Preparation method of emulsion polymerized styrene-butadiene rubber

Abstract

The invention relates to the technical field of synthetic rubber production, in particular to a preparation method of emulsion polymerized styrene-butadiene rubber. The method comprises the following steps: 1, carrying out vacuum and nitrogen replacement on a polymerization kettle, sequentially adding soft water, an emulsifier, a composite electrolyte solution, a reducing agent, tert-dodecanethiol, styrene and butadiene into the polymerization kettle, adding an initiator when the temperature of the polymerization kettle is reduced to 5 DEG C, and adding a terminating agent to terminate the reaction when the conversion rate reaches 60%, styrene butadiene rubber latex is obtained; and 2, adding the styrene-butadiene rubber latex into a dilute sulfuric acid solution, stirring, reacting for 5-10 minutes, condensing, washing and drying to obtain a crude rubber finished product. According to the invention, the compounded composite electrolyte has an excellent latex viscosity adjusting effect, only a trace amount of phosphorus-containing and chlorine-containing wastewater is generated, meanwhile, the problems of environment-friendly emission and equipment corrosion of an emulsion polymerized styrene-butadiene rubber device are solved, and a large amount of environment-friendly treatment cost and equipment maintenance and updating cost are saved for the emulsion polymerized styrene-butadiene rubber device.

Description

Technical field:

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

[0002] Electrolytes play a very important role in the polymerization system in the production of latex polystyrene butadiene. The addition of an appropriate amount of electrolyte can inhibit the gelation of latex, improve the fluidity of polymer emulsion at low temperatures, and increase the polymerization reaction rate. In addition, it also helps to increase the particle size and stability of latex. The latex is a charged colloid, and the peptization effect produced by the addition of electrolytes helps the formation of micelles. The optimal electrolyte and its dosage are different under different initiator dosages. Domestic and foreign styrene butadiene rubber plants generally use potassium phosphate or potassium chloride as electrolytes.

[0003] CN1544522A discloses a method for preparing high-benzene rubber, which uses SBR-1502 latex, SBR-1500 latex and high-benzene resin emulsion containing 23.5±1% of styrene as raw materials to prepare high-benzene rubber through emulsion blending and co-condensation method. The method is characterized in that RcooMe, RosinMe, Rso3Me and Roso3Me are used as emulsifiers, peroxide is used as initiator, mercaptan is used as regulator, and common electrolytes are used. At a temperature of 40-80°C, 5-25% of butadiene and 75-95% of styrene emulsion are copolymerized. Within 5-12 hours, under the condition that the conversion rate is greater than 98.5%, high-benzene resin emulsion is prepared; the electrolyte used refers to common electrolytes such as potassium chloride, potassium phosphate, potassium carbonate, etc., and the amount used is between 0.00-0.20%, preferably 0.01-0.15%.

[0004] CN111019205A1 discloses a method for preparing polyurethane modified emulsion polybutadiene rubber, characterized in that the prepared emulsifier, diffusant, electrolyte, active phase solution, regulator, styrene, functionalized polyurethane and soft water are injected into a polymerization kettle, replaced with nitrogen, vacuumed and oxygen removed, butadiene is added, stirring is started, the polymerization temperature is controlled to be 5-10°C, an initiator solution is added, and when the conversion rate reaches 60-72%, a terminator is added, the material is discharged, condensed, washed and dried to obtain a sample. The amount of electrolyte used is 0.3-0.5wt% of the total amount of butadiene and styrene monomers.

[0005] CN115304711A discloses a modified latex polystyrene butadiene rubber latex, a modified latex polystyrene butadiene rubber latex and a preparation method thereof. The raw materials for forming the modified latex polystyrene butadiene rubber latex include polymerizable monomers, initiators and auxiliary agents, characterized in that, by weight, the polymerizable monomers include 28 to 30 parts of styrene, 64 to 70 parts of butadiene and 2 to 8 parts of acrylamide. The modified latex polystyrene butadiene rubber latex according to claim 1 is characterized in that, by weight, the auxiliary agent also includes 0.63 to 1.05 parts of electrolyte, preferably, the electrolyte includes 0.2 to 0.3 parts of any one of phosphoric acid, hydrochloric acid and nitric acid, 0.3 to 0.5 parts of potassium hydroxide and / or sodium hydroxide, 0.03 to 0.05 parts of tetrasodium ethylenediaminetetraacetic acid and 0.1 to 0.2 parts of sodium dodecylbenzene sulfonate.

[0006] Generally speaking, the commonly used electrolytes are mainly potassium chloride and potassium phosphate. Some manufacturers also count the emulsifier sodium dodecylbenzene sulfonate, sodium m-methyl naphthalene sulfonate, and chelating agent tetrasodium ethylenediaminetetraacetic acid as electrolyte components. Each electrolyte system also has advantages and disadvantages. The potassium chloride electrolyte system is more widely used in various production devices, but the mother liquor in the coagulation unit contains a large amount of chloride ions, which seriously corrodes ordinary 304 stainless steel. Therefore, the material requirements for production equipment are relatively high, and stainless steel of 316L or above must be used. Even so, important equipment such as dehydrators also corrode slowly and require regular maintenance. After a certain number of years, the equipment must be updated. Potassium phosphate electrolyte has better polymerization stability and does not corrode equipment. The disadvantage is that phosphate is discharged from the coagulation unit into the production wastewater. As my country's requirements for the discharge of phosphorus-containing wastewater become more and more stringent, the cost of wastewater treatment has increased exponentially, and the production technology of emulsion polybutadiene rubber using potassium phosphate as electrolyte will gradually be replaced. For the production equipment of latex polybutadiene rubber with potassium phosphate as electrolyte, if the electrolyte is replaced with potassium chloride, the previously used equipment materials do not meet the anti-corrosion requirements, so the equipment from the polymerization kettle, degassing system, blending system, and coagulation system must be replaced with 316L grade stainless steel, which is a huge investment. However, few manufacturers use low molecular weight organic salts as electrolytes.

[0007] In the early stage of the development of the production process of emulsion polybutadiene rubber, the inorganic and organic chemical industries were relatively backward, and there were fewer types of additives for production and the cost was also high. Therefore, the research scope of emulsion polybutadiene rubber electrolyte was limited to more than 20 kinds of cheap chemicals at that time, and the breadth and depth of electrolyte research were insufficient. With the development and prosperity of industry, the output of various chemicals has continued to increase and the cost has continued to decrease. Therefore, there are sufficient cheap chemicals to be selected for the production process of emulsion polybutadiene rubber, which provides a basis for the research and development of emulsion polybutadiene rubber electrolyte. For example, organic salts such as citrate had very high production costs in the last century and could not be used as raw materials for the production of emulsion polybutadiene rubber. However, at present, with the continuous development of the biochemical and pharmaceutical industries, the production cost of citrate is lower than that of potassium phosphate. Experiments have proved that certain chemicals such as citrate can completely replace potassium phosphate as electrolyte. With the application of lithium iron phosphate batteries for new energy vehicles, the price of phosphoric acid has begun to soar, which has also caused the price of potassium phosphate to rise accordingly. The advantage of the cheapness of traditional electrolyte components has disappeared. In addition, organic salts have a unique advantage, that is, they will degrade during the sewage treatment process, unlike hydrochlorides and phosphates that always exist in the water body.

[0008] After a lot of tests, it was found that most inorganic salts and organic salts added to the latex polymerization system of styrene butadiene rubber make the viscosity of the latex much higher than that of potassium chloride and potassium phosphate systems, resulting in poor heat transfer in the polymerization reaction and affecting product performance. However, a small amount of chemicals such as citrate can reduce the viscosity of the latex of styrene butadiene rubber, which breaks the technical prejudice that small molecule organic salts are not suitable for styrene butadiene rubber emulsion polymerization system and provides technical guarantee for further optimization of the electrolyte of styrene butadiene rubber emulsion. This is not a simple substitution commonly used in this field, but a special use of individual chemicals discovered through a lot of 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. The method realizes the preparation of styrene butadiene rubber by emulsion polymerization using a composite electrolyte prepared from an organic salt and an inorganic salt. The composite electrolyte has an excellent effect of regulating the viscosity of the latex and only produces a trace amount of phosphorus-containing and chlorine-containing wastewater. At the same time, the environmental emission problems and equipment corrosion problems of the emulsion-polymerized styrene butadiene rubber device are solved, a large amount of environmental protection treatment costs and equipment maintenance and update costs are saved for the emulsion-polymerized styrene butadiene rubber device, and the preparation cost is not high.

[0010] The technical solution adopted by the present invention is: a method for preparing emulsion-polymerized styrene-butadiene rubber, comprising the following steps:

[0011] Step 1, vacuuming and nitrogen replacing the polymerization kettle, adding soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene, and butadiene into the polymerization kettle in sequence, wherein the composite electrolyte solution comprises the following components: potassium citrate or sodium citrate, potassium oxalate or sodium oxalate, carbonate or sulfate; when the temperature of the polymerization kettle drops to 5° C., adding an initiator, and when the conversion rate reaches 60%, adding a terminator to terminate the reaction to obtain styrene-butadiene rubber latex;

[0012] Step 2, adding styrene-butadiene rubber latex into a dilute sulfuric acid solution, stirring, controlling the pH value to 3-4, controlling the temperature to 55° C.-65° C., reacting for 5-10 minutes, and after coagulation, washing and drying to obtain a raw rubber product.

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

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

[0015] Furthermore, the emulsifier is disproportionate rosin acid potassium soap.

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

[0017] Furthermore, the initiator is p-menthane hydroperoxide.

[0018] Furthermore, the terminator is isopropylhydroxylamine.

[0019] The beneficial effects of the present invention are:

[0020] The present invention provides a composite electrolyte by compounding organic salt and inorganic salt, and prepares styrene butadiene rubber by emulsion polymerization. The composite electrolyte has pH buffering capacity, improves the fluidity of polymer emulsion under low temperature, has excellent effect of regulating latex viscosity, ensures stable polymerization reaction, stable coagulation and drying process, and has excellent product performance. Only trace phosphorus-containing and chlorine-containing wastewater is generated, and the environmental emission problem and equipment corrosion problem of emulsion styrene butadiene rubber device are solved at the same time, and a large amount of environmental treatment cost and equipment maintenance and update cost are saved for the emulsion styrene butadiene rubber device, and the preparation cost is not high. The performance of the emulsion styrene butadiene rubber finished product prepared by the present invention is equivalent to that of the traditional finished product. Specific implementation method:

[0021] The following is a detailed description of the embodiments of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and process are given, but the protection scope of the present invention is not limited to the following embodiments. The experimental methods in the following embodiments that do not specify specific conditions are usually conducted under conventional conditions.

[0022] Example 1

[0023] (1) vacuuming and nitrogen replacing the polymerization kettle. Adding soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene to the polymerization kettle in sequence, adding initiator when the temperature of the polymerization kettle drops to 5°C, adding terminator when the conversion rate reaches 60%, and terminating the reaction to obtain styrene-butadiene rubber latex;

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

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

[0026]

[0027]

[0028] The components and the number of parts contained in the composite electrolyte solution are:

[0029] Potassium citrate 0.25 parts

[0030] Potassium oxalate 0.1 part

[0031] Potassium carbonate 0.05 parts

[0032] The components and parts of the reducing agent are:

[0033] Ferrous sulfate 0.01 parts

[0034] 0.03 parts of sodium formaldehyde sulfoxylate

[0035] 0.02 parts of ethylenediaminetetraacetic acid tetrasodium salt

[0036] Example 2

[0037] (1) vacuuming and nitrogen replacing the polymerization kettle. Adding soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene to the polymerization kettle in sequence, adding initiator when the temperature of the polymerization kettle drops to 5°C, adding terminator when the conversion rate reaches 60%, and terminating the reaction to obtain styrene-butadiene rubber latex;

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

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

[0040]

[0041] The components and the number of parts contained in the composite electrolyte solution are:

[0042] 0.4 parts of sodium citrate

[0043] 0.2 parts of sodium oxalate

[0044] 0.2 parts of sodium sulfate

[0045] The components and parts of the reducing agent are:

[0046] Ferrous sulfate 0.012 parts

[0047] 0.05 parts of sodium formaldehyde sulfoxylate

[0048] 0.025 parts of ethylenediaminetetraacetic acid tetrasodium salt

[0049] Example 3

[0050] (1) vacuuming and nitrogen replacing the polymerization kettle. Adding soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene to the polymerization kettle in sequence, adding initiator when the temperature of the polymerization kettle drops to 5°C, adding terminator when the conversion rate reaches 60%, and terminating the reaction to 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° C., and coagulate for 10 minutes. After coagulation, wash and dry to obtain a raw rubber product.

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

[0053]

[0054] The components and the number of parts contained in the composite electrolyte solution are:

[0055] 0.35 parts of sodium citrate

[0056] Potassium oxalate 0.15 parts

[0057] Potassium sulfate 0.10 parts

[0058] The components and parts of the reducing agent are:

[0059] Ferrous sulfate 0.011 parts

[0060] 0.046 parts of sodium formaldehyde sulfoxylate

[0061] 0.023 parts of ethylenediaminetetraacetic acid tetrasodium salt

[0062] Comparative Example 1

[0063] (1) vacuuming and nitrogen replacing the polymerization kettle. Adding soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene to the polymerization kettle in sequence, adding initiator when the temperature of the polymerization kettle drops to 5°C, adding terminator when the conversion rate reaches 60%, and terminating the reaction to obtain styrene-butadiene rubber latex;

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

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

[0066]

[0067] The components and weight proportions of the composite electrolyte solution are as follows:

[0068] 0.5 parts potassium chloride

[0069] 0.03 parts of ethylenediaminetetraacetic acid tetrasodium salt

[0070] 0.13 parts of sodium dodecylbenzene sulfonate

[0071] The components and weight proportions of the reducing agent are as follows:

[0072] Ferrous sulfate 0.01 parts

[0073] 0.04 parts of sodium formaldehyde sulfoxylate

[0074] 0.02 parts of ethylenediaminetetraacetic acid tetrasodium salt

[0075] Comparative Example 2

[0076] (1) vacuuming and nitrogen replacing the polymerization kettle. Adding soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene and butadiene to the polymerization kettle in sequence, adding initiator when the temperature of the polymerization kettle drops to 5°C, adding terminator when the conversion rate reaches 60%, and terminating the reaction to obtain styrene-butadiene rubber latex;

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

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

[0079]

[0080]

[0081] The components and weight proportions of the composite electrolyte solution are as follows:

[0082]

[0083] The components and weight proportions of the reducing agent are as follows:

[0084] Ferrous sulfate 0.01 parts

[0085] 0.04 parts of sodium formaldehyde sulfoxylate

[0086] 0.02 parts of ethylenediaminetetraacetic acid tetrasodium salt

[0087] Table 1 Performance test of products of Examples 1-3 and Comparative Examples 1-2

[0088]

[0089] It can be seen from Table 1 that the mechanical properties of the products prepared in the three embodiments are basically consistent with those of the two comparative examples, which proves that the present invention successfully prepares an emulsion-polymerized styrene-butadiene rubber, and its performance is comparable to that of existing products.

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

[0091]

[0092] As can be seen from Table 2, the phosphorus content and chlorine content of the discharged wastewater of the three embodiments are very low compared with the two comparative examples. Comparative Example 1 is a potassium chloride electrolyte system, and the wastewater contains a large amount of chloride ions, which are easy to corrode the production equipment. Comparative Example 2 is a potassium phosphate electrolyte system, and the wastewater contains a large amount of phosphorus ions. The cost of processing phosphorus-containing wastewater by the production equipment each year requires tens of millions of yuan. The discharged wastewater of the three embodiments contains only trace amounts of phosphorus and chlorine. The present invention provides a green and environmentally friendly production technology.

Claims

1. A method for preparing emulsion-polymerized styrene-butadiene rubber, characterized in that: The following steps are involved: Step 1, vacuuming and nitrogen replacing the polymerization kettle, adding soft water, emulsifier, composite electrolyte solution, reducing agent, tert-dodecyl mercaptan, styrene, and butadiene into the polymerization kettle in sequence, wherein the composite electrolyte solution comprises the following components: potassium citrate or sodium citrate, potassium oxalate or sodium oxalate, carbonate or sulfate; when the temperature of the polymerization kettle drops to 5° C., adding an initiator, and when the conversion rate reaches 60%, adding a terminator to terminate the reaction to obtain styrene-butadiene rubber latex; Step 2, adding styrene-butadiene rubber latex into a dilute sulfuric acid solution, stirring, controlling the pH value to 3-4, controlling the temperature to 55° C.-65° C., reacting for 5-10 minutes, and after coagulation, washing and drying to obtain a raw rubber product.

2. The method for preparing emulsion-polymerized styrene-butadiene rubber according to claim 1, characterized in that: The polymerization components and their weight proportions contained in the step 1 are: 56-74 parts of butadiene, 26-44 parts of styrene, 4.1-4.9 parts of emulsifier, 0.40-0.80 parts of composite electrolyte solution, 0.03-0.09 parts of initiator, 0.06-0.087 parts of reducing agent, 0.11-0.19 parts of tert-dodecyl mercaptan, 181-199 parts of soft water, and 0.36-0.39 parts of terminator.

3. The method for preparing emulsion-polymerized styrene-butadiene rubber according to claim 1, characterized in that: The composite electrolyte solution contains the following components in parts by weight: 0.25 to 0.40 parts of potassium citrate or sodium citrate, 0.10 to 0.20 parts of potassium oxalate or sodium oxalate, and 0.05 to 0.20 parts of carbonate or sulfate.

4. The method for preparing emulsion-polymerized styrene-butadiene rubber according to claim 1, characterized in that: The emulsifier is disproportionate rosin acid potassium soap.

5. 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 proportions: 0.01 to 0.012 parts of ferrous sulfate, 0.03 to 0.05 parts of sodium formaldehyde sulfoxylate, and 0.02 to 0.025 parts of tetrasodium ethylenediaminetetraacetic acid.

6. The method for preparing emulsion-polymerized styrene-butadiene rubber according to claim 1, characterized in that: The initiator is p-menthane hydroperoxide.

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

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