JPH0626711B2 - Coding film manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a coating film by drying a low-viscosity coating material coated on a substrate composed of a sheet-like material in an oven to dry it.

[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 base materials, etc., the base materials are continuously conveyed and the spinneret is placed on them 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 the gas separation membranes, liquid separation membranes, moisture-permeable waterproof membranes, etc., mentioned above, 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.

[Problems to be Solved by the Invention] However, for example, in a gas separation membrane, a coating material in which a highly separable material such as a polyolefin-based polymer is dissolved in a solvent is coated on a substrate, but these are better than water. It may have a low viscosity, while the substrate often has a thickness unevenness larger than the coating film thickness (for example, within 0.1 μm), so it is extremely difficult to uniformly coat the 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. 3, when the base material 1 has a slight thickness unevenness and the surface of the base material 1 has wavy fine irregularities, the coated low-viscosity paint 2 is dried and fixed in an oven. In addition, as shown in FIG. 4, it flows into the concave and convex valleys 3 and is dried in this state, so that a predetermined pinhole-free functional thin film or the like is not formed on the peaks 4, resulting in the quality of the product. May be significantly inhibited. Also,
As shown in FIG. 5, 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 low-viscosity coating material 2 in a thin film aggregates to form a base material. Material 5
Only the island pattern film can be formed on the upper surface, which may also significantly impair the quality of the product.

The present invention focuses on the above-mentioned problems, and in coating a low-viscosity coating material such as a functional material of a gas separation membrane with a thin film, a low-viscosity coating material discharged from a die onto a base material,
It is an object of the present invention to dry and fix without causing flow and aggregation on a substrate to form a coating layer having a uniform film thickness without interruption on the substrate.

[Means for Solving the Problems] A method for producing a coating film of the present invention which meets this object is
In a drying method in coating, a low-viscosity coating material is discharged from a die onto a substrate that is continuously conveyed, and the low-viscosity coating material is passed through an oven to dry the low-viscosity coating material. And the oven inlet are insulated, and a film is manufactured by setting the time from the discharge of the low-viscosity paint from the die until the low-viscosity paint is dried in the oven within 6 seconds. There is.

Here, the means for insulating between the mouthpiece and the inlet of the oven is simply constituted by a heat insulating material, or, when the oven is a hot air oven, provided in the hot air oven inlet portion, It is composed of suction means for sucking hot air inside the oven, or a combination of the suction means and a heat insulating material.

[Operation] In the method for producing a coating film having such a structure, the low-viscosity coating material discharged from the die onto the base material has the function of drying quickly before the coating material penetrates into the base material. Play. For example, when polydimethylsiloxane is coated on a polysulfone porous support film as described later, it can be dried before the polydimethylsiloxane penetrates into the support film. Next, while transporting the composite film coated with polydimethylsiloxane (hereinafter simply referred to as the composite film), the risk of the low-viscosity paint flowing or agglomerating on the composite film is extremely low and within the oven within 6 seconds after discharge. And is dried and fixed on the composite film in an oven. Therefore, even if the viscosity is low, a low-viscosity paint coating layer having a uniform thickness without interruption is formed on the substrate after drying, as long as it is discharged from the die onto the substrate with a uniform thickness. .

In addition, since the die is insulated from the oven, boiling of the paint in the die due to abnormally high temperature of the die, occurrence of thermal strain due to local heating of the die or temperature difference between the oven side surface and the opposite side surface of the die, The physical properties of the coating material are maintained and the mechanical accuracy of the slit of the die and the like is maintained, so that the film thickness of the discharged low-viscosity coating material is maintained at a uniform thickness.

Therefore, the low-viscosity paint discharged onto the base material with a stable and uniform thickness is dried quickly in a short time, so even if it is a thin film coating, it will have a uniform thickness over the entire predetermined area after drying. A spreading coating layer is formed.

In the present invention, since the material can be dried quickly while the coating material does not penetrate into the inside of the base material, for example, a polysulfone porous support membrane is used as the base material, which is first impregnated with water, and then water droplets on the surface are removed. By coating the silicone polymer in the scattered state, and then quickly drying,
It is also possible to obtain a composite membrane in which the silicon-based polymer is relatively impregnated into the porous support membrane.

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

FIG. 1 shows an apparatus for carrying out a method for producing a coating membrane according to an embodiment of the present invention, and shows an apparatus to which the present invention is applied 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. On this base material 11, a low-viscosity coating material 15 is discharged from a die 14 provided above the transport roll 12, and the base material 11 coated with the low-viscosity coating material 15 is passed through an oven 13 to Low viscosity paint 15
Are dried.

The oven 13 is configured as a hot air oven in the present embodiment, and a slight air velocity of hot air is sent from the air supply port 16 into the oven 13 by an appropriate air blowing means such as a circulation fan. A part is exhausted from the main exhaust port 17. At the inlet of the oven 13, there is provided a sub-exhaust port 19 as suction means for sucking hot air that is about to leak from the inlet 18 to the mouthpiece 14 side, and part of the hot air sent is from the sub-exhaust port 19. Exhausted. Sub exhaust port 19
A heat insulating material 20 is provided between the oven 13 and the base 14 on the outer surface side of the. This heat insulating material 20 and auxiliary exhaust port 1
Reference numeral 9 constitutes an adiabatic means for blocking heat transfer from the oven 13 side to the base 14 side. Although both the heat insulating material 20 and the sub-exhaust port 19 are provided in this embodiment, only one of them may be provided. Further, the oven is not limited to the hot air oven.

The positional relationship between the die 14 and the oven 13 is such that the distance between the die 14 and the inlet of the oven 13 is within 6 seconds in the transportation time of the base material 11. This distance is preferably short, and a distance of 1.8 seconds or less is more preferable when coating a low-viscosity paint in which a polyolefin polymer or the like is dissolved in a solvent in the gas separation membrane. However,
If the base 14 and the oven 13 are directly adjacent to each other,
Since heat from the oven 13 is transferred to the base 14, it is preferable to provide a gap at least between them.

Reference numeral 21 in the drawing denotes a slit of the mouthpiece 14 that discharges the low-viscosity paint 15 in the form of a thin sheet.
2 is a pipe for supplying the low-viscosity paint 15 to the base 14, 23
Indicates 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. . As the gas separation membrane material, polyacrylonitrile, polymethacrylonitrile, Lopac (Monsanto, Co.) polyvinylidene chloride, Barex (Sohio, Co.),
Polyethylene terephthalate, nylon-6, polyvinyl chloride (non-plastic), polyethylene, (density 0.964),
Cellulose acetate, butyl rubber, polycarbonate, polypropylene (density 0.907), polystyrene, polyethylene density 0.922), neoprene, Teflon, poly (2,6-dimethylphenylene oxide), natural rubber,
Any of poly-4-methylpentene-1 can be used.

FIG. 2 shows an example of the oxygen-enriched film. 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 method of the present invention is carried out as follows using the apparatus of the embodiment configured as described above.

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 21 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
In 3, the low-viscosity paint 15 is dried and fixed on the base material 11.

The inlet of the oven 13 is opened to allow the base material 11 to pass continuously, and a part of the hot air supplied into the oven 13 tends to leak. However, the auxiliary exhaust port 19 is provided at the inlet of the oven 13. Since it is provided, the entrance 18 to the base 14
The hot air that is about to leak to the side is sucked into the auxiliary exhaust port 19,
It is exhausted through the auxiliary exhaust port 19. Therefore, the base 1
4 is blocked from reaching the hot air by the hot air, and the base 14 is insulated from the hot air as a result, so that the hot air hits the base 14 to prevent the base 14 from abnormally high temperature and local heating. It As a result, the 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 21 is maintained. The low-viscosity coating material 15 is discharged onto the material 11 with a uniform thickness.

In addition, a heat insulating agent 20 is provided between the oven 13 and the base 14.
Since the heat insulating material 20 is also provided, heat transfer from the oven 13 side to the die 14 side is blocked, and the discharge of the low-viscosity paint 15 in a thin film is further stabilized.

The low-viscosity coating material 15 thus coated on the base material 11 with a uniform thickness is conveyed to the oven 13 and dried as the base material 11 is conveyed. The time from discharge to the start of drying is
Since it is suppressed within 6 seconds, the low-viscosity paint 15 is dried quickly after application. The time of 6 seconds is determined as a very short time in which the ordinary low-viscosity coating material does not flow or aggregate on the base material 11, and the time from discharge to the start of drying is set within this time. As a result, the flow phenomenon shown in FIG. 4 and the aggregation phenomenon shown in FIG. 5 are prevented from occurring, and the low-viscosity coating material 15 is dried in the discharged state. Therefore, the low-viscosity paint 15 having a uniform thickness and a thin film discharged onto the base material 11
However, since it is dried while maintaining its uniform state, a coating layer having a uniform thickness and having no island pattern or the like is formed on the substrate 11 over the entire predetermined area after drying. To be done.

[Effects of the Invention] As described above, according to the method for producing a coating film of the present invention, heat is not provided between the die and the inlet of the oven to prevent thermal influence from the oven side to the die side. , It takes a very short time from the discharge of low-viscosity paint from the die until the low-viscosity paint begins to dry in the oven, and the low-viscosity paint may flow or aggregate on the base material before the start of drying. Since it is not done, it is possible to apply the low-viscosity paint uniformly on the base material, and it is possible to dry and fix it on the base material while ensuring a uniform thin film thickness, and a good coating without quality defects. The effect that layers can be realized is obtained.

When the present invention is applied to the coating of a gas separation membrane, a coating layer of a functional thin film of pinhole-free (a state without pinhole) of about 0.05μ can be uniformly formed on a base material. Since the gas permeation performance of the separation membrane is inversely proportional to the film thickness, an extremely high performance gas separation membrane can be realized.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a coating film manufacturing apparatus according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of an oxygen-enriched film as an example of a coating material for coating a low viscosity paint, and FIG. Material and low-viscosity paint partial cross-sectional view, Fig. 4 shows the flow state of the low-viscosity paint on the base material and the low-viscosity paint partial cross-sectional view, and Fig. 5 shows the low-viscosity paint base material FIG. 3 is a partial cross-sectional view of a base material and a low-viscosity coating material showing the aggregation state of FIG. 11 ... Substrate 12 ... Conveyor roll 13 ... Oven 14 ... Mouth 15 ... Low viscosity paint 16 ... Air inlet 17 ... Main exhaust port 18 ... Oven inlet 19 ... Sub-exhaust as heat insulating means Mouth 20 ... Insulating material as heat insulating means 21 ... Slit

Claims (1)

[Claims] 1. A base material (11) coated with the low-viscosity paint (15) by discharging a low-viscosity paint (15) from a die (14) onto a base material (11) which is continuously conveyed. In a coating method for drying a low-viscosity paint (15) by passing it through an oven (13), heat insulation between the die (14) and the oven inlet (18) and a viscosity lower than that of the die (14) are provided. A method for producing a coating film, which comprises producing a film within 6 seconds from the time when the paint (15) is discharged to the time when the low-viscosity paint (15) begins to be dried in the oven (13). .