Process for rapidly producing cationic flocculant based on microwave polymerization

Abstract

The invention discloses a process for rapidly producing a cationic flocculant based on microwave polymerization, and belongs to the technical field of flocculant production and preparation processes. Comprising the following steps: S1, mixing ingredients; s2, solution pretreatment; s3, carrying out microwave-induced polymerization; s4, reaction control; and S5, post-processing. According to the invention, the rapid, efficient and green production of the cationic flocculant is realized through a microwave-initiated polymerization technology, and the reaction time is shortened from several hours to several minutes. According to the process, by means of uniform heating and accurate process control, high-quality products with high molecular weight, narrow distribution and low residues can be stably obtained, and good batch consistency and industrialization potential are achieved.

Description

Technical Field

[0001] This invention provides a rapid process for producing cationic flocculants based on microwave polymerization, belonging to the field of flocculant production and preparation technology. Background Technology

[0002] Water treatment and sludge dewatering are crucial links in environmental protection and resource recycling. Cationic polyacrylamide (CPAM), as an important class of organic polymeric flocculants, is widely used due to its excellent charge neutralization and adsorption bridging capabilities. Traditional cationic flocculant production processes mainly rely on thermally initiated polymerization, which typically employs aqueous solution polymerization or reverse emulsion polymerization. In the aqueous solution polymerization route, acrylamide (AM) and cationic monomers (such as methacryloyloxyethyltrimethylammonium chloride, DMC) are reacted for a long time at a specific temperature (usually 30-60℃) in the presence of an initiator (such as a persulfate-bisulfite redox system). Although the process is mature, it has significant shortcomings: First, the polymerization rate is slow, usually requiring several hours or even longer, resulting in low production efficiency and high energy consumption; second, because the traditional heating method transfers heat from the reactor wall to the internal material, a temperature gradient exists, which can easily lead to local overheating, broadening the molecular weight distribution and affecting the regularity of the product's molecular structure and the stability of its flocculation performance; third, in order to obtain high molecular weight products, the monomer concentration and reaction conditions must be strictly controlled, which can easily lead to cross-linking or explosive polymerization, resulting in poor product solubility and high residual monomer content, posing environmental and health risks.

[0003] While reverse emulsion polymerization can yield higher molecular weight products and improve dissolution rates, its process is more complex, involving large amounts of organic solvents (oil phase) and emulsifiers. This not only increases production costs but also introduces challenges in subsequent product post-processing (such as demulsification and drying) and environmental issues related to volatile organic compound (VOC) emissions. Furthermore, both aqueous solution and reverse emulsion methods are extremely temperature-sensitive initiation and chain growth processes. Conventional temperature control methods suffer from lag and difficulty in achieving precise reaction control, resulting in poor batch-to-batch product quality stability.

[0004] In summary, the production of cationic flocculants in existing technologies generally faces core challenges such as low reaction efficiency, high energy consumption, poor controllability of product molecular weight and distribution, susceptibility to side reactions affecting product performance, complex processes, and potential environmental hazards. Therefore, developing a new, rapid, efficient, controllable, and environmentally friendly process for synthesizing cationic flocculants to meet the growing demand for high-quality water treatment chemicals has become an urgent technical problem to be solved in this field. Microwave polymerization technology, as an emerging heating method, holds promise for providing solutions to the above problems due to its unique bulk heating and "non-thermal effects." However, its successful application in the continuous or batch rapid production of cationic flocculants, and precise control of product performance, still requires in-depth process exploration and equipment innovation. Summary of the Invention

[0005] The technical problem to be solved by this invention is the technical defects of existing cationic flocculant thermal polymerization processes, such as slow reaction rate, high energy consumption, wide molecular weight distribution of products, unstable performance, and the complexity and poor environmental performance of traditional reverse emulsion polymerization processes.

[0006] To address the aforementioned problems, the present invention proposes the following technical solution: a rapid production process for cationic flocculants based on microwave polymerization, comprising the following steps: S1. Ingredient Mixing: Acrylamide monomer, cationic monomer, deionized water, complexing agent and chain transfer agent are mixed in a mixing tank and stirred to dissolve, forming a homogeneous aqueous solution; the cationic monomer is methacryloyloxyethyltrimethylammonium chloride (DMC) or acryloyloxyethyltrimethylammonium chloride (DAC). S2. Solution pretreatment: Adjust the pH of the aqueous solution obtained in step S1 to 5.0-7.0, and introduce inert gas for bubbling deoxygenation for 15-30 minutes. S3. Microwave-initiated polymerization: The deoxygenated mixed solution is transferred to a special polymerization reactor with a built-in microwave generator, and then a water-soluble initiator is added. Microwave radiation is then immediately started to carry out the polymerization reaction. S4. Reaction control: Control the microwave power to 300-1500W, the reaction temperature to 55-75℃, and the reaction time to 8-25 minutes. Under these conditions, the monomers are rapidly polymerized to obtain a viscous cationic polyacrylamide colloid. S5. Post-processing: The obtained colloid is granulated, dried and pulverized to obtain a powdered cationic flocculant product.

[0007] Preferably, in step S1, the mass ratio of the acrylamide monomer to the cationic monomer is (60:40) to (90:10); and the total monomer mass fraction of the aqueous solution is 30%-50%.

[0008] Preferably, in step S1, the complexing agent is disodium ethylenediaminetetraacetate (EDTA-2Na), and its addition amount is 0.01%-0.05% of the total mass of the monomer; the chain transfer agent is isopropanol or sodium formate, and its addition amount is 0.1%-1.0% of the total mass of the monomer.

[0009] Preferably, in step S3, the water-soluble initiator is a redox initiator system composed of ammonium persulfate and sodium bisulfite, wherein the amount of ammonium persulfate added is 0.2%-0.8% of the total mass of the monomers, and the amount of sodium bisulfite added is 0.1%-0.4% of the total mass of the monomers.

[0010] Preferably, in step S3, the dedicated polymerization reactor is a closed microwave reactor equipped with a variable frequency stirring system, an infrared temperature sensor, and a pressure sensor; the stirring speed of the variable frequency stirring system is 50-200 rpm to ensure uniform heating of the material.

[0011] Preferably, in step S4, the microwave radiation adopts an intermittent or gradient power control mode, specifically: a lower power of 300-500W is used in the initial 0-3 minutes of the reaction, the main reaction power is increased to 800-1200W in the middle 3-15 minutes of the reaction, and the ripening power is reduced to 400-600W in the later 15-25 minutes of the reaction.

[0012] Preferably, in step S4, the pressure of the polymerization reaction is controlled within the range of 0.1-0.3 MPa.

[0013] Preferably, in step S5, the drying process adopts a two-stage drying: first, preliminary drying is carried out at 80-100℃ until the moisture content is 15%-20%, and then low-temperature deep drying is carried out at 60-80℃ until the moisture content of the final product is less than 8%.

[0014] The beneficial effects of this invention are: By employing microwave-initiated polymerization technology, the bulk heating and non-thermal effects of microwaves are utilized to greatly accelerate the initiation and chain growth processes of the polymerization reaction, reducing the reaction time from several hours in traditional methods to several minutes, significantly improving production efficiency and reducing energy consumption.

[0015] Microwave heating ensures uniformity, avoiding localized overheating, resulting in a narrower polymer molecular weight distribution, a more regular product structure, and stable and reliable flocculation performance. Secondly, this invention employs an aqueous solution polymerization system. By optimizing the monomer ratio, initiator system, and precisely controlling key parameters such as microwave power, temperature, and pressure, a product with high molecular weight, high solubility, and low residual monomer content was successfully obtained without the use of organic solvents and emulsifiers. The process is green and environmentally friendly.

[0016] Through stepped power control and dedicated reaction equipment, precise regulation of the polymerization process is achieved, ensuring batch-to-batch consistency of product quality and facilitating continuous industrial production. Attached Figure Description

[0017] Figure 1 This is a flowchart of a rapid production process for cationic flocculants based on microwave polymerization according to the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited to the embodiments described. Example

[0019] Prepare a mixed aqueous solution with a total mass of 1000g. The solution contains 350g of acrylamide (AM) monomer and 150g of methacryloyloxyethyltrimethylammonium chloride (DMC) monomer, for a total monomer mass fraction of 50%. Add 0.25g of disodium ethylenediaminetetraacetate (EDTA-2Na) (0.05% of the total monomer mass) and 3g of isopropanol (0.6% of the total monomer mass) to the solution. After stirring until completely dissolved, adjust the pH to 6.0 with dilute sulfuric acid solution. Then, bubble the solution with high-purity nitrogen gas for 30 minutes to thoroughly remove dissolved oxygen.

[0020] Transfer the deoxygenated mixed solution to a microwave polymerization reactor and start stirring at 100 rpm. Add 2.5 g of ammonium persulfate (0.5% of the total monomer mass) and 1.0 g of sodium bisulfite (0.2% of the total monomer mass) sequentially. Immediately start the microwave reactor using a gradient power control mode: 0-3 minutes, microwave power is set to 400 W to allow the system temperature to rise steadily to 60℃; 3-15 minutes, the power is increased to 1000 W to maintain the reaction temperature at 65±2℃; 15-20 minutes, the power is reduced to 500 W for ripening. Throughout the reaction, the pressure inside the reactor is maintained at approximately 0.2 MPa using the cooling system.

[0021] After reacting for 20 minutes, a colorless, transparent, viscous elastic colloid was obtained. The colloid was then removed and granulated using a screw granulator, followed by a two-stage drying process: first, drying at 95°C to a moisture content of approximately 18%, and then further drying at 70°C to a moisture content below 7%. Finally, the colloid was pulverized to obtain a white, powdery cationic polyacrylamide flocculant product. Testing showed that its intrinsic viscosity was 14.2 dL / g, its cationicity was 30%, and its residual acrylamide monomer content was 0.03%. Example

[0022] Prepare a mixed aqueous solution with a total mass of 1000g. The solution contains 400g of acrylamide (AM) monomer and 100g of acryloyloxyethyltrimethylammonium chloride (DAC) monomer, for a total monomer mass fraction of 50%. Add 0.15g of EDTA-2Na (0.03% of the total monomer mass) and 2.5g of sodium formate (0.5% of the total monomer mass) to the solution. After stirring to dissolve, adjust the pH to 5.5 with dilute sodium hydroxide solution. Purge with nitrogen gas and bubble for 25 minutes to remove oxygen.

[0023] Transfer the solution to a microwave polymerization reactor and set the stirring speed to 150 rpm. Add 4.0 g of ammonium persulfate (0.8% of the total monomer mass) and 1.5 g of sodium bisulfite (0.3% of the total monomer mass). Start the microwave and control the following strategies: 0-3 minutes, 500 W power, heat to 55℃; 3-12 minutes, 1200 W power, temperature controlled at 70±2℃; 12-18 minutes, 600 W power for ripening. Control the reaction pressure at 0.25 MPa.

[0024] After reacting for 18 minutes, a viscous colloid was obtained. Subsequent granulation, drying (first stage at 100°C to 16% moisture content, second stage at 65°C to 6.5% moisture content), and pulverization processes were the same as in Example 1. The resulting product had an intrinsic viscosity of 12.8 dL / g, a cationicity of 20%, and a residual acrylamide monomer content of 0.025%.

[0025] The above embodiments demonstrate that the process of the present invention can rapidly and stably produce high-performance cationic flocculant products.

[0026] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A rapid production process for cationic flocculants based on microwave polymerization, characterized in that, Includes the following steps: S1. Ingredient Mixing: Acrylamide monomer, cationic monomer, deionized water, complexing agent and chain transfer agent are mixed in a mixing tank and stirred to dissolve, forming a homogeneous aqueous solution; the cationic monomer is methacryloyloxyethyltrimethylammonium chloride (DMC) or acryloyloxyethyltrimethylammonium chloride (DAC). S2. Solution pretreatment: Adjust the pH of the aqueous solution obtained in step S1 to 5.0-7.0, and introduce inert gas for bubbling deoxygenation for 15-30 minutes. S3. Microwave-initiated polymerization: The deoxygenated mixed solution is transferred to a special polymerization reactor with a built-in microwave generator, and then a water-soluble initiator is added. Microwave radiation is then immediately started to carry out the polymerization reaction. S4. Reaction control: Control the microwave power to 300-1500W, the reaction temperature to 55-75℃, and the reaction time to 8-25 minutes. Under these conditions, the monomers are rapidly polymerized to obtain a viscous cationic polyacrylamide colloid. S5. Post-processing: The obtained colloid is granulated, dried and pulverized to obtain a powdered cationic flocculant product.

2. The process according to claim 1, characterized in that, In step S1, the mass ratio of acrylamide monomer to cationic monomer is (60:40) to (90:10); the total monomer mass fraction of the aqueous solution is 30%-50%.

3. The process according to claim 1, characterized in that, In step S1, the complexing agent is disodium ethylenediaminetetraacetate (EDTA-2Na), and its addition amount is 0.01%-0.05% of the total mass of the monomer; the chain transfer agent is isopropanol or sodium formate, and its addition amount is 0.1%-1.0% of the total mass of the monomer.

4. The process according to claim 1, characterized in that, In step S3, the water-soluble initiator is a redox initiator system composed of ammonium persulfate and sodium bisulfite, wherein the amount of ammonium persulfate added is 0.2%-0.8% of the total mass of the monomers, and the amount of sodium bisulfite added is 0.1%-0.4% of the total mass of the monomers.

5. The process according to claim 1, characterized in that, In step S3, the special polymerization reactor is a closed microwave reactor equipped with a variable frequency stirring system, an infrared temperature sensor, and a pressure sensor; the stirring speed of the variable frequency stirring system is 50-200 rpm to ensure uniform heating of the material.

6. The process according to claim 5, characterized in that, In step S4, the microwave radiation adopts an intermittent or gradient power control mode, specifically: a lower power of 300-500W is used in the initial 0-3 minutes of the reaction, the main reaction power is increased to 800-1200W in the middle 3-15 minutes of the reaction, and the ripening power is reduced to 400-600W in the later 15-25 minutes of the reaction.

7. The process according to claim 1, characterized in that, In step S4, the pressure of the polymerization reaction is controlled within the range of 0.1-0.3 MPa.

8. The process according to claim 1, characterized in that, In step S5, the drying process adopts a two-stage drying: first, preliminary drying is carried out at 80-100℃ until the moisture content is 15%-20%, and then low-temperature deep drying is carried out at 60-80℃ until the moisture content of the final product is less than 8%.

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