CN110042488B - Low-cost, green and efficient preparation method of high-strength cellulose filaments - Google Patents

Abstract

The invention discloses a low-cost, green and efficient preparation method of high-strength cellulose filaments. The solvent prepared by the method after optimizing the ratio of sodium hydroxide/urea/zinc oxide is pre-cooled to -20～-8°C, which can quickly dissolve a high proportion of cellulose. The 4-10% cellulose solution is spinned by wet spinning and mixed in citric acid, sodium citrate, ethylene glycol and water (concentrations are preferably 5-35%, 2-20%, 5-60% and 10 to 70%) of the mixed solution for regeneration and coagulation, and the temperature of the coagulation bath is preferably 0 to 25°C. Regenerated cellulose fibers are obtained after preliminary stretching orientation, water washing and drying. The solvent and coagulation bath used in the method are of low cost, the prepared cellulose fibers are constructed of nanofibers, and have excellent mechanical properties; and after optimizing the solvent composition ratio, the solubility of cellulose is higher, and the production efficiency is also significantly improved; the production process is simple and safe No pollution, it is a green process for producing pure cellulose silk. This method is expected to replace the existing industrial spinning process.

Description

A low-cost, green and efficient preparation method of high-strength cellulose filaments

technical field

The invention belongs to the field of natural polymer material processing, and in particular relates to a low-cost, green and efficient preparation method of high-strength cellulose filaments.

Background technique

There are various methods for wet spinning of cellulose. At present, the most commonly used method in China is viscose method, which still occupies a dominant position in the domestic fiber production industry. However, the production process of viscose fiber is not ideal, and the production process is accompanied by toxic and harmful by-products such as CS ₂ , H ₂ S and heavy metals, and the production process is lengthy; in addition, the environmentally friendly solvent N-methylmorphine-N- Oxide-dissolved cellulose can also be spun to obtain Lyocell fibers. Compared with viscose fiber, Lyocell fiber has higher mechanical properties and excellent dimensional stability, but the solvent is expensive, difficult to recover, and the conditions for dissolving cellulose are harsh, which limit the development of Lyocell fiber. In recent years, the use of ionic liquids as new cellulose solvents for spinning has the disadvantages of toxicity, high price, and high solvent purity requirements in the preparation process, which increases the manufacturing cost of fibers. In addition, the mechanical properties of regenerated cellulose fibers are poor, which hinders their further industrialization. Therefore, the use of green, low-cost, and high-efficiency methods to prepare fibers with ideal properties is still a hot and difficult point for regenerated cellulose fibers.

Patent CN 107653502 A uses phytic acid as a coagulation bath to prepare high-strength fiber filaments based on nanofibers. However, the price of phytic acid is relatively high, which greatly increases the production cost.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a low-cost, green, high-efficiency industrially produced cellulose filament and a preparation method thereof.

The invention uses alkali/urea/zinc oxide/water as a solvent system, and after optimizing each composition ratio, it can effectively dissolve high-concentration cellulose, has low cost and is environmentally friendly, and the high-concentration solution is conducive to improving spinning production efficiency. In the subsequent coagulation spinning process, an inexpensive mixed solvent of citric acid/sodium citrate/ethylene glycol/water is used as a coagulation bath, which can delay the Brownian motion, diffusion and solvent/non-solvent interaction between substances. Exchange, so that the coagulation bath can slowly destroy the alkali-urea inclusion complex on the surface of the cellulose molecule to expose the cellulose chain, and the exposed cellulose chain spontaneously tends to align in parallel (length direction) in a mild environment, and then pass through intermolecular hydrogen. The bonds form nanofibers, which in turn make the mechanical strength of the nanofibers significantly improved. The fiber filament provided by the invention has high fiber strength, and can reduce the production cost while ensuring the high strength of the fiber filament. The method for preparing fiber filaments provided by the invention has the advantages of simple technological process, cheap and easily available raw materials, low equipment requirements, short production period, and is beneficial to cost control and industrialization.

The technical scheme provided by the present invention is as follows:

A low-cost, green and efficient method for preparing high-strength cellulose filaments, comprising the following steps:

(1) Dissolving high-concentration cellulose with a solvent body prepared from alkali/urea/zinc oxide/water;

(2) Using a mixed solution of citric acid/sodium citrate/ethylene glycol/water as a coagulation bath, high-strength cellulose fibers based on nanofibers are prepared through an extruder;

(3) immersing the cellulose filaments in a water bath for drawing and drawing;

(4) After washing with water, oiling and drying.

In the above step (1), the cellulose viscosity average molecular weight is less than 1.5×10 ⁵ .

In the above step (1), the solvent is pre-cooled to -20～-8°C, and then cellulose is added, and it can be completely dissolved after high-speed stirring.

In the above-mentioned steps (1), in the solvent, the alkali is sodium hydroxide

In the above step (1), the concentration of alkali in the solvent is 5-10wt%, the concentration of urea is 5-20wt%, the concentration of zinc oxide is 0.5-5wt%, and the balance is water.

The contents of citric acid, sodium citrate, ethylene glycol and water in the above step (2) are respectively 5-35wt%, 2-20wt%, 5-60wt% and 10-70wt%.

In the above step (2), the temperature of the coagulation bath is 0-25°C.

The extrusion rate of the extruder in the above step (2) is 3-10 m/min.

In the above step (3), the temperature of the water bath is 40-85°C.

In the above-mentioned step (3), the drafting is secondary drafting, and the drafting ratio is 1.2-2.8 (1.0 means no drafting).

The present invention also provides high-strength cellulose filaments prepared by the above method.

Beneficial effects of the present invention:

(1) The composition of the solvent and the coagulation bath is cheap and easy to obtain, and the nanofiber-based silk material can be regenerated in the coagulation bath. The arrangement of the nanofibers along the length direction contributes to the improvement of the tensile strength, and can impart a higher viscosity than that of the coagulation bath. The mechanical strength of the rubber wire;

(2) The optimized components and proportions of solvent and coagulation bath improve the solubility of cellulose and improve production efficiency;

(3) The spinning cycle is greatly shortened, and the whole process from dissolution to filamentation takes only 8 hours, which is much lower than that of traditional viscose spinning;

(4) Green, environmental protection, energy saving and consumption reduction, no sulfonation, desulfurization, bleaching and other processes are required in the production process, and no toxic gas is generated, which is in line with the road of sustainable development;

(5) The process is simple, the cost is low, and it can be industrialized.

Description of drawings

Fig. 1 is the surface and cross-sectional topography of the cellulose filament prepared in Example 1;

FIG. 2 is a graph showing the mechanical properties of the cellulose filaments prepared in Example 2. FIG.

Detailed ways

The technical solutions of the present invention will be further described below through specific embodiments and accompanying drawings, the purpose of which is to help better understand the content of the present invention, but these specific embodiments do not limit the protection scope of the present invention in any way. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

Example 1

Prepare 1000g of 5wt%NaOH/20wt%urea/0.5wt%ZnO/74.5wt%water solvent, pre-cool the solvent to -20°C, add 75 grams of cellulose to the solvent and start stirring at room temperature, after 5 minutes the cellulose i.e. completely dissolved. Use a centrifuge at 3000 r/min for 5 minutes to defoam to obtain a clear and transparent cellulose spinning solution.

The spinning solution was poured into a sealed tank, and the spinning head was immersed in a coagulation bath consisting of 10wt% citric acid/2wt% sodium citrate/18wt% ethylene glycol/70wt% water, and the extrusion rate of the spinning solution was controlled to be 3 m/min, and the coagulation bath temperature was 25°C. After the spinning solution enters the coagulation bath, it is solidified and formed into filaments. After being collected by the drum, the filaments are drawn into a constant temperature bath containing 50°C water. 1.2 Cellulose filaments. After washing, drying, and collecting into rolls, high-strength cellulose filaments are obtained.

The spun cellulose filaments were observed by scanning electron microscope (SEM) (Figure 1), and the circular fiber structure could be seen, and the cross-sectional morphology of the filaments proved that the inside of the cellulose filaments was indeed composed of nanometers with a diameter of about 30-40 nanometers. Fiber composition, this structure helps to improve the mechanical properties of the silk.

Example 2

Prepare 1000g of 10wt%NaOH/5wt% urea/4.0wt% zinc oxide/81wt% water solvent, pre-cool the solvent to -8°C, add 40 grams of cellulose into the solvent and start stirring at room temperature, after 5 minutes the cellulose i.e. completely dissolved. Use a centrifuge at 4000 r/min for 5 minutes to defoam to obtain a clear and transparent cellulose spinning solution.

The spinning solution was poured into a sealed tank, and the spinning head was immersed in a coagulation bath composed of 20wt% citric acid/20wt% sodium citrate/5wt% ethylene glycol/55wt% water, and the extrusion rate of the spinning solution was controlled to be 6 m/min, and the coagulation bath temperature was 10°C. After the spinning solution enters the coagulation bath, it is solidified and formed into filaments. After being collected by the drum, the filaments are drawn into a constant temperature tank filled with 60°C water. 1.8 cellulose filaments. After washing, drying, and collecting into rolls, high-strength cellulose filaments are obtained.

The mechanical properties of the silk reached 2.7 cN/dtex (Fig. 2), which was higher than the reported strength of cellulose silk prepared by viscose method (2.2 cN/dtex).

Example 3

Prepare 1000g of 8wt%NaOH/15wt%urea/5wt%zinc oxide/72wt%water solvent, pre-cool the solvent to -12°C, add 100 grams of cellulose into the solvent and start stirring at room temperature. After 5 minutes, the cellulose is completely dissolved. Use a centrifuge at 4000 r/min for 5 minutes to defoam to obtain a clear and transparent cellulose spinning solution.

The spinning solution was poured into a sealed tank, and the spinning head was immersed in a coagulation bath composed of 5wt% citric acid/15wt% sodium citrate/30wt% ethylene glycol/50wt% water, and the extrusion rate of the spinning solution was controlled to be 8 m/min, and the coagulation bath temperature was 20°C. After the spinning solution enters the coagulation bath, it is solidified and formed into filaments. After being collected by the drum, the filaments are drawn into a constant temperature bath containing 70°C water. 2.2 Cellulose filaments. After washing, drying, and collecting into rolls, high-strength cellulose filaments are obtained.

Example 4

Prepare 1000 grams of 6wt% NaOH/11wt% urea/1.0wt% zinc oxide/82wt% water solvent, pre-cool the solvent to -12°C, add 65 grams of cellulose into the solvent and start stirring at room temperature, after 5 minutes the fiber The element is completely dissolved. Use a centrifuge at 4000 r/min for 5 minutes to defoam to obtain a clear and transparent cellulose spinning solution.

The spinning solution was poured into a sealed tank, and the spinning head was immersed in a coagulation bath consisting of 25wt% citric acid/5wt% sodium citrate/60wt% ethylene glycol/10wt% water, and the extrusion rate of the spinning solution was controlled to be 10 m/min, and the coagulation bath temperature was 0°C. After the spinning solution enters the coagulation bath, it is solidified and formed into filaments. After being collected by the drum, the filaments are drawn into a constant temperature tank filled with water at 85 °C. 2.8 of cellulose filaments. After washing, drying, and collecting into rolls, high-strength cellulose filaments are obtained.

Example 5

Prepare a solvent of 1000g 8wt%NaOH/10wt%urea/2.0wt%zinc oxide/80wt%water, pre-cool the solvent to -15°C, add 85 grams of cellulose into the solvent and start stirring at room temperature. After 5 minutes, the cellulose i.e. completely dissolved. Use a centrifuge at 4000 r/min for 5 minutes to defoam to obtain a clear and transparent cellulose spinning solution.

The spinning solution was poured into a sealed tank, and the spinning head was immersed in a coagulation bath consisting of 35wt% citric acid/20wt% sodium citrate/35wt% ethylene glycol/10wt% water, and the extrusion rate of the spinning solution was controlled to be 10 m/min, and the coagulation bath temperature was 5°C. After the spinning solution enters the coagulation bath, it is solidified and formed into filaments. After being collected by the drum, the filaments are drawn into a constant temperature bath containing 40°C water. 2.0 cellulose filaments. After washing, drying, and collecting into rolls, high-strength cellulose filaments are obtained.

The above results show that the method for preparing high-strength cellulose fibers based on nanofibers has the advantages of low cost, low pollution, short cycle and high efficiency.

The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited to this. Any modifications made by any person skilled in the art within the technical scope disclosed by the present invention are equivalent Substitutions and improvements, etc., should all be included within the protection scope of the invention.

Claims (9)

1. a preparation method of low-cost, green, efficient high-strength cellulose silk, is characterized in that, comprises the steps: (1) Use the solvent prepared by alkali/urea/zinc oxide/water to dissolve the solid cellulose of high mass fraction; (2) Using a mixed solution of citric acid/sodium citrate/ethylene glycol/water as a coagulation bath, high-strength cellulose fibers based on nanofibers were prepared by an extruder; citric acid, sodium citrate, The contents of ethylene glycol and water are respectively 5-35wt%, 2-20wt%, 5-60wt% and 10-70wt%; (3) immersing the cellulose filaments in a water bath for drawing and drawing; (4) After washing with water, oiling and drying. 2 . The method according to claim 1 , wherein the viscosity-average molecular weight of the cellulose in the step (1) is less than 1.5×10 ⁵ . 3 . 3. The method according to claim 1, characterized in that: in the step (1), the solvent is pre-cooled to -20～-8°C, and then cellulose is added, and it can be completely dissolved after high-speed stirring. 4. The method according to claim 1 or 2, characterized in that: in the step (1), the alkali in the solvent is sodium hydroxide. 5. method according to claim 1 and 2 is characterized in that: in the described step (1), the concentration of alkali in solvent is 5～10wt%, the concentration of urea is 5～20wt%, the concentration of zinc oxide is 0.5 ~5 wt% with the balance being water. 6 . The method according to claim 1 , wherein in the step (2), the temperature of the coagulation bath is 0-25° C. 7 . 7. The method according to claim 1, wherein the extrusion rate of the extruder in the step (2) is 3-10 m/min. 8 . The method according to claim 1 , wherein the temperature of the water bath in the step (3) is 40-85° C.; the traction is secondary traction, and the draft ratio is 1.2-2.8. 9 . 9 . A low-cost, green, and high-efficiency high-strength cellulose filament, characterized in that: it is prepared by the method according to any one of claims 1 to 8. 10 .

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