JP2003128985A - One-pack type coating composition for metal material and coated metal material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a one-pack type coating composition for metal materials, which is useful as a coating for coated metal materials to be used for exterior building materials, etc., and has low staining properties, excellent luster stability and storage stability not to mention processability. SOLUTION: This one-pack type coating composition comprises a polyester resin having 1,000-30,000 number-average molecular weight and 0-100 deg.C glass transition temperature, a curing agent, a hydrolyzable silyl group-containing compound, a dehydrating agent and resin particles which have no compatibility with the polyester resin, are neither swollen with nor dissolved in a solvent to solve the polyester resin and has no functional group to be reacted with a compound containing the hydrolyzable silyl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-pack type coating composition for a metal material, which can form a surface having excellent antifouling property on the coated metal material.

[0002]

2. Description of the Related Art Since PCM coated steel sheets are processed and molded after the coils before molding are continuously coated in advance, they greatly contribute to streamlining the coating line and improving productivity compared to conventional spray coating after molding. is doing. On the other hand, while maintenance-free materials are required mainly in the field of civil engineering and building materials, coated steel sheets that are excellent in durability as well as stain resistance, especially raindrop contamination, are required. In order to improve the raindrop contamination property, JP-A-6-34039 discloses that a silicate compound is introduced.

However, conventional rain dripping stain resistant paints using silicate compounds have problems of thickening and gelation of the paint due to condensation of silicate compounds. For this reason, it is inevitable to use the two-component type, but the demand for the one-component type is increasing because it leads to a decrease in productivity during coating. In addition, silica is generally used for gloss adjustment, but since silanol on the silica surface reacts with silicate, the gloss becomes unstable even within a short time, after which the viscosity of the paint increases.
It leads to gelation.

[0004]

As a coating material for coating metal materials used for exterior building materials, it is excellent in processability, low stain resistance, gloss stability, and storage stability.
A liquid type coating composition is provided.

[0005]

Means for Solving the Problems By using specific resin particles, the inventors of the present invention have completed a paint having low stain resistance, stable matte gloss, and excellent storage stability.

That is, the present invention has a number average molecular weight of 1,0.
Polyester resin having a glass transition temperature of 0 to 30,000, a curing agent, a compound having a hydrolyzable silyl group, a dehydrating agent and a polyester resin which is incompatible with the polyester resin and dissolves the polyester resin. A one-pack type coating composition for a metal material, comprising resin particles which do not swell or dissolve in a solvent and which has no functional group capable of reacting with the compound having a hydrolyzable silyl group. . The present invention also provides a cured coating layer of the one-pack type coating composition for a metal material, which is 1 to 10 μm, on the outermost surface layer of the coated metal material.
The present invention relates to a coated metal material, which is further provided with a thickness of 1.

The present invention provides a one-pack type coating composition for metal materials which is excellent in processability, low stain resistance, gloss stability and storage stability by the above means.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The one-pack type coating composition for metal materials of the present invention will be described in detail below. The polyester resin used in the present invention is a resin mainly obtained by an ester reaction of a polybasic acid and a polyhydric alcohol. Polybasic acids include terephthalic acid, isophthalic acid, succinic acid,
Adipic acid, sebacic acid, phthalic acid, maleic anhydride,
Tetrahydromaleic anhydride, dibasic acid such as hexahydrophthalic anhydride, trimellitic anhydride, methylhydroexcentricarboxylic acid, trivalent or more polybasic acid such as pyromellitic anhydride are used, and these may be used in combination. .

As the polyhydric alcohol, aliphatic or alicyclic compounds such as ethylene glycol, propylene glycol, diethylene glycol, butanediol, neopentyl glycol, 3-methylpentadiol, 1,4-hexanediol and 1,6-hexanediol. The above dihydric alcohols are mainly used, and if necessary, polyhydric alcohols having 3 or more valences such as glycerin, trimethylolethane, trimethylolpropane and pentaerythritol may be used in combination. Esterification of polybasic acids and polyhydric alcohols can be carried out by known methods.

The number average molecular weight of the polyester resin is 1,0
The glass transition temperature is 0 to 30,000.
Is in the range of -100 ° C. If the number average molecular weight is less than 1,000, the processability is poor, and if it exceeds 30,000, the compatibility with the silicate compound is poor. More preferably, it is 2,000 to 20,000. If the glass transition temperature is lower than 0 ° C, stains are easily attached to the coating film,
If it exceeds 100 ° C, the workability becomes poor. More preferably, it is 10 to 80 ° C.

(Compound Having Hydrolyzable Silyl Group) The compound having a hydrolyzable silyl group forms a silanol group after hydrolysis and contributes to the raindrop stain resistance of the coating film due to the hydrophilicity of the silanol group. The compound having a hydrolyzable silyl group is not particularly limited as long as it is a compound having a hydrolyzable silyl group, and specific examples include tetramethyl silicate, tetraethyl silicate, tetra-
n-propyl silicate, tetra-iso-propyl silicate, tetra-n-butyl silicate, tetra-2
-Alkyl silicates such as methoxyethyl silicate and tetra-2-ethylhexyl silicate, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, methyltriphenoxysilane, vinyltrimethoxysilane, vinyltrimethoxysilane Ethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane,
N- (2-aminoethyl) 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-
Examples include alkoxysilanes such as (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane, and condensates thereof. .

The above-mentioned condensate can be obtained by a hydrolysis reaction of a compound having a hydrolyzable silyl group.
That is, water and alcohols (methanol, ethanol, isopropyl alcohol, butanol, methyl cellosolve,
(Ethyl cellosolve, butyl cellosolve, etc.) can be used, but an acidic catalyst such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid or p-toluenesulfonic acid may be used in combination in order to accelerate the hydrolysis reaction as necessary. Absent. The compound having a hydrolyzable silyl group and / or its condensate may be used alone or in combination of two or more kinds.

The compounding amount of the compound having a hydrolyzable silyl group is such that the total amount of nonvolatile components of the polyester resin and the curing agent is 1
From the viewpoint of stain resistance, it is preferably about 3 parts by mass or more, and from the viewpoint of workability, it is preferably less than about 30 parts by mass. In the case of an enamel paint having a color pigment, the above blending amount is preferable with respect to 100 parts by mass of the total nonvolatile content of the polyester resin, the curing agent and the pigment.

(Dehydrating Agent) A dehydrating agent is used in order to prevent gelation which may be caused by the above-mentioned compound having a hydrolyzable silyl group reacting with a trace amount of water in the coating material. As the dehydrating agent, both a chemical dehydrating agent which reacts with water to hydrolyze and a physical dehydrating agent which adsorbs water can be used. Known chemical dehydrating agents include 2,2-dimethoxypropane, triethyl orthoformate, trimethyl orthoformate, triethyl orthoacetate, p-toluenesulfonyl isocyanate, 3-ethyl-2-methyl-2- (3-methylbutyl)-. 1,3-oxazolidine and the like can be mentioned. Examples of physical dehydrating agents include molecular sieves. These dehydrating agents may be used alone or in combination of two or more kinds.

From the viewpoint of the dehydrating effect, the amount of the dehydrating agent is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the nonvolatile content of the polyester resin and the curing agent. In the case of an enamel paint having a color pigment, the above blending amount is preferable with respect to 100 parts by mass of the total nonvolatile content of the polyester resin, the curing agent and the pigment.

(Resin Particles) Functionality that is incompatible with the above polyester resin, does not swell or dissolve in a solvent that dissolves the polyester resin, and can react with a compound having a hydrolyzable silyl group. Examples of the resin particles having no group include polyacrylonitrile beads, polytetrafluoroethylene beads, urea beads, acrylic beads, ceramic fibers and the like, which act as a gloss adjusting agent.
Among these, polyacrylonitrile beads and polytetrafluoroethylene beads are particularly preferable from the viewpoints of gloss adjusting ability and storage stability of the paint. The preferred particle size is 1
It is about 50 μm.

(Curing Agent) In the one-pack type coating composition for metal materials of the present invention, a melamine resin or an isocyanate resin can be used as a curing agent for the above polyester resin. The compounding amount of the curing agent is preferably about 5 to 50 parts by mass with respect to 100 parts by mass of the polyester resin.

(Pigment, etc.) The one-pack type coating composition for metallic materials of the present invention can be used as an enamel coating containing a color pigment.
It can also be used as a clear paint containing no coloring pigment. As the color pigment, inorganic pigments such as titanium dioxide, carbon black, iron oxide, lead chromate and calcium carbonate, organic pigments such as cyanine green and cyanine blue, metal powders such as aluminum powder and iron powder are used. Other extender pigments such as talc and barium sulfate can also be used. The blending amount is not particularly limited because it changes depending on the physical properties and color tone of the coating film, but from the viewpoint of physical properties, 1 to 100 parts by mass of the total nonvolatile content of the polyester resin and the curing agent is particularly preferable.
It is preferably about 150 parts by mass.

(Other Additives) In addition to the above-mentioned components, the one-pack type coating composition for metallic materials of the present invention contains, if necessary, a defoaming agent, a leveling agent, a wax, an ultraviolet absorber, a cup. Ring agents, additives such as curing catalysts, antibacterial agents, flame retardants such as triphenyl phosphate, inorganic fibers such as potassium titanate fibers and boron fibers, or silane coupling agents such as epoxy-based, amino-based, urethane-based, etc. It is possible to add an organic fiber represented by aramid fiber, carbon fiber, etc.

(Method for producing coating material) The one-pack type coating composition for metal materials of the present invention can be produced by the following method. In the case of an enamel paint having a color pigment, it is preferable that the pigment is kneaded and dispersed in advance with a skeleton resin. For dispersion, for example, a bead mill can be used. After kneading the pigment component, a curing agent is added. Then, a dehydrating agent and a compound having a hydrolyzable silyl group are added in this order. By adding the dehydrating agent before the compound having the hydrolyzable silyl group, the influence of the trace amount of water in the coating material on the compound having the hydrolyzable silyl group can be removed. Then, various gloss adjusting agents are added according to the target gloss value. Also in the case of a clear paint having no coloring pigment, the paint can be prepared by the same procedure except for the kneading process.

(Coating metal material) The form of the coating metal material using the one-pack type coating composition for metal materials of the present invention is described below. Examples of the metal plate include hot-dip galvanized steel plate, electrogalvanized steel plate, aluminum-zinc alloy-plated steel plate, zinc-iron alloy-plated steel plate, aluminum-plated steel plate, aluminum plate, stainless plate and the like. These metal plates are subjected to surface treatments such as degreasing, acid cleaning, zinc phosphate treatment, and chromate treatment, if necessary. A primer layer containing an anticorrosive pigment is provided on these metal plates to a dry film thickness of about 2 to 10 μm. Examples of the primer include epoxy primer, polyester primer, polyurethane primer and the like.

After applying the primer layer to the metal plate, (1)
As the top coat layer, an enamel coating having the one-pack type coating composition for steel sheet of the present invention is applied to a dry film thickness of about 10 to 25 μm, and (2) a dry film thickness of 10 to 20 μm is applied through an intermediate coating layer of the present invention. Enamel coating having a one-pack type coating composition for steel sheet is applied to a dry film thickness of 10 to 20 μm, or clear coating is applied to a dry film thickness of about 1 to 10 μm, (3) Dry film thickness of 5 to 20
After baking the intermediate coating layer having a thickness of μm, gravure offset printing was performed, and a clear coating having a one-pack coating composition for a metal material of the present invention as a top coat was dried to a thickness of 1 to 10
Various forms such as coating about m are mentioned as preferable use forms of the one-pack type coating composition for metal materials of the present invention.

For the purpose of imparting further low pollution performance to the existing coated steel sheet, a coating having the one-pack type coating composition for metal materials of the present invention is formed on the outermost surface as a thin film having a dry film thickness of about 1 to 10 μm. It should be provided. In this case, a clear paint is particularly preferable.

(Coating method) As these coating methods,
Any known roll coater, curtain coater, bar coater, die coater, spray coater, gravure offset, or the like can be used.

(Various uses) These coated metal plates having a cured coating film of the one-pack type coating composition for metal materials of the present invention are
It has excellent workability and stain resistance, especially raindrop stain resistance, and is used for building exterior walls, civil engineering and building materials, air conditioner outdoor units, automobiles, trains,
Used for exterior applications such as aircraft materials.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples. Parts and% represent parts by mass and% by mass.

(Preparation of Topcoat Paint) The topcoat paint was 45 parts of polyester resin having a number average molecular weight of 3,000 and a glass transition temperature of 40 ° C. (manufactured by Dainippon Ink and Chemicals, Inc .: Beckolite M-6163). (Solid content), 50 parts of titanium oxide pigment, 60 parts of a mixed solvent of cyclohexanone / xylol = 90/10 are mixed, and the mixture is kneaded in a bead mill. After kneading, a melamine resin (Dainippon Ink and Chemicals ( Co., Ltd .: Super Beckamine L-105-60) 5 parts (solid content) as a dehydrating agent 2,2-
A compound having 5 parts of dimethoxypropane and a hydrolyzable silyl group (MKC silicate MS5 manufactured by Mitsubishi Chemical Corporation)
6) It was prepared by adding 5 parts. The gloss was adjusted to 15% by using various gloss modifiers in the paint. Table 1 shows the composition of the prepared top coating composition.

[0028] Using the prepared top coat, it is coated on a galvanized steel sheet to which an epoxy primer has been applied in advance so that the dry film thickness is 20 µm, and baked for 45 seconds so that the maximum temperature reaches 220 ° C. I got a plate.

[0029]

[Table 1]

In Table 1, polyacrylonitrile is a tough AM (manufactured by Toyobo Co., Ltd.) (average particle size 10 μm).
m), polytetrafluoroethylene is L150J (average particle size 9 μm) manufactured by Asahi Glass Co., Ltd., acrylic beads are Toughtic AR-650-S (average particle size 10 μm) manufactured by Toyobo Co., Ltd., and ceramic fibers are Ceramic fiber ZFM20-SFD manufactured by Toshiba Monoflux Co., Ltd.
(Average diameter 3 μm, average fiber length 20 μm), Urea beads are MARTINSWERK's Pergo Pack M3 (average particle size 6 μm), Mica is Yamaguchi Mica Industrial Mica A
-21 (average particle size 8 μm) and silica (untreated) are Sylysia 450 (average particle size 8 μm) manufactured by Fuji Silysia K.K.
m), silica (*) is Syroid ED40 (average particle size 7 μm), which is an organically coated silica manufactured by Grace Japan Co., Ltd., and silica (**) is a surface chemically modified silica manufactured by Nippon Silica Industry Co., Ltd. SS-30P (average particle size 8
μm).

(Evaluation method of pot life) The pot life of the paint was tightly stoppered so that the solvent of the prepared topcoat paint would not volatilize, and stored at 40 ° C. 1 month, 3 months, 6
The state of increase in viscosity of the paint for months was evaluated. No increase in viscosity was evaluated as O, increase in viscosity was evaluated as Δ, and gelation of the paint was evaluated as X.

(Evaluation Method of Rain Dripping Contamination) For the evaluation of rain dripping contamination, each sample plate is set up vertically so that rainwater falls under the corrugated plate, and exposed for 6 months. The degree was evaluated on a three-point scale. No stain was evaluated as ◯, light stains were evaluated as Δ, and conspicuous stains were evaluated as x. "-" In Table 2 means "the coating is gelled and coating cannot be performed, and there is no evaluation." The exposure test was conducted in accordance with the pot life survey, and a paint plate was prepared using paints that had been aged for 1 month, 3 months, and 6 months.
The evaluation was performed after a month of exposure.

(Comprehensive Evaluation) A comprehensive evaluation of the pot life of the paint and the raindrop contamination property is carried out in three stages. Particularly excellent ones are ⊚, insufficient but usable ones are ○, unsuitable ones are ×. And The above results are shown in Table 2.

[0034]

[Table 2]

As can be seen from the test results shown in Table 2,
It has been found that the paint formed from the paint composition of the present invention has excellent stability over time, and the coating film applied with it has very good resistance to raindrop contamination. On the other hand, Comparative Examples 1 and 2
The paint thickened in one month, and the raindrop-like stain after exposure of the coated plate coated with it was also very noticeable. After 3 months, the paint gelled and was not ready for painting. This phenomenon means that the silanol on the surface of silica and the compound having a hydrolyzable silyl group are reacting. Therefore, we evaluated the silica surface with organic coating and the chemical modification with methylsilane, but the results were the same. This is because all the silanols are not sufficiently treated because the silica is porous, and the silanols newly appear on the surface due to the rupture of the secondary silica particles during stirring during the paint production. I think that is the cause.

Next, the effects of the amount of dehydrating agent added, the presence or absence, and the film thickness were confirmed. The compositions of the prepared topcoat paints are shown in Tables 3 and 4. Paints were prepared in the same manner as in Examples 1 to 6 and Comparative Examples 1 to 3. However, since Examples 13 and 14 and Comparative Examples 7 to 9 are clear coatings containing no pigment, the kneading process using a bead mill was not performed. Polyacrylonitrile was used as a gloss adjusting agent, and the gloss was adjusted to 15% at the film thicknesses shown in Tables 3 and 4. The coated plate was also treated in the same manner as in Example 1, but the dry film thicknesses are as shown in Tables 3 and 4, and when the top coat was clear, a commercially available exterior in which titanium oxide was dispersed was used. A polyester coating material for building materials (SRF50: manufactured by Dainippon Ink and Chemicals, Inc.) was applied by the same method as the top coating material so as to have a dry film thickness of 20 μm and provided as an intermediate coating layer.
And an overcoat layer having a film thickness shown in Table 4 was formed.

[0037]

[Table 3]

[0038]

[Table 4]

With the above composition, Examples 1-6 and Comparative Examples 1-3
Similarly to the above, the pot life and the resistance to raindrop contamination after exposure for 6 months were evaluated. The evaluation results are shown in Tables 5 and 6.

[0040]

[Table 5]

[0041]

[Table 6]

As can be seen from the test results shown in Tables 5 and 6, by adding a dehydrating agent, the temporal stability of the coating material is significantly improved, and the stain resistance is excellent regardless of the presence or absence of the pigment and the film thickness. I understood. Further, when the amount of the compound having a hydrolyzable silyl group added is 2% with respect to the coating solid content, a thin stain tends to adhere, but when it is 3% or more, particularly excellent raindrop contamination performance is exhibited.

[0043]

According to the present invention, it is possible to provide a one-pack type coating composition for metal materials, which is excellent in low stain resistance, low gloss and storage stability, as a coating material for coating metal materials used for exterior building materials. .

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Claims (4)

[Claims] 1. A number average molecular weight of 1,000 to 30,000.
0, a polyester resin having a glass transition temperature of 0 to 100 ° C., a curing agent, a compound having a hydrolyzable silyl group, a dehydrating agent, and a solvent which is incompatible with the polyester resin and dissolves the polyester resin. Does not swell or dissolve,
Further, a one-pack type coating composition for a metal material, comprising resin particles having no functional group capable of reacting with the compound having a hydrolyzable silyl group. 2. The one-pack type coating composition for a metal material according to claim 1, wherein the resin particles are polyacrylonitrile or polytetrafluoroethylene resin particles. 3. A compound having a hydrolyzable silyl group in an amount of 3 to 30 parts by mass, a dehydrating agent in an amount of 1 to 100 parts by mass, and a resin particle in an amount of 1 to 50 per 100 parts by mass of the nonvolatile content of the polyester resin and the curing agent. The composition is blended in a ratio of parts by mass.
Alternatively, the one-pack type coating composition for metal materials according to the item 2. 4. The outermost surface layer of the coated metal material has a number average molecular weight of 1,000 to 30,000 and a glass transition temperature of 0 to 10.
The polyester resin having a temperature of 0 ° C., the compound having a hydrolyzable silyl group, the dehydrating agent and the polyester resin are not compatible with each other, do not swell or dissolve in a solvent that dissolves the polyester resin, and 1 to 10 cured coating layers of a one-component coating composition for metal materials containing resin particles having no functional group capable of reacting with a compound having a degradable silyl group
A coated metal material having a thickness of μm.