JPH0319245B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an aqueous resin dispersion used in a cold-curing aqueous coating composition. Prior Art Emulsion-type paints and water-soluble type paints are mainly used as cold-curable aqueous coating compositions. Emulsion type paints have a relatively high paint solids content and are also rich in thixotropic viscosity, making them suitable for thick film coating, and at the same time drying extremely quickly after coating. However, on the other hand, it has the disadvantage that so-called flash last occurs during the drying process after coating, and the gloss of the cured coating film is low. On the other hand, water-soluble paints are relatively less likely to cause flash rust and have excellent gloss, but they dry slowly, tend to sag during painting, and are difficult to coat with thick films. It has the disadvantage of being unsuitable. Purpose of the Invention The present invention eliminates the drawbacks of the existing room-temperature-curing aqueous coating compositions, combines the features of both types, suppresses the occurrence of flash last, improves the drying properties of the coating film, and improves gloss. An object of the present invention is to provide an aqueous resin dispersion for use in a cold-curable aqueous coating composition that has excellent properties and is suitable for thick film coating. Structure of the Invention The aqueous resin dispersion of the present invention consists of 100 parts of a copolymer resin of an α,β-ethylenically unsaturated acid and another polymerizable unsaturated monomer, and a mixture selected from drying oil fatty acids and semi-drying oil fatty acids. glycidyl esters of unsaturated fatty acids
It contains the following two types of resin (A) and resin (B) obtained by reacting 10 to 200 parts. Resin (A): 20 acid value 150, hydroxyl value 15-150, number average molecular weight 1000-200000 Resin (B): 0 acid value <20, hydroxyl value 15-150, number average molecular weight 1000-200000 Aqueous resin of the present invention The dispersion consists of the resin (A) versus the resin.
The ratio of (B) is in the range of 20/80 to 90/10 in solid content weight ratio, and is obtained by neutralizing with a base and dissolving or suspending it in an aqueous medium. The cold-curable aqueous coating composition using the aqueous resin dispersion of the present invention is characterized by having oxidative curability despite being a so-called acrylic resin, and having both hydrophilic and hydrophobic properties. be. In other words, it compensates for the drawbacks of emulsion-type paints and water-soluble type paints, and has the features of each type. α, β- constituting the copolymer resin in the present invention
Examples of ethylenically unsaturated acids include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, and fumaric acid. In addition, other polymerizable unsaturated monomers constituting the copolymer resin include the following formula: (R ₁ in the formula represents H or CH ₃ , R ₂ is C _o H _2o+1
(where n is an integer of 1n18) represents an alkyl group) and methacrylic esters can be mentioned. Here, the reason for limiting the value of n of the alkyl group in the formula is that when n exceeds 18, monomers that can be used on an industrial scale are extremely limited, and furthermore, the number of monomers that can be used on an industrial scale is extremely limited. Due to small advantages. Also, acrylic acid or methacrylic acid esters having a hydroxyl group, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl acrylate, etc.
-Hydroxypropyl, etc. can be used.
In addition, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N-methoxyacrylamide, N-
Methoxymethacrylamide, styrene, vinyltoluene, etc. are used. The copolymer resin that is the raw material of the present invention has the above-mentioned α, β
- The ethylenically unsaturated acid and the other polymerizable unsaturated monomers are combined using known polymerization techniques widely adopted in the industry, i.e., solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. etc. can be manufactured.
However, in consideration of the next reaction between the copolymer resin obtained by this copolymerization reaction and the glycidyl ester of unsaturated fatty acid, the most preferable method among these polymerization methods is the solution polymerization method. Resin (A) and resin (B) constituting the aqueous resin dispersion of the present invention are obtained by dissolving the above copolymer resin in an organic solvent and reacting the carboxyl group with glycidyl ester of unsaturated fatty acid. The unsaturated fatty acids that make up the glycidyl esters of unsaturated fatty acids can be any unsaturated fatty acids that show oxidative hardening properties due to oxygen in the atmosphere, but from the viewpoint of economic efficiency and the abundance of raw materials, natural drying fatty acids are suitable. Oil fatty acids, semi-drying oil fatty acids, or fatty acids obtained by processing them are suitable. That is, fatty acids obtained from linseed oil, tung oil, tall oil, soybean oil, safflower oil, bran oil, oiticica oil, etc. are used. In addition, dehydrated castor oil fatty acids, high diene fatty acids, and the like can be used. These unsaturated fatty acids are used in the reaction with the copolymer resin in the form of glycidyl esters, but in order to form glycidyl esters, a known glycidylation reaction, such as a dehydrochlorination reaction by reacting the fatty acids with epichlorohydrin, is performed. Alternatively, it can be easily produced by a method such as methyl esterifying an unsaturated fatty acid and reacting this with glycidol. For the reaction between the copolymer resin and the glycidyl ester of unsaturated fatty acid, the appropriate amount of the glycidyl ester is 10 to 200 parts per 100 parts of the copolymer resin. If the amount is less than 10 parts, the curing speed due to the oxidative polymerization reaction will be slow and insufficient, and if it exceeds 200 parts, the oxidative curing reaction will proceed excessively, resulting in a loss of durability and flexibility of the coating film, which is not preferable. The above-described reaction between the copolymer resin and the glycidyl ester of an unsaturated fatty acid is carried out by first dissolving the copolymer resin in an organic solvent, adding the glycidyl ester of an unsaturated acid, and stirring with heating. The reaction solvent is not particularly limited as long as it does not react with epoxy groups or carboxyl groups. Usually, ethers, ketones, secondary alcohols, tertiary alcohols,
Esters etc. are suitable. Since the final use form is a water-based paint, it is preferable to use one that is soluble or partially soluble in water. However, if a step is added to remove the reaction solvent by vacuum removal or freeze-drying after the reaction is completed, the water-solubility of the solvent used can be improved. There is no need to consider the presence or absence of Furthermore, even if the solvent is water-soluble, it is required to reduce the content of the organic solvent as much as possible from the viewpoint of preventing air pollution, and for this purpose, it is desirable to remove part or all of the solvent after the reaction. The reaction between the copolymer resin and the glycidyl ester of unsaturated fatty acid is suitably carried out at a reaction temperature of 80 to 160°C and a reaction time of about 30 minutes to 6 hours. Moreover, various epoxy group ring-opening catalysts can be used if necessary. Of the resin (A) and resin (B) obtained by such a reaction, resin (A) has water solubility or water dispersibility in order to stably solubilize or emulsify and disperse resin (B) in an aqueous medium. It is preferable to have the polarity as shown below, and the acid value is suitably in the range of 20 to 150, and the hydroxyl value is in the range of 15 to 150. If the acid value is lower than 20 and the hydroxyl value is lower than 15, the hydrophilicity will be insufficient and it will be difficult to obtain a stable resin dispersion, and if the acid value exceeds 150 and the hydroxyl value is higher than 150, the hydrophilicity will be too large. Excessive build-up can cause flash rust, and the water resistance and corrosion resistance of the coating film may deteriorate.
It impairs weather resistance, etc. The molecular weight of resin (A) is 1000-200000
A range of is suitable. If the value is less than 1000, the molecular weight will be too low and the curing properties and durability of the coating will be poor.
If it exceeds 200,000, the viscosity of the resin becomes too high, making it difficult to obtain an aqueous resin dispersion, and at the same time, the solid content of the paint decreases, making it difficult to ensure a sufficient film thickness during coating. The resin (B) is preferably insoluble in water by itself and highly hydrophobic, with an acid value of 0<20 and a hydroxyl value of 15 to 15.
Has a range of 150. Acid value is 20 or more, hydroxyl value is
When it exceeds 150, the hydrophilicity increases, the effect of forming a dispersed phase is poor, and thick film coating properties and drying properties are poor. still,
The lower limit of the hydroxyl value of 15 is a value inevitably produced by reacting the copolymer resin and the glycidyl ester in the above ratio. The molecular weight of resin (B) is 1000~
200000, and as in the case of resin (A),
If it is less than 1000, the hardness and durability of the coating film will be poor.
If it exceeds 200,000, the resin viscosity will be high and it will be difficult to obtain an aqueous resin dispersion. In the above reaction to obtain resin (A) and resin (B),
Resin (A) and resin (B) can be synthesized individually, or resin (B) can be produced first and a copolymer resin for resin (A) can be added thereto, and then glycidyl for resin (A) can be synthesized. Preferably, esters are added. The ratio of resin (A) to resin (B) is suitably in the range of 20/80 to 90/10 in terms of solid content weight ratio. If the proportion of resin (A) in the total resin is less than 20%, it is difficult to stably suspend resin (B) in the aqueous medium.
Moreover, if it exceeds 90%, the properties will be very similar to those of conventional water-soluble paints, which is undesirable as the effect of the present invention will be diminished. To produce the aqueous resin dispersion of the present invention, the resin
A homogeneous mixture of (A) and resin (B) is neutralized by adding a base corresponding to 50 to 150 mol% of the total carboxyl groups in the mixture, and water is added while stirring. Alternatively, instead of adding a base to the resin mixture, the base can be added to water in advance, and the resin mixture can be added to the water gradually or all at once while stirring.
As the base used for neutralization, alkylamines, alkanolamines, ammonia, etc., which are commonly used in water-based paints, are used. Among these, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, dimethylethanolamine, Diethylethanolamine, ammonia and the like are preferred. Various oxidative polymerization catalysts called driers are generally used in oxidation-curing paints, but dryers can also be added to adjust the drying speed for room-temperature curable aqueous coating compositions using aqueous resin dispersions. Can be done. As a dryer, cobalt, manganese, zirconium, calcium, lead,
Various organic acid salts or complex compounds such as zinc and iron are used. In addition, various additives and auxiliary organic solvents can be added for the purpose of adjusting paintability. A water-based coating composition that cures at room temperature using an aqueous resin dispersion can be used as a clear paint or as an enamel with added pigments, and is suitable for coating water-based materials, metal materials, inorganic materials, and plastic materials. . For coating, spraying, roller coating, brush coating, dipping coating, etc. can be used, and not only drying at room temperature but also forced drying and curing can be performed as necessary. Room-temperature curable aqueous coating compositions using a water-based resin dispersion are made of a water-based resin dispersion of a weather-resistant acrylic resin with an oxidation-polymerizable unsaturated fatty acid attached to the side chain. In addition, due to the effect of the dissolution form, it provides various performances necessary for a room-temperature curing type paint, and forms a coating film particularly excellent in gloss and flash last resistance. Also, when painting,
It has the effect of making it possible to coat thickly and with excellent drying properties. The present invention will be explained below based on Examples and Comparative Examples. In the examples, parts mean parts by weight. Example 1 (1) Synthesis of resin (A) In a glass flask equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer, the ingredients shown in Table 1, A
According to the compounding ratio shown in (1), 27.7 parts of diethylene glycol dimethyl ether as a reaction solvent is added and heated to 115 to 125°C while passing nitrogen gas. 10.4 parts of acrylic acid, 23.0 parts of butyl methacrylate under stirring
8.9 parts of styrene, 5.3 parts of 2-hydroxyethyl methacrylate, and 1.4 parts of t-butyl peroxybenzoate as a polymerization initiator.
It was added dropwise to the flask over a period of about 4 hours, and after stirring for about 1 hour, t-butyl peroxybenzoate was added.
A mixture of 0.1 part of methyl isobutyl ketone and 2.3 parts of methyl isobutyl ketone was added dropwise over about 10 minutes, and stirring was continued for an additional hour. Thereafter, the reactant was cooled to about 60°C, 20.8 parts of glycidyl ester of soybean oil fatty acid and 0.1 part of triethylamine as a reaction catalyst were added, and the temperature of the reactant was raised to 130°C over about 1 hour.
Keep at 120-130℃ for about 4 hours, then 90-110℃
A portion of the reaction solvent was removed under reduced pressure at °C to finally obtain Resin A (1) with a solid content of 80%. As shown in the lower part of Table 1, resin A (1) has a resin acid value of 72, a resin hydroxyl value of 81,
The number average molecular weight was approximately 13,000. (2) Synthesis of Resin (B) A resin was synthesized by the same method and under the same conditions as the synthesis of A(1), with the blending ratio changed to that shown in Table 1 B(1). After the synthesis, the solvent was removed under reduced pressure to finally obtain resin B(1) having a resin solid content of 80%, a resin acid value of 10, a resin hydroxyl value of 80, and a number average molecular weight of about 16,000. (3) Production of aqueous resin dispersion and paint According to the composition ratio shown in Example 1 in Table 2, 16.9 parts of resin A (1) and 11.3 parts of resin B (1) were obtained in this manner.
1 part was placed in a metal container, heated to approximately 50°C, 1.2 parts of 28% ammonia water was added, thoroughly mixed using a powerful tabletop stirrer, and 47.82 parts of deionized water was gradually added with stirring. , a uniform aqueous resin dispersion was obtained. To this aqueous resin dispersion, 0.28 parts of a cobalt naphthenate solution (4% metal content), 0.10 parts of a manganese naphthenate solution (5% metal content), and 22.4 parts of rutile titanium oxide were added and mixed uniformly.
A white enamel with a pigment to resin ratio of 1:1 and a solids content of about 45% was produced by dispersing in a three-roll mill. The paint obtained as described above was diluted with deionized water so that the viscosity measured using a Burtskfield rotational viscometer at a rotational speed of 6 rpm was approximately 1500 centipoise, and the temperature was 25°C. relative humidity 80
% on a vertically erected degreased iron plate, and the paintability and appearance were evaluated. The results are shown in Table 3. As is clear from Table 3, the paint obtained in this example did not sag or sag, and the maximum dry film that could be coated at one time was 38 μm. Furthermore, after coating to a dry film thickness of 25 μm, the time taken to reach a dry-to-touch state and a semi-cured state was investigated, and it was found to be 60 minutes and 6 hours, respectively. The gloss value of the cured coating film obtained was 87, and no flash luster was observed, giving a pure white and smooth finish. Example 2 (1) Synthesis of resin (A) Under the same manufacturing conditions as in Example 1 (1), Table 1 A (2)
Resin A (2) was synthesized using the reaction solvent, monomer, polymerization initiator, glycidyl ester, and catalyst shown in , and the solvent was removed under reduced pressure and concentrated to a solid content of 80%. The characteristic values of the obtained resin are as shown in the lower part of Table 1. (2) Synthesis of resin (B) Table 1 B (2) under the same manufacturing conditions as in Example 1 (2)
Resin B(2) was synthesized at the blending ratio shown in , and concentrated to a solid content of 80% by removing solvent under reduced pressure. The characteristic values of the obtained resin are as shown in the lower part of Table 1. (3) Production of aqueous resin dispersion and paint Under the same production conditions as in (3) of Example 1, an aqueous resin dispersion with a composition ratio shown in Table 2 and a solid content of approximately 50%
produced white enamel. The paint thus obtained was diluted to about 1500 centipoise by adding deionized water, and applied under the same conditions as in Example 1, at a temperature of 25° C. and a relative humidity of 80%. The results are shown in Table 3. Similar to Example 1, good results were obtained. Example 3 (1) Synthesis of Resin (B) Resin B (3) was synthesized under the same manufacturing conditions as in Example 1 (2) and at the blending ratio shown in Table 1 B(3). As shown in the lower part of Table 1, the solid content was reduced without desolventizing under reduced pressure.
70%, a resin acid value of 6, a resin hydroxyl value of 70, and a number average molecular weight of about 18,000. (2) Production of aqueous resin dispersion and paint Using the same synthesis equipment as in Example 1 (1), 20.1 parts of methyl isobutyl ketone as a reaction solvent was placed in a flask according to the compounding ratio shown in Resin 1 in Table 4. Heat to 115-125°C while bubbling nitrogen gas.
While stirring, add 6.5 parts of acrylic acid, 9.7 parts of butyl titacrylate, 4.8 parts of styrene, and 0.7 parts of t-butyl peroxybenzoate as a polymerization initiator.
of the mixture was added dropwise over a period of approximately 3 hours. After stirring for about 2 hours, a mixture consisting of 0.1 part of t-butyl peroxybenzoate and 0.6 part of methyl isobutyl ketone was added dropwise over about 10 minutes. moreover,
After stirring for about 60 minutes, the temperature of the reaction mixture was cooled to about 60°C, 46.2 parts of resin B (3) synthesized in (1) above and 11.3 parts of soybean fatty acid glycidyl ester were added, and the mixture was heated to 120-130°C.
The temperature was raised to 1, and the reaction was carried out for about 4 hours. After the reaction was completed, a portion of the reaction solvent was removed under reduced pressure at 80 to 100°C to finally obtain Resin 1 consisting of Resin B (3) and Resin (A) with a solid content of 85%. As shown in the lower part of Table 4, resin 1 has a resin acid value of 56 and a resin hydroxyl value of
63, and the number average molecular weight was approximately 15,000. As shown in Table 2, 1.5 parts of ammonia water, 0.3 parts of cobalt naphthenate solution, and 0.1 part of manganese naphthenate solution were added to 28.2 parts of Resin 1 thus obtained, mixed uniformly, and further desorbed. 45.9 parts of ionized water was added and emulsified and dispersed using a powerful tabletop stirrer to obtain an aqueous resin dispersion. 24.0 parts of rutile titanium oxide was added to 76 parts of this aqueous resin dispersion, mixed uniformly, and then dispersed in a three-roll mill to produce white enamel with a solid content of about 48%. Deionized water was added to this white enamel to dilute it to a viscosity of about 1500 centipoise, and it was painted under the same painting conditions as in Example 1, and the paintability and appearance of the paint film were evaluated. The results are shown in Table 3. Similar good results as in Examples 1 and 2 were obtained. Example 4 (1) Synthesis of Resin (B) Resin B (4) was synthesized under the same manufacturing conditions as in Example 1 (2) and at the blending ratio shown in Table 1 B (4). As shown in the lower part of Table 1, a solid content of 70%, a resin acid value of 6, a resin hydroxyl value of 50, and a number average molecular weight of about 12,000 were obtained without performing solvent removal under reduced pressure. (2) Production of aqueous resin dispersion and paint In the same manner as in Example 3 (2), resin 2 in Table 4 was prepared.
With the blending ratio shown in , solid content is 85%, resin acid value
Resin 2, which is a mixture of Resin (A) and Resin B (4), having a resin hydroxyl value of 50 and a number average molecular weight of about 12,000, was obtained. Next, in the same manner as in Example 3, white enamel having a solid content of about 47% and having the composition ratios shown in Table 2 was produced. Deionized water was added to this white enamel to dilute it to a viscosity of about 1500 centipoise, and it was painted under the same painting conditions as in Example 1, and the paintability and appearance of the paint film were evaluated. The results are shown in Table 3. Good results were obtained similarly to Examples 1-3.

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【table】

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[Table] Comparative Example 1 A water-soluble paint was produced using only Resin A (2) obtained in Example 2 (1) without using Resin B.
A comparison was made with Example 2 of the present invention. That is, 21.9 parts of resin A(2), 28% ammonia water
2.1 parts cobalt naphthenate solution (metal content 4
%), 0.1 part of manganese naphthenate solution (metal content 5%) was added, and after thoroughly mixing with a strong tabletop stirrer, 58.2 parts of deionized water was added.
An aqueous resin solution was obtained. Add 17.5 parts of rutile-type titanium oxide to this aqueous resin solution, mix uniformly, and then disperse in a three-roll mill, resulting in a pigment-to-resin ratio of 1:1 and a solid content of approximately 35%.
produced white enamel. This white enamel was diluted to about 1500 centipoise by adding deionized water and tested in the same manner as in Example 2, with the results shown in Table 5. Compared to Example 2, there are no problems with the coating film gloss, occurrence of flash rust, and smoothness, but the sag limit film thickness is small and it is not suitable for thick film coating, and the time required for drying to the touch and semi-curing is lower. A common shortcoming of water-soluble paints was their long drying and curing properties. Comparative Examples 2 and 3 Two types of commercially available emulsion-type water-based paints that cure at room temperature were obtained, diluted with deionized water to about 1500 centipoise, and tested in the same manner as in Example 2. Comparative Example 2 used water-based wide white, and Comparative Example 3 used water-based glossy paint white. The results are shown in Table 5. Compared to the examples of the present invention (Table 3), there are no problems in sagging limit film thickness, touch dry time, half-curing time, and smoothness, but the film gloss is inferior and flash last occurs in the early drying stage. This caused the white paint film to yellow in spots, a common defect with emulsion types. As described above, the room temperature curable aqueous coating composition using the aqueous resin dispersion of the present invention comprises a resin (A) having an acid value, a hydroxyl value, and a number average molecular weight within a specific range;
Since (B) is used in a certain ratio, it can have the characteristics of both water-soluble type and emulsion type compared to conventional paints.

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Claims (1)

[Scope of Claims] 1 100 parts of a copolymer resin of α,β-ethylenically unsaturated acid and other polymerizable unsaturated monomers is added with an unsaturated fatty acid selected from drying oil fatty acids or semi-drying oil fatty acids. Obtained by reacting 10 to 200 parts of glycidyl ester. Resin (A): 20 acid value <20, hydroxyl value 15-150, number average molecular weight 1000-200000, and resin (B): 0 acid value <20, hydroxyl value 15-150, number average molecular weight 1000-200000, The ratio of resin (A) to resin (B) is the solid content weight ratio.
An aqueous resin dispersion in the range of 20/80 to 90/10, which is neutralized with a base and dissolved or suspended in an aqueous medium.