JP7722155B2 - Curable composition and cured product thereof - Google Patents

Description

The present invention relates to a curable composition and a cured product thereof.

It is known that polymers having reactive silicon groups undergo crosslinking through the formation of siloxane bonds accompanying hydrolysis and condensation reactions of the reactive silicon groups, thereby forming rubber-like cured products.
Depending on the various required properties, it has been proposed to combine polymers that differ in main chain structure, reactive silicon group structure, reactive silicon group content, etc.

In the examples of Patent Document 1, it is shown that when a polyoxyalkylene polymer (B-1) having 1.7 dimethoxymethylsilyl groups per terminal group and 3.4 dimethoxymethylsilyl groups per molecule is added to a polyoxyalkylene polymer (A-1) having 0.8 dimethoxymethylsilyl groups per terminal group and 1.6 dimethoxymethylsilyl groups per molecule, the skinning time (surface hardening speed) is shortened compared to when only (A-1) is used, and the results of a 1,000-hour weather resistance test are improved (Table 1).

An example in Patent Document 2 shows that a cured product of a mixture (BC-4) of 60 parts by mass of a polyoxyalkylene polymer (B-4) having 1.6 trimethoxysilyl groups per terminal group and 3.2 trimethoxysilyl groups per molecule and 40 parts by mass of a (meth)acrylic acid ester copolymer (C-1) having 1.5 trimethoxysilyl groups per molecule exhibits significantly improved strength compared to a cured product of a mixture (SC-4) in which a polyoxyalkylene polymer (S-4) having 0.8 trimethoxysilyl groups per terminal group and 1.6 trimethoxysilyl groups per molecule was used instead of (B-4) (Table 2).

The examples of Patent Document 3 describe a curable composition that combines polyoxyalkylene polymer A3 having 0.73 dimethoxysilyl groups per terminal group and 1.46 per molecule, polyoxyalkylene polymer A5 having 1.6 dimethoxymethylsilyl groups per terminal group and 3.2 per molecule, and acrylic acid ester polymer B2 having 2.0 dimethoxymethylsilyl groups per molecule (Table 4).

The examples of Patent Document 4 describe a curable composition that combines a polyoxyalkylene polymer A1 having 1.6 dimethoxymethylsilyl groups per terminal group and 3.2 per molecule, an acrylic acid ester polymer B1 having dimethoxymethylsilyl groups at both ends of the main chain, a polyoxyalkylene polymer C1 having 0.75 dimethoxymethylsilyl groups per terminal group and 1.5 per molecule, and a polyoxyalkylene polymer D1 having 0.4 dimethoxymethylsilyl groups per terminal group and 0.8 per molecule (Table 3, Example 6).

Patent No. 6096320 Patent No. 6275036 Japanese Patent Application Laid-Open No. 2020-117583 Patent No. 6579206

Curable compositions using polymers having reactive silicon groups are available in two types: a two-component type in which a base composition containing a component having a reactive silicon group and a curing agent composition containing a condensation catalyst are stored separately and then mixed together before use, and a one-component type in which all of the components are mixed in advance and stored in a sealed container. From the viewpoint of workability, the one-component type is preferable.
After application, one-component curable compositions tend to cure insufficiently from the surface toward the interior due to moisture in the air, resulting in insufficient curing in the deeper areas.

According to the findings of the present inventors, it is difficult to simultaneously achieve good deep curing properties and good stretch durability and weather resistance of the cured product with the polymer combinations used in Patent Documents 1 to 4.
The present invention provides a curable composition that exhibits good deep curing properties and provides a cured product with good durability to stretching and weather resistance.

The present invention has the following aspects.
[1] A curable composition comprising the following polymer A, the following polymer B, and a condensation catalyst, wherein A/B, which represents a mass ratio of the polymer A to the polymer B, is 80/20 to 95/5.
Polymer A: A polyoxyalkylene polymer having more than 1.0 reactive silicon group per terminal group, represented by the following formula 1:
Polymer B: At least one selected from the group consisting of a (meth)acrylic acid ester polymer B1 having a reactive silicon group represented by the following formula 2, and a polyoxyalkylene polymer B2 having more than 0.5 and not more than 1.0 reactive silicon groups represented by the following formula 2 per terminal group.
-SiR _a X ¹ _3-a formula 1
In formula 1, R represents a monovalent organic group having 1 to 20 carbon atoms other than a hydrolyzable group, ^X1 represents a hydroxyl group, a halogen atom, or a hydrolyzable group, and a is 1 or 2; when a is 1 , the two ^X1s may be the same or different, and when a is 2 , the two Rs may be the same or different.
-SiX ² ₃ formula 2
In formula 2, X ² represents a hydroxyl group, a halogen atom, or a hydrolyzable group, and X ² may be the same or different.
[2] The curable composition according to [1], wherein the polymer A has a terminal group containing a group represented by the following formula 3 or 4:

[In formula 3, R ¹ and R ³ each independently represent a divalent linking group having 1 to 6 carbon atoms, and the atom bonded to the carbon atom in the linking group is a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom; R ² and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms; Si ¹ represents a reactive silicon group represented by formula 1 above; n represents an integer of 1 to 10; and Si ¹ may be the same or different.]

[In formula 4, ^R5 represents a single bond or a divalent linking group having 1 to 6 carbon atoms, the atom bonded to the carbon atom in the linking group is a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom, X represents a monovalent group represented by any of formulas 5 to 8, in which in formulas 5 to 8, ^R6 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, ^R7 and ^R8 each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 9 carbon atoms, and ^Si1 represents a reactive silicon group represented by formula 1, and multiple ^Si1s may be the same or different.]
[3] The curable composition according to [1] or [2], wherein the polymer A is linear.
[4] The curable composition according to any one of [1] to [3], wherein the number average molecular weight of the polymer A is 8,000 to 150,000.
[5] The curable composition according to any one of [1] to [4], wherein the number average molecular weight of the polymer B is 5,000 to 50,000.
[6] The curable composition according to any one of [1] to [5], wherein the content of the polymer B1 relative to the total mass of the polymer B is 45 to 100 mass%.
[7] The curable composition according to any one of [1] to [6], further comprising the following polymer C:
Polymer C: A polyoxyalkylene polymer having two terminal groups, one of which is an inert organic group, and which contains more than 0 but not more than 0.5 reactive silicon groups represented by formula 1 or formula 2 per terminal group, and which has a number average molecular weight of 2,000 to 15,000.
[8] The curable composition according to any one of [1] to [7], wherein the condensation catalyst comprises at least one selected from the group consisting of a tetravalent tin catalyst, a titanium catalyst, an aluminum catalyst, a zirconium catalyst, a carboxylic acid, a metal salt of a carboxylic acid, and an amine compound.
[9] The curable composition according to any one of [1] to [8], wherein the content of the condensation catalyst is 0.03 to 0.7 parts by mass relative to 100 parts by mass of the total of the polymer A and the polymer B.
[10] The curable composition according to any one of [1] to [9], which is for use as a sealant or adhesive.
[11] A cured product of the curable composition according to any one of [1] to [10].

The present invention provides a curable composition that exhibits excellent deep curing properties and exhibits excellent stretch resistance and weather resistance in the cured product.

The meanings and definitions of terms used in this specification are as follows:
A numerical range expressed as "to" means that the numerical values before and after "to" are the lower and upper limits of the numerical range.
"Polyoxyalkylene polymer" means a polymer having a polyoxyalkylene chain formed from cyclic ether-based units.
The polyoxyalkylene polymer has a main chain containing a polyoxyalkylene chain and a terminal group bonded to the main chain. The "terminal group" refers to an atomic group containing the oxygen atom in the polyoxyalkylene chain that is closest to the molecular end of the polyoxyalkylene polymer.
The "active hydrogen-containing group" is at least one group selected from the group consisting of a hydroxyl group bonded to a carbon atom, a carboxyl group, an amino group, a monovalent functional group obtained by removing one hydrogen atom from a primary amine, and a sulfanyl group.
The term "active hydrogen" refers to a hydrogen atom derived from the active hydrogen-containing group and a hydrogen atom derived from the hydroxyl group of water.
An "initiator" is a compound that has an active hydrogen-containing group.
An "unsaturated group" is a group that contains double or triple bonds between carbon atoms.

The number-average molecular weight (hereinafter referred to as "Mn") and weight-average molecular weight (hereinafter referred to as "Mw") of the polymer are polystyrene-equivalent molecular weights obtained by GPC measurement. The molecular weight distribution is a value calculated from Mw and Mn, and is the ratio of Mw to Mn (hereinafter referred to as "Mw/Mn").

The curable composition of the present embodiment contains polymer A, polymer B, and a condensation catalyst.
<Polymer A>
Polymer A is a polyoxyalkylene polymer having a main chain containing a polyoxyalkylene chain and an end group bonded to the main chain.
Polymer A has more than 1.0 reactive silicon group represented by the following formula 1 (hereinafter also referred to as "first reactive silicon group") per terminal group.
-SiR _a X ¹ _3-a formula 1
In Formula 1, R represents a monovalent organic group having 1 to 20 carbon atoms. R does not contain a hydrolyzable group.
Examples of R include hydrocarbon groups, halohydrocarbon groups, and triorganosiloxy groups.
R is preferably an alkyl group, a cycloalkyl group, an aryl group, a 1-chloroalkyl group, or a triorganosiloxy group. It is more preferably at least one selected from the group consisting of a linear or branched alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, a phenyl group, a benzyl group, a 1-chloromethyl group, a trimethylsiloxy group, a triethylsiloxy group, and a triphenylsiloxy group. From the viewpoints of good curability of the polymer A and stability of the curable composition, a methyl group or an ethyl group is preferred. A methyl group is more preferred from the viewpoint of ease of availability.

In the formula 1, ^X1 represents a hydroxyl group, a halogen atom, or a hydrolyzable group. The hydrolyzable group is a group that can react with water to form a silanol group.
Examples of the hydrolyzable group include an alkoxy group, an acyloxy group, a ketoximate group, an amino group, an amide group, an acid amide group, an aminooxy group, a sulfanyl group, and an alkenyloxy group.
^X1 is preferably an alkoxy group because it is mildly hydrolyzable and easy to handle. The alkoxy group is preferably a methoxy group, an ethoxy group, or an isopropoxy group, and more preferably a methoxy group or an ethoxy group. When the alkoxy group is a methoxy group or an ethoxy group, a siloxane bond is rapidly formed, making it easier to form a crosslinked structure in the cured product, and the physical properties of the cured product are better.

In the formula 1, a is 1 or 2. When a is 1, two ^X1s may be the same or different. When a is 2, two Rs may be the same or different.

Examples of the first reactive silicon group represented by Formula 1 include dimethoxymethylsilyl, diethoxymethylsilyl, dimethoxyethylsilyl, diisopropoxymethylsilyl, dimethylmethoxysilyl, diethylmethoxysilyl, dimethylethoxysilyl, dimethylisopropoxysilyl, chloromethyldimethoxysilyl, and chloromethyldiethoxysilyl. In view of the good elongation and stretch durability of the cured product, the dimethoxymethylsilyl and dimethylmethoxysilyl groups are preferred, and the dimethoxymethylsilyl group is more preferred.

The main chain of polymer A has a residue of an initiator having two or more active hydrogens and a polyoxyalkylene chain formed by ring-opening addition polymerization of a cyclic ether.
The initiator is preferably an initiator having two or more hydroxyl groups, more preferably an initiator having 2 to 6 hydroxyl groups, and even more preferably an initiator having 2 or 3 hydroxyl groups.
Examples of initiators having two hydroxyl groups include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, and low-molecular-weight polyoxypropylene glycol.
Examples of initiators having three or more hydroxyl groups include glycerin, trimethylolpropane, trimethylolethane, low-molecular-weight polyoxyethylenetriol, polyoxypropylenetriol, pentaerythritol, sorbitol, and sucrose.

Examples of cyclic ethers include alkylene oxides such as ethylene oxide, propylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide, and cyclic ethers other than alkylene oxides such as tetrahydrofuran, etc. Ethylene oxide and propylene oxide are preferred, and propylene oxide is more preferred.
The polyoxyalkylene chain may be a copolymer chain having two or more kinds of oxyalkylene groups, and may be a block copolymer chain or a random copolymer chain.
Examples of the polyoxyalkylene chain of polymer A include a polyoxypropylene chain, a polyoxyethylene chain, a poly(oxy-2-ethylethylene) chain, a poly(oxy-1,2-dimethylethylene) chain, a poly(oxytetramethylene) chain, a poly(oxyethylene-oxypropylene) chain, and a poly(oxypropylene-oxy-2-ethylethylene) chain. A polyoxypropylene chain and a poly(oxyethylene-oxypropylene) chain are preferred, and a polyoxypropylene chain is more preferred.

The number of terminal groups of polymer A is preferably 2 to 6, more preferably 2 or 3. The number of terminal groups of polymer A is the same as the number of active hydrogens present in the initiator.
The polymer A is preferably linear because this results in better deep section curing properties and stretch durability. The linear polymer A means that the main chain of the polymer A is linear. The linear main chain has a polyoxyalkylene chain formed by ring-opening addition polymerization of a residue of an initiator having two active hydrogens and a cyclic ether, and has two terminal groups.

The terminal group of polymer A preferably contains at least one type selected from the group consisting of a first reactive silicon group, an active hydrogen-containing group, or an unsaturated group.
The total number of first reactive silicon groups, active hydrogen-containing groups, and unsaturated groups present in the terminal groups of polymer A is preferably 2 to 6, and more preferably 2 to 4, per terminal group.
The number of first reactive silicon groups in polymer A per terminal group is more than 1.0, preferably 1.1 to 3.0, and more preferably 1.2 to 2.0. When the number is at least the lower limit of the above range, deep curing and stretch durability are improved, while when the number is at most the upper limit, the cured product tends to have good elongation and stretch durability.

It is preferable that polymer A has a terminal group containing a group represented by the following formula 3 or 4. X in the following formula 4 is a monovalent group represented by any one of the following formulas 5 to 8.
Si ¹ in the following formula 3 and the following formulas 5 to 8 represents the first reactive silicon group represented by the formula 1. When multiple Si ^1s are present in one terminal group, they may be the same or different.

In Formula 3, R ¹ and R ³ each independently represent a divalent linking group having 1 to 6 carbon atoms, and the atom bonded to the carbon atom in the linking group is a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom.
Examples of R ¹ and R ³ include —CH ₂ —, —C ₂ H ₄ —, —C ₃ H ₆ —, —C ₄ H ₈ —, —C ₅ H ₁₀ —, —C ₆ H ₁₂ —, —C(CH ₃ ) ₂ —, —CH ₂ O—, —CH _{2 —O} —CH ₂ —, —CH ₂ —O—CH ₂ —O—CH 2 —, —C≡C—, —C(═O)—, —C(═O)—O—, —C(═O)—NH—, —CH═N—, and —CH═N—N═CH—.
R ¹ is preferably —CH ₂ —O—CH ₂ —, —CH ₂ O— or —CH ₂ —, and more preferably —CH ₂ —O—CH ₂ —.
R ³ is preferably —CH ₂ — or —C ₂ H ₄ —, and more preferably —CH ₂ —.

In formula 3, R ² and R ⁴ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.
The hydrocarbon group is preferably a linear or branched alkyl group having 1 to 10 carbon atoms.
Examples of the straight-chain alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group.
Examples of branched alkyl groups include an isopropyl group, an s-butyl group, a t-butyl group, a 2-methylbutyl group, a 2-ethylbutyl group, a 2-propylbutyl group, a 3-methylbutyl group, a 3-ethylbutyl group, a 3-propylbutyl group, a 2-methylpentyl group, a 2-ethylpentyl group, a 2-propylpentyl group, a 3-methylpentyl group, a 3-ethylpentyl group, a 3-propylpentyl group, a 4-methylpentyl group, a 4-ethylpentyl group, a 4-propylpentyl group, a 2-methylhexyl group, a 2-ethylhexyl group, a 2-propylhexyl group, a 3-methylhexyl group, a 3-ethylhexyl group, a 3-propylhexyl group, a 4-methylhexyl group, a 4-ethylhexyl group, a 4-propylhexyl group, a 5-methylhexyl group, a 5-ethylhexyl group, and a 5-propylhexyl group.
R ² and R ⁴ each independently represent preferably a hydrogen atom, a methyl group, or an ethyl group, more preferably a hydrogen atom or a methyl group.

In formula 3, n represents an integer of 1 to 10, preferably 1 to 7, more preferably 1 to 5, and even more preferably 1.

In Formula 4, ^R5 represents a single bond or a divalent linking group having 1 to 6 carbon atoms, and the atom bonded to the carbon atom in the linking group is a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom.
Examples of the divalent linking group in ^R5 are the same as the examples of the divalent linking group in ^R1 and ^R3 .
R ⁵ is preferably a single bond or a hydrocarbon group having 1 to 4 carbon atoms, more preferably a single bond or an alkylene group having 1 to 3 carbon atoms, and even more preferably a single bond or a methylene group.

In formula 7, R ⁶ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.
Examples of the monovalent hydrocarbon group in ^R6 are the same as the examples of the monovalent hydrocarbon group in ^R2 and ^R4 .
^R6 is preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group.

In formula 8, R ⁷ and R ⁸ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 9 carbon atoms.
The hydrocarbon group is preferably a linear or branched alkyl group having a carbon number of 1 to 9. Examples of the alkyl group as R ⁷ and R ⁸ are the same as the examples of the alkyl group as R ² and R ⁴ above.
It is preferable that R ⁷ and R ⁸ are both hydrogen atoms.

The Mn of polymer A is preferably 8,000 to 150,000, more preferably 9,000 to 100,000, and even more preferably 10,000 to 70,000. When Mn is at or above the lower limit of the above range, good stretch durability is likely to be achieved, while when Mn is below the upper limit, the viscosity of the curable composition tends to be sufficiently low, making it easier to achieve good workability.

<Production Method of Polymer A>
Polymer A is obtained by introducing more than 1.0 first reactive silicon groups per terminal group into a polyoxyalkylene polymer (hereinafter also referred to as a "precursor polymer") obtained by ring-opening addition polymerization of a cyclic ether to the active hydrogen of an initiator.
A preferred method involves introducing more than 1.0 unsaturated group per terminal group into the terminal groups of the precursor polymer, and then reacting the unsaturated group with a silylating agent to introduce a reactive silicon group.

The precursor polymer is preferably a hydroxyl-containing polyoxyalkylene polymer having terminal hydroxyl groups, which is obtained by ring-opening addition polymerization of a cyclic ether with a hydroxyl group-containing initiator, and the number of hydroxyl groups in the initiator is the same as that in the hydroxyl-containing polyoxyalkylene polymer.
In particular, a hydroxyl group-containing polyoxyalkylene polymer having a linear main chain, which is obtained by ring-opening addition polymerization of a cyclic ether to an initiator having two hydroxyl groups, is preferred.

As the ring-opening addition polymerization catalyst for ring-opening addition polymerization of a cyclic ether to an initiator, a conventionally known catalyst can be used, and examples thereof include an alkali catalyst (e.g., KOH), a transition metal compound-porphyrin complex catalyst (e.g., a complex obtained by reacting an organoaluminum compound with a porphyrin), a composite metal cyanide complex catalyst, and a catalyst composed of a phosphazene compound.
A composite metal cyanide complex catalyst is preferred because it can narrow the Mw/Mn of the polymer A and easily produce a curable composition with a low viscosity. Conventionally known compounds can be used as the composite metal cyanide complex catalyst, and known methods can also be used to produce polymers using composite metal cyanide complexes. For example, compounds and production methods disclosed in International Publication No. 2003/062301, International Publication No. 2004/067633, JP 2004-269776, JP 2005-15786, International Publication No. 2013/065802, and JP 2015-010162 can be used.

As a method for introducing more than 1.0 unsaturated groups per terminal group into the terminal groups of the precursor polymer, any known method can be used without particular limitation. For example, the methods described in WO 2013/180203, WO 2014/192842, JP 2015-105293, JP 2015-105322, JP 2015-105323, JP 2015-105324, WO 2015/080067, WO 2015/105122, WO 2015/111577, WO 2016/002907, JP 2016-216633, and JP 2017-39782 can be used.

Preferred methods for introducing more than 1.0 unsaturated groups per terminal group into the terminal groups of a precursor polymer include reacting an alkali metal salt with the precursor polymer, then reacting with an epoxy compound having an unsaturated group, and then reacting with a halogenated hydrocarbon compound having an unsaturated group, or reacting an alkali metal salt with the precursor polymer, then reacting with a halogenated hydrocarbon compound having a carbon-carbon triple bond.

Examples of alkali metal salts include sodium hydroxide, sodium alkoxide, potassium hydroxide, potassium alkoxide, lithium hydroxide, lithium alkoxide, cesium hydroxide, and cesium alkoxide.
In terms of ease of handling and solubility, sodium hydroxide, sodium methoxide, sodium ethoxide, potassium hydroxide, potassium methoxide, and potassium ethoxide are preferred, and sodium methoxide and potassium ethoxide are more preferred, with sodium methoxide being particularly preferred in terms of availability.
The alkali metal salt may be used in a state of being dissolved in a solvent.

Examples of epoxy compounds having unsaturated groups include allyl glycidyl ether, methallyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, butadiene monoxide, and 1,4-cyclopentadiene monoepoxide. Allyl glycidyl ether is preferred.

The epoxy compound having an unsaturated group is preferably a compound represented by the following formula 9:

R ¹ and R ² in the formula 9 are the same as R ¹ and R ² in the formula 3.

As the halogenated hydrocarbon compound having an unsaturated group, one or both of a halogenated hydrocarbon compound containing a carbon-carbon double bond and a halogenated hydrocarbon compound containing a carbon-carbon triple bond can be used.
Examples of halogenated hydrocarbon compounds containing a carbon-carbon double bond include vinyl chloride, allyl chloride, methallyl chloride, vinyl bromide, allyl bromide, methallyl bromide, vinyl iodide, allyl iodide, and methallyl iodide. Allyl chloride and methallyl chloride are preferred.
Examples of halogenated hydrocarbon compounds containing a carbon-carbon triple bond include propargyl chloride, 1-chloro-2-butyne, 4-chloro-1-butyne, 1-chloro-2-octyne, 1-chloro-2-pentyne, 1,4-dichloro-2-butyne, 5-chloro-1-pentyne, 6-chloro-1-hexyne, propargyl bromide, 1-bromo-2-butyne, 4-bromo-1-butyne, 1-bromo- Examples include 2-octyne, 1-bromo-2-pentyne, 1,4-dibromo-2-butyne, 5-bromo-1-pentyne, 6-bromo-1-hexyne, propargyl iodide, 1-iodo-2-butyne, 4-iodo-1-butyne, 1-iodo-2-octyne, 1-iodo-2-pentyne, 1,4-diiodo-2-butyne, 5-iodo-1-pentyne, and 6-iodo-1-hexyne. Propargyl chloride, propargyl bromide, and propargyl iodide are preferred.
Two or more of the halogenated hydrocarbon compounds having an unsaturated group may be used in combination.

The reaction results in a derivative of the precursor polymer in which an unsaturated group is introduced into the terminal group of the precursor polymer. The derivative of the precursor polymer may contain an unreacted active hydrogen-containing group at the terminal group.
The number of active hydrogen-containing groups contained in the derivative of the precursor polymer is preferably 0.3 or less, more preferably 0.1 or less per molecule, from the viewpoint of storage stability.

The unsaturated group of the precursor polymer derivative is reacted with a silylating agent capable of introducing a first reactive silicon group (hereinafter also referred to as the "first silylating agent") to introduce the first reactive silicon group into the terminal group, thereby obtaining polymer A.
Examples of the first silylating agent include a compound having both a group capable of reacting with an unsaturated group to form a bond (e.g., a sulfanyl group) and a first reactive silicon group, and a hydrosilane compound represented by HSiR _a X ¹ _3-a (where R, X ¹ , and a are the same as in Formula 1 above).
Examples of the hydrosilane compound include dimethoxymethylsilane, diethoxymethylsilane, dimethoxyethylsilane, diisopropoxymethylsilane, dimethylmethoxysilane, diethylmethoxysilane, dimethylethoxysilane, dimethylisopropoxysilane, chloromethyldimethoxysilane, and chloromethyldiethoxysilane.

Preferably, an alkali metal salt is allowed to act on a hydroxyl group-containing polyoxyalkylene polymer (precursor polymer), followed by reaction with an epoxy compound having an unsaturated group, and then reaction with a halogenated hydrocarbon compound having an unsaturated group to obtain an unsaturated group-containing polyoxyalkylene polymer (a derivative of the precursor polymer), and the unsaturated group of the unsaturated group-containing polyoxyalkylene polymer is reacted with a first silylating agent to obtain polymer A.
Alternatively, an alkali metal salt is allowed to act on a precursor polymer, and then a halogenated hydrocarbon compound having a carbon-carbon triple bond is reacted therewith to obtain an unsaturated group-containing polyoxyalkylene polymer (a derivative of the precursor polymer), and the unsaturated group of the unsaturated group-containing polyoxyalkylene polymer is reacted with a first silylating agent to obtain polymer A.
The number of reactive silicon groups per terminal group can be adjusted by the amount of the first silylating agent used.

<Polymer B>
Polymer B is at least one selected from the group consisting of polymer B1 and polymer B2 shown below.
Polymer B1: a (meth)acrylic acid ester polymer having a reactive silicon group represented by the following formula 2 (hereinafter also referred to as "second reactive silicon group").
Polymer B2: a polyoxyalkylene polymer having more than 0.5 and not more than 1.0 second reactive silicon groups represented by the following formula 2 per terminal group.

-SiX ² ₃ formula 2
In formula 2, ^X2 represents a hydroxyl group, a halogen atom, or a hydrolyzable group. The three ^X2 may be the same or different.
Examples of ^X2 in the formula 2 are the same as the examples of ^X1 in the formula 1, including preferred embodiments.
Examples of the second reactive silicon group represented by formula 2 include a trimethoxysilyl group, a triethoxysilyl group, a triisopropoxysilyl group, a tris(2-propenyloxy)silyl group, and a triacetoxysilyl group. From the viewpoint of superior curability, a trimethoxysilyl group and a triethoxysilyl group are preferred, and a trimethoxysilyl group is more preferred.

The number of reactive silicon groups per molecule of polymer B is preferably 1.0 to 5.0, and more preferably 1.0 to 3.0. Within this range, it is easy to adjust the modulus of the cured product to a good range.

The Mn of polymer B is preferably 5,000 to 80,000, more preferably 6,000 to 70,000, even more preferably 6,000 to 60,000, still more preferably more than 8,000 and not more than 60,000, and particularly preferably more than 8,000 and not more than 50,000. When the Mn is equal to or greater than the lower limit of the above range, the weather resistance is excellently improved. When the Mn is equal to or less than the upper limit, the viscosity of the curable composition tends to be sufficiently low, and good workability tends to be obtained.
<Polymer B1>
Polymer B1 is a (meth)acrylic acid ester polymer having a second reactive silicon group.

The main chain of the polymer B1 is formed by polymerizing a monomer containing a (meth)acrylic acid ester.
The main chain of polymer B1 may contain, in addition to units based on a (meth)acrylic acid alkyl ester, units based on a monomer having an unsaturated group copolymerizable with a (meth)acrylic acid alkyl ester.
The (meth)acrylic acid ester monomer preferably accounts for 50% by mass or more, more preferably 70% by mass or more, and may even be 100% by mass, based on all the monomers constituting the polymer B1.

In polymer B1, the second reactive silicon group may be present at the end of the main chain, on a side chain, or on both.
(Polymer B1-i)
As the monomer constituting the polymer B1-i having a second reactive silicon group at the end of the main chain, for example, conventionally known monomers described in JP-B-3-14068, JP-A-6-211922, and JP-A-11-130931 can be used.
The polymer B1-i can be produced by any of the conventionally known methods described in the above-mentioned literature. Living radical polymerization is preferred because it produces a polymer with a narrow Mw/Mn ratio and low viscosity.
Examples of living radical polymerization methods include those using a cobalt porphyrin complex as disclosed in Journal of American Chemical Society (J. Am. Chem. Soc.), 1994, Vol. 116, p. 7943, those using a nitroxide radical as disclosed in JP-A-2003-500378, and atom transfer radical polymerization (ATRP) using an organic halide, a halogenated sulfonyl compound, or the like as an initiator and a transition metal complex as a catalyst as disclosed in JP-A-11-130931.

For example, a living radical polymerization method is used, and a compound having two alkenyl groups is reacted at the end of the polymerization reaction to obtain an unsaturated group-containing acrylic ester polymer having an alkenyl group at the end of its main chain. The alkenyl group of the obtained unsaturated group-containing acrylic ester polymer is reacted with a second silylating agent to obtain a polymer B1-i having a second reactive silicon group at the end of its main chain.
Examples of the second silylating agent include a compound having both a group capable of reacting with an unsaturated group to form a bond (e.g., a sulfanyl group) and a second reactive silicon group, and a hydrosilane compound represented by HSiX ² _{O 3} (X ² is the same as in Formula 2 above).
Examples of the hydrosilane compound include trimethoxysilane, triethoxysilane, triisopropoxysilane, tris(2-propenyloxy)silane, and triacetoxysilane.

(Polymer B1-ii)
An example of the polymer B1-ii having a second reactive silicon group in a side chain is a (meth)acrylic acid ester polymer obtained by copolymerizing a monomer containing a second reactive silicon group and an unsaturated group with a monomer containing a (meth)acrylic acid ester.
As the (meth)acrylic acid ester-containing monomer, the monomers used in the polymer B1-i can be used without any limitation.
Examples of the second monomer containing a reactive silicon group and an unsaturated group include vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane. These may be used alone or in combination of two or more.
Polymer B1-ii can be polymerized by a conventionally known polymerization method described in, for example, JP 2006-257405 A, JP 2006-37076 A, or JP 2008-45059 A. For example, the polymer can be polymerized by radical polymerization. Examples of radical polymerization methods include solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Conventionally known secondary materials such as initiators required for polymerization can also be used, and reaction conditions such as reaction temperature and reaction pressure can also be selected appropriately.

The number of reactive silicon groups per molecule of polymer B1 is preferably from 1.0 to 5.0, more preferably from 1.0 to 3.0.
The number of reactive silicon groups per molecule of polymer B1 is calculated by "concentration of reactive silicon groups in polymer B1 [mol/g] × Mn of polymer B1". The concentration of reactive silicon groups in polymer B1 [mol/g] can be measured by NMR.

<Polymer B2>
Polymer B2 is a polyoxyalkylene polymer having a main chain containing a polyoxyalkylene chain and an end group bonded to the main chain.
Polymer B2 has more than 0.5 and not more than 1.0 second reactive silicon groups represented by formula 2 per terminal group.

Examples of the main chain of polymer B2 are the same as the examples of the main chain of polymer A.
The polyoxyalkylene chain of polymer B2 is more preferably a polyoxypropylene chain, a polyoxyethylene chain, or a poly(oxyethylene-oxypropylene) chain.
The poly(oxyethylene-oxypropylene) chain may be a block copolymer chain or a random copolymer chain, and a block copolymer chain having an oxyethylene group block chain at the terminal group side is more preferred.
When the polyoxyalkylene chain of polymer B2 is a poly(oxyethylene-oxypropylene) chain, the content of oxyethylene groups (hereinafter also referred to as "EO content") is preferably 1 to 30 mass%, and more preferably 5 to 20 mass%, relative to the total mass of polymer B2. When the content is at least the lower limit of the above range, the cured product has excellent deep curing properties, and when the content is at most the upper limit, the cured product has excellent stretch durability and water resistance.

The number of terminal groups of polymer B2 is preferably 2 to 5, more preferably 2 or 3. The number of terminal groups of polymer B2 is the same as the number of active hydrogens present in the initiator.
The terminal group of polymer B2 preferably contains at least one type selected from the group consisting of a second reactive silicon group, an active hydrogen-containing group, or an unsaturated group.
The total number of second reactive silicon groups, active hydrogen-containing groups, and unsaturated groups present in the terminal groups of polymer B2 is preferably more than 0.5 and not more than 4.0 per terminal group, preferably 0.60 to 3.0, more preferably 0.65 to 2.0, and even more preferably 0.70 to 1.0.
The number of second reactive silicon groups per terminal group of polymer B2 is more than 0.5 and not more than 1.0, preferably 0.60 to 1.0, and more preferably 0.65 to 1.0.

[Production method of polymer B2]
Polymer B2 is obtained by introducing more than 0.5 but not more than 1.0 second reactive silicon groups per terminal group into a polyoxyalkylene polymer (precursor polymer) obtained by ring-opening addition polymerization of a cyclic ether to the active hydrogen of an initiator.
The precursor polymer is preferably a hydroxyl-containing polyoxyalkylene polymer having a hydroxyl terminal group, which is obtained by ring-opening addition polymerization of a cyclic ether with an initiator having a hydroxyl group.
The hydroxyl group-containing polyoxyalkylene polymer can be produced in the same manner as the hydroxyl group-containing polyoxyalkylene polymer in Polymer A.

The method for producing the polymer B2 is preferably the following production method (I) or production method (II).
Production method (I): A method in which an active hydrogen-containing group present in the terminal group of a precursor polymer is reacted with a compound having an isocyanate group and a second reactive silicon group.
Production method (II): A method in which more than 0.5 and not more than 1.0 unsaturated groups per terminal group are introduced into the terminal groups of a precursor polymer, and then the precursor polymer is reacted with a silylating agent (hereinafter also referred to as a "second silylating agent") capable of reacting with the unsaturated groups to introduce a second reactive silicon group.

In the above-mentioned production method (I), the compound having an isocyanate group and a second reactive silicon group is preferably a compound represented by the following formula 10.
O=C=N-Q ¹ -SiX ² ₃ (X ² is the same as in formula 2) Formula 10
In the formula 10, ^X2 is the same as in the formula 2, and ^Q1 is a divalent organic group having 1 to 20 carbon atoms. ^Q1 is preferably a divalent hydrocarbon group, more preferably an alkylene group. ^Q1 preferably has 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, and even more preferably 1 to 8 carbon atoms.
Examples of the compound represented by the formula 10 include isocyanate methyltrimethoxysilane, isocyanate methyltriethoxysilane, 3-isocyanate propyltrimethoxysilane, and 3-isocyanate propyltriethoxysilane.
The reaction of the compound represented by the formula 10 with the precursor polymer can be carried out by a known method.
The number of reactive silicon groups per terminal group of polymer B2 can be adjusted by the molar ratio of the total number of isocyanate groups of the compound represented by formula 10 to the total number of active hydrogens of the precursor polymer.
In this way, a polymer B2 having more than 0.5 and not more than 1.0 second reactive silicon groups per terminal group is obtained.

The production method (II) can be a conventionally known method, and examples thereof include methods proposed in JP-B No. 45-36319, JP-A No. 50-156599, JP-A No. 61-197631, JP-A No. 3-72527, JP-A No. 8-231707, U.S. Pat. No. 3,632,557, and U.S. Pat. No. 4,960,844.
For example, an alkali metal salt is allowed to act on a precursor polymer, and then a halogenated hydrocarbon compound having an unsaturated group is reacted therewith to introduce more than 0.5 and not more than 1.0 unsaturated group per terminal group into the terminal groups of the precursor polymer.
The reaction yields a derivative of the precursor polymer in which an unsaturated group has been introduced into the terminal group of the precursor polymer. The derivative of the precursor polymer may contain an unreacted active hydrogen-containing group at the terminal group.
The number of active hydrogen-containing groups contained in the derivative of the precursor polymer is preferably 0.3 or less, more preferably 0.1 or less per molecule, from the viewpoint of storage stability.
The unsaturated group of the derivative of the precursor polymer is reacted with a second silylating agent to introduce a second reactive silicon group into the terminal group, thereby obtaining polymer B2.

Examples of the alkali metal salt are the same as those exemplified in the method for producing polymer A.
Examples of the halogenated hydrocarbon compound are the same as those exemplified in the method for producing polymer A. Preferred are halogenated hydrocarbon compounds containing a carbon-carbon double bond.
Examples of the second silylating agent include a compound having both a group capable of reacting with an unsaturated group to form a bond (e.g., a sulfanyl group) and a second reactive silicon group, and a hydrosilane compound represented by HSiX ² _{O 3} (X ² is the same as in Formula 2 above).
Examples of the hydrosilane compound include trimethoxysilane, triethoxysilane, and triisopropoxylsilane.

The content of polymer B1 relative to the total mass of polymer B is preferably 45 to 100 mass%, more preferably 50 to 100 mass%. When it is at or above the lower limit of this range, the cured product is effectively improved in weather resistance.

In the curable composition of the present embodiment, A/B, which represents the mass ratio of polymer A to polymer B, is 80/20 to 95/5, preferably 82/18 to 95/5, and more preferably 85/15 to 95/5.
When the mass ratio of polymer A to polymer B is at least the lower limit of the above range, the cured product will have better deep curing properties, and when it is at most the upper limit, the cured product will have better stretch durability and weather resistance.

<Condensation catalyst>
The condensation catalyst can be a compound known as a silanol catalyst, such as those described in International Publication Nos. 2013-180203 and 2015-080067.
Specific examples include divalent tin catalysts, tetravalent tin catalysts, titanium catalysts, aluminum catalysts, zirconium catalysts, carboxylic acids, metal carboxylates, and amine compounds.
In terms of better compatibility with other additives, one or more catalysts selected from the group consisting of tetravalent tin catalysts, titanium catalysts, aluminum catalysts, zirconium catalysts, carboxylic acids, metal carboxylates, and amine compounds are preferred.

Examples of divalent tin catalysts include tin versatate, tin 2-ethylhexanoate, tin neodecanoate, and tin pivalate.
Examples of tetravalent tin catalysts include organic tin carboxylates such as dialkyltin dicarboxylates (dibutyltin dilaurate, dibutyltin diacetate, dibutyltin monoacetate, dibutyltin maleate, etc.) and dialkoxytin monocarboxylates; tin chelate compounds such as dibutyltin bis(acetylacetonate), dibutyltin bis(ethylacetoacetate), and dibutyltin monoacetylacetonate monoalkoxide; reaction products of dialkyltin oxides and ester compounds, and reaction products obtained by further reacting such reaction products with alkoxysilane compounds; reaction products of dialkyltin oxides and alkoxysilane compounds; and dialkyltin dialkyl sulfides.
Examples of the ester compounds include phthalate esters such as bis-2-ethylhexyl phthalate, diisononyl phthalate, and dioctyl phthalate; other esters of aliphatic and aromatic carboxylic acids; and tetraethyl silicate and its partial hydrolysis condensates.

Examples of carboxylic acids include organic carboxylic acids having 1 to 20 carbon atoms, such as acetic acid, propionic acid, butyric acid, 2-ethylhexanoic acid, lauric acid, stearic acid, oleic acid, linoleic acid, neodecanoic acid, versatic acid, adipic acid, oxalic acid, citric acid, acrylic acid, methacrylic acid, and benzoic acid.

Examples of titanium catalysts, aluminum catalysts, and zirconium catalysts include the compounds described in Japanese Patent No. 5,225,582, examples of carboxylic acid metal salts include the compounds described in Japanese Patent No. 4,150,220, and examples of amine compounds include the compounds described in Japanese Patent No. 5,226,217.
The condensation catalysts may be used alone or in combination of two or more.
Among the condensation catalysts, tetravalent tin catalysts and carboxylic acids are preferred, with tetravalent tin catalysts being more preferred, as they provide particularly good deep section curing properties.

The content of the condensation catalyst in the curable composition is preferably 0.03 to 0.7 parts by mass, more preferably 0.04 to 0.6 parts by mass, and even more preferably 0.04 to 0.55 parts by mass, relative to 100 parts by mass of the total amount of polymer A and polymer B.
When the content of the condensation catalyst is at least the lower limit of the above range, the cured product has better curability, and when it is at most the upper limit, the cured product has better durability to stretching.

<Polymer C>
The curable composition of the present embodiment may further contain a polymer C.
Polymer C is a polyoxyalkylene polymer having a linear main chain containing a polyoxyalkylene chain and two end groups bonded to the main chain, one of the end groups being an inert organic group, containing more than 0 and not more than 0.5 reactive silicon groups per end group, and having an Mn of 2,000 to 15,000.
The reactive silicon group present in polymer C is either the first reactive silicon group represented by formula 1 above or the second reactive silicon group represented by formula 2 above.
The reactive silicon group in polymer C is present on the other end group.

The inert organic group at one end of polymer C does not contain any of the first reactive silicon group, the second reactive silicon group, an active hydrogen-containing group, or an unsaturated group, and is, for example, an end group derived from an initiator having one active hydrogen.
The initiator is preferably an initiator having one hydroxyl group, and specific examples thereof include monohydric alcohols such as methanol, ethanol, 2-propanol, n-butyl alcohol, isobutyl alcohol, 2-butyl alcohol, t-butyl alcohol, 2-ethylhexanol, decyl alcohol, lauryl alcohol, tridecanol, cetyl alcohol, stearyl alcohol, and oleyl alcohol; and low-molecular-weight polyoxyalkylene monools.
When the initiator is a monohydric alcohol, the residue (for example, an alkoxy group) obtained by removing an active hydrogen from the initiator becomes one of the terminal groups of the polymer C.
When the initiator is a polyoxyalkylene monool, one of the end groups is an oxygen atom-containing end group (for example, an alkoxy group) that is closest to the end of the polymer C among the residues obtained by removing active hydrogen from the initiator.

The other terminal group of polymer C preferably contains at least one type selected from the group consisting of a reactive silicon group, an active hydrogen-containing group, and an unsaturated group.
The total number of reactive silicon groups, active hydrogen-containing groups, and unsaturated groups present in the other terminal group is preferably 0.25 to 2.0 per terminal group, more preferably 0.30 to 1.2, and even more preferably 0.3 to 1.0.
The number of reactive silicon groups per terminal group of polymer C is more than 0 and not more than 0.5, preferably 0.25 to 0.50, and more preferably 0.30 to 0.50.
When the number of reactive silicon groups is within the above range, the cured product has better durability against expansion and contraction.

[Production method of polymer C]
Polymer C can be obtained by introducing more than 0 and not more than 0.5 reactive silicon groups, which are the first reactive silicon group or the second reactive silicon group, per terminal group into a polyoxyalkylene polymer (precursor polymer) obtained by ring-opening addition polymerization of a cyclic ether to an initiator having one active hydrogen.
A preferred method involves introducing more than 0 unsaturated groups per terminal group into the precursor polymer, and then reacting the unsaturated groups with a silylating agent to introduce reactive silicon groups so that the number of reactive silicon groups per terminal group is more than 0 but not more than 0.5.
One end group of the precursor polymer is an inert organic group derived from the initiator, and an unsaturated group is introduced only into the other end group.
The method for introducing more than 0 but not more than 0.5 unsaturated groups per terminal group into the precursor polymer is the same as in Production Method 2 for Polymer B2.
The method for introducing more than 0.5 unsaturated groups per terminal group into the precursor polymer is the same as in the method for producing polymer A described above.

The precursor polymer derivative into which an unsaturated group has been introduced in this manner may contain an unreacted active hydrogen-containing group at the other end group.
The number of active hydrogen-containing groups contained in one molecule of the precursor polymer derivative is preferably 0.3 or less, more preferably 0.1 or less, per molecule, from the viewpoint of storage stability.
The unsaturated group of the precursor polymer derivative is reacted with a first silylating agent or a second silylating agent to introduce a first reactive silicon group or a second reactive silicon group into the other terminal group, thereby obtaining polymer C.
The first silylating agent is the same as the first silylating agent in the method for producing polymer A. The second silylating agent is the same as the second silylating agent in the method for producing polymer B2 (II).

The Mn of polymer C is 2,000 to 15,000, more preferably 3,000 to 14,000, and even more preferably 4,000 to 12,000. Within this range, the curable composition tends to have a lower viscosity.

Although polymer C is not essential, when the curable composition contains polymer C, the content of polymer C relative to 100 parts by mass of the total amount of polymer A and polymer B is preferably 1 to 400 parts by mass, more preferably 2 to 200 parts by mass, and even more preferably 3 to 150 parts by mass.
When the content of polymer C is at least the lower limit of the above range, a sufficient effect of addition is likely to be obtained, and when it is at most the upper limit, the viscosity of the curable composition is likely to be lower.

<Other ingredients>
The curable composition may contain one or more other components that do not fall under any of the polymer A, the polymer B, the polymer C, and the condensation catalyst.
Examples of other components include additives according to the intended use of the curable composition, such as fillers, anti-sagging agents, thixotropy-imparting agents, antioxidants, ultraviolet absorbers, light stabilizers, dehydrating agents, adhesion-imparting agents, amine compounds, modulus adjusters, plasticizers, air-oxidation-curable compounds, photocurable compounds, and curing catalysts.
Other components include those described in WO 2013/180203, WO 2014/192842, WO 2016/002907, JP 2014-88481 A, JP 2015-10162 A, JP 2015-105293 A, JP 2017-214541 A, etc., and can be used in combination without limitation.

Examples of air-oxidation-curable compounds include drying oils such as tung oil and linseed oil, alkyd resins obtained by modifying drying oils, acrylic polymers modified with drying oils, silicone resins, polybutadiene, diene polymers such as polymers and copolymers of dienes having 5 to 8 carbon atoms, modified products of these polymers and copolymers (malein-modified, boiled oil-modified, etc.), air-curable polyester compounds, etc. Air-oxidation-curable compounds may be used alone or in combination of two or more.
In terms of storage stability of the curable composition, a drying oil having an acid value of 0.05 to 4.0 (unit: mgKOH/g) is preferred.
Although an air-oxidation-curable compound is not essential, when the curable composition contains an air-oxidation-curable compound, the content of the air-oxidation-curable compound is preferably 0.1 to 20 parts by mass, and more preferably 0.5 to 15 parts by mass, per 100 parts by mass of the total mass of polymer A and polymer B. When the content is at least the lower limit of the above range, a sufficient effect of addition is likely to be obtained, and when the content is at most the upper limit, the weather resistance of the cured product is improved.

Specific examples of the adhesion promoter include organic silane coupling agents such as silanes having a (meth)acryloyloxy group, silanes having an amino group, silanes having an epoxy group, and silanes having a carboxyl group; organometallic coupling agents such as isopropyltri(N-aminoethyl-aminoethyl)propyltrimethoxytitanate and 3-mercaptopropyltrimethoxititanate; and epoxy resins.
Silanes having an amino group are preferred because of their good reactivity with reactive silicon groups. Specific examples of silanes having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-ureidopropyltriethoxysilane, N-(N-vinylbenzyl-2-aminoethyl)-3-aminopropyltrimethoxysilane, and 3-anilinopropyltrimethoxysilane.
Although an adhesion promoter is not essential, when the curable composition contains an adhesion promoter, the content of the adhesion promoter is preferably 0.1 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the total mass of polymer A and polymer B. When the content is equal to or greater than the lower limit of the above range, a sufficient effect of addition is likely to be obtained, and when the content is equal to or less than the upper limit, the stretch durability of the cured product is improved.

As a modulus modifier, a compound having two or more hydroxyl groups is preferred, from the viewpoint of lowering the modulus and improving elongation of the cured product obtained by curing the curable composition, and a compound having a partial structure with hydroxyl groups in at least two bonding positions selected from the α-, β-, and γ-positions is more preferred. When the curable composition contains tetravalent tin as a silanol condensation catalyst, a compound having a partial structure with hydroxyl groups in at least two bonding positions selected from the α-, β-, and γ-positions is preferred as a modulus modifier, from the viewpoint of lowering the modulus and improving elongation of the cured product obtained by curing the curable composition, and also of easily suppressing changes over time in the surface of the cured product.

Examples of the compound having a partial structure with hydroxyl groups at at least two bonding positions selected from the α-, β- and γ-positions include divalent or higher polyols, carboxylic acid esters, and alkyl ethers.
Examples of the divalent or higher polyols include diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, pinacol, and 2,2-dimethyl-1,3-propanediol; triols such as glycerin, 1,2,6-hexanetriol, 1,1,1-tris(hydroxymethyl)propane, 2,2-bis(hydroxymethyl)butanol, and 2-methyl-2-hydroxymethyl-1,3-propanediol; and tetravalent or higher polyols such as pentaerythritol, D-sorbitol, D-mannitol, diglycerin, and polyglycerin.
Examples of the carboxylic acid esters include glycerin monocarboxylic acid esters such as glycerin monostearate, glycerin monoisostearate, glycerin monooleate, glycerin monolaurate, glycerin monopalmitate, glycerin monocaprylate, glycerin monoacetate, and glycerin monobehenate; diglycerin monostearate, diglycerin monooleate, diglycerin monolaurate, tetraglycerin monostearate, tetraglycerin monooleate, tetraglycerin monolaurate, tetraglycerin distearate, tetraglycerin dioleate, tetraglycerin dilaurate, decaglycerin monostearate, decaglycerin monooleate, decaglycerin monolaurate, decaglycerin distearate, and decaglycerin dioleate; pentaerythritol monocarboxylic acid esters such as pentaerythritol monostearate, pentaerythritol monooleate, and pentaerythritol monolaurate; pentaerythritol dicarboxylic acid esters such as pentaerythritol distearate, pentaerythritol dioleate, and pentaerythritol dilaurate; sorbitan monocarboxylic acid esters such as sorbitan monostearate, sorbitan monooleate, sorbitan monolaurate, sorbitan monopalmitate, and sorbitan monobehenate; and sorbitan dicarboxylic acid esters such as sorbitan distearate, sorbitan dioleate, sorbitan dilaurate, sorbitan dipalmitate, and sorbitan dibehenate.
Examples of the alkyl ethers include glycerin monoalkyl ethers such as glycerin monostearyl ether, glycerin monooleyl ether, glycerin monolauryl ether, and glycerin mono-2-ethylhexyl ether; diglycerin monostearyl ether, diglycerin monooleyl ether, diglycerin monolauryl ether, tetraglycerin monostearyl ether, tetraglycerin monooleyl ether, tetraglycerin monolauryl ether, tetraglycerin distearyl ether, tetraglycerin dioleyl ether, tetraglycerin dilauryl ether, decaglycerin monostearyl ether, decaglycerin monooleyl ether, decaglycerin monolauryl ether, decaglycerin distearyl ether, and decaglycerin. pentaerythritol monoalkyl ethers such as pentaerythritol monostearyl ether, pentaerythritol monooleyl ether, and pentaerythritol monolauryl ether; pentaerythritol dialkyl ethers such as pentaerythritol distearyl ether, pentaerythritol dioleyl ether, and pentaerythritol dilauryl ether; sorbitan monoalkyl ethers such as sorbitan monostearyl ether, sorbitan monooleyl ether, and sorbitan monolauryl ether; and sorbitan dialkyl ethers such as sorbitan distearyl ether, sorbitan dioleyl ether, and sorbitan dilauryl ether.

<Curable composition>
The curable composition of the present embodiment is obtained by mixing polymer A, polymer B, a condensation catalyst, and optionally polymer C and other components.
The curable composition of this embodiment is preferably a one-component curable composition in which all ingredients are mixed in advance, stored in a sealed state, and cured by moisture in the air after application.
The one-component curable composition preferably does not contain water. It is preferable to dehydrate and dry the components containing water in advance, or to dehydrate them by applying a reduced pressure during mixing and kneading.
A dehydrating agent may be added to improve storage stability.

The curable composition of the present embodiment crosslinks by forming siloxane bonds accompanied by a hydrolysis reaction of reactive silicon groups, etc., to give a rubber-like cured product.
The curable composition is particularly suitable for use as a sealant or adhesive.
Examples of sealants include elastic sealing materials for construction, sealing materials for double glazing, sealing materials for rust prevention and waterproofing of glass edges, sealing materials for the backside of solar cells, sealing materials for buildings, sealing materials for ships, sealing materials for automobiles, and sealing materials for roads.

The curable composition of the present embodiment can simultaneously achieve good deep curing properties and good stretch resistance and weather resistance of the cured product.
For example, in the evaluation of deep curing described in the Examples below, the hardened product has a consistency of 120 or less after aging at 10°C for 40 hours; in the evaluation of expansion and contraction durability described below, the hardened product has an expansion and contraction durability of 3,000 or more times at which a crack in the hardened product reaches 2.5 mm or more; and in the weather resistance test described below, the hardened product does not fade (whiten) or only fades partially even after 1,500 hours.

The second reactive silicon group is more reactive than the first reactive silicon group. Polymer A having more than 1.0 first reactive silicon group per terminal group is excellent in improving durability, but deep curing tends to be insufficient, particularly in the case of a cured product obtained from a one-component curable composition. If the first reactive silicon group of polymer A is changed to the second reactive silicon group, curing properties are improved, but stretch durability tends to be insufficient.
It is believed that by blending such polymer A with polymer B selected from polymer B1 and polymer B2 having a second reactive silicon group in a specific ratio, it is possible to simultaneously achieve good deep curing properties and good stretch durability and weather resistance of the cured product.

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

<Measurement and evaluation methods>
<Mn, Mw/Mn>
Mw, Mn and Mw/Mn were determined using HLC-8220GPC (product name of Tosoh Corporation).
<Number of reactive silicon groups>
The number of reactive silicon groups contained in the polymer was measured by the internal standard method of ¹ H-NMR.

<Evaluation of deep curing properties (method of measuring consistency)>
450 g of the curable composition was placed in a container (size: length 10.5 cm x width 7.0 cm x depth 4.0 cm), and nitrogen gas was sprayed onto the surface to remove air bubbles. The container was then placed horizontally in an atmosphere at 10°C and cured for 40 hours to prepare a sample. The consistency of the sample was measured using an automatic consistency/penetration tester (RPM-101 model). Specifically, a stainless steel cone (tip diameter 0.38 mm) was penetrated into the center of the surface of the sample under a load of 100 g, and the length of penetration (penetration depth, unit: mm) in 5 seconds was measured, and the penetration depth was multiplied by 10 to obtain the consistency value. The smaller the consistency value, the better the deep curing property. Based on the consistency value, evaluation was performed according to the following criteria.
A: 70 or less.
B: Over 70 and under 90.
C: More than 90 and less than 120.
D: Over 120.

<Evaluation of stretch durability (fatigue resistance test)>
The test was conducted in accordance with the fatigue resistance classification CR90 of the fatigue resistance test described in 5.22 of JIS A 1439 (2016). The adherend used was anodized aluminum whose surface had been treated with a primer (MP-2000, a product name of Cemedine Co., Ltd.).
The cured product was observed for cracks near the adhesive interface between the adherend and the cured product every 500 stretches, and the number of stretches at which the cracks reached 2.5 mm or more was recorded. The higher the number of stretches, the better the stretch durability. Evaluation was based on the number of stretches and flexions and the following criteria.
A: More than 5,000 times.
B: 4,000 times or more but less than 5,000 times.
C: 3,000 times or more but less than 4,000 times.
D: Less than 3,000 times.

<Weather resistance evaluation (weather resistance test)>
The curable composition was applied to a thickness of 5.0 mm on the surface of a siding board (trade name: Honban, manufactured by Asahi Glass Co., Ltd.) measuring 5 cm in length and 5 cm in width. This was cured for one week under conditions of a temperature of 23°C and a humidity of 60% to prepare a weather resistance test sample. The weather resistance of the sample was evaluated using a Sunshine Weatherometer, an accelerated weather resistance tester. The surface condition of each sample was visually observed after 500, 1000, and 1500 hours of testing. The surface color of the sample was compared with the state before the test and evaluated according to the following criteria.
A: It remains the same as it was before the test began.
B: Partial discoloration (whitening).
C: The entire surface was discolored (whitened).

<Polymer synthesis example>
(Synthesis Example 1: Polymer A-1)
Propylene oxide was polymerized using polyoxypropylene glycol as an initiator and a zinc hexacyanocobaltate complex (hereinafter also referred to as "TBA-DMC catalyst") whose ligand is t-butyl alcohol as a catalyst, to obtain a hydroxyl group-containing polyoxyalkylene polymer having hydroxyl groups at both ends.
Next, using sodium methoxide, allyl glycidyl ether, and allyl chloride (3-chloro-1-propene), unsaturated groups were introduced into the terminal groups of the hydroxyl group-containing polyoxyalkylene polymer to obtain an unsaturated group-containing polyoxyalkylene polymer. As the sodium methoxide, a methanol solution containing 28% by mass of sodium methoxide was used (the same applies hereinafter).
Specifically, 1.15 molar equivalents of sodium methoxide were added relative to the hydroxyl groups of the hydroxyl group-containing polyoxyalkylene polymer, and methanol was distilled off under reduced pressure. 1.05 molar equivalents of allyl glycidyl ether was added, and the mixture was reacted at 130°C for 2 hours. 0.28 molar equivalents of sodium methoxide was added, and methanol was removed. 2.10 molar equivalents of allyl chloride were added, and the mixture was reacted at 130°C for 2 hours, and unreacted allyl chloride was removed under reduced pressure. The mixture was purified to remove metal salts, and an unsaturated group-containing polyoxyalkylene polymer having 2.0 allyl groups per terminal group was obtained.
Next, the unsaturated group-containing polyoxyalkylene polymer was reacted with dimethoxymethylsilane as a silylating agent to obtain Polymer A-1.
Specifically, a zero-valent platinum 1,1,3,3-tetramethyl-1,3-divinyldisiloxane complex (hereinafter also referred to as "platinum catalyst") was used as a catalyst, and 0.80 molar equivalents of dimethoxymethylsilane were added relative to the allyl groups of the unsaturated group-containing polyoxyalkylene polymer. The mixture was reacted at 70°C for 5 hours, and then unreacted dimethoxymethylsilane was removed under reduced pressure to obtain Polymer A-1.
The Mn of the obtained polymer A-1, the number of terminal groups per molecule, the number of reactive silicon groups per molecule, the number of reactive silicon groups per terminal group, and the type of reactive silicon group (reactive silicon group represented by formula 1 or formula 2) are shown in Table 1 (the same applies hereinafter).

(Synthesis Example 2: Polymer A-2)
Polymer A-2 was obtained in the same manner as in Synthesis Example 1, except that allyl glycidyl ether was used in an amount of 2.0 molar equivalents and dimethoxymethylsilane in an amount of 0.53 molar equivalents.
(Synthesis Example 3: Polymer A-3)
Polymer A-3 was obtained in the same manner as in Synthesis Example 1, except that the amount of dimethoxymethylsilane added was changed to 0.55 molar equivalents.

(Synthesis Example 4: Polymer A-4)
Polymer A-4 was obtained in the same manner as in Synthesis Example 1, except that the silylating agent in Synthesis Example 1 was changed to dimethylmethoxysilane.

(Synthesis Example 5: Polymer A-5)
The hydroxyl group-containing polyoxyalkylene polymer obtained in Synthesis Example 1 was reacted with sodium methoxide and propargyl bromide to introduce unsaturated groups into the terminal groups of the hydroxyl group-containing polyoxyalkylene polymer.
Specifically, 1.05 molar equivalents of sodium methoxide was added to the hydroxyl groups of the hydroxyl-containing polyoxyalkylene polymer, and methanol was distilled off under reduced pressure. Next, an excess amount of propargyl bromide was reacted with the hydroxyl groups of the hydroxyl-containing polyoxyalkylene polymer to obtain a polyoxyalkylene polymer having 1.0 propargyl group per terminal group.
Next, the polyoxyalkylene polymer having a propargyl group was reacted with methyldimethoxysilane, a silylating agent, to obtain Polymer A-4.
Specifically, in the presence of a platinum catalyst, 3.2 molar equivalents of methyldimethoxysilane were added to the propargyl groups of the polyoxyalkylene polymer having propargyl groups, and the mixture was reacted at 100°C for 5 hours. After that, unreacted methyldimethoxysilane was removed under reduced pressure to obtain Polymer A-5.

(Synthesis Example 6: Polymer A-6)
In the same manner as in Synthesis Example 1, a hydroxyl group-containing polyoxyalkylene polymer was obtained.
Next, in Synthesis Example 1, allyl chloride was changed to methallyl chloride (3-chloro-2-methyl-1-propene) to introduce an unsaturated group into the terminal group of the hydroxyl group-containing polyoxyalkylene polymer.
Specifically, in the same manner as in Synthesis Example 1, sodium methoxide was added to a hydroxyl group-containing polyoxyalkylene polymer, methanol was distilled off, 1.05 molar equivalents of allyl glycidyl ether was added and reacted, sodium methoxide was added, and methanol was removed. Then, 2.10 molar equivalents of methallyl chloride was added, and the reaction was carried out at 130°C for 2 hours, and unreacted methallyl chloride was removed under reduced pressure. The resulting mixture was purified to remove metal salts, yielding an unsaturated group-containing polyoxyalkylene polymer having 2.0 methallyl groups per terminal group.
Next, a silylating agent was reacted in the same manner as in Synthesis Example 1 to obtain Polymer A-6. The amount of the silylating agent added was 0.8 molar equivalents relative to the methallyl group.

(Synthesis Example 7: Polymer A-7)
The initiator was changed to glycerin in Synthesis Example 1. That is, propylene oxide was polymerized using glycerin as the initiator in the presence of a TBA-DMC catalyst to obtain a hydroxyl group-containing polyoxyalkylene polymer.
Except for this, the procedure was the same as in Synthesis Example 1 to obtain Polymer A-7.

(Synthesis Examples 8 to 13: Polymer A-8 to Polymer A-13)
Polymers A-8 to A-13 were obtained in the same manner as in Synthesis Example 1, except that the amount of propylene oxide to be polymerized in Synthesis Example 1 was adjusted to change the molecular weight of the hydroxyl group-containing polyoxyalkylene polymer.

(Synthesis Example 14: Polymer a-1)
Polymer a-1 was obtained in the same manner as in Synthesis Example 1, except that the amount of dimethoxymethylsilane added was changed to 0.50 molar equivalents.

(Synthesis Example 15: Polymer a-2)
Polymer a-2 was obtained in the same manner as in Synthesis Example 1, except that the silylating agent in Synthesis Example 1 was changed to trimethoxysilane.

(Synthesis Example 16: Polymer a-3)
In Synthesis Example 1, the amount of propylene oxide to be polymerized was adjusted to change the molecular weight of the hydroxyl group-containing polyoxyalkylene polymer.
Next, an unsaturated group-containing polyoxyalkylene polymer was obtained by changing the amounts of sodium methoxide, allyl glycidyl ether, and allyl chloride used in Synthesis Example 1.
Specifically, 1.0 molar equivalent of sodium methoxide was added relative to the hydroxyl groups of the hydroxyl group-containing polyoxyalkylene polymer, and methanol was distilled off under reduced pressure. 1.0 molar equivalent of allyl glycidyl ether was added, and the mixture was reacted at 130°C for 2 hours. 0.28 molar equivalent of sodium methoxide was added, and methanol was removed. 1.79 molar equivalent of allyl chloride was added, and the mixture was reacted at 130°C for 2 hours, and unreacted allyl chloride was removed under reduced pressure. The mixture was purified to remove metal salts, and an unsaturated group-containing polyoxyalkylene polymer having 2.0 allyl groups per terminal group was obtained.
Next, polymer a-3 was obtained by changing the silylating agent in Synthesis Example 1 to trimethoxysilane. The amount of trimethoxysilane added was 0.8 molar equivalents relative to the allyl groups of the unsaturated group-containing polyoxyalkylene polymer.

(Synthesis Example 17: Polymer B1-1)
An unsaturated group-containing acrylic ester polymer was synthesized by reacting a compound having two alkenyl groups with a living radical polymerization method at the end of the polymerization reaction.
Specifically, 8.39 g of cuprous bromide and 112 mL of acetonitrile were added to a 2-L flask and heated and stirred at 70°C for 20 minutes under a nitrogen stream. To this was added 17.6 g of diethyl 2,5-dibromoadipate, 130 mL of ethyl acrylate, 720 mL of butyl acrylate, and 251 g of stearyl acrylate, followed by heating and stirring at 70°C for an additional 40 minutes. To this was added 0.41 mL of pentamethyldiethylenetriamine (hereinafter also referred to as "triamine") to initiate the reaction. Heating and stirring were continued at 70°C, and an additional 2.05 mL of triamine was added. 330 minutes after the start of the reaction, 244 mL of 1,7-octadiene and 4.1 mL of triamine were added, followed by heating and stirring at 70°C. Heating was stopped 570 minutes after the start of the reaction. The resulting reaction solution was diluted with toluene and filtered, and the filtrate was heated under reduced pressure to obtain an unpurified acrylic ester polymer having alkenyl groups at its termini. The number of alkenyl groups per molecule of the unpurified acrylic acid ester polymer was 2.8. The number of alkenyl groups per molecule was determined by ¹ H-NMR analysis (the same applies hereinafter).
Furthermore, the crude acrylic acid ester polymer was purified to obtain an unsaturated group-containing acrylic acid ester polymer.
Specifically, under a nitrogen atmosphere, the entire amount of the unpurified acrylic acid ester polymer, 17.2 g of potassium acetate, and 700 mL of N,N-dimethylacetamidomethyl (hereinafter referred to as "DMAc") were added to a 2 L flask, and the mixture was heated and stirred at 100°C for 10 hours. The reaction solution was heated under reduced pressure to remove DMAc, and toluene was added and filtered. The filtrate was heated under reduced pressure to remove volatiles, and the remainder was added to a 2 L flask, to which 100 g of an adsorbent (a 1:1 mass ratio mixture of Kyoward 500SN and Kyoward 700SN (both product names of Kyowa Chemical Industry Co., Ltd.)) was added, and the mixture was heated and stirred at 130°C for 9 hours under a nitrogen stream. The mixture was diluted with toluene, filtered to remove the adsorbent, and the toluene in the filtrate was distilled off under reduced pressure to obtain an unsaturated group-containing acrylic acid ester polymer.
Next, the unsaturated group-containing acrylic acid ester polymer was reacted with trimethoxysilane, which is a silylating agent, to obtain polymer B1-1.
Specifically, 700 g of the unsaturated group-containing acrylic acid ester polymer, 22.2 mL of trimethoxysilane, 7.71 mL of methyl orthoformate, and a platinum catalyst (1,1,3,3-tetramethyl-1,3-divinyldisiloxane complex of zero-valent platinum) were added to a 1 L pressure-resistant reaction vessel. The amount of platinum catalyst added was 9 x 10 ^-3 molar equivalents relative to the alkenyl groups of the unsaturated group-containing acrylic acid ester polymer. The mixture in the reaction vessel was heated and stirred at 100°C for 195 minutes. Volatiles from the reaction mixture were distilled off under reduced pressure to obtain polymer B1-1 having trimethoxysilyl groups at its termini. The Mw/Mn of polymer B1-1 was 1.40.

(Synthesis Example 18: Polymer B1-2)
Polymer B1-2 was produced by a polymerization method using a monomer having a reactive silicon group.
Specifically, 50 g of isobutanol was added to a pressure-resistant reactor equipped with a stirrer, and the temperature was raised to about 80° C. While maintaining the internal temperature of the reactor at about 80° C. and stirring under a nitrogen atmosphere, the following mixed solution was added dropwise over 2 hours to polymerize, thereby obtaining a polymer B1-2 having trimethoxysilyl groups in its side chains.
Mixed solution: a mixture of 1.65 g of methyl methacrylate, 373.1 g of n-butyl acrylate, 110.0 g of stearyl acrylate, 6.5 g of 3-methacryloxypropyltrimethoxysilane (KBM-503, product name of Shin-Etsu Silicones), and 7.3 g of 2,2'-azobis-2,4-dimethylvaleronitrile (V-65, product name of Wako Pure Chemical Industries, Ltd.).

(Synthesis Examples 19 to 22: Polymers B1-3 to B1-6)
In Synthesis Example 17, the Mn and Mw/Mn of the unpurified acrylic acid ester polymer were changed. The number of alkenyl groups per molecule was 2.8 in all cases. Except for this, polymers B1-3 to B1-6 were obtained in the same manner as in Synthesis Example 17. The Mw/Mn of polymers B1-3 to B1-6 was as follows.
Synthesis Example 19: Polymer B1-3, Mw/Mn 1.20.
Synthesis Example 20: Polymer B1-4, Mw/Mn 1.20.
Synthesis Example 21: Polymer B1-5, Mw/Mn 1.40.
Synthesis Example 22: Polymer B1-6, Mw/Mn 1.41.

(Synthesis Example 23: Polymer B2-1)
Propylene oxide was polymerized using polyoxypropylene glycol as an initiator and a zinc hexacyanocobaltate complex (hereinafter also referred to as "Gly-DMC catalyst") with a glyme ligand as a catalyst. Next, a 48% by mass aqueous solution of KOH was added as a catalyst, and after dehydration and alcoholation, ethylene oxide was supplied and reacted. After completion of the reaction, the catalyst was neutralized and removed using an adsorbent (Kyowado 600S, product name of Kyowa Chemical Industry Co., Ltd.), yielding a hydroxyl group-containing polyoxyalkylene polymer. The EO content in the hydroxyl group-containing polyoxyalkylene polymer was 10% by mass.
Next, the hydroxyl group-containing polyoxyalkylene polymer was reacted with a compound having an isocyanate group and a reactive silicon group to obtain polymer B2-1.
Specifically, the atmosphere inside a reactor containing a hydroxyl group-containing polyoxyalkylene polymer was purged with nitrogen gas, and while maintaining the internal temperature at 50°C, 3-isocyanatepropyltrimethoxysilane was added so that the molar ratio of isocyanate groups to hydroxyl groups (NCO/OH) was 0.97, and dioctyltin bisisooctylthioglycol (Neostan U-860, product name of Nitto Kasei Co., Ltd.) was added as a catalyst. The temperature was raised to 80°C, and stirring was continued while maintaining the temperature at 80°C. Analysis was performed using a Fourier transform infrared spectrophotometer, and the reaction was continued until completion of the reaction between the hydroxyl groups and the isocyanate groups could be confirmed. After that, 0.06 parts by mass of 3-mercaptopropyltrimethoxysilane was added as a storage stabilizer relative to 100 parts by mass of the hydroxyl group-containing polyoxyalkylene polymer, to obtain Polymer B2-1.

(Synthesis Example 24: Polymer B2-2)
Using polyoxyethylene triol as an initiator, propylene oxide was polymerized in the presence of a Gly-DMC catalyst to obtain a hydroxyl group-containing polyoxyalkylene polymer.
Next, in the same manner as in Synthesis Example 23, the hydroxyl group-containing polyoxyalkylene polymer was reacted with 3-isocyanatepropyltrimethoxysilane to obtain Polymer B2-2.

(Synthesis Example 25: Polymer B2-3)
Using polyoxypropylene glycol as an initiator, ethylene oxide was polymerized in the presence of a Gly-DMC catalyst to obtain a hydroxyl group-containing polyoxyalkylene polymer.
Next, in the same manner as in Synthesis Example 23, the hydroxyl group-containing polyoxyalkylene polymer was reacted with 3-isocyanatepropyltrimethoxysilane to obtain Polymer B2-3.

(Synthesis Example 26: Polymer B2-4)
Using polyoxypropylene glycol as an initiator, propylene oxide was polymerized in the presence of a TBA-DMC catalyst to obtain a hydroxyl group-containing polyoxyalkylene polymer.
Next, using sodium methoxide and allyl chloride, unsaturated groups were introduced into the terminal groups of the hydroxyl group-containing polyoxyalkylene polymer to obtain an unsaturated group-containing polyoxyalkylene polymer.
Specifically, 1.05 molar equivalents of sodium methoxide was added to the hydroxyl groups of the hydroxyl-containing polyoxyalkylene polymer, and methanol was distilled off under reduced pressure. An excess amount of allyl chloride was added to the hydroxyl groups of the hydroxyl-containing polyoxyalkylene polymer to react with the polymer, and unreacted allyl chloride was removed under reduced pressure. The resulting mixture was purified to remove metal salts, yielding an unsaturated group-containing polyoxyalkylene polymer having 1.0 allyl group per terminal group.
Next, the unsaturated group-containing polyoxyalkylene polymer was reacted with trimethoxysilane, a silylating agent, to obtain polymer B2-4.
Specifically, in the presence of a platinum catalyst, 1.0 molar equivalent of trimethoxysilane was added relative to the allyl groups of the unsaturated group-containing polyoxyalkylene polymer, and the mixture was reacted at 70°C for 5 hours. After that, unreacted trimethoxysilane was removed under reduced pressure to obtain polymer B2-4.

(Synthesis Example 27: Polymer B2-5)
The initiator was changed to glycerin in Synthesis Example 26. That is, propylene oxide was polymerized using glycerin as the initiator in the presence of a TBA-DMC catalyst to obtain a hydroxyl group-containing polyoxyalkylene polymer.
Except for the above, the procedure was the same as in Synthesis Example 26 to obtain Polymer B2-5.

(Synthesis Example 28: Polymer b-1)
In Synthesis Example 26, the amount of propylene oxide to be polymerized was adjusted to change the molecular weight of the hydroxyl group-containing polyoxyalkylene polymer.
An unsaturated group-containing polyoxyalkylene polymer was obtained in the same manner as in Synthesis Example 26.
Polymer b-1 was obtained in the same manner as in Synthesis Example 26, except that the silylating agent in Synthesis Example 26 was changed to 0.73 molar equivalents of dimethoxymethylsilane.

(Synthesis Example 29: Polymer b-2)
Polymer b-2 was obtained in the same manner as in Synthesis Example 28, except that the silylating agent was changed to 0.80 molar equivalents of dimethoxymethylsilane.
(Synthesis Example 30: Polymer b-3)
Polymer b-3 was produced by a polymerization method using a monomer having a reactive silicon group.
Specifically, in Synthesis Example 18, 3-methacryloxypropyltrimethoxysilane was changed to 3-methacryloxypropylmethyldimethoxysilane to change the molecular weight. Otherwise, the same procedure as in Synthesis Example 18 was repeated to obtain polymer b-3.

(Synthesis Example 31: Polymer b-4)
Polymer b-4 was produced by a living radical polymerization method.
Specifically, polymer b-4 was obtained in the same manner as in Synthesis Example 17, except that trimethoxysilane was changed to dimethoxymethylsilane.

(Synthesis Example 32: Polymer b-5)
In Synthesis Example 26, the TBA-DMC catalyst was changed to a Gly-DMC catalyst, and the amount of propylene oxide to be polymerized was adjusted to change the molecular weight of the hydroxyl group-containing polyoxyalkylene polymer.
An unsaturated group-containing polyoxyalkylene polymer was obtained in the same manner as in Synthesis Example 26.
Polymer b-5 was obtained in the same manner as in Synthesis Example 26, except that the silylating agent in Synthesis Example 26 was changed to 0.75 molar equivalents of dimethoxymethylsilane.

(Synthesis Example 33: Polymer C-1)
Using n-butyl alcohol as an initiator, propylene oxide was polymerized in the presence of a TBA-DMC catalyst to obtain a hydroxyl group-containing polyoxyalkylene polymer.
Next, in the same manner as in Synthesis Example 26, an unsaturated group was introduced into one of the terminal groups of the hydroxyl group-containing polyoxyalkylene polymer using sodium methoxide and allyl chloride to obtain an unsaturated group-containing polyoxyalkylene polymer having one terminal group which is a butyloxy group and the other terminal group which has 1.0 allyl group per molecule (0.5 allyl groups per terminal group).
Next, the unsaturated group-containing polyoxyalkylene polymer was reacted with dimethoxymethylsilane as a silylating agent to obtain polymer C-1.
Specifically, in the presence of a platinum catalyst, 1.0 molar equivalent of dimethoxymethylsilane was added relative to the allyl groups of the unsaturated group-containing polyoxyalkylene polymer, and the mixture was reacted at 70°C for 5 hours. After that, unreacted dimethoxymethylsilane was removed under reduced pressure to obtain polymer C-1.

(Synthesis Example 34: Polymer C-2)
A hydroxyl group-containing polyoxyalkylene polymer was obtained in the same manner as in Synthesis Example 33.
Next, an unsaturated group was introduced into one terminal group of the hydroxyl group-containing polyoxyalkylene polymer using sodium methoxide, allyl glycidyl ether and allyl chloride to obtain an unsaturated group-containing polyoxyalkylene polymer.
Specifically, 1.15 molar equivalents of sodium methoxide were added relative to the hydroxyl groups of the hydroxyl group-containing polyoxyalkylene polymer, and methanol was distilled off under reduced pressure. 1.05 molar equivalents of allyl glycidyl ether was added, and the mixture was reacted at 130°C for 2 hours. 0.28 molar equivalents of sodium methoxide was added, and methanol was removed. 1.79 molar equivalents of allyl chloride was added, and the mixture was reacted at 130°C for 2 hours, and unreacted allyl chloride was removed under reduced pressure. The mixture was purified to remove metal salts, and an unsaturated group-containing polyoxyalkylene polymer was obtained, having one terminal group as a butyloxy group and the other terminal group as 2.0 allyl groups per molecule (1.0 per terminal group).
Next, the silylating agent was reacted in the same manner as in Synthesis Example 33, except that the amount of the silylating agent added was 0.5 molar equivalents relative to the allyl groups, to obtain Polymer C-2.

(Synthesis Example 35: Polymer C-3)
Polymer C-3 was obtained in the same manner as in Synthesis Example 33, except that the silylating agent in Synthesis Example 33 was changed to trimethoxysilane.

(Other ingredients)
The additives listed in Tables 2 to 7 are as follows:
Hakuenka CCR: Colloidal calcium carbonate, Hakuenka CCR, product name of Shiraishi Kogyo Co., Ltd.
Whiten SB: Heavy calcium carbonate, product name of Shiraishi Kogyo Co., Ltd.
R820: Titanium oxide, product name of Ishihara Sangyo Kaisha.
Viscolite EL20: Colloidal calcium carbonate, product name of Shiraishi Calcium Co., Ltd.
Disparlon 6500: fatty acid amide wax, manufactured by Kusumoto Chemical Co., Ltd.
Glycerin monostearate: Reagent, manufactured by Tokyo Chemical Industry Co., Ltd.
DINP: Sanso Cizer DINP, diisononyl phthalate, product name of New Japan Chemical Co., Ltd.
DIDP: diisodecyl phthalate, manufactured by Mitsubishi Chemical Corporation.
KBM-1003: Vinyltrimethoxysilane, product name of Shin-Etsu Chemical Co., Ltd.
A-171: Vinyltrimethoxysilane, SILQUEST A-171, product name of Momentive.
KBM-403: 3-glycidoxypropyltrimethoxysilane, product name of Shin-Etsu Chemical Co., Ltd.
KBM-603: 3-(2-aminoethylamino)propyltrimethoxysilane, product name of Shin-Etsu Chemical Co., Ltd.
A-1120: N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, SILQUEST A-1120, product name of Momentive Corporation.
TINUVIN 765: Tertiary amine-containing hindered amine light stabilizer, product name of BASF.
TINUVIN 770: Hindered amine light stabilizer, product name of BASF.
Sanol LS770: Hindered amine light stabilizer, product name of Sankyo Lifetech Co., Ltd.
IRGANOX 1135: Hindered phenol-based antioxidant, product name of BASF.
TINUVIN 326: Benzotriazole-based ultraviolet absorber, product name of BASF.
TINUVIN 327: Benzotriazole-based ultraviolet absorber, product name of BASF.
U-220H: silanol condensation catalyst, dibutyltin bis(acetylacetonate), product name of Nitto Kasei Co., Ltd.
Versatic 10: Silanol condensation catalyst, neodecanoic acid, product name of Japan Epoxy Resins Co., Ltd.
SCAT-32A: silanol condensation catalyst, divalent tin catalyst, product name of Nitto Kasei Co., Ltd.
Air oxidation curing compound: tung oil, manufactured by Kimura Co., Ltd., acid value 2.0 (unit: mgKOH/g).

<Preparation of Curable Composition>
Examples 1 to 41 are working examples, and Examples 42 to 50 are comparative examples.
Polymers, catalysts, air oxidation curable compounds, and common component D1 shown in Table 2 were mixed in the formulations shown in Tables 3 to 7 to prepare curable compositions.
The cured products of the curable compositions were evaluated for deep curing, stretch durability, and weather resistance by the methods described above. The results are shown in Tables 3 to 7.

The curable compositions of Examples 1 to 41 were excellent in deep curing properties, and the cured products were excellent in stretch durability and weather resistance.
In Examples 1 to 41, the common component can be changed to D3 or D4 shown in Table 2. The curable compositions obtained by changing the common component in Examples 1 to 41 to D3 or D4 have excellent deep curing properties, and the cured products thereof have excellent stretch durability and weather resistance.

Claims (11)

A curable composition comprising the following polymer A, the following polymer B, and a condensation catalyst, wherein A/B, which represents a mass ratio of the polymer A to the polymer B, is 80/20 to 95/5.
Polymer A: A polyoxyalkylene polymer having more than 1.0 reactive silicon group per terminal group, represented by the following formula 1:
Polymer B: One or more polymers selected from the group consisting of (meth)acrylic acid ester polymers B1 having a reactive silicon group represented by the following formula 2, and polyoxyalkylene polymers B2 having more than 0.5 and not more than 1.0 reactive silicon groups represented by the following formula 2 per terminal group.
-SiR _a X ¹ _3-a formula 1
In formula 1, R represents a monovalent organic group having 1 to 20 carbon atoms other than a hydrolyzable group, ^X1 represents a hydroxyl group, a halogen atom, or a hydrolyzable group, and a is 1 or 2; when a is 1 , the two ^X1s may be the same or different from each other, and when a is 2 , the two Rs may be the same or different from each other.
-SiX ² ₃ formula 2
In formula 2, X ² represents a hydroxyl group, a halogen atom, or a hydrolyzable group, and X ² may be the same or different. The curable composition according to claim 1 , wherein the polymer A has a terminal group containing a group represented by the following formula 3 or 4:
[In formula 3, R ¹ and R ³ each independently represent a divalent linking group having 1 to 6 carbon atoms, and the atom bonded to the carbon atom in the linking group is a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom; R ² and R ⁴ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms; Si ¹ represents a reactive silicon group represented by formula 1 above; n represents an integer of 1 to 10; and Si ¹ may be the same or different.]
[In formula 4, ^R5 represents a single bond or a divalent linking group having 1 to 6 carbon atoms, the atom bonded to the carbon atom in the linking group is a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom, X represents a monovalent group represented by any of formulas 5 to 8, in which in formulas 5 to 8, ^R6 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, ^R7 and ^R8 each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 9 carbon atoms, and ^Si1 represents a reactive silicon group represented by formula 1, and multiple ^Si1s may be the same or different.] The curable composition according to claim 1 or 2, wherein the polymer A is linear. The curable composition according to any one of claims 1 to 3, wherein the number average molecular weight of polymer A is 8,000 to 150,000. The curable composition according to any one of claims 1 to 4, wherein the number average molecular weight of polymer B is 5,000 to 50,000. The curable composition according to any one of claims 1 to 5, wherein the content of polymer B1 relative to the total mass of polymer B is 45 to 100 mass%. The curable composition according to any one of claims 1 to 6, further comprising the following polymer C:
Polymer C: A polyoxyalkylene polymer having two terminal groups, one of which is an inert organic group, and which contains more than 0 but not more than 0.5 reactive silicon groups represented by formula 1 or formula 2 per terminal group, and which has a number average molecular weight of 2,000 to 15,000. The curable composition according to any one of claims 1 to 7, wherein the condensation catalyst comprises one or more selected from the group consisting of tetravalent tin catalysts, titanium catalysts, aluminum catalysts, zirconium catalysts, carboxylic acids, metal carboxylate salts, and amine compounds. The curable composition according to any one of claims 1 to 8, wherein the content of the condensation catalyst is 0.03 to 0.7 parts by mass per 100 parts by mass of the total of the polymer A and the polymer B. The curable composition according to any one of claims 1 to 9, which is used as a sealant or adhesive. A cured product of the curable composition described in any one of claims 1 to 10.