JP2000264927A - Aqueous dispersion of alkali-soluble resin and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aqueous dispersion of an alkali-soluble resin capable of affording a coating film good in dispersibility of a pigment and excellent in water resistance, smoothness and glossiness by an emulsion polymerization, to provide a method for producing the aqueous dispersion and to produce an aqueous coating composition using the aqueous dispersion. SOLUTION: This aqueous dispersion comprises (I) an alkali-soluble resin prepared by copolymerizing (A-1) 5-60 wt.% of an ethylenically unsaturated carboxylic acid unit with (A-2) 40-95 wt.% of an unsaturated monomer unit copolymerizable therewith. The alkali soluble resin (I) has <=0.15 μm average particle diameter and a weight-average molecular weight within the range of 1,000-50,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an aqueous solution of an alkali-soluble resin which can be easily dissolved at the time of addition of an alkali, and has a good pigment dispersibility and can form a coating film having excellent water resistance, smoothness and gloss. The present invention relates to a dispersion, a method for producing the same, and an aqueous coating composition using the same.

[0002]

2. Description of the Related Art A pigment dispersant is generally used when compounding a pigment with various aqueous resin compositions for coatings. As general pigment dispersants, for example, polyphosphates such as sodium tripolyphosphate, sodium tetraphosphate and sodium hexametaphosphate, formalin condensate of sodium alkylnaphthalenesulfonate, low molecular weight polyacrylic acid or low molecular weight (acrylic acid-acrylic acid) Acid ester) ammonium or sodium salt of the copolymer,
Polymer electrolytes such as ammonium salt or sodium salt of a low molecular weight (styrene-maleic acid) copolymer are exemplified.

The synthesis of such a polymer electrolyte pigment dispersant is generally carried out in a homogeneous solution such as aqueous solution polymerization or solution polymerization. However,
Aqueous solution polymerization is limited to polymerization of water-soluble monomers only, and has the disadvantage of narrowing the range of molecular design. Also,
Solution polymerization is easy to design because there are many types of monomers that can be applied, but it requires environmental problems due to the use of organic solvents and complicated steps of removing the polymerization solvent and replacing with water. Have the disadvantage of

[0004] As a heterogeneous polymerization method, there is suspension polymerization or emulsion polymerization. In these heterogeneous polymerization methods, it has been difficult to polymerize a composition containing a large amount of a hydrophilic component, particularly an ethylenically unsaturated carboxylic acid such as acrylic acid or methacrylic acid. Because the hydrophilic component is
In general, the probability of being subjected to polymerization in water in addition to polymerization in monomer droplets acting as a polymerization field or in micelles of an emulsifier increases. As a result, the polymerization reaction becomes unstable and the composition of the polymer becomes non-uniform. Naturally, such a resin having a non-uniform composition has low solubility upon addition of an alkali,
Since the dispersibility of the pigment was low, it was not suitable as a pigment dispersant. Thus, the synthesis of the polymer electrolyte pigment dispersant has various problems.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to an alkali-soluble polymer which can provide a coating film having good pigment dispersibility and excellent water resistance, smoothness and gloss by emulsion polymerization, which has been considered difficult. An object of the present invention is to provide an aqueous dispersion of a resin, a method for producing the same, and an aqueous coating composition using the same.

[0006]

The invention according to claim 1 is characterized in that 5 to 60% by weight of an ethylenically unsaturated carboxylic acid (A-1) unit and 40 to 40% by weight of an unsaturated monomer (A-2) unit copolymerizable therewith. An aqueous dispersion containing an alkali-soluble resin (I) obtained by copolymerizing 95% by weight of the alkali-soluble resin (I).
Is an aqueous dispersion of an alkali-soluble resin having an average particle size of 0.01 to 0.15 μm and a weight average molecular weight in a range of 1,000 to 50,000.

According to the present invention, the alkali-soluble resin (I) contains the specific range of the amount of the ethylenically unsaturated carboxylic acid (A-1) unit, and the average particle size of the alkali-soluble resin (I) And the weight average molecular weight are in the above specific range. Therefore, the alkali-soluble resin (I) easily dissolves in the added alkali, and a water-soluble resin having a highly uniform resin composition can be obtained. Therefore, when the alkali-soluble resin (I) is used as a pigment dispersant, the dispersibility of the pigment is improved. Further, a coating film having excellent water resistance, smoothness and glossiness can be obtained. Hereinafter, these will be described in detail.

[0008] The aqueous dispersion of the present invention, as described above,
An alkali-soluble resin obtained by copolymerizing 5 to 60% by weight of an ethylenically unsaturated carboxylic acid (A-1) unit and 40 to 95% by weight of an unsaturated monomer (A-2) unit copolymerizable therewith ( I).

The above ethylenically unsaturated carboxylic acid (A-
1) may be a monocarboxylic acid or a dicarboxylic acid, but is preferably a monoolefinic unsaturated carboxylic acid having 3 to 5 carbon atoms. Among them, acrylic acid, methacrylic acid and itaconic acid are particularly preferred.

The proportion of the ethylenically unsaturated carboxylic acid (A-1) unit in the alkali-soluble resin (I) is 5 to 60% by weight. If the amount is less than 5% by weight, the solubility of the alkali-soluble resin (I) at the time of adding the alkali is low, and the dispersibility of the pigment is lowered. On the other hand, if it exceeds 60% by weight, the stability of the aqueous dispersion containing the alkali-soluble resin (I) is extremely reduced, causing thickening and phase separation, and when used as a pigment dispersant, The water resistance of the obtained coating film becomes extremely low.

Preferably, the ethylenically unsaturated carboxylic acid (A-1) unit in the alkali-soluble resin (I) is 20 to 50% by weight. Thereby, pigment dispersibility and stability are improved, and the water resistance of the obtained coating film is further improved.

The content of the unsaturated monomer (A-2) unit in the alkali-soluble resin (I) is from 40 to
95% by weight. If the amount is less than 40% by weight, the stability of the aqueous dispersion containing the alkali-soluble resin (I) is extremely lowered, causing thickening and phase separation, and the use of the aqueous dispersion as a pigment dispersant. In addition, the water resistance of the obtained coating film becomes extremely low. If it exceeds 95% by weight, the solubility of the alkali-soluble resin (I) at the time of adding an alkali is low, and the dispersibility of the pigment is lowered.

The unsaturated monomer (A-2) unit is not particularly limited as long as it can be copolymerized with the ethylenically unsaturated carboxylic acid (A-1) unit. There is. C1-C18 alkyl esters of acrylic acid or methacrylic acid (for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, Butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate);

Vinyl aromatics such as styrene, 4-methylstyrene, α-methylstyrene; saturated vinyl esters of carboxylic acids such as vinyl acetate and vinyl propionate; monoolefinically unsaturated carboxylic acid amides (for example,
Acrylamide, methacrylamide, etc.) N-alkyl and / or N-alkylol derivatives of monoolefinically unsaturated carboxylic acid amides (for example, N-
Methylacrylamide, N-methylolacrylamide, N-methylolacrylamide, etc.);

An unsaturated monomer containing an ald group or a keto group (eg, acrolein, diacetone acrylamide, vinyl methyl ketone, etc.); a monoolefinically unsaturated sulfonic acid (eg, vinyl sulfonic acid, methyl acrylamide propane sulfone) acid)
And salts thereof;

An adduct of polyethylene glycol and methacrylic acid (Blemmer PE series: trade name, manufactured by NOF Corporation); an adduct of polypropylene glycol and methacrylic acid (Blemmer PP series: trade name, manufactured by NOF Corporation); A diolefinically unsaturated monomer (such as 1,4-diacryloxybutane or divinylbenzene);

Acrylonitrile; hydroxyethyl acrylate; hydroxyethyl methacrylate; hydroxypropyl acrylate; hydroxypropyl methacrylate; glycidyl methacrylate; vinylidene chloride; vinyl chloride;

Among these, the above-mentioned monoolefinically unsaturated sulfonic acid or a salt thereof is used in the synthesis of the above-mentioned alkali-soluble resin (I).
It is effective in reducing the particle size of the particles and providing stable particles. The proportion of the monoolefinically unsaturated sulfonic acid or its salt in the alkali-soluble resin (I) is 0.1%.
It is preferably from 0.5 to 1% by weight. When the amount is less than 0.05% by weight, the effect is low. When the amount exceeds 1% by weight, the stability of the alkali-soluble resin (I) is rather impaired, and when the resin is used as a pigment dispersant. The water resistance of the coating film may be reduced.

Further, as in the invention of claim 4, the unsaturated monomer (A-2) unit is a carbonyl group-containing unsaturated monomer containing an ald group or a keto group (A-2-
1) The above carbonyl group-containing unsaturated monomer (A-2-1) unit in the alkali-soluble resin (I), which comprises two or more types of unsaturated monomer units having a unit as an essential component. Is preferably 1 to 30% by weight.

In this case, the water resistance of the coating film formed using the alkali-soluble resin containing (A-2) is further improved. As described below, the coating film is prepared by adding the alkali-soluble resin to an aqueous resin solution by adding an alkali, adding a pigment and an alkali-insoluble resin aqueous dispersion to this, and then preparing an aqueous coating composition. The aqueous coating composition has at least two hydrazino groups (—NH
It is obtained by adding a hydrazine derivative having NH ₂ ) and forming a film.

On the other hand, in the alkali-soluble resin (I), the carbonyl group-containing unsaturated monomer (A-2-
1) When the content ratio of the unit is less than 1% by weight, the crosslinking density with the hydrazine derivative decreases, and the effect of improving the water resistance decreases. If it exceeds 30% by weight, the balance between hydrophilicity and hydrophobicity of the alkali-soluble resin (I) is lost, and the dispersibility of the pigment is reduced.

As the carbonyl group-containing unsaturated monomer (A-2-1) unit containing an ald group or keto group, for example, acrolein, diacetone acrylamide and vinyl methyl ketone can be used.

The average particle size of the alkali-soluble resin (I) is 0.01 to 0.15 μm. 0.15
If it exceeds μm, the uniformity of the composition of the alkali-soluble resin (I) decreases, and the solubility with alkali decreases. This lowers the dispersibility of the pigment. If it is less than 0.01 μm, there is a problem that the stability of the aqueous dispersion containing the alkali-soluble resin (I) is reduced.

Preferably, the alkali-soluble resin (I) has an average particle size of 0.1.
01 to 0.1 μm. This further improves the dispersibility of the pigment in the alkali-soluble resin (I). In the present invention, the “average particle size” refers to a weight average particle size measured by a dynamic light scattering method.

The weight average molecular weight of the alkali-soluble resin (I) is from 1,000 to 50,000. When it is smaller than 1000, the steric stability of the alkali-soluble resin (I) as a pigment dispersant is reduced, and the dispersibility of the pigment in the alkali-soluble resin (I) is reduced. 50
If it exceeds 000, the solubility at the time of addition of an alkali decreases, and the action as a flocculant becomes strong, so that the dispersibility of the pigment decreases.

The aqueous dispersion of the alkali-soluble resin of the present invention is made into an aqueous resin solution by adding an alkali, as described later, and then a pigment and an alkali-insoluble resin aqueous dispersion are added thereto, followed by coating and drying. As a result, a coating film is formed.

The method for producing the aqueous dispersion of the alkali-soluble resin (I) is as follows.
An unsaturated monomer mixture (A) comprising 5 to 60% by weight of an ethylenically unsaturated carboxylic acid (A-1) unit and 40 to 95% by weight of an unsaturated monomer (A-2) unit copolymerizable therewith. )
Is produced by emulsion polymerization in water in the presence of an emulsifier (B) and a chain transfer agent (C).

In the present production method, the unsaturated monomer mixture (A) comprises 5 to 60% by weight of an ethylenically unsaturated carboxylic acid (A-1) unit and an unsaturated monomer (A) copolymerizable therewith. -2) Units consisting of 40 to 95% by weight, which are the same as the monomers of the alkali-soluble resin in the aqueous dispersion.

Various methods can be used to supply the unsaturated monomer mixture (A) into the polymerization vessel. For example, various methods such as a batch charging method, a monomer addition method, and an emulsion addition method are used.

As the emulsifier (B) used for the emulsion polymerization,
For example, anionic surfactants and reactive emulsifiers such as sulfates of higher alcohols, higher alkyl sulfonates, alkylbenzene sulfonates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phenol ether sulfates, and vinyl sulfosuccinates. Used. Polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, ethylene oxide propylene oxide block copolymer,
Nonionic surfactants such as sovitan derivatives can also be used.

Generally, the particle size of the aqueous resin obtained by emulsion polymerization depends on the amount of the emulsifier, and can be made finer by increasing the amount of the emulsifier. However, the use of a large amount of emulsifier reduces the water resistance of the finally obtained coating film.

As described in the sixth aspect of the present invention, the emulsifier (B) preferably contains a higher alcohol sulfate or a higher alkyl sulfonate. In this case, even in the polymerization of a monomer mixture containing a large amount of unsaturated carboxylic acid monomers, an alkali-soluble resin (I) having a small amount of an emulsifier and having a stable and fine particle size can be obtained. Preferably, the higher alcohol has 8 to 18 carbon atoms, and the higher alkyl has 8 to 18 carbon atoms.

Chain transfer agent (C) used during emulsion polymerization
As mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan; methyl thioglycolate, propyl thioglycolate, thioglycolic acid 2
Thioglycolic acid esters such as ethylhexyl; β-
Β-mercaptopropionate such as methyl mercaptopropionate and octyl β-mercaptopropionate; α-methylstyrene dimer;

In particular, as described in the seventh aspect of the present invention, the chain transfer agent (C) preferably contains an α-methylstyrene dimer. Although the reason is not well understood, in this case, the particle size of the obtained alkali-soluble resin (I) can be made finer. In particular, when polymerizing the unsaturated monomer mixture (A) in which the proportion of the ethylenically unsaturated carboxylic acid is 25% by weight or more, the particle size of the alkali-soluble resin (I) is further reduced.

Examples of the polymerization initiator used in the emulsion polymerization include persulfates such as potassium persulfate and sodium persulfate;
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.

The method of adding the polymerization initiator includes a method in which an aqueous solution of the polymerization initiator is added to the reaction mother liquor in advance and a method in which the aqueous solution of the polymerization initiator is continuously added over time. However, from the viewpoint of reducing the particle size of the alkali-soluble resin (I), the former method is more preferable.

An eighth aspect of the present invention is an aqueous coating composition comprising an aqueous resin aqueous solution obtained by neutralizing the alkali-soluble resin (I) with an alkali, a pigment, and an aqueous resin dispersion. It is.

According to the present composition, as described in the above alkali-soluble resin (I), a coating film having excellent water resistance, smoothness and gloss can be provided.

The aqueous resin aqueous solution is obtained by neutralizing the alkali-soluble resin (I) with an alkali, and is alkali-soluble. Examples of the alkali used for neutralization of the alkali-soluble resin (I) include inorganic water-soluble alkalis (eg, sodium hydroxide, potassium hydroxide, etc.); inorganic salts which dissolve in water and show alkalinity (eg, sodium hydrogen carbonate) , Sodium pyrophosphate, etc.); organic amines (eg, triethylamine, N, N
-Dimethylethanolamine, triethanolamine, etc.); ammonia and the like. Among these,
Ammonia is preferred in terms of water resistance and workability.

The amount of the aqueous resin solution added was 10
The non-volatile content must be in the range of 0.05 to 5% by weight with respect to 0% by weight. If the content is less than 0.05% by weight, the pigment dispersibility is significantly reduced, the viscosity of the pigment paste is increased, and the gloss of the coating film is reduced. If the content is more than 5% by weight, the dispersibility of the pigment is reduced and the water resistance is remarkably reduced because the aqueous resin exhibits a function as a flocculant. More preferably, the amount of the aqueous resin solution added is 0.2 to 3% by weight in terms of non-volatile content based on 100% by weight of the pigment. Thereby, pigment dispersibility, water resistance, and glossiness are further improved.

The pigment may be either an organic pigment or an inorganic pigment, or both pigments may be used in combination. In addition, both the extender and the color pigment can be used, and both can be used in combination. Specific examples of pigments include calcium carbonate, clay,
Inorganic pigments such as talc, mica powder, barite, finely divided silica, diatomaceous earth, calcium silicate, aluminum silicate, barium carbonate, magnesium carbonate; titanium oxide, zinc oxide, lithopone, carbon black, black iron oxide, loess , Yellow iron oxide, titanium yellow, red iron oxide, iron oxide powder, ultramarine blue, chromium oxide and other inorganic coloring pigments; Hiza yellow, permanent yellow, permanent red,
Organic coloring pigments such as phthalocyanine blue and phthalocyanine green are exemplified.

These pigments may be added directly to the aqueous resin dispersion described below, but generally, they are generally added to the aqueous resin dispersion as a pigment paste. In preparing the pigment paste, the above aqueous resin aqueous solution is used as a pigment dispersant. At this time, other pigment dispersants and thickeners can be used as long as the properties of the aqueous resin solution are not impaired.

The aqueous resin dispersion refers to an aqueous dispersion of an alkali-insoluble resin, which is different from an alkali-soluble aqueous resin aqueous solution in that it is alkali-insoluble.
As the resin aqueous dispersion, aqueous dispersions of various synthetic resins can be used, but an aqueous resin dispersion obtained by emulsion polymerization is preferable.

In particular, as described in the ninth aspect of the present invention, the aqueous resin dispersion contains 0.3 to 20% by weight of a carbonyl group-containing unsaturated monomer containing an ald group or a keto group and a copolymerizable with the same. Is an aqueous dispersion of a copolymer resin obtained by emulsion polymerization of an unsaturated monomer mixture consisting of 80 to 97.7% by weight of an unsaturated monomer, and the aqueous coating composition has Preferably contains a hydrazine derivative having at least two hydrazino groups (—NHNH ₂ ).

In this case, a cross-linking is generated between the resin particles of the aqueous resin dispersion using a hydrazine derivative as a medium. Thereby, the water resistance of the coating film is significantly improved. Further, as described above, when the carbonyl group-containing unsaturated monomer unit containing an ald group or a keto group is present in the alkali-soluble resin (I) of the aqueous resin aqueous solution, the water resistance is further improved. .

The unsaturated monomer mixture contains 0.3 to 20% by weight of a carbonyl group-containing unsaturated monomer containing an ald group or a keto group and 80 to 97% of an unsaturated monomer copolymerizable therewith. 0.7% by weight. When the content of the carbonyl group-containing unsaturated monomer in the unsaturated monomer mixture is less than 0.3% by weight, the crosslinking density with the hydrazine derivative decreases, and the effect of improving water resistance is low. When the content exceeds 20% by weight, there is a problem that the flexibility of the coating film is reduced and the coating film becomes brittle.

When the content of the unsaturated monomer copolymerizable with the carbonyl group-containing unsaturated monomer in the unsaturated monomer mixture is less than 80% by weight, the durability of the coating film is reduced. Is reduced, and 97.7
If the content exceeds 10% by weight, there is a problem that the effect of improving water resistance is reduced.

As the carbonyl group-containing unsaturated monomer containing an ald group or keto group, for example, acrolein, diacetone acrylamide, vinyl methyl ketone can be used.

The unsaturated monomer copolymerizable with the carbonyl group-containing unsaturated monomer containing an ald group or keto group is a component (A-1) of the alkali-soluble resin (I). And the same monomers as in (A-2).

Examples of the hydrazine derivative having at least two hydrazino groups (—NHNH ₂ ) in the above molecule include the following. Dicarboxylic acid dihydrazides having 2 to 10, especially 4 to 6 carbon atoms (eg oxalic acid dihydrazide,
Malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, etc.), aliphatic water-soluble dihydrazide having 2 to 4 carbon atoms ( For example, ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, butylene-1,4-dihydrazine, etc.).

Further, all carbonyl groups (> C ＝ O) based on ald groups or keto groups contained in the resin contained in the aqueous resin aqueous solution and the aqueous resin dispersion and the hydrazino group (—NHNH ₂ ) of the hydrazine derivative are used. number of moles of, namely (> C = O) / - the molar ratio of (NHNH ₂₎ is preferably in the range of 0.2 to 5.0. If the molar ratio is greater than 5.0, crosslinking may be insufficient, and the water resistance and durability of the coating film may decrease. If it is lower than 0.2, the coating film may be opaque and brittle, and the water resistance may be reduced.

The coating composition is applied to an adherend and dried to form a coating film.

Since the aqueous coating composition of the present invention provides a coating film having excellent water resistance and smoothness, it can be used as an aqueous paint, a sealing agent, an adhesive, an adhesive, a paper processing material, or a raw material for producing them. Can be used.

[0054]

BEST MODE FOR CARRYING OUT THE INVENTION The alkali-soluble resin (I) and the aqueous resin dispersion will be described in detail below with reference to production examples, examples and comparative examples. In these examples,
Means parts by weight, and% means "% by weight".

[Production Example 1 of Alkali-Soluble Resin (I)]
Temperature controller, irrigated stirrer, reflux cooler, supply vessel,
An emulsifier aqueous solution comprising the following composition was introduced into a reaction vessel equipped with a thermometer and a nitrogen inlet tube.・ Water ・ ・ ・ 100 parts ・ 30% aqueous solution of sodium dodecyl sulfonate (hereinafter referred to as emulsifier B-1 aqueous solution) ・ ・ ・ 3 parts Separately, a mixture of the following composition was prepared as feeds (1) and (2). .

Feed (1) Water 100 parts Emulsifier B-1 aqueous solution 2 parts Diacetone acrylamide 10 parts Acrylic acid 30 parts Methyl methacrylate 20 parts ・ Methyl acrylate ・ ・ ・ 15 parts ・ Butyl acrylate ・ ・ ・ 25 parts ・ Sodium vinyl sulfonate ・ ・ ・ 0.1 parts ・ Octyl thioglycolate (OTG) ・ ・ ・ 3 parts ・ α-methylstyrene Oligomer (MSD) ... 0.
5 copies

Feed (2) Aqueous solution of 1.5 parts of sodium persulfate dissolved in 35 parts of water

After the inside of the reaction vessel into which the above aqueous solution of the emulsifier was introduced was replaced with nitrogen gas, the reaction vessel was heated to 80.degree. Then,
After the entire amount of the feed (2) was added and the temperature was raised to 85 ° C., the feed (1) was gradually and uniformly fed over 2 hours to carry out polymerization. 1.5 hours after the end of the supply 85
C. to complete the emulsion polymerization.

The aqueous dispersion of the obtained alkali-soluble resin (I) had a nonvolatile content of 30% and a weight average particle size (measured by a dynamic light scattering particle size measuring device manufactured by Otsuka Electronics Co., Ltd.) of 0.06 μm.
Met. The weight-average molecular weight (in terms of polystyrene) of the aqueous resin measured by gel permeation chromatography (GPC) was about 10,000.

[Production example 2 of alkali-soluble resin (I)
10] Table 1 shows the types and amounts of the monomer, emulsifier, and chain transfer agent used in Production Example 1 of alkali-soluble resin (I).
The aqueous dispersion of the alkali-soluble resin (I) was prepared in the same manner as in Production Example 1 of the alkali-soluble resin (I) except for the following changes. The nonvolatile content, the weight average particle size, of the aqueous dispersion of each alkali-soluble resin (I),
The weight average molecular weights are summarized in Tables 1 and 2.

[Production Example 1 of Aqueous Resin Dispersion] An emulsifier aqueous solution comprising the following composition was introduced into the same apparatus as in Production Example 1 of the alkali-soluble resin (I). 43 parts of water 35% aqueous solution of sulfuric acid half ester salt of p-nonylphenol added with 20 mol of ethylene oxide (hereinafter referred to as emulsifier B-3)
2.2 parts ・ 20% aqueous solution of p-nonylphenol added with 25 moles of ethylene oxide (hereinafter referred to as emulsifier B-4 aqueous solution)
・ 2.2 parts Separately, a mixture having the following composition was prepared as feeds (1) and (2).

Feed (1) Water 43 parts Emulsifier B-3 aqueous solution 6.5 parts Diacetone acrylamide 2.5 parts Acrylic acid 2.5 parts Methyl methacrylate: 52 partsButyl acrylate: 43 parts

Feed (2) An aqueous solution in which 0.5 part of potassium persulfate is dissolved in 18 parts of water

After replacing the inside of the reaction vessel into which the above-mentioned emulsifier aqueous solution was introduced with nitrogen gas, 10% of the above-mentioned feed (1) was added.
Was added and the mixture was heated to 85 ° C. Next, 10% of the feed (2) was added, and while maintaining the same temperature, the remaining feeds (1) and (2) were gradually and uniformly fed over 3.5 hours to carry out polymerization. . After the completion of the supply, the emulsion polymerization was maintained at 85 ° C. for 1.5 hours to complete the emulsion polymerization.

After the completion of the emulsion polymerization, the pH was adjusted to pH 8 by adding 25% aqueous ammonia to obtain an aqueous resin dispersion. The nonvolatile content of this aqueous dispersion was 47%.

[Production Examples 2 and 3 of Aqueous Resin Dispersion] An aqueous resin dispersion was prepared in the same manner as in Production Example 1 of the aqueous resin dispersion except that the monomer composition was changed to the composition shown in Table 3. did. Table 3 summarizes the nonvolatile content of the obtained resin dispersion.

Next, examples and comparative examples of the aqueous coating composition according to the present invention will be described.

Examples 1 to 8 and Comparative Examples 1 to 4 Preparation of Alkali-Soluble Resin (I) The alkali shown in Table 4 was added to the aqueous dispersion of the alkali-soluble resin (I) obtained in Examples 1 to 11. An aqueous resin solution was prepared by adding water so that the pH became 8, and further adding water so that the solid content became 26%. Using the prepared aqueous resin solution as a pigment dispersant, a pigment paste was prepared by the following method.

Method for preparing pigment paste: Water: 40 parts 28% ammonia water: 0.5 parts Aqueous resin solution (26% aqueous solution): 0.8 parts Defoaming agent (Sannopco) SN deformer 315)
..1 part ・ Titanium oxide ・ ・ ・ 50 parts were mixed in this order, and mixed by a disper for 30 minutes.

To 50 parts of the obtained pigment paste, 100 parts of an aqueous resin dispersion shown in Tables 4 and 5 and Texanol / benzyl alcohol [1/1] as a film-forming aid were used.
(W / w)] was added so that the minimum film-forming temperature (MFT) of the water-based paint would be 0 ° C., and 0.5 part of a thickener (SN Thickener 612 manufactured by San Nopco) and adipate dihydrazide were further added. The amounts shown in Tables 4 and 5 were blended to obtain aqueous coating compositions.

With respect to these water-based paints, the following tests were conducted on the gloss of the coating film, the water resistance of the coating film, and the salt spray resistance of the coating film. (A) Film gloss The aqueous coating composition was applied to a glass plate to a thickness of 150 μm wet (undried), at 20 ° C. and 65% RH.
After drying for 48 hours at 60 °, the 60 ° specular gloss (%) was measured.

(B) Water resistance of the coating film The aqueous coating composition was coated on a flexible plate (150 × 7
0mm) twice with a brush, 7 ° C at 20 ° C and 65% RH.
The specimen was dried for days. After immersing this test piece in water for 7 days, the 60 ° specular gloss was measured,
° Gloss retention was determined from the ratio to the specular gloss and evaluated according to the following criteria.・ ◎ ・ ・ ・ Gloss retention of 90% or more ・ ○ ・ ・ ・ Gloss retention of 80% or more ・ △ ・ ・ ・ Gloss retention of 60% or more ・ × ・ ・ ・ Gloss retention of less than 60%

Further, the state of blister generation in the coating film after immersion was visually inspected and evaluated according to the following criteria.・ ○ ・ ・ ・ Blister is not recognized at all ・ △ ・ ・ ・ Blister is partially recognized ・ × ・ ・ ・ Blister is recognized over the entire surface

(C) Salt water spray resistance The aqueous coating composition was applied to a mild steel sheet to a thickness of 150 μm wet (undried), dried at 20 ° C. and 65% RH for 5 days, and then JIS Z2371 The salt spray test was performed for 8 hours and 24 hours using the specified spray device under the use conditions specified in JIS K 5400 9.1, and the rust (rust) generation state was evaluated according to the following criteria.・ ○ ・ ・ ・ No rust is observed at all ・ △ ・ ・ ・ Rust is observed at a part ・ × ・ ・ ・ Rust is observed at the entire surface

The state of blister formation in the coating film after spraying with salt water was visually inspected, and evaluated according to the following criteria.・ ○ ・ ・ ・ Blister is not recognized at all ・ △ ・ ・ ・ Blister is partially recognized ・ × ・ ・ ・ Blister is recognized over the entire surface

The evaluation results of these water-based paints are shown in Tables 4 and 5.
And as shown in Table 6.

As known from Tables 4, 5 and 6,
Alkali-soluble resin according to the present invention (Examples 1 to 3)
Has a good balance of gloss, water resistance and salt spray resistance.
It turns out that it gives an excellent coating film.

[0078]

[Table 1]

[0079]

[Table 2]

[0080]

[Table 3]

[0081]

[Table 4]

[0082]

[Table 5]

[0083]

[Table 6]

[0084]

According to the present invention, an aqueous dispersion of an alkali-soluble resin which can provide a coating film having good pigment dispersibility and excellent water resistance, smoothness and gloss by emulsion polymerization. It is possible to provide a production method thereof, and an aqueous coating composition using the same.

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Claims (9)

[Claims] 1. An ethylenically unsaturated carboxylic acid (A-1)
An aqueous dispersion containing an alkali-soluble resin (I) obtained by copolymerizing 5 to 60% by weight of a unit and 40 to 95% by weight of an unsaturated monomer (A-2) unit copolymerizable therewith, The alkali-soluble resin (I) has an average particle size of 0.01
0.15 μm and weight average molecular weight of 1000-5
An aqueous dispersion of an alkali-soluble resin, wherein the aqueous dispersion is in the range of 0000. 2. The aqueous dispersion of an alkali-soluble resin according to claim 1, wherein the alkali-soluble resin (I) has an average particle size of 0.01 to 0.1 μm. 3. The alkali-soluble resin (I) according to claim 1, wherein the content of the ethylenically unsaturated carboxylic acid (A-1) unit in the alkali-soluble resin (I) is 20 to 50% by weight. An aqueous dispersion of an alkali-soluble resin. 4. The method according to claim 1, wherein:
The unsaturated monomer (A-2) unit is a carbonyl group-containing unsaturated monomer (A-
2-1) The alkali-soluble resin (I), which is composed of two or more types of unsaturated monomer units having a unit as an essential component, and
Wherein the carbonyl group-containing unsaturated monomer (A-2-
1) An aqueous dispersion of an alkali-soluble resin, wherein the content ratio of units is 1 to 30% by weight. 5. An ethylenically unsaturated carboxylic acid (A-1)
An unsaturated monomer mixture (A) consisting of 5 to 60% by weight of a unit and 40 to 95% by weight of an unsaturated monomer (A-2) unit copolymerizable therewith is mixed with an emulsifier (B) and a chain transfer agent ( A process for producing an aqueous dispersion of an alkali-soluble resin, which comprises carrying out emulsion polymerization in water in the presence of C). 6. The emulsifier (B) according to claim 5, wherein
Is a method for producing an aqueous dispersion of an alkali-soluble resin, which comprises a sulfate or higher alkyl sulfonate of a higher alcohol. 7. The method for producing an aqueous dispersion of an alkali-soluble resin according to claim 5, wherein the chain transfer agent (C) contains an α-methylstyrene dimer. 8. An aqueous coating comprising an aqueous resin aqueous solution, a pigment and an aqueous resin dispersion obtained by neutralizing the alkali-soluble resin (I) according to claim 1 with an alkali. Composition. 9. The resin aqueous dispersion according to claim 8, wherein the aqueous dispersion of the resin comprises 0.3 to 20% by weight of a carbonyl group-containing unsaturated monomer containing an ald group or a keto group and an unsaturated monomer copolymerizable therewith. Is an aqueous dispersion of a copolymer resin obtained by emulsion polymerization of an unsaturated monomer mixture consisting of 80 to 97.7% by weight of a copolymer, and the aqueous coating composition has at least two copolymers per molecule. Hydrazino group (-NHN
An aqueous coating composition comprising a hydrazine derivative having H ₂ ).