JPH10168393A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition excellent in storage stability, capable of providing a coating film excellent in hardness, water resistance, stain resistance, etc., by compounding an emulsion of a specific graft block copolymer with colloidal silica subjected to specific surface treatment. SOLUTION: This composition comprises (A) an emulsion of a graft block copolymer comprising (i) a polymer block composed of dimethylsiloxane as a repeating unit, (ii) a polymer block composed of a vinyl polymerizable monomer as a repeating unit and (iii) a silicon-containing graft cross-linked unit copolymerized with the components (i) and (ii) and (B) colloidal silica subjected to surface treatment with a silane compound of the formula SiR<1> n+1 (OR<2> )3-n (R<1> is H or a 1-10C hydrocarbon; R<2> is H or a 1-10C hydrocarbon which may contain an ether bond; (n) is 0-2) (preferably trimethoxymethylsilane) in the ratio of 1-300 pts.wt. of the solid content of the component B based on 100 pts.wt. of the component A. Preferably, the component (ii) contains an alkoxysilyl group and/or silanol group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition, and more particularly, to an aqueous coating composition which forms a film having excellent storage stability, hardness, water resistance, stain resistance and weather resistance. It relates to a composition.

[0002]

2. Description of the Related Art Conventionally, solvent-based paints have been mainly used as paints. However, solvent-based paints may cause inflammation and poisoning and may cause environmental pollution. The transition to paint is progressing rapidly. However, water-based paints have lower coating properties such as weather resistance and water resistance than solvent-based paints, and there are currently many problems to be solved.

[0003] A variety of aqueous paints have been developed to solve these problems. For example, as a resin for a water-based paint, an emulsion of an acrylic resin obtained by emulsion polymerization has been widely studied because it has a feature that the obtained coating film has relatively good weather resistance and the like. For example, JP-A-54-144432 proposes a resin composition comprising an emulsion of an acrylic resin containing a carbonyl group based on an aldehyde group or a keto group and an organic hydrazine compound having two or more hydrazine residues. It is possible to form a coating film at room temperature, and has the excellent feature that it can be used as a one-pack type, but has the problem that the water resistance of the obtained coating film is insufficient, Have a problem that when they are exposed outdoors, they are easily contaminated by dust, soot, sand and the like.

A variety of aqueous paints have been developed for the purpose of improving the water resistance of a coating film. One of them is an emulsion of an acrylic resin having a hydrolyzable silyl group obtained by emulsion polymerization. I have. But this is
Since the hydrolysis and condensation of the hydrolyzable silyl group are promoted during the emulsion polymerization, aggregates are formed in the emulsion,
There is a problem that the reaction system is apt to gel during the polymerization and the production stability of the emulsion is poor.

As a method for solving these problems, for example, Japanese Patent Application Laid-Open No. 2-67324 discloses a silane monomer containing both free radical polymerizable functionality and self-condensable crosslinkable silane functionality. It has been proposed to use a linear polysiloxane precursor capable of initiating cations, and JP-A-3-22712 discloses the use of a specific alkyl methacrylate and an acrylic ester having a specific functional group. JP-A-3-227313 proposes to use a polymerizable monomer having a cyano group at the time of emulsion polymerization, but it is difficult to make these emulsions high solid. In addition, there is a problem that restrictions on the composition of the emulsion and the conditions for emulsion polymerization are large.

[0006]

On the other hand, various polysiloxane-based water-based paints have been developed as water-based paints. The polysiloxane resin used as a raw material of such a silicone-based water-based paint has excellent heat resistance, water repellency, and weather resistance, and has characteristics useful as a resin for a paint. However, there are still some problems in practical use of an aqueous paint containing a polysiloxane resin as a main component, and the present situation is that it has not yet been widely used for general paint applications.

For example, Japanese Patent Publication No. 63-23212 discloses a method for producing a water-soluble paint using a resin having a plurality of alcoholic hydroxyl groups introduced into the side chain of polysiloxane. However, in the case of a paint using such a polysiloxane that completely dissolves in water, it is necessary to increase the molecular weight of the polysiloxane resin in order to improve the properties of the coating film. In this case, the viscosity of the paint increases, There is a problem that the paintability is reduced. Further, a coating film formed from this paint has a problem in that the coating film has low water repellency and low water resistance because it has a large amount of hydrophilic functional groups.

Further, as a means for improving the performance of the water-based paint, a method of containing an inorganic substance has been proposed. For example, Japanese Patent Publication No. 41180/1989 proposes a coating composition containing colloidal silica in an aqueous emulsion obtained by copolymerizing vinyl silane and an acrylic monomer, and has heat resistance, water resistance, and adhesion of a coating film. It has the feature of being excellent. However, this coating composition has a solid content of 500 parts by weight based on 100 parts by weight of the solid content of the aqueous emulsion.
Since a relatively large amount of colloidal silica of up to 20,000 parts by weight is required, there is a problem that storage stability is poor. On the other hand, when the colloidal silica solid content is less than 500 parts by weight, the storage stability tends to be improved, but there is a problem that the coating properties such as hardness are reduced.

An object of the present invention is to provide an aqueous coating composition for coatings which forms a coating film having excellent storage stability and excellent hardness, water resistance, stain resistance and weather resistance.

[0010]

Means for Solving the Problems In view of the above-mentioned problems of the prior art, the present inventors have made intensive studies on an aqueous coating composition for paints, and as a result, have reached the present invention.

That is, the gist of the present invention is as follows.
A polymer block (A) having a repeating unit of dimethylsiloxane, a polymer block (B) having a repeating unit of a vinyl polymerizable monomer, and a copolymer block (A) and a polymer block (B). It contains an emulsion of a graft block copolymer (I) composed of a polymerized silicon-containing graft crosslinking unit (C) and colloidal silica (II) surface-treated with a silane compound represented by the following general formula (1). Wherein the solid content of component (II) is from 1 to 300 parts by weight per 100 parts by weight of component (I).

[0012]

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(Wherein R ¹ is a hydrogen atom or a group having 1 to 1 carbon atoms)
0 hydrocarbon group, R ² represents a hydrocarbon group having 1 to 10 carbon atoms which may contain a hydrogen atom or an ether bond, n represents an integer of 0 to 2. )

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous coating composition of the present invention is prepared by emulsifying and dispersing a graft block copolymer (I) in an aqueous medium in the presence of a surfactant. It contains a surface-treated colloidal silica (II).

The graft block copolymer (I) constituting the aqueous coating composition of the present invention comprises a polymer block (A) having dimethylsiloxane as a repeating unit (hereinafter referred to as a polymer block (A)), a vinyl polymer A polymer block (B) (hereinafter, referred to as a polymer block (B)) and a silicon-containing graft-crossing unit (C) (hereinafter, referred to as a graft-crossing unit (C)) having a functional monomer as a repeating unit, The graft-crossing unit (C) is copolymerized to both the polymer block (A) and the polymer block (B) via at least one siloxane bond.

The copolymerization of the graft-linking unit (C) and the polymer block (B) is carried out by the polymerization of the vinyl-crosslinkable functional group and / or mercapto group in the graft-linking agent used as a raw material of the graft-linking unit (C). This can be achieved by radical copolymerization with a vinyl polymerizable monomer as a raw material of the block (B).

The graft block copolymer (I) of the present invention
Is a dimethyldialkoxysilane such as dimethyldimethoxysilane and dimethyldiethoxysilane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexa. Siloxane, tetradecamethylcycloheptasiloxane,
It can be synthesized using dimethylsiloxane cyclic oligomers such as dimethylcyclics (a mixture of dimethylsiloxane cyclic oligomers 3 to 7-mer), dimethyldichlorosilane and the like as raw materials. Considering performance and cost such as thermal stability of the obtained resin, the most preferable raw material for the polymer block (A) is a dimethylsiloxane cyclic oligomer.

The weight average molecular weight of the polymer block (A) of the present invention is preferably 10,000 or more. If the weight average molecular weight is less than 10,000, the durability of the resulting coating film tends to decrease. More preferably, it is 50,000 or more.

The graft block copolymer (I) of the present invention
As the vinyl polymerizable monomer constituting the polymer block (B) in, a known radically polymerizable monomer can be used. For example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, n-lauryl methacrylate, n-stearyl methacrylate, cyclohexyl methacrylate, etc. Methacrylic acid alkyl ester, methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, acrylic acid 2
-Ethyl hexyl, n-lauryl acrylate, n-stearyl acrylate, alkyl acrylates such as cyclohexyl acrylate, methacrylic acid, acrylic acid,
Carboxyl group-containing vinyl monomers such as crotonic acid, fumaric acid, maleic acid, itaconic acid, and sorbic acid; acid anhydrides such as maleic anhydride and itaconic anhydride; N-phenylmaleimide; N-cyclohexylmaleimide; N-butyl Maleimide derivatives such as maleimide, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 2-hydroxyethyl acrylate, acrylic acid Vinyl polymerizable monomers having a hydroxyalkyl group such as 2-hydroxypropyl, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, methacrylamide, acrylamide, croton Bromide, amide group-containing vinyl monomers such as N- methylolacrylamide, allyl glycidyl ether, glycidyl acrylate, epoxy group-containing vinyl monomers such as glycidyl methacrylate, styrene,
Examples include aromatic vinyl monomers such as α-methylstyrene, nitrile group-containing vinyl monomers such as acrylonitrile, and olefin monomers such as butadiene. These components can be used alone or in combination of two or more as necessary. If necessary, a cross-linking agent such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, allyl acrylate, allyl methacrylate, divinylbenzene, and trimethylolpropane triacrylate can be used.

The hardness of the coating film is further improved by using an alkoxysilane compound as the vinyl polymerizable monomer and introducing an alkoxysilyl group and / or a silanol group into the polymer block (B). be able to.

The amount of the alkoxysilane compound used is 100 vinyl polymerizable monomers constituting the polymer block (B).
It is preferably 20 parts by weight or less based on parts by weight.
This is because when the amount of the alkoxysilane compound exceeds 30 parts by weight, the storage stability of the obtained aqueous coating composition tends to decrease. More preferably, 0.5
In the range of 10 to 10% by weight.

The alkoxysilane compound used in the emulsion of the present invention is represented by the following general formula (2):
Examples shown in (7) can be given.

[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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(Wherein R ¹ is a hydrogen atom or a group having 1 to 1 carbon atoms)
10 hydrocarbon groups, R ² is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain an ether bond, R ³ is a hydrogen atom or a methyl group, n is an integer of 0 to 2, p is 1 to 10 Integer and q represent an integer of 0 to 10. Specific examples of the general formula (2) include γ-mercaptopropyltrimethoxysilane and γ-mercaptopropylmethyldimethoxysilane.

As a specific example of the above general formula (3), γ-
Acryloyloxypropyltrimethoxysilane, γ-
Acryloyloxypropyltriethoxysilane, γ-
Acryloyloxypropylmethyldimethoxysilane,
γ-acryloyloxypropylmethyldiethoxysilane, γ-acryloyloxypropylethyldimethoxysilane, β-acryloyloxyethyltrimethoxysilane, β-acryloyloxyethylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxy Propyltriethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-methacryloyloxypropylmethyldiethoxysilane, γ-methacryloyloxypropylethyldimethoxysilane, γ-methacryloyloxypropyldimethylmethoxysilane, β-methacryloyloxyethyltrimethoxysilane And β-methacryloyloxyethylmethyldimethoxysilane.

Specific examples of the general formula (4) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri-n-butoxysilane, vinyltris (β-methoxyethoxy) silane, vinylmethyldimethoxysilane, and vinylmethyldiethoxysilane. Silane, vinylethyltrimethoxysilane, vinyldimethylmethoxysilane, isopropenyltrimethoxysilane, isopropenylmethyldimethoxysilane, allyltrimethoxysilane, 5-hexenyltrimethoxysilane, 9-decenyltrimethoxysilane, and the like can be given. .

As a specific example of the above general formula (5), p-
Vinylphenyltrimethoxysilane (p-trimethoxysilylstyrene), p-vinylphenyltriethoxysilane, p-vinylphenyltriisopropoxysilane,
p-vinylphenylmethyldimethoxysilane, p-vinylphenylmethyldiethoxysilane, p-vinylphenylethyldimethoxysilane, p-vinylphenylpropyldimethoxysilane, p-vinylphenylphenyldimethoxysilane, p-vinylphenyldimethylmethoxysilane, o -Vinylphenyltrimethoxysilane, o-vinylphenylmethyldimethoxysilane, m-vinylphenyltrimethoxysilane, o-vinylphenylmethyldimethoxysilane, p-isopropenylphenyltrimethoxysilane, p-isopropenylphenylmethyldimethoxysilane, m -Isopropenylphenyltrimethoxysilane, m-isopropenylphenylmethyldimethoxysilane and the like.

Specific examples of the general formula (6) include trimethoxysilylpropyl vinyl ether and methyldimethoxysilylpropyl vinyl ether.

As a specific example of the general formula (7), 11
-Vinyl trimethoxysilylundecanoate.

Preferred among the above-mentioned alkoxysilane compounds are the alkoxysilane compounds having a mercapto group and / or an ethylenically unsaturated group of (2) to (4), among which γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane,
γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane and vinyltrimethoxysilane are particularly preferred.
These components can be used alone or in combination of two or more as necessary.

The vinyl polymerizable monomers include acrolein, diacetone acrylamide, formyl styrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, diacetone acrylate, diacetone methacrylate, and acetoacetate. Using a vinyl monomer having a carbonyl group based on an aldehyde group or a keto group such as nyl acrylate, acryloxyalkyl propenal, and methacryloxyalkyl propenal, introducing a carbonyl group into the polymer block (B); By including an organic hydrazine compound (III) having two or more hydrazine residues in the aqueous coating composition,
The hardness, low-temperature curability, solvent resistance, and the like of the coating film can be further improved.

In this case, the amount of the vinyl monomer having a carbonyl group based on an aldehyde group or a keto group is 100 parts by weight of the vinyl polymerizable monomer constituting the polymer block (B).
It is preferably 30 parts by weight or less based on parts by weight.
This is because when the amount exceeds 30 parts by weight, the effect of improving the coating film performance cannot be obtained any more, and conversely, the water resistance of the coating film tends to decrease. More preferably, it is in the range of 1 to 10 parts by weight. Within this range, the water resistance and solvent resistance of the coating film are particularly good.

The amount of the organic hydrazine compound (III) used is determined by the number of moles (i) of the carbonyl group based on the aldehyde group or the keto group in the graft block copolymer (I),
It is preferable that the ratio of the number of moles of the hydrazine residue (ii) in the organic hydrazine compound (III) is in the range of 0.05 ≦ (ii) / (i) ≦ 5. When (ii) / (i) is less than 0.05, the progress of the crosslinking reaction becomes insufficient, and the water resistance and solvent resistance of the formed coating film tend to decrease. If it exceeds 5, the unreacted organic hydrazine compound remains, and the appearance and water resistance of the coating film tend to decrease. More preferably, 0.5 ≦ (ii) / (i)
≦ 2. In this range, the appearance, water resistance and solvent resistance of the coating film are particularly good.

Specific examples of the above organic hydrazine compound (III) include dicarboxylic dihydrazides containing 2 to 10, especially 4 to 6, carbon atoms, such as oxalic dihydrazide, malonic dihydrazide, succinic dihydrazide, Glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide and itaconic acid dihydrazide, and aliphatic water-soluble dihydrazine having 2 to 4 carbon atoms, for example, ethylene-1,2- Dihydrazine,
Propylene-1,3-dihydrazine, butylene-1,4
-Dihydrazine and the like. Of these, adipic dihydrazide, isophthalic dihydrazide, sebacic dihydrazide and succinic dihydrazide are preferred. These may be used in combination of two or more.

The polymer block (B) is preferably contained in the range of 50 to 98% by weight in the graft block copolymer (I). When the content of the polymer block (B) is 5
If the amount is less than 0% by weight, the strength and durability of the coating film formed from the resin composition tend to decrease. When the content of the polymer block (A) exceeds 98% by weight,
Water resistance and blocking resistance of the coating film tend to decrease. More preferably, it is in the range of 70 to 95% by weight.

Graft block copolymer (I) of the present invention
Is a constituent unit necessary for ensuring the transparency of the resulting coating film, and contains the graft-crossing unit (C) in the graft block copolymer (I) of the present invention. The amount is preferably in the range of 1 to 50 mol%, based on the silicon atoms in the graft block copolymer (I) of the present invention. When the content of the graft-crossing unit (C) is less than 1 mol%, the transparency of the obtained resin coating tends to decrease, and when it exceeds 50 mol%, it is disadvantageous in terms of raw material cost. In addition, by-products such as alcohols eliminated during condensation tend to decrease the stability and handleability of the emulsion, and further, the coating film performance. It is more preferably in the range of 1.5 to 40 mol%, and still more preferably in the range of 3 to 20 mol%. When the content is 3 mol% or more, the transparency of the obtained coating film is extremely good, and when the content is 20 mol% or less, latex stability during emulsion polymerization becomes good.

The graft-crosslinking agent constituting the graft-crossing unit (C) of the present invention contains at least one hydrolyzable silyl group and at least one vinyl polymerizable functional group or mercapto group in the molecule. Compounds can be mentioned.
As the hydrolyzable silyl group, an alkoxysilyl group is preferable in consideration of polymerization reactivity, ease of handling, cost, and the like. Specific examples of the graft crossing agent include vinylsilanes such as vinylmethyldimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and γ-methacryloxy. Methacryloxyalkylsilanes such as propyltriethoxysilane, acryloxyalkylsilanes such as γ-acryloxypropyltrimethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-mercaptopropyl Mercaptoalkyl such as trimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldiethoxysilane Although orchids and the like, among which vinyl-polymerizable, consider a methacryloxy alkyl silanes such as cost and acryloxy alkylsilanes and mercaptoalkyl silanes are particularly preferred. These components can be used alone or in combination of two or more as necessary.

A production method that can suitably produce an emulsion of the graft block copolymer (I) will be described below, but it is not particularly limited to this method.

The emulsion of the graft block copolymer (I) is obtained by emulsifying a grafting agent comprising a cyclic dimethylsiloxane oligomer and a polyfunctional alkoxysilane containing a vinyl polymerizable functional group and / or a mercapto group in the presence of an acidic emulsifier. After polymerization and neutralization, a vinyl polymerizable monomer can be suitably produced by graft copolymerization in the presence of a radical polymerization initiator.

The ratio of the total amount of the cyclic dimethylsiloxane oligomer and the grafting agent to water can be arbitrarily selected, but is preferably in the range of 1: 1 to 1: 9 by weight.

The acidic emulsifier is not particularly limited as long as it can open the cyclic dimethylsiloxane oligomer, and examples of the acidic emulsifier suitable for polymerization include dodecylbenzenesulfonic acid. The amount of the acidic emulsifier used varies depending on the particle size of the target emulsion, the solid content, the polymerization temperature and the use of other surfactants, but in order to promptly promote the polymerization of the siloxane, grafting with the cyclic dimethylsiloxane oligomer is required. It is preferable to use 0.5% by weight or more based on the total amount of the crosslinking agent.

The emulsion polymerization temperature of the cyclic dimethylsiloxane oligomer and the graft-linking agent is not particularly limited, but in order to increase the reaction rate and promote the polymerization more quickly,
It is preferable to receive a heat history of at least 60 ° C. at least once, more preferably at least 75 ° C.

The particle size of the obtained siloxane polymer emulsion can be controlled by the degree of preliminary dispersion of the raw materials, the amount of the emulsifier, the polymerization temperature and the method of supplying the raw materials. For example,
For emulsions with a small particle size, the raw material and water are pre-emulsified by a high shear generator such as a homogenizer in the presence of an emulsifier, the raw material or pre-emulsion is dropped into water, the emulsifier is increased, or the polymerization temperature is increased. It can be obtained by any of these methods or by appropriately combining these methods.

Since the obtained emulsion of the siloxane polymer is strongly acidic, it is necessary to neutralize it after the siloxane polymerization is completed. The basic compound used for neutralization is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, ammonia, and triethylamine. Neutralization is performed by adding these basic compounds directly or in an aqueous solution to the emulsion.

As the radical polymerization initiator used in the subsequent graft copolymerization of the vinyl polymerizable monomer, known radical polymerization initiators can be used. Specifically, azobisisobutyronitrile, azobisdimethylvaleronitrile, dimethyl-2,
Azo compounds such as 2'-azobisisobutyrate, inorganic peroxides such as ammonium persulfate, potassium persulfate and sodium persulfate, benzoyl peroxide, lauroyl peroxide, t-butyl hydroperoxide, di-t-butyl Peroxides, organic peroxides such as cumene hydroperoxide, combinations of potassium persulfate or ammonium persulfate and sodium bisulfite or Rongalit, and organic hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, etc. Redox initiators and the like by combining an oxidizing agent composed of a peroxide and a reducing agent such as a sugar-containing iron pyrophosphate formulation, a sulfoxylate formulation, or a mixed formulation of a sugar-containing iron pyrophosphate formulation / sulfoxylate formulation. Can be

The amount of the radical polymerization initiator added is usually 0.01 to 10% by weight based on the total amount of the vinyl polymerizable monomer.
The range is preferably 0.1 to 5% by weight in consideration of the progress of polymerization and the control of the reaction. Further, a compound containing a divalent iron ion such as iron sulfate and a chelating agent such as disodium ethylenediaminetetraacetate can be used to impart the activity of the polymerization initiator. The method of charging the vinyl polymerizable monomer is not particularly limited, and may be any method such as batch charging, dropping, or dropping the remainder after charging a part in advance.
When dropping, it may be dropped as it is, or may be dropped after pre-emulsification in the presence of an emulsifier. Further, an emulsifier may be additionally added at the time of graft copolymerization of the vinyl polymerizable monomer or at the end of the graft copolymerization. The polymerization temperature is not particularly limited, but is usually in the range of 40 to 90 ° C.

As the emulsifier used for the preliminary emulsification or additional addition, a known emulsifier can be used. Specific examples thereof include sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium diphenylether disulfonate, sodium dialkyl sulfosuccinate, and polyoxyethylene alkylphenyl. Sulfonate emulsifiers such as sodium ether sulfate, phosphate emulsifiers such as sodium polyoxyethylene alkylphenyl ether phosphate, potassium oleate, sodium N-lauroyl sarcosine, sodium N-myristoyl sarcosine, alkenyl succinic acid Carboxylic acid emulsifiers such as potassium, nonionic emulsifiers such as polyoxyethylene alkyl ester and polyoxyethylene alkyl aryl ether, sulfonate milk Agents, salts emulsifier phosphoric acid, anionic emulsifiers, such as carboxylate salt emulsifier. These emulsifiers may be used alone or in combination of two or more. In particular, the use of an anionic emulsifier is preferable because colloidal silica can be uniformly dispersed. The use amount of these emulsifiers is usually about 0.5 to 10 parts by weight based on 100 parts by weight of the vinyl polymerizable monomer.

As the chain transfer agent, for example, t-
Dodecyl mercaptan, n-octyl mercaptan, n
-Mercaptans such as tetradecyl mercaptan and n-hexyl mercaptan; and halogen compounds such as carbon tetrachloride and ethylene bromide. The use amount of these chain transfer agents is usually 1 part by weight or less based on 100 parts by weight of the radical polymerizable compound.

Further, in the case of emulsion polymerization, various known electrolytes, pH adjusters and the like can be used as required.

The emulsion particle size of the present invention can be arbitrarily changed depending on the production conditions.
The thickness is preferably about 1 to 1 μm.

The aqueous coating composition of the present invention uses a relatively small amount of colloidal silica (II) surface-treated with a specific silane compound to provide water resistance, stain resistance, hardness, and weather resistance. The coating film performance can be improved.

(II) in the aqueous coating composition of the present invention
It is necessary that the solid content of the component is in the range of 1 to 300 parts by weight with respect to 100 parts by weight of the polymer component constituting the aqueous emulsion. If the amount is less than 1 part by weight, the hardness, water resistance and stain resistance of the coating film tend to be insufficient, and if it exceeds 300 parts by weight, the storage stability of the aqueous coating composition tends to decrease. That's why. Preferably it is in the range of 1 to 150 parts by weight.

As the colloidal silica before surface treatment used in the present invention, various commercial products using water as a dispersion medium can be used, but those having an average particle diameter of 300 nm or less are preferable. When the thickness exceeds 300 nm, the transparency, rigidity (elastic modulus) and heat resistance of the obtained coating film tend to be low, and more preferably 1 to 80 nm.
Range.

In the present invention, these colloidal silicas are subjected to a surface treatment with a silane compound represented by the above general formula (1).

Specific examples of the silane compound represented by the general formula (1) include trimethoxysilane, dimethoxymethylsilane, dimethoxydimethylsilane, methoxytrimethylsilane, triethoxysilane, diethoxymethylsilane, dimethylethoxysilane, phenyl Examples thereof include trimethoxysilane, dimethoxyphenylsilane, phenyltriethoxysilane, and diethoxyphenylsilane. These can be used alone or in combination of two or more, but trimethoxymethylsilane is particularly preferred.

As a method for treating the surface of colloidal silica with a silane compound, the graft block copolymer (I)
A method in which colloidal silica and at least one silane compound selected from the above silane compounds are added to the above emulsion, and the mixture is stirred at room temperature to 100 ° C. for an arbitrary time.

As another method, at least one of colloidal silica and a silane compound is previously added at room temperature to 10
A method in which colloidal silica surface-treated with a silane compound obtained by stirring at a temperature of 0 ° C. for an arbitrary time is added to the emulsion of the graft block copolymer (I), etc. The method is not limited.

The amount of the silane compound used in the surface treatment of the colloidal silica is preferably in the range of 1 to 60 parts by weight based on 100 parts by weight of the solid content of the colloidal silica. If the amount is less than 1 part by weight, the weather resistance of the obtained coating film tends to be insufficient, and if it exceeds 60 parts by weight, the storage stability of the aqueous coating composition and the water resistance and This is because the contamination tends to be insufficient. More preferably, it is in the range of 5 to 40 parts by weight.

The polymer component content of the aqueous coating composition of the present invention is preferably in the range of 20 to 70% by weight. When the content of the polymer component is less than 20% by weight, the thickness of the obtained coating film tends to be thin, and the coating workability tends to decrease. On the other hand, if it exceeds 70% by weight, the viscosity of the system tends to increase significantly, and it tends to be difficult to obtain a stable emulsion. More preferably, 3
It is in the range of 0 to 60% by weight.

In the aqueous coating composition of the present invention, as a method of mixing the aqueous emulsion and colloidal silica, a method of mixing a colloidal silica dispersion with an aqueous emulsion of a polymer obtained by emulsion polymerization is preferable. Further, a method of emulsion polymerization of a radically polymerizable compound in an aqueous medium containing colloidal silica to obtain an aqueous emulsion may be used, but in this method, although the production process is simplified, the polymerization stability tends to be low. It is in.

The aqueous coating composition of the present invention contains various additives such as a pigment, an ultraviolet absorber, an antioxidant, a heat resistance improver, a leveling agent, an anti-sagging agent and a matting agent, if necessary. Or a mixture with another emulsion resin, a water-soluble resin, a viscosity controlling agent, and a curing agent such as melamine.

The resin composition of the present invention can be applied by a method such as brush coating, roll coating, spray coating and the like, and can be cured by standing at room temperature or heating to 50 to 200 ° C.

[0068]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” are “parts by weight” and “%”.
Indicates "% by weight".

The evaluation of the performance in the examples and comparative examples was performed using the following method.

(1) Transparency A spot-like coating film was formed on a glass plate, and the transparency was visually judged. ○: transparent △: translucent ×: cloudy (2) Hardness Using Mitsubishi Pencil Uni (45 ° angle) (3) Water resistance After dipping in hot water of 50 ° C. for 100 hours, the appearance of the coating film was visually judged. Furthermore, the 60-60 degree specular reflectance after immersion (hereinafter referred to as 60 ° gloss) is measured as a gloss value, and is divided by the 60 ° gloss (initial gloss value) immediately after the coating film formation to obtain a gloss retention rate (gloss value / gloss value). Retention) was calculated. ：: no change △: no change except slight swelling ×: remarkable swelling and gloss shrinkage (4) Stain resistance A carbon paste obtained by well mixing carbon black and water at a weight ratio of 20/80 is applied. Smear at 60 ° C for 30 minutes
After heating for minutes, it was washed with running water, and the state of adhesion of carbon was visually determined. ：: No change from before carbon paste application ：: Slight trace remains X: Marked trace remains (5) Storage stability The state of the aqueous coating composition after standing at room temperature for one month is visually judged 判定: No change × : Agglomeration, gelation (6) Weather resistance The 60 ° gloss immediately after the formation of the coating film was measured as the initial gloss,
Sunshine-type waza meter (Suga Test Machine Co., Ltd.)
(WEL-SUN-DC type) was used to perform an exposure test (rain cycle: 12 minutes / hour, black panel temperature: 63 ± 3 ° C.). Gloss value was measured by measuring the gloss at 60 degrees after exposure for 1000 hours, and the gloss retention was calculated.

[Production Example 1] Dimethyl Cyclic (Cyclic dimethylsiloxane oligomer tri- to heptamer mixture) 9
0 parts, γ-methacryloyloxypropyldimethoxymethylsilane (graft cross-linking agent) 10 parts, deionized water 30
After preliminarily mixing a composition consisting of 0 parts and 0.5 part of sodium dodecylbenzenesulfonate (surfactant) with a homomixer, 200 kg /
The mixture was sheared at a pressure of cm ² and forcedly emulsified to obtain a silicone raw material emulsion.

Next, 100 parts of deionized water and 10 parts of dodecylbenzenesulfonic acid (acidic emulsifier) were added to a stirrer,
The flask was equipped with a condenser, a temperature controller and a dropping pump, and the above-mentioned silicone raw material emulsion was dropped over 3 hours while maintaining the temperature in the flask at 85 ° C. After completion of the dropwise addition, heating and stirring were further continued for 1 hour, and then the obtained emulsion was cooled to room temperature, and dodecylbenzenesulfonic acid was neutralized with sodium hydroxide to obtain a silicone emulsion (hereinafter, SEm). The number average molecular weight (GPC measurement value) of the obtained silicone was about 100,000.

[0073]

Example 1 500 parts of SEm, 164 parts of deionized water and 2.4 parts of potassium persulfate were mixed with a stirrer, a condenser,
After charging into a flask equipped with a temperature control device, a dropping pump, and a nitrogen inlet tube, heating to 70 ° C., and stirring under a nitrogen atmosphere, methyl methacrylate (hereinafter referred to as MMA) 1 was added.
68 parts, n-butyl methacrylate (hereinafter n-BMA) 1
68 parts, 2-ethylhexyl acrylate (hereinafter referred to as 2-EH
A) A mixture of 44 parts, methacrylic acid (hereinafter, MAA) 8 parts, and diacetone acrylamide (hereinafter, DAAm) 12 parts was dropped over 4 hours. After dropping is completed,
Then, the temperature was raised to 80 ° C. and maintained for 1 hour.
The reaction solution was cooled to room temperature and neutralized with aqueous ammonia to obtain a graft block copolymer emulsion. The polymerization proceeded stably, and no formation of aggregates was observed.

Next, an aqueous dispersion of colloidal silica having an average particle diameter of 10 to 20 nm (silica content 20% by weight, trade name: Snowtex O, manufactured by Nissan Chemical Industries, Ltd.) 50
0 parts by weight, 50 parts of methyltrimethoxysilane are added,
The aqueous dispersion of the surface-treated colloidal silica obtained by stirring at 60 ° C. for 1 hour was added to the above aqueous emulsion with stirring.

Thereafter, adipic dihydrazide (hereinafter A)
DH) 7.6 parts, butyl cellosolve (hereinafter BC) 100
Parts while stirring, and further stirred for 30 minutes,
An aqueous coating composition was obtained.

The aqueous coating composition was applied on a test steel plate using a bar coater # 40, left at room temperature for 30 minutes, and then cured at 70 ° C. for 3 hours. The resulting coating is smooth,
Transparent and tough, 60
° Gloss value was 83. Table 1 shows the evaluation results of the obtained coating films.

[0077]

Examples 2 to 6 An aqueous coating composition was prepared in the same manner as in Example 1 except that the composition was changed as shown in Table 1.
Further, a coating film was obtained using this. Table 1 shows the properties of the obtained aqueous coating composition.

[0078]

Comparative Examples 1 to 3 An aqueous coating composition was prepared in the same manner as in Example 1 except that the composition was changed as shown in Table 1.
Further, a coating film was obtained using this. As shown in Table 1, the properties of the obtained aqueous coating composition were inferior to those of the examples.

[0079]

[Table 1]

1) Shin-Etsu Chemical Co., Ltd., γ-methacryloxypropyltrimethoxysilane 2) Shin-Etsu Chemical Co., Ltd., mercaptopropylmethyldimethoxysilane 3) Nissan Chemical Industries, Ltd., Colloidal silica aqueous dispersion ( 4) Water-soluble melamine (melamine solid content 80% by weight) manufactured by Sumitomo Chemical Co., Ltd.

[0081]

The aqueous coating composition of the present invention provides a film excellent in storage stability, hardness, water resistance and stain resistance,
It can be used for various paint applications as a resin for aqueous emulsion paints, and is industrially very useful.

Claims (3)

[Claims] 1. A polymer block (A) having dimethylsiloxane as a repeating unit, a polymer block (B) having a vinyl polymerizable monomer as a repeating unit, and the polymer block (A) and the polymer block. (B) an emulsion of a graft block copolymer (I) composed of a silicon-containing graft crosslinking unit (C) copolymerized with colloidal silica surface-treated with a silane compound represented by the following general formula (1) ( An aqueous coating composition comprising (II), wherein the solid content of component (II) is 1 to 300 parts by weight based on 100 parts by weight of component (I). Embedded image (Wherein, R ¹ represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, R ² represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms which may contain an ether bond, and n represents an integer of 0 to 2) . 2. The aqueous coating composition according to claim 1, wherein the polymer block (B) contains an alkoxysilyl group and / or a silanol group. 3. An emulsion of a graft block copolymer (I) in which the polymer block (B) contains a carbonyl group based on an aldehyde group or a keto group, and an organic hydrazine compound (III) having two or more hydrazine residues. 2. The aqueous coating composition according to claim 1, which comprises: