Preparation method of rubber for low-density closed-cell foaming automobile sealing strip

Abstract

The invention discloses a preparation method of rubber for a low-density closed-cell foaming automobile sealing strip, and relates to the technical field of rubber preparation. Comprising the following raw materials: ethylene propylene diene monomer, zinc oxide, an activating auxiliary agent, carbon black N550, nano hydrotalcite, maleic anhydride grafted ethylene propylene diene monomer, modified hydrogenated polybutadiene oil, azodicarbonamide, sulfur, N-cyclohexyl-2-benzothiazole sulfenamide, triallyl isocyanurate, an antioxidant, modified zinc stearate and modified zinc borate. According to the invention, the modified zinc stearate is added, azodicarbonamide can be efficiently activated at low temperature, foaming is more sufficient and uniform so as to reduce the rubber density, the nano rigid shell can enhance the supporting force of the cell wall to avoid collapse and deformation, and the alkyl phosphoimide can improve the dispersion uniformity of the nano rigid shell in the non-polar ethylene propylene diene monomer; and meanwhile, stronger combination with a rubber matrix is formed, so that the foaming fineness is optimized, agglomeration and blooming are reduced, and the rubber is assisted to form a stable and uniform closed-cell structure.

Description

Technical Field

[0001] This invention relates to the field of rubber preparation technology, and in particular to a method for preparing low-density closed-cell foamed rubber for automotive sealing strips. Background Technology

[0002] Rubber is a type of highly elastic polymer material, mainly divided into natural rubber obtained from natural plants (such as rubber trees) and synthetic rubber obtained through chemical synthesis. Its unique molecular chain structure allows it to undergo significant deformation under external force and return to its original shape after the external force is removed. It is a key basic material for manufacturing various elastic products such as tires, seals, and shock-absorbing products.

[0003] Traditional sealing strips suffer from problems such as uneven rubber foaming, high density, poor closed-cell effect, and numerous interconnected pores, resulting in poor waterproof performance, high water absorption, easy cell collapse and rupture, uneven filler aggregation, poor flowability during rubber compounding and extrusion, and susceptibility to additive migration, blooming, and surface whitening. Furthermore, they suffer from insufficient crosslinking density, poor compression resilience, low mechanical strength, and weak heat aging resistance. Therefore, this invention provides a method for preparing low-density closed-cell foamed rubber for automotive sealing strips. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing a low-density closed-cell foamed automotive sealing strip rubber with low apparent density and high closed-cell ratio, which is applied in a method for preparing a low-density closed-cell foamed automotive sealing strip rubber.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing low-density closed-cell foamed rubber for automotive sealing strips, the method comprising the following steps: S1. Add EPDM rubber to a mixer and masticate. Set the temperature to 65-70℃, the speed to 60rpm, and the pressure to 0.3-0.5MPa. Masturbate for 2 minutes. Add zinc oxide and activator and mix for 2 minutes. Add carbon black N550, nano-hydrotalcite, and maleic anhydride-grafted EPDM rubber and mix for 4 minutes. Add modified hydrogenated polybutadiene oil and mix for 3 minutes. Add antioxidant, modified zinc stearate, and modified zinc borate and mix for 3 minutes. Heat the mixer to 105℃, discharge the rubber, and obtain the rubber compound. Press the rubber compound to a thickness of 8-10mm. Allow the pressed rubber compound to cool naturally to 25℃ to obtain the rubber sheet.

[0006] S2. Place the rubber sheet into the rubber mixing mill, set the temperature to 55-65℃, the roller gap to 0.5-1.0mm, and the rotation speed to 25-30rpm. After wrapping the rollers, pass through the mill twice, add azodicarbonamide, cut the rubber three times, add sulfur, cut the rubber three times, add N-cyclohexyl-2-benzothiazole sulfenamide, cut the rubber three times, add triallyl isocyanurate, cut the rubber three times, and obtain a mixture. Pass the mixture through the mill six times, adjust the roller gap to 4-5mm, and discharge the material to obtain a mixed rubber sheet. Cool the mixed rubber sheet to 25℃ and then vulcanize it. First, send it to a microwave vulcanizing tunnel with a microwave frequency of 2450MHz and a temperature of 170-178℃ for 40-60 seconds. Then send it to a hot air vulcanizing chamber with a temperature of 185-195℃ for 3-4 minutes to obtain a vulcanized material.

[0007] S3. The vulcanized material is fed into a three-stage water-cooling tank for cooling and shaping. The cooling water temperature is set to 70℃, 45℃ and 25℃ respectively, and the temperature is reduced step by step for 5-8 minutes. After cooling, the vulcanized material is cut into segments at a traction speed of 1-2m / min to obtain low-density closed-cell foamed rubber for automotive sealing strips.

[0008] The low-density closed-cell foamed automotive sealing strip rubber comprises the following raw materials in parts by weight: 95-105 parts EPDM rubber, 2.5-3.5 parts zinc oxide, 0.7-0.9 parts activating agent, 10-14 parts carbon black N550, 5-7 parts nano-hydrotalcite, 0.8-1.2 parts maleic anhydride-grafted EPDM rubber, 14-16 parts modified hydrogenated polybutadiene oil, 3.5-4.5 parts azodicarbonamide, 0.6-0.7 parts sulfur, 0.6-0.8 parts N-cyclohexyl-2-benzothiazole sulfenamide, 0.25-0.35 parts triallyl isocyanurate, 0.7-0.9 parts antioxidant, 1.8-2.2 parts modified zinc stearate, and 1.6-2 parts modified zinc borate.

[0009] Zinc oxide is activated zinc oxide, which can quickly form a highly efficient activation system with stearic acid, significantly improving the efficiency of vulcanization reaction and crosslinking density. It can also synergistically modify zinc stearate to optimize the foaming rhythm, making foaming more uniform, while enhancing the mechanical strength and heat resistance of rubber, thus taking into account both vulcanization activation and cell structure regulation.

[0010] Carbon black N550 can moderately reinforce rubber, improving the tensile and tear strength of foamed rubber without significantly increasing the density of the rubber compound or hindering foaming. It also improves the processing performance of the rubber compound, giving the cell walls basic support and preventing cell collapse at low densities.

[0011] Nano-hydrotalcite is hydrophobic, which can effectively enhance the toughness and density of the cell walls, improve the closed-cell rate and waterproofness of rubber, reduce water absorption, and optimize cell uniformity in rubber compounds. It also reduces the cost of rubber compounds, and its hydrophobic properties can further inhibit water penetration, making it suitable for waterproof foamed rubber applications.

[0012] Azodicarbonamide has a large gas production and a moderate decomposition temperature, which can stably release gas during vulcanization to form uniform cells, effectively reducing rubber density and achieving lightweighting. It also has less decomposition residue, which has little impact on rubber properties, and strong controllability in foaming.

[0013] Sulfur, as a vulcanizing crosslinking agent, can enable rubber molecules to form a three-dimensional network structure, giving foamed rubber good elasticity, resilience and mechanical properties, providing structural support for the cells, preventing cell deformation and collapse, and the crosslinking speed is moderate, which can match the foaming rhythm to ensure stable molding of closed-cell structure.

[0014] Furthermore, the antioxidant is composed of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite.

[0015] Furthermore, the mass ratio of the tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester to tris(2,4-di-tert-butylphenyl)phosphite is 5:3.

[0016] Furthermore, the activating agent is one of stearic acid and palmitic acid.

[0017] Further, the preparation of the modified hydrogenated polybutadiene oil includes the following steps: adding hydrogenated polybutadiene oil to a reaction vessel, introducing nitrogen gas and stirring, setting the reaction vessel temperature to 70-75℃, the rotation speed to 600 rpm, stirring for 10 minutes, adding boron-nitrogen heterocyclic alkylphosphine chelating agent and stirring for 30 minutes, adding perfluorocyclic ether-terminated cyclic olefin monomer and benzoyl peroxide and stirring, setting the temperature to 80℃, the rotation speed to 600 rpm, stirring for 40 minutes, reducing the reaction vessel temperature to 70℃, adding thiophosphate cage-type POSS and stirring for 20 minutes, and allowing the temperature to cool naturally to 25℃ to obtain the modified hydrogenated polybutadiene oil.

[0018] Furthermore, the mass ratio of the hydrogenated polybutadiene oil, boron-nitrogen heterocyclic alkylphosphine chelating agent, thiophosphate cage-type POSS, perfluorocyclic ether-terminated cyclic olefin monomer, and benzoyl peroxide is 100:2.5:1.5:2:0.1.

[0019] Furthermore, the preparation of the modified zinc stearate includes the following steps: A1. Zinc stearate is pulverized in an air jet mill with a pressure of 0.8-1.0 MPa until D90 < 1 μm. The pulverized zinc stearate is then placed in a vacuum drying oven with a temperature of 100℃ and a vacuum of -0.095 MPa for 2 hours to obtain dried zinc stearate powder.

[0020] A2. Place the dried zinc stearate powder into a mixer, set the mixer temperature to 90℃, add alkenyl naphthenate zirconium chelate and stir at 800 rpm for 15 minutes. Heat the mixer temperature to 95-105℃, add methacrylate-based POSS and dicumyl peroxide and stir at 1200 rpm for 20 minutes. Reduce the mixer temperature to 75-85℃, add long-chain alkyl phosphate imide and stir at 500 rpm for 10 minutes. Allow the mixer temperature to cool naturally to 25℃ to obtain modified zinc stearate.

[0021] Furthermore, the mass ratio of the dried zinc stearate powder, alkenyl naphthenate zirconium chelate, methacrylate-based POSS, dicumyl peroxide, and long-chain alkyl phosphate imide is 100:4:3:0.2:2.2.

[0022] Furthermore, the preparation of the modified zinc borate includes the following steps: B1. Vacuum dry zinc borate at a set temperature of 105℃ for 2 hours. After drying, put the zinc borate into a pulverizer and pulverize it until D90 < 1μm to obtain zinc borate powder.

[0023] B2. Place zinc borate powder into a mixer, set the mixer temperature to 90-95℃, add fluoroalkylphosphine nitrogen heterocyclic chelate and stir at 800 rpm for 12 minutes. Adjust the mixer temperature to 100-105℃, add cycloolefin cage-like thiophosphate and dicumyl peroxide and stir at 1200 rpm for 15 minutes. Reduce the mixer temperature to 75-80℃, add alkylborazine small molecules and stir at 500 rpm for 10 minutes. Allow the mixer temperature to cool naturally to 25℃ to obtain modified zinc borate.

[0024] Furthermore, the mass ratio of the zinc borate powder, fluoroalkylphosphine nitrogen heterocyclic chelate, alkylborazine small molecule, cycloolefin cage-like thiophosphate ester and dicumyl peroxide is 100:2:3:2.5:0.2.

[0025] The present invention has the following beneficial effects: 1. In this invention, modified hydrogenated polybutadiene oil is added, in which three modifiers—boron-nitrogen heterocyclic alkylphosphine chelating agent, perfluorocyclic ether-terminated cyclic olefin monomer, and thiophosphate cage-type POSS—are used to modify the hydrogenated polybutadiene oil through coordination grafting anchoring, hydrophobic crosslinking grafting, and nano-rigid point dispersion, respectively. This gives the oil molecules coordination binding sites, a strong hydrophobic fluorine chain structure, and nano-foam stabilizing function, significantly improving its anti-migration, thermal stability, and interfacial compatibility. When the modified oil is added to rubber, it can act as a plasticizer to improve the processing fluidity of the rubber compound. Relying on the strong hydrophobic structure, it enhances the waterproof and water-repellent properties of the rubber. Through coordination bonds, it forms a synergistic binding with the modified filler, and with the crosslinkable structure, it prevents blooming at the source. At the same time, the cage-type POSS nanopoints can uniformly support the foam cells, achieving low density of the rubber while stabilizing the closed-cell structure, thus balancing flexibility and mechanical stability.

[0026] 2. In this invention, modified zinc stearate is added, in which three modifiers—alkenyl naphthenate zirconium chelate, methacrylate-based POSS, and long-chain alkyl phosphate imide—are added. These modifiers sequentially modify zinc stearate by disrupting crystal regularity through lattice doping, constructing a rigid coating shell through nano-grafting, and improving lubrication and dispersibility through interface modification. This significantly improves its foaming activation efficiency, rubber compatibility, and anti-precipitation ability. When the modified material is added to rubber, it can efficiently activate azodicarbonamide at low temperature, allowing for more complete and uniform foaming to reduce rubber density. The nano-rigid shell can enhance the support of the cell walls to prevent collapse and deformation, while the alkyl phosphate imide improves its dispersion uniformity in non-polar EPDM rubber and forms a stronger bond with the rubber matrix. This optimizes the fineness of the foam, reduces agglomeration and blooming, and helps the rubber form a stable and uniform closed-cell structure.

[0027] 3. In this invention, modified zinc borate is added, comprising three modifiers: fluoroalkylphosphine nitrogen heterocyclic chelate, cycloolefin cage-like thiophosphate, and alkylborazine small molecule. These modifiers, through lattice embedding to impart strong hydrophobicity, cage-like grafting to enhance bubble wall reinforcement, and homologous interface modification to improve dispersibility, modify zinc borate to possess multiple properties including hydrophobic closed-cell, bubble stabilization and reinforcement, and anti-migration. When the modified material is added to rubber, its strong hydrophobic structure significantly improves the rubber's waterproof and water-repellent properties. The cage-like rigid structure strengthens the toughness of the bubble wall, inhibits bubble rupture and cross-contamination to improve the closed-cell rate, and the alkylborazine allows for more uniform dispersion in the rubber compound. Working synergistically with the other two modifiers, it stabilizes the bubble structure under low-density conditions, while preventing filler precipitation and blooming, thus improving the long-term stability and sealing performance of the rubber. Detailed Implementation

[0028] 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.

[0029] It should be noted that all raw materials used in the following experiments are commercially available.

[0030] Example 1: A method for preparing low-density closed-cell foamed rubber for automotive sealing strips. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips includes the following steps: S1. Add EPDM rubber to a mixer and masticate. Set the temperature to 65℃, the speed to 60rpm, and the pressure to 0.3MPa. Masturbate for 2 minutes. Add zinc oxide and activator and mix for 2 minutes. Add carbon black N550, nano-hydrotalcite and maleic anhydride-grafted EPDM rubber and mix for 4 minutes. Add modified hydrogenated polybutadiene oil and mix for 3 minutes. Add antioxidant, modified zinc stearate and modified zinc borate and mix for 3 minutes. Heat the mixer to 105℃, discharge the rubber, and obtain the rubber compound. Press the rubber compound to a thickness of 8mm. Allow the pressed rubber compound to cool naturally to 25℃ to obtain a rubber sheet. S2. Place the rubber sheet into the rubber mixing mill, set the temperature to 55℃, the roller gap to 0.5mm, and the rotation speed to 25rpm. After wrapping the rollers, pass through the mill twice, add azodicarbonamide, cut the rubber three times, add sulfur, cut the rubber three times, add N-cyclohexyl-2-benzothiazole sulfenamide, cut the rubber three times, add triallyl isocyanurate, cut the rubber three times, and obtain a mixture. Pass the mixture through the mill six times, adjust the roller gap to 4mm, and discharge the material to obtain a mixed rubber sheet. Cool the mixed rubber sheet to 25℃ and vulcanize it. First, send it to the microwave vulcanizing tunnel to vulcanize it. Set the microwave frequency to 2450MHz and the temperature to 170℃, and hold for 60 seconds. Then send it to the hot air vulcanizing box to vulcanize it. Set the temperature to 185℃ and hold for 3 minutes to obtain the vulcanized material. S3. The vulcanized material is fed into a three-stage water cooling tank for cooling and shaping. The cooling water temperature is set to 70℃, 45℃ and 25℃ respectively, and the temperature is reduced step by step for 5 minutes. After cooling, the vulcanized material is cut into segments at a traction speed of 1m / min to obtain low-density closed-cell foamed rubber for automotive sealing strips. The low-density closed-cell foamed automotive sealing strip rubber comprises the following raw materials in parts by weight: 95 parts EPDM rubber, 2.5 parts zinc oxide, 0.7 parts activating agent, 10 parts carbon black N550, 5 parts nano-hydrotalcite, 0.8 parts maleic anhydride-grafted EPDM rubber, 14 parts modified hydrogenated polybutadiene oil, 3.5 parts azodicarbonamide, 0.6 parts sulfur, 0.6 parts N-cyclohexyl-2-benzothiazole sulfenamide, 0.25 parts triallyl isocyanurate, 0.7 parts antioxidant, 1.8 parts modified zinc stearate, and 1.6 parts modified zinc borate.

[0031] The antioxidant is composed of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite.

[0032] The mass ratio of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] to tris(2,4-di-tert-butylphenyl)phosphite is 5:3.

[0033] The activating agent is stearic acid.

[0034] The preparation of modified hydrogenated polybutadiene oil includes the following steps: adding hydrogenated polybutadiene oil to a reaction vessel, introducing nitrogen gas and stirring, setting the reaction vessel temperature to 70℃ and the rotation speed to 600 rpm, stirring for 10 minutes, adding boron-nitrogen heterocyclic alkylphosphine chelating agent and stirring for 30 minutes, adding perfluorocyclic ether-terminated cyclic olefin monomers and benzoyl peroxide and stirring, setting the temperature to 80℃ and the rotation speed to 600 rpm, stirring for 40 minutes, reducing the reaction vessel temperature to 70℃, adding thiophosphate cage-type POSS and stirring for 20 minutes, and allowing the temperature to cool naturally to 25℃ to obtain modified hydrogenated polybutadiene oil.

[0035] The mass ratio of hydrogenated polybutadiene oil, boron-nitrogen heterocyclic alkylphosphine chelating agent, thiophosphate cage-type POSS, perfluorocyclic ether-terminated cyclic olefin monomer and benzoyl peroxide is 100:2.5:1.5:2:0.1.

[0036] The preparation of modified zinc stearate includes the following steps: A1. Zinc stearate was pulverized in an air jet mill at a pressure of 0.8 MPa until D90 < 1 μm. The pulverized zinc stearate was then placed in a vacuum drying oven at a temperature of 100℃ and a vacuum of -0.095 MPa for 2 hours to obtain dried zinc stearate powder. A2. Place the dried zinc stearate powder into a mixer, set the mixer temperature to 90°C, add the alkenyl naphthenate zirconium chelate and stir at 800 rpm for 15 minutes. Heat the mixer temperature to 95°C, add methacrylate-based POSS and dicumyl peroxide and stir at 1200 rpm for 20 minutes. Reduce the mixer temperature to 75°C, add the long-chain alkyl phosphate imide and stir at 500 rpm for 10 minutes. Allow the mixer temperature to cool naturally to 25°C to obtain modified zinc stearate.

[0037] The mass ratio of dried zinc stearate powder, alkenyl naphthenate zirconium chelate, methacrylate-based POSS, dicumyl peroxide, and long-chain alkyl phosphate imide is 100:4:3:0.2:2.2.

[0038] The preparation of modified zinc borate includes the following steps: B1. Vacuum dry zinc borate at 105℃ for 2 hours. After drying, put the zinc borate into a pulverizer and pulverize it until D90 < 1μm to obtain zinc borate powder. B2. Place zinc borate powder into a mixer, set the mixer temperature to 90℃, add fluoroalkylphosphine nitrogen heterocyclic chelate and stir at 800 rpm for 12 minutes. Adjust the mixer temperature to 100℃, add cycloolefin cage-like thiophosphate and dicumyl peroxide and stir at 1200 rpm for 15 minutes. Reduce the mixer temperature to 75℃, add alkylborazine small molecules and stir at 500 rpm for 10 minutes. Allow the mixer temperature to cool naturally to 25℃ to obtain modified zinc borate.

[0039] The mass ratio of zinc borate powder, fluoroalkylphosphine nitrogen heterocyclic chelate, alkylborazine small molecule, cycloolefin cage-like thiophosphate ester and diisopropylbenzene peroxide is 100:2:3:2.5:0.2.

[0040] Example 2: A method for preparing low-density closed-cell foamed rubber for automotive sealing strips. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips includes the following steps: S1. Add EPDM rubber to a mixer and masticate. Set the temperature to 68℃, the speed to 60rpm, and the pressure to 0.4MPa. Masturbate for 2 minutes. Add zinc oxide and activator and mix for 2 minutes. Add carbon black N550, nano-hydrotalcite and maleic anhydride-grafted EPDM rubber and mix for 4 minutes. Add modified hydrogenated polybutadiene oil and mix for 3 minutes. Add antioxidant, modified zinc stearate and modified zinc borate and mix for 3 minutes. Heat the mixer to 105℃, discharge the rubber, and obtain the rubber compound. Press the rubber compound to a thickness of 9mm. Allow the pressed rubber compound to cool naturally to 25℃ to obtain a rubber sheet. S2. Place the rubber sheet into the rubber mixing mill, set the temperature to 60℃, the roller gap to 0.7mm, and the rotation speed to 28rpm. After wrapping the rollers, pass through the mill twice, add azodicarbonamide, cut the rubber three times, add sulfur, cut the rubber three times, add N-cyclohexyl-2-benzothiazole sulfenamide, cut the rubber three times, add triallyl isocyanurate, cut the rubber three times to obtain a mixture. Pass the mixture through the mill six times, adjust the roller gap to 4.5mm, and discharge the material to obtain a mixed rubber sheet. Cool the mixed rubber sheet to 25℃ and vulcanize it. First, send it to the microwave vulcanizing tunnel to vulcanize it. Set the microwave frequency to 2450MHz and the temperature to 174℃, and hold for 50 seconds. Then send it to the hot air vulcanizing box to vulcanize it. Set the temperature to 190℃ and hold for 3.5 minutes to obtain the vulcanized material. S3. The vulcanized material is fed into a three-stage water cooling tank for cooling and shaping. The cooling water temperature is set to 70℃, 45℃ and 25℃ respectively, and the temperature is reduced step by step for 6.5 minutes. After cooling, the vulcanized material is cut into segments at a traction speed of 1.5m / min to obtain low-density closed-cell foamed rubber for automotive sealing strips. The low-density closed-cell foamed automotive sealing strip rubber comprises the following raw materials in parts by weight: 100 parts EPDM rubber, 3 parts zinc oxide, 0.8 parts activating agent, 12 parts carbon black N550, 6 parts nano-hydrotalcite, 1 part maleic anhydride-grafted EPDM rubber, 15 parts modified hydrogenated polybutadiene oil, 4 parts azodicarbonamide, 0.65 parts sulfur, 0.7 parts N-cyclohexyl-2-benzothiazole sulfenamide, 0.3 parts triallyl isocyanurate, 0.8 parts antioxidant, 2 parts modified zinc stearate, and 1.8 parts modified zinc borate.

[0041] The antioxidant is composed of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite.

[0042] The mass ratio of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] to tris(2,4-di-tert-butylphenyl)phosphite is 5:3.

[0043] The activating agent is palmitic acid.

[0044] The preparation of modified hydrogenated polybutadiene oil includes the following steps: adding hydrogenated polybutadiene oil to a reaction vessel, introducing nitrogen gas and stirring, setting the reaction vessel temperature to 73℃ and the rotation speed to 600 rpm, stirring for 10 minutes, adding boron-nitrogen heterocyclic alkylphosphine chelating agent and stirring for 30 minutes, adding perfluorocyclic ether-terminated cyclic olefin monomers and benzoyl peroxide and stirring, setting the temperature to 80℃ and the rotation speed to 600 rpm, stirring for 40 minutes, reducing the reaction vessel temperature to 70℃, adding thiophosphate cage-type POSS and stirring for 20 minutes, and allowing the temperature to cool naturally to 25℃ to obtain modified hydrogenated polybutadiene oil.

[0045] The mass ratio of hydrogenated polybutadiene oil, boron-nitrogen heterocyclic alkylphosphine chelating agent, thiophosphate cage-type POSS, perfluorocyclic ether-terminated cyclic olefin monomer and benzoyl peroxide is 100:2.5:1.5:2:0.1.

[0046] The preparation of modified zinc stearate includes the following steps: A1. Zinc stearate was pulverized in an air jet mill at a pressure of 0.9 MPa until D90 < 1 μm. The pulverized zinc stearate was then placed in a vacuum drying oven at a temperature of 100℃ and a vacuum of -0.095 MPa for 2 hours to obtain dried zinc stearate powder. A2. Place the dried zinc stearate powder into a mixer, set the mixer temperature to 90℃, add alkenyl naphthenate zirconium chelate and stir at 800 rpm for 15 minutes. Heat the mixer temperature to 100℃, add methacrylate-based POSS and dicumyl peroxide and stir at 1200 rpm for 20 minutes. Reduce the mixer temperature to 80℃, add long-chain alkyl phosphate imide and stir at 500 rpm for 10 minutes. Allow the mixer temperature to cool naturally to 25℃ to obtain modified zinc stearate.

[0047] The mass ratio of dried zinc stearate powder, alkenyl naphthenate zirconium chelate, methacrylate-based POSS, dicumyl peroxide, and long-chain alkyl phosphate imide is 100:4:3:0.2:2.2.

[0048] The preparation of modified zinc borate includes the following steps: B1. Vacuum dry zinc borate at 105℃ for 2 hours. After drying, put the zinc borate into a pulverizer and pulverize it until D90 < 1μm to obtain zinc borate powder. B2. Place zinc borate powder into a mixer, set the mixer temperature to 93℃, add fluoroalkylphosphine nitrogen heterocyclic chelate and stir at 800 rpm for 12 minutes. Adjust the mixer temperature to 103℃, add cycloolefin cage-like thiophosphate and dicumyl peroxide and stir at 1200 rpm for 15 minutes. Reduce the mixer temperature to 78℃, add alkylborazine small molecules and stir at 500 rpm for 10 minutes. Allow the mixer temperature to cool naturally to 25℃ to obtain modified zinc borate.

[0049] The mass ratio of zinc borate powder, fluoroalkylphosphine nitrogen heterocyclic chelate, alkylborazine small molecule, cycloolefin cage-like thiophosphate ester and diisopropylbenzene peroxide is 100:2:3:2.5:0.2.

[0050] Example 3: A method for preparing low-density closed-cell foamed rubber for automotive sealing strips. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips includes the following steps: S1. Add EPDM rubber to a mixer and masticate. Set the temperature to 70℃, the speed to 60rpm, and the pressure to 0.5MPa. Masturbate for 2 minutes. Add zinc oxide and activator and mix for 2 minutes. Add carbon black N550, nano-hydrotalcite and maleic anhydride-grafted EPDM rubber and mix for 4 minutes. Add modified hydrogenated polybutadiene oil and mix for 3 minutes. Add antioxidant, modified zinc stearate and modified zinc borate and mix for 3 minutes. Heat the mixer to 105℃, discharge the rubber, and obtain the rubber compound. Press the rubber compound to a thickness of 10mm. Allow the pressed rubber compound to cool naturally to 25℃ to obtain a rubber sheet. S2. Place the rubber sheet into the rubber mixing mill, set the temperature to 65℃, the roller gap to 1.0mm, and the rotation speed to 30rpm. After wrapping the rollers, pass through the mill twice, add azodicarbonamide, cut the rubber three times, add sulfur, cut the rubber three times, add N-cyclohexyl-2-benzothiazole sulfenamide, cut the rubber three times, add triallyl isocyanurate, cut the rubber three times, and obtain a mixture. Pass the mixture through the mill six times, adjust the roller gap to 5mm, and discharge the material to obtain a mixed rubber sheet. Cool the mixed rubber sheet to 25℃ and vulcanize it. First, send it to the microwave vulcanizing tunnel to vulcanize it. Set the microwave frequency to 2450MHz and the temperature to 178℃, and hold for 40 seconds. Then send it to the hot air vulcanizing box to vulcanize it. Set the temperature to 195℃ and hold for 3 minutes to obtain the vulcanized material. S3. The vulcanized material is fed into a three-stage water cooling tank for cooling and shaping. The cooling water temperature is set to 70℃, 45℃ and 25℃ respectively, and the temperature is reduced step by step for 8 minutes. After cooling, the vulcanized material is cut into segments at a traction speed of 2m / min to obtain low-density closed-cell foamed rubber for automotive sealing strips. The low-density closed-cell foamed automotive sealing strip rubber comprises the following raw materials in parts by weight: 105 parts EPDM rubber, 3.5 parts zinc oxide, 0.9 parts activating agent, 14 parts carbon black N550, 7 parts nano-hydrotalcite, 1.2 parts maleic anhydride-grafted EPDM rubber, 16 parts modified hydrogenated polybutadiene oil, 4.5 parts azodicarbonamide, 0.7 parts sulfur, 0.8 parts N-cyclohexyl-2-benzothiazole sulfenamide, 0.35 parts triallyl isocyanurate, 0.9 parts antioxidant, 2.2 parts modified zinc stearate, and 2 parts modified zinc borate.

[0051] The antioxidant is composed of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite.

[0052] The mass ratio of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] to tris(2,4-di-tert-butylphenyl)phosphite is 5:3.

[0053] The activating agent is stearic acid.

[0054] The preparation of modified hydrogenated polybutadiene oil includes the following steps: adding hydrogenated polybutadiene oil to a reaction vessel, introducing nitrogen gas and stirring, setting the reaction vessel temperature to 75℃ and the rotation speed to 600 rpm, stirring for 10 minutes, adding boron-nitrogen heterocyclic alkylphosphine chelating agent and stirring for 30 minutes, adding perfluorocyclic ether-terminated cyclic olefin monomer and benzoyl peroxide and stirring, setting the temperature to 80℃ and the rotation speed to 600 rpm, stirring for 40 minutes, reducing the reaction vessel temperature to 70℃, adding thiophosphate cage-type POSS and stirring for 20 minutes, and allowing the temperature to cool naturally to 25℃ to obtain modified hydrogenated polybutadiene oil.

[0055] The mass ratio of hydrogenated polybutadiene oil, boron-nitrogen heterocyclic alkylphosphine chelating agent, thiophosphate cage-type POSS, perfluorocyclic ether-terminated cyclic olefin monomer and benzoyl peroxide is 100:2.5:1.5:2:0.1.

[0056] The preparation of modified zinc stearate includes the following steps: A1. Zinc stearate was pulverized in an air jet mill at a pressure of 1.0 MPa until D90 < 1 μm. The pulverized zinc stearate was then placed in a vacuum drying oven at a temperature of 100℃ and a vacuum of -0.095 MPa for 2 hours to obtain dried zinc stearate powder. A2. Place the dried zinc stearate powder into a mixer, set the mixer temperature to 90℃, add alkenyl naphthenate zirconium chelate and stir at 800 rpm for 15 minutes. Heat the mixer temperature to 105℃, add methacrylate-based POSS and dicumyl peroxide and stir at 1200 rpm for 20 minutes. Reduce the mixer temperature to 85℃, add long-chain alkyl phosphate imide and stir at 500 rpm for 10 minutes. Allow the mixer temperature to cool naturally to 25℃ to obtain modified zinc stearate.

[0057] The mass ratio of dried zinc stearate powder, alkenyl naphthenate zirconium chelate, methacrylate-based POSS, dicumyl peroxide, and long-chain alkyl phosphate imide is 100:4:3:0.2:2.2.

[0058] The preparation of modified zinc borate includes the following steps: B1. Vacuum dry zinc borate at 105℃ for 2 hours. After drying, put the zinc borate into a pulverizer and pulverize it until D90 < 1μm to obtain zinc borate powder. B2. Place zinc borate powder into a mixer, set the mixer temperature to 95℃, add fluoroalkylphosphine nitrogen heterocyclic chelate and stir at 800 rpm for 12 minutes. Adjust the mixer temperature to 105℃, add cycloolefin cage-like thiophosphate and dicumyl peroxide and stir at 1200 rpm for 15 minutes. Reduce the mixer temperature to 80℃, add alkylborazine small molecules and stir at 500 rpm for 10 minutes. Allow the mixer temperature to cool naturally to 25℃ to obtain modified zinc borate.

[0059] The mass ratio of zinc borate powder, fluoroalkylphosphine nitrogen heterocyclic chelate, alkylborazine small molecule, cycloolefin cage-like thiophosphate ester and diisopropylbenzene peroxide is 100:2:3:2.5:0.2.

[0060] Comparative Example 1: The difference between this comparative example and Example 1 is that: Unmodified hydrogenated polybutadiene oil was used in this comparative example.

[0061] Comparative Example 2: The difference between this comparative example and Example 1 is that: Unmodified zinc stearate was used in this comparative example.

[0062] Comparative Example 3 differs from Example 1 in that: Unmodified zinc borate was used in this comparative example.

[0063] Performance testing: The preparation method of a low-density closed-cell foamed rubber for automotive sealing strips prepared in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 was tested.

[0064] Performance testing: The relevant properties of the samples prepared by the method of low-density closed-cell foamed rubber for automotive sealing strips provided in Examples 1-3 and Comparative Examples 1-3 were tested respectively, and the test data are recorded in Table 1 below: Based on the above data, the following conclusions can be drawn: Among them, the blooming level test of a low-density closed-cell foamed automotive sealing strip rubber prepared using the test methods in HG / T4604-2014, Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3; Apparent density test of a low-density closed-cell foamed rubber for automotive sealing strips prepared according to the test methods in GB / T6343-2023, namely Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3; The closed-cell rate of a low-density closed-cell foamed automotive sealing strip rubber prepared according to the test methods in GB / T10799-2008 (Examples 1, 2, 3, Comparative Examples 1, 2, and 3) was tested.

[0065] Modified hydrogenated polybutadiene oil, through coordination anchoring with boron-nitrogen heterocyclic alkylphosphine chelators, covalent crosslinking with perfluorocyclic ether monomers, and nano-dispersion by thiophosphate cage-type POSS, achieves strong bonding between oil molecules and the rubber matrix and fillers, eliminating their existence as free small molecules and significantly reducing oil phase migration and surface precipitation tendency. Modified zinc stearate, after lattice doping with alkenyl naphthenate zirconium chelates, exhibits significantly enhanced low-temperature activation ability for azodicarbonamide, allowing for more complete decomposition of the foaming agent and greater gas evolution. The rigid shell of methacrylate-based POSS stabilizes cell growth, prevents cell collapse, and improves foaming uniformity, effectively reducing the bulk density of the material while ensuring the integrity of the closed-cell structure. Modified zinc borate, relying on the hydrophobic modification of fluoroalkylphosphine nitrogen heterocyclic chelates, the cell wall reinforcement of cycloolefin cage-like thiophosphates, and the interface homogenization effect of alkylborane, increases the melt surface tension and enhances the cell wall strength during rubber foaming, effectively inhibiting bubble rupture, merging, and cross-cell formation, and forcing the cells to maintain an independent closed structure.

[0066] Through the above demonstrations, the present invention is significantly superior to the control group in terms of blooming level, apparent density and closed-pore ratio, thus verifying the advanced nature and rationality of the preparation method.

[0067] 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.

[0068] 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 method for preparing low-density closed-cell foamed rubber for automotive sealing strips, characterized in that, The preparation method of the low-density closed-cell foamed automotive sealing strip rubber includes the following steps: S1. Add EPDM rubber to a mixer for plasticizing, add zinc oxide and activating agent for mixing, add carbon black N550, nano-hydrotalcite and maleic anhydride-grafted EPDM rubber for mixing, add modified hydrogenated polybutadiene oil for mixing, add antioxidant, modified zinc stearate and modified zinc borate for mixing, discharge the rubber to obtain a rubber compound, press the rubber compound into a thin film, and allow the pressed rubber compound to cool naturally to obtain a rubber sheet; S2. Place the rubber sheet into the rubber mixing mill, roll it through the mill, add azodicarbonamide, cut the rubber, add sulfur, cut the rubber, add N-cyclohexyl-2-benzothiazole sulfenamide, cut the rubber, add triallyl isocyanurate, cut the rubber to obtain a mixture, pass the mixture through the mill, discharge the mixture to obtain a mixed rubber sheet, cool the mixed rubber sheet and vulcanize it to obtain a vulcanized material; S3. The vulcanized material is fed into a three-stage water cooling tank for cooling and shaping. After cooling, the vulcanized material is pulled and cut into sections to obtain low-density closed-cell foamed rubber for automotive sealing strips. The low-density closed-cell foamed automotive sealing strip rubber comprises the following raw materials in parts by weight: 95-105 parts EPDM rubber, 2.5-3.5 parts zinc oxide, 0.7-0.9 parts activating agent, 10-14 parts carbon black N550, 5-7 parts nano-hydrotalcite, 0.8-1.2 parts maleic anhydride-grafted EPDM rubber, 14-16 parts modified hydrogenated polybutadiene oil, 3.5-4.5 parts azodicarbonamide, 0.6-0.7 parts sulfur, 0.6-0.8 parts N-cyclohexyl-2-benzothiazole sulfenamide, 0.25-0.35 parts triallyl isocyanurate, 0.7-0.9 parts antioxidant, 1.8-2.2 parts modified zinc stearate, and 1.6-2 parts modified zinc borate.

2. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 1, characterized in that, The antioxidant is composed of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and tris(2,4-di-tert-butylphenyl)phosphite.

3. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 2, characterized in that, The mass ratio of the tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester to tris(2,4-di-tert-butylphenyl)phosphite is 5:

3.

4. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 2, characterized in that, The activating agent is one of stearic acid and palmitic acid.

5. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 1, characterized in that, The preparation of the modified hydrogenated polybutadiene oil includes the following steps: adding hydrogenated polybutadiene oil into a reaction vessel, introducing nitrogen gas and stirring, adding boron-nitrogen heterocyclic alkylphosphine chelating agent and stirring, adding perfluorocyclic ether-terminated cyclic olefin monomer and benzoyl peroxide and stirring, adding thiophosphate cage-type POSS and stirring, to obtain modified hydrogenated polybutadiene oil.

6. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 5, characterized in that, The mass ratio of the hydrogenated polybutadiene oil, boron-nitrogen heterocyclic alkylphosphine chelating agent, thiophosphate cage-type POSS, perfluorocyclic ether-terminated cyclic olefin monomer, and benzoyl peroxide is 100:2.5:1.5:2:0.

1.

7. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 1, characterized in that, The preparation of the modified zinc stearate includes the following steps: A1. Zinc stearate is pulverized in an air jet mill, and the pulverized zinc stearate is dried in a vacuum drying oven to obtain dried zinc stearate powder; A2. Place the dried zinc stearate powder into a mixer, add alkenyl naphthenate zirconium chelate and stir, add methacrylate-based POSS and dicumyl peroxide and stir, add long-chain alkyl phosphate imide and stir to obtain modified zinc stearate.

8. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 7, characterized in that, The mass ratio of the dried zinc stearate powder, alkenyl naphthenate zirconium chelate, methacrylate-based POSS, dicumyl peroxide, and long-chain alkyl phosphate imide is 100:4:3:0.2:2.

2.

9. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 1, characterized in that, The preparation of the modified zinc borate includes the following steps: B1. Vacuum dry zinc borate, then pulverize the dried zinc borate in a pulverizer to obtain zinc borate powder; B2. Place zinc borate powder into a mixer, add fluoroalkylphosphine nitrogen heterocyclic chelate and stir, add cycloolefinic cage-like thiophosphate and diisopropylbenzene peroxide and stir, add alkylborazine small molecules and stir to obtain modified zinc borate.

10. The method for preparing low-density closed-cell foamed rubber for automotive sealing strips according to claim 9, characterized in that, The mass ratio of zinc borate powder, fluoroalkylphosphine nitrogen heterocyclic chelate, alkylborazine small molecule, cycloolefin cage-like thiophosphate ester and dicumyl peroxide is 100:2:3:2.5:0.2.

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