JPH1060170A - Preparation of cellulose ester solution and production of cellulose ester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a suitable viscosity by cooling a mixture of a mixed fatty acid ester of cellulose with a solution containing a solvent selected among specified ketones, specified esters and specified ethers and an alcoholic solvent and heating the cooled mixture. SOLUTION: A mixed fatty acid ester of cellulose (e.g. cellulose acetate propionate) satisfying formulas I to III (wherein DSace is the degree of substitution of hydroxyl groups by acetyl groups, and DSacy is the degree of substitution of hydroxyl groups by 3C or higher acyl groups) and having an average degree of polymerization of 350-800 is prepared. Next, 10-40wt.% obtained mixed ester is mixed with 60-90wt.% mixed solvent containing 40-70wt.% solvent selected among 3-12C ketones (e.g. acetone), esters (e.g. methyl acetate) and 3-12C ethers (e.g. dimethoxymethane) and 30-60wt.% 2-8C alcohol (e.g. ethanol). The resulting mixture is cooled to -100 to -10 deg.C to form a solid, and this solid is molten by heating to 0-100 deg.C to obtain a uniform solution. This solution is cast over a support and formed into a film by the evaporation of the solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for preparing a cellulose ester solution. Further, 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. Hei 5-17844 proposes reducing the time from casting to stripping by casting a high-concentration dope on a cooled support (eg, a drum). I have. 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. The solvent is required to be easily evaporated and to have a small residual amount in the film.

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, cellulose triacetate having a substitution degree of 2.80 (acetylation degree: 60.1%) or more only swells in acetone or methyl acetate, but hardly dissolves.

Japanese Patent Publication No. Hei 6-501040 proposes to use a melt casting method instead of the solvent casting method having the above-mentioned problems. However,
The melt casting method has a problem that the melting point of cellulose triacetate is higher than the decomposition temperature. That is, cellulose triacetate having a high degree of substitution of an acetyl group is
Decomposes before heating before melting. In order to solve this problem, in the invention described in the publication, the degree of substitution of the acetyl group in cellulose acetate is adjusted to 1.9 to 2.6. The publication further discloses cellulose acetate propionate, which defines the degree of substitution of the propionyl group as 0 to 0.9. Specifically, Example B of the publication describes cellulose acetate propionate having a degree of substitution of an acetyl group of 1.90 and a degree of substitution of a propionyl group of 0.71. In addition, Example C of the publication describes cellulose acetate propionate having a degree of substitution of an acetyl group of 2.10 and a degree of substitution of a propionyl group of 0.50. However, as described above, the solvent cast method can produce a film having higher flatness than the melt cast method. In other words,
Films manufactured by the melt casting method have a problem in flatness. Although the planarity of the film can be improved by biaxial stretching, stretching the film orients the molecules and increases the optical anisotropy of the film. Except for special uses,
Films used for photographic materials and optical materials are required to have optical isotropy. Therefore, in the production of the cellulose ester film, it is desirable to adopt the solvent cast method rather than the melt cast method in principle.

[0006] As a solution in the solvent casting method, EP Publication Nos. 0723986 and 07239 are disclosed.
No. 93 describes a mixture of cellulose acetate having an average acetylation degree of 58.0 to 62.5% (generally classified as cellulose triacetate) and an organic solvent (eg, acetone, methyl acetate). -100 to -10
Cooling the mixture to 0 to 50 ° C. to prepare a cellulose acetate solution in which cellulose acetate is dissolved in an organic solvent, and casting the cellulose acetate solution on a support. There is described a method for producing a cellulose acetate film, comprising a step of forming a film by evaporating a solvent. As described above, when the mixture is cooled and then heated, a solution can be prepared even with a combination of cellulose acetate and an organic solvent which does not dissolve (swell only) when stirred at room temperature or high temperature. Hereinafter, such a method of preparing a solution by cooling and heating is referred to as a cooling dissolution method.

[0007]

SUMMARY OF THE INVENTION Using a cooling melting method,
It has become possible to prepare a solution in which cellulose acetate is dissolved in an organic solvent substantially free of halogenated hydrocarbons such as acetone and methyl acetate. But,
As a result of research conducted by the present inventors, the cellulose acetate solution obtained by the cooling dissolution method faced a problem that it was difficult to adjust the viscosity. Solution viscosity is an important condition in the manufacture of products such as films. If the viscosity of the solution is too high, it is difficult to handle the solution. That is, in the piping,
In the case of transporting a solution by pressure, if the viscosity of the solution is high, a high pressure is required for sending the solution in a pipe. On the other hand, as described in Japanese Patent Publication No. 17844/1993, the time required for film production can be reduced by casting a high-concentration dough on a cooling support. But,
In order to actually shorten the processing time, it is necessary that the viscosity of the solution rapidly increases (finally solidifies) by cooling.
When the dope is cast on a support at room temperature, the viscosity of the solution must be rapidly increased (finally solidified) by drying in order to reduce the processing time. Even if the concentration of the cellulose acetate solution obtained by the cooling dissolution method was adjusted, it was difficult to obtain appropriate viscosity characteristics.

An object of the present invention is to prepare a cellulose ester solution having appropriate viscosity characteristics without using a halogenated hydrocarbon-based organic solvent such as methylene chloride. Another object of the present invention is to produce an excellent cellulose ester film without using a halogenated hydrocarbon organic solvent such as methylene chloride.

[0009]

The above object has been achieved by the following method (1) for preparing a cellulose ester solution. (1) 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, and an organic solvent substantially free of halogenated hydrocarbons, A first solvent selected from a ketone having 3 to 12 atoms, an ester having 3 to 12 carbon atoms and an ether having 3 to 12 carbon atoms is 40 to 70% by weight and a first solvent having 2 to 8 carbon atoms. 30-60% by weight of a second solvent selected from alcohols
A cellulose having a step of cooling the mixture with the mixed organic solvent to -100 to 0 ° C, and a step of heating the cooled mixture to 10 to 120 ° C to dissolve the mixed fatty acid ester of cellulose in the mixed organic solvent. Preparation of ester solution.

The cellulose ester solution has the following (2)
It may be prepared in the mode of (5). (2) The substitution degree (DSace) of the acetyl group and the substitution degree (DSacy) of the acyl group having 3 or more carbon atoms in the mixed fatty acid ester of cellulose are represented by the following formulas (I) to (I).
The preparation method according to (1), which satisfies (III). (I) 2.0 <DSace ≦ 2.7 (II) 0.3 <DSacy ≦ 0.8 (III) 2.6 <DSace + DSacy ≦ 3.0 (3) Degree of substitution of acetyl group in mixed fatty acid ester of cellulose (DSace) and the degree of substitution (DSacy) of an acyl group having 3 or more carbon atoms are further represented by the following formula (I)
The preparation method according to (2), which satisfies V). (IV) 5 × DSace + 3 × DSacy ≦ 13.3 (4) The mixed organic solvent contains 35 to 50% by weight of a second solvent selected from alcohols having 2 to 8 carbon atoms (1) Preparation method described in 1. (5) The preparation method according to (1), in which the treatment from mixing the mixed fatty acid ester of cellulose and the organic solvent within 3 hours to ending the heating is completed.

The present invention further provides the following (6) and (7)
The present invention also provides a method for producing a cellulose ester film. (6) A step of casting the cellulose ester solution obtained by the preparation method according to any one of (1) to (5) on a support, and a step of evaporating the solvent to form a film. A method for producing a cellulose ester film. (7) The production method according to (6), wherein the cellulose ester solution is cast on a support cooled to 15 ° C. or lower.

[0012]

The present inventors have conducted research on a cellulose ester solution, and found that the organic solvent has two carbon atoms.
It has been found that adding 30% by weight or more of the alcohol of No. 8 to No. 8 theoretically gives a solution having ideal viscosity properties. However, as alcohol is known as a poor solvent for cellulose acetate, it is extremely difficult to dissolve cellulose acetate in alcohol. That is, cellulose acetate hardly dissolves in an organic solvent containing 30% by weight or more of alcohol even when the above-described cooling dissolution method is used. The present inventors have further studied and finally used 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 by a cooling dissolution method, A cellulose ester solution with ideal viscosity properties was successfully prepared. The viscosity of the cellulose ester solution prepared according to the present invention is easy to adjust, and upon cooling or drying, the viscosity rapidly increases and gels. Such viscosity properties are advantageous for the production of cellulose ester products such as films. For example, the solution obtained according to the present invention is cooled to a low temperature (for example, 15
(° C. or lower), the film rapidly gels when cast on a support, so that the formed film can be peeled off from the support in a short time. Even when cast on a support at room temperature, it gels quickly by drying. As a result, the time required for the production of the film can be shortened, and the productivity is significantly improved. The method for preparing a cellulose ester solution of the present invention has an effect that a cellulose ester solution having excellent stability, fluidity and transparency can be prepared without substantially using a halogenated hydrocarbon such as methylene chloride. There is also.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

[Mixed fatty acid ester of cellulose] The mixed fatty acid ester of cellulose is obtained by replacing the hydroxyl group of cellulose with an acetyl group and an acyl group having 3 or more carbon atoms. The substitution degree (DSace) of the acetyl group and the substitution degree (DSacy) of the acyl group having 3 or more carbon atoms in the mixed fatty acid ester of cellulose are represented by the following formulas (I) to (III).
Is preferably satisfied. (I) 2.0 <DSace ≦ 2.7 (II) 0.3 <DSacy ≦ 0.8 (III) 2.6 <DSace + DSacy ≦ 3.0 The above formula (I) is within the range of the following formula (Ia). Is more preferable. (Ia) 2.0 <DSace ≦ 2.4 The above formula (II) is more preferably in the range of the following formula (IIa). (IIa) 0.3 <DSacy <0.7 The degree of substitution of acetyl group (DSace) and the degree of substitution of acyl group having 3 or more carbon atoms (DSacy) are represented by the following formula (I)
More preferably, V) is satisfied. (IV) 5 × DSace + 3 × DSacy ≦ 13.3

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 definition of the substitution degree will be described with reference to FIG. FIG. 1 is a graph in which the horizontal axis represents the degree of substitution of an acetyl group (DSace) and the vertical axis represents the degree of substitution of an acyl group having 3 or more carbon atoms (DSacy). Regions hatched by vertical lines are represented by formulas (I) to (I).
This corresponds to a range of values satisfying (III). A region hatched by a horizontal line corresponds to a range of values satisfying Expressions (I) to (IV). In addition, 1, 2 and 3 in FIG. 1 mean the mixed fatty acid ester of cellulose used in Examples 1-10, 11-20 and 21-30, respectively. When the substitution degree of the acetyl group is lower or the substitution degree of another acyl group is higher than the range defined by FIG. 1 (the value on the left side or the upper side of the hatched area in FIG. 1), the molecular chain of the cellulose ester is reduced. And the mechanical strength (elastic modulus, bending strength) of the film to be produced decreases. In addition, when the degree of substitution of the acetyl group is higher or the degree of substitution of another acyl group is lower than the range defined by FIG. The solubility of the cellulose ester in the organic solvent decreases. Further, when the degree of substitution of all acyl groups (DSace + DSacy) is lower than the range defined by FIG. 1 (the value on the lower left side of the hatched area in FIG. 1), the dimensional stability and moisture-heat resistance of the produced film Decrease.

As described above, the substitution degree of the acetyl group (DS
ace) and the degree of substitution of the acyl group having 3 or more carbon atoms (D
Sacy) is a value determined in consideration of the solubility of the cellulose ester in the organic solvent and the physical properties of the film to be produced. 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 preferably has a weight average polymerization degree of 350 to 800, and more preferably 370 to 600. The mixed fatty acid ester of cellulose preferably has a number average molecular weight of 70,000 to 230,000, and 75,000 to 2300.
More preferably, it has a number average molecular weight of
Most preferably, it has a number average molecular weight of 8,000 to 120,000.

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.

In order to obtain a cellulose ester having a high degree of polymerization (high molecular weight), it is important to adjust the maximum temperature in the esterification reaction step to 50 ° C. or less.
The maximum temperature is preferably adjusted to 35 to 50 ° C, more preferably 37 to 47 ° C. If the reaction temperature is lower than 35 ° C., the esterification reaction may not proceed smoothly.
When the reaction temperature exceeds 50 ° C., the degree of polymerization of the cellulose ester tends to decrease. When the reaction is stopped after suppressing the temperature rise after the esterification reaction, a decrease in the degree of polymerization can be further suppressed, and a cellulose ester having a high degree of polymerization can be synthesized. That is, when a reaction terminator (eg, water, acetic acid) is added after the completion of the reaction, the excess acid anhydride that did not participate in the esterification reaction is hydrolyzed to form a corresponding organic acid. This hydrolysis reaction is accompanied by intense heat generation, and the temperature inside the reactor rises. If the addition rate of the reaction terminator is high,
It generates heat rapidly beyond the cooling capacity of the reactor. Therefore, the hydrolysis reaction of the cellulose main chain remarkably progresses, and the degree of polymerization of the obtained cellulose ester decreases. Also,
During the esterification reaction, part of the catalyst is bound to the cellulose, most of which dissociates from the cellulose during the addition of the terminator. However, when the addition rate of the reaction terminator is high, there is not enough reaction time for the catalyst to dissociate, and a part of the catalyst remains in a state bound to cellulose. Cellulose esters to which a strong acid catalyst is partially bonded have extremely poor stability, and are easily decomposed by heat during drying of the product, and the degree of polymerization is reduced. For these reasons, after the esterification reaction, preferably 4 minutes or more, more preferably 4 to 30 minutes.
It is desirable to stop the reaction by adding a reaction terminator over a period of minutes. The addition time of the reaction terminator is 30.
Beyond this, industrial productivity decreases. As the reaction terminator, water or alcohol which decomposes an acid anhydride is generally used. However, in the present invention, a mixture of water and an organic acid is preferably used as a reaction terminator in order not to precipitate triesters having low solubility in various organic solvents. When the esterification reaction is carried out under the above conditions, a high molecular weight cellulose ester having a weight average polymerization degree of 500 or more can be easily synthesized.

[Organic Solvent] In the present invention, an organic solvent is used for preparing a cellulose acetate solution. 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 less than 2% by weight). The organic solvent used in the present invention is a mixed solvent of two or more solvents.

The first solvent is selected from ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and ethers having 3 to 12 carbon atoms. Ketone,
Esters and ethers may have a cyclic structure. Compounds having two or more of the functional groups of ketones, esters and ethers (i.e., -CO-, -COO- and -O-) can also be used as the organic solvent. Ketones, esters and ethers may have other functional groups such as alcoholic hydroxyl groups. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. Examples of the ester having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate and 2-methoxyethyl acetate. Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-
Includes dioxolane, tetrahydrofuran, anisole and phenetole. Examples of ketones, esters or ethers having two or more functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2
-Butoxyethanol. Ketones and esters are preferred, and esters are most preferred. 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 organic solvent is the first
40 to 70% by weight, preferably 45 to 65%
It is included in the range of weight%.

The second solvent is selected from alcohols having 2 to 8 carbon atoms. 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 alcohols having 2 to 8 carbon atoms include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-pentanol, and 3-pentanol. , 2-methyl-2-butanol and cyclohexanol. The organic solvent contains the second solvent in the range of 30 to 60% by weight, preferably 35 to 50% by weight.

Further, three or more kinds of mixed solvents may be used in combination with another organic solvent. Examples of the organic solvent (third solvent) that can be used in combination include methanol, hydrocarbon, and nitromethane. 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, hexane, benzene, toluene and xylene. The proportion of the third solvent (solvent other than the first and second solvents) in the organic solvent is preferably 20% by weight or less,
It is more preferably at most 15% by weight, most preferably at most 10% by weight.

[Solution preparation (cooling dissolution method)]
The mixed fatty acid ester of cellulose is dissolved in the above mixed organic solvent by a cooling dissolution method to prepare a solution (dope). In the preparation of the solution, first, the mixed fatty acid ester of cellulose is gradually added to an organic solvent at room temperature while stirring. The amount of the mixed fatty acid ester of cellulose is adjusted so that the mixture contains 10 to 40% by weight. More preferably, the amount of the mixed fatty acid ester of cellulose is 10 to 30% by weight. Any additive described below may be added to the mixed solvent. Next, the mixture was cooled to -100 to -10 ° C.
(Preferably -80 to -10 ° C, more preferably-
50 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.). When cooled in this way, the mixture of the mixed fatty acid ester of cellulose and the mixed solvent solidifies.

Further, when the mixture is heated to 0 to 100 ° C., the mixed fatty acid ester of cellulose is dissolved 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. In the cooling dissolution method, it is desirable to use a closed container in order to avoid water contamination due to condensation during cooling. Also, in the cooling and heating operation, pressurization during cooling,
By reducing the pressure during the heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container. In addition, after mixing the mixed fatty acid ester of cellulose and the organic solvent within 3 hours,
It is preferable to complete the processing until the heating is completed.

[Production of Film] The prepared cellulose ester solution can be used for production of a film.
Specifically, the solution is used as a dope in a solvent casting method. The dope is cast on a support and the solvent is evaporated to form a film. The dope before casting is
It is preferable to adjust the concentration so that the solid content is 18 to 35%. The surface of the support is preferably finished in a mirror surface state. A drum or a band is used as the support. Regarding the casting and drying methods in the solvent casting method, US Pat. No. 2,336,310,
No. 2367603, No. 2492078, No. 2492
977, 2492978, 2607704,
Nos. 2739069 and 2739070, British Patent 6
Nos. 40731 and 736892, Japanese Patent Publication No. 45
Nos. -4554 and 49-5614, JP-A-60-17
No. 6834, No. 60-203430, No. 62-115
No. 035 is described in each publication.

The dope is preferably cast on a support having a surface temperature of 15 ° C. or lower. The surface temperature of the support is −
More preferably, the temperature is 10 to 15 ° C. It is preferable to dry it by blowing it on the cast for 2 seconds. The obtained film was peeled off from the support, and then 100 to 160
It is also possible to evaporate the residual solvent by drying with high-temperature air whose temperature is gradually changed up to ° C. The above method is described in
No. 844 discloses this. 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 support during casting. The solution (dope) prepared according to the present invention satisfies this condition.
The thickness of the film produced according to the invention is between 5 and 500
μm, more preferably 20 to 200 μm, and most preferably 60 to 120 μm.

[Other Additives] A plasticizer can be added to the cellulose ester film in order to improve mechanical properties or to increase the drying speed.
As the plasticizer, a phosphoric acid ester or a carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative carboxylic esters include phthalic esters and citric esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate,
(DOP) and diethylhexyl phthalate (DEH)
P) is included. Examples of citrate esters include acetyltriethyl citrate (OACTE) and acetyltributyl citrate (OACTB). Examples of other carboxylic esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic esters.

Further, a compound generally known as a crystal nucleating agent (nucleating agent) may be added. Crystal nucleating agents have been used as modifiers to improve the optical, mechanical, thermal, and moldability of crystalline polymers (especially polypropylene) when they are melt molded. ing. In the present invention, such a compound can be used to increase the gelation temperature of the dope, instead of using it as a crystal nucleating agent. The above compound has an interaction with a cellulose ester due to its amphiphilic chemical structure. On the other hand, since the self-aggregating action of the compound is higher than that of the cellulose ester, it is considered that the aggregation of the cellulose ester is promoted as a result, and the gelation temperature is increased. The compound has an effect of lowering the viscosity of the dope. It is considered that the above compound prevents the solvation of the organic solvent with the hydroxyl group of the cellulose ester, thereby suppressing the spread of the polymer.

Examples of compounds known as crystal nucleating agents (nucleating agents) include 2,2'-methylenebis (4,4
6-di-t-butylphenyl) sodium (ADEKA STAB NA-11, manufactured by Asahi Denka Co., Ltd.), bisphosphate (4-t
-Butylphenyl) sodium (ADK STAB NA-1)
0, manufactured by Asahi Denka Co., Ltd.), bis (p-methylbenzylidene) sorbidol (Gerol MD, Shin Nippon Rika Co., Ltd.)
And bis (p-ethylvindylidene) sorbitol (NC-4, manufactured by Mitsui Toatsu Chemicals, Inc.). A deterioration inhibitor (eg, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger) or an ultraviolet inhibitor may be added to the cellulose ester film. The deterioration inhibitor is described in JP-A-5-1907073. The UV inhibitors are described in JP-A-7-11056.

[0029]

【Example】

[Example 1] The degree of substitution of the acetyl group was 2.18, the degree of substitution of the propionyl group was 0.72, the weight average polymerization degree was 560,
A solution was prepared by the following cooling dissolution method using cellulose acetate propionate having a number average molecular weight of 78,000. At room temperature, a mixture having the following composition was put into a tank, and after swelling the cellulose acetate propionate at room temperature, the mixture was cooled to -70 ° C, further heated to 70 ° C, and stirred for 30 minutes to obtain cellulose acetate. A solution was prepared. In addition, cellulose acetate propionate is mixed with an organic solvent, and heated up to 70 ° C.
The process was completed in 2 hours.

組成 Mixture composition ───────── ─────────────────────────── Cellulose acetate propionate 15 parts by weight Methyl acetate 60 parts by weight Ethanol 30 parts by weight Methanol 10 parts by weight Triphenyl Phosphate 1.5 parts by weight Biphenyl diphenyl phosphate 0.5 parts by weight ────────────────────────────────────

When the obtained solution was observed, it was clear that cellulose acetate propionate was very well dissolved.

Examples 2 to 10 Solutions were prepared in the same manner as in Example 1 except that the composition of the mixed solvent was changed as shown in Table 1 below. The composition of cellulose acetate propionate (15 parts by weight) and a plasticizer (1.5 parts by weight of triphenyl phosphate and 0.5 parts by weight of biphenyldiphenyl phosphate) are the same as in Example 1.

[0033]

Table 1 Table 1 Example 1 2 3 4 5 6 7 8 9 10 {Methyl acetate 60 65 60 60 60 60 60 60 60 65 65 ──────────────────────────────────── ethanol 30 35 40 30 30 25 n-propanol 40 Isopropanol 40 10 n-butanol 405 cyclohexanol 40 methanol 10 Cyclohexane 10────────────────────────────────────

Observation of the obtained solutions revealed that all of them were transparent and cellulose acetate propionate was very well dissolved.

[Comparative Examples 1 to 10] A mixture having the same composition as in Examples 1 to 10 was charged into a tank, and cellulose acetate propionate was swollen at room temperature. Then, stirring was continued for 2 hours. In Comparative Examples 1, 3 to 6 and 8 (the same composition as in Examples 1, 3 to 6 and 8), cellulose acetate propionate did not dissolve at all. Comparative Examples 2, 9 and 1
At 0 (the same composition as in Examples 2, 9 and 10), some of the cellulose acetate propionate dissolved, but most remained swollen. In Comparative Example 7 (same composition as in Example 7), about half of the cellulose acetate propionate was dissolved, but the rest remained swollen.

Example 11 The degree of acetyl substitution was 2.
21, except that a cellulose acetate propionate having a degree of substitution of propionyl group of 0.59, a weight average degree of polymerization of 605, and a number average molecular weight of 83,800 was used. Prepared. Observation of the obtained solution revealed that cellulose acetate propionate was transparent and very well dissolved.

[Examples 12 to 20]
Changes as shown in Table 1 described above (Examples 11 to 20)
Corresponded to the compositions of Examples 1 to 10, respectively), except that solutions were prepared in the same manner as in Example 11. Observation of the resulting solutions revealed that they were all transparent and very well dissolved cellulose acetate propionate.

[Comparative Examples 11 to 20] A mixture having the same composition as in Examples 11 to 20 was charged into a tank, and cellulose acetate propionate was swollen at room temperature. Then, stirring was continued for 2 hours. In Comparative Examples 11, 13 to 16, and 18 (the same composition as in Examples 11, 13 to 16, and 18), cellulose acetate propionate did not dissolve at all.
In Comparative Examples 12, 19 and 20 (the same composition as in Examples 12, 19 and 20), a part of the cellulose acetate propionate was dissolved, but the majority remained swollen. In Comparative Example 17 (the same composition as in Example 17), about half of the cellulose acetate propionate was dissolved, but the rest remained swollen.

Example 21 The degree of substitution of the acetyl group was 2.
30, the same procedure as in Example 1 was carried out except that a cellulose acetate propionate having a degree of substitution of propionyl group of 0.50, a weight average degree of polymerization of 580 and a number average molecular weight of 78900 was used. Prepared. Observation of the obtained solution revealed that cellulose acetate propionate was transparent and very well dissolved.

Examples 22 to 30 The composition of the mixed solvent was
Changes as shown in Table 1 (Examples 21 to 30)
Corresponded to the compositions of Examples 1 to 10, respectively), except that solutions were prepared in the same manner as in Example 21. Observation of the resulting solutions revealed that they were all transparent and very well dissolved cellulose acetate propionate.

[Comparative Examples 21 to 30] A mixture having the same composition as in Examples 21 to 30 was charged into a tank, and cellulose acetate propionate was allowed to swell at room temperature. Then, stirring was continued for 2 hours. In Comparative Examples 21, 23 to 26 and 28 (the same composition as in Examples 21, 23 to 26 and 28), cellulose acetate propionate did not dissolve at all.
In Comparative Examples 22, 29 and 30 (the same composition as Examples 22, 29 and 30), a part of the cellulose acetate propionate was dissolved, but the majority remained swollen. In Comparative Example 27 (the same composition as in Example 27), about half of the cellulose acetate propionate was dissolved, but the rest remained swollen.

[Examples 31 to 60] The solutions obtained in Examples 1 to 30 were dried by using a hopper
After casting on a stainless steel mirror support (surface temperature: 10 ° C.) so as to have a thickness of 0 μm, it was dried with hot air at 80 ° C.
The time during which the film could be peeled from the support was measured. Films produced from any of the solutions could be peeled off from the support within 20 seconds after casting.

[Brief description of the drawings]

FIG. 1 is a graph in which the horizontal axis represents the degree of substitution of acetyl groups (DSace), and the vertical axis represents the degree of substitution of acyl groups having 3 or more carbon atoms (DSac).
It is a graph set to y).

[Explanation of symbols]

1 Substitution degree of mixed fatty acid ester of cellulose used in Examples 1 to 2 2 Substitution degree of mixed fatty acid ester of cellulose used in Examples 11 to 20 3 Substitution of mixed fatty acid ester of cellulose used in Examples 21 to 30 Every time

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location C08K 5/06 C08K 5/06 5/07 5/07 5/10 5/10 // B29K 1: 00 B29L 7:00

Claims (7)

[Claims] 1. 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, and an organic solvent substantially free of halogenated hydrocarbons. A first solvent selected from a ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms and an ether having 3 to 12 carbon atoms, in an amount of 40 to 70% by weight, and The second solvent selected from the alcohols of 8 to 30 to 6
0-100% by weight of a mixture with a mixed organic solvent containing 0% by weight.
And cooling the cooled mixture to 10 to 1 ° C.
A method for preparing a cellulose ester solution, comprising a step of heating to 20 ° C. to dissolve a mixed fatty acid ester of cellulose in a mixed organic solvent. 2. The method according to claim 1, wherein the substitution degree (DSase) of the acetyl group in the mixed fatty acid ester of cellulose and the number of carbon atoms are 3
The preparation method according to claim 1, wherein the degree of acyl group substitution (DSacy) satisfies the following formulas (I) to (III). (I) 2.0 <DSace ≦ 2.7 (II) 0.3 <DSacy ≦ 0.8 (III) 2.6 <DSace + DSacy ≦ 3.0 3. The method according to claim 3, wherein 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 preparation method according to claim 2, wherein the degree of acyl group substitution (DSacy) further satisfies the following formula (IV). (IV) 5 × DSace + 3 × DSacy ≦ 13.3 4. A mixed organic solvent containing 35 to 50 second solvents selected from alcohols having 2 to 8 carbon atoms.
The preparation method according to claim 1, which is contained by weight%. 5. The preparation method according to claim 1, wherein the treatment from mixing the mixed fatty acid ester of cellulose and the organic solvent to finishing the heating is completed within 3 hours. 6. A method comprising: casting a cellulose ester solution obtained by the preparation method according to claim 1 on a support; and evaporating a solvent to form a film. A method for producing a cellulose ester film. 7. The production method according to claim 6, wherein the cellulose ester solution is cast on a support cooled to 15 ° C. or less.