KR0185687B1 - Process for preparing a homogeneous solution of cellulose in n-methyl morpholine n-oxide using ammonia or an amine - Google Patents

Abstract

The present invention relates to a method for producing a highly homogeneous cellulose solution which can be used for producing cellulose fibers and films, characterized in that cellulose pulp swelled with ammonia or an amine is directly dissolved in an NMMO solvent in an extruder or a kneader . According to the present invention, a homogeneous cellulose solution can be prepared directly without any swelling process in an extruder because a swelled cellulose pulp is used which easily permeates the solvent. Therefore, the method for producing a cellulose solution of the present invention is simpler in process than the conventional method and can produce a highly homogeneous solution in a short time.

Description

Method for preparing homogeneous cellulose N-methylmorpholine-N-oxide solution using ammonia or amine

The present invention relates to a process for producing a cellulose pulp swollen with ammonia (NH ₃ ) or a low molecular weight amine by dissolving directly in a liquid N-methylmorpholine-N-oxide (NMMO) To a process for preparing a highly homogeneous cellulose solution. The highly homogeneous cellulose solution prepared according to the present invention can be used to prepare cellulose fibers or cellulose films.

Since the method of producing a cellulose solution using a tertiary amine oxide-based solvent has been proposed by Graenacher et al. In US Pat. No. 2,179,181, a more efficient and economical solution production method has been continuously proposed.

U.S. Patent Nos. 4,142,913,4,144,080,4,196,282 and 4,246,221 disclose a method for producing a slurry by first swelling cellulose in an aqueous solution of a tertiary amine oxide having a water content of 22% by weight or more and not capable of dissolving cellulose, And a method for producing a cellulose solution by a reduced-pressure distillation method in which cellulose is dissolved by removing excess water by distillation under reduced pressure. However, since the manufacturing method of such a cellulose solution is a complicated process because a solution is produced through a long-time decompression distillation, the solution is discolored due to pyrolysis of the solvent and cellulose, and the problem of time and energy waste due to long- .

European Patent No. 356,419 to Stefan et al. Discloses a method for continuously producing a 72 kg cellulose solution per hour using the concentration process as described above. This patent discloses a method for producing cellulose by swelling cellulose by using an aqueous solution of N-methylmorpholine-N-oxide (hereinafter referred to as NMMO) containing 40% water and drying the swollen cellulose slurry using a screw equipped with a fan- To thereby produce a cellulose solution by distillation under reduced pressure. Quigley also discloses a process for preparing a solution using a thin film still, which is a vacuum distillation apparatus, in International Patent WO 94/06530. However, these methods require a concentrated cellulose slurry having a high viscosity, so that the production efficiency is reduced and the apparatus is complicated because it is required to carry out distillation under reduced pressure.

U.S. Patent No. 4,211,574 discloses a process for producing cellulose fibers by immersing and swelling a cellulose pulp sheet in a liquid tertiary amine oxide capable of dissolving cellulose at a moisture content of 5 to 15% Thereby producing a cellulose solution. However, in this method, since the amine oxide solvent swells only a part of the surface of the cellulose pulp sheet and forms a film on the surface thereof, the amine oxide solvent does not penetrate deeply into the pulp, so that the undissolved cellulose remains in the solution of the prepared cellulose Of the population. When a film is formed on the pulp sheet, a solution that is uniformly dissolved even when stirred or heated can not be produced. Accordingly, the method of producing a solution according to this patent has a disadvantage that a homogeneous cellulose solution can not be produced.

On the other hand, U.S. Patent No. 4,416,698 suggests a method of simply mixing a cellulose powder and a solid phase NMMO powder and transferring the powder to an extruder for dissolution. However, since the cellulose powder and the solid phase solvent are simply mixed with each other in this method, when a large amount of the mixture is prepared, the cellulose powder and the solid phase NMMO powder are not uniformly mixed with each other, There are disadvantages of non-existent cellulose particles, and it is difficult to industrialize due to low flow rate. Therefore, it is unsuitable for producing a large amount of the mixture, has a disadvantage in that the production efficiency is low, and the powder has a possibility of dust explosion.

As described above, the conventional method for producing a cellulose solution is a technique for producing a homogeneous cellulose solution by sufficiently uniformly swelling the cellulose. However, while excess moisture is removed, NMMO, which is a solvent, There are drawbacks to be experienced.

It is an object of the present invention to provide a method of producing a cellulose solution by using a tertiary amine oxide type NMMO solvent and a method of producing a highly homogeneous cellulose solution by a simple process, .

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a process flow diagram schematically illustrating a cellulose swelling process of the present invention.

FIG. 2 is a process overview diagram showing a solution manufacturing process of the present invention. FIG.

3 is an illustration of a typical block diagram among various block diagrams of a twin-screw extruder used in the present invention.

In order to solve the problems of the prior art as described above, the crystal structure of natural cellulose has been analyzed and studied. As a result, the present inventors have found that the action of liquid ammonia or low molecular weight amines under pressure increases the interval between cellulose molecules, It was found that the action can be greatly promoted.

That is, the natural cellulose is changed from cellulose I to cellulose III under the action of ammonia as shown in Reaction Scheme 1 below.

Such a technique is well known as a technique of mercerizing natural fiber cotton to make it look like a silk thread. Cellulose treated with liquid ammonia or low molecular weight amines is dissolved intact in NMMO (15% by weight or less of the function) to make a homogeneous cellulose solution, which simplifies the process. Ammonia or amines can be completely recovered by heating under reduced pressure after reacting with cellulose under normal pressure at room temperature and can be circulated. That is, cellulose is mercerized in a dry state.

Cellulose pulp treated with liquid ammonia is separately or mixed with NMMO and sent to a kneading extruder or kneader to prepare a cellulose-NMMO solution. The cellulose-NmMO solution thus prepared is much more homogeneous than the cellulose-NHMO solution prepared by other methods, so that it has an advantage that the defects of the single yarn in the spinning hardly appear.

Therefore,

(a) swelling the cellulose pulp into a swelling agent selected from ammonia and low molecular weight amines,

(b) injecting the swelled cellulose pulp into an extruder or kneader at a constant speed and dissolving the pulp in a liquid N-methylmorpholine-N-oxide,

(c) defoaming the dissolved solution,

(d) stabilizing the degassed and filtered solution in a reservoir. The present invention also provides a method for producing a highly homogeneous cellulose solution.

The highly homogeneous cellulose solution prepared in the present invention can be directly used to produce fibers, films, and membranes through a processing machine.

The method for producing a cellulose solution of the present invention has the following features and advantages.

First, the cellulose pulp is swelled using liquid or gaseous ammonia or a low molecular weight amine as a swelling agent. The method of directly dissolving the cellulose pulp sheet in the NMMO solution is difficult to completely dissolve because it forms a film on the surface of the pulp sheet, but the cellulose pulp sheet swollen with ammonia or amine has an advantage of being easily dissolved in the NMMO solution. Also, ammonia or amine used as a swelling agent can be recovered and recycled as low energy and can be reused.

Secondly, since the conventional method of producing a cellulose solution by a vacuum distillation method is produced over a long period of time, decomposition of cellulose and a solvent is severe, but the method of the present invention can be carried out by a simple extruder May be used but the use of a biaxial extruder is more preferred) or to produce a homogeneous cellulose solution in a kneader, resulting in less decomposition of the cellulose and solvent.

Thirdly, since the conventional method is manufactured through the concentration process by the reduced pressure distillation, it takes a long time to process and the apparatus are complicated. However, the method of the present invention is simple in the process and the apparatus because the dissolving process is simple.

A method for producing the homogeneous cellulose solution of the present invention will be described with reference to the accompanying drawings.

Fig. 1 is a process flow chart schematically showing the cellulose swelling process of the present invention, Fig. 2 is a process overview diagram showing a solution production process of the present invention, and Fig. 3 is a flowchart showing various block diagrams / RTI > is an example of a typical block diagram. The process for producing the cellulose solution according to the present invention is simple. First, the cellulose pulp sheet is swollen as described below using liquid or gaseous ammonia or an amine as the swelling agent. The swollen cellulose pulp sheet may be directly dissolved in the NMMO solvent. Preferably, the cellulose pulp sheet is finely cut to a predetermined size of 10 mm x 10 mm or less, and the finely cut cellulose pulp chips are extruded in a liquid phase Of NMMO is sprayed to completely dissolve the cellulose chip to prepare a stable solution. At this time, in order to obtain a stable and homogeneous solution, a kneader or an extruder can be used independently or an extruder-kneader can be used in combination.

The conventional method of producing a cellulose solution by reduced pressure distillation requires a long time and a cost because it is necessary to remove excess water from a slurry composed of cellulose and a tertiary amine oxide-based solvent. However, So that a high concentration solvent of 5 to 20% by weight can be easily produced. Therefore, the method of the present invention is short in time and simple in process because it does not undergo a vacuum distillation process from the slurry.

A cellulose pulp sheet or chip is put into the reactor A and liquid or gaseous ammonia or amine is added to swell the cellulose pulp sheet or the chip. Here, the pulp chip means that the pulp sheet is cut to 10 mm x 10 mm or less. At this time, a cellulose pulp sheet or a chip is put into the reactor B. If the pulp sheet or chip of reactor A swells more than twice the original thickness, the liquid or gaseous ammonia or amine in reactor A is depressurized and transferred to reactor B, and reactor A is completely depressurized to remove ammonia or amine. During the swelling of the pulp of the reactor B, the swollen cellulose of the reactor A is cut through a cutting process to a predetermined size (10 mm x 10 mm or less) (cutting process is omitted when a cellulose chip is used) And the reactor A is filled with a new cellulose pulp sheet or chip. When the cellulose pulp sheet or chip of the reactor B is swollen, the liquid or gaseous ammonia or amine is reduced in pressure and transferred to the reactor A, and the swollen pulp sheet of the reactor B is transferred to the cutting process (the cutting process is omitted when using a cellulose chip) B replenishes the new cellulose pulp sheet or chip again and repeats the above process continuously. On the other hand, the swollen and cut cellulose pulp chips are transferred to an extruder or a kneader through an air transfer tube, and then completely dissolved in liquid NMMO to form a homogeneous solution.

Hereinafter, the process for producing the solution of the present invention will be described in detail.

Cellulose sheets are swollen with liquid or gaseous ammonia or amines and used after cutting to a certain size (10 mm x 10 mm or less). In addition, the cellulosic chips cut to a certain size may be swollen to ammonia or amines. In a conventional cellulose chip which is not subjected to a swelling process, it is difficult to prepare a homogeneous solution because a large particle is not dissolved directly in a solvent in a dissolving process and a film is formed on a surface. However, a swollen cellulosic pulp chip before dissolution easily dissolves in a solvent do. After swelling, the cut cellulose chips are passed through an air transfer tube and fed to an extruder or kneader at a constant speed using a horse feeder. The cellulosic chips injected into the extruder or kneader are completely dissolved by the liquid NMMO solvent. The NMMO solvent for directly dissolving cellulose uses a liquid solution containing 5 to 15% by weight of water. At this time, the liquid NMMO solution is maintained at 80 to 130 캜. The liquid NMMO solution is sprayed into the extruder or kneader at a constant speed through a gear pump. The mixing ratio of the NMMO solvent is appropriately selected so that the cellulose concentration of the solution is 5 to 20% by weight, preferably 12 to 20% by weight.

On the other hand, an example of an extruder used for producing the homogeneous cellulose solution of the present invention is a corotating twin screw extruder having the structural characteristics exemplified in FIG.

The configuration of the twin-screw extruder is composed of three blocks. The first block is divided into a feed section and a compression section. The second block is divided into a pressure reducing section, a mixed kneading section, and a pressure (reverse screw) section. The third block is divided into a vent section and a metering section. At this time, two extruders are equipped with two hoppers. The first hopper is used to feed the swollen cellulosic chip mounted on the first block, and the second hopper is mounted on the depressurization section of the second block to feed the liquid NMMO solvent.

The structural characteristics of the twin-screw extruder used in the present invention will be described in more detail as follows.

In order to remove the air contained in the swollen cellulose chips, the transporting section compression ratio of the first block was set to 1.1 to 2.5, and the screw pitch of the second block gradually decreased from the tip to the tail to maximize the pressure in the barrel . It is preferable that the pressure at the end of the second block is 300 psi or more in order to completely remove the bubbles of the cellulose solution. To this end, as illustrated in FIG. 2, a reverse screw section is inserted at the end of the second block, and a mixing and kneading section is inserted just before the reverse screw section. The third block melts the mixture more homogeneously and removes minute bubbles. The compression ratio is 2.0 to 4.0. A vent vacuum line was connected to the vent section for effective defoaming.

Hereinafter, the process of dissolving the swollen cellulose chips injected into the first hopper into the liquid NMMO solvent injected into the second hopper in the biaxial extruder having the above-described structural features will be described in detail.

The swollen cellulose chips injected into the first hopper at a constant speed are passed through the first block having a relatively large screw pitch and transferred to the second block. That is, the loaded swelled cellulose chips are transferred to the zero pressure zone through the transfer section of the first block. The compression ratio of the first block is preferably 1.1 to 2.5. The liquid NMMO maintained at 80 to 130 캜 is supplied at a point where the pressure decreases due to the decrease in the diameter of the screw in the second block, that is, the mixing ratio is adjusted so that the concentration of the cellulose solution becomes 5 to 20% by weight through the second hopper Adjust and spray. In the second block, a mixture of cellulose and a liquid NMMO solvent is sufficiently homogeneously mixed to form a kneaded mixture. The mixture is gradually compressed and then kneaded in a mixing and kneading section maintained at 80 to 130 ° C. The kneaded solution is defoamed in a vent section to remove the gas contained in the solution to prepare a homogeneous solution capable of extrusion.

The cellulose solution prepared in the extruder is transferred to a storage tank equipped with a pressure regulator and then stabilized for several minutes to produce a highly homogeneous cellulose solution. The highly homogeneous cellulose solution of the present invention is used to prepare cellulose fibers and films.

Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the present invention is not limited to the embodiments. The evaluation method performed in the embodiment is as follows.

a) Weight average degree of polymerization (DPw)

The change in the molecular weight of the cellulose produced during the preparation of the cellulose solution was measured by the following method.

The intrinsic viscosity of the cellulose was measured in a concentration range of 0.1 to 0.6 g / l using a 0.5 M cupriethylenediamine hydroxide solution prepared according to the method of ASTM (D 539-51T). The viscosity was measured using a Ubbelohde viscometer at 25 占 0.01 占 폚. 1 (supplied by Fisher). The intrinsic viscosity (IV) of the sample is the boiling point for each concentration (c) Was calculated from the following equation (1). The weight average degree of polymerization (DPw) can be calculated from the intrinsic viscosity obtained from the formula (1) by the formula (Mark-Houwink formula (M. Marx. Makromol. Chem., 16, 157 (1955); J. Brandrup, EH Immergut, Polymer Handbook, 3rd ed., V144, wiley-Interscience, New York, 1989).

[IV] = 0.98 x 10 < ^{-2 & gt ;} DP ^0.9

b) Concentration of coloring impurities

Changes in the solvent produced during the preparation of the cellulose solution were measured by equilibrium 30% aqueous solution of NMMO by immersing 10 g of the solution in the prepared cellulosic solution and immersing it in 16.17 ml of distilled water for 60 minutes. At this time, the concentration of the colored impurities in the recovered NMMO (N-methylmorpholine-N-oxide) aqueous solution was measured using a UV-visible speotrophotometer (model: Hewlett Packard HP8453). The absorbance of the solution according to the dissolution of the solvent was measured at 450 nm and the result of the absorbance of the solution was expressed as the optical density of amine oxide (AOOD) of the solution containing 1% NMMO by weight. The AOOD of the 50% NMMO aqueous solution used in this experiment was 0.0006.

c) homogeneity of solution

The homogeneity of the solution prepared in the present invention was evaluated from the presence of undissolved cellulose particles in the solution passed through the extruder. At this time, the undissolved particles were observed and evaluated with a Zeiss polarized microscope.

Example 1

The twin-screw extruder used in this embodiment has the following structural characteristics. In order to maximize the pressure in the barrel to remove the air contained in the cellulose chip, the pitch of the screw of the second block is designed to gradually decrease from the tip of the block to the tail. The pressure at the end of the second block was more than 300 psi to completely remove the cellulosic solution bubbles. For this, a reverse screw section is inserted at the end of the second block as shown in FIG. 2, and a mixing and kneading section is inserted just before the reverse screw section. The compression ratio of the first block was 1.3, the third block melted the mixture more homogeneously, and the compression ratio was 2.5 to increase the bubble removal efficiency.

The material of the barrel part and the screw was SACM, and when the diameter D of the extruder was? 80 mm, L / D was 34.

Liquid or gaseous ammonia was added to a sheet-type cellulose (TTT, Cellunier-E) having a cellulose polymerization degree (DPw) of 660 and swollen until the thickness of the cellulose pulp sheet increased to twice or more. After the liquid ammonia was completely removed under vacuum, Cut into specimens (5 mm x 5 mm) and passed through an air transfer tube to a hopper of a coaxial twin screw extruder of the same structure as shown in Fig. 3 at a rate of 2000 g per minute using a hose feeder Respectively. The chopped cellulose pulp chips injected into the first hopper were passed through a pressure reducing section through a conveying section having a compression ratio of 1.3. That is, the cellulose pulp chips were transferred to the second block through the first block having a relatively large screw pitch. At this time, 88% by weight of the liquid NMMO solution maintained at 90 DEG C was sprayed and injected into the second hopper of the second block installed at the decompression section at a rate of 12290 g / minute to prepare a mixture. In this liquid NMMO solution, propyl gallate was dissolved in 0.2 wt% with respect to cellulose. The cellulosic chip injected into the extruder and the NMMO solvent formed a primary mixture. Subsequently, the mixture was kneaded in a kneading section maintained at 100 캜 while being gradually compressed. The kneading solution passed through the kneading section was passed through the vent section, and the homogeneous solution defoamed while passing through the metering section of the third block having the compression ratio of 2.5. At this time, the cellulose solution formed a concentration of 14% by weight. The solution thus prepared was stabilized in a storage tank equipped with a pressure regulator for 5 minutes. At this time, if the thickness of the cellulose pulp sheet or the chip is not increased more than twice, a film is formed on the surface of the cellulose and is not completely dissolved. As the size of the chip increases, the time for dissolving increases and it is difficult to dissolve completely in the twin-screw extruder. When the size of the chip was limited to 5 mm x 5 mm, the time to completely dissolve was measured to be less than 5 minutes, and the residence time in the extruder was measured within 6 minutes as measured by carbon black injection method.

The degree of polymerization of the cellulose obtained from the prepared solution was 600, and the AOOD of the solvent was 0.013. The solution observed from the microscope was in a very homogeneous state, and no undissolved cellulose particles were observed.

Example 2

The biaxial extruder used in this example is the same as the structure of the extruder used in Example 1. Liquid or gaseous ammonia was put into a 5 mm x 5 mm chip-type cellulose (cellunier-F ITT company) having a cellulosic polymerization degree (DPw) of 660 and swollen until the thickness of the cellulose pulp chip was increased to twice or more, Was completely removed under vacuum, and the swollen pulp chips were passed through a transfer tube and injected into a first hopper of a co-rotating twin-screw extruder having the same structure as shown in Fig. 3 at a rate of 2000 g per minute using a hose feeder . The swelled cellulose pulp chips injected into the first hopper were passed through a pressure reducing section through a conveying section having a compression ratio of 1.3. That is, the cellulose chips passed through the first block having a relatively large screw pitch and transferred to the second block. At this time, 88% by weight of the liquid NMMO solution maintained at 90 DEG C was sprayed and injected into the second hopper of the second block installed at the decompression section at a rate of 12290 g / minute to prepare a mixture. In this liquid NMMO solution, propyl gallate was dissolved in 0.2 wt% with respect to cellulose. The cellulosic chip injected into the extruder and the NMMO solvent formed a primary mixture. Subsequently, the mixture was kneaded in a kneading section maintained at 100 캜 while being gradually compressed. The kneading solution passed through the kneading section was passed through a vent section to prepare a defoamed homogeneous solution. At this time, the cellulose solution formed a concentration of 14% by weight. The solution thus prepared was stabilized in a storage tank equipped with a pressure regulator for 5 minutes.

The degree of polymerization of the cellulose obtained from the prepared solution was 600, and the AOOD of the solvent was 0.013. The solution observed from the microscope was in a very homogeneous state, and no undissolved cellulose particles were observed.

Example 3

The structure of the biaxial extruder used in this example is the same as that of the extruder used in Example 1. [ Sheet type cellulose (ITT, Rayon-EXP) having a cellulose polymerization degree (DPw) of 1,000 was swollen into liquid or gaseous ammonia as in Example 1, and then finely cut to a predetermined size (10 mm x 10 mm) or less and passed through a transfer tube Was fed into a hopper of a twin screw extruder at a rate of 2000 g per minute. Cellulose chips injected into the first hopper were passed through the first block and transferred to the second block.

At this time, 89 wt% of the liquid NMMO solution maintained at 100 DEG C was sprayed and injected into the second hopper at a rate of 14670 g per minute to prepare a mixture. In this solution, 0.2% by weight of propyl gallate was dissolved in cellulose. The mixture was kneaded in an extruder. The mixture was kneaded and mixed in a kneading section maintained at 120 DEG C, and passed through a defoaming section to prepare a homogeneous solution. At this time, the cellulose solution formed a concentration of 12% by weight. The solution thus prepared was stabilized in a storage tank with pressure regulator for 5 minutes.

The degree of polymerization of the cellulose obtained from the prepared solution was 890, and the AOOD of the solvent was 0.015. The solution observed from the microscope was in a very homogeneous state, and no undissolved cellulose particles were observed.

Example 4

The difference from Example 2 was that liquid methylamine was used instead of liquid ammonia to swell the cellulose chips. A cellulose solution having a concentration of 12% by weight was produced in the same manner as in Example 2 except for the above.

The degree of polymerization of the cellulose obtained from the prepared solution was 890, and the AOOD of the solvent was 0.015. The solution observed from the microscope was in a very homogeneous state, and no undissolved cellulose particles were observed.

Example 5

Sheet-type cellulose (ITT, Rayon-EXP) having a cellulose polymerization degree (DPw) of 1,000 was swollen to liquid or gaseous ammonia as in Example 1 and then finely cut to a predetermined size (10 mm x 10 mm) or less and passed through a transfer tube And injected at a rate of 2,000 g per minute into a cone (IKA, multiple-chamber kneading and extrusion machine). At the same time, 89 wt% liquid NMMO solution maintained at 100 캜 was sprayed at a rate of 14,670 g per minute to prepare a kneaded mixture, which was then gradually heated and kneaded at 120 캜 to prepare a solution. When this is defoamed, a 12 wt% homogeneous cellulose-NMMO solution is obtained. The solution thus prepared was stabilized in a storage tank with pressure regulator for 5 minutes.

The degree of polymerization of the cellulose obtained from the prepared solution was 860, and the AOOD of the solvent was 0.017. The solution observed from the microscope was in a very homogeneous state, and no undissolved cellulose particles were observed.

Comparative Example

The following comparative examples were carried out in order to compare the production process of the cellulose solution by the concentration method of the conventional method with the process by the direct dissolution method of the present invention.

In order to prepare a cellulose solution, pulp (cellulose DPw: 1000) containing 6% of water was first cut into irregular shape having a size of 3 to 15 cm2. 240 g of the cut pulp was immersed and swelled in 1673 g of an aqueous solution of N-methylmorpholine-N-oxide containing 22% of water at 80 DEG C for 1 hour to prepare a swollen material, 5 L, and the mixture was put into a small grinder having a blade at its bottom. At this time, 0.2% by weight of propyl gallate, which is an antioxidant, was added to cellulose. The swollen cellulose thus charged was pulverized at 3,000 rpm for 11 minutes to prepare a uniform preliminary mixture. Subsequently, the preliminary mixture was distilled under reduced pressure at 20 mmHg at 120 DEG C for 60 minutes to remove excess water to prepare a cellulose solution. The concentration of the prepared cellulose solution was 14% by weight.

The degree of polymerization of the cellulose obtained from the solution prepared by the above-mentioned concentration method was 650 and the AOOD of the solvent was found to be 0.05.

From the above results, it can be seen that when the cellulose solution was prepared by the concentration method of producing the solution for at least 30 minutes, the molecular weight of the cellulose decreased by 30% or more over a long period of time, and the AOOD of the solvent was 80 Times more than that of the control group. On the other hand, when the preparation time of the solution was less than 10 minutes, it was found that the decreasing rate of the cellulose molecular weight was less than 20%, and the increase of the AOOD value of the solvent was less than 30 times of the initial value.

Therefore, the process of producing the cellulose solution by the concentration method of the present invention is excessive and time consuming, but the production time of the present invention is short, and excessive decomposition of the cellulose and the solvent can be suppressed. From these facts, it can be seen that the present invention is superior to the conventional process.

According to the present invention, a homogeneous cellulose solution can be produced directly in the extruder without a separate swelling process since a swelled cellulose pulp that easily permeates the solvent is used. Therefore, the method for producing a cellulose solution of the present invention is simpler in process than the conventional method and can produce a highly homogeneous solution in a short time. The highly homogeneous cellulose solution thus prepared can be immediately used to produce cellulose fibers, films, and separating membranes through a processing machine.

Claims (7)

(a) swelling the cellulose pulp into a swelling agent selected from ammonia and low molecular weight amines, (b) dissolving the swollen cellulose pulp in a liquid N-methylmorpholine-N-oxide having a moisture content of 5 to 15% and a temperature of 80 to 130 ° C by injecting the swelled cellulose pulp into an extruder or kneader at a constant rate, (c) defoaming the dissolved solution, (d) stabilizing the defoamed filtrate in a reservoir ≪ RTI ID = 0.0 > 1, < / RTI > The method according to claim 1, wherein the cellulose pulp injected into step (b) is a cellulose pulp sheet swollen with a swelling agent or a pulp sheet thereof cut to a size of 10 mm x 10 mm or less. The method of any one of claims 1 or 2, wherein the swelling agent is liquid or gaseous ammonia. 3. The method of claim 1 or 2, wherein the swelling agent is liquid or gaseous methylamine. The method according to claim 1 or 2, wherein in step (a), the cellulose pulp is swollen to a thickness at least twice. The method according to claim 1 or 2, wherein the dissolution in step (b) is carried out by injecting cellulose pulp into an extruder at a constant speed and transferring the cellulose pulp to a decompression section where the N-methylmorpholine- Way. The method according to claim 1 or 2, wherein the extruder of step (b) is a single-screw extruder or a twin-screw extruder.