JPH02273213A - Manufacture of uniform coat film - Google Patents

Abstract

PURPOSE:To readily obtain a high quality film with a uniform film thickness and having no any defects such as pin holes or the like by constantly controlling the film material viscosity of a coated film immediately before the coat film is wound. CONSTITUTION:After the dope is coated on a mold release film in a uniform thickness, and in the process wherein the coating material is wound in a state of being kept the fluidity, a coat film is manufactured by spraying a certain constant temperature gas within the range of + or -20 deg.C on a film immediately before being wound. At this time, the dope (coating material) as a film material has a degree of the viscosity or higher that it may not flow as coated on the film, and as the viscosity of the dope is so high, it becomes hard to spread over the whole of the film. On the contrary, the viscosity of the dope is very low, it becomes hard to mold a film. That is, it is necessary for the dope to have a degree of viscosity capable of being coated on the film uniformly, and it may be suitable for it in 1000-30000cp in ordinary, and preferably in 2000-20000cp.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a coated membrane used for various separation membranes such as ultrafiltration, dialysis, electrodialysis, reverse osmosis, and gas separation.

More specifically, the present invention provides a method for forming a film by coating, winding, and polymerizing a film raw material on the surface of a release film, which can achieve uniform film formation with relatively simple installation of equipment and extremely simple condition settings. The present invention provides a method for obtaining a thick coated film product.

(Conventional techniques and issues) There are many known methods for producing films with uniform thickness. Among them, when thermoplastic polymers that can be melt-molded can be used as film-forming raw materials, there are methods such as one-way calender method, inflation method, and An extremely highly efficient film forming method such as a melt extrusion film forming method using a T-die method or the like can be employed.

However, depending on the application, it is often necessary to use quite complex raw materials due to the required performance of the membrane.
For example, if the film needs to be three-dimensionally cross-linked, a seven-dimensional polymer or a polymer with a degree of polymerization suppressed below a certain level (hereinafter referred to as dope or coating material) is used as a raw material and stretched thinly onto a release film. After that, it is wound up while still being fluid and unstable in shape, and polymerized and crosslinked three-dimensionally.

However, in this method, troubles such as the shape of the roll after winding collapses and the coating material flowing out from the end of the winding roll occur.

Such deformation of the roll shape is noticeable when the thickness of the film is increased, and it is very difficult to control the thickness of the product film in the width direction. It is extremely difficult to achieve uniform thickness throughout the center, middle, and outer periphery of the roll, even if the roll does not lose its shape.

Furthermore, when textiles or other materials are simultaneously rolled up as the core material of the membrane, the core material may appear partially raised, or unevenness along the weave of the core material may appear on the membrane surface, and in extreme cases, pins may appear. It can also cause holes.

To this end, various methods have been proposed to increase the viscosity of the coating material before coating by lowering the composition and temperature of the coating material (for example, Japanese Patent Publication No. 38-3592, Japanese Patent Publication No. 40-28951, Special Public Service 1975-3
Publication No. 9570).

However, changing the composition to one that increases the viscosity impairs the performance of the product, creates excessive thixotropy, making it difficult to coat uniformly, and makes the viscosity more sensitive to changes in room temperature. This makes it extremely difficult to maintain constant coating conditions.

Under such unfavorable conditions, workers are constantly busy making fine adjustments to viscosity, etc., but it is difficult to suppress not only individual differences among workers but also the effects of seasonal and daily fluctuations in room temperature. be. Furthermore, there is a limit to how much the defective rate can be reduced.

In particular, from the start of operation of the coating equipment until it reaches a steady state, roll collapse is likely to occur, and a large amount of so-called start-up loss often occurs. In order to reduce this loss as much as possible, workers must take into account the viscosity and temperature of the dope before coating, the contact pressure of the doctor knife and the spray nozzle adjustment, and the running speed and tension of the film, while considering the surrounding temperature and air flow. ;
It was necessary to make fine adjustments such as the contact pressure of the touch roll just before winding.

However, due to subtle differences in this adjustment, the coated film may meander or the dope, which should have been coated to a uniform thickness, may ooze out from the ends of the wound roll. Further, even if the product appears to be rolled neatly, there are various problems such as subtle differences in the winding pressure resulting in variations in the thickness of the product film.

(Means for Solving the Problems) As a result of intensive study on various coating conditions during the production of a coated film (film), the present inventors found that By controlling the viscosity of the coating material (film) at a constant level,
Surprisingly, the inventors discovered that it is extremely easy to obtain a high-quality film with uniform thickness and no defects such as pinholes, leading to the completion of the present invention.

That is, the present invention is: In the process of coating a release film with a dope to a uniform thickness and then winding the coating material while maintaining its fluidity, the film is heated to room temperature ±
Provided is a method for producing a coating film, characterized by spraying a gas at a certain temperature within a range of 20°C.

Below, the method of the present invention will be explained in more detail.

The dove (coating material) that serves as the raw material for the film must have a viscosity that is at least high enough to prevent it from running off when coated onto the film. If the viscosity of the dope is too high, it will be difficult to spread throughout the film. Furthermore, if the viscosity of the dope is too low, it will be difficult to form a film. That is, the dope needs to have a viscosity that allows it to be applied uniformly to a film, and usually 1,000 to 30,000 centivoise, preferably 2,000 to 20,000 centivoise is appropriate.

Specific examples of this dope include divinylbenzene,
It is a compound that can form a three-dimensional crosslinked structure containing polyvinyl or polyaryl compounds such as diaryl, diacrylate, and dimethacrylate as one component. Other components in this case generally include, for example, styrenes: chloromethylstyrenes; alkylated styrenes such as vinyltoluene; acrylonitriles; vinylpyridines; vinylimidazoles, vinylpiperazines; acrylic acid and its salts. or esters; methacrylic acid and its salts or esters; vinylsulfonic acid and its salts or esters; styrenesulfonic acid and its salts or esters.

In addition, inert low-molecular compounds such as plasticizers, polyvinyl chloride, polyethylene fine powder, butadiene-acrylonitrile, butadiene-styrene, natural rubber, and other inert high-molecular compounds with good solubility and dispersibility. There is no problem even if they coexist.

These polymer compounds are preferably used in the form of particles or powder, and are useful for adjusting the viscosity of the dope, improving the physical properties of the coated film, and the like.

After these dopes are applied to the release film, they are rolled up into a roll together with the release film. The roll-shaped product is heated, for example, in an autoclave to carry out crosslinking polymerization. For this reason, a polymerization catalyst (initiator) is often added to the dope in advance.

As the polymerization catalyst (initiator), there are various polymerization catalysts (initiators) depending on the heptamers constituting the dope and the type of polymerization method, such as radical polymerization initiators such as benzoyl peroxide and abisobutyronitrile. Friedel-Crafts catalysts such as titanium tetrachloride, aluminum chloride complexes, and boron trifluoride are used.

Coating devices include a method in which dope is ejected from a slit die onto a release film running at a constant speed, and excess dope is scraped off with a doctor knife to maintain a constant dope thickness, and a spray device injected from a nozzle. Although this method is common, it is not particularly limited.

It is preferable to use an appropriate core material in order to increase the mechanical strength and improve the dimensional stability of the coating film.

The core material to be used may be any organic or inorganic cloth-like or net-like material, such as glass fiber, cotton, polyester, polyamide, acrylic, etc.
Examples include fabrics such as halogenated vinyl-based and polyolefin-based synthetic fibers, and non-woven fabrics.

When a core material is embedded in a coating film, the core material is superimposed on a release film, and dope-f-coating is applied thereon.

The release film used in the method of the present invention serves as a support for the produced coating film as well as for preventing the coating films from adhering to each other, and there are various materials for the release film. Specific examples of the material include polyethylene terephthalate,
Examples include polyamide, polyimide, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polycarbonate, cellophane, cellulose acetate, fluororesin, hydrochloric acid rubber, and the like.

In the method of the present invention, it is necessary that the temperature of the gas sprayed onto the coated film immediately before winding is not very different from the manufacturing process temperature. A coated film that approaches the temperature of the gas will be immediately rolled up into a roll, and since the heat conduction of the coated film is generally not good, the entire roll will be at approximately the temperature of the gas. It is preserved.

However, if the ambient temperature of the take-up roll is extremely different from the manufacturing process temperature, the temperature particularly at the ends of the roll will change. Therefore, it is necessary that the gas blown onto the coated film has a certain temperature within the range of room temperature ±20°C.

Note that the gas does not necessarily have to be pure air adjusted to a constant temperature. When using outside air at a temperature considerably lower than room temperature in winter, a gas obtained by blending a portion of fossil fuel combustion gas with air may be used to obtain the gas at the temperature specified in the present invention. On the other hand, if you want to cool the outside air or indoor air you want to use, you can use a mixture of some low-temperature gas from dry ice, which is made by cooling and solidifying carbon dioxide. That is, there are no restrictions on the type of gas as long as it is not harmful to the dove, coated film, coating equipment, or humans or animals.

The device for blowing the gas is not particularly limited, but it is usually preferable to make the temperature of the cough film substantially uniform in the width direction.

The temperature, flow rate, flow rate, and application angle of the gas may be adjusted so that the coated film receives the amount of heat necessary to reach a predetermined temperature. If the temperature around the winder (roll) is relatively stable, sufficiently close to the temperature of the gas, and the running speed of the coated film is low, then only a small amount of heat is needed. In such a case,
The gas is set at a temperature close to the average value of the manufacturing process temperature, and a small gas flow rate is sufficient.

On the other hand, if the temperature around the winder (roll) varies depending on the position or changes over time, or if the running speed of the coated film is high, a large amount of heat will be released from the gas accordingly. I need.

The angle and flow rate at which the gas is applied to the coated film are not very important when applying the gas to the uncoated surface of the coated film, but when applying the gas to the coated surface, it is important to avoid waving or the like on the coated surface. To prevent this, it is necessary to suppress the flow velocity on the coated surface by spraying at an angle that does not go against the running direction. Furthermore, if the amount of heat is insufficient, it is preferable to compensate for it by increasing the flow rate.

(Function) According to the method of the present invention, even if the temperature around the running coated film fluctuates slightly, as long as the manufacturing process temperature is fixed within a certain range immediately before winding, it will eventually be maintained under certain conditions. This is the same as if a coated film were manufactured.

In addition, once a coated film is wound up, coated films of the same temperature are wound up one after another, so the temperature of the wound roll remains almost constant unless the temperature difference with the surrounding area is extremely large. It will be preserved.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited by these examples.Example 1: 100 parts of styrene, 10 parts of divinylbenzene, 1 part of benzoyl peroxide, and 20 parts of dioctyl terephthalate. were mixed, and 100 parts of finely powdered polyvinyl chloride was added thereto as a viscosity improver.

This film-forming dope has a viscosity of 5°C at 20°C.
Indicates 00 centivoise. Spread this on one side of a 120cm wide polyethylene terephthalate film, with 5cm on both ends.
The coating amount is 100 g/rr? Apply it evenly.

This coated film is run in the longitudinal direction with the coated side facing up, and wound up into a roll onto a paper tube having an outer diameter of 100 m. At this time, the coated film is run at a speed of 30 m/sec while being subjected to a tension of 200 kg. The ambient temperature during the process from coating to winding is 15°C to 25°C.
fluctuating between.

20cm before the coated film is wound up, 25m parallel to the paper tube axis toward the uncoated side of the running film.
A stainless steel perforated pipe with a diameter of m is set, and compressed air is applied from below at right angles to the coated film through the perforation.

The holes in the pipe had a diameter of 5 mm, a center spacing of 20 holes, and were arranged in two rows in a staggered pattern. The air supplied to this pipe is 4kg/cIi controlled at 20°C.
I compressed air. This outlet is set at a distance of 15 cm from the running film surface.

In this way, a roll-shaped coated film with an outer diameter of 30 cm is obtained. This roll has neatly trimmed edges. This is treated at 70°C for 8 hours to three-dimensionally cross-link and polymerize the monomers in the dope.

After slowly cooling this, the film is peeled off from the polyethylene terephthalate film while being unwound. The membrane thus obtained is translucent and flexible with an effective width of 100 cm and a thickness of 90±3 μ.

Example 2 50 parts of styrene, 50 parts of 2-methyl-5-vinylpyridine
parts, 15 parts of divinylbenzene, 2 parts of benzoyl peroxide,
A film-forming dope consisting of 50 parts of polyvinyl chloride fine powder is prepared.

The above dope was applied to a polyethylene terephthalate film layered with a polyvinyl chloride long fiber fabric in the same manner as in Example 1, and then heated for 4 m at a controlled temperature of 15°C.
Cool with /ci compressed air. After winding up, heat treatment is performed at 80°C for 8 hours while the roll is still in the form of a roll.

The membrane obtained by unrolling the roll is so uniform that the texture of the reinforcing fibers embedded therein can be faintly discerned with the naked eye.

Comparative Example The procedure is carried out in the same manner as in Example, except that when the compressed air blowing is stopped, the coated film being wound up begins to meander. If the roll is heat-treated with these uneven edges, the resulting membrane will have partially visible textures of the reinforcing fibers. When this part is observed with an optical microscope, it can be seen that the fiber fabric serving as the core material is protruding from the surface of the membrane, or is not embedded near the center of the membrane, but is biased to one side.

Such defective areas occur as a result of some of the dope flowing to other areas and becoming locally reduced.

In addition, if the components contained in the dope swell the fibers, uneven swelling will occur if the amount of dope is unevenly distributed, causing uneven tension in the fiber fabric, and the finished film will lose its flatness. , similar to the above, the texture of the fabric becomes noticeable.

Furthermore, such unevenness occurs even after the film is wound. That is, as mentioned above, it is practically impossible to expect that the fluid dope will not flow when it is sandwiched and rolled up between the films.

Further, the dope in the locally tightened portion within the roll may ooze out from the edge of the film.

In such cases, by using the method of the present invention to lower the temperature before winding to suppress the fluidity of the dope, the degree of swelling decreases due to the temperature drop, making it easier to obtain a uniform film even with a core material. Become.

(Effects of the Invention) When the method of the present invention is effectively utilized, the influence of individual differences and room temperature differences becomes substantially negligible, and a coating film with significantly fewer defects can be obtained relatively easily. This means that according to the method of the present invention, for applications such as separation membranes, where the performance of the membrane is extremely degraded if there is a thin part, not to mention a pinhole,
This not only improves the production yield of coated films, but also enables the industrial production of ultra-thin films or ultra-high quality films with no defects.

Furthermore, the range of dope selection is widened, and the tension and winding hardness applied to the coating film before and after coating can also be selected from a relatively wide range. In this way, various restrictions on the production of coating films are largely freed, and coating films, which were considered difficult to manufacture industrially, can always be produced stably.

Claims (3)

[Claims] (1) In a coating film production method in which a release film is coated with a membrane raw material, the membrane raw material is wound while maintaining its fluidity, and a polymerized film is produced, the viscosity of the membrane raw material immediately before winding is controlled. A method for producing a coating film, characterized by: (2) The method for producing a coated film according to claim (1), wherein the viscosity of the film raw material is controlled by keeping the temperature immediately before winding to a constant temperature within ±20° C. of the production process temperature. (3) In claim (2), ±20°C of the manufacturing process temperature
A method for producing a coating film, characterized in that the method is carried out by spraying a gas at a constant temperature in the range of .