JPS6057394B2 - Pretreatment method for powder coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pretreatment method for powder coating, and more specifically, a pretreatment method for powder coating to improve the corrosion resistance and adhesion of a powder coating film when powder coating a metal object. Regarding processing method.

Powder coating uses polymer resin to obtain a high-performance coating, does not require the use of any solvents from the paint manufacturing process to the paint, and requires the use of a water-washing booth during painting. It has recently been in the spotlight for several reasons, including the fact that there is no wastewater treatment process required.

In powder coating as well, when coating iron or other metal objects, the surface of the metal object is pretreated in order to improve the corrosion resistance and adhesion of the formed coating film. In reality, phosphate chemical conversion treatment, which is a common pretreatment method for solvent-based paints, is actually used as is. However, this phosphate chemical conversion treatment cannot satisfy the desired corrosion resistance and adhesion of the powder coating film. This is understandable considering that powder coatings have completely different compositions from solvent-based coatings, and the coating film formation process is also different. Second, the quality of the powder coating film performance is determined by the pre-treatment film on the base surface (base film).
Defects in corrosion resistance, underarm (foaming)
Problems such as occurrence of color, poor gloss, and poor adhesion occur.
The object of the present invention is to provide a pretreatment method for powder coating that improves the processing performance of the phosphate chemical conversion treatment, that is, can satisfy the desired degree of corrosion resistance and adhesion of the powder coating film. It is about providing.

Still another object is to provide the above pretreatment method which can be applied to various types of powder coatings, particularly preferably thermosetting powder coatings, without being limited to the types of powder coatings. As a result of intensive research to achieve this objective, the present inventors have found that, as a pretreatment method, in addition to or in place of the above-mentioned phosphate chemical treatment, a specific type and amount of a water-soluble polymer is added as an emulsifier. When an emulsion consisting of a water-soluble chromium compound and a treatment solution containing a water-soluble chromium compound as a main component are applied to a metal object, a base film of an organic polymer compound containing a chromium compound is formed. The coating film of various powder coatings is strongly bonded to the coating film, and the corrosion resistance and adhesion of the coating film are improved.If semimetal or metal oxide is added to the treatment liquid, the above corrosion resistance and adhesion can be improved. We found that it could be further improved.

Furthermore, it has been found that the corrosion resistance of the corrosion layer can be improved by making the treatment liquid substantially free of alkali metal ions. Moreover, in this treatment method, since the chromium compound is encapsulated in the organic polymer compound layer in the base film, there is no need to wash away the excess chromium compound with water, eliminating the need for a water washing step. At the same time, the problem of discharging chromium-containing wastewater does not occur. The present invention was completed based on the above-mentioned knowledge, and the gist thereof is that when powder coating a metal object, the object to be coated should be subjected to a phosphate chemical conversion treatment or the like. An emulsion prepared by emulsion polymerization of α,β-monoethylenically unsaturated monomers, containing 30 to 9% of the total chromium.
Treatment liquid (hereinafter referred to as Em/Cr/M
In the method of surface treatment by coating a polyacrylic acid and/or acrylic acid and methacrylic acid, acrylamides, methacrylamides and the general formula or a methyl group, R represents a C2-4 substituted or unsubstituted alkylene group, and x represents a functional group having at least one of an oxygen atom, a phosphorus atom, and a sulfur atom. ]
A copolymer with at least one selected from the group of hydrophilic monomers shown in the following is used in a solid content ratio of 2 parts by weight or more per 10 parts by weight of the above α,β-monoethylenically unsaturated monomer. A pretreatment method for powder coating, characterized in that it is used in

The emulsion in the present invention is produced by emulsion polymerization of a conventional α,β-monoethylenically unsaturated monomer using a specific water-soluble polymer in a specific ratio as an emulsifier.

The above-mentioned water-soluble polymers include polyacrylic acid, acrylic acid and methacrylic acid, acrylamides (e.g. acrylamide and N-methylolacrylamide), methacrylamides (e.g. methacrylamide and N-methylolmethacrylamide), and those represented by the above general formula. Hydrophilic monomers (for example, when X is a functional group having an oxygen atom, monomers include 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, 3-hydroxybutyl acrylate, acrylic acid 2,
2-bis(hydroxymethyl)ethyl, methacrylic acid 2
, 3-dihydroxypropyl, 3-hydroxybutyl methacrylate, etc., when X is a functional group having a phosphorus atom, monomers include 5-mono(2-hydroxyethyl methacrylate) acid phosphate, 5-mono(3-chloro-2-hydroxypropyl methacrylate) ) Sulfonylethyl methacrylate, etc. as a monomer when X is a functional group having a sulfur atom, such as acid phosphate, etc.)
The copolymer is a copolymer with at least one selected from the group consisting of: 1 or a mixture of 2 or more thereof.

The structures of the monomers 5 and 5 are as follows. The ratio of acrylic acid and other hydrophilic monomers in the above copolymer is usually such that the acrylic acid content in all monomers is 5% or more, preferably from the viewpoint of system stability of the emulsion and adhesion to metal substrates. may be appropriately selected so that it is within a range of 6% or more.

Such a water-soluble polymer can be produced by a conventional method (polymerization method in an aqueous solution, bulk polymerization method, polymerization method in an organic solvent, etc.)
It may be carried out according to the following.

For example, in order to perform polymerization in an aqueous solution, the constituent monomers acrylic acid alone or a mixture of acrylic acid in a predetermined proportion and at least two other hydrophilic monomers and a water-soluble free material containing no alkali metal ions are used. Radical catalyst (
For example ammonium persulfate and 2,7-azobis(
(amidinopropane)-hydrochloride) containing water (
(preferably deionized water) are simultaneously dropped into water (preferably deionized water) maintained at the reaction temperature from separate dropping ports, and if necessary, ripened at the same temperature. The reaction is carried out under stirring, and the reaction temperature is usually 70-90°C.
°C, and the reaction time (dropping time + aging time is usually 3 to 5 hours. Examples of the α,β-monoethylenically unsaturated monomer include acrylic esters (methyl acrylate, Ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-acrylate
Ethylhexyl, decyl acrylate, isooctyl acrylate, 2-ethylbutyl acrylate, octyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, 3-ethoxypropyl acrylate, etc.), methacrylate esters (methyl methacrylate, methacrylate, etc.) Ethyl, isopropyl methacrylate, methacrylic acid n
-butyl, isobutyl methacrylate, n- methacrylate
hexyl, lauryl methacrylate, decyl octyl methacrylate, stearyl methacrylate, 2-methacrylate
methylhexyl, glycidyl methacrylate, 2-ethoxyethyl methacrylate, cetyl methacrylate, benzyl methacrylate, 3-methoxybutyl methacrylate, etc.)
, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, vinyl ketone, vinyltoluene, and styrene, and one or a mixture of two or more of these may be used. In addition to these, acrylamides, which are constituent monomers of the water-soluble copolymer mentioned above,
A small amount of methacrylamide and a hydrophilic monomer represented by the above general formula may be added. In particular, methacrylic acid 2
- By adding a monomer having an OH group such as hydroxyethyl, the emulsion polymer adopts a crosslinked structure with the COOH group in the emulsifier, so the formed base film has significantly improved adhesion to the metal substrate. Is recognized. The above-mentioned emulsion polymerization was carried out under normal conditions and methods, except for using the above-mentioned water-soluble polymer as an emulsifier and the above-mentioned water-soluble catalyst that does not contain alkali metal ions that adversely affect corrosion resistance and moisture resistance as a catalyst. May be implemented.

For example, α, β
- the monoethylenically unsaturated monomer and a water-soluble catalyst without alkali metal ions (e.g. ammonium persulfate) and optionally water containing the remainder of the emulsifier (preferably deionized water) are added simultaneously through separate dropping ports. It may be added dropwise and, if necessary, aged at the same temperature. Polymerization is carried out under stirring, and the polymerization temperature is usually 50 to 70°C, preferably 5°C.
The temperature is 5 to 65°C. The polymerization time (dropping time + aging time) may normally be 3 to 7 hours. The amount of the emulsifier to be used is 2 parts by weight or more, preferably 20 to 5 parts by weight, based on 100 parts by weight of the α,β-monoethylenically unsaturated monomer to be subjected to emulsion polymerization. - Select sea urchins. If the amount used is less than 2 parts by weight, the storage stability of the emulsion itself will deteriorate and it will no longer be usable.
Furthermore, even if the amount exceeds 5 parts, the storage stability of the emulsion itself and the chemical stability against water-soluble chromium compounds will not be particularly improved, and on the contrary, the emulsion may become foamy. A problem arises. By such emulsion polymerization, a uniform and stable emulsion with a solid content of about 3% by weight can be obtained.

In addition, when using this emulsion, if necessary, an ordinary epoxy resin (for example, a commercially available bisphenol type product manufactured by Shell Chemical Co., Ltd. under the trade name 1 Epikote 828J) may be used.
1 Do1 Engineering Picault Day 001J) may be used in combination as a curing agent, and this epoxy resin may be used in the above emulsion polymerization with α,
It may be dissolved in a β-monoethylenically unsaturated monomer and subjected to polymerization dropwise to be present in the emulsion. By using an epoxy resin, it is possible to form a base film with superior adhesion to the metal surface.As the water-soluble chromium compound in the present invention, any known compound can be used; It is important that the coating does not contain metal ions such as alkali metal ions (and anions) that are harmful to the corrosion-resistant coating, and ordinary chromates and the like are not suitable.

From this point of view, chromic anhydride (CrO3) is practically optimal.

In the present invention, it is important that the content ratio of hexavalent chromium in the water-soluble chromium compound is set in the range of 30 to 90% by weight, preferably 30 to 7% by weight based on the total amount of chromium. be.

Therefore, the water-soluble chromium compound may be partially reduced in advance with formalin, hydrogen peroxide, etc. to the extent that these conditions are satisfied. If the content ratio of hexavalent chromium is less than 3% by weight, not only the corrosion resistance of the coated plate will decrease, but also the workability during molding will deteriorate. Moreover, when the amount exceeds 9%, chromium tends to be eluted from the base film, resulting in poor corrosion resistance. Examples of semimetal or metal oxides in the present invention include aluminum oxide, silicon oxide, titanium oxide, zinc oxide,
A powder or sol of molybdenum oxide is used.

Among these, silicon oxide powder commonly called 1 white carbon dioxide is particularly suitable. The above white carbon generally includes (1) anhydrous silicic acid (10 to 50 mμ), (2) hydrated silicic acid (15 to 50 mμ), (3) hydrated calcium silicate (20 to 100 mμ), and (4) hydrated aluminum silicate ( 20 to 50 mp), but preferable white carbons for the present invention include those that meet the following conditions.

(4) Water-soluble white carbon whose primary particles have a particle size of 0.1 to 3μ and which are difficult to aggregate in the processing solution and exist suspended as almost single particles; (B) primary particles of water-soluble white carbon; Water-insoluble white carbon that has a large cohesive property and exists as coagulated particles of 0.1 to 3μ in the processing solution even if the primary particles are colloidal particles, and/or (C) substantially contains alkali metal ions. No water-insoluble white carbon.

Commercially available water-insoluble white carnobons that meet these conditions include RASPJ (manufactured by Engel Hard Minerals & Chemical Corporation), 1 Satin Tonyo (manufactured by the company), 1 Thyroid J (manufactured by Davinon),
Examples include 1 Silnetx J (manufactured by Mizusawa Chemical Industry Co., Ltd.), 1 Aerosil' IT6OO (manufactured by Degussa), RTK8OO (manufactured by Degussa), and RHK125J (manufactured by Degussa).

The Em/Cr/M treatment liquid used in the method of the present invention is prepared by first sufficiently dispersing the metalloid or oxide in water (preferably deionized water), and then mixing this with an emulsion and a water-soluble chromium compound at once. If necessary, the specified concentration (solid content 0)
．． 5-10% by weight) diluted with water (preferably deionized water).

The blending ratio of the emulsion and the water-soluble chromium compound is desirably set in the range of 10011 to 1, preferably 10 to 1'5, in terms of solid content. If the proportion of water-soluble chromium compounds is smaller than the above range, the corrosion resistance of the painted plate will decrease,
Moreover, the adhesion between the base film and the metal surface becomes insufficient.
Moreover, if it is larger than the above range, a problem will arise in the adhesion of the painted plate. The blending ratio of the emulsion and the metalloid or metal oxide is preferably 211 to 1011 in terms of solid content.
It is desirable to set it in the range of ~112. If the proportion of the above oxide is smaller than the above range, no particular improvement will be observed in the adhesion or corrosion resistance of the coating film, and if it is larger than the above range, no further performance improvement will be observed, which is not economically desirable. . In addition, sources of various metal ions (excluding alkali metal ions) and inorganic ions may be added to the processing liquid within a range that does not impair its stability. This ion addition makes it possible to form a base film that is more uniform and has better adhesion to the metal surface. Such additive ions include, for example, Zn2+, CO2+, Ni2+, Fe2
+, Fe3+, PO[, F-, BFI, SiF Kinichi, and the like. In this way, a desired treatment solution containing an emulsion, a water-soluble chromium compound, and a metalloid or metal oxide is prepared. The pretreatment method for powder coating of the present invention involves two steps: 2. Applying the usual phosphate chemical conversion treatment (for example, degreasing → washing → iron phosphate) to the metal (iron, galvanized steel, aluminum, etc.) to be coated for powder coating. Alternatively, after forming a chemical conversion film (which consists of the steps of zinc phosphate film formation → water washing → drying) or without applying it, it can be coated using methods such as dipping, spraying, brush coating, and roll coating. The Em/Cr/M treatment solution described above may be applied and dried without washing with water (the drying conditions may be similar to those in phosphate chemical conversion treatment).

In this way, as mentioned above, a pre-treatment film of an organic polymer compound containing a chromium compound and a metalloid or metal oxide (hereinafter referred to as Em/Cr/M-based film) is applied to the metal coating. Formed directly on the surface or via a chemical conversion coating. The weight of the above chemical conversion coating is usually 0.1 to 3.5y.
/d1 and the weight of the Em/Cr/M film is usually 0.
It may be set within a range of 0.01 to 5 f/a, preferably 0.05 to 0.7 f/a. In addition, such Em/Cr
Drying is essential for the formation of /M-based film, but if preheating (usually heated at 200°C or higher) is performed in the next powder coating, it may be combined with this, and drying may be performed before preheating. You can do it. It can be implemented according to the actual situation of each line. According to the method of the present invention having the above configuration, the total amount of chromium compounds in the Em/Cr/M treatment solution can be reduced directly on the surface of the metal to be coated or through a phosphating film formed using the conventional method. It is coated with an organic polymer compound and a metalloid or metal oxide, and a physical and chemical bond 5 is formed between the organic polymer compound, the metalloid or metal oxide, and chromium during the drying process. A necessary and sufficient amount of the substantially water-insoluble or slightly water-soluble Em/Cr/M-based film is fixed.

Therefore, by varying the concentration and application amount of the treatment liquid, any desired amount of chromium can be applied to the metal surface. In this way, a base coat is formed that is compatible with the powder paint coating. By the way, with the general romic acid cleaning treatment method, the amount of chromium deposited after washing with water and drying is at most 5T.
A value of about n9/a was insufficient to improve the corrosion resistance and adhesion of the powder coating film. It is believed that the above-mentioned specific polymer compound layer constituting the Em/Cr/M film is bonded to the resin component in the paint during powder coating, and that chromium and semimetal or metal oxides also assist in this bonding. It will be done.
The powder coating paint that is the object of the present invention may be of any type, such as thermosetting powder paints such as acrylic, polyester, or epoxy, or thermoplastic paints such as polyolefin, vinyl chloride, or polyester. Any powder coating may be used, and a thermosetting powder coating is particularly suitable. Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Note that 1 part and 1% in the example sentences mean 1 part by weight and 1% by weight, and Examples 6 to 8 include examples for comparison. Example 1 Preparation of emulsion In a flask equipped with a stirrer, reflux condenser, thermometer and two dropping ports, 15 g of deionized water and acrylic acid and 2-hydroxyethyl methacrylate were added in a weight ratio of 8:2. A water-soluble copolymer (25% aqueous solution, molecular weight (M″w) 66,000) 120ff1) obtained by copolymerization at a ratio of 1 is added, and the temperature is raised to 60 to 65°C while stirring.

Next, 35 parts of methyl methacrylate and 1 part of styrene were added to this.
A monomer mixture consisting of 5 parts of 2-hydroxyethyl methacrylate and 4 parts of n-butyl acrylate, and a catalyst solution consisting of 2 parts of ammonium persulfate and (1) part of deionized water were added from separate dropping ports. Drop simultaneously over 8 hours. After completion of the dropwise addition, aging was performed at 60 to 65°C for about 2 hours to complete the polymerization reaction, and the solid content was reduced to 30.
Obtain a 1% emulsion. Preparation of Em/Cr/M-based treatment solution 8.1 parts of the above emulsion and a dispersion (solid content) in which fine-particle silicic acid anhydride (trade name: 1 Aerosil TT'600, manufactured by Degussa) were sufficiently dispersed in deionized water. 10%) 20
m1 and 5 parts of formalin (37% aqueous solution) to 95 parts of chromic anhydride 17% aqueous solution to obtain approximately 50 parts of hexavalent chromium amount.
Chromium aqueous solution obtained by reducing % to trivalent chromium (
7.4 parts (solid content: 16.5%) were mixed at room temperature, and deionized water was added to this to prepare a treatment liquid with a solid content of 2.3%.

Metal surface treatment and painted steel plates are subjected to degreasing and cleaning treatment (using Nippon Paint Co., Ltd.'s trade name 1 Ridrin #75N as a degreasing liquid), and then zinc phosphate film chemical conversion treatment (Nippon Paint Co., Ltd.'s trade name as a chemical conversion treatment liquid) 1 Granodin #1 N-1J used, film amount 1.
After 5 f/a), the Em/Cr/M treatment solution prepared above was spray applied and the treatment was carried out for 10 min without washing with water.
Dry for 2 minutes at 0C.

Next, the surface-treated steel plate was coated with acrylic powder paint (product name "Powdax A.j" manufactured by Nippon Paint Co., Ltd. (baking conditions: 170C x'), 3 powders, coating thickness 50μ).
The formed coating films were then subjected to salt spray tests and impact resistance tests, and the results are shown in Table 1. Comparative Example 1 Production of emulsion 7 In the same flask as in Example 1, 100 parts of deionized water and a nonionic surfactant (trade name 1 manufactured by Kao Atlas Co., Ltd.) were added.
Add 7 parts of Emulgen (950 g) and raise the temperature to 60-65°C while stirring.

Next, a monomer mixture having the same composition as in Example 1 was added to this,
2 parts ammonium persulfate and 20ml deionized water. and a catalyst solution consisting of the following components were simultaneously added dropwise from separate dropping ports over a period of 1 hour. After completion of the dropwise addition, aging was performed at 60 to 65°C for about 1 hour to complete the polymerization reaction, and the solid content was reduced to 46.
A 3% emulsion is obtained. Preparation of Comparative Treatment Solution To 5.3 parts of the above emulsion, 20 ml of the same white carbon dispersion (solid content 10%) as in Example 1 and 7.4 parts of a chromium aqueous solution (solid content 16.5%) were blended. Ionized water is added to prepare a treatment liquid with a solid content of 2.4%.

In Metal Surface Treatment and Painting Example 1, except for using the above comparative treatment liquid,
Surface treatment and painting were carried out under similar conditions to obtain a coated board.
The test results are shown in Table 1.

Comparative Example 2 Emulsion polymerization was carried out under the same conditions as in Comparative Example 1, except that 5 parts of an anionic surfactant (product name 1Levenol WXJ, manufactured by Kao Atlas Co., Ltd., 25% solution) was used instead of 7 parts of 1Emulgen 950J. Solid content 45.5
% emulsion and then this emulsion 5.4
2 m of the same white carbon dispersion (solid content 10%) as in Example 1 and a chromium aqueous solution (solid content 16.5%)
) When 7.4 parts of chromium was added, the entire husk agglomerated instantly, and the supernatant liquid had the color of an aqueous chromium solution.

Example 2 Preparation of Em/Cr/M-based treatment solution 8.1 parts of the emulsion obtained in Example 1 and ultrafine silica gel (trade name: 1 Silnetx P-526, manufactured by Mizusawa Chemical Co., Ltd.) were prepared in advance.
J) in deionized water (solid content: 1
Similar to Example 1, a ROM aqueous solution (solid content 16.5%) 2(H) was mixed at room temperature, and deionized water was added to this to prepare a treatment solution with a solid content of 2.4%. Prepare.

Surface treatment and painting were carried out under the same conditions as in Example 1 of Metal Surface Treatment and Painting, except that the above-mentioned m/Cr/M-based treatment liquid was used to obtain a coated plate, and the test results are shown in Table 1. show.

Example 3 Preparation of emulsion In Example 1, instead of 120 parts of acrylic acid/2-hydroxyethyl methacrylate water-soluble copolymer,
Polyacrylic acid (25% aqueous solution, molecular weight (MW) 590
00) under the same conditions except that 2 (4) parts were used and the composition of the monomer mixture was 35 parts of methyl methacrylate, 15 parts of styrene, w parts of ethyl methacrylate, and 40 m of n-butyl acrylate. Perform emulsion polymerization, solid content 30
．． An 8% emulsion is obtained.

Preparation of Em/Cr/M-based treatment liquid Add the same white carbon dispersion (solid content 10%) as in Example 1 to the emulsion 7 (branch) part and chromium aqueous solution (solid content 16.5%) 7. 4 parts were mixed and deionized water was added to prepare a treatment liquid with a solids content of 2.3%.

Metal Surface Treatment and Painting A coated plate was obtained by surface treatment and painting under the same conditions as in Example 1, except that the above &μSm/Cr/M type treatment liquid was used. The test results are shown in Table 1.

Example 4 Preparation of emulsion In Example 1, instead of 120 parts of acrylic acid/2-hydroxyethyl methacrylate water-soluble copolymer,
Emulsion polymerization was carried out under the same conditions except that polyacrylic acid 12 of Example 3 was used to obtain an emulsion with a solid content of 29.4%.

Preparation of Em/Cr/M treatment solution Above emulsion 5.1
7 parts of formalin (37% aqueous solution) was added to 15 parts of the same white carbon dispersion (solid content 10%) as in Example 1 and 95 parts of a 17% chromic acid anhydride aqueous solution to reduce about 70% of the amount of hexavalent chromium. A proportion of aqueous chromium solution (solid content: 16.2%) obtained by reduction to trivalent chromium is mixed at room temperature, and deionized water is added to prepare a treatment liquid having a solid content of 2.4%.

In Metal Surface Treatment and Painting Example 1, the above? ? Coated plates were obtained by surface treatment and coating under the same conditions except that m/Cr/M treatment liquid was used. Table 1 shows the test results.

Example 5 Preparation of emulsion In Example 1, instead of 120 parts of acrylic acid/2-hydroxyethyl methacrylate water-soluble copolymer,
A water-soluble copolymer obtained by copolymerizing acrylic acid and acrylamide at a weight ratio of 8:2 (25% aqueous solution,
Except for using molecular weight (MW) 34000) 12
Emulsion polymerization was carried out under similar conditions to obtain an emulsion with a solid content of 31.5%.

Preparation of Em/Cr/M treatment solution Above emulsion 5.1
1 part, 15 parts of a dispersion (solid content 10%) in which fine particle silicic anhydride (trade name 1 Aerosil 200J, manufactured by Degussa) was sufficiently dispersed in deionized water, and a ROM aqueous solution (solid content 16%) as in Example 1. .5%) and add deionized water to prepare a treatment liquid with a solid content of 3.1%.

Metal surface treatment and painting A coated plate was obtained by performing surface treatment and painting under the same conditions as in Example 1, except that the above-mentioned m/Cr/M-based treatment liquid was used, and the test results are shown in Table 1. show.

7 Comparative Example 3 After degreasing and cleaning a steel plate in the same manner as in Example 1,
This was coated in the same manner as in Example 1 to obtain a coated plate, and the test results are shown in Table 1.

Comparative Example 4 A steel plate was subjected to degreasing and cleaning treatment and zinc phosphate film conversion treatment in the same manner as in Example 1, and then painted in the same manner as in Example 1 to obtain a coated plate. Shown in the table.

Comparative Example 5 Preparation of Comparative Treatment Solution From the formulation of Example 1, the chromium component was removed and the solid content was reduced to 2.3.
% treatment solution is prepared.

In Metal Surface Treatment and Painting Example 1, except for using the above comparative treatment liquid,
Surface treatment and painting were carried out under similar conditions to obtain a coated board.
The test results are shown in Table 1.

Comparative Example 6 Preparation of Comparative Treatment Solution A treatment solution with a solid content of 2.3% is prepared by removing the white carbon component from the formulation of Example 1.

Metal Surface Treatment and Painting A coated plate was obtained by performing surface treatment and painting under the same conditions as in Example 1, except that the above-mentioned comparative treatment liquid was used, and the test results are shown in Table 1.

Comparative Example 7 Preparation of Comparative Treatment Solution A treatment solution with a solid content of 2.3% is prepared by removing the emulsion component from the formulation of Example 1.

In Metal Surface Treatment and Painting Example 1, except for using the above comparative treatment liquid,
Surface treatment and painting were carried out under similar conditions to obtain a coated board.
The test results are shown in Table 1.

Comparative Example 8 Preparation of Comparative Treatment Solution During the formulation of Example 1, 0 sodium (as NaOH) was added.
．． 6 parts to prepare a treatment liquid with a solid content of 2.3%.

In Metal Surface Treatment and Painting Example 1, the above comparative treatment liquid is used. A coated board was obtained by surface treatment and painting under the same conditions except for the above, and the test results are shown in Table 1.

Note 1: Tested using a method that complies with JIS-K-5400.7-8. A cross cut was made on the test plate, a tape peel test was performed on the cross cut part, and the spray time (Hr) at which no peeling occurred was evaluated. 2JIS-K-5400
・Evaluated in 6-12, depending on the peeling condition, ××, ×, Δ
The evaluation was based on a five-point scale of , 0, and ◎.

Example 6 Steel plate subjected to degreasing and cleaning treatment in the same manner as in Example 1, such degreasing and cleaning treatment and iron phosphate coating chemical conversion treatment (Nippon Paint Co., Ltd. product name 1 Diuridine 210-BJ was used as the chemical conversion treatment liquid, film amount was Em/Cr/M-based treatment solution prepared in Example 1 was applied to each of the steel sheets subjected to the degreasing and cleaning treatment and the zinc phosphate coating chemical conversion treatment in the same manner as in Example 1. Apply with a roll and apply 100
℃ for 2 minutes (this treatment is referred to as the pretreatment).
The same applies below), then apply a polyester powder coating (Nippon Paint Co., Ltd., trade name 1 Baudax P Whiteo) (baking conditions: 170°C x 3 powders, coating thickness 50μ), and the coating film formed is the same as in Example 1. A similar test was conducted, and the results are shown in Table 2. (However, the evaluation of the salt spray test is based on the tape peeling width after the spray time of 240 F1r or 840 hr. (performed during evaluation).

Example 7 Each of the three treated steel plates prepared in the same manner as in Example 6 was coated as is or with the Em/Cr/M treatment solution prepared in Example 1, and heated at 150°C.
After drying for 1 minute, an epoxy powder coating (trade name 1 Powdax E Clay J manufactured by Nippon Paint Co., Ltd.) was applied (baking conditions: 170°C x 3 minutes, coating thickness 50μ), and the coating film formed was described in Examples. The test was conducted in the same manner as in Example 6.

The results are shown in Table 3. Example 8 A shot-blasted steel material was pretreated in the same manner as in Example 7, and preheated (2
After applying 50℃ x 1 powder), each was coated with epoxy powder paint Tamoto Paint Co., Ltd. (trade name: 1 Powdax E Clay J).
(Baking conditions: 230'C x 1 powder, coating thickness 300μ), vinyl chloride powder paint (laboratory prototype) (Baking conditions: 21
0°C x 1 powder, coating thickness 300μ) and a two-component epoxy paint using a solvent as a comparative example (product name 1 Koponyo manufactured by Nippon Paint Co., Ltd.) (drying conditions: natural drying x 7 days, coating thickness 300μ) , and salt chlorine test (Sa
ltCrOckTest) and the results are shown in Table 4.

Claims (1)

[Scope of Claims] 1. When applying powder coating to a metal object, the object to be coated may be subjected to a phosphate chemical conversion treatment beforehand or without being subjected to α, β treatment.
- An emulsion obtained by emulsion polymerization of monoethylenically unsaturated monomers, whose main components are a water-soluble chromium compound in which 30 to 90% by weight of the total chromium is hexavalent chromium, and a metalloid or metal oxide, and which contains substantially In a method of surface treatment by coating a treatment liquid containing no alkali metal ions, polyacrylic acid and/or polyacrylic acid are used as emulsifiers in the emulsion.
or acrylic acid and methacrylic acid, acrylamides,
Methacrylamides and general formulas▲Mathematical formulas, chemical formulas, tables, etc.▼[In the formula, A is a hydrogen atom or a methyl group, R
represents a C_2 to_4 substituted or unsubstituted alkylene group, and X represents a functional group having at least one of an oxygen atom, a phosphorus atom, and a sulfur atom. ] A copolymer with at least one selected from the group of hydrophilic monomers shown in the above is used at a solid content of 20 parts by weight or more based on 100 parts by weight of the α,β-monoethylenically unsaturated monomer. A pretreatment method for powder coating, characterized in that it is used. 2 The solid content ratio of the emulsion and the water-soluble chromium compound in the treatment liquid is 100/1 to 1/10, and the solid content ratio of the emulsion and the metalloid or metal oxide is 10/1 to 1/10.
1 to 1/10. 3. The method according to item 1 above, wherein the content ratio of hexavalent chromium in the water-soluble chromium compound is 40 to 60% by weight based on the total amount of chromium. 4. Water-insoluble white carbon is used as a type of metalloid or metal oxide, and as the white carbon,
White carbon and /
Or the secondary agglomeration of primary particles is large and is 0.1 in the processing liquid.
2. The method of claim 1, wherein the white carbon is present as agglomerated particles of ~3μ. 5. The method according to item 1 above, wherein the emulsifier of the emulsion is polyacrylic acid. 6. The method according to item 1 above, wherein the emulsifier of the emulsion is an acrylic acid/acrylamide water-soluble copolymer. 7. The method according to item 1 above, wherein the emulsifier of the emulsion is an acrylic acid/methacrylamide water-soluble copolymer. 8. The method according to item 1 above, wherein the emulsifier of the emulsion is an acrylic acid/2-hydroxyethyl methacrylate water-soluble copolymer. 9. The method according to item 1 above, wherein the emulsifier of the emulsion is an acrylic acid/mono(2-hydroxymethacrylate) acid phosphate water-soluble copolymer. 10. The method according to item 1 above, wherein the emulsifier of the emulsion is an acrylic acid/2-hydroxyethyl methacrylate/mono(2-hydroxyethyl methacrylate) acid phosphate water-soluble copolymer. 11. The method according to item 1 above, wherein the emulsifier of the emulsion is an acrylic acid/methacrylic acid water-soluble copolymer.