JP2684678B2 - Aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an aqueous coating composition. More specifically, it relates to an aqueous coating composition comprising an aqueous polyurethane resin and an aqueous dispersion of an acrylic copolymer, which has elasticity and abrasion resistance of the urethane resin and weather resistance and toughness of the acrylic resin. It is a composition that is functionally bound and can be widely used as a coating agent for cement, concrete, metal, paper, leather, wood and the like.

[Prior art and its problems] As an aqueous coating composition, an acrylic polymer aqueous dispersion has been conventionally used for coating interior and exterior, leather, metal, wood, etc. and fibers due to its excellent weather resistance and toughness. It has been used in a wide variety of applications such as impregnation or binders, adhesives, pastes, etc.

However, in recent years, with higher quality, changes in the coating base material, use in new applications, etc., the demand for performance of the coating composition has become highly functional, and in addition to conventional weather resistance,
Applications that require elasticity and abrasion resistance of the film comparable to urethane resin are increasing. To obtain such physical properties,
As a method for improving an acrylic copolymer aqueous dispersion, various acrylic functional group monomers have been studied, but it is difficult to obtain an acrylic resin having elasticity comparable to urethane resin, and the study is desired. It was

On the other hand, an aqueous polyurethane resin as an aqueous coating composition has been conventionally used for coating fabrics, papers, leathers, plastics, wooden floors, etc., paying attention to elasticity and abrasion resistance which are the characteristics of this resin. However, when it is used in a normal dry condition, the water resistance, alkali resistance, and weather resistance, which are considered to be due to the water-soluble substance used for making it water-soluble, and the strength of the cohesive force inside the particles of the urethane dispersion, Due to the poor film-forming property between the particles, which is considered to be caused, the range of use was almost limited to indoors. Further, in practice, in most cases, a crosslinking agent is also used in combination with a high-temperature heat drying treatment, and the elasticity peculiar to the urethane resin is obtained only under these conditions.

In order to develop an aqueous coating composition that has not only elasticity and abrasion resistance of urethane resin but also weather resistance and toughness of acrylic resin, mixing of aqueous polyurethane resin and acrylic copolymer water dispersion, etc. However, the mere mixing, on the contrary, has the drawbacks of the respective resins, namely, the weak elasticity of the acrylic copolymer aqueous dispersion,
In many cases, only a combination of the properties of the aqueous polyurethane resin and the poor weather resistance can be obtained, and the development of a resin that combines the properties of both has been eagerly awaited.

[Means for Solving the Problems] The present inventors have conducted research to develop an aqueous coating composition having not only elasticity and abrasion resistance of urethane resin but also weather resistance and toughness of acrylic resin. As a result of overlapping
The present invention has been completed by finding that the above problems can be solved by functionally linking both the aqueous polyurethane resin and the acrylic copolymer aqueous dispersion, rather than simply mixing them. .

That is, the present invention is an aqueous polyurethane resin obtained by neutralizing a urethane prepolymer obtained by reacting a diisocyanate and a glycol containing a carboxylic acid group-containing glycol, and chain-extending with a hydrazine derivative. An acrylic copolymer containing (A) and at least 0.5 part by weight of a carbonyl group-containing monomer or an amide group-containing monomer in the constituent monomers of the acrylic copolymer based on 100 parts by weight of the total polymerizable monomer. Consisting of the polymer aqueous dispersion (B),
The aqueous coating composition is characterized in that the solid content weight ratio is (A) / (B) = 100/5 to 5/100.

 Hereinafter, the present invention will be described in detail.

The aqueous polyurethane resin used in the present invention is produced, for example, as follows. That is, first, a diisocyanate, a glycol and a glycol having a carboxylic acid group are subjected to a urethane reaction to obtain a urethane prepolymer.

The diisocyanates used at this time include aliphatic, alicyclic or aromatic diisocyanates, and examples of these include 2,4-tolylene diisocyanate and 2,6.
-Tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, m-phenylene diisocyanate, xylylene diisocyanate, tetramethylene diisocyanate, lysine diisocyanate, 1,4-cyclohexylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3 '-Dimethyl-4,4'-
Biphenylene diisocyanate, 3,3'-dimethoxy-
4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate and the like can be mentioned.

As the glycols for preparing the urethane prepolymer, low molecular weight glycols, high molecular weight glycols, polyester polyols, polycarbonate polyols and the like may be used alone, respectively, and they are well known in the urethane technology. In addition, low molecular weight glycol may be used in combination with polyester polyol or high molecular weight glycol.

As low molecular weight glycols, ethylene glycol, diethylene glycol, triethylene glycol,
1,2-propylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, octanediol, tricyclodecane dimethylol, hydrogenated bisphenol A,
There are cyclohexanedimethanol and the like, and two or more kinds thereof may be mixed.

High molecular weight glycols include polyethylene glycol,
Examples thereof include polypropylene glycol and polytetramethylene glycol.

The polyester polyols may be those obtained by reacting a glycol component and a dicarboxylic acid component, and can be easily produced by a known method. That is, the transesterification reaction is not limited to the esterification reaction. That is, the polyester polyol of the present invention can also be produced by a transesterification reaction using a lower alkyl ester of glycol and dicarboxylic acid.

Glycols having a carboxylic acid group include 2,2-
Dimethylolpropionic acid, 2,2-dimethylolbutyric acid,
2,2-dimethylol valeric acid and the like can be mentioned.

The reaction includes dioxane, acetone, methyl ethyl ketone, N-methylpyrrolidone, tetrahydrofuran, etc.
It is desirable to carry out in an organic solvent which is inert to isocyanate groups and has a high affinity for water.

Then, the prepolymer is neutralized and chain-extended, and distilled water is added to obtain an aqueous polyurethane resin. The organic solvent used in the reaction may be removed by a known method as necessary.

Examples of the neutralizing agent include amines such as trimethylamine, triethylamine, tri-n-propylamine, tributylamine and triethanolamine; sodium hydroxide, potassium hydroxide, ammonia and the like.

In the present invention, it is a requirement to use a hydrazine derivative as a chain extender. As the hydrazine derivative, hydrazine, ethylene-1,2-dihydrazine, propylene-
Examples thereof include 1,3-dihydrazine and butylene-1,4-dihydrazine.

Generally as a chain extender for urethane prepolymer,
Polyols such as ethylene glycol and propylene glycol; ethylenediamine, propylenediamine, hexamethylenediamine, tolylenediamine, xylylenediamine, diphenyldiamine, diaminodiphenylmethane, diaminocyclohexylmethane, piperazine, 2-
Aliphatic, alicyclic and aromatic diamines such as methylpiperazine and isophoronediamine are well known, but in the present invention, such a compound has a functional association with an acrylic copolymer aqueous dispersion. No effect is observed.

That is, it is necessary to hold the chemical structure of --NHNH ₂ at the polymer molecule end of the aqueous polyurethane resin obtained when the chain extension of the urethane prepolymer is carried out. ,first,
The aqueous urethane resin and the acrylic copolymer aqueous dispersion can be functionally linked.

In the present invention, the acid value in the aqueous polyurethane resin is preferably 10 to 200 per resin solid component. When the acid value is less than 10,
When the urethane prepolymer reacted in an organic solvent is made aqueous with a neutralizing agent, a chain extender, and distilled water, aggregates are likely to occur, and the storage stability of the obtained aqueous polyurethane resin may be poor. . On the other hand, if the acid value exceeds 200,
When the aqueous dispersion of the acrylic copolymer is functionally bound, preferable physical properties such as durability and water resistance may not be obtained.

As the acrylic monomer used to obtain the acrylic copolymer aqueous dispersion of the present invention, a carbonyl group-containing monomer or an amide group-containing monomer is a total polymerizable monomer 10
It is a requirement that at least 0.5 part by weight is contained with respect to 0 part by weight, but as the surfactant, protective colloid, and polymerization initiator used when carrying out emulsion polymerization, those conventionally known may be used. it can.

The carbonyl group-containing monomer is a monomer containing an aldo group or a keto group, and has an ester bond. And carboxyl groups Compounds having only are not included in this monomer. Examples of the carbonyl group-containing monomer corresponding to the present invention,
Examples thereof include acrolein, diacetone acrylamide, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone, diacetone acrylate and acetonitrile acrylate.

Examples of the amide group-containing monomer include monoolefinic unsaturated carboxylic acid amides, N-alkyl derivatives of monoolefinic unsaturated carboxylic acid amides, and N-alkylol derivatives of monoolefinic unsaturated carboxylic acid amides. . Examples of applicable monomers are amides of acrylic acid, methacrylic acid, itaconic acid or maleic acid; N-methylacrylamide, N-isobutylacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N-methylolmethacryl. Amide,
Examples thereof include N-ethoxymethylacrylamide, Nn-butoxymethylacrylamide, N-isopropoxymethacrylamide and the like.

These carbonyl group-containing monomers or amide group-containing monomers may be used alone or in combination, but at least 0.5 part by weight is necessary for 100 parts by weight of the total polymerizable monomer. The particularly preferable range is 1.0 to 10.0 parts by weight. If less than 0.5 parts by weight, the functional effect of the aqueous polyurethane resin and the acrylic polymer aqueous dispersion is not observed, weather resistance, water resistance, alkali resistance, elasticity,
It is difficult to improve the physical properties such as abrasion resistance.

In addition, examples of acrylic monomers other than the above that are used for emulsion polymerization in the present invention include acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate,
Examples thereof include methacrylic acid esters such as ethyl methacrylate.

In the present invention, other polymerizable unsaturated monomers that can be copolymerized with the above acrylic monomer can also be used.

Examples of the polymerizable unsaturated monomer include maleic acid, fumaric acid, itaconic acid esters; vinyl acetate, vinyl propionate, tertiary vinyl carboxylate and other vinyl esters; styrene, vinyltoluene, etc. Such as aromatic vinyl esters; heterocyclic vinyl compounds such as vinylpyrrolidone; vinyl chloride, acrylonitrile, vinyl ether, vinyl ketone, vinylamide, etc .; vinylidene halide compounds such as vinylidene chloride, vinylidene fluoride, .alpha.-, such as ethylene, propylene, etc. Olefins;
Dienes such as butadiene may be mentioned.

As the polymerizable unsaturated monomer having a reactive polar group, glycidyl acrylate, glycidyl methacrylate, glycidyl compounds such as allyl glycidyl ether: vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ
A silane compound such as methacryloxypropyltrimethoxysilane; acrylic acid, methacrylic acid, maleic acid or a half ester thereof, fumaric acid or a half ester thereof,
Examples thereof include carboxyl compounds such as itaconic acid or its half ester and crotonic acid; hydroxyl compounds such as β-hydroxyethyl acrylate and β-hydroxyethyl methacrylate; amine compounds such as alkylaminoacrylate and alkylaminomethacrylate.

In the present invention, as the surfactant (emulsifier) used when carrying out emulsion polymerization, conventionally known ones can be used. Anionic emulsifiers such as sodium dodecylbenzene sulfate, sodium dodecylbenzene sulfonate, alkylaryl polyether sulfate, etc .; polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene-polyoxypropylene block copolymer Nonionic emulsifiers such as coalescing;
A cationic emulsifier such as cetyltrimethylammonium bromide or laurylpyridinium chloride can be appropriately selected and used. Also, instead of the emulsifier as described above,
Alternatively, a water-soluble oligomer can be used as a dispersant in combination with an emulsifier. Further, it is also effective to use a water-soluble polymer substance such as polyvinyl alcohol or hydroxyethyl cellulose together with the above emulsifier or to add it to the emulsion after polymerization.

The total amount of emulsifier, water-soluble oligomer, and water-soluble polymer substance used is 0.5 to 10 per 100 parts by weight of the acrylic monomer.
It is preferably used in the range of parts by weight. If the amount is more than this, the water resistance of the coating film of the final acrylic copolymer aqueous dispersion may be significantly reduced, and if the amount used is less than this, the stability during emulsion polymerization, the stability of the produced emulsion polymer May decrease.

As the radical polymerization initiator used in the emulsion polymerization for obtaining the acrylic copolymer aqueous dispersion of the present invention, those used in ordinary emulsion polymerization are used. Examples thereof include potassium sulfate, ammonium persulfate, azobisisobutyronitrile and hydrochloride thereof, cumene hydroperoxide,
Organic peroxides such as tert-butyl hydroperoxide can also be used if necessary. Furthermore, known redox-based initiators using a combination of these persulfates or peroxides, metal ions such as iron ions, and reducing agents such as sodium sulfoxylate formaldehyde, sodium pyrosulfite, and L-ascorbic acid. Can also be used.

From the viewpoint of practical suitability, the concentration during emulsion polymerization is preferably such that the final composition has a solid content concentration of 25 to 65% by weight, and the ethylenically unsaturated monomer and radical polymerization to the reaction system. The initiator can be added by any known method such as batch charging, continuous dropping and divided addition.

The temperature at the time of emulsion polymerization may be in the range which is known in the known emulsion polymerization, and the emulsion polymerization is carried out under normal pressure, or under pressure when a gaseous ethylenically unsaturated monomer is used.

In the present invention, by mixing the carbonyl group- or amide group-containing acrylic copolymer aqueous dispersion thus obtained with an aqueous polyurethane resin chain-extended with a hydrazine derivative, a functional bond is strengthened. Expressed in. This bond is caused by the organic reaction between the -NHNH ₂ group at the polymer molecule end of the aqueous polyurethane resin and the carbonyl group or amide group of the acrylic copolymer aqueous dispersion when forming a coating film. It is considered to be an aqueous coating composition that organically combines the functions of a condensation resin and a radical polymerization resin.

Further speaking, the water-based coating composition of the present invention has not only the elasticity and abrasion resistance of the urethane resin, but also the weather resistance and toughness of the acrylic resin.
The solvent resistance and the like are also significantly improved as compared with the individual resins. For example, a coating film obtained from an aqueous urethane resin is easily dissolved in ketones such as methyl ethyl ketone, and a coating film obtained from an aqueous dispersion of an acrylic copolymer is easily dissolved in toluene. However, an aqueous coating composition satisfying the requirements of the present invention becomes insoluble in both methyl ethyl ketone and toluene solvents.

Further, the thermal softening temperature of the aqueous coating composition satisfying the requirements of the present invention is higher than the thermal softening temperature of each of the aqueous polyurethane resin, the acrylic copolymer water dispersion, and the individual, and in a simple mixed system, It develops properties that cannot be obtained.

On the other hand, in a mixed system of an aqueous polyurethane resin and an acrylic copolymer aqueous dispersion that lacks even one of the requirements of the present invention, the functional bond as obtained in the present invention cannot be obtained, and the urethane resin has The elasticity and wear resistance cannot be combined with the weather resistance of acrylic resin. Also,
Regarding the solvent resistance, no compounding effect is observed, and no remarkable increase in the thermal softening temperature is observed.

The blending ratio of the aqueous polyurethane resin and the acrylic copolymer aqueous dispersion is a requirement of the present invention that the solid content weight ratio is in the range of 100/5 to 5/100, and 100/10 to 10/100. Is more preferably in the range. If it deviates from this range, it becomes difficult to combine the properties of the aqueous polyurethane resin and the acrylic copolymer dispersion, and it is difficult to obtain a coating film having the above-mentioned characteristics. By adjusting the blending ratio of the aqueous polyurethane resin and the acrylic copolymer dispersion within the scope of the present invention so as to match the required performance, the characteristics of the urethane resin can be emphasized or the characteristics of the acrylic resin can be improved. Can be emphasized.

The aqueous coating composition of the present invention is a water-based coating using a conventional acrylic copolymer aqueous dispersion using a composition comprising the above-specified aqueous polyurethane resin and acrylic copolymer aqueous dispersion as a vehicle. It is manufactured in exactly the same manner as the preparation of the agent composition. That is, pigments, fillers, bone agents, dispersants, wetting agents, thickeners and / or rheology control agents, defoamers, plasticizers, film-forming aids, organic solvents, preservatives, mildew-proofing agents, pH adjustment Agents, rust preventives, etc. are selected and combined according to their respective purposes, and are made into a paint by a usual method.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. In the following, both parts and% are values based on weight.

Production Example 1 Production of Aqueous Polyurethane Resin (A) 1,780 g of 1,6-hexanediol, 2545 g of adipic acid and 567 g of 2,2-dimethylolpropionic acid were mixed to 170 ° C.
The temperature is raised to 0 ° C, and the reaction is performed at this temperature for 23 hours.
A polyester polyol having a valency and an acid value of 60 was obtained.

This polyester polyol was diluted by adding 1815 g of methyl ethyl ketone. After 240 g of the polyester polyol solution (I), 220 g of methyl ethyl ketone, 30 g of 2,2-dimethylolpropionic acid and 27 g of cyclohexanedimethanol were sufficiently stirred and mixed at 70 ° C., 4,4′-
Add 236 g of dicyclohexylmethane diisocyanate
The temperature was raised to 80 ° C., the reaction was carried out for 6 hours, and then the mixture was cooled to 30 ° C. to obtain a urethane prepolymer solution.

This polyurethane prepolymer solution was
A 80% aqueous hydrazine solution (40 g) and triethylamine (40 g) were gradually poured into an amine aqueous solution obtained by dissolving 1500 g of ion-exchanged water with stirring to obtain a viscous and translucent product. After removing the solvent under reduced pressure at 55 ° C, ion-exchanged water was added to adjust the concentration, and the non-volatile content was 23.7%, viscosity (BM viscometer, 60 rpm, 25 ° C), 23 cPs, pH 8.4, semi-transparent A water-based polyurethane resin (A-1) was obtained.

In the same manner as above, the raw materials shown in Table-1 were used to prepare aqueous polyurethane resins (A-2) to (A-4) having the properties shown in Table-1.

Production Example 2 Production of Acrylic Copolymer Aqueous Dispersion (B) The following raw materials were prepared.

Polymerizable monomers 2-Ethylhexyl acrylate 265 g Styrene 165 g Acrylonitrile 50 g Acrylic acid 10 g Diacetone acrylamide 10 g Surfactants Newcol 707SF (solid content 30%) ^{* 1)} 50 g Ion-exchanged water 360 g Polymerization initiator Ammonium persulfate 2.5g * 1) Special anion emulsifier manufactured by Nippon Emulsifier Co., Ltd. 30g of surfactant and 210g of deionized water in a four-necked flask.
And start stirring, raise the temperature to 80 ° C in a nitrogen stream,
Then a polymerization initiator was added. Then polymerizable monomers 50
A monomer pre-emulsion was prepared by mixing 0 g of the surfactant, 20 g of the surfactant and 150 g of ion-exchanged water, and the monomer pre-emulsion was added dropwise to the above flask over 3 hours. The reaction temperature at this time was maintained at 80 ± 3 ° C. After the dropping is completed, the reaction is continued under stirring while maintaining the same temperature range for 2 hours, then cooled and adjusted to pH 8-9 with 14% ammonia water, nonvolatile content 55.1%, viscosity 3000 cPs, pH 8. Acrylic copolymer aqueous dispersion (B-1) of 5 was obtained.

In the same manner as above, the raw materials shown in Table-2 were used to obtain acrylic copolymer aqueous dispersions (B-2) to (B-4) having the properties shown in Table-2.

Examples 1 to 6 and Comparative Examples 1 to 9 The aqueous polyurethane resin (A) obtained in each production example and the acrylic copolymer aqueous dispersion (B) were blended as shown in Table 3 to prepare an aqueous coating agent. Composition (Examples 1 to 6, Comparative Example 1)
~ 9) was obtained.

The physical properties of the film were tested using each of the obtained aqueous coating composition alone. The results are shown in Table-4.

Test method (1) Water resistance: A sample was applied to a glass plate with a 3 mil applicator to form a film. After drying at room temperature for 3 days, the film is immersed in water. After soaking at room temperature for 7 days, the film state is visually evaluated.

(○: good, Δ: normal, ×: bad, the same applies below) (2) Alkali resistance: The film prepared in the same manner as (1) was immersed in a 2% sodium hydroxide aqueous solution for 7 days, and then the film state was changed. Determined visually.

(3) Solvent resistance: A film prepared in the same manner as (1)
Immerse in toluene and methyl ethyl ketone for 1 day, and visually judge the film state.

(4) Abrasion resistance: A sample is applied to a standard tile for JFPA standard test (vinyl asbestos tile) so that 10 ± 2 ml per square meter. After the test piece coated 5 times by the same operation method was dried at room temperature for 7 days, the abrasion degree was measured and evaluated by a Taber tester (wearing wheel CS-17, load 1000 g).

(5) Film strength / elongation: A sample was cast on a glass plate and dried for 7 days before use. The sample has a film thickness of 0 after drying.
It was sampled so as to be 2 mm.

(6) Flow start temperature: 1.5 to 2.0 g of a film dried on a glass plate is used as a sample. Heating rate 3 ℃ / min,
Measure the flow start temperature with a load of 30 kgf and a die of 1 mmφ x 1 mml.

Test results As can be seen from Table-4, the aqueous coating composition of the present invention is much more excellent in solvent resistance and film elongation than other compositions that do not satisfy the requirements of the present invention. become. Further, the flow starting temperature is also markedly high, and it can be seen that there is a functional connection between the aqueous urethane resin and the acrylic copolymer aqueous dispersion.

Next, the following coating composition was prepared using each of the aqueous coating composition obtained in the composition shown in Table 3 to prepare an elastic coating composition.

(Compound) Taipaque R-930 ^{* 4)} 100.0 Hi-Metroses 90SH-15000 ^{* 5)} 0.6 Primal 850 ^{* 6)} 1.0 5% KTPP (potassium tripolyphosphate) 2.0 Neugen EA-120 ^{* 7)} 1.0 Adecanol SX-568 ^{* 8 )} 2.5 Ethylene glycol 10.0 Water 35.2 28% Ammonia water 1.0 Disperse the above composition with a high speed disperser and add the following composition.

39% emulsion of each aqueous coating composition ^{* 9)} 391.0 Texanol 26.4 Xylene 6.6 Adecanol UH-420 ^{* 10)} / Water = 1/2 (adjusted by paint viscosity) Total 577.3 NV (%) 43.7 PVC (%) 15.2 PWC (%) 39.6 * 4) Rutile type titanium oxide; Ishihara Sangyo Co., Ltd. * 5) Methyl cellulose; Shin-Etsu Chemical Co., Ltd. * 6) Polycarboxylic acid type dispersant; Rohm and Haas Company (USA) * 7) Interface Activator; Dai-ichi Kogyo Seiyaku Co., Ltd. * 8) Defoaming agent; Asahi Denka Co., Ltd. * 9) Adjusted by the nonvolatile content (%) of emulsion * 10) Thickener; Asahi Denka Co., Ltd. Examples 1 to 6 and Comparative Examples 1 to 9
The applied physical properties of the above aqueous coating composition were tested.

 The results are shown in Table-5.

Test method Paint viscosity; BH type 4 rpm paint viscosity (cPs) Coating gloss: Coated on a glass plate with a 3 mil applicator, dried at 1 day and measured 60 ° reflectance (%).

JIS A6910; Elongation rate ... A test piece was prepared so that the coating film thickness was about 1 mm when dry, then cured according to the JIS elongation test method and punched with a No. 2 dumbbell to obtain a test piece.

(Coating → curing for 7 days → curing for 7 days on back side → punching) Deterioration during elongation ... The above test pieces were punched test pieces with No. 1 dumbbell.

Adhesion strength ... Apply Acridic 53-448 as an undercoat, dry for 3 hours, then apply the sample according to the test method.
The four sides of the test piece used for the test after 14 days of curing and the adhesion strength after immersion in water were coated with a vinyl chloride resin paint 3 days before the completion of curing. The adhesive used was a two-part epoxy adhesive.

Resistance to repeated hot and cold action: (20 ± 2 ℃ 18Hrs in water → -20 ± 3 ℃ × 3Hrs → 50 ± 3 ℃ × 3
Hrs) × 10 cycles Water permeability… Conforms to JIS elongation test method Impact resistance… 〃Weather resistance… 〃Film strength; JIS A6910 Displays the film strength at the time of measuring elongation.

Accelerated weathering resistance; 20 ° C after irradiating a standard weather meter with the same coating film as that used for measuring elongation for 500 hours.
And measure the coating film elongation at -10 ℃.

Test Results As can be seen from Table-5, the aqueous coating composition of the present invention has good weather resistance even when a pigment is added, and exhibits the property that the coating strength does not deteriorate even after immersion in water.

Claims (1)

(57) [Claims] 1. An aqueous polyurethane resin obtained by neutralizing a urethane prepolymer obtained by reacting a diisocyanate with a glycol containing a carboxylic acid group-containing glycol, and chain-extending with a hydrazine derivative. (A)
And, based on 100 parts by weight of the total polymerizable monomer, a carbonyl group-containing monomer or an amide group-containing monomer in the constituent monomers of the acrylic copolymer, an acrylic copolymer aqueous solution containing at least 0.5 part by weight. An aqueous coating composition comprising a dispersion (B) and a solid content weight ratio of (A) / (B) = 100/5 to 5/100.