JP2835783B2 - Method and apparatus for producing high concentration cellulose triacetate solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for producing cellulose triacetate.

[0002]

2. Description of the Related Art As a support for photosensitive materials such as photographs,
Cellulose triacetate films have been used.
The production of this type of cellulose triacetate film basically comprises a step of preparing a high-concentration solution (also referred to as a dope) of cellulose triacetate, a filtration step, a casting step, and a drying step.

[0003] The dope is cast on a drum or an endless belt in a film forming process, and a part of the solvent is evaporated in the process (first drying process), and when the base has a self-holding property, Peeled from drum or endless belt. Then, it is finally dried by a dryer (second drying step). In this case, single-sided drying is performed in the first drying step, and double-sided drying is performed in the second drying step. Therefore, the efficiency of the entire film forming process is the first.
The residence time on the drum or endless belt in the drying process is rate-limiting.

[0004] As a result, as the concentration of the residual solvent in the casting dope is lower, the amount of the solvent evaporated until the residual solvent concentration at the time of peeling from the drum or the endless belt is reduced, and the residence time in the first drying step is reduced. As a result, the productivity of the film forming process is increased.

[0005] From such a viewpoint, a method for obtaining the following high-concentration dope has been developed. (1) A method in which cellulose triacetate is mixed with a solvent and dissolved under high temperature and high pressure (US Pat. No. 2,858,228;
-129031). (2) A continuous high-concentration dope preparation method in which cellulose triacetate and a solvent are continuously supplied to a container, dissolved under high temperature and high pressure, and a high-concentration dope is continuously extracted from the opposite side of the container (Japanese Patent Application Laid-Open No. Sho 61) No. -106628). (3) A low-concentration dope, which has been heated in advance, is blown into the vessel from the nozzle, and a part of the solvent is flash-evaporated until the dope hits the inner wall of the vessel from the nozzle. (USP 2,541,012, 2,858,229, 4,414,341)
No. 4,504,355).

[0006]

However, the above (1)
The methods (2) and (2) have a drawback in that the filterability is poor as compared with the dope produced using the concentration method.

The flash concentration method (3) has an advantage that a high concentration dope can be prepared from a low concentration dope. However, since the evaporation mechanism of the solvent is limited by the internal diffusion of the dope, the surface evaporation rate of the solvent is limited by the internal diffusion. Faster than the diffusion rate, causing partial overdrying of the surface. According to the findings of the present inventors, this is because evaporation of the solvent on the inner wall surface of the container cannot be prevented, and the surface is not renewed.

As a result, gel is mixed in the obtained high concentration dope. When the dope containing the gel is filtered, the clogging of the filter medium is accelerated, and the burden on the filtration step is increased. Furthermore, the gel-like solid may deform and pass through the filter medium, and when the resulting high-concentration dope is formed into a photosensitive material support by, for example, a casting method, a base failure occurs, which is completely suitable for practical use. May not be available.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to obtain a high-concentration dope from a low-concentration dope reliably and with high productivity, and to obtain a high-concentration dope free of gel.

[0010]

The object of the present invention is to provide a method for preparing a low-concentration cellulose triacetate solution and then transferring the solution between the cylindrical body and the rotation locus of the outer periphery of the rotating blade rotating in the circumferential direction inside the cylindrical body. This can be solved by obtaining a high-concentration cellulose triacetate solution while evaporating the solvent by giving a temperature difference to the solution.

In addition, in terms of the apparatus, a supply port of a low-concentration cellulose triacetate solution communicating between a cylindrical body, a rotating blade rotating in the circumferential direction inside the cylindrical body, and a rotation locus on the outer periphery of the rotating blade, Solvent gas leaving the rotating area of the rotating blade
Outlet , the solvent gas outlet is separate, the high-concentration cellulose triacetate solution outlet separated from the rotating region of the rotary blade, at least the supply port of the low-concentration cellulose triacetate solution and the solvent gas outlet Heating means for heating the cellulose triacetate solution in substantially the entire region between the two can be solved.

[0012]

According to the present invention, the low-concentration cellulose triacetate solution is introduced between the cylindrical body and the rotation locus of the outer periphery of the rotating blade rotating in the circumferential direction, and the solvent is evaporated by giving a temperature difference between the solution and the solution. The high-concentration cellulose triacetate solution is obtained while the low-concentration cellulose triacetate solution is constantly being renewed in the gap between the cylindrical body and the rotation locus of the outer periphery of the rotating blades rotating in the circumferential direction inside the cylinder. As a result, there is an advantage that no gel is generated as in the conventional example, and heat of agitation is generated, thereby evaporating the solvent. In addition, as in the examples described below, according to the present invention, a cellulose triacetate solution having a high concentration of 14 to 43% by weight based on the cellulose triacetate solution can be obtained.
What that coupled with no occurrence of the gel, can be the burden of the filtration process is or is not necessary lightly.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings.

FIGS. 1 and 2 show an example of the apparatus according to the present invention. Reference numeral 1 denotes a cylindrical body, in which a drive motor 2 rotates in a circumferential direction via a rotating shaft 3 in a radial direction. Four groups of rotating blades are provided. A slight gap G is secured between the outer edge of the rotary blade 4 and the inner surface of the inner wall 1A of the cylindrical body 1, and a supply port 5 for a low-concentration cellulose triacetate solution is formed in communication with the gap G.

The low-concentration cellulose triacetate solution is supplied to the supply port 5 of the low-concentration cellulose triacetate solution through the pump 7 from the preparation device 6 and supplied into the gap G. On the other hand, as shown in FIG. 1, the rotating blade 4 has one end close to one end of the cylinder 1 and the other end separated from the other end of the cylinder 1, and A solvent gas outlet 8 is formed at a position away from the region and communicates with the inside of the cylinder 1. In addition, apart from the solvent gas outlet 8, a high-concentration cellulose triacetate solution outlet 9 is formed in a similar manner to the inside of the cylinder 1 at a position away from the rotation region of the rotary blade.

On the other hand, the cylindrical body 1 has an inner wall 1A and an outer wall 1B.
And a heating medium 1 inside the annular chamber.
0, for example, hot water is introduced from one end and taken out from the other end, whereby the cellulose triacetate solution is configured to be evaporated and concentrated.

In the apparatus for producing a high-concentration cellulose triacetate solution thus constituted, the cellulose triacetate is preferably dissolved in a solvent, for example, a mixed solvent of methylene chloride and an alcohol having 6 or less carbon atoms. A low concentration solution is prepared which is 7 to 17% by weight on a solution basis. When this is guided between the cylindrical body 1 and the rotation trajectory of the outer periphery of the rotating blade 4 rotating in the circumferential direction inside the cylindrical body 1, that is, when introduced into the gap G, a thin doped thin film corresponding to the gap is formed, Upon receiving the heat from the inner wall 1A, the solvent in the solution undergoes an evaporating action. The evaporated solvent is supplied to the solvent gas outlet 8
And cooled by the condenser 11 to recover the solvent.

Since the evaporation rate of the solvent in the dope is determined by the diffusion rate in the film, if only the film surface is excessively dried, a gel of cellulose triacetate is generated. However, the dope on the film surface rotates during the evaporation process. Since the solvent is evaporated while being constantly updated by the rotation of the blades 4, no gel is generated as in the conventional example, and heat of stirring is generated.
There is also an advantage that the evaporation of the solvent is promoted.

In this way, since the concentration by evaporation can be carried out without worrying about the generation of gel, according to the present invention, as shown in Examples described below, the cellulose having a high concentration of 14 to 43% by weight based on the cellulose triacetate solution is used. A triacetate solution can be obtained. As a result, the burden on the filtration step can be reduced or eliminated, in combination with the absence of gel. The obtained high-concentration cellulose triacetate solution is guided from the outlet 9 by a pump 12 to a filtration step or directly to a storage tank.

The evaporation rate of the solvent or the high concentration of cellulose triacetate to be obtained can be controlled by the opening of the discharge control valve 13 and / or the temperature or the supply flow rate of the heating medium 10.

Generally, the temperature of the heating medium is 40 to 20
0 ° C, especially 40-150 ° C, is desirable.

The cellulose triacetate preferably contains acetyl cellulose triacetate in an amount of 58 to 62.5% by weight. The rotation speed of the rotating blade is 10 to 2000 rp
m is preferable, and a gap (in other words, a thickness of the thin film) between the trajectory of the outer periphery of the rotating blade and the inner surface of the inner wall is preferably 0.001 to 100 mm, particularly 0.1 to 10 mm. The shape of the rotating blade can be appropriately selected, and for example, the shape shown in FIGS. 3 and 4 can be used.

In the apparatus of the present invention, the cylindrical body may be of a vertical type in addition to the horizontal type as in the embodiment. Further, a taper may be used. It is desirable that the solvent gas outlet 8 preferably avoids the rotation range of the rotary blade 4.

(Examples) Examples will be shown below to clarify the effects of the present invention.

A low-concentration cellulose triacetate solution was prepared in advance by a conventionally known method under conditions where no gel was generated. The preparation conditions are as follows. Cellulose triacetate 100 parts by weight TPP 16 parts Methylene chloride 455 parts Ethyl alcohol 75 parts This solution is supplied to the apparatus shown in FIGS. 1 and 2 at a supply speed of 1.7 × 10 ⁻² kg / sec. Warm water was flowed through the jacket so that the temperature at the triacetate solution outlet was maintained at 90 ° C., and while adjusting the opening of the control valve at the solvent gas outlet so that the internal pressure was 2 kgf / cm ² , 21.1
A weight percent high concentration cellulose triacetate solution was prepared.

When the filterability of this solution was evaluated by a constant speed filtration method, the filterability was about twice that of the dope directly dissolved at the same temperature.

[0027]

As described above, according to the present invention, a high-concentration dope can be produced from a low-concentration dope reliably and with high productivity, and a high-concentration dope free from gel mixing can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an example of an apparatus according to the present invention.

FIG. 2 is a cross-sectional view thereof.

FIG. 3 is a cross-sectional view of another example of a rotating blade.

FIG. 4 is a side view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical body 3 Rotating shaft 4 Rotating blade 6 Low concentration cellulose triacetate preparation device 8 Solvent gas outlet 9 High concentration cellulose triacetate solution outlet 10 Heating medium 11 Condenser

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshiyuki Hagiwara 1 Sakuracho, Hino-shi, Tokyo Inside Konica Corporation (58) Field surveyed (Int. Cl. ⁶ , DB name) B29B 13/00-13 / 06 C08J 3/09

Claims (5)

(57) [Claims] After a low-concentration cellulose triacetate solution is prepared, it is guided between a cylindrical body and a rotation locus of an outer periphery of a rotating blade rotating in a circumferential direction inside the cylindrical body, and a temperature difference is given between the solution and the solution. And obtaining a high-concentration cellulose triacetate solution while evaporating the solvent by heating. 2. The low-concentration cellulose triacetate solution has a concentration of 7 to 17% by weight based on the cellulose triacetate solution.
The method of claim 1, wherein 3. The high-concentration cellulose triacetate solution has a concentration of 14 to 43% by weight based on the cellulose triacetate solution.
The method of claim 1, wherein 4. The method according to claim 1, wherein the cellulose triacetate contains 58 to 62.5% by weight of acetyl cellulose triacetate. 5. A supply port for a low-concentration cellulose triacetate solution communicating between a cylindrical body, a rotating blade rotating in the circumferential direction therein, and a rotation locus on the outer periphery of the rotating blade, and a rotation area of the rotating blade. Solvent gas outlet, which is separated from the solvent gas outlet, which is separate from the rotating region of the rotary blade, a high-concentration cellulose triacetate solution outlet, and at least a supply port for the low-concentration cellulose triacetate solution and a solvent gas outlet. Heating means for heating the cellulose triacetate solution in substantially the entire region between the outlet and the outlet.