 part by mass to 20 parts by mass, per 100 parts by mass of polymerizable monomer. Using a moderately large amount of polymer particles can further enhance the toughness of the cured film. On the other hand, if the amount of polymer particles is not too large, a sufficient amount of polymerizable monomer and polymerization initiator can be used, which tends to further improve curability.

[0048] (Elastomer) The adhesive composition of this embodiment preferably contains one or more elastomers. Preferably, the elastomers exclude the aforementioned polymer particles. By using elastomers, the cured adhesive composition will have appropriate elasticity, for example, further improvement in toughness can be achieved.

[0049] Examples of elastomer components include (meth)acrylonitrile-butadiene-(meth)acrylic acid copolymers, (meth)acrylonitrile-butadiene-methyl(meth)acrylate copolymers, and styrene-based thermoplastic elastomers such as (meth)acrylonitrile-butadiene copolymers, styrene-butadiene copolymers, chlorosulfonated polyethylene, and styrene-polybutadiene-styrene synthetic rubber, as well as polybutadiene with (meth)acrylic-modified ends and urethane elastomers.

[0050] In particular, one or more selected from the group consisting of (meth)acrylonitrile-butadiene-(meth)acrylic acid copolymer and (meth)acrylonitrile-butadiene copolymer (NBR, etc.) are preferred in terms of solubility and adhesion.

[0051] When using an elastomer, the amount is preferably 5 to 40 parts by mass, and more preferably 10 to 30 parts by mass, in total with polymer particles, per 100 parts by mass of polymerizable monomer.

[0052] (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 enhanced, or room temperature curing can be achieved. The reducing agent can be any known reducing agent that reacts with the polymerization initiator to generate radicals. Preferably, the reducing agent is at least one selected from the group consisting of tertiary amines, thiourea derivatives, and transition metal salts, with transition metal salts being more preferred. Examples of thiourea derivatives include acetylthiourea and ethylenethiourea. Examples of transition metal salts include cobalt naphthenate, cobalt octoate, copper naphthenate, and vanadylacetylacetonate. Among the transition metal salts, vanadylacetylacetonate is preferred.

[0053] When a reducing agent is used, the amount used is preferably 0.01 parts by mass or more and 10 parts by mass or less per 100 parts by mass of polymerizable monomer, and more preferably 0.1 parts by mass or more and 5 parts by mass or less. Using 0.01 parts by mass or more results in a sufficiently fast curing rate, and using 10 parts by mass or less results in better storage stability.

[0054] (paraffin) The adhesive composition of this embodiment may contain paraffin. Specifically, various types of paraffin can be used to expedite the hardening of the parts exposed to air. Examples of paraffin include paraffin wax, microcrystalline wax, carnauba wax, beeswax, lanolin, whale wax, ceresin, and candelilla wax.

[0055] If the adhesive composition of this embodiment contains paraffin, it may contain only one type of paraffin, or it may contain two or more types of paraffin. When the adhesive composition of this embodiment contains paraffin, the amount is preferably 0.01 parts by mass or more and 3 parts by mass or less, and more preferably 0.5 parts by mass or more and 2 parts by mass or less, per 100 parts by mass of polymerizable monomer. By using a sufficiently large amount of paraffin, the effect of accelerating curing can be obtained to the fullest extent. On the other hand, by not using too much paraffin, it is possible to obtain sufficient adhesion while also obtaining the effect of accelerating curing.

[0056] (Other ingredients) The adhesive composition of this embodiment may or may not contain any other optional components. As an example, the adhesive composition of this embodiment may contain spacers (particles) or the like to adjust the film thickness during use. The spacers are typically spherical particles made of resin such as polyolefin.

[0057] 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 polymerization inhibitors like phenothiazine, and (iv) stable radical-type compounds having stable radicals. Among these, it is desirable to use stable radical-type compounds in order to improve storage stability without impairing the performance as an adhesive (tensile shear adhesive strength and storage modulus).

[0058] Nitroxide radicals are preferred as stable radicals. Specific examples of stable radical compounds that are nitroxide radicals 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 using stable radical compounds, it is preferable to use one or more of these.

[0059] When using stabilizers such as stable radical compounds, the content thereof should be, in order to improve storage stability without impairing the performance as an adhesive, for example, 0.001 parts by mass or more and 1 part by mass or less, preferably 0.001 parts by mass or more and 0.5 parts by mass or less, more preferably 0.01 parts by mass or more and 0.3 parts by mass or less, and even more preferably 0.02 parts by mass or more and 0.1 parts by mass or less, per 100 parts by mass of polymerizable monomer.

[0060] ( 1 Dosage form / 2 Dosage form) The adhesive composition of this embodiment is so 1 It can be a dosage form, 2 It may also be a dosage form (an adhesive composition in which two components, filled in separate containers, are mixed immediately before use). 2 In the case of dosage forms, preferably the radical polymerization initiator is 1 The agent contains a reducing agent. 2 Each is contained in the agent. However, tertiary amines are tertiary amines. 1 It is preferable that the agent be included, and thiourea derivatives and transition metal salts are preferred. 2 It is preferable that it be included in the agent. Other ingredients may be included as appropriate. 2 It can be mixed with the agent. Immediately before use, 1 Agent and 2 It is sufficient to mix the agent with the other agent before use. Incidentally, the adhesive composition of this embodiment is 2 If it is a dosage form, 1 Agent and 2 The adhesive composition after mixing the agents contains each component within the range of preferred content of each component described above. 1 Agents and the 2 It is preferable to adjust the amount of each component in the preparation.

[0061] <Method for manufacturing adhesive composition> The method for producing the adhesive composition of this embodiment is not limited. However, from the viewpoint of appropriately controlling the particle size distribution of secondary particles, which are aggregates of polymer particles, it is preferable to adopt an appropriate manufacturing method and manufacturing conditions. Key points regarding the manufacturing method and manufacturing conditions include, for example, appropriately controlling the temperature when mixing the polymerizable monomer and polymer particles, and the stirring speed during mixing.

[0062] The method for producing the adhesive composition of this embodiment preferably includes a dispersion step in which polymer particles are added to a container containing polymerizable monomers and stirred to disperse the polymer particles in the polymerizable monomers. In this dispersion step, the temperature of the polymerizable monomers in the container when the polymer particles are added is preferably 0°C to 40°C, more preferably 15°C to 35°C. When polymer particles are added, the polymerizable monomer is at a temperature of 0°C or higher, which allows the polymer particles to disperse more easily in a shorter time. Furthermore, by keeping the temperature of the polymerizable monomer below 40°C during addition, it becomes less likely for polymer particles to clump together (aggregates, granular powder), making it easier to obtain a good polymer dispersion state.

[0063] The dispersion step preferably involves mixing the polymerizable monomer and polymer particles using a stirring blade. To ensure sufficient and uniform dispersion of the polymer particles within the polymerizable monomer, the stirring peripheral speed of the stirring blade is preferably 300 mm / s or higher, more preferably 500 mm / s or higher. There is no particular upper limit to the stirring peripheral speed, but due to equipment limitations, it is, for example, 300,000 mm / s or lower.

[0064] <Applications of adhesive compositions / bonding bodies> By applying the adhesive composition of this embodiment to an article and curing it, a joint including a cured body of the adhesive composition can be obtained. Specifically, by using the adhesive composition of this embodiment, a joint can be obtained that includes a first structural member, a second structural member, and a cured body of the adhesive composition that joins the first structural member and the second structural member. The adhesive composition of this embodiment, especially when it contains a reducing agent, preferably cures without heating (at room temperature) and can bond articles. Of course, heating is not excluded when obtaining the bonded product.

[0065] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0066] Embodiments of the present invention will be described in detail based on examples and comparative examples. It should be noted that the present invention is not limited to these examples.

[0067] <Manufacturing of adhesive compositions> Agent A (Part 1) and Agent B (Part 2) for each example and comparative example were prepared as follows. (1) The monomers listed under "Polymerizable Monomers" in the table below (unit: parts by mass, the same applies to other components) and the NBR listed under "Elastomer" were placed in a temperature-controllable mixing container and stirred at 60°C for 1 hour using a stirring blade (anchor blade). (2) Polymer particles listed under "Polymer Particles" in the table below were added to the container. The temperature at which the polymer particles were added is shown in the table below. The mixture was then mixed for 1 hour using a stirring blade. The rotation speed, diameter, and peripheral speed of the stirring blade were as shown in the table. (3) The remaining ingredients were added to the container and stirred at room temperature for 24 hours to ensure thorough mixing.

[0068] In the table below, polymerizable monomers, radical polymerization initiators, reducing agents, and 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl were appropriately selected from those available on the market. Details of the polymer particles and elastomers are as follows: Product 1: Core-shell type particles, methyl methacrylate-acrylonitrile-butadiene-styrene copolymer, swelling degree measured as described in paragraph 0049 of Patent Document 1: 14.0 Product 2: Core-shell type particles, acrylonitrile-butadiene-styrene copolymer, swelling degree measured as described in paragraph 0049 of Patent Document 1: 10.1 NBR: JSR Corporation "230S" (Bound acrylonitrile content: 35%, Mooney viscosity: 56) The structure of ethoxylated bisphenol A dimethacrylate is as follows.

[0069] [ka]

[0070] <Measurement of particle size distribution of polymer particles in adhesive compositions> The measurement was performed using the following procedure. (1) Place 1 g of the adhesive composition into a 10 mL glass vial, and add 4 g of methyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd., >99.8%) thereto (methyl methacrylate was used to dilute the composition and facilitate the measurement of the particle size distribution). (2) The glass vial was closed and left to stand at 23°C for 24 hours without shaking. After standing, the supernatant was taken from the glass vial with a dropper, and the particle size distribution of the polymer particles contained in this supernatant was measured. The particle size distribution was measured in accordance with JIS Z 8825:2013 using a Shimadzu Corporation laser diffraction particle size distribution analyzer "SALD-2200", with a measurement temperature of 23°C and a measurement solvent of methyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd., >99.8%). (3) From the measurement results, the following was determined: • The proportion of secondary particles with a diameter of 1 μm or more and 200 μm or less in the particle size distribution of secondary particles. • Median diameter D of secondary particles 50 • Cumulative 90% diameter of secondary particles D 90

[0071] To clarify, generally, when measuring particle size distribution, ultrasonic dispersion or similar methods are often used to minimize secondary particles. However, in this case, in order to obtain information on particle size distribution that reflects the aggregation state of polymer particles in the adhesive composition, dispersion treatments such as ultrasonic dispersion were not performed, and only dilution treatment with methyl methacrylate was carried out.

[0072] <Measurement of particle size distribution of polymer particles themselves (primary particles)> The measurement was performed using the following procedure. (1) 0.1 g of polymer particles (product 1 or product 2) was placed in a 10 mL glass vial, 4.9 g of a 0.2% by mass aqueous solution of sodium hexametaphosphate was added, and the mixture was dispersed using ultrasound (130 W) for 10 minutes. (2) The particle size distribution of the polymer particles contained in this dispersion was measured. The particle size distribution was measured in accordance with JIS Z 8825:2013 using a Shimadzu Corporation laser diffraction particle size distribution analyzer "SALD-2200" at a measurement temperature of 23°C and using pure water as the measurement solvent. (3) Of the measurement results, the volume-average particle diameter of the primary polymer particles was used.

[0073] <Measurement and evaluation of viscosity> In accordance with JIS K 6838, the viscosity of each adhesive composition (component A and component B) was measured using a B-type viscometer at a rotor speed of 20 rpm, a measurement time of 2 minutes, and a measurement ambient temperature of 25°C (unit: mPa·s). This viscosity measurement value was designated as A1. Prior to measurement, each adhesive composition (component A and component B) was left to stand in a 25°C atmosphere for at least 24 hours to ensure the liquid temperature reached 25°C. Furthermore, 500g of each adhesive composition (component A and component B) was filled into 500mL polyethylene bottles and left to stand at 23°C for one week. The viscosity of components A and B after standing was then measured using the same method. This viscosity measurement was designated as A2. The viscosity retention rate A (%) was then calculated using the following formula. A(%) = (A2 / A1) × 100

[0074] Furthermore, the thixotropic index (TI) was also measured to assess viscosity. Specifically, the TI was calculated by A1' / A1 from the viscosity A1', which was measured in the same manner as A1, except that the value of A1 and the rotation speed were changed from 20 rpm to 2 rpm.

[0075] <Evaluation of adhesive toughness> The evaluation was conducted as follows, in accordance with JIS K 6854. The evaluation was carried out in an environment with a temperature of 23°C and a relative humidity of 50%. First, a mixture was prepared by mixing equal amounts of component A and component B of the adhesive composition for each example and comparative example. This mixture was quickly applied to one side of a test piece (200 mm × 25 mm × 1.6 mm, SECC steel plate). Immediately thereafter, the other test piece (200 mm × 25 mm × 0.5 mm, SECC steel plate) was placed on top and bonded together, then secured with clips. The pieces were then cured at room temperature for 24 hours. In this way, evaluation samples were obtained. The peel adhesion strength (peel strength, unit: kN / m) was measured using the obtained evaluation samples. The peel adhesion strength (unit: kN / m) was measured at a tensile speed of 50 mm / min under conditions of 23°C and 50% relative humidity. Three measurements were taken, and the average value was recorded as the peel strength in the table. The standard deviation of the three measurements is also recorded in the table. Furthermore, the results of observing the fracture state are also recorded in the table. For the fracture state, the area ratio of the fracture type was determined. Generally, strong adhesive strength is obtained when cohesive fracture occurs, so cohesive fracture is preferred as the fracture state.

[0076] The various pieces of information mentioned above are summarized in the table below. The units for the amounts of polymerizable monomers, polymer particles, elastomers, radical polymerization initiators, reducing agents, and other components are parts by mass.

[0077] [Table 1]

[0078] As shown in the table above, the viscosity retention rate A of adhesive compositions in which the proportion of secondary particles with a polymer particle diameter of 1 μm to 200 μm was 30% by volume or more was approximately 100%. In other words, the storage stability was good. Furthermore, by using an adhesive composition in which secondary polymer particles with a diameter of 1 μm to 200 μm account for 30% or more by volume, it was possible to strongly bond SECC steel plates together. In other words, high adhesive strength was achieved.

[0079] The inventors conducted various studies to improve the storage stability of adhesive compositions. Through these studies, it was estimated that in conventional adhesive compositions such as those described in Patent Document 1, polymer particles (such as diene-based core-shell polymers) in the composition excessively aggregate to form coarse secondary particles, which leads to a decrease in adhesive strength over time. Specifically, the adhesive composition described in Patent Document 1 has the problem that the desired adhesive strength may not be obtained as time passes after manufacturing, and it is preferable to use it as soon as possible after manufacturing. Based on this estimation, the inventors set the proportion of secondary particles with a diameter of 1 μm to 200 μm in the particle size distribution of secondary particles, which are aggregates of polymer particles, to be 30% by volume or more, as described above. As a result, it was possible to provide an adhesive composition that has good storage stability and high adhesive strength.

[0080] This specification primarily describes an "adhesive composition" comprising a polymerizable monomer having a (meth)acryloyl group, a radical polymerization initiator, and polymer particles having the property of swelling with an organic solvent, characterized by a particle size distribution of secondary particles which are aggregates of polymer particles. However, the adhesive composition described herein can also be used in fields other than adhesion, such as coatings and injection materials. In other words, the adhesive composition described herein can also be used as a composition with no limited applications, a curable composition, or a resin composition.

[0081] This application claims priority based on Japanese Patent Application No. 2021-059627, filed on 31 March 2021, and incorporates all of its disclosures herein.

Claims

1. A polymerizable monomer having a (meth)acryloyl group, Radical polymerization initiator, An adhesive composition comprising polymer particles having the property of swelling in an organic solvent, An adhesive composition in which, as determined by laser diffraction and scattering, the particle size distribution of secondary particles which are aggregates of polymer particles in the adhesive composition, the proportion of secondary particles with a diameter of 1 μm or more and 200 μm or less is 50% by volume or more. The polymer constituting the polymer particles includes a diene polymer. The degree of swelling of the polymer particles calculated by the method described below is 5 times or more and 15 times or less. The median diameter D 50 of the secondary particles, determined from the particle size distribution of the secondary particles, is 1 μm or more and 200 μm or less. The cumulative 90% diameter D 90 of the secondary particles, determined from the particle size distribution of the secondary particles, is 10 μm or more and 500 μm or less. The volume-average particle diameter of the primary particles of the polymer particles is 0.01 μm or more and 1 μm or less. If the adhesive composition is a two-component adhesive composition comprising a first component and a second component, the first component comprises the polymerizable monomer and the polymer particles, and the second component comprises the polymerizable monomer and the polymer particles, In the particle size distribution of secondary particles, which are aggregates of polymer particles, in the first agent as determined by laser diffraction and scattering, the proportion of secondary particles with a diameter of 1 μm or more and 200 μm or less is 50% by volume or more, and in the particle size distribution of secondary particles, which are aggregates of polymer particles, in the second agent as determined by laser diffraction and scattering, the proportion of secondary particles with a diameter of 1 μm or more and 200 μm or less is 50% by volume or more. The median diameter D 50 of the secondary particles determined from the particle size distribution of the secondary particles of the first agent is 1 μm or more and 200 μm or less, and the median diameter D 50 of the secondary particles determined from the particle size distribution of the secondary particles of the second agent is 1 μm or more and 200 μm or less, The cumulative 90% diameter D90 of the secondary particles determined from the particle size distribution of the secondary particles of the first agent is 10 μm or more and 500 μm or less, and the cumulative 90% diameter D90 of the secondary particles determined from the particle size distribution of the secondary particles of the second agent is 10 μm or more and 500 μm or less, An adhesive composition wherein the volume-average particle diameter of the primary polymer particles of the first agent is 0.01 μm or more and 1 μm or less, and the volume-average particle diameter of the primary polymer particles of the second agent is 0.01 μm or more and 1 μm or less. (method) At 25°C, 1 g of the polymer particles is left to stand in 100 mL of toluene for 24 hours, and then the gel that has swollen in toluene is filtered through a 100-mesh wire mesh (mass A). After 1 minute, the mass B of the swollen gel and wire mesh is measured. After air-drying at room temperature for 24 hours, vacuum drying is performed, and the mass C of the dried gel and wire mesh is measured. The degree of swelling is then calculated using the formula: Swelling degree (times) = (B - A) / (C - A).

2. The adhesive composition according to claim 1, The polymer constituting the polymer particles is an adhesive composition comprising a (meth)acrylonitrile-butadiene-styrene copolymer and / or a methyl (meth)acrylate-(meth)acrylonitrile-butadiene-styrene copolymer.

3. The adhesive composition according to claim 1 or 2, The polymer particles are an adhesive composition containing core-shell type polymer particles.

4. An adhesive composition according to any one of claims 1 to 3, Furthermore, an adhesive composition containing an elastomer.

5. An adhesive composition according to any one of claims 1 to 4, Furthermore, an adhesive composition containing a stable radical-type compound having a stable radical.

6. The adhesive composition according to claim 5, An adhesive composition in which the stable radical is a nitroxide radical.

7. The adhesive composition according to claim 5 or 6, The adhesive composition comprises at least one stable radical-type 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.

8. An adhesive composition according to any one of claims 5 to 7, An adhesive composition in which the content of the stable radical-type compound is 0.001 parts by mass or more and 0.5 parts by mass or less per 100 parts by mass of the polymerizable monomer.

9. An adhesive composition according to any one of claims 1 to 8, Furthermore, an adhesive composition containing a reducing agent.

10. The adhesive composition according to claim 9, The adhesive composition is a two-part adhesive composition comprising the first agent and the second agent, which are mixed immediately before use, wherein the first agent further contains the radical polymerization initiator and the second agent further contains the reducing agent.

11. The first structural member and The second structural member, A joint comprising a cured body of an adhesive composition according to any one of claims 1 to 10, which joins the first structural member and the second structural member.

12. A method for producing an adhesive composition according to any one of claims 1 to 10, The process includes a dispersion step in which polymer particles are added to a container containing the polymerizable monomer and stirred to disperse the polymer particles in the polymerizable monomer. A method for producing an adhesive composition, wherein the temperature of the polymerizable monomer at the time of addition is 0°C or higher and 40°C or lower.

13. A manufacturing method according to claim 12, The method for producing an adhesive composition, wherein the stirring is performed using a stirring blade at a stirring peripheral speed of 300 mm / s or more.

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