Method for improving dispersion of multi-rubber formula carbon black

Abstract

The invention discloses a method for improving dispersion of multi-rubber formula carbon black, and relates to the technical field of rubber mixing processes. The method specifically comprises the following steps: carrying out first-stage mixing on 40-60 parts of natural rubber, 40-60 parts of synthetic rubber, 55-70 parts of carbon black and an auxiliary agent to obtain a first-stage rubber master batch; 5-20 parts of delayed adding parts are determined according to the Mooney viscosity 40-70 of synthetic rubber, the delayed adding parts and the first-stage rubber master batch are subjected to second-stage mixing, a power-time curve of the internal mixer is monitored during mixing, and power fluctuation serves as a rubber discharging criterion; and finally, carrying out final smelting with sulfur, an accelerant and a scorch retarder. Optionally, 5-10 parts of synthetic rubber is added before final mixing. According to the invention, through quantitative matching of Mooney viscosity and online monitoring of a power curve, the problem that the dispersion grade of carbon black is low and unstable when multiple rubber types are used together is solved, the dispersion grade is improved from grade 6 to grade 8 or above, the standard deviation between batches is controlled within grade 0.2, and meanwhile, the tensile strength, wear resistance and dynamic mechanical balance of the rubber materials are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of rubber compounding technology, and more specifically, to a method for improving the dispersion of carbon black in multi-rubber formulations. Background Technology

[0002] This invention relates to the field of rubber composite material preparation technology, and more specifically, to a method for improving the dispersion uniformity of carbon black filler in multi-rubber blend systems.

[0003] Carbon black, as the most widely used reinforcing filler in the rubber industry, has a dispersion state in the polymer matrix that is a key factor determining the final performance of rubber products. In multi-rubber formulations (such as natural rubber / butadiene rubber / styrene-butadiene rubber blends), the differences in viscosity, polarity, and unsaturation among different rubber types lead to uneven distribution of carbon black in each phase, making it prone to agglomeration. To improve this situation, existing technologies mainly employ the following methods: First, by extending the mixing time or adjusting process parameters such as the rotor speed, temperature, and pressure of the internal mixer, mechanical shear force is used to break up carbon black agglomerates; second, liquid-phase mixing technology is used to pre-prepare a slurry of carbon black and blend and settle it with latex; third, surface chemical modification of carbon black, such as grafting or oxidation treatment, is performed to enhance its compatibility with rubber; fourth, dispersing agents such as fatty acid salts and resins are added during the mixing process to reduce the interaction forces between fillers.

[0004] However, the above methods all have significant shortcomings in practical applications: simple optimization of process parameters is difficult to control precisely; too short a mixing time leads to insufficient dispersion, while too long a time easily results in over-mixing of the rubber compound; furthermore, the optimal process window is narrow for different rubber types, and debugging is complex; although liquid-phase mixing technology has excellent dispersion effects, it requires large equipment investment, has a long process flow, and presents environmental challenges such as wastewater treatment; carbon black surface modification usually involves complex wet chemical treatment and the use of organic solvents, which is costly and environmentally unfriendly; while traditional dispersing agents have the problem of high dosage sensitivity, with limited effect when the amount added is insufficient, and excessive addition easily migrates to the interface, weakening the bonding force between the filler and the rubber, and affecting the overall physical and mechanical properties of the vulcanizate. Therefore, developing a carbon black dispersion method that is simple in process, cost-controllable, and has stable effects has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for improving the dispersion of carbon black in multi-colloid formulations, so as to solve the problems mentioned in the background art.

[0006] In a first aspect, embodiments of this application provide a method for improving the dispersion of carbon black in multi-colloid formulations, comprising the following steps: S1. Mix 40-60 parts by weight of natural rubber, 40-60 parts by weight of synthetic rubber, 55-70 parts by weight of carbon black, antioxidant, softener and activator in an internal mixer to obtain a first-stage masterbatch. S2. Determine the mass fraction of synthetic rubber to be added a second time based on the Mooney viscosity of the synthetic rubber; mix the synthetic rubber and the first-stage masterbatch in a mixer to obtain the second-stage masterbatch; S3. Add the second-stage masterbatch, sulfur, accelerator, and anti-scorching agent to a mixer for final mixing to obtain the final rubber.

[0007] In some embodiments of this application, the Mooney viscosity ML(1+4) of the synthetic rubber at 100°C is 40-70.

[0008] In some embodiments of this application, the synthetic rubber is at least one of styrene-butadiene rubber, cis-butadiene rubber, and isoprene rubber; The antioxidant is at least one of quinoline, p-phenylenediamine, and naphthylamine. The softener is at least one of the oil processing aids; The activator is at least one of metal oxides and stearic acid.

[0009] In some embodiments of this application, the mixing method specifically involves setting the rotor speed of the internal mixer to 45-60 r / min and the pressure of the top bolt to 16-18 MPa. When the temperature reaches 120-140°C, 2-8 parts by mass of oil are added, and the rotor speed is reduced to 25-40 r / min. Mixing continues until the temperature reaches 165-175°C, at which point the glue is discharged.

[0010] In some embodiments of this application, the specific mass fraction of synthetic rubber added a second time is as follows: When the Mooney viscosity is 40-50, add 5-10 parts; When the Mooney viscosity is 51-60, add 10-15 parts; When the Mooney viscosity is 61-70, add 15-20 parts.

[0011] In some embodiments of this application, the two-stage mixing method is as follows: the rotor speed of the internal mixer is set to 50-60 r / min, the pressure of the top plug is set to 16-18 MPa, and the power-time curve of the main motor of the internal mixer is monitored. When the power curve shows a second peak and then declines and tends to stabilize, and the power fluctuation amplitude is ≤ ±0.6 kW within 20-40 seconds of operation, the glue discharge begins.

[0012] In some embodiments of this application, the heating rate of the two-stage mixing is 1-2℃ / s. When the temperature reaches 155-165℃, it is kept at the temperature and mixed at a constant temperature for 1-3 minutes, and then the temperature is further increased to 165-175℃.

[0013] In some embodiments of this application, 5-10 parts of synthetic rubber need to be added before final mixing.

[0014] In some embodiments of this application, the accelerator is at least one of thiazoles, sulfenamides, thiurams, thioureas, dithiocarbamates, aldehydes, guanidines, and xanthates; The scorching inhibitor is at least one of sulfur-nitrogen compounds, organic acids, phthalic anhydrides, and nitroso compounds.

[0015] In some embodiments of this application, the final mixing method is as follows: the second-stage masterbatch, sulfur, accelerator, and anti-scorching agent are mixed at a rotation speed of 20-30 rad / min and a pressure of 14-16 MPa, and the rubber is discharged when the temperature is 110-120°C.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The delayed addition amount was determined based on the Mooney viscosity of synthetic rubber. A correspondence between the delayed addition amount of 5-20 parts and the Mooney viscosity range of 40-70 was established, which solved the problem of lack of quantitative basis for delayed addition amount. This improved the carbon black dispersion grade and the tensile strength of the rubber compound, and reduced the abrasion amount.

[0017] 2. During a mixing process, the power-time curve is monitored, and the power fluctuation is used as the criterion for dispersing. By identifying the secondary peak signal generated by the melting of delayed synthetic rubber, the dispersion endpoint can be accurately determined. This avoids the quality instability caused by equipment fluctuations and raw material differences in the fixed-time dispersing method, and reduces the standard deviation of dispersion grades between batches.

[0018] 3. Add 5-10 parts of synthetic rubber again in the second stage of mixing, so that the delayed addition of synthetic rubber is distributed around the carbon black in the low temperature mixing stage, which inhibits the secondary agglomeration of carbon black during the vulcanization process, further improves the carbon black dispersion grade, and optimizes the dynamic mechanical properties of the rubber compound, thereby increasing the loss factor tanδ value at 0℃ and 60℃ and achieving a performance balance between wet skid resistance and rolling resistance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0020] Figure 1 The overall process flow diagram provided for this invention; Figure 2 A schematic diagram of the secondary addition amount of synthetic rubber provided by the present invention; Figure 3 This is a schematic diagram of the two-stage mixing power-time curve monitoring provided by the present invention; Figure 4 The two-stage process flow diagram provided for this invention; Figure 5 The final refining process flow diagram provided for this invention. Detailed Implementation

[0021] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1 Please see Figure 1 and Figure 2 This invention provides a method for improving the dispersion of carbon black in multi-rubber formulations, used in the preparation of tire tread compounds. This embodiment uses a typical tread formulation as an example for detailed explanation. This formulation includes natural rubber, synthetic rubber, carbon black, and various processing aids. The synthetic rubber used is a blend of styrene-butadiene rubber (SBR1500) and butadiene rubber (BR9000), and the carbon black used is the high-structure grade N234.

[0024] The specific implementation steps are as follows: S1, a first-stage mixing process First, prepare the materials for the mixing process. Weigh out 50 parts by weight of natural rubber, specifically No. 10 standard rubber from Hainan. Weigh out 45 parts of synthetic rubber, including 30 parts of styrene-butadiene rubber (SBR1500) and 15 parts of butadiene rubber (BR9000). Weigh out 65 parts of carbon black N234, produced by Jiangxi Black Cat Carbon Black Co., Ltd., which has a high structure and an oil absorption value of approximately 125 × 10⁻⁶. -5 per cubic meter per kilogram. At the same time, weigh out the antioxidants, softeners and activators, specifically including 2 parts of antioxidant 6PPD, 1 part of antioxidant TMQ, 5 parts of environmentally friendly aromatic oil TDAE as softener, and 3.5 parts of zinc oxide and 2 parts of stearic acid as activators.

[0025] All the above materials were fed into a BB620 internal mixer for primary mixing. This mixer is equipped with a 4WH rotor manufactured by Kobe Steel, Japan, which provides high-intensity shearing action. The mixing process parameters were set as follows: rotor speed was set to 55 rpm, and the top bolt pressure was maintained at 17 MPa to ensure the rubber compound received sufficient compression and shearing within the mixing chamber. After mixing began, the temperature change of the rubber compound was closely monitored. When the rubber compound temperature rose to 130°C, 2 parts of environmentally friendly aromatic oil were added through the feed port as a supplementary softener. At this time, the rotor speed was reduced to 30 rpm to adjust the shear rate and prevent overheating and degradation of the rubber compound. Mixing continued until the rubber compound temperature reached 170°C, at which point the discharge gate was immediately opened to discharge the rubber, obtaining the first-stage masterbatch. In this first-stage masterbatch, carbon black was initially broken down in the matrix of natural rubber and some synthetic rubber, forming a bound rubber network, laying the foundation for subsequent deep dispersion. The entire primary mixing process corresponds to... Figure 1 The starting part of the overall process flow diagram shown.

[0026] S2, Two-stage mixing process The core of two-stage mixing lies in precisely controlling the amount of delayed addition based on the rheological properties of synthetic rubber, and using online monitoring technology to determine the dispersion endpoint.

[0027] First, the specific proportion of the delayed-added synthetic rubber is determined based on its Mooney viscosity. In this embodiment, the synthetic rubber to be added in the second-stage mixing is a mixture of SBR1500 and BR9000, with the ratio remaining consistent with the synthetic rubber added in the first stage, i.e., 2:1. The Mooney viscosity of this mixture is tested according to GB / T1232 standard, under the conditions of ML(1+4)min*100℃, and the result is 58. This value falls within the range of 51 to 60. Figure 2 The flowchart shown illustrates the determination of the delayed addition amount of synthetic rubber based on Mooney viscosity. When the Mooney viscosity is in the range of 51 to 60, the corresponding delayed addition amount is 10 to 15 parts. In this embodiment, the middle value is taken, and 12 parts are added, of which 8 parts are styrene-butadiene rubber SBR1500 and 4 parts are butadiene rubber BR9000.

[0028] Next, the second-stage mixing operation is performed. The first-stage masterbatch obtained in step S1 is added back into the internal mixer along with the 12 parts of synthetic rubber weighed above. The internal mixer model remains unchanged, still a BB620. The process parameters are set as follows: rotor speed is set to 55 rpm, and the top bolt pressure is maintained at 17 MPa. The key difference is that in this step, the real-time power monitoring system of the internal mixer's main motor is activated. This system is equipped with a high-precision power sensor with a measurement accuracy of ±0.1 kW, used to continuously record the power-time curve during the mixing process, such as... Figure 3 As shown.

[0029] After mixing begins, the power curve exhibits a specific pattern over time. In the initial stage, because the delayed-added synthetic rubber exists in solid form, mixing resistance is high, and the power remains at a high level. As the rubber compound temperature rises, the delayed-added synthetic rubber gradually softens and melts, and begins to mix with the first stage of the masterbatch. The power curve shows a significant increase, reaching a peak at a certain point. Figure 3 The term "secondary peak" is indicated by the label. The appearance of this peak signifies that the delayed-added synthetic rubber has completely melted, and the internal frictional resistance of the system has reached its maximum. Subsequently, as the synthetic rubber gradually spreads and disperses in the masterbatch, the carbon black redistributes at the interface of the newly formed phases, and the power curve begins to slowly decline. When the power curve enters a relatively stable range, i.e., when the power value fluctuates very little within a certain time, it indicates that the rubber compound has reached a uniform dispersion state. In this embodiment, when the power curve fluctuates within 30 seconds of stable operation, and the measured fluctuation amplitude is ±0.3 kW, far below the set threshold of ±0.5 kW, the system determines that the dispersion endpoint has been reached and immediately performs the discharge operation. At this time, the measured discharge temperature is 168℃, resulting in the second stage of masterbatch. This endpoint control method based on power curve characteristics avoids the under-mixing or over-mixing that may occur with traditional timed discharge methods, ensuring batch-to-batch quality stability.

[0030] S3, Final Refining Process Finally, the final mixing process is performed. The second-stage masterbatch obtained in step S2 is fed into an internal mixer along with the vulcanization system auxiliaries. The vulcanization system auxiliaries include 1.8 parts sulfur, 1.5 parts CBS (a sulfenamide accelerator), and 0.2 parts PVI (a scorch inhibitor). The final mixing process parameters are set to a low shear strength to prevent scorching: the rotor speed is set to 25 rpm, and the top bolt pressure is set to 15 MPa. The temperature is closely monitored during mixing, and when the rubber compound temperature rises to 115°C, the rubber is immediately discharged to obtain the final mixed rubber. This step corresponds to... Figure 1 The end of the process shown is the final refining process.

[0031] Effect evaluation Comprehensive performance tests were conducted on the final rubber compound prepared in this embodiment. Following GB / T6038 standards, the carbon black dispersion grade was determined by observing cross-sections of the rubber compound after vulcanization using a carbon black dispersion analyzer manufactured by Alpha Corporation, USA. The results showed that the carbon black dispersion grade of the final rubber compound obtained in this embodiment was grade 8, significantly higher than grade 6 of the traditional process. The traditional process refers to adding all synthetic rubber during the first mixing stage. Further testing of the physical and mechanical properties of the rubber compound revealed that the tensile strength increased from 22.5 MPa in the traditional process to 24.8 MPa; the tear strength increased from 45 kN / m to 52 kN / m; and the abrasion resistance was characterized by the DIN abrasion test, with the abrasion loss decreasing from 0.22 cm³ to 0.18 cm³. These data fully demonstrate that this invention, by combining a delayed addition process with Mooney viscosity matching with online power curve monitoring technology, effectively improves the uniformity of the microscopic distribution of carbon black in the multiphase system of natural and synthetic rubber, thereby resulting in a significant improvement in overall performance.

[0032] Example 2 Please see Figure 3 This embodiment focuses on illustrating the precise control and advantages of power curve monitoring technology on the dispersion endpoint during the two-stage mixing process. The tread formulation in this embodiment is basically the same as in Example 1, namely 50 parts natural rubber, 45 parts synthetic rubber added in the first stage, and 65 parts carbon black N234. The types and amounts of additives remain consistent. The only change is the delayed addition of the synthetic rubber and its corresponding Mooney viscosity.

[0033] In this embodiment, the synthetic rubber added late is BR9000, a butadiene rubber with a high Mooney viscosity. This rubber is used alone and is not combined with styrene-butadiene rubber. Testing showed that this batch of BR9000 had a Mooney viscosity ML(1+4)min*100℃ of 65, falling within the high Mooney viscosity range of 61 to 70. According to... Figure 2 According to the decision rule shown, a higher Mooney viscosity requires a higher amount of delayed addition to facilitate dispersion, so the number of delayed addition parts is determined to be 18 parts.

[0034] The specific steps for the two-stage mixing process are as follows: Figure 4 A section of masterbatch and 18 parts of BR9000 were fed into a BB620 internal mixer. The process parameters were set to a rotor speed of 60 rpm and a top bolt pressure of 16 MPa. Simultaneously, the real-time power monitoring system was activated to record the complete power-time curve. Figure 3 As shown, the power in the initial stage of mixing is approximately 100 kW. The power gradually increases as the rubber compound temperature rises and shearing occurs. At 48 seconds into mixing, a significant double peak appears in the power curve, reaching a peak power of 155 kW. This peak indicates that the high Mooney viscosity BR9000 has completely melted and is interacting violently with the masterbatch.

[0035] Subsequently, the power curve began to decline slowly. By the 80th second of mixing, the power had dropped to 138 kW. Afterward, the power value fluctuated within a very small range of 135 kW to 138 kW, and the curve entered a stable phase. When this stable state lasted for 35 seconds, that is, when mixing reached the 115th second, the system calculated that the power fluctuation over the past 35 seconds was only ±0.4 kW, fully meeting the preset discharge condition of less than or equal to ±0.6 kW. At this point, the system automatically triggered the discharge command, with the discharge temperature at 167℃.

[0036] For comparison, a control group was set up. The control group used the exact same formula and a single-stage mixing process, but instead of power curve monitoring during the second-stage mixing, a traditional fixed-time discharge method was used. Regardless of the rubber compound's state, the compound was uniformly mixed for 120 seconds before discharge. Testing of the control group's rubber compound revealed a carbon black dispersion grade of only 7, and microscopic observation of rubber compound sections showed the presence of a small number of micron-sized carbon black agglomerates. In contrast, the rubber compound prepared using the power curve monitoring process in this embodiment consistently achieved a dispersion grade of 8. Furthermore, statistical analysis of multiple batches showed a standard deviation of only 0.2 for the dispersion grade, demonstrating excellent batch stability. This comparison strongly proves that the stable range after the second peak of the power curve is a reliable criterion for determining whether the rubber compound has reached its optimal dispersion state. This method effectively avoids the problems of insufficient or excessive mixing at fixed times due to equipment fluctuations and batch differences in raw materials, and is a key technical feature for achieving intelligent process and quality stability.

[0037] Example 3 Please see Figure 5 This embodiment, based on Embodiments 1 and 2, further explores the synergistic effect of multi-stage delayed addition, namely, introducing a portion of synthetic rubber again during the final refining stage. This embodiment aims to verify whether adding 5 to 10 parts of synthetic rubber before the final refining stage can bring additional performance gains.

[0038] The formulation design of this embodiment is as follows: the amount of natural rubber is adjusted to 40 parts. 40 parts of synthetic rubber are added during the first stage of mixing, of which styrene-butadiene rubber (SBR1500) and butadiene rubber (BR9000) each account for 20 parts. Carbon black of grade N115 is selected, with a dosage of 70 parts. This carbon black has a large specific surface area and requires higher dispersion. The types and amounts of additives are the same as in Example 1. The total number of delayed-added synthetic rubber parts is designed to be 20 parts, but instead of being added entirely in the second stage, it is allocated: 15 parts are added during the second stage of mixing, and the remaining 5 parts are reserved for the final stage. The composition ratio of the synthetic rubber used in the second and final stages is consistent with that added in the first stage.

[0039] The specific implementation steps are as follows: S1. First stage mixing: 40 parts natural rubber, 40 parts synthetic rubber, 70 parts carbon black N115, and all additives are put into an internal mixer. The mixing process parameters are the same as in Example 1, namely, rotor speed of 55 rpm, pressure of 17 MPa, and when the temperature reaches 130°C, 2 parts of oil are added and the speed is reduced. Finally, the rubber is discharged at 168°C to obtain the first stage masterbatch.

[0040] S2, Two-stage mixing: First, the Mooney viscosity of the 15 parts of synthetic rubber to be added in the second stage was tested, and the measured value was 55, falling within the 51 to 60 range. According to... Figure 2 The rule is that this range corresponds to 10 to 15 parts; in this embodiment, the upper limit of 15 parts is added. The first stage of masterbatch and these 15 parts of synthetic rubber are fed into an internal mixer, and the mixing is performed using a power curve monitoring system, with a power fluctuation threshold set to not exceed ±0.6 kW. Once the curve enters a stable range, the rubber is discharged at a temperature of 166℃, yielding the second stage of masterbatch.

[0041] S3, Final Refinement: (e.g., ...) Figure 5 As shown, the final mixing in this step differs from conventional final mixing. The second-stage masterbatch obtained in step S2 is fed into an internal mixer along with 1.8 parts sulfur, 1.5 parts CBS accelerator, and 0.2 parts PVI anti-scorching agent. Simultaneously, the reserved 5 parts synthetic rubber are also added. The final mixing process parameters are set to relatively low strengths: rotor speed 22 rpm, top bolt pressure 14 MPa. The mixture is discharged when the temperature reaches 112°C, yielding the final final rubber.

[0042] Effect evaluation The final compound obtained in this embodiment was subjected to performance tests. The carbon black dispersion grade test results showed that the dispersion grade of this compound reached level 9, significantly higher than level 8 of Example 1. To further investigate the reasons, dynamic mechanical analysis (DMA) tests were performed on the compound. The test results showed that the loss factor tanδ value at 0°C, representing anti-slip performance, was 0.142, and the tanδ value at 60°C, representing rolling resistance, was 0.098. For comparison, the same DMA test was performed on the compound from Example 1, which did not contain synthetic rubber in the final mixing stage, and the results were tanδ = 0.135 at 0°C and tanδ = 0.105 at 60°C.

[0043] Analysis suggests that the small amount of synthetic rubber added in the final mixing stage, at a lower mixing temperature, preferentially distributes around the carbon black particles or existing carbon black network. During subsequent vulcanization, this newly added rubber acts as a "wrapper" or "isolate" for the carbon black, effectively suppressing secondary agglomeration of the carbon black at high vulcanization temperatures, thus achieving a higher dispersion grade. Simultaneously, this optimized microstructure also improves the composition of the rubber phase in the compound, resulting in a better balance of dynamic mechanical properties—that is, improving wet skid resistance without sacrificing excessive rolling resistance. This embodiment confirms that the three-stage delay scheme described in claim 8 is an effective extension and performance enhancement of the core two-stage delay process.

[0044] Example 4 This embodiment includes multiple comparative examples to systematically verify the indispensability of each technical feature in the claims of this invention and the synergistic effect of the overall technical solution through comparative experiments. Unless otherwise specified, the raw materials in all comparative examples are the same as in Example 1.

[0045] Comparative Example 1: Traditional One-Stage Mixing Method This comparative example simulates a common traditional process in the industry. All 60 parts of synthetic rubber, 40 parts of natural rubber, 65 parts of carbon black N234, and all additives were added to a mixer for a single-stage mixing process. The process parameters for the first-stage mixing were exactly the same as in Example 1. After mixing, the resulting masterbatch skipped the second-stage mixing step and proceeded directly to the final mixing. The final mixing steps were the same as in Example 1. Testing of the final rubber compound revealed a carbon black dispersion grade of only 4. Its tensile strength was 20.1 MPa, and its DIN abrasion loss was 0.26 cm³, all significantly inferior to those of Example 1. This comparative example demonstrates that for multi-rubber blending systems, traditional single-stage mixing cannot effectively solve the problem of uneven dispersion caused by differences in the affinity of different rubbers for carbon black; a staged addition strategy is necessary.

[0046] Comparative Example 2: Fixed Delay Method Ignoring Mooney Viscosity This comparative example aims to verify the necessity of the feature regarding "determining the number of parts based on Mooney viscosity". The process steps of this comparative example are exactly the same as in Example 1, namely, the three-step method of one-stage mixing, two-stage mixing, and final mixing. The only difference is that the number of synthetic rubber parts added late during the two-stage mixing is fixed at 10 parts and is not adjusted according to its actual Mooney viscosity. The late-added synthetic rubber used in this comparative example is BR9000 butadiene rubber with a Mooney viscosity as high as 68. According to the rules of this invention, the reasonable number of parts added corresponding to a Mooney viscosity of 61 to 70 should be 15 to 20 parts. However, this comparative example only added 10 parts.

[0047] Experimental results showed that the carbon black dispersion grade of the obtained rubber compound was grade 7, failing to reach grade 8. More importantly, testing the Mooney viscosity of multiple batches of rubber compounds revealed a large fluctuation range, with a range of ±5 Mooney viscosity values, indicating poor uniformity and stability of the rubber compound. Analysis revealed that for high Mooney viscosity synthetic rubber, insufficient addition of carbon black prevented the formation of an effective continuous phase during the two-stage mixing process to promote carbon black redistribution, resulting in poor dispersion in localized areas. This comparative example clearly demonstrates that simply implementing "segmented addition" is far from sufficient; the addition amount must be quantitatively determined based on the rheological properties and Mooney viscosity of the synthetic rubber itself to consistently achieve the desired dispersion effect.

[0048] Comparative Example 3: Timed glue removal method without power monitoring This comparative example aims to verify the irreplaceable nature of the "power curve monitoring" feature. The formulation and the number of parts added in stages in this comparative example are exactly the same as in Example 1, i.e., the delayed addition is 12 parts, determined based on Mooney viscosity 58. The process steps are also consistent. The only difference is that the power curve monitoring function is not activated during the second-stage mixing, and power fluctuations are not used as the criterion for discharge. Instead, the traditional fixed-time discharge method is adopted, and discharge is performed after a uniform 120 seconds of mixing, regardless of the state of the rubber compound.

[0049] Due to subtle differences in equipment condition, cooling water temperature, and raw material batches, the quality of multiple batches of products using a fixed dispersing time varied. Some batches achieved a carbon black dispersion grade of 8, comparable to Example 1; however, some batches only achieved a dispersion grade of 7. Microscopic observation of these grade 7 products revealed localized areas of insufficiently dispersed carbon black agglomerates. This indicates that a fixed mixing time cannot adapt to all operating conditions. When certain factors slow down the melting and dispersion process of the delayed adhesive, a fixed time leads to insufficient mixing. In contrast, the power curve monitoring method used in Example 1 can detect changes in the internal state of the adhesive in real time, dispersing the adhesive only when complete dispersion is ensured, thus guaranteeing that each batch of products consistently achieves a high quality level. This comparative example demonstrates the crucial role of online monitoring technology in process stability and product consistency.

[0050] Summary of Comparative Examples 1 to 3 As can be seen from the above three comparative examples, the technical solution of this invention is an organic whole. Comparative Example 1 illustrates the necessity of staged addition; Comparative Example 2 demonstrates that the amount added in stages must match the Mooney viscosity of the synthetic rubber; Comparative Example 3 shows that even with matching Mooney viscosity, intelligent endpoint control is still required to ensure process stability. Lacking any one of these steps makes it impossible to stably and reliably obtain high-performance rubber compounds with a carbon black dispersion grade of 8 or higher. Therefore, the set of technical features defined in the claims of this invention constitutes a complete and non-obvious technical solution to the problem of dispersing carbon black in blends of multiple rubber types.

[0051] 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 improving the dispersion of carbon black in multi-colloid formulations, characterized in that, Includes the following steps: S1. Mix 40-60 parts by weight of natural rubber, 40-60 parts by weight of synthetic rubber, 55-70 parts by weight of carbon black, antioxidant, softener and activator in an internal mixer to obtain a first-stage masterbatch. S2. Determine the mass fraction of synthetic rubber to be added a second time based on the Mooney viscosity of the synthetic rubber; mix the synthetic rubber and the first-stage masterbatch in a mixer to obtain the second-stage masterbatch; S3. Add the two-stage masterbatch, sulfur, accelerator, and anti-scorching agent to a mixer for final mixing to obtain the final rubber.

2. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, The Mooney viscosity ML(1+4) of the synthetic rubber at 100°C is 40-70.

3. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, The synthetic rubber is at least one of styrene-butadiene rubber, cis-butadiene rubber, and isoprene rubber; The antioxidant is at least one of quinoline, p-phenylenediamine, and naphthylamine. The softener is at least one of the oil processing aids; The activator is at least one of a metal oxide and stearic acid.

4. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, The specific method of the first-stage mixing is as follows: set the rotor speed of the internal mixer to 45-60 r / min, set the top bolt pressure to 16-18 MPa, add 2-8 parts by mass of oil when the temperature reaches 120-140℃, reduce the rotor speed to 25-40 r / min, and continue mixing until the temperature reaches 165-175℃ and then discharge the glue.

5. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, The specific mass fraction of the synthetic rubber added in the second step is as follows: When the Mooney viscosity is 40-50, add 5-10 parts; When the Mooney viscosity is 51-60, add 10-15 parts; When the Mooney viscosity is 61-70, add 15-20 parts.

6. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, The two-stage mixing method is as follows: the rotor speed of the internal mixer is set to 50-60 r / min, the pressure of the top plug is set to 16-18 MPa, and the power-time curve of the main motor of the internal mixer is monitored. When the power curve shows a second peak and then declines and tends to stabilize, and the power fluctuation range is ≤ ±0.6 kW within 20-40 seconds of operation, the glue discharge begins.

7. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, The heating rate of the two-stage mixing is 3-5℃ / min. When the temperature reaches 155-165℃, it is kept at the temperature and mixed for 1-3 minutes, and then the temperature is increased to 165-175℃.

8. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, Before the final grinding, 5-10 parts of synthetic rubber need to be added.

9. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, The accelerator is at least one of the following: thiazoles, sulfenamides, thiurams, thioureas, dithiocarbamates, aldehydes and amines, guanidines, and xanthates. The anti-scorching agent is at least one of sulfur-nitrogen compounds, organic acids, phthalic anhydrides, and nitroso compounds.

10. The method for improving the dispersion of multi-colloid carbon black formulations according to claim 1, characterized in that, The specific method for final mixing is as follows: the second-stage masterbatch, sulfur, accelerator, and anti-scorching agent are mixed at a rotation speed of 20-30 rad / min and a pressure of 14-16 MPa, and the rubber is discharged when the temperature is 110-120℃.

Images