A method for preparing emulsion polymerized styrene-butadiene rubber

Abstract

The present application relates to the technical field of synthetic rubber production, in particular to a preparation method of emulsion polymerization styrene-butadiene rubber. The method comprises the following steps: step one, vacuum and nitrogen replacement are performed on a polymerization kettle, and soft water, an emulsifier, a complex electrolyte solution, a reducing agent, tertiary dodecyl mercaptan, styrene and butadiene are sequentially added into the polymerization kettle; when the temperature of the polymerization kettle is reduced to 5 DEG C, an initiator is added; when the conversion rate reaches 60%, a terminating agent is added to terminate the reaction, and styrene-butadiene rubber latex is obtained; step two, the styrene-butadiene rubber latex is added into a dilute sulfuric acid solution, stirred, and reacted for 5-10 minutes; after coagulation, washing and drying, raw rubber products are obtained. The complex electrolyte with compounding function has an excellent effect of regulating the viscosity of the latex, only produces trace amounts of phosphorus-containing and chlorine-containing wastewater, solves the problems of environmental protection discharge and equipment corrosion of the emulsion polymerization styrene-butadiene rubber device, and saves a large amount of environmental protection treatment cost and equipment maintenance and updating cost of the emulsion polymerization styrene-butadiene rubber device.

Description

Technical fields:

[0001] This invention relates to the field of synthetic rubber production technology, and in particular to a method for preparing emulsion styrene-butadiene rubber. Background technology:

[0002] Electrolytes play a crucial role in the polymerization system of latex styrene-butadiene rubber (SBR) production. The addition of an appropriate amount of electrolyte can inhibit latex gelation, improve the fluidity of the polymer emulsion at low temperatures, and increase the polymerization rate. Furthermore, it helps to increase latex particle size and stability. The latex is a charged colloid, and the peptization effect produced by the addition of electrolytes facilitates micelle formation. The optimal electrolyte and its dosage vary depending on the amount of initiator used. Domestic and international SBR plants generally use potassium phosphate or potassium chloride as the electrolyte.

[0003] CN1544522A discloses a method for preparing high-styrene rubber. The method uses SBR-1502 latex containing 23.5±1% styrene, SBR-1500 latex, and high-styrene resin emulsion as raw materials, and prepares the high-styrene rubber through an emulsion blending and co-coagulation method. The method is characterized by using RcooMe, RosinMe, Rso3Me, and Roso3Me as emulsifiers, peroxide as initiator, thiol as regulator, and common electrolytes. At a temperature of 40-80℃, 5-25% butadiene and 75-95% styrene emulsion are copolymerized, and the conversion rate is >98.5% within 5-12 hours to obtain the high-styrene resin emulsion. The electrolytes used are common electrolytes such as potassium chloride, potassium phosphate, and potassium carbonate, with a dosage between 0.00-0.20%, preferably 0.01-0.15%.

[0004] CN111019205A1 discloses a method for preparing polyurethane-modified emulsion styrene-butadiene rubber. The method involves injecting a prepared emulsifier, dispersant, electrolyte, activating phase solution, regulator, styrene, functionalized polyurethane, and soft water into a polymerization reactor. After purging with nitrogen and removing oxygen under vacuum, butadiene is added, stirring is started, and the polymerization reaction temperature is controlled at 5-10°C. An initiator solution is then added. When the conversion rate reaches 60-72%, a terminator is added. The mixture is then discharged, coagulated, washed, and dried to obtain the sample. The amount of electrolyte used is 0.3-0.5 wt% of the total butadiene and styrene monomers.

[0005] CN115304711A discloses a modified latex styrene-butadiene rubber (SBR) latex, modified SBR, and a method for preparing both. The raw materials for forming the modified SBR latex include polymerizable monomers, initiators, and additives. The polymerizable monomers, by weight, include 28-30 parts of styrene, 64-70 parts of butadiene, and 2-8 parts of acrylamide. According to claim 1, the modified SBR latex, by weight, further includes 0.63-1.05 parts of an electrolyte, preferably including 0.2-0.3 parts of any one of phosphoric acid, hydrochloric acid, and nitric acid, 0.3-0.5 parts of potassium hydroxide and / or sodium hydroxide, 0.03-0.05 parts of tetrasodium ethylenediaminetetraacetate, and 0.1-0.2 parts of sodium dodecylbenzenesulfonate.

[0006] Generally, the commonly used electrolytes are potassium chloride and potassium phosphate. Some manufacturers also include co-emulsifiers such as sodium dodecylbenzenesulfonate, sodium m-methylnaphthalenesulfonate, and complexing agent tetrasodium ethylenediaminetetraacetate as electrolyte components. Each electrolyte system has its advantages and disadvantages. Potassium chloride electrolyte systems are more widely used in production facilities, but the mother liquor in the coagulation unit contains a large amount of chloride ions, which severely corrodes ordinary 304 stainless steel. Therefore, the material requirements for production equipment are high, requiring stainless steel of 316L or higher grade. Even so, important equipment such as dewatering machines corrode slowly, requiring regular maintenance, and eventually, replacement after a certain number of years. Potassium phosphate electrolytes offer better polymerization stability and do not corrode equipment. The disadvantage is the discharge of phosphates from the coagulation unit into the production wastewater. As my country's requirements for phosphorus-containing wastewater discharge become increasingly stringent, wastewater treatment costs are increasing exponentially, and the emulsion polymerization technology for styrene-butadiene rubber using potassium phosphate as an electrolyte will gradually be replaced. For emulsion styrene-butadiene rubber (SBR) production plants using potassium phosphate as the electrolyte, replacing it with potassium chloride would require replacing all previously used equipment materials with 316L-grade stainless steel, as these materials would no longer meet corrosion resistance requirements. This represents a significant investment. However, few manufacturers utilize low-molecular-weight organic salts as electrolytes.

[0007] In the early stages of developing emulsion styrene-butadiene rubber (ESBR) production technology, the inorganic and organic chemical industries were relatively underdeveloped, resulting in a limited variety of auxiliary agents available for production, and their costs were also high. Therefore, research on EBR electrolytes was limited to a mere 20-odd inexpensive chemicals at the time, lacking breadth and depth. With industrial development and prosperity, the output of various chemicals has continuously increased, and costs have steadily decreased. Consequently, a sufficient number of inexpensive chemicals are available for EBR production processes, providing a foundation for the research and development of EBR electrolytes. For example, organic salts such as citrates were extremely expensive to produce in the last century, making them unsuitable as raw materials for EBR production. However, with the continuous development of the biochemical and pharmaceutical industries, the production cost of citrates is now lower than that of potassium phosphate. Experiments have shown that citrates and certain other chemicals can completely replace potassium phosphate as electrolytes. With the application of lithium iron phosphate batteries in new energy vehicles, the price of phosphoric acid has skyrocketed, leading to a corresponding increase in the price of potassium phosphate, eliminating the advantage of traditional electrolyte components being inexpensive. Furthermore, organic salts have a unique advantage: they degrade during wastewater treatment, unlike hydrochlorides and phosphates which remain in water bodies indefinitely.

[0008] Extensive testing revealed that the addition of most inorganic and organic salts to the latex polymerization system of styrene-butadiene rubber (SBR) significantly increased the latex viscosity compared to systems using potassium chloride and potassium phosphate, resulting in poor heat transfer during polymerization and impacting product performance. However, small amounts of chemicals such as citrate can reduce the viscosity of SBR latex. This overcomes the technical prejudice that small-molecule organic salts are unsuitable for SBR latex polymerization systems, providing a technical guarantee for further optimization of the electrolyte in SBR polymerization. This is not a simple substitution commonly used in the field, but rather a specific application of certain chemicals discovered through extensive research. Summary of the Invention:

[0009] The technical problem to be solved by the present invention is to provide a method for preparing emulsion-polymerized styrene-butadiene rubber (SBR). This method realizes the preparation of SBR through emulsion polymerization using a composite electrolyte made of organic and inorganic salts. The composite electrolyte has an excellent effect on regulating latex viscosity, and only generates trace amounts of phosphorus- and chlorine-containing wastewater. At the same time, it solves the environmental emission problems and equipment corrosion problems of emulsion-polymerized SBR equipment, saving a lot of environmental treatment costs and equipment maintenance and replacement costs for emulsion-polymerized SBR equipment, and the preparation cost is also low.

[0010] The technical solution adopted in this invention is: a method for preparing emulsion polystyrene-butadiene rubber, comprising the following steps:

[0011] Step 1: Vacuum and nitrogen purging are performed on the polymerization reactor. Soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene, and butadiene are added to the polymerization reactor in sequence. The composite electrolyte solution contains the following components: potassium citrate or sodium citrate, potassium oxalate or sodium oxalate, carbonate or sulfate. When the temperature of the polymerization reactor drops to 5°C, an initiator is added. When the conversion rate reaches 60%, a terminator is added to terminate the reaction, resulting in styrene-butadiene rubber latex.

[0012] Step 2: Add styrene-butadiene rubber latex to a dilute sulfuric acid solution, stir, control the pH value to 3-4, control the temperature to 55℃-65℃, react for 5-10 minutes, after coagulation, wash and dry to obtain the raw rubber product.

[0013] Further, the polymerization components and their weight parts included in step one are as follows: 56-74 parts butadiene, 26-44 parts styrene, 4.1-4.9 parts emulsifier, 0.40-0.80 parts composite electrolyte solution, 0.03-0.09 parts initiator, 0.06-0.087 parts reducing agent, 0.11-0.19 parts tert-dodecyl mercaptan, 181-199 parts soft water, and 0.36-0.39 parts terminator.

[0014] Furthermore, the composite electrolyte solution comprises the following components and weight parts: 0.25-0.40 parts of potassium citrate or sodium citrate, 0.10-0.20 parts of potassium oxalate or sodium oxalate, and 0.05-0.20 parts of carbonate or sulfate.

[0015] Furthermore, the emulsifier is potassium disproportionated rosinate soap.

[0016] Furthermore, the reducing agent comprises the following components and weight parts: 0.01-0.012 parts ferrous sulfate, 0.03-0.05 parts sodium formaldehyde sulfoxylate, and 0.02-0.025 parts tetrasodium ethylenediaminetetraacetate.

[0017] Furthermore, the initiator is p-menthol peroxide.

[0018] Furthermore, the terminating agent is isopropyl hydroxylamine.

[0019] The beneficial effects of this invention are:

[0020] This invention provides a composite electrolyte using a combination of organic and inorganic salts to prepare styrene-butadiene rubber (SBR) via emulsion polymerization. The composite electrolyte possesses pH buffering capacity, improves the fluidity of the polymer emulsion at low temperatures, and effectively regulates latex viscosity, ensuring stable polymerization and coagulation / drying processes. This results in high-performance products with only trace amounts of phosphorus and chlorine-containing wastewater. Simultaneously, it solves the environmental emission and equipment corrosion problems associated with emulsion SBR production, significantly reducing environmental treatment and equipment maintenance / replacement costs, while also keeping production costs low. The performance of the emulsion SBR prepared by this invention is comparable to that of conventionally produced products. Detailed implementation method:

[0021] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments without specific conditions are generally performed under conventional conditions.

[0022] Example 1

[0023] (1) Vacuum and nitrogen purging are performed on the polymerization reactor. Soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene are added to the polymerization reactor in sequence. When the temperature of the polymerization reactor drops to 5°C, the initiator is added. When the conversion rate reaches 60%, the terminating agent is added to terminate the reaction and obtain styrene-butadiene rubber latex.

[0024] (2) Add styrene-butadiene rubber latex to a dilute sulfuric acid solution, stir, control the pH value to 3.0, control the temperature to 55℃, coagulate for 5 minutes, wash and dry after coagulation to obtain raw rubber product.

[0025] The components and their weight percentages included in step (1) of the emulsion polymerization above are as follows:

[0026]

[0027]

[0028] The composite electrolyte solution contains the following components and proportions:

[0029] 0.25 parts potassium citrate

[0030] 0.1 parts potassium oxalate

[0031] 0.05 parts potassium carbonate

[0032] The reducing agent comprises the following components and proportions:

[0033] 0.01 parts ferrous sulfate

[0034] Sodium formaldehyde bisulfite 0.03 parts

[0035] 0.02 parts of tetrasodium ethylenediaminetetraacetate

[0036] Example 2

[0037] (1) Vacuum and nitrogen purging are performed on the polymerization reactor. Soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene are added to the polymerization reactor in sequence. When the temperature of the polymerization reactor drops to 5°C, the initiator is added. When the conversion rate reaches 60%, the terminating agent is added to terminate the reaction and obtain styrene-butadiene rubber latex.

[0038] (2) Add styrene-butadiene rubber latex to a dilute sulfuric acid solution, stir, control the pH value to 3.5, control the temperature to 60℃, and coagulate for 7.5 minutes. After coagulation, wash and dry to obtain the raw rubber product.

[0039] The components and their weight percentages included in step (1) of the emulsion polymerization above are as follows:

[0040]

[0041] The composite electrolyte solution contains the following components and proportions:

[0042] Sodium citrate 0.4 parts

[0043] Sodium oxalate 0.2 parts

[0044] Sodium sulfate 0.2 parts

[0045] The reducing agent comprises the following components and proportions:

[0046] 0.012 parts ferrous sulfate

[0047] Sodium formaldehyde bisulfite 0.05 parts

[0048] 0.025 parts of tetrasodium ethylenediaminetetraacetate

[0049] Example 3

[0050] (1) Vacuum and nitrogen purging are performed on the polymerization reactor. Soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene are added to the polymerization reactor in sequence. When the temperature of the polymerization reactor drops to 5°C, the initiator is added. When the conversion rate reaches 60%, the terminating agent is added to terminate the reaction and obtain styrene-butadiene rubber latex.

[0051] (2) Add styrene-butadiene rubber latex to a dilute sulfuric acid solution, stir, control the pH value to 4.0, control the temperature to 65℃, coagulate for 10 minutes, wash and dry after coagulation to obtain raw rubber product.

[0052] The components and their weight percentages included in step (1) of the emulsion polymerization above are as follows:

[0053]

[0054] The composite electrolyte solution contains the following components and proportions:

[0055] Sodium citrate 0.35 parts

[0056] 0.15 parts potassium oxalate

[0057] 0.10 parts potassium sulfate

[0058] The reducing agent comprises the following components and proportions:

[0059] 0.011 parts ferrous sulfate

[0060] Sodium formaldehyde bisulfite 0.046 parts

[0061] 0.023 parts of tetrasodium ethylenediaminetetraacetate

[0062] Comparative Example 1

[0063] (1) Vacuum and nitrogen purging are performed on the polymerization reactor. Soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene are added to the polymerization reactor in sequence. When the temperature of the polymerization reactor drops to 5°C, the initiator is added. When the conversion rate reaches 60%, the terminating agent is added to terminate the reaction and obtain styrene-butadiene rubber latex.

[0064] (2) Add styrene-butadiene rubber latex to a dilute sulfuric acid solution, stir, control the temperature at 55℃, coagulate for 5 minutes, wash and dry after coagulation to obtain raw rubber product.

[0065] The components and their weight percentages included in step (1) of the emulsion polymerization above are as follows:

[0066]

[0067] The composite electrolyte solution comprises the following components and their weight proportions:

[0068] 0.5 parts potassium chloride

[0069] 0.03 parts of tetrasodium ethylenediaminetetraacetate

[0070] Sodium dodecylbenzenesulfonate 0.13 parts

[0071] The reducing agent comprises the following components and their weight proportions:

[0072] 0.01 parts ferrous sulfate

[0073] Sodium formaldehyde bisulfite 0.04 parts

[0074] 0.02 parts of tetrasodium ethylenediaminetetraacetate

[0075] Comparative Example 2

[0076] (1) Vacuum and nitrogen purging are performed on the polymerization reactor. Soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene are added to the polymerization reactor in sequence. When the temperature of the polymerization reactor drops to 5°C, the initiator is added. When the conversion rate reaches 60%, the terminating agent is added to terminate the reaction and obtain styrene-butadiene rubber latex.

[0077] (2) Add styrene-butadiene rubber latex to a dilute sulfuric acid solution, stir, control the temperature at 55℃, coagulate for 5 minutes, wash and dry after coagulation to obtain raw rubber product.

[0078] The components and their weight percentages included in step (1) of the emulsion polymerization above are as follows:

[0079]

[0080]

[0081] The composite electrolyte solution comprises the following components and their weight proportions:

[0082]

[0083] The reducing agent comprises the following components and their weight proportions:

[0084] 0.01 parts ferrous sulfate

[0085] Sodium formaldehyde bisulfite 0.04 parts

[0086] 0.02 parts of tetrasodium ethylenediaminetetraacetate

[0087] Table 1. Product performance testing of Examples 1-3 and Comparative Examples 1-2

[0088]

[0089] As can be seen from Table 1, the mechanical properties of the products prepared in the three examples are basically consistent with those of the two comparative examples, proving that the present invention has successfully prepared an emulsion polymerized styrene-butadiene rubber with properties comparable to those of existing products.

[0090] Table 2. Wastewater discharge detection of products from Examples 1-3 and Comparative Examples 1-2.

[0091]

[0092] As shown in Table 2, the wastewater discharge from the three embodiments showed significantly lower phosphorus and chlorine content compared to the two comparative examples. Comparative Example 1 used a potassium chloride electrolyte system, resulting in wastewater containing a large amount of chloride ions, which easily corroded the production equipment. Comparative Example 2 used a potassium phosphate electrolyte system, resulting in wastewater containing a large amount of phosphorus ions, requiring tens of millions of yuan annually to treat the phosphorus-containing wastewater. The wastewater discharge from the three embodiments contained only trace amounts of phosphorus and chlorine, demonstrating that this invention provides a green and environmentally friendly production technology.

Claims

1. A method for preparing emulsion-polymerized styrene-butadiene rubber, characterized in that: Includes the following steps: Step 1: Vacuum and nitrogen purging are performed on the polymerization reactor. Soft water, emulsifier, composite electrolyte, reducing agent, tert-dodecyl mercaptan, styrene, and butadiene are added to the polymerization reactor in sequence. The composite electrolyte contains the following components: potassium citrate or sodium citrate, potassium oxalate or sodium oxalate, carbonate or sulfate, wherein the carbonate is potassium carbonate and the sulfate is sodium sulfate or potassium sulfate. When the temperature of the polymerization reactor drops to 5°C, an initiator is added. When the conversion rate reaches 60%, a terminator is added to terminate the reaction, yielding styrene-butadiene rubber latex. The polymerization components and their weight percentages in step one are as follows: butadiene 56-74 parts, styrene 26-44 parts, emulsifier 4.1-4.9 parts, composite electrolyte 0.40-0.80 parts, initiator 0.03-0.09 parts, reducing agent 0.06-0.087 parts, tert-dodecyl mercaptan 0.11-0.19 parts, soft water 181-199 parts, and terminator 0.36-0.39 parts; The composite electrolyte comprises the following components and weight parts: 0.25-0.40 parts of potassium citrate or sodium citrate, 0.10-0.20 parts of potassium oxalate or sodium oxalate, and 0.05-0.20 parts of carbonate or sulfate. Step 2: Add styrene-butadiene rubber latex to a dilute sulfuric acid solution, stir, control the pH value to 3-4, control the temperature to 55℃-65℃, react for 5-10 minutes, after coagulation, wash and dry to obtain the raw rubber product.

2. The method for preparing emulsion-polymerized styrene-butadiene rubber according to claim 1, characterized in that: The emulsifier is potassium disproportionated rosinate soap.

3. The method for preparing emulsion-polymerized styrene-butadiene rubber according to claim 1, characterized in that: The reducing agent comprises the following components and weight parts: 0.01-0.012 parts ferrous sulfate, 0.03-0.05 parts sodium formaldehyde sulfoxylate, and 0.02-0.025 parts tetrasodium ethylenediaminetetraacetate.

4. The method for preparing emulsion-polymerized styrene-butadiene rubber according to claim 1, characterized in that: The initiator is p-menthol peroxide.

5. The method for preparing emulsion-polymerized styrene-butadiene rubber according to claim 1, characterized in that: The terminator is isopropyl hydroxylamine.

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