JPH0753902A - Electrodeposition coating composition - Google Patents

Abstract

PURPOSE:To form an electrodeposition coating film excellent in corrosion resistance without impairing the stability of an electrodeposition coating compsn. used by incorporating a specified amt. of zinc oxide coated with an inorg. siloxane compd. and/or an org. acrylic compd. into the compsn. CONSTITUTION:A paste is obtd. by adding an inorg. siloxane compd. (having siloxane bonds in the main chain and a number-average mol.wt. of 140-2,000) and/or an org. acrylic compd. (having a wt.-average mol.wt. of 15,000-70,000 and a number average mol.wt. of 10,000-30,000) to an active zinc oxide having a particle size of 0.01-0.1 um and a specific surface area of 40-100m<2>/g and dispersing them in each other with a dispersing machine. The paste is compounded into an electrodeposition coating compsn. in an amt. of 0.5-10 pts.wt. based on 100 pts.wt. solid resin content of the compsn., which is then diluted with deionized water to a 5-40wt.% concn., and adjusted to a pH of 5. 5-9.0 to provide an electrodeposition bath. A 10-40mum-thick coating film is formed at a bath temp. of 15-35 deg.C under a voltage applied of 100-400V, and baked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an 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 a coating film having excellent performance such as durability and corrosion resistance. For example, it is widely used for painting automobile bodies, painting electric appliances, and the like.

In order to further improve the anticorrosion property of the electrodeposition paint, 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 non-toxic or low-toxic rust-preventive pigments replacing the lead compounds, zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc molybdate, calcium molybdate, zinc oxide (zinc white), oxidation The use of iron, aluminum phosphomolybdate, zinc phosphomolybdate, etc. has been investigated, but these compounds do not have the anticorrosive ability of the above-mentioned lead compounds and chromium compounds, and zinc-based pigments have a low electrical conductivity. Since it is unstable in the coating bath, it is not practically satisfactory.

[0004]

The main object of the present invention is to form a coating film having an excellent anticorrosive property equivalent to or better than the above-mentioned rust-preventive pigment, which is problematic in terms of pollution control, without using it. A possible electrodeposition coating composition.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on a metal species that exhibits an excellent anticorrosive ability equivalent to or higher than that of a lead compound or a chromium compound in an electrodeposition coating, and as a result, By blending a specific amount of zinc white coated with a coating of a specific compound, an electrodeposition coating composition which gives a coating having very excellent anticorrosion properties without impairing the stability of the coating can be obtained. This has led to the completion of the present invention.

That is, the present invention contains 0.5 to 10 parts by weight of zinc white, the surface of which is coated with a siloxane inorganic compound and / or an acrylic organic compound, per 100 parts by weight of the resin solid content of the composition. The present invention provides an electrodeposition coating composition characterized by the above.

In the present invention, zinc white (hereinafter sometimes referred to as "encapsulated zinc white") having a surface coated with a siloxane-based inorganic compound and / or an acrylic organic compound has a particle size of 0.01 to 0.1 μm, specific surface area 40
To 100 m ² / g of so-called active zinc white so-called active zinc white, siloxane-based inorganic compound or acrylic-based organic compound alone compound or the compounding ratio of the compound containing both are appropriately mixed and refluxed. By a method such as reacting in the presence of an acid or alkali catalyst, the one whose surface is coated with the film of the above compound is separated,
A product obtained by drying and pulverizing after washing can be used, and examples thereof include those disclosed in JP-A-4-161245.

That is, as the siloxane-based inorganic compound,

[0009]

[Chemical 1]

(Wherein n is an integer of 1 or more, R is an alkyl group, a reactive functional group, an alkoxyl group or hydrogen), which is an inorganic compound having a siloxane bond in the main chain, and is used as a monomer, an oligomer or a polymer. Inorganic compounds having siloxane in the main chain and carbon in the terminal or side chain may be used, and the polymer of such inorganic compounds preferably has a number average molecular weight of 140 to 2,000. Examples of commercially available siloxane-based inorganic compounds having a siloxane bond in the main chain include: Colcoat Co., Ltd .: ethyl silicate (containing monomer), Colac Co .: ethyl silicate 40C, ethyl silicate 48S (high polymerization without monomer), Dainippon Ink. Chemical Industry Co., Ltd .: Acridic BZ-1163 is mentioned.

As the acrylic organic compound, an acrylic chain having an acryloyl group CH ₂ ═CHCO— or a methacryloyl group CH ₂ ═C (CH ₃ ) CO— in the main chain,

[0012]

[Chemical 2]

An organic compound having one or more functional groups (n, p and q are integers) selected from the group consisting of can be used. The weight average molecular weight of the above organic compound is 1
5,000 to 70,000 and the number average molecular weight is 1
About 30,000 to 30,000 is preferable. Among such acrylic organic compounds, examples in which the functional group is a monomer include acrylic acid, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, acrylamide, N-methylol acrylamide methacrylic acid, hydroxypropyl methacrylate, glycidyl. Examples of the raw material monomer of acrylic resin such as methacrylate. Commercially available acrylic organic compounds having an acryloyl group or a methacryloyl group in the main chain include those manufactured by Dainippon Ink and Chemicals, Inc .: Acridic A-9510, BZ-116.
0, HZ-448. These are polymers containing tertiary amino groups.

When the siloxane-based inorganic compound and the acrylic-based organic compound are polymers, they can also be converted into crosslinked polymers by generating radicals between the molecules of the main chain.

Examples of commercially available encapsulated zinc white include FC zinc oxide MI-W (manufactured by Hayashi Metal Industry Co., Ltd.) and Microbeads FINEX25 (manufactured by Sakai Chemical Co., Ltd.).

The encapsulated zinc white obtained as described above can be introduced into the electrodeposition coating composition by the same method as in the case of adding a pigment to the electrodeposition coating composition.
Specifically, for example, first, the encapsulated zinc white together with an appropriate dispersing resin component is sufficiently stirred with a mixer such as a disper to prepare a dispersion resin adsorbed on the encapsulated zinc white, This is mixed with a pigment paste prepared by treating pigments and the like with a dispersing resin component and the like in a dispersion mixer such as a ball mill to prepare a paste-like material, and used as a binder (vehicle) resin component for electrodeposition paint. A method of blending may be mentioned. In this way, the paste is prepared separately from the pigments and then mixed with the paste of the pigments, etc., because the capsule (coating film) of the encapsulated zinc white can be dispersed and mixed in the paint without crushing, and electrodeposition can be performed. It is suitable because it does not impair the stability of the paint.

As the above-mentioned pigments, any pigment can be used without particular limitation as long as it is a pigment usually used in electrodeposition paints. For example, coloring pigments such as titanium oxide, carbon black and red iron oxide; clay, mica and barita. , Talc, calcium carbonate, silica and other extender pigments; and aluminum phosphomolybdate, aluminum tripolyphosphate and other rust preventive pigments.

The content of the encapsulated zinc white in the electrodeposition coating composition of the present invention is such that the resin solid content in the composition is 100.
It is essential that the amount is 0.5 to 10 parts by weight, preferably 1 to 3 parts by weight. If the content is less than 0.5 part by weight, the rust preventive property of the coating film formed is not sufficient.
If the amount exceeds 0 parts by weight, the stability of the coating composition decreases, which is not preferable.

The 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, acrylic type, Although any of polybutadiene-based, alkyd-based, and polyester-based resins can be used, polyamine resins represented by amine-added epoxy resins are preferred.

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 polyamine (for example, US Pat. 984
299); (ii) Addition products of polyepoxide compounds with secondary mono- and polyamines having ketiminated primary amino groups (see, for example, US Pat. No. 4,017,
No. 438); (iii) a reaction product obtained by etherification of a polyepoxide compound and a ketiminated hydroxy compound having a primary amino group (see, for example, JP-A-59-43013). .

The polyepoxide compound used in the production of the amine-added epoxy resin is a compound having two or more epoxy groups in one molecule, and generally at least 20.
0, preferably 400 to 4,000, more preferably 8
Those having a number average molecular weight in the range of 00 to 2,000 are suitable, and those obtained by reacting a polyphenol compound with epichlorohydrin are particularly preferable. Examples of the polyphenol compound that can be used to form 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-dihydroxydiphenyl sulfone, phenol novolac, cresol novolac and the like can be mentioned.

The polyepoxide 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, and further, ε-caprolactone, an acrylic monomer or the like. May be graft-polymerized.

The above-mentioned base resin may be of either an external cross-linking type or an internal (or self) cross-linking type, and examples of the curing agent used in combination with the external cross-linking type resin include (block ) It can be a conventionally known crosslinking agent such as a polyisocyanate compound or an amino resin,
A blocked polyisocyanate compound is particularly preferable. Further, as the internal cross-linking type resin, one introduced with a block polyisocyanate type is suitable.

The blocked isocyanate compound that can be used in the above-mentioned external crosslinking type can be an addition reaction product of a theoretical amount of a 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 aliphatic compounds. Group polyisocyanate compounds and excesses of these isocyanate compounds in ethylene glycol, propylene glycol,
Examples thereof include a terminal isocyanate-containing compound obtained by reacting a low-molecular active hydrogen-containing compound such as trimethylolpropane, hexanetriol and castor oil.

On the other hand, the above-mentioned isocyanate blocking agent is one which blocks by adding to the isocyanate group of the polyisocyanate compound, and the blocked isocyanate compound produced by the addition is stable at room temperature and when heated to about 100 to 200 ° C. It is desirable that the blocking agent can be dissociated to regenerate a free isocyanate group. Examples of the blocking agent satisfying such requirements are lactam compounds such as ε-caprolactam and γ-butyrolactam; methylethylketoxime,
Oxime-based compounds such as cyclohexanone oxime; phenol-based compounds such as phenol, para-t-butylphenol and cresol; aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatics such as phenylcarbinol and methylphenylcarbinol Alkyl alcohols; ether alcohol compounds such as ethylene glycol monobutyl ether and the like can be mentioned.

Of these, the oxime-based and lactam-based blocking agents are blocking agents that dissociate at a relatively low temperature, and thus are particularly preferable from the viewpoint of curability of the electrodeposition coating composition.

As a method of introducing a blocked isocyanate group into a base resin in a type having a blocked isocyanate group in a base resin molecule and self-crosslinking, a conventionally known method can be used. For example, a partially blocked polyisocyanate compound can be used. It can be introduced by reacting the free isocyanate group therein with the active hydrogen-containing portion in the base resin.

In the case of a cationic resin, the base resin is usually neutralized and made water-soluble by neutralizing the resin with a water-soluble organic acid such as formic acid, acetic acid or lactic acid to make it water-soluble or water-dispersible. In the case of an anionic resin, it can be carried out by neutralizing with an alkali such as amine or alkali metal hydroxide in place of the water-soluble organic acid, and solubilizing / dispersing in water. .

If desired, the electrodeposition coating composition of the present invention may contain coating additives such as an organic solvent, a pigment dispersant, a coating surface modifier, and a curing catalyst such as an organic tin catalyst. .

The electrodeposition coating composition of the present invention can be applied to 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 9.0.
The electrodeposition bath composed of the electrodeposition coating composition of the present invention adjusted to within the range of 1 is usually adjusted to a bath temperature of 15 to 35 ° C. and a load voltage of 1
It can be performed under the condition of 00 to 400V.

The film thickness of the electrodeposition coating composition which can be formed using the composition of the present invention is not particularly limited, but it is generally 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
A range of 200 ° C is suitable.

[0032]

[Effects and Effects of the Invention] When zinc flower is used as it is in the electrodeposition coating, its surface activity may cause poor dispersion or agglomeration of the paste at the time of enamelization with the resin for the electrodeposition coating, or may cause electrodeposition. Although there are problems such as a decrease in the stability of the paint bath and an increase in filtration residue, by using zinc white whose surface is coated with a specific compound as in the present invention, such a coating film is It improves the stability of the flower in the electrodeposition coating bath and, on the other hand, melts it together with the resin for the electrodeposition coating during baking of the formed electrodeposition coating film to make the zinc white exhibit anticorrosion properties. It is presumed to have been resolved.

Therefore, according to the present invention, the electrodeposition coating composition contains a specific amount of zinc white, the surface of which is coated with a siloxane-based inorganic compound and / or an acrylic-based organic compound. PROBLEM TO BE SOLVED: To provide an electrodeposition coating composition which gives an electrodeposition coating film having an excellent rust-preventing property which is almost equal to or higher than the case where the rust-preventing pigment is blended, without using the rust-preventing pigment such as a lead compound Is what you can do.

[0034]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. "Parts" and "%" mean "parts by weight" and "% by weight".

Production of Paste Containing Encapsulated Zinc White Pastes A and B were obtained by mixing the compounding ingredients shown in Table 1 below and dispersing them with a disper for 20 hours.

Manufacture of Pigment Paste The ingredients shown in Table 1 were added to a ball mill.
It was dispersed for 40 hours to obtain pigment pastes of Formulas 1 to 3.

[0037]

[Table 1]

Example 1 1,900 parts of Epon 1004 ^{(* 1)} was dissolved in 1,012 parts of butyl cellosolve, and 124 parts of diethylamine was added to 80 parts.
After dropping at -100 ° C and holding at 120 ° C for 2 hours, an epoxy resin-amine adduct having an amine value of 47 was obtained.

Next, 1,000 parts of a dimer acid type polyamide resin having an amine value of 100 (trade name "Versamide 460", manufactured by Henkel Hakusui Co., Ltd.) was dissolved in 429 parts of methyl isobutyl ketone and heated under reflux at 130 to 150 ° C. Then, 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 solid content of resin), 30 parts of 2-ethylhexyl alcohol blocked product of xylylene diisocyanate (by solid content), 1
After 15 parts of 0% acetic acid was mixed and uniformly stirred, 150 parts of deionized water was added dropwise over about 15 minutes with strong stirring to obtain a cationic emulsion for cationic electrodeposition having a solid content of 33.6%. To 298 parts of this clear emulsion, 10 parts of the paste A in Table 1 and 46.3 parts of the pigment paste having the formulation shown in Formula 1 in the table are added with stirring, and diluted with 271.3 parts of deionized water to prepare a cationic electrodeposition coating. Got

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

Example 2 The same operation as in Example 1 was carried out except that the paste B shown in Table 1 was used instead of the paste A to obtain the cationic electrodeposition coating composition of Example 2.

Comparative Example 1 The same operation as in Example 1 was carried out except that the paste A was not blended to obtain a cationic electrodeposition coating composition of Comparative Example 1.

Comparative Examples 2 and 3 In Comparative Example 1, instead of the pigment paste of Formula 1,
Cationic electrodeposition paints of Comparative Examples 2 and 3 were obtained in the same manner as Comparative Example 1 except that the pigment pastes of Formulations 2 and 3 were used.

Coating test In the electrodeposition paints obtained in Examples 1 and 2 and Comparative Examples 1 to 3,
0.8 × 150 × 70 chemical conversion treated with Palbond # 3020 (Nippon Parkerizing Co., Ltd., zinc phosphate treatment agent)
A mm cold rolled dull steel plate was dipped, and electrodeposition coating was performed using it as a cathode. The electrodeposition conditions were a voltage of 250 V, and 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. For baking, the ambient temperature is 4
It was carried out using an electric hot air drier with the baking time set to 20 minutes. The performance test results of the obtained coated plate are shown in Table 2 below. Table 3 shows the stability of each electrodeposition paint bath.

[0046]

[Table 2]

[0047]

[Table 3]

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

(* 2) Anticorrosion: Cross-cut scratches were made on the electrodeposition coating film with a knife so as to reach the base, and this was JIS
A salt spray test was performed for 840 hours according to Z2371, 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 from the cut part 2
Less than mm (one side). Δ: The maximum width of rust or blisters is 2 mm or more from the cut part 3
Less than mm (one side) and the blister is noticeable on the flat surface. ×: 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 electrodeposition coated plates obtained 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 rubbing 20 times was visually evaluated.

◯: No scratch is observed on the coated surface. Δ: A scratch is observed on the coated surface, but the base material is not visible. X: The coating film is dissolved and the base material is visible.

(* 4) Impact resistance: Using a DuPont type impact tester, the diameter of the impact center is 1/2 inch, the height of the falling weight is 50 cm,
The test was carried out under the condition of 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 "Amilak 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-based top coating "Amilak TM13 White" was applied by spray coating to a dry film thickness of about 35 microns and baked at 140 ° C for 20 minutes. The image clarity measuring device [Suga Tester ( Co., Ltd.].

⊚: 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

(* 6) Paint bath stability: Electrodeposition paint at 30 ° C
After stirring for 1 month in a state of being kept at 1, the mixture was filtered through a 400-mesh wire net, and the amount of the residue was evaluated according to the following criteria.

◎: Less than 5 mg / l ○: 5 mg / l or more and less than 10 mg / l △: 10 mg / l or more and less than 15 mg / l ×: 15 mg / l or more

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C09C 1/04 PAF

Claims (1)

[Claims] 1. A zinc white obtained by coating the surface with a siloxane-based inorganic compound and / or an acrylic organic compound,
An electrodeposition coating composition comprising 0.5 to 10 parts by weight per 100 parts by weight of resin solids of the composition.