JP2001354910A - Cationic electrodeposition coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cationic electrodeposition coating composition which improves long-term anticorrosion properties of a zinc-nickel alloy plated steel plate, or the like. SOLUTION: This cationic electrodeposition coating composition comprises a hydrate of bismuth oxide having the largest particle size of at most 2 μm to improve its long-term anticorrosion properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the corrosion resistance of a cationic electrodeposition coating film for improving the long-term corrosion resistance of a zinc nickel steel sheet or the like.

[0002]

2. Description of the Related Art Cationic electrodeposition coatings can form coating films having excellent anticorrosion properties and smoothness of the coated surface. It is widely used in the field, for example, for painting automobile bodies and parts. In order to further improve the corrosion resistance of the cationic electrodeposition paint, anticorrosive pigments, for example, lead chromate, basic lead silicate, lead compounds and chromium compounds such as strontium chromate are often compounded, These rust-preventive pigments are very harmful substances, and their use is problematic in terms of pollution control. Therefore, the use of bismuth compounds as non-toxic or low-toxic rust-preventive pigments in place of these harmful rust-preventive pigments has been studied. Generally, a cationic electrodeposition coating containing a bismuth compound is composed of a dispersing resin, a hydrate of bismuth oxide, a pigment (titanium oxide, purified clay, carbon black, etc.), an organotin catalyst, a neutralizing agent, deionized water, etc. It is manufactured by adding an enameled paste obtained by dispersing and mixing the products to a cationic electrodeposition emulsion. However, the paint produced in this way does not have the same anti-corrosion ability as the above-mentioned lead compounds and chromium compounds in the long-term anti-corrosion properties of zinc-nickel steel sheets, and improvement in anti-corrosion properties has been demanded. Therefore, it was found that the anticorrosion property was improved by dispersing bismuth oxide in water together with an organic acid such as acetic acid and lactic acid and adding it to the cationic electrodeposition paint, but in this case, a large amount of bismuth oxide was used. Then, a large amount of an organic acid such as lactic acid added to the paint is also added at the same time, so that the suitability for coating on the rust-preventive steel sheet is reduced, and as a result, there is a problem that the finish appearance of the coating film becomes poor.

[0003]

Means for Solving the Problems The present inventors have conducted intensive studies to improve the above problems, and as a result, the maximum particle diameter was 2
It has been found that the addition of a hydrate of bismuth oxide having a particle size of not more than μm is effective in improving the long-term corrosion resistance of the electrodeposition coating on the zinc-nickel steel sheet, and has completed the present invention. That is, the present invention provides: “1. A cationic electrodeposition coating composition characterized by improving the long-term corrosion resistance by incorporating a hydrate of bismuth oxide having a maximum particle size of 2 μm or less. 2. An aqueous dispersion paste obtained by dispersing a composition comprising a resin for use, a hydrate of bismuth oxide, a neutralizing agent, and deionized water, is added to the cationic electrodeposition coating composition. 2. The content of the hydrate of bismuth oxide in the aqueous dispersion paste was 10 to 100 parts by mass of the solid content of the resin for dispersion.
3. The cationic electrodeposition coating composition according to item 2, wherein the amount is 0 to 1000 parts by mass. 4. Item 3. The cationic electrodeposition coating composition according to item 2 or 3, wherein the aqueous dispersion paste has a solid content of 30 to 60% by mass. 5. The cationic electrodeposition coating composition according to any one of items 2 to 4, wherein the dispersing resin is an amino group-containing epoxy resin. 6. 6. The cationic electrodeposition coating composition according to any one of items 2 to 5, wherein the neutralizing agent is at least one organic acid selected from acetic acid, formic acid, and lactic acid. 7. Neutralizing agent, 0.5 to the amino group of the resin for dispersion
Item 7. The cationic electrodeposition coating composition according to any one of Items 2 to 6, wherein the composition is 1.2 equivalents. 8. In the above cationic electrodeposition coating composition, the mixing ratio of the aqueous dispersion paste is 100% in solid content of the cationic electrodeposition coating.
0.5 parts by mass based on the solids content of the aqueous dispersion paste
Item 8. The cationic electrodeposition coating composition according to any one of Items 2 to 7, wherein the amount is from 10 to 10 parts by mass. About.

[0004]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail below. The method of the present invention is characterized in that a hydrate of bismuth oxide having a maximum particle diameter of 2 μm or less is contained. If the maximum particle diameter exceeds 2 μm, the effect of improving the corrosion resistance of the coating film is small. Specifically, by adding an aqueous dispersion paste obtained by dispersing a composition comprising a dispersing resin, a hydrate of bismuth oxide, a neutralizing agent and deionized water to a cationic electrodeposition coating composition, and the like. Achieved. In the above aqueous dispersion paste, the content of the hydrate of bismuth oxide is 1 to 100 parts by mass of the solid content of the resin for dispersion.
The range is from 00 to 1000 parts by mass, preferably from 400 to 800 parts by mass. When the amount is less than 100 parts by mass, the amount of the dispersing resin becomes excessive, and when the amount exceeds 1000 parts by mass, the stability of the paste decreases. The solid content of the aqueous dispersion paste is 30 to
It is 60% by mass, preferably 45 to 55% by mass. When the solid content is less than 30% by mass, the hydrate of bismuth oxide precipitates and impairs the stability of the aqueous dispersion paste. Also 60
If the amount is more than 10% by mass, the aqueous dispersion paste is liable to agglomerate, resulting in a problem of stability. Dispersion resins used in the aqueous dispersion paste include amino group-containing epoxy resins such as tertiary amines, quaternary ammonium salt-type epoxy resins, and quaternary ammonium salt-type acrylic resins. A contained epoxy resin is preferable, and a tertiary amine epoxy resin is more preferable.

[0005] Examples of the neutralizing agent for neutralizing the epoxy tertiary amine type dispersing resin include water-soluble organic acids such as acetic acid, formic acid, lactic acid, propionic acid, hydroxyacetic acid, methoxyacetic acid, maleic acid and fumaric acid. And inorganic acids such as hydrochloric acid and sulfuric acid. Among these, it is preferable to use at least one organic acid selected from acetic acid, formic acid, and lactic acid. The neutralization equivalent is 0.5 to 1.2 equivalents, preferably 0.6 to 0.8 equivalents, based on the amino groups of the resin for dispersion. If the neutralization equivalent is less than 0.5 equivalent, the stability of the aqueous dispersion paste becomes poor, and if the neutralization equivalent exceeds 1.2, the acid content becomes excessive, which is not preferable.

A method for producing an aqueous dispersion paste is, for example, as follows:
A dispersing resin, a hydrate of bismuth oxide, a neutralizing agent, and water are blended, and the mixture is dispersed after pre-kneading. As a dispersing machine,
Conventionally used dispersers such as ball mill, pebble mill, sand mill, and shaker can be used,
A ball mill is preferred in terms of workability. The dispersion time by a ball mill is 1 to 96 hours, preferably 10 to 48 hours.

In addition to the aqueous dispersion paste of the present application, a dispersing resin and coloring pigments such as titanium oxide, carbon black and red iron oxide, extenders such as clay, mica, barita, talc, calcium carbonate and silica, phosphomolybdic acid A combination of a rust-preventive pigment such as aluminum and aluminum tripolyphosphate, an organic tin compound such as dibutyltin oxide (DBTO) and dioctyltin oxide (DOTO), the above neutralizing agent, and a pigment paste obtained by dispersing in water. Can be.

Next, the emulsion composition of the cationic electrodeposition paint will be described. Epoxy,
Any of acrylic, polybutadiene, alkyd, and polyester resins can be used. Among them, polyamine resins represented by, for example, amine-added epoxy resins are preferable. Examples of the amine-added epoxy resin include, for example, adducts of a polyepoxide compound (I) with primary mono- and polyamines, secondary mono- and polyamines, or mixed primary and secondary polyamines (for example, US Pat. No. 3,984,299). (II) adducts of polyepoxide compounds with ketiminated secondary mono- and polyamines having primary amino groups (see, for example, U.S. Pat. No. 4,017,438); (III A) a reaction product obtained by etherification of a polyepoxide compound with a ketiminated hydroxy compound having a primary amino group (for example, see JP-A-59-43013). The polyepoxide compound used for producing the amine-added epoxy resin is a compound containing two or more epoxy groups in a molecule, and generally has at least two epoxy groups.
Those having a number average molecular weight in the range of 00, preferably 400 to 4000, more preferably 800 to 2000 are suitable, and particularly those obtained by reacting a polyphenol compound with epichlorohydrin. Examples of the polyphenol compound that can be used for forming the polyepoxide compound include bis (4-hydroxyphenyl) -2,2-propane, 4,4-dihydroxybenzophenone, bis (4-hydroxyphenyl) -1,
1-ethane, bis- (4-hydroxyphenyl) -1,
1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane,
Tetra (4-hydroxyphenyl) -1,1,2,2-
Ethane, 4,4-dihydroxydiphenylsulfone),
Phenol novolak, cresol novolak and the like can be mentioned. The epoxide compound may be partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamidoamine, a polycarboxylic acid, a polyisocyanate compound, or the like.
Those obtained by graft polymerization of caprolactone, an acrylic monomer, or the like may be used.

The above-mentioned base resin may be any of an external cross-linking type and an internal (or self-cross-linking) type. In the case of an external cross-linking type resin, the curing agent used in combination is, for example, a (block) ) Can be a conventionally known crosslinking agent such as a polyisocyanate compound or an amino resin,
Particularly, a blocked polyisocyanate compound is preferred. Further, as the internal cross-linkable resin, a resin into which a blocked polyisocyanate type is introduced is preferable. The blocked isocyanate compound that can be used in the external cross-linking type can be an addition reaction product of a stoichiometric amount of a polyisocyanate compound and an isocyanate blocking agent. Examples of the polyisocyanate compound include aromatic, alicyclic or aliphatic such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanatemethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate. Group isocyanate compounds and terminal isocyanate-containing compounds obtained by reacting an excess amount of these isocyanate compounds with a low-molecular-weight active hydrogen-containing compound such as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, or castor oil. Can be On the other hand, the isocyanate blocking agent is one that blocks by adding to the isocyanate group of the polyisocyanate compound, and the blocked isocyanate compound formed by the addition is stable at ordinary temperature and when heated to about 100 to 200 ° C. Desirably, it is capable of dissociating to regenerate a free isocyanate group. Examples of the blocking agent satisfying such requirements include lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenol compounds such as phenol, para-t-butylphenol and cresol. Aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatic alkyl alcohols such as phenylcarbinol and methylphenylcarbinol; and ether alcohol compounds such as ethylene glycol monobutyl ether. Among these, oxime-based and lactam-based blocking agents are blocking agents that dissociate at a relatively low temperature, and are particularly suitable from the viewpoint of curability of the electrodeposition coating composition.

The method of introducing a blocked isocyanate group into a base resin in a type in which a blocked isocyanate group is contained in a base resin molecule and self-crosslinking can be performed by a conventionally known method. By reacting a free isocyanate group of the above with an active hydrogen-containing portion in the base resin. Emulsion preparation (neutralization / water-based) of the base resin and the blocked isocyanate compound is usually carried out by neutralizing the resin with a water-soluble organic acid such as formic acid, acetic acid, lactic acid, etc. to make the resin water-soluble / water-dispersed. Can be. Also, if necessary, an organic solvent, a surface conditioner, an organic tin compound, for example, dibutyltin laurate, dioctyltin dilaurate, dibutyltin diacetate, dioctyltin benzoateoxy, dibutyltin benzoateoxy,
Dioctyltin dibenzoate, dibutyltin dibenzoate, or the like dissolved in an organic solvent can also be added.

The mixing ratio of the aqueous dispersion paste is 0.5 to 10 parts by mass in terms of the solid content of the aqueous dispersion paste based on 100 parts by mass of the solid content of the cationic electrodeposition paint. If the compounding ratio is less than 0.5 part by mass, there is no effect on the anticorrosion property, and if it exceeds 10 parts by mass, the stability of the cationic electrodeposition coating material is reduced. Next, a coating method of the cationic electrodeposition coating composition obtained by blending the aqueous dispersion paste will be described below. In general, the cationic electrodeposition coating has a solid content of about 5 to 40% by mass,
Preferably, the electrodeposition coating composition of the present invention is diluted with deionized water or the like so as to have a concentration of 15 to 25% by mass, and further adjusted to have a pH within the range of 5.5 to 9.0. And the like, and usually adjusted to a bath temperature of 15 to 35 ° C., and can be carried out under a load voltage of 100 to 400 V. The thickness of the electrodeposition coating film is not particularly limited, but is generally 5 to 50 μm, preferably 10 to 50 μm based on the cured film thickness.
It is better to be within a range of ４０40 μm. The baking curing temperature of the coating film is generally 100 to 200 ° C, preferably 140 to 200 ° C.
180 ° C range is suitable, and baking time is 5 minutes to 1
20 minutes, preferably 15 to 40 minutes are suitable. The electrodeposition baking coating generally has a heat shrinkage stress at 40 ° C. of the coating within the range of 70 to 130 kgf / cm ² ,
It is preferable to form a cured coating film having a coating film Tg in the range of 60 to 85 ° C.

[0012]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by this. Production Example of Bismuth Oxide Hydrate Paste A-1 0.5 part by mass of the following epoxy-based tertiary amine-type dispersing resin,
2.0 parts by mass of a hydrate of bismuth oxide, 0.3 parts by mass of a 10% by mass neutralizing agent (acetic acid) and 2.47 parts by mass of deionized water were added, and the mixture was dispersed in a ball mill for 10 hours and discharged. The paste A- having a maximum particle size of bismuth oxide of 1.5 μm
1 was obtained.

Production Example of Bismuth Oxide Hydrate Paste A-2 The paste having a maximum particle size of bismuth oxide hydrate of 1.5 μm was prepared in the same manner as paste A-1 with the composition shown in Table 1. A-2 was obtained.

Production Example of Bismuth Oxide Hydrate Paste A-3 The paste A-1 having a maximum particle size of bismuth oxide hydrate of 2 μm was prepared in the same manner as paste A-1 with the composition shown in Table 1. 3 was obtained.

Preparation Example of Bismuth Oxide Hydrate Paste A-4 The paste A-1 having a maximum particle size of bismuth oxide hydrate of 2 μm was prepared in the same manner as paste A-1 with the composition shown in Table 1. 4 was obtained.

Production Example of Pigment Dispersion Paste B-1 3.5 parts by mass of the following epoxy tertiary amine type dispersing resin:
14.5 parts by mass of titanium oxide, 7.0 parts by mass of purified clay,
0.46 parts by mass of carbon black, 1.0 part by mass of organotin, 2.38 parts by mass of a 10% by mass neutralizing agent (acetic acid), and 20.58 parts by mass of deionized water are dispersed in a ball mill for 20 hours and discharged. Thus, a pigment dispersion paste B-1 was obtained.

Production Example of Pigment Dispersion Paste B-2 3.5 parts by mass of the following epoxy-based tertiary amine type dispersing resin:
14.5 parts by mass of titanium oxide, 7.0 parts by mass of purified clay,
0.46 parts by mass of carbon black, 1.0 parts by mass of organic tin, 2.38 parts by mass of a 10% by mass neutralizing agent (acetic acid), 18.58 parts by mass of deionized water, and the above hydrate paste of bismuth oxide 3.5 parts by mass of A-2 was added, dispersed in a ball mill for 20 hours, and then discharged.
I got

Examples of Preparation of Pigment Dispersion Pastes B-3 and B-4 Pigment dispersion pastes B-3 and B-4 were prepared in the same manner as in paste B-2 except that deionized water was adjusted in the composition shown in Table 2.
3 and B-4 were obtained.

Production Example of Pigment Dispersion Paste C-1 3.5 parts by mass of the following epoxy tertiary amine type dispersing resin,
14.5 parts by mass of titanium oxide, 7.0 parts by mass of purified clay,
0.46 parts by mass of carbon black, 1.0 parts by mass of organic tin, 2.0 parts by mass of hydrate of bismuth oxide, 2.38 parts by mass of a 10% by mass neutralizing agent (acetic acid), 22.58 parts by mass of deionized water The resulting mixture was dispersed in a ball mill for 20 hours and then discharged to obtain a pigment dispersion paste C-1 having a maximum particle size of bismuth oxide hydrate of 4.5 μm.

Production Example of Pigment Dispersion Paste C-2 In the composition shown in Table 3, the maximum particle diameter of the hydrate of bismuth oxide was 6 μm in the same manner as in Pigment Dispersion Paste C-1.
m of pigment dispersion paste C-2 was obtained. The above-mentioned bismuth oxide hydrate paste and pigment dispersion base are shown in the following table.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

Production Example of Epoxy Tertiary Amine Type Dispersion Resin A flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser was charged with 398 parts by mass of ethylene glycol monobutyl ether and EHPE-3150 (epoxy equivalent 18
0 alicyclic epoxy resin (manufactured by Daicel Chemical Industries, Ltd.) 9
Then, 00 parts by mass, 371 parts by mass of the following amine compound and 1651 parts by mass of the following epoxyamine product were charged, gradually heated with mixing and stirring, and reacted at 150 ° C., and it was confirmed that the epoxy equivalent became 0. Thus, an epoxy-based tertiary amine-type dispersing resin was obtained. Amine compound: 285 parts by mass of stearic acid, 104 parts by mass of hydroxyethylaminoethylamine and 80 parts by mass of toluene are charged into a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a water separator, and gradually mixed and stirred. An amino compound obtained by heating, removing toluene as needed, separating and removing 18 parts by mass of reaction water while increasing the temperature, and removing the remaining toluene under reduced pressure. Amine value 150, freezing point 76 ° C.
Epoxyamine product: In a flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 105 parts by weight of diethanolamine, 760 parts by weight of bisphenol A diglycidyl ether having an epoxy equivalent of 190, 456 parts by weight of bisphenol A, and ethylene glycol monobutyl ether An epoxyamine product obtained by adding 330 parts by mass and reacting at 150 ° C. until the remaining amount of epoxy groups becomes zero. Solid content 80%.

Production example of cationic electrodeposition resin Epicoat 828EL (product name, epoxy resin, manufactured by Yuka Shell Epoxy Co., Ltd.) 1010 parts by mass, bisphenol A
390 parts by mass and 0.2 parts by mass of dimethylbenzylamine were added and reacted at 130 ° C. until the epoxy equivalent became 800. Next, 260 parts by mass of ε-caprolactone and 0.03 parts by mass of tetrabutoxytitanium were added, the temperature was raised to 170 ° C., sampling was performed over time while maintaining this temperature, and unreacted ε-caprolactone was measured in the infrared absorption spectrum measurement. The amount was tracked and the temperature was lowered to 120 ° C. when the conversion was greater than 98%. Next, 160 parts by mass of diethanolamine and 65 parts by mass of methyl isobutyl diketimine compound of diethylenetriamine were added, and reacted at 120 ° C. for 4 hours. 420 parts by mass of butyl cellosolve was added, and amine addition plastic having an amine value of 58 and a resin solid content of 80% was added. A modified epoxy resin was obtained.

Production Example of Cationic Electrodeposition Emulsion 87.5 parts by mass of the amine-added plastically modified epoxy resin obtained in the above Production Example (70 g in terms of resin solid content), and a methyl ethyl ketoxime blocked product of hexamethylene diisocyanurate as a crosslinking agent 33.3 parts by mass (resin solid content of 3
0g), LSN-105 (trade name, manufactured by Sankyoki Gosei Co., Ltd.)
2.5 parts by mass of dibutyltin dibenzoate (solid content: 40%), 15 parts by mass of 10% acetic acid were blended and uniformly stirred.
The mixture was added dropwise over a period of minutes to obtain a clear emulsion for cationic electrodeposition having a solid content of 34.0%.

Example 1 To 297 parts by mass of the above cationic electrodeposition emulsion, 3.0 parts by mass of hydrate paste A-1 of bismuth oxide, 47.3 parts by mass of pigment dispersion paste B-1 and deionized water By adding 283 parts by mass, a cationic electrodeposition coating composition of Example 1 having a solid content of 20% was obtained.

Example 2 49.8 parts by mass of pigment dispersion paste B-2, 297 parts by mass of a cationic electrodeposition emulsion, and 28 parts of deionized water
By adding 3 parts by mass, a cationic electrodeposition coating composition of Example 2 having a solid content of 20% was obtained.

Example 3 After adding 49.8 parts by mass of the pigment dispersion paste B-3 to 297 parts by mass of the above emulsion for cationic electrodeposition, 283 parts by mass of deionized water was added, and the solid content was 20%. 3
Was obtained.

Example 4 After adding 49.8 parts by mass of the pigment dispersion paste B-4 to 297 parts by mass of the above emulsion for cationic electrodeposition, 283 parts by mass of deionized water were added, and the solid content was 20%. 4
Was obtained.

Comparative Example 1 After adding 49.8 parts by mass of the pigment dispersion paste C-1 to 297 parts by mass of the above-mentioned cationic electrodeposition emulsion, 283 parts by mass of deionized water was added, and the solid content was 20%. 1
Was obtained.

Comparative Example 2 After adding 49.8 parts by mass of the pigment dispersion paste C-2 to 297 parts by mass of the above-mentioned cationic electrodeposition emulsion, 283 parts by mass of deionized water was added, and the solid content was 20%. 2
Was obtained.

Test The cationic electrodeposition paints obtained in the above Examples and Comparative Examples were
After forming a coating film by the following coating method, it was subjected to a salt water immersion test and a scratch long-term corrosion resistance test. Salt water immersion test: The cationic electrodeposition paints obtained in Examples and Comparative Examples were used as electrodeposition paints, and hot dip galvanized steel sheets (0.8 × 150
× 70 mm), and electrodeposition coating was performed using this as a cathode. Next, the obtained painted product is pulled up from the bath paint, washed with water, and baked at an ambient temperature at two levels of 150 ° C. and 170 ° C. for 20 minutes using an electric hot air drier and immersed in salt water. A test painted plate was prepared. In the salt water immersion test, a cross-cut wound was made on the above-mentioned coated plate with a knife at 55 ° C and 10% in 5% saline.
The result of immersion for a day was evaluated according to the following criteria. ◎ indicates the maximum width of rust and blisters is less than 3 mm from the cut part ○ indicates the maximum width of rust and blisters is 3 mm or more and less than 4 mm on one side from the cut part △ indicates the maximum width of rust and blisters is 4 mm or more on one side from the cut part ×, less than 6 mm × indicates that the maximum width of rust and blisters is 6 mm or more on one side from the cut part. Scratch long-term corrosion test: The cationic electrodeposition paints obtained in Examples and Comparative Examples were used as electrodeposition paint bath paints, and Palbond was used for this bath paint. 0.8 × 15 chemically treated with # 3020 (trade name, manufactured by Nippon Parkerizing Co., Ltd., zinc phosphate treating agent)
A 0-70 mm zinc-nickel steel plate was immersed, and electrodeposition coating was performed using this as a cathode. Next, the obtained coated product is pulled up from the bath paint, washed with water, and baked at an ambient temperature at two levels of 150 ° C. and 170 ° C. with a baking time of 20 minutes using an electric hot air drier. A coating was formed. Next, an intermediate coating TP-37 (manufactured by Kansai Paint Co., Ltd., trade name, aminoalkyd intermediate coating) was applied to the coated plate obtained at each baking temperature by spray coating at 35 μm and baked at 140 ° C. for 20 minutes. After that, Topcoat Neo 6000 (Kansai Paint Co., Ltd., trade name,
Amino alkyd top coating) 35μ by spray coating
m was applied and baked at 140 ° C. for 20 minutes to give three coats to prepare a coated plate for a scratch long-term corrosion resistance test. In the long-term scratch resistance test, the obtained coated plate was cut with a cutter knife having a blade width of 19 mm, the cutting edge was held at approximately 30 degrees with respect to the effective surface, and a cut reaching the base metal was made.
The results of performing a 180 cycle test with 1 cycle of salt spray, 6 hours of drying at -60 ° C, and 1 hour of humidification at 50 ° C as one cycle were shown by the following evaluation. ◎ indicates that the maximum width of rust and blisters is less than 2 mm from the cut portion ○ indicates that the maximum width of rust and blisters is 2 mm or more and less than 3 mm on one side from the cut portion △ indicates that the maximum width of rust and blisters is 3 mm or more on one side from the cut portion ×, less than 5 mm × indicates that the maximum width of rust and blisters is 5 mm or more on one side from the cut portion.

[0034]

[Table 4]

[0035]

As described above, according to the first to eighth aspects of the present invention, anticorrosion of zinc-nickel steel sheets and the like is achieved by adding a hydrate of bismuth oxide having a maximum particle diameter of 2 μm or less to the electrodeposition coating. The property (scratch corrosion resistance) can be improved. According to the invention of claims 2 to 4, an aqueous dispersion paste in which the content of the hydrate of bismuth oxide is 100 to 1000 parts by mass and the solids content is 30 to 60% by mass with respect to 100 parts by mass of the solid content of the dispersion resin. By so doing, it is possible to easily obtain a cationic electrodeposition coating composition containing a hydrate of bismuth oxide having a maximum particle size of 2 μm or less, and to improve the corrosion resistance (scratch corrosion resistance) of zinc-nickel steel sheets and the like. Can be planned. According to the invention of claim 8, the mixing ratio of the aqueous dispersion paste is set to 0.5 to 10 parts by mass in terms of the solid content of the aqueous dispersion paste with respect to 100 parts by mass of the solid content of the cationic electrodeposition paint. The corrosion resistance (scratch corrosion resistance) of a zinc-nickel steel plate or the like can be improved without impairing the stability of the paint.

Continuing from the front page (72) Inventor Midou Kawachi 33-1, Kanzakicho, Amagasaki-shi, Hyogo Kansai Paint Co., Ltd. (72) Inventor Hidehiko Haneishi 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. In-house F term (reference) 4J038 CG142 DB002 GA08 GA09 HA096 HA156 HA216 HA376 JA37 JA39 KA02 KA05 MA08 MA10 MA14 NA03 PA04

Claims (8)

[Claims] 1. A cationic electrodeposition coating composition comprising a hydrate of bismuth oxide having a maximum particle size of 2 μm or less to improve long-term corrosion protection. 2. An aqueous dispersion paste obtained by dispersing a composition comprising a dispersing resin, a hydrate of bismuth oxide, a neutralizing agent, and deionized water is added to a cationic electrodeposition paint. The cationic electrodeposition coating composition according to claim 1. 3. The content of the hydrate of bismuth oxide in the aqueous dispersion paste is 100 to 1000 parts by mass with respect to 100 parts by mass of the solid content of the resin for dispersion.
The cationic electrodeposition coating composition according to claim 2. 4. The solid content of the aqueous dispersion paste is 30 to 60.
The cationic electrodeposition coating composition according to claim 2, which is in mass%. 5. The cationic electrodeposition coating composition according to claim 2, wherein the dispersing resin is an amino group-containing epoxy resin. 6. The cationic electrodeposition paint according to claim 2, wherein the neutralizing agent is at least one organic acid selected from acetic acid, formic acid, and lactic acid. Composition. 7. The method according to claim 2, wherein the neutralizing agent is used in an amount of 0.5 to 1.2 equivalents based on amino groups of the resin for dispersion.
7. The cationic electrodeposition coating composition according to any one of items 6 to 6. 8. The above cationic electrodeposition coating composition,
The compounding ratio of the aqueous dispersion paste is 0.5 to 10 parts by mass in terms of the solid content of the aqueous dispersion paste with respect to 100 parts by mass of the solid content of the cationic electrodeposition paint. 3. The cationic electrodeposition coating composition according to claim 1.