Organopolysiloxane aqueous dispersion, method for producing organopolysiloxane aqueous dispersion, coating agent, cured object, and coated article

Abstract

An organopolysiloxane aqueous dispersion containing (A) an organopolysiloxane represented by formula (I) in an amount of 100 parts by mass, (B) a basic compound in such an amount that the pH becomes 7-10, and (C) water in an amount of 50-1000 parts by mass has high stability and excellent curability. (R1 represents a hydrogen atom, a monovalent saturated hydrocarbon group, an organic group having a radically polymerizable functional group, an aryl group, or an aralkyl group; R2 represents a monovalent group having a carboxylic anhydride structure, a carboxylic acid structure or a carboxylate structure; R3 represents a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, or an isopropyl group; a, b, c, d, and e are numerical values satisfying the formulae 0 ≤ a < 1, 0 < b < 1, 0 < c ≤ 0.4, 0 ≤ d < 1, 0 ≤ e < 1, and a + b + c + d + e = 1; and f is a numerical value satisfying the formula 0 < f < 4.)

Description

Aqueous organopolysiloxane dispersion, method for producing aqueous organopolysiloxane dispersion, coating agent, cured product, and coated article

[0001] The present invention relates to an aqueous organopolysiloxane dispersion, a method for producing the aqueous organopolysiloxane dispersion, a coating agent, a cured product, and a coated article.

[0002] Organopolysiloxane resins containing silanol groups are widely used in paints and coatings. Generally, when external energy such as heat energy is applied to organopolysiloxane resins, the terminal silanol groups react with each other to form a strong siloxane network. The resulting coating has excellent heat resistance and weather resistance, so it can be applied to a wide range of surfaces, from outdoor structures to automotive parts and electronic components.

[0003] On the other hand, while organopolysiloxane-based paints have the above advantages, they are solids or highly viscous liquids when used alone, so they must be diluted with a solvent before use, and they also have the disadvantage of being slow to cure and requiring high-temperature heating. In order to overcome these disadvantages, studies have been conducted on weak solvent dilution, aqueous dispersions, and low-temperature curing of organopolysiloxane resins.

[0004] For example, Patent Document 1 reports that replacing conventional toluene-xylene-based solvents with acetate-based solvents for TX-solvent-free, environmentally friendly, solvent-diluted resins eliminates TX solvents and improves curing properties. Patent Document 2 reports that a water dispersion of silicone resin is obtained by reacting a relatively low-molecular-weight organopolysiloxane with a cationic alkoxysilane, but this results in low curing properties and poor solvent resistance for the resulting cured coating. Patent Document 3 reports that combining two or more organopolysiloxanes with different molecular weights and adding a catalyst allows curing at temperatures as low as 100°C. However, the need for a catalyst for low-temperature curing makes industrialization difficult from the standpoint of pot life.

[0005] Japanese Patent Application Laid-Open No. 2021-172706 Japanese Patent Application Laid-Open No. 2013-515154 Japanese Patent Application Laid-Open No. 2021-172707

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an aqueous organopolysiloxane dispersion that is highly stable and has excellent curability.

[0007] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that an aqueous organopolysiloxane dispersion containing an organopolysiloxane having a cyclic carboxylic acid anhydride structure, or a carboxylic acid structure, a carboxylate structure, or a carboxylic acid derivative structure formed by ring-opening of the cyclic carboxylic acid anhydride structure, and a basic compound, and satisfying a specific pH range, has high dispersion stability, can be cured at room temperature to form a cured film, and the cured film has excellent solvent resistance, thereby completing the present invention.

[0008] That is, the present invention provides: 1. an aqueous organopolysiloxane dispersion comprising: (A) 100 parts by mass of an organopolysiloxane represented by the following formula (I), (B) a basic compound in an amount that results in a pH of 7 to 10, and (C) 50 to 1,000 parts by mass of water; (In the formula, R 1 each independently represents a hydrogen atom, or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms, which may be substituted with a halogen atom, an organic group having 2 to 12 carbon atoms and which has a radically polymerizable functional group, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms; R 2 each independently represents a monovalent group having a carboxylic anhydride structure, a carboxylic acid structure, or a carboxylate structure; R 3 each independently represents a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, and a, b, c, d, and e are numbers that satisfy 0≦a<1, 0<b<1, 0<c≦0.4, 0≦d<1, 0≦e<1, and a+b+c+d+e=1, and f is a number that satisfies 0<f<4.) 2. The R 2is a monovalent group having a succinic anhydride structure, a succinic acid structure, or a succinate structure, 3. The organopolysiloxane aqueous dispersion of 1, wherein in formula (I), b, d, and e satisfy 0.5≦b<1, 0≦d<0.5, and 0≦e<0.5, 4. The organopolysiloxane aqueous dispersion of 1, wherein the component (A) has a weight average molecular weight (Mw) of 1,000 to 500,000 in terms of polystyrene measured by gel permeation chromatography, 5. The organopolysiloxane aqueous dispersion of 1, wherein the basic compound of the component (B) is an amine compound, 6. The organopolysiloxane aqueous dispersion of 1, wherein the amount of surfactant is 1% by mass or less based on the total mass, 7. The organopolysiloxane aqueous dispersion of 1, wherein the amount of organic solvent is 5% by mass or less based on the total mass, 8. 8. A method for producing an aqueous organopolysiloxane dispersion according to any one of 1 to 7, comprising the following (Step α) to (Step γ): (Step α): a step of co-hydrolytic condensing a silane mixed containing a silane compound represented by the following formula (III) or a hydrolysis condensate thereof, and a silane compound represented by the following formula (IV) to obtain an organopolysiloxane having at least one of a cyclic carboxylic acid anhydride structure and a carboxylic acid structure formed by ring-opening thereof; 1 Si(OR 3 )3 (III) R 4 Si(OR 3 )3 (IV) (wherein, R 1 and R 3 has the same meaning as above, and R 4each independently represent a monovalent group having a cyclic carboxylic acid anhydride structure.) (Step β): a step of mixing the organopolysiloxane having at least one of the cyclic carboxylic acid anhydride structure or a carboxylic acid structure formed by ring-opening the cyclic carboxylic acid anhydride structure obtained in (Step α) above with a basic compound to obtain a mixture; (Step γ): a step of dispersing the mixture obtained in (Step β) above in water to obtain an aqueous organopolysiloxane dispersion. 9. A curable silicone composition comprising the aqueous organopolysiloxane dispersion of any of Items 1 to 7; 10. A coating agent comprising the aqueous organopolysiloxane dispersion of any of Items 1 to 7; 11. A cured product of the curable silicone composition of Items 9; 12. A coated article having a substrate and the cured product of Items 11 formed on at least one surface of the substrate directly or via one or more other layers.

[0009] The aqueous organopolysiloxane dispersion of the present invention has excellent dispersion stability and excellent curing properties, so that curing proceeds rapidly even at room temperature, and the resulting cured film has excellent solvent resistance, making it suitable for producing a variety of coated articles.

[0010] The present invention will be described in detail below. [1] Organopolysiloxane aqueous dispersion The organopolysiloxane aqueous dispersion of the present invention contains (A) an organopolysiloxane represented by the following formula (I), (B) a basic compound, and (C) water, and exhibits a pH of 7 to 10.

[0011] (A) Organopolysiloxane The organopolysiloxane of component (A) is represented by the following formula (I).

[0012]

[0013] In formula (I), R 1 are each independently a hydrogen atom, or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms, an organic group having 2 to 12 carbon atoms and a radically polymerizable functional group, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, which may be substituted with a halogen atom.

[0014] The monovalent saturated hydrocarbon group having 1 to 12 carbon atoms may be linear, branched, or cyclic. Specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, neopentyl, n-hexyl, cyclohexyl, n-heptyl, and n-octyl groups. An alkyl group having 1 to 3 carbon atoms is preferred, with methyl and ethyl being more preferred. Examples of organic groups having 2 to 12 carbon atoms and a radically polymerizable functional group include vinyl, allyl, 3-acryloyloxypropyl, and 3-methacryloyloxypropyl groups. Examples of aryl groups having 6 to 18 carbon atoms include unsubstituted aryl groups such as phenyl and naphthyl; and alkylaryl groups such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl. Phenyl is preferred. Examples of the aralkyl group having 7 to 20 carbon atoms include a benzyl group and a phenylethyl group.

[0015] In addition, some or all of the hydrogen atoms of the alkyl group, organic group, aryl group and aralkyl group may be substituted with halogen atoms (fluorine, chlorine, bromine, iodine atoms), and specific examples thereof include a chloromethyl group, a chloropropyl group, a bromoethyl group, a trifluoropropyl group, a chlorophenyl group, and a bromophenyl group.

[0016] In formula (I), R 2are each independently a monovalent group having a carboxylic acid anhydride structure, a carboxylic acid structure, or a carboxylate structure. Examples of the carboxylic acid anhydride structure include a succinic anhydride structure, a maleic anhydride structure, a phthalic anhydride structure, a cyclopentanedicarboxylic anhydride structure, a cyclohexanedicarboxylic anhydride structure, a norbornanedicarboxylic anhydride structure, and a norbornenedicarboxylic anhydride structure, with a succinic anhydride structure being preferred. Examples of the carboxylic acid structure include a hydrocarbon group containing one or more carboxy groups, preferably 1 to 4, and more preferably 2, carboxy groups. Preferred examples include a succinic acid structure, a maleic acid structure, a phthalic acid structure, a cyclopentanedicarboxylic acid structure, a cyclohexanedicarboxylic acid structure, a norbornanedicarboxylic acid structure, and a norbornenedicarboxylic acid structure, which are ring-opened versions of the above-mentioned carboxylic acid anhydride structure, with a succinic acid structure being more preferred. The monovalent group having a carboxylic acid structure may also have an amide bond, a urethane bond, a urea bond, or the like. Specific examples of such groups include those represented by the following formulas:

[0017] (In the formula, the wavy line represents a bond.)

[0018] Examples of the carboxylate structure include salts of a carboxy group contained in the carboxylic acid structure and a basic compound (B) described below, and particularly preferred are salts of a succinic acid structure and an amine compound. 2 The structure represented by the formula (I) may contain a carboxylic acid derivative structure such as a carboxylic acid amide or carboxylic acid ester produced by reaction of a carboxylic acid anhydride structure with an amine, alcohol, or the like.

[0019] R 2 is preferably a group represented by the following formula (II).

[0020] (In the formula, * represents a bond to a silicon atom.)

[0021] In formula (II), X is a linear or branched divalent hydrocarbon group having 1 to 40 carbon atoms which may contain oxygen, nitrogen, sulfur, or silicon atoms; Z 1is a cyclic carboxylic acid anhydride structure, or a carboxylic acid structure or carboxylate structure formed by ring-opening the cyclic carboxylic acid anhydride structure.

[0022] The divalent hydrocarbon group having 1 to 40 carbon atoms for X may contain an ether bond, an amide bond, a urethane bond, a urea bond, a sulfide bond, or the like, and is preferably an alkylene group or (poly)oxyalkylene group having 1 to 10 carbon atoms, more preferably methylene, ethylene, trimethylene, propylene, tetramethylene, hexamethylene, octamethylene, or the like, and even more preferably an ethylene group or a trimethylene group.

[0023] Z 1 Examples of the cyclic carboxylic acid anhydride structure include a succinic anhydride structure, a maleic anhydride structure, a phthalic anhydride structure, a cyclopentanedicarboxylic acid anhydride structure, a cyclohexanedicarboxylic acid anhydride structure, a norbornanedicarboxylic acid anhydride structure, and a norbornenedicarboxylic acid anhydride structure, and the succinic anhydride structure is preferred.

[0024] In formula (I), R 3 are each independently a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, and are preferably a hydrogen atom, a methyl group, or an ethyl group.

[0025] a, b, c, d, and e are numbers that satisfy 0≦a<1, 0<b<1, 0<c≦0.4, 0≦d<1, 0≦e<1, and a+b+c+d+e=1, respectively. a is a number that satisfies 0≦a<1, but from the viewpoint of crack suppression effect, a number that satisfies 0≦a≦0.3 is preferred, and a=0 is more preferred. b is a number that satisfies 0<b<1, but from the viewpoint of the scratch resistance of the obtained cured product, a number that satisfies 0.5<b<1 is preferred. c is a number that satisfies 0<c≦0.4, but from the viewpoint of water dispersibility and stability, a number that satisfies 0.03≦c≦0.2 is preferred. d is a number that satisfies 0≦d<1, but from the viewpoint of the curability of the composition and the hardness of the obtained cured product, a number that satisfies 0≦d≦0.5 is preferred, and 0≦d≦0.2 is more preferred. Although e is a number that satisfies 0≦e<1, from the viewpoint of the curability of the composition and the hardness of the obtained cured product, it is preferably a number that satisfies 0≦e≦0.5, and more preferably a number that satisfies 0≦e≦0.2. Although f is a number that satisfies 0<f<4, from the viewpoint of the crosslink density of the cured product, it is preferably a number that satisfies 0<f≦2, and more preferably a number that satisfies 0.1<f≦1.1.

[0026] The weight average molecular weight (Mw) of component (A) measured by gel permeation chromatography (GPC) in terms of polystyrene is preferably 1,000 to 500,000, more preferably 1,500 to 20,000, and even more preferably 2,000 to 3,000. When the weight average molecular weight is 1,000 or more, the aqueous dispersion exhibits excellent storage stability, coatability, and film-forming properties, while when it is 500,000 or less, the occurrence of unevenness and coating irregularities during coating can be suppressed. Note that the GPC measurement conditions can be, for example, the methods used in the examples below.

[0027] (B) Basic Compound The basic compound of component (B) may be, but is not limited to, alkali metal carbonates, alkali metal bicarbonates, alkali metal hydroxides, alkaline earth metal hydroxides, amine compounds, etc., with amine compounds being preferred. Specific examples of alkali metal carbonates include Na2CO3 and K2CO3. Specific examples of alkali metal bicarbonates include NaHCO3 and KHCO3. Specific examples of alkali metal hydroxides include NaOH and KOH. Specific examples of alkaline earth metal hydroxides include Ca(OH)2 and Mg(OH)2. Specific examples of amine compounds include ammonia, monoethanolamine, diethanolamine, triethanolamine, benzylamine, methylbenzylamine, dimethylbenzylamine, methyldiethanolamine, dimethylethanolamine, triethylamine, tributylamine, dibutylamine, etc.

[0028] The amount of basic compound added is an amount that results in a pH of the aqueous phase of 7 to 10, preferably 7 to 9, and is preferably 0.5 to 25 parts by mass per 100 parts by mass of organopolysiloxane. If the amount is 0.5 parts by mass or more, an aqueous dispersion that is excellent in dispersibility in water and stability can be obtained, while if the amount is 25 parts by mass or less, there is little risk of the pH becoming too basic. Note that the pH is a measurement value in accordance with JIS Z8802, as shown in the examples below.

[0029] (C) Water There are no particular restrictions on the water used, but from the perspective of dispersion stability of the aqueous dispersion, it is preferable to use deionized water with a pH of 6 to 8. The amount of water added is 50 to 1,000 parts by mass per 100 parts by mass of the organopolysiloxane of component (A); if less than 50 parts by mass, the stability of the aqueous dispersion may decrease, and if more than 1,000 parts by mass, the film-forming properties may be insufficient.

[0030] The aqueous dispersion of the present invention may contain a solvent miscible with water, such as alcohols such as methanol, ethanol, 2-propanol, etc. From the viewpoint of environmental load, when an organic solvent is used, the amount thereof is preferably more than 0% by mass and not more than 5% by mass relative to the total mass of the aqueous dispersion.

[0031] From the viewpoints of stability and film-forming ability, the aqueous dispersion of the present invention preferably has a non-volatile content of 5 to 70 mass% relative to the total aqueous dispersion. The non-volatile content is a value measured in accordance with JIS C2133, as will be shown in the Examples below. The aqueous dispersion of the present invention may contain a surfactant. In this case, from the viewpoint of film-forming ability, the amount of the surfactant is preferably more than 0 mass% and 1 mass% or less relative to the total aqueous dispersion.

[0032] [2] Method for Producing Aqueous Organopolysiloxane Dispersion The method for producing the aqueous organopolysiloxane dispersion of the present invention is not particularly limited, and it can be obtained, for example, by a production method including the following (Step α), (Step β), and (Step γ): (Step α): a step of obtaining an organopolysiloxane having at least one of a cyclic carboxylic acid anhydride structure and a carboxylic acid structure formed by ring-opening thereof by a co-hydrolysis condensation reaction of a silane compound represented by the following formula (III) or its hydrolysis condensate, and a mixed silane containing a silane compound represented by the following formula (IV): 1 Si(OR 3 )3 (III) R 4 Si(OR 3 )3 (IV) (wherein, R 1 and R 3 has the same meaning as above, and R 4 are each independently a monovalent group having a cyclic carboxylic acid anhydride structure. (Step β): A step of mixing the organopolysiloxane having at least one of the cyclic carboxylic acid anhydride structure and a carboxylic acid structure formed by ring-opening thereof obtained in (Step α) above with a basic compound to obtain a mixture. (Step γ): A step of dispersing the mixture obtained in (Step β) above in water to obtain an aqueous dispersion of organopolysiloxane.

[0033] <(Step α)> (Step α) is a step of obtaining an organopolysiloxane having at least one of a cyclic carboxylic acid anhydride structure and a carboxylic acid structure formed by ring-opening thereof, by a co-hydrolysis and condensation reaction of a silane mixed containing a silane compound represented by formula (III) above or a hydrolysis condensate thereof, and a silane compound represented by formula (IV) above.

[0034] In formula (III), R 1 and R 3 Specific examples of the silane compound represented by the formula (III) include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, octadecyltrimethoxysilane, silane, Examples thereof include cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, styryltrimethoxysilane, styryltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, and 3,3,3-trifluoropropyltrimethoxysilane.

[0035] In the above formula (IV), R 3 Specific examples of R include the same groups as those exemplified in formula (I). 4 is a monovalent group having a cyclic carboxylic acid anhydride structure, and is preferably a group represented by the following formula (V):

[0036] (In the formula, * represents a bond to a silicon atom.)

[0037] In formula (V), X is a linear or branched divalent hydrocarbon group having 1 to 40 carbon atoms which may contain oxygen, nitrogen, sulfur or silicon atoms; Z 2 represents a cyclic carboxylic acid anhydride structure.

[0038] The divalent hydrocarbon group having 1 to 40 carbon atoms for X may contain an ether bond, an amide bond, a urethane bond, a urea bond, a sulfide bond, or the like, and is preferably an alkylene group or (poly)oxyalkylene group having 1 to 10 carbon atoms, more preferably methylene, ethylene, trimethylene, propylene, tetramethylene, hexamethylene, octamethylene, or the like, and even more preferably an ethylene group or a trimethylene group.

[0039] Z 2 Examples of the cyclic carboxylic acid anhydride structure include a succinic anhydride structure, a maleic anhydride structure, a phthalic anhydride structure, a cyclopentanedicarboxylic acid anhydride structure, a cyclohexanedicarboxylic acid anhydride structure, a norbornanedicarboxylic acid anhydride structure, and a norbornenedicarboxylic acid anhydride structure, and the succinic anhydride structure is preferred.

[0040] Specific examples of the silane compound represented by formula (IV) include 3-trimethoxysilylpropyl succinic anhydride, 3-triethoxysilylpropyl succinic anhydride, 3-trimethoxysilylpropyl phthalic anhydride, 3-triethoxysilylpropyl phthalic anhydride, 3-trimethoxysilylpropyl cyclohexyl dicarboxylic anhydride, and 3-triethoxysilylpropyl cyclohexyl dicarboxylic anhydride.

[0041] The amount of the silane compound represented by the formula (IV) is 0.4 times or less by mole relative to the number of moles of silicon atoms in the entire silane mixture, and from the viewpoints of water dispersibility and stability, it is preferably 0.03 to 0.2 times by mole.

[0042] In (step α), the silane mixture used in the co-hydrolysis-condensation reaction may contain a silane compound other than the silane compounds represented by formula (III) and formula (IV) above, or a hydrolysis-condensation product thereof. Specific examples thereof include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, dimethylphenylmethoxysilane, dimethylphenylethoxysilane, and hydrolysis-condensation products thereof.

[0043] The conditions for the hydrolysis condensation reaction are not particularly limited, but the reaction can be carried out, for example, at 20 to 150° C. for about 0.5 to 6 hours, preferably at 20 to 100° C. for about 1 to 4 hours.

[0044] In this case, a solvent can be added as necessary. Examples of the solvent include alcohol solvents such as methanol, ethanol, and isopropyl alcohol, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, and aromatic nonpolar solvents such as benzene, toluene, and xylene.

[0045] An acidic catalyst may also be used to promote the hydrolysis reaction. A strong acid is preferred as the acidic catalyst, and although any type is acceptable, sulfuric acid, methanesulfonic acid, trifluoromethanesulfonic acid, etc. are suitable. From the perspective of ease of post-treatment, cation exchange resins having these exchange groups are particularly preferred. The amount of acidic catalyst added is preferably 100 to 10,000 ppm, more preferably 500 to 3,000 ppm, based on the total mass of the mixed silanes.

[0046] After the hydrolysis reaction, distillation under reduced pressure may be carried out. The conditions for distillation under reduced pressure are not particularly limited, but from the viewpoint of stability, it is preferable to carry out the distillation under reduced pressure at 20 to 120°C for about 0.5 to 4 hours.

[0047] <(Step β)> (Step β) is a step of mixing the organopolysiloxane having at least one of a cyclic carboxylic acid anhydride structure or a carboxylic acid structure formed by ring-opening thereof obtained in (Step α) above with a basic compound to obtain a mixture. Examples of basic compounds include those exemplified above as component (B). There are no particular restrictions on the conditions for mixing, but, for example, mixing at 20 to 70°C for 5 minutes to 4 hours is preferred, and mixing at 20 to 60°C for 10 minutes to 2 hours is more preferred.

[0048] The amount of basic compound added is an amount that will give an aqueous phase pH of 7 to 10, preferably 7 to 9, after (step γ) described below, and is preferably 0.5 to 25 parts by mass per 100 parts by mass of organopolysiloxane. If the amount is 0.5 part by mass or more, an aqueous dispersion that is excellent in dispersibility in water and stability will be obtained, and if the amount is 25 parts by mass or less, there is little risk of the pH becoming too basic.

[0049] <(Step γ)> (Step γ) is a step in which the mixture obtained in (Step β) above is dispersed in water to obtain an aqueous dispersion of organopolysiloxane. There are no particular restrictions on the dispersion method, and any known method can be used. Specific examples include methods using a paint shaker, ball mill, homogenizer, or the like at 20 to 80°C.

[0050] The amount of water used is 50 to 1,000 parts by mass relative to 100 parts by mass of the organopolysiloxane obtained in (Step α) above. If the amount is less than 50 parts by mass, the stability of the aqueous dispersion may decrease, and if the amount is more than 1,000 parts by mass, the film-forming properties may be insufficient.

[0051] Furthermore, after (Step γ), vacuum distillation may be carried out. By carrying out vacuum distillation, the amount of by-produced alcohol and unreacted low-molecular-weight components in the system can be reduced. The conditions for vacuum distillation are not particularly limited, but from the viewpoint of stability, it is preferable to carry out the distillation under conditions of 20 to 120°C for about 0.5 to 4 hours.

[0052] [3] Curable Silicone Compositions and Coating Agents The aqueous organopolysiloxane dispersions of the present invention cure at room temperature or under heated conditions to give solvent-resistant coatings, and can therefore be used as curable silicone compositions and coating agents, and are suitable for use, for example, as exterior wall paints or primer coats for paints, although there are no particular limitations on their applications. In the present invention, "room temperature" refers to an ordinary temperature without any particular heating or cooling, and generally refers to a temperature range of 0 to 40°C, preferably 5 to 35°C.

[0053] The curable silicone composition and coating agent of the present invention may contain an aqueous organic resin. Specific examples of aqueous organic resins include, but are not limited to, aqueous acrylic resins, aqueous urethane resins, aqueous epoxy resins, aqueous PVA resins, aqueous polyester resins, aqueous alkyd resins, aqueous melamine resins, and aqueous fluororesins.

[0054] [4] Cured product of curable silicone composition and coated article By applying a curable silicone composition to at least one surface of a substrate, either directly or via one or more other layers, and then curing the composition to form a coating, it is possible to obtain a coated article having a cured product of the curable silicone composition applied to at least one surface of the substrate, either directly or via one or more other layers.

[0055] The substrate may include, but is not limited to, glass, silicon wafers, metals, plastic molded bodies, ceramics, composites thereof, etc. Substrates whose surfaces have been treated with chemical conversion coating, corona discharge treatment, plasma treatment, or acid or alkali solution, as well as decorative plywood whose surface layer is coated with a different type of paint from the substrate itself, can also be used. Examples of other layers include those obtained by polyester resin coating, polyurethane resin coating, aminoalkyd resin coating, lacquer coating, spray coating, and aqueous wax coating.

[0056] The method for applying the composition to the substrate may be appropriately selected from known techniques, and various coating methods can be used, such as roll coating, bar coating, wire bar coating, spray coating, flow coating, spin coating, curtain coating, knife coating, dip coating, brush coating, etc. The amount of coating is not particularly limited, but usually, an amount that results in a coating thickness of 0.1 to 1,000 μm after drying is preferred, and an amount that results in a coating thickness of 1 to 100 μm is preferable.

[0057] Methods for curing the curable silicone composition of the present invention include room temperature curing and heat curing. There are no particular restrictions on the heating temperature, and the composition will cure in a short time of about 5 to 60 minutes at 80 to 150°C, yielding a transparent cured product. Furthermore, the resulting cured product will not discolor even if post-cured, preferably at 150 to 180°C for about 30 minutes to 3 hours, and will maintain excellent transparency.

[0058] The present invention will be explained in more detail below with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0059] The average composition of the organopolysiloxane was measured using an NMR measurement device manufactured by JEOL Ltd. 1 H-NMR and 29 The weight average molecular weight (Mw) is a value calculated from the integrated value of the Si-NMR spectrum, and is a polystyrene-equivalent value determined by GPC (gel permeation chromatography) measurement under the following conditions: [GPC conditions] Apparatus: HLC-8220 (manufactured by Tosoh Corporation) Columns: TSKgel GMHXL-L, TSKgel G4000HXL, TSKgel G2000HXL x 2 Developing solvent: tetrahydrofuran (THF) Flow rate: 1 mL / min Detector: RI Column thermostat temperature: 40°C Standard material: polystyrene

[0060] [1] Production of organopolysiloxane [Synthesis Example 1] 16.2 g (0.1 mol) of hexamethyldisiloxane (Tokyo Chemical Industry Co., Ltd.), 123.8 g (0.8 mol) of methyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., KBM-13), 7.9 g (0.03 mol) of 3-trimethoxysilylpropylsuccinic anhydride (Shin-Etsu Chemical Co., Ltd., X-12-967C), and 15 g of isopropyl alcohol (IPA) were stirred in a 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer. When the mixture became homogeneous, 30 g of ion-exchanged water was added, and the mixture was stirred at 80°C for 2 hours. The alcohol was then removed by distillation under reduced pressure (50°C, 120 mmHg), yielding a highly viscous liquid. The organopolysiloxane component in the resulting liquid had a weight average molecular weight of 2,500 and was represented by formula (I) where a = 0, b = 0.78, c = 0.03, d = 0, e = 0.19, and f = 0.2.

[0061] Synthesis Example 2 A highly viscous liquid was obtained in the same manner as in Synthesis Example 1, except that the hexamethyldisiloxane in Synthesis Example 1 was replaced with 12.2 g (0.1 mol) of dimethyldimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.). The organopolysiloxane component in the resulting liquid had a weight-average molecular weight of 3,000 and was represented by formula (I) where a = 0, b = 0.86, c = 0.03, d = 0.11, e = 0, and f = 0.3.

[0062] Synthesis Example 3 In a 500 mL separable flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, 108.4 g (0.7 mol) of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-13), 10.5 g (0.05 mol) of 3-trimethoxysilylpropylsuccinic anhydride (manufactured by Shin-Etsu Chemical Co., Ltd., X-12-967C), and 17 g of IPA were stirred in a reactor, and when the mixture became homogeneous, 30 g of ion-exchanged water was added. After stirring at 80° C. for 2 hours, 39.7 g (0.2 mol) of phenyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and the alcohol was removed by distillation under reduced pressure (50° C., 120 mmHg), to obtain a highly viscous liquid. The organopolysiloxane component in the resulting liquid had a weight average molecular weight of 2,200 and was represented by formula (I) where a=0, b=0.95, c=0.05, d=0, e=0, and f=0.5.

[0063] Synthesis Example 4 A 500 mL separable flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer was charged with 10.6 g (0.07 mol) of hexamethyldisiloxane (manufactured by Tokyo Chemical Industry Co., Ltd.), 80.5 g (0.56 mol) of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-13), 37.5 g (0.14 mol) of 3-trimethoxysilylpropylsuccinic anhydride (manufactured by Shin-Etsu Chemical Co., Ltd., X-12-967C), and 15 g of IPA, and the resulting mixture was stirred in a reactor. When the mixture became homogeneous, 30 g of ion-exchanged water was added, followed by stirring at 80°C for 2 hours. The mixture was then distilled off under reduced pressure (50°C, 120 mmHg) to remove the alcohol, yielding a highly viscous liquid. The organopolysiloxane component in the liquid had a weight average molecular weight of 2,500 and was represented by formula (I) where a=0, b=0.67, c=0.16, d=0, e=0.17, and f=0.4.

[0064] Synthesis Example 5: 12.0 g (0.1 mol) of dimethyldimethoxysilane (Tokyo Chemical Industry Co., Ltd.), 39.7 g (0.2 mol) of phenyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., KBM-103), 17.4 g (0.05 mol) of a compound represented by formula (1) below, and 15 g of IPA were stirred in a 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer. When the mixture became homogeneous, 10 g of ion-exchanged water was added, and the mixture was stirred at 80°C for 2 hours. The alcohol was then removed by distillation under reduced pressure (50°C, 120 mmHg), yielding a highly viscous liquid. The weight-average molecular weight of the organopolysiloxane component in the liquid was 1,500 and was represented by formula (I): a = 0, b = 0.55, c = 0.14, d = 0.21, e = 0, and f = 0.4.

[0065] (In the formula, Et is an ethyl group.)

[0066] Comparative Synthesis Example 1: 19.5 g (0.12 mol) of hexamethyldisiloxane (Tokyo Chemical Industry Co., Ltd.), 148.6 g (0.96 mol) of methyltrimethoxysilane KBM-13 (Shin-Etsu Chemical Co., Ltd.), and 17 g of IPA were stirred in a 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer. Once the mixture became homogeneous, 35 g of ion-exchanged water was added, and the mixture was stirred at 80°C for 2 hours. The alcohol was then removed by distillation under reduced pressure (50°C, 120 mmHg), yielding a highly viscous liquid. The organopolysiloxane component in the resulting liquid had a weight-average molecular weight of 2,500 and was represented by formula (I), where a = 0, b = 0.80, c = 0, d = 0, e = 0.20, and f = 0.3.

[0067] Comparative Synthesis Example 2 A 500 mL separable flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer was charged with 16.2 g (0.1 mol) of hexamethyldisiloxane (manufactured by Tokyo Chemical Industry Co., Ltd.), 123.8 g (0.8 mol) of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-13), 25.7 g (0.05 mol) of a 50% methanol solution of trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.), and 15 g of isopropyl alcohol (IPA) and stirred in a reactor. When the mixture became homogeneous, 30 g of 1N hydrochloric acid was added, and the mixture was stirred at 80° C. for 2 hours. After that, 5 g (0.08 mol) of propylene oxide was added, and the alcohol was removed by distillation under reduced pressure (50° C., 120 mmHg), yielding a highly viscous liquid. The organopolysiloxane component in the resulting liquid had a weight average molecular weight of 2,900 and was represented by formula (I) where a=0, b=0.78, c=0, d=0, e=0.19, and f=0.2.

[0068] [2] Production of curable silicone compositions (aqueous organopolysiloxane dispersions) [Examples 1-1 to 1-8, Comparative Examples 1-1 to 1-8] The organopolysiloxanes obtained in Synthesis Examples 1 to 5 and Comparative Synthesis Examples 1 and 2 and the basic compound were stirred at 25°C for 30 minutes in the amounts (parts by mass) shown in Tables 1 and 2, and then the dilution solvent was added with stirring and evaporated under reduced pressure (50°C, 140 mmHg) for 2 hours to produce curable silicone compositions.

[0069] The nonvolatile content, pH, appearance, and stability of the resulting curable silicone compositions were measured using the following methods. The results are shown in Tables 1 and 2. (1) Nonvolatile content: Measured in accordance with JIS C2133. (2) pH: Measured in accordance with JIS Z8802. (3) Appearance: When the composition was sealed in a container and allowed to stand at 25°C for 24 hours, compositions that showed clear separation or insolubilization were rated as x, and compositions that showed no separation and maintained a uniform dispersion were rated as ◯. (4) Stability: When the composition was sealed in a container and allowed to stand at 50°C for 3 days, compositions that showed no significant increase in viscosity or gelation were rated as ◯, and compositions that showed a significant increase in viscosity or gelation were rated as x.

[0070]

[0071]

[0072] [3] Preparation of Coated Articles [Examples 2-1 to 2-8, Comparative Examples 2-1 to 2-8] The organopolysiloxane aqueous dispersions obtained in Examples 1-1 to 1-8 and Comparative Examples 1-3, 1-4, and 1-8, as well as the MIBK solutions of the organopolysiloxanes obtained in Comparative Examples 1-6 and 1-7, were applied to aluminum substrates by flow coating. After drying at 100°C for 10 minutes, the coatings were allowed to stand at 25°C for 3 days to cure, yielding coated articles in which a cured film was formed on the surface of the aluminum substrate. The resulting coated articles were subjected to rubbing tests and pencil hardness measurements using the following methods. The results are shown in Table 3.

[0073] (1) Rubbing Test Acetone and toluene were rubbed onto a BEMCOT M-3II (manufactured by Asahi Kasei Corporation, area 4 cm). 2 ) and rubbed the surface back and forth 30 times with a load of 500 g, and the appearance of the coating film was evaluated visually. After the rubbing test with both acetone and toluene, the coating film appearance was evaluated as "Good" when no change was observed compared to the appearance before the test. After the rubbing test with toluene, the coating film appearance was evaluated as "Good" when no change was observed compared to the appearance before the test, and peeling or whitening of the coating film was observed after the rubbing test with acetone. After the rubbing test with both acetone and toluene, the coating film peeling or whitening was observed after the test. (2) Pencil hardness: Measured under a load of 750 g in accordance with JIS K5600-5-4. When scratches were observed with a 6B pencil, the rating was evaluated as <6B.

[0074]

[0075] As shown in Tables 1 to 3, the curable silicone compositions (organopolysiloxane aqueous dispersions) of Examples 1-1 to 1-8 were stably dispersed in water, and the resulting cured films exhibited excellent solvent resistance. On the other hand, Comparative Example 1-1, in which the organopolysiloxane was changed to one lacking a carboxylic acid anhydride or carboxylic acid structure, and Comparative Example 1-2, in which the amount of basic compound added was small and the pH was less than 7, failed to produce aqueous dispersions. Furthermore, Comparative Example 1-3, in which the pH exceeded 10, and Comparative Example 1-4, in which a small amount of water was added, produced cured films with no problems in solvent resistance or hardness, but the stability of the aqueous dispersions was poor. Similarly, Comparative Example 1-5, in which the water in Example 1-1 was replaced with methyl isobutyl ketone (MIBK), showed no problems with the cured films, but the liquid stability was poor. Furthermore, in Comparative Examples 1-6 and 1-7, which did not contain a basic compound and used an MIBK solution of organopolysiloxane, no problems were observed with the stability of the liquid, but the films obtained were insufficiently cured and had significantly poor solvent resistance and hardness.In addition, the aqueous dispersion of organopolysiloxane having a quaternary ammonium salt structure in Comparative Example 1-8 had high liquid stability but poor curability, and the films obtained had low solvent resistance and hardness.

Claims

1. (A) 100 parts by mass of an organopolysiloxane represented by the following formula (I): (B) a basic compound: an amount such that the pH is 7 to 10; and (C) 50 to 1,000 parts by mass of water, an organopolysiloxane aqueous dispersion. (In the formula, R 1 each independently represents a hydrogen atom, a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, an organic group having 2 to 12 carbon atoms having a radical polymerizable functional group, an aryl group having 6 to 18 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and R 2 each independently represents a monovalent group having a carboxylic anhydride structure, a carboxylic acid structure or a carboxylate structure, and R 3 each independently represents a hydrogen atom, a methyl group, an ethyl group, an n-propyl group or an isopropyl group, a, b, c, d and e are numbers satisfying 0 ≦ a < 1, 0 < b < 1, 0 < c ≦ 0.4, 0 ≦ d < 1, 0 ≦ e < 1 and a + b + c + d + e = 1, and f is a number satisfying 0 < f < 4.) 2. The R 2 The organopolysiloxane aqueous dispersion according to claim 1, wherein R is a monovalent group having a succinic anhydride structure, a succinic acid structure or a succinate structure.

3. In the formula (I), the organopolysiloxane aqueous dispersion according to claim 1, wherein b, d, and e satisfy 0.5 ≤ b < 1, 0 ≤ d < 0.5, and 0 ≤ e < 0.

5.

4. The organopolysiloxane aqueous dispersion according to claim 1, wherein the weight average molecular weight (Mw) in terms of polystyrene in the gel permeation chromatography of the component (A) is 1,000 to 500,000.

5. The organopolysiloxane aqueous dispersion according to claim 1, wherein the basic compound of the component (B) is an amine compound.

6. The organopolysiloxane aqueous dispersion according to claim 1, wherein the amount of the surfactant is 1% by mass or less based on the total mass.

7. The organopolysiloxane aqueous dispersion according to claim 1, wherein the amount of the organic solvent is 5% by mass or less based on the total mass.

8. The method for producing an organopolysiloxane aqueous dispersion according to any one of claims 1 to 7, comprising the following steps (α) to (γ). (Step α): Co-hydrolytically condensing a mixed silane containing a silane compound represented by the following formula (III) or its hydrolytic condensate and a silane compound represented by the following formula (IV) to obtain an organopolysiloxane having at least one of a cyclic carboxylic anhydride structure or a carboxylic acid structure obtained by ring-opening thereof. R 1 Si(OR 3 )3 (III) R 4 Si(OR 3 )3 (IV) (In the formula, R 1 and R 3 represent the same meaning as described above, and R 4 each independently represents a monovalent group having a cyclic carboxylic anhydride structure.) (Step β): Mixing the organopolysiloxane having at least one of the cyclic carboxylic anhydride structure or the carboxylic acid structure obtained by ring-opening thereof obtained in the above (Step α) with a basic compound to obtain a mixture. (Step γ): Dispersing the mixture obtained in the above (Step β) in water to obtain an organopolysiloxane aqueous dispersion.

9. A curable silicone composition comprising the organopolysiloxane aqueous dispersion according to any one of claims 1 to 7.

10. A coating agent comprising the organopolysiloxane aqueous dispersion according to any one of claims 1 to 7.

11. A cured product of the curable silicone composition according to claim 9.

12. A coated article having a substrate and the cured product according to claim 11 formed directly or via one or more other layers on at least one surface of the substrate.

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