JP2700322B2 - Double-sided simultaneous coating device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided simultaneous coating apparatus, and more particularly, to a reverse coating suitable for simultaneously applying a fluorine-based aqueous dispersion to both sides of a substrate made of a plastic film. The present invention relates to a roll coater type double-sided simultaneous coating apparatus.

"Prior Art and Problems" Conventionally, various apparatuses have been put into practical use as double-sided simultaneous coating apparatuses for simultaneously applying an aqueous dispersion or the like to both sides of a substrate. However, in these apparatuses, the base material is often paper, and for example, the apparatus shown in FIG. 1 is typical. The apparatus comprises a substrate (4) made of paper unwound from an unwinder (1).
Is guided through a guide roll (6) to a steel roll (5) immersed in an immersion tank (2), and a coating solution (7) is applied to both sides of a substrate (4). ′)
The coating liquid (7) penetrates the substrate (4) by squeezing, etc. to obtain a substrate (8) coated on both sides. This device is effective when the coating liquid (7) penetrates into the substrate (4), but when the plastic film is to be applied to a predetermined coating thickness using the plastic film as a substrate, the plastic film is Since the paper cannot be stably held by pressing with a roll as in the case of paper, the substrate (4) is scraped off by a roll (3),
It is extremely difficult to stably hold at a fixed position between (3 ') and the like.

FIG. 2 shows another typical apparatus. This device is of the transfer type. That is, the base material (4) unwound from the unwinder (1) passes through the guide roll (6), and the coating liquids (7) and (7 ') in the coating liquid storage tanks (9) and (9') are removed. The transfer coating is performed almost simultaneously by the pick-up rolls (10), (10 ') and the coater rolls (11), (11'), which are picked up by an appropriate amount by the cleaning doctors (12), (12 '). In the case of this apparatus, when the transfer rate is high (that is, when the combination of the base material and the coating liquid is good), good quality can be obtained. However, the transfer rate depends on the affinity of the base material and the properties of the liquid itself. In the case of a poor coating liquid, for example, a fluorine-based aqueous dispersion, it is not possible to obtain a quality, particularly a beautiful appearance.

"Means for solving the problem" In view of such circumstances, the present inventors have conducted extensive research on a double-sided simultaneous coating apparatus suitable for applying a fluorine-based aqueous dispersion to both sides of a plastic film,
The present invention has been reached.

That is, the present invention is an apparatus for simultaneously applying an aqueous dispersion containing fluorine to both surfaces of a base material made of a plastic film, and has two coater heads and each coater roll has a distance equivalent to the thickness of the base material. The reverse roll coater type double-sided simultaneous coating device is arranged such that each coater roll is provided as a backup roll for another coater head.

The substrate used in the present invention is a substrate made of a plastic film, for example, a so-called heat-resistant plastic film represented by a polyimide film, a polyamide film, a polyparabanic acid film, and an aromatic polyamide film. The thickness is not particularly limited, but is preferably 5 μm to 300 μm because if it is too thin, the film will break, and if it is too thick, the adhesion to the coater roll will be unsafe.

The aqueous dispersion containing fluorine used in the present invention includes tetrafluoroethylene (TFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA). ), An aqueous dispersion containing a fluororesin such as polychlorotrifluoroethylene containing tetrafluoroethylene-ethylene copolymer (ETFE) and chlorine.

The solid concentration of this dispersion is 10wt% ~ 70wt%
Is appropriate, but is determined in relation to the final product thickness, dispersion viscosity and the like. The viscosity of the dispersion is preferably 1 cp (centipoise) to 100 p (poise). More preferably, it is 50 cp to 5p. 1cp
When the viscosity is less than 100p or more than 100p, the transfer efficiency becomes poor, and the coated surface becomes poor in appearance.

On the other hand, it is not possible to add a thickener for adjusting the viscosity, a solvent such as methanol, an antifoaming agent for eliminating bubbles generated at the time of application, or a pigment for coloring the dispersion to the dispersion. It doesn't matter.

 The present invention will be described based on the drawings showing embodiments.

3 and 4 show that one coater head is 2
It is composed of book rolls, that is, pickup rolls and coater rolls (23) (24), and (23 ') (24'). Fig. 3 shows the base material (2
FIG. 4 shows a case where the substrate (25) made of a plastic film is pulled in the horizontal direction.

3 and 4, a base material (25) made of a plastic film is unwound from an unwinder (21), and is picked up from a coating solution storage tank (22), (22 ') by a pickup roll (23).
Pumping solution (27) and (27 ') consisting of an aqueous dispersion containing fluorine in (23'), apply it almost simultaneously on both sides of substrate (25) with coater rolls (24) and (24 ') Then, a substrate (28) having the coating liquid applied to both sides is obtained. Basically, it is preferable that the pickup rolls (23) and (23 ') are rubber rolls and the coater rolls (24) and (24') are steel rolls from the viewpoint of the accuracy of coating thickness. Regarding one of the coater heads, a steel roll may be used as the pickup roll and a rubber roll may be used as the coater roll. The pickup rolls (23) and (23 ') do not have a cleaning doctor. The clearance between the two coater rolls (24), (24 ') is set slightly larger than the thickness of the substrate (25). The lower limit of the clearance is the thickness of the substrate, and the upper limit is the clearance at which the respective coater rolls function as a mutual backup roll. Although it depends on the coating thickness, a thickness three times as large as the base material becomes the upper limit of the clearance.

Next, the speed of the substrate (25) and the coater roll (2
4), (24 ') The speed of the surface, in this coating method, coater roll and pickup roll (24)
The clearance between (23), (24 ') and (23) is basically as narrow as possible, and the coater rolls (24), (2)
It is preferable to form a thin film on 4 ′) and transfer the thin film on the coater roll (24), (24 ′) 1.1 to 20 times on the substrate (25). Accordingly, the surface speed of the coater rolls (24) and (24 ') is preferably 1.1 to 20 times the speed of the substrate (25). If the clearance between the two coater rolls (24), (24 ') is sufficiently close to the thickness of the substrate (25), the function of the backup roll will be fully exhibited and the transfer rate will be increased, and therefore the same coating thickness In order to achieve the above, it is necessary to reduce the ratio between the speed of the coater roll surface and the speed of the substrate. Conversely, if the clearance between the two coater rolls (24) and (24 ') is farther than the thickness of the base material (25), the function of the backup roll is reduced and the transfer rate is reduced. It is necessary to increase the ratio of the speed of the base material.

The direction of rotation of each roll, but the coater roll (2
4) and (24 ') are transferred in the direction opposite to the direction in which the substrate (25) advances. Meanwhile, pickup roll (23),
The direction of rotation of (23 ') does not matter. However, the fourth
As shown in the figure, when the liquid is supplied from the upper coating liquid storage tank (22 '), the rotation direction is restricted, and the coater roll (24') moves the pickup roll (2) in the direction opposite to the direction in which the substrate (25) advances.
3 ') is rotated in the direction in which the substrate (25) advances.

5 and 6 both show another embodiment of the apparatus of the present invention, in which each coater head has three rolls, ie,
It is composed of a pickup roll, a metering roll, and a coater roll (23) (29) (24), (23 ') (29') (24 '). FIG. 5 shows a case where the base material (25) made of a plastic film is pulled upward, and FIG. 6 shows a case where the base material (25) made of a plastic film is pulled in the horizontal direction.

In FIGS. 5 and 6, a base material (25) made of a plastic film is unwound from an unwinder (21), and the coating liquid storage tanks (22) and (22 ') are further pulled up by a pickup roll (2).
3), a coating solution (27) consisting of an aqueous dispersion containing fluorine in (23 '), pumping up (27'), weighing with a metering roll (29), (29 '), a coater roll (24), At (24 '), the substrate (25) is applied almost simultaneously on both sides of the substrate (25), and the application liquid is applied on both sides to obtain a substrate (28).
The material of the three rolls is a coater roll (24), (24 ')
Is steel roll, metering roll (29), (29 ')
It is preferable to use a rubber roll from the viewpoint of thickness accuracy of the coating thickness, but of the two coater heads, one coater head may be a rubber roll and a metalling roll may be a steel roll. on the other hand,
The pickup roll is preferably a rubber roll if the metalling roll is a steel roll, and a steel roll if the metalling roll is a rubber roll. Pickup roll (23),
(23 ') does not have a cleaning doctor, as is apparent from FIGS.

The clearance between the two coater rolls (24), (24 ') is the same as in FIGS. 3 and 4, and also the clearance between the substrate (25) and the coater rolls (24), (24'). The relationship of the surface speed is the same as in the case of FIGS. The direction of rotation of each roll, but coater roll (24), (2
As for 4 ′), it is rotated in the direction opposite to the direction in which the substrate (25) advances. Meanwhile, pickup rolls (23), (2
3 ') and the rotating direction of the metering rolls (29) and (29') may be either. However, as shown in FIG. 6, when the coating liquid (27 ') is supplied from the upper coating liquid storage tank (22'), the rotation direction is restricted and the pickup roll (23 ')
Is rotated in the direction in which the substrate (25) advances, and the metering roll (29 ') is rotated in the direction opposite to the direction in which the substrate (25) advances.

FIG. 7 shows still another embodiment of the present invention, in which a coater head has one coater roll and coating knives (24) (30), (24 ') for measuring the amount of application.
(30 '). In the figure, a base material (25) made of a plastic film was unwound from an unwinding machine (21) and adhered to coater rolls (24) and (24 ') in coating solution storage tanks (22) and (22'). Coating solutions (27) and (27 ') composed of an aqueous dispersion containing fluorine are weighed on coater rolls (24) and (24') by coating knives (30) and (30 '), and are coated on a substrate (25). ) Is substantially simultaneously applied to both sides, and a substrate (28) is obtained in which a coating solution is applied to both sides.

The clearance between the two coater rolls (24), (24 ') is the same as in FIGS. 3 and 4. The material of the coater rolls (24) and (24 ') may be a steel roll or a rubber roll, but if one of the two coater rolls is a steel roll, the other coater roll is a rubber roll. Something is preferred. The rotation direction of the coater roll is the coating knife and the coater roll (30) (24), (30 '), respectively.
The positional relationship of (24 ') is determined, which is opposite to the traveling direction of the substrate (25). The relationship between the speed of the coater roll surface and the speed of the base material may be the same speed, but it is preferable to form a thin coater roll thin film to finish the appearance more beautifully. The speed ratio is 1.1-20, and 1.1 times on the substrate
A method in which transfer is performed 20 times is preferable.

As the coating knife, various knives can be used, but a "cow nose type" knife as shown in FIG. 7 is preferable to make the appearance beautiful.

According to the reverse roll coater type double-sided simultaneous coating apparatus of the present invention, the aqueous dispersion containing fluorine having a poor transfer rate is made of a plastic film that is difficult to stably hold between rolls. It can be effectively transferred and coated on a substrate, and the finished product has a beautiful appearance.

The first reason why the above effect can be obtained is that each coater roll of the two coater heads is a backup roll of the other coater roll. Therefore, the clearance between the two coater rolls is equivalent to the thickness of the substrate passing between them, in other words, has a clearance slightly larger than the thickness of the substrate. Thereby, the function as a backup roll works, and the transfer rate from the coater roll to the base material is greatly increased.

The second reason is that the pickup roll is not provided with a scraping plate equivalent to a cleaning doctor. The use of the cleaning doctor leaves traces of the coating liquid that cannot be completely removed on the pickup roll in a streak form, which is transferred to the film as it is and causes a bad appearance. Since a scraping plate is unnecessary, a film having a beautiful appearance can be obtained.

Incidentally, the apparatus of the present invention, when the process after coating is the same,
For example, when applying the same coating liquid on both sides, of course,
Different coating liquids can be adopted as long as the steps after application (drying, curing, etc.) are the same.

"Example" Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.

Example The preparation method of the coating liquid is as follows.

10.2 kg of pure water and 60 g of Carbopol 934 (a thickener, manufactured by Goodrich) were weighed and stirred for 15 minutes by a mixer. Then, 112 g of aqueous ammonia (25-28 wt%) was added, and 19.8 kg of Neophoron ND-1 (FEP aqueous dispersion, manufactured by Daikin Industries, Ltd.) and KM-85 (antifoaming agent, Shin-Etsu Chemical Co., Ltd.) were continuously added. 6 g) was added, followed by stirring for 15 minutes. The obtained coating liquid has a solid content of 33 wt% and a viscosity of 100 cp.
Met.

The coating solution obtained as described above was coated on a 250 mm-wide 25 μm thick polyimide film (Apical 25AH, manufactured by Kaneka Chemical Industry Co., Ltd.) using the apparatus shown in FIG. It was applied so as to have a solid content of 2.5 μm. The specifications and conditions of the device are as follows.

(Specification of double-sided coating machine) One coater head Coater roll: 150mm diameter steel roll with 300mm surface length Pickup roll: 150mm diameter and 300mm surface length silicon rubber roll (hardness 70 degrees) Another coater head Coater roll: 150mm diameter 300mm long silicon rubber roll (hardness 70 degrees) Pickup roll: 150mm diameter, 300mm long steel roll Clearance between two coater rolls: 27μm (conditions) Line speed: 10m / min Coater roll peripheral speed: 30m / reverse rotation Min Pickup roll peripheral speed: 10m / min in reverse rotation Clearance between coater roll and pickup roll: 1
After coating under conditions such as 0 μm or more, 400 seconds in a drying oven for 30 seconds, 400
Baking was performed for 30 seconds in a curing furnace at 25 ° C. to obtain a composite film having a 2.5 μm FEP layer on both sides of a 25 μm polyimide film. The appearance of this film was beautiful, and the thickness was uniform (31 μm to 29 μm in total thickness).

[Brief description of the drawings]

FIG. 1 and FIG. 2 are schematic diagrams each showing a conventional device,
3 to 7 are schematic diagrams each showing an embodiment of the apparatus of the present invention. 21 ... Unwinder, 22, 22 '... Coating liquid storage tank 23,23' ... Pickup roll 24,24 '... Coater roll, 25 ... Base 26 ... Guide roll, 27,27' ... Coating liquid 28 ... Base material with coating liquid applied on both sides 29, 29 '... Metalling roll 30, 30' ... Coating knife

Claims (2)

(57) [Claims] 1. An apparatus for simultaneously applying an aqueous dispersion containing fluorine to both surfaces of a substrate made of a plastic film, comprising two coater heads and each coater roll having a distance corresponding to the thickness of the substrate. Make them come closer,
Reverse roll coater type double-sided simultaneous coating device arranged so that each coater roll becomes a backup roll for another coater head. 2. The apparatus according to claim 1, wherein the speed of the surface of the coater roll is 1.1 to 20 times the speed of the substrate.