JP2008050689A - Cationic electrodeposition coating material, electrodeposition coating method and coated article obtained by the electrodeposition coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cationic electrodeposition coating material which is excellent in throwing power property, electrodeposition coatability on a hot-dip galvannealed steel sheet, and finishing property. <P>SOLUTION: The cationic electrodeposition coating material is characterized in that the width (Δi) of a second peak current value (i<SB>2</SB>) of the current value (i) is lower than 0.05 mA/cm<SP>2</SP>under energizing condition that a first peak current value (i<SB>1</SB>) of the current value (i) at an energizing time (t) during electrodeposition coating becomes 4.0-6.0 mA/cm<SP>2</SP>, in the cationic electrodeposition coating, wherein a metal to be coated is dipped in a coating material tank having the cationic electrodeposition coating material and an electrode and then a current is applied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cationic electrodeposition coating material and a coated article excellent in throwing power, suitability for electrodeposition coating on a galvannealed steel sheet, and finish.

Cationic electrodeposition paints are widely used as undercoating paints for conductive metal products such as automobile bodies that require these performances because of the excellent coating workability and good corrosion resistance of the formed coating film.
Recently, the strength of the automobile body has been increased from the viewpoint of improving the collision safety of the automobile body, and a structure in which reinforcing members are overlapped in a bag structure portion or the like has been used in many cases. In such a bag structure part, it is difficult for electricity during electrodeposition coating to flow, and the current density decreases, so that it is difficult to form an electrodeposition coating film.
In the past, electrogalvanized steel sheets have been used as part of automobile bodies for the purpose of improving creter resistance (gas pinholes) of automobile bodies. Recently, however, galvannealed steel sheets are often used. It has become.
Conventionally, electrodeposition coating conditions have been devised in order to secure the inner plate film thickness of such a bag structure and obtain corrosion resistance, but electrodeposition coating has been made to ensure the inner plate thickness (for example, 10 μm). When the voltage is increased, cretering (gas pinhole) is generated on the outer plate surface using the galvannealed steel plate. On the other hand, when the coating voltage is set low so that the outer plate surface on the alloyed hot-dip galvanized steel plate does not generate cretering, there is a problem that the inner plate thickness (for example, 10 μm) cannot be secured.

  As a painting method to improve the creterability of automobile bodies, the relationship between the occurrence of cretering (gas pinholes) focusing on the second peak at the first peak and second peak of the current value during cationic electrodeposition coating The literature which examined about is disclosed (nonpatent literature 1). However, the cationic electrodeposition paint and the coating method described in Non-Patent Document 1 cannot achieve high throwing power and finish.

  In addition, in the application of the cationic electrodeposition paint, the maximum value (I) of the current density appears within 5 seconds from the start of energization, and the current density that is 1/2 the maximum value (I) of the current density (0.5I ) A method for forming a coating film in a gap is disclosed, characterized in that the time having the above is between 5 seconds from the start of energization (Patent Document 1). In the coating film forming method described in Patent Document 1, high throwing power, suitability for electrodeposition coating on a galvannealed steel sheet, and finishability cannot be achieved.

  In addition, in the electrodeposition coating, an electrodeposition coating material in which the minimum film forming temperature of the cationic electrodeposition coating material is within ± 5 ° C. of the electrodeposition coating setting temperature and the electric conductivity during coating is adjusted to 1000 to 1500 μS / cm, An electrodeposition coating film forming method of electrodeposition coating at the electrodeposition coating set temperature is disclosed (Patent Document 2). However, in the coating film forming method of Patent Document 2, a bag part (sill) film thickness of at least 9 μm is secured, no pinholes are generated on the alloyed hot-dip galvanized steel sheet, and the finish is excellent in finishing (door). It was insufficient to obtain an article having a film thickness of 15 to 17 μm.

In addition, it has a uniform coating property that can ensure the inner film thickness (μm) without increasing the outer film thickness (μm), and also has good electrodeposition coating suitability on galvannealed steel sheets. A method for forming a cationic electrodeposition coating film has been disclosed (Patent Document 3).
However, in Patent Document 3, the polarization resistance value (a) per unit film thickness is 120 to 300 kΩ · cm ² / μm, the coating deposition amount (b) per unit quantity of electricity is 50 to 150 mg / C, and the effective voltage (V). The coating film formed at 230 V or less ensured a bag part (sill) film thickness of at least 9 μm, and was insufficient to obtain an article to be coated having an outer plate (door) film thickness of 15 to 17 μm.

In addition, it is an electrodeposition coating film formation method with excellent “uniform coating properties” that improves the internal film-forming property while suppressing the film thickness of the outer plate, and is necessary for the start of coating film deposition. A coating film forming method is disclosed, characterized in that the amount of electricity is 100 to 400 C / m ² and the polarization resistance value per unit film thickness is 50 to 300 kΩ · cm ² / μm (Patent Document) 4). In Patent Document 4, although a throwing power of 10 μm (inner plate thickness) / 14 μm (outer plate thickness) = 71% is obtained in a four-box throwing power test, a high voltage is required. The suitability and finish of electrodeposition coating on galvannealed steel sheets were insufficient.

In addition, the unit film thickness of the coating film during electrodeposition coating using an amine-added epoxy resin modified with alkylphenol and polycaprolactone as the base resin and a cationic electrodeposition coating composition containing a blocked polyisocyanate curing agent as the curing component Polarization resistance value (a) per unit is 125 to 150 kΩ · cm ² / μm, and coating amount per unit quantity of electricity (b) is 28 to 50 mg / C. An electrodeposition coating film forming method is disclosed, characterized in that a coating film having a film thickness (c) of 10 μm for the inner plate and 10 μm to 12 μm for the outer plate is disclosed (Patent Document 5). . In Patent Document 5, a throwing power of 10 μm (inner plate film thickness) / 10 to 12 μm (outer plate film thickness) = 83 to 100% is obtained, but an alloyed hot dip galvanized steel sheet is required because a high voltage is required. A coating film excellent in electrodeposition coating suitability and finishability cannot be obtained.

Noboru Sato and one other, “Surface Properties of Surface-treated Steel Sheets Affecting the Cratering Phenomenon of Cationic Electrodeposition Coating”, Painting Engineering (1985), Vol. 4, p138-147 Japanese Unexamined Patent Publication No. 2001-19878 JP 2003-82498 A JP 2002-275690 A JP 2003-306796 A JP 2004-83824 A

  The problem to be solved by the present invention is to provide a cationic electrodeposition paint and a coated article excellent in throwing power, suitability for electrodeposition coating on an alloyed hot-dip galvanized steel sheet, and finish in a coated article having a bag structure. It is.

As a result of intensive studies to solve the above problems, the first peak current in the current value (i) with respect to the energization time (t) at the time of electrodeposition coating when the cationic electrodeposition coating is used as a bath. When the energization condition is such that the value (i ₁ ) is 4.0 to 6.0 mA / cm ² , the width (Δi) of the second peak current value of the current value (i) is 0.05 mA / cm ^2. The cationic electrodeposition coating composition is characterized in that the _second peak current value (i ₂ ) of the current value (i) is preferably not less than 1.

Furthermore, when cationic electrodeposition coating is performed using a cationic electrodeposition coating as a bath, a coating film is deposited on an object to be coated at the time of electrodeposition coating at a constant current density of 0.2 mA / cm ^2. The inventors have found that this can be achieved by using a cationic electrodeposition paint, and have completed the present invention.

  That is, the present invention provides an electrodeposition coating on a hot-dip, galvannealed steel sheet that has never been achieved by a cationic electrodeposition coating material having certain characteristics and an electrodeposition coating method using the cationic electrodeposition coating material. A coated article excellent in suitability and finish can be obtained.

  The cationic electrodeposition paint of the present invention can easily provide a coated article excellent in throwing power, electrodeposition coating suitability and finish of an alloyed hot-dip galvanized steel sheet. For example, when an automobile body is painted, a bag (sill) film thickness of at least 9 μm is secured, pinholes are not generated on the galvannealed steel sheet, and the outer panel (door) film thickness is excellent in finish. An object to be coated having a thickness of 15 to 17 μm can be obtained.

  Reasons for achieving the above effects are as follows: The coating film on the outer plate is formed quickly, and an electric current is applied to the inner plate to improve the electrodeposition coating property. 2. The generation of hydrogen gas during electrodeposition coating is suppressed, and the generation of pinholes on the galvannealed steel sheet is suppressed by a tough precipitation coating. 3. The deposited coating is considered to have achieved the effects of the present invention by technical contrivance, such as obtaining a coating having excellent fusing ability and excellent finish by heat flow during baking.

In the cationic electrodeposition coating in which a metal object is immersed in a coating tank having a cationic electrodeposition coating and an electrode and energized, the first in current value (i) with respect to the energization time (t). Cationic electrodeposition in which the _second peak current value (i ₂ ) of the current value (i) is controlled when the energization conditions are such that the peak current value (i ₁ ) is 4.0 to 6.0 mA / cm ^2. Related to paints.
Furthermore, when cationic electrodeposition coating is performed using a cationic electrodeposition paint as a bath, a coating film is deposited on the object to be coated at the time of electrodeposition coating with a constant current density of 0.2 mA / cm ^2. The present invention relates to a cationic electrodeposition paint.

  The cationic electrodeposition paint for obtaining the above characteristics will be described in detail below.

About the peak current value (i) of the cationic electrodeposition paint:
A graph in which the current value (i) is plotted against the energization time (t) during electrodeposition coating when the electrodeposition coating is performed using the cationic electrodeposition paint as a bath and the cationic electrodeposition paint is used as the bath. The first peak current value (i ₁ ) falls within the range of 4.0 to 6.0 mA / cm ² and the width (Δi) of the second peak current value of the current value (i) ( Note 1) is less than 0.05 mA / cm ² , and it is preferable to use a cationic electrodeposition coating that does not develop the second peak current value of the current value (i). A coated article excellent in electrodeposition coating suitability and finish can be obtained.

Preferably, the first peak current value (i ₁ ) falls within the range of 4.0 to 8.0 mA / cm ² and the width (Δi) of the second peak current value of the current value (i). (Note 1) Use a cationic electrodeposition paint that is less than 0.05 mA / cm ² , and preferably does not develop the _second peak current value (i ₂ ) of the current value (i).

More preferably, the first peak current value (i ₁ ) falls within the range of 4.0 to 10.0 mA / cm ² and the width (Δi) of the second peak current value of the current value (i) ( Note 1) is less than 0.05 mA / cm ² , and it is preferable to use a cationic electrodeposition coating that does not exhibit the second peak current value (i ₂ ) of the current value (i). Good in terms of suitability for electrodeposition coating of galvanized steel sheet.

Note that the conventional cationic electrodeposition coating has a current density peak current value (i ₁ ) in the range of 4.0 to 6.0 mA / cm ² (Note 2) as shown in the “dotted line graph”. When electrodeposition is applied, a second peak current value (i ₂ ) such as 2 in FIG. 1 appears.

Here, the cationic electrodeposition paint of the present invention has a current density peak current value (i ₁ ) in the range of 4.0 to 6.0 mA / cm ² as shown by the “solid line graph” in FIG. Even if electrodeposition is applied under the condition (Note 2), the width (Δi) (see 4 in Note 1) of the second peak current value (see 2 in FIG. 1) is suppressed to less than 0.05 mA / cm ^2. I was able to.

The coating film formation using the cationic electrodeposition paint of the present invention is carried out by applying the electrodeposition coating at the current value (i) with respect to the energization time (t) at the time of electrodeposition coating. When the first peak current value (i ₁ ) at the time of onset is formed, a dense and strong deposited film is formed, so that the formed deposited film is destroyed, and the second peak current value ( The expression of i ₂ ) can be suppressed. Cationic electrodeposition paint with these characteristics can distribute current to the bag part in the car body at an early stage, which is thought to lead to an improvement in “throwing power”.

Moreover, it contributes to the improvement of the electrodeposition coating suitability and finish of the galvannealed steel sheet without destroying the coating film deposited by “suppressing the width (Δi) of the second peak current value”. . In order to “suppress the occurrence of the _second peak current value (i ₂ )”, it is necessary to devise an electrodeposition paint composition. Therefore, the “cationic electrodeposition paint” described later in this specification Described in the description.

(Note 1) width of the second peak current value _{(i 2)} (.DELTA.i): second peak current value _(i 2) (2 in FIG. 1) and current _(i 3) (in Fig. 1 3 ) And is represented by 4 in FIG. Here, the “dotted line graph” in which the current value (i) with respect to the energization time (t) at the time of electrodeposition coating in FIG. 1 is plotted is a case where electrodeposition coating is performed using a conventional electrodeposition paint as a bath. .

(Note 2) Energizing conditions: The energizing conditions were as follows: a cationic electrodeposition paint was placed in a 3 liter tank as a bath, the bath temperature was 30 ° C., and a stirrer (cylindrical type, length 4.5 cm, diameter 1 cm) was used. Stir with a rotation of 400 rpm with a stirrer. Next, an alloyed hot-dip galvanized steel sheet (having a zinc basis weight of 45 g / m ² ) subjected to zinc phosphate plating (Nihon Parkerizing Co., Ltd.) was used as a test plate (70 mm (width) × 150 mm (length) × 0.8 mm (thickness)). )), Electrodeposition was applied at a pole ratio (anode / cathode = 1/2) and a distance between the electrodes of 15 cm so that the test plate was a cathode.
The applied voltage is between 150V and 350V in increments of 20V (150V, 170V, 190V ... 350V: each voltage is reached over 30 seconds (so-called slow start for 30 seconds), 2 minutes at constant voltage When the first peak current value (i ₁ ) of current density is in the range of 4.0 to 10.0 mA / cm ² when energized for 30 seconds, the width (Δi) of the second peak current value (See Note 1).

Regarding the current density (mA / cm ² ) of the cationic electrodeposition paint :
In addition, when cationic electrodeposition coating is performed using a cationic electrodeposition paint as a bath, a coating film is deposited on the object to be coated (Note 3) at the time of electrodeposition coating with a constant current density of 0.2 mA / cm ^2. Features.

In addition, in the case of depositing a coating film on an object at the time of electrodeposition coating with a constant current density of 0.2 mA / cm ² , the peak current value (i) of the cationic electrodeposition paint is “ A cationic electrodeposition coating with a controlled second peak current value width (Δi) ”provides a coated article having excellent throwing power, electrodeposition coating suitability on a galvannealed steel sheet, and finish. It is preferable for this purpose.

(Note 3) Coating film deposition: Using CCP500-1 (trade name, constant current electrodeposition apparatus manufactured by Takasago Seisakusho Co., Ltd.), which can obtain a constant current with a current density of 0.2 mA / cm ² , using a cationic electrodeposition paint. The voltage value at the time of electrodeposition coating is obtained, and when the increase of the polarization resistance value obtained by “each voltage / current = polarization resistance value” is recognized, it is considered that “coating film deposition” is performed.

About minimum continuous film formation temperature (MFT):
The cationic electrodeposition paint is a peak current value (i ₁ ) in the above-described graph in which the current value (i) is plotted against the energization time (t) during electrodeposition coating using the cationic electrodeposition paint as a bath. ) Is 4.0 to 6.0 mA / cm ² , and the width (Δi) (Note 1) of the second peak current value of the current value (i) is less than 0.05 mA / cm ² , Preferably, a cationic electrodeposition paint that does not express the _second peak current value (i ₂ ) of the current value (i) is used. (2) “Deposition coating” on the object to be coated at the time of electrodeposition coating with a constant current density of 0.2 mA / cm ^{2 using} a cationic electrodeposition paint as a bath. (3) Further, the minimum temperature (Note 4) for forming a continuous film of the cationic electrodeposition coating is in the range of 20 to 35 ° C., preferably 22 to 28 ° C., more preferably 23 to 27 ° C. This is effective for obtaining a cationic electrodeposition coating material that is excellent in suitability and finish for electrodeposition coating on a heat-treated galvanized steel sheet.

  Within the above range, the coating film deposited during electrodeposition coating is dense and strong without destroying the coating film (for example, coating film breakdown due to sparking between different electrodes that occurs when electrodepositing a galvanized steel sheet). Can be formed early. From this, it is considered that the current is distributed to the bag portion of the automobile body and the “throwing ability” is improved without excessively using the current for forming the outer plate surface.

(Note 4) Minimum temperature for continuous film formation: The minimum temperature for continuous film formation is the relationship between bath temperature and film thickness when electrodeposition coating is performed with a constant applied voltage using electrodeposition paint as shown in FIG. Indicated. According to FIG. 3, as the bath temperature during electrodeposition coating decreases from a low temperature, the film thickness of the electrodeposition coating film formed on the article decreases, and if it reaches a certain bath temperature or higher, Conversely, the film thickness increases. In such a relationship between the bath temperature and the film thickness, the bath temperature at which the film thickness is minimized (the bath temperature corresponding to the minimum value of the curve (4 in FIG. 3)) is referred to as the continuous film formation minimum temperature (MFT). When obtaining the minimum continuous film formation temperature, electrodeposition is applied at a constant applied voltage for each bath temperature, and the bath temperature (the minimum value of the curve) when the film thickness is minimized is obtained.

[Cation electrodeposition coating]
In order for the cationic electrodeposition paint described above to fall within the suitability range where the throwing power and the electrodeposition coating suitability and finish on the galvannealed steel sheet are good, the usual cationic electrodeposition paint is used. Different paint design is required.

  The cationic electrodeposition paint used in the present invention contains a base resin (a) and a curing agent (b) as resin components. In particular, a cationic electrodeposition paint comprising a cationic resin as a base resin and a blocked polyisocyanate compound as a curing agent is suitable.

  The cationic resin used as the base resin (a) in the cationic electrodeposition coating is a resin having a cationizable group such as an amino group, an ammonium base, a sulfonium base, or a phosphonium base in the molecule. These include those usually used as base resins for electrodeposition paints, such as epoxy resins, acrylic resins, polybutadiene resins, alkyd resins, polyester resins, and the like. In particular, an amine-added epoxy resin obtained by addition reaction of an amino group-containing compound with an epoxy resin is suitable.

  Examples of the above amine-added epoxy resins include (1) adducts of epoxy resins with primary mono- and polyamines, secondary mono- and polyamines, or primary and secondary mixed polyamines (for example, US Pat. No. 3,984,299); (2) Adducts of epoxy resins with secondary mono- and polyamines having ketiminated primary amino groups (eg, US Pat. No. 4,017,438). (3) Reactants obtained by etherification of an epoxy resin and a ketiminated hydroxy compound having a primary amino group (for example, see JP-A-59-43013) be able to.

  The epoxy resin used in the production of the above amine-added epoxy resin is a compound having at least one, preferably two or more epoxy groups in one molecule, generally at least 200, preferably 400 to 4,000, Those having a [number average molecular weight] preferably in the range of 800 to 2,500 and an epoxy equivalent weight in the range of at least 160, preferably 180 to 2,500, more preferably 400 to 1,500 are suitable, In particular, those obtained by a reaction between a polyphenol compound and epihalohydrin are preferred.

  Here, “number average molecular weight” is a separation column of TSK “GEL4000HXL”, “G3000HXL”, “G2500HXL”, “G2000HXL” (above, manufactured by Tosoh Corporation) according to the method described in JIS K 0124-83. It is a value obtained from a chromatogram obtained with an RI refractometer and a standard polystyrene calibration curve at 40 ° C. and a flow rate of 1.0 ml / min, using four for GPC as eluent.

  Examples of the polyphenol compound used for forming the epoxy resin include bis (4-hydroxyphenyl) -2,2-propane, 4,4′-dihydroxybenzophenone, and bis (4-hydroxyphenyl) -1,1. -Ethane, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-2 or 3-tert-butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4′-dihydroxydiphenylsulfone, phenol novolak, cresol novolak, and the like can be mentioned.

  The epoxy resin may be partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamidoamine, a polycarboxylic acid, a polyisocyanate compound or the like, and a lactone such as ε-caprolactone, An acrylic monomer or the like may be graft-polymerized.

  Examples of the primary mono- and polyamines, secondary mono- and polyamines, and primary and secondary mixed polyamines used in the production of the amine-added epoxy resin of (1) above include monomethylamine, dimethylamine, and monoamine. Mono- or di-alkylamines such as ethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, dibutylamine; alkanolamines such as monoethanolamine, diethanolamine, mono (2-hydroxypropyl) amine, monomethylaminoethanol; ethylenediamine And alkylene polyamines such as propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine.

  Examples of the secondary mono- and polyamines having a ketimized primary amino group used in the production of the amine-added epoxy resin (2) include, for example, the production of the amine-added epoxy resin (1). Among primary mono- and polyamines, secondary mono- and polyamines or primary and secondary mixed polyamines used, compounds having primary amino groups, such as monomethylamine, monoethanolamine, ethylenediamine, diethylenetriamine Examples thereof include ketimine compounds obtained by reacting ketone compounds with the above.

  Examples of the hydroxy compound having a ketiminated primary amino group used in the production of the amine-added epoxy resin (3) include, for example, a first compound used in the production of the amine-added epoxy resin (1). Of primary mono- and polyamines, secondary mono- and polyamines or primary and secondary mixed polyamines, compounds having a primary amino group and a hydroxyl group, such as monoethanolamine, mono (2-hydroxypropyl) amine Examples thereof include a hydroxyl group-containing ketimine compound obtained by reacting a ketone compound with the above.

  In particular, as the base resin (a), an xylene formaldehyde resin-modified amino group obtained by reacting an xylene formaldehyde resin and an amino group-containing compound with an epoxy resin having an epoxy equivalent of 180 to 3,000, preferably 250 to 2,000. It is preferable to use the contained epoxy resin to obtain the paint properties of the cationic electrodeposition paint (A) used in the present invention, and it has excellent throwing power, suitability for electrodeposition coating on an alloyed hot-dip galvanized steel sheet, and finish. A coated article can be obtained.

  As the epoxy resin used as a starting material for the production of the amino group-containing epoxy resin, the same epoxy resin as described for the cationic resin can be used.

  The xylene formaldehyde resin is useful for internal plasticization (modification) of the epoxy resin, and can be produced, for example, by subjecting xylene and formaldehyde and further optionally a phenol to a condensation reaction in the presence of an acidic catalyst.

  As said formaldehyde, the compound etc. which generate | occur | produce formaldehyde, such as formalin, paraformaldehyde, and trioxane which are industrially easy to acquire, can be illustrated.

  Furthermore, the above phenols include mono- or divalent phenolic compounds having 2 or 3 reaction sites. Specifically, for example, phenol, cresol, para-octylphenol, nonylphenol, bisphenolpropane, Bisphenol methane, resorcin, pyrocatechol, hydroquinone, para-tert-butylphenol, bisphenol sulfone, bisphenol ether, para-phenylphenol and the like can be mentioned, and these can be used alone or in combination of two or more. Of these, phenol and cresol are particularly preferred.

  Examples of the acidic catalyst used in the condensation reaction of xylene and formaldehyde as described above and further phenols include sulfuric acid, hydrochloric acid, paratoluenesulfonic acid, oxalic acid, etc. Sulfuric acid is preferred.

  The condensation reaction can be performed, for example, by heating to a temperature at which xylene, phenols, water, formalin and the like existing in the reaction system are refluxed, usually about 80 to about 100 ° C. It can be completed in about hours.

  Under the above-mentioned conditions, xylene-formaldehyde resin can be obtained by heat-reacting xylene, formaldehyde and further phenols in the presence of an acidic catalyst.

  The xylene formaldehyde resin thus obtained generally has a viscosity in the range of 20 to 50,000 mPa · s (25 ° C.), preferably 25 to 30,000, more preferably 30 to 15,000 mPa · s (25 ° C.). And preferably have a hydroxyl equivalent weight in the range of from 100 to 50,000, in particular from 150 to 30,000, more particularly from 200 to 10,000.

  The amino group-containing compound is a cationic component for introducing an amino group into an epoxy resin to make the epoxy resin cationic, and the same one as used in the production of the cationic resin is used. be able to.

  Although the reaction of the xylene formaldehyde resin and the amino group-containing compound with the epoxy resin can be performed in any order, generally, the xylene formaldehyde resin and the amino group-containing compound are simultaneously reacted with the epoxy resin. Is preferred.

  The above addition reaction can be usually performed in a suitable solvent at a temperature of about 80 to about 170 ° C., preferably about 90 to about 150 ° C. for about 1 to 6 hours, preferably about 1 to 5 hours. Examples of the solvent include hydrocarbon solvents such as toluene, xylene, cyclohexane, and n-hexane; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone. Ketone solvents; amide solvents such as dimethylformamide and dimethylacetamide; alcohol solvents such as methanol, ethanol, n-propanol, and iso-propanol; or a mixture thereof.

  The use ratio of each reaction component in the above addition reaction is not strictly limited and can be appropriately changed, but is based on the total solid content mass of the three components of epoxy resin, xylene formaldehyde resin and amino group-containing compound. Therefore, the following range is appropriate. That is, the epoxy resin is generally 50 to 90% by mass, preferably 50 to 85% by mass; the xylene formaldehyde resin is generally 5 to 45% by mass, preferably 6 to 43% by mass; It is preferably used within a range of 25% by mass, preferably 6 to 20% by mass.

  When the above cationic resin has an amino group as a cationizable group, it should be neutralized with an organic carboxylic acid such as formic acid, acetic acid, propionic acid or lactic acid; an acid such as inorganic acid such as hydrochloric acid or sulfuric acid. Can be water-soluble or water-dispersed.

  As the curing agent (b) used in combination with the base resin (a) described above, a blocked polyisocyanate compound which is an addition reaction product in a substantially stoichiometric amount of the polyisocyanate compound and the blocking agent. Is preferable from the viewpoints of the curability and anticorrosion of the coating film.

  As the polyisocyanate compound used here, those conventionally known can be used. For example, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4′-diisocyanate, diphenylmethane-4 , 4′-diisocyanate (usually called “MDI”), crude MDI [polymethylene polyphenyl isocyanate], bis (isocyanate methyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate Or cycloaliphatic polyisocyanate compounds; cyclized polymers of these polyisocyanate compounds, isocyanate bilet bodies; Ethylene glycol excess of cyanate compounds, propylene glycol, may be mentioned trimethylolpropane, hexanetriol, terminal isocyanate-containing compounds obtained by reacting a low molecular weight active hydrogen-containing compounds such as castor oil and the like. These can be used alone or in combination of two or more.

  On the other hand, the blocking agent is added and blocked to the isocyanate group of the polyisocyanate compound, and the blocked polyisocyanate compound produced by the addition is stable at room temperature, but the baking temperature of the coating film (usually about 100 to When heated to about 200 ° C., it is desirable that the blocking agent dissociates and free isocyanate groups can be regenerated.

  Examples of the blocking agent that satisfies such requirements include lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenols such as phenol, para-t-butylphenol, and cresol. Compounds; aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatic alkyl alcohols such as phenyl carbinol and methyl phenyl carbinol; ether alcohol compounds such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether Can be mentioned.

  The base resin (a) and the curing agent (b) are generally in the range of 50 to 95% by weight, particularly 65 to 85% by weight of the base resin (a), based on the total solid content of both, and the curing agent. (B) can be used in the range of 5 to 50% by mass, particularly 15 to 35% by mass.

  In addition to the cationic electrodeposition paint, a curing catalyst, a surfactant, a surface conditioner, an organic solvent, and the like can be appropriately blended. Among these, the curing catalyst promotes a crosslinking reaction between the base resin and the curing agent. It is effective for.

  In the cationic electrodeposition coating composition of the present invention, the base resin (a) and curing are required in order to make it within the suitable range in which the throwing power and the electrodeposition coating suitability and finish on the galvannealed steel sheet are good. 0.01 to 10% by mass, preferably 0.1 to 5% by mass, based on the total solid content of the agent (b), at least one of alkyltin ester compounds of aromatic carboxylic acids represented by the following formula (1): %, Preferably 0.5 to 3% by mass.

Formula (1)
(Wherein R ¹ represents an alkyl group having ¹ to 12 carbon atoms, and R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms)
Specifically, the alkyltin ester compound of the aromatic carboxylic acid represented by the formula (1) is preferably dioctyltin dibenzoate or dibutyltin dibenzoate.

In addition to the base resin (a) and the curing agent (b), the cationic electrodeposition coating is appropriately mixed with an alkyl tin ester compound of an aromatic carboxylic acid, a surfactant, a surface conditioner, an organic solvent, and the like. After preparing the compounded resin, it is possible to use an aqueous dispersion obtained by neutralizing with a water-soluble organic carboxylic acid in a normal aqueous medium and water-dispersing or dispersing the compounded resin in water.
As the organic carboxylic acid for neutralizing the compounded resin, in particular, acetic acid, formic acid or a mixture thereof is suitable. By using these acids, uniform coating properties and antirust properties of the coating composition to be formed are obtained. , Finish and paint stability are improved. The amount of the organic carboxylic acid used is in the range of 6 to 15, preferably 8 to 13 in terms of mgKOH per 1 g of resin solids in total as the neutralization value.

  Further, as a surfactant to be appropriately added for the purpose of improving water dispersibility, for example, acetylene glycol type, polyethylene glycol type, polyhydric alcohol type having HLB in the range of 3-18, preferably 5-15, etc. Nonionic surfactants. The cationic electrodeposition coating is preferably produced by mixing an emulsion in which the base resin (a) and the curing agent (b) are dispersed and a pigment dispersion paste prepared in advance.

  The pigment dispersion paste to be mixed with the emulsion is obtained by previously dispersing the above-mentioned colored pigment, rust preventive pigment, extender pigment, etc. into fine particles, for example, a pigment dispersion resin, a neutralizing agent and pigments, and further necessary The pigment dispersion paste can be prepared by blending a bismuth compound according to the above and dispersing in a dispersion mixer such as a ball mill, sand mill, or pebble mill.

  As the pigment dispersing resin, known resins can be used. For example, a base resin or a surfactant having a hydroxyl group and a cationic group can be used. Further, a tertiary amine type, a quaternary ammonium salt type, a tertiary sulfonium salt type can be used. Resins such as can be used as the dispersing resin. The amount of the pigment dispersant used is preferably 1 to 150 parts by weight, particularly 10 to 100 parts by weight per 100 parts by weight of the pigment.

The pigment can be used without any particular limitation, for example, colored pigments such as titanium oxide, carbon black, bengara, etc .; extender pigments such as clay, mica, barita, calcium carbonate, silica; rust prevention such as aluminum phosphomolybdate and aluminum tripolyphosphate And pigments.
In addition, a bismuth compound can be contained for the purpose of inhibiting corrosion or preventing rust, for example, bismuth oxide, bismuth hydroxide, basic bismuth carbonate, bismuth nitrate, bismuth silicate, two or more organic acids and the above-mentioned An organic acid bismuth produced by reacting such a bismuth compound and at least one of the organic acids is an aliphatic hydroxycarboxylic acid can be mentioned.

  Furthermore, dioctyltin oxide, dibutyltin oxide, etc. can be added as organic tin compounds other than the alkyl tin ester compound of aromatic carboxylic acid. The blending amount of these pigments is preferably in the range of 1 to 100 parts by weight, particularly 10 to 50 parts by weight, per 100 parts by weight of the total solid content of the base resin and the curing agent.

  The organic solvent used in the cationic electrodeposition coating composition used in the present invention is, for example, alcohol-based, for example, methyl alcohol (water solubility: free mixing), ethyl alcohol (water solubility: free mixing), n-butyl alcohol (water Solubility: 7.7% by mass), isopropyl alcohol (water solubility: free mixing), 2-ethylhexanol (water solubility: 0.07), benzyl alcohol (water solubility: 3.8% by mass), ethylene glycol (water solubility) : Free mixing), propylene glycol (water solubility: free mixing); ether type, for example, ethylene glycol monoethyl ether (water solubility: free mixing), ethylene glycol monobutyl ether (water solubility: free mixing), ethylene glycol monohexyl ether (Water solubility: 0.99% by mass), ethylene glycol 2-ethylhexyl ether (water solubility: 0.09% by mass), diethylene glycol monobutyl ether (water solubility: free mixing), propylene glycol monomethyl ether (water solubility: free mixing), propylene glycol monophenyl ether (water solubility: insoluble) 3-methyl-3-methoxybutanol (water solubility: free mixing), diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (water solubility: free mixing); ketone systems such as acetone (water solubility: free mixing), methyl isobutyl ketone (Water solubility: 2.0 mass%), cyclohexanone (water solubility: 5.0 mass%), isophorone (water solubility: 1.2 mass%), acetylacetone (water solubility: 12.5 mass%); ester system, For example, ethylene gluco Monoethyl ether acetate (solubility in water: 22.9 wt%), ethylene glycol monobutyl ether acetate (solubility in water: 0.9 wt%) and mixtures thereof.

In addition, by adjusting the kind of organic solvent contained in the bath of the cationic electrodeposition paint and the content of the organic solvent, 1. In cationic electrodeposition coating using a cationic electrodeposition paint as a bath, the first peak current value (i ₁ ) is 4.0 to 6.6 in the current value (i) with respect to the energization time (t) during electrodeposition coating. When the energization condition is 0 mA / cm ² , the width (Δi) (4 in FIG. 1) of the second peak current value of the current value (i) is less than 0.05 mA / cm ² .
2. When cationic electrodeposition coating is performed using a cationic electrodeposition coating as a bath, a coating film is deposited on an object to be coated at the time of electrodeposition coating at a constant current density of 0.2 mA / cm ² . 3. It has been found that a cationic electrodeposition paint characterized in that the minimum continuous film formation temperature (MFT) is within a certain range.

  Regarding the type of organic solvent (c) and the amount of organic solvent, the content of the organic solvent (c) having a solubility parameter of 8 to 10 and a water solubility of 95% by mass or more based on the mass of the cationic electrodeposition paint bath Is 0.01 to 1.0% by mass, preferably 0.01 to 0.5% by mass, and the total amount of organic solvent in the cationic electrodeposition coating bath is 0.01 to 2.0% by mass, preferably 0.05. It is good that it is -1.0 mass%.

As such an organic solvent (c), preferably ethylene glycol monobutyl ether or diethylene glycol monobutyl ether may be used to obtain the coating properties of the present invention.
The cationic electrodeposition coating is produced by adding a pigment dispersion paste, emulsion, additive, neutralizing agent, and deionized water so that the solid content concentration is within the range of about 5 to 25% by mass and the pH is within the range of 5 to 8. Adjust to.

  The conditions for electrodeposition coating using the cationic electrodeposition paint of the present invention are not particularly limited, but generally 10 to 90 seconds, preferably 30 to 60 seconds by slow start electrodeposition coating. The voltage is raised to a constant voltage over time, the energization time is 30 seconds to 10 minutes, the bath temperature is 15 to 35 ° C, preferably 20 to 30 ° C, and the voltage is 100 to 450V, preferably 200 to 350V. In addition, it is desirable to perform electrodeposition coating in a stirring state with an electrode ratio (cathode / anode) = 1/2 to 1/8 and an interelectrode distance of 0.1 to 1 m.

The film thickness of the electrodeposition coating film by the cationic electrodeposition coating may be appropriately selected according to the intended performance. However, when the automobile body is painted by using the electrodeposition coating method of the present invention, ) It is possible to obtain an object to be coated having an outer plate (door) film thickness of 15 to 17 μm with a film thickness of at least 9 to 10 μm, no pinholes on the galvannealed steel sheet, and excellent finish. it can.
After electrodeposition coating, in order to remove the excessively deposited cationic electrodeposition paint, ultrafiltration filtrate (UF filtrate), RO permeated water, industrial water, pure water, etc., adhered to the surface of the paint. Wash thoroughly with cationic electrodeposition paint so that it does not remain.

  Examples of the object to be coated with the cationic electrodeposition coating include automobile bodies, motorcycle parts, household equipment, other equipment, and the like, and are not particularly limited as long as they are metals. Electrogalvanized steel sheets, electrogalvanized iron double-layer plated steel sheets, organic composite plated steel sheets, Al materials, Mg materials, etc., and the surfaces of these materials such as steel sheets and cold-rolled steel plates are cleaned as necessary. After that, surface treatment such as phosphate chemical treatment and chromate treatment can be mentioned.

  Next, the method of baking and drying the electrodeposition coating is not particularly limited, but direct or indirect hot air drying methods such as electric furnaces and gas furnaces, heating methods using infrared rays or far infrared rays, induction heating methods using high frequencies, liquid medium immersion heating Using a drying equipment such as a method, the temperature of the coating surface is 110 ° C. to 200 ° C., preferably 140 ° C. to 180 ° C., and the time is 10 minutes to 180 minutes, preferably 20 minutes to 50 minutes. It can be cured.

  Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. In each example, “parts” indicates mass parts, and “%” indicates mass%.

Production Example 1 Base resin No. Example 1
300 parts of ε-caprolactone was added to 400 parts of PP-400 (manufactured by Sanyo Chemical Co., Ltd., trade name, polypropylene glycol molecular weight 400), and the temperature was raised to 130 ° C. Thereafter, 0.01 part of tetrabutoxy titanium was added and the temperature was raised to 170 ° C. Sampling was carried out over time while maintaining this temperature, the amount of unreacted ε-caprolactone was monitored by infrared absorption spectrum measurement, and the mixture was cooled when the reaction rate reached 98% or more to obtain modifier 1.
Separately, 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine are added to 1000 parts of jER828EL (trade name, epoxy resin, epoxy equivalent 190, molecular weight 350, manufactured by Japan Epoxy Resin Co., Ltd.) until the epoxy equivalent becomes 750 at 130 ° C. Reacted.
120 parts of nonylphenol was added thereto, and the mixture was reacted at 130 ° C. until the epoxy equivalent was 1000. Next, 200 parts of modifier 1, 95 parts of diethanolamine and 65 parts of diethylenetriamine ketiminate were added and reacted at 120 ° C. for 4 hours, followed by addition of 470 parts of methyl isobutyl ketone, amine value of 40 mg KOH / g, number average molecular weight of 2 Substrate resin No. 1 which is a polyol-modified amino group-containing epoxy resin to which nonylphenol having a resin solid content of 80% is added. 1 was obtained.

Production Example 2 Base resin no. Example 2
480 parts of 50% formalin, 110 parts of phenol, 202 parts of 98% industrial sulfuric acid and 424 parts of metaxylene were charged into a 2 liter separable flask equipped with a thermometer, a reflux condenser, and a stirrer at 84 to 88 ° C. For 4 hours. After the reaction is completed, the resin phase is separated from the sulfuric acid aqueous phase by standing, then the resin phase is washed with water three times, and unreacted metaxylene is stripped for 20 minutes under the condition of 20-30 mmHg / 120-130 ° C. 480 parts of a phenol-modified xylene formaldehyde resin having a viscosity of 1050 mPa · s (25 ° C.) were obtained.
To another flask, 1000 parts of jER828EL (manufactured by Japan Epoxy Resin, trade name, epoxy resin, epoxy equivalent 190, molecular weight 350), 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added, and epoxy equivalent of 750 at 130 ° C. The reaction was continued until
Next, after adding 300 parts of xylene formaldehyde resin, 137 parts of diethanolamine and 95 parts of ketimine compound of diethylenetriamine, the mixture was reacted at 120 ° C. for 4 hours. A base resin No. 2,000 which is an amino group-containing epoxy resin modified with xylene formaldehyde resin having a resin solid content of 80% and 2,000%. 2 was obtained.

Production Example 3 Base resin no. Production Example 3 A flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a reflux condenser was charged with 518 parts of an epoxy resin having a number average molecular weight of 370 and an epoxy equivalent of 185 obtained by the reaction of bisphenol A and epichlorohydrin. A 205 parts, 213 parts of ε-caprolactone, 0.05 parts of tetrabutoxytitanium and 0.05 parts of tetraethylammonium bromide were added, the temperature was raised to 170 ° C., the reaction was carried out at this temperature for 2 hours, and then triphenylethylphosphonium iodide 0 .05 parts was charged and reacted for another 2 hours until the epoxy equivalent was 936.
Next, 257.4 parts of methyl isobutyl ketone and 28.3 parts of diethylamine 68.3 parts of diethanolamine were added and reacted at 80 ° C. for 2 hours. The amine value was 54.5 mgKOH / g, the number average molecular weight was 2,000, and the resin solid content was 80%. Base resin No. which is an amino group-containing epoxy resin. 3 was obtained.

Production Example 4 Base resin No. 4 Production Example 15 parts of methyl isobutyl ketone was charged into a 2-liter four-necked flask having a volume of 2 liters, and maintained at 110 ° C. after nitrogen substitution. In this, the mixture shown below was dripped over 3 hours.
Styrene 8 parts n-Butyl acrylate 8 parts Isobutyl methacrylate 30 parts 2-Ethylhexyl methacrylate 20 parts 2-Hydroxyethyl acrylate 25 parts Dimethylaminoethyl methacrylate 9 parts 1,2'-Azobis A solution prepared by dissolving 8 parts of (2-methylbutyronitrile) in 10 parts of methyl isobutyl ketone was added dropwise over 1 hour. After completion of the dropwise addition, this was further maintained at 110 ° C. for 1 hour, and the base resin No. 1 was an amino group-containing acrylic resin having a hydroxyl value of 100 mgKOH / g, an amine value of 30 mgKOH / g, a weight average molecular weight of 16,000 and a solid content of 80%. 4 was obtained.

Production Example 5 Curing Agent No. Production Example 1 In a reaction vessel, 270 parts of Cosmonate M-200 (Note 5) and 25 parts of methyl isobutyl ketone were added and heated to 70 ° C. In this, 15 parts of 2,2-dimethylolbutanoic acid was gradually added, and then 70 parts of methyl isobutyl ketone was added dropwise, reacted at 70 ° C. for 1 hour, cooled to 60 ° C., and propylene glycol 152 Parts were added. While maintaining this temperature, sampling was carried out over time, and it was confirmed by infrared absorption spectrum measurement that there was no absorption of unreacted isocyanato groups. 1 was obtained.
(Note 5) Cosmonate M-200: trade name, manufactured by Mitsui Chemicals, Crude MDI.

Production Example 6 Curing Agent No. Production Example 2 In a reaction vessel, 222 parts of isophorone diisocyanate and 80 parts of methyl isobutyl ketone were added, and the temperature was raised to 50 ° C. In this, methyl ethyl ketoxime 1
After adding 74 parts slowly, it heated up at 60 degreeC. While maintaining this temperature, sampling was conducted over time, and it was confirmed by infrared absorption spectrum measurement that there was no absorption of unreacted isocyanate. 2 was obtained.

Emulsion production:
Production Example 7 Emulsion No. Production Example 1 Substrate resin No. obtained in Production Example 1 No. 1 87.5 parts (solid content 70 parts), the curing agent No. 1 obtained in Production Example 5. 1 is mixed with 33.3 parts (solid content 30 parts), and further mixed with 13 parts of 10% acetic acid and stirred uniformly, and then 156.2 parts of deionized water is vigorously stirred and takes about 15 minutes. To obtain an emulsion.
Subsequently, the obtained emulsion was extracted (so-called desolvation) at 35 ° C. under reduced pressure (50 mmHg or less), so that the content of methyl isobutyl ketone in the emulsion was 1% by mass or less.
Next, 4 parts of ethylene glycol monobutyl ether was added to the emulsion, and emulsion No. 3 having a solid content of 34% was added. 1 was obtained.

Production Examples 8 to 19 Emulsion No. 2-No. Production Example No. 13 Emulsion No. 13 was prepared in the same manner as in Production Example 7 except that the contents of Table 1 were used. 2-No. 13 was obtained.

Production Example 20 Pigment Dispersion Resin Production Example jER828EL (trade name, epoxy resin, manufactured by Japan Epoxy Resin Co., Ltd.) 1010 parts, bisphenol A 390 parts, polycaprolactone diol (number average molecular weight about 1200) 240 parts and dimethylbenzylamine 0.2 part was added and reacted at 130 ° C. until the epoxy equivalent was about 1090.
Next, 134 parts of dimethylethanolamine and 90 parts of acetic acid were added and reacted at 120 ° C. for 4 hours. Then, methyl isobutyl ketone was added to adjust the solid content, and the ammonium salt value was 44 mg KOH / g, and the ammonium content was 60%. A salt-type resin for pigment dispersion was obtained.

Production Example 21 Production Example of Pigment Dispersion Paste 8.3 parts of pigment dispersion resin obtained in Production Example 20 (solid content 5 parts), titanium oxide 14.5 parts, refined clay 7.0 parts, carbon 0.3 parts of black, 1 part of dioctyl tin oxide, 1 part of bismuth hydroxide and 20.3 parts of deionized water were added and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste having a solid content of 55%.

Production of cationic electrodeposition paints:
Production Example 22
Emulsion no. 1 was added to 294 parts (solid content: 100 parts), 55% pigment dispersion paste was added to 52.4 parts (solid content: 28.8 parts), and deionized water (297.6 parts). No. 1 was produced.

Production Examples 23 to 34
With the formulation as shown in Table 2, the cationic electrodeposition paint No. 2-No. 13 was produced.

Examples and Comparative Examples Example 1
Cationic electrodeposition paint no. 1 (3 liters) was placed in a bath, the bath temperature was adjusted to 30 ° C., and a cold-rolled steel sheet (0.8 mm × 70 mm × 150 mm) treated with zinc phosphate was immersed as a cathode. Current value measurement (Note 6) was performed at a ratio (anode / cathode) = 1/2.
Furthermore, constant current electrodeposition coating (Note 7) and continuous film formation minimum temperature (Note 8) were measured according to the following test methods.

(Note 6) current value measurement: current measurement obtains a current value (mA / cm ²⁾ by measuring the current value every second during electrodeposition coating, the current value for the current time (mA / cm ²⁾ The first peak value (i ₁ ) and the second peak value (i ₂ ) were obtained by graphing. The energization conditions were performed according to the contents of the above (Note 2).
A: The first peak value (i ₁ ) of the current value (i) is expressed in the range of 4.0 to 6.0 mA / cm ² and the second peak value of the current value (i) is expressed. No B: The first peak value (i ₁ ) of the current value (i) appears in the range of 4.0 to 6.0 mA / cm ² and the second peak value of the current value (i) The width (Δi) (see 4 in FIG. 1) is less than 0.05 mA / cm ² C: the first peak value (i ₁ ) of the current value (i) is 4.0 to 6.0 mA / cm ² And the width (Δi) (see 4 in FIG. 1) of the second peak value of the current value (i) is 0.05 mA / cm ² or more.

(Note 7) Constant current electrodeposition coating: CCP500-1 (trade name, constant current electrodeposition apparatus manufactured by Takasago Seisakusho Co., Ltd.) is used for electrodeposition coating at a constant current density (bath temperature 30 ° C., distance between electrodes 15 cm) The pole ratio (anode / cathode = 1/2) was measured, and the polarization resistance value was graphed (see FIG. 3) to observe the increase in polarization resistance value.
A: An increase in polarization resistance is observed at a current density of 0.2 mA / cm ² , and deposition of a coating film is observed on the object to be coated.
B: No increase in polarization resistance value was observed at a current density of 0.2 mA / cm ^{2, and} an increase in polarization resistance value was observed at a current density of 0.25 mA / cm ² . Is recognized.
C: At a current density of 0.25 mA / cm ² , there is no increase in polarization resistance even after 15 minutes from the start of energization, and no coating film is deposited on the object to be coated.

(Note 8) Continuous film formation minimum temperature:
Using each cationic electrodeposition paint, the minimum continuous film formation temperature (MFT) was determined according to the contents described in (Note 4).

(Note 9) Amount of organic solvent in bath: 10 μl of each cationic electrodeposition paint is collected with a micro syringe and injected into GC-15A (manufactured by Shimadzu Corporation, trade name, gas chromatography) and measured under the following conditions: did.
Conditions: Column WAX-10 (manufactured by Spelco), column temperature at 5 ° C./min temperature increase, up to 200 ° C., carrier gas was measured with He.

Examples 2-8
The results of Examples 2 to 8 were obtained in the same manner as in Example 1 except that the contents in Table 3 were used. Furthermore, the test result of the coating film obtained by these Examples is combined with Table 3, and is shown.

  (Note 10) Organic solvent A: ethylene glycol monobutyl ether, SP value 8.87, water solubility is 100% by mass.

  (Note 11) Organic solvent B: diethylene glycol monobutyl ether, SP value 9.78, water solubility is 100% by mass.

Comparative Example 1
Cationic electrodeposition paint No. obtained in Production Example 19 1, 1.6% of the organic solvent A is added to the mass of the electrodeposition paint, and the electrodeposition paint No. 1 is added. 1B was produced.
The above cationic electrodeposition coating was bathed at 30 ° C., and a cold-rolled steel sheet (0.8 mm × 70 mm × 150 mm) treated with zinc phosphate was immersed as a cathode, the distance between the electrodes was 15 cm, and the electrode ratio (anode / cathode) = Current value measurement (Note 6) was performed at 1/2. Furthermore, constant current electrodeposition coating (Note 7) and continuous film formation minimum temperature (Note 8) were measured according to the following test methods.

Comparative Example 2
Cationic electrodeposition paint No. obtained in Production Example 20 2 was added 1.8% of organic solvent A with respect to the mass of the electrodeposition paint. 2B was produced. Electrodeposition coating was performed in the same manner as in Comparative Example 1.

Comparative Examples 3-7
The results of Comparative Examples 2 to 7 were obtained in the same manner as Comparative Example 1 except that the contents of Table 4 were used. Furthermore, the test result of the coating film obtained by these comparative examples is combined with Table 4, and is shown.

  (Note 12) Throwing power: Using a four-box method throwing power test jig as shown in Fig. 4, electrodeposition coating at a coating bath temperature of 30 ° C and a film thickness (side A) of 15 µm For 3 minutes. For evaluation of throwing power, the outer plate (A surface) film thickness, inner plate (G surface) film thickness, and "inner plate (G surface) / outer plate (A surface) = throwing power (%)" are measured. And evaluated.

(Note 13) Suitability for electrodeposition coating of galvannealed steel sheet: 0.8 x 150 x 70 mm galvannealed alloy treated with Palbond # 3020 (trade name, zinc phosphate treatment agent, manufactured by Nihon Parkerizing Co., Ltd.) The plated steel sheet is immersed as a cathode in an electrodeposition paint bath (30 ° C.) and electrodeposition is applied for 3 minutes at the same voltage as when the throwing power of (Note 12) is evaluated. The resulting coating film is 170 ° C. The number of pinholes in 10 × 10 cm is counted for the test piece after baking and curing for 20 minutes.
◎ indicates no pinholes.
○ indicates that one small pinhole (gas dent) is generated, but there is no problem as long as it can be covered with an intermediate coating film.
△ is 2-5 pinholes,
X indicates occurrence of 10 or more pinholes.

(Note 14) Anticorrosion property: A 0.8 × 150 × 70 mm cold-rolled steel sheet chemically treated with Palbond # 3020 (trade name, zinc phosphate treatment agent manufactured by Nihon Parkerizing Co., Ltd.) is immersed in each cationic electrodeposition coating. Electrodeposition coating was performed.
Subsequently, it baked for 20 minutes at 170 degreeC with the hot air dryer, and obtained the test board with a dry film thickness of 20 micrometers. A crosscut flaw is made in the coating film with a cutter knife so as to reach the base of the test plate, and this is subjected to a 35 ° C. salt spray test in accordance with JIS Z-2371 for 840 hours. Evaluation was made according to the following criteria depending on the coating surface state (blister) of the part.
◎: The maximum width of rust and blisters is 2.0 mm or less from the cut part (one side)
○ indicates that the maximum width of rust and blistering exceeds 2.0 and 3.0 mm or less (one side)
△ indicates that the maximum width of rust and blistering exceeds 3.0 mm from the cut and 3.5 mm or less (one side)
X indicates that the maximum width of rust and swelling exceeds 3.5 mm from the cut portion.

(Note 15) Finishing property: 0.8 × 150 × 70 mm cold-rolled steel sheet chemically treated with Palbond # 3020 (manufactured by Nihon Parkerizing Co., Ltd., trade name, zinc phosphate treating agent) is immersed in each cationic electrodeposition paint. The coating film obtained by electrodeposition coating was baked at 170 ° C. for 20 minutes with a hot air dryer, and the surface roughness of the electrodeposition coating film on the outer plate portion was measured using Surf Test 301 (trade name, manufactured by Mitutoyo Corporation). The Ra value was measured with a surface roughness measuring machine.
○: Ra value is less than 0.25 Δ: Ra value is 0.25 or more and less than 0.35 ×: Ra value exceeds 0.35

It is the graph which plotted the electric current value (i) with respect to the electricity supply time (t) at the time of electrodeposition coating, when performing cationic electrodeposition coating using a cationic electrodeposition coating material as a bath. It is a graph which shows the raise of the polarization resistance value when performing constant current electrodeposition coating, when performing cationic electrodeposition coating using a cationic electrodeposition paint as a bath. It is a graph which shows the continuous film formation minimum temperature. FIG. 3 is a model diagram of a “four-sheet throwing power test jig” used for a throwing power test.

Explanation of symbols

1. The first peak current value (i ₁ ) is shown.
2. The second peak current value (i ₂ ) is shown.
3. The minimum current value (i ₃ ) immediately before the _second peak current value (i ₂ ) appears is shown.
4). The width (Δi) of the second peak current value is shown.
5. It is a graph which shows the raise of the polarization resistance value in electric current density 0.2mA / cm < ² >.
6). Indicates the lowest continuous film formation temperature.
7. The outer plate (A surface) in the throwing power test jig of the four-sheet box method is shown.
8 shows the inner plate (G surface) in the throwing power test jig of the 4-box method.
9. An electrodeposition paint bath is shown.

  INDUSTRIAL APPLICABILITY The present invention can provide a coated article excellent in throwing power, suitability for electrodeposition coating on a galvannealed steel sheet, and finish.

Claims (8)

In a cationic electrodeposition coating in which a metal coating is immersed in a paint tank having a cationic electrodeposition coating and an electrode and energized, the first current value (i) with respect to the energization time (t) during the electrodeposition coating When the current-carrying conditions are such that the peak current value (i ₁ ) is 4.0 to 6.0 mA / cm ² , the width (Δi) of the second peak current value of the current value (i) is 0.05 mA. Cationic electrodeposition paint characterized by being less than / cm ² . A metal coating is immersed in a coating tank having a cationic electrodeposition coating and an electrode, and a coating film is deposited on the coating in the cationic electrodeposition coating at a constant current density of 0.2 mA / cm ^2. The cationic electrodeposition paint according to claim 1. In a cationic electrodeposition coating in which a metal coating is immersed in a coating tank having a cationic electrodeposition coating and an electrode and energized, the minimum continuous film formation temperature (MFT) of the cationic electrodeposition coating is 20 to 35 ° C. The cationic electrodeposition paint according to claim 1 or 2, wherein Based on the mass of the cationic electrodeposition coating bath, the content of the organic solvent (c) having a solubility parameter of 8 to 10 and a water solubility of 95% by mass or more is 0.01 to 1.0% by mass, and the cation The cationic electrodeposition paint according to any one of claims 1 to 3, wherein the total amount of the organic solvent in the electrodeposition paint bath is 0.01 to 2.0 mass% or less. For the total solid content of the base resin (a) and the curing agent (b) of the cationic electrodeposition paint, the following formula (1)

Formula (1)
(Wherein R ¹ represents an alkyl group having ¹ to 12 carbon atoms, and R ² represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). The cationic electrodeposition paint according to any one of claims 1 to 4, comprising 0.01 to 10% by mass of at least one tin ester compound. The xylene formaldehyde resin-modified amino group-containing epoxy resin obtained by reacting an xylene formaldehyde resin and an amino group-containing compound with an epoxy resin having an epoxy equivalent of 180 to 2,500 as the base resin (a). The cationic electrodeposition paint according to any one of the above. The electrodeposition coating method using the cationic electrodeposition coating material of any one of Claims 1-6. A coated article obtained by electrodeposition coating the cationic electrodeposition paint according to claim 1.

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