JP2005298561A - Method for producing aqueous organopolysiloxane solution and coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous organopolysiloxane solution which can be used as a coating composition that forms a coating film excellent in storage stability and also excellent in curability, stain resistance, hot water resistance and adhesiveness. <P>SOLUTION: The aqueous organopolysiloxane solution is prepared by the steps of: (I) mixing (a) 100 pts.mass of a partially hydrolyzed copolycondensate for example of phenyltrimethoxysilane and dimethyldimethoxysilane, (b) 5-70 pts.mass of methyltrimethoxysilane and dimethyldimethoxysilane, (c) 3-30 pts.mass of an amino group-containing alkoxysilane with 0.2-0.5 Eq water based on 1 Eq of a hydrolyzable functional group in the (a)-(c) components and subjecting the resulting mixture to hydrolysis-condensation reaction; (II) adding a predetermined amount of acid (d) and water (c) to a reactant solution obtained in step (I) and subjecting the resulting mixture to hydrolysis-condensation reaction; (III) adding a predetermined amount (e) of an epoxy group-containing alkoxysilane, acid and water to a reactant solution obtained in step (II); and then (IV) optionally adding water to the resulting mixture. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing an aqueous organopolysiloxane solution having excellent storage stability, and a coating composition containing the aqueous organopolysiloxane as a binder, which has excellent curability, stain resistance, hot water resistance, and adhesion. The present invention relates to a coating composition that forms an excellent coating film.

In recent years, environmental regulations regarding the reduction of volatile organic compounds (VOC) and toxicity have become stricter, and from the viewpoint of resource saving, the paint industry has changed from paints using organic solvents to paints using water as a solvent. The change is being made. Water-based paints using water as a solvent have been widely put into practical use, but inorganic paints using water-based organopolysiloxane as a binder have poor adhesion to many organic coatings, and during storage It is easily gelled, has poor storage stability, and has not been sufficiently put into practical use as a coating composition.
A method using an aqueous dispersion compound in which an organopolysiloxane component is combined with a water-soluble acrylic resin as a coating composition (for example, see Patent Documents 1 and 2), or an emulsion composition obtained by acrylic emulsion polymerization in the presence of an organopolysiloxane component ( For example, see Patent Document 3.
However, in these coating films, since the polysiloxane component is uniformly dispersed outside the coating film surface or the coating film surface, the effects of weather resistance and prevention of contamination cannot be expected so much.

Japanese Patent Laid-Open No. 10-60280 Japanese Patent Laid-Open No. 10-36514 JP 11-49984 A

  The present invention has been made against the background of the problems of the prior art, and includes a method for producing an aqueous organopolysiloxane solution having excellent storage stability, and the aqueous organopolysiloxane as a binder, which is cured. It aims at providing the coating composition which forms the coating film excellent in property, stain resistance, hot water resistance, and adhesiveness.

As a result of diligent investigations to solve the above problems, the present inventors have prepared a water-based organopolysiloxane having the following constitution, thereby producing a coating film excellent in curability, stain resistance, hot water resistance, and adhesion. A coating composition to be formed is provided.
That is, the present invention relates to a method for preparing an aqueous organopolysiloxane solution having the following steps and a coating composition containing the aqueous organopolysiloxane obtained thereby.
(I) (a) R ¹ _n Si (OR ² ) _4-n [wherein R ¹ is a phenyl group, R ² is a methyl group, and n is 1 or 2] Partial hydrolysis of silane with an organosilane represented by the general formula (2) R ³ _n Si (OR ⁴ ) _{4-n wherein} R ³ and R ⁴ are methyl groups and n is 1 or 2. 100 parts by mass of condensate and (b) general formula (3) R ⁵ _n Si (OR ⁶ ) _4-n [wherein R ⁵ is an organic group having 1 to 8 carbon atoms, R ⁶ is 1 to 5 carbon atoms] In the alkyl group, n is 1 or 2], (c) 3-30 parts by mass of an amino group-containing alkoxysilane, and the components (a) to (c) A step of mixing 0.2 to 0.5 equivalents of water with respect to 1 equivalent of hydrolyzable functional group, followed by hydrolysis condensation reaction,

(II) In the reaction product solution obtained in step (I), (d) 0.25 to 0.65 equivalents of acid with respect to 1 equivalent of the amino group of (c), and (a) to (c) ) A step of adding at least 0.8 equivalents of water to 1 equivalent of hydrolyzable functional groups in the component, followed by hydrolysis condensation reaction,
(III) In the reactant solution obtained in the step (II), (e) 0.3 to 1.0 equivalent of an epoxy group-containing alkoxysilane with respect to 1 equivalent of the amino group of (c) and the above (c) ) Add 0.35 to 0.75 equivalent of acid to 1 equivalent of amino group and 1 equivalent or more of water to 1 equivalent of hydrolyzable functional group in component (e), followed by hydrolysis condensation reaction and addition Reacting, then
(IV) A step of adding water to the reaction solution obtained in step (III) as necessary.

  INDUSTRIAL APPLICABILITY According to the present invention, an aqueous organopolysiloxane solution having excellent storage stability can be produced, and a coating composition that forms a coating film having excellent curability, stain resistance, and hot water resistance can be provided. .

Hereinafter, the present invention will be described in detail.
Each component used for manufacture of the aqueous | water-based organopolysiloxane solution of this invention is demonstrated.
Component (a) Component (a) is represented by the general formula (1) R ¹ _n Si (OR ² ) _4-n [wherein R ¹ is a phenyl group, R ² is a methyl group, and n is 1 or 2] An organosilane represented by the general formula (2): R ³ _n Si (OR ⁴ ) _{4-n wherein} R ³ and R ⁴ are methyl groups, and n is 1 or 2. It is a partial hydrolysis-condensation product.
The polystyrene-converted weight average molecular weight of the condensate is, for example, 300 to 5000, preferably 500 to 3000. By using a condensate having such a molecular weight, the storage stability is not deteriorated. A coating film with good adhesion can be obtained.

In the component (a), the condensate contains the organosilane represented by the general formula (1) and the organosilane represented by the general formula (2) in a mass ratio of 20:80 to 90:10. It is preferable.
Specific examples of such condensates include commercially available products such as DC3037 and DC3074 manufactured by Toray Dow Corning, and KR-510 manufactured by Shin-Etsu Chemical Co., Ltd. These organosilane partial hydrolysis condensates can be used alone or in combination of two or more.

(B) Component (b) component is represented by the general formula _{^{(3), R 5 n Si}} (OR 6) in _4-n [wherein, R ⁵ is an organic group having 1 to 8 carbon atoms, R ⁶ is 1 to carbon atoms 5 is an alkyl group, and n is 1 or 2.
In the above formula (3), examples of the organic group as R ⁵ include an alkyl group, a cycloalkyl group, a vinyl group, and an aryl group.
Here, the alkyl group may be linear or branched. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, Examples thereof include alkyl groups such as heptyl group and octyl group. Preferred alkyl groups are those having 1 to 4 carbon atoms.

Preferred examples of the cycloalkyl group include a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and the like.
Preferable examples of the aryl group include a phenyl group.
Each of the functional groups may optionally have a substituent. Examples of such a substituent include a halogen atom (for example, a chlorine atom, a bromine atom, and a fluorine atom), a (meth) acryloyl group, a mercapto group, and an alicyclic group.

The alkyl group as R ⁶ may be linear or branched. Examples of such an alkyl group include a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, and pentyl group. And preferred alkyl groups are those having 1 to 2 carbon atoms.
Specific examples of the organosilane represented by the above formula (3) include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxysilane. , Isopropyltrimethoxysilane, isopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane,

γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldi Examples include ethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, dimethoxymethylphenylsilane, dimethyldipropoxysilane, and the like, preferably methyltrimethoxysilane, methyltriethoxysilane, dimethyl Dimethoxysilane and dimethyldiethoxysilane. These organosilanes can be used singly or in combination of two or more.

Component (c) The component (c) is an alkoxysilane having an amino group in the molecule and capable of undergoing a hydrolytic condensation reaction. Preferably, an alkoxysilane represented by the following formula (4) is preferably used. it can. Formula ^{(4) (R 7 -NH-} R 8 -) m SiR 9 n (OR 10) 4-mn wherein, R ⁷ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, C5-8 A cycloalkyl group, an aryl group having 6 to 8 carbon atoms, or an amino group, R ⁸ is an alkylene group having 1 to 5 carbon atoms, and R ⁹ and R ¹⁰ are alkyl groups having 1 to 5 carbon atoms. Yes, m is 0 or 1, and n is 1 or 2.

In the formula (4), the alkyl group as R ⁷ may be linear or branched. Examples of such an alkyl group include a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, and pentyl group. Is mentioned.
Preferable examples of the cycloalkyl group as R ⁷ include a cyclopentyl group and cyclohexyl.
Preferable examples of the aryl group as R ⁷ include a phenyl group.
Preferred examples of the amino group as R ⁷ include a substituted or unsubstituted amino group. Preferred examples of the amino group for R ⁷ include one in which one or both hydrogen atoms of the amino group are substituted with, for example, an alkyl group having 1 to 5 carbon atoms. The range of such an alkyl group is the same as the range of the alkyl group as R ⁹ and R ¹⁰ described below.

The alkylene group as R ⁸ may be linear or branched. Examples of such an alkylene group include a methylene group, an ethylene group, a propylene group, and a butylene group.
The alkyl group as R ⁹ and R ¹⁰ may be linear or branched. Examples of the alkyl group as R ⁹ and R ¹⁰ include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, and pentyl group. A group is preferably mentioned. Preferred alkyl groups are those having 1 to 2 carbon atoms, for example.

  Specific examples of the amino group-containing alkoxysilane include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- ( β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldiethoxysilane, N-cyclohexyl-γ-aminopropyltrimethoxysilane, N-cyclohexyl-γ- Examples include aminopropyltriethoxysilane, γ- (2-aminoethyl) -aminopropyltrimethoxysilane, γ- (2-aminoethyl) -aminopropylmethyldimethoxysilane, and γ-anilinopropyltrimethoxysilane. These amino group-containing alkoxysilanes can be used alone or in combination of two or more.

Component (d) The component (d) is an acid added to act as a neutralizing agent for the amino group-containing alkoxysilane of the above (c) and facilitate dissolution / dispersion in water. Specific examples include inorganic acids such as nitric acid and hydrochloric acid, and organic acids such as acetic acid, formic acid, propionic acid, and lactic acid.
(E) Component The component (e) is a compound having both an epoxy group and a hydrolyzable alkoxysilyl group, and is used for the purpose of further improving the curability and hot water resistance of the coating film.
Such compounds include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropylmethyl. Typical examples include epoxy compounds such as diethoxysilane. These epoxy group-containing alkoxysilanes can be used singly or in combination of two or more.

Next, the manufacturing method of the aqueous | water-based organopolysiloxane solution of this invention is demonstrated.
First, in the step (I), the component (a), the component (b), and the component (c) are hydrolyzed and condensed in the presence of water.
The mixing ratio of each component is suitably 5 to 70 parts by mass, preferably 20 to 50 parts by mass with respect to 100 parts by mass of (a) component. Moreover, 3-30 mass parts of (c) component with respect to 100 mass parts of (a) component, Preferably, 10-25 mass parts is suitable.
In addition, when the amount of the component (b) is less than the above range, gelation is likely to occur during the hydrolysis-condensation reaction. On the other hand, when the amount is too large, water dispersibility becomes difficult.

If the amount of the component (c) is less than the above range, the resulting organopolysiloxane does not dissolve or disperse stably in water, resulting in poor storage stability. Therefore, it is not preferable.
The amount of water added is 0.2 to 0.5 equivalent, preferably 0.25 to 0.4 equivalent, relative to 1 equivalent of the total hydrolyzable functional group in the mixture of components (a) to (c). Is appropriate. In addition, when the amount of water is less than the above range, water dispersibility is deteriorated. On the other hand, when the amount is too large, polymerization stability such as gelation is deteriorated, which is not preferable.
Unreacted organosilane in component (a) is included in component (b).

The hydrolysis condensation reaction in the step (I) is usually 40 to 80 ° C., preferably 45 to 65 ° C., for example, a method of reacting for 2 to 5 hours is preferable, but the method is limited to this method. is not.
The obtained reaction product is usually a hydrolysis-condensation product having a polystyrene-equivalent weight average molecular weight of about 2500 to 20000. In addition, in this reaction system, it will be in a solution state with the alcohol which hydrolyzed and removed. In the step (I), since the reaction is performed in the absence of an acid described later, unreacted organosilane is likely to remain, so that the storage stability and the curability of the coating film are deteriorated. In step II), the hydrolysis condensation reaction is carried out in the presence of acid and water. In addition, when it is made to react in presence of an acid at (I) process, since sclerosis | hardenability of a coating film will worsen, it is unpreferable.

  In the step (II), an acid in an amount for neutralizing 0.25 to 0.65 equivalents, preferably 0.35 to 0.60 equivalents, with respect to 1 equivalent of the amino group in the above (c), and the step (I ) At least 0.8 equivalents, preferably 1.0 equivalents or more (maximum, for example, 25 equivalents are preferred) with respect to 1 equivalent of the total hydrolyzable functional groups in the hydrolysis condensate obtained in Water is added to cause hydrolysis and condensation reaction. If the amount of acid is less than the above range, unreacted organosilane is likely to remain, storage stability and coating curability deteriorate, and conversely if too much, polymerization stability such as gelation deteriorates. Therefore, it is not preferable. Further, when the amount of water is less than the above range, the hydrolysis condensation reaction of unreacted organosilane tends to be insufficient. The upper limit of the amount of water is such that the solid content is 10 to 60% by mass, preferably 10 to 40% by mass.

The acid has a reaction catalyst function and is blended in order to cause the reaction in a state where organopolysiloxane is stably dispersed or dissolved in the solution.
For the hydrolysis condensation reaction in step (II), for example, a method of reacting at 40 to 80 ° C., preferably 45 to 65 ° C., for example, for 2 to 5 hours is suitable, but is not limited to this method. Absent. The reaction product obtained in the step (II) is usually a hydrolysis condensate having a weight average molecular weight of about 5000 to 50000 in terms of polystyrene, and the remaining unreacted organosilane in the reaction solution is almost eliminated.

  In step (III), first, a neutralizing agent and water are added so that the reaction product solution obtained in step (II) can be stably used as a coating composition. As the neutralizing agent, the aforementioned acid can be used, and the amount thereof is 0.35 to 0.75 equivalent, preferably 0.40 to 0.70 equivalent, with respect to 1 equivalent of the amino group of the component (c). It is preferable to do. Next, (e) an epoxy group-containing alkoxysilane is added in an amount of 0.3 to 1.0 equivalent, preferably 0.35 to 0.67 equivalent to 1 equivalent of the amino group of the component (c). ) Add 1 equivalent or more, preferably 3 equivalents or more of water to 1 equivalent of hydrolyzable functional group in the component, and react at 40 to 80 ° C., preferably 45 to 65 ° C., for example, for 1 to 3 hours. However, the method is not limited to this method.

In addition, when there are few epoxy group containing alkoxysilanes of (e) component from the said range, the hot water resistance of a coating film is inferior, and on the contrary, since the storage stability of an aqueous organopolysiloxane solution is inferior, it is unpreferable.
Step (IV) is for adjusting the solid content by adding water to the reaction product solution obtained in step (III). The solid content of the finally obtained reaction solution is, for example, 10 to 10. 60% by mass, preferably 15 to 40% by mass. Even if the solid content of the reactant solution is within this range, water may not be added depending on the solution viscosity . In the aqueous organopolysiloxane solution thus obtained, alcohol is eliminated by the hydrolysis condensation reaction described above, and this remains in the solution. Therefore, the alcohol may be removed as necessary.

Moreover, in the reaction of each step, if necessary, a small amount of an organic solvent that does not participate in the reaction may be added. Examples of such an organic solvent include isopropanol, methanol, ethanol, butyl cellosolve, etc., and these may be used alone or in combination.
Moreover, the water used for manufacture of the aqueous | water-based organopolysiloxane solution of this invention can use pure water, distilled water, ion-exchange water, tap water, etc.
Next, the coating composition using the aqueous organopolysiloxane of the present invention will be described.

  It is preferable that a coating composition contains 20-98 mass% in conversion of solid content by using the above-mentioned aqueous organopolysiloxane as a binder. Furthermore, if necessary, the solid content of the coating composition is preferably adjusted to 10 to 50% by mass, and water and organic solvents for improving the storage stability and coating workability of the coating composition, In addition, fillers, dyes, and various additives such as curing accelerators, thickeners, and pigment dispersants may be blended. Examples of the organic solvent include hydrophilic organic solvents such as methanol, alcohols such as ethanol, propanol, isopropanol, and butanol, alcohol ethers such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether, and ketones such as acetone and methyl ethyl ketone. A solvent or a mixed organic solvent with various hydrophobic organic solvents for paints such as toluene, xylene, ethyl acetate, and butyl acetate can be used.

  As the filler, various extender pigments and coloring pigments such as talc, barium carbonate, calcium carbonate, bentonite, titanium oxide, carbon black, Bengala, and lithopone can be used. Examples of the curing accelerator include organic tin compounds such as tin octylate, dibutyltin dilaurate, dibutyltin dimaleate, and tributyltin laurate and their emulsions, and amine compounds such as ethylenediamine, diethylenetriamine, piperidine, phenylenediamine, and triethylamine. Etc. are typical examples.

These curing accelerators are desirably added in order to cure the coating composition at a relatively low temperature more quickly, and the amount is suitably 0.01 to 15 parts by mass with respect to 100 parts by mass of the binder, for example. It is. The coating composition of the present invention can form a cured coating film by coating the surface of an object to be coated with a brush, spray, roll, dipping, or other coating means, and baking at room temperature or a temperature of 300 ° C. or lower. It is.
In addition, as a to-be-coated object, various to-be-coated objects, such as inorganic ceramic industry base materials, various metal base materials, such as stainless steel and aluminum, a glass base material, a plastic base material, and a paper base material, are applicable suitably.

Hereinafter, the present invention will be described in more detail with reference to examples.
In the examples, “parts” and “%” are based on mass unless otherwise specified.
<Preparation of aqueous organopolysiloxane solution>

Example 1
In a reactor equipped with a reflux condenser and a stirrer, (a) partially hydrolyzed cocondensate of phenyltrimethoxysilane and dimethyldimethoxysilane (DC3074 manufactured by Toray Dow Corning Co., Ltd .; solid content 100%, polystyrene conversion (Weight average molecular weight 2400) 44 parts, (b) methyltrimethoxysilane 6 parts and dimethyldimethoxysilane 24 parts, and (c) N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane 6 parts. After stirring, 5 parts of isopropanol and 3.5 parts of ion-exchanged water (corresponding to 0.5 equivalents with respect to 1 equivalent of the total hydrolyzable functional groups) were added and subjected to a hydrolysis condensation reaction at 60 ° C. for 3 hours. . For 100 parts of the resulting solution, 130 parts of ion-exchanged water (corresponding to 17.8 equivalents relative to 1 equivalent of total hydrolyzable functional groups) and 3.3 parts of (d) lactic acid (amino in component (c)) (Corresponding to 0.5 equivalent to 1 equivalent of group) was added and reacted at 60 ° C. for 2 hours. Then, (e) 20 parts of γ-glycidoxypropyltrimethoxysilane (corresponding to 0.97 equivalent to 1 equivalent of amino group in component (c)) and 4 parts of lactic acid (amino group in component (c)) 1 equivalent and 0.6 equivalents) and 130 parts of ion-exchanged water (corresponding to 17.8 equivalents with respect to 1 equivalent of the hydrolyzable functional group in the component (e)) and added at 50 ° C. for 1 hour After reacting and cooling, 92 parts of ion-exchanged water was added to prepare an aqueous organopolysiloxane solution S-1 containing amino silane and epoxy silane having a solid content of 17.0% and pH 5.0.

Example 2
In a reactor equipped with a reflux condenser and a stirrer, (a) partially hydrolyzed cocondensate of phenyltrimethoxysilane and dimethyldimethoxysilane (DC3074 manufactured by Toray Dow Corning Co., Ltd .; solid content 100%, polystyrene conversion (Weight average molecular weight 2400) 44 parts, (b) 29 parts of dimethyldimethoxysilane and (c) 6 parts of N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane were added and mixed. 5 parts and 3.3 parts of ion-exchanged water (corresponding to 0.5 equivalents relative to 1 equivalent of the total hydrolyzable functional groups) were added and subjected to a hydrolytic condensation reaction at 60 ° C. for 3 hours. For 100 parts of the resulting solution, 130 parts of ion-exchanged water (corresponding to 18.9 equivalents relative to 1 equivalent of total hydrolyzable functional groups) and 3.3 parts of (d) lactic acid (amino in component (c)) (Corresponding to 0.5 equivalent to 1 equivalent of group) was added and reacted at 60 ° C. for 2 hours. Next, (e) 20 parts of γ-glycidoxypropyltrimethoxysilane (corresponding to 0.97 equivalents relative to 1 equivalent of amino group in component (c)) and 4 parts of lactic acid (amino in component (c)) Group equivalent to 0.6 equivalent) and 130 parts of ion-exchanged water (corresponding to 18.9 equivalent to 1 equivalent of hydrolyzable functional group in component (e)), reacted at 50 ° C. for 1 hour, cooled Thereafter, 92 parts of ion-exchanged water was added to prepare an aqueous organopolysiloxane solution S-2 containing aminosilane and epoxysilane having a solid content of 17.0% and pH 5.0.

Comparative Example 1
In a reactor equipped with a reflux condenser and a stirrer, (a) partially hydrolyzed cocondensate of phenyltrimethoxysilane and dimethyldimethoxysilane (DC3074 manufactured by Toray Dow Corning Co., Ltd .; solid content 100%, polystyrene conversion (Weight average molecular weight 2400) 30 parts, (b) 4 parts of methyltriethoxysilane and 16 parts of dimethyldiethoxysilane, and (c) 4 parts of N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane After mixing, 2.6 parts of ion-exchanged water (corresponding to 0.6 equivalents relative to 1 equivalent of total hydrolyzable functional groups) was added with stirring, and a hydrolysis condensation reaction was performed at 60 ° C. for 3 hours. To 100 parts of the obtained solution, 10 parts of ion-exchanged water (equivalent to 2.3 equivalents relative to 1 equivalent of total hydrolyzable functional groups) was added and reacted at 60 ° C. for 3 hours. Next, after cooling, 80 parts of ion-exchanged water and 5N hydrochloric acid are added so that the pH of the solution is 4.3 to prepare an aqueous organopolysiloxane solution S-3 containing only aminosilane having a solid content of 25.2%. did.

Comparative Example 2
In a reactor equipped with a reflux condenser and a stirrer, (a) hydrolysis condensate of methyltrimethoxysilane (SR2402, manufactured by Toray Dow Corning Co., Ltd., polystyrene equivalent weight average molecular weight 1300) 44 parts, (b) After adding and mixing 30 parts of methyltrimethoxysilane and 6 parts of (c) N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, 5 parts of isopropanol and 5 parts of ion-exchanged water ( (Corresponding to 0.46 equivalent to 1 equivalent of the total hydrolyzable functional groups) was added, and a hydrolysis condensation reaction was carried out at 60 ° C. for 3 hours. To 100 parts of the obtained solution, 130 parts of ion-exchanged water and 3.3 parts of (d) lactic acid (corresponding to 0.5 equivalents with respect to 1 equivalent of the amino group in the component (c)) are added, and at 60 ° C. The reaction was performed for 2 hours. Next, 23 parts of γ-glycidoxypropyltrimethoxysilane (corresponding to 1.12 equivalents relative to 1 equivalent of amino group in component (c)), 4 parts of lactic acid (1 equivalent of amino group in component (c)) (Corresponding to 0.6 equivalents) and 130 parts of ion-exchanged water (corresponding to 17.8 equivalents per 1 equivalent of the hydrolyzable functional group in component (e)), and reaction at 50 ° C. for 1 hour After cooling, 92 parts of ion-exchanged water was added to prepare an aqueous organopolysiloxane solution S-4 containing aminosilane and epoxysilane having a solid content of 17.0% and pH 5.0.

<Storage stability test>
In order to examine the storage stability of each aqueous organopolysiloxane solution obtained in Examples 1 and 2 and Comparative Examples 1 and 2, each solution was allowed to stand in a sealed container at 50 ° C., and after 3 months. The change in viscosity of the solution was compared with the initial value, and the storage stability was determined as follows. The results are shown in Table 1.
○: Viscosity change with respect to the initial value is less than 1.2 times Δ: Viscosity change with respect to the initial value is less than 1.2 to 2.0 ×: Viscosity change with respect to the initial value is 2.0 times or more

<Performance evaluation of coating composition>
A coating composition was prepared by adding 5 parts of a 10% aqueous dispersion (curing accelerator) of dibutyltin dilaurate to 100 parts of the aqueous organopolysiloxane solution obtained in Examples 1 and 2 and Comparative Examples 1 and 2. Each coating composition was subjected to various tests on the appearance, hardness, hot water resistance, stain resistance, alkali resistance, and solvent resistance of the obtained coating film, and the results are shown in Table 1.
The test method and its evaluation followed the following method.

<Film performance test>
A gypsum slag perlite plate (thickness 12 mm, size 30 × 30 cm) is used as a material, and a polyisocyanate prepolymer solution sealer “V-Selan # 100 sealer” (Dainippon Paint Co., Ltd., butyl acetate: xylene) = 100% diluted with a 1: 1 solvent) was spray-coated with a spray so that the coating amount was 90 to 100 g / m ² (wet mass). This was dried at 100 ° C. for 5 minutes. Next, an acrylic silicone resin-based paint “V-Selan # 500 Enamel” (Dainippon Paint Co., Ltd., diluted 40% with a solvent of butyl acetate: xylene = 1: 1) was applied in an amount of 80 to 90 g / m ^2. (Wet mass), spray coating was performed with a spray so that the film thickness was 30 μm. This was dried at 120 ° C. for 15 minutes. Subsequently, each of the coating compositions described above was spray-coated by spraying so that the coating amount was 130 ± 10 g / m ² (wet mass). This was dried at 120 ° C. for 15 minutes and then at room temperature for 3 days to prepare a test plate.

<Appearance of Coating Film> The appearance of the coating film thus prepared was visually determined as follows.
○: Good Δ: Slightly turbid ×: Fine cracks <Hardness of coating film> The hardness of the prepared coating film was measured in accordance with JIS K 5600-5-4. Was evaluated by the hardness of the pencil.

<Adhesiveness of the coating film> According to JIS K 5600-5-6, the adhesiveness of the prepared coating film was cross-cut to make 25 grids at intervals of 1 mm, and peeled off with cellophane adhesive tape. Evaluation was based on the number of eyes without peeling.

<Heat-resistant water> The produced test plate was immersed in 60 degreeC tap water for one month, and the external appearance of the coating film was determined visually.
○ ・ ・ ・ No change △ ・ ・ ・ Slight change such as decrease in gloss and whitening × ・ ・ ・ Large decrease in gloss, whitening etc.

<Contamination Resistance> 24 hours after drawing on the produced test plate with red and black magic inks, it was wiped with a cloth wetted with n-butanol, and the decontamination property was visually determined as follows.
◎ ・ ・ ・ Complete removal ○ ・ ・ ・ Minimum contamination △ ・ ・ ・ Slight contamination × ・ ・ ・ Significant contamination

<Alkali Resistance> The prepared test plate was immersed in a saturated slaked lime aqueous solution for 1 week, and the coating state was visually determined as follows.
◎ ・ ・ ・ No change ○ ・ ・ ・ Slight reduction in gloss △ ・ ・ ・ Low gloss and slight whitening × ・ ・ ・ Low gloss and significant whitening

<Solvent resistance> Using a test plate, methyl ethyl ketone and n-butanol were used as solvents, a rubbing test was performed 50 times with a cloth wetted with each solvent, and the coating state was visually determined as follows.
○: No change in coating film for both solvents. Δ: Only one solvent is whitened. × ... Both solvents are whitened.

As is clear from Table 1, the storage stability of Examples 1 and 2 which are aqueous organopolysiloxane solutions of the present invention was superior to Comparative Examples 1 and 2. In Examples 1 and 2 where the aqueous organopolysiloxane of the present invention was used as a binder as a binder, the coating performance was excellent in each coating performance test.
On the other hand, Comparative Example 1 not containing an epoxy group-containing alkoxysilane and Comparative Example 2 having a different organosilane hydrolysis condensate used were particularly poor in hot water resistance and alkali resistance of the coating film. These poor coating states are due to insufficient coating curability.

  The aqueous organopolysiloxane solution of the present invention is excellent in storage stability, and is a coating composition that forms a coating film excellent in curability, stain resistance, hot water resistance, and adhesion on the surface of a base material or an old coating film. Can provide.

Claims (2)

A method for producing an aqueous organopolysiloxane solution comprising the following steps:
(I) (a) R ¹ _n Si (OR ² ) _4-n [wherein R ¹ is a phenyl group, R ² is a methyl group, and n is 1 or 2] Partial hydrolysis of silane with an organosilane represented by the general formula (2) R ³ _n Si (OR ⁴ ) _{4-n wherein} R ³ and R ⁴ are methyl groups and n is 1 or 2. 100 parts by mass of condensate and (b) general formula (3) R ⁵ _n Si (OR ⁶ ) _4-n [wherein R ⁵ is an organic group having 1 to 8 carbon atoms, R ⁶ is 1 to 5 carbon atoms] In the alkyl group, n is 1 or 2], (c) 3-30 parts by mass of an amino group-containing alkoxysilane, and the components (a) to (c) In the reaction product solution obtained in (II) step (I), a step of mixing 0.2 to 0.5 equivalents of water with 1 equivalent of hydrolyzable functional group, followed by hydrolysis condensation reaction (D) 0.25 to 0.65 equivalent of acid with respect to 1 equivalent of amino group of (c), and 1 equivalent of hydrolyzable functional group in the hydrolysis condensate obtained in step (I) Adding at least 0.8 equivalents or more of water to the hydrolytic condensation reaction,
(III) In the reactant solution obtained in the step (II), (e) 0.3 to 1.0 equivalent of an epoxy group-containing alkoxysilane with respect to 1 equivalent of the amino group of (c) and the above (c) ) Add 0.35 to 0.75 equivalent of acid to 1 equivalent of amino group and 1 equivalent or more of water to 1 equivalent of hydrolyzable functional group in component (e), followed by hydrolysis condensation reaction and addition Reacting, then
(IV) A step of adding water to the reaction solution obtained in step (III), if necessary,
The manufacturing method characterized by having.   A coating composition comprising the aqueous organopolysiloxane obtained in claim 1 as a binder.