JP7775595B2 - Curable composition and sealant composition - Google Patents

Description

The present invention relates to a curable composition and a sealant composition that produce a cured product with excellent tensile properties and weather resistance.

Conventionally, adhesives, sealants, paints, coating agents, etc. have been used in the fields of architecture, civil engineering, electrical and electronics, vehicles, etc., and for example, those made of a curable composition containing a polymer having a reactive group have been widely used. As such curable compositions, the following techniques are known.
Patent Document 1 discloses a sealant composition containing a vinyl polymer (A) having a weight average molecular weight of 4,000 to 70,000, a glass transition temperature of -70 to 10°C, and an alkoxysilyl group, a polyoxyalkylene compound (B) having an alkoxysilyl group at a terminal, and a polypropylene glycol (C1) having a weight average molecular weight of 1,000 to 50,000 or a vinyl monomer (C2) having a weight average molecular weight of 800 to 15,000, a glass transition temperature of -70 to -10°C, and no alkoxysilyl group, which is obtained by continuously polymerizing at a temperature of 150 to 350°C.
Patent Document 2 describes a composition containing 20 to 99.7 parts by mass of component (A): a crosslinkable polymer (excluding (meth)acrylic polymers containing 30% by mass or more of structural units derived from vinyl monomers having an alkyl group having 10 or more carbon atoms), 0.3 to 35 parts by mass of component (B): a (meth)acrylic polymer having a reactive silyl group, and 0 to 79.7 parts by mass of component (C): a plasticizer,
(where the total of components (A), (B), and (C) is 100 parts by mass), the curable composition disclosed contains component (B) having an average of 0.03 to 0.5 reactive silyl groups per molecule and containing 30% by mass or more of structural units derived from a vinyl monomer having an alkyl group having 10 or more carbon atoms.
Patent Document 3 discloses a curable composition containing an oxyalkylene polymer (A) having a reactive silyl group and a (meth)acrylic polymer (B), in which the (meth)acrylic polymer (B) has double bonds in the molecule in an amount of 0.01 meq/g or more and 1.0 meq/g or less.
Patent Document 4 discloses a curable composition containing a (meth)acrylic polymer (A) having a weight-average molecular weight of 500 or more and less than 10,000, and a (meth)acrylic polymer (B) having a weight-average molecular weight of 10,000 or more and 100,000 or less, in which the (meth)acrylic polymer (A) has double bonds in the molecule in an amount of 0.01 meq/g or more and 1.0 meq/g or less, and the (meth)acrylic polymer (B) has a reactive silyl group in the molecule.

JP 2004-18748 Patent Publication No. 2017-88766 Patent Publication No. 2019-56098 Patent Publication No. 2019-143014

Conventionally, when known curable compositions are used, cured products having good mechanical properties and weather resistance are formed. However, there is an increasing demand for further improvement in weather resistance.
An object of the present invention is to provide a curable composition and a sealant composition that give a cured product having excellent tensile properties and weather resistance.

The inventors discovered that the above-mentioned problems could be solved by using two types of (meth)acrylic polymers, each of which contains structural units derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms, and each of which has a weight-average molecular weight and a proportion of reactive silyl groups within a specific range, and thus completed the present invention.

The present invention is illustrated below.
1. A curable composition comprising: (A) a (meth)acrylic polymer containing structural units derived from a (meth)acrylic acid alkyl ester, wherein the structural units derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms account for 20 mass% or more of the polymer; the (meth)acrylic polymer having a weight-average molecular weight of 6,000 or more; and the average number of reactive silyl groups per molecule being less than 0.5; and (B) a (meth)acrylic polymer containing structural units derived from a (meth)acrylic acid alkyl ester, wherein the (meth)acrylic polymer contains structural units derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms; the (meth)acrylic polymer having a weight-average molecular weight of 10,000 to 100,000; and the average number of reactive silyl groups per molecule being 0.5 or more.
2. The curable composition according to item 1, wherein the average number of the reactive silyl groups contained in the (meth)acrylic polymer (A) is 0.05 to 0.35.
3. The curable composition according to item 1 or 2, wherein the (meth)acrylic polymer (A) further contains a structural unit derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 10 or more carbon atoms.
4. The curable composition according to any one of items 1 to 3, wherein the (meth)acrylic polymer (A) has carbon-carbon double bonds in a proportion of 0.01 to 0.30 meq/g.
5. The curable composition according to any one of items 1 to 4, wherein the (meth)acrylic polymer (B) further contains a structural unit derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 10 or more carbon atoms.
6. The curable composition according to any one of items 1 to 5, wherein the (meth)acrylic polymer (B) has a weight average molecular weight of 15,000 to 80,000.
7. The curable composition according to any one of items 1 to 6, wherein, when the total of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) is taken as 100% by mass, the content of the (meth)acrylic polymer (A) is 20 to 85% by mass and the content of the (meth)acrylic polymer (B) is 15 to 80% by mass.
8. The curable composition according to any one of items 1 to 7, having a viscosity at 25°C of 10 to 250 Pa·s.
9. The curable composition according to any one of items 1 to 8, further comprising (C) an oxyalkylene polymer having a reactive silyl group.
10. The curable composition according to item 9, wherein the (meth)acrylic polymer (B) is contained in an amount of 25 to 80% by mass and the oxyalkylene polymer (C) is contained in an amount of 20 to 75% by mass, where the total amount of the (meth)acrylic polymer (B) and the oxyalkylene polymer (C) is taken as 100% by mass.
11. The curable composition according to any one of items 1 to 10, further comprising a curing accelerator.
12. A sealant composition containing the curable composition according to item 11.

In this specification, "(meth)acrylate" means acrylate and/or methacrylate. Also, "(meth)acryloyl" means acryloyl and/or methacryloyl. Furthermore, "(meth)acrylic" means acrylic and/or methacrylic.
In this specification, the "weight average molecular weight (Mw)" and "number average molecular weight (Mn)" are values calculated as standard polystyrene by gel permeation chromatography (GPC).

In the present invention, when a curable composition containing a curing accelerator is used, a three-dimensional crosslinked structure is formed by atmospheric moisture, etc., making it easy to obtain a cured product with rubber-like elasticity. Because such cured products have excellent tensile properties and weather resistance, the curable composition of the present invention can be suitably used in fields such as architecture, civil engineering, electrical and electronics, and vehicles. Furthermore, the curable composition of the present invention containing the above-mentioned (meth)acrylic polymers (A) and (B) has a viscosity suitable for coating, and can therefore be used in the above fields to produce adhesives, sealants, paints, coating agents, and the like that have excellent coating workability.

The curable composition of the present invention comprises, as component (A), a (meth)acrylic polymer containing structural units derived from a (meth)acrylic acid alkyl ester, wherein the structural units (hereinafter referred to as "structural units (a1)") derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms are contained in 20 mass% or more of the polymer, the (meth)acrylic polymer having a weight-average molecular weight of 6,000 or more, and the average number of reactive silyl groups per molecule is less than 0.5; and as component (B), a (meth)acrylic polymer containing structural units derived from a (meth)acrylic acid alkyl ester, wherein the structural units (hereinafter referred to as "structural units (b1)") derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms are contained, the (meth)acrylic polymer having a weight-average molecular weight of 10,000 to 100,000, and the average number of reactive silyl groups per molecule is 0.5 or more.
The term "reactive silyl group" refers to a group that can form a crosslinked structure based on a siloxane bond through hydrolysis and condensation. Specifically, it is a group in which a hydroxy group or a hydrolyzable group (such as an alkoxy group) is bonded to a silicon atom.

Component (A) according to the present invention is a (meth)acrylic polymer containing structural unit (a1). It may be either a homopolymer or a copolymer, but as described above, it may contain a reactive silyl group. In this case, it is preferable that the component (A) is a copolymer further containing a structural unit having a reactive silyl group (hereinafter referred to as "structural unit (a2)"). Component (A) made of such a copolymer may further contain, in addition to structural units (a1) and (a2), another structural unit (hereinafter also referred to as "structural unit (a3)"). Furthermore, in the case of a copolymer, it may be either a random copolymer or a block copolymer.

Examples of alkyl (meth)acrylate esters that provide structural unit (a1) include ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, and n-hexyl (meth)acrylate. In the present invention, alkyl acrylate esters having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms are preferred, as they provide a curable composition suitable for forming a cured product with a low homopolymer Tg and excellent tensile properties and weather resistance.

The content of structural unit (a1) in component (A) is 20% by mass or more, preferably 20 to 90% by mass, and more preferably 25 to 60% by mass, since this results in a curable composition suitable for forming a cured product with excellent tensile properties and weather resistance. Component (A) may contain only one type of structural unit (a1), or two or more types.

The compound that provides structural unit (a2) is a monomer compound having a polymerizable unsaturated double bond and, as a reactive silyl group, preferably an alkoxysilyl group (trialkoxysilyl groups such as trimethoxysilyl, triethoxysilyl, dimethoxyethoxysilyl, and methoxydiethoxysilyl; dialkoxysilyl groups such as methyldimethoxysilyl, methyldiethoxysilyl, ethyldimethoxysilyl, and ethyldiethoxysilyl; monoalkoxysilyl groups such as dimethylmethoxysilyl, dimethylethoxysilyl, diethylmethoxysilyl, and diethylethoxysilyl), a halogenosilyl group ((chloromethyl)dimethoxysilyl, (chloromethyl)diethoxysilyl), or a silanol group. In the present invention, a compound having an alkoxysilyl group is preferred because it allows for the production of a curable composition that is suitable for forming a cured product with excellent tensile properties and weather resistance.

Examples of the compound having an alkoxysilyl group include vinylsilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, and vinyldimethylmethoxysilane; silyl group-containing (meth)acrylic acid esters such as trimethoxysilylpropyl (meth)acrylate, triethoxysilylpropyl (meth)acrylate, dimethylmethoxysilylpropyl (meth)acrylate, methyldimethoxysilylpropyl (meth)acrylate, and methyldiethoxysilylpropyl (meth)acrylate; silyl group-containing vinyl ethers such as trimethoxysilylpropyl vinyl ether; and silyl group-containing vinyl esters such as vinyl trimethoxysilylundecanoate. Among these, silyl group-containing (meth)acrylic acid esters are preferred from the viewpoint of copolymerizability with the (meth)acrylic acid alkyl ester that gives the structural unit (a1) and the (meth)acrylic acid alkyl ester that gives the structural unit (a1).
When component (A) contains a reactive silyl group, the position of the reactive silyl group in the polymer is not particularly limited, and the reactive silyl group may be located in a side chain or at the end of the polymer.

When structural unit (a2) is contained in component (A), its content is not particularly limited as long as the average number of reactive silyl groups per molecule of component (A) is less than 0.5. It is typically less than 5.0% by mass, preferably 0.75 to 3.0% by mass, and more preferably 0.5 to 2.0% by mass. Component (A) may contain only one type of structural unit (a2), or two or more types.

Component (A) can contain only one type or two or more types of structural unit (a3). Examples of compounds that provide this structural unit (a3) include (meth)acrylic acid alkyl esters having an alkyl ester moiety containing an alkyl group having 7 or more carbon atoms (hereinafter referred to as "(meth)acrylic acid alkyl esters (M)"), (meth)acrylic acid aromatic esters having an ester moiety containing an aromatic hydrocarbon group, (meth)acrylic acid alkoxyalkyl esters, hydroxy group-containing vinyl compounds, amino group-containing vinyl compounds, epoxy group-containing vinyl compounds, aromatic vinyl compounds, vinyl cyanide compounds, unsaturated acids or their alkyl esters (excluding (meth)acrylic acid alkyl esters), unsaturated acid anhydrides, maleimide compounds, vinyl esters, fluorine-containing (meth)acrylic acid esters, alkenes, dienes, vinyl chloride, vinylidene chloride, allyl chloride, and allyl alcohol.

The above (meth)acrylic acid alkyl esters include n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, and methyl (meth)acrylate. Heptadecyl (meth)acrylate, Stearyl (meth)acrylate, Nonadecyl (meth)acrylate, Eicosyl (meth)acrylate, Heneicosyl (meth)acrylate, Behenyl (meth)acrylate, Tetracosyl (meth)acrylate, Hexacosyl (meth)acrylate, Octacosyl (meth)acrylate, Triacontyl (meth)acrylate, Dotriacontyl (meth)acrylate, Tetratriacontyl (meth)acrylate, Hexatriacontyl (meth)acrylate, O-(meth)acrylate Tridecyl (meth)acrylate, tetracontyl (meth)acrylate, isodecyl (meth)acrylate, isoundecyl (meth)acrylate, isolauryl (meth)acrylate, isotridecyl (meth)acrylate, isotetradecyl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isostearyl (meth)acrylate, isononadecyl (meth)acrylate, isoeicosyl (meth)acrylate, (meth)acrylate Examples of acrylates include isoheneicosyl (meth)acrylate, isobehenyl (meth)acrylate, isotetracosyl (meth)acrylate, isohexacosyl (meth)acrylate, isooctacosyl (meth)acrylate, isotriacontyl (meth)acrylate, isodotriacontyl (meth)acrylate, isotetratriacontyl (meth)acrylate, isohexatriacontyl (meth)acrylate, isooctatriacontyl (meth)acrylate, and isotetracontyl (meth)acrylate.

Examples of the aromatic (meth)acrylate include phenyl (meth)acrylate, toluyl (meth)acrylate, and benzyl (meth)acrylate.
Examples of the (meth)acrylic acid alkoxyalkyl ester include methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, methoxyhexyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, ethoxybutyl (meth)acrylate, ethoxyhexyl (meth)acrylate, butoxymethyl (meth)acrylate, butoxyethyl (meth)acrylate, butoxybutyl (meth)acrylate, and butoxyhexyl (meth)acrylate.

Examples of the hydroxy group-containing vinyl compound include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono(meth)acrylate, poly(ethylene glycol-propylene glycol) mono(meth)acrylate, polyethylene glycol-polypropylene glycol mono(meth)acrylate, poly(ethylene glycol-tetramethylene glycol) mono(meth)acrylate, and polyethylene glycol-polytetramethylene glycol mono(meth)acrylate.
Examples of the amino group-containing vinyl compound include 2-aminoethyl (meth)acrylate.
Examples of the amide group-containing vinyl compound include acrylamide and methacrylamide.
Examples of the epoxy group-containing vinyl compound include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether.

Examples of the aromatic vinyl compound include styrene, vinyltoluene, α-methylstyrene, chlorostyrene, styrenesulfonic acid and salts thereof.
Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile.
Examples of the unsaturated acid include (meth)acrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, cinnamic acid, etc. Esterification products of these acids exclude alkyl (meth)acrylates and may be methylated products, ethylated products, etc.
Examples of the unsaturated acid anhydride include maleic anhydride, itaconic anhydride, and citraconic anhydride.

Examples of the maleimide compounds include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-hexylmaleimide, N-octylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide.
Examples of the vinyl ester include vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, and vinyl cinnamate.
Examples of the fluorine-containing (meth)acrylic acid ester include trifluoromethyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, β-(perfluorooctyl)ethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 2,2,3,4,4,4-hexafluorobutyl (meth)acrylate, 1H,1H,9H-perfluoro-1-nonyl (meth)acrylate, 1H,1H,11H-perfluoroundecyl (meth)acrylate, and perfluorooctyl (meth)acrylate.

In the present invention, component (A) preferably contains, as structural unit (a3), a structural unit derived from a (meth)acrylic acid alkyl ester (M), preferably a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 10 or more carbon atoms (the upper limit is usually 22), and particularly preferably containing a structural unit derived from an acrylic acid alkyl ester (hereinafter referred to as "acrylic acid alkyl ester (M1)"). When component (A) containing a structural unit derived from an acrylic acid alkyl ester (M1) is used to form a curable composition that also contains component (C), an oxyalkylene polymer having a reactive silyl group, good compatibility between components (A), (B), and (C) is ensured, and a cured product with excellent weather resistance can be obtained.

The content of structural unit (a3) in component (A) is 75% by mass or less, preferably 15 to 70% by mass, and more preferably 30 to 60% by mass. The content of structural units derived from alkyl acrylate (M1) in component (A) is preferably 2.5 to 30% by mass, and more preferably 10 to 20% by mass.

Component (A) according to the present invention contains an average of less than 0.5 reactive silyl groups per molecule. The number of reactive silyl groups may be 0, but preferably exceeds 0. The average number is preferably 0.05 to 0.35, more preferably 0.15 to 0.25, since this results in a curable composition that provides a cured product with excellent tensile properties and weather resistance. The number of reactive silyl groups contained in a (meth)acrylic polymer having reactive silyl groups can be calculated by ^1H -NMR measurement and GPC measurement. That is, after identifying the structural units constituting the polymer and determining the monomers used, the polymer composition and the molar fraction of the silane coupling agent are calculated from the integrated value of the signal derived from a hydrogen atom bonded to a carbon atom of methoxysilane, which is observed around 3.5 ppm in the ^1H -NMR spectrum. Next, the number of reactive silyl groups per molecule can be calculated by multiplying this molar fraction by the number average molecular weight (Mn) obtained by GPC measurement.

Component (A) according to the present invention preferably has a carbon-carbon double bond in the molecule, since this allows for the production of a curable composition that provides a cured product with excellent tensile properties and weather resistance. In particular, it is preferable for the component (A) to have a portion containing a carbon-carbon double bond at the terminal side of a structural unit at the end of the polymer. Such a portion containing a double bond is preferably ^one portion of C═C—CO—O—R in the following general formula (1):
[In the formula, ^R1 is a monovalent organic group or a hydrogen atom, (M) is a structural unit (a1) to (a3), etc., and n is a natural number representing the degree of polymerization.]

Examples of ^R1 in the general formula (1) include an alkyl group, a hydroxyalkyl group, an alkoxyalkyl group, an alkyl group which may have other substituents, a phenyl group, a benzyl group, a polyalkylene glycol group, a dialkylaminoalkyl group, a trialkoxysilylalkyl group, and an alkyldialkoxysilylalkyl group.

In the present invention, when component (A) has carbon-carbon double bonds in its molecule, the content of carbon-carbon double bonds is preferably 0.01 to 0.30 meq/g, more preferably 0.05 to 0.30 meq/g, and even more preferably 0.10 to 0.30 meq/g.

In the present invention, the weight average molecular weight (Mw) of component (A) is 6,000 or more, preferably 7,500 or more, and more preferably 9,000 or more. The upper limit is preferably 25,000, and more preferably 15,000. A curable composition containing component (A) having the above weight average molecular weight (Mw) can have a viscosity that is excellent for coating workability, and the resulting cured product also has excellent weather resistance.

Furthermore, the viscosity of component (A) at 25°C is 60 Pa·s or less, preferably 6.0 to 40 Pa·s, and more preferably 8.0 to 20 Pa·s. The above viscosity can be measured by the method described in the Examples section.

Component (B) according to the present invention is a (meth)acrylic polymer containing structural unit (b1), which, as described above, contains a reactive silyl group and is therefore typically a copolymer containing a structural unit having a reactive silyl group (hereinafter referred to as "structural unit (b2)"). Component (B) made of such a copolymer can further contain, in addition to structural units (b1) and (b2), another structural unit (hereinafter also referred to as "structural unit (b3)"). The copolymer may be either a random copolymer or a block copolymer.

As the (meth)acrylic acid alkyl ester that provides structural unit (b1), the compounds exemplified above as the (meth)acrylic acid alkyl ester that provides structural unit (a1) can be used. In the present invention, an acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms is preferred.

The content of structural unit (b1) in component (B) is preferably 50 to 90% by mass, and more preferably 70 to 85% by mass, since this results in a curable composition suitable for forming a cured product with excellent tensile properties and weather resistance. Component (B) may contain only one type of structural unit (b1), or two or more types.

As the compound that provides the structural unit (b2), a compound that provides the structural unit (a2) can be used, and a monomer compound having an alkoxysilyl group is preferred. In the present invention, vinylsilane and silyl group-containing (meth)acrylic acid ester are preferred, and vinylsilane is more preferred.
The position of the reactive silyl group contained in component (B) is not particularly limited, and it may be on a side chain or at the end of the polymer.

The content of structural unit (b2) in component (B) is not particularly limited, as long as the average number of reactive silyl groups per molecule of component (B) is 0.5 or more. It is typically 1.5% by mass or more, preferably 1.75 to 5.0% by mass, and more preferably 2.0 to 3.5% by mass. Component (B) may contain one type of structural unit (b2) or two or more types.

Component (B) can contain only one type or two or more types of structural unit (b3). Examples of compounds that provide this structural unit (b3) include the above-mentioned (meth)acrylic acid alkyl ester (M), (meth)acrylic acid aromatic esters containing an ester moiety containing an aromatic hydrocarbon group, (meth)acrylic acid alkoxyalkyl esters, hydroxy group-containing vinyl compounds, amino group-containing vinyl compounds, epoxy group-containing vinyl compounds, aromatic vinyl compounds, vinyl cyanide compounds, unsaturated acids or their alkyl esters (excluding (meth)acrylic acid alkyl esters), unsaturated acid anhydrides, maleimide compounds, vinyl esters, fluorine-containing (meth)acrylic acid esters, alkenes, dienes, vinyl chloride, vinylidene chloride, allyl chloride, and allyl alcohol.

In the present invention, component (B) preferably contains, as structural unit (b3), a structural unit derived from the above-mentioned (meth)acrylic acid alkyl ester (M), more preferably a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 10 or more carbon atoms (the upper limit is usually 22), and particularly preferably a structural unit derived from the above-mentioned acrylic acid alkyl ester (M1). When component (B) containing a structural unit derived from acrylic acid alkyl ester (M1) is used to form a curable composition that also contains component (C), good compatibility between components (A), (B), and (C) is ensured, and a cured product with excellent weather resistance can be obtained.

The content of structural units (b3) contained in component (B) is 50% by mass or less, preferably 5 to 40% by mass, and more preferably 10 to 25% by mass. The content of structural units derived from alkyl acrylate (M1) contained in component (B) is preferably 7.5 to 40% by mass, and more preferably 15 to 30% by mass.

Component (B) according to the present invention contains an average of 0.5 or more reactive silyl groups per molecule. The average number of reactive silyl groups is preferably 0.8 to 5.2, as this results in a curable composition that gives a cured product with excellent tensile properties and weather resistance.

In the present invention, the weight-average molecular weight (Mw) of component (B) is 10,000 to 100,000, preferably 15,000 to 80,000, and more preferably 25,000 to 80,000. A curable composition containing component (B) with this weight-average molecular weight (Mw) can have a viscosity that is excellent for coating workability, and the resulting cured product has excellent weather resistance.

The viscosity of component (B) at 25°C is 30 to 450 Pa·s, preferably 45 to 400 Pa·s. The viscosity can be measured using the method described in the Examples section.

In the curable composition of the present invention, the content ratios of components (A) and (B) are preferably 20 to 85% by mass and 15 to 80% by mass, more preferably 30 to 75% by mass and 25 to 70% by mass, and even more preferably 40 to 60% by mass and 40 to 60% by mass, respectively, assuming the total of both to be 100% by mass, in order to obtain a cured product with excellent tensile properties and weather resistance.

The method for producing components (A) and (B) according to the present invention is not particularly limited, and conventionally known methods can be used. For example, radical polymerization or living radical polymerization can be used in any of solution polymerization, bulk polymerization, and dispersion polymerization. Furthermore, when introducing a double bond into a polymer, methods that can be used include copolymerizing a monomer having multiple double bonds in the molecule, or producing a (meth)acrylic polymer having a functional group and then reacting it with a compound having a functional group and a double bond that can react with the functional group.

The curable composition of the present invention may contain other polymers. In the present invention, it is preferable to contain an oxyalkylene polymer having a reactive silyl group as component (C). The reactive silyl group in component (C) may be the same or a different type of reactive silyl group as that contained in components (A) and (B).

The component (C) according to the present invention is a polymer containing a repeating unit represented by the following general formula (2).
-O-R ^3- (2)
[In the formula, ^R3 is a divalent hydrocarbon group.]

Examples of ^R3 in the general formula (2) include _{-CH(CH3)-CH2-, -CH(C2H5 ) -CH2- , -C} ( _CH3 ) _{2 -CH2-} , and _{-CH2CH2CH2CH2-} . Of these, -CH( _CH3 ) _-CH2- is preferred. The repeating unit contained in component (C) may be of one type or _{two or more} types.

The position of the reactive silyl group contained in component (C) is not particularly limited, and it may be on a side chain or at the end of the polymer.
When the curable composition of the present invention contains component (C), the component (C) may be one type only or two or more types. In the latter case, for example, the curable composition may be composed mainly of either a linear polymer or a polymer having a side chain, or may be a combination of a linear polymer and a polymer having a side chain.

From the viewpoint of the tensile properties and weather resistance of the resulting cured product, the average number of reactive silyl groups contained per molecule of component (C) is preferably 1.5 to 3.5, and more preferably 1.8 to 3.0.

In the present invention, the weight average molecular weight (Mw) of component (C) is preferably 10,000 to 35,000, more preferably 15,000 to 32,000, and even more preferably 20,000 to 30,000. By using a curable composition containing component (C) with an Mw within the above range, it is possible to obtain a cured product with excellent tensile properties and weather resistance.

There are no particular limitations on the method for producing component (C), and conventional, well-known methods can be used. For example, component (C) can be produced by introducing an olefin moiety into a polyoxyalkylene polymer having a terminal hydroxy group, taking advantage of the reactivity of the hydroxy group, and then reacting this olefin moiety with a compound having a silyl group.

In the curable composition of the present invention containing component (C), the contents of components (B) and (C) are preferably 25 to 80 mass% and 20 to 75 mass%, more preferably 35 to 60 mass% and 40 to 65 mass%, respectively, when the total of these is taken as 100 mass%, in order to obtain a cured product having excellent tensile properties and weather resistance.
Furthermore, the content of component (A) is preferably 15 to 80 parts by mass, more preferably 30 to 60 parts by mass, relative to 100 parts by mass of the total content of components (B) and (C), because the viscosity of the composition is excellent in coating workability and a cured product having excellent tensile properties can be obtained.

In order to produce a cured product using the curable composition of the present invention, a curing accelerator (a component that accelerates the moisture curing reaction) is usually blended.
Examples of the curing accelerator include organic tin compounds, organic titanium compounds, organic aluminum compounds, organic zirconium compounds, organic iron compounds, organic vanadium compounds, amine compounds, acidic phosphate esters, reaction products of acidic phosphate esters and amine compounds, saturated or unsaturated polycarboxylic acids and their acid anhydrides, and reaction products (salts, etc.) of carboxylic acid compounds and amine compounds. Among these, organic tin compounds are preferred. The curing accelerator contained in the curable composition of the present invention may be one type only or two or more types.

Organotin compounds include dibutyltin dicarboxylates such as dibutyltin dilaurate, dibutyltin maleate, dibutyltin diacetate, dioctyltin maleate, dibutyltin phthalate, and dibutyltin bis(alkylmaleate); divalent tin carboxylates such as tin octoate, tin oleate, tin stearate, tin naphthenate, tin stearate, and tin versatate; alkoxide derivatives of dialkyltin such as dibutyltin dimethoxide and dibutyltin diphenoxide; intramolecularly coordinating derivatives (chelate compounds) of dialkyltin such as dibutyltin diacetylacetonate and dibutyltin acetoacetate; reaction products of dibutyltin oxide and ester compounds, such as the reaction product of dibutyltin oxide and phthalate esters; and reaction products of dibutyltin oxide and silicate compounds.

Organotitanium compounds include titanium alkoxides such as tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, and tetra(2-ethylhexyl titanate); chelate compounds such as titanium tetraacetylacetonate and titanium ethylacetoacetate; and triethanolamine titanate.

Examples of organoaluminum compounds include aluminum alkoxides such as aluminum isopropylate, monosec-butoxyaluminum diisopropylate, and aluminum sec-butylate; and chelate compounds such as aluminum trisacetylacetonate, aluminum trisethylacetoacetate, and diisopropoxyaluminum ethylacetoacetate.

Organozirconium compounds include zirconium alkoxides such as zirconium tetraisopropoxide and zirconium tetrabutoxide; and chelate compounds such as zirconium monoacetylacetonate, zirconium bisacetylacetonate, zirconium tetraacetylacetonate, zirconium acetylacetonate bisethylacetoacetate, and zirconium acetate.

Organic iron compounds include iron carboxylates such as iron 2-ethylhexanoate (divalent), iron 2-ethylhexanoate (trivalent), iron neodecanoate (divalent), iron neodecanoate (trivalent), iron oleate (divalent), iron oleate (trivalent), iron naphthenate (divalent), and iron naphthenate (trivalent).

Amine compounds include butylamine, octylamine, laurylamine, dibutylamine, monoethanolamine, diethanolamine, triethanolamine, diethylenetriamine, triethylenetetramine, oleylamine, cyclohexylamine, benzylamine, diethylaminopropylamine, xylylenediamine, triethylenediamine, dibutylamine-2-ethylhexoate, guanidine, diphenylguanidine, 2,4,6-tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine, 2-ethyl-4-methylimidazole, and 1,8-diazabicyclo(5,4,0)undecene-7 (DBU).

The content of the curing accelerator in the curable composition of the present invention is not particularly limited, and is preferably 0.25 to 2.5 parts by mass, more preferably 0.5 to 1.5 parts by mass, based on 100 parts by mass of the total of components (A) and (B).
Furthermore, when the total amount of components (A), (B), and (C) is taken as 100 parts by mass, the content of the curing accelerator is preferably 0.16 to 1.6 parts by mass, and more preferably 0.3 to 1.0 part by mass.

The curable composition of the present invention can contain conventionally known additives depending on the purpose, application, etc. Examples of additives include fillers, plasticizers, antioxidants, UV absorbers, light stabilizers, heat stabilizers, flame retardants, defoamers, lubricants, weather resistance stabilizers, tackifiers, anti-sagging agents, anti-tack agents, dehydrating agents, conductivity imparting agents, antistatic agents, water repellents, oil repellents, preservatives, colorants (pigments, dyes, etc.), and fluorescent brighteners.

Fillers include light calcium carbonate (average particle size approximately 0.02 to 2.0 μm), heavy calcium carbonate (average particle size approximately 1.0 to 5.0 μm), titanium oxide, carbon black, synthetic silicic acid, talc, zeolite, mica, silica, calcined clay, kaolin, bentonite, aluminum hydroxide, barium sulfate, glass balloons, silica balloons, and polymethyl methacrylate balloons.

Plasticizers include liquid polyurethane resins, polyester-based plasticizers obtained from dicarboxylic acids and diols; etherified or esterified products of polyalkylene glycols such as polyethylene glycol and polypropylene glycol; polyether-based plasticizers such as sugar-based polyethers obtained by addition polymerization of alkylene oxides such as ethylene oxide and propylene oxide to a sugar polyhydric alcohol such as sucrose, followed by etherification or esterification; polystyrene-based plasticizers such as poly-α-methylstyrene; and poly(meth)acrylates without crosslinkable functional groups. Since component (A) of the present invention exhibits the effects of a plasticizer, even a small amount of the above plasticizers can be used.

Examples of the antioxidant include hindered phenol compounds, monophenol compounds, bisphenol compounds, and polyphenol compounds.
Examples of ultraviolet absorbers include benzophenone compounds, benzotriazole compounds, salicylate compounds, substituted tolyl compounds, and metal chelate compounds.
Examples of the light stabilizer include benzotriazole compounds, hindered amine compounds, and benzoate compounds.
In the present invention, an antioxidant, an ultraviolet absorber, and a light stabilizer or a heat stabilizer can be used in appropriate combination as an antiaging agent.

Examples of tackifiers include alkoxysilanes having an amino group or a substituted amino group, such as 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, γ-(N-trimethylsilyl)-3-aminopropyltrimethoxysilane, and 1,1-dimethoxy-2-trimethylsilyl-1-sila-2-azacyclopentane; coumarone-indene resins; coumarone resins obtained by mixing coumarone resins with naphthene resins, phenolic resins, rosin, etc.; p-tert-butylphenol-acetylene resins; phenol-formaldehyde resins; and xylene-phenylene resins. These include phenol resins; xylene resins; terpene resins; terpene-based resins such as terpene-phenol resins; synthetic polyterpene resins; aromatic hydrocarbon resins; aliphatic hydrocarbon resins; aliphatic cyclic hydrocarbon resins; hydrogenated hydrocarbon resins; rosin; pentaerythritol esters of rosin; glycerol esters of rosin; hydrogenated rosin; hydrogenated wood resins; methyl esters of hydrogenated rosin; triethylene glycol esters of hydrogenated rosin; pentaerythritol esters of hydrogenated rosin; polymerized rosin; glycerol esters of polymerized rosin; zinc resinate; hardened rosin; low molecular weight polystyrene, etc.

Dehydrating agents include methyl orthoformate, methyl orthoacetate, vinyltrimethoxysilane, vinylmethyldimethoxysilane, tetraethoxysilane, tetramethoxysilane, etc.

The viscosity of the curable composition of the present invention used to form a cured product is preferably 10 to 250 Pa·s, more preferably 15 to 200 Pa·s, and even more preferably 20 to 160 Pa·s. The above viscosity can be measured by the method described in the Examples section.

In the present invention, the curable composition containing a curing accelerator can be easily cured at a sufficient rate by atmospheric moisture or the like. A three-dimensional crosslinked structure is formed, and a cured product having rubber-like elasticity can be obtained. Therefore, the curable composition of the present invention is useful as a sealant, paint, coating agent, etc. that forms such a cured product in the fields of architecture, civil engineering, electrical and electronics, and vehicles.
When the curable composition of the present invention is used as is to form a cured product, it can be used as a one-component type in which all components are mixed in advance and stored in a sealed container, which is opened when used and then cured by absorbing moisture in the air after application, or it can be used as a two-component type in which a curing agent composition containing a curing accelerator and the like is prepared separately from components (A), (B), and (C), and all components are mixed when used.

The sealant composition of the present invention can have the configuration of the curable composition of the present invention described above, and can be used, for example, to fill the gap between one adherend (hereinafter referred to as the "first adherend") and another adherend (hereinafter referred to as the "second adherend") placed adjacent to the first adherend with a gap between them. The constituent materials of the first adherend and the second adherend may be the same or different, and may be, for example, ceramics, metal, concrete, glass, etc. The cured product obtained by the present invention has excellent weather resistance and is therefore suitable for applications where it will be exposed outdoors for long periods of time.

The following examples further illustrate embodiments of the present invention, but the present invention is not limited to these examples. In the following, "parts" and "%" are by weight unless otherwise specified.

1. Methods for Measuring Physical Properties of Polymers The methods for measuring the molecular weight (Mw and Mn), average number of reactive silyl groups contained, terminal double bond concentration, and viscosity of the (meth)acrylic polymer are shown below.

(1) Molecular Weight Four columns "TSKgel SuperMultipore HZ-M" (product name) manufactured by Tosoh Corporation were connected together and placed in a gel permeation chromatograph "HLC-8320" (model name) manufactured by Tosoh Corporation, and the number average molecular weight (Mn) and weight average molecular weight (Mw) were measured in terms of polystyrene under the following measurement conditions. The molecular weight distribution (Mw/Mn) was calculated from the obtained measurements.
Column temperature: 40°C
Eluent: tetrahydrofuran Detector: RI

(2) Number of reactive silyl groups per molecule (average value) f(Si)
The number (average number) f(Si) of alkoxysilyl groups, which are reactive silyl groups, was calculated using the following formula from the mass proportion of monomers having alkoxysilyl groups, assuming that the total of all monomers used in the production of the polymer is 100 mass%.
f(Si)=[mass proportion of monomer having an alkoxysilyl group/(molecular weight of monomer having an alkoxysilyl group×100/Mn of polymer)]

(3) Carbon-Carbon Double Bond Concentration at Polymer Terminals In an NMR spectrum obtained by ¹ H-NMR measurement using deuterated chloroform as a solvent, the double bond concentration per mass of the polymer was calculated from the ratio of the integral of a signal derived from a hydrogen atom bonded to a carbon atom constituting the carbon-carbon double bond, which is observed around 5.5 ppm, to the integral of a signal derived from a hydrogen atom bonded to a carbon atom adjacent to an ester group, which is observed between 3.0 and 4.5 ppm, and from the composition of the polymer.

(4) Viscosity The E-type viscosity was measured under the following conditions using a TVE-20H viscometer (product name, salt water/plate method) manufactured by Toki Sangyo Co., Ltd.
No. 1 cone: angle 1°34', radius 24 mm (for pressures less than 10 Pa s)
No. 7 cone: angle 3°, radius 7.7 mm (for pressures of 10 Pa·s or more)
Temperature: 25℃±0.5℃
Rotor rotation speed: 1 rpm (when using No. 1 cone)
10 rpm (when using No. 7 cone and 10 to 100 Pa·s)
1.5 rpm (when using No. 7 cone and the viscosity exceeds 100 Pa·s)

2. Synthesis of (meth)acrylic polymer (A) Various polymers were synthesized in the following Synthesis Examples 1-1 to 1-15 and Comparative Synthesis Examples 1-1 to 1-3.

Synthesis Example 1-1
The temperature of a pressurized stirred tank reactor equipped with an oil jacket was set to the following reaction temperature. Next, while maintaining the internal pressure of the reactor constant under pressure, 30 parts of n-butyl acrylate (hereinafter referred to as "BA"), 15 parts of tetradecyl acrylate (hereinafter referred to as "TDA"), 43.6 parts of 2-ethylhexyl acrylate (hereinafter referred to as "HA"), 10 parts of methyl methacrylate (hereinafter referred to as "MMA"), and 3-methacryloxypropylmethyldimethoxysilane "Z6033" (trade name, hereinafter referred to as "DMS") manufactured by Dow-Toray Industries, Inc. were added. A monomer mixture consisting of 1.4 parts of ethanol (hereinafter referred to as "IPA"), 9.1 parts of isopropyl alcohol (hereinafter referred to as "IPA"), 8.8 parts of methyl ethyl ketone (hereinafter referred to as "MEK"), and 0.25 parts of di-tert-butyl peroxide "Perhexyl D" (trade name, hereinafter referred to as "DTBP") manufactured by NOF Corporation as a polymerization initiator was continuously fed from a raw material tank to the reactor at a constant feed rate (48 g/min), and the polymerization reaction was allowed to proceed with a residence time of 12 minutes. Then, a reaction liquid equivalent to the amount of the monomer mixture fed was continuously withdrawn and recovered from the outlet of the reactor. Immediately after the start of the reaction, the reaction temperature temporarily dropped, but a temperature rise due to the heat of polymerization was observed. Therefore, the reaction temperature was maintained at 188 to 190°C by controlling the temperature of the oil jacket.
The point at which the liquid temperature in the reactor stabilized after the start of supplying the monomer mixture was defined as the start point for collecting the reaction liquid, and the reaction was continued for 25 minutes from this point. As a result, the amount of the monomer mixture supplied was 1.2 kg, and the amount of the reaction liquid recovered was 1.2 kg.
The reaction solution was then introduced into a thin-film evaporator, and volatile components such as unreacted monomers were separated to obtain a (meth)acrylic copolymer (hereinafter referred to as "Polymer A-1"). The composition of Polymer A-1 was determined by subjecting the volatile components to gas chromatography under the following analytical conditions, and subtracting the analytical value obtained from the amount of raw material monomer used (see Table 1). In addition, the weight-average molecular weight (Mw), number-average molecular weight (Mn), number of reactive silyl groups per molecule, concentration of carbon-carbon double bonds at molecular terminals, and viscosity were measured (see Table 1).

(Gas chromatography measurement conditions)
Column: Agilent capillary column "CP-Wax52CB" (60 m x 0.32 mm ID, df = 0.5 μm) and Agilent "DB-1" (30 m x 0.32 mm ID, df = 1.0 μm)
Solvent: tetrahydrofuran Column temperature: 50°C (5 min), 7°C/min, 230°C (5 min)

Synthesis Example 1-2
An acrylic copolymer (hereinafter referred to as "Polymer A-2") was obtained by the same operation as in Synthesis Example 1-1, except that the monomer mixture supplied to the pressurized stirred tank reactor consisted of 30 parts of BA, 15 parts of TDA, 43.9 parts of HA, 10 parts of MMA, 1.1 parts of DMS, 2 parts of IPA, 4 parts of trimethyl orthoacetate (manufactured by Nippoh Chemical Co., Ltd., trade name "MOA", hereinafter referred to as "MOA"), 5 parts of MEK, and 0.08 parts of di-tert-hexyl peroxide (manufactured by NOF Corp., trade name "Perhexyl D", hereinafter referred to as "DTHP") and the reaction temperature was 192°C (see Table 1).

Synthesis Examples 1-3 to 1-15 and Comparative Synthesis Examples 1-1 to 1-3
A (meth)acrylic copolymer was obtained by the same procedure as in Synthesis Example 1-2, except that the composition of the monomer mixture and the reaction temperature were as shown in Tables 1 and 2 (see Tables 1 and 2).

3. Synthesis of (Meth)acrylic Polymer (B) Various polymers were synthesized in the following Synthesis Examples 2-1 to 2-11 and Comparative Synthesis Examples 2-1 and 2-2.

Synthesis Example 2-1
The temperature of a pressurized stirred tank reactor equipped with an oil jacket was set to the following reaction temperature. Next, while maintaining the internal pressure of the reactor constant at a pressurized state, a monomer mixture consisting of 84.6 parts BA, 10 parts TDA, 5.4 parts vinyldimethoxysilane (hereinafter referred to as "VDMS"), 3 parts IPA, 3 parts MOA, 4 parts MEK, and 0.02 parts DTHP was continuously fed from a raw material tank to the reactor at a constant feed rate, and the polymerization reaction was allowed to proceed with a residence time of 12 minutes. Then, a reaction liquid equivalent to the amount of the monomer mixture fed was continuously withdrawn and recovered from the outlet of the reactor. Immediately after the start of the reaction, the reaction temperature temporarily dropped, but a temperature rise due to the heat of polymerization was observed. Therefore, the reaction temperature was maintained at 187°C to 189°C by controlling the temperature of the oil jacket.
The point at which the liquid temperature in the reactor became stable after the start of feeding the monomer mixture was determined as the start point for sampling the reaction liquid, and the reaction was carried out for 25 minutes from this point.
The reaction solution was then introduced into a thin-film evaporator, and volatile components such as unreacted monomers were separated to obtain a (meth)acrylic copolymer (hereinafter referred to as "Polymer B-1"). The composition of Polymer B-1 was determined by subjecting the volatile components to gas chromatography, and subtracting the analytical values obtained from the amounts of the raw material monomers used (see Table 3). The weight-average molecular weight (Mw), number-average molecular weight (Mn), number of reactive silyl groups per molecule, and viscosity were also measured (see Table 3).

Synthesis Examples 2-2 to 2-8 and Comparative Synthesis Examples 2-1 to 2-2
A (meth)acrylic copolymer was obtained by carrying out the same operation as in Synthesis Example 2-1, except that the composition of the monomer mixture and the reaction temperature were as shown in Table 3 (see Table 3).

Synthesis Example 2-9
A flask equipped with a stirrer and a thermometer was charged with 14.9 parts of S,S-dibenzyl trithiocarbonate (hereinafter referred to as "DBTTC") as a RAFT agent, 0.6 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (hereinafter referred to as "V-65"), 132 parts of BA, 8.8 parts of ethyl acrylate (hereinafter also referred to as "EA"), 35.1 parts of TDA, 59.6 parts of DMS, 200 parts of ethyl acetate, and 50 parts of MOA, and the mixture was thoroughly degassed by nitrogen bubbling. Then, under stirring, the mixed raw material was heated to 58 ° C. to initiate polymerization. After 2 hours, the reaction solution was heated to 70 ° C. over 1 hour and reacted at 70 ° C. for a further 4 hours. Thereafter, the reaction was stopped by cooling to room temperature, and a solution containing 50% of polymer b-1x (hereinafter referred to as "reaction solution L1") was obtained.
Next, 16.7 parts of the above reaction liquid L1, 132 parts of BA, 8.8 parts of EA, 35.1 parts of TDA, 0.25 parts of 2,2'-azobis(2-methylbutyronitrile) (hereinafter referred to as "ABN-E"), 80.0 parts of ethyl acetate, and 21.3 parts of MOA were charged into a flask equipped with a stirrer and a thermometer, and thoroughly degassed by nitrogen bubbling. Then, the flask was placed in a thermostatic bath at 70 ° C., and polymerization was initiated under stirring. After 30 minutes, a monomer mixture consisting of 263 parts of BA, 17.5 parts of EA, and 70.2 parts of TDA, and 50.2 parts of polymer b-1x were continuously fed into the flask over 4 hours. After the continuous supply was completed, a solution obtained by mixing 0.16 parts of ABN-E and 5.0 parts of ethyl acetate was supplied, the internal temperature of the reaction solution was raised to 60°C over 30 minutes, and polymerization was continued for 2 hours with stirring. The reaction solution was then cooled to room temperature to terminate the polymerization reaction, yielding a solution containing 80% of the triblock copolymer b-1y.
Thereafter, 690 parts of the solution containing polymer b-1y, 7.86 parts of DMS, 0.43 parts of ABN-E, and 1.54 parts of MOA were charged into a flask equipped with a stirrer and a thermometer, and the mixture was thoroughly degassed by nitrogen bubbling. Then, the internal temperature was set to 60°C, and polymerization was initiated under stirring. After the polymerization reaction was carried out for 7 hours, the mixture was cooled to room temperature to terminate the reaction, and a solution containing 80% of pentablock copolymer b-1z was obtained. This pentablock copolymer b-1z had polymer blocks (X ¹ ) and (X ² ) consisting of BA, EA, TDA, and DMS, and a polymer block (Y) consisting of BA, EA, and TDA, and had a block structure of (X ¹ )-(Y)-(X ² )-(Y)-(X ¹ ).
Next, the solution containing the pentablock copolymer b-1z was thoroughly degassed by nitrogen bubbling, and then 5 molar equivalents of n-propylamine relative to the trithiocarbonate groups contained in the polymer block (X ² ) of the pentablock copolymer b-1z was added. The mixture was then heated to 40°C and stirred for 5 hours to allow the decomposition reaction of the trithiocarbonate groups to proceed, after which the mixture was cooled to room temperature to terminate the reaction. This yielded a solution containing (meth)acrylic polymer B-11, which was a triblock copolymer having an (X)-(Y)-(X') block structure. The solution was then vacuum-dried to obtain (meth)acrylic polymer B-11 (see Table 4).

Synthesis Example 2-10
A flask equipped with a stirrer and a thermometer was charged with 29.9 parts of DBTTC, 1.3 parts of V-65, 263 parts of BA, 17.5 parts of EA, 70.2 parts of TDA, 119 parts of DMS, 400 parts of ethyl acetate, and 99 parts of MOA, and the mixture was thoroughly degassed by nitrogen bubbling. Then, under stirring, the mixed raw material was heated to 58 ° C. to initiate polymerization. After 2 hours, the reaction solution was heated to 70 ° C. over 1 hour and reacted at 70 ° C. for a further 4 hours. Thereafter, the reaction was stopped by cooling to room temperature, and a solution containing 50% of polymer b-2x (hereinafter referred to as "reaction solution L2") was obtained.
Next, 47.8 parts of the above reaction solution L2, 356 parts of BA, 25.1 parts of MMA, 100 parts of TDA, 1.1 parts of ABN-E, 232 parts of ethyl acetate, and 60.6 parts of MOA were charged into a flask equipped with a stirrer and a thermometer, and thoroughly degassed by nitrogen bubbling. Then, the flask was placed in a thermostatic bath at 70 ° C., and polymerization was initiated under stirring. After 30 minutes, a monomer mixture consisting of 752 parts of BA, 50.1 parts of MMA, and 200 parts of TDA, and 143 parts of polymer b-2x were continuously fed into the flask over 4 hours. After the continuous feeding was completed, a solution obtained by mixing 0.9 parts of ABN-E and 10.0 parts of ethyl acetate was fed, and the internal temperature of the reaction solution was raised to 60 ° C. over 30 minutes, and polymerization was continued for 2 hours under stirring. The reaction solution was then cooled to room temperature to terminate the polymerization reaction, yielding a solution containing 80% of the triblock copolymer b-2y.
Thereafter, 1990 parts of the solution containing polymer b-2y, 22.7 parts of DMS, 0.75 parts of ABN-E, and 4.9 parts of MOA were charged into a flask equipped with a stirrer and a thermometer, and the mixture was thoroughly degassed by nitrogen bubbling. Then, the internal temperature was raised to 60°C, and polymerization was initiated under stirring. After the polymerization reaction was carried out for 7 hours, the mixture was cooled to room temperature to terminate the reaction, yielding a solution containing 80% of pentablock copolymer b-2z. This pentablock copolymer b-2z had polymer blocks (X ¹ ) and (X ² ) consisting of BA, EA, TDA, and DMS, and a polymer block (Y) consisting of BA, MMA, and TDA, and had a block structure of (X ¹ )-(Y)-(X ² )-(Y)-(X ¹ ).
Next, the solution containing the pentablock copolymer b-2z was subjected to the same procedure as in Synthesis Example 2-12 to obtain a solution containing a (meth)acrylic polymer B-12 composed of a triblock copolymer having an (X)-(Y)-(X') block structure. This solution was then dried in vacuo to obtain a (meth)acrylic polymer B-12 (see Table 4).

Synthesis Example 2-11
A flask equipped with a stirrer and a thermometer was charged with 14.3 parts of DBTTC, 0.6 parts of V-65, 126 parts of BA, 8.4 parts of EA, 33.5 parts of TDA, 68.3 parts of DMS, 200 parts of ethyl acetate, and 50 parts of MOA, and the mixture was thoroughly degassed by nitrogen bubbling. Then, under stirring, the mixed raw material was heated to 58 ° C. to initiate polymerization. After 2 hours, the reaction solution was heated to 70 ° C. over 1 hour and reacted at 70 ° C. for a further 4 hours. Thereafter, the reaction was stopped by cooling to room temperature, and a solution containing 50% of polymer b-3x (hereinafter referred to as "reaction solution L3") was obtained.
Next, 53.7 parts of the above reaction solution L3, 280 parts of BA, 18.7 parts of EA, 74.6 parts of TDA, 0.33 parts of ABN-E, 58.3 parts of ethyl acetate, and 14.6 parts of MOA were charged into a flask equipped with a stirrer and a thermometer, and thoroughly degassed by nitrogen bubbling. Then, the flask was placed in a thermostatic bath at 70 ° C., and polymerization was initiated under stirring. After 7 hours from the start of polymerization, the reaction solution was cooled to room temperature to stop the polymerization reaction, and a solution containing 80% of the triblock copolymer b-3y was obtained.
Thereafter, 490 parts of the solution containing polymer b-3y, 7.2 parts of DMS, 0.3 parts of ABN-E, and 1.5 parts of MOA were charged into a flask equipped with a stirrer and a thermometer, and the mixture was thoroughly degassed by nitrogen bubbling. The internal temperature was then raised to 60°C, and polymerization was initiated under stirring. After the polymerization reaction was carried out for 7 hours, the mixture was cooled to room temperature to terminate the reaction, yielding a solution containing 80% of pentablock copolymer b-3z. This pentablock copolymer b-3z had polymer blocks (X ¹ ) and (X ² ) consisting of BA, EA, TDA, and DMS, and a polymer block (Y) consisting of BA, EA, and TDA, and had a block structure of (X ¹ )-(Y)-(X ² )-(Y)-(X ¹ ).
Next, the solution containing the pentablock copolymer b-3z was subjected to the same procedure as in Synthesis Example 2-12 to obtain a solution containing (meth)acrylic polymer B-13 composed of a triblock copolymer having an (X)-(Y)-(X') block structure. This solution was then dried in vacuo to obtain (meth)acrylic polymer B-13 (see Table 4).

4. Production and Evaluation of Curable Compositions Liquid curable compositions were produced using each polymer listed in Tables 1 to 4 and the following raw material components (1) to (8). Then, cured products were produced and various evaluations were performed.

(1) Oxyalkylene Polymer Having Reactive Silyl Groups Oxyalkylene polymer C-1 having methoxysilyl groups at both ends, produced by the following synthesis method, was used.
0.05 parts of zinc hexacyanocobaltate glyme complex, 50 parts of polypropylene glycol (Mn: 2,000) and 520 parts of propylene glycol were placed in a pressurized stirred tank reactor equipped with an oil jacket, heated to 120 ° C., and reacted until the pressure change disappeared. Next, the mixture was heated under vacuum at 120 ° C. for 1 hour, and the volatile components were distilled off. Thereafter, 15.2 parts of a 28% methanol solution of sodium methoxide was added, and the mixture was reduced pressure at 100 ° C. for 1 hour, and the methanol was distilled off. Next, 6.3 parts of allyl chloride was added, and the mixture was heated at 100 ° C. for 2 hours. Thereafter, the reaction solution was washed twice with 300 parts of water to remove salt. After dehydration by vacuum heating at 100 ° C. for 2 hours, 0.02 parts of chloroplatinic acid hexahydrate and 8.3 parts of methyldimethoxysilane were added, and the mixture was reacted for 4 hours to obtain a polypropylene glycol both ends silylated product. As a result of GPC measurement, Mn was 19,000 and Mw was 20,700.

(2) Precipitated calcium carbonate (filler)
Shiraishi Calcium "White Gloss CCR" (product name)
(3) Ground calcium carbonate (filler)
Maruo Calcium "Super SS" (product name)
(4) Titanium oxide (pigment)
Ishihara Sangyo Kaisha's "Tipake R-820" (product name)
(5) Antioxidant: BASF hindered phenol "Tinuvin B75" (trade name)
(6) Curing accelerator: dibutyltin diacetylacetonate "Neostan U-220H" (trade name) manufactured by Nitto Kasei Co., Ltd.
(7) Aminosilane (tackifier)
3-(2-aminoethyl)aminopropyltrimethoxysilane "SH6020" (trade name) manufactured by Dow Toray Industries, Inc.
(8) Vinylsilane (dehydrating agent)
Vinyltrimethoxysilane "SZ6300" (product name) manufactured by Dow Toray

Example 1
50 parts of (meth)acrylic polymer A-1, 50 parts of (meth)acrylic polymer B-4, 50 parts of oxyalkylene polymer C-1, 100 parts of light calcium carbonate, 60 parts of heavy calcium carbonate, 2.5 parts of titanium oxide, 2 parts of an antioxidant, 1 part of a curing catalyst, 3 parts of an aminosilane, and 2 parts of a vinylsilane were mixed using a planetary mixer to obtain a paste-like curable composition. The viscosity of the composition (25°C) was measured to be 170 Pa s.

Next, the following tests were carried out to evaluate the weather resistance and tensile properties of the cured products, and the results are shown in Table 5.
(Weather resistance test)
The curable composition was applied to a Teflon (registered trademark) sheet to a coating thickness of 2 mm and aged for one week at 23°C and 50% RH to produce a cured sheet. The cured sheet was then subjected to an accelerated weathering test using a Daipla Wintes metaling weather meter "DAIPLA METAL WEATHER KU-R5NCI-A" (trade name). The accelerated conditions were irradiation at 63°C, 70% RH, and an illuminance of 80 mW/ ^cm² , with a 2-minute shower every two hours. The time from the start of the accelerated weathering test to the onset of abnormalities such as cracks in the appearance of the cured sheet was measured.
(Tensile test)
The curable composition was applied to a Teflon (registered trademark) sheet to a coating thickness of 2 mm, and cured for one week at 23°C and 50% RH to produce a cured sheet. Then, a tensile test dumbbell (JIS K 6251 No. 3) was prepared from the resulting cured sheet, and the breaking elongation and breaking strength were measured at a tensile speed of 200 mm/min using a Shimadzu Corporation tensile tester "Autograph AGS-J" (trade name).

Examples 2 to 29 and Comparative Examples 1 to 5
The same procedures as in Example 1 were carried out except that the raw materials shown in Tables 5 to 8 were used, and curable compositions were produced and cured products were evaluated (see Tables 5 to 8).

The following is clear from Tables 5 to 8.
Comparative Example 1 is an example in which a (meth)acrylic polymer A'-1 having a Mw of less than 6,000 was used in place of component (A), and the weather resistance was insufficient. Comparative Example 2 is an example in which a (meth)acrylic polymer A'-2 having a large average number of reactive silyl groups per molecule (0.60) was used in place of component (A), and the tensile properties (elongation at break) were insufficient. Comparative Example 3 is an example in which a (meth)acrylic polymer A'-3 having a content of structural units derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms of less than 20 mass% relative to the polymer was used in place of component (A), and the weather resistance was insufficient. Comparative Example 4 is an example in which a (meth)acrylic polymer B'-1 having a Mw of less than 10,000 was used in place of component (B), and the weather resistance was insufficient. Comparative Example 5 is an example in which (meth)acrylic polymer B'-2, which has an average of only 0.30 reactive silyl groups per molecule, was used instead of component (B), and the weather resistance was insufficient.

The curable composition of the present invention forms a three-dimensional crosslinked structure due to atmospheric moisture and other factors, making it easy to obtain a cured product with rubber-like elasticity. Such cured products have excellent tensile properties and weather resistance, making them suitable for use in fields such as construction, civil engineering, electrical and electronics, and automotive. Furthermore, the curable composition of the present invention has a viscosity suitable for coating, making it particularly useful as a sealant in the above fields. It can also be used as a paint, coating agent, etc.

Claims (11)

(A) A (meth)acrylic polymer containing structural units derived from a (meth)acrylic acid alkyl ester, the (meth)acrylic polymer containing 20 mass% or more of structural units derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms, based on the polymer, the (meth)acrylic polymer having a weight-average molecular weight of 6,000 or more, and an average number of reactive silyl groups per molecule of 0.05 to 0.35 ;
and,
(B) A curable composition containing a (meth)acrylic polymer containing a structural unit derived from a (meth)acrylic acid alkyl ester, the (meth)acrylic polymer containing a structural unit derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 2 to 6 carbon atoms, the (meth)acrylic polymer having a weight average molecular weight of 10,000 to 100,000, and having an average number of reactive silyl groups per molecule of 0.5 or more. The curable composition according to claim 1, wherein the (meth)acrylic polymer (A) further contains a structural unit derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 10 or more carbon atoms. 3. The curable composition according to claim 1 , wherein the (meth)acrylic polymer (A) has carbon-carbon double bonds in an amount of 0.01 to 0.30 meq/g. The curable composition according to any one of claims 1 to 3 , wherein the (meth)acrylic polymer (B) further comprises a structural unit derived from a (meth)acrylic acid alkyl ester having an alkyl ester moiety containing an alkyl group having 10 or more carbon atoms. The curable composition according to any one of claims 1 to 4 , wherein the (meth)acrylic polymer (B) has a weight average molecular weight of 15,000 to 80,000. 6. The curable composition according to claim 1, wherein a content of the (meth)acrylic polymer (A) is 20 to 85 mass% and a content of the (meth)acrylic polymer (B) is 15 to 80 mass%, when the total of the (meth)acrylic polymer (A) and the ( meth )acrylic polymer (B) is 100 mass%. The curable composition according to any one of claims 1 to 6 , which has a viscosity at 25°C of 10 to 250 Pa·s. Furthermore,
The curable composition according to claim 1 , further comprising (C) an oxyalkylene polymer having a reactive silyl group. 9. The curable composition according to claim 8, wherein, when the total amount of the (meth)acrylic polymer (B) and the oxyalkylene polymer (C) is taken as 100% by mass, a content of the (meth)acrylic polymer (B) is 25 to 80% by mass, and a content of the oxyalkylene polymer (C) is 20 to 75% by mass. The curable composition according to claim 1 , further comprising a curing accelerator. A sealant composition comprising the curable composition according to claim 10 .