JPH11172151A - Aqueous coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition having extremely quickly drying properties while retaining excellent physical properties of coated film without using a low-boiling organic solvent, by adding a hydrazide compound to a specific copolymer. SOLUTION: This composition is obtained by compounding (A) a copolymer prepared by subjecting (ii) a radically polymerizable unsaturated monomer containing (i) a water-soluble carbonyl group-containing unsaturated monomer to emulsion polymerization with (B) a hydrazide compound in the equivalent ratio to the carbonyl group contained in the component A of 0.5-1.5. The solution is acidic. Preferably the amount of the component (i) in the component (ii) is 0.1-20 wt.% in 100 pts.wt. of the component (ii), an emulsifying agent used in the emulsion polymerization is a reactive emulsifying agent containing a radically polymerizable unsaturated double bond in the molecule and 0.1-10 pts.wt. of the reactive emulsifying agent is used based on 100 pts.wt. of the component (ii).

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, and more particularly, to a stable and fast-drying aqueous coating composition which can be used for substrates such as paper, plastic, metal, glass, ceramics and wood. It is about things.

[0002]

2. Description of the Related Art Conventionally, organic solvent-based paints have been demanded to be changed to water-based paints in terms of resource saving, energy saving, low pollution, and safety and health. Among water-based resins used for water-based coatings, water-based emulsion resins using surfactants have a high molecular weight and are used in all fields to form excellent coating films even at a relatively low temperature. However, since the solvent is water, ordinary water-based paints have much slower drying properties than solvent-based paints. In the field of paint for building exterior walls, there is a strong demand for water-saving and labor-saving and shortening the construction period. Further, outflow of paint due to pollution or rainfall due to poor drying properties after painting has been regarded as a problem.

[0003] In order to solve these problems, as a method of accelerating the drying property, a method of adding a low-boiling organic solvent, a method of adding a cationic compound or a metal blocked with a volatile base to a resin containing an anionic functional group, or the like. A method of accelerating the drying property by ionic bonding by volatilization of a volatile base and a method of accelerating the drying property by oxidative crosslinking by modifying a resin with a drying oil and adding a metal dryer or the like are also known.

[0004]

However, these methods have the following problems. The addition of a low-boiling organic solvent is not preferred because the amount of the organic solvent in the coating increases. In addition, the introduction of ionic bonds has a problem in alkali resistance when applied to an alkaline substrate used for building materials and the like. further,
At present, the introduction of oxidative cross-linking has not yet reached the level of quick drying.

Therefore, the present invention provides an aqueous solution having an extremely fast drying property while maintaining excellent coating film properties even when applied to an alkaline substrate used for building materials without adding a low boiling organic solvent. It is an object to provide a coating composition. Here, the extremely fast drying property refers to the degree to which the paint does not flow out upon contact with water after drying for 30 minutes at a temperature of 5 ° C. and a humidity of 90% after coating.

[0006]

An aqueous coating composition according to the present invention is a copolymer obtained by emulsion polymerization of a radically polymerizable unsaturated monomer containing a water-soluble carbonyl group-containing unsaturated monomer. (A) and a hydrazide compound (B) having an equivalent ratio of 0.5 to 1.5 with respect to the carbonyl group contained in the copolymer (A). An aqueous coating composition, characterized in that: The amount of the water-soluble carbonyl group-containing unsaturated monomer in the above-mentioned radical polymerizable unsaturated monomer is 10
It is preferably 0.1 to 20% by weight in 0 parts.

Further, the emulsifier used in the emulsion polymerization of the radically polymerizable unsaturated monomer is a reactive emulsifier having a radically polymerizable unsaturated double bond in the molecule. 0.1 parts reactive emulsifier per part by weight
It is preferably from 10 to 10 parts by weight.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below, but the present invention is not limited to the following description.

The present invention is characterized in that a water-soluble unsaturated monomer containing a carbonyl group is used. Copolymers rich in carbonyl group-containing unsaturated monomers can be present. As a result, when water evaporates after coating, the hydrazide compound dissolved in water can be easily crosslinked on the coating film surface,
The paint can be prevented from flowing out upon contact with water. Conversely, when an oil-soluble unsaturated monomer containing a carbonyl group is used, a large amount of the copolymer containing a large amount of the unsaturated monomer containing a carbonyl group is present in the particles, and the cross-linking reaction on the surface of the coating film is slowed to dry. Sex tends to be slow.

The unsaturated carbonyl group-containing monomer used in the present invention includes diacetone acrylamide,
It can be selected from one or more of diacetone methacrylamide, acrolein, N-vinylformamide and the like.

The water-soluble unsaturated monomer having a carbonyl group is contained in an amount of 0.1 to 2 per 100 parts of the radically polymerizable unsaturated monomer.
It is desirably 0% by weight. When the content of the water-soluble carbonyl group-containing unsaturated monomer is less than 0.1%, the effect of drying property of the obtained aqueous coating composition is hardly observed.
On the other hand, when it is more than 20%, the polymerization stability and the storage stability are deteriorated, and at the same time, the water resistance tends to be inferior due to the increase of the hydrophilic functional groups.

The radically polymerizable unsaturated monomers used in the present invention include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate,
Acrylates such as isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, dodecyl acrylate, methyl methacrylate, Propyl methacrylate,
Methacrylates such as n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, decyl methacrylate, dodecyl methacrylate, styrene, Styrene-based monomers such as vinyl toluene, 2-methylstyrene, t-butylstyrene, chlorostyrene, hydroxy-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, N-methylol Acrylamide, N-butoxymethylacrylamide, N
-Methyl methacrylamide, N-substituted acrylics such as N-butoxymethyl methacrylamide, methacrylic monomers, glycidyl acrylate, epoxy group-containing monomers such as glycidyl methacrylate, and one or more selected from acrylonitrile and the like. Can be.

Furthermore, polymerizable unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and their anhydrides maintain the storage stability during polymerization or in the aqueous resin dispersion. Therefore, it is preferable to use them together. For this purpose, polymerizable unsaturated carboxylic acids can be used in an amount of 0.05 to 5% by weight, based on the total monomers.

The aqueous coating composition is acidic and has a pH of from 2 to
7 is desirable. More preferably, it is 4-6.5.
Is preferred. When emulsion-polymerizing a radical-polymerizable unsaturated monomer, it is preferable to use a polymerizable unsaturated carboxylic acid and an anhydride thereof for maintaining the storage stability of the aqueous resin dispersion as described above. As mentioned above, this causes the pH of the aqueous resin dispersion to be on the acidic side. Generally, ammonia and organic amines are added to make them alkaline. However, in the aqueous coating composition of the present invention, a part of the acid may be neutralized with ammonia and organic amines after emulsion polymerization or during coating. Is performed in a range where the pH does not exceed 7. When the pH exceeds 7, the rate of crosslinking becomes slow, and the drying property is poor from the prior art. If the pH is 2 or less, a problem occurs in the stability of the coating.

As described above, when neutralizing, ammonia or alkylamines such as trimethylamine, triethylamine and butylamine, alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine and aminomethylpropanol, and morpholine Can be neutralized.

The reactive emulsifier of the present invention has one or more radically polymerizable unsaturated groups in the molecule, and is, for example, a sulfosuccinate ester (a commercially available product such as Latemul S-120 manufactured by Kao Corporation, S-180P, S
-180A, Sanyo Kasei Co., Ltd. Eleminor JS-2
And alkylphenol ethers (commercially available, for example, Aqualon HS-1 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
0, RN-20, etc.). At the time of emulsion polymerization, one or more of these may be mixed. When the amount of the reactive emulsifier used is small and the emulsification is insufficient, a non-reactive emulsifier can be used in combination, if necessary. As the non-reactive emulsifier, an anionic or nonionic emulsifier used in ordinary emulsion polymerization can be used.

The reactive emulsifier is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 7 parts by weight, per 100 parts by weight of the unsaturated monomer.
Use parts by weight. If the amount is less than 0.1 part by weight, the emulsion has poor stability at the time of polymerization and aggregation is likely to occur. When the amount is more than 10 parts by weight, the particle size becomes small, but since a large amount of emulsifier is used, the water resistance of the coating film is deteriorated as an adverse effect.

As the initiator used in the emulsion polymerization, an inorganic peroxide polymerization initiator such as ammonium peroxide and sodium peroxide and a water-soluble azo initiator are used. These initiators can be used alone, or may be used in a redox type in combination with a reducing agent such as sodium ersorbate.

During the emulsion polymerization, transition metal ions such as copper ions such as cupric sulfate and cupric chloride, and iron ions such as ferric sulfate and ferric chloride are ^added to the polymerization system in an amount of 10 ⁻⁷ to 10 ⁻⁷ . It can be added in the range of 10 ^-5 mol / l.

Further, sodium acetate, sodium citrate, sodium bicarbonate and the like are used as buffers, polyvinyl alcohol and water-soluble cellulose derivatives are used as protective colloids, and mercaptans such as stearyl mercaptan and t-dodecyl mercaptan are used as chain transfer agents. Can be used.

The aqueous coating composition of the present invention contains a hydrazide compound containing two or more hydrazide groups in the molecule as a crosslinking agent. As for the method of addition, a water-soluble substance may be added as it is or after dilution with water. Oil-soluble ones are not so preferred in view of the form of the present invention, but when used, it is better to emulsify with a surfactant and add as necessary.

Examples of the hydrazide compound include aliphatic hydrazides such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, and sebacic acid dihydrazide; Aromatic bissemicarbazide, aromatic dicarboxylic acid dihydrazide,
Examples include polyhydrazide of polyacrylic acid, dihydrazide of aromatic hydrocarbon, hydrazine-pyridine derivative, and dihydrazide of unsaturated dicarboxylic acid such as maleic dihydrazide.

The hydrazide compound containing two or more hydrazide groups in the molecule is preferably blended at a ratio of 0.5 to 1.5 equivalents to 1 equivalent of the carbonyl group. When the hydrazide group is less than 0.5 equivalent, the effect of drying property of the aqueous coating composition is poor. On the other hand, if it is more than 1.5 equivalents, the water resistance of the resulting coating film tends to be poor.

The aqueous coating composition of the present invention comprises a colorant such as a pigment and a dye, a filler, a thixotropic agent such as finely divided silica, colloidal silica, and alumina sol.
Polyvinylpyrrolidone, polyvinyl alcohol, water-soluble polyester resin, water-soluble or water-dispersible polyurethane resin, emulsifier, defoamer, leveling agent, slip agent, tackifier, preservative, fungicide, film-forming aid An organic solvent or the like is blended as needed.

The aqueous coating composition of the present invention can be used mainly as a paint for architectural exterior walls, but can be used as a printing ink, a coating agent, a paint, an adhesive, a paper material, a fiber material, etc. , Plastic, metal, glass, ceramics, wood, concrete, slate, non-woven fabric, leather,
It can be applied to a base material such as synthetic leather and dried at room temperature or a low temperature of 120 ° C. or lower.

[0026]

The present invention will be described below with reference to examples. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

Production Example 1 In a reaction vessel equipped with a thermometer, a dropping funnel, a reflux condenser, and purged with nitrogen gas, the amount of ion-exchanged water shown in Table 1 was charged. The dropping amounts in Table 1 are mixed in advance to prepare a pre-emulsion. After the internal temperature was raised to 80 ° C., dropping was started. While maintaining the internal temperature at 80 ° C., the pre-emulsion was added dropwise over 3 hours, and further reacted at that temperature for 2 hours. After cooling, solid content 51.0%, viscosity 2100 cps,
An aqueous resin dispersion having a pH of 2.2 was obtained.

[0028]

[Table 1]

Production Examples 2 to 5 The compositions shown in Table 2 were polymerized in the same manner as in Production Example 1 to obtain respective aqueous resin dispersions.

[0030]

[Table 2]

Examples 1 to 9

Further, paints shown in Table 3 were prepared using the obtained aqueous resin dispersions of Production Examples 1 to 5, and the physical properties of the coating films were evaluated. The coating is made according to the following formulation. The evaluation of the physical properties of the coating film is also shown below. Table 3 also shows the physical property results of the samples obtained in each test.

Paint Formulation 1. 370 parts of aqueous resin dispersion 2. Primal ASE60 (Nippon Acrylic Co., Ltd. thickener) 4 parts 3. Butyl carbitol 30 parts 4. Sannopco SN-364 (antifoaming agent) 5 parts Ion exchange water 10 parts 6. Adipic dihydrazide (crosslinking agent) 7.25% aqueous ammonia (for pH adjustment)

[0034]

[Table 3]

Evaluation of Aqueous Resin Dispersion and Coating (1) Polymerization Stability: The amount of resin adhered to the reaction vessel after the completion of the reaction and the amount of aggregates after filtration with a filter cloth were visually evaluated. The evaluation criteria are as follows. ◎: good. ：: This is a level having no practical problem. Δ: The level is slightly problematic. ×: Poor.

(2) Storage stability: The aqueous resin solution was placed in a closed glass container and stored at 40 ° C. for one month, and the rate of change in viscosity was measured. Further, the aggregate at the bottom of the glass container was visually evaluated. The evaluation criteria are as follows. A: Viscosity change rate ≤ ± 10%, no agglomerate observed. ：: Viscosity change rate ≦ ± 10%, and slight aggregation is observed. Δ: Viscosity change rate ± 10% to ± 30%, or some aggregates were observed. ×: Change in viscosity ≧ ± 30% or considerable sedimentation is observed.

(3) Water Whitening Resistance: The coating film prepared above was applied to a glass plate with an applicator and dried at room temperature for 7 days, and the coating film obtained was immersed in warm water at 50 ° C. for 1 hour. The degree of whitening was visually evaluated. In addition, evaluation was performed by five-point evaluation. 5 points: No whitening. 1 point: Significant whitening is observed on the entire surface.

(4) Quick-drying property: The above-prepared paint is applied on a glass plate with an applicator, and then dried at a temperature of 5 ° C. and a humidity of 90%. Water was contacted at intervals of 5 minutes, and the evaluation was made based on the time when the paint stopped flowing.

[0039]

According to the present invention, storage stability is good,
After the coating, the coating is dried for 30 minutes under conditions of a temperature of 5 ° C. and a humidity of 90%, and an aqueous coating composition having an extremely fast drying property in which the coating does not flow out upon contact with water can be obtained. This water-based coating composition can form a coating having excellent coating properties such as excellent water resistance, substrate adhesion, stain resistance, and film forming property, and is particularly useful as a coating for building exterior walls.

Claims (3)

[Claims] 1. A copolymer (A) obtained by emulsion polymerization of a radically polymerizable unsaturated monomer containing a water-soluble carbonyl group-containing unsaturated monomer, and the copolymer (A) An aqueous coating composition obtained by adding a hydrazide compound (B) having an equivalent ratio of 0.5 to 1.5 with respect to a carbonyl group contained therein, wherein the solution is acidic. 2. The amount of the water-soluble carbonyl group-containing unsaturated monomer in the radical polymerizable unsaturated monomer is 0.1 to 20% by weight based on 100 parts of the radical polymerizable unsaturated monomer. The aqueous coating composition according to claim 1, wherein: 3. An emulsifier used for emulsion polymerization of a radically polymerizable unsaturated monomer is a reactive emulsifier having a radically polymerizable unsaturated double bond in a molecule thereof. 0.1 to 10 parts by weight of reactive emulsifier
3. The aqueous coating composition according to claim 1, wherein the aqueous coating composition is in parts by weight.