JPH0987586A - Water-base coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-base coating compsn. which can give a coating film excellent in weatherability and exhibits a good stability during preparation and storage. SOLUTION: This compsn. manily comprises a silanolated vinyl copolymer emulsion which is obtd. by subjecting a polymerizable vinyl monomer and a silanolated (meth)acrylsiloxane represented by the formula [wherein R<1> is H or methyl; R<2> is a 1-8C monovalent org. group; R<3> to R<5> are each a 1-8C monovalent org. group or a siloxy group represented by-OSiR<6> R<7> R<8> (wherein R<6> to R<8> are each a 1-8C monovalent org. group); (n) is an integer of 1-12; and (a) is 0 or 1 ]to emulsion polymn. in the presence of a reactive surfactant and a polymn. intiator in a water-base medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based coating composition, and more particularly to a water-based coating composition having a vinyl copolymer emulsion containing a siloxane-crosslinkable silanol group as a main component and having excellent weather resistance.

[0002]

2. Description of the Related Art A weather-resistant paint is a paint that has resistance regardless of weather conditions.
It is a paint that is effective in preventing the deterioration of the gloss of a coating film due to acid rain, the deterioration such as generation of stains, and the darkening of the coating film due to water stains such as raindrops. Fluorine resin, acrylic urethane resin, acrylic melamine resin, acrylic silicone resin and the like have been conventionally known as the resin component of the weather resistant paint.

However, among these, the acrylic urethane resin and the acrylic melamine resin do not have sufficient weather resistance, and the fluororesin which is known for its high weather resistance also has a manufacturing defect that it uses an isocyanate of which toxicity is a concern. In addition, there is a drawback that it is expensive. On the other hand, in recent years, acrylic silicone paints containing acrylic silicone resin as a main component have been receiving attention. The acrylic silicone resin is composed of a main chain of an acrylic resin and a side chain of an alkoxysilyl group, and the alkoxysilyl group is hydrolyzed and condensed by moisture to crosslink the siloxane and develop weather resistance.

An acrylic silicone resin is obtained by polymerizing an acrylic acid ester monomer and a polymerizable vinyl group-containing alkoxysilane using a radical polymerization initiator (Japanese Patent Publication No. 63-443), which is used. Most of the existing paints are solvent-based using organic solvents. However,
At the time of application, the organic solvent has an adverse effect on the global environment and the human body, so water-based, powder-based, reactive diluent (UV curing)
The trend is toward the use of coatings and high-solidification paints. Among these, water-based paints, which can use the conventional solvent-type equipment and lines as they are, have received the most attention, and water-based acrylic silicone paints have been developed (JP-A-56-57860 and 59-67396).
No. 63-295677, etc.).

However, when a resin having an alkoxysilyl group introduced is used in an aqueous paint, it reacts with water during emulsification, during paint formation, and during storage to crosslink, resulting in a minimum film forming temperature (MF).
There is a drawback that T) is likely to increase, thicken, and gel. This drawback is due to the stabilization technology for water-based paints
However, according to the stabilization technology, a low-reactivity alkoxysilane has to be used or only a small amount of an alkoxysilyl group (crosslinking group) is introduced. Therefore, there is a drawback that the crosslinking effect is reduced, the effect of modifying the surface characteristics by the siloxane bond is reduced, and the weather resistance is reduced.

[0006]

Therefore, as a result of intensive studies made by the present inventors in order to solve such a drawback, as a result, an aqueous coating composition containing a silanol group-containing vinyl copolymer emulsion capable of siloxane cross-linking as a main component was emulsion polymerized. It was found that the obtained coating film is excellent in weather resistance as well as stable when being made into a paint and during storage, and thus the present invention has been completed. Therefore, an object of the present invention is to provide a water-based coating composition which can provide a coating film excellent in weather resistance and has good stability during emulsion polymerization, during coating, and during storage.

[0007]

The above objects of the present invention are (A) a polymerizable vinyl monomer, and (B)
A silanol group-containing vinyl copolymer obtained by emulsion-polymerizing a silanol group-containing (meth) acrylic siloxane represented by the formula (3) in an aqueous medium in the presence of (C) a reactive surfactant and (D) a polymerization initiator. It has been achieved by a water-based coating composition characterized by having a polymer emulsion as a main component.

Embedded image However, in the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a monovalent organic group having 1 to 8 carbon atoms, and R ^{3 to} R ⁵ are 1 to 8 carbon atoms.
A monovalent organic group or -OSiR ⁶ R ⁷ R ⁸ (provided that R ^{6 to} R ⁸ in the formula are
Is a siloxy group represented by a monovalent organic group having 1 to 8 carbon atoms), n is an integer of 1 to 12, and a is 0 or 1.

The polymerizable vinyl monomer which is the component (A) of the composition of the present invention is a monomer capable of forming either a thermoplastic polymer or a rubber elastic polymer, and has a silanol group in the molecule. Unless it does, it is not particularly limited. Examples of such a monomer include (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate;

Styrenes such as styrene, o-methylstyrene, p-methylstyrene and α-methylstyrene; olefins such as ethylene and propylene; fatty acid vinyls such as vinyl chloride, vinylidene chloride and vinyl acetate; methyl vinyl ether and ethyl. Alkyl vinyl ethers such as vinyl ether; Alkyl vinyl ketones such as methyl vinyl ketone and ethyl vinyl ketone;

Vinyltrimethylsilane, 3- (meth) acryloxypropyltrimethylsilane, p-trimethylsilylstyrene, vinyltris (trimethylsiloxy)
No silanol groups such as silane, 3- (meth) acryloxypropyltris (trimethylsiloxy) silane, p-tris (trimethylsiloxy) silylsterene,
Silicon-containing polymerizable monomer and fluorine-containing polymerizable monomer such as 3,3,3-trifluoropropyl (meth) acrylate and 2,2,2-trifluoro-1-trifluoromethylethyl (meth) acrylate The body etc. are mentioned.

The term "(meth) acrylate" as used herein means to include both acrylate and methacrylate, and the same applies to other cases. Since the outline of the coating film characteristics is almost determined by the composition of the component (A), the above-mentioned monomers may be used alone or in combination depending on the purpose of the coating film to be used.
Any combination of two or more species can be used. In the present invention, in particular, methyl (meth) acrylate,
At least one selected from ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, styrene, and vinyl acetate.
Preference is given to using seed monomers.

Further, (meth) acrylic acid, maleic acid,
Unsaturated organic acids such as itaconic acid, citraconic acid, maleic anhydride, and itaconic anhydride, and acid anhydrides thereof; hydroxyl group-containing compounds such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; glycidyl ( Epoxy group-containing compounds such as (meth) acrylate and 2- (3,4-epoxycyclohexyl) ethyl (meth) acrylate; amino-group containing compounds such as 2- (diethylamino) ethyl (meth) acrylate and 2-aminoethyl vinyl ether; ( A polymerizable vinyl monomer having a polar group such as (meth) acrylamide and acrylonitrile may be included in the copolymerization component.

The silanol group-containing (meth) acrylic siloxane which is the component (B) of the composition of the present invention can be obtained by a dehydrohalogenation reaction of an organohalosilane and silanols and a hydrolysis reaction (special Kaihei 7
-53570 gazette). In formula 2, the component (B) when R ¹ is a hydrogen atom is an acrylate ester, and the component (B) when R ¹ is a methyl group is a methacrylic acid ester. They can be selected or both can be used together.

Specific examples of R ^{2 to} R ⁸ in the chemical formula ² are, for example, alkyl groups such as methyl group, ethyl group, propyl group and butyl group, cycloalkyl groups such as cyclopentyl group and cyclohexyl group; Aryl groups such as phenyl groups;
Examples thereof include aralkyl groups such as benzyl group; alkenyl groups such as vinyl group and allyl group; and substituted hydrocarbon groups such as chloromethyl group, 3,3,3-trifluoropropyl group and 2-cyanoethyl group.

These R ^{2 to} R ⁸ may be the same or different in one molecule. Therefore, different silanol group-containing (meth) acrylic siloxanes having different groups may be used together. Considering the availability of raw materials, the ease of synthesis, and the characteristics of the copolymer, it is most preferable that all of R ^{2 to} R ⁸ are methyl groups.

The amounts of the components (A) and (B) used in the present invention are such that the weight ratio of component (A) / component (B) is 99.
The range of 9 / 0.1 to 70/30 is preferable, and the range of 95/5 to 90/10 is particularly preferable. When the proportion of the component (B) exceeds 30% by weight, the degree of cross-linking is improved, but the shrinkage due to condensation is increased, which tends to cause cracks in the coating film and lower flexibility. On the contrary, if the amount of the component (B) is less than 0.1% by weight, the crosslinkability will be insufficient.

The reactive surfactant which is the component (C) of the composition of the present invention is an emulsifier for emulsifying and dispersing the components (A) and (B) in an aqueous medium, and particularly in the molecule. It is a reactive surfactant having a polymerizable group. When the reactive surfactant is used, the polymerizable group in the molecule is incorporated into the main chain of the vinyl copolymer and constrained, so that it is not partially concentrated.

On the other hand, when a non-reactive surfactant is used, the surfactant can move freely in the system, so that the surfactant is not transferred to the surface during the drying step after coating on the substrate. As a result, the coating film is gradually concentrated at the interface and, as a result, problems such as deterioration of water resistance of the coating film and deterioration of adhesion occur.

The reactive surfactant used in the present invention can be appropriately selected from known ones. Specific examples thereof include anionic reactive surfactants represented by Chemical formulas 3 to 12, nonionic reactive surfactants represented by Chemical formulas 13 to 17, or quaternary ammonium salts and tertiary amines. Examples thereof include a cationic reactive surfactant containing a salt and a polymerizable group.

[0020]

Embedded image However, in the formula, R ¹ and R ² are hydrogen atoms or methyl groups, and R ³ is C
_{7-21 is} an alkyl group or an alkenyl group, and M is an alkali metal or ammonium group (JP-A-54-144).
317).

Embedded image However, R in the formula is a hydrogen atom or a methyl group, and M is an alkali metal or an ammonium group (JP-A-55-11).
5419).

[0021]

Embedded image However, in the formula, R is a hydrogen atom or a methyl group, A is an alkylene group, M is a monovalent or divalent cation, and n is an integer of 2 or more (JP-A-62-34947).

[Chemical 6] However, in the formula, R ¹ is a hydrogen atom or a methyl group, R ² is an unsubstituted or substituted hydrocarbon group, A is a C _2-4 alkylene group or a substituted alkylene group, and n is an integer of 0 or more. (JP-A-49-46291).

[0022]

[Chemical 7] However, in the formula, R ¹ is a hydrogen atom or a methyl group, R ² is an unsubstituted or substituted hydrocarbon group, an amino group, A is a C _2-4 alkylene group, and M is a monovalent or divalent cation. , N is 0 to 10
It is an integer of 0 (Japanese Patent Laid-Open No. 58-203960).

Embedded image However, in the formula, R ¹ is a C _6-18 alkyl group, R ² is a hydrogen atom or a C _6-18 alkyl group, R ³ is a hydrogen atom or a propenyl group, A is a C _2-4 alkylene group, and substituted. Alkylene group, M
Is an alkali metal or ammonium group, and n is 1 to 2
00 is an integer (Japanese Patent Laid-Open No. 4-53802).

[0023]

Embedded image However, in the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a C _8-24 hydrocarbon group, A is a C _2-4 alkylene group, M is a hydrogen atom, an alkali metal, or an alkaline earth metal or It is an ammonium group, L is an integer of 0 to 20 and m is an integer of 0 to 50 (JP-A-62-104802).

Embedded image However, in the formula, R is a C _8-32 hydrocarbon group, and M is an alkali metal or ammonium group (JP-A-49-40388).
Issue).

Embedded image However, in the formula, R is a C _8-22 hydrocarbon group, and M is an alkali metal or ammonium group (JP-A-49-40388).
Issue).

[0024]

[Chemical 12] However, R in the formula is an alkyl group or an alkylphenyl group,
A is an ethylene group, M is an ammonium group, or an alkali metal, and m is an integer of 0 to 50 (JP-A-52-1).
34658 publication).

Embedded image However, R ¹ in the formula is a hydrogen atom or a methyl group, R ² represents a hydrogen atom, a methyl group or a -C ₆ H ₄ - is (CH _{2) m} -H, n is 4
30 and m are integers of 0 to 20 (JP-A-53-124)
6093).

[0025]

Embedded image However, R ¹ and R ² in the formula are hydrogen atoms or methyl groups,
x, y, and z are each an integer of 0 to 100, and 1
≦ x + y + z ≦ 100 (JP-A-56-28208)
Issue).

[Chemical 15] However, in the formula, R ¹ is a C _6-18 alkyl group, R ² is a hydrogen atom or a C _6-18 alkyl group, R ³ is a hydrogen atom or a propenyl group, A is a C _2-4 alkyl group or a substituent. It is an alkylene group, and n is an integer of 1 to 200 (JP-A-4-5020).
No. 4).

[0026]

Embedded image However, in the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a C _8-24 hydrocarbon group or an acyl group, A is a C _2-4 alkylene group, L is 0 to 100, and m is 0. It is an integer of -50 (Japanese Patent Laid-Open No. 62-104802).

Embedded image In the formula, R ¹ and R ² are hydrogen atoms, C _1-36 hydrocarbon groups or acyl groups, A ¹ and A ² are C _2-4 alkylene groups or substituted alkylene groups, and L is 1 or 2, m and n are integers of 0 or more (provided that m + n ≧ 3), and when both R ¹ and R ² are hydrogen atoms, m and n are 1 or more (JP-A-50-98484). Gazette).

These reactive surfactants may be used alone or in combination of two or more, but from the viewpoint of further improving the stability during emulsion polymerization, during coating and during storage.
It is preferable to use the anionic type and the nonionic type together, and it is particularly preferable to use the β-methylstyrene type of Chemical formula 8 or Chemical formula 15 together. The amount used is preferably 0.1 to 10% by weight, and more preferably 1 to 5% by weight, based on the total amount of the components (A) and (B).

The polymerization initiator which is the component (D) of the composition of the present invention is not particularly limited as long as it cleaves to generate radicals, and specific examples thereof include peroxides such as potassium persulfate and ammonium persulfate. Water-soluble types such as sulfates, hydrogen peroxide solution, t-butyl hydroperoxide, azobisamidinopropane hydrochloride; benzoyl peroxide,
Examples thereof include oil-soluble types such as cumene hydroperoxide, dibutyl peroxide, diisopropyl peroxydicarbonate, cumyl peroxy neodecanoate, cumyl peroxy octoate, and azobisisobutyro nitrolyl.

Further, if necessary, a redox system in which a reducing agent such as acidic sodium sulfite, Rongalit, or ascorbic acid is used together can be used. These polymerization initiators and reducing agents may be used alone or in combination of two or more. In the present invention, it is preferable to use a redox system in combination with t-butyl hydroperoxide or hydrogen peroxide solution. The amount used is usually preferably 0.05 to 10% by weight, and particularly preferably 0.1 to 1% by weight, based on the total amount of the components (A) and (B). .

The water-based coating composition of the present invention may optionally contain additives such as silanol group condensation catalysts, film-forming aids, adhesion aids, colorants, pigments and dispersants. it can. Specific examples of silanol group condensation catalysts include tin compounds such as dibutyltin dilaurate, dibutyltin dioctoate, dibutyltin bis (benzyl maleate), dibutyltin diacetate, dioctyltin dilaurate, tetrapropoxy titanium, tetrabutoxy titanium, etc. The titanium compounds of The addition amount of these is preferably 0.01 to 5 parts by weight of the coating composition (active ingredient) excluding water,
Particularly, it is preferably 0.1 to 1% by weight.

Specific examples of the film forming aid include, for example,
Cellosolve such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether; Propylene glycol ether such as propylene glycol monomethyl ether, propylene glycol monoethyl ether; Carbitol such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether , Triethylene glycol monomethyl ether, tripropylene glycol monomethyl ether, and other triglycol ethers; glycol ethers such as Solfit (trade name of Kuraray Co., Ltd.), acetates of the above glycol ethers, Solfit AC (Co., Ltd.) Kuraray's product name) and the like. The amount of the film-forming auxiliary added is preferably 1 to 50% by weight of the active ingredient, and particularly 10
It is preferable to set it to 20% by weight.

Specific examples of the adhesion aid include vinyltrimethoxysilane, (meth) acryloxypropyltrimethoxysilane, glycidyloxypropyltrimethoxysilane, (3,4-epoxycyclohexyl) ethyltrimethoxysilane, Silane coupling agents such as aminopropyltriethoxysilane, (2-aminoethyl) aminopropyltrimethoxysilane, mercaptopropyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltributanone oxime silane, etc. Other silanes are listed. The amount of these adhesion aids added is 0.1
It is preferably from 20 to 20% by weight, and particularly preferably from 1 to 10% by weight.

Specific examples of the colorant include titanium oxide and carbon black, and specific examples of the pigment include talc, mica, clay, red iron oxide and the like.

The silanol group-containing vinyl copolymer emulsion, which is the main component of the coating material of the present invention, can be polymerized by using a known emulsion polymerization method. For example, a batch charge polymerization method in which all the monomers are charged and polymerized, a seed polymerization method in which a part of the monomers is polymerized and then the remaining monomers are added, and the monomer composition is the core portion and the shell portion. Examples include different core-shell polymerization methods and power polymerization methods in which the monomer compositions are continuously different.

As the medium used in the polymerization, water such as ion-exchanged water may be used alone, or a water-soluble organic solvent such as acetone, methanol, or tetrahydrofuran may be used in combination. It is also possible to use a chain transfer agent such as dodecyl mercaptan for the purpose of adjusting the molecular weight. In the present invention, the silanol group-containing vinyl copolymer preferably has a molecular weight in the range of 10,000 to 1,000,000.

In the present invention, the above-mentioned emulsion and the above-mentioned additives are blended to prepare a water-based coating composition.
For example, it can be carried out by a known coating method using a sand mill, a dyno mill, a paint shaker, an attritor, a ball mill or the like. In this coating using the water-based coating composition of the present invention, the MFT (minimum film forming temperature) does not rise, and therefore the stability is superior to the conventional one in which the crosslinking group is an alkoxysilane.

Crosslinking of the water-based coating composition of the present invention progresses by gradually dehydrating and condensing silanol groups to form a siloxane bond even when dried at room temperature. Crosslinking can also be performed.
For example, if the film thickness after drying is about 30 μm,
It is completely crosslinked and cured by heating at 150 ° C. for 5 to 30 minutes.

Further, the addition of the above silanol group condensation catalyst can further improve the crosslinking rate, and the addition of a film-forming auxiliary can lower the MFT, so that the glass transition temperature (Tg) is high. Even an emulsion can be formed into a film at room temperature, and when an adhesion aid is added, it is incorporated into the crosslinking of silanol groups, so that the crosslinking can be further strengthened.

In the case of a coating film obtained by curing the water-based coating composition of the present invention, since the crosslinking group is a silanol group, the elimination substance is one molecule of water, and the crosslinking group is an alkoxysilane, and the elimination substance is The weight loss is smaller than that of the conventional water-based paint containing two alcohol molecules. Therefore, a coating film which is not easily cracked and has excellent flexibility is obtained, and water repellency corresponding to the siloxane content is imparted. In addition, when crosslinking is performed, substantially no water is required, and since it has a siloxane bond from the beginning, its surface characteristics are easily exhibited.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION The coating composition of the present invention does not volatilize an organic solvent at the time of application, and therefore can be widely used both indoors and outdoors. Therefore, it is particularly suitable for surface coating on large articles such as building materials such as aluminum sashes and outdoor signboards. Further, the heat-cured coating has high strength and is suitable for roof materials such as roof tiles and exteriors of vehicles such as automobiles.

[0041]

Since the main component of the water-based coating composition of the present invention is an acrylic silicone resin, it has excellent weather resistance.
Furthermore, since it is not necessary to use an organic solvent, the manufacturability at the time of preparing the coating material and the workability at the time of coating are good.

[0042]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.
Unless otherwise specified, “parts” and “%” described below mean “parts by weight” and “% by weight”, respectively.

Production Examples 1-3. A 2 liter polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet was charged with 250 parts of ion-exchanged water and 2.8 parts of a 10% sodium carbonate aqueous solution. Separately, the raw materials were mixed in the distribution shown in Table 1 and emulsified using a homomixer. Twenty-six parts of the obtained emulsified mixture was added as a seed monomer to the polymerization vessel and mixed, and then the temperature was raised to 60 ° C. by exchanging nitrogen. Next, 0.3 part of t-butyl hydroperoxide (69% of pure content) and Rongalit 0.6 were added to the mixture.
Parts, 0.135 parts of a 1% aqueous solution of disodium ethylenediaminetetraacetate, and 0.04% of a 1% aqueous solution of iron (II) sulfate.
Seed polymerization was carried out by adding 5 parts.

[0044]

[Table 1]

Next, the temperature was raised to 80 ° C., and 888 parts of the remaining amount of the emulsion was added dropwise over 3 hours while maintaining the temperature at 80 ° C., and at the same time, t-butyl hydroperoxide (pure content 69%) was added. A mixture of 5 parts and 30 parts of ion-exchanged water and a mixture of 0.4 parts of Rongalit and 70 parts of ion-exchanged water were added dropwise over 3 hours, respectively, and further reacted at 80 ° C for 2 hours to complete the polymerization. Let

Solid content concentration and pH of the obtained emulsion
And the results of the average molecular weight of the polymer measured by GPC are shown in Table 2, respectively.

[Table 2] From the results in Table 2, in the case of the emulsion of Production Example 2 using the alkoxysilane, the weight average molecular weight was equal to or higher than the exclusion limit of GPC (1000 × 10 ³ ), and during emulsion polymerization,
It can be seen that some crosslinking is in progress.

Production Examples 4-7. The composition was changed as shown in Table 1, and the emulsion obtained after the polymerization was neutralized with 25% ammonia water. The measured weight molecular weight of the polymer is shown in Table 2. Dodecyl mercaptan is a chain transfer agent.

Examples 1-6 and Comparative Examples 1-2. The silanol group-containing vinyl copolymer emulsions produced in Production Examples 1 to 5 were each mixed with titanium oxide in the distribution shown in Table 3 as a colorant, and a batch type tabletop sand mill (trade name manufactured by Campehapio Co., Ltd.) was used. Then, the titanium oxide was dispersed until the average particle diameter became about 7 μm to prepare a coating material.
At this time, in order to evaluate the stability during coating, MFT (minimum film forming temperature) before and after dispersion of titanium oxide by a sand mill
Was measured.

[0049]

[Table 3]

Then, the condensation catalyst, the film-forming auxiliary and the adhesion auxiliary having the distributions shown in the same table are added to each and mixed,
Further, it was diluted with ion-exchanged water to obtain an aqueous coating composition.
Each of the resulting water-based coating compositions was applied to an aluminum substrate using a # 36 bar coater, and the composition was applied at room temperature for 1 hour.
The film was dried for an hour and cured in a dryer at 150 ° C. for 20 minutes. The thickness of each of the obtained films was about 30 μm.

Table 4 shows the results of the following evaluations performed on the obtained film samples. -Film appearance: visual inspection. -Adhesion property: 10 (1 mm) x 10 (1 mm) scoring tape peeling.・ Pencil hardness: Uni-pencil made by Mitsubishi Pencil Co., Ltd. is used. -Initial gloss: 60 ° gloss ratio.

Gloss retention (accelerated weathering resistance): Gloss / initial gloss after 2,000 hours of sunshine weatherometer. -Acid resistance: A drop of about 0.5 ml of 10% sulfuric acid aqueous solution is formed on the coating film, heated at 50 ° C for 10 minutes, and observed for changes in the coating film (blister, gloss, etc.) after washing with water.・ Contact angle of water (water repellency): Measured with a contact angle meter by making a droplet of 5 μl of ion-exchanged water on the coating film.

[0053]

[Table 4] From the results shown in Table 4, the film using the coating composition of the present invention has good film characteristics, good weather resistance, and water repellency depending on the siloxane content. It was proved.

Further, in order to evaluate the storage stability of the obtained water-based coating composition, the MFT immediately after preparation and the MFT after storage in a dryer at 50 ° C. for 2 weeks were measured. Table 5 shows the results of evaluation of the stability during coating and during storage by MFT change (° C).

[Table 5] From the results in Table 5, it was confirmed that the coating composition of the present invention did not increase in MFT when it was made into a coating and during storage, and was excellent in stability.

On the other hand, in Comparative Example 1 which is a type which is cross-linked with a conventional alkoxysilyl group, cracks may occur in the film, probably due to the high content of alkoxysilane, and the initial gloss and weather resistance are poor. It was confirmed that the stability was also insufficient because the MFT increased (partial crosslinking proceeded) during coating and during storage. Further, Comparative Example 2 using the non-reactive surfactant is inferior in adhesion, weather resistance, acid resistance and water resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Ichinohe No. 1 Hitomi, Matsuida-cho, Usui-gun, Gunma Prefecture Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory (72) Inventor Hiroyuki Ohata Kitafu, Takefu City, Fukui Prefecture 2-17-33 Nisshin Kagaku Kogyo Co., Ltd. (72) Inventor Hiroshi Saga 2-3-1733 Kitafu, Takefu City, Fukui Prefecture Nisshin Kagaku Kogyo Co., Ltd.

Claims (4)

[Claims] 1. A polymerizable vinyl monomer (A), and
(B) A silanol group-containing (meth) acrylic siloxane represented by the following chemical formula 1 is emulsion polymerized in an aqueous medium in the presence of (C) a reactive surfactant and (D) a polymerization initiator. And a silanol group-containing vinyl copolymer emulsion as a main component. Embedded image However, in the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a monovalent organic group having 1 to 8 carbon atoms, and R ^{3 to} R ⁵ are 1 to 8 carbon atoms.
A monovalent organic group or -OSiR ⁶ R ⁷ R ⁸ (provided that R ^{6 to} R ⁸ in the formula are
Is a siloxy group represented by a monovalent organic group having 1 to 8 carbon atoms), n is an integer of 1 to 12, and a is 0 or 1. 2. The aqueous coating composition according to claim 1, which contains a silanol group condensation catalyst. 3. The aqueous coating composition according to claim 1, which contains a film-forming auxiliary. 4. The water-based coating composition according to claim 1, further comprising an adhesion aid.