JP3344037B2 - Aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to new and useful aqueous coating compositions. More specifically, the present invention relates to an emulsion polymerization of a monomer mixture mainly composed of N-alkoxymethylated (meth) acrylamides in the presence of an emulsion copolymer mainly composed of a hydroxyl group-containing unsaturated monomer. Aqueous coating composition for forced drying and baking which has a self-crosslinking property and provides a coating film having a high crosslinking density, comprising a specific emulsion polymer obtained at least as an essential film-forming component. About.

[0002]

2. Description of the Related Art In order to protect various substrates to be coated and to improve the appearance, various types of coatings are applied. Among these coatings, coatings using a crosslinked resin as a binder can be obtained. It is a class of heavy use because of its excellent coating durability.

[0003] In recent years, from the viewpoint of resource saving and environmental protection, there is a strong demand for water-based paints, and studies on the water-based use of various resins have been actively conducted. It is well known that among aqueous resins, the emulsion polymer contains almost no organic solvent and is an optimal resin form for obtaining a coating material having a low organic solvent content.

However, when an attempt is made to introduce a crosslinking group (also referred to as a crosslinking bond) into the emulsion polymer, these crosslinking groups include, for example, a hydroxyl group, a carboxyl group,
Such as glycidyl, amide or amino groups,
There are many so-called high hydrophilic ones, and therefore, because of the high hydrophilicity of the monomer containing such a class of cross-linking, the cross-linking group is easily localized on the surface of the polymer particles during emulsion polymerization. .

[0005] For this reason, crosslinking is likely to be localized due to localization within the particles, and even if an attempt is made to increase the crosslinking density of the coating film obtained, a large amount of a crosslinking group-containing monomer is copolymerized.
Because of the high hydrophilicity of these monomers, emulsion polymerization itself is difficult.

As disclosed in Japanese Patent Application Laid-Open No. 57-65704, a reactive polar group (also referred to as a crosslinking group) is formed in the form of an emulsion polymer which forms a multilayer structure. Although methods of improving handling, crosslinkability or reactivity have been proposed, they have not yet achieved sufficient performance as aqueous coating compositions for forced drying and baking.

[0007]

SUMMARY OF THE INVENTION However, in view of the above-mentioned various disadvantages or difficulties in the prior art, the present inventors have developed a coating film having a self-crosslinking property and a high crosslinking density. In order to obtain an aqueous coating composition for specific forced drying and baking, research has been started earnestly.

Accordingly, an object of the present invention is to provide an aqueous coating composition having a sufficiently low organic solvent content in a coating material, a high crosslink density of a coating film, and a very high practicality. Is to try to provide.

[0009]

Means for Solving the Problems Accordingly, the present inventors have:
Focusing on the advantages and disadvantages of the prior art as described above, together with the problem to be solved by the invention as described above, earnestly, as a result of repeated studies, a specific monomer composition and a specific polymerization method The present invention has been completed by finding that the aqueous coating composition containing the novel emulsion polymer obtained by the above has desired performance.

That is, the present invention basically provides an emulsion polymerization of a monomer mixture containing a hydroxyl group-containing unsaturated monomer, and then, in the presence of the specific emulsion polymer thus obtained,
The emulsion polymer (A) obtained by emulsion polymerization of a monomer mixture mainly composed of N-alkoxymethylated (meth) acrylamides is contained as an essential binder component. It is intended to provide an aqueous coating composition.

Here, the above-mentioned emulsion polymer (A), which is a main binder component of the aqueous coating composition of the present invention, will be described. The emulsion polymer (A)
Is obtained by a two-stage polymerization method. First, as a first stage, a specific hydroxyl group-containing non-containing compound having a crosslinking reactivity with N-alkoxymethylated (meth) acrylamides as described later. Emulsion polymerization of a monomer mixture containing a saturated monomer is carried out using a polymerization initiator in the presence of water and an emulsifier to obtain an emulsion polymer having a hydroxyl group. Hereinafter, this is referred to as an emulsion polymer precursor.

Next, in the second stage, a monomer mixture containing N-alkoxymethylated (meth) acrylamides as an essential raw material is emulsified in the presence of the above-mentioned hydroxyl group-containing emulsion polymer (A) precursor. The desired emulsion polymer (A) can be obtained by polymerization.

The emulsion polymer (A) mainly has a hydroxyl group in the inner shell (core) of the polymer particles, while it mainly has N-alkoxymethylated in the outer shell (shell). It has an amide group.

For this purpose, when the coating composition containing the emulsion polymer (A) is heated and dried, a crosslinking reaction between a hydroxyl group and an N-alkoxymethylated amide group occurs inside the polymer particles, or A crosslinking reaction between N-alkoxymethylated amide groups is likely to occur,

On the other hand, between the polymer particles, N-alkoxymethylated amide groups are combined with each other, or, at the time of compounding the coating material, are mixed with a methylol group or a methoxyalkyl group of an amino resin or the like. The crosslinking reaction of the N-alkoxymethylated amide group in the polymer (A) is likely to occur.

As a result, a cross-linking reaction easily occurs inside and between the polymer particles, and the cross-link density of the obtained coating film tends to increase. In addition, N-alkoxymethylated (meth) acrylamides are generally more hydrophobic than hydroxyl-containing unsaturated monomers, and if necessary,
A large amount can be copolymerized.

Here, the proportion or use ratio of the emulsion polymer precursor based on the emulsion polymer (A) is not particularly limited, but is 5 to 50 in terms of solid content. % Is preferably 1% by weight.
A range of 0 to 40% by weight is appropriate.

The hydroxyl group-containing unsaturated monomer, which is an essential component of the monomer mixture used for the preparation of the emulsion polymer precursor, is not particularly limited, however, when considering the crosslinking reactivity during heating and drying. It is preferable to use mainly a monomer having a primary hydroxyl group.

The amount of the hydroxyl group-containing unsaturated monomer used is:
The range of about 0.5 to 10% by weight based on all monomers used for the emulsion polymer precursor is appropriate, and the amount used for the second-stage reaction is also adjusted to obtain the emulsified polymer. A suitable range is about 0.5 to 8% by weight, based on all monomers used for the preparation of the polymer (A).

Further, an unsaturated monomer having a functional group having a crosslinking reactivity with a hydroxyl group or a methoxyalkylated amide group, such as (meth) acrylamide, may be copolymerized with the emulsion polymer precursor. It may be.

Subsequently, the amount of N-alkoxymethylated (meth) acrylamides, which is an essential component of the monomer used in the second-stage emulsion polymerization reaction, is determined by the amount of monomer used in the second-stage polymerization. Suitably, it is used in a range of about 4 to 40% by weight, based on the body.

Of course, a part of the emulsion polymer precursor may be used at the time of preparation of the emulsion polymer. However, based on all monomers used for preparing the emulsion polymer (A), The N-alkoxymethylated (meth) acrylamides are preferably used in an amount of 3 to 30% by weight,
Suitably, it is used in the range of 4 to 20% by weight.

In the case of using less than about 3% by weight,
Inevitably, the cross-linking reactivity of the resulting coating film tends to be insufficient, while the N-alkoxymethylated (meth) acrylamide may be used in an excessive amount exceeding about 30% by weight. Either case is not preferred because the effect of use of the class is only saturated.

Here, among the unsaturated monomers used for preparing the emulsion polymer (A), only typical ones will be exemplified. When only typical examples are given as examples, various N-hydroxymethylated acrylamides represented by N-methylol (meth) acrylamide and the like,

2-hydroxyethyl (meth) acryle
2-hydroxypropyl (meth) acrylate, 3
-Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxy Various hydroxyalkyl esters of various (meth) acrylic acids, as represented by propyl (meth) acrylate, polyethylene glycol mono (meth) acrylate and the like;

Various unsaturated group-containing polyhydroxyalkyl esters such as various di-hydroxyalkyl esters of various polycarboxylic acids, such as maleic acid and fumaric acid; And various hydroxyalkyl vinyl ethers represented by hydroxyethyl vinyl ether and the like.

Next, only typical representative examples of N-alkoxymethylated (meth) acrylamides will be given below. N-methoxymethylated (meth) acrylamide, N-ethoxymethylated (meth) acrylamide , N-propoxymethylated (meth) acrylamide,
N-butoxymethylated acrylamide or N, N-dimethoxymethylated (meth) acrylamide.

As the other unsaturated monomers, only typical ones are exemplified, that is, other unsaturated monomers copolymerizable with both essential monomers as described above. As typical examples, only methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate Various (meth) acrylates having a linear, branched or cyclic alkyl group, such as represented by cyclohexyl (meth) acrylate;

Styrene, α-methylstyrene, p-te
Various aromatic vinyl compounds represented by rt-butyl-styrene, p-methylstyrene, etc .; various (substituted) compounds represented by benzyl (meth) acrylate, etc. Aromatic nucleus-containing (meth) acrylates; diesters of various unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid with monohydric alcohols;

Vinyl acetate, vinyl benzoate, "Veoba"
(Vinyl esters of branched aliphatic monocarboxylic acids manufactured by Shell, Netherlands), and the like,
Various vinyl esters; "Biscoat 8F, 8F
M, 3F or 3FM "[manufactured by Osaka Organic Chemical Co., Ltd.
(Fluorine-containing (meth) acrylic monomers], perfluorocyclohexyl (meth) acrylate, di-perfluorocyclohexyl fumarate or Ni-propyl perfluorooctanesulfonamidoethyl (meth) acrylate Various (par) as represented
Vinyl esters containing a fluoroalkyl group;

Vinyl chloride, vinylidene chloride, vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene,
Various olefins represented by ethylene, propylene, etc .; various dienes represented by butadiene, isoprene, etc .; (meth) acrylamide, N, N-dimethyl (meth) acrylamide Various carboxylic acid amide group-containing monomers represented by, for example, diacetone acrylamide, N-methylol (meth) acrylamide and the like;

P-styrenesulfonamide, N-methyl-p-styrenesulfonamide, N, N-dimethyl-p
-Various sulfonic acid amide group-containing monomers represented by styrene sulfonamide, etc .;
Various N, N-dialkylaminoalkyl (meth) acrylates, such as dimethylaminoethyl (meth) acrylate, and various polycarboxylic acid anhydride-containing monomers such as maleic anhydride Body and
Various tertiary amino group-containing monomers represented by adducts with compounds having an active hydrogen group and a tertiary amino group capable of reacting with the monomers;

Various cyano group-containing monomers represented by (meth) acrylonitrile and the like; (meth)
Various types of α, β-ethylenically unsaturated carboxylic acids, such as those represented by hydroxyalkyl acrylates, and various hydroxyalkyl esters obtained by a condensation reaction with phosphoric esters. Phosphoric ester group-containing monomers; 2-acrylamide-2
-Various sulfonic acid group-containing monomers or organic amine salts thereof, such as represented by methylpropanesulfonic acid;

As represented by (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, itaconic anhydride, etc.
Various carboxyl group-containing monomers, including various acid anhydride group-containing monomers and various unsaturated bond-containing hydroxyalkyl ester monocarboxylic acids such as adducts with glycols, or Dicarboxylic acids; or various polycarboxylic acid anhydride group-containing unsaturated monomers represented by maleic anhydride, itaconic anhydride and the like.

Particularly, so-called acid groups such as carboxylic acid group, sulfonic acid group and phosphoric acid group have a function of accelerating a crosslinking reaction at the time of curing of the coating film. It is desirable to use group-containing unsaturated monomers.

The use of the acid group-containing unsaturated monomer is desirable in order to improve the cross-linking curability, pigment dispersibility, substrate adhesion and the like of the obtained paint. It is appropriate that the content is within a range of about 0.5 to 5% by weight based on the balance between water resistance and curability.

The above-mentioned monomers, that is, N-alkoxymethylated (meth) acrylamides or hydroxyl-containing unsaturated monomers, which can be copolymerized with the above both essential monomers The unsaturated monomers of
They may be used alone or in combination of two or more, and may be appropriately used or applied in consideration of their copolymerizability. However, if the properties of the resulting coating film are taken into consideration, the emulsion polymer ( As the polymer composition of A), an acrylic type or an acrylic-styrene type is particularly desirable.

Although the theoretical glass transition temperature and the average particle diameter of the emulsion polymer (A) are not particularly limited, the theoretical glass transition temperature is about -20 ° C. to + 60 ° C., respectively. The range is appropriate, while the average particle size is about 0.04-1.
A range of micron (μm) is appropriate, and is particularly practical.

The method for preparing the emulsion polymer (A) is not particularly limited, and various known and commonly used methods may be used. That is, a polymerizable unsaturated monomer is subjected to a polymerization reaction in the presence of an emulsifier and water by using a polymerization initiator.

The emulsifier used in this case is, for example, only the typical emulsifiers, and examples thereof include alkyl sulfates, alkyl benzene sulfonates, and sulfates of ethylene oxide adducts of alkyl phenols. Various anionic emulsifiers, such as

Various nonionic emulsifiers, such as those represented by ethylene oxide adducts of alkylphenols; various cationic emulsifiers, such as those represented by quaternary ammonium salts; or polyvinyl alcohol, polyvinylpyrrolidone , Including various water-soluble resins, such as those represented by acrylic polyesters,

Further, there are various protective colloids such as various cellulose derivatives, which may be used alone or in combination of two or more.
Among these, it is particularly desirable to use a combination of an anionic emulsifier and a nonionic emulsifier.

In addition, if only typical examples of the above-mentioned polymerization initiator (hereinafter, also referred to as a catalyst) are given as examples, ammonium persulfate, potassium persulfate, sodium persulfate and the like can be used. As represented,
Various persulfates; various azo compounds represented by azobisisobutyronitrile and the like;

Alternatively, various organic peroxides represented by tert-butyl hydroperoxide, cumene hydroperoxide and the like, and further, hydrogen peroxide and the like can be mentioned. It goes without saying that they may be used alone or in combination of two or more.

Separately, a metal ion and a reducing agent are used in combination.
It goes without saying that it may be used as a so-called redox catalyst system, and the use amount of these polymerization initiators described above is not particularly limited, but is usually 100 parts by weight of the total amount of monomers. In the range of about 0.05 to 2% by weight.

In addition to the above, it is a matter of course that various known and used raw materials such as a chain transfer agent and a solvent are also used.

The emulsion polymer (A) thus obtained
The solid content (hereinafter also abbreviated as solid content) is not particularly limited, but in order to increase the solid content of the obtained paint, about 35% or more is appropriate. About 45% or more is appropriate.

In the present invention, as long as the emulsion polymer (A) obtained as described above is used as an essential base resin component, the base resin component alone can be used without any problems. The aqueous coating composition of the present invention contains, in addition to the emulsion polymer (A),

Further, if necessary, the emulsion polymer represented by an amino resin, an epoxy resin, a urethane resin, a polyisocyanate, a polyester resin, an alkyd resin, a phenol resin or an acrylic resin. Except for (A), various resins, pigments or various commonly used additives for coatings, etc., can be blended.

Among the various resins, amino resins (hereinafter abbreviated as amino resin (B)) are also used. ) Has good cross-linking reactivity with the emulsion polymer (A), and it is particularly recommended that the emulsion polymer (A) be used in combination with the emulsion polymer (A).

Here, the amount of the component (B) used will be described by representing the amino resin (B). The amount of the component used is expressed in terms of solid content. Thus, it is appropriate to use the emulsion polymer (A) so that the weight ratio of the amino resin is in the range of 70:30 to 98: 2. Shall conform to this.

If only typical examples of the amino resin (B) are mentioned, a compound such as melamine, benzoguanamine, acetoguanamine, urea, thiourea or ethylene urea, and formaldehyde or its equivalent substance may be used. It is a condensate obtained by reacting by a known and usual method, or a form in which these condensates are etherified with an alcohol.

These are used as aqueous resins.
Those in which many methylol groups remain or those having a high degree of methyl etherification have high hydrophilicity of themselves and can be used as such as an aqueous resin.

In addition, those having poor hydrophilicity can be used in the form of being dispersed in water by using another aqueous resin or emulsifier in combination as a dispersing component. Of course, these aqueous melamine resins may be used alone or in combination of two or more.

Next, the above-mentioned pigments are used as needed for improving the concealing properties, hardness, rust-preventive properties and adhesion of the substrate to the obtained coating film, and for coloring as required. However, in consideration of various physical properties of the obtained coating film, the amount used is about 200 parts by weight based on 100 parts by weight of the resin (binder) solid content.
% Or less is suitable, preferably about 150% or less.

The pigment to be used is not particularly limited, and known pigments can be used. Among them, particularly typical ones are exemplified by titanium oxide, zinc oxide and the like. Various metal oxides represented by talc, mica, calcium carbonate, clay, barium sulfate, etc .;

Various rust preventive pigments represented by barium metaborate, aluminum hydrogen phosphate, calcium molybdate, strontium chromate, etc .; or various iron oxides represented by red stalks, etc.
Carbon black, represented by phthalocyanine blue and the like, various organic or inorganic color pigments and the like,

Of course, these may be used alone or in combination of two or more. In addition, various kinds of commercially available so-called color pigments in which these various color pigments are dispersed in water in advance are used. Pastes can, of course, also be used.

Although there is no particular limitation on the method of forming a coating, the above-mentioned emulsion polymer (A) itself generally does not have good mechanical stability but is easily foamed. With a resin other than the emulsion polymer (A), a pigment is dispersed in advance, and
It is particularly desirable to form a coating by such a method as adding the emulsion polymer (A).

In preparing such a coating material, if necessary, a thickener, an antifoaming agent, a leveling agent, a film-forming aid, a wetting agent, a crosslinking agent, a drier, a preservative and deodorant, a thixotropic agent, Water repellent, pigment dispersant, freeze stabilizer, ultraviolet absorber,
Various known and conventional additives such as antioxidants or flame retardants can be used.

The method of coating the composition of the present invention thus obtained is also not particularly limited, but may be applied by a roller, a roll coater, a flow coater, a shower ring or spray coating. Alternatively, it is appropriately performed by electrostatic painting or the like.

Although there is no particular limitation on the heating and drying conditions, it is desirable to set the conditions as low as possible and in a short time as much as possible from the gist of the present invention of resource saving and energy saving. Needless to say.

The aqueous coating composition of the present invention obtained as described above is not intended to limit its use at all, but the coating film obtained is tough and has high durability. In particular, starting from vehicles such as automobiles, and further, such as industrial machinery or industrial parts, respectively, undercoating, intermediate coating, or a coating agent suitable as a coating agent for topcoating, respectively. I can say that there is.

[0064]

EXAMPLES Next, the present invention will be described more specifically with reference examples, examples and comparative examples. In the following, unless otherwise specified, all parts are by weight. .

Reference Example 1 [Preparation Example of Emulsion Polymer (A)] In a stainless steel reaction vessel equipped with a stirrer, a nitrogen inlet tube, a condenser, a thermometer, and a dropping device, 500 water was added.
And 5 parts of “HITENOL N-08” [an anionic emulsifier manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], and “Emal 1
0 "[anionic emulsifier manufactured by Kao Corporation] and 10 parts of" Neugen EA-170 "[nonionic emulsifier manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] and heated to 80 ° C. Warmed.

Here, 45 of n-butyl acrylate
Parts, 50 parts of methyl methacrylate, 5 parts of β-hydroxyethyl methacrylate and 2 parts of methacrylic acid, and a catalyst solution obtained by dissolving 1 part of potassium persulfate in 20 parts of water. 1 hour.

Thereafter, at the same temperature, 165 parts of n-butyl acrylate, 170 parts of methyl methacrylate, β part
-A mixture of 5 parts of hydroxyethyl methacrylate, 50 parts of N-butoxymethylmethacrylamide and 8 parts of methacrylic acid, and a catalyst solution obtained by dissolving 2 parts of potassium persulfate in 40 parts of water, Each was dropped over 3 hours.

Further, one part of potassium persulfate was added, and the mixture was maintained at the same temperature for 3 hours to complete the polymerization reaction. After cooling to room temperature, water and 14% ammonia water were added. Thus, the solid content and the pH were adjusted.
The target emulsion polymer (A) thus obtained has a solid content of 4
It was 5% and the pH was 8.5. Less than,
This is abbreviated as (A-1).

Reference Example 2 (same as above) In a reaction vessel similar to that of Reference Example 1, 500 parts of water and "Levenol WZ" [25 anionic emulsifier manufactured by Kao Corporation) were added.
% Aqueous solution] and 10 parts of “Neugen EA-170”, and the temperature was raised to 80 ° C.

The n-butyl acrylate 55
Parts, 45 parts of n-butyl methacrylate, 2 parts of styrene
20 parts of a monomer mixture consisting of 5 parts, 20 parts of methyl methacrylate, 10 parts of β-hydroxyethyl acrylate, 10 parts of N-butoxymethyl methacrylamide and 3 parts of methacrylic acid, and 1 part of potassium persulfate And a catalyst solution dissolved in water were added dropwise over 1 hour.

Subsequently, 115 of n-butyl acrylate
Parts, 35 parts of n-butyl methacrylate, 5 parts of styrene
0 parts, 55 parts of methyl methacrylate, 65 parts of N-butoxymethyl methacrylamide and 1 part of methacrylic acid
A monomer mixture consisting of 2 parts and a catalyst solution obtained by dissolving 2 parts of potassium persulfate in 40 parts of water were each added dropwise over 3 hours.

Further, one part of potassium persulfate was added,
After maintaining the temperature at the same temperature for 3 hours to complete the polymerization reaction, the mixture was cooled to room temperature, and then the solid content and the pH were adjusted with water and 14% aqueous ammonia. The target emulsion polymer (A) thus obtained has a solid content of 45%.
And the pH was 8.4. Hereinafter, this is abbreviated as (A-2).

Reference Example 3 (Preparation Example of Emulsion Polymer for Control) In a reaction vessel similar to Reference Example 1, 500 parts of water, 5 parts of "Hytenol N-08", and 2. 5 parts and 10 parts of “Neugen EA-170” were charged, and the temperature was raised to 80 ° C.

Here, 45 of n-butyl acrylate
Parts, a monomer mixture consisting of 50 parts of methyl methacrylate and 2 parts of methacrylic acid, and a catalyst solution obtained by dissolving 1 part of potassium persulfate in 20 parts of water were each added dropwise over 1 hour.

Thereafter, at the same temperature, 165 parts of n-butyl acrylate, 170 parts of methyl methacrylate, β part
A monomer mixture consisting of 10 parts of hydroxyethyl methacrylate, 50 parts of N-butoxymethyl methacrylamide and 8 parts of methacrylic acid;
Parts were dissolved in 40 parts of water,
It was dropped over time.

Further, 1 part of potassium persulfate was added,
After maintaining the temperature at the same temperature for 3 hours to complete the reaction, the mixture was cooled to room temperature, and then the solid content and pH were adjusted with water and 14% aqueous ammonia. The control emulsion polymer thus obtained had a solid content of 45% and a pH of 8.5. Hereinafter, this is abbreviated as (A'-1).

REFERENCE EXAMPLE 4 (Same as above) In a reaction vessel similar to Reference Example 1, 500 parts of water, 5 parts of "Hytenol N-08", 2.5 parts of "Emal 10" and "Neugen EA- 170 ", and the temperature was raised to 80 ° C.

Here, 45 of n-butyl acrylate
Parts, 50 parts of methyl methacrylate, 5 parts of β-hydroxyethyl methacrylate and 2 parts of methacrylic acid, and a catalyst solution obtained by dissolving 1 part of potassium persulfate in 20 parts of water. 1 hour.

Thereafter, at the same temperature, 175 parts of n-butyl acrylate, 180 parts of methyl methacrylate, β part
A monomer mixture consisting of 35 parts of hydroxyethyl methacrylate and 8 parts of methacrylic acid and a catalyst solution obtained by dissolving 2 parts of potassium persulfate in 40 parts of water were each added dropwise over 3 hours.

Further, 1 part of potassium persulfate was added,
After maintaining the temperature at the same temperature for 3 hours to complete the reaction, the mixture was cooled to room temperature, and then the solid content and pH were adjusted with water and 14% aqueous ammonia.

The control emulsion polymer thus obtained had a solid content of 45% and a pH of 8.5. Hereinafter, this is abbreviated as (A'-2), but this control emulsion polymer could not be subjected to an application test due to extremely poor stability.

REFERENCE EXAMPLE 5 (Same as above) In a reaction vessel similar to Reference Example 1, 500 parts of water, 30 parts of "Levenol WZ" and "Neugen EA-17" were added.
0 "was charged, and the temperature was raised to 80 ° C.

Here, 20 of n-butyl acrylate
Parts, 15 parts of n-butyl methacrylate, 2 parts of styrene
20 parts of a monomer mixture consisting of 5 parts, 20 parts of methyl methacrylate, 10 parts of β-hydroxyethyl acrylate, 75 parts of N-butoxymethyl methacrylamide and 3 parts of methacrylic acid, and 1 part of potassium persulfate And a catalyst solution dissolved in water were added dropwise over 1 hour.

Next, 150 parts of n-butyl acrylate
Parts, 65 parts of n-butyl methacrylate, 5 parts of styrene
0 parts, a monomer mixture consisting of 55 parts of methyl methacrylate and 12 parts of methacrylic acid, and a catalyst solution obtained by dissolving 2 parts of potassium persulfate in 40 parts of water,
It was added dropwise over 3 hours.

Further, 1 part of potassium persulfate was added,
After maintaining the temperature at the same temperature for 3 hours to complete the reaction, the reaction solution was cooled to room temperature, and the solid content and the pH were adjusted with water and 14% aqueous ammonia.

The thus obtained control emulsion polymer had a solid content of 45% and a pH of 8.4. Hereinafter, this is abbreviated as (A'-3).

Reference Example 6 (same as above) In a reaction vessel similar to Reference Example 1, 500 parts of water, 30 parts of "Levenol WZ" and "Neugen EA-17" were added.
0 "was charged, and the temperature was raised to 80 ° C.

Here, 170 parts of n-butyl acrylate
Parts, 80 parts of n-butyl methacrylate, 7 parts of styrene
60 parts of a monomer mixture consisting of 5 parts, 75 parts of methyl methacrylate, 75 parts of N-butoxymethylmethacrylamide, 10 parts of β-hydroxyethyl acrylate and 15 parts of methacrylic acid, and 3 parts of potassium persulfate And a catalyst solution dissolved in water were added dropwise over 3 hours.

Further, 1 part of potassium persulfate was added,
After maintaining at the same temperature for 3 hours to complete the reaction, the mixture was cooled to room temperature, and then the solid content and pH were adjusted with water and 14% aqueous ammonia.

The thus obtained control emulsion polymer had a solid content of 45% and a pH of 8.4. Hereinafter, this is abbreviated as (A'-4).

The raw material use ratio of each of these emulsion polymers was
The results are shown in Table 1.

[0092] As other water-based resins, "Watersol S-695" [a methyl etherified melamine resin manufactured by Dainippon Ink and Chemicals, Inc .;
Solid content = 66%] and "Watersol S-12
6 "(water-soluble alkyd resin manufactured by Dojo Co .; solid content = 50)
%).

[0093]

[Table 1]

<< Footnotes in Table 1 >> Numerical values in parentheses indicate the amounts used in the first stage when performing two-stage polymerization.

1) β-hydroxyethyl acrylate 2) β-hydroxyethyl methacrylate 3) N-butoxymethyl methacrylamide 4) Styrene 5) Methyl methacrylate 6) ... n-butyl acrylate 7) ... n-butyl methacrylate 8) ... methacrylic acid

[0096]

[Table 2]

[0097]

[Table 3]

Examples 1 and 2 and Comparative Examples 1 to 4 Various paints were prepared according to the following formulations.

Paint Formulation Example 1 (Preparation Example of Clear Paint) According to the paint composition as described below, various clear paints having a solid content of 40% were prepared by stirring and mixing according to a conventional method.

Emulsion polymer (solid content adjusted to 45%) 100 parts Mixture of butyl cellosolve / water = 1: 1 (weight ratio) 5 parts “Boncoat 3750” [0.5 parts by Dainippon Ink and Chemicals, Inc.] Polycarboxylic acid-based thickener] "SN Deformer 373" [Antifoaming agent manufactured by San Nopco Co., Ltd.] 0.1 part Water 7 parts

Coating Formulation Example 2 (Preparation Example of White Coating) According to the coating formulation as described below, according to a conventional method, firstly, the mixture was kneaded with a sand mill, then the mixture was stirred and mixed to obtain a solid content of 53%. Various clear paints having a PWC (pigment weight concentration) of 40% within a range of ~ 56% were prepared.

"Watersol S-126" (supra) 20 parts "Taipek R-930" [80 parts titanium oxide manufactured by Ishihara Sangyo Co., Ltd.] "SN Deformer 373" (supra) 0.2 parts "BYK-080" [BYK / Hemimy 0.05 parts Defoamer manufactured by the company] Water 30 parts ──────────────────────── ─────────── (The above components are dispersed by a sand mill.)

"Watersol S-695" (supra) 15 parts Emulsion polymer (adjusted solid content to 45%) 178 parts "Boncoat 3750" (supra) 0 to 1.5 parts triethylamine dodecylbenzenesulfonate 0.1 part water appropriate amount ─────────────────────────────────── )

Each of the coating materials thus obtained was applied to a substrate to be coated as described below and cured to obtain various cured coating films. Next, with respect to each cured coating film, an application test was performed to evaluate and evaluate various properties of the coating film. The results are summarized in Tables 2 and 3.
See the table.

Base material: zinc phosphate treated steel sheet

Procedures for application tests

First, the coating compositions having the respective formulations were placed on the above-mentioned zinc phosphate-treated steel sheet as a predetermined substrate to be coated.
The coating is performed so that the dry film thickness becomes 30 μm, and left (setting) for 1 hour at room temperature. In the case of white paint, respectively, at 140 ° C. for 20 minutes,
In the case of the clear paint, it was heated and dried under the condition of 180 ° C. for 20 minutes, and left at room temperature for 3 days to produce various cured coating films.

Thereafter, it was subjected to various performance evaluation tests as described below. The results are shown in Table 2 and 3
It is as shown in the table. In addition, the following test items (5)-
In (9), the surface other than the coated surface was sealed with an acrylic urethane-based sealing agent.

Test method

(1) Hikarizawa: A gloss meter, 60
Measure specular reflectance (%).

(2) Adhesion to base material: 100 squares were cut in a 1 cm square on the coating surface with a cutter knife, and a cellophane tape was applied and peeled off.

"100": Completely adhered "0": Completely peeled

(3) Impact resistance: A durable drop height (cm) was measured with a DuPont impact tester (load = 500 g).

(4) Solvent resistance: A gauze impregnated with xylene was used, and after a rubbing test of 20 reciprocations, the state of change of the coated surface was visually determined.

(5) Water resistance: The substrate was completely immersed in water at room temperature, and the state of change of the coated surface one week after that was visually judged.

(6) Acid resistance: The substrate was completely immersed in 1% dilute sulfuric acid, and the state of change of the coated surface four days later was visually determined.

(7) Alkali resistance: The substrate was completely immersed in a 2% aqueous sodium hydroxide solution, and the state of change of the coated surface after 4 days was visually judged.

(8) Rust-preventing property: The state of change of the coated surface after a 250-hour test using a salt spray tester was visually judged.

(9) Accelerated weathering resistance: Gloss retention measured in the same manner as in the case of "gloss" after conducting an accelerated weathering test for 800 hours with a sunshine weather meter (%).

[0120]

[Table 4]

<< Footnotes in Table 2 >> Evaluation criteria are as follows.

○: good good △: slightly poor ×: bad

[0123]

[Table 5]

[0124]

[Table 6]

<< Footnotes in Table 3 >> The criteria for the evaluation judgment are as follows.

…: Good good △: slightly poor ×: bad

[0127]

[Table 7]

[0128]

The aqueous coating composition of the present invention thus obtained is itself water-based and has an excellent substrate protecting effect. It is easy to know that it is also excellent in durability.

Accordingly, the aqueous coating composition of the present invention
It is extremely practical.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 5/00-201/10 C08F 2/22-2/30 C08F 220/00-220/70

Claims (4)

(57) [Claims] 1. A monomer mixture containing a hydroxyl group-containing unsaturated monomer is emulsion-polymerized, and then a monomer mixture containing N-alkoxymethylated (meth) acrylamides in the presence of the emulsion polymer. An aqueous coating composition comprising, as an essential film-forming component, an emulsion polymer (A) obtained by emulsion polymerization of 2. A monomer mixture containing a hydroxyl group-containing unsaturated monomer is emulsion-polymerized, and then a monomer mixture containing N-alkoxymethylated (meth) acrylamides in the presence of the emulsion polymer. An aqueous coating composition comprising, as essential film-forming components, an emulsion polymer (A) obtained by emulsion polymerization of an amino resin (A) and an amino resin (B). 3. The above-mentioned emulsion polymer (A) is added with 0.5 to 8% by weight of a hydroxyl group-containing monomer and N-alkoxymethylated (meth), based on the total amount of all monomers. )
The aqueous coating composition according to claim 1 or 2, which is obtained by using 3 to 30% by weight of acrylamides as an essential monomer. 4. The above-mentioned emulsion polymer (A) is added with 0.5 to 8% by weight of a hydroxyl group-containing monomer and N-alkoxymethylated (meth), based on the total amount of all monomers. )
The aqueous solution according to claim 1 or 2, which is obtained by using 3 to 30% by weight of acrylamides and 0.5 to 5% by weight of an acid group-containing monomer as essential monomers. Coating composition.