Polyurethane / chitosan composite porous fiber and its spinning method

Abstract

This invention provides a polyurethane / chitosan composite porous fiber and its spinning method. A polyurethane solution and a chitosan solution of specific concentrations are prepared, and a coaxial wet spinning technique is employed. The outer axis is the polyurethane solution, and the inner axis is the chitosan solution. The coagulation bath is a mixture of water, ethanol, and alkali solution. After coagulation and molding, nascent fibers are obtained, and finally, vacuum freeze-drying is performed to obtain the polyurethane / chitosan composite porous fiber. This invention adjusts the spinnability and formability of the fiber by regulating the concentration of the spinning solution, and achieves control over the molding process of the composite spinning solution through the synergistic effect of the components in the coagulation bath. This promotes the molding of the composite fiber without destroying its coaxial structure, achieving successful preparation of nascent fibers with a coaxial structure. The spinning method of this invention is simple, low-cost, and can be continuously produced, making it suitable for industrial mass production. The prepared composite porous fiber possesses high elasticity, high strength, and good warmth retention, and has significant market application value.

Description

Technical Field

[0001] This invention relates to the field of textile technology, and in particular to a polyurethane / chitosan composite porous fiber and its spinning method. Background Technology

[0002] Polyurethane (PU) is a widely used polymer material characterized by high strength, good abrasion resistance, tear resistance, flexural strength, oil resistance, and excellent blood compatibility. PU resin can be used to prepare foam plastics, elastomer materials, paints, adhesives, elastic fibers, and synthetic leather, etc. Its structure and properties can be customized by controlling the combination of hard and soft segments, playing an important role in modern industry. However, when polyurethane materials are applied to fabrics or clothing, they suffer from problems such as poor moisture absorption, breathability, and thermal insulation, resulting in poor comfort and affecting its market development prospects.

[0003] Natural polysaccharide materials possess good biodegradability and antibacterial properties, making them one of the major chemical raw materials for the future. Chitosan, obtained from the N-deacetylation reaction of chitin under thermal alkaline conditions, exhibits excellent biocompatibility, biodegradability, adhesion, and low toxicity. As the world's most abundant alkaline natural polysaccharide, chitosan shows promising application prospects. Chitosan aerogel, as a unique lightweight material, possesses characteristics such as low density, high porosity, and large specific surface area, showing potential application value in fields such as thermal insulation materials, adsorbent materials, carrier materials, and biomedical materials. However, chitosan aerogel suffers from drawbacks such as weak mechanical properties, poor tensile strength, and easy degradation, which significantly hinders the application and development of chitosan aerogel materials.

[0004] In the prior art, the production of composite polymer materials using chemical and / or physical methods has become a research hotspot. For example, an invention patent (application number CN 201910088955.X) discloses a flexible conductive fiber with a core-sheath structure and its preparation method. The method uses an aqueous solution of graphene oxide as the core spinning solution, mixes aramid nanofibers or polyimide precursors with a solvent to obtain a sheath spinning solution, and then uses a coaxial wet spinning process to prepare a coaxial fiber with a core-sheath structure containing aramid or polyimide encapsulating graphene oxide. This fiber is flexible while also possessing excellent conductivity and mechanical properties, achieving a combination of core-sheath material properties.

[0005] However, due to the completely different properties and molding conditions of polyurethane and chitosan, as well as polyurethane fiber and chitosan aerogel, achieving the complementary advantages of natural macromolecular chitosan and high molecular polymer polyurethane remains a challenge.

[0006] In view of this, it is necessary to design an improved polyurethane / chitosan composite porous fiber and its spinning method to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a polyurethane / chitosan composite porous fiber and its spinning method. A polyurethane solution and a chitosan solution are spun using a coaxial wet spinning technique, and then shaped using a specific coagulation bath to obtain nascent fibers with a coaxial layered structure. The nascent fibers are then freeze-dried under vacuum to obtain the polyurethane / chitosan composite porous fiber. This composite porous fiber possesses high elasticity, high strength, and good warmth retention, and has significant market application value.

[0008] To achieve the above-mentioned objective, this invention provides a spinning method for polyurethane / chitosan composite porous fibers, comprising the following steps:

[0009] S1. Polyurethane masterbatch is dissolved in an organic solvent and mechanically stirred to obtain a polyurethane solution with a concentration of 10 wt.% to 30 wt.%. Chitosan is dissolved in dilute acid to obtain a chitosan solution with a concentration of 0.5 wt.% to 3.0 wt.%.

[0010] S2. Wet spinning is performed using a coaxial injection device. The outer shaft of the spinning head contains the polyurethane solution, and the inner shaft contains the chitosan solution. The coagulation bath is a mixed solution of water, ethanol and alkali. The spinning solution is formed in the coagulation bath to obtain nascent fibers, which are then further immersed and cleaned in the aqueous solution.

[0011] S3. The nascent fibers cleaned in step S2 are subjected to vacuum freeze-drying to obtain the polyurethane / chitosan composite porous fibers.

[0012] As a further improvement of the present invention, in step S2, the volume ratio of water, ethanol and alkaline solution in the coagulation bath is 5:(2.5-3.5):(1.5-2.5).

[0013] As a further improvement of the present invention, in step S2, in the coaxial injection device, the ratio of the width of the outer shaft containing the polyurethane solution to the radius of the inner shaft containing the chitosan solution is (0.1~0.3):1.

[0014] As a further improvement of the present invention, the volume ratio of water, ethanol and alkaline solution in the coagulation bath is 5:3:2.

[0015] As a further improvement of the present invention, the outer shaft inner diameter of the spinning head is 200μm to 1mm, and the spinning speed of the spinning head is 10 to 30m / min, so as to ensure the stable preparation of the polyurethane / chitosan composite porous fiber.

[0016] As a further improvement of the present invention, in step S3, the vacuum freeze-drying is to freeze the nascent fiber at -20°C to -10°C for 8 to 12 hours, and then freeze-dry it at -80°C to -50°C for 24 to 48 hours.

[0017] As a further improvement of the present invention, in step S1, the organic solvent includes one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, or dimethyl sulfoxide; the pH value of the dilute acid is 5-6, and the dilute acid includes one of dilute hydrochloric acid and acetic acid.

[0018] As a further improvement of the present invention, in step S1, when preparing the polyurethane solution, the dissolution temperature is 50-100°C, and the mechanical stirring speed is 50-200 r / min.

[0019] A polyurethane / chitosan composite porous fiber prepared by any one of the spinning methods described above, wherein the inner layer of the polyurethane / chitosan composite porous fiber is a chitosan porous aerogel structure, the chitosan porous aerogel structure is wrapped by an outer layer, and the outer layer is an elastic microporous polyurethane material.

[0020] As a further improvement of the present invention, the diameter of the polyurethane / chitosan composite porous fiber is 150 μm to 1 mm; the elongation of the polyurethane / chitosan composite porous fiber is 225% to 255%, the resilience is 92% to 100%, and the tensile strength is 2.4 to 4.0 cN / dtex.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention discloses a polyurethane / chitosan composite porous fiber and its spinning method. The method involves spinning a polyurethane solution and a chitosan solution using coaxial wet spinning technology. The spinnability of the fiber is adjusted by regulating the concentration of the spinning solution, and a specific coagulation bath is used to coagulate the spinning solution, promoting the formation of the composite spinning solution without destroying its coaxial structure. This achieves the successful preparation of nascent fibers with a coaxial layered structure. The nascent fibers are then freeze-dried under vacuum to obtain the polyurethane / chitosan composite porous fiber. The spinning method of this invention is simple, low-cost, and allows for continuous production, making it suitable for industrial-scale mass production. Furthermore, the prepared polyurethane / chitosan composite porous fiber possesses high elasticity, high strength, and good warmth retention, exhibiting significant market application value.

[0023] 2. In this invention, water, ethanol, and alkaline solution are selected as the coagulation bath for the coaxial spinning solution. During the coagulation process, because the concentration of the outer polyurethane spinning solution is much higher than that of the inner chitosan spinning solution, and the polyurethane spinning solution has a high affinity for water, the polyurethane first undergoes rapid solvent exchange with the water in the coagulation bath, causing the polyurethane to swell. As the number of water molecules in the polyurethane increases, a concentration difference is formed between the polyurethane and the inner chitosan solution, and then the coagulation bath undergoes phase replacement with the chitosan. This is beneficial to the formation of a uniform microporous structure in the chitosan. At the same time, due to the hydrophobicity of polyurethane, solvent exchange channels are formed in the outer polyurethane layer, which further facilitates the coagulation bath to enter the interior and exchange solvent with the chitosan. The presence of alkali promotes the phase exchange rate between chitosan and the coagulation bath, increasing the molding speed of chitosan. Furthermore, ethanol can reduce the exchange rate between solvent and water in the later stage of polyurethane coagulation, further ensuring the preferential molding of internal chitosan and avoiding instability of the fiber structure caused by the early molding of the outer polyurethane layer, which leads to internal collapse of the fiber during freeze-drying. In addition, when the proportion of undesirable solvents for polyurethane in the coagulation bath is relatively reduced in the later stage of molding, it is conducive to the formation of a uniform and dense polyurethane structure. Finally, nascent fibers with a coaxial layered structure were successfully obtained in the coagulation bath.

[0024] 3. Before freeze-drying, the nascent fibers are soaked and cleaned in an aqueous solution. This removes excess solvent from the fibers and increases the liquid content, allowing microporous channels to form in the outer polyurethane layer during freeze-drying. This facilitates the release of internal vapors and simultaneously forms a porous chitosan aerogel structure inside, improving the warmth and comfort of the fiber material. Attached Figure Description

[0025] Figure 1 This is a micro-electron microscopy image of the polyurethane / chitosan composite porous fiber prepared in Example 1.

[0026] Figure 2 This is an electron microscope image of the outer polyurethane layer of the polyurethane / chitosan composite porous fiber from Example 1 after it has been cut open.

[0027] Figure 3 This is a micro-electron microscopy image of the polyurethane / chitosan composite porous fiber prepared in Example 2.

[0028] Figure 4 Electron micrograph of the non-coaxial polyurethane fiber prepared for Comparative Example 1.

[0029] Figure 5 Electron micrograph of the hollow polyurethane fiber prepared for Comparative Example 2.

[0030] Figure 6 The image shows the microscopic electron microscope image of the composite fiber prepared for Comparative Example 3. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0033] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] A method for spinning polyurethane / chitosan composite porous fibers includes the following steps:

[0035] S1. Polyurethane masterbatch is dissolved in an organic solvent and mechanically stirred to obtain a polyurethane solution with a concentration of 10 wt.% to 30 wt.%. Chitosan is dissolved in dilute acid to obtain a chitosan solution with a concentration of 0.5 wt.% to 3.0 wt.%. The polyurethane masterbatch is unmodified hydrophobic polyurethane.

[0036] The concentration of polyurethane or chitosan spinning solution not only affects the fiber forming process but also the fiber spinnability. By adjusting the spinning solution concentration to regulate the fiber spinnability and coagulating the spinning solution with a specific coagulation bath, the forming of the composite spinning solution is promoted without destroying its coaxial structure, so as to achieve the successful preparation of nascent fibers with a coaxial layered structure.

[0037] S2. Wet spinning is carried out using a coaxial injection device. The outer shaft of the spinning head contains a polyurethane solution, and the inner shaft contains a chitosan solution. The coagulation bath is a mixed solution of water, ethanol and alkali. The spinning solution is formed in the coagulation bath to obtain nascent fibers, which are then further immersed and cleaned in the aqueous solution.

[0038] Before freeze-drying, the nascent fibers are soaked and washed in an aqueous solution. This removes excess solvent from the fibers and increases the liquid content, allowing microporous channels to form in the outer polyurethane layer during freeze-drying. This facilitates the release of internal vapors and creates a porous chitosan aerogel structure inside, improving the warmth and comfort of the fiber material.

[0039] S3. The nascent fibers cleaned in step S2 are subjected to vacuum freeze-drying to obtain polyurethane / chitosan composite porous fibers.

[0040] Specifically, in step S2, water, ethanol, and alkaline solution are selected as the coagulation bath for the coaxial spinning solution. During the coagulation process, because the concentration of the outer polyurethane spinning solution is much higher than that of the inner chitosan spinning solution, and the polyurethane spinning solution has a high affinity for water, the polyurethane solution first undergoes rapid solvent exchange with the water in the coagulation bath, causing the polyurethane to swell. As the number of water molecules in the polyurethane increases, a concentration difference is formed between the polyurethane solution and the inner chitosan solution. Then, the coagulation bath undergoes phase replacement with the inner chitosan, which is beneficial to the formation of a uniform microporous structure of chitosan. At the same time, due to the hydrophobicity of polyurethane, solvent exchange channels are formed in the outer polyurethane layer, which further facilitates the coagulation bath to enter the inner chitosan spinning solution for solvent exchange. The presence of alkali promotes the phase exchange rate between chitosan and the coagulation bath, increasing the molding speed of chitosan. Furthermore, ethanol can reduce the exchange rate between solvent and water in the later stage of polyurethane coagulation, further ensuring the preferential molding of internal chitosan and avoiding instability of the fiber structure caused by the early molding of the outer polyurethane layer, which leads to internal collapse of the fiber during freeze-drying. In addition, when the proportion of undesirable solvents for polyurethane in the coagulation bath is relatively reduced in the later stage of molding, it is conducive to the formation of a uniform and dense polyurethane structure. Finally, nascent fibers with a coaxial layered structure were successfully obtained in the coagulation bath.

[0041] Specifically, in step S2, the volume ratio of water, ethanol, and alkali in the coagulation bath is 5:(2.5-3.5):(1.5-2.5). The preferred volume ratio is 5:3:2. Based on the characteristics of polyurethane and chitosan in the coaxial composite spinning solution, water in the coagulation bath serves as the main exchange solvent, alkali is used to promote the exchange rate of chitosan, and ethanol is used to reduce the exchange rate between water and solvent in the later stages of polyurethane coagulation. This ensures the pre-forming of the inner chitosan and the post-forming of the outer polyurethane layer, resulting in a polyurethane with a uniform outer structure.

[0042] In step S2, in the coaxial injection device, the ratio of the width of the outer shaft containing the polyurethane solution to the radius of the inner shaft containing the chitosan solution is (0.1–0.3):1. The inner diameter of the outer shaft of the spinning head is 200 μm–1 mm, and the spinning speed of the spinning head is 10–30 m / min to ensure the stable preparation of polyurethane / chitosan composite porous fibers. The diameter of the porous composite fiber can be adjusted by changing the ratio of the outer to inner shaft of the spinning head and the inner diameter of the outer shaft. However, due to the special nature of the fiber structure and molding process, limitations are necessary to avoid excessively thin fibers or excessively thick polyurethane outer layers, which could affect the successful preparation of the fiber.

[0043] Specifically, in step S3, vacuum freeze drying involves freezing the nascent fibers at -20°C to -10°C for 8 to 12 hours, and then freeze-drying them at -80°C to -50°C for 24 to 48 hours.

[0044] In some specific embodiments, in step S1, the organic solvent includes one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), tetrahydrofuran (THF), or dimethyl sulfoxide (DMSO); the pH value of the dilute acid is 5-6, and the dilute acid includes one of dilute hydrochloric acid and acetic acid.

[0045] In some specific implementations, the alkaline solution includes either sodium hydroxide or potassium hydroxide.

[0046] In some specific embodiments, in step S1, when preparing the polyurethane solution, the dissolution temperature is 50-100°C and the mechanical stirring speed is 50-200 r / min.

[0047] A polyurethane / chitosan composite porous fiber prepared by the above spinning method, wherein the inner layer of the polyurethane / chitosan composite porous fiber is a chitosan porous aerogel structure, the chitosan porous aerogel structure is wrapped by an outer layer, and the outer layer is an elastic microporous polyurethane material.

[0048] Specifically, the diameter of the polyurethane / chitosan composite porous fiber is 150 μm to 1 mm; the elongation of the polyurethane / chitosan composite porous fiber is 225% to 255%, the resilience is 92% to 100%, and the tensile strength is 2.4 to 4.0 cN / dtex. The spinning method of this invention is simple, low-cost, and can be continuously produced, making it suitable for industrial mass production; moreover, the prepared polyurethane / chitosan composite porous fiber has high elasticity, high strength, and good warmth retention, and has great market application value.

[0049] Example 1

[0050] This embodiment provides a polyurethane / chitosan composite porous fiber and its spinning method, including the following steps:

[0051] S1. Dissolve 10g of hydrophobic polyurethane masterbatch in DMF at a dissolution temperature of 60℃ and a mechanical stirring speed of 100r / min to obtain a polyurethane solution with a concentration of 20wt.%; dissolve chitosan in dilute hydrochloric acid with a pH of 5.5 to obtain a chitosan solution with a concentration of 2.0wt.%.

[0052] S2. Wet spinning is carried out using a coaxial push-in device. The outer shaft of the spinning head contains a polyurethane solution, and the inner shaft contains a chitosan solution. The coagulation bath is a mixed solution of water, ethanol and alkaline sodium hydroxide (volume ratio of 5:3:2). The spinning solution is formed in the coagulation bath to obtain nascent fibers, which are then further immersed and cleaned in the aqueous solution.

[0053] S3. The nascent fibers cleaned in step S2 are subjected to vacuum freeze-drying at a freezing temperature of -20℃ for 8 hours and a freeze-drying temperature of -80℃ for 48 hours to obtain polyurethane / chitosan composite porous fibers.

[0054] Please see Figures 1-2 As shown, Figure 1 This is a micro-electron microscopy image of the polyurethane / chitosan composite porous fibers prepared in Example 1. Figure 2 The image shows an electron microscope (EMS) image of the outer polyurethane layer of the polyurethane / chitosan composite porous fiber from Example 1 after it has been cut open. As can be seen from the image, the outer layer of the composite fiber is a polyurethane material with a microporous structure and a smooth surface, and the outer layer is relatively thin. The interior is a porous chitosan aerogel structure with dense pores; this fiber combines elasticity, strength, and warmth retention.

[0055] Examples 2-5

[0056] Examples 2-5 provide a polyurethane / chitosan composite porous fiber and its spinning method. Compared with Example 1, the difference lies in the different concentrations of the polyurethane solution and the chitosan solution, as shown in Table 1 below. The rest is roughly the same as Example 1 and will not be repeated here.

[0057] Comparative Examples 1-3

[0058] Comparative Examples 1-3 provide a fiber and its spinning method. Compared with Example 1, the difference lies in the different concentrations of polyurethane solution and chitosan solution, as shown in Table 1 below. Furthermore, Comparative Example 1 prepares solid polyurethane fiber, while Comparative Example 2 prepares hollow polyurethane fiber. The rest is roughly the same as Example 1, and will not be repeated here.

[0059] Table 1. Parameter settings and fiber spinnability characterization of Examples 2-5 and Comparative Examples 1-3

[0060]

[0061]

[0062] Please see Figure 3 The image shown is a microscopic electron microscope image of the polyurethane / chitosan composite porous fiber prepared in Example 2. As can be seen from the image, the interior of the composite fiber is chitosan aerogel and the outer layer is polyurethane material. Compared with Example 1, the uniformity of the internal chitosan aerogel structure is poor.

[0063] Please see Figures 4-6 As shown, Figure 4 The image shows an electron microscope image of the non-coaxial polyurethane fiber prepared in Comparative Example 1. Figure 5 The image shown is an electron microscope image of the hollow polyurethane fibers prepared in Comparative Example 2. Figure 6The image shows a microscopic electron microscope (EM) image of the composite fibers prepared for Comparative Example 3. Figure 6 It can be seen that the spinnability of the spinning solution is poor under the polyurethane spinning solution concentration of Comparative Example 3, and the polyurethane pores of the prepared composite fiber are large, and the chitosan fibers inside are also mostly irregular macroporous structures. This is because the polyurethane concentration of the outer layer is low, which cannot slow down the solvent exchange rate of chitosan during solidification, and cannot protect the chitosan fibers inside during freeze drying.

[0064] The fibers prepared in Examples 1-6 and Comparative Examples 1-3 were tested for elasticity and strength, and the results are shown in the table below.

[0065] Table 2. Performance test results of fibers prepared in Examples 1-5 and Comparative Examples 1-3

[0066]

[0067] As shown in Table 2, the elongation of the fiber depends on the concentration of polyurethane. The higher the polyurethane concentration, the higher the elongation of the composite fiber, and the corresponding increase in the fiber resilience. The tensile strength of the fiber is not only related to polyurethane, but also to the concentration of chitosan and the structure of the composite fiber prepared by the synergy of the two. When the concentration of polyurethane solution is 10wt.% to 30wt.% and the concentration of chitosan solution is 0.5wt.% to 3.0wt.%, the obtained composite porous fiber not only has good elastic properties, but also excellent tensile strength.

[0068] Comparative Example 4

[0069] Comparative Example 4 provides a polyurethane / chitosan composite porous fiber and its spinning method. Compared with Example 1, the difference is that the coagulation bath does not contain ethanol, and the volume ratio of water to alkali solution is 8:2. The rest is roughly the same as Example 1, and will not be repeated here.

[0070] Comparative Example 5

[0071] Comparative Example 5 provides a polyurethane / chitosan composite porous fiber and its spinning method. Compared with Example 1, the difference is that the coagulation bath does not contain alkali solution, the volume ratio of water to ethanol is 7:3, and the rest is roughly the same as Example 1, which will not be repeated here.

[0072] Comparative Example 6

[0073] Comparative Example 6 provides a polyurethane / chitosan composite porous fiber and its spinning method. Compared with Example 1, the difference is that the coagulation bath does not contain water, the volume ratio of alkali solution to ethanol is 2:3, and the rest is roughly the same as Example 1, which will not be repeated here.

[0074] Comparative Example 7

[0075] Comparative Example 7 provides a polyurethane / chitosan composite porous fiber and its spinning method. The difference from Example 1 is that the volume ratio of water, ethanol and alkali in the coagulation bath is 2:3:5. The rest is roughly the same as Example 1 and will not be repeated here.

[0076] Comparative Example 8

[0077] Comparative Example 8 provides a polyurethane / chitosan composite porous fiber and its spinning method. Compared with Example 1, the difference is that the volume ratio of water, ethanol and alkali in the coagulation bath is 3:5:2. The rest is roughly the same as Example 1, and will not be repeated here.

[0078] The properties of the polyurethane / chitosan composite porous fibers prepared in Comparative Examples 4-8 were tested, and the results are shown in the table below.

[0079] Table 3 shows the performance test results of the fibers prepared in Comparative Examples 4–8.

[0080]

[0081]

[0082] Table 3 shows that different coagulation baths have a significant impact on the mechanical properties of the composite aerogel fibers. This is because different coagulation baths affect the formation of the porous composite structure. Specifically, the coagulation bath in Comparative Example 4, which does not contain ethanol, accelerates the formation of polyurethane, resulting in a barrier layer on the outside of the fiber. This hinders solvent exchange of the internal chitosan, leading to poorer mechanical properties of the composite fiber. The coagulation bath in Comparative Example 5, which does not contain alkali, reduces the solidification of chitosan, which is detrimental to the formation of the internal chitosan and thus affects the formation of the porous chitosan aerogel structure within the composite fiber. The coagulation bath in Comparative Example 6, which does not contain water, not only hinders fiber formation in the coagulation bath but also makes the composite fiber difficult to dry during freeze-drying, as excessive alkali present inside the fiber is difficult to remove during subsequent cleaning and freeze-drying. The reduced water specific gravity in the coagulation baths of Comparative Examples 7 and 8 also affects the formation process of the composite fiber in the coagulation bath, thus impacting the mechanical properties of the composite fiber.

[0083] In summary, this invention provides a polyurethane / chitosan composite porous fiber and its spinning method. A polyurethane solution and a chitosan solution are spun using coaxial wet spinning technology. The spinnability of the fiber is adjusted by regulating the concentration of the spinning solution, and a specific coagulation bath is used to coagulate the spinning solution, promoting the formation of the composite spinning solution without destroying its coaxial structure. This achieves the successful preparation of nascent fibers with a coaxial layered structure. The nascent fibers are then vacuum freeze-dried to obtain the polyurethane / chitosan composite porous fiber. Water, ethanol, and alkaline solution are selected as the coagulation bath for the coaxial spinning solution. During the coagulation process, these three substances work synergistically to control the formation process of the composite spinning solution in the coagulation bath, ensuring that the inner chitosan forms preferentially and preventing the fiber from collapsing during freeze-drying due to the outer layer forming first. This successfully yields nascent fibers with a coaxial layered structure. The spinning method of the present invention is simple, low-cost, and can be continuously prepared, making it suitable for industrial mass production; moreover, the prepared polyurethane / chitosan composite porous fibers have high elasticity, high strength, and good warmth retention, and have great market application value.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A spinning method for polyurethane / chitosan composite porous fibers, characterized in that, Includes the following steps: S1. Polyurethane masterbatch is dissolved in an organic solvent and mechanically stirred to obtain a polyurethane solution with a concentration of 10 wt.% to 30 wt.%. Chitosan is dissolved in dilute acid to obtain a chitosan solution with a concentration of 0.5 wt.% to 3.0 wt.%. S2. Wet spinning is performed using a coaxial injection device. The outer shaft of the spinning head contains the polyurethane solution, and the inner shaft contains the chitosan solution. The coagulation bath is a mixed solution of water, ethanol and alkali. The spinning solution is formed in the coagulation bath to obtain nascent fibers, which are then further immersed and cleaned in the aqueous solution. S3. The nascent fibers cleaned in step S2 are subjected to vacuum freeze-drying to obtain the polyurethane / chitosan composite porous fibers.

2. The spinning method for polyurethane / chitosan composite porous fibers according to claim 1, characterized in that, In step S2, the volume ratio of water, ethanol and alkaline solution in the coagulation bath is 5:(2.5-3.5):(1.5-2.5).

3. The spinning method for polyurethane / chitosan composite porous fibers according to claim 1, characterized in that, In step S2, in the coaxial injection device, the ratio of the width of the outer shaft containing the polyurethane solution to the radius of the inner shaft containing the chitosan solution is (0.1~0.3):

1.

4. The spinning method of polyurethane / chitosan composite porous fiber according to claim 2, characterized in that, The volume ratio of water, ethanol and alkaline solution in the coagulation bath is 5:3:

2.

5. The spinning method of polyurethane / chitosan composite porous fiber according to claim 3, characterized in that, The outer shaft inner diameter of the spinning head is 200μm to 1mm, and the spinning speed of the spinning head is 10 to 30m / min, so as to ensure the stable preparation of the polyurethane / chitosan composite porous fiber.

6. The spinning method of polyurethane / chitosan composite porous fiber according to claim 1, characterized in that, In step S3, the vacuum freeze-drying involves freezing the nascent fibers at -20°C to -10°C for 8 to 12 hours, and then freeze-drying them at -80°C to -50°C for 24 to 48 hours.

7. The spinning method for polyurethane / chitosan composite porous fibers according to claim 1, characterized in that, In step S1, the organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide; the pH value of the dilute acid is 5-6, and the dilute acid includes one of dilute hydrochloric acid and acetic acid.

8. The spinning method of polyurethane / chitosan composite porous fiber according to claim 1, characterized in that, In step S1, when preparing the polyurethane solution, the dissolution temperature is 50-100°C, and the mechanical stirring speed is 50-200 r / min.

9. A polyurethane / chitosan composite porous fiber prepared by the spinning method according to any one of claims 1 to 8, characterized in that, The inner layer of the polyurethane / chitosan composite porous fiber is a chitosan porous aerogel structure, which is wrapped by an outer layer, which is an elastic microporous polyurethane material.

10. The polyurethane / chitosan composite porous fiber according to claim 9, characterized in that, The polyurethane / chitosan composite porous fiber has a diameter of 150 μm to 1 mm; the polyurethane / chitosan composite porous fiber has an elongation of 225% to 255%, a resilience of 92% to 100%, and a tensile strength of 2.4 to 4.0 cN / dtex.

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