JPH11123732A - Manufacture of cellulose triacetate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve planeness and mechanical characteristics by controlling heat history (drying history) even in the case the manufacturing rate of a film is quick. SOLUTION: When a cellulose triacetate film is manufactured by the solution cast film manufacturing method using dope having the solvent content of 300 wt.% or more to a dry web, the solvent content of the web is reduced at the rate of 300 wt. % or less per minute on a substrate of a casting section on a drying area of a drying section after releasing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a cellulose triacetate film useful for a silver halide photographic material or a liquid crystal image display.

[0002]

2. Description of the Related Art Cellulose triacetate film is
It is used for a silver halide photographic material or a protective film for a polarizing plate of a liquid crystal image display device, and is generally manufactured by a solution casting film forming method. This solution casting film forming method will be described with reference to FIGS. 1 to 3. A good solvent for cellulose triacetate, for example, a poor solvent for methylene chloride and cellulose triacetate, for example, methanol, ethanol,
In a mixed solvent to which butanol or cyclohexane is added,
A dope in which cellulose triacetate and a plasticizer are dissolved is uniformly cast on a continuously rotating endless support 3 from a die 2 by a precision gear pump or the like that feeds a certain amount of the dope per hour. After the dope is solidified, the web 1 is peeled off from the support 3 at a peeling point 4, and the web 1 is dried through a roll group 6 and dried through a tenter 8.
This is to obtain a cellulose triacetate film.

FIG. 4 is a schematic cross-sectional view of a solution casting film forming apparatus similar to FIG. 2, but when the application is a silver halide photographic material, an undercoating apparatus 9 is generally provided. It is a target. Reference numeral 10 denotes an undercoat coating machine, and 11 denotes an undercoat drying device.

In producing a cellulose triacetate film by a solution casting film forming method, various techniques have been used to improve the film forming speed. For example, as a method of accelerating the solidification of the dope on the support, a method in which the dope contains a poor solvent to be solidified after casting, a layer casting method in which the dope is divided and cast from a plurality of dies, or a support method. Some solidify by setting the surface temperature of the body to 10 ° C. or lower. In the method using a poor solvent, by mixing and using a poor solvent having a boiling point higher than that of a good solvent in addition to a good solvent of cellulose triacetate, the ratio of the poor solvent increases with evaporation of the solvent, and the dope solidifies. There is also a method of increasing the film-forming speed by performing multilayer casting from two or more dies.
FIG. 7 is a view showing one example of the multilayer casting method, and 2 'is a second die. In the multilayer casting method, for example, half of the film thickness of the final film (the film thickness ratio is arbitrary) is cast from each die, and the initial web is thinned to accelerate the peeling ( Tokiko Sho60
-27562). Another method utilizes the property of solidifying by casting a dope on a support whose surface temperature is kept at 10 ° C. or lower to lower the temperature (JP-A-62-37113, Id 62-
Nos. 64514 and 62-115035). With these methods, the web can be peeled from the support with a relatively high solvent content, and after the peeling, the web can be dried with a large amount of solvent from both sides. Can be shortened to

[0005] However, in these methods, the web is rapidly dried after peeling, and the surface properties and mechanical properties are deteriorated. Therefore, it has been difficult to obtain a preferable cellulose triacetate film.

[0006]

As described above, in the conventional method for producing a cellulose triacetate film, the flatness and mechanical properties and the production speed of the film cannot be simultaneously satisfied.

[0007] The present invention solves the above problems, and controls the heat history (drying history) even when the film production speed is high, so that the cellulose triacetate having good flatness and mechanical properties can be obtained. An object is to provide a method for producing a film.

[0008]

Means for Solving the Problems The present inventors have found out the relationship between flatness and mechanical properties of a cellulose triacetate film and drying conditions (preferred heat history) in order to achieve the above object, and have found the present invention. It has been completed.

The present invention has been achieved by the following constitutions (1) to (5).

(1) In preparing a cellulose triacetate film by a solution casting method using a dope having a solvent content of 300% by weight or more based on a dry web, the web is placed on a support in a casting section. Alternatively, in the drying area of the drying section after peeling, the solvent content is set to 3 per minute.
A method for producing a cellulose triacetate film, wherein the cellulose triacetate film is reduced at a rate of 00% by weight or less.

(2) The method for producing a cellulose triacetate film according to (1), wherein the film is peeled off from the support when the content of the solvent is 20% by weight or more and 120% by weight or less.

(3) The method for producing a cellulose triacetate film according to (1) or (2), wherein the decrease in the solvent content in one minute from immediately after casting is 300% by weight or less.

(4) In the region of the solvent content A (% by weight) with respect to each of the following dry webs of the web, the surface temperature T (° C.) of each web is determined by the solvent content A (% by weight) and the boiling point Tbp ( ° C), and heating is performed so as to satisfy the following relationship.
The method for producing a cellulose triacetate film according to any one of (1) to (3), wherein the amount is reduced by not less than% by weight.

In the region of 50 <A ≦ 100, T ≦ −0.5
In the region of A + Tbp + 950 <A ≦ 50, T ≦ −2A + Tbp + 170 (5) An organic solvent containing 50% by weight or more of methylene chloride is used as a main solvent of the dope, any of (1) to (4). A method for producing a cellulose triacetate film according to any one of the above.

Here, the boiling point is a value under 1 atm.
In the case of a mixed solvent, the boiling point corresponds to the composition of the solvent in the step of preparing the dope.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail.

The first invention (described with reference to FIGS. 1 to 3) uses a dope having a solvent content (hereinafter simply referred to as a solvent content) of 300% by weight or more based on a dry web to flow from a die 2 using a dope. The web 1 is cast on the support 3 of the extension.
Is dried on the support 3 of the casting section, or when dried by the drying device 5 or the tenter 8 after peeling at the peeling point 4, or on the support 3 and the subsequent drying section (that is, the drying device 5 or When the web 1 is dried through a tenter 8), the solvent content of the web 1 is reduced at a rate of 300% by weight or less per minute so that the flatness is not disturbed by the conventional rapid drying, the flatness is excellent, and the mechanical property is improved. This is a method for producing a cellulose triacetate film having strong properties.

In the second invention, the surface temperature T of each of the webs is increased during or after the drying process in two successive solvent content region stages of 100 ≧ A> 50 and 50 ≧ A> 0. , T ≦ −0.
5A + Tbp + 95, or T ≦ −2A +
By heating the web at each stage so that the relationship of Tbp + 170 is obtained and drying the web with a heat history so as to reduce the amount of solvent by 80% by weight or more in each region, excellent flatness and mechanical It was found that a cellulose triacetate film with strong mechanical properties could be produced.

The present invention is an essential requirement to satisfy the first invention.

The dope used in the present invention refers to a cellulose triacetate solution obtained by dissolving cellulose triacetate in a mixed solvent of a good solvent and a poor solvent. After casting the dope, the dope is solidified or dried on a support. The solid doped film formed by this is called a web. The web dries into a film, and may be referred to as a film when the solvent content in the web is significantly reduced. However, it should be noted that a clear boundary between the web and the film is not clear, and the present invention does not make a clear distinction.

The solvent content (% by weight) used in the present invention is determined by measuring a web weight A (g) by placing a web sampled at an arbitrary measurement point in a weighing bottle, and then weighing the web sample at 115 ° C. for 1 hour. After heating, the mixture is cooled to room temperature so as not to adsorb moisture, the weighing bottle is weighed, and the weight B (g) of the dry web is calculated according to the following equation.

Solvent content (% by weight) = {(A−B) / B} × 100 The surface of the web of the present invention refers to a dope film on a support, or both surfaces after peeling are air or other dry materials. The surface of the web that is exposed to the gas. The drying gas of the drying air is not limited to the above, and may be nitrogen gas, carbon dioxide gas, or the like, other than air, as long as the gas can evaporate the solvent.

As the solution casting film forming method of the present invention, any of the generally used methods can be used, but the accelerated solution casting film forming method can be preferably used. In the present invention, a method such as a method using a poor solvent for dope, a multilayer casting method, or the like can be preferably used as the accelerated solution casting film forming method.

In general, the higher the solvent content, the higher the drying speed. Therefore, the drying speed is reduced by several hundred percent in one minute after casting, and it is important to control the speed. Factors of the heating rate include heating temperature, heat transfer coefficient, bulk solvent vapor concentration, and the like. The drying rate as in the present invention can be achieved by controlling the temperature or the heat transfer coefficient.

The heat transfer coefficient depends on the air volume in the case of blast drying (gas heat transfer), the type of liquid in the case of liquid heat transfer,
Although control is possible by the contact area, the circulation amount, and the like, in this case, heat is transmitted to the web through the belt or the drum surface, so that the heat is indirectly transmitted to the web.

A method for heating the support in the casting section will be described. The support is an endless belt (or band) or drum that rotates infinitely, the belt being generally made of stainless steel with a mirror-finished surface, supported by two drums, and pinned and tensioned. On the other hand, the drum is generally made of a casting having a mirror-plated surface.

As the heating method useful in the present invention, any method can be used as long as it is used in a usual solution casting method.

In the case of a belt, heating can be performed from both sides of the belt. On the back side, there are a method of transferring heat from two drums (12 and 13 in FIGS. 5, 6, and 7) supporting the belt and a method of transferring heat from the back side of the belt. Since the heating area is overwhelmingly larger on the back side of the belt, it is advantageous to use this method in terms of promoting drying. Inside the drum there is generally a stretched pipe through which liquid is circulated and the temperature of the liquid is transmitted to the belt through the surface of the drum. In many cases, at least one of the two drums is a heating drum. The portion where the belt is not in contact with the drum is blown with heated air from both the front and back surfaces of the belt by an air-drying device (15 and 16 in FIGS. 5, 6, and 7), or the back heat transfer device 1 from the back surface.
4, the liquid is brought into direct contact with the belt (FIGS. 5 and 6).
Also, there is a method of conducting heat transfer (see, for example, Japanese Patent Publication No. 61-39890).

In the case of a drum (without a belt), there is a drawback that the drying length before peeling cannot be made much longer than that of the belt (18 in FIG. 10, large drying drum). Heat transfer is performed by laying a pipe inside the drum so that the temperature distribution is uniform, and flowing the liquid at the temperature required for drying in the same way as the drum with the belt stretched earlier But the sizes are different. Of course, even in the case of a drum, heat transfer by wind is also performed from the surface side of the dope film by a blow drying device (19 in FIG. 10).

There are a number of ways to transfer heat in this way.
Various selections can be made depending on the degree of heat transfer. In order to give a temperature near the boiling point to the doped film or web by heat transfer by wind,
Since it cannot be achieved unless the air volume is extremely large or the temperature is increased, the planarity is often impaired or foamed, so that the purpose may not be achieved. Liquid heat transfer is a preferred method for the present invention because it has a large heat transfer coefficient, facilitates control of the temperature of the doped film or web, and can be efficiently heated.

As described above, one of the methods for quickly peeling the web is a cooling drum (see FIGS. 8 and 9) in which the surface temperature of a relatively small drum as a support is reduced to 10 ° C. or less.
By using 17), solidification can be accelerated and peeling can be accelerated, and the film forming speed can be increased. The solvent content immediately after peeling is extremely large. Care must be taken in drying after peeling, since it may be too rapid to impair flatness or deteriorate mechanical properties.

In the present invention, the reduction of the solvent content in both the casting section and the drying section is preferably 300% by weight or less per minute, more preferably 280% by weight or less per minute. In the method in which the drum is not cooled, if the decrease in the solvent is 0.1% by weight or less per minute, it becomes difficult to peel off the solvent. Therefore, the solvent is preferably 0.1% by weight or more.

The solvent useful in the present invention has a boiling point of 30 ≦ Tbp ≦ 130, preferably 35 ≦ Tbp ≦ 130, because it is difficult to dry the solvent if it is too high, and it is inconvenient to handle it if it is too low. 85 is preferred.

The good and poor solvents for cellulose triacetate useful in the present invention include the following (the boiling point in parentheses).

As a good solvent, methylene chloride (4
0 ° C), methyl acetate (56 ° C), acetone (56 ° C),
Preferred are 1,3-dioxolane (78 ° C.), 1,4-dioxane (101 ° C.), fluoroalcohols and the like. Examples of fluoroalcohols include perfluoro-t-butanol (45 ° C), 1,3-difluoro-2-propanol (55 ° C), 1,1,1,3,3,3-hexafluoro-2-propanol ( 59 ° C), 1,1,1,3
3,3-hexafluoro-2-methyl-2-propanol (62 ° C), 2,2,2-trifluoroethanol (80 ° C), 2,2,3,3,3-pentafluoro-1
-Propanol (80 ° C), 1- (pentafluorophenyl) ethanol (82 ° C), 3,3,4,4,5
5,6,6,7,7,8,8,8-tridecafluoro-
1-octanol (95 ° C), 2,2,3,3,4
4,4-heptafluoro-1-butanol (97 ° C.),
2-fluoroethanol (103 ° C), 2,2,3,3
-Tetrafluoro-1-propanol (109 ° C),
2,2,3,3,4,4-hexafluoro-1,5-pentanediol (111.5 ° C), 2,2,3,4
4,4-hexafluoro-1-butanol (114
° C), 2,3,4,5,6-pentafluorobenzyl alcohol (115 ° C), and the like.
Of these, those having a boiling point in the above range can be particularly preferably mentioned. Particularly, it is preferably used because methylene chloride is used and the boiling point is low.
As poor solvents, methanol (64 ° C), ethanol (78 ° C), cyclohexane (81 ° C), isopropanol (82 ° C), propanol (97 ° C), n-butanol (117 ° C), s-butanol (98 ° C) ) Can be preferably used. The main solvent is preferably used in an amount of 50% by weight or more based on the total amount of the solvent.

[0036]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

(Evaluation method) <Flatness> Each sample was cut out to a size of 90 cm in width and 100 cm in length, and five 50 W fluorescent lamps were arranged side by side on a sample stand.
Fixed at a height of 1.5 m to illuminate from an angle of °, placed each film sample on the sample stage, visually observed the unevenness reflected on the film surface, and judged as follows .

A: All five fluorescent lamps looked straight B: Some fluorescent lamps seemed to bend slightly C: Fluorescent lamps seemed to be slightly bent D: Fluorescent lamps seemed to undulate E: Fluorescent Small undulations can be seen even in large turns with large lights.

<Coating unevenness> An undercoat layer and a back layer having the following formulation were applied to each film and dried using an undercoat apparatus 9 as shown in FIG. 4, and a gelatin solution containing the following dye was coated on the undercoat surface. Was applied and dried.

(Undercoat coating solution) Vinyl acetate: maleic anhydride alternating copolymer 3 g Acetone 810 g Isopropanol 150 g (Back layer coating solution) Tin oxide: antimony oxide composite fine particles (average particle diameter 0.05 μm) 14 g Cellulose diacetate 6 g Acetone 800 g Cyclohexanone 200 g (Gelatin coating solution) Gelatin 4 g Water 100 g Methyl violet (dye) 0.2 g Saponin 0.1 g Each sample was placed on a charkasten, and coating unevenness was evaluated as follows.

A: Very smooth with no unevenness B: Some fine unevenness C: Somewhat uneven feeling D: Clearly visible unevenness E: Very large unevenness visible

<Tear Strength of Film> A dried film was dried in a room conditioned at a temperature of 23 ° C. and a relative humidity of 55% RH.
After humidifying for a time, cut out to a sample size of 50 mm × 63.5 mm, insert a cut of 12.7 mm, and apply ISO 6383.
/ 2-1983, using a light load tear tester (Toyo Seiki Seisaku-sho, Ltd.).

(Example 1) Cellulose triacetate 1
A dope consisting of 00 parts by weight, 400 parts by weight of methylene chloride, 80 parts by weight of ethanol, and 12 parts by weight of triphenyl phosphate was put into each of two dies of an overlapping casting apparatus as shown in FIG. And 35%, and the dope film was formed by layer casting on a belt maintained at 39 ° C. At this time, the solvent content was 440% by weight. FIG. 11 shows the change in the solvent content during the multilayer casting. The increase in the solvent content per 70 seconds was the second.
From the die 2 '(of FIG. 7). The web was dried in a pattern as shown in FIG. 12 so that the maximum drying rate per minute was 300% by weight or less, and the surface temperature of the web with a solvent content of 100% by weight or less was as shown in FIG. Drying was performed by blowing air from the belt surface to both surfaces in addition to heating the back surface.
The web was peeled from the support at a solvent content of 105% by weight, and after peeling, the web was dried through a roll group and a tenter to obtain a film of Example 1 having a final solvent content of 2.1% by weight.

As shown in FIG. 11, the maximum drying rate per minute was 262% by weight. The boiling point of the solvent in the dope composition was 54.6 ° C.

(Examples 2 and 3) Solvent content of web 1
The same operation as in Example 1 was carried out except that the surface temperature of not more than 00% by weight was changed as shown in and of FIG. 12, and an example film having a final solvent content of 2.4% by weight and 1.8% by weight, respectively. 2 and 3 were obtained.

(Comparative Example 1) As shown in Fig. 11, the maximum drying rate per minute was 318% by weight, and the solvent content of the web at the time of peeling was 103% by weight. The same operation was performed to obtain Comparative Example Film 1 having a final solvent content of 2.1% by weight.

Table 1 shows the results of the evaluation of the flatness and the applicability of the sample film and the measurement of the tear strength as a mechanical property.

[0048]

[Table 1]

(Results) The film of the present invention was excellent in flatness and coating unevenness, and had a tear strength of 36 g or more, which was superior to the comparative film.

[0050]

According to the present invention, by controlling the heat history through the casting process and the drying process, the flatness,
The applicability can be greatly improved, and the tear strength can also be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a solution casting film forming apparatus.

FIG. 2 is a schematic sectional view of a solution casting film forming apparatus using a tenter.

FIG. 3 is a schematic sectional view of a solution casting film forming apparatus using a tenter.

FIG. 4 is a schematic sectional view of a solution casting film forming apparatus using a tenter, which has a drawing apparatus.

FIG. 5 is a schematic sectional view of a solution casting film forming apparatus provided with a belt front and back surface heat transfer device.

FIG. 6 is a schematic sectional view of a solution casting film forming apparatus provided with a belt front and back surface heat transfer device.

FIG. 7 is a schematic sectional view of a solution casting film forming apparatus provided with a multilayer casting die and a belt front and back surface heat transfer device.

FIG. 8 is a schematic sectional view of a solution casting film forming apparatus provided with a cooling drum.

FIG. 9 is a schematic sectional view of a solution casting film forming apparatus provided with a cooling drum.

FIG. 10 is a schematic sectional view of a solution casting film forming apparatus provided with a large drying drum.

FIG. 11 is a graph showing drying histories (solvent content to time) of Example 1 and Comparative Example 1.

FIG. 12 is a graph showing drying histories (web surface temperature to solvent content) of Examples 1 to 3 and Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Web 2, 2 'dice (2' is a die for multilayer casting) 3 Support 4 Peeling point 5 Drying device 6 Roll (group) 7 Dry air 8 Tenter 9 Undercoating device 10 Undercoating coating device 11 Undercoating drying device Reference Signs List 12 drum 13 drum 14 backside heat transfer device 15 blow drying device 16 blow drying device 17 cooling drum 18 large drying drum 19 blow drying device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C08L 1/12 C08L 1/12 B29K 1:00 B29L 7:00 (72) Inventor Kazuyuki Shimizu Sakuracho, Hino City, Tokyo No. 1 Konica Stock Company In-house (72) Inventor Masami Akiyama 1 Konica Stock Company In-house Sakuracho, Hino City, Tokyo

Claims (5)

[Claims] 1. The solvent content of the dry web is 300
In preparing a cellulose triacetate film by a solution casting method using a dope having a weight percent or more, a web is placed on a support in a casting section or in a dry region of a drying section after peeling. A method for producing a cellulose triacetate film, wherein the rate is reduced at a rate of 300% by weight or less per minute. 2. The solvent content is not less than 20% by weight and not more than 120% by weight.
The method for producing a cellulose triacetate film according to claim 1, wherein the cellulose triacetate film is peeled from the support at a weight percent or less. 3. The method for producing a cellulose triacetate film according to claim 1, wherein the amount of decrease in the solvent content in one minute immediately after casting is 300% by weight or less. 4. In the region of the solvent content A (% by weight) for each of the following dry webs, the surface temperature T (° C.) of each web is determined by the solvent content A (% by weight) and the boiling point Tbp (° C.) of the solvent used. ) Is heated so that the following relationship is obtained, and 80% by weight of each solvent content in each solvent content region is obtained.
The method for producing a cellulose triacetate film according to any one of claims 1 to 3, wherein the above is reduced. In the region of 50 <A ≦ 100, T ≦ −0.5A + Tbp +
In the region of 950 <A ≦ 50, T ≦ −2A + Tbp + 170 5. The method for producing a cellulose triacetate film according to claim 1, wherein an organic solvent containing 50% by weight or more of methylene chloride is used as a main solvent of the dope.