JP4236228B2 - Method and apparatus for producing thermoplastic resin sheet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermoplastic resin sheet having a smooth and smooth surface appearance over the entire width of the sheet, particularly an ethylene-vinyl acetate copolymer saponified product (that is, an ethylene-vinyl alcohol copolymer, hereinafter abbreviated as “EVOH” if necessary). ) Relates to a method and an apparatus for manufacturing a sheet.
[0002]
[Prior art]
When the molten resin sheet of the thermoplastic resin extruded from the die is brought into close contact with the cooling roll , the suction nozzle faces the portion where the molten resin sheet comes into close contact with the cooling roll, while sucking air from the suction nozzle ( In other words, a method of obtaining a target sheet by forming a film (while forming a negative pressure) is known.
[0003]
For example, in Japanese Patent Laid-Open No. 10-272637 (Document 1), a suction nozzle faces a location where a liquid film of resin discharged from a slit-shaped base comes into close contact with the moving cast surface, and air is sucked from the suction nozzle. In the method for producing a resin film while forming a film, the resin film is produced so that the suction port of the suction nozzle extends along the width direction of the liquid film and the air is sucked with a width narrower than the discharge width of the liquid film. The method is shown. The resin is not particularly limited as long as it can be melted or formed into a film as a solution, but specific mention is made of polyolefin, polyester, and aramid resin. An example of the cast surface is an endless belt surface, but a drum or any other shape can be adopted.
[0004]
In JP-A-10-272638 (Document 2), in the same resin film manufacturing method as in JP-A-10-272737, the suction port of the suction nozzle is set along the width direction of the liquid film, There is shown a method for producing a resin film in which air is sucked by providing a stepped portion cut away in a direction away from the liquid film at least in the width direction both ends of the suction port.
[0005]
[Problems to be solved by the invention]
The methods described in Documents 1 and 2 cited above control the flow of air entering from the end of the liquid film so as to be substantially perpendicular to the moving direction of the liquid film, or are generated on the surface of the liquid film. The vortex is intended to keep away from the surface of the liquid film, but even with these methods, when the cast surface is the casting roll surface (cooling roll surface), a good surface appearance is achieved over the entire sheet width. It is not always easy to stably obtain the thermoplastic resin sheet having the surface, and as a result, the surface appearance of the region on both ear ends of the sheet tends to be inferior to the surface appearance of the region on the center side. Such a tendency was particularly conspicuous when the thermoplastic resin was EVOH.
[0006]
In view of such a situation, the present invention makes a molten resin sheet of a thermoplastic resin extruded from a die into a sheet shape adhere to a rotating cooling roll, and the sheet after cooling on the roll surface is removed from the roll surface. Saishi to form a film by peeling, the melted resin sheet to face the site to a suction nozzle of the roll rotation direction upstream side of the point of contact with the cooling roll, to a film while sucking air from the suction nozzle In the method of obtaining the target sheet, by devising a current plate arranged in the suction nozzle, a thermoplastic resin sheet (especially with a smooth and smooth surface appearance over the entire width of the sheet including both ends of the sheet) An object of the present invention is to provide a method capable of manufacturing an EVOH sheet) and to provide an apparatus therefor.
[0007]
[Means for Solving the Problems]
The method for producing the thermoplastic resin sheet of the present invention includes:
The molten resin sheet of a thermoplastic resin extruded from a die into a sheet in close contact with the cooling roll which is rotating, Saishi the sheet after cooling on the roll surface to a film by peeling from the roll surface, In the method of obtaining the target sheet by forming a film while sucking air from the suction nozzle, facing the suction nozzle to the upstream side in the roll rotation direction where the molten resin sheet is in close contact with the cooling roll,
A flow straightening plate facing the roll is disposed in the suction nozzle, and an opening ratio Rc per unit area of a portion facing the roll central side region (region corresponding to the sheet central side) of the flow straightening plate is determined at both ends of the roll. It is characterized in that it is set to be larger than the opening ratio Re per unit area of the portion facing the side region (region corresponding to the both ear end sides of the sheet).
[0008]
The apparatus for producing the thermoplastic resin sheet of the present invention comprises:
When the target sheet is obtained by bringing the molten resin sheet of thermoplastic resin extruded from the die into close contact with the rotating cooling roll and peeling the cooled sheet from the roll surface on the roll surface , It is an apparatus equipped with a suction nozzle that sucks air by facing the upstream side of the roll rotation direction where the molten resin sheet is in close contact with the cooling roll,
A flow straightening plate facing the roll is disposed in the suction nozzle, and an opening ratio Rc per unit area of a portion facing the roll central side region (region corresponding to the sheet central side) of the flow straightening plate It is characterized in that it is set to be larger than the aperture ratio Re per unit area of the portion facing both end side regions (regions corresponding to the both ear end sides of the sheet).
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
[0010]
<Thermoplastic resin, especially EVOH>
Examples of the thermoplastic resin in the present invention include various thermoplastic resins including EVOH, polyamide, polyester, polyolefin, and polycarbonate, and these may be a blend of two or more of the same or different resins. . Since EVOH is particularly important among these, EVOH will be described in detail below.
[0011]
EVOH has an ethylene content of 10 to 60 mol% (preferably 20 to 60 mol%, more preferably 25 to 55 mol%), and a saponification degree of the vinyl acetate component of 90 mol% or more (preferably 95 mol% or more). And more preferably 98 mol% or more). When the ethylene content is too low, the water resistance of the film is insufficient and the gas barrier property at high humidity is insufficient. On the other hand, when the ethylene content is too high, the gas barrier property is insufficient. When the saponification degree is too low, the water resistance of the film is insufficient and the gas barrier property is also insufficient.
[0012]
EVOH may be a mixture of two or more types of EVOH having different ethylene contents and different saponification degrees. Further, it may be modified EVOH by copolymerization or graft polymerization for obtaining an ethylene-vinyl acetate copolymer (EVA) before saponification, or an addition reaction utilizing a functional group of EVOH. Furthermore, it may be a blended product by blending with another polymer during or after the EVOH production process.
[0013]
Examples of modification by copolymerization or graft polymerization of EVOH are α-olefins such as propylene, isobutylene, α-octene, α-dodecene, α-octadecene; acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, Ethylenically unsaturated carboxylic acids such as itaconic acid or salts, anhydrides, mono- or dialkyl esters thereof; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; alkyl vinyl ethers; polyoxyethylene (meth) Polyoxyalkylene (meth) allyl ethers such as allyl ether and polyoxypropylene (meth) allyl ether; polyoxyalkylene (meth) acrylates such as polyoxyethylene (meth) acrylate and polyoxypropylene (meth) acrylate Relate; polyoxyethylene (meth) acrylamide, polyoxyalkylene (meth) acrylamide such as polyoxypropylene (meth) acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester; polyoxyethylene Vinyl ether, polyoxypropylene vinyl ether; polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine; olefin sulfonic acid such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid or salts thereof; N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride; dimethylallyl vinyl ketone; N-vinyl pyro This is a case where it is modified with a monomer such as pyrrolidone ring-containing monomer such as lidone; vinyl chloride, vinylidene chloride; silicon-containing monomer; allyl acetate; isopropenyl acetate.
[0014]
Examples of modification by addition reaction using the functional group of EVOH include modification by cyanoethyl group, modification by addition of alkylene oxide (addition of polyether component), and the like.
[0015]
Examples of blends by blending with other polymers during or after EVOH production include blending polyolefin, polyamide, polyester, polystyrene, polyvinyl alcohol, polyurethane, polymethylmethacrylate and their modifications as other polymers Is the case. In this case, other resins can be blended in an amount of about 0.1 to 150 parts by weight (particularly 0.1 to 100 parts by weight, more preferably 0.1 to 80 parts by weight) with respect to 100 parts by weight of EVOH (including a modified product). .
[0016]
The EVOH preferably has a total metal content of Na and K of 0.01 to 50 ppm (particularly 0.1 to 30 ppm). If the sum of the metal contents of Na and K is less than 0.01 ppm, there is a risk of coloring (yellowing) during extrusion, while if the sum exceeds 50 ppm, the frequency of gel generation increases, which is attributed to this. This is because the film tends to break during stretching.
[0017]
The content of metals other than Na and K is not particularly limited, but the sum of the metal contents of Ca and Mg is 1 to 200 ppm (preferably 2 to 150 ppm), of which the metal content of Ca is 100 ppm or less, Mg The content of Ca and / or Mg having a content of 100 ppm or less is effective in suppressing the generation of gel.
[0018]
In addition, when EVOH contains the above metal components, these metal components are mixed with organic acids such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, behenic acid, sulfuric acid, sulfurous acid, carbonic acid, boron. It is desirable to contain it as a metal salt of an inorganic acid such as acid or phosphoric acid. Among these, acetates, borates, phosphates, and hydrogen phosphates are preferable.
[0019]
The method for containing an alkali metal in EVOH is not particularly limited. (I) A metal compound is contained by bringing a porous precipitate of EVOH having a water content of 20 to 80% by weight into contact with an aqueous solution of the above metal compound. (Ii) After a metal compound is contained in a uniform EVOH solution (water / alcohol solution, etc.), the solution is extruded into a coagulating solution in the form of a strand, and then the resulting strand is cut. (Iii) A method in which EVOH and a metal compound are mixed together and then melt-kneaded with an extruder, etc. (iv) The alkali used in the saponification step during the production of EVOH A method that neutralizes (sodium hydroxide, potassium hydroxide, etc.) with acetic acid, and adjusts the amount of by-product sodium acetate, potassium acetate, etc. by washing with water, etc. It is.
[0020]
<Molding into sheets>
In the present invention, the molten resin sheet of thermoplastic resin extruded from the die into a sheet shape is brought into close contact with the rotating cooling roll, and the cooled sheet is peeled off from the roll surface on the roll surface. Get. The molten resin sheet may be not only a single-layer molten resin sheet but also a multilayer molten resin sheet.
[0021]
As an extruder for extruding the thermoplastic resin, a general screw type extruder such as a single screw extruder or a twin screw extruder is used. Taking the case where the thermoplastic resin is EVOH as an example, the melting temperature is suitably 10 to 80 ° C. (preferably 20 to 60 ° C.) higher than the melting point of EVOH, but as long as the kneading of the resin is sufficient. In order to suppress the generation of gel, it is preferable to set it as low as possible.
[0022]
Only with a screw type extruder, quantitative extrudability may be lacking, and the film thickness accuracy in the flow direction (MD direction) of an unstretched sheet may be deteriorated. When such a trouble occurs, it is desirable to provide a gear pump between the extruder and the die (T die). The main structure of the gear pump is an inline type, a block mount type, etc., the number of gears is 2 gears, 3 gears, etc., and the gear shape is spar, helical or the like.
[0023]
Moreover, between the gear pump and the T die, if necessary, a heat exchanger for the purpose of cooling the resin generated by the gear pump to suppress deterioration due to heat, a filter for the purpose of removing gel foreign matter, and the width direction of the T die A thermogenizer for the purpose of making the temperature of the resin uniform may be provided as appropriate.
[0024]
The molten resin sheet is cooled in contact with the rotating cooling roll, and becomes the target sheet. At this time, the temperature of the cooling roll is usually 60 ° C. when the thermoplastic resin is EVOH. Hereinafter, the temperature is preferably set to 40 ° C. or less.
[0025]
In the present invention, the target sheet is obtained by forming a film while sucking air from the suction nozzle, facing the suction nozzle at the upstream side in the roll rotation direction where the molten resin sheet is in close contact with the cooling roll. However, at this time, a current plate facing the roll is arranged in the suction nozzle, and a unit area per unit area of the current plate facing the roll center side area (area corresponding to the sheet center side) is arranged. Special measures are taken to set the opening ratio Rc to be larger than the opening ratio Re per unit area of the part facing the roll both ends side area (area corresponding to both ends of the sheet).
[0026]
At this time, the opening ratio Rc per unit area of the part facing the roll center side area (area corresponding to the sheet center side) 70% of the current plate arranged in the suction nozzle and the roll both end side areas (sheet both ears) The region corresponding to the end side) The difference from the aperture ratio Re per unit area of the portion facing each 15% is Rc−Re ≧ 5 (%)
It is preferable that A more preferred range is
Rc-Re ≧ 10 (%)
It is. As a result, a thermoplastic resin sheet having a smooth and beautiful surface appearance in a region extending over the entire width of the sheet including both ear ends of the sheet can be obtained. If Rc-Re is less than 5%, the surface appearance on the both ear ends of the sheet may be impaired.
[0027]
If Rc−Re is set as described above, the absolute value of the difference ΔP between the pressure Pe at the center of both ends of the roll in the suction nozzle and the pressure Pc at the center of the roll central area is approximately 3 mmAq or more, preferably Approximately 5mmAq or more.
[0028]
The opening of the rectifying plate is configured by making the rectifying plate into a plate shape and providing a through-hole of an appropriate shape such as a circle or a rectangle on the plate, or by designing the mesh eyes appropriately by making the rectifying plate into a mesh shape. The
[0029]
As a method of differentiating the aperture ratio Rc and the aperture ratio Re, the number per unit area is the same and the hole diameter is different, the hole diameter is the same and the number per unit area is different, or a combination of these. It can be carried out.
[0030]
<Secondary processing after sheet forming>
The sheet (unstretched sheet) obtained as described above can be used for various purposes as a single sheet. Moreover, this unstretched sheet can be used for a stretching process to form a uniaxially stretched film or a biaxially stretched film. Alternatively, the unstretched film or stretched film can be laminated with a base material to form a laminate film, or another substance can be coated to form a composite film. The unstretched film or stretched film may be subjected to vapor deposition of metal or inorganic oxide, sputtering, or ion plating to form a film.
[0031]
<Application>
When the obtained sheet or its secondary processed product is an EVOH film or its secondary processed product, it has not only appearance characteristics but also properties such as gas barrier properties, aroma retention, solvent resistance, and oil resistance. Because it is excellent, it is particularly useful as a film, sheet, tube, bag, container, etc. for packaging foods, pharmaceuticals, agricultural chemicals, industrial chemicals, fragrances, oils, etc. be able to.
[0032]
【Example】
The following examples further illustrate the present invention.
[0033]
<Raw material EVOH>
As an example of the thermoplastic resin, as shown in Table 1 described later, EVOH resins having different copolymer compositions and alkali metal or alkaline earth metal contents were prepared. The alkali metal and alkaline earth metal were quantified by atomic absorption analysis.
[0034]
<Manufacturing equipment, electrodes>
FIG. 1 is a side view showing an example of the manufacturing apparatus of the present invention. FIG. 2 is an enlarged view of a main part of the apparatus of FIG.
[0035]
1 and 2, (1) is a single screw extruder, (2) is a gear pump, (3) is a die (T die), (4) is a cooling roll (casting roll), (5) is a peeling roll, (6) is a suction nozzle. (S ₁ ) is a molten resin sheet, and (S ₂ ) is a sheet after cooling.
[0036]
FIG. 3 is an enlarged view of the suction nozzle (6) of the apparatus of FIG. In FIG. 3, the suction nozzle (6) is composed of a first chamber (62) on the front side and a second chamber (63) on the rear side, and between the first chamber (62) and the second chamber (63). A partition wall (64) having a partition wall adjusting plate (65) capable of adjusting the clearance between the two chambers (62) and (63) is provided. The first chamber (62) is composed of a first main chamber (62a) and a first sub chamber (62b), and a first suction pipe (66 connected to an intake valve) is provided on the back side of the first sub chamber (62b). ) Is provided. The second chamber (63) is composed of a second main chamber (63a) and a second sub chamber (63b). A second suction pipe (67) connected to an intake valve is provided on the back side of the second sub chamber (63b). ) Is provided.
[0037]
In the first chamber (62) of the suction nozzle (6), the first rectification is performed between the first main chamber (62a) and the first sub chamber (62b) in the plane direction along the surface of the cooling roll (4). One plate (61A) is provided. (68) is a first bracket that supports the first current plate (61A). The second baffle plate (61B) is disposed in the second chamber (63) of the suction nozzle (6) between the second main chamber (63a) and the second sub chamber (63b). One second rectifying plate (61B) is arranged in the surface direction along the surface. (69) is a second bracket that supports the second current plate (61B).
[0038]
FIG. 4 is an explanatory view of the current plate (61) (first current plate (61A) and second current plate (61B)). In FIG. 4, an opening having a diameter of 4 mm is provided at a portion facing the roll center side region (region corresponding to the sheet center side) 70% of the current plate 61 so that the opening ratio Rc per unit area becomes a predetermined value. (H ₁ ) is provided, and the opening ratio Re per unit area is predetermined at a portion facing 15% of the roll both ends side area (area corresponding to both ends of the sheet) of the baffle plate (61). An opening (H ₂ ) with a diameter of 3 mm is provided so that In addition, the pressure in the center of the roll center side area of the first chamber (62) and the second chamber (63) and the center of the roll both end side area is measured by combining the pressures of both chambers through a duct (not shown). It has been made possible.
[0039]
<Film forming conditions>
Using the above apparatus, a sheet was formed under the following conditions. That is, the EVOH is supplied to a single-screw extruder (1), melt-extruded from a T-die (3) through a gear pump (2), and cooled to a temperature of 20 ° C., which is a 600 mm diameter cooling roll (casting roll, SUS). (4) Quenched above. Molten resin sheet (S ₁₎ is the site of the roll rotation direction upstream side of a portion in close contact with the cooling roll (4) is made to face the suction nozzle (6) as shown in Figure 1, by the suction nozzle (6) Aspiration was performed. As a result, an EVOH sheet (unstretched film) (S ₂ ) having a thickness of 150 μm was obtained. The thickness was adjusted by adjusting the rotation speed of the cooling roll (4).
[0040]
1. Extrusion conditions with single screw extruder (1)-Screw inner diameter: 65mm
・ L / D: 28
・ Screw compression ratio: 3.8
Extrusion temperature: C ₁ 210 ° C, C ₂ 220 ° C, C ₃ 230 ° C, C ₄ 230 ° C, C ₅ 220 ° C
[0041]
2. Gear pump (2)
・ Number of gears: 2
・ Gear shape: Spar ・ Model: Inline type ・ Gear pump temperature: 220 ℃
[0042]
3. T-die (3)
・ Coat hanger type manifold type ・ Die width: 450 mm (430 mm in molten resin sheet width)
-Die temperature: 220 ° C
[0043]
4). Mode of suction nozzle (6) and its baffle plate (61) Mode 1 (mode of embodiment)
-Tip open height: 8mm
-Opening ratio Rc of the current plate (61) in the roll center side area 70%: 63%
・ Rolling area Re of the rectifying plate (61) of each region on both ends of the roll is 35%
・ Rc -Re = 28%
・ Suction static pressure ΔP = | Pe−Pc | = 40 mmAq
Pe: pressure in the center of the both ends of the roll in the suction nozzle (6) Pc: pressure in the center of the roll in the suction nozzle (6)
Aspect 2 (Aspect of Comparative Example)
-Tip open height: 8mm
-Opening ratio Rc of the current plate (61) in the roll center side area 70%: 50%
・ Rolling opening ratio Re of the flow straightening plate (61) in each of the roll both end side regions: 50%
・ Rc -Re = 0%
・ Suction static pressure ΔP = | Pe−Pc | = 0 mmAq
Pe: pressure in the center of the both ends of the roll in the suction nozzle (6) Pc: pressure in the center of the roll in the suction nozzle (6)
<Appearance evaluation method>
The film appearance was evaluated visually. Evaluation was made into the following five stages of A, A ′, B, C, and D.
A: Smooth and beautiful A ': Smooth, beautiful but slightly inferior to A B: Slightly textured (uneven size less than 0.5mm)
C: Pear texture (unevenness size 0.5mm or more)
D: Air is entrained vertically in the MD direction. [0046]
<Summary of conditions and results>
Conditions and results are summarized in Table 1. In Table 1, “region X” is a 15% region on each side of the sheet ear, “region Y ₂ ” is a 40% region on the sheet center side, and “region Y ₁ ” is region X and region Y ₂ . Each region is 15% sandwiched. “Et” in the EVOH column is the ethylene content (mol%), and “SV” is the degree of saponification (mol%).
[0047]
[Table 1]

EVOH Metal content (ppm) Appearance evaluation of rectifying plate sheet
Et SV Na + K Ca Mg embodiment Region X Region Y ₁ Region Y ₂
Comparative Example 1 32 99.8 20 10 1 Aspect 2 C to B B to A ′ A
Example 1 32 99.8 20 Ten 1 embodiment 1 A A A
Comparative Example 2 44 99.8 20 10 1 Aspect 2 C B to A ′ A ′
Example 2 44 99.8 20 Ten 1 embodiment 1 A 'A' A '
Comparative Example 3 32 99.8 1 0 25 Aspect 2 C B to A A
Example 3 32 99.8 1 0 25 Aspect 1 A A A
Comparative Example 4 44 99.8 80 10 1 Aspect 2 D B to A ′ A ′
Example 4 44 99.8 80 Ten 1 embodiment 1 A ' A ' A '
[0048]
From Table 1, when EVOH having the same composition and the same metal content is used, the surface appearance of the area over the entire width of the sheet is smooth and beautiful, while the comparative example is the area on the both ears side of the sheet and its area. It can be seen that the surface appearance of the region adjacent to the ear end side is inferior. Also, when EVOH having different metal contents is used among the examples, the examples 1 to 3 in which the sum of the metal contents of Na and K is in the range of 0.01 to 50 ppm are out of the range. It can be seen that a more preferable surface appearance can be obtained as compared with Example 4.
[0049]
【The invention's effect】
According to the present invention, it is possible to obtain a thermoplastic (especially EVOH) sheet having a smooth surface appearance over the entire width of the sheet including the both ear ends of the sheet only by devising the current plate of the suction nozzle. Can do. If the sum of the metal contents of Na and K contained in EVOH is 0.01 to 50 ppm, a much better surface appearance can be obtained. Therefore, the industrial value of the present invention is great.
[Brief description of the drawings]
FIG. 1 is a side view showing an example of a manufacturing apparatus according to the present invention.
FIG. 2 is an enlarged view of a main part of the apparatus shown in FIG.
FIG. 3 is an enlarged view of the suction nozzle (6) of the apparatus of FIG.
4 is an explanatory diagram of a current plate (6a) viewed from the direction of a white arrow in FIG. 3;
[Explanation of symbols]
(1)… Single screw extruder,
(2)… gear pump,
(3) Die (T-die),
(4)… Cooling roll (casting roll),
(5)… peeling roll,
(6)… Suction nozzle,
(61) ... Rectifying plate,
(61A)… first rectifying plate, (61B)… second rectifying plate,
(H ₁ ), (H ₂ ) ... opening,
(62) ... Room 1
(62a) ... 1st main room, (62b) ... 1st subchamber,
(63)… Room 2
(63a)… second main chamber, (63b)… second subchamber,
(64) ... partition wall,
(65) ... partition adjustment plate,
(66) ... 1st suction pipe,
(67) ... second suction pipe,
(68) ... 1st bracket,
(69) ... 2nd bracket,
(S ₁ ) ... Molten resin sheet,
(S ₂ )… (After cooling) sheet

Claims (5)

The molten resin sheet of a thermoplastic resin extruded from a die into a sheet in close contact with the cooling roll which is rotating, Saishi the sheet after cooling on the roll surface to a film by peeling from the roll surface, In the method of obtaining the target sheet by forming a film while sucking air from the suction nozzle, facing the suction nozzle to the upstream side in the roll rotation direction where the molten resin sheet is in close contact with the cooling roll,
A flow straightening plate facing the roll is disposed in the suction nozzle, and an opening ratio Rc per unit area of a portion facing the roll central side region (region corresponding to the sheet central side) of the flow straightening plate is determined at both ends of the roll. A method for producing a thermoplastic resin sheet, characterized in that it is set to be larger than an opening ratio Re per unit area of a portion facing a side region (a region corresponding to both ear ends of the sheet). The opening ratio Rc per unit area of the part facing the roll center side area (area corresponding to the sheet center side) 70% of the current plate arranged in the suction nozzle, and the roll both end side areas (on the both ear ends of the sheet) Corresponding region) The difference from the aperture ratio Re per unit area of the part facing each 15% is Rc−Re ≧ 5 (%)
The production method according to claim 1, wherein the production method is set to be   The process according to claim 1, wherein the thermoplastic resin is a saponified ethylene-vinyl acetate copolymer. The process according to claim 3 , wherein the sum of the metal contents of Na and K contained in the saponified ethylene-vinyl acetate copolymer is 0.01 to 50 ppm. When the target sheet is obtained by bringing the molten resin sheet of thermoplastic resin extruded from the die into close contact with the rotating cooling roll and peeling the cooled sheet from the roll surface on the roll surface , It is an apparatus equipped with a suction nozzle that sucks air by facing the upstream side of the roll rotation direction where the molten resin sheet is in close contact with the cooling roll,
A flow straightening plate facing the roll is disposed in the suction nozzle, and an opening ratio Rc per unit area of a portion facing the roll central side region (region corresponding to the sheet central side) of the flow straightening plate An apparatus for producing a thermoplastic resin sheet, characterized in that it is set to be larger than an opening ratio Re per unit area of a portion facing both end regions (regions corresponding to both ends of the sheet).

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