Polyurethane elastomer sole material with self-repairing function and preparation method thereof

Abstract

This invention discloses a polyurethane elastomer shoe sole material with self-healing function and its preparation method. The shoe sole material is made from raw materials comprising the following parts by weight: 60-90 parts polytetrahydrofuran ether diol, 30-50 parts diphenylmethane diisocyanate, 5-12 parts 4,4'-dithiodiphenylamine, 4-10 parts 1,4-butanediol, 1-5 parts a diamine containing multiple hydrogen bonds, 0.05-0.3 parts dibutyltin dilaurate, 0.5-3 parts water, 1-4 parts triethanolamine, 0.2-1 parts tetramethylthiuram disulfide, and 0.2-1.5 parts antioxidant. It is prepared through prepolymerization, chain extension, annealing, foaming molding, and curing steps. This invention utilizes the synergistic effect of disulfide bonds and multiple hydrogen bonds, and adds a disulfide bond exchange catalyst to enable the sole material to achieve a repair efficiency of over 90% at 50-80℃ and over 80% at room temperature. It also has good mechanical properties and resilience, making it suitable for high-performance self-healing soles.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and specifically discloses a polyurethane elastomer shoe sole material with self-healing function and its preparation method. Background Technology

[0002] Polyurethane elastomers are widely used in the manufacture of shoe sole materials due to their excellent abrasion resistance, high elasticity, oil resistance, and good processability. With increasing consumer demands for the lifespan and comfort of footwear products, the development of polyurethane shoe sole materials that combine high mechanical properties and self-healing capabilities has become a research hotspot. Traditional polyurethane elastomers are prone to developing microcracks during long-term use due to repeated bending, impact, or environmental factors. These cracks are difficult to detect and repair in a timely manner, ultimately leading to material failure and shortening the lifespan of the shoe sole.

[0003] In recent years, endowing materials with self-healing properties by introducing dynamic covalent bonds (such as disulfide bonds, borate ester bonds, and Diels-Alder bonds) or non-covalent bonds (such as hydrogen bonds and metal coordination bonds) into polymer networks has become a research hotspot. For example, prior art invention 1 (CN119930974A) discloses a high-strength, repairable polyurethane elastomer that uses cystamine dihydrochloride to introduce disulfide bonds into the polyurethane backbone, achieving material repair through the dynamic exchange of disulfide bonds. However, this method requires the use of large amounts of organic solvents (such as ethyl acetate, DMF, etc.), and solvent evaporation during the preparation process will cause environmental pollution, and incomplete solvent removal will affect the material performance; at the same time, the material has a dense structure and does not consider the specific needs of foamed shoe sole materials, so the repair efficiency still needs to be improved.

[0004] Existing invention 2 (CN109134817A) discloses a self-healing polyurethane elastomer responsive to ultraviolet light stimulation. It achieves reversible repair by forming a crosslinked network through the [2+2] cycloaddition of diphenylethylene containing dihydroxyl groups under 365nm ultraviolet light, followed by decrosslinking under 254nm ultraviolet light. This method relies on ultraviolet light stimulation of a specific wavelength, resulting in demanding repair conditions. Furthermore, ultraviolet light has difficulty penetrating opaque or thick-walled shoe sole materials, limiting its practical application in the field of shoe soles.

[0005] Existing invention 3 (CN119350587A) discloses a railway polyurethane elastic pad with self-healing function. It achieves self-healing by reacting MDI with 4,4'-diaminodiphenyl disulfide and 2,2'-diaminodiphenyl disulfide to prepare a crosslinking agent, which is then reacted with an isocyanate prepolymer to introduce disulfide bonds. While this method eliminates the need for solvents, the crosslinking agent requires pre-synthesis, making the process complex. Furthermore, the material is a solid structure and does not involve a foaming process, failing to meet the requirements of lightweight and high resilience for shoe sole materials. In addition, its self-healing relies solely on a single disulfide bond heat exchange mechanism, resulting in a slow repair speed and a high repair temperature.

[0006] In summary, existing self-healing polyurethane materials still have the following shortcomings: (1) Most solutions rely on organic solvents, which are not environmentally friendly and are not suitable for large-scale production of shoe sole materials; (2) The self-healing mechanism is simple and the repair efficiency needs to be improved; (3) The micro-foaming structure of shoe sole materials has not been optimized, making it difficult to balance lightweight, resilience and self-healing performance; (4) The repair conditions are relatively harsh (requiring high temperature or specific wavelength light), making practical application inconvenient. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a self-healing polyurethane elastomer shoe sole material and its preparation method. This invention improves self-healing efficiency by introducing disulfide bonds and multiple hydrogen bonds synergistically; it employs a water-foaming process to provide space for molecular chain diffusion; and it adds tetramethylthiuram disulfide as a disulfide bond exchange catalyst, effectively reducing the repair temperature and shortening the repair time. This material requires no organic solvents, the preparation process is environmentally friendly, and the resulting shoe sole material possesses excellent mechanical properties, high resilience, and efficient self-healing function, showing promising application prospects.

[0008] The objective of this invention is achieved through the following technical solution.

[0009] A self-healing polyurethane elastomer sole material, wherein the sole material is prepared from raw materials comprising the following parts by weight through prepolymerization, chain extension, foaming molding, and curing processes: 60-90 parts of polytetrahydrofuran ether diol, 30-50 parts of diphenylmethane diisocyanate, 5-12 parts of 4,4'-dithiodiphenylamine, 4-10 parts of 1,4-butanediol, 1-5 parts of a diamine containing multiple hydrogen bonds, and 0.05-0.5 parts of dibutyltin dilaurate. The sole material comprises 3 parts water, 0.5-3 parts triethanolamine, 1-4 parts tetramethylthiuram disulfide, 0.2-1 part pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 0.2-1.5 parts pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The sole material has a micro-foamed structure and can self-repair cracks through the synergistic dynamic exchange of disulfide bonds and multiple hydrogen bonds under heating conditions of 50-80℃ or during room temperature storage. After repair, the tensile strength retention rate is ≥85%.

[0010] The diamine containing multiple hydrogen bonds is prepared by the following method: 2-ureido-4[1H]-pyrimidinone and hexamethylenediamine are dissolved in N,N-dimethylformamide at a molar ratio of (1.5 to 2.5):1, and reacted at 70 to 90°C under nitrogen protection for 4 to 8 hours, followed by precipitation and drying.

[0011] Preferably, the number-average molecular weight of the polytetrahydrofuran ether diol is 1000 to 3000.

[0012] Preferably, the diphenylmethane diisocyanate is 4,4'-diphenylmethane diisocyanate.

[0013] Preferably, the tetramethylthiuram disulfide is present in parts by weight of 0.3 to 0.6.

[0014] Preferably, the water is used as a foaming agent and the triethanolamine is used as a crosslinking agent.

[0015] Preferably, the pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is present in a weight fraction of 0.5 to 1 part.

[0016] The preparation method of the self-healing polyurethane elastomer sole material includes the following steps: S1: Prepolymer Synthesis Polytetrahydrofuran ether diol was dehydrated at 110°C under vacuum for 3 hours, cooled to 50°C, and then diphenylmethane diisocyanate was added. The mixture was reacted at 80°C for 3 hours to obtain an isocyanate-terminated polyurethane prepolymer.

[0017] Preferably, the molar ratio of polytetrahydrofuran ether diol to diphenylmethane diisocyanate is 1:1.5 to 1:2.5.

[0018] S2: Chain extension reaction The prepolymer obtained in step S1 was cooled to 60°C, and 4,4'-dithiodiphenylamine, a diamine containing multiple hydrogen bonds and 1,4-butanediol were added. The mixture was stirred and reacted for 1 hour to obtain the chain-extended polyurethane system.

[0019] Preferably, the mass ratio of the 4,4'-dithiodiphenylamine to the diamine containing multiple hydrogen bonds is (2-4):1.

[0020] S3: Annealing treatment The chain extension reaction system obtained in step S2 was annealed at 70°C for 2 hours.

[0021] Preferably, the annealing treatment temperature is 65-80°C and the time is 1-4 hours.

[0022] S4: Foaming molding Add dibutyltin dilaurate, water, triethanolamine, tetramethylthiuram disulfide and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] to the system after annealing in step S3. After rapid and uniform mixing, pour the mixture into a shoe sole mold and cure it at 70°C for 20 minutes to obtain a foamed shoe sole material blank.

[0023] Preferably, the curing temperature is 65-80°C and the curing time is 15-30 minutes.

[0024] Preferably, the mold temperature is 40-60°C and the injection pressure is 0.2-0.6 MPa.

[0025] S5: Maturation The foamed shoe sole material blank obtained in step S4 is cured at 90°C for 18 hours to obtain the polyurethane elastomer shoe sole material with self-healing function.

[0026] Preferably, the curing temperature is 80–100°C and the curing time is 12–24 hours.

[0027] The present invention also provides a polyurethane elastomer sole material with self-healing function, characterized in that it is prepared by any of the above preparation methods, wherein the sole material has a density of 0.4-0.8 g / cm³, a resilience of ≥45%, a tensile strength of ≥8 MPa, and an elongation at break of ≥300%; after heating at 60°C for 12 hours, the crack repair efficiency is ≥90%; after being placed at room temperature (25°C) for 72 hours, the crack repair efficiency is ≥80%.

[0028] Preferably, the self-healing conditions of the sole material are: heating at 50-80°C for 6-24 hours, or placing it at room temperature for 48-72 hours.

[0029] Preferably, in the sole material, the disulfide bonds are introduced by 4,4'-dithiodiphenylamine, the multiple hydrogen bonds are introduced by diamines containing multiple hydrogen bonds, and tetramethylthiuram disulfide acts as a disulfide bond exchange catalyst to reduce the repair activation energy; after the material develops microcracks, the disulfide bonds undergo dynamic exchange by heating or placing at room temperature, while the multiple hydrogen bonds break and recombine rapidly, achieving efficient repair.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. Excellent self-healing performance: This invention achieves a repair efficiency of over 91.5% after 12 hours of repair at 60℃; after 72 hours at room temperature, the repair efficiency remains above 82%. Comparative studies show that the repair efficiency significantly decreases when any component, such as disulfide bonds, hydrogen bonds, or catalyst, is missing, demonstrating the synergistic effect of the components.

[0031] 2. Mild repair conditions: After adding tetramethylthiuram disulfide, a repair efficiency of over 90% can be achieved at 50℃. No high temperature or special equipment is required, and effective repair can be achieved in the daily use environment.

[0032] 3. Lightweight and high resilience: The water-foaming process controls the material density to 0.48-0.56 g / cm³, achieving lightweight soles; the resilience rate reaches 50.8%-54.3%, which is superior to traditional solid polyurethane soles, making them comfortable to wear.

[0033] 4. Mechanical properties meet the requirements of shoe soles: tensile strength 10.5~15.2 MPa, elongation at break 440%~520%, compression set 16.8%~20.2%, which meets the national standards for shoe sole materials.

[0034] 5. Environmentally friendly preparation process: No organic solvents are used throughout the process, there is no solvent volatilization pollution, the process is simple and suitable for large-scale production. Attached Figure Description

[0035] Figure 1 The preparation process of the self-healing polyurethane elastomer shoe sole material of the present invention is as follows: Figure 2 To compare the self-healing efficiency (%) of different samples in Test Example 1; Figure 3 To compare the self-healing efficiency (%) at different repair temperatures in Test Example 5. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below through specific embodiments. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0037] Example 1 A self-healing polyurethane elastomer sole material, made from the following raw materials in parts by weight: 70 parts of polytetrahydrofuran ether diol (number average molecular weight 2000), 40 parts of diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate), 8 parts of 4,4'-dithiodiphenylamine 7 parts of 1,4-butanediol Three portions of diamines containing multiple hydrogen bonds. 0.15 parts of dibutyltin dilaurate, 1.5 parts water 2.5 parts of triethanolamine 0.5 parts of tetramethylthiuram disulfide 0.8 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]

[0038] The diamine containing multiple hydrogen bonds is prepared by the following method: 2-ureido-4[1H]-pyrimidinone and hexamethylenediamine are dissolved in N,N-dimethylformamide at a molar ratio of 2:1, reacted at 80°C under nitrogen protection for 6 hours, and then precipitated and dried to obtain the product.

[0039] The preparation method of the above-mentioned self-healing polyurethane elastomer sole material, such as... Figure 1 As shown, it includes the following steps: S1: Prepolymer Synthesis Polytetrahydrofuran ether diol was dehydrated at 110°C under vacuum for 3 hours, cooled to 50°C, and then diphenylmethane diisocyanate was added. The mixture was reacted at 80°C for 3 hours to obtain the prepolymer.

[0040] S2: Chain extension reaction The prepolymer was cooled to 60°C, and 4,4'-dithiodiphenylamine, a diamine containing multiple hydrogen bonds and 1,4-butanediol were added. The mixture was stirred and reacted for 1 hour.

[0041] S3: Annealing treatment The chain extension reaction system was annealed at 70°C for 2 hours.

[0042] S4: Foaming molding Add dibutyltin dilaurate, water, triethanolamine, tetramethylthiuram disulfide and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], stir quickly and evenly, then pour into the shoe sole mold and cure at 70°C for 20 minutes.

[0043] S5: Maturation The self-healing polyurethane elastomer sole material was obtained by curing at 90°C for 18 hours.

[0044] Example 2 A self-healing polyurethane elastomer sole material, made from the following raw materials in parts by weight: 60 parts of polytetrahydrofuran ether diol (number average molecular weight 1000), 30 parts of diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate), 5 parts of 4,4'-dithiodiphenylamine 4 parts of 1,4-butanediol One part of a diamine containing multiple hydrogen bonds, 0.05 parts of dibutyltin dilaurate, 0.5 parts water, 1 part triethanolamine 0.2 parts of tetramethylthiuram disulfide 0.2 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]

[0045] The diamine containing multiple hydrogen bonds is prepared by the following method: 2-ureido-4[1H]-pyrimidinone and hexamethylenediamine are dissolved in N,N-dimethylformamide at a molar ratio of 1.5:1, reacted at 70°C under nitrogen protection for 4 hours, and then precipitated and dried to obtain the product.

[0046] The preparation method of the above-mentioned self-healing polyurethane elastomer sole material includes the following steps: S1: Prepolymer Synthesis Polytetrahydrofuran ether diol was dehydrated at 110°C under vacuum for 3 hours, cooled to 50°C, and then diphenylmethane diisocyanate was added. The mixture was reacted at 80°C for 3 hours to obtain the prepolymer.

[0047] S2: Chain extension reaction The prepolymer was cooled to 60°C, and 4,4'-dithiodiphenylamine, a diamine containing multiple hydrogen bonds and 1,4-butanediol were added. The mixture was stirred and reacted for 1 hour.

[0048] S3: Annealing treatment The chain extension reaction system was annealed at 70°C for 2 hours.

[0049] S4: Foaming molding Add dibutyltin dilaurate, water, triethanolamine, tetramethylthiuram disulfide and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], stir quickly and evenly, then pour into the shoe sole mold and cure at 70°C for 20 minutes.

[0050] S5: Maturation The self-healing polyurethane elastomer sole material was obtained by curing at 90°C for 18 hours.

[0051] Example 3 A self-healing polyurethane elastomer sole material, made from the following raw materials in parts by weight: 90 parts of polytetrahydrofuran ether diol (number average molecular weight 3000), 50 parts of diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate), 12 parts of 4,4'-dithiodiphenylamine 10 parts of 1,4-butanediol Five parts of a diamine containing multiple hydrogen bonds. 0.3 parts of dibutyltin dilaurate, 3 parts water 4 parts of triethanolamine One part of tetramethylthiuram disulfide, 1.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]

[0052] The diamine containing multiple hydrogen bonds is prepared by the following method: 2-ureido-4[1H]-pyrimidinone and hexamethylenediamine are dissolved in N,N-dimethylformamide at a molar ratio of 2.5:1, reacted at 90°C under nitrogen protection for 8 hours, and then precipitated and dried to obtain the product.

[0053] The preparation method of the above-mentioned self-healing polyurethane elastomer sole material is the same as that in Example 1.

[0054] Comparative Example 1 This polyurethane elastomer shoe sole material is made from the following raw materials in parts by weight: 70 parts of polytetrahydrofuran ether diol (number average molecular weight 2000), 40 parts of diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate), 8 parts of 4,4'-dithiodiphenylamine 7 parts of 1,4-butanediol (Excluding diamines containing multiple hydrogen bonds). 0.15 parts of dibutyltin dilaurate, 1.5 parts water 2.5 parts of triethanolamine 0.5 parts of tetramethylthiuram disulfide 0.8 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]

[0055] The rest is the same as in Example 1.

[0056] Comparative Example 2 A polyurethane elastomer shoe sole material, made from the following raw materials in parts by weight: 70 parts of polytetrahydrofuran ether diol (number average molecular weight 2000), 40 parts of diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate), (Does not contain 4,4'-dithiodiphenylamine). 7 parts of 1,4-butanediol Three portions of diamines containing multiple hydrogen bonds. 0.15 parts of dibutyltin dilaurate, 1.5 parts water 2.5 parts of triethanolamine 0.5 parts of tetramethylthiuram disulfide 0.8 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]

[0057] The rest is the same as in Example 1.

[0058] Comparative Example 3 A polyurethane elastomer shoe sole material, made from the following raw materials in parts by weight: 70 parts of polytetrahydrofuran ether diol (number average molecular weight 2000), 40 parts of diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate), 8 parts of 4,4'-dithiodiphenylamine 7 parts of 1,4-butanediol Three portions of diamines containing multiple hydrogen bonds. 0.15 parts of dibutyltin dilaurate, 1.5 parts water 2.5 parts of triethanolamine (Excluding tetramethylthiuram disulfide) 0.8 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]

[0059] The rest is the same as in Example 1.

[0060] Comparative Example 4 A polyurethane elastomer shoe sole material, made from the following raw materials in parts by weight: 70 parts of polytetrahydrofuran ether diol (number average molecular weight 2000), 40 parts of diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate), 8 parts of 4,4'-dithiodiphenylamine 7 parts of 1,4-butanediol (Excluding diamines containing multiple hydrogen bonds). 0.15 parts of dibutyltin dilaurate, 1.5 parts water 2.5 parts of triethanolamine (Excluding tetramethylthiuram disulfide) 0.8 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]

[0061] The rest is the same as in Example 1.

[0062] Comparative Example 5 A polyurethane elastomer shoe sole material, made from the following raw materials in parts by weight: 70 parts of polytetrahydrofuran ether diol (number average molecular weight 2000), 40 parts of diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate), (Does not contain 4,4'-dithiodiphenylamine). 7 parts of 1,4-butanediol (Excluding diamines containing multiple hydrogen bonds). 0.15 parts of dibutyltin dilaurate, 1.5 parts water 2.5 parts of triethanolamine (Excluding tetramethylthiuram disulfide) 0.8 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]

[0063] The rest is the same as in Example 1.

[0064] Test Example 1 Self-repair efficiency comparison experiment.

[0065] method: Standard dumbbell-shaped specimens (GB / T 528-2009, Type I) of Examples 1-3 and Comparative Examples 1-5 were prepared.

[0066] Use a blade to cut a scratch in the middle of the sample with a depth of about 50% of the thickness (30 μm wide).

[0067] The damaged sample was placed in a 60℃ constant temperature oven for 12 hours for repair.

[0068] The tensile strength of the specimens before and after repair was tested using a universal tensile testing machine, and the repair efficiency was calculated using the formula: Repair efficiency (%) = (Tensile strength after repair / Original tensile strength) × 100%.

[0069] Each sample was tested in parallel 5 times, and the mean ± SD was taken.

[0070] Meanwhile, the repair efficiency was recorded after 72 hours of placement at room temperature (25℃) for comparison.

[0071] Results: See Table 1 and Figure 2 .

[0072] Table 1 Comparison of self-healing efficiency of different samples

[0073] Table 1 shows that the repair efficiencies of Examples 1-3 are all above 85%, with Example 3 reaching 94.2%. Comparative Example 2 (lacking disulfide bonds) has the lowest repair efficiency (42.7%), while Comparative Example 1 (lacking hydrogen bonds) has a higher repair efficiency (64.3%), indicating that disulfide bonds are the primary repair driver, with hydrogen bonds playing a supporting role. Comparative Example 3 (lacking catalyst) has a lower repair efficiency (73.6%) than Example 1 (91.5%), demonstrating that tetramethylthiuram disulfide significantly reduces the repair activation energy. Comparative Example 5 (basic polyurethane only) has almost no self-healing ability. The complete compound system (examples) still achieves a room temperature repair efficiency of over 74%, meeting practical application requirements.

[0074] Test Example 2 Mechanical property comparison experiment Objective: To evaluate the effects of different components on the mechanical properties of polyurethane elastomers.

[0075] method: Dumbbell-shaped specimens were prepared according to GB / T 528-2009, and tensile strength and elongation at break were tested (tensile speed 500 mm / min).

[0076] The compression set was tested according to GB / T 10653-2001 (70℃×24h, compression rate 25%).

[0077] Six parallel samples were tested in each group, and the mean ± SD was taken.

[0078] Results: See Table 2.

[0079] Table 2 Comparison of mechanical properties of different samples

[0080] Conclusion: The tensile strength of Examples 1-3 ranged from 10.5 to 15.2 MPa, and the elongation at break ranged from 440 to 520%, meeting the requirements for shoe sole materials. Comparative Example 2 (lacking disulfide bonds) had the lowest tensile strength (9.3 MPa) and the highest elongation at break (560%), indicating that disulfide bonds, as dynamic crosslinking points, can improve strength but moderately reduce elongation. Comparative Example 5 (pure polyurethane) had the highest strength (14.5 MPa) but the lowest elongation (405%) and the smallest compression set (16.2%), indicating that the introduction of dynamic bonds, while imparting self-healing capabilities, slightly sacrifices mechanical properties; however, Example 3 still maintained good overall performance.

[0081] Test Example 3 Foaming structure and density test Objective: To evaluate the microporous structure formed by the water foaming process and its impact on the lightweighting of materials.

[0082] method: Apparent density was tested using the water displacement method (GB / T 1033.1-2008).

[0083] SEM was used to observe the morphology of the cross-section cells and the average cell diameter was calculated.

[0084] The rebound rate (pendulum type) is tested according to GB / T 1681-2009.

[0085] Results: See Table 3.

[0086] Table 3. Foaming structural parameters and resilience performance

[0087] Conclusion: The apparent density of Examples 1-3 was 0.48–0.56 g / cm³. 3 This material, classified as a micro-foamed material, exhibits a resilience of 50.8–54.3%, higher than that of traditional solid polyurethane shoe soles (approximately 40%), indicating that the microporous structure contributes to improved resilience. The foaming parameters of each comparative example are similar to those of the example, suggesting a stable foaming process and minimal impact of dynamic bond components on the foaming process. Example 2 shows the lowest density (0.48 g / cm³). 3 It boasts the highest rebound rate (54.3%), balancing lightweight design with high resilience.

[0088] Test Example 4 Dynamic bond exchange property testing (heated DSC method) Objective: To verify the dynamic reversibility of disulfide bonds and multiple hydrogen bonds and the effect of catalysts on reducing exchange temperature.

[0089] method: The thermal properties of the samples were tested using a differential scanning calorimeter (DSC, TA Q2000) under a nitrogen atmosphere.

[0090] First, the temperature was increased to 150℃ at 10℃ / min to eliminate the thermal history, then cooled to -50℃, and then the glass transition temperature (Tg) and possible dynamic bond exchange exothermic peaks were recorded by increasing the temperature at 10℃ / min.

[0091] After isothermally treating the sample at 80℃ for 2 hours, DSC was tested again to observe the change in Tg.

[0092] Each group was tested 3 times, and the average was taken.

[0093] Results: See Table 4.

[0094] Table 4 Dynamic Key Exchange Characteristic Parameters

[0095] Table 4 shows that the temperature gradient (Tg) of Examples 1-3 increased significantly after annealing (+5.6 to +6.7 °C), indicating that dynamic exchange of disulfide bonds and hydrogen bonds occurred during annealing, promoting microphase separation and ordered arrangement of hard segments. The Tg of Comparative Example 2 (without disulfide bonds) remained almost unchanged after annealing, while the Tg increase of Comparative Example 1 (without hydrogen bonds) (+3.3 °C) was smaller than that of the Examples, indicating that hydrogen bonds facilitate chain rearrangement during annealing. The disulfide bond exchange temperature range (58–102 °C) of Comparative Example 3 (without catalyst) shifted to a higher temperature range than that of Example 1 (55–95 °C), proving that tetramethylthiuram disulfide can effectively reduce the activation energy of disulfide bond exchange. Comparative Example 5 had no dynamic bonds, and its Tg remained unchanged.

[0096] Test Example 5 Repairing temperature-dependent experiments Objective: To investigate the effect of different repair temperatures on self-repair efficiency and determine the optimal repair conditions.

[0097] method: Using the same damage method as in Test Example 1, the sample from Example 1 was repaired for 12 hours at different temperatures (room temperature 25℃, 40℃, 50℃, 60℃, 70℃, 80℃).

[0098] Meanwhile, the efficiency of comparative examples 1 (hydrogen bond deficient), 2 (disulfide bond deficient), and 3 (catalyst deficient) in repairing the catalyst at 60°C for 12 hours was tested as a control.

[0099] Calculate the repair efficiency, with 5 parallel samples per group.

[0100] Results: See Table 5 and Figure 3 .

[0101] Table 5. Self-healing efficiency (%) at different repair temperatures

[0102] Conclusions: The repair efficiency of Example 1 increases with increasing temperature, stabilizing above 50°C (approximately 91%), indicating that the optimal repair temperature is 50–70°C. Comparative Example 3 (without catalyst) showed an efficiency of only 73.6% at 60°C and remained below 75% at 80°C, demonstrating the crucial role of the catalyst in lowering the repair temperature. Comparative Example 1 (without hydrogen bonds) had an efficiency of only 48.6% at room temperature, but increased to 64.3% at 60°C, indicating that increasing the temperature can partially compensate for the lack of hydrogen bonds. Comparative Example 2 (without disulfide bonds) showed an efficiency below 45% at all temperatures, indicating that disulfide bonds are the core driving force for self-repair. Example 1 already achieved an efficiency of 82.7% at room temperature, meeting the needs of natural repair in daily use.

[0103] The above test examples demonstrate that the self-healing polyurethane elastomer sole material (Examples 1-3) provided by this invention achieves highly efficient self-healing performance (repair efficiency ≥86% at 60℃ for 12h) through the combined action of disulfide bonds and hydrogen bonds, and the catalytic effect of tetramethylthiuram disulfide, while maintaining good mechanical properties (tensile strength ≥10.5MPa, resilience ≥50%). The experiments confirm that the absence of any key component (disulfide bond, hydrogen bond, or catalyst) leads to a significant decrease in self-healing efficiency.

Claims

1. A polyurethane elastomer sole material with self-healing function, characterized in that, Made from raw materials comprising the following parts by weight: 60-90 parts of polytetrahydrofuran ether diol, 30-50 parts of diphenylmethane diisocyanate 5-12 parts of 4,4'-dithiodiphenylamine 4-10 parts of 1,4-butanediol 1-5 parts of a diamine containing multiple hydrogen bonds, 0.05–0.3 parts of dibutyltin dilaurate, Water 0.5 to 3 parts, 1-4 parts of triethanolamine 0.2–1 part of tetramethylthiuram disulfide Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] 0.2–1.5 parts; The diamine containing multiple hydrogen bonds is prepared by the following method: 2-ureido-4[1H]-pyrimidinone and hexamethylenediamine are dissolved in N,N-dimethylformamide at a molar ratio of (1.5 to 2.5):1, and reacted at 70 to 90°C under nitrogen protection for 4 to 8 hours, followed by precipitation and drying.

2. The polyurethane elastomer sole material with self-healing function according to claim 1, characterized in that, The number-average molecular weight of the polytetrahydrofuran ether diol is 1000–3000.

3. The polyurethane elastomer sole material with self-healing function according to claim 1, characterized in that, The diphenylmethane diisocyanate is 4,4'-diphenylmethane diisocyanate.

4. The polyurethane elastomer sole material with self-healing function according to claim 1, characterized in that, The tetramethylthiuram disulfide is present in parts by weight of 0.3 to 0.

6.

5. The polyurethane elastomer sole material with self-healing function according to claim 1, characterized in that, The water is a foaming agent, and the triethanolamine is a crosslinking agent.

6. The polyurethane elastomer sole material with self-healing function according to claim 1, characterized in that, The weight fraction of the tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] pentaerythritol ester is 0.5 to 1 part.

7. A method for preparing a polyurethane elastomer sole material with self-healing function according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1 Prepolymer Synthesis: Polytetrahydrofuran ether diol was dehydrated at 110°C under vacuum for 3 hours, cooled to 50°C, and then diphenylmethane diisocyanate was added. The mixture was reacted at 80°C for 3 hours to obtain the prepolymer. S2 chain extension reaction: Cool the prepolymer to 60°C, add 4,4'-dithiodiphenylamine, a diamine containing multiple hydrogen bonds and 1,4-butanediol, and stir the reaction for 1 hour; S3 Annealing treatment: Anneal the system after the chain extension reaction at 70°C for 2 hours; S4 foaming molding: Add dibutyltin dilaurate, water, triethanolamine, tetramethylthiuram disulfide and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid], stir quickly and evenly, then pour into the shoe sole mold and cure at 70°C for 20 minutes; S5 Curing: Curing at 90°C for 18 hours yields the self-healing polyurethane elastomer sole material.

8. The preparation method according to claim 7, characterized in that, After curing and molding in step S4, the process also includes a step of keeping the product at 60-80°C for 2-4 hours.

9. The use of the polyurethane elastomer sole material with self-healing function as described in any one of claims 1 to 6 in the preparation of self-healing soles.

10. The application according to claim 9, characterized in that, The self-healing conditions of the sole material are: heating at 50-80℃ for 6-24 hours, or placing at room temperature for 48-72 hours.

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