A rubber composition for a shoulder pad and a method for producing the same

Abstract

The application relates to the technical field of rubber materials, and provides a rubber composition for a shoulder pad and a preparation method thereof, raw materials of the rubber composition including a rubber matrix, a functional additive, an interface modifier, a reinforcing agent and a processing additive; the rubber matrix includes natural rubber, ethylene-propylene-diene rubber and butadiene rubber; the functional additive includes a thermotropic liquid crystal polymer; the interface modifier is a maleic anhydride graft; and the processing additive includes an antioxidant, a plasticizer, a vulcanizing agent, an accelerator and an activator. The thermotropic liquid crystal polymer forms a micro-fibrillar heat conduction channel in the rubber matrix, and the maleic anhydride graft forms a chemical bond to reduce the interface thermal resistance, so that the technical bottleneck that the traditional shoulder pad is difficult to simultaneously consider heat dissipation and low heat generation is broken, and the synchronous optimization of the heat dissipation performance and the heat generation performance is realized.

Description

Technical Field

[0001] This invention relates to the field of rubber materials, and more specifically to a rubber composition for tire shoulder pad adhesive and its preparation method. Background Technology

[0002] The tire shoulder pad rubber is located below the transition area between the tire tread and sidewall, playing a crucial role in buffering stress and filling gaps. This area is subjected to high-frequency flexural deformation during tire rolling, making it prone to heat accumulation. If heat dissipation is inadequate, it can lead to thermo-oxidative aging of the rubber, decreased adhesion, and even premature damage such as shoulder gaps and delamination. Therefore, an ideal tire shoulder pad rubber needs to possess both low heat generation and high heat dissipation characteristics.

[0003] In existing technologies, CN110591234A employs the addition of high thermal conductivity fillers, such as silicon carbide, alumina, and graphene, to improve the heat dissipation performance of rubber compounds. However, the large modulus difference between inorganic fillers and the rubber matrix leads to significant interfacial friction, resulting in increased hysteresis loss and thus increased heat generation under high-frequency dynamic strain, creating a vicious cycle of heat dissipation through filler addition but increased heat generation. On the other hand, to reduce heat generation, existing technology CN116178805B uses methods such as optimizing filler dispersion, using low-hysteresis rubber (such as butadiene rubber), or adding silane coupling agents. However, these methods have extremely limited effects on improving thermal conductivity and cannot solve the temperature rise problem caused by heat accumulation. Therefore, existing technologies consistently struggle to achieve the dual goals of high heat dissipation and low heat generation.

[0004] Therefore, further improvements and development are still needed. Summary of the Invention

[0005] To address the shortcomings of existing technologies and solve the aforementioned problems, a rubber composition for tire shoulder pads and its preparation method are proposed, and the following technical solution is provided:

[0006] A rubber composition for tire shoulder pad adhesive, the raw materials of which include a rubber matrix, functional additives, interface modifiers, reinforcing agents, and processing aids;

[0007] The rubber matrix includes natural rubber, EPDM rubber, and butadiene rubber.

[0008] The functional additives include thermotropic liquid crystal polymers.

[0009] The interface modifier is a maleic anhydride graft.

[0010] The processing aids include antioxidants, plasticizers, vulcanizing agents, and accelerators;

[0011] By weight, the raw materials of the rubber composition for tire shoulder pad rubber include 30-50 parts natural rubber, 20-40 parts EPDM rubber, 20-30 parts butadiene rubber, 3-15 parts functional additives, 5-12 parts maleic anhydride grafts, 3-6 parts antioxidants, 2-5 parts plasticizers, 40-60 parts reinforcing agents, 1.5-3 parts vulcanizing agents, and 3-8 parts accelerators.

[0012] Furthermore, the mass ratio of the thermotropic liquid crystal polymer to the maleic anhydride graft is 0.3-0.7:1.

[0013] Furthermore, the average particle size of the thermotropic liquid crystal polymer is less than 50 μm.

[0014] The thermotropic liquid crystal polymer is subjected to low-temperature pulverization or airflow pulverization to control its average particle size to below 50 μm.

[0015] Preferably, the thermotropic liquid crystal polymer has an average particle size of 10-30 μm.

[0016] Furthermore, the functional additives also include a polyolefin elastomer, which is pre-melted with a thermotropic liquid crystal polymer at a temperature of 200-250°C.

[0017] The thermotropic liquid crystal mixture and the polyolefin elastomer are blended using a twin-screw extruder at 200-250°C to obtain a masterbatch. In the masterbatch, the thermotropic liquid crystal polymer is dispersed in the polyolefin elastomer matrix in the form of microfibrils or microregions.

[0018] Furthermore, the mass ratio of the thermotropic liquid crystal polymer to the polyolefin elastomer is 0.5-1.2:1.

[0019] Furthermore, the polyolefin elastomer includes at least one of ethylene-octene copolymer, ethylene-butene copolymer, or ethylene-propylene copolymer.

[0020] Furthermore, the thermotropic liquid crystal polymer is at least one of liquid crystal polyester or liquid crystal polyesteramide, and the maleic anhydride graft is at least one of maleic anhydride-grafted EPDM rubber or maleic anhydride-grafted polyolefin elastomer.

[0021] The thermotropic liquid crystal polymer is selected from at least one of Vectra RD501 (Celanis: trade name), Vectra B950 (Celanis: trade name), SumikaSuper LCP E5008 (Sumitomo Chemical Co., Ltd.: trade name), and SumikaSuper LCPE52008 (Sumitomo Chemical Co., Ltd.: trade name). The polyolefin elastomer is selected from at least one of Engage 8150 (Dow Chemical: trade name), Engage 8200 (Dow Chemical: trade name), Exact 8210 (ExxonMobil: trade name), TAFMER DF610 (Mitsui Chemicals: trade name), TAFMER DF940 (Mitsui Chemicals: trade name), and TAFMER DF810 (Mitsui Chemicals: trade name).

[0022] Furthermore, the antioxidant includes at least two of antioxidant 4020, antioxidant RD, and microcrystalline wax; the plasticizer includes at least one of environmentally friendly aromatic oil, homogenizer, and stearic acid; the reinforcing agent is carbon black; the vulcanizing agent is sulfur; and the accelerator is at least one of zinc methacrylate and nano-active zinc oxide.

[0023] The present invention also provides a method for preparing a rubber composition for a tire shoulder pad, comprising the following steps:

[0024] The rubber matrix, interface modifier, functional additives and reinforcing agent are mixed and milled, and then left to stand for 4-24 hours before final milling. Processing aids are added during the final milling process. After the final milling is completed, vulcanization is carried out to obtain a rubber composition for tire shoulder pad rubber.

[0025] Furthermore, the mixing temperature is 100℃-180℃, and the mixing process includes mixing at a speed of 40-50 rpm for 60-90 seconds, then increasing the speed to 70-80 rpm and mixing for 30-40 seconds, then reducing the speed to 40-70 rpm and maintaining the mixing for 30-60 seconds, at which point the mixing is complete.

[0026] Due to the adoption of the above technical solutions, the beneficial technical effects of the present invention are as follows:

[0027] 1. This invention forms microfiber-like thermally conductive channels in a rubber matrix through a thermotropic liquid crystal polymer, and forms chemical bonds with maleic anhydride grafts to reduce interfacial thermal resistance. This design breaks through the technical bottleneck of traditional tire shoulder rubber, which is difficult to balance heat dissipation and low heat generation, and achieves simultaneous optimization of heat dissipation performance and heat generation performance.

[0028] 2. This invention pre-mixes and granulates thermotropic liquid crystal polymers with polyolefin elastomers, so that the thermotropic liquid crystal polymers (LCPs) are pre-melted into fibers and then uniformly dispersed in the rubber matrix during mixing. This avoids the risk of thermal damage to natural rubber caused by high-temperature mixing and allows existing conventional internal mixers to use high-performance LCPs without modification. At the same time, the pre-formed microfiber structure in the masterbatch ensures the stability of the heat conduction network. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application.

[0030] Unless otherwise specified in the examples, standard conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products. Unless otherwise specified, all reagents used in the examples are commercially available.

[0031] A rubber composition for tire shoulder adhesive, the raw materials of which include a rubber matrix, functional additives, interface modifiers, reinforcing agents, and processing aids;

[0032] The rubber matrix includes natural rubber (NR), ethylene propylene diene monomer (EPDM) rubber, and butadiene rubber (BR).

[0033] The functional additives include thermotropic liquid crystal polymers.

[0034] The interface modifier is a maleic anhydride graft.

[0035] The processing aids include antioxidants, plasticizers, vulcanizing agents, accelerators, and activators.

[0036] During the mixing and open milling stages of rubber, thermotropic liquid crystal polymers (LCPs) are dispersed and stretched into elongated fibers under shear force. During this stretching process, the rigid molecular chains of the thermotropic liquid crystals are highly oriented along the fiber axis; this regular arrangement is called microfiber. The elongated microfibers are then fixed within the rubber matrix as the rubber temperature rapidly cools, ultimately forming a microfiber network. This microfiber network facilitates heat dissipation.

[0037] Simultaneously, the maleic anhydride graft in the rubber matrix forms covalent ester bonds with the hydroxyl groups on the LCP surface, eliminating the gaps between the LCP microfibers and the rubber matrix, thus achieving low thermal resistance and high strength. This allows for smooth heat dissipation and eliminates interfacial friction, resulting in high heat dissipation and low heat generation. The LCP molecular chains typically have hydroxyl or carboxyl groups at their ends, while the maleic anhydride graft contains highly reactive maleic anhydride rings. During the mixing and vulcanization processes, these maleic anhydride rings open and undergo esterification with the hydroxyl groups on the LCP surface to form ester bonds. The maleic anhydride graft is completely compatible with the rubber matrix (NR / EPDM / BR) and undergoes co-vulcanization with the rubber molecular chains during vulcanization. These ester bonds eliminate the gaps between the rubber matrix and the microfiber network, forming a continuous energy transfer path. Phonons can enter the highly oriented LCP microfibers from the rubber lattice through chemical bonds and then rapidly exit along the microfibers, thereby increasing the thermal conductivity of the rubber. Chemical bonds fix LCP microfibers to the rubber network. During deformation, stress is directly transferred to the LCP microfibers through chemical bonds, and no friction occurs at the interface, thereby reducing the heat generation of the rubber.

[0038] The average particle size of the thermotropic liquid crystal polymer is less than 50 μm. By controlling the average particle size of the thermotropic liquid crystal polymer to below 50 μm (preferably 10-30 μm) and by using low-temperature milling or airflow milling, the melting temperature requirement of the LCP is significantly reduced.

[0039] The functional additives also include polyolefin elastomers, which are pre-melted with thermotropic liquid crystal polymers at a temperature of 200-250°C.

[0040] The functional additives are blended with a thermotropic liquid crystal polymer (LCP) and a polyolefin elastomer (POE) using a twin-screw extruder at 200-250°C. The LCP is dispersed in the polyolefin elastomer matrix as microfibrils or microregions. The LCP is pre-blended with the polyolefin elastomer, allowing it to melt and form microfibrils or microregions within the POE carrier. This approach avoids the high-temperature requirements of the rubber compounding process, while the pre-formed microfibril structure ensures the stability of the thermally conductive network, avoiding the risk of fiber formation failure due to uneven temperature fields in in-situ fiber formation processes.

[0041] The maleic anhydride graft is at least one of maleic anhydride-grafted EPDM rubber or maleic anhydride-grafted polyolefin elastomer. Using maleic anhydride-grafted EPDM rubber or maleic anhydride-grafted polyolefin elastomer as an interface modifier, its main chain structure is completely identical to that of EPDM in the rubber matrix or POE in the masterbatch, enabling complete compatibility and co-curing with the matrix.

[0042] The present invention also provides a method for preparing a rubber composition for tire shoulder pad adhesive, comprising the following steps:

[0043] The rubber matrix, interface modifier, functional additives, and reinforcing agents are mixed and open-milled, then left to stand for 4-24 hours before final milling. Processing aids are added during final milling. After final milling, vulcanization is performed to obtain the rubber composition for tire shoulder pads. The preparation process employs mixing-open milling-standing-final milling-vulcanization, avoiding mutual interference between functional components through stepwise dispersion. High-temperature masterbatch melting disperses the LCP, while thin-pass milling stretches the LCP into fibers and rapidly cools and sets them. A 4-24 hour standing period allows for sufficient interfacial reaction.

[0044] The mixing temperature is 100℃-180℃. The mixing process includes mixing at a speed of 40-50 rpm for 60-90 seconds, then increasing the speed to 70-80 rpm and mixing for 30-40 seconds, then reducing the speed to 40-70 rpm and maintaining the mixing for 30-60 seconds to complete the mixing. The first stage involves mixing at a low speed of 40-50 rpm for 60-90 seconds to soften the rubber matrix and coat the LCP. The second stage involves increasing the speed to 70-80 rpm and using strong shear to stretch the molten LCP into microfibers. The third stage involves reducing the speed to 40-70 rpm and maintaining the mixing for 30-60 seconds. Before the fibers cool, a constraint force in one stretching direction is continuously applied to prevent the molecular chains from curling back and to ensure that the high aspect ratio of the microfibers is maintained.

[0045] Example 1

[0046] In this embodiment, the functional additive is a thermotropic liquid crystal polymer.

[0047] Vectra RD501 thermotropic liquid crystal polymer was fed into an air jet mill, and the milling pressure was controlled at 0.8 MPa and the classifier speed was 4000 rpm to prepare micronized thermotropic liquid crystal polymer with an average particle size of 28 μm (detected by laser particle size analyzer, D50=28 μm).

[0048] 40 parts of natural rubber, 30 parts of EPDM rubber, 25 parts of butadiene rubber, 10 parts of maleic anhydride-grafted EPDM rubber, 5 parts of thermotropic liquid crystal polymer, and 50 parts of carbon black were mixed in an internal mixer.

[0049] The mixing temperature is 175℃. The speed is controlled at 45 rpm for 80 seconds. Then the speed is increased to 75 rpm and mixed for 30 seconds. Finally, the speed is reduced to 60 rpm and mixed for 40 seconds. The mixing is then complete.

[0050] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0051] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, one part of antioxidant RD, three parts of environmentally friendly aromatic oil, five parts of nano-active zinc oxide, and two parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 35 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0052] Example 2

[0053] The functional additives used in this embodiment are thermotropic liquid crystal polymers and polyolefin elastomers.

[0054] The preparation process of the functional additive in this embodiment is as follows: 5 parts of Vectra RD501 and 8 parts of Engage 8200 are fed into a twin-screw extruder. The barrel temperature is set as follows: feeding section 180℃, compression section 220℃, metering section 240℃, die head 240℃; screw speed 300 rpm; after melt blending, extrusion granulation is performed to obtain masterbatch. In the masterbatch, LCP is uniformly dispersed in the POE matrix as microfibers.

[0055] 40 parts of natural rubber, 30 parts of EPDM rubber, 25 parts of butadiene rubber, 10 parts of maleic anhydride-grafted polyolefin elastomer, 13 parts of the above masterbatch, and 50 parts of carbon black are mixed in an internal mixer.

[0056] The mixing temperature is 175℃. The speed is controlled at 45 rpm for 80 seconds. Then the speed is increased to 75 rpm and mixed for 30 seconds. Finally, the speed is reduced to 60 rpm and mixed for 40 seconds. The mixing is then complete.

[0057] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0058] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, one part of antioxidant RD, three parts of environmentally friendly aromatic oil, five parts of zinc methacrylate, and two parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 40 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0059] Example 3

[0060] Compared to Example 1, this example changes the mass ratio of the thermotropic liquid crystal polymer to the maleic anhydride graft. The specific scheme is as follows:

[0061] Vectra RD501 thermotropic liquid crystal polymer was fed into an air jet mill, and the milling pressure was controlled at 0.8 MPa and the classifier speed was 4000 rpm to prepare micronized thermotropic liquid crystal polymer with an average particle size of 28 μm (detected by laser particle size analyzer, D50=28 μm).

[0062] 40 parts of natural rubber, 30 parts of EPDM rubber, 25 parts of butadiene rubber, 10 parts of maleic anhydride-grafted EPDM rubber, 3 parts of thermotropic liquid crystal polymer, and 50 parts of carbon black were mixed in an internal mixer.

[0063] The mixing temperature is 175℃. The speed is controlled at 45 rpm for 80 seconds. Then the speed is increased to 75 rpm and mixed for 30 seconds. Finally, the speed is reduced to 60 rpm and mixed for 40 seconds. The mixing is then complete.

[0064] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0065] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, one part of antioxidant RD, three parts of environmentally friendly aromatic oil, five parts of nano-active zinc oxide, and two parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 35 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0066] Example 4

[0067] Compared to Example 1, this example changes the mass ratio of the thermotropic liquid crystal polymer to the maleic anhydride graft. The specific scheme is as follows:

[0068] Vectra RD501 thermotropic liquid crystal polymer was fed into an air jet mill, and the milling pressure was controlled at 0.8 MPa and the classifier speed was 4000 rpm to prepare micronized thermotropic liquid crystal polymer with an average particle size of 28 μm (detected by laser particle size analyzer, D50=28 μm).

[0069] 40 parts of natural rubber, 30 parts of EPDM rubber, 25 parts of butadiene rubber, 10 parts of maleic anhydride-grafted EPDM rubber, 7 parts of thermotropic liquid crystal polymer, and 50 parts of carbon black were mixed in an internal mixer.

[0070] The mixing temperature is 140℃. The speed is controlled at 45 rpm for 80 seconds. Then the speed is increased to 75 rpm and mixed for 30 seconds. Finally, the speed is reduced to 60 rpm and mixed for 40 seconds. The mixing is then complete.

[0071] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0072] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, one part of antioxidant RD, three parts of environmentally friendly aromatic oil, five parts of nano-active zinc oxide, and two parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 35 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0073] Example 5

[0074] Compared to Example 2, this example changes the mass ratio of thermotropic liquid crystal polymer to polyolefin elastomer in the masterbatch. The specific scheme is as follows:

[0075] The preparation process of the functional additive in this embodiment is as follows: 5 parts of Vectra RD501 and 10 parts of Exact 8210 are fed into a twin-screw extruder. The barrel temperature is set as follows: feeding section 180℃, compression section 220℃, metering section 240℃, die head 240℃; screw speed 300 rpm; after melt blending, extrusion granulation is performed to obtain masterbatch. In the masterbatch, LCP is uniformly dispersed in the POE matrix as microfibers.

[0076] 40 parts of natural rubber, 30 parts of EPDM rubber, 25 parts of butadiene rubber, 10 parts of maleic anhydride-grafted polyolefin elastomer, 15 parts of the above masterbatch, and 50 parts of carbon black are mixed in an internal mixer.

[0077] The mixing temperature is 100℃. The speed is controlled at 45 rpm for 80 seconds. Then the speed is increased to 75 rpm and mixed for 30 seconds. The speed is then reduced to 60 rpm and mixed for 40 seconds. The mixing is now complete.

[0078] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0079] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, one part of antioxidant RD, three parts of environmentally friendly aromatic oil, five parts of zinc methacrylate, and two parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 40 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0080] Example 6

[0081] Compared to Example 2, this example changes the mass ratio of thermotropic liquid crystal polymer to polyolefin elastomer in the masterbatch. The specific scheme is as follows:

[0082] The preparation process of the functional additive in this embodiment is as follows: 5 parts of Vectra RD501 and 4 parts of TAFMER DF940 are fed into a twin-screw extruder. The barrel temperature is set as follows: feeding section 180℃, compression section 220℃, metering section 240℃, die head 240℃; screw speed 300 rpm; after melt blending, extrusion granulation is performed to obtain masterbatch. In the masterbatch, LCP is uniformly dispersed in the POE matrix as microfibers.

[0083] 40 parts of natural rubber, 30 parts of EPDM rubber, 25 parts of butadiene rubber, 10 parts of maleic anhydride-grafted polyolefin elastomer, 9 parts of the above masterbatch, and 50 parts of carbon black are put into an internal mixer and mixed.

[0084] The mixing temperature is 175℃. The speed is controlled at 45 rpm for 80 seconds. Then the speed is increased to 75 rpm and mixed for 30 seconds. Finally, the speed is reduced to 60 rpm and mixed for 40 seconds. The mixing is then complete.

[0085] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0086] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, one part of antioxidant RD, three parts of environmentally friendly aromatic oil, five parts of zinc methacrylate, and two parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 40 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0087] Example 7

[0088] Compared with Example 1, this example changes the formulation and processing parameters of the rubber composition for tire shoulder pad adhesive.

[0089] In this embodiment, the functional additive is a thermotropic liquid crystal polymer.

[0090] Vectra RD501 thermotropic liquid crystal polymer was fed into an air jet mill, and the milling pressure was controlled at 0.8 MPa and the classifier speed was 4000 rpm to prepare micronized thermotropic liquid crystal polymer with an average particle size of 28 μm (detected by laser particle size analyzer, D50=28 μm).

[0091] 50 parts of natural rubber, 40 parts of EPDM rubber, 30 parts of butadiene rubber, 12 parts of maleic anhydride-grafted EPDM rubber, 15 parts of thermotropic liquid crystal polymer, and 60 parts of carbon black were mixed in an internal mixer.

[0092] The mixing temperature is 180℃. The speed is controlled at 50 rpm for 90 seconds. Then the speed is increased to 80 rpm and mixed for 40 seconds. The speed is then reduced to 70 rpm and mixed for 60 seconds. The mixing is now complete.

[0093] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0094] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Four parts of antioxidant 4020, two parts of antioxidant RD, five parts of environmentally friendly aromatic oil, eight parts of nano-active zinc oxide, and three parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 25 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0095] Example 8

[0096] Compared with Example 1, this example changes the formulation and processing parameters of the rubber composition for tire shoulder pad adhesive.

[0097] In this embodiment, the functional additive is a thermotropic liquid crystal polymer.

[0098] Vectra RD501 thermotropic liquid crystal polymer was fed into an air jet mill, and the milling pressure was controlled at 0.8 MPa and the classifier speed was 4000 rpm to prepare micronized thermotropic liquid crystal polymer with an average particle size of 28 μm (detected by laser particle size analyzer, D50=28 μm).

[0099] 30 parts of natural rubber, 20 parts of EPDM rubber, 20 parts of butadiene rubber, 12 parts of maleic anhydride-grafted EPDM rubber, 6 parts of thermotropic liquid crystal polymer, and 40 parts of carbon black were mixed in an internal mixer.

[0100] The mixing temperature is 170℃. The speed is controlled at 40 rpm for 60 seconds. Then the speed is increased to 70 rpm and mixed for 30 seconds. The speed is then reduced to 40 rpm and mixed for 30 seconds. The mixing is now complete.

[0101] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0102] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, four parts of antioxidant RD, three parts of environmentally friendly aromatic oil, two parts of nano-active zinc oxide, and 1.5 parts of sulfur were added. The mixture was stirred until homogeneous at a temperature controlled at ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 30 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0103] Example 9

[0104] Compared to Example 1, the average particle size of the thermotropic liquid crystal polymer in this example is changed.

[0105] Vectra RD501 thermotropic liquid crystal polymer was fed into an air jet mill, and the milling pressure was controlled at 0.8 MPa and the classifier speed was 4000 rpm to prepare micronized thermotropic liquid crystal polymer with an average particle size of 42 μm (detected by laser particle size analyzer, D50=42 μm).

[0106] 40 parts of natural rubber, 30 parts of EPDM rubber, 25 parts of butadiene rubber, 10 parts of maleic anhydride-grafted EPDM rubber, 5 parts of thermotropic liquid crystal polymer, and 50 parts of carbon black were mixed in an internal mixer.

[0107] The mixing temperature is 175℃. The speed is controlled at 45 rpm for 80 seconds. Then the speed is increased to 75 rpm and mixed for 30 seconds. Finally, the speed is reduced to 60 rpm and mixed for 40 seconds. The mixing is then complete.

[0108] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0109] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, one part of antioxidant RD, three parts of environmentally friendly aromatic oil, five parts of nano-active zinc oxide, and two parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 35 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0110] Comparative Example 1

[0111] Compared with Example 1, this comparative example does not contain a thermotropic liquid crystal polymer, but all other aspects are the same as in Example 1.

[0112] Comparative Example 2

[0113] Compared with Example 2, this comparative example does not contain a thermotropic liquid crystal polymer, but all other aspects are the same as in Example 2.

[0114] Comparative Example 3

[0115] Compared with Example 1, the mass ratio of the thermotropic liquid crystal polymer to the maleic anhydride graft in this comparative example is 1.5:1, and all other aspects are the same as in Example 1.

[0116] Comparative Example 4

[0117] Compared with Example 2, the mass ratio of thermotropic liquid crystal polymer to polyolefin elastomer in the masterbatch of this comparative example is 2:1, and all other aspects are the same as in Example 2.

[0118] Comparative Example 5

[0119] Compared with Example 1, the mixing process of this comparative example is different, but all other aspects are the same as in Example 1.

[0120] The specific process for this comparative example is as follows:

[0121] Vectra RD501 thermotropic liquid crystal polymer was fed into an air jet mill, and the milling pressure was controlled at 0.8 MPa and the classifier speed was 4000 rpm to prepare micronized thermotropic liquid crystal polymer with an average particle size of 28 μm (detected by laser particle size analyzer, D50=28 μm).

[0122] 40 parts of natural rubber, 30 parts of EPDM rubber, 25 parts of butadiene rubber, 10 parts of maleic anhydride-grafted EPDM rubber, 5 parts of thermotropic liquid crystal polymer, and 50 parts of carbon black were mixed in an internal mixer.

[0123] The mixing temperature is 175℃, and the mixing speed is controlled at 45 rpm for 150 seconds to complete the mixing.

[0124] The discharged high-temperature rubber compound is immediately fed onto an open mill (roller temperature 45℃, roll gap 1.5mm) and passed through it 5 times to stretch the LCP into fibers and rapidly cool and set them. After being sheeted, it is left to stand for 12 hours.

[0125] The masterbatch, after being left to stand, was put back into the internal mixer for final mixing. Two parts of antioxidant 4020, one part of antioxidant RD, three parts of environmentally friendly aromatic oil, five parts of nano-active zinc oxide, and two parts of sulfur were added. The mixture was stirred until homogeneous at a controlled temperature of ≤105℃, and then discharged to obtain the final rubber compound. The final rubber compound was then vulcanized at 150℃ for 35 minutes on a flat vulcanizing machine to obtain a rubber composition for tire shoulder pads.

[0126] Test Example 1

[0127] The heat dissipation performance of the rubber compositions for tire shoulder pads obtained in Examples 1-9 and Comparative Examples 1-5 was determined according to GB / T 11205-2009.

[0128] The thermal conductivity of the rubber composition was determined using a heat flow meter method. The vulcanized sample was cut into circular pieces with a diameter of 50 mm and a thickness of 5 mm. These pieces were placed between the upper and lower plates of the heat flow meter, with the hot plate temperature set to 40°C and the cold plate temperature to 20°C. Appropriate pressure was applied to ensure close contact between the sample and the plate surfaces. After the heat flow stabilized, the heat flow rate through the sample and the temperature difference between the upper and lower surfaces were recorded. The thermal conductivity λ (W / m·K) was calculated using Fourier's law of thermal conductivity. Each sample was tested three times, and the average value was taken as the final result.

[0129] Test Example 2

[0130] The heat generation properties of the rubber compositions for tire shoulder pads obtained in Examples 1-9 and Comparative Examples 1-5 were determined according to GB / T 1687.3-2016.

[0131] The compression temperature rise of the rubber composition was determined using a compression heat generation tester. The vulcanized sample was prepared as a cylinder with a diameter of 17.8 mm and a height of 25 mm. After preheating in a 55℃ constant temperature chamber, it was placed in the tester, and a load of 1.0 MPa was applied. The stroke was adjusted to 4.45 mm, and periodic compression-flexure tests were conducted at a frequency of 30 Hz. During the test, the temperature at the bottom of the sample was continuously monitored using thermocouples, and the maximum temperature rise ΔT (℃) within 25 min was recorded to characterize the heat generation performance. Each sample was tested three times, and the average value was taken.

[0132] The results of test example 1-2 are shown in Table 1 below.

[0133] Table 1 Performance tests of the rubber compositions for tire shoulder pads obtained in Examples 1-9 and Comparative Examples 1-5

[0134]

[0135] This invention significantly improves the thermal conductivity of the tire shoulder pad adhesive and reduces the compression temperature rise by introducing a thermotropic liquid crystal polymer (LCP), demonstrating the core role of LCP in constructing an efficient thermally conductive network and reducing interfacial friction. Specifically, Examples 2, 5, and 6, using an LCP / polyolefin elastomer (POE) masterbatch method, exhibited superior thermal conductivity and heat generation properties compared to the direct addition of LCP in Examples 1, 3, and 4, confirming that masterbatch technology facilitates the uniform dispersion of LCP and the effective formation of the microfiber network. In Examples 3 and 4, the mass ratio of LCP to maleic anhydride graft (MAH) was controlled at 0.3-0. Within the 0.7:1 range, performance optimization is crucial, but the imbalanced ratio of LCP to maleic anhydride graft in Comparative Example 3 leads to performance degradation. The optimal LCP particle size is 10-30 μm; for example, the excessively large 42 μm particle size in Example 9 weakens fiber-forming effect and dispersibility. Furthermore, the mass ratio of LCP to POE in the masterbatches of Examples 5 and 6 needs to be controlled within the range of 0.5-1.2:1; the excessively high ratio in Comparative Example 4 leads to poor dispersion. In addition, the three-stage variable-speed mixing process of this invention plays a key role in the in-situ fiber formation and shaping of LCP; Comparative Example 5, which did not use this process, showed significant performance degradation. In summary, this invention, through component synergy and process optimization, successfully achieves simultaneous improvement in both high heat dissipation and low heat generation of the tire shoulder pad rubber.

[0136] Test Example 3

[0137] The mechanical properties of the rubber compositions for tire shoulder pads obtained in Examples 1-9 and Comparative Examples 1-5 were measured, and the results are shown in Table 2 below.

[0138] Table 2 Mechanical property tests of the rubber compositions for tire shoulder pads obtained in Examples 1-9 and Comparative Examples 1-5

[0139]

[0140] The tensile strength of Examples 1-9 of this invention all reached above 19.9 MPa, with Example 7 reaching 23.5 MPa. This is attributed to the reinforcing effect of LCP microfibers and the interfacial chemical bonding of the maleic anhydride graft. Comparative Examples 1-5 all had tensile strengths below 19 MPa, indicating that the addition of LCP and interface optimization are crucial for strength improvement. The LCP microfiber network improved strength without excessively sacrificing elongation, demonstrating a balanced formulation design. Examples 5 and 7 of this invention both achieved tensile fatigue lives exceeding 220,000 cycles, significantly better than the 120,000-140,000 cycles of the comparative examples. This verifies the chemical bonding interface formed between the maleic anhydride graft and LCP, effectively delaying fatigue failure. The tire shoulder area is subjected to high-frequency flexural deformation, and flexural fatigue life directly reflects the rubber compound's resistance to crack propagation. Example 7 achieved a flexural fatigue life of 215,000 cycles, nearly double that of the comparative examples. This is attributed to the inhibitory effect of LCP microfibers on crack propagation, the strong interface constructed by the maleic anhydride graft, and the three-stage variable-speed process ensuring uniform microfiber dispersion. Examples 2, 5, and 6 (masterbatch method) showed better performance than Examples 1, 3, and 4 (direct addition), confirming that masterbatch modification helps to achieve uniform dispersion of LCP and effective formation of microfiber networks. Examples 5 and 6 verified the advantage of controlling the mass ratio of LCP to POE within the range of 0.5-1.2:1.

[0141] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A rubber composition for tire shoulder pad adhesive, characterized in that, Its raw materials include rubber matrix, functional additives, interface modifiers, reinforcing agents, and processing aids; The rubber matrix includes natural rubber, EPDM rubber, and butadiene rubber. The functional additive is a thermotropic liquid crystal polymer, and the average particle size of the thermotropic liquid crystal polymer is less than 50 μm. Alternatively, the functional additive is a masterbatch obtained by melt blending a thermotropic liquid crystal polymer and a polyolefin elastomer; the melt blending temperature is 200-250℃; and the mass ratio of the thermotropic liquid crystal polymer to the polyolefin elastomer is 0.5-1.2:

1. The interface modifier is a maleic anhydride graft. The mass ratio of the thermotropic liquid crystal polymer to the maleic anhydride graft is 0.3-0.7:1; The processing aids include antioxidants, plasticizers, vulcanizing agents, and accelerators; By weight, the composition includes 30-50 parts natural rubber, 20-40 parts EPDM rubber, 20-30 parts butadiene rubber, 3-15 parts functional additives, 5-12 parts maleic anhydride graft, 3-6 parts antioxidant, 2-5 parts plasticizer, 40-60 parts reinforcing agent, 1.5-3 parts vulcanizing agent, and 3-8 parts accelerator. The method for preparing the rubber composition for tire shoulder pad adhesive includes the following steps: The rubber matrix, interface modifier, functional additives and reinforcing agent are mixed and open milled, and then left to stand for 4-24 hours before final milling. Processing aids are added during the final milling process. After the final milling is completed, vulcanization is carried out to obtain a rubber composition for tire shoulder pad rubber. During the mixing process, the mixing temperature is 100℃-180℃. The mixing process includes mixing at a speed of 40-50 rpm for 60-90 seconds, then increasing the speed to 70-80 rpm and mixing for 30-40 seconds, then reducing the speed to 40-70 rpm and maintaining the mixing for 30-60 seconds, at which point the mixing is complete.

2. The rubber composition for tire shoulder pad adhesive according to claim 1, characterized in that, The polyolefin elastomer includes at least one of ethylene-octene copolymer, ethylene-butene copolymer, or ethylene-propylene copolymer.

3. The rubber composition for tire shoulder pad adhesive according to claim 1, characterized in that, The thermotropic liquid crystal polymer is at least one of liquid crystal polyester or liquid crystal polyesteramide, and the maleic anhydride graft is at least one of maleic anhydride-grafted EPDM rubber or maleic anhydride-grafted polyolefin elastomer.

4. The rubber composition for tire shoulder pad adhesive according to claim 1, characterized in that, The antioxidant includes at least two of antioxidant 4020, antioxidant RD, and microcrystalline wax; the plasticizer includes at least one of environmentally friendly aromatic oil, homogenizer, and stearic acid; the reinforcing agent is carbon black; the vulcanizing agent is sulfur; and the accelerator is at least one of zinc methacrylate and nano-active zinc oxide.

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