Silk fibroin-sodium alginate-chitosan bionic leather as well as preparation method and application thereof

Abstract

The invention discloses silk fibroin-sodium alginate-chitosan bionic leather and a preparation method and application thereof.The preparation method comprises the following steps that a silk fibroin solution and a sodium alginate solution are mixed, after calcium salt is added, a chitosan solution continues to be added and mixed with waterborne polyurethane, and a mixed solution is obtained; and carrying out surface activation treatment on base cloth, coating the activated base cloth with the mixed solution, and carrying out drying curing and ultrasonic lamination to obtain the silk fibroin-sodium alginate-chitosan bionic leather. The silk fibroin, sodium alginate and chitosan bionic leather prepared by the invention not only has high strength and good ductility, but also has excellent tensile strength, folding resistance and wear resistance, and also has good biodegradability, so that the burden of waste post-treatment on the environment can be reduced, and the raw material cost and post-treatment cost of the bionic leather can be remarkably reduced; the method has both environmental benefits and outstanding economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biomimetic leather, and particularly relates to a silk fibroin-sodium alginate-chitosan biomimetic leather and a preparation method and application thereof. BACKGROUND

[0002] To solve the systematic defects of traditional animal leather, current biomimetic leather products are mainly divided into two categories: one is petrochemical-based synthetic leather, such as polyurethane (PU) synthetic leather and polyvinyl chloride (PVC) synthetic leather. Although this type of material has low cost and is easy to mass-produce, it is non-degradable, produces toxic plasticizers during production, is difficult to recycle and process, has a high carbon footprint throughout its life cycle, and releases harmful gases when incinerated, which still poses significant environmental risks. The other is bio-based biomimetic leather, such as mycelium leather. Although it has the advantages of being green, environmentally friendly and biodegradable, the preparation process is complex, and the finished product has low tensile strength, making it difficult to meet the mechanical performance requirements of leather in daily use. The high production cost also restricts its industrialization and popularization.

[0003] Silk fibroin, as a natural polymer material, has good biocompatibility, degradability and adjustable mechanical properties, making it an important candidate for biomimetic leather substrate. However, unmodified silk fibroin degrades too quickly and cannot maintain its shape stability for a long time when used alone to prepare leather, limiting its application. Sodium alginate and chitosan, as common natural polymer materials, belong to polyanions and polycations, respectively. They can form a composite gel through electrostatic interaction, which is simple to prepare, has non-toxic degradation products and is environmentally friendly, making it an ideal candidate component for biomimetic leather. However, the tensile strength of the composite gel formed by sodium alginate and chitosan is insufficient, and when used alone or simply compounded, it still cannot meet the comprehensive performance requirements of leather for high toughness, folding resistance and wear resistance.

[0004] Therefore, it is a technical problem to be solved in the current leather industry to develop a biomimetic leather material that is environmentally friendly, has excellent mechanical properties, low cost and easy to mass-produce. SUMMARY

[0005] To solve the above technical problems, the present application aims to provide a silk fibroin-sodium alginate-chitosan biomimetic leather and a preparation method and application thereof. The biomimetic leather prepared by compounding silk fibroin, sodium alginate and chitosan performs excellently in key mechanical indicators such as folding resistance, wear resistance and tensile properties, and the raw materials are widely available, and the preparation process is energy-saving and environmentally friendly. The biomimetic leather prepared by the present application is biodegradable, which not only reduces the environmental burden of waste disposal, but also significantly reduces the raw material cost and post-processing cost of biomimetic leather, combining environmental benefits with outstanding economic benefits.

[0006] The above-mentioned objective of this invention is achieved through the following technical solutions: The first aspect of this invention provides a method for preparing silk fibroin-sodium alginate-chitosan biomimetic leather, comprising the following steps: S1. Dissolve sodium alginate in water to obtain a sodium alginate solution; dissolve chitosan in an organic acid solution, add a coloring agent, heat and stir to obtain a chitosan solution; S2. Mix the silk fibroin solution with the sodium alginate solution, add calcium salt, then add the chitosan solution and waterborne polyurethane to prepare a mixed solution; the weight-average molecular weight of the silk fibroin in the silk fibroin solution is 100-300 kDa; the mass ratio of sodium alginate in the sodium alginate solution to silk fibroin in the silk fibroin solution is 1:(1-2). S3. Surface activation treatment is performed on the base fabric, the mixed solution is coated on the activated base fabric, and after drying, curing and ultrasonic bonding, the silk fibroin-sodium alginate-chitosan biomimetic leather is obtained.

[0007] In this invention, silk fibroin, as a biomimetic leather substrate, has outstanding advantages in terms of sustainability, biocompatibility, and functional designability: silk fibroin has excellent mechanical properties, with the tensile strength of pure silk fibroin film reaching 12-15 MPa, which can be further increased to 30-50 MPa (close to top-grade calfskin) after β-sheet crystallization regulation. Moreover, the elongation at break can be controlled by precisely adjusting the degree of crosslinking, allowing the leather to have both flexibility and tear resistance. Silk fibroin also has excellent biocompatibility and safety. As a non-toxic and harmless natural polymer material, its degradation products are amino acids, making it suitable for sensitive individuals. At the same time, silk fibroin is environmentally friendly and highly sustainable, with production energy consumption only 1 / 5 that of PU leather and 1 / 15 that of natural leather. Silk fibroin can be derived from silkworm waste, which reduces costs and achieves resource recycling. Sodium alginate can form a tough gel film through calcium ion crosslinking, giving the leather substrate good flexibility and strength. Chitosan, as a natural cationic polymer, has strong film-forming properties and can further enhance the tensile strength, wear resistance and other mechanical properties of the composite film through electrostatic interaction with sodium alginate.

[0008] The high strength and toughness of natural leather stems from its unique tertiary structure: collagen fibers with a diameter of 50-100 nm aggregate to form fiber bundles of 1-10 μm, which in turn construct a network layer, achieving 5000 J / m through a fiber slippage mechanism. 2 The fracture energy. Based on this biomimetic principle, this invention constructs a silk fibroin-sodium alginate-chitosan triple interpenetrating network. First, a silk fibroin solution and a sodium alginate solution are mixed, and Ca is added. 2+ After that, Ca 2+The carboxyl groups of sodium alginate crosslink through an "egg box" model, forming localized rigid crosslinking points. Simultaneously, the hydrophobic water regions of silk fibroin interweave within the sodium alginate network, entangled with the sodium alginate molecular chains through van der Waals forces, further reinforcing the network structure and providing rigid support. Subsequently, a chitosan solution is added, where the negatively charged sodium alginate and the positively charged chitosan combine through electrostatic interactions to form a stable composite system. The Schiff base reaction between the two further strengthens the interfacial bonding force, ultimately constructing a triple interpenetrating network structure that combines rigid support with excellent toughness. The resulting leather coating exhibits both strong surface activity and adhesion. Subsequently, ultrasonic bonding technology is used to adhere this coating to the surface of a plasma-activated base fabric. The resulting biomimetic leather possesses abrasion resistance, tensile strength, and biodegradability. Moreover, ultrasonic bonding technology can retain the activity of natural polymers while avoiding the emission of volatile organic compounds (VOCs) from traditional adhesives. This invention achieves triple network synergy enhancement, and the product has a total bio-based content of >95%, which is expected to replace highly polluting animal leather and provide a truly sustainable alternative to animal leather for high-end application scenarios.

[0009] Further, in step S1, sodium alginate is dissolved in water and heated and stirred to obtain a sodium alginate solution; the heating temperature is 40-80 ℃, the heating time is 5 min-5 h, and the heating is carried out under stirring conditions. The heating temperature can be 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, or any range formed by any two values; the heating time can be 5 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, or any range formed by any two values.

[0010] Further, in S1, the concentration of sodium alginate in the sodium alginate solution is 2-10 wt%, for example, it can be 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or a range formed by any two values.

[0011] If the concentration is <2 wt%, the network structure formed by subsequent cross-linking is sparse, and the mechanical properties of the material are insufficient; if the concentration is >10 wt%, the solution viscosity is too high, making it difficult to coat evenly and easily causing the coating to crack.

[0012] Further, in S1, the concentration of the organic acid in the organic acid solution is 1-10 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or a range formed by any two values.

[0013] Furthermore, in S1, the organic acid in the organic acid solution is selected from one or more of citric acid, acetic acid, malic acid, and tartaric acid.

[0014] Furthermore, the pH value of the organic acid solution is 2-5.

[0015] Furthermore, in S1, the choice of the colorant is not particularly limited, and commonly used leather dyeing colorants known in the art can be used, such as azo colorants, anthraquinone colorants, natural plant colorants, etc., preferably caramel color.

[0016] Further, in S1, the mass ratio of chitosan to colorant is (10-50):1, for example, it can be 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, or any range of two ratios.

[0017] Further, in S1, the heating temperature is 40-80 ℃, the heating time is 5 min-5 h, and the heating is carried out under stirring conditions. The heating temperature can be 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, or any range formed by any two values; the heating time can be 5 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, or any range formed by any two values.

[0018] Further, in S1, the concentration of chitosan in the chitosan solution is 2-10 wt%, for example, it can be 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any range formed by any two values. If the concentration is too low, the network structure will be sparse; if it is too high, the viscosity will be out of control.

[0019] Further, in S2, the concentration of silk fibroin in the silk fibroin solution is 1-5 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or a range formed by any two values.

[0020] Furthermore, the silk fibroin is prepared by degumming, dissolving, and purifying silk.

[0021] Further, in S2, the mass ratio of sodium alginate in the sodium alginate solution to silk fibroin in the silk fibroin solution is 1:(1-2), for example, it can be 1:1, 1:1.5, 1:2, or any range of two ratios.

[0022] Furthermore, in S2, the calcium salt is selected from one or more of calcium chloride, calcium acetate, calcium nitrate, and calcium bromide.

[0023] Further, in S2, the mass ratio of sodium alginate to calcium salt in the sodium alginate solution is (3-12):1, for example, it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, or any range of two ratios.

[0024] Further, in S2, the mass ratio of sodium alginate in the sodium alginate solution to chitosan in the chitosan solution is (1-3):1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, or any range of two ratios.

[0025] Further, in S2, the waterborne polyurethane is selected from one or more of waterborne polyester polyurethane, waterborne polyether polyurethane, and waterborne polycarbonate polyurethane. The addition of waterborne polyurethane is to improve the adhesion between the coating and the base fabric, and its waterborne characteristics do not affect the biodegradability of the material.

[0026] Further, in S2, the mass ratio of sodium alginate to the aqueous polyurethane in the sodium alginate solution is 1:(0.5-1.5), for example, it can be 1:0.5, 1:1, 1:1.5, or any range formed by any two ratios.

[0027] Furthermore, in S2, the mixing is carried out at room temperature under stirring conditions.

[0028] Furthermore, in S3, the selection of the base fabric is not particularly limited, and the base fabric type commonly used in the art for leather substrates can be selected, such as one of textile base fabrics (including natural fiber base fabrics, chemical fiber base fabrics, etc.), non-woven base fabrics, and knitted base fabrics.

[0029] Furthermore, in S3, the coating thickness is 0.5-5 mm.

[0030] Furthermore, in S3, the drying temperature is 40-60 ℃, and the drying time is 1-24 h.

[0031] Furthermore, in S3, the ultrasonic bonding process involves an ultrasonic frequency of 20-40 kHz, a pressure of 0.2-0.5 MPa, and a time of 1-20 min.

[0032] Further, in S3, the base fabric is surface activated using a plasma spray gun, and the mixed solution is scraped onto the activated base fabric. After drying, curing, and ultrasonic bonding, the silk fibroin-sodium alginate-chitosan biomimetic leather is obtained.

[0033] Furthermore, the plasma spray gun has a power of 100-1000 W and a processing speed of 1-10 m / min.

[0034] Furthermore, the plasma spray gun is an air plasma spray gun, a helium plasma spray gun, or an argon plasma spray gun.

[0035] The second aspect of the present invention provides a silk fibroin-sodium alginate-chitosan biomimetic leather prepared by the preparation method described in the first aspect.

[0036] Furthermore, the tensile strength of the silk fibroin-sodium alginate-chitosan biomimetic leather is ≥400 N / mm². 2 .

[0037] The third aspect of this invention provides an application of the silk fibroin-sodium alginate-chitosan biomimetic leather described in the second aspect in the preparation of leather products, such as clothing, bags, furniture, automotive interiors, medical devices, electronic products, sporting goods, and industrial consumables.

[0038] The beneficial effects of this invention are: 1. In the silk fibroin-sodium alginate-chitosan biomimetic leather provided by this invention, silk fibroin provides rigid support, and sodium alginate provides support through Ca... 2+ Crosslinking imparts toughness, chitosan strengthens interfacial bonding and introduces antibacterial properties, and the three work synergistically to achieve a balance between strength, toughness and functionality. This invention solves the problem of weak interfacial bonding between different polymers through the multiple effects of crosslinking using an egg carton model, van der Waals entanglement, and Schiff base reaction, significantly improving the overall mechanical properties of the material. The biomimetic leather provided by this invention has a total bio-based content of >95%, and uses ultrasonic bonding technology to replace traditional adhesives, avoiding VOC emissions. At the same time, the raw materials can be derived from silk waste, enabling resource recycling.

[0039] 2. The silk fibroin-sodium alginate-chitosan biomimetic leather prepared by this invention integrates multiple excellent properties. It not only has high strength and good ductility, but also excellent tensile strength, flexural strength and abrasion resistance, which can meet the durability requirements of practical applications; it also has good biodegradability, and the degradation products are non-toxic and can be absorbed by the environment or organisms, avoiding the burden on the environment after disposal; at the same time, it fully integrates the excellent mechanical properties of silk fibroin, the flexibility of sodium alginate and the antibacterial function of chitosan, achieving a synergistic unity of mechanical properties, durability, environmental protection and functionality. Attached Figure Description

[0040] Figure 1 An optical photograph of the silk fibroin-sodium alginate-chitosan biomimetic leather prepared in Example 1.

[0041] Figure 2 Optical photographs of the folded portion of the silk fibroin-sodium alginate-chitosan biomimetic leather prepared in Example 1 after a folding endurance test. Detailed Implementation

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0044] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available. Sodium carbonate (Na2CO3) was purchased from Sinopharm, item number 10019260; lithium bromide (LiBr) was purchased from Aladdin, item number L108934; acetic acid was purchased from Sinopharm, item number 10000208; chitosan was purchased from Beijing Bio-Lab Technology Co., Ltd., item number QN1535-AEM; caramel color was purchased from Zhengzhou Best Food Additives Co., Ltd., item number 122402; sodium alginate was purchased from Shanghai Hans Chemical Co., Ltd., item number S817373; calcium chloride was purchased from Sinopharm, item number 20011160; waterborne polyester polyurethane was purchased from Covestro, model Impranil@DL 1380; citric acid was purchased from Sinopharm, item number 10019418; calcium carbonate was purchased from Sinopharm, item number 10005760; waterborne polyether polyurethane was purchased from Huntsman, item number IROGRAN PE88-204; tartaric acid was purchased from Sinopharm, item number 10022018; calcium nitrate was purchased from Sinopharm, item number 80029062; waterborne polycarbonate polyurethane was purchased from Anhui Feimiao New Materials Co., Ltd., item number WPU-2946; hydrochloric acid was purchased from Sinopharm, item number 10011018.

[0045] Example 1 A method for preparing silk fibroin-sodium alginate-chitosan biomimetic leather includes the following steps: S1. Take 20 g of sodium alginate, add 500 g of deionized water, heat in an 80 ℃ water bath, and stir slowly for 2 h to prepare a sodium alginate solution; take 20 g of acetic acid, add 500 g of deionized water, stir to dissolve, pH=2.8, add 20 g of chitosan and 1 g of caramel color, heat in an 80 ℃ water bath, and stir slowly for 2 h to prepare a chitosan solution; add silk to 0.5 g / L Na2CO3 solution and boil for 1 h, then remove the degummed silk, wash it 3 times with water and dry it, then dissolve it in 9.3 M lithium bromide solution, and dialysis to purify it to obtain a silk fibroin solution with a concentration of 3 wt% and a weight average molecular weight of 150 kDa.

[0046] S2. Mix 250 mL of silk fibroin solution and 150 mL of sodium alginate solution at room temperature with stirring. Add 1 g of calcium chloride and stir until homogeneous. Then add 100 mL of chitosan solution and stir until homogeneous. Finally, add 8 g of waterborne polyester polyurethane and mix until homogeneous to prepare a mixed solution.

[0047] S3. Cut a 30 cm × 20 cm piece of textile base fabric and perform surface activation treatment on the fabric using an argon plasma spray gun. During the process, keep the nozzle 1 cm away from the fabric, set the power of the plasma spray gun to 600 W, and the processing speed to 1 m / min. Evenly coat the mixed solution obtained in S2 onto the activated textile base fabric to a thickness of 2 mm, and cure it in a 40 ℃ oven for 24 h. Finally, ultrasonically bond the mixture, setting the ultrasonic frequency to 30 kHz, the pressure to 0.5 MPa, and the ultrasonic time to 10 min, to obtain silk fibroin-sodium alginate-chitosan biomimetic leather. Optical photographs are shown below. Figure 1 As shown.

[0048] Example 2 A method for preparing silk fibroin-sodium alginate-chitosan biomimetic leather includes the following steps: S1. Take 15 g of sodium alginate, add 500 g of deionized water, heat in a 40 ℃ water bath, and stir slowly for 5 h to prepare a sodium alginate solution; take 15 g of citric acid, add 450 g of deionized water, stir to dissolve until pH=2.5, add 20 g of chitosan and 1 g of caramel color, heat in a 40 ℃ water bath, and stir slowly for 5 h to prepare a chitosan solution; add silk to 0.5 g / L Na2CO3 solution and boil for 1 h, then remove the degummed silk, wash it 3 times with water and dry it, then dissolve it in 9.3 M lithium bromide solution, and dialysis to purify it to obtain a silk fibroin solution with a concentration of 4 wt% and a weight average molecular weight of 200 kDa.

[0049] S2. Mix 150 mL of silk fibroin solution and 150 mL of sodium alginate solution at room temperature with stirring. Add 1 g of calcium acetate and stir until homogeneous. Then add 100 mL of chitosan solution and stir until homogeneous. Finally, add 4 g of waterborne polyether polyurethane and mix until homogeneous to prepare a mixed solution.

[0050] S3. Cut a 30 cm × 20 cm piece of nonwoven fabric base. Surface activate the nonwoven fabric base using an air plasma spray gun, maintaining a nozzle distance of 1 cm from the base. Set the plasma spray gun power to 1000 W and the processing speed to 2 m / min. Evenly coat the mixed solution obtained in S2 onto the activated nonwoven fabric base to a thickness of 2 mm. Cur the coating in a 60 ℃ oven for 4 h. Finally, ultrasonically bond the coating, setting the ultrasonic frequency to 40 kHz, the pressure to 0.5 MPa, and the ultrasonic time to 10 min to obtain silk fibroin-sodium alginate-chitosan biomimetic leather.

[0051] Example 3 A method for preparing silk fibroin-sodium alginate-chitosan biomimetic leather includes the following steps: S1. Take 10 g of sodium alginate, add 500 g of deionized water, heat in a 60 ℃ water bath, and stir slowly for 5 h to prepare a sodium alginate solution; take 10 g of tartaric acid, add 500 g of deionized water, stir to dissolve until pH=2.2, add 10 g of chitosan and 1 g of caramel color, heat in a 60 ℃ water bath, and stir slowly for 4 h to prepare a chitosan solution; add silk to 0.5 g / L Na2CO3 solution and boil for 1 h, then remove the degummed silk, wash it 3 times with water and dry it, then dissolve it in 9.3 M lithium bromide solution, and dialysis to purify it to obtain a silk fibroin solution with a concentration of 2 wt% and a weight average molecular weight of 250 kDa.

[0052] S2. Mix 200 mL of silk fibroin solution and 150 mL of sodium alginate solution at room temperature with stirring. Add 1 g of calcium nitrate and stir until homogeneous. Then add 100 mL of chitosan solution and stir until homogeneous. Finally, add 4 g of waterborne polycarbonate polyurethane and mix until homogeneous to prepare a mixed solution.

[0053] S3. Cut a 30 cm × 20 cm piece of knitted base fabric and perform surface activation treatment on the knitted base fabric using an air plasma spray gun. During the process, keep the nozzle 1 cm away from the knitted base fabric, set the power of the plasma spray gun to 800 W, and the treatment speed to 5 m / min. Evenly coat the mixed solution obtained in S2 onto the activated knitted base fabric to a thickness of 2 mm, place it in a 60 ℃ oven for curing for 2 h, and finally perform ultrasonic bonding. Set the ultrasonic frequency to 40 kHz, the pressure to 0.2 MPa, and the ultrasonic time to 15 min to obtain silk fibroin-sodium alginate-chitosan biomimetic leather.

[0054] Comparative Example 1 A method for preparing a silk fibroin-sodium alginate-chitosan biomimetic leather is basically the same as that in Example 1, except that in S1, the weight-average molecular weight of the silk fibroin solution is 50 kDa.

[0055] Comparative Example 2 A method for preparing a silk fibroin-sodium alginate-chitosan biomimetic leather is basically the same as that in Example 1, except that in S2, acetic acid is replaced with hydrochloric acid, 500 g of deionized water is added, and the mixture is stirred to dissolve. The pH is adjusted to 2.8 by adjusting the amount of hydrochloric acid.

[0056] Comparative Example 3 A method for preparing sodium alginate-chitosan biomimetic leather includes the following steps: S1. Take 20 g of sodium alginate, add 500 g of deionized water, heat in an 80 ℃ water bath, and stir slowly for 2 h to prepare a sodium alginate solution; take 20 g of acetic acid, add 500 g of deionized water, stir to dissolve, pH=2.8, add 20 g of chitosan and 1 g of caramel color, heat in an 80 ℃ water bath, and stir slowly for 2 h to prepare a chitosan solution.

[0057] S2. At room temperature, add 1 g of calcium chloride to 150 mL of sodium alginate solution, stir well, then add 100 mL of chitosan solution, stir well, then add 8 g of waterborne polyester polyurethane, mix well, and prepare a mixed solution.

[0058] S3. Cut a 30 cm × 20 cm piece of textile base fabric and perform surface activation treatment on the textile base fabric using a plasma spray gun. During the process, keep the nozzle 1 cm away from the textile base fabric, set the power of the plasma spray gun to 600 W, and the treatment speed to 1 m / min. Evenly coat the mixed solution obtained in S2 onto the activated textile base fabric to a thickness of 2 mm, place it in a 40 ℃ oven for curing for 24 h, and finally perform ultrasonic bonding. Set the ultrasonic frequency to 30 kHz, the pressure to 0.5 MPa, and the ultrasonic time to 10 min to obtain sodium alginate-chitosan biomimetic leather.

[0059] Comparative Example 4 A method for preparing silk fibroin-sodium alginate biomimetic leather includes the following steps: S1. Take 20 g of sodium alginate, add 500 g of deionized water, heat in an 80 ℃ water bath, and stir slowly for 2 h to prepare a sodium alginate solution; add silk to a 0.5 g / L Na2CO3 solution and boil for 1 h, then remove the degummed silk, wash it 3 times with water and dry it, then dissolve it in a 9.3 M lithium bromide solution and dialysis to purify it, to obtain a silk fibroin solution with a concentration of 3 wt% and a weight average molecular weight of 150 kDa.

[0060] S2. Mix 250 mL of silk fibroin solution and 150 mL of sodium alginate solution at room temperature with stirring. Add 1 g of calcium chloride and stir until homogeneous. Then add 8 g of waterborne polyester polyurethane and mix until homogeneous to prepare a mixed solution.

[0061] S3. Cut a 30 cm × 20 cm piece of textile base fabric and perform surface activation treatment on the textile base fabric using an argon plasma spray gun. During the process, keep the nozzle 1 cm away from the textile base fabric, set the power of the plasma spray gun to 600 W, and the treatment speed to 1 m / min. Uniformly coat the mixed solution obtained in S2 onto the activated textile base fabric to a thickness of 2 mm, place it in a 40 ℃ oven for curing for 24 h, and finally perform ultrasonic bonding. Set the ultrasonic frequency to 30 kHz, the pressure to 0.5 MPa, and the ultrasonic time to 10 min to obtain silk fibroin-sodium alginate biomimetic leather.

[0062] Comparative Example 5 A method for preparing a silk fibroin-sodium alginate-chitosan biomimetic leather is basically the same as that in Example 1, except that: in S2, 100 mL of chitosan solution and 150 mL of sodium alginate solution are mixed at room temperature and under stirring conditions, 1 g of calcium chloride is added, and after stirring evenly, 250 mL of silk fibroin solution is added and stirred evenly, and then 8 g of waterborne polyester polyurethane is added and mixed evenly to prepare a mixed solution.

[0063] Comparative Example 6 A method for preparing a silk fibroin-sodium alginate-chitosan biomimetic leather is basically the same as that in Example 1, except that in S2, 250 mL of silk fibroin solution is replaced with 100 mL of silk fibroin solution.

[0064] Test case The biomimetic leathers prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to tensile strength, abrasion resistance, and folding resistance tests, using the following methods: (1) Tensile strength test: First, fix both ends of the sample (i.e., bionic leather) to the upper and lower clamps of the tensile testing machine, ensuring that the sample is aligned with the axis of the clamps and is firmly clamped to avoid skewing or slippage affecting the accuracy of the data; then set the tensile speed to 100 mm / min, start the testing machine to stretch until the sample breaks, record the maximum load, the original length of the sample and the length at break, and then calculate the tensile strength according to the formula (unit: N / mm). 2 (or MPa) and elongation at break (unit: %): Tensile strength = maximum load / sample cross-sectional area; Elongation at break = [(Length at break - Original length) / Original length] × 100%.

[0065] (2) Abrasion resistance test: Fix the sample in the sample holder, ensure that the sample surface is in close contact with the sandpaper, set the test pressure to 9 kPa and the number of test cycles to 5000, start the Martindale abrasion tester to perform friction test; stop the machine after the test reaches the set number of cycles, and evaluate the wear degree of the sample by visual inspection with reference to Table 1.

[0066] Table 1

[0067] (3) Folding endurance test: Adjust the folding angle of the folding endurance tester to 135° and the folding speed to 100 times / minute. Then fix the sample on the upper and lower clamps of the equipment and ensure alignment. At the same time, set 5000 folding times according to the standard. Start the folding endurance tester to perform the folding test. The equipment will automatically record the number of folds. The machine will automatically stop when the set number of folds is reached or the sample breaks. During the test, the folded parts of the sample should be checked regularly to observe whether cracks, damage or delamination occur. If cracks occur, the surface crack length should be measured with a ruler.

[0068] The test results are shown in Table 2: Table 2

[0069] As can be seen from Table 2, the silk fibroin-sodium alginate-chitosan biomimetic leathers prepared in Examples 1-3 all have tensile strengths greater than 400 N / mm². 2 The processing requirements are met; the wear resistance grade is 5, indicating excellent wear resistance; optical photographs of the folded parts of the silk fibroin-sodium alginate-chitosan biomimetic leather prepared in Example 1 after folding endurance testing are shown below. Figure 2 As shown, after 5000 folding tests, there were no cracks, damage, or delamination, indicating good folding resistance.

[0070] Comparative Example 1 uses low molecular weight silk fibroin, which has shorter molecular chains, resulting in insufficient interpenetrating network links and a low content of β-sheets that can form physical cross-linking points in the structure. As a result, the tensile strength does not meet the requirements, and the abrasion resistance and flexural strength are also poor.

[0071] Comparative Example 2 uses an inorganic strong acid to dissolve chitosan. On the one hand, the solubility of chitosan in inorganic acids is weaker than that in organic acids. On the other hand, when inorganic acids are mixed with silk fibroin, non-specific hydrolysis of silk fibroin will occur (the degree of hydrolysis of silk fibroin in organic acids is significantly lower than that in inorganic acids). In addition, high-temperature drying aggravates instantaneous hydrolysis, resulting in the biomimetic leather having lower tensile strength, abrasion resistance and folding resistance than the example.

[0072] Comparative Example 3 did not contain silk fibroin; it was simply a binary mixture of sodium alginate and chitosan. Due to the lack of structural penetration and physical cross-linking of silk fibroin in the three-component system, the biomimetic leather prepared by this binary system had lower tensile strength, abrasion resistance, and folding resistance than the examples, and could not meet the processing requirements.

[0073] Comparative Example 4 did not contain chitosan and was only a binary mixture of silk fibroin and sodium alginate. Due to the lack of electrostatic binding effect of chitosan in the three-component system, the tensile strength, abrasion resistance, and folding resistance of the biomimetic leather prepared by this binary system were all lower than those of the examples, and could not meet the processing requirements.

[0074] Comparative Example 5 changed the order of adding silk fibroin solution and chitosan solution: chitosan and sodium alginate were mixed first, and after calcium salt was added for cross-linking, the solution had already formed a gel. The silk fibroin added later could not penetrate the cross-linking network and could only form mechanical mixing with the chitosan-sodium alginate system. It could not build an interpenetrating network structure. Therefore, the tensile strength, abrasion resistance and folding resistance of the biomimetic leather were lower than those of the example and did not meet the processing requirements.

[0075] Comparative Example 6 reduced the mass ratio of sodium alginate to silk fibroin, resulting in insufficient physical cross-linking points formed by silk fibroin penetrating sodium alginate in the structure. The tensile strength, abrasion resistance, and folding resistance of the prepared biomimetic leather were all lower than those of the Example, and could not meet the processing requirements.

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a silk fibroin-sodium alginate-chitosan biomimetic leather, characterized in that, Includes the following steps: S1. Dissolve sodium alginate in water to obtain a sodium alginate solution; dissolve chitosan in an organic acid solution, add a coloring agent, heat and stir to obtain a chitosan solution; S2. Mix the silk fibroin solution with the sodium alginate solution, add calcium salt, then add the chitosan solution and waterborne polyurethane to prepare a mixed solution; The weight-average molecular weight of the silk fibroin in the silk fibroin solution is 100-300 kDa; the mass ratio of sodium alginate to silk fibroin in the sodium alginate solution is 1:(1-2). S3. Surface activation treatment is performed on the base fabric, the mixed solution is coated on the activated base fabric, and after drying, curing and ultrasonic bonding, the silk fibroin-sodium alginate-chitosan biomimetic leather is obtained.

2. The preparation method according to claim 1, characterized in that, In S1, the concentration of sodium alginate in the sodium alginate solution is 2-10 wt%.

3. The preparation method according to claim 1, characterized in that, In S1, the organic acid in the organic acid solution is selected from one or more of citric acid, acetic acid, malic acid and tartaric acid; the mass ratio of chitosan to the colorant is (10-50):1; and the concentration of chitosan in the chitosan solution is 2-10 wt%.

4. The preparation method according to claim 1, characterized in that, In S2, the concentration of silk fibroin in the silk fibroin solution is 1-5 wt%.

5. The preparation method according to claim 1, characterized in that, In S2, the calcium salt is selected from one or more of calcium chloride, calcium acetate, calcium nitrate and calcium bromide; the mass ratio of sodium alginate to the calcium salt in the sodium alginate solution is (3-12):1; the mass ratio of sodium alginate to chitosan in the sodium alginate solution is (1-3):

1.

6. The preparation method according to claim 1, characterized in that, In S2, the waterborne polyurethane is selected from one or more of waterborne polyester polyurethane, waterborne polyether polyurethane, and waterborne polycarbonate polyurethane; the mass ratio of sodium alginate to waterborne polyurethane in the sodium alginate solution is 1:(0.5-1.5).

7. The preparation method according to claim 1, characterized in that, In S3, the ultrasonic bonding process uses an ultrasonic frequency of 20-40 kHz, a pressure of 0.2-0.5 MPa, and a time of 1-20 min.

8. The preparation method according to claim 1, characterized in that, In step S3, the base fabric is surface activated using a plasma spray gun. The mixed solution is then coated onto the activated base fabric, dried, cured, and ultrasonically bonded to obtain the silk fibroin-sodium alginate-chitosan biomimetic leather. The power of the plasma spray gun is 100-1000 W, and the processing speed is 1-10 m / min.

9. A silk fibroin-sodium alginate-chitosan biomimetic leather prepared by the preparation method according to any one of claims 1-8.

10. The application of the silk fibroin-sodium alginate-chitosan biomimetic leather according to claim 9 in the preparation of leather products.

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