In-situ synthesis wet process mixing granular rubber and preparation method thereof

Abstract

The invention discloses in-situ synthesized wet-process mixed particle rubber and a preparation method thereof. The wet-process mixed particle rubber comprises the following raw materials in parts by weight: 90-110 parts of natural latex, 25-45 parts of water glass, 2-4 parts of a silane coupling agent and 0.5-1.5 parts of zinc oxide, wherein the dry weight of the natural latex is 90-110 parts; the dry weight of the water glass is 25-45 parts; the preparation method comprises the following steps: S1, hydrolyzing the silane coupling agent; and S2, preparing the wet-process mixed granular rubber. By utilizing an acidic microenvironment formed by hydrolysate of the silane coupling agent, while the white carbon black is generated, grafting of the silane coupling agent and the white carbon black and bridging of the silane coupling agent and natural latex are completed, and the dispersity of the white carbon black is remarkably improved. The in-situ synthesis method is adopted to prepare the wet-process mixed particle rubber, so that the method is energy-saving and environment-friendly, simple in process and low in equipment requirement, the cost is reduced, the efficiency is improved, and the prepared product is good in performance.

Description

Technical Field

[0001] This invention relates to an in-situ synthesized wet-mixed granular rubber and its preparation method, belonging to the field of rubber new material preparation technology. Background Technology

[0002] The rubber industry is one of the important basic industries of the national economy. It not only provides people with essential light industrial rubber products such as daily necessities and medical supplies, but also provides various rubber production equipment or rubber parts to heavy industries and emerging industries such as mining, automobiles, construction, machinery, and electronics. Mixing, as the first and indispensable step in the preparation of rubber materials, plays a decisive role in the performance of rubber materials and is a key technology for obtaining high-quality mixed rubber and rubber products. It is mainly divided into two types: dry mixing and wet mixing. Currently, the rubber mixing process widely used in China is traditional dry mixing. However, dry mixing suffers from problems such as dust pollution, high energy consumption, low mixing efficiency, and unsatisfactory dispersion of compounding agents. Wet mixing, on the other hand, completes the mixing and dispersion of fillers and rubber in a liquid phase, which can solve the above-mentioned problems of dry mixing.

[0003] Traditional wet compounding processes first modify silica using dispersants or coupling agents through physical adsorption or chemical bonding, then wet-blend the silica with natural rubber latex. This process suffers from secondary agglomeration of silica, is complex, and has high production costs. To address these issues, in-situ synthesis involves adding silica, natural rubber latex, and coupling agents to the reaction system almost simultaneously. By precisely controlling the in-situ reaction conditions and rate, the quality and performance of rubber composites can be improved. However, silica production generally involves the emission of large amounts of toxic waste gases, nano-silica dust, and high-salt wastewater. Furthermore, spray drying is used to reduce silica agglomeration, requiring significant energy consumption. Therefore, there is a need to explore more energy-efficient and environmentally friendly wet compounding processes for rubber preparation.

[0004] Shao Yashi from Qingdao University of Science and Technology modified precipitated silica in situ by adding Si69 and PEG2000 during the preparation process, producing nanoscale precipitated silica with particle sizes ranging from 0.5 to 0.9 μm. Ma Zhe from Hainan University mixed sodium silicate solution with natural latex and uniformly introduced carbon dioxide gas, causing sodium silicate to generate precipitated silica nanoparticles with a particle size less than 100 nm in situ within the natural latex, thus preparing a nanoscale precipitated silica / NR composite material. However, scanning electron microscopy images of the tensile cross-section of the NR / SiO2 vulcanizate showed that even with the addition of surfactants, some agglomeration of the precipitated silica remained. Currently, the in-situ synthesis method suffers from drawbacks such as complex processes, unstable finished product performance, large precipitated silica particle size, and agglomeration, which affect the performance of wet-process compounded rubber. Therefore, it is necessary to explore an in-situ synthesis process that is simple, produces stable finished products, and yields precipitated silica with smaller particle sizes. Summary of the Invention

[0005] To address at least one problem existing in the prior art, the present invention provides an in-situ synthetic wet-mixing granular adhesive and its preparation method, which further reduces the particle size of silica, improves dispersibility and interfacial bonding, and the preparation process is simple and easy to operate.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an in-situ synthesized wet-mixed granular rubber, wherein the wet-mixed rubber comprises the following raw materials in parts by weight: 90-110 parts by dry weight of natural rubber latex, 25-45 parts by dry weight of water glass, 2-4 parts by dry weight of silane coupling agent, and 0.5-1.5 parts by zinc oxide.

[0007] Preferably, in the preparation of wet-mixed granular adhesive, the water glass reacts to form nano-silica, and the silica particle size is less than 35 nm, and the silica loss rate is less than 5%.

[0008] Preferably, the particle size of the wet-mixed granular rubber is less than 3 mm.

[0009] Preferably, the silane coupling agent is a sulfur- or mercapto-silane coupling agent.

[0010] Preferably, the silane coupling agent is one of Si69, Si75 or Si747.

[0011] Preferably, the natural latex is a fresh latex or a concentrated natural latex diluted to a mass fraction of 15-25 wt.%.

[0012] Preferably, the water glass is a solution of sodium silicate diluted to a mass fraction of 5-20 wt.%.

[0013] This invention also provides a method for preparing in-situ synthesized wet-mixed granular rubber, comprising the following steps: S1. Hydrolysis of silane coupling agent: Add 5-30 wt.% hydrochloric acid to diluted alcohol to adjust the pH of the solution to acidic, then add silane coupling agent, stir for 5-30 min to hydrolyze it, and let it stand for 5-12 h to obtain silane coupling agent hydrolysate. S2. Preparation of wet-process compounded granular rubber containing silica: Natural rubber latex and water glass are mixed evenly, and the mixture is kept in a constant temperature water bath at 40~60 ℃ and magnetically stirred at 100~2000 rpm. Silane coupling agent hydrolysate is added dropwise, and nano zinc oxide is added. The reaction is carried out for 5~12 h, and then acetic acid with a concentration of 5~30 wt.% is used to break the emulsion, so that the whole mixture forms a granular coprecipitate. The pH of the system is made neutral, and the coprecipitated particles are washed and dried to obtain wet-process compounded granular rubber.

[0014] Preferably, during the reaction process in step S2, the stirring speed is varied under magnetic stirring conditions of 100~2000 rpm.

[0015] Preferably, in the reaction process of step S2, the stirring is carried out in stages at a speed of 100~2000 rpm, and the speed-changing stirring is gradually reduced from 2000 rpm to 100 rpm in a segmented constant speed stirring manner. As the stirring speed gradually decreases, the corresponding stirring time remains unchanged or increases, and the sum of all stirring times is the reaction time.

[0016] Preferably, in step S1, the diluted alcohol is medical alcohol, industrial alcohol, or alcohol prepared by mixing anhydrous ethanol and deionized water in a mass ratio of 9:1.

[0017] Preferably, in step S1, the mass of the diluted alcohol is 10 to 12 times the mass of the silane coupling agent; the pH of the solution is 3 to 5.

[0018] Preferably, in step S2, after the co-precipitated particles are washed, they do not need to be thinned or creped and are directly dried.

[0019] Preferably, in step S2, the moisture content after drying is 3-5%.

[0020] The in-situ synthesized wet-mixed granular rubber of the present invention is applied to the preparation of tire tread rubber, that is, the preparation of wet-mixed final compound rubber. The specific preparation process is as follows: (1) The wet-mixed granulated rubber prepared above is mixed with high abrasion-resistant carbon black, silane coupling agent, antioxidant, protective wax, stearic acid, zinc oxide and dispersant in an internal mixer at a speed of 40~50 rpm. The mixture is then mixed to 135~140℃, discharged into an extruder, and extruded by the screw. The extruded rubber is then rolled off the sheet, cooled to 40~45℃, and left to stand for 8~24 hours to obtain a first-stage mixed masterbatch. (2) Mix the first stage of masterbatch with sulfur, accelerator, anti-scorching agent and anti-sulfurization reducing agent in a mixer at a speed of 20~30 rpm for two stages of mixing. Mix until 110~115℃, then discharge the rubber to obtain tire tread rubber.

[0021] The beneficial effects of this invention are: First, in this invention, a hydrolyzed silane coupling agent solution is added to a water glass solution. The water glass solution is alkaline, while the silane coupling agent solution is acidic. Hydrogen ions form hydrogen bonds with oxygen in the silane coupling agent, making the silane coupling agent acidic. When added, an acidic microenvironment is formed in the water glass solution, thereby forming nano-silica. The microenvironment makes the generated nano-silica smaller, with a particle size of less than 35 nm. At the same time, the overall alkaline environment ensures that the silica is uniformly dispersed without agglomeration.

[0022] Secondly, in the aforementioned acidic microenvironment, the protective layer on the surface of natural latex undergoes micro-cracks. Furthermore, during heating, some of the ammonia in the natural latex is released as ammonia gas, reducing the alkalinity of the solution and further damaging the protective layer of the natural latex. Nano-silica enters the natural latex particles under the action of van der Waals forces and mechanical stirring. The added zinc oxide promotes the bridging of sulfur atoms on the silane coupling agent with the natural latex, enhancing interfacial bonding.

[0023] Third, the present invention uses acetic acid to demulsify, which on the one hand neutralizes the ammonia in natural latex, making it easier for the waste liquid to meet the discharge conditions, and on the other hand, the system is neutral after demulsification, reducing environmental pollution; the wet-mixed rubber is granular, does not require the pressing and creping process, and is directly dried, which does not corrode the equipment during drying.

[0024] Fourth, the in-situ synthesis method for preparing wet-mixed granulated rubber of the present invention is environmentally friendly, has a simplified process, and is convenient to operate. Compared with dry-mixed rubber, the carbon black dispersion of the tread rubber prepared by the present invention is significantly improved, and it has advantages in terms of performance enhancement, reduced rolling resistance, improved vulcanization efficiency, enhanced rubber properties, innovation, and wide application. Attached Figure Description

[0025] Figure 1 The flowchart for the preparation of in-situ synthesized wet-mixed granular rubber provided by the present invention; Figure 2 These are SEM images of the wet-process compound rubber of Example 1 and Comparative Example 1 of the present invention, Example 1(a) and Comparative Example 1(b). Figure 3 The graph shows the test results of the particle size of silica in the wet-process compound prepared in Examples 1-10 and Comparative Examples 1-2 of this invention. Figure 4 The graph shows the test results of the loss rate of silica in the wet-process compound prepared in Examples 1-10 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, and not all of them. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply.

[0027] This invention provides an in-situ synthesized wet-mixed granular rubber, wherein the wet-mixed rubber comprises the following raw materials in parts by weight: 90-110 parts by dry weight of natural rubber latex, 25-45 parts by dry weight of water glass, 2-4 parts by dry weight of silane coupling agent, and 0.5-1.5 parts by weight of zinc oxide.

[0028] In this invention, the particle size of the wet-mixed granulated adhesive is less than 3 mm. In the preparation of the wet-mixed granulated adhesive, the water glass reaction forms nano-silica, and the silica particle size is less than 35 nm, and the silica loss rate is less than 5%.

[0029] In this invention, water glass and natural latex are first directly blended, eliminating the need for adjusting the pH of the latex and adding surfactants, simplifying the process. Secondly, the introduced catalyst, zinc oxide (ZnO), can promote vulcanization in subsequent processes after the catalytic reaction is completed, making it a multi-purpose, energy-saving, and environmentally friendly product.

[0030] In this invention, the raw materials used are sodium silicate, natural rubber latex, silane coupling agent, and zinc oxide. Natural rubber latex is the raw material for rubber, sodium silicate is the raw material for silica, the silane coupling agent modifies silica, and zinc oxide catalyzes the bridging of the silane coupling agent and natural rubber latex. If the dry weight of natural rubber latex is 100 parts, the dry weight of water glass is 25-45 parts. Too high a weight results in poor performance of the wet-mixed rubber, while too low a weight leads to easy agglomeration of silica. The silane coupling agent is used in quantities of 2-4 parts. Too low a weight results in poor modification of silica, while too high a weight leads to excessive cross-linking between silica and natural rubber latex. The zinc oxide is used in quantities of 0.5-1.5 parts. Too low a weight results in poor bridging between the silane coupling agent and natural rubber latex, while too high a weight leads to side reactions and waste.

[0031] In addition, such as Figure 1 As shown, the present invention also provides a method for preparing in-situ synthesized wet-mixed granular rubber, comprising the following steps: S1. Hydrolysis of silane coupling agent: Add 5-30 wt.% hydrochloric acid to diluted alcohol to adjust the pH of the solution to acidic, then add silane coupling agent, stir for 5-30 min to hydrolyze it, and let it stand for 5-12 h to obtain silane coupling agent hydrolysate. S2. Preparation of wet-process compounded granular rubber containing silica: Natural rubber latex and water glass are mixed evenly, and the mixture is kept in a constant temperature water bath at 40~60 ℃ and magnetically stirred at 100~2000 rpm. Silane coupling agent hydrolysate is added dropwise, and nano zinc oxide is added. The reaction is carried out for 5~12 h, and then acetic acid with a concentration of 5~30 wt.% is used to break the emulsion, so that the whole mixture forms a granular coprecipitate. The pH of the system is made neutral, and the coprecipitated particles are washed and dried to obtain wet-process compounded granular rubber.

[0032] In this invention, during the specific preparation process in step S1, the mass of diluted alcohol is 10 to 12 times the mass of the silane coupling agent; hydrochloric acid with a mass fraction of 5 to 20 wt.% is added dropwise to make the pH of the solution 3 to 5, and then the silane coupling agent is added. After stirring for 5 to 30 minutes, the solution is allowed to stand for 5 to 12 hours.

[0033] In this invention, the diluent alcohol is medical alcohol, industrial alcohol, or alcohol prepared by mixing anhydrous ethanol and deionized water at a mass ratio of 9:1. The natural latex is an emulsion diluted to a mass fraction of 15-25 wt.% using fresh or concentrated natural latex as raw material. The water glass is a solution of sodium silicate diluted to a mass fraction of 5-20 wt.%.

[0034] In this invention, during the specific preparation process of step S2, fresh latex or concentrated latex is diluted to a mass fraction of 15-25 wt.% to obtain natural latex. Sodium silicate is dissolved in deionized water and diluted to a mass fraction of 5-20 wt.% to obtain water glass. The water glass solution is poured into the natural latex and stirred evenly. The constant temperature water bath temperature is 40-60 ℃, and the magnetic stirring speed is 100-2000 rpm. The hydrolyzed silane coupling agent hydrolysate is added. Zinc oxide is added to deionized water and stirred to disperse, and then added to the reaction system. The reaction is carried out for 5-12 h. Acetic acid with a mass fraction of 10-30 wt.% is added dropwise to the reaction system to obtain granular coprecipitate. After washing with water, it is dried at 50-80 ℃ to constant weight to obtain wet-mixed granular rubber. Within these ranges, after complete precipitation during demulsification, the pH of the system is approximately neutral. After washing, the wet compound shows no acetic acid adhesion and is granular, requiring no pressing or creping process; it can be dried directly. Drying does not corrode equipment, and the moisture content after drying is 3-5%. The silica particle size in the wet compound is less than 35 nm, and the silica loss rate is less than 5%.

[0035] In this invention, in step S2, the stirring speed is varied during the reaction process, that is, the stirring is carried out in stages from 100 to 2000 rpm. The stirring is carried out in stages from 2000 rpm to 100 rpm in a way that gradually reduces the speed. As the stirring speed gradually decreases, the stirring time remains unchanged or increases. The sum of all stirring times is the reaction time.

[0036] Example 1 A method for preparing an in-situ synthesized wet-mixed granular adhesive includes the following steps: First, 3 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=4 for 8 hours. Then, 20 wt.% natural latex (100 parts by dry weight) and 10 wt.% water glass (37 parts by dry weight) are mixed evenly and stirred magnetically at 2000 rpm in a 50 ℃ constant-temperature water bath. The Si69 hydrolysate is then added dropwise, followed by 0.7 parts by weight of nano-zinc oxide. The reaction is carried out for 9 hours, with the stirring speed adjusted to 2000 rpm for 1 hour, 1500 rpm for 2 hours, 1000 rpm for 3 hours, and 500 rpm for 3 hours. Finally, 20 wt.% acetic acid is used to break the emulsion, resulting in a co-precipitate of granules. The co-precipitated granules are then washed and dried. The average particle size of the silica in the finished granular adhesive is 20 nm (e.g., 20 wt.% acetic acid). Figure 2 As shown in a), the loss rate of silica was 4.1%, and the dispersion of silica improved by 7 grades.

[0037] Example 2 An in-situ synthetic wet-process compounded granular adhesive and its preparation method are disclosed. The process involves: hydrolyzing 3 parts by weight of Si69 in diluted alcohol at pH=4 for 10 h; mixing 15 wt.% natural latex (100 parts by dry weight) and 8 wt.% water glass (37 parts by dry weight) evenly in a 50 ℃ constant temperature water bath with magnetic stirring at 2000 rpm; adding the Si69 hydrolysate dropwise; adding 0.7 parts by weight of nano-zinc oxide; reacting for 10 h; first, magnetic stirring at 1500 rpm for 1 h, then at 1000 rpm for 2 h, then at 500 rpm for 3 h, then at 200 rpm for 3 h; finally, breaking the emulsion with 20 wt.% acetic acid to form a co-precipitate of granules; and then washing and drying the co-precipitated granules. The average particle size of silica in the finished granular adhesive is 19 nm, the silica loss rate is 3.2%, and the carbon black dispersion is improved by 5 grades.

[0038] Example 3 An in-situ synthetic wet-process compounded granular rubber and its preparation method are disclosed. The process involves: hydrolyzing 3 parts by weight of Si69 in diluted alcohol at pH=4 for 10 h; mixing 25 wt.% natural latex (100 parts by dry weight) and 15 wt.% water glass (37 parts by dry weight) uniformly in a 50℃ constant temperature water bath with magnetic stirring at 2000 rpm; adding the Si69 hydrolysate dropwise; adding 0.7 parts by weight of nano-zinc oxide; reacting for 12 h; first, magnetic stirring at 2000 rpm for 1 h, then stirring at 1500 rpm for 2 h, then stirring at 1000 rpm for 3 h, then stirring at 500 rpm for 3 h; finally, breaking the emulsion with 20 wt.% acetic acid to form granular co-precipitate. The average particle size of silica in the finished granular rubber is 25 nm, the silica loss rate is 4.5%, and the carbon black dispersion is improved by 6 grades.

[0039] Example 4 An in-situ synthetic wet-process compounded granular adhesive and its preparation method are disclosed. The process is as follows: First, 2 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=3 for 6 h. Then, 20 wt.% natural latex (90 parts by dry weight) and 10 wt.% water glass (25 parts by dry weight) are mixed evenly and stirred magnetically at 2000 rpm in a 40 ℃ constant temperature water bath. The Si69 hydrolysate is then added dropwise, followed by 0.5 parts by weight of nano-zinc oxide. The reaction is carried out for 9 h. The mixture is then magnetically stirred at 2000 rpm for 1 h, then at 1000 rpm for 4 h, and finally at 500 rpm for 4 h. Finally, 20 wt.% acetic acid is used to break the emulsion, resulting in a co-precipitate of granules. The co-precipitated granules are then washed and dried. The average particle size of silica in the finished granular adhesive is 22 nm, the silica loss rate is 3.3%, and the silica dispersion is improved by 3 grades.

[0040] Example 5 An in-situ synthetic wet-process compounded granular adhesive and its preparation method are disclosed. The process is as follows: First, 4 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=4 for 9 h. Then, 20 wt.% natural latex (dry weight 110 parts) and 10 wt.% water glass (dry weight 45 parts) are mixed evenly and stirred magnetically at 2000 rpm in a 60 ℃ constant temperature water bath. The Si69 hydrolysate is then added dropwise, followed by 1.5 parts by weight of nano-zinc oxide. The reaction is carried out for 9 h. The mixture is then magnetically stirred at 2000 rpm for 1 h, then at 1500 rpm for 2 h, then at 1000 rpm for 3 h, and finally at 500 rpm for 3 h. Finally, 20 wt.% acetic acid is used to break the emulsion, resulting in a co-precipitate of granules. The co-precipitated granules are then washed and dried. The average particle size of silica in the finished granular adhesive is 20 nm, the silica loss rate is 4.6%, and the carbon black dispersion is improved by 5 grades.

[0041] Example 6 An in-situ synthetic wet-process compounded granular adhesive and its preparation method are disclosed. The process is as follows: First, 3 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=4 for 10 h. Then, 20 wt.% natural latex (100 parts by dry weight) and 10 wt.% water glass (30 parts by dry weight) are mixed evenly and stirred magnetically at 2000 rpm in a 50 ℃ constant temperature water bath. The Si69 hydrolysate is then added dropwise, followed by 1 part by weight of nano-zinc oxide. The reaction is carried out for 9 h. The mixture is then magnetically stirred at 2000 rpm for 1 h, then at 1000 rpm for 2 h, then at 500 rpm for 3 h, and finally at 200 rpm for 3 h. Finally, 25 wt.% acetic acid is used to break the emulsion, resulting in a co-precipitate of granules. The co-precipitated granules are then washed and dried. The average particle size of silica in the finished granular adhesive is 22 nm, the silica loss rate is 4.7%, and the silica dispersion is improved by 5 grades.

[0042] Example 7 An in-situ synthetic wet-process compounded granular adhesive and its preparation method are disclosed. The process is as follows: First, 2 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=4 for 12 h. Then, 20 wt.% natural latex (90 parts by dry weight) and 10 wt.% water glass (45 parts by dry weight) are mixed evenly and stirred magnetically at 2000 rpm in a 50 ℃ constant temperature water bath. The Si69 hydrolysate is then added dropwise, followed by 1.5 parts by weight of nano-zinc oxide. The reaction is carried out for 9 h. The mixture is then magnetically stirred at 2000 rpm for 1 h, then at 1500 rpm for 3 h, then at 500 rpm for 2 h, and finally at 200 rpm for 3 h. Finally, 30 wt.% acetic acid is used to break the emulsion, resulting in a co-precipitate of granules. The co-precipitated granules are then washed and dried. The average particle size of silica in the finished granular adhesive is 26 nm, the silica loss rate is 4.8%, and the silica dispersion is improved by 4 grades.

[0043] Example 8 An in-situ synthetic wet-process compounded granular adhesive and its preparation method are disclosed. The process is as follows: First, 4 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=4 for 11 h. Then, 20 wt.% natural latex (dry weight 110 parts) and 10 wt.% water glass (dry weight 25 parts) are mixed evenly and stirred magnetically at 2000 rpm in a 60 ℃ constant temperature water bath. The Si69 hydrolysate is then added dropwise, followed by 1.5 parts by weight of nano-zinc oxide. The reaction is carried out for 9 h. The mixture is then magnetically stirred at 2000 rpm for 1 h, then at 1000 rpm for 2 h, then at 500 rpm for 2 h, and finally at 200 rpm for 4 h. Finally, 30 wt.% acetic acid is used to break the emulsion, resulting in a co-precipitate of granules. The co-precipitated granules are then washed and dried. The average particle size of silica in the finished granular adhesive is 20 nm, the silica loss rate is 2.8%, and the silica dispersion is improved by 3 grades.

[0044] Example 9 An in-situ synthetic wet-mixed granular rubber and its preparation method are disclosed. The process is as follows: First, 3 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=3.5 for 10 h. 20 wt.% natural latex (100 parts by dry weight) and 10 wt.% water glass (45 parts by dry weight) are mixed evenly and stirred magnetically at 2000 rpm in a 50 ℃ constant temperature water bath. The Si69 hydrolysate is added dropwise, followed by 1.5 parts by weight of nano zinc oxide. The reaction is carried out for 9 h. The mixture is then stirred magnetically at 2000 rpm for 1 h, then at 1800 rpm for 2 h, then at 1000 rpm for 2 h, then at 500 rpm for 2 h, and finally at 200 rpm for 2 h. Finally, 30 wt.% acetic acid is used to break the emulsion, resulting in the formation of granular coprecipitates. The coprecipitated particles are then washed and dried. The average particle size of silica in the finished granulated adhesive is 28 nm, the silica loss rate is 4.5%, and the carbon black dispersion is improved by 5 levels.

[0045] Example 10 An in-situ synthetic wet-process compounded granular adhesive and its preparation method are disclosed. The process is as follows: First, 2 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=4 for 10 h. Then, 20 wt.% natural latex (90 parts by dry weight) and 10 wt.% water glass (30 parts by dry weight) are mixed evenly and stirred magnetically at 2000 rpm in a 45 ℃ constant temperature water bath. The Si69 hydrolysate is then added dropwise, followed by 1 part by weight of nano-zinc oxide. The reaction is carried out for 9 h. The mixture is then magnetically stirred at 2000 rpm for 1 h, then at 1000 rpm for 4 h, then at 500 rpm for 3 h, and finally at 200 rpm for 1 h. Finally, 15 wt.% acetic acid is used to break the emulsion, resulting in a co-precipitate of granules. The co-precipitated granules are then washed and dried. The average particle size of silica in the finished granular adhesive is 25 nm, the silica loss rate is 4.1%, and the silica dispersion is improved by 6 grades.

[0046] Comparative Example 1 A wet-process compounded granular rubber and its preparation method are disclosed. The process is as follows: First, 3 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=4 for 8 h, and then added to 37 parts by weight of 10 wt.% water glass. The mixture is reacted at 50 ℃ and 1000 rpm for 3 h to generate silica. Silica slurry is then added to 100 parts by weight of 20 wt.% natural rubber latex, and the mixture is reacted at 50 ℃ and a constant speed of 1000 rpm for 5 h. Finally, 20 wt.% acetic acid is used to break the emulsion to obtain the wet-process compounded rubber. The silica in the finished rubber is agglomerated, with an average particle size of 158 nm (e.g., ...). Figure 2 As shown in b), the loss rate of silica was 37.6%, and the dispersion of silica improved by 6 levels.

[0047] Comparative Example 2 A wet-process compounded granular rubber and its preparation method are disclosed. The process is as follows: First, 3 parts by weight of Si69 are hydrolyzed in diluted alcohol at pH=4 for 8 h, and then added to 37 parts by weight of 10 wt.% water glass. The mixture is reacted at 50 ℃ and 1000 rpm for 3 h to generate silica. After washing away the sodium salts, deionized water is added to make the silica mass fraction 10 wt.%. Silica slurry is added to 100 parts by weight of 20 wt.% natural rubber latex, and the mixture is reacted at 50 ℃ and a constant speed of 1000 rpm for 5 h. The mixture is then demulsified with 20 wt.% acetic acid to obtain the wet-process compounded rubber. In the finished rubber, silica agglomerates with an average particle size of 42 nm, silica loss rate is 17.7%, and silica dispersion is improved by 6 grades.

[0048] The particle size of the silica in the in-situ synthesized wet-mixed granulated rubber of Examples 1-10 was tested, and the results were analyzed as follows: Figure 3 As shown, the loss rate of its silica was tested, and the results were analyzed as follows. Figure 4 As shown.

[0049] Combination Figures 2-3 Compared with Comparative Examples 1 and 2, Examples 1-10 involved adding a hydrolyzed silane coupling agent solution to a water glass solution. The water glass solution was alkaline, while the silane coupling agent solution was acidic. Hydrogen ions formed hydrogen bonds with oxygen in the silane coupling agent, making the silane coupling agent acidic. Upon addition, an acidic microenvironment was formed in the water glass solution, thereby forming nano-silica. This microenvironment resulted in smaller nano-silica with a particle size of less than 35 nm. At the same time, the overall alkaline environment ensured uniform dispersion of the silica without agglomeration.

[0050] The in-situ synthesized wet-mixed granular rubber prepared in Examples 1-10 above can be used to prepare tread rubber, that is, to prepare wet-mixed final rubber.

[0051] Application Example 1 A method for preparing tire tread compound by in-situ synthesis of wet-mixed granular rubber is described below: (1) The 128 phr wet-mixed granulated rubber, 12 phr high abrasion-resistant carbon black, 3 phr silane coupling agent, 3 phr antioxidant, 2 phr protective wax, 2 phr stearic acid, 4 phr zinc oxide and 2 phr dispersant prepared in Example 3 above are mixed in an internal mixer at a speed of 40~50 rpm until the temperature reaches 135~140℃. The rubber is discharged into an extruder and extruded by the screw. The rubber is then rolled off the sheet, cooled to 40~45℃ and left to stand for 8~24 hours to obtain a first-stage mixed masterbatch. (2) Mix the first stage of masterbatch with 1.5 phr sulfur, 1.5 phr accelerator, 0.1 phr anti-scorching agent and 1 phr anti-sulfurization reducing agent in a mixer at a speed of 20~30 rpm for two stages of mixing. Mix until 110~115℃, discharge the rubber, and obtain tire tread rubber.

[0052] Comparative Example 3 A type of tread compound, the manufacturing process of which is as follows: (1) 100 phr smoked sheet rubber, 12 phr high abrasion resistant carbon black, 3 phr silane coupling agent, 3 phr antioxidant, 2 phr protective wax, 2 phr stearic acid, 4 phr zinc oxide and 2 phr dispersant are placed in an internal mixer and internally mixed at a speed of 40~50 rpm until the temperature reaches 135~140℃. The rubber is discharged into an extruder and extruded by the screw. The rubber is then rolled off the sheet and cooled to 40~45℃. The sheet is left to stand for 8~24 hours to obtain a first-stage compound masterbatch. (2) Mix the first stage of masterbatch with 1.5 phr sulfur, 1.5 phr accelerator, 0.1 phr anti-scorching agent and 1 phr anti-sulfurization reducing agent in a mixer at a speed of 20~30 rpm for two stages of mixing. Mix until 110~115℃, discharge the rubber, and obtain tire tread rubber.

[0053] Comparative Example 4 A wet-process method for preparing tire tread compound from granulated rubber is described below: (1) The 128 phr wet-mixed granulated rubber, 12 phr high abrasion-resistant carbon black, 3 phr silane coupling agent, 3 phr antioxidant, 2 phr protective wax, 2 phr stearic acid, 4 phr zinc oxide and 2 phr dispersant prepared in Comparative Example 2 were mixed in an internal mixer at a speed of 40~50 rpm until the temperature reached 135~140℃. The rubber was discharged into an extruder and extruded by the screw. The rubber was then rolled off the sheet and cooled to 40~45℃. The sheet was left to stand for 8~24 hours to obtain a first-stage mixed masterbatch. (2) Mix the first stage of masterbatch with 1.5 phr sulfur, 1.5 phr accelerator, 0.1 phr anti-scorching agent and 1 phr anti-sulfurization reducing agent in a mixer at a speed of 20~30 rpm for two stages of mixing. Mix until 110~115℃, discharge the rubber, and obtain tire tread rubber.

[0054] The performance of the tire tread compounds prepared in Application Example 1, Comparative Example 3 and Comparative Example 4 was tested, and the results are shown in Table 1 and Table 2.

[0055] Table 1. Vulcanization characteristics of tire tread compound ; As can be seen from Table 1, the tread rubber of Application Example 1 has basically the same processing performance as the tread rubbers of Comparative Example 3 and Comparative Example 4, but its vulcanization speed is slightly faster than that of Comparative Example 3 and Comparative Example 2.

[0056] Table 2 Tire tread compound ; As can be seen from Table 2, the physical and mechanical strength and tear strength of the tread compound of Application Example 1 are basically the same as those of the tread compound of Comparative Example 3, and the tread compound of Comparative Example 4 has better performance. Moreover, the heat generation performance, hysteresis performance and carbon black dispersion performance of the tread compound of Application Example 1 are better than those of Comparative Example 3 and Comparative Example 4.

[0057] Referring to Tables 1 and 2, in Example 3 of this invention, the protective layer on the surface of the natural rubber latex underwent micro-cracks in the aforementioned acidic microenvironment. Furthermore, upon heating, a portion of the ammonia in the natural rubber latex was released as ammonia gas, reducing the alkalinity of the solution and further damaging the protective layer. Nano-silica then entered the natural rubber latex particles under van der Waals forces and mechanical stirring. The added zinc oxide promoted the bridging of sulfur atoms on the silane coupling agent with the natural rubber latex, enhancing interfacial bonding. Moreover, the carbon black dispersion in the tread rubber prepared by this invention is significantly improved, offering advantages such as performance enhancement, reduced rolling resistance, increased vulcanization efficiency, enhanced rubber properties, innovation, and wide applicability.

[0058] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit and essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0059] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An in-situ synthesized wet-mixed granular rubber, characterized in that, The wet-process compound comprises the following raw materials in parts by weight: 90-110 parts by dry weight of natural rubber latex, 25-45 parts by dry weight of water glass, 2-4 parts by dry weight of silane coupling agent, and 0.5-1.5 parts by weight of zinc oxide.

2. The in-situ synthesized wet-mixed granular rubber according to claim 1, characterized in that, In the preparation of wet-mixed granulated adhesive, the water glass reacts to form nano-silica, and the silica particle size is less than 35nm, and the silica loss rate is less than 5%; the particle size of the wet-mixed granulated adhesive is less than 3mm.

3. The in-situ synthesized wet-mixed granular rubber according to claim 1, characterized in that, The silane coupling agent is a sulfur- or mercapto-containing silane coupling agent.

4. The in-situ synthesized wet-mixed granular rubber according to claim 3, characterized in that, The silane coupling agent is one of Si69, Si75, or Si747.

5. The in-situ synthesized wet-mixed granular rubber according to claim 1, characterized in that, The natural latex is a fresh latex or a concentrated natural latex diluted to a mass fraction of 15-25 wt.%; The water glass is a solution of sodium silicate diluted to a mass fraction of 5-20 wt.%.

6. A method for preparing in-situ synthesized wet-mixed granular rubber according to claim 1, characterized in that, Includes the following steps: S1. Hydrolysis of silane coupling agent: Add 5-30 wt.% hydrochloric acid to diluted alcohol to adjust the pH of the solution to acidic, then add silane coupling agent, stir for 5-30 min to hydrolyze it, and let it stand for 5-12 h to obtain silane coupling agent hydrolysate. S2. Preparation of wet-process compounded granular rubber containing silica: Natural rubber latex and water glass are mixed evenly, and the mixture is kept in a constant temperature water bath at 40~60 ℃ and magnetically stirred at 100~2000 rpm. Silane coupling agent hydrolysate is added dropwise, and nano zinc oxide is added. The reaction is carried out for 5~12 h, and then acetic acid with a concentration of 5~30 wt.% is used to break the emulsion, so that the whole mixture forms a granular coprecipitate. The pH of the system is made neutral, and the coprecipitated particles are washed and dried to obtain wet-process compounded granular rubber.

7. The method for preparing an in-situ synthesized wet-mixed granular rubber according to claim 6, characterized in that, In step S1, the diluted alcohol is medical alcohol, industrial alcohol, or alcohol prepared by mixing anhydrous ethanol and deionized water at a mass ratio of 9:1; the mass of the diluted alcohol is 10 to 12 times the mass of the silane coupling agent; and the pH of the solution is 3 to 5.

8. The method for preparing an in-situ synthesized wet-mixed granular rubber according to claim 6, characterized in that, In step S2, after the co-precipitated particles are washed, they do not need to be pressed or creped; they are dried directly. The moisture content after drying is 3-5%.

9. The method for preparing an in-situ synthesized wet-mixed granular rubber according to claim 6, characterized in that, During the reaction in step S2, the stirring speed is varied under magnetic stirring conditions of 100~2000 rpm; The variable speed stirring is carried out in stages at a speed of 100~2000 rpm. The variable speed stirring is a segmented constant speed stirring that gradually decreases from 2000 rpm to 100 rpm. As the stirring speed gradually decreases, the corresponding stirring time remains unchanged or increases. The sum of all stirring times is the reaction time.

10. An in-situ synthesized wet-mixed granular rubber prepared according to any one of claims 1 to 9 is used in the preparation of tire tread compound, wherein the specific preparation process of the tire tread compound is as follows: (1) Wet-mixed granulated rubber is mixed with high abrasion-resistant carbon black, silane coupling agent, antioxidant, protective wax, stearic acid, zinc oxide and dispersant in an internal mixer at a speed of 40~50 rpm. The mixture is then mixed to 135~140℃, discharged into an extruder, and extruded by the screw. The extruded rubber is then rolled off the sheet, cooled to 40~45℃, and left to stand for 8~24 hours to obtain a first-stage mixed masterbatch. (2) Mix the first stage masterbatch with sulfur, accelerator, anti-scorching agent and anti-sulfurization reducing agent in a mixer at a speed of 20~30 rpm for two stages of mixing. Mix until 110~115℃, then discharge the rubber to obtain tire tread rubber.

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