Modified silicon dioxide capable of reducing heat generation as well as preparation method and application of modified silicon dioxide

Abstract

The invention provides modified silicon dioxide capable of reducing heat generation and a preparation method and application thereof, and the preparation method comprises the following steps: forming a silicon layer on the surface layer of silicon dioxide through a thermal reduction method, and cooling to room temperature at a rate of 30-50 DEG C / min to obtain the modified silicon dioxide capable of reducing heat generation. The silicon dioxide surface layer is reduced into the silicon layer under the high-temperature condition, then the temperature is reduced to the room temperature at the high cooling rate, cracks are generated on the silicon layer through the thermal expansion coefficient difference between silicon dioxide and silicon, the influence on the mechanical property is reduced, meanwhile, the hydroxyl content of the silicon dioxide surface is further reduced, and the corrosion resistance is improved. And the dispersing performance of the silicon dioxide is further improved, so that the Mooney viscosity in the rubber processing process is reduced, the scorching time of the rubber compound is prolonged, the overall vulcanization efficiency is improved, and agglomeration caused by relatively strong interaction force between silicon dioxide is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, relates to a kind of silicon dioxide, and particularly relates to a modified silicon dioxide for reducing heat generation, its preparation method and application. Background Art

[0002] Silicon dioxide is the main component of white carbon black, is a white amorphous powder, and has a three-dimensional network structure connected by silicon-oxygen bonds. This structure does not deform under high temperature or high stress, has high strength and toughness, and is widely used as a reinforcing additive for tires.

[0003] The surface of white carbon black is rich in silanol groups, shows strong polarity, has high wet skid resistance, and at the same time, through the coupling action of silane coupling agents, can well balance the wet skid resistance and rolling resistance. Nano-silicon dioxide has a large specific surface area and strong adsorption, but its surface contains a large number of active hydroxyl groups and has strong polarity. During the application process as a reinforcing agent, it is easy to agglomerate in the rubber matrix, thus reducing the reinforcing effect of white carbon black on rubber. Moreover, due to the existence of excessive hydroxyl groups, white carbon black will also adsorb too much vulcanizing agent and accelerator, making it impossible for rubber macromolecules to fully contact and interact with them, resulting in a decrease in the vulcanization rate and processing performance of the mixed rubber. Moreover, the dispersibility of silicon dioxide in rubber will affect its reinforcing effect and vulcanization performance, and further affect the heat generation of tires.

[0004] Therefore, in order to solve the heat generation problem of silicon dioxide in tire rubber, reduce the hydroxyl group content on the surface of silicon dioxide, improve the dispersibility of silicon dioxide when applied to tire rubber, reduce the Mooney viscosity during the rubber processing process, extend the scorch time of the mixed rubber, improve the overall vulcanization efficiency, and reduce the agglomeration caused by the strong interaction between silicon dioxides, it is necessary to provide a modified silicon dioxide for reducing heat generation, its preparation method and application. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide a modified silicon dioxide for reducing heat generation, its preparation method and application. The modified silicon dioxide prepared by the present invention, while reducing the influence on mechanical properties, further reduces the hydroxyl group content on the surface of silicon dioxide, further improves its dispersibility, thereby reducing the Mooney viscosity during the rubber processing process, extending the scorch time of the mixed rubber, improving the overall vulcanization efficiency, and reducing the agglomeration caused by the strong interaction between silicon dioxides.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a preparation method of a modified silicon dioxide for reducing heat generation, and the preparation method includes:

[0008] A silicon layer is formed on the surface layer of silica by a thermal reduction method, and the temperature is reduced to room temperature at a rate of 30 °C / min to 50 °C / min to obtain the modified silica with reduced heat generation.

[0009] In the present invention, the surface layer of silica is reduced to a silicon layer under high temperature conditions, and then the temperature is reduced to room temperature at a relatively fast cooling rate. By utilizing the difference in thermal expansion coefficients between silica and silicon, cracks are generated in the silicon layer. While reducing the impact on mechanical properties, the hydroxyl content on the surface of silica is further reduced, and its dispersion performance is further improved, thereby reducing the Mooney viscosity during the rubber processing, prolonging the scorch time of the mixed rubber, enhancing the overall vulcanization efficiency, and reducing the agglomeration caused by the strong interaction between silicas.

[0010] Among them, the cooling rate after the thermal reduction method is relatively important. If the cooling rate is too low, sufficient cracks cannot be generated in the silicon layer, which affects the interaction between the modified silica and the rubber material, and further affects the application of the modified silica as a rubber reinforcing agent; while if the cooling rate is too fast, there will be too many cracks in the silicon layer, which affects the structural strength of the modified silica and also reduces the performance of the modified silica as a rubber reinforcing agent. In the present invention, the cooling rate after the thermal reduction method needs to be controlled at 30 °C / min to 50 °C / min. For example, it can be 30 °C / min, 35 °C / min, 40 °C / min, 45 °C / min or 50 °C / min, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0011] Preferably, the thermal reduction method includes a metal thermal reduction method or a non-metal thermal reduction method.

[0012] Preferably, the temperature of the thermal reduction method is 1200 °C to 1400 °C.

[0013] Preferably, the reducing agent used in the metal thermal reduction method includes any one or a combination of at least two of magnesium, aluminum or zinc.

[0014] Preferably, the molar ratio of the reducing agent to silica used in the metal thermal reduction method is 0.2:1 to 0.4:1.

[0015] Preferably, the time of the metal thermal reduction method is 8 min to 10 min.

[0016] Preferably, the reducing agent used in the non-metal thermal reduction method includes carbon materials.

[0017] Preferably, the molar ratio of the reducing agent to silica used in the non-metal thermal reduction method is 0.2:1 to 0.4:1.

[0018] Preferably, the time of the non-metal thermal reduction method is 14 min to 16 min.

[0019] Preferably, before the thermal reduction method is carried out on the silica, a preheating treatment is carried out.

[0020] Preferably, the temperature of the preheating treatment is 360°C to 400°C.

[0021] Preferably, the time of the preheating treatment is 30 min to 60 min.

[0022] As a preferred technical solution of the preparation method described in the first aspect of the present invention, the preparation method includes the following steps:

[0023] A silicon layer is formed on the surface layer of the silica by a thermal reduction method at 1200°C to 1400°C, and the temperature is lowered to room temperature at a rate of 30°C / min to 50°C / min to obtain the heat-generation-reducing modified silica;

[0024] The thermal reduction method includes a metal thermal reduction method or a non-metal thermal reduction method;

[0025] The reducing agent used in the metal thermal reduction method includes any one or a combination of at least two of magnesium, aluminum or zinc; the time of the metal thermal reduction method is 8 min to 10 min;

[0026] The reducing agent used in the non-metal thermal reduction method includes charcoal and / or petroleum coke; the time of the non-metal thermal reduction method is 14 min to 16 min;

[0027] Before the thermal reduction method is carried out on the silica, a preheating treatment at 360°C to 400°C is carried out for 30 min to 60 min;

[0028] The silica is prepared by a precipitation method, which includes the following steps:

[0029] Mix the silica wet gel with water to make the water content 81 wt% to 83 wt%, adjust the temperature to 75°C to 90°C and the pH value to 6 to 9, then mix with the pre-hydrolyzed composite silane coupling agent and carry out a modification reaction for 30 min to 150 min; after the modification reaction is completed, successively carry out ethanol washing, filtration and drying to obtain silica;

[0030] The composite silane coupling agent includes a main silane coupling agent A151 and a co-silane coupling agent with a mass ratio of 0.3:1 to 4:1; the co-silane coupling agent is a silane coupling agent PTMS and / or a silane coupling agent DPDMS;

[0031] The dosage of the composite silane coupling agent is 3 wt% to 9 wt% of the silica wet gel.

[0032] Second aspect, the present invention provides a heat - generating - reducing modified silica, and the heat - generating - reducing modified silica is prepared by the preparation method described in the first aspect.

[0033] Third aspect, the present invention provides an application of the heat - generating - reducing modified silica as described in the second aspect, and the heat - generating - reducing modified silica is used as a rubber reinforcing agent.

[0034] The numerical ranges described in the present invention not only include the exemplified point values above, but also include any point values between the above - mentioned numerical ranges that are not exemplified. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the ranges.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] Under high - temperature conditions, the present invention reduces the surface layer of silica to a silicon layer, and then reduces the temperature to room temperature at a relatively fast cooling rate. By utilizing the difference in thermal expansion coefficients between silica and silicon, cracks are generated in the silicon layer. While reducing the impact on mechanical properties, the hydroxyl content on the surface of silica is further reduced, its dispersion performance is further improved, thereby reducing the Mooney viscosity during rubber processing, extending the scorch time of the mixed rubber, enhancing the overall vulcanization efficiency, and reducing the agglomeration caused by strong interaction between silicas. Specific Embodiments

[0037] The technical solutions of the present invention will be further described below through specific embodiments.

[0038] An embodiment of the present invention provides a preparation method of a heat - generating - reducing modified silica, and the preparation method includes:

[0039] Form a silicon layer on the surface layer of silica by a thermal reduction method, and cool down to room temperature at a rate of 30 °C / min to 50 °C / min to obtain the heat - generating - reducing modified silica.

[0040] Under high - temperature conditions, the present invention reduces the surface layer of silica to a silicon layer, and then reduces the temperature to room temperature at a relatively fast cooling rate. By utilizing the difference in thermal expansion coefficients between silica and silicon, cracks are generated in the silicon layer. While reducing the impact on mechanical properties, the hydroxyl content on the surface of silica is further reduced, its dispersion performance is further improved, thereby reducing the Mooney viscosity during rubber processing, extending the scorch time of the mixed rubber, enhancing the overall vulcanization efficiency, and reducing the agglomeration caused by strong interaction between silicas.

[0041] Among them, the cooling rate after the thermal reduction method is relatively important. If the cooling rate is too low, sufficient cracks cannot be generated in the silicon layer, affecting the interaction between the modified silica and the rubber material, and further affecting the application of the modified silica as a rubber reinforcing agent. If the cooling rate is too fast, there will be too many cracks in the silicon layer, affecting the structural strength of the modified silica and also reducing the performance of the modified silica as a rubber reinforcing agent. In the present invention, the cooling rate after the thermal reduction method needs to be controlled at 30°C / min to 50°C / min. For example, it can be 30°C / min, 35°C / min, 40°C / min, 45°C / min or 50°C / min, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0042] In some embodiments, the method for preparing the silica includes the following steps:

[0043] Mix the silica wet gel with water, adjust the temperature and pH value to the reaction conditions, then mix with the pre-hydrolyzed composite silane coupling agent, and carry out the modification reaction; after the modification reaction is completed, through post-treatment, silica is obtained;

[0044] The composite silane coupling agent includes a main silane coupling agent and a co-silane coupling agent;

[0045] The main silane coupling agent is silane coupling agent A151;

[0046] The co-silane coupling agent is silane coupling agent PTMS and / or silane coupling agent DPDMS.

[0047] A preferred method for preparing silica effectively reduces the surface hydroxyl number of silica by adding an appropriate amount of composite silane coupling agent to modify the silica, and at the same time adjusts the modification temperature, modification pH, reaction time, etc., improving the dispersibility of silica in rubber tires; when used as a rubber reinforcing agent, it greatly improves the processing and mechanical properties of rubber.

[0048] Among them, the unsaturated carbon-carbon double bond in the structure of the main silane coupling agent can enhance the cross-linking effect with the rubber, improve the compatibility between the silica and the rubber compound, thereby improving the structural strength and the structural strength when used as a rubber reinforcing agent, and can also reduce the flexibility of the rubber; while the co-silane coupling agent is grafted on the surface of the silica, the steric hindrance of its benzene ring increases, and the energy required for deformation increases. At the same time, due to the large π-electron cloud density of the benzene ring and the strong attraction to atoms, a greater van der Waals force is required to make the molecules slip, thereby improving the cross-linking density, tensile properties and wear resistance of the rubber compound. The co-silane coupling agent and the main silane coupling agent cooperate with each other, and can also graft more silane coupling agents on the rubber compound, improving the processing and mechanical properties of the rubber.

[0049] In some embodiments, the thermal reduction method includes a metal thermal reduction method or a non-metal thermal reduction method.

[0050] In some embodiments, the temperature of the thermal reduction method is from 1200°C to 1400°C. For example, it can be 1200°C, 1250°C, 1300°C, 1350°C or 1400°C, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0051] In some embodiments, the reducing agent used in the metal thermal reduction method includes any one or a combination of at least two of magnesium, aluminum or zinc. Typical but non-limiting combinations include the combination of magnesium and aluminum, the combination of aluminum and zinc, the combination of magnesium and zinc, or the combination of magnesium, aluminum and zinc.

[0052] In some embodiments, the molar ratio of the reducing agent used in the metal thermal reduction method to silicon dioxide is from 0.2:1 to 0.4:1. For example, it can be 0.2:1, 0.3:1 or 0.4:1, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0053] In the present invention, the longer the time of the metal thermal reduction method, the thicker the thickness of the obtained silicon layer. If the time is too long, the reinforcing performance of silicon dioxide will be significantly affected. Therefore, in order to exert the coating modification effect of the silicon layer and avoid excessive influence of the silicon layer on the reinforcing performance of silicon dioxide, it is necessary to control the time of the metal thermal reduction method.

[0054] In some embodiments, the time of the metal thermal reduction method is from 8 min to 10 min. For example, it can be 8 min, 9 min or 10 min, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0055] In some embodiments, the reducing agent used in the non-metal thermal reduction method includes carbon materials.

[0056] In some embodiments, the molar ratio of the reducing agent used in the non-metal thermal reduction method to silicon dioxide is from 0.2:1 to 0.4:1. For example, it can be 0.2:1, 0.3:1 or 0.4:1, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0057] In the present invention, the longer the time of the non-metal thermal reduction method, the thicker the thickness of the obtained silicon layer. If the time is too long, the reinforcing performance of silicon dioxide will be significantly affected. Therefore, in order to exert the coating modification effect of the silicon layer and avoid excessive influence of the silicon layer on the reinforcing performance of silicon dioxide, it is necessary to control the time of the non-metal thermal reduction method.

[0058] In some embodiments, the time of the non-metallic thermal reduction method is from 14 min to 16 min, for example, it can be 14 min, 15 min or 16 min, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0059] In some embodiments, before the thermal reduction method is carried out on the silicon dioxide, a preheating treatment is carried out.

[0060] The preheating treatment can pre-remove the surface hydroxyl groups of the silicon dioxide, but too high a temperature will affect the pore size distribution in the silicon dioxide and the specific surface area of the finally obtained modified silicon dioxide, while too low a temperature cannot achieve the purpose of the preheating treatment.

[0061] In some embodiments, the temperature of the preheating treatment is from 360 °C to 400 °C, for example, it can be 360 °C, 370 °C, 380 °C, 390 °C or 400 °C, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0062] In some embodiments, the time of the preheating treatment is from 30 min to 60 min, for example, it can be 30 min, 40 min, 50 min or 60 min, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0063] In some embodiments, the preparation method comprises the following steps:

[0064] A silicon layer is formed on the surface layer of the silicon dioxide by a thermal reduction method at 1200 °C to 1400 °C, and the temperature is lowered to room temperature at a rate of 30 °C / min to 50 °C / min to obtain the modified silicon dioxide with reduced heat generation;

[0065] The thermal reduction method includes a metal thermal reduction method or a non-metallic thermal reduction method;

[0066] The reducing agent used in the metal thermal reduction method includes any one or a combination of at least two of magnesium, aluminum or zinc; the time of the metal thermal reduction method is from 8 min to 10 min;

[0067] The reducing agent used in the non-metallic thermal reduction method includes charcoal and / or petroleum coke; the time of the non-metallic thermal reduction method is from 14 min to 16 min;

[0068] Before the thermal reduction method is carried out on the silicon dioxide, a preheating treatment at 360 °C to 400 °C is carried out for 30 min to 60 min;

[0069] The silicon dioxide is prepared by a precipitation method, and the method comprises the following steps:

[0070] Mix the silica wet gel with water to make the water content 81 wt% to 83 wt%, adjust the temperature to 75°C to 90°C and the pH value to 6 to 9, then mix with the pre-hydrolyzed composite silane coupling agent and carry out the modification reaction for 30 min to 150 min; after the modification reaction ends, obtain silica through ethanol washing, filtration, and drying in sequence;

[0071] The composite silane coupling agent includes a main silane coupling agent A151 and a co-silane coupling agent with a mass ratio of 0.3:1 to 4:1; the co-silane coupling agent is silane coupling agent PTMS and / or silane coupling agent DPDMS;

[0072] The dosage of the composite silane coupling agent is 3 wt% to 9 wt% of the silica wet gel.

[0073] A certain embodiment of the present invention provides a heat-generation-reducing modified silica, and the heat-generation-reducing modified silica is prepared by the preparation method described in any embodiment.

[0074] A certain embodiment of the present invention provides an application of the heat-generation-reducing modified silica described in any embodiment, and the heat-generation-reducing modified silica is used as a rubber reinforcing agent.

[0075] In the following examples and comparative examples, silica is prepared by the following preparation method: Mix the silica wet gel with water to make the water content 82 wt%, adjust the temperature and pH value to the reaction conditions, then mix with the pre-hydrolyzed composite silane coupling agent and carry out the modification reaction for 90 min; after the modification reaction ends, obtain silica through ethanol washing, filtration, and drying in sequence; the composite silane coupling agent includes a main silane coupling agent A151 and a co-silane coupling agent PTMS with a mass ratio of 1:1; the dosage of the composite silane coupling agent is 6.5 wt% of the silica wet gel; the temperature of the reaction conditions is 80°C and the pH value is 8.

[0076] Among them, the pre-hydrolyzed composite silane coupling agent means that the composite silane coupling agent, ethanol, and water are mixed in a mass ratio of 1:2:1, and then stirred and hydrolyzed for 30 min; among them, the water content of the silica wet gel is 75 wt%, and the balance is silica.

[0077] The room temperature in the present invention is 20°C to 30°C, and the room temperature in the examples and comparative examples is 25°C unless otherwise specified.

[0078] Example 1

[0079] This example provides a preparation method of a heat-generation-reducing modified silica, and the preparation method includes the following steps:

[0080] A silicon layer is formed on the surface of silica by a metallothermic reduction method at 1300 °C, and the temperature is decreased to room temperature at a rate of 40 °C / min to obtain the heat-generation-reducing modified silica;

[0081] The reducing agent used in the metallothermic reduction method is magnesium, and the molar ratio of the reducing agent to silica is 0.3:1;

[0082] The time of the metallothermic reduction method is 9 min.

[0083] Example 2

[0084] This example provides a preparation method of heat-generation-reducing modified silica, and the preparation method includes the following steps:

[0085] A silicon layer is formed on the surface of silica by a metallothermic reduction method at 1200 °C, and the temperature is decreased to room temperature at a rate of 30 °C / min to obtain the heat-generation-reducing modified silica;

[0086] The reducing agent used in the metallothermic reduction method is aluminum, and the molar ratio of the reducing agent to silica is 0.2:1;

[0087] The time of the metallothermic reduction method is 8 min.

[0088] Example 3

[0089] This example provides a preparation method of heat-generation-reducing modified silica, and the preparation method includes the following steps:

[0090] A silicon layer is formed on the surface of silica by a metallothermic reduction method at 1400 °C, and the temperature is decreased to room temperature at a rate of 50 °C / min to obtain the heat-generation-reducing modified silica;

[0091] The reducing agent used in the metallothermic reduction method is zinc, and the molar ratio of the reducing agent to silica is 0.4:1;

[0092] The time of the metallothermic reduction method is 10 min.

[0093] Example 4

[0094] This example provides a preparation method of heat-generation-reducing modified silica. Except that silica is preheated at 380 °C for 45 min before the metallothermic reduction method, the rest are the same as in Example 1.

[0095] Example 5

[0096] This example provides a preparation method of heat-generation-reducing modified silica. Except that silica is preheated at 360 °C for 60 min before the metallothermic reduction method, the rest are the same as in Example 1.

[0097] Example 6

[0098] This example provides a method for preparing modified silica with reduced heat generation. Except that the silica is preheated at 400 °C for 30 min before the metal thermal reduction method, the rest are the same as in Example 1.

[0099] Example 7

[0100] This example provides a method for preparing modified silica with reduced heat generation. Except that the preheating temperature is 320 °C, the rest are the same as in Example 4.

[0101] Example 8

[0102] This example provides a method for preparing modified silica with reduced heat generation. Except that the preheating temperature is 450 °C, the rest are the same as in Example 4.

[0103] Example 9

[0104] This example provides a method for preparing modified silica with reduced heat generation. The preparation method includes the following steps:

[0105] A silicon layer is formed on the surface layer of silica by a non-metal thermal reduction method at 1300 °C, and the temperature is reduced to room temperature at a rate of 40 °C / min to obtain the modified silica with reduced heat generation;

[0106] The reducing agent used in the non-metal thermal reduction method is charcoal, and the molar ratio of the reducing agent to silica is 0.3:1;

[0107] The time of the non-metal thermal reduction method is 15 min.

[0108] Example 10

[0109] This example provides a method for preparing modified silica with reduced heat generation. The preparation method includes the following steps:

[0110] A silicon layer is formed on the surface layer of silica by a non-metal thermal reduction method at 1200 °C, and the temperature is reduced to room temperature at a rate of 30 °C / min to obtain the modified silica with reduced heat generation;

[0111] The reducing agent used in the non-metal thermal reduction method is charcoal, and the molar ratio of the reducing agent to silica is 0.2:1;

[0112] The time of the non-metal thermal reduction method is 14 min.

[0113] Example 11

[0114] This embodiment provides a method for preparing modified silica with reduced heat generation, and the preparation method includes the following steps:

[0115] A silicon layer is formed on the surface of silica by a non-metallic thermal reduction method at 1400 °C, and the temperature is cooled to room temperature at a rate of 50 °C / min to obtain the modified silica with reduced heat generation;

[0116] The reducing agent used in the non-metallic thermal reduction method is charcoal, and the molar ratio of the reducing agent to silica is 0.4:1;

[0117] The time of the non-metallic thermal reduction method is 16 min.

[0118] Example 12

[0119] This embodiment provides a method for preparing modified silica with reduced heat generation. Except that silica is preheated at 380 °C for 45 min before the non-metallic thermal reduction method, the rest are the same as in Example 9.

[0120] Example 13

[0121] This embodiment provides a method for preparing modified silica with reduced heat generation. Except that silica is preheated at 360 °C for 60 min before the non-metallic thermal reduction method, the rest are the same as in Example 9.

[0122] Example 14

[0123] This embodiment provides a method for preparing modified silica with reduced heat generation. Except that silica is preheated at 400 °C for 30 min before the non-metallic thermal reduction method, the rest are the same as in Example 9.

[0124] Example 15

[0125] This embodiment provides a method for preparing modified silica with reduced heat generation. Except that the preheating temperature is 320 °C, the rest are the same as in Example 12.

[0126] Example 16

[0127] This embodiment provides a method for preparing modified silica with reduced heat generation. Except that the preheating temperature is 450 °C, the rest are the same as in Example 12.

[0128] Comparative Example 1

[0129] This comparative example provides a method for preparing modified silica. Except that the cooling rate is 20 °C / min, the rest are the same as in Example 1.

[0130] Comparative Example 2

[0131] This comparative example provides a method for preparing modified silica. Except that the cooling rate is 60 °C / min, the rest are the same as in Example 1.

[0132] Comparative Example 3

[0133] This comparative example provides a method for preparing modified silica. Except that the cooling rate is 20 °C / min, the rest are the same as in Example 9.

[0134] Comparative Example 4

[0135] This comparative example provides a method for preparing modified silica. Except that the cooling rate is 60 °C / min, the rest are the same as in Example 9.

[0136] Performance Test

[0137] The hydroxyl group content and dispersity of the modified silica obtained from the above examples and comparative examples were measured, and the results are shown in Table 1.

[0138] The method for measuring the hydroxyl group content is as follows:

[0139] According to the specific measurement steps of T / FSI 049-2020, the surface hydroxyl group number of the modified silica was measured. Weigh 2 g of the modified silica into a 200 mL beaker, add 25 mL of absolute ethanol, and then add 75 mL of 20 wt% NaCl solution; after magnetic stirring evenly, add a standard solution of 0.1 mol / L NaOH (or 0.1 mol / L HCl) dropwise to adjust the pH of the test solution to 4, and then slowly add 0.1 mol / L NaOH to make the pH reach 9 and keep the pH unchanged within 20 s. The hydroxyl group content (α OH ) of the modified silica was calculated according to the formula:

[0140] α OH = [(C × V × 17.007) / (m × 1000)] × 100%;

[0141] α OH : The content of silanol groups, mass percentage (%);

[0142] C: The accurate concentration of the NaOH standard solution (mol / L);

[0143] V: The volume consumed (mL) when adding 0.1 mol / L NaOH to increase the pH value of the solution from 4 to 9;

[0144] m: The mass (g) of the modified silica.

[0145] The dispersion degree was determined according to the provisions of GB / T 6030-2006 "Rapid Comparative Method for the Evaluation of the Dispersion of Carbon Black and Carbon Black-Silica in Rubber".

[0146] Table 1

[0147] Hydroxyl number (%) Dispersion degree Example 1 0.559 9 Example 2 0.572 9 Example 3 0.598 9 Example 4 0.501 10 Example 5 0.526 10 Example 6 0.514 10 Example 7 0.547 <![CDATA[9 1 / 2 > Example 8 0.529 <![CDATA[9 1 / 2 > Example 9 0.563 9 Example 10 0.579 9 Example 11 0.601 9 Example 12 0.512 10 Example 13 0.539 10 Example 14 0.524 10 Example 15 0.541 <![CDATA[9 1 / 2 > Example 16 0.556 <![CDATA[9 1 / 2 > Comparative Example 1 0.634 <![CDATA[8 1 / 2 > Comparative Example 2 0.658 8 Comparative Example 3 0.647 8 Comparative Example 4 0.633 <![CDATA[8 1 / 2 >

[0148] The rubber mixing properties of the modified silica obtained from the above-mentioned examples and comparative examples were tested: rubber mixing was carried out according to HG / T2404-2008 "Identification of Precipitated Hydrated Silica in Styrene-Butadiene Rubber", and its formula was: 200 g of styrene-butadiene rubber, 100 g of modified silica, 10 g of zinc oxide, 2 g of stearic acid, 6 g of polyethylene glycol, 2.4 g of accelerator DM (2,2'-dithiobenzothiazole), 1.4 g of accelerator M (2-mercaptobenzothiazole), 1 g of accelerator DPG (1,3-diphenylguanidine), and 4 g of sulfur; then the silica-butadiene rubber masterbatch was vulcanized by heating under a flat plate vulcanizer at 160 °C, and then its Mooney viscosity, vulcanization properties, and stress-strain characteristics were tested. The results are shown in Table 2.

[0149] The test of Mooney viscosity was carried out according to GB / T1232 "Determination of Unvulcanized Rubber by Disc Shear Viscometer - Part 1: Determination of Mooney Viscosity".

[0150] The test of vulcanization characteristics was carried out according to GB / T9869-1997 "Determination of Vulcanization Characteristics of Rubber Compounds (Disc Oscillation Vulcanizer Method)".

[0151] The test of stress-strain characteristics was carried out according to GB / T528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber".

[0152] Table 2

[0153]

[0154]

[0155] To sum up, in the present invention, the surface layer of silica is reduced to a silicon layer under high-temperature conditions, and then the temperature is reduced to room temperature at a relatively fast cooling rate. By utilizing the difference in thermal expansion coefficients between silica and silicon, cracks are generated in the silicon layer. While reducing the impact on mechanical properties, the hydroxyl content on the surface of silica is further reduced, its dispersion performance is further improved, thereby reducing the Mooney viscosity during the rubber processing process, extending the scorch time of the masterbatch, enhancing the overall vulcanization efficiency, and reducing the agglomeration caused by the strong interaction between silicas.

[0156] The specific embodiments described above further elaborate on the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing modified silicon dioxide with reduced heat generation, characterized in that: The preparation method comprises: A silicon layer is formed on the surface of the silicon dioxide by a thermal reduction method, and the temperature is lowered to room temperature at a rate of 30° C. / min to 50° C. / min to obtain the modified silicon dioxide with reduced heat generation.

2. The preparation method according to claim 1, characterized in that: The thermal reduction method includes a metal thermal reduction method or a non-metal thermal reduction method; Preferably, the temperature of the thermal reduction method is 1200°C to 1400°C.

3. The preparation method according to claim 2, characterized in that: The reducing agent used in the metal thermal reduction method includes any one of magnesium, aluminum or zinc or a combination of at least two thereof; Preferably, the molar ratio of the reducing agent to silicon dioxide used in the metal thermal reduction method is 0.2:1 to 0.4:1; Preferably, the metal thermal reduction method is carried out for 8 to 10 minutes.

4. The preparation method according to claim 2, characterized in that: The reducing agent used in the non-metal thermal reduction method includes a carbon material; Preferably, the molar ratio of the reducing agent to silicon dioxide used in the non-metal thermal reduction method is 0.2:1 to 0.4:1; Preferably, the non-metal thermal reduction method is carried out for 14 to 16 minutes.

5. The preparation method according to claim 1, characterized in that: The silicon dioxide is preheated before being subjected to the thermal reduction method.

6. The preparation method according to claim 5, characterized in that: The preheating temperature is 360°C to 400°C.

7. The preparation method according to claim 5, characterized in that: The preheating time is 30 min to 60 min.

8. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: Forming a silicon layer on the surface of silicon dioxide by a thermal reduction method at 1200° C. to 1400° C., and cooling to room temperature at a rate of 30° C. / min to 50° C. / min to obtain the modified silicon dioxide with reduced heat generation; The thermal reduction method includes a metal thermal reduction method or a non-metal thermal reduction method; The reducing agent used in the metal thermal reduction method includes any one of magnesium, aluminum or zinc or a combination of at least two thereof; the time of the metal thermal reduction method is 8 to 10 minutes; The reducing agent used in the non-metal thermal reduction method includes charcoal and / or petroleum coke; the time of the non-metal thermal reduction method is 14 minutes to 16 minutes; The silicon dioxide is preheated at 360° C. to 400° C. for 30 to 60 minutes before being subjected to thermal reduction; The silicon dioxide is prepared by a precipitation method, which comprises the following steps: Mixing the wet silica gel with water to make the water content 81wt% to 83wt%, adjusting the temperature to 75°C to 90°C and the pH value to 6 to 9, and then mixing with the pre-hydrolyzed composite silane coupling agent to carry out a modification reaction for 30min to 150min; after the modification reaction is completed, washing with ethanol, filtering and drying are carried out in sequence to obtain silica; The composite silane coupling agent comprises a main silane coupling agent A151 and an auxiliary silane coupling agent in a mass ratio of 0.3:1 to 4:1; the auxiliary silane coupling agent is silane coupling agent PTMS and / or silane coupling agent DPDMS; The amount of the composite silane coupling agent used is 3wt% to 9wt% of the silicon dioxide wet gel.

9. A modified silicon dioxide for reducing heat generation, characterized in that: The modified silicon dioxide for reducing heat generation is prepared by the preparation method according to any one of claims 1 to 8.

10. A use of modified silicon dioxide for reducing heat generation as claimed in claim 9, characterized in that: The modified silica with reduced heat generation is used as a rubber reinforcing agent.

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