Graft copolymer and curable composition

Abstract

To provide a reactive silicon group-containing graft copolymer having a (meth)acrylic acid ester-based polymer block and a polyoxyalkylene-based polymer block and capable of forming a cured product which achieves both high strength and high restorability.SOLUTION: There is provided a graft copolymer in which a (meth)acrylic acid ester-based polymer block (A) having a reactive silicon group and a polyoxyalkylene-based polymer block (B) are bonded in the order of A-B-A. The number-average molecular weight of (B) is 5000 or more and the molecular weight distribution (Mw / Mn) of (B) is 1.40 or less. In the graft copolymer, the ratio of (A) is 35 to 65 wt.% and the ratio of (B) is 35 to 65 wt.%. (A) contains a structural unit derived from a (meth)acrylic acid ester (a1) and a structural unit derived from a chain transfer agent (a2) having a mercapto group. The sulfur atom concentration derived from (a2) is 5000 to 15000 ppm in the graft copolymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a graft copolymer having reactive silicon groups and to a curable composition containing said polymer. [Background technology]

[0002] Organic polymers that have hydroxyl or hydrolyzable groups on the silicon atom and can form siloxane bonds through hydrolysis and condensation reactions (hereinafter referred to as "reactive silicon groups") react with moisture even at room temperature. It is known that such organic polymers can be crosslinked by the siloxane condensation reaction of the reactive silicon groups to produce rubber-like cured products.

[0003] Among these organic polymers, polyoxyalkylene polymers having reactive silicon groups have a relatively low viscosity, which makes them easy to work with when preparing and using blended compositions, and the resulting cured products have a good balance of mechanical properties, weather resistance, dynamic durability, and other performance characteristics, making them widely used in applications such as sealants, adhesives, and paints.

[0004] Furthermore, in order to improve the weather resistance and adhesiveness of polyoxyalkylene polymers having reactive silicon groups, curable compositions are also known which use a reactive silicon group-containing polyoxyalkylene polymer in combination with a reactive silicon group-containing (meth)acrylic acid ester polymer.

[0005] Patent Document 1 aims to overcome the drawback of slow curing speed of one-component moisture-curing adhesives containing modified silicones or acrylic-modified silicones, and describes a reactive silicon group-containing graft copolymer synthesized by radical polymerization of an oligomer having a polyether skeleton and double bonds at both ends, a vinyl monomer such as a (meth)acrylic acid ester, and a chain transfer agent as a curable resin with fast curing speed and excellent adhesive properties.

[0006] Patent Document 2 describes a method for producing such a reactive silicon group-containing graft copolymer by radical polymerization.

[0007] Patent Document 3 discloses that in a (meth)acrylic acid ester copolymer composed of a (meth)acrylic acid ester, a polyoxyalkylene polymer having more than one (meth)acryloyl group in the molecule, and a chain transfer agent having a mercapto group, by setting the molar ratio of the polyoxyalkylene polymer to the chain transfer agent to 0.06 or more, it is possible to achieve good physical properties after curing while maintaining low viscosity.

[0008] Patent Documents 4 and 5 disclose that a hot-melt curable composition can be formed by using the (meth)acrylic acid ester copolymer in combination with a polyester having a reactive silicon group or a tackifier resin. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2007 / 023669 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-15512 [Patent Document 3] International Publication No. 2022 / 203064 [Patent Document 4] Japanese Patent Publication No. 2023-100363 [Patent Document 5] International Publication No. 2023 / 132324 Summary of the Invention [Problem to be solved by the invention]

[0010] Cured products obtained by curing organic polymers having reactive silicon groups are required to exhibit high strength, but at the same time, they are also required to exhibit high resilience (the ability to return to their original shape after being subjected to a specified deformation).

[0011] However, Patent Documents 1 to 5 make no mention of recovery, and it has been difficult to obtain a cured product that combines strength and recovery with the graft copolymers disclosed in these documents.

[0012] In view of the above-mentioned current situation, an object of the present invention is to provide a reactive silicon group-containing graft copolymer having a (meth)acrylic acid ester polymer block and a polyoxyalkylene polymer block, which is capable of forming a cured product having both high strength and high recovery. [Means for solving the problem]

[0013] As a result of intensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by bonding the blocks of a graft copolymer having a (meth)acrylic acid ester polymer block having a reactive silicon group and a polyoxyalkylene polymer block in a specific order, and by setting the number-average molecular weight and molecular weight distribution of the polyoxyalkylene polymer block, the weight ratio of each block, and the concentration of sulfur atoms derived from the chain transfer agent within specific ranges, respectively, and have completed the present invention.

[0014] That is, the present invention relates to a compound represented by the general formula (1): -SiR 1 3-a X a (1) (In the formula, R 1 represents a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms; X represents a hydroxyl group or a hydrolyzable group; and a represents 2 or 3. and a polyoxyalkylene polymer block (B) are bonded in the order ABA, the polyoxyalkylene polymer block (B) has a number average molecular weight of 5,000 or more and a molecular weight distribution (Mw / Mn) of 1.40 or less; In the graft copolymer, the proportion of the polymer block (A) is 35 to 65% by weight, and the proportion of the polymer block (B) is 35 to 65% by weight, the polymer block (A) contains a structural unit derived from a (meth)acrylic acid ester (a1) and a structural unit derived from a chain transfer agent (a2) having a mercapto group, The present invention relates to a graft copolymer, wherein the concentration of sulfur atoms derived from the chain transfer agent (a2) is 5,000 to 15,000 ppm in the graft copolymer. The present invention also relates to a curable composition or a hot-melt adhesive comprising the graft copolymer. [Effects of the Invention]

[0015] According to the present invention, there is provided a reactive silicon group-containing graft copolymer having a (meth)acrylic acid ester polymer block and a polyoxyalkylene polymer block, which is capable of forming a cured product that has both high strength and high recovery. The graft copolymer according to a preferred embodiment of the present invention is solid at room temperature and can be used as a main resin component of a hot melt adhesive. [Brief explanation of the drawings]

[0016] [Figure 1] Conceptual diagram of an H-type structure that may be contained in the graft copolymer according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following describes specific embodiments of the present invention, but the present invention is not limited to these embodiments.

[0018] The graft copolymer according to this embodiment is formed by bonding a (meth)acrylic acid ester polymer block (A) and a polyoxyalkylene polymer block (B). The graft copolymer has a reactive silicon group, and the reactive silicon group is bonded to the (meth)acrylic acid ester polymer block (A). In the present application, "(meth)acrylic" means "acrylic and / or methacrylic".

[0019] <Reactive silicon group> The (meth)acrylic acid ester polymer block (A) has a reactive silicon group represented by the following general formula (1) at the molecular chain terminal and / or side chain (non-terminal site). -SiR 1 3-a X a (1) (In the formula, R 1 represents a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms; X represents a hydroxyl group or a hydrolyzable group; and a represents 2 or 3.

[0020] R 1 The hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, and even more preferably 1 to 3 carbon atoms. 1 Specific examples of include a methyl group, an ethyl group, a chloromethyl group, a methoxymethyl group, and an N,N-diethylaminomethyl group. Preferred are a methyl group, an ethyl group, a chloromethyl group, and a methoxymethyl group, and more preferred are a methyl group and a methoxymethyl group.

[0021] Examples of X include a hydroxyl group, a halogen, an alkoxy group, an acyloxy group, a ketoximate group, an amino group, an amide group, an acid amide group, an aminooxy group, a mercapto group, an alkenyloxy group, etc. Among these, an alkoxy group is more preferred because it is mildly hydrolyzable and easy to handle, and a methoxy group and an ethoxy group are particularly preferred.

[0022] Specific examples of the reactive silicon group include, but are not limited to, a trimethoxysilyl group, a triethoxysilyl group, a tris(2-propenyloxy)silyl group, a triacetoxysilyl group, a dimethoxymethylsilyl group, a diethoxymethylsilyl group, a dimethoxyethylsilyl group, a (chloromethyl)dimethoxysilyl group, a (chloromethyl)diethoxysilyl group, a (methoxymethyl)dimethoxysilyl group, a (methoxymethyl)diethoxysilyl group, an (N,N-diethylaminomethyl)dimethoxysilyl group, and an (N,N-diethylaminomethyl)diethoxysilyl group. Among these, methyldimethoxysilyl group, trimethoxysilyl group, triethoxysilyl group, (chloromethyl)dimethoxysilyl group, (methoxymethyl)dimethoxysilyl group, (methoxymethyl)diethoxysilyl group, and (N,N-diethylaminomethyl)dimethoxysilyl group are preferred because they exhibit high activity and give cured products with good mechanical properties. Trimethoxysilyl group and triethoxysilyl group are more preferred, and trimethoxysilyl group is even more preferred, because they give cured products with high breaking strength.

[0023] From the viewpoint of achieving the above-mentioned effects of the present invention, the reactive silicon group equivalent of the graft copolymer according to this embodiment is preferably 0.2 to 0.8 mmol / g, more preferably 0.3 mmol / g or more, and is preferably 0.6 mmol / g or less, more preferably 0.5 mmol / g or less.

[0024] <(Meth)acrylic acid ester polymer block (A)> The (meth)acrylic acid ester-based polymer block (A) is a polymer block containing at least a structural unit derived from a (meth)acrylic acid ester (a1) and a structural unit derived from a chain transfer agent (a2) having a mercapto group.

[0025] <(Meth)acrylic acid ester (a1)> The (meth)acrylic acid ester (a1) is roughly classified into (meth)acrylic acid ester (a1-1) having no reactive silicon group and (meth)acrylic acid ester (a1-2) having a reactive silicon group. The (meth)acrylic acid ester (a1-1) not having a reactive silicon group is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2- Examples of such an acrylate include hydroxypropyl, ethylene oxide adduct of (meth)acrylic acid, 2,2,2-trifluoroethyl (meth)acrylate, 3,3,3-trifluoropropyl (meth)acrylate, 3,3,4,4,4-pentafluorobutyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, trifluoromethyl (meth)acrylate, perfluoroethyl (meth)acrylate, bis(trifluoromethyl)methyl (meth)acrylate, 2-trifluoromethyl-2-perfluoroethylethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, 2-perfluorohexadecylethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, chloroethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, and 2-aminoethyl (meth)acrylate. One type may be used alone, or two or more types may be used in combination. The (meth)acrylic acid ester (a1-1) having no reactive silicon group is preferably a (meth)acrylic acid alkyl ester.

[0026] From the viewpoint of achieving high tensile strength, the content of the (meth)acrylic acid ester (a1-1) having no reactive silicon group is preferably 30% by weight or more, more preferably 40% by weight or more, and even more preferably 50% by weight or more of the total amount of structural units forming the (meth)acrylic acid ester-based polymer block (A). The upper limit is preferably 90% by weight or less, more preferably 80% by weight or less.

[0027] The (meth)acrylic acid ester (a1-1) having no reactive silicon group preferably contains an alkyl methacrylate ester having an alkyl carbon number of 4 or less, since this allows the formation of a hard polymer block (A) and the production of a cured product with high strength. The content of this monomer in the graft copolymer according to this embodiment is preferably 10% by weight or more, more preferably 20% by weight or more, and particularly preferably 30% by weight or more.

[0028] However, from the viewpoint of reducing the viscosity of the graft copolymer when heated and melted and ensuring a long time for lamination after application of the graft copolymer, the content of the monomer in the graft copolymer according to this embodiment is preferably 45% by weight or less, and more preferably 42% by weight or less.

[0029] The content of the (meth)acrylic acid alkyl ester having 7 or more alkyl carbon atoms, which corresponds to the (meth)acrylic acid ester (a1-1) not having a reactive silicon group, is preferably set in the range of 0 to 7% by weight in the graft copolymer. By reducing the amount of the (meth)acrylic acid alkyl ester having a long-chain alkyl group used, the cured product obtained from the graft copolymer can exhibit high strength and high elongation properties. The upper limit is preferably 6% by weight, more preferably 5% by weight, and even more preferably 3% by weight.

[0030] The content of butyl acrylate, which corresponds to the (meth)acrylic acid ester (a1-1) having no reactive silicon group, in the graft copolymer is preferably 0 to 8% by weight, more preferably 6% by weight, and even more preferably 5% by weight, in order to improve the strength and elongation of the cured product.

[0031] The (meth)acrylic acid ester (a1-2) having a reactive silicon group is an optional monomer and may not be used, but is preferably used. The reactive silicon group contained in (a1-2) is the reactive silicon group represented by the above-mentioned general formula (1). By using the monomer (a1-2), the reactive silicon group can be introduced into the side chain (non-terminal portion) of the (meth)acrylic acid ester polymer block (A).

[0032] The (meth)acrylic acid ester (a1-2) having a reactive silicon group is not particularly limited, and examples thereof include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropyldimethoxymethylsilane, (meth)acryloxymethyltrimethoxysilane, (meth)acryloxymethyldimethoxymethylsilane, etc. These compounds may be used alone or in combination of two or more.

[0033] When a (meth)acrylic acid ester (a1-2) having a reactive silicon group is used, the content of (a1-2) is, from the viewpoint of improving recovery, preferably from 0 to 30% by weight, more preferably from 0 to 10% by weight, even more preferably from 0.1 to 7% by weight, and particularly preferably from 0.5 to 5% by weight, of the total amount of structural units forming the (meth)acrylic acid ester-based polymer block (A).

[0034] <Chain transfer agent (a2) having a mercapto group> The use of a chain transfer agent (a2) having a mercapto group makes it possible to control the molecular weight of the (meth)acrylic acid ester polymer block (A). It also narrows the molecular weight distribution of the graft copolymer and suppresses gelation during synthesis of the graft copolymer. It also makes it possible to preferentially synthesize polymer molecules in which one polyoxyalkylene polymer block (B) is introduced into one graft copolymer molecule.

[0035] The chain transfer agent (a2) having a mercapto group may not have a reactive silicon group, but preferably has a reactive silicon group. The reactive silicon group is the reactive silicon group represented by the above-mentioned general formula (1). When the chain transfer agent (a2) having a mercapto group has a reactive silicon group, the reactive silicon group can be introduced into the molecular chain terminal of the (meth)acrylic acid ester polymer block (A).

[0036] The chain transfer agent (a2) having a mercapto group is not particularly limited, and examples thereof include 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyltrimethoxysilane, (mercaptomethyl)dimethoxymethylsilane, (mercaptomethyl)trimethoxysilane, n-dodecyl mercaptan, tert-dodecyl mercaptan, and lauryl mercaptan.

[0037] The content of the chain transfer agent (a2) having a mercapto group is preferably from 1 to 25% by weight, more preferably from 2 to 20% by weight, and even more preferably from 3 to 15% by weight, of the total amount of structural units forming the (meth)acrylic acid ester polymer block (A).

[0038] Furthermore, the content of the chain transfer agent (a2) having a mercapto group preferably accounts for 1 mol % or more and 30 mol % or less of the total amount of structural units forming the (meth)acrylic acid ester-based polymer block (A), more preferably 3 mol % or more and 25 mol % or less, even more preferably 5 mol % or more and 20 mol % or less, and particularly preferably 7 mol % or more and 18 mol % or less.

[0039] The molar ratio of the polyoxyalkylene polymer block (B) to the chain transfer agent (a2) having a mercapto group is preferably 0.05 or more, more preferably 0.06 or more, even more preferably 0.08 or more, and particularly preferably 0.10 or more, because high tensile strength and recovery are obtained. The upper limit of the molar ratio is not particularly limited, but is preferably 0.50 or less, more preferably 0.30 or less, and even more preferably 0.20 or less, because the final strength of the cured product is high.

[0040] The graft copolymer or (meth)acrylic acid ester polymer block (A) according to this embodiment has a substituent (-SR , which will be described later) derived from the chain transfer agent (a2) having a mercapto group. 8 Since it has a structure represented by the following formula (II), it may contain a sulfur atom.

[0041] In the graft copolymer according to this embodiment, the concentration of sulfur atoms derived from the chain transfer agent (a2) is set to 5,000 ppm or more and 15,000 ppm or less in the graft copolymer. The sulfur atom concentration is a value relative to the solid content of the graft copolymer, and the solvent is excluded from the calculation.

[0042] The sulfur atom concentration is a value that reflects the proportion of chain transfer agent used in the graft polymer. If the sulfur atom concentration is less than 5,000 ppm, the proportion of chain transfer agent used is small, so block (A) tends to have a relatively high molecular weight. As a result, the cured product of the graft copolymer becomes too hard, resulting in poor recovery. If the sulfur atom concentration exceeds 15,000 ppm, the proportion of chain transfer agent used is large, so block (A) tends to have a relatively low molecular weight. As a result, the strength of the cured product may decrease.

[0043] The lower limit of the sulfur atom concentration is preferably 5,000 ppm or more, more preferably 7,000 ppm or more, and even more preferably 8,500 ppm or more, and the upper limit is preferably 15,000 ppm or less, more preferably 14,000 ppm or less, and even more preferably 13,000 ppm or less.

[0044] The method for measuring the sulfur atom concentration is not particularly limited. It can be measured by known elemental analysis methods such as organic elemental analysis and X-ray fluorescence analysis. The sulfur atom concentration may also be a theoretical value calculated from the total amount of the constituent components used in the production of the graft copolymer and the amount of the chain transfer agent (a2) having a mercapto group.

[0045] The (meth)acrylic acid ester polymer block (A) can have a reactive silicon group by satisfying either or both of the following two conditions: Condition 1: The (meth)acrylic acid ester (a1) includes a (meth)acrylic acid ester having a reactive silicon group. Condition 2: The chain transfer agent (a2) having a mercapto group further has a reactive silicon group.

[0046] In order to obtain a cured product with high strength, it is preferable to introduce reactive silicon groups by both condition 1 and condition 2. Specifically, from the viewpoint of the recovery of the cured product, the reactive silicon group equivalent derived from (a1) is preferably 0.01 mmol / g or more, more preferably 0.03 mmol / g or more, in the graft copolymer, and from the viewpoint of the elongation of the cured product, the reactive silicon group equivalent derived from (a1) is preferably 0.40 mmol / g or less, more preferably 0.20 mmol / g or less, and even more preferably 0.15 mmol / g or less. On the other hand, the reactive silicon group equivalent derived from (a2) is preferably 0.1 mmol / g or more, more preferably 0.15 mmol / g or more, and even more preferably 0.20 or more, and the reactive silicon group equivalent derived from (a2) is preferably 0.60 mmol / g or less, more preferably 0.50 mmol / g or less, and even more preferably 0.40 mmol / g or less.

[0047] The constituent components forming the (meth)acrylic acid ester-based polymer block (A) may or may not contain another monomer (a3) ​​that does not fall under either (a1) or (a2) described in detail above.

[0048] Examples of the other monomer (a3) ​​include styrene-based monomers such as styrene, vinyltoluene, α-methylstyrene, chlorostyrene, and styrenesulfonic acid; fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, and vinylidene fluoride; maleic acid and its derivatives such as maleic acid, maleic anhydride, maleic acid monoalkyl esters, and maleic acid dialkyl esters; fumaric acid and its derivatives such as fumaric acid, fumaric acid monoalkyl esters, and fumaric acid dialkyl esters; maleimide, methylmaleimide, ethylmaleimide, propylmaleimide, and butylmaleimide. Examples of the other monomers include maleimide monomers such as hexylmaleimide, octylmaleimide, dodecylmaleimide, stearylmaleimide, phenylmaleimide, and cyclohexylmaleimide; vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, and vinyl cinnamate; olefin monomers such as ethylene and propylene; conjugated diene monomers such as butadiene and isoprene; (meth)acrylamide; (meth)acrylonitrile; and vinyl monomers such as vinyl chloride, vinylidene chloride, allyl chloride, allyl alcohol, ethyl vinyl ether, and butyl vinyl ether. These other monomers may be used alone or in combination.

[0049] <Polyoxyalkylene polymer block (B)> The polyoxyalkylene polymer constituting the polyoxyalkylene polymer block (B) is not particularly limited, and examples thereof include polyoxyethylene, polyoxypropylene, polyoxybutylene, polyoxytetramethylene, polyoxyethylene-polyoxypropylene copolymer, polyoxypropylene-polyoxybutylene copolymer, etc. Among these, polyoxypropylene is preferred.

[0050] The main chain skeleton of the polyoxyalkylene polymer may be linear or branched, but is preferably linear.

[0051] The number-average molecular weight of the polyoxyalkylene polymer block (B) is 5,000 or more. Within this range, the cured product obtained from the graft copolymer can exhibit high strength and high elongation properties. The number-average molecular weight is preferably 8,000 or more, more preferably 10,000 or more, and even more preferably 12,000 or more. From the viewpoint of viscosity during heat melting, the upper limit is preferably 100,000 or less, more preferably 50,000 or less, even more preferably 30,000 or less, even more preferably 26,000 or less, and particularly preferably 23,000 or less.

[0052] The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the polyoxyalkylene polymer block (B) is 1.40 or less. This can improve the strength and recovery of the cured product obtained from the graft copolymer. If the molecular weight distribution of the polymer block (B) is greater than 1.40, it becomes difficult to form a graft polymer component in which the ABA groups are bonded in this order, which tends to result in reduced strength and recovery. The molecular weight distribution is preferably 1.3 or less, more preferably 1.2 or less, and even more preferably 1.1 or less. Furthermore, the narrower the molecular weight distribution, the lower the viscosity when heated and melted. Furthermore, the initial adhesive strength tends to be readily developed within a short time after lamination.

[0053] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the polyoxyalkylene polymer block (B) are values ​​measured in terms of polystyrene using the polyfunctional macromonomer (a4) described below by gel permeation chromatography (GPC). The detailed measurement method is described in the Examples.

[0054] The polyoxyalkylene polymer block (B) can be introduced into the graft copolymer by using a polyoxyalkylene polymer (a4) having, on average, more than one (meth)acryloyl group per molecule. The polymer (a4) is itself a polymer, but is one of the components constituting the graft copolymer according to this embodiment. The polymer (a4) can be copolymerized with the (meth)acrylic acid ester (a1) by virtue of having a (meth)acryloyl group. Furthermore, since the polymer (a4) has more than one (meth)acryloyl group per molecule, it can function as a so-called polyfunctional macromonomer. Hereinafter, the polymer (a4) will also be referred to as the polyfunctional macromonomer (a4).

[0055] The (meth)acryloyl group contained in the polyfunctional macromonomer (a4) is not particularly limited, but can be represented by the following general formula (4) or (5). CH2=C(R 7 )-C(=O)-OR-NH-C(=O)-OB (4) CH2=C(R 7 )-C(=O)-OB (5) In each formula, R 7 represents hydrogen or a methyl group. B represents a polyoxyalkylene polymer block (B). R represents a divalent hydrocarbon group having 1 to 20 carbon atoms. The number of carbon atoms is preferably 1 to 10, more preferably 1 to 6, and particularly preferably 1 to 3.

[0056] The polyfunctional macromonomer (a4) has, on average, more than one (meth)acryloyl group per molecule. The average number of (meth)acryloyl groups per molecule of the polyfunctional macromonomer (a4) is preferably 1.1 to 5, more preferably 1.3 to 4, even more preferably 1.6 to 2.5, and particularly preferably 1.8 to 2.0. The polyfunctional macromonomer (a4) may have only acryloyl groups, only methacryloyl groups, or both acryloyl and methacryloyl groups, as the (meth)acryloyl groups.

[0057] The polyfunctional macromonomer (a4) may have a (meth)acryloyl group at either or both of the molecular chain terminal and / or side chain of the polyoxyalkylene polymer. From the viewpoint of excellent mechanical properties, it is preferable to have the group at the molecular chain terminal. It is particularly preferable that the polyfunctional macromonomer (a4) has a linear main chain skeleton and has a (meth)acryloyl group at each of both molecular chain terminals.

[0058] The method for synthesizing the polyfunctional macromonomer (a4) is not particularly limited, but an example thereof includes a method in which a polyoxyalkylene polymer having more than one hydroxyl group in the molecule (preferably a linear polyoxyalkylene polymer having hydroxyl groups at both ends) is prepared, and a (meth)acryloyl group is introduced using the hydroxyl group.

[0059] As an example of a method for synthesizing the polyfunctional macromonomer (a4), a polyoxyalkylene polymer having a hydroxyl group can be reacted with a compound having an isocyanate group and a (meth)acryloyl group to form a urethane bond and introduce a (meth)acryloyl group. Specific examples of the compound having an isocyanate group and a (meth)acryloyl group include isocyanate ethyl (meth)acrylate, isocyanate propyl (meth)acrylate, isocyanate butyl (meth)acrylate, and isocyanate hexyl (meth)acrylate.

[0060] As another example of a method for synthesizing the polyfunctional macromonomer (a4), a diisocyanate compound may be reacted with a polyoxyalkylene polymer having a hydroxyl group to introduce an isocyanate group into the polymer, and then a compound having a hydroxyl group and a (meth)acryloyl group may be reacted to introduce a (meth)acryloyl group. Specific examples of the diisocyanate compound include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-diphenylmethane diisocyanate. Specific examples of the compound having a hydroxyl group and a (meth)acryloyl group include, for example, hydroxybutyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate.

[0061] As yet another example of a method for synthesizing the polyfunctional macromonomer (a4), a polyoxyalkylene polymer having a hydroxyl group is reacted with an acid anhydride to introduce a carboxyl group into the polymer, and then a compound having an epoxy group and a (meth)acryloyl group is reacted to introduce a (meth)acryloyl group. Specific examples of the acid anhydride include succinic anhydride, maleic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylhimic anhydride, trimellitic anhydride, methylnadic anhydride, and dodecylsuccinic anhydride. Specific examples of the compound having an epoxy group and a (meth)acryloyl group include glycidyl (meth)acrylate.

[0062] Another example of a method for synthesizing the polyfunctional macromonomer (a4) is a method in which a polyoxyalkylene polymer having a hydroxyl group is subjected to dehydration condensation with methacrylic acid or acrylic acid. To carry out the reaction under milder conditions, a method in which a polyoxyalkylene polymer having a hydroxyl group is reacted with methacrylic acid chloride, methacrylic acid bromide, methacrylic acid iodide, acrylic acid chloride, acrylic acid bromide, acrylic acid iodide, or the like is reacted with the polyoxyalkylene polymer having a hydroxyl group.

[0063] In the graft copolymer according to this embodiment, the proportion of block (A) relative to the total of the (meth)acrylic acid ester polymer block (A) and the polyoxyalkylene polymer block (B) is 35 to 65% by weight, and the proportion of block (B) is 35 to 65% by weight. Within these ranges, the balance between the physical properties achieved by block (A) and the physical properties achieved by block (B) is good, and the effects of the invention described above can be achieved. If the proportion of block (B) is less than 35% by weight, the viscosity of the graft copolymer when heated and melted may increase, or the elongation of the cured product obtained from the graft copolymer may decrease. On the other hand, if the proportion of block (B) exceeds 65% by weight, the initial adhesive strength and the final strength of the cured product may decrease. The proportion of block (A) is preferably 40 to 65% by weight and the proportion of block (B) is preferably 35 to 60% by weight, more preferably 45 to 60% by weight for the former and 40 to 55% by weight for the latter.

[0064] Furthermore, from the viewpoint of the above-mentioned invention, the content of the polyoxyalkylene polymer block (B) is preferably from 0.05 mol % to 6.0 mol % of the total amount of structural units forming the graft copolymer, more preferably from 0.1 mol % to 2.3 mol %, and even more preferably from 0.2 mol % to 1.5 mol %.

[0065] The average number of polyoxyalkylene polymer blocks (B) per molecule of the graft copolymer according to this embodiment is preferably 0.05 or more and 2.0 or less, from the viewpoint of the strength of the resulting cured product. The lower limit is more preferably 0.07 or more, and even more preferably 0.08 or more. The upper limit is more preferably 1.5 or less, and even more preferably 1.0 or less. The average number can be calculated using the following formula: Formula: Number average molecular weight of graft copolymer (g / mol) / (Weight of graft copolymer (g) / (Number of moles of polymer block (B)))

[0066] <Block combination format> The graft copolymer according to this embodiment has a (meth)acrylic acid ester polymer block (A) and a polyoxyalkylene polymer block (B) bonded in the order ABA. However, the graft copolymer is not limited to a triblock copolymer, and may have a structure in which a block (B) and / or a block (A) is further bonded to the triblock copolymer.

[0067] The graft copolymer according to this embodiment may be prepared by free radical polymerization. When prepared by free radical polymerization, some molecules of the graft copolymer may contain polymer components in which the block (A) and the block (B) are not bonded to each other. In this application, the term "graft copolymer" is defined as including such non-bonded polymer components. The ratio of the graft copolymer in which the block (A) and the block (B) are bonded to each other and the non-bonded polymer components can be easily determined by known means, for example, GPC analysis.

[0068] In the graft copolymer according to this embodiment, the block (A) and the block (B) are preferably bonded via an ester bond derived from the (meth)acryloyl group in the polyfunctional macromonomer (a4) (i.e., the ester bond in the general formula (4) or (5)).

[0069] The bonding form between block (A) and block (B) is not particularly limited, but can be represented by the following general formula (2) or (3). AC(=O)-OR-NH-C(=O)-OB (2) AC(=O)-OB (3) In each formula, A represents the polymer block (A) and B represents the polymer block (B). R represents a divalent hydrocarbon group having 1 to 20 carbon atoms. The number of carbon atoms is preferably 1 to 10, more preferably 1 to 6, and particularly preferably 1 to 3.

[0070] Since a cured product with high strength and elongation is easily obtained, it is preferable that block (A) is composed of a hard polymer and block (B) is composed of a soft polymer. Here, a hard polymer refers to a polymer with a high glass transition temperature. A soft polymer refers to a polymer with a low glass transition temperature.

[0071] When the block (A) is composed of a hard polymer, as described above, the (meth)acrylic acid ester (a1-1) preferably contains an alkyl methacrylate ester having an alkyl carbon number of 4 or less.

[0072] Since the block (A) is a molecular chain formed by reacting with a chain transfer agent (a2) having a mercapto group, the terminal of the block (A) is provided with a substituent derived from (a2), such as -SR 8 In the formula, S represents a sulfur atom, and R 8 represents a hydrocarbon group which may have a reactive silicon group. Examples of the hydrocarbon group include an alkyl group, an aryl group, or an aralkyl group having 1 to 20 carbon atoms. The reactive silicon group is a reactive silicon group represented by the general formula (1) described above. R 8 Specific examples of the group include a reactive silicon group-containing methyl group, a reactive silicon group-containing propyl group, an n-dodecyl group, a tert-dodecyl group, and a lauryl group.

[0073] The graft copolymer according to this embodiment may have a linear structure in which the end of block (A) and the end of block (B) are linked, but preferably contains an H-type structure. Figure 1 shows a conceptual diagram of the H-type structure. In this structure, two vertical bars correspond to block (A) and one horizontal bar corresponds to block (B). Both ends of block (B) are bonded to the non-terminal sites of block (A). One end of each of the two blocks (A) contains a substituent, -SR, derived from a chain transfer agent having a mercapto group and a reactive silicon group. 8 -SiR 1 3-a X a In addition, -SiR is also bonded to the non-terminal portion of block (A).1 3-a X a are randomly bonded, which are derived from a (meth)acrylic acid ester (a1-2) having a reactive silicon group.

[0074] The H-type structure can be formed by randomly polymerizing a polyfunctional macromonomer (a4) having a (meth)acryloyl group at each end of the polyoxyalkylene polymer molecular chain, a (meth)acrylic acid ester (a1), and a chain transfer agent (a2) having a mercapto group.

[0075] <Molecular weight of graft copolymer> The number average molecular weight of the graft copolymer according to this embodiment is not particularly limited, but is preferably 500 to 50,000, more preferably 500 to 30,000, and particularly preferably 1,000 to 10,000, in terms of polystyrene equivalent molecular weight as measured by GPC. Among these, a number average molecular weight of 7,000 or less is preferred, since a low-viscosity graft copolymer can be obtained. Furthermore, a number average molecular weight of 4,000 or less is preferred, since good adhesiveness can be achieved at low viscosity.

[0076] The weight-average molecular weight of the graft copolymer is not particularly limited, but is preferably 500 to 80,000, more preferably 3,000 to 70,000, and particularly preferably 5,000 to 65,000, as measured by GPC in terms of polystyrene. Of these, a weight-average molecular weight of 40,000 or less is preferred, as this allows for the production of a cured product with low viscosity and high strength.

[0077] The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the graft copolymer according to this embodiment is preferably 6.5 or more and 10.0 or less. By making the molecular weight distribution of the graft copolymer 10.0 or less, the strength and recovery of the resulting cured product can be increased. Furthermore, by making the molecular weight distribution 6.5 or more, the melt viscosity of the graft copolymer can be reduced. The molecular weight distribution is more preferably 7.0 or more and 9.8 or less, even more preferably 7.5 or more and 9.6 or less, and particularly preferably 8.0 or more and 9.2 or less.

[0078] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the graft copolymer are values ​​measured by gel permeation chromatography (GPC) in terms of polystyrene. The detailed measurement method will be described in the Examples. As described above, the graft copolymer may also contain a polymer component in which the block (A) and the block (B) are not bonded to each other. The number average molecular weight, weight average molecular weight, and molecular weight distribution of the graft copolymer are values ​​measured for the graft copolymer including such a polymer component.

[0079] <Method for producing graft copolymer> The graft copolymer according to this embodiment can be produced by subjecting a (meth)acrylic acid ester (a1), a chain transfer agent (a2) having a mercapto group, any other monomer (a3), and a polyfunctional macromonomer (a4) to a polymerization reaction. The polymerization method is not particularly limited, but may be a general free radical polymerization. According to this embodiment, despite being free radical polymerization, the polymerization can be controlled, a graft copolymer can be produced, and the molecular weight distribution can be made relatively narrow.

[0080] Examples of polymerization initiators that can be used in the free radical polymerization include azo compounds such as 2,2'-azobis(2-methylbutyronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], and 1,1'-azobis(cyclohexane-1-carbonitrile). Diacyl peroxides such as benzoyl peroxide, isobutyryl peroxide, isononanoyl peroxide, decanoyl peroxide, lauroyl peroxide, parachlorobenzoyl peroxide, and di(3,5,5-trimethylhexanoyl) peroxide; diisopropyl percarbonate, di-sec-butyl percarbonate, di-2-ethylhexyl percarbonate, di-1-methylheptyl percarbonate, and di-3-methoxybutyl percarbonate peroxydicarbonates such as tert-butyl perbenzoate, tert-butyl peracetate, tert-butyl per-2-ethylhexanoate, tert-butyl perisobutyrate, tert-butyl perpivalate, tert-butyl diperadipate, and cumyl perneodecanoate; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; dialkyl peroxides such as di-tert-butyl peroxide, dicumyl peroxide, tert-butyl cumyl peroxide, and 1,1-di(tert-hexylperoxy)-3,3,5-trimethylcyclohexane; hydroperoxides such as cumene hydroxyperoxide and tert-butyl hydroperoxide; and peroxides such as 1,1-di(tert-hexylperoxy)-3,3,5-trimethylcyclohexane. These polymerization initiators may be used alone or in combination of two or more.

[0081] Examples of solvents that can be used in the free radical polymerization include aromatic solvents such as toluene, xylene, styrene, ethylbenzene, paradichlorobenzene, di-2-ethylhexyl phthalate, and di-n-butyl phthalate; aliphatic hydrocarbon solvents such as hexane, heptane, octane, cyclohexane, and methylcyclohexane; carboxylic acid ester compounds such as ethyl acetate, butyl acetate, n-propyl acetate, and isopropyl acetate; ketone compounds such as methyl isobutyl ketone and methyl ethyl ketone; dialkyl carbonate compounds such as dimethyl carbonate and diethyl carbonate; and alcohol compounds such as n-propanol, 2-propanol, n-butanol, 2-butanol, isobutanol, tert-butanol, and amyl alcohol. Since the resulting graft copolymer tends to be difficult to dissolve in alcoholic solvents, non-alcoholic solvents are preferred. Carboxylic acid ester solvents are particularly preferred. Aromatic solvents are preferred due to their high dissolving power.

[0082] As described above, the graft copolymer can have reactive silicon groups by using a (meth)acrylic acid ester having a reactive silicon group or by using a chain transfer agent having a reactive silicon group in addition to a mercapto group. Both methods may be used in combination. By using a (meth)acrylic acid ester having a reactive silicon group, reactive silicon groups can be introduced randomly into the side chains of the (meth)acrylic acid ester-based polymer block (A). Furthermore, by using a chain transfer agent having a reactive silicon group in addition to a mercapto group, reactive silicon groups can be introduced into the terminals of the (meth)acrylic acid ester-based polymer block (A).

[0083] However, in order to further introduce reactive silicon groups into the graft copolymer, the following method can also be used in combination. (i) A method of copolymerizing a monomer having a reactive functional group (V group) with a (meth)acrylic acid ester (a1) or the like, and then reacting the resulting copolymer with a compound having a functional group reactive with the V group and a reactive silicon group. Specific examples include a method of copolymerizing 2-hydroxyethyl acrylate and then reacting with an isocyanate silane compound having a reactive silicon group, and a method of copolymerizing glycidyl acrylate and then reacting with an aminosilane compound having a reactive silicon group. (ii) A method of modifying the terminal functional groups of a (meth)acrylic acid ester copolymer synthesized by living radical polymerization to introduce reactive silicon groups. The (meth)acrylic acid ester copolymer obtained by living radical polymerization has terminal functional groups that can be easily introduced, and by modifying it, reactive silicon groups can be introduced at the terminals of the polymer.

[0084] Examples of the compound having a functional group reactive with the V group and a reactive silicon group used in the method (i) include isocyanate silane compounds such as 3-isocyanatepropyldimethoxymethylsilane, 3-isocyanatepropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, isocyanatemethyldimethoxymethylsilane, isocyanatemethyltrimethoxysilane, and isocyanatemethyltriethoxysilane; 3-glycidoxypropyldimethoxymethylsilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and glycidoxymethylsilane; epoxy silane compounds such as 3-aminopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, aminomethyldimethoxymethylsilane, aminomethyltrimethoxysilane, aminomethyltriethoxysilane, N-cyclohexylaminomethyldimethoxymethylsilane, N-cyclohexylaminomethyltrimethoxysilane, N-cyclohexylaminomethyltriethoxysilane, and the like.

[0085] In method (ii), any modification reaction can be used. Examples include a method using a compound having a reactive silicon group and a reactive group capable of reacting with a terminal functional group obtained by living radical polymerization, and a method in which a double bond is introduced into the polymer terminal using a compound having a reactive group and a double bond capable of reacting with a terminal functional group, and then a reactive silicon group is introduced using a hydrosilylation reaction or the like.

[0086] <<Curable composition>> The graft copolymer according to this embodiment can be used in a curable composition, which preferably contains a silanol condensation catalyst to promote the condensation reaction of the reactive silicon groups in the graft copolymer.

[0087] <Silanol condensation catalyst> Examples of silanol condensation catalysts include organotin compounds, metal carboxylates, amine compounds, carboxylic acids, and alkoxy metals.

[0088] Specific examples of organotin compounds include dibutyltin dilaurate, dibutyltin dioctanoate, dibutyltin bis(butyl maleate), dibutyltin diacetate, dibutyltin oxide, dibutyltin bis(acetylacetonate), dioctyltin bis(acetylacetonate), dioctyltin dilaurate, dioctyltin distearate, dioctyltin diacetate, dioctyltin oxide, a reaction product of dibutyltin oxide with a silicate compound, a reaction product of dioctyltin oxide with a silicate compound, and a reaction product of dibutyltin oxide with a phthalate ester.

[0089] Specific examples of the metal carboxylate include tin carboxylate, bismuth carboxylate, titanium carboxylate, zirconium carboxylate, iron carboxylate, etc. The metal carboxylate can be a combination of the following carboxylic acids and various metals.

[0090] Specific examples of the amine compound include amines such as octylamine, 2-ethylhexylamine, laurylamine, and stearylamine; nitrogen-containing heterocyclic compounds such as pyridine, 1,8-diazabicyclo[5,4,0]undecene-7 (DBU), and 1,5-diazabicyclo[4,3,0]nonene-5 (DBN); guanidines such as guanidine, phenylguanidine, and diphenylguanidine; biguanides such as butylbiguanide, 1-o-tolylbiguanide, and 1-phenylbiguanide; amino group-containing silane coupling agents; and ketimine compounds.

[0091] Specific examples of carboxylic acids include acetic acid, propionic acid, butyric acid, 2-ethylhexanoic acid, lauric acid, stearic acid, oleic acid, linoleic acid, neodecanoic acid, and versatic acid.

[0092] Specific examples of alkoxy metals include titanium compounds such as tetrabutyl titanate titanium tetrakis(acetylacetonate) and diisopropoxytitanium bis(ethylacetoacetate), aluminum compounds such as aluminum tris(acetylacetonate) and diisopropoxyaluminum ethylacetoacetate, and zirconium compounds such as zirconium tetrakis(acetylacetonate).

[0093] When a silanol condensation catalyst is used, the amount used is preferably 0.001 to 20 parts by weight, more preferably 0.01 to 15 parts by weight, and even more preferably 0.01 to 10 parts by weight, per 100 parts by weight of the graft copolymer according to this embodiment, from the viewpoint of promoting the condensation reaction of the reactive silicon groups.

[0094] <<Other additives>> In addition to the graft copolymer and silanol condensation catalyst according to the present embodiment, additives such as a plasticizer, a filler, an adhesion promoter, a dehydrating agent, a rheology control agent, an antioxidant, a light stabilizer, an ultraviolet absorber, and other resins may be added to the curable composition according to the present embodiment.

[0095] Furthermore, various additives may be added to the curable composition according to this embodiment as needed for the purpose of adjusting the physical properties of the curable composition or the cured product. Examples of such additives include solvents, diluents, photocurable substances, oxygen-curable substances, surface property improvers, silicates, curability regulators, radical inhibitors, metal deactivators, antiozonants, phosphorus-based peroxide decomposers, lubricants, pigments, mildew inhibitors, flame retardants, and foaming agents.

[0096] <Plasticizer> A plasticizer can be blended into the curable composition. By blending a plasticizer, the viscosity of the curable composition can be reduced, making it easier to handle.

[0097] The plasticizer is not particularly limited, but examples thereof include phthalate ester compounds such as dibutyl phthalate, diisononyl phthalate (DINP), diheptyl phthalate, di(2-ethylhexyl) phthalate, diisodecyl phthalate (DIDP), and butyl benzyl phthalate; terephthalate ester compounds such as bis(2-ethylhexyl)-1,4-benzenedicarboxylate; non-phthalate ester compounds such as 1,2-cyclohexanedicarboxylic acid diisononyl ester; and fatty acids such as dioctyl adipate, dioctyl sebacate, dibutyl sebacate, diisodecyl succinate, and acetyl tributyl citrate. unsaturated fatty acid ester compounds such as butyl oleate and methyl acetylricinoleate; phosphate ester compounds; trimellitic acid ester compounds; chlorinated paraffins; hydrocarbon oils such as alkyl diphenyls and partially hydrogenated terphenyls; process oils; epoxy plasticizers such as epoxidized soybean oil, epoxidized linseed oil, bis(2-ethylhexyl)-4,5-epoxycyclohexane-1,2-dicarboxylate (E-PS), epoxy octyl stearate, epoxy butyl stearate, and epoxy benzyl stearate; alkyl sulfonic acid esters, etc.

[0098] As the plasticizer, a polymer plasticizer can also be used. Specific examples of the polymer plasticizer include vinyl polymers, polyester plasticizers, polyether polyols such as polyethylene glycol and polypropylene glycol having a number average molecular weight of 500 or more, and polyether plasticizers such as derivatives in which the hydroxy groups of these polyether polyols are converted to ester groups, ether groups, etc., polystyrenes, polybutadiene, polybutene, polyisobutylene, butadiene-acrylonitrile, polychloroprene, etc. Among these, polymer plasticizers are preferred, polyether plasticizers are more preferred, and polypropylene glycol is particularly preferred. As the plasticizer, one type may be used alone, or two or more types may be used in combination.

[0099] The amount of the plasticizer to be added is preferably 5 to 150 parts by weight, more preferably 10 to 120 parts by weight, and particularly preferably 20 to 100 parts by weight, relative to 100 parts by weight of the graft copolymer.

[0100] <Filler> The curable composition may contain a filler, which can improve the strength of the cured product.

[0101] Examples of fillers include heavy calcium carbonate, colloidal calcium carbonate, magnesium carbonate, diatomaceous earth, clay, talc, titanium oxide, fumed silica, precipitated silica, crystalline silica, fused silica, anhydrous silicic acid, hydrous silicic acid, alumina, carbon black, ferric oxide, fine aluminum powder, zinc oxide, activated zinc white, PVC powder, PMMA powder, glass fiber, and filaments. Organic or inorganic balloons may be added to reduce the weight (specific gravity) of the composition. Only one type of filler may be used, or two or more types may be used in combination.

[0102] The amount of the filler to be added is preferably 1 to 300 parts by weight, more preferably 10 to 250 parts by weight, based on 100 parts by weight of the graft copolymer.

[0103] <Adhesion promoter> The curable composition may contain an adhesion promoter. As the adhesion promoter, a silane coupling agent or a reaction product of a silane coupling agent can be added.

[0104] Specific examples of the silane coupling agent include amino group-containing silanes such as γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and (2-aminoethyl)aminomethyltrimethoxysilane; γ-isocyanatepropyltrimethoxysilane, γ-isocyanatepropyltriethoxysilane, and γ-isopropyltriethoxysilane. Examples of suitable adhesives include isocyanate group-containing silanes such as cyanatepropylmethyldimethoxysilane, α-isocyanatemethyltrimethoxysilane, and α-isocyanatemethyldimethoxymethylsilane; mercapto group-containing silanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropylmethyldimethoxysilane; and epoxy group-containing silanes such as γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Reaction products of various silane coupling agents can also be used. The adhesion promoter may be used alone or in combination with two or more.

[0105] The amount of the adhesion promoter to be added is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the graft copolymer.

[0106] <Dehydrating agent> A dehydrating agent can be added to the curable composition. Here, the dehydrating agent is preferably a compound capable of reacting with water, more preferably a silicon compound capable of reacting with water (excluding compounds that fall under the category of adhesion promoters), and particularly preferably a trialkoxysilane compound.

[0107] Specific examples of the dehydrating agent include, but are not limited to, vinyl group-containing silanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, etc. Only one type of dehydrating agent may be used, or two or more types may be used.

[0108] The amount of the dehydrating agent to be added is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, and even more preferably 1 to 5 parts by weight, based on 100 parts by weight of the graft copolymer.

[0109] <Rheology control agent> If necessary, a rheology control agent may be added to the curable composition to prevent sagging and improve workability.

[0110] The rheology control agent is not particularly limited, but examples thereof include fatty acid amide waxes, hydrogenated castor oil derivatives, metal soaps such as calcium stearate, aluminum stearate, and barium stearate, dry silica, wet silica, etc. These rheology control agents may be used alone or in combination of two or more.

[0111] The amount of the rheology control agent to be added is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the graft copolymer.

[0112] <Antioxidants> The curable composition may contain an antioxidant (antiaging agent), which can improve the weather resistance of the cured product. Examples of antioxidants include hindered phenols, monophenols, bisphenols, and polyphenols. Specific examples of antioxidants are also described in JP-A-4-283259 and JP-A-9-194731. The amount of the antioxidant to be added is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the graft copolymer.

[0113] <Light stabilizer> The curable composition may contain a light stabilizer, which can prevent photo-oxidative deterioration of the cured product. Examples of light stabilizers include benzotriazole-based, hindered amine-based and benzoate-based compounds, with hindered amine-based compounds being particularly preferred. The amount of the light stabilizer to be added is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the graft copolymer.

[0114] <UV absorber> The curable composition may contain an ultraviolet absorber, which can improve the weather resistance of the surface of the cured product. Examples of ultraviolet absorbers include benzophenone-based, benzotriazole-based, salicylate-based, substituted tolyl-based, and metal chelate-based compounds, with benzotriazole-based compounds being particularly preferred, and examples include those commercially available under the names Tinuvin P, Tinuvin 213, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin 329, and Tinuvin 571 (all manufactured by BASF). The amount of the ultraviolet absorber to be added is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the graft copolymer.

[0115] The curable composition according to one embodiment of the present invention can be prepared as a one-component composition in which all ingredients are mixed in advance and stored in a sealed container, and the composition is cured by moisture in the air after application. In this case, it is preferable to dehydrate and dry ingredients containing water before use, or to dehydrate them by reducing the pressure during mixing and kneading.

[0116] Furthermore, the curable composition according to one embodiment of the present invention is composed of a base agent containing a graft copolymer and a curing agent containing components such as a silanol condensation catalyst, a filler, a plasticizer, and water, and can also be prepared as a two-component composition in which the base agent and the curing agent are mixed before use.

[0117] The method for preparing the curable composition according to one embodiment of the present invention is not particularly limited. For example, a common method may be used, such as blending the above components and kneading them at room temperature or under heat using a mixer, roll, kneader, or the like, or dissolving the above components in a small amount of an appropriate solvent and mixing them.

[0118] The curable composition according to one embodiment of the present invention exhibits good adhesion to various adherends, including plastics, metals, and composites. Furthermore, when used as an adhesive for nonpolar materials such as polypropylene or engineering plastics with rigid molecular chains such as polyphenylene sulfide, the adherends can be pre-surface-treated by a known method to enhance adhesion to these adherends and obtain stable adhesive strength. For example, surface treatment techniques such as sanding, flame treatment, corona discharge, arc discharge, and plasma treatment can be used. Plasma treatment is preferred because it causes minimal damage to the adherend and provides stable adhesion. These surface treatments are also effective for removing release agents remaining on the adherend surface after molding.

[0119] The cured product obtained by curing the curable composition according to one embodiment of the present invention has good adhesion to various adherends, and therefore the curable composition can be used as an adhesive, a sealant, or a pressure-sensitive adhesive. In particular, the curable composition according to one embodiment of the present invention is solid at room temperature, but becomes fluid when heated and melted, making it possible to apply it to a substrate, and therefore can be suitably used as a hot-melt curable composition, particularly a hot-melt adhesive.

[0120] In order to ensure workability when applying the curable composition according to one embodiment of the present invention to an adherend, it is preferable to reduce the viscosity by heating to a high temperature, and the temperature at that time is preferably about 70 to 180° C., more preferably 90 to 160° C., and even more preferably 100 to 150° C. The heating method is not particularly limited, and a conventionally known method can be used.

[0121] The curable composition according to one embodiment of the present invention can exhibit the desired physical properties by undergoing a long-term curing (aging) step after bonding the adherends. The conditions for the curing (aging) step are not particularly limited, but examples include a temperature of 5 to 90°C and a time of 24 hours to 1 week.

[0122] When the curable composition according to one embodiment of the present invention is used as a hot-melt curable composition, it can be used as a reactive hot-melt adhesive. This curable composition is suitable for use as an adhesive for joining panels of buses, trailers, trains, etc., as an adhesive for connecting displays and housings in smartphones, tablet devices, laptops, etc., and for joining dissimilar materials such as aluminum-steel, steel-composite materials, and aluminum-composite materials. When joining dissimilar materials, it is preferable to cover the joint with a sealer to prevent corrosion. Polymers having reactive silicon groups, as described herein, can be used as the sealer.

[0123] More specifically, the curable composition according to one embodiment of the present invention is preferably used as an adhesive for automobile parts such as vehicle panels, large vehicle parts such as trucks and buses, train parts, aircraft parts, ship parts, electrical parts, various machine parts, and the like.

[0124] Each of the following items lists preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] General formula (1): -SiR 1 3-a X a (1) (In the formula, R 1 represents a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms; X represents a hydroxyl group or a hydrolyzable group; and a represents 2 or 3. and a polyoxyalkylene polymer block (B) are bonded in the order ABA, the polyoxyalkylene polymer block (B) has a number average molecular weight of 5,000 or more and a molecular weight distribution (Mw / Mn) of 1.40 or less; In the graft copolymer, the proportion of the polymer block (A) is 35 to 65% by weight, and the proportion of the polymer block (B) is 35 to 65% by weight, the polymer block (A) contains a structural unit derived from a (meth)acrylic acid ester (a1) and a structural unit derived from a chain transfer agent (a2) having a mercapto group, A graft copolymer, wherein the concentration of sulfur atoms derived from the chain transfer agent (a2) is 5,000 to 15,000 ppm in the graft copolymer. [Item 2] Item 2. The graft copolymer according to item 1, wherein the content of the (meth)acrylic acid alkyl ester having an alkyl carbon number of 7 or more is 7% by weight or less in the graft copolymer. [Item 3] 3. The graft copolymer according to item 1 or 2, wherein the polyoxyalkylene polymer block (B) has a number average molecular weight of 10,000 to 50,000. [Item 4] 4. The graft copolymer according to any one of items 1 to 3, wherein the molar ratio of the polyoxyalkylene polymer block (B) to the chain transfer agent (a2) having a mercapto group is 0.05 or more. [Item 5] 5. The graft copolymer according to any one of items 1 to 4, wherein the sulfur atom concentration is 8,500 to 15,000 ppm. [Item 6] 6. The graft copolymer according to any one of items 1 to 5, wherein the graft copolymer has a reactive silicon group equivalent of 0.2 to 0.8 mmol / g. [Item 7] The bond between the polymer block (A) and the polymer block (B) is represented by general formula (2) or (3): AC(=O)-OR-NH-C(=O)-OB (2) AC(=O)-OB (3) (wherein A represents the polymer block (A), B represents the polymer block (B), and R represents a divalent hydrocarbon group having 1 to 20 carbon atoms.) [Item 8] A curable composition comprising the graft copolymer according to any one of items 1 to 7. [Item 9] 8. A hot melt adhesive comprising the graft copolymer according to any one of items 1 to 7. [Example]

[0125] The present invention will be specifically explained below by way of examples, but the present invention is not limited to these examples.

[0126] The number average molecular weight and weight average molecular weight in the examples are GPC molecular weights measured under the following conditions. Liquid delivery system: Tosoh HLC-8120GPC Column: Tosoh TSK-GEL H type Solvent: THF Molecular weight: Polystyrene equivalent Measurement temperature: 40℃

[0127] The end group-based molecular weight in the examples is a molecular weight calculated by determining the hydroxyl value according to the measurement method of JIS K 1557 and the iodine value according to the measurement method of JIS K 0070, taking into consideration the structure of the organic polymer (the degree of branching determined by the polymerization initiator used).

[0128] The average number of carbon-carbon unsaturated bonds introduced per terminal of the polymer shown in the examples was calculated by the following formula. (Average number of introductions) = [Unsaturated group concentration of polymer obtained from iodine value (mol / g) - Unsaturated group concentration of precursor polymer obtained from iodine value (mol / g)] / [Hydroxyl group concentration of precursor polymer obtained from hydroxyl value (mol / g)]

[0129] (Sulfur atom concentration) The sulfur atom concentration is a theoretical value calculated from the total amount of the constituent components used in the production of the graft copolymer and the amount of the chain transfer agent (a2) having a mercapto group.

[0130] (Synthesis Example 1) Using polyoxypropylene glycol with a number average molecular weight of approximately 4,020 (terminal group equivalent molecular weight 2,980) as an initiator, propylene oxide was polymerized using a zinc hexacyanocobaltate glyme complex catalyst to obtain polyoxypropylene with hydroxyl groups at both ends and a number average molecular weight of 14,810 (terminal group equivalent molecular weight 9,130). To the obtained polyoxypropylene was added 60 ppm of U-360, and 0.95 equivalents of Karenz AOI (2-isocyanatoethyl acrylate, Resonac Co., Ltd.) relative to the hydroxyl groups of the polyoxypropylene were added dropwise. The reaction was carried out at 90°C for 1 hour in a nitrogen atmosphere, yielding a polyoxyalkylene polymer (a4-1) having acryloyl groups at both ends (i.e., approximately two acryloyl groups per polymer molecule), a number average molecular weight of 14,810, a weight average molecular weight of 17,030, and a molecular weight distribution Mw / Mn=1.15.

[0131] (Synthesis Example 2) Using polyoxypropylene glycol with a number-average molecular weight of approximately 4,020 (2,980 molecular weight in terms of terminal groups) as an initiator, propylene oxide was polymerized with a zinc hexacyanocobaltate glyme complex catalyst to obtain polyoxypropylene with hydroxyl groups at both ends and a number-average molecular weight of 27,130 (17,700 molecular weight in terms of terminal groups). To the resulting polyoxypropylene, 60 ppm of U-360 was added, and 0.93 equivalents of Karenz AOI relative to the hydroxyl groups of the polyoxypropylene were added dropwise. The reaction was carried out in a nitrogen atmosphere at 90°C for 1 hour to obtain a polyoxyalkylene polymer (a4-2) with acryloyl groups at both ends (i.e., approximately two acryloyl groups per polymer molecule), a number-average molecular weight of 27,130, a weight-average molecular weight of 34,150, and a molecular weight distribution Mw / Mn = 1.26.

[0132] (Synthesis Example 3) The polyoxyalkylene polymer (a4-1) synthesized in Synthesis Example 1 and the polyoxyalkylene polymer (a4-2) synthesized in Synthesis Example 2 were mixed in a ratio of 60:40 to obtain a polyoxyalkylene polymer (a4-3) having a number average molecular weight of 17,950, a weight average molecular weight of 23,870, and a molecular weight distribution Mw / Mn=1.33.

[0133] (Synthesis Example 4) The polyoxyalkylene polymer (a4-1) synthesized in Synthesis Example 1 and the polyoxyalkylene polymer (a4-2) synthesized in Synthesis Example 2 were mixed in a ratio of 40:60 to obtain a polyoxyalkylene polymer (a4-4) having a number average molecular weight of 20,060, a weight average molecular weight of 28,280, and a molecular weight distribution Mw / Mn=1.41.

[0134] (Synthesis Example 5) Using polyoxypropylene glycol with a number-average molecular weight of approximately 4,020 (2,980 molecular weight converted into terminal groups) as an initiator, propylene oxide was polymerized with a zinc hexacyanocobaltate glyme complex catalyst to obtain polyoxypropylene with hydroxyl groups at both ends and a number-average molecular weight of 14,810 (9,130 ​​molecular weight converted into terminal groups). 100 ppm of bismuth tris(2-ethylhexanoate) was added to the resulting polyoxypropylene, and hexamethylene diisocyanate was added to achieve an NCO equivalent / OH equivalent ratio of 0.5. The mixture was reacted at 80°C for 1 hour in a nitrogen atmosphere. Karenz AOI (0.95 equivalents relative to the hydroxyl groups of the obtained polyoxypropylene) was added dropwise, and the reaction was carried out at 80°C for 1 hour in a nitrogen atmosphere, yielding a polyoxyalkylene polymer (a4-5) having acryloyl groups at both ends (i.e., approximately two acryloyl groups per polymer molecule), a number average molecular weight of 25,950, a weight average molecular weight of 44,810, and a molecular weight distribution Mw / Mn=1.73.

[0135] (Synthesis Example 6) A four-neck flask equipped with a stirrer was charged with 42.2 parts by weight of butyl acetate, and the temperature was raised to 115° C. under a nitrogen atmosphere. A mixed solution prepared by dissolving 41.8 parts by weight of methyl methacrylate, 50.0 parts by weight of the polyfunctional macromonomer (a4-1) prepared in Synthesis Example 1, 1.4 parts by weight of 3-methacryloxypropyltrimethoxysilane, 6.8 parts by weight of 3-mercaptopropyltrimethoxysilane, and 0.9 parts by weight of 2,2′-azobis(2-methylbutyronitrile) in 17.1 parts by weight of butyl acetate was added dropwise thereto over 3 hours. A mixed solution of 0.3 parts by weight of 2,2'-azobis(2-methylbutyronitrile) dissolved in 5.7 parts by weight of butyl acetate was added and polymerized at 115°C for 2 hours to obtain a butyl acetate solution (solids content 60%) of reactive silicon group-containing graft copolymer (A-1) with a number average molecular weight of 1,930 (GPC molecular weight), a weight average molecular weight of 16,890, and a molecular weight distribution Mw / Mn = 8.8. The polyfunctional macromonomer equivalent of the solid content of this solution was 0.034 mmol / g, the reactive silicon group equivalent was 0.40 mmol / g, and the sulfur atom concentration was 11,085 ppm. The polymer solution was clear.

[0136] (Synthesis Example 7) A four-neck flask equipped with a stirrer was charged with 42.2 parts by weight of butyl acetate, and the temperature was raised to 115° C. under a nitrogen atmosphere. A mixed solution prepared by dissolving 41.8 parts by weight of methyl methacrylate, 50.0 parts by weight of the multifunctional macromonomer (a4-3) prepared in Synthesis Example 3, 1.4 parts by weight of 3-methacryloxypropyltrimethoxysilane, 6.8 parts by weight of 3-mercaptopropyltrimethoxysilane, and 0.9 parts by weight of 2,2′-azobis(2-methylbutyronitrile) in 17.1 parts by weight of butyl acetate was added dropwise thereto over 3 hours. A mixed solution of 0.3 parts by weight of 2,2'-azobis(2-methylbutyronitrile) dissolved in 5.7 parts by weight of butyl acetate was added and polymerized at 115°C for 2 hours to obtain a butyl acetate solution (solids content 60%) of reactive silicon group-containing graft copolymer (A-2) with a number average molecular weight of 2,150 (GPC molecular weight), a weight average molecular weight of 20,700, and a molecular weight distribution Mw / Mn = 9.6. The polyfunctional macromonomer equivalent of the solid content of this solution was 0.028 mmol / g, the reactive silicon group equivalent was 0.40 mmol / g, and the sulfur atom concentration was 11,085 ppm. The polymer solution was clear.

[0137] (Synthesis Example 8) A four-necked flask equipped with a stirrer was charged with 42.2 parts by weight of butyl acetate and heated to 115°C under a nitrogen atmosphere. A mixed solution of 41.8 parts by weight of methyl methacrylate, 50.0 parts by weight of the multifunctional macromonomer (a4-4) prepared in Synthesis Example 4, 1.4 parts by weight of 3-methacryloxypropyltrimethoxysilane, 6.8 parts by weight of 3-mercaptopropyltrimethoxysilane, and 0.9 parts by weight of 2,2'-azobis(2-methylbutyronitrile) dissolved in 17.1 parts by weight of butyl acetate was added dropwise over 3 hours. A mixed solution of 0.3 parts by weight of 2,2'-azobis(2-methylbutyronitrile) dissolved in 5.7 parts by weight of butyl acetate was then added and polymerization was carried out at 115°C for 2 hours to obtain a butyl acetate solution (solids content 60%) of a reactive silicon group-containing graft copolymer (P-1) having a number average molecular weight of 2,100 (GPC molecular weight). The polyfunctional macromonomer equivalent of the solid content of the solution was 0.025 mmol / g, the reactive silicon group equivalent was 0.40 mmol / g, and the sulfur atom concentration was 11,085 ppm. The polymer solution was transparent.

[0138] (Synthesis Example 9) A four-necked flask equipped with a stirrer was charged with 42.2 parts by weight of butyl acetate and heated to 115°C under a nitrogen atmosphere. A mixed solution of 41.8 parts by weight of methyl methacrylate, 50.0 parts by weight of the multifunctional macromonomer (a4-5) prepared in Synthesis Example 5, 1.4 parts by weight of 3-methacryloxypropyltrimethoxysilane, 6.8 parts by weight of 3-mercaptopropyltrimethoxysilane, and 0.9 parts by weight of 2,2'-azobis(2-methylbutyronitrile) dissolved in 17.1 parts by weight of butyl acetate was added dropwise over 3 hours. A mixed solution of 0.3 parts by weight of 2,2'-azobis(2-methylbutyronitrile) dissolved in 5.7 parts by weight of butyl acetate was then added and polymerization was carried out at 115°C for 2 hours to obtain a butyl acetate solution (solids content 60%) of a reactive silicon group-containing graft copolymer (P-2) having a number average molecular weight of 2,100 (GPC molecular weight). The polyfunctional macromonomer equivalent weight of the solid content of the solution was 0.019 mmol / g, the reactive silicon group equivalent weight was 0.40 mmol / g, and the sulfur atom concentration was 11,085 ppm. The polymer solution was transparent.

[0139] Example 1 The butyl acetate solution of the graft copolymer obtained in Synthesis Example 6 was heated and devolatilized to obtain a graft copolymer (A-1) that was solid at room temperature.

[0140] (Complex viscosity and complex modulus) Dynamic viscoelasticity measurements were carried out on the obtained graft copolymer (A-1) using parallel circular plates with a diameter of 20 mm as a jig, with a gap set to 0.5 mm, while the temperature was lowered from 150°C to 10°C. The complex viscosity was recorded at 120°C, and the complex modulus was recorded at 23°C. The results are shown in Table 1. A TA Instruments rheometer (DHR-2) was used.

[0141] (Tensile properties) 100 parts by weight of graft copolymer (A-1) was heated to 140°C for melting, and 2 parts by weight of KBM-603 (N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.2 parts by weight of U-810 (dioctyltin dilaurate, manufactured by Nitto Kasei Co., Ltd.) were added and mixed. A sheet approximately 2 mm thick was prepared and aged for 7 days at 23°C and 50% RH. The resulting sheet was punched into a No. 3 dumbbell shape (JIS K 6251) and subjected to a tensile strength test at an elongation rate of 50 mm / min to measure the stress at 50% elongation (M50) and the strength at break (TB). A Shimadzu Autograph (AGS-X) was used. The results are shown in Table 1.

[0142] (Recovery rate) The No. 3 dumbbells obtained above were stretched to 100% and held in that state at 50°C for 24 hours, then released and left to stand at 23°C for 1 hour, after which the recovery rate was measured. The recovery rate was calculated using the following formula: 100 × {(gauge length at 100% stretch) - (gauge length after standing)} / {(gauge length at 100% stretch) - (gauge length before stretch)}. The results are shown in Table 1.

[0143] (Example 2 and Comparative Examples 1 and 2) The butyl acetate solutions obtained in Synthesis Examples 7 to 9 were heated and devolatilized to obtain graft polymers (A-2) and (P-1) to (P-2) that were solid at room temperature in the same manner as in Example 1. The results are shown in Table 1.

[0144] [Table 1]

[0145] The following can be seen from Table 1: In Examples 1 and 2, both the breaking strength and recovery rate showed high values, indicating that cured products having both strength and recovery were obtained. Furthermore, the small value of the complex viscosity measured at 120°C indicates that the viscosity when heated and melted is low and the coating properties are good. Furthermore, the complex modulus measured at 23°C after cooling from 150°C is small, which indicates that the graft copolymer has adhesive properties, and that after applying the graft copolymer to an adherend, it is possible to ensure a long period of time during which it can be bonded to another adherend. If the complex modulus is 0.25 or higher, the adhesiveness of the graft copolymer is low, making it difficult to bond it to an adherend.

[0146] On the other hand, in Comparative Examples 1 and 2, in which the graft copolymer (P-1) or (P-2) containing the polyoxyalkylene polymer block (B) having a molecular weight distribution (Mw / Mn) greater than a predetermined value was evaluated, the breaking strength was slightly lower than in Examples 1 and 2, and the recovery rate was significantly lower, indicating insufficient recovery.

Claims

1. General formula (1): -SiR １ ３－ａ X ａ (1) (In the formula, R １ represents a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms; X represents a hydroxyl group or a hydrolyzable group; and a represents 2 or 3. and a polyoxyalkylene polymer block (B) are bonded in the order A-B-A, the polyoxyalkylene polymer block (B) has a number average molecular weight of 5,000 or more and a molecular weight distribution (Mw / Mn) of 1.40 or less; In the graft copolymer, the proportion of the polymer block (A) is 35 to 65% by weight, and the proportion of the polymer block (B) is 35 to 65% by weight, the polymer block (A) contains a structural unit derived from a (meth)acrylic acid ester (a1) and a structural unit derived from a chain transfer agent (a2) having a mercapto group, A graft copolymer, wherein the concentration of sulfur atoms derived from the chain transfer agent (a2) is 5,000 to 15,000 ppm in the graft copolymer.

2. 2. The graft copolymer according to claim 1, wherein the content of the (meth)acrylic acid alkyl ester having an alkyl group having 7 or more carbon atoms is 7% by weight or less in the graft copolymer.

3. 3. The graft copolymer according to claim 1, wherein the polyoxyalkylene polymer block (B) has a number average molecular weight of 10,000 to 50,000.

4. 3. The graft copolymer according to claim 1, wherein the molar ratio of the polyoxyalkylene polymer block (B) to the chain transfer agent (a2) having a mercapto group is 0.05 or more.

5. 3. The graft copolymer according to claim 1, wherein the sulfur atom concentration is 8,500 to 15,000 ppm.

6. 3. The graft copolymer according to claim 1, wherein the reactive silicon group equivalent of the graft copolymer is 0.2 to 0.8 mmol / g.

7. The bond between the polymer block (A) and the polymer block (B) is represented by general formula (2) or (3): AC(=O)-OR-NH-C(=O)-OB (2) AC(=O)-OB (3) (wherein A represents polymer block (A), B represents polymer block (B), and R represents a divalent hydrocarbon group having 1 to 20 carbon atoms).

8. A curable composition comprising the graft copolymer of claim 1 or 2.

9. A hot melt adhesive comprising the graft copolymer according to claim 1 or 2.

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