JP2000355043A - Method and apparatus for producing polymer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the thickness irregularity caused by an air chamber method by diffusing the leaked air blown out of an air chamber along a sheetlike article in a cap direction toward the upper opened part of the space formed by a cap, the sheetlike article and the air chamber. SOLUTION: The sheetlike article 12 extruded from a cap 11 is passed through the gap between a leaked air diffusing means 16 and a cooling roll to be guided on a cooling roll 13 rotated at a high speed and the edge corresponding part of the sheetlike article is electrostatically brought into close contact with the cooling roll by a needle-like electrode 14 to which high voltage is applied and the sheetlike article is passed through the gap between the lower end 17 arcuate on the cap side of the outer wall on the cap side and the cooling roll to be guided to a chamber 15 and closely brought into contact with the surface of the cooling roll by the pressure of air to be solidified. The air blown out of the chamber is diffused to be avoided from the concn. toward an orifice direction and the amt. or speed of the air impinging against a molten sheet is lowered to avoid the deterioration of the thickness uniformity of the sheet and a thin sheet of high quality can be stably produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a sheet by extruding a molten polymer into a sheet and cooling and solidifying the sheet. More specifically, the present invention relates to a method for producing a thin sheet of a polymer having excellent uniformity in thickness by an air chamber. The present invention relates to a method and an apparatus for manufacturing a sheet to be cast at high speed.

[0002]

2. Description of the Related Art A static gas pressing method, particularly a casting method using an air chamber (Japanese Patent Publication No. 47-3993)
No. 0) is conveniently carried out for forming a sheet of a polymer having a high viscosity in a molten state, for example, polypropylene. However, in the case of a polymer having a low viscosity, for example, polyethylene terephthalate, there is a problem in uniformity of thickness. is there.

[0003] The cause of the thickness unevenness is that an airflow blown toward the upstream of the cooling roll from a gap between the outer wall on the side of the base of the chamber and the cooling roll collides with the sheet coming out of the base and vibrates the sheet. Occur. Therefore, as a measure for improving thickness unevenness in the air chamber, for example, Japanese Patent Application Laid-Open
Japanese Patent Publication No.-135725 discloses an air knife similar to the conventional air knife installed upstream of the conventional air chamber to blow high-speed airflow from the air knife into the air chamber to avoid airflow from the air chamber. A device that presses the inside of an air chamber to closely adhere a sheet has been proposed.

In Japanese Utility Model Laid-Open Publication No. Hei 6-728, the gap between the outer wall of the chamber and the sheet is automatically adjusted to the minimum with a high degree of precision in accordance with the conditions, thereby minimizing the amount of air blown from the chamber. There has been proposed a device for improving thickness unevenness.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The improvement described in Japanese Patent No. 5725 has a problem that the operation method is difficult because the function of preventing the blowout from the air chamber and the function of pressurizing the air chamber are not independent. In the apparatus described in Japanese Utility Model Application Laid-Open No. 6-728, vibration is easily picked up by a polymer having low viscosity such as polyester, so that if the gap between the outer wall on the base side of the chamber and the sheet is made too small, the sheet may be moved into the chamber. There is a problem that a trouble such as cutting due to contact is likely to occur, a sufficient effect cannot be obtained, and the equipment becomes large.

The present invention proposes a solution to the above-mentioned problems, which eliminates the need for a large-scale facility, is easy to operate, and is effective in reducing unevenness in thickness even for a polymer having a low viscosity such as polyester. The main cause of the unevenness of thickness in the air chamber method depends on the casting conditions such as the relative position of the die and the cooling roll,
From the total amount of air blown out from the gap, flow from the base to the sheet, paying attention to the fact that the air flow or the wind speed that flows on the surface of the sheet and collides with the sheet in free space often has a greater effect. By providing a diffusing means between the contact point of the article to the cooling roll and diffusing the airflow toward the upper opening of the space formed by the base, the sheet article, and the air chamber, the problem of the prior art is solved. The inventors have found that the present invention is improved, and arrived at the present invention.

[0007]

That is, the present invention provides a method for producing a polymer sheet in which a molten polymer is extruded into a sheet form from an orifice-shaped die, and is brought into close contact with a cooling roll surface and solidified by pressing a pressurized gas by an air chamber. In the method, at least a part of the leaked gas blown out from the air chamber along the sheet-like material in the direction of the mouthpiece from the die to a contact point of the sheet-like material to the cooling roll, in the width direction of the sheet-like material. This is a method for producing a polymer sheet that is diffused by a diffusion means provided transversely in the direction of an upper opening portion of a space formed by the base, the sheet material, and the air chamber.

[0008] In a preferred aspect of the present invention, the cross-sectional shape of the diffusing means is a part of an arc having a ratio of a major axis to a minor axis of 1 to 100, and is arcuate on the chamber side, and the diffusing means is in a sheet-like shape. The gap formed between the sheet and the object is a gap that expands in an arc shape in the direction of the die, and the shortest portion between the lower end of the diffusion unit and the sheet-like object is preferably 0.5 to 8 mm.

In the present invention, the provision of at least two diffusing means and the use of a polymer having a large neck-in tend to reduce the width of the sheet and the uniformity of the thickness in the width direction. Forcibly adhered to the surface of the cooling roll by means of an electrostatic adhesion method, a liquid film adhesion method and / or a roll pressing method, and that the polymer is an aromatic polyester.

The present invention further provides a polymer sheet having an orifice-shaped die for extruding a molten polymer into a sheet, a cooling roll, and an air chamber, wherein the sheet is adhered to the cooling roll surface by the air chamber and solidified. In the manufacturing apparatus, a diffusion means is provided across the width of the sheet from the die to the point of close contact of the sheet with the cooling roll, and the diffusion means is provided along the sheet in the direction of the die from the air chamber. An apparatus for producing a polymer sheet, in which at least a part of the leaked gas to be blown out is diffused by the diffusion means in the direction of an upper open portion of a space formed by the base, the sheet, and the air chamber. The cross-sectional shape is a part of an arc having a ratio of a major axis to a minor axis of 1 to 100, an arc on the air chamber side, and a sheet shape with the diffusing means. Is formed in the direction of the die, more preferably at least two arc-shaped diffusing means are provided, and the leaked gas is diffused in the direction of the opening through the arc-shaped space formed between the diffusing means. The cooling roll has a rough surface having a ventilation resistance of 10,000 seconds or less. The rough surface of the present invention is a matte surface or a micro cracked surface, and has a ventilation resistance of 1000 according to the method for measuring the ventilation resistance described below.
It is a rough surface of 0 seconds or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the polymer is
For example, polyethylene terephthalate, polyethylene
Thermoplastic polymers such as aromatic polyesters such as 2,6-naphthalate, polyolefins such as polypropylene, polyvinyls such as polystyrene, polyamides such as nylon, and polycarbonates. Among them, aromatic polyesters are particularly preferable.

In the present invention, the orifice-shaped base is
For example, a die having a linear opening, such as a T-die, a fishtail die, an I-die, or the like.

In the present invention, the gas pressure is a pressure applied to a sheet or a sheet by the static pressure of air or a gas mainly composed of air and containing mist, and can be generated by an air chamber or the like.

Preferably, the gas is pressed by setting the internal pressure in the air chamber to 5 to 500 Pa. The length of the air chamber in the sheet traveling direction depends on the casting speed, but is preferably 50 to 700 mm.

In the present invention, the leaked gas blown out from the air chamber along the sheet-like material in the direction of the die is about 0.3 to 5 mm between the lower end of the outer wall on the upstream side of the side wall constituting the air chamber and the cooling roll. The sheet-like material extruded from the mouthpiece is guided into the chamber through the gap, is solidified on the cooling roll by the pressure of the gas in the chamber, and is formed between the downstream outer wall of the chamber and the cooling roll. It is guided to the outside of the chamber through the gap, is further cooled, and is transferred to the next step such as a winding step or a stretching step. The higher the internal pressure of the chamber and the wider the gap, the greater the velocity and volume of the leaked gas, which collides with the sheet extruded from the die, Vibrating the over preparative like material worsen the thickness plaques.

In the present invention, the diffusion means provided transversely to the width direction of the sheet-like material forms a gap which expands in an arc shape in the direction of the mouthpiece to form the Coanda effect of the wall jet ("Mechanical Engineering", edited by the Japan Society of Mechanical Engineers). Handbook "Fluid Engineering A5-66 or JSME (Maruzen) Photobook" Flow "p. 40), part of the air flow blown out of the chamber is spread along the arc-shaped outer peripheral wall surface of the diffusion means. It is a means for diffusing in the direction of the upper open part of the space formed by the object and the air chamber. Means for diffusing another part of the blown air flow along the arc-shaped inner peripheral wall surface can also be used.

Since the arc-shaped diffusing means of the present invention is a means for efficiently expressing the Coanda effect and diffusing the blown airflow toward the upper opening, the present invention is formed between the diffusing means and the sheet-like material. Is a gap that expands in the direction of the die, and the cross-sectional shape of the surface of the diffusion unit facing the cooling roll is an arc on the outer surface, and the arc shape has a ratio of the major axis to the minor axis of 1 to 1.
100 is preferably 1 to 50, more preferably a part of a circle or an ellipse of 1 to 20, and the entire cross-sectional shape can be a columnar shape or a fallen columnar shape, but a preferred embodiment is a plate shape formed into an arc shape Thus, it can be diffused along the arc-shaped inner peripheral surface. When the curvature of the outer surface of the arc is 1 to 1000 mm and the curvature is less than 1 mm or more than 1000 mm, the gas diffusion effect is small, and the preferable curvature of the arc is 3 to 200 mm. The circumference of the arc is 2 to 200 mm, preferably 5 to 100
mm. The gap between the lower end of the diffusing means and the sheet is 0.5 to 8 mm, preferably 0.8 to 5 mm.

The tangent at the lower end of the arc of the diffusion means facing the cooling roll may be parallel to the tangent of the opposing cooling roll face, but can be inclined from 0 to 60 degrees in the direction of the chamber.

According to the present invention, the diffusing means having an arc-shaped cross section of 5 to 5 is used.
By providing at least two at intervals of 100 mm, more of the leaked gas can be diffused toward the upper opening portion through the arc-shaped space formed between the respective diffusion means, and the effect of reducing the thickness unevenness of the sheet is further improved. .

Further, according to the present invention, if the outer lower end of the outer wall on the base side of the air chamber is beveled in an arc shape so that the fulcrum is located on the chamber side, a diffusion action of the leaked gas is developed along the beveled shape, and A synergistic effect of diffusion with the diffusion means provided between the chambers occurs, and more of the leaked gas can be diffused toward the upper opening. A preferable curvature of the corner cutting is 1 to 500 mm, and a particularly preferable curvature is 2 to 500 mm.
200 mm.

At least a part of the leaked airflow blown out of the chamber is diffused toward the upper opening by the Coanda effect of the arc-shaped diffusion means, and the wind speed and flow rate of the airflow colliding with the sheet-like material coming out of the die are greatly reduced. As a result, vibration of the sheet is suppressed, and unevenness in the thickness of the sheet is improved.

In the present invention, when the polymer is a polymer having a large neck-in such as an aromatic polyester, the width of the sheet and the uniformity of the thickness in the width direction are easily deteriorated. It is convenient to forcibly contact the surface of the cooling roll by means of an electrostatic adhesion method, a liquid film adhesion method and / or a roll pressing method.

In the present invention, the surface of the cooling roll may be an ordinary mirror-polished surface. However, the surface of the cooling roll may be roughened to have a ventilation resistance of 10,000 seconds or less, further 1000 seconds or less, particularly 500 seconds or less. This facilitates removal and facilitates control of streamlines of the sheet-like material, thereby suppressing vibration of the sheet-like material and improving the uniformity of the thickness.
Rough surfaces suitable for the present invention are porous surfaces, or matte surfaces, or microcracked surfaces, or surfaces with multiple linear grooves.

In the present invention, the thickness of the sheet is 5 to 140.
μm is preferable, and if it is less than 5 μm, it is difficult to obtain a uniform thickness,
On the other hand, if the thickness exceeds 140 μm, a defect of poor adhesion to the cooling roll may occur or a sheet may be poorly cooled. A more preferred sheet thickness range is 6 to 100 μm.

Hereinafter, the present invention will be further described with reference to the drawings. FIG. 1 shows an example of an embodiment of the present invention, and FIG. 2 shows an example of a conventional method. 1 and 2, 11 and 21 are caps, 13 and 23 are cooling rolls, 12 and 22 are sheet-like materials, 14 and 24 are needle-like electrodes, 15 and 25 are air chambers, 16 is a leakage gas diffusion means, Reference numeral 17 denotes the lower end of the outer wall on the base side of the air chamber.

Referring to FIG. 1, the casting method will be described. The sheet-like material 12 extruded from the mouthpiece 11 is passed through a gap between the leaking gas diffusion means 16 having an arc-shaped cross section and the cooling roll. The cooling roll is guided on a high-speed rotating cooling roll 13, and a portion corresponding to the ear of the sheet is electrostatically adhered to by a needle-shaped electrode 14 to which a high voltage is applied. The sheet is guided to the chamber 15 through the gap between the sheet and the sheet and adheres to the cooling roll surface by the pressure of the gas to be solidified.

The leaked airflow blown from the gap between the outer wall on the mouth side of the chamber and diffuses in the direction away from the sheet due to the Coanda effect, and then diffuses when passing through the gap expanding toward the mouth side between the lower end of the outer wall and the sheet. A part of the leaked air flow passes through the gap between the lower end of the arc-shaped diffusing means provided across the width of the sheet and the sheet and further along the outer peripheral wall of the diffusing means by the Coanda effect. The other part diffuses toward the opening part of the upper part of the seat, and the other part similarly diffuses toward the opening part of the upper part of the seat along the arc-shaped inner peripheral wall surface.

In FIG. 2, which is an example of the conventional method, since there is no means for diffusing the leaked airflow blown from the outer wall on the base side of the chamber in the direction of the opening at the top of the sheet, the anti-cooling roll is produced by the Coanda effect of the cooling roll. The blowout concentrates in the direction of the orifice of the die along the surface of the sheet with almost no diffusion in the plane direction, strongly collides with the molten sheet in free space and vibrates, significantly deteriorating the uniformity of the sheet thickness. .

However, according to the present invention, the air blown out of the chamber is diffused to avoid concentration in the direction of the orifice.
By reducing the amount and / or speed of the air that collides with the molten sheet, it is possible to avoid the deterioration of the uniformity of the sheet thickness.

The surface of the cooling roll in the present invention is more preferably a rough surface having a ventilation resistance of 10,000 seconds or less than that of the mirror roll. This is presumed to be because the air layer on the roll surface can be easily removed even if the associated airflow is interrupted once, such as a new associated airflow generated downstream thereof.

The airflow resistance in the present invention means that when a vacuum area is provided on the surface of a rough surface, air flows in through a groove of the rough surface, and when vacuum suction is stopped at this time, the degree of vacuum is reduced.
The time required for the degree of vacuum to decrease from a certain value to another certain value is represented. As shown in FIG. 3, a specific method of measuring the ventilation resistance is to connect a vacuum pump 34 to one end of a container 31 provided with a vacuum gauge 32 through a vacuum cock 33 and to connect a vacuum hose to the other end. A rubber suction cup (for example, FPM.PFYK-40 manufactured by Myotoku Co., Ltd.) 36 is attached via 35, and the effective vacuum volume from the vacuum cock 33 to the suction cup 36 is 100 CC. As shown in a schematic view of an enlarged cross section of the suction cup portion in FIG.
Is pressed against the cooling roll surface 44, and a porous sheet having a diameter of 30 mm (for example, a Naslon low-density sintered product 8-L-50 manufactured by Nippon Seisen Co., Ltd.) so that the outer peripheral surface of the sucker comes into contact with the porous sheet.
0) 43 is placed at the center of the suction cup and pressed. Then, the container of 100 CC was moved to -700 mmH by the vacuum pump 34.
When the cock 33 is closed with a vacuum of not more than g, the degree of vacuum is reduced because air flows into the vacuum system through the groove on the rough surface of the suction cup portion. At this time, the degree of vacuum is reduced from -700 mmHg to -6.
The time required to decrease to 50 mmHg is defined as the ventilation resistance. In order to check the vacuum leak of the measuring instrument before measuring the ventilation resistance, it is confirmed that the ventilation resistance of the polished glass plate is 10,000 seconds or more.

The casting speed in the present invention is preferably 20 m / min or more at the peripheral speed of the cooling roll. The upper limit is not particularly limited, but is preferably 170 m / min.

The sheet formed according to the present invention can be stretched favorably in the biaxial stretching step, and has the same thickness unevenness and physical properties as the film obtained by forming the entire width of the sheet by the electrostatic adhesion method and biaxially stretching. .

[0034]

The present invention will be further described with reference to the following examples.

[Examples 1 to 6] Polyethylene terephthalate was extruded with the apparatus shown in FIG. 1 and a direct current voltage of 7 KV was applied to the needle-shaped strip electrodes corresponding to both ends of the sheet. And the thickness unevenness was evaluated. Under the conditions of the present invention, the unevenness of the thickness of the sheet was good.

[0036]

[Table 1]

As is clear from the results shown in Table 1, the thickness unevenness of the sheet according to the present invention was good. In addition, in Table 1, Table 2, and Table 3, it shows that the evaluation result of the thickness unevenness column is as follows. ◎: Thickness unevenness of less than 4% ····· Excellent ○: Thickness unevenness of 4% or more and less than 5% ··· Good Δ: Thickness unevenness of 5% or more and less than 7% · Poor ×: Thickness Spots are more than 7% ... extremely bad

[Examples 7 to 9] In the same apparatus as in Examples 1 to 6, except that the surface of the cooling roll was rough and the shape of the lower end of the outer wall on the mouth side of the chamber was fixed to an arc R15, polyethylene was obtained under the conditions shown in Table 2. A sheet of -2,6-naphthalate was formed. Under the conditions of the present invention, the unevenness of the thickness of the sheet was good.

[0039]

[Table 2]

As is clear from the results shown in Table 2, the thickness unevenness of the sheet according to the present invention was good.

[Comparative Examples 1 to 3] Polyethylene terephthalate was extruded on the surface of a cooling roll using the conventional apparatus shown in FIG. 2, and a sheet was similarly formed under the conditions shown in Table 3 to evaluate uneven thickness.

[0042]

[Table 3]

As is evident from the results shown in Table 3, it was difficult to improve the unevenness of the thickness of the sheet by the conventional method, and vibration of the sheet was induced during the sheet forming, causing an accident such as cutting.

[0044]

According to the present invention, in the high-speed casting of a thin brand by the air pinning method, while the sheet-like material coming out of the die reaches the cooling roll, the leakage airflow blown out from the air chamber in the direction of the die is reduced. By the diffusion means provided across the width direction, the air volume and wind speed of the airflow which diffuses into the open space opposite to the sheet-like material by utilizing the Coanda effect and collides with the sheet-like material to deteriorate the uniformity of the thickness. , The unevenness of the thickness of the sheet is improved, the stability of the film formation is improved, and a high-quality thin sheet can be produced at high speed and stably.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of a conventional casting method.

FIG. 3 is a schematic view of an apparatus for measuring a ventilation resistance of a rough surface of a cooling roll surface.

FIG. 4 is a schematic diagram showing an enlarged cross section of a suction cup portion of the airflow resistance measuring device.

[Explanation of symbols]

 11, 21: Base 12, 22: Sheet 13, 23: Cooling roll 14, 24: Needle electrode 15, 25: Air chamber 16: Diffusion means 17: Lower end of the outer wall on the base side of the air chamber 31: Container 32: Vacuum gauge 33: Vacuum cock 34: Vacuum pump 35, 41: Vacuum hose 36, 42: Sucker 43: Porous sheet 44: Cooling roll surface

Claims (11)

[Claims] 1. A method for producing a polymer sheet in which a molten polymer is extruded from an orifice-shaped die into a sheet shape and adhered to a cooling roll surface by gas pressure from an air chamber to be solidified. At least a part of the leaked gas blown out from the air chamber along the sheet in the direction of the base while reaching the contact point of the base is diffused by the diffusion means provided in the width direction of the sheet, the base and the sheet. A method for producing a polymer sheet, comprising: diffusing an object and an air chamber in a direction toward an upper opening of a space formed by the object. 2. The cross-sectional shape of the diffusing means is a part of an arc having a ratio of a major axis to a minor axis of 1 to 100, and is an arc on the air chamber side, and is formed between the diffusing means and the sheet-like material. The gap that is formed is a gap that expands in the direction of the die.
A method for producing the polymer sheet according to the above. 3. The weight according to claim 1, wherein at least two diffusing means having an arc-shaped cross section are provided, and at least a part of the leaked gas is diffused toward the upper opening through an arc-shaped space formed between the diffusing means. Manufacturing method of united sheet. 4. The method according to claim 1, wherein an outer lower end of the outer wall on the base side of the air chamber is chamfered in an arc shape toward the air chamber, and at least a part of the leaked gas is diffused along the chamfer toward the upper opening portion. A method for producing the polymer sheet according to the above. 5. The method for producing a polymer sheet according to claim 4, wherein the curvature of the chamfer is 1 to 500 mm. 6. The method for producing a polymer sheet according to claim 1, wherein the gap between the lower end of the diffusion means and the sheet is 0.5 to 8 mm. 7. The production of a polymer sheet according to claim 1, wherein both end portions of the sheet material are forcibly brought into close contact with the cooling roll surface by means of an electrostatic adhesion method, a liquid film adhesion method and / or a roll pressing method. Method. 8. An apparatus for producing a polymer sheet, comprising: an orifice-shaped die for extruding a molten polymer into a sheet, a cooling roll, and an air chamber, wherein the sheet is closely adhered to the cooling roll surface by the air chamber and solidified. In the above, a diffusion means is provided across the width of the sheet from the base to the point of close contact of the sheet with the cooling roll, and a leaking gas blown along the sheet from the air chamber in the direction of the base. Characterized in that at least a part of the polymer sheet is diffused by the diffusion means in the direction of the upper opening of the space formed by the die, the sheet material and the air chamber. 9. The cross-sectional shape of the diffusing means is a part of an arc having a ratio of a major axis to a minor axis of 1 to 100, an arc on the air chamber side, and a gap between the diffusing unit and the sheet-like material. The gap that is formed is a gap that expands in the direction of the die.
An apparatus for producing the polymer sheet according to the above. 10. The apparatus for producing a polymer sheet according to claim 9, wherein at least two arc-shaped diffusion means are provided, and the leaked gas is diffused in the direction of the opening through an arc-shaped space formed between the respective diffusion means. 11. The surface of the cooling roll has a ventilation resistance of 1000.
9. The apparatus for producing a polymer sheet according to claim 8, wherein the rough surface has a duration of 0 second or less.