KR100540344B1 - A process for preparing a highly homogeneous cellulose solution - Google Patents

Abstract

The present invention relates to a method for producing a homogeneous cellulose solution even at low temperature, by dissolving a small amount of cellulose powder in a liquid concentrated N-methylmorpholine N-oxide (NMMO), and then supplying the solution and cellulose powder to an extruder It relates to a method of mixing, swelling and dissolving in a homogeneous cellulose solution at low temperature.

This can supply the NMMO solution to the extruder at a relatively low temperature due to the effect of dissolving a small amount of pulp in the liquid concentrated NMMO to lower the melting point of the NMMO. Due to the above-described reasons, not only a wide process temperature range is possible, but also swelling of cellulose powder and NMMO solution at low temperature can be prevented from forming film on the surface of cellulose powder by instant dissolution by high temperature NMMO. It is possible to produce a homogeneous cellulose solution even at a low temperature, and also to suppress cellulose decomposition generated during the high temperature swelling dissolution process in the extruder, thereby providing a cellulose fiber having excellent flexibility and strength.

Homogeneous Cellulose Solution, Cellulose Fiber, N-Methylmorpholine N-Oxide, Kneader, Extruder

Description

A process for preparing a highly homogeneous cellulose solution             

1 is a process schematic diagram for preparing a homogeneous cellulose solution of the present invention.

2 is a change in the solidification temperature according to the cellulose concentration

The present invention relates to a method for producing a homogeneous cellulose solution even at low temperature. More specifically, a small amount of cellulose powder is dissolved in liquid concentrated N-methylmorpholine N-oxide (hereinafter referred to as 'NMMO'), and then The present invention relates to a method for producing a homogeneous cellulose solution at low temperature by feeding cellulose powder into an extruder, mixing, swelling and dissolving in an extruder.

Cellulose has a very high affinity with other materials, but due to the crystal structure made of strong hydrogen bonds in molecular chains or chains, it is difficult to dissolve as a general solvent and is widely used among solvents that can break down this structure to prepare a solution. to be.

The manufacturing process of cellulose fiber using NMMO solvent is more than 99% of solvent recovery rate, which is very high compared to other wet spinning and very low concentration of NMMO is discharged from the process. Because of the high mechanical strength of the dots and the fabrics and films produced, many methods have been proposed, such as starting with U.S. Patent No. 3,447,935.

US Patent Nos. 4,142,913, 4,144,080, 4,196,282 and 4,246,221 swell cellulose in an aqueous NMMO solution containing up to 50% water, and distill the water under reduced pressure from an aqueous NMMO solution containing swelled cellulose. After preparing the extrusion method was proposed to make a fiber.

Since these methods take a long time from dissolution to spinning, physical properties may be degraded by pyrolysis.

In addition, the amount of energy used is high, which contributes to an increase in manufacturing cost.

PCT International Publication No. WO 94/06530 proposes a method for producing a cellulose solution by removing water with a thin film distillation apparatus. This method has a disadvantage in that the apparatus is complicated and the production efficiency is low to prepare a high viscosity cellulose solution. have.

In addition, US Patent No. 4,221,574 proposed a method of swelling the cellulose sheet at 65 to 95 ℃ by using a liquid tertiary amine oxide containing 5 to 15% by weight of water as a solvent and immediately stirring and spinning it.

This method was unable to obtain a homogeneous cellulose solution because of the film formed on the pulp sheet surface.

In addition, U.S. Patent No. 4,416,698 proposes a method of spinning solid NMMO and cellulose pulp rather than liquid phase by stirring in an extruder. This method uses a large amount of two mixed powders, resulting in a large amount of undissolved powder in the solution. It has a big problem in production.

In addition, PCT International Publication No. WO 1997/47790 discloses, instead of cellulose pulp sheets, fibrillated cellulose powder and a highly concentrated NMMO aqueous solution having a temperature of 50 to 130 ° C. and a water content of 5 to 20% by weight in a twin screw extruder. How to do it.

This method not only has the disadvantage of increasing the cost by increasing the number of replacements of undissolved powder and impurities during spinning, but also makes it impossible to produce a homogeneous cellulose solution due to the large amount of undissolved powder remaining in the solution. There was a problem that the physical properties of the.

In addition, US Patent No. 4,416,698 and PCT International Publication No. WO 1997/47790, which present a method for preparing a cellulose solution, disclose a method for preparing a cellulose solution by mixing, swelling, and dissolving in an extruder. It had a disadvantage that it could not be sufficiently dissolved.

The present invention has been made to solve the problems and disadvantages described above, by first dissolving a small amount of 0.01 to 5% by weight of cellulose powder in liquid concentrated N-methylmorpholine N-oxide (NMMO) to prepare an NMMO solution Due to the effect of dissolving a small amount of pulp in liquid concentrated NMMO to lower the melting point of NMMO, NMMO solution can be supplied to the extruder at a relatively low temperature, allowing a wide process temperature range, as well as cellulose powder and NMMO solution at low temperatures. It is possible to smoothly swell to prevent the formation of a film on the surface of the cellulose powder, and finally to produce a homogeneous cellulose solution even at low temperatures.

In addition, the present invention by using the homogeneous cellulose solution prepared at a low temperature, it is possible to provide a cellulose fiber excellent in flexibility and strength by suppressing the decomposition of cellulose and NMMO during the high temperature swelling dissolution process in the extruder.

Accordingly, the present invention comprises the steps of preparing a cellulose-dissolved NMMO solution by dissolving a small amount of 0.01 to 3% by weight of cellulose powder in a liquid concentrated N-methylmorpholine N-oxide (NMMO); Supplying the NMMO solution and cellulose powder to an extruder to produce a swelled and homogenized cellulose solution through an extruder in which screws are arranged to impart dispersion, mixing, shearing, kneading, dissolving and metering performance in the extruder It is characterized by including (B).                     

In addition, it is preferable that the cellulose solution is continuously prepared without attaching a separate water evaporator in step (B).

In addition, the apparent diameter of the cellulose powder administered in the step (A) or (B) is preferably 500 μm or less.

In addition, after mixing, swelling and dissolving in the extruder of the step (B), the final cellulose solution is preferably a concentration of 3 to 20% by weight of cellulose relative to the total weight.

In addition, the NMMO solution in the step (A) is preferably 10 to 15% by weight of the water content relative to the total weight.

In addition, the liquid NMMO in which a small amount of cellulose is dissolved in step (B) is preferably maintained at a temperature of 40 ℃ to 90 ℃ supplied.

In addition, the extruder used to prepare the NMMO solution and the cellulose powder in the swelling and homogenizing solution in the step (B) using a twin screw extruder and the L / D of 3 to 16 barrels or screws in the range of 12 to 64 Is preferably.

In addition, the twin screw extruder is preferably maintained at a temperature of 30 ℃ to 110 ℃.

In addition, the screw rotational speed of the twin screw extruder is preferably performed at 100rpm to 1,200rpm.

In addition, the cellulose powder of the step (A) or (B) can be used by mixing with other polymer materials.                     

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

Figure 1 schematically shows the process sequence for producing a homogeneous cellulose solution at low temperature as an embodiment of the present invention.

The cellulose powders 2a and 2b used in FIG. 1 have a particle diameter of 500 μm or less using a grinder with a knife bar, and preferably 300 μm or less.

If the size of the powder exceeds 500 μm, there is no uniform dispersion and swelling in the kneader or the extruder 4.

A small amount of cellulose powder (2a) made to 500 µm or less as possible in the concentrated liquid NMMO (1) is first dissolved.

The content of the cellulose powder (2a) to the concentrated liquid NMMO (1) is to be 0.01 to 5% by weight, more preferably 0.1 to 3% by weight.

In addition, the concentration of the antioxidant is also dissolved with the pulp to be 0.005 to 0.5% by weight relative to the final cellulose.

At this time, if the content of the cellulose powder (2a) is less than 0.01% by weight, the swellability and melting point of the NMMO does not contribute to lowering, if it exceeds 5% by weight the viscosity of the NMMO solution (3) is increased to the extruder (4) There is a problem with the supply.

On the other hand, in the present invention, the concentration of 10 to 50% by weight of the NMMO solution is concentrated in a conventional manner to have a concentrated liquid NMMO (1) having a water content of 10 to 15% by weight. This increases the cost of concentrating the water content to less than 10%, which is disadvantageous in terms of economics, and when the water content exceeds 15%, it is insoluble.                     

NMMO solution (3) in which small amounts of cellulose powder (2a) and cellulose powder (2b) were continuously supplied to an extruder (4) maintained at 65 to 105 ° C, mixed, swelled and dissolved in the extruder (4). One cellulose solution is prepared.

The NMMO solution 3 in which a small amount of the cellulose powder 2a is dissolved may be supplied to the extruder 4 by a gear pump or a screw feeder, and the cellulose powder 2b is injected into the extruder 4 by a screw feeder. It is desirable to.

The content of the cellulose powder (2a) in the mixed, swelled and dissolved cellulose solution in the extruder (4) is 3 to 20% by weight relative to the liquid NMMO (1), more preferably 7 depending on the degree of polymerization of the cellulose polymer. To 14% by weight.

At this time, when the cellulose powder (2a) content is less than 3% by weight does not have physical properties as a fiber, when it exceeds 20% by weight it is difficult to dissolve in the liquid NMMO (1) to obtain a homogeneous solution.

In the present invention, the extruder (4) used in the step (B) is used to prepare a swelling and homogenized cellulose solution by administering the powdered cellulose and solid NMMO in step (B) is preferably a twin screw extruder, the twin screw extruder 3 to 16 It is preferable that the L / D of the dog barrel or screw is in the range of 12 to 64. If there are less than 3 barrels or less than 12 L / D of the screw, the cellulose solution has less time to pass through the barrel, resulting in undissolved dissolution and more than 16 barrels or more than 64 L / D of the screw. Excessive stress acts and the screw deforms.

In addition, in the present invention, the cellulose powder (2a, 2b) of the step (A) or (B) may be used by mixing other polymer materials or additives. Polymeric materials include polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, and the like, and additives include viscosity enhancers, titanium dioxide, silica dioxide, carbon, and ammonium chloride.

2 shows the change in the solidification temperature of NMMO according to the concentration of cellulose, and shows that the solidification temperature of NMMO is rapidly decreased from 75 ° C. to 40 ° C. even when only a small amount of cellulose is dissolved (about 0.01 to 5%).

In the present invention, due to the effect of dissolving a small amount of pulp in the liquid NMMO (1) to lower the melting point of the liquid NMMO (1), it is possible to supply the NMMO solution (3) to the extruder (4) at a relatively low temperature. This enables not only a wide process temperature range but also a smooth swelling of the cellulose powder (2b) and the NMMO solution (3) at low temperatures, which can prevent the formation of a film on the surface of the cellulose powder (2b), resulting in low temperature. Even homogeneous cellulose solution can be prepared.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples. In the Examples, the following evaluation methods and measuring methods were utilized.

(a) Homogeneity of cellulose solution

The solubility evaluation of the cellulose powder prepared in the present invention evaluated the undissolved particles by polarizing microscope when the sample outlet was made in the extruder and the cellulose powder was dissolved in a certain condition against monohydrate NMMO (monohydrate NMMO). The number of undissolved fractions in the slide glass 5 × 5 mm 2 area was calculated.

(b) weight average degree of polymerization (DPw)

The intrinsic viscosity [IV] of the dissolved cellulose was measured in a concentration range of 0.1 to 0.6 g / dl at 25 ± 0.01 ° C. with 0.5M cupriethylenediamine hydroxide solution made according to ASTM D539-51T using a Uberod viscometer. .

The intrinsic viscosity is obtained by extrapolating the specific viscosity according to the concentration and obtaining the degree of polymerization by confronting it with the formula of Mark-Houwink.

[IV] = 0.98 × 10 ^-2 DP _w ^0.9

(c) The physical properties of the cellulose fibers produced in the present invention were measured as follows.

Drying strength: 107 ℃, strength after 2 hours drying (g / d)

Wet strength: strength measured after conditioning at 25 ℃ for 65 hours at 65RH (g / d)

Example 1

A cellulose sheet having a weight average degree of polymerization of 1000 was placed in a grinder equipped with a 100 mesh filter to prepare a cellulose powder having a diameter of 500 μm or less, and the cellulose powder was dissolved in NMMO. At this time, the content of cellulose in the NMMO solution was 1% by weight, the antioxidant was dissolved so that 0.070% by weight relative to the final cellulose.

The NMMO solution in which 1% by weight of cellulose was dissolved is injected into the extruder 4, which is maintained at 78 ° C. at an injection temperature of 68 ° C. at a speed of 6900 g / hour with a gear pump, and the cellulose powder is extruder at 784 g / hour using a screw feeder. After the injection, the residence time in the extruder swelling zone was 0.8 minutes and the temperature was raised to 60-80 ° C. to sufficiently swell the cellulose powder in the NMMO solution. Then, each block temperature was maintained at 90-95 ° C. in the melting zone of the extruder. The screw was operated at 200 rpm to completely dissolve and then discharged through the nozzle.

The discharged solution had a concentration of 11.1 wt%, a homogeneous state free of undissolved cellulose particles, and a degree of cellulose polymerization of 915.

Example 2

A cellulose sheet having a weight average degree of polymerization of 1200 was placed in a grinder equipped with a 100 mesh filter to prepare a cellulose powder having a diameter of 500 µm or less, and the cellulose powder was dissolved in NMMO. At this time, the antioxidant was dissolved so that the content of cellulose in the NMMO solution is 2% by weight to 0.08%. The NMMO solution containing 2% by weight of cellulose was injected into the extruder maintained at 78 ° C. at a speed of 6900 g / hour at an injection temperature of 59 ° C., and the cellulose powder was extruded at a screw feeder at 676 g / hour to extruder. The residence time in the swelling zone was 1.1 minutes, and the temperature range was 40-70 ° C. The cellulose powder was sufficiently swollen in NMMO solution, and each block temperature was maintained at 90-95 ° C in the dissolution zone in the extruder, and the screw was 200 rpm. Run and dissolve and then discharge through the nozzle.

The concentration of the discharged solution was 10.7 wt%, homogeneous without undissolved cellulose particles, and the degree of cellulose polymerization in the discharged solution was 1030.

Example 3

Only the temperature of the dissolution zone in the extruder was changed to 100 ° C. and the other method was the same as in Example 2 and discharged through the nozzle.

Almost no undissolved cellulose particles were found and the degree of cellulose polymerization in the discharged solution was 1015.

Example 4

A cellulose sheet having a weight average degree of polymerization of 850 was placed in a grinder equipped with a 100 mesh filter to prepare a cellulose powder having a diameter of 500 μm or less, and the cellulose powder was dissolved in NMMO. At this time, the content of cellulose in the NMMO solution was dissolved so that 1.5% by weight of antioxidant was 0.13%.

The 63 ° C. NMMO solution and the cellulose powder in which 1.5% by weight of the cellulose were dissolved were injected into a twin screw extruder such that the final concentration of the cellulose solution was 14.5% by weight.

The swelling zone temperature of the twin extruder was maintained at 45-75 ° C. and the block temperature of the dissolution zone was kept at 95 ° C., and the screw was operated at 300 rpm to dissolve and then spun through a nozzle.

Almost no undissolved cellulose particles were found and the degree of cellulose polymerization in the discharged solution was 760.

Comparative Example 1

After cellulose with a weight average degree of polymerization of 1200 was injected into a twinscrew extruder with a liquid NMMO (monohydrate) of 89 ° C, which was ground to 500 µm or less in diameter, each block temperature was maintained at 95 ° C and dissolved. Scour was discharged by spinning at 250 rpm.

The concentration of the solution was 11% by weight. When the solution was observed under a polarizing microscope, an undissolved powder having a diameter of 50 to 100 μm was present, and the degree of cellulose polymerization was 973.

Comparative Example 2

The temperature of the dissolution zone in the extruder was changed to 110 ° C. and the other conditions were the same as in Comparative Example 1, and then discharged through the nozzle.

The amount of undissolved cellulose particles was small, but the cellulose polymerization degree of the discharged solution was 820.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Beauty Analysis ¹⁾ 0-1 0-2 0-6 0-9 24-36 14-19 Dry strength (g / d) 6.2 7.3 5.9 5.5 5.4 4.3 Dry modulus (g / d) 310 321 267 273 240 191 Wet strength (g / d) 5.6 6.4 5.1 4.7 4.2 3.6

1) Number of undissolved powders in the area of 5 × 5㎡

The present invention includes preparing a NMMO solution by first dissolving a small amount of 0.01 to 3% by weight of cellulose powder in a liquid concentrated N-methylmorpholine N-oxide (NMMO). This can supply the NMMO solution to the extruder at a relatively low temperature due to the effect of dissolving a small amount of pulp in the liquid concentrated NMMO to lower the melting point of the NMMO. Due to the above-described reasons, not only a wide process temperature range is possible, but also swelling of cellulose powder and NMMO solution at low temperature can be prevented from forming a film on the surface of cellulose powder by instant dissolution by high temperature NMMO. A homogeneous cellulose solution can be produced even at low temperatures.

In addition, it is possible to provide cellulose fibers with excellent flexibility and strength by inhibiting cellulose decomposition generated during the high temperature swelling dissolution process in the extruder.

Claims (10)

(A) Dissolve the cellulose powder so that the content of cellulose in the liquid concentrated N-methylmorpholine N-oxide (NMMO) solution is 0.01 to 3% by weight to obtain a solution of N-methylmorpholine N-oxide (NMMO) in which cellulose is dissolved. Manufacturing step; (B) an extruder in which screws are arranged to supply the N-methylmorpholine N-oxide (NMMO) solution and cellulose powder to an extruder to impart dispersion, mixing, shearing, kneading, dissolving and metering performance in the extruder. Method for producing a cellulose solution, characterized in that it comprises the step of producing a swelling and homogenized cellulose solution at low temperature through. The method of claim 1, Method for producing a cellulose solution, characterized in that the apparent diameter of the cellulose powder administered in the step (A) or (B) is less than 500㎛. The method of claim 1, After mixing, swelling and dissolving in the extruder of the step (B), the final cellulose solution is a method of producing a cellulose solution, characterized in that the concentration of 3 to 20% by weight of cellulose relative to the total weight. The method of claim 1, NMMO solution in the step (A) is a method for producing a cellulose solution, characterized in that the water content of 10 to 15% by weight relative to the total weight. The method according to any one of claims 1 to 3, The method of producing a cellulose solution, characterized in that the liquid NMMO in which a small amount of cellulose dissolved in step (B) is maintained at a temperature of 40 ℃ to 90 ℃. The method of claim 1, The extruder used to prepare the NMMO solution and the cellulose powder in the swelling and homogenizing solution in step (B) uses a twin screw extruder and the L / D of 3 to 16 barrels or screws is in the range of 12 to 64. Method for producing a cellulose solution, characterized in that. The method of claim 6, A twin screw extruder is maintained at a temperature of 30 ℃ to 110 ℃ is carried out, in particular the method of producing a cellulose solution, characterized in that the temperature of the swelling section is 30 ~ 80 ℃. The method of claim 1, The cellulose powder of step (A) or (B) is a method for producing a cellulose solution, characterized in that used in combination with other polymer materials. delete delete

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