JP2001191008A - Method and device for drying coating film, and coating film product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drying method and a device for drying a coating film capable of efficiently decreasing a residual solvent in the coating film in the case that the coating film is thick, and to provide a coating film product. SOLUTION: In the drying method in which a coating liquid is applied so that wet thickness rightly after the coating is >=50 μm to form the coating film to have >=3 μm dry thickness on a supporting body and heated wind is blown on both surfaces of the coated surface having the coating film and the uncoated surface opposite to the coated surface to vaporize the solvent in the coating film, the velocity of the heated wind blown on the uncoated surface is larger than that of the heated wind blown on the coated surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of drying a coating film, a drying apparatus and a coating film manufacturing method, in which a coating solution is applied onto a support to form a coating film, and then the solvent in the coating film is evaporated. About things. In particular, it can be effectively used for coating and drying photographic light-sensitive materials, heat-developable light-sensitive materials and the like.

[0002]

2. Description of the Related Art The most common drying method for a coating film is a heating air drying method, and various methods have been proposed. For example, those which specify a heating and drying temperature represented by Japanese Patent Publication No. 53-10691, and Japanese Patent Publication No. 1-5727
Numerous proposals have been made, such as those that regulate the direction of heated air as represented by No. 6. However, when the film thickness in the dry state after drying (dry film thickness) is as thick as 3 μm or more, there is a problem that the residual solvent is likely to remain in the coating film. The amount of the residual solvent often affects the performance of the coating film. If a large amount of the residual solvent remains, the product often changes over time.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for drying a coating film, a drying apparatus, and a coating film product which efficiently reduce the residual solvent in the coating film when the dry film thickness is large. It is.

[0004]

The above object of the present invention has been attained by the following constitutions.

(1) A coating film is formed on a support by applying a coating solution with a wet film thickness of 50 μm or more immediately after coating so that the dry film thickness becomes 3 μm or more, and a coating film having the coating film is formed. In the drying method of supplying heat to both the surface and the opposite coating surface opposite to the coating surface and evaporating the solvent in the coating film, the amount of heat supplied to the coating surface is supplied to the coating surface. A method for drying a coating film, wherein the drying method is larger than the heat value.

(2) A coating liquid is applied on a support with a wet film thickness of 50 μm or more immediately after coating so that the dry film thickness is 3 μm or more, and a coating film is formed. In the drying method of blowing the heating air to both sides of the surface and the opposite anti-coating surface opposite to the coating surface, and evaporating the solvent in the coating film, the wind speed of the heating air blowing to the anti-coating surface is:
A method for drying a coating film, wherein the drying speed is higher than the velocity of the heated air blown onto the coating surface.

(3) The wind speed of the heated air blown to the anti-coating surface is 1.2 times the wind speed of the heated air blown to the coated surface.
3. The drying method as described in 2 above, wherein the drying method is 3 to 3 times.

(4) A coating film is formed by applying a coating solution on the support with a wet film thickness of 50 μm or more immediately after coating so that the dry film thickness is 3 μm or more, In a drying method in which heated air is blown on both sides of the surface and the anti-coated surface opposite to the coated surface, and the solvent in the coated film is evaporated, the temperature of the heated air blown on the anti-coated surface is
A method for drying a coating film, wherein the temperature is higher than the temperature of the heated air blown onto the coating surface.

(5) The temperature of the hot air blown against the coating surface is 2 to 2 times lower than the temperature of the hot air blown against the coated surface.
5. The drying method according to the above item 4, wherein the temperature is higher by 50 ° C.

(6) A drying apparatus for applying a coating solution on a support to form a coating film and then supplying heated air to evaporate a solvent in the coating film. It has a coating surface side nozzle that blows hot air, and an anti-coating surface side nozzle that blows heating air to the opposite coating surface opposite to the coating surface, and the wind speed of the heating air blown out by the coating surface nozzle is the same as that of the above. A drying apparatus characterized in that the velocity is lower than the velocity of heated air blown from a nozzle on a coating surface side.

(7) In a drying apparatus for applying a coating solution on a support to form a coating film and then supplying heated air to evaporate a solvent in the coating film, An application surface side nozzle that blows heated air, and an anti-application surface side nozzle that blows heated air to the opposite application surface opposite to the application surface, the distance between the application surface side nozzle and the support, A drying device, wherein the drying device is longer than the distance between the nozzle on the side opposite to the coating surface and the support.

(8) The distance between the nozzle on the coating side and the support is 1.2 to 10 times the distance between the nozzle on the side opposite to the coating and the support. Drying equipment.

(9) A drying apparatus for applying a coating solution on a support to form a coating film and then supplying heated air to evaporate a solvent in the coating film. An application surface side nozzle that blows heated air, and an anti-application surface side nozzle that blows heated air to the opposite application surface opposite to the application surface, wherein the application surface side nozzle and the anti-application surface side nozzle are respectively It has a blower that supplies heating air independently, and the blower of the coating surface side nozzle and the anti-coating surface side nozzle has a temperature controller that controls the temperature of the heating air independently. A drying device characterized by the above-mentioned.

(10) A coating film product dried by the drying method according to any one of the above items 1 to 5.

(11) A coating film product dried by the drying device according to any one of the above items 6 to 9.

Hereinafter, the present invention will be described in detail. When the dry film thickness is large, the film thickness in a wet state immediately after coating (wet film thickness) is generally large. As a result of analyzing the case where the wet film thickness is large, it has been clarified that the solvent concentration distribution becomes evident in the thickness direction of the coating film in the process of drying the solvent from the wet state. Where "dry film thickness"
The term “thickness” of a coating film in a state where a coating process including a coating process of coating a coating solution on a support and a drying process of drying is completed and the product is shipped as a product. The term “wet film thickness immediately after coating” refers to the film thickness of the coating film immediately after leaving the coater after the coating solution has been placed on the support. As a method for measuring the dry film thickness, for example, the dry film thickness can be calculated by measuring the total thickness of “support + coated film” and then subtracting the thickness of the support. Further, the wet film thickness immediately after the application can be uniquely determined in order to obtain a desired dry film thickness.

In the drying step of the coating film, the solvent concentration near the surface rapidly decreases due to evaporation of the solvent from the coating film surface, and only the surface is formed into a film, and the movement of the solvent from the inside of the coating film to the surface is hindered. In addition, it is considered that the solvent concentration distribution becomes apparent in the thickness direction of the coating film. It has been found that such a tendency is particularly remarkable when the wet film thickness immediately after coating is 50 μm or more. Such a tendency is particularly remarkable when the viscosity of the coating liquid is high. It is considered that the solvent is particularly slow to move from the inside of the coating film to the surface because the fluidity of the coating film is low. The viscosity of the coating liquid is 1
This tendency is likely to occur when the viscosity is higher than or equal to 00 mPa · sec.

Therefore, as a result of studying to solve this problem, it has been found that it is more effective to apply heat more aggressively to the application surface than the application surface to which the application liquid is applied in the drying step. is there. By heating from the anti-coating surface,
We believe that it promotes evaporation while uniformly dispersing the solvent in the coating film, and prevents film formation near the surface of the coating film.

Specifically, it is possible to solve the above problem by increasing the flow rate of heat from the anti-coating surface when the wind speed of the heating air blowing against the coating surface is higher than the wind speed of the heating air blowing against the coating surface. Was found. Here, the “wind velocity of the heated air blown to the coating surface” means the wind velocity in the vicinity of the coating surface on the coating surface side, and the “wind velocity of the heating air blown to the coating surface” is in the vicinity of the support surface on the opposite coating surface side. Wind speed at When drying is performed by supplying heated air from the nozzle, if the velocity of the heated air blown from the application surface side nozzle and the non-application surface side nozzle (at the air outlet) is the same, the nozzle outlet and the nozzle are sprayed. The shorter the distance from the object (support), the faster the velocity of the heated air to blow. Further, the higher the velocity of the heated air at the outlet of the nozzle, the higher the velocity of the heated air blown to the object to be blown. Furthermore, naturally, the higher the temperature of the heated air, the greater the amount of heat given to the object to be sprayed.

The drying apparatus for carrying out the drying method of the present invention includes a coating side nozzle spraying on the coating surface on the coating side of the support and an anti-coating side nozzle spraying on the support surface on the side opposite to the coating side. And a box for transferring a support in the box. It is preferable to use a floating type in which the support is conveyed while the support is floated by heated air blown from the application surface side nozzle and the non-application surface side nozzle. Then, in order to apply a larger amount of heat to the non-coating surface side of the support than the coating surface side, it is possible to achieve a configuration in which the wind speed at the non-coating surface nozzle outlet is higher than the wind speed at the coating surface nozzle outlet. At this time, it is preferable that the wind speed sprayed on the anti-coating surface is 1.2 to 3 times the wind speed sprayed on the coating surface. More preferably, it is 1.5 to 2.0 times.

A drying apparatus in which the distance between each nozzle outlet and the support (or the surface of the coating film) is shorter (closer) on the side opposite to the coating surface than on the coating surface side is also effective. In this case, it is preferable that the distance between the nozzle on the coating side and the surface of the coating film is 1.2 to 10 times the distance between the nozzle on the side opposite to the coating side and the surface of the support. More preferably, it is 3 to 5 times.

Here, when the drying method is the floating method, the distance between the nozzle outlet and the support (or the surface of the coating film) is determined by the distance between the transfer rolls immediately before and after entering the drying device (between the transfer roll and the support). It is assumed that a straight line between the contact points) is the theoretical absolute position of the support, and the distance from the nozzle to the nozzle outlet.

In the case where a plurality of nozzles are arranged in the transport direction in the drying apparatus, the average of the distance between each nozzle and the support is indicated.

Also, by making the temperature of the heated air higher on the side opposite to the application surface than on the side of the application surface, the inflow of heat from the opposite application surface can be increased, and the above problem can be solved. The drying device for this purpose is a box-shaped nozzle having a coating surface side nozzle that sprays the coating surface on the coating surface side of the support and an anti-coating surface side nozzle that sprays the coating surface on the non-coating surface side. And a device for transporting a support in the box. It is preferable to use a floating type in which the support is conveyed while the support is floated by heated air blown from the application surface side nozzle and the non-application surface side nozzle. This can be achieved by the fact that the temperature of the heated air to be blown is higher in the nozzle on the non-coating surface side than in the nozzle on the coating surface side. For this purpose, the application surface side nozzle and the non-application surface side nozzle each have a blowing means for independently supplying heated air, and a temperature control means for independently controlling the temperature of the heated air is provided. Device. At this time, it is preferable that the temperature of the heated air blown to the anti-coating surface is higher by 2 to 50 ° C. than the temperature of the heated air blown to the coated surface. More preferably, 5 to 2
0 ° C. higher.

The support applied to the present invention is not particularly limited, and can be applied to a support such as paper, plastic, and metal. Typical materials for the support include polyethylene terephthalate for plastics and aluminum for metals.

The coating method is not particularly limited, and any coating method such as slide coating, extrusion coating and roll coating can be selected. The coating film can be applied not only to a single-layer coating film but also to a multilayer coating film.

The type of the coating liquid is not particularly limited, and can be applied to a solution, a dispersion, and the like. The solvent in the coating liquid is not particularly limited, and the present invention can be applied to a system using water or an organic solvent as a solvent. In particular, the present invention is effective for an organic solvent having high volatility, since rapid evaporation occurs in the early stage of drying.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a drying apparatus applicable to the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 shows the coating and drying including the drying apparatus of the present invention.
Device. In the drawing, the member number 1 continuously travels in the direction of the arrow.
Support roll, 2 is a backup roll for supporting the support,
Reference numeral 3 denotes a coater for discharging the coating liquid, and 4 denotes a carrier row for the support.
Reference numeral 5 denotes a drying device. Backup roll 2 and
The coater 3 forms a coating device. Drying device 5
And S₁Is a blower (blower means) on the coating side, H₁Is blast
Machine S₁Heat the air coming from
Heater (temperature control means) for controlling the temperature, W ₁Ha
Data H₁Heated air whose temperature is controlled by F₁Is heated air W₁Support
Blowing means for blowing out to the coating surface side of the holding body, N₁Is
Blowing means F₁Nozzles provided on the application surface side
You. In addition, blowing means F₁Is a white arrow M as a whole₁of
It has a mechanism to drive in the vertical direction shown
Zul N₁And adjust the distance. S_Two, H
_Two, W_Two, F_Two, N_TwoAnd M_TwoIs on the opposite side of the coating surface
Note S₁, H₁, W₁, N₁And M₁Is the same member as
Blower, heater, heated air, and blowout on the opposite side of the coating surface
This is the driving direction of the cutting means, the nozzle, and the blowing means. Toes
In the drying device 5, the nozzle on the application side and the nozzle on the opposite side
The squalls independently control the blowing means and the temperature control means.
Have.

The operation of the coating device and the drying device will be described. The long support 1 unwound from the original winding (not shown) is supported by the backup roll 2 and turned by the coater 3 in the process of being inverted. The coating liquid is applied to form a coating film. Although the details are not shown, immediately after the support 1 on which the coating liquid is placed is separated from the lip of the coater 3 (the end of the coater 3 which discharges the coating liquid and faces the support 1). Is the "wet film thickness immediately after coating". Support 1 with coating film formed
Is carried into the drying device 5 via the transport roll 4. Then, heated air W ₁ is applied to the coating film surface by the coating surface side nozzle N ₁ ,
Heating air W ₂ to the support surface is provided by a counter-coating surface side nozzles N _2, the solvent is evaporated in the coating film. The support 1 carried out of the drying device 5 is completed as a coating film product through a post-processing step (not shown). The thickness of the coating film at this time is “dry film thickness”.

The amount of heat supplied to the support 1 by the respective heated air W ₁ or W ₂ is such that the amount of heat Q ₂ supplied to the non-coating surface (the surface of the support on the side opposite to the coating surface) is greater than that of the coating surface ( needs to be larger than the quantity of heat Q ₁ supplied a coating surface side to the film surface).

[0032] To the heat Q ₂ is greater than the amount of heat Q ₁ is, in the present embodiment is performed by adjusting the following.
1. To blowout means F ₁ white arrow M ₁ direction, and the blowout means F ₂ is driven to white arrow M ₂ direction, than the distance d ₁ between the front end of the coated surface side nozzles N ₁ and the support 1, anti the distance d ₂ of the front end of the coated surface side nozzles N ₂ and the support 1 is shortened. Here, the distance d ₁ and the distance d ₂ are the distances shown in FIG.
Regarding the member numbers in FIG. 2, the same members as those in FIG. 1 indicate the same members. In addition, T is a coating film. By making the distance d ₂ shorter than the distance d ₁ , the speed of the heated air on the side opposite to the coating surface can be increased, and as a result, the amount of heat Q ₂ supplied to the opposite coating surface can be increased. 2. The amount wind supplied by the blowing means S _2, it is greater than the amount of air supplied by the blowing means S _1.
This also by adjusting the blowing means, accelerating the velocity of the heated air stream of counter-coated surface side, as a result it is possible to increase the supply heat quantity Q ₂ in the counter-coated surface. 3. The temperature of the heated air stream W ₂ of the temperature controlled by the heater H _2, is higher than the temperature of the heated air W ₁ to the temperature control by a heater H _1. Of course,
It is possible to increase the supply heat quantity Q ₂ in the counter-coated surface.

[0033]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

The coating apparatus and the drying apparatus shown in FIG. 1 were used. The application device is an extrusion die, the length of the drying device 5 is 20 m, and each nozzle has a mechanism that can move up and down and change the height.

On a polyethylene terephthalate support having a width of 300 mm and a thickness of 0.1 mm, a polymer was dissolved in a solvent, methyl ethyl ketone, and the viscosity was 500 mPa · sec.
The coating solution having a surface tension of 25 × 10 ⁻³ N / m was applied immediately after the application at a wet film thickness of 100 μm and an application speed of 10 m / min. The dry film thickness after drying was 20 μm. Change the conditions as shown in Table 1 below and apply and dry.
The amount of residual solvent in the finished coating film was measured by gas chromatography. The wind speed was the wind speed at the nozzle outlet. Q ₁ is the amount of heat supplied to the application surface side, and Q ₂ is the amount of heat supplied to the opposite application surface side.

[0036]

[Table 1]

As shown in Examples, the conditions of the nozzle on the coating surface side and the nozzle on the counter coating surface side are compared, and when the blowing air velocity of the nozzle on the coating surface side is high, when the distance between the nozzle and the support is short, It can be seen that the amount of residual solvent can be reduced efficiently when the temperature is high.

[0038]

According to the present invention, it is possible to provide a method and an apparatus for drying a coating film capable of efficiently reducing the residual solvent in the coating film when the dry film thickness is large.

[Brief description of the drawings]

FIG. 1 is a coating and drying apparatus including a drying apparatus of the present invention.

FIG. 2 is a schematic diagram for explaining a distance between a nozzle and a support.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 support 2 backup roll 3 coater 4 transport roll 5 drying device S ₁ , S ₂ blower (blowing means) H ₁ , H ₂ heater (temperature control means) W ₁ , W ₂ heated air F ₁ , F ₂ blowing means N ₁ Coating surface side nozzle N ₂ Anti-coating surface side nozzle

Claims (11)

[Claims] 1. A coating film is formed by coating a coating solution on a support with a wet film thickness of 50 μm or more immediately after coating so that a dry film thickness is 3 μm or more, and a coated surface having the coating film In the drying method of supplying heat to both sides of the opposite coating surface opposite to the coating surface and evaporating the solvent in the coating film, the amount of heat supplied to the non-coating surface is equal to the amount of heat supplied to the coating surface. A method for drying a coating film characterized by being larger than the above. 2. A coating film is formed on a support by applying a coating solution with a wet film thickness of 50 μm or more immediately after coating so that a dry film thickness is 3 μm or more, and a coating surface having the coating film is formed. In the drying method of blowing heated air to both sides of the opposite coating surface opposite to the coating surface and evaporating the solvent in the coating film, the wind speed of the heating air blown to the anti-coating surface is blown to the coating surface. A method for drying a coating film, wherein the drying speed is higher than the speed of the heated air. 3. The wind speed of the heating air blown against the coating surface is 1.2 to 3 times the wind speed of the heating air blown against the coating surface.
The drying method according to claim 2, wherein the drying is performed twice. 4. A coating film is formed on a support by applying a coating solution with a wet film thickness of 50 μm or more immediately after coating so that a dry film thickness is 3 μm or more, and a coating surface having the coating film is formed. In the drying method of blowing heated air to both sides of the opposite coated surface opposite to the coated surface and evaporating the solvent in the coated film, the temperature of the heated air blown to the coated non-coated surface is sprayed to the coated surface. A method for drying a coating film, wherein the drying temperature is higher than the temperature of the heated air. 5. The temperature of the heated air blown to the anti-coating surface is 2 to 50 higher than the temperature of the heated air blown to the coated surface.
The drying method according to claim 4, wherein the drying temperature is higher by a degree. 6. A drying device for applying a coating liquid on a support to form a coating film and then supplying heated air to evaporate a solvent in the coating film, wherein the coating surface having the coating film is heated. A coating surface side nozzle for blowing air, and an anti-coating surface side nozzle for blowing heating air to the opposite coating surface opposite to the coating surface, wherein the wind speed of the heating air blown out by the coating surface nozzle is the anti-coating A drying apparatus characterized in that the velocity is lower than the velocity of the heated air blown from the surface side nozzle. 7. A drying device for applying a coating liquid on a support to form a coating film and then supplying heated air to evaporate a solvent in the coating film, wherein the coating surface having the coating film is heated. A coating surface side nozzle that blows air, and an anti-coating surface side nozzle that blows heated air to the opposite coating surface opposite to the coating surface, wherein the distance between the coating surface nozzle and the support is smaller than A drying device, wherein the drying device is longer than a distance between a coating surface side nozzle and the support. 8. The distance between the nozzle on the coating surface side and the support is 1.times. The distance between the nozzle on the non-coating surface side and the support.
The drying device according to claim 7, wherein the ratio is 2 to 10 times. 9. A drying device for applying a coating liquid on a support to form a coating film and then supplying heated air to evaporate a solvent in the coating film, wherein the coating surface having the coating film is heated. A coating surface side nozzle for blowing air, and an anti-coating surface side nozzle for blowing heated air to the opposite coating surface opposite to the coating surface, wherein the coating surface side nozzle and the anti-coating surface side nozzle are independent of each other. And a blowing means for supplying the heated air by heating, and the blowing means of the coating surface side nozzle and the anti-coating surface side nozzle each have a temperature control means for independently controlling the temperature of the heated air. A drying device characterized by the above-mentioned. 10. A coating film product dried by the drying method according to claim 1. Description: 11. A coating film product dried by the drying device according to claim 6. Description: