JPH05239386A - Composition for electrodeposition coating - Google Patents

Abstract

PURPOSE:To obtain the subject composition, comprising a lanthanum compound, excellent in corrosion and rust preventing properties and durability without using a rust preventing pigment such as a lead or a chromium compound causing problems in environmental pollution control measures and useful as automotive bodies, etc. CONSTITUTION:The objective composition comprises one or more lanthanum compounds such as lanthanum acetate in an amount within the range of preferably 0.1-10wt.% based on coating solids expressed in terms of the metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for electrodeposition coating composition capable of forming a coating film having excellent rust preventive properties.

[0002]

2. Description of the Related Art Electrodeposition paints are excellent in throwing power and can form coating films excellent in performance such as durability and corrosion resistance. For example, it is widely used for painting automobile bodies and painting electric appliances.

In order to further improve the anticorrosion property of the electrodeposition coating composition, a rust preventive pigment, for example, a lead compound such as lead chromate, basic lead silicate, strontium chromate or a chromium compound is often blended. However, the compound is a very harmful substance and its use is problematic in terms of pollution control.
Therefore, as a non-toxic or low-toxic rust preventive pigment that replaces the lead compound or the chromium compound, conventionally, zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc molybdate, calcium molybdate, zinc oxide, iron oxide, The use of aluminum phosphomolybdate, zinc phosphomolybdate, etc. has been studied (eg Japanese Patent Publication No. 3-7).
No. 224, etc.), these compounds do not have the rust preventive ability of the above-mentioned lead compounds and chromium compounds, and zinc-based pigments are unstable in an electrodeposition coating bath. Not practically satisfactory.

[0004]

SUMMARY OF THE INVENTION The main object of the present invention is to form a coating film having excellent anticorrosion properties equivalent to or better than the above-mentioned rust-preventive pigments which are problematic in pollution control. The present invention is to provide a composition for electrodeposition coating composition.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies as to a metal species that exhibits an excellent rust preventive ability equal to or higher than that of a lead compound and a chromium compound in an electrodeposition coating, and as a result, The lanthanum compound has an extremely excellent anticorrosive ability, and by adding it to an electrodeposition coating composition, it was found that it is possible to form an electrodeposition coating film having excellent anticorrosion properties, and the present invention is provided. It was completed.

Thus, the present invention provides a composition for electrodeposition coating composition containing at least one lanthanum compound.

The lanthanum compound used in the present invention is an organic or inorganic water-soluble or sparingly water-insoluble compound containing lanthanum as a constituent component. For example, lanthanum such as lanthanum acetate, lanthanum lactate and lanthanum oxalate. And organic lanthanum nitrate, lanthanum hydroxide, lanthanum oxide, inorganic lanthanum compounds such as lanthanum tungstate. Of these, a water-soluble lanthanum compound such as an organic acid salt is advantageous because it dissolves in a bath and an effect can be obtained even when used in a small amount. Lanthanum acetate is particularly preferable.

The content of the lanthanum compound in the composition for electrodeposition coating composition can be varied over a wide range depending on the other components in the composition, the application, etc., but it is usually based on the solid content of the coating composition. Therefore, it is preferably in the range of 0.1 to 10% by weight, especially 0.5 to 2% by weight in terms of metal.

The introduction of the above-mentioned lanthanum compound into the composition for electrodeposition coating is not particularly limited, and it can be carried out in the same manner as in the ordinary pigment dispersion method. For example, the lanthanum compound is previously added to the dispersion resin. Can be dispersed to prepare a dispersion paste, which can be blended, or in the case of a water-soluble lanthanum compound, it can be blended as it is after the resin emulsion for a coating is prepared. Examples of preferable cationic resins as the dispersing resin include epoxy type tertiary amine type resins, acrylic type quaternary ammonium salt type resins, and epoxy type quaternary ammonium salt type resins.

The dispersion paste can be prepared from the lanthanum compound and the dispersion resin in the same manner as in the case of adding pigments to a usual composition for electrodeposition coating, and specifically, for example, It can be carried out by dispersing the lanthanum compound together with the above-mentioned dispersing resin and the like in a dispersion mixer such as a ball mill to form a paste.
At that time, other pigments and the like may be dispersed together with the lanthanum compound.

Other pigments that can be used are not particularly limited as long as they are pigments usually used in electrodeposition paints, and any pigment can be used, for example, coloring pigments such as titanium oxide, carbon black and red iron oxide; Extender pigments such as clay, mica, barita, talc, calcium carbonate, silica;
Examples include rust preventive pigments such as aluminum phosphomolybdate and aluminum tripolyphosphate.

The composition for electrodeposition coating composition of the present invention may be either anionic type or cationic type, but in general, cationic type is preferable from the viewpoint of corrosion resistance, and the base resin is epoxy type or acrylic type. Any of polybutadiene-based, alkyd-based, and polyester-based resins can be used. Among them, polyamine resins typified by amine-added epoxy resins are preferable.

Examples of the amine-added epoxy resin include (i) an adduct of a polyepoxide compound and a primary mono- and polyamine, a secondary mono- and polyamine, or a primary and secondary mixed polyamine (for example, US Pat. 984,299
(Ii) Addition products of polyepoxide compounds with ketiminated secondary mono- and polyamines having primary amino groups (see, for example, US Pat. No. 4,017,438); (iii) ) A reaction product obtained by etherification of a polyepoxide compound and a ketiminized hydroxy compound having a primary amino group (see, for example, JP-A-59-43013).

The polyepoxide compound used for producing the amine-added epoxy resin is a compound having two or more epoxy groups in one molecule, and generally has at least 20.
0, preferably 400 to 4000, more preferably 80
Those having a number average molecular weight in the range of 0 to 2000 are suitable, and those obtained by the reaction of a polyphenol compound and epichlorohydrin are particularly preferable.

Examples of the polyphenol compound which can be used for forming the polyepoxide compound include, for example, 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-dihydroxydiphenyl sulfone, phenol novolak, cresol novo Rack and the like.

The polyepoxide compound is a polyol,
It may be one partially reacted with polyether polyol, polyester polyol, polyamidoamine, polycarboxylic acid, polyisocyanate compound, etc., and also one grafted with ε-caprolactone, acrylic monomer, etc. Good.

The above-mentioned base resin may be either an external cross-linking type or an internal (or self) cross-linking type, and examples of the curing agent used in the case of the external cross-linking type resin include (blocks). ) It may be a conventionally known crosslinking agent such as a polyisocyanate compound or an amino resin,
A block polyisocyanate compound is particularly preferable. Further, as the internal cross-linking type resin, a resin having a block isocyanate group introduced into the molecule is preferable.

The block polyisocyanate compound which can be used in the above external crosslinking type can be an addition reaction product of a theoretical amount of the polyisocyanate compound and an isocyanate blocking agent. Examples of the polyisocyanate compound include aromatic compounds such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanatomethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate, alicyclic compounds, or Ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, in excess of aliphatic polyisocyanate compounds and these isocyanate compounds,
Examples thereof include a terminal isocyanate-containing compound obtained by reacting a low molecular weight active hydrogen-containing compound such as castor oil.

On the other hand, the isocyanate blocking agent is
A block isocyanate compound that is added to the isocyanate group of a polyisocyanate compound and blocks by the addition is stable at room temperature and dissociates and releases the blocking agent when heated to about 100 to 200 ° C. It is desirable that the isocyanate group can be regenerated. Examples of the blocking agent satisfying such requirements are lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methylethylketoxime and cyclohexanone oxime; phenols such as phenol, para-t-butylphenol and cresol. Compounds; n-butanol, 2-
Aliphatic alcohols such as ethylhexanol; aromatic alkyl alcohols such as phenylcarbinol and methylphenylcarbinol; ether alcohol compounds such as ethylene glycol monobutyl ether. Of these, oxime-based and lactam-based blocking agents are particularly preferred from the viewpoint of curability of the electrodeposition coating composition, because they are blocking agents that dissociate at a relatively low temperature.

The introduction of the block isocyanate group into the base resin in the case of producing a base resin of a type having a block isocyanate group in the base resin molecule and self-crosslinking can be carried out by using a conventionally known method. , For example,
It can be introduced by reacting the free isocyanate group in the partially blocked polyisocyanate compound with the active hydrogen-containing portion in the base resin.

In the case of a cationic resin, the base resin is generally neutralized and made water-soluble by neutralizing the resin with a water-soluble organic acid such as formic acid, acetic acid or lactic acid. In the case of an anionic resin, neutralization with an alkali such as amine or alkali metal hydroxide instead of the water-soluble organic acid is carried out to make it water-soluble / dispersed. Can be done.

If desired, the composition for electrodeposition coating composition of the present invention may be mixed with a coating additive such as an organic solvent, a pigment dispersant and a coating surface adjusting agent.

The composition for electrodeposition coating composition of the present invention may optionally contain an organic tin compound as a curing catalyst. Examples of the organic tin compound include organic tin oxides such as dibutyl tin oxide and dioctyl tin oxide; dibutyl tin dilaurate, dioctyl tin dilaurate, dibutyl tin diacetate, dioctyl tin benzoate oxy, dibutyl tin benzoate oxy, dioctyl tin dibenzoate, Examples thereof include alkyltin compounds of aliphatic or aromatic carboxylic acids such as dibutyltin dibenzoate. The compounding amount and the compounding method of the organotin compound can be the same as those generally used in the past.

The composition for electrodeposition coating composition of the present invention can be coated on a desired substrate surface by electrodeposition coating. The electrodeposition coating is generally diluted with deionized water or the like so that the solid content concentration is about 5 to 40% by weight, and the pH is further adjusted to 5.5 to 9.
The electrodeposition bath composed of the composition for electrodeposition coating composition of the present invention adjusted within the range of 0 can be usually adjusted to a bath temperature of 15 to 35 ° C. and a load voltage of 100 to 400 V.

The film thickness of the electrodeposition coating film which can be formed using the composition of the present invention is not particularly limited, but in general, it is preferably in the range of 10 to 40 μm based on the cured coating film. The baking temperature of the coating film is generally 100 to 2
A range of 00 ° C is suitable.

[0026]

According to the present invention described above, by incorporating the lanthanum compound into the composition for electrodeposition coating, without using a rust preventive pigment such as a lead compound which is problematic in terms of pollution control, It is possible to provide a composition for electrodeposition coating which gives an electrodeposition coating film having an excellent rust preventive property which is almost equal to or higher than that in the case of incorporating the rust preventive pigment.

It is not clear why the composition for electrodeposition coating composition of the present invention can obtain such excellent rust-preventing property, but it is assumed that the lanthanum compound exerts some desired action at the interface with the article to be coated. Presumed. Further, it was confirmed that when the composition for electrodeposition coating composition of the present invention is a block isocyanate curing type, the curability of the electrodeposition film is enhanced. It is presumed that this is because the lanthanum compound also acts as a block isocyanate dissociation catalyst, which can contribute to the improvement of the physical properties of the coating film at low temperature curing.

[0028]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In addition, "part" and "%" show a "weight part" and "weight%."

Production of Pigment Paste Each of the compounding ingredients shown in the following Table 1 was added to a ball mill and dispersed for 40 hours to obtain pigment pastes of Compounding 1 to 7.

[0030]

[Table 1]

Example 1 1900 parts of Epon 1004 (* 1) was dissolved in 1012 parts of butyl cellosolve, 124 parts of diethylamine was added dropwise, and the mixture was kept at 120 ° C. for 2 hours to obtain an epoxy resin-amine adduct having an amine value of 47. It was

Next, 1000 parts of a dimer acid type polyamide resin having a amine value of 100 [trade name "Versamide 460" and manufactured by Henkel Hakusui Co., Ltd.] was dissolved in 429 parts of methyl isobutyl ketone and heated under reflux at 130 to 150 ° C. The produced water was distilled off to change the terminal amino group of the amide resin to ketimine. This is kept at 150 ° C. for about 3 hours and cooled to 60 ° C. after the distillation of water is stopped. Then add this to the epoxy resin-amine adduct and add 1
Heat to 00 ° C, hold for 1 hour, then cool to room temperature to give a solid content of 6
A varnish of epoxy resin-amino-polyamide addition resin with 8% and an amine value of 65 was obtained.

103 parts of the varnish obtained above (70 parts by resin solid content), 30 parts of 2-ethylhexyl alcohol block of xylylene diisocyanate (by solid content) and 15 parts of 10% acetic acid were mixed and stirred uniformly. Then, 150 parts of deionized water was added dropwise over about 15 minutes while stirring vigorously to obtain a clear emulsion for cationic electrodeposition with a solid content of 33.6%. To 298 parts of this clear emulsion, 36.3 parts of the pigment paste having the formulation shown in Formula 1 of Table 1 above was added with stirring, and diluted with 271.3 parts of deionized water to obtain a cationic electrodeposition coating composition.

(* 1) Epon 1004: Bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd. and having an epoxy equivalent of about 950.

Examples 2 and 3 and Comparative Examples 1 and 2, except that the pigment paste of the formulation 1 in Example 1 was replaced by the pigment pastes of the formulations shown in the formulations 2, 3, 6 and 7 of Table 1 above, respectively. The same operation as in Example 1 was performed to obtain the cationic electrodeposition coating composition shown in Table 1.

Example 4 In Example 1, after the vehicle components and the like were uniformly stirred when preparing the clear emulsion, 10 parts of a 10% lanthanum acetate aqueous solution (1 part by solid content) was added, and the pigment paste of Formula 1 was replaced. The same operation as in Example 1 was carried out except that the pigment paste shown in Formula 4 in Table 1 above was used to obtain the cationic electrodeposition coating composition of Example 4.

Example 5 Example 1 was repeated except that 2 parts of dioctyltin dibenzoate was added at the time of making clear emulsion in Example 1 and the pigment paste shown in Formula 5 of Table 1 above was used in place of the pigment paste of Formula 1 above. The same operation as in Example 5 is performed.
A cationic electrodeposition paint of

Coating test The electrodeposition coating compositions obtained in Examples 1-5 and Comparative Examples 1-2 were subjected to chemical conversion treatment with Palbond # 3030 (a zinc phosphate treatment agent manufactured by Nippon Parkerizing Co., Ltd.) 0.8 × 150 ×. 70 m
m cold-rolled dull steel plate was dipped, and electrodeposition coating was performed using it as a cathode. The electrodeposition conditions were a voltage of 300 V, an electrodeposition coating film having a film thickness (based on the dry film thickness) of about 20 μm was formed, washed with water, and then baked. The baking was carried out by using an electric hot air dryer with the atmospheric temperature at four stages and the baking time at 20 minutes. The performance test results of the obtained coated plate are shown in Table 2 below.

[0039]

[Table 2]

The performance test was carried out according to the following method.

(* 2) Anticorrosion property: A cross cut scratch was put into the electrodeposition coating film with a knife so as to reach the substrate, and this was JIS.
A salt spray test was conducted according to Z2371 for 840 hours, and evaluated by rust from knife scratches and blistering width.

⊚: The maximum width of rust or blisters is less than 1 mm from the cut portion (one side).

◯: The maximum width of rust or blisters is 1 mm or more and less than 2 mm (one side) from the cut portion. Δ: The maximum width of rust or blisters is 2 mm or more and less than 3 mm (one side) from the cut portion, and blisters are considerably noticeable on the flat surface portion.

X: The maximum width of rust or blisters is 3 mm or more from the cut portion, and blisters are observed on the entire coated surface.

(* 3) Curability: The coated surface of each of the obtained electrodeposited coated plates was covered with four layers of gauze impregnated with methyl isobutyl ketone to give a length of about 3-4 cm at a pressure of about 4 kg / cm ^2. The appearance of the coated surface after 20 reciprocating rubbing was visually evaluated.

◯: No scratch is observed on the coated surface.

Δ: Scratches are recognized on the coated surface, but the base material is not visible.

X: The coating film is dissolved and the substrate is visible.

(* 4) Impact resistance: Using a DuPont type impact tester, the impact diameter is 1/2 inch and the falling weight is 50c.
The test was conducted under the conditions of m and a measurement atmosphere of 20 ° C., and the impacted recesses were visually evaluated.

◯: No abnormality

Δ: Some small cracks are seen.

X: A large crack is seen.

(* 5) 3 coat image clarity: on the electrodeposition coated surface,
Kansai Paint Co., Ltd. Amino-alkyd intermediate coating "Amirak TP-37 Gray" was applied by spray coating to a dry film thickness of about 35 microns, baked at 140 ° C for 20 minutes, and then Kansai Paint Co., Ltd. Amino-alkyd top coat paint "Amirak TM13 White" made by Spray Co., Ltd. was applied by spray coating so that the dry film thickness would be about 35 microns, and baked at 140 ° C for 20 minutes. Manufactured by K.K.) was used for evaluation.

⊚: Measured value of 80 or more ◯: Measured value of 75 or more and less than 80 Δ: Measured value of 70 or more and less than 75 ×: Measured value of less than 70

Claims (3)

[Claims] 1. A composition for electrodeposition coating composition, which comprises at least one lanthanum compound. 2. The composition according to claim 1, which contains the lanthanum compound in the range of 0.1 to 10% by weight in terms of metal based on the solid content of the coating material. 3. The composition according to claim 1, wherein the lanthanum compound is lanthanum acetate.