JPH0776785A - Organic composite coated steel sheet excellent in electrodeposition paintability and corrosion resistance and method for producing the same - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] Excellent water-resistant secondary adhesion, rust resistance, low-temperature chipping resistance and spot weldability, as well as cold-rolled steel sheet,
Provided is an organic composite-coated steel sheet having excellent electrodeposition coatability (especially image clarity) equivalent to that of a zinc-based plated steel sheet. [Composition] C on the surface of zinc or zinc alloy plated steel sheet
It has a chromate coating of 5 to 500 mg / m ^{2 in} terms of r, and mainly contains silica and a binder resin under specific conditions in the upper layer of the chromate coating, and further comprises a polyamide resin,
An organic composite-coated steel sheet having a dry weight of 0.1 to 3 g / m ^{2 of} a resin layer obtained by adding 1 to 10% by weight of at least one selected from the group consisting of polyamine resin and polyimine resin, and a method for producing the same. The average primary particle diameter of the constituent silica is 5 to 30 nm. The silica has an average thickness of 0.2 to 2 in the resin layer.
μm, average diameter of 5 to 300 μm, aggregated in a plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly used as a steel sheet for automobile bodies, and is an organic composite coating excellent in electrodeposition coating property (particularly image clarity after electrodeposition coating), rust prevention, corrosion resistance and spot weldability. The present invention relates to a steel plate and a method for manufacturing the same.

[0002]

2. Description of the Related Art In response to the strong social demand for high corrosion resistance of automobile bodies, the application of various surface-treated steel sheets is expanding year by year. Examples of such a surface-treated steel sheet include a galvanized steel sheet and a zinc alloy plated steel sheet. However, the coating applied after assembly of the vehicle body is not sufficiently spread, and the bag structure portion and the bending portion (hemming portion) on the inner surface of the vehicle body exposed to high humidity are required to have higher corrosion resistance.

Steel plates satisfying such requirements are disclosed in, for example, Japanese Patent Laid-Open Nos. 03-130141 and 02-2583.
No. 35 is proposed. These are organic composite coated steel sheets obtained by applying an organic polymer resin layer containing a chromate layer and silica on a zinc or zinc alloy plated steel sheet,
Since it has very good corrosion resistance even in a state where no coating is applied after the vehicle body is assembled, the organic composite-coated steel sheet is often used on the inner surface of the vehicle body.

On the other hand, the outer surface (front surface) side of the automobile body has a lower wet condition than the inner surface side, and the coating after the vehicle body assembly is 10
Since 0 μm (electrodeposition coating, intermediate coating, top coating) is applied, the proportion of holes that reach the holes due to rust from the outer surface is smaller than that on the inner surface, so the cold rolled surface is conventionally used on the outer surface of the vehicle body. It had been. However, as the demand for higher corrosion resistance of automobile bodies has further increased, the requirements for rust prevention on the outer surface of the vehicle body have become stricter, and steel sheets with surface treatment on the outer surface are being put to practical use. For example, it is a surface-treated steel sheet plated with zinc, zinc-based alloy, or the like. These zinc-based plated steel sheets show better rust prevention performance than cold-rolled steel sheets.

However, since these zinc-based plated steel sheets do not have very good plating adhesion, they are inferior in low temperature chipping resistance. When a coating is applied on the zinc-based plating layer, the stress of a thick coating film is applied to the plating, so pebbles, etc. may hit while the vehicle is running, and the impact may cause the plating layer to peel off. Rust prevention does not exert its effect, and external rust progresses. Therefore, JP-A-04-27536 and JP-A-04-26775 have been proposed in which an organic composite coating having excellent low-temperature chipping resistance and outer surface rust resistance superior to that of a zinc-based plated steel sheet is also applied to the outer surface.

The exterior surface of the automobile has conventionally been emphasized in appearance as compared with the interior surface, and its evaluation method and evaluation standard are different from those of the interior surface. In recent years, appearance standards have become more stringent due to the trend toward higher grades due to improvements in living standards, etc., and in combination with improvements in processing technology, laser dull cold-rolled steel sheets rolled by rolls with regular laser dull marks, or Laser dull galvanized steel sheets with zinc-based plating have come to be used for external surfaces.

The above organic composite coated steel sheet is excellent in the above-mentioned low temperature chipping resistance and outer surface rust resistance, but gas pinholes due to traces of hydrogen gas generated during electrodeposition coating due to electrodeposition coating,
Although craters do not occur, a so-called Yuzu skin is formed with an electro-deposited coating that has severe surface irregularities and is uneven, and cold-rolled steel sheets and zinc-based plating that have been used for external surfaces in the past, if not even with Yuzu skin. Compared with the steel plate, the surface was uneven and a non-uniform electrodeposition coating film was formed, and the image clarity was deteriorated, and the strict appearance evaluation standard could not be satisfied.

Conventionally, the crispness of image clarity was only judged by visual observation, but as described above, the criterion becomes stricter, and the PGD value measured using a PGD meter is digitized and judged. It was Based on the findings of the inventors, what is conventionally called Yuzu skin has a PGD value of 0.2.
Below, the cold rolled steel sheet and zinc-based plated steel sheet are 0.4 ~
Since it was 0.6, it was very difficult to clear the image clarity equivalent to that of a cold-rolled steel sheet or a zinc-based plated steel sheet without causing yuzu skin.

On the other hand, as a method for improving the electrodeposition coating property of this organic composite coated steel sheet, JP-A-62-283161,
There is JP-A-63-35798. This is a solvent-based coating composition in which silica (a small particle size of 1 to 100 nm is used for bare corrosion resistance and smoothing of coating film), hydrophilic polyamide resin, and polyethylene wax is mixed with a binder resin on a chromate film. It was done. in this case,
Although defects such as orange peels, gas pinholes, and craters due to hydrogen gas generation during electrodeposition coating can be improved, the image clarity standard is the same as that of cold-rolled steel sheets and zinc-based plated steel sheets required for external surfaces. Was not satisfied. Further, since the viscosity of the coating composition becomes high, the thickness of the coating film cannot be delicately controlled, and a large amount of expensive polyamide resin is required, which is not practical. Resin and /
Alternatively, JP-A-03-26906 using polyimine resin
No. 7 and JP-A No. 03-268939 are proposed, but this can also improve electrodeposition coating defects such as orange peel, gas pinholes and craters due to traces of hydrogen gas generated during electrodeposition coating. However, it does not satisfy the current image clarity standard required for external surfaces.

Further, silica used for improving the electrodeposition coatability in these prior arts has a particle size of 1 to 100 from the viewpoints of electrodeposition coatability and bare corrosion resistance.
Fine particle silica of nm is used. However, as described above, the items required on the outer surface side of the automobile body are different from those on the inner surface side, and corrosion resistance after coating with three coats and appearance after coating are required rather than bare corrosion resistance. When fine particle silica is used, it may be because the energization point is not sufficiently secured at the time of electrodeposition coating as described later, or the electrodeposition coatability cannot be improved unless a large amount of polyamide resin, polyamine resin or polyimine resin is added. . For this reason, a large amount of expensive polyamide resin, polyamine resin, and polyimine resin are required, and further, there arises a problem that the water-resistant secondary adhesion after three coats is deteriorated due to the influence of many hydrophilic groups of these resins. Will be lost.

[0011]

DISCLOSURE OF THE INVENTION The present invention solves the problems of these prior arts such as electrodeposition paintability, water resistant secondary adhesion, spot weldability, etc., and has excellent rust prevention and low temperature chipping resistance. Further, it is an object of the present invention to provide an organic composite coated steel sheet having excellent electro-deposition coatability (particularly image clarity) equivalent to that of a cold-rolled steel sheet and a galvanized steel sheet, and a method for producing the same.

[0012]

DISCLOSURE OF THE INVENTION The inventors of the present invention have used organic composite coatings having excellent rust prevention and low temperature chipping resistance as compared with conventional cold-rolled steel sheets, galvanized or zinc alloy plated steel sheets for outer surfaces of automobile bodies. As a result of attempting a method of improving the electrodeposition coatability (particularly the image clarity), which is a problem of steel sheets, by examining the types of resin and silica without lowering the water-resistant secondary adhesion, the present invention has been accomplished.

That is, the present invention has a chromate coating of 5 to 500 mg / m ^{2 in} terms of Cr on the surface of a zinc- or zinc-based alloy-plated steel sheet, and the upper layer of the chromate coating mainly contains silica and a binder resin under the following conditions. And at least one resin selected from the group consisting of polyamide resin, polyamine resin, and polyimine resin.
The resin layer formed by adding 10 wt% has a dry weight of 0.1.
The present invention provides an organic composite-coated steel sheet excellent in electrodeposition coatability and corrosion resistance, which is characterized by having 3 to 3 g / m ² . The average primary particle diameter of the constituent silica is 5 to 30 nm. The silica has an average thickness of 0.2 to 2 in the resin layer.
μm, average diameter of 5 to 300 μm, aggregated in a plane.

Suitable for producing the above organic composite coated steel sheet
There are the following two methods. (1) Cr on the surface of zinc or zinc alloy plated steel sheet
5 to 500 mg / m in conversion²Forming a chromate layer of
On top of that, the average primary particle size is 5 to 30 nm,
Chains with an average length of 0.1 μm or more
Incorporating silica-like vapor phase silica and binder resin,
Amide resin, polyamine resin and polyimine resin
A coating composition containing at least one resin added
Cloth, dry, the amount of adhesion is 0.1-3g / m in dry weight
²To form a coating film. (2) Conversion of Cr onto the surface of zinc or zinc alloy plated steel sheet
5-500 mg / m in total ²Chromate treatment of
Has an average primary particle size of 5 to 30 nm and an average aggregation
The particle size is 0.1 to 2 μm (100 to 2000 nm)
And has a specific surface area of 50 to 800 m²/ G is an organic solvent
Mix the agent-dispersed silica sol and binder resin and
Liamide resin, polyamine resin and polyimine resin
Add at least one resin selected from the group consisting of
Apply the coating composition and dry it until the adhesion amount becomes dry weight.
0.1 to 3 g / m²To form a coating film.

The total blending ratio of the binder resin and at least one resin selected from the polyamide resin, the polyamine resin and the polyimine resin in the solid components of the coating composition is 40 to 90 wt%, and the blending ratio of chain-like vapor phase silica or silica sol. Is preferably 10 to 60 wt%.

In the solid components of the coating composition, the total compounding ratio of the binder resin and at least one resin selected from polyamide resin, polyamine resin and polyimine resin is 40 to 90 wt%, and chain-like vapor phase silica or silica sol is used. The compounding ratio is 10 to 60 wt%, and the compounding ratio of at least one of the polyamide resin, the polyamine resin and the polyimine resin among the above solid components is 1
It is preferably 10 to 10 wt%.

Further, the binder resin is 500 to 500
With respect to 1 equivalent of epoxy group of epichlorohydrin-bisphenol A type epoxy resin having an epoxy equivalent of 0,
It is possible to use a composition in which 0.5 to 10 parts by weight of a silane coupling agent and 5 to 70 parts by weight of an amino resin are mixed with 100 parts by weight of a modified epoxy resin to which 0.8 to 1.0 mol of dialkanolamine is added. Desirable in terms of rust resistance.

As another binder resin, epichlorohydrin-bisphenol A type epoxy resin 10 is used.
0 to 0 parts by weight of an isocyanate compound is reacted with 10 to 100 parts by weight of an epoxy equivalent of 1000 to 5000, and an epoxy group of 0.
A modified epoxy resin having 5 to 1.0 mol of dialkanolamine added thereto is preferable from the viewpoint of rust resistance.

The present invention will be described in more detail below. A zinc or zinc-based alloy plated steel sheet is used as the material of the present invention. Pure Z is the type of plating applied to the steel sheet.
Binary alloy plating such as n plating, Zn-Ni alloy plating, Zn-Fe alloy plating, Zn-Cr alloy plating, Z
n-Ni-Cr alloy plating, Zn-Co-Cr, etc. ternary alloy plating, such as alloy plating may be used, also Zn-SiO ₂ plating, Zn-Co-Cr-Al 2 O
Composite dispersion plating such as ₃ plating can also be used.
These plating methods may be any method such as an electroplating method, a hot dipping method, or a vapor phase plating method.

Chromate treatment is performed on these zinc or zinc-based alloy plated steel sheets in order to improve the adhesion with the organic polymer resin layer described later and to impart corrosion resistance. Chromate adhesion amount is 5 to 50 in terms of metallic Cr
0 mg / m ^2, preferably in the range of 10-150 mg / m ^2. When the amount of deposited Cr is less than 5 mg / m ² , not only the corrosion resistance is insufficient, but also the adhesion with the resin layer is poor, which is not preferable. Even if it exceeds 500 mg / m ² , there is no further effect of improving the corrosion resistance, the resistance of the insulating coating increases, and the spot weldability is impaired, which is not preferable.

Such chromate treatment may be carried out by any of a coating chromate method using a roll coater, an electrolytic chromate method, a reactive chromate method and the like.

On the upper layer of the chromate coating, a composite coating made of silica and an organic polymer resin is applied. The binder resin used in the present invention is not particularly limited, and examples thereof include modified epoxy resin, urethane resin, acrylic resin, phenol resin, alkyd resin and the like, and two or more kinds of the above resins may be mixed and used. Especially epichlorohydrin-
It is desirable to use a resin composition based on a bisphenol A type epoxy resin from the viewpoint of toughness and corrosion resistance.

As one of the binder resins, 500 to 5
100 parts by weight of a modified epoxy resin having 0.8 to 1.0 mol of dialkanolamine added to 100 parts by weight of a silane coupling agent based on 1 equivalent of epoxy groups of an epichlorohydrin-bisphenol A type epoxy resin having an epoxy equivalent of 000. It is preferable to use a composition containing 10 to 10 parts by weight and 5 to 70 parts by weight of an amino resin.

When the epoxy equivalent is less than 500, the molecular weight of the resin inevitably becomes too low, sufficient alkali resistance cannot be obtained, and the adhesion of the coating film after the electrodeposition coating property is deteriorated. Further, when the epoxy equivalent exceeds 5,000, the amount of dialkanolamine to be added to the epoxy group becomes small, and the sufficient reinforcing effect with silica and the low temperature curability with amino resin are insufficient, and the electrodeposition is also expected. The adhesion of the coating film after paintability decreases. If the addition amount of dialkanolamine is less than 0.8 mol per 1 equivalent of epoxy group, sufficient reinforcing and curing with silica cannot be obtained, so that the high swelling of the interface during electrodeposition coating swells the coating, The film adhesion decreases. The addition amount of dialkanolamine was 1.
If it exceeds 0 mol, an excess of dialkanolamine that does not participate in the reinforcing effect with silica will be present, which is not economically preferable and also remains in the coating film as an unreacted component, thereby lowering the corrosion resistance.

The silane coupling agent is added to improve the adhesion between the resin and the chromate layer, but if it is less than 0.5 parts by weight with respect to 100 parts by weight of the modified epoxy resin, the adhesion between the resin and the chromate layer is improved. Does not appear. On the other hand, if it exceeds 10 parts by weight, unreacted portions may occur, and this unreacted portion may cause poor adhesion, which is not preferable.

The amino resin acts as a cross-linking agent through a dehydration condensation reaction with the hydroxyl group of the modified epoxy resin to form a stronger and more dense coating, and can impart water resistance and alkali resistance. When the compounding ratio of the amino resin is less than 5 parts by weight, the resin does not cure and is meaningless. On the other hand, if the amount exceeds 70 parts by weight, unreacted portions may remain in the case of low temperature baking, which may cause poor adhesion and is not preferable.

Another binder resin having excellent corrosion resistance is an epoxy equivalent of 1000 obtained by reacting 10 to 100 parts by weight of an isocyanate compound with 100 parts by weight of epichlorohydrin-bisphenol A type epoxy resin.
~ 5000 epoxy modified epoxy resin 1
A modified epoxy resin having 0.5 to 1.0 mol of dialkanolamine added to the equivalent amount can be used. If the amount of the isocyanate compound is less than 10 parts by weight, not only is the processability insufficient, but also the polymerization is insufficient, so good alkali resistance cannot be obtained, and the film elution and soft swelling occur during electrodeposition coating. Subsequent sufficient coating film adhesion cannot be obtained. If the amount of the isocyanate compound exceeds 100 parts by weight, the polymerization of the resin becomes too high. This inevitably leads to an increase in the viscosity of the coating composition and lowers the coating properties, so it is also undesirable, so the range was limited to this range. Other reasons for limitation are as described above.

Next, in the present invention, at least one selected from the group consisting of polyamide resin, polyamine resin and polyimine resin as a resin component together with the binder resin.
Seed resin is used. The addition of the above resin markedly improves the electrodeposition coatability. The polyamide resin and / or polyamine resin and / or polyimine resin to be used are not particularly limited as long as they have an amide group and / or an amino group.

When the dry weight ratio of the polyamide resin and / or the polyamine resin and / or the polyimine resin is 1 to 10% by weight based on the dry weight of the entire resin layer, the electrocoating property is greatly improved. If it is less than 1%, the effect of the added resin does not appear and the image clarity after electrodeposition coating does not exceed the standard. In particular, when the content is 3% by weight or more, an organic composite coated steel sheet having excellent electrodeposition coatability can be obtained. Further, when the amount of the added resin is large, the electrodeposition coating property is good, but even if added more than necessary, there is no further effect of improving the electrodeposition coating property, and it becomes economically disadvantageous, Furthermore, the water-resistant secondary adhesiveness (paint secondary adhesiveness) deteriorates. Although the reason for the improvement of the electrodeposition coating property by the above-mentioned added resin is not clear, it is considered that, as described later, it has many hydrophilic groups, the electrodeposition coating solution easily penetrates, and many conduction points can be formed. When the amount of the added resin is large, the hydrophilicity is high, so that water permeation is accelerated and the water-resistant secondary adhesion is lowered. Therefore, it is desirable that the content of the added resin be 10% by weight or less.

The electrodeposition coatability which is the object of the present invention, in particular the image clarity after electrodeposition coating, is agglomerated with the above-mentioned added resin (one or more resins selected from polyamide resin, polyamine resin and polyimine resin) and aggregated silica. Can be brought about by a combination of. When silica that is uniformly dispersed in an organic solvent is used, the image clarity after electrodeposition coating is at a level comparable to that of cold-rolled steel sheets and zinc-based plated steel sheets, even when the above resins are added. Could not reach. Not only that, when the binder resin dissolved in an organic solvent is mixed with the above-mentioned addition resin and silica which is uniformly dispersed in the organic solvent, the viscosity of the coating increases, and the thickness of the coating film cannot be delicately controlled. There was a problem.

Although the reason for the improvement of the electrodeposition coating property by the above-mentioned added resin is not clear, the electrodeposition coating liquid is easily permeated by one or more resins selected from polyamide resin, polyamine resin and polyimine resin, and the electrodeposition coating solution is easily permeated. It is probable that many energizing points were created during painting. Silica itself and resin itself have almost no electrical conductivity, and it is considered that electricity is caused by water passing through the resin. Although silica itself does not conduct electricity, the silanol groups around silica have very good water absorption and can serve as an energizing point during electrodeposition coating, but since the silanol groups are usually surrounded by the binder resin, the inside of the coating surface It is difficult to create a continuous water path.
When the above resin is added, the amide group and / or amino group is easily bonded to the silanol group and exists around silica, forming a continuous water path from the surface of the coating film to the inside thereof, and the current-carrying point during electrodeposition coating. It is considered that the number of coatings is large and the electrodeposition coatability is improved.

In the case where silica is aggregated in a plane form in the organic resin, the silica has a path through the silanol group to some extent. Therefore, the resin selected from the above-mentioned resins (polyamide resin, polyamine resin and polyimine resin) It is considered that the addition of (more than one kind) secures the current-carrying point and improves the electrodeposition coatability. When silica is uniformly dispersed in the organic resin layer, there is no continuous path due to silanol groups, and even if the above resin is added, the effect of improving the electrodeposition coatability does not remarkably appear, so a sufficient electrode It is considered that the coatability cannot be obtained. Further, the surface of silica is covered with silanol groups as described above, and since the silanol groups easily bond with amide groups and / or amino groups in the added resin, the added resin surrounds the silica, ,
It is considered that silica is connected to each other by the added resin. It is considered that the added resin, which is added after all the silanol groups on the outermost surface of silica are bound to the added resin, is free in the paint and serves as a path for water in the resin to improve the electrodeposition coatability. When silica does not form aggregates, the specific surface area is large, so the amount of silanol groups per unit paint is large, the above-mentioned added resin that is present free is small, and a large amount of expensive added resin is used. If this is not done, the effect of improving the electrodeposition coating property will not be apparent, which is economically disadvantageous. Further, as described above, when a large amount of the added resin is used, the hydrophilicity becomes high, so that water permeation is accelerated and the secondary resistance to water resistance is lowered, which causes a problem in performance.

Further, when fine particle silica is used, the paint thickens and the workability deteriorates. When silica does not form an agglomerate, it is considered that small silica particles are connected to each other by the added resin, which causes an increase in viscosity.

Specifically, the primary particle diameter of the constituent silica is set to 5 to 30 nm, and in the organic resin layer of these silicas, the average thickness is 0.2 to 2 μm and the average diameter is 5 to 300.
It is desirable to aggregate them into a flat plate having a size of μm. FIG. 1 is a conceptual representation of a cross section of the present silica in the existing state. As the aggregation form of silica, there are an elliptical flat plate-like form and a mesh / belt-like flat form. In FIG.
Reference numeral 1 is a steel plate, 2 is a Zn or Zn-based alloy plating layer, 3 is a chromate layer, and 4 is an organic resin layer. In the organic resin layer 4, the primary particles 6a of silica aggregate within the organic resin 7 to form primary aggregates 6 of silica, and these further aggregate to form secondary aggregates 8 of silica. This secondary aggregate 8 is the planar aggregate referred to in the present invention, a is the average diameter of the silica primary aggregate, b is the average diameter of the planar aggregate, and c is the average thickness of the planar aggregate. .

If the average primary particle size of silica is less than 5 nm, excessive aggregation will proceed in the coating material, and it should be stably maintained at an appropriate aggregation size suitable for adjusting the coating material and coating the steel sheet. Was extremely difficult. 30n again
If it exceeds m, the silanol groups necessary for contributing to corrosion resistance cannot be secured, so the average particle size of silica constituting the organic resin layer is limited to 5 to 30 nm.

The silica in the present invention has an average thickness (c in FIG. 1) of 0.2 to 2 μm in the organic resin layer.
m, an average diameter (b in FIG. 1) of 5 to 300 μm, and aggregated in a flat plate shape. When silica that is uniformly dispersed in an organic solvent is used, a state in which silica particles are uniformly dispersed is formed without secondary aggregation in the organic resin layer. In this case, the above resin is dispersed in the organic resin layer. Even if it is allowed to exist in
The image clarity after electrodeposition coating could not reach a level as good as that of the cold-rolled steel sheet and the zinc-based plated steel sheet as described above. Moreover, when a binder resin dissolved in an organic solvent is mixed with a polyamide resin and / or a polyamine resin and / or a polyimine resin and silica which is uniformly dispersed in the organic solvent, the viscosity of the coating increases and the coating film thickness increases. There is a problem that you can not control delicately.

In the present invention, when the average thickness of the tabular agglomerates is less than 0.2 μm, the same phenomenon as in the case of uniformly dispersed silica occurs and the effect of improving the image clarity after electrodeposition coating does not sufficiently appear. . Further, even if it exceeds 2 μm, there is no further improvement effect on the image clarity after electrodeposition coating, and silica aggregates are exposed to the outside of the organic resin layer, which on the contrary hinders uniform formation of the coating film. And the sharpness after electrodeposition coating is deteriorated, and the electric resistance between the electrode and the steel plate is remarkably increased during spot welding, which causes welding sparks to promote electrode damage and deteriorates spot weldability.

The average diameter of the tabular silica aggregate is 5 μm.
When it is less than the same, the same phenomenon as in the case of uniformly dispersed silica occurs and the effect of improving the image clarity after electrodeposition coating does not appear. Further, if the average particle size exceeds 300 μm, not only the electric resistance in this portion becomes a problem, but also the area of the organic resin portion lacking silica becomes large and the corrosion resistance deteriorates remarkably, which is not preferable. The average diameter of the tabular aggregate means the average value of the major axis and the minor axis when the tabular aggregates are aggregated, and the width when they are aggregated in the mesh / belt tabular shape. Means the average value of.

The coating amount of the organic resin layer of the present invention is limited to 0.1 to 3 g / m ² in terms of dry weight. If it is less than 0.1 g / m ² , the organic resin layer cannot be sufficiently covered, and the effect of improving rust prevention and low temperature chipping resistance does not appear. Again 3
This is because if it exceeds g / m ² , the film resistance increases and the spot weldability deteriorates.

The raw material of silica used in the present invention is not particularly limited as long as it satisfies the existing conditions in the organic resin layer such as the above-mentioned silica particle size and distribution state.

For example, hydrophobic fumed silica can be preferably used as a raw material of silica used in the present invention. This silica is also chain-shaped, or the silica particles are agglomerated, resulting in an average agglomerated particle diameter of 0.1.
If it is in the range of ˜2 μm, the same action is exhibited.

Specifically, it is preferable to use chain-like vapor phase silica in which the average primary particle diameter of the constituent silica is 5 to 30 nm and the average length of chain-like bonds is 0.1 μm or more. When the average primary particle size of silica is less than 5 nm, alkali resistance is deteriorated, which is not good. If it exceeds 30 nm, the silanol groups necessary for contributing to corrosion resistance cannot be secured, so the average primary particle size of silica used is limited to 5 to 30 nm. If the average length of the chain to be formed is less than 0.1 μm, the effect of forming a chain of silica does not appear remarkably, and not only the electrodeposition coating property is not sufficiently improved, but also the addition of a polyamide resin or the like increases the viscosity and the workability is improved. Since it deteriorates, it is set to 0.1 μm or more. If it is too long, there is no problem, but if it is too long, the workability of the coating film deteriorates, so 50 μm or less is desirable.

Further, the charge state of the surface of the water-dispersed silica sol is controlled by adjusting the amount of alkali metal ions and the amount of polyvalent metal ions to cause secondary aggregation, and then butanol, xylene, ethylene glycol monoethyl ether, ethylene glycol. An organic solvent-dispersed silica sol obtained by substitution and dispersion in an organic solvent such as monobutyl ether or ethylene glycol monopropyl ether can be preferably used.

Specifically, the organic solvent-dispersed silica sol used in the present invention has an average primary particle diameter of the constituent silica of 5 to 5.
The average agglomerated particle size is 0.1 to 2 μm (1
0 to 2000 nm) and a specific surface area of 50 to 8
Uses of 00 m ² / g. As the aggregation form of silica, there are an elliptical flat plate-like form and a mesh / belt-like flat form. If the average primary particle size of silica is less than 5 nm, excessive aggregation will proceed in the paint, and it will be extremely difficult to stably maintain an appropriate aggregation size suitable for adjusting the paint and applying it to steel sheets. Met. 30 nm
When it exceeds, the silanol groups necessary for contributing to corrosion resistance cannot be secured, so the average primary particle diameter of silica used is limited to 5 to 30 nm. Further, if the average aggregate particle size is less than 0.1 μm, the amount of silanol groups on the outermost surface of the silica aggregate increases per unit paint, so that the silica agglomeration effect does not appear remarkably and the improvement in electrodeposition coatability is not sufficient. However, the addition of polyamide resin or the like causes the viscosity to increase and the workability to deteriorate. On the other hand, if the average agglomerated particle size exceeds 2 μm, the uniform coating property of the coating film is impaired, which is not preferable from the viewpoint of uniform electrodeposition coating property and corrosion resistance. Specific surface area of 50m ²
When it is less than / g, the silanol groups on the surface of the silica aggregate are few, the water absorbing effect by the silanol groups does not appear, and sufficient electrodeposition coatability cannot be obtained. If the specific surface area exceeds 800 m ² / g, the amount of silanol groups on the outermost surface of the silica agglomerate will increase per unit paint, so not only the effect of improving the electrodeposition coatability by the added resin will not appear, but the viscosity will increase. , Workability deteriorates.

Examples of the method of secondarily assembling the particles include a method of reducing the alkali such as Na ₂ O normally contained in silica sol to 0.05% by weight or less. When Na ₂ O is contained in the silica sol, Na ⁺ is coordinated to the surface of the silica particles as a counter ion, and further an electric double layer having a hydrated layer is formed around the silica particles, so that the silica particles repel each other. The colloidal state is maintained and the particles are uniformly dispersed, but the amount of Na ₂ O contained in the silica sol is 0.
By reducing the amount to 05% by weight or less, an electric double layer is formed on the surface of silica to prevent it from having an electric charge, and primary particles are secondary-assembled.

The secondary pseudo-assembly can also be performed by depositing a predetermined amount of Al ³⁺ on the surface of silica. 0.1% by weight based on the total weight of silica converted to Al on the silica surface
When the above Al ³⁺ is bonded, a site that is partially positively charged is generated. Since the charge of silica itself is negative, the charge of the silica particles as a whole is canceled out. Adhesion of 20% by weight or more based on the total weight of silica in terms of Al results in a small amount of silanol groups effective for corrosion resistance, which is not desirable. In this way, even by a method of depositing Al ^3+, which is 0.1 to 20% by weight based on the total weight of silica in terms of Al, on the silica surface, it is possible to prevent the formation of an electric double layer on the surface of the silica so as to have a charge. Secondary particles can be secondarily quasi-assembled to suitably obtain secondary particles having an average particle size range of 0.1 to 2 μm.

Examples of the dispersion medium of the silica sol include organic solvents such as ethylene glycol monoethyl ether, ethylene glycol monomethyl ether and xylene. The concentration of the silica sol in the organic solvent is not limited to the above but is usually 15 to 40 wt%. What is used.

The dry weight ratio of silica in the coating composition is 10-6 silica based on the total dry weight of the resin layer.
It is preferably set to 0 wt%. When the amount of silica is less than 10 wt%, as described above, the energization point cannot be sufficiently secured during the electrodeposition coating by the silanol group of the silica pseudo-collection, and good electrodeposition coating property cannot be obtained, and the chromate by the silanol group is not obtained. Since the adhesiveness with the layer is not secured, the water-resistant secondary adhesiveness deteriorates. This is because if the silica content exceeds 60 wt%, the compatibility with the resin composition will not be obtained and it will be difficult to apply it to the steel sheet as a paint.

Therefore, the total resin amount of the binder resin and at least one resin selected from polyamide resin, polyamine resin and polyimine resin is 40 to 90 wt% with respect to the dry weight of the resin layer. Among these, the amount of one or more resins selected from polyamide resins, polyamine resins and polyimine resins is preferably 1 to 10 wt% with respect to the dry weight of the resin layer.

In addition to the above essential components, the coating composition for forming the composite coating of the present invention is added to a solvent, a lubricant, a curing agent, and an ordinary coating as long as the characteristics of the present invention are not impaired. A pigment, a rust preventive, a dispersion stabilizer, etc. may be added.

The method for producing an organic composite coated steel sheet according to the present invention comprises:
After the surface of the steel sheet is washed by pickling and degreasing, it is plated with the specified zinc or zinc-based alloy, then the specified chromate solution is applied, and baked at the maximum attainable plate temperature of 120 ° C to form the chromate film layer Is coated with a coating composition having a predetermined composition and baked at a maximum reaching temperature of 160 ° C. to form an organic composite coating layer.

[0052]

EXAMPLES Next, the effects of the present invention will be specifically described based on examples. (Example) A low carbon steel plate having a plate thickness of 0.8 mm was pickled and degreased, and then a Zn-Ni alloy plating (12 wt% Ni) having a basis weight of 30 g / m ² was applied, and then Cr ⁶⁺ was used using a roll coater.
/ After applying a chromate treatment liquid with a total Cr ratio of 50%, baking was performed at a maximum attainable plate temperature of 120 ° C to form a chromate coating layer. The upper layer is coated with an organic composite coating composition having a predetermined composition by a roll coater, and the maximum plate temperature reaches 160 ° C.
An organic resin film layer was formed by baking with. Table 1 shows the chain-like silica, and Table 2 shows the aggregated silica, and their compositions and evaluation results are shown in Examples 1 to 13 of the present invention and Comparative Examples 1 to 11, respectively.

Various test methods and their evaluation methods are as follows. (Chemical conversion treatment method) Normal alkali degreasing is performed, followed by surface conditioning and phosphate treatment (SD2 manufactured by Nippon Paint Co., Ltd.)
Immersion in 500 MZL for 2 minutes).

(Electrodeposition coating) U-manufactured by Nippon Paint Co., Ltd.
53 at a bath temperature of 28 to 30 ° C. and an electrodeposition voltage of 250 V, 180
It was energized for 2 seconds and baked at 165 ° C. for 20 minutes.

(Electrodeposition coating property) After the chemical conversion treatment, electrodeposition coating was carried out, and the electrodeposition coating property was evaluated by gas pinholes, presence / absence of craters, electrodeposition coating film thickness, and image clarity. The presence or absence of gas pinholes and craters was evaluated by observation. The electrodeposition coating film thickness is preferably the same as that of Zn-Ni plating. When the film thickness is large, it is economically disadvantageous, which is bad. Regarding the sharpness, the polyester adhesive tape No. 31B (manufactured by Nitto Denko Co., Ltd.) is attached, and the portable color definition gloss meter PGD- manufactured by Japan Color Research Institute
The PGD value was measured using type IV. In addition, PGD (sharpness glossiness meter) is based on automotive technology Vol. 141 (198
7), No. 279, p. It is a device for simply measuring the glossiness of the coated surface described in 1394. The higher the PGD value, the better the sharpness. Based on the findings of the present inventors, it was found that the PGD value is 0.2 or less in the case of yuzu skin, which has been a conventional evaluation standard for electrodeposition coatability. When the PGD value is 0.3 or more and less than 0.5, no bumpy skin is obtained, but slight irregularities are observed in the electrodeposition coating film. PGD value 0.
In No. 5, the electrodeposition coating film becomes uniform, and the unevenness of the shape of the electrodeposition coating film base appears as it is. The target is Zn-N
The PGD value of the i-alloy-plated steel sheet is 0.4 to 0.6 depending on the electrodeposition coating conditions, so the pass criterion for the sharpness is 0.4.
˜0.6. When the PGD value is 0 to 0.2, the skin is orange.

(Low temperature chipping resistance) After chemical conversion treatment, electrodeposition coating was carried out, and then intermediate coating for automobiles (TO-4830, 40 μm, manufactured by Nippon Paint Co., Ltd.), top coating (Nihon Paint Co., Ltd.) Made TO-4640-2, 40μ
m) was spray painted. The obtained sample was subjected to a diamond shot test under the following conditions. After the test, a peeling test was performed with a tape. Evaluation method is shot 1
It is the total area of the coating peeling area of 0 points. In addition, 210k
The shot speed of m / h is more severe than the normal test conditions in Japan. (Normal shot speed 170 km / h or less) Diamond: 10 mg Test temperature: -20 ° C Shot speed: 210 km / h

(Outer surface rust resistance) After chemical conversion treatment, electrodeposition coating is performed, and further, intermediate coating for automobiles (Nippon Paint Co., Ltd.)
TO-4830 (40 μm manufactured by Nippon Paint Co., Ltd.) and top coating (TO-4640-2, 40 μm manufactured by Nippon Paint Co., Ltd.) were spray-coated. A saw blade scratch after painting was used as a sample. The obtained sample was exposed to the seashore, and the Volvo test of spraying seawater twice a week was performed for 3 months. The exposed area is the coast of Tokyo Bay. For the evaluation, the maximum coating film swelling width (or corrosion width) from the scratched portion was measured and judged according to the following criteria. ⊚: No coating swelling (or corrosion) ○: Maximum coating swelling width (or corrosion width) 0 to 1 mm or less Δ: Maximum coating swelling width (or corrosion width) 1 to 2 mm or less ×: Maximum coating swelling width ( Or corrosion width) over 2 mm

(Water-resistant secondary adhesion) After chemical conversion treatment, electrodeposition coating, intermediate coating for automobiles (TO-4830, 40 μm, manufactured by Nippon Paint Co., Ltd.), top coating (Nihon Paint Co., Ltd.) Company TO-4640-2, 40μ
m) was spray painted. The obtained sample was immersed in pure water at 50 ° C. for 240 hours. Take each sample, 1
A cross-cut tape peeling test was performed within 0 minutes. (100 grids at 2 mm intervals) was evaluated by measuring the coating film peeling area ratio. Peeling area ratio ◎: 0% ◯: 1 to 5% △: 6 to 15% ×: 16 to 35% XX: 35% or more

(Chromium elution resistance) The amount of chromium before and after the chemical conversion treatment was measured by fluorescent X-ray analysis, and the difference was regarded as the amount of chromium elution, and evaluated according to the following criteria. ◎: Less than 1 mg / m ² ○: 1 or more and less than 2 mg / m ² △: 2 or more and less than 5 mg / m ² ×: 5 mg / m ² or more

(Spot Weldability) In order to evaluate the spot weldability, a steel sheet having both surfaces subjected to an organic composite coating treatment is used, a welding tip made of an Al ₂ O ₃ dispersed steel alloy with a tip of 5 mmφ is used, and a pressing force of 200 kgf. Continuous welding was performed at a welding current of 9 kA and a welding time of 10 Hz, and the number of continuous welding points until the nugget diameter fell below the reference diameter was measured. The evaluation criteria are shown below. ◎: 2000 points or more ○: 1000 to 2000 points △: 500 to 1000 points ×: Less than 500 points

In Table 1, Invention Examples 1 to 13 satisfy the conditions of the present invention, in particular, have good electrodeposition coating properties and have the performance required for the outer surface of the automobile body.

In Table 1, in Comparative Examples 1 and 9, since the amount of the added resin was small, not only the electrodeposition coating film thickness was large, but also the sharpness after electrodeposition coating was poor. In Comparative Example 2, since silica not forming a chain was used, the electrodeposition coating film thickness was large and the image clarity after electrodeposition coating was poor. Furthermore, the state of the paint was poor and it was difficult to control the amount of adhesion. The test was performed using a portion having an adhesion amount of 1.0 g / m ² . Comparative Example 3
Since the amount of the added resin was large, the electrodeposition coatability was good, but the water resistant secondary adhesion was poor. In Comparative Example 4, silica is
Since it was uniformly dispersed in the paint, the result was poor image clarity after electrodeposition coating. Also, the amount of added resin was large, and the water-resistant secondary adhesion and chromium elution resistance were poor. In Comparative Example 5, since the amount of the organic resin coating film was small, the effect of improving the low temperature chipping resistance due to the organic resin coating did not significantly appear. Further, since the chromate film layer was not sufficiently covered with the organic resin, the chromium elution resistance was also poor. In Comparative Example 6, since a uniform dispersion type silica sol was used as silica, not only the image clarity after electrodeposition coating was bad, but also the state of the paint was bad. In Comparative Example 7, since the amount of the organic coating film was small, the effect of improving the low temperature chipping resistance did not significantly appear. Also, since the amount of added resin was large, the external surface rust resistance, the water secondary adhesion, and the chromium elution resistance were poor. In Comparative Example 8, the content of silica in the solid content of the coating was low, so that the external surface rust resistance and the water secondary adhesion were poor. Comparative Example 10 showed the performance of a normal Zn-Ni alloy plated steel sheet, and Comparative Example 11 showed the performance of a cold rolled steel sheet.

In Table 2, Invention Examples 1 to 13 satisfy the conditions of the present invention, in particular, have good electrodeposition coating properties and have the performance required for the outer surface of the automobile body.

In Table 2, in Comparative Examples 1 and 9, since the amount of the added resin was small, not only the electrodeposition coating film thickness was large, but also the sharpness after electrodeposition coating was poor. In Comparative Example 2, since silica that was uniformly dispersed in the solvent was used, not only the electrodeposition coating film thickness was large and the image clarity after electrodeposition coating was poor, but also the state of the coating material was poor and it was difficult to control the adhesion amount. there were. The test was performed using a portion having an adhesion amount of 1.0 g / m ² . Comparative Example 3
Since the amount of added resin was large, the electrodeposition coatability was good, but
Water resistance secondary adhesion was poor. In Comparative Example 4, since the aggregate of silica was as large as 4 μm, the coating film was not uniform, resulting in poor image clarity after electrodeposition coating. Further, since the amount of added resin was large, the water-resistant secondary adhesion and the chromium elution resistance were poor.
In Comparative Example 5, since the amount of the organic resin coating film was small, the effect of improving the low temperature chipping resistance due to the organic resin coating did not significantly appear. Further, since the chromate film layer was not sufficiently covered with the organic resin, the chromium elution resistance was also poor. Comparative Example 6
, Silica forms aggregates, but it is not sufficient, the aggregate particle size is small as 0.03 μm, and the specific surface area is 100 m ² /
Since it was as large as g, not only the image clarity after electrodeposition coating was bad as in Comparative Example 2, but also the state of the paint was bad. Comparative Example 7
Since the amount of the organic coating was small, the effect of improving the low temperature chipping resistance did not significantly appear. Also, since the amount of added resin was large, the external surface rust resistance, the water secondary adhesion, and the chromium elution resistance were poor. In Comparative Example 8, the content of silica in the solid content of the coating was low, so that the external surface rust resistance and the water secondary adhesion were poor. Comparative Example 10 showed the performance of a normal Zn-Ni alloy plated steel sheet, and Comparative Example 11 showed the performance of a cold rolled steel sheet.

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

[Table 3]

[0068]

[Table 4]

[0069]

[Table 5]

[0070]

[Table 6]

[0071]

[Table 7]

[0072]

[Table 8]

Specific names of symbols in the table are as follows. 1) Binder resin 1: Urethane-modified epoxy resin (A) Production of isocyanate compound Hexamethylene diisocyanate: 528 parts by weight, methyl isobutyl ketone: 620 in a reactor equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen gas blowing device. Part by weight is uniformly dissolved and heated to 80 ° C., 92 parts by weight of glycerin is gradually added dropwise over 1 hour, and 100 parts by weight are further added.
The reaction was carried out at 4 ° C for 4 hours to obtain an isocyanate compound A having a nonvolatile content of 50%. The isocyanate equivalent weight of this compound A was 207 in terms of solid content.

(B) Manufacture of base resin Epicoat 1007 (Epoxy resin: Epoxy equivalent = 2000) manufactured by Shell Chemical Co., Ltd. in a reactor equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen gas blowing device 20
00 parts by weight and 1000 parts by weight of toluene were added and the temperature was raised to 80 ° C. to obtain a uniform solution. Next, 600 parts by weight (solid content) of this isocyanate compound A was gradually added dropwise over 1 hour, and further reacted at 80 ° C. for 3 hours. The end point of the reaction is determined by absorption of an isocyanate group (2270) by an infrared spectrophotometer.
cm ^-1 ) was defined as the point at which it disappeared. In this way, a urethanized epoxy resin having an epoxy equivalent of 2600 was obtained.
Subsequently, 105 parts by weight of diethanolamine was added to the urethane-modified epoxy resin, and the mixture was reacted at 80 ° C. for 2 hours.

2: Amine-modified epoxy resin Epicoat 1007 (Epoxy resin manufactured by Shell Chemical Co., Ltd .: epoxy equivalent = 2000) 20 in a reactor equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen gas blowing device.
00 parts by weight (1 equivalent of epoxy group) and 1000 parts by weight of toluene were added, and the temperature was raised to 80 ° C. to obtain a uniform solution. Next, 52.5 parts by weight of diethanolamine was added dropwise to this solution over 30 minutes and reacted for 1 hour. Then add γ to this solution.
-Aminopropyltrimethoxysilane (110.5 parts by weight, manufactured by Nippon Unicar Co., Ltd., trade name A-1100) was added dropwise over 30 minutes, and the mixture was further reacted at 80 ° C for 2 hours. Methylated melamine resin (manufactured by Dainippon Ink and Chemicals, Super Beckamine L-
105-60) was mixed with 40 parts by weight with respect to 100 parts by weight (solid content) of the composite resin.

3: Acrylic resin: (Mitsubishi Rayon Co., Ltd.)
(Manufactured by DIANAR HR633)

2) Polyamide resin A: Versamide 115D manufactured by Henkel Hakusui Co., Ltd. B: Newmide 505-6 manufactured by Casey Co., Ltd.
5 Polyamine resin C: manufactured by Otsuka Chemical Co., Ltd. PAH-LD D: Acrylic resin synthesis example A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a cooling tube was charged with 100 parts of ethylene glycol monoethyl ether.
After adding parts by weight and raising the temperature to 90 ° C., the following monomers and initiator were added dropwise over 3 hours. Dimethylaminoethyl methacrylate 60 parts by weight, methyl acrylate 10 parts by weight, iso-butyl acrylate 25 parts by weight, Nn-methoxymethyl acrylamide 5 parts by weight,
0.5 parts by weight of azobisisobutyronitrile. After completion of the dropping, 30 parts of 0.25 parts by weight of azobisisobutyronitrile are added.
It was added in four portions every minute and further reacted at the same temperature for 4 hours to obtain a copolymer solution of NV50%. Polyimine resin E: Nippon Shokubai Co., Ltd. Epomin SP-018 F: Nippon Shokubai Co., Ltd. Epomin SP-200

3) Silica (related to chain-like silica, Table 1) a. AEROSIL 200CF (manufactured by Nippon Aerosil Co., Ltd.) was mixed with a resin to give a nonvolatile content of 20%, and the mixture was stirred with a disper for 10 minutes to obtain a chain-like vapor phase silica. b. AEROSIL R972 (Japan Aerosil Co., Ltd.)
(Manufactured by Mitsui Chemicals Co., Ltd.) was mixed with a resin to make the nonvolatile component 20%, and the mixture was stirred with a disper for 10 minutes to obtain chain-like vapor phase silica. c. AEROSIL 200CF (manufactured by Nippon Aerosil Co., Ltd.) was mixed with a resin to give a nonvolatile content of 20%, and the mixture was stirred with a disper for 1 hour and further kneaded to uniformly disperse silica. d. AEROSIL OX50 (Japan Aerosil Co., Ltd.)
(Manufactured by Mitsui Chemicals Co., Ltd.) was mixed with a resin to make a nonvolatile content of 20%, and the mixture was stirred with a disper for 10 minutes, whereby silica was uniformly dispersed. e. Snowtex 30 (manufactured by Nissan Kagaku Co., Ltd.) is mixed with a resin to make the nonvolatile content 20%, and then 10 with a disper.
After stirring for 1 minute, the silica was uniformly dispersed.

4) Silica (related to aggregated silica, Table 2) The average particle size of silica sol dispersed in ethylene glycol monoethyl ether is shown. The average primary particle size is obtained by a centrifugal sedimentation method (C
2 ml of silica sol was measured using APA) and the average value was obtained. In addition, the average aggregate particle diameter was obtained by measuring the silica sol in the state after the secondary aggregation and measuring 2 ml of the silica sol by using the centrifugal sedimentation method (CAPA) to obtain an average value. Specific surface area is BE
It was measured by the T method.

[0080]

EFFECTS OF THE INVENTION By producing an organic composite coated steel sheet according to the present invention, it has excellent electrodeposition coating properties, particularly sharpness after electrodeposition coating, and has an appearance similar to that of conventional zinc-based plated steel sheets and cold rolled steel sheets. Further, it is possible to provide an excellent material for an automobile body which exhibits excellent water secondary adhesion, rust prevention, low temperature chipping resistance and spot weldability. This contributes to the improvement of the durability of the automobile body, and eventually to the saving of global resources.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a distribution state of secondary aggregates of silica in an organic resin layer.

[Explanation of symbols]

 1 Steel plate 2 Zn or Zn-based alloy plating layer 3 Chromate layer 4 Organic resin layer 6a Silica primary particles 6 Silica primary aggregate 7 Organic resin 8 Silica secondary aggregate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinko Tada, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Headquarters (72) Inventor Ryoichi Mukai Kawasaki, Chuo-ku, Chiba-shi, Chiba Town No. 1 Kawasaki Steel Co., Ltd., Technical Research Headquarters (72) Inventor Kazuo Mochizuki No. 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Headquarters (72) Inventor Mori Tonobu Chiba Kawasaki Steel Co., Ltd., Chuo-ku, Chiba City, Chiba Prefecture (72) Inventor Hiroyuki Tanabe 1382-12 Shimoishigami, Otawara City, Tochigi Daini Nippon Paint Co., Ltd. (72) Inventor Masanori Nagai 1382-12 Shimoishigami, Otawara-shi, Tochigi Dainippon Paint Co., Ltd.Nasu factory (72) Inventor Osamu Ogawa 1382-12 Shimoishigami, Otawara-shi, Tochigi Dai Nippon Paint Co., Ltd. Nasu in the factory (72) inventor, Tochigi Prefecture Otawara Kei Shin Kato Shimoishigami 1382-12 Dai Nippon paint Co., Ltd. Nasu in the factory

Claims (13)

[Claims] 1. A zinc or zinc-based alloy-plated steel sheet surface has a chromate coating of 5 to 500 mg / m ^{2 in} terms of Cr, and the upper layer of the chromate coating mainly contains silica and a binder resin under the following conditions: Polyamide resin,
Electrodeposition coatability, characterized in that the resin layer containing 1 to 10% by weight of at least one resin selected from the group consisting of polyamine resins and polyimine resins has a dry weight of 0.1 to 3 g / m ² . And an organic composite coated steel sheet with excellent corrosion resistance. The average primary particle diameter of the constituent silica is 5 to 30 nm. The silica has an average thickness of 0.2 to 2 in the resin layer.
μm, average diameter of 5 to 300 μm, aggregated in a plane. 2. The binder resin is used in an amount of 0.8 per 1 epoxy group of an epichlorohydrin-bisphenol A type epoxy resin having an epoxy equivalent of 500 to 5000.
Silane coupling agent 0.5 to 100 parts by weight of the modified epoxy resin added with ˜1.0 mol dialkanolamine
The organic composite-coated steel sheet according to claim 1, which is a composition containing 10 to 10 parts by weight and 5 to 70 parts by weight of an amino resin. 3. The binder resin is epichlorohydrin-
0.5 to 1.0 mol of dialkanol per 1 equivalent of epoxy group of urethane modified epoxy resin having epoxy equivalent of 1000 to 5000 obtained by reacting 10 to 100 parts by weight of isocyanate compound with 100 parts by weight of bisphenol A type epoxy resin The organic composite-coated steel sheet according to claim 1, which is a modified epoxy resin to which an amine is added. 4. A chromate layer of 5 to 500 mg / m ^{2 in} terms of Cr is formed on the surface of a zinc- or zinc-based alloy-plated steel sheet, and the average primary particle diameter is 5 to 30 nm on the chromate layer. Blended chain-like vapor phase silica having an average length of 0.1 μm or more and a binder resin,
Furthermore, a coating composition obtained by adding at least one resin selected from polyamide resin, polyamine resin and polyimine resin is applied and dried, and the adhesion amount becomes 0.1% by dry weight.
A method for producing an organic composite-coated steel sheet excellent in electrodeposition coatability, which comprises forming a coating film of ˜3 g / m ² . 5. A binder resin and a total compounding ratio of at least one resin selected from a polyamide resin, a polyamine resin and a polyimine resin among solid components in a coating composition is 40 to 90 wt%, and a compounding ratio of chain-like vapor phase silica. Is 10-60 wt%, The manufacturing method of the organic composite coating steel plate of Claim 4. 6. A binder resin and, in the solid component of a coating composition, a total compounding ratio of at least one resin selected from a binder resin, a polyamide resin, a polyamine resin and a polyimine resin, and a compounding ratio of chain-like vapor phase silica. Is 10 to 60 wt%, and the compounding ratio of at least one of the polyamide resin, the polyamine resin and the polyimine resin is 1 to 10 wt%, and the method for producing an organic composite coated steel sheet according to claim 4. 7. The binder resin is 0.8 relative to 1 equivalent of epoxy group of epichlorohydrin-bisphenol A type epoxy resin having an epoxy equivalent of 500 to 5000.
100 parts by weight of the modified epoxy resin added with 1.0 to 1.0 mol of dialkanolamine was added to the silane coupling agent 0.
The method for producing an organic composite-coated steel sheet according to any one of claims 4 to 6, which is a composition in which 5 to 10 parts by weight and 5 to 70 parts by weight of an amino resin are mixed. 8. The binder resin is epichlorohydrin-
0.5 to 1.0 mol of dialkanolamine per 1 equivalent of epoxy group of urethane modified epoxy resin having epoxy equivalent of 1000 to 5000 obtained by reacting 10 to 100 parts by weight of isocyanate compound with 100 parts by weight of bisphenol A type epoxy resin The method for producing an organic composite-coated steel sheet according to any one of claims 4 to 6, which is a modified epoxy resin to which is added. 9. A zinc or zinc-based alloy plated steel sheet surface is subjected to a chromate treatment of 5 to 500 mg / m ^{2 in} terms of Cr, and the average primary particle diameter is 5 to 30 nm, and the average aggregate particle diameter is 0. .1-2 μm (100-2000n
m) and a specific surface area of 50 to 800 m ² / g, and an organic solvent-dispersed silica sol is mixed with a binder resin,
Furthermore, a coating composition obtained by adding at least one resin selected from the group consisting of polyamide resin, polyamine resin and polyimine resin is applied and dried, and the adhesion amount is 0.1 to 3 g / m ² in terms of dry weight. A method for producing an organic composite-coated steel sheet having excellent image clarity and corrosion resistance after electrodeposition coating, and secondary adhesion of paint, which is characterized by forming the above-mentioned coating film. 10. At least one selected from the group consisting of a binder resin, a polyamide resin, a polyamine resin and a polyimine resin in the solid components in the coating composition.
The method for producing an organic composite-coated steel sheet according to claim 9, wherein the total compounding ratio of the seed resins is 40 to 90 wt% and the compounding ratio of silica sol is 10 to 60 wt%. 11. At least one selected from the group consisting of a binder resin and a polyamide resin, a polyamine resin and a polyimine resin in the solid components in the coating composition.
The total mixing ratio of the seed resins is 40 to 90 wt%, the mixing ratio of the silica sol is 10 to 60 wt%, and the mixing ratio of at least one of the polyamide resin, the polyamine resin and the polyimine resin is 1 to 10 wt.
%, The method for producing an organic composite coated steel sheet according to claim 9. 12. The binder resin is 500 to 500.
With respect to 1 equivalent of epoxy group of epichlorohydrin-bisphenol A type epoxy resin having an epoxy equivalent of 0,
A binder resin composition in which 0.5 to 10 parts by weight of a silane coupling agent and 5 to 70 parts by weight of an amino resin are mixed with 100 parts by weight of a modified epoxy resin to which 0.8 to 1.0 mol of dialkanolamine is added. The manufacturing method of the organic composite coating steel plate in any one of Claims 9-11. 13. The binder resin is prepared by reacting 10 to 100 parts by weight of an isocyanate compound with 100 parts by weight of an epichlorohydrin-bisphenol A type epoxy resin, based on 1 equivalent of epoxy group of an epoxy modified epoxy resin having an epoxy equivalent of 1000 to 5000. , 0.5 to 1.0
The method for producing an organic composite-coated steel sheet according to any one of claims 9 to 11, which is a modified epoxy resin to which mole dialkanolamine is added.