CN116411365B

CN116411365B - Preparation method of chitosan/calcium alginate composite monofilament

Info

Publication number: CN116411365B
Application number: CN202111683780.0A
Authority: CN
Inventors: 侯秀良; 王力; 张宇; 徐荷澜; 马博谋
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2025-03-11
Anticipated expiration: 2041-12-30
Also published as: CN116411365A

Abstract

The invention discloses a method for preparing a chitosan/calcium alginate composite monofilament, and belongs to the field of bio-based novel materials. The present invention promotes the mutual complexation between chitosan and sodium alginate by adding calcium chloride solution to a chitosan solution, and then gel spinning with a sodium alginate solution, so that the molecular chains of sodium alginate and chitosan are entangled more closely, and the complexation state of the composite monofilament is well improved. At the same time, the calcium ions in the chitosan spinning solution undergo ion exchange with sodium alginate through diffusion, realize sol-gel transformation, obtain a gel with better strength, and can achieve gravity drafting of up to more than 10cm, so as to obtain a dense and uniform chitosan/calcium alginate composite monofilament. The chitosan/calcium alginate composite monofilament prepared by the present invention has excellent performance, and the strength can reach more than 0.94cN/dtex.

Description

Preparation method of chitosan/calcium alginate composite monofilament

Technical Field

The invention relates to a preparation method of chitosan/calcium alginate composite monofilaments, belonging to the field of novel bio-based materials.

Background

At present, chitosan fibers are mainly prepared by wet spinning. However, the solid content of the chitosan spinning solution is only 1.5-2.5%, so that the spinning solution is difficult to quickly solidify into filaments after being sprayed from a spinneret to a coagulating bath, and is easy to break.

In solution, the amino cation of Chitosan (CS) interacts with the negatively charged carboxyl anion of Sodium Alginate (SA), forming a polyelectrolyte complex through ionic bonding. For medical dressing, the two have synergistic effect, sodium alginate can absorb redundant wound exudates, chitosan provides antibacterial and hemostatic effects, so that the wound environment can be better improved, tongyao Zhao et al combine the advantages of biodegradable fiber materials and Polyelectrolyte (PEC) systems, and Sodium Alginate (SA) and quaternary ammonium chitosan composite fibers are prepared, so that the medical dressing has advantages in the aspects of wound dressing, medical gauze, medical absorbable suture, tissue engineering and the like. Lihong Fan et al produced alginate-chitosan fibers by mixing chemically modified water-soluble chitosan with sodium alginate and then extruding into a calcium chloride bath, the produced calcium alginate- (N, O) -carboxymethyl chitosan fibers proved to have antibacterial activity after the addition of silver. They may be the best choice for healthcare related materials.

However, since the opposite charges in the solution are attracted by static electricity, the blended solution is agglomerated, so that it is difficult to prepare a uniform mixed solution of chitosan and sodium alginate.

To solve these problems, many researchers have made efforts, for example DaikiKomoto et al (Costalat M,Alcouffe P,David L,et al.Macro-hydrogels versus nanoparticles by the controlled assembly of polysaccharides[J].Carbohydrate Polymers.2015,134:541-546.) to prepare oligomeric chitosan, which, due to its low molecular weight, can be dissolved in an alkaline aqueous solution and then mixed with sodium alginate solution without immediate agglomeration, but by such modification, its mechanical properties are very weak, WATTHANAPHANIT et al (A.Watthanaphanit P S T F.Novel chitosan-spotted alginate fibers from wet-spinning of alginate solutions containing emulsified chitosan–citrate complex and their characterization[J].Biomacromolecules,10(2009),pp.320-327.2009,10(1).) by emulsifying unmodified chitosan and sodium alginate, and then extruding into a calcium chloride bath, to produce a novel spotted alginate chitosan fiber. However, chitosan is not uniformly distributed along the length of these fibers and is irregular.

Disclosure of Invention

[ Technical problem ]

The amino cations of Chitosan (CS) and the carboxyl anions of Sodium Alginate (SA) with negative charges can be subjected to ionic bond action, so that the blended solution can be agglomerated into blocks, spinning is difficult, and the monofilament has poor mechanical properties.

Technical scheme

In order to solve the problems, the invention promotes the mutual complexation between chitosan and sodium alginate by adding the calcium chloride solution into the chitosan solution and then carrying out gel spinning with the sodium alginate solution, so that the molecular chains of the sodium alginate and the chitosan are more tightly entangled, and the complexation state of the composite monofilament is well improved. Meanwhile, calcium ions in the chitosan spinning solution are subjected to ion exchange with sodium alginate through diffusion, so that sol-gel conversion is realized, gel with better strength is obtained, and gravity drafting of more than 10cm can be realized, so that the chitosan/calcium alginate composite monofilament with compact and uniform structure is obtained.

The first object of the present invention is to provide a method for preparing chitosan/calcium alginate composite monofilament, comprising the steps of:

(1) Uniformly mixing a chitosan solution and a calcium chloride solution to obtain a chitosan/calcium chloride mixed solution;

(2) Respectively placing the chitosan/calcium chloride mixed solution and the sodium alginate solution into two spinning solution boxes, and performing gel spinning through a spinning nozzle with a core-shell structure, wherein the chitosan/calcium chloride mixed solution is arranged at a shell part, the sodium alginate solution is arranged at a core part, and the gravity drafting is performed in a gravity drafting area of more than 10 cm;

(3) And (3) washing, drawing and drying the composite gel drawn by gravity to obtain the chitosan/calcium alginate composite monofilament.

In one embodiment of the invention, the concentration of the chitosan solution in step (1) is 0.5-2% (mass percent).

In one implementation of the spinning of the present invention, the preparation method of the chitosan solution in the step (1) comprises:

Chitosan was dissolved in 2% by volume aqueous acetic acid solution, wherein the dissolution was stirred for 24h at 40 ℃.

In one embodiment of the present invention, the calcium chloride solution in step (1) is an aqueous solution of calcium chloride, and the mass concentration is 5-7%, and more preferably 6%.

In one embodiment of the invention, the calcium chloride solution in step (1) is used in an amount of 4-13% by mass of the chitosan solution.

In one embodiment of the invention, the air bubbles are removed by ultrasonic treatment at a vibration frequency of 20KHz for 15min after the uniform mixing in step (1).

In the implementation spinning of the invention, the device adopted in the gel spinning in the step (2) comprises a chitosan/calcium chloride mixed solution spinning box, a sodium alginate solution spinning box and a spinning head of a core-shell structure, wherein the spinning head of the core-shell structure comprises two coaxial tubular channels, and the nozzle is of the core-shell structure with the outer diameter of 1.2mm and the inner diameter of 0.7 mm.

In one embodiment of the invention, in step (2), a booster is used to place the chitosan/calcium chloride mixed solution and sodium alginate solution into two spinning solution boxes at a speed of 0.5 mL/min.

In one embodiment of the invention, the gel spinning in the step (2) is that two spinning solutions are mutually permeated under the interaction of positive and negative ions, the interface of a spinneret is replaced, and the gel is formed by the coupling effect of gel formed by the ion exchange of sodium alginate under the diffusion effect of calcium ions, and then the gel with uniform components (not a core-shell structure) is formed by the composite gel under the gravity drafting.

In one embodiment of the invention, the water washing in step (3) is performed by washing the composite gel in a water bath.

In one embodiment of the present invention, the drawing in step (3) is drawing the gel fiber after washing with water by a factor of 1.1 to 1.3.

In one embodiment of the invention, the drying in step (3) is performed in air.

The second purpose of the invention is to prepare the chitosan/calcium alginate composite monofilament by the method.

The third object of the invention is the application of the chitosan/calcium alginate composite monofilament in the fields of wound dressing, medical gauze, medical absorbable suture and tissue engineering.

[ Advantageous effects ]

(1) The method solves the problem of inverse charge agglomeration of the mixed liquid of chitosan and sodium alginate, and forms gel with the existence of calcium ions through the synergistic effect of ionic bonds formed between amino positive charges of polyelectrolyte chitosan and carboxyl negative charges of sodium alginate and gel formed by sodium alginate, so that the spinning solution can form gel with certain strength after being sprayed out of a spinning hole, and can be subjected to gravity drafting, and the gravity drafting area is as high as more than 10 cm.

(2) The invention gradually forms chitosan and calcium alginate composite gel with better strength through the synergistic effect of positive and negative ion bonds and ion exchange, and then facilitates the molecular chain to be aligned along the axial direction of the fiber through gravity drafting, meanwhile, in the drafting process, chitosan molecules with amino positive charges and alginic acid molecules with carboxyl negative charges form ion crosslinking, and calcium ions gradually undergo ion exchange with sodium alginate through diffusion to form calcium alginate. These all contribute to the formation of high strength chitosan/calcium alginate composite monofilaments.

(3) The gel subjected to gravity drawing is put into water for washing, chitosan is further solidified, then dried, and drawing (drawing multiple is 1.1-1.3 times) is carried out in the drying process, so that the chitosan/calcium alginate composite monofilament is obtained.

(4) The chitosan/calcium alginate composite monofilament prepared by the method has excellent performance, the strength can reach more than 0.94cN/dtex, and the elongation at break is more than 3.2%.

Drawings

Fig. 1 is a drawing of a spinning apparatus.

FIG. 2 is an SEM image of the fracture surface and longitudinal surface of a composite monofilament, wherein a and c are the CS/SA composite monofilament of comparative example 1, a is the fracture surface, c is the longitudinal surface, b and d are the CS/CA composite monofilament of example 1, b is the fracture surface, and d is the longitudinal surface.

FIG. 3 is an EDS N element distribution diagram of a composite monofilament, wherein a is the CS/SA composite monofilament of comparative example 1, and b is the CS/CA composite monofilament of example 1.

FIG. 4 is an FT-IR spectrum of CS fibers, CS/SA composite filaments, CS/CA composite filaments, and SA fibers.

FIG. 5 is an X-ray diffraction pattern of the CS/SA composite monofilament of comparative example 1 and the CS/CA composite monofilament of example 1.

FIG. 6 shows the results of the thermal stability test of the CS/SA composite monofilament of comparative example 1 and the CS/CA composite monofilament of example 1, wherein a is a TG curve and b is a DTG curve.

Fig. 7 shows the tensile rheological properties of the spinning solution, wherein a is the tensile rheological properties of the chitosan spinning solution with different calcium chloride solution dosage, b is the tensile rheological properties of the sodium alginate and the chitosan/sodium alginate spinning solution, c is the chitosan/sodium alginate complexation added with calcium ions, and d is the chitosan/sodium alginate complexation state without calcium ions.

Fig. 8 shows the state of the composite filaments obtained by using different amounts of calcium chloride solution in water, wherein a is 0% -dry, b is 0% -swell, c is 4% -dry, d is 4% -swell, e is 7% -dry, f is 7% -swell, g is 10% -dry, h is 10% -swell, i is 13% -dry, and j is 13% -swell.

Fig. 9 shows the complexation state of chitosan solutions with different concentrations and sodium alginate solutions with different concentrations.

Detailed Description

The following description of the preferred embodiments of the present invention is provided for better illustration of the invention, and should not be construed as limiting the invention.

The testing method comprises the following steps:

1. Characterization of morphology the morphology of the cross-section and longitudinal surface of the composite filaments brittle snap-through with liquid nitrogen was observed using a HITACHI SU1510 electron microscope (Japanese Ri Li Co.). And placing the two composite monofilaments subjected to constant temperature and humidity balance on conductive adhesive, spraying metal, and observing under an electron microscope with an accelerating voltage of 5 kV.

2. N element distribution and content test, namely, the atomic composition of the section can be known by taking the structure of the section of the wire through an EDX (Zeiss, germany) scanning electron microscope, and the content and distribution of chitosan and alginic acid in the section of the composite monofilament can be known because the calcium atom is the characteristic of calcium alginate and the nitrogen atom is the characteristic of chitosan. And placing the two filament samples subjected to constant temperature and humidity balance on conductive adhesive, spraying metal, and performing element analysis on the composite filaments under the acceleration voltage of 15 kV.

3. Fourier infrared transformation spectrum the composite filaments were placed in a vacuum oven, dried at 50 ℃ for 24 hours, and then infrared absorption spectra in the range 4000 to 450cm ^-1 were recorded at a resolution of 4cm ^-1.

4. Crystallization Structure test the crystallization structure of the filaments was analyzed using a D8 Advance X (Broker AXS, germany) ray diffractometer. The sample was scanned at a rate of 4/min, in the range of 10 ° -60 °, with a step size of 0.02 °.

5. Tensile mechanical properties test the mechanical properties of the filaments were tested by a single fiber strength tester (YG 004D, second textile Instrument Co., ltd.). The gauge length was set to 20mm, the speed of the crosshead was set to 20mm/min, the breaking strength (cN/dtex) and elongation at break (%) of the sample filaments were tested separately, and at least 50 fibers were tested repeatedly for each sample and the average value was calculated.

6. Thermal stability test the thermal stability of the filaments was analyzed by a thermal analysis system (TA-Q500 American TA instruments Co.). The sample was heated from 50 ℃ to 800 ℃ at a heating rate of 20 ℃ per minute in nitrogen at a flow rate of 50mL/min, with a sample mass range of 5mg.

7. And (3) testing water swelling performance, namely weighing the composite monofilaments balanced by constant temperature and constant humidity, respectively soaking the composite monofilaments subjected to constant temperature and constant humidity in a certain amount of distilled water at room temperature for different times (5 min, 10min, 15min, 20min, 25min, 30mins, 35min, 40min, 45min, 50min, 55min and 60 min) to fully swell the composite monofilaments, taking out the swelled filaments from the distilled water, and drying the surfaces of the filaments by using filter paper to weigh the mass. The swelling performance is represented by a swelling ratio R, and the calculation formula of R is as follows (1):

Where R is the swelling ratio, W _d is the mass of the composite filaments after swelling, W ₀ is the mass of the dried composite filaments, and each sample is tested at least three times repeatedly and the average value is calculated.

The chitosan (viscosity 1250mpa.s, degree of deacetylation 93%) used in the examples was purchased from source biologicals, inc. of the Fangfang sea, and sodium alginate (viscosity 740mpa.s, purity >90 wt%), anhydrous calcium chloride, acetic acid (all analytically pure) were purchased from chemical agents, inc. of the national pharmaceutical groups.

The device for gel spinning in the embodiment comprises a chitosan/calcium chloride mixed solution spinning box, a sodium alginate solution spinning box, a spinning nozzle of a core-shell structure and a water washing pool, wherein the chitosan/calcium chloride mixed solution spinning box is connected with a spinning nozzle shell part, the sodium alginate solution spinning box is connected with the spinning nozzle core part, the spinning nozzle of the core-shell structure comprises two coaxial tubular channels, the nozzle is of the core-shell structure with the outer diameter of 1.2mm and the inner diameter of 0.7mm, and the device is specifically shown in figure 1.

Example 1

A method for preparing chitosan/calcium alginate composite monofilaments, comprising the following steps:

(1) Dissolving chitosan in 2% (v/v) acetic acid aqueous solution, mechanically stirring in 40 ℃ water bath for 24 hours to obtain a chitosan solution with the mass concentration of 2%, dissolving calcium chloride in water to obtain a calcium chloride aqueous solution with the mass fraction of 6%, and uniformly mixing the chitosan solution and the calcium chloride solution to obtain a chitosan/calcium chloride mixed solution, wherein the consumption of the calcium chloride solution is 7% of the mass of the chitosan solution;

(2) Dissolving sodium alginate in water to obtain sodium alginate aqueous solution with the mass concentration of 1.5%;

(3) Placing the mixed solution of chitosan and calcium chloride in a spinning solution box connected with a spinneret shell part at a speed of 0.5mL/min by adopting a booster, placing sodium alginate solution in the spinning solution box connected with a spinneret core part, performing gel spinning through a spinneret with a core-shell structure, mutually penetrating the two spinning solutions under the interaction of positive ions and negative ions, replacing at the interface of the spinneret, and simultaneously forming a gel coupling effect by virtue of ion exchange between the two spinning solutions and sodium alginate under the diffusion effect of calcium ions to form a composite gel, and forming a gel with uniformly mixed components (not with the core-shell structure) under the gravity draft of up to 10 cm;

(3) And (3) putting the composite gel subjected to gravity drawing into a water bath for water washing, drawing the gel fiber subjected to water washing (drawing multiple is 1.2), and finally drying in air to obtain the chitosan/calcium alginate composite monofilament.

Comparative example 1

The calcium chloride solution in step (1) of example 1 was omitted, and the other was the same as in example 1 to obtain a chitosan/sodium alginate (CS/SA) composite monofilament.

The composite monofilaments obtained in example 1 and comparative example 1 were subjected to performance testing, and the test results were as follows:

FIG. 2 is an SEM image of the fracture surface and longitudinal surface of a composite monofilament, wherein a and c are the CS/SA composite monofilament of comparative example 1, a is the fracture surface, c is the longitudinal surface, b and d are the CS/CA composite monofilament of example 1, b is the fracture surface, and d is the longitudinal surface. As can be seen from fig. 2, the chitosan added with calcium ions has good compatibility with sodium alginate, and compared with the CS/SA composite monofilament, the CS/CA composite monofilament has smooth cross section, fewer grooves, uniform structure and no obvious change of the longitudinal surface.

FIG. 3 is an EDS N element distribution diagram of a composite monofilament, wherein a is the CS/SA composite monofilament of comparative example 1, and b is the CS/CA composite monofilament of example 1. Table 1 shows the content of each element in the cross section of the composite filament. As can be seen from FIG. 3 and Table 1, the CS/CA composite monofilament of example 1, to which calcium ions are added, has a uniform distribution of N element in the cross section and a content of 46.49%, while the CS/SA composite monofilament of comparative example 1, to which no calcium ions are added, has a N element of 17.57%, because in the chitosan solution, due to the addition of calcium ions, the effect of electrostatic complexation with sodium alginate is increased, so that the solidification and crosslinking of the chitosan solution and the sodium alginate solution are simultaneously carried out, and the calcium ions and the sodium alginate are also non-covalently crosslinked, so that the content of chitosan in the composite monofilament is increased, and the content of N element is increased. According to calculation, before complexing, the sodium ion content in the spinning fluid is twice that of calcium ion, during complexing, calcium ions replace a part of sodium, chitosan also crosslinks a part of sodium, and after washing a part of chitosan, a little sodium element is remained in CS/CA composite monofilaments due to some limitations of a spinning device.

TABLE 1 content of elements of the composite monofilament section

FIG. 4 is an FT-IR spectrum of CS fibers, CS/SA composite filaments, CS/CA composite filaments, and SA fibers. As can be seen from FIG. 4, CS shows two absorption peaks at 1649cm ^-1 and 1591cm ^-1, a C=O stretching vibration peak of the amide I band and an N-H plane deformation peak of the amide II band, respectively, SA shows asymmetric and symmetric stretching vibration absorption peaks of-COO-at 1673cm ^-1 and 1475cm ^-1, respectively, and CS shows the possibility that its disappearance in CS/SA and CS/CA at 1649cm ^-1 and 1591cm ^-1 is due to the protonation of-NH ₂ to-NH ₃ ⁺. Characteristic peaks at 1673cm ^-1 and 1475cm ^-1 in SA are shifted to 1591cm ^-1 and 1414cm ^-1 respectively, which indicate that-COO-is ionically crosslinked with-NH ₃ ⁺ and Ca ²⁺, and the peak of OH stretching vibration at 3500-3200cm ^-1 becomes narrower in CS/CA, which indicates that hydrogen bonds between CS/CA are weakened and the ability to absorb water molecules is reduced. Furthermore, a new peak appears at 2833cm ^-1 after CS/CA formation, possibly with partial-COO-protonation. The infrared results also indicate electrostatic interactions between CS and SA, calcium ions.

FIG. 5 is an X-ray diffraction pattern of the CS/SA composite monofilament of comparative example 1 and the CS/CA composite monofilament of example 1. It can be seen from fig. 5 that the diffraction peaks of the CS/SA composite monofilament and the CS/CA composite monofilament are similar in shape and size, and that the CS/SA composite monofilament and the CS/CA composite monofilament show two main peaks at 14 ° and 20 °. The crystallinity of CS/CA is improved and the mechanical properties are improved.

FIG. 6 shows the results of the thermal stability test of the CS/SA composite monofilament of comparative example 1 and the CS/CA composite monofilament of example 1, wherein a is a TG curve and b is a DTG curve. As can be seen from FIG. 6, the CS/CA composite filaments with added calcium ions have a higher initial thermal decomposition temperature than the CS/SA composite filaments. The corresponding temperature of the CS/CA composite filaments at the highest thermal decomposition rate was increased by 10 ℃. These results all indicate that the addition of calcium ions can improve the thermal stability of the composite filaments.

Example 2

The amount of the calcium chloride solution in the step (1) of the example 1 was adjusted to 4, 10 and 13% of the mass of the chitosan solution, and the other components were kept the same as the example 1 to obtain a composite monofilament.

The composite monofilaments obtained in examples 1 and 2 and comparative example 1 were subjected to performance testing, and the test results were as follows:

Fig. 7 shows the tensile rheological properties of the spinning solution, wherein a is the tensile rheological properties of the chitosan spinning solution with different calcium chloride solution dosage, b is the tensile rheological properties of the sodium alginate and the chitosan/sodium alginate spinning solution, c is the chitosan/sodium alginate complexation added with calcium ions, and d is the chitosan/sodium alginate complexation state without calcium ions. It can be seen from fig. 7a that the spinning solutions blended with chitosan in different amounts of calcium chloride solution have an increasing and then decreasing break time from the beginning of drawing into fluid filaments to breaking. It is apparent that it takes longer to draw the blended yarn solution into fluid yarn to the same diameter than if a proper amount of calcium chloride solution was added to the pure chitosan spinning solution. The extension of the break time indicates that the ductility of the spinning solution is improved, the molecular chains of the fluid filaments are better aligned, and thus the mechanical properties of the composite filaments can be improved. From the graph 7 b, it can be seen that after the 2% chitosan solution and the 1.5% sodium alginate solution are mixed and agglomerated, the mixed tensile rheology is better improved compared with the tensile rheology of a single solution. From fig. 7 c and d, it can be seen that the calcium chloride-added chitosan sodium alginate blend state and the calcium ion-free chitosan sodium alginate blend state. The result shows that after the calcium chloride is added, the chitosan and the sodium alginate are better combined together, and the calcium ions in the calcium chloride solution and the sodium ions of the sodium alginate are possibly subjected to ion exchange to form a network structure, so that electrostatic complexation is more likely to occur with the chitosan, and meanwhile, the calcium ions replace the sodium ions, so that calcium alginate is generated.

Table 2 shows the tensile mechanical properties of chitosan spinning solutions with different amounts of calcium chloride solution. As can be seen from Table 2, when the amount of the calcium chloride solution was 7% of the mass of the chitosan solution, the breaking strength of the composite monofilament reached the maximum of 1.14cN/dtex, which was improved by 55.4% as compared with that before the calcium chloride solution was added. With the increase of the consumption of the calcium chloride solution, the elongation at break is continuously increased, and the breaking strength of the composite monofilament is firstly increased and then decreased. When the dosage of the calcium chloride solution is smaller, the quantity of calcium ions combined by chitosan macromolecules is less, and the crosslinking points in the composite monofilaments are fewer, so that the intermolecular acting force is weaker, and the strength of the filaments is smaller. With the increase of the dosage of the calcium chloride solution, the quantity of calcium ions combined by chitosan macromolecules is increased, crosslinking points in silk are increased, and the strength is increased. However, when the dosage of the calcium chloride solution is too high, the diffusion rate of calcium ions is high, a compact cortex layer is formed by combining the calcium ions with chitosan macromolecules on the surface of the silk, so that the diffusion of the calcium ions into the silk and the diffusion of sodium ions in the silk to the outer layer are prevented, the cross-linking points in the silk are reduced, and the strength is reduced.

TABLE 2 tensile mechanical Properties of Chitosan spinning solutions with different calcium chloride solutions

CaCl ₂ dosage (%)	Breaking strength/(cN/dtex)	Elongation at break (%)
			0	0.747	2.452
4	0.94	3.238
			7	1.142	3.585
10	1.01	3.856
			13	0.893	4.229

Fig. 8 shows the state of the composite filaments obtained by using different amounts of calcium chloride solution in water, wherein a is 0% -dry, b is 0% -swell, c is 4% -dry, d is 4% -swell, e is 7% -dry, f is 7% -swell, g is 10% -dry, h is 10% -swell, i is 13% -dry, and j is 13% -swell. As can be seen from FIG. 8, the composite filaments without calcium ions are partially disintegrated during swelling, and after swelling, the strength is lower than other composite filaments, but the swelling degree is maximized. Experimental calculation shows that the calcium ion dosage has little influence on the swelling degree of the composite monofilament (the swelling degree tends to be gradually weakened), but when the calcium ion dosage is 7% from the outside of the swelled composite monofilament, the swelled composite monofilament is transparent and uniform. Swelling experiments also demonstrated an increase in the number of crosslinking sites, with swelling being progressively inhibited.

Table 3 shows the swelling ratios of the obtained composite filaments after various amounts of calcium chloride solution were immersed in water for various times. As can be seen from Table 3, the swelling ratio of all the composite filaments increased significantly from the first 5 minutes to 20 minutes, and remained substantially constant after 20 minutes. These results indicate that all composite filaments take about 20 minutes to reach swelling equilibrium. The swelling ratio is reduced along with the increase of the calcium ion dosage, the swelling ratio of the composite monofilament without adding the calcium ion is highest in the same swelling time, the mixed structure formed by the chitosan and the sodium alginate is beneficial to the penetration of moisture into the fiber, and the amino groups in the chitosan are consumed due to the crosslinking reaction along with the increase of the calcium ion concentration, so that the capability of crosslinking the chitosan and the water molecules to form hydrogen bonds is reduced, and the equilibrium swelling degree is reduced.

TABLE 3 swelling ratio of the resulting composite monofilaments with different amounts of calcium chloride solution after soaking in water for various times

Example 3

The concentrations of chitosan in example 1 were adjusted to 0.5, 1.0, 1.5, 2.0 and 2.5%, and the concentrations of sodium alginate were adjusted to 0.5, 1.0, 1.5, 2.0 and 2.5%, respectively, and the other conditions were kept the same as in example 1, to obtain a spinning solution.

And performing performance test on the obtained spinning solution, wherein the test result is as follows:

Fig. 9 shows the complexation state of chitosan solutions with different concentrations and sodium alginate solutions with different concentrations. As can be seen from FIG. 9, the complexing is a rapid process, and in the experimental range (0-2% of the solubility of the spinning solution), the concentration of the CS solution should not be less than the solubility of the SA solution (black area), the polyelectrolyte diffusion effect of positive and negative charges is good, and the spinnability can be ensured. Black dots indicate good fluid complexation, while polygons indicate poor fluid complexation (beads of water form continuously along the spinning fluid, voids on the fluid surface, uneven structure, and susceptibility to breakage). It may be that the outer higher molecular weight cationic polyelectrolytes are able to form more viscous complexes to stabilize the interface, so that their attraction is better, facilitating complexation. Thus, 2% CS and 1.5% SA were selected to prepare the composite monofilament.

Comparative example 2

(1) Dissolving chitosan in 2% (v/v) acetic acid aqueous solution, and mechanically stirring in a water bath at 40 ℃ for 24 hours to obtain a chitosan solution with the mass concentration of 2%;

(3) Placing chitosan solution into a spinning solution box connected with a spinneret shell part at a speed of 0.5mL/min by adopting a booster, placing sodium alginate solution into a spinning solution box connected with a spinneret core part, performing gel spinning through a spinneret with a core-shell structure, and forming gel with components uniformly mixed (not with the core-shell structure) under the gravity draft of up to 10 cm;

(4) And directly feeding the chitosan/sodium alginate fiber subjected to gravity drawing into a 6% calcium chloride solution to be coagulated, so as to obtain the chitosan/calcium alginate composite monofilament.

The obtained chitosan/calcium alginate composite monofilament is tested, and the test result is as follows:

the breaking strength of the chitosan/calcium alginate composite monofilament is only 0.20cN/dtex, the breaking elongation is 10%, and the chitosan/calcium alginate composite monofilament has almost no swelling. This is due to the rapid solidification of chitosan/sodium alginate in calcium chloride solution and low degree of orientation of the fibrous macromolecules.

While the invention has been described with reference to the preferred embodiments, it is not limited thereto, and 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 chitosan/calcium alginate composite monofilaments, which is characterized by comprising the following steps:

(1) Uniformly mixing a chitosan solution and a calcium chloride solution to obtain a chitosan/calcium chloride mixed solution, wherein the mass concentration of the chitosan solution is 2%, the mass concentration of the calcium chloride solution is 6%, and the dosage of the calcium chloride solution is 7% of the mass of the chitosan solution;

(2) Respectively placing the chitosan/calcium chloride mixed solution and the sodium alginate solution into two spinning solution boxes, and carrying out gel spinning through a spinning nozzle with a core-shell structure, wherein the chitosan/calcium chloride mixed solution is arranged on a shell part, and the sodium alginate solution is arranged on a core part and is subjected to gravity drafting, wherein the gravity drafting area is more than 10cm, and the sodium alginate solution is sodium alginate aqueous solution with the mass concentration of 1.5%;

2. The method according to claim 1, wherein the device used in the gel spinning in the step (2) comprises a chitosan/calcium chloride mixed solution spinning box, a sodium alginate solution spinning box and a spinneret with a core-shell structure, wherein the spinneret with the core-shell structure comprises two coaxial tubular channels, and the nozzle is with an outer diameter of 1.2mm and an inner diameter of 0.7 mm.

3. The method according to claim 1, wherein the gel spinning in the step (2) is characterized in that two spinning solutions are mutually permeated under the interaction of positive and negative ions, the interface of a spinneret is replaced, and the gel is formed by the coupling effect of the gel formed by the ion exchange of the spinning solutions and sodium alginate under the diffusion effect of calcium ions, and then the gel is formed by the composite gel under the gravity drafting, wherein the components are uniformly mixed.

4. The method according to claim 1, wherein the drawing in the step (3) is drawing the gel fiber after washing with water by a factor of 1.1 to 1.3.

5. The method according to claim 1, wherein the chitosan solution of step (1) is prepared by dissolving chitosan in 2% by volume of aqueous acetic acid.

6. The chitosan/calcium alginate composite monofilament produced by the method of any one of claims 1 to 5.

7. Use of the chitosan/calcium alginate composite monofilament of claim 6 in the fields of wound dressing, medical gauze, medical absorbable suture and tissue engineering.