Method for producing joined body

Abstract

A joined body 10 is produced by using, as an adhesive composition 14, a photocurable adhesive composition that contains a 2-cyanoacrylate compound, a group-8 transition metal metallocene compound, and a photoradical generator, and that has a viscosity of 40-5,000 mPa·s as measured at 25°C by an E-type viscometer, and using a production method comprising: a formation step for forming a state in which the adhesive composition 14 is disposed along a boundary portion 15 between a first adherend 11 and a second adherend 12 with the first adherend 11 and the second adherend 12 attached together by the adhesive composition 14 at an attachment portion 13 between the first adherend 11 and the second adherend 12; and a curing step for curing the adhesive composition 14 disposed along the boundary portion 15 by irradiation with actinic radiation.

Description

Manufacturing method of the bonded body

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Japanese Patent Application No. 2023-141254, filed on August 31, 2023, the entire contents of which are incorporated herein by reference. The present disclosure relates to a method for manufacturing a conjugate.

[0002] Cyanoacrylate instant adhesives are one-component, solvent-free adhesives that cure when exposed to moisture in the air or on the surface of a substrate (moisture-curing properties) and cure instantly even at room temperature. Because of these characteristics, cyanoacrylate instant adhesives are widely used as industrial and general-purpose adhesives (see, for example, Patent Document 1).

[0003] In recent years, photocurable adhesive compositions have been proposed that combine the property of being cured by light irradiation with the conventional moisture-curable adhesive composition (see, for example, Patent Document 2). Patent Document 2 discloses a photocurable adhesive composition containing a photoinitiator system selected from a ferrocene compound and an acylgermane compound, a cyanoacrylate compound, and an acid stabilizer compound selected from Lewis acids.

[0004] JP 2022-101160 A International Publication No. 2017 / 021785

[0005] When bonding adherends together using a typical cyanoacrylate-based instant adhesive containing only a 2-cyanoacrylate compound, the adhesive composition instantly cures due to moisture in the air or on the substrate surface, allowing for rapid bonding of the two materials. On the other hand, the adhesive composition that spills out laterally from the bonded joint cures slowly and contributes little to improving adhesive strength. Therefore, when bonding adherends together using a cyanoacrylate-based instant adhesive, it is necessary to ensure that the adhesive strength is sufficient at the contact points between the adherends. In such cases, if the contact area between the adherends is small, there is concern that the adhesive strength will be insufficient, resulting in poor load-bearing capacity.

[0006] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a method for producing a joined body that can produce a joined body having excellent load-bearing capacity in a simple manner.

[0007] According to the present disclosure, the following method for producing a bonded body is provided.

[0008] [1] A method for producing a bonded body in which a first adherend and a second adherend are bonded with a photocurable adhesive composition, the photocurable adhesive composition containing a 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound, and a photoradical generator, and having a viscosity of 40 mPa·s or more and 5,000 mPa·s or less as measured at 25°C with an E-type viscometer, the method comprising: forming a state in which the photocurable adhesive composition is arranged along the boundary between the first adherend and the second adherend at a bonding portion between the first adherend and the second adherend, where the first adherend and the second adherend are bonded with the photocurable adhesive composition; and curing a cured body by irradiating the photocurable adhesive composition arranged along the boundary with active energy rays. [2] The method for manufacturing a joined body according to [1] above, wherein the forming step includes a first application step of applying the photocurable adhesive composition to an area of ​​at least one of the first adherend and the second adherend corresponding to the bonded portion, a bonding step of bonding the first adherend and the second adherend together after the photocurable adhesive composition has been applied to the area, and a second application step of applying the photocurable adhesive composition along the boundary after bonding the first adherend and the second adherend together. [3] The method for manufacturing a joined body according to [1] above or [2] above, wherein the viscosity of the photocurable adhesive composition measured at 25°C with an E-type viscometer is 100 mPa s or more and 3,000 mPa s or less. [4] The method for producing a bonded body according to any one of [1] to [3] above, wherein at least one of the first adherend and the second adherend is a substrate having a transmittance of less than 50% at the emission line wavelength of a light source emitting the active energy rays. [5] The method for producing a bonded body according to [4] above, wherein at least one of the first adherend and the second adherend is a resin substrate. [6] The method for producing a bonded body according to any one of [1] to [5] above, wherein at least one of the first adherend and the second adherend is a metal substrate.

[0009] According to the manufacturing method of the present disclosure, a bonded body having excellent load-bearing capacity can be obtained by a simple method.

[0010] FIG. 1 is a schematic diagram of a bonded body. FIG. 2A is a diagram showing the process of producing a bonded body, and is a diagram showing a first application step. FIG. 2B is a diagram showing the process of producing a bonded body, and is a diagram showing a bonding step. FIG. 2C is a diagram showing the process of producing a bonded body, and is a diagram showing a second application step. FIG. 2D is a diagram showing the process of producing a bonded body, and is a diagram showing a curing step. FIG. 2E is a diagram showing the process of producing a bonded body, and is a diagram showing an example of a bonded body obtained by this production method. FIG. 3 is a diagram showing how a photocurable adhesive composition is applied to a boundary portion. FIG. 4 is a diagram showing bonded bodies obtained in Examples 3 and 4. FIG. 5 is a diagram showing a method for an adhesion test.

[0011] Matters related to the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification, a numerical range indicated by "to" includes the numerical values ​​before and after the range as upper and lower limits. The term "process" includes not only an independent process but also the implementation of a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0012] The present disclosure relates to a manufacturing method for bonding a first adherend and a second adherend with a photocurable adhesive composition to obtain a bonded structure, and to a bonded structure obtained by the method. The manufacturing method of the present disclosure (hereinafter also referred to as the "present manufacturing method") includes the following forming and curing steps. Forming step: A state in which the photocurable adhesive composition is arranged along the boundary between the first adherend and the second adherend at the bonded portion of the first adherend and the second adherend, where the first adherend and the second adherend are bonded with the photocurable adhesive composition, is formed. Curing step: The photocurable adhesive composition arranged along the boundary between the first adherend and the second adherend is irradiated with active energy rays to be cured.

[0013] An example of a bonded structure obtained by this manufacturing method is shown in Fig. 1. The bonded structure 10 in Fig. 1 is formed by bonding a first adherend 11 and a second adherend 12 with a photocurable adhesive composition (adhesive composition 14). Fig. 1 shows the bonded structure 10 in which plate materials are used as the first adherend 11 and the second adherend 12, and one of the side surfaces 12A of the second adherend 12 is bonded to one plate surface 11A of the first adherend 11.

[0014] In this manufacturing method, in the forming step, at a bonding portion 13 formed by bonding a first adherend 11 and a second adherend 12 together, the first adherend 11 and the second adherend 12 are bonded together with an adhesive composition 14, and in this bonded state, the adhesive composition 14 is arranged along a boundary portion 15 between the first adherend 11 and the second adherend 12. In the subsequent curing step, the adhesive composition 14 arranged along the boundary portion 15 is irradiated with active energy rays and cured. As a result, the first adherend 11 and the second adherend 12 are bonded together at the bonding portion 13, and a reinforcing material (fillet 16) made of a cured product of the adhesive composition 14 is formed at the boundary portion 15.

[0015] The adhesive composition used in this production method is a photocurable composition containing a 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound, and a photoradical generator. The 2-cyanoacrylate compound in the adhesive composition reacts with moisture in the air or on the substrate surface to instantly cure and exhibit adhesive properties. Therefore, simply by placing a small amount of the photocurable adhesive composition in the contact area between the first and second adherends (i.e., the bonding area), the contact surfaces of the two adherends can be instantly and firmly bonded together, even at room temperature.

[0016] Furthermore, the photocurable adhesive composition used in this manufacturing method contains, in addition to the 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound and a photoradical generator. This allows the curing reaction of the 2-cyanoacrylate compound to be accelerated by irradiation with active energy rays, resulting in high curability. Therefore, by disposing the photocurable adhesive composition along the boundary between the first and second adherends bonded at the bonding portion, and then irradiating the photocurable adhesive composition disposed at the boundary with active energy rays to cure it, a reinforcing material made of a cured product can be formed at the boundary (reference numeral 15 in FIG. 1 ) between the first and second adherends bonded at the bonding portion.

[0017] Furthermore, the photocurable adhesive composition used in this manufacturing method has a moderately high viscosity of 40 mPa·s or more and 5,000 mPa·s or less, allowing the photocurable adhesive composition to be applied thickly to the interface between the first and second adherends bonded at the bonding portion while suppressing dripping, clumping, and spreading of the photocurable adhesive composition. Thus, according to this manufacturing method, in which the photocurable adhesive composition applied to the interface between the first and second adherends is cured, when bonding the first and second adherends to obtain a bonded structure, a bonded structure with excellent load-bearing capacity can be easily obtained using a single adhesive composition. Furthermore, the photocurable adhesive composition can also form a transparent cured product, which is less noticeable and visually pleasing.

[0018] <Adherend> The material, size, and shape of the adherends (first adherend, second adherend) are not particularly limited. Furthermore, the uses of the first adherend, the second adherend, and the bonded structure obtained by bonding the first adherend and the second adherend are also not particularly limited. Examples of adherends include substrates formed from resin, metal, ceramic, rubber, glass, wood, cloth, porcelain, leather, or a combination of two or more of these. The adherend may further contain a reinforcing material such as carbon fiber or glass fiber, a colorant, or the like. The materials of the first adherend and the second adherend may be the same or different. A photocurable adhesive composition (hereinafter simply referred to as "adhesive composition") containing a 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound, and a photoradical generator can exhibit high adhesive performance when adhering adherends made of the above materials together.

[0019] Examples of resins that may be used to form the adherend include vinyl chloride resins (polyvinyl chloride, ethylene-vinyl chloride copolymer, polyvinylidene chloride, etc.), polyvinyl acetate resin, polyurethane resin, polystyrene resin, AS resin (acrylonitrile-styrene copolymer), ABS resin (acrylonitrile-butadiene-styrene copolymer), AXS resin (styrene copolymer of a rubber component other than acrylonitrile-butadiene), acrylic resin, polymethyl methacrylate resin, polyester resin, polyamide resin, polybutylene terephthalate resin, polycarbonate resin, polyphenylene sulfide (PPS) resin, and polyether ether ketone (PEEK) resin.

[0020] Examples of metals include copper, aluminum, iron, gold, silver, titanium, nickel, zinc, tin, alloy steel (stainless steel, manganese steel, nickel steel, etc.), and composites of two or more of these.

[0021] This manufacturing method is preferably applied as a method for bonding adherends when at least one of the first and second adherends is a substrate that is impermeable or poorly permeable to the actinic energy rays used to cure the photocurable adhesive composition (hereinafter also referred to as a "non-transparent substrate"). Here, when bonding the first and second adherends together using an adhesive composition containing only a 2-cyanoacrylate compound (a typical instant adhesive), the adhesive composition instantly cures due to moisture in the air or on the substrate surface, enabling the two to be bonded together. However, the adhesive composition that spills out to the sides of the bonded area cures slowly, and measures such as wiping off the spilled adhesive composition are usually taken. In such cases, the first and second adherends are substantially bonded only in the area where they contact each other (i.e., the bonded area), and if the area of ​​the bonded area is small, the adhesive strength is insufficient.

[0022] Furthermore, when a first adherend and a second adherend are joined using a general photocurable adhesive composition that does not have the ability to bond instantly, if the adherends are formed from a non-transparent substrate, the adhesive composition may not cure at the bonded portion because the active energy rays do not or do not easily penetrate the adherends. In such cases, the first adherend and the second adherend cannot be bonded, or even if they are bonded, the adhesive strength may be insufficient.

[0023] In contrast, the present production method uses a photocurable adhesive composition containing a 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound, and a photoradical generator. Therefore, even if at least one of the first and second adherends is a non-transparent substrate, the first and second adherends can be firmly and instantly bonded together at their adhesive surfaces. Furthermore, the photocurable adhesive composition disposed at the interface between the first and second adherends can be rapidly cured by irradiating the interface with active energy rays from outside the first and second adherends. Therefore, according to the present production method, even if at least one of the first and second adherends is a non-transparent substrate, the first and second adherends can be bonded together with high adhesive strength and exhibit excellent load-bearing capacity.

[0024] Specifically, with regard to the transparency of the non-transparent substrate, in this manufacturing method, even a substrate having a transmittance (hereinafter simply referred to as "transmittance") of less than 50% at the emission line wavelength of a light source emitting active energy rays can be preferably used as an adherend. Here, "light source emitting active energy rays" refers to a light source used when curing a photocurable adhesive composition by irradiation with active energy rays. The transmittance of the non-transparent substrate may be 40% or less, 30% or less, or 20% or less. Both the first adherend and the second adherend may be non-transparent substrates. In this specification, the transmittance of the substrate is a value measured using an ultraviolet-visible spectrophotometer.

[0025] <Forming Step> Next, the forming step in this manufacturing method will be described with reference to the drawings as appropriate. The method for forming the state in which the adhesive composition 14 is disposed along the boundary 15 is not particularly limited. The forming step preferably includes the following first application step, bonding step, and second application step, because it allows the first adherend 11 and the second adherend 12 to be bonded instantly at the bonding portion 13 with high adhesive strength, and allows an appropriate amount of adhesive composition 14 to be disposed at the boundary 15 while enhancing the reinforcing effect. First application step: The adhesive composition 14 is applied to the bonded region 17 of at least one of the first adherend 11 and the second adherend 12. Bonding step: After applying the adhesive composition 14 to the bonded region 17, the first adherend 11 and the second adherend 12 are bonded together. Second application step: After bonding the first adherend 11 and the second adherend 12 together, the adhesive composition 14 is applied along the boundary 15. Each step will be described below.

[0026] (First Application Step) The area to which the adhesive composition 14 is applied may be the portion where the first adherend 11 and the second adherend 12 are in contact with each other and bonded together (i.e., the bonded area 17). The bonded area 17 is an area corresponding to the bonded portion 13 of at least one of the first adherend 11 and the second adherend 12. In Figures 1 and 2A to 2E, a portion of the plate surface 11A of the first adherend 11 is the bonded area 17A of the first adherend 11, and the side surface 12A of the second adherend 12 is the bonded area 17B of the second adherend 12. Figure 2A shows the case where the adhesive composition 14 is applied to the side surface 12A, which is the bonded area 17B of the second adherend 12.

[0027] The method for applying the adhesive composition 14 to the bonded region 17 is not particularly limited. For example, various methods can be used, such as dropping the adhesive composition 14 onto the bonded region 17 or applying the adhesive composition 14 to the bonded region 17 in the form of lines, strips, or dots. The adhesive composition 14 may be applied to the entire surface of the bonded region 17, or may be applied locally. The amount of adhesive composition 14 to be applied is not particularly limited, but it is preferable to use an appropriately small amount in order to instantly develop high adhesive strength. The adhesive composition 14 containing a 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound, and a photoradical generator can develop sufficiently high adhesive strength with a small amount. A specific application amount is typically 1 to 10 mg / cm. ２ and preferably 2 to 8 mg / cm ２ is.

[0028] (Bonding Process) Next, the bonded region 17A of the first adherend 11 and the bonded region 17B of the second adherend 12 are bonded together (see FIGS. 2A and 2B ). This instantly bonds the first adherend 11 and the second adherend 12. After the first adherend 11 and the second adherend 12 are bonded together, pressure may be applied continuously for a time sufficient for moisture curing of the adhesive composition 14 to begin (for example, several seconds to 1-2 minutes), thereby stabilizing the bonded state between the first adherend 11 and the second adherend 12.

[0029] (Second Application Step) Next, the adhesive composition 14 is applied from the outside of the adherend along the boundary 15 (see FIGS. 2C and 3). This results in the boundary 15 being covered with the adhesive composition 14. When applying the adhesive composition 14 along the boundary 15, it may be applied over the entire area of ​​the boundary 15 (i.e., the entire circumference of the bonded portion 13). Alternatively, the adhesive composition 14 may be applied to a portion of the boundary 15 (i.e., a portion of the entire circumference of the bonded portion 13). In order to more strongly reinforce the connection between the first adherend 11 and the second adherend 12 and obtain a bonded body 10 with superior load-bearing properties, it is preferable to apply the adhesive composition 14 to more than half of the boundary 15, and it is preferable to apply the adhesive composition 14 over almost the entire area of ​​the boundary 15. Furthermore, in order to improve the appearance after curing, the adhesive composition 14 applied along the boundary 15 may be smoothed with a round-tipped stick or the like to adjust the shape of the adhesive composition 14 before curing.

[0030] In addition to the above, methods for forming the state in which the adhesive composition 14 is disposed along the boundary 15 may include, for example, applying a relatively large amount of adhesive composition 14 to at least one of the bonded regions 17A and 17B when bonding the first adherend 11 and the second adherend 12 with the adhesive composition 14, and then pressing one of the first adherend 11 and the second adherend 12 against the other to bond them together, thereby causing the adhesive composition 14 to protrude laterally from the bonded portion 13. In other words, the adhesive composition 14 protruding from the bonded portion 13 forms a state in which the adhesive composition 14 is disposed along the boundary 15. In this case, the second application step can be omitted when producing the bonded body 10. In this method, it is also preferable to smooth the adhesive composition 14 protruding laterally from the bonded portion 13 with a round-tipped stick or the like to adjust the thickness and shape.

[0031] <Curing Step> Next, the adhesive composition 14 arranged along the boundary portion 15 is irradiated with active energy rays (see FIG. 2D ). Examples of active energy rays include ultraviolet rays, visible light, and electron beams. Of these, ultraviolet rays or visible light are preferred, and ultraviolet rays or visible light with a wavelength of 300 to 550 nm are more preferred. The irradiation energy can be set appropriately depending on the type of active energy rays, the formulation of the adhesive composition 14, and the like.

[0032] The light source of the active energy rays is not particularly limited, and examples thereof include ultraviolet light-emitting diodes (UV-LEDs), high-pressure mercury lamps, halogen lamps, xenon lamps, and deuterium lamps. ２ More than 20 mJ / cm is preferable. ２ or more, and 50 mJ / cm ２ The upper limit of the cumulative light amount is set to 500 mJ / cm from the viewpoint of reducing energy. ２ Preferably, 300 mJ / cm or less ２ The following is more preferable: The illuminance and irradiation time of the active energy rays may be appropriately set so that the cumulative amount of light reaches a desired amount.

[0033] Through the above steps, a bonded body 10 can be obtained in which the first adherend 11 and the second adherend 12 are bonded together at the bonding portion 13 with the adhesive composition 14, and a fillet 16 formed from a cured product of the adhesive composition 14 is provided at the boundary portion 15 (see Figure 2E).

[0034] <Photocurable adhesive composition> Next, the photocurable adhesive composition used in the present production method will be described. The photocurable adhesive composition is a liquid composition containing a 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound, and a photoradical generator.

[0035] (2-Cyanoacrylate Compound) Examples of the 2-cyanoacrylate compound to be incorporated into the photocurable adhesive composition include compounds represented by the following formula (1): CH ２ =C(CN)-COOR １ ...(1) (In formula (1), R １represents a saturated or unsaturated linear hydrocarbon group having 1 to 20 carbon atoms which may have a halogen atom or an ether bond, a saturated or unsaturated branched hydrocarbon group having 3 to 20 carbon atoms which may have a halogen atom or an ether bond, a saturated or unsaturated alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a halogen atom or an ether bond, or an aromatic hydrocarbon group having 5 to 20 carbon atoms which may have a halogen atom or an ether bond, provided that R １ When contains an ether linkage, either or both of the hydrocarbon residue chains linked by the ether linkage have from 5 to 20 carbon atoms.

[0036] Specific examples of 2-cyanoacrylate compounds include those in which the hydrogen atom in the carboxyl group of 2-cyanoacrylic acid is replaced with a methyl group, an ethyl group, a chloroethyl group, an n-propyl group, an i-propyl group, an allyl group, a propargyl group, an n-butyl group, an i-butyl group, an n-pentyl group, an n-hexyl group, an amyl group, a 2-methyl-3-butenyl group, a 3-methyl-3-butenyl group, a 2-pentenyl group, a 6-chlorohexyl group, a cyclohexyl group, a phenyl group, a tetrahydrofurfuryl group, a 2-hexenyl group, a 4-methylpentenyl group, a 3-methyl-2-cyclohexenyl group, a norbornyl group, a heptyl group, a cyclohexanemethyl group, a cycloheptyl group, a 1-methylcyclohexyl group, a 2-methylcyclohexyl group, a 3-methyl-cyclohexyl group, a 2-ethylhexyl group, an n-octyl group, a 2-octyl group, a cyclooctyl group, a cyclopenten ... and ester compounds in which each of the alkyl groups is substituted with a methyl group, a 2,3-dimethylcyclohexyl group, an n-nonyl group, an isononyl group, an oxononyl group, an n-decyl group, an isodecyl group, an n-dodecyl group, a 2-methoxyethyl group, a 2-ethoxyethyl group, a 2-ethoxy-2-ethoxyethyl group, a butoxyethoxyethyl group, a 1-(2-methoxy-1-methylethoxy)propyl group, a 2,2,2-trifluoroethyl group, a hexafluoroisopropyl group, a lauryl group, an isotridecyl group, a myristyl group, a cetyl group, a stearyl group, an oleyl group, a behenyl group, a hexyldecyl group, an octyldodecyl group, a benzyl group, a chlorophenyl group, a 2-pentyloxyethyl group, a 2-hexyloxyethyl group, a 2-cyclohexyloxyethyl group, a 2-(2-ethylhexyloxy)ethyl group, or a 2-phenoxyethyl group.

[0037] Among the above-mentioned 2-cyanoacrylate compounds, preferred are ester compounds in which the hydrogen atom in the carboxyl group of 2-cyanoacrylic acid is replaced with a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a cyclohexyl group, a phenyl group, a tetrahydrofurfuryl group, a 2-ethylhexyl group, an n-octyl group, a 2-octyl group, a 2-methoxyethyl group, a 2-ethoxyethylethyl group, or a 1-(2-methoxy-1-methylethoxy)propyl group. The photocurable adhesive composition may contain one type of 2-cyanoacrylate compound alone, or two or more types.

[0038] In the photocurable adhesive composition, the content of the 2-cyanoacrylate compound is preferably 40 mass % or more, and more preferably 60 mass % or more, relative to the total amount of the photocurable adhesive composition, from the viewpoints of curability, curing speed, and strength of the cured product.

[0039] (Group 8 Transition Metal Metallocene Compound) The Group 8 transition metal metallocene compound is not particularly limited as long as it is a metallocene compound containing a Group 8 transition metal element of the periodic table. It is believed that when an active energy ray is irradiated onto a photocurable adhesive composition containing a 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound, and a photoradical generator, radicals generated by the photoradical generator attack the Group 8 transition metal metallocene compound to generate anions, thereby accelerating the anionic polymerization of the 2-cyanoacrylate compound. Based on this mechanism, the Group 8 transition metal metallocene compound is also referred to as a "synergist" hereinafter.

[0040] Examples of Group 8 transition metal metallocene compounds include ferrocene compounds in which the transition metal is iron, osmocene compounds in which the transition metal is osmium, ruthenocene compounds in which the transition metal is ruthenium, and cobaltocene compounds in which the transition metal is cobalt.

[0041] Specific examples of the Group 8 transition metal metallocene compound include ferrocene, ethylferrocene, n-butylferrocene, benzoylferrocene, acetylferrocene, t-amylferrocene, 1,1'-dimethylferrocene, 1,1'-di-n-butylferrocene, 1,1'-dibenzoylferrocene, 1,1'-di(acetylcyclopentadienyl)iron, bis(pentamethylcyclopentadienyl)iron, bis(cyclopentadienyl)osmium, bis(pentamethylcyclopentadienyl)osmium, ruthenocene (bis(cyclopentadienyl)ruthenium), bis(pentamethylcyclopentadienyl)ruthenium, etc. Furthermore, as the Group 8 transition metal metallocene compound, a transition metal metallocene compound of Group 8 of the periodic table having an aromatic electron system ligand, as described in JP-A-2003-277422, can also be preferably used.

[0042] From the viewpoint of curability and storage stability, the Group 8 transition metal metallocene compound incorporated into the photocurable adhesive composition is preferably a ferrocene compound or a ruthenocene compound, and more preferably a ferrocene compound.

[0043] From the viewpoints of curability, curing speed, cost-effectiveness, and storage stability, the Group 8 transition metal metallocene compound is preferably at least one selected from the group consisting of ferrocene, ethylferrocene, n-butylferrocene, benzoylferrocene, and ruthenocene, and more preferably at least one selected from the group consisting of ferrocene, benzoylferrocene, and ruthenocene. The photocurable adhesive composition may contain one or more Group 8 transition metal metallocene compounds.

[0044] From the viewpoints of curability and storage stability, the content of the Group 8 transition metal metallocene compound in the photocurable adhesive composition is preferably 0.0001 mass% or more, more preferably 0.001 mass% or more, and even more preferably 0.0015 mass% or more, relative to the total amount of the photocurable adhesive composition. The upper limit of the content of the Group 8 transition metal metallocene compound is preferably 5 mass% or less, more preferably 1 mass% or less, and even more preferably 0.2 mass% or less.

[0045] (Photoradical Generator) Examples of photoradical generators contained in the photocurable adhesive composition include acylgermane compounds, acylphosphine oxide compounds, alkylphenone compounds, acetophenone compounds, benzoin compounds, etc. From the viewpoints of the curability, curing speed, and storage stability of the photocurable adhesive composition, the photoradical generator is preferably at least one selected from the group consisting of acylgermane compounds and acylphosphine oxide compounds, and from the viewpoint of storage stability, an acylgermane compound is more preferred.

[0046] The acylgermane compound is preferably at least one selected from the group consisting of monoacylgermane compounds and bisacylgermane compounds, with bisacylgermane compounds being more preferred.

[0047] Specific examples of the acylgermane compound include dibenzoyldiethylgermanium, bis(4-methoxybenzoyl)dimethylgermanium, bis(4-methoxybenzoyl)diethylgermanium, ferrocenylacylgermanium, benzoyldimethylgermanium, bis(4-methylbenzoyl)diethylgermanium, bis(4-methylbenzoyl)dimethylgermanium, and dibenzoyldibutylgermanium.

[0048] As the acylphosphine oxide compound, at least one selected from the group consisting of monoacylphosphine oxide compounds and bisacylphosphine oxide compounds can be preferably used, and among these, monoacylphosphine oxide compounds are more preferred.

[0049] Preferred examples of the monoacylphosphine oxide compound include compounds represented by the following formula (A-1).

[0050] (In formula (A-1), R Ａ１ and R Ａ２each independently represents an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a phenyl group, or a phenyl group substituted with 1 to 3 alkyl groups having 1 to 8 carbon atoms or alkoxy groups having 1 to 8 carbon atoms; R Ａ３ represents an unsubstituted or acetyloxy-substituted linear or branched alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms; an unsubstituted aryl group; an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an aryl group substituted with a halogen atom; or a group represented by the following formula (A-2):

[0051] (In formula (A-2), R Ａ４ and R Ａ５ each independently represents an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a phenyl group, or a phenyl group substituted with 1 to 3 alkyl groups having 1 to 8 carbon atoms or alkoxy groups having 1 to 8 carbon atoms; X Ａ１ represents a p-phenylene group.

[0052] Specific examples of the monoacylphosphine oxide compound include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, methyl isobutyroylmethylphosphinate, methyl isobutyroylphenylphosphinate, methyl pivaloylphosphinate, methyl-2-ethylhexanoylphosphinate, isopropyl-2-ethylhexanoylphenylphosphonate, methyl-p-tolylphenylphosphinate, methyl-o-tolyl-phenylphosphinate, methyl-2,4-dimethylbenzoylphosphinate, Examples of the diphenylphosphine oxide include benzoylphenylphosphine oxide, methyl acryloylphenylphosphine oxide, methyl acyloylphenylphosphonate, isobutyroyldiphenylphosphine oxide, 2-methylhexanoyldiphenylphosphine oxide, o-toluyldiphenylphosphine oxide, p-t-butylbenzoyldiphenylphosphine oxide, 3-polyzylcarbonyldiphenylphosphine oxide, acryloyldiphenylphosphine oxide, benzoyldiphenylphosphine oxide, and adiboylbis(diphenylphosphine oxide).

[0053] A preferred example of the bisacylphosphine oxide compound is a compound represented by the following formula (A-3).

[0054] (R in formula (A-3) ｐ are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkylthio group having 1 to 8 carbon atoms, or a halogen atom, and each R ｐ may be the same or different.)

[0055] R in formula (A-3) ｐ The alkyl group having 1 to 12 carbon atoms in formula (A-3) may be linear or branched, and examples thereof include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl. The alkyl group having 1 to 12 carbon atoms preferably has 1 to 6 carbon atoms, and more preferably has 1 to 4 carbon atoms. R in formula (A-3) ｐ The alkylthio group having 1 to 8 carbon atoms in the formula (I) may be linear or branched, and examples thereof include a methylthio group, an ethylthio group, a propylthio group, an isopropylthio group, a butylthio group, a tert-butylthio group, a hexylthio group, and an octylthio group. Of these, a methylthio group is preferred. Examples of halogen atoms include a chlorine atom, a bromine atom, and an iodine atom. Of these, a chlorine atom is preferred.

[0056] Specific examples of the bisacylphosphine oxide compound include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and the like.

[0057] Examples of the acetophenone compound include 4-phenoxydichloroacetophenone, 4-t-butyldichloroacetophenone, 4-t-butyltrichloroacetophenone, and diethoxyacetophenone.

[0058] Examples of the benzoin compound include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl methyl ketal, etc. The photocurable adhesive composition may contain one type of photoradical generator alone or two or more types.

[0059] From the viewpoints of the curability, curing rate, and storage stability of the photocurable adhesive composition, the content of the photoradical generator in the photocurable adhesive composition is preferably 0.01 to 5 mass %, more preferably 0.02 to 2 mass %, and even more preferably 0.05 to 1 mass %, relative to the total amount of the photocurable adhesive composition.

[0060] In the photocurable adhesive composition, the mass ratio of the photoradical initiator to the Group 8 transition metal metallocene compound (photoradical initiator / Group 8 transition metal metallocene compound) is preferably 10 to 1,000, more preferably 15 to 500, and even more preferably 15 to 90.

[0061] (Other Components) The photocurable adhesive composition may further contain a component (hereinafter also referred to as "other component") that is different from any of the 2-cyanoacrylate compound, the Group 8 transition metal metallocene compound, and the photoradical generator. Examples of other components include a thickener, an organic thixotropic agent, and silica.

[0062] Thickener The photocurable adhesive composition may be blended with a thickener for the purpose of adjusting the viscosity of the photocurable adhesive composition. As the thickener, compounds known as viscosity-imparting additives can be appropriately used.

[0063] Specific examples of thickeners include polymethyl methacrylate, copolymers of methyl methacrylate and acrylic esters, copolymers of methyl methacrylate and methacrylic esters other than methyl methacrylate, acrylic rubber, polyvinyl chloride, polystyrene, cellulose esters, polyalkyl-2-cyanoacrylates, ethylene-vinyl acetate copolymers, vinyl chloride-vinyl acetate copolymers, (meth)acrylic ester-butadiene-styrene copolymers, vinyl chloride-acrylonitrile copolymers, ethylene-vinyl acetate copolymers, lactic acid-caprolactone copolymers, cellulose acetate, cellulose acetate propionate, polyvinyl acetate, polyvinylpyrrolidone, etc. The photocurable adhesive composition may contain one type of thickener alone, or two or more types.

[0064] When a thickener is blended into the photocurable adhesive composition, the amount of the thickener is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more, based on the total amount of the photocurable adhesive composition, from the viewpoint of appropriately increasing the viscosity of the photocurable adhesive composition. Furthermore, from the viewpoint of suppressing a decrease in the curability of the photocurable adhesive composition due to an excessive amount of thickener, the content of the thickener is preferably 30% by mass or less, more preferably 25% by mass or less, based on the total amount of the photocurable adhesive composition.

[0065] Organic thixotropic agents are optionally blended in order to adjust the flow behavior of the photocurable adhesive composition. Examples of organic thixotropic agents include hydrogenated castor oil, amine-modified hydrogenated castor oil, and polyamides. In the case of amine-modified hydrogenated castor oil, the amine compound used to modify the hydrogenated castor oil is preferably an aliphatic diamine. Specific examples of aliphatic diamines include 1,2-ethylenediamine, 1,3-propanediamine, and 1,6-hexanediamine.

[0066] When an organic thixotropic agent is blended into the photocurable adhesive composition, the content of the organic thixotropic agent is, for example, 2 to 10 mass % relative to the total amount of the photocurable adhesive composition.

[0067] Silica Silica is an inorganic thixotropic agent that is optionally added to the photocurable adhesive composition to adjust its flow behavior. Examples of silica include hydrophobic fumed silica, precipitated silica, or a combination thereof. When silica is added to the photocurable adhesive composition, the content of silica is, for example, 1 to 10 mass % relative to the total amount of the photocurable adhesive composition.

[0068] In addition to the above, other components include, for example, stabilizers, plasticizers, anionic polymerization accelerators, inorganic fillers, colorants, fragrances, solvents, strength improvers, etc. The contents of these components can be appropriately set depending on the application of the photocurable adhesive composition, etc., within a range that does not impair the effects of the present disclosure.

[0069] (Viscosity) The viscosity of the photocurable adhesive composition used in this manufacturing method is 40 mPa·s or more and 5,000 mPa·s or less. If the viscosity is less than 40 mPa·s, the photocurable adhesive composition tends to flow on the surface of the adherend, which may prevent the photocurable adhesive composition from being placed along the boundary between the first and second adherends when they are bonded together, or the photocurable adhesive composition may spread and not achieve a sufficient thickness. In this case, the effect of reinforcing the connection between the first and second adherends in the bonded structure by placing a cured product of the photocurable adhesive composition at the boundary cannot be fully achieved. Furthermore, if the viscosity exceeds 5,000 mPa·s, it becomes difficult to properly adjust the thickness of the photocurable adhesive composition at the boundary, which may result in a decrease in adhesive strength or a long curing time.

[0070] From the above viewpoints, the viscosity of the photocurable adhesive composition is preferably 70 mPa·s or more, more preferably 100 mPa·s or more, even more preferably 120 mPa·s or more, even more preferably 150 mPa·s or more, and even more preferably 200 mPa·s or more. Furthermore, the viscosity of the photocurable adhesive composition is preferably 4,000 mPa·s or less, more preferably 3,500 mPa·s or less, and even more preferably 3,000 mPa·s or less. In this specification, the viscosity of the photocurable adhesive composition is a value measured at 25°C using an E-type viscometer (cone-plate viscometer).

[0071] The preferred range of viscosity of the photocurable adhesive composition can be set by appropriately combining the above lower and upper limits. The viscosity range of the photocurable adhesive composition is preferably 70 to 4,000 mPa·s, more preferably 100 to 3,500 mPa·s, even more preferably 100 to 3,000 mPa·s, and even more preferably 200 to 3,000 mPa·s. The viscosity of the photocurable adhesive composition can be adjusted to the above range by appropriately adjusting the type and content of the thickener, organic thixotropic agent, and silica.

[0072] According to the manufacturing method described above, a photocurable adhesive composition is applied along the boundary between a first and second adherends bonded at a bonding site. The photocurable adhesive composition covering the boundary between the first and second adherends is then irradiated with active energy rays to cure the composition. This allows a cured product of the photocurable adhesive composition to be provided as a reinforcing material at the boundary between the first and second adherends bonded at the bonding site. This allows a bonded structure with excellent load-bearing capacity to be obtained in a simple manner. This manufacturing method can be applied to the production and repair of, for example, shelves, metal racks, boxes, plastic models, miniatures, accessories, etc., thereby improving the workability, accuracy, and quality of the production and repair work. This manufacturing method is particularly suitable for use when the adherends are substrates with a small bonding area, such as thin rods or thin plates.

[0073] The present disclosure will be specifically described below based on examples. However, the present disclosure is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0074] The viscosity of the adhesive composition was measured using an E-type viscometer (cone-plate type viscometer) under the following conditions: (Measurement conditions) Apparatus: TVE-20H type viscometer (salt water / plate type, manufactured by Toki Sangyo Co., Ltd.) Cone shape: angle 1°34', radius 24 mm Temperature: 25°C ± 0.5°C

[0075] 1. Preparation of Adhesive Composition (Preparation Example 1) 84.9 parts by mass of ethyl-2-cyanoacrylate as a 2-cyanoacrylate compound, ferrocene (FeCp ２ 0.02 parts by mass of bis(4-methoxybenzoyl)diethylgermanium (a compound represented by the following formula) as a photoradical generator, 0.08 parts by mass of bis(4-methoxybenzoyl)diethylgermanium (a compound represented by the following formula) as a photoradical generator, and 15 parts by mass of polymethyl methacrylate (weight average molecular weight 120,000) as a thickener were mixed to prepare adhesive composition (B-1). The viscosity of adhesive composition (B-1) was measured at 25°C using an E-type viscometer (cone-plate type viscometer) and was found to be 300 mPa s.

[0076]

[0077] (Preparation Examples 2 to 5 and Comparative Preparation Examples 1 and 2) Adhesive compositions (B-2) to (B-7) were prepared in the same manner as in Preparation Example 1, except that the formulation of the adhesive composition was changed as shown in Table 1 below. In addition, the viscosity of each of the prepared adhesive compositions was measured in the same manner as in Preparation Example 1. The measurement results are shown in Table 1.

[0078]

[0079] In Table 1, the abbreviations are as follows: PMMA: polymethyl methacrylate INA: bis(4-methoxybenzoyl)diethylgermanium

[0080] 2. Production and Evaluation of Bonded Structure (Example 1) Two ABS plates (size: 25 mm × 50 mm, thickness: 2 mm) were prepared as adherends (first adherend, second adherend). The transmittance of the ABS plates at the emission wavelength (405 nm) of the LED lamp used to cure the adhesive composition was measured using an ultraviolet-visible spectrophotometer and found to be less than 1%. A small amount of adhesive composition (B-1) was applied to the short side of one of the two ABS plates. The surface of the ABS plate coated with adhesive composition (B-1) (i.e., the bonded area) was attached to the surface of the other ABS plate so that the two ABS plates formed a T-shape, and the two ABS plates were then supported by hand for approximately 60 seconds until moisture curing began. Thereafter, a thin layer of adhesive composition (B-1) was applied along the boundary between the two ABS plates after lamination, and the applied adhesive composition (B-1) was irradiated with light from an LED light (wavelength 405 nm) for 10 seconds to cure, resulting in a bonded structure. The bonded structure was then aged for at least 24 hours to allow complete moisture cure of the joint between the two ABS plates, before being subjected to an adhesion test. Two aluminum plates (5052P plates, size: 25 mm x 50 mm, thickness: 2 mm) were prepared as adherends, and after degreasing with ethanol, a bonded structure was produced in the same manner as when using ABS plates. The bonded structure was then aged for at least 24 hours before being subjected to an adhesion test.

[0081] (Examples 2 to 5 and Comparative Examples 1 and 2) Bonded bodies were prepared in the same manner as in Example 1, except that the adhesive compositions shown in Table 2 were used instead of adhesive composition (B-1), and adhesion tests were performed. Figure 4 shows the bonded bodies (adherend: aluminum plate) prepared in Examples 3 and 4. The bonded body of Example 3 is shown on the left, and the bonded body of Example 4 is shown on the right. In Figure 4, the area surrounded by an ellipse is the area where the adhesive composition was applied to the boundary between the adherends after they were bonded together, and then cured by light irradiation.

[0082] Details of the adhesion test are as follows. <Adhesion Test (Load-bearing Capacity Evaluation)> As shown in Figure 5, of the two ABS plates constituting the bonded structure, the lower part of the ABS plate arranged so as to extend vertically was gripped and fixed with a jig 21, and then the upper surface of the ABS plate not gripped by the jig 21 was pressed downward (in the direction of the arrow in Figure 5) at a position 10 mm away from the joint between the two ABS plates, and the adhesion strength was evaluated under the following measurement conditions. A bonded structure produced using an aluminum plate instead of an ABS plate was also evaluated in the same way. The results are shown in Table 2. In Table 2, "AL plate" refers to an aluminum plate. (Measurement Conditions) Apparatus: Autograph AGS-X (Shimadzu Corporation) Test mode: Compression Test speed: 10 mm / min The adhesion strength was evaluated by compressing the bonded area by 2 x 25 = 50 mm. ２ It was calculated as:

[0083]

[0084] As shown in Table 2, in the ABS plate / ABS plate bonding, Examples 1 to 5 had adhesive strengths 1.5 times or more higher than Comparative Examples 1 and 2. Furthermore, Comparative Examples 1 and 2 exhibited interfacial failure, whereas Examples 1 to 5 exhibited substrate failure. It is believed that the high adhesive strength was achieved by forming a fillet with the adhesive composition at the boundary (connection) between the two ABS plates joined in a T-shape. Furthermore, the transparent fillet was less noticeable, providing a visually pleasing result.

[0085] Furthermore, in the case of AL plate / AL plate bonding, Example 1 had adhesive strength that was two times higher than Comparative Examples 1 and 2, Example 2 had adhesive strength that was six times higher than Comparative Examples 1 and 2, and Examples 3 to 5 had adhesive strength that was eight times higher than Comparative Examples 1 and 2. It is believed that the adhesive strength of the AL plate / AL plate was also increased by forming a fillet at the boundary between the two aluminum plates joined in a T-shape.

[0086] The present invention is not limited to the above-described embodiments, and encompasses various modifications and equivalent modifications within the scope of the spirit of the present invention. Therefore, in light of the above teachings, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are to be understood as falling within the scope and spirit of the present invention.

[0087] REFERENCE SIGNS LIST 10...bonded body, 11...first adherend, 12...second adherend, 13...bonded portion, 14...adhesive composition, 15...boundary portion, 16...fillet (reinforcement material), 17...adhered region, 21...jig

Claims

1. A method for producing a bonded body in which a first adherend and a second adherend are bonded with a photocurable adhesive composition, the photocurable adhesive composition containing a 2-cyanoacrylate compound, a Group 8 transition metal metallocene compound, and a photoradical generator, and having a viscosity of 40 mPa·s to 5,000 mPa·s as measured at 25°C with an E-type viscometer, the method comprising: a forming step of forming a state in which the photocurable adhesive composition is arranged along the boundary between the first adherend and the second adherend at a bonding portion between the first adherend and the second adherend, where the first adherend and the second adherend are bonded with the photocurable adhesive composition; and a curing step of irradiating the photocurable adhesive composition arranged along the boundary with active energy rays to cure it.

2. A method for producing a joint as described in claim 1, wherein the forming step includes: a first application step of applying the photocurable adhesive composition to an area corresponding to the bonded portion in at least one of the first adherend and the second adherend; a bonding step of bonding the first adherend and the second adherend together after applying the photocurable adhesive composition to the area; and a second application step of applying the photocurable adhesive composition along the boundary portion after bonding the first adherend and the second adherend together.

3. The method for producing a joint body according to claim 1 or 2, wherein the viscosity of the photocurable adhesive composition measured at 25°C with an E-type viscometer is 100 mPa·s or more and 3,000 mPa·s or less.

4. A method for producing a bonded body as described in claim 1 or 2, wherein at least one of the first adherend and the second adherend is a substrate having a transmittance of less than 50% at the emission line wavelength of a light source that emits the active energy rays.

5. The method for producing a bonded body according to claim 4, wherein at least one of the first adherend and the second adherend is a resin substrate.

6. The method for producing a bonded body according to claim 1 or 2, wherein at least one of the first adherend and the second adherend is a metal substrate.

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