KR20080061162A - Method for producing environment-friendly cellulose solution - Google Patents

Abstract

A method for preparing an eco-friendly cellulose solution is provided to obtain pretreated cellulose easily applicable to a conventional rayon manufacturing process and to improve the stability after forming a solution from the pretreated cellulose. A method for preparing an eco-friendly cellulose solution comprises: a step(S11) of dipping and swelling cellulose in an aqueous alkali solution; a step(S12) of warming the swollen cellulose and aging the cellulose under mechanical agitation to reduce the polymerization degree; a step(S13) of removing the liquid component from the cellulose, followed by neutralization, washing with water and dewatering; and a step(S14) of dissolving the dewatered cellulose in an aqueous alkali solution comprising at least one cation and at least one anion so that the cellulose concentration is 0.5-12%.

Description

METHOD FOR PRODUCING ENVIRONMENT-FRIENDLY CELLULOSE SOLUTION}

1 shows a process for producing a cellulose solution according to the present invention.

The present invention relates to a method for improving the stability of a solution in which the cellulose is dissolved and the cellulose excellent in solubility in an aqueous alkali solution, and more particularly, (A) swelling the cellulose pulp sufficiently in a low temperature aqueous alkali solution; (B) the step of lowering the degree of polymerization by swelling the swelled cellulose pulp for a certain time after the temperature increase process and the temperature increase; (C) dehydrating, neutralizing, washing with water, and dehydrating cellulose having a lower polymerization degree; And (D) dissolving the treated pulp in an aqueous alkali solution containing at least one ion.

Until now, most of the researches on dissolving cellulose by alkaline aqueous solution are related to the pretreatment process to improve solubility. As a result, cellulose is subjected to physical and chemical changes.

Due to mechanical movement, that is, rotation, kneading and transfer, the shape of cellulose changes from pulp aggregates into dispersed forms such as cotton or powder.In chemical terms, the degree of polymerization decreases due to molecular chain cutting and oxidation of cellulose, and the cellulose crystal structure is also large. Undergo a change.

Such pretreatment processes include a treatment method with an acid aqueous solution, a high temperature high pressure treatment method, an alkali aqueous solution treatment method, and the like. Recently, a microbial treatment method has been disclosed in the patent, but industrialization has not been progressed yet.

In World Patent No. 01/96402, the pulp is dispersed in water or a buffer solution having a pH of 2.5 or more, or a catalyst solution such as Xylanases or Cellulase in one step of pretreatment, and the excess water is removed. The induced catalyst complex leads to a decrease in the degree of polymerization for a certain time. The pulp, which has undergone such a process, is washed, dissolved in 5% or more of an aqueous alkaline solution at 0 ° C. or more, and discharged through spinnerets to an aqueous acid solution, followed by defoaming and filtering, followed by stretching, washing and drying to form a final fiber.

However, the pretreatment method using these microorganisms is difficult to manage the microorganisms and the pretreatment results are not always constant, which makes it difficult to industrialize.

 U.S. Patent No. 4,634,470 proposes a cellulose bombardment pretreatment method in about 10% alkaline aqueous solution at -5 ° C to 5 ° C. According to this patent, 100 g of pulp is mixed well with 10 to 1000 g of a hydrogen bond decomposer and heated to 100 to 350 ° C. at 10 to 250 atm and then discharged at atmospheric pressure. At this time, the cellulose treated with the explosive cellulose and the alkaline aqueous solution acting as a hydrogen bond decomposing agent are stored at 50 ° C. or lower for a predetermined time and then dissolved at 10 ° C. or lower.

In addition to the aqueous alkali solution, inorganic acid aqueous solution, hydrogen peroxide, amide (urea), urea (urea) aqueous solution, or glycol (glycol) and the like were used as the cellulose hydrogen bond decomposing agent.

In US Pat. No. 5,401,447, the pulp is immersed in water having a weight ratio of 10-20 times for 3 hours and then pressed to have a moisture content of 180-190%, and treated with steam at 235 ° C. for about 25 seconds to treat pulp with a degree of polymerization of about 300. Pretreatment digested to -350. The treated pulp was dissolved in 5-15% aqueous alkali solution, solidified in an aqueous solution coagulation bath below zero or below 20 ℃, elongated about 1.05 ~ 2.0 times, and then fibrized after steam heat treatment.

However, the above pretreatment methods have a disadvantage in that the physical properties of the fibers are not uniform compared to the conventional viscose process because the degradation is not uniform because the progress of the continuous process control is not easy and the cellulose is not sufficiently swollen.

As described above, the pretreatment pulp manufacturing process used in the conventional method for producing a water-soluble alkaline cellulose solution is composed of very difficult conditions to be applied industrially and has a disadvantage that it cannot be easily used in a conventional rayon production process. New pretreatment processes that can be more easily applied to rayon processes and methods for increasing solution stability have been developed.

An object of the present invention is to overcome the above-mentioned problems and to provide a technique that can be applied industrially through the improvement of the existing rayon manufacturing process, and to produce a pre-treated cellulose dissolved in an aqueous alkali solution and excellent solution even after dissolution It is to provide a process for manufacturing.

The present invention relates to a process for preparing and dissolving cellulose that is well dissolved in an aqueous alkali solution and whose alpha (α) -cellulose content is 93% or more even after the degree of polymerization decreases.

According to a preferred embodiment of the present invention, the method for producing an aqueous solution of cellulose alkali comprises (A) swelling by dipping cellulose in an aqueous alkali solution; (B) raising the swelled cellulose and then aging while mechanically stirring to reduce the degree of polymerization; (C) dehydrating, neutralizing, washing with water and dehydrating the cellulose having a lower polymerization degree; And (D) dissolving the dehydrated cellulose in an aqueous alkaline solution composed of at least one cation and at least one anion such that the concentration of cellulose is 0.5 to 12%.

According to another suitable embodiment of the present invention, the cellulose of the step (A) is characterized in that the sheet or powder size of 0.1 ~ 5mm.

According to another suitable embodiment of the present invention, the step (A) is characterized by swelling for 5 minutes to 2 hours at -5 ~ 15 ℃.

According to another suitable embodiment of the present invention, the concentration of the aqueous alkali solution in step (A) is 15 to 25%, characterized in that the liquid ratio is 8 to 20 times.

According to another suitable embodiment in the present invention, the degree of polymerization targeted in the step (B) is characterized in that 100 ~ 500.

According to another suitable embodiment of the present invention, in the step (B), the temperature increase temperature is 30 ~ 70 ℃, the aging time is characterized in that 4 to 15 hours.

According to another suitable embodiment of the present invention, the ratio (y / x) of the time (x) to the set temperature and the holding time (y) when the temperature is raised in the step (B) is 2 to 50. do.

According to another suitable embodiment of the present invention, the alkali used in the step (C) is one selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, ammonium hydroxide It is characterized by using the above alkaline salt.

According to another suitable embodiment of the present invention, the cation used in the step (C) is characterized by having an ionic volume of 0.5 to 4 times compared to the anion.

According to another suitable embodiment of the present invention, the aqueous alkali solution in the step (C) is characterized in that it has a conductivity of 150 ~ 500m

Hereinafter, the present invention will be described in detail.

Figure 1 shows the manufacturing process of the aqueous solution of cellulose alkali according to the present invention.

According to Figure 1, the manufacturing process of the present invention is the step of immersing and swelling cellulose in an aqueous alkali solution (S11); Ripening while heating the swollen cellulose (S12); Deaerated, washed with water and neutralized aged cellulose (S13); And dissolving the neutralized cellulose in an aqueous alkali solution containing at least one anion and a cation (S14).

In the step (S11), the cellulose may be used in the form of a sheet or pulverized powder, and a finer powder is used for uniform swelling and molecular weight reduction, and the size of the cellulose may be 0.1 mm to 5 mm, preferably 2 mm or less.

In addition, the swelling temperature of the cellulose in the alkaline aqueous solution of step (S11) is -10 ℃ or more, -5 ℃ ~ 15 ℃ is more preferred, the swelling time is characterized in that within 5 minutes to 2 hours.

In addition, the concentration of the alkaline solution at the time of swelling in step (S11) is 5% or more but preferably 15 to 25%, and the liquid ratio (weight ratio) of the alkaline aqueous solution to cellulose is between 8 and 20 times. When the concentration of the alkaline solution is less than 5% when the swelling is poor polymerization degree or time-consuming and when the liquid ratio is less than 8 times, the polymerization degree is uneven.

The degree of polymerization aimed at (S12) is 100-500, and 100-400 is good in order to improve the solubility in aqueous alkali solution.

In addition, the treatment temperature in the step (S12) is 30 ~ 70 ℃ and the treatment time is 2-24 hours, preferably 4-15 hours. If the temperature is below 30 ℃, the treatment time is uneconomical because it takes more than 24 hours, but if it is over 70 ℃, the treatment time can be reduced to less than 10 hours. Resulting in poor throughput.

In addition, in order to prevent a sudden decrease in the polymerization degree when the temperature is increased in the step (S12), the polymerization reactor for reducing the polymerization degree is heated in an outer jacket type, and the ratio of the time (x) to the internal setting temperature (x) and the holding time (y) is y / x 2-50 or preferably between 3-15.

The alkaline aqueous solution used in step (S14) is composed of one or more cations and anions, respectively, in order to improve the dissolution of cellulose and the stability of the solution, and the concentration is added to 0.5 to 20 times with respect to cellulose.

If the cation and anion of the alkaline aqueous solution is 0.5 times or less with respect to the cellulose, it will not be dissolved. If it is 20 times or more, the economy will be inferior due to the use of excessive salts.

As the alkali used in the step (S14), alkaline salts such as sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, or ammonium hydroxide are used, and the dissolution of the cellulose solution and the stability of the solution are used. One alkaline salt may be used alone or two or more salts may be used together to improve the performance.

The cation used in step (S14) has an ionic volume of 0.5 to 4 times that of sodium ions, and these cations are added to dissolve and dissolve depending on the composition and dissolution conditions of the cellulose solution by the role of cation volume and electrical conductivity. Added to increase solution stability.

Alkali aqueous solution in step (S14) is a solution characterized in that it has a conductivity between 150 ~ 500m

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.

(1) Homogeneity of Cellulose Solution

The solubility evaluation of the cellulose solution prepared in the present invention was evaluated after dissolving in an alkaline solution for a certain time, sampling and observing with 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'. In addition, it was divided into 2, 3, 4 according to the extent of undissolved cellulose.

(2) 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. .

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} DP w 0 .9

Example 1

A sheet form of cellulose pulp (Buckeye, Glade V-60, DP 910) is pulverized to a powder form of 0.5 mm or less, and 50 g of the pulverized pulp is an aqueous 15 ° C. alkali solution composed of 180 g of caustic soda and 820 g of ion-exchanged water. The mixture was immersed in the mixture and swelled with a mixer (10 rpm) for 2 hours, and then heated to a temperature of 55 ° C. for 6 hours or longer to induce a decrease in polymerization degree.

The sample was dehydrated by dehydration in a centrifugal dehydrator, washed repeatedly with ion-exchanged water, neutralized in 0.5N aqueous glacial acetic acid solution, and dehydrated. The samples swollen at low temperature and pretreated by elevated temperature had a moisture content of 150-300% and were mostly dissolved in -4 ° C and 9% alkaline solution in 1-30 minutes. The solubility according to the polymerization deterioration time is shown in Table 1 below.

TABLE 1

Example 2

The cellulose pulp (Buckeye Co., Glade AO-2, DP 780) in the form of a sheet is pulverized to form a powder of 3 to 5 mm, and 500 g of the pulverized pulp is an aqueous alkaline solution of -4 ° C. composed of 2000 g of caustic soda and 8000 g of ion-exchanged water. After swelling in water and mechanically (20rpm) stirring, the temperature was raised over 1 hour and maintained at 50 ° C for 12 hours to induce a decrease in polymerization degree. Subsequently, alkaline cellulose was dewatered and neutralized as in Example 1 to obtain pretreated cellulose. In the above process, the analysis result of the sample according to the swelling time and 60 g of the pretreated sample at -10 ° C were 10% of caustic soda. The solubility after 0.5 hour dissolution in aqueous solution is shown in Table 2 below.

The less swelling time, the more undissolved dissolution occurred.

TABLE 2

Example 3

80 g of the pulverized pulp of 3 to 5 mm used in Example 2 was immersed in 1400 g of an aqueous 7% potassium hydroxide solution (KOH) at 5 ° C. for 1 hour, and then swelled to contain an excess of an alkaline solution in a centrifugal dehydrator for 300%. After that, the polymerization degree was lowered at 50 ° C. for 2 hours or more. The sample was washed with water and neutralized to analyze solubility and physical properties at -0 ° C and is shown in Table 3 below.

TABLE 3

Example 4

50 g of the pretreated sample (containing 200% water content) is dissolved in an alkaline aqueous solution and the concentration of ions is 0.5 to 20 times higher than that of cellulose in an alkaline aqueous solution composed of one or more cations and anions to improve the stability of the solution. The mixture was dissolved at -0 ° C or lower, and some of the experimental results are shown in Table 4 below.

To improve dissolution and stability of the solution, an alkaline aqueous solution composed of one or more cations and anions has a conductivity between 150 and 500 m, and in certain conditions is prepared by two salts rather than a solution prepared by one salt. The stability of the solution was excellent.

TABLE 4

* Solution stability-Determined by gelation time when stored at below 10 ℃ after dissolution

                A: more than 1 week

                B: 2 days or more

         C: 1 day or less

In the present invention, the cellulose is swelled uniformly after being immersed in a low temperature aqueous alkali solution for a certain time, and the temperature is raised for 2 to 24 hours to induce a decrease in the degree of polymerization. After liquefaction or neutral washing with water, cellulose dissolved in a low-temperature constant concentration of aqueous alkali solution was prepared, and the solution produced therefrom was stabilized.

Claims (10)

In the manufacturing method of the aqueous solution of cellulose alkali, (1) swelling by dipping cellulose in an aqueous alkali solution; (2) lowering the degree of polymerization by raising the swelled cellulose and then aging while stirring mechanically; (3) dehydrating, neutralizing, washing with water, and dehydrating cellulose having a lower polymerization degree; And (4) dissolving the dehydrated cellulose in an aqueous alkaline solution composed of at least one cation and at least one anion such that the concentration of cellulose is 0.5-12%; Method for producing an aqueous cellulose alkali solution comprising a. According to claim 1, wherein the cellulose of the step (1) is a method of producing an aqueous solution of cellulose alkali, characterized in that the sheet or powder form of size 0.1 ~ 5mm. According to claim 1, wherein the step (1) is a method for producing an aqueous solution of cellulose alkali, characterized in that swelling for 5 minutes to 2 hours at -5 ~ 15 ℃. The method of claim 1, wherein the concentration of the aqueous alkali solution in the step (1) is 15 to 25% and the liquid ratio is 8 to 20 times the manufacturing method of the aqueous solution of cellulose alkali. The method according to claim 1, wherein the degree of polymerization aimed at step (2) is 100 to 500. The method of claim 1, wherein in the step (2), the temperature rise temperature is 30 ~ 70 ℃, the aging time is 4 to 15 hours, characterized in that the manufacturing method of alkaline cellulose aqueous solution. The aqueous cellulose alkali solution according to claim 1, wherein the ratio (y / x) of the time (x) to the set temperature and the holding time (y) when the temperature is raised in the step (2) is 2 to 50. Manufacturing method The method of claim 1, wherein the alkali used in the step (3) is at least one alkaline salt selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, and ammonium hydroxide. Method for producing an aqueous cellulose alkali solution, characterized in that to use. The method of claim 1, wherein the cation used in the step (3) has an ionic volume of 0.5 to 4 times compared to the anion. The method of claim 1, wherein the aqueous alkali solution in the step (3) has a conductivity of 150 ~ 500m characterized in that the manufacturing method of the aqueous solution of cellulose alkali.

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