JP2002161233A - Coating composition and coated metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating composition capable of preventing deterioration such as damage or corrosion of films and exhibiting excellent scratch resistance and to provide a coated metal plate. SOLUTION: This coating composition is characterized as comprising a resin component composed of (a) an oligomer having a chemical structure represented by general formula (1) [wherein, n is an integer of 2-10; R is -(CH2)m- (m is 1-10); and R' is represented by general formula (2) or general formula (3)] in an amount of 1-10 wt.% based on the weight of the resin solid content, (b) one or more kinds of a polyester resin, an acrylic resin and an epoxy resin in an amount of 40-95 wt.% based on the weight of the resin content and (c) an amino resin and/or a polyisocyanate resin which is a curing agent. The coated metal plate is obtained by coating the surface of a metal plate with the coating composition and forming a coated film having >=10 μm thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a phenomenon in which, for example, pebbles, gravel or the like collide at high speed on the surface of a coating film coated on a metal plate, thereby damaging the coating film and causing deterioration such as corrosion. On the other hand, the present invention relates to a coating composition exhibiting excellent scratch resistance and a coated metal plate using the coating composition.
The coated metal sheet obtained by the present invention is suitable for, for example, automobiles and building materials, but is not necessarily limited to these uses.

[0002]

2. Description of the Related Art For example, in painting in the field of automobiles,
Intermediate and top coats are applied after the chemical conversion treatment of the steel sheet, and especially so-called chipping, where pebbles, gravel, etc. hit the coating surface at high speed and reach the metal substrate. In order to prevent the phenomenon, it was necessary to further apply a coating film called a chipping primer between the electrodeposition coating and the intermediate coating.

[0003] In the field of building materials, undercoating and / or topcoating is performed by increasing the thickness of the coating.
The coating film damage after the construction as described above was prevented.

[0004]

However, the above-mentioned method has problems such as an increase in the number of steps and an increase in material cost, and a new method to replace these methods is desired at present.

Accordingly, it is an object of the present invention to provide a method for coating damage,
It is an object of the present invention to provide a coating composition and a coated metal plate which prevent deterioration such as corrosion and exhibit excellent scratch resistance.

[0006]

Means for Solving the Problems A coating composition and a coated metal plate according to the present invention for solving such problems are provided by the following:
It has the following features.

[1] a) An oligomer having a chemical structure represented by the general formula (2): 1 to 10 in a ratio to a solid content of a resin.
Weight percent,

[0008]

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B) one or more of a polyester resin, an acrylic resin and an epoxy resin: 40 to 95% by weight based on the solid content of the resin; c) an amino resin and / or polyisocyanate as a curing agent A coating composition comprising a resin component comprising a resin.

[2] A coated metal plate wherein the coating composition according to [1] is applied on a metal plate surface to form a coating film having a thickness of 10 μ or more.

[3] The coated metal plate according to [2], wherein at least one of the metal plate surfaces is coated to form a coating film.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below together with the reasons for limiting the same.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, one or more of a polyester resin, an acrylic resin, and an epoxy resin are used as a main component, and terephthalic acid, Naphthalene-2,6
-It has been found that by adding a dicarboxylic acid and / or an oligomer obtained from these lower alkyl esters and an alcohol component, a coating composition and a coated metal plate exhibiting excellent scratch resistance against chipping can be obtained. Furthermore, it has been found that the coated metal sheet thus obtained not only has excellent scratch resistance against chipping, but also has excellent workability and scratch resistance.

The oligomer of the above (a), which can be used in the present invention, comprises terephthalic acid, naphthalene-
An oligomer obtained from 2,6-dicarboxylic acid and / or a lower alkyl ester thereof and an alcohol component.

The amount of the oligomer in the coating composition may be 1 to 1 with respect to the resin solid content.
0% by weight. Preferably 2 to 7% by weight
It is.

When the amount of the oligomer is less than 1% by weight, and when it is more than 10% by weight, sufficient scratch resistance cannot be obtained in any case.

In the present invention, terephthalic acid, naphthalene-2,6-dicarboxylic acid and / or lower alkyl esters thereof are mainly used as the acid component, and a part thereof is isophthalic acid or naphthalene-
It can be replaced with a dicarboxylic acid such as 2,7-dicarboxylic acid or diphenylcarboxylic acid, or a lower alkyl ester of dicarboxylic acid.

Examples of the lower alkyl ester include methyl esters and ethyl esters having 1 to 2 carbon atoms. When the acid component is replaced in the above, the main naphthalene-2,6-dicarboxylic acid is preferably at least 85 mol% of the entire acid component, and the ratio of the other compound that can be replaced is preferably less than 15 mol%. .

In the present invention, diol is mainly used as the alcohol component. In addition to the diol component, a trihydric or higher polyhydric alcohol component can be used. Examples of the polyhydric alcohol component include triethylene glycol, glycerin, pentaerythritol, trimethylolpropane, and trimethylolethane.

The glycol component is a polyalkylene glycol having 10 or less carbon atoms, preferably a polyalkylene glycol having 6 or less carbon atoms. These glycols may be used alone or in combination.

The acid component and the alcohol component react with each other,
The oligomer used in the present invention is produced. This oligomer can be obtained by a usual polyester production method such as a transesterification method or a direct esterification method. Normal,
The acid component and the diol component react at a molar ratio of 1: 2. In order to carry out the reaction efficiently, it is desirable to add the acid component and the diol component at a molar ratio as close as possible to 1: 2.
The oligomers can be used either alone or in combination of two or more.

The above (b) which can be combined with the above oligomer and which can be used in the present invention includes polyester resin, acrylic resin and epoxy resin.

The compounding amount of the coating composition may be such that one or more of a polyester resin, an acrylic resin, and an epoxy resin is 40 to 40% in a resin solid content.
95% by weight. Desirably 50 to 90
% By weight.

When the amount is less than 40% by weight,
The film becomes brittle and the chipping resistance is reduced. On the other hand, 9
If the amount is more than 5% by weight, the curing reaction becomes insufficient and the pencil hardness decreases.

The above-mentioned polyester resin, acrylic resin and epoxy resin are resins used as ordinary coating resins, and these resins can react with hydroxyl groups of oligomers selected from amino resins and / or polyisocyanate resins. Curing agents can be used in combination. The oligomer forms a three-dimensional crosslinked structure together with the resin and the curing agent.

In the present coating composition, a coloring pigment, an extender pigment, a solvent, an additive and the like can be blended as necessary, in addition to the essential components described above.

The coating composition is used by dissolving it in an organic solvent. Examples of the organic solvent include methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, Solvesso 100, Solvesso 200, toluene, xylene, methyl cellosolve, butyl cellosolve, cellosolve acetate, butyl cellosolve acetate, carbitol, ethyl carbitol, butyl carbitol, ethyl acetate, and acetic acid. Butyl, petroleum ether, petroleum naphtha and the like.

The coating composition according to the present invention may contain a curing catalyst such as p-toluenesulfonic acid, tin octoate, dibutyltin dilaurate, and 2-ethylhexoate, and calcium carbonate, kaolin and clay, depending on the purpose and application. Pigment, titanium oxide, talc, barium sulfate, mica, red iron oxide, manganese blue, carbon black, aluminum powder, pearl mica, etc., and other additives such as antifoaming agent, anti-flow agent, etc. Can be.

In preparing the coating composition, an ordinary dispersing machine or kneading machine such as a sand grind mill, a ball mill, or a blender can be selectively used and blended.

The present coating composition may be a galvanized steel sheet, a zinc-based 5% aluminum alloy-coated steel sheet, a 55% aluminum-zinc alloy-coated steel sheet, or the like, a galvanized steel sheet, an aluminum-coated steel sheet, etc. It can be applied to a surface of a stainless steel plate, an aluminum plate, a cold rolled steel plate or the like, which has been subjected to a chemical conversion treatment such as a phosphate treatment or a chromate treatment. Further, it is also useful to coat a steel sheet which has been subjected to a chemical conversion treatment on a painted surface further subjected to electrodeposition coating or the like. Further, an overcoat film can be applied to the upper layer coated with the coating composition of the present invention.

The coating method is not particularly limited. It can be selected from various methods such as spray coating, roll coater coating and curtain flow coating. Usually, after the application, the coating film is baked by a heating means such as hot-air drying, infrared heating, induction heating or the like to crosslink the resin to obtain a cured coating film. The thickness of the coating film formed in this manner is 10 μm because of chipping resistance.
Above. The coating is not particularly limited as long as at least one of the metal plate surfaces is coated to form a coating film.

[0032]

Next, the present invention will be described with reference to embodiments. In the examples, parts and% mean parts by weight and% by weight, respectively, unless otherwise specified.

[Oligomer Synthesis Example 1] 1.0 mol of dimethyl terephthalate and 2.1 mol of ethylene glycol were placed in a reaction vessel equipped with a heating device, a stirrer, a rectification tower and a thermometer, and heated and melted at 180 ° C. afterwards,
As a catalyst, calcium acetate was added at 0.03 mol% to dimethyl terephthalate, and the reaction temperature was increased stepwise to 22
The temperature was raised to 0 ° C. and 64 g of the theoretical amount of methanol (2.
(0 mol) was distilled off, and the reaction was terminated by adding 0.03 mol% of trimethyl phosphate to dimethyl terephthalate. Thus, an oligomer (1) was obtained.
The reduced viscosity of the oligomer (1) was 0.04 dl / g.

[Oligomer Synthesis Example 2] Naphthalene-2,6-dicarboxylic acid dimethyl ether was placed in a reaction vessel equipped with a heating device, a stirrer, a rectification column, and a thermometer in an amount of 1.0 m.
ol, 2.1 mol of ethylene glycol, 200
Heated and melted at ℃. Thereafter, as a catalyst, manganese acetate was added in an amount of 0.03 mol% based on dimethyl ether of naphthalene-2,6-dicarboxylic acid, and the reaction temperature was increased stepwise by 2%.
Raise the temperature to 30 ° C and the theoretical amount of methanol 64g
(2.0 mol) was distilled off, and trimethyl phosphate was added to naphthalene-2,6-dicarboxylic acid dimethyl ether at 0.03 mol% to terminate the reaction. Thus, an oligomer (2) was obtained. Oligomer (2)
Had a reduced viscosity of 0.05 dl / g.

Examples 1-2 The coating compositions were prepared according to the formulations shown in Table 1. The coating composition obtained had a plating adhesion amount per side of 20 mg /
Electrolytic zinc is m ² - 20 nickel alloy plated steel sheet
After performing the epoxy-based cationic electrodeposition coating of μm, the coating was performed by a bar coater, and the coating was baked and dried at 150 ° C. for 20 minutes. Further, a 35 μm polyester melamine-based white coating film was applied on the upper layer, and baked and dried at 150 ° C. for 20 minutes. Thus, a coated metal plate was obtained. The coating film performance of the obtained coated metal plate was evaluated by the method described below. Table 2 shows the results.

Comparative Examples 1-4 Coating compositions were prepared according to the formulations shown in Table 1. The coating, baking and evaluation methods of the obtained coating composition were performed under the same conditions as in Examples 1 and 2. Table 3 shows the results.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

Test / Evaluation Methods (1) Pencil hardness Peel hardness was measured using Mitsubishi Pencil Uni in accordance with JIS K5400.

(2) Chipping resistance Using a rough diamond having a mass of 10 ± 1 mg as a shot material, a test temperature of -20 ° C. and a shot speed of 170 km
/ H and an air pressure of 0.1 MPa. The following evaluation was performed based on the diameter of the scratches on the coating film surface. ：: flaw diameter of less than φ5 mm ×: flaw diameter of φ5 mm or more (3) Corrosion resistance 2 hours of spraying salt water at 35 ° C, 30% relative humidity, 4 hours drying at 60 ° C, 95% relative humidity, 2 hours humidity at 50 ° C Was performed for 180 cycles, and the corrosion resistance was evaluated. The test plate was previously cross-cut with a cutter knife, and the corrosion resistance was evaluated based on the swollen width from the cross-cut portion after the test. ：: The swollen width after the test is less than 8 mm ×: The swollen width after the test is 8 mm or more From Tables 2 and 3, the coated metal plate coated with the coating composition of the present invention shown in Examples 1 and 2 is the present invention. It can be seen that, in comparison with Comparative Examples 1 to 4, which are out of the range, performance such as chipping resistance is extremely excellent.

[0042]

As described above, according to the coating composition of the present invention, the coating film is prevented from being damaged or deteriorated by corrosion, and excellent scratch resistance is obtained. Further, it is possible to provide a coated metal sheet having excellent performance, particularly suitable for automobiles and building materials.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 167/00 C09D 167/00 (72) Inventor Takahiro Kubota 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan (72) Inventor Masaaki Yamashita 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Japan F-term (reference) 4D075 CA04 DB02 DC12 EB22 EB33 EB35 4J038 CG001 DA132 DB001 DD001 DD072 DG111 DG261 KA03 MA07 MA10 NA03 NA11 PA19 PB05 PB07 PC02

Claims (3)

[Claims] 1. An oligomer having a chemical structure represented by the general formula (1): 1 to 10% by weight in a solid content of a resin; B) One or more of a polyester resin, an acrylic resin, and an epoxy resin: 40 to 40% in the resin solid content
A coating composition comprising a resin component consisting of 95% by weight and c) an amino resin and / or a polyisocyanate resin as a curing agent. 2. A coated metal plate, wherein the coating composition according to claim 1 is applied on a metal plate surface to form a coating film having a thickness of 10 μ or more. 3. The coated metal plate according to claim 2, wherein at least one of the metal plate surfaces is coated to form a coating film.