Hydroxyl group-containing organopolysiloxane, method for producing same, curable composition containing said organopolysiloxane, coating agent, and coated article

Abstract

Provided is a hydroxyl group-containing organopolysiloxane represented by formula (I). (SiO4 / 2) a (R1SiO3 / 2) b (R12SiO2 / 2) C (R13SiO1 / 2) d (R2O1 / 2) e (R3O1 / 2) f (I) (In the formula, R1 is a monovalent saturated hydrocarbon group or the like, R2 is a methyl group or the like, R3 is a group represented by formula (II), a, b, c and d are numbers satisfying 0 < = a < 1, 0 < b < = 1, 0 < = c < = 0.5, 0 < = d < 1, and a + b + c + d = 1, e is a number satisfying 0 < = e < = 1, and f is a number satisfying 0 < f < 4). ) # imgabs0 # (In the formula, R4 is a monovalent saturated hydrocarbon group or the like, R5 is a hydrogen atom or a monovalent saturated hydrocarbon group, X is a divalent hydrocarbon group, n is a number from 0 to 400, and * represents a bond to an oxygen atom. ).

Description

Technical Field

[0001] The present invention relates to an organopolysiloxane containing a hydroxyl group, a method for producing the same, a curable composition containing the organopolysiloxane, a coating agent, and a coated article. Background Art

[0002] Alkoxysilyl-containing organopolysiloxanes are widely used in paints and coatings. Typically, organopolysiloxanes with terminal alkoxy groups are compounded with a curing catalyst and subjected to external energy such as heat, causing the terminal alkoxy groups to react with each other, forming a strong siloxane network. The resulting films exhibit excellent heat and weather resistance, making them suitable for a wide range of applications, from outdoor structures to automotive parts and electronic components.

[0003] On the other hand, organopolysiloxane-based coatings have the advantages described above, but also have disadvantages such as slow curing speed and poor crack resistance and flex resistance of the resulting coating film.

[0004] In order to improve these disadvantages, methods of using a composition obtained by compounding an organopolysiloxane with an organic resin such as an alkyd resin, a polyester resin, or an acrylic resin as a coating material have been known (Patent Documents 1 to 4).

[0005] The most common functional group in organic resins is hydroxyl group. Hydroxyl group is a common functional group in alkyd resins, polyester resins, and acrylic resins, and polyol resins having hydroxyl group are widely available in the market.

[0006] On the other hand, branched organopolysiloxanes containing hydroxyl groups that can form strong siloxane networks are currently almost non-existent on the market. Alkoxysilanes contained in typical organopolysiloxanes undergo hydrolysis by water, and the same reaction occurs even with hydroxyl groups. Consequently, organopolysiloxanes containing hydroxyl groups have the disadvantages of concerns about their stability over time and difficulty in marketing.

[0007] Against this backdrop, Non-Patent Documents 1 and 2 propose methods for synthesizing hydroxyl-containing organopolysiloxanes by forming an organopolysiloxane into a cage-like structure, thereby eliminating the alkoxysilane in the molecule. However, this method requires the reaction to be carried out under sufficiently diluted conditions to form the organopolysiloxane into a cage-like structure, resulting in low yields and difficulty in industrialization.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 11-116683

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 5-345877

[0012] Patent Document 3: Japanese Patent No. 5384939

[0013] Patent Document 4: Japanese Patent No. 6113456

[0014] Non-patent literature

[0015] Non-patent document 1: H. Mori et al., Langmuir, 2007, 23, 17, 9014-9023

[0016] Non-patent document 2: H. Takeuchi et al., Reactive and Functional Polymers, 2017, 115, 43-52 Summary of the Invention

[0017] Problems to be solved by the invention

[0018] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydroxyl group-containing organopolysiloxane that has excellent storage stability and curability when used in a curable composition and can form a film having excellent chemical resistance and flex resistance.

[0019] Means for solving problems

[0020] The present inventors have conducted intensive studies to achieve the above-mentioned objectives and have discovered that a hydroxyl-containing organopolysiloxane represented by the following formula (I) has high storage stability, excellent curability when used in a curable composition, and can form a film having excellent chemical resistance and flex resistance. The inventors have also discovered that such a hydroxyl-containing organopolysiloxane can be obtained under specified conditions, thereby completing the present invention.

[0021] That is, the present invention provides:

[0022] 1. A hydroxyl-containing organopolysiloxane represented by the following formula (I),

[0023] [Chemistry 1]

[0024] (SiO 4 / 2 ) a (R 1 SiO 3 / 2 ) b (R 1 2SiO 2 / 2 ) c (R 1 3SiO 1 / 2 ) d (R 2 O 1 / 2 ) e (R 3 O 1 / 2 )f (I) (Where R 1 are each independently a hydrogen atom, or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms which may be substituted by a halogen atom, an aralkyl group having 7 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms, 2 is a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, R 3 It is a group represented by the following formula (II), a, b, c and d are each a number satisfying 0≤a<1, 0<b≤1, 0≤c≤0.5, 0≤d<1, and a+b+c+d=1, and e and f are each a number satisfying 0≤e≤1, 0<f<4, and 0<e+f<4.

[0025] [Chemistry 2]

[0026]

[0027] (Where R 4 are each independently a hydrogen atom, or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms which may be substituted by a halogen atom, an aralkyl group having 7 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms, 5 Each independently represents a hydrogen atom or a monovalent saturated hydrocarbon group having 1 to 8 carbon atoms, X represents a divalent hydrocarbon group having 2 to 8 carbon atoms, n represents a number from 0 to 400, and * represents a bond with an oxygen atom.

[0028] 2. The hydroxyl-containing organopolysiloxane according to 1, wherein in the formula (I), at least one R 1 is an aryl group having 6 to 18 carbon atoms;

[0029] 3. The hydroxyl-containing organopolysiloxane according to 1 or 2, wherein in the formula (I), R 1 are each independently methyl or phenyl;

[0030] 4. The hydroxyl-containing organopolysiloxane according to any one of 1 to 3, wherein in the formula (I), R 2 is methyl;

[0031] 5. The hydroxyl-containing organopolysiloxane according to any one of 1 to 4, wherein in the formula (I), b is a number satisfying 0.5≤b≤1;

[0032] 6. The hydroxyl-containing organopolysiloxane according to any one of 1 to 5, wherein in the formula (I), a and d are 0;

[0033] 7. The hydroxyl-containing organopolysiloxane according to any one of 1 to 6, wherein in the formula (II), R 4 is methyl, R5 is a hydrogen atom, X is an alkylene group having 3 carbon atoms, and n is 1;

[0034] 8. The hydroxyl group-containing organopolysiloxane according to any one of 1 to 7, wherein the polystyrene-reduced weight average molecular weight (Mw) in gel permeation chromatography is 1,000 to 500,000;

[0035] 9. A method for producing a hydroxyl group-containing organopolysiloxane according to any one of 1 to 8, comprising:

[0036] Step (α): A step of obtaining an organopolysiloxane having a SiH group by a hydrolysis and condensation reaction of an organopolysiloxane represented by the following formula (I') and a silane compound represented by the following formula (III) or an equilibration reaction using an acid catalyst of an organopolysiloxane represented by the following formula (I') and a disiloxane compound represented by the following formula (IV); and

[0037] [Chemical formula 3]

[0038] (SiO 4 / 2 ) a (R 1 SiO 3 / 2 ) b (R 1 38>2SiO 2 / 2 ) c (R 1 3SiO 1 / 2 ) d (R 2 O 1 / 2 ) g (I′)

[0039] In the formula, R 1 、R 2 、a, b, c and d are the same as above, and g is a number satisfying 0 < g < 4,

[0040] [Chemical formula 4]

[0041]

[0042] In the formula, R 4 is the same as above, R 6 is a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 4 carbon atoms,

[0043] Step (β): A step of subjecting the organopolysiloxane having a SiH group obtained in Step (α) to a hydrosilylation reaction with a compound represented by the following formula (V)

[0044] [Chemical formula 5]

[0045] It should be noted that there seems to be a small error in the original text where "R d 2 " in item ID 32 should probably be "R d 1 " for consistency. This translation is based on the provided text with the best effort to maintain the integrity and accuracy of the patent content.

[0046] Where R 5 and n are the same as above, R 7 It is a monovalent aliphatic unsaturated hydrocarbon group having 2 to 8 carbon atoms;

[0047] 10. A curable composition comprising the hydroxyl-containing organopolysiloxane according to any one of 1 to 8 and a curing agent reactive with the hydroxyl group;

[0048] 11. A coating agent comprising the curable composition according to 10;

[0049] 12. A cured film of the curable composition according to 10;

[0050] 13. A coated article comprising a substrate and the cured film according to 12 formed on at least one surface of the substrate directly or through one or more other layers.

[0051] Effects of the Invention

[0052] The hydroxyl-containing organopolysiloxane of the present invention has excellent storage stability and cures rapidly when mixed with a curing agent and applied. The resulting cured film has excellent chemical resistance and flex resistance and is therefore suitable for the production of various film-coated articles. DETAILED DESCRIPTION

[0053] The present invention will be described in detail below.

[0054] (1) Hydroxyl-containing organopolysiloxane

[0055] The hydroxyl group-containing organopolysiloxane of the present invention is represented by the following formula (I).

[0056] [Chemistry 6]

[0057] (SiO 4 / 2 ) a (R 1 SiO 3 / 2 ) b (R 1 2SiO 2 / 2 ) c (R 1 3SiO 1 / 2 ) d (R 2 O 1 / 2 ) e (R 3 O 1 / 2 ) f (I)

[0058] In formula (I), R 1Each is independently a hydrogen atom, or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms which may be substituted by a halogen atom, an aralkyl group having 7 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms.

[0059] As R 1 The monovalent saturated hydrocarbon group having 1 to 12 carbon atoms may be straight-chain, branched or cyclic. Specific examples thereof include straight-chain or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, neopentyl, n-hexyl, n-heptyl and n-octyl; and cycloalkyl groups such as cyclopentyl and cyclohexyl. Preferably, the alkyl group has 1 to 6 carbon atoms, more preferably, the alkyl group has 1 to 3 carbon atoms, and further preferably, the methyl group and ethyl group.

[0060] The aralkyl group having 7 to 20 carbon atoms is preferably an aralkyl group having 7 to 10 carbon atoms, and specific examples thereof include benzyl and phenylethyl groups.

[0061] The aryl group having 6 to 18 carbon atoms is preferably an aryl group having 6 to 10 carbon atoms. Specific examples thereof include unsubstituted aryl groups such as phenyl and naphthyl; alkylaryl groups such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl; and the like, preferably phenyl.

[0062] Among these, R 1 Preferred are methyl and phenyl.

[0063] Furthermore, in the case of the monovalent saturated hydrocarbon group, aralkyl group and aryl group, part or all of the hydrogen atoms thereof may be substituted by halogen atoms (fluorine, chlorine, bromine or iodine atoms), and specific examples thereof include chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, chlorophenyl and bromophenyl. 1 At least one of them is preferably a halogen-substituted or unsubstituted aryl group having 6 to 18 carbon atoms.

[0064] R 2 It is a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, preferably a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, more preferably a methyl group or an ethyl group, and further preferably a methyl group.

[0065] R 3 It is a group represented by the following formula (II).

[0066] [Chemistry 7]

[0067]

[0068] In formula (II), R 4Each independently represents a hydrogen atom, or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms, which may be substituted with a halogen atom. Specific examples of these monovalent saturated hydrocarbon groups, aralkyl groups, and aryl groups include the groups corresponding to the above R 1 The same groups as those exemplified in 4 Preferred are methyl, ethyl and phenyl, and more preferred are methyl.

[0069] Again, R 4 As for the monovalent saturated hydrocarbon group, aralkyl group and aryl group, part or all of the hydrogen atoms thereof may be substituted by halogen atoms. Specific examples thereof include the following: 1 The same groups as exemplified in .

[0070] R 5 Each independently represents a hydrogen atom or a monovalent saturated hydrocarbon group having 1 to 8 carbon atoms, and R 5 The monovalent saturated hydrocarbon group may be straight chain, branched or cyclic. Specific examples thereof include: 1 The groups having 1 to 8 carbon atoms are the same as those exemplified in the group. 5 A hydrogen atom or an alkyl group having 1 to 3 carbon atoms is preferred, a hydrogen atom, a methyl group or an ethyl group is more preferred, and a hydrogen atom is further preferred.

[0071] X is a divalent hydrocarbon group having 2 to 8 carbon atoms, preferably a straight-chain or branched divalent aliphatic hydrocarbon group. Specific examples thereof include alkylene groups such as ethylene, trimethylene, propylene, tetramethylene, hexamethylene, and octamethylene. Among them, alkylene groups having 2 or 3 carbon atoms are preferred, alkylene groups having 3 carbon atoms are more preferred, and trimethylene is even more preferred.

[0072] n is a number of 0 to 400, and is preferably a number of 0 to 100, more preferably 0 or 1, and further preferably 1, from the viewpoint of solubility.

[0073] As the group represented by the above formula (II), R 4 Methyl, R 5 is a hydrogen atom, X is an alkylene group having 3 carbon atoms, and n is 1.

[0074] In formula (I), a is a number satisfying 0≤a<1, and preferably satisfies 0≤a≤0.3 from the viewpoint of crack suppression effect, and more preferably a=0.

[0075] b is a number satisfying 0<b≤1, and preferably a number satisfying 0.5≤b≤1 from the viewpoint of the scratch resistance of the obtained cured product.

[0076] c is a number satisfying 0≤c≤0.5, and preferably satisfies 0≤c≤0.4, and more preferably satisfies 0≤c≤0.3, from the viewpoint of curability of the composition and hardness of the obtained cured product.

[0077] d is a number satisfying 0≤d<1, and preferably satisfies 0≤d≤0.2 from the viewpoint of curability of the composition and hardness of the obtained cured product, and more preferably d=0.

[0078] Furthermore, a, b, c, and d are numbers that satisfy a+b+c+d=1.

[0079] e is a number satisfying 0≤e≤1, and preferably a number satisfying 0≤e≤0.8 from the viewpoint of suppressing the condensation reaction caused by the condensable functional group.

[0080] f is a number satisfying 0<f<4, and preferably satisfies 0.2<f≤2, and more preferably satisfies 0.4<f≤1.1, from the viewpoint of the crosslinking density of the cured product.

[0081] Furthermore, e and f are numbers satisfying 0<e+f<4, preferably numbers satisfying 0.2<e+f≤2.8.

[0082] As the hydroxyl-containing organopolysiloxane of the present invention, it is preferred that R 1 is methyl or phenyl, R 2 is a methyl group, a is 0, b is a number satisfying 0.5≤b≤1, c is a number satisfying 0≤c≤0.5, d is 0 and a number satisfying a+b+c+d=1, e is a number satisfying 0≤e≤0.8, f is a number satisfying 0.2<f≤2, and R in the above formula (II) 4 Methyl, R 5 An organopolysiloxane containing a hydroxyl group wherein X is a hydrogen atom, X is an alkylene group having 3 carbon atoms, and n is 1.

[0083] The polystyrene-equivalent weight average molecular weight (Mw) of the hydroxyl-containing organopolysiloxane of the present invention as measured by gel permeation chromatography (GPC) is preferably 1,000 to 500,000, more preferably 1,500 to 10,000. A weight average molecular weight of 1,000 or greater provides excellent storage stability and flex resistance, while a weight average molecular weight of 500,000 or less eliminates concerns about unevenness or uneven coating during coating.

[0084] In addition, as the measurement conditions of GPC, for example, the method used in the following Examples can be adopted.

[0085] The kinematic viscosity of the hydroxyl-containing organopolysiloxane of the present invention at 25°C is preferably 5 to 2000 mm 2 / s, more preferably 20 to 1000 mm 2 / s. If 5mm2 If it is 2000 mm / s or more, the storage stability and flex resistance are more excellent. 2 If it is 2000 mm / s or less, unevenness or coating thickness non-uniformity during coating does not need to be worried about. Incidentally, the kinematic viscosity can be measured using, for example, a Cannon-Fenske viscometer.

[0086] From the viewpoints of storage stability and adhesion to a substrate, the amount of alkoxy groups in the hydroxy group-containing organopolysiloxane of the present invention is preferably 0.5 to 10% by mass relative to the organopolysiloxane.

[0087] The hydroxy group-containing organopolysiloxane of the present invention may have a single composition or may be a mixture of multiple compounds having different compositions.

[0088] (2) Method for producing hydroxy group-containing organopolysiloxane

[0089] The method for producing the hydroxy group-containing organopolysiloxane of the present invention is not particularly limited. For example, it can be obtained by a production method including the following steps (α) and (β).

[0090] (Step α): A step of obtaining an organopolysiloxane having a SiH group by a hydrolysis and condensation reaction of an organopolysiloxane represented by the following formula (I') and a silane compound represented by the following formula (III) or by an equilibration reaction using an acid catalyst of an organopolysiloxane represented by the following formula (I') and a disiloxane compound represented by the following formula (IV)

[0091] [Chemical formula 8]

[0092] (SiO 4 / 2 ) a (R 1 SiO 3 / 2 ) b (R 1 2SiO 2 / 2 ) c (R 1 3SiO 1 / 2 ) d (R 2 O 1 / 2 ) g (I′)

[0093] (In the formula, R 1 , R 2 , a, b, c, and d are the same as above, and g is a number satisfying 0 < g < 4.)

[0094] [Chemical formula 9]

[0095]

[0096] (In the formula, R4 Same as above, R 6 is a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 4 carbon atoms.

[0097] (Step β): A step of subjecting the organopolysiloxane having SiH groups obtained in the above (Step α) to a hydrosilylation reaction with a compound represented by the following formula (V):

[0098] [Chemistry 10]

[0099]

[0100] (Where R 5 and n are the same as above, R 7 It is a monovalent aliphatic unsaturated hydrocarbon group having 2 to 8 carbon atoms.

[0101] <(Process α)>

[0102] (Step α) is a step of obtaining an organopolysiloxane having a SiH group by a hydrolysis-condensation reaction of the organopolysiloxane represented by the above formula (I') and the silane compound represented by the above formula (III), or by an equilibration reaction of the organopolysiloxane represented by the above formula (I') and the disiloxane compound represented by the above formula (IV) using an acid catalyst.

[0103] In formula (I'), g is a number satisfying 0<g<4, and preferably a number satisfying 0.2<g≤2.8.

[0104] As the organopolysiloxane represented by formula (I'), R 1 is methyl or phenyl, R 2 An organopolysiloxane which is a methyl group, a is 0, b is a number satisfying 0.5≤b≤1, c is a number satisfying 0≤c≤0.5, d is 0 and a number satisfying a+b+c+d=1, and g is a number satisfying 0.2<g≤2.8.

[0105] The organopolysiloxane represented by formula (I') can be produced by a general method for producing organopolysiloxane, for example, by hydrolyzing and condensing a silane compound having a hydrolyzable group.

[0106] The silane compound having a hydrolyzable group is not particularly limited as long as it contains 1 to 4 chloro groups or alkoxy groups as hydrolyzable groups on the silicon atom and has an organic substituent that satisfies the above-mentioned conditions.

[0107] Specific examples thereof include tetrachlorosilane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiisopropoxysilane, trimethylchlorosilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylisopropoxysilane, ethyltrichlorosilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrichlorosilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrichlorosilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrichlorosilane, hexyltrimethoxysilane, hexyltriethoxysilane, benzene, Among the methylsilanes, methyltrichlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, cyclohexyltrichlorosilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, propylmethyldichlorosilane, propylmethyldimethoxysilane, propylmethyldiethoxysilane, hexylmethyldichlorosilane, hexylmethyldimethoxysilane, hexylmethyldiethoxysilane, phenylmethyldichlorosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, diphenyldichlorosilane, diphenyldimethoxysilane, diphenyldiethoxysilane, dimethylphenylchlorosilane, dimethylphenylmethoxysilane, dimethylphenylethoxysilane, and partial hydrolyzates thereof, methoxysilane and ethoxysilane are preferred from the viewpoints of handleability, ease of distillation of by-products, and ease of availability of raw materials.

[0108] The above-mentioned silane compounds may be used alone or in combination of two or more.

[0109] When performing the hydrolysis, a hydrolysis catalyst may be used. Conventionally known catalysts may be used, preferably catalysts whose aqueous solutions exhibit acidity of pH 2 to 7 (acidic catalysts), particularly preferably acidic hydrogen halides, sulfonic acids, carboxylic acids, acidic or weakly acidic inorganic salts, solid acids such as ion exchange resins, and the like.

[0110] Specific examples of the acidic catalyst include hydrogen fluoride, hydrochloric acid, nitric acid, sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, formic acid, acetic acid, maleic acid, benzoic acid, lactic acid, phosphoric acid, and cation exchange resins having sulfonic acid groups or carboxylic acid groups on their surfaces.

[0111] The amount of the hydrolysis catalyst used is not particularly limited, but is preferably 0.0002 to 0.5 mol per 1 mol of the hydrolyzable silane in consideration of rapid reaction and ease of removal of the catalyst after the reaction.

[0112] The mass ratio of the silane compound having a hydrolyzable group to the water required for the hydrolysis-condensation reaction is not particularly limited. However, in order to prevent catalyst deactivation, allow the reaction to proceed sufficiently, and facilitate removal of water after the reaction, a ratio of 0.1 to 10 mol of water per 1 mol of the hydrolyzable silane is preferred.

[0113] The reaction temperature during the hydrolysis and condensation is not particularly limited, but is preferably -10 to 150° C. in order to increase the reaction rate and prevent the decomposition of the organic functional groups. The reaction time is not particularly limited, but is preferably 0.5 to 6 hours.

[0114] Furthermore, an organic solvent may be used during the hydrolysis and condensation. Specific examples of the organic solvent include methanol, ethanol, propanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, toluene, and xylene.

[0115] In the above formula (III), R 6 Examples of the halogen atom include fluorine, chlorine, bromine, and iodine atoms, and examples of the alkoxy group having 1 to 4 carbon atoms include methoxy, ethoxy, n-propoxy, and n-butoxy. 6 A chlorine atom, a hydroxyl group, a methoxy group or an ethoxy group is preferred.

[0116] Specific examples of the silane compound represented by the above formula (III) include methoxysilane, dimethylmethoxysilane, ethoxysilane, dimethylethoxysilane, chlorosilane, dimethylchlorosilane, and dimethylhydroxysilane.

[0117] Specific examples of the disiloxane compound represented by the above formula (IV) include 1,1,3,3-tetramethyldisiloxane.

[0118] In the step of obtaining the organopolysiloxane having SiH groups by the hydrolysis-condensation reaction of the organopolysiloxane represented by the above formula (I') and the silane compound represented by the above formula (III), the conditions for the hydrolysis-condensation reaction are not particularly limited and can be carried out under the same conditions as those for the production of the organopolysiloxane represented by the above formula (I').

[0119] In this case, the ratio of the organopolysiloxane represented by the above formula (I') to the silane compound represented by the above formula (III) is not particularly limited. However, the amount of the silane compound represented by the above formula (III) is preferably 5 to 80 parts by mass, more preferably 10 to 70 parts by mass, per 100 parts by mass of the organopolysiloxane represented by the above formula (I').

[0120] The amount of the hydrolysis catalyst used is not particularly limited, but is preferably 0.0002 to 0.5 mol per 1 mol of the silane compound represented by formula (III).

[0121] The mass ratio of the hydrolyzable groups contained in the organopolysiloxane represented by formula (I') to the water required for the hydrolysis-condensation reaction is not particularly limited. Since the reaction rate can be varied depending on the amount of water added, a mass ratio that corresponds to the desired reaction rate is preferred. From the perspective of reducing the number of highly reactive alkoxy groups at the ends of the organopolysiloxane and ensuring storage stability, the reaction rate of the alkoxy groups is preferably 50 to 100%, and more preferably 60 to 100%.

[0122] On the other hand, in the step of obtaining an organopolysiloxane having SiH groups by an equilibration reaction (cleavage / recombination reaction of siloxane bonds) between the organopolysiloxane represented by the above formula (I') and the disiloxane compound represented by the above formula (IV) using an acid catalyst, the conditions for the equilibration reaction are not particularly limited. For example, the equilibration reaction can be carried out at 20 to 150°C for about 0.5 to 6 hours, preferably at 20 to 100°C for about 1 to 4 hours.

[0123] At this time, it is optional to add a solvent as needed. Examples of the solvent include alcohol solvents such as methanol, ethanol, and isopropanol; and aromatic non-polar solvents such as benzene, toluene, and xylene.

[0124] The ratio of the organopolysiloxane represented by the above formula (I') to the disiloxane compound represented by the above formula (IV) is not particularly limited. However, the disiloxane compound represented by the above formula (IV) is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, per 100 parts by mass of the organopolysiloxane represented by the above formula (I').

[0125] As the acidic catalyst for promoting the equilibration reaction, a strong acid is preferably used. The type is not particularly limited, and sulfuric acid, methanesulfonic acid, trifluoromethanesulfonic acid, etc. can be preferably used. From the perspective of ease of post-treatment, a cation exchange resin having these exchange groups is particularly preferred.

[0126] The amount of the acidic catalyst added is preferably 100 to 10,000 ppm, more preferably 500 to 3,000 ppm, relative to the total mass of the organopolysiloxane represented by the formula (I') and the disiloxane compound represented by the formula (IV).

[0127] Furthermore, during the equilibration reaction, water may be added to promote the hydrolysis-condensation reaction between the organopolysiloxane represented by formula (I') and the disiloxane compound represented by formula (IV). The amount of water used is not particularly limited, and the reaction rate can be varied depending on the amount of water added. Therefore, a mass ratio that corresponds to the desired reaction rate is preferred. To reduce the number of highly reactive alkoxy groups at the ends of the organopolysiloxane and ensure storage stability, the alkoxy group reaction rate is preferably 50-100%, and more preferably 60-100%.

[0128] <(Process β)>

[0129] (Step β) is a step of subjecting the organopolysiloxane having SiH groups obtained in the above (Step α) to a hydrosilylation reaction with the compound represented by the above formula (V) to obtain an organopolysiloxane having a hydroxyl group.

[0130] In the above formula (V), R 7 The monovalent aliphatic unsaturated hydrocarbon group has 2 to 8 carbon atoms, preferably a monovalent aliphatic unsaturated hydrocarbon group has 2 to 6 carbon atoms. Specific examples thereof include vinyl, allyl, 3-butenyl, 5-hexenyl, 7-octenyl and other alkenyl groups, preferably vinyl and allyl, and more preferably allyl.

[0131] As the compound represented by the above formula (V), in consideration of compatibility with the organopolysiloxane, vinyl alcohol, allyl alcohol, and ethylene glycol monoallyl ether are preferred, and ethylene glycol monoallyl ether is more preferred.

[0132] The amount of the compound represented by the above formula (V) used in the hydrosilylation reaction is preferably 1 mol or more per 1 mol of SiH groups in the SiH group-containing organopolysiloxane obtained in (Step α).

[0133] The hydrosilylation reaction is preferably carried out in the presence of a catalyst. As the hydrosilylation catalyst, compounds comprising platinum group metals such as platinum, rhodium, palladium can be used. Among these, compounds preferably comprising platinum include, for example, platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid, complexes of chloroplatinic acid and olefins, vinyl siloxanes, acetylenic alcohols, platinum carbonyl vinyl methyl complexes, platinum-divinyltetramethyldisiloxane complexes, platinum-cyclovinylmethylsiloxane complexes, platinum-octanal / octanol complexes, etc.

[0134] The amount added may be a so-called catalytic amount capable of promoting the addition reaction, and is usually 0.1 to 500 ppm, preferably 1 to 200 ppm, relative to the mass of the compound represented by formula (V), calculated as the mass of the platinum group metal.

[0135] The conditions for the hydrosilylation reaction are not particularly limited. For example, the reaction temperature is preferably 20 to 120° C. and the reaction time is 1 to 8 hours, and more preferably 20 to 100° C. and the reaction time is 1 to 6 hours.

[0136] Thus, the hydroxyl-containing organopolysiloxane of the present invention can be obtained by introducing SiH groups into the terminals of the hydrolyzable group-containing organopolysiloxane represented by formula (I') and then subjecting it to a hydrosilylation reaction with a hydroxyl-containing compound represented by formula (V).

[0137] (3) Curable composition

[0138] The hydroxyl group-containing organopolysiloxane of the present invention can be used as a curable composition by adding a curing agent having a substituent reactive with the hydroxyl group.

[0139] The curing agent is not particularly limited as long as it is a curing agent generally used in polyol-based coatings. Examples thereof include metal driers, polyisocyanates, amino resins such as melamine resins, benzoguanamine resins, urea-formaldehyde resins, and thiourea resins, epoxy resins, and polycarboxylic acid anhydrides, with polyisocyanates being preferred.

[0140] As the polyisocyanate, known polyisocyanates such as aromatic, aliphatic, aromatic aliphatic, and alicyclic polyisocyanates can be used. From the viewpoint of long-term outdoor use, aliphatic polyisocyanates containing aliphatic diisocyanates as a main raw material are preferred.

[0141] Examples of the aliphatic diisocyanate include tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate (hereinafter referred to as "HDI"), 2,2,4-(or 2,4,4)-trimethyl-1,6-hexamethylene diisocyanate, lysine isocyanate, isophorone diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,4-diisocyanatocyclohexane, 1,3-bis(diisocyanatomethyl)cyclohexane, and 4,4'-dicyclohexylmethane diisocyanate.

[0142] Among these, HDI is particularly preferred from the viewpoint of crack resistance of the resulting coating film and cost.

[0143] Examples of the aliphatic polyisocyanate obtained from an aliphatic diisocyanate include allophanate-type polyisocyanates, biuret-type polyisocyanates, adduct-type polyisocyanates, and isocyanurate-type polyisocyanates, and any of these can be preferably used.

[0144] Furthermore, as the above-mentioned polyisocyanate, so-called blocked polyisocyanates blocked with various blocking agents can also be used.

[0145] As blocking agents, for example, alcohols such as methanol, ethanol, and lactic acid esters; compounds containing phenolic hydroxyl groups such as phenol and salicylic acid esters; amides such as ε-caprolactam and 2-pyrrolidone; oximes such as acetone oxime and methyl ethyl ketone oxime; active methylene compounds such as methyl acetoacetate, ethyl acetoacetate, and acetylacetone; etc.

[0146] The amount of the curing agent is not particularly limited, but the ratio of the number of isocyanate groups in the curing agent to the number of hydroxyl groups in the hydroxyl-containing polysiloxane (NCO / OH) is preferably 0.5 to 1.1, more preferably 0.7 to 1.0.

[0147] The curing agent may be used alone or in combination of two or more.

[0148] The curable composition of the present invention may further contain a curing catalyst. The curing catalyst is not particularly limited as long as it is a curing catalyst generally used in organosiloxane-based coatings, but is preferably an organometallic compound, for example, metal alkoxide compounds such as Ti, Al, Zr, and Sn, metal chelate compounds, and metal ester compounds.

[0149] Specific examples of the metal alkoxide compound include aluminum alkoxides such as trimethoxyaluminum, triethoxyaluminum, tri-n-propoxyaluminum, tri-isopropoxyaluminum, tri-n-butoxyaluminum, tri-isobutoxyaluminum, tri-sec-butoxyaluminum, and tri-tert-butoxyaluminum; titanium alkoxides such as tetramethyl titanate, tetraethyl titanate, tetra-n-propyl titanate, tetra-isopropyl titanate, tetra-n-butyl titanate, tetra-isobutyl titanate, tetra-tert-butyl titanate, tetra-n-hexyl titanate, tetra-isooctyl titanate, and tetra-n-dodecyl titanate; zirconium alkoxides such as tetraethyl zirconate, tetra-n-propyl zirconate, tetra-isopropyl zirconate, tetra-n-butyl zirconate, tetra-sec-butyl zirconate, tetra-tert-butyl zirconate, tetra-n-pentyl zirconate, tetra-tert-hexyl zirconate, tetra-n-heptyl zirconate, tetra-n-octyl zirconate, and tetra-n-stearyl zirconate; and dibutyltin dibutoxide.

[0150] Specific examples of the metal chelate compound include tris(ethyl acetoacetate)aluminum, tris(n-propyl acetoacetate)aluminum, tris(isopropyl acetoacetate)aluminum, tris(n-butyl acetoacetate)aluminum, isopropoxybis(ethyl acetoacetate)aluminum, tris(acetylacetonate)aluminum, tris(propionylacetonate)aluminum, diisopropoxypropionylacetonatealuminum, acetylacetonate-bis(propionylacetonate)aluminum, monoethyl acetoacetate-bis(acetylacetonate)aluminum, di-sec-butoxyaluminum acetylacetonate, di-sec-butoxyaluminum methyl acetoacetate, mono-tert-butoxybis(methyl acetoacetate)aluminum, diisopropoxyacetylacetonate aluminum, monoethyl Aluminum chelate compounds such as acylacetonate-bis(ethyl acetoacetate)aluminum; titanium chelate compounds such as diisopropoxybis(ethyl acetoacetate)titanium, diisopropoxybis(acetylacetonate)titanium, and di-n-butoxybis(acetylacetonate)titanium; zirconium chelate compounds such as tetrakis(acetylacetonate), zirconium tetrakis(n-propyl acetoacetate), and zirconium tetrakis(ethyl acetoacetate); tin chelate compounds such as dibutyltin diacetate, dibutyltin di(2-ethylhexanoate), dibenzyltin di(2-ethylhexanoate), dibutyltin dilaurate, dibutyltin diisooctylmaleate, and dibutyltin di(acetylacetonate);

[0151] When a curing catalyst is added, the amount thereof may be an amount sufficient to cure the composition, and is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the nonvolatile component of the hydroxyl group-containing organopolysiloxane.

[0152] The curing catalyst may be used alone or in combination of two or more.

[0153] The curable composition of the present invention may contain a hydroxyl-containing compound other than the hydroxyl-containing organopolysiloxane. Specific examples of such curable compositions include, but are not limited to, polyester- or alkyd-based curable compositions comprising the hydroxyl-containing organopolysiloxane of the present invention, a polyol, and a polyacid; a polyurethane-based curable composition comprising the hydroxyl-containing organopolysiloxane of the present invention, a polyol, and a polyisocyanate; an epoxy-based curable composition comprising the hydroxyl-containing organopolysiloxane of the present invention, a polyol, and an epoxy resin; and a curable composition comprising the hydroxyl-containing organopolysiloxane of the present invention, a polyol, an etherified melamine resin, and / or a benzoguanamine resin.

[0154] Furthermore, the reaction product of the hydroxyl-containing organopolysiloxane of the present invention and a compound having a substituent reactive with a hydroxyl group and a radically polymerizable group can be used as a photocurable composition or a thermosetting composition by adding a photoradical polymerization initiator or a thermal radical polymerization initiator. Specific examples of such curable compositions include photocurable compositions comprising the reaction product of the hydroxyl-containing organopolysiloxane of the present invention and an isocyanate-containing (poly)acrylate, and a photoradical polymerization initiator.

[0155] (4) Cured films of curable compositions and coated articles

[0156] The curable composition of the present invention can be preferably used as a coating agent, and can be particularly preferably used as an exterior coating, and its application is not particularly limited. When used as a coating agent, for example, by applying the curable composition of the present invention directly or via one or more other layers to at least one side of a substrate and curing it to form a film, a coated article can be obtained having a cured film of the curable composition formed directly or via one or more other layers on at least one side of the substrate.

[0157] The substrate is not particularly limited, and examples thereof include glass, silicon wafers, metals, plastic molded bodies, ceramics, and composites thereof.

[0158] Alternatively, substrates whose surfaces have been treated with chemical conversion, corona discharge, plasma, or acid or alkali solutions may be used; and decorative plywood in which the substrate body and the surface layer are coated with different types of coatings may also be used. Examples of other layers include those obtained by coating with polyester resins, polyurethane resins, aminoalkyd resins, oil paints, spray coatings, and water-based varnishes.

[0159] The method for applying the curable composition of the present invention to a substrate can be appropriately selected from known methods. For example, various coating methods such as roll coating, rod coating, wire bar coating, spray coating, flow coating, spin coating, curtain coating, knife coating, dip coating, and brush coating can be used. The coating amount is not particularly limited, but generally, it is preferably an amount that provides a film thickness after drying of 0.1 to 1000 μm, more preferably 1 to 100 μm.

[0160] Examples of methods for curing the composition include room temperature curing and heat curing. The heating temperature is not particularly limited, but is preferably 50 to 200°C, more preferably 80 to 150°C.

[0161] Example

[0162] The present invention will be described in more detail below with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples. The kinematic viscosity is a value measured at 25°C using a Canon-Fenske viscometer, and the average composition of the organopolysiloxane is a value measured using an NMR measuring apparatus manufactured by JEOL Ltd. 1 H-NMR and 29 The values ​​are calculated from the integrated values ​​of the Si-NMR spectrum, and the weight average molecular weight (Mw) is a polystyrene-equivalent value determined by GPC (gel permeation chromatography) measurement under the following conditions.

[0163] [GPC conditions]

[0164] Device: HLC-8220 (manufactured by Tosoh Corporation)

[0165] Column: TSKgelGMHXL-L, TSKgelG4000HXL, TSKgelG2000HXL×2

[0166] Elution solvent: tetrahydrofuran (THF)

[0167] Flow rate: 1 mL / min

[0168] Detector: RI

[0169] Column thermostat temperature: 40°C

[0170] Standard material: polystyrene

[0171] [1] Synthesis of hydroxyl-containing organopolysiloxane

[0172] Organopolysiloxanes of Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-3 were produced using the following organopolysiloxanes A to D as raw materials.

[0173] <Raw material: organopolysiloxane>

[0174] Organopolysiloxane A: In the above formula (I'), a=0, b=0.6, c=0.4, d=0, g=1.1, R 1 Indicated by methyl, phenyl, R 2 Organopolysiloxane represented by methyl group (weight average molecular weight 1500, kinematic viscosity 100mm 2 / s)

[0175] Organopolysiloxane B: In the above formula (I'), a=0, b=0.9, c=0.1, d=0, g=1.3, R 1 Indicated by methyl, phenyl, R 2 Organopolysiloxane represented by methyl group (weight average molecular weight 1800, kinematic viscosity 70mm 2 / s)

[0176] Organopolysiloxane C: In the above formula (I'), a=0, b=1, c=0, d=0, g=1.3, R 1 Indicated by methyl, phenyl, R 2 Organopolysiloxane represented by methyl group (weight average molecular weight 1000, kinematic viscosity 30mm 2 / s)

[0177] Organopolysiloxane D: In the above formula (I'), a=0, b=0, c=1, d=0, g=0.2, R 1 In terms of methyl, R 2 Organopolysiloxane represented by methyl group (weight average molecular weight 350, kinematic viscosity 2.5mm 2 / s)

[0178] [Example 1-1]

[0179] In a 500 mL separable flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, 100 parts by mass of organopolysiloxane A, 55 parts by mass of tetramethyldisiloxane, 35 parts by mass of methanol, and 2 parts by mass of a strongly acidic cation exchange resin (LEWATITK2629 manufactured by LANXESS) were added, and 11 parts by mass of water was added dropwise while stirring. After stirring at 25°C for 3 hours, the resulting reaction solution was filtered. Next, the fraction was removed by vacuum distillation (90°C, 1.3 kPa). 1 H-NMR and 29 The reaction rate of Si-OCH3 groups calculated from the integrated value of the Si-NMR detection spectrum was 80%.

[0180] Furthermore, 0.1 parts by mass of a 1,3-divinyltetramethyldisiloxane complex of Pt(0) and 64 parts by mass of ethylene glycol monoallyl ether were added thereto, and after heating at 80°C for 4 hours, unreacted ethylene glycol monoallyl ether was removed by distillation under reduced pressure (90°C, 1.3 kPa), thereby obtaining an organopolysiloxane containing hydroxyl groups (yield 150 parts by mass).

[0181] [Examples 1-2 to 1-5, Comparative Examples 1-1 to 1-3]

[0182] Except that the raw material organopolysiloxane was changed to the substance shown in Table 1 and the reaction rate of the Si-OCH3 group was changed by using the same recipe as Example 1-1, Examples 1-2 to 1-5 and Comparative Examples 1-1 to 1-3 were prepared with hydroxyl-containing organopolysiloxanes.

[0183] The values ​​of e and f in formula (I), the weight average molecular weight (Mw), and the stability of the obtained organopolysiloxane are shown in Table 1. Regarding stability, when the organopolysiloxane was heated in a dryer at 50°C for 10 days and showed no significant increase in viscosity or gelation, it was evaluated as "OK", and when it showed an increase in viscosity or gelation, it was evaluated as "NG".

[0184] [Table 1]

[0185]

[0186] [2] Preparation of curable composition

[0187] [Examples 2-1 to 2-5, Comparative Examples 2-1 to 2-4]

[0188] The organopolysiloxanes obtained in Examples 1-1 to 1-5 and Comparative Example 1-3, the organopolysiloxane A, the organopolysiloxane B, the following curing agent, and the curing catalyst were mixed at 25° C. in the composition ratio (mass ratio) shown in Table 2 to prepare curable compositions.

[0189] Curing agent

[0190] Curing agent A: DURANATE TPA100 (polyisocyanate curing agent, isocyanate content 23.2% by mass, manufactured by Asahi Kasei Corporation)

[0191] Curing agent B: Burnock DN-901S (polyisocyanate curing agent, isocyanate content 23.1% by mass, manufactured by DIC Corporation)

[0192] Curing catalyst

[0193] Curing catalyst A: NEOSTANN U-810 (dioctyltin, manufactured by Nitto Kasei Co., Ltd.)

[0194] Curing catalyst B: ORGATIX TC-750 (titanium-based catalyst, manufactured by Matsumoto Fine Chemical Co., Ltd.)

[0195] [3] Preparation of cured film

[0196] The resulting curable composition was applied to a polished steel plate that had been surface-oiled using a bar coater to a thickness of 10 μm. The film was then left to stand at 23°C and 50% RH for 7 days to produce a cured film. The resulting cured film was evaluated for solvent resistance and flex resistance. The results are shown in Table 2.

[0197] (1) Solvent resistance

[0198] Acetone was immersed in BEMCOT M-3II (manufactured by Asahi Kasei Corporation, area 4 cm 2 ), rubbed the surface with a load of 500 gf 30 times, and the coating appearance was visually evaluated. After the friction test, the coating appearance was marked as 0 if no change was observed compared to the appearance before the test, and marked as x if the coating peeled off or turned white.

[0199] (2) Bending resistance

[0200] The bending resistance was tested according to the cylindrical mandrel method (JIS K5600-5-1: 1999). In the bending resistance test using a cylindrical mandrel with a diameter of 6 mm, a value of ◯ was given when no cracks or peeling occurred in the appearance, and a value of × was given when cracks or peeling occurred.

[0201] [Table 2]

[0202]

[0203] As shown in Table 2, it was found that the cured films of the curable compositions of Examples 2-1 to 2-5 were excellent in solvent resistance and exhibited high flex resistance.

[0204] On the other hand, it was found that the cured films obtained from the compositions of Comparative Examples 2-1 and 2-2, which used organopolysiloxanes that did not sufficiently contain hydroxyl groups, had poor solvent resistance and did not fully cure even with the use of a polyisocyanate curing agent. Furthermore, in Comparative Examples 2-3 and 2-4, which cured organopolysiloxanes that did not sufficiently contain hydroxyl groups by increasing the amount of a condensation curing catalyst, the cured films had sufficient solvent resistance but poor flex resistance.

Claims

1. A hydroxyl-containing organopolysiloxane represented by the following formula (I), [Chemistry 1] (SiO 4 / 2 ) a (R 1 SiO 3 / 2 ) b (R 1 2SiO 2 / 2 ) c (R 1 3SiO 1 / 2 ) d (R 2 O 1 / 2 ) e (R 3 O 1 / 2 ) f (I) Where R 1 are each independently a hydrogen atom, or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms which may be substituted by a halogen atom, an aralkyl group having 7 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms, 2 is a hydrogen atom, a methyl group, an ethyl group, an n-propyl group or an isopropyl group, R 3 is a group represented by the following formula (II), a, b, c and d are each a number satisfying 0≤a<1, 0<b≤1, 0≤c≤0.5, 0≤d<1, and a+b+c+d=1, and e and f are each a number satisfying 0≤e≤1, 0<f<4, and 0<e+f<4, [Chemistry 2] Where R 4 are each independently a hydrogen atom, or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms which may be substituted by a halogen atom, an aralkyl group having 7 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms, 5 Each independently represents a hydrogen atom or a monovalent saturated hydrocarbon group having 1 to 8 carbon atoms, X represents a divalent hydrocarbon group having 2 to 8 carbon atoms, n represents a number from 0 to 400, and * represents a bond with an oxygen atom.

2. The hydroxyl-containing organopolysiloxane according to claim 1, wherein In the formula (I), at least one R 1 It is an aryl group having 6 to 18 carbon atoms.

3. The hydroxyl-containing organopolysiloxane according to claim 1 or 2, wherein In the formula (I), R 1 Each is independently a methyl group or a phenyl group.

4. The hydroxyl-containing organopolysiloxane according to any one of claims 1 to 3, wherein In the formula (I), R 2 It is a methyl group.

5. The hydroxyl-containing organopolysiloxane according to any one of claims 1 to 4, wherein In the above formula (I), b is a number satisfying 0.5≤b≤1.

6. The hydroxyl-containing organopolysiloxane according to any one of claims 1 to 5, wherein In the formula (I), a and d are 0.

7. The hydroxyl-containing organopolysiloxane according to any one of claims 1 to 6, wherein In the formula (II), R 4 is methyl, R 5 is a hydrogen atom, X is an alkylene group having 3 carbon atoms, and n is 1.

8. The hydroxyl group-containing organopolysiloxane according to any one of claims 1 to 7, wherein The polystyrene-equivalent weight average molecular weight Mw in gel permeation chromatography is 1,000 to 500,000.

9. The method for producing a hydroxyl-containing organopolysiloxane according to any one of claims 1 to 8, comprising: (Step α): a step of obtaining an organopolysiloxane having a SiH group by a hydrolysis-condensation reaction of an organopolysiloxane represented by the following formula (I') and a silane compound represented by the following formula (III), or an equilibration reaction of an organopolysiloxane represented by the following formula (I') and a disiloxane compound represented by the following formula (IV) using an acid catalyst; and [Chemistry 3] (SiO 4 / 2 ) a (R 1 SiO 3 / 2 ) b (R 1 2SiO 2 / 2 ) c (R 1 3SiO 1 / 2 ) d (R 2 O 1 / 2 ) g (I') (Where R 1 、R 2 , a, b, c, and d are the same as above, and g is a number satisfying 0<g<4.) [Chemistry 4] (Where R 4 Same as above, R 6 is a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 4 carbon atoms. (Step β): a step of subjecting the organopolysiloxane having SiH groups obtained in the above (Step α) to a hydrosilylation reaction with a compound represented by the following formula (V); [Chemistry 5] (Where R 5 and n are the same as above, R 7 It is a monovalent aliphatic unsaturated hydrocarbon group having 2 to 8 carbon atoms. 10 . A curable composition comprising the hydroxyl group-containing organopolysiloxane according to claim 1 and a curing agent reactive with the hydroxyl group.

11. A coating agent comprising the curable composition according to claim 10. 12 . A cured film of the curable composition according to claim 10 .

13. A coated article comprising a substrate and the cured film according to claim 12 formed on at least one surface of the substrate directly or through one or more other layers.

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