High-scratch-resistance automobile armrest coating part and preparation process thereof

Abstract

The invention discloses a high-scratch-resistance automobile armrest coating part and a preparation process thereof, and relates to the technical field of automobile armrest coating parts. Double bonds in the modified ethylene propylene diene monomer and 3-thiohydracrylic acid are subjected to a thiol-ene click reaction, so that the dynamic fatigue performance is improved; carboxyl is introduced to react with epoxy groups to construct an efficient cross-linked network, so that the compatibility is improved, and the mechanical property is remarkably enhanced; dicumyl peroxide is decomposed to generate free radicals, the free radicals and a modified ethylene propylene diene monomer molecular chain form a high-density cross-linked network, the elasticity and heat resistance of the material are improved, meanwhile, modified ethylene propylene diene monomer particles are dispersed in a thermoplastic elastomer matrix, and the scratch resistance is remarkably improved. Modified boron nitride is added, phosphomolybdic acid and guanidine phosphate are subjected to electrostatic adsorption to form an intumescent flame-retardant synergistic layer, and in addition, an inorganic filler and a flame retardant enhance rigidity and flame retardance; and the ethylene-zinc acrylate ionomer can improve the adhesion and the scratch resistance. The product can be widely applied to the field of automobile industry.

Description

Technical Field

[0001] This invention relates to the field of automotive armrest covering technology, specifically to a highly scratch-resistant automotive armrest covering and its manufacturing process. Background Technology

[0002] In the modern automotive industry, car armrests, as crucial components in contact between passengers and drivers, directly impact the driving and riding experience with their performance and comfort. The ever-increasing demands for automotive interior components, such as high scratch resistance, weather resistance, comfort, and environmental friendliness, have spurred the continuous research and application of new materials and advanced processes. However, traditional car armrest coverings are prone to surface scratches due to daily use, environmental factors, and mechanical friction, affecting their aesthetics and lifespan. Currently, most common car armrest coverings on the market are made of thermoplastic plastics or rubber. While they possess some scratch resistance, their scratch resistance remains significantly insufficient under high-frequency, high-intensity usage conditions, especially under high temperature, high humidity, or extreme climate conditions, where the material's durability and scratch resistance are poor.

[0003] Thermoplastic elastomers (TEEs) are gradually replacing traditional materials due to their excellent processability and tactile properties. For example, hydrogenated styrene-butadiene block copolymers can be directly coated onto an acrylonitrile-butadiene-styrene or polycarbonate backbone through secondary injection molding, simplifying the manufacturing process while providing a matte finish and scratch resistance. However, the low hardness of hydrogenated styrene-butadiene block copolymers makes it difficult to meet high scratch resistance requirements. Ethylene propylene diene monomer (EPDM) rubber is widely used in automotive components such as sealing strips, hydraulic braking systems, and air conditioning ventilation systems due to its excellent weather resistance, ozone resistance, heat resistance, and low-temperature flexibility. However, it still has limitations in some applications. EPDM rubber lacks active groups in its molecular structure, has low cohesive energy, poor self-adhesion and mutual adhesion, and relatively poor processability. Further optimization and material modification of EPDM rubber properties remain important directions for future research.

[0004] To address the aforementioned problems, this invention provides a high-scratch-resistant automotive armrest covering and its manufacturing process. By controlling the proportions of each component and process parameters, the scratch resistance and service life of the automotive armrest are improved, enhancing both the scratch resistance and weather resistance of the covering. With the continuous development of the automotive industry, this type of high-performance, high-value-added automotive interior component will have broad application prospects. Summary of the Invention

[0005] The purpose of this invention is to provide a highly scratch-resistant automotive armrest covering and its manufacturing process, in order to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A manufacturing process for a highly scratch-resistant automotive armrest cover, comprising the following steps: S1: Heat to 60-80℃, dry the thermoplastic elastomer and polyolefin grafted maleic anhydride for 2-3 hours and mix them together, add modified EPDM rubber, vulcanizing agent, crosslinking agent and antioxidant, heat to 150-170℃ and vulcanize and mix for 10-20 minutes to obtain vulcanized rubber. S2: Add ethylene-zinc acrylate ionomer and inorganic filler to vulcanized rubber, stir for 10-20 minutes, extrude at 140-160℃ using a twin-screw extruder, add modified boron nitride and flame retardant to the side feed port, melt blend, and granulate underwater to obtain the molding compound; S3: Injection molding with the prepared mold material to obtain the skin; plasma treatment of the car armrest, spraying water-based polyurethane adhesive on the outer surface, placing the skin on the outer surface of the car armrest, hot pressing, cutting, rolling, and welding, heat setting in an oven at 70-80℃ for 1-3 hours to obtain the car armrest covering.

[0007] In a more optimized manner, by weight parts, the raw material composition of the vulcanized rubber in step S1 is: 25-35 parts thermoplastic elastomer, 5-8 parts polyolefin grafted maleic anhydride, 45-60 parts modified EPDM rubber, 0.5-1 parts vulcanizing agent, 0.3-0.8 parts co-crosslinking agent, and 0.2-0.5 parts antioxidant; In step S2, the raw material composition of the molding compound is: 90-100 parts vulcanized rubber, 8-12 parts ethylene-zinc acrylate ionomer, 15-25 parts inorganic filler, 15-30 parts flame retardant, and 3-5 parts modified boron nitride. More preferably, the thermoplastic elastomer is one or more of hydrogenated polystyrene-butadiene copolymer, styrene-butadiene-styrene block copolymer, and styrene-ethylene-propylene-styrene block copolymer; the polyolefin grafted with maleic anhydride is ethylene-octene copolymer grafted with maleic anhydride; the vulcanizing agent is dicumyl peroxide; and the co-crosslinking agent is triallyl isocyanurate. The antioxidant is one or a combination of pentaerythritol tetrakis[β-propionate], 2,4-di(n-octylthionyl)-6-methylphenol, and tris(2,4-di-tert-butylphenyl) phosphite; the inorganic filler is one or a combination of talc, mica powder, wollastonite, barium sulfate, carbon black, silica, and titanium dioxide; the flame retardant is one of zinc borate, hypophosphite, aluminum hydroxide, and magnesium hydroxide. Ideally, the skin thickness is 1.0-1.5 mm; In a more optimized manner, the preparation process of the ethylene-octene copolymer grafted with maleic anhydride is as follows: ethylene-octene copolymer, maleic anhydride, and initiator are mixed at a mass ratio of 100:1:0.15 and melt-extruded; the extruder temperature is 160-180℃, and the screw speed is 240-280 r / min; the initiator is dicumyl peroxide. In a more optimized manner, the preparation process of the modified EPDM rubber is as follows: heat to 60-80℃, plasticize the EPDM rubber on a two-roll mill for 5-10 min, add 3-mercaptopropionic acid and 2,2-azobisisobutyronitrile and react for 10-20 min, then add paraffin oil, antioxidant and epoxidized soybean oil in sequence and mix for 15-30 min, and then sheet out after thin-passing to obtain the modified EPDM rubber; The modified EPDM rubber, by weight, comprises the following raw materials: 50-65 parts EPDM rubber, 6-10 parts 3-mercaptopropionic acid, 1-3 parts 2,2-azobisisobutyronitrile, 0.5-1.5 parts antioxidant, 6-10 parts paraffin oil, and 0.5-1.0 parts epoxidized soybean oil; the antioxidant is N-isopropyl-N'-phenyl-p-phenylenediamine. In a more optimized manner, the preparation process of the modified boron nitride is as follows: Boron nitride is added to a 30% (w / w) hydrogen peroxide aqueous solution, stirred for 5-10 min, sonicated for 1-2 h, centrifuged, washed, and dried to obtain hydroxylated boron nitride; the hydroxylated boron nitride is dispersed in deionized water, sonicated for 10-20 min, guanidine phosphate is added, stirred at 80-90℃ for 6-8 h, centrifuged, washed, and centrifuged again to obtain boron nitride-guanidine phosphate; the boron nitride-guanidine phosphate is sonicated and dispersed in deionized water, phosphomolybdic acid hydrate is added, reacted for 10-12 h, centrifuged, washed, centrifuged again, and dried to obtain modified boron nitride.

[0008] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a high scratch-resistant automotive armrest cover and its manufacturing process. By optimizing the material formula and adjusting the process parameters, the scratch resistance of the automotive armrest cover is significantly improved, providing a new technical path for the high performance and long life of automotive interior parts.

[0009] In modified EPDM rubber, the double bonds of EPDM rubber undergo a mercapto-olefin click reaction with 3-mercaptopropionic acid, improving dynamic fatigue performance. The introduction of carboxyl groups provides reaction sites for subsequent reactions, improving compatibility with other materials. The carboxyl groups crosslink with the epoxy groups in epoxidized soybean oil, constructing a highly efficient crosslinking network based on the "epoxy-carboxylic acid" reaction, providing rigid support and significantly enhancing mechanical properties. The β-hydroxy ester bonds in epoxidized soybean oil improve thermal stability and aging resistance. N-isopropyl-N-phenyl-p-phenylenediamine is used as an antioxidant to delay thermo-oxidative aging, extending the service life of rubber products, and simultaneously providing amine-catalyzed epoxy ring-opening. The carboxyl groups form hydrogen bonds with the hydroxyl groups on the surface of talc, improving filler dispersibility. Flexible thioether bonds absorb stress, increasing crack propagation resistance and improving dynamic fatigue performance.

[0010] Dicumyl peroxide decomposes to generate free radicals. Triallyl isocyanurate acts as a co-crosslinking agent, forming a high-density crosslinked network with the modified EPDM rubber molecular chains, improving the material's elasticity and heat resistance. The polystyrene in the thermoplastic elastomer melts at high temperatures, and the crosslinked modified EPDM rubber particles are dispersed within the thermoplastic elastomer matrix, forming a thermoplastic vulcanizate. When the surface is subjected to scratches, the rubber particles resist penetration, significantly improving scratch resistance and elastic recovery rate. Ethylene-octene copolymer grafted with maleic anhydride grafts maleic anhydride onto the copolymer via double bonds, while also providing anhydride groups that can form covalent bonds with hydroxyl and amino groups in the molding compound, improving fiber-matrix interfacial adhesion and enhancing the mechanical properties of the filled system.

[0011] The modified boron nitride involves a three-step chemical modification process to enhance its dispersibility and flame retardant synergy in polymers. Hydroxyl groups are introduced onto the boron nitride surface to enhance hydrophilicity. Guanidine phosphate grafting forms PN bonds, introducing phosphorus / nitrogen flame retardant elements. Phosphomolybdic acid composite electrostatic adsorption ion bonding constructs an intumescent flame retardant system. The boron nitride-guanidine phosphate-phosphomolybdic acid decomposes at high temperatures, releasing phosphoric acid substances that catalyze polymer dehydration into char. Phosphomolybdic acid forms a dense protective layer with the char layer, isolating oxygen and producing a synergistic effect with aluminum hydroxide, achieving a UL94V-0 flame retardancy rating.

[0012] Inorganic fillers and flame retardants enhance rigidity and flame retardancy; in modified boron nitride, boron nitride modified with guanidine phosphate and phosphomolybdic acid improves filler dispersion and flame retardant effect; the zinc carboxylate groups of ethylene-zinc acrylate ionomer form a dynamic ionic crosslinking network with the carboxyl groups introduced into the modified EPDM rubber, while the zinc carboxylate groups can also form coordination bonds with the hydroxyl groups on the surface of inorganic filler talc, enhancing interfacial adhesion, dispersing stress at ionic crosslinking points, and enhancing the scratch resistance of the final product; the anhydride groups of polyolefin grafted with maleic anhydride form ionic cluster physical crosslinking points with the hydroxyl groups of ethylene-zinc acrylate ionomer, improving scratch resistance, enhancing interfacial adhesion between vulcanized rubber and ionomer, and increasing tensile strength.

[0013] With the continuous development of the automotive industry, such high-performance, high-value-added automotive interior parts will have broad application prospects. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Example 1: A highly scratch-resistant automotive armrest covering and its manufacturing process, the manufacturing process including the following steps: S1: Heat to 70℃, dry and blend hydrogenated polystyrene butadiene copolymer and ethylene-octene copolymer grafted with maleic anhydride for 3 hours, add modified EPDM rubber, dicumyl peroxide, triallyl isocyanurate, and pentaerythritol tetrakis[β-propionate], heat to 160℃ and vulcanize and mix for 15 minutes to obtain vulcanized rubber. S2: Add ethylene-zinc acrylate ionomer, talc, and aluminum hydroxide to vulcanized rubber, stir for 15 minutes, extrude at 150°C using a twin-screw extruder, add modified boron nitride and aluminum hydroxide to the side feed port, melt-blend, and granulate underwater to obtain the molding compound; S3: Injection molding with the prepared mold material to obtain the skin; plasma treatment of the car armrest, spraying water-based polyurethane adhesive on the outer surface, placing the skin on the outer surface of the car armrest, hot pressing, cutting, rolling, and welding, heat setting in a 75℃ oven for 2 hours to obtain the car armrest covering. By weight, in step S1, the raw material composition of the vulcanized rubber is: 30 parts hydrogenated polystyrene-butadiene copolymer, 6 parts ethylene-octene copolymer grafted with maleic anhydride, 60 parts modified ethylene propylene diene monomer (EPDM) rubber, 0.7 parts dicumyl peroxide, 0.5 parts triallyl isocyanurate, and 0.4 parts pentaerythritol tetrakis[β-propionate]. In step S2, the raw material composition of the molding compound is: 95 parts vulcanized rubber, 10 parts ethylene-zinc acrylate ionomer, 20 parts talc, 20 parts aluminum hydroxide, and 5 parts modified boron nitride. The thickness of the skin is 1.0 mm; The preparation process of the ethylene-octene copolymer grafted with maleic anhydride is as follows: ethylene-octene copolymer, maleic anhydride and dicumyl peroxide are mixed in a mass ratio of 100:1:0.15 and melt-extruded; the extruder temperature is 170℃ and the screw speed is 250r / min. The preparation process of the modified EPDM rubber is as follows: the temperature is raised to 70°C, the EPDM rubber is plasticized in a two-roll mill for 8 minutes, 3-mercaptopropionic acid and 2,2-azobisisobutyronitrile are added and reacted for 15 minutes, paraffin oil, N-isopropyl-N'-phenyl-p-phenylenediamine and epoxidized soybean oil are added in sequence and mixed for 20 minutes, and then sheeted after thin-passing to obtain the modified EPDM rubber; The modified EPDM rubber has the following raw material composition: 60 parts EPDM rubber, 8 parts 3-mercaptopropionic acid, 2 parts 2,2-azobisisobutyronitrile, 1.5 parts N-isopropyl-N'-phenyl-p-phenylenediamine, 8 parts paraffin oil; 50-65 parts EPDM rubber, 0.8 parts epoxidized soybean oil; The preparation process of the modified boron nitride is as follows: 2g of boron nitride is added to a 30% hydrogen peroxide aqueous solution, stirred for 10min, sonicated for 1h, centrifuged, washed, and dried to obtain hydroxylated boron nitride; the hydroxylated boron nitride is dispersed in 300mL of deionized water, sonicated for 20min, 5g of guanidine phosphate is added, stirred at 85℃ for 7h, centrifuged, washed, and centrifuged again to obtain boron nitride-guanidine phosphate; the boron nitride-guanidine phosphate is sonicated and dispersed in 300mL of deionized water, 2g of phosphomolybdic acid hydrate is added, reacted for 10h, centrifuged, washed, centrifuged again, and dried to obtain modified boron nitride.

[0016] Example 2: A highly scratch-resistant automotive armrest covering and its manufacturing process, the manufacturing process including the following steps: S1: Heat to 60℃, dry and blend hydrogenated polystyrene butadiene copolymer and ethylene-octene copolymer grafted with maleic anhydride for 3 hours, add modified EPDM rubber, dicumyl peroxide, triallyl isocyanurate and pentaerythritol tetrakis[β-propionic acid], heat to 170℃ and vulcanize and mix for 10 minutes to obtain vulcanized rubber. S2: Add ethylene-zinc acrylate ionomer and talc to vulcanized rubber, stir for 10 min, extrude at 160℃ using a twin-screw extruder, add modified boron nitride and aluminum hydroxide to the side feed port, melt blend, and granulate underwater to obtain the molding compound; S3: Inject the prepared mold material to obtain the skin; plasma treat the car armrest, spray the outer surface with water-based polyurethane adhesive, place the skin on the outer surface of the car armrest, hot press, cut the edges, roll the edges, weld, heat set in an 80℃ oven for 2 hours to obtain the car armrest covering. By weight, in step S1, the raw material composition of the vulcanized rubber is: 25 parts hydrogenated polystyrene-butadiene copolymer, 8 parts ethylene-octene copolymer grafted with maleic anhydride, 50 parts modified ethylene propylene diene monomer (EPDM) rubber, 1 part dicumyl peroxide, 0.5 parts triallyl isocyanurate, and 0.5 parts pentaerythritol tetrakis[β-propionate]. In step S2, the raw material composition of the molding compound is: 100 parts vulcanized rubber, 8 parts ethylene-zinc acrylate ionomer, 25 parts talc, 15 parts aluminum hydroxide, and 4 parts modified boron nitride. The thickness of the skin is 1.0 mm; The preparation process of the ethylene-octene copolymer grafted with maleic anhydride is as follows: ethylene-octene copolymer, maleic anhydride and dicumyl peroxide are mixed in a mass ratio of 100:1:0.15 and melt-extruded; the extruder temperature is 160℃ and the screw speed is 280r / min. The preparation process of the modified EPDM rubber is as follows: the temperature is raised to 60°C, the EPDM rubber is plasticized in a two-roll mill for 10 min, 3-mercaptopropionic acid and 2,2-azobisisobutyronitrile are added and reacted for 20 min, paraffin oil, N-isopropyl-N'-phenyl-p-phenylenediamine and epoxidized soybean oil are added in sequence and mixed for 30 min, and then sheeted after thin-passing to obtain the modified EPDM rubber; The modified EPDM rubber has the following raw material composition: 60 parts EPDM rubber, 7 parts 3-mercaptopropionic acid, 1.5 parts 2,2-azobisisobutyronitrile, 0.5 parts N-isopropyl-N'-phenyl-p-phenylenediamine, 8 parts paraffin oil, and 1.0 part epoxidized soybean oil. The preparation process of the modified boron nitride is as follows: 2g of boron nitride is added to a 30% hydrogen peroxide aqueous solution, stirred for 10min, sonicated for 1h, centrifuged, washed, and dried to obtain hydroxylated boron nitride; the hydroxylated boron nitride is dispersed in 300mL of deionized water, sonicated for 20min, 5g of guanidine phosphate is added, stirred at 85℃ for 7h, centrifuged, washed, and centrifuged again to obtain boron nitride-guanidine phosphate; the boron nitride-guanidine phosphate is sonicated and dispersed in 300mL of deionized water, 2g of phosphomolybdic acid hydrate is added, reacted for 10h, centrifuged, washed, centrifuged again, and dried to obtain modified boron nitride.

[0017] Example 3: A highly scratch-resistant automotive armrest covering and its manufacturing process, the manufacturing process including the following steps: S1: Heat to 65℃, dry and blend hydrogenated polystyrene butadiene copolymer and ethylene-octene copolymer grafted with maleic anhydride for 3 hours, add modified EPDM rubber, dicumyl peroxide, triallyl isocyanurate and pentaerythritol tetrakis[β-propionate], heat to 155℃ and vulcanize and mix for 140 minutes to obtain vulcanized rubber; S2: Add ethylene-zinc acrylate ionomer, talc, and aluminum hydroxide to vulcanized rubber, stir for 10 min, extrude at 145℃ using a twin-screw extruder, add modified boron nitride and aluminum hydroxide to the side feed port, melt-blend, and granulate underwater to obtain the molding compound; S3: Inject the prepared mold material to obtain the skin; plasma treat the car armrest, spray the outer surface with water-based polyurethane adhesive, place the skin on the outer surface of the car armrest, hot press, cut the edges, roll the edges, weld, heat set in an 80℃ oven for 2 hours to obtain the car armrest covering. By weight, in step S1, the raw material composition of the vulcanized rubber is: 27 parts hydrogenated polystyrene-butadiene copolymer, 8 parts ethylene-octene copolymer grafted with maleic anhydride, 45 parts modified ethylene propylene diene monomer (EPDM) rubber, 0.7 parts dicumyl peroxide, 0.5 parts triallyl isocyanurate, and 0.3 parts pentaerythritol tetrakis[β-propionate]. In step S2, the raw material composition of the molding compound is: 95 parts vulcanized rubber, 10 parts ethylene-zinc acrylate ionomer, 25 parts talc, 27 parts aluminum hydroxide, and 3 parts modified boron nitride. The thickness of the skin is 1.0 mm; The preparation process of the ethylene-octene copolymer grafted with maleic anhydride is as follows: ethylene-octene copolymer, maleic anhydride and dicumyl peroxide are mixed in a mass ratio of 100:1:0.15 and melt-extruded; the extruder temperature is 175℃ and the screw speed is 275r / min. The preparation process of the modified EPDM rubber is as follows: the temperature is raised to 65°C, the EPDM rubber is plasticized in a two-roll mill for 8 min, 3-mercaptopropionic acid and 2,2-azobisisobutyronitrile are added and reacted for 18 min, paraffin oil, N-isopropyl-N'-phenyl-p-phenylenediamine and epoxidized soybean oil are added in sequence and mixed for 30 min, and then sheeted after thin-passing to obtain the modified EPDM rubber; The modified EPDM rubber has the following raw material composition: 55 parts EPDM rubber, 6 parts 3-mercaptopropionic acid, 3 parts 2,2-azobisisobutyronitrile, 1.5 parts N-isopropyl-N'-phenyl-p-phenylenediamine, 10 parts paraffin oil, and 1.0 part epoxidized soybean oil. The preparation process of the modified boron nitride is as follows: 2g of boron nitride is added to a 30% hydrogen peroxide aqueous solution, stirred for 10min, sonicated for 1h, centrifuged, washed, and dried to obtain hydroxylated boron nitride; the hydroxylated boron nitride is dispersed in 300mL of deionized water, sonicated for 20min, 5g of guanidine phosphate is added, stirred at 85℃ for 7h, centrifuged, washed, and centrifuged again to obtain boron nitride-guanidine phosphate; the boron nitride-guanidine phosphate is sonicated and dispersed in 300mL of deionized water, 2g of phosphomolybdic acid hydrate is added, reacted for 10h, centrifuged, washed, centrifuged again, and dried to obtain modified boron nitride.

[0018] Comparative Example 1: Using Example 1 as the control group, EPDM rubber was used instead of modified EPDM rubber, and other processes were carried out normally.

[0019] Comparative Example 2: Example 1 was used as the control group. No modified boron nitride was added, and other processes were carried out normally.

[0020] Sources of raw materials used (for illustrative purposes only): The raw materials used in this technical solution are all products currently available on the market: hydrogenated polystyrene-butadiene copolymer: sold by Yueyang Longxing Industrial Co., Ltd. under product number YH-502T; pentaerythritol tetrakis[β-propionic acid] (6683-19-8, 99%): Hubei Yongkuo Technology Co., Ltd.; dicumyl peroxide (80-43-3, 99%): Shanghai Yuejiang Titanium Dioxide Chemical Products Co., Ltd.; triallyl isocyanurate (1025-15-6, 99%): Hubei Xinhongli Chemical Co., Ltd.; ethylene-zinc acrylate ionomer: sold by Dongguan Zhangmutou Yutao Plastic Raw Material Business Department under product number 1702; ethylene-octene copolymer: sold by Shaanxi Didu Pharmaceutical Chemical Co., Ltd. under product name POLY (ETHYLENE-CO-1-OCTENE); maleic anhydride (10 8-31-6, 99.5%: Shandong Xinheng Chemical Co., Ltd.; Talc (14807-96-6, 99%, 5μm): Ruichengkang Pharmaceutical Technology (Shaanxi) Co., Ltd.; Aluminum hydroxide (21645-51-2, 99.9%, 15μm): Wuhu Jikang New Materials Co., Ltd.; EPDM rubber: Wuhan Oliver New Materials Co., Ltd., selling the product under the product name Exxon EPDM V3666; 3-Mercaptopropionic acid (107-96-0, 99%): Tianmen Hengchang Chemical Co., Ltd.; 2,2-Azobisisobutyronitrile (78-67-1, 99%): Shandong Weijin Chemical Technology Co., Ltd.; Epoxidized soybean oil (8013-07-8, 99%): Tesco Chemical (Hubei) Co., Ltd.; Waterborne polyurethane adhesive: Shanghai Yiwang New Materials Technology Co., Ltd., under the product number WT. Products sold by 3200: N-isopropyl-N'-phenyl-p-phenylenediamine (101-72-4, 99%): Hubei Guangao Biotechnology Co., Ltd.; Paraffin oil (8012-95-1, 99%): Hubei Yongkuo Technology Co., Ltd.; Boron nitride (10043-11-5, 99.9%, 100nm): Anhui Kerun Nanotechnology Co., Ltd.; Guanidine phosphate (5423-23-4, 99%): Hubei Yongkuo Technology Co., Ltd.; Phosphomolybdic acid (51429-74-4, 99%): Wuhan Nengren Pharmaceutical Chemical Co., Ltd.; 30% hydrogen peroxide (analytical grade, commercially available).

[0021] Performance testing: The epidermis prepared in the examples and comparative examples was tested: Pencil hardness test: According to GB / T 6739-2022 standard, a 9H-6B series hardness pencil was selected and scratched at a 45° angle on the coating surface with a load of 750g.

[0022] Abrasion Resistance: The Taber abrasion resistance test uses a CS-10 grinding wheel. The sample is cut into a circle with a diameter of 100mm and a center hole, fixed on a turntable, and a 500g weight is loaded. The mass loss after 1000 revolutions is recorded. Before the test, the initial mass m0 of the sample is accurately weighed. After the test, the sample is cleaned to remove loose debris and the final mass m1 is accurately weighed. The mass loss Δm is calculated as follows: Δm = m0 - m1 (mg).

[0023] Flame retardancy: Using a UL94 vertical burning tester, the samples were cut into standard dimensions of 125mm × 13mm × 3mm and vertically fixed on the sample holder. A methane flame (flame height 20mm) was applied to the lower end of the sample for 10 seconds, and the burning time, whether the dripping material ignited the absorbent cotton, and the self-extinguishing time were recorded. Five samples were tested in each group, and the V-0, V-1, or V-2 rating was determined based on the burning behavior.

[0024] Humidity and heat aging test: A constant temperature and humidity test chamber was used. The coated part samples were prepared with dimensions of 100mm × 100mm × 1.2mm and placed in the test chamber. The conditions were set at 85℃ and 85%RH, and the samples were continuously exposed for 500 hours. During the test, the samples were taken out every 24 hours and visually inspected according to ISO 4892-3 standard. Defects such as discoloration, blistering, and delamination were visually evaluated. The surface hardness change was measured according to ASTM D2240. A Shore A hardness change of ≤5° was considered acceptable.

[0025] The test results are as follows: Table 1 The analysis results are as follows: Combining Example 1 with Comparative Examples 1, 2, and 3, and referring to the data in Table 1, it can be seen that the introduction of modified EPDM rubber and various functional additives significantly improved the hardness of the material. By synergistically adjusting the vulcanization system and filler system, the surface hardness of the material exhibited good consistency. In the modified EPDM rubber, the double bonds of the EPDM rubber react with the mercapto groups of 3-mercaptopropionic acid, introducing carboxyl groups to form hydrogen bonds with the hydroxyl groups on the surface of the inorganic filler. This crosslinks with zinc ions in the ethylene-zinc acrylate ionomer, enhancing interfacial adhesion. The flexible sulfide bonds absorb stress, increasing crack propagation resistance and improving tear strength and resistance to damp heat aging. The ionic crosslinking network of the ethylene-zinc acrylate ionomer collectively enhances surface rigidity. The thermoplastic elastomer polystyrene melts at high temperatures, crosslinking with the modified EPDM rubber to form a thermoplastic vulcanizate, significantly improving scratch resistance. The high crosslinking density of the modified EPDM rubber improves the elastic recovery rate. Test results show that the modified material exhibits high performance in pencil hardness and abrasion resistance tests, meeting the requirements for high scratch resistance.

[0026] In addition, the flame retardant and modified boron nitride synergistically enhance the flame retardant properties of the material, enabling it to maintain good flame retardant performance even at high temperatures, achieving a UL94V-0 rating. This effectively prevents the material from burning and thermally decomposing, thus improving its safety. The material also maintains good physical properties under high temperature and humidity conditions, exhibiting excellent resistance to damp heat aging. Modified boron nitride can also improve surface hardness and scratch resistance. Without its addition during the preparation process, the pencil hardness will decrease, scratches will be visible under load, and the flame retardancy and durability will deteriorate.

[0027] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A manufacturing process for a highly scratch-resistant automotive armrest covering, characterized in that, The preparation process includes the following steps: S1: Heat up, dry the thermoplastic elastomer and polyolefin grafted maleic anhydride for 2-3 hours and mix them together, add modified EPDM rubber, vulcanizing agent, crosslinking agent and antioxidant, heat up and vulcanize and mix for 10-20 minutes to obtain vulcanized rubber. S2: Add ethylene-zinc acrylate ionomer and inorganic filler to vulcanized rubber, stir for 10-20 minutes, extrude with a twin-screw extruder, add modified boron nitride and flame retardant to the side feed port, melt blend, and cut into pellets underwater to obtain the molding compound; S3: Injection molding with the prepared mold material to obtain the skin; plasma treatment of the car armrest, spraying water-based polyurethane adhesive on the outer surface, placing the skin on the outer surface of the car armrest, hot pressing, cutting, rolling, and welding, heat setting in an oven at 70-80℃ for 1-3 hours to obtain the car armrest covering.

2. The manufacturing process of a high scratch-resistant automotive armrest covering according to claim 1, characterized in that, By weight, in step S1, the raw material composition of the vulcanized rubber is: 25-35 parts thermoplastic elastomer, 5-8 parts polyolefin grafted maleic anhydride, 45-60 parts modified EPDM rubber, 0.5-1 parts vulcanizing agent, 0.3-0.8 parts co-crosslinking agent, and 0.2-0.5 parts antioxidant.

3. The manufacturing process of a high scratch-resistant automotive armrest covering according to claim 1, characterized in that, By weight, in step S2, the raw material composition of the molding compound is: 90-100 parts vulcanized rubber, 8-12 parts ethylene-zinc acrylate ionomer, 15-25 parts inorganic filler, 15-30 parts flame retardant, and 3-5 parts modified boron nitride.

4. The manufacturing process of a high scratch-resistant automotive armrest covering according to claim 1, characterized in that, The thermoplastic elastomer is one or more of hydrogenated polystyrene-butadiene copolymer, styrene-butadiene-styrene block copolymer, and styrene-ethylene-propylene-styrene block copolymer; the antioxidant is one or more of pentaerythritol tetrakis[β-propionate], 2,4-di(n-octylthionyl)-6-methylphenol, and tris(2,4-di-tert-butylphenyl) phosphite; the polyolefin grafted with maleic anhydride is an ethylene-octene copolymer grafted with maleic anhydride.

5. The manufacturing process of a high scratch-resistant automotive armrest covering according to claim 4, characterized in that, The preparation process of the ethylene-octene copolymer grafted with maleic anhydride is as follows: ethylene-octene copolymer, maleic anhydride and initiator are mixed at a mass ratio of 100:1:0.15 and melt-extruded; the extruder temperature is 160-180℃ and the screw speed is 240-280r / min.

6. The manufacturing process of a high scratch-resistant automotive armrest covering according to claim 1, characterized in that, The inorganic filler is one or more of the following: talc, mica, wollastonite, barium sulfate, carbon black, silica, and titanium dioxide; the flame retardant is one of the following: zinc borate, hypophosphite, aluminum hydroxide, and magnesium hydroxide; and the skin thickness is 1.0-1.5 mm.

7. The manufacturing process of a high scratch-resistant automotive armrest covering according to claim 1, characterized in that, The preparation process of the modified EPDM rubber is as follows: heat to 60-80℃, plasticize EPDM rubber on a two-roll mill for 5-10 min, add 3-mercaptopropionic acid and 2,2-azobisisobutyronitrile and react for 10-20 min, then add paraffin oil, antioxidant and epoxidized soybean oil in sequence and mix for 15-30 min, then sheet after thin-passing to obtain modified EPDM rubber.

8. The manufacturing process of a high scratch-resistant automotive armrest covering according to claim 7, characterized in that, The modified EPDM rubber, by weight, comprises the following raw materials: 50-65 parts EPDM rubber, 6-10 parts 3-mercaptopropionic acid, 1-3 parts 2,2-azobisisobutyronitrile, 0.5-1.5 parts antioxidant, 6-10 parts paraffin oil, and 0.5-1.0 parts epoxidized soybean oil.

9. The manufacturing process of a high scratch-resistant automotive armrest covering according to claim 1, characterized in that, The preparation process of the modified boron nitride is as follows: boron nitride is added to a 30% hydrogen peroxide aqueous solution, stirred for 5-10 min, sonicated for 1-2 h, centrifuged, washed, and dried to obtain hydroxylated boron nitride; hydroxylated boron nitride is dispersed in deionized water, sonicated for 10-20 min, guanidine phosphate is added, stirred at 80-90℃ for 6-8 h, centrifuged, washed, and centrifuged again to obtain boron nitride-guanidine phosphate; boron nitride-guanidine phosphate is sonicated and dispersed in deionized water, phosphomolybdic acid hydrate is added, reacted for 10-12 h, centrifuged, washed, centrifuged again, and dried to obtain modified boron nitride.

10. A highly scratch-resistant automotive armrest cover, characterized in that, It is prepared according to any one of the preparation processes described in claims 1-9.

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