A slow-rebound shock-absorbing insole material for foot rehabilitation and its preparation method

Abstract

This invention relates to the field of polymer foam materials technology, specifically to a slow-rebound shock-absorbing insole material for foot rehabilitation and its preparation method. The slow-rebound shock-absorbing insole material for foot rehabilitation is prepared by mixing and foaming component A and component B at a mass ratio of 100:60-70. Component A consists of the following raw materials by weight percentage: 15-18% polyether polyol, 18-23% polymer polyol, 0.3-0.8% crosslinking agent, 0.8-1.5% catalyst, 8-12% cell opener, 0.3-0.6% silicone oil, 0.2-0.5% water, with the balance being vegetable oil polyol. Component B is modified MDI. The slow-rebound shock-absorbing insole material prepared by this invention maintains moderate hardness while achieving a longer slow rebound time, better anti-collapse ability, and more significant foot pressure reduction effect. It can effectively disperse foot pressure and provide continuous and stable support, meeting the professional needs of foot rehabilitation and medical orthotic insoles.

Description

Technical Field

[0001] This invention relates to the field of polymer foam materials technology, specifically to a slow-rebound shock-absorbing insole material for foot rehabilitation and its preparation method. Background Technology

[0002] Foot rehabilitation is an important component of orthopedics, rehabilitation medicine, and sports medicine. As the core structure for weight-bearing and walking, the foot bears the entire body weight and ground reaction forces over a long period. When the plantar fascia, arch structure, or related soft tissues are injured, inflamed, or post-operatively, patients often experience significant foot pain, gait abnormalities, and instability. Common foot conditions include plantar fasciitis, flat feet, high arches, heel pain, and diabetic foot ulcers. In the rehabilitation process for these conditions, insoles, as assistive devices that directly contact the sole of the foot, have their material properties directly affecting rehabilitation outcomes and patient compliance.

[0003] Traditional insole materials mostly use ordinary EVA, rubber, or ordinary polyurethane foam. Their main problem is that they rebound too quickly and have limited pressure dispersion capabilities, failing to create a continuous and gentle cushioning interface between the foot and the ground. For rehabilitation needs requiring relief of foot pressure or postoperative support, slow rebound materials are increasingly becoming the professional choice. Slow rebound materials (also known as memory foam) can slowly return to their original shape after being compressed, thereby evenly distributing peak pressure across different areas of the foot, reducing localized stress concentration, and providing continuous and stable support, which is beneficial for tissue repair and gait reconstruction.

[0004] However, existing slow-rebound insole materials still have significant shortcomings: on the one hand, some products lack sufficient support and are prone to collapsing after prolonged use; on the other hand, improper control of the perforation structure leads to poor breathability or unstable rebound performance. Furthermore, medical orthotic insoles have specific requirements for material density, hardness, rebound rate, and durability.

[0005] Therefore, the present invention provides a slow rebound shock-absorbing insole material for foot rehabilitation and its preparation method to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention provides a slow-rebound shock-absorbing insole material for foot rehabilitation and its preparation method. The prepared slow-rebound shock-absorbing insole material for foot rehabilitation maintains moderate hardness while achieving a longer slow rebound time, better anti-collapse ability, and more significant foot pressure reduction effect. It can effectively disperse foot pressure and provide continuous and stable support, meeting the professional needs of foot rehabilitation and medical orthotic insoles. It has clear clinical application value and good industrialization prospects.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A slow-rebound shock-absorbing insole material for foot rehabilitation is made by mixing and foaming component A and component B at a mass ratio of 100:60-70. Component A consists of the following raw materials by weight percentage: 15-18% polyether polyol, 18-23% polymer polyol, 0.3-0.8% crosslinking agent, 0.8-1.5% catalyst, 8-12% cell opener, 0.3-0.6% silicone oil, 0.2-0.5% water, and the balance being vegetable oil polyol. Component B is modified MDI.

[0008] Furthermore, the polyether polyol is any one of PTMEG-1800, FR1830, PTMEG-2000, FR2026, and PTMEG-3000.

[0009] Furthermore, the polymer polyol is any one of ZS-350G, POP93 / 28, ZS-3160, and POP36 / 28.

[0010] Furthermore, the crosslinking agent is any one of diethanolamine, 1,4-butanediol, trimethylolpropane, and triethanolamine.

[0011] Furthermore, the catalyst is any one of catalyst A33, catalyst PC41, and catalyst TMR-2.

[0012] Furthermore, the pore-opening agent is any one of pore-opening agent O501, pore-opening agent Yukol 8331, pore-opening agent GK-350D.

[0013] Furthermore, the silicone oil is any one of silicone oil B8681, silicone oil BL-8002M, and silicone oil BL-898.

[0014] Furthermore, the method for preparing the vegetable oil polyol includes the following steps: Step 1: Mix palm oil, oxalic acid, and urea evenly in a mass ratio of 3-5:1:0.025-0.035. Add 30-60wt% hydrogen peroxide of palm oil dropwise to the mixture while stirring at 40-70℃ for 1-2 hours. React at 55-70℃ for 1-2 hours, and then at 80-100℃ for 5-8 hours. Step 2: After the reaction is complete, wash the resulting reaction product with deionized water at 70-80℃ for 20-30 minutes, then wash with ammonia water at 28wt% concentration and 20-25% of palm oil for 15-20 minutes, and then wash with deionized water at 70-80℃ for 20-30 minutes. Repeat the washing process 3-4 times. Step 3: After washing, the product is subjected to adsorption and decolorization with bleaching clay and then dried. The final product is plant polyol. The drying temperature is 70-110℃ and the drying time is 1-3 hours.

[0015] Furthermore, the modified MDI is prepared as follows: zinc decanoate and butanol are added to the MDI melt under nitrogen protection, and the mixture is stirred and reacted at 70-80℃ for 2-4 hours; after the reaction is completed, the temperature of the product is lowered to 50-60℃ and vacuum-dried polyether diol is added, and the mixture is stirred and heated to 70-90℃ for 2-4 hours; then benzoyl chloride is added, and the reaction continues for 1-2 hours. The product is then naturally cooled to room temperature to obtain the modified MDI. The amounts of zinc decanoate and benzoyl chloride used are 0.02-0.04 wt% and 0.03-0.06 wt% of the MDI melt, respectively; and the molar ratio of MDI melt, butanol and polyether diol is 8-10:1:0.4-0.6. The MDI used is Wanhua Chemical MDI100; the polyether diol is polytetrahydrofuran diol with a molecular weight of 1000-4000, and its vacuum drying temperature is 110-120℃ and the vacuum drying time is 20-30h.

[0016] A method for preparing a slow-rebound shock-absorbing insole material for foot rehabilitation includes the following steps: Step 1: Accurately weigh the raw materials corresponding to component A and component B according to the formula; add the polyether polyol, polymer polyol and vegetable oil polyol from component A to the reaction vessel, mix and stir evenly, then add the remaining raw materials of component A, mix and stir evenly, and react at 40-60℃ for 3-5 hours. Store the resulting component A for later use. The second step is to add components A and B into the reaction vessel according to the ratio, mix them evenly, and then pour them into the mold. After 4-6 minutes, open the mold and then cure it at 45-60℃ to obtain the slow rebound shock-absorbing insole material for foot rehabilitation. The mold temperature is 50-60℃ and the material temperature is 25-35℃.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention significantly improves the slow rebound characteristics and resistance to compression set of slow-rebound shock-absorbing insole materials by replacing a portion of traditional petroleum-based polyether polyols with vegetable oil polyols and combining them with modified MDI for foaming. The polar groups introduced in the vegetable oil polyols form a stable cross-linking network with the zinc decanoate and benzoyl chloride modified segments in the modified MDI, resulting in a slow and uniform recovery speed of the slow-rebound shock-absorbing insole material after compression. This effectively prolongs the contact time between the foot and the insole, thereby diffusing the peak pressure of the foot to the surrounding area and reducing local stress concentration. It is especially suitable for patients with plantar fasciitis and those recovering from surgery.

[0018] 2. This invention rationally introduces an opening agent and silicone oil while controlling the amount of water, enabling the slow-rebound shock-absorbing insole material to form a moderately open-cell structure. This structure, while ensuring the slow-rebound effect, improves the breathability and compression resilience of the slow-rebound shock-absorbing insole material, avoiding skin maceration or discomfort caused by moisture and heat accumulation during long-term use. Furthermore, the slow-rebound shock-absorbing insole material prepared by this invention also has the advantages of low density and moderate hardness, meeting the dual requirements of softness and support for medical orthopedic insoles.

[0019] 3. The modified MDI in this invention, through the synergistic modification of zinc decanoate and polyether diol, reduces the fluctuation of MDI's reactivity, improves its compatibility with vegetable oil polyols, makes the foaming process more stable, and results in high batch stability of the finished product. Simultaneously, this slow-rebound shock-absorbing insole material can be molded and customized according to the arch shape of the foot, making it suitable for personalized medical orthotic insoles with specific arch support and heel cup stability requirements.

[0020] In summary, the slow-rebound shock-absorbing insole material prepared by this invention maintains moderate hardness while achieving a longer slow rebound time, better anti-collapse ability, and more significant foot pressure reduction effect. It can effectively disperse foot pressure and provide continuous and stable support, meeting the professional needs of foot rehabilitation and medical orthotic insoles. It has clear clinical application value and good industrialization prospects. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1

[0022] A slow-rebound shock-absorbing insole material for foot rehabilitation is made by foaming a mixture of component A and component B in a mass ratio of 100:60. Component A consists of the following raw materials by weight percentage: 15% polyether polyol, 18% polymer polyol, 0.3% crosslinking agent, 0.8% catalyst, 8% cell opener, 0.3% silicone oil, 0.2% water, and the balance being vegetable oil polyol; component B is modified MDI. Among them, the polyether polyol is PTMEG-1800; the polymer polyol is ZS-350G; the crosslinking agent is diethanolamine; the catalyst is catalyst A33; the pore opener is pore opener O501; and the silicone oil is silicone oil B8681.

[0023] The preparation method of vegetable oil polyols includes the following steps: Step 1: Mix palm oil, oxalic acid and urea evenly in a mass ratio of 3:1:0.025. Add 30wt% hydrogen peroxide of palm oil dropwise at 40℃ with stirring for 2 hours. React at 55℃ for 2 hours first, and then at 80℃ for 8 hours. Step 2: After the reaction is complete, the resulting reaction product is washed with deionized water at 70°C for 20 minutes, then washed with ammonia water at 28wt% concentration and 20% of palm oil for 15 minutes, and then washed with deionized water at 70°C for 20 minutes. This washing process is repeated 3 times. Step 3: After washing, the product is subjected to adsorption and decolorization with bleaching clay and then dried. The final product is plant polyol. The drying temperature is 70℃ and the drying time is 3 hours.

[0024] The modified MDI is prepared as follows: zinc decanoate and butanol are added to the MDI melt under nitrogen protection, and the mixture is stirred at 70°C for 4 hours. After the reaction is completed, the temperature of the product is lowered to 50°C and vacuum-dried polyether diol is added. The mixture is stirred and heated to 70°C for 4 hours. Then benzoyl chloride is added and the reaction continues for 1 hour. The product is then naturally cooled to room temperature to obtain the modified MDI. The amounts of zinc decanoate and benzoyl chloride used were 0.02 wt% and 0.03 wt% of the MDI melt, respectively; and the molar ratio of MDI melt, butanol and polyether diol was 8:1:0.4. The MDI used was Wanhua Chemical MDI100; the polyether diol used was polytetrahydrofuran diol with a molecular weight of 1000, and the vacuum drying temperature was 110℃ and the vacuum drying time was 30h.

[0025] A method for preparing a slow-rebound shock-absorbing insole material for foot rehabilitation includes the following steps: Step 1: Accurately weigh the raw materials corresponding to component A and component B according to the formula; add the polyether polyol, polymer polyol and vegetable oil polyol from component A to the reaction vessel, mix and stir evenly, then add the remaining raw materials of component A, mix and stir evenly, and react at 40℃ for 5 hours. Store the resulting component A for later use. The second step involves adding components A and B to a reaction vessel in proportion, mixing them thoroughly, and then pouring the mixture into a mold. After 4 minutes, the mold is opened, and the mixture is then cured at 45°C to obtain a slow-rebound shock-absorbing insole material for foot rehabilitation. The mold temperature is 50°C, and the material temperature is 25°C. Example 2

[0026] A slow-rebound shock-absorbing insole material for foot rehabilitation is made by foaming a mixture of component A and component B in a mass ratio of 100:65. Component A consists of the following raw materials by weight percentage: 17% polyether polyol, 20% polymer polyol, 0.5% crosslinking agent, 1.0% catalyst, 10% cell opener, 0.5% silicone oil, 0.3% water, and the balance being vegetable oil polyol. Component B is modified MDI. Among them, the polyether polyol is FR1830; the polymer polyol is POP93 / 28; the crosslinking agent is 1,4-butanediol; the catalyst is catalyst PC41; the pore opener is pore opener Yukol 8331; and the silicone oil is silicone oil BL-8002M.

[0027] The preparation method of vegetable oil polyols includes the following steps: Step 1: Mix palm oil, oxalic acid and urea evenly in a mass ratio of 4:1:0.03. Stir and add 50wt% hydrogen peroxide of palm oil dropwise at 55℃ for 2 hours. React at 60℃ for 2 hours first, and then at 90℃ for 6 hours. Step 2: After the reaction is complete, the resulting reaction product is washed with deionized water at 75°C for 25 min, then washed with ammonia water at 28 wt% concentration and 25% of palm oil for 20 min, and then washed with deionized water at 75°C for 25 min. This washing process is repeated 4 times. Step 3: After washing, the product is subjected to adsorption and decolorization with bleaching clay and then dried. The final product is plant polyol. The drying temperature is 70-110℃ and the drying time is 1-3 hours.

[0028] The modified MDI is prepared as follows: zinc decanoate and butanol are added to the MDI melt under nitrogen protection, and the mixture is stirred at 75°C for 3 hours. After the reaction is completed, the temperature of the product is lowered to 55°C and vacuum-dried polyether diol is added. The mixture is stirred and heated to 80°C for 3 hours. Then benzoyl chloride is added and the reaction continues for 2 hours. The product is naturally cooled to room temperature to obtain the modified MDI. The amounts of zinc decanoate and benzoyl chloride used were 0.03 wt% and 0.05 wt% of the MDI melt, respectively; and the molar ratio of MDI melt, butanol and polyether diol was 10:1:0.5. The MDI used was Wanhua Chemical MDI100; the polyether diol used was polytetrahydrofuran diol with a molecular weight of 2000, and the vacuum drying temperature was 120℃ and the vacuum drying time was 20h.

[0029] A method for preparing a slow-rebound shock-absorbing insole material for foot rehabilitation includes the following steps: Step 1: Accurately weigh the raw materials corresponding to component A and component B according to the formula; add the polyether polyol, polymer polyol and vegetable oil polyol from component A to the reaction vessel, mix and stir evenly, then add the remaining raw materials of component A, mix and stir evenly, and react at 50℃ for 4 hours. Store the resulting component A for later use. The second step is to add components A and B into the reaction vessel according to the ratio, mix them evenly, and then pour them into the mold. After 5 minutes, open the mold and then cure it at 55°C to obtain the slow rebound shock-absorbing insole material for foot rehabilitation. The mold temperature is 55°C and the material temperature is 30°C. Example 3

[0030] A slow-rebound shock-absorbing insole material for foot rehabilitation is made by foaming a mixture of component A and component B in a mass ratio of 100:70. Component A consists of the following raw materials by weight percentage: 18% polyether polyol, 23% polymer polyol, 0.8% crosslinking agent, 1.5% catalyst, 12% cell opener, 0.6% silicone oil, 0.5% water, and the balance being vegetable oil polyol. Component B is modified MDI. Among them, the polyether polyol is PTMEG-2000; the polymer polyol is ZS-3160; the crosslinking agent is trimethylolpropane; the catalyst is catalyst TMR-2; the pore opener is pore opener GK-350D; and the silicone oil is silicone oil BL-898.

[0031] The preparation method of vegetable oil polyols includes the following steps: Step 1: Mix palm oil, oxalic acid and urea evenly in a mass ratio of 5:1:0.035. Add 60wt% hydrogen peroxide of palm oil dropwise to the mixture at 70℃ with stirring for 1 hour. React at 70℃ for 1 hour first, and then at 100℃ for 5 hours. Step 2: After the reaction is complete, the resulting reaction product is washed with deionized water at 80°C for 20 minutes, then washed with ammonia water at 28wt% concentration and 25% of palm oil for 20 minutes, and then washed with deionized water at 80°C for 20 minutes. This washing process is repeated 4 times. Step 3: After washing, the product is subjected to adsorption and decolorization with bleaching clay and then dried. The final product is plant polyol. The drying temperature is 110℃ and the drying time is 1 hour.

[0032] The modified MDI is prepared as follows: zinc decanoate and butanol are added to the MDI melt under nitrogen protection, and the mixture is stirred at 80°C for 2 hours. After the reaction is completed, the temperature of the product is lowered to 60°C and vacuum-dried polyether diol is added. The mixture is stirred and heated to 90°C for 2 hours. Then benzoyl chloride is added and the reaction continues for 2 hours. The product is then naturally cooled to room temperature to obtain the modified MDI. The amounts of zinc decanoate and benzoyl chloride used were 0.04 wt% and 0.06 wt% of the MDI melt, respectively; and the molar ratio of MDI melt, butanol and polyether diol was 10:1:0.6. The MDI used was Wanhua Chemical MDI100; the polyether diol used was polytetrahydrofuran diol with a molecular weight of 4000, and the vacuum drying temperature was 120℃ and the vacuum drying time was 20h.

[0033] A method for preparing a slow-rebound shock-absorbing insole material for foot rehabilitation includes the following steps: Step 1: Accurately weigh the raw materials corresponding to component A and component B according to the formula; add the polyether polyol, polymer polyol and vegetable oil polyol from component A to the reaction vessel, mix and stir evenly, then add the remaining raw materials of component A, mix and stir evenly, and react at 60℃ for 3 hours. Store the resulting component A for later use. The second step involves adding components A and B into a reaction vessel according to a certain ratio, mixing them evenly, and then pouring the mixture into a mold. After 6 minutes, the mold is opened, and the mixture is then cured at 60°C to obtain a slow-rebound shock-absorbing insole material for foot rehabilitation. The mold temperature is 60°C and the material temperature is 35°C.

[0034] Performance testing The slow rebound shock-absorbing insole material samples for foot rehabilitation prepared in Examples 1-3 and the comparative example were subjected to the following performance tests, and the test data are recorded in the table below: 1. Density test: According to GB / T 6343-2009 standard, each slow rebound shock-absorbing insole material is cut into 50mm×50mm×50mm samples. After being placed in a standard environment (23±2℃, 50±5%RH) for 24 hours, the mass is weighed and the volume is calculated. Density = mass / volume.

[0035] 2. Hardness test: According to GB / T 10807-2006 standard, a type C Shore hardness tester was used. The thickness of the slow rebound shock-absorbing insole material sample was 15mm. Five points were measured at different positions on the surface of each slow rebound shock-absorbing insole material sample, and the average value was taken.

[0036] 3. Slow rebound time test: According to ASTM D3574-17 standard, a cylindrical sample of slow rebound shock-absorbing insole material with a diameter of 30 mm and a thickness of 15 mm was compressed to 50% of its original thickness at 23℃, held for 60 seconds, and then the pressure was quickly released. The time required for each cylindrical sample of slow rebound shock-absorbing insole material to recover to 90% of its original thickness was recorded (unit: s).

[0037] 4. Compression permanent deformation test: According to GB / T6669-2008 standard, each 50mm×50mm×25mm slow rebound shock-absorbing insole material cylindrical sample was compressed by 50% at 70℃, kept for 22h and then released. After being placed at room temperature for 30min, the thickness change rate was measured.

[0038] 5. Peak plantar pressure dispersion rate test: The slow rebound shock-absorbing insole materials prepared in Examples 1-3 and the comparative examples were used to make insoles. Then, 10 healthy volunteers (foot size matched with insole size) were selected. The peak plantar pressure was measured when wearing the insole and when not wearing the insole under a constant walking state. The peak pressure dispersion rate was calculated as follows: peak pressure dispersion rate = (peak pressure when not wearing insole - peak pressure when wearing insole) / peak pressure when not wearing insole × 100%.

[0039]

[0040] By comparing and analyzing the relevant data in the table, it can be seen that the slow-rebound shock-absorbing insole material prepared by this invention, while maintaining moderate hardness, achieves a longer slow-rebound time, better anti-collapse ability, and a more significant foot pressure reduction effect. It can effectively disperse foot pressure and provide continuous and stable support, meeting the professional needs of foot rehabilitation and medical orthotic insoles, and has clear clinical application value and good industrialization prospects. Therefore, this invention provides a slow-rebound shock-absorbing insole material for foot rehabilitation and its preparation method, which has a broader market prospect and is more suitable for promotion.

[0041] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A slow-rebound cushioning insole material for plantar rehabilitation, which is made by mixing and foaming A component and B component in a mass ratio of 100:60-70; characterized in that: Component A consists of the following raw materials by weight percentage: 15-18% polyether polyol, 18-23% polymer polyol, 0.3-0.8% crosslinking agent, 0.8-1.5% catalyst, 8-12% pore-opening agent, 0.3-0.6% silicone oil, 0.2-0.5% water, with the balance being vegetable oil polyol; Component B is modified MDI.

2. The slow-rebound shock-absorbing insole material for foot rehabilitation according to claim 1, characterized in that: The polyether polyol is any one of PTMEG-1800, FR1830, PTMEG-2000, FR2026, and PTMEG-3000.

3. The slow-rebound shock-absorbing insole material for foot rehabilitation according to claim 1, characterized in that: The polymer polyol is any one of ZS-350G, POP93 / 28, ZS-3160, and POP36 / 28.

4. The slow-rebound shock-absorbing insole material for foot rehabilitation according to claim 1, characterized in that: The crosslinking agent is any one of diethanolamine, 1,4-butanediol, trimethylolpropane, and triethanolamine.

5. The slow-rebound shock-absorbing insole material for foot rehabilitation according to claim 1, characterized in that: The catalyst is any one of catalyst A33, catalyst PC41, and catalyst TMR-2.

6. The slow-rebound shock-absorbing insole material for foot rehabilitation according to claim 1, characterized in that: The pore-opening agent is any one of pore-opening agent O501, pore-opening agent Yukol 8331, and pore-opening agent GK-350D.

7. The slow-rebound shock-absorbing insole material for foot rehabilitation according to claim 1, characterized in that: The silicone oil is any one of silicone oil B8681, silicone oil BL-8002M, or silicone oil BL-898.

8. The slow-rebound shock-absorbing insole material for foot rehabilitation according to claim 1, characterized in that, The method for preparing the plant oil polyol includes the following steps: Step 1: Mix palm oil, oxalic acid, and urea evenly in a mass ratio of 3-5:1:0.025-0.

035. Add 30-60wt% hydrogen peroxide of palm oil dropwise to the mixture while stirring at 40-70℃ for 1-2 hours. React at 55-70℃ for 1-2 hours, and then at 80-100℃ for 5-8 hours. Step 2: After the reaction is complete, wash the resulting reaction product with deionized water at 70-80℃ for 20-30 minutes, then wash with ammonia water at 28wt% concentration and 20-25% of palm oil for 15-20 minutes, and then wash with deionized water at 70-80℃ for 20-30 minutes. Repeat the washing process 3-4 times. Step 3: After washing, the product is subjected to adsorption and decolorization with bleaching clay and then dried. The final product is plant polyol. The drying temperature is 70-110℃ and the drying time is 1-3 hours.

9. A slow-rebound shock-absorbing insole material for foot rehabilitation according to claim 1, characterized in that, The modified MDI is prepared as follows: zinc decanoate and butanol are added to the MDI melt under nitrogen protection, and the mixture is stirred and reacted at 70-80℃ for 2-4 hours; after the reaction is completed, the temperature of the product is lowered to 50-60℃ and vacuum-dried polyether diol is added, and the mixture is stirred and heated to 70-90℃ for 2-4 hours; then benzoyl chloride is added, and the reaction continues for 1-2 hours. The product is then naturally cooled to room temperature to obtain the modified MDI. The amounts of zinc decanoate and benzoyl chloride used are 0.02-0.04 wt% and 0.03-0.06 wt% of the MDI melt, respectively; and the molar ratio of MDI melt, butanol and polyether diol is 8-10:1:0.4-0.

6. The MDI used is Wanhua Chemical MDI100; the polyether diol is polytetrahydrofuran diol with a molecular weight of 1000-4000, and its vacuum drying temperature is 110-120℃ and the vacuum drying time is 20-30h.

10. A method for preparing a slow-rebound shock-absorbing insole material for foot rehabilitation according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Accurately weigh the raw materials corresponding to component A and component B according to the formula; The polyether polyol, polymer polyol, and vegetable oil polyol from component A are added to the reactor and mixed thoroughly. Then, the remaining raw materials from component A are added and mixed thoroughly again. The mixture is then reacted at 40-60℃ for 3-5 hours. The resulting component A is stored for later use. The second step is to add components A and B into the reaction vessel according to the ratio, mix them evenly, and then pour them into the mold. After 4-6 minutes, open the mold and then cure it at 45-60℃ to obtain the slow rebound shock-absorbing insole material for foot rehabilitation. The mold temperature is 50-60℃ and the material temperature is 25-35℃.

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