A micro-foamed, micro-crosslinked, low-VOC antibacterial sealing material, its manufacturing method and applications

Abstract

The present invention discloses a micro-foamed and micro-crosslinked low-VOC antibacterial sealing material and its manufacturing method. The material includes ethylene propylene diene monomer (EPDM), unsaturated polyurethane prepolymer (USPU), ionized polyurethane elastomer (i-TPU), reinforcing agent, and other additives. Among them, USPU is a polyurethane prepolymer with double bonds in the side chain, which can perform surface coating treatment on the reinforcing agent and chemically crosslink with the EPDM matrix to form a multi-level network. i-TPU is a polyurethane elastomer containing quaternary ammonium ions, which forms a solid filler network structure through non-covalent interaction with inorganic particles, and the ionic moiety endows the material with antibacterial and antistatic properties. The micro-foaming process during the vulcanization of the material promotes the rapid volatilization of VOC small molecules, and USPU vulcanizes to form a chemical crosslinking network, which cooperates with the non-covalent interaction of i-TPU to achieve the barrier effect on VOC small molecules after the material is formed. The material can be used as a low-VOC, antibacterial, antistatic, anti-aging, and fatigue-resistant sealing material for high-speed trains such as maglev trains and passenger cars.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials technology and science, and particularly relates to a micro-foamed and micro-crosslinked low-VOC antibacterial sealing material, a manufacturing method thereof, and an application thereof. Background Art

[0002] With the continuous enhancement of people's health awareness, the air quality inside maglev trains, high-speed trains, and ordinary passenger cars has gradually attracted the attention of consumers, and higher requirements for the antibacterial performance of materials have also been put forward in the public domain. Therefore, how to endow materials with low-VOC, low-odor, antibacterial, and other characteristics on the basis of meeting the service performance of materials has become a research hotspot. In particular, sealing materials that can meet the performance requirements of high performance, low-VOC, low-odor, antibacterial, etc. for high-speed trains such as maglev trains, Harmony Express, and Fuxing Hao, and ordinary passenger cars are the current development focus.

[0003] Patent CN202010896735.2 discloses a low-VOC rubber sealing strip and a preparation method thereof. Through continuous vulcanization and a cooling relaxation process, VOC is fully emitted. Patent CN201811038680.0 discloses a low-odor passenger car rubber sealing strip. By compounding high vinyl polybutadiene rubber and butyl pentene rubber and filling with cashew shell oil, the vulcanization speed is increased, the dosage of sulfur and vulcanization accelerators is reduced, and the generation of odor is reduced. However, in the above research, the improvement of the mechanical properties of the materials is limited, and antibacterial, antistatic, etc. are not mentioned.

[0004] Patent CN202210939104.3 discloses a highly weather-resistant TPV composite material and a preparation method thereof. Using modified fluoroplastics as the matrix and modified silicone rubber as the dispersed phase, a TPV composite material that can meet the requirements of automotive window sealing strips is prepared through dynamic vulcanization. It not only has excellent mechanical properties and weather resistance, but also improves various properties such as antibacterial and hydrophobic properties. Patent CN201510099100.9 discloses a PVC pellet composition with low compression set, a preparation method thereof, and uses. Utilizing the excellent low compression set characteristics of crosslinked nitrile rubber and its good compatibility with PVC to achieve the purpose of reducing compression set at high temperatures, and at the same time, antibacterial agents and weathering agents are added to improve the durability, antibacterial properties, and service life of its products. However, there are a large number of halogen elements in the above materials, and there are no clear requirements for VOC emissions of the materials, making it difficult to meet the application requirements under current environmental protection and human health.

[0005] Therefore, developing low-VOC antibacterial sealing materials with independent intellectual property rights has important practical significance. Summary of the Invention

[0006] The present invention discloses a micro-foamed and micro-crosslinked low-VOC antibacterial sealing material, its manufacturing method and application. It is characterized in that the raw materials are proportioned by mass parts as follows: 100-150 parts of ethylene propylene diene monomer (EPDM), 2-10 parts of unsaturated polyurethane prepolymer (USPU), 2-10 parts of ionized polyurethane elastomer (i-TPU), 150-200 parts of reinforcing agent, 2-8 parts of vulcanizing agent, 2-5 parts of vulcanization accelerator, 1-5 parts of foaming agent, 50-80 parts of lubricant, and 1-3 parts of antioxidant. Among them, USPU is a polyurethane prepolymer with double bonds in the side chain. The surface of the reinforcing agent is coated to construct a core-shell structure pre-treated reinforcing filler with the reinforcing filler as the "hard core" and USPU as the "soft shell", which weakens the interaction between inorganic particles, improves the aggregation behavior of the filler, and chemically cross-links with the EPDM matrix to form a multi-level network. i-TPU is a polyurethane elastomer containing quaternary ammonium ions, which improves the antibacterial and antistatic properties of the material, and further promotes its dispersion through non-covalent bond interaction with inorganic particles to form a solid filler network structure. The material of the present invention is processed and formed by a micro-foaming and micro-crosslinking process, and foams during vulcanization. The foaming process can promote the rapid volatilization of small VOC molecules, while USPU vulcanizes to form a chemical cross-linking network, and cooperates with the non-covalent bond action of i-TPU to achieve the barrier of small VOC molecules after the material is formed, and a low-VOC, antibacterial, antistatic, anti-aging, and fatigue-resistant sealing material for high-speed trains such as maglev trains and passenger cars is prepared. The specific scheme is as follows:

[0007] A micro-foamed and micro-crosslinked low-VOC antibacterial sealing material, wherein the sealing material is prepared by the following method. It is characterized in that first, the unsaturated polyurethane prepolymer USPU and the reinforcing agent are added to a mixer and melt-blended to obtain a pre-treated reinforcing filler with a core-shell structure coated with USPU; then the above-mentioned pre-treated reinforcing filler, ionized polyurethane elastomer i-TPU, foaming agent, lubricant, and antioxidant are added to a mixer and melt-blended to obtain a micro-foamed mixed rubber; then the above-mentioned micro-foamed mixed rubber, ethylene propylene diene monomer EPDM, vulcanizing agent, and vulcanization accelerator are added to a mixer and fully mixed, and then melt-blended and extruded through a twin-screw extruder, and then successively subjected to microwave vulcanization and hot vulcanization treatment, and micro-foaming occurs during vulcanization to obtain the micro-foamed and micro-crosslinked low-VOC antibacterial sealing material;

[0008] The unsaturated polyurethane prepolymer USPU is an isocyanate group-terminated polyurethane prepolymer with double bonds in the side chain, and its structural formula satisfies formula I, M w is 17000-34000 g / mol,

[0009]

[0010] Where x, n, and y are the number of repeating units, n is independently a positive integer between 100 and 200, and x and y are independently positive integers between 50 and 100;

[0011] The ionized polyurethane elastomer i-TPU is a quaternary ammonium cationic polyurethane elastomer containing the structure of Formula II, M w is 37800 - 73000 g / mol,

[0012]

[0013] where n is the number of repeating units, and n is independently a positive integer between 100 and 200.

[0014] Furthermore, the mass parts of each raw material of this material are as follows:

[0015] Ethylene propylene diene monomer rubber EPDM 100 - 150 parts;

[0016] Unsaturated polyurethane prepolymer USPU 2 - 10 parts;

[0017] Ionized polyurethane elastomer i-TPU 2 - 10 parts;

[0018] Reinforcing agent 150 - 200 parts;

[0019] Vulcanizing agent 2 - 8 parts;

[0020] Vulcanization accelerator 2 - 5 parts;

[0021] Foaming agent 1 - 5 parts;

[0022] Lubricant 50 - 80 parts;

[0023] Antioxidant 1 - 3 parts.

[0024] Furthermore, the ethylene mass content of the EPDM is 50 - 75%, the ethylidene norbornene mass content is 2 - 10%, the Mooney viscosity [ML(1+4)125℃] is 50 - 85 MU, the Shore hardness A is 45 - 85, the tensile strength is 5 - 25 MPa, and the elongation at break is 200 - 550%;

[0025] The reinforcing agent is one or a mixture of two or more of carbon black, silica, ultrafine calcium carbonate, and kaolin;

[0026] The vulcanizing agent is one or a mixture of two or more of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, benzoyl peroxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, and diisopropyl peroxydicarbonate;

[0027] The vulcanization accelerator is one or a mixture of two or more of tetrabenzylthiuram disulfide, ethylene thiourea, and tellurium diethyldithiocarbamate;

[0028] The foaming agent is one or a mixture of two or more of azodicarbonamide, dinitrosopentamethylenetetramine, 4,4'-oxybisbenzenesulfonylhydrazide and p-toluenesulfonylsemicarbazide;

[0029] The lubricant is one or a mixture of two or more of paraffin oil, polyethylene wax and montan wax;

[0030] The antioxidant is one of N-phenyl-2-naphthylamine, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, N,N'-di(β-naphthyl)-p-phenylenediamine or a mixture of two or more thereof.

[0031] A method for manufacturing a micro-foamed micro-cross-linked low-VOC antibacterial sealing material, characterized by comprising the following steps:

[0032] Firstly, USPU and reinforcing agent are added into an internal mixer in proportion and melt-blended to obtain a USPU-coated pretreated reinforcing filler with a core-shell structure;

[0033] Then the pretreated reinforcing filler, i-TPU, foaming agent, lubricant, and antioxidant are added into an internal mixer in proportion and melt-blended to obtain a micro-foamed rubber compound;

[0034] The above-mentioned micro-foamed rubber compound, EPDM, vulcanizer, and vulcanization accelerator are placed in an internal mixer in proportion for melt blending. After being fully mixed, they are placed in a twin-screw extruder for melt blending and extrusion, and then subjected to microwave vulcanization and hot vulcanization treatments in sequence. Micro-foaming is generated during the vulcanization process to obtain the micro-foamed micro-cross-linked low-VOC antibacterial sealing material.

[0035] Further, the method specifically includes the following steps:

[0036] Firstly, USPU and reinforcing agent were added into an internal mixer in proportion and melt-blended for 10 min at 100°C and 60 rpm to obtain a USPU-coated core-shell structure pretreated reinforcing filler;

[0037] Then the pretreated reinforcing filler, i-TPU, foaming agent, lubricant, and antioxidant are added into an internal mixer in proportion, and melt-blended for 10 minutes at 150° C. and 60 rpm to obtain a micro-foamed rubber compound;

[0038] The above-mentioned microcellular compounding rubber, EPDM, vulcanizing agent, and vulcanization accelerator are added to a kneader in proportion, melt-blended at 150 °C and 60 rpm for 15 min, then placed in a twin-screw extruder and melt-blended and extruded at a temperature of 150 - 170 °C according to different die structures, and then successively subjected to microwave vulcanization at 250 °C with a power of 5 kW and heat vulcanization treatment at 250 °C. Microcellular foaming occurs during the vulcanization process to obtain the microcellular micro-crosslinked low-VOC antibacterial sealing material.

[0039] Furthermore, it also includes the preparation of the unsaturated polyurethane prepolymer USPU, which specifically includes the following steps:

[0040] Add dichloromethane (CH 2 Cl 2 ) to a container, then add polypropylene glycol (PPG), control the temperature at 0 - 5 °C, add the catalyst boron trifluoride ethyl ether complex (BF 3 ·Et 2 O), stir evenly, and then continuously dropwise add allyl glycidyl ether (AGE) monomer for 12 h to obtain a crude product. Wash the crude product with sodium bicarbonate (NaHCO 3 ) solution and a large amount of deionized water multiple times until the product is neutral, separate the liquid, distill the crude product under reduced pressure at 65 °C to remove the residual solvent, dry it with anhydrous magnesium sulfate, and then filter it to obtain a pale yellow viscous liquid;

[0041] Add the above-mentioned yellow viscous liquid to a container, then add isophorone diisocyanate (IPDI), and then dropwise add the catalyst dibutyltin dilaurate (DBTDL). After the addition is completed, first keep the reaction system at 30 °C for 30 min under the protection of nitrogen, then raise the temperature to 80 °C and react for 4 h, and then collect the product to obtain the unsaturated polyurethane prepolymer USPU represented by Formula I,

[0042]

[0043] where x, n, and y are the number of repeating units, n is independently a positive integer between 100 and 200, and x and y are independently positive integers between 50 and 100.

[0044] Furthermore, it also includes the preparation of the ionized polyurethane elastomer i-TPU, which specifically includes the following steps:

[0045] Add PPG to a container, then add IPDI, and then dropwise add the catalyst DBTDL. After the addition is completed, first keep the reaction system at 30 °C for 30 min under the protection of nitrogen, then raise the temperature to about 80 °C and react for 4 h, and then gradually dropwise add N-methyldiethanolamine and react for 2 h, and then collect the product to obtain the thermoplastic polyurethane elastomer TPU;

[0046] Iodomethane was added to a reaction flask containing TPU and acetonitrile, stirred at room temperature until the reaction mixture became homogeneous, the solvent was removed at 60 °C, then dissolved in benzene, washed with an aqueous solution of sodium hydroxide (NaOH) and sodium chloride (NaCl), washed twice with deionized water and a small amount of water was removed using molecular sieves, the organic phase was filtered, the solvent was removed, washed twice with petroleum ether, and dried under reduced pressure at 60 °C to obtain a quaternary ammonium cation polyurethane elastomer containing the structure of formula II;

[0047]

[0048] Where n is the number of repeating units, and n is independently a positive integer between 100 and 200.

[0049] The micro-foamed and micro-crosslinked low-VOC antibacterial sealing material is applied to the seals for maglev high-speed trains and passenger cars.

[0050] The present invention has the following beneficial effects:

[0051] 1) By stepwise blending, a core-shell structure pre-treated reinforcing filler with a reinforcing filler as the "hard core" and USPU as the "soft shell" is constructed to enhance the interaction between the EPDM matrix and the filler and promote the uniform dispersion of the filler.

[0052] 2) A large number of double bonds are contained in the side chain of USPU. When it coats the surface of the filler, the double bonds can crosslink with the EPDM matrix. While promoting the dispersion of the filler, it further improves the interaction between the filler and the matrix, and USPU can be used as a co-crosslinking agent to increase the crosslinking degree of EPDM. The above dual effects can synergistically improve the comprehensive performance of the material.

[0053] 3) In the present invention, USPU and i-TPU are used as dispersants. Their large molecular weight overcomes the problem that traditional small molecule dispersants are prone to generate VOCs. Moreover, USPU and i-TPU have good compatibility, have a similar structure to the blowing agent, and can promote the dispersion of the blowing agent in the matrix and the rapid volatilization of VOC small molecules during the foaming process. At the same time, i-TPU can further promote its dispersion through non-covalent bond interactions with inorganic particles to form a solid filler network structure. The multi-level network structure inside the material can cooperate with the non-covalent bond action of i-TPU to achieve the barrier effect on VOC small molecules after the material is formed.

[0054] 4) The multi-level physical and chemical networks and interactions inside the material can effectively prevent the slippage of molecular chains, absorb a large amount of energy when subjected to force, thereby improving the mechanical properties of the material, achieving anti-aging and fatigue resistance, and meeting the application requirements in complex environments.

[0055] 5) A large number of quaternary ammonium ion motifs exist in i-TPU, endowing the material with excellent antibacterial and antistatic properties.

[0056] 6) By means of a process in series of microwave vulcanization and thermal vulcanization, the vulcanization efficiency is increased, the perfection degree of the internal crosslinking network of the material is improved, and small molecules generated during the melt processing are effectively removed during the vulcanization process. At the same time, after the material is fully foamed, it can further reduce the VOC of the sealant product while making it have high flexibility and environmental stress resistance. Detailed implementation mode

[0057] The present invention will be described in more detail below through specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0058] The raw materials used in the following examples are as follows:

[0059] EPDM: The ethylene mass content is 57.5%, the ethylidene norbornene mass content is 5%, the Mooney viscosity [ML(1+4)125°C] is 78 MU, and EPDM 3110M of Mitsui of Japan is selected.

[0060] USPU: An isocyanate group-terminated polyurethane prepolymer with double bonds in the side chain, and its preparation includes the following steps:

[0061] Add 100 ml of CH 2 Cl 2 to a round-bottomed flask equipped with a stirrer. Then add 40 g of PPG, and control the temperature at 0-5°C. Add 7.14 ml of BF 3 ·Et 2 O and stir evenly, then continuously dropwise add 200 g of AGE monomer for 12 h to obtain a crude product. Transfer the crude product into a separatory funnel, and add a 10% mass fraction of NaHCO 3 solution and a large amount of deionized water to wash the system multiple times until the product is neutral, and separate the liquid. Distill the crude product under reduced pressure at 65°C to remove the residual solvent, dry it over anhydrous magnesium sulfate overnight and then filter it by suction to obtain a pale yellow viscous liquid.

[0062] Add the above yellow viscous liquid to a three-necked flask equipped with a stirrer, a condenser and a nitrogen protection device. Then add 19 g of IPDI to the three-necked flask, and then dropwise add 0.1 g of the catalyst DBTDL to the system. After the feeding is completed, first keep the reaction system at 30°C for 30 min, then raise the temperature to 80°C and react for 4 h, and then collect the product to obtain the unsaturated polyurethane prepolymer USPU represented by Formula I.

[0063]

[0064] Where x, n, and y are the number of repeating units, n is independently a positive integer between 100 and 200, and x and y are independently positive integers between 50 and 100.

[0065] Among which, the used CH 2 Cl 2 , PPG, BF 3 ·Et 2 O, AGE, NaHCO 3 , anhydrous magnesium sulfate, IPDI, DBTDL are all selected from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0066] i-TPU: Polyurethane elastomer containing quaternary ammonium cations, and its preparation includes the following steps:

[0067] First, add 41 g of PPG into a three-necked flask equipped with a stirrer, a condenser and a nitrogen protection device. Then add 19 g of IPDI into the three-necked flask, and then add 0.1 g of catalyst DBTDL dropwise into the system. After the feeding is completed, first keep the reaction system at 30 °C for 30 min, then raise the temperature to about 80 °C and react for 4 h, and then gradually add 9.8 g of N-methyldiethanolamine dropwise. After reacting for 2 h, collect the product to obtain 6.7 g of thermoplastic polyurethane elastomer TPU.

[0068] Add 2.7 g of methyl iodide into a reaction flask containing TPU and 20 ml of acetonitrile, stir at room temperature until the reaction mixture becomes homogeneous, extract the solvent at 60 °C, then dissolve it in 50 ml of benzene, wash it with 70 ml of NaOH∶NaCl (1∶10) aqueous solution, wash it twice with 70 ml of deionized water and use molecular sieve to absorb trace water, filter the organic phase, extract the solvent, wash it twice with 35 ml of petroleum ether, and dry it under reduced pressure at 60 °C to obtain quaternary ammonium cation polyurethane elastomer i-TPU containing the structure of formula II.

[0069]

[0070] Where n is the number of repeating units, and n is independently a positive integer between 100 and 200.

[0071] Among which, the used PPG, IPDI, DBTDL, methyl iodide, acetonitrile, benzene, NaOH, NaCl, petroleum ether are all selected from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0072] Reinforcing agent: A mixture of carbon black and ultrafine calcium carbonate in a mass ratio of 5∶1. The carbon black is selected from Cabot CSX880 of the United States, and the ultrafine calcium carbonate is selected from SA-200 of Neolight of Japan.

[0073] Vulcanizing agent: 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, selected from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0074] Vulcanization accelerator: tetramethylthiuram disulfide, selected from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0075] Foaming agent: azodicarbonamide, selected from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0076] Lubricant: paraffin oil, SUNPAR115 from Sunoco, USA is selected.

[0077] Antioxidant: a mixture of 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline and N-phenyl-N'-cyclohexyl-p-phenylenediamine in a mass ratio of 2:1, both are selected from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0078] The mass ratio of each raw material in the following examples is shown in Table 1.

[0079] Table 1 Raw materials and dosages of the micro-foamed, micro-crosslinked, low-VOC and antibacterial sealing material examples (by mass fraction)

[0080] Component Example 1 Example 2 Example 3 Example 4 Example 5 EPDM 100 100 100 100 100 USPU 5 2 4 6 8 i-TPU 5 8 6 4 2 Reinforcing agent 180 180 180 180 180 Vulcanizing agent 4 4 4 4 4 Vulcanization accelerator 3 3 3 3 3 Blowing agent 2 2 2 2 2 Lubricant 70 70 70 70 70 Antioxidant 1 1 1 1 1

[0081] Table 2 Raw materials and dosages of the micro-foamed, micro-crosslinked, low-VOC and antibacterial sealing material comparative examples (by mass fraction)

[0082]

[0083]

[0084] Example 1

[0085] The raw materials and formula of this example are shown in Table 1, and its preparation method is carried out according to the following steps:

[0086] First, USPU and the reinforcing agent are added to the internal mixer in proportion and melt-blended at 100 °C and 60 rpm for 10 min to obtain a core-shell structure pretreated reinforcing filler coated with USPU.

[0087] Then, the above-mentioned pretreated reinforcing filler, i-TPU, foaming agent, lubricant, and antioxidant are added to the internal mixer in proportion and melt-blended at 150 °C and 60 rpm for 10 min to obtain a micro-foamed mixed rubber.

[0088] The above-mentioned micro-foamed mixed rubber, EPDM, vulcanizing agent, and vulcanization accelerator are added to the internal mixer in proportion and melt-blended at 150 °C and 60 rpm for 15 min to obtain a mixture.

[0089] Finally, the above mixture is placed in a twin-screw extruder and melt-blended and extruded at a temperature of 150 - 170 °C according to the die structure. The processing temperature is 150 °C, 155 °C, 160 °C, 165 °C, 170 °C, 170 °C from the feed port to the die port. Then, it is treated by microwave vulcanization at 250 °C with a power of 5 kW and heat vulcanization at 250 °C to obtain the product of the present invention.

[0090] Example 2

[0091] The raw materials and formulations of this example are shown in Table 1, and the preparation process is the same as that of Example 1.

[0092] Example 3

[0093] The raw materials and formulations of this example are shown in Table 1, and the preparation process is the same as that of Example 1.

[0094] Example 4

[0095] The raw materials and formulations of this example are shown in Table 1, and the preparation process is the same as that of Example 1.

[0096] Example 5

[0097] The raw materials and formulations of this example are shown in Table 1, and the preparation process is the same as that of Example 1.

[0098] Comparative Example 1

[0099] The raw materials and formulations of this comparative example are shown in Table 1, and the preparation process is the same as that of Example 1.

[0100] Comparative Example 2

[0101] The raw materials and formulations of this comparative example are shown in Table 1, and the preparation process is the same as that of Example 1.

[0102] Comparative Example 3

[0103] The raw materials and formulations of this comparative example are shown in Table 1, and the preparation process is the same as that of Example 1.

[0104] Comparative Example 4

[0105] The raw materials and formulations of this comparative example are shown in Table 1, and the preparation process is the same as that of Example 1

[0106] Comparative Example 5

[0107] The raw materials and formulations of this comparative example are the same as those of Example 1, as shown in Table 1, and the preparation process is carried out according to the following steps:

[0108] EPDM, USPU, i-TPU, reinforcing agent, vulcanizing agent, vulcanization accelerator, foaming agent, lubricant, and antioxidant were simultaneously added to a kneader in proportion and melt-blended at 150 °C and 60 rpm for 15 min, and then melt-blended and extruded in a twin-screw extruder at a temperature of 150-170 °C according to the die structure. The processing temperature was 150 °C, 155 °C, 160 °C, 165 °C, 170 °C, and 170 °C from the feeding port to the die orifice. Then, it was placed in a hot air vulcanizing box for hot vulcanization at 250 °C to obtain the product of Comparative Example 5.

[0109] The main performance indexes of the sealing materials prepared in Examples 1-5 are shown in Table 3:

[0110] Performance test results of the examples described in Table 3

[0111]

[0112]

[0113]

[0114] The main performance indexes of the sealing materials prepared in Comparative Examples 1-5 are shown in Table 4:

[0115] Performance test results of the comparative examples described in Table 4

[0116]

[0117]

[0118] As shown in Tables 3 and 4, Example 1 has the best comprehensive performance.

[0119] Construct a pretreated reinforcing filler with a reinforcing filler as the "hard core" and USPU as the "soft shell" through step-by-step blending, and enhance the interaction between the EPDM matrix and the filler to promote the uniform dispersion of the filler. At the same time, a large number of double bonds are contained in the side chain of USPU. When coated on the surface of the filler, a cross-linking reaction occurs with the EPDM matrix. While promoting the dispersion of the filler, it further improves the interaction between the filler and the matrix. Moreover, USPU can act as a co-crosslinking agent to increase the cross-linking degree of EPDM and synergistically improve the comprehensive properties of the material. USPU and i-TPU are used as macromolecular dispersants, overcoming the problem of easy generation of VOC by traditional small-molecular dispersants, and having a similar structure to the foaming agent, which can promote the dispersion of the foaming agent in the matrix and the rapid volatilization of VOC small molecules during the foaming process. At the same time, i-TPU can further promote its dispersion through non-covalent bond interaction with inorganic particles to form a solid filler network structure. The multi-level network structure inside the material can synergistically realize the barrier effect on VOC small molecules after the material is formed with the non-covalent bond interaction of i-TPU. And the multi-level network structure can effectively prevent the slippage of molecular chains, absorb a large amount of energy when subjected to force, thereby improving the mechanical properties of the material, achieving anti-aging and fatigue resistance, and meeting the application requirements in complex environments. A large number of quaternary ammonium ion motifs exist in i-TPU, endowing the material with excellent antibacterial and antistatic properties. The process of tandem microwave vulcanization and thermal vulcanization increases the vulcanization efficiency, improves the perfection degree of the cross-linking network inside the material, and effectively removes small molecules generated during the melt processing during the vulcanization process. At the same time, after the material is fully foamed, it can further reduce the VOC of the seal product while making it have high flexibility and environmental stress resistance.

[0120] Comparative Example 1 compared with Example 1, USPU and i-TPU were not introduced. There was a lack of a multi-level network structure and ionic motifs inside the material, making it difficult to achieve the functions of VOC barrier, antibacterial, and antistatic. Moreover, the molecular chains were prone to relative slippage, resulting in poor anti-aging and fatigue resistance of the material. At the same time, the interaction between the filler and EPDM was poor, leading to uneven dispersion of the filler and easy generation of stress concentration, reducing the mechanical properties of the material. Comparative Example 2 compared with Example 1, USPU was introduced to construct a core-shell structure with the filler as the "hard core" and USPU as the "soft shell". This weakened the interaction between the filler particles, enabling the filler to be evenly dispersed in the matrix to form a solid filler network, which had a partial barrier effect on small molecules. At the same time, a large number of double bonds were contained in the side chain of USPU. When coated on the surface of the filler, it underwent a cross-linking reaction with the EPDM matrix, further improving the interaction between the filler and the matrix while promoting the dispersion of the filler. And USPU could act as a co-crosslinking agent to increase the cross-linking degree of EPDM, playing a partial role in fatigue resistance and anti-aging. However, due to the lack of i-TPU, the non-covalent interaction was lacking, weakening the locking of VOC and making it difficult to achieve antibacterial and antistatic functions, and the overall performance was still not good. Comparative Example 3 compared with Example 1, i-TPU was introduced, which could further promote its dispersion through non-covalent bond interaction with inorganic particles to form a solid filler network structure, reducing the VOC volatilization amount. But due to the lack of USPU, there was no dense chemical cross-linking network inside the material, and the performance improvement effect was limited. In Comparative Example 4, when the amounts of USPU and i-TPU were increased in equal proportions, obvious dispersed phase particles were formed in EPDM, resulting in a performance gap compared with Example 1. In summary, the superiority of the formulation designed in Example 1 was demonstrated.

[0121] Comparative Example 5 had the same formulation system as Example 1, but different processing techniques were used. With the traditional one-step mixing and hot air vulcanization process, it was difficult to form a core-shell structure with USPU coating the inorganic filler. There was still a strong interaction between the inorganic particles, resulting in uneven dispersion and making it difficult to achieve the regulation of the structure and interface of the chemical micro-foamed composite material. Moreover, the traditional hot air vulcanization process had low vulcanization efficiency and incomplete vulcanization, resulting in an imperfect chemical cross-linking network inside the material and poor comprehensive performance of the material, demonstrating the superiority of the preparation process.

[0122] Combined with the test data analysis, it can be seen that the performance of the micro-foamed and micro-crosslinked low-VOC antibacterial rubber and plastic sealing material has been greatly improved, and there are the following reasons: (1) Through step-by-step blending, a core-shell structure pretreatment reinforcing filler with a reinforcing filler as the "hard core" and USPU as the "soft shell" is constructed to enhance the interaction between the EPDM matrix and the filler and promote the uniform dispersion of the filler. (2) A large number of double bonds are contained in the side chain of USPU. When it coats the surface of the filler, the double bonds can undergo a crosslinking reaction with the EPDM matrix. While promoting the dispersion of the filler, it further improves the interaction between the filler and the matrix. Moreover, USPU can act as a co-crosslinking agent to increase the crosslinking degree of EPDM. The above dual effects can synergistically improve the comprehensive performance of the material. (3) USPU and i-TPU are used as dispersants. Their large molecular weight overcomes the problem that traditional small molecule dispersants are prone to generate VOCs. And USPU and i-TPU have good compatibility, similar structures to the blowing agent, and can promote the dispersion of the blowing agent in the matrix and the rapid volatilization of VOC small molecules during the foaming process. At the same time, i-TPU can further promote its dispersion through non-covalent bond interactions with inorganic particles to form a solid filler network structure. The multi-level network structure inside the material can cooperate with the non-covalent bond action of i-TPU to achieve the barrier effect on VOC small molecules after the material is formed. (4) The multi-level physical and chemical networks and interactions inside the material can effectively prevent the slippage of molecular chains, absorb a large amount of energy when subjected to force, thereby improving the mechanical properties of the material, achieving anti-aging and fatigue resistance, and meeting the application requirements in complex environments. (5) A large number of quaternary ammonium ion motifs exist in i-TPU, endowing the material with excellent antibacterial and antistatic properties. (6) Through the process of tandem microwave vulcanization and thermal vulcanization, the vulcanization efficiency is increased, the perfection degree of the crosslinking network inside the material is improved, and small molecules generated during the melt processing are effectively removed during the vulcanization process. At the same time, after the material is fully foamed, it can further reduce the VOC of the seal product while making it have high flexibility and environmental stress resistance.

[0123] The present invention synthesizes USPU and i-TPU with specific structures, and uses step-by-step blending to coat USPU on the surface of reinforcing fillers, constructing a core-shell structure pre-treated reinforcing filler with the reinforcing filler as the "hard core" and PUP as the "soft shell", weakening the interaction between inorganic particles, improving the aggregation behavior of the fillers. At the same time, USPU chemically cross-links with the EPDM matrix to form a multi-level network. The quaternary ammonium ions in i-TPU improve the antibacterial and antistatic properties of the material, and further promote its dispersion through non-covalent bond interactions with inorganic particles, forming a solid filler network structure. The material of the present invention is also processed and formed by micro-foaming and micro-crosslinking processes, foaming during the vulcanization process, which can promote the rapid volatilization of VOC small molecules, while USPU vulcanizes to form a chemical cross-linking network, and cooperates with the non-covalent bond action of i-TPU to achieve the barrier of VOC small molecules after the material is formed, finally endowing the material with properties such as low VOC, antibacterial, antistatic, anti-aging, and fatigue resistance. The material and related technologies are applied to seals for high-speed trains such as maglev trains and passenger cars.

[0124] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be regarded as a limitation of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A micro-foamed and micro-crosslinked low-VOC antibacterial sealing material, wherein the sealing material is prepared by the following method, characterized in that, first, an unsaturated polyurethane prepolymer USPU and a reinforcing agent are added to a mixer and melt-blended to obtain a pretreated reinforcing filler with a core-shell structure coated with the unsaturated polyurethane prepolymer USPU; then, the above-mentioned pretreated reinforcing filler, ionized polyurethane elastomer i-TPU, foaming agent, lubricant, and antioxidant are added to a mixer and melt-blended to obtain a micro-foamed masterbatch; then, the above-mentioned micro-foamed masterbatch, ethylene propylene diene monomer EPDM, vulcanizing agent, and vulcanization accelerator are added to a mixer and fully mixed, and then melt-blended and extruded through a twin-screw extruder, and then successively subjected to microwave vulcanization and hot vulcanization treatment to generate micro-foaming during the vulcanization process, thereby obtaining the micro-foamed and micro-crosslinked low-VOC antibacterial sealing material; The unsaturated polyurethane prepolymer USPU is an isocyanate group-terminated polyurethane prepolymer with double bonds in the side chain, and its structural formula satisfies Formula I, where M w is 17,000 - 34,000 g / mol, where x, n, and y are the number of repeating units, n is independently a positive integer between 100 and 200, and x and y are independently positive integers between 50 and 100; The ionized polyurethane elastomer i-TPU is a quaternary ammonium cationic polyurethane elastomer containing the structure of Formula II, and M w is 37800 - 73000 g / mol, where n is the number of repeating units, n is independently a positive integer between 100 and 200.

2. The sealing material according to claim 1, characterized in that, the mass parts of each raw material of this material are: ethylene propylene diene monomer EPDM 100-150 parts; unsaturated polyurethane prepolymer USPU 2-10 parts; ionized polyurethane elastomer i-TPU 2-10 parts; reinforcing agent 150-200 parts; vulcanizing agent 2-8 parts; vulcanization accelerator 2-5 parts; foaming agent 1-5 parts; lubricant 50-80 parts; antioxidant 1-3 parts.

3. The sealing material according to claim 1, characterized in that: the ethylene mass content of the ethylene propylene diene monomer EPDM is 50-75%, the ethylidene norbornene mass content is 2-10%, the Mooney viscosity [ML(1+4)125°C] is 50-85 MU, the Shore hardness A is 45-85, the tensile strength is 5-25 MPa, and the elongation at break is 200-550%; the reinforcing agent is one or a mixture of two or more of carbon black, silica, ultrafine calcium carbonate, and kaolin; the vulcanizing agent is one or a mixture of two or more of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, benzoyl peroxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, and diisopropyl peroxydicarbonate; the vulcanization accelerator is one or a mixture of two or more of tetrabenzylthiuram disulfide, ethylene thiourea, and tellurium diethyldithiocarbamate; the foaming agent is one or a mixture of two or more of azodicarbonamide, dinitrosopentamethylenetetramine, 4,4'-oxybis(benzenesulfonylhydrazide), and p-toluenesulfonyl semicarbazide; the lubricant is one or a mixture of two or more of paraffin oil, polyethylene wax, and montan wax; the antioxidant is one or a mixture of two or more of N-phenyl-2-naphthylamine, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and N,N'-di(β-naphthyl) paraphenylenediamine.

4. The method for producing a sealing material according to any one of claims 1 to 3, It is characterized in that The following steps are involved: Firstly, unsaturated polyurethane prepolymer USPU and reinforcing agent are added into an internal mixer in proportion and melt-blended to obtain a pretreated reinforcing filler with a core-shell structure coated with unsaturated polyurethane prepolymer USPU; Then, the pretreated reinforcing filler, ionized polyurethane elastomer i-TPU, foaming agent, lubricant, and antioxidant are added to an internal mixer in proportion and melt-blended to obtain a micro-foamed rubber compound; The above-mentioned micro-foamed rubber compound, EPDM, vulcanizer, and vulcanization accelerator are placed in an internal mixer in proportion for melt blending. After being fully mixed, they are placed in a twin-screw extruder for melt blending and extrusion, and then subjected to microwave vulcanization and hot vulcanization treatments in sequence. Micro-foaming is generated during the vulcanization process to obtain the micro-foamed micro-cross-linked low-VOC antibacterial sealing material.

5. A method for manufacturing the sealing material according to claim 4, It is characterized in that The specific steps include: Firstly, unsaturated polyurethane prepolymer USPU and reinforcing agent are added into an internal mixer in proportion and melt-blended for 10 minutes at 100°C and 60rpm to obtain a core-shell structure pretreated reinforcing filler coated with unsaturated polyurethane prepolymer USPU; Then the pretreated reinforcing filler, ionized polyurethane elastomer i-TPU, foaming agent, lubricant, and antioxidant are added into an internal mixer in proportion, and melt-blended for 10 minutes at 150° C. and 60 rpm to obtain a micro-foamed rubber compound; The above-mentioned micro-foamed rubber compound, EPDM, vulcanizing agent, and vulcanization accelerator are added to an internal mixer in proportion, melt-blended at 150° C. and 60 rpm for 15 minutes, and then placed in a twin-screw extruder at a temperature of 150-170° C. to perform melt-blending and extrusion according to different die structures, and then subjected to microwave vulcanization at 250° C. and 5 kW power and hot vulcanization at 250° C. in sequence, to generate micro-foaming during the vulcanization process, thereby obtaining the micro-foamed, micro-cross-linked, low-VOC antibacterial sealing material.

6. The manufacturing method according to claim 4 or 5, further comprising preparing the unsaturated polyurethane prepolymer USPU, specifically The following steps are involved: Add dichloromethane (CH 2 Cl 2 ) into a container, then add polypropylene glycol (PPG), control the temperature at 0 - 5 °C, add the catalyst boron trifluoride ether complex (BF 3 ·Et 2 O), stir evenly, and then continuously dropwise add allyl glycidyl ether (AGE) monomer for 12 h to obtain a crude product. Wash the crude product with sodium bicarbonate (NaHCO 3 ) solution and a large amount of deionized water for multiple times until the product is neutral. Separate the liquid, distill the crude product under reduced pressure at 65 °C to remove the residual solvent, filter it by suction after drying with anhydrous magnesium sulfate, and a pale yellow viscous liquid is obtained; The yellow viscous liquid is added into a container, and then isophorone diisocyanate (IPDI) is added, and then a catalyst dibutyltin dilaurate (DBTDL) is added dropwise. After the addition is completed, the reaction system is first kept at 30° C. for 30 minutes under the protection of nitrogen, and then the temperature is raised to 80° C. for reaction for 4 hours, and then the product is collected to obtain the unsaturated polyurethane prepolymer USPU represented by formula I. Wherein x, n, and y are the numbers of repeating units, n is independently a positive integer between 100 and 200, and x and y are independently positive integers between 50 and 100.

7. The manufacturing method according to claim 4 or 5, further comprising preparing the ionized polyurethane elastomer i-TPU, specifically The following steps are involved: Add polypropylene glycol (PPG) into a container, then add isophorone diisocyanate (IPDI), and then dropwise add the catalyst dibutyltin dilaurate (DBTDL). After the feeding is completed, keep the reaction system at 30 °C for 30 min under nitrogen protection, then raise the temperature to 80 °C and react for 4 h. Then gradually dropwise add N-methyldiethanolamine. After reacting for 2 h, collect the product to obtain the thermoplastic polyurethane elastomer TPU; Add methyl iodide into a reaction flask containing TPU and acetonitrile, stir at room temperature until the reaction mixture becomes homogeneous, extract the solvent at 60 °C, then dissolve it in benzene, wash it with an aqueous solution of sodium hydroxide (NaOH) and sodium chloride (NaCl), wash it twice with deionized water and use molecular sieves to absorb trace water, filter the organic phase, extract the solvent, wash it twice with petroleum ether, and dry it under reduced pressure at 60 °C to obtain a quaternary ammonium cationic polyurethane elastomer containing the structure of formula II; Where n is the number of repeating units, and n is independently a positive integer between 100 and 200.

8. Use of the sealing material according to any one of claims 1-3 or the sealing material obtained by the manufacturing method according to any one of claims 4-7, Characterized in that: The sealing material is applied to the seals of maglev high-speed trains and passenger cars.

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