JP2003192982A - Aqueous resin composition and two-pack type aqueous coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous (meth)acrylic resin composition and a two-pack type aqueous coating composition which have excellent polymerization ability and give a beautiful coating surface upon impasto painting. <P>SOLUTION: An aqueous resin composition containing a (meth)acrylic polymer is obtained by an emulsion polymerization of a (meth)acrylic ester monomer using a reactive emulsifier in the presence of a hydroxy group containing a neutralized product of a poly(meth)acrylic acid copolymer, and to obtain a two-pack type aqueous coating composition by combining this aqueous resin composition with an isocyanate compound. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous resin composition containing a (meth) acrylic polymer and a two-pack type aqueous coating composition comprising the same and an isocyanate compound.

[0002]

2. Description of the Related Art Conventional aqueous urethane emulsions include urethane emulsions composed of a polyacrylate resin dissolved or dispersed in water as a binder and a polyisocyanate having free isocyanate groups emulsified in this dispersion or solution. A urethane emulsion comprising a polyol emulsion using the above emulsifier and a self-emulsifying polyisocyanate is known.

However, when such a urethane emulsion is coated thickly, irregular groove-like irregularities, that is, cracks may occur on the surface of the coating film.

In order to prevent the occurrence of such cracks, methods for adjusting the water absorption of the resin and for improving the strength by isocyanate crosslinking have been studied. For example, a method in which an acrylic monomer containing a hydroxyl group-containing acrylic acid is copolymerized, neutralized, and treated with an isocyanate can be given.

[0005]

However, when the above-mentioned method is used, the viscosity of the copolymer may be increased, or adhesion or unevenness may be remarkable during coating.

[0006] Therefore, an object of the present invention is to provide a (meth) acrylic aqueous resin composition and a two-component aqueous coating composition which have good polymerizability and can obtain a clean coated surface during thick coating.

[0007]

The present invention is to emulsify a (meth) acrylic acid ester monomer using a reactive emulsifier in the presence of a neutralized product of a hydroxyl group-containing poly (meth) acrylic acid copolymer. The above problem is solved by polymerizing to obtain an aqueous resin composition containing a (meth) acrylic polymer. Then, a two-pack type aqueous coating composition is obtained by combining this aqueous resin composition with an isocyanate compound.

Since a two-step polymerization method is adopted as a method for producing the above-mentioned aqueous resin composition, an increase in viscosity of the obtained aqueous resin composition is suppressed. For this reason, the polymerizability becomes good, and the occurrence of unevenness during thick coating is suppressed,
A clean painted surface can be obtained.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The aqueous resin composition according to the present invention is an emulsion containing a (meth) acrylic polymer produced by a two-step polymerization reaction.

The first stage reaction is a reaction for producing a hydroxyl group-containing (meth) acrylic acid type copolymer. That is,
In the presence of a reactive emulsifier, hydroxyl group-containing monomer and (meth)
It is a reaction to obtain a copolymer with an acrylic acid monomer.

The above-mentioned reactive emulsifier contains a radical-polymerizable carbon-carbon unsaturated double bond and a hydroxyl group reactive with a polyisocyanate compound in one molecule. The anionic type represented by the formulas (1) to (2) and the nonionic type represented by the formulas (3) to (4) are preferably used, but the compounds are not limited to these compounds. .

[0012]

[Chemical 1]

[0013]

[Chemical 2]

[0014]

[Chemical 3]

[0015]

[Chemical 4]

Further, this reactive emulsifier is copolymerized with the monomer used in the above emulsion polymerization and, as a result, is incorporated into the molecular chain in the above hydroxyl group-containing (meth) acrylic acid type copolymer particles. . Of these reactive emulsifiers, the anionic one can be used alone as an emulsifier during emulsion polymerization, but of course there is no problem even if it is used in combination with a nonionic reactive emulsifier. Further, the nonionic type is generally not used alone, but is preferably used in combination with an anionic emulsifier.

The above-mentioned hydroxyl group-containing monomer is a monomer used for imparting a hydroxyl value to the resulting hydroxyl group-containing poly (meth) acrylic acid type copolymer. As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2
-Hydroxy-3-chloropropyl methacrylate, acryloyloxyethyl hydrogen phthalate, β-hydroxyethyl-β-acryloyloxyethyl phthalate,
1,4-butylene glycol monoacrylate, N-methylol acrylamide, hydroxystyrene, vinyl alcohol, allyl alcohol, methallyl alcohol,
Isopropenyl alcohol, 1-butenyl alcohol,
Examples thereof include ethylene glycol monoacrylate and 1,4-butanediol monoacrylate.

The (meth) acrylic acid monomer means acrylic acid or methacrylic acid. As a monomer other than the hydroxyl group-containing monomer and (meth) acrylic acid monomer,
A (meth) acrylic acid ester-based monomer or a crosslinkable monomer can be added. Examples of the (meth) acrylic acid ester-based monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate,
Butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth)
Examples include lauryl acrylate and the like. Examples of the crosslinkable monomer include allyl methacrylate, divinylbenzene, silane coupling agent and the like.

The mixing ratio of the above-mentioned hydroxyl group-containing monomer and (meth) acrylic acid monomer is 20/80 to 90/10 (weight ratio) of hydroxyl group-containing monomer / (meth) acrylic acid monomer. Is preferable, and 30/70 to 70/30 is preferable. When the ratio of the both exceeds 90/10 and the amount of the hydroxyl group-containing monomer increases, the viscosity of the produced emulsion becomes high and the handleability may deteriorate. On the other hand, when the amount of the hydroxyl group-containing monomer is low such that the ratio of both is less than 20/80, the durability of the coating film may be deteriorated.

The amount of the above-mentioned crosslinkable monomer used is preferably 0.05 to 5% by weight, based on the total amount of other monomers, and 0.1 to 5% by weight.
3% by weight is preferred. The amount of crosslinkable monomer used is 0.05
If it is less than wt%, the durability of the coating film may deteriorate.
On the other hand, when it exceeds 5% by weight, the viscosity of the obtained emulsion becomes high and the handling property tends to be deteriorated.

The amount of the reactive emulsifier used is preferably 0.1 to 5% by weight, and more preferably 0.5 to 3% by weight, based on the total amount of the monomers to be emulsion polymerized. When the content of the reactive emulsifier is less than 0.1% by weight, the amount of aggregates generated during the polymerization is increased, and the yield may be significantly reduced. On the other hand, if the amount exceeds 5% by weight, even a reactive emulsifier has a hydrophilic portion, so that the durability of the coating film may be deteriorated.

Any method can be adopted as the method of the emulsion polymerization in the first step. For example, a method may be mentioned in which the mixture of the above monomers is added dropwise to a mixture of an aqueous medium such as water kept at a predetermined temperature, a reactive emulsifier and a polymerization initiator. Examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile), and organic compounds such as t-butyl peroxide and t-butylperoxybenzoate. Examples thereof include peroxides.

The weight average molecular weight of the hydroxyl group-containing poly (meth) acrylic acid-based copolymer obtained by the above-mentioned first step reaction is preferably in the range of 2,000 to 100,000, and 3,0.
The range of 00 to 50,000 is preferable. If it is less than 2,000, the water resistance may decrease. On the other hand, 10
If it is more than 10,000, the formation of aggregates during polymerization may increase.

The hydroxyl value of the above-mentioned hydroxyl group-containing poly (meth) acrylic acid type copolymer is 10 to 100 mmKOH / g.
Is preferable and 20 to 50 mmKOH / g is preferable. 10m
If it is less than mKOH / g, the durability of the coating film may deteriorate. On the other hand, if it is larger than 100 mmKOH / g,
The water resistance of the coating film may deteriorate.

The hydroxyl group-containing poly (meth) acrylic acid type copolymer obtained by the above-mentioned first step polymerization reaction is neutralized in order to form an aqueous solution. As the neutralizing agent used at this time, as long as it exhibits alkalinity, any one of hydroxides such as sodium hydroxide and potassium hydroxide and ammonia can be used. Among these, ammonia is more preferable from the viewpoint of water resistance of the obtained aqueous resin composition.

In the second step reaction, the (meth) acrylic acid ester-based monomer is reacted with a reactive emulsifier in the presence of the hydroxyl group-containing neutralized poly (meth) acrylic acid-based copolymer. It is a reaction of emulsion polymerization.

As the above reactive emulsifier, the above reactive emulsifier can be used. Further, as the (meth) acrylic acid ester-based monomer, the same (meth) acrylate as described above is used.
Acrylic acid ester-based monomers can be used.

The amount of the (meth) acrylic acid ester-based monomer used is preferably 50 to 200 parts by weight with respect to 100 parts by weight of the hydroxyl group-containing neutralized poly (meth) acrylic acid copolymer. 70 to 150 parts by weight is preferable. If it is more than 200 parts by weight, the stability of the emulsion may be insufficient. On the other hand, if it is less than 50 parts by weight, the water resistance of the coating film tends to be insufficient.

The amount of the above-mentioned reactive emulsifier used is 0.
2 to 5% by weight is preferable, and 0.3 to 3% by weight is preferable.
If it is less than 0.2% by weight, the stability of the (meth) acrylic acid ester-based monomer during emulsion polymerization may be insufficient, and the formation of aggregates and abnormal reactions may occur. On the other hand, if it exceeds 5% by weight, the viscosity of the produced emulsion may be high or the water resistance of the resulting coating film may be insufficient.

Any method can be adopted as the method of the second step emulsion polymerization. For example, the neutralized product of the hydroxyl group-containing poly (meth) acrylic acid copolymer and the reactive emulsifier are dissolved in an aqueous medium such as water, a polymerization initiator is added and the mixture is maintained at a predetermined temperature, and the Examples thereof include a method of dropping a (meth) acrylic acid ester-based monomer. As the above-mentioned polymerization initiator, the same polymerization initiator as described above can be used.

The weight average molecular weight of the (meth) acrylic polymer obtained by the above second-stage polymerization reaction is 5,000.
~ 1,000,000 range is good, 10,000-5
A range of 0,000 is preferred. If it is less than 5,000, the water resistance may be insufficient. On the other hand, 1,000,
If it is more than 000, it becomes difficult to obtain a stable emulsion.

In the aqueous resin composition containing the above (meth) acrylic polymer, a thickener, a film forming aid, a pigment dispersant, a pigment, a defoaming agent, a pH adjuster, and Preservative,
A fungicide or the like can be added.

The obtained aqueous resin composition containing the (meth) acrylic polymer can be used as a two-component aqueous coating composition in combination with an isocyanate compound.

As the above-mentioned isocyanate compound, phenylene diisocyanate, tolylene diisocyanate,
Xylene diisocyanate, tetramethyl xylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate and aromatic diisocyanates consisting of these isomers, 1,6-hexamethylene diisocyanate, aliphatic diisocyanates such as 1,12-dodecane disocyanate, cyclohexane diisocyanate, dicyclohexylmethane Examples thereof include alicyclic diisocyanates such as diisocyanate and isophorone diisocyanate. Among these, since the aqueous resin composition containing the (meth) acrylic polymer emulsion is water-soluble or water-dispersible, a water-soluble or water-dispersible polyisocyanate such as 1,6-hexamethylene diisocyanate is used. Particularly preferred.

The viscosity of this polyisocyanate compound is
Although not particularly limited, it is 50 to 1000 in an emulsified state.
mPa · s is preferable, and 100 to 500 mPa · s is more preferable. When it is less than 50 mPa · s, the emulsion is likely to be separated. On the other hand, when it is more than 1000 mPa · s, poor dispersion is apt to occur at the time of mixing with the aqueous resin composition containing the (meth) acrylic polymer.

The ratio of the above aqueous resin composition to the isocyanate compound used is the equivalent ratio of the hydroxyl groups to the isocyanate groups, and the hydroxyl group-containing poly (meth) acrylic acid type copolymer / polyisocyanate = 0.5 / 1 to 5/1 is good, 1
/1.5 to 4/1 is preferable. If the equivalent ratio of the isocyanate compound is more than 0.5 / 1, the amount of carbon dioxide gas is increased, which may impair the appearance of the coating film. On the other hand, when the equivalent ratio of the isocyanate compound is smaller than 5/1, a tough coating film may not be obtained.

In the two-pack type aqueous coating composition of the present invention, an isocyanate compound may be directly blended with an aqueous resin composition containing a (meth) acrylic polymer immediately before coating,
Also, after first dispersing the isocyanate compound in water,
You may mix | blend with the aqueous resin composition containing a (meth) acrylic-type polymer.

The two-pack type aqueous coating composition of the present invention is applied to the surface of an object to be coated by a coating means such as a brush, spray, roll, dipping, etc., and dried at room temperature or forcedly dried at about 120 ° C. to form a cured coating film. It is possible to

The object to be coated is an inorganic ceramic substrate,
It can be applied to various coated materials such as various metal substrates such as iron, stainless steel and aluminum, glass substrates and paper substrates.

[0040]

EXAMPLES The present invention will be described in more detail below with reference to examples. First, the evaluation method is shown below. [Water resistance evaluation test] On a glass plate, 1 part of the aqueous resin composition and the isocyanate compound prepared in the examples or comparative examples were prepared.
It was applied so that the weight ratio of 00:30 was 0.15 mm. After drying at room temperature for 1 day, soak in water at room temperature for 1
I left it on the day. The condition after 1 day was observed and evaluated according to the following criteria. ○: no whitening △: whitening ×: severe whitening

[Evaluation of Cracking Resistance] On a glass plate,
The aqueous resin composition and the isocyanate compound prepared in the examples or comparative examples were applied at a weight ratio of 100: 30 to a thickness of 2 mm. Then, it was dried at 50 ° C. for 1 day, and the surface condition, particularly whether or not irregular groove-like irregularities (that is, cracks) were observed on the surface, was observed and evaluated according to the following criteria. ○: no cracks ×: cracks

[Evaluation of Tack Resistance] Aqueous resin compositions and isocyanate compounds prepared in Examples or Comparative Examples were coated on a glass plate so as to have a thickness of 2 mm at a weight ratio of 100: 30. Then, it was dried at 50 ° C. for 1 day and touched with a finger to evaluate according to the following criteria. ○: No tack △: Some tack ×: Many cracks

Example 1 In a flask equipped with a condenser, a thermometer and a stirring blade, 50 parts by weight of ion-exchanged water, 0.5 parts by weight of anionic reactive emulsifier Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). Parts, as a weight initiator,
0.5 parts by weight of potassium persulfate was added. To this, a monomer mixture liquid in which 10 parts by weight of ethyl acrylate, 5 parts by weight of 2-hydroxymethacrylate, 3 parts by weight of acrylic acid, and 3 parts by weight of a chain transfer agent (Thiocalcol 08, manufactured by Kao Co., Ltd.) were blended in advance was used for 2 hours. It was dropped and polymerized. The weight average molecular weight of the obtained polymer was 4000 (by GPC measurement).

Next, 5 parts by weight of 25% by weight aqueous ammonia as a neutralizing agent was added to and dissolved in the obtained polymer to obtain an aqueous acrylic dispersion liquid. Then, 2 parts by weight of azobisisobutylnitrile as a polymerization initiator was added to this aqueous acrylic dispersion. To this, 45 parts by weight of methyl methacrylate, 37 parts by weight of butyl acrylate, 0.5 parts by weight of anionic reactive emulsifier Aqualon HS-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and 50 parts by weight of ion-exchanged water were stirred and mixed. The thing was dripped over 3 hours and superposed | polymerized. In this polymerization, an antifoaming agent and an antifungal agent were appropriately added. The resulting aqueous resin composition has a nonvolatile content of 50% and a viscosity of 500.
0 mPa · s, pH is 8, weight average molecular weight is 400,0
00 (according to GPC measurement), the gel fraction was 5%.
When the obtained aqueous resin composition was taken out, no adhesion of polymer was found on the bottom of the kettle and the stirring blade.

The resulting aqueous resin composition and isocyanate compound (hexamethylene diisocyanate (isocyanurate type), manufactured by Sumitomo Chemical Co., Ltd .; Sumidule N3
300, viscosity in emulsified state (solid content 40% by weight);
200 mPa · s) was combined with the ratio (polymerization ratio) shown in Table 1 to perform each of the above evaluation tests. The results are shown in Table 1.

Reference Example The amount of each raw material used is the same as in Example 1.
In the same manner as above, when they were charged all at once into a flask and polymerization was carried out, the viscosity of the obtained aqueous dispersion became remarkably high and the fluidity was poor, so the coating film was not evaluated.

[0047]

[Table 1]

[0048]

According to the present invention, since the two-step polymerization method is adopted as the method for producing the (meth) acrylic polymer emulsion, the viscosity increase of the obtained emulsion is suppressed. Therefore, the polymerizability becomes good, and also
The occurrence of irregularities during thick coating is suppressed and a clean coated surface is obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08F 220/02 C08F 220/02 265/06 265/06 C09D 5/02 C09D 5/02 133/00 133 / 00 175/04 175/04 F-term (reference) 4J011 KA04 KA06 KA14 KB14 KB29 PA69 PB40 PC02 PC06 4J026 AA18 AA20 AA29 AA30 AA31 AA43 AA48 AA50 AA62 BA27 DA04 DA07 DA12 DA15 DA01 DA1 DA1 CH1 CG01 CH4J1 001 CG01 4J01 CH1 CH121 DG232 FA04 FA11 JC30 KA03 KA09 MA10 NA01 NA25 4J100 AB07P AB16R AD01P AD02P AD03P AJ02Q AL08P AL09P AL75R AM21P BA03P BA16P BB03P BC43P CA04 CA05 DA01 EA07 FA20 HA31 HB43 JA01

Claims (8)

[Claims] 1. A reactive emulsifier is used in the presence of a neutralized product of a hydroxyl group-containing poly (meth) acrylic acid type copolymer (meth).
An aqueous resin composition containing a (meth) acrylic polymer obtained by emulsion polymerization of an acrylic ester monomer. 2. The weight average molecular weight of the hydroxyl group-containing poly (meth) acrylic acid-based copolymer is 2,000 to 100,0.
The aqueous resin composition according to claim 1, which is in the range of 00. 3. The hydroxyl group-containing poly (meth) acrylic acid-based copolymer is obtained by copolymerizing a hydroxyl group-containing monomer and a (meth) acrylic acid monomer in the presence of a reactive emulsifier. The aqueous resin composition according to claim 1 or 2, which is a copolymer. 4. The hydroxyl group-containing poly (meth) acrylic acid-based copolymer comprises a hydroxyl group-containing monomer, a (meth) acrylic acid monomer and a crosslinkable monomer in the presence of a reactive emulsifier. The aqueous resin composition according to claim 1 or 2, which is a copolymer obtained by polymerization. 5. A hydroxyl group-containing monomer is copolymerized with a (meth) acrylic acid monomer in the presence of a reactive emulsifier to obtain a hydroxyl group-containing poly (meth) acrylic acid copolymer, and then,
This is neutralized, and in the presence of the obtained neutralized product, an aqueous resin composition containing a (meth) acrylic polymer by emulsion-polymerizing a (meth) acrylic ester monomer using a reactive emulsifier. A method of manufacturing things. 6. A two-pack aqueous coating composition comprising the aqueous resin composition according to claim 1 and an isocyanate compound. 7. The two-component aqueous coating composition according to claim 6, wherein the isocyanate compound is a water-soluble or water-dispersible polyisocyanate. 8. The polyisocyanate has a viscosity in an emulsified state of 50 to 1000 mPa · s, and the use ratio of the hydroxyl group-containing poly (meth) acrylic acid-based copolymer to the polyisocyanate is such that the hydroxyl group-containing polyisocyanate is used. (Meth) acrylic acid type copolymer / polyisocyanate of 0.
The two-component aqueous coating composition according to claim 7, which has a ratio of 5/1 to 5/1 (equivalent ratio of hydroxyl group to isocyanate group).