JPH11343464A - Resin composition for aqueous coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition for an aqueous coating material having low-temperature film forming property similar to a conventional aqueous coating material having an emulsion base containing a film-forming assistant even though the resin composition contains no VOC or only in a minute amount, at the same time, free from stickiness on the surface of the formed film and stable even after repeated cycles of freezing and fusing of the coating material. SOLUTION: This resin composition is composed of (A) an aqueous emulsion of a copolymer having the lowest film-forming temperature of 0 deg.C or less and having the resin's glass transition temperature of from -20 deg.C to 20 deg.C, and (B) a resin having a glass transition temperature of >=20 deg.C and made water-soluble by an alkali. The ratio of the components A and B in terms of the weight of the non-volatile matter is in the range A/B=95/5 to 60/40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel resin composition for water-based paints, and more particularly to a resin composition suitable for use in aqueous interior paints.

[0002]

2. Description of the Related Art In recent years, the conversion of solvent-based paints to water-based paints has been progressing in terms of odor and safety in interior paints, and water-based paints based on water-based emulsions are now used except for some limited uses. It has become mainstream. Further, in recent years, since the problem of indoor air pollution has been highlighted, even in the case of water-based paints, a trace amount of volatile organic compounds (VOC) contained therein has been regarded as a problem.

[0003] Although there is not always a unified definition of this VOC, it is generally a classification based on the boiling point by the WHO (World Health Organization), and the boiling point is 50-260.
Refers to organic compounds up to ° C. According to this classification, conventional water-based paints for indoor use include, as VOCs, film-forming aids for ensuring low-temperature film formability of emulsions, antifreeze agents for preventing freezing of paints, and the like. ing. However, these VOCs have been considered as necessary components to satisfy various performances as interior paints.

[0004] That is, in general, indoor coating materials are required to have a film-forming property at 5 ° C or less. If this is to be achieved without a film-forming aid, the glass transition temperature (Tg) of the resin in the emulsion must be determined in advance. ) Must be set low. However,
As a result, the coating surface becomes sticky and easily stained. On the other hand, it is possible to use an antifreezing agent as an aqueous paint without adding it.
Even if frozen at ℃, it is premised that if it is thawed, it can be used as a paint again. For this reason, it is necessary to devise a method in which the base emulsion is stable even when it is frozen and thawed.

[0005]

The present invention has been made in view of such a problem,
Despite containing little or no VOC, it has low-temperature film formability comparable to that of conventional emulsion-based water-based paints containing a film-forming aid, and has an adhesive property on the surface of the resulting coating film. It is an object of the present invention to provide a water-based paint resin composition which is free from defects and is stable even when the paint is subjected to cycles of freezing and thawing.

[0006]

According to the first aspect of the present invention, the minimum film forming temperature is 0 ° C. or less and the resin has a glass transition temperature of −20 ° C.
Aqueous emulsion of copolymer (A) at a temperature of from 20 to 20 ° C
And a resin (B) solubilized in water with an alkali having a glass transition temperature of 20 ° C. or more, wherein the weight ratio of the non-volatile components of (A) and (B) is A / B
= 95/5 to 60/40.

As a result of intensive studies, the present inventors have found that an aqueous emulsion of a copolymer having a minimum film-forming temperature of 0 ° C. or less and a resin having a glass transition temperature (Tg) in a specific range and a specific emulsion. The present inventors have found that a composition in a specific ratio with a water-soluble resin having Tg satisfies the object, and have reached the present invention.

In the present invention, the minimum film forming temperature is 0 ° C.
Examples of the aqueous emulsion (A) of a copolymer having a resin having a glass transition temperature of −20 ° C. to 20 ° C. include an aqueous emulsion of styrene and a butadiene copolymer, and a styrene (meth) acrylate ester. Examples include an aqueous emulsion of a polymer and an aqueous emulsion of a (meth) acrylate copolymer. Of these, aqueous emulsions of styrene (meth) acrylate copolymers and aqueous emulsions of (meth) acrylate copolymers are based on molecules derived from a wide variety of (meth) acrylate monomers. It is particularly preferable in terms of ease of design and durability.

The above minimum film forming temperature is defined as a temperature above which the aqueous emulsion gives a uniform film without cracks, and is a temperature measured by the method and apparatus described in ISO standard 2115. And the aqueous copolymer emulsion has a specific value.

On the other hand, the Tg of the copolymer is obtained from the Tgi of the homopolymer of the monomer i used for the polymerization and the fraction Xi of the monomer i by the following relational expression. 1 / Tg (copolymer) = Σ (Xi / Tgi) Xi: fraction of monomer i Tgi: Tg of monomer i

There is a correlation between the minimum film-forming temperature of the emulsion and the Tg of the copolymer, but it is not strict, and the combination of the monomers or the method of adding the monomers at the time of producing the emulsion, etc. Generally, the correlation is shifted by

Examples of the above monomers include alkyl esters of acrylic acid or methacrylic acid having 1 to 18 carbon atoms, such as methyl acrylate (22 ° C .; Tg is shown; the same applies hereinafter), and ethyl acrylate (-8 ° C.). Butyl acrylate (-43 ° C), 2-ethylhexyl acrylate (-58
° C) lauryl acrylate (-17 ° C), cyclohexyl acrylate (19 ° C), methyl methacrylate (105 ° C)
° C), ethyl methacrylate (67 ° C), butyl methacrylate (32 ° C), t-butyl methacrylate (102 ° C).
° C) and cyclohexyl methacrylate (83 ° C).

Further, vinyl aromatics such as styrene (107 ° C.) and α-methylstyrene (168 ° C.), saturated vinyl carboxylate such as vinyl acetate (28 ° C.) and vinyl propionate (5 ° C.), vinylidene chloride ( -18 ° C) vinyl chloride (74 ° C) and butadiene (-78 ° C).

In order to impart various polarities to the aqueous emulsion, acrylonitrile (105 ° C.), acrylamide (220 ° C.), hydroxyethyl acrylate (−34 ° C.), hydroxyethyl methacrylate (55 ° C.)
C), hydroxypropyl acrylate (-21 C),
Monomers such as hydroxypropyl methacrylate (26 ° C.) and diacetone acrylamide (65 ° C.) can be used. The copolymerization ratio of such a monomer is usually 0 to 15% by weight, preferably 0 to 10% by weight from the viewpoint of water resistance.

In the production of the above aqueous emulsion,
It is preferable to use an unsaturated carboxylic acid as a copolymer component mainly to ensure stability during production.
Specific examples thereof include unsaturated monocarboxylic acids and dicarboxylic acids having 3 to 5 carbon atoms, such as acrylic acid (130 ° C), methacrylic acid (162 ° C), and itaconic acid (130 ° C). Can be Two or more of these unsaturated carboxylic acids may be used in combination. Further, the copolymerization ratio is preferably from 0.1 to from the viewpoint of polymerization stability and water resistance.
It is 7% by weight, more preferably 0.5 to 5% by weight.

In the production of the above-mentioned aqueous emulsion, it is necessary to use the above-mentioned monomers in an appropriate combination and to design the copolymer so that the Tg of the copolymer is -20 to 20 ° C. The minimum film forming temperature of the copolymer aqueous emulsion thus obtained must be 0 ° C. or lower.

If the Tg of the copolymer exceeds 20 ° C. or the minimum film forming temperature exceeds 0 ° C., the film-forming properties of the coating composition obtained from the present composition will decrease. Conversely, the Tg of the copolymer
Is less than −20 ° C., even if the minimum film-forming temperature is 0 ° C. or lower, the surface of the coating film obtained from the coating material has adhesiveness, and is not practical. In addition, more preferably, from the point of compatibility between adhesiveness and film forming property, -15 to 1 is preferable.
5 ° C, most preferably -10 to 10 ° C.

The polymerization of the aqueous emulsion (A) may be carried out by a known method, such as an emulsion polymerization method using an emulsifier for emulsion polymerization, or a water-soluble or alkali-soluble copolymer as a dispersant. It can be produced by a protective colloid polymerization method. Also, a so-called core / shell polymerization method in which the monomer mixture is fed in multiple stages, or a power feed method in which the composition of the monomer fed during polymerization is gradually changed can be used. Further, two or more kinds of aqueous dispersions produced by the above method can be mixed and used.

Examples of the emulsifiers used in the above production include sulfates of higher alcohols, higher alkyl sulfonates, alkylbenzene sulfonates, polyoxyethylene alkyl sulfates, polyoxyethylene alkylphenol ether sulfates, and vinyl sulfonates. And anionic surfactants such as vinyl sulfosuccinate and reactive emulsifiers.

In addition, nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, ethylene oxide propylene oxide block copolymer, and sorbitan derivative are also used in combination with these anionic surfactants. Can be.

As the protective colloid, celluloses such as starch and hydroxyethylcellulose, polyoxyethylenes, polycarboxylic acids and the like can be used, and the compatibility with the resin (B) solubilized in water, A polycarboxylic acid is preferred in view of the water resistance of the coating film obtained from the coating material.

Examples of the polymerization initiator used in the production include persulfates such as potassium persulfate and sodium persulfate, and peroxides such as hydrogen peroxide, benzoyl peroxide and t-butyl hydroperoxide. These polymerization initiators can be used as a redox polymerization initiator system in combination with an organic amine, Rongalit, or the like. In order to control the molecular weight of the copolymer, various chain transfer agents such as mercaptans and alcohols may be used.

On the other hand, as the resin (B) having a glass transition temperature of 20 ° C. or more and solubilized in water with an alkali,
For example, an alkali is added to a copolymer produced from a monomer mixture containing a monomer having a carboxyl group, a styrene-maleic acid copolymer, an aqueous urethane resin, etc., and a part or all of the acid is added to the medium. It is manufactured by summing.
Among them, those obtained by neutralizing a copolymer produced from a monomer mixture containing a monomer having a carboxyl group are preferable from the viewpoint of compatibility with the aqueous emulsion (A).

Specific examples of the monomer having a carboxyl group include unsaturated monocarboxylic acids and dicarboxylic acids having 3 to 5 carbon atoms, and acrylic acid (130
° C), methacrylic acid (162 ° C), itaconic acid (130
° C) is particularly preferred. The resin (B) solubilized in water is
These unsaturated carboxylic acids and the monomers exemplified in the case of producing the aqueous emulsion (A) are appropriately combined and copolymerized, and then produced by adding an alkali. The copolymer has a Tg of 20 ° C. or higher. It is necessary to combine them so that

When the Tg of the resin (B) is lower than 20 ° C.,
It is not preferable because the adhesiveness of the coating film of the paint obtained from the resin composition increases.

In the copolymerization, two or more of these carboxyl-containing monomers may be used in combination, and the copolymerization ratio is preferably 2 to 40% by weight, more preferably 4 to 20% by weight. It is. When the copolymerization ratio of the unsaturated carboxylic acid is less than 2% by weight, the obtained copolymer does not become water-soluble, and the low-temperature film formability of the paint obtained from the present composition is deteriorated. Freeze-thaw stability also tends to decrease. Conversely, if it is more than 40% by weight, the water resistance of the coating film obtained from the coating material may be deteriorated.

The alkali used for the neutralization is not particularly limited except that it is a water-soluble alkali. However, from the viewpoint of maintaining good water resistance of a coating film obtained from the present composition, a volatile alkali is used. Is preferred, and ammonia is most suitable for similar reasons. The method of neutralization is to add an alkali after producing the copolymer, add an alkali sufficient to solubilize the copolymer in water to the aqueous emulsion (A) in advance, or Any method of mixing with the emulsion (A) and adding an alkali to neutralize the emulsion can be employed.

The method for producing the copolymer of the resin (B) is known to those skilled in the art. The most common production methods are a solution polymerization method, a suspension polymerization method, and a bulk polymerization method, but the emulsion polymerization method can also be used. However, when the solution is produced by solution polymerization, the solvent used in the production must be almost completely distilled off. In particular, the suspension polymerization method,
When the emulsion polymerization method is used, various mercaptans,
It is preferable to control the molecular weight by using a chain transfer agent such as alcohols and α-methylstyrene dimer in combination to improve the alkali solubility of the copolymer and the miscibility with the aqueous emulsion (A).

The aqueous emulsion (A) has a weight ratio (A / A / N) of the resin (B) and the non-volatile content of (A) and (B).
B) is mixed so as to be in the range of 95/5 to 60/40. When the weight ratio exceeds 95/5, the low-temperature film-forming property deteriorates, and the freeze-thaw stability decreases. Conversely, 60/4
When it is less than 0, the low-temperature film-forming property is deteriorated and the water resistance is also deteriorated.

The production of the aqueous resin dispersion for low VOC paint and the aqueous paint composition using the same is basically carried out by the method of (A)
And (B), but there is no limitation in the blending method. (A) may be added to (A), or (B) may be added to (A). Alternatively, a method in which the solubilized resin (B) is used as a protective colloid and copolymerized to produce an aqueous emulsion, and as a result, a composition in which (A) and (B) coexist can be employed. Further, an alkali is added to the present composition, and the addition amount may be an amount necessary for solubilizing the resin component (B) or more.

According to the present invention, it has a low-temperature film formability comparable to that of a conventional emulsion-based water-based paint containing a film-forming aid, although it contains no or very little VOC. It is possible to provide a resin composition for water-based paint which has no tackiness on the surface of the obtained coating film and is stable even when the paint is subjected to a cycle of freezing and thawing.

Next, as in the second aspect of the present invention, the above resin composition for water-based paint may further contain a polyhydric alcohol compound (C). In this case, especially the freeze stability is further improved. Specific examples of the polyhydric alcohol compound (C) include glycerin, pentaerythritol, polyvinyl alcohol and the like, but it is necessary that the compound is not classified into the VOC defined above. Glycerin and pentaerythritol are particularly preferred from the viewpoint of the stabilizing effect.

Next, as in the third aspect of the present invention, the polyhydric alcohol compound (C) is used in an amount of 0.1 to 0.1 with respect to the total amount of the aqueous emulsion (A) and the resin (B).
It is preferable to add 5% by weight. 0.1
If the amount is less than 5% by weight, the effect of stabilizing against freezing and thawing hardly appears, whereas if it exceeds 5% by weight, the water resistance of the coating film obtained from the present composition may be reduced. The content is more preferably 0.3 to 3% by weight.

Regarding the freeze-thaw stability, especially when a carbonyl group is present in the copolymer of the aqueous emulsion (A) and / or the solubilized resin (B), the hydrazino group is contained in the present composition. Is significantly reduced when a compound having two or more of the above is present.

The above composition can be used as it is as a coating agent, or it can be used as a color pigment, an extender pigment, a filler, an aggregate, a dispersant, a wetting agent, a film forming aid, an antifoaming agent, etc. And various additives are used as a paint. However, additives with as low a VOC content as possible are used, and the total VOC content finally contained in the paint is 1%.
It is preferred to keep it below. The pigment volume concentration (PVC) of the water-based paint thus formulated is not particularly limited, but is usually used in the range of 1 to 90%.

Next, as in the invention of claim 4, it is preferable that the resin composition for water-based paint is used as a resin composition for water-based indoor paint. In this case, the above effects are best exhibited. You.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 Hereinafter, a production example, an example, and a comparative example of an aqueous resin dispersion will be described. "Part" and "%" described in these examples
Means "parts by weight" and "% by weight", respectively, unless otherwise specified.

Production Example 1 of Resin (B) In order to produce the resin (B), first, 200 parts of water was placed in a reactor equipped with a temperature controller, a stirrer, a reflux condenser, a supply container, and a nitrogen inlet tube. After the insertion, the inside of the reaction vessel was replaced with nitrogen gas. Separately, the following were prepared as Feed I. Feed II was prepared as a polymerization initiator.

[Feed I] Water 200 parts 35% aqueous solution of sodium sulfate of p-nonylphenol to which 20 mol of ethylene oxide is added 30 parts 20% aqueous solution of p-nonylphenol to which 25 mol of ethylene oxide is added 30 parts Methacrylic acid Methyl 248 parts Butyl acrylate 112 parts Acrylic acid 20 parts Methacrylic acid 20 parts t-dodecyl mercaptan 4 parts

[Supply II] 85 parts of water 2.5 parts of potassium persulfate

Next, 10% of the above-mentioned feed I was added to the above-mentioned reactor purged with nitrogen gas, and the mixture was heated at 90 ° C.
Heated. Next, 10% of the feed II is charged into the reactor, and the remainder of the feed I and the feed II are transferred to 3.5.
The mixture was fed uniformly to the reactor over time. After the completion of the supply, the mixture was kept at 90 ° C. for 2 hours to carry out emulsion polymerization to obtain an aqueous emulsion in which the resin (B) before solubilization was dispersed. The resin concentration of this aqueous emulsion was about 45%.

Production Examples 2 to 4 of Resin (B) Using the same apparatus as in Production Example 1 of Resin (B), the monomer composition was changed as shown in Table 1 to obtain each uniform aqueous emulsion. . Also, the solid content of the obtained resin (B) is 20%.
%, Adjusted to pH 8.5 with ammonia,
Their solubility was evaluated and the results are shown in Table 1.

Production Example 5 of Resin (B) Using the same apparatus as in Production Example 1, 800 parts of isopropyl alcohol was charged into the reactor and purged with nitrogen. Then, after heating the reactor to 80 ° C., a monomer mixed solution consisting of 160 parts of methyl methacrylate, 120 parts of butyl acrylate, 60 parts of acrylic acid, and 60 parts of methacrylic acid was supplied from a supply container.
A solution prepared by dissolving 16 parts of azobisisobutyronitrile in 400 parts of isopropyl alcohol was added uniformly from separate supply containers over 2 hours each. After completion of the addition, the reactor was kept at 80 ° C. and aged for 1 hour to obtain a uniform polymer solution.

Next, the excess isopropyl alcohol was distilled off under reduced pressure using a rotary evaporator, followed by adding deionized water and further adding ammonia to neutralize. Further, the remaining isopropyl alcohol was distilled off under reduced pressure by azeotropic distillation, neutralization with ammonia, and addition of deionized water were repeated, so that the resin solid content of the resin (B) solubilized in water of pH 8.3 was 27%. Was obtained.

Production Example 6 of Resin (B) Using the same apparatus as in Production Example 5 of Resin (B), the monomer composition was changed as shown in Table 1 to obtain each uniform polymer solution. The above resin (B) is shown in Table 1.

Production Example 1 of Aqueous Emulsion (A) In order to produce the resin (A), first, 200 parts of water was placed in a reactor equipped with a temperature controller, a stirrer, a reflux condenser, a supply container and a nitrogen inlet tube. And then the inside of the reaction vessel was replaced with nitrogen gas. Separately, the following were prepared as Feed I. Feed II was prepared as a polymerization initiator.

[Supply I] Water 200 parts 35% aqueous solution of sodium sulfate of p-nonylphenol to which 20 mol of ethylene oxide is added 30 parts 20% aqueous solution of p-nonylphenol to which 25 mol of ethylene oxide is added 30 parts Methacrylic acid Methyl 136 parts Butyl acrylate 256 parts Acrylic acid 4 parts Itaconic acid 4 parts

[Feed II] Water 85 parts Potassium persulfate 2.5 parts

Next, 10% of the above-mentioned feed I was added to the above-described reactor in which nitrogen gas had been replaced, and the mixture was heated at 90 ° C.
Heated. Next, 10% of the feed II is charged into the reactor, and the remainder of the feed I and the feed II is 3.5.
The mixture was fed uniformly to the reactor over time. After the end of the supply, the emulsion polymerization was carried out at 90 ° C. for 2 hours to obtain an aqueous emulsion (A). The resin concentration of this aqueous emulsion was about 50%.

Production Example 2 of Aqueous Emulsion (A) Using the same apparatus as in Production Example 1, water 150 was added to the reactor.
Part, 7.2 parts of a 35% aqueous solution of sodium sulfate of p-nonylphenol to which 20 mol of ethylene oxide had been added, and p-to which 25 mol of ethylene oxide had been added.
After inserting 8 parts of a 20% aqueous solution of nonylphenol,
The inside of the reaction vessel was replaced with nitrogen gas. Separately, feed I,
II and III were prepared.

[Feed I] Water 150 parts 35% aqueous solution of sodium sulfate of p-nonylphenol to which 20 mol of ethylene oxide is added 14.8 parts 20% aqueous solution of p-nonylphenol to which 25 mol of ethylene oxide is added 14 parts Methyl methacrylate 117 parts Butyl acrylate 154 parts 2-ethylhexyl acrylate 48 parts Acrylic acid 1.3 parts

[Feed II] Water 32 parts 35% aqueous solution of sodium sulfate of p-nonylphenol to which 20 mol of ethylene oxide is added 3.2 parts 20% aqueous solution of p-nonylphenol to which 25 mol of ethylene oxide is added 2 parts Methyl methacrylate 74.4 parts Butyl acrylate 2.4 parts Acrylic acid 3.2 parts

[Supply III] 48 parts of water 2 parts of potassium persulfate

Next, 10% of the above-mentioned feed I was added into the above-mentioned reactor which had been purged with nitrogen gas, and the mixture was heated to 90 ° C. Next, 10% of the feed III is charged into the reactor, and the remainder of the feed I is uniformly fed to the reactor over 3 hours.
Added over time. Feed III was continuously and uniformly fed from the start of the addition of Feed I to the end of the addition of Feed II. After the supply was completed, the emulsion polymerization was carried out at 90 ° C. for 1.5 hours to obtain an aqueous emulsion (A). The resin concentration of the aqueous emulsion (A) was about 50%.

Production Examples 3-6 of Aqueous Emulsion (A) Using the same apparatus as in Production Example 1 of Aqueous Emulsion (A),
An aqueous resin emulsion was synthesized according to Production Example 1 of the aqueous emulsion (A), except that the monomer composition was changed as shown in Table 2. Regarding Production Example 4,
To the obtained aqueous emulsion (A), 10 parts of a 20% aqueous solution of adipic dihydrazide was added. The results are summarized in Table 2.

Production Example 7 of Aqueous Emulsion (A) Using the same apparatus as in Production Example 1 of Aqueous Emulsion (A),
305 parts of water and 380 parts of resin (B) produced in Production Example 2 of resin (B) were inserted into the reactor, and ammonia was added to completely solubilize. Separately, Feed I and Feed II shown below were prepared.

[Supply I] Methyl methacrylate 100 parts Butyl acrylate 280 parts Styrene 20 parts

[Feed II] 100 parts of water 2 parts of sodium persulfate 2 parts of ammonia 0.5 part

Next, the above water-dispersible copolymer (A)
After the inside of the reactor charged with the initiator solution was purged with nitrogen gas, 10% of the above feed I was added into the reactor, and the mixture was heated to 90 ° C. Then 10% of feed II
Was charged into the reactor, and the remaining of Feed I and Feed II were uniformly fed to the reactor over 3 hours. After the completion of the supply, the emulsion was kept at 90 ° C. for 1.5 hours to carry out emulsion polymerization to obtain an aqueous resin emulsion (I). The resin concentration of this aqueous resin emulsion was about 46%. The above aqueous emulsion (A) is shown in Table 2. The actually measured MFT in the lowermost column of Table 2 refers to the lowest film formation temperature actually measured by the method and apparatus described in ISO Standard 2115.

Examples 1 to 8 and Comparative Examples 1 to 6 The aqueous emulsions (A) and the resins (B) produced in the above Production Examples were mixed at the ratios shown in Tables 3 and 4, and The pH was adjusted to 8.5 to 9.0 by adding a neutralizing agent, and if necessary, a polyhydric alcohol was added to adjust the resin composition for an aqueous paint. However, in Example 3, since the resin obtained in Production Example 7 of the aqueous emulsion (containing the solubilized resin (B)) was used, further addition of the resin (B) was not performed. The obtained resin composition was formed into a paint by the following paint formulation.

(Coating composition) Water 80 parts NOPCOSPARS 44C (manufactured by San Nopco) 1.4 parts Titanium oxide JR600A (manufactured by Shiika) 72 parts Calcium carbonate KS1000 (manufactured by Dowa Calfine) 86 parts are mixed and thoroughly dispersed. A pigment paste was made. 98 parts of the composition shown in Table 3 (solid content 5
0%) and 1 part of Thickener 612 (San Nopco) as a thickener, further add alkali to add PV
A 50% C paint was prepared.

The test methods are described above. <Low-temperature film-forming property> The test method is as follows: According to JIS K 5400, at 5 ° C, paint is 500 µm thick and 100 µm thick.
The following criteria were used to evaluate the film forming properties when the coating was applied at a thick thickness. ○ Good film-forming property at 500 μm thickness △ Film formation possible at 100 μm thickness × Poor film-forming properties at both 500 μm and 100 μm

<Surface Adhesion>
The coating was applied in a thickness of 150 μm and dried at 50 ° C. for one week, and the adhesion of the coating film surface was evaluated by finger touch. ◎ No stickiness ○ Slight stickiness △ Sticky × Strong sticky

<Low-temperature stability> The test method is based on JIS K5
According to 400, the operation of placing the paint in a low-temperature incubator kept at -10 ° C for 18 hours and then leaving it at room temperature for 6 hours was repeated to evaluate the presence or absence of deterioration of the paint. ○ No abnormalities in 3 repetitions △ No abnormalities in 2 repetitions × Deterioration of paint by the second time

<Water resistance> The test method is based on JIS K566.
The test piece coated on the flexible plate was subjected to 20 ℃
The coating film after immersion for 7 days was evaluated. ◎ No abnormalities ○ Blisters occur in less than 5% of substrate surface △ Blisters occur in less than 20% of substrate surface × Blister on entire surface

Tables 3 and 4 show the results of these tests. In Tables 3 and 4, the polyhydric alcohol compound (C) (based on 100 parts of the disc) refers to the above (A)
Means the ratio of the component (C) to 100 parts by weight of the resin composition for aqueous paint (dispersion) consisting of (B) and (B). As can be seen from Table 3, Examples 1 to 8 according to the present invention did not show "x" in any of low-temperature film-forming properties, surface tackiness, low-temperature stability and water resistance, and exhibited excellent performance in overall evaluation. have. On the other hand, as can be seen from Table 4, Comparative Examples 1 to 6 have one or two “x”, which is inferior to the product of the present invention.

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

[Table 3]

[0070]

[Table 4]

[0071]

According to the present invention, the low-temperature film-forming properties of a conventional emulsion-based water-based paint containing a film-forming aid can be obtained despite the fact that VOC is not contained at all or is contained in a very small amount. It is possible to provide a resin composition for water-based paint which has no stickiness on the surface of the coating film obtained and is stable even when the paint is subjected to a cycle of freezing and thawing.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeo Tsukamoto 1000 Kawajiri-cho, Yokkaichi, Mie Prefecture Mitsubishi Chemical BSF Inc.

Claims (4)

[Claims] An aqueous emulsion (A) of a copolymer having a minimum film-forming temperature of 0 ° C. or lower and a resin having a glass transition temperature of −20 ° C. to 20 ° C .;
A composition comprising a resin (B) solubilized in water with an alkali at a temperature of at least 0 ° C., wherein the weight ratio of the nonvolatile components (A) and (B) is A / B = 95 / 5-5. A resin composition for a water-based paint, which is in the range of 60/40. 2. The resin composition for an aqueous paint according to claim 1, wherein the resin composition for an aqueous paint further comprises a polyhydric alcohol compound (C). 3. The method according to claim 2, wherein the polyhydric alcohol compound (C) is added in an amount of 0.1 to 5% by weight based on the total amount of the aqueous emulsion (A) and the resin (B). A resin composition for a water-based paint, comprising: 4. The method according to claim 1, wherein:
The resin composition for an aqueous paint is a resin composition for an aqueous indoor paint.