JPS63171669A - Dip coating method - Google Patents

Abstract

PURPOSE:To carry out dip coating while preventing the running of a paint and controlling the evaporation of the paint solvent without changing the pulling up method and pulling up velocity, by keeping a narrow interval between the surface of the paint and a lid, and pulling up a material to be coated at a specified velocity. CONSTITUTION:The dip coating device is composed of a coating tank 1 opened at the upper part and having a paint inlet 7 at the lower part, a jacket groove 4 provided at the upper outer edge of the coating tank 1 and having a paint outlet 8, and a lid 5 having an opening for inserting and pulling up the material to be coated at its center. The material 3 to be coated is dipped in a paint 2 charged in the coating tank 1, then pulled up, and coated. The interval between the liq. surface of the paint 2 and the lid 5 is set to <=10mm, and the material 3 to be coated is pulled up at such a velocity that the material 3 to be coated is passed through the space between the liq. surface and the lid in 5sec. As a result, the running of paint can be prevented without changing the pulling up method and pulling up velocity, the evaporation of paint can be controlled, and dip coating is efficiently carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a dip coating method in which an object to be coated is dipped in a coating material and then pulled up for coating.

Conventional technology Traditionally, equipment for applying paint to objects such as cylinders, etc.
Various coating methods are known, and a dip coating device is used especially when the smoothness of the coating film is important. In a typical dip coating device, the object to be coated is dipped into the paint and then pulled up at an appropriate speed for coating. In this case, the thickness of the coating film is determined by the concentration of the coating material and the pulling speed, and the higher both of them are, the thicker the coating film becomes. However, if the pulling speed is high, by the time the coating film dries and is fixed, it will sag, resulting in a phenomenon where the film thickness is thinner at the upper part of the object to be coated and thicker at the lower part. Particularly, when the concentration of the coating solution is low and the viscosity is high, the amount of solvent is large, and the dripping phenomenon is very likely to occur. This tendency becomes more likely to occur as the film thickness is increased, so it has been difficult to uniformly apply a thick coating film from top to bottom by dip coating.

As a method to prevent this, for example, Japanese Patent Application Laid-Open No. 55-733
No. 69 describes that the object to be coated is pulled up to a certain distance, dipped into the paint again, and then pulled up. Further, Japanese Patent Application Laid-Open No. 57-5048 describes changing the pulling speed so that it is fast at the beginning and slow at the end.

However, these methods require a control mechanism to control the pulling state.
The drawback is that the dip coating equipment becomes complex.

Regarding dip coating equipment, for example, Japanese Patent Application Laid-Open No. 59-1270
49, Japanese Patent Application Laid-Open No. 59-174843, or Japanese Utility Model Application Publication No. 60-179367@, for example, the dip coating apparatus shown in FIG. 3 is used. In FIG. 3, reference numeral 1 denotes a coating tank, in which paint 2 is introduced from a paint inlet at the bottom, overflows from the upper edge, collected by a mantle groove 4, and discharged from a paint outlet 9. The top of the coating tank 1 is covered with an M7 having an opening in the center.

Problems to be Solved by the Invention Incidentally, the sagging phenomenon of the paint film occurs because the paint film slides downward before it dries.To prevent this, it is necessary to dry the paint film quickly. good. On the other hand, one of the factors that delays drying is that due to evaporation of the solvent from the paint, the vapor accumulates around the object to be coated, increasing the vapor pressure and delaying the drying of the paint film.

In the above-mentioned dip coating equipment, there is a wide gap between the paint surface and the lid, so solvent vapor accumulates between them, delaying the drying of the paint film, and if there is no lid, the solvent evaporates. The disadvantage is that the amount of loss due to Japanese Patent Publication No. 59-1
In the case described in Publication No. 27049, air is introduced,
A step is provided to reduce the concentration of solvent vapor,
Furthermore, in the case described in JP-A-59-174843, a gap is provided in the lid to promote the evaporation of the solvent vapor, but in both cases, the evaporation of the paint solvent is As a result, the amount of evaporation loss increases, and there is also a risk that the composition of the paint will vary.

The present invention has been made in view of the above-mentioned problems in the conventional technology.

An object of the present invention is to provide a method for dip coating, which prevents the occurrence of sagging and suppresses evaporation of the paint solvent without changing the pulling method or speed.

Means and operation for solving the problems The above object of the present invention is achieved by keeping the distance between the liquid level of the paint and the coating narrow in the dip coating apparatus and pulling up the object to be coated at a predetermined speed. They have discovered that this is the case, and have completed the present invention.

The present invention provides a coating tank having a paint inlet at the bottom and an open top; an outer groove having a paint discharge port provided at the outer edge of the upper end of the coating tank; and a groove for inserting and pulling up objects to be coated. In the dip coating method, in which the object to be coated is immersed in the paint introduced into the coating tank of the dip coating device, which consists of a lid with an opening in the center, and then pulled up for painting, the relationship between the liquid level of the paint and the lid is The method is characterized in that the distance between the two is set to 10 m or less, and the object to be coated is pulled up at a pulling speed such that the object to be coated passes between the liquid level and the roof within 5 seconds.

In the present invention, when pulling up the object to be coated, it is more preferable to pull it up while creating an air flow around the object. □The present invention will be explained in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a dip coating apparatus for carrying out the present invention, in which (a) shows the state of the object to be coated before it is immersed, and (b) shows the state that the object is being pulled up after being dipped. .

Further, FIG. 2 is a partially enlarged view of FIG. 1. In FIGS. 1 and 2, 6 is a coating film, and the other symbols have the same meanings as shown in FIG. 3 above.

A paint 2 is introduced into the coating tank 1 from a paint inlet 3, overflows from the upper edge of the coating tank, flows through a mantle groove 4, and is discharged from a paint discharge port 8. The object 3 to be coated is dipped into the paint in the coating tank 1 through an opening provided in the center of the lid 5, and then pulled up to form a coating film on the object 3 to be coated.

In this case, it is necessary to set the lid so that the distance between the paint liquid level and the lid is 10 m or less, and it is particularly preferable to set the lid so that the distance is 1 to 5 m. If the distance between the paint liquid surface and the lid exceeds 10 m, the amount of solvent evaporated from the liquid surface will increase, and the solvent vapor will delay the drying of the paint film, resulting in increased dripping. In the present invention, if the lid may be stained with paint, the lid may be in contact with the surface of the paint liquid.

The opening in the center of the lid is preferably slightly larger than the outer dimensions of the object to be coated, and is usually 1 to 1.
A gap of about 51M1 may be created. If this gap becomes too wide, the paint solvent will evaporate and the drying of the paint film will be delayed.

In the present invention, the object to be coated needs to be pulled up at such a speed that it passes between the paint liquid level and the lid within 5 seconds. If the object to be coated is pulled up for more than 5 seconds, the solvent vapor accumulated between the liquid level and the lid will cause
No one will be able to prevent it.

In the present invention, particularly preferred conditions are such that the distance between the paint liquid level and the lid in the dip coating device is 5M, and the rate of pulling up the object to be coated is 2 m/sec or more. In this case, the object to be coated will be pulled up so as to pass between the liquid level and the lid within 2.5 seconds.

Further, in the present invention, it is preferable to generate air flow at the top of the lid because this further accelerates the drying of the coating film. It is desirable that the air flow gently and uniformly hit the object to be coated. This is because if it hits the object unevenly, uneven drying will occur, and if it hits hard, it will cause disturbances in Ill.

Exhaust means for discharging the evaporated solvent from the coating film are advantageously used as the means for generating the air flow.

Function In the present invention, as described above, a lid is provided at the top of the coating tank of the dip coating device, and the distance between the paint liquid level and the lid is set to 10 m or less, and the distance between the paint liquid level and the lid is set to 10 m or less. Since the object to be coated is pulled up at such a speed that the object passes through the gap within 5 seconds, evaporation of the paint solvent is suppressed, and the coating film formed on the object is It does not come into contact with the vapor of the solvent for a long time, and comes into contact with the outside air immediately.

Example The present invention will be explained below with reference to Examples.

Example 1 as paint N,N''-diphenyl-N shown by the structural formula.

4 parts by weight of N'-bis(3-methylphenyl)-(i,1-biphenyl)-4,4''-diamine and 6% by weight of a polycarbonate Z resin with a viscosity average molecular weight of !126,000 were mixed into a monomer. A solution dissolved in 34 parts by weight of chlorobenzene was used.The concentration of this paint was 22.7% by weight,
The viscosity is 290 mPa at 20°C, and it is ivy at s.

The above coating material was put into the dip coating apparatus shown in FIG. 1, and was circulated by feeding the coating material from the bottom coating inlet at a flow rate of 2 Ω/min.

An aluminum pipe with an outer diameter of 84 m and a length of 338 # was prepared as an object to be coated. The lid has a hole with an inner diameter of 87 m,
It was installed so that the distance from the overflowing liquid level was 1#ri. An aluminum pipe was immersed through this Bodhisattva hole at a speed of 500 nm/min, and then '11
It was pulled up at a speed of 0 an/min (passage time between the liquid level and the lid: 0.55 seconds). Thereafter, it was heated and dried at 120° C. for 1 hour to form a coating film on the aluminum pipe.

When the film thickness was measured sequentially from the upper end of the coated material, the results shown in FIG. 4 were obtained. FIG. 4 is a cross-sectional view of the coating film at the upper end of the coated article, where the vertical axis indicates the film thickness and the horizontal axis indicates the distance from the upper end of the coated article. As shown in FIG. 4, the thickness of the flat portion of the coating was 18 μm, and the distance from the top of the 16 μm thick portion was 25 m.

Comparative Example 1 A coating operation was carried out in the same manner as in Example 1 using the dip coating apparatus shown in FIG. However, the distance between the paint liquid level and the lid in the dip coating device was 20 m, and the paint film passed through this distance in 10.9 seconds. Further, the inner diameter of the hole in the lid was 110 m. The results are shown in Table 4. In this case, the thickness of the flat part of the coating was 18 μm, and the distance from the top of the 16 μm thick portion was 40 mm, which was large.

Comparative Example 2 Comparative Example 1 except that the coating operation was performed in an open system without roofing.
The same operation was performed. The results are shown in Figure 4. In this case, since there are many evaporation chambers for the paint solvent, the viscosity is approximately 0.8 mPa per hour.

There was a tendency for the temperature to increase by S, making it unsuitable for rapid coating operations.

Example 2 In Example 1, the viscosity of the paint was set to 300 mPa at 20°C.
, adjusted to S. Further, the lid of the coating tank used had a distance of 10 ann from the liquid level of the paint.

Under these conditions, the coating work for the aluminum pipe was carried out in the same manner as in Example 1 except for the pulling speed of 120 m/min. (Transit time between the liquid level and the lid: 5 seconds) When the film thickness was measured, as shown in FIG. 4, exactly the same results as in Example 1 were obtained.

Example 3 The coating operation was carried out in the same manner as in Example 1, except that the operation was carried out with ventilation from the intake duct above Coating II. In this case, the wind speed during the lifting operation of the object to be coated is
The velocity was approximately 0.2 m/sec downward. The results are shown in Figure 4. The thickness of the flat part of the coating was 18 μm, and the distance from the top of the 16 μm thick portion was 20 m.

Application Example An electrophotographic photoreceptor was prepared using the dip coating method of the present invention.

First, a solution prepared by dissolving a nylon resin in a methanol-butanol mixed solvent was dip coated onto the aluminum pipe described in Example 1 by a conventional method to form a barrier layer with a thickness of 1 μm. Next, a paint obtained by dispersing the dibromanthanthrone pigment in a polyvinyl butyral resin solution (the ratio of the pigment to the resin was 8:1) was applied by dip coating using a conventional method to form a charge generation layer with a thickness of 2 μm. Formed. Since these layers were thin, almost no sagging of the coating film occurred even without the use of the present invention.

Next, a charge transport layer was formed using the paint described in Example 1 and the method described in Example 1 to obtain an electrophotographic photoreceptor.

Similarly, a charge transport layer was formed by the method described in Example 2 and Comparative Examples 1 and 2, and an electrophotographic photoreceptor was prepared.

These four types of electrophotographic photoreceptors were installed in an electrophotographic copying machine that has processes such as constant voltage charging with a Scorotron M electric device, image exposure, development with dry toner, transfer, and cleaning treatment with a rubber blade, and image evaluation was performed. Ta. In the case of Comparative Examples 1 and 2, fogging occurred in the portion of the obtained image corresponding to the film thickness drop, whereas in the case of Example 1
In cases 2 and 2, images of good quality without fog were obtained.

Effects of the Invention In the present invention, as described above, a lid is provided at the top of the coating tank of an IH dip coating system, and the distance between the paint liquid level and the lid is set to 10 sQ below, and the paint liquid level and Since the object to be coated is pulled up at such a speed that it passes between the lid and the lid within 5 seconds, the coating film formed on the object to be coated will sag due to delayed drying. A coating film with a uniform thickness is formed from the beginning of coating.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram illustrating the state of dip coating of the present invention, (a) shows the state before dipping, (b) shows the state after dipping,
FIG. 2 is a partial cross-sectional view of a dip coating apparatus, FIG. 3 is a schematic cross-sectional view of a conventional dip coating apparatus, and FIG. 4 is a cross-sectional view of the coating film at the upper end of the coated article. 1... Application tank, 2... Paint, 3... Object to be coated, 4
...mantle groove, 5... gain. Patent applicant Fuji Xerox Co., Ltd. Agent
Patent Attorney Tsuyoshi Watanabe Figure 1 HE To Ward 0 Hyakubo W & Tan Procedural Amendment (Voluntary) July 13, 1985 Commissioner of the Patent Office Kunio Ogawa Address 3-3-5 Akasaka, Minato-ku, Tokyo Name (
549) Fuji Xerox Co., Ltd. Representative Yota Kobayashi 6 Contents of amendment (1) ``Table 4'' on page 11, line 5 of the detailed statement (Figure 4)
Correct to. ■Correct "pipon" in the third line of page 12 to "pipe". (3) In the same page, page 14, line 8, amend "Because I raise you" to "Because I raise you."

Claims (1)

[Claims] (1) A coating tank with a paint inlet at the bottom and an open top;
A paint introduced into a coating tank of a dip coating device, which is composed of a mantle groove having a paint discharge port provided at the outer edge of the upper end of the coating tank, and a lid having an opening in the center for inserting and pulling up the object to be coated. In the dip coating method, in which the object to be coated is immersed in the liquid and then pulled up for painting, the distance between the liquid level of the paint and the lid is set to 10 mm or less, and the object to be coated is placed between the liquid level and the lid. A dip coating method characterized in that the object to be coated is pulled up at such a pulling speed that the object passes within 5 seconds.