Silk fibroin-sodium alginate-chitosan biomimetic leather and preparation method and application thereof

Abstract

The application discloses a silk fibroin-sodium alginate-chitosan biomimetic leather and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a silk fibroin solution and a sodium alginate solution, adding calcium salt, continuously adding a chitosan solution and an aqueous polyurethane, and obtaining a mixed solution; performing surface activation treatment on a base cloth, coating the mixed solution on the activated base cloth, and performing drying and solidification and ultrasonic lamination to obtain the silk fibroin-sodium alginate-chitosan biomimetic leather. The silk fibroin-sodium alginate-chitosan biomimetic leather prepared by the application has high strength, good ductility, excellent tensile resistance, folding resistance and wear resistance, and good biodegradability, can reduce the burden of waste disposal on the environment, can significantly reduce the raw material cost and post-processing cost of the biomimetic leather, and has 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 object of the present application is achieved by the following technical solutions:

[0007] The present application provides a preparation method of silk fibroin-sodium alginate-chitosan biomimetic leather, comprising the following steps:

[0008] S1. Dissolve sodium alginate in water to obtain a sodium alginate solution; dissolve chitosan in an organic acid solution, add a colorant, and then heat and stir to obtain a chitosan solution;

[0009] S2. Mix the silk fibroin solution with the sodium alginate solution, add calcium salt, and then mix the chitosan solution with aqueous polyurethane to prepare a mixed solution; the weight average molecular weight of 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);

[0010] S3. Perform surface activation treatment on the base cloth, coat the mixed solution on the activated base cloth, and then perform drying and curing and ultrasonic bonding to obtain the silk fibroin-sodium alginate-chitosan biomimetic leather.

[0011] In the present application, silk fibroin is used as the biomimetic leather substrate, which has advantages in sustainability, biocompatibility, and functional designability: the mechanical properties of silk fibroin are excellent, the tensile strength of pure silk fibroin film can reach 12-15 MPa, and after β-fold crystallization regulation, it can be further improved to 30-50 MPa (close to the top calf leather), and the elongation at break can be controlled by accurately adjusting the crosslinking degree, so that the leather has both flexibility and tear resistance; silk fibroin also has excellent biocompatibility and safety, as a non-toxic and harmless natural polymer material, the degradation product is amino acid, which is suitable for sensitive people to use; at the same time, silk fibroin is environmentally friendly and sustainable, the production energy consumption is only 1 / 5 of PU leather and 1 / 15 of natural leather; silk fibroin can come from silk waste, which not only reduces the cost but also realizes resource recycling. Sodium alginate can be crosslinked by calcium ions to form a tough gel film, which gives the leather substrate good flexibility and strength, and chitosan, as a natural cationic polymer, has strong film-forming property, and can further enhance the mechanical properties such as tensile strength and wear resistance of the composite film through electrostatic interaction with sodium alginate.

[0012] The high strength and toughness of natural leather is due to its unique three-level structure: collagen fibers with a diameter of 50-100 nm aggregate to form fiber bundles with a diameter of 1-10 μm, which in turn form a network layer, and the fiber slip mechanism is used to achieve a breaking energy of 5000 J / m 2 . Based on this biomimetic principle, a silk fibroin-sodium alginate-chitosan triple interpenetrating network is constructed, first, the silk fibroin solution is mixed with the sodium alginate solution, then Ca 2+ is added, and then the chitosan solution is added,2+ The carboxyl groups of sodium alginate are cross-linked through the "egg box" model to form local rigid cross-linking points; at the same time, the hydrophobic domains of silk fibroin are inserted into the sodium alginate network, and are entangled with the sodium alginate molecular chains through van der Waals force, further reinforcing the network structure and providing rigid support; then, the negatively charged sodium alginate and the positively charged chitosan are combined through electrostatic interaction to form a stable composite system, and the Schiff base reaction between the two further strengthens the interfacial bonding force, finally constructing a triple interpenetrating network structure with rigid support and excellent toughness; the leather coating prepared by the method has extremely strong surface activity and adhesion; subsequently, the coating is adhered to the surface of the base fabric treated by plasma activation by using the ultrasonic bonding technology, and the finally formed biomimetic leather has wear resistance, tensile resistance and biodegradability, and the ultrasonic bonding technology can not only preserve the activity of natural macromolecules, but also avoid the emission of volatile organic compounds (VOC) caused by traditional adhesives. The invention realizes triple network synergistic enhancement, and the product has a total bio-based content of >95%, which is expected to replace high-pollution animal leather and provide a truly sustainable animal leather replacement solution for high-end application scenarios.

[0013] Further, in S1, the 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. The heating temperature can be 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, or a range value formed by any two of the values; the heating time can be 5 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, or a range value formed by any two of the values.

[0014] 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 value formed by any two of the values.

[0015] 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, it is difficult to uniformly coat, and it is easy to cause the coating to crack.

[0016] 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 value formed by any two of the values.

[0017] Further, 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.

[0018] Further, the pH value of the organic acid solution is 2-5.

[0019] Further, in S1, the colorant is not particularly limited in selection, and a colorant commonly used in leather dyeing known in the art can be selected, such as an azo colorant, an anthraquinone colorant, a natural plant colorant, etc., and preferably caramel color.

[0020] Further, in S1, the mass ratio of the chitosan to the colorant is (10-50):1, such as 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, or a range value formed by any two of the values.

[0021] Further, in S1, the heating temperature is 40-80 ℃, the heating time is 5 min-5 h, and the heating is performed under stirring. The heating temperature can be 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, or a range value formed by any two of the values; the heating time can be 5 min, 30 min, 1 h, 2 h, 3 h, 4 h, 5 h, or a range value formed by any two of the values.

[0022] Further, in S1, the concentration of chitosan in the chitosan solution is 2-10 wt%, such as 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or a range value formed by any two of the values. Too low concentration results in sparse network structure, and too high concentration results in uncontrolled viscosity.

[0023] Further, in S2, the concentration of silk fibroin in the silk fibroin solution is 1-5 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or a range value formed by any two of the values.

[0024] Further, the silk fibroin is prepared by degumming, dissolving and purifying of silk.

[0025] 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), such as 1:1, 1:1.5, 1:2, or a range value formed by any two of the values.

[0026] Further, in S2, the calcium salt is selected from one or more of calcium chloride, calcium acetate, calcium nitrate and calcium bromide.

[0027] Further, in S2, the mass ratio of sodium alginate in the sodium alginate solution to the calcium salt 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 a range value formed by any two ratio values.

[0028] 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 a range value formed by any two ratio values.

[0029] Further, in S2, the aqueous polyurethane is selected from one or more of aqueous polyester polyurethane, aqueous polyether polyurethane, and aqueous polycarbon polyurethane. The addition of the aqueous polyurethane is to improve the adhesion of the coating to the base cloth, and its aqueous characteristics do not affect the biodegradability of the material.

[0030] Further, in S2, the mass ratio of sodium alginate in the sodium alginate solution to the aqueous polyurethane is 1:(0.5-1.5), for example, it can be 1:0.5, 1:1, 1:1.5, or a range value formed by any two ratio values.

[0031] Further, in S2, the mixing is carried out at room temperature under stirring conditions.

[0032] Further, in S3, the selection of the base cloth is not particularly limited, and a base cloth type commonly used in the art for leather substrates can be selected, for example, selected from one of a woven base cloth (including a natural fiber base cloth, a chemical fiber base cloth, etc.), a non-woven base cloth, and a knitted base cloth.

[0033] Further, in S3, the thickness of the coating is 0.5-5 mm.

[0034] Further, in S3, the temperature of the drying is 40-60 ℃, and the time of the drying is 1-24 h.

[0035] Further, in S3, the ultrasonic frequency of the ultrasonic lamination is 20-40 kHz, the pressure is 0.2-0.5 MPa, and the time is 1-20 min.

[0036] Further, in S3, the surface activation treatment of the base cloth is carried out using a plasma spray gun, the mixed solution is scraped and coated on the activated base cloth, and after drying and curing, ultrasonic lamination is carried out to obtain the silk fibroin-sodium alginate-chitosan biomimetic leather.

[0037] Further, the power of the plasma spray gun is 100-1000 W, and the processing speed is 1-10 m / min.

[0038] Further, the plasma torch is an air plasma torch, a helium plasma torch or an argon plasma torch.

[0039] The second aspect of the present application provides a silk fibroin-sodium alginate-chitosan biomimetic leather prepared by the preparation method of the first aspect.

[0040] Further, the tensile strength of the silk fibroin-sodium alginate-chitosan biomimetic leather is greater than or equal to 400 N / mm 2 .

[0041] The third aspect of the present application provides an application of the silk fibroin-sodium alginate-chitosan biomimetic leather of the second aspect in the preparation of leather products, such as clothing, luggage, furniture, automotive interiors, medical devices, electronic products, sports equipment, industrial consumables, etc.

[0042] The beneficial effects of the present application are:

[0043] 1. In the silk fibroin-sodium alginate-chitosan biomimetic leather provided by the present application, the silk fibroin provides rigid support, the sodium alginate imparts toughness through Ca 2+ crosslinking, and the chitosan strengthens the interfacial bonding and introduces antibacterial properties, and the three work together to achieve a balance of strength, toughness and functionality; the present application solves the problem of weak interfacial bonding between different polymers through the multiple effects of egg box model crosslinking, van der Waals force winding and Schiff base reaction, significantly improving the overall mechanical properties of the material; the biomimetic leather provided by the present application has a total bio-based content of > 95%, and uses ultrasonic bonding technology instead of traditional adhesives to avoid VOC emissions, while the raw materials can come from silk waste, enabling resource recycling.

[0044] 2. The silk fibroin-sodium alginate-chitosan biomimetic leather prepared by the present application integrates multiple excellent properties, not only has high strength and good ductility, but also has excellent tensile resistance, folding resistance and wear resistance, and can meet the durability requirements in actual 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 flexible properties of sodium alginate and the antibacterial function of chitosan, achieving the synergistic unity of mechanical properties, durability, environmental friendliness and functionality. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 Optical photograph of the silk fibroin-sodium alginate-chitosan biomimetic leather prepared in Example 1.

[0046] Figure 2Optical photo of folding part of the silk fibroin-sodium alginate-chitosan biomimetic leather prepared in Example 1 after folding resistance test. DETAILED DESCRIPTION

[0047] 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 application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0048] The present application is further described in detail by reference to the following drawings and examples. The examples are provided for illustration purposes only and are not intended to be limiting.

[0049] The experimental methods used in the following examples are routine methods unless otherwise specified. The materials, reagents, etc. used are commercially available unless otherwise specified. Sodium carbonate (Na2CO3) was purchased from Sinopharm, with the item number 10019260; lithium bromide (LiBr) was purchased from Aldrich, with the item number L108934; acetic acid was purchased from Sinopharm, with the item number 10000208; chitosan was purchased from Beijing Bao'elai Bosi Technology Co., Ltd., with the item number QN1535-AEM; caramel color was purchased from Zhengzhou Baisite Food Additives Co., Ltd., with the item number 122402; sodium alginate was purchased from Shanghai Hansi Chemical Co., Ltd., with the item number S817373; calcium chloride was purchased from Sinopharm, with the item number 20011160; aqueous polyester-based polyurethane was purchased from Covestro, with the item number Impranil@DL 1380; citric acid was purchased from Sinopharm, with the item number 10019418; calcium carbonate was purchased from Sinopharm, with the item number 10005760; aqueous polyether-based polyurethane was purchased from Huntsman, with the item number IROGRAN PE88-204; tartaric acid was purchased from Sinopharm, with the item number 10022018; calcium nitrate was purchased from Sinopharm, with the item number 80029062; aqueous polycarbonate-based polyurethane was purchased from Anhui Feisun New Material Co., Ltd., with the item number WPU-2946; hydrochloric acid was purchased from Sinopharm, with the item number 10011018.

[0050] Example 1

[0051] A preparation method of a silk fibroin-sodium alginate-chitosan biomimetic leather, comprising the following steps:

[0052] S1. Take 20 g of sodium alginate, add 500 g of deionized water, heat in a 80 ℃ water bath, slowly stir for 2 h, prepare sodium alginate solution; take 20 g of acetic acid, add 500 g of deionized water, after stirring and dissolving, pH = 2.8, add 20 g of chitosan and 1 g of caramel color, heat in a 80 ℃ water bath, slowly stir for 2 h, prepare chitosan solution; the silk is added to 0.5 g / L Na2CO3 solution and boiled for 1 h, then the degummed silk is taken out, washed with water for 3 times and dried, then dissolved in 9.3 M lithium bromide solution, dialyzed and purified to obtain a silk fibroin solution with a concentration of 3 wt% and a weight average molecular weight of 150 kDa.

[0053] S2. Mix 250 mL of silk fibroin solution with 150 mL of sodium alginate solution at room temperature and under stirring conditions, add 1 g of calcium chloride, stir uniformly, then add 100 mL of chitosan solution, stir uniformly, then add 8 g of water-based polyester polyurethane, mix uniformly to prepare a mixed solution.

[0054] S3. Cut a piece of 30 cm×20 cm textile substrate, use argon plasma spray gun to perform surface activation treatment on the textile substrate, keep the nozzle distance from the textile substrate at 1 cm during the process, set the power of the plasma spray gun at 600 W, and the processing speed at 1 m / min. The mixed solution obtained in S2 is uniformly scraped and coated on the activated textile substrate, the scraping thickness is 2 mm, placed in a 40 ℃ oven for curing for 24 h, finally ultrasonic bonding, set the ultrasonic frequency at 30 kHz, the pressure at 0.5 MPa, and the ultrasonic time at 10 min, to obtain a silk fibroin-sodium alginate-chitosan biomimetic leather, the optical photograph is as shown in Figure 1

[0055] Example 2

[0056] A preparation method of a silk fibroin-sodium alginate-chitosan biomimetic leather, comprising the following steps:

[0057] S1. Take 15 g of sodium alginate, add 500 g of deionized water, heat in a 40 ℃ water bath, slowly stir for 5 h, prepare sodium alginate solution; take 15 g of citric acid, add 450 g of deionized water, stir and dissolve, then pH = 2.5, add 20 g of chitosan and 1 g of caramel color, heat in a 40 ℃ water bath, slowly stir for 5 h, prepare chitosan solution; the silk is added to 0.5 g / L Na2CO3 solution and boiled for 1 h, then the degummed silk is taken out, washed with water for 3 times and dried, then dissolved in 9.3 M lithium bromide solution, dialyzed and purified to obtain a silk fibroin solution with a concentration of 4 wt% and a weight average molecular weight of 200 kDa.

[0058] ​S2. 150 mL of the silk fibroin solution was mixed with 150 mL of the sodium alginate solution at room temperature under stirring, 1 g of calcium acetate was added, after uniform stirring, 100 mL of the chitosan solution was added, after uniform stirring, 4 g of the aqueous polyether type polyurethane was added, and the mixture was uniformly prepared to obtain a mixed solution.

[0059] S3. A piece of non-woven fabric base cloth with a size of 30 cm*20 cm was cut, and the non-woven fabric base cloth was subjected to surface activation treatment by using an air plasma spray gun, during the process, the nozzle distance from the non-woven fabric base cloth was kept at 1 cm, the power of the plasma spray gun was set to 1000 W, and the processing speed was 2 m / min. The mixed solution obtained in S2 was uniformly scraped and coated on the activated non-woven fabric base cloth, the scraping thickness was 2 mm, and the non-woven fabric base cloth was placed in a 60 ℃ oven for curing for 4 h, and finally ultrasonic lamination was performed, the ultrasonic frequency was set to 40 kHz, the pressure was 0.5 MPa, and the ultrasonic time was 10 min, thereby obtaining a silk fibroin-sodium alginate-chitosan biomimetic leather.

[0060] Example 3

[0061] A preparation method of a silk fibroin-sodium alginate-chitosan biomimetic leather, comprising the following steps:

[0062] S1. 10 g of sodium alginate was added into 500 g of deionized water, and placed in a 60 ℃ water bath for heating, and slowly stirred for 5 h to prepare a sodium alginate solution; 10 g of tartaric acid was added into 500 g of deionized water, and stirred and dissolved to obtain a solution with a pH of 2.2, 10 g of chitosan and 1 g of caramel color were added, and placed in a 60 ℃ water bath for heating, and slowly stirred for 4 h to prepare a chitosan solution; the silk was boiled in a 0.5 g / L Na2CO3 solution for 1 h, the degummed silk was taken out, washed with water for 3 times, dried, dissolved in a 9.3 M lithium bromide solution, and dialyzed to obtain a silk fibroin solution with a concentration of 2 wt% and a weight average molecular weight of 250 kDa.

[0063] S2. 200 mL of the silk fibroin solution was mixed with 150 mL of the sodium alginate solution at room temperature under stirring, 1 g of calcium nitrate was added, after uniform stirring, 100 mL of the chitosan solution was added, after uniform stirring, 4 g of the aqueous polycarbon type polyurethane was added, and the mixture was uniformly prepared to obtain a mixed solution.

[0064] S3. Cut a piece of 30 cm x 20 cm knitted substrate, and use an air plasma spray gun to perform surface activation treatment on the knitted substrate, keeping the nozzle distance of 1 cm from the knitted substrate, setting the power of the plasma spray gun to 800 W, and the processing speed to 5 m / min. Uniformly coat the mixed solution obtained in S2 on the activated knitted substrate, with a coating thickness of 2 mm, place it in a 60 ℃ oven for curing for 2 h, and finally perform ultrasonic bonding, setting the ultrasonic frequency to 40 kHz, the pressure to 0.2 MPa, and the ultrasonic time to 15 min, to obtain a silk fibroin-sodium alginate-chitosan biomimetic leather.

[0065] Comparative Example 1

[0066] A method for preparing a silk fibroin-sodium alginate-chitosan biomimetic leather, which is basically the same as Example 1, except that in S1, the weight average molecular weight of the silk fibroin solution is 50 kDa.

[0067] Comparative Example 2

[0068] A method for preparing a silk fibroin-sodium alginate-chitosan biomimetic leather, which is basically the same as Example 1, except that in S2, acetic acid is replaced by hydrochloric acid, 500 g of deionized water is added, and the pH is adjusted to 2.8 by the amount of hydrochloric acid.

[0069] Comparative Example 3

[0070] A method for preparing a sodium alginate-chitosan biomimetic leather, comprising the following steps:

[0071] S1. Take 20 g of sodium alginate, add 500 g of deionized water, and place it in a 80 ℃ water bath for heating, and slowly stir for 2 h to prepare a sodium alginate solution; take 20 g of acetic acid, add 500 g of deionized water, and stir to dissolve, then adjust the pH to 2.8, add 20 g of chitosan and 1 g of caramel color, place it in a 80 ℃ water bath for heating, and slowly stir for 2 h to prepare a chitosan solution.

[0072] S2. At room temperature, add 1 g of calcium chloride to 150 mL of the sodium alginate solution, stir until uniform, then add 100 mL of the chitosan solution, stir until uniform, then add 8 g of water-based polyester polyurethane, and mix until uniform to prepare a mixed solution.

[0073] S3. Cut a piece of 30 cm x 20 cm textile substrate, and use a plasma spray gun to activate the surface of the textile substrate, keeping the nozzle 1 cm away from the textile substrate during the process, and setting the power of the plasma spray gun to 600 W and the processing speed to 1 m / min. Uniformly spread the mixed solution obtained in S2 on the activated textile substrate by blade coating, with a coating thickness of 2 mm, and place it in a 40 °C oven for curing for 24 h. Finally, perform ultrasonic bonding, setting the ultrasonic frequency to 30 kHz, the pressure to 0.5 MPa, and the ultrasonic time to 10 min, to obtain the sodium alginate-chitosan biomimetic leather.

[0074] Comparative Example 4

[0075] A method for preparing a silk fibroin-sodium alginate biomimetic leather, comprising the following steps:

[0076] S1. Take 20 g of sodium alginate, add 500 g of deionized water, and place it in a 80 °C water bath for heating, with slow stirring for 2 h, to prepare a sodium alginate solution. Add the silk to a 0.5 g / L Na2CO3 solution and boil for 1 h, then remove the degummed silk, wash it with water for 3 times, and dry it, and then dissolve it in a 9.3 M lithium bromide solution, and dialyze and purify it, to obtain a silk fibroin solution with a concentration of 3 wt% and a weight average molecular weight of 150 kDa.

[0077] S2. Mix 250 mL of the silk fibroin solution with 150 mL of the sodium alginate solution at room temperature under stirring, add 1 g of calcium chloride, stir until uniform, then add 8 g of water-based polyester polyurethane, and mix until uniform, to prepare a mixed solution.

[0078] S3. Cut a piece of 30 cm x 20 cm textile substrate, and use a plasma spray gun to activate the surface of the textile substrate, keeping the nozzle 1 cm away from the textile substrate during the process, and setting the power of the plasma spray gun to 600 W and the processing speed to 1 m / min. Uniformly spread the mixed solution obtained in S2 on the activated textile substrate by blade coating, with a coating thickness of 2 mm, and place it in a 40 °C oven for curing for 24 h. Finally, perform ultrasonic bonding, setting the ultrasonic frequency to 30 kHz, the pressure to 0.5 MPa, and the ultrasonic time to 10 min, to obtain the silk fibroin-sodium alginate biomimetic leather.

[0079] Comparative Example 5

[0080] A preparation method of a silk fibroin-sodium alginate-chitosan biomimetic leather, which is basically the same as that of Example 1, except that in S2, 100 mL of a chitosan solution is mixed with 150 mL of a sodium alginate solution at room temperature under stirring, 1 g of calcium chloride is added, after uniform stirring, 250 mL of a silk fibroin solution is added, uniform stirring is performed, 8 g of a water-based polyester polyurethane is added, and uniform mixing is performed to prepare a mixed solution.

[0081] Comparative Example 6

[0082] A preparation method of a silk fibroin-sodium alginate-chitosan biomimetic leather, which is basically the same as that of Example 1, except that in S2, 250 mL of a silk fibroin solution is replaced by 100 mL of a silk fibroin solution.

[0083] Test Example

[0084] The biomimetic leather prepared in Examples 1-3 and Comparative Examples 1-6 is subjected to tensile strength, wear resistance, and folding resistance tests, and the test method is as follows:

[0085] (1) Tensile strength test: first, fix the two ends of the sample (i.e., the biomimetic leather) to the upper and lower clamps of a tensile testing machine, respectively, to ensure that the sample is aligned with the clamp axis and firmly clamped, avoiding skewing or slipping to affect data accuracy; then set the tensile speed to 100 mm / min, start the testing machine for tensile test 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 (unit: N / mm 2 or MPa) and the elongation at break (unit: %) according to the formula:

[0086] Tensile strength = maximum load / sample cross-sectional area;

[0087] Elongation at break = [(length at break-original length) / original length] x 100%.

[0088] (2) Wear resistance test: fix the sample in the sample holder to ensure that the surface of the sample is in close contact with the sandpaper, set the test pressure to 9 kPa and the test number to 5000, start the Martindale wear resistance testing machine for friction test; stop the machine when the test reaches the set number, and evaluate the wear degree of the sample by visual method according to Table 1.

[0089] Table 1

[0090]

[0091] (3) Folding resistance test: adjust the folding angle of the folding tester to 135°, set the folding speed to 100 times / min, then fix the sample on the upper and lower clamps of the equipment and ensure alignment, and set 5000 folding times according to the standard; start the folding tester for folding test, and the equipment automatically records the folding times and automatically stops when the set number of times or the sample is broken; during the test, the folding part of the sample needs to be checked regularly to observe whether cracks, damage or delamination occur, and if cracks occur, measure the length of the surface cracks with a ruler.

[0092] The test results are shown in Table 2:

[0093] Table 2

[0094]

[0095] As can be seen from Table 2, the tensile strength of the silk fibroin-sodium alginate-chitosan biomimetic leather prepared in Examples 1-3 is greater than 400 N / mm 2 , which meets the processing requirements; the wear resistance grade is 5, and the wear resistance is excellent; the optical photograph of the folding part of the silk fibroin-sodium alginate-chitosan biomimetic leather prepared in Example 1 after the folding resistance test is shown in Figure 2 , and after 5000 folding tests, there is no crack, damage or delamination, and the folding resistance is good.

[0096] Comparative Example 1 uses low molecular weight silk fibroin, which has a short molecular chain, resulting in insufficient interpenetrating network linking points, and the content of β-sheet that can form physical crosslinking points in the structure is low, so that the final tensile strength does not meet the requirements, and the wear resistance and folding resistance are also poor.

[0097] Comparative Example 2 uses inorganic strong acid to dissolve chitosan, on the one hand, the solubility of chitosan in inorganic acid is weaker than that in organic acid, and on the other hand, after mixing with silk fibroin, it will cause non-specific hydrolysis of silk fibroin (the degree of hydrolysis of silk fibroin in organic acid is significantly lower than that in inorganic acid), and the high temperature drying further accelerates the instantaneous hydrolysis, so that the tensile strength, wear resistance and folding resistance of the biomimetic leather are lower than those of the examples.

[0098] Comparative Example 3 does not add silk fibroin, but only a binary mixture of sodium alginate-chitosan. Due to the lack of structural penetration and physical crosslinking of silk fibroin in the three-component system, the tensile strength, wear resistance and folding resistance of the biomimetic leather prepared by the binary system are lower than those of the examples, which cannot meet the processing requirements.

[0099] Comparative Example 4 does not add chitosan, but only a binary mixture of silk fibroin-sodium alginate. Due to the lack of electrostatic bonding of chitosan in the three-component system, the tensile strength, wear resistance and folding resistance of the biomimetic leather prepared by the binary system are lower than those of the examples, which cannot meet the processing requirements.

[0100] Comparative Example 5 changes the adding sequence of the silk fibroin solution and the chitosan solution: the chitosan and sodium alginate are mixed first, and the solution has formed a gel after cross-linking with calcium salt, the silk fibroin added subsequently is difficult to penetrate the cross-linking network, and can only form a mechanical mixture with the chitosan-sodium alginate system, and thus the interpenetrating network structure cannot be constructed, and thus the tensile strength, wear resistance and folding resistance of the artificial leather are all lower than those of the examples, and cannot meet the processing requirements.

[0101] Comparative Example 6 reduces the mass ratio of sodium alginate and silk fibroin, and thus the number of silk fibroin penetrating the physical cross-linking points formed by sodium alginate is insufficient, and thus the tensile strength, wear resistance and folding resistance of the prepared artificial leather are all lower than those of the examples, and cannot meet the processing requirements.

[0102] Obviously, the above examples of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Those skilled in the art should understand that on the basis of the above description, other different forms of changes or variations can also be made. Here, it is not necessary and also impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A method for preparing a silk fibroin-sodium alginate-chitosan biomimetic leather, characterized by, The method comprises the following steps: S1. Dissolve sodium alginate in water to obtain a sodium alginate solution; the concentration of sodium alginate in the sodium alginate solution is 2-10 wt%; dissolve chitosan in an organic acid solution, add a colorant, and then heat and stir to obtain a chitosan solution; the concentration of chitosan in the chitosan solution is 2-10 wt%; S2. Mix a silk fibroin solution with the sodium alginate solution, add calcium salt, and then mix the chitosan solution with aqueous polyurethane to prepare a mixed solution; The weight average molecular weight of 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); the concentration of silk fibroin in the silk fibroin solution is 1-5 wt%; S3. Perform surface activation treatment on a base fabric by using a plasma spray gun, coat the mixed solution on the activated base fabric, and then perform drying and curing and ultrasonic bonding to obtain the silk fibroin-sodium alginate-chitosan biomimetic leather.

2. The production method according to claim 1, characterized by, 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.

3. 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 in the sodium alginate solution to the calcium salt is (3-12):1; the mass ratio of sodium alginate in the sodium alginate solution to chitosan in the chitosan solution is (1-3):

1.

4. The method of claim 1, wherein, In S2, the aqueous polyurethane is selected from one or more of aqueous polyester polyurethane, aqueous polyether polyurethane, and aqueous polycarbon polyurethane; the mass ratio of sodium alginate in the sodium alginate solution to the aqueous polyurethane is 1:(0.5-1.5).

5. The production method according to claim 1, characterized by, In S3, the ultrasonic frequency of the ultrasonic bonding is 20-40 kHz, the pressure is 0.2-0.5 MPa, and the time is 1-20 min.

6. The production method according to claim 1, characterized by, In S3, the surface activation treatment on the base fabric is performed by using a plasma spray gun, the mixed solution is blade-coated on the activated base fabric, and then drying and curing and ultrasonic bonding are performed 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.

7. The silk fibroin-sodium alginate-chitosan biomimetic leather prepared by the preparation method in any one of claims 1-6.

8. Use of the silk fibroin-sodium alginate-chitosan biomimetic leather in claim 7 in the preparation of leather products.

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