CN101240461A - A kind of preparation method of cellulose spinning solution - Google Patents

Abstract

The invention relates to a preparation method of cellulose spinning liquid, which comprises using low boiling point, volatile, polar organic solvent as auxiliary agent and N-methylmorpholine-N oxide (NMMO ) are mixed to form a mixed solvent; the cellulose pulp is mixed with the mixed solvent to form a uniform mixed material; the low boiling point volatile organic solvent is removed from the mixed material until the content of the low boiling point volatile organic solvent is less than 5%, And dissolving the cellulose in the mixed material in NMMO under heating to obtain a cellulose spinning solution. In the present invention, due to the use of additives to delay the swelling of cellulose, prevent premature dissolution of cellulose, reduce the viscosity of the solvent, the cellulose can be dissolved uniformly and thoroughly, and overcome the advantages of directly impregnating pulp with a high-concentration solvent. It has the disadvantage of being difficult to mix evenly with cellulose pulp, and the additives used are easy to extract and recover.

Description

A kind of preparation method of cellulose spinning solution

technical field

The invention relates to a preparation method of a cellulose spinning solution, in particular to a method for dissolving cellulose pulp in N-methylmorpholine-N oxide (NMMO) to form a spinning solution, which belongs to the technical field of textiles.

Background technique

The use of N-methylmorpholine-N oxide (NMMO) as a solvent for non-toxic spinning to produce cellulose fibers has published hundreds of patents. But in terms of dissolution process, nothing more than the following two methods.

One method is to mix medium-concentration NMMO (moisture content 20-60%) with cellulose pulp to make pulp porridge, and then pass through a thin-film evaporator-type dissolution kettle to remove excess water under vacuum and heating , so that the system enters the solution state. As patent US 509469, CN 1181788, CN 1072284, WO 94/653 etc., this method has been used in industrial production. Some patents do not use thin-film evaporator-type dissolution kettles, but use similar kneader-type dissolution kettles for vacuum dehydration and dissolution, such as US 4246221, US 4416698, CN 1501990, CN 111161C, CN 1435529, CN 1449460, etc. This method has been adopted in some pilot-scale devices, but it has not been reported for large-scale production.

Another method is to use high-concentration NMMO (moisture content 8-15%) to directly mix with cellulose pulp. Since the system has no excess water, it does not need to go through the dehydration process, so it can be directly heated and extruded with a screw extruder. Press to dissolve. As in CN 1336451, the cellulose pulp is first pulverized into powder, then mixed with NMMO with a moisture content of less than 15%, and then directly squeezed and dissolved by a twin-screw extruder. CN 1468889 is similar to this, first crush the cellulose pulp into a powder of about 1mm size, and then add NMMO with a water content of 12% in proportion to the two feeding ports of the twin-screw extruder respectively, Mix, heat and squeeze to dissolve in a twin-screw extruder. In CN 1435529, NMMO with a moisture content of 13.3% is first heated and melted, quenched to 50°C to make a supercooled solution, mixed with cellulose pulp in a biaxial swelling mixture maker, and then entered into a single-screw extruder Squeeze out to dissolve. The advantage of this method is that the dehydration process is omitted, the dissolution time can be shortened, and it is beneficial to reduce the decomposition of the solvent. But the disadvantage is that it is difficult to mix the solvent and cellulose pulp evenly, especially it is more difficult to prepare a spinning solution with a higher concentration of cellulose.

KR20010093598 discloses a method for preparing cellulose spinning solution, which uses an NMMO organic solvent mixture containing at least 25% methanol, ethanol or acetone to swell cellulose, evaporates the organic solvent under reduced pressure until the content of the organic solvent is 5-20% %, while completely dissolving the cellulose, defoaming the dissolved cellulose solution, filtering, and spinning the spinning solution directly into an organic solvent bath. The invention uses methanol, ethanol or acetone instead of water to combine with NMMO. Due to the strong water absorption of NMMO, it is difficult to realize the mixing of anhydrous NMMO and the appealing organic solvent, and using an organic solution as the coagulation bath will use a large amount of appealing volatile organic solvents. Solvents have increased in cost and brought new difficulties in operation.

Contents of the invention

The purpose of the present invention is to provide a preparation method of cellulose spinning solution, which can ensure the uniform mixing of solvent and cellulose pulp, and without dehydration process, to obtain a uniformly mixed cellulose spinning solution without changing the existing There is a spinning process and direct spinning.

In order to realize the object of the present invention, the present invention provides a kind of preparation method of cellulose spinning liquid, comprises the following steps:

(1) Mixing a low boiling point, volatile, polar organic solvent as an auxiliary agent with N-methylmorpholine-N oxide (NMMO) with a water content of 8-18% to form a mixed solvent;

(2) The cellulose pulp is mixed with a mixed solvent to form a uniform mixed material;

(3) The low boiling point volatile organic solvent is removed from the mixed material until the content of the low boiling point volatile organic solvent is lower than 5%.

(4) Send the mixed material into a dissolving device for processing until the cellulose is completely dissolved in NMMO to obtain a cellulose spinning solution.

In the above preparation method of the present invention, after mixing the cellulose pulp and the mixed solvent to form a mixed material, it may also include placing the mixed material in a temperature-controllable mixed material device, and stirring until the material is uniformly mixed. The mixing material device can be a vertical or horizontal mixing tank with jacket and temperature control with stirring.

In the present invention, the amount of cellulose pulp added can be 10-20% of the amount of NMMO with a water content of 8-18%, and the amount of polar organic solvent can be 0.2-2.0 times the weight of cellulose.

In the present invention, a low boiling point, volatile, polar organic solvent is used as an auxiliary agent and N-methylmorpholine-N oxide (NMMO) with a water content of 8-18% is mixed to form a mixed solvent, which is based on the content of NMMO Depending on the amount of water, carry out at 30-100°C, and stir if necessary;

In the present invention, the cellulose pulp is mixed with the mixed solvent to form a uniform mixed material, which is also carried out at 30-100°C according to the water content of NMMO. If necessary, it can be stirred or a temperature-controllable mixed material device can be used In the case of a vertical or horizontal mixing tank with jacket and temperature control, the treatment time is preferably 30 minutes;

In the present invention, the low-boiling point volatile organic solvent is removed from the mixed material until the content of the low-boiling point volatile organic solvent is lower than 5%. It is carried out under negative pressure or normal pressure, and the time can be 20-60 minutes. It can be adjusted as needed, generally at 50-70°C.

In the present invention, the mixed material is sent to the dissolution equipment for processing until the cellulose is completely dissolved in NMMO, and the cellulose spinning solution can be obtained by using equipment such as a dissolution kettle and an extruder, and the temperature can be set at 70-120°C.

In the present invention, the organic solvent can be aliphatic volatile monohydric alcohol, aliphatic volatile monohydric ketone, aliphatic volatile monohydric ether or a mixture thereof. The present invention can also select other organic solvents, and its addition also can be adjusted according to specific conditions. Preferably, the aliphatic volatile monohydric alcohol is methanol or ethanol; the aliphatic volatile monohydric ketone is acetone.

In the present invention, preferably, the low-boiling point volatile organic solvent is removed from the mixed material until the content of the low-boiling point volatile organic solvent is less than 1%.

In the present invention, the method of vacuum devolatilization can be used to remove the low-boiling point volatile organic solvent from the mixed material.

The cellulose pulp in the present invention can be one of wood pulp, cotton pulp, bamboo pulp or hemp pulp or a mixture thereof.

After removing the low-boiling point organic solvent, the cellulose in the mixed material can be completely dissolved in NMMO by using single-screw extruder, twin-screw extruder, dissolution kettle and other dissolving equipment under heating to obtain cellulose spinning solution .

In one embodiment of the present invention, a low boiling point, polar, volatile organic solvent is uniformly mixed with an NMMO solution with a water content of 8-18% to form a mixed solvent, and the amount of the organic solvent is 0.2-2.0% of the weight of the cellulose pulp times, which is equivalent to the content of organic solvent in the mixed solvent is not more than 20%, then the raw material pulp is added to the mixed solvent, and stirred and mixed in a water bath at 40-80 ° C, so that the cellulose pulp can be more evenly mixed with the mixed solvent mix. Then the polar organic solvent is recovered under reduced pressure, and finally the mixed material is sent to the dissolution equipment for further dissolution until the cellulose is completely dissolved in the NMMO solvent.

The solution provided by the present invention makes it possible to use a common single-screw extruder or a twin-screw extruder as a dissolving device, and other dissolving devices can also be used.

The cellulose spinning solution obtained in the present invention can be spun by a spinning machine, and the NMMO solution with a water content of 8-18% is used as a coagulation bath to obtain regenerated cellulose fibers through coagulation, washing and winding.

The present invention adopts low boiling point, polarity, volatile organic solvent, and its effect is reflected in:

·The presence of volatile organic solvent increases the volume of the solvent, which can ensure the uniform mixing of the solvent and the pulp.

·Volatile organic solvent is a non-solvent of cellulose, which will delay the swelling of cellulose, prevent premature dissolution of cellulose, and make the dissolution of cellulose more uniform.

The addition of volatile organic solvents will reduce the viscosity of the solvent, promote the penetration of the solvent into various parts of the fiber cells, improve the dissolution quality of cellulose, and reduce the content of insoluble particles in the solution.

The volatile organic solvent used in the present invention is liquid at normal temperature. After the cellulose pulp is fully mixed and impregnated with the mixed solvent mixed with the volatile organic solvent, the organic additives in the mixed material can be rapidly mixed under normal pressure or vacuum conditions. Pumping away to speed up the process of removing the organic solvent, so that the material system quickly enters the dissolution zone (equivalent to about 13% moisture content of NMMO), so it can be directly dissolved by using a screw extruder or other dissolution equipment, and the organic additives can be recycled After repeated use, it will not cause additional pollution to the environment. The invention does not need to dehydrate after adding the pulp, but because of the presence of the organic solvent, the volume of the solvent is increased, the swelling of the cellulose is delayed, the premature dissolution of the cellulose is prevented, and the cellulose can be dissolved more uniformly and thoroughly. Moreover, the addition of a volatile organic solvent will reduce the viscosity of the solvent, promote the penetration of the solvent into various parts of the fibroblast, improve the dissolution quality of cellulose, and reduce the content of insoluble particles in the solution.

KR20010093598 uses at least 25% methanol, ethanol or acetone to replace water and mix with NMMO, and utilizes the low specific heat and low boiling point of the above organic matter to reduce the cost of subsequent extraction steps. However, due to the strong water absorption of NMMO, it is difficult to obtain anhydrous NMMO, so its application is difficult. However, the method of the present invention adopts common NMMO containing a certain amount of crystal water, and adds a small amount of organic solvent to delay the swelling of cellulose, prevent the premature dissolution of cellulose, reduce the viscosity of the solvent, and wait until the cellulose and the mixed solvent are mixed evenly. The organic solvent is extracted, and finally the cellulose is completely dissolved under heating conditions, so the present invention does not need anhydrous NMMO, and there will be no new problems caused by using anhydrous NMMO. In addition, due to the use of methanol, ethanol or acetone instead of water, the method disclosed in KR20010093598 also needs to use a large amount of ethanol, methanol or acetone as a coagulation bath, resulting in an increase in production costs, and these three substances are all volatile. It will also bring new problems, and the spinning solution obtained by the present invention uses the traditional NMMO and water mixture as the coagulation bath, which can be realized by using existing technical equipment and processes.

The present invention will be further described below in conjunction with specific examples, and the described examples are used to explain the present invention rather than limit the present invention.

Detailed ways

Example 1

Take 9 grams of NMMO with a water content of 13%, put it in a 100ml beaker, place it in a water bath at 65-70°C, and until the solvent is completely melted, add 0.7 grams of ethanol, mix well, and mix 1 gram of wood pulp (firstly in 80- Dry in an oven at 90°C for 30-40 minutes) Add the mixed solvent and stir continuously and place the beaker in a water bath at 65-70°C for half an hour to immerse the pulp in the mixed solvent and mix evenly, then move the beaker into a vacuum oven for 50 Vacuum at -70°C for 30 minutes to remove ethanol. Finally, stir the material with a glass rod, and move the beaker into an oven at 90-100°C. After 100 minutes, the material dissolves and becomes a transparent orange-yellow liquid.

Example 2

Take 8.8 grams of NMMO with a water content of 11%, put it into a 100ml beaker, place it in a water bath at 65-70°C, and until the solvent is completely melted, add 1.2 grams of a mixture of methanol and ethanol (0.6 grams each), mix well, and mix 1.2 Add one gram of bamboo pulp (dried in an oven at 80-90°C for 30-40 minutes first) into the mixed solvent and stir continuously, and place the beaker in a water bath at 65-70°C for half an hour to immerse the pulp in the mixed solvent and mix evenly. Then move the beaker into a vacuum oven and vacuumize at 50-70°C for 30 minutes to remove methanol and ethanol. Finally, stir the material with a glass rod, and move the beaker into a 90-100°C oven. After 150 minutes, the material dissolves, and the solution is transparent, but the color is slightly darker than that of Example 1 and Example 2.

Example 3

Take 8.7 grams of NMMO with a water content of 13%, put it in a 100ml beaker, place it in a water bath at 65-70°C, and until the solvent is completely melted, add 1.3 grams of ethanol, mix well, and mix 1.3 grams of cotton pulp (first in 80- Dry in an oven at 90°C for 30-40 minutes) Add the mixed solvent and stir continuously and place the beaker in a water bath at 65-70°C for half an hour to immerse the pulp in the mixed solvent and mix evenly, then move the beaker into a vacuum oven for 50 Vacuum at -70°C for 30 minutes to remove ethanol. Finally, stir the material with a glass rod, and move the beaker into an oven at 90-100°C. After 210 minutes, the material dissolves, but the solution is dark brown.

Example 4

Take 9 grams of NMMO with a water content of 13%, put it into a 100ml beaker, place it in a water bath at 65-70°C, until the solvent is completely melted, add 1 gram of acetone, mix well, mix 0.5 gram of wood pulp and 0.5 gram of cotton pulp Pulp (dried in an oven at 80-90°C for 30-40 minutes first) is added to the mixed solvent and stirred continuously, so that the pulp is immersed in the mixed solvent and mixed evenly, then the beaker is moved into a vacuum oven, and vacuumed at 50-70°C for 30 minutes to remove the acetone. Finally, stir the material with a glass rod, and move the beaker into an oven at 90-100°C. After 100 minutes, the material dissolves and becomes a transparent orange-yellow liquid.

Example 5

Take 9 parts of NMMO with a moisture content of 8% and heat and melt at 65-70°C, add 0.36 parts of acetone, mix well, then add 1.8 parts of cotton pulp, place in a vertical mixing kettle with stirring and jacket heating, and stir 30 minutes; connect the vacuum tube to remove acetone under reduced pressure (50-70°C) until the acetone content is less than 5%, then send the mixed material into the dissolution kettle and heat to dissolve at 90-100°C to obtain orange, transparent, viscous Cellulose solution. The cellulose solution is spun by a single-head spinning machine, and the NMMO-water solution with a water content of 8% is used as a coagulation bath, and the regenerated cellulose fiber is obtained through coagulation, washing and winding.

Example 6

Take 9 parts of NMMO with a water content of 13% and heat it at 65-70°C to melt, add 1.3 parts of ethanol, mix well, then add 1.3 parts of wood pulp, put it in a vertical mixing kettle with stirring and jacket heating, and stir 30 minutes; connect the vacuum tube, remove ethanol under reduced pressure (70-80°C) until the ethanol content is less than 1%, then send the mixed material into a twin-screw extruder to heat and extrude to dissolve, and the screw speed is 80-120 rpm , the temperature of each heating zone is 80-120°C, and an orange, transparent, viscous cellulose solution is obtained. The cellulose solution is spun by a single-head spinning machine, and the NMMO-water solution with a water content of 13% is used as a coagulation bath, and the regenerated cellulose fiber is obtained through coagulation, washing and winding.

Example 7

Take 9 parts of NMMO with a water content of 18% and heat and melt at 65-70 °C, add 1.8 parts of methanol, mix well, then add 0.9 parts of bamboo pulp, place in a vertical mixing kettle with stirring and jacket heating, and stir 30 minutes; connect the vacuum tube at 70-80°C, remove methanol under reduced pressure until the methanol content is less than 3%, then send the mixed material into a single-screw extruder to heat and extrude to dissolve, and the screw speed is 20-50 rpm , the temperature of each heating zone is 70-110°C, and an orange, transparent, viscous cellulose solution is obtained. The cellulose solution is spun by a single-head spinning machine, and the NMMO-water solution with a water content of 18% is used as a coagulation bath, and the regenerated cellulose fiber is obtained through coagulation, washing and winding.

Claims (10)

1. A preparation method for cellulose spinning solution, comprising the following steps: (1) Mixing a low boiling point, volatile, polar organic solvent as an auxiliary agent with N-methylmorpholine-N oxide (NMMO) with a water content of 8-18% to form a mixed solvent; (2) The cellulose pulp is mixed with a mixed solvent to form a uniform mixed material; (3) The low-boiling point volatile organic solvent is removed from the mixed material until the content of the low-boiling point volatile organic solvent is lower than 5%. (4) Dissolving the cellulose in the mixed material in NMMO under heating to obtain a cellulose spinning solution. 2. The preparation method of a kind of cellulose spinning solution according to claim 1, wherein after the cellulose pulp is mixed with the mixed solvent to form a mixed material, it also includes placing the mixed material in a temperature-controllable mixed material device in, and stir until the ingredients are evenly combined. 3. the preparation method of a kind of cellulose spinning solution according to claim 1, is characterized in that, the add-on of described cellulose pulp is 10-20% of the NMMO consumption of water content 8-18%. 4. the preparation method of cellulose spinning solution according to claim 1, is characterized in that, the consumption of polar organic solvent in mixed solvent is 0.2-2.0 times of cellulose weight. 5. according to the preparation method of the cellulose spinning solution described in any one of claim 1 to 4, it is characterized in that, described organic solvent is aliphatic volatile monoalcohol, aliphatic volatile monohydric ketone, aliphatic volatile Sexual monohydric ether or its mixture, preferably described aliphatic volatile monohydric alcohol is methanol or ethanol; Described aliphatic volatile monohydric ketone is acetone. 6. The method for preparing cellulose spinning solution according to claim 1, characterized in that, the low-boiling point volatile organic solvent is removed from the mixed material until the content of the low-boiling point volatile organic solvent is less than 1%. 7. The preparation method of cellulose spinning liquid according to claim 1, is characterized in that, adopts the method for decompression that low boiling point volatile organic solvent is removed from mixed material. 8. according to the preparation method of the cellulose spinning solution described in any one of claim 1-4, it is characterized in that described cellulose pulp is wood pulp, cotton pulp, bamboo pulp or hemp pulp one or a combination thereof. 9. the preparation method of cellulose spinning solution according to claim 1, is characterized in that, can adopt single-screw extruder, twin-screw extruder or dissolving tank to make the cellulose in the mixed material be dissolved in NMMO, A cellulose spinning solution is obtained. 10. The method for spinning the spinning solution obtained by the preparation method of the cellulose spinning solution as claimed in claim 1, wherein the obtained cellulose spinning solution is spun through a spinning machine, and the obtained cellulose spinning solution is spun with water The NMMO solution with a rate of 8-18% is used as a coagulation bath, and the cellulose fibers are obtained through coagulation, water washing and winding.