Polyurethane prepolymer, foaming material, preparation method of polyurethane prepolymer and foaming material, and application of polyurethane prepolymer and foaming material in midsole of diabetic foot protection shoe

Abstract

The invention discloses a polyurethane prepolymer, a foaming material, a preparation method of the foaming material and application of the foaming material in a middle sole of a diabetic foot protection shoe, relates to the technical field of high polymer materials, and solves the problem that a middle sole material of the diabetic foot protection shoe is poor in pressure dispersion performance. The method comprises the following steps: dissolving trimethanol propane in dichloromethane, adding a catalyst, uniformly mixing, dropwise adding a mixed solution of epoxypropane and tetrahydrofuran, washing with saturated sodium bicarbonate, washing to be neutral, extracting an organic phase, dissolving in DMF, filtering, washing filtrate with water, settling to obtain a crude product, extracting, and carrying out reduced pressure distillation to obtain a product 1; adding polytetrahydrofuran and the product 1 into a flask, introducing nitrogen, heating, adding toluene diisocynate, continuously heating, adding dibutyltin dilaurate, and stirring for reaction to obtain a polyurethane prepolymer; the foaming material comprises polyether triol, water, silicone oil, a triethylene diamine aqueous solution, stannous octoate and a polyurethane prepolymer. The method can be used for preparing the middle sole of the diabetic foot shoe, and reliable material guarantee is provided for preventing diabetic foot complications.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a polyurethane prepolymer, a foaming material, a method for preparing the same, and its application in the midsole of a protective shoe for diabetic foot. Background Technology

[0002] Diabetic foot is a serious complication of diabetes caused by long-term neuropathy and vascular disease. Patients experience decreased sensation and impaired blood circulation in their feet, making them susceptible to developing slow-healing ulcers even from minor friction, pressure, or trauma. In severe cases, this can lead to infection and even amputation. Therefore, diabetic foot protective shoes are crucial medical assistive devices for preventing this complication, and the performance of their core component, the midsole, directly determines their protective effectiveness and safety.

[0003] An ideal midsole for diabetic shoes must simultaneously meet five core requirements. First, excellent cushioning and shock absorption to effectively absorb the impact of the ground on the foot during walking, reducing the risk of joint and soft tissue damage. Second, even pressure distribution to distribute body weight and gait pressure evenly across the entire sole, preventing localized high pressure in areas prone to ulceration such as the metatarsal heads and heels. Third, stable support to limit excessive pronation or supination, maintaining foot stability during walking and reducing joint strain. Fourth, lightweight characteristics, with the material's weight controlled within a reasonable range to avoid increasing the burden on patients. Fifth, long-term durability, maintaining cushioning and support performance over a long period without easily deforming due to repeated stress.

[0004] Currently, the mainstream midsole materials for diabetic shoes on the market include ethylene-vinyl acetate copolymer (EVA), traditional polyurethane (PU), memory foam / slow rebound foam, and gel. However, all of these materials have performance shortcomings. EVA is difficult to balance cushioning and durability, and is prone to compression and deformation after long-term use; traditional PU has insufficient uniform pressure distribution; memory foam has a slow rebound speed and limited support; while gel materials have excellent cushioning effects, they are heavy and have poor durability.

[0005] In summary, existing materials cannot simultaneously achieve the comprehensive performance requirements of excellent pressure distribution, superior cushioning-rebound balance, and long-term durability, making it difficult to fully meet the core protection needs of diabetic foot patients. Therefore, developing a midsole material with comprehensive performance and adapted to the protection needs of diabetic foot has become an urgent technical problem to be solved in the industry. Summary of the Invention

[0006] To address the technical problems of poor pressure dispersion and cushioning-rebound performance in existing diabetic shoe midsole materials, this invention proposes a polyurethane prepolymer, a foaming material, its preparation method, and its application in the midsole of diabetic foot protection shoes.

[0007] The specific technical solution of this invention is as follows: This invention provides a polyurethane prepolymer with the following structural formula: ; Where n1, n2, n3, m1, m2, and m3 all represent the number of links in the repeating unit, and R is selected from... or .

[0008] The present invention also provides a method for preparing the above-mentioned polyurethane prepolymer, comprising the following steps: S1. Dissolve trimethylolpropane in dichloromethane, add boron trifluoride diethyl ether catalyst diluted with 1,2-dichloroethane, mix well, and then add dropwise a mixed solution of propylene oxide and tetrahydrofuran. The reaction yields a pale yellow liquid. S2. Wash the reaction mixture three times with saturated NaHCO3 solution, then wash with deionized water until neutral, extract the organic phase, dissolve it in N,N-dimethylformamide, filter to remove insoluble matter; wash the filtrate with a large amount of water to remove DMF and then precipitate to obtain crude product. Extract the crude product again and then distill it under reduced pressure at 110°C to obtain product 1, a pale yellow viscous liquid. S3. After drying the polytetrahydrofuran, add it together with product 1 into a flask, introduce N2, and stir at 55°C. S4. Heat to 80°C and add toluene diisocyanate. Continue heating to 85°C and add dibutyltin dilaurate. Stir the reaction to obtain a solvent-free polyurethane prepolymer.

[0009] Preferably, the molar ratio of product 1 to toluene diisocyanate (TDI) is 1:4.

[0010] Preferably, the mass of the boron trifluoride ether is 4% of that of triethanolpropane; and the mass of the propylene oxide is 4 times that of triethanolpropane.

[0011] Preferably, the stirring time in step S3 is 30 minutes.

[0012] Preferably, the stirring reaction time in step S4 is 3 hours.

[0013] The present invention also provides a polyurethane foam material, the raw materials of which include the above-mentioned polyurethane prepolymer.

[0014] Preferably, the component comprises the following parts by mass: Voranol CP 3322 polyether triol, 70-100 parts; water, 3.0-4.5 parts; silicone oil DC-190, 1.0-1.4 parts; 33% triethylenediamine aqueous solution, 0.06-0.08 parts; stannous octoate, 0.12 parts; polyurethane prepolymer, 40.7-56.6 parts.

[0015] The present invention also provides a method for preparing the above-mentioned polyurethane foam material, specifically: mixing the components in proportion, stirring evenly, and foaming at 60°C to obtain the material.

[0016] The present invention also provides an application of the above-mentioned polyurethane foam material in the midsole of a diabetic foot protection shoe.

[0017] Compared with the prior art, the specific beneficial effects of the present invention are as follows: This invention, through special molecular structure design and formulation optimization, provides a foaming material that can evenly distribute the pressure of the patient's foot striking the ground across the entire support surface. This effectively reduces the high-pressure area in key areas such as the metatarsal heads and heels, lowers local pressure peaks, and reduces the risk of ulcers caused by local compression from the source. It is also suitable for the physiological characteristics of diabetic foot, such as reduced sensation and poor blood circulation. The material's deformation is controlled within a reasonable range, allowing for moderate elastic deformation under gait impact. This efficiently absorbs the impact energy of the ground on the foot while avoiding excessive deformation that could affect walking stability. Combined with its excellent elongation at break, it can quickly rebound after deformation, reducing repeated damage to joints and soft tissues from impact forces, balancing cushioning effect and walking flexibility. The material density meets lightweight requirements, without increasing the burden on patients while the ASKERC stiffness can be flexibly adjusted. It provides sufficient support to limit abnormal foot movements and maintain walking stability, without causing foot discomfort due to excessive stiffness, thus adapting to the foot support needs of different patients. The material has a dense and uniform internal cross-linked structure, which avoids the problem of conflict between cushioning and durability in traditional materials. It can maintain stable cushioning and support performance even after long-term repeated stress, and is not easy to be compacted and deformed, thus extending the service life of the midsole and reducing the cost of use for patients.

[0018] In summary, the material provided by this invention comprehensively covers the core technical requirements of the midsole of diabetic shoes through its integrated performance of uniform pressure distribution, excellent cushioning and shock absorption, lightweight and balanced support, and long-term durability. Compared with existing materials, it is more suitable for the pathological characteristics and usage scenarios of diabetic foot patients, and provides a more reliable material guarantee for the prevention of diabetic foot complications. Attached Figure Description

[0019] Figure 1 The synthetic route for the polyurethane prepolymer described in this invention is as follows; Figure 2 Thermal images of the feet under stress when no shoe midsole material is worn; Figure 3 Thermal images of the stress on both feet when wearing the midsole material of the shoe; Figure 4 The force-time curve of both feet when no shoe midsole material is worn; Figure 5The overall force-time curve of both feet when wearing the midsole material of the shoe; Figure 6 The stress decomposition curve of the left foot when no shoe midsole material is worn; Figure 7 The stress decomposition curve of the left foot when wearing the midsole material of the shoe; Figure 8 The stress decomposition curve of the right foot when no shoe midsole material is worn; Figure 9 This is the stress decomposition curve of the right foot when wearing the midsole material of the shoe. Detailed Implementation

[0020] To make the technical solution of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to better understand the technical solution of the present invention and should not be construed as limiting the present invention. The raw materials used in the following embodiments are all commercially available. Voranol CP 3322 polyether triol has a hydroxyl value of 47.5 and a molecular weight of 3400.

[0021] Example 1. In this embodiment, a polyurethane prepolymer was prepared by the following steps: In a dry 500 mL four-necked flask, add 10.0 g of triethanolamine propane, followed by 40.0 mL of dichloromethane. Turn on the electric stirrer to completely dissolve the triethanolamine propane. Weigh 0.4 g of boron trifluoride diethyl ether, dilute it with 2.0 mL of 1,2-dichloroethane, and slowly add it to the flask through a constant-pressure dropping funnel. Stir and mix for 10 min. Mix 40.0 g of propylene oxide and 40.0 g of tetrahydrofuran thoroughly, pour the mixture into a constant-pressure dropping funnel, and add it dropwise to the reaction system at a rate of 1 mL / min at room temperature (25 °C) for 60 min. After the addition is complete, continue the reaction at this temperature for another 60 min to obtain a pale yellow transparent liquid.

[0022] The reaction mixture was transferred to a 250 mL separatory funnel, and 50.0 mL of saturated NaHCO3 solution was added. The mixture was vigorously shaken for 3 min, then allowed to stand for separation. The lower aqueous phase was discarded. This washing operation was repeated 3 times. The organic phase was washed with deionized water, shaken, and allowed to stand for separation. The pH of the aqueous phase was measured until pH=7, and this was repeated 3 times. The upper organic phase was collected and transferred to a dry beaker. 50.0 mL of DMF was added, and the mixture was stirred until the organic phase was completely dissolved. The solution was filtered through qualitative filter paper to remove insoluble impurities. The filtrate was transferred to a separatory funnel and washed 3 times with deionized water to remove DMF. After standing, a pale yellow oily substance was observed to settle in the lower layer. The settled oily substance was collected and extracted again with 50.0 mL of dichloromethane. The extract was transferred to a vacuum distillation apparatus and distilled at 110 °C and -0.095 MPa for 2 h to remove the solvent and low-boiling substances, yielding a pale yellow viscous liquid product 1.

[0023] Take 149.0 g of polytetrahydrofuran and place it in a vacuum drying oven. Dry it at 100℃ and -0.09 MPa for 5 h to remove moisture. Add the dried PTHF and 79.2 g of product 1 to a 500 mL four-necked flask. Install a stirrer, nitrogen delivery tube, and thermometer. Turn on the nitrogen cylinder and introduce N2 at a flow rate of 10 mL / min to purge air from the system. Turn on the constant temperature water bath and heat it to 55℃. Adjust the stirring speed to 300 rpm and stir at the same temperature for 30 min to ensure thorough mixing.

[0024] With N2 continuously introduced, the reaction system was heated to 80°C. 51.9 g of toluene diisocyanate was slowly added through a constant-pressure dropping funnel over 30 minutes, maintaining a stable temperature of 80 ± 2°C. After the TDI was added, the temperature was further increased to 85°C. 0.3 g of dibutyltin dilaurate was weighed and added to the reaction system using a dropper. The stirring speed was adjusted to 350 rpm, and the reaction was maintained at this temperature for 3 hours. After the reaction was complete, the heating device and nitrogen gas were turned off, and the mixture was allowed to cool naturally to room temperature to obtain a solvent-free polyurethane prepolymer.

[0025] Synthetic routes of polyurethane prepolymers are as follows: Figure 1 As shown. The number-average molecular weight of the prepared polyurethane prepolymer was determined to be 20,500 by gel permeation chromatography (GPC).

[0026] Example 2. This embodiment prepares a polyurethane foam material by mixing the components in the following formula in proportion, stirring evenly, and foaming at 60°C to obtain the material.

[0027]

[0028] Example 3. This embodiment prepares a polyurethane foam material by mixing the components in the following formula in proportion, stirring evenly, and foaming at 60°C to obtain the material.

[0029]

[0030] Example 4. This embodiment prepares a polyurethane foam material by mixing the components in the following formula in proportion, stirring evenly, and foaming at 60°C to obtain the material.

[0031]

[0032] Example 5. This embodiment prepares a polyurethane foam material by mixing the components in the following formula in proportion, stirring evenly, and foaming at 60°C to obtain the material.

[0033]

[0034] Example 6. This embodiment prepares a polyurethane foam material by mixing the components in the following formula in proportion, stirring evenly, and foaming at 60°C to obtain the material.

[0035]

[0036] Example of an effect 1. The foamed materials prepared in Examples 2-6 were cut into sample blocks of 100×100×10mm and subjected to the following performance tests. The test results are as follows:

[0037] As can be seen, the material density of this invention meets the requirements for lightweight design and will not increase the burden on patients while walking. The ASKERC hardness can be flexibly adjusted within a wide range of 20-42, providing sufficient support to limit abnormal foot movement and maintain walking stability, while avoiding foot discomfort due to excessive hardness, thus adapting to the foot support needs of different patients. Within a reasonable range of deformation, it can produce moderate elastic deformation under gait impact, efficiently absorbing the impact energy of the ground on the foot, while avoiding excessive deformation that affects walking stability. Combined with its excellent elongation at break, it can quickly rebound after deformation, reducing repeated damage to joints and soft tissues from impact, balancing cushioning effect and walking flexibility. The material has excellent overall performance, resulting in a long service life as a midsole for diabetic foot shoes, reducing the cost of use for patients.

[0038] Example of effect 2. The foamed material obtained in Example 1 was applied to the midsole of a shoe, and the stress distribution on the soles of diabetic foot patients before and after wearing the shoes was tested, resulting in a thermal map of the stress distribution on both feet. Figure 2, Figure 3 As shown in Figure 2, the colors in the heat map, from blue to yellow / red, represent increasing stress intensity. Without a midsole, the high-stress areas of both feet are concentrated in the forefoot and arch, while the low-stress blue areas are small, indicating that without a midsole, pressure is concentrated in localized areas. Figure 3 After wearing the midsole material, the high stress area is significantly reduced, the blue low stress area is more widely covered, and the stress distribution on both feet is more even, demonstrating the pressure dispersion effect of the midsole material of this invention.

[0039] The overall force-time curve of both feet is as follows: Figure 4 , Figure 5 As shown, the horizontal axis represents gait time (ms), and the vertical axis represents force (kg). Figure 4 When the midsole material is not worn, the force fluctuations of the left and right feet are intense, with a peak value close to 80kg. The force rises / falls rapidly, reflecting that the pressure and impact on both feet are more direct when the midsole is not worn. Figure 5 After wearing the midsole material, the peak force on both feet is significantly reduced, and the curve fluctuation is smoother, indicating that the midsole plays a role in pressure distribution and shock absorption.

[0040] The local force decomposition curve of the left foot is as follows: Figure 6 , Figure 7 As shown. Figure 6 Without a midsole material, the peak total force is high, with a sharp rise and fall in heel force in the early stage and a rapid surge in metatarsal force in the later stage, resulting in large local force fluctuations and concentrated load. Figure 7 shows that after wearing a midsole material, the peak total force decreases, the force changes in the heel and metatarsals are more gradual, the force distribution in various parts is more balanced, and the risk of local overload is reduced.

[0041] The local force decomposition curve of the right foot is as follows: Figure 8 , Figure 9 As shown. Figure 8 Without midsole material, the peak total force is high, with a noticeable spike in the early stage of heel stress and a rapid increase in metatarsal stress in the later stage, resulting in abrupt changes in localized stress. The figure shows that after wearing midsole material, the peak total force is reduced, and the stress connection between the heel and metatarsals is smoother, demonstrating the midsole's optimization effect on localized stress in the right foot.

[0042] Based on the test results, the foam material provided by this invention, as the midsole material for diabetic foot shoes, can effectively distribute the force on both feet, cushion the impact, balance the local load, improve the rationality of force distribution during gait, reduce the pain of diabetic patients, and improve wearing comfort.

[0043] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A polyurethane prepolymer, characterized in that, The structural formula is as follows: ； Where n1, n2, n3, m1, m2 and m3 all represent the number of links in the repeating unit; R is selected from or .

2. A method for preparing the polyurethane prepolymer as described in claim 1, characterized in that, Includes the following steps: S1. Dissolve trimethylolpropane in dichloromethane, add boron trifluoride diethyl ether catalyst diluted with 1,2-dichloroethane, mix well, and then add dropwise a mixed solution of propylene oxide and tetrahydrofuran. The reaction yields a pale yellow liquid. S2. Wash the reaction mixture three times with saturated NaHCO3 solution, then wash with deionized water until neutral, extract the organic phase, dissolve it in N,N-dimethylformamide, and filter to remove insoluble matter. The filtrate was washed with a large amount of water to remove DMF and then settled to obtain a crude product. The crude product was extracted again and then distilled under reduced pressure at 110°C to obtain product 1, a pale yellow viscous liquid. S3. After drying the polytetrahydrofuran, add it together with product 1 into a flask, introduce N2, and stir at 55°C. S4. Heat to 80°C and add toluene diisocyanate. Continue heating to 85°C and add dibutyltin dilaurate. Stir the reaction to obtain a solvent-free polyurethane prepolymer.

3. The method for preparing the polyurethane prepolymer according to claim 2, characterized in that, The molar ratio of product 1 to toluene diisocyanate is 1:

4.

4. The method for preparing the polyurethane prepolymer according to claim 2, characterized in that, The mass of the boron trifluoride ether is 4% of that of triethanolpropane; the mass of the propylene oxide is 4 times that of triethanolpropane.

5. The method for preparing the polyurethane prepolymer according to claim 2, characterized in that, The stirring time in step S3 is 30 minutes.

6. The method for preparing the polyurethane prepolymer according to claim 2, characterized in that, The stirring reaction time in step S4 is 3 hours.

7. A polyurethane foam material, characterized in that, The raw materials used in the preparation include the polyurethane prepolymer as described in claim 1.

8. The polyurethane foam material according to claim 7, characterized in that, The components include the following parts by mass: Voranol CP 3322 polyether triol, 70-100 parts; water, 3.0-4.5 parts; silicone oil DC-190, 1.0-1.4 parts; 0.06-0.08 parts of a 33% triethylenediamine aqueous solution; 0.12 parts of stannous octoate; and 40.7-56.6 parts of polyurethane prepolymer.

9. A method for preparing a polyurethane foam material as described in claim 7 or 8, characterized in that, After mixing the components in the specified proportions and stirring evenly, the mixture is kept at 60°C for foaming to obtain polyurethane foam material.

10. The use of a polyurethane foam material as described in claim 7 or 8 in the midsole of a diabetic foot protection shoe.

Images