JP7757066B2 - Curable composition, sealant, and adhesive - Google Patents

Description

The present invention relates to a curable composition, a sealant, and a pressure-sensitive adhesive.

For example, curable compositions that can be cured by heating or by irradiation with active energy (e.g., light) are used in applications such as inks, paints, adhesives, sealants, precision parts for electrical and electronic applications, and shaped objects.

The properties required for materials used in these fields include durability and gas barrier properties, and one example of a resin that possesses these properties is polyisobutylene-based polymer.

For example, Patent Documents 1 and 2 disclose pressure-sensitive adhesive compositions containing a polyisobutylene polymer having 0.8 or more specific functional groups per molecule and a (meth)acrylate compound having a saturated cyclic hydrocarbon group or a linear or branched hydrocarbon group having 18 or more carbon atoms. Patent Document 3 discloses a curable composition containing a polyisobutylene polymer having a specific molecular weight and molecular weight distribution and 1.2 or more (meth)acryloyl groups per molecule, and a polyisobutylene polymer having a specific molecular weight and molecular weight distribution and 0.5 to 1.0 (meth)acryloyl groups per molecule. Patent Document 4 discloses a vinyl comb copolymer, which is a copolymer of a polyisobutylene macromonomer having at least 0.8 specific (meth)acryloyl groups per molecule at one end of the main chain, and a vinyl monomer. Patent Document 5 discloses an adhesive tape comprising a backing layer made of a specific copolymer and a pressure-sensitive adhesive layer made of a polyisobutylene polymer.

Japanese Patent Application Laid-Open No. 2019-157029 Japanese Patent Application Laid-Open No. 2019-157030 WO2018/155401 publication WO2018/168992 publication Special Publication No. 2012-528919

However, the above-mentioned conventional technologies were not sufficient in terms of achieving both durability and adhesiveness, and there was room for further improvement.

One embodiment of the present invention has been developed in consideration of the above-mentioned problems, and its purpose is to provide a novel curable composition that can provide a cured product that combines high adhesion and durability.

The inventors conducted extensive research to solve the above problems and have now completed the present invention.

That is, one embodiment of the present invention includes the following configuration.
[1] A curable composition comprising: a polyisobutylene polymer (A) having 0.5 to 1.0 (meth)acryloyl groups per molecule; a polyfunctional vinyl monomer (B); and a polymerization initiator (C).
[2] The curable composition according to [1], wherein the (meth)acryloyl group is a group represented by the following general formula (1):

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents a divalent saturated hydrocarbon group having 2 to 6 carbon atoms and containing no heteroatoms, and R ³ to R ⁶ each independently represent a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or an alkoxy group.)
[3] The curable composition according to [1] or [2], further comprising a monofunctional vinyl monomer (D).
[4] The curable composition according to [3], comprising 0.01 to 100 parts by weight of the polyfunctional vinyl monomer (B), 0.01 to 20.0 parts by weight of the polymerization initiator (C), and 0.1 to 1,000 parts by weight of the monofunctional vinyl monomer (D) relative to 100 parts by weight of the polyisobutylene polymer (A).
[5] The curable composition according to any one of [1] to [4], further comprising: (i) 20 parts by weight or less of a polyisobutylene polymer having more than 1.0 (meth)acryloyl group per molecule, based on 100 parts by weight of the polyisobutylene polymer (A); or (ii) no polyisobutylene polymer is contained.
[6] The curable composition according to any one of [1] to [5], wherein the polyfunctional vinyl monomer (B) is at least one selected from the group consisting of 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate.
[7] The curable composition according to any one of [1] to [6], wherein the polyisobutylene polymer (A) has 0.8 to 1.0 (meth)acryloyl groups per molecule.
[8] The curable composition according to any one of [1] to [7], wherein the polymerization initiator (C) is a photoradical polymerization initiator.
[9] A sealant obtained by curing the curable composition according to any one of [1] to [8].
[10] A pressure-sensitive adhesive obtained by curing the curable composition according to any one of [1] to [8].

One embodiment of the present invention has the effect of providing a curable composition that can produce a cured product that combines high adhesion and durability.

One embodiment of the present invention is described below, but the present invention is not limited to this. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by appropriately combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be created by combining the technical means disclosed in each embodiment. All academic and patent literature described in this specification is incorporated herein by reference. Furthermore, unless otherwise specified in this specification, the expression "A to B" representing a numerical range means "greater than or equal to A (including A and greater than A) and less than or equal to B (including B and less than B)."

1. Technical Concept of the Present Invention
[0003] A cured product obtained by curing a curable composition containing a polyisobutylene-based polymer as a main component has good gas barrier properties and flexibility, but due to the low polarity of the polyisobutylene-based polymer, sufficient adhesion to a substrate may not be obtained, leaving room for improvement. In addition, in recent years, the performance of electric and electronic components has improved, and high-precision equipment such as organic EL displays has become increasingly widespread. Therefore, there is a demand for a curable composition that can provide a cured product that combines good gas barrier properties and flexibility with higher durability and adhesion than conventional products.

In contrast, the technologies described in Patent Documents 1 to 5 above leave room for improvement, as described below. For example, Patent Documents 1 and 2 evaluate the adhesive properties of pressure-sensitive adhesive compositions, but do not consider improving durability.

Furthermore, Patent Documents 3 and 4 evaluate the ability of the curable composition to conform to deformation, but do not consider adhesion or durability, or the compatibility of these.

Furthermore, Patent Document 5 does not consider polyisobutylene polymers into which functional groups have been introduced. Furthermore, Patent Document 5 does not consider adhesion, durability, or achieving both.

As mentioned above, Patent Documents 1 to 5 do not address the compatibility of adhesiveness and durability, and there remains a need for curable compositions that can provide cured products that combine high durability and adhesiveness. Therefore, the present inventors investigated further improving the durability and adhesiveness of cured products primarily composed of polyisobutylene-based polymers that have good gas barrier properties and flexibility. Through extensive research, the present inventors surprisingly discovered the following new findings: (a) As the content of polyisobutylene-based polymers having 1.0 or less (meth)acryloyl groups per molecule increases in a polyisobutylene-based polymer, adhesiveness tends to increase while heat resistance and durability tend to decrease due to a decrease in crosslink density; and (b) As the content of polyisobutylene-based polymers having more than 1.0 (meth)acryloyl groups per molecule increases in a polyisobutylene-based polymer, durability tends to increase while adhesiveness tends to decrease. Based on this new finding, the inventors further investigated how to achieve both durability and adhesiveness, which are in a trade-off relationship. As a result, the inventors discovered that the above-mentioned problem can be solved by using a polyisobutylene polymer (A) having 0.5 to 1.0 (meth)acryloyl groups per molecule in combination with a multifunctional vinyl monomer (B), and thus completed the present invention.

[2. Curable composition]
A curable composition according to one embodiment of the present invention comprises a polyisobutylene polymer (A) having 0.5 to 1.0 (meth)acryloyl groups per molecule, a polyfunctional vinyl monomer (B), and a polymerization initiator (C).

In this specification, the "polyisobutylene polymer (A) having 0.5 to 1.0 (meth)acryloyl groups per molecule," the "polyfunctional vinyl monomer (B)," and the "polymerization initiator (C)" may be referred to as the "(A) component," the "(B) component," and the "(C) component," respectively. Furthermore, the "curable composition according to one embodiment of the present invention" may be referred to as the "curable composition."

Because the present curable composition has the above-described structure, it has the advantage of being able to provide a cured product that combines high adhesion and durability. Furthermore, the cured product obtained by curing the present curable composition (hereinafter also simply referred to as the "present cured product") also has the advantage of having good gas barrier properties and flexibility because it contains the polyisobutylene polymer (A).

In this specification, "excellent adhesiveness" means that an adhesive product comprising a curable composition or its cured product as an adhesive layer on a substrate has excellent adhesive strength when attached to an adherend. "Excellent durability" means that the cured product has a small compression set. "Excellent gas barrier properties" means that the cured product has a small moisture permeability. "Flexibility" is evaluated based on the tensile properties (tensile strength at break (Tb), tensile elongation at break (Eb), and 30% modulus (M30)) and hardness of the cured product. Adhesion, durability (compression set), moisture permeability, and each tensile property are evaluated using the methods described in the examples below.

Because this curable composition has the advantages described above, it can be particularly well suited for use as a sealant and adhesive for a variety of applications, including electrical and electronic components.

<Polyisobutylene Polymer (A)>
The present curable composition contains, as a curable resin, a polyisobutylene polymer (A) (component (A)) having 0.5 to 1.0 (meth)acryloyl groups per molecule. Component (A) in the present curable composition has a main chain made of a polyisobutylene polymer and an average of 0.5 to 1.0 (meth)acryloyl groups per molecule.

In this specification, a "polyisobutylene polymer having 0.5 to 1.0 (meth)acryloyl groups per molecule" refers to an aggregate of polyisobutylene polymer molecules having different numbers of (meth)acryloyl groups per molecule, where the average number of (meth)acryloyl groups per molecule is 0.5 to 1.0. This aggregate is an aggregate of polyisobutylene polymer molecules having no (meth)acryloyl groups (hereinafter also simply referred to as "non-functionalized polymer molecules") and polyisobutylene polymer molecules having one (meth)acryloyl group per molecule (e.g., at only one end of the main chain) (hereinafter also simply referred to as "monofunctionalized polymer molecules"), where more than half of all molecules in the aggregate are monofunctionalized polymer molecules. A "polyisobutylene polymer having 0.5 to 1.0 (meth)acryloyl groups per molecule" will hereinafter also be referred to simply as a "monofunctionalized polymer." Note that, as long as a monofunctionalized polymer has 0.5 to 1.0 (meth)acryloyl groups per molecule, it may also contain polyisobutylene polymer molecules (hereinafter also referred to simply as "polyfunctionalized polymer molecules") that are generated during the manufacturing process and have two or more (meth)acryloyl groups per molecule (e.g., at both ends of the main chain).

In contrast, a "polyisobutylene polymer having more than 1.0 (meth)acryloyl groups per molecule" is an aggregate of monofunctionalized polymer molecules and polyfunctionalized polymer molecules. Hereinafter, a "polyisobutylene polymer having more than 1.0 (meth)acryloyl groups per molecule" will also be referred to simply as a "polyfunctionalized polymer."

In this specification, the term "(meth)acryloyl group" refers to an acryloyl group and/or a methacryloyl group (either an acryloyl group or a methacryloyl group, or both). Furthermore, in this specification, the "main chain" of component (A) refers to the remaining portion of component (A) excluding the (meth)acryloyl group.

The number of (meth)acryloyl groups contained in one polyisobutylene polymer molecule is, on average, 0.5 to 1.0, more preferably 0.6 to 1.0, even more preferably 0.7 to 1.0, even more preferably 0.8 to 1.0, and particularly preferably 0.9 to 1.0. When the number of (meth)acryloyl groups contained in one polyisobutylene polymer molecule is within the above-mentioned range, the curable composition has the advantages of excellent productivity and rapid curing, and the cured product obtained by curing the curable composition exhibits desired physical properties. When the number of (meth)acryloyl groups contained in one polyisobutylene polymer molecule is less than 0.5 on average, the tackiness of the cured product decreases, and various physical properties (e.g., desired high level of adhesion) may not be achieved. When the number of (meth)acryloyl groups contained in one polyisobutylene polymer molecule is 0.5 or more, as the number of (meth)acryloyl groups increases, the tackiness of the cured product improves, and a desired level of high adhesiveness tends to be achieved. Furthermore, when the average number of (meth)acryloyl groups contained in one polyisobutylene polymer molecule is greater than 1.0, a trade-off exists between durability and adhesiveness depending on the ratio of monofunctionalized polymer molecules to polyfunctionalized polymer molecules, making it difficult to obtain a curable composition that exhibits an excellent balance between durability and adhesiveness.

The "number of (meth)acryloyl groups contained in one molecule of polyisobutylene polymer" can also be said to be the "number of (meth)acryloyl groups introduced per molecule of polyisobutylene polymer (or functionalization rate)."

The number of (meth)acryloyl groups contained in one molecule of a polyisobutylene polymer can be calculated by the following method: (i) performing ¹ H NMR measurement of the polyisobutylene polymer; (ii) using the results obtained, (ii-1) calculating the relative number (A) of polymer molecules present in the polyisobutylene polymer from the peak area (peak integral value) of protons attributed to groups derived from the polymerization initiator, and (ii-2) calculating the relative number (B) of (meth)acryloyl groups present in the polyisobutylene polymer from the peak area (peak integral value) of protons attributed to (meth)acryloyl groups; (iii) calculating the ratio (B/A) of the relative number (B) of (meth)acryloyl groups to the relative number (A) of polymer molecules, thereby determining the number (introduction number) of (meth)acryloyl groups contained in one molecule.

The polyisobutylene polymer that constitutes the main chain of component (A) may be (a) a homopolymer of isobutylene, (b) a block copolymer, random copolymer, or graft copolymer of isobutylene and a monomer other than isobutylene, or (c) a mixture of two or more of these.

When the polyisobutylene polymer constituting the main chain of component (A) is a copolymer containing structural units derived from a monomer other than isobutylene, the ratio of the structural units derived from isobutylene to the structural units derived from the monomer other than isobutylene is not particularly limited as long as it does not impair the effects of the present invention. When the main chain of component (A) is a copolymer, the content of structural units derived from isobutylene is preferably 50% by weight or more, and more preferably 60% by weight or more, in order to achieve excellent gas barrier properties and flexibility. A content of structural units derived from isobutylene of 50% by weight or more has the advantages of easily exhibiting good gas barrier properties and flexibility, and also easily achieving good vibration damping properties, adhesion, and mechanical properties.

Monomers other than isobutylene are not particularly limited as long as they are capable of cationic polymerization with isobutylene. Examples of monomers other than isobutylene include aliphatic olefins such as 1-butene; aromatic vinyls such as styrene, methylstyrene, and α-methylstyrene; dienes such as 1,3-butadiene and isoprene; vinyl ethers such as butyl vinyl ether; silanes such as vinyltrimethylsilane and allyltrimethylsilane; terpenes such as α-pinene, β-pinene, and limonene; vinylcarbazole; and acenaphthylene. These may be used alone or in combination of two or more. Among these, from the viewpoints of copolymerizability with isobutylene and the physical properties of the resulting copolymer, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, α-pinene, β-pinene, limonene, isoprene, 1-butene, and 1,3-butadiene are particularly preferred as monomers other than isobutylene.

The molecular weight of component (A) is not particularly limited, but from the standpoint of ease of handling of the curable composition and the physical properties of the cured product, the number average molecular weight is preferably 500 to 300,000, more preferably 1,000 to 300,000, even more preferably 2,000 to 200,000, and even more preferably 3,000 to 100,000. A number average molecular weight of component (A) of 500 or more has the advantages of (a) easily achieving sufficient strength in the cured product, (b) making the curable composition more likely to exhibit a suitable range of tackiness and providing good handleability, and (c) easily achieving the physical properties characteristic of polyisobutylene-based polymers (good gas barrier properties, flexibility, etc.). Furthermore, a number average molecular weight of component (A) of 300,000 or less has the advantage of easily achieving good fluidity and processability.

The molecular weight distribution of component (A) (the ratio of weight-average molecular weight Mw to number-average molecular weight Mn (Mw/Mn)) is preferably 1.00 to 2.00, and more preferably 1.10 to 1.80. A molecular weight distribution within this range has the advantages of (a) lowering the melt viscosity of the resin, which tends to improve handleability during molding and processing, and (b) making it easier to obtain good physical properties for the cured product.

In this specification, the number average molecular weight and weight average molecular weight are values calculated using size exclusion chromatography (SEC, also known as gel permeation chromatography (GPC)) in terms of polystyrene.

There are no particular limitations on the manner in which the (meth)acryloyl group of component (A) is bonded to the main chain, but examples include an ester bond, an ether bond, an amide bond, a urethane bond, a thioether bond, a carbonate bond, a urea bond, and a bond consisting of a divalent or higher hydrocarbon group that does not contain a heteroatom. Of these, ester bonds, ether bonds, amide bonds, and urethane bonds are preferred due to their ease of synthesis.

There are no particular restrictions on the bonding position of the (meth)acryloyl group in component (A), and it may be at the end of the main chain or on a side chain. For reasons of (a) ease of synthesis, (b) favorable physical properties as an elastomer material of the resulting cured product, (c) ease of control of the number of functional groups per polymer molecule, and (d) ease of industrially obtaining the raw materials, it is preferable that the (meth)acryloyl group in component (A) be bonded to the end of the main chain.

In a particularly preferred embodiment, component (A) preferably has 0.5 to 1.0 (meth)acryloyl groups per molecule at the end of the main chain, more preferably 0.6 to 1.0, even more preferably 0.7 to 1.0, even more preferably 0.8 to 1.0, and particularly preferably 0.9 to 1.0. This configuration can further improve the adhesion and durability of the cured product.

There are no particular restrictions on the structure of the (meth)acryloyl group in component (A), but from the standpoints of the physical properties of the cured product, availability of raw materials, and ease of production, a structure represented by the following general formula (1) is preferred.

In general formula (1), ^R1 represents a hydrogen atom or a methyl group. ^R2 represents a divalent saturated hydrocarbon group having 2 to 6 carbon atoms and containing no heteroatoms. ^R3 to ^R6 each independently represent a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or an alkoxy group. The wavy line represents the bonding point to the main chain.

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group. When R ¹ is a hydrogen atom, the general formula (1) becomes an acryloyl group, and when R ¹ is a methyl group, the general formula (1) becomes a methacryloyl group.

Depending on the combination with other components to be incorporated into the curable composition, either an acryloyl group or a methacryloyl group can be selected as the (meth)acryloyl group of component (A).

For example, when an acrylate-based monomer is added as component (B) to adjust the physical properties of the present curable composition or the resulting cured product, it may be preferable to select an acryloyl group in which R ¹ is a hydrogen atom as the (meth)acryloyl group in component (A). Furthermore, when a methacrylate-based monomer is added as component (B) for the purpose of improving the physical properties, such as the heat resistance, of the present curable composition or the resulting cured product, it may be preferable to select a methacryloyl group in which R ¹ is a methyl group as the (meth)acryloyl group in component (A). These selections have the advantage that the reactivities of component (A) and component (B) become similar, making it easier to obtain a cured product with a uniform structure.

Alternatively, when it is preferable that components (A) and (B) have different reactivities, when an acrylate monomer is added as component (B), a methacryloyl group in which R ^{1 is a methyl group may be selected as the (meth)acryloyl group of component (A). Similarly, when a methacrylate monomer is added as component (B), an acryloyl group in which R 1 is} a hydrogen atom may be selected as the (meth)acryloyl group of component (A).

In general formula (1), R ² is a divalent saturated hydrocarbon group having 2 to 6 carbon atoms and containing no heteroatoms. Specific examples of R ² include, for example, -CH ₂ CH 2 -, _-CH 2 CH ₂ CH ₂ -, -CH 2 CH ₂ CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ CH _{2 CH 2 -} , and -CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -. Of these, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, and -CH ₂ CH ₂ CH ₂ CH ₂ - are preferred from the viewpoints of availability of raw materials and reactivity.

In general formula (1), R ³ to R ⁶ are each independently a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or an alkoxy group. Specific examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, 2-ethylhexyl, nonyl, and decanyl. Specific examples of alkoxy groups include methoxy, ethoxy, propoxy, isopropoxy, and butoxy. Among these, from the standpoint of reactivity, one or more selected from the group consisting of a hydrogen atom, a methyl group, and a methoxy group are preferred, and taking into consideration the availability of raw materials, a hydrogen atom is more preferred.

In a particularly preferred embodiment, component (A) preferably has 0.5 to 1.0 groups represented by general formula (1) per molecule at the terminal of the main chain, more preferably 0.6 to 1.0 groups, even more preferably 0.7 to 1.0 groups, even more preferably 0.8 to 1.0 groups, and particularly preferably 0.9 to 1.0 groups. This configuration can further improve the adhesion and durability of the cured product.

The method for producing component (A) is not particularly limited, and known methods can be applied. For reasons of high availability of raw materials, high productivity, and being suitable for industrial use, the production methods described in, for example, WO 2013/047314, JP 2013-216782, and WO 2017/099043, etc. can be suitably used. The production method includes, for example, (i) a step of producing a polyisobutylene polymer skeleton (main chain) by performing living cationic polymerization of isobutylene using a monofunctional polymerization initiator (e.g., cumyl chloride, tert-butyl chloride, 2-chloro-2,4,4-trimethylpentane, etc.) and a Lewis acid catalyst (e.g., _TiCl4 , etc.) in the presence of an electron donor component such as a nitrogen-containing compound (e.g., 2-methylpyridine, 2,6-dimethylpyridine, triethylamine, etc.), and (ii) a step of functionalizing the terminal of the main chain with a (meth)acrylate phenoxyalkyl compound or the like. This method makes it possible to produce a polyisobutylene polymer having a (meth)acryloyl group at the terminal of the main chain. In this method, methyl chloride, butyl chloride, hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, toluene, etc. are particularly preferred as solvents in terms of availability, solubility of raw materials and polymers, and economy. In this method, the reaction is preferably carried out at a low temperature (for example, −70° C.) In step (ii) of this method, the functionalization rate can be controlled by adjusting the amount of the phenoxyalkyl (meth)acrylate compound used.

An alternative method includes, for example, (i) producing a monomer having both a functional group capable of cationically polymerizing with isobutylene (cationically polymerizable functional group) and a (meth)acryloyl group, and (ii) randomly copolymerizing isobutylene with the monomer obtained in (i) by cationic polymerization. This method makes it possible to produce a polyisobutylene-based polymer having a (meth)acryloyl group in a side chain of the main chain.

<Polyfunctional vinyl monomer (B)>
Component (B) is a compound that polymerizes due to active species generated from a polymerization initiator (C) (component (C)) described below, and is a vinyl monomer having two or more polymerizable functional groups in one molecule.

The functions of component (B) in this curable composition include (a) adjusting the physical properties of the cured product, (b) acting as a reactive diluent, and (c) forming crosslinking points. Furthermore, by including component (B) in this curable composition, it is possible to prevent the decline in heat resistance and durability that often occurs with the use of the monofunctionalized polymer of component (A). Therefore, by using components (A) and (B) in combination, it is possible to provide a cured product that combines durability and adhesiveness.

Examples of component (B) include compounds described in WO 2013/047314 and JP 2013-216782 A. Among these, (meth)acrylate monomers having an alkyl group or alicyclic group having 1 to 30 carbon atoms are preferred from the standpoint of excellent compatibility with component (A) and/or photocurability. These components (B) may be used alone or in combination of two or more.

Preferred examples of component (B) include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, glycerin di(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, di(meth)acrylate of ethylene oxide adduct of bisphenol A, hydroxypivalic acid neopentyl glycol acrylic acid adduct, polyethylene glycol (PEG) 200 di(meth)acrylate, polyethylene glycol (PEG ) 400 di(meth)acrylate, polyethylene glycol (PEG) 600 di(meth)acrylate, tripropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 2-(meth)acryloyloxyethyl acid phosphate, trimethylolpropane tri(meth)acrylate, trimethylolpropane acrylic acid benzoate, Ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethylene oxide-modified diglycerin tetraacrylate, dipentaneerythritol hexa(meth)acrylate, (meth)acrylic acid adduct of ethylene glycol diglycidyl ether, (meth)acrylic acid adduct of diethylene glycol diglycidyl ether, (meth)acrylic acid adduct of polyethylene glycol diglycidyl ether, (meth)acrylic acid adduct of propylene glycol diglycidyl ether, (meth)acrylic acid adduct of tripropylene glycol diglycidyl ether Examples include (meth)acrylic acid adduct of polypropylene glycol diglycidyl ether, (meth)acrylic acid adduct of neopentyl glycol diglycidyl ether, (meth)acrylic acid adduct of 1,6-hexanediol diglycidyl ether, (meth)acrylic acid adduct of glycerin diglycidyl ether, (meth)acrylic acid adduct of trimethylolpropane triglycidyl ether, (meth)acrylic acid adduct of bisphenol A diglycidyl ether, (meth)acrylic acid adduct of diglycidyl ether of bisphenol A propylene oxide 2 mole adduct, and (meth)acrylic acid adduct of hydrogenated bisphenol A diglycidyl ether.

From the standpoints of availability and reactivity, it is even more preferable that component (B) be at least one selected from the group consisting of 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate.

If the divalent or higher alkyl group or alicyclic group of component (B) has isomers, either isomer can be used, or a mixture of these isomers can be used.

The number average molecular weight of component (B) is not particularly limited, but is preferably 2000 or less, and more preferably 1000 or less. A number average molecular weight of component (B) of 2000 or less has the advantage that the viscosity of the curable composition falls within a suitable range, making it easier to achieve good handleability. There is no particular limit on the lower limit of the number average molecular weight of component (B), but in order to ensure excellent handleability of the curable composition, it is preferable that it be 150 or more, and more preferably 170 or more.

There are no particular restrictions on the number of polymerizable functional groups per molecule of component (B), as long as it is two or more, but 10 or fewer per molecule is preferred, 6 or fewer is more preferred, and 3 or fewer is even more preferred.

The content of component (B) in the curable composition is preferably 0.01 to 100 parts by weight, more preferably 0.10 to 100 parts by weight, even more preferably 0.50 to 50 parts by weight, even more preferably 0.50 to 30 parts by weight, and particularly preferably 0.50 to 20 parts by weight, per 100 parts by weight of component (A). When the content of component (B) is 0.01 part by weight or more per 100 parts by weight of component (A), the above-mentioned effects of component (B) are effectively exhibited. Furthermore, when the content of component (B) is 100 parts by weight or less per 100 parts by weight of component (A), the cured product has the advantage of having a hardness within a suitable range.

<Polymerization initiator (C)>
Component (C) is a compound that generates active species (e.g., radical species) that can initiate polymerization of the monomer in response to an external stimulus. Component (C) is not particularly limited, but examples thereof include known photoradical polymerization initiators and thermal radical polymerization initiators.

In order to achieve excellent rapid curing properties for the curable composition, it is preferable that component (C) be a photoradical polymerization initiator that generates radical species upon irradiation with active energy rays. In this specification, active energy rays encompass all light in the broad sense, including, for example, radiation such as alpha rays and beta rays, electromagnetic waves such as gamma rays and X-rays, electron beams (EB), ultraviolet rays (wavelength 100 to 400 nm), and visible light (wavelength 400 to 800 nm), with ultraviolet rays being preferred.

Examples of photoradical polymerization initiators include the compounds described in WO 2013/047314 and JP 2013-216782 A. Among these, (a) compounds having a hydroxyl group and a phenyl ketone structure, (b) compounds having a benzophenone structure, and (c) compounds having an acylphosphine oxide structure are preferably used.

(a) Examples of compounds having a hydroxyl group and a phenyl ketone structure include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanon-1-one, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one.

(b) Examples of compounds having a benzophenone structure include benzophenone, 3-methoxybenzophenone, 4-methylbenzophenone, 4,4'-bis(diethylamino)benzophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, and 4-chloro-4'-benzylbenzophenone.

(c) Examples of compounds having an acylphosphine oxide structure include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.

Among these, benzophenone, 4,4'-bis(diethylamino)benzophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide are particularly preferred due to their excellent curability and storage stability.

One type of photoradical polymerization initiator may be used alone, or two or more types may be used in combination. Furthermore, one or more types of photoradical polymerization initiator may be used in combination with other compounds. When a photoradical polymerization initiator is used in combination with other compounds, suitable examples of the other compounds include amines such as diethanolmethylamine, dimethylethanolamine, and triethanolamine. A photoradical polymerization initiator may be used in combination with the above-mentioned amines, and further with an iodonium salt such as phenyliodonium chloride. A photoradical polymerization initiator may be used in combination with the above-mentioned amines, and further with a dye such as methylene blue.

When a photoradical polymerization initiator is used as component (C), a polymerization inhibitor can also be added as needed. The presence of both a photoradical polymerization initiator and a polymerization inhibitor in the curable composition has the advantage of preventing unintended curing of the curable composition and making it easier to handle. Examples of polymerization inhibitors include hydroquinone, hydroquinone monomethyl ether, benzoquinone, and p-tert-butylcatechol.

If the curable composition can be heated for curing, a thermal radical polymerization initiator that generates radical species when heated can be used as component (C). Alternatively, a photoradical polymerization initiator and a thermal radical polymerization initiator can be used in combination as component (C).

Examples of thermal radical polymerization initiators include azo initiators, peroxides, persulfuric acid, and redox initiators. Of these, azo initiators and peroxides are more preferred.

Azo initiators include 2,2'-azobis(isobutyronitrile) and 2,2'-azobis-2-methylbutyronitrile.

Peroxides include t-butyl peroxypivalate, di(4-t-butylcyclohexyl) peroxydicarbonate, t-butylperoxyisopropyl monocarbonate, dicumyl peroxide, and benzoyl peroxide.

Thermal radical polymerization initiators may be used alone or in combination of two or more.

The content of component (C) in the curable composition is preferably 0.01 to 20.0 parts by weight, more preferably 0.05 to 20.0 parts by weight, even more preferably 0.10 to 20.0 parts by weight, even more preferably 0.10 to 10.0 parts by weight, and particularly preferably 0.10 to 5.0 parts by weight, per 100 parts by weight of component (A). When the content of component (C) is 0.01 part by weight or more per 100 parts by weight of component (A), the effect of component (C) is exerted, resulting in good curability. Furthermore, when the content of component (C) is 20.0 parts by weight or less per 100 parts by weight of component (A), the following advantages are achieved: (a) external stimuli (light, heat, etc.) can penetrate deep into the composition, preventing the occurrence of uncured areas, and (b) the cured product is likely to exhibit good heat resistance.

<Monofunctional vinyl monomer (D)>
The present curable composition preferably further contains a monofunctional vinyl monomer (D) (component (D)). Functions of component (D) in the present curable composition include (a) adjusting various physical properties (e.g., flexibility) of the cured product, and (b) acting as a reactive diluent.

Component (D) is a compound that polymerizes due to the active species generated from component (C), and is a vinyl monomer having one polymerizable functional group per molecule.

Examples of component (D) include compounds described in WO 2013/047314 and JP 2013-216782 A. Examples of such compounds include linear or cyclic (meth)acrylate monomers, styrene monomers, conjugated diene monomers, acrylonitrile, N-vinylpyrrolidone, acrylamide monomers, vinyl ketone monomers, and vinyl ester monomers. These components (D) may be used alone or in combination of two or more.

Among these, (meth)acrylate monomers having an alkyl group or alicyclic group having 1 to 30 carbon atoms are preferred from the viewpoint of excellent compatibility with component (A) and/or photocurability.

Preferred examples of component (D) from the standpoint of the good physical properties of the resulting cured product and ease of adjusting the viscosity of the curable composition include 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate. Furthermore, preferred examples of component (D) from the standpoint of availability include isononyl (meth)acrylate, isostearyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate.

If the alkyl group or alicyclic group in component (D) has isomers, either isomer can be used, and mixtures of these can also be used.

The number average molecular weight of component (D) is not particularly limited, but is preferably 1,000 or less, and more preferably 500 or less. A number average molecular weight of component (D) of 1,000 or less has the advantage that the viscosity of the curable composition falls within a suitable range, making it easier to achieve good handleability. There is no particular limit on the lower limit of the number average molecular weight of component (D), but in order to ensure the curable composition is easy to handle and safe, it is preferable for it to be 50 or more, and more preferably 70 or more.

The content of component (D) in the curable composition is preferably 0.1 to 1,000 parts by weight, more preferably 0.50 to 1,000 parts by weight, even more preferably 1.0 to 1,000 parts by weight, even more preferably 1.0 to 500 parts by weight, and particularly preferably 1.0 to 300 parts by weight, per 100 parts by weight of component (A). When the content of component (D) is 0.1 part by weight or more per 100 parts by weight of component (A), the above-mentioned effects of component (D) are effectively exhibited. Furthermore, when the content of component (D) is 1,000 parts by weight or less per 100 parts by weight of component (A), the cured product has the advantages of having a suitable range of hardness, as well as good mechanical properties and heat resistance.

<Other ingredients>
The curable composition may contain other components as needed, provided that the effects of the present invention are not impaired. Examples of other components include additives (e.g., fillers, plasticizers, storage stabilizers, antioxidants, UV absorbers, flame retardants, antistatic agents, and pigments), elastomers for adjusting the rubber properties of the cured product (e.g., photocurable (meth)acryloyl group-containing oligomers and styrene-based block copolymers, which are different from component (A)), thiol compounds, tertiary amine compounds, and adhesion promoters.

(Additives)
The contents of the filler and plasticizer in the present curable composition are not particularly limited, but from the viewpoint of balancing the effects obtained by their addition with economic efficiency, the contents are preferably 0.1 to 500 parts by weight, and more preferably 1.0 to 300 parts by weight, per 100 parts by weight of component (A).

The contents of the storage stabilizer, antioxidant, UV absorber, flame retardant, antistatic agent, and pigment in the curable composition are not particularly limited, but from the perspective of balancing the effects obtained by adding them with economic efficiency, they are preferably contained in an amount of 0.01 to 20.0 parts by weight, and more preferably 0.10 to 10.0 parts by weight, per 100 parts by weight of component (A).

These additives include various additives described in WO2013/047314 and JP2013-216782A, etc.

((Meth)acryloyl group-containing oligomer)
The (meth)acryloyl group-containing oligomer may be a compound having a main chain made of an oligomer that does not contain a structural unit derived from isobutylene and an average of one or more (meth)acryloyl groups per molecule. The (meth)acryloyl group-containing oligomer may be used alone or in combination of two or more.

Examples of oligomers that make up the main chain include polybutadiene, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, polyether, polyester, polycarbonate, polyacrylate, polymers of epoxy compounds, castor oil, and silicone-based polymers.

Among these, compounds containing a main chain made of an oligomer selected from the group consisting of polybutadiene, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, polyacrylate, polymers of epoxy compounds, and castor oil are preferred because they have excellent compatibility with the other components of the curable composition.

The number average molecular weight of the (meth)acryloyl group-containing oligomer is not particularly limited, but is preferably 200 to 500,000, and more preferably 1,000 to 100,000, in view of availability, compatibility with other components of the curable composition, and ease of handling of the curable composition.

The content of the (meth)acryloyl group-containing oligomer in the curable composition is not particularly limited, but is preferably 0.1 to 1,000 parts by weight, and more preferably 1.0 to 300 parts by weight, per 100 parts by weight of component (A), in order to (i) achieve a suitable viscosity range for the curable composition and/or (ii) achieve excellent compatibility with the other components of the curable composition.

(styrene-based block copolymer)
Examples of styrene-based block copolymers include styrene-butadiene copolymer (SBS), styrene-isoprene copolymer (SIS), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-isobutylene-styrene copolymer (SIBS), acrylonitrile-styrene copolymer (AS), and styrene-butadiene-acrylonitrile copolymer (ABS). These styrene-based block copolymers may be used alone or in combination of two or more.

Among these, styrene-butadiene copolymer (SBS), styrene-isoprene copolymer (SIS), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), and styrene-isobutylene-styrene copolymer (SIBS) are preferred because they have excellent compatibility with the other components of the curable composition and provide favorable rubber properties.

There are no particular restrictions on the number average molecular weight of the styrene-based block copolymer, but it is preferably 10,000 to 500,000, and more preferably 50,000 to 300,000, in order to (i) ensure that the viscosity of the curable composition falls within a suitable range, and/or (ii) ensure excellent compatibility with the other components of the curable composition.

There are no particular restrictions on the amount of styrene-based block copolymer in the curable composition, but from the perspective of balancing adhesion and durability, it is preferably 0.1 to 1,000 parts by weight, and more preferably 1.0 to 300 parts by weight, per 100 parts by weight of component (A).

(Thiol compounds)
By including a thiol-based compound as another component, the present curable composition appropriately has the following advantages: (a) by increasing the number of crosslinking points, it is possible to improve curability and provide a cured product with high hardness and strength; or (b) by reducing the number of crosslinking points through chain transfer, it is possible to provide a cured product with excellent flexibility and adhesiveness.

Thiol compounds include decanethiol, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptobutyrate), trimethylolethane tris(3-mercaptobutyrate), trimethylolethane tris(3-mercaptobutyrate), ethylene glycol bis(3-mercaptoglycolate), butanediol bis(3-mercaptoglycolate), trimethylolpropane tris(3-mercaptoglycolate), pentaerythritol tetrakis(3-mercaptoglycolate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, pentaerythritol tetrakis(3-mercaptopropionate), tetraethylene glycol bis(3-mercaptopropionate), and dipentaerythritol Examples include hexakis(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, and 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. These thiol compounds may be used alone or in combination of two or more.

The amount of thiol compound contained in the curable composition is not particularly limited, but in order to achieve excellent curability and ease of handling of the curable composition, it is preferably 0.1 to 100 parts by weight, and more preferably 0.50 to 30 parts by weight, per 100 parts by weight of component (A).

(Tertiary amine compounds)
The present curable composition has the advantage that the photocurability can be improved by including a tertiary amine compound as another compounding component.

Tertiary amine compounds include trimethylamine, triethylamine, tributylamine, N,N'-diethanolamine, N,N'-dimethyl-p-toluidine, N,N'-dimethyl-aniline, N-methyl-diethanolamine, N-methyl-dimethanolamine, N,N'-dimethylamino-acetophenone, N,N'-dimethylaminobenzophenone, N,N'-diethylamino-benzophenone, and triisopropanolamine. These tertiary amine compounds may be used alone or in combination of two or more.

The amount of the tertiary amine compound in the curable composition is not particularly limited, but in order to achieve excellent curing properties of the curable composition, it is preferably 0.1 to 100 parts by weight, and more preferably 0.50 to 30 parts by weight, per 100 parts by weight of component (A).

(Adhesion imparting agent)
The curable composition of the present invention advantageously contains an adhesion promoter (also referred to as an "adhesion promoter") as another blending component, which can improve the adhesiveness of the cured product.

Adhesion promoters include 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, (meth)acryloxyoctyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, 3-glycidyloxypropyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-chloropropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane Examples of suitable adhesion promoters include silane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-mercaptopropyltriethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 2-hydroxyethyl(meth)acrylate phosphate ester, methacryloxyoxyethyl acid phosphate monoethylamine half salt, 2-hydroxyethyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate. These adhesion promoters may be used alone or in combination of two or more.

Among these, the following are particularly recommended due to their excellent adhesive properties: 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane Particularly preferred are silane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 2-hydroxyethyl(meth)acrylate phosphate ester, 2-hydroxyethyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate.

There are no particular restrictions on the amount of adhesion promoter in the curable composition, but from the perspective of balancing curability and adhesion, it is preferably 0.01 to 20.0 parts by weight, and more preferably 0.1 to 10.0 parts by weight, per 100 parts by weight of component (A).

<Physical Properties of the Curable Composition>
In a preferred embodiment, the curable composition comprises 100 parts by weight of the polyisobutylene polymer (A), 0.01 to 100 parts by weight of the polyfunctional vinyl monomer (B), and 0.01 to 20.0 parts by weight of the polymerization initiator (C). This configuration has the advantage that the cured product obtained from the curable composition can have both higher adhesiveness and durability.

In a preferred embodiment, the curable composition contains 0.01 to 100 parts by weight of a polyfunctional vinyl monomer (B), 0.01 to 20.0 parts by weight of a polymerization initiator (C), and 0.1 to 1,000 parts by weight of a monofunctional vinyl monomer (D) per 100 parts by weight of the polyisobutylene polymer (A). This configuration has the advantage that the cured product obtained from the curable composition exhibits both higher adhesion and durability, and also has various desirable physical properties (e.g., flexibility).

In the present curable composition, the content of the polyisobutylene polymer having more than 1.0 (meth)acryloyl group per molecule is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and even more preferably 10 parts by weight or less, per 100 parts by weight of component (A). It is particularly preferred that the composition does not contain a polyisobutylene polymer having more than 1.0 (meth)acryloyl group per molecule. This configuration has the advantage of making it easier to obtain a cured product with an excellent balance of durability and adhesiveness. The lower the content of the polyisobutylene polymer having more than 1.0 (meth)acryloyl group per molecule, the less the content of the polyfunctionalized polymer molecule, and therefore, the easier it tends to be to obtain a cured product with an excellent balance of durability and adhesiveness.

From the viewpoint of ease of handling, the present curable composition is preferably liquid at room temperature. Furthermore, since this makes it easier to obtain a composition with excellent curability by photocuring, the appearance of the present curable composition is preferably colorless and transparent, pale yellow and transparent, pale yellow and translucent, or white and translucent.

There are no particular restrictions on the viscosity of the curable composition, but in order to accommodate various application or filling methods, a viscosity of 0.0001 to 10,000 Pa·sec at 25°C is preferred, and from the standpoint of ease of handling, a viscosity of 0.001 to 5,000 Pa·sec is even more preferred.

When the curable composition is applied or filled using a method suitable for applying or filling low-viscosity compositions (e.g., spray, inkjet, and screen printing, caulking gun, spray gun, etc.), the viscosity of the curable composition at 25°C is preferably, for example, 0.0001 to 5000 Pa·sec, and more preferably 0.0001 to 3000 Pa·sec. When the viscosity of the curable composition is within the above range, it is easy to handle and can be easily discharged from the discharge port.

When the curable composition is used for applications such as form-in-place gaskets (FIPG), cured-in-place gaskets (CIPG), molded-in-place gaskets (MIPG), liquid injection molding (LIM), and other dispensing applications, the viscosity of the curable composition at 25°C is preferably, for example, 0.001 to 10,000 Pa·sec, and more preferably 0.001 to 5,000 Pa·sec. If the viscosity of the curable composition at 25°C is 0.001 Pa·sec or more, good thixotropy is obtained, which has the advantage of making it easy to mold into the desired shape. Furthermore, if the viscosity of the curable composition at 25°C is 10,000 Pa·sec or less, it can be discharged at a good discharge rate, which has the advantage of preventing a decrease in productivity.

The viscosity of the curable composition can be measured at a measurement temperature of 25°C using a cone-plate viscometer TVE-25H manufactured by Toki Sangyo Co., Ltd.

<Form of the present curable composition>
The present curable composition may be a one-component type, a two-component type, or a multi-component type having three or more components.

A one-component curable composition is one in which all ingredients are blended in advance and then stored in a sealed container. One-component curable compositions eliminate the need to mix and knead multiple ingredients during application, and also eliminate the measuring errors that can occur during this process, making them a preferred form from the perspective of preventing quality defects such as poor curing.

A two-component curable composition is one in which the components are divided into two parts, Part A and Part B, taking into account factors such as the storage stability of the curable composition, and then mixed before use. Various combinations of methods for dividing the components into two parts are possible, taking into account the mixing ratio, storage stability, mixing method, pot life, etc. of the curable composition.

If necessary, a third component can be prepared in addition to liquids A and B to create a three-component curable composition, and further divisions can also be adjusted as needed.

The method for mixing the ingredients is not particularly limited, and examples include methods using a hand mixer, static mixer, planetary mixer, disperser, roll, kneader, single-screw extruder, twin-screw extruder, Banbury mixer, Brabender mixer, high-shear mixer, etc. Mixing may be performed in the dark, if necessary.

The mixing temperature is preferably 10 to 100°C, and more preferably 20 to 80°C. The mixing time is preferably approximately 0.1 to 5 hours, and more preferably approximately 10 minutes to 3 hours.

<Application method or filling method>
The method for applying or filling the curable composition onto an adherend is not particularly limited, and any known method for applying or filling a sealant or adhesive can be used, including dispensing using an automatic coater, spraying, inkjet printing, screen printing, gravure printing, dipping, spin coating, and filling using a caulking gun or spray gun.

If the viscosity of the curable composition at room temperature is high and handling is difficult, the curable composition may be heated to the desired viscosity. The temperature at this time is preferably 100°C or lower, and more preferably 80°C or lower. Heating the curable composition at 100°C or lower makes components (C) and (D) less likely to volatilize. This offers safety benefits and the advantage of preventing changes in the blending ratio of each component in the curable composition.

[3. Cured product]
A cured product according to one embodiment of the present invention is obtained by curing the present curable composition described in the section [2. Curable Composition]. The cured product according to one embodiment of the present invention is also simply referred to as the present cured product.

Because this cured product has the above-described structure, it is able to achieve both high adhesion and durability. Furthermore, this cured product has good gas barrier properties and flexibility.

<Physical properties of the cured product>
The present cured product has good flexibility and can be used in a variety of applications, but is particularly suitable for applications requiring rubber-like properties and/or relatively hard properties. When the present cured product is used in such applications, the hardness of the present cured product is preferably 1 to 90 degrees, and more preferably 5 to 85 degrees. A hardness of 1 degree or higher provides the advantage of being not too soft and providing good tackiness and ease of handling, while a hardness of 90 degrees or lower provides the advantage of being less likely to crack. In this specification, the hardness of the cured product refers to the value measured in accordance with JIS K 6253:2012. The method for measuring the hardness of the cured product is described in detail in the Examples below.

The tensile break strength (Tb) of the cured product is preferably 0.010 to 50 MPa, and more preferably 0.10 to 40 MPa. If the tensile break strength (Tb) of the cured product is 0.010 MPa or higher, the cured product has good strength and is easy to handle. If it is 50 MPa or lower, the cured product has the advantage of retaining its rubber-like properties. Furthermore, if the tensile break strength (Tb) of the cured product is within the above range, it has the advantage of being easily applicable to a variety of applications, such as sealants, moisture-proofing agents, potting agents, and gasket materials. Note that, in this specification, the tensile break strength (Tb) of the cured product refers to the value measured in accordance with JIS K 6251:2017. The method for measuring the tensile break strength (Tb) of the cured product is described in detail in the Examples below.

The compression set of the cured product is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. A compression set of 70% or less has the advantage of maintaining good airtightness and making it suitable for a variety of applications, including sealing agents, moisture-proofing agents, potting agents, and gasket materials. Note that, in this specification, the compression set of the cured product refers to a value measured in accordance with JIS K 6262:2013. The method for measuring the compression set of the cured product is described in detail in the Examples below.

The moisture permeability of the cured product is preferably 50 g/ ^m2 ·24 hrs or less, and more preferably 25 g/ ^m2 ·24 hrs or less. If the moisture permeability of the cured product is 50 g/ ^m2 ·24 hrs or less, it has the advantage of being easily applicable to various applications requiring high gas barrier properties (e.g., sealants, sealing materials, moisture-proofing agents, gasket materials, potting agents, conformal coatings, etc.). In this specification, the moisture permeability of the cured product refers to the value measured using a 0.5 mm thick test piece in accordance with JIS Z 0208:1976. The method for measuring the moisture permeability of the cured product will be described in detail in the Examples below.

The adhesive strength of the cured product, as measured against a stainless steel plate (SUS304, manufactured by Engineering Test Services), is preferably 0.10 N/25 mm or more, and more preferably 1.0 N/25 mm or more. If the adhesive strength of the cured product is 0.10 N/25 mm or more, it is less likely to peel from the substrate, which is advantageous in that it is easily applicable to a variety of applications requiring high adhesiveness (e.g., sealants, sealing materials, moisture-proofing agents, gasket materials, potting agents, conformal coatings, etc.). The method for measuring the adhesive strength of the cured product is described in detail in the Examples below.

<Curing method>
The present cured product can be obtained by applying an external stimulus (light or heat) to the present curable composition to cure it.

When component (C) is a photoradical polymerization initiator, the external stimulus is irradiation with light (active energy rays). Examples of light sources for active energy rays include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, sodium lamps, halogen lamps, xenon lamps, LEDs, fluorescent lamps, sunlight, electron beam irradiation devices, and lasers.

The irradiation amount of the active energy rays is preferably an integrated light amount of 1 kJ/m ² or more, more preferably 10 kJ/m ² or more. When the integrated light amount is 1 kJ/m ² or more, the present curable composition can be sufficiently cured.

Efficient curing can be achieved by matching the wavelength of the active energy rays emitted from the light source as closely as possible to the absorption wavelength (and/or maximum absorption wavelength) of component (C).

When component (C) is a thermal radical polymerization initiator, the external stimulus is heat (heating). The heating temperature and heating time are not particularly limited and vary depending on the type of thermal radical polymerization initiator used, but are typically between 50 and 250°C, and more preferably between 70 and 200°C. The heating time (curing time) varies depending on the type of thermal radical polymerization initiator used, additives, heating temperature (reaction temperature), etc., but is typically in the range of 1 minute to 5 hours.

The curable composition can be cured under various atmospheres, including air, nitrogen, and argon. It is preferable to cure the curable composition under air, as this method does not require special equipment and can be easily performed. Furthermore, if there is concern that oxygen in the air may inhibit curing, it is preferable to cure the composition under an inert gas such as nitrogen or argon.

[4. Use]
The present curable composition provides a cured product that combines high adhesiveness and durability and further has excellent gas barrier properties and flexibility, making it suitable for use in a variety of applications requiring high levels of adhesiveness, durability, gas barrier properties, and flexibility. Examples of such applications include sealing materials, pressure-sensitive adhesives, sealants, gaskets, adhesives, coating materials, covering materials, resist materials, vibration-proofing materials, vibration-damping materials, shock-absorbing materials, buffer materials, electrical insulating materials, foams, paints, inks, casting agents, potting agents, molding materials, underfill materials, die-bonding materials, and fillers in electrical and electronic components (LEDs, batteries, sensors, semiconductors, circuit boards, displays, home appliances, optical communications and optical circuits, optical recording, magnetic recording, etc.), pharmaceuticals and medical products, automotive and marine components, building components, and acoustic components. The present curable products used in these applications can be used in various forms, such as sheets (films), tapes, and molded products (packings, O-rings, belts, tubes, valves, hoses, etc.).

The present cured product can be particularly suitably used as a sealant and adhesive. The sealant and adhesive according to one embodiment of the present invention are obtained by curing the present curable composition described in Section [2. Curable Composition]. The sealant and adhesive according to one embodiment of the present invention are also simply referred to as the present sealant and the present adhesive, respectively.

Because this sealing material and adhesive have the above-mentioned configuration, they are able to achieve both high adhesion and durability. Furthermore, this sealing material has good gas barrier properties and flexibility.

The sealant and adhesive can be produced by applying the curable composition to an adherend or filling the space between two or more adherends and curing the curable composition. For methods of applying, filling, and curing the curable composition, the descriptions in sections [2. Curable composition] and [3. Cured product] are incorporated herein by reference as appropriate.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

Measurements and evaluations in the examples and comparative examples were performed using the following methods.

<Molecular weight>
The "weight average molecular weight Mw,""number average molecular weight Mn," and "molecular weight distribution (ratio of weight average molecular weight to number average molecular weight (Mw/Mn))" were calculated by a standard polystyrene conversion method using size exclusion chromatography (SEC).

A Waters GPC system was used as the measurement device, and measurements were performed using a sample solution with a polymer concentration of 4 mg/ml at a column temperature of 35°C and chloroform as the mobile phase. The column (stationary phase) used was one packed with cross-linked polystyrene gel (Shodex GPC K-804 and K-802.5; both manufactured by Showa Denko K.K.).

<Viscosity>
The viscosity of the sample (curable composition) was measured at a measurement temperature of 25° C. using a cone-plate viscometer TVE-25H manufactured by Toki Sangyo Co., Ltd.

<Tensile properties>
The curable composition was applied to a PET film to a thickness of 0.5 mm. The composition was then cured by irradiating it with UV light (irradiation conditions: illuminance 500 mW/cm ² , light quantity 5000 mJ/cm ² ) using a UV irradiation device (manufactured by Fusion UV Systems Japan Co., Ltd., model: LH6) to obtain a sheet-like cured product. No. 7 dumbbell-shaped test pieces were prepared from the obtained cured product.

Using the obtained test specimens, tensile tests were conducted in accordance with JIS K 6251:2017 at room temperature (23°C) at a tensile speed of 200 mm/min to measure the tensile strength at break (Tb), tensile elongation at break (Eb), and 30% modulus (M30). The tensile strength at break (Tb) is the tensile strength (MPa) at the time the test specimen breaks. The tensile elongation at break (Eb) is the relative value (%) of the length of the test specimen at the time of break, with the length of the test specimen at the start of the tensile test being 100%. The 30% modulus (M30) is the tensile strength (MPa) when the test specimen is elongated by 30%.

<Hardness (Type A)>
The curable composition was cured to a thickness of 0.5 mm to prepare a sheet-like test piece. The cured test pieces were then stacked to a thickness of 6 mm, and the hardness (Type A) was measured in accordance with JIS K 6253:2012 using a Type A durometer.

<Compression set>
The curable composition was cured to a thickness of 12.5 mm to prepare a cylindrical test piece. The compression set of the obtained test piece was measured at 120°C for 24 hours under 25% compression in accordance with JIS K 6262:2013.

<Moisture permeability>
The curable composition was cured to a thickness of 0.5 mm to prepare a sheet-like test piece, and the moisture permeability of the resulting test piece was measured at 40°C and a relative humidity of 90% RH in accordance with JIS Z 0208:1976.

<Adhesive strength>
The curable composition was coated to a thickness of 0.5 mm on a 25 μm thick PET film, and a release PET film was attached to the coated surface. Next, the curable composition was cured by UV irradiation using a UV irradiation device under the same conditions as in the measurement method for tensile properties. The resulting sheet-like cured product (adhesive) was cut to a width of 25 mm. Next, the release PET film was peeled off, and the surface of the cured product was attached to a stainless steel plate (SUS304, manufactured by Engineering Test Services Co., Ltd.) and pressed with a 2 kg pressure roller. Three days after attachment, a 180° peel test was performed using an autograph (manufactured by Shimadzu Corporation, AG-2000A) at 23°C and a peel rate of 300 mm/min, and the adhesive strength (N/25 mm) was measured.

<Functionalization rate>
The number of (meth)acryloyl groups contained in one molecule of a polyisobutylene polymer was calculated by the following method: (i) ¹ H NMR measurement of the polyisobutylene polymer was performed; (ii) from the obtained results, (ii-1) the relative number (A) of polymer molecules present in the polyisobutylene polymer was calculated from the peak area (peak integral value) of protons attributed to groups derived from the polymerization initiator, and (ii-2) the relative number (B) of (meth)acryloyl groups present in the polyisobutylene polymer was calculated from the peak area (peak integral value) of protons attributed to (meth)acryloyl groups; (iii) the ratio (B/A) of the relative number (B) of (meth)acryloyl groups to the relative number (A) of polymer molecules was calculated, and the number (introduced number) of (meth)acryloyl groups contained in one molecule was determined.

(Production Example 1) Synthesis of Polyisobutylene Polymer (A-1) Having 0.5 to 1.0 (Meth)acryloyl Groups per Molecule The gas in a 1 L separable flask was replaced with nitrogen. Then, 30 mL of n-hexane (dried over molecular sieves) and 400 mL of butyl chloride (dried over molecular sieves) were added to the flask. The raw materials in the flask were then cooled to −70°C while stirring under a nitrogen atmosphere. Next, 200 mL (2.12 mol) of isobutylene, 1.56 g (0.0101 mol) of cumyl chloride, and 0.378 g (0.00353 mol) of 2,6-lutidine were added to the flask. After the reaction mixture in the flask was cooled to −70°C, 1.44 mL (0.0131 mol) of titanium tetrachloride was added to the flask to initiate polymerization. After the start of polymerization, the minimum amount of reaction mixture necessary for measurement was removed from the vessel at regular intervals. The removed reaction mixture was subjected to gas chromatography to measure the residual isobutylene concentration in the reaction mixture and the amount of isobutylene consumed. The isobutylene polymerization was terminated when 99.9% or more of the isobutylene introduced was consumed. This procedure yielded a polyisobutylene polymer (main chain). Next, without removing the polyisobutylene polymer from the vessel, 2.44 g (0.0111 mol) of phenoxybutyl acrylate and 4.98 mL (0.0454 mol) of titanium tetrachloride were added to the vessel containing the polymerized polyisobutylene polymer. The functionalization reaction was carried out by continuing to stir the reaction mixture in the vessel at −75 to −80°C for an additional 3 hours.

After the reaction was completed, a large amount of methanol was poured into the reaction mixture to deactivate the catalyst. The methanol, butyl chloride, and hexane-based solvent were removed from the reaction mixture, yielding a viscous precipitate. The resulting precipitate was dissolved in 1,000 g of butyl chloride, and 20 g of powdered activated carbon (manufactured by Futamura Chemical Co., Ltd., product name "Taiko A") was added to the resulting solution. The resulting mixture was stirred overnight at room temperature. The mixture was then filtered to remove the activated carbon, yielding a filtrate. 0.0123 g of 4-methoxyphenol was added to the filtrate, and the solvent in the resulting mixture was distilled off under reduced pressure to yield a polyisobutylene polymer (A-1) having acryloyl groups. The number-average molecular weight (Mn) of A-1 was 15,100, the molecular weight distribution (Mw/Mn) was 1.26, and the number of acryloyl groups introduced per molecule was 0.93. In other words, polyisobutylene polymer (A-1) is a monofunctional polymer and can be said to be an aggregate of polyisobutylene polymer molecules, the majority of which are polyisobutylene polymer molecules having an acryloyl group at only one end of the main chain.

(Production Example 2) Synthesis of Polyisobutylene Polymer (A-2) Having 0.5 to 1.0 (Meth)acryloyl Groups per Molecule The gas in a 2-L separable flask was replaced with nitrogen. Then, 60 mL of n-hexane (dried over molecular sieves) and 800 mL of butyl chloride (dried over molecular sieves) were added to the vessel. The raw materials in the vessel were then cooled to -70°C while stirring under a nitrogen atmosphere. Next, 306 mL of isobutylene, 8.36 g of cumyl chloride, and 0.82 g of triethylamine were added to the vessel. After the reaction mixture in the vessel was cooled to -70°C, 2.84 mL of titanium tetrachloride was added to the vessel to initiate polymerization. After the initiation of polymerization, the minimum amount of reaction mixture necessary for measurement was removed from the vessel at regular intervals, and the removed reaction mixture was subjected to gas chromatography to measure the residual isobutylene concentration in the reaction mixture and the consumption of the added isobutylene. The polymerization of isobutylene was terminated when 99.9% or more of the isobutylene introduced was consumed. Through this operation, a polyisobutylene polymer (main chain) was obtained. Next, without removing the polyisobutylene polymer from the vessel, 17.0 g of phenoxybutyl acrylate and 23.7 mL of titanium tetrachloride were added to the vessel containing the polymerized polyisobutylene polymer, and the reaction mixture in the vessel was stirred continuously at −75 to −80°C for an additional 3 hours to carry out a functionalization reaction.

After the reaction was completed, a large amount of methanol was poured into the reaction mixture to deactivate the catalyst. The methanol, butyl chloride, and hexane-based solvent were removed from the reaction mixture, yielding a viscous precipitate. The resulting precipitate was dissolved in 1500 g of butyl chloride, and 30 g of powdered activated carbon (manufactured by Futamura Chemical Co., Ltd., product name "Taiko A") was added to the resulting solution. The resulting mixture was stirred overnight at room temperature. The mixture was then filtered to remove the activated carbon, yielding a filtrate. 0.0300 g of 4-methoxyphenol was added to the filtrate, and the solvent in the resulting mixture was distilled off under reduced pressure to yield a polyisobutylene polymer (A-2) having acryloyl groups. The number-average molecular weight (Mn) of A-2 was 5100, the molecular weight distribution (Mw/Mn) was 1.31, and the number of acryloyl groups introduced per molecule was 0.85. In other words, polyisobutylene polymer (A-2) is a monofunctional polymer and can be said to be an aggregate of polyisobutylene polymer molecules, the majority of which have an acryloyl group at only one end of the main chain.

(Production Example 3) Synthesis of Polyisobutylene Polymer (X-1) Having More than 1.0 (Meth)acryloyl Groups per Molecule (Comparative Component for Component (A)) The gas in a 1-L separable flask was replaced with nitrogen. Then, 30 mL of n-hexane (dried over molecular sieves) and 350 mL of butyl chloride (dried over molecular sieves) were added to the flask. The raw materials in the flask were then cooled to −70°C while stirring under a nitrogen atmosphere. Next, 150 mL of isobutylene, 1.76 g of p-dicumyl chloride, and 0.29 g of 2,6-lutidine were added to the flask. After the reaction mixture in the flask was cooled to −70°C, 0.85 mL of titanium tetrachloride was added to the flask to initiate polymerization. After the start of polymerization, the minimum amount of reaction mixture necessary for measurement was removed from the vessel at regular intervals, and the removed reaction mixture was subjected to gas chromatography to measure the residual isobutylene concentration in the reaction mixture and the amount of isobutylene consumed. The isobutylene polymerization was terminated when 99.9% or more of the isobutylene introduced was consumed. This procedure yielded a polyisobutylene polymer (main chain). Next, without removing the polyisobutylene polymer from the vessel, 3.70 g of phenoxybutyl acrylate and 5.00 mL of titanium tetrachloride were added to the vessel containing the polymerized polyisobutylene polymer, and the functionalization reaction was carried out by continuing to stir the reaction mixture in the vessel at -70 to -80°C for an additional 3 hours.

After the reaction was completed, a large amount of methanol was poured into the reaction mixture to deactivate the catalyst. The methanol, butyl chloride, and hexane-based solvent were removed from the reaction mixture, yielding a viscous precipitate. The resulting precipitate was dissolved in 650 g of butyl chloride, and 10 g of powdered activated carbon (manufactured by Futamura Chemical Co., Ltd., product name "Taiko A") was added to the resulting solution. The resulting mixture was stirred overnight at room temperature. The mixture was then filtered to remove the activated carbon, yielding a filtrate. 0.0160 g of 4-methoxyphenol was added to the filtrate, and the solvent in the resulting mixture was distilled off under reduced pressure to yield a polyisobutylene polymer (X-1) having acryloyl groups. X-1 had a number-average molecular weight (Mn) of 14,200, a molecular weight distribution (Mw/Mn) of 1.20, and an acryloyl group count per molecule of 1.85. In other words, polyisobutylene polymer (X-1) is a multifunctional polymer and can be said to be an aggregate of polyisobutylene polymer molecules, the majority of which have acryloyl groups at both ends of the main chain.

In the following examples and comparative examples, the various blending components used were as follows:
<Component (A)>
A-1: Polyisobutylene polymer obtained in Production Example 1 A-2: Polyisobutylene polymer obtained in Production Example 2 <Comparative component for component (A)>
X-1: Polyisobutylene polymer (component (B)) obtained in Production Example 3
B-1: 1,6-hexanediol diacrylate (Kyoeisha Chemical Co., Ltd., Light Acrylate 1,6HX-A)
B-2: Trimethylolpropane triacrylate (Kyoeisha Chemical Co., Ltd., Light Acrylate TMP-A)
<(C) component>
C-1: Photopolymerization initiator 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Ciba Specialty Chemicals, Darocure 1173)
C-2: Photopolymerization initiator: bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (manufactured by BASF Japan, Irgacure 819)
<(D) component>
D-1: Isononyl acrylate D-2: Dicyclopentanyl acrylate (manufactured by Showa Denko Materials Co., Ltd., FA-513AS)
<Other ingredients>
E-1: Hindered phenol-based antioxidant: n-octadecyl 3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate (manufactured by ADEKA, Adeka Stab AO-50)
E-2: Hydrophobic fumed silica (filler) (Evonik, Aerosil R972)
Examples 1 to 3
A-1 as the (A) component, B-1 as the (B) component, C-1 and C-2 as the (C) component, D-1 as the (D) component, and E-1 as another blending component were mixed in the weight ratios shown in Table 1 to obtain a pale yellow, transparent curable composition. The viscosity of the obtained curable composition was measured. In addition, the tensile properties, hardness, compression set, moisture permeability, and adhesive strength of the colorless, transparent cured product obtained by curing the curable composition were measured. The measurement results are shown in Table 1.

Example 4
A curable composition was obtained in the same manner as in Example 3, except that E-2 was added as another blending component in the weight ratio shown in Table 1. The viscosity of the obtained curable composition was measured. In addition, the tensile properties, hardness, compression set, moisture permeability, and adhesive strength of the colorless and transparent cured product obtained by curing the curable composition were measured. The measurement results are shown in Table 1.

Example 5
A curable composition was obtained in the same manner as in Example 3, except that B-2 was used as component (B) instead of B-1 in the weight ratio shown in Table 1. The viscosity of the obtained curable composition was measured. In addition, the tensile properties, hardness, compression set, moisture permeability, and adhesive strength of a colorless and transparent cured product obtained by curing the curable composition were measured. The measurement results are shown in Table 1.

Example 6
A curable composition was obtained in the same manner as in Example 3, except that D-1 and D-2 were used in combination as component (D) in the weight ratio shown in Table 1. The viscosity of the obtained curable composition was measured. In addition, the tensile properties, hardness, compression set, moisture permeability, and adhesive strength of the colorless and transparent cured product obtained by curing the curable composition were measured. The measurement results are shown in Table 1.

Example 7
A curable composition was obtained in the same manner as in Example 3, except that D-2 was used as component (D) in place of D-1 in the weight ratio shown in Table 1. The viscosity of the obtained curable composition was measured. In addition, the tensile properties, hardness, compression set, moisture permeability, and adhesive strength of a colorless and transparent cured product obtained by curing the curable composition were measured. The measurement results are shown in Table 1.

(Example 8)
A curable composition was obtained in the same manner as in Example 7, except that A-2 was used as component (A) instead of A-1 in the weight ratio shown in Table 1. The viscosity of the obtained curable composition was measured. In addition, the tensile properties, hardness, compression set, moisture permeability, and adhesive strength of a colorless and transparent cured product obtained by curing the curable composition were measured. The measurement results are shown in Table 1.

(Comparative Examples 1 to 3)
X-1, A-1, C-1, C-2, D-1, and E-1 were mixed in the weight ratios shown in Table 1 to obtain a pale yellow, transparent curable composition. The viscosity of the obtained curable composition was measured. In addition, the tensile properties, hardness, compression set, moisture permeability, and adhesive strength of the colorless, transparent cured product obtained by curing the curable composition were measured. The measurement results are shown in Table 1.

When measuring the adhesive strength of Examples 6 and 7, the adhesive strength of Examples 6 and 7 was so high that peeling occurred between the cured product (adhesive) and the substrate (PET film), making it impossible to measure the adhesive strength between the cured product and the stainless steel plate. Therefore, in Table 1, the adhesive strength of Examples 6 and 7 is the peel stress at the time peeling occurred between the cured product and the substrate.

As shown in Table 1, in Comparative Examples 1 to 3, which contain X-1 (multifunctionalized polymer) but no component (B), increasing the proportion of A-1 (monofunctionalized polymer) increases adhesion, but compression set also increases, resulting in decreased durability. This leads to the following considerations (a) and (b): (a) When a monofunctionalized polymer is added to a curable composition containing a multifunctionalized polymer to increase adhesion, durability is significantly reduced; and (b) when the amount of monofunctionalized polymer added is limited to prevent a decrease in durability, the adhesion improvement effect is not fully achieved. Furthermore, based on these considerations, it can be said that it is difficult to imagine focusing on a curable composition that contains only a monofunctionalized polymer and no multifunctionalized polymer, and attempting to achieve both adhesion and durability in such a curable composition.

However, surprisingly, in Examples 1 to 3, it was found that by varying the amount of component (B) added to a curable composition containing only a monofunctionalized polymer, it was possible to provide a cured product with an excellent balance of adhesion and durability. Furthermore, all of the cured products had excellent flexibility and gas barrier properties.

The curable composition of Example 4, by including a filler (hydrophobic fumed silica), was able to provide a cured product with high strength while maintaining high adhesiveness and durability. The curable composition of Example 5, by using a trifunctional vinyl monomer as component (B), was able to provide a cured product with excellent flexibility, adhesiveness, and durability. In Examples 6 and 7, it was found that the effects of the present invention could be obtained even when two types of component (D) were used in combination or when the type of component (D) was changed. Furthermore, in Example 8, it was found that the effects of the present invention could be obtained even when the molecular weight of component (A) was changed.

The curable composition of the present invention can be suitably used for applications such as sealants, pressure sensitive adhesives, sealing agents, gasket materials, vibration dampers, shock absorbers, buffer materials, acoustic components, and tubes.

Claims (8)

The composition comprises a polyisobutylene polymer (A) having 0.5 to 1.0 (meth)acryloyl groups per molecule, a polyfunctional vinyl monomer (B), and a polymerization initiator (C),
Further containing a monofunctional vinyl monomer (D),
a curable composition comprising 0.01 to 100 parts by weight of the polyfunctional vinyl monomer (B), 0.01 to 20.0 parts by weight of the polymerization initiator (C), and 0.1 to 1,000 parts by weight of the monofunctional vinyl monomer (D) relative to 100 parts by weight of the polyisobutylene polymer (A). The curable composition according to claim 1 , wherein the (meth)acryloyl group is a group represented by the following general formula (1):
(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents a divalent saturated hydrocarbon group having 2 to 6 carbon atoms and containing no heteroatoms, and R ³ to R ⁶ each independently represent a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or an alkoxy group.) 3. The curable composition according to claim 1, further comprising: (i) 20 parts by weight or less of a polyisobutylene polymer having more than 1.0 (meth)acryloyl group per molecule, based on 100 parts by weight of the polyisobutylene polymer (A); or (ii) no polyisobutylene polymer is contained. The curable composition according to any one of claims 1 to 3, wherein the polyfunctional vinyl monomer (B) is at least one selected from the group consisting of 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth ) acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. 5. The curable composition according to claim 1 , wherein the polyisobutylene polymer (A) has 0.8 to 1.0 (meth)acryloyl groups per molecule. The curable composition according to any one of claims 1 to 5 , wherein the polymerization initiator (C) is a photoradical polymerization initiator. A sealant obtained by curing the curable composition according to any one of claims 1 to 6 . A pressure-sensitive adhesive obtained by curing the curable composition according to any one of claims 1 to 6 .