JPS60215796A - Formation of coated film of electrodeposition paint - Google Patents

Abstract

PURPOSE:To form a coated film in which advantage is taken of the characteristic of respective electrodeposition paints by electrodepositing the 1st paint on the surface of a metal for the shorter time with the lower voltage than the standard and electrodepositing the 2nd paint having the characteristics different from the characteristics of the 1st paint on said surface then curing the coated paints. CONSTITUTION:The 1st paint is electrodeposited on the surface of a metal in the 1st bath contg. the 1st paint consisting of acryl, urethane, polyester or the like having excellent weatherability for the time shorter than the standard electrodeposition time for said paint and with the voltage lower than the standard electrodeposition voltage thereof and thereafter the surface is washed to remove the paint sticking physically thereto. The washed metal is then immersed in the 2nd bath contg. the 2nd paint consisting of epoxy, alkyd, polybutadiene or the like having excellent adhesion and the 2nd paint is electrodeposited thereon for the standard electrodeposition time and with the standard electrodeposition voltage for said paint. The electrodeposition paint is thereafter baked and cured under prescribed conditions to form the coated film of the electrodeposition paints having excellent corrosion resistance and weatherability on the surface of the metal.

Description

[Detailed Description of the Invention] R Masumei's #Technical Minute Hand] This invention relates to a method for forming a coating film of an electrodeposition paint, and the present invention relates to a method for forming a coating film of an electrodeposition paint, in which two types of electrodeposition paints having different characteristics are successively electrodeposited separately, and each paint is The object of the present invention is to provide a coating film forming method in which a desired coating performance is obtained by forming a layer of coating materials and making use of the characteristics of each coating material.

[Prior art]

Conventionally, a method of spraying an organic solvent-diluted paint has been widely used for anticorrosion painting. As high-performance paint film performance is increasingly required these days, it is difficult to satisfy these demands with just one coat, and in most cases two coats are applied.In general, the first coat is Epoxy paints, such as epoxy paints, are often used because they have excellent adhesion to the underlying metal, which means they have good corrosion resistance, and acrylic paints, which have excellent appearance and weather resistance, are often used for the a-th coating. .

At this time, there are two methods: one is to bake and harden the paint after each coat (Cocoat Cobake), and the other is to bake and cure the paint at 7 degrees after applying it twice (2 coats/bake).The latter is more energy efficient than the former.

It has the advantage of process saving. In any case, the above-mentioned spray coating has the disadvantage that the paint adhesion efficiency is poor and it is difficult to coat every corner of the object having a complicated shape (poor throwing power).

Therefore, an electrodeposition coating method has been developed to overcome these drawbacks. However, even in this method, excellent coating appearance and coating film properties can be obtained with one coating. Although so-called one-coat finish electrodeposition paints have been considered, they have not yet achieved sufficient properties for practical use (Special Publication No. Sho!r!r-tl110!r). Therefore, both anionic electrodeposition coating and cationic electrodeposition coating are used as a primer, and in many cases, ordinary organic solvent-diluted paint is spray-painted on top of this. Therefore, problems arise here as well, such as poor paint adhesion efficiency and poor throwing power.
The disadvantage was that the characteristics of electrodeposition coating could not be fully utilized. Furthermore, due to differences in curing conditions, curing is usually performed twice, which is not preferable from the viewpoint of energy saving.

Furthermore, if corrosion resistance is improved by improving adhesion to metal objects, weather resistance is generally insufficient, and conversely, if weather resistance is emphasized, ice resistance tends to be poor. Therefore, we took advantage of the characteristics of electrodeposition coating.

Attempts to simultaneously satisfy both weather resistance and corrosion resistance in one coat include, for example, mixing acrylic paints with excellent weather resistance and epoxy paints with good corrosion resistance, or electrocoating paints that incorporate both into the molecular framework. (Publication No. 13341/1987). Although these properties can be controlled by changing the ratio of each resin component, they have not yet fully satisfied both corrosion resistance and weather resistance. In other words, in these coating films, each resin in the mixture compensates for the defects of each other, but since the properties of each resin are inferior to those of each resin alone, the properties of the coating film as a whole had to be inadequate in the end. .

Therefore, the inventors of the present invention have conducted extensive research into using two types of paints in coating, each forming a separate coating layer, and have arrived at the present invention.

[Summary of the invention]

This invention was made for the purpose of improving the above-mentioned drawbacks, and by performing electrodeposition coating separately and successively in a co-bath using AM type paints, it is possible to make use of the characteristics of the two types of paints. The present invention relates to a method for forming an electrodeposition coating film in a substantially layered manner.

The present invention provides a method for forming an electrodeposition coating film that can simultaneously satisfy corrosion resistance and weather resistance of the coating film.

It is also applicable to anionic electrodeposition paints and cationic electrodeposition paints. In electrodeposition coating.

The paint that is illuminated later over time has a characteristic that it adheres to the object to be coated, that is, to the lower layer of the coating film. Furthermore, as the coating film adheres, the electrical resistance increases and electrodeposition gradually becomes impossible, until a saturation point is reached and current no longer flows. The present inventors have discovered that by controlling the electrodeposition conditions, that is, the voltage, time, and amount of electricity, it is possible to successively electrodeposit different paints in a λ bath.

That is, the present invention provides a method for applying a first paint to a metal surface in a first bath containing a first paint at a time shorter than the normal electrodeposition time and at a voltage lower than the standard electrodeposition voltage. After arriving,
The paint physically adhering to the metal is removed by washing with water, and the washed metal is immersed in a second bath containing a first paint having different properties from the first paint to perform standard electrodeposition of the second paint. Coating of an electrodeposition paint characterized by electrodepositing a second paint at a standard electrodeposition voltage for a certain period of time, and then curing the seventh and first paints having '1&' deposited on the metal surface under predetermined curing conditions. A film forming method.

Here, standard overlap voltage 1. The standard electrodeposition time is the voltage and time at which a film thickness of about 0μ can be obtained when the paint is applied alone onto a steel plate.

The standard electrodeposition voltage for both anionic electrodeposition paints and cationic electrodeposition paints is 00 to 300V, and the standard deposition time is about 1 to 3 minutes, which varies depending on the paint. As a result, the area near the metal object is the second
The amount of the C material becomes large, and a substantially layered ζ film having a composition that differs in stages can be obtained, the surface layer being covered with the first paint.

The state of adhesion of both paints at this time depends on the negative voltage of the electrodeposition coating for 9 hours. In other words, in the 7th bath, if the voltage or time is too low, the amount of paint deposited on one surface layer will be small, making it impossible to produce the desired color.On the other hand, if the voltage or time is too high, the paint film will be destroyed or the paint on the surface layer will be damaged. The amount of adhesion increases, making it impossible to paint in the first tower. Therefore, the electrodeposition of the first bath is performed for a time shorter than the standard electrodeposition time of the first paint, e.g. 70% to H, and at a voltage lower than the standard electrodeposition voltage, e.g. It is preferable to use a low voltage.

・In the second bath, if the voltage or time during electrodeposition is low, the film thickness of the base paint will be small, causing problems with corrosion resistance, and conversely, if it is high, the amount of base paint that adheres will increase. This will bring about a change in the color of the surface layer. Therefore, it is desirable that the electrodeposition of the first column be carried out using the standard deposition time and standard blue voltage of the first paint.

In the present invention, as the first paint, an acrylic, urethane, or polyester electrodeposition paint having excellent weather resistance can be used, and an acrylic electrodeposition paint is preferable. As the second paint, an epoxy-based, alkyd-based, or polybutadiene-based electrodeposition paint can be used, and an epoxy-based or polybutadiene-based electrodeposition paint is preferable.

In this way, two coats of electrodeposition paints, which could not be done conventionally, are now possible by the method of the present invention, and by combining these paints, it is possible to obtain a film having a predetermined coating performance.

In addition, curing is performed after electrodeposition in a λ bath.

It becomes a so-called cocote l-bake, which saves energy.”
I":, 1"4'"'Q"'6・months.

Normally, coating films are often required to have both corrosion resistance and weather resistance, but the method of the present invention can satisfy both of these requirements at the same time.

[Embodiments of the invention]

Next, the present invention will be specifically explained with reference to Examples.

Example l Paint used in the first bath Acrylic cationic electrodeposition paint (Nisbia cationic ED,
Product name manufactured by Shinto Paint Co., Ltd.) Concentration: ts weight%, pH:! r, 0~mu θ, specific resistance:
(20℃) Paint used in the second bath Epoxy cationic electrodeposition paint (Aqua A4' 200゜Product name manufactured by NOF Corporation) Concentration: l? Weight %, pH: l-λ~Aff, specific resistance: 6
QOΩcIL (-0°C) First, the first bath was pretreated with zinc phosphate.
Immerse a steel plate of X/gOXO, GTM, is.

Electrodeposition painting was performed at V for 30 seconds. After that, immediately take it out of the bath, wash it with water, drain it, and immerse it in the first column.
Electrodeposition coating was performed at 00V for 60 seconds.

After washing with water and draining, it was baked and hardened at 200° C. for 20 minutes.

Example λ Using the same paint and test plate as in Example 1, tzov in the first bath
After using the electrodeposition coating tool for tS seconds, wash and drain the water, and then apply the electrodeposition coating using OOV for 0 seconds in the second bath.
After draining, it was baked and hardened at 100°C for 20 minutes.

Example 3 Paint used in the 7th bath Acrylic anionic electrodeposition paint (Aqua A 1a100°, trade name manufactured by Nippon Oil & Fats Co., Ltd.) Concentration near 2% by weight, pH: 9, resistivity: tts.

Ω (20℃) Paint used in the first tower Polybutadiene-based anionic paint (Nisbia MD
-2! ;00. Manufactured by Kagura Paint Co., Ltd. Product name) Concentration: /! r weight i
t%, pH: g, specific resistance: t3. o.

Ωtx (20℃) Dimensions with zinc phosphate pretreatment applied to the first bath/! rO
×70XOgtml)) Immerse the steel plate and l at /IOV!
8 After the second electrodeposition coating was applied, the steel plate was immediately taken out of the bath, washed with water, drained, and immersed in the first column.
Electrodeposition was performed under conditions of ov and 60 seconds. Curing is at 170℃
This was done for 30 minutes.

Example Using the same paint and test plate as in Example 3, immersion in the first bath/
! After applying one layer of paint at tOV for 75 seconds, it was washed and drained, and then electrodeposited for 100 seconds in the first column, washed and drained, and then baked and hardened at 170° C. for 3θ minutes.

Using the paint test board created in this way, the film thickness of the paint film,
@ Front pillar, weather resistance, corrosion resistance, and moisture resistance tests were conducted.

Film thickness The coating thickness on the flat surface of the test plate was measured using an electromagnetic film thickness meter.

Adhesion JI8K! ; Measured according to the 4400 board test.

The evaluation was performed as follows.

0: Very good (evaluation score specified by JIS 1
0 points) ○: Good (〃〃 5 points) 7 Δ: Slightly poor (〃〃 lh hiro point), X: Poor (〃〃 20 points) Weather resistance Ultraviolet carbon arc baking type weather resistance tester (light irradiation only)
The coating was left for a WOO period of time, and the state of the coating film was observed.

The evaluation was performed as follows.

◎: Very good (no change in coating film gloss/color and no abnormality in coating film adhesion) Q: Good (slight change in coating film 2 gloss/color, but
There is no abnormality in the paint film adhesion) To: Slightly poor (There is a noticeable change in the paint film gloss and color, but there is no abnormality in the paint film adhesion) ×: Poor (There is a noticeable change in the paint film gloss and color. Corrosion resistance (salt spray resistance) Measured according to the JIS Kklloo salt spray test. Note that the test time was 2≠θ hours.

The evaluation was performed as follows.

0: Very good (no blistering occurs at all) ○: Good (some rust and blisters occur) Δ: Slightly poor (rust and blisters are slightly noticeable) ×: Poor (
The condition of the coating film was observed after it was left in a constant temperature and humidity chamber of ``Moisture Resistance BO''C (S%RH) for 00 hours in the evening.

The evaluation was conducted in the same manner as the salt water spray resistance test described above. The results of these tests are summarized in a table.

As a comparison with the conventional 'rII coating, the test results of the electrodeposition coating used in the examples applied alone on a steel plate are listed as a control example. Electrodeposition is 00V and the film thickness is 2O.
-2jtμ becomes temporal.

Control example A Niacrylic cationic electrodeposition paint (Nisbia cationic electrodeposition paint, trade name manufactured by Kagura Toyo Co., Ltd.) Control example B: Eboxy cationic electrodeposition paint (Aqua/j6'
12θ01 Nippon Oil Co., Ltd. product name) Control example C Niacryl anion electrodeposition paint (Aqua*6too, Nippon Oil Co. product name) Versus Ifft Example: Polybutadiene anion electrodeposition paint Subia MD-2SOO1 Shinto Toyo Co., Ltd. product [Effects of the Invention] As explained above, the present invention involves electrodepositing one type of electrodeposition paint with different characteristics separately and successively to form a substantially layered layer of each paint, thereby taking advantage of the characteristics of each paint. This is a coating film formation method that achieves the desired coating performance.The coated products produced using this method have high paint adhesion efficiency, which is the characteristic of electrodeposition coating,
It not only has advantages such as high throwing power, but also has advantages such as high weather resistance and corrosion resistance of the coating film.

Claims (1)

[Claims] (/) The first paint is applied to the metal surface in a bath containing the first paint for a time shorter than the standard electrodeposition time of the first paint and at a voltage lower than the standard electrodeposition voltage. After wearing, wash the metal with water,
immersing the washed metal in a second bath containing a second paint having different properties from the first paint, and electrodepositing the second paint at the standard electrodeposition time and standard electrodeposition voltage of the first paint; A method for forming a coating film of an electrodeposition paint, which comprises curing the first and second paints electrodeposited on a metal surface under predetermined curing conditions. (c) The first paint is an acrylic, urethane, or polyester electrodeposition paint, and the first paint is an epoxy, pulqueid, or polybutadiene electrodeposition paint.Claim 1 A method for forming a coating film using an electrodeposition paint as described in Section 1.