JP3292754B2 - Composition for metal surface treatment containing sol of trivalent chromium compound and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal surface treatment composition containing a sol of a trivalent chromium compound and a method for producing the same. The composition of the present invention includes various metals, particularly steel sheets, galvanized steel sheets (particularly zinc-iron alloy-plated steel sheets,
Excellent coating performance (paint adhesion) on the surfaces of aluminum and zinc alloy plated steel sheets, etc., aluminum and zinc alloy plated steel sheets, etc. , Corrosion resistance after painting, rust resistance after painting), fingerprint resistance, and bare corrosion resistance.

[0002]

2. Description of the Related Art Conventionally, in order to impart bare corrosion resistance and paintability to a galvanized steel sheet, for example, a chemical conversion treatment is performed with a phosphating solution mainly composed of zinc phosphate, and the surface of the steel sheet is coated. A surface treatment method such as a method of forming a phosphate film and washing and drying it, or a method of drying after performing a post-treatment with an aqueous chromate solution before the drying in order to improve corrosion resistance is applied. . In addition, a surface treatment method is used in which an aluminum or aluminum alloy plate is subjected to a chemical conversion treatment using, for example, an aqueous solution mainly containing chromic acid, and then washed and dried to form a chromate film.

In recent years, for the purpose of simplifying the process and improving the productivity, an aqueous solution mainly containing a mixture of hexavalent chromium ion, trivalent chromium ion and silica sol is applied to the surface of the metal material, and without washing with water. A coating type chromate treatment for completing a film by drying is being widely adopted. However, the coating-type chromate treatment method generally involves a method in which the chromium elution property of water of a film formed by the coating is affected by drying conditions, and the adhesion of a coating film formed on the coating-type chromate film (hereinafter simply referred to as “coating-type chromate treatment”). Described as adhesion)
Are insufficient. In order to solve these problems, various types of improved coating type chromate treatment solutions have been proposed. The advantages and disadvantages of these prior arts will be described below.

[0004] Japanese Patent Publication No. 3-68950 discloses that a treatment liquid containing chromic anhydride, fluorine ions or fluorine complex ions, a silicate compound, and a silane coupling agent is applied to the surface of a galvanized steel sheet and dried. A method of forming a chromate film and forming a coating base is disclosed.The film formed by this method has relatively good corrosion resistance because it is relatively smooth and excellent in uniformity. Due to the smoothness, physical anchoring effect cannot be obtained,
Therefore, the coating film adhesion performance is inadequate, and the silane coupling agent contained in the processing solution generally has the effect of reducing chromic anhydride, so that the stability of the processing solution is low and the coating workability is low. Has the disadvantage of being insufficient.

Japanese Patent Application Laid-Open No. Sho 60-218483 discloses a chromate film formed by applying and drying an aqueous composition comprising a hexavalent chromium compound, silica, a silicate compound and a phosphate. There is disclosed a method for obtaining an effect of improving corrosion resistance and an anchoring effect by silica contained in a chromate film. However, although the film formed by this method is excellent in corrosion resistance, since the physical shape of silica is fine, it is inevitable that only fine irregularities can be obtained. Is not yet reached.

As a method of solving such a drawback, there is disclosed a method of forming a chromate film by applying a treatment liquid containing an aqueous emulsion of a resin and a water-soluble chromium compound to the surface of a galvanized steel sheet and drying it. ing. That is, a large number of treatment liquids are disclosed in JP-B-49-31026, JP-B-49-40865, JP-B-50-31026, and JP-A-50-57931. In a chromate solution mixed with an aqueous resin emulsion, it is essential to use a nonionic or anionic surfactant during emulsion production in order to maintain the stability of the emulsion itself against chromium compounds. Usually, the film formed on the metal surface by the emulsion resin containing these surfactants,
It is widely known that these surfactants are concentrated at the interface between the metal and the film, so that the adhesion between the film and the metal is inhibited and the corrosion resistance is further reduced.

Therefore, a technique is disclosed in which a water-soluble organic high molecular compound is used as an emulsifier during the production of an emulsion in order to measure the chemical stability of the emulsion, particularly the mixing stability with an aqueous chromium compound solution, without using a surfactant. Have been. For example, JP-A-51-74934,
No. 6,39,393 discloses an emulsion obtained by emulsion polymerization of an α, β-ethylenically unsaturated monomer using polyacrylic acid or its ammonium salt, polyacrylic acid or acrylic acid copolymer as an emulsifier. A method of mixing with a chromium compound to form a coating type chromate liquid is disclosed. However, in the method disclosed in JP-A-51-74934, consideration is given to the processing adhesion of the coating film, but no consideration is given to scratch resistance. On the other hand, in the method of Japanese Patent Publication No. 56-39393, a mixture of an emulsion, water-soluble chromium, and water-soluble white carbon is used. When the amount of trivalent chromium ions is large, the storage stability of the stock solution is poor. There are also problems.

As methods for improving these problems, JP-A-59-197575 and JP-A-59-20076 are known.
No. 8 and JP-A-63-145785. That is, JP-A-59-2076
No. 8 discloses "polyacrylic acid and / or acrylic acid and methacrylic acid, acrylamides, methacrylamides and the general formula (II):

Embedded image (Where A represents a hydrogen atom or a methyl group, and R ³ represents 2
Represents a substituted or unsubstituted alkylene group having from 4 to 4 carbon atoms, and X represents a functional group having at least one selected from an oxygen atom, a phosphorus atom and a sulfur atom.
And α, β-monoethylenically unsaturated monomer as a emulsifier using a copolymer with at least one selected from the group consisting of hydrophilic monomers represented by the following formula: As a part of the α, β-monoethylenically unsaturated monomer having a particle size in the range of 0.1 to 3 μm obtained by emulsion polymerization. Internal gelation may be caused by using a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule, or glass may be selected by selecting the above α, β-monoethylenically unsaturated monomer. Transition temperature 15 ℃ ~
An emulsion consisting of hard polymer particles obtained by setting the temperature within the range of 110 ° C .; and a water-soluble chromium compound in which 25 to 50% by weight of the total amount of chromium is trivalent chromium. A corrosion resistant metal surface treatment composition excellent in bending workability and scratch resistance, wherein the weight ratio of chromium metal is 1/9 to 2/1. Is disclosed.

A feature of the composition disclosed in JP-A-59-200768 is that the composition of the polymer emulsion does not contain a functional group which reacts with a metal ion, or even if it contains a relatively small amount of the functional group. And a glass transition temperature of 15 ° C. to 11 by a method such as internal gelation.
A high temperature such as 0 ° C. or a relatively low molecular weight material such as polyacrylic acid or an acrylic acid copolymer is used as a protective colloid to measure the miscibility with water-soluble chromium. However, an emulsion having such a configuration necessarily has insufficient adhesion to a metal, and a composition obtained by mixing the emulsion and water-soluble chromium forms a film by coating and drying. ,
Such a coating has a problem in that the coating performance is greatly affected by the drying temperature due to its properties.

On the other hand, the composition disclosed in JP-A-59-197575 has a weight ratio of solid emulsion to metal chromium of 1/10 to 5/1 and contains silica as an optional component only. It is different from the composition of JP-A-59-200768. In each of these methods, an acrylic acid component is contained in an emulsion, and since these emulsions themselves are composed of α, β-ethylenically unsaturated monomers, an aqueous solution in which hexavalent chromium ions coexist. Is applied and dried, the resin component is oxidized, thereby deteriorating the resin film itself and reducing corrosion resistance due to the dual cause of reduction of hexavalent chromium. Furthermore, when these films are used as a base and coated thereon, the above-mentioned tendency is particularly remarkable since the coating is usually heated at a high temperature exceeding 150 ° C. in order to cure the coating. Becomes

JP-A-63-145785 discloses an acrylic polymer emulsion obtained by emulsion polymerization using hexavalent chromium ion, hexavalent chromium ion and trivalent chromium ion, and a nonionic emulsifier. A metal surface treatment composition is disclosed. The feature of this composition is that a specific nonionic emulsifier is used as a protective colloid in order to secure the stability of the acrylic polymer emulsion against coagulation and oxidation by the aqueous solution of chromic acid, which is a strong acid and also a strong oxidizer. Where to use. However, a film formed from an emulsion containing a large amount of a surfactant in this way may cause a phenomenon called bleeding of the surfactant to the surface of the film. It is known to inhibit the adhesion of the film, and has a serious drawback that it is not useful as a coating undercoat.

In recent years, instead of a zinc phosphate coating which has been conventionally used as a coating base for a coated steel sheet called a pre-coated metal, a coating type chromate coating has been adopted for reasons such as simplification of a manufacturing process and simplification of work management. However, as outlined above, the coating type chromate film has a drawback that the chromium elution rate decreases with an increase in the heating and drying temperature. It is self-evident that the heat-curing temperature of paint applied during the production of pre-coated metal is generally higher than 200 ° C, and the coating type chromate film used as the base is also heated to the same temperature. . When the coating type chromate film is exposed under such a high temperature environment, the elution of chromium from the chromate film disappears or becomes very small. Therefore, the self-repair ability cannot be exhibited by the hexavalent chromium ion eluted from the chromate film with respect to the damaged portion of the chromate film or the effect thereof is greatly reduced. .

It is a matter of course that an idea is proposed in which an aqueous resin and a chromate liquid are mixed to protect a metal surface from a corrosive environment by forming a continuous film of the resin and an inhibitory effect of the chromate film. is there. On the other hand, it is widely known in the literature that the oxidizing power of chromic acid (hexavalent chromium ion) depends on the pH of an aqueous solution, and the oxidizing power is weaker in a higher pH range and stronger in a lower pH range. By the way. However, when only chromic acid is dissolved in the aqueous solution, the oxidizing power of chromic acid is reduced by adding a basic compound such as ammonium water to a high pH region, and then mixed with the aqueous resin to form the aqueous resin. Preventing oxidation and increasing the stability of the solution can be easily realized. However, when a basic compound such as aqueous ammonia is added to an aqueous solution containing trivalent chromium ions to form a high pH region, trivalent chromium ions form coarse particles such as insoluble chromium hydroxide and precipitate. Easily occur. for that reason,
Even if such an aqueous solution is mixed with an aqueous resin, it cannot be a practical coating type chromate solution at all.

As a method for improving the water resistance, corrosion resistance and adhesion of a resin film formed from an aqueous resin, an aqueous resin stabilized with a volatile basic compound such as ammonia or amine has recently been used for building. Exterior wall, fiber, fiberglass,
It is widely used for coating metals and the like.
However, when the pH of the resin emulsion stabilized by such a basic compound fluctuates or when it is mixed with a divalent or higher cation such as a polyvalent metal ion, the surface charge of the emulsion particles is neutralized. It is known that the emulsion is destabilized, and aggregation and gelation of the resin emulsion occur.

However, even in the case of an aqueous resin emulsion stabilized by a basic compound having volatility as described above, the pH of an aqueous chromium compound solution is increased and trivalent chromium ions are contained in the form of a hardly soluble compound. In aqueous solution, 3
Since trivalent chromium does not have ionicity as a polyvalent cation or is very weak, if at all, even if this aqueous solution is mixed with an aqueous resin, trivalent chromium contained in the aqueous solution is not contained. It can be naturally predicted that both the aggregation of the resin emulsion due to the above and the aggregation of the resin emulsion due to the fluctuation of the pH can be prevented.

Usually, a strongly basic compound such as sodium hydroxide or potassium hydroxide is added to an acidic aqueous solution containing a polyvalent metal ion such as trivalent chromium ion to raise the pH,
When so-called neutralization causes polyvalent metal ions such as trivalent chromium ions to precipitate in the form of poorly soluble compounds such as hydroxides, a local increase in pH near the added strongly basic compound is inevitable. Therefore, it is inevitable that the trivalent chromium compound or the like forms a coarse particulate precipitate. When a film is formed by applying a composition obtained by mixing an aqueous solution containing a precipitate of such a coarse-grained trivalent chromium compound and an aqueous resin and drying the film, the resulting film necessarily contains Contains a coarse-grained trivalent chromium compound. The coating containing coarse particles is non-uniform, and it is difficult to form a continuous coating with a thin film, and thus the corrosion resistance is also insufficient.

As a method of avoiding the formation of such coarse particles and keeping the fine particles in an aqueous solution stably, a method of adding a basic compound while vigorously stirring an acidic aqueous solution can be considered. Local pH near compound addition
It is difficult to sufficiently avoid the rise.

[0018]

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of such prior art chromating,
Excellent coating performance (coating adhesion, corrosion resistance after painting, rust resistance after painting), fingerprint resistance, and nakedness on the surface of metals, especially steel sheets, galvanized steel sheets, aluminum-coated steel sheets, and aluminum-based sheet materials It is an object of the present invention to provide a metal surface treatment composition suitable for imparting corrosion resistance, that is, a novel coating type chromate treatment solution, and a method for producing the same.

[0019]

Means for Solving the Problems In order to solve the above-mentioned various problems of the prior art, the present inventors have made intensive studies and as a result, have found that a dispersion stabilizer and ammonia formed by hydrolysis of urea are dissolved. In the presence, a composition comprising a sol of a trivalent chromium compound stably dispersed in water as colloidal particles and an aqueous emulsion of a resin solves the above problem as a metal surface treatment composition, The present invention has been completed.

The metal surface treatment composition of the present invention is prepared by adding urea to an aqueous solution of an acidic chromium compound containing a trivalent chromium ion and a dispersion stabilizer and having a pH value of less than 3, and hydrolyzing the urea. It is characterized by containing the produced sol of a trivalent chromium compound and an aqueous emulsion of a resin by having the produced ammonia present, and having a pH value adjusted to 3 to 10.

The process for producing a metal surface treatment composition according to the present invention comprises adding urea to an aqueous solution of an acidic chromium compound containing trivalent chromium ions and a dispersion stabilizer and having a pH of less than 3, and adding the urea. Decomposing to generate ammonia to adjust the pH value of the acidic chromium compound aqueous solution to 3 to 10, thereby preparing a sol of the trivalent chromium compound, and mixing the sol with an aqueous emulsion of a resin. Is what you do.

In the composition of the present invention and the method for producing the same, the aqueous emulsion of the resin is at least one selected from aqueous emulsions of vinyl monomer polymers and copolymers, alkyd resins, epoxy resins, and urethane resins. It preferably comprises In the composition of the present invention and the method for producing the same, the dispersion stabilizer is phosphoric acid, chromic anhydride, hydrofluoric acid, hydrofluoric acid, hydrofluoric acid, titanium hydrofluoric acid, zircon hydrofluoric acid, formic acid Acetic acid, acrylic acid, polyacrylic acid, maleic acid, polymaleic acid, citric acid, tartaric acid, and malic acid. In the composition of the present invention and the method for producing the same, the following additional components: (a) ions of zinc, iron, nickel, cobalt, manganese, tungsten, molybdenum, aluminum, titanium, zircon, and barium; and (b) silica sol, The method according to claim 5, wherein it is preferable to further include or mix at least one selected from alumina sol, titania sol, zirconia sol, antimony oxide sol, tin oxide sol, and iron oxide sol.

[0023]

The composition for metal surface treatment of the present invention comprises a trivalent chromium ion and a dispersion stabilizer, and urea is added to an aqueous solution of an acidic chromium compound having a pH value of less than 3 by adding and dispersing the urea. 3 obtained in the presence of ammonia formed
It contains a sol of a valent chromium compound and an aqueous emulsion of a resin, and has a pH value adjusted to 3 to 10.

The aqueous emulsion of the resin used in the present invention comprises at least one selected from an aqueous emulsion of a vinyl monomer polymer and a copolymer, an alkyd resin, an epoxy resin, and a urethane resin. Is preferred.

Specific examples of the aqueous resin emulsion used in the present invention include, for example, a polymer emulsion obtained by emulsion-polymerizing a vinyl polymerizable monomer with an emulsifier and then using a polymerization initiator, or an alkyd. A normal emulsion obtained by emulsifying a resin, an epoxy resin, a urethane resin or the like in water using an emulsifier can be used. In addition, ethylene-based monomers and vinyl-polymerizable monomers having a carboxylic acid such as acrylic acid are copolymerized and then converted to a salt such as ammonium ion, and a self-emulsifying ethylene-acrylic acid-based resin emulsion, carboxylic acid or An amine is introduced into the molecule, and a carboxylic acid is introduced into the molecule using a self-emulsifying epoxy resin emulsion or a carboxylic acid having two primary OH groups such as dimethylolpropionic acid in one molecule. A self-emulsifying urethane resin emulsion can also be used.

The sol of the trivalent chromium compound used in the present invention is prepared by dissolving a soluble trivalent chromium compound such as chromium nitrate, chromium chloride, chromium phosphate, chromium sulfate, chromium acetate, and chromium citrate in water. A gel obtained by adding urea to this aqueous solution of acidic chromium compound in the presence of a dispersion stabilizer and hydrolyzing it to generate aqueous ammonia can be used, or disintegrating it after coagulation and washing with water. It is also possible to use glue.

An important point in the composition of the present invention is to stably disperse the sol chromium compound in water.
As described above, a dispersion stabilizer is used as the stabilization method. Examples of the dispersion stabilizer include phosphoric acid, chromic anhydride, hydrofluoric acid, hydrofluoric acid, hydrofluoric acid, and titanium hydrogen fluoride. Use one or more selected from the group consisting of an inorganic acid group consisting of acid and zircon hydrofluoric acid and an organic acid group consisting of formic acid, acetic acid, acrylic acid, polyacrylic acid, maleic acid, polymaleic acid, citric acid, tartaric acid and malic acid. Is preferred.

The sol chromium compound used in the present invention is prepared by the method according to the present invention, ie, trivalent chromium ion,
Urea is added to an aqueous solution of an acidic chromium compound containing a dispersion stabilizer and having a pH of less than 3, and urea is hydrolyzed to produce ammonia, and a sol of a trivalent chromium compound obtained in the presence of the ammonia It is. In the present invention, ammonia can be supplied in the same reaction system by hydrolysis of urea.

In the composition of the present invention, the solid content weight ratio between the sol of the trivalent chromium compound and the aqueous resin emulsion is not particularly limited, but is generally in the range of 1: 500 to 1: 1. Is preferred. This solid content weight ratio is 1 /
If it is less than 500, the content of the trivalent chromium compound in the film formed on the metal surface is too small, so that the naked corrosion resistance of this film may be insufficient. On the other hand, when the weight ratio is higher than 1/1, the content of the resin binder in the film formed on the metal surface becomes too small, so that the mechanical strength of the film may be reduced and the film may become brittle.

The aqueous solution of the acidic chromium compound used for preparing the sol of the trivalent chromium compound includes phosphoric acid, chromic acid (hexavalent chromium ion), nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid,
Inorganic acids such as complex hydrofluoric acid, formic acid, organic carboxylic acids such as acetic acid, organic sulfonic acids such as toluenesulfonic acid,
It is possible to appropriately use such acid radicals. Particularly preferred acids are inorganic acids consisting of phosphoric acid, chromic anhydride, hydrofluoric acid, hydrofluoric acid, hydrofluoric acid, titanium hydrofluoric acid, zircon hydrofluoric acid, formic acid, acetic acid, acrylic acid, poly One or more organic acids selected from the group consisting of acrylic acid, maleic acid, polymaleic acid, citric acid, tartaric acid, and malic acid can be used. The amount of these acids to be added is preferably 6 or less in terms of an acid / trivalent chromium ion equivalent ratio. When an acid in an equivalent ratio of acid / trivalent chromium ion exceeding 6 is added, the amount of urea required to form a sol-like chromium compound inevitably increases, which is not economically preferable. The effect of the addition of phosphoric acid is effective in making the sol-like chromium finer, and the addition of chromic acid (hexavalent chromium ion) is effective in improving the corrosion resistance of hexavalent chromium.

The aqueous solution of the acidic chromium compound further contains one or more metal ions selected from the group consisting of zinc, iron, nickel, cobalt, manganese, tungsten, molybdenum, aluminum, titanium, zirconium and barium. It may be added using a neutral salt. Here, the added metal ion forms a sol-like metal compound by adding urea to an acidic chromate aqueous solution containing the same and adjusting the pH to 3 to 10, which forms a sol of a trivalent chromium compound. Means. Further, when the metal ion coexists with chromic acid in the acidic chromium compound aqueous solution, forms a poorly soluble salt of the metal ion and chromic acid,
Suppresses the elution of hexavalent chromium ions from the formed film,
Effective for improving corrosion resistance.

Further, as an auxiliary means for improving the coating film adhesion and corrosion resistance of the obtained film, a conventionally known oxide sol is previously added to an aqueous solution of an acidic chromium compound containing a trivalent chromium ion having a pH of less than 3. You may keep it. Also, pH
Is set to 3 to 10 and after forming the sol-like chromium compound,
The oxide sol may be added and mixed. Examples of usable oxide sols include silica sol, alumina sol, titania sol, zirconia sol, antimony oxide sol, tin oxide sol, iron oxide sol, and the like.More preferred oxide sols include silica sol and fumed silica. Can be

In the above acidic chromium compound aqueous solution,
The urea was added to make the ammonia produced by the hydrolysis exist, and the pH was adjusted to 3 to 10 to form 3
An aqueous emulsion of a resin is mixed with the sol containing a valent chromium compound. Thereby, the composition for metal surface treatment of the present invention is obtained.

The surface treatment composition containing a sol of a trivalent chromium compound obtained by the above-described method has a raised pH of 3 to 10 even when it contains chromic acid. Because the oxidizing power of has disappeared or its reaction rate becomes substantially negligible,
Even if an aqueous emulsion of a resin that has not been specially treated to enhance stability against a strong oxidizing agent is used, mixing can be performed without any problem.Also, since the acidity is also low, an aqueous emulsion of the resin is also used. Since agglomeration and gelation of the resin due to pH fluctuation are not generated, it is possible to use a widely-used resin aqueous emulsion.

In recent years, a large number of self-emulsifying polymer urethane resin emulsions and self-emulsifying epoxy resin emulsions have been developed by introducing a carboxyl group or the like as a hydrophilic group into a resin skeleton to improve water resistance. However, even if these are used, a chromate aqueous solution containing a sol of a trivalent chromium compound according to the present invention can be stably maintained for a long time even after being mixed with an aqueous emulsion of the resin.

In the present invention, the amount of urea used is determined according to the acidity of the acidic chromium compound aqueous solution, but does not require a strict equivalent relation in practical use. The amount of urea used can be determined by calculation from the equivalent amount of ammonia formed by the hydrolysis, but does not require a strict equivalent relation in practical use. Further, in order to increase the formation rate of the sol of the trivalent chromium compound, urea may be added, if necessary, and then heated at 100 ° C. or lower.

The content of the trivalent chromium compound sol contained in the composition for metal surface treatment according to the present invention is not specified, but it is particularly preferably 1 to 50 g / liter in terms of trivalent chromium. . 1g converted to trivalent chromium
If the amount is less than 1 / liter, the amount of the trivalent chromium compound sol contained in the chromate film formed by coating becomes too small, and the paint adhesion, post-coating corrosion resistance, and coating performance of the obtained composition tend to decrease, and If it exceeds 50 g / l, the performance of the resulting composition reaches saturation and becomes economically expensive. The average particle size of the colloid particles contained in the trivalent chromium compound is 0.005 to 1.0 μm.

The coating type chromate treatment liquid produced by the method of the present invention may be added with a coloring pigment such as phthalocyanine blue or carbon black to color the film, if necessary, or a wax or the like. It is also possible to add a lubricant to impart lubricity to improve press workability and scratch resistance. The coating type chromate liquid thus adjusted is applied to a metal surface such as a zinc-based plated steel sheet or an aluminum-based sheet material by a method such as a roll coating method, a roll squeezing method after dipping or showering, or a spray method, and then the coating method. It is possible to form a film by drying. Also, when the coating is applied and heat-cured in a continuous process to obtain a pre-coated metal, the expected chromium elution rate does not change significantly, and even when chromic acid is added, the elution of hexavalent chromium ions occurs. The present invention enables the production of a pre-coated metal which does not impair the self-repairing property and has excellent corrosion resistance at a film defect portion caused by damage during cutting and processing of a plate material after coating.

[0039]

EXAMPLES The present invention will be described in detail with reference to the following Examples, but the scope of the present invention is not particularly limited by these Examples. Preparation Example 1 of Trivalent Chromium Compound Sol Trivalent chromium ion (Cr ³⁺ ) was 14.4 g / liter,
An acidic chromate aqueous solution having a pH of about 1.5 containing 33.6 g / liter of chromic acid as a hexavalent chromium acid as an acid.
ml was placed in a beaker, to which 24 g of urea was then added. This aqueous solution was heated to 80 ° C. with stirring and maintained for 4 hours. At this stage, the pH of the solution rises to about 3.0,
Thus, a sol of the trivalent chromium compound was formed. After cooling, aqueous ammonia (containing NH ₃ = 28%) was further added to adjust the pH to about 8.5, and then diluted with water to a volume of 1 liter to prepare a chromate solution having a total chromium concentration of 12 g / liter. did. The average particle diameter of the colloid contained in the chromate solution was measured and found to be 0.05 μm. This chromate solution retained a uniform appearance of the colloid solution even when left at room temperature for one week.

Preparation Example 2 of Trivalent Chromium Compound Sol 2 A pH of about 1.3 containing 10 g / l of trivalent chromium ions and 53 g / l of phosphoric acid as an acid in terms of PO ₄ ^3-.
Was placed in a beaker, and then 8 g of ammonium bicarbonate and 20 g of urea were added. This aqueous solution was heated to 80 ° C. with stirring and maintained for 4 hours. At this stage, the pH of the solution increased to about 6.0, thereby forming a sol of the trivalent chromium compound. After cooling, aqueous ammonia (containing NH ₃ = 28%) was added to adjust the pH to about 8.8, and the mixture was diluted with water to a volume of 1 liter to prepare a chromate solution having a total chromium concentration of 8 g / liter.
When the average particle diameter of the colloid contained in the chromate solution was measured, it was 0.03 μm. This chromate solution retained a uniform appearance of the colloid solution even when left at room temperature for one week.

Preparation Example 3 of Trivalent Chromium Compound Sol 3 g of trivalent chromium ion is 8 g / l, chromic acid is 8 g / l in terms of hexavalent chromium as an acid, and phosphoric acid is PO ₄ ^3−.
500 ml of an aqueous solution of acidic chromate having a pH of about 1.4 and containing 0.4 g / l of zinc ion as a metal ion and 10 g / l in terms of metal ions is placed in a beaker, and then 4 g of aqueous ammonia (containing NH ₃ = 28%) and 50 g of urea Was added. This aqueous solution was heated to 80 ° C. with stirring and maintained for 4 hours. At this stage, the pH of the solution rises to about 8.5,
As a result, a sol of the trivalent chromium compound was formed. After cooling, the mixture was diluted with water to a volume of 1 liter to prepare a chromate solution having a total chromium concentration of 8 g / liter. The average particle diameter of the colloid contained in the chromate solution was 0.04 μm. This chromate solution retained a uniform appearance of the colloid solution even when left at room temperature for one week.

Preparation Example 4 of Trivalent Chromium Compound Sol Aqueous chromate aqueous solution having a pH of about 1.4 and containing 3.6 g / liter of trivalent chromium ion and 10 g / liter of phosphoric acid as PO ₄ ³⁻ as an acid. 800 ml was placed in a beaker, and then 15 g of silica sol (* 1) was added as a metal oxide sol, followed by 20 g of urea. This aqueous solution was heated to 70 ° C. with stirring and maintained for 6 hours. At this stage, the pH of the solution increased to about 4.5, thereby forming a sol of the trivalent chromium compound. After cooling, 12.4 g of ammonium bichromate was added and dissolved, and diluted with water to a volume of 1 liter to prepare a chromate solution having a total chromium concentration of 8 g / liter. When the average particle diameter of the colloid contained in the chromate solution was measured, 0.05 μm was obtained.
m. This chromate solution retained a uniform appearance of the colloid solution even when left at room temperature for one week.

Preparation Example 5 of Trivalent Chromium Compound Sol: 4.2 g / liter of trivalent chromium ion, 9.8 g / liter of chromic acid as an acid in terms of hexavalent chromium, and 7 g of phosphoric acid (in terms of PO ₄ ³⁻ ) Per liter and 500 ml of an aqueous acidic chromate solution having a pH of about 1.2 and containing 2.1 g / liter of barium ion as a metal ion were placed in a beaker, and then 40 g of urea was added. This aqueous solution was heated to 90 ° C. with stirring and maintained for 3 hours. At this stage, the pH of the solution increased to about 9.0, thereby forming a sol of the trivalent chromium compound. After cooling, dilute with water to a liquid volume of 8
00 ml. The average particle size of the colloid contained in this aqueous solution was 0.04 μm. Furthermore,
After dispersing 10 g of fumed silica as a metal oxide sol (Note 1) in this aqueous solution, water was added to make the total volume 1 liter, total chromium concentration 8 g / l, silica concentration 10 g.
Per liter of chromate solution was prepared. This chromate solution retained a uniform appearance of the colloid solution even when left at room temperature for one week.

Comparative Chromate Preparation Example 1 A chromate aqueous solution having a pH of about 1.5 and containing 3 g / l of trivalent chromium ion (Cr ³⁺ ) and 7 g / l of hexavalent chromium ion (Cr ⁶⁺ ) was prepared. This chromate solution maintained a uniform solution appearance even when left at room temperature for one week.

Comparative Chromate Preparation Example 2 500 ml of an aqueous solution containing 6 g / l of trivalent chromium ions and 14 g / l of hexavalent chromium ions were placed in a beaker, and then 10 g of fumed silica (* 1) as a metal oxide sol. Was dispersed in water to make the volume 1 liter, and a chromate solution having a total chromium concentration of 10 g / l and a silica concentration of 10 g / l was prepared. The chromate solution maintained a uniform appearance even after one week at room temperature.

Comparative Chromate Preparation Example 3 900 ml of an acidic chromate aqueous solution containing 5 g / l of trivalent chromium ions, 5 g / l of hexavalent chromium ions and 5 g / l of phosphate ions and having a pH of about 1.5 was placed in a beaker. While stirring, aqueous ammonia (ammonia concentration 28% by weight) was added to adjust the pH of the chromate solution to about 3.
It was set to 5. The solution was further diluted with water to a volume of 1 liter to prepare an aqueous chromate solution having a total chromium concentration of 9 g / liter. This aqueous solution had a precipitate after standing at room temperature for one day.

Comparative Chromate Preparation Example 4 After dissolving 28.8 g of chromic anhydride (CrO ₃ ) in 800 ml of water, aqueous ammonia (28% by weight of ammonia) was added to adjust the pH of the aqueous solution to about 9.0. The solution was further diluted with water to a volume of 1 liter to prepare a chromate solution having a total chromium concentration of 12 g / liter. The chromate solution maintained a uniform appearance even after one week at room temperature.

(Note 1) Silica sol: manufactured by Nippon Aerosil Co., Ltd. (trademark: Aerosil # 200)

Example 1 Aqueous urethane emulsion (Note 2) commercially available as an aqueous resin: 536 g, sol of trivalent chromium compound of Preparation Example 1:
208 g and water: 256 g were mixed and stirred, and the resin solid content was 1
A treatment liquid having 8.8% and a total chromium concentration of 2.5 g / liter was prepared. This treatment liquid was in a stable state even when left at room temperature for one week.

Example 2 As a resin aqueous emulsion, 469 g of a commercially available urethane resin aqueous emulsion (Note 3), 312 g of the trivalent chromium compound sol of Preparation Example 2: 312 g, and water: 219 g were mixed and stirred to prepare a treatment liquid. . This treatment liquid was in a stable state even when left at room temperature for one week.

Example 3 As an aqueous resin emulsion, 335 g of a commercially available aqueous epoxy resin emulsion (Note 4), 312 g of a sol of the trivalent chromium compound of Preparation Example 3, and 353 g of water were mixed.
The mixture was stirred to prepare a treatment liquid. This treatment liquid was in a stable state even when left at room temperature for one week.

Example 4 As an aqueous resin emulsion, a commercially available aqueous urethane resin emulsion (Note 2): 536 g, a sol of the trivalent chromium compound of Preparation Example 4: 312 g, and water 152 g were mixed and stirred. A liquid was prepared. This treatment liquid was in a stable state even when left at room temperature for one week.

Example 5 As a resin aqueous emulsion, a commercially available urethane resin aqueous emulsion (Note 3): 469 g, a sol of the trivalent chromium compound of Preparation Example 5: 312 g, and water: 219 g were mixed.
The mixture was stirred to prepare a treatment liquid. This treatment liquid was in a stable state even when left at room temperature for one week.

Example 6 As a resin aqueous emulsion, 536 g of a commercially available aqueous urethane resin emulsion (Note 2), 312 g of the sol of the trivalent chromium compound of Preparation Example 6, and 152 g of water were mixed.
The mixture was stirred to prepare a treatment liquid. This treatment liquid was in a stable state even when left at room temperature for one week.

Example 7 As a resin aqueous emulsion, 536 g of a commercially available aqueous urethane resin emulsion (Note 2), 312 g of the trivalent chromium compound sol of Preparation Example 3, and 152 g of water were mixed and stirred. Prepared. This treatment liquid was in a stable state even when left at room temperature for one week.

Example 8 A commercially available urethane resin aqueous emulsion (Note 3): 469 g, a trivalent chromium compound sol of Preparation Example 4: 312 g, and water: 219 g were mixed and stirred as a resin aqueous emulsion. Prepared. This treatment liquid was in a stable state even when left at room temperature for one week.

Example 9 As a resin aqueous emulsion, 335 g of a commercially available aqueous emulsion of an epoxy resin (Note 4), 208 g of the trivalent chromium compound of Preparation Example 1, and 457 g of water were mixed and stirred. Prepared. This treatment liquid was in a stable state even when left at room temperature for one week.

Comparative Example 1 As a resin aqueous emulsion, 536 g of a commercially available urethane resin aqueous emulsion (Note 2), 250 g of the chromate solution of Comparative Preparation Example 1 and 214 g of water were mixed and stirred to obtain a resin solid content of 18. A treatment liquid having a concentration of 8% and a total chromium concentration of 2.5 g / liter was prepared. This treatment liquid gelled immediately after preparation and could not be applied.

Comparative Example 2 A commercially available urethane resin aqueous emulsion (Note 3): 469 g as a resin aqueous emulsion, 250 g of the chromate solution of Comparative Preparation Example 2 and 281 g of water were mixed and stirred to prepare a treatment liquid. . This treatment liquid gelled immediately after preparation and could not be applied.

Comparative Example 3 A commercially available aqueous emulsion of an epoxy resin (Note 4): 335 g, a chromate solution of Comparative Preparation Example 3: 278 g, and water: 387 g were mixed and stirred as an aqueous emulsion of a resin. Prepared. This treatment liquid contained a precipitate in an aqueous chromate solution, and after standing at room temperature for one day, a precipitate was formed and separated into two layers.

Comparative Example 4 As an aqueous resin emulsion, 536 g of a commercially available aqueous urethane resin emulsion (Note 2), 278 g of the chromate solution of Comparative Preparation Example 3, and 186 g of water were mixed and stirred. Prepared. This treatment liquid contained a precipitate in an aqueous chromate solution, and after standing at room temperature for one day, a precipitate was formed, and two layers were separated.

Comparative Example 5 A commercially available aqueous emulsion of a urethane resin (Note 3): 469 g, a chromate solution of Comparative Preparation Example 3: 278 g, and water: 253 g were mixed and stirred as an aqueous emulsion of the resin. Prepared. This treatment liquid contained a precipitate in an aqueous chromate solution, and after standing at room temperature for one day, a precipitate was formed, and two layers were separated.

Comparative Example 6 As an aqueous resin emulsion, 536 g of a commercially available aqueous urethane resin emulsion (Note 2), 208 g of the chromate solution of Comparative Preparation Example 4 and 256 g of water were mixed and stirred. Prepared. This treatment liquid was in a stable state even when left at room temperature for one week.

Comparative Example 7 A commercially available aqueous urethane resin emulsion (Note 3): 469 g, a chromate solution of Comparative Preparation Example 4: 208 g, and water: 323 g were mixed and stirred as an aqueous resin emulsion. Prepared. This treatment liquid was in a stable state even when left at room temperature for one week.

Comparative Example 8 As an aqueous resin emulsion, 335 g of a commercially available aqueous emulsion of an epoxy resin (Note 4), 208 g of the chromate solution of Comparative Preparation Example 4 and 457 g of water were mixed and stirred, and the treated liquid was mixed. Prepared. This treatment liquid was in a stable state even when left at room temperature for one week.

Comparative Example 9 JP-A-63-14578 as an aqueous emulsion of a resin
No. 5, 437 g of the aqueous acrylic resin emulsion described in Production Example 1 (Note 5), 250 g of the chromate solution of Comparative Preparation Example 1, and 313 g of water were mixed and stirred to prepare a treatment liquid. This treatment liquid was in a stable state even when left at room temperature for one week.

Comparative Example 10 As an aqueous emulsion of a resin, JP-A-59-19977
No. 5 Aqueous emulsion of acrylic resin described in Reference Example 1 (Note 6): 627 g, chromate solution of Comparative Preparation Example 1: 2
50 g and 123 g of water were mixed and stirred to prepare a treatment liquid. This treatment liquid was in a stable state even when left at room temperature for one week.

Comparative Example 11 As an aqueous emulsion of the resin, the resin described in (Note 5): 4
37 g and the chromate solution of Comparative Preparation Example 2: 125 g,
Water: 438 g was mixed and stirred to prepare a treatment liquid. This treatment liquid was in a stable state even when left at room temperature for one week.

Comparative Example 12 As an aqueous emulsion of the resin, the resin described in (Note 6):
627 g and the chromate solution of Comparative Preparation Example 2: 125 g
And 248 g of water were mixed and stirred to prepare a treatment liquid. This treatment liquid was in a stable state even when left at room temperature for one week.

(Note 2) Trade name: Permusen urethane emulsion UE-40-455, manufactured by ICI, nonvolatile content:
35% (Note 3) Manufactured by Bayer, trade name: Impranil DLV dispersion, nonvolatile content: 40% (Note 4) Manufactured by CIBA-GEIGY, trade name: Araldite MS-
6869, nonvolatile content: 56% (Note 5) Resin by the method described in Production Example 1 of JP-A-63-145785, nonvolatile content: 43% (Note 6) Refer to Reference Example 1 of JP-A-59-197575. Resin according to the method described, nonvolatile content: 30.2%

Application Examples 1-36 and Comparative Application Examples 1-2
6 (I) Preparation of Test Plate In each of Application Examples 1 to 36 and Comparative Application Examples 1 to 26, the test plates described in Table 1 were previously prepared using an alkaline degreasing agent (trade name: FC-4336, manufactured by Nippon Parkerizing Co., Ltd.). Concentration = 20 g / liter, degreasing agent temperature = 60 ° C., degreasing time = 10 seconds, degreasing method = spray), rinsing with water, draining and drying, and then prepared in Examples 1 to 9 and Comparative Examples 6 to 12. Using a bar coater, each of the processing solutions
After the coating was performed so that the coating amount became 8 ml / m ² , the coating was dried for 5 seconds so that the ultimate plate temperature reached 150 ° C. The amounts of resin adhering and chromium adhering (in terms of metal chromium) after drying of each coated plate were as shown in Tables 1 and 2.
In addition, since the liquid stability of Comparative Examples 1 to 5 was remarkably inferior, a test plate could not be produced.

(II) Performance test (a) Fingerprint resistance test Using the various treated steel sheets prepared under the above conditions, the L value, a value, and b value were measured in advance by a color difference meter. Next, petrolatum was thinly and uniformly applied to the same portion of the sample used for this measurement, and the L value, a value, and b value were measured again with the color difference meter, ΔE was determined from both values, and the fingerprint resistance was determined from the value. Was evaluated as follows. Fingerprint resistance evaluation criteria: Excellent ：: ΔE is less than 1 ↑ ○: ΔE is 1 or more, less than 2 ↓ △: ΔE is 2 or more, less than 4 Poor ×: ΔE is 4 or more

(B) Bare corrosion resistance test The JIS-Z
The salt spray test according to -2731 was performed for each material for 240 hours for electrogalvanized steel sheet, 200 hours for galvannealed steel sheet, 300 hours for 5% aluminum / galvanized steel sheet, and 300 hours for aluminized steel sheet. The test was performed for 40 hours, and the area where corrosion occurred was visually determined.

(C) Chromium elution resistance The test plate prepared as described above was immersed in boiling water for 10 minutes.
The amount of chromium adhering before and after immersion in boiling water was measured by X-ray fluorescence analysis, and the elution rate was calculated by the following equation. Chromium dissolution rate = (1-A / B) × 100 (%) where, A: chromium deposition amount after immersion in boiling water (mg / m ²⁾ B: chromium deposition amount before immersion in boiling water (mg / m ² That is, the closer the value of the chromium elution rate is to 0, the more excellent the chromium elution resistance is.

(D) Coating performance test A melamine alkyd paint (trade name: Delicon # 700) manufactured by Dainippon Paint Co., Ltd. was applied to various treated steel sheets prepared under the conditions shown in Table 1 so as to have a coating thickness of 25 μm. And coated and baked at 140 ° C. for 30 minutes to produce a coated plate. Using the coated plate prepared as described above, a coating performance test was performed under the following conditions.

(1) Primary adhesion test: <DuPont impact test> Shooting pin shape 1/2 inch φ, load 5
After performing the DuPont impact test under the condition of 00 g and a distance of 30 cm from the back of the painted surface and from the surface of the painted surface in two ways, the cellophane tape was peeled off, and the coating of the convex portions and concave portions was performed. The remaining state of the film was visually determined.

<Goban-Erichsen Test> After 100 cuts having a 1 mm-square shape were cut into the coating film surface with a cutter knife, the goblin portions were extruded 5 mm by an Erichsen tester, and the cellophane tape was peeled off. The evaluation was made based on the number of remaining grooves in the coating film.

(2) Secondary adhesion test: After the coated plate was immersed in boiling water for 4 hours, an adhesion test was performed under the following conditions. <DuPont impact test> firing pin shape 1/2 inch φ, load 5
After performing the DuPont impact test under the condition of 00 g and a distance of 30 cm from the back of the painted surface and from the surface of the painted surface in two ways, the cellophane tape was peeled off, and the coating of the convex portions and concave portions was performed. The remaining state of the film was visually determined.

<Goban Eye Erichsen Test> After making 100 gobang eye-like incisions in a 1 mm square with a cutter knife on the coating film surface, the gobang eye spots were cut with an Erichsen tester.
It was evaluated by the number of remaining gouges in the coating film after extruding mm and peeling off the cellophane tape. That is, the larger the number of remaining coating films, the better the coating film adhesion.

(3) Corrosion resistance test after painting: A cross-cut was made on the painted surface until it reached the metal substrate, and JIS-Z
After performing the salt spray test according to −2371 for 500 hours,
The peeling width of the coating film from the cross cut portion was measured in mm.
That is, the smaller the mm number, the better the corrosion resistance after painting. Tables 3 and 4 show the results of various performance tests.

[0081]

[Table 1]

[0082]

[Table 2]

[0083]

[Table 3]

[0084]

[Table 4]

As shown in Examples 1 to 9, the surface treatment composition according to the present invention can be used without using an aqueous resin emulsion having particularly good stability to an aqueous chromate solution.
It is clear that the composition of the present invention has excellent mixing stability. Therefore, it is possible to arbitrarily select an aqueous emulsion of a resin having excellent corrosion resistance, adhesion, and water resistance, and use it appropriately according to the intended purpose. Furthermore, the performance of the films formed using Examples 1 to 9 according to the present invention is excellent in any of chromium elution resistance, bare corrosion resistance, and coating adhesion as shown in Application Examples 1 to 36. It also shows excellent post-paint corrosion resistance. However, all of the compositions of Comparative Examples 1 to 5 according to the prior art lacked stability as a composition for metal surface treatment and were of low practicality. In the category of the prior art, even in Comparative Application Examples 1 to 26 in which the compositions of Comparative Examples 6 to 12, which could be applied, were applied, the coating performance after application was high in coating adhesion, especially in secondary adhesion. Poor chromium elution resistance,
The corrosion resistance after painting is also poor.

[0086]

According to the present invention, the composition for metal surface treatment containing a sol of a trivalent chromium compound and a binder resin is applied to the surface of a steel plate, a zinc-plated steel plate, an aluminum-plated steel plate, or an aluminum-based plate, and dried. By doing so, regardless of conditions such as the presence or absence of heating in the subsequent process, the level of the heating temperature, and the length of time, it has excellent treatment liquid stability, and therefore, the coating workability is good. In addition, it is possible to form a surface-treated film having various functions such as paintability (coating adhesion, corrosion resistance after painting, rust resistance after painting), fingerprint resistance, and bare corrosion resistance at the same time. .

Continuation of the front page (56) References JP-A-55-76078 (JP, A) JP-A-55-76077 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22 / 00-22/86

Claims (8)

(57) [Claims] 1. An aqueous solution of an acidic chromium compound comprising a trivalent chromium ion and a dispersion stabilizer and having a pH value of less than 3,
A sol of a trivalent chromium compound obtained by adding urea and hydrolyzing and dispersing the urea to form ammonia, and an aqueous resin emulsion;
A metal surface treatment composition having a pH value adjusted to zero. 2. The aqueous emulsion of the resin according to claim 1, wherein the aqueous emulsion of the resin comprises at least one selected from an aqueous emulsion of a polymer and a copolymer of a vinyl monomer, an alkyd resin, an epoxy resin, and a urethane resin. Composition. 3. The dispersion stabilizer according to claim 1, wherein the dispersion stabilizer is phosphoric acid, chromic anhydride, hydrofluoric acid, hydrofluoric acid, hydrofluoric acid, titanium hydrofluoric acid, zircon hydrofluoric acid, formic acid, acetic acid, acrylic acid, The composition according to claim 1, comprising at least one selected from polyacrylic acid, maleic acid, polymaleic acid, citric acid, tartaric acid, and malic acid. 4. The following additional components: (a) ions of zinc, iron, nickel, cobalt, manganese, tungsten, molybdenum, aluminum, titanium, zircon, and barium; and (b) silica sol, alumina sol, titania sol, zirconia sol. 2. The composition according to claim 1, further comprising at least one selected from the group consisting of sol, antimony oxide sol, tin oxide sol, and iron oxide sol.
A composition according to claim 1. 5. An aqueous solution of an acidic chromium compound containing a trivalent chromium ion and a dispersion stabilizer and having a pH of less than 3, to which urea is added and hydrolyzed to generate ammonia, thereby producing ammonia. A method for producing a composition for metal surface treatment, comprising adjusting the pH value of an aqueous solution to 3 to 10, thereby preparing a sol of a trivalent chromium compound, and mixing the sol with an aqueous emulsion of a resin. 6. The aqueous emulsion of the resin according to claim 5, wherein the aqueous emulsion of the resin comprises at least one selected from an aqueous emulsion of a polymer and a copolymer of a vinyl monomer, an alkyd resin, an epoxy resin, and a urethane resin. Method. 7. The method according to claim 1, wherein the dispersion stabilizer is phosphoric acid, chromic anhydride, hydrofluoric acid, hydrofluoric acid, hydrofluoric acid, titanium hydrofluoric acid, zircon hydrofluoric acid, formic acid, acetic acid, acrylic acid, The method according to claim 5, comprising at least one selected from polyacrylic acid, maleic acid, polymaleic acid, citric acid, tartaric acid, and malic acid. 8. The following additional components: (a) ions of zinc, iron, nickel, cobalt, manganese, tungsten, molybdenum, aluminum, titanium, zircon, and barium; and (b) silica sol, alumina sol, titania sol, zirconia sol. 6. An antimony oxide sol, a tin oxide sol, and an iron oxide sol.
The method described in.