Preparation method of low-viscosity chitosan solution and high-strength chitosan fiber thereof

Abstract

The invention discloses a preparation method of a low-viscosity chitosan solution and a high-strength chitosan fiber thereof, chitosan molecules are dissolved and hydrated shells of the chitosan molecules are reduced under the combined action of weak acid and low alcohol, and meanwhile, the low alcohol plays a role in lubrication and dispersion, so that the viscosity of the chitosan solution is greatly reduced. The low-viscosity chitosan solution is squeezed into an organic solvent containing metal salt to be solidified into filaments, and then the high-strength chitosan fibers are obtained after drafting and drying. According to the method, the property of the chitosan solution is remarkably improved, high-speed spinning is facilitated, the requirement for efficient and clean production of the chitosan fibers is met, and the obtained chitosan fibers are high in mechanical performance, can be used for manufacturing filaments, yarns, fabrics and non-fabrics and are suitable for large-scale popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of natural polymer material processing, and particularly relates to a method for preparing a low-viscosity chitosan solution and a high-strength chitosan fiber thereof. Background Art

[0002] Chitosan is the only alkaline polysaccharide polymer in nature. Due to its excellent biological properties, it is considered to be a biological resource with greater application potential than cellulose. Chitosan is usually dissolved in an acid solution, but commonly used acids such as acetic acid and hydrochloric acid will cause serious degradation of chitosan molecules in a short period of time. In addition, the molecular weight of chitosan molecules is large and the water absorption is strong, resulting in a low concentration of chitosan solution but a high viscosity, which is not conducive to the full dissolution and homogenization of chitosan powder, and also causes a large number of bubbles in the chitosan solution and is difficult to eliminate, which greatly affects the efficient processing and utilization of chitosan-based biomaterials, especially the manufacture of chitosan fibers. The existing method basically solves the problem of rapid degradation of chitosan molecules by using weak acids such as citric acid, oxalic acid, and carbonate solution to dissolve chitosan. Patent CN111748870B introduces carbon dioxide into the chitosan dispersion to dissolve chitosan under the action of carbonic acid, and obtains a chitosan solution with a pH value of 6 to 8 after degassing, and then the chitosan solution is subjected to wet spinning or dry-jet wet spinning to obtain chitosan fibers. Patent CN116005295A dissolves chitosan in an acidic solution such as citric acid and oxalic acid, squeezes the chitosan solution into a coagulation bath of anionic surfactant to form high-strength chitosan fiber. However, the problem of high viscosity of chitosan solution still exists, which greatly hinders the degassing, filtration and spinning speed increase of spinning solution. Therefore, preparing a low-viscosity chitosan solution and maintaining good stability are of great significance for the efficient preparation of chitosan fiber and its large-scale production. Summary of the invention

[0003] The present invention aims to provide a method for preparing a low-viscosity chitosan solution and a high-strength chitosan fiber thereof. The chitosan is dissolved by a mixed system of a low-grade alcohol and a weak acid, thereby achieving the purpose of greatly reducing the viscosity of the chitosan solution. Meanwhile, the chitosan solution is easy to degas and filter, and the low-viscosity chitosan spinning solution is suitable for high-speed spinning.

[0004] To achieve this object, the present invention provides a low-viscosity chitosan solution and a method for preparing high-strength chitosan fiber thereof. The low-viscosity chitosan solution consists of chitosan, weak acid, lower alcohol and water, wherein the mass fractions of chitosan, weak acid and lower alcohol are 2%-4%, 3%-30% and 40%-80% respectively; the molecular weight of the chitosan is 100000-300000Da, the weak acid is a mixture of boric acid and lactic acid, and the lower alcohol is a mixture of methanol and ethylene glycol, propylene glycol, glycerol or butanediol; the method for preparing high-strength chitosan fiber comprises the following steps: S1. The chitosan powder is added to a lower alcohol solution and stirred to disperse, wherein the lower alcohol is a mixture of methanol and ethylene glycol, propylene glycol, glycerol or butanediol; S2. adding a weak acid to the chitosan dispersion obtained in S1, stirring until the chitosan is uniformly dissolved, centrifuging the solution at high speed, and filtering to obtain a low-viscosity chitosan solution, wherein the weak acid is a mixture of boric acid and lactic acid; S3. The low viscosity chitosan solution obtained in S2 is squeezed into a coagulation bath to coagulate into primary silk, wherein the coagulation bath is an ethanol solution containing a zinc salt or a magnesium salt, wherein the zinc salt is any one of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate, and zinc lactate, and the magnesium salt is any one of magnesium chloride, magnesium nitrate, magnesium acetate, and magnesium sulfate; S4. After the primary filaments obtained in S3 are drawn, they are immersed in the coagulation bath described in S3 for secondary coagulation, and then led out and dried to obtain high-strength chitosan fibers.

[0005] Furthermore, the volume ratio of methanol to ethylene glycol, propylene glycol, glycerol or butanediol in the lower alcohol described in S1 is 1:1~4.

[0006] Furthermore, the mass ratio of boric acid to lactic acid in the weak acid described in S2 is 1:1~14.

[0007] Furthermore, the mass concentration of the zinc salt or magnesium salt in S3 is 0.5%~5%.

[0008] Furthermore, the drafting rate of the spun yarn in S4 is 50% to 200%.

[0009] Furthermore, the drying temperature in S4 is 50-130°C.

[0010] In addition, the present invention also provides low-viscosity chitosan solution and high-strength chitosan fiber prepared by the method.

[0011] Furthermore, the present invention also provides the use of high-strength chitosan fibers in the preparation of filaments, yarns, fabrics and non-fabricated fabrics.

[0012] The beneficial effects are: 1) The low-viscosity chitosan solution of the present invention has good stability, is easy to degas, filter, and extrude, has a simple preparation method, and is low in cost, which greatly improves the efficiency of the preparation process of the chitosan spinning solution; 2) The method for preparing chitosan fiber from the low-viscosity chitosan solution of the present invention is simple and more suitable for high-speed spinning, meeting the requirements of efficient and clean production; the chitosan fiber has good molding, is easy to draw, has high strength, and has broad application prospects. DETAILED DESCRIPTION

[0013] The present invention is further described in detail below with reference to the embodiments, but is not intended to limit the present invention. Example

[0014] 0.6g chitosan powder was added to a mixture of 24g methanol and ethylene glycol (volume ratio 1:4), 4.5g pure water was added, stirred and dispersed, and then 0.9g boric acid and lactic acid (mass ratio 1:1) were added, stirred until the chitosan was completely dissolved, and the chitosan solution was centrifuged for degassing and filtered to obtain a low-viscosity chitosan solution. The chitosan solution was extruded through a nozzle into 200ml of ethanol containing 0.5 wt% zinc sulfate for coagulation, and the coagulated primary filaments were drawn by 50%, then immersed in a coagulation bath for secondary coagulation, and then extracted and sent to a 50°C oven for drying to obtain high-strength chitosan fibers. Example

[0015] 1.2g chitosan powder was added to a mixture of 15g methanol and glycerol (volume ratio 1:1), 4.8g pure water was added, stirred and dispersed, and then 9g boric acid and lactic acid (mass ratio 1:14) were added, stirred until the chitosan was completely dissolved, and the chitosan solution was centrifuged for degassing and filtered to obtain a low-viscosity chitosan solution. The chitosan solution was extruded through a nozzle into 200ml of ethanol containing 5 wt% zinc acetate for coagulation, and the coagulated primary filaments were drawn 100%, then immersed in a coagulation bath for secondary coagulation, and then led out and sent to a 130°C oven for drying to obtain high-strength chitosan fibers. Example

[0016] 0.9g chitosan powder was added to a mixture of 18g methanol and glycerol (volume ratio 1:2), 8.1g pure water was added, stirred and dispersed, and then 3g boric acid and lactic acid (mass ratio 1:4) were added, stirred until the chitosan was completely dissolved, and the chitosan solution was centrifuged for degassing and filtered to obtain a low-viscosity chitosan solution. The chitosan solution was extruded through a nozzle into 200ml of ethanol containing 2 wt% magnesium chloride for coagulation, and the coagulated primary filaments were drawn by 200%, then immersed in a coagulation bath for secondary coagulation, and then led out and sent to an 80°C oven for drying to obtain high-strength chitosan fibers. Example

[0017] 0.75g chitosan powder was added to a mixture of 21g methanol and butanediol (volume ratio 1:2), 3.75g pure water was added, and the mixture was stirred and dispersed. Then 4.5g boric acid and lactic acid (mass ratio 1:2) were added and stirred until the chitosan was completely dissolved. The chitosan solution was centrifuged for degassing and filtered to obtain a low-viscosity chitosan solution. The chitosan solution was extruded through a nozzle into 200ml of ethanol containing 4wt% magnesium nitrate for coagulation. The coagulated primary filaments were drawn by 150%, and then immersed in a coagulation bath for secondary coagulation, and then extracted and sent to a 60°C oven for drying to obtain high-strength chitosan fibers. Example

[0018] 1.2g chitosan powder was added to a mixture of 12g methanol and glycerol (volume ratio 1:3), 15g pure water was added, stirred and dispersed, and then 1.8g boric acid and lactic acid (mass ratio 1:1) were added, stirred until the chitosan was completely dissolved, and the chitosan solution was centrifuged for degassing and filtered to obtain a low-viscosity chitosan solution. The chitosan solution was extruded through a nozzle into 200ml of ethanol containing 3 wt% zinc lactate for coagulation, and the coagulated primary filaments were drawn 100%, then immersed in a coagulation bath for secondary coagulation, and then extracted and sent to an 80°C oven for drying to obtain high-strength chitosan fibers.

Claims

1. A method for preparing a low-viscosity chitosan solution and a high-strength chitosan fiber thereof, characterized in that: The low-viscosity chitosan solution is composed of chitosan, weak acid, lower alcohol and water, wherein the mass fractions of chitosan, weak acid and lower alcohol are 2%-4%, 3%-30% and 40%-80% respectively; the molecular weight of the chitosan is 100000-300000 Da, the weak acid is a mixture of boric acid and lactic acid, and the lower alcohol is a mixture of methanol and ethylene glycol, propylene glycol, glycerol or butanediol; the preparation method of the high-strength chitosan fiber comprises the following steps: S1. The chitosan powder is added to a lower alcohol solution and stirred to disperse, wherein the lower alcohol is a mixture of methanol and ethylene glycol, propylene glycol, glycerol or butanediol; S2. adding a weak acid to the chitosan dispersion obtained in S1, stirring until the chitosan is uniformly dissolved, centrifuging the solution at high speed, and filtering to obtain a low-viscosity chitosan solution, wherein the weak acid is a mixture of boric acid and lactic acid; S3. The low viscosity chitosan solution obtained in S2 is squeezed into a coagulation bath to coagulate into primary silk, wherein the coagulation bath is an ethanol solution containing a zinc salt or a magnesium salt, wherein the zinc salt is any one of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate, and zinc lactate, and the magnesium salt is any one of magnesium chloride, magnesium nitrate, magnesium acetate, and magnesium sulfate; S4. After the primary filaments obtained in S3 are drawn, they are immersed in the coagulation bath described in S3 for secondary coagulation, and then led out and dried to obtain high-strength chitosan fibers.

2. The method for preparing a low-viscosity chitosan solution and high-strength chitosan fiber according to claim 1, characterized in that: The volume ratio of methanol to ethylene glycol, propylene glycol, glycerol or butanediol in the lower alcohol described in S1 is 1:1-4.

3. The method for preparing a low-viscosity chitosan solution and high-strength chitosan fiber according to claim 1, characterized in that: The mass ratio of boric acid to lactic acid in the weak acid S2 is 1:1-14.

4. The method for preparing a low-viscosity chitosan solution and high-strength chitosan fiber according to claim 1, characterized in that: The mass concentration of the zinc salt or magnesium salt in S3 is 0.5%~5%.

5. The method for preparing a low-viscosity chitosan solution and high-strength chitosan fiber according to claim 1, characterized in that: The drafting rate of the spun yarn described in S4 is 50% to 200%.

6. The method for preparing a low-viscosity chitosan solution and high-strength chitosan fiber according to claim 1, characterized in that: The drying temperature in S4 is 50-130°C.

7. A low-viscosity chitosan solution and high-strength chitosan fiber prepared according to the method of any one of claims 1 to 6.

8. Use of the high-strength chitosan fiber according to claim 7 in the preparation of filaments, yarns, fabrics and non-woven fabrics.