JP2001113544A - Method of manufacturing cellulose ester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve speed-up by preventing an air accompanying phenomenon by the application of static electricity in producing a cellulose ester film by a solution film forming method and to prevent the generation of a fire or explosion due to static electricity applying energy even in a solvent gas atmosphere. SOLUTION: Respective dopes are sent into a casting die 23 through first, second and third dope introducing channels 60, 70, 80 and cast on a casting band 21 as a cast ribbon 24 in a laminated state. A large quantity of nitrogen gas is sent into a casting/drying casing 10 from a nitrogen gas supply pipe 51 to reduce the concentration of oxygen gas to 10 vol.% or less. Since an oxygen concentration value is sent to a static electricity applying control device 42 by an oxygen densitometer 43, the static electricity applying control device 42 starts a static electricity applying electrode 41 to apply static electricity. Nitrogen gas is supplied so as not to raise the concentration of oxygen while the concentration of oxygen in the casting/drying casing 10 is measured by the oxygen densitometer 43 to continue the casting due to the application of static electricity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cellulose ester film by which a cellulose ester film can be produced at a high speed by a solution casting method.

[0002]

2. Description of the Related Art Cellulose ester (including cellulose acetate, cellulose acetate butyrate and cellulose acetate propionate) films have good transparency, high mechanical strength, and dimensional fluctuations due to changes in humidity and heat. Because of its small size (good dimensional stability), it is used as a support for optical materials such as photographic light-sensitive materials and polarizing plate protective films. For example, cellulose acetate films, especially cellulose triacetate (triacetyl cellulose, TAC) films Widely used. Such a cellulose ester film is produced by a solution casting method. In this solution casting method, a dope in which a polymer is dissolved in an organic solvent is cast as a casting ribbon from a casting die onto a casting support. To form a film.

[0003] When a cellulose ester film is formed by such a solution casting method, it is required to form the film at a high speed. However, when the film is formed at a high speed, an air entrainment phenomenon occurs and defects occur on the film surface. Was something. Therefore, conventionally, in order to prevent the air entrainment phenomenon, the viscosity and concentration of the dope have been reduced or the back suction method has been used.

On the other hand, in the field of melt film formation, as a measure for entrainment of air, a method of increasing the adhesion by applying static electricity between an extruded film and a support and removing the entrained air film is used. JP-A-7-52232 (method for producing ultra-thin polyolefin film and sheet), JP-A-8-111347 (polyester film for a capacitor), JP-A-10-315306 (an electrostatic application casting device), JP-A-10-315306 10-3238
No. 81 (a method for molding a thermoplastic resin sheet) and the like.

[0005]

However, the above-mentioned methods for making the dope low in viscosity and low in concentration do not increase the drying load after casting a film on a casting support, or cause unevenness in wind due to drying air. Drying unevenness was liable to occur, leading to an increase in energy loss and a decrease in film quality. Also,
In the backsuction method, it is necessary to increase the degree of decompression on the upstream side of the casting ribbon as the speed becomes higher, which causes wind unevenness due to inflow wind and an unstable phenomenon of the end portion of the casting ribbon, which leads to deterioration of the quality of the film formed. Was something.

The above-described method of increasing the adhesion by applying static electricity can cope with high speed without generating wind unevenness or drying unevenness. Explosion could occur. That is, in the solution casting method,
Since a dope consisting of a polymer solution dissolved in an organic solvent is used, the solvent evaporates in the casting step and the subsequent drying step. Therefore, the casting step and the drying step are performed in a substantially closed casing so that the evaporated organic solvent gas does not spread to the surroundings. A fire or explosion may occur due to the application.

[0007] The present invention solves the above problems, and when producing a cellulose ester film by a solution casting method, it is possible to prevent the air entrainment phenomenon by applying static electricity, to increase the speed, and even in a solvent gas atmosphere. It is an object of the present invention to provide a method for producing a cellulose ester film capable of preventing occurrence of fire, explosion, and the like due to energy applied to static electricity.

[0008]

According to the method for producing a cellulose ester film of the present invention, there is provided a method for producing a film by casting a casting ribbon from a casting die onto a casting support. The oxygen concentration in the inside is 10vol%
And applying static electricity between the casting ribbon and the casting support.

In the above-mentioned method for producing a cellulose ester film, it is preferable that a sequence condition is that at least an oxygen concentration in the casting step is less than 10 vol% as a condition for starting electrostatic application. It is possible to maintain the oxygen concentration at less than 10 vol% by supplying at least an inert gas such as the above or a mixed gas of an inert gas and air and having an oxygen concentration of less than 10 vol% into the casting step. preferable.

Further, it is preferable that a metal compound is contained in the dope constituting the casting ribbon. Further, the casting ribbon comprises at least two or more layers, and a layer which is in close contact with the casting support is provided. It is preferable to include a metal compound only in the constituent dope.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a cellulose ester film of the present invention, at least the oxygen concentration in the casting step is less than 10 vol%, preferably 8 v
ol%. When the drying step following the casting step is arranged in the same casing as the casting step,
Even in the drying step, the oxygen concentration will be less than 10 vol%, but if there is no air permeability between the casting step and the drying step, the oxygen concentration is 10 vol% only in the casting step.
What is necessary is just to make it less than.

By setting the oxygen concentration to less than 10 vol% as described above, it is possible to prevent the explosion of the organic solvent gas, etc., which is particularly effective when the concentration of the organic solvent gas in the casting process is high. is there. That is, it is particularly effective when the concentration of the organic solvent gas is 25% or more of the lower explosive limit.

As the organic solvent, chlorides of lower aliphatic hydrocarbons and lower aliphatic alcohols are generally used. Examples of chlorides of lower aliphatic hydrocarbons include methylene chloride. Examples of lower aliphatic alcohols include methanol, ethanol, n-propyl alcohol, isopropyl alcohol and n-butanol. Examples of other solvents include acetone that is substantially free of halogenated hydrocarbons, and examples of ketones having 4 to 12 carbon atoms include methyl ethyl ketone,
It contains diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone, and has 3 carbon atoms.
Examples of the ester from to 12 are ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate,
Propyl acetate, butyl acetate, pentyl acetate, 2-ethoxy-ethyl acetate and the like. Examples of the alcohol having 1 to 6 carbon atoms include methanol, ethanol, propanol, iso-propanol, 1-butanol, t-butanol, 2-methyl-2-butanol,
2-methoxyethanol and 2-butoxyethanol and the like, and examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-
Examples include dioxolane, tetrahydrofuran, anisole, and phenetole, and examples of cyclic hydrocarbons having 5 to 8 carbon atoms include cyclopentane, cyclohexane, cycloheptane, cyclooctane, and the like.

Among the above solvents, methylene chloride is particularly preferred. Other solvents may be mixed with methylene chloride and used. However, the mixing ratio of methylene chloride is preferably 70% by weight or more. Particularly preferred mixing ratios are 75 to 93% by weight of methylene chloride and 7 to 25% by weight of another solvent. The solvent is removed in forming the cellulose ester film. The residual amount of solvent is generally less than 5% by weight. The residual amount is 1
It is preferably less than 0.5% by weight, more preferably less than 0.5% by weight.

In order to reduce the oxygen concentration in the casting process to less than 10 vol%, an inert gas such as nitrogen gas or carbon dioxide, or a mixture of an inert gas and air and an oxygen concentration of 1 vol.
It can be performed by supplying a mixed gas of less than 0 vol%. It is preferable that the oxygen concentration in the casting step is measured by an oxygen concentration meter, and the supply amount of an inert gas or the like is controlled according to the measured value.

In the present invention, the adhesion between the casting ribbon and the casting support is enhanced by applying static electricity between the casting ribbon and the casting support. As the application electrode, an electrode used for forming a molten resin film can be used. Further, it is preferable that the sequence condition is that at least the oxygen concentration in the casting step is less than 10 vol% as the electrostatic application starting condition.

It is preferable that a metal compound is contained in the dope constituting the casting ribbon. By including the metal compound, the adhesion to the casting support can be increased. When the casting ribbon is composed of at least two or more layers by co-casting, all the layers may contain a metal compound. It is preferable that only the metal compound be contained. By including the metal compound only in the dope forming the layer that is in close contact with the casting support, the adhesion to the casting support can be increased without reducing the transparency of the entire film.

As the metal compound, for example, tin oxide is used. The content of the metal compound is determined in consideration of the improvement in adhesion by applying electrostatic force, transparency, and the like.
To 0.1% by weight, preferably 0.03 to 0.08% by weight
Is more preferred. When the amount is less than 0.01% by weight, the effect of adhesion is not so much due to the application of static electricity.
If it exceeds, the transparency becomes poor.

An embodiment of a production apparatus for carrying out the method for producing a cellulose ester film according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an apparatus for producing a cellulose ester film. In FIG. 1, reference numeral 10 denotes a casting
This casting and drying casing for the drying process
The drying casing 10 is configured in a substantially airtight state, and is divided into a casting step section 20 for a casting step and a drying step section 30 for a drying step. In the casting section 20, a casting band 21 as a casting support is wound around a roller 22 and can run. A casting die 23 is provided above an end portion of the casting band 21, and a casting ribbon 24 is cast from the casting die 23 to the casting band 21, thereby forming the casting band 21.
A cellulose ester film 25 is formed thereon. The drying section 30 is provided with a drying unit (not shown) for drying the cellulose ester film 25 peeled off from the belt 21.

On the downstream side of the casting die 23 and in the vicinity of the casting ribbon 24, an electrostatic application electrode 41 is provided. Casting cellulose ester film 25 to casting band 2
1. This electrostatic application electrode 4
1 is connected to an electrostatic application control device 42 provided outside the casting / drying casing 10. Further, an oxygen concentration meter 43 for measuring the oxygen concentration in the casting / drying casing 10 is provided, and the measured value of the oxygen concentration measured by the oxygen concentration meter 43 is sent to the electrostatic application control device 42. It has become. Then, the electrostatic application controller 42 determines that the oxygen concentration value sent from the oximeter 43 is 10 vol.
%, The application of static electricity is started, and when the oxygen concentration value exceeds 10 vol%, the application of static electricity is stopped.

In the casting / drying casing 10,
The casting section 20 is provided with a nitrogen gas supply pipe 51 for supplying nitrogen gas, and the drying section 30 is provided with an exhaust pipe 52 for exhausting gas in the casting and drying casing 10. The exhaust pipe 52 exhausts approximately the same amount of nitrogen gas as the nitrogen gas supplied from the nitrogen gas supply pipe 51.

To the casting die 23, three dope introduction paths are connected so that the cellulose ester film 25 is composed of three layers. That is, a first dope introduction path 60 including a first storage tank 61 for storing a dope for forming a main layer located in the middle during casting, a first liquid feed pump 62 and a first filter 63, A second storage tank 71 for storing a dope for forming a sub-layer located at the top (a layer located on the opposite side to the belt 21), a second liquid pump 72, and a second filter 73. A third storage tank 81 for storing a dope for forming a dope introduction path 70, and a sub-layer (a layer that is in close contact with the casting band 21) positioned at the lowermost part during casting, a third liquid sending pump 82, and a third filter A third dope introduction path 80 composed of 83 is connected to the casting die 23.

In addition, on the downstream side of the drying section 30,
First trimming section 90, coating section 1 for applying emulsion and the like
00, post-drying process section 11 for drying the coated emulsion and the like
0, a second trimming step 120 and a winding step 130 for cutting the product to the width of the product are provided.

In order to produce a cellulose ester film with the above-described apparatus for producing a cellulose ester film, each dope is cast by a first dope introduction path 60, a second dope introduction path 70 and a third dope introduction path 80. The casting dope 23 is cast on a casting band 21 as a casting ribbon 24 in a state where these dopes are stacked. At this time, the casting / drying casing 1 is supplied from the nitrogen gas supply pipe 51.
A large amount of nitrogen gas is sent into the chamber and the oxygen gas
vol%, for example, about 8 vol%. Then, the oxygen concentration value is sent from the oxygen concentration meter 43 to the electrostatic application control device 42, so that the electrostatic application control device 42 activates the electrostatic application and applies the static electricity by the electrostatic application electrode 41. Therefore, the casting ribbon 24 can be firmly adhered to the casting band 21 and the influence of the accompanying air can be prevented.

Then, while continuously measuring the oxygen concentration in the casting / drying casing 10 by the oxygen concentration meter 43, while supplying nitrogen gas from the nitrogen gas supply pipe 51 so as not to increase the oxygen concentration, Continue casting by applying electricity. If the oxygen concentration exceeds 10 vol% for some reason, the electrostatic application control device 42 stops the application of static electricity, and waits until the oxygen concentration becomes less than 10 vol%, and then performs the electrostatic application again.

In order to produce the above-mentioned cellulose ester film, a co-casting method, a sequential casting method, a coating method and the like can be used, but it is preferable to produce the film by the co-casting method. The co-casting method has a simple process, has high productivity, and can easily obtain the flatness of the film.

FIG. 2 shows an internal merging type co-casting die. FIG. 2 is a cross-sectional view of the internal merging type co-casting die. The high viscosity polymer resin solution 203d to be the main layer is sent to the main flow pocket portion 224c through the main flow tube 224a, and further sent to the slit 221. Low viscosity polymer resin solution 2 to be a sublayer
06d is sent to the outer flow pocket portions 225c and 226c through the outer flow tubes 225a and 226a, and further sent to the slits 222 and 223, respectively. Slit 221
The layer of the high-viscosity polymer resin solution 203d sent through the slit and the layer of the low-viscosity polymer resin solution 206d sent through the slits 222 and 223 join at the die slit 227 and from there onto the support. It is simultaneously extruded and cast. Reference numerals 224b, 225b, and 236b denote boundaries between the respective tubes and the pockets.

FIG. 3 shows an external confluence type co-casting die. FIG. 3 is a cross-sectional view of the external confluence type co-casting die. The high-viscosity polymer resin solution 203d serving as the main layer is sent to the main flow pocket portion 233b through the main flow pipe 233a of the feed block attached to the top of the die, and the low-viscosity polymer resin solution 206d serving as the sub-layer is transferred to the top of the die. Are fed to the outer flow pocket portions 235b and 236b through the outer flow tubes 235a and 236a of the feed block attached to the feed block. A layer of high viscosity polymer resin solution 203d sent through mainstream pocket 233b and outer layer pockets 235b, 236b
The layers of the low-viscosity polymer resin solution 206d sent through are merged at the die feed pipe 234a, extruded onto the support from the die slit 231 through the die feed pocket 234c, and cast. . 234b is a boundary line between the liquid supply pipe and the pocket portion.

FIG. 4 shows the layer structure of the film obtained by the co-casting method. High viscosity polymer resin solution layer (main layer) 24
The width of 1 is generally in the range of 100 to 9000 mm.
The thickness of the low-viscosity polymer resin solution layer (sub-layer) 242 covering the upper and lower surfaces of the high-viscosity polymer resin solution layer at the time of extrusion is as follows:
In any case, the thickness is preferably 1/10 or less of the high viscosity polymer resin solution layer 241. Further, the thickness (undried state) of the extruded high-viscosity polymer resin solution layer 241 is 100
２０００2000 μm is common, and 300-100
A range of 0 μm is preferred. The thickness (undried state) of the low-viscosity polymer resin solution layer 242 is generally in the range of 1 to 60 μm, and preferably in the range of 2 to 20 μm.

The width of the high viscosity polymer resin solution layer 241 after drying is generally in the range of 100 to 9000 mm. Further, the thickness of the low-viscosity polymer resin solution layer 242 covering the upper and lower surfaces of the high-viscosity polymer resin solution layer 241 after drying is 1/10 or less of that of the high-viscosity polymer resin solution layer 241. Is preferred. Further, the thickness of the high-viscosity polymer resin solution layer 241 after drying is generally in the range of 20 to 400 μm, and preferably in the range of 60 to 400 μm. Further, the thickness of the low-viscosity polymer resin solution layer 242 after drying is
The range of 0.2 to 20 μm is common, and 0.5 to 10 μm.
The range of μm is preferred.

As shown in FIG. 4, the polymer resin solution layer extruded from the slit of the die to the support is composed of a high viscosity polymer resin solution layer 241 and a low viscosity polymer resin solution layer 24.
No. 2 constitutes a laminate without mixing. Therefore, the surface of the high-viscosity polymer resin solution layer 241 is a low-viscosity layer, and does not generate sharkskin on the surface even when extruded at a shear rate larger than the die slit.
A film having good surface quality such as smoothness can be obtained.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing apparatus shown in FIG.
(Using a reduced pressure chamber) to produce a cellulose triacetate film composed of a main layer and upper and lower sub-layers. In the embodiment, the oxygen concentration in the casting / drying casing is maintained at 8 vol%, and the supply amount of nitrogen gas is 1 vol.
0 Nm ³ / min. The average gas concentration of the organic solvent was 6 vol% (50% of the lower explosive limit). Table 1 shows the voltage of the electrostatic application electrode and the back suction pressure by the reduced pressure chamber (only in Comparative Example 2).

Example 1 The dope used was as follows. <Main layer> Cellulose triacetate 20% by weight Triphenyl phosphate 1.6% by weight Biphenyl diphenyl phosphate 0.8% by weight Colloidal silica 0.01% by weight Dichloromethane 62% by weight Alcohol 15.59% by weight <Sublayer> Cellulose triacetate 20 Weight% triphenyl phosphate 1.6 weight% biphenyl diphenyl phosphate 0.8 weight% colloidal silica 0.01 weight% dichloromethane 62 weight% alcohol 15.59 weight%

Example 2 The dope formulation used was such that tin oxide was added to the main layer and the sub-layer (main layer: 0.05% by weight,
Sublayer: 0.05% by weight) except that it was the same as in Example 1.

Example 3 The dope formulation used was such that tin oxide was added only to the sub-layer in close contact with the casting band (0.03%).
5% by weight), except that it was 5% by weight.

Comparative Example 1 The dope used was the same as in Example 1.

Comparative Example 2 The dope used was the same as in Example 1.

The air entrainment generation speed, surface quality immediately before air entrainment occurred, and transparency in the above Examples and Comparative Examples were examined. Table 1 shows the results.

[0040]

[Table 1]

The evaluation method is as follows. <Air entrainment generation speed> The speed at which a film surface defect occurs due to air entrainment is measured by an online transmission surface inspection device.

<Surface Quality Immediately before Air Entrainment Occurs> Sensory evaluation of the sampled sample with transmitted light and reflected light was conducted visually.
The evaluation in the table is as follows. ：: No influence by air entrainment. Δ: The effect of air entrainment was recognized, but the quality was acceptable. X: Quality failure due to air entrainment.

<Transparency> A transparency meter (eg, KOT)
The transmittance of visible light was measured using AKI Seisakusho). The evaluation in the table is as follows. ：: Product performance level. Δ: below product performance level, but acceptable in quality.

[0044]

According to the present invention, it is possible to apply static electricity between the casting ribbon and the casting support without generating a fire or explosion even in a solvent atmosphere. It is possible to enhance the adhesion to the casting support and eliminate the entrained air film. As a result, a cellulose ester film can be manufactured at a high speed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a manufacturing apparatus for performing a method for manufacturing a cellulose ester film according to the present invention.

FIG. 2 is a side sectional view of an example of an internal merging type co-casting die.

FIG. 3 is a side sectional view of an example of an external confluence type co-casting die.

FIG. 4 is a front sectional view showing a layer structure of a film extruded from a slit of a co-casting die to a support.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Casting and drying casing 20 ... Casting process part 21 ... Casting band 23 ... Casting die 24 ... Casting ribbon 25 ... Cellulose ester film 30 ... Drying process part 41 ... Electrostatic application electrode 42 ... Electrostatic application control Apparatus 43 ... oxygen concentration meter 51 ... nitrogen gas supply pipe 52 ... exhaust pipe 60 ... first dope introduction path 70 ... second dope introduction path 80 ... third dope introduction path

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA09 AH12 BB02 BC01 4F205 AA01 AB16 AC05 AD32 AG01 AM30 AP20 AR20 GA07 GC07 GE25 GF01 GF06 GF24 GN24 GN25 GN25 GN26

Claims (5)

[Claims] In a method for producing a film by casting a casting ribbon from a casting die onto a casting support, the oxygen concentration in at least the casting step is set to less than 10 vol%, and the casting ribbon is mixed with the casting ribbon. A method for producing a cellulose ester film, comprising applying electrostatic force to a rolled support. 2. The method for producing a cellulose acetate film according to claim 1, wherein a sequence condition is that at least an oxygen concentration in the casting step is less than 10 vol% as a condition for starting electrostatic application. 3. An oxygen gas containing at least an inert gas such as a nitrogen gas or a carbon dioxide gas or a mixture of an inert gas and air having an oxygen concentration of less than 10 vol% is supplied to at least the casting step. The method for producing a cellulose ester film according to claim 1, wherein the concentration is maintained at less than 10 vol%. 4. The method for producing a cellulose ester film according to claim 1, wherein a metal compound is contained in the dope constituting the casting ribbon. 5. The casting ribbon according to claim 4, wherein the casting ribbon comprises at least two or more layers by co-casting, and the metal compound is contained only in the dope forming the layer in close contact with the casting support.
3. The method for producing a cellulose ester film according to item 1.