JPH01249169A - Coating method - Google Patents

Abstract

PURPOSE:To prevent thick coating and to prevent the staining of rolls and the adhesion of the stain to a product by suspending the feed of a coating liq. by a pump immediately before coating. CONSTITUTION:A polyethylene terephthalate film is travelled as a web 1 at a certain speed. Immediately before coating, the feed of the coating liq. 4 by the pump 12 is suspended, e.g., for 5 sec, a stand 8 for moving up and down a coater is moved up and coating is carried out. In the midst of regular coating, the pump is stopped and the coater is moved down to finish coating. Thus, coating and drying efficiencies and yield are enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to photographic materials such as photographic film and photographic paper, photolithographic materials, magnetic recording materials such as magnetic recording tape, pressure-sensitive recording paper, and heat-sensitive recording paper. Regarding improvements in the process of applying a liquid coating composition to a continuously running long flexible support (hereinafter referred to as "web") in the production of recording materials, more specifically, improved bar coating methods and roller coating. Related to Methods [Prior Art] Various methods have been proposed as methods for applying a coating liquid to a continuously running web. Generally, the coating process involves the part where the coating liquid is transferred to the web (hereinafter referred to as "
"Application system". ) and a part that measures the coating liquid transferred to the web to the desired coating amount (hereinafter referred to as the "measuring system"), so coating methods are classified according to the differences between the application system and the measuring system. Ta.

Based on the difference in application system, roller coating method,
Known methods include dip coating, fountain coating, and air knife coating, blade coating, bar coating, etc. based on differences in metering systems.

In addition, extrusion coating methods, bead coating methods, and curtain coating methods are known as methods in which the applicator and metering are performed in the same part.

Among these coating methods, the bar coating method and the roller coating method transfer excess coating liquid to the web and then remove the excess coating liquid using a bar or roller that is stationary or rotating at a slower circumferential speed in the opposite direction to the web. The coating liquid is scraped off to achieve the desired coating amount, and it has been widely used because it has the feature of being able to apply a thin layer at high speed with a simple device and operation.

For example, FIG. 5 shows a bar coating device (Japanese Patent Laid-Open No. 53-225
4), in which a coating rod 2 is rotated in the same direction or in the opposite direction to the continuously running web 1. A bar support member 3 is provided over the entire length of the bar 2, and has the function of preventing the bar 2 from being bent and serving as a liquid supply device for supplying the coating liquid 4 to the bar 2. That is, the coating liquid 4 is supplied to the weir member 6 from the liquid supply port 5 provided on the bar support member 3.
The coating liquid 4 is supplied into the liquid supply guide groove 7 formed between the web 1 and the rotating bar 2, and is picked up by the rotating bar 2 and applied to the web 1. As a result, only the desired coating amount is applied to the web 1, and the rest flows down and the newly supplied coating liquid 4 is applied.
At the same time, a liquid reservoir 8 is formed. Therefore, in a steady state, the coating liquid 4 is applied to the web 1 via the liquid reservoir 8.

In the roller coating method, as shown in FIG. 2, a continuously running web L is supported by a support roller 13, the liquid in a liquid receiver 16 is transferred to a coating roller 14 by a pickup roller 15, and the liquid is transferred from the coating roller 14 onto the web 1. This is a method in which it is applied to

[Problem to be Solved by the Invention] However, at the start and end of coating, when the coating rod or roller and the web come into contact with or separate from each other by raising or lowering the coater upper and lower tables, etc., the liquid on the coating rod or roller is not measured. Therefore, there was a problem that the coating was extremely thick as a result of being coated on the web. This extremely thick coating varies depending on the physical property of the coating liquid (3), the shape of the coating rod or roller, and the type of web, but it may be more than 5 times thicker than the steady area, so be careful not to dry in the drying zone. If countermeasures were not taken, the subsequent rollers would be significantly contaminated, which would adhere to the products that were subsequently passed through, resulting in loss of products.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a stable coating method that eliminates contamination of rollers and adhesion of products.

[Means to solve the problem]

The above-mentioned object of the present invention is to prevent a thick coating from occurring at the start and end of coating in a method of coating a continuously running long flexible support using a coating rod or coating roller. This is achieved by a coating method characterized in that the liquid feeding by a pump is temporarily stopped just before coating and then stopped just before the coating is finished.

The continuously running web in the present invention includes paper, plastic film, resin coated paper, aluminum web, synthetic paper and the like.

Examples of the material of the plastic film include polyolefins such as polyethylene and polypropylene, vinyl polymers such as polyvinyl acetate, polyvinyl chloride, and polystyrene;
Polyamides such as 6.6-nylon and 6-nylon, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polycarbonates, and cellulose acetates such as cellulose triacetate and cellulose diacetate are used. Further, the resin used for resin-coated Indian paper is typically polyolefin such as polyethylene, but is not necessarily limited thereto.

The thickness of the web is also not particularly limited, but can range from o to 1.
Something with about 0 saliva is advantageous in terms of handling and versatility.

In the present invention, the pump for feeding the coating liquid is temporarily stopped just before coating or just before the end of coating. This means that when the coating rod or roller surface is wet but the coating liquid has not been replenished when the coating rod or roller is brought into contact or separated by raising or lowering the table, etc.

When starting coating, restart the pump immediately after the coating rod or roller finishes contacting it to achieve the specified amount of coating, and when finishing coating, stop pumping just before the end of coating and turn off the coating rod or roller when the supply amount decreases. It means moving away from the web.

[For production]

In the present invention, by temporarily stopping the liquid feeding by the pump that sends the coating liquid just before coating and just before the end of coating, when the web comes into contact with the coating liquid just before coating, the coating rod or roller is Since only a very thin coating liquid is attached, it will not be coated thickly. However, unless the coating liquid is replenished immediately, the desired coating thickness cannot be obtained, so it is important to temporarily stop the coating.

Further, when the coating rod or roller is removed from the web at the end of coating, by stopping replenishment of liquid by the pump immediately before this, thick coating can be prevented since the coating liquid is not replenished when the coating rod or roller is removed.

〔Example〕

Example-1 Coating liquid: Viscosity 5 cps solution with the following components Acrylic acid copolymer: 10 parts Methyl glycol: 78.8 parts Methanol: 10 parts Dye 20.1 parts Apparatus as shown in Figure 1 Using a polyethylene terephthalate film as a web 1, it was run at a coating speed of 70 m/min, and before coating, the liquid feeding of the 5see pump 12 was stopped, and then the coater upper and lower tables 8 were raised to perform coating within 2 seconds. The plan view of the pattern of the coating area is shown in Figure 3 (b,), and the thick coating rate (a,) at the start of coating is
was up to 15%.

The definition of thick coating rate is as follows.

Next, during the steady coating, the pump was stopped for 1 sec, and 3 sec after the pump stopped, the coater was lowered to complete the coating. At that time, the pattern at the end of coating will be as shown in (ax) and (bt) in Figure 3, where (at) is the thick coating rate at the end of coating, and (h) is the web running surface at the end of coating. FIG. 2 is a plan view illustrating the situation. It was found that thick coating hardly occurs.

Comparative example-1 Turn on the pump using the same device with exactly the same coating solution.

Coating was started and finished using exactly the same operations except for no OFF operation. The distribution of thick coating in the longitudinal direction at this time is as shown in Fig. 4, and the thick coating rate (a,) is the thick coating rate at the start of coating, and the web is about 20M at the start of coating.
0. (at) was the thick coating rate at the end of coating, which was 2.3 over 30 m of the web at the end of coating, which was a much larger result.

[Effects of the Invention] The present invention provides a method for coating a continuously running long flexible support using a coating rod or a coating roller, in which J
In order to prevent this, the thickness at the start and end of coating is reduced by a coating method characterized by temporarily stopping the pump that sends the coating liquid just before coating and then stopping just before the end of coating. Prevents coating and prevents accidents such as contaminating the roller or adhesion of the web (and improving coating and drying productivity.

This contributed to an increase in profit margins.

[Brief explanation of the drawing]

1 and 2 are partial sectional side views of a coating device according to an embodiment of the coating method of the present invention, and FIG. 3 is a side sectional view of a coating device related to the coating method of the present invention. 1... Web 2... Coating rod (bar) 3... Bar support member 4... Coating liquid 5... Supply port 6... Head portion 7... Liquid supply guide groove 8... -Liquid reservoirs 9a, 9b...Backup roller 10...Coated web 11...Liquid feeding pipe 12...Pump 13...Support roller 14...Coaching roller 15...Pickup roller 16 ...Liquid receiver (3 others) Figure 1, Figure 32 Figure 3 <a, > (b2) Distance 11 (to the chapter) Figure 4 J and string (n-on un(--)

Claims (1)

[Claims] In the method of coating a continuously running long flexible support using a coating rod or coating roller, in order to prevent thick coating that occurs at the start and end of coating, it is necessary to use a pump to feed the coating liquid. A coating method characterized by temporarily stopping just before coating and stopping just before finishing coating.