JP3473755B2 - Surface treatment agent for galvanized steel sheet, and galvanized steel sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving the corrosion resistance and scratch resistance of galvanized steel sheets such as electrogalvanized steel sheets, hot-dip galvanized steel sheets and galvanized steel sheets containing 5% aluminum. In particular, the present invention relates to a surface treatment agent for a zinc-based plated steel sheet, which is used for improving corrosion resistance and scratch resistance by providing a zinc-based plated steel sheet with a resin film having excellent corrosion resistance, scratch resistance, and coating adhesion.

[0002]

Conventionally, zinc or zinc-based plated steel sheets have been widely used for household appliances, building materials and the like. These steel sheets are insufficient in corrosion resistance and coating adhesion (overcoating coatability) as they are, so they are subjected to chromate chemical conversion treatment or phosphate chemical conversion treatment, and then pressed or bent. Often molded and painted.

Depending on the intended use, it is often the case that it is used as it is without coating.

When used without coating, a surface-treated steel sheet called a chromate conversion steel sheet has been often applied.

However, in this case, there are problems such as adhesion of fingerprints during molding and assembling, and variation in color tone due to difference in chromate film amount.

Therefore, in order to solve these problems, a fingerprint resistant steel plate having an organic film formed on a chromate film has come to be used.

This fingerprint-resistant steel plate is formed by forming an organic resin layer having a thickness of about 1 μm on the surface of a zinc-based plated steel plate after chromate treatment for the purpose of preventing the adhesion of fingerprints. In addition to fingerprint resistance, this fingerprint-resistant steel sheet is required to have various film properties such as corrosion resistance, solvent resistance, coating adhesion, and scratch resistance.

Of these performances, the demand for scratch resistance has become particularly strong in recent years.

That is, due to vibration generated when the molded product is transported, the molded products rub against each other or the container (cardboard box or the like) containing the molded product and the molded product, and the surface of the molded product is scratched. Occurs. The scratched portion is inferior in corrosion resistance to a normal organic coated steel sheet. Therefore, the quality is inevitably deteriorated. In order to prevent this, scratch resistance is strongly required.

Therefore, there have been proposed some techniques relating to surface-treated steel sheets in consideration of scratch resistance in addition to corrosion resistance and coating film adhesion.

For example, Japanese Unexamined Patent Publication (Kokai) No. 3-17189 discloses a technique relating to a resin coating in which urethane-modified polyolefin resin is mixed with fluorine resin particles and silica particles. A characteristic of this technique is that the scratched portion is protected by using the fluorine-based resin particles. However, since the fluorine-based particles are uniformly dispersed in the aqueous solution, the use of a surfactant is indispensable. Because of the use of this surfactant,
The level of corrosion resistance is generally low, and satisfactory corrosion resistance is not obtained.

Japanese Patent Publication No. 6-104799 discloses a polyester resin, a crosslinking agent, and an average molecular weight of 2000 to 800.
Techniques relating to coatings containing 0 polyethylene wax have been disclosed. In this technique, since the polyester resin is used as the base resin, the hydrolysis resistance of the film itself is insufficient and satisfactory corrosion resistance cannot be obtained.

Japanese Unexamined Patent Publication (Kokai) No. 6-292859 relates to a film in which a urethane resin having active hydrogen in the molecule contains a room temperature crosslinkable epoxy resin, and spherical polyethylene wax particles and chain colloidal silica are contained in the resin. The technology is disclosed. Colloidal silica has a property called a lubricant that adheres to a solid surface to increase the friction coefficient, and when such a chain colloidal silica is used, the scratch resistance is improved due to the structure of the colloidal silica itself. descend. For this reason, spherical polyethylene wax is blended in this technique, but since the drying temperature is lower than 100 ° C., the polyethylene wax is buried in the resin film and the lubricity becomes insufficient, which is satisfactory. Scratch resistance is not obtained.

As described above, at present, no surface-treated steel sheet having excellent corrosion resistance and coating film adhesion and good corrosion resistance at the scratched portion has been obtained.

Therefore, the problem to be solved by the present invention is to provide a zinc-based plated steel sheet which is excellent in corrosion resistance and coating film adhesion and has good corrosion resistance in the scratched portion.

[0016]

As a result of intensive research and development by the present inventors for solving the above-mentioned problems, a specific urethane resin, a specific epoxy resin, colloidal silica, a specific dispersant, and a polyethylene wax. It was found that the above-mentioned problems can be solved by using a surface treatment agent containing, and the present invention has been completed.

That is, the above-mentioned problems have a bisphenol A type skeleton and a glass transition temperature of -40 to 0 ° C.
Urethane resin (A), a water-soluble epoxy resin (B) having three or more epoxy groups in one molecule, colloidal silica (C), and a compound (D) represented by the following general formula (I): And a polyethylene wax (E) and a solvent are contained in the surface treatment agent for zinc-based plated steel sheet.

Particularly, a urethane resin (A) having a bisphenol A type skeleton and having a glass transition temperature of −40 to 0 ° C. and a water-soluble epoxy resin (B) having three or more epoxy groups in one molecule. And colloidal silica (C),
A compound (D) represented by the following general formula (I), a polyethylene wax (E), a water-soluble organic solvent (F),
This is solved by a surface treatment agent for zinc-based plated steel sheet, which is characterized by containing water (G).

Further, a urethane resin (A) having a bisphenol A type skeleton and having a glass transition temperature of −40 to 0 ° C. and a water-soluble epoxy resin (B) having three or more epoxy groups in one molecule. And the ratio of the urethane resin (A) to the water-soluble epoxy resin (B) is urethane resin (A) / water-soluble epoxy resin (B) = 5/95.
It is solved by a surface treatment agent for zinc-based plated steel sheet, which is characterized by being ~ 95/5.

A surface-treating agent for zinc-based plated steel sheet, which contains a water-soluble urethane resin, a compound (D) represented by the following general formula (I), and a polyethylene wax (E): Will be solved by.

A water-soluble urethane resin, a water-soluble epoxy resin, and a compound (D) represented by the following general formula (I)
And a polyethylene wax (E) are contained in the surface treatment agent for zinc-based plated steel sheet.

The water-soluble urethane resin is particularly a water-soluble urethane resin having a bisphenol A type skeleton and having a glass transition temperature of -40 to 0 ° C. The water-soluble epoxy resin is a water-soluble epoxy resin having 3 or more epoxy groups in one molecule. And [sum of solid amount of (D) and (E)] / [sum of solid amount of water-soluble urethane resin, water-soluble epoxy resin, (D) and (E)]
= 2 to 20% by weight in particular.

General formula (I)

[0024]

[Chemical 5] [However, in the general formula (I), R ¹ represents an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms;
² represents (EO) _m- (PO) _n (wherein E represents an ethylene group, P represents a propylene group, m represents an integer of 5 to 20, and n represents an integer of 0 or 1 to 10). ), R
³ is a hydrogen atom, or SO ₃ M (provided that M represents a hydrogen atom, an alkali metal ion or an ammonium ion).
The stands, R ⁴ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
Alternatively, it represents an alkenyl group having 2 to 4 carbon atoms. In the present invention, a urethane resin (A) having a bisphenol A type skeleton and having a glass transition temperature in the range of -40 to 0 ° C is used.

As a result, the coating film formed has improved adhesion to the zinc-based plated steel sheet and excellent chemical resistance as well as excellent corrosion resistance and wear resistance. done. The amount of the bisphenol A type skeleton urethane resin (A) having such characteristics is preferably 10 to 50 parts by weight based on 100 parts by weight of the resin solid content. It is more preferably 15 to 40% by weight. That is, bisphenol A in urethane resin
If the amount of the type skeleton introduced is less than 10% by weight, the effect of improving the corrosion resistance tends to be low. On the contrary, if it exceeds 50% by weight, the bisphenol A type skeleton is a rigid skeleton. This is because the coating tends to be too hard and the adhesion tends to decrease.

The urethane resin (A) must have a glass transition temperature of -40 to 0 ° C. Preferably -35 to -5 ° C, more preferably -35 to -10.
It is in the range of ° C. That is, the glass transition temperature is −
When a urethane resin having a temperature lower than 40 ° C. is used, the resulting film has poor blocking resistance. Also, the physical properties of the resin film tend to change greatly at the glass transition temperature. Normally, the temperature after which the molded product is handled is 10-5.
Although it is in the range of 0 ° C., if the glass transition temperature is within this temperature range, the physical properties of the resin film may change depending on the air temperature, and the scratch resistance of the film may be poor. Further, when the glass transition temperature exceeds 50 ° C., the film-forming property of the coating film deteriorates, so that it is necessary to increase the drying temperature of the treatment agent, which is economically wasteful. Therefore, it is necessary to use the urethane resin (A) having a glass transition temperature of -40 to 0 ° C.

The urethane resin (A) used in the present invention is
Those that do not use a surfactant called an emulsifier are preferable. A urethane resin dispersed in water using a surfactant is not preferable because the water resistance of the film obtained by the influence of the surfactant is lowered.

From this point of view, as the urethane resin suitable for the present invention, a carboxyl group is introduced into the resin,
Further, the carboxyl group is neutralized with ammonia, amine or the like to be dispersed in water or made water-soluble.

A certain degree of corrosion resistance can be obtained using only the urethane resin.

However, in order to further bring out the characteristics of the resin, in the present invention, the water-soluble epoxy resin (B) having three or more epoxy groups in one molecule is used together.

Examples of the epoxy resin (B) used together with the urethane resin (A) in the present invention include sorbitol polyglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether,
Examples thereof include pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, and the like.

The amount of the urethane resin (A) and the epoxy resin (B) used is [the sum of the solid amounts of (A) and (B)] / [(A), (B) and (C)] The sum of the solid amounts of (D) and (E)] = 50 to 95% by weight is preferable. It is more preferably 60% by weight or more, further 65% by weight or more, and further preferably 85% by weight or less, further 80% by weight or less. That is, if this proportion is less than 50% by weight, the water resistance of the coating itself tends to decrease.
On the other hand, if it exceeds 95% by weight, the corrosion resistance of the scratched portion tends to decrease.

In the present invention, colloidal silica (C) is further used. That is, the use of colloidal silica (C) enhances the corrosion resistance and the effect of coating film adhesion.

Colloidal silica (C) used in the present invention
The particle size, shape, and type are not particularly limited. However, regarding the particle size, the average particle size is 3 to 30.
The range of nm is preferable.

The amount of colloidal silica (C) used is
[Solid content of (C)] / [total solid content of (A), (B), (C), (D) and (E)] = 3 to 40% by weight is preferable. More preferably, it is 10% by weight or more, and
It is more preferably 30% by weight or less. When the proportion of colloidal silica (C) is less than 3% by weight, the effect of improving the corrosion resistance tends to be poor, and when it exceeds 40% by weight, the binder effect of the urethane resin (A) tends to be poor. It tends to become smaller and the corrosion resistance tends to decrease.

In the present invention, polyethylene wax (E) is further used. This improves the level of scratch resistance.

The polyethylene wax (E) having an average particle diameter of 0.01 to 0.2 μm is extremely preferable.
Particularly, those having an average particle diameter of 0.05 to 0.18 μm are more preferable. Generally, the coefficient of friction used as an index of lubricity tends to decrease as the wax particle size increases. However, this friction coefficient and scratch resistance do not always match. And the number of sliding times (or sliding distance)
The relationship between the friction coefficient and friction coefficient (galling resistance) is more important.
The present inventor diligently studied the relationship between the average particle size of the wax and the number of times of sliding, and as a result, the average particle size of the wax was 0.01 to
It has been found that when the thickness is 0.2 μm, markedly excellent scratch resistance can be obtained. That is, when the average particle diameter of the wax is less than 0.01 μm, it tends to be uneconomical because it is necessary to use a higher performance machine to disperse the wax, and conversely, 0.2μ
If it exceeds m, the wax protruding from the coating surface tends to be easily removed during sliding, and as a result, continuous slidability tends to be deteriorated.

In the present invention, polyethylene wax (E) is used.
There is no particular limitation on the molecular weight or melting point of. However, the acid value is preferably in the range of 5 to 50. Especially 10-30
The range of is more preferable. That is, when the acid value is less than 5, the wax and the resin tend not to be compatible with each other,
When the film is formed, the wax is perfectly oriented on the surface of the film, and the scratch resistance and coating adhesion tend to be reduced. On the other hand, when the acid value exceeds 50, the hydrophilicity of the wax becomes strong,
This is because it was recognized that the slipperiness of the wax itself was lowered and the scratch resistance was lowered.

Usually, a surfactant called a dispersant is used to disperse the resin and pigment. This surfactant causes poor dispersion (resin or pigment aggregates to separate and settle or float) when the amount of the resin or pigment is small, and conversely, when the amount is large, the resulting film is obtained. To reduce the water resistance of.

The present inventor has found that polyethylene wax (E)
As a result of diligent study of the dispersant, the polyethylene wax (E) was obtained by using the compound (D) represented by the general formula (I).
It was confirmed that when dispersed, excellent uniform dispersion stability and water resistance were obtained.

In the general formula (I) of the compound (D) used as a dispersant for the polyethylene wax (E) of the present invention, R ¹ is an alkyl group having 5 to 20 carbon atoms or 2 to 5 carbon atoms. An alkenyl group is preferred. R ² is
(EO) _m- (PO) _n (provided that E represents an ethylene group, P represents a propylene group, m represents an integer of 5 to 20, and n represents an integer of 0 or 1 to 5). Those are preferable. R ³ is preferably a hydrogen atom or SO ₃ NH ₄ . R ⁴ is preferably a hydrogen atom or an alkenyl group having 2 to 4 carbon atoms.

The method for dispersing the polyethylene wax (E) using the compound (D) is not particularly limited and may be an industrially used method. The average particle size of the polyethylene wax (E) is the value in this water dispersion.

The ratio of the solid content of the compound (D) to the solid content of the water dispersion is preferably 5 to 40% by weight, more preferably 5 to 30% by weight. If the above proportion is less than 5% by weight, the polyethylene wax tends to be insufficiently dispersed, and conversely, if it exceeds 40% by weight, the water resistance of the resulting coating tends to be lowered.

The polyethylene wax (E) used for improving the scratch resistance is [sum of solid amount of (D) and (E)] / [(A), (B), (C) and ( The sum of the solid amounts of D) and (E)] = 2 to 20% by weight is preferable. It is more preferably at least 3% by weight, and more preferably 18
It is less than or equal to wt. That is, when this ratio is less than 2% by weight, the effect of improving the scratch resistance is small, and conversely, it is 20%.
When it exceeds the weight%, the overcoatability tends to be deteriorated.

In the present invention, for the purpose of improving the film forming property,
As the solvent for the surface treatment agent, an organic solvent and water are particularly used. This solvent is added in a proportion of 1 to 10% by weight.
2-8% by weight is more preferable. If the ratio is less than 1% by weight, the effect of improving the film-forming property is small, and if it exceeds 10% by weight, the effect of improving the film-forming property is saturated, which is not economical.

The above-mentioned organic solvent is not particularly limited, but those capable of azeotroping with water are preferable. Examples of such a solvent include acetone, methyl ethyl ketone, N-methyl-2-pyrrolidone, dioxane, and isopropyl alcohol. Of these, N-methyl-2-pyrrolidone is preferable.

The surface-treating agent of the present invention contains a surfactant called a wettability improving agent for forming a uniform film on the surface to be coated, a conductive substance for improving weldability, and a design improving property. A coloring pigment for the purpose may be contained.

The surface treating agent of the present invention can be obtained by mixing the above components and dissolving / dispersing them. The order of adding the components is not particularly limited. The mixing is suitably carried out by stirring using, for example, a propeller stirrer.

The surface treating agent of the present invention obtained preferably has a solid content concentration of 5 to 50% by weight.
More preferably, it is within the range of 40% by weight. When the solid content concentration is less than 5% by weight, the drying time is long. On the contrary, when the solid content concentration exceeds 50% by weight,
The surface treatment agent itself has a high viscosity, which may cause trouble in handling.

The galvanized steel sheet to which the surface treatment agent of the present invention is applied is preferably an electrogalvanized steel sheet, a hot dip galvanized steel sheet, or a galvanized steel sheet containing 5% aluminum.

The method for applying the surface treatment agent of the present invention is not particularly limited, but a roll coater method, a dipping method, an electrostatic coating method or the like can be used.

The surface treatment agent of the present invention is applied at 10 to 50 ° C., and the ultimate plate temperature is 60 to 180 ° C., preferably 70 to 1
By drying at 60 ° C, a film having excellent scratch resistance can be formed on the surface of the zinc-based plated steel sheet. If the ultimate plate temperature is lower than 60 ° C, it is difficult to obtain satisfactory corrosion resistance, and conversely, if the ultimate plate temperature exceeds 180 ° C, the cost increases.

The resin film (coating film) obtained by applying and drying the surface treatment agent of the present invention has a content of 0.1 to 3 g /
A thickness of m ² is preferred. In particular, 0.2-2 g /
A thickness of m ² is preferred. Thickness is 0.1g / m ²
If it is less than less than, it is difficult to obtain satisfactory corrosion resistance, and conversely,
If it exceeds 3 g / m ² and is too thick, it is not economical.

The surface-treating agent of the present invention may be applied to a zinc-based plated steel sheet treated by a chromium-free treatment method such as pickling or phosphate chemical conversion treatment. In order to draw it out, it is preferable to apply it to a zinc-based plated steel sheet treated with a treatment agent containing chromium.

Examples of the treatment containing chromium include a reactive chromate chemical conversion treatment, a coating type chromate chemical conversion treatment, and an electrolytic chromate chemical conversion treatment. Chromium-containing film containing chromium atoms is 3 to 200 mg / m in terms of metallic chromium.
A thickness of ² is preferred. More preferably 5 mg /
The thickness is preferably m ² or more, more preferably 150 mg / m ² or less, and further 100 mg / m 2.
The thickness is ² or less. That is, it was confirmed that when the surface treatment agent of the present invention was applied onto the chromium-containing film having such characteristics, the effect of improving the corrosion resistance was further enhanced.

The zinc-plated steel sheet having excellent scratch resistance obtained by applying and drying the surface treatment agent of the present invention is excellent in flat surface corrosion resistance, scratch corrosion resistance and coating adhesion.

There is no particular limitation on the top coat paint to be applied to the zinc-based plated steel sheet having excellent scratch resistance of the present invention, but for example, a constantly dry melamine alkyd paint, a baking melamine alkyd paint, an acrylic resin paint, Examples include ultraviolet curable resin-based paints.

[0058]

BEST MODE FOR CARRYING OUT THE INVENTION A surface treating agent for zinc-based plated steel sheet according to the present invention has a bisphenol A type skeleton, and
Urethane resin (A) having a glass transition temperature of -40 to 0 ° C
A water-soluble epoxy resin (B) having three or more epoxy groups in one molecule, colloidal silica (C), a compound (D) represented by the general formula (I), and a polyethylene wax (E). ) And a solvent. In particular, it has a bisphenol A type skeleton and has a glass transition temperature of -40.
To 0 ° C urethane resin (A), water-soluble epoxy resin (B) having three or more epoxy groups in one molecule, colloidal silica (C), and a compound represented by the above general formula (I). (D), a polyethylene wax (E), a water-soluble organic solvent (F), and water (G).

The amount of the bisphenol A type skeleton introduced into the urethane resin (A) used in the present invention is 10% resin solids.
The ratio is 10 to 50 parts by weight with respect to 0 parts by weight. Particularly, it is 15 to 40% by weight. Also, urethane resin (A)
Has a glass transition temperature of −40 to 0 ° C.
Particularly, it is in the range of −35 to −5 ° C., and more preferably −35 to −10 ° C.

The glass transition temperature was measured by a commercially available dynamic viscoelasticity measuring device (Rheolograph Solid S manufactured by Toyo Seiki Seisaku-sho, Ltd.).
-1). The test piece was dried at 100 ° C. for 30 minutes and had a film thickness of 100 μm, a width of 8 mm, and a length of 30 mm.
The glass transition temperature was calculated from the inflection point of the elastic loss rate by using the above-mentioned one and measuring at a frequency of 100 Hz.

The urethane resin (A) used in the present invention does not use a surfactant called an emulsifier. In particular, a urethane resin (A) was used in which a carboxyl group was introduced into the resin, and the carboxyl group was neutralized with ammonia, amine or the like to be dispersed in water or solubilized in water.

In the present invention, the water-soluble epoxy resin (B) having 3 or more epoxy groups in one molecule is used together with the urethane resin (A).

Examples of the epoxy resin (B) used together with the urethane resin (A) include sorbitol polyglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, trimethylol. Propane polyglycidyl ether and the like.

The amount of the urethane resin (A) and the epoxy resin (B) used is [the sum of the solid amounts of (A) and (B)] / [(A), (B) and (C)] The sum of the solid amounts of (D) and (E)] = 50 to 95% by weight. Especially 60
It is not less than 65% by weight, more preferably not less than 85% by weight, further not more than 80% by weight.

In the present invention, colloidal silica (C) is further used. As the colloidal silica (C), one having an average particle size in the range of 3 to 30 nm was used.

The amount of colloidal silica (C) used is
[Solid amount of (C)] / [sum of solid amounts of (A), (B), (C), (D) and (E)] = 3 to 40% by weight. Particularly, it is 10% by weight or more and 30% by weight or less.

In the present invention, polyethylene wax (E) was further used. The polyethylene wax (E) used had an average particle size of 0.01 to 0.2 μm. In particular, an average particle size of 0.05 to 0.18 μm was used. A polyethylene wax (E) having an acid value of 5 to 50, particularly 10 to 30, was used.

In the present invention, the polyethylene wax (E) is dispersed using the compound (D) represented by the general formula (I).

The ratio of the solid content of the compound (D) to the solid content of the water dispersion is 5 to 40% by weight, particularly 5 to 30%.
% By weight. Polyethylene wax (E) is
[Sum of Solids of (D) and (E)] / [Sum of Solids of (A), (B), (C), (D) and (E)] =
It is 2 to 20% by weight, especially 3 to 18% by weight.

In the present invention, for the purpose of improving the film forming property,
As the solvent for the surface treatment agent, an organic solvent and water were used in particular. The solvent was blended in a proportion of 1 to 10% by weight, particularly 2 to 8% by weight.

The organic solvent is not particularly limited, but acetone, methyl ethyl ketone, N-methyl-2-pyrrolidone, dioxane, isopropyl alcohol and the like were used.

The surface treatment agent of the present invention includes a surfactant called a wettability improving agent for forming a uniform film on the surface to be coated, a conductive substance for improving weldability, and a designing property improving agent. A coloring pigment for the purpose was added as needed.

The surface treating agent of the present invention was obtained by mixing, dissolving and dispersing the above components. Mixing was performed using, for example, a propeller stirrer.

The surface treating agent of the present invention obtained had a solid content concentration of 5 to 50% by weight, particularly 5 to 40% by weight.

The zinc-based plated steel sheet to which the surface treatment agent of the present invention is applied is an electrogalvanized steel sheet, a hot-dip galvanized steel sheet, and a galvanized steel sheet containing 5% aluminum.

As a method for applying the surface treatment agent of the present invention, a roll coater method, a dipping method, an electrostatic coating method and the like have been adopted.

The surface treatment agent of the present invention is applied at 10 to 50 ° C., and the ultimate plate temperature is 60 to 180 ° C., especially 70 to 160.
By drying at ℃, it was possible to form a film having excellent scratch resistance on the surface of the zinc-based plated steel sheet.

The resin film (coating film) obtained by applying and drying the surface treatment agent of the present invention has a content of 0.1 to 3 g /
It has a thickness of m ² , in particular 0.2 to ² g / m ² .

The surface treatment agent of the present invention was applied to a zinc-based plated steel sheet treated with a treatment agent containing chromium. As the treatment containing chromium, a reactive chromate chemical conversion treatment, a coating type chromate chemical conversion treatment, an electrolytic chromate chemical conversion treatment and the like were adopted. The chromium-containing film containing chromium atoms,
3 to 200 mg / m ^{2 in} terms of metallic chromium, especially 5 to 15
0 mg / m ^2, even at thickness of 5 to 100 mg / m ^2.

The zinc-based plated steel sheet obtained by applying and drying the surface treatment agent of the present invention was excellent in flat surface corrosion resistance, scratched area corrosion resistance and coating adhesion.

There is no particular limitation on the top coat paint to be applied to the zinc-based plated steel sheet having excellent scratch resistance of the present invention, but examples thereof include a constantly dry melamine alkyd paint, a baking melamine alkyd paint, an acrylic resin paint, Examples include UV-curable resin-based paints.

The surface treatment agent for zinc-based plated steel sheet according to the present invention has a bisphenol A-type skeleton, a urethane resin (A) having a glass transition temperature of −40 to 0 ° C., and an epoxy group of 1 A water-soluble epoxy resin (B) having 3 or more in a molecule is contained, and the ratio of the urethane resin (A) and the water-soluble epoxy resin (B) is urethane resin (A) / water-soluble epoxy resin ( B) = 5/95 to 95 /
5 of them. If the urethane resin (A) / water-soluble epoxy resin (B) is less than 5/95 (there is a large amount of water-soluble epoxy resin), the water-soluble epoxy resin becomes excessive and the water resistance of the coating film decreases, which is not preferable. . Conversely, 95 /
When it exceeds 5 (there is a large amount of urethane resin), the effect of improving the corrosion resistance is poor.

The surface treatment agent for zinc-based plated steel sheet according to the present invention comprises a water-soluble urethane resin and the above general formula (I).
The compound (D) represented by and the polyethylene wax (E) are contained.

The surface treatment agent for zinc-based plated steel sheet according to the present invention is a water-soluble urethane resin, a water-soluble epoxy resin, the compound (D) represented by the above general formula (I), and a polyethylene wax. (E) and are contained.

The water-soluble urethane resin has a bisphenol A type skeleton and has a glass transition temperature of -4.
It is a water-soluble urethane resin at 0 to 0 ° C., and the water-soluble epoxy resin is particularly a water-soluble epoxy resin having 3 or more epoxy groups in one molecule. The compounding amount of these compounds is, in particular, [sum of solid amounts of (D) and (E)] / [solid amount of water-soluble urethane resin, water-soluble epoxy resin, (D) and (E)] Is 2 to 20% by weight.

Hereinafter, a specific description will be given using examples and comparative examples. It should be noted that these examples are provided for the purpose of explaining the present invention, and do not limit the present invention in any way.

[0087]

[Examples] [Preparation of test plate] (1) Test material The following commercially available zinc-based plated steel sheets were used as test materials. The size of the test material is 200 mm × 300 mm.

[Electrogalvanized steel plate (EG)] Plate thickness 0.8 mm, basis weight = 20/20 (g / m ² ) [Hot dip galvanized steel plate (GI)] Plate thickness 0.8 mm, basis weight = 60 / 60 (g / m ² ) [Galvanized steel sheet (GF) containing 5% aluminum] Plate thickness 0.8 mm, basis weight = 90/90 (g / m ² ) (2) Degreasing treatment Each of the above test materials was silicate A degreasing treatment was performed using Fine Cleaner 4336 (registered trademark: manufactured by Nippon Parkerizing Co., Ltd.), which is a system alkaline degreasing agent. After spraying for 2 minutes at a concentration of 20 g / L and a temperature of 60 ° C., it was washed with tap water. (3) Substrate treatment (3-1) Reactive chromate treatment Zinchrome 357 (registered trademark: manufactured by Nippon Parkerizing Co., Ltd.) was used for spray treatment at a liquid temperature of 50 ° C. for 5 seconds, washed with tap water, and then air dried. . (3-2) Coating Chromate Treatment Zinchrome 1300AN (registered trademark: manufactured by Nippon Parkerizing Co., Ltd.) was used for coating by a roll coater method, and immediately dried for 10 seconds at an ambient temperature of 200 ° C. without washing with water. The ultimate plate temperature at this time is 100 ° C. (3-3) Phosphate conversion treatment Palbond L3020 (registered trademark: manufactured by Nippon Parkerizing Co., Ltd.) was used for immersion treatment at a liquid temperature of 43 ° C for 2 minutes, followed by washing with water and air drying.

[Preparation of Surface Treatment Agent] At room temperature, urethane resin of Table 1, epoxy resin of Table 2, silica of Table 3, and Table 4
The wax water dispersion of Example 1 and the organic solvent of Table 5 were mixed in this order with stirring using a propeller stirrer, distilled water was added to adjust the solid content concentration, and the surface treatment agent shown in Table 6 was adjusted.

The aqueous dispersion of the wax was prepared by placing the wax shown in Table 4, the compound (D) represented by the general formula (I), and water in an autoclave, heating the mixture to 130 ° C. and stirring the mixture. It was adjusted by doing.

Table 1 (Urethane resin) Urethane resin Bisphenol A type glass transition temperature Solid content concentration A1 Yes -27 ° C 30% Invention A2 Yes + 40 ° C 30% Outside invention A3 No -27 ° C 31% Outside invention * A1 is Daiichi Kogyo Seiyaku Co., Ltd. Super Flex 370 * A2 is Daiichi Kogyo Seiyaku Co., Ltd. Super Flex 150 * A3 is Asahi Denka Kogyo Co., Ltd. ADEKA BON TITER HUX-386 Table 2 (epoxy resin) Epoxy resin Epoxy group in one molecule Number Solids concentration B1 4 100% Present invention B2 2 40% Outside of invention * B1 is Nagase Kasei's Dinacol EX-512 * B2 is Asahi Denka Kogyo's EM-0410 Table 3 (Colloidal silica) Silica Silica type Solid content concentration C1 Colloidal system 20% Present invention C2 Gas phase system 20% Outside the invention * C1 is Nissan Chemical Snowtex-N * C2 of a business company is an aqueous dispersion of Aerosil # 200 of Nippon Aerosil Co., Ltd. Table 4 (Wax) No Wax E Compound D Compounding amount E / D Average particle size W1 E1 D1 75/25 0.08 μm W2 E2 D2 95/5 0.12 μm Invention W3 E1 D3 90/10 0.15 μm Invention W4 E1 D4 80/20 0.15 μm Invention W5 E1 D5 85/15 0.45 μm Invention W6 E3 D2 70/30 0.10 μm Non-invention W7 E1 None --- Non-invention * E1 and E2 are polyethylene wax manufactured by Mitsui Chemicals, Inc. E1 is Mitsui High Wax 100P, E2 is Mitsui High Wax 220MP * E3 is Mitsui Chemicals, Inc. in manufacturing a polypropylene wax, Mitsui Haiwakku scan NP055 * D1, in the above general formula (I), R ¹ _{-C 9 H 19, m = 12} , n = 0, R 3 = H, R 4 = -CH = CHCH 3 * D2 , in the above general formula ^{(I), R 1 = -C} 18 H 37, m = 20, n = 0, R 3 = -SO 3 NH 4, R 4 = H * D3 , in the above general formula ^{(I), R 1 = -C} 8 H 17, m = 10, n = 5, ^{R 3 = H, R 4 =} H * D4 , in the above general formula ^{(I), R 1 = -CH} 2 CH = CH 2, m = 10, n = 5, R 3 = H, R 4 = H * D5 is R ¹ = -C ₉ H ₁₉ , m = 12, n = 0, R ³ = H, R ⁴ = H in the above general formula (I) Table 5 (organic solvent) Organic solvent Product name Purity F1 Wako Pure Chemical Industries, Ltd. N-methyl-2-pyrrolidone 98% or more F2 Wako Pure Chemical Industries, Ltd. acetone 99% or more Table 6 (Surface treatment agent) Surface treatment agent Urethane resin Epoxy resin Silica w Mix Organic solvent No1 A1 (72) B1 (3) C1 (20) W1 (5) F1 (5) No2 A1 (72) B1 (3) C1 (20) W2 (5) F1 (5) No3 A1 (72) B1 (3) C1 (20) W3 (5) F1 (5) No4 A1 (72) B1 (3) C1 (20) W4 (5) F1 (5) No5 A1 (72) B1 (3) C1 (20) W5 (5) F1 (5) No6 A1 (72) B1 (3) C1 (20) W1 (5) F2 (5) No7 A1 (50) B1 (5) C1 (40) W1 (5) F1 (5) No8 A1 (85) B1 (5) C1 (5) W1 (5) F1 (5) No9 A1 (75) B1 (3) C1 (20) W1 (2) F1 (5) No10 A1 (58) B1 (2 ) C1 (20) W1 (20) F1 (5) No11 A1 (72) B1 (3) C1 (20) W1 (5) F1 (2) No12 A1 (72) B1 (3) C1 (20) W1 (5 ) F1 (9) No13 A2 (72) B1 (3) C1 (20) W1 (5) F1 (5) No14 A3 (72) B1 (3) C1 (20) W1 (5) F1 (5) No15 A1 ( 72) B2 (3) C1 (20) W1 (5) F1 (5) No16 A1 (72) B1 (3) C1 (20) W6 (5) F (5) No17 A1 (72) B1 (3) C1 (20) W7 (5) F1 (5) No18 A1 (80) B1 (8) None W1 (10) F1 (5) No19 A1 (76) B1 (3 ) C1 (20) None F1 (5) No20 A1 (72) B1 (3) C1 (20) W1 (5) None * Numbers in parentheses are compounding amounts * No1 to No12 are surface treatment agents of the present invention * No13 to No. 20 is a surface treatment agent other than the invention [Method of applying surface treatment agent to test plate] Each surface treatment agent prepared above is applied to the test plate with a bar coater,
It was dried for 10 seconds at an ambient temperature of 240 ° C. The ultimate plate temperature at this time is 100 ° C. The amount of adhesion was adjusted by appropriately changing the solid content concentration of the surface treatment agent and the type of bar coater.

Table 7 shows the contents of the test plate thus obtained.

[0093]                         Table 7 (Test plate) No materialsurface treatment  Surface treatment agent             Type Adhesion amount (g / m²) No Adhesion amount (g / m²) Plate temperature reached 1 EG Reactive Chromate 0.02 1 1.0 120 ° C 2 EG reactive chromate 0.02 2 1.0 120 ° C 3 EG reactive chromate 0.02 3 1.0 120 ° C 4 EG Reactive Chromate 0.02 4 1.0 120 ° C 5 EG Coating Chromate 0.02 5 1.0 120 ° C 6 EG Reactive Chromate 0.02 6 1.0 120 ° C 7 EG Phosphate formation 2.00 7 1.0 120 ° C 8 EG Reactive Chromate 0.02 8 1.0 120 ° C 9 EG reactive chromate 0.02 9 1.0 120 ° C 10 EG Coating Chromate 0.02 10 1.0 120 ° C 11 EG Reactive Chromate 0.02 11 1.0 120 ° C 12 EG reactive chromate 0.02 12 1.0 120 ° C 13 EG Coating Chromate 0.02 1 1.0 120 ° C 14 EG Reactive Chromate 0.02 1 0.5 120 ° C 15 EG Reactive Chromate 0.02 1 3.0 120 ° C 16 GI Coating Chromate 0.02 1 1.0 120 ° C 17 GF Coated Chromate 0.02 1 1.0 120 ° C 18 EG Reactive Chromate 0.02 1 1.0 60 ° C 19 EG Reactive Chromate 0.02 1 1.0 180 ° C 20 EG Reactive Chromate 0.02 12 1.0 120 ° C 21 EG Reactive Chromate 0.02 13 1.0 120 ° C 22 EG Reactive Chromate 0.02 14 1.0 120 ° C 23 EG Reactive Chromate 0.02 15 1.0 120 ° C 24 EG Reactive Chromate 0.02 16 1.0 120 ° C 25 EG Reactive Chromate 0.02 17 1.0 120 ° C 26 EG Reactive Chromate 0.02 18 1.0 120 ° C 27 EG Reactive Chromate 0.02 20 1.0 120 ° C [Coated board performance test] (1) Corrosion resistance of flat surface The salt spray test according to JIS-Z-2371 is used for EG materials.
240 hours in total, 480 hours for GF material, white rust occurs
The situation was observed and evaluated according to the following criteria. <Evaluation criteria> ◎: White rust occurrence area is less than 3% of the total area ◯: White rust occurrence area is 3% or more and less than 10% of the total area Δ: White rust occurrence area is 10% or more and less than 30% of the total area X: White rust occurrence area is 30% or more of the total area (2) Corrosion resistance of scratched area Cut the test piece into a size of 30 mm × 300 mm and
-Bead test (bead tip 1mmR, bead height 4m
m, die shoulder 1 mmR, pressure bonding load 500 kg, temperature 30
C)). About the sliding part of this test piece JIS-Z
-2371 salt spray test 120 for EG material
Time, 240 hours for GF material to see white rust occurrence
And evaluated according to the following criteria.

<Evaluation Criteria> ⊚: White rust occurrence area is less than 3% of the total area ◯: White rust occurrence area is 3% or more and less than 10% △: White rust occurrence area is 10% or more of the total area , Less than 30% ×: White rust occurrence area is 30% or more of the total area (3) A scratched portion appearance test piece is cut into a size of 30 mm × 300 mm, and a draw bead test (bead tip 1 mmR, bead height 4 m
m, die shoulder 1 mmR, pressure bonding load 500 kg, temperature 30
C)). The condition of the sliding portion of this test piece was observed and evaluated according to the following criteria.

<Evaluation Criteria> ◎: Scratch area of sliding part is less than 5% ○: Scratch area of sliding part is 5% or more and less than 10% Δ: Scratch area of sliding part is 10% or more and less than 30% ×: Sliding Scratch area of the part is 30% or more (4) Paint adhesion melamine alkyd paint (registered trademark: Amylak # 1
000, manufactured by Kansai Paint Co., Ltd. is applied so that the film thickness after baking and drying becomes 25 μm, and baking is performed at 125 ° C. for 20 minutes. Using a test piece that has been left for 24 hours after baking, 1 mm grid is 100 according to JIS-Z-5400.
After drawing individually, the coating film was peeled off with Cellotape (registered trademark) and evaluated according to the following criteria.

<Evaluation criteria> ⊚: No peeling of coating film, 100 remaining coating film ◯: Very slight peeling of coating film, 100 remaining coating film Δ: 95 to 99 remaining coating films X: Number of remaining coating films is 94 or less The test results are shown in Table 8.

[0097]                                   Table 8 Test plate No Flat surface corrosion resistance Scratch area corrosion resistance Scratch area appearance Paint adhesion 1 ◎ ◎ ◎ ◎ 2 ◎ ◎ ◎ ◎ 3 ◎ ◎ ◎ ◎ 4 ◎ ◎ ◎ ◎ ◎ 5 ◎ ◎ ◎ ◎ 6 ◎ ◎ ◎ ◎ 7 ◎ ○ ○ ◎ 8 ◎ ○ ○ ◎ 9 ◎ ○ ○ ◎ 10 ◎ ◎ ◎ ◎ 11 ◎ ◎ ◎ ◎ 12 ◎ ◎ ◎ ◎ 13 ◎ ◎ ◎ ◎ ◎ 14 ◎ ◎ ◎ ◎ 15 ◎ ◎ ◎ ◎ ◎ 16 ◎ ○ ○ ◎ 17 ◎ ◎ ◎ ◎ ◎ 18 ◎ ◎ ◎ ◎ ◎ 19 ◎ ◎ ◎ ◎ ◎ 20 ◎ ○ ○ ◎                21 ○ × × ○ 22 ○ △ △ ○ 23 △ × × △ 24 △ × × △ 25 △ × × △ 26 ○ × × ○ 27 △ △ △ ○

The surface treatment agent of the present invention is excellent in corrosion resistance of flat surface portion, corrosion resistance of scratched portion and coating adhesion.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C09D 175/04 C09D 175/04 C23C 22/24 C23C 22/24 28/00 28/00 C // B05D 7/14 B05D 7 / 14 A (72) Inventor Keiichi Ueno 1-1-15-1 Nihonbashi, Chuo-ku, Tokyo Within Nippon Parkerizing Co., Ltd. (72) Inventor Katsuji Kawanishi, 3rd Hibiki, Kashima City, Ibaraki Prefecture Sumitomo Metal Industries, Ltd. Kashima Works (72) Inventor Atsuhisa Yagawa 3 Hikari 3 Kaji, Kashima City, Ibaraki Sumitomo Metal Industries, Ltd. Kashima Works (56) Reference JP 2000-265111 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 22/00 B32B 15/08 B32B 15/18 C09D 163/00 C09D 175/04 C23C 22/24 C23C 28/00 B05D 7/14

Claims (17)

(57) [Claims] 1. A bisphenol A type skeleton, and
Urethane resin (A) having a glass transition temperature of -40 to 0 ° C
And a water-soluble epoxy resin (B) having three or more epoxy groups in one molecule, wherein the ratio of the urethane resin (A) and the water-soluble epoxy resin (B) is the urethane resin (A). / Water-soluble epoxy resin (B) = 5/95 to 95/5, a surface treatment agent for zinc-based plated steel sheet. 2. A bisphenol A type skeleton, and
Urethane resin (A) having a glass transition temperature of -40 to 0 ° C
A water-soluble epoxy resin (B) having three or more epoxy groups in one molecule, colloidal silica (C), a compound (D) represented by the following general formula (I), and a polyethylene wax (E) ) And a solvent are contained, The surface treatment agent for zinc-based plated steel sheets characterized by the above-mentioned. General formula (I) [However, in the general formula (I), R ¹ represents an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms;
² represents (EO) _m- (PO) _n (wherein E represents an ethylene group, P represents a propylene group, m represents an integer of 5 to 20, and n represents an integer of 0 or 1 to 10). ), R
³ is a hydrogen atom, or SO ₃ M (provided that M represents a hydrogen atom, an alkali metal ion or an ammonium ion).
The stands, R ⁴ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
Alternatively, it represents an alkenyl group having 2 to 4 carbon atoms. ] 3. A bisphenol A type skeleton, and
Urethane resin (A) having a glass transition temperature of -40 to 0 ° C
A water-soluble epoxy resin (B) having three or more epoxy groups in one molecule, colloidal silica (C), a compound (D) represented by the following general formula (I), and a polyethylene wax (E) ), A water-soluble organic solvent (F), and water (G). General formula (I) [However, in the general formula (I), R ¹ represents an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms;
² represents (EO) _m- (PO) _n (wherein E represents an ethylene group, P represents a propylene group, m represents an integer of 5 to 20, and n represents an integer of 0 or 1 to 10). ), R
³ is a hydrogen atom, or SO ₃ M (provided that M represents a hydrogen atom, an alkali metal ion or an ammonium ion).
The stands, R ⁴ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
Alternatively, it represents an alkenyl group having 2 to 4 carbon atoms. ] 4. The surface treatment agent for zinc-based plated steel sheet according to claim 2, wherein the polyethylene wax (E) is dispersed in water with the compound (D). 5. The surface treatment for zinc-based plated steel sheet according to claim 2, wherein the polyethylene wax (E) has an average particle size of 0.01 to 0.2 μm. Agent. 6. [Sum of solid amount of (A) and (B)] /
[Sum of solid amount of (A), (B), (C), (D) and (E)] = 50 to 95% by weight, [solid amount of (C)] /
[Sum of solid amount of (A), (B), (C), (D) and (E)] = 3 to 40% by weight, [sum of solid amount of (D) and (E)] / [The total amount of solids of (A), (B), (C), (D), and (E)] = 2 to 20% by weight, and the composition is blended. Item 5. A surface treatment agent for zinc-plated steel sheet according to any one of items 5. 7. The surface treating agent for a zinc-plated steel sheet according to claim 1, wherein the solvent is mixed in a ratio of 1 to 10% by weight. 8. A surface treatment agent for a zinc-based plated steel sheet, comprising a water-soluble urethane resin, a compound (D) represented by the following general formula (I), and a polyethylene wax (E): . General formula (I): [However, in the general formula (I), R ¹ represents an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms;
² represents (EO) _m- (PO) _n (wherein E represents an ethylene group, P represents a propylene group, m represents an integer of 5 to 20, and n represents an integer of 0 or 1 to 10). ), R
³ is a hydrogen atom, or SO ₃ M (provided that M represents a hydrogen atom, an alkali metal ion or an ammonium ion).
The stands, R ⁴ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
Alternatively, it represents an alkenyl group having 2 to 4 carbon atoms. ] 9. A zinc-based resin containing a water-soluble urethane resin, a water-soluble epoxy resin, a compound (D) represented by the following general formula (I), and a polyethylene wax (E). Surface treatment agent for plated steel sheet. General formula (I): [However, in the general formula (I), R ¹ represents an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms;
² represents (EO) _m- (PO) _n (wherein E represents an ethylene group, P represents a propylene group, m represents an integer of 5 to 20, and n represents an integer of 0 or 1 to 10). ), R
³ is a hydrogen atom, or SO ₃ M (provided that M represents a hydrogen atom, an alkali metal ion or an ammonium ion).
The stands, R ⁴ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms,
Alternatively, it represents an alkenyl group having 2 to 4 carbon atoms. ] 10. The water-soluble urethane resin has a bisphenol A type skeleton and has a glass transition temperature of −40 to 0.
A surface treatment agent for zinc-based plated steel sheet according to claim 8 or 9, which is a water-soluble urethane resin at ℃. 11. The surface treatment agent for zinc-based plated steel sheet according to claim 9, wherein the water-soluble epoxy resin is a water-soluble epoxy resin having three or more epoxy groups in one molecule. 12. [Sum of solid contents of (D) and (E)]
/ [Water-soluble urethane resin and water-soluble epoxy resin (D)
And the total amount of solids of (E)] = 2 to 20% by weight.
Surface treatment agent for any zinc-plated steel sheet. 13. A zinc-based plated steel sheet having a coating film containing chromium, which is applied to the chromium-containing coating film to obtain a zinc-based plated steel sheet having excellent scratch resistance. The surface treatment agent for a zinc-based plated steel sheet according to claim 1. 14. A film of the surface treatment agent for zinc-based plated steel sheet according to claim 1, which is provided on the chromium-containing film of the zinc-based plated steel sheet provided with a film containing chromium. Zinc-based plated steel sheet characterized by 15. The chromium-containing coating is converted to metallic chromium.
3 to 200 mg / m ² A contract characterized by a thickness of
The zinc-based plated steel sheet of claim 14. 16. The zinc-based plated steel sheet according to claim 14, wherein the film of the surface treatment agent for zinc-based plated steel sheet has a thickness of 0.1 to 3 g / m ² . 17. The coating of the surface treatment agent for zinc-based plated steel sheet comprises drying the applied coating of the surface treatment agent for zinc-based plated steel sheet at 60 to 180 ° C. The zinc-based plated steel sheet according to claim 14, which is obtained by