JPS58159862A - Method and device for dip painting - Google Patents

Abstract

PURPOSE:To obtain dip painted films having an approximately constant thickness easily, by adjusting the vertical position of a flat article to be pulled up from the liquid surface of paint relatively to the value determined by the specific equation defining a relation between the time and the pulled up positions after it is dipped therein. CONSTITUTION:A flat article 1 mounted to a chain conveyor 3 by means of a hanger 2 is dipped in the paint 5 in a paint tank 4. More specifically, the tank 4 is moved relatively downward by the upward operation of a pantagraph jack 6 and a hydraulic cylinder 7 to dip the article in the paint. The viscosity of the paint is measured with a viscosity detector 8 and the vertical position of the tank with a detector 9, respectively. In the stage of pulling up the article 1 dipped in the paint 5 relatively from the liquid surface of the paint by moving the tank 4 downward, the vertical position Y in this relative pulling-up is adjusted to the value determined by the equation with respect to the time (t). As a result, the thickness of the paint films on the flat object is made approximately constant with ease.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dip coating method and apparatus for applying a coating film of a substantially constant thickness to objects (sometimes simply referred to as articles).

Spray painting has traditionally been a common method for painting articles, but since it uses a large amount of diluting solvent, it has drawbacks such as polluting the atmosphere and causing a large amount of paint to be lost.

On the other hand, dip coating, or so-called dobu-dipping, has been known for a long time, but although this method does not have the above disadvantages, it does have the disadvantage that there is a difference in film thickness between the first F part and the lower part of the product due to the adhering paint flowing down. .

The inventors of the present invention have conducted intensive studies to automate the dip coating method in a relatively simple manner to save labor and improve the uniformity of the quality of coated articles. Taking into account various aspects of the uniformity of the film thickness of the product, we found that a certain relational expression holds true for the relationship between the lifting speed of the object to be coated, that is, the vertical position of lifting, and the time. The present invention has been completed by being able to easily obtain a dip-coated film with a substantially constant coating thickness using an apparatus embodying this method.

That is, the present inventors conducted an experiment in which a plastic flat plate article as shown in FIG. 1 was dip coated. This article has, for example, a 1° hole for attaching the article and has no large irregularities on its surface. After dipping this material into a paint tank, it was pulled up at a constant speed to dry and harden. When the thickness of the paint film was measured, the film thickness varied depending on the position of the pulled up flat plate (
It was found that the farther away from the paint liquid surface, the thinner the coating), and that the higher the drawing speed, the greater the non-uniformity of the film thickness (see Figure 2).

Other factors that change the film thickness include the type of paint, viscosity, specific gravity, and environmental temperature, and these factors combine to change in a complex manner. It has been found that the following relationship holds between the speed, the vertical pulling position Y, and the coating film thickness T.

If we put T-a-Y-N+b (where a and b are constants)...listen to the tune 1), the equation (]) is Y''V = k,
becomes. ...(3) fY"dY = /Jdt. It is difficult to solve this Y3: k, t 10, (k2 is a constant) Y = m (t + n) ...・(
4) is obtained.

In other words, the relationship between the vertical pulling position and time for achieving a constant film thickness has been obtained, and once m and n are determined, the pulling vertical position can be derived from the above equation if the time is known. In this case, m and n are constants determined experimentally depending on the type of paint, viscosity, specific gravity, working temperature, etc. As shown in FIG. 3, in order to maintain a constant film thickness, as the vertical position of the film is pulled farther from the liquid surface, the time becomes longer, that is, the pulling speed must be lowered.

Here, the article to which the method of the present invention can be applied is an article that has a relatively flat surface, and does not necessarily have to be a flat plate, but an article that has large irregularities on the surface, such as an article that has holes, etc. It is not preferable to have a surface that causes large changes.

Next, an apparatus capable of carrying out the dip coating method for achieving a constant film thickness according to the present invention, that is, a dip coating apparatus will be described with reference to the drawings.

FIG. 4 is a diagram showing an example of a dipping paint tank lifting device, in which a flat plate product 1 is attached to a chain conveyor 3 by a hanger 2. A paint tank 4 is filled with paint, and the paint tank is raised and lowered by the actions of a pantograph jack 6 and a hydraulic cylinder 7, thereby performing immersion. A viscosity detector 8 is installed inside the tank, and a tank vertical position detector 9 is installed on the side of the tank.

The mechanism for raising and lowering the paint tank using hydraulic pressure can be done in any way, but for example, in the case of -F lift, IJ IJ
- By sending oil from the oil tank to the hydraulic cylinder with a pump using the hydraulic pressure set through the valve and check valve, in the case of descent, the oil in the hydraulic cylinder returns to the oil tank through the throttle valve and solenoid valve. This is done by
Both are caused by the activation of the tank vertical position detector.

Particularly in the case of descending, it is necessary to change the drawing speed in order to keep the film thickness constant, so a speed control electric circuit is provided to adjust the speed. This electrical circuit is shown in block diagram form in FIG. The film thickness is set in the microcomputer 11, and then a start signal is input, and a set position signal R is output. On the other hand, tank vertical position detector 9
A tank vertical position signal (detected position signal) is output.

When the difference E between the set position signal R and the detected position signal R is inputted into the microcomputer 13, it is calculated and a throttle valve operation signal is generated, whereby the throttle valve control device 14 is actuated to correct the tank lowering speed. As a result, the process of lowering the tank is adjusted according to a program that has been calculated and set in advance based on data such as film thickness.

6 is a plan view schematically showing an embodiment of the dip coating method and apparatus including the dip tank shown in FIG. 4; FIG.

Products 1 are set at equal intervals on a product transfer chain 3 driven by a constant speed rotation stop motor 21, and the chain 3 transfers the products 1. Since the constant speed rotation stop motor rotates for a certain period of time and then stops, it transfers the product at a certain speed and a certain distance and then stops. A cleaning tank 24, an undercoating paint tank 25, and a finishing paint tank 26 are installed directly below the place where the vehicle should stop. Further, the timer is used to set the transfer stop time to be longer than the time required for the dipping operation.

When the product to be dip coated stops on top of the dip coating paint tank, it will be dip coated using the method described above, and once the coating is finished, the product will be pulled out of the paint tank so that the thickness of the coating is constant. As explained.

The product thus pulled up passes through the drying tunnel ovens 27, 2τ while suspended from the chain 3, and the coating film is cured by heating. The moving speed of the chain, stopping time, moving distance, length of the drying tunnel oven, heating temperature, etc. are adjusted depending on the type of paint used, viscosity, specific gravity, etc.

By the dip coating method and apparatus of the present invention, dip coating of articles for which uniform coating was conventionally difficult has been significantly improved.
As a result, it helps improve coating productivity and quality, and its industrial value is extremely large.

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

Paint used in the example Toss Guard 51o (manufactured by Toshiba Silicone ■) Product material Polycarbonate flat plate painting Environment 25°C 4 degrees RH Dry curing conditions 120°C 1 hour Measuring device Coating film thickness Beta Technostar (manufactured by Densoku Kogyo ■) Viscosity B Model viscometer viscosity 7 cps Specific gravity 0.95 Experimental example 1 (1) Conventional method (high-speed pulling method) Pulling speed 3
0 w/5ee constant coating film thickness 4 to 6 μ (range from liquid level to 400 was)
Difference in coating film thickness: 2 μ Required time: 13.3 sec (2) Method of the present invention (30 wl/s up to 200 m)
a-Constant velocity) Pulling speed No. 3 to 30 variable coating film thickness 4 to 5μ (range from liquid level to 400m) Difference in coating film thickness 1μ Required time 20 crowns In this case, time is the difference compared to the conventional method Although it costs 5096 more, the difference in film thickness is halved.

Experimental example 2 (]) Conventional method (low speed pulling method) Pulling speed 1
0 mm/see Constant coating film thickness 4 to 54μ (range from liquid level to 400 wa) Difference in coating film thickness 1.1μ Required time 40 sec (2) Method of the present invention (however, 30 m/see up to 200++n)
Sa-constant velocity) Pulling speed 3 to 1 variable Coating film thickness 4 to 5 μ (range from liquid level to 400 ttrm)
Difference in coating film thickness: 1.0μ Required time: 20 seconds In this case, the difference in film thickness is almost the same, but the required time is halved, which helps improve productivity.

[Brief explanation of the drawing]

FIG. 1 is a front view (4) and a plan view 03) showing an example of a flat plate article used in the present invention. Figure 2 is a graph showing the relationship between film thickness and vertical position at different pulling speeds.
The figure is a graph showing the relationship between vertical position and time in the case of a constant film thickness (5μ). FIG. 4 is a diagram showing an example of a paint tank elevating device in the dipping device of the present invention, and a plan view schematically showing an example of the entire fifth device. 1... flat plate article 2... no-nger 3...
・Chain conveyor 4...Paint tank 5...
Paint 6... Pantograph jack 7... Hydraulic cylinder 8... Viscosity detector 9.
...Tank vertical position detector 10...hole 11.13
... Computer 14 ... Throttle valve control device D
...Detection position signal R...Setting position signal E ・
... R-D 21... Constant speed rotation stop motor 24... Cleaning tank 5... Undercoat paint tank 26... Finishing paint tank 27.2 P... Drying tunnel furnace patent Applicant Toshiba Chemical Co., Ltd. Agent Patent Attorney Akira Ito” Figure 1 Figure 2 - Yt vertical direction Figure 3! -; t (sec) Figure 4 Figure 6

Claims (1)

[Claims] (1) When dip-coating an article with a relatively flat surface, the relative lifting vertical position Y of the article from the paint liquid surface after dipping is determined by Y = m for time t.
, n is a constant determined experimentally depending on the type of paint, viscosity, specific gravity, and working temperature), whereby the thickness of the coating film of the article is made almost constant by adjusting the thickness to a value determined by Dip coating method for articles with relatively flat surfaces (2) A constant-speed rotation stop motor, and a chain conveyor for conveying articles that is driven by the motor and sets and conveys articles having relatively flat surfaces at equal intervals. The dip coating means consists of a dipping coating means and a heating drying means, and the dipping coating means determines the vertical position Y of the article relative to the paint liquid surface after dipping in the range Y −= m to Rho (where m, n is a constant determined experimentally depending on the type of paint, viscosity, specific gravity, and working temperature), which makes it possible to keep the thickness of the coating film on the article almost constant. Dip coating equipment for articles with relatively flat surfaces that can be