A degradable leather based on mycelium fiber and a preparation method thereof

Abstract

The application discloses a kind of degradable leather based on mycelium fiber and preparation method thereof, belong to biological base material technical field.The application is with mycelium fiber as raw material, by modification, strengthening, bonding, post-processing etc. Process is prepared degradable leather, including the following steps: after surface grafting modification, the mycelium fiber obtained by fermentation is dispersed into water suspension by ultrasonic, and reinforcing fiber is added, after being uniformly dispersed, it is filtered, dried, hot-rolled to obtain the preliminary reinforced mycelium fiber felt, and then it is crosslinked, polyurethane impregnation, drying etc. Leather base is prepared;Finally, through sanding, veneering, vacuum suction lines or embossing process, the degradable leather product with mycelium fiber as main body is prepared.The preparation process of the application has no pollution to environment, and the finished product leather has excellent water vapor permeability, bending resistance, wear resistance, mechanical properties and biodegradability, and has application prospect in fashion field, luggage, home, clothing decoration and other fields.

Description

Technical Field

[0001] This invention relates to a biodegradable leather based on mycelial fibers and its preparation method, belonging to the field of bio-based materials technology. Background Technology

[0002] Leather, as a traditional material, has been widely used since ancient times. With the development of human technology, the application of leather products has gradually expanded. Its durable, beautiful, and high-end properties have led to its use in clothing, shoes, handbags, furniture, automobiles, and aircraft manufacturing. However, with increasing public awareness of environmental protection, more and more brands are paying attention to the environmental impact of leather production processes, posing a significant challenge to traditional animal leather. Against this backdrop, synthetic leather has emerged. Among them, microfiber synthetic leather products are of high quality, diverse in variety, and their performance is comparable to, and in some cases even surpasses, natural leather. It is gradually replacing natural leather in several fields. However, the production process of microfiber synthetic leather also uses large amounts of organic solvents, which are difficult to degrade after disposal. Therefore, developing environmentally friendly, biodegradable leather products is of great significance. At the same time, some brands have launched sustainable leather products, such as outdoor clothing and shoes made from sustainable leather.

[0003] Regarding biodegradable leather, patent CN109736097A introduces bacterial cellulose into traditional microfiber, incorporating natural fiber components into the leather. Patent CN115418866A reports a method for preparing biodegradable artificial leather using plant bast fibers, such as pineapple leaf fiber and coconut shell fiber, through a bottom-up layering process. Patent CN111455681A reports a method for preparing biodegradable artificial leather using agricultural and forestry waste, such as crop straw and wood, through steaming and pulping. In addition, leathers based on natural materials or waste, such as apple, pineapple, cactus, and mycelium, are receiving increasing attention. Mycelium, in particular, is a mycelial aggregate composed of interwoven microfibers of various morphologies obtained through bio-fermentation. First, mycelial plastics were produced by Ecovative Design in the United States, exhibiting excellent biocompatibility, water permeability, and biodegradability. In recent years, eco-leather products based on mycelium have been gradually developed for applications in decoration and clothing. Given the broad application prospects of this technology, it is necessary for my country to conduct independent development to cope with future market competition. However, pure mycelial fiber aggregates have low strength and are relatively brittle, usually requiring reinforcement treatment to achieve the desired performance. Directly combining mycelial fibers with reinforcing fibers, however, does not create bonding between the fibers; the reinforcement effect is limited due to the entanglement between the fibers alone. Furthermore, when making leather, the hydrophilic mycelial fibers can negatively impact the performance of the final leather products due to poor compatibility with PU. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a novel method for preparing biodegradable leather based on mycelial fibers. The inventors also understand that leather directly pressed from cultured mycelial fibers has an uneven surface, causing numerous inconveniences for finishing.

[0005] This invention provides a method for preparing biodegradable mycelium glycoside leather, the method comprising the following steps:

[0006] (1) Preparation of mycelial fiber mat

[0007] The mycelial fibers obtained from fermentation were hydrophobically modified, and then dispersed in an aqueous glycerol solution using an ultrasonic cell disruptor to prepare a suspension. A certain amount of reinforcing short fibers were then added, and after being evenly dispersed, the suspension was filtered, extruded, dried, and hot-rolled to obtain a preliminarily reinforced mycelial fiber mat.

[0008] (2) Preparation of mycelial leather base

[0009] The mycelium fiber felt obtained in step (1) is cross-linked, then impregnated with polyurethane, and dried to obtain mycelium leather base.

[0010] (3) Preparation of mycelium leather

[0011] The leather base prepared in step (2) is polished, laminated, textured, or embossed to obtain a biodegradable leather product based on mycelial fibers.

[0012] In one embodiment of the present invention, the mycelial fibers in step (1) are obtained by liquid submerged fermentation or solid fermentation.

[0013] In one embodiment of the present invention, the hydrophobic modification in step (1) is achieved by coating polydopamine on the surface of mycelial fibers and using the hydroxyl and amino groups on the surface of polydopamine to initiate the ring-opening polymerization of lactide in situ, thereby obtaining modified mycelial fibers with polylactic acid molecular chain segments grafted on the surface.

[0014] Alternatively, modified mycelial fibers with 18-alkyl grafts can be prepared by coating the surface of the mycelial fibers with tannic acid and reacting it with a Schiff base of octadecylamine.

[0015] In one embodiment of the present invention, the hydrophobic modification in step (1) specifically includes: adding 10.0g of mycelial fiber to 100mL of 5% dopamine aqueous solution and reacting at room temperature with pH=10 for 24h to form a polydopamine thin layer on the surface of the mycelial fiber by the oxidative polymerization of dopamine. Then, filtering is used to obtain polydopamine-modified mycelial fiber, and the unreacted material on the surface is washed with ethanol. Then, it is added to molten lactide of the same mass as the mycelial fiber, and 5‰ of stannous octoate is added as a catalyst. The reaction is carried out at 120℃ for 5h. The mycelial fiber is taken out, and the ungrafted polylactic acid component on the fiber surface is removed with dichloromethane to obtain modified mycelial fiber with polylactic acid segments grafted on the surface.

[0016] In one embodiment of the present invention, the reinforcing short fiber in step (1) is a 1-5D core-sheath structure polylactic acid short fiber, wherein the sheath is low-melting-point polylactic acid with a melting point of 120-130℃, and the core is high-melting-point polylactic acid with a melting point of 165-175℃, and the addition amount is 10-100% of the dry weight of the mycelial fiber. Specifically, 20%, 50%, etc. can be selected.

[0017] In one embodiment of the present invention, the hot rolling temperature in step (1) is 115-125°C. The purpose is to allow the core-sheath polylactic acid fiber to bond with the modified mycelium fiber through the surface layer, thereby fixing the relative position of the mycelium fiber and achieving the purpose of mycelium fiber felt reinforcement.

[0018] In one embodiment of the present invention, the crosslinking treatment in step (2) refers to dipping and rolling the mycelial fiber mat three times in a crosslinking treatment solution, and then drying it at 100-120°C for 30-60 minutes. The crosslinking treatment solution is an aqueous solution of citric acid, butanetetracarboxylic acid, or ethylene glycol diglycidyl ether; the concentration of the crosslinking treatment solution is 1-10 wt%.

[0019] In one embodiment of the present invention, the polyurethane impregnation in step (2) refers to the process of immersing and grappling the cross-linked mycelial fiber mat three times in a mixed solution containing 20-80 wt% bio-based aqueous polyurethane, 0.5-2 wt% thickener carboxymethyl cellulose, and 1-5 wt% pore-forming agent salt particles. Further, the concentration of the bio-based aqueous polyurethane in the mixed solution can be specifically selected as 40% or 80%.

[0020] In one embodiment of the present invention, the prepared mycelium leather base needs to be polished, laminated, textured or embossed before the final biodegradable leather product can be obtained.

[0021] The present invention provides a biodegradable mycelium leather based on the above method.

[0022] The present invention also provides the application of the above-mentioned biodegradable mycelium leather in the fields of home sofas, car seats, clothing and footwear.

[0023] Beneficial effects

[0024] 1. This invention achieves physical bonding with reinforcing fibers by hydrophobically modifying mycelial fibers, thereby enhancing compatibility with PU and improving the overall performance of the final leather products.

[0025] 2. This invention uses polylactic acid fiber with a core and sheath as a reinforcing material. Hot rolling bonding effectively fixes the relative positions of the mycelial fibers, improving the mechanical properties of the mycelial layer. Simultaneously, the low melting point of the surface polylactic acid reduces the damage to the mycelial fibers caused by high-temperature hot rolling, ensuring the mechanical properties of the final product.

[0026] 3. This invention effectively solves the problem of uneven surface of the mycelial fiber layer by breaking down and then recombining the fermented mycelial fibers, thus facilitating subsequent coating. Furthermore, this method allows for the incorporation of any high-strength fiber material to improve mechanical properties.

[0027] 4. This invention uses water-based polyurethane instead of solvent-based polyurethane, which is safe and environmentally friendly, with the advantage of less environmental pollution. The selected reinforcing fiber, polylactic acid fiber, also has biodegradable properties, thus maintaining the overall degradability of the material.

[0028] 5. The biodegradable leather products prepared by the method of this invention have a high content of biodegradable components, ranging from 60% to 90%, and exhibit excellent overall performance, with a water vapor permeability of 1-5 mg / cm³. 2 •h, bending resistance is 10,000-30,000 times, abrasion resistance is 500-2,000 times, breaking strength is 10-30 MPa, and elongation at break is 50-200%. Detailed Implementation

[0029] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0030] Water vapor permeability test: The test method for water vapor permeability of leather in GB / T 1811-1993 was adopted.

[0031] Bending resistance test: The test was conducted according to the method described in GB / T 4689.9-1984.

[0032] Abrasion resistance test: At 23±2℃, the surface of the abrasion machine is observed after rotating a certain number of revolutions under a load of 1kg.

[0033] Mechanical property testing: The sample was cut into thin strips of 1×10cm and subjected to tensile testing on a universal testing machine at a tensile speed of 5cm / min.

[0034] Example 1

[0035] Preparation of mycelial fibers by liquid submerged fermentation: Take 1cm 2 Mushroom fruiting bodies were inoculated onto PDA medium and cultured at 28°C for 5 days. Colonies with good growth were then inoculated onto fresh PDA medium and cultured at 28°C for 5 days. This process was repeated multiple times to obtain a pure strain. Four 1cm pieces were then placed on the medium. 2 PDA inoculum was inoculated into shake flasks filled to 2 / 5 capacity, allowing the aerial mycelia to suspend upwards. After static incubation for 24 hours, the flasks were placed in a shaking incubator and cultured at 28°C and 150 rpm for 5 days to obtain shake flask seed culture. The shake flask seed culture was then inoculated into a 5L fermenter with a liquid volume of 50%–60%, an inoculum size of 8%–10%, an aeration rate of 8 L / min, a temperature of 20–32°C, a shaking speed of 100–250 rpm, and a pH of 4.5–7.5. After 5 days of fermentation, the mycelia were removed, filtered, and rinsed with water to obtain a large amount of mycelial fibers.

[0036] Hydrophobic modification: Modified mycelial fibers with polylactic acid (PLA) molecular segments grafted onto their surface were prepared by in-situ ring-opening polymerization of lactide initiated by surface hydroxyl groups in liquid deep fermentation mycelial fibers. Specifically, 10.0 g of mycelial fibers were added to 100 mL of a 5% (w / w) dopamine aqueous solution and reacted at room temperature (pH=10) for 24 h. The oxidative polymerization of dopamine formed a polydopamine thin layer on the surface of the mycelial fibers. The resulting polydopamine-modified mycelial fibers were then filtered, and the unreacted material on the surface was washed off with ethanol. Next, 10 g of molten lactide was added, along with 5‰ (w / w) stannous octoate as a catalyst. The reaction was carried out at 120 °C for 5 h. The mycelial fibers were then removed, and the ungrafted PLA components on the fiber surface were removed with dichloromethane to obtain modified mycelial fibers with PLA segments grafted onto their surface.

[0037] Then, under the action of an ultrasonic cell disruptor, 50g of modified mycelial fiber was evenly dispersed in 200mL of 5% glycerol aqueous solution. Subsequently, 20% of the modified mycelial fiber mass of core-sheath polylactic acid fiber with a monofilament fineness of 3D and a length of 5mm was added (fiber with a core-sheath structure made of low-melting-point polylactic acid in the sheath layer and high-melting-point polylactic acid in the core layer, purchased from Hengtian Changjiang Biomaterials Co., Ltd.). After filtration, room temperature extrusion to remove water, and hot air drying at 100℃, it was then hot-rolled at 120℃. At this time, the surface layer of the core-sheath polylactic acid fiber melted and bonded with itself and the modified mycelial fiber, thereby reinforcing the mycelial fiber and obtaining a preliminary mycelial fiber felt.

[0038] A 5 wt% citric acid aqueous solution was prepared, and the above-mentioned mycelial fiber felt was dipped and rolled three times in it. Then, it was dried at 120°C under tension for 30 minutes to induce cross-linking between the mycelial fibers. A mixed solution consisting of 40 wt% bio-based waterborne polyurethane (purchased from Shenzhen Tongtai Chemical Technology Co., Ltd., brand name LUR10), 1 wt% carboxymethyl cellulose, and 2 wt% salt granules was prepared, and the cross-linked mycelial fiber felt was dipped and rolled three times in it. Then, it was dried at 100°C for 10 minutes under tension to remove moisture, while the polyurethane cross-linked and cured. After completion, it was boiled in hot water at 50°C for 10 minutes to dissolve the pore-forming salt granules. Finally, it was dried in a forced-air drying oven at 100°C to obtain mycelial leather base.

[0039] Following conventional microfiber leather processing methods, the aforementioned base is sanded, laminated, and embossed to produce a biodegradable leather product based on mycelial fibers.

[0040] Calculations show that the content of biodegradable components in this leather product is approximately 80%, and its water vapor permeability is measured to be 3.5 mg / m³. 2 It can withstand 20,000 bends, 1,500 abrasion cycles, has a breaking strength of 22 MPa, and an elongation at break of 95%.

[0041] Comparative Example 1

[0042] Based on Example 1, without hydrophobic modification of the mycelial fibers, and with other production processes and conditions unchanged, the resulting leather product showed little change in its biodegradable components and water vapor permeability. However, its bending resistance and abrasion resistance decreased to 8000 cycles and 300 cycles, respectively, while its tensile strength also decreased to 8 MPa and its elongation at break was 58%. It is speculated that this may be because the modified mycelial fibers can physically bond with the reinforced polylactic acid fiber surface layer and improve compatibility with the impregnated polyurethane resin.

[0043] Comparative Example 2

[0044] Based on Example 1, replacing the polylactic acid (PLA) core fiber with conventional single-component PLA fiber with a melting point of 170°C, while keeping other manufacturing processes and conditions unchanged, resulted in leather products with minimal changes in biodegradable components and water vapor permeability. However, the bending resistance and abrasion resistance decreased to 9000 cycles and 450 cycles, respectively. Simultaneously, the tensile strength also decreased compared to Example 1, to 16 MPa, and the elongation at break was 85%. This is presumably because the hot-rolling temperature of Example 1 is insufficient to bond the reinforced PLA fibers together, or between the PLA fibers and the modified mycelium fibers; instead, they are simply physically overlapped, with the primary mechanical properties provided by the impregnated polyurethane resin. While hot-rolling near the PLA fiber melting point of 170°C can bond the fiber felt, it significantly damages the mechanical properties of the mycelium, leading to a decline in the overall performance of the final leather product.

[0045] Comparative Example 3

[0046] Based on Example 1, the polylactic acid fiber core was replaced with PE / PP fiber, while other manufacturing processes and conditions remained unchanged. The resulting leather product showed a reduction in the content of degradable components to approximately 55%, and a significant decrease in water vapor permeability, approximately 0.8 mg / m³. 2 The decrease in water vapor permeability is presumably due to the fact that, compared to PE / PP core-sheath fibers, core-sheath polylactic acid fibers have a better wicking effect, which helps water vapor to escape in a timely manner.

[0047] Comparative Example 4

[0048] Based on Example 1, the polylactic acid fiber in the core was replaced with PET fiber, while other manufacturing processes and conditions remained unchanged. The resulting leather product showed a reduction in the content of degradable components to approximately 55%, and a significant decrease in water vapor permeability, approximately 0.8 mg / m³. 2 The material can withstand 13,000 bends, 1,200 abrasion cycles, has a breaking strength of 8 MPa, and an elongation at break of 80%. The performance degradation is speculated to be due to two factors: firstly, PET's poor moisture conductivity leads to decreased moisture permeability; secondly, at the hot-rolling temperature of Example 1, the reinforced PET fibers cannot bond together, nor can the PET fibers bond with the modified mycelium fibers, instead they are physically overlapped, resulting in poor mechanical properties due to a lack of interaction between the fibers. While hot-rolling at around the PET fiber melting point of 260°C can bond the fiber felt, it severely damages the mechanical properties of the mycelium, leading to a significant decrease in the overall performance of the final leather product.

[0049] Example 2

[0050] Based on Example 1, the amount of polylactic acid short fibers added to the reinforcing fiber core was increased to 50%, while other production processes and conditions remained unchanged. Under the condition of ensuring consistent thickness of the final leather product, the content of degradable components remained approximately 80%, but the water vapor permeability decreased to 2.2 mg / m³. 2 •h, bending resistance is improved to 22,000 cycles, wear resistance is increased to 1,600 cycles, breaking strength is 25 MPa, and elongation at break is 90%.

[0051] Example 3

[0052] Based on Example 1, the bio-based waterborne polyurethane content during impregnation was increased to 80%, while other production processes and conditions remained unchanged. Calculations showed that the biodegradable content of the final leather product decreased to 68%, and the water permeability decreased to 1.8 mg / m³. 2 The bending resistance is increased to 26,000 cycles, the wear resistance is increased to 1,800 cycles, the breaking strength is 28 MPa, and the elongation at break is 120%.

[0053] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing biodegradable mycelium glycoside leather, characterized in that, Includes the following steps: (1) Preparation of mycelial fiber mat The mycelial fibers obtained from fermentation are hydrophobically modified, then dispersed in an aqueous glycerol solution using an ultrasonic cell disruptor to form a suspension. A certain amount of reinforcing short fibers are then added, dispersed evenly, and then filtered, extruded, dried, and hot-rolled to obtain a preliminarily reinforced mycelial fiber felt. The hydrophobic modification involves adding the mycelial fibers to an aqueous dopamine solution to form a polydopamine thin layer on the surface of the mycelial fibers through oxidative polymerization of dopamine. This layer is then added to molten lactide, and the hydroxyl and amino groups on the surface of the polydopamine initiate the ring-opening polymerization of lactide in situ to obtain modified mycelial fibers with polylactic acid molecular chain segments grafted onto the surface. The reinforcing short fibers are polylactic acid short fibers with a core-sheath structure. (2) Preparation of mycelial leather base The mycelium fiber felt obtained in step (1) is cross-linked, then impregnated with polyurethane, and dried to obtain mycelium leather base. (3) Preparation of mycelial leather The leather base prepared in step (2) is polished, laminated, textured, or embossed to obtain a biodegradable leather product based on mycelial fibers.

2. The method according to claim 1, characterized in that, The mycelial fibers in step (1) are obtained by liquid deep fermentation or solid fermentation.

3. The method according to claim 1, characterized in that, The reinforcing short fiber in step (1) is a 1-5D core-sheath structure polylactic acid short fiber, with the sheath being low-melting-point polylactic acid with a melting point of 120-130℃ and the core being high-melting-point polylactic acid with a melting point of 165-175℃.

4. The method according to claim 1, characterized in that, The amount of reinforcing short fibers added in step (1) is 10-100% of the dry weight of the mycelial fibers.

5. The method according to claim 1, characterized in that, The hot rolling temperature in step (1) is 115-125℃.

6. The method according to claim 1, characterized in that, The cross-linking treatment in step (2) refers to dipping and rolling the mycelial fiber mat three times in the cross-linking treatment solution, and then drying it at 100-120℃ for 30-60 minutes; the cross-linking treatment solution is an aqueous solution of citric acid, butanetetracarboxylic acid or ethylene glycol diglycidyl ether; the concentration of the cross-linking treatment solution is 1-10 wt.

7. The method according to any one of claims 1-6, characterized in that, The impregnation of polyurethane in step (2) refers to the process of immersing and rolling the cross-linked mycelial fiber felt three times in a mixed solution containing 20-80 wt% bio-based aqueous polyurethane, 0.5-2 wt% thickener carboxymethyl cellulose, and 1-5 wt% pore-forming agent salt particles.

8. The biodegradable mycelium leather prepared by the method according to any one of claims 1-7.

9. The application of the biodegradable mycelium leather according to claim 8 in the fields of home sofas, car seats, clothing and footwear.