CN112323181B

CN112323181B - Preparation method of high-performance chitosan fiber

Info

Publication number: CN112323181B
Application number: CN202011322456.1A
Authority: CN
Inventors: 侯秀良; 胡天娇; 彭亚倩; 张祝辉; 李蔚
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2022-03-04
Anticipated expiration: 2040-11-23
Also published as: CN112323181A

Abstract

The invention discloses a preparation method of high-performance chitosan fibers, and belongs to the technical field of textiles. The method comprises the steps of mixing citric acid solution and chitosan to prepare spinning solution, and preparing the high-performance chitosan fiber through wet spinning. According to the invention, citric acid which is non-toxic, environment-friendly and low in cost is simultaneously used as a solvent and a crosslinking agent, and chitosan is subjected to modification treatment to improve the mechanical property of the chitosan material, so that after the chitosan fiber is subjected to crosslinking treatment, the dry breaking strength is improved by 36.36%, and the dry breaking elongation is improved by 31%; the wet fracture strength is improved by 39.81 percent, and the wet fracture elongation is improved by 31 percent.

Description

Preparation method of high-performance chitosan fiber

Technical Field

The invention relates to a preparation method of high-performance chitosan fibers, and belongs to the technical field of textiles.

Background

In the field of textile, chemical fibers such as terylene and chinlon are widely applied from petroleum at present, and a bio-based textile material with more abundant resources is required to be searched under the background of excessive consumption of non-renewable resources. Although bio-based fibers are still deficient in certain properties relative to petroleum-based fibers, they can be continuously improved to expand their applications and realize a gradual replacement for petroleum-based fibers. The research on bio-based textile materials has become an important direction of research in the textile field. A large amount of biomass wastes such as waste crabs and shrimp shells are generated in coastal areas every year, and the chitin extracted from the waste crabs and shrimp shells is further applied to the chitin and derivatives thereof in an expanded way, so that the waste crabs and shrimp shells can be recycled, the additional value of the waste crabs and shrimp shells can be improved, and the environmental pollution of the coastal areas can be relieved. Chitosan is deacetylated chitin, and is now commercially produced and provides a raw material for various chitosan and derivative materials.

Chitosan has many excellent properties including biocompatibility, biodegradability and bacteriostatic properties, but it has disadvantages of low strength and cannot be melt-spun since the chitosan polymer is decomposed before melting, and at present, chitosan can be prepared only by solution spinning. The viscosity of the spinning solution is too high due to too strong hydrogen bonds among the macromolecules of the chitosan, and the content of the chitosan in the spinning solution is difficult to greatly improve, so that the spinnability of the spinning solution is poor; and the spun filaments need to be subjected to complex working steps such as subsequent cleaning and drying, so that the spinning cost is increased, the problems are common problems for limiting the application of chitosan fibers, and the problems are difficult to be improved in the spinning process. Therefore, it is highly desirable to provide a preparation method capable of improving the mechanical properties of chitosan fibers.

Disclosure of Invention

In order to solve the problems, citric acid which is non-toxic, environment-friendly and low in cost is simultaneously used as a solvent and a cross-linking agent, and chitosan is subjected to modification treatment, so that the mechanical property of the chitosan material is improved, and the application of the chitosan material is further expanded.

The first purpose of the invention is to provide a preparation method of high-performance chitosan fiber, which is to mix citric acid solution and chitosan to prepare spinning solution and prepare the high-performance chitosan fiber through wet spinning.

In one embodiment of the invention, the citric acid solution has a concentration of 4.5% to 5.5% (w/v, g/100 mL).

In one embodiment of the invention, the mass percentage of chitosan in the spinning dope is 2-2.8% (w/w).

In one embodiment of the present invention, the preparation of the spinning solution is specifically: dissolving chitosan in a citric acid solution to obtain a chitosan citric acid solution, mechanically stirring and uniformly mixing, and performing ultrasonic treatment to remove bubbles in the solution to obtain a spinning solution; the mass concentration of the chitosan in the solution is 2-2.8%.

In one embodiment of the present invention, the wet spinning specifically comprises: injecting the spinning solution into a reaction tank of a wet spinning machine, extruding and spinning by a metering pump, wherein the spinning temperature is from room temperature to 60 ℃, the number of spinneret holes is 50-200, the aperture is 0.1-0.2mm, and the coagulating bath is a mixed solution of a sodium hydroxide solution and absolute ethyl alcohol; the coagulation bath draft ratio is 0.9-1.9, and the water washing draft ratio is 1.1-2.0; washing the fiber to be neutral, then soaking the washed chitosan fiber in glycerol, freezing and drying to obtain the chitosan fiber.

In one embodiment of the invention, the concentration of NaOH solution in the coagulation bath is 3-7% (w/v, g/100 mL); the volume ratio of NaOH solution to absolute ethyl alcohol in the coagulating bath is (3-8): (2-7).

The second purpose of the invention is to provide a high-performance chitosan fiber prepared by the method.

The third purpose of the invention is to provide a textile containing the high-performance chitosan fiber.

In one embodiment of the invention, the textile is: any one of yarn, blanket, woven fabric, knitted fabric, thermal insulating wadding, filling material, non-woven fabric, medical and sanitary articles or special work clothes.

The fourth purpose of the invention is to provide the application of the high-performance chitosan fiber in the aspects of textile or medical health.

In one embodiment of the invention, the application comprises: can be used for preparing clothes with health promotion function, clothes with fluorescence effect, medical suture, medical dressing, artificial skin or drug sustained-release material.

The invention has the beneficial effects that:

1. after the chitosan fiber is subjected to crosslinking treatment under the optimized conditions, the dry breaking strength is improved by 36.36 percent, and the dry breaking elongation is improved by 31 percent; the wet fracture strength is improved by 39.81 percent, and the wet elongation at break is improved by 31 percent; the fiber surface depressions are no longer evident;

2. the dry and wet mechanical properties of the chitosan fiber are improved because ionic crosslinking and chemical crosslinking are generated between the citric acid carboxyl and amino groups on the chitosan macromolecules.

Drawings

FIG. 1 is a schematic diagram of CS (AA) fibers (a) and CS (CA) fibers (b).

FIG. 2 shows dry and wet breaking strength (a), initial modulus (b) and elongation at break (c) for CS (AA), CS (CA), and CS (CA) -CA fibers.

FIG. 3 is an SEM image of longitudinal surfaces of CS (AA) fibers (a) and CS (CA) fibers (b), and SEM images of tensile fracture surfaces of CS (AA) fibers (c), CS (CA) fibers (d) and CS (CA) -CA fibers (e).

FIG. 4 is an X-ray diffraction pattern of CS (AA), CS (CA), and CS (CA) -CA fibers.

Detailed Description

The following description of the preferred embodiments of the present invention is provided for the purpose of better illustrating the invention and is not intended to limit the invention thereto.

1. Testing mechanical properties of chitosan fibers

According to the test standard GB9997-88 of the breaking strength and the breaking elongation of the chemical single fiber, the mechanical property of the balanced fiber is tested by adopting a YG004 electronic fiber strength tester in the environment with the temperature of 20 ℃ and the relative humidity of 65 percent. The holding distance was set to 20mm, the drawing rate was set to 20mm/min, and the dry breaking strength (in cN/dtex) and the dry elongation at break (%) of the fiber were obtained, respectively, and the average of the 50 data was taken. The fibers were immersed in water for 2min and then removed and tested as above to obtain the wet breaking strength (in cN/dtex) and the wet elongation at break (%) of the fibers.

2. Characterization of microscopic morphology of chitosan fiber

And (3) observing the surface morphology of the chitosan fiber by using a HITACHI SU1510 scanning electron microscope. And placing the two balanced fiber samples on conductive adhesive, spraying gold, and observing under an electron microscope with the accelerating voltage of 5 kV.

3. Infrared spectroscopic characterization of chitosan fibers

Testing the chitosan fibers before and after crosslinking treatment by using a Fourier transform infrared spectrometer, wherein the resolution ratio is 4cm^-1Scanning range 500-4000cm^-1。

4. Fiber fineness test

Shearing the chitosan fibers balanced under the standard condition into 50mm tows, counting 400 fibers with consistent length and uniform thickness, weighing the fibers by using an electronic balance to obtain the mass (unit g) of the fibers, and calculating the fineness (unit dtex) of the fibers.

5. Microstructural characterisation

And observing the surface and the tensile section appearance of the chitosan fiber by adopting an electronic scanning microscope. And (3) placing the fiber sample on conductive adhesive, spraying gold, and observing under an electron microscope with the acceleration voltage of 5 kV.

6. XRD test

The crystallization condition of the fiber sample is tested by using an X-ray diffractometer under the following test conditions: the working voltage of the Cu target X-ray tube is 40kV, the working current is 40mA, the scanning speed is 3 degrees/min, the scanning range is 5 degrees to 50 degrees, and the step length is 0.02 degrees.

Example 1:

preparation of spinning solution and coagulation bath

(1) Preparing a spinning solution: preparing a citric acid solution 5% (v/v) as a solvent, adding chitosan to enable the mass percent of the chitosan in the spinning solution to be 2.5% (w/w), heating the mixed solution in water bath at 40 ℃, and mechanically stirring at the speed of 500r/min for 24 hours to obtain a fully dissolved chitosan spinning solution; defoaming the spinning solution for 20min at the vibration frequency of 20KHz by an ultrasonic instrument for later spinning;

(2) and (3) coagulation bath preparation: 6 percent NaOH solution and absolute ethyl alcohol are mixed according to the volume ratio of 7:3 to obtain coagulating liquid for the wet spinning process.

Chitosan fiber wet spinning

The chitosan fiber is spun by a wet spinning machine, and the flow of the wet spinning process comprises the following steps: preparing a spinning solution, defoaming, metering, filtering, spinning, solidifying, washing and drafting, winding, drying and obtaining a finished fiber. And slowly injecting the defoamed chitosan spinning solution into a solution storage barrel of a spinning machine, conveying the spinning solution by adopting air pressure, extruding the spinning solution from a spinneret orifice into a coagulating bath by a metering pump at a certain speed, and controlling the drafting multiple and the speed of a winding device in the whole spinning process. Taking the fibers off the winding device, washing the fibers with a large amount of deionized water until the fibers are neutral, soaking the washed chitosan fibers in deionized water with the glycerol content of 1% for 2 hours to prevent the fibers from being excessively adhered, taking the fibers out, putting the fibers into an ultralow-temperature refrigerator, freezing the fibers for 2 hours at the temperature of 80 ℃ below zero, then putting the fibers into a freeze dryer for freeze drying for 24 hours to obtain CS (CA) fibers, and balancing the CS (CA) fibers for 24 hours under the constant-humidity and constant-humidity conditions that the temperature is 21 ℃ and the relative humidity is 65%.

The main process parameters used in this experiment were:

spinning solution: dissolving chitosan spinning solution by using citric acid solution;

number of spinneret holes and hole diameter: 90X 0.15 mm;

pump supply of a metering pump: 0.3 ml/r;

spinning temperature: room temperature;

coagulation bath: a mixed solution of a sodium hydroxide solution and absolute ethyl alcohol;

temperature of the coagulation bath: room temperature;

the ratio of the speed of the first guide roller to the extrusion speed of the spinning solution from the spinneret orifice is 0.9;

draft ratio of nascent fiber after water washing (ratio of speed of second godet roller to speed of first godet roller): 0.9.

example 2: CS (CA) fiber wet spinning process

1. Effect of citric acid concentration on CS (CA) Primary fiber Performance

Chitosan fibers were prepared according to the method of example 1, with the only difference that: the concentrations of citric acid solutions were adjusted to 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, and 6% v/v, and the other conditions were the same as in example 1.

The effect of citric acid concentration on cs (ca) nascent fiber performance is shown in table 1. The citric acid solution with the concentration of below 4 percent can not completely dissolve the chitosan, and part of chitosan flakes are still suspended in the solution, so that the uniform spinning solution can not be prepared. When the citric acid concentration is higher than 4%, the chitosan can be dissolved in the citric acid solution until the solution is in a uniform state, but when the spinning solution is filtered, the agglomerated transparent chitosan lumps are still found in the solution, indicating that the chitosan is not sufficiently dissolved. However, when the concentration of the citric acid solution reaches 5%, the chitosan can be completely dissolved in the system to form a uniform spinning solution, no blocky agglomeration is found after filtration, the breaking strength of the nascent fiber also reaches the maximum value, the concentration of the citric acid is continuously increased, the acidity of the solvent is continuously increased, the partial degradation of the chitosan is caused, and the mechanical property of the nascent fiber is reduced. In summary, the optimal concentration of citric acid solution as the solvent for dissolving chitosan may be selected from the range of 4.5% to 5.5%.

TABLE 1 influence of citric acid concentration on CS (CA) nascent fiber Performance (chitosan concentration 2.5%, NaOH concentration in coagulation bath 6%, ratio of NaOH solution to absolute ethanol 7:3, orifice diameter 0.15mm)

2. Study of Chitosan concentration on CS (CA) nascent fiber performance

Chitosan fibers were prepared according to the method of example 1, with the only difference that: the amount of chitosan added was adjusted so that the mass percentage of chitosan in the spinning solution was 1.9%, 2.1%, 2.3%, 2.5%, 2.7%, 2.9% w/w, and the other conditions were the same as in example 1.

The effect of chitosan concentration on cs (ca) nascent fiber performance is shown in table 2. In table 2, too low a chitosan concentration results in too low a viscosity of the chitosan spinning solution, and the spinning solution is difficult to form into fibers after extrusion. However, as the concentration of chitosan increases, the solid content in the spinning solution increases, the viscosity increases, and the spinning solution can be extruded and then passed through a coagulation bath to form uniform filaments. When the concentration of the chitosan is too high, the viscosity of the spinning solution is too high, the chitosan can swell in an acid solution, the too high chitosan spinning solution can become a jelly-like swelling substance, the spinning solution is difficult to extrude, the spinning is difficult to carry out, and the spinning cannot be finished. The concentration of chitosan is an important parameter for preparing chitosan fibers with excellent performance, the concentration of chitosan polymers is properly increased within a reasonable range, the nascent fiber structure can be more compact, the fiber structure is more uniform and consistent, the breaking strength and the breaking elongation of the fibers are increased, and the toughness of the fibers is improved.

TABLE 2 influence of Chitosan concentration on CS (CA) nascent fiber Performance (citric acid concentration 5%, NaOH concentration 6% in coagulation bath, NaOH to absolute ethanol ratio 7:3, orifice diameter 0.15mm)

3. Studies of NaOH concentration in coagulation bath on CS (CA) nascent fiber Performance

Chitosan fibers were prepared according to the method of example 1, with the only difference that: the NaOH solution concentrations were adjusted to 3%, 4%, 5%, 6%, and 7%, and the other conditions were the same as in example 1.

The effect of NaOH concentration in the coagulation bath on cs (ca) as-spun fiber performance is shown in table 3. When the concentration of NaOH is lower than 3%, the fiber cannot be formed, when the concentration of NaOH is higher than 4%, the spinning condition is good, and the mechanical property of the nascent fiber reaches the best at 6%, and in a coagulating bath, the mechanical property of the nascent fiber tends to be reduced by continuously increasing the concentration of NaOH. The spinning solution is an acid solution, when the spinning solution is extruded into a coagulating bath, alkali in the coagulating bath can instantly neutralize the acid, and the chitosan is drawn to be in a filament-like thread. When the concentration of NaOH is too low, the coagulation of the nascent fiber is slow, so that the strength of the fiber is low and even the fiber cannot be formed, and when the concentration of NaOH is too high, the surface coagulation of the nascent fiber is fast, so that the internal coagulation of the fiber is insufficient, the integral uniformity of the fiber is influenced, and the mechanical property of the fiber is reduced.

TABLE 3 influence of NaOH concentration in coagulation bath on CS (CA) nascent fiber Performance (citric acid concentration 5%, chitosan concentration 2.5%, ratio of NaOH to absolute ethanol 7:3, orifice diameter 0.15mm)

4. Studies of coagulation bath Components on CS (CA) Primary fiber Performance

Chitosan fibers were prepared according to the method of example 1, with the only difference that: the volume ratio of the NaOH solution to the absolute ethyl alcohol was adjusted to 10:0, 8:2, 7:3, 5:5, 3:7, 2:8, and 0:10, and the other conditions were the same as in example 1.

The effect of coagulation bath components on cs (ca) nascent fiber performance is shown in table 4. When the proportion of the NaOH solution is high, the spinning condition of the nascent fiber is poor, the breaking strength is low, the performance of the fiber gradually becomes good along with the increase of the proportion of the absolute ethyl alcohol until the optimal value is reached, and when the proportion of the absolute ethyl alcohol is too high, the performance of the fiber becomes poor or even is not formed, so that the ratio of the NaOH solution to the absolute ethyl alcohol can obviously influence the fiber forming condition and the mechanical property of the chitosan. Because the strand silk coagulation process is actually the result of acid in the spinning solution and alkali in the coagulation and interdiffusion, the pure NaOH solution can make the nascent fiber take shape too fast, form the skin-core structure easily, the fiber structure is inhomogeneous, the speed that the fibre solidifies can be slowed down to proper addition ethanol, make the fiber structure more even compact, and excessive dilution NaOH solution can make the alkali concentration of solution reduce, the fibre takes shape poorly and then influences mechanical properties, select suitable coagulation bath component and proportion and can make the fibre that structure and performance are better.

TABLE 4 Effect of coagulation bath composition on CS (CA) nascent fiber Performance (citric acid concentration 5%, chitosan concentration 2.5%, NaOH concentration in coagulation bath 6%, spinneret hole diameter 0.15mm)

5. Draw ratio versus CS (CA) fiber Performance

Chitosan fibers were prepared according to the method of example 1, with the only difference that: the draft ratios of the as-spun fibers were adjusted to 0.9, 1.1, 1.3, 1.5, 1.7 and 1.9, and the other conditions were the same as in example 1.

The effect of draw down on CS (CA) fiber properties is shown in Table 5. With the increase of the drafting multiple, the breaking strength of the fiber shows a trend of increasing and then decreasing, the breaking elongation shows a trend of decreasing all the time, and under the optimal drafting multiple, the breaking strength of the fiber can reach 1.38cN/dtex, and the breaking elongation is 11.67%. The drafting can improve the crystallization and orientation of the fiber, and further improve and enhance the structure and performance of the fiber. The structure of the as-spun fiber in the coagulation bath is not yet perfect and the fiber strength is still low, so that the as-spun fiber is prevented from breaking by negative draft of 0.9 times, which also makes it difficult to improve the axial orientation by the draft of the as-spun fiber in the coagulation bath. Can carry out appropriate draft through the later process in the washing process for fibrous macromolecule arrangement is more neat orderly, and the orientation degree is higher, and fiber structure becomes more compact, and can extrude the inside solution of partly nascent fibre, does benefit to fibrous drying and shaping more. Drafting is an important factor influencing the mechanical properties of the fiber, but too high drafting can cause fiber breakage during drafting, so finding a proper drafting multiple is an important parameter for spinning the fiber.

TABLE 5 influence of draft factor on CS (CA) fiber properties (citric acid concentration 5%, chitosan concentration 2.5%, NaOH concentration 6% in coagulation bath, NaOH/absolute ethanol ratio 7:3, orifice diameter 0.15mm)

6. Study on CS (CA) fiber performance of spinneret orifice aperture

Chitosan fibers were prepared according to the method of example 1, with the only difference that: the number of spinneret holes and the diameter of each spinneret hole were adjusted to 200X 0.1mm, 90X 0.15mm and 50X 0.2mm, and the other conditions were the same as in example 1.

The effect of orifice size on the CS (CA) fiber properties is shown in Table 6. As can be seen from Table 6, the CS (CA) fibers have the best mechanical properties when the orifice diameter is 0.15 mm. Too large or too small a hole diameter of the spinneret orifice adversely affects the mechanical properties of the fiber. When the spinning speed is fixed, the larger the aperture of the spinneret plate is, the slower the spinning solution is extruded from the aperture, the larger the draw ratio of the nascent fiber is, and further the draw tension applied to the nascent fiber is increased, which can effectively induce the crystallization of the fiber and promote the improvement of the orientation degree, but the too large aperture can cause the nascent fiber to be excessively drawn and the yarn breakage phenomenon; on the contrary, when the spinning speed is fixed, the smaller the pore diameter of the spinneret plate is, the faster the extrusion speed of the spinning solution is, the smaller the draw ratio of the corresponding nascent fiber is, the smaller the drawing tension applied to the nascent fiber is, so that the crystallization and orientation of the fiber are affected poorly, and the mechanical property of the fiber is reduced.

TABLE 6 influence of spinneret hole diameter on CS (CA) fiber properties (citric acid concentration 5%, chitosan concentration 2.5%, NaOH concentration 6% in coagulation bath, NaOH/absolute ethanol ratio 7:3, draft multiple 1.5 times)

7. Drying Studies on CS (CA) defibration

Chitosan fibers were prepared according to the method of example 1, with the only difference that: the drying mode is adjusted to be normal temperature air drying and oven drying, and other conditions are the same as example 1.

The effect of drying on CS (CA) defibration is shown in Table 7. Drying in air-drying and the stoving all can making the fibre produce the adhesion through normal atmospheric temperature, if high temperature fast drying, fibrous adhesion condition is more serious, nevertheless adopts freeze-dried fibre can not produce the adhesion phenomenon, as shown in figure 1, the separation condition is better between the fibre in the tow, and is smooth glossy. Because the chitosan macromolecules contain a plurality of hydrophilic groups (amino and hydroxyl) and can adsorb a large amount of water, the chitosan nascent fiber is formed into a jelly-shaped filament, the nascent fiber contains a large amount of water inside, the fiber can be adhered under the condition of quick drying, and freeze drying is a mode of slowly volatilizing water, so that the fiber with better form and performance can be obtained.

TABLE 7 Effect of drying on CS (CA) defibration

Example 3:

the CS (CA) fiber is subjected to crosslinking post-treatment according to the method and parameter conditions of example 1 to obtain the CS (CA) -CA fiber.

Comparative example 1:

chitosan fibers were prepared according to the method of example 1, with the only difference that: the citric acid was replaced by acetic acid, and the chitosan fiber prepared in example 1 was cs (aa) fiber.

The mechanical properties and structures of the chitosan fibers prepared in example 1, example 3 and comparative example 1 were analyzed, and the results were as follows:

(1) analysis of mechanical Properties

The dry and wet breaking strengths, initial moduli and elongations at break of the CS (AA), CS (CA) and CS (CA) -CA fibers are shown in FIG. 2. In fig. 2(a), the dry breaking strength of chitosan fiber (cs (CA)) spun with citric acid was increased by 21.9% compared to that of chitosan fiber (cs (aa)) spun with acetic acid, and the dry breaking strength of chitosan fiber (cs (CA) -CA) cross-linked with citric acid solution was increased by 57% compared to that of chitosan fiber (cs (aa)); the wet break strength of the Cs (CA) and Cs (CA) -CA fibers was improved by 28.0% and 55.8%, respectively, compared to the cs (aa) fibers. In fig. 2(b), the dry initial modulus was increased by 24.7% and 58.8% and the wet initial modulus was increased by 33.1% and 61.1% respectively for Cs (CA) fibers and Cs (CA) -CA fibers, respectively, as compared to cs (aa) fibers. In fig. 2(c), the dry elongation at break of the Cs (CA) fibers and the Cs (CA) -CA fibers were increased by 14.1% and 43.8%, respectively, and the wet elongation at break was increased by 25.7% and 50.4%, respectively, as compared to the cs (aa) fibers. For CS (CA) fiber, the citric acid effectively improves the mechanical property of chitosan fiber, and because the spinning solution is prepared by using citric acid solution, the citric acid is possibly partially remained in the chitosan fiber under the action of ionic crosslinking and plays a role of reinforcing the fiber. From the above data, and in conjunction with the previous studies, chitosan and citric acid resulted in a significant increase in both the breaking strength and initial modulus of chitosan fibers in the dry and wet state due to ionic crosslinking, and the elongation at break was also increased due to the plasticizing effect of citric acid. Therefore, the citric acid is an effective and environment-friendly method for enhancing the mechanical property of the chitosan fiber by using the citric acid as a solvent and a crosslinking agent.

(2) Micro-topography analysis

FIG. 3 is an SEM image of longitudinal surfaces of CS (AA) fibers (a) and CS (CA) fibers (b), and SEM images of tensile fracture surfaces of CS (AA) fibers (c), CS (CA) fibers (d) and CS (CA) -CA fibers (e). As can be seen from fig. 3(a) and (b), the surfaces of both fibers are relatively flat and smooth, and have uniform thickness and no obvious longitudinal surface ravines. As can be seen from fig. 3(c), (d) and (e), the tensile fracture surface of the chitosan fiber is more flush and shows a brittle fracture state, the tensile fracture surface of the Cs (CA) fiber is a slope shape of slip separation, the fiber shows ductile fracture, and the tensile fracture surface of the Cs (CA) -CA fiber also shows ductile fracture state. Because the latter two fibers contain citric acid inside, the fibers are broken more coarsely in the process of tensile breaking due to the plasticizing effect of the citric acid; the elongation at break of the CS (CA) and CS (CA) -CA fibers can be shown to be greater from the microscopic tensile fracture surface of the fibers.

(3) Analysis of crystallization

The X-ray diffraction (XRD) profiles of CS (AA) fibers, CS (CA) fibers, and CS (CA) -CA fibers are shown in FIG. 4. As can be seen from the figure, the cs (aa) fiber shows two main crystallization diffraction peaks at 9.6 ° and 20.6 °, while the cs (ca) fiber shows two crystallization peaks at 10.1 ° and 20.4 °, the peaks around 10 ° are hydrated lattices formed by water molecules in the chitosan, the peaks around 20 ° are regular crystals of chitosan, and the positions of the crystallization peaks of the two fibers are not substantially changed. The peaks were used to calculate the crystallinity for the CS (AA) and CS (CA) fibers, 41.0% and 62.0%, respectively, and the crystallinity for the CS (CA) fiber increased, as well as the improvements in the breaking strength and initial modulus for the CS (CA) fiber. For Cs (CA) -CA fibers, the crystallinity does not change much from that of Cs (CA) fibers, but it shows a new peak at 11.9 °, which may result in the formation of anhydrous crystals of chitosan-citrate on the surface of Cs (CA) -CA fibers due to post-treatment of Cs (CA) -CA fibers with a citric acid solution.

1. The best CS (CA) fiber is obtained by researching a wet spinning process, and the main best process conditions are as follows: the concentration of the citric acid solution is 5 percent, the concentration of the chitosan is 2.5 percent, the concentration of NaOH in the coagulating bath is 6 percent, the ratio of the NaOH solution to absolute ethyl alcohol in the coagulating bath is 7:3, the drawing multiple is 1.5, and the aperture of a spinneret orifice is 0.15 mm.

2. Compared with CS (AA) fiber, the dry breaking strength and the wet breaking strength of the CS (CA) fiber are respectively improved by 21.9 percent and 28.0 percent, the dry initial modulus and the wet initial modulus are respectively improved by 24.7 percent and 33.1 percent, and the dry breaking elongation and the wet breaking elongation are respectively improved by 14.1 percent and 25.7 percent; the dry breaking strength and the wet breaking strength of the CS (CA) -CA fiber are respectively improved by 57 percent and 55.8 percent, the dry initial modulus and the wet initial modulus are respectively improved by 58.8 percent and 61.1 percent, and the dry breaking elongation and the wet breaking elongation are respectively improved by 43.8 percent and 50.4 percent. The addition of citric acid can obviously improve the mechanical property of chitosan fiber.

3. From the microstructure, the chitosan fiber has enhanced toughness due to the addition of citric acid; the crystallinity of cs (ca) fibers is increased compared to cs (aa) fibers resulting in increased breaking strength and initial modulus.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for preparing high-performance chitosan fiber is characterized in that citric acid solution and chitosan are mixed to prepare spinning solution, and the high-performance chitosan fiber is prepared through wet spinning; the concentration of the citric acid solution is 4.5 to 5.5 percent; the mass percent of chitosan in the spinning solution is 2.1-2.7%; the coagulating bath in the wet spinning is a mixed solution of a sodium hydroxide solution and absolute ethyl alcohol; the concentration of the NaOH solution in the coagulation bath is 5-7%; the volume ratio of NaOH solution to absolute ethyl alcohol in the coagulating bath is (3-8): (2-7); the draft multiple in wet spinning is 1.1-1.5; the method also comprises a cross-linking post-treatment step, namely cross-linking the chitosan fiber obtained by the preparation and a citric acid solution.

2. The high-performance chitosan fiber prepared by the method of claim 1.

3. A textile product comprising the high performance chitosan fiber of claim 2.

4. The textile product of claim 3, wherein the textile product is: any one of yarn, blanket, woven fabric, knitted fabric, thermal insulating wadding, filling material, non-woven fabric, medical and sanitary articles or special work clothes.

5. Use of the high performance chitosan fiber of claim 2 in textile or medical hygiene.

6. The application according to claim 5, wherein the application comprises: can be used for preparing clothes with health promotion function, clothes with fluorescence effect, medical suture, medical dressing, artificial skin or drug sustained-release material.