JP2002338601A - Cellulose acetate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose acetate wherein the degrees of acetyl substitution at the 2-, 3-, and 6-positions are controlled appropriately. SOLUTION: A cellulose acetate is subjected to aging in the presence of an acetyl group donor and a catalyst, wherein the amount of water or an alcohol is limited to <10 mol% of the acetyl group donor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cellulose acetate, a cellulose acetate solution and a cellulose acetate film.

[0002]

2. Description of the Related Art Cellulose acetate, especially cellulose acetate having a total degree of acetyl substitution at the 2-, 3- and 6-positions of 2.60 or more (generally classified as cellulose triacetate) has high toughness and flame retardancy. It is used in various fields due to its nature. Cellulose acetate film is a typical support for photographic light-sensitive materials. Also,
Due to its optical isotropy, cellulose acetate films are also used in liquid crystal display devices, which have been expanding in market in recent years. Typical applications in liquid crystal display devices include polarizer protective films, retardation films, and color filters. The cellulose acetate film is generally manufactured by a solvent 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. Recently, 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 (Japanese Patent Laid-Open No. 9-95544). , 9-95557 and 9-95538). A method having a cooling step and a heating step (hereinafter, referred to as a cooling dissolution method)
According to the method, a solution can be prepared even with a combination of cellulose acetate and an organic solvent, which could not be dissolved by a conventional method. The cooling dissolution method is
It is particularly effective when a film is produced from cellulose triacetate having low solubility (the total degree of acetyl substitution at the 2-, 3- and 6-positions is 2.60 or more).

[0003] In the production of a cellulose acetate film by a solvent casting method, the stability of a cellulose acetate solution is particularly important. When transferring the solution, it is necessary to avoid the occurrence of undissolved matter in the piping and the occurrence of solidification during the downtime for maintenance of the manufacturing equipment. When a cellulose acetate film is used as an optical material, the retardation value in the thickness direction needs to be low. The cellulose acetate solution obtained by the cooling dissolution method has a problem of low stability.
Further, the cellulose acetate film produced by the cooling dissolution method has a problem that the retardation value in the thickness direction is high. Japanese Patent Application Laid-Open No. 11-5851 discloses that
A cellulose acetate film having a total degree of acetyl substitution at the 2-position and the 6-position of not less than 2.67 and a total degree of acetyl substitution at the 2- and 3-positions of not more than 1.97. It has been disclosed. Producing a cellulose acetate film having a low retardation value in the thickness direction from a stable cellulose acetate solution by adjusting the degree of acetyl substitution at the 2-, 3- and 6-positions as described in the publication. Can be.

[0004]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. H11-5851
As described in Japanese Patent Application Laid-Open Publication No. H10-260, the physical properties and optical properties of cellulose acetate, a cellulose acetate solution or a cellulose acetate film can be adjusted by adjusting the degree of acetyl substitution at the 2-, 3-, and 6-positions. . However, in the method for producing cellulose acetate disclosed in JP-A-11-5851,
It is difficult to properly adjust the relationship between the sum of the acetyl substitution degrees at the 2- and 3-positions and the acetyl substitution degree at the 6-position. Further, the publication does not disclose a method for adjusting the relationship between the degree of acetyl substitution at the 2-position and the degree of acetyl substitution at the 3-position.

[0005] It is an object of the present invention to provide a cellulose acetate in which the relationship between the total degree of acetyl substitution at the 2-position and the 3-position and the degree of acetyl substitution at the 6-position is appropriately adjusted. Another object of the present invention is to provide a cellulose acetate in which the relationship between the degree of acetyl substitution at the 2-position and the degree of acetyl substitution at the 3-position is appropriately adjusted. Still another object of the present invention is to provide a cellulose acetate solution in which solubility and viscosity can be easily adjusted. Still another object of the present invention is to provide a cellulose acetate film having appropriate physical and optical properties.

[0006]

An object of the present invention is to provide a method for producing cellulose acetate according to the following (1):
Method for adjusting the acetyl substitution degree of cellulose acetate,
The following (3) to (5) cellulose acetate, the following (6) and (7) cellulose acetate solutions, the following (8) cellulose acetate film manufacturing method, and the following (9) and (10) cellulose acetate films Achieved by

(1) a step of synthesizing cellulose acetate by reacting cellulose with acetic acid or acetic anhydride in a solvent in the presence of a catalyst; A process for aging in the presence of from 10 to 10 mol% of water and a catalyst. (2) The cellulose acetate is aged in the presence of an acetyl group donor and a catalyst and in a condition in which the amount of water or alcohol is less than 10 mol% of the acetyl group donor, whereby the cellulose acetate is aged at the second, third, and sixth positions. A method for adjusting the degree of acetyl substitution of cellulose acetate, which comprises changing the degree of acetyl substitution of cellulose acetate. (3) 3450 to a wavenumber of 3550 cm ^-1 has an absorption maximum in the infrared absorption spectrum, cellulose acetate, wherein the half-width of the absorption maximum is 135 cm ^-1 or less.

(4) Cellulose acetate wherein the degree of acetyl substitution at the 2-, 3- and 6-positions satisfies the following formulas (I) to (III): (I) 2DS + 3DS <6DS × 4-1 .70 (II) 2DS + 3DS <−6DS × 4 + 5.70 (III) 2DS + 3DS> 1.80 [where 2DS is the degree of acetyl substitution at the 2-position; 3D
S is the degree of acetyl substitution at position 3; and 6DS
Is the degree of acetyl substitution at the 6-position].

(5) Cellulose acetate characterized in that the degree of acetyl substitution at the 2-, 3- and 6-positions satisfies the following formulas (III) to (V): (III) 2DS + 3DS> 1.80 (IV) 3DS <2DS (V) 6DS> 0.80 wherein 2DS is the degree of acetyl substitution at the 2-position;
S is the degree of acetyl substitution at position 3; and 6DS
Is the degree of acetyl substitution at the 6-position].

(6) A cellulose acetate solution in which the cellulose acetate according to (3), (4) or (5) is dissolved in an organic solvent. (7) The cellulose acetate solution according to (6), wherein the organic solvent contains substantially no halogenated hydrocarbon. (8) a step of swelling the cellulose acetate according to (3), (4) or (5) with an organic solvent; a step of cooling the obtained swelling mixture to -100 to -10 ° C;
Heating the cooled mixture to 0 to 200 ° C. to obtain an organic solvent solution of cellulose acetate; and applying the obtained organic solvent solution on a support to form a cellulose acetate film. A method for producing a cellulose acetate film.

(9) A cellulose acetate film comprising the cellulose acetate according to (3), (4) or (5). (10) 3450 to have an absorption maximum in the infrared absorption spectrum of a cellulose acetate originating at a wavenumber of 3550 cm ^-1, cellulose acetate film, wherein the half width of the maximum absorption is 135 cm ^-1 or less.

[0012]

As a result of the study of the present inventors, when the cellulose acetate is aged in the presence of an acetyl group donor and a catalyst, if the amount of water or alcohol is limited to less than 10 mol% of the acetyl group donor, It has been found that the degree of acetyl substitution at the 2-, 3- and 6-positions can be adjusted easily and appropriately. With respect to the degree of acetyl substitution at the 2-, 3- and 6-positions, an effective means of regulation was obtained, so that the above-mentioned formulas (I) to
Cellulose acetate having an appropriate relationship between the sum of the degree of acetyl substitution at the 2-position and the 3-position and the degree of acetyl substitution at the 6-position that satisfies the formula (III) or the cellulose acetate satisfying the above formulas (III) to (V) The relationship between the degree of acetyl substitution at the 2-, 3- and 6-positions makes it possible to obtain cellulose acetate suitable. By using cellulose acetate in which the degree of acetyl substitution at the 2-, 3-, and 6-positions is appropriately adjusted, a cellulose acetate solution in which solubility and viscosity can be easily adjusted can be easily prepared. Further, according to the present invention, a cellulose acetate film having appropriate physical properties and optical properties can be easily produced.

As a result of further study by the present inventors, it has been found that cellulose acetate having good solubility has a unique infrared absorption spectrum. That is, 3
The wave number of 450 to 3550 cm ^-1 has an absorption maximum in the infrared absorption spectrum of a cellulose acetate origin, the half-value width of the maximum absorption is to use cellulose acetate having a 135 cm ^-1 or less, the cellulose acetate is readily soluble Solution is obtained. By using the cellulose acetate solution, a cellulose acetate film having appropriate physical and optical properties can be produced.

[0014]

DETAILED DESCRIPTION OF THE INVENTION [Production of Cellulose Acetate]
As the cellulose as the cellulose acetate raw material, cotton linter or wood pulp can be used. Raw cellulose may be mixed and used. Cellulose acetate is synthesized by reacting cellulose acetate with acetic acid or acetic anhydride in the presence of a catalyst in a solvent. It is common to use acetic acid as solvent, sulfuric acid as catalyst and acetic anhydride as acetyl donor.

The basic principle of the method for synthesizing cellulose acetate is described in Migita et al., Wood Chemistry, pp. 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using acetic anhydride (acetyl group donor) -acetic acid (solvent) -sulfuric acid (catalyst). Specifically, after a cellulose raw material such as wood pulp is pretreated with an appropriate amount of acetic acid, it is put into a pre-cooled acetylation mixed solution and esterified with acetic acid to synthesize cellulose acetate. The acetylation mixture generally contains acetic acid as a solvent, acetic anhydride as an acetyl group donor (esterifying agent), and sulfuric acid as a catalyst. The acetic anhydride is usually used in a stoichiometric excess of the sum of the cellulose reacted therewith and the water present in the system. After completion of the acetylation reaction, a neutralizing agent (for example, sodium, potassium, calcium, magnesium, iron, or the like) is used to hydrolyze excess acetic anhydride remaining in the system and neutralize a part of the esterification catalyst. An aqueous solution of aluminum, zinc or ammonium carbonate, acetate or oxide) is added.

In the conventional method, the obtained cellulose acetate is saponified and ripened by keeping the cellulose acetate at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, residual sulfuric acid). The cellulose acetate having a substitution degree and a polymerization degree is changed. Then, when the desired cellulose acetate is obtained, the catalyst remaining in the system is completely neutralized using the neutralizing agent as described above, or is neutralized with water or diluted water. Put cellulose acetate solution in acetic acid (or put water or dilute acetic acid in cellulose acetate solution)
Then, the cellulose acetate was separated and washed and stabilized to obtain cellulose acetate. The above-mentioned Japanese Patent Application Laid-Open No. 11-5851 discloses that cellulose acetate having a relatively high degree of substitution at the 6-position can be obtained by selecting a small amount of sulfuric acid in the acetylation reaction. However, cellulose acetate produced under such low sulfuric acid conditions may cause cloudiness in a solution or may cause problems such as poor solubility. The acetylation reaction proceeds while the solid-phase cellulose raw material undergoes acetylation and is gradually dissolved. In the reaction under the low sulfuric acid condition, a qualitative difference was caused between the previously dissolved portion and the later dissolved portion, and as a result, it can be considered that heterogeneous cellulose acetate was produced.

As a result of the study by the present inventors, cellulose acetate was converted to an acetyl group donor, 0.1% of the acetyl group donor.
To 10 mol% (0.1 mol% or more and less than 10 mol%)
It has been found that aging in the presence of water or an alcohol and a catalyst can easily and appropriately adjust the degree of acetyl substitution at the 2-, 3- and 6-positions. When the degree of acetyl substitution is adjusted continuously with the synthesis reaction of cellulose acetate, 0.1 mol% or more of water or alcohol is required for the decomposition of sulfate, but the cellulose acetate already produced is required. When adjusting the degree of acetyl substitution, water or alcohol may not be present. An acetyl group donor has an acetyl group (—COCH ₃ ) in the molecule.
And a compound capable of providing an acetyl group to an unreacted hydroxyl group (-OH) of cellulose acetate by a transesterification reaction or an ester forming reaction in the presence of a catalyst. According to the study of the present inventors, when the amount of water or alcohol is 10 mol% or more of the acetyl group donor,
Cellulose acetate having a high degree of substitution (the total acetyl substitution degree at the 2-, 3- and 6-positions is 2.70 or more)
The acetyl group is easily separated. Conversely, when the amount of water or alcohol present is reduced to less than 10 mol% (preferably less than 7 mol%) of the acetyl group donor, the acetylation reaction of the free hydroxyl group (particularly the hydroxyl group at the 6-position) causes the elimination reaction. Dominates over Therefore, by adjusting the amount of water or alcohol to be less than 10 mol% of the acetyl group donor, the reaction between the acetyl group donor and cellulose acetate can be reversible. That is, as shown in the following formula, a glucose unit having an unreacted hydroxyl group at the 2-, 3- or 6-position and an acetyl group donor (R-COCH
₃ : R is 2-position, 3-position and 6-position by adjusting the equilibrium conditions with HO, alkoxy group, aryloxy group).
Acetyl substitution degree can be adjusted effectively.

[0018]

Embedded image

The catalyst in the aging step is preferably an acid or a metal (eg, titanium, tin) ion. As the acid, not only ordinary protonic acid but also Lewis acid is effective. The ripening reaction is performed with an acetate (acetyl group donor)
-When the reaction is carried out in an alcohol (solvent) system, a metal alkoxide or an organic base (eg, dialkylaminopyridine, N
-Methylimidazole) can also be used as a catalyst. The most preferred catalyst is an acid. The acid catalyst is a strong acid (eg, sulfonic acid, perchloric acid, sulfuric acid, boron trifluoride,
Tetrafluoroboronic acid) is preferred. Considering properties such as availability, stability, toxicity and corrosivity, sulfuric acid is most preferred. Under the reaction conditions of 100 ° C. or higher, acetic acid, which is an acetyl group donor, can be used as an acid catalyst. An aspect in which acetic acid also functions as an acetyl group donor and a catalyst is also included in the present invention. The amount of the catalyst used is determined in consideration of the catalyst function (acidity in the case of an acid catalyst) and the reaction temperature.

The aging reaction has conventionally been usually carried out in an acetic acid (acetyl group donor) -water (solvent) system.
However, the conventional aging reaction was carried out under the condition that water was present in an amount of 10 mol% or more based on acetic acid. Under such conditions, only the decomposition reaction of the ester bond of cellulose acetate proceeds, and the degree of substitution decreases. Therefore, the degree of acetyl substitution at the 2-, 3-, and 6-positions could not be adjusted by such an aging reaction. In the ripening reaction of the present invention, the degree of acetyl substitution at the 2-, 3- and 6-positions is reduced by limiting the amount of water or alcohol present to less than 10 mol% (preferably less than 7 mol%) of the acetyl donor. adjust. In the process of synthesizing cellulose acetate, an excess amount of acetic anhydride is generally used, but before the aging step, the excess acetic anhydride is hydrolyzed to acetic acid (the aging step does not include acetic anhydride). Is preferred.

In order to properly adjust the above-mentioned equilibrium reaction between the acetyl group donor and cellulose acetate, the reaction conditions in the aging step are set so that the reaction history parameter (R) defined by the following formula exceeds 20. It is preferable to adjust so that R is more preferably a value exceeding 30 and most preferably a value exceeding 40. R = ∫YZ / Xdt where X is the molar ratio of water or alcohol to acetyl donor in the reaction system; Y is the molar ratio of catalyst to acetyl donor in the reaction system; Is the temperature conversion factor (3 ^{(T-30) / 20} : T is the reaction temperature (° C.)); and t is the reaction time. Note that X is 0.1
If it is less than mol%, it is calculated as 0.1.

[Cellulose Acetate] By employing the above-described production method, it is possible to synthesize cellulose acetate in which the degree of acetyl substitution at the 2-, 3- and 6-positions is appropriately adjusted.

When a cellulose acetate having a degree of acetyl substitution at the 2-, 3- and 6-positions satisfy the following formulas (I) to (III), a cellulose acetate film having appropriate physical properties and optical properties is produced. be able to. (I) 2DS + 3DS <6DS × 4-1.70 (II) 2DS + 3DS <−6DS × 4 + 5.70 (III) 2DS + 3DS> 1.80 In the formulas (I) to (III), 2DS is the degree of acetyl substitution at the 2-position. , 3DS is the degree of acetyl substitution at the 3-position, and 6DS is the degree of acetyl substitution at the 6-position.

FIG. 1 is a graph for explaining the definition of the degree of acetyl substitution in the formulas (I) to (III) and the degree of acetyl substitution in the cellulose acetates of the examples and comparative examples. The horizontal axis of the graph is the sum of the acetyl substitution degree at the 2-position (2DS) and the acetyl substitution degree at the 3-position (2DS) (2DS + 3DS).
The vertical axis of the graph indicates the degree of acetyl substitution at the 6-position (6D
S). The formulas (I) to (III) correspond to an isosceles triangular area hatched in the graph. The black circles 1 to 5, 7 to 10 correspond to Examples 1 to 5, 7 to 10, respectively.
The white circle C1 is the cellulose acetate of Comparative Example 1.
(Comparative Example 2 is out of the range of the graph).

When a cellulose acetate having a degree of acetyl substitution at the 2-, 3- and 6-positions satisfy the following formulas (III) to (V), a cellulose acetate solution having appropriate viscosity and solubility is prepared. can do. (III) 2DS + 3DS> 1.80 (IV) 3DS <2DS (V) 6DS> 0.80 In formulas (III) to (V), 2DS is the degree of acetyl substitution at the 2-position, and 3DS is the degree of acetyl substitution at the 3-position. The degree of acetyl substitution, and 6DS is the degree of acetyl substitution at position 6.

FIG. 2 is a graph for explaining the definition of the acetyl substitution degree of the formulas (III) and (IV) and the acetyl substitution degree of the cellulose acetates of the examples and the comparative examples.
The horizontal axis of the graph is the degree of acetyl substitution at the second position (2DS), and the vertical axis of the graph is the degree of acetyl substitution at the third position (3DS). The formulas (III) and (IV) correspond to an isosceles triangular area hatched in the graph. The black circles 1 to 5, 7 to 10 correspond to Examples 1 to 5, 7 to 10, respectively.
, And white circles C1 and C2 are the cellulose acetates of Comparative Examples 1 and 2.

Cellulose acetate satisfying all the formulas (I) to (V) is most preferred. The degree of acetyl substitution at the 2-, 3- and 6-positions of cellulose acetate was determined by 13 C-NMR after propionylation of cellulose acetate.
Can be determined. The details of the measurement method are described in Tezuka et al. (Carbohydr. Res. 273 (1995) 83-91).

Further, the degree of acetyl substitution at the 2-, 3- and 6-positions preferably satisfies the following formula (VI). (VI) 2DS + 3DS-6DS <1 In formula (VI), 2DS is the degree of acetyl substitution at position 2, 3DS is the degree of acetyl substitution at position 3, and 6DS is the degree of acetyl substitution at position 6. is there. Equation (VI)
Is the area on the left side of the solid line (2DS + 3DS-6DS = 1) shown as (VI) in FIG.

[0029] Infrared absorption spectrum] Cellulose acetate has an absorption maximum in the infrared absorption spectrum in the wave number of 3450 to 3550 cm ^-1, is preferably half-width of the absorption maximum is 135 cm ^-1 or less. More preferably, the absorption maximum exists at a wave number of 3455 to 3540 cm ^-1 , and most preferably at a wave number of 3460 to 3530 cm ^-1 . The half width of the absorption maximum is
Still more preferably 130 cm ^-1 or less, 125
Most preferably, it is not more than cm ^-1 . The infrared absorption spectrum of cellulose acetate is measured after preparing a cellulose acetate film by a solvent casting method. A specific measurement procedure will be described later in Example 7.

From the infrared absorption spectrum obtained by the measurement, the absorption maximum and the half width are determined. The analysis of the absorption band of the infrared absorption spectrum is described in Hiroyuki Tadokoro, Structures of Polymers (Kagaku Dojin, 1976), pp. 219-221. FIG. 3 is a chart for explaining the half width of the infrared absorption spectrum. In the spectrum shown in FIG. 3, an absorption band of a hydroxyl group is observed at a wavelength around 3500 cm ^-1 . High wavenumber side of absorption band (3700cm
^-1 ) and a base line (AB) in contact with the base (B) on the low wavenumber side (around 3250 cm ^-1 ). A vertical line is drawn on the horizontal axis from the peak (E) of the absorption band. An intersection (C) between the perpendicular and the baseline (AB) is determined, and an intermediate point (D) between the peak (E) and the intersection (C) is determined. Through the midpoint (D), the baseline (AB)
Draw a straight line parallel to and obtain two intersections (A ′, B ′) with the spectrum. A perpendicular line is drawn from the two intersections (A ′, B ′) to the horizontal axis, and the width of the two intersections on the horizontal axis is defined as the half-value width (Δν1 / 2) of the band. When a plurality of absorption peaks exist in the absorption band (wave number of 3450 to 3550 cm ⁻¹ ), the maximum absorption peak may be used as a measurement standard (E in FIG. 3).

Regarding the infrared absorption spectrum of methylcellulose, a report by Kondo (Kondo, Cellulose, 4, 281 (1
997)). It is preferable that the manufactured cellulose acetate film also has an absorption maximum at a wave number of 3450 to 3550 cm ^-1 in the infrared absorption spectrum measured in the same manner, and the half width of the absorption maximum is 135 cm ^-1 or less. However, in the manufactured cellulose acetate film, additives (for example, infrared absorbers)
May affect the absorption spectrum. Therefore, in the manufactured cellulose acetate film, an infrared absorption spectrum originating from cellulose acetate is measured.

[Organic Solvent] Cellulose acetate is generally dissolved in an organic solvent to prepare a cellulose acetate solution and used for various purposes (for example, film production). Examples of organic solvents include ketones, esters, ethers, hydrocarbons and alcohols. In addition,
Technically, halogenated hydrocarbons such as methylene chloride can be used without any problem, but from the viewpoint of the global environment and work environment, it is preferable that the organic solvent contains substantially no halogenated hydrocarbons. “Substantially free” means that the proportion of halogenated hydrocarbon in the organic solvent is less than 5% by mass (preferably less than 2% by mass). Also,
It is preferable that no halogenated hydrocarbon such as methylene chloride be detected at all from the produced cellulose acetate film.

The organic solvent preferably contains a solvent selected from ethers having 2 to 12 carbon atoms, ketones having 3 to 12 carbon atoms and esters having 2 to 12 carbon atoms. Ethers, ketones and esters may have a cyclic structure. Functional groups of ether, ketone and ester (i.e., -O-, -CO- and-
Compounds having two or more of any of COO-) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any one of the functional groups.

Examples of the ether having 2 to 12 carbon atoms include dimethyl ether, methyl ethyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole and phenetole. included. Examples of the ketone having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone, methylcyclohexanone and acetylacetone. 2 carbon atoms
Examples of -12 esters include methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. A methyl acetate organic solvent containing 50% by mass or more of methyl acetate (methyl acetate) is particularly preferably used. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

Particularly preferred organic solvents are mixed solvents of three different solvents, wherein the first solvent is a ketone having 3 to 12 carbon atoms and a ketone having 2 to 12 carbon atoms.
Wherein the second solvent is selected from linear monohydric alcohols having 1 to 5 carbon atoms, and the third solvent is an alcohol having a boiling point of 30 to 170 ° C and a boiling point of 30 to 170 ° C. Hydrocarbons. The ketone and ester of the first solvent are as described above. Note that two types of the first solvent may be used in combination. For example, a mixed solvent of a ketone (eg, acetone) and an ester (eg, methyl acetate) may be used as the first solvent. The second solvent is selected from linear monohydric alcohols having 1 to 5 carbon atoms. 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 second solvent is specifically methanol, ethanol, 1
-Propanol, 2-propanol, 1-butanol,
It is selected from 2-butanol, 1-pentanol, 2-pentanol and 3-pentanol. The linear monohydric alcohol preferably has 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, and still more preferably 1 or 2 carbon atoms.
Is most preferred. Ethanol is particularly preferably used.

The third 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. The hydrocarbon portion is
Preferably, it 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 (78.325C), 1-propanol (97.15C), 2-propanol (82.4).
C), 1-butanol (117.9C), 2-butanol (99.5C), t-butanol (82.45C),
1-pentanol (137.5 ° C), 2-methyl-2-
Butanol (101.9 ° C.), cyclohexanol (1
61 ° C.), 2-fluoroethanol (103 ° C.), 2,
2,2-trifluoroethanol (80 ° C), 2,2
3,3-tetrafluoro-1-propanol (109
C), 1,3-difluoro-2-propanol (55
° C), 1,1,1,3,3,3-hex-2-methyl-
2-propanol (62 ° C), 1,1,1,3,3,3
-Hexafluoro-2-propanol (59 ° C), 2,
2,3,3,3-pentafluoro-1-propanol (80 ° C), 2,2,3,4,4,4-hexafluoro-1-butanol (114 ° C), 2,2,3,3 4,
4,4-heptafluoro-1-butanol (97 ° C.),
Perfluoro-tert-butanol (45 ° C), 2,2
3,3,4,4,5,5-octfluoro-1-pentanol (142 ° C.), 2,2,3,3,4,4-hexafluoro-1,5-pentanediol (111.5
° C), 3,3,4,4,5,5,6,6,7,7,8,
8,8-tridecafluoro-1-octanol (95
° C), 2,2,3,3,4,4,5,5,6,6,7,
7,8,8,8-pentadecafluoro-1-octanol (165 ° C.), 1- (pentafluorophenyl) ethanol (82 ° C.) and 2,3,4,5,6-pentafluorobenzyl alcohol (115 ° C.) ) Is included.

As for the alcohol, the definition of the second solvent overlaps with that of the second solvent. However, any alcohol of a different kind from the alcohol used as the second solvent can be used as the third solvent. For example, when ethanol is used as the second solvent, other alcohols (methanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol) included in the definition of the second solvent are used. , 2-pentanol or 3-pentanol)
May be used as the third solvent. The hydrocarbon may be linear, branched or cyclic. Both aromatic hydrocarbons and aliphatic hydrocarbons can be used. Aliphatic hydrocarbons may be saturated or unsaturated. Is more preferable. Examples of the hydrocarbon include cyclohexane (boiling point: 80.7 ° C.),
Hexane (69 ° C), benzene (80.1 ° C), toluene (110.6 ° C) and xylene (138.4-14)
4.4 ° C).

The first solvent is preferably contained in the mixed solvent in an amount of 50 to 95% by mass, more preferably 60 to 92% by mass, and more preferably 65 to 90% by mass.
More preferably, the content is more preferably 70 to 88% by mass. The second solvent is preferably contained in an amount of 1 to 30% by mass, more preferably 2 to 27% by mass, still more preferably 3 to 24% by mass, and more preferably 4 to 22% by mass. Most preferred. The third solvent is preferably contained in an amount of 1 to 30% by mass, more preferably 2 to 27% by mass, still more preferably 3 to 24% by mass, and more preferably 4 to 22% by mass. Most preferred.
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. As a solvent other than the above-mentioned three kinds of solvents, ethers having 3 to 12 carbon atoms (eg, diisopropyl ether, dimethoxyethane, diethoxyethane,
1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole, phenetole) or nitromethane may be used in combination.

The boiling point of the organic solvent is preferably from 20 to 300 ° C., more preferably from 30 to 200 ° C., even more preferably from 40 to 100 ° C., and most preferably from 50 to 80 ° C. preferable. In the present invention, it is preferable to form a solution by dissolving cellulose acetate in the above organic solvent by a cooling dissolution method. The cooling dissolution method includes a swelling step, a cooling step, and a heating step. In addition, even if it is an organic solvent which can dissolve cellulose acetate at room temperature, there is an effect that a uniform solution can be obtained quickly by the cooling dissolution method.

[Swelling Step] In the swelling step, cellulose acetate and an organic solvent are mixed, and the cellulose acetate is swelled by the solvent. The temperature of the swelling process is-
The temperature is preferably from 10 to 55 ° C. It is usually performed at room temperature. The ratio of cellulose acetate and organic solvent is
It is determined according to the concentration of the solution finally obtained. Generally, the amount of cellulose acetate in the mixture is between 5 and 3
It is preferably 0% by mass, more preferably 8 to 20% by mass, and most preferably 10 to 15% by mass. It is preferable that the mixture of the solvent and the cellulose acetate is stirred until the cellulose acetate swells sufficiently. The stirring time is preferably from 10 to 150 minutes, more preferably from 20 to 120 minutes. In the swelling step, components other than the solvent and cellulose acetate, for example, a plasticizer, a deterioration inhibitor,
A dye or an ultraviolet absorber may be added.

[Cooling Step] In the cooling step, the swollen mixture is cooled to -100 to -10 ° C. The cooling temperature is
Preferably, the temperature is such that the swelling mixture solidifies. The cooling rate is preferably 4 ° C / min or more, more preferably 8 ° C / min or more, and most preferably 12 ° C / min or more. The cooling rate is preferably as high as possible, but the theoretical upper limit is 10,000 ° C./sec.
C second is a technical upper limit, and 100 C / second 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 final cooling temperature is reached. The examples described in JP-A-9-95544, JP-A-9-95557 and JP-A-9-95538 have a temperature of 3 ° C.
/ Min cooling rate. In the cooling step, it is desirable to use an airtight container in order to avoid water contamination due to dew condensation during cooling. If the pressure is reduced during cooling, the cooling time can be shortened. To perform decompression,
It is desirable to use a pressure-resistant container. Various methods or devices can be employed as specific cooling means.

For example, when the swollen mixture is conveyed in a cylindrical container while stirring, and the swollen mixture is cooled from around the container, the swollen mixture can be cooled quickly and uniformly. For that purpose, a cylindrical container, a spiral conveying mechanism provided in the container for conveying the swollen mixture while stirring the swollen mixture, and a periphery of the container for cooling the swollen mixture in the container. Is preferably used. Further, a solvent cooled to -105 to -15 ° C can be added to the swelling mixture to cool more quickly.

Further, the swollen mixture is poured into a liquid cooled to -100 to -10 ° C. to a diameter of 0.1 to 20.0 m.
swelling mixture by extruding into a thread of m
It is also possible to cool the swollen mixture more quickly.
There is no particular limitation on the liquid used for cooling. When using a method of cooling the swollen mixture by extruding the swollen mixture into a cooled liquid into a thread, a step of separating the thread-shaped swollen mixture and the liquid for cooling is performed between the cooling step and the heating step. Is preferred. In the cooling step, since the swelling mixture is gelled into a thread, the swelling mixture and the cooling liquid can be easily separated. For example, it is possible to remove the thread-like swollen mixture from the liquid using a net. Instead of a net, a plate-like material having slits or holes may be used. The material of the net or plate is not particularly limited as long as the material does not dissolve in the liquid. Nets and plate-like objects can be manufactured from various metals and various plastic materials. The size of the mesh, the width of the slit, and the size of the hole are adjusted according to the diameter of the thread so that the thread does not pass through. Further, a belt for conveying the thread-like swollen mixture from the cooling device to the heating device may be formed in a mesh shape, and the separation and the conveyance may be simultaneously performed.

[Heating Step] In the heating step, the cooled swelled mixture is heated to 0 to 200 ° C. The final temperature of the heating step is usually room temperature. The heating rate is preferably 4 ° C / min or more, more preferably 8 ° C / min or more, and most preferably 12 ° C / min or more. The heating rate is preferably as fast as possible.
Seconds is the theoretical upper limit, 1000 ° C. seconds is the technical upper limit, and 100 ° C./second is the practical upper limit. 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 heating is started until the temperature reaches the final heating temperature. Incidentally, Japanese Patent Application Laid-Open No. 9-95
Nos. 544, 9-95557 and 9-95538
In the examples described in the above publications, the heating rate is about 3 ° C./min. Heating while applying pressure can shorten the heating time. In order to perform pressurization, it is desirable to use a pressure-resistant container. If the dissolution is insufficient, the steps from the cooling step to the heating step may be repeated. Whether or not the dissolution is sufficient can be determined only by visually observing the appearance of the solution. Various methods or devices can be adopted as specific heating means.

For example, when the swollen mixture is transported in a cylindrical container while being stirred, and the swollen mixture is heated from around the container, the swollen mixture can be quickly and uniformly heated. For this purpose, a cylindrical container, a spiral transport mechanism provided in the container for transporting the swollen mixture in the cylindrical container while stirring the mixture, and a container for heating the swollen mixture in the container. A heating device including a heating mechanism provided in the periphery is preferably used.

In addition, 0.1 mm in diameter is introduced into the heated liquid.
By heating the swelling mixture by adding a thread-like swelling mixture having a thickness of 20.0 mm to 20.0 mm, the swelling mixture can be heated more quickly. In the case where a method of extruding the swelling mixture into a thread in the cooling step is employed, the thread-like swelling mixture may be introduced into a heating liquid. When the cooling step is performed by a method other than the thread extrusion, the swelled mixture cooled in the heating step is extruded into a heating liquid in a thread form. In the case where the thread-like extrusion is performed continuously, the produced cellulose acetate solution can be sequentially used as a liquid for heating the next swollen mixture. That is, the thread-like swelling mixture is put into the manufactured and heated cellulose acetate solution, and the mixture is quickly heated to obtain a cellulose acetate solution.

Further, the cooled swelling mixture is introduced into a cylindrical container, the flow of the swelling mixture is divided into a plurality of parts in the container, and the flow direction of the divided mixture is rotated in the container. By repeating the rotation, the swollen mixture can be heated from around the container. As described above,
Containers provided with partitions for dividing and rotating the flow of a substance are generally known as static mixers. A typical static mixer, Static MixerTM (Kenix), divides the material flow into two and rotates it clockwise 180 degrees, and the material flow into two. The counterclockwise elements that rotate 180 degrees counterclockwise are alternately arranged at 90 degrees in the container. Furthermore, the swollen mixture may be heated to a temperature equal to or higher than the boiling point of the solvent under a pressure adjusted so that the solvent does not boil. The temperature is determined according to the type of the solvent, but is generally from 60 to 200 ° C. The pressure is determined by the relationship between the temperature and the boiling point of the solvent, and is generally 1.2 to 20 kgw.
/ Cm ² .

[Treatment after Production of Solution] The produced solution can be subjected to processes such as concentration adjustment (concentration or dilution), filtration, temperature adjustment, and addition of components as required. The components to be added are determined according to the use of the cellulose acetate solution. In the case of a cellulose acetate film, typical additives are a plasticizer, a deterioration inhibitor (eg, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger),
Dyes and UV absorbers. Further, at this stage, it is preferable to add fine particles (preferably, a diluted solution of cellulose acetate in which the fine particles are dispersed).

[Fine Particles] The cellulose acetate film may contain fine particles having an average particle diameter of 1.0 μm or less. The fine particles function as a slip agent to improve the coefficient of kinetic friction of the film. It is preferable to use an inorganic compound as the fine particles. Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc,
Includes clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. Silicon dioxide, titanium dioxide and zirconium oxide are preferred,
Silicon dioxide is particularly preferred. Fine particles of inorganic compounds
A methyl group can be introduced into the particle surface by the surface treatment. For example, fine particles of silicon oxide may be treated with dichlorodimethylsilane or bis (trimethylsilyl) amine.

Fine particles of silicon dioxide are already commercially available (eg, Aerosil R972TM, R972DTM, R9
74TM, R812TM, manufactured by Nippon Aerosil Co., Ltd.). Also, there are commercially available zirconium oxide fine particles (eg,
Aerosil R976TM, R811TM, manufactured by Nippon Aerosil Co., Ltd.). The average particle size of the fine particles is preferably 1.0 μm or less. The average particle size is more preferably from 0.1 to 1.0 μm, most preferably from 0.1 to 0.5 μm. The fine particles are preferably used in an amount of 0.005 to 0.3% by mass, more preferably 0.01 to 0.1% by mass, based on the cellulose acetate. The fine particles may be added at any stage of the film manufacturing process described below. Preferably, a diluted solution having a composition similar to that of the organic solvent solution of cellulose acetate is prepared, and the fine particles are dispersed in the diluted solution. Then, when a film is formed from the mixed solution by mixing the organic solvent solution and the dilute solution containing the fine particles, a film in which the fine particles are uniformly dispersed can be manufactured.

[Plasticizer] A plasticizer is generally added to the cellulose acetate film. As the plasticizer, a phosphoric acid ester or a carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate,
Includes tricresyl phosphate, octyl diphenyl phosphate, triethyl phosphate and tributyl phosphate. Representative carboxylic esters include phthalic esters, citric esters, oleic esters and linoleic esters. Examples of phthalates include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dimethoxyethyl phthalate, dioctyl phthalate and diethylhexyl phthalate. Examples of the citrate include acetyltriethyl citrate and acetyltributyl citrate. Examples of oleic acid esters include butyl oleate. Examples of other carboxylic esters include ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, triacetin, methyl acetyl ricinoleate, dibutyl sebacate and various trimellitate esters. The amount of plasticizer added is
Generally, it is in the range of 0.1 to 40% by mass of the amount of cellulose acetate, and more preferably in the range of 1 to 20% by mass.

[Deterioration inhibitor] A degradation inhibitor may be added to the cellulose acetate film. Examples of the deterioration inhibitor include a peroxide decomposer, a radical inhibitor, a metal deactivator and an acid scavenger. As for the deterioration inhibitor, JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, and JP-A-5-271471.
There is a description in each publication of 07854. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (B
HT). The addition amount of the deterioration inhibitor
It is preferably 0.01 to 0.5% by mass of the cellulose acetate film, and 0.05 to 0.2% by mass.
Is more preferable.

[Ultraviolet Absorber] An ultraviolet absorber may be kneaded into the cellulose acetate film. The ultraviolet absorber improves the stability over time of the cellulose acetate film. It is desirable that the ultraviolet absorber has no absorption in the visible region. As the ultraviolet absorber, benzophenone-based compounds (eg, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,
2-hydroxy-4-n-octoxybenzophenone,
4-dodecyloxy-2-hydroxybenzophenone,
2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone), benttriazole compounds (eg,
-(2'-hydroxy-5-methylphenyl) benzotriazole, 2- (2'-hydroxy3 ', 5'-di-
t-butylphenyl) benzotriazole, 2 (2′-
Hydroxy-3'-di-t-butyl-5'-methylphenyl) benzotriazole) and salicylic acid-based compounds (eg, phenyl salicylate, methyl salicylate). The amount of the ultraviolet absorber added is preferably in the range of 0.5 to 20% by mass, more preferably in the range of 1 to 10% by mass, based on the cellulose acetate film.

[Dye] A light-piping phenomenon may be prevented by adding a dye to the cellulose acetate film. The hue of the dyeing is preferably gray. It is preferable to use a compound having excellent heat resistance in the production temperature range of the cellulose acetate film and excellent compatibility with the cellulose acetate as the dye. Two or more dyes may be used as a mixture.

[Film film formation] The preparation of an organic solvent solution (dope) of cellulose acetate by the cooling dissolution method described above is completely different from the preparation of a solution (stirring at room temperature or high temperature) in a usual solvent casting method. The step of forming a film from the solution obtained can be carried out in the same manner as in a usual solvent casting method. The cellulose acetate solution is cast on a support and the solvent is evaporated to form a film. The concentration of the solution before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the support is preferably finished in a mirror surface state. As the support, a drum or a band is used. For the casting and drying methods in a normal solvent casting method, see US Pat. Nos. 2,336,310 and 2,367,603;
No. 2492078, No. 2492977, No. 2492
No. 978, No. 2607704, No. 2739069,
No. 2739070, British Patent No. 640731, No. 73
Nos. 6892, JP-B Nos. 45-4554 and 4
9-5614, JP-A-60-176834 and JP-A-60-176834.
These are described in JP-A-203430 and JP-A-62-115035.

It is preferable that the cellulose acetate film formed on the support is peeled off from the support before the drying is completed (the organic solvent is 30% by mass or more of the film), and is further dried. For that purpose, gelation of the solution on the support needs to proceed rapidly. In order to promote the gelation of the solution, it is effective to use a poor solvent such as alcohol (the third solvent described above). Further, gelation can be promoted by improving the casting method. When the solution is cast on a support cooled to 10 ° C. or lower, gelation of the solution is promoted (described in Japanese Patent Publication No. 5-17844). The cooling of the support can be performed by using a refrigerant or cold air. In the method of cooling the support, the film on the support may be dried using a drying air for 2 seconds or more. The obtained film can be peeled off from the support, and further dried with high-temperature air having a temperature gradually changed from 100 to 160 ° C. to evaporate the residual solvent. Even if the solution is cast on a support heated to 30 ° C. or higher and then cooled to 20 ° C. or lower, gelation of the solution is promoted (Japanese Patent Application Laid-Open Nos. 61-148413 and 61-158413). No. in each publication). Heating of the support can be performed by attaching a heater to the surface of the support, blowing hot air, or passing hot water through the drum. It is preferable to raise the temperature immediately after casting the solution. In the initial stage of heating, a large amount of latent heat due to evaporation of the solvent is required. Therefore, in the initial stage of heating,
In addition to the above heating means, it is preferable to use auxiliary heating means such as hot air from the back surface or a heater (steam heater, infrared heater) from the back. The support can be cooled by forced cooling, such as blowing cold air or passing cold water through the drum, in addition to cooling.

The cellulose acetate film produced as described above can be used for various applications by utilizing its excellent optical properties and physical properties. In particular, the film of the present invention is effective for optical use of a liquid crystal display device. For optical applications, the cellulose acetate film may be subjected to an AG (anti-glare) treatment or an AR (anti-reflection treatment). In particular, when the AR process is used, the light transmittance of the film can be improved by about 3%. In the AR processing, specifically, an anti-reflection film (single layer, two-layer film, or a multilayer film of three or more layers) is provided on the film to reduce the reflection loss. Specific materials for the antireflection film are described in Thin Film Handbook (Ohm, December 10, 1983) at pages 818 to 821.

[Polarizing Plate Protective Film and Liquid Crystal Display Device] As an optical application of the cellulose acetate film, a polarizing plate protective film or a retardation plate of a liquid crystal display device is particularly preferable. A liquid crystal display generally has a liquid crystal display element and a polarizing plate. The liquid crystal display element includes a liquid crystal layer, a substrate for holding the liquid crystal layer, and an electrode layer for applying a voltage to the liquid crystal. Both the substrate and the electrode layer are manufactured using a transparent material for display. As the transparent substrate, a thin glass plate or a resin film is used. In the case of a liquid crystal display device that requires some flexibility, it is necessary to use a resin film. The liquid crystal substrate is required to have low birefringence and heat resistance in addition to high transparency. A liquid crystal display device may be provided with a phase difference plate. The retardation film is a birefringent film for removing coloring of the liquid crystal screen and realizing black and white. The retardation plate is also manufactured using a resin film.
The retardation plate is required to have a high birefringence. The polarizing plate is
It consists of a protective film and a polarizing film. The polarizing film is a resin film using iodine or a dichroic dye as a deflecting element.
The protective film is provided on one side or both sides of the polarizing film for the purpose of protecting the polarizing film. When a protective film is provided on only one surface of the polarizing film, the above-described liquid crystal substrate generally functions as a protective film on the other surface. Since the polarizing plate protective film is required to have transparency and a low birefringence (low retardation value), the cellulose acetate film of the present invention is particularly advantageously used.

As the polarizing film of the polarizing plate, there are an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. Each polarizing film is generally manufactured using a polyvinyl alcohol-based film. The polarizing plate protective film preferably has a thickness of 25 to 350 μm, and 50 to 2 μm.
More preferably, it has a thickness of 00 μm. An ultraviolet absorber, a slipping agent, a deterioration inhibitor or a plasticizer may be added to the protective film. A surface treatment film may be further provided on the polarizing plate protective film. The functions of the surface treatment film include a hard coat, an anti-fog treatment, an anti-glare treatment and an anti-reflection treatment. The polarizing plate and its protective film are described in JP-A-4-24-2.
Nos. 19703, 5-212828 and 6-51
No. 117 is described in each publication.

[0060]

EXAMPLES Example 1 (Synthesis Step of Cellulose Acetate) Wood pulp having an α-cellulose content of about 97% by mass (water content: 7.31% by mass) was crushed. 14 against 302.1 g of pulp
After 0 g of glacial acetic acid was uniformly dispersed and stirred, the mixture was allowed to stand at room temperature for 90 minutes. The pulp was charged into a pre-cooled mixture of 769.7 g of acetic anhydride, 1170.3 g of acetic acid and 23.08 g of 98% sulfuric acid, and mixed. The reaction temperature was increased from 0 ° C. at the start of the reaction to 60
The temperature was raised linearly to 7 ° C. and kept at 37 ° C. for a further 90 minutes. Thus, cellulose acetate was synthesized.

(Aging Step of Cellulose Acetate) 62.05 g of an aqueous acetic acid solution was added to the synthesized cellulose acetate solution, the temperature was raised to 47 ° C., and the mixture was kept for 90 minutes to ripen the cellulose acetate. The mixing ratio was 1658 parts by mass of acetic acid (acetyl group donor), 23.3 parts by mass of water, and 22.6 parts by mass of sulfuric acid (catalyst) based on 499 parts by mass of cellulose acetate. Therefore, the amount of water based on acetic acid (acetyl group donor) was 4.68 mol%. The obtained solution was kept at 30 ° C. for 3 hours to ripen the cellulose acetate. The value of the reaction history parameter (R = ∫YZ / Xdt) in the aging step was calculated to be 32.

(Post-treatment) After the completion of ripening, 188 g of a 24% by mass aqueous magnesium acetate solution was added and stirred. The resulting solution was added to about 6 liters of a 10% by mass aqueous acetic acid solution with vigorous stirring. And dried at 50 ° C.

(Analysis of Cellulose Acetate) For the produced cellulose acetate, the degree of substitution at the 2-position (2D
S) Degree of substitution at position 3 (3DS), degree of substitution at position 6 (6D
S) and the degree of polymerization were measured. The measurement results are shown in Table 1. In addition, the substitution degree at the second position (2DS) and the substitution degree at the third position (3DS)
DS) and the degree of substitution at the 6-position (6DS)
And, in the graph of FIG.
The degree of substitution was measured by Tezuka, Carbohydr. Res. 273,
83 (1995)). That is, the free hydroxyl group of the sample cellulose acetate is propionylated with propionic anhydride in pyridine. The obtained sample is dissolved in deuterated chloroform, and the spectrum of carbon 13 is measured. The signal of the carbonyl carbon of the acetyl group is 169
2 to 3 from high magnetic field
The signal of the carbonyl carbon of the propionyl group appears in the same order in the region from 172 ppm to 174 ppm. The distribution of acetyl groups in the original cellulose acetate can be determined from the ratios of acetyl and propionyl at the corresponding positions.

Example 2 (Aging Step of Cellulose Acetate) 200 g of commercially available cellulose acetate (having a degree of polymerization of 360 obtained by acetylation of cotton linter under ordinary conditions and a degree of substitution of 2.84 by NMR measurement) was used. 1167 ml of dichloromethane
And 834 ml of acetic acid, and dichloromethane was evaporated and distilled off by a rotary evaporator. 2050 g of acetic acid, 2.65 g of water and 7 of perchloric acid
24.4 g of a 0 mass% aqueous solution was added to dissolve the cellulose acetate. The amount of water relative to acetic acid (acetyl group donor) (the sum of the amount of water added and the amount of water contained in the aqueous solution of perchloric acid) was 1.63 mol%. The obtained solution was kept at 30 ° C. for 3 hours to ripen the cellulose acetate. Reaction history parameter (R
= ∫YZ / Xdt) was 55.

(Post-treatment) After aging, sodium acetate (1.75 parts by mass with respect to 1 part by mass of a 70% by mass aqueous solution of perchloric acid) equivalent to 2 equivalents to perchloric acid was added.
After thorough stirring, 7.5 liters of water was slowly added with vigorous stirring to form a precipitate. The precipitate was washed with running water until the odor of acetic acid disappeared, centrifuged, and then washed with running water and centrifuged for 3 hours, and dried at 50 ° C.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 1. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
Plotted as 2 black circles.

Example 3 (Aging Step of Cellulose Acetate) 200 g of the commercially available cellulose acetate used in Example 2 was dissolved in a mixture of 1167 ml of dichloromethane and 834 ml of acetic acid, and dichloromethane was evaporated by a rotary evaporator to distill off. did. 2050 g of acetic acid, 2.65 g of water, and 24.4 g of a 70% by mass aqueous solution of perchloric acid were added to dissolve cellulose acetate. The amount of water relative to acetic acid (acetyl group donor) (the sum of the amount of water added and the amount of water contained in the aqueous solution of perchloric acid) was 1.63 mol%. The above solution was kept at 30 ° C. for 5 hours to ripen the cellulose acetate. When the value of the reaction history parameter (R = ∫YZ / Xdt) in the aging step was calculated,
92.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 1. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
Plotted as 3 solid circles.

Example 4 (Aging Step of Cellulose Acetate) 200 g of the commercially available cellulose acetate used in Example 2 was dissolved in a mixture of 1167 ml of dichloromethane and 834 ml of acetic acid, and dichloromethane was evaporated by a rotary evaporator to distill off. did. 2050 g of acetic acid, 18.35 g of water and 24.4 g of a 70% by mass aqueous solution of perchloric acid were added,
Cellulose acetate was dissolved. The amount of water relative to acetic acid (acetyl group donor) (the sum of the amount of water added and the amount of water contained in the aqueous solution of perchloric acid) was 4.18 mol%. The above solution was kept at 30 ° C. for 10 hours to ripen the cellulose acetate. The value of the reaction history parameter (R = ∫YZ / Xdt) in the aging step was calculated to be 72.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 1. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
4 are plotted as solid circles.

Example 5 (Aging Step of Cellulose Acetate) 200 g of the commercially available cellulose acetate used in Example 2 was dissolved in a mixed solution of 1167 ml of dichloromethane and 834 ml of acetic acid. did. 2050 g of acetic acid, 18.35 g of water and 24.4 g of a 70% by mass aqueous solution of perchloric acid were added,
Cellulose acetate was dissolved. The amount of water relative to acetic acid (acetyl group donor) (the sum of the amount of water added and the amount of water contained in the aqueous solution of perchloric acid) was 4.18 mol%. The above solution was kept at 30 ° C. for 15 hours to ripen the cellulose acetate. The value of the reaction history parameter (R = ∫YZ / Xdt) in the aging step was calculated to be 107.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 1. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
5 are plotted as black circles.

Comparative Example 1 (Aging Step of Cellulose Acetate) 200 g of the cellulose acetate synthesized in Example 1 was added to dichloromethane 11
It was dissolved in a mixture of 67 ml and 834 ml of acetic acid, and dichloromethane was evaporated and removed by a rotary evaporator. 2050 g of acetic acid, 54.13 g of water and 24.4 g of a 70% by mass aqueous solution of perchloric acid were added to dissolve the cellulose acetate. The amount of water relative to acetic acid (acetyl group donor) (the sum of the amount of water added and the amount of water contained in the aqueous solution of perchloric acid) was 10.00 mol%. The above solution was kept at 30 ° C. for 20 hours to ripen the cellulose acetate. The value of the reaction history parameter (R = ∫YZ / Xdt) in the aging step was calculated to be 60.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 1. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
Plotted as open circles for C1.

Comparative Example 2 (Aging Process of Cellulose Acetate) 200 g of cellulose acetate synthesized in Example 1 was added to dichloromethane 11
It was dissolved in a mixture of 67 ml and 834 ml of acetic acid, and dichloromethane was evaporated by a rotary evaporator and distilled off. 2050 g of acetic acid, 54.13 g of water and 24.4 g of a 70% by mass aqueous solution of perchloric acid were added to dissolve the cellulose acetate. Acetic acid (acetyl donor)
(The sum of the amount of water added and the amount of water contained in the aqueous solution of perchloric acid) was 10.00 mol%. The above solution was kept at 30 ° C. for 30 hours to ripen the cellulose acetate. The value of the reaction history parameter (R = ∫YZ / Xdt) in the aging step was calculated to be 90.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 1. Further, regarding the substitution degree at the 2-position (2DS) and the substitution degree at the 3-position (3DS),
In the graph of FIG. 2, it is plotted as a white circle of C2 (FIG. 1).
Then, out of service area).

[0077]

[Table 1] Table 1 ──────────────────────────────────── Cellulose Amount of water Paramecellulose acetate Degree of substitution acetate (mol%) Data R 2DS 3DS 6DS Degree of polymerization ─────────────────────────────────── ─ Example 1 4.68 32 0.959 0.955 0.940 284 Example 2 1.63 55 0.962 0.960 0.932 302 Example 3 1.63 92 0.960 0.953 0. 943 284 Example 4 4.18 72 0.937 0.917 0.932 305 Example 5 4.18 107 0.929 0.896 0.940 291 Comparative Example 1 10.00 60 0.917 0.869 0 .898 350 Comparative Example 2 10.00 90 0.882 0 .826 0.907 339

Example 6 (Production of Cellulose Acetate Film) At room temperature, 17 parts by mass of the cellulose acetate obtained in Example 1 was mixed with a mixed solvent of methyl acetate / methanol / n-butanol (mixing ratio = 80/15/5). 80.28 parts by mass) and 2.72 parts by mass of triphenyl phosphate (plasticizer) were mixed. At room temperature, the cellulose acetate did not dissolve and swelled in the mixed solvent. The resulting swollen mixture is
A slurry was formed without dissolving. Next, the swelling mixture was placed in a double-layered container. The water / ethylene glycol mixture was poured as a coolant into the outer jacket while stirring the mixture slowly. Thereby, the mixture in the inner container was cooled to −30 ° C. (cooling rate: 8 ° C./min). Cooling with the refrigerant was continued until the mixture was uniformly cooled and solidified (30 minutes).

[0079] The refrigerant in the jacket outside the container was removed and warm water was instead poured into the jacket. At a stage where the sol formation of the content has progressed to some extent, stirring of the content was started. In this way, the mixture was heated to room temperature (heating rate: 8).
° C / min). Further, the above cooling and heating operations were repeated once. When the state of the solution (or slurry) obtained by the cooling dissolution method was observed while standing at room temperature (23 ° C.), transparency and uniformity were maintained even after aging for 20 days. The properties and solution stability were shown.

The obtained solution was cast using a band casting machine having an effective length of 6 m so that the dry film thickness became 100 μm. The band temperature was 0 ° C. After drying for 2 seconds, the film was peeled off from the band and dried for 100 seconds.
The film was dried stepwise at 3 ° C. for 3 minutes, 130 ° C. for 5 minutes, and 160 ° C. for 5 minutes while fixing the edges of the film to evaporate the remaining solvent. Thus, a cellulose acetate film was produced. The obtained film was further dried at 120 ° C. for 3 hours. The cellulose acetate film showed good optical properties (high optical isotropy and transparency).

[Example 7] (Synthesis process of cellulose acetate) 9.2 parts by mass of sulfuric acid, 276 parts by mass of acetic anhydride and 551 parts by mass of acetic acid were added to 100 parts by mass of cellulose using cotton linter as a raw material. To esterify the cellulose. Cellulose acetate obtained by neutralization with magnesium acetate was kept at 62 ° C. for 40 minutes. Thus, cellulose acetate was synthesized.

(Aging Step of Cellulose Acetate) Using the synthesized cellulose acetate, the amount of water to acetic acid (acetyl group donor) was 1.63 mol%, and the amount of perchloric acid (catalyst) to acetic acid (acetyl group donor) was 0.49 amount
8 mol%, and a reaction history parameter (R = ∫YZ / X
The aging step was performed in the same manner as in Example 1 except that dt) was changed to 55.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 2. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
7 are plotted as black circles.

(Measurement of Infrared Absorption Spectra) 200 mg of absolutely dried cellulose acetate was dissolved in 5 g of methylene chloride / methanol (9/1: mass ratio). The obtained solution was cast on a glass plate, and the thickness was made uniform using a bar coater. This was air-dried to obtain a cellulose acetate film sample. The thickness of the film was adjusted so that the transmittance (at the peak of the absorption band derived from unsubstituted hydroxyl groups of cellulose acetate) was about 40%. The produced film was vacuum-dried at 105 ° C. for 30 minutes or more. Then, the film was cut into a sufficient size (24 mm × 27 mm) with respect to the window frame of the infrared ray generator. Thereby, infrared rays were not shielded by the sample holder. The film sample is placed under a nitrogen atmosphere.
It was maintained until the absorption peak observed at around 3650 cm ^-1 supposed to be derived from adsorbed water disappeared. The measurement was performed using an FT-IR1650 model manufactured by PerkinElmer.
The measured infrared absorption spectrum was analyzed as described above to determine the half width (Δν1 / 2). The results are shown in Table 2.

Example 8 (Aging Step of Cellulose Acetate) 1150 parts by mass of cellulose acetate synthesized in Example 7 was dissolved in a mixture of 8220 parts by mass of dichloromethane and 4800 parts by mass of acetic acid, and dichloromethane was removed by a rotary evaporator. Evaporated and evaporated. The obtained acetic acid dope of cellulose acetate was transferred to a reaction vessel, and 11788 parts by mass of acetic acid and 7 parts of water were added to 1150 parts by mass of cellulose acetate.
8 parts by weight and 98 parts by weight of perchloric acid were added. The amount of water based on acetic acid (acetyl group donor) is 2.2 mol%.
Met. The above solution was kept at 30 ° C. for 5 hours to ripen the cellulose acetate.

(Post-treatment) After the ripening, 1.75 equivalents of peracetic acid was added to a 10% by mass acetic acid solution of sodium acetate, and the mixture was stirred for 10 minutes to stop the reaction. Thus, a cellulose acetate having a viscosity average degree of polymerization of 288 and a degree of substitution of 2.84 was obtained.

(Analysis of Cellulose Acetate) The obtained cellulose acetate was analyzed in the same manner as in Example 1.
The results are shown in Table 2. In addition, the substitution degree at the second position (2D
S) The substitution degree at the 3-position (3DS) and the substitution degree at the 6-position (6
DS) was plotted on the graphs of FIG. 1 and FIG.

(Measurement of Infrared Absorption Spectrum) An infrared absorption spectrum of the obtained cellulose acetate was measured in the same manner as in Example 7, and the half width (Δν1 / 2) was determined. The results are shown in Table 2.

(Preparation of Cellulose Acetate Solution) 15 parts by mass of the obtained cellulose acetate was added at room temperature (25%).
C), 68 parts by mass of methyl acetate and 17 parts by mass of acetone were mixed to prepare a slurry having a cotton concentration of 15% by mass. The resulting slurry was transparent gel, partially opaque, and lump-like. The slurry was cooled for 2 hours in a methanol bath adjusted to -40 ° C with dry ice. Many bubbles were generated in the removed slurry due to the permeation of the solvent. This at room temperature for 10
After standing for 10 minutes, it was kept for 10 minutes in a water bath set at a temperature of 40 ° C. The cellulose acetate solution thus obtained was transparent and had good fluidity.

Example 9 (Aging Step of Cellulose Acetate) 200 parts by mass of cellulose acetate synthesized in Example 7 was dissolved in a mixed solution of 1600 parts by mass of dichloromethane and 867 parts by mass of acetic acid, and dichloromethane was removed by a rotary evaporator. Evaporated and evaporated. The obtained acetic acid dope of cellulose acetate was transferred to a reaction vessel, and cellulose acetate 2 was added.
2050 parts by mass of acetic acid, 26 parts by mass of water and 17 parts by mass of perchloric acid were added to 00 parts by mass. The amount of water based on acetic acid (acetyl donor) was 4.2 mol%. The above solution was kept at 30 ° C. for 10 hours to ripen the cellulose acetate.

(Post-treatment) After completion of ripening, sodium acetate equivalent to 1.75 equivalents to perchloric acid was added to a 10% by mass acetic acid solution, and the mixture was stirred for 10 minutes to stop the reaction. Thus, a cellulose acetate having a viscosity average degree of polymerization of 318 and a degree of substitution of 2.81 was obtained.

(Analysis of Cellulose Acetate) The obtained cellulose acetate was analyzed in the same manner as in Example 1.
The results are shown in Table 2. In addition, the substitution degree at the second position (2D
S) The substitution degree at the 3-position (3DS) and the substitution degree at the 6-position (6
DS) was plotted as 9 black circles on the graphs of FIGS.

(Measurement of Infrared Absorption Spectrum) An infrared absorption spectrum of the obtained cellulose acetate was measured in the same manner as in Example 7, and the half width (Δν1 / 2) was determined. The results are shown in Table 2.

(Preparation of Cellulose Acetate Solution) 15 parts by mass of the obtained cellulose acetate was added at room temperature (25%).
C), 68 parts by mass of methyl acetate and 17 parts by mass of acetone were mixed to prepare a slurry having a cotton concentration of 15% by mass. The resulting slurry was transparent gel, partially opaque, and lump-like. The slurry was cooled for 2 hours in a methanol bath adjusted to -40 ° C with dry ice. Many bubbles were generated in the removed slurry due to the permeation of the solvent. This at room temperature for 10
After standing for 10 minutes, it was kept for 10 minutes in a water bath set at a temperature of 40 ° C. The cellulose acetate solution thus obtained was transparent and had good fluidity.

Example 10 (Aging Step of Cellulose Acetate) Using the cellulose acetate synthesized in Example 7, the time required for the aging of cellulose acetate was 15 hours, and the amount of water relative to acetic acid (acetyl group donor) was determined. 4.18 mol%, the amount of perchloric acid (catalyst) to acetic acid (acetyl group donor) was 0.498.
Mole%, and the reaction history parameter (R = ∫YZ / Xd
The aging step was performed in the same manner as in Example 1 except that t) was changed to 107.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 2. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
Plotted as 10 black circles.

(Measurement of Infrared Absorption Spectra) An infrared absorption spectrum of the obtained cellulose acetate was measured in the same manner as in Example 7, and the half width (Δν1 / 2) was obtained. The results are shown in Table 2.

[0098]

[Table 2] Table II ──────────────────────────────────── Water reaction Half value cellulose acetate substitution degrees example (mole%) R duration 2DS 3DS 6DS polymerization degree ──────────────────────────────────── 7 1.63 55 3 128 0.965 0.963 0.933 300 8 2.20 685 123 0.959 0.943 0.937 288 9 4.18 71 10 121 0.945 0.926 0.935 318 10 4.18 107 15 119 0.925 0.896 0.941 301 註 (Note) R : reaction history parameters reaction time: time spent ripening cellulose acetate (hour) half-value width: put the wavenumber 3450～3550Cm ^-1 Full width at half maximum of the absorption maxima (cm ^-1)

[Example 11] (Measurement of infrared absorption spectrum) Total substitution degree (2DS + 3)
DS + 6DS) is 2.896, 2DS + 3DS-6DS
The infrared absorption spectrum was measured in the same manner as in Example 7 for cellulose acetate having a value of 0.896. FIG. 4 shows the results. The half width (Δν1 / 2) was 90.

[Example 12] (Measurement of infrared absorption spectrum) Total substitution degree (2DS + 3)
(DS + 6DS) is 2.877, 2DS + 3DS-6DS
Was measured for infrared absorption spectrum in the same manner as in Example 7 for cellulose acetate having a value of 0.967. FIG. 4 shows the results. The half width (Δν1 / 2) was 118.

[Comparative Example 3] (Measurement of infrared absorption spectrum) Total substitution degree (2DS + 3)
DS + 6DS) is 2.845, 2DS + 3DS-6DS
Was measured for infrared absorption spectrum in the same manner as in Example 7 for cellulose acetate having a value of 1.069. FIG. 4 shows the results. The half width (Δν1 / 2) was 137.

[Comparative Example 4] (Measurement of infrared absorption spectrum) Total substitution degree (2DS + 3)
DS + 6DS) is 2.925, 2DS + 3DS-6DS
Of cellulose acetate having a value of 1.075 was measured for the infrared absorption spectrum in the same manner as in Example 7. FIG. 4 shows the results. The half width (Δν1 / 2) was 137.

Example 13 (Aging Step of Cellulose Acetate) 500 g of dried and commercially available cellulose acetate (having a degree of polymerization of 311 obtained by acetylating wood pulp under ordinary conditions and a degree of substitution of 2.85 by NMR measurement). With dichloromethane 1333
g and 1033 g of acetic acid. Water 13.3
150 g of acetic acid containing 1 g was added thereto with stirring. 150 g of acetic acid containing 36.92 g of toluenesulfonic acid monohydrate was added with stirring,
The aging reaction was started. The amount of water based on acetic acid (acetyl donor) was 4.2 mol%. After 7 hours, 260 g of acetic acid in which 29 g of anhydrous sodium acetate was dissolved was added dropwise to terminate the aging reaction. The value of the reaction history parameter (R = ∫YZ / Xdt) in the aging step was calculated to be 151.

(Post-treatment) Dichloromethane was distilled off from the acetic acid solution after the reaction with a rotary evaporator, and about 4.5 liters of water was added with vigorous stirring as in Example 2 to form a precipitate. The precipitate was separated, washed, centrifuged, and further washed with running water and centrifuged, and dried at 50 ° C.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 3. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
Plotted as 13 black circles.

[Example 14] (Aging step of cellulose acetate) The amount of water to be added was changed to 2.91 g (the amount of water based on acetic acid (acetyl group donor) was 1.6 mol%), and the reaction time was changed. Was changed to 2 hours and 20 minutes, and the cellulose acetate was aged and post-treated in the same manner as in Example 13. The value of the reaction history parameter (R = ∫YZ / Xdt) in the aging step was calculated to be 132.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 3. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
Plotted as 14 black circles.

Example 15 (Synthesis Step of Cellulose Acetate) Moisture 8.2% by mass
698 g of acetic acid was uniformly sprayed on 1520 g of the crushed pulp containing, and after stirring, the mixture was allowed to stand at room temperature for 90 minutes.
3930.6 g of acetic anhydride cooled to about −10 ° C., acetic acid 5
The acetic acid-impregnated pulp described above was charged into a mixture of 755 g and 115.4 g of 98% sulfuric acid, and mixed. By external cooling and external heating, the reaction temperature was linearly increased from 0 ° C. at the start of the reaction to 37 ° C. 70 minutes later, and then maintained at 37 ° C. for 80 minutes to synthesize cellulose acetate.

(Aging Step of Cellulose Acetate) To a solution of the synthesized cellulose acetate, 383.7 g of a 30% acetic acid aqueous solution was added and kept at a reaction temperature of 47 ° C. for 130 minutes. The amount of water based on acetic acid (acetyl donor) is
6.0 mol%. Thereafter, 297 g of an aqueous solution of magnesium acetate tetrahydrate was added to stop the reaction. Reaction history parameter in aging process (R = ∫YZ / Xdt)
Was 43.

(Post-treatment) The obtained solution was poured into about 30 liters of a 10% aqueous acetic acid solution with vigorous stirring to form a precipitate. The precipitate was separated by filtration, washed with running water, washed with hot water, further washed with running water and centrifuged, and dried at 50 ° C.

(Analysis of Cellulose Acetate) Aged cellulose acetate was treated in the same manner as in Example 1,
analyzed. The results are shown in Table 3. The substitution degree at the second position (2DS), the substitution degree at the third position (3DS) and the substitution degree at the sixth position (6DS) are shown in the graphs of FIGS.
Plotted as 15 black circles.

[0112]

[Table 3] Table 3 ──────────────────────────────────── Cellulose Amount of water Paramecellulose acetate Degree of substitution acetate (mol%) Data R 2DS 3DS 6DS Degree of polymerization ─────────────────────────────────── ─ Example 13 4.20 151 0.953 0.936 0.925 288 Example 14 1.60 132 0.972 0.967 0.916 298 Example 15 6.00 43 0.973 0.967 0. 923 303 ────────────────────────────────────

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the definition of the degree of acetyl substitution of formulas (I) to (III) and the degree of acetyl substitution of cellulose acetate in Examples 1 to 5, 7 to 10, 13 to 15 and Comparative Example 1. It is a graph.

FIG. 2 illustrates the definition of the degree of acetyl substitution in formulas (III) and (IV) and the degree of acetyl substitution in cellulose acetate in Examples 1 to 5, 7 to 10, 13 to 15 and Comparative Examples 1 and 2. It is a graph for.

FIG. 3 is a chart for explaining a half width of an infrared absorption spectrum.

FIG. 4 is a chart showing infrared absorption spectra of Examples 11 and 12 and Comparative Examples 3 and 4.

[Explanation of symbols]

2DS 2nd acetyl substitution degree 3DS 3rd acetyl substitution degree 6DS 6th acetyl substitution degree 2DS + 3DS Total of 2nd acetyl substitution degree and 3rd acetyl substitution degree Black circle of 1 Black circle of cellulose acetate 2 of Example 1 Black circle of cellulose acetate 3 of Example 2 Black circle of cellulose acetate 4 of Example 3 Black circle of cellulose acetate 5 of Example 4 Black circle of cellulose acetate 7 of Example 5 Black circle of cellulose acetate 8 of Example 7 Cellulose acetate of Example 8 Black circle of 9 Cellulose acetate of Example 9 Black circle of 10 Cellulose acetate of Example 10 Black circle of 13 Cellulose acetate of Example 13 Black circle of 14 Cellulose acetate of Example 14 Black circle of 15 Cellulose acetate of Example 15 White circle of C1 Comparative Example 1 cellulo White circle of acetate C2 Cellulose acetate of Comparative Example 2 (VI) Solid line corresponding to 2DS + 3DS = 6DS + 1 A High-frequency base of absorption band B Low-frequency base of absorption band C Perpendicular line from peak (E) to horizontal axis and baseline (A
-B) Intersection with peak D Intermediate point between peak (E) and intersection (C) E Peak of absorption band A ', B' Intermediate point (D) and baseline (A-
Two intersections between the straight line parallel to B) and the spectrum Δν1 / 2 half width 11 Infrared absorption spectrum of Example 11 12 Infrared absorption spectrum of Example 12 C3 Infrared absorption spectrum of Comparative example 3 C4 Infrared absorption of Comparative example 4 Spectrum

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuichiro Shuto 1365-2, Shinzai-ku, Aboshi-ku, Himeji-shi, Hyogo (72) Inventor Masaaki Ito 1365-2, Shinzai-ku, Abashiri-ku, Himeji-shi, Hyogo F-term (reference) 4C090 AA05 AA10 BA26 BB12 BB36 BB52 BB97 DA32 4F071 AA09 AF35 AH12 AH19 BB02 BC01

Claims (10)

[Claims] 1. A step of reacting cellulose with acetic acid or acetic anhydride in a solvent in the presence of a catalyst to synthesize cellulose acetate. A process for producing cellulose acetate, comprising a step of aging in the presence of 10 mol% of water or alcohol and a catalyst. 2. The cellulose acetate is aged in the presence of an acetyl group donor and a catalyst and in a condition in which water or an alcohol is present in an amount of less than 10 mol% of the acetyl group donor. A method for adjusting the acetyl substitution degree of cellulose acetate, which comprises changing the acetyl substitution degree at the 6-position. 3. A having an absorption maximum in the infrared absorption spectrum in the wave number of 3450 to 3550 cm ^-1, cellulose acetate, wherein the half-width of the absorption maximum is 135 cm ^-1 or less. 4. A cellulose acetate wherein the degree of acetyl substitution at the 2-, 3- and 6-positions satisfies the following formulas (I) to (III): (I) 2DS + 3DS <6DS × 4-1. 70 (II) 2DS + 3DS <−6DS × 4 + 5.70 (III) 2DS + 3DS> 1.80 [wherein 2DS is the degree of acetyl substitution at the 2-position; 3D
S is the degree of acetyl substitution at position 3; and 6DS
Is the degree of acetyl substitution at the 6-position]. 5. A cellulose acetate wherein the degree of acetyl substitution at the 2-, 3- and 6-positions satisfies the following formulas (III) to (V): (III) 2DS + 3DS> 1.80 (IV) 3DS <2DS (V) 6DS> 0.80 wherein 2DS is the degree of acetyl substitution at the 2-position;
S is the degree of acetyl substitution at position 3; and 6DS
Is the degree of acetyl substitution at the 6-position]. 6. A cellulose acetate solution in which the cellulose acetate according to claim 3, 4 or 5 is dissolved in an organic solvent. 7. The cellulose acetate solution according to claim 6, wherein the organic solvent contains substantially no halogenated hydrocarbon. 8. A step of swelling the cellulose acetate according to claim 3, 4 or 5 with an organic solvent; a step of cooling the obtained swelling mixture to −100 to −10 ° C .; A method of producing a cellulose acetate film by heating the mixture to a temperature of 0 ° C. to obtain an organic solvent solution of cellulose acetate; and applying the obtained organic solvent solution onto a support to form a cellulose acetate film. 9. A cellulose acetate film comprising the cellulose acetate according to claim 3, 4 or 5. 10. It has an absorption maximum of an infrared absorption spectrum derived from cellulose acetate at a wave number of 3450 to 3550 cm ^-1 , and the half width of the maximum absorption is 135c
m- ¹ or less, wherein the cellulose acetate film is not more than m- ¹ .