JP7234541B2 - Decompression chamber, cast cooling device, resin sheet manufacturing device, and resin sheet manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a decompression chamber and a cast cooling device used for manufacturing a resin sheet, and a resin sheet manufacturing apparatus and a resin sheet manufacturing method using the cast cooling device.

A resin sheet, typified by a microporous polyolefin resin sheet, is generally formed by extruding a resin melted and kneaded by an extruder into a sheet through a die, followed by cast cooling rolls equipped with a cooling surface such as a cooling roll (also called a chill roll). It is produced by cooling and solidifying. At this time, the extruded resin comes into contact with the rotating cooling surface of the cast cooling roll, that is, the cast surface, and is cooled while it is transported along with the movement of the cast surface. In order to improve the moldability of the resin sheet, by improving the flatness of the cast surface that is in close contact with the sheet, a resin sheet with excellent surface properties can be produced.

In recent years, the demand for resin sheets has been increasing, and there has been a demand for speeding up the film-forming speed of resin sheets. As the film forming speed increases, the amount of air flowing between the sheet extruded from the spinneret and the casting surface of the cast cooling roll increases, and the pressure at which the sheet lands on the casting surface increases. Therefore, the adhesion of the sheet to the cast surface is lowered. In particular, when the film-forming speed exceeds a certain level, air tends to be trapped between the sheet and the cast surface, which may cause thickness unevenness and physical property unevenness in the resin sheet product. Therefore, in order to reduce the pressure at which air enters the resin sheet at the point where the resin sheet lands on the cast surface, Patent Document 1 describes a resin sheet manufacturing apparatus in which the resin sheet is applied to the cast surface of a cast cooling device (cast cooling roll). It is disclosed that a decompression chamber for sucking air between the cast surface and the resin sheet is provided near the landing point to prevent air from entering between the resin sheet and the cast surface. In Patent Document 1, in order to prevent excess air from entering the decompression chamber during suction, the surface of the decompression chamber main body facing the casting surface is arranged in a square shape at a position slightly distant from the casting surface. , a sealing material is provided in contact with the casting surface at four peripheral edges of this surface of the decompression chamber main body other than the portions close to the landing point of the sheet to prevent air from flowing in even through this small gap. Since the cast surface slides against the sealing material, for example, porous resin or rubber, which has a small compressive load and can ensure the sealing performance of the sealing surface with a low load, is used as the sealing material. be done.

The resin that is extruded from the die during the production of the resin sheet may contain not only the resin but also a diluent and the like. A microporous polyolefin resin sheet is used as a separator placed between electrodes in a lithium ion secondary battery. The mixture is kneaded to form a resin solution, which is extruded into a sheet from a spinneret and cooled and solidified by cast cooling rolls. In this case, even after the cooled resin sheet is separated from the casting cooling roll, some of the diluent and low molecular weight components derived from the resin remain as deposits on the casting surface of the casting cooling roll. Therefore, the deposits remaining on the cast surface are removed by a scraping device such as a scraper or a doctor blade at a position that does not interfere with the cooling operation of taking off the resin sheet. Patent Document 1 discloses a scraping device that scrapes off the diluent remaining on the casting surface.

WO2016/125526

However, the device disclosed in Patent Literature 1 cannot sufficiently prevent defects caused by foreign matter even when combined with a scraping device. Such defects can be removed through an inspection process as long as they affect the physical properties, but there is a problem that the yield is lowered. In addition, there is a problem that even if the substance does not substantially affect physical properties, it is repelled by users. On the other hand, shortening the cleaning/replacement cycle of the sealing material can suppress the occurrence of defects, but this also has the problem of lowering production efficiency.

An object of the present invention is to shorten the cleaning/replacement cycle of the sealing material, thereby ensuring the sealing performance in a decompression chamber without lowering the production efficiency, and making it possible to manufacture a resin sheet that is less prone to defects. be.

As a result of intensive studies, the inventors of the present invention found the following reasons why the prior art could not sufficiently prevent the defects. FIG. 6 shows an enlarged view of a position where a conventional porous rubber sealing material 50 is provided. The position where the lower end side of the sealing material 50 abuts against the cooling roll 2 is upstream of the position where the resin sheet 3 is cast as the cooling roll 2 rotates in the sheet conveying direction, and the scraper 17 described above is positioned upstream. is located downstream in the sheet conveying direction. At this position, the scraper 17 has removed the foreign matter and the diluent, but the low-molecular-weight resin component adheres to the roll surface. If the sealing material 50 scrapes off such a low-molecular-weight resin component, the scraped foreign matter will continue to accumulate on the sealing material 50 and flow into the area below the sealing material 50. can not be performed, and flows to the casting position of the resin sheet 3, causing defects in the resin sheet.

Then, the present inventors have found that the defects can be suppressed by adopting a specific material for the sealing material of the decompression chamber, leading to the present invention.

That is, the present invention is a decompression chamber that is used so as to cover a part of the surface of a roll, and has a sealing material at one end in the circumferential direction of the roll in a region that covers the roll, and the sealing material is a decompression chamber characterized in that is made of a flexible resin film.

Further, the present invention includes a roll that receives and cools the resin sheet discharged from the nozzle, and the decompression chamber of the present invention, and is upstream of the contact point of the resin sheet with the roll in the conveying direction of the resin sheet. The cast cooling apparatus is characterized in that a decompression chamber is installed so that the sealing material is located at a position spaced apart from the above.

It is preferable that the seal member seals with the roll at the lower end side of the seal member.

Further, the present invention is an apparatus for manufacturing a resin sheet, which includes the cast cooling device of the present invention and a die, and discharges the resin from the die in the form of a sheet.

Further, in the present invention, the cast cooling apparatus of the present invention is used, the resin is discharged from the die onto a roll in sheet form, and the air between the resin sheet discharged from the die and the roll is sucked in a decompression chamber. In this method, a resin sheet and a roll are brought into close contact with each other, and the resin sheet is cooled and solidified while being conveyed by the roll.

According to the present invention, by shortening the cleaning/replacement cycle of the sealing material, the resin sheet can ensure the sealing performance in the decompression chamber without lowering the production efficiency, and furthermore, does not generate extra foreign matter and is less likely to cause defects. manufacturing becomes possible.

1 is a schematic perspective view of a microporous polyolefin resin sheet manufacturing apparatus equipped with a decompression chamber according to an embodiment of the present invention; FIG. FIG. 2 is a top view of the manufacturing apparatus shown in FIG. 1; FIG. 3 is a longitudinal cross-sectional view taken along line AA of FIG. 2; FIG. 4 is an enlarged side view for explaining a sealing material; 1 is a flow chart showing a manufacturing process of a microporous polyolefin resin sheet. FIG. 5 is an enlarged side view for explaining a sealing material in a comparative example;

Next, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments, including the following examples.

FIG. 1 shows a main part of a resin sheet manufacturing apparatus (hereinafter also referred to as a sheet manufacturing apparatus) equipped with a decompression chamber of the present invention. As shown in FIG. 1, the sheet manufacturing apparatus includes a nozzle 1 for discharging a molten resin solution supplied from an extruder (not shown) in the form of a sheet, and a resin sheet 3 discharged from the nozzle 1, which is picked up and conveyed. It has a cast chiller for cooling and solidifying. In FIG. 1, the cast cooling device is depicted as a device comprising a cooling roll 2 and a vacuum chamber 4, which will be described later, and the outer peripheral surface of the cooling roll 2 serves as a cooling surface, ie, a casting surface. Accordingly, the cooling roll 2 is rotationally driven in the directions of the arrows (counterclockwise and counterclockwise) to convey the resin sheet 3 rightward in FIG. A resin sheet 3 discharged from the die 1 is cast on the surface of the rotating cooling roll 2 . When the resin sheet 3 containing the diluent is cooled by the cooling roll 2, after the cooled resin sheet 3 is separated from the cooling roll 2, the diluent such as liquid paraffin and the low content of the resin are applied to the casting surface of the cooling roll 2. Molecular weight components remain as deposits. Therefore, on the upstream side in the sheet conveying direction by the cooling roll 2 of the landing point of the resin sheet 3 discharged from the die 1 on the casting surface, there is a scraping for scraping off deposits such as diluent remaining on the casting surface. As a member, a plate-like scraper 17 made of silicone rubber that extends parallel to the rotation axis of the cooling roll 2 and contacts the casting surface is fixed to the cooling roll 2 by a holding member (not shown). The scraper 17 is arranged so as to be tilted toward the downstream side in the rotation direction of the cooling roll 2 with respect to the tangential plane of the outer peripheral surface of the cooling roll 2 . The area between the scraper 17 and the landing point of the resin sheet 3 on the casting surface in the rotation direction of the cooling roll 2 is almost dry because the scraper 17 removes the diluent from the casting surface as a deposit. . A resin doctor blade may be used as the scraping member instead of the rubber scraper.

On the back side of the spinneret 1, that is, on the upstream side in the sheet conveying direction of the landing point of the resin sheet 3 on the cast surface, there is a decompressor adjacent to the spinneret 1, the lower end surface of which has a shape along the outer peripheral surface of the cooling roll 2. A chamber 4 is provided so as to partially cover the surface of the chill roll 2 . This decompression chamber 4 generates a negative pressure region on the back side of the resin sheet 3 , that is, on the side of the resin sheet 3 that contacts the cooling roll 2 . The decompression chamber 4 has an opening and a decompression chamber for sucking air through this opening, and the resin sheet 3 starts to adhere to the outer peripheral surface of the cooling roll 2, which is the casting surface, at the opening. It is formed over the entire width of the resin sheet 3 in the immediate vicinity of the portion. A suction pipe extending from a suction device (not shown) is connected to the upper surface of the decompression chamber in the decompression chamber 4, and the air in the decompression chamber is sucked through the suction pipe. Along with this, the air in the vicinity of the contact portion between the resin sheet 3 and the cooling roll 2 is sucked through the opening of the decompression chamber 4 . As a result, the pressure in the contact portion is reduced, and the amount of air trapped between the resin sheet 3 and the casting surface of the cooling roll 2 is reduced. In addition, a pressure gauge (not shown) is provided in the suction pipe, and the degree of pressure reduction of the pressure reduction chamber of the pressure reduction chamber 4 is controlled to a predetermined value by a control device (not shown), whereby the resin sheet 3 of the molten resin is removed. It can be brought into close contact with the cooling roll 2 stably. At this time, the degree of pressure reduction in the pressure reduction chamber of the pressure reduction chamber 4 is preferably controlled to a predetermined value according to the film forming conditions such as the viscosity of the molten resin, the thickness of the resin sheet 3, the sheet conveying speed of the cooling roll 2, and the like. The suction pressure with respect to the atmospheric pressure in the decompression chamber of the decompression chamber 4 is preferably in the range of -2500 Pa or more and -20 Pa or less. The lower limit of the suction pressure with respect to the atmospheric pressure in the decompression chamber is more preferably −1500 Pa or more, and the upper limit is more preferably −50 Pa or less.

2 is a top view of the sheet manufacturing apparatus shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along line AA of FIG. As shown in FIG. 3, when the decompression chamber 4 is installed at a predetermined position, the decompression chamber 4 faces the casting surface so that excess air does not enter the decompression chamber 4b of the decompression chamber 4 during suction. The facing surface (ceiling surface) is positioned slightly upward from the cooling roll 2 . Among the peripheral portions of the ceiling surface facing the casting surface of the decompression chamber 4, both edges in the width direction of the decompression chamber 4 and the edge on the upstream side in the sheet conveying direction have a slight gap between the decompression chamber 4 and the casting surface. Sealing members 7b and 10 for suppressing the inflow of air from are provided respectively. That is, the sealing material 7b is provided in an arc shape along the outer edge of the cooling roll 2 at positions corresponding to both ends of the decompression chamber 4 in the sheet width direction, and is made of, for example, porous resin or rubber, and has a low load. abuts on the cast surface and constitutes a sealing surface. The sheet width direction is a direction perpendicular to the longitudinal direction of the resin sheet 3, that is, the direction perpendicular to the conveying direction by the rotating rolls 2, and the direction perpendicular to the film thickness direction of the sheet. The position where the sealing material 7b abuts on the cast surface of the cooling roll 2 is a position where the resin sheet 3 extruded from the die 1 does not contact even if the cooling roll 2 rotates. This position does not affect the quality of the resin sheet 3 . Examples of materials that can be used as the sealing material 7b, preferable pressing force of the sealing material 7b against the cast surface, and mounting methods are described in Patent Document 1. On the other hand, the sealing member 10 constitutes a sealing surface between the decompression chamber 4 and the casting surface at a position on the upstream side of the casting surface in the sheet conveying direction. The sealing material 10 will be described later.

As shown in FIG. 3, a seal member 7a that contacts the mouthpiece 1 is arranged on the downstream edge of the upper plate 4a of the decompression chamber 4b in the conveying direction. The sealing material 7a is preferably made of porous resin or rubber. The method of attaching the upper plate 4a to the mouthpiece 1 is not limited to this. It may be fixedly installed by Alternatively, the upper plate 4a may be configured integrally with the mouthpiece 1 . Furthermore, the resin sheet 3 discharged from the die 1 and the cast surface are located downstream of the lip of the die 1 in the conveying direction of the cast surface and outside of the positions of both ends of the resin sheet 3 discharged from the die 1 in the sheet width direction. Rectifying plates 6 installed so as to close the gap between the base 1 and the base 1 are provided at both ends in the width direction. For example, the current plate 6 can be attached to the base 1 via a bracket (not shown), but the method of attaching the current plate 6 is not limited to this. The lip of the die 1 means a slit-like opening provided in the die 1 for extruding a molten resin or resin liquid into a sheet.

Next, the sealing material 10 will be described. FIG. 4 is an enlarged view of the position where the sealing member 10 is provided in the sheet manufacturing apparatus, and the drawing omits the sealing members 7b provided on both sides of the decompression chamber 4 in the sheet width direction. The sealing material 10 forms a sealing surface by coming into contact with the cast surface of the rotating cooling roll 2 . The sealing material 10 extends in the sheet width direction so as to close the gap between the lower end surface of the upstream end portion of the decompression chamber 4 in the sheet conveying direction and the casting surface of the cooling roll 2 .

It is important that the sealing material 10 of the present invention is made of a flexible resin film. By doing so, the low-molecular-weight resin components that have not been removed by the scraper are not scraped off, but left uncollected, thereby preventing generation of excess foreign matter and ensuring sealing performance. The above-described flexibility makes it possible to suppress abrasion and breakage of the sealing material due to contact with the roll 2, and also suppress the generation of foreign matter due to this.

As the resin forming the sealing material 10, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), or the like is used.

The thickness of the sealing material 10 is preferably 25 μm or more and 500 μm or less, more preferably 50 μm or more and 250 μm or less, and still more preferably 75 μm or more and 200 μm or less, depending on the material of the sealing material 10 . If the sealing material 10 is thinner than this thickness, the strength of the sealing material 10 is insufficient, and the lower end side of the sealing material 10 may be pulled by the negative pressure in the decompression chamber 4 and lifted from the surface of the cooling roll 2. If the thickness of 10 is thicker than the above range, the flexibility is lost and the sealing property cannot be ensured. That is, as the cooling roll 2 rotates, the height position of the decompression chamber 4 (sealing material 10) with respect to the cooling roll 2 moves up and down very slightly. Therefore, if the sealing material 10 does not have flexibility, the lower end surface of the sealing material 10 may separate from the upper surface of the cooling roll 2 or the lower end portion of the sealing material 10 may move away from the cooling roll 2 due to the vertical movement. 2 may collide and be damaged. On the other hand, in the present invention, as described above, the thickness of the sealing material 10 is set so that it has flexibility. The reduced pressure in the reduced pressure chamber 4 is maintained while following the movement.

The number of sealing members 10 is not limited to one, and a plurality of sealing members may be arranged along the sheet conveying direction. Two sealing members 10 are provided in the illustrated one. When a minute foreign matter adheres to the surface of the cooling roll 2, along with the rotation of the cooling roll 2, the lower end side of the sealing member 10 on the upstream side in the sheet conveying direction and the lower end side of the sealing member 10 on the downstream side in the sheet conveying direction This foreign object may pass through sequentially. When foreign matter passes through the lower end side of the sealing material 10, the lower end side of the sealing material 10 separates from the surface of the cooling roll 2, so the role of the decompression sealing in the sealing material 10 becomes less than usual. Since the two seal members 10, 10 are provided, even if the sealing performance of one of the seal members 10 becomes difficult to function temporarily, the other seal member 10 maintains the reduced pressure in the decompression chamber 4.例文帳に追加

Since the sealing material 10 is a member that seals between the decompression chamber 4 and the casting surface, both ends of the sealing material 10 are in contact with or extremely close to the sealing materials 7b provided at both ends of the decompression chamber 4 in the sheet width direction. It is preferably located at a short distance (see Figure 2). As shown in FIG. 4, the sealing material 10 is attached to the pressing plate 11 by being sandwiched between the grooves of the pressing plate 11 provided at the lower end of the decompression chamber 4 . It is fixed by a screw 12 to a member 4d forming the wall surface of 4b. Thereby, the sealing material 10 is attached to the decompression chamber 4 .

As shown in FIG. 4, when viewed in a cross section perpendicular to the rotation axis of the cooling roll 2, that is, in a cross section perpendicular to the sheet width direction, the sealing material 10 extends from the pressing plate 11 toward the cooling roll 2 substantially downward. extended. Since the sealing material 10 has flexibility, the lower end portion is pressed against the casting surface of the cooling roll 2 by its elastic force. At this time, the sealing material 10 is curved toward the downstream side in the sheet conveying direction in the vicinity of the casting surface as the cooling roll 2 rotates. The surface of is in contact with the cast surface.
The angle at which the sealing material is applied to the roll is the angle formed by the direction in which the sealing material extends from the main body of the decompression chamber and the roll rotation direction of the tangent to the outer periphery of the roll at the point where the extension direction and the roll intersect ( θ) in FIG. 4 is preferably 5° or more and 85° or less, or 95° or more and 175° or less. θ is more preferably 25° or more and 75° or less or 105° or more and 155° or less, and still more preferably 45° or more and 65° or less or 115° or more and 135° or less. By setting θ within such a range, the contact pressure of the sealing material 10 against the cast surface can be made appropriate for ensuring the sealing performance.

The contact pressure of the sealing material 10 to the cast surface is preferably 0.2 kPa or more and 29.0 kPa or less, more preferably 1.3 kPa or more and 6.0 kPa or less. Sufficient sealing performance can be ensured by setting it within this range.

The sheet manufacturing apparatus described in this embodiment is used for manufacturing various resin sheets, but can also be used for manufacturing microporous polyolefin resin sheets.

When the sheet manufacturing apparatus of the present invention is applied to manufacturing a resin sheet, the resin is extruded from the die 1 onto the cooling roll 2 and cooled to obtain the resin sheet. Then, a stretching step or the like is performed on the cooled resin sheet.

In the case of manufacturing a microporous polyolefin resin sheet, the polyolefin resin contained in the polyolefin resin solution extruded from the die 1 may be polyethylene, polypropylene, polystyrene, polymethylpentene, or the like. The diluent contained in the polyolefin resin solution determines the structure for forming micropores in the microporous polyolefin resin sheet and is a plasticizer for making the polyolefin resin into a solution. It contributes to improvement. The diluent is not particularly limited as long as it is a substance that can be mixed or dissolved in the polyolefin resin. Diluents that are solid at room temperature include stearyl alcohol, ceryl alcohol, paraffin wax, and the like. The diluent is preferably liquid at room temperature in order to prevent the occurrence of spots during stretching and in consideration of subsequent coating. Liquid diluents include aliphatic, cycloaliphatic or aromatic hydrocarbons such as nonane, decane, decalin, paraxylene, undecane, dodecane, liquid paraffin, and boiling points within the boiling point range of these compounds. Mineral oil fractions and phthalates that are liquid at room temperature, such as dibutyl phthalate and dioctyl phthalate, can be mentioned. In order to obtain a gel-like sheet with a stable liquid diluent content, it is more preferable to use liquid paraffin as the diluent. For example, the liquid diluent preferably has a viscosity of 20-200 cSt at 40°C. A solvent which is miscible with the polyolefin in a melt-kneaded state but solid at room temperature may be mixed with the diluent. The mixing ratio of the polyolefin resin and the diluent is preferably 10 to 50% by mass from the viewpoint of improving the moldability of the extrudate, with the total of the polyolefin resin and the diluent being 100% by mass.

FIG. 5 shows the entire process of obtaining a microporous polyolefin resin sheet product. First, a polyolefin resin powder and a plasticizer as a diluent are melt-kneaded in an extruder (S11). A polyolefin resin solution is thus prepared. The prepared polyolefin resin solution is extruded into a sheet by the nozzle 1 and discharged (S12). The discharged sheet-like polyolefin resin solution, that is, the resin sheet 3 is cooled by the cooling roll 2 to form a gel-like sheet (S13). Next, the gel-like sheet is subjected to wet biaxial stretching (S14), and the biaxially-stretched gel-like sheet is immersed in a solvent (S15). Since the solvent removes the plasticizer, a microporous polyolefin resin sheet is produced. The produced microporous polyolefin resin sheet is subsequently subjected to dry biaxial stretching (S16), and after thermal relaxation (S17) and cooling (S18), the microporous polyolefin resin sheet is wound up ( S19), a microporous polyolefin resin sheet product can be obtained. Since each step from melt-kneading to winding can be carried out continuously, a microporous polyolefin resin sheet can be obtained as a web.

According to the above-described present invention, the sealing material 10 on the upstream side in the sheet conveying direction in the decompression chamber 4 is not a rigid or bulk member having no flexibility, but a flexible sheet-like sealing material 10. is used. Therefore, while suppressing wear and damage due to contact with the cooling roll 2, and furthermore, deposits are prevented from accumulating so much, the sealing performance can be ensured. That is, in contrast to the conventional idea that it is better to remove as much as possible the deposits that are not involved in the cooling process of the sheet, in the present invention, even if the deposits are adhered to the surface of the cooling roll 2, they are coarse. On the cooling roll 2 while using the decompression chamber 4, while allowing a certain amount of deposits to remain on the cooling roll 2, after grasping in advance that it will not cause a defect unless an excessive deposit is generated. The resin sheet 3 is cast on. Therefore, it is possible to ensure the sealing performance of the decompression chamber 4 and to suppress the occurrence of defects in the microporous membrane. In order to allow the deposits that have reached the sealing material 10 to flow downstream without being collected as much as possible, the aforementioned inclination angle θ of the sealing material 10 is made smaller than 90°. He is trying to even out the adhering matter in the rotation direction of the cooling roll 2. - 特許庁Therefore, damage to the lower end portion of the sealing material 10 is suppressed, which leads to extension of the life of the sealing material 10 . In constructing the sealing material 10 so as not to scrape off the deposits on the cooling roll 2 as much as possible, the scraper 17 for scraping off the deposits is provided in the present invention. , the sealing material 10 can focus on ensuring the sealing performance. Therefore, by combining the sealing material 10 and the scraper 17, the durability of the sealing material 10 is improved and the foreign matter recoverability is excellent.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and the like. However, the present invention is not limited to these examples.

[Example 1]
Using the sheet manufacturing apparatus shown in FIGS. 1 to 3, a microporous polyolefin resin sheet was produced according to the procedure shown in FIG.

(1) Sheet material High-density polyethylene (HDPE) with a viscosity of 1000 Pa·s was used as the polyolefin for the microporous polyolefin resin sheet material. Here, the viscosity is measured by the method specified in JIS K7117-2 under conditions of shear rate of 100/s and temperature of 200°C. Liquid paraffin (LP) with a kinematic viscosity of 51 cSt (at 40° C.·mm ² /s) was used as a diluent.

(2) Preparation After the sheet material was dried, it was supplied to an extruder, melted and kneaded together with a diluent, and then supplied to a die for sheet molding. In addition, the temperature of the device up to the nozzle was set to 230°C.

(3) Sheet Molding Die A die 1 having a slit width of 300 mm was used, and the resin solution after melt-kneading was discharged at 70 kg/hr. The LP concentration in the resin solution is 70% by mass, and LP is 49 kg/hr.

(4) Cast Cooling Device As the cooling roll 2 of the cast cooling device, a sheet forming roll having a mirror surface was used. After being extruded into a sheet from a sheet molding die, it was molded at a casting speed of 3 m/min on a sheet molding roll whose roll temperature was set to 35°C.

(5) Decompression chamber The clearance between the sheet forming die (die 1) and the sheet forming roll (cooling roll 2) is set to 40 mm, and the entire upper plate 4a of the decompression chamber 4 is horizontally oriented toward the upstream side in the sheet conveying direction. A constant slope of 10° downward with respect to was used. The rectifying plate 6 is positioned so that it is an extension of the side surface of the main body of the decompression chamber 4 (decompression chamber 4b). 4 was installed. Expanded polytetrafluoroethylene (PTFE) was used as the sealing material 7a between the mouthpiece 1 and the upper plate 4a. Of the sealing materials for the cast surface, silicone sponge rubber (tear hardness 0.25 MPa) is used for the sealing material 7b provided on the side surface of the decompression chamber 4, and for the sealing material 10 provided on the upstream side in the sheet conveying direction. used a PET film. The installation situation of the sealing material 10 is the same as that shown in FIG. The sealing material 10 made of a PET film had a thickness of 125 μm, an inclination angle θ of 60°, and was installed so that the contact pressure to the cast surface was 3 kPa. Further, the degree of pressure reduction in the pressure reduction chamber 4b was set to -0.1 kPa with respect to the atmospheric pressure.

(6) Scraper (doctor blade)
As shown in FIG. 4, a scraper 17 made of silicone rubber having a hardness of 70 degrees was provided. The angle α between the direction in which the scraper 17 extends from the position where the scraper 17 contacts the cast surface and the direction in which the cooling roll 2 rotates was set to 30°.

(7) Defect detection Adopting the above conditions (1) to (6), further stretching etc. are performed as shown in Fig. 5 to produce a microporous polyolefin resin sheet (microporous membrane), Defects in the film were detected using a transmission type defect detector. Defects having dimensions of 10 mm or more in both the film forming flow direction (MD direction) and the width direction (TD direction) were regarded as defects caused by foreign matter generated in the decompression chamber.

(8) Results In the manufactured microporous membrane of width 1800 mm×length 60 m, the number of defects caused by foreign matter generated in the decompression chamber was one, and the number of defects was small.

[Comparative Example 1]
A microporous membrane was produced in the same manner as in Example 1, except that the configuration of the sealing material in the decompression chamber 4 was changed. A specific method for producing a resin sheet is as follows.

(1) Sheet material Same as in Example 1.

(2) Preparation It was the same as in Example 1.

(3) Sheet molding die Same as in Example 1.

(4) Cast cooling device Same as in Example 1.

(5) Decompression chamber The clearance between the sheet forming die (die 1) and the sheet forming roll (cooling roll 2) is set to 40 mm, and the entire upper plate 4a of the decompression chamber 4 is horizontally oriented toward the upstream side in the sheet conveying direction. A constant slope of 10° downward with respect to was used. A rectifying plate 6 was installed in the same manner as in Example 1, and a decompression chamber 4 was installed after the lip position of the nozzle 1 was arranged on the top of the cooling roll 2 . The same materials as in Example 1 were used for the sealing material 7a between the mouthpiece 1 and the upper plate 4a and the sealing material 7b provided between the side surface of the decompression chamber 4 and the casting surface. Instead of the sealing material 10 provided on the upstream side in the sheet conveying direction in Example 1, in this Comparative Example 1, as shown in FIG. A block-shaped sealing material 50 made of was used. The sealing material 50 was fixed with a screw 52 to the member 4 d forming the wall surface of the decompression chamber 4 b of the decompression chamber 4 with the holding plate 51 interposed therebetween. The degree of pressure reduction in the pressure reduction chamber 4b was set to -0.1 kPa with respect to the atmospheric pressure.

(6) Scraper (doctor blade)
Same as Example 1.

(7) Defect detection Same as the first embodiment.

(8) Results In the manufactured microporous membrane of width 1800 mm × length 60 m, the number of defects caused by foreign matter generated in the reduced pressure chamber was 20, and the number of defects increased compared to Example 1. Production yield decreased.

[Comparative Example 2]
A microporous membrane was produced in the same manner as in Example 1, except that the configuration of the sealing material in the decompression chamber 4 was changed. A specific method for producing a resin sheet is as follows.

(1) Sheet material Same as in Example 1.

(2) Preparation It was the same as in Example 1.

(3) Sheet molding die Same as in Example 1.

(4) Cast cooling device Same as in Example 1.

(5) Decompression Chamber For each of the sealing material 7b provided between the side surface of the decompression chamber 4 and the casting surface and the sealing material 50 provided on the upstream side of the decompression chamber 4 in the sheet conveying direction, silicone sponge rubber (tear hardness The same as Comparative Example 1 except that 0.08 MPa) was used.

(6) Scraper (doctor blade)
Same as Example 1.

(7) Defect detection Same as the first embodiment.

(8) Result During the production of the microporous polyolefin resin sheet, the sealing member 50 provided on the upstream side in the conveying direction of the decompression chamber 4 was torn, and the decompression seal was broken, resulting in the decompression chamber 4b. It was not possible to create a negative pressure inside. As a result, it was not possible to manufacture a microporous membrane.

REFERENCE SIGNS LIST 1 mouthpiece 2 cooling roll 3 resin sheet 4 decompression chamber 4b decompression chamber 4c opening 6 current plate 7a, 7b, 10 sealing material 11 pressing plate 12 screw 17 scraper

Claims (8)

A box-shaped decompression chamber used so as to cover a part of the surface of the roll in an arc shape , wherein the arc shape when viewed from the central axis direction of the circle formed by the arc-shaped portion of the decompression chamber A sealing material is provided at one end of the portion, the sealing material is made of a flexible resin film , and the direction in which the sealing material extends from the main body of the decompression chamber, the extending direction, and the roll are aligned. The angle formed with the tangent line of the outer periphery of the roll at the intersection point is 5 ° or more and 85 ° or less, or 95 ° or more and 175 ° or less, and the sealing material is fixed to the decompression chamber. vacuum chamber. A cooling roll that receives and cools the resin sheet discharged from the nozzle, and the decompression chamber according to claim 1 are provided, and the cooling roll is provided upstream in the conveying direction of the resin sheet from the contact point where the resin sheet contacts the roll. A cast cooling apparatus, wherein a decompression chamber is installed so that the sealing material is positioned at a spaced apart position. 3. The cast cooling apparatus according to claim 2 , wherein the sealing member seals between the decompression chamber and the cooling roll so that the lower end side of the sealing member is pressed against the surface of the cooling roll. 4. The cast cooling apparatus according to claim 2 or 3 , wherein said decompression chamber has a plurality of said sealing members arranged along the circumferential direction of said cooling roll at an upstream end in said conveying direction. An apparatus for manufacturing a resin sheet, comprising: the cast cooling device according to any one of claims 2 to 4 ; 6. The resin according to claim 5 , having a doctor blade or a scraper in contact with the cast surface of the cooling roll at a position upstream in the conveying direction from the decompression chamber in order to remove deposits adhering to the cast surface of the cooling roll. Sheet manufacturing equipment. Using the cast cooling device according to any one of claims 2 to 4 , the resin is discharged from the die onto the cooling roll in a sheet form, and the resin sheet discharged from the die and the cooling roll Air between is sucked in the decompression chamber, the resin sheet and the cooling roll are brought into close contact, and the resin sheet is cooled and solidified while being conveyed by the cooling roll. 8. The method for producing a resin sheet according to claim 7 , wherein the resin discharged from the die is a resin solution obtained by kneading a polyolefin resin and a diluent.

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