A tire tread rubber composition and a method for producing the same
By plasma activation and in-situ grafting modification of recycled tire rubber powder, and by constructing a dynamic network with a reversible crosslinking agent, the problem of uneven dispersion of recycled tire rubber powder in the rubber matrix was solved, achieving high-ratio filling and performance improvement, reducing rolling resistance, and enhancing the overall performance of the tire.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG HUASHENG RUBBER
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-02
AI Technical Summary
In existing technologies, recycled tire rubber powder is difficult to disperse uniformly in the rubber matrix, resulting in poor interfacial compatibility, which limits its filling amount. Furthermore, traditional processing methods are unable to maintain the mechanical and dynamic properties of composite materials under high filling ratios.
After plasma activation of recycled tire rubber powder, oxygen-containing polar groups are introduced and grafted in situ with mercaptosilane and thioester silane. Combined with a reversible crosslinking agent, a dynamic reversible crosslinking network is constructed, forming a dual crosslinking network with both high elasticity and energy dissipation capacity.
It achieves a high proportion of recycled tire rubber powder filling in the rubber matrix, improves interfacial bonding, reduces production costs, and significantly reduces rolling resistance through a dynamic cross-linking network, thereby improving the fuel economy and overall performance of the tire.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of rubber materials technology, and more specifically to a tire tread rubber composition and its preparation method. Background Technology
[0002] Tires are a critical component of automobiles, and their performance directly affects driving safety, fuel economy, and ride comfort. As the part that directly contacts the road surface, the tire tread compound plays a decisive role in the tire's rolling resistance, wet traction, and wear resistance. With the continuous rise in raw material costs, adding recycled tire rubber (GTR) to tire tread compounds has become an industry trend.
[0003] However, recycled tire rubber powder is a vulcanized cross-linked rubber with an inert surface, resulting in inherent interfacial compatibility issues with the fresh rubber matrix. This makes it difficult for the recycled rubber powder to disperse uniformly in the matrix, forming weak interfacial regions that severely limit its filler content. High filler ratios typically lead to a significant decrease in the mechanical and dynamic properties of the composite material. While existing technologies have attempted to improve the compatibility of recycled rubber powder through surface treatment, the effects are limited, and it remains difficult to maintain performance under high filler ratios. For example, invention patent CN 107674238 A discloses a method of sequentially treating waste rubber powder with water, alkaline solution, coupling agent, and nano-silica coating to obtain modified waste rubber powder agglomerates, which are then crushed and used. This method improves the surface activity of rubber powder to some extent through multi-step surface treatment, but the process is cumbersome. Furthermore, due to the inherent cross-linking inertness of the rubber powder surface, single coupling agent treatment and physical coating with nano-silica are insufficient to form a stable, high-density chemical graft layer on the powder surface, resulting in limited modification effects and unsatisfactory mechanical properties of the composite material. In addition, the traditional permanent vulcanized network structure makes it difficult to reconcile key tire properties such as rolling resistance, wear resistance, and wet skid resistance. Therefore, further improvement and development are needed. Summary of the Invention
[0004] To address the shortcomings of existing technologies and solve the aforementioned problems, a tire tread compound composition and its preparation method are proposed, and the following technical solution is provided: A tire tread compound composition, by weight, comprises the following raw materials: 100 parts of rubber matrix; 15-25 parts of modified recycled tire rubber powder; 5-10 parts of reversible crosslinking agent; 2.5-3.3 parts of vulcanization system; and 73-100 parts of rubber additives. The modified recycled tire rubber powder is prepared by introducing oxygen-containing polar groups onto the surface of recycled tire rubber powder, followed by in-situ grafting with a mixture of mercaptosilane and thioester silane. The reversible crosslinking agent is polybutadiene with end groups linked to aromatic disulfide bonds via urea bonds, urethane bonds, or amide bonds. The rubber additives include: 60-80 parts of silica, 8-12 parts of silane coupling agent, and 5-8 parts of bio-based hydrocarbon resin.
[0005] Furthermore, the modified recycled tire rubber powder is prepared by plasma activation of recycled tire rubber powder, followed by in-situ grafting with mercaptosilane and thioester silane at 120-140℃ for 8-12 minutes, with a mass ratio of mercaptosilane to thioester silane of 1:1-2.
[0006] Furthermore, the modified recycled tire rubber powder has a particle size of 40-80 mesh.
[0007] Furthermore, the reversible crosslinking agent is prepared by end-group modification of polybutadiene with a number average molecular weight of 2000-5000 using 4,4'-diaminodiphenyl disulfide or 4,4'-dihydroxydiphenyl disulfide as raw materials.
[0008] Furthermore, the vulcanization system comprises 1.0-1.3 parts of sulfur and 1.5-2.0 parts of accelerator CZ.
[0009] Furthermore, the silane coupling agents include mercaptosilanes and thioester silanes, and the bio-based hydrocarbon resins are hydrogenated rosin esters or polyterpene resins.
[0010] This application also provides a method for preparing the above-mentioned tire tread compound composition, comprising the following steps: (1) Modification of recycled tire rubber powder: After plasma activation, recycled tire rubber powder is grafted in situ with mercaptosilane and thioester silane; (2) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer and control the discharge temperature to 160-162℃; (3) Second stage final refining: Add the vulcanization system at ≤110℃; (4) After extrusion molding, vulcanize at 150-155℃ for 20-25 minutes.
[0011] Furthermore, the plasma activation conditions are atmospheric pressure, air or nitrogen-oxygen mixed atmosphere, power 100-200W, and treatment time 5-10 minutes.
[0012] Due to the adoption of the above technical solutions, the beneficial technical effects of the present invention are as follows: 1. This invention performs specific "activation + grafting" surface modification on recycled tire rubber powder, that is, first introduces oxygen-containing polar groups and then grafts them in situ with mixed silanes, which significantly improves the interfacial bonding force with the rubber matrix and overcomes the problem of poor compatibility. This allows for a high proportion of filling of 15-25 parts in the formulation, which effectively reduces the dependence on virgin rubber, lowers production costs, and promotes the recycling of waste tire resources while ensuring or even improving performance.
[0013] 2. This invention introduces a reversible crosslinking agent with a specific structure containing aromatic disulfide bonds to construct dynamically reversible crosslinking points within a traditional permanent vulcanization network. This dual network structure of "permanent + dynamic" can effectively dissipate energy through the dynamic exchange of disulfide bonds during tire rolling, thereby significantly reducing the hysteresis loss of the rubber compound and ultimately translating into a reduction in tire rolling resistance, thus improving vehicle fuel economy. Detailed Implementation
[0014] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application.
[0015] A tire tread compound composition, by weight, comprises the following raw materials: 100 parts of rubber matrix; 15-25 parts of modified recycled tire rubber powder; 5-10 parts of reversible crosslinking agent; 2.5-3.3 parts of vulcanization system; and 73-100 parts of rubber additives. The modified recycled tire rubber powder is prepared by introducing oxygen-containing polar groups onto the surface of recycled tire rubber powder, followed by in-situ grafting with a mixture of mercaptosilane and thioester silane. By introducing a reversible crosslinking agent and recycled tire rubber powder modified in a specific manner, a dual crosslinking network with both high elasticity and energy dissipation capacity is synergistically constructed, thereby achieving high-value utilization of waste resources while endowing the tire tread compound with excellent comprehensive performance.
[0016] The modified recycled tire rubber powder is prepared as follows: the recycled tire rubber powder is activated by plasma to introduce oxygen-containing polar groups, and then in-situ grafted with a mixture of mercaptosilane and thioester silane in a weight ratio of 1:1 to 1:2 at 120-140℃. The poor compatibility between recycled rubber powder and the matrix in existing technologies stems from its inert surface after cross-linking. The purpose of this design is to change this situation through a two-step method: the first step, "plasma activation," creates a large number of oxygen-containing polar groups on the rubber powder surface as reaction "anchors"; the second step utilizes these anchors to chemically bond silane molecules that can react with the groups on the rubber powder surface and with the rubber matrix to the rubber powder surface, solving the problem of interface separation and laying the foundation for achieving high-proportion filling.
[0017] Reversible crosslinking agents are chemically defined as polybutadiene with aromatic disulfide bonds linked to their end groups via urea, urethane, or amide bonds. The polybutadiene main chain segments exhibit good physical compatibility with the rubber matrix and can be uniformly dispersed within it. The aromatic disulfide bonds at the end groups are dynamic chemical bonds that can reversibly break and recombine under external energy. By introducing these dynamic bonds into the traditional permanent vulcanization network, a "dynamic" crosslinking network is constructed. This network can dissipate energy through bond exchange during tire rolling, thereby reducing hysteresis losses in the material.
[0018] The polybutadiene of the reversible crosslinking agent preferably has a number-average molecular weight of 2000-5000, and the aromatic disulfide bond structure is preferably introduced by 4,4'-diaminodiphenyl disulfide or 4,4'-dihydroxydiphenyl disulfide. At this number-average molecular weight, the polybutadiene possesses sufficient chain length to form effective "flow" within the rubber matrix, without being too large and affecting processing fluidity. The explicit introduction of aromatic disulfide bonds in the raw material ensures that the formed reversible chemical bonds have suitable bond energy and exchange activity, enabling efficient reversible exchange within the normal operating temperature range of the tire, thereby maximizing its effect in reducing rolling resistance.
[0019] The rubber additives preferably include 60-80 parts of silica, 8-12 parts of silane coupling agent, and 5-8 parts of bio-based hydrocarbon resin; meanwhile, the vulcanization system preferably includes 1.0-1.3 parts of sulfur and 1.5-2.0 parts of N-cyclohexyl-2-benzothiazole sulfenamide. The high content of silica serves as the main reinforcing filler; while the specific ratio of sulfur and accelerator CZ constitutes a "semi-effective vulcanization system." The permanent cross-linked network formed by this system provides basic mechanical strength while retaining some polysulfide bonds, which can synergistically optimize the dynamic properties of the material with the dynamic exchange behavior of the reversible cross-linking agent.
[0020] The rubber matrix includes solution-polymerized styrene-butadiene rubber and cis-butadiene rubber.
[0021] A method for preparing the above-mentioned tire tread rubber composition. The method includes three core steps: (1) firstly, surface treatment and in-situ grafting of recycled tire rubber powder are performed to obtain modified recycled tire rubber powder; (2) then a first-stage mastering process is carried out, in which the rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and most of the rubber additives are mixed at a high temperature of 160-162℃; (3) finally, a second-stage final process is carried out, in which the vulcanization system is added and mixed at a lower temperature not exceeding 110℃. This segmented process of "high temperature mastering + low temperature final process" is a mature technology in the rubber industry. Its design purpose in this invention is that the high temperature stage is conducive to the full reaction of silane coupling agent and silica and the uniform dispersion of modified rubber powder and reversible crosslinking agent, while the low temperature final process can effectively prevent the rubber compound containing the vulcanization system from undergoing early vulcanization (i.e., scorching), thereby ensuring the processing safety of the rubber compound and the quality uniformity of the final product.
[0022] Furthermore, in a preferred embodiment, the surface treatment process in step (1) is specifically defined as plasma activation, with the preferred conditions being: atmospheric pressure, air or nitrogen-oxygen mixed atmosphere, power 100-200W, and treatment time 5-10 minutes. Compared to traditional chemical reagent treatment, plasma activation is an environmentally friendly surface modification technology with controllable treatment depth. By precisely controlling the process parameters, the desired functional groups can be efficiently introduced onto the surface of the adhesive powder without damaging its bulk properties, providing a good reaction basis for subsequent grafting reactions.
[0023] The preparation method of tire tread includes three core steps: (1) First, the recycled tire rubber powder is surface treated and grafted in situ to obtain modified recycled tire rubber powder; (2) Then, a mastering process is carried out, in which the rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and most of the rubber additives are mixed at a high temperature of 160-162℃; (3) Finally, a second-stage final process is carried out, in which the vulcanization system is added and mixed at a lower temperature not higher than 110℃. The high temperature stage is conducive to the full reaction of silane coupling agent and silica and the uniform dispersion of modified rubber powder and reversible crosslinking agent, while the low temperature final process can effectively prevent the rubber compound containing the vulcanization system from undergoing early vulcanization, thereby ensuring the processing safety of the rubber compound and the quality uniformity of the final product.
[0024] The surface treatment process in step (1) employs plasma activation, with the preferred conditions being: atmospheric pressure, air or a nitrogen-oxygen mixture atmosphere, power 100-200W, and treatment time 5-10 minutes. Compared to traditional chemical reagent treatment, plasma activation is an environmentally friendly surface modification technology with controllable treatment depth. By precisely controlling the process parameters, the desired functional groups can be efficiently introduced onto the surface of the adhesive powder without damaging its bulk properties, providing a good reaction basis for subsequent grafting reactions.
[0025] The vulcanization process involves curing at 150-155°C for 20-25 minutes. During this step, the vulcanization system is activated, forming stable chemical crosslinks, i.e., permanent crosslinking points, between the rubber matrix chains. Simultaneously, the reversible crosslinking agent of this invention is also uniformly distributed within this network, ultimately forming a dual crosslinked network structure composed of permanent crosslinking points and the reversible crosslinking agent. By precisely controlling the vulcanization temperature and time, it can be ensured that both types of crosslinked networks are fully developed.
[0026] The raw materials used in the following examples are as follows: solution-polymerized styrene-butadiene rubber, SSBR2466, styrene content 25%, vinyl content 63%; cis-butadiene rubber, BR9000, cis-1,4-structure content ≥96%; mercaptosilane, KH-580 (3-mercaptopropyltrimethoxysilane); thioester silane NXT (3-octanoylthiopropyltriethoxysilane).
[0027] Example 1 A tire tread rubber composition, by weight, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts butadiene rubber, 19 parts modified recycled tire rubber powder, 6 parts reversible crosslinking agent, 70 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0028] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 8 min at 150W power. The activated recycled tire rubber powder was then mixed with a mixture of mercaptosilane (KH-580) and thioester silane (NXT) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of recycled tire rubber powder to the mixture of mercaptosilane (KH-580) and thioester silane (NXT) was 100:12; the mass ratio of mercaptosilane (KH-580) to thioester silane (NXT) was 1:1.5. (2) Preparation of reversible crosslinking agent: Hydroxyl-terminated polybutadiene (HTPB) is reacted with hexamethylene diisocyanate at 60°C for 2h to form an isocyanate-terminated prepolymer, and then reacted with an equimolar amount of 4,4'-diaminodiphenyl disulfide at 80°C for 4h. The amino group is linked to the isocyanate through a urea bond to obtain polybutadiene with aromatic disulfide bonds at the end group.
[0029] (3) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer, speed 60 rpm, control the discharge temperature 161℃, and let it stand at room temperature for ≥4h; (4) Second stage final refining: Add the vulcanization system at 98℃; (5) After extrusion molding, vulcanize at 152℃ for 21 min.
[0030] Example 2 A tire tread rubber composition, by weight, comprises the following raw materials: 74 parts solution-polymerized styrene-butadiene rubber, 26 parts butadiene rubber, 15 parts modified recycled tire rubber powder, 5 parts reversible crosslinking agent, 60 parts silica, 8.5 parts silane coupling agent (including 4 parts mercaptosilane and 4.5 parts thioester silane), 5 parts hydrogenated rosin ester, 1.05 parts sulfur, and 1.55 parts accelerator CZ.
[0031] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 8 min at 150W power. The activated recycled tire rubber powder was then mixed with a mixture of mercaptosilane (KH-580) and thioester silane (NXT) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of mercaptosilane (KH-580) to thioester silane (NXT) was 1:1.5. (2) Preparation of reversible crosslinking agent: Hydroxyl-terminated polybutadiene (HTPB) is reacted with hexamethylene diisocyanate at 60°C for 2h to form an isocyanate-terminated prepolymer, and then reacted with an equimolar amount of 4,4'-diaminodiphenyl disulfide at 80°C for 4h. The amino group is linked to the isocyanate through a urea bond to obtain polybutadiene with aromatic disulfide bonds at the end group.
[0032] (3) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer, speed 60 rpm, control the discharge temperature 161℃, and let it stand at room temperature for ≥4h; (4) Second stage final refining: Add the vulcanization system at 98℃; (5) After extrusion molding, vulcanize at 152℃ for 21 min.
[0033] Example 3 A tire tread rubber composition, comprising, by weight parts, the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts butadiene rubber, 25 parts modified recycled tire rubber powder, 10 parts reversible crosslinking agent, 80 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0034] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 8 min at 150W power. The activated recycled tire rubber powder was then mixed with a mixture of mercaptosilane (KH-580) and thioester silane (NXT) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of recycled tire rubber powder to the mixture of mercaptosilane (KH-580) and thioester silane (NXT) was 100:12; the mass ratio of mercaptosilane (KH-580) to thioester silane (NXT) was 1:1.5. (2) Preparation of reversible crosslinking agent: Hydroxyl-terminated polybutadiene (HTPB) is reacted with hexamethylene diisocyanate at 60°C for 2h to form an isocyanate-terminated prepolymer, and then reacted with an equimolar amount of 4,4'-diaminodiphenyl disulfide at 80°C for 4h. The amino group is linked to the isocyanate through a urea bond to obtain polybutadiene with aromatic disulfide bonds at the end group.
[0035] (3) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer, speed 60 rpm, control the discharge temperature 161℃, and let it stand at room temperature for ≥4h; (4) Second stage final refining: Add the vulcanization system at 98℃; (5) After extrusion molding, vulcanize at 152℃ for 21 min.
[0036] Example 4 A tire tread rubber composition, by weight parts, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts cis-butadiene rubber, 21 parts modified recycled tire rubber powder, 6 parts reversible crosslinking agent, 70 parts silica, 12 parts silane coupling agent (including 5 parts mercaptosilane and 7 parts thioester silane), 8 parts hydrogenated rosin ester, 1.3 parts sulfur, and 2 parts accelerator CZ.
[0037] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 8 min at 150W power. The activated recycled tire rubber powder was then mixed with a mixture of mercaptosilane (KH-580) and thioester silane (NXT) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of recycled tire rubber powder to the mixture of mercaptosilane (KH-580) and thioester silane (NXT) was 100:12; the mass ratio of mercaptosilane (KH-580) to thioester silane (NXT) was 1:1.5. (2) Preparation of reversible crosslinking agent: Hydroxyl-terminated polybutadiene (HTPB) is reacted with hexamethylene diisocyanate at 60°C for 2h to form an isocyanate-terminated prepolymer, and then reacted with an equimolar amount of 4,4'-diaminodiphenyl disulfide at 80°C for 4h. The amino group is linked to the isocyanate through a urea bond to obtain polybutadiene with aromatic disulfide bonds at the end group.
[0038] (3) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer, speed 60 rpm, control the discharge temperature 161℃, and let it stand at room temperature for ≥4h; (4) Second stage final refining: Add the vulcanization system at 98℃; (5) After extrusion molding, vulcanize at 152℃ for 21 min.
[0039] Example 5 A tire tread rubber composition, by weight, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts butadiene rubber, 19 parts modified recycled tire rubber powder, 6 parts reversible crosslinking agent, 70 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0040] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 10 min at 100W power. The activated recycled tire rubber powder was then mixed with a mixture of mercaptosilane (KH-580) and thioester silane (NXT) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of recycled tire rubber powder to the mixture of mercaptosilane (KH-580) and thioester silane (NXT) was 100:10; the mass ratio of mercaptosilane (KH-580) to thioester silane (NXT) was 1:1. (2) Preparation of reversible crosslinking agent: Hydroxyl-terminated polybutadiene (HTPB) is reacted with hexamethylene diisocyanate at 60°C for 2h to form an isocyanate-terminated prepolymer, and then reacted with an equimolar amount of 4,4'-diaminodiphenyl disulfide at 80°C for 4h. The amino group is linked to the isocyanate through a urea bond to obtain polybutadiene with aromatic disulfide bonds at the end group.
[0041] (3) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer, speed 60 rpm, control the discharge temperature 162℃, and let it stand at room temperature for ≥4h; (4) Second stage final refining: Add the vulcanization system at 110℃; (5) After extrusion molding, vulcanize at 150°C for 25 min.
[0042] Example 6 A tire tread rubber composition, by weight, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts butadiene rubber, 19 parts modified recycled tire rubber powder, 6 parts reversible crosslinking agent, 70 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0043] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 8 min at 150W power. The activated recycled tire rubber powder was then mixed with a mixture of mercaptosilane (KH-580) and thioester silane (NXT) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of recycled tire rubber powder to the mixture of mercaptosilane (KH-580) and thioester silane (NXT) was 100:12; the mass ratio of mercaptosilane (KH-580) to thioester silane (NXT) was 1:1.5. (2) Preparation of reversible crosslinking agent: Hydroxyl-terminated polybutadiene (HTPB) is reacted with hexamethylene diisocyanate at 60°C for 2h to form an isocyanate-terminated prepolymer, and then reacted with an equimolar amount of 4,4'-diaminodiphenyl disulfide at 80°C for 4h. The amino group is linked to the isocyanate through a urea bond to obtain polybutadiene with aromatic disulfide bonds at the end group.
[0044] (3) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer, speed 60 rpm, control the discharge temperature 161℃, and let it stand at room temperature for ≥4h; (4) Second stage final refining: Add the vulcanization system at 98℃; (5) After extrusion molding, vulcanize at 152℃ for 21 min.
[0045] Comparative Example 1 A tire tread rubber composition, by weight parts, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts cis-butadiene rubber, 70 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0046] The preparation method includes the following steps: (1) First stage master mixing: Add rubber matrix and rubber additives to internal mixer, speed 60 rpm, control the discharge temperature at 161℃, and let stand at room temperature for ≥4 hours; (2) Second stage final refining: Add the vulcanization system at 98℃; (3) After extrusion molding, vulcanize at 152℃ for 21 min.
[0047] Comparative Example 2 A tire tread rubber composition, by weight, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts butadiene rubber, 19 parts unmodified recycled tire rubber powder, 70 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0048] The preparation method includes the following steps: (1) First stage master mixing: Add rubber matrix, unmodified recycled tire rubber powder and rubber additives to the internal mixer, rotate at 60 rpm, control the discharge temperature at 161℃, and let stand at room temperature for ≥4 hours; (2) Second stage final refining: Add the vulcanization system at 98℃; (3) After extrusion molding, vulcanize at 152℃ for 21 min.
[0049] Comparative Example 3 A tire tread rubber composition, by weight, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts butadiene rubber, 19 parts modified recycled tire rubber powder, 70 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0050] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 8 min at 150W power. The activated recycled tire rubber powder was then mixed with a mixture of mercaptosilane (KH-580) and thioester silane (NXT) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of recycled tire rubber powder to the mixture of mercaptosilane (KH-580) and thioester silane (NXT) was 100:12; the mass ratio of mercaptosilane (KH-580) to thioester silane (NXT) was 1:1.5. (2) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder and rubber additives to the internal mixer, rotate at 60 rpm, control the discharge temperature at 161℃, and let stand at room temperature for ≥4 hours; (3) Second stage final refining: Add the vulcanization system at 98℃; (4) After extrusion molding, vulcanize at 152℃ for 21 min.
[0051] Comparative Example 4 A tire tread rubber composition, by weight, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts butadiene rubber, 30 parts modified recycled tire rubber powder, 4 parts reversible crosslinking agent, 70 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0052] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 8 min at 150W power. The activated recycled tire rubber powder was then mixed with a mixture of mercaptosilane (KH-580) and thioester silane (NXT) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of recycled tire rubber powder to the mixture of mercaptosilane (KH-580) and thioester silane (NXT) was 100:12; the mass ratio of mercaptosilane (KH-580) to thioester silane (NXT) was 1:1.5. (2) Preparation of reversible crosslinking agent: Hydroxyl-terminated polybutadiene (HTPB) is reacted with hexamethylene diisocyanate at 60°C for 2h to form an isocyanate-terminated prepolymer, and then reacted with an equimolar amount of 4,4'-diaminodiphenyl disulfide at 80°C for 4h. The amino group is linked to the isocyanate through a urea bond to obtain polybutadiene with aromatic disulfide bonds at the end group.
[0053] (3) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer, speed 60 rpm, control the discharge temperature 161℃, and let it stand at room temperature for ≥4h; (4) Second stage final refining: Add the vulcanization system at 98℃; (5) After extrusion molding, vulcanize at 152℃ for 21 min.
[0054] Comparative Example 5 A tire tread rubber composition, by weight, comprises the following raw materials: 68 parts solution-polymerized styrene-butadiene rubber, 32 parts butadiene rubber, 19 parts modified recycled tire rubber powder, 6 parts reversible crosslinking agent, 70 parts silica, 9.5 parts silane coupling agent (including 3.8 parts mercaptosilane and 5.7 parts thioester silane), 5.5 parts hydrogenated rosin ester, 1.15 parts sulfur, and 1.65 parts accelerator CZ.
[0055] The preparation method includes the following steps: (1) Modification of recycled tire rubber powder: Commercially available recycled tire rubber powder was spread in a plasma device and activated by passing a nitrogen-oxygen mixture (volume ratio N2:O2=4:1) under atmospheric pressure for 8 min at 150W power. The activated recycled tire rubber powder was then mixed with mercaptosilane (KH-580) in a high-speed mixer at 130°C for 10 min to covalently graft silane onto surface groups. The mass ratio of recycled tire rubber powder to mercaptosilane (KH-580) was 100:12. (2) Preparation of reversible crosslinking agent: Hydroxyl-terminated polybutadiene (HTPB) is reacted with hexamethylene diisocyanate at 60°C for 2h to form an isocyanate-terminated prepolymer, and then reacted with an equimolar amount of 4,4'-diaminodiphenyl disulfide at 80°C for 4h. The amino group is linked to the isocyanate through a urea bond to obtain polybutadiene with aromatic disulfide bonds at the end group.
[0056] (3) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer, speed 60 rpm, control the discharge temperature 161℃, and let it stand at room temperature for ≥4h; (4) Second stage final refining: Add the vulcanization system at 98℃; (5) After extrusion molding, vulcanize at 152℃ for 21 min.
[0057] The rubber compounds prepared in Examples 1-6 and Comparative Examples 1-5 were subjected to performance tests, and the test results are shown in Tables 1 and 2.
[0058] Test standards: Hardness (Shore A) GB / T 39693.4-2025; Tensile strength, 300% constant elongation stress GB / T528-2009; DIN abrasion volume GB / T 9867-2008; Wet grip performance using DMA (tanδ@0℃); Rolling resistance performance using DMA (tanδ@60℃).
[0059] tanδ@0℃ and tanδ@60℃: DMA temperature scan, frequency 10Hz, strain 0.1%.
[0060] Table 1 Performance test results of the rubber compounds prepared in Examples 1-6 Table 2 Performance test results of the rubber compounds prepared in Comparative Examples 1-5 A comprehensive analysis of the performance test data from all six examples and five comparative examples reveals that this invention, through plasma activation combined with in-situ grafting modification technology using mercaptosilane (KH-580) and thioester silane (NXT) in a 1:1–1:2 ratio, effectively solves the problem of poor interfacial compatibility caused by the surface inertness of recycled tire rubber powder. This allows the modified recycled tire rubber powder to achieve uniform dispersion and good bonding within the rubber matrix. Compared to the pure new rubber baseline of Comparative Example 1, Examples 1–6, after introducing the modified recycled tire rubber powder, maintained a tensile strength of 17.48–18.03 MPa and a DIN abrasion of only 0.088–0.098 MPa. The measured cm³ indicates that the modified recycled tire rubber powder particles not only did not become a weakness in mechanical and wear resistance, but also effectively participated in the reinforcing network through improved interfacial bonding. Simultaneously, the introduction of the reversible crosslinking agent played a crucial role in dynamic mechanical properties, reducing tanδ@60°C to 0.09647–0.1093 and increasing tanδ@0°C to 0.295–0.3482, successfully achieving synergistic optimization of the "devil's triangle" performance of the tire tread compound. Furthermore, it maintained the best dynamic dissipation effect in Example 3. In contrast, Comparative Example 2, lacking surface modification, suffered a severe decline in mechanical properties and a deterioration in dynamic performance. Comparative Example 5 also demonstrated the necessity of a mixed silane system. Comparative Example 4 further verified the rationality of the upper limit of the filling range of the modified recycled tire rubber powder; exceeding this limit, even with modification, led to increased wear and a significant decrease in mechanical strength. Fine-tuning the process parameters in Example 5 still maintained excellent performance, demonstrating the robustness of the technical solution. Overall, this invention achieves high-value recycling of waste tire resources and reduces reliance on virgin rubber, while significantly improving tire rolling resistance and wet grip at the cost of minimal mechanical and wear resistance improvements.
[0061] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A tire tread compound composition, characterized in that, By weight, it includes the following raw materials: 100 parts rubber matrix; 15-25 parts modified recycled tire rubber powder; 5-10 parts reversible crosslinking agent; 2.5-3.3 parts vulcanization system; 73-100 parts of rubber additives; the modified recycled tire rubber powder is prepared by introducing oxygen-containing polar groups onto the surface of recycled tire rubber powder, and then grafting it in situ with a mixture of mercaptosilane and thioester silane; The reversible crosslinking agent is polybutadiene with end groups connected to aromatic disulfide bonds via urea bonds, urethane bonds, or amide bonds; Rubber additives include: 60-80 parts of silica, 8-12 parts of silane coupling agent, and 5-8 parts of bio-based hydrocarbon resin.
2. The tire tread compound composition according to claim 1, characterized in that, The modified recycled tire rubber powder is prepared by plasma activation of recycled tire rubber powder, followed by in-situ grafting with mercaptosilane and thioester silane at 120-140℃ for 8-12 minutes, with a mass ratio of mercaptosilane to thioester silane of 1:1-2.
3. The tire tread compound composition according to claim 1, characterized in that, The modified recycled tire rubber powder has a particle size of 40-80 mesh.
4. The tire tread compound composition according to claim 1, characterized in that, The reversible crosslinking agent is prepared by modifying polybutadiene with a number average molecular weight of 2000-5000 using 4,4'-diaminodiphenyl disulfide or 4,4'-dihydroxydiphenyl disulfide as raw materials.
5. The tire tread compound composition according to claim 1, characterized in that, The vulcanization system comprises: 1.0-1.3 parts of sulfur and 1.5-2.0 parts of accelerator CZ.
6. The tire tread compound composition according to claim 1, characterized in that, Silane coupling agents include mercaptosilanes and thioester silanes, and bio-based hydrocarbon resins are hydrogenated rosin esters or polyterpene resins.
7. A method for preparing a tire tread compound composition according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Modification of recycled tire rubber powder: After plasma activation, recycled tire rubber powder is grafted in situ with mercaptosilane and thioester silane; (2) First stage master mixing: Add rubber matrix, modified recycled tire rubber powder, reversible crosslinking agent and rubber additives to the internal mixer and control the discharge temperature to 160-162℃; (3) Second stage final refining: Add the vulcanization system at ≤110℃; (4) After extrusion molding, vulcanize at 150-155℃ for 20-25 minutes.
8. The method for preparing the tire tread compound composition according to claim 7, characterized in that, The plasma activation conditions are atmospheric pressure, air or nitrogen-oxygen mixed atmosphere, power 100-200W, and treatment time 5-10 minutes.