Hardening composition, hardened product, and sealing material

Abstract

To provide a curable composition capable of obtaining a cured product at a sufficient curing speed and obtaining a cured product excellent in restorative property, following property to an adherend and elongation.SOLUTION: There is provided a curable composition which comprises an oxyalkylene polymer A having 3 or more terminal groups in one molecule, a number average molecular weight of 6,000 or more per terminal group and a reactive silicon group represented by -SiXaR3-a in the terminal group, an oxyalkylene polymer B having a reactive silicon group represented by -SiX3 in the terminal group and less than 0.5 pt.mass of a silanol condensation catalyst based on 100 pts.mass of the total of the polymer A and the polymer B, wherein the content ratio of the polymer B in the curable composition is 0.5 to 50 mass%. R: a monovalent organic group having 1 to 20 carbon atoms which contains no hydrolyzable groups, X: a hydroxyl group or a hydrolyzable group, a: 1 or 2.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a moisture-curable curable composition containing a polymer having a reactive silicon group, a cured product, and a sealing material.

[0002] The present invention relates to a curable composition containing a polymer having a hydroxyl group or a hydrolyzable group bonded to a silicon atom and capable of crosslinking by forming a siloxane bond (hereinafter referred to as a "reactive silicon group").

Background Art

[0003] Polymers having at least one reactive silicon group in the molecule are known to have the property of crosslinking by forming a siloxane bond accompanied by a hydrolysis reaction of the reactive silicon group due to moisture or the like even at room temperature, and obtaining a rubbery cured product.

[0004] Among these polymers having reactive silicon groups, oxyalkylene polymers, unsaturated hydrocarbon polymers, acrylate polymers, and methacrylate polymers have already been industrially produced and are widely used in applications such as sealing materials, adhesives, and paints (for example, Patent Document 1). When a curable composition containing these polymers having reactive silicon groups is used as a sealing material, in addition to curability, adhesiveness to adherends, and elongation of the cured product, it is required to have restorability that can follow the structural expansion and contraction of joints generated by being exposed to an outdoor environment for a long time, and to be less likely to generate cracks.

[0005] Patent Document 2 discloses a one-component curable resin composition containing an organic polymer having a reactive silicon group having three or more hydrolyzable groups on silicon and less than 0.5 parts by weight of a silanol condensation catalyst with respect to the organic polymer. In the examples, it is shown that in the example of mixing a linear oxypropylene polymer having a number average molecular weight of 11,000 having a trimethoxysilyl group at the terminal and a silanol condensation catalyst, and in the example of mixing a linear oxypropylene polymer having a number average molecular weight of 17,000 having a trimethoxysilyl group at the terminal and a silanol condensation catalyst, a cured product excellent in curability and restorability was obtained. On the other hand, in the example of mixing a linear oxypropylene polymer having a number average molecular weight of 11,000 having a methyldimethoxysilyl group at the terminal and a silanol condensation catalyst, poor curability and inferior restorability were shown. Patent Document 3 discloses a silicone-based resin composition obtained by mixing an oxyalkylene polymer having a trialkoxysilyl group and an oxyalkylene polymer having a dialkoxysilyl group. In the examples, it is shown that in the example of mixing a branched oxypropylene polymer having a number average molecular weight of 10,000 having a trimethoxysilyl group at the terminal and a branched oxypropylene polymer having a methyldimethoxysilyl group at the terminal, 30 parts by weight of a curing catalyst was mixed with respect to 1000 parts by mass in total, and excellent storage stability and curability in a short time were shown.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when the one-component curable resin composition described in Patent Document 2 or the silicone-based resin composition described in Patent Document 3 is used as a sealing material, the restorability is poor, the followability to the adherend is insufficient, or the elongation of the cured product may be insufficient. The present invention has been made in view of the above circumstances, and an object thereof is to provide a curable composition capable of obtaining a cured product excellent in any of the curing rate, restorability of the cured product, followability to the adherend, and elongation.

Means for Solving the Problems

[0008] The present invention is as follows [1] to

[13] . [1] A curable composition, A polymer A which is an oxyalkylene polymer, has 3 or more terminal groups in one molecule, has a number average molecular weight of 6,000 or more per terminal group, has a reactive silicon group represented by the following formula (1) at the terminal group, and does not have a reactive silicon group represented by the following formula (2), A polymer B which is an oxyalkylene polymer, has 2 terminal groups in one molecule, and has a reactive silicon group represented by the following formula (2) in an average of more than 0.5 and 1.0 or less per terminal group, Contains 0.05 to 0.5 parts by mass of a silanol condensation catalyst with respect to a total of 100 parts by mass of polymer A and polymer B, The mass ratio of polymer A to polymer B is 99 / 1 to 50 / 50, A curable composition, wherein the content ratio of polymer B in the curable composition is 0.5 to 50% by mass. -SiX a R 3-a ···(1) [In the formula, R represents a monovalent organic group having 1 to 20 carbon atoms that does not contain a hydrolyzable group, X represents a hydroxyl group or a hydrolyzable group, and a is 1 or 2. When a is 1, R may be the same or different from each other, and when a is 2, X may be the same or different from each other.] -SiX 3 ···(2) [In the formula, X represents a hydroxyl group or a hydrolyzable group, and X may be the same or different from each other.] -SiX3 ···(2) [In the formula, X represents a hydroxyl group or a hydrolyzable group, and the Xs may be the same as or different from each other.]

[0009] [2] The curable composition according to [1], wherein the polymer A has, on average, more than 0.5 and 1.0 or less reactive silicon groups represented by the formula (1) per terminal group, and the number average molecular weight is 18,000 to 40,000. [3] The curable composition according to [1] or [2], wherein the polymer B has a number average molecular weight of 5,000 to 30,000. [4] The terminal group having the reactive silicon group represented by the formula (1) in the polymer A is -OCH 2 CH 2 CH 2 -SiX a R 3-a The curable composition according to any one of [1] to [3]. [5] The terminal group having the reactive silicon group represented by the formula (2) in the polymer B is a monovalent organic group having a urethane bond (-OC(=O)NH-) and -SiX 3 and, or, -OCH 2 CH 2 CH 2 -SiX 3 The curable composition according to any one of [1] to [4]. [6] The terminal group having the reactive silicon group represented by the formula (2) in the polymer B is a monovalent organic group having the urethane bond (-OC(=O)NH-) and -SiX 3 and, and the content of the urethane bond (-OC(=O)NH-) in the polymer B is 0.33 mmol / g or less. The curable composition according to [5].

[0010] [7] Further, an oxyalkylene polymer having two terminal groups in one molecule, and having more than 0 and 0.5 or less reactive silicon groups represented by the formula (1) or the formula (2) on average per terminal group. The curable composition according to any one of [1] to [6], containing the polymer C. [8] The curable composition according to [7], wherein one of the two terminal groups of the polymer C is an alkoxy group. [9] The curable composition according to [7] or [8], wherein the reactive silicon group in the polymer C is the reactive silicon group represented by the formula (2).

[10] The curable composition according to any one of [7] to [9], wherein the number average molecular weight of the polymer C is from 2,000 to 12,000.

[11] The curable composition according to any one of [1] to

[10] , which is a one-component type.

[12] A cured product obtained by curing the curable composition according to any one of [1] to

[11] .

[13] A sealing material comprising the cured product of

[12] . [Effect of the Invention]

[0011] The curable composition of the present invention can obtain a cured product at a sufficient curing rate, and can obtain a cured product excellent in any of resilience, followability to an adherend, and elongation. The cured product of the present invention is obtained at a sufficient curing rate and has good resilience, good followability to an adherend, and good elongation. [Embodiments for Carrying Out the Invention]

[0012] As used herein, the "oxyalkylene polymer" refers to a compound having a polyoxyalkylene chain formed by ring-opening addition polymerization of a cyclic ether such as alkylene oxide. As used herein, the "precursor polymer" is an oxyalkylene polymer before introduction of a reactive silicon group, and is a compound having a polyoxyalkylene chain obtained by subjecting a cyclic ether such as alkylene oxide to ring-opening addition polymerization with an initiator having an active hydrogen-containing group. Since the active hydrogen is bonded to the terminal oxygen atom of the polyoxyalkylene chain in the precursor polymer, it is regarded as a polymer having a hydroxyl group as the terminal group. Similarly, the terminal group of the oxyalkylene polymer is also a group containing the terminal oxygen atom of the polyoxyalkylene chain. Note that the number of terminal groups of the oxyalkylene polymer and the precursor polymer is equal to the number of active hydrogens of the initiator described above. However, when the initiator has one active hydrogen, the initiator residue (the group bonded to the terminal carbon atom of the polyoxyalkylene chain) is regarded as the terminal group, and the number of terminal groups of such an oxyalkylene polymer and its precursor polymer is taken as 2. The "reactive terminal group" refers to a terminal group that reacts with a silylating agent when introducing a reactive silicon group into a precursor polymer or a derivative thereof. Examples of the reactive terminal group include alkenyloxy groups such as allyloxy group and hydroxyl group. The number of alkenyloxy groups can be calculated by a method of measuring the unsaturated group concentration by titration analysis based on the principle of the method for measuring iodine value as defined in JIS K 0070 (1992). The "non-reactive terminal group" refers to a terminal group that does not react with a silylating agent. The "silylating agent" means a compound that can react with a reactive terminal group to form a terminal group having a reactive silicon group. The "(meth)acrylate polymer" means a polymer containing units based on (meth)acrylate. Note that "(meth)acrylate" is a general term for acrylate and methacrylate.

[0013] The "silylation rate" is the ratio of the number of reactive silicon groups to the total number of terminal groups of the polymer. The value of the silylation rate can be measured by NMR analysis. Also, when introducing the above reactive silicon group into the reactive terminal group of the polymer with a silylating agent described later, it can also be expressed by the charged equivalent amount of the silylating agent with respect to the number of reactive terminal groups.

[0014] The "hydroxyl group equivalent molecular weight" is a value calculated by calculating the hydroxyl value of an initiator or a precursor polymer having a hydroxyl group based on JIS K 1557 (2007) as "56,100 / (hydroxyl value) × (the number of hydroxyl groups in one molecule of the initiator or the precursor polymer)". The hydroxyl group equivalent molecular weight of the oxyalkylene polymer is equivalent to or slightly smaller than the oxyalkylene polymer equivalent molecular weight described later. As used herein, the "number average molecular weight" (hereinafter referred to as "Mn") and the "weight average molecular weight" (hereinafter referred to as "Mw") are the oxyalkylene polymer-converted molecular weights measured by creating a calibration curve using a gel permeation chromatography (hereinafter referred to as "GPC") with tetrahydrofuran (hereinafter referred to as "THF") as an eluent and using an oxyalkylene polymer with a known hydroxyl group-converted molecular weight. The molecular weight distribution is a value calculated from Mw and Mn, and is the ratio of Mw to Mn (Mw / Mn).

[0015] The molecular weight per terminal group is calculated by applying the value of the hydroxyl value in the precursor polymer to the formula "56,100 / (hydroxyl value of the precursor polymer)", or by creating a calibration curve of the molecular weight per terminal group obtained from the hydroxyl value and the Mn obtained by GPC measurement in advance for each number of active hydrogens of the initiator, and applying the measurement result of the Mn to be determined to this relationship to convert it to the molecular weight per terminal group.

[0016] As used herein, the polystyrene-converted number average molecular weight (hereinafter referred to as "PS-converted Mn") and the polystyrene-converted weight average molecular weight (hereinafter referred to as "PS-converted Mw") are the polystyrene-converted molecular weights measured by creating a calibration curve using GPC with THF as an eluent and using a polystyrene polymer with a known molecular weight. In the oxyalkylene polymer, PS-converted Mn and PS-converted Mw tend to be measured larger than the above-mentioned Mn and Mw. The value calculated by PS-converted Mw / PS-converted Mn is the same as the above-mentioned Mw / Mn.

[0017] The curable composition of the present invention contains polymer A and polymer B, and contains a silanol condensation catalyst of less than 0.5 parts by mass with respect to a total of 100 parts by mass of polymer A and polymer B. Furthermore, it may contain polymer C described later.

[0018] <Polymer A> The curable composition of the present invention contains polymer A. The polymer A is an oxyalkylene polymer, having three or more terminal groups in one molecule, with a number-average molecular weight per terminal group of 6,000 or more, having a reactive silicon group represented by the formula (1) at the terminal group, and not having a reactive silicon group represented by the formula (2). The curable composition of the present invention may contain two or more types of polymers A. Since the polymer A is branched, a curable composition containing the polymer A easily gives a cured product excellent in resilience. The polymer A does not have a reactive silicon group represented by the formula (2). However, as an impurity, it may have a reactive silicon group represented by the formula (2). The content of the reactive silicon group represented by the formula (2) is preferably 2000 ppm or less, more preferably 1000 ppm or less, and particularly preferably not contained in the polymer A. Whether the reactive silicon group represented by the formula (2) is contained in the polymer A can be confirmed by NMR. If it can be calculated or is not detected at 2000 ppm or less with respect to the polymer A by a conventionally known quantitative method using NMR analysis, it can be considered that the polymer A does not contain a reactive silicon group represented by the formula (2). The reactive silicon group has a hydroxyl group or a hydrolyzable group bonded to a silicon atom and can form a siloxane bond to crosslink. The reaction to form a siloxane bond is promoted by a curing catalyst. The reactive silicon group in the polymer A is represented by the formula (1). -SiX a R 3-a ···(1) In the 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 a hydrocarbon group, a halogenated hydrocarbon group, and a triorganosiloxy group. As R, an alkyl group, a cycloalkyl group, an aryl group, a 1-chloroalkyl group, and a triorganosiloxy group are preferred. Further, a linear or branched alkyl group having 1 to 4 carbon atoms, a cyclohexyl group, a phenyl group, a benzyl group, a chloromethyl group, a trimethylsiloxy group, a triethylsiloxy group, and a triphenylsiloxy group are more preferred. From the viewpoint of good balance between the curability and stability of the polymer having a reactive silicon group, a methyl group and an ethyl group are particularly preferred. From the viewpoint of fast curing rate of the cured product, a chloromethyl group is particularly preferred. From the viewpoint of easy availability, a methyl group is particularly preferred.

[0019] In formula (1), X represents a hydroxyl group or a hydrolyzable group. Examples of the hydrolyzable group include a halogen atom, 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. As X, an alkoxy group is preferred from the viewpoint of gentle hydrolysis and easy handling. As the alkoxy group, a methoxy group, an ethoxy group, and an isopropoxy group are preferred, and a methoxy group and an ethoxy group are more preferred. When the alkoxy group is a methoxy group or an ethoxy group, it is easy to rapidly form a siloxane bond and form a crosslinked structure in the cured product, and the physical property values of the cured product tend to be good.

[0020] In formula (1), a is 1 or 2. When a is 1, the Rs may be the same as or different from each other. When a is 2, the Xs may be the same as or different from each other. For good curability, a is preferably 2.

[0021] Examples of the reactive silicon group represented by the formula (1) include methyldimethoxysilyl group, methyldiethoxysilyl group, ethyldimethoxysilyl group, ethyldiethoxysilyl group, methyldiisopropoxysilyl group, methoxymethyldiethoxysilyl group, methoxymethyldimethoxysilyl group, chloromethyldimethoxysilyl group, and chloromethyldiethoxysilyl group. From the viewpoint of high activity and good curability, methyldimethoxysilyl group and methyldiethoxysilyl group are preferred, and methyldimethoxysilyl group is more preferred.

[0022] Polymer A has a trivalent or higher initiator residue, a polyoxyalkylene chain formed by ring-opening addition polymerization of a cyclic ether, and a terminal group containing a terminal oxygen atom of the polyoxyalkylene chain. Since the polyoxyalkylene chain having a terminal group is a monovalent group, Polymer A has three or more polyoxyalkylene chains having a terminal group. Examples of the cyclic ether 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. In particular, propylene oxide is preferred. The polyoxyalkylene chain may be a copolymer chain having two or more oxyalkylene groups. In that case, the copolymer chain may be a block copolymer chain or a random copolymer chain. Examples of the polyoxyalkylene chain of Polymer A include polyoxypropylene chain, polyoxyethylene chain, poly(oxy-2-ethylethylene) chain, poly(oxy-1,2-dimethylethylene) chain, poly(oxytetramethylene) chain, poly(oxyethylene·oxypropylene) chain, and poly(oxypropylene·oxy-2-ethylethylene) chain. As the polyoxyalkylene chain, polyoxypropylene chain and poly(oxyethylene·oxypropylene) chain are preferred, and polyoxypropylene chain is particularly preferred. The terminal groups of polymer A are groups having a reactive silicon group represented by formula (1), hydroxyl groups, alkenyloxy groups, alkoxy groups, etc., and at least a part thereof is a group having a reactive silicon group represented by formula (1). The precursor polymer of polymer A is a polymer having a hydroxyl group as a terminal group, and polymer A is produced by converting the hydroxyl group of the precursor polymer into a group having a reactive silicon group represented by formula (1). When unreacted hydroxyl groups remain in the process of producing this polymer A, polymer A has a hydroxyl group as a terminal group. Also, when the hydroxyl group of the precursor polymer is converted into an alkenyloxy group and then the alkenyloxy group is converted into a group having a reactive silicon group represented by formula (1), if unreacted alkenyloxy groups remain, if an inactive alkenyloxy group is generated due to unsaturated group transfer of the alkenyloxy group, etc., in such cases, polymer A has an alkenyloxy group as a terminal group. Furthermore, when a part of the hydroxyl groups of the precursor polymer is inactivated for the purpose of adjusting the number of reactive silicon groups of polymer A, etc., polymer A has a non-reactive group such as an alkoxy group as a terminal group. Polymer A has 3 or more terminal groups. From the viewpoint of the resilience of the cured product, those having 3 to 8 terminal groups are preferred, those having 3 to 6 terminal groups are more preferred, and those having 3 or 4 terminal groups are even more preferred. Polymer A preferably has more than 0.5 and 1.0 or less reactive silicon groups on average per terminal group. Since the tensile strength of the cured product is likely to be good, those having 0.55 to 0.98 reactive silicon groups are more preferred.

[0023] The Mn per terminal group of polymer A is 6,000 or more, and as the Mn per terminal group, 6,500 to 13,000 is preferred, and 7,000 to 12,000 is more preferred. When within the above range, the elongation of the cured product is more excellent and the viscosity is likely to be sufficiently low. The Mn of polymer A is preferably 18,000 to 40,000, more preferably 19,000 to 38,000, and even more preferably 21,000 to 37,000. When within the above range, the elongation of the cured product is more excellent and the viscosity is likely to be sufficiently low. The Mn of the polymer A in terms of PS is preferably from 23,000 to 52,000, more preferably from 24,000 to 50,000, and even more preferably from 27,000 to 48,000. When within the above range, the elongation of the cured product is more excellent and the viscosity is likely to be sufficiently low. The polymer A preferably has more than 0.5 and 1.0 or less reactive silicon groups represented by the formula (1) on average per terminal group and an Mn of 18,000 to 40,000, and more preferably has 0.55 to 0.98 reactive silicon groups represented by the formula (1) on average per terminal group and an Mn of 19,000 to 38,000. The molecular weight distribution of the polymer A is preferably 1.8 or less. Since good elongation is easily obtained, the smaller the molecular weight distribution, the better. More preferably, it is from 1.0 to 1.5, even more preferably from 1.02 to 1.4, and particularly preferably from 1.04 to 1.2.

[0024] The polymer A is obtained by converting the hydroxyl groups of the precursor polymer described below into groups having the above reactive silicon groups. Specifically, the hydroxyl groups of the precursor polymer are converted into alkenyloxy groups, and then a silylating agent capable of introducing -SiX a R 3-a to the unsaturated group of the alkenyloxy group is reacted to form an alkoxy group having -SiX a R 3-a (hereinafter referred to as method (a)), a silylating agent having a functional group capable of reacting with the hydroxyl group and -SiX a R 3-a is reacted with the hydroxyl groups of the precursor polymer to convert the hydroxyl groups into groups having -SiX a R 3-a (hereinafter referred to as method (b)), and the hydroxyl groups of the precursor polymer are converted into groups having isocyanate groups, and then a silylating agent having a reactive group capable of reacting with the isocyanate group and -SiX a R 3-a is reacted to convert the hydroxyl groups into groups having -SiX a R 3-a (hereinafter referred to as method (c)) can be mentioned. In method (a), examples of the alkenyloxy group include alkenyloxy groups having a double bond at the terminal such as allyloxy group, 3-butenyloxy group, vinyloxy group, etc., and the allyloxy group is particularly preferred. For the unsaturated group -SiX a R 3-a Examples of the silylating agent capable of introducing include a compound having a group capable of reacting with an unsaturated group to form a bond (for example, a sulfanyl group) and -SiX a R 3-a and a hydrosilane compound (HSiX a R 3-a , provided that X, R and a are the same as those in the above formula (1).). Particularly, a hydrosilane compound is preferred. In method (b), examples of the silylating agent having a functional group capable of reacting with a hydroxyl group and -SiX a R 3-a include a silylating agent having an isocyanate group and -SiX a R 3-a . Particularly, an isocyanate silane compound having an isocyanate alkyl group and -SiX a R 3-a is preferred. In method (c), as a method for converting the hydroxyl group of the prepolymer into a group having an isocyanate group, it is preferable to use a polyisocyanate compound and react one of its isocyanate groups with the hydroxyl group of the prepolymer to form a group having an isocyanate group. Examples of the reactive group of the silylating agent having a reactive group capable of reacting with an isocyanate group and -SiX a R 3-a include a hydroxyl group, an amino group, etc. As the polymer A, the polymer A obtained by the above method (a) is preferred. Particularly, a polymer A obtained by converting the hydroxyl group of the prepolymer into an allyloxy group and then reacting the allyloxy group with a hydrosilane compound is preferred. The group having a reactive silicon group generated by reacting the allyloxy group with a hydrosilane compound is a group represented by -OCH 2 CH 2 CH 2 -SiX a R 3-a . As the number of groups having the reactive silicon group introduced into the precursor polymer, as described above, it is preferably more than 0.5 and 1.0 or less on average per terminal group, and from the viewpoint of good tensile strength, 0.55 to 0.98 is more preferable.

[0025] The precursor polymer for obtaining Polymer A is an oxyalkylene polymer having a hydroxyl group at the terminal, which is obtained by subjecting a cyclic ether to ring-opening addition polymerization in the presence of a ring-opening addition polymerization catalyst to an initiator having three or more active hydrogens. As the active hydrogen-containing group of the initiator, a hydroxyl group is preferable. As the cyclic ether, an alkylene oxide is preferable, and propylene oxide is particularly preferable. Therefore, as the precursor polymer for obtaining Polymer A, a precursor polymer obtained by subjecting propylene oxide to ring-opening addition polymerization to an initiator having three or more hydroxyl groups is preferable. The number of active hydrogens of the initiator is preferably 3 to 8, more preferably 3 to 6, and particularly preferably 3 or 4. When the active hydrogen-containing group of the initiator is a hydroxyl group, the number of hydroxyl groups of the initiator is similarly preferably 3 to 8, more preferably 3 to 6, and particularly preferably 3 or 4. Further, as the hydroxyl group, an alcoholic hydroxyl group is preferable. Examples of the initiator having three or more hydroxyl groups include glycerin, trimethylolpropane, pentaerythritol, sucrose, and sorbitol, and glycerin and trimethylolpropane are preferable from the viewpoint of good elongation of the cured product. Two or more initiators may be used in combination as the initiator. That is, a mixture of two or more initiators having 3 or more active hydrogens may be used as the initiator.

[0026] As the ring-opening addition polymerization catalyst when subjecting the cyclic ether to ring-opening addition polymerization to the initiator, a conventionally known catalyst can be used. For example, an alkali catalyst such as KOH, a transition metal compound-porphyrin complex catalyst such as a complex obtained by reacting an organoaluminum compound with porphyrin, a double metal cyanide complex catalyst, and a catalyst composed of a phosphazene compound can be mentioned. As the ring-opening addition polymerization catalyst, a double metal cyanide complex catalyst is preferred because it can narrow the molecular weight distribution of the prepolymer and, ultimately, that of Polymer A, and a curable composition with low viscosity can be easily obtained. As the double metal cyanide complex catalyst, conventionally known compounds can be used, and a conventionally known method can be adopted for the method of producing a polymer using the double metal cyanide complex. For example, the compounds and production methods disclosed in International Publication No. 2003 / 062301, International Publication No. 2004 / 067633, JP-A-2004-269776, JP-A-2005-15786, International Publication No. 2013 / 065802, and JP-A-2015-010162 can be used.

[0027] Specific examples of the hydrosilane compound that is the silylating agent used in the method (a) include, for example, methyldimethoxysilane, methyldiethoxysilane, ethyldimethoxysilane, methoxymethyldiethoxysilane, methoxymethyldimethoxysilane, methyldiisopropoxysilane, chloromethyldimethoxysilane, and chloromethyldiethoxysilane. From the viewpoint of high activity and good curability, methyldimethoxysilane and methyldiethoxysilane are preferred, and methyldimethoxysilane is more preferred. Note that as the silylating agents used in the method (b) and the method (c) and the method for producing Polymer A using these silylating agents, silylating agents similar to those used for producing Polymer B described later are preferably used, and methods similar to the method for producing Polymer B described later are preferred, except for the difference in the reactive silicon group. Conventionally known methods can be used for the method of producing Polymer A. Examples thereof include the methods proposed in each of JP-B-45-36319, JP-A-50-156599, JP-A-61-197631, JP-A-3-72527, JP-A-8-231707, US Patent No. 3632557, and US Patent No. 4960844.

[0028] The silylation rate of Polymer A is preferably more than 50 mol% and 100 mol% or less, more preferably 50 to 97 mol%, and even more preferably 52 to 95 mol%. When the curable composition contains two or more polymers A, the average silylation rate in the whole polymer A may be within the above range.

[0029] <Polymer B> The curable composition of the present invention contains a polymer B. The polymer B is an oxyalkylene polymer having a reactive silicon group represented by the formula (2) at the terminal group. The polymer B in the curable composition of the present invention may be one kind or two or more kinds. -SiX 3 ···(2) In the formula (2), X represents a hydroxyl group or a hydrolyzable group, and X may be the same or different from each other. A preferred embodiment of X is the same as the above formula (1). Since the polymer B has a reactive silicon group represented by the formula (2), the cured product obtained from the curable composition containing the polymer B has good restorability and excellent followability to the adherend. The polyoxyalkylene chain in the polymer B is the same as the polyoxyalkylene chain in the polymer A, and the preferred embodiments are also the same. Each terminal group of the polymer B is a group having a reactive silicon group represented by the formula (2), a hydroxyl group, an alkenyloxy group, an alkoxy group, etc., and at least a part thereof is a group having a reactive silicon group represented by the formula (2). The terminal group other than the group having a reactive silicon group represented by the formula (2) is preferably a hydroxyl group or an allyloxy group. The plurality of terminal groups in one molecule of the polymer B may be the same as or different from each other.

[0030] The polymer B has an average of more than 0.5 and 1.0 or less reactive silicon groups represented by the formula (2) per terminal group. Since the tensile strength is likely to be good, a polymer B having an average of 0.55 to 0.98 reactive silicon groups per terminal group is more preferred. The number of terminal groups in one molecule of the polymer B is two or more, and preferably 2 to 6. Since the elongation of the cured product is likely to be good, a polymer B having two terminal groups in one molecule is particularly preferred.

[0031] The Mn of polymer B is preferably from 5,000 to 30,000, more preferably from 6,000 to 28,000, still more preferably from 7,000 to 27,000, and particularly preferably from 12,000 to 26,000. When within the above range, the cured product has better elongation and the viscosity is more likely to be sufficiently low. The Mn of polymer B in terms of PS conversion is preferably from 7,000 to 40,000, more preferably from 8,000 to 36,000, still more preferably from 9,000 to 35,000, and particularly preferably from 17,500 to 34,000. When within the above range, the cured product has better elongation and the viscosity is more likely to be sufficiently low. The molecular weight distribution of polymer B is preferably 1.8 or less. Since good elongation is easily obtained, the smaller the molecular weight distribution, the better. It is more preferably from 1.0 to 1.5, still more preferably from 1.02 to 1.4, and particularly preferably from 1.04 to 1.2.

[0032] Polymer B is obtained by converting the hydroxyl group of the precursor polymer into a group having a reactive silicon group represented by formula (2). Polymer B can be produced by a method similar to the production method of polymer A except that a silylating agent capable of forming a group having a reactive silicon group represented by formula (2) is used as the silylating agent. In particular, it is preferably produced by a method similar to the above method (a) or the above method (b) except for the difference in the silylating agent. A polymer B having 3 or more end groups in one molecule can be produced using a precursor polymer having 3 or more hydroxyl groups in the same manner as polymer A. Since it is preferable that the number of end groups of polymer B is 2, that is, polymer B is a linear polymer, as the precursor polymer for obtaining polymer B, an oxyalkylene polymer having hydroxyl groups at both ends, which is obtained by subjecting a cyclic ether to ring-opening addition polymerization in the presence of a ring-opening addition polymerization catalyst to an initiator having 2 active hydrogens, is preferable. As the initiator having 2 active hydrogens, a compound having 2 hydroxyl groups is preferable. One type of initiator may be used, or two or more types may be used in combination. Examples of the compound having two carboxyl 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.

[0033] Polymer B can be produced in the same manner as the production method of Polymer A, except that the precursor polymer of the above Polymer B and a silylating agent having a reactive silicon group represented by the formula (2) are used as the silylating agent. Specifically, the following production methods corresponding to the above methods (a) to (c) can be mentioned. Method (a): A method of converting the hydroxyl group of the precursor polymer into an alkenyloxy group, and then reacting with a silylating agent capable of introducing -SiX 3 to an unsaturated group of the alkenyloxy group to form an alkoxy group having -SiX 3 . Method (b): A method of reacting a silylating agent having a functional group capable of reacting with the hydroxyl group and -SiX 3 with the hydroxyl group of the precursor polymer to convert the hydroxyl group into a group having -SiX 3 . Method (c): A method of converting the hydroxyl group of the precursor polymer into a group having an isocyanate group, and then reacting with a silylating agent having a reactive group capable of reacting with the isocyanate group and -SiX 3 to convert the hydroxyl group into a group having -SiX 3 .

[0034] Examples of the silylating agent used in Method (a) include compounds having both a group capable of reacting with an unsaturated group to form a bond (for example, a sulfanyl group) and -SiX 3 , and hydrosilane compounds (for example, HSiX 3 ). Specifically, for example, trimethoxysilane, triethoxysilane, triisopropoxysilane, tris(2-propenyloxy)silane, and triacetoxysilane can be mentioned. From the viewpoint of high activity and good curability, trimethoxysilane and triethoxysilane are preferred, and trimethoxysilane is more preferred.

[0035] As the silylating agent used in method (b), an isocyanate silane compound represented by the following formula (3) is preferable. OCN-(CH 2 ) n -SiX 3 ···(3) X in formula (3) is the same as in the above formula (2). n is an integer from 1 to 8, preferably from 1 to 3. By the reaction of the hydroxyl group of the prepolymer with the above isocyanate silane compound, the hydroxyl group of the prepolymer is converted to a terminal group having a urethane bond (-O-C(=O)NH-) and -SiX 2 ) n -SiX 3 represented by 3 . Examples of the isocyanate silane compound include 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, isocyanatomethyltrimethoxysilane, and isocyanatomethyltriethoxysilane. As the isocyanate silane compound, 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane are preferable in view of the reactivity with the prepolymer and ease of handling. This reaction may be carried out in the presence of a urethanization catalyst. The urethanization catalyst is not particularly limited, and known urethanization catalysts can be appropriately used. For example, organotin compounds such as dibutyltin dilaurate and dioctyltin dilaurate, metal catalysts such as bismuth compounds, and base catalysts such as organic amines can be mentioned. The reaction temperature is preferably 20 to 200°C, more preferably 50 to 150°C. Further, the urethanization reaction is preferably carried out in an inert gas atmosphere. Nitrogen is preferable as the inert gas.

[0036] In method (c), a polyisocyanate compound is reacted with the hydroxyl groups of the precursor polymer to convert the hydroxyl groups into isocyanate group-containing monovalent organic groups having a urethane bond (-O-C(=O)NH-) on the bond terminal side, and then, the isocyanate group-containing monovalent organic groups are reacted with a silylating agent having a reactive group capable of reacting with the isocyanate group and -SiX 3 to obtain a monovalent organic group having a urethane bond (-O-C(=O)NH-) at the terminal and a silylating agent residue reacted with the isocyanate group. Hereinafter, the polyisocyanate compound will be described as a diisocyanate compound represented by the following formula (4), and the silylating agent having a reactive group capable of reacting with the isocyanate group and -SiX 3 will be described as a compound represented by the following formula (5), but the method (c) is not limited thereto. OCN-R 1 -NCO ···(4) In the formula (4), R 1 represents a divalent organic group. W-R 2 -SiX 3 ···(5) In the formula (5), W is a monovalent reactive group (having one or more active hydrogens), R 2 is a divalent organic group, and -SiX 3 is the same as the above formula (2). The isocyanate group-containing monovalent organic group having a urethane bond (-O-C(=O)NH-) on the bond terminal side is a group represented by -O-C(=O)NH-R 1 -NCO. The monovalent organic group having a silylating agent residue reacted with the isocyanate group is a group represented by -O-C(=O)NH-R 1 -NHC(=O)-W’-R 2 -SiX 3 (wherein W’ is W from which one active hydrogen has been removed). For example, when W is a hydroxyl group, the latter group is -O-C(=O)NH-R 1 -NHC(=O)-O-R 2 -SiX 3 represented by. In this case, the latter group has two urethane bonds. R 1As the divalent organic group, a divalent organic group having 2 to 20 carbon atoms is preferable, and examples thereof include an alkylene group, a cycloalkylene group, a bicycloalkylene group, a monocyclic or polycyclic divalent aromatic hydrocarbon group, a divalent group having a bond to each of the carbon atoms of the side chain group of a cycloaliphatic hydrocarbon containing a side chain hydrocarbon group and the carbon atoms constituting the ring, and a divalent group having a bond to each of the carbon atoms of two side chain groups of an aromatic hydrocarbon containing a side chain hydrocarbon group. Examples of the diisocyanate compound represented by the formula (4) and other polyisocyanate compounds include aromatic polyisocyanates, non-yellowing aromatic polyisocyanates (compounds having no isocyanate group directly bonded to the carbon atoms constituting the aromatic ring), aliphatic polyisocyanates, alicyclic polyisocyanates, and urethane-modified products, burette-modified products, allophanate-modified products, carbodiimide-modified products, and isocyanurate-modified products obtained from the above polyisocyanates. Examples of the aromatic polyisocyanate include naphthalene-1,5-diisocyanate, polyphenylene polymethylene polyisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, and 2,6-tolylene diisocyanate. Examples of the non-yellowing aromatic polyisocyanate include xylylene diisocyanate and tetramethylxylylene diisocyanate. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, and 2,4,4-trimethyl-hexamethylene diisocyanate. Examples of the alicyclic polyisocyanate include isophorone diisocyanate and 4,4'-methylenebis(cyclohexyl isocyanate). As the polyisocyanate compound, those having two isocyanate groups are preferred, and hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate are preferred. Since the strength of the cured product is easily obtained, tolylene diisocyanate is more preferred. The polyisocyanate compound may be used alone or in combination of two or more.

[0037] A reactive group capable of reacting with the isocyanate group represented by formula (5) and -SiX 3 In the silylating agent having R 2 As, a divalent organic group having 1 to 20 carbon atoms is preferred, and an aromatic hydrocarbon group having 1 to 10 carbon atoms, an aromatic hydrocarbon group having 1 to 10 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms, a cyclic hydrocarbon group having 1 to 10 carbon atoms, a linear hydrocarbon group having 1 to 12 carbon atoms are more preferred, a linear hydrocarbon group having 1 to 8 carbon atoms is further preferred, and a linear hydrocarbon group having 1 to 6 carbon atoms is particularly preferred. As W, a group having one or two active hydrogens selected from a hydroxyl group, a carboxy group, a mercapto group, an amino group, and an amino group in which one hydrogen atom is substituted with an alkyl group having 1 to 6 carbon atoms is preferred, a hydroxyl group, a mercapto group, an amino group, a methylamino group, an ethylamino group, and a butylamino group are preferred, and a hydroxyl group, an amino group, a methylamino group, an ethylamino group, and a butylamino group are more preferred.

[0038] When the polymer B is the polymer B obtained by the method (b) or the method (c), the polymer B usually has a terminal group containing a urethane bond (-O-C(=O)NH-). When the polymer B contains a urethane bond, the content of the urethane bond in the polymer B is preferably 0.33 mmol / g or less, more preferably 0.29 mmol / g or less. Further, the content of the urethane bond in the polymer B is preferably 0.01 mmol / g or more, more preferably 0.02 mmol / g or more, and even more preferably 0.05 mmol / g or more. Within the above range, elongation and resilience are better, and heat resistance is likely to be improved. The concentration (mmol / g) of the urethane bond can be calculated by dividing the number of moles of the urethane bond calculated by NMR by Mn determined by GPC. The silylation rate of the polymer B is preferably more than 50 mol% and 100 mol% or less, more preferably 51 to 97 mol%, and even more preferably 52 to 95 mol%. When the curable composition contains two or more kinds of polymer B, the average silylation rate of the whole polymer B may be within the above range.

[0039] <Polymer C> The curable composition of the present invention may further contain a polymer C. The polymer C is an oxyalkylene polymer having two terminal groups in one molecule and having more than 0 and 0.5 or less reactive silicon groups represented by the above formula (1) or formula (2) on average at one terminal. The curable composition may contain two or more kinds of polymer C. The polymer C acts as a reactive plasticizer and contributes to lowering the viscosity of the curable composition and improving the paint stainability. The reactive silicon group in the polymer C is preferably a reactive silicon group represented by the formula (2).

[0040] The Mn of the polymer C is preferably 2,000 to 12,000, more preferably 2,200 to 10,000, and even more preferably 2,500 to 9,000. Within the above range, the elongation of the cured product is more excellent, and the paint stainability and bleed-out of the cured product are likely to be good. The Mn of the polymer C in terms of PS is preferably from 2,600 to 16,000, more preferably from 2,800 to 14,000, and even more preferably from 3,000 to 13,000. When within the above range, the elongation of the cured product is more excellent, and the paint stainability and bleed-out of the cured product tend to be good. The molecular weight distribution of the polymer C is preferably 1.8 or less. From the viewpoint of viscosity reduction, the smaller the molecular weight distribution, the better. It is more preferably from 1.0 to 1.6, even more preferably from 1.02 to 1.5, and particularly preferably from 1.04 to 1.4.

[0041] The polymer C is obtained by introducing the above reactive silicon group into a precursor polymer having two or one hydroxyl group in an average amount of more than 0 and 0.5 or less per terminal group. Examples of the precursor polymer having two hydroxyl groups include linear precursor polymers having two hydroxyl groups similar to those of the precursor polymer of the polymer B. Examples of the precursor polymer having one hydroxyl group include linear precursor polymers having a hydroxyl group bonded to the initiator residue, polyoxyalkylene chain, and carbon atom at the end of the polyoxyalkylene chain, which are obtained by ring-opening addition polymerization of a cyclic ether to an initiator having one active hydrogen. As the precursor polymer of the polymer C, the latter precursor polymer having one hydroxyl group is preferred. As the initiator having one active hydrogen, R 10 -O-H (R 10 is a monovalent hydrocarbon group) is preferred. As the cyclic ether for obtaining the precursor polymer having one hydroxyl group, alkylene oxide is preferred, and propylene oxide is particularly preferred, in the same manner as the polymer A and the polymer B. The precursor polymer having one hydroxyl group obtained by using these has a polyoxyalkylene chain, R 10 -O- bonded to the terminal carbon atom of the polyoxyalkylene chain, and an active hydrogen bonded to the terminal oxygen atom of the polyoxyalkylene chain (however, the terminal group is regarded as a hydroxyl group including the terminal oxygen atom). The polymer C can be produced by converting more than 0 and 1 or less of the average hydroxyl groups of this precursor polymer into a group having a reactive silicon group by the methods (a) to (c) in the same manner as the polymer A and the polymer B. One terminal group of the obtained polymer C is R 10-O-, and on average, more than 0 and 1 or less of the other terminal groups are groups having a reactive silicon group, so that Polymer C has, on average, more than 0 and 0.5 or less reactive silicon groups per terminal group.

[0042] R 10 As the initiator represented by -O-H, a monohydric alcohol in which R 10 is a linear or branched hydrocarbon group is preferred. Specifically, methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-butyl alcohol, t-butyl alcohol, 2-ethylhexanol, decyl alcohol, lauryl alcohol, tridecanol, cetyl alcohol, stearyl alcohol, oleyl alcohol can be exemplified. R 10 is preferably a saturated hydrocarbon group, more preferably an alkyl group having 10 or less carbon atoms, and even more preferably an alkyl group having 6 or less carbon atoms. As the production method of Polymer C, a conventionally known method can be used, and the same methods (a) to (c) as those of Polymer A or B can be used.

[0043] Polymer C has two terminal groups in one molecule, and the terminal groups are groups having the above reactive silicon group, initiator residues, hydroxyl groups, alkenyloxy groups, alkoxy groups, etc., and at least a part thereof is a group having a reactive silicon group. As Polymer C, those in which one of the terminal groups is an initiator residue are preferred. The silylation rate of Polymer C is preferably 45 mol% or more, more preferably 50 mol% or more, and even more preferably 55 mol% or more. When the curable composition contains two or more kinds of Polymer C, the average silylation rate in the whole Polymer C may be within the above range.

[0044] When the curable composition contains polymer C, the content of polymer C is preferably 1 to 600 parts by mass, more preferably 5 to 500 parts by mass, and even more preferably 10 to 300 parts by mass with respect to 100 parts by mass in total of polymer A and polymer B. When the content of polymer C is within the above range, it is likely to have a low viscosity, has more excellent workability, and bleed-out hardly occurs in the cured product.

[0045] <Polymer D> The curable composition of the present invention may contain one or more vinyl polymers having one or more reactive silicon groups represented by formula (1) or formula (2) in one molecule (hereinafter referred to as "polymer D"). The reactive silicon group in polymer D may be introduced at the main chain terminal of the vinyl polymer, at the side chain, or at both the main chain terminal and the side chain. The average number of reactive silicon groups per molecule of polymer D is preferably 1.0 or more. As the average number of reactive silicon groups, 1.2 or more is preferable, and 1.6 or more is more preferable from the viewpoint of the strength after curing. From the viewpoint of good elongation of the cured product, 4.0 or less is preferable, and 3.0 or less is more preferable. The average number of reactive silicon groups per molecule of polymer D is calculated by "[concentration of reactive silicon groups in polymer D [mol / g] × Mn in terms of PS of polymer D]". The concentration of reactive silicon groups in polymer D [mol / g] can be measured by NMR. As the monomer constituting the main chain of polymer D, for example, conventionally known monomers described in Japanese Patent Publication No. 3-14068, Japanese Unexamined Patent Application Publication No. 6-211922, and Japanese Unexamined Patent Application Publication No. 11-130931 can be used. Examples of the monomer containing a reactive silicon group and a polymerizable unsaturated group copolymerizable with the above monomer include vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinylmethyldichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, tris(2-methoxyethoxy)vinylsilane, 3-(methyldimethoxysilyl)propyl (meth)acrylate, 3-(trimethoxysilyl)propyl (meth)acrylate, and 3-(triethoxysilyl)propyl (meth)acrylate. These may be used alone or in combination of two or more. With respect to the total monomer units constituting Polymer C, the content of (meth)acrylate units is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 100% by mass.

[0046] Polymer D can be polymerized by a conventionally known polymerization method described in, for example, JP-A-2006-257405, JP-A-2006-37076, JP-A-2008-45059, etc. Conventionally known auxiliary materials such as initiators required for the polymerization can be used, and reaction conditions such as reaction temperature and reaction pressure can also be appropriately selected. Examples of the polymerization method include a polymerization method using a radical polymerization initiator by solution polymerization, emulsion polymerization, suspension polymerization, or bulk polymerization, and living radical polymerization. Examples of the living radical polymerization method include those using a cobalt porphyrin complex as shown in Journal of American Chemical Society (J.Am.Chem.Soc.), 1994, Vol. 116, p. 7943, those using a nitroxide radical as shown in JP-T-2003-500378, and atom transfer radical polymerization (Atom Transfer Radical Polymerization: ATRP method) using an organic halide or a sulfonyl halide compound as an initiator and a transition metal complex as a catalyst as shown in JP-A-11-130931. The polymer obtained by living radical polymerization tends to have a narrow molecular weight distribution and low viscosity. Commercially available polymer D can also be used. Examples of commercially available products include XMAP series (product name of Kaneka), ARUFON US-6000 series (for example, US-6110, US-6120, etc., all product names of Toagosei), Actflow NE series (for example, NE-1000, NE-3000, both product names of Soken Chemical & Engineering Co., Ltd.), etc.

[0047] As the Mn in terms of PS of polymer D, 10,000 to 100,000 is preferable, 12,000 to 80,000 is more preferable, and 13,000 to 60,000 is even more preferable. When it is at or above the lower limit value of the above range, the cured product has more excellent elongation and weather resistance, and when it is at or below the upper limit value, the workability is more excellent. As the molecular weight distribution of polymer D, 4.0 or less is preferable, and 3.0 or less is more preferable. When it is at or below the upper limit value of the above range, the workability is more excellent. When the curable composition contains polymer D, the content of polymer D is preferably 1 to 600 parts by mass, more preferably 5 to 500 parts by mass, and even more preferably 10 to 300 parts by mass with respect to 100 parts by mass in total of polymer A and polymer B. When it is at or above the lower limit value of the above range, the surface contamination property is likely to decrease, and when it is at or below the upper limit value, it is likely to have a low viscosity and the workability is more excellent.

[0048] <Polymer E> The curable composition of the present invention may contain one or more polymers having no reactive silicon group and having an Mn in terms of PS of 1,000 or more (hereinafter referred to as "polymer E"). Polymer E contributes to reducing the contamination of the surface of the cured product, improving the drying property of the paint on the surface of the cured product, and reducing the contamination of the paint surface. As polymer E, an unsaturated hydrocarbon polymer, a (meth)acrylate polymer, and an oxyalkylene polymer having no reactive silicon group are preferable.

[0049] The unsaturated hydrocarbon polymer is a polymer containing units based on unsaturated hydrocarbon monomers, and examples thereof include polyethylene and polypropylene. Examples of the (meth)acrylate polymer include polymers or copolymers of monomers containing (meth)acrylates such as methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl, lauryl (meth)acrylate, and stearyl (meth)acrylate. Examples of commercially available (meth)acrylate polymers include ARUFON UP-1000, ARUFON UP-1110, and ARUFON UP-1171 (all product names of Toagosei Co., Ltd.). Examples of the oxyalkylene polymer include polyether polyols (e.g., polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol), and derivatives obtained by blocking the hydroxyl groups of the above polyether polyols to form esters or ethers. Examples of commercially available oxyalkylene polymers include Preminol S3011, Preminol S4012, and Preminol S4013F (all product names of AGC Inc.).

[0050] The Mn in terms of PS of polymer E is preferably from 1,000 to 40,000, more preferably from 1,500 to 35,000, and even more preferably from 2,000 to 30,000. When it is at or above the lower limit value of the above range, outflow due to heat or rainfall is likely to be prevented, and when it is at or below the upper limit value, the viscosity is low and the workability is more excellent. The molecular weight distribution of polymer E is preferably less than 6.0, more preferably 5.5 or less, and even more preferably 5.0 or less in the case of (meth)acrylate polymers. In the case of oxyalkylene polymers, it is preferably less than 2.0, more preferably 1.8 or less, and even more preferably 1.6 or less. When the curable composition contains polymer E, the content of polymer E is preferably from 1 to 600 parts by mass, more preferably from 5 to 500 parts by mass, and even more preferably from 10 to 300 parts by mass with respect to 100 parts by mass in total of polymer A and polymer B. When it is at or above the lower limit value of the above range, the surface contaminability is likely to decrease, and when it is at or below the upper limit value, it is likely to have a low viscosity and the workability is more excellent.

[0051] <Silanol condensation catalyst> The curable composition of the present invention contains a silanol condensation catalyst in an amount of less than 0.5 parts by mass based on a total of 100 parts by mass of polymer A and polymer B. The curable composition may contain one or more of the above curing catalysts. The silanol condensation catalyst acts as a catalyst in the formation of silanol bonds by promoting the hydrolysis reaction of the hydroxyl group in the reactive silicon group represented by formula (1) and formula (2) and the hydrolyzable group. Examples of the silanol condensation catalyst include salts of metals such as tin and bismuth with organic acids, alkyl tin catalysts, and the like. Examples of the salts with organic acids include tin octylate, tin naphthenate, tin laurate, tin ferulate, tin tris(2-ethylhexanoate), and carboxylates of bismuth and titanium. Examples of the alkyl tin catalysts include dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin maleate, dibutyltin phthalate, dibutyltin dioctanoate, dibutyltin bis(2-ethylhexanoate), dibutyltin bis(methylmaleate), dibutyltin bis(ethylmaleate), dibutyltin bis(butylmaleate), dibutyltin bis(octylmaleate), dibutyltin bis(tridecylmaleate), dibutyltin bis(benzylmaleate), dibutyltin diacetate, dioctyltin bis(ethylmaleate), dioctyltin bis(octylmaleate), dibutyltin dimethoxide, dibutyltin bis(nonylphenoxide), dibutenyltin oxide, dibutyltin oxide, dibutyltin bis(acetylacetonate), dioctyltin bis(acetylacetonate), dibutyltin bis(ethylacetoacetonate), the reaction product of dibutyltin oxide and a silicate compound, the reaction product of dioctyltin oxide and a silicate compound, and the reaction product of dibutyltin oxide and a phthalic acid ester. As the silanol condensation catalyst, tin octylate or an alkyl tin catalyst is preferred because good curability can be easily obtained, and an alkyl tin catalyst is more preferred from the viewpoint of ease of construction. Dibutyltin dilaurate, dibutyltin maleate, dibutyltin phthalate, dibutyltin diacetate, dibutyltin bis(acetylacetonate), dioctyltin bis(acetylacetonate), dibutyltin bis(ethyl acetoacetonate), the reaction product of dibutyltin oxide and a silicate compound, and the reaction product of dioctyltin oxide and a silicate compound are more preferred. These silanol condensation catalysts may be used alone or in combination of two or more. Further, a conventionally known cocatalyst such as laurylamine may be used in combination. As the content of the silanol condensation catalyst in the curable composition, 0.01 to 0.5 parts by mass is preferable, 0.05 to 0.4 parts by mass is more preferable, and 0.1 to 0.3 parts by mass is further preferable with respect to 100 parts by mass in total of Polymer A and Polymer B. When it is within the above range, the curing reaction easily proceeds sufficiently, local heat generation and foaming hardly occur during curing, and a good cured product is easily obtained.

[0052] <Curable Composition> The curable composition is obtained by mixing Polymer A, Polymer B, a silanol condensation catalyst, and other components described later. When the polymers coexisting in the curable composition have reactive silicon groups, the respective reactive silicon groups may be the same or different from each other. The mass ratio of Polymer A to Polymer B in the curable composition is 99 / 1 to 50 / 50, preferably 98 / 2 to 60 / 40, and more preferably 95 / 5 to 70 / 30 as the mass of Polymer A / mass of Polymer B. If it is within the above range, the elongation and resilience of the cured product will be good. As the content ratio of Polymer A in the curable composition, 3 to 80% by mass is preferable, 5 to 60% by mass is more preferable, and 10 to 50% by mass is further preferable. When it is within the above range, the elongation is more excellent. In the curable composition, the content ratio of polymer B is preferably 0.5 to 50% by mass, more preferably 0.7 to 40% by mass, and still more preferably 1 to 30% by mass. When it is within the above range, the elongation and resilience of the cured product are more excellent. In the curable composition, the content ratio of polymer A and polymer B is preferably 3.5 to 80.5% by mass, more preferably 5.7 to 60.7% by mass, and still more preferably 11 to 51% by mass. When it is within the above range, the curability is likely to be good, and the elongation and resilience of the cured product are more excellent. As shown in the examples described later, the elastic recovery rate of the cured product obtained from the curable composition of the present invention, based on the test method for building sealants of JIS A 1439 5.2 (2016), is likely to be 70% or more, and further likely to be 72% or more. If it is 70% or more, good resilience can be obtained, it is easy to follow the structural changes of the adherend over time, and the followability of the curable composition is easily obtained. Also, as shown in the examples described later, the value of the maximum elongation in the tensile property test of the durability test specimen 1 type based on the test method for building sealants of JIS A 1439 (2016) of the cured product obtained from the curable composition of the present invention is likely to be 500% or more, and further likely to be 580% or more. If it is 500% or more, good elongation can be obtained, and it is suitable as a building sealant.

[0053] The curable composition may be a one-component type in which all the compounding components are compounded in advance, sealed and stored, and cured by moisture in the air after construction. Or it may be a two-component type in which a main agent composition containing at least a component having a reactive silicon group and a curing agent composition containing at least a curing catalyst are stored separately, and the curing agent composition and the main agent composition are mixed before use. Since the construction is easy, a one-component type curable composition is preferred.

[0054] The one-component type curable composition preferably does not contain moisture. It is preferable to dehydrate and dry the compounding components containing moisture in advance, or to dehydrate under reduced pressure during compounding and kneading. In a two-component curable composition, the curing agent composition may contain water. The main agent composition is difficult to gel even if it contains a small amount of moisture, but from the viewpoint of storage stability, it is preferable to dehydrate and dry the compounding components in advance. In order to improve the storage stability, a dehydrating agent may be added to a one-component curable composition or the main agent composition of a two-component curable composition.

[0055] [Other Components] The curable composition may contain other components other than the above polymers A to E and the silanol condensation catalyst. Examples of other components include curable compounds, fillers, plasticizers, thixotropic agents, stabilizers, adhesion-imparting agents, physical property modifiers, tackifier resins, reinforcing materials such as fillers, surface modifiers, flame retardants, foaming agents, solvents, and silicates. Each of the other components can be used in any combination of conventionally known ones described in, for example, International Publication No. 2013 / 180203, International Publication No. 2014 / 192842, International Publication No. 2016 / 002907, Japanese Patent Application Laid-Open No. 2014-88481, Japanese Patent Application Laid-Open No. 2015-10162, Japanese Patent Application Laid-Open No. 2015-105293, Japanese Patent Application Laid-Open No. 2017-039728, Japanese Patent Application Laid-Open No. 2017-214541, etc., without limitation.

[0056] [Mechanism of Action] The curable composition of the present invention contains polymer A and polymer B in a specific ratio and contains a silanol condensation catalyst in an amount less than a specific amount. As shown in the examples described later, the curable composition is excellent in curability, and the obtained cured product has good elongation and resilience, so it is particularly suitable for a sealing material for an outer wall that is exposed outdoors for a long time. When the curable composition of the present invention is used as a sealing material for an outer wall, it follows the structural changes of the adherend over time and is less likely to crack, so the appearance is easily maintained well.

[0057] [Applications] As uses of the curable composition, sealants (for example, elastic sealants for construction, sealants for double - glazed glass, rust - proof and waterproof sealants for glass edges, back - side sealants for solar cells, building sealants, ship sealants, automobile sealants, road sealants), electrical insulating materials (insulating coating materials for electric wires and cables), and adhesives are suitable. Particularly, it is suitable for uses where elongation and resilience of the cured product are required, for example, sealants applied outdoors.

Examples

[0058] Hereinafter, the present invention will be described in more detail with specific examples, but the present invention is not limited to the following examples.

[0059] [Molecular weight of the precursor polymer] The molecular weight of the precursor polymer, which is an oxyalkylene polymer having a hydroxyl group as a terminal group and obtained by polymerizing alkylene oxide with an initiator, is calculated based on the formula "56,100 / (hydroxyl value of the precursor polymer) × number of active hydrogens of the initiator" from the hydroxyl value calculated based on JIS K 1557 (2007) (hereinafter referred to as "molecular weight in terms of hydroxyl group").

[0060] [Mn and Mw / Mn] Using HLC - 8220GPC (product name of Tosoh Corporation), a calibration curve for the molecular weight in terms of hydroxyl group was created using an oxyalkylene polymer with a known molecular weight in terms of hydroxyl group, Mw and Mn were determined, and Mw / Mn was calculated.

[0061] [Mn in terms of PS] Using HLC - 8220GPC (product name of Tosoh Corporation), a calibration curve for the molecular weight in terms of polystyrene was created using a polystyrene polymer with a known molecular weight, and Mn in terms of PS was calculated.

[0062] [Silylation rate, number of silyl groups] In a method of converting a terminal hydroxyl group of a precursor polymer into an allyloxy group using allyl chloride and reacting a hydrosilane compound as a silylating agent with the allyloxy group to introduce a reactive silicon group, the charged equivalent (molar ratio) of the silylating agent to the allyloxy group was defined as the silylation rate. In the reaction of the allyloxy group with the silylating agent, approximately 10% of the allyloxy groups that do not react with the silylating agent due to side reactions. Therefore, when reacting with a silylating agent corresponding to less than 90 mol% of the allyloxy groups, the above-mentioned charged equivalent becomes equivalent to the silylation rate.

[0063] [Tack-free time (TFT)] The tack-free time (TFT) is the finger-touch drying time measured in accordance with JIS A 1439 (2016) at 23°C. TFT is an index indicating the curability of the composition, and the smaller it is, the faster the curing rate and the better the curability.

[0064] [Evaluation of tensile properties] As the adherend, a surface anodized aluminum plate coated with primer MP-2000 (product name of Cemedine Co., Ltd.) on the surface was used, and a durability test specimen type 1 was prepared and a tensile property test was conducted in accordance with the test method for building sealants of JIS A 1439 (2016). Specifically, the curable composition was poured into the space formed by sandwiching a spacer between two of the above aluminum plates, cured at a temperature of 23°C and a humidity of 50% for 7 days, and further cured at a temperature of 50°C and a humidity of 65% for 7 days to obtain a durability test specimen type 1. For the obtained durability test specimen type 1, a tensile property test was conducted using a tensilon tester, and the stress (hereinafter referred to as "M100". Unit: N / mm 2 ), maximum point cohesion (unit: N / mm 2 ) and maximum point elongation (unit: %) were measured. The smaller the value of M100, the softer the cured product. The larger the value of the maximum point cohesion, the higher the tensile strength of the cured product. The larger the value of the maximum point elongation, the better the elongation of the cured product. If the maximum point elongation is 500% or more, it shows good elongation.

[0065] [Evaluation of Elastic Recovery] As the adherend, a surface anodized aluminum plate with primer MP-2000 (product name of Semidain Co., Ltd.) applied on the surface was used, and an aluminum adherend was prepared and the elastic recovery was evaluated in accordance with the test method for building sealants of JIS A 1439 5.2 (2016). Specifically, in the same manner as the evaluation of the above tensile properties, the curable composition was poured between two of the above aluminum plates, cured at a temperature of 23°C and a humidity of 50% for 7 days, and further cured at a temperature of 50°C and a humidity of 65% for 7 days to obtain an aluminum adherend. The distance between the two aluminum plates of the obtained aluminum adherend was designated as L0. Using a predetermined jig, in an environment of a temperature of 23°C and a humidity of 50%, the distance between the two aluminum plates was extended by 100% with respect to L0. At this time, the distance between the two aluminum plates was designated as L1. After holding the distance between the two aluminum plates at L1 for 24 hours, the jig was removed and left standing for 1 hour, and the distance between the two aluminum plates was measured as L2. From the values of L0, L1, and L2, the elastic recovery rate (unit: %) was determined by the following formula (5). The higher the value of the elastic recovery rate, the better the recovery. If the elastic recovery rate is 70% or more, the recovery is good. Elastic recovery rate = (L1 - L2 / L1 - L0) × 100 ···(5)

[0066] [Synthesis of Polymer A, Polymer B, and Polymer C] (Synthesis Example 1: Polymer A1) Using glycerin as an initiator, propylene oxide was polymerized using a zinc hexacyanocobaltate complex with t-butyl alcohol as a ligand (hereinafter referred to as "TBA-DMC catalyst") as a catalyst to obtain an oxypropylene polymer (precursor polymer). The hydroxyl group-equivalent molecular weight of the precursor polymer was 24,000. Next, a methyl alcohol solution of sodium methoxide in an amount of 1.05 molar equivalents with respect to the hydroxyl groups of the precursor polymer was added to alcoholize the precursor polymer. Next, methyl alcohol was distilled off by heating under reduced pressure, and an excess amount of allyl chloride was added with respect to the amount of hydroxyl groups of the precursor polymer to convert the hydroxyl groups of the precursor polymer into allyloxy groups. Next, in the presence of chloroplatinic acid hexahydrate, 0.75 molar equivalents of methyldimethoxysilane was added with respect to the allyloxy groups, and the reaction was carried out at 70 °C for 5 hours to convert the hydroxyl groups of the precursor polymer to -OCH 2 CH 2 CH 2 -Si(OCH 3 ) 2 CH 3 to obtain an oxypropylene polymer (Polymer A1) converted thereto. Table 1 shows the Mn, Mn per terminal group, Mw / Mn, Mn in terms of PS, and the average number of reactive silicon groups per terminal group of the obtained Polymer A1. The same is shown in Table 1 for the polymers obtained in the following Synthesis Examples 2 to 7.

[0067] (Synthesis Example 2: Polymer a1) Using glycerin as an initiator, propylene oxide was polymerized in the presence of a TBA-DMC catalyst in the same manner as in Synthesis Example 1 to obtain a precursor polymer having a hydroxyl group-equivalent molecular weight of 16,500. Next, in the same manner as in Synthesis Example 1, the hydroxyl groups of the precursor polymer were converted into allyloxy groups, 0.70 molar equivalents of methyldimethoxysilane was added with respect to the allyloxy groups, and the hydroxyl groups of the precursor polymer were converted to -OCH 2 CH 2 CH 2 -Si(OCH 3 ) 2 CH 3 to obtain an oxypropylene polymer (Polymer a1) converted thereto.

[0068] (Synthesis Example 3: Polymer a2) Using glycerin as an initiator, propylene oxide was polymerized in the presence of a TBA-DMC catalyst in the same manner as in Synthesis Example 1 to obtain a prepolymer having a hydroxyl group-equivalent molecular weight of 10,000. Subsequently, the hydroxyl groups of the prepolymer were converted to allyloxy groups in the same manner as in Synthesis Example 1, and 0.60 molar equivalents of methyldimethoxysilane were added to the allyloxy groups to convert the hydroxyl groups of the prepolymer to -OCH 2 CH 2 CH 2 -Si(OCH 3 ) 2 CH 3 to obtain an oxypropylene polymer (polymer a2).

[0069] (Synthesis Example 4: Polymer B1) Using propylene glycol as an initiator, propylene oxide was polymerized in the presence of a TBA-DMC catalyst to obtain a prepolymer having a hydroxyl group-equivalent molecular weight of 12,000. Subsequently, 0.97 molar equivalents of 3-isocyanatopropyltrimethoxysilane were reacted with the hydroxyl groups of the prepolymer using U860 (dioctyltin bis(isooctylthioglycolate), product name of Nitto Kasei Co., Ltd.) to convert the hydroxyl groups of the prepolymer to -OC(=O)NH-CH 2 CH 2 CH 2 Si(OCH 3 ) 3 to obtain an oxypropylene polymer (polymer B1). Polymer B1 had 0.16 mmol / g of urethane bonds.

[0070] (Synthesis Example 5: Polymer B2) Using propylene glycol as an initiator, propylene oxide was polymerized in the presence of a TBA-DMC catalyst to obtain a prepolymer having a hydroxyl group-equivalent molecular weight of 18,000. Subsequently, in the same manner as in Synthesis Example 4, 0.97 molar equivalents of 3-isocyanatopropyltrimethoxysilane were reacted with the hydroxyl groups of the prepolymer to convert the hydroxyl groups of the prepolymer to -OC(=O)NH-CH 2 CH 2 CH 2 Si(OCH 3 ) 3An oxypropylene polymer (Polymer B2) converted to [the specified form] was obtained. Polymer B2 had urethane bonds at 0.11 mmol / g.

[0071] (Synthesis Example 6: Polymer B3) Using propylene glycol as an initiator, in the presence of a TBA-DMC catalyst, propylene oxide was polymerized to obtain a prepolymer with a hydroxyl-equivalent molecular weight of 12,000. Subsequently, in the same manner as in Synthesis Example 1, the hydroxyl groups of the prepolymer were converted to allyloxy groups, and 0.75 molar equivalents of trimethoxysilane were added to the allyloxy groups, and the hydroxyl groups of the prepolymer were converted to -OCH 2 CH 2 CH 2 -Si(OCH 3 ) 3 An oxypropylene polymer (Polymer B3) was obtained. Polymer B3 did not have urethane bonds.

[0072] (Synthesis Example 7: Polymer C1) Using n-butyl alcohol as an initiator, in the presence of a TBA-DMC catalyst, propylene oxide was polymerized to obtain polyoxypropylene. The polyoxypropylene had hydroxyl groups at the terminals and a prepolymer with a hydroxyl-equivalent molecular weight of 5,000 was obtained. Subsequently, in the same manner as in Synthesis Example 1, the hydroxyl groups of the prepolymer were converted to allyloxy groups, and 0.80 molar equivalents of methyldimethoxysilane were added to the allyloxy groups, and the hydroxyl groups of the prepolymer were converted to -OCH 2 CH 2 CH 2 -Si(OCH 3 ) 2 CH 3 An oxypropylene polymer (Polymer C1) converted to [the specified form] was obtained.

[0073] [Other Components] The additives listed in Table 2 are as follows. Whiton SB: Heavy calcium carbonate, product name by Shiraishi Kogyo Co., Ltd. CCR: Colloidal calcium carbonate, white-coated CCR, product name by Shiraishi Kogyo Co., Ltd. R-820: Titanium oxide, product name by Ishihara Sangyo Co., Ltd. UP-1110: ARUFON UP-1110, an acrylic polymer with Mn = 1,500, product name of Toagosei Co., Ltd. EL3020: Excenol 3020, an oxyalkylene polymer having two hydroxyl groups per molecule and a hydroxyl equivalent molecular weight of 3,000, product name of AGC Inc. DINP: Viniser 90, diisononyl phthalate, product of Kao Corporation. N-12D: Cactus Normal Paraffin N-12D, n-dodecane, purity 98.0%, product of JXTG Energy Corporation. Sanso Sizer EPS: 4,5-epoxycyclohexane-1,2-dicarboxylic acid-di-2-ethylhexyl, product name of Shin Nippon Rika Co., Ltd. Glycerin monostearate: Reagent, manufactured by Tokyo Chemical Industry Co., Ltd. KBM-202: Diphenyldimethoxysilane, product name of Shin-Etsu Chemical Co., Ltd. IRGANOX1135: Hindered phenol antioxidant, product name of BASF SE. TINUVIN327: Benzotriazole ultraviolet absorber, product name of BASF SE. TINUVIN770: Hindered amine light stabilizer, product name of BASF SE. LA-63P: Adeka Stab LA-63P, product name of ADEKA Corporation. KBM-1003: Vinyltrimethoxysilane, product name of Shin-Etsu Chemical Co., Ltd. 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. Laurylamine: Reagent, manufactured by Junsei Chemical Co., Ltd. Farmin CS: Coconut amine, product name of Kao Corporation. U-220H: Dibutyltin bis(acetylacetonate), tin catalyst, product name of Nitto Kasei Co., Ltd.

[0074] [Adjustment of curable composition] Examples 1 to 6 and Examples 14 to 29 are examples, and Examples 7 to 13 are comparative examples.

[0075] (Examples 1 to 13) A curable composition was prepared by adding a polymer having a reactive silicon in the formulation shown in Table 3 and an additive in the formulation amount shown in Table 2. The obtained curable composition was subjected to a tensile property test and an elastic recovery test. The results are shown in Table 3.

[0076] (Examples 14 to 29) In the formulation shown in Example 1 of Table 3, the additive formulation was changed from Additive 1 shown in Table 2 to Additives 4 to 11 respectively to prepare a curable composition, and cured products of Examples 14 to 21 were obtained in the same manner as above. In the formulation shown in Example 2 of Table 3, the additive formulation was changed from Additive 1 shown in Table 2 to Additives 4 to 11 respectively to prepare a curable composition, and cured products of Examples 22 to 29 were obtained in the same manner as above. The curable compositions of Examples 14 to 29 cured well. All of the obtained cured products had good elongation and recovery in the above tensile property test and elastic recovery test.

[0077]

Table 1

[0078]

Table 2

[0079]

Table 3

[0080] As shown in Table 3, the cured products obtained in Examples 1 to 6 had short TFTs, good curability, good elongation, a high elastic recovery rate, and sufficient recovery properties were exhibited. In the cured products obtained in Examples 7, 8, and 11 that did not contain Polymer B or had a high content of a silanol condensation catalyst, the elastic recovery rate was low and sufficient recovery properties were not exhibited. Further, the cured products obtained in Examples 9 and 10 in which the number average molecular weight per terminal group of Polymer A was less than 6,000, and the cured products obtained in Examples 12 and 13 in which the mass ratio of Polymer A to Polymer B was outside the scope of the present invention had inferior elongation, breakage was observed during measurement of the recovery rate, and the recovery properties were inferior. The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2018-180111 filed on September 26, 2018 are hereby incorporated by reference herein and made a part of the disclosure of the specification of the present invention.

Claims

1. 1. A curable composition comprising: Polymer A is an oxyalkylene polymer having three or more terminal groups in one molecule, a number average molecular weight per terminal group being 6,000 or more, and having a reactive silicon group represented by the following formula (1) at the terminal group, but not having a reactive silicon group represented by the following formula (2); Polymer B is an oxyalkylene polymer having two terminal groups in one molecule and having an average of more than 0.5 and not more than 1.0 reactive silicon groups represented by the following formula (2) per terminal group: and 0.05 to 0.5 parts by mass of a silanol condensation catalyst per 100 parts by mass of the total of the polymer A and the polymer B, the mass ratio of polymer A to polymer B is 99 / 1 to 50 / 50; The content of the polymer B in the curable composition is 0.5 to 50 mass %. -SiX ａ R ３－ａ ・・・(1) [In the formula, R represents a monovalent organic group having 1 to 20 carbon atoms that does not contain a hydrolyzable group, X represents a hydroxyl group or a hydrolyzable group, and a is 1 or 2. When a is 1, R may be the same or different from one another, and when a is 2, X may be the same or different from one another.] -SiX ３ ・・・(2) [In the formula, X represents a hydroxyl group or a hydrolyzable group, and X may be the same or different.]

2. The curable composition according to claim 1, wherein the polymer A has, on average, more than 0.5 and not more than 1.0 reactive silicon groups represented by formula (1) per terminal group, and has a number average molecular weight of 18,000 to 40,000.

3. The curable composition according to claim 1 or 2, wherein the number average molecular weight of the polymer B is 5,000 to 30,000.

4. The terminal group having a reactive silicon group represented by the formula (1) in the polymer A is —OCH ２ CH ２ CH ２ -SiX ａ R ３－ａ The curable composition according to any one of claims 1 to 3,

5. The terminal group having the reactive silicon group represented by the formula (2) in the polymer B is a urethane bond (-OC(=O)NH-) and -SiX ３ or a monovalent organic group having -OCH ２ CH ２ CH ２ -SiX ３ The curable composition according to any one of claims 1 to 4,

6. The terminal group having a reactive silicon group represented by formula (2) in the polymer B is a urethane bond (-OC(=O)NH-) and -SiX ３ and the content of urethane bonds (-OC(=O)NH-) in the polymer B is 0.33 mmol / g or less.

7. The curable composition according to any one of claims 1 to 6, further comprising a polymer C which is an oxyalkylene polymer having two terminal groups in one molecule and having more than 0 and not more than 0.5 reactive silicon groups represented by the formula (1) or the formula (2) on average per terminal group.

8. The curable composition according to claim 7, wherein one of the two end groups of the polymer C is an alkoxy group.

9. The curable composition according to claim 7 or 8, wherein the reactive silicon group in the polymer C is a reactive silicon group represented by the formula (2).

10. The curable composition according to any one of claims 7 to 9, wherein the number average molecular weight of the polymer C is 2,000 to 12,000.

11. The curable composition according to any one of claims 1 to 10, which is a one-component curable composition.

12. A cured product obtained by curing the curable composition according to any one of claims 1 to 11.

13. A sealant comprising the cured product according to claim 12.

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