JP2002201282A - Aqueous dispersion of polyorganosiloxane particle and its preparation process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous dispersion of polyorganosiloxane particles which shows an excellent crack resistance at a dried state when used as a coating and also exhibits an excellent weather resistance, water resistance, stain resistance and adhesion, and its preparation process. SOLUTION: The aqueous dispersion of polyorganosiloxane particles is obtained by allowing a seed polymer particle (A) having a weight average molecular weight of from 500 to 30,000 to absorb a silane component (B) comprising at least one chosen from an organosilane, its hydrolysate and its condensate in an aqueous medium and subsequently subjecting it to a condition under which the silane component (B) is hydrolyzed and condensed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous dispersion of polyorganosiloxane particles and a method for producing the same.
More specifically, in a binder emulsion for a water-based polyorganosiloxane paint having excellent crack resistance, weather resistance, water resistance, stain resistance, and adhesion when dried, the water content of polyorganosiloxane particles having excellent crack resistance when dried The present invention relates to a dispersion and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, paints and coating agents have been used in various fields, and the range of application has been steadily expanding. As a result, the performance requirements for paints and coating materials are becoming increasingly sophisticated. Especially in recent years,
A water-based paint / coating material excellent in weather resistance, water resistance, stain resistance, and adhesion is required. Under these circumstances, emulsions of polyorganosiloxane particles have been developed, and some of them have been put to practical use as paints and coating materials.

[0003]

However, when an emulsion of polyorganosiloxane particles, which has been developed so far, is used in, for example, a water-based paint, moisture evaporates during drying, and the coating film shrinks and cracks are easily generated. . In this case, cracks can be prevented by measures such as increasing the binder component in the paint or adding a film-forming aid, but these measures reduce paint performance or significantly increase paint prices. And other problems.

[0004] Further, when producing an emulsion of polyorganosiloxane particles, there is a great limitation in the production process that a high-energy disperser is usually required to disperse organosilanes in water. Was.

[0005] An object of the present invention is to provide an aqueous dispersion of polyorganosiloxane particles which, when used in a coating material, has excellent resistance to cracking during drying and excellent weatherability, water resistance, stain resistance and adhesion. It is in.

Another object of the present invention is to enable production with a normal stirring device without a high energy disperser,
Another object of the present invention is to provide a method for producing an aqueous dispersion of polyorganosiloxane particles that can easily control the particle diameter and particle diameter distribution of the obtained particles.

[0007]

Means for Solving the Problems The present inventors have studied diligently to solve the above-mentioned problems, and by using low molecular weight polymer particles as seeds to absorb organosilanes into the polymer particles, The inventors have found that the above-mentioned problems can be solved by forming a fine aqueous dispersion and providing it for production, and have conceived an aqueous dispersion of polyorganosiloxane particles of the present invention and a method for producing the same.

(1) The aqueous dispersion of polyorganosiloxane particles of the present invention has a weight average molecular weight of 50 in an aqueous medium.
Seed polymer particles (A) in the range of 0 to 30,000
To an organosilane, a hydrolyzate of the organosilane,
And absorbing at least one silane component (B) selected from condensates of the organosilane, and then subjecting the silane component (B) to hydrolysis and condensation conditions.

Here, the aqueous medium means water or a mixed solvent of water and a water-miscible solvent.

In the aqueous dispersion of polyorganosiloxane particles of the present invention, the component (A) of the seed polymer particles is localized on the surface of the polyorganosiloxane particles. It is presumed that it promotes fusion of the steel and prevents cracking.

Therefore, when the aqueous dispersion of polyorganosiloxane particles of the present invention is used in a paint, a coating film having excellent crack resistance upon drying, weather resistance, water resistance, stain resistance, and adhesion can be formed. . In particular, even when the coating film is thick or the mixing ratio of the pigment in the coating material is high, cracking during drying hardly occurs, and excellent practical performance can be exhibited.

In this case, the aqueous dispersion of the polyorganosiloxane particles can be obtained by using 1 to 200 parts by weight of the silane component (B) per 1 part by weight of the seed polymer particles (A).

(2) The method for producing an aqueous dispersion of polyorganosiloxane particles of the present invention is characterized in that, in an aqueous medium, 1 part by weight of seed polymer particles (A) having a weight average molecular weight in the range of 500 to 30,000 A silane component (B) 1 comprising at least one selected from an organosilane, a hydrolyzate of the organosilane, and a condensate of the organosilane;
After absorbing up to 200 parts by weight, the composition is subjected to hydrolysis and condensation conditions of the silane component (B).

According to the method for producing an aqueous dispersion of polyorganosiloxane particles of the present invention, the aqueous dispersion can be emulsified using a usual stirring device without using a high energy disperser. Process restrictions can be reduced.

Furthermore, the seed polymer particles (A) used
By adjusting the particle size and the particle size distribution of the polyorganosiloxane particles to be produced, the particle size and the particle size distribution of the polyorganosiloxane particles to be produced can be easily controlled.

In the above method for producing an aqueous dispersion of polyorganosiloxane particles, the seed polymer particles (A) are preferably carboxyl group-modified polystyrene.

(3) The coating composition of the present invention can contain an aqueous dispersion of the above-mentioned polyorganosiloxane particles as a main component.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an aqueous dispersion of polyorganosiloxane particles of the present invention and a method for producing the same will be described in detail.

(Aqueous Dispersion) (Seed Polymer Particles (A)) The aqueous dispersion of the present invention comprises:
Polymer particles having a weight average molecular weight in a specific range,
Used as so-called seed polymer particles. That is,
The seed polymer particles (A) used in the present invention have a weight average molecular weight of 500 to 30,000, preferably 1,3.
000-20,000, more preferably 1,500-
10,000.

In the present invention, the “weight average molecular weight” of the polymer particles is defined by a usual method such as viscosity measurement of the dispersion containing the polymer particles or gel permeation chromatography (GPC; polystyrene conversion) based on the viscosity measurement. The measured weight average molecular weight.

When the weight average molecular weight of the seed polymer particles (A) exceeds 30,000, the resulting polyorganosiloxane particles are not sufficiently improved in cracking during drying when used as an aqueous paint or coating material. Sometimes.
The weight average molecular weight of the seed polymer particles (A) is 5
If it is less than 00, the obtained polyorganosiloxane particles show only a mere plasticizing effect, and the cracking during drying may be insufficiently improved.

The particle size and the particle size distribution of the seed polymer particles (A) have a great influence on the particle size and the particle size distribution of the polyorganosiloxane particles to be produced. Basically, the particle size of the resulting polyorganosiloxane particles approximately matches the value calculated assuming that the seed polymer particles (A) have absorbed all of the silane component (B). Further, by using this, it is possible to control the particle size of the polyorganosiloxane particles to be generated. The particle size distribution of the resulting polyorganosiloxane particles is generally similar to the particle size distribution of the seed polymer particles (A). Normal,
Since it is often preferable that the polyorganosiloxane particles used in the coating have a narrow particle size distribution, the seed polymer particles (A) have a uniform particle size, that is,
It is desirable to use particles having a narrow particle size distribution. As the seed polymer particles (A), specifically, those having a particle size of 0.03 to 0.2 μm and a variation coefficient of the particle size distribution of 10% or less are suitably used. Here, the particle size and the particle size distribution can be determined from a transmission electron micrograph or by a laser light scattering method.

The polymer emulsion having a wide particle size distribution can be made into a high-concentration dispersion, and has the characteristic that the viscosity is low at the same concentration. Therefore, it is also possible to produce polyorganosiloxane / organic polymer composite particles having a wide particle size distribution by using the seed polymer particles (A) having a wide particle size distribution. In order to achieve such an object, specifically, the particle size is required to be in the range of 0.1 to 0.1.
And the variation coefficient of the particle size distribution is 30
About 90% of seed polymer particles (A) are preferably used.

The composition of the seed polymer particles (A) is not particularly limited as long as it dissolves or swells in the silane component (B) used for producing the aqueous dispersion of the present invention. Specifically, poly (meth) acrylates such as polystyrene and polymethyl methacrylate, polyvinyl acetates, polybutadiene, styrene-butadiene copolymer, and other polymer particles are preferably used. Among them, carboxyl group-modified polystyrene and carboxyl group-modified poly (meth) acrylate are more preferably used, and carboxyl group-modified polystyrene is particularly preferably used.

The method for obtaining the seed polymer particles (A) is not particularly limited. Examples thereof include an emulsion polymerization method using a relatively large amount of a mercaptan-based molecular weight modifier such as dodecyl mercaptan or a soap-free method. It can be synthesized by a polymerization method. According to this method, the particle size can be easily controlled, and particles having a uniform particle size distribution can be obtained. In the production of the seed polymer particles (A), it is also possible to use a seed polymerization method using seed particles in order to control the particle size.

(Silane Component (B)) The organosilane in the silane component (B) constituting the aqueous dispersion of the present invention is generally represented by the following general formula (1). (R ¹ ) _n Si (OR ² ) _4-n (1) wherein R ¹ is the same or different when two or more are present, and is a monovalent monovalent having 1 to 8 carbon atoms. R ² is the same or different and represents an alkyl group having 1 to 5 carbon atoms or an acyl group having 1 to 6 carbon atoms, and n is an integer of 0 to 3. The hydrolyzate of the organosilane is OR in the general formula (1), which is contained in 1 to 4 organosilanes.
^It is not necessary that all ^two groups be hydrolyzed, for example,
It may be one in which only one is hydrolyzed, one in which two or more are hydrolyzed, or a mixture thereof.

Further, the condensate of the organosilane is formed by condensing silanol groups of the hydrolyzate of the organosilane to form S
Although the i-O-Si bond is formed, in the present invention, it is not necessary that all the silanol groups are condensed. This is a concept that also includes mixtures and the like.

In the general formula (1), R ¹ has 1 to ¹ carbon atoms.
Examples of the monovalent organic group of 8 include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group,
i-butyl group, sec-butyl group, t-butyl group, n-
Alkyl groups such as hexyl group, n-heptyl group, n-octyl group and 2-ethylhexyl group; acyl groups such as acetyl group, propionyl group, butyryl group, valeryl group, benzoyl group, trioil group and caproyl group; vinyl group;
In addition to allyl group, cyclohexyl group, phenyl group, epoxy group, glycidyl group, (meth) acryloxy group, ureido group, amide group, fluoroacetamide group, isocyanate group and the like, and substituted derivatives of these groups are also mentioned. it can.

Examples of the substituent in the substituted derivative of R ¹ include a halogen atom, a substituted or unsubstituted amino group, a hydroxyl group, a mercapto group, an isocyanate group, a glycidoxy group, a 3,4-epoxycyclohexyl group, a (meth) An acryloxy group, a ureido group, an ammonium base and the like can be mentioned. However, the carbon number of R ¹ composed of these substituted derivatives is 8 or less including the carbon atom in the substituent.

In the general formula (1), when two or more R ¹ are present, they may be the same or different from each other.

Further, R^TwoAnd an alkyl group having 1 to 5 carbon atoms
For example, for example, methyl group, ethyl group, n-propyl
Group, i-propyl group, n-butyl group, sec-butyl
Group, t-butyl group, n-pentyl group and the like.
As an acyl group having 1 to 6 carbon atoms, for example,
Tyl, propionyl, butyryl, valeryl,
Proyl groups and the like can be mentioned. The general formula
(1) Multiple Rs in ^TwoAre the same but different
You may.

Specific examples of such organosilanes include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane and tetra-n-butoxysilane; methyl Trimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane,
n-butyltrimethoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxy Silane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3,3
3-trifluoropropyltrimethoxysilane, 3,
3,3-trifluoropropyltriethoxysilane, 3
-Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 2-hydroxypropyltrimethoxysilane, 2-
Hydroxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanate Natopropyltriethoxysilane,
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3,4
-Epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) attacryloxypropyltriethoxysilane, 3 Trialkoxysilanes such as ureidopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, di-n-propyldimethoxysilane, di-n -Propyldiethoxysilane, di-i-propyldimethoxysilane, di-i-
Propyldiethoxysilane, di-n-butyldimethoxysilane, di-n-butyldiethoxysilane, di-n-pentyldimethoxysilane, di-n-pentyldiethoxysilane, di-n-hexyldimethoxysilane, di-n −
Hexyldiethoxysilane, di-n-heptyldimethoxysilane, di-n-heptyldiethoxysilane, di-n
Dialkoxysilanes such as -octyldimethoxysilane, di-n-octyldiethoxysilane, di-n-cyclohexyldimethoxysilane, di-n-cyclohexyldiethoxysilane, diphenyldimethoxysilane and diphenyldiethoxysilane; trimethylmethoxysilane; Monoalkoxysilanes such as trimethylethoxysilane; and methyltriacetyloxysilane, dimethyldiacetyloxysilane, and the like.

Of these, those preferably used are:
Trialkoxysilanes, dialkoxysilanes and monoalkoxysilanes, and as the trialkoxysilanes, methyltrimethoxysilane and methyltriethoxysilane are preferable, and as the dialkoxysilanes, dimethyldimethoxysilane And dimethyldiethoxysilane, and as the monoalkoxysilanes, trimethylmethoxysilane is preferable.

The silane component (B) is at least one selected from an organosilane, a hydrolyzate of the organosilane, and a condensate of the organosilane. That is,
The silane component (B) may be only one of these three types, a mixture of any two types, or a mixture containing all three types. In the present invention, it is preferable that an organosilane and a condensate of an organosilane (hereinafter also referred to as “polyorganosiloxane”) are used as a mixture. In the aqueous dispersion of the present invention, by co-condensing an organosilane and a polyorganosiloxane, a film having excellent properties such as hardness, chemical resistance, weather resistance, film forming property, transparency, and crack resistance is obtained. To form. Further, there is an advantage that the polymerization stability when the vinyl compound is polymerized after emulsification is remarkably improved, and the polymerization can be performed at a high solid content, so that industrialization is easy.

When two types of organosilane and polyorganosiloxane are used, dialkoxysilanes are preferred as the organosilane. When a dialkoxysilane is used, a linear component is added as a molecular chain, and the flexibility of the obtained particles is increased. Furthermore, when a coating film is formed using the obtained aqueous dispersion, there is an effect that a coating film having excellent transparency can be obtained. As the dialkoxysilanes, dimethyldimethoxysilane, dimethyldiethoxysilane, and the like are particularly preferable.

Further, when two kinds of organosilane and polyorganosiloxane are used, the polyorganosiloxane is preferably used alone as a trialkoxysilane, or a trialkoxysilane of 40 to 95 mol% and a dialkoxysilane of 60 to 5 mol. % Is preferably a condensate. By using dialkoxysilane in combination with trialkoxysilane, the resulting coating film can be softened and alkali resistance can be improved.

The polyorganosiloxane is used as a condensate of organosilane by previously hydrolyzing and condensing organosilane. At this time, when preparing the polyorganosiloxane, it is preferable to add an appropriate amount of water to the organosilane and, if necessary, an organic solvent to hydrolyze and condense the organosilane.

Here, the amount of water used is determined based on the amount of organosilane 1
It is usually about 1.2 to 3.0 mol, preferably about 1.3 to 2.0 mol, per mol.

At this time, the organic solvent used as required is not particularly limited as long as the polyorganosiloxane can be uniformly mixed. Examples thereof include alcohols, aromatic hydrocarbons, ethers, and the like. Ketones,
Esters and the like can be mentioned.

Among these organic solvents, specific examples of alcohols include methanol, ethanol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, and n-hexyl. Alcohol, n-octyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene monomethyl ether acetate, diacetone alcohol, and the like. Can be.

Specific examples of aromatic hydrocarbons include benzene, toluene and xylene, specific examples of ethers include tetrahydrofuran and dioxane, and specific examples of ketones include acetone, methyl ethyl ketone, and the like. Specific examples of esters such as methyl isobutyl ketone and diisobutyl ketone include ethyl acetate, propyl acetate, butyl acetate, and propylene carbonate.

These organic solvents can be used alone or in combination of two or more.

When an organic solvent is contained in the polyorganosiloxane, the organic solvent can be removed from the aqueous dispersion before the condensation / polymerization reaction described later.

The polyorganosiloxane used herein has a polystyrene-equivalent weight average molecular weight (hereinafter also referred to as “Mw”) of preferably from 800 to 100,000, and more preferably from 1,000 to 50,000.

Commercially available polyorganosiloxanes include MKC silicate manufactured by Mitsubishi Chemical Corporation, ethyl silicate manufactured by Colcoat, silicon resin manufactured by Dow Corning Toray, and silicone resin manufactured by Toshiba Silicone Co., Ltd. , Silicone resin manufactured by Shin-Etsu Chemical Co., Ltd., hydroxyl group-containing polydimethylsiloxane manufactured by Dow Corning Asia Co., Ltd., and silicon oligomer manufactured by Nippon Yunika Co., Ltd. May be.

When an organosilane and a polyorganosiloxane are used as the silane component (B), the mixing ratio of the organosilane and the polyorganosiloxane is 95 to 5% by weight, preferably 90 to 10% by weight, based on the weight of the organosilane (completely hydrolyzed condensate). %, Polyorganosiloxane (completely hydrolyzed condensate equivalent) 5 to 9
5% by weight, preferably 10 to 90% by weight [organosilane + polyorganosilane = 100% by weight]. If the amount of the polyorganosiloxane is less than 5% by weight, the surface of the obtained coating film may be sticky or the curability of the coating film may be unfavorably deteriorated. On the other hand, 95% by weight
When the ratio exceeds, the proportion of the organosilane component becomes too small, so that it is difficult to emulsify the mixture containing the silane component (B) component, the stability of the emulsion after emulsification decreases, or the obtained organic-inorganic composite It is not preferable because the film forming property of the body is deteriorated.

Here, the above-mentioned completely hydrolyzed condensate means that the R ² O— group of the organosilane is hydrolyzed 100% and Si
It is an OH group, which is completely condensed to form a siloxane structure.

The amount of the silane component (B) used in the production process of the aqueous dispersion of the present invention (solid content conversion amount)
Is 1 to 2 parts by weight based on 1 part by weight of the seed polymer particles (A).
00 parts by weight, preferably 1 to 100 parts by weight, more preferably 2 to 50 parts by weight.

If the amount of the silane component (B) exceeds 200 parts by weight, the substantial effect of the present invention cannot be obtained.
When the use ratio of the silane component (B) is less than 1 part by weight, the amount of the seed polymer particles (A) in the product polymer particles is relatively increased, and the product performance such as mechanical strength and heat resistance is increased. Problems arise.

(Production Method of Aqueous Dispersion) The aqueous dispersion of the polyorganosiloxane particles of the present invention is prepared in an aqueous medium by
It is obtained by absorbing the silane component (B) into the seed polymer particles (A) and then subjecting the silane component (B) to hydrolysis and condensation conditions.

(Dispersion absorption of silane component (B)) In the present invention, the silane component (B) is added to the seed polymer particles (A).
When the silane component is absorbed, it is only necessary to add the silane component (B) to a reaction vessel containing an aqueous medium containing the seed polymer particles (A) and stir the mixture with a normal stirring blade. Alternatively, the seed polymer particles (A) are added to a reaction vessel containing an aqueous medium containing the silane component (B), and the silane component (B) is stirred with an ordinary stirring blade to convert the silane component (B) into the seed polymer particles (A). Can also be absorbed. Conventionally, the silane component (B) is particularly poorly emulsified in water, and in order to obtain a fine emulsified state, a high-pressure homogenizer, an ultrasonic homogenizer,
Usually, a high energy dispersing machine such as a colloid mill or a homomixer is required. However, in the present invention,
A large amount of the silane component (B) can be absorbed by the seed polymer particles (A), and a fine and uniform dispersion can be obtained only by ordinary stirring without using a high energy disperser.
As a result, there are merits such as the restriction on the manufacturing equipment being reduced and the manufacturing cost being greatly reduced.

(Conditions for Hydrolytic Condensation of Silane Component (B))
The hydrolytic condensation of the silane component (B) in the present invention can be performed by adjusting the pH. In water, the hydrolysis and condensation reaction of the silane component (B) proceeds, but the hydrolysis rate greatly varies depending on the pH. In general, it is known that the hydrolysis rate is the lowest (stable) when the pH is weakly acidic (around pH 5 to 6), and the hydrolysis rate greatly increases at a lower or higher pH. In the present invention, the pH
After the silane component (B) is absorbed into the seed polymer particles (A) at about 5 to 6 (preferably pH 4.5 to 6.5), the pH of the system is lowered to pH 1 to pH 4, and the silane component (B ) Is preferably carried out.

Acids added to lower the pH include:
Any of inorganic acids such as sulfuric acid and hydrochloric acid, and organic acids such as acetic acid, oxalic acid and citric acid can be used.

(Other Conditions) [Emulsifier] In the production of the aqueous dispersion according to the present invention, an emulsifier for ensuring the dispersion stability of the obtained particles can be used. These may be those commonly used in aqueous emulsion polymerization, for example, anionic surfactants such as alkyl sulfates, alkyl aryl sulfates, alkyl phosphates, and fatty acid salts; alkylamine salts, alkyl quaternary Cationic surfactants such as amine salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers and block type polyethers; carboxylic acid types (for example, amino acid types and betainic acid types); Any of amphoteric surfactants such as a sulfonic acid type can be used. These surfactants can be used alone or in combination of two or more.

[Silane Coupling Agent] In the aqueous dispersion of the present invention, if necessary, the silane component (B)
It is also possible to add a silane coupling agent in combination during the preparation of When a silane coupling agent is contained in the aqueous dispersion of the present invention, the hybrid property of the organic component and the inorganic component of the aqueous dispersion of the present invention is improved, so that crack resistance during film formation, transparency, and weather resistance are improved. Is improved. As the silane coupling agent, a compound having a group capable of forming a siloxane bond such as an alkoxysilyl group capable of co-condensing with the silane component (B) is preferable. As a specific example of such a silane coupling agent, CH ₂ ＣＨCHSi (CH ₃ )
_{(OCH 3) 2, CH 2} = CHSi (OCH 3) 3, CH 2 =
_{CHSi (CH 3) Cl 2,} CH 2 = CHSiCl 3, CH
₂ = CHCOO (CH ₂ ) ₂ Si (CH ₃ ) (OCH ₃ ) ₂ ,
CH ₂ ＣＨCHCOO (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CH ₂
ＣＨCHCOO (CH ₂ ) ₃ Si (CH ₃ ) (OCH ₃ ) ₂ , C
_{H 2 = CHCOO (CH 2)} 3 Si (OCH 3) 3, CH 2 =
CHCOO (CH ₂ ) ₂ Si (CH ₃ ) Cl ₂ , CH ₂ ＣC
HCOO (CH ₂ ) ₂ SiCl ₃ , CH ₂ ＣＨCHCOO (C
H ₂ ) ₃ Si (CH ₃ ) Cl ₂ , CH ₂ ＣＨCHCOO (C
_{H 2) 3 SiCl 3, CH} 2 = C (CH 3) COO (CH 2)
_{2 Si (CH 3) (OCH} 3) 2, CH 2 = C (CH 3) CO
O (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CH ₂ ＣC (CH ₃ ) C
OO (CH ₂ ) ₃ Si (CH ₃ ) (OCH ₃ ) ₂ , CH ₂ ＣC
(CH ₃ ) COO (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , CH ₂ =
C (CH ₃ ) COO (CH ₂ ) ₂ Si (CH ₃ ) Cl ₂ , C
_{H 2 = C (CH 3)} COO (CH 2) 2 SiCl 3, CH 2 =
C (CH ₃ ) COO (CH ₂ ) ₃ Si (CH ₃ ) Cl ₂ , C
H ₂ ＣC (CH ₃ ) COO (CH ₂ ) ₃ SiCl ₃ .

[Curing Accelerator] The aqueous dispersion of the present invention may contain a curing accelerator and the like. The curing accelerator is a catalyst that promotes the hydrolysis / condensation reaction of the silane component (B). By using a curing accelerator, the curing speed of the obtained coating film is increased, and the molecular weight of the polysiloxane resin produced by the condensation reaction of the silane component (B) is increased, and the strength and long-term durability are excellent. A coating film can be obtained, and the coating film can be made thicker and the coating operation can be facilitated.

Examples of such a curing accelerator include acidic compounds such as acetic acid, alkaline compounds such as sodium hydroxide, and the like.
Amine compounds such as aminopropyltrimethoxysilane,
Tributoxyethyl acetate zirconium, dipropoxybisacetylacetonato titanium, (C
_{8 H 17) 2 Sn (SCH} 2 CH 2 COOC 8 H 17) an organometallic compound such as ₂ can be used.

As described above, the aqueous dispersion of the polysiloxane particles and the polysiloxane / organic polymer composite particles of the present invention shows good crack resistance when dried, and can be dried even with a thick coating film or a high pigment loading. A binder emulsion for coatings having less cracking and excellent practical performance is obtained.

[0059]

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these embodiments. In the Examples and Comparative Examples, “%” and “parts” mean “% by weight” and “parts by weight” unless otherwise specified.

Example 1 (1) Production of Seed Polymer Particles (A-1) In a four-necked glass flask equipped with an irrigated stirring blade, under a nitrogen atmosphere, 500 parts of water and 5 parts of sodium dodecylbenzenesulfonate. , Potassium persulfate 1 part, styrene 97
Parts, methacrylic acid 3 parts, t-dodecyl mercaptan 10
Then, polymerization was carried out at 75 ° C. for 5 hours. By the above steps, as a seed polymer particle, a polymerization yield of 99.
An aqueous dispersion containing carboxyl group-modified polystyrene particles (A-1) having a particle size of 0.06 μm, a coefficient of variation of the particle size of 5%, and a weight average molecular weight of 4,500 at 5% was obtained.

(2) Production of Polyorganosiloxane Particles In a four-necked glass flask equipped with an irrigated stirring blade, 11 parts of an aqueous dispersion of the seed polymer particles (A-1) obtained in the above step (2 parts by solids) 0.0 part), water (300 parts), sodium dodecylbenzenesulfonate (1 part) and polyoxyethylene alkyl ether (1 part), and the mixture was stirred and adjusted to pH 5.5 with sodium hydroxide and sulfuric acid. Under a nitrogen atmosphere, 15 parts of dimethyldimethoxysilane, 5 parts of methyltrimethoxysilane, and 5 parts of methyltriethoxysilane were added as silane components, and stirring was continued at 25 ° C. for 1 hour. The resulting dispersion of the silane monomer was uniform, had no tendency to separate even after standing for 1 hour, and was stable. The droplet diameter measured by the dynamic light scattering method was 0.15 μm, and the particle diameter distribution was uniform.

Dodecylbenzenesulfonic acid was added to the obtained dispersion of the silane monomer to adjust the pH to 2, and the silane monomer was hydrolyzed and condensed at 60 ° C.

The obtained aqueous dispersion did not have any filtrate through a 300-mesh wire net, and hardly any aggregate was attached to the glass reaction vessel and the stirring blade.

The obtained polyorganosiloxane particles are
The particle diameter was 0.155 μm, the coefficient of variation of the particle diameter was 6%, and the particle diameter was small and uniform.

Example 2 (1) Production of Seed Polymer Particles (A-2) 250 parts of water and 5 parts of sodium dodecylbenzenesulfonate under a nitrogen atmosphere in a four-necked glass flask equipped with an irrigated stirring blade. , Potassium persulfate 0.5 part, styrene 4
8 parts, methacrylic acid 2 parts, t-dodecyl mercaptan 5
After polymerization at 75 ° C. for 2 hours, 5 parts of sodium dodecylbenzenesulfonate was added. Further, 250 parts of water, 5 parts of sodium dodecylbenzenesulfonate, 0.5 part of potassium persulfate, Styrene 49
, 1 part of methacrylic acid and 5 parts of t-dodecyl mercaptan were continuously added at 75 ° C for 2 hours to carry out polymerization. By the above process, an aqueous dispersion containing carboxyl group-modified polystyrene particles (A-2) having a polymerization yield of 99.8%, a particle diameter of 0.08 μm, a coefficient of variation of the particle diameter of 45%, and a weight average molecular weight of 4700 as the seed polymer particles. I got a body.

(2) Production of Polyorganosiloxane Particles Except that the seed polymer particles (A-2) having a wide particle size distribution were used instead of the seed polymer particles (A-1),
Under the same conditions as in Example 1, the polyorganosiloxane particles of Example 2 were obtained. The resulting polyorganosiloxane particles using the low molecular weight seed had a particle size of 0.159 μm, a coefficient of variation of the particle size of 43%, and a broad particle size distribution.

Comparative Example 1 Production of Polyorganosiloxane Particles Without Seed Polymer Particles Comparative Example 1 was carried out under the same conditions as in Example 1 except that no seed polymer particles were used. The silane monomer was added, and the mixture was stirred for 1 hour with a stirring blade. However, the emulsification of the silane monomer was insufficient, and the mixture was immediately separated into two layers when the stirring was stopped. Silane monomer is several tens to several tens
It was a coarse droplet of 00 μm. When the next hydrolysis-condensation step was performed as it was, the obtained aqueous dispersion was 300
Agglomerates were difficult to filter with a mesh wire mesh.

(Comparative Example 2) Production of polyorganosiloxane particles without seed polymer particles (using high-pressure homogenizer) In Example 1, no seed polymer was used, and the dispersion of the silane monomer in water was performed using a high-pressure homogenizer (Mizuho Kogyo). Microfluidizer, dispersion pressure: 600 kg / cm ² ). The obtained emulsion was fine and uniform, and after standing for 1 hour, the particle size of the emulsion was measured by a dynamic light scattering method using a laser beam to be 0.20 μm. This emulsion was subjected to hydrolysis and condensation under the same conditions as in Example 1. The resulting aqueous dispersion had no 300-mesh filtrate. The obtained polyorganosiloxane particles had a small particle size of 0.21 μm, but had a wide particle size distribution with a variation coefficient of the particle size of 45%.

Table 1 shows the components used in Examples 1 and 2 and Comparative Examples 1 and 2.

[Each component]

[0071]

[Table 1]

(Blending and Evaluation of Paint) Using the aqueous dispersions obtained in Examples 1 and 2 and Comparative Example 2, a mixture having the following formulation was mixed by a sand mill, and aqueous dibutyltin was used as a curing accelerator. Dilaurate 2% (solid content) and oxazoline-based aqueous emulsion K202
0 (manufactured by Nippon Shokubai) was added at 5% (solid content) and mixed to prepare a paint. The aqueous dispersion obtained in Comparative Example 1 had a large amount of aggregates and could not be evaluated for paint. Table 2 shows the results of the paint evaluation.

[Formulation Formulation] Aqueous dispersion 100 parts Titanium oxide (white) 26 parts HEC thickener 0.5 part [Paint evaluation results]

[0074]

[Table 2]

As shown in Table 2, the particles produced by using the low molecular weight seed of the present invention were found to have excellent dry cracking resistance.

The measurement of various physical properties in Examples and Comparative Examples was performed according to the following methods.

(1) Cracking resistance of paint at drying Primer (enamel) was applied at a dry weight of 20 g / m ² , and each paint to be tested was applied to a dried steel sheet at a dry weight of 10 to 100 g / m ² . It was applied so that the thickness changed continuously. After standing for 5 minutes after the application, the coated surface of the steel plate was set up, put in a hot air drier (temperature: 120 ° C., air speed: 1 m / sec) and dried. Twenty minutes later, the steel sheet was taken out, and the minimum film thickness in a portion where a crack had occurred was measured. This film thickness (dry film thickness: μm) was defined as “dry crack thickness”.

(2) Adhesion A cross-cut test (JIS 1005) according to JIS K5400
), The tape peel test was performed three times, and the average was used.

(3) Water Resistance After the test piece was immersed in tap water at room temperature for 60 days, the state of the coating film was visually observed. Those that did not change were regarded as “good”.

(4) Weather Resistance According to JIS K5400, an irradiation test was carried out for 3,000 hours with a sunshine weather meter, and the appearance (cracks, peeling, etc.) of the coating film was visually observed. Those that did not change were regarded as “good”.

(5) Stain resistance Carbon black / kerosene = 1/2 (weight ratio) on the coating film
Was left at room temperature for 24 hours, washed with water using a sponge, the state of contamination of the coating film was observed, and evaluated according to the following criteria.

：: No contamination Δ: Slightly contaminated X: Severe contamination

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Fujio Sakurai 2-11-24 Tsukiji, Chuo-ku, Tokyo JSR Co., Ltd. F-term (reference) 4F070 AA18 AA59 AB03 AB11 CB02 CB12 4J002 AA00W BC12X GH01 HA06 4J038 CC022 DL031 GA06 LA02 MA08 MA10 MA14 NA03 NA04 NA05 NA11 NA12

Claims (5)

[Claims] 1. An aqueous medium having a weight average molecular weight of 500 to 3
The seed polymer particles (A) having an average molecular weight of at least one selected from the group consisting of an organosilane, a hydrolyzate of the organosilane, and a condensate of the organosilane.
An aqueous dispersion of polyorganosiloxane particles obtained by absorbing a seed silane component (B) and subjecting the silane component (B) to hydrolysis and condensation conditions. 2. The aqueous dispersion of polyorganosiloxane particles according to claim 1, obtained by using 1 to 200 parts by weight of the silane component (B) per 1 part by weight of the seed polymer particles (A). 3. An aqueous medium having a weight average molecular weight of 500 to 3
1 part by weight of the seed polymer particles (A) in the range of 0.000,000 is added to a silane component (B) 1 comprising at least one selected from an organosilane, a hydrolyzate of the organosilane, and a condensate of the organosilane. A method for producing an aqueous dispersion of polyorganosiloxane particles, which is subjected to hydrolysis and condensation conditions of the silane component (B) after absorbing about 200 parts by weight. 4. The method for producing an aqueous dispersion of polyorganosiloxane particles according to claim 3, wherein the seed polymer particles (A) are polystyrene modified with a carboxyl group. 5. A paint comprising, as a main component, an aqueous dispersion of the polyorganosiloxane particles according to claim 1.