KR20000018318A - Cellulosic carbonate derivatives and production method of regenerated cellulosic fiber using it - Google Patents

Abstract

PURPOSE: A method is provided to produce a regenerated cellulosic fiber by melting the cellulose having the high polymerizing degree. CONSTITUTION: A production method of the regenerated cellulose fiber comprises steps of: producing the sodium cellulose by processing a cellulose material with the sodium hydroxide aqueous solution; exposing and ripening the sodium cellulose by leaving in the air; removing the excessive sodium hydroxide by repeating a washing and a filtering processes the exposed and ripened cellulose; producing an active cellulose by processing the cellulose by the carbon dioxide as an activator of high pressure under pretreating solution; producing a cellulose carbonate derivate by repeating the washing and filtering processes the active cellulose; regenerating the cellulose by moisture-spinning the cellulose spinning solution during a bath to solidify.

Description

Cellulose carbonate derivative and method for producing regenerated cellulose fiber using the same.

Field of invention

The present invention relates to a method for producing regenerated cellulose fibers. More specifically, the present invention relates to a method for producing regenerated cellulose fibers by preparing a cellulose carbonate derivative from natural cellulose, preparing a cellulose spinning solution from the derivative, and wet spinning it.

Background of the Invention

Cellulose is the most abundant organic resource on the planet and has obtained regenerated cellulose fibers from it. As a method for obtaining regenerated fiber from cellulose, a cellulose derivative is prepared through a direct solvent-based method in which cellulose is directly dissolved in a solvent, spinning the solution to obtain regenerated fiber, and a cellulose derivatization process, and then the derivative is dissolved in a solvent. There is an indirect solvent-based method in which this solution is spun to obtain regenerated fibers. Viscose rayon is the most representative example of regenerated cellulose fibers. The viscose rayon is prepared by an indirect solvent-based method. Specifically, cellulose xanthate derivative is obtained by reacting old cellulose with carbon disulfide to dissolve in an aqueous solution of sodium hydroxide, which is 10wt% sodium hydroxide. It is prepared by the process of solidification and regeneration in a coagulation bath dissolved in an aqueous solution and spinning. Cellulose obtained in nature has a high degree of crystallinity and hydrogen bonding, so that it is difficult to dissolve in a general solvent, and it is difficult to reshape into a desired shape. Many studies have been conducted to obtain regenerated fibers from natural cellulose, and some of them have been applied to mass production systems for producing regenerated fibers from cellulose, but most remain in the laboratory stage.

The known techniques for producing fibers from natural cellulose are introduced into the direct solvent method and the indirect solvent method as follows.

In the direct solvent method, N-methyl morpholine N-oxide (NMMO) process, sodium hydroxide / water process, zinc chloride / water process, and copper ammonium process are known according to the type of solvent used.

The NMMO process for producing lyocell (or tencel) (trademark) dissolves cellulose at 100-105 ° C. in the presence of NMMO and 15.5% water as a solvent to obtain a 10% cellulose solution. At the beginning of solvation, the hydrogen bonds between the cellulose molecular chains in the crystal region are broken, and a hydrogen bond is formed between the hydroxyl group of the cellulose and the amine oxide. NMMO is simple in structure and can be recovered and reused. It is used as a solvent by mixing with a small amount of water. The fiber obtained by wet and dry spinning using NMMO as a solvent has properties comparable to that of high humidity rayon. The N-oxide group of NMMO swells by cutting intermolecular hydrogen bonding force and acts as a hydrogen bond acceptor to stabilize cellulose chains in solution. NMMO can be reused because of its simple structure and easy recovery of solvents. However, NMMO has a disadvantage that it is exploded at 150 ° C or higher due to high solvent and low thermal stability. In addition, NMMO has the property of absorbing moisture in the air to hydrate from anhydride to trihydrate, the melting point of NMMO changes rapidly depending on the degree of hydration, and the solubility in cellulose shows a significant difference depending on the degree of hydration. Despite some of these technical drawbacks, production is increasing and is being evaluated as a replacement for the viscose process.

In the sodium hydroxide / water process, the cellulose whose polymerization degree was lowered to 1/3 level by steam explosion treatment was dissolved in an aqueous solution of 9-10 wt% sodium hydroxide over 4 hours at 4 ° C. The amount of cellulose in the spinning solution is about 8-12% of the weight of water in aqueous sodium hydroxide solution. Disadvantages of this process are that it does not dissolve in the sodium hydroxide aqueous solution when the degree of polymerization of steam-expanded cellulose is high, and when it dissolves 10% by weight or more of cellulose in solvent weight, it causes rapid gelation, resulting in poor radioactivity. Results in. In addition, the cellulose fiber produced through this process has a strength value of about 0.85 to 1.5 (g / den), which is relatively low compared to other processes, thus preventing industrialization.

In the zinc chloride / water process, cellulose having a degree of polymerization of 400 to 600 is stirred in a 40 wt% ZnCl ₂ solution at 60 ° C. for 15 to 60 minutes to prepare a spinning solution. In this case, a halogen compound of Mg and Al is used as a catalyst, and the composition of the spinning solution is 5 to 45 wt% cellulose and 62 to 76 wt% ZnCl _{2 based on the} weight of water. The spinning solution passes through a coagulation bath composed of water and ethanol to obtain cellulose fibers. As a result, 0.4 wt% of ZnCl ₂ remains in the cellulose fibers, which makes it impossible to manufacture fine fibers.

In the copper ammonium process, cellulose is dissolved in a manner of forming a complex with a cellulose glycol group using cuam (Cu (NH) ₃ (OH) ₂ ) as a cellulose solvent. At this time, there is a difficulty in recovering or recovering the metal complex solvent used in an environmentally stable state. In the case of using an aqueous metal complex solvent, copper should be recovered so that the copper concentration in the coagulation bath should be 0.1 ppm or less using a wet exchange ion exchange system, so that the physical properties are good, but the manufacturing cost is higher than that of other technologies. .

As an indirect solvent-based method for preparing and dissolving cellulose derivatives, a viscose process, a Carbamat process, a process using a mixed solvent of LiCl / DMAc, and the like are known.

In the textile industry's revolutionary viscose process, sodium cellulose and carbon disulfide are reacted in the middle of the process to obtain cellulose xanthate derivatives, which are dissolved in aqueous sodium hydroxide solution. The viscose solution dissolved in the concentrated aqueous sodium hydroxide solution is regenerated into cellulose upon wet spinning in a coagulation bath containing sulfuric acid. Carbon disulfide generated during the regeneration process is a highly toxic flammable liquid that causes serious occupational diseases. Side reactions produce air and wastewater pollutants such as sodium trisulfide and hydrogen sulfide. The viscose process is still of industrial importance, but due to the technical problems mentioned above, the production scale is gradually decreasing.

In the Kabamart process, cellulose having a degree of polymerization of about 400 is swollen in an ammonia solution and then reacted with 10 wt% urea at 155 ° C. to prepare cellulose carbamate as a soluble derivative. The prepared cellulose carbamate derivative is then capable of dissolving in 8wt% sodium hydroxide aqueous solution. Cellulose carbamate, a soluble derivative, is easy to hydrolyze, but has a disadvantage in that it does not dissolve cellulose having a value of various degrees of polymerization.

In the process using a mixed solvent of LiCl / DMAc (dimethyl acetamide), cellulose is swollen in one of two solutions before dissolving cellulose having a degree of polymerization of about 440 to prepare cellulose derivatives through cellulose esterification and etherification. The derivatization process leads to easier solvent access and breaks the hydrogen bonds between the cellulose molecular chains so that the cellulose derivative is dissolved in the mixed solvent of LiCl / DMAc.

Each of the processes described above has process disadvantages, and therefore, process improvement or development of a new solvent system is required. In particular, carbon disulfide used in the viscose process has caused serious occupational diseases to workers because it is harmful to the human body as well as environmental problems. In addition, in the Kabamart process, the process using a mixed solvent of LiCl / DMAc, zinc chloride / water process, there is a disadvantage in dissolving only cellulose having a low polymerization degree. In addition, in some processes, the dissolved state of cellulose is unstable, and in most direct solvent methods, solvents are expensive, inconvenient to handle, difficult to manufacture fine fibers, and difficult to recover. It is implicated.

The present inventors have come to develop the method of the present invention to prepare a cellulose carbonate derivative and to produce regenerated cellulose fibers from the technical limitations of the viscose process.

It is an object of the present invention to provide a method for producing regenerated cellulose fibers that does not cause environmental problems including occupational diseases of workers.

Another object of the present invention is to provide a method for producing regenerated cellulose fibers by dissolving cellulose having a high degree of polymerization.

Still another object of the present invention is to provide a method for preparing cellulose carbonate derivatives using carbon dioxide and manufacturing regenerated cellulose fibers from the cellulose xanthate derivatives in the conventional viscose rayon process.

The above and other objects of the present invention can be achieved by the present invention described below.

In the method for producing regenerated cellulose fibers of the present invention, the cellulose material is swelled in an aqueous sodium hydroxide solution to prepare sodium cellulose, the sodium cellulose is left to stand in air for aging, and the aged cellulose is repeatedly washed with water and filtered to remove excess hydroxide. Sodium is removed, and the aged cellulose is treated with carbon dioxide (solid dry ice) using a high pressure reactor under a pretreatment solution to prepare a cellulose carbonate derivative. The cellulose carbonate derivative is washed with water and filtered, and then the aqueous solution of sodium hydroxide and zinc oxide Dissolving in a solvent to form a cellulose spinning solution, and wet spinning the cellulose spinning solution in a coagulation bath to recover the cellulose.

The pretreatment solution is 20 to 40 wt% of zinc chloride, an aqueous lower alcohol solution or a mixture thereof, and preferred lower alcohols include methanol, ethanol, propanol and the like.

The present invention relates to a method for preparing a cellulose carbonate derivative and using the same to produce regenerated cellulose fibers.

The cellulose material is treated with aqueous sodium hydroxide solution to produce sodium cellulose. The cellulose used may be one obtained by pulverizing a commercially available cellulose pulp having a molecular weight of about 100,000 in a width and length of about 1 mm, or using cotton cellulose. The aqueous solution of sodium hydroxide having a concentration of about 17.5 wt% is swelled at 0 to 5 ° C. for 2 hours in the cellulosic material. In this process, solubles such as hemicellulose are removed. The reaction formula for producing sodium cellulose from cellulose is represented by the following formula.

Cell-OH + NaOH ――― ▶ Cell-ONa + H ₂ O

The sodium cellulose is left to age in air. Sodium cellulose is compressed to be about 2 to 3 times the weight of the original cellulose and then left in air at 50 ° C. to prepare aged cellulose.

Aged cellulose is washed with distilled water about 6 times and filtered to remove excess sodium hydroxide. The molecular weight can be adjusted according to the aging time.

The excess sodium hydroxide is removed noseong cellulose ZnCl ₂ aqueous solution and, ZnCl _2: is treated with carbon dioxide as a high-pressure reactor under the first aqueous solution: 1 weight ratio to a lower alcohol. The carbon dioxide is preferably dry ice, liquid carbon dioxide or gaseous carbon dioxide, and the reaction conditions of the high-pressure reactor are preferably 40 to 60 kgf / cm ² , and the reaction is performed at room temperature for about 2 hours. In this way, reactive cellulose is produced. The concentration of ZnCl ₂ is preferably 20 to 40 wt% and the lower alcohol is preferably methanol, ethanol or propanol.

The reaction cellulose is washed with water and filtered to produce a cellulose carbonate derivative. Water washing and filtration are usually performed twice. In this process excess zinc chloride solution and methanol solution are removed and cellulose carbonate derivatives are prepared.

A reaction formula for preparing a cellulose carbonate derivative from the sodium cellulose is as follows.

ZnCl ₂

Cell-ONa + CO ₂ ――――― ▶ Cell-OCO ₂ Na

Strictly speaking, the reactive cellulose itself may be referred to as a cellulose carbonate derivative, but various substances such as unreacted materials are included in the present invention. The cellulose carbonate derivative is dissolved in a solvent consisting of an aqueous sodium hydroxide solution and zinc oxide to prepare a cellulose spinning solution. It is preferable that the aqueous sodium hydroxide solution has a concentration of approximately 10 wt%, and a small amount of zinc oxide is used, but preferably about 3% of the weight of the aqueous sodium hydroxide solution is used. The cellulose carbonate derivative is dissolved at a temperature of 10 to 20 ° C. for about 2 hours to prepare a spinning solution. The concentration of the cellulose spinning solution to be prepared depends on the molecular weight, but preferably has a concentration of about 5 to 10%.

Regenerated cellulose fibers are obtained from the cellulose spinning solution. The cellulose spinning solution is spun in the coagulation bath. The coagulation bath is filled with a coagulation solution consisting of 10% sulfuric acid, 20% sodium sulfate and 70% water. Salt in the coagulant solidifies the spinning solution and acid serves to regenerate cellulose. Sulfuric acid penetrates into the formed fibers and neutralizes with alkali as the solvent inside the fibers exits the fibers. The spinning device for producing regenerated cellulose fibers in the present invention used a wet spinning device, which can be easily carried out by those skilled in the art. The reaction scheme for obtaining regenerated cellulose fibers from the cellulose spinning solution is as follows.

CellOCO ₂ Na + H ₂ SO ₄ ――― ▶ Cell-OH + CO ₂ + Na ₂ SO ₄

The regenerated cellulose fibers according to the invention have been found to have good fiber strength which depends on the winding speed in the spinning process. The present invention also found that the spinning properties of the cellulose spinning solution were good even if the aging time was changed. The pretreatment solution for pretreatment of cellulose before reacting carbon dioxide to old cellulose may be a mixed solution of zinc chloride aqueous solution and methanol, or a single zinc chloride aqueous solution or methanol.

The present invention can use most of the apparatus used in the conventional viscose rayon process by derivatizing cellulose using carbon dioxide instead of carbon disulfide used in the conventional viscose rayon process, and various kinds of carbon disulfide-induced processes. It is possible to produce environmentally friendly cellulose fibers that can prevent industrial accidents and air pollution, and because sodium hydroxide aqueous solution is used as the cellulose solvent, it is easy to handle or recover the solvent and the production cost can be low.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

Preparation of Cellulose Carbonate Derivatives:

Commercially available cellulose pulp (molecular weight of about 100,000) used for the production of conventional viscose rayon or lyocell (or tencel) (trademark) is pulverized to a size of about 1 mm in width and length, and is 0 to 17.5 wt% concentrated sodium hydroxide solution. Sodium cellulose was prepared by treatment at 5 ° C. for 2 hours. The sodium cellulose was compressed to be 2.5 times the weight of the original cellulose and left in air at 50 ° C. to prepare aged cellulose. The aged cellulose was washed with distilled water six times and filtered to remove excess sodium hydroxide. The aged cellulose was treated with solid dry ice using a high pressure reactor in an aqueous solution of 30 wt% zinc chloride and methanol (1: 1 by weight). The reaction cellulose was washed twice with filtration to prepare a cellulose carbonate derivative.

Preparation of Regenerated Cellulose Fibers:

A 10% by weight sodium hydroxide aqueous solution obtained above and zinc oxide corresponding to 3% of the weight of the aqueous solution were used as a solvent to dissolve for 2 hours at 10 to -20 ° C to prepare a cellulose spinning solution. The composition of the coagulation bath of the wet spinning device has a composition of 10% sulfuric acid, 20% soda sulfate and 70% water.

Example 1 Measurement of Strength of Cellulose Fiber According to Winding Speed

The strength of the cellulose fibers was measured while varying the winding speed. Viscosity measurements were measured using a Brookfield (LV DV-II +) viscometer. The measurement conditions were obtained when Spindle no. 63, 12 rpm, 5 ° C; Spindle no. When viscosity of 10,000 cps or more. 64, 15 rpm, and 5 ° C. The strength measurement of the fiber measured the fiber dried at room temperature. The results are shown in Table 1.

Table 1

Winding speed Cellulose Concentration (%) Viscosity (cps) Strength (g / d) 10 10 22,000 - 15 10 22,000 0.8 20 10 22,000 One

Example 2 Evaluation of Cellulose Radioactivity with Change in Aging Time

In order to evaluate the radioactivity of cellulose according to the aging time change, the experiment was performed by changing the aging time. Aging cellulose was prepared by the aging time of 0, 2, 4, 6 hours at a temperature of 50 ℃, the radioactivity results are shown in Table 2.

TABLE 2

Aging time (hr) Cellulose Concentration (%) Radioactive ^* 0 10 ○ 2 10 ○ 4 10 ○ 6 10 ○

Radioactive: spinnable

Example 3 Evaluation of Cellulose Radioactivity According to Change of Pretreatment Solution

The radioactivity was evaluated by changing the pretreatment liquid used to react the aged cellulose and carbon dioxide. The changed pretreatment solution is shown in Table 3, and the resulting radioactive results are also shown in Table 3.

TABLE 3

Pretreatment solution Cellulose Concentration (%) Radioactive ^* 30 wt% ZnCl ₂ : CH ₃ OH (1: 1 weight ratio) 10 ○ 30 wt% ZnCl ₂ : C ₂ H ₅ OH (1: 1 weight ratio) 10 ○ 30 wt% ZnCl ₂ : C ₃ H ₇ OH (1: 1 weight ratio) 10 ○ 40 wt% ZnCl ₂ 10 ○ 30 wt% ZnCl ₂ 10 ○ 20 wt% ZnCl ₂ 10 ○ CH ₃ OH 10 ○

Radioactive: spinnable

As shown in the above examples, the fiber strength of the regenerated cellulose fibers according to the present invention was found to be good, but it was changed according to the winding speed, and the radioactivity was good regardless of the aging time or the type of pretreatment solution.

The present invention can produce regenerated cellulose fibers by dissolving cellulose having a high degree of polymerization without causing environmental problems such as occupational diseases of workers, and easy handling and recovery of solvents by using sodium hydroxide aqueous solution as the cellulose solvent. The production cost is low. Instead of preparing a cellulose xanthate derivative in a conventional viscose rayon process, a cellulose carbonate derivative using carbon dioxide may be prepared to provide a method for producing regenerated cellulose fibers therefrom.

Simple modifications or variations of the present invention can be readily understood by those skilled in the art, and all such modifications or changes can be seen to be included within the scope of the present invention.

Claims (6)

Treating cellulose material with aqueous sodium hydroxide solution to produce sodium cellulose; Leaving the sodium cellulose in air to age; The aged cellulose was washed with water and filtered to remove excess sodium hydroxide; Treating the cellulose with a high pressure reactor under a pretreatment solution to produce a reactive cellulose; Washing the reaction cellulose with water and filtration to prepare a cellulose carbonate derivative; Preparing a cellulose spinning solution by dissolving the cellulose carbonate derivative in a solvent consisting of an aqueous sodium hydroxide solution and zinc oxide; And Wet spinning the cellulose spinning solution in a coagulation bath to regenerate cellulose; Method for producing a regenerated cellulose fiber, characterized in that consisting of steps. The method for producing regenerated cellulose fibers according to claim 1, wherein the step of preparing the spinning solution is carried out at a temperature of 10 to -20 ° C under dissolving conditions in a solvent consisting of an aqueous sodium hydroxide solution and zinc oxide. The method for producing regenerated cellulose fibers according to claim 1, wherein the carbon dioxide in the step of preparing the reactive cellulose is dry ice, liquid carbon dioxide, or gaseous carbon dioxide. The method for producing regenerated cellulose fibers according to claim 1, wherein the pretreatment liquid in the step of preparing the cellulose carbonate derivative is 20 to 40 wt% of zinc chloride, an aqueous lower alcohol solution or a mixture thereof. The method of claim 4, wherein the lower alcohol is selected from the group consisting of methanol, ethanol and propanol. Treating cellulose material with aqueous sodium hydroxide solution to produce sodium cellulose; Leaving the sodium cellulose in air to age; The aged cellulose was washed with water and filtered to remove excess sodium hydroxide; Treating the cellulose with a high pressure reactor under a pretreatment solution to produce a reactive cellulose; And Washing the reaction cellulose with water and filtering to prepare a cellulose carbonate derivative; Method for producing a cellulose carbonate derivative, characterized in that consisting of steps.