Anti-aging polyurethane sealing ring and preparation method thereof

Abstract

The invention relates to the technical field of rubber materials, in particular to an anti-aging polyurethane sealing ring and a preparation method thereof.The anti-aging polyurethane sealing ring is prepared from, by weight, polytetrahydrofuran ether glycol, 4, 4 '-diphenylmethane diisocyanate, polycaprolactone glycol, polydimethylsiloxane, polydimethylsiloxane, polydimethylsiloxane, polydimethylsiloxane, polydimethylsiloxane, polydimethylsiloxane, polydimethylsiloxane, polydimethylsiloxane, polydimethylsiloxane, polydimethylsiloxane The catalyst is 3, 3 '-dichloro-4, 4'-diaminodiphenyl methane; bis (beta-ethoxyl) terephthalic acid ester; the invention relates to tetra [beta-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester. According to the invention, polytetrahydrofuran ether glycol synthesized by plasma is taken as a main chain, so that the polytetrahydrofuran ether glycol is endowed with extreme hydrolysis resistance; compounding a rigid chain extender which is precisely chlorinated by the electrochemistry to construct a high-temperature stable cross-linked network; nano whisker silicon dioxide and polycarbodiimide cooperate to block an aging chain reaction, intrinsic decay resistance of the material is achieved, meanwhile, supercritical CO is adopted in the process to assist dispersion to eliminate filler agglomeration, and the micropore defect is eradicated through pulse pressure pouring; through the three-step gradient pressure curing technology, axial compression force is synchronously applied in the crosslinking process, and the high-temperature deformation rate is reduced to be lower.

Description

Technical Field

[0001] The invention relates to the technical field of rubber materials, in particular to an aging-resistant polyurethane sealing ring and a preparation method thereof. Background Art

[0002] Sealing rings are key components used to fill gaps between mechanical components. They elastically deform to isolate media (such as liquids and gases), preventing leakage and the intrusion of external contaminants. They are widely used in hydraulic systems, engines, pipeline connections, and other industrial fields, where their performance directly impacts the reliability and lifespan of equipment.

[0003] However, traditional rubber seals generally suffer from material aging defects: they are prone to hardening and cracking at high temperatures, and swell and hydrolyze when exposed to oil or water vapor for a long time, leading to seal failure. The manufacturing process often uses compression vulcanization, which is prone to defects such as bubbles and flash. Furthermore, the curing process makes it difficult to precisely control the crosslink density, resulting in a high compression set. More critically, traditional materials lack active anti-aging mechanisms and rely solely on surface coatings for protection. Under harsh operating conditions, their lifespan is less than 2,000 hours, and frequent replacement leads to surging equipment downtime costs.

[0004] Based on this, the present invention provides an aging-resistant polyurethane sealing ring and a preparation method thereof to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of the present invention is to provide an aging-resistant polyurethane sealing ring and a preparation method thereof, so as to solve the problems mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides an aging-resistant polyurethane sealing ring, which is composed of the following raw materials in parts by weight:

[0008] Polytetramethylene glycol: 60–75 parts;

[0009] 4,4'-diphenylmethane diisocyanate: 25–35 parts;

[0010] Polycaprolactone diol: 10–20 parts;

[0011] 3,3'-dichloro-4,4'-diaminodiphenylmethane: 8–15 parts;

[0012] Bis(β-hydroxyethyl) terephthalate: 5–10 parts;

[0013] Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]: 0.5–1.5 parts;

[0014] Tris(2,4-di-tert-butylphenyl)phosphite: 0.3–1.0 parts;

[0015] 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole: 0.5–1.2 parts;

[0016] Polycarbodiimide: 1.0–3.0 parts;

[0017] Fumed silica: 3–8 parts;

[0018] γ-aminopropyltriethoxysilane: 0.5–1.5 parts;

[0019] Microcrystalline wax: 0.5–1.5 parts.

[0020] Preferably, the polytetrahydrofuran ether diol is prepared by subjecting tetrahydrofuran monomer to plasma-induced ring-opening polymerization in an ultra-low temperature environment of -30 to -10°C.

[0021] Preferably, the 4,4'-diphenylmethane diisocyanate is prepared by carbonylating diphenylmethane diamine in a high-pressure carbon dioxide supercritical fluid at a pressure of 8-12 MPa and a temperature of 50-70°C by using solvent-free phosgene substitution.

[0022] Preferably, the 3,3'-dichloro-4,4'-diaminodiphenylmethane is prepared by selective electrochemical chlorination of 4,4'-diaminodiphenylmethane under ultrasonic irradiation at a frequency of 40-60 kHz.

[0023] Preferably, the polycarbodiimide is prepared by free radical catalytic polycondensation of dicyclohexylcarbodiimide in a microwave cracking field at a power of 800-1200 W and a temperature of 200-250° C., and has a degree of polymerization of 15-20.

[0024] Preferably, the fumed silica is produced by in-situ nanowhisker growth by silane gas in a laser-induced plasma torch at a temperature of 3000-3500° C., and has a specific surface area of ​​380-420 square meters per gram.

[0025] Preferably, the γ-aminopropyltriethoxysilane is prepared by continuous flow catalytic amination of acrylonitrile and triethoxysilane in a microchannel reactor at a temperature of 130-150° C. with a residence time of ≤10 seconds.

[0026] Preferably, the microcrystalline wax is prepared by coupling molecular distillation and nanometer self-assembly of the heavy fraction of Fischer-Tropsch synthesis in a high-gravity rotating bed with a centrifugal factor of ≥500G, and the carbon number distribution is C40-C60.

[0027] The present invention also provides a method for preparing an aging-resistant polyurethane sealing ring, comprising the following steps:

[0028] S1: Ultra-clean dehydration and activation of raw materials:

[0029] Put 60-75 parts of polytetramethylene glycol and 10-20 parts of polycaprolactone glycol into a drying kettle, and vibrate and dehydrate at 120±2℃ and vacuum degree 5-10Pa for 2 hours, and the moisture content is ≤0.03%;

[0030] Place 3-8 parts of fumed silica and 0.5-1.5 parts of γ-aminopropyltriethoxysilane in a high-speed vortex mixer at 3000 rpm and activate under nitrogen for 15 minutes;

[0031] S2: Supercritical CO2-assisted nanocomposites:

[0032] The dehydrated polyol and activated nanofiller were injected into the mixer and supercritical CO2 was introduced at a pressure of 15 MPa and a temperature of 55°C.

[0033] Circular mixing was performed at a shear rate of 5000 s⁻¹ for 30 min to form a homogeneous nanocomposite slurry;

[0034] S3: Pulse pressure field reaction casting:

[0035] Preheat 25-35 parts of 4,4'-diphenylmethane diisocyanate to 60±1°C and mix with the nanocomposite slurry at a ratio of NCO:OH=1.05:1;

[0036] Add 8-15 parts of 3,3'-dichloro-4,4'-diaminodiphenylmethane and 5-10 parts of bis(β-hydroxyethyl) terephthalate to extend the chain;

[0037] The injection frequency is 2 Hz, the amplitude is 0.5 MPa, and the pulse pressure field is poured into the mold. The temperature is controlled at 70 ± 0.5 ° C throughout the process.

[0038] S4: three-stage gradient temperature synergistic curing;

[0039] S5: Plasma Surface Nano-Modification:

[0040] After demoulding, the sealing ring passes through a helium-oxygen mixed plasma torch with a gas ratio of He:O2=9:1;

[0041] Surface scanning was performed at a substrate temperature of 150°C and a moving speed of 0.5 m / min;

[0042] Finally, dip-coat with a protective liquid containing 0.5-1.5 parts of microcrystalline wax, the solvent being supercritical CO2;

[0043] S6: In-situ penetration of anti-aging additives:

[0044] Dissolve 0.5-1.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 0.3-1.0 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.5-1.2 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 1.0-3.0 parts of polycarbodiimide in supercritical CO2;

[0045] The sealing ring is treated in an ultrasonic negative pressure environment for 45 minutes, and the penetration depth of the additive is ≥200μm.

[0046] Preferably, the three-stage temperature change in step S4 is:

[0047] Stage 1: 80℃ / 1MPa pressure for 1 hour to complete primary cross-linking;

[0048] Stage 2: Increase the temperature to 110°C / 5 MPa at a rate of 0.5°C / min and maintain constant temperature and pressure for 3 hours;

[0049] Stage 3: The temperature is lowered to 60°C at a rate of 0.2°C / min while applying axial compression with a compression rate of 15%.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention uses plasma-synthesized polytetramethylene glycol as the main chain to impart extreme hydrolysis resistance; a rigid chain extender with electrochemical precision chlorination is compounded to construct a high-temperature stable cross-linked network; nano-whisker silica and polycarbodiimide synergistically block the aging chain reaction to achieve the material's intrinsic resistance to decay. At the same time, the process uses supercritical CO2-assisted dispersion to eliminate filler agglomeration, and pulse pressure casting to eliminate microporous defects; through three-order gradient pressure curing technology, axial compression force is simultaneously applied during the cross-linking process to reduce the high-temperature deformation rate to a lower level. DETAILED DESCRIPTION

[0052] 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 embodiments described 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0053] 1. Materials:

[0054] The present invention proposes an aging-resistant polyurethane sealing ring. The materials are commercially available unless otherwise specified:

[0055] It is composed of the following raw materials in parts by weight:

[0056] Polytetramethylenetetramethylene ether glycol: 60–75 parts; 4,4'-diphenylmethane diisocyanate: 25–35 parts; Polycaprolactone glycol: 10–20 parts; 3,3'-dichloro-4,4'-diaminodiphenylmethane: 8–15 parts; Bis(β-hydroxyethyl)terephthalate: 5–10 parts; Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate : 0.5–1.5 parts; tris(2,4-di-tert-butylphenyl) phosphite: 0.3–1.0 parts; 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole: 0.5–1.2 parts; polycarbodiimide: 1.0–3.0 parts; fumed silica: 3–8 parts; γ-aminopropyltriethoxysilane: 0.5–1.5 parts; microcrystalline wax: 0.5–1.5 parts.

[0057] It should also be noted that polytetrahydrofuran ether glycol is prepared by subjecting tetrahydrofuran monomer to an ultra-low temperature environment of -30 to -10°C through plasma-induced ring-opening polymerization.

[0058] It should also be noted that 4,4'-diphenylmethane diisocyanate is prepared by carbonylating diphenylmethane diamine in a high-pressure carbon dioxide supercritical fluid at a pressure of 8-12 MPa and a temperature of 50-70°C through solvent-free phosgene substitution.

[0059] It should be noted that 3,3'-dichloro-4,4'-diaminodiphenylmethane is prepared by selective electrochemical chlorination of 4,4'-diaminodiphenylmethane under ultrasonic irradiation at a frequency of 40-60 kHz.

[0060] It should be noted that polycarbodiimide is prepared by subjecting dicyclohexylcarbodiimide to free radical catalytic polycondensation in a microwave cracking field at a power of 800-1200 W and a temperature of 200-250° C., and has a degree of polymerization of 15-20.

[0061] It should also be noted that fumed silica is produced by in-situ nanowhisker growth of silane gas in a laser-induced plasma torch at a temperature of 3000-3500°C, with a specific surface area of ​​380-420 square meters per gram.

[0062] It should be noted that γ-aminopropyltriethoxysilane is prepared by continuous flow catalytic amination of acrylonitrile and triethoxysilane in a microchannel reactor at a temperature of 130-150° C. with a residence time of ≤10 seconds.

[0063] It should also be noted that microcrystalline wax is obtained by coupling molecular distillation and nano-self-assembly of the heavy fraction of Fischer-Tropsch synthesis in a supergravity rotating bed with a centrifugal factor ≥500G, and the carbon number distribution is C40-C60.

[0064] 2. Process:

[0065] The present invention also provides a method for preparing an aging-resistant polyurethane sealing ring, comprising the following steps:

[0066] S1: Ultra-clean dehydration and activation of raw materials:

[0067] Put 60-75 parts of polytetramethylene glycol and 10-20 parts of polycaprolactone glycol into a drying kettle, and vibrate and dehydrate at 120±2℃ and vacuum degree 5-10Pa for 2 hours, and the moisture content is ≤0.03%;

[0068] Place 3-8 parts of fumed silica and 0.5-1.5 parts of γ-aminopropyltriethoxysilane in a high-speed vortex mixer at 3000 rpm and activate under nitrogen for 15 minutes;

[0069] S2: Supercritical CO2-assisted nanocomposites:

[0070] The dehydrated polyol and activated nanofiller were injected into the mixer and supercritical CO2 was introduced at a pressure of 15 MPa and a temperature of 55°C.

[0071] Circular mixing was performed at a shear rate of 5000 s⁻¹ for 30 min to form a homogeneous nanocomposite slurry;

[0072] S3: Pulse pressure field reaction casting:

[0073] Preheat 25-35 parts of 4,4'-diphenylmethane diisocyanate to 60±1°C and mix with the nanocomposite slurry at a ratio of NCO:OH=1.05:1;

[0074] Add 8-15 parts of 3,3'-dichloro-4,4'-diaminodiphenylmethane and 5-10 parts of bis(β-hydroxyethyl) terephthalate to extend the chain;

[0075] The injection frequency is 2 Hz, the amplitude is 0.5 MPa, and the pulse pressure field is poured into the mold. The temperature is controlled at 70 ± 0.5 ° C throughout the process.

[0076] S4: three-stage gradient temperature synergistic curing;

[0077] S5: Plasma Surface Nano-Modification:

[0078] After demoulding, the sealing ring passes through a helium-oxygen mixed plasma torch with a gas ratio of He:O2=9:1;

[0079] Surface scanning was performed at a substrate temperature of 150°C and a moving speed of 0.5 m / min;

[0080] Finally, dip-coat with a protective liquid containing 0.5-1.5 parts of microcrystalline wax, the solvent being supercritical CO2;

[0081] S6: In-situ penetration of anti-aging additives:

[0082] Dissolve 0.5-1.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 0.3-1.0 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.5-1.2 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 1.0-3.0 parts of polycarbodiimide in supercritical CO2;

[0083] The sealing ring is treated in an ultrasonic negative pressure environment for 45 minutes, and the penetration depth of the additive is ≥200μm.

[0084] It should be noted that the temperature changes in the three stages of step S4 are:

[0085] Stage 1: 80℃ / 1MPa pressure for 1 hour to complete primary cross-linking;

[0086] Stage 2: Increase the temperature to 110°C / 5 MPa at a rate of 0.5°C / min and maintain constant temperature and pressure for 3 hours;

[0087] Stage 3: The temperature is lowered to 60°C at a rate of 0.2°C / min while applying axial compression with a compression rate of 15%.

[0088] Example 1, please refer to Table 1. In this example, an aging-resistant polyurethane sealing ring is prepared according to the parameters in Table 1 and the following process parameters, and the steps are as follows:

[0089] S1. Dehydration and activation of raw materials: 67.5 parts of polytetramethylene glycol and 15 parts of polycaprolactone glycol were dehydrated in a two-stage vacuum vibration drying system at 120°C and a vacuum of 7.5 Pa for 2 hours, with a moisture content of ≤0.03%; 5.5 parts of fumed silica and 1.0 part of γ-aminopropyltriethoxysilane were activated in a high-speed vortex mixer at 3000 rpm under nitrogen protection for 15 minutes;

[0090] S2. Supercritical nanocomposite: Dehydrated polyol and activated filler were mixed and introduced into supercritical CO2 (15 MPa, 55°C) at a shear rate of 5000 s⁻¹ for 30 minutes.

[0091] S3. Pulse casting: 30 parts of 4,4'-diphenylmethane diisocyanate were preheated to 60°C and mixed with the composite slurry at an NCO:OH ratio of 1.05:1. 11.5 parts of 3,3'-dichloro-4,4'-diaminodiphenylmethane and 7.5 parts of bis(β-hydroxyethyl) terephthalate were added. Pulse pressure field parameters were: frequency 2 Hz, amplitude 0.5 MPa, and casting was performed at 70°C.

[0092] S4. Gradient curing:

[0093] Stage 1: 80℃ / 1MPa pressure for 1 hour;

[0094] Stage 2: Increase the temperature to 110°C / 5 MPa at a rate of 0.5°C / min and maintain constant temperature and pressure for 3 hours;

[0095] Stage 3: cooling to 60°C at 0.2°C / min while simultaneously applying 15% axial compression;

[0096] S5. Surface finishing and penetration: Helium-oxygen plasma (He:O2 = 9:1) scanning at 150°C, traverse speed 0.5 m / min; dip coating with supercritical CO2 protective fluid containing 1.0 phr microcrystalline wax;

[0097] S6. The additive was dissolved in supercritical CO2 and infiltrated under negative ultrasonic pressure (40 kHz, 0.01 Pa) for 45 minutes;

[0098] In order to verify the influence of material components on the performance of aging-resistant polyurethane sealing rings, Examples 2-5 and Comparative Examples 1-5 were designed:

[0099] Example 2, please refer to Table 1. In this example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Example 2 in Table 1, and the process parameters were the same as those of Example 1;

[0100] Example 3, please refer to Table 1. In this example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Example 3 in Table 1, and the process parameters were the same as those of Example 1;

[0101] Example 4, please refer to Table 1. In this example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Example 4 in Table 1, and the process parameters were the same as those of Example 1;

[0102] Example 5, please refer to Table 1. In this example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Example 5 in Table 1, and the process parameters were the same as those of Example 1;

[0103] Table 1: Example material composition table

[0104] Raw material name Example 1 Example 2 Example 3 Example 4 Example 5 Polytetramethylene ether glycol 67.5 60.0 67.5 67.5 67.5 4,4'-Diphenylmethane diisocyanate 30.0 30.0 30.0 30.0 30.0 Polycaprolactone diol 15.0 15.0 15.0 15.0 15.0 3,3'-Dichloro-4,4'-diaminodiphenylmethane 11.5 11.5 15.0 11.5 11.5 Bis(β-hydroxyethyl) terephthalate 7.5 7.5 7.5 7.5 7.5 Pentaerythritol tetra[β-(...)propionate 1.0 1.0 1.0 1.0 1.0 Tris(2,4-di-tert-butylphenyl)phosphite 6.5 6.5 6.5 6.5 6.5 2-(2'-Hydroxy-5'-tert-octylphenyl)benzotriazole 8.5 8.5 8.5 8.5 8.5 polycarbodiimide 2.0 2.0 2.0 2.0 1.0 Fumed silica 5.5 5.5 5.5 3.0 5.5 γ-Aminopropyltriethoxysilane 1.0 1.0 1.0 1.0 1.0 microcrystalline wax 1.0 1.0 1.0 1.0 1.0

[0105] Comparative Example 1, please refer to Table 2. In this comparative example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Comparative Example 1 in Table 2, and the process parameters were the same as those of Example 1;

[0106] Comparative Example 2, please refer to Table 2. In this comparative example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Comparative Example 2 in Table 2, and the process parameters were the same as those of Example 1;

[0107] Comparative Example 3, please refer to Table 2. In this comparative example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Comparative Example 3 in Table 2, and the process parameters were the same as those of Example 1;

[0108] Comparative Example 4, please refer to Table 2. In this comparative example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Comparative Example 4 in Table 2, and the process parameters were the same as those of Example 1;

[0109] Comparative Example 5, please refer to Table 2. In this comparative example, an aging-resistant polyurethane sealing ring was prepared according to the material components of Comparative Example 5 in Table 2, and the process parameters were the same as those of Example 1;

[0110] Table 2: Comparative Example Material Composition Table

[0111] Raw material name Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Polytetramethylene ether glycol 55.0 80.0 67.5 67.5 67.5 4,4'-Diphenylmethane diisocyanate 30.0 30.0 30.0 30.0 30.0 Polycaprolactone diol 15.0 15.0 15.0 15.0 15.0 3,3'-Dichloro-4,4'-diaminodiphenylmethane 11.5 11.5 5.0 18.0 11.5 Bis(β-hydroxyethyl) terephthalate 7.5 7.5 7.5 7.5 7.5 Pentaerythritol tetra[β-(...)propionate 1.0 1.0 1.0 1.0 1.0 Tris(2,4-di-tert-butylphenyl)phosphite 6.5 6.5 6.5 6.5 6.5 2-(2'-Hydroxy-5'-tert-octylphenyl)benzotriazole 8.5 8.5 8.5 8.5 8.5 polycarbodiimide 2.0 2.0 2.0 2.0 0.5 Fumed silica 5.5 5.5 5.5 5.5 1.0 γ-Aminopropyltriethoxysilane 1.0 1.0 1.0 1.0 1.0 microcrystalline wax 1.0 1.0 1.0 1.0 1.0

[0112] 3. Performance test:

[0113] The sealing ring samples were prepared according to the component parameters of the embodiment and the comparative example, and the performance of the sealing rings was tested according to the following standards:

[0114] a. Hydrolysis resistance: 85℃ / RH95% constant temperature and humidity chamber;

[0115] b. Heat aging: 150℃ hot air circulation oven;

[0116] c. Compression set: Tested according to GB / T 7759 standard;

[0117] d. Wear resistance: DIN 53516 grinding wheel abrasion tester

[0118] The performance test results of the embodiment are shown in Table 3:

[0119] Table 3: Performance test results of the embodiment

[0120] Test items Example 1 Example 2 Example 3 Example 4 Example 5 Tensile strength (MPa) 48.2 45.1 46.8 42.3 44.0 Elongation at break (%) 520 560 490 580 530 Compression set (150℃×24h,%) 8.3 9.5 10.1 12.8 14.0 Hydrolysis resistance (85℃ / RH95%,h) >5000 >5000 >5000 4200 3500 Strength retention after heat aging (150℃×2000h,%) 91.5 90.2 89.7 88.1 85.3 Wear resistance (mm³) 42 45 48 55 60

[0121] Comparative Example The comparative example performance test results are shown in Table 4:

[0122] Table 4: Comparative performance test results

[0123] Test items Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Tensile strength (MPa) 38.5 32.7 40.1 35.8 36.2 Elongation at break (%) 350 620 410 280 380 Compression set (150℃×24h,%) 22.4 18.9 25.7 28.3 26.1 Hydrolysis resistance (85℃ / RH95%,h) 1800 2200 2500 1900 800 Strength retention after heat aging (150℃×2000h,%) 72.3 68.5 75.1 70.8 63.2 Wear resistance (mm³) 98 115 85 132 105

[0124] 4. Data Analysis and Conclusions

[0125] According to Tables 1 to 4, the impacts caused by the following materials outside the range of the present invention are:

[0126] Regarding polytetramethylene ether glycol: 55 parts in Comparative Example 1 resulted in a 38% decrease in strength and a 64% decrease in hydrolysis resistance, as the main chain was too short, resulting in insufficient cross-linking; 80 parts in Comparative Example 2 resulted in a 128% increase in deformation rate and a 174% decrease in wear resistance, as excessive soft segments reduced rigidity;

[0127] Regarding 3,3'-dichloro-4,4'-diaminodiphenylmethane: 5 parts in Comparative Example 3 resulted in an 18% decrease in heat aging retention and a 210% increase in deformation rate. Insufficient chain extension resulted in low crosslinking density. 18 parts in Comparative Example 4 resulted in a 46% decrease in elongation and increased brittleness. Excessive crosslinking destroyed the flexibility of the molecular chain.

[0128] Regarding polycarbodiimide: 0.5 parts in Comparative Example 5 resulted in a 93% decrease in hydrolysis resistance, indicating insufficient hydrolysis stabilizer to block the autocatalytic reaction;

[0129] The performance of the sealing rings prepared in Examples 1 to 5 of the present application all meet the standards. Therefore, the component parameter ranges in the embodiments of the present invention are reasonable.

[0130] Furthermore, in Example 1, 67.5 parts of polytetramethylene glycol balance hydrolysis resistance and elasticity; 11.5 parts of 3,3'-dichloro chain extender optimizes crosslinking density and has a compression set of only 8.3%; 2.0 parts of polycarbodiimide fully blocks the hydrolysis chain reaction and has a service life of >5000 hours; at the same time, the high-temperature sealing performance has a compression permanent set of ≤8.3% at 150°C, and the extreme environment durability has no failure after 5000 hours of wet heat aging at 85°C / 95%RH; the mechanical stability has a strength retention rate of 91.5% after 2000 hours of heat aging, and the comprehensive performance is superior to Examples 2-5.

[0131] Therefore, the component range (Table 1) and gradient curing process of the aging-resistant polyurethane sealing ring material proposed in the present invention are the optimal solutions. Breaking through the range will lead to systematic degradation of performance. Example 1 is the best embodiment of the present invention because it meets the requirements of both components and the third-order pressure-coupled curing process.

[0132] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these 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 any one or more embodiments or examples.

[0133] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An aging-resistant polyurethane sealing ring, characterized in that: It is composed of the following raw materials in parts by weight: Polytetramethylene glycol: 60–75 parts; 4,4'-diphenylmethane diisocyanate: 25–35 parts; Polycaprolactone diol: 10–20 parts; 3,3'-dichloro-4,4'-diaminodiphenylmethane: 8–15 parts; Bis(β-hydroxyethyl) terephthalate: 5–10 parts; Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]: 0.5–1.5 parts; Tris(2,4-di-tert-butylphenyl)phosphite: 0.3–1.0 parts; 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole: 0.5–1.2 parts; Polycarbodiimide: 1.0–3.0 parts; Fumed silica: 3–8 parts; γ-aminopropyltriethoxysilane: 0.5–1.5 parts; Microcrystalline wax: 0.5–1.5 parts.

2. The aging-resistant polyurethane sealing ring according to claim 1, characterized in that: The polytetrahydrofuran ether diol is prepared by subjecting tetrahydrofuran monomer to plasma-induced ring-opening polymerization in an ultra-low temperature environment of -30 to -10°C.

3. The aging-resistant polyurethane sealing ring according to claim 2, characterized in that: The 4,4'-diphenylmethane diisocyanate is prepared by carbonylating diphenylmethane diamine in a high-pressure carbon dioxide supercritical fluid at a pressure of 8-12 MPa and a temperature of 50-70°C through solvent-free phosgene substitution.

4. The aging-resistant polyurethane sealing ring according to claim 3, characterized in that: The 3,3'-dichloro-4,4'-diaminodiphenylmethane is prepared by selective electrochemical chlorination of 4,4'-diaminodiphenylmethane under ultrasonic radiation of a frequency of 40-60 kHz.

5. The aging-resistant polyurethane sealing ring according to claim 4, characterized in that: The polycarbodiimide is prepared by subjecting dicyclohexylcarbodiimide to free radical catalytic polycondensation in a microwave cracking field with a power of 800-1200W and a temperature of 200-250°C, and has a polymerization degree of 15-20.

6. The aging-resistant polyurethane sealing ring according to claim 5, characterized in that: The gas-phase silicon dioxide is prepared by growing in-situ nano whiskers by silane gas in a laser-induced plasma torch at a temperature of 3000-3500° C., and has a specific surface area of ​​380-420 square meters per gram.

7. The aging-resistant polyurethane sealing ring according to claim 6, characterized in that: The gamma-aminopropyltriethoxysilane is prepared by continuous flow catalytic amination of acrylonitrile and triethoxysilane in a microchannel reactor at a temperature of 130-150° C. for a residence time of ≤10 seconds.

8. The aging-resistant polyurethane sealing ring according to claim 7, characterized in that: The microcrystalline wax is prepared by coupling molecular distillation and nanometer self-assembly of the heavy fraction of Fischer-Tropsch synthesis in a supergravity rotating bed with a centrifugal factor of ≥500G, and has a carbon number distribution of C40-C60.

9. The method for preparing an aging-resistant polyurethane sealing ring according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: Ultra-clean dehydration and activation of raw materials: Put 60-75 parts of polytetramethylene glycol and 10-20 parts of polycaprolactone glycol into a drying kettle, and vibrate and dehydrate at 120±2℃ and vacuum degree 5-10Pa for 2 hours, and the moisture content is ≤0.03%; Place 3-8 parts of fumed silica and 0.5-1.5 parts of γ-aminopropyltriethoxysilane in a high-speed vortex mixer at 3000 rpm and activate under nitrogen for 15 minutes; S2: Supercritical CO2-assisted nanocomposites: The dehydrated polyol and activated nanofiller were injected into the mixer and supercritical CO2 was introduced at a pressure of 15 MPa and a temperature of 55°C. Circular mixing was performed at a shear rate of 5000 s⁻¹ for 30 min to form a homogeneous nanocomposite slurry; S3: Pulse pressure field reaction casting: Preheat 25-35 parts of 4,4'-diphenylmethane diisocyanate to 60±1°C and mix with the nanocomposite slurry at a ratio of NCO:OH=1.05:1; Add 8-15 parts of 3,3'-dichloro-4,4'-diaminodiphenylmethane and 5-10 parts of bis(β-hydroxyethyl) terephthalate to extend the chain; The injection frequency is 2 Hz, the amplitude is 0.5 MPa, and the pulse pressure field is poured into the mold. The temperature is controlled at 70 ± 0.5 ° C throughout the process. S4: three-stage gradient temperature synergistic curing; S5: Plasma Surface Nano-Modification: After demoulding, the sealing ring passes through a helium-oxygen mixed plasma torch with a gas ratio of He:O2=9:1; Surface scanning was performed at a substrate temperature of 150°C and a moving speed of 0.5 m / min; Finally, dip-coat with a protective liquid containing 0.5-1.5 parts of microcrystalline wax, the solvent being supercritical CO2; S6: In-situ penetration of anti-aging additives: Dissolve 0.5-1.5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 0.3-1.0 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.5-1.2 parts of 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 1.0-3.0 parts of polycarbodiimide in supercritical CO2; The sealing ring is treated in an ultrasonic negative pressure environment for 45 minutes, and the penetration depth of the additive is ≥200μm.

10. The method for preparing an aging-resistant polyurethane sealing ring according to claim 9, characterized in that: The three stages of temperature change in step S4 are: Stage 1: 80℃ / 1MPa pressure for 1 hour to complete primary cross-linking; Stage 2: Increase the temperature to 110°C / 5 MPa at a rate of 0.5°C / min and maintain constant temperature and pressure for 3 hours; Stage 3: The temperature is lowered to 60°C at a rate of 0.2°C / min while applying axial compression with a compression rate of 15%.