JPH07188605A - Water-based coating composition and metal plate made using the same - Google Patents

Abstract

PURPOSE:To obtain a water-based coating compsn. excellent in water resistance, processability, retorting resistance, hardness and applicability, and capable of decreasing the solvent content thereof, by blending a specific polyol with a water-based acrylic or polyester resin and an amino resin. CONSTITUTION:A water-based coating compsn. comprises as the resin components (a) 1-30 pts.wt. polyol of the formula, (b) 20-80 pts.wt. water-based acrylic or polyester resin, and (c) 10-60 pts.wt. amino resin. In the formula,(m), (n), (p) and (q) are each 1 to 10. When the amt. of the polyol used exceeds 30 pts.wt., the water resistance of the resulting compsn. is lowered. It is pref. 1 to 10 pts.wt. When the amt. of the acrylic resin is smaller than 20 pts.wt., the resulting compsn. is lowered in adhesion to a base material and involves a poor dispersibility in water, a poor storage stability and a poor dispersibility therein of a pigment in the step of addition thereto of the pigment. When it exceeds 80 pts.wt., the resulting compsn. is lowered in hardness and involves a poor water resistance. When the amt. of the amino resin is smaller than 10 pts.wt., the hardness of the resulting compsn. is insufficient. When it exceeds 60 pts.wt., the processability of a coating film of the resulting compsn. is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based coating composition, and more specifically, by incorporating a nitrogen group-containing polyol resin in the resin component, it has excellent processability, and further has retort resistance, hardness and coating. The present invention relates to a water-based coating composition having excellent properties and capable of reducing the content of a solvent, and a metal using the same.

[0002]

2. Description of the Related Art Paints are applied to metals such as home appliances, automobiles, cans, etc., and contribute to their corrosion resistance and aesthetic appearance. However, recently, there has been a strong demand for the performance of paints, and further improvement in physical properties is required. In fields where aesthetics have been conventionally required, a method of coating an organic solvent solution of epoxy / amino resin, acrylic / amino resin, polyester / amino resin, etc. with a roll coater and baking and curing in a gas oven. Is being done.

However, these paints cause a large amount of solvent volatilization during baking, causing air pollution, which is not preferable from the viewpoint of resource saving. Therefore, the advent of a water-based paint capable of solving these problems has been desired.

There are two types of known water-based paints, water-dispersible and water-soluble, and many water-dispersible resins are usually synthesized by an emulsion polymerization method using a surfactant, and the surfactant to be used is Even after the coating film is formed, it remains in the coating film, and there is a drawback that the water resistance is lowered. On the other hand, there is also a method of synthesizing an acid component, for example, a resin containing a carboxyl group by synthesizing in an organic solvent system without using a surfactant, and neutralizing with a volatile base to make the dispersion or water-soluble. The paint requires an acid component with oxidation of 20 or more in the basic resin structure,
There was a defect that performance such as alkali resistance was inferior. In order to improve these drawbacks, a method of mixing a large amount of an aqueous amino resin such as hexamethoxymethylmelamine and methylated benzoguanamine has been carried out, but the processability is largely decreased, while the processability is improved. When the water-based amino resin is reduced for improvement, the coating film hardness tends to decrease, it is difficult to balance water resistance, coating film hardness, and processability, and it is not a water-based coating that is practically satisfactory. It was

As another method, a method of mixing a phosphoric acid- or carboxylic acid-modified epoxy resin has been carried out. However, since the compatibility with an acrylic resin is poor, the storage stability of the coating material and the leveling especially in the coating film formation are observed. However, this tendency was particularly remarkable when the pigment was dispersed. Further, the conventional water-soluble paint contains 10% or more of an organic solvent in order to improve the storage stability of the paint and the leveling in forming a coating film, and it is still unsatisfactory from the viewpoint of air pollution and resource saving due to volatilization of the solvent during baking. It was enough. Further, conventional water-based paints have been obtained that have no abnormality even when subjected to a treatment of about boiling water as water resistance.
It was difficult to balance the water resistance and the workability withstanding the retort treatment at a temperature of ℃ or above.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above situation, and its purpose is to:
The present invention provides a resin composition having water resistance, process resistance and coating film hardness, and a metal plate obtained by applying the resin composition, and also provides an aqueous coating composition having a low organic solvent content.

[0007]

The first invention is (a) 1 to 30 parts by weight of a polyol represented by the following general formula,
(B) Water-based acrylic resin or polyester resin 20
-80 parts by weight, (c) amino resin 10-60 parts by weight,
A water-based coating composition comprising the above-mentioned (a), (b), and (c) as a resin component. The second invention is
A metal plate obtained by applying and curing the aqueous coating composition of the first invention.

General formula

[0009]

[Chemical 2]

The nitrogen-containing polyol resin in the present invention is used in an amount of 1 to 20 parts by weight in the resin solid content of the entire coating composition, and if it exceeds 30 parts by weight, the water resistance will decrease. It is preferably 1 to 10 parts by weight.

The acrylic resin used in the present invention includes carboxyl group-containing vinyl monomers such as (meth) acrylic acid, fumaric acid and maleic acid, hydroxymethyl (meth) acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, and acrylic acid. Hydroxyl group-containing vinyl monomers such as acid hydroxyamyl acrylate, and monomers capable of covalently polymerizing with them, for example, acrylic acid acrylic esters such as ethyl acrylate and methyl acrylate, aromatic vinyl monomers such as styrene and vinyltoluene, N-
A wide range of compounds such as those obtained by appropriately selecting and copolymerizing with N-alkoxyalkyl-substituted amide group-containing vinyl monomers such as (methoxymethyl) acrylamide can be used. The water-based acrylic resin is used in an amount of 20 to 80 parts by weight based on the resin solid content of the entire coating composition. If it is less than 20 parts by weight, the adhesion to the base material is lowered, the water dispersibility is poor, the storage stability of the coating is poor, and the pigment dispersibility is poor when the pigment is added. If it is 80 parts by weight or more, the hardness is lowered and the water resistance is poor.

The polyester resin used in the present invention is an oil-free polyester resin or an alkyd resin, which preferably has an acid value of 5 or less by dehydration condensation reaction of a polyhydric alcohol and a polycarboxylic acid or an anhydride thereof, Further, it is a resin which can be dissolved or dispersed in an aqueous medium in the presence of a volatile base by reacting a polyvalent carboxylic acid or an anhydride to give an acid value of 10 or more. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol and other dihydric alcohols, trimethylolethane and trihydric alcohol. There are dihydric or higher alcohols such as methylolpropane, trishydroxymethylaminomethane, pentaerythritol, dipentaerythritol, and diglycerin.

As the polycarboxylic acid or acid anhydride, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid,
(Anhydrous) succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydro (anhydrous) phthalic acid, hexahydro (anhydrous) phthalic acid, (anhydrous) hymic acid (anhydrous) maleic acid, fumaric acid, itaconic acid, (anhydrous) tri Mellitic acid, methylenecyclohexene tricarboxylic acid (anhydride), (anhydrous) pyromellitic acid and the like.

The aqueous amino resin used in the present invention is an amino resin which can be dissolved or dispersed in an aqueous medium, and is a partial alkyl etherified melamine resin, a partially alkyl etherified benzoguanamine resin, or spiroguanamine alone or spiroguanamine. It is selected from spiroguanamine resins in which a mixture with melamine or benzoguanamine is methylolated and partially alkyl etherified with an alcohol having 1 to 3 carbon atoms. In particular, spiroguanamine resin is preferable in that it has less tar-like low molecular weight generated during baking of the paint as compared with melamine resin or benzoguanamine resin. The aqueous amino resin is used in an amount of 10 to 60 parts by weight based on the resin solid content of the entire coating composition. If it is less than 10 parts by weight, the hardness is not sufficient, and if it exceeds 60 parts by weight, the workability of the coating film is deteriorated.

In the coating composition of the present invention, if necessary, an acid catalyst or an amine blocking agent thereof, such as p-toluenesulfonic acid, dodicylbenzenesulfonic acid, dinolylnaphthalenesulfonic acid, etc., is used as a curing aid resin. Solid content 1
0.1 to 4 parts can be added to 00 parts.
Similarly, conventionally known leveling agents, defoaming agents, lubricants and the like can be added. Further, pigments such as titanium oxide, aluminum pigment and quinacridone are kneaded with the above acrylic resin and polyester resin using a known disperser such as a sand mill and a disperser to prepare a pigment paste, which is made into a paint by the same method as described above. it can.

Further, a water-soluble resin or water-dispersible resin which is generally used as a resin for water-based paints, for example, a water-soluble or water-dispersible epoxy resin modified with amine or acid, maleic fatty acid, etc. are mixed. It is also possible. The water-based paint of the present invention can be applied to a substrate by a known means such as roll coating, spraying or brush coating. The metal plate used in the present invention has a plate thickness of 0.01 to 2.
It is a 0 mm cold rolled steel plate, a stainless steel plate, an aluminum alloy plate, or the like. In some cases, the surface of these metal plates is plated, vapor-deposited, coated or further coated with an inorganic metal such as chromium, tin, zinc or nickel, or an alloy or composite of one or more organic substances such as acrylic resin. , Alumite, phosphoric acid treatment, etc. A metal plate obtained by laminating a resin film such as polyethylene terephthalate or polybutylene terephthalate on these plates can also be used.

[0017]

EXAMPLES The present invention will be described below with reference to examples. In the examples, “part” means “part by weight” and “%” means “% by weight”.

Production Example 1 (Production of Aqueous Acrylic Resin Solution A) A four-necked flask equipped with a temperature type, a stirrer, a reflux condenser, a dropping tank, and a nitrogen gas blowing tube was charged with 100 parts of n-butanol and charged with nitrogen gas. While stirring while introducing the temperature
Keeping at 5 ° C, 20% styrene, 40% ethyl acrylate, 10% 2-hydroxyethyl acrylate from the dropping tank.
%, Methyl methacrylate 20%, acrylic acid 10%
What melt | dissolved benzoyl peroxide 5 parts in 100 parts of the mixture of was added dropwise over 3 hours. After that, the temperature was kept at 105 ° C., the reaction was carried out for 1 hour, 5 parts of benzoyl peroxide was added, and the reaction was further continued for 1 hour to complete the reaction. It is n
-Butanol was distilled off until the non-volatile content became 83%, and then 14.6 parts of diethanolamine and water were added to obtain a transparent and viscous aqueous acrylic resin A having a solid content of 50% and residual n-butanol of 10%. .

Production Example 2 (Production of Aqueous Polyester Resin Solution B) Ethylene glycol was added to a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser with a separation tank, and a nitrogen gas blowing tube.
9 parts, neopentyl glycol 21.6 parts, adipic acid 23.3 parts, and terephthalic acid 26.5 parts were charged and heated to 230 ° C. while stirring while introducing nitrogen gas, and reacted until the acid value became 5 or less. Then, 15.8 parts of adipic acid cooled to 160 ° C. was added, and the reaction was further continued, and the reaction was terminated when the acid value reached 35. After cooling to 80 ° C or lower, 17.5 parts of ethylene glycol monobutyl ether, 4.8 parts of dimethylethanolamine and 55.2 parts of water were added, and a transparent viscous pre-neutralizing acid having a solid content of 50% and an organic solvent of 11% was added. Aqueous polyester resin solution B having a valence of 35 and a hydroxyl number of 88
I got it.

Examples 1-5 and Comparative Examples 1-4 Table 1 shows the ratio of the solid content of each component in percentage. After mixing each component according to this Table 1 (however,
In Example 3, the acrylic resin solution and the pigment were first kneaded. ) Butyl cellosolve and water were added to adjust the amount of organic solvent in the paint to 10% and the solid content to 35%. To this, 0.3% of an amine salt of p-toluenesulfonic acid and 0.3% of a silicone leveling agent were added to obtain an aqueous coating composition. Table 2 shows the results of investigations on the stability of coating materials and the physical properties of coating films prepared in Examples and Comparative Examples.

Each test method is as follows. Paint test ○ Paint stability test After the paint was stored at room temperature for two months, the state of gelation separation of the resin in the paint was observed. Coating film physical property test: An electroplated tin plate having a plate thickness of 0.23 mm was coated by roll coating so as to have a coating film thickness of 7 μ after drying, and a baking coated panel was prepared in a gas oven at an atmospheric temperature of 190 ° C. for 10 minutes. The scratch resistance was evaluated by preparing a 3-piece can in which a coated plate was formed so that the coated surface was the outer surface of the can.

○ Water resistance test The coated panel was immersed in water, subjected to hot water treatment at 100 ° C for 30 minutes and retort treatment at 130 ° C for 30 minutes, and then the whitening state of the coating film was evaluated. Workability test According to the Erichsen test and JISZ-2247, the state of the coating film was evaluated after extrusion processing to the point where the underlying metal plate started to crack. ○ Adhesiveness A peeling test was performed. Similarly, evaluation after retort treatment at 130 ° C. for 30 minutes was also performed.

○ Impact resistance Using a DuPont impact tester, 1/2 inch diameter, 500
Tested under g-load. ○ Pencil hardness test JIS standard “pencil scratch test” (JIS No. K54
It was performed according to the method registered in (00). Paintability test ○ Immediately after coating with a flow roll coater, baking was performed in a gas oven to evaluate the leveling state.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

EFFECTS OF THE INVENTION According to the present invention, a water-based coating composition which is excellent in water resistance, workability, hardness and coatability of a coating film and can reduce the content of a solvent, and a metal plate coated with the same Can be provided.

Claims (2)

[Claims] 1. A polyol represented by the following general formula:
1 to 30 parts by weight, (b) aqueous acrylic resin or polyester resin 20 to 80 parts by weight, (c) amino resin 1
0 to 60 parts by weight, (a), (b), and (c) as a resin component, an aqueous coating composition characterized by the above. [Chemical 1] 2. A metal plate obtained by applying and curing the aqueous coating composition according to claim 1.