A silk fibroin solution and a preparation method of silk fibroin regenerated fibers

Abstract

This invention discloses a silk fibroin solution and a method for preparing regenerated silk fibroin fibers. The silk fibroin solution is prepared by first swelling the silk fibroin fibers, then dissolving them, and finally protecting them with a polyol. The solution is stable and has good fluidity, and can be widely used in the preparation of fibers, membrane materials, hydrogels, and microspheres. The silk fibroin solution of this invention, through secondary coagulation and secondary stretching, yields regenerated silk fibroin fibers with excellent structural properties, which can be used to prepare yarns, fillers, and nonwoven fabrics. The preparation method of the silk fibroin solution and regenerated silk fibroin fibers of this invention is simple and reliable, the solvent is easily recoverable, and the cost is low, making it suitable for industrial production and large-scale application.

Description

Technical Field

[0001] This invention belongs to the field of natural polymer material processing technology, specifically relating to a silk fibroin solution and a method for preparing regenerated silk fibroin fibers. Background Technology

[0002] Silk, a natural fiber produced by silkworms during biological evolution, has won worldwide favor for its superior performance and has always been an indispensable raw material for high-end textiles and clothing. my country is a major silk-producing country, with an annual silkworm cocoon production exceeding 800,000 tons. Currently, the main use of silk is in the textile and apparel sector. However, the silk processing process generates a large amount of waste, and combined with the annual discarded silk fiber products, the amount of reusable silk fiber waste reaches tens of thousands of tons, representing a significant fiber resource. Furthermore, due to the biocompatibility, non-toxicity, and biodegradability of silk protein, silk materials are also being applied to the development of high-value-added fields such as biomedical materials and bio-optoelectronic materials, demonstrating enormous potential socio-economic value.

[0003] The main component of silk is fibroin. The utilization of fibroin fibers typically requires dissolving it into a solution and then solidifying it to prepare the desired material. Various solvent methods exist for fibroin dissolution, such as the calcium chloride-ethanol-water (1:2:8) system, 9.3 M lithium bromide solution, calcium chloride-formic acid system, and ionic liquids. However, during the dissolution process, a series of problems arise, including severe degradation of fibroin molecules, cumbersome extraction of fibroin proteins, instability of the fibroin solution, poor structure of the fibroin solution, and poor material properties. From the perspective of current technology, fibroin dissolution is not difficult, but obtaining a stable fibroin solution and processing it into a material with excellent structural properties remains challenging. Considering the fibroin molecule dissolution process, we propose a swelling-dissolution-protection strategy. First, the fibroin fibers swell to increase solvent accessibility, then dissolve them, making the dissolution process more uniform and avoiding the phenomenon of some fibers degrading while others remain undissolved. After complete dissolution, a polyol solution is added to the fibroin solution to protect the fibroin molecules, thereby preventing solvent degradation. Moreover, the silk fibroin solution containing polyols is very stable and has good fluidity. It will also coagulate gently when it encounters a coagulation bath, allowing the silk fibroin molecules to be better stretched and deformed, which is conducive to the orderly arrangement of molecules and thus improves the structural properties of the material. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a silk fibroin solution and its regenerated silk fibers, overcoming the problems of severe degradation of silk fibroin molecules caused by dissolving silk fibroin in existing technologies, as well as the cumbersome processes and poor fiber performance of existing methods for preparing regenerated silk fibroin fibers. This invention fully considers the characteristics of the silk fibroin dissolution system and the silk fibroin solution, employing a swelling-dissolution-protection strategy to prepare the silk fibroin solution, thus avoiding severe degradation of silk fibroin molecules. Simultaneously, during the solidification process, the silk fibroin solution is protected by polyols, preventing the large amount of random stacking and defects caused by violent desolventizing of silk fibroin molecules. This allows the silk fibroin molecules to be smoothly drawn and arranged in an orderly manner, significantly improving the structure and properties of the regenerated silk fibroin fibers.

[0005] To achieve this objective, the present invention provides a silk fibroin solution, which is composed of silk fibroin, zinc chloride, calcium chloride, formic acid, polyol, and water, wherein the mass fractions of each component are 5%~15% silk fibroin, 5%~10% zinc chloride, 1%~5% calcium chloride, 40%~60% formic acid, 10%~30% polyol, and the remainder is water. The preparation method of the silk fibroin solution includes the following steps:

[0006] S1. Add silk fibroin to a formic acid solution containing zinc chloride to obtain a swollen fiber pulp;

[0007] S2. Add anhydrous calcium chloride powder to the fiber slurry described in S1 and stir rapidly to obtain a transparent initial solution of silk fibroin;

[0008] S3. Filter the initial silk fibroin solution described in S2, add 50% to 90% polyol solution to it, stir evenly, and let it stand or degas under vacuum to obtain the desired silk fibroin solution.

[0009] Preferably, the polyol is one or more of ethylene glycol, propylene glycol, glycerol, and butanediol.

[0010] Preferably, the mass ratio of the initial silk fibroin solution to the polyol solution in S3 is 1 to 4:1.

[0011] Furthermore, the silk fibroin solution is used to prepare fibers, membrane materials, hydrogels, microspheres, and their composite materials.

[0012] This invention also provides a method for preparing regenerated silk fibroin fibers, comprising the following steps:

[0013] S4. The silk fibroin solution described in S3 is extruded into coagulation bath A and coagulated to form nascent silk fibroin fibers. The coagulation bath A is one or more of polyethylene glycol 200-800, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and triethanolamine.

[0014] S5. After the nascent silk fibroin fibers described in S4 are first stretched, they are immersed in coagulation bath B for a second coagulation. The coagulation bath B is any one of methanol, ethanol, isopropanol, and acetone.

[0015] S6. The coagulated silk fibroin fibers are stretched a second time, immersed in sodium carbonate solution, washed with water, dried, wound and collected to obtain the desired regenerated silk fibroin fibers.

[0016] Preferably, the first stretching ratio in S5 is 1.1 to 1.3, and the concentration of the coagulation bath B is 75% to 100%.

[0017] Preferably, the second stretching ratio in S6 is 1.2 to 2, the concentration of sodium carbonate is 1% to 5%, and the drying temperature is 20 to 80°C.

[0018] Furthermore, the present invention provides regenerated silk fibroin fibers prepared by the above method.

[0019] Furthermore, the regenerated silk fibroin fiber provided by this invention can be used to prepare yarn, filler, and nonwoven fabric.

[0020] The beneficial effects are:

[0021] 1) The silk fibroin solution preparation method of the present invention adopts a swelling-dissolution-protection strategy. The dissolution process is controllable, the silk fibroin molecules are well protected, and the resulting silk fibroin solution has good stability and fluidity, and can be stored for a long time without affecting the processing performance.

[0022] 2) The method for preparing regenerated silk fibroin fibers of the present invention is simple. The silk fibroin molecules are gently coagulated and shaped under the protection of polyols, which is conducive to the stretching and orientation of silk fibroin molecules, thereby greatly improving the structural properties of regenerated silk fibroin fibers.

[0023] 3) The technical solution of the present invention is simple and reliable, the solvent is easy to recover, and the cost is low, which is conducive to industrial production and promotion and application. Implementation

[0024] The present invention will be further described in detail below with reference to embodiments, but this is not intended to limit the present invention. Example

[0025] (1) Preparation of silk fibroin solution

[0026] Add 2g of silk fibroin and 2g of zinc chloride to 15.6g of formic acid, and stir until the zinc chloride is completely dissolved to obtain a swollen silk fibroin slurry. Add 0.4g of anhydrous calcium chloride powder to the slurry and stir rapidly until the calcium chloride is completely dissolved to obtain a clear initial silk fibroin solution. Filter the initial silk fibroin solution, add 20g of 60% glycerol solution, stir well, and allow to stand to remove bubbles to obtain the desired silk fibroin solution.

[0027] (2) Preparation of regenerated silk fibroin fibers

[0028] The silk fibroin solution obtained in (1) was extruded into polyethylene glycol 200 and solidified to obtain nascent silk fibroin fibers. The nascent silk fibroin fibers were stretched 1.1 times and immersed in a 75% ethanol solution for secondary solidification. The secondary solidified silk fibroin fibers were stretched 1.2 times again, immersed in a 5% sodium carbonate solution, washed with water, dried at 20°C, and wound and collected to obtain regenerated silk fibroin fibers. Example

[0029] (1) Preparation of silk fibroin solution

[0030] Add 2.5g of silk fibroin and 2.5g of zinc chloride to 15g of formic acid, and stir until the zinc chloride is completely dissolved to obtain a swollen silk fibroin slurry. Add 1g of anhydrous calcium chloride powder to the slurry and stir rapidly until the calcium chloride is completely dissolved to obtain a clear initial silk fibroin solution. Filter the initial silk fibroin solution, add 4g of 62.5% ethylene glycol solution, stir well, and allow to stand to remove bubbles to obtain the desired silk fibroin solution.

[0031] (2) Preparation of regenerated silk fibroin fibers

[0032] The silk fibroin solution obtained in (1) was extruded into N,N-dimethylformamide and solidified to obtain nascent silk fibroin fibers. The nascent silk fibroin fibers were stretched 1.3 times and immersed in a 100% ethanol solution for secondary solidification. The secondary solidified silk fibroin fibers were stretched 1.5 times again, immersed in a 2% sodium carbonate solution, washed with water, dried at 80°C, and wound and collected to obtain regenerated silk fibroin fibers. Example

[0033] (1) Preparation of silk fibroin solution

[0034] Add 3g of silk fibroin and 2g of zinc chloride to 9g of formic acid, and stir until the zinc chloride is completely dissolved to obtain a swollen silk fibroin slurry. Add 1g of anhydrous calcium chloride powder to the slurry and stir rapidly until the calcium chloride is completely dissolved to obtain a transparent initial silk fibroin solution. Filter the initial silk fibroin solution, add 5g of 80% butanediol solution, stir well, and allow to stand to remove bubbles to obtain the desired silk fibroin solution.

[0035] (2) Preparation of regenerated silk fibroin fibers

[0036] The silk fibroin solution obtained in (1) was extruded into N,N-dimethylacetamide and solidified to obtain nascent silk fibroin fibers. The nascent silk fibroin fibers were stretched 1.2 times and immersed in a 100% isopropanol solution for secondary solidification. The secondary solidified silk fibroin fibers were stretched 1.5 times again, immersed in a 1% sodium carbonate solution, washed with water, dried at 50°C, and wound and collected to obtain regenerated silk fibroin fibers. Example

[0037] (1) Preparation of silk fibroin solution

[0038] Add 2.1g of silk fibroin and 2.1g of zinc chloride to 14.9g of formic acid, and stir until the zinc chloride is completely dissolved to obtain a swollen silk fibroin slurry. Add 0.9g of anhydrous calcium chloride powder to the slurry and stir rapidly until the calcium chloride is completely dissolved to obtain a clear initial silk fibroin solution. Filter the initial silk fibroin solution, add 10g of 90% propylene glycol solution, stir well, and allow to stand to remove bubbles to obtain the desired silk fibroin solution.

[0039] (2) Preparation of regenerated silk fibroin fibers

[0040] The silk fibroin solution obtained in (1) was extruded into polyethylene glycol 800 and solidified to obtain nascent silk fibroin fibers. The nascent silk fibroin fibers were stretched 1.2 times and immersed in a 100% acetone solution for secondary solidification. The secondary solidified silk fibroin fibers were stretched 2 times again, immersed in a 5% sodium carbonate solution, washed with water, dried at 30°C, and wound and collected to obtain regenerated silk fibroin fibers. Example

[0041] (1) Preparation of silk fibroin solution

[0042] Add 2g of silk fibroin and 1g of zinc chloride to 12g of formic acid, and stir until the zinc chloride is completely dissolved to obtain a swollen silk fibroin slurry. Add 1g of anhydrous calcium chloride powder to the slurry and stir rapidly until the calcium chloride is completely dissolved to obtain a clear initial silk fibroin solution. Filter the initial silk fibroin solution, add 4g of 50% glycerol solution, stir well, and allow to stand to remove bubbles to obtain the desired silk fibroin solution.

[0043] (2) Preparation of regenerated silk fibroin fibers

[0044] The silk fibroin solution obtained in (1) was extruded into polyethylene glycol 600 and solidified to obtain nascent silk fibroin fibers. The nascent silk fibroin fibers were stretched 1.1 times and immersed in a 100% methanol solution for secondary solidification. The secondary solidified silk fibroin fibers were stretched 2 times again, immersed in a 2% sodium carbonate solution, washed with water, dried at 50°C, and wound and collected to obtain regenerated silk fibroin fibers.

Claims

1. A silk fibroin solution, characterized in that, The silk fibroin solution is composed of silk fibroin, zinc chloride, calcium chloride, formic acid, polyol, and water, with the following mass fractions: silk fibroin 5%~15%, zinc chloride 5%~10%, calcium chloride 1%~5%, formic acid 40%~60%, polyol 10%~30%, and the remainder being water; the polyol is one or more of ethylene glycol, propylene glycol, glycerol, and butylene glycol; the preparation method of the silk fibroin solution includes the following steps: S1. Add silk fibroin to a formic acid solution containing zinc chloride to obtain a swollen fiber pulp; S2. Add anhydrous calcium chloride powder to the fiber slurry described in S1 and stir rapidly to obtain a transparent initial solution of silk fibroin; S3. Filter the initial silk fibroin solution described in S2, add a polyol solution with a mass concentration of 50% to 90% to it, wherein the mass ratio of the initial silk fibroin solution to the polyol solution is 1 to 4:1, stir evenly, and let stand or degas under vacuum to obtain the desired silk fibroin solution.

2. The silk fibroin solution according to claim 1 is used to prepare fibers, membrane materials, hydrogels, microspheres and their composite materials.

3. A method for preparing regenerated silk fibroin fiber, characterized in that, Includes the following steps: S4. The silk fibroin solution described in S3 of claim 1 is extruded into coagulation bath A and coagulated to obtain nascent silk fibroin fibers. The coagulation bath A is one or more of polyethylene glycol 200-800, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and triethanolamine. S5. After the nascent silk fibroin fibers described in S4 are first stretched, they are immersed in coagulation bath B for a second coagulation. The coagulation bath B is any one of methanol, ethanol, isopropanol, and acetone. S6. The coagulated silk fibroin fibers are stretched a second time, immersed in sodium carbonate solution, washed with water, dried, wound and collected to obtain the desired regenerated silk fibroin fibers.

4. The method for preparing regenerated silk fibroin fiber according to claim 3, characterized in that, The first stretching ratio in S5 is 1.1 to 1.3, and the concentration of the coagulation bath B is 75% to 100%.

5. The method for preparing regenerated silk fibroin fiber according to claim 3, characterized in that, The second stretching ratio in S6 is 1.2 to 2, the concentration of sodium carbonate is 1% to 5%, and the drying temperature is 20 to 80°C.

6. Regenerated silk fibroin fiber obtained by the preparation method according to any one of claims 3-5.

7. The regenerated silk fibroin fiber according to claim 6 is used to prepare yarn, filler, and nonwoven fabric.