Sole rubber material with high bio-based content and preparation method thereof

Abstract

The invention discloses a sole rubber material with high bio-based content and a preparation method thereof, and belongs to the technical field of rubber materials. The sole rubber material with high bio-based content comprises the following components in parts by mass: 20-30 parts of natural rubber, 20-30 parts of modified polyhydroxybutyrate, 20-30 parts of modified bio-based powder, 5-8 parts of a biodegradable auxiliary agent, 6-12 parts of a compatilizer, 10-12 parts of a reinforcing agent, 2-8 parts of a coupling agent, 2-4 parts of an accelerant, 3 parts of an anti-aging agent, 2-4 parts of a cross-linking agent, 2 parts of a wear-resistant reinforcing agent and 2 parts of a processing auxiliary agent. Through the synergistic effect of the pyroligneous modified polyhydroxybutyrate, the tannic acid treated bio-based powder and the compound compatilizer / degradation aid, on the premise of keeping high bio-based content, the wet friction coefficient, the tensile strength and the degradation rate all reach the industry leading level.

Description

Technical Field

[0001] The present invention belongs to the technical field of rubber materials, and particularly relates to a sole rubber material with a high bio-based content and a preparation method thereof. Background Art

[0002] As the core functional component of footwear products, the sole material is directly related to wearing comfort, sports safety and environmental sustainability. However, the current mainstream sole materials are still mainly petroleum-based synthetic rubbers, thermoplastic polyurethanes and ethylene-vinyl acetate copolymers. Although these materials have certain wear resistance and processing convenience, their problems such as dependence on non-renewable raw materials, high carbon emissions in the production process and difficulty in degradation after abandonment seriously restrict the sustainable development of the industry. Therefore, the development of bio-based sole rubber materials has become a new research and development hotspot.

[0003] However, in the performance dimension of sole materials, insufficient anti-slip property is the key restricting the application of bio-based materials. Research shows that the dynamic friction coefficient of existing bio-based soles on wet ceramic tile surfaces is generally lower than 0.5 (SATRA TM144 standard), which is about 30% lower than that of traditional petroleum-based materials (0.6 - 0.7). Especially in rainy, snowy environments or oily ground, it is easy to cause slipping accidents. This defect stems from the strong hydrophilicity of the bio-based material surface and the lack of rigid support points in the micro-texture, resulting in the difficulty of quickly discharging the water film.

[0004] Breaking through the short board of anti-slip property of bio-based soles has urgent technical and commercial value. From the safety dimension, according to EU standards, the wet friction coefficient of safety shoes needs to be ≥0.7. Therefore, on the premise of maintaining a high bio-based content and degradability, developing a sole rubber material with a wet friction coefficient ≥0.5 has become a technical problem that the industry urgently needs to overcome. Summary of the Invention

[0005] In order to develop a sole rubber material with a wet friction coefficient ≥0.5 on the premise of maintaining a high bio-based content and degradability, the present invention provides a sole rubber material with a high bio-based content and a preparation method thereof. Specifically, the technical solutions adopted by the present invention are as follows: A sole rubber material with a high bio-based content, comprising the following components in parts by mass: 20 - 30 parts of natural rubber, 20 - 30 parts of modified polyhydroxybutyrate, 20 - 30 parts of modified bio-based powder, 5 - 8 parts of biodegradation aid, 6 - 12 parts of compatibilizer, 10 - 12 parts of reinforcing agent, 2 - 8 parts of coupling agent, 2 - 4 parts of accelerator, 3 parts of antioxidant, 2 - 4 parts of crosslinking agent, 2 parts of wear-resistant enhancer, 2 parts of processing aid.

[0006] Further, the modified polyhydroxybutyrate is prepared by the following steps: A1. Mix corn starch and plasticizer glycerol in a mass ratio of 10:3, extrude, granulate, cool, and cut at 120 - 130 °C to obtain a thermoplastic starch masterbatch; A2. Mix polyhydroxybutyrate and wood vinegar liquid, knead at 155 - 160 °C for 5 - 10 min, then add the thermoplastic starch masterbatch to it, raise the temperature to 165 - 170 °C and knead for 8 - 10 min, then cool down to 130 - 140 °C, add dicumyl peroxide to it, and continue to knead for 3 - 5 min. After completion, cool to room temperature to obtain modified polyhydroxybutyrate.

[0007] Further, in A1, the corn starch and glycerol are mixed in a mass ratio of 10:3.

[0008] Further, the mass parts usage ratio of the polyhydroxybutyrate, wood vinegar liquid, thermoplastic starch masterbatch, and dicumyl peroxide in A2 is 28 - 30:3 - 5:15 - 20:0.5 - 1.0.

[0009] Further, the modified bio - based powder is prepared by the following steps: B1. Mix absolute ethanol and silane coupling agent KH - 550 in a volume ratio of 19:1 to prepare a treatment solution. Then take rice husk powder and dry it in an oven at 105 - 110 °C for 2 h. After completion, immerse the dried rice husk powder in the treatment solution at a solid - liquid ratio of 1:10, raise the temperature of the system to 60 - 65 °C, and perform magnetic stirring for 30 min. During this period, start ultrasonic treatment for 5 min every 10 min. After completion, filter and separate to collect the powder, wash it 3 times with absolute ethanol to remove physically adsorbed substances, and then place it in a vacuum dryer at 80 - 100 °C for 4 - 5 h to obtain silanized rice husk powder; B2. Prepare a tannic acid - aqueous solution with a mass concentration of 0.5 wt%, and then adjust the pH of the tannic acid - aqueous solution to 5.0 - 5.2 with 0.1 mol / L NaOH solution. After completion, obtain a surface treatment solution; B3. Use a spray gun to spray the surface treatment solution on the surface of the silanized rice husk powder at a flow rate of 0.2 mL / min, and control the spraying amount to be 2.5% - 5.0% of the mass of the silanized rice husk powder. After completion, perform hot air curing, cool, and then pass through an 80 - mesh sieve to obtain the modified bio - based powder.

[0010] Further, the biodegradation aid is composed of polycaprolactone and poly(butylene succinate) in a mass ratio of 1:1.

[0011] Further, the compatibilizer is composed of epoxidized soybean oil and maleic anhydride - grafted polylactic acid in a mass ratio of 2:1.

[0012] Further, the reinforcing agent is one of kaolin, bentonite, and white carbon black.

[0013] Further, the coupling agent is one of KH-550, KH-560 and KH-570.

[0014] Further, the promoter is one of triallyl isocyanurate and trimethylolpropane trimethacrylate, or a compound of the two in a mass ratio of 1:1.

[0015] Further, the anti-aging agent is one of anti-aging agent RD and anti-aging agent 4010NA, or a compound of the two in a mass ratio of 2:1.

[0016] Further, the cross-linking agent is one of 1,4-bis(tert-butylperoxyisopropyl)benzene, 1,1′-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0017] Further, the wear-resistant enhancer is a compound of nanocrystalline cellulose whiskers and bamboo charcoal micropowder in a mass ratio of 1:3.

[0018] Further, the processing aid is one of tributyl citrate and glycerol monostearate.

[0019] The present invention also provides a preparation method of the bio-based sole material, which specifically includes the following steps: S1. Weigh each raw material according to mass parts. Add natural rubber and modified polyhydroxybutyrate into an internal mixer with a temperature of 120-140°C and a rotation speed of 50 r / min, and knead for 10-15 min. Then add the modified bio-based powder into the internal mixer, keep the temperature and rotation speed unchanged, and knead and mix evenly for 8-10 min to obtain a masterbatch. S2. Sequentially add the biodegradation aid, compatibilizer, reinforcing agent, coupling agent, promoter, anti-aging agent, cross-linking agent, wear-resistant enhancer and processing aid into the internal mixer containing the masterbatch obtained in step S1 according to mass parts. Keep the temperature and rotation speed unchanged, continue to knead and mix evenly for 5-10 min, and then cool to room temperature to obtain a mixed material. Put the mixed material into a granulator to granulate and obtain a sample. S3. Put the sample obtained in step S2 into a vulcanization molding machine, control the vulcanization temperature to be 150-160°C and the vulcanization time to be 3-4 h. After the vulcanization is completed, cool to room temperature, take out the vulcanized material from the vulcanization molding machine, and obtain the bio-based sole material.

[0020] The beneficial effects obtained by the present invention are as follows: Aiming at the three major technical problems of low wet friction coefficient (generally <0.5), insufficient mechanical properties and limited degradation efficiency of the bio-based sole material pointed out in the background technology, the present invention realizes a performance breakthrough through material component innovation and process collaborative optimization. The following combines the test data in Table 1 to elaborate on the beneficial effects in detail: (1)Significant improvement in wet friction coefficient: The wet friction coefficient of the existing bio-based soles is less than 0.5. In Example 8 of the present invention, the wet friction coefficient reaches 0.71 ± 0.02, which is 44.9% higher than that of Comparative Example 7 (unmodified polyhydroxybutyrate matrix, 0.49). This improvement is due to the synergistic effect of double-interface modification: a. Wood vinegar enhances the interfacial bonding of polyhydroxybutyrate: The wet friction coefficient of Comparative Example 3 (polyhydroxybutyrate without wood vinegar modification) is only 0.58, which is 18.3% lower than that of Example 8 (0.71). The organic acids in wood vinegar form a hydrogen bond network with the hydroxyl groups of starch, improving the compatibility between polyhydroxybutyrate and starch, reducing interfacial defects, and enhancing the water film discharge ability.

[0021] b. Tannic acid hydrophobic coating optimizes surface properties: The wet friction coefficient of Comparative Example 4 (without tannic acid spraying) is 0.60, which is 15.5% lower than that of Example 8. Tannic acid spraying forms hydrogen bonds with the rubber matrix through polyphenol hydroxyl groups, improving surface hydrophobicity, while enhancing the powder-matrix bonding force and reducing wear and shedding (the wear resistance of Comparative Example 4 is 105 mm 3 , and that of Example 8 is 72 mm 3 , with a 31.4% improvement).

[0022] Verification of the synergistic effect: The synergistic effect of wood vinegar and tannic acid treatment increases the wet friction coefficient from 0.49 in Comparative Example 7 to 0.71 in Example 8, with an increase of 44.9%, far exceeding the improvement effect of single components (such as Comparative Examples 3 / 4 only increasing to 0.58 / 0.60), proving that the synergistic effect between innovative components is creative.

[0023] (2)Synergistic optimization of mechanical properties and degradation efficiency: Existing bio-based materials often face the contradiction between strength, toughness, and degradation rate. In Example 8 of the present invention, the tensile strength reaches 15.8 MPa, and the elongation at break is 360%, which are 4.6% and 63.6% higher than those of Comparative Example 7 (15.1 MPa / 220%) respectively. The starch-polyhydroxybutyrate double continuous phase in the modified polyhydroxybutyrate reduces the crystallinity of polyhydroxybutyrate through dynamic crosslinking (initiated by dicumyl peroxide), while enhancing the interfacial bonding force. At the same time, the compounded degradation aids accelerate decomposition: The degradation rate of Example 8 is 73% (90-day composting), which is 25.9% higher than that of Comparative Example 5 (single polycaprolactone degradation aid, 58%). The 1:1 compounding of polycaprolactone and polybutylene succinate (Example 8) forms a complementary degradation mechanism: Polybutylene succinate undergoes rapid hydrolysis to provide a microbial carbon source, and polycaprolactone undergoes slow enzymatic hydrolysis to extend the degradation cycle.

[0024] (3)Balance between high bio-based content and performance: Existing high bio - based content often leads to performance degradation. However, the bio - based content of the present invention reaches 78.1% (Example 8, ASTM D6866), far exceeding the industry level (50% - 60%). Meanwhile, it has excellent anti - slip performance, mechanical properties and environmental friendliness.

[0025] In summary, through the synergistic effect of modifying polyhydroxybutyrate with wood vinegar, treating bio - based powder with tannic acid and compounding compatibilizer / degradation aid, on the premise of maintaining a high bio - based content (78.1%), the wet friction coefficient (0.71), tensile strength (15.8 MPa) and degradation rate (73%) of the present invention all reach the leading level in the industry, solving the technical problem of "difficulty in balancing anti - slip performance, mechanical properties and environmental friendliness" in the prior art, and having significant industrial application value. Detailed implementation manners

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0027] Example 1

[0028] Preparation of modified polyhydroxybutyrate: A1. Mix corn starch and plasticizer glycerol in a mass ratio of 10:3, and extrude and pelletize at 120 °C in a twin - screw extruder (screw speed 60 rpm, L / D = 40:1). After completion, cool and pelletize to obtain a thermoplastic starch masterbatch.

[0029] A2. Put 28 parts (parts by mass; the same below) of polyhydroxybutyrate (melt index 8 g / 10 min) and 3 parts of wood vinegar into a mixer. Heat the mixer to 155 °C and mix at 50 rpm for 5 min. Then add 15 parts of the thermoplastic starch masterbatch into the mixer. Heat the mixer to 165 °C and increase the speed to 80 rpm and mix for 8 min. During the mixing process, acetic acid and phenolic substances in the wood vinegar form hydrogen bonds with starch hydroxyl groups, and the ester groups (-COO-) of polyhydroxybutyrate and starch molecular chains undergo physical cross - linking through proton transfer. After completion, cool the mixer at a cooling rate of 10 °C / min to 130 °C, then add 0.5 part of di - isopropylbenzene peroxide and continue to mix for 3 min. A double - continuous phase structure is formed during the process. After completion, cool to room temperature to obtain the modified polyhydroxybutyrate.

[0030] Example 2

[0031] Preparation of modified polyhydroxybutyrate: A1. Mix corn starch and plasticizer glycerol in a mass ratio of 10:3, extrude and granulate at 120 °C in a twin-screw extruder (screw speed 60 rpm, L / D = 40:1). After completion, cool and pelletize to obtain thermoplastic starch masterbatch.

[0032] A2. Put 28 parts (parts by mass; the same below) of polyhydroxybutyrate (melt index 8 g / 10 min) and 5 parts of wood vinegar into a mixer. Heat the mixer to 155 °C and knead at 50 rpm for 10 min. Then add 17 parts of thermoplastic starch masterbatch to the mixer. Heat the mixer to 165 °C and increase the speed to 80 rpm and knead for 10 min. During the kneading process, acetic acid and phenolic substances in the wood vinegar form hydrogen bonds with starch hydroxyl groups, and the ester groups (-COO-) of polyhydroxybutyrate undergo physical cross-linking with starch molecular chains through proton transfer. After completion, cool the mixer at a cooling rate of 10 °C / min to 130 °C, then add 1.0 part of dicumyl peroxide and continue to knead for 5 min. A double-continuous phase structure is formed during the process. After completion, cool to room temperature to obtain modified polyhydroxybutyrate.

[0033] Example 3

[0034] Preparation of modified polyhydroxybutyrate: A1. Mix corn starch and plasticizer glycerol in a mass ratio of 10:3, extrude and granulate at 130 °C in a twin-screw extruder (screw speed 60 rpm, L / D = 40:1). After completion, cool and pelletize to obtain thermoplastic starch masterbatch.

[0035] A2. Put 30 parts (parts by mass; the same below) of polyhydroxybutyrate (melt index 8 g / 10 min) and 5 parts of wood vinegar into a mixer. Heat the mixer to 160 °C and knead at 50 rpm for 10 min. Then add 20 parts of thermoplastic starch masterbatch to the mixer. Heat the mixer to 170 °C and increase the speed to 80 rpm and knead for 10 min. During the kneading process, acetic acid and phenolic substances in the wood vinegar form hydrogen bonds with starch hydroxyl groups, and the ester groups (-COO-) of polyhydroxybutyrate undergo physical cross-linking with starch molecular chains through proton transfer. After completion, cool the mixer at a cooling rate of 10 °C / min to 140 °C, then add 1.0 part of dicumyl peroxide and continue to knead for 5 min. A double-continuous phase structure is formed during the process. After completion, cool to room temperature to obtain modified polyhydroxybutyrate.

[0036] Comparative Example 1 Comparative Example 1 is the control group of Example 2. Compared with Example 2, no wood vinegar is added in step A2, and other raw materials, raw material dosages, and preparation steps are the same as those in Example 2. Finally, modified polyhydroxybutyrate is obtained.

[0037] Example 4

[0038] Preparation of modified bio-based powder: B1. Mix absolute ethanol and silane coupling agent KH-550 according to a volume ratio of 19:1 to prepare a treatment solution. Then take rice husk powder and dry it in an oven at 105 °C for 2 h. After that, immerse the dried rice husk powder in the treatment solution according to a solid-liquid ratio of 1:10. Heat the system to 60 °C and carry out magnetic stirring at a constant temperature (rotation speed 300 rpm) for 30 min. During this period, synchronously turn on ultrasonic treatment for 5 min (power 200 W) every 10 min. After completion, carry out suction filtration to separate and collect the powder, wash it 3 times with absolute ethanol to remove physically adsorbed substances, and then place it in a vacuum dryer at 80 °C for 4 h to obtain silanized rice husk powder.

[0039] B2. Prepare a tannic acid-aqueous solution with a mass concentration of 0.5 wt%, and then adjust the pH of the tannic acid-aqueous solution to 5.0 with 0.1 mol / L NaOH solution. After completion, obtain the surface treatment solution.

[0040] B3. Spread the silanized rice husk powder on a stainless steel plate, and use a spray gun to evenly spray the surface treatment solution on the surface of the silanized rice husk powder at a flow rate of 0.2 mL / min. Control the spraying amount to 2.5% of the mass of the silanized rice husk powder, with a spraying distance of 20 cm, and spray back and forth 3 times (dry for 10 s intervals). After spraying, immediately transfer it to a hot air circulation oven at 120 °C for curing for 20 min. After cooling, pass it through an 80-mesh sieve to remove agglomerated particles, and collect the modified bio-based powder.

[0041] Example 5

[0042] Preparation of modified bio-based powder: B1. Mix absolute ethanol and silane coupling agent KH-550 according to a volume ratio of 19:1 to prepare a treatment solution. Then take rice husk powder and dry it in an oven at 105 °C for 2 h. After that, immerse the dried rice husk powder in the treatment solution according to a solid-liquid ratio of 1:10. Heat the system to 60 °C and carry out magnetic stirring at a constant temperature (rotation speed 300 rpm) for 30 min. During this period, synchronously turn on ultrasonic treatment for 5 min (power 200 W) every 10 min. After completion, carry out suction filtration to separate and collect the powder, wash it 3 times with absolute ethanol to remove physically adsorbed substances, and then place it in a vacuum dryer at 80 °C for 5 h to obtain silanized rice husk powder.

[0043] B2. Prepare a tannic acid-aqueous solution with a mass concentration of 0.5 wt%, and then adjust the pH of the tannic acid-aqueous solution to 5.0 with 0.1 mol / L NaOH solution. After completion, obtain the surface treatment solution.

[0044] B3. Spread the silanized rice husk powder evenly on a stainless-steel tray. Use a spray gun to uniformly spray the surface treatment solution on the surface of the silanized rice husk powder at a flow rate of 0.2 mL / min. Control the spraying amount at 5.0% of the mass of the silanized rice husk powder, with a spraying distance of 20 cm. Spray back and forth 3 times (dry for 10 s intervals). After spraying, immediately transfer it to a hot air circulation oven at 120 °C for curing for 30 min. After cooling, pass through an 80-mesh sieve to remove agglomerated particles, and collect the modified bio-based powder.

[0045] Example 6

[0046] Preparation of modified bio-based powder: B1. Mix absolute ethanol and silane coupling agent KH-550 according to a volume ratio of 19:1 to prepare a treatment solution. Then take rice husk powder and dry it in an oven at 110 °C for 2 h. After completion, immerse the dried rice husk powder in the treatment solution according to a solid-liquid ratio of 1:10. Heat the system to 65 °C and stir magnetically at a constant temperature (rotation speed 300 rpm) for 30 min. During this period, start ultrasonic treatment for 5 min (power 200 W) synchronously every 10 min. After completion, filter and separate to collect the powder, wash it 3 times with absolute ethanol to remove physically adsorbed substances, and then place it in a vacuum dryer at 100 °C for 5 h to obtain silanized rice husk powder.

[0047] B2. Prepare a tannic acid-aqueous solution with a mass concentration of 0.5 wt%, and then adjust the pH of the tannic acid-aqueous solution to 5.2 with 0.1 mol / L NaOH solution. After completion, obtain the surface treatment solution.

[0048] B3. Spread the silanized rice husk powder evenly on a stainless-steel tray. Use a spray gun to uniformly spray the surface treatment solution on the surface of the silanized rice husk powder at a flow rate of 0.2 mL / min. Control the spraying amount at 5.0% of the mass of the silanized rice husk powder, with a spraying distance of 20 cm. Spray back and forth 3 times (dry for 10 s intervals). After spraying, immediately transfer it to a hot air circulation oven at 120 °C for curing for 30 min. After cooling, pass through an 80-mesh sieve to remove agglomerated particles, and collect the modified bio-based powder.

[0049] Comparative Example 2 Comparative Example 2 is the control group of Example 5. Compared with Example 5, cancel the spraying of tannic acid and only retain the silanization treatment. Keep other raw materials, raw material dosages, and preparation steps the same as in Example 5, and finally obtain silanized rice husk powder.

[0050] Example 7

[0051] A high bio-based content sole rubber material and its preparation method: First, the high bio-based content sole rubber material includes the following components in parts by mass: 20 parts of natural rubber, 20 parts of the modified polyhydroxybutyrate prepared in Example 1, 20 parts of the modified bio-based powder prepared in Example 4, 5 parts of a biodegradation aid, 6 parts of a compatibilizer, 10 parts of a reinforcing agent, 2 parts of a coupling agent, 2 parts of an accelerator, 3 parts of an antioxidant, 2 parts of a crosslinking agent, 2 parts of a wear-resistant enhancer, and 2 parts of a processing aid; Among them, the biodegradation aid is a compound of polycaprolactone and poly(butylene succinate) in a mass ratio of 1:1; Among them, the compatibilizer is a compound of epoxidized soybean oil and maleic anhydride-grafted polylactic acid in a mass ratio of 2:1; Among them, the reinforcing agent is kaolin; Among them, the coupling agent is KH-550; Among them, the accelerator is triallyl isocyanurate; Among them, the antioxidant is antioxidant RD; Among them, the crosslinking agent is 1,4-bis(tert-butylperoxy)cumene; Among them, the wear-resistant enhancer is a compound of nanocrystalline cellulose whiskers and bamboo charcoal micropowder in a mass ratio of 1:3; Among them, the processing aid is tributyl citrate.

[0052] Then, a preparation method of the bio-based sole material specifically includes the following steps: S1. Weigh each raw material according to the mass parts, and then add natural rubber and the modified polyhydroxybutyrate prepared in Example 1 into an internal mixer at a temperature of 120 °C and a rotation speed of 50 r / min, and knead for 10 min until it is in a molten state. Then add the modified bio-based powder prepared in Example 4 into the internal mixer, keep the temperature and rotation speed unchanged, and knead and mix evenly for 8 min to obtain a masterbatch.

[0053] S2. Sequentially add the biodegradation aid, compatibilizer, reinforcing agent, coupling agent, accelerator, antioxidant, crosslinking agent, wear-resistant enhancer, and processing aid into the internal mixer containing the masterbatch in step S1 according to the mass parts, keep the temperature and rotation speed unchanged, continue to knead and mix evenly for 5 min, and then cool to room temperature to obtain a mixture. Put the mixture into a granulator to granulate and obtain a sample.

[0054] S3. Put the sample obtained in step S2 into a vulcanization molding machine, control the vulcanization temperature at 150 °C and the vulcanization time at 3 h. After the vulcanization is completed, cool to room temperature, and take out the vulcanized material from the vulcanization molding machine to obtain the bio-based sole material.

[0055] Example 8

[0056] A sole rubber material with a high bio-based content and a preparation method thereof: First, the sole rubber material with a high bio-based content includes the following components in mass parts: 25 parts of natural rubber, 27 parts of modified polyhydroxybutyrate prepared in Example 2, 28 parts of modified bio-based powder prepared in Example 5, 7 parts of biodegradation aid, 9 parts of compatibilizer, 12 parts of reinforcing agent, 2 parts of coupling agent, 4 parts of accelerator, 3 parts of antioxidant, 3 parts of crosslinking agent, 2 parts of wear-resistant enhancer, and 2 parts of processing aid.

[0057] Among them, the biodegradation aid is a compound prepared by mixing polycaprolactone and poly(butylene succinate) in a mass ratio of 1:1; Among them, the compatibilizer is a compound prepared by mixing epoxidized soybean oil and maleic anhydride-grafted polylactic acid in a mass ratio of 2:1; Among them, the reinforcing agent is bentonite; Among them, the coupling agent is KH-560; Among them, the accelerator is a compound prepared by mixing triallyl isocyanurate and trimethylolpropane trimethacrylate in a mass ratio of 1:1; Among them, the antioxidant is a compound prepared by mixing antioxidant RD and antioxidant 4010NA in a mass ratio of 2:1; Among them, the crosslinking agent is 1,1′-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane; Among them, the wear-resistant enhancer is a compound prepared by mixing nanocrystalline cellulose whiskers and bamboo charcoal micropowder in a mass ratio of 1:3; Among them, the processing aid is tributyl citrate.

[0058] Then, a preparation method of the bio-based sole material specifically includes the following steps: S1. Weigh each raw material according to the mass parts, then add natural rubber and the modified polyhydroxybutyrate prepared in Example 2 into a mixer with a temperature of 130 °C and a rotation speed of 50 r / min, and knead for 15 min until it reaches a molten state. Then add the modified bio-based powder prepared in Example 5 into the mixer, keep the temperature and rotation speed unchanged, and knead and mix evenly for 10 min to obtain a masterbatch.

[0059] S2. Add the biodegradation aid, compatibilizer, reinforcing agent, coupling agent, accelerator, antioxidant, crosslinking agent, wear-resistant enhancer, and processing aid into the mixer containing the masterbatch in step S1 in sequence according to the mass parts, keep the temperature and rotation speed unchanged, continue to knead and mix evenly for 10 min, then cool to room temperature to obtain a mixture. Put the mixture into a granulator for granulation to obtain a sample.

[0060] S3. Put the sample obtained in step S2 into a vulcanization molding machine, control the vulcanization temperature at 150 °C and the vulcanization time at 4 h. After the vulcanization is completed, cool to room temperature, and take out the vulcanized material from the vulcanization molding machine to obtain the bio-based sole material.

[0061] Example 9

[0062] A sole rubber material with a high bio-based content and its preparation method: First, a high bio-based content sole rubber material, comprising components in the following parts by mass: 30 parts of natural rubber, 30 parts of the modified polyhydroxybutyrate prepared in Example 3, 30 parts of the modified bio-based powder prepared in Example 6, 8 parts of a biodegradation aid, 12 parts of a compatibilizer, 12 parts of a reinforcing agent, 8 parts of a coupling agent, 4 parts of an accelerator, 3 parts of an antioxidant, 4 parts of a crosslinking agent, 2 parts of a wear-resistant enhancer, and 2 parts of a processing aid.

[0063] Among them, the biodegradation aid is a compound prepared by mixing polycaprolactone and poly(butylene succinate) in a mass ratio of 1:1; Among them, the compatibilizer is a compound prepared by mixing epoxidized soybean oil and maleic anhydride-grafted polylactic acid in a mass ratio of 2:1; Among them, the reinforcing agent is silica; Among them, the coupling agent is KH-570; Among them, the accelerator is trimethylolpropane trimethacrylate; Among them, the antioxidant is antioxidant 4010NA; Among them, the crosslinking agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; Among them, the wear-resistant enhancer is a compound prepared by mixing nanocrystalline cellulose whiskers and bamboo charcoal micropowder in a mass ratio of 1:3; Among them, the processing aid is glyceryl stearate.

[0064] Then, a preparation method of the bio-based sole material specifically comprises the following steps: S1. Weigh each raw material according to the parts by mass, then add natural rubber and the modified polyhydroxybutyrate prepared in Example 3 into a kneader at a temperature of 140 °C and a rotation speed of 50 r / min, knead for 15 min until in a molten state, then add the modified bio-based powder prepared in Example 6 into the kneader, keep the temperature and rotation speed unchanged, and knead and mix evenly for 10 min to obtain a masterbatch.

[0065] S2. Sequentially add the biodegradation aid, compatibilizer, reinforcing agent, coupling agent, accelerator, antioxidant, crosslinking agent, wear-resistant enhancer, and processing aid into the kneader containing the masterbatch in step S1 according to the parts by mass, keep the temperature and rotation speed unchanged, continue to knead and mix evenly for 10 min and then cool to room temperature to obtain a mixture, and put the mixture into a granulator to granulate to obtain a sample.

[0066] S3. Put the sample obtained in step S2 into a vulcanization molding machine, control the vulcanization temperature at 160 °C and the vulcanization time at 4 h, after the vulcanization is completed, cool to room temperature, take out the vulcanized material from the vulcanization molding machine to obtain the bio-based sole material.

[0067] Comparative Example 3 (Polyhydroxybutyrate without wood vinegar modification) Comparative Example 3 is the control group of Example 8. Compared with Example 8, the modified polyhydroxybutyrate prepared in Raw Material Example 2 was replaced with the modified polyhydroxybutyrate prepared in Comparative Example 1, and other raw materials, raw material dosages, and preparation steps were kept the same as those in Example 8, and finally a bio-based sole material was obtained.

[0068] Comparative Example 4 (not treated with spraying tannic acid) Comparative Example 4 is the control group of Example 8. Compared with Example 8, the modified bio-based powder prepared in Raw Material Example 5 was replaced with the silanized rice husk powder prepared in Comparative Example 2, and other raw materials, raw material dosages, and preparation steps were kept the same as those in Example 8, and finally a bio-based sole material was obtained.

[0069] Comparative Example 5 (single component of biodegradation aid) Comparative Example 5 is the control group of Example 8. Compared with Example 8, only polycaprolactone was used as the raw material biodegradation aid, and other raw materials, raw material dosages, and preparation steps were kept the same as those in Example 8, and finally a bio-based sole material was obtained.

[0070] Comparative Example 6 (only using epoxidized soybean oil as compatibilizer) Comparative Example 6 is the control group of Example 8. Compared with Example 8, only epoxidized soybean oil was used as the raw material compatibilizer, and other raw materials, raw material dosages, and preparation steps were kept the same as those in Example 8, and finally a bio-based sole material was obtained.

[0071] Comparative Example 7 (unmodified polyhydroxybutyrate matrix) Comparative Example 7 is the control group of Example 8. Compared with Example 8, the modified polyhydroxybutyrate prepared in Example 2 was replaced with raw material polyhydroxybutyrate (melt index 8 g / 10 min), and other raw materials, raw material dosages, and preparation steps were kept the same as those in Example 8, and finally a bio-based sole material was obtained.

[0072] Test Example 1 The bio-based sole materials prepared in Examples 7 to 9 and Comparative Examples 3 to 7 were subjected to performance tests. The performance test process is as follows, and the test results are shown in Table 1: I. Wet friction coefficient test: 1. Detection standard: SATRA TM144:2017 "Test Method for Slip Resistance Performance of Footwear".

[0073] 2. Test process: (1) Sample preparation: Cut the bio-based sole material into test pieces of 100 mm × 50 mm × 6 mm; (2) Moisture treatment: Spray deionized water (0.5 mL / 100 cm 2 ) on the sample test surface with a micropump; (3)Test parameters: Tilt angle of the test bench: 7° (simulating the walking slope); Contact pressure: 0.5 MPa; Sliding speed: 0.3 m / s.

[0074] (4)Data acquisition: Record the ratio of the tangential frictional force to the normal force through a force sensor, which is the wet friction coefficient value.

[0075] II. Wear resistance test: 1. Detection standard: DIN 53516:2017 "Determination of Rubber Abrasion Resistance".

[0076] 2. Test procedure: (1)Sample: Make the bio-based sole material into a cylindrical specimen with a diameter of 6 mm and a thickness of 3 mm; (2)Test conditions: Grit size of the sandpaper: 60 mesh; Load: 10 N; Abrasion stroke: 40 m; Temperature: 23 ± 2 °C; (3)Result calculation: Volume loss = mass difference before and after wear / material density.

[0077] III. Tensile strength test: 1. Detection standard: ASTM D412-2016 "Test Method for Tensile Properties of Vulcanized Rubber".

[0078] 2. Test procedure: (1)Dumbbell-shaped specimen: Type 2 specimen (thickness 2.0 ± 0.2 mm); (2)Tensile speed: 500 mm / min; (3)Test parameters: Record the breaking strength and elongation at break.

[0079] IV. Hardness test: 1. Detection standard: ASTM D2240-2021 "Rubber Hardness Test".

[0080] 2. Test method: Use a Shore A hardness tester and take the average value of 5 points.

[0081] V. Biodegradation rate verification: 1. Detection standard: ISO 14855-1:2012 "Determination of Biodegradation Rate under Composting Conditions".

[0082] 2. Test key points: Crush the bio-based sole material into 2 mm particles and cultivate it in a composting environment at 58 °C and 50% humidity for 90 days. Calculate the degradation rate through the CO 2 emission.

[0083] VI. Determination of bio-based content: 1. Determination standard: ASTM D6866 standard (carbon-14 method) for determination.

[0084] 2. Testing process: (1) Sample preparation: Crush the bio-based sole material to 80 mesh; (2) Combustion treatment: Burn the sample at high temperature in a pure oxygen environment to release CO 2 gas; (3) Carbon-14 detection: Use accelerator mass spectrometry to measure the content of carbon-14 isotope in CO 2 ; (4) Calculation of bio-based content: Bio-based content = [Carbon-14 content in the sample / Carbon-14 content in the modern carbon standard] × 100%.

[0085] Table 1 Test results Project Example 7 Example 8 Example 9 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Wet friction coefficient 0.68±0.02 0.71±0.02 0.70±0.02 0.58±0.03 0.60±0.03 0.68±0.02 0.64±0.03 0.49±0.04 <![CDATA[Wear resistance (mm 3 )]]> 76±4 72±3 73±4 78±5 105±8 80±4 81±4 87±5 Tensile strength (MPa) 14.7±0.6 15.8±0.5 15.3±0.5 12.1±0.6 14.2±0.5 13.5±0.7 14.1±0.6 15.1±0.5 Elongation at break (%) 340±10 360±10 350±10 310±10 330±10 290±15 320±10 220±10 Hardness (Shore A) 70±1 71±1 70±1 70±1 64±1 70±1 65±1 69±1 Degradation rate (%) 71±2 73±2 71±2 63±2 70±2 58±3 70±2 70±2 Biobased content (%) 76.5±1.2 78.1±1.1 77.7±1.0 74.4±1.3 75.8±1.2 76.3±1.2 74.2±1.0 77.1±0.9 Data analysis from Table 1 is as follows: I. Data analysis of Examples 7 - 9: (1) Wet friction coefficient (0.68 - 0.71): All examples meet the EU safety shoe standard (≥0.7), thanks to the synergistic effect of modified polyhydroxybutyrate (enhanced interfacial bonding by wood vinegar) and tannic acid-treated bio-based powder (improved surface hydrophobicity).

[0086] (2) Abrasion resistance (72 - 76mm 3 ): The compounding of nanocellulose whiskers and bamboo charcoal micropowder provides rigid support and reduces wear.

[0087] (3) Tensile strength (14.7 - 15.8 MPa) and elongation at break (340% - 360%): The bicontinuous phase structure of modified polyhydroxybutyrate (starch - polyhydroxybutyrate crosslinking) and the compounding of compatibilizers (epoxy soybean oil + maleic anhydride-grafted polylactic acid) optimize the mechanical properties.

[0088] (4) Biodegradation rate (71% - 73%): The degradation aid compounded with polycaprolactone (PCL) and polybutylene succinate (PBS) accelerates microbial decomposition.

[0089] II. Data analysis of Comparative Examples 3 - 7 and Example 8: 1. Comparative Example 3 (modified polyhydroxybutyrate without wood vinegar): (1) Decrease in wet friction coefficient (0.58 vs 0.71): Phenolic substances in wood vinegar form hydrogen bonds with starch / polyhydroxybutyrate, enhancing interfacial bonding. The removal of interfacial defects leads to a decrease in anti-slip performance.

[0090] (2) Decrease in degradation rate (63% vs 73%): Organic acids in wood vinegar may promote microbial activity, and their absence slows down the degradation rate.

[0091] 2. Comparative Example 4 (biobased powder not treated with tannic acid spraying): (1) Decrease in wet friction coefficient (0.60 vs 0.71): The tannic acid coating forms a hydrogen bond network with the rubber matrix through polyphenolic hydroxyl groups, improving surface hydrophobicity. After removal, it is difficult to drain the water film.

[0092] (2) Deterioration of wear resistance (105 mm 3 vs 72 mm 3 ): Tannic acid enhances the binding force between the powder and the matrix. The untreated powder is prone to falling off, leading to increased wear.

[0093] 3. Comparative Example 5 (single biodegradable additive polycaprolactone): Decrease in degradation rate (58% vs 73%): The compounding of polybutylene succinate and polycaprolactone can form a complementary degradation mechanism (rapid hydrolysis of polybutylene succinate and slow enzymatic hydrolysis of polycaprolactone). The degradation efficiency of single polycaprolactone is low.

[0094] 4. Comparative Example 6 (only using epoxidized soybean oil compatibilizer): (1) Decrease in wet friction coefficient (0.64 vs 0.71): Maleic anhydride grafted polylactic acid can improve the compatibility between polyhydroxybutyrate and natural rubber. Single epoxidized soybean oil cannot effectively reduce the interfacial tension.

[0095] (2) Decrease in hardness (65 vs 71): Insufficient compatibility leads to an increase in the porosity inside the material.

[0096] 5. Comparative Example 7 (unmodified polyhydroxybutyrate matrix): (1) Significant decrease in wet friction coefficient (0.49 vs 0.71): The compatibility between unmodified polyhydroxybutyrate and natural rubber is poor, and phase separation leads to insufficient surface roughness.

[0097] (2) Sharp drop in elongation at break (220% vs 360%): Polyhydroxybutyrate has a high crystallinity and does not form a bicontinuous phase with starch, resulting in increased brittleness.

[0098] It should be noted that in this article, terms such as "including, containing" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such a process, method, article or device.

[0099] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high bio-based content sole rubber material, characterized in that: The invention comprises the following components in parts by weight: 20-30 parts of natural rubber, 20-30 parts of modified polyhydroxybutyrate, 20-30 parts of modified bio-based powder, 5-8 parts of biodegradable aid, 6-12 parts of compatibilizer, 10-12 parts of reinforcing agent, 2-8 parts of coupling agent, 2-4 parts of accelerator, 3 parts of antioxidant, 2-4 parts of cross-linking agent, 2 parts of wear-resistant enhancer and 2 parts of processing aid.

2. The high bio-based content sole rubber material according to claim 1, characterized in that: The modified polyhydroxybutyrate is prepared by the following steps: A1. Mix corn starch and plasticizer glycerol in a mass ratio of 10:3, extrude granulate at 120-130° C., cool, and granulate to obtain thermoplastic starch masterbatch; A2. Mix polyhydroxybutyrate wood vinegar, knead at 155-160° C. for 5-10 min, add thermoplastic starch masterbatch, heat to 165-170° C. for kneading for 8-10 min, cool to 130-140° C., add dicumyl peroxide, continue kneading for 3-5 min, and cool to room temperature to obtain modified polyhydroxybutyrate.

3. The high bio-based content sole rubber material according to claim 2, characterized in that: The corn starch and glycerol described in A1 are mixed in a mass ratio of 10:3; the mass ratio of the polyhydroxybutyrate, wood vinegar, thermoplastic starch masterbatch and dicumyl peroxide described in A2 is 28-30:3-5:15-20:0.5-1.

0.

4. The high bio-based content sole rubber material according to claim 1, characterized in that: The modified bio-based powder is prepared by the following steps: B1. Anhydrous ethanol and silane coupling agent KH-550 are mixed in a volume ratio of 19:1 to prepare a treatment solution, and then the husk powder is dried in an oven at 105-110° C. for 2 hours. After completion, the dried husk powder is immersed in the treatment solution at a solid-liquid ratio of 1:10, and the system is heated to 60-65° C. and magnetically stirred at a constant temperature for 30 minutes. During this period, ultrasonic treatment is synchronously turned on for 5 minutes every 10 minutes. After completion, the powder is separated and collected by suction filtration, washed with anhydrous ethanol 3 times to remove physical adsorbents, and then placed at 80-100° C. and vacuum dried for 4-5 hours to obtain silanized husk powder; B2, prepare a tannic acid-water solution with a mass concentration of 0.5wt%, and then adjust the pH of the tannic acid-water solution to 5.0-5.2 with a 0.1mol / L NaOH solution, and after completion, obtain a surface treatment solution; B3. Use a spray gun to spray the surface treatment solution on the surface of the silanized rice husk powder at a flow rate of 0.2 mL / min. The spraying amount is controlled at 2.5% to 5.0% of the mass of the silanized rice husk powder. After completion, hot air curing, cooling, and then passing through an 80-mesh sieve to obtain a modified bio-based powder.

5. The high bio-based content sole rubber material according to claim 1, characterized in that: The biodegradable aid is prepared by compounding polycaprolactone and polybutylene succinate in a mass ratio of 1:1; the compatibilizer is prepared by compounding epoxy soybean oil and maleic anhydride grafted polylactic acid in a mass ratio of 2:

1.

6. The high bio-based content sole rubber material according to claim 1, characterized in that: The reinforcing agent is one of kaolin, bentonite and white carbon black; the coupling agent is one of KH-550, KH-560 and KH-570; the accelerator is one or two of triallyl isocyanurate and trimethylolpropane trimethacrylate mixed in a mass ratio of 1:

1.

7. The high bio-based content sole rubber material according to claim 1, characterized in that: The antioxidant is one of antioxidant RD and antioxidant 4010NA, or two of them are compounded in a mass ratio of 2:1; the cross-linking agent is one of 1,4-di-tert-butylperoxyisopropylbenzene, 1,1′-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane.

8. The high bio-based content sole rubber material according to claim 1, characterized in that: The wear-resistant reinforcing agent is a compound of nanocellulose whiskers and bamboo charcoal powder in a mass ratio of 1:

3.

9. The high bio-based content sole rubber material according to claim 1, characterized in that: The processing aid is one of tributyl citrate and glyceryl stearate.

10. A method for preparing a high bio-based content sole rubber material according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Weigh the raw materials according to their mass fractions, add the natural rubber and modified polyhydroxybutyrate into an internal mixer at a temperature of 120 to 140° C., at a speed of 50 r / min, and mix for 10 to 15 minutes. Then add the modified bio-based powder into the internal mixer, keep the temperature and speed constant, and mix for 8 to 10 minutes to obtain a masterbatch. S2, adding a biodegradation aid, a compatibilizer, a reinforcing agent, a coupling agent, an accelerator, an antioxidant, a cross-linking agent, a wear-resistant reinforcing agent and a processing aid to the internal mixer containing the masterbatch in step S1 in order by weight, controlling the temperature and the speed to remain unchanged, continuing the internal mixing for 5 to 10 minutes, and then cooling to room temperature to obtain a mixture, and placing the mixture in a granulator for granulation to obtain a sample; S3, putting the sample obtained in step S2 into a vulcanizing machine, controlling the vulcanization temperature to 150-160° C. and the vulcanization time to 3-4 hours, cooling to room temperature after the vulcanization is completed, taking the vulcanized material out of the vulcanizing machine, and obtaining a bio-based sole material.