A low heat build-up high stability crown band rubber composition, mixing method and tire

Abstract

This invention relates to the field of tire manufacturing technology, and more particularly to a low-heat-generating, high-stability crown belt rubber composition, a mixing method, and a tire. Based on 100 parts by weight of the rubber components, it includes natural rubber, first and second non-oil-extended polystyrene-butadiene rubber (BF2055H / L), and is supplemented with highly dispersed silica, carbon black, silane coupling agents, and α-methylstyrene resin, among other additives. BF2055H / L has a 20% styrene content, 55% vinyl content, and a bimodal molecular weight distribution, synergistically improving the dynamic modulus distribution of the rubber and the uniformity of filler dispersion. Optimized mixing processes achieve efficient reaction and uniform distribution of SiO2 with the rubber. Experiments have shown that, without sacrificing hardness and handling performance, the bimodal non-oil-extended SSBR is used as the core to solve the contradiction between heat generation, deformation, and processing; natural rubber ensures adhesion and elasticity; and medium-structure carbon black + silica balances reinforcement and heat generation. This achieves a comprehensive performance breakthrough in low heat generation, low deformation, high support, high durability, and environmentally friendly manufacturing.

Description

Technical Field

[0001] This invention relates to the field of tire manufacturing technology, and in particular to a crown belt rubber composition with low heat generation and high stability, a mixing method, and a tire. Background Technology

[0002] As the "restraint and protection layer" of the tire belt layer, the core function of the crown layer is to fix the end point of the belt layer, suppress the radial expansion and circumferential displacement of the belt layer during high-speed driving, and buffer the impact load transmitted by the tread. Its performance directly determines the tire's high-speed durability, handling stability and crown profile retention. With the increasing demands for high torque and long range in electric vehicles (EVs) and the implementation of the "Evaluation Method for Rolling Resistance Grading of Passenger Car Tires (2023 Edition)," crown and belt layer rubber compounds face three major technical challenges: 1) Low heat generation requirement: When EV tires travel at high speeds, the shear friction between the belt layer and the crown layer intensifies. If the rubber compound generates too much heat, it can easily lead to aging and failure of the belt layer adhesive, causing the crown layer to peel off; 2) Low permanent deformation requirement: Under long-term compression-shear cycles, the compression permanent deformation rate of traditional crown and belt layer rubber compounds (such as NR / oil-extended SSBR systems) is often >35%, which can easily lead to belt layer loosening, crown profile distortion, and reduced handling precision; 3) Balancing processing and environmental protection: Existing low heat generation formulations mostly rely on adding filler oils to reduce the viscosity of the rubber compound, but oil phase migration can lead to a rebound in heat generation later, and volatile organic compound (VOC) emissions do not meet the requirements of green manufacturing. Therefore, there is a gap in the synergistic optimization of "low heat generation - low deformation - high stability - environmentally friendly processing" in existing crown and belt layer rubber compounds, and there is an urgent need for a rubber compound system based on novel polymer design to break through the bottlenecks of traditional formulations. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a crown layer rubber composition with low heat generation and high stability, achieving a quadruple performance breakthrough of "low heat generation, low deformation, high-speed stability, and low VOC" to meet the needs of electric vehicles and high-end passenger car tires.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A low-heat-generating, high-stability crown layer rubber composition is prepared by mixing raw materials comprising the following components, based on 100 parts by weight of the rubber component:

[0006] 55–75 parts natural rubber;

[0007] 10–25 parts of first solution-polymerized styrene-butadiene rubber;

[0008] 10–25 parts of second solution-polymerized styrene-butadiene rubber;

[0009] 5–10 parts of highly dispersed silica;

[0010] 40–55 parts carbon black;

[0011] 0.5–1.5 parts of silane coupling agent;

[0012] 3–6 parts of α-methylstyrene resin;

[0013] The mass ratio of the first solution-polymerized styrene-butadiene rubber (SBR) to the second solution-polymerized SBR is 1.5:1 to 1:1.5, and both are unoil-extended high-vinyl solution-polymerized SBRs. The styrene content is 20±1wt%, the vinyl content is 55±3wt%, the glass transition temperature is -35±2℃, and the weight-average molecular weight is 380–420 kg·mol⁻¹. -1 With 280–320 kg·mol -1 .

[0014] Preferably, it is prepared by mixing raw materials comprising the following components in parts by weight:

[0015] 60–70 parts natural rubber;

[0016] 15–20 parts of first solution-polymerized styrene-butadiene rubber;

[0017] 15–20 parts of second solution-polymerized styrene-butadiene rubber;

[0018] 6–8 parts of silica;

[0019] 45–50 parts carbon black;

[0020] 0.8–1.2 parts of silane coupling agent;

[0021] 4–5 parts of α-methylstyrene resin.

[0022] Preferably, the first and second solution-polymerized styrene-butadiene rubbers are BF2055H and BF2055L solution-polymerized styrene-butadiene rubbers produced by China Petroleum & Chemical Corporation (Sinopec), respectively. BF2055H has a styrene content of 20%, a vinyl content of 55%, is unextended with oil, has a Tg of -35℃, and a weight-average molecular weight of 380–420 kg·mol⁻¹. -1 BF2055L: 20% styrene, 55% vinyl, unoiled, Tg = -35℃, weight-average molecular weight 280–320 kg·mol⁻¹ -1 The preferred mass ratio is 1.2:1–1:1.2.

[0023] Preferably, highly dispersed silica has a specific surface area (CTAB) ≥ 160 m². 2 / g, preferably CTAB is 180–195m 2 / g, BET is 195–210m 2 / g; The preferred BET specific surface area of ​​carbon black particles is 20-160m².2 / g, more preferably 40-130m 2 / g, further preferably 50-120m 2 / g; more preferably, the carbon black is one or more of N134, N220, N234, N375 or N375, N330, N339, N347, N326; more preferably, the carbon black is N326 and / or N330.

[0024] Preferably, the silane coupling agent has the structural formula YR-Si(OR)3, where Y is an organic functional group and SiOR is a silaneoxy group; preferably, the silane coupling agent is selected from one or more of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, bis-[γ-(triethoxysilyl)propyl]tetrasulfide, bis-propyltriethoxysilane disulfide, 3-(octanoylthio)propyltriethoxysilane and n-octyltriethoxysilane.

[0025] Preferably, the α-methylstyrene resin has a softening point of 95–120°C and a number-average molecular weight of 1000–3000.

[0026] Preferably, the compounded raw materials also include an activator, an antioxidant, and a vulcanizing agent; preferably, the activator includes 2-5 parts zinc oxide and 1-3 parts stearic acid; 2-4 parts antioxidant; the vulcanizing agent includes 1.0-3.0 parts insoluble sulfur and 1.0-2.0 parts accelerator; more preferably, the accelerator includes one or more of N-tert-butyl-2-benzothiazole sulfenamide or N-cyclohexyl-2-benzothiazole sulfenamide, diphenylguanidine accelerators, hexamethylenetetramine, 4,4′-dithiodimorpholine, and dicaprolactam disulfide.

[0027] Furthermore, the present invention also provides a mixing method for preparing the rubber composition, the method comprising the following steps:

[0028] (1) At 110–125℃, natural rubber, first solution polymerized styrene-butadiene rubber, second solution polymerized styrene-butadiene rubber, all silica, 1 / 2 carbon black, and silane coupling agent are put into a mixer at once and mixed for 50 seconds.

[0029] (2) Raise the mixing temperature to 145–148℃, continue mixing for 40 seconds, add the remaining carbon black and α-methylstyrene resin, and then discharge the material to obtain the masterbatch.

[0030] (3) Cool the masterbatch to 95–100°C, add sulfur and accelerator, and finally mix in an internal mixer or open mill for 60 seconds.

[0031] (4) Press and vulcanize at 165–175℃ for 12–18 min.

[0032] Furthermore, the present invention also provides the use of the rubber composition in the manufacture of tire crown layers.

[0033] Furthermore, the present invention also provides a tire in which the tire crown layer is obtained by vulcanization of the rubber composition.

[0034] By employing the aforementioned technical solution, this invention utilizes BF2055H / BF2055L series solution-polymerized styrene-butadiene rubber with a bimodal molecular weight structure, a vinyl content of 55%, and no filler oil, combined with highly dispersed silica, medium-structure carbon black, appropriate amounts of α-methylstyrene resin, and a silane coupling agent, to construct a crown layer rubber composition with low heat generation and high stability. Its specific technical effects are as follows:

[0035] 1. Significantly reduced heat generation

[0036] By using a completely unoiled bimodal SSBR with a vinyl content of 55% (Mw_H≈400 kg·mol⁻¹) -1 / Mw_L≈300kg·mol -1 It can also synergistically reinforce carbon black and silica to avoid the later heat recovery caused by traditional oil-extended SSBR; at the same time, the high vinyl segment can form a strong covalent bond with the silane coupling agent (Si69), reduce the "frictional internal friction" caused by silica / carbon black agglomeration, and reduce dynamic hysteresis at the molecular level.

[0037] 2. Significantly reduces permanent deformation and maintains long-term stability of the tire crown profile.

[0038] BF2055H is a high molecular weight segment that forms a rigid support skeleton after vulcanization, providing ample resistance to deformation. BF2055L is a low molecular weight segment that fully wets the filler surface and fills the gaps in the skeleton, resulting in uniform crosslinking density. Simultaneously, an appropriate amount of carbon black with a medium structure and moderate specific surface area can be uniformly dispersed in the rubber matrix, forming an interlocking structure with the crosslinking network of the bimodal SSBR. This prevents permanent slippage of rubber molecular chains under compression-shear cycles, avoiding the excessive rigidity and cracking problems caused by high carbon black content (>55 phr).

[0039] 3. Achieve mechanical balance, balancing impact buffering and high-speed support.

[0040] The short segments of BF2055L can reduce the initial rigidity of the rubber matrix and effectively absorb the radial impact transmitted by the tread, providing excellent impact cushioning for the crown layer rubber compound and avoiding damage to the belt layer from hard impacts; the high molecular weight long segments of BF2055H and carbon black provide sufficient tensile stress to meet the constraint and support requirements of the belt layer under high-speed conditions of 200km / h.

[0041] 4. Excellent environmental friendliness and processability, compatible with existing production lines.

[0042] The low molecular weight segments of BF2055L can act as an "internal plasticizer" to reduce the overall Mooney viscosity of the rubber compound. No additional processing oil is required, thus avoiding the volatile pollution of processing oil in traditional formulations. It can be directly adapted to existing production lines without adjusting parameters such as rotor speed and filling coefficient.

[0043] 5. Significantly improved durability, extending tire lifespan.

[0044] De-Mattia crack propagation tests show that the average lifespan of the tread layer rubber compound of this invention is >2.4 × 10⁻⁶. 5 Next, compared to the traditional formula (<1.8×10), 5 (Time) Significantly improved, extending tire lifespan.

[0045] In summary, this invention solves the contradiction between heat generation, deformation, and processing by using bimodal unfilled SSBR as the core without sacrificing hardness and handling performance. It uses natural rubber to ensure adhesion and elasticity, and medium-structure carbon black and white carbon black to balance reinforcement and heat generation. At the same time, it achieves a breakthrough in all dimensions of performance, including low heat generation, low deformation, high support, high durability, and environmentally friendly manufacturing. Detailed Implementation

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0047] I. Main Raw Materials and Models

[0048]

[0049] II. Formulation Design (PHR)

[0050] 1. The formulations (unit: phr) of the examples (E-1 to E-3) and the comparative examples (C-1 to C-4) are as follows: oil-extended raw materials are deducted from oil-extended raw materials.

[0051]

[0052]

[0053] 2. Explanation of Proportional Differences

[0054] serial number Difference type C-1 Oil-extended high-vinyl SSBR (containing 25 phr oil) was used. C-2 High-vinyl single-peak, high-Mw star-shaped unextended SSBR, without BF2055L C-3 Low-vinyl (37%) oil-extended SSBR (containing 22 phr oil) was used. C-4 Replace solution-polymerized SSBR with emulsion-polymerized SBR1502

[0055] III. The mixing process adopts a two-stage mixing process.

[0056]

[0057] IV. Test Methods and Conditions

[0058]

[0059] Unified vulcanization and temperature control conditions: ① All rubber compounds are vulcanized on a flat plate at 170℃±2℃ for 15min; ② After vulcanization, the samples are placed in an environment of 23℃±2℃ and 50%±5%RH for 24h, and then the samples are prepared and tested according to the table above.

[0060] Data processing: At least 5 samples are tested for each item (3 samples for heat generation and flexure tests); if a single value deviates from the average value by ±2.5σ, it is discarded and retested, and the final report is based on the arithmetic mean.

[0061] V. Test Experiment Data

[0062] The table below lists the complete mechanical and dynamic test data for Examples (E-1 to E-3) and Comparative Examples (C-1 to C-4). All data are averages obtained from testing 5 samples from the same batch of formulations, with the standard deviation in parentheses being 1σ.

[0063]

[0064] VI. Conclusions of Experimental Data Analysis

[0065] 1. Significantly reduced heat generation

[0066] By using a completely unoiled bimodal SSBR with a vinyl content of 55% (Mw_H≈400 kg·mol⁻¹) -1 / Mw_L≈300kg·mol -1 It synergistically reinforces with carbon black and silica, avoiding the later-stage heat recovery caused by traditional oil-extended SSBRs. Simultaneously, the high-vinyl segments can form strong covalent bonds with the silane coupling agent (Si69), reducing the "frictional internal friction" caused by silica / carbon black agglomeration and lowering dynamic hysteresis at the molecular level. As shown in the table, the tanδ (60℃) of the examples decreased to 0.072-0.075, and Example E-1 showed a 14%-25.5% reduction compared to the comparative example (tanδ (60℃) > 0.090), indicating a significant reduction in the dynamic hysteresis factor. In the Goodrich heat generation test (100℃, 0.7MPa), the steady-state temperature rise was only 62-64℃, and Example E-1 showed a 5-11℃ reduction compared to the comparative example (temperature rise > 68℃), providing long-term protection for the belt layer adhesive and avoiding the risk of interface delamination caused by high temperatures.

[0067] 2. Significantly reduces permanent deformation and maintains long-term stability of the tire crown profile.

[0068] BF2055H is a high molecular weight segment that forms a "rigid support skeleton" after vulcanization, providing sufficient resistance to deformation. BF2055L is a low molecular weight segment that can fully wet the filler surface and fill the gaps in the skeleton, resulting in uniform crosslinking density (avoiding deformation caused by a "loose skeleton"). Simultaneously, a suitable amount of carbon black with a "medium structure and moderate specific surface area" can be uniformly dispersed in the rubber matrix, forming an "interlocking structure" with the crosslinking network of the bimodal SSBR. The carbon black particles act as "reinforcing points," preventing permanent slippage of rubber molecular chains under compression-shear cycles and avoiding excessive rigidity and cracking problems caused by high carbon black content (>55 phr). The table shows that the compression set rate (70℃, 24h, 25% compression) in the examples was controlled at 27-29%, and Example E-1 showed a 20%-31.7% reduction in deformation rate compared to the comparative example (deformation rate >35%), a significant decrease.

[0069] 3. Achieve mechanical balance, balancing impact buffering and high-speed support.

[0070] The short chain segments of BF2055L reduce the initial rigidity of the rubber matrix. When the compound is subjected to small deformation (10% tensile strength), the short chain segments easily undergo elastic deformation, and the 10% tensile stress (M10) is controlled at 0.40-0.42 MPa, which can effectively absorb the radial impact transmitted by the tread and reduce the damage of road bumps to the belt layer. When the compound is subjected to large deformation (300% tensile strength), the high molecular weight long chain segments of BF2055H will fully expand and form a "strong tensile network" with the carbon black reinforcement points, providing sufficient tensile stress (M300 = 7.4-7.8 MPa). At the same time, the high elasticity of natural rubber can balance the rigidity of SSBR, avoiding "insufficient support" caused by too low M10 or "buffering failure" caused by too high M300, and finally forming an optimal balance between "buffering and support".

[0071] 4. Significantly improved durability, extending tire lifespan.

[0072] The bimodal SSBR exhibits a uniform molecular weight distribution (H / L = 1.2:1-1:1.2), and combined with Si69-optimized filler dispersion, it forms a dense and uniform cross-linked network after vulcanization—preventing crack initiation caused by localized stress concentration and extending flexural life. De-Mattia crack propagation tests show that the average life of the crown layer rubber compound in this example is >2.4 × 10⁻⁶. 5 Secondly, Example E-1 compared to the comparative example (<1.8×10 5 (Effective factor) 28%-60.6%, extending tire lifespan.

[0073] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A crown layer rubber composition with low heat generation and high stability, characterized in that, It is prepared by mixing raw materials comprising the following components, based on 100 parts by weight of rubber component: 55–75 parts natural rubber; 10–25 parts of first solution-polymerized styrene-butadiene rubber; 10–25 parts of second solution-polymerized styrene-butadiene rubber; 5–10 parts of highly dispersed silica; 40–55 parts carbon black; 0.5–1.5 parts of silane coupling agent; 3–6 parts of α-methylstyrene resin; The mass ratio of the first solution-polymerized styrene-butadiene rubber (SBR) to the second solution-polymerized SBR is 1.5:1 to 1:1.5, and both are unoil-extended high-vinyl solution-polymerized SBRs with a styrene content of 20±1wt%, a vinyl content of 55±3wt%, a glass transition temperature of −35±2℃, and a weight-average molecular weight of 380-420 kg·mol⁻¹. -1 With 280-320 kg·mol -1 .

2. The crown layer rubber composition with low heat generation and high stability according to claim 1, characterized in that, It is prepared by mixing raw materials comprising the following components in parts by weight: 60–70 parts natural rubber; 15–20 parts of first solution-polymerized styrene-butadiene rubber; 15–20 parts of second solution-polymerized styrene-butadiene rubber; 6–8 parts of silica; 45–50 parts carbon black; 0.8–1.2 parts of silane coupling agent; 4–5 parts of α-methylstyrene resin.

3. The crown layer rubber composition with low heat generation and high stability according to claim 1, characterized in that, The first and second solution-polymerized styrene-butadiene rubbers were BF2055H and BF2055L solution-polymerized styrene-butadiene rubbers produced by China Petroleum & Chemical Corporation (Sinopec). BF2055H: styrene content 20%, vinyl content 55%, unextended, Tg=-35℃, weight-average molecular weight 380–420 kg·mol⁻¹ -1 BF2055L: 20% styrene, 55% vinyl, unoiled, Tg = -35℃, weight-average molecular weight 280–320 kg·mol⁻¹ -1 The preferred mass ratio is 1.2:1–1:1.

2.

4. The crown layer rubber composition with low heat generation and high stability according to claim 1, characterized in that, Highly dispersed silica with a specific surface area (CTAB) ≥ 160 m² 2 / g, preferably CTAB is 180–195m 2 / g, BET is 195–210m 2 / g; The preferred BET specific surface area of ​​carbon black particles is 20-160m². 2 / g, more preferably 40-130m 2 / g, further preferably 50-120m 2 / g; more preferably, the carbon black is one or more of N134, N220, N234, N375 or N375, N330, N339, N347, N326; more preferably, the carbon black is N326 and / or N330.

5. The crown layer rubber composition with low heat generation and high stability according to claim 1, characterized in that, The silane coupling agent has the structural formula YR-Si(OR)3, where Y is an organic functional group and SiOR is a silaneoxy group; preferably, the silane coupling agent is selected from one or more of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, bis-[γ-(triethoxysilyl)propyl]tetrasulfide, bis-propyltriethoxysilane disulfide, 3-(octanoylthio)propyltriethoxysilane and n-octyltriethoxysilane.

6. The crown layer rubber composition with low heat generation and high stability according to claim 1, characterized in that, The softening point of α-methylstyrene resin is 95–120℃, and the number average molecular weight is 1000–3000.

7. The crown layer rubber composition with low heat generation and high stability according to claim 1, characterized in that, The compounded raw materials also include activators, antioxidants, and vulcanizing agents; preferably, the activator includes 2-5 parts zinc oxide and 1-3 parts stearic acid; 2-4 parts antioxidant; the vulcanizing agent includes 1.0-3.0 parts insoluble sulfur and 1.0-2.0 parts accelerator; more preferably, the accelerator includes one or more of N-tert-butyl-2-benzothiazole sulfenamide or N-cyclohexyl-2-benzothiazole sulfenamide, diphenylguanidine accelerators, hexamethylenetetramine, 4,4′-dithiodimorpholine, and dicaprolactam disulfide.

8. A method for preparing the rubber composition according to any one of claims 1-7, characterized in that, The method includes the following steps: (1) At 110–125°C, natural rubber, first solution-polymerized styrene-butadiene rubber, second solution-polymerized styrene-butadiene rubber, all silica, half carbon black, and silane coupling agent are added to a mixer and mixed for 50 seconds; (2) The mixing temperature is raised to 145–148°C and mixed for another 40 seconds. The remaining carbon black and α-methylstyrene resin are added and the mixture is discharged to obtain the masterbatch; (3) The masterbatch is cooled to 95–100°C, sulfur and accelerator are added, and the mixture is finally mixed in a mixer or open mill for 60 seconds; (4) The mixture is pressed into sheets and vulcanized at 165–175°C for 12–18 minutes.

9. Use of the rubber composition of any one of claims 1–7 in the manufacture of the crown layer of a tire.

10. A tire, characterized in that, The tire crown layer is obtained by vulcanization of the rubber composition described in any one of claims 1–7.

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