WO2025158737A1 - Organopolysiloxane aqueous dispersion, method for producing organopolysiloxane aqueous dispersion, coating agent, cured object, and coated article - Google Patents

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

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

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

On the other hand, while organopolysiloxane-based paints have the above advantages, they have the disadvantages that they are solids or highly viscous liquids when used alone, so they must be diluted with a solvent before use, and that they have a slow curing rate and require heating at high temperatures for curing.
In order to overcome these drawbacks, studies have been conducted on organopolysiloxane resins, such as dilution with weak solvents, aqueous dispersions, and low-temperature curing.

For example, Patent Document 1 reports that by replacing conventional toluene-xylene-based solvents with acetate-based solvents, the resin becomes TX solvent-free and at the same time, its curing properties are improved as well.
In Patent Document 2, an aqueous dispersion of a silicone resin is obtained by reacting a relatively low molecular weight organopolysiloxane with a cationic alkoxysilane, but this has the problem of low curability and poor solvent resistance of the resulting cured coating.
Patent Document 3 reports that by combining two or more organopolysiloxanes with different molecular weights and adding a catalyst, the composition can be cured at a low temperature of about 100°C. However, since a catalyst is required for curing at low temperatures, this method has the disadvantage of being difficult to commercialize from the standpoint of pot life.

Japanese Patent Application Laid-Open No. 2021-172706 Special table 2013-515154 publication Japanese Patent Application Laid-Open No. 2021-172707

The present invention was made in consideration of the above circumstances, and aims to provide an aqueous organopolysiloxane dispersion that is highly stable and has excellent curing properties.

As a result of extensive research into achieving the above-mentioned objectives, the present inventors discovered that an aqueous organopolysiloxane dispersion containing an organopolysiloxane having a cyclic carboxylic acid anhydride structure, or a carboxylic acid structure, carboxylate structure, or carboxylic acid derivative structure formed by ring-opening thereof, and a basic compound, and satisfying a specific pH range, exhibits high dispersion stability, can be cured at room temperature to form a cured film, and that this cured film has excellent solvent resistance, leading to the completion of the present invention.

That is, the present invention is
1. (A) 100 parts by mass of an organopolysiloxane represented by the following formula (I):
an organopolysiloxane aqueous dispersion comprising (B) a basic compound in an amount that results in a pH of 7 to 10, and (C) water in an amount of 50 to 1,000 parts by mass;
(In the formula, each R ¹ 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 having a radically polymerizable functional group, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms; each R ² independently represents a monovalent group having a carboxylic anhydride structure, a carboxylic acid structure, or a carboxylate structure; each R ³ 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 independently represent numbers which 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 which satisfies 0<f<4.)
2. The aqueous organopolysiloxane dispersion of 1, wherein ^R2 is a monovalent group having a succinic anhydride structure, a succinic acid structure, or a succinate structure.
3. The aqueous organopolysiloxane dispersion of 1, wherein in the formula (I), b, d, and e satisfy the relationships 0.5≦b<1, 0≦d<0.5, and 0≦e<0.5.
4. The aqueous organopolysiloxane dispersion of 1, wherein the weight average molecular weight (Mw) of the component (A) measured by gel permeation chromatography in terms of polystyrene standards is 1,000 to 500,000.
5. The aqueous organopolysiloxane dispersion of 1, wherein the basic compound of component (B) is an amine compound.
6. The aqueous organopolysiloxane dispersion of 1, wherein the amount of surfactant is 1% by mass or less based on the total mass.
7. The aqueous organopolysiloxane dispersion of 1, wherein the amount of the organic solvent is 5% by mass or less based on the total mass.
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 mixture containing a silane compound represented by the following formula (III) or its hydrolysis condensate, 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, R ¹ Si(OR ³ ) ₃ (III):
R ⁴ Si(OR ³ ) ₃ (IV)
(In the formula, ^R1 and ^R3 have the same meaning as defined above, and each ^R4 independently represents a monovalent group having a cyclic carboxylic acid anhydride structure.)
(Step β): 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; (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 one of 1 to 7;
10. A coating agent comprising the aqueous dispersion of organopolysiloxane according to any one of 1 to 7.
11. A cured product of the curable silicone composition of 9.
12. Provide a coated article having a substrate and the cured product 11 formed on at least one surface of the substrate directly or via one or more other layers.

The aqueous organopolysiloxane dispersion of the present invention has excellent dispersion stability and excellent curing properties, allowing curing to proceed rapidly even at room temperature. The resulting cured film has excellent solvent resistance, making it suitable for producing a variety of coated articles.

The present invention will be specifically described below.
[1] Organopolysiloxane Aqueous Dispersion The organopolysiloxane aqueous dispersion of the present invention comprises (A) an organopolysiloxane represented by the following formula (I), (B) a basic compound, and (C) water, and has a pH of 7 to 10.

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

In formula (I), each ^R1 is independently 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 having a radically polymerizable functional group, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms.

The monovalent saturated hydrocarbon group having 1 to 12 carbon atoms may be linear, branched, or cyclic. Specific examples thereof 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, and a methyl group or an ethyl group is more preferred.
Examples of the organic group having 2 to 12 carbon atoms and having a radically polymerizable functional group include vinyl, allyl, 3-acryloyloxypropyl, and 3-methacryloyloxypropyl groups.
Examples of the aryl group having 6 to 18 carbon atoms include unsubstituted aryl groups such as phenyl and naphthyl groups; and alkylaryl groups such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl groups, with a phenyl group being preferred.
Examples of the aralkyl group having 7 to 20 carbon atoms include a benzyl group and a phenylethyl group.

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

In formula (I), each R ² is independently a monovalent group having a carboxylic 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, and the succinic anhydride structure is preferred.
The carboxylic acid structure may be a hydrocarbon group containing one or more carboxy groups, preferably 1 to 4, and more preferably 2. Preferred examples include a succinic acid structure in which the carboxylic acid anhydride structure is ring-opened, 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, with a succinic acid structure being more preferred.
The monovalent group having a carboxylic acid structure may have an amide bond, a urethane bond, a urea bond, or the like, and specific examples of such groups include those represented by the following formulas:

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

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.
Furthermore, the structure represented by ^R2 may contain a carboxylic acid derivative structure such as a carboxylic acid amide or carboxylic acid ester formed by the reaction of a carboxylic acid anhydride structure with an amine, alcohol, or the like.

^R2 is preferably a group represented by the following formula (II).

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

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, and ^Z1 is a cyclic carboxylic acid anhydride structure, or a carboxylic acid or carboxylate structure formed by ring-opening the cyclic carboxylic acid anhydride structure.

X is a divalent hydrocarbon group having 1 to 40 carbon atoms, which may contain an ether bond, amide bond, urethane bond, urea bond, sulfide bond, etc., 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, etc., and even more preferably an ethylene group or trimethylene group.

Examples of the cyclic carboxylic acid anhydride structure for ^Z1 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.

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

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.
a is a number that satisfies 0≦a<1, but from the viewpoint of crack suppression effect, a is preferably a number that satisfies 0≦a≦0.3, and more preferably a=0.
Although b is a number that satisfies 0<b<1, it is preferably a number that satisfies 0.5<b<1 from the viewpoint of the scratch resistance of the resulting cured product.
Although c is a number that satisfies 0<c≦0.4, from the viewpoint of water dispersibility and stability, it is preferably a number that satisfies 0.03≦c≦0.2.
d is a number that satisfies 0≦d<1, but from the viewpoint of the curability of the composition and the hardness of the resulting cured product, it is preferably a number that satisfies 0≦d≦0.5, and more preferably 0≦d≦0.2.
e is a number that satisfies 0≦e<1, but from the viewpoint of the curability of the composition and the hardness of the resulting 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.

The weight average molecular weight (Mw) of component (A) in terms of polystyrene as measured by gel permeation chromatography (GPC) 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.
As the GPC measurement conditions, for example, the method used in the examples below can be adopted.

(B) Basic Compound The basic compound of component (B) is not particularly limited to alkali metal carbonates, alkali metal hydrogencarbonates, alkali metal hydroxides, alkaline earth metal hydroxides, amine compounds, etc., but amine compounds are preferred.
Specific examples of alkali metal carbonates include Na ₂ CO ₃ and K ₂ CO ₃ .
Specific examples of alkali metal hydrogen carbonates include NaHCO ₃ and KHCO ₃ .
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 the amine compound include ammonia, monoethanolamine, diethanolamine, triethanolamine, benzylamine, methylbenzylamine, dimethylbenzylamine, methyldiethanolamine, dimethylethanolamine, triethylamine, tributylamine, and dibutylamine.

The amount of basic compound added is an amount that brings the pH of the aqueous phase to 7-10, preferably 7-9, but 0.5-25 parts by mass per 100 parts by mass of organopolysiloxane is preferred. If the amount is 0.5 parts by mass or more, an aqueous dispersion with excellent dispersibility in water and stability will 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 measured in accordance with JIS Z8802, as shown in the examples below.

(C) Water There are no particular restrictions on the water used, but it is preferable to use deionized water having a pH of 6 to 8 in terms of the dispersion stability of the aqueous dispersion.
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 the amount is less than 50 parts by mass, the stability of the aqueous dispersion may decrease, and if it exceeds 1,000 parts by mass, the film-forming properties may be insufficient.

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

From the viewpoint of stability and film-forming property, the aqueous dispersion of the present invention preferably has a nonvolatile content of 5 to 70 mass % based on the total mass of the aqueous dispersion. The nonvolatile content is 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 properties, the amount of the surfactant is preferably more than 0% by mass and 1% by mass or less based on the total amount of the aqueous dispersion.

[2] Method for Producing Aqueous Organopolysiloxane Dispersion The method for producing the aqueous organopolysiloxane dispersion of the present invention is not particularly limited, and the dispersion 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 and condensation reaction of a silane compound represented by the following formula (III) or a hydrolysis and condensation product thereof, and a silane mixture containing a silane compound represented by the following formula (IV):
R ¹ Si(OR ³ ) ₃ (III)
R ⁴ Si(OR ³ ) ₃ (IV)
(In the formula, ^R1 and ^R3 have the same meaning as above, and each ^R4 is independently a monovalent group having a cyclic carboxylic acid anhydride structure.)
(Step β): A step of mixing the organopolysiloxane having at least one of a 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.

<(Process 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 its hydrolysis condensate, and a silane compound represented by formula (IV) above.

In formula (III), specific examples of R ¹ and R ³ include the same groups as those exemplified in formula (I) above.
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.

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

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

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

X is a divalent hydrocarbon group having 1 to 40 carbon atoms, which may contain an ether bond, amide bond, urethane bond, urea bond, sulfide bond, etc., and is preferably an alkylene group or (poly)oxyalkylene group having 1 to 10 carbon atoms, with methylene, ethylene, trimethylene, propylene, tetramethylene, hexamethylene, and octamethylene groups being more preferred, and ethylene and trimethylene groups being even more preferred.

Examples of the cyclic carboxylic acid anhydride structure for ^Z2 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.

Specific examples of silane compounds represented by formula (IV) above 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.

The amount of the silane compound represented by formula (IV) above 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 standpoint of water dispersibility and stability, it is preferably 0.03 to 0.2 times by mole.

In (Step α), the mixed silane used in the co-hydrolysis condensation reaction may contain silane compounds other than the silane compounds represented by formula (III) and formula (IV) above, or hydrolysis condensates thereof. Specific examples include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, dimethylphenylmethoxysilane, dimethylphenylethoxysilane, and hydrolysis condensates thereof.

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

At this time, a solvent can be added if necessary. Examples of solvents include alcohol solvents such as methanol, ethanol, and isopropyl alcohol; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; and aromatic non-polar solvents such as benzene, toluene, and xylene.

An acidic catalyst for accelerating the hydrolysis reaction may also be used. As the acidic catalyst, a strong acid is preferred, and although any type is not particularly limited, sulfuric acid, methanesulfonic acid, trifluoromethanesulfonic acid, etc. are preferably used, and in view of ease of post-treatment, cation exchange resins having these exchange groups are particularly preferred.
The amount of the 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.

Furthermore, after the hydrolysis reaction, vacuum distillation may be performed. There are no particular restrictions on the conditions for vacuum distillation, but from the perspective of stability, it is preferable to perform the distillation at 20 to 120°C for approximately 0.5 to 4 hours.

<(Process β)>
(Step β) is a step of mixing the organopolysiloxane having at least one of a 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.
Examples of the basic compound include those exemplified above as component (B).
The conditions for mixing are not particularly limited, 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.

The amount of basic compound added is an amount that will result in the aqueous phase having a pH of 7 to 10, preferably 7 to 9, after (Step γ) described below, but 0.5 to 25 parts by mass per 100 parts by mass of organopolysiloxane is preferred. At 0.5 parts by mass or more, an aqueous dispersion with excellent dispersibility in water and stability will be obtained, while at 25 parts by mass or less, there is little risk of the pH becoming too basic.

<(Process 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.
The dispersion method is not particularly limited, and known methods can be used, such as those using a paint shaker, a ball mill, or a homogenizer at 20 to 80°C.

The amount of water used is 50 to 1,000 parts by mass per 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 it exceeds 1,000 parts by mass, the film-forming properties may be insufficient.

Furthermore, after (Step γ), vacuum distillation may be performed. This reduces the amount of by-product alcohol and unreacted low-molecular-weight components in the system. There are no particular restrictions on the conditions for vacuum distillation, but from the perspective of stability, it is preferable to perform the distillation at 20 to 120°C for approximately 0.5 to 4 hours.

[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.

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.

[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.

The substrate is not particularly limited, but examples thereof include glass, silicon wafers, metals, plastic molded bodies, ceramics, and composites thereof.
In addition, substrates whose surfaces have been treated with chemical conversion coating, corona discharge treatment, plasma treatment, acid or alkali solution, decorative plywood coated with different types of paint for the substrate body and surface layer, etc. Other layers include those obtained by polyester resin coating, polyurethane resin coating, amino alkyd resin coating, lacquer coating, spray coating, water-based wax coating, etc.

The method for applying the coating to the substrate can be selected from known methods, such as roll coating, bar coating, wire bar coating, spray coating, flow coating, spin coating, curtain coating, knife coating, dip coating, and brush coating. There are no particular restrictions on the amount of coating, but it is generally preferable to apply an amount that results in a coating thickness of 0.1 to 1,000 μm after drying, and preferably an amount that results in a coating thickness of 1 to 100 μm.

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.

The following synthesis examples, working examples, and comparative examples will be presented to explain the present invention in more detail, but the present invention is not limited to the following examples.

The average composition of the organopolysiloxane is a value calculated from the integrated values of ^H -NMR and ^Si -NMR spectra obtained using an NMR measurement device manufactured by JEOL Ltd., and the weight average molecular weight (Mw) 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: 1mL/min
Detector: RI
Column thermostatic bath temperature: 40°C
Standard material: polystyrene

[1] Production of organopolysiloxane [Synthesis Example 1]
A 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer was charged with 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). The mixture was stirred in a reactor, and when the mixture became homogeneous, 30 g of ion-exchanged water was added. The mixture was stirred at 80°C for 2 hours, and then 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 2,500 and was represented by formula (I) where a = 0, b = 0.78, c = 0.03, d = 0, e = 0.19, and f = 0.2.

[Synthesis Example 2]
A highly viscous liquid was obtained in the same manner as in Synthesis Example 1, except that 12.2 g (0.1 mol) of dimethyldimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of hexamethyldisiloxane. 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.

[Synthesis Example 3]
A 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer was charged with 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. The mixture was 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.

[Synthesis Example 4]
A 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer was charged with 10.6 g (0.07 mol) of hexamethyldisiloxane (Tokyo Chemical Industry Co., Ltd.), 80.5 g (0.56 mol) of methyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., KBM-13), 37.5 g (0.14 mol) of 3-trimethoxysilylpropylsuccinic anhydride (Shin-Etsu Chemical Co., Ltd., X-12-967C), and 15 g of IPA, which were stirred in a reactor. 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 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.

[Synthesis Example 5]
A 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer was charged with 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 the following formula (1), and 15 g of IPA. The mixture was stirred in a reactor until homogeneous, at which point 10 g of ion-exchanged water was added. The mixture was stirred at 80°C for 2 hours, and then the alcohol was removed by distillation under reduced pressure (50°C, 120 mmHg) to obtain a highly viscous liquid. The weight-average molecular weight of the organopolysiloxane component in the liquid was 1,500, and the organopolysiloxane component was represented by formula (I): a = 0, b = 0.55, c = 0.14, d = 0.21, e = 0, and f = 0.4.

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

Comparative Synthesis Example 1
A 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer was charged with 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. The resulting mixture was stirred in a reactor, and once homogeneous, 35 g of ion-exchanged water was added. The mixture was stirred at 80°C for 2 hours, and then the alcohol was removed by vacuum distillation (50°C, 120 mmHg) to yield 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): a = 0, b = 0.80, c = 0, d = 0, e = 0.20, and f = 0.3.

Comparative Synthesis Example 2
A 500 mL separable flask equipped with a stirrer, reflux condenser, dropping funnel, and 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% solution of trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride in methanol (manufactured by Tokyo Chemical Industry Co., Ltd.), and 15 g of isopropyl alcohol (IPA) and stirred in the 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) to obtain 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.

[2] Preparation of curable silicone composition (aqueous organopolysiloxane dispersion) [Examples 1-1 to 1-8, Comparative Examples 1-1 to 1-8]
The organopolysiloxanes and basic compounds obtained in Synthesis Examples 1 to 5 and Comparative Synthesis Examples 1 and 2 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.

The non-volatile content, pH, appearance, and stability of the resulting curable silicone composition were measured using the methods described below. The results are shown in Tables 1 and 2.
(1) Nonvolatile content: Measured in accordance with JIS C2133.
(2) pH
Measurement was carried out in accordance with JIS Z8802.
(3) Appearance The composition was sealed in a container and allowed to stand at 25°C for 24 hours. When clear separation or insolubilization was observed, the composition was evaluated as ×, and when no separation was observed and a uniform dispersion was maintained, the composition was evaluated as ○.
(4) Stability The composition was sealed in a container and allowed to stand at 50°C for 3 days. When no significant increase in viscosity or gelation was observed, the composition was evaluated as ◯, and when a significant increase in viscosity or gelation was observed, the composition was evaluated as ×.

[3] Preparation of coated articles [Examples 2-1 to 2-8, Comparative Examples 2-1 to 2-8]
The aqueous dispersions of organopolysiloxane obtained in Examples 1-1 to 1-8 and Comparative Examples 1-3, 1-4, and 1-8, and the MIBK solutions of organopolysiloxane 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 coating was allowed to stand at 25°C for 3 days to cure, yielding a coated article in which a cured film was formed on the surface of the aluminum substrate. The resulting coated article was subjected to a rubbing test and pencil hardness measurement by the following methods. The results are shown in Table 3.

(1) Rubbing test Acetone and toluene were immersed in Bemcot M-3II (Asahi Kasei Corporation, area 4 ^cm2 ), and the surface was rubbed 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 acetone or toluene, the coating film appearance was evaluated as "Good", while after the rubbing test with toluene, the coating film appearance was evaluated as "Good", but peeling or whitening of the coating film was observed after the rubbing test with acetone, and after the rubbing test with acetone, the coating film appearance was evaluated as "Poor".
(2) Pencil hardness: Measured under a load of 750 g in accordance with JIS K5600-5-4. If scratches were observed with a 6B pencil, the hardness was rated as <6B.

As shown in Tables 1 to 3, the curable silicone compositions (aqueous organopolysiloxane dispersions) of Examples 1-1 to 1-8 were stably dispersed in water, and the resulting cured films had excellent solvent resistance.
On the other hand, it can be seen that in Comparative Example 1-1, in which the organopolysiloxane was changed to one having no carboxylic acid anhydride or carboxylic acid structure, and in Comparative Example 1-2, in which the amount of basic compound added was small and the pH was less than 7, no aqueous dispersion was obtained.
In Comparative Example 1-3, in which the pH exceeded 10, and Comparative Example 1-4, in which a small amount of water was added, the solvent resistance and hardness of the obtained cured film were not a problem, but the stability of the aqueous dispersion was poor. Similarly, in Comparative Example 1-5, in which the water in Example 1-1 was changed to methyl isobutyl ketone (MIBK), no problem was observed with the cured film, but the stability of the liquid was low.
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 solution, but the resulting film was insufficiently cured and was significantly inferior in solvent resistance and hardness.
In addition, the aqueous dispersion of organopolysiloxane having a quaternary ammonium salt structure of Comparative Example 1-8 had high liquid stability but poor curability, and the resulting film had low solvent resistance and hardness.

Claims (12)

(A) 100 parts by mass of an organopolysiloxane represented by the following formula (I):
An organopolysiloxane aqueous dispersion comprising: (B) a basic compound in an amount sufficient to achieve a pH of 7 to 10; and (C) water in an amount of 50 to 1,000 parts by mass.
(In the formula, each R ¹ 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 having a radically polymerizable functional group, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms; each R ² independently represents a monovalent group having a carboxylic anhydride structure, a carboxylic acid structure, or a carboxylate structure; each R ³ 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 independently represent numbers which 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 which satisfies 0<f<4.) 2. The aqueous organopolysiloxane dispersion according to claim 1, wherein ^R2 is a monovalent group having a succinic anhydride structure, a succinic acid structure, or a succinate structure. The aqueous organopolysiloxane dispersion according to claim 1, wherein in formula (I), b, d, and e satisfy the relationships 0.5≦b<1, 0≦d<0.5, and 0≦e<0.5. The aqueous organopolysiloxane dispersion according to claim 1, wherein the weight average molecular weight (Mw) of component (A) measured by gel permeation chromatography in terms of polystyrene is 1,000 to 500,000. The organopolysiloxane aqueous dispersion according to claim 1, wherein the basic compound of component (B) is an amine compound. The aqueous organopolysiloxane dispersion according to claim 1, wherein the amount of surfactant is 1% by mass or less based on the total mass. The organopolysiloxane aqueous dispersion according to claim 1, wherein the amount of organic solvent is 5% by mass or less based on the total mass. A method for producing the aqueous organopolysiloxane dispersion according to any one of claims 1 to 7, comprising the following (Step α) to (Step γ):
(Step α): A step of co-hydrolytic condensing a silane mixture containing a silane compound represented by the following formula (III) or its hydrolysis condensate, 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, R ¹ Si(OR ³ ) ₃ (III):
R ⁴ Si(OR ³ ) ₃ (IV)
(In the formula, ^R1 and ^R3 have the same meaning as defined above, and each ^R4 independently represents a monovalent group having a cyclic carboxylic acid anhydride structure.)
(Step β): A step of mixing the organopolysiloxane having at least one of a 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. A curable silicone composition comprising the aqueous organopolysiloxane dispersion according to any one of claims 1 to 7. A coating agent comprising the aqueous organopolysiloxane dispersion according to any one of claims 1 to 7. A cured product of the curable silicone composition described in claim 9. A coated article comprising a substrate and the cured product according to claim 11 formed on at least one surface of the substrate directly or via one or more other layers.