JP3632928B2 - Method and apparatus for producing polyvinyl alcohol polymer film - Google Patents

Description

こうして得られたフィルムＦの物性は、表１に示す通り、厚さむら、レタデーション平均値およびレタデーションむらが小さかった。これはベルト型製膜機１１の採用により乾燥時間を長くとれ、フィルムの剥離時の水分を低くすることができるからである。
【００３１】
試験例２
試験例１と同じ耐圧溶解タンク１、第２タンク５およびベルト型製膜機１１を用い、同一条件でフィルムＦを成形した後、更に熱処理機１６にて熱処理を施し、耐水性を有する厚さ７５μ、幅１．２ｍのＰＶＡフィルムを製造した。
以下に、主な製造条件を示す。

こうして得られたフィルムの物性を表１に示す。
このフィルムは、熱処理を施していながらも、なお、厚さむら、レタデーション平均値およびレタデーションむらが少なかった。
【００３２】
比較例１
試験例１と同一設備、同一条件で、溶解原液を得た。
ギヤポンプ７でダイ１０へ定量供給し、図５に示すキャストロール５６および乾燥ロール５７を備えたドラム型製膜機で厚さ７５μ、幅１．２ｍのＰＶＡフィルムを製造した。
以下に、主な製造条件を示す。

この方法により得られたフィルムの物性を表１に示す。
比較例１のフィルムは試験例１，２に比較し、厚さむら、レタデーション絶対値およびレタデーションむらが大きいことが分かる。生産性を上げるため、キャストロール５６の回転速度を上げていくと、剥離時のフィルム水分が高くなり、厚さむら、レタデーション平均値およびレタデーションむらが更に大きくなった。
【００３３】

厚さむらは、縦横方向に厚さを連続測定し、その最大値と最小値の差（Ｒ（μ））で示した。
レタデーションは、幅方向５ｃｍピッチで２０点測定し、その平均値（ｎｍ）で示し、レタデーションむらは、その最大値と最小値の差（Ｒ（ｎｍ））で示した。
【００３４】
【発明の効果】
以上説明したように、この発明によれば、ＰＶＡ系重合体と溶媒とを密閉型の耐圧の第１タンクで加温・加圧しながら溶解し、更に、第２タンクにおいて一時的に貯留して攪拌しながら脱泡することから、均質でかつ未溶解分や気泡の少ない原液を製造できる。また、スクリューポンプで原液をダイに供給するから、原液の供給量にばらつきが生じにくい。特に、ベルト型製膜機を用いて製膜するので、上記原液を長いオーステナイト系ステンレス製のベルト上で十分に乾燥させることができる。このように、均質でかつ未溶解分や気泡の少ない原液を一定量ずつ供給して、十分に乾燥できるから、フィルムのレタデーション、つまり、品質が向上する。
【００３５】
その一方で、製造や運搬上の制約をあまり受けずにベルトを長くすることができるから、ベルト速度を速くすることができるので、生産性も向上する。
【図面の簡単な説明】
【図１】この発明にかかる原液の製造から製膜までの製造装置の一実施例を示す概略構成図である。
【図２】この発明にかかる製膜後の熱処理、調湿および巻取装置の一例を示す概略構成図である。
【図３】ダイの正面図である。
【図４】フィルムの幅方向におけるレタデーションの変化を示す特性図である。
【図５】従来のドラム型製膜機の一例を示す概略構成図である。
【符号の説明】
１…第１タンク、２…（第１）加温装置、５…第２タンク、５ｂ…スクリューポンプ、５ｃ…ベント、７…ギヤポンプ、１０…ダイ、１１…ベルト型製膜機、１２…ローラ、１３…ベルト、３０…熱交換器、Ｆ…フィルム、Ｌ…原液。[0001]
[Industrial application fields]
The present invention relates to a method and an apparatus for producing a polyvinyl alcohol polymer film suitable for an optical component used as a polarizing film or a retardation plate, for example.
[0002]
[Prior art]
A polyvinyl alcohol (hereinafter referred to as “PVA”) polymer film is generally produced by a casting method (solution casting method) (for example, see Japanese Patent Publication No. 51-23981). In the conventional production method, a stock solution is obtained by dissolving and kneading a PVA polymer chip in a solvent in a tank, and this stock solution is poured from a slit-shaped opening to the outer periphery of a rotating drum and cast. At the same time, it was dried to obtain a film.
[0003]
[Problems to be solved by the invention]
However, in the above prior art, since the PVA polymer chips are dissolved and kneaded in a solvent in the tank, the kneading becomes insufficient, and bubbles in the stock solution are not easily defoamed. I can't get it. Therefore, the quality of the film may be deteriorated.
[0004]
Moreover, although the said prior art dries undiluted | stock solution on the drum which rotates, since this drum cannot obtain a large thing about 4 m or more in diameter from restrictions on manufacture or conveyance, when drying time is set sufficiently long, Because the peripheral speed of the drum is slow, the production capacity of the line is reduced.
[0005]
On the other hand, if the film is peeled off from the drum before the film is sufficiently dried, the following problems occur.
1) Since a wide film cannot be uniformly peeled from a roll, unevenness in peeling causes unevenness in thickness (thickness unevenness).
2) When the drying is insufficient, it is necessary to increase the tension at the time of peeling as compared with the case where the drying is sufficient, and since the strength of the film is small, there is a large molecular orientation in the length direction of the film. Arise. As for this molecular orientation, both ends of the film are large due to neck-in and peeling unevenness at the time of peeling, and large molecular orientation unevenness is also caused by peeling unevenness in the central portion. This degree of molecular orientation is measured by birefringence.
[0006]
Due to the problems 1) and 2), the value of retardation (birefringence × film thickness) becomes high. In particular, as shown by broken lines in FIG. And the unevenness of retardation increases.
Further, due to the problem 2), a large molecular orientation is generated in the length direction of the film, so that the stretchability in the length direction of the film after drying is lowered.
[0007]
The present invention has been made in view of the above conventional problems, and an object thereof is to provide a method and an apparatus for producing a PVA polymer film having excellent quality and productivity.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the method of the present invention first dissolves the PVA polymer with a solvent by stirring while heating the inside of the sealed pressure-resistant first tank, and the inside of the first tank is filled with the solvent. The stock solution is produced by increasing the pressure by evaporation of the liquid. Next, the stock solution is supplied into the second tank, and the supplied stock solution is temporarily stored in the second tank and defoamed while stirring. Thereafter, the stock solution in the second tank is sent out to the die by a certain amount. A stock solution is cast from a die on an austenitic stainless steel belt that runs between a pair of rollers. The cast stock solution is dried on the belt.
[0009]
The invention device is characterized in that a stock solution is produced by a first tank, a second tank and a screw pump, and a film is produced by a belt film production machine. That is, the present invention apparatus, first, the evaporation of stirring the first closed tank pressure-resistant producing stock solution, the solvent this first tank warmed with dissolving PVA polymer in a solvent A heating device that pressurizes the inside of the first tank, a second tank that temporarily stores and stirs the stock solution supplied from the first tank and degass it by venting, and the stock solution in the second tank And a screw pump for feeding a constant amount of liquid. In addition, a heat exchanger that adjusts the temperature of the stock solution supplied from the screw pump, a gear pump that boosts the stock solution, a die that uniformly flows the stock solution supplied from the gear pump in the width direction, and the stock solution that flows out from this die A belt-type film forming machine for casting and drying on an austenitic stainless steel belt. The belt travels between a pair of rollers.
[0010]
[Action]
According to the present invention, since the PVA polymer chip is melted while being heated in the sealed first tank having a pressure resistance, the pressure in the first tank is increased by the evaporation of the solvent . Therefore, since the boiling point of the solvent is increased, the temperature of the solvent is increased, so that the chip is easily dissolved. Further, the dissolved stock solution is defoamed by the vent while being temporarily stored and stirred in the second tank. Thus, since dissolution, stirring, and defoaming are performed, even a stock solution having a relatively high concentration can produce a homogeneous stock solution.
[0011]
Further, since the film is formed using a belt type film forming machine, the stock solution can be sufficiently dried on the long belt by setting the length of the austenitic stainless steel belt to be long. Therefore, the following advantages can be obtained.
1) Thickness unevenness can be reduced.
2) The molecular orientation and molecular orientation unevenness of the film can be reduced.
3) Due to the effects of 1) and 2), the retardation value can be lowered and the retardation unevenness can be reduced.
4) The stretchability in the length direction of the film is improved.
A film having such performance cannot be obtained even if any one of the first tank for dissolving the PVA polymer, the second tank for stirring and defoaming the stock solution, or the belt film forming machine is missing. .
[0012]
As described above, the present invention is a film having the above performance by combining the first tank for dissolving the PVA polymer, the second tank for stirring and defoaming the stock solution, and the belt film forming machine. In particular, a PVA polymer film suitable for a polarizing film and a retardation film can be provided.
[0013]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1 (a), a pair of first tanks 1 are provided, which are provided with a PVA polymer chip inlet 1a and a solvent (for example, water) supply port 1b at the top, and a stock solution extraction pipe 1c at the bottom. It has. The chip insertion port 1a is provided with an opening / closing lid 1d, and the solvent supply port 1b is provided with an opening / closing valve 1f. A first heating device 2 is provided on the outer periphery of the first tank 1 to heat the inside of the first tank 1 with steam and maintain the temperature at about 140 ° C. The first tank 1 produces a stock solution L by dissolving the charged PVA polymer chips with a solvent and stirring the mixture with a stirring blade 1e. At this time, the opening / closing lid 1d of the first tank 1 is closed, the first tank 1 is sealed, and since the first tank 1 is heated by the first heating device 2, it evaporates. The pressure in the first tank 1 is increased by the solvent.
[0014]
The stock solution extraction pipes 1 c of the two first tanks 1 communicate with the nozzle 4 of the second tank 5 via the switching valve 3. The switching valve 3 sets either one or both of the two stock solution extraction pipes 1c to an open state or a closed state.
[0015]
The second tank 5 includes a stirring blade 5a and a screw pump 5b provided coaxially with the stirring blade 5a. On the outer periphery of the second tank 5, a second warming device 6 is provided that keeps the inside of the second tank 5 slightly warmer than 100 ° C. with warm water. The second tank 5 stirs the stock solution L by the stirring blade 5a. In addition, a vent 5c for defoaming is provided at the upper part of the second tank 5. The stock solution L is fed by a fixed amount by a screw pump 5b provided in the lower part of the second tank 5, and the stock solution L is supplied to the heat exchanger 30 in FIG.
[0016]
The heat exchanger 30 uniformly lowers the temperature of the stock solution L to about 100 ° C. with hot water, and is provided with fixed blades inside, and the stock solution L is not skinned while mixing the stock solution L with the fixed blades. It is what you want to do. A gear pump 7, a filter 8, and a static mixer 9 are provided downstream of the heat exchanger 30. The filter 8 removes dust in the stock solution, while the static mixer 9 agitates the stock solution with a number of fixed blades to equalize the temperature of the stock solution and then feed the stock solution to the die 10. is there. The gear pump 7, the filter 8, and the static mixer 9 may be provided as necessary, and are not necessarily provided.
[0017]
As shown in the front view of FIG. 3, the die 10 has a slit-shaped opening 10 a that is long in the width direction D, and the stock solution is passed through the opening 10 a on the lower belt 13 with a uniform thickness in the width direction D. It will be washed out.
[0018]
The belt-type film forming machine 11 in FIG. 1B has the endless belt 13 that runs between a pair of rollers 12 and 12, and the stock solution flowing out from the die 10 is placed on the belt 13. It is cast and dried. The belt 13 is made of austenitic stainless steel, and the outer peripheral surface thereof is mirror-finished. On the outer periphery and inner periphery of the belt 13, partition walls 14 that partition the space in the traveling direction of the belt 13 are provided. On the outer peripheral surface and inner peripheral surface of the belt 13, hot air H of 80 ° C. to 170 ° C. is blown from a hot air fan (not shown) to promote drying of the stock solution. In the most downstream zone 14 </ b> A, the film F may be cooled by a normal temperature wind C.
[0019]
A peeling roller 15 is provided in the vicinity of the right roller 12, and the film F dried to a predetermined density is peeled off from the belt 13 by the peeling roller 15. The moisture content of the film F at the time of peeling from the belt 13 is preferably 15% by weight or less, and more preferably 2 to 10% by weight. The film F is wound around the winder 19 through the heat treatment machine 16, the humidity controller 17 and the inspection machine 18 shown in FIG. The heat treatment machine 16 blows hot air onto the film F to change the crystallinity of the film F and the like. The humidity controller 17 adjusts the humidity of the film F to about 5% on a wet basis, for example. The inspection machine 18 inspects physical defects, thickness, moisture content, and the like with visible light, infrared light, and beta rays, respectively.
[0020]
Below, the manufacturing method of a PVA film is demonstrated.
First, chips are introduced from the introduction port 1a of the first tank 1 in FIG. 1A, and the solvent is supplied from the supply port 1b. Moreover, a plasticizer may be supplied from the supply port 1b. At this time, the concentration of the PVA polymer is set to about 10 to 30% wb [weight% on wet base: (PVA + additive) × 100 / (PVA + additive + solvent)]. Next, the opening / closing lid 1d and the opening / closing valve 1f are closed. Thereafter, the mixture of the chip and the solvent is stirred by the stirring blade 1e while the first tank 1 is kept at about 140 ° C. by the first heating device 2, and the stock solution L is obtained. Here, since the first tank 1 is sealed, as the pressure rises due to evaporation of the solvent, the boiling point of the solvent increases and the temperature of the solvent rises sufficiently, so that the chip is easily dissolved. .
[0021]
The stock solution L in the first tank 1 is transferred from the nozzle 4 into the second tank 5. The stock solution L temporarily stored in the second tank 5 is defoamed by the vent 5c while being stirred by the stirring blade 5a, and then sent by a fixed amount by the screw pump 5b. The stock solution L is uniformly cooled to 100 ° C. by the heat exchanger 30 and sent to the gear pump 7.
[0022]
The stock solution L is pressure-fed from the gear pump 7 to the filter 8 to remove dust and the like, and is further sent to the die 10 after the temperature becomes uniform by the static mixer 9, and as shown in FIG. From the slit-shaped opening 10a. At this time, if the temperature of the stock solution L is not uniform in the width direction D of the belt 13, the outflow amount varies in the width direction D due to the difference in viscosity, so that the film thickness is not uniform. On the other hand, since the temperature is uniformed by the static mixer 9 of FIG. 1B as described above, the film F having a uniform thickness can be obtained.
[0023]
The stock solution that has flowed out onto the belt 13 is cast as the belt 13 travels in the direction of arrow A, and drying is promoted on the belt 13 by hot air H. Here, unlike the drum, since the belt 13 can be made long, the film F can be sufficiently dried on the belt 13, so that the film F can be easily peeled off from the belt 13. Therefore, as shown by the solid line in FIG. 4, the retardation is uniform and low. In addition, since the retardation is uniform in the width direction and a low film F is obtained, the stretchability of the film is improved. Further, since the belt type film forming machine 11 is not particularly limited in lengthening the belt 13, the drying time can be lengthened by taking the belt 13 longer. Therefore, the belt speed can be increased while the film F is sufficiently dried, and the production capacity of the line can be increased. The running speed of the belt 13 is appropriately selected within a range of about 5 to 50 m / min. The residence time on the belt 13 is appropriately selected within a range of about 1 to 10 minutes.
[0024]
Further, as in this embodiment, when a plurality of partition walls 14 are provided in the running direction of the belt 13 and the hot air H is applied to the belt 13, the temperature of the hot air H can be changed between the partition walls 14. . Therefore, the optimal temperature according to the dry state (drying stage) of the film F can be selected.
[0025]
In this invention, water is preferably used as the solvent for the PVA polymer. However, when using an explosion-proof film forming apparatus, the solvent includes dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, a diamine compound having 1 to 10 carbon atoms, a triamine compound having 1 to 10 carbon atoms, and the like. An organic solvent may be used, and dimethyl sulfoxide is preferable among these organic solvents. A mixture of these solvents may also be used.
[0026]
Examples of the plasticizer of the PVA polymer include polyhydric alcohol plasticizers such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol, and mixtures thereof. Among alcohol-based plasticizers, glycerin is preferable.
[0027]
Although there is no restriction | limiting in particular in the polymerization degree of the PVA polymer used in this invention, 1,000 or more are preferable, 1,000-20,000 are more preferable, 1,500-10,000 are still more preferable . The degree of saponification of the PVA polymer is not particularly limited, but is preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more.
[0028]
The PVA polymer of the present invention can be obtained by saponifying a polymer of a vinyl ester monomer. Vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valenate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl 2,2,4,4-tetramethylvalerate, vinyl benzoate. And vinyl pivalate and vinyl versatate. Among these, vinyl acetate, vinyl propionate, vinyl pivalate and vinyl versatate are preferably used alone or as a mixture.
[0029]
In addition, a monomer copolymerizable with the above vinyl ester monomer may be copolymerized. Examples of the copolymerizable monomer include olefins such as ethylene, propylene, 1-butene and isobutene; acrylic acid and Salts thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate Acrylic acid esters such as octadecyl acrylate; methacrylic acid and salts thereof, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, methacrylic acid T-butyl acid, methacrylic acid Methacrylic acid esters such as 2-ethylhexyl, dodecyl methacrylate, octadecyl methacrylate; acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid and salts thereof, acrylamide Acrylamide derivatives such as propyldimethylamine and salts thereof or quaternary salts thereof, N-methylolacrylamide and derivatives thereof; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamide Methacrylamide such as propyldimethylamine and salts thereof or quaternary salts thereof, N-methylol methacrylamide and derivatives thereof Conductors; vinyl ethers such as methyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts or esters thereof; itaconic acid and its salts or esters thereof; Vinylsilyl compounds such as methoxysilane; isopropenyl acetate and the like. The content of these copolymerizable monomers is preferably 10 mol% or less, and more preferably 5 mol% or less. Moreover, as a film thickness of the PVA polymer film obtained by this invention, 20-100 micrometers is preferable.
[0030]
Test example 1
100 parts by weight of PVA and 12 parts by weight of glycerin were added to a pressure-resistant dissolution tank (first tank) 1 in FIG. 1, and water corresponding to a water content of 60% wb was added, followed by heating, stirring and dissolution to obtain a stock solution.
Further, after stirring and defoaming in the second tank 5, a fixed amount was supplied to the die 10 by the gear pump 7, and a PVA polymer film having a thickness of 75 μm and a width of 1.2 m was manufactured by the belt type film forming machine 11. However, no heat treatment was performed.
The main production conditions are shown below.

As shown in Table 1, physical properties of the film F thus obtained were small in thickness unevenness, retardation average value, and retardation unevenness. This is because the use of the belt type film forming machine 11 makes it possible to increase the drying time and reduce the moisture at the time of peeling of the film.
[0031]
Test example 2
After forming the film F under the same conditions using the same pressure-resistant dissolution tank 1, the second tank 5 and the belt-type film forming machine 11 as in Test Example 1, the film F is further heat-treated by a heat treatment machine 16 to have a water-resistant thickness. A PVA film having a thickness of 75 μm and a width of 1.2 m was produced.
The main production conditions are shown below.

Table 1 shows the physical properties of the film thus obtained.
Although this film was subjected to heat treatment, it had little thickness unevenness, retardation average value, and retardation unevenness.
[0032]
Comparative Example 1
A dissolution stock solution was obtained using the same equipment and conditions as in Test Example 1.
The PVA film having a thickness of 75 μm and a width of 1.2 m was manufactured by a drum type film forming machine equipped with a cast roll 56 and a drying roll 57 shown in FIG.
The main production conditions are shown below.

The physical properties of the film obtained by this method are shown in Table 1.
As compared with Test Examples 1 and 2, the film of Comparative Example 1 has a large thickness unevenness, retardation absolute value, and retardation unevenness. When the rotation speed of the cast roll 56 was increased to increase productivity, the film moisture at the time of peeling increased, and the thickness unevenness, retardation average value, and retardation unevenness further increased.
[0033]

The thickness unevenness was measured by continuously measuring the thickness in the vertical and horizontal directions, and indicated by the difference between the maximum value and the minimum value (R (μ)).
The retardation was measured at 20 points at a pitch of 5 cm in the width direction and indicated by an average value (nm), and the retardation unevenness was indicated by a difference between the maximum value and the minimum value (R (nm)).
[0034]
【The invention's effect】
As described above, according to the present invention, the PVA polymer and the solvent are dissolved while being heated and pressurized in the sealed pressure-resistant first tank, and further temporarily stored in the second tank. Since defoaming is carried out while stirring, a stock solution that is homogeneous and has few undissolved components and bubbles can be produced. Further, since the stock solution is supplied to the die by the screw pump, the supply amount of the stock solution is unlikely to vary. In particular, since the film is formed using a belt type film forming machine, the stock solution can be sufficiently dried on a long austenitic stainless steel belt. In this way, a uniform amount of undissolved content and a small amount of undiluted stock solution can be supplied in a certain amount and sufficiently dried, so that the retardation of the film, that is, the quality is improved.
[0035]
On the other hand, since the belt can be lengthened without much restrictions on manufacturing and transportation, the belt speed can be increased, so that productivity is also improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a production apparatus from production of a stock solution to film formation according to the present invention.
FIG. 2 is a schematic configuration diagram showing an example of a heat treatment, humidity conditioning and winding device after film formation according to the present invention.
FIG. 3 is a front view of a die.
FIG. 4 is a characteristic diagram showing a change in retardation in the width direction of the film.
FIG. 5 is a schematic configuration diagram showing an example of a conventional drum-type film forming machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st tank, 2 ... (1st) heating apparatus, 5 ... 2nd tank, 5b ... Screw pump, 5c ... Vent, 7 ... Gear pump, 10 ... Die, 11 ... Belt type film forming machine, 12 ... Roller , 13 ... belt, 30 ... heat exchanger, F ... film, L ... undiluted solution.

Claims (2)

A step of dissolving the polyvinyl alcohol-based polymer with a solvent by stirring the heated first tank with pressure resistance while heating, and increasing the pressure in the first tank by evaporation of the solvent to produce a stock solution;
Supplying the stock solution into the second tank, temporarily storing the supplied stock solution in the second tank, and defoaming while stirring;
Sending the stock solution in the second tank to the die in a certain amount;
Casting the stock solution from the die on an austenitic stainless steel belt that runs across a pair of rollers; and
A method for producing a polyvinyl alcohol polymer film comprising a drying step of drying the stock solution on the belt. A sealed first pressure-resistant tank that dissolves the polyvinyl alcohol polymer in a solvent and stirs to produce a stock solution;
A heating device that heats the inside of the first tank and pressurizes the inside of the first tank by evaporation of the solvent;
A second tank for temporarily degassing the stock solution supplied from the first tank and degassing it with a vent while stirring;
A screw pump for feeding the stock solution in the second tank by a certain amount;
A heat exchanger for adjusting the temperature of the stock solution supplied from the screw pump;
A gear pump that pressurizes the stock solution;
A die that uniformly flows out the stock solution supplied from the gear pump in the width direction of the austenitic stainless steel belt described later ;
A polyvinyl alcohol polymer having an austenitic stainless steel belt running between a pair of rollers, and a belt type film forming machine for casting and drying the stock solution flowing out from the die. Film production equipment.

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