JPS607551B2 - How to paint aluminum products - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for surface treatment of aluminum products.

Specifically, the present invention relates to a method of painting an aluminum product that has been subjected to anodizing treatment and sealing treatment and has a surface structure that is in an inactive state. Conventionally, aluminum products are generally anodized in an electrolytic solution such as sulfuric acid, oxalic acid, or chromic acid for the purpose of imparting corrosion resistance.

As a result, the oxide film formed on the surface of aluminum products consists of a porous Y-N203 layer with countless micropores with a diameter of about 100 to 500 A, but this alone does not provide sufficient corrosion resistance, and it is Alternatively, a method of performing hydration sealing treatment in pressurized steam or coating the surface of the oxide film with a resin has been implemented. Resin coating methods include dissolving or dispersing the resin in an organic solvent or water and applying it by spraying, applying an electrostatic charge to the resin particles at the same time as spraying, and applying the resin electrostatically by dissolving it in an organic solvent or water. Alternatively, the object to be coated is immersed in a dispersed resin liquid and a resin film is formed using the viscosity of the resin liquid and the volatility of the solvent. A method of crushing and electrically forming a resin film between a counter electrode and a direct current or an alternating current, by spraying resin powder onto a heated object, or by injecting resin powder into a flowing powder. A method of forming a molten film by bringing the material into contact with the object to be coated is known. The present inventor previously proposed a new coating method for aluminum products that has a fundamentally different coating mechanism from these conventional methods (Japanese Patent Laid-Open No. 55-944
(See No. 95).

In this method, an aluminum product that has been anodized and has a surface structure in an active state is polymerized with one or more ethylenically unsaturated monomers so that the polymer particles are negatively charged. In this method, a water-insoluble resin layer is formed on the surface of the aluminum product by impregnating the aluminum product with a polymer latex that has been obtained and whose pH has been adjusted to 3.0 or less. In the above method, when an aluminum product having an inert surface structure in which aluminum is anodized and then sealed is applied, even if it is immersed in the polymer latex, a water-insoluble resin layer is formed in a short period of time. However, as a result of further research by the present inventors, by incorporating fluorine ions into the polymer latex, it became clear that it took a long time to form a coating film. The present invention was completed based on the knowledge that an insoluble resin layer can be formed in a short time.

To outline the present invention, an aluminum product having a surface structure in an inert state is produced by anodizing and sealing, and then polymer particles containing one or more ethylenically unsaturated monomers are negatively charged. obtained by polymerization so that the pH is
This is a method for forming a water-impregnable polymer coating layer on the surface of the aluminum product in a short period of time by adjusting it to 4.0 or less and soaking it in a polymer latex containing fluorine ions.

In the present invention, the term "surface structure in an inactive state" refers to a surface structure that is not dyed in a sealing test based on dyeability, and the anodized film is used in a JIP (Japanese Industrial Standards) day 8683 dye liquid immersion bond test. It refers to the surface structure that is not dyed at all as a result of immersing Aluminum Blue (AIum Sengawa mBlue) 4W in an aqueous solution of IW'V% at 2000 for 15 minutes and washing with water.

The process of the present invention is similar to that of the conventional bond coating method, but the mechanism for forming a resin layer on the surface of the object is completely different.

In other words, in the conventional general immersion coating method, an anodized aluminum product is immersed in a water-soluble paint, and then pulled up to form a resin layer that physically adheres to the surface. By the way, if you wash the resin layer with water immediately after forming it, most of the resin layer will be dispersed in water again.In contrast, according to the method of the present invention, the resin layer will be immersed in the specific polymer latex. The resin layer formed on the surface of the aluminum product is a water-insoluble material that adheres so tightly to the surface of the aluminum product that even if it is washed with water, the resin will not be dispersed again in the water. In the immersion coating method, in order to obtain a thick and uniform coating, it is necessary to take into account the control of the viscosity, solid content, and specific gravity of the paint, the lifting speed of the object to be coated, and the setting after painting. .

In this way, it is necessary to prepare a paint that is suitable for bond painting.In particular, when coating anodized aluminum products, water-soluble resin paint (with a viscosity of 27 ±mother ps, solid content 20-35%, pH 8.0
-8.7, specific gravity 0.955-0.975) are used. In addition, polymer latex generally has a very low viscosity and was understood to be unsuitable as a coating material for dipping and thin coating, which utilizes the viscosity of the coating material to form a coating film. Although the method of the present invention uses this polymer latex, it also has the advantage that a highly concentrated water-insoluble resin layer can be formed even from a latex with a low solid content (1%). As described above, even though the operating method of immersing grooves in resin liquid is the same, the present invention is completely different from the immersion coating method in terms of the resin coating formation mechanism.
Rather, it is similar to dew coating.

However, the method of the present invention differs from methods that use electricity such as electrodeposition coating methods; by simply impregnating the surface of the object to be coated, a "dense, high-concentration resin layer that adheres uniformly and firmly to the surface of the object to be coated" is created. This is the method that allows the formation of , and this is the most distinctive feature.

To explain the method of the present invention in more detail, aluminum products are first subjected to an anodizing treatment.

The electrolytes used for anodizing treatment include sulfuric acid, chromic acid, boric acid, phosphoric acid, pyrophosphoric acid, molybdic acid, yakic acid, sulfamic acid, sulfosalicylic acid, sulfosuccinic acid, malonic acid, tartaric acid, citric acid, etc. A mixture is used.The thickness of the anodic oxide film is not particularly limited, but
If it is less than 1, it is not practical as an oxide film, while if it is more than 35, it is unnecessary, and usually 1 to 35, preferably 3 to 3.
It is about 20 mu. Aluminum products that have been anodized are usually washed with water after treatment to remove any electrolyte that may have adhered to them.

The surface of aluminum products that has undergone normal anodizing treatment is
It is dyed by the pore sealing test based on the dyeability described above. The aluminum products used in the present invention are further sealed with boiling water, pressurized steam, a metal salt aqueous solution, etc., and are anodized to have a surface structure that is inactive, that is, not dyed in the staining test described above. Targets coatings.

In addition, we can dye aluminum products that have undergone anodizing treatment.
Items colored with coloring agents such as pigments and polymer dyes, or items colored by immersion or electrolysis in an aqueous metal salt solution,
Even if the surface has a pattern such as a wood grain pattern formed on the surface, it is subject to the method of the present invention as long as it is not dyed in the above-mentioned pore-sealing test based on dyeability after a pore-sealing treatment is performed. The polymer latex used in the present invention is obtained by emulsion polymerization of one or more monomers having ethylenically unsaturated double bonds.

Monomers having ethylenically unsaturated double bonds include acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid, alkyl acrylates, alkyl methacrylates, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, acrylamide, and methacrylates. Amides and their N-methylolated or N-alkoxymethylolated products, acrylic or methacrylic monomers such as acrylonitrile and methacrylonitrile, styrene,
It includes styrene monomers such as p-chlorostyrene and Q-methylstyrene, vinyl monomers such as vinyl acetate and vinyl propionate, and gen monomers such as butadiene, isoprene, and chloroprene. In addition, phosphate group and ethylene unsaturated double bond, mono (2 -hidroxyethyl acrylate) Acidphosphate, goods (2 -hydroxyethyl metallate) Asidohosfweet, mono (2 -hidroxip. acrylate) acid phosphate, mono(2-hydroxypropyl methacrylate) acid phosphate, mono(
Primary phosphoric acid esters of acrylates or methacrylates containing hydroxyl groups, such as 3-hydroxypropyl acrylate) acid phosphate, mono(3-hydroxypropyl methacrylate) acid phosphate, allyl alcohol acid phosphate, vinyl phosphonic acid, parapinylbenzenephosphonic acid, a monomer with a sulfonic acid group and an ethylenically unsaturated double bond,
For example, sulfomethyl acrylate, 2-sulfoethyl acrylate, 2-sulfopropyl acrylate, 3-sulfopropyl acrylate, sulfomethyl methacrylate, 2-sulfoethyl methacrylate, 2-sulfopropyl methacrylate, 3-sulfopropyl methacrylate, styrene sulfonic acid, vinyl Sulfonic acid, allylsulfonic acid, etc. can also be used. In order to obtain a polymer latex, a known method for polymerizing one or more of these monomers may be used. In the method of the present invention, an aluminum product is anodized and then sealed, and has a surface area that is not dyed in a sealing test based on dyeability. The aluminum product is immersed in a polymer latex containing fluorine ions, and the surface of the aluminum product is water-insoluble. This is a surface treatment method for forming a resin film, but the pH of the polymer latex must be adjusted to 4.0 or less, preferably 3.0 or less, and the surface of the polymer particles must be negatively charged. be.

This means that any type of polymer latex
When the pH is 4.0 or higher, almost no water-insoluble resin layer is formed, and even polymer latex whose pH is adjusted to 4.0 or lower have negatively charged polymer latex particles. This is based on the knowledge that formation of a water-insoluble resin layer is not observed in latex without water.

In order to obtain an anionic polymer latex with negatively charged polymer particles, anionic polymerization initiators and/or emulsifiers are used. Alternatively, a monomer having a functional group that causes the polymer latex to be negatively charged may be used. In the present invention, the types and amounts of these particles are not particularly limited, as long as polymer latex particles that are negatively charged as a whole can be obtained.

For example, even if an initiator such as 404-azobisisobutyramidinium hydrochloride is used, the entire particle can be negatively charged using an anionic emulsifier such as sodium lauryl sulfate. Can be used for invention methods.
・Therefore, the polymerization method for the polymer latex used in the present invention includes radical emulsion polymerization using a nonionic surfactant or anionic surfactant as an emulsifier and potassium persulfate, ammonium persulfate, etc. as an initiator, and peroxidation. Emulsion polymerization using hydrogen and a redox initiator such as Fe20 can be used.

Further, emulsion polymerization without using an emulsifier, emulsion suspension polymerization using azobisisoputilonitrile, penzoyl peroxide, etc. can also be used. Examples of nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene nonylphenol ether, sorbitan monolauryl ester, sorbitan dioleyl ester, and polyoxyethylene sorbitan monostearyl ester. ,
Examples of anionic surfactants include oleic acid sodium salt, lauryl alcohol sulfate sodium salt, stearyl alcohol sulfate trietanolamine salt, dodecylbenzenesulfonic acid sodium salt,
Potassium salt of octylnaphthalene sulfonate, sodium salt of dioctyl sulfosuccinate, sodium salt of polyoxylauryl sulfate ester, and potassium salt of polyoxyethylene nonylphenol sulfate ester.Adjustment of the pH of polymer latex can be done using sulfuric acid, hydrochloric acid, nitric acid. Potassic acid, such as
This may be carried out by adding an organic acid such as acetic acid or oxalic acid.

The present invention requires that the polymer latex contain fluoride ions.

Fluoride ions can be introduced by using hydrofluoric acid as a brewing ingredient, or by using salts of hydrofluoric acid and various inorganic or organic alkalis, K2TiF6, Na2TiF6, (NH4
)2TjF6, titanium fluoride compounds such as TiF4, K2
Silicon fluorides such as SiF6 and Na2SiF6 may be added. The fluoride in the polymer latex solution is added in an amount of 0.4 to 5, calculated as F-, the fluorine ion concentration. If it is less than 0.4 nights, the resin layer formed will be so thin that it is not practical, while if it is more than 5 nights, a normal coating film appearance cannot be obtained, which is not preferable.

The resin concentration of the polymer latex used in the present invention is 0.5
~60% by weight (resin solid content) is suitable; if it is less than 0.5% by weight, the formed water-insoluble resin layer will be thin and the adhesion to the object to be coated will be poor; on the other hand, if it is more than 6% by weight, This is not preferable because the viscosity becomes high and it becomes difficult to obtain a stable polymer latex.

Considering economic efficiency from the resin film thickness and precipitation rate, 1 to 40% by weight is preferable. Anodized and sealed,
The immersion time for forming a water-insoluble resin layer by immersing an aluminum product with an inert surface structure into a polymer latex varies depending on the desired resin film thickness.
Usually, a resin layer of 5 to 30 layers can be obtained in 3 to 10 minutes. The polymer latex bath is preferably used at a temperature ranging from room temperature to 50°C. If necessary, the aluminum product pulled from the polymer latex is further soaked in water to remove excess polymer latex, and then dried.

Drying is usually done at room temperature to 200°C for 5 to 30 minutes,
A functional unsaturated monomer, such as an ethylenically unsaturated monomer having a glycidyl group, a hydroxyl group, an amide group, a methylol group, an alkoxymethylol group, etc., is copolymerized in the polymer latex, or a thermosetting When containing an epoxy compound, an amino compound, a blocked polyisocyanate compound, a phenol compound, etc., it is necessary to use the heating temperature and time necessary for the curing reaction. The aluminum products to which the present invention is applied include plates, strips, wires, and other molded products with complex shapes, and are not limited in shape or size. Furthermore, when processing long shapes such as aluminum sashes, either horizontal or vertical hanging methods can be adopted. Next, Examples will be shown in order to explain the present invention more specifically.

In addition, all parts in the following examples are parts by weight,
In addition, the following polymer latex was used. Preparation of Latex A 27 parts of deionized water and 3 parts of polyoxyethylene nonylphenol sulfate were added to a four-ring flask equipped with a takayo machine, a thermometer, a reflux condenser, a dropping funnel, and a nitrogen gas inlet tube. The temperature was then flooded to 70°C.

To this, potassium persulfate 1. After adding the anchor and dissolving it,
A mixture of 12 parts of ethyl acrylate and 8 parts of methyl methacrylate was added dropwise from the dropping funnel over 2 hours. After the dropwise addition was completed, the reaction was continued for another 2 hours to prepare a latex with a conversion rate of 95% or more. Preparation of Latex B 218 parts of deionized water and 2.4 parts of polyoxyethylene nonylphenol sulfate were added to the same reaction vessel as used for preparing Latex A, and the mixture was flooded to 70 ml with stirring.

After adding and dissolving 0.8 parts of potassium persulfate, 76.8 parts of ethyl acrylate and 5 parts of methyl methacrylate were added.
A mixed solution of 1.2 parts of 2-hydroxyethyl methacrylate, 8 parts of N-doxymethylol acrylamide, and 2 parts of dodecyl mercaptan was added dropwise from the dropping funnel over a period of 2 hours. After the dropwise addition was completed, the reaction was continued for another 2 hours to prepare a latex with a conversion rate of 95% or more. Example 1~
4. 5 parts of latex AI, 15 parts of deionized water, and 3 parts of a 47% aqueous solution of hydrofluoric acid were placed in a beaker and thoroughly stirred to prepare a coating solution with a resin solid content of 2% by weight.

The pH of this coating liquid was 2.0. On the other hand, an aluminum plate that had been anodized and had a microporous oxide film formed on its surface was placed in boiling deionized water for 10 minutes, 20 minutes, and 3 minutes.
The material was immersed for 0 minutes and 60 minutes, and then subjected to a sealing treatment to obtain an object to be coated. These pore-sealed aluminum pieces were immersed in an aqueous solution of Aluminum Blue Sha W (a dye manufactured by Sandoz Co., Ltd.) with an IW/V% aqueous solution at 20 oo for 15 minutes, and then washed with water. As a result, the surface structure showed no staining at all. The sealed aluminum was immersed in the coating solution for 2 minutes, then taken out, washed with water, and air-dried.

The surface condition of each aluminum plate was as shown in Table 1.

Table 1 Example 5 Latex B15, 15 parts of deionized water, and 3 parts of hydrofluoric acid were placed in a beaker and thoroughly stirred to prepare a coating solution with a resin solid content of 1% by weight.

The pH of this coating liquid was 2.1. On the other hand, an aluminum plate that had been anodized and had a microporous oxide film with nine peaks formed on its surface was placed in a nickel acetate bath (nickel acetate/nickel acetate).
Then, the pores were sealed with boric acid (59%).

When this pore-sealed aluminum plate was immersed in an aqueous dye solution in the same manner as in Examples 1 to 4, it showed a surface structure that was not dyed at all. When the sealed aluminum plate was immersed in the above coating solution (20 qo) for 3 minutes, a uniform water-proof resin coating layer of about 15 quarts was formed. Examples 6 to 7 and Comparative Example 1 In the method of Example 5, a 10% aqueous ammonium solution was added to adjust the pH to 3.0, 3. Each coating solution was prepared in the same manner except that the coating solution was adjusted to F4.2.

An aluminum plate sealed with a nickel acetate bath was immersed in each coating solution for 5 minutes, washed with water, and air-dried. The resulting coating film thickness was as shown in Table 2.
Table 2

Claims (1)

[Claims] 1 An aluminum product that has been anodized and sealed and has a surface structure in an inert state is polymerized with one or more ethylenically unsaturated monomers so that the polymer particles are negatively charged. An aluminum product characterized in that a water-insoluble polymer coating layer is formed on the surface of the aluminum product by adjusting the pH to 4.0 or less and immersing it in a polymer latex containing fluorine ions. How to paint.