A low heat build-up tire tread cushion and method of making the same

Abstract

The application relates to the technical field of rubber materials, and discloses a low-heat-generation tire tread cushion rubber and a preparation method thereof, the preparation method being as follows: natural rubber and butadiene rubber are put into a banbury mixer, plasticated for 1-2 min at 60-80 DEG C, then white carbon black, carbon black, double-[gamma-(triethoxysilane) propyl] tetrasulfide, modified phosphorus-containing cashew phenol derivative, modified sulfide compound, zinc oxide, stearic acid and antioxidant RD are added, mixed for 3-5 min at 140-155 DEG C, and the rubber is discharged to obtain a masterbatch; the obtained masterbatch is cooled and then put into the banbury mixer, sulfur and accelerator CZ are added, mixed for 2-3 min at 80-100 DEG C, and the rubber is discharged to obtain the low-heat-generation tire tread cushion rubber. The low-heat-generation tire tread cushion rubber prepared by the application has excellent mechanical properties and steel wire adhesion, and also has good low-heat-generation performance and heat aging resistance.

Description

Technical Field

[0001] This invention relates to the field of rubber materials technology, specifically to a low-heat-generating tire tread pad rubber and its preparation method. Background Technology

[0002] The tread gasket is a transitional rubber layer located between the tread rubber and the belt layer in an all-steel radial truck tire. Its main functions are to cushion the impact load on the tread, coordinate the deformation differences between the tread and the steel belt layer, and also to conduct and dissipate heat within the tread. Under long-distance heavy-load transportation conditions, the tire is continuously subjected to high-frequency dynamic compression and shearing. The heat generated by hysteresis loss within the gasket layer accumulates continuously. If the rubber compound generates too much heat, the internal temperature will rise rapidly, accelerating the thermo-oxidative aging of the rubber cross-linking network, shortening the tire's service life, and in severe cases, even causing a tire blowout safety hazard. Currently, the industry's conventional approach to reducing heat generation in tire tread compound typically involves increasing the amount of silica, optimizing the vulcanization system, or adding physical plasticizers. However, in practical applications, simply increasing the amount of silica filler, especially in the absence of efficient interface modification methods, can lead to hydrogen bond aggregation of its surface silanol groups, resulting in increased friction within the filler network and consequently higher dynamic heat generation. Conventional small-molecule plasticizers do not participate in rubber crosslinking and are prone to migrating and precipitating at the rubber layer interface under long-term high-temperature conditions, leading to hardening of the rubber compound and a decrease in crosslinking density. Therefore, avoiding this phenomenon is key to solving the problem. For example, patent application CN107236157A discloses a green tire tread compound and its preparation method. Its formulation focuses on improving wear resistance and reducing the overall rolling resistance of the tire. However, this system is designed for the ground-contact tread and does not consider the special conditions of the tread compound needing to be matched with steel cord bonding and long-term dynamic heat aging resistance. When applied to the tread compound, the dynamic compression temperature rise is too high, and the heat resistance and durability are insufficient, failing to meet the requirements for heavy-duty tire tread compound use. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a low heat generation tread pad rubber and its preparation method. The low heat generation tread pad rubber prepared by the present invention has excellent mechanical properties and steel wire adhesion, as well as good low heat generation properties and heat aging resistance.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a low-heat-generating tire tread pad rubber, comprising the following weight components based on 100 parts by weight of natural rubber and butadiene rubber: 60-80 parts by weight of natural rubber, 20-40 parts by weight of butadiene rubber, 30-40 parts by weight of silica, 3-4 parts by weight of modified phosphorus-containing cashew phenol derivative, 2-4 parts by weight of modified sulfide compound, 10-20 parts by weight of carbon black, 3-4 parts by weight of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 3-5 parts by weight of zinc oxide, 1-3 parts by weight of stearic acid, 1-2 parts by weight of antioxidant RD, 1.5-2.5 parts by weight of sulfur, and 1-2 parts by weight of accelerator CZ.

[0005] Furthermore, the preparation method of the modified phosphorus-containing cashew phenol derivative is as follows:

[0006] Step 1: Add cashew nut powder, triethylamine, and chloroform to the reactor and mix well. Then, add diphenyl chlorophosphate dropwise to the reactor. After the addition is complete, reflux and condense at 55-65℃ for 5-8 hours. After the reaction is complete, filter to remove the solid precipitate. Wash the filtrate three times with deionized water, collect the organic phase and dry it with anhydrous sodium sulfate. Remove chloroform by rotary evaporation, purify by column chromatography, and distill under reduced pressure to obtain phosphorus-containing cashew nut powder.

[0007] Step 2: Under nitrogen protection, add phosphorus-containing cashew phenol and mercaptoethylamine to anhydrous ethanol solvent, stir and mix, then add 2-hydroxy-2-methylphenylacetone photoinitiator, and control the light intensity to 50-60 mW / cm² under 365 nm ultraviolet light. 2 Irradiate at room temperature for 30-40 minutes. After the reaction is complete, remove the solvent by rotary evaporation under reduced pressure, wash and dry to obtain aminated phosphorus-containing cashew phenol.

[0008] Step 3: Under nitrogen protection, add aminated phosphorus-containing cashew phenol to anhydrous dichloromethane solvent, stir to dissolve, and then add 3-isocyanate-propyltriethoxysilane dropwise. Stir and react at room temperature for 1-2 hours. After the reaction is completed, remove the solvent by rotary evaporation under reduced pressure and dry under vacuum to obtain the modified phosphorus-containing cashew phenol derivative.

[0009] Furthermore, in step one, the ratio of cashew phenol, triethylamine, chloroform, and diphenyl chlorophosphate is 9-10g:3-3.4g:50-80mL:8-9g.

[0010] Furthermore, in step two, the ratio of anhydrous ethanol, phosphorus-containing cashew phenol, mercaptoethylamine, and 2-hydroxy-2-methylphenylacetone photoinitiator is 50-60 mL: 5-6 g: 2.5-3.5 g: 0.1-0.15 g.

[0011] Furthermore, in step three, the ratio of anhydrous dichloromethane, aminated phosphorus-containing cashew phenol, and 3-isocyanate-propyltriethoxysilane is 30-40 mL: 3-3.5 g: 1.2-1.4 g.

[0012] Furthermore, the modified sulfide compound is prepared by:

[0013] S1: Add benzaldehyde to the reactor, and add thioglycolic acid dropwise while stirring. After the addition is complete, mix and stir at room temperature for 5-8 min, and then react at 70-80℃ for 15-20 min. After the reaction is complete, cool to room temperature, add petroleum ether, and a white solid precipitates. Filter the solid product, dissolve it in chloroform, heat and reflux and stir for 30-40 min, add petroleum ether again, recrystallize and wash the solid product. Repeat the above chloroform / petroleum ether recrystallization step 3 times to obtain 2,2′-(phenylmethylene)dithioacetic acid.

[0014] S2: Add 2,2′-(phenylmethylene)dithiodiacetic acid and undecenol to anhydrous toluene solvent, mix well, then add p-toluenesulfonic acid, and reflux at 110-120℃ for 4-6 h. During the reaction, continuously separate the generated water using a water separator. After the reaction is complete, cool to room temperature, and wash the organic phase with saturated sodium bicarbonate aqueous solution and deionized water until neutral. Collect the organic phase and dry it with anhydrous sodium sulfate. Finally, remove the toluene solvent by rotary evaporation under reduced pressure, and dry under vacuum to obtain the modified sulfide compound.

[0015] Furthermore, the ratio of benzaldehyde to thioglycolic acid in S1 is 4.2-4.3g:7.3-7.4g.

[0016] Further, the ratio of anhydrous toluene, 2,2′-(phenylmethylene)dithioacetic acid, undecenol, and p-toluenesulfonic acid in S2 is 30-40 mL: 4-4.5 g: 5.6-5.8 g: 0.04-0.05 g.

[0017] Further, the preparation method of the low heat-generating tread rubber is as follows: natural rubber and butadiene rubber are put into a mixer and plasticized at 60-80℃ for 1-2 minutes. Then, silica, carbon black, bis-[γ-(triethoxysilyl)propyl]tetrasulfide, modified phosphorus-containing cashew phenol derivative, modified sulfide compound, zinc oxide, stearic acid and antioxidant RD are added and mixed at 140-155℃ for 3-5 minutes. The rubber is discharged to obtain the masterbatch. After cooling the obtained masterbatch, it is put into a mixer, sulfur and accelerator CZ are added, and the rubber is mixed at 80-100℃ for 2-3 minutes. The rubber is discharged to obtain the low heat-generating tread rubber.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] This invention introduces a self-made modified phosphorus-containing cashew phenol derivative. The hydrolyzable ethoxysilane side chain at its end chemically condenses and anchors with the silanol groups on the surface of silica, firmly anchoring the additive molecules to the silica surface. Its long alkyl chain further shields the hydrogen bond interactions between silica particles, effectively depolymerizing the filler network and reducing internal friction between filler particles during dynamic compression. This results in extremely low compression heat generation and a low 60°C loss factor for the tread pad. A modified sulfide compound replaces the traditional physical plasticizer. Through its terminal carbon-carbon double bond, it integrates into the rubber crosslinking network during vulcanization, forming a long-chain flexible buffer structure containing sulfide bonds. This reduces frictional loss during reciprocating deformation of the molecular chains. Compared to small-molecule physical plasticizers that do not participate in crosslinking, this chemically bonded structure exhibits a lower tendency for interfacial migration under high-temperature dynamic conditions. The synergistic effect of both enhances the low heat generation performance of the tread pad. Meanwhile, while achieving the goal of low heat generation, this invention does not sacrifice the basic mechanical properties of the rubber compound. The thioether bonds inside the modified thioether compound molecular chain can continuously capture and consume peroxide free radicals during the thermo-oxidative aging process, effectively delaying the oxidative breakage of the rubber molecular chain, thereby improving the heat aging resistance of the tread pad rubber. Under long-term high-temperature dynamic service conditions, it can maintain excellent mechanical properties and structural integrity, significantly extending the service life of the tire. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The reagents used in the following specific embodiments are of analytical grade. Additionally:

[0022] Natural rubber: grade NR;

[0023] Butadiene rubber: grade BR9000;

[0024] Silica: Precipitated silica, grade 7000GR, with a specific surface area of ​​160 m². 2 / g;

[0025] Carbon black: grade N550;

[0026] Petroleum ether: boiling range 60-90℃;

[0027] Cashew phenol: purchased from Cardläne Company (Zhuhai, China), a pale yellow liquid composed of 3% saturated compound, 20% monoene, 36% diene and 41% triene.

[0028] Example 1

[0029] (1) Add 9g of cashew phenol, 3g of triethylamine and 50mL of chloroform to the reactor and mix well. Then add 8g of diphenyl chlorophosphate dropwise to the reactor. After the addition is complete, reflux and condense at 55℃ for 5h. After the reaction is complete, filter to remove the solid precipitate. Wash the obtained filtrate with deionized water three times, collect the organic phase and dry it with anhydrous sodium sulfate. Remove chloroform by rotary evaporation, purify by column chromatography, and distill under reduced pressure to obtain phosphorus-containing cashew phenol.

[0030] (2) Under nitrogen protection, add 5g of phosphorus-containing cashew phenol and 2.5g of mercaptoethylamine (the amount added is calculated based on the iodine value and unsaturation distribution of cashew phenol) to 50mL of anhydrous ethanol solvent, stir and mix, then add 0.1g of 2-hydroxy-2-methylphenylacetone photoinitiator, and control the light intensity to 50mW / cm under 365nm ultraviolet light. 2 Irradiate at room temperature for 30 min. After the reaction is complete, remove the solvent by rotary evaporation under reduced pressure, wash and dry to obtain aminated phosphorus-containing cashew nut alcohol.

[0031] (3) Under nitrogen protection, 3g of amino-containing phosphorus-containing cashew phenol was added to 30mL of anhydrous dichloromethane solvent and stirred to dissolve. Then, 1.2g of 3-isocyanate-propyltriethoxysilane was added dropwise and stirred at room temperature for 1h. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure and dried under vacuum to obtain the modified phosphorus-containing cashew phenol derivative.

[0032] (4) Add 4.2 g of benzaldehyde to the reactor, and add 7.3 g of thioglycolic acid dropwise while stirring. After the addition is complete, mix and stir at room temperature for 5 min, and then react at 70 °C for 15 min. After the reaction is complete, cool to room temperature, add petroleum ether, and a white solid precipitates. Filter, dissolve the obtained solid product in chloroform, heat and reflux and stir for 30 min, add petroleum ether again, recrystallize and wash the solid product. Repeat the above chloroform / petroleum ether recrystallization steps 3 times to obtain 2,2′-(phenylmethylene) dithiodiacetic acid;

[0033] (5) Add 4g of 2,2′-(phenylmethylene) dithiodiacetic acid and 5.6g of undecenol to 30mL of anhydrous toluene solvent, mix well, then add 0.04g of p-toluenesulfonic acid, reflux at 110℃ for 4h, and continuously separate the generated water through a water separator during the reaction. After the reaction is completed, cool to room temperature, wash the organic phase with saturated sodium bicarbonate aqueous solution and deionized water until neutral, collect the organic phase and dry it with anhydrous sodium sulfate, finally remove the toluene solvent by rotary evaporation under reduced pressure, and dry under vacuum to obtain the modified sulfide compound;

[0034] (6) 60 parts by weight of natural rubber and 40 parts by weight of butadiene rubber were put into a mixer and plasticized at 60°C for 1 min. Then, 30 parts by weight of silica, 10 parts by weight of carbon black, 3 parts by weight of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 3 parts by weight of modified phosphorus-containing cashew phenol derivative, 2 parts by weight of modified sulfide compound, 3 parts by weight of zinc oxide, 1 part by weight of stearic acid and 1 part by weight of antioxidant RD were added and mixed at 140°C for 3 min. The rubber was discharged to obtain masterbatch. After cooling the masterbatch, it was put into a mixer and 1.5 parts by weight of sulfur and 1 part by weight of accelerator CZ were added. The mixture was mixed at 80°C for 2 min and discharged to obtain low heat generation tread pad rubber.

[0035] Example 2

[0036] (1) Add 10g of cashew phenol, 3.4g of triethylamine and 80mL of chloroform to the reactor and mix well. Then add 9g of diphenyl chlorophosphate dropwise to the reactor. After the addition is complete, reflux and condense at 65℃ for 8h. After the reaction is complete, filter to remove the solid precipitate. Wash the obtained filtrate with deionized water 3 times, collect the organic phase and dry it with anhydrous sodium sulfate. Remove chloroform by rotary evaporation, purify by column chromatography, and distill under reduced pressure to obtain phosphorus-containing cashew phenol.

[0037] (2) Under nitrogen protection, add 6g of phosphorus-containing cashew phenol and 3.5g of mercaptoethylamine (the amount added is calculated based on the iodine value and unsaturation distribution of cashew phenol) to 60mL of anhydrous ethanol solvent, stir and mix, then add 0.15g of 2-hydroxy-2-methylphenylacetone photoinitiator, and control the light intensity to 60mW / cm under 365nm ultraviolet light. 2 Irradiate at room temperature for 40 min. After the reaction is complete, remove the solvent by rotary evaporation under reduced pressure, wash and dry to obtain aminated phosphorus-containing cashew phenol.

[0038] (3) Under nitrogen protection, 3.5 g of amino-containing phosphorus-containing cashew phenol was added to 40 mL of anhydrous dichloromethane solvent and stirred to dissolve. Then, 1.4 g of 3-isocyanate-propyltriethoxysilane was added dropwise and stirred at room temperature for 2 h. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure and dried under vacuum to obtain the modified phosphorus-containing cashew phenol derivative.

[0039] (4) Add 4.3 g of benzaldehyde to the reactor, and add 7.4 g of thioglycolic acid dropwise while stirring. After the addition is complete, mix and stir at room temperature for 8 min, and then react at 80 °C for 20 min. After the reaction is complete, cool to room temperature, add petroleum ether, and a white solid precipitates. Filter, dissolve the obtained solid product in chloroform, heat and reflux and stir for 40 min, add petroleum ether again, recrystallize and wash the solid product. Repeat the above chloroform / petroleum ether recrystallization steps 3 times to obtain 2,2′-(phenylmethylene)dithioacetic acid;

[0040] (5) Add 4.5 g of 2,2′-(phenylmethylene) dithiodiacetic acid and 5.8 g of undecenol to 40 mL of anhydrous toluene solvent, mix well, then add 0.05 g of p-toluenesulfonic acid, and reflux at 120 °C for 6 h. During the reaction, continuously separate the generated water through a water separator. After the reaction is completed, cool to room temperature, wash the organic phase with saturated sodium bicarbonate aqueous solution and deionized water until neutral, collect the organic phase and dry it with anhydrous sodium sulfate, finally remove the toluene solvent by rotary evaporation under reduced pressure, and dry under vacuum to obtain the modified sulfide compound.

[0041] (6) 80 parts by weight of natural rubber and 20 parts by weight of butadiene rubber were put into a mixer and plasticized at 80°C for 2 min. Then, 40 parts by weight of silica, 20 parts by weight of carbon black, 4 parts by weight of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 4 parts by weight of modified phosphorus-containing cashew phenol derivative, 4 parts by weight of modified sulfide compound, 5 parts by weight of zinc oxide, 3 parts by weight of stearic acid and 2 parts by weight of antioxidant RD were added and mixed at 155°C for 5 min. The rubber was discharged to obtain masterbatch. After cooling the masterbatch, it was put into a mixer and 2.5 parts by weight of sulfur and 2 parts by weight of accelerator CZ were added. The mixture was mixed at 100°C for 3 min and discharged to obtain low heat generation tread pad rubber.

[0042] Example 3

[0043] (1) Add 9.5g of cashew nut powder, 3.2g of triethylamine and 65mL of chloroform to the reactor and mix well. Then add 8.5g of diphenyl chlorophosphate dropwise to the reactor. After the addition is complete, reflux and condense at 60℃ for 6h. After the reaction is complete, filter to remove the solid precipitate. Wash the obtained filtrate with deionized water 3 times, collect the organic phase and dry it with anhydrous sodium sulfate. Remove chloroform by rotary evaporation, purify by column chromatography, and distill under reduced pressure to obtain phosphorus-containing cashew nut powder.

[0044] (2) Under nitrogen protection, add 5.5g of phosphorus-containing cashew nut shellac and 3g of mercaptoethylamine (the amount added is calculated based on the iodine value and unsaturation distribution of cashew nut shellac) to 55mL of anhydrous ethanol solvent, stir and mix, then add 0.12g of 2-hydroxy-2-methylphenylacetone photoinitiator, and control the light intensity to 55mW / cm² under 365nm ultraviolet light. 2 Irradiate at room temperature for 35 min. After the reaction is complete, remove the solvent by rotary evaporation under reduced pressure, wash and dry to obtain aminated phosphorus-containing cashew phenol.

[0045] (3) Under nitrogen protection, 3.3 g of amino-containing phosphorus-containing cashew phenol was added to 35 mL of anhydrous dichloromethane solvent and stirred to dissolve. Then, 1.3 g of 3-isocyanate-propyltriethoxysilane was added dropwise and stirred at room temperature for 1.5 h. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure and dried under vacuum to obtain the modified phosphorus-containing cashew phenol derivative.

[0046] (4) Add 4.25 g of benzaldehyde to the reactor, and add 7.35 g of thioglycolic acid dropwise while stirring. After the addition is complete, mix and stir at room temperature for 6 min, and then react at 75 °C for 18 min. After the reaction is complete, cool to room temperature, add petroleum ether, and a white solid precipitates. Filter, dissolve the obtained solid product in chloroform, heat and reflux and stir for 35 min, add petroleum ether again, recrystallize and wash the solid product. Repeat the above chloroform / petroleum ether recrystallization steps 3 times to obtain 2,2′-(phenylmethylene)dithioacetic acid;

[0047] (5) Add 4.2 g of 2,2′-(phenylmethylene) dithiodiacetic acid and 5.7 g of undecenol to 35 mL of anhydrous toluene solvent, mix well, then add 0.04 g of p-toluenesulfonic acid, reflux at 115 °C for 5 h, and continuously separate the generated water through a water separator during the reaction. After the reaction is completed, cool to room temperature, wash the organic phase with saturated sodium bicarbonate aqueous solution and deionized water until neutral, collect the organic phase and dry it with anhydrous sodium sulfate, finally remove the toluene solvent by rotary evaporation under reduced pressure, and dry under vacuum to obtain the modified sulfide compound;

[0048] (6) 70 parts by weight of natural rubber and 30 parts by weight of butadiene rubber were put into a mixer and plasticized at 70°C for 2 min. Then, 35 parts by weight of silica, 15 parts by weight of carbon black, 4 parts by weight of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 3 parts by weight of modified phosphorus-containing cashew phenol derivative, 3 parts by weight of modified sulfide compound, 4 parts by weight of zinc oxide, 2 parts by weight of stearic acid and 1 part by weight of antioxidant RD were added and mixed at 150°C for 4 min. The rubber was discharged to obtain masterbatch. After cooling the masterbatch, it was put into a mixer and 2 parts by weight of sulfur and 1 part by weight of accelerator CZ were added. The mixture was mixed at 90°C for 3 min and discharged to obtain low heat generation tread pad rubber.

[0049] Comparative Example 1

[0050] The main difference between this comparative example and Example 3 is that an equal weight of phosphorus-containing cashew phenol is used instead of the modified phosphorus-containing cashew phenol derivative. Apart from the above differences, the other raw material composition ratios, preparation processes and rubber compound mixing processes of this comparative example are completely consistent with those of Example 3.

[0051] Comparative Example 2

[0052] The main difference between this comparative example and Example 3 is that an equal part by weight of diethyl 2,2′-(phenylmethylene)dithiodiacetic acid (i.e., the esterification product of BTA and ethanol, which does not contain terminal double bonds and long carbon chains) is used instead of the modified thioether compound. Apart from the above differences, the remaining raw material proportions, the preparation process of the modified phosphorus-containing cashew nut phenol derivative, and the rubber compound mixing process of this comparative example are completely consistent with those of Example 3.

[0053] The preparation method of 2,2′-(phenylmethylene)dithiodiacetic acid diethyl ester is as follows: 2,2′-(phenylmethylene)dithiodiacetic acid is dissolved in excess anhydrous ethanol, p-toluenesulfonic acid is added as an esterification catalyst, and the mixture is heated under reflux to carry out the esterification reaction; after the reaction is completed, excess ethanol is removed by rotary evaporation under reduced pressure, the remaining solid is dissolved in dichloromethane, and the organic phase is washed successively with saturated sodium bicarbonate aqueous solution and deionized water until neutral. The organic phase is dried with anhydrous sodium sulfate, and the dichloromethane is removed by rotary evaporation under reduced pressure. The mixture is then dried under vacuum to obtain 2,2′-(phenylmethylene)dithiodiacetic acid diethyl ester.

[0054] Comparative Example 3

[0055] The main difference between this comparative example and Example 3 is that no modified phosphorus-containing cashew phenol derivative is added, and an equal weight of precipitated silica 7000GR is used as a filler instead. The amount of bis-[γ-(triethoxysilyl)propyl]tetrasulfide remains unchanged. Apart from the above differences, the other raw material ratios, preparation processes and rubber compound mixing processes of this comparative example are completely consistent with those of Example 3.

[0056] Comparative Example 4

[0057] The main difference between this comparative example and Example 3 is that no modified sulfide compound is added, and an equal amount of environmentally friendly aromatic oil TDAE is used for substitution. Apart from the above differences, the other raw material composition ratios, preparation processes and rubber compound mixing processes of this comparative example are completely consistent with those of Example 3.

[0058] Performance testing

[0059] The low heat-generating tread pads prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests.

[0060] (1) Conventional physical and mechanical properties: The tensile strength and elongation at break of the vulcanizate were determined according to GB / T528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber"; the right-angle tear strength was determined according to GB / T529-2008 "Determination of tear strength of vulcanized rubber or thermoplastic rubber (trouser-shaped, right-angle and crescent-shaped specimens)". The higher the tensile strength and tear strength, the stronger the rubber compound's resistance to breakage.

[0061] (2) Dynamic compression heat generation: Refer to GB / T1687.3-2016 "Determination of compression heat generation of vulcanized rubber - Part 3: Compression flexure test", test temperature 55℃, static compression load 1.0MPa, compression stroke 4.45mm, test the internal temperature rise (ΔT, ℃) of the rubber compound during continuous dynamic compression. The lower the temperature rise, the lower the dynamic heat generation of the rubber compound.

[0062] (3) Dynamic mechanical properties: A dynamic thermodynamic analyzer (DMA) was used to perform temperature scanning within a temperature range of -60℃ to 80℃, a frequency of 10Hz, and a strain of 0.1%, and the loss factor (tanδ) at 60℃ was recorded. The lower the tanδ value at 60℃, the smaller the hysteresis loss of the rubber compound, and the lower the tire rolling resistance and dynamic heat generation.

[0063] (4) Interfacial adhesion performance: Refer to GB / T16586-2014 "Determination of Adhesion Strength between Vulcanized Rubber and Steel Cord" to determine the pull-out force (N) between the tread pad rubber and the brass-plated steel cord. The higher the pull-out force, the better the adhesion between the pad rubber layer and the tire belt layer.

[0064] (5) Heat aging resistance: After the vulcanized rubber sample is aged in a 100℃ hot air aging chamber for 72 hours, its tensile strength is measured again. The tensile strength retention rate is calculated by the following formula: Tensile strength retention rate (%) = (tensile strength after aging / tensile strength before aging) × 100%. The higher the retention rate, the better the heat aging resistance of the rubber compound, indicating that the modified sulfide compound makes a more significant contribution to anti-reversion / anti-aging.

[0065] The test results are shown in Table 1.

[0066] Table 1: Performance Tests

[0067] project Tensile strength (MPa) Elongation at break (%) Right-angle tear strength (kN / m) Compression temperature rise (ΔT, °C) 60℃ tanδ Wire pulling force (N) Tensile strength retention rate after aging (%) Example 1 20.1 506 59.2 17.2 0.086 436 90.8 Example 2 20.8 489 62.5 16.4 0.080 454 92.2 Example 3 21.3 461 61.0 15.8 0.076 462 93.5 Comparative Example 1 17.8 432 51.6 22.5 0.120 398 87.5 Comparative Example 2 17.2 450 49.0 20.2 0.108 412 83.8 Comparative Example 3 17.0 410 46.8 23.8 0.132 385 86.0 Comparative Example 4 18.1 448 50.5 21.0 0.112 402 77.5

[0068] As can be seen from Table 1, the low heat generation tread pad adhesives prepared in Examples 1-3 not only have excellent mechanical properties and steel wire adhesion, but also good low heat generation properties and heat aging resistance.

[0069] The comparison shows that Comparative Example 1, which uses an equal part by weight of phosphorus-containing cashew phenol to replace the modified phosphorus-containing cashew phenol derivative, cannot chemically condense and anchor with the silanol hydroxyl groups on the surface of the abundant silica in the formulation because it lacks grafted hydrolyzable ethoxysilane side chains. This results in the filler network not being effectively depolymerized, causing silica to agglomerate in the rubber matrix. Under dynamic compression, the friction between filler particles increases dramatically, leading to heat generation and performance degradation. Comparative Example 2, which uses an equal part by weight of 2,2′-(phenylmethylene)dithiodiacetic acid diethyl ester to replace the modified sulfide compound, has short-chain ester molecules without terminal carbon-carbon double bonds. During vulcanization, these molecules cannot integrate into the rubber crosslinking network and are only dispersed in the rubber compound as free small molecules, failing to form a long alkyl flexible stress buffer structure. The free state of these small molecules increases intermolecular friction, leading to performance degradation. Comparative Example 3 does not add the modified phosphorus-containing cashew phenol derivative. The first example uses an equal weight portion of precipitated silica 7000GR as a filler, but lacks the targeted dispersion and interfacial modification effects of modified phosphorus-containing cashew phenol derivatives on silica. Relying solely on bis-[γ-(triethoxysilyl)propyl]tetrasulfide cannot completely handle the large quantity of silica, leading to extremely severe filler agglomeration and thus the most severe performance degradation. The second example does not add modified sulfide compounds but uses an equal weight portion of environmentally friendly aromatic oil TDAE as a substitute. TDAE is only a general physical plasticizer, which only reduces the viscosity of the rubber compound through lubrication and does not participate in vulcanization crosslinking. It cannot build flexible crosslinking buffer segments. Under long-term high-temperature dynamic conditions, small molecule aromatic oil is prone to migrate and precipitate to the rubber layer interface, causing a continuous decrease in the crosslinking density of the rubber compound, hardening and brittleness, and increased frictional loss due to reciprocating deformation of molecular chains. Moreover, it lacks the free radical capture and anti-vulcanization reversion effect of the sulfide structure, thus resulting in performance degradation.

[0070] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0072] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A low-heat-generating tire tread pad rubber, characterized in that, Based on a total weight of 100 parts by weight of natural rubber and butadiene rubber, the product comprises the following components by weight: 60-80 parts by weight of natural rubber, 20-40 parts by weight of butadiene rubber, 30-40 parts by weight of silica, 3-4 parts by weight of modified phosphorus-containing cashew phenol derivative, 2-4 parts by weight of modified sulfide compound, 10-20 parts by weight of carbon black, 3-4 parts by weight of bis-[γ-(triethoxysilyl)propyl]tetrasulfide, 3-5 parts by weight of zinc oxide, 1-3 parts by weight of stearic acid, 1-2 parts by weight of antioxidant RD, 1.5-2.5 parts by weight of sulfur, and 1-2 parts by weight of accelerator CZ. The preparation method of the modified phosphorus-containing cashew phenol derivative is as follows: Step 1: Add cashew nut powder, triethylamine, and chloroform to the reactor and mix well. Then, add diphenyl chlorophosphate dropwise to the reactor. After the addition is complete, reflux and condense at 55-65℃ for 5-8 hours. After the reaction is complete, filter to remove the solid precipitate. Wash the filtrate three times with deionized water, collect the organic phase and dry it with anhydrous sodium sulfate. Remove chloroform by rotary evaporation, purify by column chromatography, and distill under reduced pressure to obtain phosphorus-containing cashew nut powder. Step 2: Under nitrogen protection, add phosphorus-containing cashew phenol and mercaptoethylamine to anhydrous ethanol solvent, stir and mix, then add 2-hydroxy-2-methylphenylacetone photoinitiator, and control the light intensity to 50-60 mW / cm² under 365 nm ultraviolet light. 2 Irradiate at room temperature for 30-40 minutes. After the reaction is complete, remove the solvent by rotary evaporation under reduced pressure, wash and dry to obtain aminated phosphorus-containing cashew phenol. Step 3: Under nitrogen protection, add aminated phosphorus-containing cashew phenol to anhydrous dichloromethane solvent, stir to dissolve, then add 3-isocyanate-propyltriethoxysilane dropwise, stir and react at room temperature for 1-2 hours. After the reaction is completed, remove the solvent by rotary evaporation under reduced pressure, and dry under vacuum to obtain the modified phosphorus-containing cashew phenol derivative. The modified sulfide compound is prepared by: S1: Add benzaldehyde to the reactor, and add thioglycolic acid dropwise while stirring. After the addition is complete, mix and stir at room temperature for 5-8 min, and then react at 70-80℃ for 15-20 min. After the reaction is complete, cool to room temperature, add petroleum ether, and a white solid precipitates. Filter the solid product, dissolve it in chloroform, heat and reflux and stir for 30-40 min, add petroleum ether again, recrystallize and wash the solid product. Repeat the above chloroform / petroleum ether recrystallization step 3 times to obtain 2,2′-(phenylmethylene)dithioacetic acid. S2: Add 2,2′-(phenylmethylene)dithiodiacetic acid and undecenol to anhydrous toluene solvent, mix well, then add p-toluenesulfonic acid, and reflux at 110-120℃ for 4-6 h. During the reaction, continuously separate the generated water using a water separator. After the reaction is complete, cool to room temperature, and wash the organic phase with saturated sodium bicarbonate aqueous solution and deionized water until neutral. Collect the organic phase and dry it with anhydrous sodium sulfate. Finally, remove the toluene solvent by rotary evaporation under reduced pressure, and dry under vacuum to obtain the modified sulfide compound.

2. The low-heat-generating tread pad rubber according to claim 1, characterized in that, In step one, the ratio of cashew phenol, triethylamine, chloroform, and diphenyl chlorophosphate is 9-10g:3-3.4g:50-80mL:8-9g.

3. The low-heat-generating tire tread pad rubber according to claim 1, characterized in that, In step two, the ratio of anhydrous ethanol, phosphorus-containing cashew phenol, mercaptoethylamine, and 2-hydroxy-2-methylphenylacetone photoinitiator is 50-60 mL: 5-6 g: 2.5-3.5 g: 0.1-0.15 g.

4. The low-heat-generating tread pad rubber according to claim 1, characterized in that, In step three, the ratio of anhydrous dichloromethane, aminated phosphorus-containing cashew phenol, and 3-isocyanate-propyltriethoxysilane is 30-40 mL: 3-3.5 g: 1.2-1.4 g.

5. The low-heat-generating tire tread pad rubber according to claim 1, characterized in that, The ratio of benzaldehyde to thioglycolic acid in S1 is 4.2-4.3g:7.3-7.4g.

6. The low-heat-generating tread pad rubber according to claim 1, characterized in that, The ratio of anhydrous toluene, 2,2′-(phenylmethylene)dithioacetic acid, undecenol, and p-toluenesulfonic acid in S2 is 30-40 mL: 4-4.5 g: 5.6-5.8 g: 0.04-0.05 g.

7. A method for preparing a low-heat-generating tire tread pad rubber as described in any one of claims 1-6, characterized in that, The preparation method of the low heat-generating tread rubber is as follows: natural rubber and butadiene rubber are put into a mixer and plasticized at 60-80℃ for 1-2 minutes. Then, silica, carbon black, bis-[γ-(triethoxysilyl)propyl]tetrasulfide, modified phosphorus-containing cashew phenol derivative, modified sulfide compound, zinc oxide, stearic acid and antioxidant RD are added and mixed at 140-155℃ for 3-5 minutes. The rubber is discharged to obtain the masterbatch. After cooling the obtained masterbatch, it is put into a mixer, sulfur and accelerator CZ are added, and the rubber is mixed at 80-100℃ for 2-3 minutes. The rubber is discharged to obtain the low heat-generating tread rubber.