阅读说明：本技术 高性能轮胎用沉淀法白炭黑的制备方法 (Preparation method of precipitated white carbon black for high-performance tire ) 是由 任立荣 徐功智 曾志恩 徐钰兴 陈仲林 于 2021-02-25 设计创作，主要内容包括：本发明公开了一种高性能轮胎用沉淀法白炭黑的制备方法,它采用分步多段沉淀法,包括以晶体成核为主的反应初期阶段、以晶体成核与晶体生长共存的反应中期阶段以及以晶体生长为主的反应后期阶段；反应初期与中期的分界点在反应物料由澄清至出现白色悬浊无定形二氧化硅的时候,反应中期与后期的分界点在反应浆料由粘稠状态转为非粘稠状态的时候；在反应初期向中期过度的时间点、中期向后期过度的时间点以及在反应后期的中间时段均同时暂停水玻璃和硫酸的加入,在搅拌15-30min后再同时恢复水玻璃和硫酸的加入继续并流反应。本发明制备的产品粒径分布窄、结构度高、孔径分布相对集中、分散性好。(The invention discloses a preparation method of precipitated white carbon black for a high-performance tire, which adopts a step-by-step multi-section precipitation method and comprises a reaction initial stage mainly based on crystal nucleation, a reaction middle stage mainly based on coexistence of crystal nucleation and crystal growth and a reaction later stage mainly based on crystal growth; the boundary point between the initial stage and the middle stage of the reaction is when the reaction material is clear to generate white suspended amorphous silicon dioxide, and the boundary point between the middle stage and the later stage of the reaction is when the reaction slurry is converted from a viscous state to a non-viscous state; the adding of the water glass and the sulfuric acid is suspended at the time point of transition from the early stage of the reaction to the middle stage, the time point of transition from the middle stage to the later stage and the intermediate period of the later stage of the reaction, and the adding of the water glass and the sulfuric acid is resumed at the same time after stirring for 15-30min to continue the cocurrent reaction. The product prepared by the invention has narrow particle size distribution, high structure degree, relatively concentrated pore size distribution and good dispersibility.)

1. A preparation method of precipitated white carbon black for high-performance tires is characterized by comprising the following steps: amorphous silicon dioxide is prepared by a step-by-step multi-section precipitation method; the step-by-step multistage reaction comprises a reaction initial stage mainly based on crystal nucleation, a reaction middle stage coexisting with crystal nucleation and crystal growth and a reaction later stage mainly based on crystal growth; the boundary point between the initial stage and the middle stage of the reaction is when the materials in the reaction system are clear to generate white suspended amorphous silicon dioxide, and the boundary point between the middle stage and the later stage of the reaction is when the slurry of the reaction system is converted from a viscous state to a non-viscous state; the operation steps are as follows:

adding water or water and a water glass solution into a reaction kettle, wherein the initial equivalent concentration of water glass in a reaction system is 0-0.08N, uniformly stirring, and heating to 78-92 ℃;

simultaneously adding water glass and sulfuric acid to carry out parallel flow reaction, and controlling the equivalent concentration of the water glass in the reaction system to be 0.01-0.08N and the pH value of the reaction system to be 8.5-10.8;

thirdly, the adding of the water glass and the sulfuric acid is suspended at the same time at the time point of transition to the middle reaction stage in the initial reaction stage, at the time point of transition to the later reaction stage in the middle reaction stage and in the middle period of the later reaction stage, and after stirring for 15-30min, the adding of the water glass and the sulfuric acid is resumed at the same time to continue the cocurrent reaction;

(IV) continuing stirring after the parallel flow reaction is finished, and continuing aging after the pH value is 4.0 by using acid;

and (V) filtering, washing, pulping and drying the reaction slurry to obtain the precipitated hydrated silicon dioxide.

Technical Field

The invention relates to the technical field of preparation methods of inorganic powder materials for reinforcing tire rubber, in particular to a preparation method of precipitated white carbon black for a high-performance tire.

Background

The precipitated white carbon black is amorphous hydrated silica, has reinforcement performance similar to carbon black in rubber, can provide richer colors for the rubber, is applied to tire rubber, can improve the gripping force, the wear resistance and the wet skid resistance of a tire, and reduces the rolling resistance. With the development of rubber mixing technology and the implementation of a tire labeling method, the amount of white carbon black used in a tire is increased fastest.

At present, the addition part of the white carbon black in the tire rubber is as high as 80 percent or even higher. Although white carbon black has excellent performance as a rubber reinforcing agent, the white carbon black is easy to agglomerate and difficult to uniformly disperse in a rubber material, and white carbon black particles in the rubber material are easy to agglomerate again after the rubber material is stored, so that the function of the white carbon black in the tire rubber is greatly reduced.

Disclosure of Invention

The invention aims to provide a preparation method of high-performance precipitated silica for tires, which has the advantages of narrow particle size distribution, high structure degree, relatively concentrated pore size distribution and good dispersibility.

In order to realize the purpose, the preparation method of the precipitated silica white for the high-performance tire adopts a step-by-step multi-section precipitation method to prepare amorphous silica; the step-by-step multistage reaction comprises a reaction initial stage mainly based on crystal nucleation, a reaction middle stage coexisting with crystal nucleation and crystal growth and a reaction later stage mainly based on crystal growth; the boundary point between the initial stage and the middle stage of the reaction is when the materials in the reaction system are clear to generate white suspended amorphous silicon dioxide, and the boundary point between the middle stage and the later stage of the reaction is when the slurry of the reaction system is converted from a viscous state to a non-viscous state; the operation steps are as follows:

adding water or water and a water glass solution into a reaction kettle, wherein the initial equivalent concentration of water glass in a reaction system is 0-0.08N, uniformly stirring, and heating to 78-92 ℃;

simultaneously adding water glass and sulfuric acid to carry out parallel flow reaction, and controlling the equivalent concentration of the water glass in the reaction system to be 0.01-0.08N and the pH value of the reaction system to be 8.5-10.8;

thirdly, the adding of the water glass and the sulfuric acid is suspended at the same time at the time point of transition to the middle reaction stage in the initial reaction stage, at the time point of transition to the later reaction stage in the middle reaction stage and in the middle period of the later reaction stage, and after stirring for 15-30min, the adding of the water glass and the sulfuric acid is resumed at the same time to continue the cocurrent reaction;

(IV) continuing stirring after the parallel flow reaction is finished, and continuing aging after the pH value is 4.0 by using acid;

and (V) filtering, washing, pulping and drying the reaction slurry to obtain the precipitated hydrated silicon dioxide.

The time point of the transition from the initial reaction stage to the middle reaction stage and the time point of the transition from the middle reaction stage to the later reaction stage are different according to different reaction conditions, the key points are equivalent concentration or pH of water glass in a reaction system, concentration of the water glass and flow rate of the added water glass, and the difference is judged according to the boundary points of the initial reaction stage and the middle reaction stage and the later reaction stage.

The reaction process of the precipitated white carbon black is the processes of silicon dioxide nucleation, crystal nucleus growth and collision and aggregation among particles. Precipitated silica is generally prepared by continuously and simultaneously adding water glass and sulfuric acid into a reaction kettle until the water glass is stopped adding, and then continuing to acidify. The nucleation, growth and aggregation of the silicon dioxide are carried out in the reaction system at the same time, so the prepared white carbon black product has the characteristics of wide particle size distribution, small structure degree, easy agglomeration, large micropore ratio and the like. The preparation method of the precipitated silica white for the high-performance tire adopts a step-by-step multi-section precipitation method, and has the following technical characteristics and beneficial effects:

(1) because the crystal nucleus is stirred for 15-30min after the initial stage of the reaction which mainly takes the crystal nucleus formation, the grain size distribution of the crystal nucleus formed in the initial stage of the reaction is more uniform, the dispersion degree is higher, and the ratio of micropores is reduced;

(2) because the addition of the water glass and the sulfuric acid is suspended in the middle stage of the reaction in which the crystal nucleation and the crystal growth coexist, and the addition is resumed after stirring for 15-30min, the crystal nucleus growth in the middle and later stages of the reaction can be more uniform, and the structure degree of the product is improved.

(3) The three reaction stages are the commonness of the reaction process for preparing hydrated silicon dioxide by a precipitation method, because of the initial reaction stage mainly comprising crystal nucleation, the middle reaction stage mainly comprising crystal nucleation and crystal growth, and the later reaction stage mainly comprising crystal growth. Although the specific time nodes are different from each other in terms of reaction pH, reactant concentration, reaction flow and the like, the slurry states of the initial reaction stage and the middle reaction stage and the intermediate reaction stage and the later reaction stage are obviously different, the appropriate time nodes for suspending the addition of the water glass and the sulfuric acid can be selected according to the change of the slurry states, and then the product with more uniform crystal particle size and higher structure degree is obtained. Therefore, the present invention is applicable to the case of preparing precipitated hydrated silica under reaction conditions of different pH and different water glass concentrations.

Detailed Description

The preparation method of the precipitated silica for high performance tires according to the present invention is further described in detail with reference to the following embodiments.

Example 1:

adding 70 parts by volume of water and 2.3 parts by volume of water glass solution with equivalent concentration of 2.50N and modulus of 3.48 into a reaction kettle in advance to enable the initial water glass concentration of the reaction system to be 0.075N, wherein the water glass added into the reaction kettle in advance accounts for 8.2% of the total added water glass; after being stirred uniformly, the temperature is raised to 89 ℃; then adding water glass at the flow rate of 18.7 parts by volume/h, and simultaneously adding concentrated sulfuric acid to carry out parallel flow reaction, and controlling the equivalent concentration of the water glass in the reaction system to be 0.075 +/-0.02N; the total time of the parallel flow reaction is 90min, when the total time of the parallel flow reaction reaches 28min, 40min and 65min in the total time of the parallel flow reaction is 90min, the addition of the water glass and the concentrated sulfuric acid is respectively suspended, the stirring is changed to 15min, and then the addition of the water glass and the concentrated sulfuric acid is simultaneously resumed for the parallel flow reaction; continuing stirring for 15min after the parallel flow is finished, then peracid till the pH value is 4.0, and continuing aging for 30 min; the reaction slurry is filtered, washed, slurried and dried to obtain the precipitated hydrated silicon dioxide.

Example 2:

adding 70 parts by volume of water into a reaction kettle in advance, and heating to 84 ℃; then adding a water glass solution with the equivalent concentration of 2.50N and the modulus of 3.48 at the flow rate of 18.7 parts by volume/h, simultaneously adding concentrated sulfuric acid to perform a cocurrent reaction, and controlling the pH value of a reaction system to be 8.9; the total time of the parallel flow reaction is 90min, when the 25 th min, the 36 th min and the 65 th min in the total time of the parallel flow reaction are reached, the water glass and the concentrated sulfuric acid are respectively added in a pause mode, the stirring is changed to 15min, and then the water glass and the concentrated sulfuric acid are added in a recovery mode to carry out the parallel flow reaction; continuing stirring for 15min after the parallel flow is finished, then peracid till the pH value is 4.0, and continuing aging for 30 min; the reaction slurry is filtered, washed, slurried and dried to obtain the precipitated hydrated silicon dioxide.

Example 3:

adding 70 parts by volume of water into a reaction kettle in advance, and heating to 83 ℃; then adding a water glass solution with the equivalent concentration of 2.50N and the modulus of 3.48 at the flow rate of 20.5 parts by volume/h, simultaneously adding concentrated sulfuric acid for parallel-flow reaction, and controlling the pH value of a reaction system to be 8.9; the total time of the parallel flow reaction is 90min, when the 23 th min, the 32 th min and the 60 th min in the total time of the parallel flow reaction are reached, the water glass and the concentrated sulfuric acid are respectively added in a pause mode, the stirring is changed to 15min, and then the water glass and the concentrated sulfuric acid are added in a recovery mode to carry out the parallel flow reaction; continuing stirring for 15min after the parallel flow is finished, then peracid till the pH value is 4.0, and continuing aging for 30 min; the reaction slurry is filtered, washed, slurried and dried to obtain the precipitated hydrated silicon dioxide.

Comparative example 1:

the cocurrent reaction time of this comparative example was 90min and the cocurrent reaction was continued without stopping, and the other conditions were the same as in example 1.

Comparative example 2:

in this comparative example, when the reaction was carried out in parallel for 28min, the addition of water glass and concentrated sulfuric acid was stopped, and the reaction was carried out in parallel after stirring for 15min, except that the conditions were the same as in example 1.

Comparative example 3:

in the comparative example, when the parallel flow reaction is carried out to 40min, the addition of the water glass and the concentrated sulfuric acid is stopped, the parallel flow reaction is carried out after stirring for 15min, and other conditions are the same as those in example 1.

Comparative example 4:

in this comparative example, when the reaction was carried out in parallel for 65min, the addition of water glass and concentrated sulfuric acid was stopped, and the reaction was carried out in parallel after stirring for 15min, except that the conditions were the same as in example 1.

Comparative example 5:

the cocurrent reaction time of this comparative example was 90min and the cocurrent reaction was continued without stopping, and the other conditions were the same as in example 2.

Comparative example 6:

in this comparative example, when the reaction was carried out in parallel for 23min, the addition of water glass and concentrated sulfuric acid was stopped, and the reaction was carried out in parallel after stirring for 15min, except that the conditions were the same as in example 3.

The particle size distribution and the structure degree of the product prepared in the example are obviously different from those of the comparative example. The particle size and the particle size distribution of the prepared product are determined according to GBT 32698-2016 laser diffraction method for determining the particle size distribution of rubber compounding agent precipitated hydrated silica. For width of particle size distribution (D)₉₀－D₁₀)/D₅₀In this case, a smaller numerical value indicates a narrower distribution, and a larger numerical value indicates a wider distribution. The structure degree is expressed by DBP oil absorption value, the larger the DBP oil absorption value is, the higher the structure degree is, and the smaller the DBP oil absorption value is, the smaller the structure degree is. (D) of the above examples and comparative examples₉₀－D₁₀)/D₅₀The DBP test results are shown in Table 1.

TABLE 1 examples and comparative examples (D)₉₀－D₁₀)/D₅₀DBP parameter

As can be seen from Table 1, under similar conditions, the precipitated silica product prepared in the embodiment of the present invention has the narrowest particle size distribution, i.e., the most uniform particle size distribution of crystal nuclei, the highest dispersion degree and the highest structure degree, and the comprehensive quality performance index is obviously better than that of comparative example 1 and other comparative examples in the prior art.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.