JPH09118858A - Aqueous resin dispersion for coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous resin dispersion for a coating material giving a coated film having excellent water repellent.oil repellent properties, resistance to pollution, gloss and smoothness by emulsion polymerizing a vinyl monomer in an aqueous medium containing a specific aqueous graft copolymer. SOLUTION: This aqueous resin dispersion for a coating material is obtained by polymerizing (A)0.1-50wt.% macromonomer bonding a radically polymerizable group at a chain end of a copolymer obtained by polymerizing a monomer mixture composed of (i) 20-65wt.% perfluoroalkyl acrylate and/or perfluoroalkyl methacrylate with (ii) 80-35wt.% another vinyl-basedmonomer [preferably a (meth)acrylate] and containing >=70wt.% of a methacrylate-based monomer, (B) 3-40wt.% of a radically polymerizable group-containing water-soluble organic acid or its salt, (C) 1-30wt.% styrene, (D) 20-60wt.% of an alkyl methacrylate and (E) 0-75.9wt.% of other vinyl monomers to obtain an aqueous graft copolymer and then emulsion polymerizing a vinyl monomer in an aqueous medium containing the resultant copolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous resin dispersion for a fluororesin-based coating material which forms a film having excellent water and oil repellency. The aqueous resin dispersion of the present invention,
By forming a film having excellent water and oil repellency, it can be suitably used as various paints such as outdoor stain-resistant paints, moisture-proof paints for electronic parts, paints for preventing graffiti and paints for automobiles.

[0002]

2. Description of the Related Art Water-based paints have been in increasing demand in recent years because they are non-polluting and resource-saving. As for the fluorine-containing resin-based coating material which is excellent in water repellency and oil repellency, an aqueous emulsion type is desired,
Since the fluorine-containing monomer has outstanding hydrophobicity, emulsion polymerization is not easy, and at present, a method for industrially adopting a fluorine-containing resin-based water-based paint has not yet been obtained. For example, the following are proposals regarding the fluororesin-based aqueous emulsion. That is, in JP-A-6-192342, a monomer containing perfluoroalkyl acrylate is added in the presence of a carboxyl group-containing resin emulsion obtained by emulsion polymerization of an acrylic acid ester-based monomer and an unsaturated carboxylic acid. A two-stage polymerization method of emulsion-polymerizing a body mixture is disclosed.

[0003]

On the other hand, JP-A-2-132101 discloses a method of emulsion-polymerizing various vinyl monomers in the presence of an aqueous emulsion of a fluorine-containing resin. According to the method disclosed in the above publication, which uses a fluorine-containing resin as a seed for the next polymerization, JP-A-6-19234 is used.
As compared with the method proposed by No. 2, the structural unit composed of a fluorine-containing monomer can be more efficiently introduced into an emulsion product, and a coating film having excellent water and oil repellency can be formed from the obtained emulsion. However, JP-A-2-132
The fluorine-containing resin Emuljun disclosed in Japanese Patent No. 101 is inferior in gloss and smoothness of a coating film when used for a paint.
There were restrictions on usage. An object of the present invention is to provide a fluororesin aqueous dispersion which forms a coating film having excellent water / oil repellency, gloss and smoothness.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, the present invention provides the following macromonomer 0.1 to 50% by weight, a radically polymerizable group-containing water-soluble organic acid or salt thereof 3 to 40% by weight, and styrene 1 to 30.
In an aqueous medium containing an aqueous graft copolymer obtained by polymerizing a monomer mixture consisting of 20% to 60% by weight of alkyl methacrylate and 0 to 75.9% by weight of other vinyl monomer. It is an aqueous resin dispersion for coating material obtained by emulsion polymerization of a polymer. Macromonomer: (a) Perfluoroalkyl acrylate and / or perfluoroalkyl methacrylate 2
0 to 65% by weight and (b) other vinyl monomer 8
A macromonomer having a radically polymerizable group bonded to one end of a copolymer obtained by polymerizing a monomer mixture containing 0 to 35% by weight and containing a methacrylate monomer in an amount of 70% by weight or more.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. First, the macromonomer in the present invention will be described. The macromonomer in the present invention is a copolymer having a specific structure having a perfluoroalkyl group (hereinafter referred to as macromonomer skeleton) having a radically polymerizable group bonded to one end thereof. The perfluoroalkyl acrylate and / or perfluoroalkyl methacrylate (hereinafter referred to as perfluoroalkyl (meth) acrylate) of the monomer (a) forming the skeleton has a perfluoroalkyl group having 3 to 15 carbon atoms. Those having 8 carbon atoms are preferable.
Those having from ~ 15 perfluoroalkyl groups are more preferred. Specific examples of the perfluoroalkyl (meth) acrylate include those represented by the following chemical formula.

CF ₃ CH ₂ OCOC (CH ₃ ) = CH ₂ CF ₃ CF ₂ CH ₂ OCOCH = CH ₂ CF ₃ (CF ₂ ) ₄ CH ₂ OCOC (CH ₃ ) = CH ₂ CF ₃ (CF ₂ ) ₅ ( _{CH 2) 2 OCOC (CH 3} ) = CH 2 CF 3 (CF 2) 6 (CH 2) 2 OCOC (CH 3) = CH 2 CF 3 (CF 2) 7 (CH 2) 2 OCOCH = CH 2 CF 3 _{(CF 2) 7 (CH 2} ) 2 OCOC (CH 3) = CH 2 CF 3 (CF 2) 7 (CH 2) 4 OCOC (CH 3) = CH 2 (CF 3) 2 CF (CF 2) 5 ( _{CH 2) 2 OCOCH = CH 2} (CF 3) 2 CF (CF 2) 6 (CH 2) 3 OCOCH = CH 2 (CF 3) 2 CF (CF 2) 8 (CH 2) 3 OCOCH = CH 2 (CF _{3) 2 CF (CF 2)} 10 (CH 2) 3 OCOCH = CH 2 (CF 3) 2 CF (CF 2 _{6 CH 2 CH (OH) CH} 2 OCOCH = CH 2

Perfluoroalkyl (meth) in a monomer mixture that is subjected to polymerization to obtain a macromonomer skeleton
The proportion of acrylate is 20 to 65% by weight, based on the total amount of all monomers, and more preferably 30.
５０50% by weight. When the polymerization ratio of perfluoroalkyl (meth) acrylate is less than 20% by weight, the resulting aqueous resin dispersion does not exhibit water repellency, oil repellency and stain resistance, while when it exceeds 65% by weight, the aqueous resin dispersion is dispersed. The smoothness of the body coating is poor.

As the other vinyl monomer (b) which constitutes the macromonomer skeleton together with the above-mentioned monomer (a),
(Meth) acrylates are preferable, and specifically, methyl (meth) acrylate, ethyl (meth) acrylate,
Alkyl (meth) acrylates such as propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate and cyclohexyl (meth) acrylate; hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate , Polyethylene glycol monoacrylate and polyethylene glycol monomethacrylate.

Further, the total amount of the methacrylate-based monomers in the monomer mixture for obtaining the macromonomer skeleton,
That is, the total amount of perfluoroalkylmethacrylate, alkylmethacrylate, hydroxyalkylmethacrylate, etc. must be 70% by weight or more of the total monomers. If the total amount of the methacrylate-based monomers in the monomer mixture is less than 70% by weight, the weather resistance of the coating film formed from the resulting aqueous resin dispersion will be poor.

Examples of the radical-polymerizable group bonded to one end of the copolymer serving as the macromonomer skeleton include (meth) acryloyl group, styryl group and allyl group. The preferred molecular weight of the macromonomer in the present invention is 1,000 to 30, in terms of polystyrene-reduced number average molecular weight by gel permeation chromatography.
000, and more preferably 2,000 to 10,000
0. Number average molecular weight of macromonomer is 1,000
When it is less than 3, the water-repellent and oil-repellent properties of the resulting aqueous resin dispersion tend to be insufficient, while when it exceeds 30,000, the polymerizability of the macromonomer is poor, and unpolymerized macromonomer is contained in the aqueous resin dispersion. Easy to remain. The macromonomer is
It can be synthesized by a known method, specifically, a carboxyl group-containing copolymer obtained by radically polymerizing the perfluoroalkyl (meth) acrylate and alkyl (meth) acrylate in the presence of a chain transfer agent having a carboxyl group. It can be synthesized by a method such as adding glycidyl methacrylate to.

Next, the method for obtaining the aqueous graft copolymer of the present invention will be described. The aqueous graft copolymer is obtained by copolymerizing the following components. Macromonomer: 0.1-50% by weight Water-soluble organic acid having a radical-polymerizable group or salt thereof: 3-40% by weight Styrene: 1-30% by weight Alkyl methacrylate: 20-60% by weight Vinyl monomer: 0 to 75.9% by weight (however, the total amount of the above components is 100% by weight) If the proportion of macromonomer is less than 0.1% by weight, water and oil repellency will be reduced. On the other hand, if it exceeds 50% by weight, the coating film is inferior in smoothness and gloss. If the proportion of the water-soluble organic acid having a radical polymerizable group or its salt is less than 3% by weight, the resulting graft copolymer cannot be dissolved or dispersed in water in a stable state, while 40% by weight. If it exceeds, the water resistance of the coating film becomes poor. When the proportion of styrene is less than 1% by weight, the coating film is significantly deteriorated by hydrolysis, while when it exceeds 30% by weight, the weather resistance of the coating film is poor. If the proportion of alkyl methacrylate is less than 20% by weight, the weather resistance of the coating film will be poor, while if it exceeds 60% by weight, the adhesion of the coating material to the substrate will be poor.

Examples of the water-soluble organic acid having a radical polymerizable group or a salt thereof include unsaturated carboxylic acids such as (meth) acrylic acid, crotonic acid, maleic acid and itaconic acid, or their ammonium salts or amine salts; styrene. Examples thereof include unsaturated sulfonic acids such as sulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid, or their ammonium salts or amine salts; unsaturated organic acids having a phosphoric acid group such as acid phosphooxyethylene methacrylate, and the like. Specific examples of amines for neutralization are preferably triethylamine, trimethylamine, diisopropylamine, diethanolamine and triethanolamine. When the constitutional unit of the graft copolymer is a salt, the hydrophilicity of the graft copolymer is higher than in the case of an organic acid. Therefore, the organic acid or salt may be appropriately selected with reference to this point. The acid group may be neutralized after the polymerization reaction is completed.

Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate and cyclohexyl methacrylate. Further, other vinyl monomers include styrene, hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, alkyl acrylates having an alkyl group having 1 to 8 carbon atoms, acrylamide, vinyl acetate and the like.

The copolymerization of the above components is preferably carried out by a polymerization method using a radical polymerization initiator in an organic solvent.
The polymerization solvent is preferably a solvent such as acetone, methyl ethyl ketone, isopropanol, butanol, methyl cellosolve, ethyl cellosolve or butyl cellosolve, which is miscible with water at an arbitrary ratio, and these can be used alone or in admixture of two or more. The polymer solution obtained by using the hydrophilic organic solvent can easily convert the solvent into water. As the polymerization initiator, an azo radical generating compound such as azobisisobutyronitrile or azobismethylbutyronitrile, or cumene hydroperoxide, an organic peroxide such as benzoyl peroxide can be preferably used, and the amount thereof is used. Is 0.5 per 100 parts by weight of the monomer.
An appropriate amount is about 8 parts. The polymerization temperature is 60 to 1
00 ° C is appropriate. The preferred number average molecular weight of the aqueous graft copolymer obtained by the above polymerization is 5,000.
~ 100,000. The molecular weight of the aqueous graft copolymer can be adjusted by adding a chain transfer agent such as mercaptoacetic acid, mercaptopropionic acid or dodecyl mercaptan to the polymerization system.

By the above polymerization, a solution of the aqueous graft copolymer in an organic solvent is obtained. In the present invention, for example, obtained from the organic solvent solution by the following operations,
The vinyl monomer is emulsion polymerized using an aqueous solution or aqueous emulsion dispersion of the aqueous graft copolymer as a polymerization medium. To convert the solvent of the organic solvent solution of the aqueous graft copolymer into water, water is added to the solution and then heated to evaporate the organic solvent, or most of the organic solvent is evaporated and then water is added. Means can be adopted. The preferred content of the copolymer in the aqueous solution or aqueous emulsion dispersion of the aqueous graft copolymer used as the polymerization medium is 5 to 20% by weight, and the preferred amount of the paint-forming monomer charged into the polymerization medium is The amount is such that the solid content concentration of the reaction liquid after polymerization is 30 to 60% by weight. Further, the preferable ratio of the aqueous graft copolymer and the polymer formed from the vinyl monomer is, in terms of coating film physical properties of the resulting aqueous resin dispersion, based on the total amount of both, the aqueous graft copolymer. 15-40% by weight of polymer and 85-polymer formed from vinyl monomer
60% by weight.

As the polymerization initiator used for emulsion polymerization, water-soluble radical generating compounds such as ammonium persulfate, potassium persulfate and hydrogen peroxide are preferable. As the vinyl monomer, a monomer generally used in producing a coating material polymer for building materials, automobiles, home appliances, etc. may be used, and specifically, it has 1 to 1 carbon atoms. One or more monomers selected from alkyl (meth) acrylates having 8 alkyl groups, hydroxyethyl (meth) acrylate, styrene, acrylonitrile, acrylamide, vinyl acetate and the like can be mentioned. In the above emulsion polymerization, a low molecular weight surfactant may be used as an emulsifier, but the use of no such emulsifier gives a coating film of an aqueous resin dispersion having excellent water resistance.

The aqueous resin dispersion for paints obtained by the above emulsion polymerization contains dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, diethylene glycol dibutyl ether, trimethylpentanediol monoisobutyrate or butyl carbyl as a film forming aid. Tall acetate can be added. Particularly preferred film forming aids are dipropylene glycol monobutyl ether and trimethylpentanediol monoisobutyrate.

Hereinafter, the present invention will be described in more detail with reference to Reference Examples and Examples. <Reference Examples 1-2> (Synthesis of macromonomer) Stirrer, two dropping funnels,
In a glass flask equipped with a gas inlet tube and a thermometer, 30 g of the monomer mixed solution shown in Table 1, 1.8 g of a chain transfer agent, mercaptopropionic acid, and 1 methylisobutylketone.
00 g was charged and the temperature was raised to 90 ° C. After that, 70 g of the monomer mixture solution was added dropwise from one dropping funnel over 2 hours, and simultaneously, 0.8 g of azobis-2-methylbutyronitrile dissolved in 54 g of methyl isobutyl ketone was added from the other funnel for 5 hours. It dripped over. Then, the reaction was further continued for 1 hour to obtain a polymer. Then
0.04 g of hydridoquinone monomethyl ether was added to the obtained solution of the polymer having a carboxyl group at one end.
Tetrabutylammonium bromide 1 g, glycidyl methacrylate 2.7 g and methyl isobutyl ketone 10 g were added and reacted at 90 ° C. for 6 hours while blowing air to obtain a macromonomer having a methacryloyl group introduced at a terminal with a purity of 99%. It was The number average molecular weight of the obtained macromonomer was 6000.

[0019]

[Table 1] In addition, FMA, MMA, EA and i-BMA in Table 1
Are the abbreviations of the following compounds, respectively. FMA: Perfluorooctylethylmethacrylate MMA: Methylmethacrylate EA: Ethylacrylate i-BMA: Isobutylmethacrylate

<Reference Examples 3 to 4> (Synthesis of aqueous graft copolymer) Stirrer, dropping funnel,
In a glass flask equipped with a gas inlet tube and a thermometer, 44 g of methyl ethyl ketone, mercaptopropionic acid 1.
5 g and 100 g of the monomer shown in Table 2 were charged, and 75
The temperature was raised to ° C. Then, 1 g of azobismethylbutyronitrile dissolved in 50 g of methyl ethyl ketone was dropped from the dropping funnel over 3 hours. After continuing the reaction for 1.5 hours, 0.5 g of azobismethylbutyronitrile dissolved in 4 g of methyl ethyl ketone was added. The reaction was further continued for 2 hours to obtain a polymer. The number average molecular weight of the polymer was 8,000. Aqueous ammonia solution having a concentration of 25% by weight was added to the obtained reaction solution for neutralization, and further 230 g of distilled water was gradually added with stirring. Then, the organic solvent 200 at a pot temperature of 50 ° C and a pressure of 200 mmHg
g was evaporated. Distilled water was added to the obtained aqueous solution to obtain an aqueous graft copolymer dispersion having a solid content concentration of 30%.
The average particle size of the dispersed particles was about 0.1 μm.

[0021]

[Table 2]

F-MM (1) and F-MM in Table 2
(2) is a macromonomer having a fluorine-based monomer unit obtained in Reference Example 1 and Reference Example 2, respectively, and is AA-6, HEMA, MAA, St, n-BMA,
HMA and PEGMA are abbreviations for the following compounds. AA-6: Toagosei Co., Ltd. macromonomer (polymethylmethacrylate type macromonomer, polymerizable group; methacryloyl group, number average molecular weight 6,000) HEMA: hydroxyethyl methacrylate MAA: methacrylic acid St: styrene n-BMA: n -Butyl methacrylate HMA: 2-ethylhexyl methacrylate PEGMA: Polyethylene glycol monomethacrylate (degree of polymerization of ethylene glycol n = 9)

[0023]

Examples 1 and 2 100 g of an aqueous solution of the graft copolymer obtained in Reference Example 3 or Reference Example 4 was dissolved in 70 g of water,
After raising the internal temperature to 80 ° C., 50 g of methyl methacrylate, 40 g of butyl acrylate, from one dropping funnel,
A mixed solution of 10 g of hydroxyethyl methacrylate and 0.6 g of perbutyl H was added dropwise over 4 hours, and 0.7 g of Rongalit was added to 15 g of distilled water from the other dropping funnel.
The solution in which was dissolved was added dropwise over 4 hours. Then 1.5
The reaction was continued for a time to obtain an aqueous resin dispersion for paint. The amount of aggregates (resin particles remaining on the net when filtered through a 200-mesh net) contained in the aqueous resin dispersion was 0.1 g or less.

A coating composition obtained by adding 5% by weight of dipropylene glycol monobutyl ether to the above aqueous resin dispersion was applied on a aluminum plate with a bar coater to obtain a membrane pressure of about 20 μm.
m. After drying at 25 ° C for one week, the coating film physical properties were measured by the following methods. Gloss: 60 ° specular gloss Water repellency: Contact angle to water Oil repellency: Contact angle to n-hexadecane Contamination resistance (Carbon): Carbon dispersed in kerosene is sprayed on the coating film, then overnight at 25 ° C. The degree of surface contamination after being left to stand and wiping the surface carbon with paper.

[0025]

[Table 3]

[0026]

EFFECTS OF THE INVENTION Perfluoroalkyl (meth) acrylates have hitherto not been easily emulsion-polymerized by water, and water-based paints made of such polymers have problems with the physical properties of coating films.
According to the present invention, an aqueous resin dispersion containing a perfluoroalkyl (meth) acrylate unit can be obtained without emulsion-polymerizing the perfluoroalkyl (meth) acrylate itself. Moreover, according to the aqueous resin dispersion for coating material of the present invention, a coating film having excellent water repellency, oil repellency and stain resistance, and excellent gloss and smoothness can be formed.

Claims (1)

[Claims] 1. A macromonomer of 0.1 to 50% by weight, a water-soluble organic acid having a radical polymerizable group or a salt thereof of 3 to 40% by weight, styrene of 1 to 30% by weight, alkyl methacrylate of 20 to 60% by weight, and Water-based coating composition obtained by emulsion-polymerizing a vinyl monomer in an aqueous medium containing an aqueous graft copolymer obtained by polymerizing a monomer mixture containing 0 to 75.9% by weight of another vinyl monomer. Resin dispersion. Macromonomer: (a) Perfluoroalkyl acrylate and / or perfluoroalkyl methacrylate 20 to 65% by weight and (b) Other vinyl monomer 80 to 35% by weight, and methacrylate type monomer 70% by weight. A macromonomer having a radically polymerizable group bonded to one end of a copolymer obtained by polymerizing the monomer mixture containing the above.