JP3474680B2 - Method for producing cellulose acetate film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a protective film, a polarizing plate protective film, a color filter, and a method for producing a cellulose acetate film used as a support for a photographic light-sensitive material.

[0002]

2. Description of the Related Art A cellulose acetate film is a polarizing plate used as a support for a photographic light-sensitive material because of its toughness and flame retardancy, and as a liquid crystal display device whose market is expanding recently due to its optical isotropy. Used for protective films and color filters. This cellulose acetate film is produced by a solution casting method in which a solution of cellulose acetate dissolved in methylene chloride (hereinafter referred to as "dope") is cast on a support. In this solution casting method, the time required from casting the dope onto the support to peeling off the film on the support greatly contributes to the productivity of the film forming step. Therefore, for example, as described in Japanese Examined Patent Publication No. 5-17844, a high-concentration dope is cast on a cooling drum to shorten the time until stripping after casting to make the casting equipment compact and It has been proposed to increase the membrane speed.

However, since the dope prepared at a high concentration has a high dope viscosity, it is necessary to enhance the ability of the liquid feeding facility and the planarity of the dope cast on the support is lowered. . As a means for solving these problems, it is possible to lower the degree of polymerization of cellulose acetate, but this will reduce the mechanical properties of the molded film, such as tensile elastic modulus, folding strength, tear strength, and the protective film. However, this is not an appropriate means because it deteriorates the quality of a cellulose acetate film used as a polarizing plate protective film, a color filter and a support for a photographic light-sensitive material.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a cellulose acetate film using cellulose acetate which has good moldability and does not easily increase the dope viscosity even when prepared at a high concentration.

[0005]

Means for Solving the Problems As a result of the examination from the above viewpoints, the present inventors have solved the present problems by the following. That is, (1) Ri der acetone extractables is 5% by weight or less, acetylation reaction
The amount of sulfuric acid catalyst is 1 for 100 parts by weight of cellulose.
Average degree of acetylation reacted from 0 to 15 parts by weight 58.0 to 6
A dope having a total concentration of 1.5% cellulose acetate and a plasticizer of 18 to 35% by weight and a ratio of methylene chloride in the solvent composition of 75 to 87% by weight was cast on a support. A method for producing a cellulose acetate film, which comprises producing the cellulose acetate film. (2) Cellulose triacetate with ketones and acetic acid
One or more selected from steals or cellosolves
By washing with the solvent of
(1) above, which is less than or equal to the amount
The manufacturing method of the above-mentioned cellulose acetate film. (3) The cellulose acetate has a viscosity average degree of polymerization
Concentrated solution viscosity by falling ball viscosity method for (DP)
(Η) is represented by the following formula (1):
(1) Method for producing cellulose acetate film
Law. Formula (1) 2.814 × ln (DP) -11.753 ≦ l
n (η) ≦ 6.29 × ln (DP) −31.469 [In the formula, DP is an integer of 290 or more, and η is between the marked lines.
Is the transit time (sec) of. ] (4) Gel permeation of the cellulose acetate
The molecular weight distribution Mw / Mn by chromatography is
(1) above, characterized in that it is 1.0 to 1.7
A method for producing a cellulose acetate film as described above. (5) Crystals of the cellulose acetate from a molten state
Specialized heat generation rate (ΔHC) of 5 to 17 J / g
The cellulose acetate film described in (1) above.
Manufacturing method

The cellulose acetate used in the present invention is
The average degree of acetylation is 58.0 to 61.5%, and the acetone extract content is 5% by weight or less. Here, the degree of acetylation refers to the amount of bound acetic acid per unit weight of cellulose, and as described later, according to the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate, etc.). It is calculated. Degree of acetylation of cellulose acetate is correlated with the mechanical strength of the full Irumu, elastic modulus when acetylation degree is reduced, the folding endurance decreases. Also,
The dimensional stability and the resistance to moist heat are also lowered, and the quality required for a photographic support or an optical film cannot be sufficiently satisfied. Therefore, the cellulose acetate used in the present invention has an average acetylation degree of 58.0 or more. The degree of polymerization of cellulose acetate used in the present invention is 250
Or more, preferably 290 or more. This is the degree of polymerization 2
This is because the strength of the obtained film becomes extremely poor with a cellulose acetate of 50 or less.

The cellulose acetate used in the present invention is
The concentrated solution viscosity (η) by the falling ball viscosity method with respect to the viscosity average degree of polymerization (DP) is cellulose acetate represented by the following formula (1). Formula (1) 2.814 × ln (DP) -11.753 ≦ l
n (η) ≦ 6.29 × ln (DP) −31.469 [where DP is an integer of 290 or more, and η is a transit time (sec) between marked lines. ] This equation is calculated from the plot of the concentrated solution viscosity and the viscosity average degree of polymerization of the experimental data. That is, in the case of a cellulose acetate having a viscosity average degree of polymerization of 290 or more, the viscosity of the concentrated solution generally increases exponentially with an increase in the degree of polymerization, whereas the cellulose acetate of the present invention is a concentrated solution with respect to the viscosity average degree of polymerization. It is characterized in that the increase in viscosity is linear, and the rate of increase in the viscosity of the concentrated solution with respect to the viscosity average degree of polymerization is small as compared with the general one.

The cellulose acetate of the present invention has a molecular weight distribution M by gel permeation chromatography.
It is preferable to have a characteristic that w / Mn (Mw represents a weight average molecular weight and Mn represents a number average molecular weight) is narrow.
That is, Mw / Mn of the cellulose acetate of the present invention
Is preferably 1.0 to 1.7, more preferably 1.
It is 3 to 1.65, more preferably 1.4 to 1.6. When the molecular weight distribution deviates from the upper limit of the above range, the dope viscosity increases and the flatness decreases. Also, if the lower limit is not reached, the mechanical properties of the molded film will deteriorate.

The cellulose acetate of the present invention is characterized in that it has a small amount of crystallization heat, that is, the degree of crystallization.
It is preferable . That is, the heat value of crystallization (ΔH _C ) from the molten state of the cellulose acetate of the present invention is preferably
17J / g is properly from 5, more preferably from 6 16J
/ G, more preferably 10 to 16 J / g. If the amount of heat generated by crystallization exceeds the upper limit of the above range, a large amount of fine crystal components will be present in the formed film, resulting in deterioration in processability of the film. If the lower limit is not reached, the mechanical strength of the formed film will decrease and
In the method described in Japanese Patent No. 17844, that is, in the method of forming a film by casting a high-concentration dope on a cooling drum, it takes a long time to peel off because the gelation of the dope is delayed, and the film forming speed is reduced. To do.

[0010] Cellulose acetate of the present invention, prepared by the following two methods. In one way, ketones and cell Ruro <br/> scan triacetate, acetic acid esters, washed with cellosolves such, remove low molecular weight cellulose acetate, which causes crystallization.

[0011] cellulose if triacetate were washed once, the amount of low molecular weight cellulose triacetate present in the washing liquid will be present 10 to 15 wt% relative to the starting weight, the cellulose acetate after washing again even if the cleaning extracted Ru der than 5%. That is, it is necessary that the low molecular weight cellulose acetate is washed and extracted so that the content of the low-molecular weight cellulose acetate is 5% by weight or less even if the washing and extraction are performed again. By low molecular weight substance is removed, becomes higher as the average molecular weight (polymerization degree), the average molecular weight of same way (degree of polymerization) low viscosity than those with, which is advantageous in terms of productivity.

[0012] cellulose thoria cetearyl over preparative wash Kiyoshimae is vinegar <br/> acid - acetic anhydride - resulting <br/> is Ru in industrial process that the reaction with sulfuric acid.

In the method for removing low molecular weight cellulose triacetate in the present invention, in order to improve the extraction efficiency, it is prepared by pulverizing or sieving so that the ratio of the particles passing through the cellulose acetate particle size of 20 mesh before washing becomes 70% by weight or more. To do. Further, as the washing extraction solvent used in the present invention, there are ketones, acetic acid esters, cellosolves, etc., but when industrially performed, it is a general-purpose solvent, low boiling point acetone, methyl acetate, methyl cellosolve is effective. Is. As a washing method, a solvent circulation method such as a Soxhlet extraction method may be used, or it may be obtained by stirring with a washing extract in a usual stirring tank to remove liquid. However, in the case of main washing extraction, 10 to 15
Since the low molecular weight cellulose triacetate of weight% is dissolved, the liquid becomes viscous and the operations such as deliquoring become difficult.
It is preferable that the amount of the processing raw material with respect to the liquid is 10% by weight or less.

[0014] Ruse cellulose acetate put to the present invention,
Pollock adjusted depending on the reacting 10 to 15 parts by weight per 100 parts by weight of cellulose the amount of sulfuric acid catalyst at the time of manufacture
It

Generally, cellulose triacetate has an acetylation degree of 59% or more, while commercially available cellulose triacetate is about 61%. The major difference between cellulose diacetate and cellulose triacetate at the time of production lies in the hydrolysis step after once converting cellulose triacetate. In the case of cellulose diacetate, it is necessary to perform hydrolysis to an acetylation degree that is soluble in acetone, but in the case of cellulose triacetate, it is preferable that the acetylation degree does not decrease. In cellulose triacetate, it is bonded to cellulose. Sulfuric acid should be hydrolyzed as quickly as possible. From the above, when the amount of the sulfuric acid catalyst in the acetylation reaction is increased, the amount of sulfuric acid bound to that amount is increased, and as a result, the degree of substitution obtained at the end of acetylation is low. Therefore, in general, cellulose triacetate, which is required to have a degree of acetylation of about 61%, reacts while reducing the amount of the sulfuric acid catalyst as much as possible.

That is, it has been found that the degree of acetylation can be increased from the conventional range of commercially available cellulose triacetate to slightly increase the amorphousness. That is, like the conventional method for producing cellulose triacetate, it can be deacetylated in the hydrolysis step, but in the present invention, highly amorphous cellulose triacetate is obtained by already reducing the degree of acetylation in the acetylation step. It is something that was discovered.

The dope of the present invention is a dope having a high concentration of cellulose acetate, and the total concentration of the cellulose acetate and the plasticizer is 18 to 35% by weight, preferably 2%.
A content of 0 to 35% by weight is suitable. The plasticizer is added to improve the mechanical properties of the molded film or to improve the solvent drying rate, and examples thereof include triphenyl phosphate (TPP) and tricresyl phosphate (TC).
P) and other phosphate compounds, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DO
P), phthalate ester compounds such as diethylhexyl phthalate (DEHP), fatty acid ester compounds such as butyl oleate, methylacetyl ricinoleate and dibutyl sebacate, acetyltriethyl citrate (OACT)
E), citric acid ester compounds such as acetyltributyl citrate (OACTB), and various trimellitic acid ester compounds. However, the above compounds are merely listed as examples, and the present invention is not limited thereto.

Examples of the additive components other than the plasticizer include, for example,
Deterioration preventing agent (peroxide decomposing agent, described in JP-A-5-97073) for improving the preservability of a molded film.
There are a radical inhibitor, a metal deactivator, an acid scavenger), or an ultraviolet inhibitor described in JP-A-7-11056. However, these are merely examples and the present invention is not limited to these.

The solvent is a mixed solvent of methylene chloride and another solvent. The other solvent is an alcohol having 1 to 4 carbon atoms, such as methanol or n-butanol, and is a poor solvent for cellulose acetate such as cyclohexane. These may be used alone or in combination of two or more. The mixing ratio is 75 for methylene chloride.
To 87% by weight, and therefore 13 to 25% of other solvents.
% By weight.

The concentration and solvent composition of cellulose acetate are arbitrarily determined within the above range. Japanese Patent Fair 5-178
According to the method described in Japanese Patent Publication No. 44-44, the gelling temperature of the dope depends on the concentration of cellulose acetate and the solvent composition in the method of performing low-temperature gelation and stripping on a support at 10 ° C. or less, and therefore, as early as possible at a predetermined temperature. It is set so that gelation proceeds. However, the manufacturing method of the present invention is not limited to this method.

[0021]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to this range.

[Measurement method and calculation method of acetylation degree (%)] The acetylation degree is measured by a saponification method. That is, the dried cellulose acetate was precisely weighed and dissolved in a mixed solvent of acetone and dimethyl sulfoxide (volume ratio 4: 1), and then a predetermined amount of 1N-sodium hydroxide aqueous solution was added, and the mixture was saponified at 25 ° C. for 2 hours. Turn into. Phenolphthalein was added as an indicator, and 1N-sulfuric acid (concentration factor:
Excess sodium hydroxide is titrated in F). In addition, a blank test is performed by the same method as above. And
The acetylation degree (%) is calculated according to the following formula. Acetification degree (%) = (6.005 × (B−A) × F) / W (In the formula, A is the amount of 1N-sulfuric acid (m) required for titration of the sample.
1) and B are 1N-sulfuric acid amount (m
1) and F are 1N-sulfuric acid factors, and W is a sample weight. )

[Molecular Weight and Molecular Weight Distribution] A high performance liquid chromatography system (GPC-LALLS) in which a gel filtration column is connected with a detector for detecting refractive index and light scattering.
Was measured using. The measurement conditions are as follows.

Solvent: Methylene chloride Column: GMHx1 (manufactured by Tosoh Corporation) Sample concentration: 0.1 w / v% Flow rate: 1 ml / min Sample injection amount: 300 μl Standard sample: polymethylmethacrylate (Mw = 188,2)
00) Temperature: 23 ° C

[Measurement method and calculation method of viscosity average degree of polymerization (DP)] About 0.2 g of absolutely dried cellulose acetate
Is precisely weighed and dissolved in 100 ml of a solution of methylene chloride: ethanol = 9: 1. This is measured for the number of seconds of dropping with an Ostwald viscometer at 25 ° C., and the degree of polymerization is determined by the following formula. η _rel = T / T ₀ T: Falling seconds of measurement sample [η] = (ln η _rel ) / C T _O : Falling seconds of solvent alone DP = [η] / Km C: Concentration (g / l) Km : 6x10 ^-4

[Measurement Method of Concentrated Solution Viscosity (η)] Cellulose acetate was dissolved in methylene chloride: methanol = 8: 2 (weight ratio) so as to be 15% by weight, and the solution was viscous tube having an inner diameter of 2.6 cm. Injected into the
Predetermined hard sphere in solution, diameter 3.15 mm, 0.135 g
Was dropped, and the number of seconds that passed between the marked lines at intervals of 10 cm was defined as the viscosity.

[Measurement Method and Calculation Method of Crystallization Calorific Value (ΔH _C )] Cellulose acetate was dissolved in a mixed solvent (methylene chloride / ethanol = 9/1 (weight ratio),
After preparing a dope having a cellulose acetate concentration of 15% by weight, pressure filtration is performed using a non-woven fabric. The dope thus obtained is cast on a smooth glass plate using a bar coater. After air-drying for 1 day, it is peeled from the glass plate and vacuum dried at 80 ° C. for 4 hours. 10 mg of the obtained film sample is packed in a standard aluminum pan and placed on a sample stand of a heat-compensated differential scanning calorimeter (DSC). The sample is melted by holding it at the melting temperature for a short time, and then cooled to room temperature at a temperature lowering rate of 4 ° C./min to crystallize.

Heat generation of the DSC curve thus obtained
The heat value of crystallization (ΔH _C). DS
C measurement is performed in a nitrogen atmosphere, and temperature calibration is In
Point: 156.60 ° C), Sn (melting point: 231.88 ° C)
In the two-point calibration, the calorific value calibration is In (heat of fusion: 28.45).
J / g) with one-point calibration. Also crystallization
The temperature analysis method is specified in JIS K7121-1987.
The analysis method of the crystallization heat value is described in JIS K 7122-
1987, respectively.

[Acetone extract (wt%)] After measuring the weight (A) of cellulose acetate, was stirred in 10 times weight of acetone at room temperature for 30 minutes, and then was obtained by pressure filtration with a filter. Was dried, and the solid content (B) was weighed. The acetone extract was calculated by the following formula. Acetone extractables (% by weight) = (B ÷ A) × 100%

[Mechanical Properties of Film] (1) Tensile Test A sample having a length of 100 mm and a width of 10 mm is ISO1184-
According to the standard of 1983, the initial sample length was 50 mm and the tensile speed was 20 mm / min, and the elastic modulus and the breaking elongation were determined. (2) Tear test A sample cut into 50 mm x 64 mm is ISO6383.
The tear load required for tearing was determined in accordance with the standard of / 2-1983. (3) Folding resistance test A sample cut to 120 mm is ISO8776-198.
According to the standard of No. 8, the number of reciprocations until bending and cutting was determined.

[0031] Reference Example 1 cellulose acetate (acetylation degree: 60.9%, polymerization degree:
322, solution viscosity: 101.5 seconds, acetone extracted:
0.4%, heating value for crystallization: 14.0 J / g) 100 parts by weight of triphenyl phosphate (TPP) 16 parts by weight, methylene chloride 310 parts by weight, n-butanol 6
A dope having a composition of 0 parts by weight and 11 parts by weight of methanol was dried with a band casting machine having an effective length of 6 m to give a dry film thickness of 100.
It was cast to have a thickness of μm. Band temperature is 5 ℃,
No air was blown for drying. The mechanical properties of the molded film were measured by the methods described below. The results are shown in Table 1.

Comparative Example 1 Cellulose triacetate obtained by a conventional method (Acetification degree: 60.9%, Polymerization degree: 299, Solution viscosity 74.7)
Second, acetone extracted: 12.1%, crystallization exotherm: 1
7.5 J / g) was cast by the same method as in Example 1, and the mechanical properties were measured by the methods described above. The results are shown in Table 1.

Comparative Examples 2 and 3 Cellulose acetate obtained by a conventional method having different physical properties such as acetylation degree, a film cast by the same method as in Example 1, and mechanical properties by the above-mentioned method. It was measured. The results are shown in Table 1.

Example 1 100 parts by weight of cellulose was esterified by a conventional method using 11.7 parts by weight of sulfuric acid, 260 parts by weight of acetic anhydride and 450 parts by weight of acetic acid, and further hydrolyzed. Obtained cellulose acetate (Acetification degree: 60.2%, Polymerization degree: 313, Solution viscosity: 92.7 seconds, Acetone extraction:
0.4%), the mechanical properties of the film cast by the same method as in Example 1 were measured by the methods described above. The results are shown in Table 1.

Example 2 100 parts by weight of cellulose was esterified by a conventional method using 11.7 parts by weight of sulfuric acid, 260 parts by weight of acetic anhydride, and 450 parts by weight of acetic acid, and further subjected to hydrolysis longer than that of Example 2. went. The obtained cellulose acetate (acetylation degree:
59.8%, degree of polymerization: 326, solution viscosity: 105.8
Sec., Acetone extracted: 0.4%), the mechanical properties of the film cast by the same method as in Example 1 were measured by the above-mentioned methods. The results are shown in Table 1.

[0036]

[Table 1]

[0037]

The cellulose acetate according to the present invention is
Of the concentrated solution viscosity (η) with respect to the viscosity average degree of polymerization (DP)
The rate of increase is small, compared to conventional cellulose acetate
And dope with high degree of polymerization cellulose acetate
Can be prepared. For this reason, molding fill with high mechanical properties
Can be manufactured economically.

[0038]

INDUSTRIAL APPLICABILITY The cellulose acetate of the present invention has a small increase rate of the concentrated solution viscosity (η) with respect to the viscosity average degree of polymerization (DP), and thus has a lower rate of increase than the conventional method.
Dopes can be prepared using highly polymerized cellulose acetate. Therefore, a molded film having high mechanical properties can be economically manufactured.

Continuation of the front page (56) Reference JP-A-4-1009 (JP, A) JP-A-62-37113 (JP, A) JP-A-61-247701 (JP, A) JP-A-8-337601 (JP , A) JP-A-9-188701 (JP, A) JP-A-9-95538 (JP, A) JP-A-9-95557 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) (Name) C08J 5/18 C08B 3/06 C08L 1/12 B29C 41/00-41/52

Claims (5)

(57) [Claims] 1. A Ri der acetone extractables is 5% by weight or less,
The amount of sulfuric acid catalyst during acetylation reaction is 100 parts by weight of cellulose.
And the average degree of acetylation reacted with 10 to 15 parts by weight is 58.0.
To 61.5% of cellulose acetate and plasticizer at a concentration of 18 to 35% by weight, and the ratio of methylene chloride in the solvent composition of 75 to 87% by weight, cast on a support. A method for producing a cellulose acetate film, which comprises: 2. Cellulose triacetate is a ketone,
1 selected from acetates or cellosolves
Acetone extractables can be removed by washing with more than one solvent.
The content is 5% by weight or less.
1. The method for producing a cellulose acetate film according to 1. 3. The cellulose acetate has a viscosity average weight.
Concentration solution viscosity by falling ball viscosity method for degree of contact (DP)
(Η) is represented by the following formula (1):
Item 2. A method for producing a cellulose acetate film according to Item 1. Formula (1) 2.814 × ln (DP) -11.753 ≦ l
n (η) ≦ 6.29 × ln (DP) −31.469 [In the formula, DP is an integer of 290 or more, and η is between the marked lines.
Is the transit time (sec) of. ] 4. A gel permeer of the cellulose acetate.
Molecular weight distribution Mw / M by solution chromatography
n is 1.0 to 1.7.
1. The method for producing a cellulose acetate film according to 1. 5. From the molten state of the cellulose acetate
Crystallization heat value (ΔHC) of 5 to 17 J / g
The cellulose acetate foam according to claim 1, characterized in that
How to make the film.