JPH0624671B2 - Drying equipment for coating - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drying device for drying a low-viscosity coating material coated on a substrate made of a sheet-like material by passing it through a hot air oven.

[Prior Art] Coating of a low-viscosity coating on a substrate, for example, coating of a sheet-shaped substrate with a gas separation membrane that allows a specific gas to permeate more than other gases, or a substrate. In the manufacturing process for coating liquid separation membranes, coating moisture-permeable waterproof membranes on fiber substrates, etc., the substrate is continuously transported and the spinneret is placed on it in order to achieve continuous production. The low-viscosity paint is discharged from the above to be coated, and the coated substrate is usually passed through an oven to dry the low-viscosity paint. Such low-viscosity paint coatings, especially gas separation membranes, liquid separation membranes, moisture-permeable waterproof membranes, etc., have an extremely thin film thickness and as uniform as possible in order to keep the performance above a certain level. It is desirable to coat low viscosity paints.

Since the coating material discharged from the die onto the base material has a low viscosity, it is likely to flow or aggregate on the base material after being discharged and dried. When a low-viscosity paint coated with a thin film flows or aggregates on the substrate, not only a coating layer with a uniform thickness cannot be obtained, but in some cases the coating layer becomes an island pattern on the substrate and the coating layer Is not formed.

More specifically, for example, in a gas separation membrane, a paint in which a functional membrane material having a gas separation performance such as a silicone polymer is dissolved in a solvent is coated on a substrate, but these are lower than water. May be viscosity,
On the other hand, the substrate has a coating film thickness (for example, within 0.1μ)
Since it often has a larger thickness unevenness than that, it is extremely difficult to uniformly coat a substrate with a thin film. Further, since it has a low viscosity, it has a weak adhesion to the base material, and it is considerably difficult to dry the coating material discharged from the die and coated on the base material without aggregating.

That is, as shown in FIG. 5, when the base material 1 has a slight thickness unevenness and the surface of the base material 1 has wavy minute irregularities, it takes a long time to dry in an oven or the drying efficiency is poor. Then, coated low viscosity paint 2
Before it is dried and fixed in the oven, it flows into the concave and convex valleys 3 as shown in FIG. 6, and since it is fixed in this state, a predetermined gas separation film or the like is not formed on the peaks 4. The product quality may be significantly impaired.
Further, as shown in FIG. 7, even if the surface of the base material 5 is a flat surface with almost no unevenness, if the time taken for drying and fixing after coating is long, the thin film low-viscosity paint 2 aggregates. ,
Only an island pattern film can be formed on the base material 5, which may also significantly impair the quality of the product.

Therefore, in order to obtain a low-viscosity paint coating layer having a thin film and a uniform thickness, it is necessary to dry and fix the paint discharged onto the base material as quickly as possible and to adopt a drying method with good thermal efficiency.

As a method with high drying efficiency, a method using a hot air oven is generally known. In the hot-air oven, the low-viscosity coating material that is continuously applied to the base material is dried by the hot air that is supplied to the oven and controlled to a predetermined temperature. Since the viscous paint easily flows or aggregates, the hot air needs to be supplied at a low air velocity. Here, the slight wind speed means a wind speed of 3 m / sec or less. Also, since the base material is continuously passed through the oven, the inlet and outlet are open, and if the pressure inside the oven becomes too high, hot air will leak from the oven inlet to the upstream die side and heat the die. Have a negative impact. Therefore, also from this aspect, the hot air needs to be supplied at a low air velocity and the inside of the oven needs to be maintained at a low pressure.

[Problems to be Solved by the Invention] However, by simply supplying hot air into the oven,
It is difficult to control the hot air velocity on the surface of the substrate during passage to a desired low air velocity, and in ordinary manufacturing equipment, the pressure loss of the exhaust system that discharges hot air from the oven must be considerably large. It is also difficult to keep the pressure inside the oven low.

The present invention focuses on the above-mentioned problems, and in the case of coating a low-viscosity paint such as a gas separation film with a thin film, while making it possible to easily control the hot air in the oven to a slight wind speed, A coating layer with a uniform film thickness on the base material, which enables the pressure to be easily maintained at a low pressure, prevents the flow and aggregation of the low-viscosity paint on the base material, and prevents the thermal adverse effect of hot air on the die. Is intended to be formed.

[Means for Solving the Problems] A drying device for coating according to the present invention, which is directed to this object, has a finely-divided device on a downstream side of a die for discharging a low-viscosity coating material on a continuously conveyed base material in a base material conveying direction. A hot air supply port side and an oven for supplying the hot air into the oven, in a drying device in a coating provided with an oven in which hot air having a wind speed is supplied, and the low viscosity coating material coated on the substrate is dried by the hot air. The hot air exhaust port side for discharging hot air from the inside is provided with a fan capable of controlling the slight air velocity of the hot air in the oven. That is, in the present drying device, the hot air control fan, which is conventionally provided only on the hot air supply port side,
It is also provided on the hot air outlet side.

[Operation] In the drying device configured as described above, since the wind speed of the hot air in the oven is controlled by the respective fans on the hot air supply port side and the hot air exhaust port side, the wind speed control accuracy is increased and the accuracy is improved. The wind speed is controlled to a predetermined level. Also, by providing a fan on the hot air exhaust side, the conventional exhaust system pressure loss is absorbed by this fan,
The inside of the oven can be kept at a low pressure, and it becomes easier to control the slight air velocity of the hot air in the oven as compared with the case of a high pressure. Further, by lowering the pressure in the oven, hot air leakage from the oven is suppressed, so that adverse effects of the leaking hot air on the die are prevented, and the accuracy of discharging the low-viscosity paint from the die to the base material is secured. Therefore, the low-viscosity paint applied on the substrate with high accuracy
It is efficiently dried by hot air whose flow speed is accurately controlled to form a target thin film coating layer uniformly on the substrate.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

1 to 3 show a drying apparatus for coating according to an embodiment of the present invention, which shows the application of the present invention to a process for producing a gas separation membrane. In the figure, reference numeral 11 denotes a base material that is continuously transferred, and the base material 11 is transferred from the transfer roll 12 into the oven 13. The low-viscosity coating material 15 is discharged as a thin film in the form of a sheet on the base material 11 from a slit 16 of a die 14 provided above the transport roll 12, and the base material 11 coated with the low-viscosity coating material 15 is oven 13. The low-viscosity paint 15 is dried by being passed through. The distance between the mouthpiece 14 and the inlet of the oven 13 is a very short distance, for example, within 6 seconds in the transportation time of the base material 11 so that the low-viscosity paint 15 discharged from the mouthpiece 14 is dried within a short time. , And more preferably within 1.8 seconds.

The oven 13 is configured as a hot air oven. The oven 13 is provided with a hot air supply port 17 for supplying hot air into the oven 13 on the inlet side and a hot air exhaust port 18 for discharging hot air from the oven 13 on the outlet side. From the hot air supply port 17, hot air whose temperature is controlled by a heat exchanger (not shown) or the like is supplied. The hot air discharged from the hot air exhaust port 18 may be circulated again to the hot air supply port 17 side through an appropriate filter or the like (not shown), or may be discharged to the outside as it is.

In the hot air passages on the hot air supply port 17 side and the hot air exhaust port 18 side,
Fans 19 and 20 are provided respectively. The fan 19 can control the supply of hot air into the oven 13 at a low air velocity through the hot air supply port 17,
The fan 20 can control the discharge of hot air from the inside of the oven 13 at a slight wind speed. This fan 1
Fan speed is controlled by 9 and 20 itself.
How to control the rotation speed of 9 and 20, fan 1
Any of the methods of providing a damper for adjusting the flow rate on the discharge side or the suction side of 9, 20 may be used.

As shown in FIG. 2, on the hot air supply port 17 side, a rectifying plate 21 having an appropriate shape is provided in the hot air passage so that the supplied hot air has a uniform wind speed in the width direction of the substrate 11. . As shown in FIG. 3, an appropriate number of air intake holes 22 capable of taking in air from the outside are provided on the hot air exhaust port 18 side in the width direction of the base material 11. This air intake hole 2
2 controls the amount of hot air discharged from the hot air exhaust port 18 to a very small amount by taking in outside air, and adjusts the opening degree of each air intake hole 22 to adjust the width of the discharged hot air in the width direction of the base material 11. This is for controlling the wind speed to be uniform.

Reference numeral 23 in the drawing denotes a pipe for supplying the low-viscosity paint 15 to the die 14, and 24 denotes a guide roll provided in the oven 13.

Further, the coating object of the present invention is not particularly limited as long as it coats a low-viscosity paint on a substrate, but as an example, the gas separation membrane targeted by the apparatus of this example will be described. .

FIG. 4 shows an example of the gas separation membrane. In the figure, 31 is a polyester non-woven fabric or taffeta, and 32 is a polysulfone porous film. On a base material 33 having a laminated structure of these, an underlayer 34 made of, for example, a silicon-based polymer having a thickness of 0.1 μm is provided. A layer of poly (4-methylpentene-) having a thickness of, for example, 0.05 μ.
An oxygen-enriched film as the low-viscosity paint 15 composed of 1) is coated. The oxygen-enriched film 15 has a lower viscosity than water in the state of paint dissolved in a solvent. For example, in the case of a silicon-based polymer, polydimethylsiloxane is dissolved with Freon to give a polymer concentration of about 0.4% by weight and a viscosity of 0.8.
It is about centipoise. When poly-4-methylpentene-1 is used, cyclohexane is first used as a solvent and dissolved, and then Freon is added as a diluent so that the polymer concentration is about 0.1% by weight and the viscosity is about 0.8 centipoise. . Underlayer 3 made of silicon-based polymer
No. 4 prevents the low-viscosity oxygen-enriched film 15 from penetrating into the porous base material 33, and should be applied twice if there is a pinhole in one underlayer 34. The reason for this is that since the probability that the pinholes will overlap with each other will be extremely low if they are applied twice, it is possible to prevent the occurrence of pinholes in which the oxygen-enriched film 15 permeates the underlayer 34.

The operation of the embodiment apparatus configured as described above will be described.

The base material 11 is continuously transported from the transport roll 12 into the oven 13 at a predetermined speed. The low-viscosity paint 15 is discharged in a sheet shape from the slit 16 of the die 14 on the base material 11, and the base material 11 coated with the low-viscosity paint 15 is passed through the oven 13 to form the oven 1
3, the low-viscosity paint 15 is dried by hot air and the base material 11
Fixed on top.

The hot air is supplied into the oven 13 from the hot air supply port 17, flows from the inlet side to the outlet side in the oven 13, and is discharged from the hot air exhaust port 18. The supply side is the fan 19 and the discharge side is the fan 20. Since both wind speeds are controlled, the flow velocity of the hot air in the oven 13 is more accurately controlled to the target wind speed than in the case where there is only one fan. Therefore, the speed of the hot air flowing over the surface of the base material 11 and drying the low-viscosity coating material 15 can be easily reduced. Further, in the apparatus of the present embodiment, since the current plate 21 is provided on the air supply side, the hot air is supplied at a uniform wind speed in the width direction, and the hot air supplied at the uniform wind speed remains at a predetermined low wind speed. Since it flows, the uniform and good drying efficiency can be obtained for the low-viscosity paint 15 on the base material 11, and the flow and aggregation of the low-viscosity paint 15 on the base material 11 are prevented. Further, since the air suction hole 22 is provided on the exhaust side to easily control the exhaust wind speed to a slight wind speed and make the exhaust wind speed in the width direction uniform, it is easier to reduce the hot air speed in the oven. To be achieved.

Further, by providing the fan 20 on the hot air exhaust port 18 side, the pressure loss on the exhaust side is not applied to the inside of the oven 13, so that the inside of the oven 13 is kept at a low pressure. Therefore, although the inlet of the oven 13 is open, leakage of hot air from the inside of the oven 13 to the mouthpiece 14 side is suppressed, and the hot air hits the mouthpiece 14 to cause an abnormally high temperature of the mouthpiece 14 and local heating. To be prevented. As a result, the high temperature of the low-viscosity paint 15 passing through the die 14 and the thermal strain of the die 14 are suppressed, the properties of the low-viscosity paint 15 are maintained at predetermined physical properties, and the accuracy of the slit 16 is maintained. The low-viscosity coating material 15 is discharged onto the material 11 with a uniform thickness.

The low-viscosity coating material 15 thus applied on the base material 11 with a uniform thickness is dried in the oven 13 at a predetermined low wind speed and a uniform wind speed, so that the flow phenomenon as shown in FIG. Also, a low-viscosity paint coating layer having a uniform thickness and a thin film is formed without causing the aggregation phenomenon as shown in FIG.

As the gas separation membrane, polyacrylonitrile, polymethacrylonitrile, Lopac (Monsanto,
Co. ), Polyvinylidene chloride, Barex (Sohi
o, Co. ), Polyethylene terephthalate, nylon-6, polyvinyl chloride (unplasticized), polyethylene, (density 0.964), cellulose acetate, butyl rubber, polycarbonate, polypropylene (density 0.907), polystyrene, polyethylene density 0.922), Neoprene,
Any of Teflon, poly (2,6-dimethylphenylene oxide), natural rubber, poly-4-methylpentene-1, and polydimethylsiloxane can be used.

[Effects of the Invention] As described above, in the case of the drying apparatus for coating of the present invention, a fan is provided not only on the hot air supply port side but also on the hot air exhaust port side, so as to facilitate uniform hot air velocity in the oven. Since the wind speed can be controlled, the low-viscosity paint can be dried and fixed on the entire surface of the base material in a predetermined area without causing flow and aggregation on the base material, and the pressure in the oven can be easily lowered. Therefore, it is possible to prevent the thermal adverse effect of the hot air on the die and ensure the ejection accuracy from the die, and it is possible to easily form a uniform thin film coating layer on the base material.

When the present invention is applied to the coating of a gas separation membrane, a coating layer of a very thin gas separation membrane of about 0.05μ can be uniformly formed on a substrate, and the oxygen permeation performance of the gas separation membrane is inverse to the thickness. Since it is proportional, an extremely high-performance gas separation membrane can be realized.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a drying device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a hot air supply port of the device of FIG. 1, and FIG. 3 is hot air exhaust of the device of FIG. Fig. 4 is a cross-sectional view of the mouth part, Fig. 4 is a cross-sectional view of a gas separation membrane as an example of a coating material for coating low-viscosity paint, Fig. 5 is a partial cross-sectional view of a base material and low-viscosity paint, and Fig. 6 is low Partial cross-sectional view of the base material and the low-viscosity paint showing the flow state of the viscous paint on the base material, and FIG. 7 is a partial cross-sectional view of the base material and the low-viscosity paint showing the aggregation state of the low-viscosity paint on the base material. ,. 11 ... Substrate 12 ... Conveyor roll 13 ... Oven 14 ... Mouth 15 ... Low viscosity paint 16 ... Slit 17 ... Hot air supply port 18 ... Hot air exhaust port 19, 20 ... Fan 21 ... Commutation Plate 22 ... Air intake hole

Claims (1)

[Claims] 1. A low-velocity hot air is supplied to the inside of a die (14) for discharging a low-viscosity coating material (15) onto a continuously conveyed substrate (11), in the substrate conveying direction. In a coating drying apparatus provided with an oven (13) for drying a low-viscosity coating material (15) coated on the substrate (11) with the hot air, a hot air supply port for supplying the hot air into the oven (13). A fan (19, 20) capable of controlling a slight air velocity of the hot air in the oven (13) is provided on each of the (17) side and the hot air exhaust port (18) side for discharging hot air from the oven (13). A drying device for coating.