Railway polyurethane elastic backing plate with self-repairing function and preparation method thereof

Abstract

The invention belongs to the technical field of polyurethane, and provides a railway polyurethane elastic backing plate with a self-repairing function and a preparation method thereof.The railway polyurethane elastic backing plate is prepared from, by mass, 60-80 parts of isocyanate prepolymer, 14-16 parts of cross-linking agent, 4-6 parts of chain extender and 0.6-0.8 part of catalyst; the cross-linking agent comprises a cross-linking agent A and a cross-linking agent B in a mass ratio of 1: (0.5-1); wherein a preparation method of the cross-linking agent A comprises the following steps: stirring and reacting diphenylmethane diisocyanate and 4, 4 '-diaminodiphenyl disulfide in a mass ratio of 2: 1 at 60-65 DEG C in the presence of a catalyst for 2-3 hours; a preparation method of the cross-linking agent B comprises the following steps: stirring and reacting diphenylmethane diisocyanate and 2, 2 '-diaminodiphenyl disulfide in a mass ratio of 2: 1 at 85-90 DEG C in the presence of a catalyst for 2-3 hours. By introducing disulfide bonds, the self-repairing function is achieved, and the service life of the elastic base plate is prolonged; meanwhile, due to the good mechanical property and stability, the composite material can be normally used in various severe environments and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane and relates to a railway polyurethane elastic pad with a self-repairing function and a preparation method thereof. Background Art

[0002] In the railway track system, elastic pads play an important role in buffering, shock absorption and noise reduction. Traditional polyurethane elastic pads may crack and break due to various external forces during long-term use, affecting their performance and service life. Once the elastic pad is damaged, the replacement cost is high and it will have a certain impact on the normal operation of the railway. Therefore, it is of great practical significance to develop a polyurethane elastic pad with self-repairing function.

[0003] At present, the introduction of reversible covalent bonds or reversible non-covalent bonds into the polyurethane chain is the main way to construct self-healing polyurethane. Among them, the reversible covalent bond has a high bond energy, and introducing it into polyurethane can improve the mechanical properties of polyurethane, but the corresponding conditions are harsh and the repair efficiency is low, which limits its application in many fields; reversible non-covalent bonds can achieve self-repair function without external stimulation, and its response speed is fast and the self-repair efficiency is high, but its bond energy is low, and its introduction into polyurethane often reduces the original mechanical properties of polyurethane. For example, polymers containing disulfide bonds can achieve self-repair function by performing reversible exchange reactions, and the self-repair performance can be further accelerated in the case of external intervention (such as heating or light).

[0004] However, there is still a lack of materials that have excellent mechanical properties and can achieve self-repair with high repair efficiency. Therefore, the existing self-repairing materials need to be further improved. Summary of the invention

[0005] The present invention proposes a railway polyurethane elastic pad with self-repairing function and a preparation method thereof. The self-repairing function is achieved by introducing disulfide bonds, thereby extending the service life of the elastic pad and reducing maintenance costs. At the same time, good mechanical properties and stability enable it to be used normally in various harsh environments, and it has broad application prospects.

[0006] The technical solution of the present invention is achieved in this way: A railway polyurethane elastic pad with self-repairing function, the raw materials of which include, by weight: 60-80 parts of isocyanate prepolymer, 14-16 parts of crosslinking agent, 4-6 parts of chain extender and 0.6-0.8 parts of catalyst; The cross-linking agent comprises a cross-linking agent A and a cross-linking agent B in a mass ratio of 1:0.5-1; The preparation method of the crosslinking agent A comprises the following steps: stirring diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 60-65°C and under the condition of an organic tin catalyst for 2-3 hours to obtain the crosslinking agent A; in the preparation process, the amount of the organic tin catalyst is 0.1-0.5% of the total mass of the reactants, that is, the amount of the organic tin catalyst is 0.1-0.5% of the total mass of the diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide; The preparation method of crosslinking agent B comprises the following steps: stirring diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 85-90°C and in the presence of an organic tin catalyst for 2-3 hours to obtain crosslinking agent B; the amount of the organic tin catalyst used is 0.1-0.5% of the total mass of the reactants, that is, the amount of the organic tin catalyst used is 0.1-0.5% of the total mass of diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide.

[0007] Preferably, the NCO index of the isocyanate prepolymer is 20-31.

[0008] Preferably, the chain extender is selected from one or more of trimethylolpropane, hydroquinone dihydroxyethyl ether, 1,4-butanediol and ethylene glycol.

[0009] Preferably, the catalyst is selected from organotin catalysts and / or organoamine catalysts.

[0010] Preferably, the organotin catalyst is selected from one or more of tin octoate, dibutyltin dilaurate, dibutyltin diacetate and dioctyltin diacetate.

[0011] Preferably, the organic amine catalyst is selected from one or more of A33, triethylenediamine and N,N-dimethylcyclohexylamine.

[0012] Preferably, dibutyltin dilaurate (DBTDL, also known as T-12) is used in the preparation process of crosslinking agent A and crosslinking agent B. The synthesis process of crosslinking agent A is as follows: The synthesis process of crosslinker B is as follows: Among them, the CAS number of 4,4'-diaminodiphenyl disulfide is 722-27-0; the CAS number of 2,2'-diaminodiphenyl disulfide is 1141-88-4.

[0013] Preferably, the method for preparing the isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol is heated to 100-110° C. and vacuum-dehydrated for 2-3 hours under stirring; then the temperature is lowered to 80-85° C., diphenylmethane diisocyanate is added, and the reaction is stirred for 2-3 hours in an inert gas atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to diphenylmethane diisocyanate is 0.5-1:2.

[0014] The synthesis process of isocyanate prepolymer is as follows: Preferably, the molecular weight of the polytetramethylene ether glycol is selected from one or more of 1000, 1500 or 2000 molecular weight.

[0015] Preferably, the catalyst comprises 0.15-0.2 parts of dibutyltin dilaurate and 0.5-0.55 parts of A33.

[0016] Preferably, the chain extender is trimethylolpropane.

[0017] The preparation method of the above-mentioned railway polyurethane elastic pad with self-repairing function comprises the following steps: mixing isocyanate prepolymer and cross-linking agent, adding chain extender and catalyst, stirring reaction, pouring the reaction product into a mold, curing and molding at 75-85°C for 15-30 minutes, and obtaining the railway polyurethane elastic pad with self-repairing function, wherein the stirring rate is 300-600rpm and the stirring time is 1-2min.

[0018] The working principle and beneficial effects of the present invention are: 1. Since the present invention introduces disulfide bonds into polyurethane, when the elastic pad is cracked or damaged, it can achieve self-repair under certain conditions, thereby extending the service life of the elastic pad, reducing maintenance costs, and solving the problem that the existing railway polyurethane elastic pad is easy to be damaged and difficult to repair during use; at the same time, by selecting suitable prepolymers, cross-linking agents and chain extenders, the elastic pad has higher strength, elasticity and wear resistance, and can meet the use requirements of the railway track system; the synthesis process of the present invention is stable and reliable, and the obtained elastic pad has good chemical stability and thermal stability, and can be used normally in various harsh environments.

[0019] 2. In the present invention, polytetramethylene ether glycol and diphenylmethane diisocyanate are polymerized in a certain proportion under specific conditions to generate an isocyanate prepolymer. The prepolymer has a certain molecular weight and reactivity, which provides a basis for the subsequent synthesis process; then, diphenylmethane diisocyanate and a specific disulfide are polymerized to form a crosslinking agent. This disulfide can introduce disulfide bonds during the synthesis process, giving the elastic pad a self-repairing function. When the elastic pad is cracked or damaged during use, the disulfide bonds can break and reconnect under certain conditions to achieve self-repair; then, a chain extender is added to the reaction system, which can react with the isocyanate groups in the prepolymer and the crosslinker to grow the molecular chain and improve the mechanical properties of the elastic pad; finally, an appropriate amount of catalyst is added to promote the entire synthesis reaction and improve the reaction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0021] Figure 1 This is a microscope picture of the polyurethane elastic pad prepared in Example 1 of the present invention after the surface is scratched; Figure 2 This is a microscope picture of the polyurethane elastic pad prepared in Example 1 of the present invention after being repaired after being scratched on the surface. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Unless otherwise specified, the equipment used in this embodiment is conventional equipment, the reagents used are conventional reagents, all of which can be commercially obtained, and the operating methods used are all recorded in textbooks in this field.

[0024] In the following examples and comparative examples, diphenylmethane diisocyanate (MDI-50) was purchased from Wanhua Chemical; toluene diisocyanate (TDI), brand TDI-80, was purchased from Cangzhou Dahua Co., Ltd.

[0025] Example 1 A method for preparing a railway polyurethane elastic pad with self-repairing function comprises the following steps: A. Prepare the raw materials by weight, including: 70 parts of isocyanate prepolymer, 15 parts of crosslinking agent, 5 parts of trimethylolpropane, 0.2 parts of dibutyltin dilaurate, 0.5 parts of A33; The cross-linking agent comprises a cross-linking agent A and a cross-linking agent B in a mass ratio of 1:0.8; The preparation method of the crosslinking agent A comprises the following steps: stirring diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 60°C and in the presence of dibutyltin dilaurate for 2 hours to obtain the crosslinking agent A; wherein the amount of dibutyltin dilaurate is 0.2% of the total mass of the reactants; The preparation method of crosslinking agent B comprises the following steps: stirring diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 85°C and in the presence of dibutyltin dilaurate for 2 hours to obtain crosslinking agent B; wherein the amount of dibutyltin dilaurate is 0.2% of the total mass of the reactants; The preparation method of isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol was heated to 100°C, and vacuum-dehydrated for 3 hours under stirring; then the temperature was lowered to 80°C, diphenylmethane diisocyanate was added, and the reaction was stirred for 2 hours in a nitrogen atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to diphenylmethane diisocyanate was 1:2; the polytetramethylene ether glycol (PTMEG) used had a molecular weight of 2000 and was purchased from BASF, Germany; B. Mix the isocyanate prepolymer and the cross-linking agent, then add trimethylolpropane, dibutyltin dilaurate and A33, stir to react, pour the product after the reaction into a mold, and cure it at 80°C for 20 minutes to obtain a railway polyurethane elastic pad with self-repairing function; wherein the stirring rate is 500 rpm and the stirring time is 1 minute.

[0026] Example 2 A method for preparing a railway polyurethane elastic pad with self-repairing function comprises the following steps: A. Prepare the raw materials by weight, including: 60 parts of isocyanate prepolymer, 16 parts of crosslinking agent, 5 parts of trimethylolpropane, 0.15 parts of dibutyltin dilaurate, 0.55 parts of A33; The cross-linking agent comprises a cross-linking agent A and a cross-linking agent B in a mass ratio of 1:0.5; The preparation method of the crosslinking agent A comprises the following steps: stirring diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 65°C in the presence of dioctyltin diacetate for 3 hours to obtain the crosslinking agent A; wherein the amount of dioctyltin diacetate is 0.1% of the total mass of the reactants; The preparation method of the crosslinking agent B comprises the following steps: stirring diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 90°C and in the presence of dioctyltin diacetate for 3 hours to obtain the crosslinking agent B; wherein the amount of dioctyltin diacetate is 0.1% of the total mass of the reactants; The preparation method of isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol was heated to 105°C, and vacuum-dehydrated for 2.5 hours under stirring; then the temperature was lowered to 85°C, diphenylmethane diisocyanate was added, and the reaction was stirred for 3 hours in a nitrogen atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to diphenylmethane diisocyanate was 0.8:2; the polytetramethylene ether glycol (PTMEG) used had a molecular weight of 1500 and was purchased from BASF, Germany; B. Mix the isocyanate prepolymer and the cross-linking agent, then add trimethylolpropane, dibutyltin dilaurate and A33, stir to react, pour the product after the reaction into a mold, and cure it at 85°C for 15 minutes to obtain a railway polyurethane elastic pad with self-repairing function; wherein the stirring rate is 300 rpm and the stirring time is 1.5 minutes.

[0027] Example 3 A method for preparing a railway polyurethane elastic pad with self-repairing function comprises the following steps: A. Prepare the raw materials by weight, including: 80 parts of isocyanate prepolymer, 14 parts of crosslinking agent, 3 parts of ethylene glycol, 3 parts of 1,4-butanediol, 0.2 parts of dibutyltin diacetate and 0.4 parts of N,N-dimethylcyclohexylamine; The cross-linking agent comprises a cross-linking agent A and a cross-linking agent B in a mass ratio of 1:1; The preparation method of the crosslinking agent A comprises the following steps: stirring diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 60°C and in the presence of dibutyltin dilaurate for 2 hours to obtain the crosslinking agent A; wherein the amount of dibutyltin dilaurate is 0.5% of the total mass of the reactants; The preparation method of the crosslinking agent B comprises the following steps: stirring diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 85°C and in the presence of dibutyltin dilaurate for 2 hours to obtain the crosslinking agent B; wherein the amount of dibutyltin dilaurate is 0.5% of the total mass of the reactants; The preparation method of isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol was heated to 110°C, and vacuum-dehydrated for 2 hours under stirring; then the temperature was lowered to 80°C, diphenylmethane diisocyanate was added, and the reaction was stirred for 2 hours in a nitrogen atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to diphenylmethane diisocyanate was 0.5:2; the polytetramethylene ether glycol (PTMEG) used had a molecular weight of 1000 and was purchased from BASF, Germany; B. Mix the isocyanate prepolymer and the cross-linking agent, then add ethylene glycol, 1,4-butanediol, dibutyltin diacetate and N,N-dimethylcyclohexylamine, stir to react, pour the product after the reaction into a mold, and cure it at 75°C for 30 minutes to obtain a railway polyurethane elastic pad with self-repairing function; the stirring rate is 600 rpm and the stirring time is 2 minutes.

[0028] Example 4 A method for preparing a railway polyurethane elastic pad with self-repairing function comprises the following steps: A. Prepare the raw materials by weight, including: 70 parts of isocyanate prepolymer, 15 parts of crosslinking agent, 5 parts of hydroquinone dihydroxyethyl ether, 0.4 parts of triethylenediamine and 0.4 parts of dioctyltin diacetate; The cross-linking agent comprises a cross-linking agent A and a cross-linking agent B in a mass ratio of 1:1; The preparation method of the crosslinking agent A comprises the following steps: stirring diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 60°C and in the presence of dibutyltin dilaurate for 2 hours to obtain the crosslinking agent A; wherein the amount of dibutyltin dilaurate is 0.1% of the total mass of the reactants; The preparation method of crosslinking agent B comprises the following steps: stirring diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 85°C and in the presence of dibutyltin dilaurate for 2 hours to obtain crosslinking agent B; wherein the amount of dibutyltin dilaurate is 0.1% of the total mass of the reactants; The preparation method of isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol was heated to 100°C, and vacuum-dehydrated for 2 hours under stirring; then the temperature was lowered to 80°C, diphenylmethane diisocyanate was added, and the reaction was stirred for 2 hours in a nitrogen atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to diphenylmethane diisocyanate was 1:2; the polytetramethylene ether glycol (PTMEG) used had a molecular weight of 2000 and was purchased from BASF, Germany; B. Mix the isocyanate prepolymer and the cross-linking agent, then add hydroquinone dihydroxyethyl ether, triethylenediamine and dioctyltin diacetate, stir to react, pour the product after the reaction into a mold, and cure it at 80°C for 20 minutes to obtain a railway polyurethane elastic pad with self-repairing function; wherein the stirring rate is 500 rpm and the stirring time is 1.5 minutes.

[0029] Comparative Example 1 A method for preparing a polyurethane elastic pad comprises the following steps: A. Prepare the raw materials by weight, including: 70 parts of isocyanate prepolymer, 15 parts of crosslinking agent B, 5 parts of trimethylolpropane, 0.2 parts of dibutyltin dilaurate, 0.5 parts of A33; The preparation method of crosslinking agent B comprises the following steps: stirring diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 85°C and in the presence of dibutyltin dilaurate for 2 hours to obtain crosslinking agent B; wherein the amount of dibutyltin dilaurate is 0.2% of the total mass of the reactants; The preparation method of isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol was heated to 100°C, and vacuum-dehydrated for 3 hours under stirring; then the temperature was lowered to 80°C, diphenylmethane diisocyanate was added, and the reaction was stirred for 2 hours in a nitrogen atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to diphenylmethane diisocyanate was 1:2; the polytetramethylene ether glycol (PTMEG) used had a molecular weight of 2000 and was purchased from BASF, Germany; B. Mix the isocyanate prepolymer and the crosslinking agent B, then add trimethylolpropane, dibutyltin dilaurate and A33, stir to react, pour the product after the reaction into a mold, and cure it at 80° C. for 20 minutes to obtain a railway polyurethane elastic pad with self-repairing function; wherein the stirring rate is 500 rpm and the stirring time is 1 minute.

[0030] Comparative Example 2 A method for preparing a polyurethane elastic pad comprises the following steps: A. Prepare the raw materials by weight, including: 70 parts of isocyanate prepolymer, 15 parts of crosslinking agent A, 5 parts of trimethylolpropane, 0.2 parts of dibutyltin dilaurate, 0.5 parts of A33; The preparation method of the crosslinking agent A comprises the following steps: stirring diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 60°C and in the presence of dibutyltin dilaurate for 2 hours to obtain the crosslinking agent A; wherein the amount of dibutyltin dilaurate is 0.2% of the total mass of the reactants; The preparation method of isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol was heated to 100°C, and vacuum-dehydrated for 3 hours under stirring; then the temperature was lowered to 80°C, diphenylmethane diisocyanate was added, and the reaction was stirred for 2 hours in a nitrogen atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to diphenylmethane diisocyanate was 1:2; the polytetramethylene ether glycol (PTMEG) used had a molecular weight of 2000 and was purchased from BASF, Germany; B. Mix the isocyanate prepolymer and the crosslinking agent A, then add trimethylolpropane, dibutyltin dilaurate and A33, stir to react, pour the product after the reaction into a mold, and cure it at 80°C for 20 minutes to obtain a railway polyurethane elastic pad with self-repairing function; wherein the stirring rate is 500 rpm and the stirring time is 1 minute.

[0031] Comparative Example 3 A method for preparing a polyurethane elastic pad comprises the following steps: A. Prepare the raw materials by weight, including: 70 parts of isocyanate prepolymer, 15 parts of crosslinking agent, 5 parts of trimethylolpropane, 0.2 parts of dibutyltin dilaurate, 0.5 parts of A33; The cross-linking agent comprises a cross-linking agent A and a cross-linking agent B in a mass ratio of 1:0.8; The preparation method of the crosslinking agent A comprises the following steps: stirring diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 60°C and in the presence of dibutyltin dilaurate for 2 hours to obtain the crosslinking agent A; wherein the amount of dibutyltin dilaurate is 0.2% of the total mass of the reactants; The preparation method of crosslinking agent B comprises the following steps: stirring diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 85°C and in the presence of dibutyltin dilaurate for 2 hours to obtain crosslinking agent B; wherein the amount of dibutyltin dilaurate is 0.2% of the total mass of the reactants; The preparation method of isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol was heated to 100°C, and vacuum-dehydrated for 3 hours under stirring; then the temperature was lowered to 80°C, toluene diisocyanate (TDI) was added, and the reaction was stirred for 2 hours in a nitrogen atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to toluene diisocyanate was 1:2; the polytetramethylene ether glycol (PTMEG) used had a molecular weight of 2000 and was purchased from BASF, Germany; B. Mix the isocyanate prepolymer and the cross-linking agent, then add trimethylolpropane, dibutyltin dilaurate and A33, stir to react, pour the product after the reaction into a mold, and cure it at 80°C for 20 minutes to obtain a railway polyurethane elastic pad with self-repairing function; wherein the stirring rate is 500 rpm and the stirring time is 1 minute.

[0032] Performance Testing: The elastic pads prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests, and the results are shown in Table 1 below.

[0033] The test method is as follows: 1. Self-repair performance test: A 10mm long and 1mm deep crack was cut into the elastic pad sample, and then placed in a 60℃ environment to observe the crack repair. After 24 hours, the crack became significantly narrower or shallower, and after 48 hours, the crack basically disappeared, indicating that the elastic pad has good self-repair performance.

[0034] Excellent: Cracks basically disappear, and mechanical properties remain above 90%; Good: The cracks have obvious changes, and the mechanical properties remain between 70-90%; Poor: The cracks are basically unchanged and the mechanical properties remain below 70%.

[0035] 2. Mechanical properties test: Tensile strength: GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0036] Elongation at break: GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0037] Compression set: GB / T10653-2001; after 24 hours of compression test at 70±2℃.

[0038] Table 1 As can be seen from Table 1, the railway polyurethane elastic pad with self-repairing function provided by the present invention provides a new type of high-performance elastic pad for the railway track system. The self-repairing function is excellent, which prolongs the service life of the elastic pad and reduces the maintenance cost. At the same time, the good mechanical properties and stability enable it to be used normally in various harsh environments, and it has broad application prospects.

[0039] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A railway polyurethane elastic pad with self-repairing function, characterized in that: The raw materials include by weight: 60-80 parts of isocyanate prepolymer, 14-16 parts of crosslinking agent, 4-6 parts of chain extender and 0.6-0.8 parts of catalyst; The cross-linking agent comprises a cross-linking agent A and a cross-linking agent B in a mass ratio of 1:0.5-1; The preparation method of the crosslinking agent A comprises the following steps: stirring diphenylmethane diisocyanate and 4,4'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 60-65° C. and under an organic tin catalyst for 2-3 hours to obtain the crosslinking agent A; The preparation method of the crosslinking agent B comprises the following steps: stirring diphenylmethane diisocyanate and 2,2'-diaminodiphenyl disulfide in a mass ratio of 2:1 at 85-90° C. and using an organic tin catalyst for 2-3 hours to obtain the crosslinking agent B; During the preparation of crosslinking agent A and crosslinking agent B, the amount of the organotin catalyst used is 0.1-0.5% of the total mass of the reactants.

2. The railway polyurethane elastic pad with self-repairing function according to claim 1 is characterized in that: The NCO index of the isocyanate prepolymer is 20-31.

3. The railway polyurethane elastic pad with self-repairing function according to claim 1, characterized in that: The chain extender is selected from one or more of trimethylolpropane, hydroquinone dihydroxyethyl ether, 1,4-butanediol and ethylene glycol.

4. The railway polyurethane elastic pad with self-repairing function according to claim 1, characterized in that: The catalyst is selected from organic tin catalysts and / or organic amine catalysts.

5. The railway polyurethane elastic pad with self-repairing function according to claim 4, characterized in that: The organotin catalyst is selected from one or more of tin octoate, dibutyltin dilaurate, dibutyltin diacetate and dioctyltin diacetate.

6. The railway polyurethane elastic pad with self-repairing function according to claim 4, characterized in that: The organic amine catalyst is selected from one or more of A33, triethylenediamine and N,N-dimethylcyclohexylamine.

7. The railway polyurethane elastic pad with self-repairing function according to claim 1, characterized in that: The preparation method of the isocyanate prepolymer comprises the following steps: The polytetramethylene ether glycol is heated to 100-110° C. and vacuum-dehydrated for 2-3 hours under stirring; then the temperature is lowered to 80-85° C., diphenylmethane diisocyanate is added, and the reaction is stirred for 2-3 hours in an inert gas atmosphere to obtain an isocyanate prepolymer; the mass ratio of the polytetramethylene ether glycol to diphenylmethane diisocyanate is 0.5-1:

2.

8. The railway polyurethane elastic pad with self-repairing function according to claim 7, characterized in that: The molecular weight of the polytetramethylene ether glycol is selected from one or more of 1000, 1500 or 2000 molecular weight.

9. The railway polyurethane elastic pad with self-repairing function according to claim 1, characterized in that: The catalyst comprises 0.15-0.2 parts of dibutyltin dilaurate and 0.5-0.55 parts of A33; and the chain extender is trimethylolpropane.

10. A method for preparing the railway polyurethane elastic pad with self-repairing function as claimed in claim 1, characterized in that: The following steps are involved: The isocyanate prepolymer and the cross-linking agent are mixed, and then the chain extender and the catalyst are added, and the reaction is stirred. The product after the reaction is poured into a mold, and cured at 75-85°C for 15-30 minutes to obtain a railway polyurethane elastic pad with self-repairing function, wherein the stirring rate is 300-600rpm and the stirring time is 1-2 minutes.

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