KR20060073137A - A solution containing cellulose dissolved in n-methylmorpholine-n-oxide and high tenacity lyocell multifilament using the same - Google Patents

Abstract

The present invention relates to a method for producing a highly homogeneous cellulose solution that can be used for high strength cellulose fibers with high production capacity. Specifically, the present invention provides a rotary blade (15-50 rpm) capable of imparting a suitable temperature (40-74 ° C.) and shear force to a liquid N-methylmorpholine N-oxide (hereinafter referred to as NMMO) with a water content of 15% by weight or less. ) Into a continuous kneader attached to prepare a liquid-solid intermediate phase, and then contact, disperse and mix the powdered cellulose with a moisture content of 5% by weight or less in the kneader to form a paste, and then 50 to 100 ° C.) and a coaxial twin screw extruder controlled at a rotational speed of screw (0 to 50 rpm) to dissolve within a short time, thereby producing a highly homogeneous cellulose solution that minimizes cellulose degradation. The cellulose solution may be manufactured into a cellulose molded article such as a fiber, a filament, a film or a tube. In particular, the fiber produced from the cellulose solution is excellent in strength and dimensional stability can be usefully used as a reinforcing material for rubber products of industrial filament fibers or tires and belts.

High strength cellulose fiber, continuous kneader, extruder, mesophase NMMO, powdered cellulose, high homogeneous cellulose solution, high productivity

Description

A solution containing cellulose dissolved in N-methylmorpholine-N-oxide and high tenacity lyocell multifilament using the same}             

1 is a state change diagram according to the temperature of the NMMO according to the present invention.

2 is an overall manufacturing process diagram according to the present invention.

3 is a method for preparing a solution according to the present invention.

The present invention relates to a method for producing a high homogeneous cellulose solution for producing a high strength lyocell fiber that can be used as a rubber reinforcing material such as filament fibers or tires and belts for the lyocell industry.

The following technique is known in the conventional method for producing a cellulose solution using NMMO hydrate.                         

U.S. Patent No. 4,142,913, 4,144,080 discloses a solution in which cellulose is dissolved by distillation under reduced pressure of cellulose swelling dispersed in NMMO hydrate, and cooled to prepare a solid phase (a kind of chipping), and then dissolved in an extruder. A method of preparing a solution is disclosed. This method can simplify the dissolution process by using an extruder, but due to the preceding process for chipping in advance, the time and energy consumption is large, there is a problem in temperature and humidity management of the precursor.

U.S. Patent No. 5,584,919 discloses a process for preparing solid NMMO with a water content of 5 to 17% and then stirring in powdered cellulose and a horizontal cylindrical high speed mixer to make a granule-shaped precursor and then dissolving it in an extruder. This method has a large dispersion and low yield of particle size of the granules produced. This shows a larger dispersion as capacity increases and a complicated cooling device must be attached for transport and storage. There is also a problem with the preparation and storage of solid NMMO solvents.

U.S. Pat.Nos. 5,094,690, 5,534,113 or 5,603,883 disclose excess water from a forced thin film distillation apparatus capable of forming a thin film solution layer of 1.5 to 5.0 mm in a slurry in which cellulose is dispersed with NMMO containing 40% water content. The process for preparing the solution was then disclosed. This method evaporates and dissolves as the slurry is lowered by the rotation of the rotor, so that the residence time is shorter and it is difficult to give sufficient shear force as it is downstream in the vertical direction. The use of a complex reduced pressure distillation unit is inevitable in order to evaporate the water to the required level within the problem of poor efficiency and solution residence time. This method has a long time for the entire solution manufacturing process, consumes a lot of energy, and has a problem in producing high strength fibers due to low purification efficiency due to decomposition of cellulose and discoloration of NMMO.

According to U.S. Pat.Nos. 5,421,525, 5,456,748, 5,534,113, or 5,888,288, pulp milled into a non-uniform plate and NMMO with a water content of 22% are mixed, swelled and stored in a horizontal cylindrical mixer. A method of swelling again by stirring for several hours in a storage hopper and then dissolving the water of the highly viscous solution supplied to the forced thin film evaporator while evaporating it is disclosed. This method requires separate management and supply of dust pulp generated during the production of plate-shaped pulp. In the horizontal cylindrical mixer, it is difficult to discharge the swelling solution. In US Patent No. 5,921, 675, a conveyor screw is attached to the outlet. A method of attaching has also been disclosed.

According to U.S. Patent No. 5,948,905, the mixture is instantaneously vacuum evaporated while passing through a nozzle consisting of 1.5 to 6.0 mm in diameter to produce a cellulose solution by evaporating water in the NMMO hydrate and cellulose mixture having a water content of about 23%. In this case, in the first chamber, the nozzle diameter was increased and the number of holes was decreased. As the chamber stage was increased, the nozzle diameter was smaller and the number of holes was increased to increase the evaporation cross-sectional area of the solution to increase the water evaporation efficiency. . In the final step, step 8, a method of using an extruder is disclosed. This method has a disadvantage in that the configuration of each chamber is different and the apparatus is complicated because there are too many chamber transfer screws and vacuum processing steps.

International patent 97/47790 relates to a method for preparing a cellulose solution by directly dissolving cellulose powder in a liquid NMMO solvent in a twin screw extruder. In this method, the first barrel of the twin screw extruder is injected with liquid NMMO containing 12% of moisture at 100 ° C, and the powdered cellulose is fed to the side barrel of the third barrel adjusted to 75 ° C through a side feeder. The solution is prepared by raising the temperature. This method already occupies three barrels for cellulose and NMMO feed, and a separate barrel for dissolution for cellulose dissolution in the extruder. Indeed, there is only a short swelling interval such that swelling and dissolution occur almost simultaneously, which is likely to result in undissolved cellulose particles due to incomplete swelling of the pulp powder. It may be effective when preparing a small amount of solution, but when the amount of cellulose solution produced increases, excessive investment of the filter system and the spinning cycle are shortened due to the generation of a large amount of undissolved solution. Increasing the swelling section shortens the melting section and increases the barrel of the twin screw extruder excessively.In addition, even if the screw L / D is increased by increasing the block, the same drive shaft is used, which makes it difficult to simultaneously control the swelling condition and the melting condition. have. That is, the production of a solution of a powdered cellulose with a low apparent specific gravity by a twin screw extruder having a low free volume may bring a limitation of productivity.

Korean Patent Laid-Open Publication No. 2002-24689 discloses a method of preparing a homogeneous cellulose solution by making a mixture of swelled cellulose pulp powder using a liquid NMMO hydrate solvent supercooled using cooling air, and dissolving it. In addition, when cooling air is used, the temperature of the quenched NMMO cannot be managed accurately, and in case of high concentration of NMMO, the moisture content of NMMO cannot be maintained uniformly due to exposure to the moisture contained in the cooling air. In addition, separate complicated cooling air ejectors and NMMO injection injectors for supercooling liquid NMMOs are installed, which is disadvantageous for commercialization.

Many patents and documents have been disclosed since tertiary amine oxide was proposed by Graenacher and Sallman in US Patent No. 2,179,181 in 1939 and British Patent No. 1,144,048 in 1966 by Johnson as the strongest solvent of cellulose. Among them, NMMO is most commonly used, and the oxygen group of the N-O group, which is an active part of NMMO, is easily intermolecularly bonded to a hydroxy-rich material such as cellulose, so that it is easy to penetrate into the crystal lattice of cellulose. In addition, Chanzy et al. Pointed out that the reaction activity of cellulose is different depending on the degree of hydration and temperature of NMMO with water.

However, the present inventors and the like, as a factor affecting the reaction activity force, the relationship between the reaction activity force and the temperature depending on the cellulose concentration, the DP of cellulose, the method and device for contacting cellulose and NMMO, and whether the NMMO is in liquid, solid or intermediate phases. It was found that there is.

As described above, in the conventional method, after NMMO containing 20 to 40% of water is first contacted with cellulose, water is evaporated using various types of evaporators to swell and dissolve. At this time, due to the problem of transporting a high viscosity solution and a device for securing a sufficient residence time to evaporate water from the high viscosity solution, there is a problem with a large capacity and energy consumption due to the vacuum device. In addition, a method of directly dissolving a liquid NMMO containing about 13% of water has been proposed. However, when the NMMO crystallization temperature is in contact with cellulose at a temperature of about 80 ° C. or more, the reaction activity against cellulose is excessively increased. There is a disadvantage in that it is dissolved immediately without high swelling and remains undissolved.

In the morphology of the cellulose fiber of the dissolving pulp, the micropores through which the water, called the pit, and the thickness of the cell wall are not uniform, so that it is easy to penetrate locally and difficultly. As a result, there is a difference in NMMO penetration within a limited time. This tendency also varies depending on the type of wood fiber used in the manufacture of the pulp and the method of producing the pulp. Therefore, in order to produce a uniform cellulose solution, the solvent used must fully penetrate the cellulose fiber entire area and relax, that is, swell. Otherwise, a difference in local solubility within or between the cellulose fibers may occur, resulting in no complete dissolution but limited dissolution resulting in undissolved cellulose. Also, in the manufacturing process, fibrous cellulose is generally agglomerated. At this time, when a high concentration of NMMO is used to directly dissolve the cellulose, the dense state of the cellulose is a factor that determines the solubility. In the case of high density of cellulose, NMMO swells or dissolves the outer surface of the cellulose bundle in advance even if it is subjected to strong shearing force or heated to a high temperature. From this point of view, controlling the dense state of cellulose and the reaction activity of NMMO is an important technique for producing a cellulose solution.

As described above, in the conventional method, a complicated process, which is disadvantageous for mass production, a burden of the purification process due to cellulose decomposition and NMMO discoloration caused by long solution preparation time, decomposition of cellulose due to high temperature, low homogeneity of cellulose solution, etc. There are disadvantages. In order to solve this problem and to prepare a cellulose solution for high strength lyocells, it is ideal that the NMMO solvent sufficiently enters the entire area with short time, low temperature and low shear force into the macro and micro tissues of the cellulose, and then swells indefinitely and then dissolves. . In addition, avoiding complex device structures for commercialization, dissolving large amounts of cellulose in a short time, and minimizing utility are important technical challenges for producing high homogeneous, low resolution cellulose solutions for high strength lyocell fibers. ..

In order to produce homogeneous high strength lyocell fibers with minimal cellulose degradation and no cellulose particles, the cellulose powder is uniformly mixed with NMMO injected into the liquid phase at low temperature within a short time, so that NMMO fully penetrates the cellulose powder. A step of swelling by necessity is necessary.

The method for producing a high-strength cellulose solution for high-strength lyocell according to the present invention for achieving the above object can be expected to have high strength and elastic modulus by inducing high orientation structure and high crystallization using cellulose molecules having high polymerization degree. In addition, in order to produce high quality cellulose fibers, it is preferable to use those having a high α-cellulose content. Therefore, the degree of polymerization (DPw) of the cellulose used in the present invention is characterized by using a pulp of 800 or more, α-cellulose content 92% or more. The cellulose sheet prepared as described above was pulverized after passing through a dryer, and the powdered cellulose and the concentrated liquid NMMO containing 5% by weight or less of water were changed in the range of 40 to 74 ° C. at a temperature of 15 to 50 rpm in a rotational speed range. The biaxial kneader is simultaneously introduced from the top through a separate inlet and then mixed and kneaded to swell the cellulose to paste. However, the liquid NMMO injected at this time is adjusted to be in contact with the cellulose in an intermediate state of the liquid-solid phase. The cellulose solution for high strength lyocell is prepared by continuously swelling and dissolving the same in a coaxial twin screw extruder which is variable at a temperature of 50 to 100 ° C. and a rotation speed of 100 to 250 rpm.

In addition, the present invention, (a) preparing a concentrated liquid NMMO solution; (b) drying, grinding the cellulose sheet to prepare a cellulose powder kept at a constant moisture; (c) the liquid NMMO solution and cellulose Weighing each of the powders and injecting them into the kneader; (d) mixing and kneading the injected liquid NMMO with the cellulose powder in a controlled state in a kneader as a liquid-solid intermediate phase to prepare a cellulose paste; (e) injecting the cellulose paste into a twin screw extruder to swell and dissolve It provides a method for producing a cellulose solution, characterized in that consisting of a step of preparing a cellulose solution.

More specifically, the high homogeneous cellulose solution according to the present invention

(a) concentrating 25% by weight of NMMO hydrate collected from the wash liquor into 86.5% by weight of liquid NMMO (monohydrate) by a thin film drop concentrator;

(b) After passing through the dryer while decomposing the roll-like cellulose sheet, the cellulose sheet is treated by adjusting the drying temperature so that the cellulose sheet has a moisture content of 7%, immediately cooled with dry air, injected into a grinder, and then to 500 μm or less. Preparing powdered cellulose;

(c) 86.5 weight of the liquid NMMO and cellulose powder prepared in (a) and (b) at 90 to 95 ℃ at the first inlet of the kneader maintained at a temperature of 40 to 74 ℃, rotation speed of 15 to 50 rpm Metering and injecting% of liquid NMMO into initial contact with the cellulose powder metered in at the second inlet in a semi-crystallized state that becomes a liquid-solid phase intermediate phase;

(d) mixing and kneading NMMO and cellulose powder, which are injected into (c) and transferred to the intermediate phase of the liquid-solid phase in the kneader, to swell the cellulose powder to prepare a paste;

(e) The cellulose paste prepared in (d) is prepared by supplying and dissolving the cellulose paste in a twin screw extruder adjusted to a temperature range of 50 to 100 ° C. In particular, the twin-screw extruder prepared at this time minimizes the decomposition of cellulose by arranging the screws to have a narrow residence time distribution.                     

U.S. Patent No. 4,416,698 and International Publication No. WO 1997/47790 disclose a method for preparing a cellulose solution by injecting liquid NMMO and cellulose powder into an extruder, followed by mixing, swelling, and dissolving. The liquid NMMO and the cellulose powder having no water content are simultaneously introduced into the twin-swelling swelling mixture maker, and then a method of dissolving in a single screw extruder is presented. However, the present invention provides a liquid-solid intermediate NMMO and water-treated cellulose powder. First, the mixture is kneaded and kneaded in a kneader, and is swelled and dissolved again in a twin screw extruder, so that the manufacturing method and principle of the solution are different from the existing patent.

In addition, the present invention comprises the steps of (a) preparing a concentrated liquid NMMO solution; (b) drying and grinding the cellulose sheet to prepare a cellulose powder maintained at a constant moisture; (c) measuring the liquid NMMO solution and the cellulose powder, respectively, and injecting the same into a kneader; (d) mixing and kneading the injected liquid NMMO with the cellulose powder in a controlled state in a kneader as a liquid-solid intermediate phase to prepare a cellulose paste; (e) injecting the cellulose paste into a twin screw extruder to swell and dissolve to prepare a cellulose solution; (f) it provides a method for producing a cellulose fiber, characterized in that consisting of spinning the cellulose solution to produce a cellulose filament.

The present invention also provides a cellulose fiber produced by the above production method.

Hereinafter, with reference to the accompanying drawings with respect to a method for producing a high-strength cellulose solution for high strength lyocell and the fiber according to the present invention will be described in more detail.                     

1 is a liquid phase of NMMO used in the present invention by using the phase change of melting point of NMMO according to water content and temperature in NMMO-water solvent system published by H. Chanzy in Carbohydrate Polymer 2. (1982). -It expresses the process of swelling and dissolving as it develops from the middle phase of the solid phase into the liquid phase. The 86.5% by weight of NMMO used in the present invention is present in the middle phase of the liquid and solid phases in the temperature range of about 40-75 ° C. H. Chanzy has already suggested in the 'CELLULOSE-AMINE OXIDE SYSTEMS' literature. Therefore, in the present invention, 86.5% by weight of NMMO is a new homogeneous cellulose solution that can be swelled and dissolved using only a temperature rise and shear force without a process of removing water at 40-74 ° C., which has an intermediate phase region of a liquid phase and a solid phase. We propose a manufacturing method.

Figure 2 schematically shows a process for producing a high homogeneous cellulose solution for high strength lyocell of the present invention. In FIG. 2, when the pulp sheet 1 is pulled by the nip roller 5 and supplied to the grinder 6, the pulp sheet 1 passes through the drying chamber 2 adjusted to a constant temperature and then dried air. Cool to (3) and keep at 25 ℃. Before passing through the nip roller 5, the contact moisture content measuring device 4 is used to manage the drying temperature of the drying chamber 2 so that the moisture content does not exceed 7%. Generally, pulp is supplied with a water content of about 8-10%, but shows a variation in the water content of the powdered cellulose stored in the storage tank 10 after pulverization according to seasonal humidity and temperature changes. High moisture content tends to cause pulp to clump together, making it difficult to obtain a homogeneous solution. In addition, since the composition of the NMMO / cellulose / water shows a deviation of the thickness of the fiber spun through the nozzle 25 also occurs, it can not have a uniform quality. The length of the powdered cellulose can be adjusted according to the size of the screen sheave mounted inside the grinder 6 with a knife. It is preferable to use a powder of 500 μm or less, preferably 300 μm or less. In the case of 500 µm or more, pulp may easily aggregate when mixed with NMMO in a kneader, and this may act as an inhibitory factor in preparing a homogeneous solution. The powdered cellulose passing through the screen sieve of the grinder 6 is supplied to the bag filter 8 through the blower 7 so that air is discharged to the outside and the powdered cellulose is supplied to the powdered cellulose reservoir 10 through the rotary valve 9. Is supplied. The powdered cellulose is supplied into the kneader 22 through the precision weighing meter 11.

A 25 wt% NMMO aqueous solution is prepared from the coagulation bath 15 recovered from the coagulation bath 13 and the water washing bath 14, and the coagulation bath 15 and the coagulation bath 13 are continuously exchanged with pure water and 50 wt%. The concentration is maintained by% NMMO. The prepared 25% by weight NMMO aqueous solution is supplied to a purification tower 17 using an ion exchange resin to remove ionic substances and carbonization impurities and stored in the feed tank 18 of the concentration tower. Again, the quantitatively supplied to three thin film falling type concentration tower 19 from the concentration tower supply tank is prepared as a final 86.5% by weight NMMO aqueous solution. NMMO concentrated to 86.5% by weight is supplied to the jacketed reservoir 20 maintained at 90 ° C., and is supplied quantitatively into the kneader 22 through the gear pump 21.

The kneader 22 whose temperature is maintained in the fruit jacket method may be adjusted to about 40 to 74 ° C., and an appropriate temperature may vary depending on the amount of NMMO introduced. The NMMO introduced into the liquid phase changes into the intermediate phase between the liquid phase and the solid phase as it is advanced by the kneader temperature and the rotor blades. In this state, when mixing and kneading the intermediate phase NMMO and cellulose in the kneader, the NMMO penetrates uniformly into the entire surface of the cellulose to form a paste. The paste begins to swell the cellulose as it is advanced, and is fed to the twin screw extruder 23 through the forced feeder 12. The internal temperature of the twin screw extruder is adjusted from 50 ° C to 100 ° C to dissolve after a complete swelling step by temperature rise and shear force. The dissolved cellulose solution passes through the filter 24 and the solution discharged through the nozzle 25 is washed with water 16, dried 26 and then formed into cellulose fibers.

Figure 3 is a schematic process diagram showing a simple method of producing a cellulose solution of the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the following Examples. The solution and the fiber prepared in Example were evaluated in the following manner.

(a) Homogeneity of cellulose solution

The solubility evaluation of the cellulose solution prepared in the present invention was evaluated after sampling in a solution transfer line immediately after discharged from the twin screw extruder and observed by a polarizing microscope. The degree of dissolution was divided into 5 grades, and the state of complete dissolution was set to '1' and the irradiated state in which a large amount of undissolved water was present was set to '5'. The middle was divided into 2, 3, and 4 according to the degree of undissolved cellulose.

(b) weight average degree of polymerization (DPw)

Intrinsic viscosity [IV] of dissolved cellulose is a 0.5M cupriethylenediamine hydroxide solution prepared according to ASTM D539-51T using a Uberod viscometer and is measured in a concentration range of 0.1 to 0.6 g / dl at 25 ± 0.01 ° C. It was. Intrinsic viscosity is obtained by extrapolating specific viscosity according to concentration, and substituting this into Mark-Houwink's formula to obtain polymerization degree.

[IV] = 0.98 × 10 -2 DPw 0.9

(c) strength of multifilament (g / d), elongation at break (%)

Immediately after drying for 2 hours at 107 ℃ in a hot air dryer. At this time, Instron's low-speed stretch type tester (Instron 4465) was used. After twisting 80 Tpm (80 twist / m), the sample was measured at 250 mm and a tensile speed of 300 m / min.

[Examples 1-11]

A cellulose sheet (Buckeye V-81) having a weight average degree of polymerization of 1,200 was passed through a drying chamber and adjusted to a moisture content of 6.5 to 10%. Nitrogen (Co-rotating twin agitator shaft type, Oil transfer, 90 ° C liquid NMMO concentrated at 86.5% by weight through a thin film falling concentration tower was maintained at 50 to 70 ℃ Inject the gear pump into the heating type. At this time, 0.001% by weight of antioxidant is added to the concentrated liquid NMMO in the concentration process to dissolve. The cellulose powder is quantified by a precision weighing device and then injected into the kneader so that the final concentration of the cellulose paste is 11% by weight. At this time, the volume of the kneader used was about 30L, the speed of the rotary blade was 20 to 30rpm. The prepared paste was forcibly transferred and fed to the coaxial twin screw extruder. At this time, the twin screw extruder used was 47mmφ in diameter and the barrel temperature of the initial supply part was maintained at 60 ° C., and the barrel temperature of the final discharge part was maintained at 95 to 105 ° C., followed by swelling and dissolution. . At this time, sampling was performed in the solution transfer line immediately after discharge from the twin screw extruder to evaluate the homogeneity of the solution. Spinning conditions carried out as needed was carried out under conditions of high applicability to industrial fibers. The orifice was 150 µm in diameter, the orifice spacing was 1.5 mm, and discharged using a nozzle having 1,000 orifices. The air bed length was maintained at 100 mm, and the temperature and relative humidity of the cooling air blown to the filament in the air bed were 20 ° C. and 45 RH%, respectively, and the wind speed was adjusted to 6 m / sec. The filaments introduced into the coagulation bath in the air layer were wound by washing, drying and emulsion treatment, and the fineness of the finally obtained multifilament was adjusted to 1500 denier. At this time, the coagulant concentration was 25% by weight NMMO aqueous solution, the coagulation solution temperature was 20 ℃ (see Table 1).

Comparative Example 1

A liquid NMMO at 90 ° C., concentrated to 86.5 wt%, is injected into a kneader (Co-rotating twin agitator shaft type, oil transfer heating type) maintained at 80 ° C. inside. The same method as in Example 1 was used (see Table 1).

[Comparative Examples 2-6]

Unlike Examples 1 to 11, 86.5% by weight of liquid NMMO maintained at 90 ° C. in a twin screw extruder is injected into a first barrel and cellulose powder is injected into a third barrel by a side twin feeder. The cellulose solution was prepared by adjusting the temperature of the twin screw extruder under conditions of swelling and dissolution. For other conditions, the same method as in Example was used. (See Table 2.)

TABLE 1

TABLE 2

The present invention is to powder the cellulose through the moisture management of the pulp sheet, the liquid and solid intermediate NMMO and powdered cellulose is mixed and kneaded in the kneader to produce a swelled cellulose paste, and then forcedly transported in a twin screw extruder Infinite swelling at and followed by dissolution at relatively low temperatures in a short time using the high shear force of the twin screw extruder.

In particular, the low specific gravity pulp can be easily injected into the kneader having a high internal space proposed in the present invention to increase the production, and by directly injecting 86.5% by weight of concentrated NMMO, a separate evaporation device of water by decompression is required. The device structure is simple. In addition, by controlling the size and moisture of the powdered cellulose, the replacement cycle of the filter can be reduced by preventing swelling and dissolution of the cellulose film due to entanglement of the powdered celluloses to form undissolved cellulose particles. In addition, it is possible to reduce the burden of the screw arrangement in the twin screw extruder by making the swollen cellulose paste in the kneader in advance and feeding the twin screw extruder with the volume minimized. That is, the insertion of the reverse screw or the kneading disk can be minimized to narrow the residence time distribution of the cellulose solution in the extruder, thereby preventing the decomposition of cellulose. In addition, by using a twin-screw extruder that is highly efficient in shearing, it is possible to reduce the dissolution time and the dissolution temperature, and to minimize the decrease in the original pulp polymerization degree, thereby maintaining the high cellulose molecular weight, thereby producing high strength lyocell fibers. Have

Claims (7)

In the method for continuously producing cellulose fibers using N-methylmorpholine N-oxide (hereinafter NMMO) / water mixed solvent, (a) preparing a concentrated liquid NMMO solution; (b) drying and pulverizing the cellulose sheet to produce a cellulose powder maintained at a constant moisture; (c) measuring each of the liquid NMMO solution and cellulose powder and injecting the same into a kneader; (d) mixing and kneading the injected liquid NMMO with the cellulose powder in a controlled state in a kneader as a liquid-solid intermediate phase to prepare a cellulose paste; (e) injecting the cellulose paste into a twin screw extruder to swell and dissolve to prepare a cellulose solution; (f) spinning the cellulose solution to produce a cellulose filament. The method of claim 1, The cellulose powder is a method for producing cellulose fibers, characterized in that the moisture content is 1 to 10%. The method of claim 1, Polymerization degree (DPw) of the cellulose sheet is a method for producing a cellulose fiber, characterized in that in the range of 800 ~ 2,000. The method of claim 1, The temperature of said liquid-solid phase intermediate phase NMMO is 40-74 degreeC. The manufacturing method of the cellulose fiber characterized by the above-mentioned. The method of claim 1, Rotor blade speed of the kneader is a manufacturing method of cellulose fibers, characterized in that 5 ~ 80rpm. A cellulose fiber produced by the method of claim 1, having a cellulose filament strength of 3.5 to 9.0 g / d and an elongation of 4 to 15%. In the method for continuously preparing a cellulose solution using a N-methylmorpholine N-oxide (hereinafter NMMO) / water mixed solvent, (a) preparing a concentrated liquid NMMO solution; (b) drying and pulverizing the cellulose sheet to produce a cellulose powder maintained at a constant moisture; (c) measuring each of the liquid NMMO solution and cellulose powder and injecting the same into a kneader; (d) mixing and kneading the injected liquid NMMO with the cellulose powder in a controlled state in a kneader as a liquid-solid intermediate phase to prepare a cellulose paste; (e) injecting the cellulose paste into a twin screw extruder to swell and dissolve to prepare a cellulose solution.

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