High-temperature-resistant and acid-alkali-resistant TPU (thermoplastic polyurethane) sealing material and preparation method thereof

Abstract

The invention relates to the technical field of advanced petrochemical and chemical new materials, in particular to a high-temperature-resistant and acid-alkali-resistant TPU (thermoplastic polyurethane) sealing material and a preparation method thereof. A modified mica functional filler; nano zirconium oxide; a plasticizer; an antioxidant; a lubricant; a light stabilizer; a silane coupling agent; according to the technical scheme, through the synergistic effect of filler modification, structure construction, component compatibility and process optimization, the prepared TPU sealing material has excellent high-temperature resistance and acid and alkali resistance, good mechanical properties and processability, can still keep stable sealing performance under the high-temperature acid and alkali severe working conditions, and is suitable for large-scale popularization and application. The service life of the sealing element is greatly prolonged, the equipment maintenance cost is reduced, and the sealing element can be widely applied to sealing scenes in the fields of chemical engineering, electric power, metallurgy and the like and has remarkable practical value and application prospect.

Description

Technical Field

[0001] This invention relates to the field of advanced petrochemical new materials technology, specifically to a high-temperature resistant and acid- and alkali-resistant TPU sealing material and its preparation method. Background Technology

[0002] Thermoplastic polyurethane (TPU), as a polymer material that combines the high elasticity of rubber and the high strength of plastic, has been widely used in the sealing field due to its good processability, wear resistance, elastic recovery and oil resistance. It has become the core raw material for the preparation of various seals, gaskets and sealing strips, and is widely used in chemical, metallurgical, power, new energy and other industrial fields as well as civil equipment.

[0003] In practical applications, sealing materials often face complex service environments, especially in scenarios such as chemical production, acid and alkali waste treatment, and high-temperature fluid transportation. These materials are in prolonged contact with strong acids and alkalis, and must also withstand temperatures exceeding 80°C. This places stringent requirements on the high-temperature resistance and acid and alkali corrosion resistance of TPU sealing materials. Traditional pure TPU materials contain polar groups such as ester and urethane groups in their molecular chains. Under high-temperature acid and alkali conditions, these groups are prone to ester bond hydrolysis, molecular chain degradation, and cross-linking reactions, leading to swelling, hardening, and brittleness. This results in a rapid decline in sealing performance, causing not only media leakage and reduced equipment operating efficiency but also potential safety accidents. It significantly shortens the service life of seals and increases equipment maintenance costs and replacement frequency.

[0004] To improve the high-temperature resistance and acid / alkali resistance of TPU materials, existing technologies often modify them by adding inorganic fillers, such as mica, talc, and zirconium oxide. The chemical stability of these inorganic fillers enhances the material's resistance to various media and its thermal stability. However, in existing modification techniques, the interfacial compatibility between inorganic fillers and the TPU organic matrix is ​​poor. The fillers are prone to agglomeration and cannot be uniformly dispersed within the matrix. This not only hinders the formation of effective structural reinforcement but also creates stress concentration points at the agglomeration sites, leading to a decrease in the material's mechanical properties and impaired elasticity and toughness. Furthermore, inorganic fillers only function locally and cannot form a dense structural barrier within the material, failing to effectively impede the thermal motion of molecular chains at high temperatures and the penetration of acid and alkali media. Consequently, the improvement in the high-temperature resistance and acid / alkali resistance of the modified TPU material is limited, and it still cannot meet the sealing requirements under harsh operating conditions.

[0005] Therefore, developing a TPU sealing material with good filler dispersibility, strong interfacial bonding, and the ability to maintain structural and performance stability in high-temperature acid and alkaline media, while also taking into account good mechanical and processing properties, has become the key to solving the shortcomings of existing technologies and is also the current research focus and development direction in the field of TPU sealing material modification. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature resistant and acid / alkali resistant TPU sealing material and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A high-temperature resistant and acid / alkali resistant TPU sealing material is prepared from the following raw materials in parts by weight: thermoplastic polyurethane matrix resin: 100 parts; modified mica functional filler: 15-25 parts; nano-zirconia: 0.3-0.8 parts; plasticizer: 5-10 parts; antioxidant: 0.5-2 parts; lubricant: 0.5-1.5 parts; light stabilizer: 0.3-1 part; silane coupling agent: 0.5-2 parts; The modified mica functional filler is obtained by compounding lamellar mica and fibrous silicate minerals at a mass ratio of 3-5:1 and then performing a stepwise surface modification treatment. The stepwise surface modification treatment involves first treating with a phosphorus-containing silane coupling agent and then treating with a titanate coupling agent to form a double-layer coating structure. The nano-zirconia and modified mica functional filler form a three-dimensional synergistic reinforcement network, filling the gaps between lamellar mica and fibrous silicate minerals; The TPU matrix resin is polyester-type TPU with a hardness range of 80A-55D.

[0008] As a further technical solution, the preparation method of the modified mica functional filler includes the following steps: S1. Lamellar mica and fibrous silicate minerals are premixed in a high-speed mixer at 60-80℃ and 600-800rpm for 10-20min to obtain a primary composite filler; the lamellar mica has a particle size of 10-20μm, and the fibrous silicate minerals are sepiolite fibers or wollastonite fibers with a length of 5-10μm and a diameter of 0.5-1μm; S2. Prepare an ethanol-water solution of silane coupling agent, wherein the volume ratio of ethanol to water in the ethanol-water solution is 4:1, the mass fraction of phosphorus-containing silane coupling agent is 3-5%, the pH is adjusted to 4.2-4.8 with acetic acid, and hydrolyzed at room temperature for 20 min to obtain the first treatment solution; S3. Add the primary composite filler to the first treatment solution with a liquid-solid ratio of 6-7:1. Stir the mixture at 70-85℃ with an ultrasonic power of 200-300W and a stirring speed of 400-500rpm for 40-60 minutes. Filter the mixture, wash it 1-2 times with anhydrous ethanol, and dry it at 80-90℃ for 30 minutes to obtain the primary modified filler. S4. Prepare an ethanol-water solution of titanate coupling agent, wherein the volume ratio of ethanol to water in the ethanol-water solution is 4:1, the mass fraction of titanate coupling agent is 3-5%, the amount of composite modifier added is 8-12% of the mass of titanate coupling agent, the pH is adjusted to 4.2-4.8 with acetic acid, and hydrolyzed at room temperature for 20 min to obtain the second treatment solution. S5. Add the modified filler to the second treatment solution at a liquid-to-solid ratio of 6-7:1. Stir the mixture at 70-85℃ with an ultrasonic power of 200-300W and a stirring speed of 400-500rpm for 40-60 minutes. Filter the mixture and wash the solid product 2-3 times with anhydrous ethanol. Vacuum dry the product to constant weight at 105-115℃ and a vacuum degree of -0.09MPa. Pulverize the product and pass it through an 80-100 mesh standard sieve to obtain the modified mica functional filler. The mass ratio of the phosphorus-containing silane coupling agent to the titanate coupling agent is 1:1.2-1.8.

[0009] As a further technical solution, the phosphorus-containing silane coupling agent in step S2 is γ-aminopropylphosphonic silane, and the titanate coupling agent is isopropyltristearate oxytitanate. The preparation method of the composite modified component includes the following steps: S21. Weigh nano-hydroxyapatite, graphene, and epoxy-terminated polyetherimide in a mass ratio of 5:2:1. Add nano-hydroxyapatite and graphene to N,N-dimethylformamide at a mass ratio of 5-6 times their total mass. Disperse the mixture by ultrasonication for 30-40 minutes at an ultrasonic power of 300-400W to obtain a dispersion. S22. Add 3-5% by weight of graphene silane coupling agent KH-570 to the dispersion, and stir at 65-75℃ and 400-500 rpm for 1-1.5 hours to obtain the grafted dispersion. S23. Add epoxy-terminated polyetherimide to the grafted dispersion, heat to 85-95℃, and stir for 2-2.5 hours. S24. After the reaction is complete, add 2-4% of the total mass of polycarbodiimide crosslinking agent to the reaction system, continue stirring for 30-40 minutes, centrifuge at 8000-10000 rpm, wash 2-3 times with anhydrous ethanol, vacuum dry at 100-120℃ to constant weight, and pulverize to a particle size ≤40nm to obtain the composite modified component; wherein the particle size of the graphene is 40-60nm and the particle size of the nano-hydroxyapatite is 20-30nm.

[0010] As a further technical solution, the plasticizer is trioctyl trimellitate.

[0011] As a further technical solution, the antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant, with a mass ratio of 2.2-2.8:1; the hindered phenolic antioxidant is antioxidant 1010, and the phosphite antioxidant is antioxidant 168.

[0012] As a further technical solution, the lubricant is calcium stearate or ethylene bis-stearamide.

[0013] As a further technical solution, the light stabilizer is a benzotriazole light stabilizer, specifically the light stabilizer UV-327; the silane coupling agent is KH-560.

[0014] A method for preparing a high-temperature and acid / alkali-resistant TPU sealing material includes the following steps: S31. Weigh each raw material according to the weight parts. Among them, nano-zirconia is first premixed with the independently added silane coupling agent KH-550 ethanol aqueous solution at a speed of 500-600 rpm for 25-30 min. After filtration and drying, the nano-composite system is obtained. S32. Add the TPU matrix resin, modified mica functional filler, nanocomposite system, plasticizer, antioxidant, lubricant, and light stabilizer into a high-speed mixer and mix at room temperature with continuous clockwise stirring at a speed of 800-1000 rpm for 5-10 minutes to obtain a uniform premix. S33. The premixed material is fed into a twin-screw extruder for melt blending, extrusion, cooling, and granulation. The temperatures of zones one to five of the twin-screw extruder are set to 160℃, 175℃, 185℃, 180℃, and 170℃, respectively. The die head temperature is 165℃, and the screw speed is 200-300 rpm. During the melt blending process, the speed of zones one to two of the extruder is 200-220 rpm, and the speed of zones three to five of the extruder is 280-300 rpm. The extrusion pressure is 16-20 MPa, and the melt blending residence time is 3-5 min. S34. The obtained granules are dried at 90-100℃ and vacuum degree -0.08MPa for 4-6 hours, and then injection molded or extruded. The injection molding temperature is 170-180℃, the injection pressure is 20-25MPa, and the injection holding time is 10-15s. The extrusion molding temperature is 165-175℃ and the molding pressure is 18-22MPa to obtain the TPU sealing material product.

[0015] As a further technical solution, the particle size of the nano-zirconia is 50-100nm, the KH-550 is an independently added modifier, the amount added is 1.2-1.8% of the mass of the nano-zirconia, and the mass ratio of KH-550, ethanol and water is 3:8:5.

[0016] As a further technical solution, in step S3, the particle size of the extruded granules is 2-3 mm, and after granulation, they are cooled to room temperature by air cooling with a cooling wind speed of 2-3 m / s; in step S4, the granules are naturally cooled to room temperature after extrusion molding.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention achieves high compatibility between the mica functional filler and the TPU matrix resin at the microscopic level through a stepwise double-layer coating surface modification of lamellar mica and fibrous silicate minerals. This fundamentally solves the technical problems of inorganic filler agglomeration and poor interfacial bonding. The lamellar mica and fibrous silicate minerals are compounded in a specific ratio to form an interwoven microstructure, laying the structural foundation for the subsequent construction of a three-dimensional reinforcement network. The stepwise modification process, first using a phosphorus-containing silane coupling agent and then a titanate coupling agent, forms a dense double-layer coating structure on the filler surface. The phosphorus-containing silane coupling agent forms strong covalent bonds with the hydroxyl groups on the filler surface, while the titanate coupling agent generates physical entanglement and chemical interaction with the polar groups of the TPU matrix. This achieves a "molecular-level" bond between the inorganic filler and the organic matrix, effectively improving the uniformity of filler dispersion in the matrix and avoiding the formation of stress concentration points. This ensures that the filler can fully exert its physical reinforcement effect without compromising the elasticity and toughness of the TPU matrix itself. Meanwhile, the composite modifying components added during the modification process can further optimize the density and stability of the coating layer, improve the acid and alkali corrosion resistance of the filler, block the erosion of the filler-matrix interface by acid and alkali media, and maintain the stability of the interface bonding at high temperatures, thus solving the defect of traditional modified fillers being prone to debonding at high temperatures.

[0018] 2. This invention utilizes modified mica functional fillers and KH-550 modified nano-zirconia to form a three-dimensional synergistic reinforcement network, achieving complementarity and synergy of the functions of each filler. This significantly improves the high-temperature resistance, acid and alkali resistance, and mechanical properties from the internal structural level of the material. The nano-zirconia particles have a diameter of 50-100 nm and can fill the microscopic gaps between lamellar mica and fibrous silicate minerals. Together with the interlaced modified mica fillers, they form a dense three-dimensional spatial structure. This structure can effectively hinder the thermal motion and thermal degradation of TPU molecular chains at high temperatures, improve the thermal stability of the material, and reduce the decay of mechanical properties at high temperatures. On the other hand, it can form a continuous structural barrier, significantly extending the penetration path of acid and alkali media inside the material, hindering the contact between the media and the TPU matrix molecular chains, reducing the occurrence of reactions such as ester bond hydrolysis, reducing the degree of swelling of the material, and improving the acid and alkali corrosion resistance. Meanwhile, the nano-zirconia modified by KH-550 has better dispersibility and stronger bonding with modified mica filler and TPU matrix. The three-dimensional synergistic reinforcement network can achieve uniform stress transmission, greatly improve the tensile strength and hardness of the material, and at the same time retain good elongation at break, so that the sealing material has both high strength and high elasticity, meeting the mechanical requirements of sealing components.

[0019] 3. This invention, through scientific raw material formulation and preparation process, achieves overall synergy among various components and process steps, ensuring the comprehensive performance and industrial production feasibility of TPU sealing materials from a macroscopic perspective. It solves the core problems of poor sealing performance and short service life of traditional TPU sealing materials under high-temperature and acidic / alkaline conditions. The plasticizer selected is trioctyl trimellitate, which combines good plasticizing effect and high-temperature resistance, avoiding material performance degradation due to plasticizer migration at high temperatures. The antioxidants are antioxidants 1010 and 168 compounded in a specific ratio, forming a synergistic antioxidant system. Antioxidant 1010 can terminate the free radical chain reaction of thermo-oxidative aging, and antioxidant 168 can decompose the hydroperoxides produced by thermo-oxidative aging, inhibiting thermo-oxidative aging of the material from different stages and improving the material's aging resistance life. The addition of light stabilizer UV-327 and silane coupling agent KH-560 further enhances the material's weather resistance and interfacial bonding strength. Meanwhile, the manufacturing process involves controlling the zoned temperature, rotation speed, and extrusion pressure of the twin-screw extruder, employing a pre-mixing followed by melt blending method to avoid thermal degradation during material processing and ensure material performance stability. The parameter design of the granulation and molding processes gives the material excellent processability, meeting the requirements of various molding methods such as injection molding and extrusion, making it suitable for large-scale industrial production. Overall, the technical solution of this invention, through the synergistic effect of filler modification, structural construction, component compatibility, and process optimization, produces a TPU sealing material that possesses excellent high-temperature resistance, acid and alkali resistance, good mechanical properties, and processing performance. It maintains stable sealing performance even under harsh high-temperature and acid / alkali conditions, significantly extending the service life of sealing components and reducing equipment maintenance costs. It can be widely used in sealing applications in chemical, power, and metallurgical fields, demonstrating significant practical value and application prospects. Attached Figure Description

[0020] Figure 1 The above is a statistical chart showing the tensile strength retention rate of the examples and comparative examples. Detailed Implementation

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

[0022] This invention provides a high-temperature and acid / alkali resistant TPU sealing material and its preparation method. The raw materials of this sealing material are scientifically formulated, and the components work synergistically to form a stable three-dimensional reinforced structure, which significantly improves the high-temperature and acid / alkali resistance of the TPU material, while retaining the good elasticity and sealing performance of the TPU matrix. The preparation method has controllable process parameters, good molding effect, and is suitable for large-scale industrial production.

[0023] The high-temperature resistant and acid-alkali resistant TPU sealing material of the present invention is prepared from the following raw materials in parts by weight: 100 parts of thermoplastic polyurethane matrix resin; 15-25 parts of modified mica functional filler; 0.3-0.8 parts of nano-zirconia; 5-10 parts of plasticizer; 0.5-2 parts of antioxidant; 0.5-1.5 parts of lubricant; 0.3-1 part of light stabilizer; and 0.5-2 parts of silane coupling agent.

[0024] In this invention, the thermoplastic polyurethane matrix resin is preferably polyester-type TPU, and its hardness range is preferably 80A-55D. Commercially available products well known to those skilled in the art can be used. The selection of polyester-type TPU can adjust the hardness according to the actual application scenario of the sealing material, taking into account both elasticity and structural strength.

[0025] In this invention, the amount of modified mica functional filler added is preferably 18-22 parts, more preferably 20 parts; the modified mica functional filler is obtained by compounding lamellar mica and fibrous silicate minerals at a mass ratio of 3-5:1, followed by stepwise surface modification treatment, with the mass ratio preferably being 3.5-4.5:1, more preferably 4:1; the stepwise surface modification treatment involves first treating with a phosphorus-containing silane coupling agent, and then treating with a titanate coupling agent to form a double-layer coating structure. The double-layer coating structure can significantly improve the interfacial compatibility between the filler and the TPU matrix resin and prevent filler agglomeration.

[0026] In this invention, the amount of nano-zirconia added is preferably 0.4-0.7 parts, more preferably 0.5 parts; the particle size of nano-zirconia is 50-100 nm, and nano-zirconia and modified mica functional filler form a three-dimensional synergistic reinforcement network, which fills the gaps between lamellar mica and fibrous silicate minerals. The three-dimensional synergistic reinforcement network can effectively improve the mechanical properties and media resistance of the material.

[0027] In this invention, the plasticizer is trioctyl trimellitate, and the preferred amount is 6-9 parts, more preferably 7.5 parts. The addition of trioctyl trimellitate can improve the processing fluidity and low-temperature flexibility of TPU material, and has excellent high-temperature resistance, and will not cause plasticizer migration due to high-temperature use.

[0028] In this invention, the antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant, with a mass ratio of 2.2-2.8:1, preferably 2.4-2.6:1, and more preferably 2.5:1; the hindered phenolic antioxidant is antioxidant 1010, and the phosphite antioxidant is antioxidant 168. The amount of antioxidant added is preferably 0.8-1.8 parts, more preferably 1.2 parts. The compound antioxidant can exert a synergistic antioxidant effect and inhibit the thermo-oxidative aging of TPU materials during high-temperature processing and use.

[0029] In this invention, the lubricant is calcium stearate or ethylene bis-stearamide, and the amount added is preferably 0.7-1.3 parts, more preferably 1.0 part. The addition of the lubricant can reduce the melt viscosity during the material processing, reduce equipment wear, and at the same time avoid the phenomenon of sticking to the mold on the surface of the product.

[0030] In this invention, the light stabilizer is a benzotriazole light stabilizer, specifically light stabilizer UV-327, and the addition amount is preferably 0.5-0.8 parts, more preferably 0.6 parts. Light stabilizer UV-327 can effectively absorb ultraviolet rays, prevent TPU materials from photoaging when used outdoors, and improve the weather resistance of the product.

[0031] In this invention, the silane coupling agent is KH-560, and the preferred addition amount is 0.8-1.8 parts, more preferably 1.2 parts. KH-560 can further enhance the interfacial bonding force between the inorganic filler and the organic TPU matrix, and enhance the structural stability of the material.

[0032] In this invention, the preparation method of the modified mica functional filler includes the following steps: S1. Lamellar mica and fibrous silicate minerals are premixed in a high-speed mixer at 60-80℃ and 600-800rpm for 10-20min to obtain a primary composite filler; the lamellar mica has a particle size of 10-20μm, preferably 12-18μm, more preferably 15μm; the fibrous silicate minerals are sepiolite fibers or wollastonite fibers, with a length of 5-10μm, preferably 6-9μm, more preferably 7.5μm, and a diameter of 0.5-1μm, preferably 0.6-0.9μm, more preferably 0.75μm; the premixing temperature is preferably 65-75℃, more preferably 70℃, the rotation speed is preferably 650-750rpm, more preferably 700rpm, and the time is preferably 12-18min, more preferably 15min.

[0033] S2. Prepare an ethanol-water solution of silane coupling agent, wherein the volume ratio of ethanol to water in the ethanol-water solution is 4:1, the mass fraction of the phosphorus-containing silane coupling agent is 3-5%, preferably 3.5-4.5%, more preferably 4%, adjust the pH to 4.2-4.8, preferably 4.4-4.6, more preferably 4.5 with acetic acid, and hydrolyze at room temperature for 20 min to obtain the first treatment solution; the phosphorus-containing silane coupling agent is γ-aminopropylphosphonosilane.

[0034] S3. Add the primary composite filler to the first treatment solution, with a liquid-to-solid ratio of 6-7:1, preferably 6.2-6.8:1, more preferably 6.5:1. Stir the mixture at 70-85°C with an ultrasonic power of 200-300W and a stirring speed of 400-500rpm for 40-60 minutes. Filter the mixture, wash it 1-2 times with anhydrous ethanol, and dry it at 80-90°C for 30 minutes to obtain the primary modified filler. The preferred reaction temperature is 75-80°C, more preferably 78°C; the preferred ultrasonic power is 220-280W, more preferably 250W; the preferred stirring speed is 420-480rpm, more preferably 450rpm; and the preferred reaction time is 45-55 minutes, more preferably 50 minutes.

[0035] S4. Prepare an ethanol-water solution of titanate coupling agent, wherein the volume ratio of ethanol to water in the ethanol-water solution is 4:1, the mass fraction of titanate coupling agent is 3-5%, preferably 3.5-4.5%, more preferably 4%, the amount of composite modifying component added is 8-12% of the mass of titanate coupling agent, preferably 9-11%, more preferably 10%, the pH is adjusted to 4.2-4.8 with acetic acid, preferably 4.4-4.6, more preferably 4.5, and hydrolyzed at room temperature for 20 min to obtain a second treatment solution; the titanate coupling agent is isopropyltristearate oxytitanate. S5. Add the primary modified filler to the second treatment solution, with a liquid-to-solid ratio of 6-7:1, preferably 6.2-6.8:1, more preferably 6.5:1. Stir the mixture at 70-85°C with ultrasonic power of 200-300W and stirring speed of 400-500rpm for 40-60 minutes. Filter the mixture, wash the solid product 2-3 times with anhydrous ethanol, and vacuum dry it to constant weight at 105-115°C and a vacuum degree of -0.09MPa. Pulverize the dried product through an 80-100 mesh standard sieve to obtain the final product. The modified mica functional filler has the following characteristics: the reaction temperature is preferably 75-80℃, more preferably 78℃; the ultrasonic power is preferably 220-280W, more preferably 250W; the stirring speed is preferably 420-480rpm, more preferably 450rpm; and the reaction time is preferably 45-55min, more preferably 50min. The mass ratio of the phosphorus-containing silane coupling agent to the titanate coupling agent is 1:1.2-1.8, preferably 1:1.4-1.6, more preferably 1:1.5.

[0036] In this invention, the preparation method of the composite modified component includes the following steps: S21. Weigh nano-hydroxyapatite, graphene, and epoxy-terminated polyetherimide at a mass ratio of 5:2:1. Add nano-hydroxyapatite and graphene to N,N-dimethylformamide at a mass ratio of 5-6 times their total mass. Disperse ultrasonically for 30-40 minutes at an ultrasonic power of 300-400W to obtain a dispersion. The particle size of the graphene is 40-60nm, preferably 45-55nm, more preferably 50nm. The particle size of the nano-hydroxyapatite is 20-30nm, preferably 22-28nm, more preferably 25nm. The solvent addition is preferably 5.2-5.8 times, more preferably 5.5 times. The ultrasonic time is preferably 32-38 minutes, more preferably 35 minutes. The ultrasonic power is preferably 320-380W, more preferably 350W.

[0037] S22. Add 3-5% (by weight of graphene) of silane coupling agent KH-570 to the dispersion, and stir at 65-75°C and 400-500 rpm for 1-1.5 hours to obtain a grafted dispersion; the preferred amount of KH-570 is 3.5-4.5%, more preferably 4%, the preferred reaction temperature is 68-72°C, more preferably 70°C, the preferred stirring speed is 420-480 rpm, more preferably 450 rpm, and the preferred reaction time is 1.1-1.4 hours, more preferably 1.2 hours.

[0038] S23. Add epoxy-terminated polyetherimide to the grafted dispersion, heat to 85-95°C, and stir for 2-2.5 hours; the preferred heating temperature is 88-92°C, more preferably 90°C, and the preferred holding time is 2.1-2.4 hours, more preferably 2.2 hours.

[0039] S24. After the reaction is complete, add 2-4% of the total mass of polycarbodiimide crosslinking agent to the reaction system, continue stirring for 30-40 min, centrifuge at 8000-10000 rpm, wash 2-3 times with anhydrous ethanol, vacuum dry at 100-120℃ to constant weight, and pulverize to a particle size ≤40 nm to obtain the composite modified component; the preferred amount of crosslinking agent is 2.5-3.5%, more preferably 3%, the preferred stirring time is 32-38 min, more preferably 35 min, the preferred centrifugation speed is 8500-9500 rpm, more preferably 9000 rpm, and the preferred drying temperature is 105-115℃, more preferably 110℃.

[0040] In this invention, the nano-zirconia needs to be modified with silane coupling agent KH-550 before use. KH-550 is an independently added modifier, and the amount added is 1.2-1.8% of the mass of nano-zirconia, preferably 1.4-1.6%, more preferably 1.5%. During modification, the mass ratio of KH-550, ethanol and water is 3:8:5. The nano-zirconia modified with KH-550 has better dispersibility and stronger bonding with TPU matrix and modified mica functional filler.

[0041] The method for preparing the high-temperature resistant and acid / alkali resistant TPU sealing material of the present invention includes the following steps: S31. Weigh each raw material according to the weight parts, wherein the nano-zirconia is first premixed with the independently added silane coupling agent KH-550 ethanol aqueous solution at a speed of 500-600 rpm for 25-30 min, and then dried by vacuum filtration to obtain the nano-composite system; the premixing speed is preferably 520-580 rpm, more preferably 550 rpm.

[0042] S32. The TPU matrix resin, modified mica functional filler, nanocomposite system, plasticizer, antioxidant, lubricant, and light stabilizer are added together into a high-speed mixer and mixed at room temperature with continuous clockwise stirring at a speed of 800-1000 rpm for 5-10 minutes to obtain a uniform premix. The stirring speed is preferably 850-950 rpm, more preferably 900 rpm, and the mixing time is preferably 6-9 minutes, more preferably 7.5 minutes.

[0043] S33. The premixed material is fed into a twin-screw extruder for melt blending, extrusion, cooling, and granulation. The temperatures of zones one to five of the twin-screw extruder are set to 160℃, 175℃, 185℃, 180℃, and 170℃, respectively, the die head temperature is 165℃, and the screw speed is 200-300 rpm. During the melt blending process, the speed of zones one and two of the extruder is 200-220 rpm, preferably 205-215 rpm, more preferably 210 rpm, and the speed of zones three and five of the extruder is 280-300 rpm, preferably 285-295 rpm, more preferably 290 rpm. The extrusion pressure is 16-20 MPa, preferably 17-19 MPa, more preferably 18 MPa, and the melt blending residence time is 3-5 min, preferably 3.5-4.5 min, more preferably 4 min.

[0044] S34. The obtained granules are dried at 90-100℃ and vacuum degree -0.08MPa for 4-6 hours, and then injection molded or extruded. The injection molding temperature is 170-180℃, preferably 172-178℃, more preferably 175℃, the injection molding pressure is 20-25MPa, preferably 21-24MPa, more preferably 22.5MPa, and the injection holding time is 10-15s, preferably 11-14s, more preferably 12.5s. The extrusion molding temperature is 165-175℃, preferably 168-172℃, more preferably 170℃, and the molding pressure is 18-22MPa, preferably 19-21MPa, more preferably 20MPa, to obtain the TPU sealing material product.

[0045] In this invention, in step S33, the particle size of the extruded granules is 2-3 mm, preferably 2.2-2.8 mm, more preferably 2.5 mm. After granulation, the granules are cooled to room temperature by air cooling, with a cooling wind speed of 2-3 m / s, preferably 2.2-2.8 m / s, more preferably 2.5 m / s. In step S34, after extrusion molding, the granules are naturally cooled to room temperature. The drying temperature is preferably 92-98℃, more preferably 95℃, and the drying time is preferably 4.5-5.5 hours, more preferably 5 hours.

[0046] The high-temperature and acid / alkali resistant TPU sealing material provided by this invention effectively improves the high-temperature and acid / alkali resistance of TPU material through a three-dimensional synergistic reinforcement network formed by modified mica functional filler and nano-zirconia, combined with the synergistic effect of various additives, while maintaining good elasticity and processing performance. The preparation method has controllable process parameters, and the steps work together to effectively avoid thermal degradation of the material during processing, ensuring the performance stability of the product. It solves the problem of easy aging and decreased sealing performance of traditional TPU sealing materials in high-temperature and acid / alkali media environments, and has a wider range of applications.

[0047] To further illustrate the present invention, the following examples provide a detailed description. In the following examples of the present invention: the polyester-type TPU matrix resin used is a commercially available conventional product with a hardness of 80A-55D; the lamellar mica has a particle size of 10-20μm, and the sepiolite fiber has a length of 5-10μm and a diameter of 0.5-1μm, all of which are commercially available industrial-grade raw materials; γ-aminopropylphosphonosilane and isopropyltristearate titanate are commercially available coupling agents; the nano-zirconia has a particle size of 50-100nm and is a commercially available nano-grade raw material; trioctyl trimellitate is a commercially available industrial-grade raw material. Industrial-grade plasticizer; antioxidants 1010 and 168 are commercially available conventional antioxidants; calcium stearate is a commercially available lubricant; light stabilizer UV-327, silane coupling agents KH-560, KH-550, and KH-570 are commercially available silane coupling agents; nano-hydroxyapatite with a particle size of 20-30nm, graphene with a particle size of 40-60nm, epoxy-terminated polyetherimide, polycarbodiimide crosslinking agent, and N,N-dimethylformamide are all commercially available chemical raw materials.

[0048] Example 1: This embodiment prepares a high-temperature resistant and acid / alkali resistant TPU sealing material. The specific steps are as follows: (I) Preparation of modified mica functional fillers: S1. Laminated mica and sepiolite fibers were premixed in a high-speed mixer at a mass ratio of 3:1 at 60°C and 600 rpm for 10 min to obtain a primary composite filler; the laminar mica had a particle size of 10 μm and the sepiolite fibers had a length of 5 μm and a diameter of 0.5 μm.

[0049] S2. Prepare an ethanol-water solution of silane coupling agent with a volume ratio of ethanol to water of 4:1 and a mass fraction of 3% for γ-aminopropylphosphonosilane. Adjust the pH to 4.2 with acetic acid and hydrolyze at room temperature for 20 min to obtain the first treatment solution.

[0050] S3. Add the primary composite filler to the first treatment solution with a liquid-to-solid ratio of 6:1. Stir the mixture at 70°C with an ultrasonic power of 200W and a stirring speed of 400rpm for 40 minutes. Filter the mixture, wash it once with anhydrous ethanol, and dry it at 80°C for 30 minutes to obtain the primary modified filler.

[0051] S4. Prepare an ethanol-water solution of titanate coupling agent with a volume ratio of ethanol to water of 4:1, a mass fraction of isopropyltristearate oxytitanate of 3%, and an amount of composite modifier added of 8% of the mass of titanate coupling agent. Adjust the pH to 4.2 with acetic acid and hydrolyze at room temperature for 20 min to obtain the second treatment solution. Preparation of the composite modified components: S21. Weigh nano-hydroxyapatite, graphene, and epoxy-terminated polyetherimide in a mass ratio of 5:2:1. Add nano-hydroxyapatite and graphene to N,N-dimethylformamide at a mass ratio of 5 times their total mass. Disperse ultrasonically for 30 minutes at an ultrasonic power of 300W to obtain a dispersion. The graphene particle size is 40nm, and the nano-hydroxyapatite particle size is 20nm. S22. Add 3% by weight of graphene silane coupling agent KH-570 to the dispersion, and stir at 65℃ and 400 rpm for 1 hour to obtain the grafted dispersion. S23. Add epoxy-terminated polyetherimide to the grafted dispersion, heat to 85°C, and stir for 2 hours. S24. After the reaction is complete, add 2% of the total mass of polycarbodiimide crosslinking agent to the reaction system, continue stirring for 30 min, centrifuge at 8000 rpm, wash twice with anhydrous ethanol, vacuum dry at 100℃ to constant weight, and pulverize to a particle size ≤40 nm to obtain the composite modified component.

[0052] S5. Add the modified filler to the second treatment solution at a liquid-to-solid ratio of 6:1. Stir the mixture at 70°C with an ultrasonic power of 200W and a stirring speed of 400rpm for 40 minutes. Filter the mixture, wash the solid product twice with anhydrous ethanol, and vacuum dry it to constant weight at 105°C and a vacuum degree of -0.09MPa. Pulverize the product and pass it through an 80-mesh standard sieve to obtain the modified mica functional filler. The mass ratio of γ-aminopropylphosphonosilane to isopropyltristearate titanate is 1:1.2.

[0053] (II) Modification of nano-zirconia: 50nm nano-zirconia was modified by mixing with silane coupling agent KH-550 in an ethanol aqueous solution; the amount of KH-550 added was 1.2% of the mass of nano-zirconia, and the mass ratio of KH-550, ethanol and water was 3:8:5.

[0054] (III) Preparation of TPU sealing material: S31. Weigh the raw materials according to the following parts by weight: 100 parts of polyester TPU matrix resin, 15 parts of modified mica functional filler, 0.3 parts of nano zirconium oxide, 5 parts of trioctyl trimellitate, 0.5 parts of antioxidant, 0.5 parts of calcium stearate, 0.3 parts of light stabilizer UV-327, and 0.5 parts of silane coupling agent KH-560; wherein the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 2.2:1; mix nano zirconium oxide with KH-550 ethanol aqueous solution at a speed of 500 rpm for 25 min, and then filter and dry to obtain a nanocomposite system.

[0055] S32. Add the TPU matrix resin, modified mica functional filler, nanocomposite system, trioctyl trimellitate, antioxidant, calcium stearate, light stabilizer UV-327, and silane coupling agent KH-560 into a high-speed mixer and mix at room temperature with continuous clockwise stirring at 800 rpm for 5 minutes to obtain a uniform premix.

[0056] S33. The premixed material is fed into a twin-screw extruder for melt blending, extrusion, cooling, and granulation. The temperatures of zones 1 to 5 of the twin-screw extruder are 160℃, 175℃, 185℃, 180℃, and 170℃, respectively. The die head temperature is 165℃. The speed of extruder zones 1-2 is 200 rpm, and the speed of extruder zones 3-5 is 280 rpm. The extrusion pressure is 16 MPa, and the melt blending residence time is 3 min. The granulated particle size after extrusion is 2 mm. After granulation, the material is cooled to room temperature by air cooling at a speed of 2 m / s.

[0057] S34. The obtained granules are dried at 90℃ and vacuum degree -0.08MPa for 4 hours, then injection molded at 170℃, with an injection pressure of 20MPa and an injection holding time of 10s. After natural cooling to room temperature, the TPU sealing material product is obtained.

[0058] Example 2: This embodiment prepares a high-temperature resistant and acid / alkali resistant TPU sealing material. The specific steps are as follows: (I) Preparation of modified mica functional fillers: S1. Laminated mica and wollastonite fibers are premixed in a high-speed mixer at a mass ratio of 5:1 at 80°C and 800 rpm for 20 min to obtain a primary composite filler; the laminar mica has a particle size of 20 μm and the wollastonite fibers have a length of 10 μm and a diameter of 1 μm.

[0059] S2. Prepare an ethanol-water solution of silane coupling agent with a volume ratio of ethanol to water of 4:1 and a mass fraction of 5% for γ-aminopropylphosphonosilane. Adjust the pH to 4.8 with acetic acid and hydrolyze at room temperature for 20 min to obtain the first treatment solution.

[0060] S3. Add the primary composite filler to the first treatment solution with a liquid-to-solid ratio of 7:1. Stir the mixture at 85°C with an ultrasonic power of 300W and a stirring speed of 500rpm for 60 minutes. Filter the mixture, wash it twice with anhydrous ethanol, and dry it at 90°C for 30 minutes to obtain the primary modified filler.

[0061] S4. Prepare an ethanol-water solution of titanate coupling agent with a volume ratio of ethanol to water of 4:1, a mass fraction of isopropyltristearate oxytitanate of 5%, and an amount of composite modifier added of 12% of the mass of titanate coupling agent. Adjust the pH to 4.8 with acetic acid and hydrolyze at room temperature for 20 min to obtain the second treatment solution. Preparation of the composite modified components: S21. Weigh nano-hydroxyapatite, graphene, and epoxy-terminated polyetherimide at a mass ratio of 5:2:1. Add nano-hydroxyapatite and graphene to N,N-dimethylformamide at a mass ratio of 6 times their total mass. Disperse ultrasonically for 40 min at an ultrasonic power of 400 W to obtain a dispersion. The graphene particle size is 60 nm, and the nano-hydroxyapatite particle size is 30 nm. S22. Add 5% by weight of graphene silane coupling agent KH-570 to the dispersion, and stir at 75℃ and 500 rpm for 1.5 hours to obtain the grafted dispersion. S23. Add epoxy-terminated polyetherimide to the grafted dispersion, heat to 95°C, and stir for 2.5 hours. S24. After the reaction is complete, add 4% of the total mass of polycarbodiimide crosslinking agent to the reaction system, continue stirring for 40 min, centrifuge at 10000 rpm, wash three times with anhydrous ethanol, vacuum dry at 120℃ to constant weight, and pulverize to a particle size ≤40 nm to obtain the composite modified component.

[0062] S5. Add the modified filler to the second treatment solution at a liquid-to-solid ratio of 7:1. Stir the mixture at 85°C with an ultrasonic power of 300W and a stirring speed of 500rpm for 60 minutes. Filter the mixture and wash the solid product three times with anhydrous ethanol. Dry the product under vacuum at 115°C and a vacuum degree of -0.09MPa to constant weight. Pulverize the product and pass it through a 100-mesh standard sieve to obtain the modified mica functional filler. The mass ratio of γ-aminopropylphosphonosilane to isopropyltristearate oxytitanate is 1:1.8.

[0063] (II) Modification of nano-zirconia: A nanocomposite system was obtained by mixing and modifying 100nm nanozirconia with silane coupling agent KH-550 in an ethanol aqueous solution. The amount of KH-550 added was 1.8% of the mass of nanozirconia, and the mass ratio of KH-550, ethanol and water was 3:8:5.

[0064] (III) Preparation of TPU sealing material: S31. Weigh the raw materials according to the following parts by weight: 100 parts of polyester TPU matrix resin, 25 parts of modified mica functional filler, 0.8 parts of nano-zirconia, 10 parts of trioctyl trimellitate, 2 parts of antioxidant, 1.5 parts of ethylene bis-stearamide, 1 part of light stabilizer UV-327, and 2 parts of silane coupling agent KH-560; wherein the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 2.8:1; premix the nano-zirconia with KH-550 ethanol aqueous solution at 600 rpm for 28 min, and then filter and dry to obtain the nanocomposite system.

[0065] S32. Add the TPU matrix resin, modified mica functional filler, nanocomposite system, trioctyl trimellitate, antioxidant, ethylene bis-stearamide, light stabilizer UV-327, and silane coupling agent KH-560 into a high-speed mixer and mix at room temperature with continuous clockwise stirring at 1000 rpm for 10 minutes to obtain a uniform premix.

[0066] S33. The premixed material is fed into a twin-screw extruder for melt blending, extrusion, cooling, and granulation. The temperatures of zones 1 to 5 of the twin-screw extruder are 160℃, 175℃, 185℃, 180℃, and 170℃, respectively. The die head temperature is 165℃. The speed of extruder zones 1-2 is 220 rpm, and the speed of extruder zones 3-5 is 300 rpm. The extrusion pressure is 20 MPa, and the melt blending residence time is 5 min. The granulated particle size after extrusion is 3 mm. After granulation, the material is cooled to room temperature by air cooling at a speed of 3 m / s.

[0067] S34. The obtained granules are dried at 100℃ and vacuum degree -0.08MPa for 6 hours, and then extruded at 175℃ and 22MPa. After natural cooling to room temperature, TPU sealing material products are obtained.

[0068] Example 3: This embodiment prepares a high-temperature resistant and acid / alkali resistant TPU sealing material. The specific steps are as follows: (I) Preparation of modified mica functional fillers: S1. Laminated mica and sepiolite fibers were premixed in a high-speed mixer at a mass ratio of 4:1 at 70°C and 700 rpm for 15 min to obtain a primary composite filler; the laminated mica had a particle size of 15 μm, and the sepiolite fibers had a length of 7.5 μm and a diameter of 0.75 μm.

[0069] S2. Prepare an ethanol-water solution of silane coupling agent with a volume ratio of ethanol to water of 4:1 and a mass fraction of 4% for γ-aminopropylphosphonosilane. Adjust the pH to 4.5 with acetic acid and hydrolyze at room temperature for 20 min to obtain the first treatment solution.

[0070] S3. Add the primary composite filler to the first treatment solution with a liquid-solid ratio of 6.5:1. Stir the mixture at 78°C with an ultrasonic power of 250W and a stirring speed of 450rpm for 50 minutes. Filter the mixture, wash it once with anhydrous ethanol, and dry it at 85°C for 30 minutes to obtain the primary modified filler.

[0071] S4. Prepare an ethanol-water solution of titanate coupling agent with a volume ratio of ethanol to water of 4:1, a mass fraction of isopropyltristearate oxytitanate of 4%, and add a composite modifier at a mass of 10% of the titanate coupling agent. Adjust the pH to 4.5 with acetic acid and hydrolyze at room temperature for 20 min to obtain the second treatment solution. Preparation of the composite modified components: S21. Weigh nano-hydroxyapatite, graphene, and epoxy-terminated polyetherimide in a mass ratio of 5:2:1. Add nano-hydroxyapatite and graphene to N,N-dimethylformamide at a mass ratio of 5.5 times their total mass. Disperse ultrasonically for 35 minutes at an ultrasonic power of 350W to obtain a dispersion. The graphene particle size is 50nm, and the nano-hydroxyapatite particle size is 25nm. S22. Add 4% by weight of graphene silane coupling agent KH-570 to the dispersion, and stir at 70℃ and 450 rpm for 1.2 hours to obtain the grafted dispersion. S23. Add epoxy-terminated polyetherimide to the grafted dispersion, heat to 90°C, and stir for 2.2 hours. S24. After the reaction is complete, add 3% of the total mass of polycarbodiimide crosslinking agent to the reaction system, continue stirring for 35 min, centrifuge at 9000 rpm, wash twice with anhydrous ethanol, vacuum dry at 110℃ to constant weight, and pulverize to a particle size ≤40 nm to obtain the composite modified component.

[0072] S5. Add the modified filler to the second treatment solution at a liquid-to-solid ratio of 6.5:1. Stir the mixture at 78°C with an ultrasonic power of 250W and a stirring speed of 450rpm for 50 minutes. Filter the mixture, wash the solid product twice with anhydrous ethanol, and vacuum dry it to constant weight at 110°C and a vacuum degree of -0.09MPa. Pulverize the product and pass it through a 90-mesh standard sieve to obtain the modified mica functional filler. The mass ratio of γ-aminopropylphosphonosilane to isopropyltristearate titanate is 1:1.5.

[0073] (II) Modification of nano-zirconia: 75nm nano-zirconia was modified by mixing with silane coupling agent KH-550 in an ethanol aqueous solution; the amount of KH-550 added was 1.5% of the mass of nano-zirconia, and the mass ratio of KH-550, ethanol and water was 3:8:5.

[0074] (III) Preparation of TPU sealing material: S31. Weigh the raw materials according to the following parts by weight: 100 parts of polyester TPU matrix resin, 20 parts of modified mica functional filler, 0.5 parts of nano zirconium oxide, 7.5 parts of trioctyl trimellitate, 1.2 parts of antioxidant, 1.0 part of calcium stearate, 0.6 parts of light stabilizer UV-327, and 1.2 parts of silane coupling agent KH-560; wherein the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 2.5:1; premix the nano zirconium oxide and KH-550 ethanol aqueous solution at 550 rpm for 30 min, and then filter and dry to obtain the nanocomposite system.

[0075] S32. Add the TPU matrix resin, modified mica functional filler, nanocomposite system, trioctyl trimellitate, antioxidant, calcium stearate, light stabilizer UV-327, and silane coupling agent KH-560 into a high-speed mixer and mix at room temperature with continuous clockwise stirring at 900 rpm for 7.5 minutes to obtain a uniform premix.

[0076] S33. The premixed material is fed into a twin-screw extruder for melt blending, extrusion, cooling, and granulation. The temperatures of zones 1 to 5 of the twin-screw extruder are 160℃, 175℃, 185℃, 180℃, and 170℃, respectively. The die head temperature is 165℃. The speed of extruder zones 1-2 is 210 rpm, and the speed of extruder zones 3-5 is 290 rpm. The extrusion pressure is 18 MPa, and the melt blending residence time is 4 min. The granulated particle size after extrusion is 2.5 mm. After granulation, the material is cooled to room temperature by air cooling at a speed of 2.5 m / s.

[0077] S34. The obtained granules are dried at 95℃ and vacuum degree -0.08MPa for 5 hours, and then injection molded at an injection temperature of 175℃, an injection pressure of 22.5MPa, and an injection holding time of 12.5s. After natural cooling to room temperature, TPU sealing material products are obtained.

[0078] Comparative Example 1: The preparation method of Example 3 was used, except that no nano-zirconia was added and no nano-zirconia modification step was performed. The other raw material types, addition amounts and process parameters were the same as in Example 3.

[0079] Comparative Example 2: The preparation method of Example 3 was adopted, except that the modified mica functional filler was replaced with a simple mixture of unmodified lamellar mica and sepiolite wool at a mass ratio of 4:1. The other raw material types, addition amounts and process parameters were the same as in Example 3.

[0080] Comparative Example 3: The preparation method of Example 3 was adopted, except that the modified mica functional filler was prepared by monolayer modification with γ-aminopropylphosphonic silane only, without secondary modification with titanate coupling agent. The other raw material types, addition amounts and process parameters were the same as in Example 3.

[0081] Performance testing experiments: Experiment 1: High Temperature Resistance Test 1.1 Experimental Objective: The thermal aging performance of TPU sealing materials in Examples 1-3 and Comparative Examples 1-3 was tested under high temperature conditions to verify the effects of nano-zirconia, modified mica functional filler, and double-layer coating modification process on the high temperature resistance of the materials. The retention rate of tensile strength and elongation at break after thermal aging were used as the core evaluation indicators. The higher the retention rate, the better the high temperature thermal aging resistance of the material.

[0082] 1.2 Test Methods: The TPU sealing material products of Examples 1-3 and Comparative Examples 1-3 were processed into standard tensile specimens, and 5 parallel specimens were prepared for each group.

[0083] The sample was placed in a thermal aging test chamber, the temperature was set to 150℃, and thermal aging was performed for 1000 hours. During the thermal aging process, air circulation was ensured inside the test chamber.

[0084] After the heat aging process, the sample was removed and placed at room temperature for 24 hours. The tensile strength and elongation at break of the sample were then tested using an electronic universal testing machine.

[0085] Simultaneously, the tensile strength and elongation at break of the blank specimens that had not undergone heat aging treatment were tested, and the tensile strength retention rate and elongation at break retention rate after heat aging were calculated: Tensile strength retention rate = (Tensile strength after heat aging / Tensile strength of blank specimen) × 100% Elongation at break retention rate = (Elongation at break after heat aging / Elongation at break of blank specimen) × 100% The average of five parallel test results for each group of samples was taken as the final data.

[0086] 1.3 Experimental Data: Table 1

[0087] As can be seen from the data of Experiment 1, the TPU sealing materials of Examples 1-3 all exhibited excellent high-temperature heat aging resistance, with tensile strength retention rate all above 85% and elongation at break retention rate all above 82%.

[0088] Comparing Example 3 with Comparative Example 1, it can be seen that without the addition of nano-zirconia, the tensile strength retention rate of Comparative Example 1 decreased from 90.5% to 70.3%, and the elongation at break retention rate decreased from 87.6% to 65.8%, resulting in a significant decline in performance. The reason is that the three-dimensional synergistic reinforcing network formed by nano-zirconia and modified mica functional filler is the key to improving high-temperature resistance. Nano-zirconia fills the gaps between fillers and can effectively hinder the thermal movement of molecular chains at high temperatures, thereby improving the thermal stability of the material. Without nano-zirconia, the three-dimensional reinforcing network structure is destroyed, and the material is prone to thermal degradation at high temperatures, resulting in a rapid decline in mechanical properties.

[0089] Comparing Example 3 and Comparative Example 2, it can be seen that the performance of Comparative Example 2 decreased most significantly after replacing the modified mica functional filler with an unmodified mica-sepiolite mixture. The tensile strength retention rate was only 62.5%, and the elongation at break retention rate was only 58.2%. The reason is that the unmodified inorganic filler has extremely poor interfacial compatibility with the TPU organic matrix. The filler is prone to agglomeration to form stress concentration points. At high temperatures, debonding is likely to occur at the interface, resulting in the collapse of the overall material structure and a sharp decline in mechanical properties.

[0090] Comparing Example 3 with Comparative Example 3, it can be seen that Comparative Example 3 only uses a single-layer silane coupling agent for modification, and the retention rates of tensile strength and elongation at break are reduced to 75.6% and 71.3%, respectively. The reason is that the interface layer formed by double-layer coating modification is denser than that of single-layer modification, which can effectively improve the bonding force between the filler and the matrix and inhibit interface debonding at high temperature. The improvement of interface compatibility of single-layer modification is limited, and the phenomenon of separation between the filler and the matrix still occurs at high temperature.

[0091] Experiment 2: Acid and alkali resistance test: 2.1 Experimental Objective: The TPU sealing materials of Examples 1-3 and Comparative Examples 1-3 were tested for their resistance to strong acid and strong alkali media. The effects of the three-dimensional synergistic reinforcement network and the double-layer coating modification process on the acid and alkali resistance of the materials were verified. The mass change rate and tensile strength retention rate of the samples after immersion in acid and alkali media were used as the core evaluation indicators. The closer the mass change rate is to 0 and the higher the tensile strength retention rate is, the better the acid and alkali resistance of the material is.

[0092] 2.2 Test Methods: The TPU sealing material products of Examples 1-3 and Comparative Examples 1-3 were processed into standard samples. Ten parallel samples were prepared for each group and divided into two groups for immersion in acid and alkali media, respectively.

[0093] Preparation of corrosive media: Acidic media is a 10% hydrochloric acid aqueous solution, and alkaline media is a 10% sodium hydroxide aqueous solution.

[0094] The samples were immersed in acidic and alkaline media respectively at a temperature of 60°C for 72 hours to ensure that the samples were completely submerged in the media.

[0095] After soaking, the sample was removed, rinsed with deionized water, and dried at room temperature to constant weight. The mass of the sample was then weighed, and the rate of mass change was calculated. Simultaneously, the tensile strength of the sample was tested using an electronic universal testing machine, and the tensile strength retention rate was calculated: Rate of mass change = (Mass after soaking - Mass before soaking) / Mass before soaking × 100% Tensile strength retention rate = (Tensile strength after soaking / Tensile strength of blank sample) × 100% The average of five parallel test results for each group of samples was taken as the final data.

[0096] 2.3 Experimental Data: Table 2.1 10% hydrochloric acid medium immersion test data

[0097] Table 3.2 Immersion test data in 10% sodium hydroxide medium

[0098] The data from Experiment 2 show that the TPU sealing materials of Examples 1-3 all exhibit excellent resistance to strong acid and strong alkali media, with mass change rates all within 1% and tensile strength retention rates all above 82%.

[0099] Comparing Example 3 with Comparative Example 1, it can be seen that Comparative Example 1, without the addition of nano-zirconia, has a mass change rate of over 2% in acid and alkaline media and a tensile strength retention rate of less than 68%. The reason is that the three-dimensional synergistic reinforcement network can form a dense structural barrier, which hinders the penetration of acid and alkaline media into the material. Without nano-zirconia, there are a large number of voids in the structure, and acid and alkaline media can easily penetrate and react with the TPU matrix, resulting in swelling of the material and a decrease in mechanical properties.

[0100] Comparing Example 3 and Comparative Example 2, it can be seen that Comparative Example 2, which uses unmodified filler, has a mass change rate of over 3% and a tensile strength retention rate of only about 55%. The reason is that the unmodified filler has a large interfacial gap with the matrix, and acid and alkaline media are prone to accumulate and swell at the interface, leading to interface debonding. At the same time, the filler itself is prone to slight dissolution in acid and alkaline media, which further aggravates the damage to the material structure. The mass change and mechanical property decay are the most significant.

[0101] Comparing Example 3 with Comparative Example 3, it can be seen that the acid and alkali resistance of Comparative Example 3, which uses a single-layer modified filler, is reduced. The reason is that the double-layer modified layer is denser than the single-layer modified layer, which can effectively block the contact between acid and alkali media and filler and matrix, while improving the interfacial bonding force and inhibiting the penetration of media at the interface. The barrier effect of single-layer modification is limited, and the media can easily penetrate the interface, leading to material swelling and performance degradation.

[0102] Experiment 3: Mechanical property testing: 3.1 Experimental Objective: The room temperature basic mechanical properties of the TPU sealing materials in Examples 1-3 and Comparative Examples 1-3 were tested to verify the effects of nano-zirconia, modified mica functional filler, and double-layer coating modification process on the tensile strength, elongation at break, and Shore hardness of the materials, and to verify the role of each innovative technical feature in improving the mechanical properties of the materials.

[0103] 3.2 Test Methods: The TPU sealing material products of Examples 1-3 and Comparative Examples 1-3 were processed into standard tensile test specimens and hardness test specimens, with 5 parallel test specimens prepared for each group.

[0104] The room temperature tensile strength and elongation at break of the specimens were tested using an electronic universal testing machine at a test rate of 500 mm / min.

[0105] The Shore D hardness tester was used to test the Shore hardness of the sample. Before testing, the sample surface was ensured to be flat. Five different points were tested for each sample, and the average value was taken.

[0106] The average of five parallel test results for each group of samples was taken as the final data.

[0107] 3.3 Experimental Data: Table 4

[0108] The data from Experiment 3 show that the TPU sealing materials of Examples 1-3 all exhibit excellent room-temperature mechanical properties, with tensile strengths all above 42 MPa, elongation at break all above 485%, and Shore D hardness between 62 and 68, balancing good strength and elasticity. Among them, Example 2 has the best mechanical properties, with a tensile strength of 48.8 MPa and an elongation at break of 520%, indicating that the synergistic effect of the components and processes of the present invention can improve the strength and hardness of the material while retaining the good elasticity and toughness of the TPU matrix.

[0109] Comparing Example 3 with Comparative Example 1, it can be seen that without the addition of nano-zirconia, the tensile strength of Comparative Example 1 decreased from 46.5 MPa to 35.2 MPa, the elongation at break decreased from 505% to 420%, and the hardness decreased to 58. The reason is that the three-dimensional synergistic reinforcing network formed by nano-zirconia and modified mica functional filler can effectively transfer stress and improve the load-bearing capacity of the material. At the same time, the nanoscale size of nano-zirconia will not excessively reduce the elasticity of the material. Without it, the stress transfer efficiency of the material decreases significantly, and both the strength and elasticity are significantly reduced.

[0110] Comparing Example 3 with Comparative Example 2, it can be seen that Comparative Example 2, which uses unmodified filler, has the worst mechanical properties, with a tensile strength of only 28.5 MPa and an elongation at break of only 355%. The reason is that the unmodified filler has a serious agglomeration phenomenon, forming a large number of stress concentration points. When subjected to external force, the stress is easy to accumulate at the concentration points and cause crack propagation, resulting in easy fracture of the material and a significant decrease in both strength and elongation. At the same time, the interface bonding between the filler and the matrix is ​​poor, which cannot effectively improve the hardness of the material.

[0111] Comparing Example 3 with Comparative Example 3, it can be seen that the mechanical properties of Comparative Example 3, which uses a single-layer modified filler, are somewhat reduced. The reason is that the double-layer coating modification improves the interfacial compatibility between the filler and the matrix, making the filler uniformly dispersed in the matrix. Stress can be effectively transferred through the interfacial layer. The single-layer modified filler has poor dispersion and interfacial bonding force, and there are still local agglomeration and stress concentration, resulting in mechanical properties lower than those of Example 3.

[0112] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0113] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high-temperature resistant and acid / alkali resistant TPU sealing material, characterized in that, It is prepared from the following raw materials in parts by weight: thermoplastic polyurethane matrix resin: 100 parts; modified mica functional filler: 15-25 parts; nano zirconia: 0.3-0.8 parts; plasticizer: 5-10 parts; antioxidant: 0.5-2 parts; Lubricant: 0.5-1.5 parts; Light stabilizer: 0.3-1 part; Silane coupling agent: 0.5-2 parts; The modified mica functional filler is obtained by compounding lamellar mica and fibrous silicate minerals at a mass ratio of 3-5:1 and then performing a stepwise surface modification treatment. The stepwise surface modification treatment involves first treating with a phosphorus-containing silane coupling agent and then treating with a titanate coupling agent to form a double-layer coating structure. The nano-zirconia and modified mica functional filler form a three-dimensional synergistic reinforcement network, filling the gaps between lamellar mica and fibrous silicate minerals; The TPU matrix resin is polyester-type TPU with a hardness range of 80A-55D.

2. The high-temperature resistant and acid / alkali resistant TPU sealing material according to claim 1, characterized in that, The preparation method of the modified mica functional filler includes the following steps: S1. Lamellar mica and fibrous silicate minerals are premixed in a high-speed mixer at 60-80℃ and 600-800rpm for 10-20min to obtain a primary composite filler; the lamellar mica has a particle size of 10-20μm, and the fibrous silicate minerals are sepiolite fibers or wollastonite fibers with a length of 5-10μm and a diameter of 0.5-1μm; S2. Prepare an ethanol-water solution of silane coupling agent, wherein the volume ratio of ethanol to water in the ethanol-water solution is 4:1, the mass fraction of phosphorus-containing silane coupling agent is 3-5%, the pH is adjusted to 4.2-4.8 with acetic acid, and hydrolyzed at room temperature for 20 min to obtain the first treatment solution; S3. Add the primary composite filler to the first treatment solution with a liquid-solid ratio of 6-7:

1. Stir the mixture at 70-85℃ with an ultrasonic power of 200-300W and a stirring speed of 400-500rpm for 40-60 minutes. Filter the mixture, wash it 1-2 times with anhydrous ethanol, and dry it at 80-90℃ for 30 minutes to obtain the primary modified filler. S4. Prepare an ethanol-water solution of titanate coupling agent, wherein the volume ratio of ethanol to water in the ethanol-water solution is 4:1, the mass fraction of titanate coupling agent is 3-5%, the amount of composite modifier added is 8-12% of the mass of titanate coupling agent, the pH is adjusted to 4.2-4.8 with acetic acid, and hydrolyzed at room temperature for 20 min to obtain the second treatment solution. S5. Add the modified filler to the second treatment solution at a liquid-to-solid ratio of 6-7:

1. Stir the mixture at 70-85℃ with an ultrasonic power of 200-300W and a stirring speed of 400-500rpm for 40-60 minutes. Filter the mixture and wash the solid product 2-3 times with anhydrous ethanol. Vacuum dry the product to constant weight at 105-115℃ and a vacuum degree of -0.09MPa. Pulverize the product and pass it through an 80-100 mesh standard sieve to obtain the modified mica functional filler. The mass ratio of the phosphorus-containing silane coupling agent to the titanate coupling agent is 1:1.2-1.

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3. The high-temperature resistant and acid-alkali resistant TPU sealing material according to claim 2, characterized in that, The phosphorus-containing silane coupling agent mentioned in step S2 is γ-aminopropylphosphonic silane, and the titanate coupling agent is isopropyltristearate oxytitanate. The preparation method of the composite modified component includes the following steps: S21. Weigh nano-hydroxyapatite, graphene, and epoxy-terminated polyetherimide in a mass ratio of 5:2:

1. Add nano-hydroxyapatite and graphene to N,N-dimethylformamide at a mass ratio of 5-6 times their total mass. Disperse the mixture by ultrasonication for 30-40 minutes at an ultrasonic power of 300-400W to obtain a dispersion. S22. Add 3-5% by weight of graphene silane coupling agent KH-570 to the dispersion, and stir at 65-75℃ and 400-500 rpm for 1-1.5 hours to obtain the grafted dispersion. S23. Add epoxy-terminated polyetherimide to the grafted dispersion, heat to 85-95℃, and stir for 2-2.5 hours. S24. After the reaction is complete, add 2-4% of the total mass of polycarbodiimide crosslinking agent to the reaction system, continue stirring for 30-40 minutes, centrifuge at 8000-10000 rpm, wash 2-3 times with anhydrous ethanol, vacuum dry at 100-120℃ to constant weight, and pulverize to a particle size ≤40nm to obtain the composite modified component; wherein the particle size of the graphene is 40-60nm and the particle size of the nano-hydroxyapatite is 20-30nm.

4. The high-temperature resistant and acid / alkali resistant TPU sealing material according to claim 1, characterized in that, The plasticizer is trioctyl trimellitate.

5. The high-temperature resistant and acid-alkali resistant TPU sealing material according to claim 1, characterized in that, The antioxidant is a compound of hindered phenolic antioxidant and phosphite antioxidant, with a mass ratio of 2.2-2.8:1; the hindered phenolic antioxidant is antioxidant 1010, and the phosphite antioxidant is antioxidant 168.

6. The high-temperature resistant and acid-alkali resistant TPU sealing material according to claim 1, characterized in that, The lubricant is calcium stearate or ethylene bis-stearamide.

7. The high-temperature resistant and acid-alkali resistant TPU sealing material according to claim 1, characterized in that, The light stabilizer is a benzotriazole light stabilizer, specifically light stabilizer UV-327; the silane coupling agent is KH-560.

8. A method for preparing a high-temperature resistant and acid-alkali resistant TPU sealing material according to any one of claims 1-7, characterized in that, Includes the following steps: S31. Weigh each raw material according to the weight parts. Among them, nano-zirconia is first premixed with the independently added silane coupling agent KH-550 ethanol aqueous solution at a speed of 500-600 rpm for 5-8 min. After filtration and drying, the nano-composite system is obtained. S32. Add the TPU matrix resin, modified mica functional filler, nanocomposite system, plasticizer, antioxidant, lubricant, and light stabilizer into a high-speed mixer and mix at room temperature with continuous clockwise stirring at a speed of 800-1000 rpm for 5-10 minutes to obtain a uniform premix. S33. The premixed material is fed into a twin-screw extruder for melt blending, extrusion, cooling, and granulation. The temperatures of zones one to five of the twin-screw extruder are set to 160℃, 175℃, 185℃, 180℃, and 170℃, respectively. The die head temperature is 165℃, and the screw speed is 200-300 rpm. During the melt blending process, the speed of zones one to two of the extruder is 200-220 rpm, and the speed of zones three to five of the extruder is 280-300 rpm. The extrusion pressure is 16-20 MPa, and the melt blending residence time is 3-5 min. S34. The obtained granules are dried at 90-100℃ and vacuum degree -0.08MPa for 4-6 hours, and then injection molded or extruded. The injection molding temperature is 170-180℃, the injection pressure is 20-25MPa, and the injection holding time is 10-15s. The extrusion molding temperature is 165-175℃ and the molding pressure is 18-22MPa to obtain the TPU sealing material product.

9. The high-temperature resistant and acid-alkali resistant TPU sealing material according to claim 8, characterized in that, The nano-zirconia has a particle size of 50-100 nm. KH-550 is an independently added modifier, with an addition amount of 1.2-1.8% of the mass of the nano-zirconia. The mass ratio of KH-550, ethanol, and water is 3:8:

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10. The preparation method according to claim 8, characterized in that, In step S3, the granulated particle size after extrusion is 2-3 mm. After granulation, it is cooled to room temperature by air cooling with a cooling wind speed of 2-3 m / s. In step S4, it is naturally cooled to room temperature after extrusion molding.

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