JPH04122471A - Method and device for gelling web coating layer - Google Patents

Abstract

PURPOSE:To gel the coating layer of a web without causing an uneven coating to take place by a method wherein the speed of a gas sprayed from each noncontact supporting means in a gas speed increasing region to the web surface is increased gradually in response to the position of the web in its traveling direction. CONSTITUTION:The gas spray openings 7a composing a noncontact supporting means 7 are arranged in opposed zigzag relation and in a manner to interpose therebetween a web 1 having on at least one side thereof a coating layer adapted to be gelled by the spray of a gas and the web 1 is continuously run between the noncontact supporting means 7 in a floating and wavy form to subject the aforesaid coating layer to gelation. In an gas speed increasing zone extending from at least the noncontact supporting means on the most upstream side to a certain noncontact supporting means within the entire web traveling region, the speed of the gas sprayed from the noncontact supporting means 7 to the web surface is gradually increased in response to the position of the web 1 in its traveling direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for gelling a web coating layer and an apparatus therefor, and particularly relates to a gelling method and an apparatus for gelling a web coating layer. Effective for gelling a double-sided coated web that has a gelled coating layer on one side and a pre-gelled coating layer on the other side while supporting and continuously conveying the coating layer in a non-contact state. The present invention relates to a gelling method applied to and an apparatus therefor.

[Conventional technology]

Conventionally, in the production of photographic materials having coating layers on both sides of a web to be coated, a coating solution is applied to one side of the web to be coated, and after being gelled and dried, the same process is passed through again. , apply coating liquid to the other side, kelize it,
However, in recent years, due to the demand for improved production efficiency,
Various one-line double-sided coating methods have been proposed in which the coating, gelling, and drying steps are performed by passing through a line at -.degree.

This type of double-sided coating method includes, for example,
Examples include coating methods described in Japanese Patent Publication No. 44171-44171 and Japanese Patent Publication No. 48-44171. The present applicant also proposed a method in which a coater and a gas injector were disposed at positions facing each other across a continuously running web in the previous application. have disclosed and put to practical use a method in which coating is carried out by the coater while floating and supporting the web by injecting gas toward the web from the gas injector.

On the other hand, as described above, a web with double-sided coating layers has a gelled coating layer on one side and an ungelled coating layer on the other side, and is continuously sent to the gelling process. In order to prevent the coated layer from being damaged, a web having such undried coated layers on both sides needs to be gelled while being floated and conveyed in a non-contact state.

As such a gelling method, for example, Japanese Patent Publication No. 48-4
4171 Publication, Japanese Patent Publication No. 4421102, Japanese Patent Publication No. 51-45819, and Japanese Patent Application Publication No. 1987-72847
Examples of gelling methods include those described in Japanese Patent Publication No.

However, even with the above gelling method, there are problems such as uneven web blowing, flutter, and uneven coating due to flutter.In order to solve these problems, the present applicant has developed an improved gelling method as described in the previous patent. It was disclosed in Publication No. 62-24148.

In the gelling method disclosed in JP-A-62-24148, as shown in FIG. Then, air is blown from the air outlets 23a, 23a... of the hollow cylindrical body 23 onto the side where gelation has been completed, and the coating layer 21 is formed on the other side by the coating coater 20 while the web 22 is floated and conveyed. After letting
The double-sided coated web 22 is continuously supplied with a gas supply body A each having a gas injection port and a non-contact curved surface;
B is guided to cold air zones arranged oppositely and in a staggered manner, where it is kelized and dried.

In the invention, in particular, in order to prevent uneven blowing of the coating layer before gelatinization and to suppress so-called flapping so as not to adversely affect the coating, the gas supply body A disposed on the upper side is provided in a non-contact manner. The curvature of the surface is smaller than the curvature of the non-contact surface of the gas supply body B disposed below, specifically, for example, the curvature of the non-contact curved surface of the gas supply body B is set to 1150 to 1.
/150, and the curvature of the non-contact surface of the gas supply body A is about 1/2 to 1/4 of that of the gas supply body B, and the gap between the gas supply bodies A and B is wavy and non-contact. While being conveyed in this state, the gel pre-treatment coating layer 21 is gelled and dried.

[Problem to be solved by the invention]

In recent years, in order to meet the demands for high-speed coating and rapid development of products, there has been a trend towards thin film coating and reduced gelatin content. However, in general, when the gelatin content is lowered, the coating film is inevitably more likely to flow during gelation, making it more likely that uneven blowing will occur. In addition, as the web is coated at high speed, it becomes more susceptible to web vibrations that occur during the gelling process.
Problems such as this are occurring.

The method described in Japanese Patent Publication No. 62-24148 is also effective in conventional low-speed coating and coating with high gelatin content, but as mentioned above, high-speed coating, low gelatin content coating, etc. The request could not be met, and problems such as uneven blowing and web vibration during the gelling process due to high-speed conveyance were increasing. To deal with this, if the curvature of the non-contact surface of one side of the gas supply body is reduced,
In addition to increasing the size of the device in the web traveling direction, a large number of gas injection slits are required to increase the size of the non-contact surface. In addition, since a large amount of the injected air flows between the web and the non-contact surface in the width direction of the web, this discharged air causes uneven flow at the edges of the web as well as cooling unevenness in the width direction of the web. Moreover, as mentioned above, in order to keep the curvature of the non-contact surface small, the wind pressure for floating the web is small (but conversely, the back pressure is small, so the support stability of the web during tension fluctuations is reduced). Problems such as lack of sexuality were occurring.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for gelling a coated web, and to prevent uneven coating due to uneven blowing, uneven flow, and web vibration (flapping) even under high-speed coating conditions and when using a coating liquid with a low gelatin content. An object of the present invention is to provide a gelation method and device that does not induce gelation.

[Means to solve the problem]

The above-mentioned problem can be solved by arranging non-contact support means in which gas injection ports are formed in a staggered manner facing each other, sandwiching a web having a coating layer that is gelatinized by gas spraying on at least one side of the web. In the method of gelling the coating layer by continuously traveling between the contactless support means in a floating state in a wavy manner, at least from the most upstream contactless support means to a certain contactless support means within the entire travel area. This problem can be solved by sequentially increasing the wind speed at which the gas jetted from each non-contact support means in the wind speed increasing region reaches the web surface in accordance with the position in the traveling direction of the web.

In addition, in terms of the apparatus, non-contact support means in which gas injection ports are formed are arranged oppositely and in a staggered manner, sandwiching a web having a coating layer that is sludged by blowing gas on at least one side. In the apparatus for gelling the coating layer by continuously traveling in a wave-like manner between the respective non-contact support means in a floating state, the apparatus includes at least the most upstream non-contact support means in the entire travel area to a certain non-contact support means. The non-contact support means disposed in the wind speed increasing area has a slit-shaped gas injection port along the width direction of the web, and a diffused flow is generated as a jet gas flow within the slit that is recessed from the open end of the gas injection port. This problem can be solved by providing a transmission resistor.

[Effect]

In order to increase the speed of double-sided coating and reduce the content of ceratin, the present inventors first promoted gelation in a low-temperature atmosphere and windless conditions, and then further promoted gelation using non-contact support. However, this method had problems such as an increase in the space required for the gelling process and unstable web transport in windless areas due to the web's own weight, making it difficult to put it into practical use.

Subsequently, after conducting various tests, the present inventors found that the stiffness of the coated layer of a photographic photosensitive material using ceratin as a binder gradually increases as the temperature decreases, although this depends somewhat on its physical properties. We focused on the fact that the uneven blowing greatly depends on the force (wind pressure) per unit area of the blown wind, ρV2 (ρ: air density, V: wind speed). As the rigidity of the layer increases, the final non-contact support increases the wind speed that the gas injected toward the coating layer reaches on the web surface from the non-contact support means disposed on the most upstream side within the wind speed increase area. It has been found that gelation can be efficiently performed without uneven blowing by gradually increasing the amount of water. Furthermore, according to this method, the wind speed reaching the web from the non-contact support means closest to the coating coater is minimal, so even if there is vibration of the web due to floating conveyance, the amount of vibration is extremely small. Coating failures in the coating coater due to web vibration can be prevented. On the other hand, even if the wind velocity reaching the web from a non-contact support means located a certain distance from the coating coater is high, and the vibration of the web is therefore large, the effect of the vibration of the web on the coating properties of the coating coater is substantially negligible. Since the amount is small, good applicability can be obtained.

Furthermore, in the device of the present invention, as a method of reducing the velocity of the gas jetted toward the web of the blown air, the same effect can be achieved by turning the blown air into a fine jet stream, that is, a diffusion flow. Focusing on this possibility, a permeation resistor for the injected gas is provided at least inside the gas injection port of the non-contact support means disposed in the gas wind speed adjustment region. Therefore, since gas is injected statically, web vibration and uneven blowing can be significantly suppressed compared to the conventional method of injecting gas dynamically. In this case, the gas injection area is substantially reduced by the gas permeation resistor, but by expanding the opening area of the gas injection port, the overall air volume can be compensated for and the stability of the web can be ensured. .

Furthermore, in the device of the present invention, since the gas resistor is disposed within the slit, even if the web should come into contact with the web-side surface of the non-contact support means, the gas resistor will not be contaminated by the coating liquid. It is possible to always blow out with a stable diffusion flow.

On the other hand, the non-contact surfaces of the non-contact supporting means of each group disposed facing each other with the double-sided coated web sandwiched therebetween have curvatures, and the curvatures are different as in the invention described in Japanese Patent Publication No. 62-24148. In this case, regions with different centrifugal forces due to the weight of the sea urchin are arranged alternately in the web running direction, which is rather unfavorable from the viewpoint of web vibration suppression, and it is desirable that the curvature be substantially the same.

In addition, the shape of the gas injection port of the non-contact support means disposed oppositely with the double-sided coated web sandwiched therebetween, and the shape of the gas injection port 17 is slit-like.
Alternatively, a shape such as a small hole may be considered, but in the present invention, jet ports are formed in the shape of a sleeve I in the width direction of the web at both ends of the web facing surface. With this slit-shaped injection port, the nozzle itself can be made relatively small while maintaining thermal conductivity to the coating surface, making it possible to suppress the amount of air flowing out in the web width direction and It is possible to more effectively suppress flow unevenness occurring at the ends and cooling unevenness in the width direction of the web.

It goes without saying that a combination of the method and apparatus according to the present invention will be more effective.

[Specific structure of the invention]

Hereinafter, the present invention will be explained in detail based on specific examples.

FIG. 1 shows a gelling device according to the invention.

The web 1 is a web having a coating layer on one side 1a which has been coated by a combination of a sly I/hotbar type coating device and a gas jet, and which has been gelled and dried. Uncoated surface (
On the other side) coating is performed on lb.

In this coating method, first, a blower 2 is connected to a hollow air blowing drum 3 in which a large number of blowing ports 3a, 3a are formed in the inner portion of the cylindrical wall surface, and the air from the blower 2 is It is discharged from each outlet 3a, 3a, etc., and the web 1 is conveyed in a floating state.

The web 1 enters the gas injector, travels around the drum 3, and is bead coated from the slide hopper type coating coater 4 while being floated and conveyed by the air pressure discharged from the gas injector. In a specific example, this application coater 4 has an outflow slit 4A, and the application liquid 5 pushed into a liquid reservoir 4B formed in the application coater 4 via a pump (not shown) flows out from the outflow slit 4A. , head over to Web 1. At this time, there is a slight clearance G between the head shoulder of the coating coater 4 and the surface of the web 1, and since the web 1 is being conveyed continuously, each coating liquid 5 is applied to the clearance G. It is applied continuously in a crosslinked state while forming beads.

The injection pressure from the gas injector is preferably 300 to 2000 mmAq based on the internal pressure of the drum 10. The injection amount of gas, normal air, is 0.3 to 5.0.
cc/cm27sec is desirable. The air injection port may be a randomly formed circle or an appropriate shape. Further, the opening area ratio can also be varied in the width direction of the drum 3.

Further, it is usually desirable to use a circular cross-sectional shape for the drum 3, but as long as an arc is formed from the entrance position of the web 1 to the bead formation position, the shape of other parts can be changed. Not necessarily limited.

With the coating device configured as described above, one part of the web 1 can be coated.
The web 1 whose b side has been coated is sent to the gelling process.

The gelling device that performs gelling first uses a plurality of non-contact support means 71.
72.7. ... will be installed. The non-contact support means 7
(hereinafter simply referred to as supporting means) are slit-shaped injection lowers a extending along the web width direction at the front and back of the web traveling direction.
, 7a is a two-slit type support means. Further, as the support means, as shown in FIG.
On the side facing the web 1, a curved surface with a constant curvature is formed,
and a plurality of ribs l-1, oa along the width direction of the web]
, 10a, etc. can also be used.

Further, as a modification of the two-slit support means, for example, as shown in FIG. 3, two slits t-1, ], a
, 1.1 The injection direction of a may be directed inward.

According to the findings of the present inventors, the two slit-type support means 7 are formed at the front and back of the web 1 in the traveling direction.
．． 11 is the curved surface multi-sleeve type support means 10.
Compared to this, a static pressure region is formed between the two slots 1 and 1.
Support stability during high-speed conveyance is improved, and web 1
It has been confirmed that the amount of air flowing in the width direction is reduced, and uneven flow and cooling at the edge of the web 1 are suppressed.

Pressurized air is supplied by the blower 6 through the air supply pipe 9 to the support means groups 70.7□... arranged in a staggered manner, and the support means groups 70.7□, 72.・
An air volume adjustment valve 81.8 is installed in the middle of the supply pipe 9 that branches into
2... are provided respectively.

In the present invention, [QUEB] is injected from the support means 7I installed on the most second stream side under the gelling device.
Adjustment is made so that the reaching wind speed relative to the surface is set as the minimum value, and then the reaching wind speed is gradually increased toward the downstream side.

For example, as shown in Fig. 6, which shows an example of the relationship between the position of the support means in the direction of line movement and the gas jet speed of the support means, the support means may be installed in a certain section from the support means disposed on the most upstream side. The support means used for this purpose are adjusted by the air volume adjusting valves 8°, 8□, etc. so that the wind speed gradually increases as the line progresses, and then adjusted to maintain a constant wind speed. As a specific numerical value, for example, the minimum wind speed value in the support means 7 is 1 to 5 m/sec.
In particular, it is desirable to set the wind speed to about 2 to 4 m/see. Further, the above-mentioned - wind speed value is preferably 16 m/
sec.

More preferably, the speed is 12 m/sec.

Further, the length of the wind speed adjustment section can be determined using as a guideline until the surface temperature of the coating layer reaches about 10° C., at which point the fluidity of seratin is significantly reduced. On the other hand, as can be inferred from the above explanation, when the conveyance length of the web 1 is short, the first
From the first support means to the final support means, the wind speed reached by each support means can be made different in stages.

Note that in areas where the gas injection wind speed is extremely low, specifically in the support means 717□, the support stability and thermal conductivity of the web 1 decrease, but this can be solved by increasing the slit width and reducing the air volume from the slit. This can be countered by methods such as increasing the

By the way, the same effect can be obtained by diffusing the blown air (making it into a small jet) without adjusting the gas jet wind velocity of each support means as described above.

Specifically, as shown in FIGS. 4 and 5, a gas permeation resistor 12 such as a metal mesh, sintered metal, or nylon net is placed inside the injection port of the support means 7.11. It is also possible to provide one.

The gas permeation resistor 12 is temporarily connected to the support means 7 and the web 1.
If the gas permeation resistor 12 comes into contact with the gas permeation resistor 12, it is difficult to clean the gas permeation resistor 12 and the gas permeation resistor 12 needs to be replaced, which causes problems such as a decrease in production efficiency. It should be noted that mounting the gas permeation resistor 12 recessed from the injection port can be sufficiently effective even if the position l is a few holes.

In addition, if the porosity (total pore area/injection port area) of the surface of the gas permeation resistor 12 is too large, the diffusion effect will be lost, and if it is too small, the support stability of the web 1 will be lacking. 10-60%, preferably 20-40%
is desirable. Furthermore, even if the pore size is the same, it is better to make the pores smaller and not increase the number of pores. For example, in the case of metal mesh, it is better to reduce the wire diameter and increase the linear density.

In addition, examples of the web 1 in the present invention include polyethylene terephthalate (PET), cellulose triacetate, and the like.

Furthermore, although the present invention is effectively applied to coating while floating and conveying using a gas jet, it can also be applied to coating while guiding the web in contact with a back roll or the like.

In addition, the coating device may be of a slide hopper type or may be of an extrusion type. Moreover, the present invention is not limited to double-sided coating, but can be applied favorably to gelation in single-sided coating.

〔Example〕

Hereinafter, the effects of the present invention will be explained in detail based on Examples.

(Example 1) Depending on the gelling method according to Japanese Patent Publication No. 62-24148 previously disclosed by the present applicant, coating conditions (web conveyance speed of 60.../sec or more, gelatin content of 45% or less) However, it was not possible to obtain a good coating layer due to problems such as coating failure due to unevenness and flaking of the coating layer.Therefore, a gelling device shown in Fig. 1 was used to adjust the coating conditions - web transport. Double-sided coating was performed at a speed of 60 m7 sec and a gelatin content of 4.5.

In addition, the adjusted wind speed in each support means 71, 7□, 73 is shown in Table 1. In addition, the support means numbers are 1 from the upstream side,
The numbers will be 2, 3, etc.

Table 1 As a result of the above test, according to the method of the present invention, a good product could be obtained with no coating defects due to uneven blowing, uneven flow, or flopping of the web in the coating layer of the obtained double-sided coated web. .

(Example 2) In Example 2, without adjusting the wind speed of each support means, as shown in FIG.
A similar test was conducted using a method in which a SUS mesh was used to diffuse the injected gas.

The SUS mesh used had a number of wires of 50 per inch and a porosity of 30%. Further, the blowing wind pressure was kept constant at 20 mmAq. Incidentally, under the same conditions of the above-mentioned blowout wind pressure of 20 mmAq,
When the wind speed reaching the web surface without the SUS mesh was measured, it was 16.5 m/sec, whereas with the SUS mesh, the wind speed was reduced to 5.8 m/sec. .

As a result of the above-mentioned test, the coating layer of the double-sided coated web obtained by the method of the present invention was good, with no coating defects due to uneven blowing, uneven flow, or flopping of the web.

〔Effect of the invention〕

As described in detail, according to the present invention, when gelling a double-sided coated web, even with high speed coating and low gelatin content, uneven blowing, uneven flow, and web vibration (flutter) can be avoided. Does not cause coating defects.

[Brief explanation of the drawing]

FIG. 1 shows a gelling device for a double-sided coated web according to the present invention, FIGS. 2 and 3 show modifications of the non-contact support means, and FIGS. 4 and 5 show a non-contact support means. 6 is a diagram showing an example of the relationship between the support means placement position in the line traveling direction and the gas injection wind pressure by the support means, and FIG. 7 is a diagram showing the conventional FIG. 2 is a diagram showing a gelling device for a double-sided coated web.

Claims (2)

[Claims] (1) Non-contact support means in which gas injection ports are formed are arranged oppositely and in a staggered manner, sandwiching a web having a coating layer that gels when sprayed with gas on at least one side, and supporting each of the above-mentioned non-contact supports In the method of gelling the coating layer by continuously traveling between supporting means in a floating state in a wavy manner, at least in a wind speed increasing region from the most upstream non-contact supporting means to a certain non-contact supporting means within the entire traveling region. ,
A method for gelling a web coating layer, the method comprising sequentially increasing the wind speed at which the gas jetted from each non-contact support means in the wind speed increasing region reaches the web surface in accordance with the position in the traveling direction of the web. . (2) Non-contact support means in which gas injection ports are formed are arranged facing each other in a staggered manner, sandwiching a web having a coating layer that gels when sprayed with gas on at least one side, and supporting each of the above-mentioned non-contact supports. In an apparatus that gels the coating layer by continuously traveling between support means in a floating state in a wavy manner, the wind speed is increased in a wind speed increasing region from at least the most upstream non-contact support means to a certain non-contact support means within the entire travel region. The non-contact support means arranged has a slit-shaped gas injection port along the width direction of the web, and a permeation resistor that is recessed from the open end of the gas injection port and inside the slit is arranged to make the ejected gas flow diffuse. A gelling device for a web coating layer, characterized in that: