JP2000219844A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous coating composition having excellent adhesivity to coatings using fluororesins and having improved compatibility by adding an emulsion comprising a copolymer obtained from specific monomers. SOLUTION: This aqueous coating composition comprises an emulsion of a copolymer obtained from (A) 5-80 pts.wt. of tertiary butyl (meth)acrylate, (B) 0. 1-10 pts.wt. of an ethylenic unsaturated carboxylic acid monomer [preferably a monomer of the formula: CH2=CR1-COO-C2H4-OC(O)-R2-COOH (R1 is H or CH3; R2 is a 2-28C group), concretely 1, 2-cyclohexanedicarboxylic acid monohydroxyethyl (meth)acrylate or the like], (C) 10-94.9 pts.wt. of another ethylenic unsaturated monomer [for example, methyl (meth)acrylate]. The mixing ratio of the components is preferably set so that a theoretical glass transition temperature of the copolymer is -20 to 70 deg.C which is determined by the calculating formula of Fox.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition having good adhesion and compatibility with a fluororesin, and can be widely used for various aqueous coatings.

[0002]

2. Description of the Related Art In the field of architectural coatings, in order to meet the needs of users for maintaining the aesthetics of a building for a long period of time, a top coat using a weather-resistant resin such as a silicone resin or a fluorine resin is used. The development of paints for use is in progress.

However, paints using these resins, especially fluororesins, are inferior in adhesion to paints using other acrylic resins. Therefore, intermediate coatings using acrylic resins which have been conventionally used. In some cases, paints and primers could not be used.

[0004] Further, since the fluorine-based resin has poor compatibility with the conventionally used acrylic resin, if the fluorine-based resin and the acrylic resin are blended and used,
In some cases, there was a problem such as a decrease in gloss compared to a case where each resin was used alone.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has excellent adhesion to a coating material using a fluororesin,
It is another object of the present invention to provide an aqueous coating composition having improved compatibility.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, when an emulsion obtained by emulsion copolymerization of a monomer having a specific structure is used, a fluororesin is used. It has been found that the composition has excellent adhesion to a coating material using, and that the compatibility is also improved, thereby completing the present invention.

That is, the present invention provides (a) 5 to 80 parts by weight of tertiary butyl (meth) acrylate, (b) 0.1 to 10 parts by weight of an ethylenically unsaturated carboxylic acid monomer,
And (c) other ethylenically unsaturated monomers 10 to 9
An aqueous coating composition comprising an emulsion comprising a copolymer obtained from 4.9 parts by weight (the total amount of components (a) to (c) is 100 parts by weight).

[0008] In the present invention, "(meth) acrylate" refers to "acrylate and / or methacrylate".

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

Tertiary butyl (meth) acrylate, which is the component (a) for constituting the emulsion copolymer, is 5-80 parts by weight based on 100 parts by weight of the total of the components (a)-(c). It is necessary to use it in the range of 10 parts by weight, and it is particularly preferable to use it in the range of 10 to 70 parts by weight. By using in this range, it becomes possible to exhibit excellent adhesion and compatibility with the fluororesin. That is, when the amount is 5 parts by weight or more, sufficient adhesion and compatibility with the fluororesin can be obtained. On the other hand, when the content is 80 parts by weight or less, compatibility and adhesion to the fluororesin can be maintained without hardening the coating film.

The ethylenically unsaturated carboxylic acid monomer, which is the component (b) for constituting the emulsion copolymer, is used in an amount of 0.1 parts by weight based on 100 parts by weight of the total amount of the components (a) to (c). It is necessary to use it in the range of 1 to 10 parts by weight, particularly preferably in the range of 2 to 10 parts by weight, and more preferably in the range of 2 to 8 parts by weight. That is, when the amount is 0.1 parts by weight or more, the dispersion stability of the emulsion is improved, and when the aqueous coating composition is colored by adding a pigment, there is a problem that an aggregate is generated during mixing. Can be avoided. When the amount is 10 parts by weight or less, the dispersion stability can be maintained without increasing the viscosity of the emulsion, and the water resistance of the obtained coating film does not decrease.

Examples of the ethylenically unsaturated carboxylic acid monomer as the component (b) include, for example, (meth) acrylic acid, itaconic acid, monohydroxyethyl (meth) acrylate of 1,2-cyclohexanedicarboxylic acid, and 1,2. -Monohydroxypropyl cyclohexanedicarboxylate (meth)
Acrylate, monohydroxyethyl tetrahydrophthalate (meth) acrylate, monohydroxypropyl tetramethyl phthalate (meth) acrylate, monohydroxyethyl 5-methyl-1,2-cyclohexanedicarboxylate (meth) acrylate, monohydroxyethyl phthalate (meth) A) acrylate, monohydroxypropyl phthalate (meth) acrylate, monohydroxyethyl oxalate (meth) acrylate, and the like.

Further, as the ethylenically unsaturated carboxylic acid monomer, the following general formula (I) CH ₂ ＝ CR ¹ —COO—C ₂ H ₄ —OC (O) —R ² —COOH (I) In the formula, R ¹ represents H or CH ₃ , and R ² has 2 to 2 carbon atoms.
28 groups are shown. It is preferable to use the monomer represented by the formula (1).

By using an ethylenically unsaturated carboxylic acid monomer having the structural formula shown by the general formula (I), excellent adhesion can be imparted to a metal substrate or the like while maintaining stability as an emulsion. it can.

Examples of the ethylenically unsaturated monomer represented by the general formula (I) include, for example, monohydroxyethyl (meth) acrylate 1,2-cyclohexanedicarboxylate and monohydroxyethyl (meth) acrylate tetrahydrophthalate. , Monohydroxypropyl (meth) acrylate tetrahydrophthalate, 5-methyl-1,2
Monohydroxyethyl (meth) acrylate cyclohexanedicarboxylate, monohydroxyethyl (meth) acrylate phthalate, 2-methacryloyloxyethyl hexahydrophthalate, and the like.

Other ethylenically unsaturated monomers which are the component (c) for constituting the emulsion copolymer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl ( Having an alkyl group having 1 to 18 carbon atoms such as meth) acrylate, i-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate ( Alkyl (meth) acrylate; 2
Hydroxyalkyl (meth) acrylates such as -hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; ethylene glycol di (meth) acrylate, butylene glycol di (meth)
Glycol di (meth) acrylates such as acrylates;
Alkylamino (meth) acrylates such as dimethylaminoethyl (meth) acrylate; dimethylaminoethyl (meth) acrylate methyl chloride salt; allyl (meth) acrylate; trimethylolpropane tri (meth) acrylate; glycidyl (meth) acrylate;
Aromatic vinyl compounds such as styrene, α-methylstyrene and p-methylstyrene; vinyl acetate; vinyl propionate; (meth) acrylonitrile; benzyl (meth) acrylate; and isobornyl (meth) acrylate.

The copolymer of the emulsion has a theoretical glass transition temperature (theoretical Tg) determined from the formula of Fox, preferably from -20 ° C to 70 ° C, more preferably from -10 ° C to 10 ° C.
The mixing ratio of the components (a) to (c) is preferably set so as to be 60 ° C. When the theoretical Tg is -20 ° C or higher, the coating film has no tackiness, and dirt hardly adheres to the periphery of the coated portion before applying the overcoating fluororesin. The temperature of 70 ° C. or lower is preferable because the formed coating film does not become too hard, and cracks and the like do not occur in a cooling / heating cycle test.

The Fox equation is the following relational equation for the glass transition temperature (Tg) of the copolymer.

1 / Tg = Σ (Wi / Tgi) (Wi is the weight fraction of monomer i, Tgi is the Tg of a homopolymer of monomer i.) To obtain an emulsion of the copolymer, a surfactant is required. is necessary. The amount of the surfactant used is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the total of the components (a) to (c). When the surfactant is present in the emulsion within this range, the stability at the time of blending the paint, the stability over time, and the like can be maintained without significantly reducing the water resistance of the coating film.

Examples of the surfactant include conventionally known anionic, cationic, and nonionic surfactants, and further, a polymer emulsifier. Further, a so-called reactive emulsifier having an ethylenically unsaturated bond in a surfactant component can also be used.

Further, the emulsion constituting the aqueous coating composition of the present invention uses a carbonyl group or aldehyde group-containing vinyl monomer as the component (c), and uses an aqueous medium of the emulsion (water as a main dispersion medium) )), It is preferable to include an organic hydrazine derivative having two or more hydrazine residues. With such a configuration, while maintaining high substrate adhesion in a wet state, water resistance, a room temperature crosslinkable one-part aqueous coating composition capable of forming a coating film with improved solvent resistance is obtained. be able to.

The carbonyl group or aldehyde group-containing vinyl monomer can polymerize in the molecule with at least one of a keto group other than a carboxylic acid group, an ester group and an amide group, and at least one aldehyde group. It is a monomer having a heavy bond.

The amount of the carbonyl group or aldehyde group-containing vinyl monomer is preferably 1 to 10 parts by weight, more preferably 1.5 to 9 parts by weight. This usage is 1
When the amount is at least part by weight, the solvent resistance, water resistance and the like of the coating film are sufficiently improved. When the amount is 10 parts by weight or less, emulsion polymerization can be performed stably.

Examples of the vinyl monomer having a carbonyl group or an aldehyde group include acrolein, diacetone acrylamide, formylstyrene, and vinyl alkyl ketone. Preferably, vinyl methyl ketone having 4 to 7 carbon atoms, vinyl ethyl ketone, vinyl isobutyl ketone, the following general formula (II): CH ₂ ＣＲCR ³ —COO—CHR ⁴ —CR ⁵ R ⁶ —CHO (II) ( Wherein R ³ is H or CH ₃ , and R ⁴ and R ⁵ are H
Alternatively, it represents an alkyl group having 1 to 3 carbon atoms, and R ⁶ represents an alkyl group having 1 to 4 carbon atoms. In addition to (meth) acryloyloxyalkylpropanal represented by), (meth) acrylamidopivalinaldehyde, diacetone (meth)
Examples include acrylate, acetonitrile acrylate, 2-hydroxypropyl acrylate acetyl acetate, acetoacetoxyethyl (meth) acrylate, butanediol-1,4-acrylate-acetyl acetate, and acrylamidomethylanisaldehyde. Among them, acrolein, diacetone acrylamide and vinyl methyl ketone are particularly preferred. It is also possible to use these carbonyl group or aldehyde group-containing vinyl monomers in combination of two or more.

When an organic hydrazine derivative having two or more hydrazine residues is used, the ratio of the number of moles of carbonyl groups in the copolymer (A) to the number of moles of hydrazine residues in the dispersion medium (B) Is preferably added such that 0.1 ≦ (A) / (B) ≦ 10, and 0.8 ≦ (A) /
It is more preferable to add (B) so that ≦ 2.
When the ratio (A) / (B) is at least 0.1, the stability of the aqueous coating composition will be improved, and long-term stable storage will be possible. When it is less than 10, the solvent resistance of the coating film is sufficiently improved.

Examples of the organic hydrazine derivative include dicarboxylic acid hydrazide having 2 to 10, preferably 4 to 6 carbon atoms, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid Dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, isophthalic acid dihydrazide, itaconic acid dihydrazide and aliphatic water-soluble hydrazine having 2 to 4 carbon atoms, for example, ethylene-1,2-dihydrazine, propylene -1,3-dihydrazine, butylene-1,4-dihydrazine and the like. Among these, adipic dihydrazide, sebacic dihydrazide, isophthalic dihydrazide, and succinic dihydrazide are particularly preferable. These can be used in combination of two or more.

In order to obtain an emulsion constituting the aqueous coating composition of the present invention, a method of supplying a monomer mixture into a polymerization system in the presence of an emulsifier, and performing polymerization with a water-soluble initiator, or a method of preparing an inorganic coating may be used. A method using a redox initiator such as a peroxide and a reducing agent such as sodium thiosulfate can be used. The method for supplying the monomer into the polymerization system is not particularly limited, and various conventionally known methods can be used.

Further, after the emulsion obtained by the emulsion polymerization method is polymerized, the pH of the system is adjusted to a neutral range to a weak alkalinity, that is, pH 6.5 to 10.0 by adding a basic compound, thereby stabilizing the system. Can be enhanced.

Examples of the basic compound to be added include ammonia, triethylamine, propylamine, dibutylamine, amylamine, 1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, 2-diethylaminoethanol, and 1-amino-2-amine. Propanol, 2-amino-1-propanol, 3-amino-1-propanol, 1-dimethylamino-2-propanol,
3-dimethylamino-1-propanol, 2-propylaminoethanol, ethoxypropylamine, aminobenzyl alcohol, morpholine, sodium hydroxide, potassium hydroxide and the like.

When it is necessary to adjust the molecular weight of the vinyl polymer, the molecular weight can be adjusted by using a chain transfer agent such as n-dodecyl mercaptan, t-dodecyl mercaptan, or α-methylstyrene dimer as a molecular weight regulator. Is possible.

The aqueous coating composition of the present invention containing the thus obtained emulsion as a main component can be used in various types of pigments, defoamers, and pigment dispersants in order to exhibit high performance as a coating material. , Slip agent, preservative,
A plasticizer or the like may be added for use.

When a coating film is formed on the surface of various materials using the aqueous coating composition of the present invention, a spray coating method, a roller coating method, a bar coating method, an air knife coating method, a brush coating method, a dipping method For example, various known coating methods may be appropriately selected and performed, and there is no particular limitation.

When the aqueous coating composition of the present invention is used as a coating material, it is usually dried in a temperature range of room temperature to about 120 ° C. for about 10 minutes to 1 hour to obtain a sufficiently formed coating film. Can be.

[0034]

The present invention will be described in more detail with reference to the following examples. The compatibility and adhesion were evaluated by the following methods.

(1) Evaluation of compatibility Fluororesin-based emulsion (Lumiflon FE-3000 and Lumiflon FE-410, trade names, manufactured by Asahi Glass Co., Ltd.)
0) and an acrylic emulsion were blended at a solid content ratio of 1: 1 and butyl cellosolve as a plasticizer was added at 10% by weight based on the total solid content, and the mixture was sufficiently stirred and mixed.
This mixed emulsion was filtered through a 300 mesh nylon gauze, coated on a glass plate with an applicator (4ML), set at room temperature for 30 minutes, and dried at 80 ° C. with a dryer.
Dried for 0 minutes. After the drying was completed, the transparency of the coating film was evaluated according to the following criteria, and was used as an index of compatibility. "C": The coating film after drying is completely transparent (very good compatibility). "VHS": The coating film after drying is slightly turbid (good compatibility). "SH": The dried coating film is more turbid than VHS (the compatibility is not so good). "H": The coating film after drying is cloudy (poor compatibility).

(2) Evaluation of Adhesion 10 parts by weight of butylcellosolve as a plasticizer (based on solid content) and 3 parts by weight of a thickener (RHEOLATE 350, manufactured by RHEOX) (based on solid content) were added to the acrylic emulsion. After adding and stirring sufficiently, the mixture was filtered with a 300 mesh nylon gauze. Next, this acrylic emulsion was applied to a slate plate and a mortar plate with a wet film thickness of 3.
It was coated so as to have a thickness of 0 μm, set at room temperature for 30 minutes, and dried at 80 ° C. for 30 minutes.

The dried coated plate is completely cooled to room temperature, and the same blending and filtration as in the above-mentioned acrylic emulsion is performed on a fluororesin emulsion (Lumiflon FE-3000 and FE-4000, manufactured by Asahi Glass Co., Ltd.). The fluororesin-based emulsion obtained above was applied on this coated plate (on the acrylic emulsion coating film of a slate plate and a mortar plate) so as to have a wet film thickness of 30 μm, and was set at room temperature for 30 minutes. 3 in the dryer
Dried for 0 minutes.

The coated plate for evaluation was cooled completely to room temperature, and only the layer coated with the fluorine-based emulsion was
100 square cuts were made in a grid pattern, and the cellophane tape peeling test was performed three times at the same location, and the cells that did not peel off after the three times peeling test were counted.

Example 1 A polymerization vessel equipped with a stirrer, a cooler, and a thermometer was charged with 60 parts by weight of deionized water.
The temperature rose. Thereafter, 100 parts by weight of a monomer mixture having the resin composition shown in Table 1, an emulsifier (surfactant) and deionized water 4
0 parts by weight were sufficiently mixed to prepare a pre-emulsion in a uniform emulsified state (hereinafter abbreviated as “PE liquid”).

5 parts by weight of this PE solution was placed in a polymerization vessel,
The temperature was raised to 0 ° C., and when the internal temperature was stabilized, a solution prepared by dissolving 0.1 part by weight of sodium persulfate in 5 parts by weight of deionized water was added and left for 1 hour. After one hour, the remaining PE solution and 0.2 parts by weight of sodium persulfate are added to 10 parts of deionized water.
The solution dissolved in parts by weight was dropped into the polymerization vessel over 3 hours while maintaining the internal temperature of the polymerization vessel at 80 ° C. After the completion of the dropping, the internal temperature was maintained at 80 ° C for 2 hours to complete the reaction. After the reaction was completed, cooling was performed, the emulsion was taken out, and 28% aqueous ammonia was added so that the pH of the emulsion was between 7.5 and 10.

Table 2 shows the solid content, pH, adhesion and compatibility with the fluororesin of the obtained acrylic emulsion.
Shown in

[Examples 2 to 6 and Comparative Examples 1 to 4] Table 1
An acrylic emulsion was obtained in the same manner as in Example 1 except that the resin composition and emulsifier shown in the following were changed. However, in Examples 3 to 5 and Comparative Example 1, 1.9 parts of adipic dihydrazide was added as a crosslinking agent.

The solid content, pH, adhesion and compatibility with the fluororesin of the obtained acrylic emulsion are shown in Table 2.
Shown in

[0044]

[Table 1] The abbreviations in Table 1 indicate the following compounds.

T-BMA: tert-butyl methacrylate t-BA: tertiary butyl acrylate MMA: methyl methacrylate MAA: methacrylic acid AA: acrylic acid St: styrene n-BMA: normal butyl methacrylate n-BA: normal butyl acrylate IBXA: Isobornyl acrylate CHMA: cyclohexyl methacrylate 2-EHA: 2-ethylhexyl acrylate DAAm: diacetone acrylamide HH: 2-methacryloyloxyethyl hexahydrophthalate (Acryester HH, manufactured by Mitsubishi Rayon Co., Ltd.) Sannole NP- 2030: Surfactant manufactured by Lion Corporation ABEX 23S: Surfactant manufactured by Rhodia Nika Co., Ltd. Adecaria Soap SE-10N: Asahi Denka Co., Ltd. Surfactants

[0046]

[Table 2] As shown in Table 2, the aqueous coating compositions of Examples 1 to 6,
It had excellent compatibility and adhesion to fluorine-based resins.

On the other hand, in Comparative Example 1, the tertiary butyl (meth) acrylate as the component (a) and the ethylenically unsaturated carboxylic acid monomer as the component (b) were not used. Was inferior in adhesion and compatibility. In Comparative Example 2, the components (b) and (c)
Since only the component (a) was used without using any components,
The stability required as an emulsion is lacking,
Agglomerates were generated in large quantities during the addition of the plasticizer and the like, and the compatibility and adhesion could not be evaluated. In Comparative Example 3,
Since the component (a) was not used and the theoretical Tg was too high, cracks occurred in the coating film when the emulsion was dried after coating, and the adhesion could not be evaluated. In Comparative Example 4, only a very small amount of the component (a) was used and the theoretical Tg
Is too low, the coated plate of the emulsion has stickiness (tack) after drying, dust adheres remarkably to the surface of the coating film during cooling, the clean coating surface cannot be maintained, and the adhesion is slightly poor. Was.

[0048]

As described above, the aqueous coating composition of the present invention has excellent compatibility and adhesion with a fluororesin, and has excellent transparency even when blended with a fluororesin. A film can be obtained, and it can be suitably used for an intermediate coating and an undercoat when a coating using a fluororesin is used as a top coat, and is extremely practical.

Claims (5)

[Claims] (1) 5 to 80 parts by weight of tertiary butyl (meth) acrylate, (b) 0.1 to 10 ethylenically unsaturated carboxylic acid monomers.
Parts by weight, and (c) 10 to 94.9 other ethylenically unsaturated monomers.
An aqueous coating composition comprising an emulsion comprising a copolymer obtained from parts by weight [the total amount of the components (a) to (c) is 100 parts by weight]. 2. The aqueous coating composition according to claim 1, wherein the theoretical glass transition temperature obtained from the Fox formula of the copolymer is -20 ° C. to 70 ° C. 3. The emulsion according to claim 1, wherein the content of the surfactant in the emulsion is in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the total of the components (a) to (c). Aqueous coating composition. 4. The aqueous coating composition according to claim 1, wherein a monomer represented by the following general formula (I) is used as the component (b). CH ₂ ＣＲCR ¹ —COO—C ₂ H ₄ —OC (O) —R ² —COOH (I) (wherein R ¹ represents H or CH ₃ , and R ² has 2 to 2 carbon atoms)
28 groups are shown. ) 5. An organic hydrazine derivative having two or more hydrazine residues in an aqueous medium of an emulsion, wherein 1 to 10 parts by weight of a carbonyl group or aldehyde group-containing vinyl monomer is used as the component (c). The aqueous coating composition according to claim 1, which is contained.