High-thermal-conductivity rubber for tires and preparation method of high-thermal-conductivity rubber

Abstract

The invention discloses high-thermal-conductivity rubber for tires and a preparation method of the high-thermal-conductivity rubber, and belongs to the technical field of rubber materials. The rubber comprises the following raw materials in parts by weight: 60-70 parts of natural rubber, 20-30 parts of butadiene styrene rubber, 30-40 parts of carbon black, 5-10 parts of white carbon black, 15-25 parts of core-shell porous boron nitride heat-conducting microspheres, 5-7 parts of modified aluminum oxide whiskers, 1-2 parts of a silane coupling agent, 1.5-2.5 parts of sulfur, 0.8-1.2 parts of an accelerant, 1-1.5 parts of an anti-aging agent, 4-6 parts of zinc oxide and 1-2 parts of stearic acid. Through the synergistic effect of the core-shell BN microspheres and the surface activated whiskers, a three-dimensional continuous heat-conducting network with strong interface bonding is constructed in a rubber matrix. The obtained rubber material has excellent heat-conducting property, good mechanical property and heat aging resistance, and is especially suitable for heavy duty tires with high heat dissipation requirements.

Description

Technical Field

[0001] This invention belongs to the field of rubber materials technology, specifically relating to a high thermal conductivity rubber for tires and its preparation method. Background Technology

[0002] With continuous societal progress and rising living standards, car usage has increased significantly, driving sustained growth in tire demand. However, as a flammable rubber product, tires have limited application scope, and heat dissipation performance is crucial. Compared to light-duty tires, heavy-duty tires (such as loader, truck, and bus tires) are more prone to rapid internal heat buildup under heavy loads due to insufficient thermal conductivity, causing them to operate at higher temperatures and affecting their long-term thermal durability. Improving the thermal conductivity of tire carcass materials ensures timely release of heat generated by deformation during use, effectively reducing operating temperature, protecting tire performance, and extending service life.

[0003] Currently, the main ways to improve the thermal conductivity of rubber include adding high thermal conductivity fillers (such as metal powder, carbon fiber, graphene, etc.) and optimizing the material structure design.

[0004] For example, Chinese patent application CN202310360496.2 discloses a high thermal conductivity, low heat generation rubber and its preparation method, as well as a tire. The high thermal conductivity, low heat generation rubber comprises the following raw materials in parts by weight: 100 parts natural rubber; 38-51 parts reinforcing material; 1-3 parts stearic acid; 1.5-2.5 parts antioxidant; 1-2 parts silane coupling agent; 0.5-2 parts carbon nanotube dispersion; 1-2 parts tackifying resin; 1.5-3.0 parts insoluble sulfur; 0.5-1.2 parts accelerator; 0.5-1.0 parts vulcanizing agent; 0.1-0.5 parts anti-reversion agent; and 0.1-0.3 parts anti-scorching agent.

[0005] Chinese patent application CN201610237521.8 discloses a high thermal conductivity tire triangle rubber composition, comprising the following components: 100 parts by weight of rubber main material: including 70-100 parts by weight of natural rubber and 10-30 parts by weight of emulsion styrene-butadiene rubber; compounding agents: based on 100 parts by weight of rubber main material, the compounding agents include 1-20 parts by weight of graphite powder, 60-90 parts by weight of carbon black, 5-8 parts by weight of phenolic reinforcing resin, 2-5 parts by weight of tackifying resin, 1-5 parts by weight of zinc oxide, 1-3.5 parts by weight of stearic acid, 3-8 parts by weight of environmentally friendly aromatic oil TDAE, 1-3 parts by weight of sulfur powder, 0.5-3 parts by weight of accelerator, and 1-3 parts by weight of antioxidant RD.

[0006] However, the addition of traditional single fillers often faces problems such as limited improvement in thermal conductivity or poor compatibility with the rubber matrix, leading to a decline in the mechanical properties of the rubber material and making it difficult to meet the comprehensive performance requirements of tires in actual use. Therefore, developing a tire rubber material that combines excellent thermal conductivity and good mechanical properties has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies where it is difficult to simultaneously achieve both thermal conductivity and mechanical properties in tire rubber materials, and to provide a high thermal conductivity rubber for tires and its preparation method. By optimizing the rubber matrix formulation, employing the synergistic effect of core-shell porous boron nitride thermally conductive microspheres and modified alumina whiskers, and combining this with a specific preparation process, the thermal conductivity of the rubber material is significantly improved while ensuring its good mechanical and processing properties, thus meeting the requirements of heavy-duty tires and other applications with high demands for heat dissipation and structural strength.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 60-70 parts of natural rubber NR, 20-30 parts of styrene-butadiene rubber SBR, 30-40 parts of carbon black, 5-10 parts of silica, 15-25 parts of thermally conductive filler, 5-7 parts of modified alumina whiskers, 1-2 parts of silane coupling agent, 1.5-2.5 parts of sulfur, 0.8-1.2 parts of accelerator, 1-1.5 parts of antioxidant, 4-6 parts of zinc oxide, and 1-2 parts of stearic acid; wherein the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

[0009] Furthermore, the natural rubber is smoked sheet rubber RSS3, with a Mooney viscosity ML(1+4) of 60±5 at 100°C.

[0010] Furthermore, the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere, and its preparation method is as follows: (1) Take 5.0g of hexagonal boron nitride, add 100mL of deionized water, and then add 0.3g of sodium carbonate (Na2CO3) as an activator. Mill the mixture in a planetary ball mill at 300rpm for 2h (ball-to-material ratio 10:1, grinding balls made of zirconium oxide). During milling, sodium carbonate weakens the van der Waals forces between hexagonal boron nitride particles and introduces more hydroxyl groups (-OH) onto the particle surface. After activation, wash with deionized water until pH=7, and vacuum dry at 60℃ for 4h to obtain activated hexagonal boron nitride. This step improves the dispersibility of hexagonal boron nitride and reduces the aggregate particle size. (2) Add 20.0g of polystyrene PS microspheres, 5.0g of activated hexagonal boron nitride, and 0.8g of sodium dodecylbenzene sulfonate to 1000mL of deionized water. Disperse the mixture ultrasonically at 30℃ and 500rpm for 30-40min to form a uniform suspension with a solid content of 2.5%. Send the suspension into a spray dryer and spray to obtain composite microspheres of BN-coated PS with a particle size of 6-9μm. (3) The composite microspheres were placed in a tube furnace, nitrogen gas was introduced, and the temperature was increased to 600℃ at 5℃ / min and held for 2.5h to completely carbonize the polystyrene PS microspheres and generate BN@C core-shell structure in situ, thus obtaining the porous BN microsphere core. (4) Take 10.0g of porous BN microsphere core, add 500mL of ethanol-water mixture (volume ratio 6:4), then add 2.0g of KH550, and reflux at 80℃ and 300rpm for 4h (to ensure that the amino group is grafted onto the BN surface); after the reaction, filter (filter membrane pore size 0.22μm), wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ (vacuum degree -0.09MPa) for 8h to obtain aminated BN microspheres; (5) Add the aminated BN microspheres to 200 mL of natural rubber latex (solid content 30%), add 0.15 g of initiator ammonium persulfate (APS), and react for 2 h at 60 °C and 500 rpm (APS initiates the grafting reaction between rubber molecular chains and amino groups); after the reaction, centrifuge (8000 rpm, 10 min), collect the precipitate, and vacuum dry at 60 °C for 12 h to obtain core-shell porous boron nitride thermally conductive microspheres (shell thickness 200-500 nm, particle size 5.4-10.5 μm).

[0011] Furthermore, the ultrasonic power is 300W, the frequency is 40kHz, the spray drying inlet temperature is 180-200℃, and the outlet temperature is 80-90℃.

[0012] Furthermore, the modified alumina whiskers are prepared as follows: 10.0g of alumina whiskers are dispersed in 500mL of anhydrous ethanol and sonicated for 30min; 3.0g of sulfur-containing silane coupling agent Si-69 is added and refluxed for 6h; the mixture is filtered, washed three times with ethanol, and vacuum dried at 60℃ for 8h to obtain modified alumina whiskers with sulfur-based or polysulfide segments on the surface that can participate in the sulfidation reaction, an aspect ratio of 25-35, and a diameter of 0.8-1.2μm.

[0013] Furthermore, the silane coupling agent is one of KH550, KH560, or KH570.

[0014] Furthermore, the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide (CZ) or tetramethylthiuram disulfide (TMTD), and the antioxidant is N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) or 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ).

[0015] A method for preparing high thermal conductivity rubber for tires includes the following preparation steps: (1) First stage of mixing: Add natural rubber and styrene-butadiene rubber to the internal mixer, with an initial temperature of 80-90℃ and a rotation speed of 40-50rpm, and plasticize for 3-5 minutes until the rubber completely covers the rollers; then add carbon black, silica, silane coupling agent, zinc oxide and stearic acid in sequence, raise the temperature to 110-120℃, and mix for 6-8 minutes, during which the rubber is discharged once every 2 minutes (each discharge lasts 10-15 seconds). After the mixing is completed, discharge the rubber compound and cool it to room temperature to obtain the first stage of mixed rubber. (2) Two-stage mixing: The first-stage compound is added back into the internal mixer at a temperature of 85-95℃ and a speed of 35-45rpm. Thermally conductive filler, modified alumina whiskers, and antioxidant are added and mixed for 6-8 minutes to ensure that the filler is evenly dispersed. The compound is then discharged and cooled to room temperature to obtain the second-stage compound. (3) Final mixing: Add the two-stage compounded rubber to the open mill, with a roller temperature of 60-70℃ and a roller gap of 3-5mm. After passing through the mill 2-3 times, add sulfur and accelerator, mix for 2-4 minutes, turning the rubber 3-4 times during the process, and finally passing through the mill 3-5 times (roller gap 1-2mm) to obtain the final compounded rubber. (4) Vulcanization: Cut the final rubber into the specified size, put it into the mold, and use a segmented vulcanization process in a flat vulcanizing machine: first vulcanize at 150℃ and 15-20MPa for 5 minutes, then raise the temperature to 160℃ and keep the pressure constant for 15-20 minutes; after vulcanization, demold and cool to room temperature to obtain high thermal conductivity rubber for tires.

[0016] Furthermore: the initial working pressure of the internal mixer in step (1) is 0.6-0.8 MPa, and the heating rate of the flat vulcanizing machine in step (4) is 5℃ / min.

[0017] Compared with the prior art, the present invention has the following significant advantages and beneficial effects: (1) This invention creatively combines two complementary thermally conductive fillers. Core-shell porous boron nitride (BN) microspheres serve as thermally conductive nodes, with their porous cores greatly increasing the specific surface area and phonon transport paths; the surface-grafted rubber shell allows them to perfectly integrate into the rubber matrix and be uniformly distributed. Modified alumina whiskers serve as thermally conductive bridges, which can overlap between the microspheres and work together with the BN microspheres to construct a stable and continuous three-dimensional thermally conductive network.

[0018] (2) The rubber shell of the core-shell BN microspheres and the matrix rubber are of the same type of material, forming a "fuzzy interface" and even chemical bonding (through amino groups and rubber molecules), eliminating the weak physical interface between traditional fillers and rubber. Alumina whiskers modified with sulfur-containing silane coupling agents (such as Si-69) can have sulfur groups or polysulfide segments on their surface directly participate in the vulcanization and crosslinking reaction of rubber, forming strong CS covalent bonds with rubber molecular chains, thus achieving strong bonding between fillers and matrix at the molecular level.

[0019] (3) Carbon black and silica constitute the main reinforcing system, ensuring the basic strength, modulus and wear resistance of the rubber. The addition of thermally conductive filler not only did not weaken the system, but its own rigidity and good dispersibility also provided additional reinforcing effect. The final product achieves a perfect balance between thermal conductivity and mechanical properties.

[0020] (4) By optimizing the ratio of natural rubber to styrene-butadiene rubber and combining it with a three-stage mixing process (first stage plasticizing and reinforcing system dispersion, second stage thermally conductive filler and whisker dispersion, and final vulcanization system addition), the uniform dispersion of the thermally conductive filler was ensured, while avoiding the problem of excessive hardness of the rubber compound caused by high filler content. The resulting rubber has a tensile strength ≥25MPa, an elongation at break ≥530%, and a Shore A hardness of 65-75 degrees, meeting the mechanical performance requirements of tire carcass materials.

[0021] (5) The antioxidants (6PPD or TMQ) added to the formula can effectively inhibit the oxidative degradation of rubber at high temperature. After aging in hot air at 100℃ for 72h, the tensile strength retention rate is ≥90%. At the same time, the segmented vulcanization process (pre-vulcanization at 150℃ for 5min + final vulcanization at 160℃ for 15-20min) can make the vulcanization more uniform and thorough, reduce internal bubbles and stress concentration, and improve the heat durability of rubber.

[0022] (6) In summary, this invention successfully prepared a high thermal conductivity rubber for tires by synergistically constructing a three-dimensional thermally conductive network using core-shell porous boron nitride thermally conductive microspheres and modified alumina whiskers, combined with an optimized rubber matrix formulation and a three-stage mixing and segmented vulcanization process. This rubber material can effectively improve the heat dissipation efficiency of tires during use, reduce driving temperature, and thus significantly improve the thermal durability and service life of tires. It is particularly suitable for applications such as heavy-duty tires with high requirements for heat dissipation and structural strength, and has significant practical application value and broad market prospects. Attached Figure Description

[0023] Figure 1 This is an electron microscope image of the overall morphology of the core-shell porous boron nitride thermally conductive microspheres of the present invention; Figure 2This is an electron microscope image of the internal structure of the core-shell porous boron nitride thermally conductive microspheres of this invention. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0025] Example 1 A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 60 parts natural rubber NR, 30 parts styrene-butadiene rubber SBR, 30 parts carbon black, 5 parts silica, 15 parts thermally conductive filler, 5 parts modified alumina whiskers, 1 part silane coupling agent, 1.5 parts sulfur, 0.8 parts accelerator, 1 part antioxidant, 4 parts zinc oxide, and 1 part stearic acid; wherein the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

[0026] The natural rubber is smoked sheet rubber RSS3, with a Mooney viscosity ML(1+4) of 60±5 at 100℃.

[0027] The thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere, and its preparation method is as follows: (1) Take 5.0g of hexagonal boron nitride, add 100mL of deionized water, and then add 0.3g of sodium carbonate (Na2CO3) as an activator. Mill the mixture in a planetary ball mill at 300rpm for 2h (ball-to-material ratio 10:1, grinding balls made of zirconium oxide). During milling, sodium carbonate weakens the van der Waals forces between hexagonal boron nitride particles and introduces more hydroxyl groups (-OH) onto the particle surface. After activation, wash with deionized water until pH=7, and vacuum dry at 60℃ for 4h to obtain activated hexagonal boron nitride. This step improves the dispersibility of hexagonal boron nitride and reduces the aggregate particle size. (2) Add 20.0g of polystyrene PS microspheres, 5.0g of activated hexagonal boron nitride, and 0.8g of sodium dodecylbenzene sulfonate to 1000mL of deionized water. Disperse the mixture ultrasonically at 30℃ and 500rpm for 30-40min to form a uniform suspension with a solid content of 2.5%. Send the suspension into a spray dryer and spray to obtain composite microspheres of BN-coated PS with a particle size of 6-9μm. (3) The composite microspheres were placed in a tube furnace, nitrogen gas was introduced, and the temperature was increased to 600℃ at 5℃ / min and held for 2.5h to completely carbonize the polystyrene PS microspheres and generate BN@C core-shell structure in situ, thus obtaining the porous BN microsphere core. (4) Take 10.0g of porous BN microsphere core, add 500mL of ethanol-water mixture (volume ratio 6:4), then add 2.0g of KH550, and reflux at 80℃ and 300rpm for 4h (to ensure that the amino group is grafted onto the BN surface); after the reaction, filter (filter membrane pore size 0.22μm), wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ (vacuum degree -0.09MPa) for 8h to obtain aminated BN microspheres; (5) Add the aminated BN microspheres to 200 mL of natural rubber latex (solid content 30%), add 0.15 g of initiator ammonium persulfate (APS), and react for 2 h at 60 °C and 500 rpm (APS initiates the grafting reaction between rubber molecular chains and amino groups); after the reaction, centrifuge (8000 rpm, 10 min), collect the precipitate, and vacuum dry at 60 °C for 12 h to obtain core-shell porous boron nitride thermally conductive microspheres (shell thickness 200-500 nm, particle size 5.4-10.5 μm).

[0028] The surface and internal structure of core-shell porous boron nitride thermally conductive microspheres were observed using scanning electron microscopy, such as... Figure 1-2 As shown, it exhibits a regular spherical structure with a loose and porous BN@C core and an outer rubber shell. This structural feature endows it with excellent interfacial compatibility and stress buffering capacity, significantly improving its dispersion stability and thermal conductivity continuity in the rubber matrix.

[0029] The ultrasonic power is 300W, the frequency is 40kHz, the spray drying inlet temperature is 180-200℃, and the outlet temperature is 80-90℃.

[0030] The modified alumina whiskers are prepared as follows: 10.0g of alumina whiskers are dispersed in 500mL of anhydrous ethanol and sonicated for 30min; 3.0g of sulfur-containing silane coupling agent Si-69 is added and refluxed for 6h; the mixture is filtered, washed three times with ethanol, and vacuum dried at 60℃ for 8h to obtain modified alumina whiskers with sulfur groups or polysulfide segments on the surface that can participate in the sulfidation reaction, an aspect ratio of 25-35, and a diameter of 0.8-1.2μm.

[0031] The silane coupling agent is KH550.

[0032] The accelerator is N-cyclohexyl-2-benzothiazole sulfenamide (CZ), and the antioxidant is N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD).

[0033] A method for preparing high thermal conductivity rubber for tires includes the following preparation steps: (1) First stage of mixing: Add natural rubber and styrene-butadiene rubber to a mixer, with an initial temperature of 80-90℃ and a rotation speed of 40rpm, and plasticize for 5 minutes until the rubber completely covers the rollers; then add carbon black, silica, silane coupling agent, zinc oxide and stearic acid in sequence, raise the temperature to 110-120℃, mix for 6 minutes, and discharge the rubber every 2 minutes (each discharge lasts 10 seconds). After the mixing is completed, discharge the rubber compound and cool it to room temperature to obtain the first stage of mixed rubber. (2) Two-stage mixing: The first-stage compound is added back into the internal mixer at a temperature of 85-95℃ and a speed of 35rpm. Thermally conductive filler, modified alumina whiskers, and antioxidant are added and mixed for 6 minutes to ensure that the filler is evenly dispersed. The compound is discharged and cooled to room temperature to obtain the second-stage compound. (3) Final mixing: Add the two-stage compounded rubber to the open mill, with a roller temperature of 60-70℃ and a roller gap of 3-5mm. After passing through the mill 2-3 times, add sulfur and accelerator, mix for 4 minutes, turning the rubber 3-4 times during the process, and finally passing through the mill 3-5 times (roller gap 1-2mm) to obtain the final compounded rubber. (4) Vulcanization: Cut the final rubber into the specified size, put it into the mold, and use a segmented vulcanization process in a flat vulcanizing machine: first vulcanize at 150℃ and 15MPa for 5 minutes, then raise the temperature to 160℃ and keep the pressure constant for 20 minutes; after vulcanization, demold and cool to room temperature to obtain high thermal conductivity rubber for tires.

[0034] In step (1), the initial working pressure of the internal mixer is 0.6 MPa, and in step (4), the heating rate of the flat vulcanizing machine is 5 °C / min.

[0035] Example 2 A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 65 parts natural rubber NR, 25 parts styrene-butadiene rubber SBR, 33 parts carbon black, 6 parts silica, 18 parts thermally conductive filler, 6 parts modified alumina whiskers, 1 part silane coupling agent, 2 parts sulfur, 1 part accelerator, 1.2 parts antioxidant, 5 parts zinc oxide, and 1.5 parts stearic acid; wherein the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

[0036] The natural rubber is smoked sheet rubber RSS3, with a Mooney viscosity ML(1+4) of 60±5 at 100℃.

[0037] The thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere, and its preparation method is as follows: (1) Take 5.0g of hexagonal boron nitride, add 100mL of deionized water, and then add 0.3g of sodium carbonate (Na2CO3) as an activator. Mill the mixture in a planetary ball mill at 300rpm for 2h (ball-to-material ratio 10:1, grinding balls made of zirconium oxide). During milling, sodium carbonate weakens the van der Waals forces between hexagonal boron nitride particles and introduces more hydroxyl groups (-OH) onto the particle surface. After activation, wash with deionized water until pH=7, and vacuum dry at 60℃ for 4h to obtain activated hexagonal boron nitride. This step improves the dispersibility of hexagonal boron nitride and reduces the aggregate particle size. (2) Add 20.0g of polystyrene PS microspheres, 5.0g of activated hexagonal boron nitride, and 0.8g of sodium dodecylbenzene sulfonate to 1000mL of deionized water. Disperse the mixture ultrasonically at 30℃ and 500rpm for 30-40min to form a uniform suspension with a solid content of 2.5%. Send the suspension into a spray dryer and spray to obtain composite microspheres of BN-coated PS with a particle size of 6-9μm. (3) The composite microspheres were placed in a tube furnace, nitrogen gas was introduced, and the temperature was increased to 600℃ at 5℃ / min and held for 2.5h to completely carbonize the polystyrene PS microspheres and generate BN@C core-shell structure in situ, thus obtaining the porous BN microsphere core. (4) Take 10.0g of porous BN microsphere core, add 500mL of ethanol-water mixture (volume ratio 6:4), then add 2.0g of KH550, and reflux at 80℃ and 300rpm for 4h (to ensure that the amino group is grafted onto the BN surface); after the reaction, filter (filter membrane pore size 0.22μm), wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ (vacuum degree -0.09MPa) for 8h to obtain aminated BN microspheres; (5) Add the aminated BN microspheres to 200 mL of natural rubber latex (solid content 30%), add 0.15 g of initiator ammonium persulfate (APS), and react for 2 h at 60 °C and 500 rpm (APS initiates the grafting reaction between rubber molecular chains and amino groups); after the reaction, centrifuge (8000 rpm, 10 min), collect the precipitate, and vacuum dry at 60 °C for 12 h to obtain core-shell porous boron nitride thermally conductive microspheres (shell thickness 200-500 nm, particle size 5.4-10.5 μm).

[0038] The ultrasonic power is 300W, the frequency is 40kHz, the spray drying inlet temperature is 180-200℃, and the outlet temperature is 80-90℃.

[0039] The modified alumina whiskers are prepared as follows: 10.0g of alumina whiskers are dispersed in 500mL of anhydrous ethanol and sonicated for 30min; 3.0g of sulfur-containing silane coupling agent Si-69 is added and refluxed for 6h; the mixture is filtered, washed three times with ethanol, and vacuum dried at 60℃ for 8h to obtain modified alumina whiskers with sulfur groups or polysulfide segments on the surface that can participate in the sulfidation reaction, an aspect ratio of 25-35, and a diameter of 0.8-1.2μm.

[0040] The silane coupling agent is KH560.

[0041] The accelerator is tetramethylthiuram disulfide (TMTD), and the antioxidant is 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ).

[0042] A method for preparing high thermal conductivity rubber for tires includes the following preparation steps: (1) First stage of mixing: Add natural rubber and styrene-butadiene rubber to the internal mixer, with an initial temperature of 80-90℃ and a rotation speed of 50rpm, and plasticize for 5 minutes until the rubber completely covers the rollers; then add carbon black, silica, silane coupling agent, zinc oxide and stearic acid in sequence, raise the temperature to 110-120℃, mix for 8 minutes, and discharge the rubber every 2 minutes (each discharge lasts 15 seconds). After the mixing is completed, discharge the rubber compound and cool it to room temperature to obtain the first stage of mixed rubber. (2) Two-stage mixing: The first-stage compound is added back into the internal mixer at a temperature of 85-95℃ and a speed of 45rpm. Thermally conductive filler, modified alumina whiskers, and antioxidant are added and mixed for 8 minutes to ensure that the filler is evenly dispersed. The compound is discharged and cooled to room temperature to obtain the second-stage compound. (3) Final mixing: Add the two-stage compounded rubber to the open mill, with a roller temperature of 60-70℃ and a roller gap of 3-5mm. After passing through the mill 2-3 times, add sulfur and accelerator, mix for 2 minutes, turning the rubber 3-4 times during the process, and finally passing through the mill 3-5 times (roller gap 1-2mm) to obtain the final compounded rubber. (4) Vulcanization: Cut the final rubber into the specified size, put it into the mold, and use a segmented vulcanization process in a flat vulcanizing machine: first vulcanize at 150℃ and 20MPa for 5 minutes, then raise the temperature to 160℃ and keep the pressure constant for 15 minutes; after vulcanization, demold and cool to room temperature to obtain high thermal conductivity rubber for tires.

[0043] In step (1), the initial working pressure of the internal mixer is 0.8 MPa, and in step (4), the heating rate of the flat vulcanizing machine is 5 °C / min.

[0044] Example 3 A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 66 parts natural rubber NR, 22 parts styrene-butadiene rubber SBR, 35 parts carbon black, 8 parts silica, 20 parts thermally conductive filler, 6 parts modified alumina whiskers, 1.5 parts silane coupling agent, 2.2 parts sulfur, 1.1 parts accelerator, 1.3 parts antioxidant, 5 parts zinc oxide, and 1.3 parts stearic acid; wherein the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

[0045] The natural rubber is smoked sheet rubber RSS3, with a Mooney viscosity ML(1+4) of 60±5 at 100℃.

[0046] The thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere, and its preparation method is as follows: (1) Take 5.0g of hexagonal boron nitride, add 100mL of deionized water, and then add 0.3g of sodium carbonate (Na2CO3) as an activator. Mill the mixture in a planetary ball mill at 300rpm for 2h (ball-to-material ratio 10:1, grinding balls made of zirconium oxide). During milling, sodium carbonate weakens the van der Waals forces between hexagonal boron nitride particles and introduces more hydroxyl groups (-OH) onto the particle surface. After activation, wash with deionized water until pH=7, and vacuum dry at 60℃ for 4h to obtain activated hexagonal boron nitride. This step improves the dispersibility of hexagonal boron nitride and reduces the aggregate particle size. (2) Add 20.0g of polystyrene PS microspheres, 5.0g of activated hexagonal boron nitride, and 0.8g of sodium dodecylbenzene sulfonate to 1000mL of deionized water. Disperse the mixture ultrasonically at 30℃ and 500rpm for 30-40min to form a uniform suspension with a solid content of 2.5%. Send the suspension into a spray dryer and spray to obtain composite microspheres of BN-coated PS with a particle size of 6-9μm. (3) The composite microspheres were placed in a tube furnace, nitrogen gas was introduced, and the temperature was increased to 600℃ at 5℃ / min and held for 2.5h to completely carbonize the polystyrene PS microspheres and generate BN@C core-shell structure in situ, thus obtaining the porous BN microsphere core. (4) Take 10.0g of porous BN microsphere core, add 500mL of ethanol-water mixture (volume ratio 6:4), then add 2.0g of KH550, and reflux at 80℃ and 300rpm for 4h (to ensure that the amino group is grafted onto the BN surface); after the reaction, filter (filter membrane pore size 0.22μm), wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ (vacuum degree -0.09MPa) for 8h to obtain aminated BN microspheres; (5) Add the aminated BN microspheres to 200 mL of natural rubber latex (solid content 30%), add 0.15 g of initiator ammonium persulfate (APS), and react for 2 h at 60 °C and 500 rpm (APS initiates the grafting reaction between rubber molecular chains and amino groups); after the reaction, centrifuge (8000 rpm, 10 min), collect the precipitate, and vacuum dry at 60 °C for 12 h to obtain core-shell porous boron nitride thermally conductive microspheres (shell thickness 200-500 nm, particle size 5.4-10.5 μm).

[0047] The ultrasonic power is 300W, the frequency is 40kHz, the spray drying inlet temperature is 180-200℃, and the outlet temperature is 80-90℃.

[0048] The modified alumina whiskers are prepared as follows: 10.0g of alumina whiskers are dispersed in 500mL of anhydrous ethanol and sonicated for 30min; 3.0g of sulfur-containing silane coupling agent Si-69 is added and refluxed for 6h; the mixture is filtered, washed three times with ethanol, and vacuum dried at 60℃ for 8h to obtain modified alumina whiskers with sulfur groups or polysulfide segments on the surface that can participate in the sulfidation reaction, an aspect ratio of 25-35, and a diameter of 0.8-1.2μm.

[0049] The silane coupling agent is KH570.

[0050] The accelerator is N-cyclohexyl-2-benzothiazole sulfenamide (CZ), and the antioxidant is 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ).

[0051] A method for preparing high thermal conductivity rubber for tires includes the following preparation steps: (1) First stage of mixing: Add natural rubber and styrene-butadiene rubber to the internal mixer, with an initial temperature of 80-90℃ and a rotation speed of 50rpm, and plasticize for 3 minutes until the rubber completely covers the rollers; then add carbon black, silica, silane coupling agent, zinc oxide and stearic acid in sequence, raise the temperature to 110-120℃, mix for 8 minutes, and discharge the rubber every 2 minutes (each discharge lasts 10 seconds). After the mixing is completed, discharge the rubber compound and cool it to room temperature to obtain the first stage of mixed rubber. (2) Two-stage mixing: The first-stage compound is added back into the internal mixer at a temperature of 85-95℃ and a speed of 45rpm. Thermally conductive filler, modified alumina whiskers, and antioxidant are added and mixed for 8 minutes to ensure that the filler is evenly dispersed. The compound is discharged and cooled to room temperature to obtain the second-stage compound. (3) Final mixing: Add the two-stage compounded rubber to the open mill, with a roller temperature of 60-70℃ and a roller gap of 3-5mm. After passing through the mill 2-3 times, add sulfur and accelerator, mix for 4 minutes, turning the rubber 3-4 times during the process, and finally passing through the mill 3-5 times (roller gap 1-2mm) to obtain the final compounded rubber. (4) Vulcanization: Cut the final rubber into the specified size, put it into the mold, and use a segmented vulcanization process in a flat vulcanizing machine: first vulcanize at 150℃ and 20MPa for 5 minutes, then raise the temperature to 160℃ and keep the pressure constant for 20 minutes; after vulcanization, demold and cool to room temperature to obtain high thermal conductivity rubber for tires.

[0052] In step (1), the initial working pressure of the internal mixer is 0.8 MPa, and in step (4), the heating rate of the flat vulcanizing machine is 5 °C / min.

[0053] Example 4 A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 70 parts natural rubber NR, 20 parts styrene-butadiene rubber SBR, 40 parts carbon black, 10 parts silica, 25 parts thermally conductive filler, 7 parts modified alumina whiskers, 2 parts silane coupling agent, 2.5 parts sulfur, 1.2 parts accelerator, 1.5 parts antioxidant, 6 parts zinc oxide, and 2 parts stearic acid; wherein the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

[0054] The natural rubber is smoked sheet rubber RSS3, with a Mooney viscosity ML(1+4) of 60±5 at 100℃.

[0055] The thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere, and its preparation method is as follows: (1) Take 5.0g of hexagonal boron nitride, add 100mL of deionized water, and then add 0.3g of sodium carbonate (Na2CO3) as an activator. Mill the mixture in a planetary ball mill at 300rpm for 2h (ball-to-material ratio 10:1, grinding balls made of zirconium oxide). During milling, sodium carbonate weakens the van der Waals forces between hexagonal boron nitride particles and introduces more hydroxyl groups (-OH) onto the particle surface. After activation, wash with deionized water until pH=7, and vacuum dry at 60℃ for 4h to obtain activated hexagonal boron nitride. This step improves the dispersibility of hexagonal boron nitride and reduces the aggregate particle size. (2) Add 20.0g of polystyrene PS microspheres, 5.0g of activated hexagonal boron nitride, and 0.8g of sodium dodecylbenzene sulfonate to 1000mL of deionized water. Disperse the mixture ultrasonically at 30℃ and 500rpm for 30-40min to form a uniform suspension with a solid content of 2.5%. Send the suspension into a spray dryer and spray to obtain composite microspheres of BN-coated PS with a particle size of 6-9μm. (3) The composite microspheres were placed in a tube furnace, nitrogen gas was introduced, and the temperature was increased to 600℃ at 5℃ / min and held for 2.5h to completely carbonize the polystyrene PS microspheres and generate BN@C core-shell structure in situ, thus obtaining the porous BN microsphere core. (4) Take 10.0g of porous BN microsphere core, add 500mL of ethanol-water mixture (volume ratio 6:4), then add 2.0g of KH550, and reflux at 80℃ and 300rpm for 4h (to ensure that the amino group is grafted onto the BN surface); after the reaction, filter (filter membrane pore size 0.22μm), wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ (vacuum degree -0.09MPa) for 8h to obtain aminated BN microspheres; (5) Add the aminated BN microspheres to 200 mL of natural rubber latex (solid content 30%), add 0.15 g of initiator ammonium persulfate (APS), and react for 2 h at 60 °C and 500 rpm (APS initiates the grafting reaction between rubber molecular chains and amino groups); after the reaction, centrifuge (8000 rpm, 10 min), collect the precipitate, and vacuum dry at 60 °C for 12 h to obtain core-shell porous boron nitride thermally conductive microspheres (shell thickness 200-500 nm, particle size 5.4-10.5 μm).

[0056] The ultrasonic power is 300W, the frequency is 40kHz, the spray drying inlet temperature is 180-200℃, and the outlet temperature is 80-90℃.

[0057] The modified alumina whiskers are prepared as follows: 10.0g of alumina whiskers are dispersed in 500mL of anhydrous ethanol and sonicated for 30min; 3.0g of sulfur-containing silane coupling agent Si-69 is added and refluxed for 6h; the mixture is filtered, washed three times with ethanol, and vacuum dried at 60℃ for 8h to obtain modified alumina whiskers with sulfur groups or polysulfide segments on the surface that can participate in the sulfidation reaction, an aspect ratio of 25-35, and a diameter of 0.8-1.2μm.

[0058] The silane coupling agent is KH550.

[0059] The accelerator is tetramethylthiuram disulfide (TMTD), and the antioxidant is N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD).

[0060] A method for preparing high thermal conductivity rubber for tires includes the following preparation steps: (1) First stage of mixing: Add natural rubber and styrene-butadiene rubber to the internal mixer, with an initial temperature of 80-90℃ and a rotation speed of 40rpm, and plasticize for 5 minutes until the rubber completely covers the rollers; then add carbon black, silica, silane coupling agent, zinc oxide and stearic acid in sequence, raise the temperature to 110-120℃, mix for 8 minutes, and discharge the rubber every 2 minutes (each discharge lasts 15 seconds). After the mixing is completed, discharge the rubber compound and cool it to room temperature to obtain the first stage of mixed rubber. (2) Two-stage mixing: The first-stage compound is added back into the internal mixer at a temperature of 85-95℃ and a speed of 45rpm. Thermally conductive filler, modified alumina whiskers, and antioxidant are added and mixed for 8 minutes to ensure that the filler is evenly dispersed. The compound is discharged and cooled to room temperature to obtain the second-stage compound. (3) Final mixing: Add the two-stage compounded rubber to the open mill, with a roller temperature of 60-70℃ and a roller gap of 3-5mm. After passing through the mill 2-3 times, add sulfur and accelerator, mix for 4 minutes, turning the rubber 3-4 times during the process, and finally passing through the mill 3-5 times (roller gap 1-2mm) to obtain the final compounded rubber. (4) Vulcanization: Cut the final rubber into the specified size, put it into the mold, and use a segmented vulcanization process in a flat vulcanizing machine: first vulcanize at 150℃ and 20MPa for 5 minutes, then raise the temperature to 160℃ and keep the pressure constant for 20 minutes; after vulcanization, demold and cool to room temperature to obtain high thermal conductivity rubber for tires.

[0061] In step (1), the initial working pressure of the internal mixer is 0.8 MPa, and in step (4), the heating rate of the flat vulcanizing machine is 5 °C / min.

[0062] Comparative Example 1 In this comparative example, except that neither modified alumina whiskers nor core-shell porous boron nitride thermally conductive microspheres were used as thermally conductive fillers, the other components and process parameters were completely consistent with those of Example 1, namely: A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 60 parts natural rubber NR, 30 parts styrene-butadiene rubber SBR, 30 parts carbon black, 5 parts silica, 15 parts thermally conductive filler, 5 parts alumina whiskers, 1 part silane coupling agent, 1.5 parts sulfur, 0.8 parts accelerator, 1 part antioxidant, 4 parts zinc oxide, and 1 part stearic acid; wherein the thermally conductive filler is boron nitride.

[0063] The alumina whiskers are ordinary alumina whiskers with an aspect ratio of 25-35 and a diameter of 0.8-1.2 μm.

[0064] The thermally conductive filler is ordinary hexagonal boron nitride powder with a particle size of 5-10 μm.

[0065] Comparative Example 2 In this comparative example, except for the absence of modified alumina whiskers, the other components and process parameters are completely consistent with those of Example 1; that is, an equal amount of unmodified alumina whiskers are used instead, and other conditions remain unchanged.

[0066] A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 60 parts natural rubber NR, 30 parts styrene-butadiene rubber SBR, 30 parts carbon black, 5 parts silica, 15 parts thermally conductive filler, 5 parts alumina whiskers, 1 part silane coupling agent, 1.5 parts sulfur, 0.8 parts accelerator, 1 part antioxidant, 4 parts zinc oxide, and 1 part stearic acid; wherein the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

[0067] The alumina whiskers are ordinary alumina whiskers with an aspect ratio of 25-35 and a diameter of 0.8-1.2 μm.

[0068] Comparative Example 3 In this comparative example, except for the absence of core-shell porous boron nitride thermally conductive microspheres as thermally conductive fillers, the other components and process parameters are consistent with those of Example 1; that is, an equal amount of ordinary boron nitride powder is used instead, and the other steps are exactly the same.

[0069] A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 60 parts natural rubber NR, 30 parts styrene-butadiene rubber SBR, 30 parts carbon black, 5 parts silica, 15 parts thermally conductive filler, 5 parts modified alumina whiskers, 1 part silane coupling agent, 1.5 parts sulfur, 0.8 parts accelerator, 1 part antioxidant, 4 parts zinc oxide, and 1 part stearic acid; wherein the thermally conductive filler is boron nitride.

[0070] The thermally conductive filler is ordinary hexagonal boron nitride powder with a particle size of 5-10 μm.

[0071] The modified alumina whiskers are prepared as follows: 10.0g of alumina whiskers are dispersed in 500mL of anhydrous ethanol and sonicated for 30min; 3.0g of sulfur-containing silane coupling agent Si-69 is added and refluxed for 6h; the mixture is filtered, washed three times with ethanol, and vacuum dried at 60℃ for 8h to obtain modified alumina whiskers with sulfur groups or polysulfide segments on the surface that can participate in the sulfidation reaction, an aspect ratio of 25-35, and a diameter of 0.8-1.2μm.

[0072] Comparative Example 4 The composition is exactly the same as in Example 1, but the mixing process is changed: the first and second stages of mixing are combined into one stage. That is, all rubber and fillers (carbon black, silica, thermally conductive fillers, modified alumina whiskers, etc.) are added at once in an internal mixer and mixed for the same total time in the same stage. The remaining final mixing and vulcanization steps are the same. A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 60 parts natural rubber NR, 30 parts styrene-butadiene rubber SBR, 30 parts carbon black, 5 parts silica, 15 parts thermally conductive filler, 5 parts modified alumina whiskers, 1 part silane coupling agent, 1.5 parts sulfur, 0.8 parts accelerator, 1 part antioxidant, 4 parts zinc oxide, and 1 part stearic acid; wherein the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

[0073] A method for preparing high thermal conductivity rubber for tires includes the following preparation steps: (1) First stage of mixing: Add natural rubber and styrene-butadiene rubber to the internal mixer, with an initial temperature of 80-90℃ and a rotation speed of 40rpm, and plasticize for 5 minutes until the rubber completely covers the rollers; then add carbon black, silica, thermally conductive filler, modified alumina whiskers, antioxidant, silane coupling agent, zinc oxide and stearic acid in sequence, raise the temperature to 110-120℃, mix for 12 minutes, and discharge the rubber every 2 minutes (each discharge lasts 10 seconds). After the mixing is completed, discharge the rubber and cool it to room temperature to obtain the first stage of mixed rubber; (2) Final mixing: Add a section of mixed rubber to the open mill, with a roller temperature of 60-70℃ and a roller gap of 3-5mm. After passing through the mill 2-3 times, add sulfur and accelerator, mix for 4 minutes, turning the rubber 3-4 times during the process, and finally passing through the mill 3-5 times (roller gap 1-2mm) to obtain the final mixed rubber. (3) Vulcanization: Cut the final rubber into the specified size, put it into the mold, and use a segmented vulcanization process in a flat vulcanizing machine: first vulcanize at 150℃ and 15MPa for 5 minutes, then raise the temperature to 160℃ and keep the pressure constant for 20 minutes; after vulcanization, demold and cool to room temperature to obtain high thermal conductivity rubber for tires.

[0074] In step (1), the initial working pressure of the internal mixer is 0.6 MPa, and in step (4), the heating rate of the flat vulcanizing machine is 5 °C / min.

[0075] Comparative Example 5 The composition is exactly the same as in Example 1, but the vulcanization process is changed: a conventional single-stage vulcanization process is adopted, that is, direct vulcanization at 160°C and 15MPa for 20-25 minutes (the total vulcanization time is comparable to the segmented vulcanization in Example 1), eliminating the pre-vulcanization stage at 150°C. That is: A high thermal conductivity rubber for tires comprises the following raw materials in parts by weight: 60 parts natural rubber NR, 30 parts styrene-butadiene rubber SBR, 30 parts carbon black, 5 parts silica, 15 parts thermally conductive filler, 5 parts modified alumina whiskers, 1 part silane coupling agent, 1.5 parts sulfur, 0.8 parts accelerator, 1 part antioxidant, 4 parts zinc oxide, and 1 part stearic acid; wherein the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

[0076] A method for preparing high thermal conductivity rubber for tires includes the following preparation steps: (1) First stage of mixing: Add natural rubber and styrene-butadiene rubber to a mixer, with an initial temperature of 80-90℃ and a rotation speed of 40rpm, and plasticize for 5 minutes until the rubber completely covers the rollers; then add carbon black, silica, silane coupling agent, zinc oxide and stearic acid in sequence, raise the temperature to 110-120℃, mix for 6 minutes, and discharge the rubber every 2 minutes (each discharge lasts 10 seconds). After the mixing is completed, discharge the rubber compound and cool it to room temperature to obtain the first stage of mixed rubber. (2) Two-stage mixing: The first-stage compound is added back into the internal mixer at a temperature of 85-95℃ and a speed of 35rpm. Thermally conductive filler, modified alumina whiskers, and antioxidant are added and mixed for 6 minutes to ensure that the filler is evenly dispersed. The compound is discharged and cooled to room temperature to obtain the second-stage compound. (3) Final mixing: Add the two-stage compounded rubber to the open mill, with a roller temperature of 60-70℃ and a roller gap of 3-5mm. After passing through the mill 2-3 times, add sulfur and accelerator, mix for 4 minutes, turning the rubber 3-4 times during the process, and finally passing through the mill 3-5 times (roller gap 1-2mm) to obtain the final compounded rubber. (4) Vulcanization: Cut the final rubber into the specified size, put it into the mold, and vulcanize it in a flat vulcanizing machine: vulcanize directly at 160℃ and 15MPa pressure for 22 minutes; after vulcanization, demold and cool to room temperature to obtain high thermal conductivity rubber for tires.

[0077] In step (1), the initial working pressure of the internal mixer is 0.6 MPa, and in step (4), the heating rate of the flat vulcanizing machine is 5 °C / min.

[0078] Comparative Example 6 The tire adhesive was prepared in accordance with the existing technical method CN 116355292 A.

[0079] Performance testing The performance of the rubber compounds obtained in Examples 1-4 and Comparative Examples 1-6 of this invention was tested. Five samples were set up for each group of experiments, and the average value of the results was taken.

[0080] Thermal conductivity: The test shall be conducted using a thermal conductivity meter in accordance with GB / T 32064-2015 "Temperature conductivity and thermal diffusivity of building materials - transient planar heat source method" or ASTM D5470 "Standard test method for measuring the heat transfer properties of thermally conductive and insulating materials by steady-state heat flow method".

[0081] Tensile properties: Tested using a universal testing machine in accordance with GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0082] Tear strength: The test was conducted using a universal testing machine in accordance with GB / T 529-2008 "Determination of tear strength of vulcanized rubber or thermoplastic rubber (trouser-shaped, right-angled and crescent-shaped specimens)".

[0083] Mooney viscosity: Refer to GB / T 1232.1-2000 "Determination of uncured rubber by disc shear viscometer - Part 1: Determination of Mooney viscosity", and use a Mooney viscometer to test ML(1+4) at 100℃.

[0084] Hot air aging: Refer to GB / T 3512-2014 "Accelerated aging and heat resistance test of vulcanized rubber or thermoplastic rubber in hot air", and test the retention rate of tensile properties after being treated in an aging chamber at 100℃ for 72 hours.

[0085] Compression heat generation: Refer to GB / T 1687-2016 "Determination of temperature rise and fatigue resistance of vulcanized rubber in flexural test" Part II (Goodrich method) to evaluate dynamic heat generation properties (ΔT).

[0086] Table 1 Performance Test Results Table 2 Performance Test Results As can be seen from the data in Tables 1-2, the high thermal conductivity rubbers for tires prepared in Examples 1-4 exhibit significant advantages in all performance aspects. Regarding thermal conductivity, the thermal conductivity of Example 1 is 0.35 W / (m·K). With the optimization and adjustment of the relevant formulations or process parameters in Examples 2 to 4, the thermal conductivity gradually increases to 0.60 W / (m·K), demonstrating a good trend of improved thermal conductivity. This is significantly better than Comparative Examples 1-6, for example, Comparative Example 1 is only 0.15 W / (m·K), and Comparative Example 6 is only 0.25 W / (m·K). This fully demonstrates that the present invention, through a specific combination of raw materials, such as the synergistic effect of modified alumina whiskers and core-shell porous boron nitride thermally conductive microspheres, and an optimized preparation process, successfully constructs an efficient thermal conductivity pathway, effectively improving the thermal conductivity of the rubber material.

[0087] In terms of mechanical properties, the tensile strength of Examples 1-4 increased from 26.1 MPa to 30.1 MPa, the tear strength increased from 121 kN / m to 160 kN / m, and the elongation at break also increased from 530% to 590%. These data indicate that the rubber material of the present invention not only has excellent thermal conductivity, but its mechanical properties are also simultaneously enhanced, meeting the strength, toughness, and elasticity requirements of tires in actual use. In contrast, the tensile strength of Comparative Example 1 is only 18.5 MPa, the tear strength is 85 kN / m, and the elongation at break is 480%, all far lower than those of the Examples. Even compared with the relatively better-performing Comparative Example 4 (tensile strength 24.3 MPa, tear strength 120 kN / m) and Comparative Example 5 (tensile strength 25.0 MPa, tear strength 125 kN / m), the Examples still have significant advantages.

[0088] Mooney viscosity reflects the processing performance of rubber. The Mooney viscosity ML(1+4) at 100°C of Examples 1-4 is between 48 and 53, which is within a suitable processing range, indicating that the rubber compound has good flowability and plasticity, facilitating subsequent molding processes. The Mooney viscosity of Comparative Example 1 is 55, which is relatively high and may increase processing difficulty; the Mooney viscosity of Comparative Example 6 is 56, which also indicates poor processing performance.

[0089] Regarding hot air aging performance, Examples 1-4 all maintained a tensile strength retention rate of over 90% after aging at 100℃ for 72 hours, with the highest reaching 94%, demonstrating excellent heat aging resistance and ensuring the stability of tire performance during long-term use. In contrast, Comparative Example 1 had a tensile strength retention rate of only 75%, Comparative Example 3 had 78%, and Comparative Example 6 had 80%, all lower than the Examples, indicating poor performance in resisting heat aging.

[0090] In the compression heat generation test, the temperature rise (ΔT) of Examples 1-4 decreased from 8.5℃ to 6.6℃, indicating good dynamic heat generation performance. Tires generate heat during driving due to repeated compression and deformation; a lower temperature rise helps delay tire aging and improves safety and lifespan. The temperature rise of Comparative Example 1 reached 12.5℃, and that of Comparative Example 2 was 10.2℃, both significantly higher than the Examples, indicating that their heat generation problem under dynamic conditions was more prominent.

[0091] Regarding Shore A hardness, the hardness of Examples 1-4 ranged from 68 to 74, showing a slight increase as the examples progressed. This may be related to the increase in components such as thermally conductive fillers, but overall it remains within the reasonable hardness range for tire use. The hardness of Comparative Example 1 was 72, and that of Comparative Example 6 was 73, which are close to some of the values ​​in the Examples. However, considering other properties, the overall performance of the Examples is more balanced and superior.

[0092] In summary, this invention, through the use of a specific raw material formulation, such as a blend of natural rubber and styrene-butadiene rubber, combined with carbon black and silica as reinforcing fillers, and the introduction of modified alumina whiskers and core-shell porous boron nitride thermally conductive microspheres as composite thermally conductive fillers, combined with an optimized three-stage mixing (first-stage mixing, second-stage mixing, and final mixing) and segmented vulcanization process, achieves synergistic improvements in thermal conductivity, mechanical properties, processing performance, heat aging resistance, and dynamic heat generation performance of the prepared high thermal conductivity tire rubber. In particular, the synergistic effect of the modified alumina whiskers and core-shell porous boron nitride thermally conductive microspheres, as well as the precise control of the segmented mixing and vulcanization processes, are the key factors enabling this invention to achieve superior performance compared to comparative examples. Comparative Example 1, due to the lack of modified alumina whiskers and core-shell porous boron nitride thermally conductive microspheres, resulted in a significant decrease in thermal conductivity and mechanical properties. Comparative Example 2, using only unmodified alumina whiskers, showed improved performance, but not as good as the examples. Comparative Example 3, using ordinary boron nitride powder instead of core-shell porous boron nitride thermally conductive microspheres, also yielded unsatisfactory results. Comparative Example 4, by merging the first and second stages of mixing, disrupted the orderly mixing process, affecting filler dispersion and performance. Comparative Example 5, employing a single-stage vulcanization process, failed to fully utilize the vulcanization system, resulting in performance degradation. Comparative Example 6, using existing techniques, exhibited overall performance far inferior to the embodiments of the present invention. Therefore, the high thermal conductivity rubber for tires and its preparation method of the present invention possess significant advancements and practicality.

[0093] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A high thermal conductivity rubber for tires, characterized in that, The raw materials include the following parts by weight: 60-70 parts of natural rubber (NR), 20-30 parts of styrene-butadiene rubber (SBR), 30-40 parts of carbon black, 5-10 parts of silica, 15-25 parts of thermally conductive filler, 5-7 parts of modified alumina whiskers, 1-2 parts of silane coupling agent, 1.5-2.5 parts of sulfur, 0.8-1.2 parts of accelerator, 1-1.5 parts of antioxidant, 4-6 parts of zinc oxide, and 1-2 parts of stearic acid; the thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere.

2. The high thermal conductivity rubber for tires according to claim 1, characterized in that, The natural rubber is smoked sheet rubber RSS3, with a Mooney viscosity ML(1+4) of 60±5 at 100℃.

3. The high thermal conductivity rubber for tires according to claim 1, characterized in that, The silane coupling agent is one of KH550, KH560 or KH570.

4. The high thermal conductivity rubber for tires according to claim 1, characterized in that, The thermally conductive filler is a core-shell porous boron nitride thermally conductive microsphere, and its preparation method is as follows: (1) Take 5.0g of hexagonal boron nitride, add 100mL of deionized water, and then add 0.3g of sodium carbonate Na2CO3 as an activator. Ball mill in a planetary ball mill at 300rpm for 2h. After activation, wash with deionized water until pH=7, and vacuum dry at 60℃ for 4h to obtain activated hexagonal boron nitride. (2) Add 20.0g of polystyrene PS microspheres, 5.0g of activated hexagonal boron nitride, and 0.8g of sodium dodecylbenzene sulfonate to 1000mL of deionized water. Disperse the mixture ultrasonically at 30℃ and 500rpm for 30-40min to form a uniform suspension with a solid content of 2.5%. Send the suspension into a spray dryer and spray to obtain composite microspheres of BN-coated PS with a particle size of 6-9μm. (3) The composite microspheres were placed in a tube furnace, nitrogen gas was introduced, and the temperature was increased to 600℃ at 5℃ / min and held for 2.5h to completely carbonize the polystyrene PS microspheres and generate BN@C core-shell structure in situ, thus obtaining the porous BN microsphere core. (4) Take 10.0g of porous BN microsphere core, add 500mL of ethanol-water mixture, then add 2.0g of KH550, and reflux at 80℃ and 300rpm for 4h. After the reaction, filter, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ for 8h to obtain aminated BN microspheres. (5) Add the aminated BN microspheres to 200 mL of natural rubber latex, add 0.15 g of initiator ammonium persulfate (APS), and react for 2 h at 60 °C and 500 rpm. After the reaction, centrifuge, collect the precipitate, and vacuum dry at 60 °C for 12 h to obtain core-shell porous boron nitride thermally conductive microspheres.

5. The high thermal conductivity rubber for tires according to claim 4, characterized in that, The ultrasonic power is 300W, the frequency is 40kHz, the spray drying inlet temperature is 180-200℃, and the outlet temperature is 80-90℃.

6. The high thermal conductivity rubber for tires according to claim 1, characterized in that, The modified alumina whiskers are prepared as follows: 10.0g of alumina whiskers are dispersed in 500mL of anhydrous ethanol and sonicated for 30min; 3.0g of sulfur-containing silane coupling agent Si-69 is added and refluxed for 6h; the mixture is filtered, washed three times with ethanol, and dried under vacuum at 60℃ for 8h to obtain modified alumina whiskers with sulfur groups or polysulfide segments on the surface that can participate in the sulfidation reaction.

7. The high thermal conductivity rubber for tires according to claim 1, characterized in that, The accelerator is N-cyclohexyl-2-benzothiazole sulfenamide or tetramethylthiuram disulfide, and the antioxidant is N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine or 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

8. A method for preparing high thermal conductivity rubber for tires according to any one of claims 1-7, characterized in that: The preparation steps include the following: (1) First stage of mixing: Add natural rubber and styrene-butadiene rubber to the internal mixer, with an initial temperature of 80-90℃ and a rotation speed of 40-50rpm, and plasticize for 3-5 minutes until the rubber completely covers the rollers; then add carbon black, silica, silane coupling agent, zinc oxide and stearic acid in sequence, raise the temperature to 110-120℃, and mix for 6-8 minutes, during which the rubber is discharged once every 2 minutes. After the mixing is completed, the rubber compound is discharged and cooled to room temperature to obtain the first stage of compound; (2) Two-stage mixing: The first-stage compound is added back into the internal mixer at a temperature of 85-95℃ and a speed of 35-45rpm. Thermally conductive filler, modified alumina whiskers, and antioxidant are added and mixed for 6-8 minutes to ensure that the filler is evenly dispersed. The compound is then discharged and cooled to room temperature to obtain the second-stage compound. (3) Final mixing: Add the two-stage compounded rubber to the open mill, with a roller temperature of 60-70℃ and a roller gap of 3-5mm. After passing through the mill 2-3 times, add sulfur and accelerator, mix for 2-4 minutes, turning the rubber 3-4 times during the process, and finally passing through the mill 3-5 times to obtain the final compounded rubber. (4) Vulcanization: Cut the final rubber into the specified size, put it into the mold, and use a segmented vulcanization process in a flat vulcanizing machine: first vulcanize at 150℃ and 15-20MPa for 5 minutes, then raise the temperature to 160℃ and keep the pressure constant for 15-20 minutes; after vulcanization, demold and cool to room temperature to obtain high thermal conductivity rubber for tires.

9. The method for preparing high thermal conductivity rubber for tires according to claim 8, characterized in that: In step (1), the initial working pressure of the internal mixer is 0.6-0.8 MPa, and in step (4), the heating rate of the flat vulcanizing machine is 5℃ / min.

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