A mixing processing method of a high wear-resistant environment-friendly tire tread reclaimed rubber composition

Abstract

This invention discloses a compounding and processing method for a high-wear-resistant and environmentally friendly tire tread reclaimed rubber composition, comprising the following steps: Step 1, mixing diene rubber with metallurgical waste slag powder, reinforcing filler, mercaptosilane coupling agent, and terminal amine liquid rubber at 80°C to 115°C, so that the coupling agent is anchored to the surface of the waste slag; Step 2, without discharging, heating to 120°C to 150°C to condense the terminal amine liquid rubber with the anchoring coupling agent, forming a double-layer continuous chemical bond interface; Step 3, adding stearic acid and zinc oxide, followed by adding a vulcanizing agent and a vulcanization accelerator, and mixing at 150°C to 170°C before discharging. This invention achieves the synergistic effect of in-situ anchoring of the coupling agent, in-situ bridging of the liquid rubber, and in-situ saponification of metal ions, reducing the amount of zinc oxide by more than 70%, significantly enhancing the interfacial bonding force, and extending the scorch time, thus obtaining a high-wear-resistant and environmentally friendly tire tread reclaimed rubber composition.

Description

Technical Field

[0001] This invention belongs to the field of rubber composite materials and tire manufacturing technology, and particularly relates to a mixing and processing method for a high wear-resistant and environmentally friendly tire tread recycled rubber composition. Background Technology

[0002] All-steel radial tire treads typically use natural rubber and / or styrene-butadiene rubber as the matrix, with carbon black added as a reinforcing filler, and cross-linked using a sulfur / zinc oxide vulcanization system. Carbon black, as a traditional reinforcing filler, is mainly derived from fossil materials such as petroleum, and its manufacturing process is energy-intensive and highly polluting. In recent years, utilizing industrial waste (such as desulfurization tailings from molten iron, steel slag, converter slag, etc.) to partially replace carbon black as a rubber filler has become a research hotspot. The chemical composition of metallurgical waste such as desulfurization tailings from molten iron is mainly CaO, , Metallurgical waste, primarily composed of zinc oxide and MgO, can be utilized as a high-value filler in rubber production. This would reduce the manufacturing cost of rubber products and mitigate the environmental impact of solid waste accumulation. Existing technologies have reported the direct use of metallurgical waste as a rubber filler after crushing and screening, as well as schemes involving pre-modification of the waste with coupling agents before mixing it with rubber. Furthermore, in terms of vulcanization activation systems, current technologies commonly use a combination of zinc oxide and stearic acid as vulcanization activators, with zinc oxide typically used at 2.5 to 5.0 parts. Regarding the mixing process, the conventional approach is to feed the components into a mixer in a specific order for one or two stages of mixing.

[0003] However, the existing technologies still have the following shortcomings. First, in existing technologies, the modification of waste residue by coupling agents usually adopts an offline pre-modification method, that is, the waste residue and coupling agent are first mixed and treated separately before being compounded with rubber. This method is cumbersome, and the coupling agent and rubber matrix only form a single-point short chain structure of "filler-coupling agent-rubber", with limited interfacial bonding strength and low reinforcement efficiency. Second, the amount of zinc oxide used in existing vulcanization systems is relatively high, while zinc ions have potential hazards to the aquatic ecological environment. The development of low-zinc vulcanization systems has become an urgent need in the industry, but existing low-zinc solutions mostly use nano zinc oxide or organic zinc as substitutes, which are costly and difficult to disperse. Third, the surface of metallurgical waste residue contains a large number of active metal ions (calcium ions, iron ions, magnesium ions, etc.). Existing technologies only regard them as filler components and fail to effectively utilize their potential vulcanization activation function. Fourth, in existing compounding processes, stearic acid and zinc oxide are usually added simultaneously with the vulcanizing agent. Although the operation is simple, it is easy to cause problems such as excessively fast early vulcanization speed and shortened scorch time. Fifth, the existing mixing process has poor adaptability to different types of waste residue. When the composition of waste residue generated from different smelting processes fluctuates, the existing process struggles to maintain stable performance. These shortcomings limit the high-value application of industrial waste residue in tire tread compounds, necessitating a technical solution that can simultaneously address these issues. Summary of the Invention

[0004] To overcome the aforementioned shortcomings of the prior art, this invention provides a compounding and processing method for a high-wear-resistant and environmentally friendly tire tread reclaimed rubber composition. This method solves the problems of the prior art, such as cumbersome offline pre-modification process of coupling agent, low interface reinforcement efficiency, large zinc oxide usage leading to zinc pollution, failure to use calcium, iron and magnesium ions in waste residue as vulcanization activators, short scorching time due to simultaneous addition of vulcanizing agent, and poor adaptability of the process to different types of waste residue.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for compounding a high-wear-resistant and environmentally friendly reclaimed rubber composition for tire treads, comprising the following steps in a closed mixer: Step 1: After plasticizing the diene rubber in an internal mixer, add metallurgical waste slag powder containing free calcium oxide and iron oxide, reinforcing filler, mercaptosilane coupling agent and terminal amine liquid rubber, and mix at a temperature of 80°C to 115°C. Step 2: Without discharging, continue mixing and heat to 120℃ to 150℃; Step 3: Add stearic acid and zinc oxide to the internal mixer, mix, then add vulcanizing agent and vulcanization accelerator, mix at 150℃ to 170℃ and then discharge. In this process, the stearic acid reacts with free calcium, iron, and magnesium ions on the surface of the metallurgical waste powder at 150°C to 170°C in an in-situ exchange reaction to generate a metal soap salt containing calcium stearate, iron stearate, and magnesium stearate. The metal soap salt and the zinc oxide together serve as a sulfidation activator. The stearic acid and the zinc oxide are added before the sulfidation agent and the sulfidation accelerator.

[0006] Preferably, the metallurgical waste slag powder is at least one of desulfurization tailings of molten iron, steel slag, and converter slag, and its particle size D90≤10μm.

[0007] Preferably, in step one, the diene rubber is 100 parts by weight, the metallurgical waste powder is 30 to 60 parts by weight, the reinforcing filler is 20 to 40 parts by weight, the mercaptosilane coupling agent is 2 to 6 parts by weight, and the terminal amine liquid rubber is 3 to 10 parts by weight; in step three, the stearic acid is 0.5 to 1.5 parts by weight, the zinc oxide is 0.8 to 1.5 parts by weight, the vulcanizing agent is 1.5 to 2.5 parts by weight, and the vulcanization accelerator is 1.0 to 2.0 parts by weight.

[0008] Preferably, the mixing time in step one is 3 to 8 minutes; the mixing time in step two is 3 to 8 minutes; in step three, after adding stearic acid and zinc oxide, the mixture is mixed for 0.5 to 1.5 minutes, and after adding vulcanizing agent and vulcanization accelerator, the mixture is mixed for 1 to 3 minutes before being discharged.

[0009] Preferably, the mercaptosilane coupling agent is γ-mercaptopropyltriethoxysilane, and the molar ratio of γ-mercaptopropyltriethoxysilane to the terminal amine liquid rubber is 1:0.5 to 1.5.

[0010] Preferably, the terminal amine liquid rubber is a terminal amine liquid nitrile rubber with an amine value of 0.5 to 1.5 mmol / g and a number-average molecular weight of 1000 to 5000, wherein the number-average molecular weight is determined by gel permeation chromatography.

[0011] Preferably, the reinforcing filler is carbon black, and the carbon black is at least one of N220, N234 or N330; The diene rubber is at least one of natural rubber and styrene-butadiene rubber.

[0012] Preferably, the vulcanization accelerator is a sulfenamide accelerator, specifically N-cyclohexyl-2-benzothiazole sulfenamide and / or N-tert-butyl-2-benzothiazole sulfenamide.

[0013] Preferably, the rotor speed of the internal mixer in step one is 30 to 50 r / min, and the filling coefficient is 0.60 to 0.75; the discharge temperature in step three is 155°C to 165°C.

[0014] Preferably, the compounded rubber after discharge is thinly sheeted on a two-roll mill, cooled to room temperature, left to stand for 8 to 24 hours, and then vulcanized to the positive vulcanization state at 145°C to 155°C and above 10MPa. The vulcanization time is determined by the positive vulcanization time value measured by a vulcanizer.

[0015] The technical effects and advantages of the mixing and processing method of the high wear-resistant and environmentally friendly tire tread recycled rubber composition of the present invention are as follows: 1. This invention constructs a bilayer continuous chemical bonding interface of "metallurgical waste powder - mercaptosilane coupling agent - terminal amine liquid rubber" through the chemical anchoring of the surface of metallurgical waste powder by the mercaptosilane coupling agent at 80℃ to 115℃ in step one, and the condensation bridging reaction between the terminal amine liquid rubber and the anchored coupling agent at 120℃ to 150℃ in step two. In this interface structure, one end of the mercaptosilane coupling agent forms a covalent bond with the active hydroxyl groups on the surface of the waste powder, and the other end undergoes a condensation reaction with the terminal amine groups of the terminal amine liquid rubber to form a chemical connection. The double bonds in the molecular chain of the terminal amine liquid rubber participate in the rubber crosslinking network during vulcanization. This bilayer continuous chemical bonding structure is significantly different from the single-point short-chain structure of "filler - coupling agent - rubber" in the prior art, effectively enhancing the interfacial bonding force between the filler and the rubber matrix, reducing interfacial stress concentration, and thus significantly improving the tensile strength, tear strength, and resistance to damage of the vulcanized rubber.

[0016] 2. This invention utilizes the free calcium, iron, and magnesium ions on the surface of metallurgical waste slag powder to undergo an in-situ exchange reaction with stearic acid in the high-temperature range of 150°C to 170°C in step three, generating in-situ metal soaps such as calcium stearate, iron stearate, and magnesium stearate. These in-situ generated metal soaps, together with added zinc oxide, constitute a composite sulfidation active system, replacing most of the function of added zinc oxide in traditional sulfidation systems. This allows the amount of zinc oxide used to be reduced from 2.5 to 5.0 parts in conventional formulations to 0.8 to 1.5 parts, a reduction of 70% to 85%, significantly reducing the risk of zinc pollution. Simultaneously, the metallurgical waste slag powder requires no pre-modification treatment, eliminating the need for pre-processing such as filler drying and surface treatment, thus reducing production energy consumption and equipment investment. This invention transforms industrial metallurgical waste slag into functional fillers, achieving high-value utilization of solid waste and meeting the green manufacturing requirements under the "dual carbon" target.

[0017] 3. This invention simplifies the complex process of "filler pre-modification + multi-stage mixing" in existing technologies into a three-stage continuous temperature-controlled mixing process carried out continuously in the same internal mixer: step one, a low-temperature anchoring stage; step two, a medium-temperature bridging stage; and step three, a high-temperature in-situ saponification stage. There is no material discharge or equipment change between the three steps, and no need to remove materials for separate processing, reducing material transfer and equipment switching steps. The entire process of filler surface modification, interface compatibilization, and vulcanization activation can be completed with a single feeding, shortening the mixing cycle and reducing overall energy consumption.

[0018] 4. In step three of this invention, stearic acid and zinc oxide are added before the vulcanizing agent and vulcanization accelerator. This allows the in-situ generated metal soap salts to react with the active groups in the rubber matrix earlier, effectively reducing the early vulcanization rate and extending the scorch time. The processing safety is significantly better than conventional one-time feeding processes. Simultaneously, the composite vulcanization activation system formed by the in-situ generated metal soap salts and low-dose zinc oxide increases the crosslinking density after positive vulcanization and shortens the positive vulcanization time, achieving simultaneous improvement in processing safety and vulcanization efficiency.

[0019] 5. This invention has broad applicability to various types of metallurgical waste slag powder. Regardless of whether desulfurization tailings from molten iron, steel slag, or converter slag is used as the metallurgical waste slag powder, its surface contains free calcium, iron, and magnesium ions. These ions can undergo an in-situ exchange reaction with stearic acid in step three to generate the corresponding metal soaps and perform sulfidation activation. Therefore, the method of this invention is applicable to various metallurgical waste slags containing free calcium oxide and iron oxide, which is beneficial for its widespread application in different regions and under different steel smelting waste slag conditions.

[0020] 6. Through the synergistic effect of the three-stage continuous temperature-controlled mixing process of low-temperature anchoring in step one, medium-temperature bridging in step two, and high-temperature in-situ saponification in step three, as well as the control of the feeding sequence of stearic acid and zinc oxide before vulcanizing agent and vulcanization accelerator, this invention achieves increased crosslinking density, enhanced mechanical properties, and improved wear resistance of vulcanized rubber under the condition of significantly reduced zinc oxide dosage. It obtains a highly wear-resistant and environmentally friendly tread reclaimed rubber composition that can meet the high-performance requirements of all-steel radial tire treads. Attached Figure Description

[0021] Figure 1 This is a flowchart of a mixing and processing method for a high wear-resistant and environmentally friendly tire tread recycled rubber composition proposed in this invention; Figure 2 This is a schematic diagram of the three-stage temperature-time curve of the mixing process of a high wear-resistant and environmentally friendly tire tread recycled rubber composition proposed in this invention. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include," "contain," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes 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 "includes..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0024] refer to Figure 1-2This invention discloses a mixing and processing method for a high-wear-resistant and environmentally friendly tire tread recycled rubber composition, providing a method for continuous three-stage temperature-controlled mixing in the same internal mixer: In step one, after plasticizing diene rubber, metallurgical waste slag powder containing free calcium oxide and iron oxide, reinforcing filler, mercaptosilane coupling agent, and terminal amine liquid rubber are added, and mixed at 80°C to 115°C, so that the mercaptosilane coupling agent is hydrolyzed and chemically anchored to the surface of the waste slag powder; In step two, without discharging, the temperature is further raised to 120°C to 150°C for mixing, so that the terminal amine groups of the terminal amine liquid rubber couple with the anchored mercaptosilane. The coupling agent undergoes a condensation reaction to form a double-layer continuous chemical bonding interface of "waste residue powder - mercaptosilane coupling agent - terminal amine liquid rubber". In step three, stearic acid and zinc oxide are added to the internal mixer and mixed. Then, vulcanizing agent and vulcanization accelerator are added and mixed at 150°C to 170°C before being discharged. In this step, stearic acid undergoes an in-situ exchange reaction with free calcium, iron and magnesium ions on the surface of the waste residue powder to generate metal soap salts containing calcium stearate, iron stearate and magnesium stearate. These metal soap salts and zinc oxide together act as vulcanization activators, and stearic acid and zinc oxide are added before the vulcanizing agent and vulcanization accelerator. This invention achieves integrated continuous mixing through three-stage temperature control. The in-situ anchoring of the coupling agent and the in-situ bridging of the liquid rubber construct a double-layer continuous chemical bonding interface, which significantly enhances the interfacial bonding force between the filler and the rubber matrix. The natural calcium, iron, and magnesium ions in the waste residue are used to generate metal soap salts in situ, reducing the amount of zinc oxide by more than 70% and avoiding zinc pollution. The addition of stearic acid and zinc oxide before the vulcanizing agent effectively prolongs the scorch time, improves processing safety and vulcanization efficiency, and obtains a highly wear-resistant and environmentally friendly tread reclaimed rubber composition.

[0025] Example 1 Purpose of implementation: The purpose of this embodiment is to verify the feasibility and comprehensive performance of using desulfurization tailings of molten iron as metallurgical waste powder, KH-580 as mercaptosilane coupling agent, and ATBN as terminal amine liquid rubber, and achieving in-situ saponification reaction through a three-stage temperature-controlled mixing process under medium dosage ratio, thereby obtaining a high wear-resistant, low-zinc, environmentally friendly tread rubber composition.

[0026] Composition formulation: In this embodiment, the composition is as follows: natural rubber 70 parts, styrene-butadiene rubber (SBR1502) 30 parts, desulfurization tailings from molten iron (D90 8.5 μm) 45 parts, carbon black N330 30 parts, γ-mercaptopropyltriethoxysilane (KH-580) 4.0 parts, terminal amine liquid acrylonitrile butadiene rubber (ATBN, amine value 0.9 mmol / g, number average molecular weight 2500, number average molecular weight determined by gel permeation chromatography) 6.0 parts, stearic acid 1.0 part, zinc oxide 1.2 parts, sulfur 2.0 parts, accelerator CZ 1.5 parts, and antioxidant 4020 2.0 parts. The molar ratio of γ-mercaptopropyltriethoxysilane to terminal amine liquid acrylonitrile butadiene rubber is 1:0.9.

[0027] Mixing and processing methods: The mixing was carried out using an internal mixer with a filling coefficient of 0.65 and a rotor speed of 40 r / min. The following steps were performed continuously in the same internal mixer: Step 1: Put 70 parts of natural rubber and 30 parts of styrene-butadiene rubber into a mixer and masticate for 1.5 minutes. Then add 45 parts of desulfurization tailings of molten iron, 30 parts of carbon black N330, 4.0 parts of γ-mercaptopropyltriethoxysilane and 6.0 parts of terminal amine liquid nitrile rubber. Control the mixing temperature to 90℃ to 105℃ and mix for 4 minutes.

[0028] Step 2: After completing Step 1, do not discharge the material. Continue mixing. The mixing temperature will rise to 130°C to 140°C through the shearing action of the internal mixer rotor. Mix at this temperature for 5 minutes.

[0029] Step 3: Add 1.0 part stearic acid, 1.2 parts zinc oxide, 2.0 parts sulfur, 1.5 parts accelerator CZ and 2.0 parts antioxidant 4020 to the internal mixer. Stearic acid and zinc oxide are added before sulfur and accelerator. Control the mixing temperature to 155℃ to 160℃ and mix for 1.5 minutes before discharging.

[0030] Subsequent processing: After discharge, the compounded rubber was passed through a two-roll mill three times and then sheeted, cooled to room temperature, and left to stand for 12 hours. The t90 value was measured using a rotorless vulcanizer, and then vulcanized at 150℃ and 12MPa to the positive vulcanization state.

[0031] Implementation results: The vulcanizate prepared by the above method has a tensile strength of 26.5 MPa, a tear strength of 108 kN / m, an Akron abrasion loss of 0.09 cm³ / 1.61 km, and a crosslinking density of 2.8 × 10⁻⁶ m / m. mol / cm³, scorch time The vulcanization time was 13.5 minutes, and the positive vulcanization time was 25.0 minutes. This indicates that through the low-temperature anchoring of the desulfurization tailings of molten iron by KH-580 in step one, the medium-temperature bridging by ATBN in step two, and the high-temperature in-situ saponification of calcium, iron, and magnesium ions on the surface of the desulfurization tailings by stearic acid in step three, a double-layer continuous chemical bonding interface of "desulfurization tailings of molten iron - KH-580 - ATBN" was formed. At the same time, the calcium stearate, iron stearate, and magnesium stearate generated in situ synergistically activated the vulcanization system with a low dose of zinc oxide, achieving a significant improvement in crosslinking density and mechanical properties with only 1.2 parts of zinc oxide.

[0032] Example 2 Purpose of implementation: The purpose of this embodiment is to verify the applicability and performance reproducibility of the three-stage temperature-controlled mixing process of the present invention under conditions of pure natural rubber system, high natural rubber ratio and different KH-580 to ATBN molar ratio.

[0033] Composition formulation: In this embodiment, the composition is as follows: natural rubber 100 parts, desulfurization tailings from molten iron (D90 7.2 μm) 35 parts, carbon black N234 35 parts, γ-mercaptopropyltriethoxysilane (KH-580) 3.0 parts, terminal amine liquid nitrile rubber (ATBN, amine value 1.2 mmol / g, number average molecular weight 1800, number average molecular weight determined by gel permeation chromatography) 5.0 parts, stearic acid 0.8 parts, zinc oxide 1.0 part, sulfur 1.8 parts, accelerator NS 1.2 parts, and antioxidant RD 2.5 parts. The molar ratio of γ-mercaptopropyltriethoxysilane to terminal amine liquid nitrile rubber is 1:0.8.

[0034] Mixing and processing methods: The mixing was carried out using an internal mixer with a filling factor of 0.68 and a rotor speed of 35 r / min. The following steps were performed continuously in the same internal mixer: Step 1: Put 100 parts of natural rubber into a mixer and masticate for 2 minutes. Then add 35 parts of desulfurization tailings of molten iron, 35 parts of carbon black N234, 3.0 parts of γ-mercaptopropyltriethoxysilane and 5.0 parts of terminal amine liquid nitrile rubber. Control the mixing temperature to 85℃ to 100℃ and mix for 5 minutes.

[0035] Step 2: After completing Step 1, do not discharge the material. Continue mixing. The mixing temperature will rise to 125°C to 135°C through the shearing action of the internal mixer rotor. Mix at this temperature for 6 minutes.

[0036] Step 3: Add 0.8 parts stearic acid, 1.0 parts zinc oxide, 1.8 parts sulfur, 1.2 parts accelerator NS and 2.5 parts antioxidant RD to the internal mixer. Stearic acid and zinc oxide are added before sulfur and accelerator. Control the mixing temperature to 150℃ to 155℃ and discharge the material after mixing for 2 minutes.

[0037] Subsequent processing: After discharge, the compounded rubber was passed through a two-roll mill three times and then sheeted, cooled to room temperature, and left to stand for 12 hours. The t90 value was measured using a rotorless vulcanizer, and then vulcanized at 150℃ and 12MPa to the positive vulcanization state.

[0038] Implementation results: The vulcanizate prepared by the above method has a tensile strength of 25.8 MPa, a tear strength of 102 kN / m, an Akron abrasion loss of 0.10 cm³ / 1.61 km, and a crosslinking density of 2.6 × 10⁻⁶ m / m. mol / cm³, scorch time The curing time was 14.2 minutes, and the positive vulcanization time was 26.5 minutes. In this example, with only 1.0 part of zinc oxide, the tensile strength was increased by 41% compared to Comparative Example 1, the tear strength was increased by 42%, the abrasion loss was reduced by 47%, the crosslinking density was increased by 63%, the scorch time was extended by 78%, and the positive vulcanization time was shortened by 12%. All performance indicators were significantly better than Comparative Example 1 and comparable to those of Example 1, proving that the present invention has good applicability in pure natural rubber systems and under different molar ratios of coupling agent to liquid rubber.

[0039] Example 3 Purpose of implementation: The purpose of this embodiment is to verify the process feasibility and product performance under the conditions of high-speed iron molten iron desulfurization tailings dosage, short-time mixing, and a relatively high KH-580 to ATBN molar ratio.

[0040] Composition formulation: In this embodiment, styrene-butadiene rubber (SBR1502) comprises 100 parts, desulfurization tailings from molten iron (D90 of 9.0 μm) comprises 55 parts, carbon black N220 comprises 25 parts, γ-mercaptopropyltriethoxysilane (KH-580) comprises 5.0 parts, terminal amine liquid acrylonitrile butadiene rubber (ATBN, amine value of 0.6 mmol / g, number-average molecular weight of 4000, determined by gel permeation chromatography) comprises 8.0 parts, stearic acid comprises 1.3 parts, zinc oxide comprises 1.4 parts, sulfur comprises 2.2 parts, accelerator CZ comprises 1.8 parts, and antioxidant 4010NA comprises 1.5 parts. The molar ratio of γ-mercaptopropyltriethoxysilane to terminal amine liquid acrylonitrile butadiene rubber is 1:1.1.

[0041] Mixing and processing methods: The mixing was carried out using an internal mixer with a filling coefficient of 0.62 and a rotor speed of 45 r / min. The following steps were performed continuously in the same internal mixer: Step 1: Put 100 parts of styrene-butadiene rubber into a mixer and masticate for 1 minute. Then add 55 parts of desulfurization tailings of molten iron, 25 parts of carbon black N220, 5.0 parts of γ-mercaptopropyltriethoxysilane and 8.0 parts of terminal amine liquid nitrile rubber. Control the mixing temperature to 100℃ to 110℃ and mix for 3 minutes.

[0042] Step 2: After completing Step 1, do not discharge the material. Continue mixing. The mixing temperature will rise to 135℃ to 145℃ through the shearing action of the internal mixer rotor. Mix at this temperature for 4 minutes.

[0043] Step 3: Add 1.3 parts stearic acid, 1.4 parts zinc oxide, 2.2 parts sulfur, 1.8 parts accelerator CZ and 1.5 parts antioxidant 4010NA to the internal mixer. Stearic acid and zinc oxide are added before sulfur and accelerator. Control the mixing temperature to 160℃ to 165℃ and discharge the material after mixing for 1 minute.

[0044] Subsequent processing: After discharge, the compounded rubber was passed through a two-roll mill three times and then sheeted, cooled to room temperature, and left to stand for 12 hours. The t90 value was measured using a rotorless vulcanizer, and then vulcanized at 150℃ and 12MPa to the positive vulcanization state.

[0045] Implementation results: The vulcanized rubber prepared by the above method has a tensile strength of 25.2 MPa, a tear strength of 98 kN / m, an Akron abrasion loss of 0.11 cm³ / 1.61 km, and a crosslinking density of 2.5 × 10⁻⁶ m / m. mol / cm³, scorch time The mixing time was 12.8 minutes, and the positive vulcanization time was 23.5 minutes. Under the process conditions of using up to 55 parts of waste residue and relatively short mixing times for each stage (3 minutes for step one, 4 minutes for step two, and 1 minute for step three), this embodiment showed a 38% increase in tensile strength, a 36% increase in tear strength, a 42% reduction in abrasion loss, a 56% increase in crosslinking density, a 60% extension in scorch time, and a 22% reduction in positive vulcanization time compared to Comparative Example 1. All performance indicators were significantly better than Comparative Example 1 and comparable to those of Examples 1 and 2, demonstrating the stability and operability of this invention within a wide formulation range and a short process window.

[0046] Example 4 Purpose of implementation: The purpose of this embodiment is to verify the applicability and product performance of the three-stage temperature-controlled mixing process of the present invention when steel slag is used to replace the desulfurization tailings of molten iron as metallurgical waste slag powder.

[0047] Composition formulation: In this embodiment, natural rubber comprises 60 parts, styrene-butadiene rubber (SBR1502) comprises 40 parts, and steel slag (D90 is 8.8 μm, free CaO content is not less than 5%). The composition of the active ingredient is as follows: 40 parts of γ-mercaptopropyltriethoxysilane (KH-580), 32 parts of carbon black N330, 3.5 parts of γ-mercaptopropyltriethoxysilane (KH-580), 5.5 parts of terminal amine-terminated liquid nitrile rubber (ATBN, amine value 1.0 mmol / g, number average molecular weight 3000, determined by gel permeation chromatography), 1.0 part of stearic acid, 1.1 parts of zinc oxide, 2.0 parts of sulfur, 1.4 parts of accelerator NS, and 2.0 parts of antioxidant 4020. The molar ratio of γ-mercaptopropyltriethoxysilane to terminal amine-terminated liquid nitrile rubber is 1:0.9.

[0048] Mixing and processing methods: The mixing was carried out using an internal mixer with a filling coefficient of 0.65 and a rotor speed of 40 r / min. The following steps were performed continuously in the same internal mixer: Step 1: Put 60 parts of natural rubber and 40 parts of styrene-butadiene rubber into a mixer and masticate for 1.5 minutes. Then add 40 parts of steel slag, 32 parts of carbon black N330, 3.5 parts of γ-mercaptopropyltriethoxysilane and 5.5 parts of terminal amine liquid nitrile rubber. Control the mixing temperature to 90℃ to 105℃ and mix for 4 minutes.

[0049] Step 2: After completing Step 1, do not discharge the material. Continue mixing. The mixing temperature will rise to 130°C to 140°C through the shearing action of the internal mixer rotor. Mix at this temperature for 5 minutes.

[0050] Step 3: Add 1.0 part stearic acid, 1.1 part zinc oxide, 2.0 part sulfur, 1.4 part accelerator NS and 2.0 part antioxidant 4020 to the internal mixer. Stearic acid and zinc oxide are added before sulfur and accelerator. Control the mixing temperature to 155℃ to 160℃ and mix for 1.5 minutes before discharging.

[0051] Subsequent processing: After discharge, the compounded rubber was passed through a two-roll mill three times and then sheeted, cooled to room temperature, and left to stand for 12 hours. The t90 value was measured using a rotorless vulcanizer, and then vulcanized at 150℃ and 12MPa to the positive vulcanization state.

[0052] Implementation results: The vulcanizate prepared by the above method has a tensile strength of 25.5 MPa, a tear strength of 104 kN / m, an Akron abrasion loss of 0.10 cm³ / 1.61 km, and a crosslinking density of 2.7 × 10⁻⁶ kN / m. mol / cm³, scorch time The tensile strength was 13.0 minutes, and the positive sulfidation time was 25.5 minutes. In this embodiment, steel slag was used to replace the desulfurization tailings of molten iron. Compared with Comparative Example 1, the tensile strength increased by 39%, the tear strength increased by 44%, the abrasion loss decreased by 47%, the crosslinking density increased by 69%, the scorch time was extended by 63%, and the positive sulfidation time was shortened by 15%. All performance indicators were basically equivalent to those of Examples 1 to 3, proving that the method of this invention also has excellent modification effects on steel slag. The free calcium, iron, and magnesium ions on the surface of the steel slag can also undergo in-situ substitution reactions with stearic acid in step three to generate corresponding metal soaps, further proving the rationality of the general term "metallurgical waste slag powder containing free calcium oxide and iron oxide" in this invention.

[0053] Example 5 Purpose of implementation: The purpose of this embodiment is to verify the applicability and product performance of the three-stage temperature-controlled mixing process of the present invention when using converter slag to replace desulfurization tailings of molten iron as metallurgical waste slag powder.

[0054] Composition formulation: In this embodiment, the composition is as follows: natural rubber 80 parts, styrene-butadiene rubber (SBR1502) 20 parts, converter slag (D90 9.2 μm) 50 parts, carbon black N234 28 parts, γ-mercaptopropyltriethoxysilane (KH-580) 4.5 parts, terminal amine liquid nitrile butadiene rubber (ATBN, amine value 0.8 mmol / g, number average molecular weight 3500, number average molecular weight determined by gel permeation chromatography) 7.0 parts, stearic acid 1.2 parts, zinc oxide 1.3 parts, sulfur 2.2 parts, accelerator CZ 1.6 parts, and antioxidant RD 2.2 parts. The molar ratio of γ-mercaptopropyltriethoxysilane to terminal amine liquid nitrile butadiene rubber is 1:1.0.

[0055] Mixing and processing methods: The mixing was carried out using an internal mixer with a filling coefficient of 0.65 and a rotor speed of 40 r / min. The following steps were performed continuously in the same internal mixer: Step 1: Put 80 parts of natural rubber and 20 parts of styrene-butadiene rubber into a mixer and masticate for 1.5 minutes. Then add 50 parts of converter slag, 28 parts of carbon black N234, 4.5 parts of γ-mercaptopropyltriethoxysilane and 7.0 parts of terminal amine liquid nitrile rubber. Control the mixing temperature to 90℃ to 105℃ and mix for 4 minutes.

[0056] Step 2: After completing Step 1, do not discharge the material. Continue mixing. The mixing temperature will rise to 130°C to 140°C through the shearing action of the internal mixer rotor. Mix at this temperature for 5 minutes.

[0057] Step 3: Add 1.2 parts stearic acid, 1.3 parts zinc oxide, 2.2 parts sulfur, 1.6 parts accelerator CZ and 2.2 parts antioxidant RD to the internal mixer. Stearic acid and zinc oxide are added before sulfur and accelerator. Control the mixing temperature to 155℃ to 160℃ and mix for 1.5 minutes before discharging.

[0058] Subsequent processing: After discharge, the compounded rubber was passed through a two-roll mill three times and then sheeted, cooled to room temperature, and left to stand for 12 hours. The t90 value was measured using a rotorless vulcanizer, and then vulcanized at 150℃ and 12MPa to the positive vulcanization state.

[0059] Implementation results: The vulcanized rubber prepared by the above method has a tensile strength of 25.0 MPa, a tear strength of 99 kN / m, an Akron abrasion loss of 0.11 cm³ / 1.61 km, and a crosslinking density of 2.5 × 10⁻⁶ m / m. mol / cm³, scorch time The tensile strength was 12.5 minutes, and the positive sulfidation time was 24.0 minutes. In this embodiment, converter slag was used instead of desulfurization tailings from molten iron. Compared to Comparative Example 1, the tensile strength increased by 37%, the tear strength increased by 38%, the abrasion loss decreased by 42%, the crosslinking density increased by 56%, the scorching time was extended by 56%, and the positive sulfidation time was shortened by 20%. All performance indicators were essentially equivalent to those of Examples 1 to 4, demonstrating that the method of this invention also has excellent modification effects on converter slag. Combining the results of Examples 4 and 5, when using steel slag and converter slag, all performance indicators were essentially equivalent to those when using desulfurization tailings from molten iron, fully demonstrating that the method of this invention is universally applicable to different types of metallurgical waste containing free calcium oxide and iron oxide.

[0060] Comparative Example 1 Purpose of implementation: The purpose of this comparative example is to verify the difference between the performance of the rubber composition and that of Example 1 of the present invention under the conditions of not adding KH-580 and ATBN (i.e. not performing the low-temperature anchoring in step one and the medium-temperature bridging in step two), using the conventional amount of zinc oxide (5.0 parts), and using the conventional one-stage mixing process (rather than the three-stage temperature control, stearic acid and zinc oxide added before vulcanizing agent and accelerator of the present invention), thereby proving the synergistic effect of steps one to three in the present invention and the technical effect of the low-zinc formulation.

[0061] Composition formulation: In this comparative example, natural rubber accounted for 70 parts, styrene-butadiene rubber (SBR1502) accounted for 30 parts, desulfurization tailings of molten iron (unmodified, D90 of 8.5μm) accounted for 45 parts, carbon black N330 accounted for 30 parts, stearic acid accounted for 2.0 parts, zinc oxide accounted for 5.0 parts, sulfur accounted for 2.0 parts, accelerator CZ accounted for 1.5 parts, and antioxidant 4020 accounted for 2.0 parts.

[0062] The difference between this comparative example and Example 1 is that KH-580 and ATBN are not added; the amount of zinc oxide is 5.0 parts; the three-stage temperature-controlled mixing process and the feeding sequence of this invention are not used.

[0063] Mixing and processing methods: The mixing was carried out using an internal mixer with a filling factor of 0.65 and a rotor speed of 40 r / min. Add 70 parts natural rubber and 30 parts styrene-butadiene rubber to a mixer and masticate for 1.5 minutes. Then, add 45 parts desulfurization tailings from molten iron, 30 parts carbon black N330, 2.0 parts stearic acid, 5.0 parts zinc oxide, 2.0 parts sulfur, 1.5 parts accelerator CZ, and 2.0 parts antioxidant 4020 all at once. Control the mixing temperature at 150℃ and mix for 8 minutes before discharging. All components are added at once, without regard to the order of addition.

[0064] Subsequent processing: After discharge, the compounded rubber was passed through a two-roll mill three times and then sheeted, cooled to room temperature, and left to stand for 12 hours. The t90 value was measured using a rotorless vulcanizer, and then vulcanized at 150℃ and 12MPa to the positive vulcanization state.

[0065] Implementation results: The vulcanizate prepared by the above method has a tensile strength of 18.3 MPa, a tear strength of 72 kN / m, an Akron abrasion loss of 0.19 cm³ / 1.61 km, and a crosslinking density of 1.6 × 10⁻⁶ m / m. mol / cm³, scorch time The curing time is 8.0 minutes, and the positive vulcanization time is 30.0 minutes.

[0066] Compared with Example 1, Comparative Example 1 showed a 31% decrease in tensile strength, a 33% decrease in tear strength, a 111% increase in abrasion loss, a 43% decrease in crosslinking density, a 41% reduction in scorch time, and a 20% extension in positive vulcanization time. The results indicate that without the addition of KH-580 and ATBN, an effective chemical bonding interface cannot be formed between the desulfurization tailings of molten iron and the rubber matrix, leading to a significant decrease in mechanical and wear resistance properties. Using a conventional amount of 5.0 parts zinc oxide without utilizing the in-situ generation of metal soaps from metal ions on the surface of the desulfurization tailings, the crosslinking density was actually lower than that of Example 1 using only 1.2 parts zinc oxide. The conventional mixing process, which involves one-time feeding without distinguishing the feeding sequence, resulted in excessively fast vulcanization (short scorch time), poor processing safety, and a prolonged positive vulcanization time, leading to reduced vulcanization efficiency. The above comparisons fully demonstrate the synergistic effect of the three-stage temperature-controlled mixing process, in-situ saponification reaction, and low-zinc formulation in steps one to three of this invention.

[0067] Performance testing: The vulcanizates prepared in Examples 1 to 5 and Comparative Example 1 were subjected to performance tests. The test methods and results are as follows.

[0068] Tensile strength was tested according to GB / T528, using dumbbell-shaped specimens at a tensile speed of 500 mm / min. Tear strength was tested according to GB / T529, using right-angled specimens at a tensile speed of 500 mm / min. Abrasion loss was tested according to GB / T1689 using an Akron abrasion tester. Crosslinking density was determined using the equilibrium swelling method, with toluene as the solvent, and swelling at 25°C for 72 hours. Scorch time t5 and positive vulcanization time were tested according to GB / T16584 using a rotorless vulcanizer at a test temperature of 150°C.

[0069] The tensile strength of Example 1, as determined by the above testing methods, was 26.5 MPa, the tear strength was 108 kN / m, the abrasion loss was 0.09 cm³ / 1.61 km, and the crosslinking density was 2.8 × 10⁻⁶ kN / m. mol / cm³, scorch time The curing time was 13.5 minutes, and the positive vulcanization time was 25.0 minutes. Example 2 showed a tensile strength of 25.8 MPa, a tear strength of 102 kN / m, an abrasion loss of 0.10 cm³ / 1.61 km, and a crosslinking density of 2.6 × 10⁻⁶. mol / cm³, scorch time The curing time was 14.2 minutes, and the positive vulcanization time was 26.5 minutes. Example 3 showed a tensile strength of 25.2 MPa, a tear strength of 98 kN / m, an abrasion loss of 0.11 cm³ / 1.61 km, and a crosslinking density of 2.5 × 10⁻⁶. mol / cm³, scorch time The curing time was 12.8 minutes, and the positive vulcanization time was 23.5 minutes. Example 4 showed a tensile strength of 25.5 MPa, a tear strength of 104 kN / m, an abrasion loss of 0.10 cm³ / 1.61 km, and a crosslinking density of 2.7 × 10⁻⁶. mol / cm³, scorch time The curing time was 13.0 minutes, and the positive vulcanization time was 25.5 minutes. Example 5 showed a tensile strength of 25.0 MPa, a tear strength of 99 kN / m, an abrasion loss of 0.11 cm³ / 1.61 km, and a crosslinking density of 2.5 × 10⁻⁶. mol / cm³, scorch time The curing time was 12.5 minutes, and the positive vulcanization time was 24.0 minutes. Comparative Example 1 showed a tensile strength of 18.3 MPa, a tear strength of 72 kN / m, an abrasion loss of 0.19 cm³ / 1.61 km, and a crosslinking density of 1.6 × 10⁻⁶. mol / cm³, scorch time The curing time is 8.0 minutes, and the positive vulcanization time is 30.0 minutes.

[0070] Results analysis: The test results above show that the tensile strength of Examples 1 to 5 is 25.0 to 26.5 MPa, which is 36% to 45% higher than that of Comparative Example 1 (18.3 MPa). This indicates that the low-temperature anchoring of KH-580 in step one and the medium-temperature bridging of ATBN in step two construct a double-layer continuous chemical bonding interface of "metallurgical waste slag - KH-580 - ATBN", which significantly enhances the interfacial bonding force between the filler and the rubber matrix.

[0071] The tear strength of Examples 1 to 5 was 98 to 108 kN / m, which was 36% to 50% higher than that of Comparative Example 1 (72 kN / m). This indicates that the ATBN flexible molecular bridge effectively buffered the modulus difference between the inorganic filler and the organic rubber, and reduced the stress concentration at the interface.

[0072] The wear rate of Examples 1 to 5 was 0.09 to 0.11 cm³ / 1.61 km, which was 42% to 53% lower than that of Comparative Example 1 (0.19 cm³ / 1.61 km), indicating that the enhanced interfacial bonding effectively improved the wear resistance of the vulcanizate.

[0073] The crosslinking density of Examples 1 to 5 is 2.5 × Up to 2.8× mol / cm³, compared to 1.6× in Comparative Example 1. The increase in mol / cm³ by 56% to 75% indicates that the calcium stearate, iron stearate, and magnesium stearate formed by the in-situ exchange reaction between stearic acid and free calcium, iron, and magnesium ions on the surface of metallurgical waste powder at 150℃ to 170℃, synergistically with low-dose zinc oxide (0.8 to 1.5 parts), effectively activated the vulcanization system. The crosslinking density was significantly higher than that of Comparative Example 1 with conventional zinc oxide dosage (5.0 parts). These crosslinking density data directly correspond to the technical characteristic of adding stearic acid before the vulcanizing agent in step three, fully demonstrating the technical effectiveness of the in-situ saponification reaction in generating metal soap salts and exerting a vulcanization activation effect.

[0074] Scorch time of Examples 1 to 5 The time was 12.5 to 14.2 minutes, which is 56% to 78% longer than the 8.0 minutes of Comparative Example 1. This indicates that the order of adding stearic acid and zinc oxide first, followed by the vulcanizing agent and vulcanization accelerator in step three, combined with the in-situ generated metal soap salts, effectively reduced the early vulcanization rate and significantly improved processing safety. At the same time, the positive vulcanization time was 23.5 to 26.5 minutes, which is 12% to 22% shorter than the 30.0 minutes of Comparative Example 1, and the vulcanization efficiency was improved.

[0075] Examples 4 and 5 use steel slag and converter slag respectively to replace the desulfurization tailings of molten iron. The performance indicators are basically equivalent to those of Examples 1 to 3 (using desulfurization tailings of molten iron), demonstrating that the method of the present invention is universally applicable to different types of metallurgical waste slag containing free calcium oxide and iron oxide. Furthermore, the above data directly correspond to the technical feature in claim 2 that "the metallurgical waste slag powder is at least one of desulfurization tailings of molten iron, steel slag, and converter slag," providing sufficient experimental data support for the limitation on the type of waste slag in claim 2.

[0076] In summary, this invention achieves a comprehensive improvement in crosslinking density, tensile strength, tear strength, abrasion resistance, and processing safety by employing a three-stage continuous temperature-controlled mixing process: low-temperature anchoring in step one, medium-temperature bridging in step two, and high-temperature in-situ saponification in step three, along with controlled feeding order of stearic acid and zinc oxide before the vulcanizing agent and vulcanization accelerator, while reducing the zinc oxide content by 74% to 76% (from 5.0 parts to 1.0 to 1.4 parts). Specifically, the crosslinking density data from Examples 1 to 5 directly demonstrate the effectiveness of the metal soap salt generated in step three through in-situ saponification, which synergistically acts as a vulcanization activator with zinc oxide; the tensile strength and tear strength data directly demonstrate the reinforcing effect of the bilayer continuous chemical bonding interface constructed by the chemical anchoring of KH-580 in step one and the molecular bridging of ATBN in step two; and the scorch time data directly demonstrate the improvement in processing safety achieved by feeding stearic acid and zinc oxide before the vulcanizing agent and vulcanization accelerator. The data from the above embodiments and comparative examples together constitute a complete support for all the technical features of the present invention, fully demonstrating the advanced nature and non-obviousness of the technical solution of the present invention.

[0077] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0078] In conclusion, the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for mixing and processing a high-wear-resistant and environmentally friendly recycled rubber composition for tire treads, characterized in that, The following steps are included in a closed mixing mill: Step 1: After plasticizing the diene rubber in an internal mixer, add metallurgical waste slag powder containing free calcium oxide and iron oxide, reinforcing filler, mercaptosilane coupling agent and terminal amine liquid rubber, and mix at a temperature of 80°C to 115°C. Step 2: Without discharging, continue mixing and heat to 120℃ to 150℃; Step 3: Add stearic acid and zinc oxide to the internal mixer, mix, then add vulcanizing agent and vulcanization accelerator, mix at 150℃ to 170℃ and then discharge. In this process, the stearic acid reacts with free calcium, iron, and magnesium ions on the surface of the metallurgical waste powder at 150°C to 170°C in an in-situ exchange reaction to generate a metal soap salt containing calcium stearate, iron stearate, and magnesium stearate. The metal soap salt and the zinc oxide together serve as a sulfidation activator. The stearic acid and the zinc oxide are added before the sulfidation agent and the sulfidation accelerator.

2. The mixing and processing method of a high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, The metallurgical waste slag powder is at least one of desulfurization tailings of molten iron, steel slag, and converter slag, and its particle size D90≤10μm.

3. The mixing and processing method of the high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, In step one, the diene rubber is 100 parts by weight, the metallurgical waste powder is 30 to 60 parts by weight, the reinforcing filler is 20 to 40 parts by weight, the mercaptosilane coupling agent is 2 to 6 parts by weight, and the terminal amine liquid rubber is 3 to 10 parts by weight; in step three, the stearic acid is 0.5 to 1.5 parts by weight, the zinc oxide is 0.8 to 1.5 parts by weight, the vulcanizing agent is 1.5 to 2.5 parts by weight, and the vulcanization accelerator is 1.0 to 2.0 parts by weight.

4. The mixing and processing method of the high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, The mixing time in step one is 3 to 8 minutes; the mixing time in step two is 3 to 8 minutes; in step three, after adding stearic acid and zinc oxide, the mixture is mixed for 0.5 to 1.5 minutes, and after adding vulcanizing agent and vulcanization accelerator, the mixture is mixed for 1 to 3 minutes before being discharged.

5. The mixing and processing method of a high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, The mercaptosilane coupling agent is γ-mercaptopropyltriethoxysilane, and the molar ratio of γ-mercaptopropyltriethoxysilane to the terminal amine liquid rubber is 1:0.5 to 1.

5.

6. The mixing and processing method of the high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, The terminal amine-based liquid rubber is a terminal amine-based liquid nitrile rubber with an amine value of 0.5 to 1.5 mmol / g and a number-average molecular weight of 1000 to 5000, the number-average molecular weight being determined by gel permeation chromatography.

7. The mixing and processing method of a high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, The reinforcing filler is carbon black, and the carbon black is at least one of N220, N234 or N330; The diene rubber is at least one of natural rubber and styrene-butadiene rubber.

8. The mixing and processing method of a high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, The vulcanization accelerator is a sulfenamide accelerator, specifically N-cyclohexyl-2-benzothiazole sulfenamide and / or N-tert-butyl-2-benzothiazole sulfenamide.

9. The mixing and processing method of a high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, The rotor speed of the internal mixer in step one is 30 to 50 r / min, and the filling coefficient is 0.60 to 0.75; the discharge temperature in step three is 155℃ to 165℃.

10. The mixing and processing method of a high wear-resistant and environmentally friendly tire tread recycled rubber composition as described in claim 1, characterized in that, After discharge, the compounded rubber is thinly processed on a two-roll mill and sheeted out. It is then cooled to room temperature and left to stand for 8 to 24 hours. Finally, it is vulcanized to the positive vulcanization state at 145°C to 155°C and above 10MPa. The vulcanization time is determined by the positive vulcanization time value measured by a vulcanizer.

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