A process for the preparation of a full-formulated sulfur-containing rubber composite material by wet mixing

Abstract

This invention relates to a method for preparing a sulfur-containing fully formulated wet-process rubber composite material: First, silica-coated sulfur (SiO2@S) is prepared using a liquid-phase synthesis method, and then spray-dried to obtain its powder. Next, a wet-process mixing process is used to prepare a dispersion of SiO2@S with other reinforcing fillers and various rubber additives. This dispersion is then mixed with latex, flocculated, and dried to obtain the SiO2@S fully formulated wet-process rubber composite material. The method utilizes in-situ liquid-phase growth to coat the sulfur surface with nano-silica, followed by spray drying, effectively controlling the powder particle size and reducing agglomeration. The silica coating helps improve the stability of the sulfur-containing fully formulated wet-process rubber compound during subsequent high-temperature drying, preventing pre-vulcanization. Pre-mixing various additives and fillers in the liquid phase, followed by flocculation and precipitation with the rubber latex or solvent evaporation after mixing with the rubber solution, improves the dispersibility of fillers and additives, reduces mixing losses, minimizes losses during the addition of rubber additives, and enhances the overall performance of the rubber.

Description

Technical Field

[0001] This invention belongs to the technical field of wet-process rubber composite materials, specifically relating to a method for preparing a sulfur-containing, fully formulated wet-process rubber composite material. The prepared wet-process rubber compound can be used in rubber-related fields such as tires, footwear materials, and tracks. Background Technology

[0002] Traditional rubber product manufacturing primarily relies on dry mixing, but this method is energy-intensive, limits the amount of filler that can be added, results in poor dispersibility between fillers and additives, and poses significant environmental and worker hazards, leading to its gradual replacement by wet mixing. Currently, wet mixing technology can effectively improve filler dispersibility, reduce production energy consumption, and increase the amount of filler added to the rubber matrix. However, most production methods still rely on dry mixing to add rubber additives to the rubber.

[0003] By pre-dispersing fillers and all rubber additives in a suitable solvent through wet mixing, a fully formulated wet mixing process can be achieved. This improves the dispersibility of fillers and rubber additives in the rubber matrix, significantly reducing energy consumption in subsequent rubber processing. Simultaneously, the fully formulated wet mixing technology can improve the overall performance of rubber, achieving environmentally friendly, energy-saving, and efficient production. Currently, there are relevant patents, such as Chinese patent CN 111171390 B, which discloses a method for preparing a silica / natural rubber composite material. This method utilizes a wet mixing process, where silica is mechanically ground to prepare a uniform dispersion solution. After mixing with natural latex, slow stirring ensures sufficient contact between the natural latex and silica. The positive charge generated by high-temperature atomization flocculates the negatively charged natural latex, encapsulating the silica within it. After dehydration and drying, the silica / natural rubber composite material is obtained. Chinese Patent CN 114316388 A discloses a low-energy wet-process rubber compounding method and its preparation method. Step 1: Weigh each raw material component according to the specified weight proportions; Step 2: Mix the protective agent with the rubber latex, then add an activator, accelerator, sulfur, antioxidant, and other dispersants and mix thoroughly. Add an active reinforcing agent, disperse and stir until viscous and coagulated; Step 3: Extrude the coagulated emulsion through a double-roller press and air-dry naturally to obtain wet-process compounded raw rubber. Chinese Patent CN 105690587 B discloses a wet-process rubber compounding method involving atomization followed by mixing. The materials are prepared into various solutions, atomized, and then introduced into a mixing chamber to complete diffusion, contact, and mixing, thus achieving the compounding effect. The atomized solutions are then collected and stirred to obtain a rubber composite.

[0004] However, existing full-formula wet mixing technologies only achieve wet mixing of fillers and some additives, while vulcanizing agents and accelerators are still added through dry mixing using an open mill or internal mixer; or the full-formula wet technology does not fully achieve high-temperature drying, which will lead to excessively long drying time and low production efficiency in actual production. Therefore, in order to further optimize the process and expand the applicability of full-formula wet mixing, this application was developed. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for preparing a sulfur-containing full-formulation wet-process rubber composite material. By coating the sulfur surface with silica, the stability of the sulfur-containing full-formulation wet-process rubber compound during the subsequent high-temperature drying process is improved, and pre-vulcanization is avoided. Pre-mixing various additives and fillers in the liquid phase and then mixing them with latex for flocculation and precipitation is beneficial to improving the dispersibility of fillers and additives, reducing mixing losses, minimizing losses during the rubber additive addition process, and enhancing the overall performance of the rubber.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a sulfur-containing, fully formulated wet-mixed rubber composite material, comprising the following steps: 1) Preparation of SiO2@S dispersion by liquid phase synthesis: Sulfur is dispersed in the reaction medium using surfactants, polymers or nanoparticles. Sodium silicate or silicate ester is used to carry out hydrolysis reaction in the reaction medium and adsorb onto the surface of sulfur. Then, the mixture is aged and further hydrolyzed on the surface of sulfur to form a dense silica shell, thus obtaining SiO2@S dispersion. 2) Spray drying: The SiO2@S dispersion is mixed with a binder and then spray dried to granulate, thus obtaining SiO2@S powder; 3) Preparation of sulfur-containing water-based fully formulated wet-process rubber composite material: The reinforcing filler is dispersed in a certain amount of pure water, and vulcanizing agent, silane coupling agent, antioxidant, protective wax, activator and accelerator are added in sequence. The filler and fully formulated additives are heated and stirred to obtain an aqueous dispersion of filler and fully formulated additives. The flocculant is prepared into a dispersion of a certain concentration, and the rubber latex is mixed with the aqueous dispersion and dispersion, stirred and flocculated, filtered and dried to obtain the sulfur-containing fully formulated wet-process rubber composite material. Alternatively, the preparation of sulfur-containing oil-based fully formulated wet-mixed rubber composite materials is as follows: reinforcing fillers are dispersed in a certain amount of organic solvent or pure water, and vulcanizing agents, silane coupling agents, antioxidants, protective waxes, activators, and accelerators are added. The fillers and fully formulated additives are heated and stirred to obtain an emulsion dispersion of fillers and fully formulated additives. The oil-based rubber solution is mixed and stirred with the emulsion dispersion, and then distilled under reduced pressure and dried to obtain the final product.

[0007] Specifically, the sulfur includes, but is not limited to, one or two of sublimed sulfur and oil-extended sulfur; the reaction medium can be one or more combinations of water, C2-C12 alcohols, acetone, etc.

[0008] Specifically, the surfactant can be one or more of the following: anionic surfactants such as sulfonates, carboxylic acids, sulfates, and phosphates; cationic surfactants such as quaternary ammonium salts, amine salts, and heterocyclic types; nonionic surfactants such as polyoxyethylene, polyols, polyethers, and alkanolamides; and amphoteric surfactants such as amino acids and betaines. The polymer is one or more of the following: polyvinyl alcohol, polyethylene glycol, and polyvinylpyrrolidone. The nanoparticles are one or more of the following: silica, titanium dioxide, calcium carbonate, zinc oxide, kaolin, and magnesium oxide. The amount of surfactant, polymer, or nanoparticle used is 1%-10% of the sulfur mass, the dispersion time is 1-3 hours, and the dispersion temperature is 20℃-80℃.

[0009] Specifically, the silicate ester is a C1-C6 orthosilicate with a concentration of 0.1-5 mol / L in the reaction medium; the sodium silicate has a concentration of 0.1 mol / L-5 mol / L in the reaction medium; the amount of sodium silicate or silicate ester modified with sulfur is 3%-10%; the hydrolysis reaction temperature is 40℃-80℃; the hydrolysis reaction time is 1-3 h; and the stirring and aging time is 1-3 h at a temperature of 20℃-80℃.

[0010] Furthermore, the hydrolysis reaction occurs between pH 3 and 11, and the pH can be adjusted using acid, ammonia, or ammonium salt solution. The acids that can be used are inorganic acids and organic acids, including but not limited to inorganic acids such as hydrochloric acid and sulfuric acid, and water-soluble organic acids with carboxyl groups, sulfonic acid groups, sulfinic acid groups, or thiocarboxylic acid groups, such as citric acid, formic acid, and acetic acid.

[0011] Further, the binder is one or more of the following saturated or unsaturated polymers: natural rubber latex, styrene-butadiene rubber latex, itaconic acid ester rubber latex, chloroprene rubber latex, polyurethane rubber latex, nitrile rubber latex, polyvinyl acetate latex, gum arabic, gelatin, dextrin, cellulose, polyvinyl alcohol, polyvinylpyrrolidone, etc., and its dosage is 1%-42% of the sulfur mass. When the binder is natural rubber latex, styrene-butadiene rubber latex, itaconic acid ester rubber latex, chloroprene rubber latex, polyurethane rubber latex, nitrile rubber latex, or polyvinyl acetate latex, more preferably, the binder dosage, based on solid content, is 1%-30% of the sulfur mass. The inlet air temperature of the spray dryer is 150℃-300℃, the outlet air temperature is 100℃-150℃, the solid content of the SiO2@S dispersion is 5%-30%, and the feed rate is 5-100 rpm.

[0012] Specifically, the vulcanizing agent can be one or more of sublimed sulfur, oil-extended sulfur, SiO2@S powder, etc.; the reinforcing filler can be one or more of silica, calcium carbonate, carbon black, duplex carbon black, pyrolysis carbon black, titanium dioxide, reactive silica, waste rubber powder, modified waste rubber powder, etc.; wherein the reactive silica is purchased from Henan Hebei University Nanomaterials Engineering Research Center Co., Ltd., and its surface has one or more functional groups of mercapto, polysulfide, epoxy, amino, double bond, etc. The silane coupling agent can be an organic chain segment containing 1-3 silicon-carbon bonds and functional groups, the organic chain containing 1-12 carbon atoms, and the functional groups including one or more of thiol, polysulfide, epoxy, amino, double bond, etc.; the antioxidant includes one or more of ketone amines, aldehyde amines, diaryl secondary amines, diphenylamine, p-phenylenediamine, and alkylaryl secondary amines, etc.; the protective wax includes one or more of paraffin wax, microcrystalline wax, polyethylene wax, etc.; the activator is one or more of zinc oxide, magnesium oxide, lead oxide, stearic acid, amine, etc.; the accelerator includes one or more of thiourea, aldehyde amines, guanidines, thiazoles, sulfenamides, thiurams, dithiocarbamates, xanthates, etc.

[0013] Specifically, the rubber includes water-based rubber latex and oil-based rubber solution (oil-based rubber dissolved in an organic solvent to obtain a solution). The water-based rubber latex includes natural rubber latex and synthetic rubber emulsions, including but not limited to one or more mixtures of natural rubber latex, styrene-butadiene rubber emulsion, itaconic acid ester rubber emulsion, chloroprene rubber emulsion, polyurethane rubber emulsion, and nitrile rubber emulsion. The oil-based rubber solution (oil-based rubber dissolved in an organic solvent to obtain a solution, distinct from synthetic rubber emulsions) includes but not limited to one or more mixtures of solution-polymerized styrene-butadiene rubber, ethylene propylene diene monomer (EPDM), cis-butadiene rubber, and styrene-acrylic rubber. The total solid content of the rubber components in the aqueous dispersion or emulsion dispersion is 1%-60%. The flocculant includes but is not limited to one or more of formic acid, acetic acid, sodium chloride, calcium chloride, magnesium chloride, zinc sulfate, and aluminum sulfate. The oil-based rubber solution does not require the addition of flocculants. The organic solvent includes but is not limited to one or more of benzene, toluene, n-hexane, and cyclohexane.

[0014] Further, in step 3), the amounts of each raw material, by weight, are as follows: 60-140 parts of dry rubber, 30-70 parts of reinforcing filler, 0.1-5 parts of vulcanizing agent, 3-7 parts of silane coupling agent, 0.1-5 parts of antioxidant, 0.1-5 parts of protective wax, 0.1-10 parts of activator, 0.1-5 parts of accelerator, and 6-14 parts of flocculant. The water-based rubber latex or oil-based rubber solution is measured in dry rubber. More preferably, based on 100 parts of dry rubber, the amount of flocculant is 6-14 parts.

[0015] Preferably, the preparation method of the sulfur-containing fully formulated wet-mixed rubber composite material includes the following specific steps: 1) Preparation of sulfur-containing water-based fully formulated wet-mixed rubber composite materials: Step 1: Disperse the reinforcing filler in a certain amount of pure water to prepare a dispersion with a solid content of 5%-20%. Stir and disperse the mixture in a sand mill at a speed of 1200-1800 rpm for 20-60 minutes. Step 2: Add vulcanizing agent, stir and disperse in a sand mill at 1200-1800 rpm for 20-60 minutes; Step 3: Add silane coupling agent, and disperse by stirring in a sand mill at 1200-1800 rpm for 20-60 minutes; Step 4: Add antioxidants, protective waxes, and some activators and other oily additives. Heat and stir the mixture in a sand mill to disperse it. The polymer or special functional groups grafted onto the surface of the reactive silica are emulsified and dispersed in the aqueous dispersion. The reaction temperature is 60-90℃, the rotation speed is 1200-1800rpm, and the time is 20-60min. Step 5: Add the remaining activator and accelerator, and disperse by stirring in a sand mill at a speed of 1200-1800 rpm for 20-60 minutes to obtain an aqueous dispersion of filler and all the additives in the formulation. Step 6: Prepare a second dispersion of flocculant with a certain concentration, the second dispersion having a solid content of 1%-15%; Step 7: Dilute the rubber latex to a solid content of 5%-40%, mix it with the above-mentioned aqueous dispersion one and dispersion two, stir and flocculate, filter, and dry to obtain a water-based fully formulated wet-mixed rubber composite material containing sulfur.

[0016] 2) Preparation of sulfur-containing oil-based fully formulated wet-mixed rubber composites: Step 1: Disperse the reinforcing filler in a certain amount of organic solvent to prepare a dispersion with a solid content of 5%-20%, and disperse it by mechanical stirring at a speed of 200-1000 rpm for 20-60 min. Step 2: Add vulcanizing agent, silane coupling agent, antioxidant, protective wax, activator, and accelerator; disperse by mechanical stirring; heat at 200-1000 rpm for 20-60 minutes. Step 3: The organic solvent is recovered by vacuum distillation and dried to obtain a sulfur-containing oil-based wet-mixed rubber composite material.

[0017] The innovations of this invention are as follows: First, nano-silica is coated onto the surface of sulfur through in-situ liquid-phase growth, followed by spray drying, effectively controlling the powder particle size and reducing agglomeration. Second, the silica coating helps improve the stability of the sulfur-containing full-formulation wet-process rubber compound during subsequent high-temperature drying, preventing pre-vulcanization. Third, pre-mixing various additives and fillers in the liquid phase before mixing them with the latex for flocculation and precipitation improves the dispersibility of fillers and additives, reduces mixing losses, minimizes losses during rubber additive addition, and enhances the overall performance of the rubber. Fourth, the sulfur-containing full-formulation wet-process rubber compound can be directly vulcanized into finished products by downstream users, reducing mixing steps, lowering production energy consumption, and saving production costs.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention first introduces a vulcanizing agent into a fully formulated wet-process rubber compound, further simplifying the rubber processing technology, reducing processing energy consumption, and facilitating downstream manufacturers' processing and molding. Furthermore, the performance of the fully formulated wet-process rubber compound is improved through the coating of sulfur with silica. Specifically, it offers the following advantages: ① Silica coating helps improve the stability of the sulfur-containing fully formulated wet-process rubber compound during subsequent high-temperature drying, preventing pre-vulcanization; ② Pre-mixing various additives and fillers in the liquid phase before mixing them with the latex for flocculation and precipitation improves the dispersibility of fillers and additives, reduces mixing losses, minimizes losses during the addition of rubber additives, and enhances the overall performance of the rubber; ③ The sulfur-containing fully formulated wet-process rubber compound can be directly vulcanized into finished products by downstream users, reducing mixing steps, lowering production energy consumption, and saving production costs. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be described in complete and clear form below. The described embodiments are only some embodiments of the present invention, and not all embodiments. The following descriptions are only preferred embodiments of the present invention and are used merely to explain the present invention. They should not be construed as limiting the scope of the present invention, that is, the protection scope of the present invention is not limited thereto.

[0020] Unless otherwise specified, all raw materials used are commercially available products that can be directly purchased or prepared using conventional methods in the field. For example, reactive silica was purchased from Henan Hebei University Nanomaterials Engineering Research Center Co., Ltd., including models 251, 308, and 315. Model 251 reactive silica was used in the following examples and comparative examples. Antioxidant was purchased from Sheng'ao Chemical Technology Co., Ltd., model 4020. Here, phr refers to parts by mass.

[0021] The present invention will be further illustrated by the following examples.

[0022] Example 1 Weigh 20g of sublimed sulfur, 1.00g of PEG-4000 polyethylene glycol-4000, and 1.00g of CTAB cetyltrimethylammonium bromide. Add 178.00g of pure water to prepare a dispersion with a solid content of 10%. Stir at 300-500 rpm and ultrasonically stir at room temperature for 1 hour to obtain a sulfur dispersion.

[0023] Based on a silica modification amount of 6%, 5.00 g of sodium silicate and 3.00 g of sulfuric acid (pre-prepared with a concentration of 20%) were weighed and added to 19.41 g and 23.89 g of pure water respectively to prepare solutions with concentrations of 1.00 mol / L and 0.25 mol / L.

[0024] The prepared sodium silicate solution and sulfuric acid solution were added to the sulfur dispersion in a co-current flow for 2 hours. The reaction temperature was 40℃, the pH value was 9, and the stirring speed was controlled at 300-500 rpm. After the co-current reaction was completed, the mixture was aged at a constant temperature for 2 hours to form a silica shell on the surface of the sulfur.

[0025] The reacted sulfur dispersion was mixed with 8.33g of styrene-butadiene rubber latex (solid content 60%), stirred at 800rpm for 30min, and then spray-dried to obtain SiO2@S powder. The inlet air temperature was 180-220℃, the outlet air temperature was 100-120℃, and the feed rate was 25rpm.

[0026] 50 phr of reactive silica was dispersed in 450 phr of pure water to prepare an aqueous dispersion with a solid content of 10%. The dispersion was stirred in a sand mill at 1500 rpm for 30 minutes.

[0027] Add 1.5 phr of SiO2@S vulcanizing agent powder, and disperse it in a sand mill at 1500 rpm for 30 minutes.

[0028] Add 5 phr of silane coupling agent Si-69, and disperse in a sand mill at 1500 rpm for 30 minutes.

[0029] Add 1.5 phr of antioxidant 4020, 1.5 phr of microcrystalline wax, and 1.5 phr of stearic acid. Disperse the mixture by heating and stirring in a sand mill at 90°C, 1500 rpm, and 30 min.

[0030] Add 1.5 phr of zinc oxide, 2 phr of accelerator CZ, and 1 phr of accelerator D, and disperse in a sand mill at 1500 rpm for 30 min to obtain an aqueous dispersion of filler and all the additives in the formulation.

[0031] Prepare a dispersion of 10 phr of calcium chloride flocculant with a solid content of 10%.

[0032] Based on a dry weight of natural rubber of 100 phr, a concentrated natural latex with a solid content of 60% and a preservative ammonia content of 166.7 phr (Hainan Natural Rubber Industry Group Co., Ltd., the same below) was diluted to 30% and mixed with the above two aqueous dispersions, dispersion one and dispersion two. After stirring and flocculation, filtration and drying, a sulfur-containing full-formula wet-mixed rubber composite material was obtained.

[0033] The sulfur-containing wet-process compound rubber composite material prepared above was plasticized and shaped on a two-roll mill to obtain a compound rubber composite material. Then it was vulcanized (vulcanization temperature: 150℃, vulcanization time: T90+5min, vulcanization pressure 20MPa) to make vulcanized test pieces. Relevant performance tests were conducted, and the results are shown in Table 1.

[0034] Example 2 Weigh 20.00g of sublimed sulfur, 1.00g of CTAB, and 1.00g of OP-10 dodecylphenol polyoxyethylene ether, add 178.00g of pure water, and prepare a dispersion with a solid content of 10%. Stir at 300-500 rpm and ultrasonically stir at room temperature for 1 hour to obtain a sulfur dispersion.

[0035] Based on a silica modification amount of 5%, 4.12g of sodium silicate and 2.50g of sulfuric acid (pre-prepared with a concentration of 20%) were weighed and added to 16.16g and 19.91g of pure water respectively to prepare concentrations of 1.00mol / L and 0.25mol / L.

[0036] The prepared sodium silicate solution and sulfuric acid solution were fed into the sulfur dispersion in a co-current manner for 1.5 hours. The reaction temperature was 40°C, the pH value was 9, and the stirring speed was controlled at 300-500 rpm. After the co-current reaction was completed, the mixture was aged at a constant temperature for 2 hours to form a silica shell on the surface of the sulfur.

[0037] The reacted sulfur dispersion was mixed with 7.27g of natural rubber latex (solid content 55%), stirred at 800rpm for 30min, and then spray-dried to obtain SiO2@S powder. The inlet air temperature was 180-220℃, the outlet air temperature was 100-120℃, and the feed rate was 25rpm.

[0038] 50 phr of reactive silica was dispersed in 450 phr of pure water to prepare an aqueous dispersion with a solid content of 10%. The dispersion was then stirred in a sand mill at 1700 rpm for 30 minutes.

[0039] Add 1.5 phr of SiO2@S vulcanizing agent powder, and disperse it in a sand mill at 1700 rpm for 30 minutes.

[0040] Add 5 phr of silane coupling agent Si-69, and disperse in a sand mill at 1700 rpm for 30 minutes.

[0041] Add 1.5 phr of antioxidant 4020, 1.5 phr of microcrystalline wax, and 1.5 phr of stearic acid. Disperse the mixture by heating and stirring in a sand mill at 90°C, 1700 rpm, and 30 min.

[0042] Add 1.5 phr of zinc oxide, 2 phr of accelerator CZ, and 1 phr of accelerator D, and disperse in a sand mill at 1700 rpm for 30 min to obtain an aqueous dispersion of filler and all the additives in the formulation.

[0043] Prepare a dispersion of 10 phr of calcium chloride flocculant with a solid content of 10%.

[0044] Based on 100 phr of dry styrene-butadiene rubber, 500 phr of styrene-butadiene rubber emulsion with a solid content of 20% was mixed with the above two aqueous dispersions, dispersion one and dispersion two. After stirring and flocculation, filtration, and drying, the S@SiO2 fully formulated wet-mixed rubber composite material was obtained.

[0045] The fully formulated wet-mixed rubber composite material prepared above was plasticized and shaped on a two-roll mill to obtain a fully formulated rubber composite compound. Then it was vulcanized (vulcanization temperature: 150℃, vulcanization time: T90+5min, vulcanization pressure 20MPa) to make vulcanized test pieces. Relevant performance tests were conducted, and the results are shown in Table 1.

[0046] Comparative Example 1 100 parts of natural rubber dry rubber were weighed out, and 50 parts of reactive silica, 5 parts of silane coupling agent Si-69, 1.5 parts of antioxidant 4020, 1.5 parts of microcrystalline wax, 1.5 parts of stearic acid, 5 parts of activator zinc oxide, 2 parts of accelerator CZ, 1 part of accelerator D, and 1.5 parts of accelerator S were added through dry mixing to obtain dry-mixed rubber. Then, vulcanization was performed (vulcanization temperature: 150℃, vulcanization time: T90+3min, vulcanization pressure: 20MPa) to prepare vulcanized test pieces. Relevant performance tests were conducted, and the results are shown in Table 1.

[0047] Comparative Example 2 50 phr of reactive silica was dispersed in 450 phr of pure water to prepare an aqueous dispersion with a solid content of 10%. This dispersion was then dispersed by stirring in a sand mill at 1700 rpm for 30 minutes to obtain filler aqueous dispersion one. 10 phr of flocculant calcium chloride was prepared to prepare dispersion two with a solid content of 10%. All values ​​are based on 100 phr of dry natural rubber. Concentrated natural latex with a solid content of 60% (166.7 phr, ammonia content of preservative: 0.6%, Hainan Natural Rubber Industry Group Co., Ltd., the same below) was diluted to 30% and mixed with the above two aqueous dispersions I and II. The mixture was stirred and flocculated, filtered, and dried to obtain wet masterbatch. Then, 5 parts of silane coupling agent Si-69, 1.5 parts of antioxidant 4020, 1.5 parts of microcrystalline wax, 1.5 parts of stearic acid, 5 parts of activator zinc oxide, 2 parts of accelerator CZ, 1 part of accelerator D, and 1.5 parts of S were added to a two-roll mill to obtain wet compound. The compound was then vulcanized (vulcanization temperature: 150℃, vulcanization time: T90+3min, vulcanization pressure: 20MPa) to prepare vulcanized test pieces for relevant performance tests. The results are shown in Table 1.

[0048] Comparative Example 3 Taking 100 parts of dry styrene-butadiene rubber as the weight, 100 parts of dry styrene-butadiene rubber were weighed out, and 50 parts of reactive silica, 5 parts of silane coupling agent Si-69, 1.5 parts of antioxidant 4020, 1.5 parts of microcrystalline wax, 1.5 parts of stearic acid, 5 parts of activator zinc oxide, 2 parts of accelerator CZ, 1 part of accelerator D, and 1.5 parts of S were added by dry mixing to obtain dry compound rubber, and then vulcanized (vulcanization temperature: 150℃, vulcanization time: T90+3min, vulcanization pressure 20MPa) to make vulcanized test pieces, and relevant performance tests were carried out. The results are shown in Table 1.

[0049] Comparative Example 4 50 phr of reactive silica was dispersed in 450 phr of pure water to prepare an aqueous dispersion with a solid content of 10%. This dispersion was then dispersed by stirring in a sand mill at 1700 rpm for 30 minutes, yielding filler aqueous dispersion one. 10 phr of flocculant calcium chloride was prepared to prepare dispersion two with a solid content of 10%. Based on a dry weight of styrene-butadiene rubber (SBR) of 100 phr, 500 phr of SBR latex with a solid content of 20% was mixed with the above two aqueous dispersions (dispersion one and dispersion two), stirred to flocculate, filtered, and dried to obtain a wet-process masterbatch. This masterbatch was then added to a two-roll mill with 5 parts of silane coupling agent Si-69, 1.5 parts of antioxidant 4020, 1.5 parts of microcrystalline wax, 1.5 parts of stearic acid, 5 parts of activator zinc oxide, 2 parts of accelerator CZ, 1 part of accelerator D, and 1.5 parts of S to obtain a wet-process compound. Then, vulcanization was performed (vulcanization temperature: 150℃, vulcanization time: T90+3min, vulcanization pressure: 20MPa) to prepare vulcanized test pieces, and relevant performance tests were conducted. The results are shown in Table 1.

[0050] Table 1 Performance Tests Table 1 shows that, under fixed formulation conditions, the vulcanized rubber properties of compounds prepared by different mixing methods differ significantly. In the preparation of fully formulated wet-process rubber compounds, various rubber additives and fillers are pre-dispersed, avoiding uneven mixing of rubber additives during subsequent processing. This also reduces the shearing of rubber molecular chains during plasticizing, retaining more rubber macromolecular chains, which can form more three-dimensional network structures during vulcanization. Therefore, the mechanical properties of vulcanized rubber compounds prepared by fully formulated wet-process rubber compounds are significantly better than those prepared by dry or wet processes.

Claims

1. A process for the preparation of a full-formulated sulfur-containing wet-mixed rubber composite material, characterized in that, Includes the following steps: 1) Preparation of SiO2@S dispersion by liquid phase synthesis: Sulfur is dispersed in the reaction medium using surfactants, polymers or nanoparticles, and hydrolyzed in the reaction medium using sodium silicate or silicate esters, and then aged to obtain SiO2@S dispersion; 2) Spray drying: The SiO2@S dispersion is mixed with the binder and then spray dried and granulated to obtain SiO2@S powder, which is the vulcanizing agent; 3) Preparation of sulfur-containing water-based fully formulated wet-process rubber composite material: The reinforcing filler is dispersed in a certain amount of pure water, and vulcanizing agent, silane coupling agent, antioxidant, protective wax, activator and accelerator are added. The mixture is heated and stirred to obtain an aqueous dispersion of the reinforcing filler and fully formulated additives. The flocculant is prepared into a dispersion of a certain concentration, which is then mixed with the water-based rubber latex and the aqueous dispersions, stirred and flocculated, filtered and dried to obtain the final product. Alternatively, the preparation of sulfur-containing oil-based fully formulated wet-mixed rubber composite material is as follows: the reinforcing filler is dispersed in a certain amount of organic solvent, and vulcanizing agent, silane coupling agent, antioxidant, protective wax, activator and accelerator are added. The mixture is heated and stirred to obtain an emulsion dispersion of the reinforcing filler and the fully formulated additives. The oil-based rubber solution is mixed and stirred with the emulsion dispersion, and then distilled under reduced pressure and dried to obtain the final product. The sulfur includes one or both of sublimed sulfur and oil-extended sulfur; the reaction medium is water. The polymer is one or more of polyvinyl alcohol, polyethylene glycol, and polyvinylpyrrolidone; the nanopowder is one or more of silicon dioxide, titanium dioxide, calcium carbonate, zinc oxide, kaolin, and magnesium oxide; the amount of surfactant, polymer, or nanopowder used is 1%-10% of the mass of sulfur. The concentration of the silicate ester in the reaction medium is 0.1 mol / L to 5 mol / L; the concentration of sodium silicate in the reaction medium is 0.1 mol / L to 5 mol / L. The binder is one or more of the following: natural rubber latex, styrene-butadiene rubber latex, itaconic acid ester rubber latex, chloroprene rubber latex, polyurethane rubber latex, nitrile rubber latex, polyvinyl acetate latex, gum arabic, gelatin, dextrin, cellulose, polyvinyl alcohol, and polyvinylpyrrolidone, and its dosage is 1%-42% of the sulfur mass. In step 3), the water-based rubber latex and oil-based rubber solution are measured as dry rubber and, by weight, the amounts of each raw material are as follows: 60-140 parts dry rubber, 30-70 parts reinforcing filler, 0.1-5 parts vulcanizing agent, 3-7 parts silane coupling agent, 0.1-5 parts antioxidant, 0.1-5 parts protective wax, 0.1-10 parts activator, 0.1-5 parts accelerator, and 6-14 parts flocculant; however, no flocculant is required for oil-based rubber solution.

2. The process for preparing a full-formulated sulfur-containing rubber composite material according to claim 1, characterized in that, The surfactant is anionic, cationic, nonionic, or amphoteric. The anionic surfactant is one or more of sulfonates, carboxylic acids, sulfates, and phosphates; the cationic surfactant is one or more of quaternary ammonium salts, amine salts, and heterocyclic types; the nonionic surfactant is one or more of polyoxyethylene, polyols, polyethers, and alkanolamides; and the amphoteric surfactant is one or two of amino acids and betaines. The dispersion time is 1-3 hours, and the dispersion temperature is 20℃-80℃.

3. The method for preparing the sulfur-containing fully formulated wet-mixed rubber composite material as described in claim 1, characterized in that, The silicate ester is a C1 to C6 orthosilicate; the amount of sodium silicate or silicate ester modified with sulfur is 3%-10%, the hydrolysis reaction temperature is 40℃-80℃, the aging time is 1-3h, and the aging temperature is 20℃-80℃.

4. The method for preparing the sulfur-containing fully formulated wet-mixed rubber composite material as described in claim 1, characterized in that, The hydrolysis reaction occurs between pH 3 and 11, and the pH is adjusted with acid, ammonia, or ammonium salt solution. The acids that can be used are inorganic acids and organic acids. The inorganic acids include hydrochloric acid and sulfuric acid, and the organic acids include water-soluble organic acids with carboxyl groups, sulfonic acid groups, sulfinic acid groups, or thiocarboxylic acid groups.

5. The method for preparing the sulfur-containing fully formulated wet-mixed rubber composite material as described in claim 4, characterized in that, The organic acids include citric acid, formic acid, or acetic acid.

6. The method for preparing the sulfur-containing fully formulated wet-mixed rubber composite material as described in claim 1, characterized in that, The solid content of the SiO2@S dispersion is 5%-30%.

7. The method for preparing the sulfur-containing fully formulated wet-mixed rubber composite material as described in claim 1, characterized in that, The reinforcing filler is one or more of calcium carbonate, silica, carbon black, and titanium dioxide; the antioxidant includes one or more of ketone amines, aldehyde amines, diaryl secondary amines, diphenylamine, p-phenylenediamine, and alkylaryl secondary amines; the protective wax includes one or more of paraffin wax, microcrystalline wax, and polyethylene wax; the activator is one or more of zinc oxide, magnesium oxide, lead oxide, and stearic acid; and the accelerator includes one or more of thiourea, aldehyde amines, guanidines, thiazoles, sulfenamides, thiurams, dithiocarbamates, and xanthates.

8. The method for preparing the sulfur-containing fully formulated wet-mixed rubber composite material as described in claim 1, characterized in that, The reinforcing filler is pyrolysis carbon black.

9. The method of claim 1, wherein the sulfur-containing, fully-formulated, wet- mixed rubber composite is prepared by the steps of: a) mixing the sulfur-containing, fully-formulated, wet-mixed rubber composite of claim 1; and b) curing the sulfur-containing, fully-formulated, wet-mixed rubber composite of claim 1. The flocculant includes one or more of formic acid, acetic acid, sodium chloride, calcium chloride, magnesium chloride, zinc sulfate, and aluminum sulfate, and the organic solvent includes one or more of benzene, toluene, n-hexane, and cyclohexane.

10. The method for preparing the sulfur-containing fully formulated wet-mixed rubber composite material as described in claim 1, characterized in that, The specific steps are as follows: 1) Preparation of sulfur-containing water-based fully formulated wet-mixed rubber composite materials: Step 1: Disperse the reinforcing filler in a certain amount of pure water to prepare a dispersion with a solid content of 5%-20%. Stir and disperse the mixture in a sand mill at a speed of 1200-1800 rpm for 20-60 minutes. Step 2: Add vulcanizing agent, stir and disperse in a sand mill at 1200-1800 rpm for 20-60 minutes; Step 3: Add silane coupling agent, and disperse by stirring in a sand mill at 1200-1800 rpm for 20-60 minutes; Step 4: Add antioxidant, protective wax, and some activator. Heat and stir in a sand mill to disperse the mixture at a temperature of 60-90℃, a speed of 1200-1800 rpm, and a time of 20-60 minutes. Step 5: Add the remaining activator and accelerator, and disperse by stirring in a sand mill at a speed of 1200-1800 rpm for 20-60 minutes to obtain an aqueous dispersion of reinforcing filler and all-formulation additives. Step 6: Prepare a second dispersion of flocculant with a certain concentration, the second dispersion having a solid content of 1%-15%; Step 7: Dilute the water-based rubber latex to a solid content of 5%-40%, mix it with water dispersion one and dispersion two, stir to flocculate, filter, and dry to obtain the final product; 2) Preparation of sulfur-containing oil-based fully formulated wet-mixed rubber composites: Step 1: Disperse the reinforcing filler in a certain amount of organic solvent to prepare a dispersion with a solid content of 5%-20%, and disperse it by mechanical stirring at a speed of 200-1000 rpm for 20-60 min. Step 2: Add vulcanizing agent, silane coupling agent, antioxidant, protective wax, activator, and accelerator; disperse by mechanical stirring; heat at 200-1000 rpm for 20-60 minutes. Step 3: Recover the organic solvent by vacuum distillation, and dry to obtain the final product.

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