JPS5934743B2 - Matte coating method for aluminum and aluminum alloys - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for matte coating aluminum and/or aluminum alloys.

In recent years, the use of aluminum and aluminum alloys for window frames, sashes, gates, etc. has rapidly increased, and the surface treatment is usually done by anodizing, followed by electrodeposition, heated dipping, electrostatic painting, etc., with or without sealing treatment. A transparent coating film is produced using this method. On the other hand, there has been a growing demand for matte surface treatments for use in sashes and the like. Conventionally, in order to obtain a matte coating film, it is common to add fine particle silica as a matting agent to a coating composition.

However, paint films obtained using silica-based matting agents usually suffer from a decline in performance such as chemical resistance, or the degree of matting changes during storage, or if left in a diluted state, may regenerate. There were problems with stability, such as hard sedimentation that was difficult to disperse, and coating could not be performed stably. As mentioned above, the paints conventionally used for surface treatment of aluminum and/or aluminum alloys are overwhelmingly transparent paints.
When a silica-based matting agent is used to obtain a matte coating film with a transparent paint, the stability is particularly poor and a uniform matte coating film cannot be obtained. In order to eliminate these drawbacks, it is known to use plastic matting agents such as polycarbonate and polyester.

However, when using a plastic matting agent, it is necessary to pulverize the matting agent itself or to disperse it together with a vehicle binder. Furthermore, Japanese Patent Publication No. 51-8975 discloses that two or more α
, a method for obtaining a plastic matting agent by polymerizing a reactive monomer having a β-ethylenically unsaturated bond has been disclosed, but this method also requires a step of micronizing the matting agent. It is. On the other hand, since paints for transparent coatings do not contain pigments, there is no need for a dispersion process unlike in general paints, and it is sufficient to uniformly mix the resin, crosslinking agent, additives, etc. if necessary. Therefore, the use of matting agents that require dispersion or mechanical pulverization in transparent paints is disadvantageous in the paint manufacturing process. As a result of intensive studies to improve the above-mentioned drawbacks, the inventors of the present invention found that after anodizing aluminum and/or aluminum alloys by an arbitrary method, or after anodizing, a treatment that generates hydrates to an extent that does not block the conduction holes. After this, a reactive monomer consisting of tri(meth)acrylate, which will be described later, has a viscosity of 0.5 to 50 poise at the polymerization temperature, and is substantially the same as the reactive monomer. Contains carboxyl and hydroxyl groups, has an acid value of 20 to 150, and a hydroxyl value of 20
-150% by polymerization in an acrylic resin solution and a coating composition containing a melamine resin as a hardening agent. A stable and uniform matte coating can be obtained without deterioration in chemical resistance, etc., and the matting agent added to the paint composition does not need to be mechanically pulverized or undergoes a dispersion process. He discovered that paint could be produced and completed the present invention.

The acrylic resin solution used in the present invention contains carboxyl groups and hydroxyl groups, and has an acid value of 20 to 150.
An acrylic resin solution having a hydroxyl value of 20 to 150 is used.

For the carboxyl group, use a carboxyl group-containing monomer such as acrylic acid, methacrylic acid, itaconic acid, or maleic acid, and for the hydroxyl group, use a hydroxyl group-containing monomer such as hydroxyl ethyl acrylate, hydroxyl ethyl methacrylate, hydroxyl propyl acrylate, or hydroxypropyl methacrylate. They can be incorporated into an acrylic resin by copolymerizing them with other monomers that can be copolymerized with them. Other monomers include methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, ethylhexyl acrylate,
Alkyl esters of acrylic acid or methacrylic acid such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, and ethylhexyl methacrylate, N-methylolacrylamide, N-methylolmethacrylamide, dimethylacrylamide, dimethylmethacrylamide, N-n-butoxyacrylamide , acrylamide or methacrylamide and derivatives thereof such as N-n-butoxymethacrylamide, nonpolar monomers such as styrene and vinyltoluene, and vinyl esters such as vinyl acetate.

The solvent for the acrylic resin solution may be any solvent as long as it has a suitable relationship between resin solid content and viscosity. However, when considering the use of water-soluble resins, alcohol-based, glycol-based, glycol ether, and derivatives thereof may be used. etc. are preferred.

The acrylic resin solution is adjusted with a solvent to have a viscosity of 0.5 to 50 poise, preferably 1 to 10 poise, at the polymerization temperature of a reactive monomer made of tri(meth)acrylate, which will be described later. ) A reactive monomer consisting of acrylate (hereinafter referred to as a polyfunctional monomer) is polymerized to produce synthetic resin fine particles (hereinafter referred to as microgel) of 1 to 50 μm.

As mentioned above, the produced microgel is a fine particle of 1 to 50 microns and is uniformly dispersed in the acrylic resin solution, and steps such as mechanical pulverization or dispersion are not necessary.

In addition, O to 50% by weight of the above polyfunctional monomer (meth)
It is possible to substitute a monomer (hereinafter referred to as a monofunctional monomer) consisting of an acrylic ester and/or styrene as necessary. At this time, the viscosity of the acrylic resin solution, the content of the microgel, the composition of the monomer used as the microgel, the type of solvent, the reaction temperature, the stirring mode, etc. are factors that determine the particle size of the microgel particles.
In particular, the viscosity of the resin solution and the microgel content are important. The higher the viscosity and the lower the microgel content, the smaller the particle size, and vice versa. As a specific example, an acrylic resin consisting of methyl methacrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid is used, and trimethylolpropane trimethacrylate is added as a monomer at 90°C under constant various conditions. Viscosity of acrylic resin solution at 90°C and microgel content (parts by weight of microgel based on 100 parts by weight of acrylic resin, Phr)
) and the particle size of the obtained microgel are shown in Table 1 below. The viscosity of the acrylic resin solution at the reaction temperature is preferably 0.5 to 50 poise, particularly 1 to 10 poise.

If it exceeds 50 poise, stirring will not be sufficient and a uniform microgel will not be produced.

In addition, when the viscosity is 0.5 poise or less, the particle size becomes 50 μm or more, which requires a mechanical process for miniaturization. The microgel content is preferably 1 to 50 parts by weight, particularly 1 to 20 parts by weight, based on 100 parts by weight of the resin solid content.

If it exceeds 50 parts by weight, stirring becomes uneven and the particle size becomes 50 μm or more, which is unsuitable.

If the amount is less than 1 part by weight, the microgel particles will become too fine and a sufficient matting effect will not be obtained. The thus obtained microgel has a particle size of 1 to 50 μm, and the polyfunctional monomer or the polyfunctional monomer and the monofunctional monomer cause a cross-linking gelation reaction by themselves, and the resin liquid as a dispersion medium without substantially reacting with each other,
Formed as fine particles.

The polyfunctional monomer used here includes tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, and trimethylolmethane tri(meth)acrylate.

Examples of monofunctional monomers include (meth)acrylic acid ester and styrene. The monomers used for microgel production are one or a mixture of two or more polyfunctional monomers, or one or two or more polyfunctional monomers,
It is preferable to use one type of monofunctional monomer or a mixture of two or more types of monofunctional monomers.

When the amount of monofunctional monomer components increases, the particle size of the microgel becomes larger and the reaction tends to stick to the reactor wall, so the mixing ratio of polyfunctional monomer and monofunctional monomer is 100:0 to 50:50 by weight,
Preferably it is in the range of 100:0 to 70:30. The microgel-containing acrylic resin liquid obtained as described above is used as it is or mixed with other acrylic resins as an acrylic resin for paint.

When electrocoating is performed, 60 to 120% of the carboxyl groups contained are neutralized with a basic substance such as amine to make them water-soluble. In the composition used in the method of the present invention, melamine resin, which is commonly used as a curing agent for acrylic resins, is used.

For example, alkyl etherified methylolmelamine such as hexamethoxymethylolmelamine, methyl and butyl mixed ether type methylolmelamine is suitable. The proportion of these to be used is well known to those skilled in the art, but is generally 100 to 5 parts by weight, preferably 40 to 20 parts by weight, per 100 parts by weight of the solid acrylic resin. For coating aluminum and/or aluminum alloy, any conventional coating method such as air spray, airless spray, dip coating, roll coating, flow coating, etc. can be used, but electrodeposition coating is particularly preferred. .

Electrodeposition coating is carried out in the same manner as ordinary (glossy) paint coating.

That is, the alumite-treated aluminum was sufficiently washed with water and then washed with hot water at a temperature of 50°C or higher, or without hot water washing, or treated with an aqueous solution of 50°C or higher containing a trace amount of metal salt such as nickel sulfate, and then washed with water. Thereafter, it is immersed in the above microgel-containing electrodeposition bath solution, and DC or AC current is applied using aluminum as one pole. Electrodeposited anodized aluminum is washed with water or baked dry without washing. Bake hardening is usually 15 to 150℃ at 150 to 220℃.
It takes about 30 minutes. The coating film obtained in this way has a uniform appearance with no spots or repellents, and has physical properties such as hardness and impact resistance, chemical resistance such as acid resistance and alkali resistance, and other boiling water resistance and moisture resistance. , CASS test, weather resistance test, etc. In addition, even in a turnover test in which coating was performed continuously while replenishing the paint to keep the solid content of the electrodeposition bath liquid constant, there was no change in the gloss value or uniformity, and the stability was maintained. This is also an excellent painting method. The present invention will be explained in more detail by showing comparative examples and examples below, but the present invention is not limited to the present invention in any way.

Parts, proportions and percentages are by weight.

Example 1 and Reference Examples 6.5 parts of methacrylic acid, 42.5 parts of methyl methacrylate, 25 parts of butyl acrylate.
Ethyl cellosolve/isopropanol = 2/8 5 of acrylic resin with acid value 42.4 and hydroxyl value 101.3 consisting of 0 parts and 26.0 parts of hydroxypropyl methacrylate.
The viscosity of the 5% solution at 90°C was 9.5 poise.

When 4 parts of trimethylolproban trimethacrylate and 0.04 parts of azobisisobutyronitrile were added to 100 parts of this solution and reacted at 90°C for 1 hour, a milky liquid containing microgels with a particle size of 10 to 15 μm was obtained. It was done. Add 60 parts of this microgel-containing liquid to 100 parts of the above acrylic resin liquid.
and 30 parts of hexamethoxymethylolmelamine (manufactured by Mitsui Toatsu Chemical Co., Ltd., Cymel 300), neutralized 80% of the carboxyl groups with triethylamine, and diluted with water to obtain an aqueous dispersion with a solid content of 12%. It was made into a liquid. A colored alumite-treated aluminum plate with unsealed pores was immersed in this aqueous dispersion, a direct current was applied using the aluminum as an anode, the plate was pulled up, washed with water, and baked and dried at 180° C. for 20 minutes. Gloss value 4
A uniform matte transparent coating film of No. 7 was obtained. The performance of this coating film is as shown in Table 2 (reference example:
That is, in the above example, in 100 parts of acrylic resin liquid,
This is equivalent to the case where an aqueous dispersion with a solid content of 12%, which was prepared by adding 60 parts of the same acrylic resin liquid and performing the same treatment instead of 60 parts of the microgel-containing liquid, was used. There was no deterioration in coating film performance due to the presence of erasing agent. Example 2 9 parts of acrylic acid, 41 parts of methyl methacrylate, 25 parts of 2-ethylhexyl acrylate, 15 parts of styrene, 2-
Acid value 70 consisting of 10 parts of hydroxyethyl acrylate
．． 1. 55% solution of butyl cellosolve/isopropanol 2/8 of acrylic resin with hydroxyl value 112.2 at 95°C
The viscosity was 8.1 poise.

To 100 parts of this solution, 7 parts of trimethylolpropane trimethacrylate, 1 part of methyl methacrylate, and 0.1 part of azobisisobutyronitrile were added and reacted at 95°C for 1 hour. A microgel-containing solution was obtained. To 130 parts of the above acrylic resin liquid, 30 parts of this microgel-containing liquid, 3 parts of hexamethoxymethylolmelamine (manufactured by Mitsui Toatsu Chemical Co., Ltd., Cymel 300)
Add 0 parts and add 90 parts of carboxyl group with triethylamine.
% and then diluted with water to obtain an aqueous dispersion with a solid content of 13%. A coating film obtained by electrodeposition using this aqueous dispersion in the same manner as in Example 1 had a uniform matte appearance and a gloss value of 25. Moreover, the coating film performance was good as shown in Table 2. Example 3 The viscosity at 90°C of a 1/1 50% solution of butyl acetate/butyl cellosolub of an acrylic resin consisting of 3 parts of acrylic acid, 46 parts of methyl methacrylate, 25 parts of butyl acrylate, and 26 parts of hydroxyethyl methacrylate was 9 poise. It was hot.

5 parts of trimethylolpropane trimethacrylate and 0.05 part of azobisisobutyronitrile were added to 100 parts of this solution and reacted at 90°C for 1 hour.
A microgel-containing liquid with a particle size of ~14μ was obtained. 100 parts of the above acrylic resin solution, 60 parts of microgel-containing solution, hexamethoxymethylolmelamine (manufactured by Mitsui Toatsu Chemical Co., Ltd.,
30 parts of Cymel 300) was added to form a paint. The created paint is xylene/Solbetsuso 100 (manufactured by Etsuso Chemical Co., Ltd.)
= 1/1 thinner to reduce viscosity for 13 seconds (Food cup #
Electrostatic coating was applied to an aluminum plate with unsealed holes that had been anodized after being adjusted to 4.25°C.
Baking was performed for 0 minutes. The gloss value of the obtained aluminum sheet was 40, and its performance is shown in Table 2. Example
4 To 100 parts of the acrylic resin solution used in Example 2, 8 parts of trimethylolmethane trimethacrylate, 2 parts of ethyl methacrylate, and 0.1 part of azobisisobutyronitrile were added and reacted at 95°C for 1 hour, resulting in a milky liquid. Particle size 15
A ~25μ microgel-containing solution was obtained.

This microgel-containing solution was used to form a paint in the same manner as in Example 2, and the resulting paint film was electrodeposited and had a uniform matte appearance, with a gloss value of 33. The performance of this coating is shown in the table below.
As shown in Figure 2, the results were good.

Example 5 8 parts of trimethylolmethane triacrylate, 2 parts of styrene, and 0.1 part of azobisisobutyronitrile were added to 100 parts of the acrylic resin solution used in Example 3.
When reacted at 0℃ for 1 hour, it was like an emulsion and the particle size was 15 ~
A 20μ microgel-containing solution was obtained.

This microgel-containing liquid was used to form a paint in the same manner as in Example 1, and the resulting coating film was electrodeposited and had a uniform matte appearance with a gloss value of 36. The performance of this process was good as shown in Table 2.

Example 6 Acid value 4 consisting of 6.5 parts of methacrylic acid, 42.5 parts of methyl methacrylate, 25.0 parts of butyl acrylate, and 26.0 parts of hydroxypropyl methacrylate.
2.4, 90% solution of acrylic resin with hydroxyl value 101.3 in 2/8 ethyl cellosolve/isopropanol
The viscosity at °C was 9.5 poise.

To 100 parts of this solution, 4 parts of trimethylolethane trimethacrylate and 0.04 parts of azobisisobutyronitrile were added and reacted at 90°C for 1 hour.The result was a milky liquid containing microgels with a particle size of 10 to 15μ. A liquid was obtained. To 100 parts of the microgel-containing liquid obtained as described above, 30 parts of methyl and butyl mixed ether type methylolmelamine (Sumimar M-66B, manufactured by Oyu Kagaku Co., Ltd.) was added, and an aqueous dispersion was prepared in the same manner as in Example 1. As shown in Table 2, the coating film obtained by electrodeposition coating had good performance and a uniform matte coating appearance with a gloss value of 12.

j Comparative Example 1 30 parts of butyl cellosolve, 70 parts of isopropanol, 10 parts of trimethylolpropane trimethacrylate, and 0.1 part of azobisisobutyronitrile were mixed at 90°C with stirring.
Allowed time to react.

The microgel particles produced had a particle size of 100-500μ. 30 parts of this microgel-containing liquid was mixed with 150 parts of the 55% solution of the acrylic resin used in Example 1 and 30 parts of hexamethoxymethylolmelamine (Cymel 300, manufactured by Mitsui Toatsu Chemical Co., Ltd.), and the carboxyl group was removed with trinoethylamine. After neutralizing 80%, it was diluted with water to obtain an aqueous dispersion with a solid content of 12%. The coating film obtained by electrodeposition using this aqueous dispersion in the same manner as in Example 1 exhibited a rough surface, with little matte effect observed. Comparative Example 2 Fine particle silica (manufactured by Fuji Davison Chemical Co., Ltd., Thyroid #
244), 30 parts of hexamethoxymethinolol melamine (manufactured by Mitsui Toatsu Chemical Co., Ltd., Cymel 300),
A bath solution having a solid content of 12% was prepared in the same manner as in Example 1, and the coating film was electrodeposited, baked and dried, and had a gloss value of 43 and a slightly uneven coated surface.

Claims (1)

[Claims] 1. Trimethylolpropane tri(meth) after anodizing aluminum and/or aluminum alloy, or after anodizing and performing a treatment that generates hydrates to the extent that it does not block the current carrying holes. A reactive monomer selected from acrylate, trimethylolethane tri(meth)acrylate, and trimethylolmethane tri(meth)acrylate has a viscosity of 0.5 to 50 at the polymerization temperature of the above reactive monomer.
is a poise, has substantially no reactivity with the above-mentioned reactive monomer, and contains a carboxyl group and a hydroxyl group,
It is characterized by coating with a coating composition containing a liquid containing synthetic resin fine particles obtained by polymerization in an acrylic resin solution having an acid value of 20 to 150 and a hydroxyl value of 20 to 150, and a melamine resin as a curing agent. A matte coating method for aluminum and/or aluminum alloys. 2. The matte coating method according to claim 1, wherein the coating is performed by electrodeposition coating.