A high-efficiency energy-saving mixing method of white carbon black filled rubber composition

Abstract

The application relates to the technical field of rubber mixing, and discloses a mixing method of a white carbon black filled rubber composition, which mixes rubber and fine materials separately, and realizes the following advantages by utilizing the advantages of high shearing dispersion efficiency and precise temperature control: the degree of silanization reaction of the white carbon black filled rubber composition is improved under the premise of reducing the amount of silane coupling agent, the dispersion of the white carbon black filler is improved, the addition of processing oil is cancelled or reduced, the wear performance of the high-filled white carbon black rubber composition is improved, the mixing shearing of the internal mixer is not required to be repeated for multiple times, and the use of electric power energy is reduced.

Description

Technical Field

[0001] This invention relates to the field of rubber compounding technology, and more specifically, to a method for compounding a high-efficiency and energy-saving silica-filled rubber composition. Background Technology

[0002] Silica-filled rubber compositions have advantages such as low heat generation and excellent grip performance. However, due to the large number of silanol groups on the surface of silica, it is very difficult to disperse silica filler in rubber polymers, and it is also very easy to agglomerate after dispersion. By using silane coupling agents to carry out silanization reactions with the silanol groups in silica, the surface of silica is modified, the surface polarity is reduced, the dispersion of silica is improved, and thus the grip is enhanced and the rolling resistance is reduced.

[0003] Currently, to ensure the dispersion and silanization reaction degree of silica, multi-stage mixing and constant-temperature mixing technologies are generally used in workshop production. To reduce the impact of other chemicals (such as zinc oxide) on the silanization reaction of silica, they are typically added in the remaining stages after the addition of silica and silane coupling agents. That is, rubber, silica, silane, and fines (antioxidant, resin, processing oil) are first mixed, followed by a constant-temperature reaction stage to discharge a sulfur-free rubber composition. This rubber composition is then repeatedly sheared and mixed using a Banbury mixer until a suitable Mooney viscosity is reached. Finally, sulfur is added and mixed to obtain the final rubber composition product.

[0004] Because domestically produced low-heat rubber compositions filled with high-precision silica involve adding all chemical raw materials to a mixer at once, the process generally includes plasticizing, mixing, and isothermal reaction. Due to the high silica content, mercaptosilanes are needed to control heat generation. This makes it impossible to achieve high-temperature mixing due to the reactivity of silanes. Consequently, repeated mixing and shearing in the mixer are unavoidable due to excessively high Mooney viscosity, which poses a significant challenge to energy and production efficiency. Furthermore, the above production method will adversely affect the performance of the rubber composition and makes it difficult to control the degree of silanization reaction.

[0005] Chinese invention patent (publication number: CN102825674B, publication date: 2015.01.28) discloses a continuous extrusion apparatus and method for in-situ modification and compounding of high-filled silica, relating to the field of processing equipment and technology for rubber composite materials. The entire apparatus consists of a set of internal mixer units and 1 to 10 sets of screw extruder units; each screw extruder unit consists of one screw extruder or 2 to 10 screw extruders connected in series via side-to-side connection at the die head. This apparatus can improve production efficiency and is more conducive to the molding and processing of rubber compounds in subsequent production processes. However, this apparatus requires a large number of screw extruder units, making the assembly relatively complex. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for mixing a silica-filled rubber composition.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for mixing a silica-filled rubber composition includes the following stages: 1) Raw material mixing stage: Rubber component 1 and rubber component 2 are mixed in different internal mixers; rubber component 1 is a mixture of 3 / 4 to 4 / 5 of the total rubber, silica, carbon black and silane coupling agent; rubber component 2 is a mixture of 1 / 5 to 1 / 4 of the total rubber, activator, antioxidant, resin and processing oil. a. Use a mixer N to mix rubber component 1, heat the mixture to the set temperature, and then discharge it into extruder A; b. Use a mixer M to mix rubber component 2, heat the mixture to the set temperature, and then discharge it into an extruder E; 2) Heating stage: a. Set the screw speed and sleeve temperature of extruder A, and while further mixing rubber component 1, heat it to the reaction temperature of silane coupling agent, and then extrude rubber component 1 into extruder B; b. Set the screw speed and sleeve temperature of extruder E, and while further mixing rubber component 2, heat it to the reaction temperature of silane coupling agent, and then extrude rubber component 2 into extruder C; 3) Reaction stage: Set the screw speed and sleeve temperature of extruder B, keep rubber component 1 at a constant temperature in extruder B, and use a vacuum pump to extract by-products to obtain the reacted rubber component 1 and discharge it into extruder C. 4) Component mixing stage: Rubber component 1 and rubber component 2 are finally mixed in extruder C to obtain rubber composition Q; 5) Extrusion stage: Set the screw speed and sleeve temperature of the extruder D, and finally discharge and collect the rubber composition Q through the extruder D.

[0008] Preferably, the internal mixer N is set to a temperature of 115-125°C, a speed of 30-60 rpm, and a pressurization time of 30 seconds; the internal mixer M is set to a temperature of 110-120°C, a speed of 30-60 rpm, and a pressurization time of 30 seconds. Preferably, the rotor of the internal mixer N is a shearing rotor, and the rotor of the internal mixer M is a meshing rotor.

[0009] Preferably, extruder A and extruder E are single-screw extruders or twin-screw extruders, preferably single-screw extruders; the rotational speed of extruder A and extruder E is 15–35 rpm, preferably 25–30 rpm; the barrel temperature of extruder A and extruder E is 110–150°C, preferably 120–140°C for extruder A and 110–120°C for extruder E; the outlet thermocouple temperature of extruder A is 130–135°C, and the outlet thermocouple temperature of extruder E is 120–125°C.

[0010] Preferably, the extruder B is a single-screw extruder or a twin-screw extruder, preferably a twin-screw extruder; the speed of the extruder B is 100-200 rpm, preferably 100-150 rpm; the sleeve temperature of the extruder B is 120-140℃, preferably 125-130℃.

[0011] Preferably, the extruder C is a single-screw extruder or a twin-screw extruder, preferably a twin-screw extruder; the speed of the extruder C is 15-20 rpm, the sleeve temperature is 120-130°C, and the outlet thermocouple temperature is 120-125°C.

[0012] Preferably, the extruder D is a single-screw extruder with a rotational speed of 10-25 rpm, more preferably 15-20 rpm; and the sleeve temperature of the extruder D is 80-110°C.

[0013] Preferably, the rubber composition B is kept at a constant temperature in the extruder D for no less than 40 seconds.

[0014] The beneficial effects of this invention are as follows: This method separates and mixes rubber and fine materials, and by utilizing the advantages of extrusion equipment such as high shearing and dispersion efficiency and precise temperature control, it achieves an increased degree of silanization reaction in the silica-filled rubber composition while reducing the amount of silane coupling agent used, thereby improving the dispersion of silica filler. At the same time, it reduces the amount of processing oil used, improves the abrasion performance of the highly filled silica rubber composition, and eliminates the need for repeated mixing and shearing in a mixer, thus reducing the use of electrical energy. Attached Figure Description

[0015] Figure 1 This is the process flow of the rubber composition mixing method of the present invention. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0017] The specific formulations of the comparative examples, Examples 1 to 4, and Comparative Examples 1 to 2 are shown in Table 1.

[0018] Table 1 raw materials Reference example Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Solution-polymerized styrene-butadiene rubber A*1 55 55 55 55 55 55 Solution-polymerized styrene-butadiene rubber B*2 20 20 20 20 20 20 Solution-polymerized styrene-butadiene rubber C*3 25 25 25 25 25 25 softening oil *4 20 20 10 0 10 0 5g of silica 120 120 120 120 120 120 Silane coupling agent Si474*6 10 10 10 5．0 10 5．0 Silane coupling agent Si69*7 4.0 4.0 4.0 2.0 4．0 2．0 Total softening oil * 8 36.5 26.5 16.5 16.5 26.5 16.5 Other raw materials *9 35.7 35.7 35.7 35.7 35.7 35.7 Total number of copies 306.2 296.2 286.2 279.2 296.2 279.2 Raw material source: *1: The trade name of solution-polymerized styrene-butadiene rubber A is E581. Styrene accounts for 36% of the total weight of the polymer, and the weight-average molecular weight (Mw) is 2.02 million. It is a product of Asahi Kasei Corporation of Japan.

[0019] *2: The trade name of solution-polymerized styrene-butadiene rubber B is NS612. Styrene accounts for 10% of the total polymer weight. The weight-average molecular weight (Mw) is 510,000. It is a product of Zeon Corporation of Japan.

[0020] *3: The trade name of solution-polymerized styrene-butadiene rubber C is NS560. Styrene accounts for 42% of the total weight of the polymer, and the weight-average molecular weight (Mw) is 660,000. It is a product of Zeon Corporation of Japan.

[0021] *4: The softening oil is marketed as V700 and is a product of Ningbo Hansheng Company.

[0022] *5: The trade name for silica is 200MP, Solvay Chemicals.

[0023] *6: Silane coupling agent Si747, a product of Jiangsu Qixiang Company. *7: Silane coupling agent Si69, Jingdezhen Hongbai Chemical Products *8: Total softening oil is the sum of the oil in solution-polymerized styrene-butadiene and the oil added to the formulation.

[0024] *9: Other raw materials include N234 4.0, ZnO 1.5, stearic acid 2.0, antioxidant 4020 2.0, microcrystalline wax 2.0, resin 20, accelerator CZ 2.0, accelerator DPG 0.5, sulfur 1.7, totaling 31.7 parts.

[0025] The preparation process for the example is as follows: A 25L internal mixer is selected. The extruder used in the heating section is a single-screw extruder, the extruder used in the reaction section is a twin-screw extruder, the extruder used in the mixing section is a twin-screw extruder, and the extruder used in the discharge section is a single-screw extruder. The vulcanization process uses an internal mixer. The method for compounding silica-filled rubber compositions according to this invention includes the following steps: (1) Raw material mixing stage: a. Add solution-polymerized styrene-butadiene rubber (3 / 4 of the total rubber weight), silica, and silane to a 25L internal mixer N, with a speed of 30-60 rpm and pressure for 30 seconds; lift the top plug once and heat to 115-125℃ to discharge the rubber. b. Add solution-polymerized styrene-butadiene rubber (1 / 4 of the total rubber weight), stearic acid, zinc oxide, carbon black, resin, softening oil, and microcrystalline wax to a 25L internal mixer M. The speed is 30-60 rpm, and the pressure is applied for 30 seconds. Then, pressurize the top plug once and heat the mixture to 110-120℃ to discharge the rubber. (2) Heating stage: a. Feed the rubber component 1 discharged from the internal mixer N into the single screw extruder A in the heating section using a double cone feeder, keep the screw speed at 25-30 rpm, control the sleeve temperature at 120-140℃, and ensure that the thermocouple temperature at the extruder outlet is within the range of 130-135℃. b. Feed the rubber component 2 discharged from the internal mixer M into the single screw extruder E in the heating section using a double cone feeder, keep the screw speed at 25-30 rpm, control the sleeve temperature at 110-120℃, and ensure that the thermocouple temperature at the outlet of extruder E is within the range of 120-125℃. (3) Reaction stage: Rubber component 1 discharged from the single-screw extruder A in the heating section is directly fed into the twin-screw extruder B in the reaction section. The sleeve temperature is controlled at 125-130℃, and the twin-screw speed is controlled at 100-150rpm to ensure that the rubber composition stays in the twin-screw extruder in the reaction section for no less than 40 seconds. At the same time, a vacuum pump is used to discharge the reaction byproducts such as water and alcohol generated in the extruder in the reaction section. (4) Component mixing stage: Rubber component 1 and rubber component 2 are directly fed into the twin-screw extruder C in the mixing section. The sleeve temperature is controlled at 120-130℃, the screw speed is controlled at 15-20 rpm, and the sleeve temperature is controlled at 120-130℃. The thermocouple temperature at the extruder outlet is kept within the range of 120-125℃ to obtain rubber composition Q.

[0026] (5) Discharge stage: The rubber composition Q discharged from the extruder C in the mixing section is directly fed to the single screw extruder D in the discharge section. The sleeve temperature is controlled at 80-100℃ and the screw speed is controlled at 15-20rpm. The fumed silica is filled into the rubber composition through the nozzle and discharged from the equipment. The rubber composition Q is obtained by stacking and collecting.

[0027] (6) Vulcanization stage: Sulfur and accelerator are added to rubber composition Q, and the discharge temperature is 100℃ to obtain rubber composition Q1.

[0028] The preparation process for the comparative example is as follows: A 25L internal mixer was selected. The extruder in the heating section was a single-screw extruder, the extruder in the reaction section was a twin-screw extruder, the extruder in the mixing section was a twin-screw extruder, the extruder in the rubber discharge section was a single-screw extruder, and the internal mixer was used in the vulcanization process.

[0029] (1) Mixing stage in internal mixer: natural rubber, synthetic rubber, silica, silane coupling agent and chemical additives are added to a 25L internal mixer, the speed is set to 30-60 rpm and the pressure is applied for 30 seconds; the pressure is increased once by the top plug, the temperature is raised to 115-125℃ and the rubber is discharged to obtain rubber composition A; (2) Heating stage: The rubber composition A is fed into the single screw extruder A in the heating section using a double cone feeder. The screw speed is set to 25-30 rpm and the sleeve temperature is controlled at 120-140℃ to ensure that the thermocouple temperature at the extruder outlet is 130-135℃. (3) Reaction stage: Rubber composition A is fed directly into the twin-screw extruder B in the reaction section. The sleeve temperature is controlled at 125-130℃, and the twin-screw speed is controlled at 100-150rpm to ensure that the residence time of rubber composition A in the twin-screw extruder in the reaction section is not less than 40 seconds. At the same time, a vacuum pump is used to discharge the reaction byproducts such as water and alcohol generated in the extruder in the reaction section. (4) Discharge stage: Rubber composition A is directly fed into the discharge section of the single screw extruder. The sleeve temperature is controlled at 80-100℃ and the screw speed is controlled at 15-20rpm. The silica-filled rubber composition is discharged through the nozzle and stacked for collection to obtain rubber composition B. (6) Vulcanization stage: Sulfur and accelerator are added to rubber composition B, and the discharge temperature is 100℃ to obtain rubber composition B1.

[0030] The preparation process for the reference example is as follows: Using a 25L internal mixer, control the rotor speed of the internal mixer to 10-60 rpm and the cooling water temperature of the internal mixer to 30-40℃, including the following steps: (1) Add solution-polymerized styrene-butadiene rubber, carbon black, silica, silane, softening oil, antioxidant, resin, zinc oxide, stearic acid, and microcrystalline wax into a mixer, press the top plug and heat to 110°C, press the top plug once and heat to 130°C, reduce the speed and maintain the temperature at 135°C for 120 seconds, then discharge the rubber to obtain rubber composition R. (2) The rubber composition R is repeatedly re-milled twice in an internal mixer, with a re-milling discharge temperature of 130°C; (3) After adding sulfur and accelerator to the refining rubber composition R, the rubber composition R1 is obtained by discharging rubber at 100°C.

[0031] Relevant testing methods: The RPA silanization reaction rate test conditions refer to the patent: A method and application for detecting the degree of silanization reaction of silica and silane coupling agent in rubber compound. CN113834903B; RPA Payne effect test method: strain scan range: 0.28%~100%, test temperature set at 65℃, test frequency at 1.67Hz, Payne effect (△G') equals G' (0.28%) - G' (42%), characterizing the dispersion of silica filler in rubber and the degree of silanization reaction; Mooney viscosity test method: The processability of the rubber composition is evaluated by using a Mooney viscometer at ML(1+4)@100℃. DMA test method: test temperature range -50~80℃, strain 7%±0.25%, 12Hz, 2℃ / min.

[0032] The test results are based on the performance of the reference example as 100%. The test results of the R, Q, and B properties of rubber compositions prepared by different mixing methods are shown in Table 2. The test results of the vulcanized properties of the R1, Q1, and B1 rubber compositions prepared by different mixing methods are shown in Table 3.

[0033] Table 2 Table 3 Mooney viscosity was measured using a Mooney viscometer to evaluate the processing properties of the rubber composition. The Payne effect of the silica-filled rubber composition was evaluated using the RPA test, characterizing the dispersion of silica filler in the rubber and the degree of silanization. Mooney viscosity was used to characterize the processing properties of the rubber composition. The dynamic properties of the silica-filled rubber composition were evaluated using the DMA test. The abrasion resistance of the rubber composition was characterized using Akron abrasion and DIN abrasion tests.

[0034] The results showed that, compared with Examples 1 and 2 and the reference example and Comparative Example 1, the silica dispersion, silanization reaction degree, processing performance, and dynamic performance of the examples were relatively superior. Compared with Example 3 and the reference example, with a reduction in the amount of silane used, the Payne effect decreased by 31%, the silanization reaction degree increased by up to 21%, and the Mooney viscosity decreased by 10%; the dynamic performance of the vulcanized rubber composition was improved, with the tanδ value at 0℃ increasing by 14%, the tanδ value at 60℃ decreasing by 7%, and the abrasion performance improving by nearly 13%. Example 3 reduced the amount of silane by nearly half compared to the comparative example and did not add any additional softening oil; the silica dispersion, silanization reaction degree, processing performance, and dynamic performance were all superior to those of Comparative Example 2.

[0035] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

Claims

1. A method for mixing a silica-filled rubber composition, characterized in that, Includes the following stages: 1) Raw material mixing stage: Rubber component 1 and rubber component 2 are mixed separately in different internal mixers; Rubber component 1 is a mixture of 3 / 4 to 4 / 5 of the total rubber volume, precipitated silica, carbon black, and silane coupling agent; rubber component 2 is a mixture of 1 / 5 to 1 / 4 of the total rubber volume, activator, antioxidant, resin, and processing oil. a. Mix rubber component 1 in a mixer N, heat the mixture to the set temperature, and then discharge it into an extruder A; b. Use a mixer M to mix rubber component 2, heat the mixture to the set temperature, and then discharge it into an extruder E; The internal mixer N is set to a temperature of 115-125℃, a speed of 30-60 rpm, and a pressurization time of 30 seconds; the internal mixer M is set to a temperature of 110-120℃, a speed of 30-60 rpm, and a pressurization time of 30 seconds. 2) Heating stage: a. Set the screw speed and sleeve temperature of extruder A, and while further mixing rubber component 1, heat it to the reaction temperature of silane coupling agent, and then extrude rubber component 1 into extruder B; b. Set the screw speed and sleeve temperature of extruder E, and while further mixing rubber component 2, heat it to the reaction temperature of silane coupling agent, and then extrude rubber component 2 into extruder C; The extruders A and E operate at speeds of 15–35 rpm, with the sleeve temperature of extruder A at 120–140°C and the sleeve temperature of extruder E at 110–120°C; the outlet thermocouple temperature of extruder A is 130–135°C and the outlet thermocouple temperature of extruder E is 120–125°C. 3) Reaction stage: Set the screw speed and sleeve temperature of extruder B, keep rubber component 1 at a constant temperature in extruder B, and use a vacuum pump to extract by-products to obtain the reacted rubber component 1 and discharge it into extruder C; The speed of extruder B is 100-200 rpm, and the sleeve temperature of extruder B is 120-140℃. 4) Component mixing stage: Rubber component 1 and rubber component 2 are finally mixed in extruder C to obtain rubber composition Q; the speed of extruder C is 15-20 rpm, the sleeve temperature is 120-130℃, and the outlet thermocouple temperature is 120-125℃. 5) Extrusion stage: Set the screw speed and sleeve temperature of extruder D, and finally discharge and collect the rubber composition Q through extruder D; the extruder D is a single screw extruder with a speed of 10-25 rpm; the sleeve temperature of the extruder D is 80-110℃; the rubber composition B is kept at a constant temperature in extruder D for no less than 40 seconds.

2. The mixing method according to claim 1, characterized in that, The N rotor of the internal mixer is a shearing type rotor, and the M rotor of the internal mixer is a meshing type rotor.

3. The mixing method according to claim 1, characterized in that, Extruder A and extruder E are either single-screw extruders or twin-screw extruders.

4. The mixing method according to claim 1, characterized in that, The speed of extruder A and extruder E is 25-30 rpm.

5. The mixing method according to claim 1, characterized in that, The extruder B is a single-screw extruder or a twin-screw extruder.

6. The mixing method according to claim 1, characterized in that, The extruder B operates at a speed of 100–150 rpm; the sleeve temperature of the extruder B is 125–130°C.

7. The mixing method according to claim 1, characterized in that, The extruder C is a single-screw extruder or a twin-screw extruder.

8. The mixing method according to claim 1, characterized in that, The extruder D has an extruder speed of 15-20 rpm.

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