JP5468802B2 - Aqueous paint composition and topcoat paint - Google Patents

Description

The present invention relates to a water-based paint composition and a topcoat paint. More specifically, the present invention relates to a composition for water-based paints useful in the field of paints that handle buildings, civil engineering structures, and the like, and a topcoat paint containing the same.

In the field of paints dealing with construction and civil engineering structures, in recent years, from the concern of the health hazards of painters and residents, environmental pollution such as water pollution and air pollution, etc. The conversion to water-based paints using water-based compositions that do not require organic solvents is progressing.
However, a coating film made of a water-based paint generally has a coating film hardness lower than that of a solvent-type paint, and tends to have a high penetration when contaminated substances adhere. Therefore, in order to solve the problem of such a water-based paint, for example, a polymer obtained by polymerizing a monomer component essentially comprising an oxazoline group-containing monomer, a reactive group-containing monomer and a reactive emulsifier. An aqueous resin composition containing a coalescence (see Patent Document 1), a (meth) acrylic emulsion and a water-soluble resin are essential, and the (meth) acrylic emulsion and the water-soluble resin form a crosslinked structure. Techniques such as an aqueous resin composition for paints (see Patent Document 2) to be obtained have been developed.

JP 2008-069249 A International Publication No. 2008/102816 Pamphlet

As described above, various compositions for water-based paints have been developed. In particular, in the compositions described in Patent Documents 1 and 2, the cured film has a stain resistance, weather resistance, hot water whitening resistance, and the like. Therefore, it is a very useful material in the paint field.

In recent years, emulsion-type compositions are being diversified in the paint field, such as the compositions described in Patent Documents 1 and 2. Since an emulsion type composition forms a coating film by evaporating water and fusing emulsion particles (resin particles) to each other, the composition often requires low-temperature film-forming properties depending on the drying temperature. Therefore, means for incorporating an organic solvent such as a volatile organic compound as a film-forming auxiliary (also referred to as a film-forming auxiliary) is usually employed in conventional compositions. For example, in Patent Documents 1 and 2, in specific examples, a mixed solution of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate and butyl cellosolve is used as a film forming aid. .
Such a film-forming auxiliary is usually contained at least about 5 to 6% by mass or more in 100% by mass of the total amount of the composition. Amount is used.

By the way, volatile organic compounds (VOC) have been greatly reduced not only in building interior paints as a countermeasure against sick house syndrome but also in exterior paints due to increased awareness of health hazards and environmental problems. A free (VOC free) paint is desired. However, it is a common perception in the industry that if the film-forming aid is removed or significantly reduced from the emulsion-type composition for paint, the formation of the coating film itself, which is a major premise for the paint composition, will not be easy. For this reason, the technology itself for reducing even the volatile organic compound used as a film forming aid from such a composition has not yet been studied.

In view of the present situation, the present invention exhibits extremely good low-temperature film-forming properties even when the volatile organic compound usually contained in the coating composition is greatly reduced or substantially free of the volatile organic compound. A composition for water-based paints that can give a coating film with excellent physical properties such as stain resistance, weather resistance, hot water whitening resistance and the like, and can greatly reduce the burden on health and the environment, and for top coats using the same The object is to provide a paint.

The inventors of the present invention have studied various compositions for water-based paints, and paying attention to the fact that they can exhibit advantageous performance such as water resistance by including (meth) acrylic emulsions. Thus, oxazoline group-containing polymers and / or oxazoline compounds If it is a composition for water-based paints containing water, it not only gives a coating film excellent in properties such as stain resistance, weather resistance, and hot water whitening resistance, but also can exhibit extremely good low-temperature film-forming properties. I found it. That is, it has been found that by incorporating a compound or polymer having an oxazoline group into the aqueous coating composition, the composition is imparted with a low-temperature film-forming property, which is a remarkable effect. And in such a composition for water-based paints, it is equivalent to or more than that of the conventional composition even if the volatile organic compound that is usually used as a film-forming auxiliary or the like is significantly reduced or substantially free of the volatile organic compound. The present inventors have newly found that a very different action and effect that can defeat the conventional common sense of being capable of exhibiting the ability to form a coating film can be exhibited, and have devised that the above problems can be solved brilliantly. That is, the present invention has found that even if the volatile organic compound naturally contained in the conventional water-based paint composition is significantly reduced or substantially free of the volatile organic compound, it can function sufficiently as a paint. There is an important technical significance of the invention. Therefore, if such a composition is used, it is possible to realize a VOC-free paint that has high performance and substantially does not contain volatile organic compounds. Moreover, since such a composition for water-based paints is excellent also in low-temperature film-forming properties, it has been found useful for various topcoat paints, and has reached the present invention.

That is, the present invention is an aqueous coating composition containing a (meth) acryl emulsion, wherein the composition contains an oxazoline group-containing polymer and / or an oxazoline compound, and 100% by mass of the composition. On the other hand, it is the composition for water-based coatings whose total content of a volatile organic compound is less than 3 mass%.
The present invention is also a top coat paint comprising the above-mentioned aqueous paint composition.
The present invention is described in detail below.

The aqueous coating composition of the present invention (hereinafter also simply referred to as “composition”) contains a (meth) acrylic emulsion, an oxazoline group-containing polymer and / or an oxazoline compound as essential components. A form including an oxazoline group-containing polymer as a polymer constituting the acrylic emulsion is also included in the present invention. These essential components can be used alone or in combination of two or more.
In such a composition, as long as the effects of the present invention are not hindered, other components may be included, but the (meth) acrylic emulsion, the oxazoline group-containing polymer and / or the oxazoline compound are contained in the composition. The main component is preferred. The main component means that the total amount of the (meth) acrylic emulsion, the oxazoline group-containing polymer and the oxazoline compound is 50% by mass or more in 100% by mass of the composition. The content ratio varies depending on the required physical properties, but is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more.

In the aqueous coating composition, the oxazoline group-containing polymer means a polymer having an oxazoline group, and may be obtained by polymerizing a monomer component containing an oxazoline group-containing monomer. . In the present invention, those containing at least an oxazoline group-containing polymer in the aqueous coating composition are particularly suitable.
As the oxazoline group-containing monomer, the following general formula (1);

Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents a hydrogen, halogen, alkyl, phenyl or substituted phenyl group. R ⁵ is an acyclic ring having an addition polymerizable unsaturated bond. An organic group is preferred.
Examples of the oxazoline group-containing monomer represented by the general formula (1) include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, and 2-vinyl-5-methyl-2. -Oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, etc. Can be used. Of these, 2-isopropenyl-2-oxazoline is preferable from the viewpoint of industrial availability.

In the aqueous coating composition, the oxazoline compound means a compound having an oxazoline group other than the oxazoline group-containing polymer, and one or more of the above-mentioned oxazoline group-containing monomers are used. Can do.

In the aqueous coating composition, the blending ratio of the oxazoline group-containing polymer and / or the oxazoline compound is 0.1 to 10% by mass as the total content of the oxazoline compound with respect to 100% by mass of the aqueous coating composition. Is preferred. If it is less than 0.1% by mass, the low-temperature film-forming property and low contamination are not sufficient, and there is a possibility that it cannot be suitably used by, for example, a top coat paint. There is a risk that it will not. More preferably, it is 0.2-5 mass%.
The “total content of the oxazoline compound with respect to 100% by mass of the aqueous coating composition” as used herein is a polymerization component for all components constituting the aqueous coating composition when an oxazoline group-containing polymer is used. Of oxazoline group-containing monomers.

In the composition for water-based paints, the (meth) acrylic emulsion means an emulsion obtained by emulsion polymerization of a monomer component that essentially contains a (meth) acrylic monomer.
The molecular weight of such a (meth) acrylic emulsion is preferably 10,000 to 3,000,000. If the molecular weight is less than 10,000, the water resistance may not be sufficient, and if it exceeds 3 million, the film-forming property may not be further improved. More preferably, it is 50,000 to 1,500,000.
Here, the molecular weight is a weight average molecular weight (Mw). For example, a solution in which a (meth) acrylic emulsion is dissolved in THF (tetrahydrofuran) so as to be a 0.2 mass% solution is used as a sample, and the following conditions are satisfied. , And can be measured by gel permeation chromatography (hereinafter referred to as “GPC”).
<GPC measurement conditions>
GPC body: "HLL-8120GPC" manufactured by Tosoh Corporation
GPC column: Tosoh Corporation “TSK-GEL G5000HXL” and “GMHXL-L” connected column mobile phase: tetrahydrofuran calibration curve: prepared using polystyrene standard sample.

The (meth) acrylic emulsion preferably has an average particle size of 30 to 300 nm. If the average particle size is less than 30 nm, the particle stability may not be more sufficient, and if it is greater than 300 nm, the water resistance may not be further improved. More preferably, it is 50-200 nm.
The average particle diameter means a volume average particle diameter and can be determined by a dynamic light scattering method. For example, it can be determined using a particle size distribution analyzer (“NICOMP Model 380” manufactured by Particle Sizing Systems) by a dynamic light scattering method.

The particle structure of the (meth) acrylic emulsion is not particularly limited as long as the effects of the present invention are exhibited, and examples thereof include a core-shell structure, a power feed structure, and a uniform structure. Among these, a core-shell structure is preferable, and by having such a particle structure, it is possible to make the hardness and the film-forming property more compatible.

The (meth) acrylic emulsion preferably has an overall glass transition temperature (Tg) of −50 to 100 ° C. If the Tg is less than -50 ° C, the coating film hardness may not be sufficient, and if it exceeds 100 ° C, the low-temperature film-forming property may not be improved. More preferably, it is -40-50 degreeC, More preferably, it is -30-30 degreeC.

The (meth) acrylic emulsion is further preferably composed of two or more polymers having different Tg. In this case, it is preferable that there are at least one kind of component that imparts hardness (hard portion) and one component that imparts softness (soft portion).
The Tg of the two or more polymers is preferably 50 to 200 ° C. in the polymer having the highest Tg. When it is less than 50 ° C, the coating film hardness is not sufficient, and when it exceeds 200 ° C, the low-temperature film-forming property may not be further improved. More preferably, it is 60-150 degreeC, More preferably, it is 70-120 degreeC.
Moreover, in the polymer with the lowest Tg, it is suitable that it is -40-40 degreeC. When it is less than -40 ° C, the coating film hardness is not sufficient, and when it exceeds 40 ° C, the low-temperature film-forming property may not be further improved. More preferably, it is -40 ~ 15 degreeC, More preferably, it is -40 ~ 0 degreeC.

The glass transition temperature (unit: K) of the (meth) acrylic emulsion can be calculated from the following Fox equation using the glass transition temperature (Tgn) of the homopolymer of each monomer component constituting the emulsion.
1 / Tg = Σ (Wn / Tgn) / 100
(Wn represents the mass fraction (mass%) of monomer n. Tgn represents the glass transition temperature (K: absolute temperature) of the homopolymer of monomer n.)
In addition, although the numerical value (glass transition temperature) of Tg mentioned above is a calculated value by the Fox formula mentioned above, the same range is preferable also in the case of a measured value. The actual measured value of Tg can be determined by, for example, differential thermal scanning calorimetric analysis of the aqueous coating composition.

The measuring device for performing differential thermal scanning calorimetry is not particularly limited, and examples thereof include commercially available products such as DSC220C (manufactured by Seiko Instruments Inc.). In addition, the method for drawing a DSC curve, the method for obtaining a first derivative curve from the DSC curve, the method for performing the smoothing process, and the method for obtaining the temperature of the target peak point are not particularly limited, and are based on the data obtained by the measuring device. There is a method of drawing. This method is preferably performed using analysis software that can perform normal mathematical processing. The analysis software is not particularly limited, and examples thereof include EXSTAR6000 (analysis software manufactured by Seiko Instruments Inc.). Note that the peak point temperature thus obtained may include an error of about 5 ° C. in the vertical direction as an error due to drawing.

When the (meth) acrylic emulsion is composed of two or more kinds of polymers having different Tg, the content of each polymer is such that the polymer having the highest Tg constitutes the (meth) acrylic emulsion. It is preferable to set the amount to 1 to 30% by mass with respect to 100% by mass of the total amount of the polymer. When the polymer having the highest Tg is less than 1% by mass, the coating film hardness is not sufficient, and when it is more than 30% by mass, the low-temperature film-forming property may not be further improved. More preferably, it is 5-30 mass%, More preferably, it is 10-30 mass%.

In the present invention, it is particularly preferable that 1 to 30% by mass of a polymer having a Tg of 50 to 200 ° C. is contained with respect to 100% by mass of the total amount of all the polymers constituting the (meth) acrylic emulsion. Thereby, the effect | action which provides sufficient coating-film hardness and low-temperature film-forming property can be exhibited with sufficient balance, and it becomes a more useful thing as a composition for coating materials.

In the monomer component used to obtain the (meth) acrylic emulsion, the (meth) acrylic monomer may be a compound having a (meth) acryloyl group (CH ₂ ═CHCO—) in the molecule. For example, it is preferable to use one or more of the following monomers.
In addition, it is suitable that content of a (meth) acrylic-type monomer is 10 mass% or more with respect to 100 mass% of the total amount of the monomer component used in order to obtain a (meth) acryl emulsion. . More preferably, it is 30 mass% or more.

Methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, sec-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (Meth) such as tridecyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth) acrylate, n-lauryl (meth) acrylate, benzyl (meth) acrylate, 2- (acetoacetoxy) ethyl (meth) acrylate Acrylic acid alkyl esters;
It has a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate ( (Meth) acrylates;
(Meth) acrylates having an acidic functional group such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, and acid anhydrides thereof;
Polymerizable monomers having an oxo group such as ethylene glycol (meth) acrylate, ethylene glycol methoxy (meth) acrylate, diethylene glycol (meth) acrylate, diethylene glycol methoxy (meth) acrylate;

Fluorine-containing polymerizable monomers such as trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, and octafluoropentyl (meth) acrylate;
Nitrogen atom-containing polymerizable monomers such as (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, diacetone (meth) acrylamide;
Polymerizable monomers having an epoxy group such as glycidyl (meth) acrylate;
2- [2′-hydroxy-5 ′-(meth) acryloyloxyethylphenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-tert-butyl-5 ′-(meth) acryloyloxyethylphenyl ] -2H-benzotriazole, 2-hydroxy-4- (2-hydroxy-3- (meth) acryloyloxypropoxy) benzophenone, 2-hydroxy-4- (2- (meth) acryloyloxyethoxy) benzophenone, etc. Absorbable polymerizable monomers;
4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino- UV-stable polymerizable monomers such as 2,2,6,6-tetramethylpiperidine and 4- (meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine.

Among these, (meth) acrylic acid alkyl esters, UV-absorbing polymerizable monomers, and UV-stable polymerizable monomers are particularly preferable from the viewpoint of weather resistance. As the (meth) acrylic acid alkyl esters, a polymerizable monomer having at least one group selected from the group consisting of a cycloalkyl group, a t-butyl group and an isobutyl group is particularly preferable among the above exemplary compounds. . By including such a polymerizable monomer as a polymerizable monomer component, it is possible to suitably exhibit blocking resistance and to further improve weather resistance and warm water whitening resistance. Among these, a polymerizable monomer having at least a cycloalkyl group is preferable. In this case, although the usage-amount of a cycloalkyl group containing monomer is not specifically limited, For example, it is preferable that it is 5-60 mass% with respect to 100 weight part of all the monomer components. More preferably, it is 10-60 mass%, More preferably, it is 20-60 mass%.

The monomer component may also contain an oxazoline group-containing monomer. In this case, since the obtained (meth) acrylic emulsion contains a polymer having an oxazoline group, in addition to the (meth) acrylic emulsion, the present invention can be used without further containing an oxazoline group-containing polymer or an oxazoline compound. This constitutes the composition for water-based paints of the invention. That is, an aqueous coating composition containing a (meth) acrylic emulsion containing an oxazoline group-containing polymer is also a preferred embodiment of the present invention. However, it goes without saying that, in addition to such a (meth) acrylic emulsion, an oxazoline group-containing polymer and / or an oxazoline compound may be further contained.
As the oxazoline group-containing monomer, one or more of the oxazoline group-containing monomers described above can be used.

The monomer component may further contain a monomer copolymerizable with the above (meth) acrylic monomer or an oxazoline group-containing monomer contained as necessary. . Examples of such monomers include vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and divinylbenzene; vinyl esters such as vinyl acetate; one or more of N-vinylpyrrolidone and the like. Can be mentioned.
When a monomer having a functional group capable of forming a cross-linked structure such as an oxazoline group is used as the monomer component, the monomer is preferably polymerized in the final stage. However, it may be included in the previous polymerization step. When manufacturing what has a power feed structure as a (meth) acryl emulsion, it is preferable to increase gradually the functional group which can form crosslinked structures, such as an oxazoline group.

The (meth) acrylic emulsion is also preferably obtained using a silane coupling agent together with the monomer component. Thereby, the water resistance etc. of the obtained composition for water-based coating materials improve more.
Examples of the silane coupling agent include vinyl polymerizable silane compounds, epoxy group-containing silane compounds, and the like, and specifically, one or more of the following compounds can be used.

Alkoxy such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane Silanes;
Vinylsilanes such as vinyltris (β-methoxyethoxy) silane, vinylethoxysilane, vinyltrimethoxysilane;
(meth) acrylsilanes such as γ-methacryloxypropyltrimethoxysilane;
β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) methyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, β- (3, 4-epoxycyclohexyl) epoxysilanes such as methyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane;
N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldiethoxysilane, γ-amino Aminosilanes such as propyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltriethoxysilane;
Thiosilanes such as γ-mercaptopropyltrimethoxysilane and γ-mercaptopropyltriethoxysilane.

As the silane coupling agent, the following general formula (2)
^{(R 10) n-Si- (} R 11) 4-n (2)
(In formula (2), R ¹⁰ is a radically polymerizable group, and R ¹¹ is selected from a hydroxyl group, an alkyl group, an epoxy group, a halogen atom, an alkoxy group, an acyloxy group, a phenoxy group, and a mercapto group. It is preferable that it contains the Si containing monomer shown by the substituent which has 1 or more types by which n is an integer of 1-3. As a result, a structure in which the acrylic polymer chain is firmly cross-linked by a siloxane bond can be formed, and for example, suppression of polymer degradation due to a photooxidation catalytic reaction, warm water whitening resistance, and further blocking resistance can be improved.

In the above general formula (2), specific examples of the group having radical polymerizability represented by R ¹⁰ include (meth) acryloxy group, vinyl group and the like. Moreover, in General formula (2), when the number of n or 4-n becomes 2 or more, multiple R ¹⁰ and R ¹¹ may be the same or different.
Specific examples of the Si-containing monomer itself represented by the general formula (2) include, for example, vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane. , Γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, and the like. Of these, (meth) acrylsilanes are preferred in view of stain resistance and hot water whitening resistance. Particularly preferably, γ-methacryloyloxyethylmethyldimethoxysilane, γ-methacryloyloxyethyltrimethoxysilane, γ-methacryloyloxyethyltriethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ -Methacryloyloxypropyltriethoxysilane. In addition, only 1 type may be used for Si containing monomer and 2 or more types may be sufficient as it.

The blending ratio of the silane coupling agent is not particularly limited. For example, with respect to the total amount of the monomer components used to obtain the (meth) acryl emulsion and the total amount of the silane coupling agent of 100% by mass. 0.1 to 10% by mass is preferable. If the silane coupling agent is less than 0.1% by mass, water resistance such as warm water whitening resistance and water whitening resistance may not be sufficiently improved, and if it exceeds 10% by mass, sufficient film formation may not be possible. is there. More preferably, it is 0.3-5 mass%, More preferably, it is 0.5-3 mass%.
In addition, it is suitable that the ratio for which the said Si containing monomer accounts is 70 mass% or more in the total amount of 100 mass% of a silane coupling agent. More preferably, it is 80 mass% or more, More preferably, it is 90 mass% or more.

The (meth) acrylic emulsion can be obtained by emulsion polymerization of the monomer component and a silane coupling agent used as necessary in the presence of an emulsifier. It is not limited, For example, it can carry out using well-known methods, such as a multistage feed method and a power feed method. Specifically, a method of dissolving an emulsifier in water or an aqueous medium containing an organic solvent such as alcohol as required, and dropping a monomer component and a polymerization initiator as raw materials under heating and stirring, The method etc. which are dripped similarly the monomer component used as the raw material emulsified previously using an emulsifier and water can be mentioned.

The polymerization initiator is not particularly limited, and examples thereof include azo compounds such as 2,2-azobis (2-diaminopropane) hydrochloride; persulfates such as potassium persulfate; peroxides such as hydrogen peroxide. These can be used, and one or more of these can be used. Specifically, for example, azo oily compounds (for example, azobisisobutyronitrile, 2,2-azobis (2-methylbutyronitrile), 2,2-azobis (2,4-dimethylvaleronitrile) Etc.), aqueous compounds (eg anionic 4,4-azobis (4-cyanovaleric acid), cationic 2,2-azobis (2-methylpropionamidine)); redox oily peroxides (eg Benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide, t-butyl perbenzoate, etc.), aqueous peroxides (for example, potassium persulfate and ammonium peroxide), and the like.

Although the usage-amount of the said polymerization initiator is not specifically limited, For example, it shall be 0.05-1 weight part with respect to 100 weight part of total amounts of the said monomer component and the silane coupling agent contained as needed. Is preferred. When the amount of the polymerization initiator used is less than 0.05 parts by weight, the polymerization rate is not sufficient, and unreacted polymerizable monomers are likely to remain, and when the amount exceeds 1 part by weight, the polymerization initiator is formed. There is a possibility that the water resistance of the coating film may not be sufficient. More preferably, it is 0.1-0.5 weight part.
In addition, the addition method of a polymerization initiator is not specifically limited, For example, any methods, such as batch preparation, division | segmentation preparation, and continuous dripping, may be sufficient. In order to speed up the completion of the polymerization, a part of the polymerization initiator may be added before and after the completion of the dropwise addition of the polymerizable monomer component in the final stage.

In the above emulsion polymerization, for the purpose of accelerating the decomposition of the polymerization initiator, for example, a reducing agent such as sodium bisulfite or a transition metal salt such as ferrous sulfate may be added, and if necessary, pH buffering may be performed. Commonly used additives such as agents, chelating agents, chain transfer agents and the like may be added. Examples of the chain transfer agent include compounds having a thiol group such as t-dodecyl mercaptan.

Examples of the emulsifier include an anionic emulsifier, a nonionic emulsifier, a cationic emulsifier, an amphoteric emulsifier, and a polymer emulsifier, and one or more of these can be used.
Examples of the anionic emulsifier include alkyl sulfonate salts such as sodium alkyl diphenyl ether disulfonate (for example, “Perex SSL” manufactured by Kao), ammonium dodecyl sulfonate, sodium dodecyl sulfonate, and the like; ammonium dodecyl benzene sulfone And alkylaryl sulfonate salts such as sodium dodecyl naphthalene sulfonate; polyoxyethylene alkyl sulfonate salts (for example, “Hitenol 18E” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., “Latemul E-118B” manufactured by Kao Corporation, etc. ); Dialkylsulfosuccinate; arylsulfonic acid formalin condensate; fatty acid salt such as ammonium laurate, sodium stearate; bis (polyoxyethylene polycyclic phenyl ether) methacrylate Sulfonated salt (for example, “Antox MS-60” manufactured by Nippon Emulsifier Co., Ltd.), propenyl-alkylsulfosuccinate ester salt, (meth) acrylic acid polyoxyethylene sulfonate salt, (meth) acrylic acid polyoxyethylene Phosphonate salts (for example, “Eleminol RS-30” manufactured by Sanyo Chemical Industries, Ltd.), sulfonate salts of allyloxymethylalkyloxypolyoxyethylene (for example, “Aqualon KH-10” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), etc. A sulfate ester (salt) having an allyl group, a sulfate ester salt of allyloxymethylalkoxyethyl polyoxyethylene (for example, “Adekaria Soap SR-10” manufactured by Asahi Denka Kogyo Co., Ltd.), polyoxyalkylene alkenyl ether ammonium sulfate (for example, , "Latemul PD-" manufactured by Kao 04 ", etc.) and the like are suitable.

Examples of the nonionic emulsifier include polyoxyethylene alkyl ethers (for example, “Naroacty N-200” manufactured by Sanyo Chemical Industries, Ltd., “Neugen TDS series”, “Neugen SD series” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Kao Corporation. "Emulgen 1118S" manufactured by Kao Corporation; "Emulgen 1108S" manufactured by Kao Corporation); condensate of polyethylene glycol and polypropylene glycol; sorbitan fatty acid ester; polyoxyethylene sorbitan fatty acid ester; fatty acid monoglyceride; polyoxyalkylene decyl ether (Daiichi Kogyo Seiyaku Co., Ltd.) "Neugen XL series"), polyoxyethylene styrenated phenol ether ("Neugen EA series" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); condensation product of ethylene oxide and aliphatic amine; allyloxymethylalkoxy Ethylhydroxypolyoxyethylene (for example, “Adekaria soap ER-20” manufactured by Asahi Denka Kogyo Co., Ltd.), polyoxyalkylene alkenyl ether (for example, “Latemul PD-420”, “Latemul PD-430” manufactured by Kao Corporation) Etc. are suitable.

As the cationic emulsifier, for example, alkylammonium salts such as dodecylammonium chloride are suitable.
As the amphoteric emulsifier, for example, a betaine ester type emulsifier is suitable.
Examples of the polymer emulsifier include poly (meth) acrylates such as sodium polyacrylate; polyvinyl alcohol; polyvinylpyrrolidone; polyhydroxyalkyl (meth) acrylates such as polyhydroxyethyl acrylate; and these polymers. A copolymer having one or more of the polymerizable monomers as a copolymerization component is suitable.

Among the emulsifiers, when emphasizing water resistance in particular, it is preferable to use an emulsifier having a polymerizable group, that is, a so-called reactive emulsifier, and the (meth) acryl emulsion uses a reactive emulsifier. It is particularly preferable that the product is obtained in the above manner.
The reactive emulsifier means a surfactant that has an unsaturated double bond in the monomer and can be polymerized with other monomers. Specifically, it is an emulsifier that has radical polymerizable double bonds such as vinyl group, (meth) acryloyl group, allyl group, propenyl group, etc. in the molecule and has an emulsifying and dispersing function in the same manner as a non-reactive emulsifier. is there. From the viewpoint of polymerization stability and coating film performance, those having a polyoxyalkylene chain in the molecular structure are particularly preferred.

Examples of the reactive emulsifier include bis (polyoxyethylene polycyclic phenyl ether) methacrylated sulfonate salts (for example, Antox MS-60 manufactured by Nippon Emulsifier Co., Ltd.), propenyl-alkylsulfosuccinic acid ester salts, (meth) Acrylic acid polyoxyethylene sulfonate salt, (meth) acrylic acid polyoxyethylene phosphonate salt (eg Sanyo Chemical Industries, Eleminol RS-30), polyoxyethylene alkylpropenyl phenyl ether sulfonate salt ( For example, Aqualon HS-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), sulfonate salts of allyloxymethylalkyloxypolyoxyethylene (for example, Aqualon KH-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and allyloxymethylnonylphenoxyethyl Hydro Polyoxyethylene sulfonate salt (for example, Asahi Denka Kogyo Co., Ltd., Adekaria Soap SE-10, etc.), allyloxymethylalkoxyethyl hydroxy polyoxyethylene sulfate ester salt (for example, Asahi Denka Kogyo Co., Ltd., Adeka Soap SR- 10, SR-30, etc.), allyloxymethylalkoxyethylhydroxypolyoxyethylene (for example, manufactured by Asahi Denka Kogyo Co., Ltd., Adecalia Soap ER-20, etc.), polyoxyethylene alkylpropenyl phenyl ether (for example, Daiichi Kogyo Seiyaku Co., Ltd.) Manufactured by Aqualon RN-20, etc.), allyloxymethylnonylphenoxyethylhydroxypolyoxyethylene (for example, manufactured by Asahi Denka Kogyo Co., Ltd., Adecalia Soap NE-10, etc.) and the like. Can be used. In particular, when importance is attached to the environment, it is preferable to use a non-nonylphenyl emulsifier. Examples of such reactive emulsifiers are shown below.

In the above chemical formula, R represents an alkyl group. R ^{6 to} R ⁸ represent an alkyl group or a hydrogen atom. A represents an alkylene group. M represents a light metal or an ammonium ion. n is an integer.

The proportion of the reactive emulsifier is preferably, for example, 50% by mass or more with respect to 100% by mass of the total amount of the emulsifier used. Thereby, the coating film excellent in water resistance will be obtained. More preferably, it is 60 mass% or more, More preferably, it is 70 mass% or more.

The blending ratio of all emulsifiers used in the emulsion polymerization is 100% from the viewpoint of ensuring both water resistance and polymerization stability of the coating film, and the total amount of the monomer components and the total amount of silane coupling agents is 100. It is preferable to set it as 0.5-10 weight part with respect to a weight part. If the amount of the reactive emulsifier used is too large, the water resistance of the coating film may not be sufficient, and if it is too small, the polymerization stability may not be sufficient. More preferably, it is 1-8 weight part, More preferably, it is 2-6 weight part.

Although it does not specifically limit regarding the polymerization conditions in the said emulsion polymerization, Preferably it is 0-100 degreeC, More preferably, it is good to set it as 40-95 degreeC. The polymerization temperature may be constant or may be changed during the polymerization or at each stage. The polymerization time is not particularly limited and may be set as appropriate according to the progress of the reaction. For example, the polymerization time is preferably in the range of 2 to 8 hours. About the atmosphere at the time of superposition | polymerization, in order to improve the efficiency of a polymerization initiator, it is suitable to carry out in inert gas atmosphere, such as nitrogen.

The (meth) acrylic emulsion is also preferably produced by polymerizing stepwise in two or more stages (multistage). As the stepwise polymerization step, it is preferable that the monomer component (i) containing a carboxyl group-containing monomer is first polymerized, and then the monomer component (ii) is further added to perform polymerization. is there. When the oxazoline group-containing monomer is used, it is preferable to include the oxazoline group-containing monomer in the monomer component (ii), and the reaction system before polymerization of the monomer component (ii) is performed. It is preferable that the pH of the is 6 or more. As a result, the crosslinking reaction between the carboxyl group and the oxazoline group can be suppressed (blocked) and curing control can be performed, so that long-term storage stability is good, and the pH in the reaction system is 6 or more when a coating film is formed. Thus, a so-called self-crosslinkable emulsion can be obtained in which the neutralizing agent used for the evaporation volatilizes and the crosslinking reaction proceeds in the particles.
Examples of the carboxyl group-containing monomer contained in the monomer component (i) include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, and acid anhydrides thereof. And (meth) acrylates having an acidic functional group such as

Examples of the neutralizing agent that can be used when the pH in the reaction system is 6 or more include organic amines such as ammonia and triethylamine, alkali metals such as sodium hydroxide and potassium hydroxide, and alkaline earth metals. Alkaline substances such as hydroxides, alkali metals such as calcium carbonate, and carbonates of alkaline earth metals can be used. Among these, volatile alkaline substances such as organic amines such as ammonia and triethylamine are preferable, and ammonia is particularly preferable.

The pH of the reaction system before the step of polymerizing the monomer component (ii) is preferably set in the range of 6 or more and less than 10. When the pH is less than 6, the reaction between the polymer obtained from the monomer component (i) and the polymer obtained from the monomer component (ii) cannot be sufficiently controlled, and the resulting (meth) acrylic emulsion There is a risk that the film forming property of the film will not be sufficient. On the other hand, if it is 10 or more, the progress of cross-linking during the formation of the coating film may be delayed, and the hardness may be difficult to be exhibited. More preferably, they are 7 or more and less than 9.5, More preferably, they are 8 or more and less than 9.

The aqueous coating composition of the present invention preferably further contains a polymer having an N-vinyl cyclic lactam unit. Thereby, it is possible to further improve the low pollution property. Such a polymer preferably has 20% by mass or more of N-vinyl cyclic lactam units with respect to 100% by mass of the polymer. When the N-vinyl cyclic lactam unit is less than 20% by mass, the hydrophilicity of the coating film obtained from the aqueous coating composition is not sufficient, and there is a possibility that a higher degree of stain resistance cannot be exhibited. More preferably, it has 40 mass% or more of N-vinyl cyclic lactam units.

The polymer having the N-vinyl cyclic lactam unit is, for example, a homopolymer obtained by polymerizing or copolymerizing monomers constituting the N-vinyl cyclic lactam unit such as N-vinyl pyrrolidone and N-vinyl caprolactam ( 1 type, or 2 or more types, such as a homopolymer) or a copolymer, can be used.
Examples of the copolymer include N-vinyl pyrrolidone and N-vinyl caprolactam, vinyl acetate, (meth) acrylic acid and its ester, maleic acid and its ester, acrylonitrile, styrene, alkyl vinyl ether, N-vinyl imidazole and vinyl pyridine. , Copolymers obtained by copolymerization with allyl alcohol, olefins and the like. Among these, a copolymer obtained by copolymerizing N-vinylpyrrolidone or N-vinylcaprolactam with vinyl acetate is preferable. Examples of (meth) acrylic acid and maleic acid esters include alkyl esters having 1 to 20 carbon atoms, dimethylaminoalkyl esters and quaternary salts thereof, hydroxyalkyl esters, and the like.

The molecular weight of the polymer having the N-vinyl cyclic lactam unit is preferably 1,000 to 3,000,000. More preferably, it is 3000-1 million, More preferably, it is 5000-500,000. Moreover, it is particularly preferably 7000 to 300,000, and most preferably 10,000 to 100,000.
In addition, the molecular weight here is a weight average molecular weight, and can be obtained by, for example, the GPC measurement method described above.

When the composition for water-based paint contains the polymer having the N-vinyl cyclic lactam unit, the content thereof is, for example, 0 to 20% by weight with respect to 100% by weight of the composition for water-based paint. Is preferred. If it exceeds 20% by mass, the water resistance may not be sufficient. More preferably, it is 0.5-15 mass%, More preferably, it is 1-10 mass%.

The polymer having the N-vinyl cyclic lactam unit can be synthesized by a polymerization method such as solution polymerization, emulsion polymerization, suspension polymerization, precipitation polymerization, etc., but solution polymerization is preferable, and aqueous solution polymerization using water as a solvent. Is more preferable. The polymerization conditions may be normal polymerization conditions.

The aqueous coating composition of the present invention has a total content of volatile organic compounds of less than 3% by mass with respect to 100% by mass of the composition. Due to the recent increase in awareness of health hazards and environmental problems, it is desired to avoid the use of volatile organic compounds as much as possible, but conventional coating compositions contain volatile organic compounds as film-forming aids, etc. It was normal. However, in the present invention, by configuring the aqueous coating composition as described above, a good low-temperature film-forming property can be exhibited without significantly reducing or substantially using volatile organic compounds, It was found that a revolutionary effect that the characteristics as a paint can be fully exhibited was obtained, and this resulted in a paint composition that significantly reduced the burden on health and the environment compared to conventional compositions. Will be realized. In order to fully exhibit the effects of the present invention, the total content of the volatile organic compound is more preferably less than 2% by mass, and still more preferably less than 1% by mass. Further, it is particularly preferably 0.5% by mass or less, and most preferably substantially free of volatile organic compounds.
Here, “substantially free” means that a volatile organic compound is not intentionally added. For example, when measuring the content of a volatile organic compound contained in a paint, It is mentioned that it is below the quantity which is not detected.

The aqueous coating composition preferably has a minimum film-forming temperature (MFT) of 0 ° C. or lower. If the temperature exceeds 0 ° C., a small amount of an organic compound such as a film forming aid (also referred to as a film forming aid) may be required. More preferably, it is -5 degrees C or less, Most preferably, it is -10 degrees C or less.
MFT is measured according to JIS K6828-2 (2003), and the boundary between the film-formed part and the non-film-formed part when the emulsion is applied in a strip shape on a flat plate having an appropriate temperature gradient. It is the temperature and is defined as “the lowest temperature at which a uniform film without cracks is obtained”. Specifically, the composition was applied to a glass plate placed on a thermal gradient tester with a 0.2 mm thick applicator and dried, and the temperature at which the coating film was cracked was set to the minimum film formation temperature ( MFT) (° C.).

The composition for water-based paints is useful for various paint applications such as, for example, for building construction materials and paints for building exteriors, and the paint containing the composition for water-based paints is a preferred embodiment of the present invention. One. Such a paint is remarkably excellent in low-temperature film-forming properties, and the coating film formed thereby can exhibit properties such as hardness, water resistance, weather resistance and the like, and is extremely advantageous from the environment. . Among the paints, a topcoat paint that can be suitably used for a topcoat paint and includes the above-described aqueous paint composition is also one aspect of the present invention. Since it is remarkably excellent in low-temperature film-forming properties, it is particularly suitably used for building exteriors. However, since it is also excellent in film-forming properties at high temperatures, it can be preferably applied to building interiors and the like.

In the top coat paint, the content of the aqueous paint composition of the present invention is preferably, for example, 10 to 90% by mass with respect to 100% by mass of the top coat paint. Thereby, the effect of the composition for water-based paint can be more fully exhibited, and the paint for top coat becomes more suitable. More preferably, it is 15-85 mass%, More preferably, it is 20-80 mass%.

The above-mentioned topcoat paint will contain additives as required. Examples of additives include pigments and aggregates. Moreover, you may contain 1 type (s) or 2 or more types, such as a filler, a leveling agent, a dispersing agent, a thickener, a wetting agent, a plasticizer, a stabilizer, dye, antioxidant.
Examples of the pigment include inorganic pigments such as white pigments such as titanium oxide, antimony trioxide, zinc white, lithopone, lead white, and colored pigments such as carbon black, yellow lead, molybdenum red, and bengara, and organic pigments. Examples thereof include azo compounds such as benzidine and Hansa Yellow, and phthalocyanines such as phthalocyanine blue. In addition, these may be used independently and may be used in combination of 2 or more types.
Among the above pigments, it is preferable to select those having good weather resistance so as not to lower the weather resistance of the coating film. For example, regarding titanium oxide which is a white pigment, anatase type titanium oxide is preferable. From the viewpoint of the weather resistance of the coating film, it is more preferable to use rutile type titanium oxide than to use. As the rutile type, chlorine-based titanium oxide is more preferable than sulfuric acid-based titanium oxide because weather resistance can be maintained and expressed over a long period of time.

The aggregate may be a transparent aggregate or a colored aggregate, but examples of the transparent aggregate include feldspar, cinnabar, meteorite, cold water sand, glass beads, synthetic resin beads, etc. Examples of the colored aggregate include marble powder, granite powder, serpentine, fluorite, colored cinnabar powder, and colored ceramic powder. In addition, these may be used independently and may use 2 or more types together.

In the case where the additive such as the pigment or the aggregate is included, in order to sufficiently exert the effect, it is preferable that the amount is less than 40% by mass when used for the clear coating in 100% by mass of the top coat paint. It is. Moreover, when using for an enamel paint etc., Preferably it is 5-80 mass%, More preferably, it is 10-70 mass%, More preferably, it is 20-60 mass%.

As a construction form of the above-mentioned top coat paint, it may be a form coated on one layer alone, or may be a form coated repeatedly on two or more layers. Further, when two or more layers are overcoated, only a part of the layers may be formed by the top coat paint, or all layers may be formed by the top coat paint. .
For example, the above-described overcoating method may be performed by applying a first layer (undercoat layer) paint to a coating object that has been subjected to primer treatment or sealer treatment, and then drying, followed by the second layer (overcoat layer) paint. The method of overcoating and drying can be mentioned. As a method for applying the paint, spray, roller, brush, or iron can be used.

The water-based paint composition of the present invention and the topcoat paint containing the composition can be used for various applications. Specifically, for example, for plastic molded products, for home appliances, steel products, large structures, Use for various undercoats, intermediate coats, top coats, etc. for vehicles (for example, for solid colors for automotive repairs, for metallic bases, for clear tops), for building materials, for interior / exterior buildings, for tiles, and for woodwork Can do. In particular, it can be suitably used for building materials and interior / exterior of buildings, and can be more suitably used for building materials and exterior of buildings. Among them, it can be more suitably used for environmentally friendly low-contamination and stone-type clear top coats.

When the composition for water-based paint of the present invention and the paint for top coat containing the same are used for building materials, examples of the base material include slate board, flexible board, cement slag papermaking board, cement slag molded board, and hard wood chip. Cement board, extrusion-molded cement board, metal board, plastic board, ceramic board, calcium silicate board, wood board, metal part steel plate, etc. can be used, and a coating film is formed by applying on these substrates Can do. In addition, when used for building exteriors, as the base material, for example, concrete, PC panel, cement mortar, ALC panel, concrete block, slate board, asbestos cement siding, etc. can be used. A coating film can be formed by applying on top.

Since the composition for water-based paints of the present invention is configured as described above, even if the volatile organic compounds usually contained in conventional paint compositions are greatly reduced or substantially free, Demonstrates good low-temperature film-forming properties, can provide coatings with excellent physical properties such as stain resistance, weather resistance, and hot water whitening resistance, and can greatly reduce the burden on health and the environment. . In particular, when such a composition is used, it becomes possible to realize a VOC-free coating material substantially free of volatile organic compounds. It can form a coating film with excellent physical properties and is very useful as an environmentally friendly exterior paint in the field of civil engineering and architecture.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “% by mass”.

In the following production examples and examples, various physical properties were evaluated as follows.
<Evaluation method>
(1) pH
The value at 25 ° C. was measured with a pH meter (“F-23” manufactured by Horiba, Ltd.).
(2) Viscosity Viscosity was measured with a BM viscometer (manufactured by Tokyo Keiki Co., Ltd.) at 30 min−1 and 25 ° C. When measuring the viscosity, the rotor was selected according to the viscosity.
(3) Average particle diameter The volume average particle diameter was measured using a particle size distribution analyzer (“NICOMP Model 380” manufactured by Particle Sizing Systems) by a dynamic light scattering method.
(4) Minimum film-forming temperature (MFT)
An aqueous resin dispersion obtained with an applicator having a thickness of 0.2 mm is coated on a glass plate placed on a thermal gradient tester, dried, and the temperature at which cracks occurred in the coating film is set to the minimum film formation temperature ( MFT) (° C.).

(5) Glass transition temperature (Tg, unit: K)
Using the glass transition temperature of the homopolymer of each monomer component constituting the (meth) acrylic emulsion, the value calculated from the above Fox formula was adopted.
(6) K value of polyvinyl pyrrolidone polymer The viscosity of a solution obtained by dissolving polyvinyl pyrrolidone polymer in water at a concentration of 1% by mass was measured at 25 ° C. with a capillary viscometer, and using this measured value, the following Fikencher formula:
(Log η _rel ) / C = [(75 Ko ² ) / (1 + 1.5 KoC)] + KoK = 1000 Ko
(Where C represents the number of grams of polyvinylpyrrolidone in 100 ml of the solution, and η _rel represents the viscosity of the solution relative to the solvent). It can be said that the higher the K value, the higher the molecular weight.
(7) NV (Nonvolatile matter)
NV (%) in the sample was determined from the mass of the residue after heating 1 g of the sample at 150 ° C. for 20 minutes.

<Evaluation method of paint>
(1) Evaluation method of paint VOC amount (%) The paint prepared in Example / Comparative Example was applied in a constant temperature and humidity box with a wind speed of 1 m / s at 1 ° C., and the coating film was observed after 6 hours. Check for cracks. About the coating material which a crack produced, until the crack does not enter, "CS-12" which is a film-forming auxiliary (manufactured by Chisso Corporation, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate) is used. The test was conducted by adding 1% at a time, and the required amount of film forming aid was found to be the amount of paint VOC (%). No coating aid was used for the paint that did not crack (ie 0%).
In addition, the film-forming auxiliary agent amount during the paint blending in the paint evaluation tests (2) to (4) described below was blended with the above-mentioned minimum amount not causing cracks in the low-temperature film-forming test.

(2) Low contamination (contamination resistance) test A slate plate (70 mm x 150 mm x 6 mm, manufactured by Nippon Test Panel Co., Ltd.) according to JIS A5430 (2004), a solvent sealer (manufactured by SK Kaken Co., Ltd., trade name " EX sealer ”) was applied by air spray to a dry weight of 20 g / m ² , dried at 23 ° C. and humidity of 50% for 24 hours, and then the paints of Examples and Comparative Examples were applied with a 6 mil applicator. The test specimen was obtained by static curing for 2 weeks at 23 ° C. and 50% humidity. After curing, the L value (L0) of the test plate was measured with a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., spectral color difference meter SE-2000), and in accordance with JIS Z2381 (general rules for atmospheric exposure test methods) An outdoor exposure test was conducted under the conditions. After 1 month and 6 months, the test plate was pulled up, and the L value (L1) was measured with the color difference meter.
The change value of the L value was calculated as ΔL = (L1) − (L0), and the initial contamination property was evaluated by the L value after 1 month, and the long-term contamination property was evaluated by the L value after 6 months.
-Test conditions-
South surface 30 °, direct exposure (exposed location: Suita City, Osaka / Nippon Shokubai Co., Ltd.)
-Evaluation criteria-
◎: ΔL = less than 2.0 ○: ΔL = 2.0 or more, less than 3.0 Δ: ΔL = 3.0 or more, less than 4.0 ×: ΔL = 4.0 or more

(3) Weather resistance test The gloss value (Gs60 °) of the test specimen after curing adjusted in the stain resistance test was measured and evaluated by a xenon weather meter in accordance with JIS A6909 (weather resistance B method). .
-Evaluation criteria-
○: JIS classification, 1 type of rust resistance △: JIS classification, 2 types of weather resistance type ×: JIS classification, 3 types of rust resistance type (4) Water resistance test The test specimen after curing adjusted in the stain resistance test is water at 23 ° C. The film was immersed in 3 days, and the coating state after 3 days was observed and evaluated based on the criteria.
-Evaluation criteria-
○: No abnormality Δ: Swelling / peeling is observed in an area of less than 5% ×: Swelling / peeling is observed in an area of 5% or more

<Aqueous resin composition ((meth) acrylic emulsion) (A)>
Production Example A1
335 parts of deionized water was charged into a flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer, and a reflux condenser. To a dropping funnel, from 78 parts of deionized water, 40 parts of a 25% aqueous solution of an emulsifier (“Aqualon HS-10 / Daiichi Kogyo Seiyaku”), 90 parts of 2-ethylhexyl acrylate, 155 parts of methyl methacrylate, and 5 parts of acrylic acid The first stage pre-emulsion is prepared, and 144 parts, which is 10% of the total amount of the combined monomer components, is put into the flask, and the temperature is raised to 80 ° C. while gently blowing nitrogen gas. Polymerization was started by adding 60 parts of a 5% aqueous solution. Thereafter, the remainder of the first pre-emulsion was uniformly added dropwise over 90 minutes. After completion of the dropping, the temperature was maintained at the same temperature for 60 minutes to complete the first stage polymerization. Next, 4.7 parts of a 25% aqueous ammonia solution was added, and it was confirmed that the pH of the system was 7 or more. Subsequently, 233 parts of deionized water, emulsifier (“AQUALON HS-10 / Daiichi Kogyo Seiyaku Co., Ltd.) were added. The second stage pre-emulsion consisting of 120 parts of 25% aqueous solution, 250 parts of 2-ethylhexyl acrylate, 180 parts of methyl methacrylate, 300 parts of cyclohexyl methacrylate and 2 parts of acrylic acid is uniformly added dropwise over 180 minutes. did. After completion of the dropwise addition, the temperature was maintained for 180 minutes and the polymerization was completed in the second stage. The obtained reaction solution was cooled to room temperature, and then filtered through a 300-mesh wire mesh to obtain an aqueous resin composition (referred to as an aqueous resin composition (A1)).
In Table 1, the amount of each monomer used in the first and second stages is shown as a ratio (parts by weight) to 100 parts of the total amount of all monomer components used in both stages.

Production Examples A2 to A7
Except having polymerized using the emulsifier and monomer components shown in Table 1 (Production Examples A6 and A7 were polymerized in three stages, and neutralization was performed after the completion of the second stage), the same as Production Example A1 Aqueous resin compositions (A2) to (A7) were obtained.

<Aqueous resin composition (B)>
Production Example B1
To a polymerization vessel equipped with a cooling pipe, a nitrogen introduction line, and a thermometer, 206 parts of deionized water and 90 parts of N-vinylpyrrolidone were added, and nitrogen was introduced to form a nitrogen atmosphere. While stirring at room temperature, 0.045 parts of 0.1% aqueous copper sulfate solution, 0.5 parts of 25% aqueous ammonia solution and 2.1 parts of 30% aqueous hydrogen peroxide solution were added to initiate polymerization. After the internal temperature increased due to the heat of polymerization, stirring was continued at 80 ° C. for 1.5 hours. Next, after adding 1.0 part of 30% hydrogen peroxide aqueous solution, the mixture was further heated and stirred for 1 hour to obtain a polyvinylpyrrolidone (PVP) polymer solution. The resulting polymer solution had an NV of 30.0% and a K value of 29.8.

Production Example B2
39.1 parts of deionized water and 400 parts of the PVP polymer solution obtained in Production Example B1 were added to a polymerization vessel equipped with a cooling pipe, a nitrogen introduction line, and a thermometer, and nitrogen was introduced to form a nitrogen atmosphere. While stirring at room temperature, the temperature was raised to 85 ° C. When the temperature became constant, 37.5 parts of 80% acrylic acid aqueous solution, 75.2 parts of deionized water, and 34.5 parts of 25% aqueous ammonia solution were mixed. The aqueous solution was added over 90 minutes. In parallel, an initiator aqueous solution in which 3.7 parts of ammonium persulfate was dissolved in 69.5 parts of deionized water was similarly added over 90 minutes. After completion of the addition, stirring was continued for 1 hour at the same temperature to complete the reaction. The obtained polymer solution (polymer B2: also referred to as VP-AA) was NV29.6%.
In addition, in Table 2, the mass ratio of the PVP polymer used in order to obtain polymer B2 and acrylic acid is shown.

Production Example B3
39.1 parts of deionized water and 400 parts of the PVP polymer solution obtained in Production Example B1 were added to a polymerization vessel equipped with a cooling pipe, a nitrogen introduction line, and a thermometer, and nitrogen was introduced to form a nitrogen atmosphere. While stirring at room temperature, the temperature was raised to 85 ° C., and when the temperature became constant, 30.0 parts of 2-isopropenyl-2-oxazoline, 82.7 parts of deionized water, 34.5% aqueous ammonia 34.5 parts The aqueous solution in which the parts were mixed was added over 90 minutes. In parallel, an initiator aqueous solution in which 3.7 parts of ammonium persulfate was dissolved in 69.5 parts of deionized water was similarly added over 90 minutes. After completion of the addition, stirring was continued for 1 hour at the same temperature to complete the reaction. The obtained polymer solution (polymer B3: also referred to as VP-OX) was NV29.4%.
In addition, in Table 2, the mass ratio of the PVP polymer used in order to obtain polymer B2 and an oxazoline group containing monomer (2-isopropenyl-2-oxazoline) is shown.

The descriptions in the table are as follows.
<Emulsifier>
Aqualon HS-10: Dai-ichi Kogyo Seiyaku Co., Ltd. Aqualon KH-10: Dai-ichi Kogyo Seiyaku Co., Ltd. Adekaria Soap SR-10: Asahi Denka Kogyo Co., Ltd. Aqualon RN-20: Dai-ichi Kogyo Seiyaku Co., Ltd.

<Monomer component>
2EHA: 2-ethylhexyl acrylate (Tg: -70 ° C)
MMA: Methyl methacrylate (Tg: 105 ° C)
St: Styrene (Tg: 100 ° C.)
CHMA: cyclohexyl methacrylate (Tg: 83 ° C)
t-BMA: Tertiary butyl methacrylate (Tg: 107 ° C.)
IBMA: Isobornyl methacrylate (Tg: 180 ° C.)
MAA: methacrylic acid (Tg: 130 ° C.)
AA: Acrylic acid (Tg: 106 ° C)
IPO: 2-isopropenyl-2-oxazoline (Tg: 100 ° C.)
HEMA: hydroxyethyl methacrylate (Tg: 55 ° C.)
RUVA: 2- [2′-hydroxy-5′-methacryloyloxyethylphenyl] -2
HALS: 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine (Tg: 130 ° C.)
In addition, Tg shown in parentheses after the compound name of the monomer is Tg (° C.) of a homopolymer made of the monomer.

Examples and Comparative Examples Water-based paint compositions were prepared using the water-based resin compositions (A) and (B) with the formulations shown in Table 4. In Examples 1 to 4 and Comparative Examples 1 to 3 , since the aqueous resin composition (B) was not used, only the aqueous resin composition (A) was used as the aqueous coating composition.
About each of the obtained composition for aqueous coating materials, it changed into a paint by the coating-material composition in Table 3-2, and various physical properties were evaluated. The evaluation results are shown in Table 4.

In Table 3-2, the blending amount (* 1) of the composition for water-based paint obtained in Examples or Comparative Examples means the amount described in Table 4. That is, the compounding quantity as a composition for water-based paints is 200 parts in Examples 1-4 and Comparative Examples 1-3 , and 207 parts in Examples 6-7. Further, the compounding amount (* 2) of “CS-12” was added until cracks did not occur in the low-temperature film-forming property test, as described in detail in the evaluation method of the coating VOC amount (%). Is the minimum amount.

Table 4 shows that the composition of the present invention exhibits extremely good low-temperature film-forming properties even when the volatile organic compound usually contained in the coating composition is greatly reduced or substantially free. It is confirmed that a composition for water-based paints can be obtained, which can give a coating film with excellent physical properties such as stain resistance, weather resistance, and warm water whitening resistance, and can greatly reduce the burden on health and the environment. It was done.
That is, Comparative Examples 1 and 2 are examples of compositions containing neither an oxazoline group-containing polymer nor an oxazoline compound. However, as in Comparative Example 1, a normal amount of film-forming auxiliary (composition 100 for water-based paints) was used. When used, the initial contamination property and long-term contamination property are inferior, and the load on the environment cannot be reduced because a large amount of film forming aid is used. Comparative Example 2 is an example in which the content of the film-forming auxiliary is reduced as compared with Comparative Example 1, but in this case, both initial contamination property and long-term contamination property are inferior and weather resistance is not good. On the other hand, in Examples 1 to 4 and 6 to 7 using the oxazoline group-containing polymer and / or oxazoline compound, the content of the film forming aid is greatly reduced or not substantially contained even at a low temperature. It is clear that cracks do not occur after drying, that is, remarkably excellent in low-temperature film-forming property, initial contamination, long-term contamination, and weather resistance are also excellent, and it is very useful for various paints.

Claims (8)

A composition for water-based paint containing a (meth) acrylic emulsion,
The compositions are those containing an oxazoline group-containing polymer and / or an oxazoline compound, and the formulation to 100% by weight, Ri total content of Der less than 3% by weight of volatile organic compounds,
The (meth) acrylic emulsion is obtained by polymerizing a monomer component (i) containing a carboxyl group-containing monomer, and further adding a monomer component (ii) containing an oxazoline group-containing monomer. It is obtained by a stepwise polymerization step to be performed, and is composed of two or more kinds of polymers having different glass transition temperatures (Tg). Among them, the Tg of the polymer having the highest Tg is 70 to 200. A composition for water-based paint, characterized by being at ° C. A composition for water-based paint containing a (meth) acrylic emulsion,
The composition contains an oxazoline group-containing polymer and / or an oxazoline compound, and the total content of volatile organic compounds is less than 3% by mass with respect to 100% by mass of the composition.
The composition for water-based paints comprising a polymer having an N-vinyl cyclic lactam unit. The total content of the said volatile organic compound is less than 1 mass% with respect to 100 mass% of the said composition for aqueous coating materials, The composition for aqueous coating materials of Claim 1 or 2 characterized by the above-mentioned. The (meth) acrylic emulsion contains 1 to 30% by mass of a polymer having a glass transition temperature of 50 to 200 ° C. with respect to 100% by mass of the total amount of all polymers constituting the (meth) acrylic emulsion. The composition for water-based coatings in any one of Claims 1-3. The blending ratio of the oxazoline group-containing polymer and / or the oxazoline compound is the total content of the oxazoline compound (in the case of using the oxazoline group-containing polymer, oxazoline as a polymerization component with respect to all the components constituting the aqueous coating composition). The proportion of the group-containing monomer is 0.1) to 10% by mass with respect to 100% by mass of the aqueous coating composition. A composition for water-based paints. The oxazoline group-containing polymer is obtained by polymerizing a monomer component containing an oxazoline group-containing monomer,
The oxazoline group-containing monomer is represented by the following general formula (1);

(Wherein R ¹ , R ² , R ³ And R ⁴ Are the same or different and each represents a hydrogen, halogen, alkyl, phenyl or substituted phenyl group. R ⁵ Represents an acyclic organic group having an addition-polymerizable unsaturated bond. The composition for water-based paints in any one of Claims 1-5 characterized by the above-mentioned. The composition for water-based paint according to any one of claims 1 to 6, wherein the (meth) acrylic emulsion is a particle. A topcoat paint comprising the aqueous paint composition according to any one of claims 1 to 7 .