JP2000095876A - Production of cellulose ester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cellulose ester film capable of being rapidly allowed to gel, having excellent physical and optical properties, and useful as a photographic material, etc., by processing a cellulose ester solution by a solvent cast method. SOLUTION: This method for producing a cellulose ester film comprises dissolving (A) a cellulose fatty acid ester mixture obtained by esterifying the hydroxy groups of cellulose with acetyl groups and >=3C acyl groups in (B) an organic solvent selected from the group consisting of 3-12C esters, 3-12C ketones and 3-12C ethers, mixing the prepared cellulose ester solution with (C) an alcohol having a boiling point of 30-170 deg.C or (D) a hydrocarbon having a boiling point of 30-170 deg.C, casting the prepared mixture on a support and subsequently evaporating the solvents. The component C or D is preferably used in an amount of 5-60 pts.wt. per 40-95 pts.wt. of the component B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a cellulose ester film by a solvent casting method.

[0002]

2. Description of the Related Art Cellulose acetate films are used for various photographic materials and optical materials because of their toughness and flame retardancy. Cellulose acetate film is a typical support for photographic light-sensitive materials. In addition, cellulose acetate films are used in liquid crystal display devices, which have been expanding in market in recent years because of their optical isotropy. As a specific application in the liquid crystal display device, a protective film of a polarizing plate and a color filter are typical. The cellulose acetate film is generally produced by a solvent casting method or a melt casting method. In the solvent casting method, a solution (dope) in which cellulose acetate is dissolved in a solvent is cast on a support, and the solvent is evaporated to form a film. In the melt casting method, cellulose acetate melted by heating is cast on a support and cooled to form a film. The solvent cast method can produce a film having higher flatness than the melt cast method. For this reason, practically, the solvent cast method is generally employed.

[0003] The solvent casting method is described in many documents. In the recent solvent casting method,
An object is to reduce the time required from casting the dope on the support to peeling off the formed film on the support, thereby improving the productivity of the film forming process. For example, Japanese Patent Publication No. 17844/1993 proposes to reduce the time from casting to stripping by casting a high concentration dope on a cooling drum. The solvent used in the solvent casting method requires various conditions in addition to simply dissolving cellulose acetate. That is, in order to economically and efficiently produce a film having excellent planarity and uniform thickness, it is necessary to prepare a solution (dope) having an appropriate viscosity and a polymer concentration and having excellent storage stability. The dope is also required to be easily gelled and easily peeled from the support. To prepare such a dope, the choice of solvent type is very important. For the solvent,
It is also required that evaporation is easy and the amount of residue in the film is small.

Various organic solvents have been proposed as a solvent for cellulose acetate, but the solvent satisfying all of the above requirements has been practically limited to methylene chloride. In other words, solvents other than methylene chloride have hardly been put to practical use. However, in recent years, the use of halogenated hydrocarbons such as methylene chloride has been significantly restricted from the viewpoint of global environmental protection. In addition, since methylene chloride has a low boiling point (41 ° C.), it is easy to volatilize in the production process. For this reason, it is also a problem in the working environment. In order to prevent these problems, the manufacturing process is closed, but there is a technical limit even if it is hermetically closed. On the other hand, acetone (boiling point: 56 ° C.) and methyl acetate (boiling point: 57 ° C.), which are general-purpose organic solvents, have an appropriate boiling point and the drying load is not so large. Also, there are fewer problems with respect to the human body and the global environment as compared with chlorine-based organic solvents. However, acetone and methyl acetate have low solubility in cellulose acetate. In particular, the degree of substitution is 2.80 (degree of acetylation:
(60.1%) or more of cellulose triacetate swells only in acetone or methyl acetate, but hardly dissolves.

A method has been proposed in which a mixture of cellulose acetate and an organic solvent is cooled and further heated to dissolve the cellulose acetate in an organic solvent to prepare a cellulose acetate solution (JP-A-9-95).
538, 9-95544, and 9-95557). According to a method having a cooling step and a heating step (hereinafter, referred to as a cooling dissolution method), a solution is prepared even with a combination of cellulose acetate and an organic solvent, which cannot be dissolved by a conventional method. be able to. The cooling dissolution method is particularly effective when producing a film from triacetyl cellulose having low solubility (average degree of acetylation is 58% or more). As the organic solvent used in the cooling dissolution method, esters having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and ethers having 3 to 12 carbon atoms have been proposed in the above publications. There is also a description that an alcohol having 1 to 6 carbon atoms may be used in addition to ether, ketone or ester.

[0006]

According to the study of the present inventors, in the production of a cellulose acetate film, when a poor solvent such as alcohol is used in combination with a good solvent such as methylene chloride, the prepared cellulose acetate solution can be obtained. It turned out to gel rapidly. As described above, in the production of a cellulose acetate film by the solvent casting method, it is important to shorten the time from the casting of the dope (solution) to the peeling. When a poor solvent such as alcohol is used in combination with a good solvent,
The time required for producing a cellulose acetate film can be significantly reduced.

The inventor of the present invention has examined the application of the method using a poor solvent in combination with a good solvent to the above-mentioned cooling dissolution method, and found that the use of the poor solvent causes a problem in the cooling dissolution method. According to the study of the present inventors, when a poor solvent is used, it is necessary to set a lower cooling temperature in the cooling dissolution method or lower the concentration of the solution to be prepared. As described above, the use of the cooling dissolution method significantly improves the solubility of cellulose acetate in an organic solvent. However, when a poor solvent is used in combination with another organic solvent, the effect of this cooling dissolution method is impaired, and it becomes difficult to prepare a high-concentration solution unless the cooling temperature is set lower. To set the cooling temperature lower, it is necessary to use a large and powerful cooling device. In order to maintain a low cooling temperature, a large amount of energy needs to be consumed.
On the other hand, in order to produce a cellulose acetate film, it is necessary to use a cellulose acetate solution having a certain high concentration as a dope. An object of the present invention is to use a cellulose ester solution capable of rapid gelation,
It is to produce a cellulose ester film having excellent physical properties and optical properties by a solvent casting method.

[0008]

Means for Solving the Problems The object of the present invention has been attained by the following method [1] to [12] for producing a cellulose ester film. [1] A method for producing a cellulose ester film, in which the following steps (1) to (4) are performed in the following order. (1) A mixed fatty acid ester of cellulose obtained by substituting a hydroxyl group of cellulose with an acetyl group and an acyl group having 3 or more carbon atoms is converted into an ester having 3 to 12 carbon atoms and 3 to 12 carbon atoms. Dissolving in an organic solvent selected from the group consisting of ketones and ethers having 3 to 12 carbon atoms to prepare a cellulose ester solution; (2) adding an alcohol having a boiling point of 30 to 170 ° C. to the cellulose ester solution; Mixing a hydrocarbon having a boiling point of 30 to 170 ° C., (3) casting the resulting mixture on a support, and (4) evaporating the solvent to form a film.

[2] 5 to 60 parts by weight of alcohol or hydrocarbon is used in step (2) with respect to 40 to 95 parts by weight of an organic solvent selected from the group consisting of ester, ketone and ether used in step (1). The production method according to [1]. [3] In the step (1), the organic solvent selected from the group consisting of esters, ketones and ethers has one carbon atom.
And the mixed fatty acid ester of cellulose is dissolved in the resulting mixture [1].
The production method described in 1. [4] Organic solvents 40 to 9 selected from the group consisting of esters, ketones and ethers used in step (1)
In step (2), 2 to 60 parts by weight of alcohol or hydrocarbon and in step (1), 2 to 60 parts by weight of linear monohydric alcohol having 1 to 5 carbon atoms are added to 5 parts by weight.
The production method according to [3], wherein the amount is from 60 to 60 parts by weight. [5] The production method according to [1], wherein in the step (2), a linear monohydric alcohol having 1 to 5 carbon atoms is mixed with the cellulose ester solution in addition to the alcohol or the hydrocarbon. [6] Organic solvents 40 to 9 selected from the group consisting of esters, ketones and ethers used in step (1)
In step (2), 2 to 60 parts by weight of alcohol or hydrocarbon and in step (2), 2 to 60 parts by weight of linear monohydric alcohol having 1 to 5 carbon atoms with respect to 5 parts by weight.
The production method according to [5], wherein the amount is from 60 to 60 parts by weight.

[7] The following steps (1a) to (1c) and (3) to (4) are carried out in the following order, and between steps (1b) and (3), (2) A method for producing a cellulose ester film, comprising a step of mixing an alcohol having a boiling point of 30 to 170 ° C. or a hydrocarbon having a boiling point of 30 to 170 ° C. with a mixture or solution of the cellulose ester. (1a) A mixed fatty acid ester of cellulose obtained by substituting a hydroxyl group of cellulose with an acetyl group and an acyl group having 3 or more carbon atoms is converted into an ester having 3 to 12 carbon atoms and an ester having 3 to 12 carbon atoms. Mixing with an organic solvent selected from the group consisting of ketones and ethers having 3 to 12 carbon atoms, thereby swelling the lower fatty acid ester of cellulose in the organic solvent; (1b) swelling the swelled mixture from -100 to 100; Cooling to −10 ° C., (1
c) heating the cooled mixture to 0 to 200 ° C. to prepare a cellulose ester solution in which the lower fatty acid ester of cellulose is dissolved in an organic solvent; (3) flowing the obtained solution onto a support. Extending and (4) evaporating the solvent to form a film.

[8] In step (2), 5 to 60 parts by weight of alcohol or hydrocarbon is used with respect to 40 to 95 parts by weight of an organic solvent selected from the group consisting of esters, ketones and ethers used in step (1a). The production method according to [7]. [9] In the step (1a), a linear monohydric alcohol having 1 to 5 carbon atoms is mixed with an organic solvent selected from the group consisting of esters, ketones and ethers, and the resulting mixture is mixed with a mixed fatty acid of cellulose. The production method according to [7], wherein an ester is mixed. [10] With respect to 40 to 95 parts by weight of an organic solvent selected from the group consisting of esters, ketones and ethers used in step (1a), 2 to 60 parts by weight of alcohol or hydrocarbon in step (2); 1
The production method according to [9], wherein 2) to 60 parts by weight of a linear monohydric alcohol having 1 to 5 carbon atoms in a) is used. [11] The production method according to [7], wherein in the step (2), a linear monohydric alcohol having 1 to 5 carbon atoms is mixed with the mixture or solution of the cellulose ester in addition to the alcohol or the hydrocarbon. . [12] With respect to 40 to 95 parts by weight of an organic solvent selected from the group consisting of ester, ketone and ether used in step (1a), 2 to 60 parts by weight of alcohol or hydrocarbon in step (2); 2)
The method according to [11], wherein a linear monohydric alcohol having 1 to 5 carbon atoms is used in an amount of 2 to 60 parts by weight.

[0012]

According to the cooling dissolution method, the solubility of the cellulose ester in an organic solvent is remarkably improved. However, when a poor solvent is used, a problem in solubility occurs even in the cooling dissolution method. Therefore, the present inventors have studied means for improving the solubility different from the cooling dissolution method. As a result of the study, it was found that the problem could be solved by combining the two types of improvement means. The first measure is to improve the cellulose ester itself. Use of a mixed fatty acid ester of cellulose obtained by replacing the cellulose acetate with an acetyl group and an acyl group having 3 or more carbon atoms in place of cellulose acetate significantly improves the solubility.

[0013] The second means relates to the use period of the poor solvent. According to the study of the present inventors, a poor solvent (having a boiling point of 30 to 1)
The alcohol at 70 ° C. or the hydrocarbon having a boiling point of 30 to 170 ° C.) may be added to the solution or the mixture after the step of preparing the solution (the step of cooling the mixture in the cooling dissolution method) is completed, It was found that an effect (rapid gelation of the prepared solution) was obtained. If the poor solvent is added to the solution or the mixture after the step of preparing the solution (or the step of cooling the mixture), the solubility of the cellulose ester in the organic solvent does not decrease. As described above, in the method of the present invention, a high-concentration cellulose ester solution can be prepared without using a cooling dissolution method, even though a poor solvent is used. Further, even when the cooling melting method is employed, the cooling temperature can be set relatively high. A cellulose ester solution having a high concentration was obtained, and as a result of using a poor solvent therein, it was possible to produce a cellulose ester film having excellent physical properties and optical properties in a short time.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Mixed fatty acid ester of cellulose] In the present invention, a mixed fatty acid ester of cellulose obtained by replacing a hydroxyl group of cellulose with an acetyl group and an acyl group having 3 or more carbon atoms is used as the cellulose ester. Is used. The substitution degree (DSace) of the acetyl group in the mixed fatty acid ester of cellulose and the number of carbon atoms are 3
The degree of substitution (DSacy) of the acyl group described above preferably satisfies the following formulas (I) to (III). (I) 2.0 <DSace ≦ 2.9 (II) 0.1 <DSacy ≦ 0.9 (III) 2.5 <DSace + DSacy ≦ 3.0 The above formula (I) is within the range of the following formula (Ia). Is more preferable. (Ia) 2.1 <DSace ≦ 2.8 The above formula (II) is more preferably in the range of the following formula (IIa). (IIa) 0.15 <DSacy <0.8 The substitution degree (DSace) of the acetyl group and the substitution degree (DSacy) of the acyl group having 3 or more carbon atoms are represented by the following formula (I)
More preferably, V) is satisfied. (IV) 5 × DSace + 3 × DSacy ≦ 14

The degree of substitution is determined by the structural unit of cellulose (β1 →
It means the ratio of three hydroxyl groups present in (4 glycoside-linked glucose) are ester-linked.
The degree of substitution can be calculated by measuring the amount of bound fatty acid per unit weight of cellulose. The measuring method is AS
Performed according to TM-D817-91. The acyl group other than the acetyl group preferably has 3 to 6 carbon atoms. The other acyl group is more preferably a propionyl group or a butyryl group, and most preferably a propionyl group. The mixed fatty acid ester of cellulose is 350
It preferably has a weight average degree of polymerization of from to 800,
More preferably, it has a weight average degree of polymerization of 400 to 650. The mixed fatty acid ester of cellulose is 60
It preferably has a number average molecular weight of from 000 to 230,000, more preferably from 65,000 to 200,000, more preferably from 68,000 to 120,000.
Most preferably it has a number average molecular weight of 000.

The mixed fatty acid ester of cellulose can be synthesized using an acid anhydride or an acid chloride as an acylating agent.
When the acylating agent is an acid anhydride, an organic acid (eg, acetic acid) or methylene chloride is used as a reaction solvent. As the catalyst, a protic catalyst such as sulfuric acid is used. When the acylating agent is an acid chloride, a basic compound is used as a catalyst. The most common synthetic method in industry is to use cellulose as an organic acid (acetic acid, propionic acid, butyric acid) or an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride) corresponding to acetyl and other acyl groups.
To synthesize a cellulose ester. In this method, cellulose such as cotton linter or wood pulp is activated with an organic acid such as acetic acid, and then esterified using a mixture of the above organic acid components in the presence of a sulfuric acid catalyst. Often do. The organic acid anhydride component is generally used in an excess amount relative to the amount of hydroxyl groups present in cellulose. In this esterification treatment, in addition to the esterification reaction, a hydrolysis reaction (depolymerization reaction) of the cellulose main chain (β1 → 4 glycoside bond) proceeds. As the hydrolysis reaction of the main chain proceeds, the degree of polymerization of the cellulose ester decreases, and the physical properties of the produced cellulose ester film decrease. Therefore, the reaction conditions such as the reaction temperature need to be determined in consideration of the degree of polymerization and the molecular weight of the obtained cellulose ester.

[Organic solvent (main solvent, poor solvent, auxiliary solvent)] In the present invention, an organic solvent is used for producing a cellulose ester film. Preferably, the organic solvent is substantially free of halogenated hydrocarbons such as methylene chloride. “Substantially free” means that the proportion of halogenated hydrocarbon in the organic solvent is less than 5% by weight (preferably 2% by weight).
% By weight). Preferably, no halogenated hydrocarbon such as methylene chloride is detected from the produced film. The organic solvent used in the present invention includes a solvent used for preparing a cellulose ester solution (hereinafter, referred to as a main solvent), a poor solvent added after the solution preparation or after the cooling step, and an auxiliary solvent which can be optionally added. Can be classified into types.

The main solvent is selected from esters having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms and ethers having 3 to 12 carbon atoms. Esters, ketones and ethers may have a cyclic structure.
Ester, ketone and ether functional groups (ie,
A compound having two or more of —O—, —CO— and —COO—) can also be used as the organic solvent. Esters, ketones and ethers may have other functional groups such as alcoholic hydroxyl groups. Examples of the ester having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. 3 to 12 carbon atoms
Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-
Includes dioxane, 1,3-dioxolan, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more functional groups include 2-methoxyethyl acetate, 2-ethoxyethyl acetate,
-Methoxyethanol and 2-butoxyethanol. Two or more esters, ketones or ethers may be used in combination as the main solvent. Esters and ketones are preferred over ethers. Esters are preferred over ketones. The ester preferably has 3 to 10 carbon atoms, more preferably 3 to 8, more preferably 3 to 6, and most preferably 3 to 5. Methyl acetate is particularly preferably used.

The poor solvent is selected from alcohols having a boiling point of 30 to 170 ° C. and hydrocarbons having a boiling point of 30 to 170 ° C. Preferably, the alcohol is monovalent. The hydrocarbon portion of the alcohol may be linear, branched, or cyclic. Preferably, the hydrocarbon moiety is a saturated aliphatic hydrocarbon. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of alcohol include methanol (boiling point: 64.65 ° C.),
Ethanol (78.325 ° C.), 1-propanol (9
7.15 ° C), 2-propanol (82.4 ° C), 1-
Butanol (117.9 ° C.), 2-butanol (99.
5 ° C.), t-butanol (82.45 ° C.), 1-pentanol (137.5 ° C.), 2-methyl-2-butanol (101.9 ° C.) and cyclohexanol (161 ° C.).
° C). The hydrocarbon may be linear, branched, or cyclic. Both aromatic hydrocarbons and aliphatic hydrocarbons can be used. Aliphatic hydrocarbons may be saturated or unsaturated. Examples of the hydrocarbon include cyclohexane (boiling point: 80.7
° C), hexane (69 ° C), benzene (80.1 ° C),
Toluene (110.6 ° C) and xylene (138.4)
１４144.4 ° C.). In a normal dissolution method, the poor solvent is added to the solution after the preparation of the solution is completed. After the addition of the poor solvent, the mixture is preferably mixed well.
In the cooling dissolution method, the poor solvent is used after the step of cooling the mixture, before the step of heating, during the step, or after the step.
Add to the mixture. It is preferable to add during or after the step of heating. After the addition of the poor solvent, the mixture is preferably mixed well. The ratio of the main solvent to the poor solvent is preferably such that 5 to 60 parts by weight of the poor solvent is used with respect to 40 to 95 parts by weight of the main solvent, and 8 to 50 parts by weight of the poor solvent is used with respect to 50 to 92 parts by weight of the main solvent. More preferably, the poor solvent is used in an amount of 1 to 60 to 90 parts by weight of the main solvent.
It is more preferable to use 0 to 40 parts by weight, and it is most preferable to use 12 to 35 parts by weight of the poor solvent with respect to 65 to 88 parts by weight of the main solvent.

It is preferable to use a linear monohydric alcohol having 1 to 5 carbon atoms as an optional auxiliary solvent. The hydroxyl group of the alcohol may be bonded to the terminal of the hydrocarbon straight chain (primary alcohol) or may be bonded in the middle (secondary alcohol). The auxiliary solvent is specifically methanol, ethanol, 1-propanol,
2-propanol, 1-butanol, 2-butanol,
It is selected from 1-pentanol, 2-pentanol and 3-pentanol. The number of carbon atoms of the linear monohydric alcohol is preferably 1 to 4, more preferably 1 to 3, and most preferably 1 or 2. Ethanol is particularly preferably used. The definition of the co-solvent overlaps with the definition of the poor solvent alcohol. Therefore, the same alcohol as the alcohol used as the poor solvent may be used as the auxiliary solvent. For example,
When using ethanol as a poor solvent, ethanol can be further used as an auxiliary solvent. Also,
A different type of alcohol than the alcohol used as the poor solvent may be used as the auxiliary solvent. For example, when using ethanol as a poor solvent, other alcohols included in the definition of a poor solvent can be used as an auxiliary solvent. There is no particular limitation on the timing of adding the auxiliary solvent. The co-solvent may be used simultaneously with the main solvent, or the co-solvent may be used simultaneously with the poor solvent.

When the co-solvent is used in addition to the main solvent and the poor solvent, the ratio of the three solvents is from 40 to 9
It is preferable to use 2 to 60 parts by weight of the poor solvent and 2 to 60 parts by weight of the auxiliary solvent with respect to 5 parts by weight, and 3 to 50 parts by weight of the poor solvent with 50 to 92 parts by weight of the main solvent. It is more preferable to use 3 to 50 parts by weight.
More preferably, the poor solvent is used in an amount of 5 to 30 parts by weight and the auxiliary solvent is used in an amount of 5 to 30 parts by weight based on 65 to 88 parts by weight of the main solvent. preferable. Further, another organic solvent may be used in combination to form a mixed solvent of four or more kinds.
When four or more kinds of mixed solvents are used, the fourth and subsequent solvents are preferably selected from the three kinds of solvents described above. Nitromethane may be used in combination as a solvent other than the above three types of solvents.

[Preparation of Solution (General Method)] In the present invention, a solution can be prepared by a general method without employing the cooling dissolution method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (normal temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a usual solvent casting method. The amount of cellulose ester is 10
It is adjusted to be contained in an amount of about 40% by weight. More preferably, the amount of cellulose ester is from 10 to 30% by weight. In the organic solvent (main solvent), any additives described below may be added. The solution can be prepared by stirring the cellulose ester and the organic solvent (main solvent) at normal temperature (0 to 40 ° C.). The highly concentrated solution may be stirred under pressure and heating conditions. Specifically, the mixed fatty acid ester of cellulose and the organic solvent are placed in a pressurized container and sealed, and the mixture is stirred while being heated under pressure to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C. Each component may be roughly mixed in advance and then placed in a container. Moreover, you may put in a container sequentially. The container must be configured to be able to stir. The container can be pressurized by injecting an inert gas such as nitrogen gas. Further, an increase in the vapor pressure of the solvent due to heating may be used. Alternatively, each component may be added under pressure after the container is sealed. When heating, it is preferable to heat from outside the container. For example, a jacket-type heating device can be used. Alternatively, a plate heater may be provided outside the container, and the entire container may be heated by circulating the liquid through piping. It is preferable to provide a stirring blade inside the container and stir using the stirring blade.
The stirring blade preferably has a length reaching the vicinity of the container wall. At the end of the stirring blade, a scraping blade is preferably provided to renew the liquid film on the container wall. Instruments such as a pressure gauge and a thermometer may be installed in the container. Dissolve each component in the solvent in the container. The prepared dope is taken out of the vessel after cooling, or is taken out and then cooled using a heat exchanger or the like.

[Preparation of Solution (Cooling Dissolution Method)] A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, first, a cellulose ester is gradually added to an organic solvent (main solvent) at room temperature while stirring. At this stage, the cellulose ester generally swells but does not dissolve in the organic solvent. Even if the cellulose ester can be dissolved at room temperature, a uniform solution can be obtained quickly by the cooling dissolution method. The amount of the cellulose ester is adjusted so that the mixture contains 10 to 40% by weight. More preferably, the amount of cellulose ester is from 10 to 30% by weight. Optional additives described below may be added to the organic solvent.

Next, the mixture is cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -10 ° C).
To -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). Upon such cooling, the mixture of the cellulose ester and the organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and 12 ° C./min.
/ Min or more is most preferable. A higher cooling rate is preferred, but 10,000 ° C./sec is a theoretical upper limit, 1000 ° C./sec is a technical upper limit, and
0 ° C./sec is a practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at which the cooling is started and the final cooling temperature by the time from when the cooling is started to when the temperature reaches the final cooling temperature.

Further, when this is heated to 0 to 200 ° C., the cellulose ester dissolves in the mixed solvent. The temperature may be raised only by leaving it at room temperature or may be heated in a warm bath. In this way, a homogeneous solution is obtained. If the dissolution is insufficient, the operation of cooling and heating may be repeated. Whether or not the dissolution is sufficient can be determined only by visually observing the appearance of the solution. The heating rate is preferably 4 ° C./min or more,
It is more preferably at least 8 ° C./min, most preferably at least 12 ° C./min. The heating rate is preferably as fast as possible, but 10,000 ° C./sec is the theoretical upper limit,
1000 ° C / sec is a technical upper limit, and 100 ° C
/ Sec is a practical upper limit. Note that the heating rate is a value obtained by dividing the difference between the temperature at which heating is started and the final heating temperature by the time from when the heating is started until the final heating temperature is reached. . Before, during or after this heating step,
The above-mentioned poor solvent is added. The addition method is not particularly limited, but it is preferable to add and mix as quickly as possible in consideration of productivity.

As described above, a uniform solution is obtained. If the dissolution is insufficient, the operation of cooling and heating may be repeated. Whether or not the dissolution is sufficient can be determined only by visually observing the appearance of the solution. In the cooling dissolution method, it is preferable to use a closed container in order to avoid water contamination due to condensation during cooling. In addition, in the cooling and heating operation, if the pressure is increased during cooling and the pressure is reduced during heating, the dissolution time can be shortened.
In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.

[Production of Film] Prior to production of the film, it is desirable to filter the prepared cellulose ester solution (dope) with a filter in order to remove dust and foreign matters. By removing dust and foreign matter, the surface condition of the film is improved. The pore size of the filter is preferably 100 μm or less, more preferably 30 μm or less, and most preferably 10 μm or less.
Filtration through a filter is generally performed under pressure. The prepared cellulose ester solution is used as a dope in a solvent casting method. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35% by weight. It is preferable that the surface of the drum or the band is finished in a mirror state. The casting and drying methods in the solvent casting method are described in US Pat.
No. 67603, No. 2492078, No. 2492977
No. 2492978, No. 2607704, No. 27
No. 39069, No. 2739070, British Patent 6407
Nos. 31, 736,892, JP-B-45-4
554, 49-5614, JP-A-60-1768
No. 34, No. 60-203430, No. 62-11503
There is a description in each gazette of No. 5.

The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry by blowing on the air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried with high-temperature air whose temperature is gradually changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in JP-B-5-17844. According to this method, the time from casting to stripping can be reduced. In order to carry out this method, it is necessary that the dope gels at the surface temperature of the drum or band during casting. The solution (dope) prepared according to the present invention satisfies this condition. The film to be manufactured preferably has a thickness of 5 to 500 μm,
The thickness is more preferably 0 to 200 μm, and most preferably 60 to 150 μm.

The cellulose ester film may be added with a deterioration inhibitor (eg, an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, an amine) or an ultraviolet inhibitor. Good. Regarding the deterioration inhibitor, see JP-A-Hei 3
-199201, 5-1907073, 5-1
No. 94789, No. 5-271471, No. 6-1078
No. 54 describes each of them. The addition amount of the deterioration inhibitor
It is preferably 0.01 to 1% by weight, more preferably 0.1 to 0.2% by weight of the solution (dope) to be prepared. The cellulose ester film can be preferably used as a support for a silver halide photographic light-sensitive material. In a liquid crystal display device, a cellulose ester film can be advantageously used also as a protective film for a polarizing plate or a support for an optical compensation sheet. The cellulose ester film obtained according to the present invention is particularly effective in a TFT type liquid crystal display device.

[Production Apparatus] A production apparatus preferably used for the cooling and melting method will be described with reference to the drawings.
A large number of manufacturing apparatuses have been proposed for use in a general solution preparation method, and a commercially available apparatus can also be used. FIG. 1 is a flowchart showing a combination of each step and apparatus of the cooling and melting method. In the swelling step, the cellulose ester (P) and the main solvent (S1) are added to the stirring tank (1). The cellulose ester and the main solvent are mixed in the stirring tank, and the cellulose ester is swollen by the main solvent. The swollen mixture is sent from the liquid sending pump (2) to the cooling device (3). As the liquid sending pump (2), a snake pump suitable for sending a viscous liquid is used.

The cooling device (3) is provided with a rotatable helical transfer mechanism (3-) provided in the container for transferring the swollen mixture through the cylindrical container while stirring the swollen mixture.
1) and a cooling mechanism (3-2) provided around the container for cooling the swollen mixture in the container. The rotation of the spiral transport mechanism (3-1) allows the swelling mixture to stay without shearing (for example, the swelling mixture remaining on the wall surface of the container is also scraped off) while being sheared, mixed, and cooled. And send the liquid. The cooling mechanism (3-
2) is mounted around the container in a jacket shape. The refrigerant (24) sent from the refrigerant tank (21) flows inside the cooling mechanism (3-2). As the refrigerant, for example, a mixture of methanol and water is used. The refrigerant used for cooling returns to the refrigerant tank (21). The refrigerant is cooled by the refrigerator (22). The heat generated by this cooling is processed in the cooling tower (23). The cooling device (3) shown in FIG. 1 has a mechanism for refilling the main solvent cooled to −105 to −15 ° C. into the container. The replenishing main solvent (S2) is cooled to a required temperature in the cooling stock tank (19), and sent to the container of the cooling device (3) by the liquid sending pump (20). By adding the replenisher solvent thus cooled, the swollen mixture can be cooled very quickly. In the above cooling device, the swollen mixture is cooled quickly and uniformly. The cooled swollen mixture is sent to a heating device (4).

A heating device (4) is provided in a cylindrical container, a plurality of which are provided in the container to divide the flow of the substance in the container into two and rotate the flow of the divided substance in the container. And a heating mechanism (4-2) provided around the container for heating the swollen mixture in the container. As the swollen mixture passes through the partition element in the container, the swollen mixture is uniformly heated. The heating mechanism (4-2) shown in FIG. 1 is mounted around the container in a jacket shape. Heating mechanism (4-
The warm water sent from the thermostat (27) flows inside 2). The warm water used for heating was supplied to a heat exchanger (2
In 5), heat is exchanged with water from the cooling tower (23). Thereby, the energy efficiency of the entire device can be improved. The heat-exchanged warm water returns to the thermostat (27). In the above heating device, the swelling mixture is quickly and uniformly heated, and the cellulose ester is dissolved in the solvent. The obtained solution is supplied by the liquid sending pump (5).
After passing through a heater (6), a filter (7) and a pressure control valve (8), temperature control, filtration and pressure control are performed.

The solution is further concentrated in a concentration tank (9). That is, the solution brought into a high temperature and high pressure state by the heater (6) and the pressure adjusting valve (8) is rapidly reduced in the concentration tank (9), whereby the solvent is evaporated and concentrated. The evaporated solvent is supplied to the liquefier (1).
After 8), the liquid is sent to the cooling stock tank (19). The liquefied solvent is sent again to the container of the cooling device (3) by the pump (20) together with the main solvent for replenishment (S2). According to the method of the present invention, a high-concentration solution can be prepared, so that the above-mentioned concentration step can be omitted. The solution is sent to the stock tank (12) via the temperature adjusting device (11) by the liquid sending pump (10). In order to carry out the method of the present invention with the above-mentioned apparatus, it is preferable to add a poor solvent at the point A, B or C in FIG. In A, the poor solvent is replenished at the connection between the cooling device (3) and the heating device (4). In B, the poor solvent is replenished from the inlet provided in the heating device (4). In C, the poor solvent is replenished to the stock tank (12). B or C
It is preferred that the poor solvent be replenished at the point. When replenishing the poor solvent at the point A or B, the mixed solvent of the main solvent and the poor solvent collected from the concentration tank (9) is used.
The main solvent is separated and reused.

The apparatus shown in FIG. 1 is further provided with an apparatus for producing a cellulose ester film by a solvent casting method. The solution in the stock tank (12)
Through the filter (14) by the liquid sending pump (10),
It is sent to a slit-shaped die (15). Solution is die (1
The film is extruded into a film by 5), cast on a band-shaped support (16), dried, and then stripped to produce a film (17). The film (17) is further dried and wound up.

[0035]

[Example 1] (Formulation 1, Preparation method a, cooling temperature -50 ° C) At room temperature, a mixture having the following composition was charged into a tank and stirred for 1 hour to swell cellulose acetate propionate. Was. Cool the swollen mixture to −50 ° C. (cooling rate: 2 ° C.)
/ Sec), and further heated to 50 ° C (heating rate: 1 ° C /
Sec), the cellulose acetate propionate was dissolved in methyl acetate. At 50 ° C., 33 parts by weight of ethanol (16.5 parts by weight as an auxiliary solvent + 16.5 parts by weight as a poor solvent).
5 parts by weight) to prepare a cellulose acetate propionate solution.

<< Mixture Composition (1a) >> ────────────────────────────── Cellulose acetate propionate (substitution degree of acetyl group: 2.20, propionyl group Substitution degree: 0.70, weight average polymerization degree: 560, number average molecular weight: 78 500) 17 parts by weight methyl acetate (main solvent) 50 parts by weight triphenyl phosphate (plasticizer) 1.81 parts by weight biphenyl diphenyl phosphate (plasticity) 0.91 parts by weight ────────────────────────────────────

When the obtained solution was observed, cellulose acetate propionate was well dissolved, and no undissolved matter was observed. Further, when the cellulose acetate propionate solution was left at 50 ° C. for 2 weeks, no precipitation of undissolved substances was observed. The obtained solution was cast into a band using a band casting machine having an effective length of 6 m, dried, and then the film was peeled off from the band. As a result, a good cellulose acetate propionate film was obtained.

(Formulation 1, Preparation method b, Cooling temperature -50
C) At room temperature, a mixture having the following composition was charged into a tank and stirred for 1 hour to swell cellulose acetate propionate. The swollen mixture was cooled to −50 ° C. (cooling rate: 2 ° C./second), and further heated to 50 ° C. (heating rate: 1 ° C./second) to dissolve the cellulose acetate propionate in methyl acetate. Further, at 50 ° C., 16.5 parts by weight of ethanol (poor solvent) was added to prepare a cellulose acetate propionate solution.

<< Mixture Composition (1b) >> ────────────────────────────── Cellulose acetate propionate (substitution degree of acetyl group: 2.20, propionyl group Substitution degree: 0.70, weight average polymerization degree: 560, number average molecular weight: 78 500) 17 parts by weight Methyl acetate (main solvent) 50 parts by weight Ethanol (co-solvent) 16.5 parts by weight Triphenyl phosphate (plasticizer) 1.81 parts by weight Biphenyl diphenyl phosphate (plasticizer) 0.91 parts by weight ───

When the obtained solution was observed, cellulose acetate propionate was well dissolved, and no undissolved matter was observed. Further, when the cellulose acetate propionate solution was left at 50 ° C. for 2 weeks, no precipitation of undissolved substances was observed.

(Formulation 1, Preparation method x, Cooling temperature -50
C) At room temperature, a mixture having the following composition was charged into a tank and stirred for 1 hour to swell cellulose acetate propionate. The swelled mixture is cooled to -50 ° C (cooling rate: 2 ° C / sec), further heated to 50 ° C (heating rate: 1 ° C / sec), and cellulose acetate propionate is dissolved in methyl acetate. A cellulose acetate propionate solution was prepared.

──────────────────────────────────── Mixture composition (1x) ────── ────────────────────────────── Cellulose acetate propionate (substitution degree of acetyl group: 2.20, propionyl group Substitution degree: 0.70, weight average polymerization degree: 560, number average molecular weight: 78 500) 17 parts by weight Methyl acetate (main solvent) 50 parts by weight Ethanol 33 parts by weight (16.5 parts by weight as auxiliary solvent + as poor solvent) 16.5 parts by weight) Triphenyl phosphate (plasticizer) 1.81 parts by weight Biphenyl diphenyl phosphate (plasticizer) 0.91 parts by weight ────────────────

When the obtained solution was observed, a little undissolved material was observed, and the solution was turbid.

(Changes in formulation, preparation method and cooling temperature)
Various cellulose acetate propionate solutions were prepared by changing the formulation (1-6), the preparation method (a, b, x) and the temperature (−50 ° C., −30 ° C., 25 ° C.). At a preparation temperature of 25 ° C., the cooling dissolution method was
The mixture was stirred at 5 ° C. The prescriptions 2 to 7 correspond to the prescription 1
The only poor solvent was ethanol, which was changed to the following poor solvent. Formula 2: Methanol Formula 3: 1-propanol Formula 4: isopropanol Formula 5: 1-butanol Formula 6: t-butanol Formula 7: cyclohexane

Preparation methods a, b and x are as follows. Preparation method a: Cellulose acetate propionate
The plasticizer (triphenyl phosphate and biphenyl diphenyl phosphate) was gradually added to the dissolved main solvent (methyl acetate) with stirring, and after swelling for 1 hour, cooled as described above, and heated to 50 ° C. While stirring, the poor solvent and the auxiliary solvent (ethanol) are added. Preparation method b: Cellulose acetate propionate
Plasticizers (triphenyl phosphate and biphenyl diphenyl phosphate) are gradually added to a mixed solvent of a main solvent (methyl acetate) and an auxiliary solvent (ethanol) with stirring, and after swelling for 1 hour, cooled as described above. Then, the mixture is heated to 50 ° C., and the poor solvent is added with stirring. Preparation method x: Cellulose acetate propionate,
Main solvent (methyl acetate) in which plasticizer (triphenyl phosphate and biphenyl diphenyl phosphate) is dissolved,
The mixture is gradually added to a mixed solvent of an auxiliary solvent (ethanol) and a poor solvent with stirring, swollen for 1 hour, cooled as described above, and then heated to 50 ° C.

Observation of the resulting solution revealed that very many undissolved substances of cellulose acetate propionate were observed (Evaluation: D), those in which some undissolved substances were observed (Evaluation: C), and cellulose acetate propionate. The pionate was classified into those in which the pionate was well dissolved and no undissolved substance was observed (evaluation: B or A). Cellulose acetate propionate solution in which no undissolved substance is observed has an additional 5
After leaving at 0 ° C. for 2 weeks, precipitation of undissolved substances was observed,
The solution was classified into a solution in which turbidity occurred (evaluation: B) and a solution in which no undissolved substance was precipitated (evaluation: A). The above results are shown in Table 1 below.

[0047]

Table 1 Table 1 Preparation cooling temperature: -50 ° C Cooling temperature: -30 ° C Preparation temperature: 25 ° C Prescription {method x ab x ab x ab} １ 1 CA AD A AD ABB B 2 CA A D A AD A D B B 3 C A A D A A D A D B B B 4 C A A D A D A A D B B 5 C A AD A A D B B 6 C A A D A A D A D B B 7 C A A D A A D A D B B} ───────────────

The solutions obtained by the preparation methods a and b were cast into a band using a band casting machine having an effective length of 6 m.
After drying, the film was peeled off from the band. In each case, a cellulose acetate propionate film (thickness: 80 μm) having good physical properties and optical properties was obtained. In the preparation method x, when the cooling temperature was changed to -70 ° C, a cellulose acetate propionate solution could be prepared. Using the obtained solution, a cellulose acetate propionate film having a thickness of 80 μm was produced in the same manner as described above. When the optical properties of the produced cellulose acetate propionate film were compared with those of the films produced by the preparation methods a and b,
The films produced by preparation methods a and b were about 0.2% better in light transmittance. The number of minute undissolved substances (50 μm or less) per 1 cm ^{2 of} the film was about half that of the films produced by the preparation methods a and b, compared to the film produced by the preparation method x.

Example 2 The degree of substitution of the acetyl group was 2.2.
0, the substitution degree of propionyl group is 0.70, the weight average polymerization degree is 560, and the number average molecular weight is 78500. Instead of cellulose acetate propionate, the substitution degree of acetyl group is 2.40 and the substitution degree of propionyl group is Various cellulose acetate propionate solutions were prepared and evaluated in the same manner as in Example 1 except that a cellulose acetate propionate having a weight average polymerization degree of 605 and a number average molecular weight of 83,300 was used. The results are shown in Table 2 below.

[0050]

Table 2 Preparation cooling temperature: -50 ° C Cooling temperature: -30 ° C Preparation temperature: 25 ° C Prescription {method x ab x ab x ab} １ 1 CA AD A AD ABB B 2 CA A D A AD A D B B 3 C A A D A A D A D B B B 4 C A A D A D A A D B B 5 C A AD A A D B B 6 C A A D A A D A D B B 7 C A A D A A D A D B B} ───────────────

The solutions obtained by the preparation methods a and b were cast into a band using a band casting machine having an effective length of 6 m.
After drying, the film was peeled off from the band. In each case, a cellulose acetate propionate film (thickness: 80 μm) having good physical properties and optical properties was obtained. In the preparation method x, when the cooling temperature was changed to -70 ° C, a cellulose acetate propionate solution could be prepared. Using the obtained solution, a cellulose acetate propionate film having a thickness of 80 μm was produced in the same manner as described above. When the optical properties of the produced cellulose acetate propionate film were compared with those of the films produced by the preparation methods a and b,
The films produced by preparation methods a and b were about 0.2% better in light transmittance. The number of minute undissolved substances (50 μm or less) per 1 cm ^{2 of} the film was about half that of the films produced by the preparation methods a and b, compared to the film produced by the preparation method x.

Example 3 The degree of substitution of the acetyl group was 2.2.
0, the substitution degree of propionyl group is 0.70, the weight average polymerization degree is 560, and the number average molecular weight is 78500. Instead of cellulose acetate propionate, the substitution degree of acetyl group is 2.60 and the substitution degree of propionyl group is Various cellulose acetate propionate solutions were prepared and evaluated in the same manner as in Example 1 except that a cellulose acetate propionate having a weight average polymerization degree of 580 and a number average molecular weight of 78700 was used. The results are shown in Table 3 below.

[0053]

[Table 3] Table III Preparation cooling temperature: -50 ° C Cooling temperature: -30 ° C Preparation temperature: 25 ° C Prescription {method x ab x ab x ab} １ 1 CA AD A AD ABB B 2 CA A D A AD A D B B 3 C A A D A A D A D B B B 4 C A A D A D A A D B B 5 C A AD A A D B B 6 C A A D A A D A D B B 7 C A A D A A D A D B B} ───────────────

The solutions obtained by the preparation methods a and b were cast into a band using a band casting machine having an effective length of 6 m.
After drying, the film was peeled off from the band. In each case, a cellulose acetate propionate film (thickness: 80 μm) having good physical properties and optical properties was obtained. In the preparation method x, when the cooling temperature was changed to -70 ° C, a cellulose acetate propionate solution could be prepared. Using the obtained solution, a cellulose acetate propionate film having a thickness of 80 μm was produced in the same manner as described above. When the optical properties of the produced cellulose acetate propionate film were compared with those of the films produced by the preparation methods a and b,
The films produced by preparation methods a and b were about 0.2% better in light transmittance. The number of minute undissolved substances (50 μm or less) per 1 cm ^{2 of} the film was about half that of the films produced by the preparation methods a and b, compared to the film produced by the preparation method x.

[Example 4] The amount of cellulose acetate propionate used was changed from 17 to 20 parts by weight, the amount of the main solvent (methyl acetate) was changed from 50 to 48 parts by weight, and the amount of poor solvent used. From 16.5 parts by weight to 16 parts by weight, the amount of auxiliary solvent (ethanol) from 16.5 parts by weight to 16 parts by weight, and the amount of triphenyl phosphate (plasticizer) from 1.81 parts by weight to 2 parts by weight. .13 parts by weight,
Various cellulose acetate propionate solutions were prepared and evaluated in the same manner as in Example 1 except that the amount of biphenyl diphenyl phosphate (plasticizer) was changed from 0.91 part by weight to 1.07 part by weight, respectively. . The results are shown in Table 4 below.

[0056]

[Table 4] Preparation cooling temperature: -50 ° C Cooling temperature: -30 ° C Preparation temperature: 25 ° C Prescription {method x ab x ab x ab} １ 1 CA AD A AD ABB B 2 CA A D A AD A D B B 3 C A A D A A D A D B B B 4 C A A D A D A A D B B 5 C A AD A A D B B 6 C A A D A A D A D B B 7 C A A D A A D A D B B} ───────────────

The solutions obtained by the preparation methods a and b were cast into a band using a band casting machine having an effective length of 6 m.
After drying, the film was peeled off from the band. In each case, a cellulose acetate propionate film (thickness: 80 μm) having good physical properties and optical properties was obtained. In the preparation method x, when the cooling temperature was changed to -70 ° C, a cellulose acetate propionate solution could be prepared. Using the obtained solution, a cellulose acetate propionate film having a thickness of 80 μm was produced in the same manner as described above. When the optical properties of the produced cellulose acetate propionate film were compared with those of the films produced by the preparation methods a and b,
The films produced by preparation methods a and b were about 0.2% better in light transmittance. The number of minute undissolved substances (50 μm or less) per 1 cm ^{2 of} the film was about half that of the films produced by the preparation methods a and b, compared to the film produced by the preparation method x.

Example 5 The amount of cellulose acetate propionate used was changed from 17 to 20 parts by weight, the amount of the main solvent (methyl acetate) was changed from 50 to 48 parts by weight, and the amount of poor solvent used was changed. From 16.5 parts by weight to 16 parts by weight, the amount of auxiliary solvent (ethanol) from 16.5 parts by weight to 16 parts by weight, and the amount of triphenyl phosphate (plasticizer) from 1.81 parts by weight to 2 parts by weight. .13 parts by weight,
Various cellulose acetate propionate solutions were prepared and evaluated in the same manner as in Example 2 except that the amount of biphenyl diphenyl phosphate (plasticizer) was changed from 0.91 part by weight to 1.07 part by weight, respectively. . The results are shown in Table 5 below.

[0059]

[Table 5] Preparation cooling temperature: -50 ° C Cooling temperature: -30 ° C Preparation temperature: 25 ° C Prescription {method x ab x ab x ab} １ 1 CA AD A AD ABB B 2 CA A D A AD A D B B 3 C A A D A A D A D B B B 4 C A A D A D A A D B B 5 C A AD A A D B B 6 C A A D A A D A D B B 7 C A A D A A D A D B B} ───────────────

The solutions obtained by the preparation methods a and b were cast into a band using a band casting machine having an effective length of 6 m.
After drying, the film was peeled off from the band. In each case, a cellulose acetate propionate film (thickness: 80 μm) having good physical properties and optical properties was obtained. In the preparation method x, when the cooling temperature was changed to -70 ° C, a cellulose acetate propionate solution could be prepared. Using the obtained solution, a cellulose acetate propionate film having a thickness of 80 μm was produced in the same manner as described above. When the optical properties of the produced cellulose acetate propionate film were compared with those of the films produced by the preparation methods a and b,
The films produced by preparation methods a and b were about 0.2% better in light transmittance. The number of minute undissolved substances (50 μm or less) per 1 cm ^{2 of} the film was about half that of the films produced by the preparation methods a and b, compared to the film produced by the preparation method x.

Example 6 The amount of cellulose acetate propionate used was changed from 17 to 20 parts by weight, the amount of the main solvent (methyl acetate) was changed from 50 to 48 parts by weight, and the amount of poor solvent used. From 16.5 parts by weight to 16 parts by weight, the amount of auxiliary solvent (ethanol) from 16.5 parts by weight to 16 parts by weight, and the amount of triphenyl phosphate (plasticizer) from 1.81 parts by weight to 2 parts by weight. .13 parts by weight,
Various cellulose acetate propionate solutions were prepared and evaluated in the same manner as in Example 3, except that the used amount of biphenyl diphenyl phosphate (plasticizer) was changed from 0.91 part by weight to 1.07 part by weight. . The results are shown in Table 6 below.

[0062]

[Table 6] Preparation cooling temperature: -50 ° C Cooling temperature: -30 ° C Preparation temperature: 25 ° C Prescription {method x ab x ab x ab} １ 1 CA AD A AD ABB B 2 CA A D A AD A D B B 3 C A A D A A D A D B B B 4 C A A D A D A A D B B 5 C A AD A A D B B 6 C A A D A A D A D B B 7 C A A D A A D A D B B} ───────────────

The solutions obtained by the preparation methods a and b were cast into a band using a band casting machine having an effective length of 6 m.
After drying, the film was peeled off from the band. In each case, a cellulose acetate propionate film (thickness: 80 μm) having good physical properties and optical properties was obtained. In the preparation method x, when the cooling temperature was changed to -70 ° C, a cellulose acetate propionate solution could be prepared. Using the obtained solution, a cellulose acetate propionate film having a thickness of 80 μm was produced in the same manner as described above. When the optical properties of the produced cellulose acetate propionate film were compared with those of the films produced by the preparation methods a and b,
The films produced by preparation methods a and b were about 0.2% better in light transmittance. The number of minute undissolved substances (50 μm or less) per 1 cm ^{2 of} the film was about half that of the films produced by the preparation methods a and b, compared to the film produced by the preparation method x.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a combination of each step and apparatus of a cooling and melting method.

[Explanation of symbols]

 S1 Main solvent P Cellulose ester S2 Main solvent for replenishment A, B, C Addition points of poor solvent 1 Stirring tank 2 Liquid feed pump 3 Cooling device 3-1 Spiral transport mechanism 3-2 Jacket-like cooling mechanism 4 Heating Apparatus 4-1 Partition element 4-2 Jacket-like heating mechanism 5 Liquid feed pump 6 Heater 7 Filter 8 Pressure control valve 9 Concentration tank 10 Liquid feed pump 11 Temperature control device 12 Stock tank 13 Liquid feed pump 14 Filter 15 Die 16 Belt-like support 17 Film 18 Liquefaction device 19 Cooling stock tank 20 Liquid feed pump 21 Refrigerant tank 22 Refrigerator 23 Cooling tower 24 Refrigerant 25 Heat exchanger 27 Thermostat

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 5/30 G02B 5/30 G03C 1/795 G03C 1/795 // C08J 3/07 C08J 3/07 3 / 09 3/09 B29K 1:00 B29L 7:00

Claims (12)

[Claims] 1. A method for producing a cellulose ester film, wherein the following steps (1) to (4) are performed in the following order. (1) A mixed fatty acid ester of cellulose obtained by substituting a hydroxyl group of cellulose with an acetyl group and an acyl group having 3 or more carbon atoms is converted into an ester having 3 to 12 carbon atoms and 3 to 12 carbon atoms. Dissolving in an organic solvent selected from the group consisting of ketones and ethers having 3 to 12 carbon atoms to prepare a cellulose ester solution; (2) adding a boiling point of 30 to 17 to the cellulose ester solution;
Mixing an alcohol at 0 ° C. or a hydrocarbon having a boiling point of 30 to 170 ° C., (3) casting the resulting mixture on a support, and (4) evaporating the solvent to form a film. Process. 2. An organic solvent 4 selected from the group consisting of esters, ketones and ethers used in step (1).
The alcohol or hydrocarbon is used in the step (2) in an amount of 5 to 60 parts by weight based on 0 to 95 parts by weight.
The production method described in 1. 3. In step (1), a linear monohydric alcohol having 1 to 5 carbon atoms is mixed with an organic solvent selected from the group consisting of esters, ketones and ethers. The production method according to claim 1, wherein the mixed fatty acid ester is dissolved. 4. An organic solvent 4 selected from the group consisting of esters, ketones and ethers used in step (1).
In step (2), 2 to 60 parts by weight of alcohol or hydrocarbon, and in step (1), 2 to 60 parts by weight of linear monohydric alcohol having 1 to 5 carbon atoms with respect to 0 to 95 parts by weight. 4. The method according to claim 3, wherein the first part is used. 5. The method according to claim 1, wherein in the step (2), a linear monohydric alcohol having 1 to 5 carbon atoms is added to the cellulose ester solution in addition to the alcohol or the hydrocarbon. 6. An organic solvent 4 selected from the group consisting of esters, ketones and ethers used in step (1).
In step (2), 2 to 60 parts by weight of alcohol or hydrocarbon, and in step (2), 2 to 60 parts by weight of linear monohydric alcohol having 1 to 5 carbon atoms with respect to 0 to 95 parts by weight. The production method according to claim 5, wherein a part is used. 7. The following steps (1a) to (1c) and (3) to (4) are carried out in the following order, and between the steps (1b) and (3), (2) cellulose A method for producing a cellulose ester film, comprising: mixing an ester mixture or solution with an alcohol having a boiling point of 30 to 170 ° C or a hydrocarbon having a boiling point of 30 to 170 ° C. (1a) A mixed fatty acid ester of cellulose obtained by substituting a hydroxyl group of cellulose with an acetyl group and an acyl group having 3 or more carbon atoms is converted into an ester having 3 to 12 carbon atoms and an ester having 3 to 12 carbon atoms. Mixing with an organic solvent selected from the group consisting of ketones and ethers having 3 to 12 carbon atoms, thereby swelling the lower fatty acid ester of cellulose in the organic solvent, (1b) swelling the swelled mixture from -100 to (1c) heating the cooled mixture to 0 to 200 ° C. to prepare a cellulose ester solution in which a lower fatty acid ester of cellulose is dissolved in an organic solvent; (3) obtaining Casting the solution onto a support; and (4) evaporating the solvent to form a film. 8. An ester used in step (1a),
The method according to claim 7, wherein 5 to 60 parts by weight of alcohol or hydrocarbon is used in step (2) with respect to 40 to 95 parts by weight of an organic solvent selected from the group consisting of ketones and ethers. 9. In the step (1a), a linear monohydric alcohol having 1 to 5 carbon atoms is mixed with an organic solvent selected from the group consisting of esters, ketones and ethers. The production method according to claim 7, wherein a mixed fatty acid ester is mixed. 10. An organic solvent selected from the group consisting of esters, ketones and ethers used in the step (1a), in an amount of 40 to 95 parts by weight, an alcohol or a hydrocarbon in the step (2) in an amount of 2 to 60 parts by weight, and The method according to claim 9, wherein in the step (1a), 2 to 60 parts by weight of a linear monohydric alcohol having 1 to 5 carbon atoms is used. 11. The process according to claim 7, wherein in the step (2), a linear monohydric alcohol having 1 to 5 carbon atoms is mixed with the mixture or solution of the cellulose ester in addition to the alcohol or the hydrocarbon. Production method. 12. An alcohol or a hydrocarbon is used in the step (2) in an amount of 2 to 60 parts by weight, based on 40 to 95 parts by weight of an organic solvent selected from the group consisting of an ester, a ketone and an ether used in the step (1a); The method according to claim 11, wherein 2 to 60 parts by weight of a linear monohydric alcohol having 1 to 5 carbon atoms is used in the step (2).