JPH0529661B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating base treatment composition for metals, and more specifically to a specific particle size obtained by emulsion polymerization of an α,β-monoethylenically unsaturated monomer using a specific water-soluble polymer as an emulsifier. A water-based polymer emulsion consisting of hard polymer particles having a specific glass transition temperature and a water-soluble chromium compound in which a specific percentage of the total chromium content is trivalent chromium as the main components, especially for folding workability and scratch resistance. The present invention relates to a metal surface treatment composition with excellent properties and corrosion resistance. Various chemical conversion treatments have been carried out on iron, galvanized steel sheets, aluminum, and other metal substrates to improve their corrosion resistance and coating adhesion. A metal surface treatment method using a so-called non-rinse chromate treatment agent, which is simply applied to the metal surface, has recently become particularly popular due to its ease of treatment operation and management, avoidance of wastewater pollution problems, and shortening of the treatment process. It is attracting attention. As an example of a metal surface treatment method using a treatment liquid containing such an emulsion and a water-soluble chromium compound,
No. 57931; Special Publication No. 49-31026, No. 49-40865,
A number of proposals were made, including No. 50-1889, but the problem with these early treatment solutions was the presence of surfactants and emulsifiers in the production of emulsions. In other words, in order to maintain the stability of the emulsion itself, the use of nonionic or anionic surfactants is considered to be unavoidable, and on the other hand, the presence of these surfactants may cause problems in subsequent coatings after the formation of the base film. Naturally, this would have a significant adverse effect on the adhesion, corrosion resistance, moisture resistance, etc. of the film. Therefore, research continued with the aim of solving the chemical stability of emulsions without using surfactants during production and at the same time obtaining a stable composition with chromium compounds. A technique for use as an emulsifier in the production of emulsions has now been provided. In other words, Japanese Patent Publication No. 1973
-74934 is a polymer obtained by polymerizing α,β-ethylenically unsaturated monomers at a specified temperature in the presence of a water-soluble persulfate using a specified amount of a specified polyacrylic acid or its ammonium salt. A composition formed by blending an emulsion with a hexavalent chromium compound is
Furthermore, in Japanese Patent Publication No. 56-39393, an emulsion obtained by emulsion polymerization of an α,β-monoethylenically unsaturated monomer using a specific amount of polyacrylic acid and/or an acrylic acid copolymer as an emulsifier, and a water-soluble chromium compound. Various methods of surface treatment of metals using treatment liquids containing water-soluble white carbon as a main component have been disclosed. Emulsions obtained by using such water-soluble organic polymers as emulsifiers are chemically stable in themselves, and when combined with chromium compounds, provide stable processing solutions and form films with excellent corrosion resistance and paint adhesion. It is useful as a metal surface treatment agent. However, when considering the method for treating the surface of a metal material for painting, it is important to take into account not only the adhesion between the treated surface and the paint, but also the adhesion of the paint film and scratch resistance when the metal is folded or otherwise processed after painting. It is necessary to In the first place, adhesion during folding processing and scratch resistance are requirements that conflict with each other, but the invention of JP-A-51-74964 focuses only on processing adhesion and does not give any consideration to scratch resistance. No, also special public service 1984-39393
In the issue, the effect is based on the synergistic effect of the three components of emulsion, water-soluble chromium compound, and water-soluble white carbon, and there is no mention of scratch resistance or folding resistance of the system consisting of emulsion and chromium compound. It has also been found that the effects of the three-component system on scratch resistance and folding resistance vary and do not always give good results. In particular, there are problems with folding resistance at low temperatures, and problems such as poor storage stability of the stock solution are also recognized when the amount of trivalent chromium is large. Therefore, the object of the present invention is to provide a metal surface treatment composition containing an emulsion and a chromium compound as main components, in which the emulsion itself is stable even without a surfactant, and provides a stable combination with a chromium compound. It has excellent storage stability as a stock solution before dilution, and when formed into a coating, it provides a coating with excellent corrosion resistance and water resistance, as well as a well-balanced treated coating in terms of scratch resistance and folding resistance at room temperature and low temperature. An object of the present invention is to provide a composition for treating a metal surface that is moisturizing. The present invention maintains the stability of the emulsion itself and chemical stability without including a surfactant, and provides a treated film with excellent corrosion resistance, water resistance, and coating adhesion. 51−
No. 74934, which is an extension of the invention of Japanese Patent Publication No. 56-39393, focuses on stress relaxation on the treated surface in order to balance the conflicting requirements of folding workability and scratch resistance. It is. In recent years, original plates for pre-coated metals aimed at improving post-processing corrosion resistance, ie, original plates that do not have any cracks or are difficult to form cracks on the surface during folding, have been commercially available. In this case, since stress relaxation due to cracks is essentially rejected, it is natural that the coating adhesion deteriorates with the conventional uniform coating, and it is impossible to deal with this problem. However, if it is possible to intentionally disperse the adhesion points of particles in a non-uniform film, it is quite conceivable that it will be useful for stress relaxation. Naturally, metal surfaces are extremely uneven from a microscopic perspective. Therefore, if the resin particle size is made small enough so that the particles can fit into these depressions, and the particles themselves are made to be somewhat hard, the resistance to shear stress will be large and this will help alleviate stress in the vicinity of the particles. Become. As a result of various studies based on the above-mentioned theoretical considerations (although not bound by the theory in any way), the present inventors found that the particle size of the polymer particles of the emulsion is within a certain range, If you select a hard material with a glass transition temperature within a specific range, it will have corrosion resistance,
The present invention was completed after discovering that a coating type non-rinse chromate treatment agent can be obtained which provides a film with excellent folding resistance, scratch resistance, etc. That is, according to the present invention, "polyacrylic acid and/or acrylic acid and methacrylic acid, acrylamides, metallylamides and the general formula (In the formula, A is a hydrogen atom or a methyl group, R is C ₂ ~
At least one copolymer selected from the group of hydrophilic monomers represented by C ₄ substituted or unsubstituted alkylene group, and α, β as emulsifiers
- a monoethylenically unsaturated monomer,
The above-mentioned emulsifier is used at a solid content of 5 to 100 parts by weight, and the particle size is within the range of 0.1 to 3μ, and α,β-monoethylenically unsaturated monomers are obtained by emulsion polymerization. An emulsion of hard polymer particles obtained by adjusting the glass transition temperature within the range of 80°C to 110°C by selecting polymers, and water-soluble chromium in which 30 to 50% by weight of the total chromium is trivalent chromium. A corrosion-resistant metal surface treatment composition with excellent folding workability and scratch resistance, which is characterized by containing a compound as a main component and having a weight ratio of emulsion solid content to metal chromium of 2:1 to 5:1. Provided. The emulsion in the present invention uses a specific water-soluble polymer as an emulsifier in a specific ratio, and is selected from ordinary α,β-monoethylenically unsaturated monomers so that the glass transition temperature of the resulting polymer falls within a specific range. Manufactured by polymerization means. The above water-soluble polymer is polyacrylic acid and/or
or acrylic acid and methacrylic acid, acrylamides (e.g. acrylamide and N-methylol acrylamide), methacrylamides (e.g. methacrylamide and N-methylol methacrylamide), and hydrophilic monomers represented by the above general formula (e.g. X is oxygen When the monomer is a functional group having an atom, acrylic acid 2-
Hydroxyethyl, 3-hydroxybutyl acrylate, 2,2-bis(hydroxymethyl)ethyl acrylate, 2,3-dihydroxypropyl methacrylate, 3-hydroxybutyl methacrylate, etc.; X is a functional group having a phosphorus atom Mono(2-hydroxyethyl methacrylate) acid phosphate and mono(3-
It is a copolymer with at least one selected from chloro-2-hydroxypropyl methacrylate) acid phosphate, etc.; and when X is a functional group having a sulfur atom, the monomer is sulfonylethyl methacrylate, etc.), and one of them. Or it can be used as a mixture of two or more. The ratio of acrylic acid to other hydrophilic monomers in the above copolymer is usually such that the acrylic acid content in the total monomers is 50% by weight or more, preferably from the viewpoint of stability of the emulsion system and adhesion to metal substrates.
It is appropriately selected so that the content is 60% by weight or more. Examples of α,β-monoethylenically unsaturated monomers to be emulsion polymerized include acrylic esters (methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, Decyl acrylate, isooctyl acrylate, 2-ethylbutyl acrylate, octyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, 3-ethoxypropyl acrylate, etc.), methacrylic esters (methyl methacrylate, ethyl methacrylate, Isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, decyl octyl methacrylate, stearyl methacrylate, 2-methylhexyl methacrylate, glycidyl methacrylate, 2-methacrylate
ethoxyethyl, cetyl methacrylate, benzyl methacrylate, 3-methoxybutyl methacrylate, etc.), acrylonitrile, methacrylonitrile,
Mention may be made of vinyl acetate, vinyl chloride, vinyl ketone, vinyltoluene and styrene. One or a mixture of two or more of these may be used.
In addition to these, a small amount of acrylamides, methacrylamides, and hydrophilic monomers represented by the above general formula, which are constituent monomers of the water-soluble copolymer described above, may be added. Especially methacrylic acid 2
- By adding a monomer having an OH group such as hydroxyethyl, the emulsion polymer forms 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. Although not essential in the present invention, it has also been found that it is preferable to include acrylonitrile in an amount of 5 to 10% in the total monomers, as this further improves the adhesion between the emulsion particles and the metal surface. In the present invention, as described later, hard polymer particles are defined by their glass transition temperature Tg, and the hard polymer particles are defined by their glass transition temperature Tg.
Since Tg can be calculated and predicted from the type and amount of monomers to be polymerized, the above-mentioned various monomers are provided and used as appropriate based on the desired Tg value of the polymer. The emulsion polymerization in the present invention is carried out in an aqueous solvent in the presence of a water-soluble free radical catalyst without alkali metal ions, such as ammonium persulfate and 2,2-azobis-(2-amidinopropane) hydrochloride, under conventional conditions and techniques. It will be implemented. For example, in water (preferably deionized water) containing all or a part of the emulsifier maintained at a polymerization temperature, α, β, as desired, are added.
- 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) from separate dropping funnels; They may be added dropwise at the same time and, if necessary, aged at the same temperature. Polymerization is carried out under stirring, and the polymerization temperature is usually 50° to 90°C. The polymerization time (dropping time + aging time) is usually 3 to 7 hours.
The amount of emulsifier used is selected within the range of 5 to 100 parts by weight in terms of solid content per 100 parts by weight of the α,β-monoethylenically unsaturated monomer to be subjected to emulsion polymerization. If the amount used is less than 5 parts by weight, the storage stability of the emulsion itself will be reduced, and even if it is used in excess of 100 parts by weight, the storage stability of the emulsion itself and its chemical stability against water-soluble chromium compounds will be particularly impaired. This does not improve the results, and instead causes problems such as foaming of the emulsion. However, in the present invention, the particle size of the emulsion particles obtained by such emulsion polymerization method is
Must be within the range of 0.1 to 3μ. As already mentioned, in the formation of a non-uniform film, it is necessary for the emulsion particles to be coarsely distributed and to be able to fit into the minute depressions and depressions of the metal surface and be adhered to the metal surface in order to have good adhesion to the metal surface. According to research by the present inventors, the particle size of emulsion particles is 0.1
It has also been found that significant adhesion is obtained when the particle size is in the range ~3μ, with a particularly preferred particle size between 0.3 and 2μ. Generally, in emulsion polymerization, a heating means is used under restricted stirring to obtain fine emulsion particles, but it is also known that the particle size can be controlled by controlling the operating conditions. Therefore, optimal conditions for keeping the particle size within the above range will be appropriately selected by those skilled in the art. In the present invention, another important condition is that the glass transition temperature (Tg) of the polymer is specified within the range of 80° to 110°C in order to make the emulsion particles hard particles with relatively high resistance to shear stress. did.
Emulsion particles fit into minute recesses on the metal surface because of their specific particle size, but if the particles are relatively hard, it is thought that they can help relieve stress in the vicinity of the particles. The inventors have in fact determined the Tg of the polymer.
is in the range of 40°C to 110°C, more preferably 80°C to 110°C
It has been found that if the temperature is within 10°C, the folding processability and scratch resistance of the film can be significantly improved. If the Tg of the polymer is lower than this, a film with sufficient properties, especially folding resistance and scratch resistance, cannot be obtained. On the other hand, polymers with a Tg of 110° C. or higher cannot be obtained from commonly used α,β-ethylenically unsaturated monomers. The Tg of a polymer can be calculated to some extent and predicted based on the type and amount of monomers to be polymerized, and those skilled in the art can easily design the glass transition temperature within the above range. In the present invention, a specific amount of a water-soluble chromium compound is added to the emulsion obtained as described above to prepare a metal surface treatment composition. In the present invention, it is important that the content ratio of trivalent chromium in the water-soluble chromium compound is set in the range of 30 to 50% by weight, preferably 35 to 45% by weight based on the total amount of chromium. Therefore, chromium compounds such as CrO ₃ may be partially reduced in advance with formalin, hydrogen peroxide, etc. within a range that satisfies these conditions. If the content ratio of trivalent chromium is less than 30% by weight, folding resistance etc. will deteriorate. Moreover, if it exceeds 50% by weight, the stability of the stock solution will be poor when it is blended as a processing agent. The metal treatment composition of the present invention is prepared by mixing the above emulsion and water-soluble chromium compound in water (preferably deionized water) all at once. It is possible to store a concentrated stock solution composition using a relatively small amount of water and dilute it appropriately with water before use, or to prepare a treatment solution directly using a relatively large amount of water. The mixing ratio of the emulsion and the water-soluble chromium compound needs to be within the range of 2:1 to 5:1 in terms of the solid content of the emulsion and the polymerization ratio of metallic chromium, and the most preferable ratio is 3:1. If the proportion of metallic chromium is smaller than the above range, the corrosion resistance of the coated plate will decrease and the adhesion between the base film and the metal surface will not be sufficient, and if it is larger than the above range, problems will arise in the adhesion of the coated plate. Incidentally, if desired, fine particle silica (7 to 60 mμ) can be added to the metal surface treatment composition of the present invention in an amount comparable to that of chromium to further improve the scratch resistance. Further, sources of various metal ions (excluding alkali metal ions) and inorganic ions may be added within a range that does not impair the 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 added ions are, for example,
Zn ²⁺ , Co ²⁺ , Ni ²⁺ , PO ₄ ^3- , F ^- , BF ₄ ^- , SiF ₆ ^2-
etc. can be mentioned. The metal surface treatment composition according to the present invention is applied to the surface of various metals (for example, iron, galvanized steel, aluminum, etc.) according to a conventional method (for example, roll coating method, mist spray method, dip method), and then By appropriately drying, a desired base film can be formed. The amount of such base film formed is usually 5 mg/m ² to 5 mg/m 2 in terms of the amount of metal chromium film.
The amount may be selected within the range of 1 g/m ² , preferably 5 mg/m ² to 100 mg/m ² , and if it deviates from this range, the processing performance of the resulting coated board tends to deteriorate.
Among the above coating methods, roll coating is suitable for galvanized steel, iron, and aluminum coil coating lines, and provides a thin and uniform base film without color unevenness. The above drying conditions may be such as to evaporate the moisture in the base film, and the maximum board temperature is 120℃ or less.
Preferably a temperature of 80°C to 110°C for 1 to 60 seconds is suitable for the present invention. Outside this range, unfavorable results may occur in improving the adhesion, especially the scratch resistance, of the coated film after painting. The formed film does not contain surfactants or other substances mixed into the emulsion in the treatment solution, has extremely good corrosion resistance and moisture resistance after painting, and also significantly improves paint adhesion such as processability and scratchability. . In this way, when the treatment composition of the present invention is used for metal surface treatment, it does not require maintenance of the treatment solution, so it is only necessary to periodically replenish the treatment solution of the same composition, and uniform coating can be achieved continuously. It is easy to carry out, and a desired base film can be formed by drying. Further, there is no need for washing with water after application of the treatment liquid and post-treatment steps, making it possible to shorten the process, and also eliminating the need for equipment for treating contaminated wastewater. The formed film exhibits the above-mentioned good properties, and is particularly excellent in process resistance and scratch resistance, making it extremely useful for surface treatment of metals. It is also a feature of the composition of the present invention that it exhibits a much more remarkable effect than conventional compositions, particularly in terms of storage stability of the treatment source solution and processability at low temperatures. The present invention will be explained below with reference to Examples, Reference Examples, and Comparative Examples. In the example sentences, "parts" and "%" mean "parts by weight" and "% by weight," respectively. Reference Example of Emulsion Synthesis 1 (High Tg Emulsion EM No. 1) In a flask equipped with a stirrer, reflux condenser, thermometer and two dropping funnels, add 150 parts of deionized water and 2-hydroxy acrylic acid and methacrylic acid. A water-soluble copolymer obtained by copolymerizing with ethyl at a weight ratio of 8:2 (25% aqueous solution, molecular weight MW =
66,000) and raise the temperature to 80-85°C while stirring. Then 50 parts of methyl methacrylate, 30 parts of styrene
10 parts of 2-hydroxyethyl methacrylate and 10 parts of n-butyl methacrylate from one funnel, and a catalyst solution of 2 parts of ammonium persulfate and 50 parts of deionized water from the other funnel. Drop simultaneously over 3 hours. After dropping, heat at 80℃ to further complete the polymerization reaction.
Aging is performed at ~85°C for about 2 hours. The resulting aqueous polymer was a uniform emulsion with a solid content of 30.1%, a pH of 1.6, a particle size of 0.2μ, and a Tg of 89°C. Reference Example 2 (Emulsion EM No. 2 containing acrylonitrile and high Tg) Monomer mixture is 50 parts of methyl methacrylate, 25 parts of styrene, and 10 parts of 2-hydroxyethyl methacrylate.
Emulsion polymerization was carried out in the same manner as in Reference Example 1, except that 10 parts of n-butyl methacrylate and 5 parts of acrylonitrile were used. The obtained aqueous polymer was a uniform and stable emulsion with solid content of 30.3%, pH of 1.6, particle size of 0.2μ, and Tg point of 89°C. Reference Example 3 (Comparative emulsion EM No. 3 with low Tg) All procedures were carried out in the same manner as in Reference Example 1 except that the monomer mixture consisted of 75 parts of ethyl acrylate, 15 parts of sterine, and 10 parts of 2-hydroxyethyl methacrylate. Emulsion polymerization was carried out. The resulting aqueous polymer had a solid content of 30.2% and a pH of
1.6, a particle size of 0.2μ, and a uniform and stable emulsion with a Tg of -2°C. Example Preparation of treatment liquid Add 37% formalin to 29.6 parts of the emulsion EM No. 1 obtained in Reference Example 1 (solid content 30.1%, particle size 0.2μ, Tg 89°C) and a 17% aqueous solution of chromic anhydride to prepare a hexavalent mixture. 33.6 parts of chromium aqueous solution obtained by reducing 40% of chromium to trivalent chromium [metallic chromium content = 33.6×
A processing composition stock solution obtained by stirring and mixing 0.17×(Cr/CrO ₃ coefficient 0.52)] and 36.8 parts of deionized water at room temperature was diluted 5 times with deionized water to prepare a processing solution. The weight ratio of emulsion solids to metallic chromium was 3:1. Metal surface treatment and painting Regular galvanized steel plate (zero spangle plate, with skin pass) that is prone to cracks when folded. Degreased and cleaned with a commercially available alkaline degreaser (manufactured by Nippon Paint Co., Ltd., trade name: Ridrin 155), washed with water, and dried. The above treatment solution was applied to the surface of the object using a #3 bar at a coating amount of metallic chromium of 30 mg/m ² , and then dried with hot air at 70° C. to obtain a uniform base film. Next, the surface-treated spangle plate as described above was coated with Nippon Paint Co., Ltd.'s product name "Super Rack DIF P-75 Primer" as an undercoat to a dry film thickness of 3 μm.
Baked to reach a plate temperature of 204°C in 50 seconds, then applied topcoat paint manufactured by Nippon Paint Co., Ltd. under the trade name ``Super Lux DIF F-50 Red Rust Color'' to a dry film thickness of 11μ. , reached plate temperature in 50 seconds
Baked to 204℃. Table 1 shows the test results for the treatment agent stock solution composition and the obtained coated board. Example 2 Emulsion EM No. 2 obtained in Reference Example 2 was
A treatment composition stock solution was prepared in the same manner as in Example 1 from 29.4 parts of the chromium aqueous solution described in Example 1 and 37.0 parts of deionized water, and diluted 5 times with deionized water to prepare a treatment solution. Then, in the same manner as in Example 1, this was applied to a zero spangle board to form a base film, which was then painted with an undercoat and a topcoat. However, the amount of treatment liquid applied when forming the base film is 30mg/metal chromium.
I set it to ^m2 . The test results were as shown in Table 1. Comparative Example 1 The same method as in Example 1 was carried out except that 29.5 parts of the emulsion (low Tg) obtained in Reference Example 3 was used, and the test results are shown in Table 1. In addition, in Table 1 below, the stability of the stock solution was evaluated by visually observing the condition of the stock solution after keeping the processing composition stock solution in a sealed polyethylene container at 20°C for one month. Cases are indicated by ◯, and cases where gelled substances are generated are indicated by ×. OT folding processability was evaluated on a 10-point scale from 10 points (no abnormality) to 1 point (full peeling) after adhering the folded surface with adhesive tape and peeling it off.

[Table] Examples 3 to 7 and Comparative Examples 2 to 6 The emulsions obtained in Reference Examples 1 to 3 were used in Examples 3 and 4 and Comparative Example 2, and the emulsions obtained in Reference Example 1 were used as emulsions. They were used in Examples 5 to 7 and Comparative Examples 3 to 6, respectively, in the same manner as in Example 1 according to the formulations shown in Table 2 below (however, in the case of adding silica, Aerosil 300 (trade name manufactured by Nippon Aerosil Co., Ltd.) was used.
(adding a 10% dispersion of) to make a treatment composition stock solution,
Each treatment solution was prepared by adding deionized water to the dilution ratio shown in Table 2. Hot-dip galvanized steel plate that is difficult to crack when folded (regular spangle, no skin pass)
was used as the metal material, a base film was made with the above treatment liquid in the same manner as in Example 1, and a base coat was applied with the base coat "Super Lak".
DIF P-75 Primer'' and top coat ``Super Lux DIF F-50 Red Rust Color'' were applied and subjected to an OT folding test (20°C). Separately, after forming the above base film, apply Nippon Paint Co., Ltd.'s product name "Super Rack DIF F-15 Beige Color" to a dry film thickness of 11μ, and bake to reach a board temperature of 210℃ in 50 seconds. The following coin scratch test was conducted on 1C/1B (one coat, one bake) products. Coin scratchability: Scratch the coated surface of a 10 yen coin with no notches on the circumference and evaluate it on a 5-point scale from 5 points (excellent) to 1 point (poor). The composition of the stock solution, treatment solution, treatment, and performance are shown in Table 2 below. In the table, regarding the stability of the stock solution, the symbol △ means that thickening was observed.

【table】

[Table] Reference example 4 (Emulsion EM No. 4 with Tg of 98°C) Monomer mixture is 60 parts of male methacrylate, 30 parts of styrene, and 10 parts of 2-hydroxyethyl methacrylate.
Emulsion polymerization was carried out in the same manner as in Reference Example 1 except that the emulsion polymerization was performed in the same manner as in Reference Example 1. The resulting aqueous polymer has a solid content of 30.0
%, pH 1.6, grain size 0.3μ, and Tg 98°C, it was a uniform and stable emulsion. Reference Example 5 (Emulsion EM No. 5 used in Example 1 of Japanese Patent Publication No. 56-39393) A monomer mixture was prepared by adding 35 parts of methyl methacrylate, 15 parts of styrene, 10 parts of 2-hydroxyethyl methacrylate, and 40 parts of n-butyl acrylate. to 60℃~65
Emulsion polymerization was carried out in the same manner as in Reference Example 1, except that the dropwise addition time was 8 hours at 60°C to 65°C, and the aging was 2 hours at 60°C to 65°C.
The obtained aqueous polymer was a homogeneous emulsion with solid content of 30.1%, pH of 1.6, particle size of 0.1μ, and Tg of 15°C. Example 8 and Comparative Example 7 Using the emulsions of Reference Examples 4 and 5, a treatment solution was prepared in the same manner as in Example 1 with the following formulation, and the metal surface treatment, undercoat and topcoat were performed in the same manner as in Example 1, and the performance was evaluated. The following results were obtained. Example 8 Comparative Example 7 Tg (℃) 98 15 Particle size (μ) 0.3 0.1 Solid content (%) 30.3 30.1 Mixing ratio 19.5 8.1 CrO ₃ (%) 17 17 Reduction rate (%) 40 50 Mixing ratio 22.2 7.4 SiO ₂ (%) 10 10 Mixing ratio 10 20 Deionized water (parts) 48.2 64.5 EM/Cr ratio 3 3.8 SiO ₂ /Cr ratio 0.5 3.2 Dilution rate ×3.3NV 3.2% ×2.5NV 2.3% 3.2% 2.3% Cr coating amount 30 33 Stability ○ ○ 20℃ OT 7 5 Coin Scratch 3.5 2 The composition of the present invention not only provides a film with excellent corrosion resistance and water resistance, but also has excellent storage stability, scratch resistance, and folding processability. It will be readily understood that this process provides a treated coating.

Claims (1)

[Claims] 1. Polyacrylic acid and/or acrylic acid and methacrylic acid, acrylamides, methacrylamides, and general formula (In the formula, A is a hydrogen atom or a methyl group, R is C ₂ ~
A copolymer with at least one hydrophilic monomer selected from the group of _C4 substituted or unsubstituted alkylene group, and X representing a functional group having at least one of an oxygen atom, a phosphorus atom, and a sulfur atom. is used as an emulsifier, and an α,β-monoethylenically unsaturated monomer is used, provided that the emulsifier is used at a solid content of 5 to 100 parts by weight per 100 parts by weight of the monomer, and obtained by emulsion polymerization. particle size of 0.1
The glass transition temperature can be adjusted within the range of ~3μ and by selecting the α,β-monoethylenically unsaturated monomer.
The emulsion solid content is mainly composed of an emulsion of hard polymer particles obtained by heating the temperature within the range of 80℃ to 110℃ and a water-soluble chromium compound in which 30 to 50% by weight of the total chromium is trivalent chromium. 1. A corrosion-resistant metal surface treatment composition having excellent folding workability and scratch resistance, characterized in that the weight ratio of chromium and metal chromium is from 2:1 to 5:1. 2. The composition according to claim 1, wherein the content of trivalent chromium in the water-soluble chromium compound is 35 to 45% by weight based on the total amount of chromium. 3. The composition according to any one of claims 1 to 2, wherein the weight ratio of emulsion solid content to metal chromium is 3:1.