JPH01298198A - Formation of high-corrosion resistant cationic electrodeposited film - Google Patents

Abstract

PURPOSE:To form a high-corrosion resistant cationic electrodeposited film by blending water dispersion of specified cation-base wax with epoxy-base cationic electrodeposition coating and performing electrodeposition coating for a material to be coated in this bath, heating and curing the deposited film. CONSTITUTION:A high-corrosion resistant cationic electrodeposition coating bath is prepared by adding about 1-10 pts.wt. cation-base wax having surface tension (about 30-45dyne/cm<2>) of >=5dyne/cm<2> layer than a film formed from epoxy-base cationic electrodeposition coating (heretofore utilized amine-additional epoxy resin) as water dispersion to 100 pts.wt. epoxy-base cationic electrodeposition coating. Further solid content of this bath is regulated to about 15-25wt.% and as the cation-base wax, carnauba wax, bees wax and polyethylene wax, etc., are utilized. Electrodeposition coating is performed for a material to be coated under the conditions of about 20-30 deg.C bath temp., about 100-400V voltage and about 1-5 minutes time for applying electric current while utilizing this bath. The deposited film formed thereby is washed and baked at about 150-230 deg.C in about 10-30 minutes to obtain the cured film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a highly anticorrosive epoxy cationic electrodeposition coating.

Makibei 9 10 μ/-1Δ Overview■ Electrodeposition coating has traditionally been used in the fields of automobiles, electrical equipment, etc. compared to air spray painting using organic solvent-based paints or electrostatic spray painting. It has been widely put into practical use because it has the characteristics of good throwing power and the ability to easily obtain a coating film with a relatively uniform thickness. In particular, recently, since cationic electrodeposition coating forms a coating film with excellent corrosion resistance, it is being replaced by anionic electrodeposition coating in fields where corrosion resistance is important, such as automobiles. The use of cationic electrodeposition coating has improved corrosion resistance, but it has not been used in environments where salts, etc., used to prevent roads from freezing in cold regions such as North America and Northern Europe, remain indefinitely. The reality is that corrosion progresses to a high degree in the lower parts of automobiles, and a coating film with sufficient anticorrosion properties has not yet been obtained.

In general, cationic electrodeposition coating uses an electrodeposition coating whose vehicle components are an amine-added epoxy resin and a blocked isocyanate compound as a crosslinking agent as a coating bath to form a precipitated coating film on the object to be coated, and then heats this coating. Then, a cured coating film is formed by flow crosslinking, but the coating film obtained in this way has a high hydrophilicity, such as an amine-added epoxy resin, as the base resin. When the surface tension increases and the material is exposed to a corrosive substance for a long period of time, it gradually becomes more compatible with the corrosive substance, and the substance permeates through the coating and corrodes the underlying metal. Therefore, the corrosion resistance is inferior.

. The purpose of the present invention is to solve the above-mentioned problems in cationic electrodeposition finishing methods by forming a cationic electrodeposition coating that maintains a low surface tension for a long period of time. As a result of extensive research, we found that an epoxy cationic electrodeposition paint is blended with an aqueous dispersion of a cationic wax that has a surface tension lower in a specific range than the coating film formed from the epoxy cationic electrodeposition paint. It was discovered that the coating film formed by applying an electrocoated paint as a bath paint to an object to be coated, forming a precipitated coating film on the object, and then heating the coating film has excellent anticorrosion properties, and has developed the present invention. It was completed.

The epoxy-based cationic electrodeposition paint used in the present invention includes polyamine resins such as amine-added epoxy resins conventionally used in the field of cationic electrodeposition paints,
For example, adducts of polyepoxides with primary mono- and polyamines, secondary polyamines, or mixed primary and secondary polyamines (see, for example, U.S. Pat. No. 3,984,299).
; Adducts of polyepoxides with secondary mono- and polyamines having ketiminated primary amino groups (see, for example, U.S. Pat. No. 4.01.7.438): polyepoxides and ketiminated primary amino groups; A reaction product obtained by etherification with a hydroxy compound having (for example, JP-A-59-430i3) is used.

These polyamine resins can be cured using alcohol-blocked polyisocyanate compounds to form electrodeposited coatings.

In addition, amine-added epoxy resins that can be cured without using blocked isocyanate compounds can also be used. (see Japanese Patent Laid-Open No. 1983-1993): Vine type resin that is cured by transesterification (for example, JP-A-55-
80436), etc. can also be used.

The aforementioned polyepoxides include, for example, polyglycidyl ethers of polyphenols that can be produced by reacting polyphenols with epichlorohydrin in the presence of an alkali, and typical examples of such polyepoxides include bis(4-hydroxyphenyl). −
2,2-propane, bis(4-hydroxyphenyl)-
1,1-ethane, bis(4-hydroxyphenyl)-methane, 4.4゛-dihydroxydiphenyl ether, 4
．． Examples include glycidyl ethers of polyphenols such as 4'-dihydroxydiphenyl sulfone, phenol novolak, and cresol novolak, and polymers thereof.

Among the above-mentioned polyepoxides, those which are particularly preferred from the viewpoint of cost and corrosion resistance have a molecular weight of at least about 380
．． Preferably within the range of about 800 to 2.000 and an epoxy equivalent weight of 190 to 2,000, preferably 400 to 1.0.
Polyglycidyl ethers of polyphenols within the range of 0.00, in particular the polyepoxides shown below - bottom.

In addition, the epoxy cationic paint used in the present invention includes:
In addition to the above-mentioned epoxy resin and curing agent, there are also curing catalysts, coloring pigments, and anti-corrosion 111 extender pigments.

It is also possible to add fluidity modifiers and the like.

In this specification, the surface tension J described with respect to the cationic epoxy coating film and the cationic wax described below was measured as follows.

Epoxy cationic electrodeposition coating is made by electrodepositing epoxy cationic electrodeposition paint on a smooth tin plate to a dry film thickness of approximately 10μ, air-drying the plate once at room temperature, and then drying it once at room temperature.
After drying at 10° C. and 1 atm for 1 hour, it was left to stand at room temperature for 10 minutes. On the other hand, cationic wax was prepared by coating it on a smooth tin plate to a dry film thickness of about 10 μm, and then heating it to a temperature above the melting temperature of the cationic wax to form a film.

Deionized water is dropped onto the coating film prepared above, and the contact angle (&) with the coating film is measured.

Then, Sel I and Neumann's empirical formula 1 formula %]
) In the formula, γL: surface tension of water (72, 8 dyne/cn+
) γ3: Determine the surface tension of the coating film from the surface tension (dyne/cn+) of the coating film.

The aqueous dispersion of cationic wax which is an additive component of the coating composition used in the method of the present invention has a surface tension difference of 5 dyne between the surface tension of the cationic wax and the surface tension of the cationic electrodeposition paint film. /cm or more, preferably 10d
If the difference in surface tension is less than 5 dyne/cm, the cationic wax component will not be deposited during the coating film formation process during melting and fluidization of the coating film. It becomes difficult to form a multilayer film by separating from the film, and the water repellency of the upper layer coating becomes worse, resulting in inferior corrosion resistance of the lower layer coating. The surface tension of the cationic wax is 30 to 45, preferably 30 to 38 ay/c, from the viewpoint of easy separation from the electrodeposition coating to form a multilayer coating.
+w range.

As the water body of the cationic wax, - it can be used without particular restrictions as long as it satisfies the above conditions.
For example, natural waxes and/or synthetic waxes are water-dispersed with a cationic surfactant, and natural waxes and/or synthetic waxes have a cationic group that can be neutralized with an acidic compound to be water-dispersed. An aqueous dispersion of wax can be used. The natural waxes mentioned above are classified into vegetable, animal, mineral, and petroleum waxes, and among the vegetable waxes, there are carnauba wax, candelilla wax, wax, etc.
Animal-based products include beeswax, lanolin, spermaceti, etc.; mineral-based products include montan wax, lignite wax, etc., and petroleum-based paraffin waxes, microstarine wax, and Be!
~ Loracum etc. 0 Synthetic waxes are classified into synthetic hydrocarbons, hydrogenated waxes, and amine amides 1 Synthetic hydrocarbons include polyethylene wax, oxidized polyethylene wax, Fischer-Tropsch wax, etc. and hydrogen Examples of chemical waxes include castor wax and the like. The natural waxes and/or synthetic waxes having a cationic group include, for example, modified products thereof obtained by reacting the natural waxes and/or synthetic waxes with a basic compound, or synthetic waxes. These derivatives or modified products obtained by using basic compounds as raw materials during the production of can be used, but are not limited to these production methods.
Examples of the basic compound include nitrogen-containing unsaturated compounds such as vinylpyrrolidone, vinylpyridine, vinylpiperidine, vinylimidazole, N-acryloylmorpholine, N-acryloylpyrrolidine, aminoethyl (meth)acrylate, ethylenediamine, diethylenetriamine, and Examples include compounds such as xylaminopropylamine, monoethanolamine, jetanolamine, propatoolamine, N-methylethanolamine, diethylaminoethanol, and aminoethylethanolamine. The above-mentioned basic compounds include functional groups of the compounds, natural waxes and/or synthetic waxes, and functional groups of their raw materials or intermediates (e.g., craftable unsaturated groups, tertiary carbon, and hydroxyl groups). or active hydrogen groups such as carboxy, etc.).

The cationic surfactants used to water-disperse the above natural waxes and/or synthetic waxes include:
Particularly suitable are aliphatic, aromatic, and alicyclic amine salts such as primary amine salts, secondary amine salts, tertiary amine salts, and alkanolamine salts.

In addition, as the acidic compound used to water-disperse natural waxes and/or synthetic waxes having cationic groups, low molecular weight organic acids such as acetic acid, hydroxyacetic acid, formic acid, and propionic acid are suitable. Can be mentioned.

The cationic wax used in the present invention includes chu・1
From the viewpoint of forming a coating film with excellent aqueous properties, it is preferable to use an aqueous dispersion of a wax having a cationic group without using a surfactant.

The cationic wax may be used in an amount of 1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the epoxy cationic electrodeposition paint in terms of solid content. If the proportion used is less than 1 part by weight, the surface of the formed coating film will not have sufficient water repellency and will not exhibit excellent corrosion protection over a long period of time.On the other hand, if the proportion used is more than 10 parts by weight, the epoxy cation This results in poor adhesion of the electrodeposition paint to the metal base, resulting in poor corrosion resistance and mechanical properties.

The coating film forming method of the present invention uses the above-mentioned highly anticorrosive cationic electrodeposition paint Rakuchu (solid content 15 to 25% by weight) as a cathode,
Cationic electrodeposition is performed using a stainless steel or carbon plate as an anode to deposit an electrodeposited coating film on the object to be coated. The object to be coated is not particularly limited as long as it can conduct electricity, but it is preferable to use a blade treated with zinc phosphate or iron phosphate. As for the conditions for carrying out cationic electrodeposition, it is generally preferable to carry out electrodeposition at a bath temperature of 20 DEG to 30 DEG C., a voltage of 100 to 400 V, and a current application time of 1 to 5 minutes.

Next, the coating film deposited on the object to be coated was approximately 150 to 2
It can be cured by baking at 30°C for about 10-30 minutes.

According to the method of the present invention, the cationic wax component of the 1π-coated paint used in the present invention has the same polarity (ion) as the epoxy cationic resin component, so these components can be used during paint manufacturing or storage. It exhibits excellent dispersion and storage stability because the components do not separate or aggregate. Furthermore, when the electrocoating paint is used for electrocoating, the cationic wax component and the epoxy cationic resin component have the same cationic properties, so the electrocoating material is coated with a uniform mixture of each component. It is possible to form a coating film that has excellent adhesion and transfer properties and is free from coating defects such as abnormal precipitation. Historically, when a coating film deposited on an object is baked, the cationic epoxy resin, which is a component with high surface tension, is distributed closest to the surface of the object. It forms a base with excellent adhesion and anti-corrosion properties.
Cationic wax, a component with low surface tension, is -1
- Many of these exist on or near the surface of the substrate (in the opposite direction from the object to be coated), and they themselves have excellent water repellency, so a coating film that prevents corrosion from corrosive substances is required. It has a remarkable effect that it can be formed. Further, in the present invention, special effects can be exhibited by implementing the L-coating-F coating method in particular.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Production example of electrodeposition paint ■ Bisphenol type epoxy resin (Ciba Geigy Co., Ltd. "Araldite #6071J") 930 parts by weight ■ Bi weight parts Nobisphenol resin (Ciba Geigy Co., Ltd. [Araldite GY2600J) 380 〃■
Polycaprolactone diol (Daicel “Plaxel #205J”) 550 //■
Dimethylbenzylamine vinegar ei salt 2.6〃■p-
Nonylphenol 79
-ruamine /θ5 〃■Bu'+1 Shishi Old V Rub゛Yuso7v■Cellosolve 723〃Heating component ■ to 130℃, and adding components ■～■ dropwise over 5 hours at 130℃,
Maintain at 130°C for 2 hours, drop ingredients ① and ② over 2 hours at 130°C, maintain in the river at 1.30°C for 2 hours, then add ingredient ② and cool.

Thus, a number average molecular weight of approximately 5.000 was obtained with a solids content of 62%.

Next, ■-1- resin solution (as solid content) 82.6 parts by weight ■4.4'-Diphenylmetal diisocyanate ethylene glycol mono-2-ethylhexyl ether dibrothate 5.0 ■Isophorone diisocyanate methyl ether Ketone ketoxime diblock 12.4 //■
Polypropylene glycol 4000 0.5 //
■Lead acetate 1.0〃■io%
Acetic acid 9.3〃■Deionized water
1g5.75 // Ingredients ■ to ■ are mixed uniformly, ingredients ■ to ■ are added and mixed further uniformly, then component ■ is added and stirred and mixed uniformly to achieve a non-volatile content of 32% (120℃~It An emulsion of (r,) is obtained.

60% quaternary chlorinated epoxy resin s, T 31-
i Irase ÷ Izai ← −Hirrin ÷−
Titanium white 14.5 //
Carbon 0.54/J
Extender pigment (clay) 7. Q //
Lead silicate 2,3 Dibdeltin oxide 2,0 Deionized water
27.49 // to obtain a pigment paste with a non-volatile content of 50% (120° C. to 1[-1r,)].

Examples 1 to 4 and Comparative Examples A cationic electrodeposition paint was prepared by mixing 317.2 parts of an emulsion obtained based on the resin mixing ratio shown in Table 1, 59.56 parts of pigment paste, and 279.64 parts of deionized water. A composition (20% solids) is obtained.

An iron plate treated with curved lead phosphate was immersed as a conductive object in a stirred electrodeposition bath containing these electrodeposition paint compositions at a bath temperature of 28°C, and between it and the anode, which was the counter electrode, Electricity was applied for 3 minutes at a voltage that gave a film thickness of 20 μm after baking. The performance of the coated film obtained in parentheses ( ) is shown in Table 1 below. Baking is done at 170℃ 2
Baked for 0 minutes.

The conditions of the electrodeposition paint baths of Examples 1 to 4 were good, with no separation or aggregation.

[Performance test] ・Eriksen...Using a coating film extruder manufactured by Eriksen Co., Ltd.
.

・Salt water sprayability: Peeling m*a (am) due to rust from the cross cut part and degree of blistering of the paint film after making a cross cut in the paint and spraying with salt water (5% immersion) for 2000 hours. was evaluated.

Claims (1)

[Claims] 1. The epoxy cationic electrodeposition paint contains 5 dyne/c less than the coating film formed from the epoxy cationic electrodeposition paint.
The object to be coated is electrodeposited in a highly anticorrosive cationic electrodeposition paint bath prepared by blending an aqueous dispersion of a cationic wax with a surface tension as low as m or more to form a precipitated coating film on the object. 1. A method for forming a highly anticorrosive cationic electrodeposited coating film, which comprises curing and then heating to form a cured coating film.