Preparation method of ternary copolymerized cationic polyacrylamide

The invention discloses a preparation method of ternary copolymerized cationic polyacrylamide, including the following steps: stirring to dissolve cationic monomer diallyl dimethyl ammonium chloride,methacrylamide, propyl trimethylammonium chloride, nonionic monomer acrylamide, a metal ion chelating agent, and a chaotropic agent in water, adding a chain transfer agent and an initiating agent in turn after injecting nitrogen for removing oxygen, which evenly mixes the chain transfer agent and initiating agent and reaction liquid by effect of the nitrogen flow to obtain the ternary copolymerized cationic polyacrylamide colloid product, obtaining the colloidal particles by prilling the colloid product, adding anti-crosslinking agent solution into the colloidal particles for mixing, drying and milling the colloidal particles into powder, after sieving, obtaining powder product of the ternary copolymerized cationic polyacrylamide. The ternary copolymerized cationic polyacrylamide has significant hydrolysis resistance property, flocculent property is maintained and improved, the product economy is optimized relative to copolymerized products of MAPTAC and acrylamide. The method is applicable to large kettle production, which is easy to implement industrialization.

1.A preparation method of ternary copolymerization cationic polyacrylamide is characterized by the following steps:

(1) Adding monomers, metal ion chelating agents, accelerating solvents and pure water into the stirring tank, stirring until all materials are dissolved, the reaction liquid [1] is prepared, and the monomers include cationic monomers, dimethyl diallyl ammonium chloride, methacrylamide propyl trimethyl ammonium chloride and nonionic monomer acrylamide.

(2) Adjusting the pH of the reaction liquid in step (1) and cooling the reaction liquid;

(3) The reaction liquid [1]described in step (2) is transferred into the heat preservation reactor, after nitrogen gas is opened to displace oxygen, chain transfer agent and initiator are added in turn, and the chain transfer agent, initiator and reaction liquid are uniformly mixed through the effect of nitrogen gas flow. When the reaction system becomes sticky and the temperature starts to rise, nitrogen is stopped, and the static reaction of the heat preservation reactor is closed to produce reaction liquid [2].

(4) The reaction liquid is heated to a constant temperature and then matured to obtain a ternary copolymerized cationic polyacrylamide colloid product.

(5) The colloidal product in step (4) is granulated to prepare colloidal particles, in which anti-crosslinking agent solution is added and mixed, and then the colloidal particles are dried, ground and sifted to produce terpolymer cationic polyacrylamide powder product.

2.The preparation method of the ternary copolymer cationic polyacrylamide described in the Claim 1 is characterized in that the stirring kettle in the step (1) is an insulated stirring kettle with a cooling coil.

3.The preparation method of the ternary copolymer cationic polyacrylamide described in Claim 1 is characterized by the total mass fraction of monomers in the reaction solution 1 being 25% - 35%, the percentage of cationic monomers dimethyldiallylammonium chloride and methacrylamide propyl trimethylammonium chloride in the total monomer mass being 5% - 60%, methacrylamide propyl trimethylammonium chloride and dimethyldiene.The mass ratio of propyl ammonium chloride is 1:1-1:19.

4.According to the preparation method of ternary copolymerized cationic polyacrylamide described in claim 3, the characteristics are as follows: the metal ion chelating agent is trisodium ammonia triacetate, which accounts for 0.01% - 0.05% of the total monomer mass fraction.

5.According to the preparation method of the ternary copolymerized cationic polyacrylamide described in claim 3, the characteristics are as follows: the solvent is urea and sodium chloride, and the total mass fraction of the total monomer is 0.1% - 0.5% and 1% - 5%, respectively.

6.The preparation method of the ternary copolymerized cationic polyacrylamide described in Claim 1 is characterized in that phosphoric acid is used to adjust the pH to 4.0-5.5 in step (2).

7.According to the preparation method of the ternary copolymerized cationic polyacrylamide described in claim 6, the characteristics are as follows: in the step (2), the reaction liquid is cooled below 5 ℃.

8.The preparation method of the ternary copolymer cationic polyacrylamide described in Claim 1 is characterized by that the chain transfer agent is sodium formate or sodium hypophosphite, accounting for 0.002% - 0.02% of the total monomer mass fraction, and the chain transfer agent is added with a reaction liquid before the initiator.

9.The preparation method of the ternary copolymerization cationic polyacrylamide described in Claim 1 is characterized by the combination of oxidation-reduction initiator and azo initiator, the oxidant in the oxidation-reduction initiator is potassium persulfate, the reductant is sodium formaldehyde bisulfate and ferrous sulfate, the azo initiator is azodiisobutyronitrile, and the adding order of the initiator system is azodiisobutyronitrile.Nitrile butadiene, potassium persulfate, sodium formaldehyde bisulfate and ferrous sulfate were added at intervals of 2-5 min. The total mass fractions of azodiisobutyronitrile, potassium persulfate, sodium formaldehyde bisulfate and ferrous sulfate were 0.05% - 0.3%, 0.001% - 0.008%, 0.002% - 0.02%, 0.0015% - 0.01% respectively.

10.The preparation method of ternary copolymerized cationic polyacrylamide, the characteristics of which are described in Claim 1, and the method for preparing the ternary copolymerized cationic polyacrylamide are described.

The anti-crosslinking agent is sodium hypophosphite, the concentration of solution is 1.0% - 1.5%, and the dosage of solution is 1% of the mass of colloidal particles.

Preparation of Ternary Copolymerized Cationic Polyacrylamide

[0001] The invention relates to a preparation method of polyacrylamide, in particular to a preparation method of ternary copolymer cationic polyacrylamide.

[0002] Cationic polyacrylamide is one of the most widely used water-soluble polymers, which is widely used in water treatment, oil recovery, paper making, textile and other fields.Because cationic polyacrylamide is positively charged, it can combine with negatively charged particles in water to neutralize electricity and build bridges for adsorption. It is very suitable for the treatment of industrial wastewater with high organic content, such as printing and dyeing, papermaking, oily wastewater, and for the use as flocculant in the dewatering treatment of sewage and sludge.At present, cationic polymers are mainly obtained by copolymerization of acrylamide monomer (AM) and cationic monomer. Dimethyldiallyl ammonium chloride (DMDAAC), acryloyloxyethyl trimethyl ammonium chloride (DAC) or acryloxyethyl trimethyl ammonium chloride (DMC) are the main cationic polymer flocculants at home and abroad, and a lot of research has been done.Focus on the development of this kind of cationic polyacrylamide polymerization process. However, the molecular structure of DAC and DMC both contain ester groups, which are easy to hydrolyze and reduce the flocculation performance under the conventional use concentration of polymers, and can not be used at high pH value. There are obvious shortcomings. DMDAAC has no hydrolysis problem, but its polymerization activity is not high. It is difficult to obtain polymer products with high molecular weight and high monomer conversion when preparing high cationic polyacrylamide.

[0003] (methyl) acrylamide alkyl ammonium chloride quaternary ammonium salts have similar structure to acryloxy cationic monomers and high polymerization activity. At the same time, because of the substitution of amide group for ester group, the cationic polyacrylamide obtained from DAC or DMC can be hydrolyzed easily and can not be used in high pH environment. The water solution is stable, and the flocculation effect is not affected by the use of environmental pH, compared with the current market.The sale of cationic flocculants has obvious advantages, which has attracted the attention of foreign research and development developers and manufacturers.The patent No. 21310516086.9 discloses an aqueous solution copolymerization method of (methyl) acrylamide propyl trimethyl ammonium chloride (MAPTAC) and acrylamide copolymer. Cationic monomer (methyl) acrylamide propyl trimethyl ammonium chloride and nonionic monomer acrylamide are used as raw materials, metal ion chelating agent and chain transfer agent are added, and oxidation-reduction composite initiator is passed under water bath.Binary copolymers with high relative molecular weight and cationic degree were prepared by two-stage constant temperature aqueous solution polymerization and ripening.In order to exchange heat smoothly, it needs to be carried out in a special thin plate reactor.Due to the limitation of raw material price and preparation technology, the price of MAPTAC is much higher than that of DAC and DMDAAC at present. Therefore, the preparation of cationic polyacrylamide by using MAPTAC completely has been greatly improved in performance, but there is no choice and balance in economy and efficiency.Cationic polyacrylamide was synthesized by DMDAAC, MAPTAC and AM ternary copolymerization, which can achieve a better balance between economy and performance of hydrolysis-resistant cationic polyacrylamide.At the same time, due to the high activity of MAPTAC, the problem of low activity of DMDAAC was overcome to some extent by means of ternary copolymerization to coordinate the polymerization activities of the three monomers.

[0004] Adiabatic autoclave polymerization is the most common production technology used in the production of polyacrylamide at present. It is a method to maintain the continuous polymerization by using the reaction heat of acrylamide and cationic monomer polymerization after the polymerization reaction system is initiated by initiator in autoclave. It is suitable for large-scale industrial production, but at the same time, the control requirements of initiator and reaction system are relatively high. Due to the particularity of the reactivity of DMDAAC, MAPTAC and AM monomers, there is no industrialized method to prepare DMDAAC, MAPTAC and AM cationic polyacrylamide.

 [0005] In order to solve the above technical problems, the invention provides a preparation method of ternary copolymerized cationic polyacrylamide, which can be industrialized with good product economy.

[0006] In order to achieve the above purpose, the technical scheme of the present invention is as follows: a preparation method of ternary copolymerized cationic polyacrylamide, including the following steps:

[0007] (1) Adding monomers, metal ion chelating agents, accelerating solvents and pure water into the stirring kettle, stirring until all materials are dissolved, the reaction liquid [1] is prepared, in which the monomers include cationic monomers dimethyl diallyl ammonium chloride, methacrylamide propyl trimethyl ammonium chloride and nonionic monomer acrylamide.

[0008] (2) adjusting the pH of the reaction liquid [1] in step (1) and cooling the reaction liquid [1];

[0012] As a preferred choice, the stirring kettle in the step (1) is an insulated stirring kettle with a cooling coil.The heat exchange between inside and outside of the stirring tank during cooling process is avoided by using the heat preservation stirring tank, and the energy consumption required for cooling is saved.

[0014] As a preferred choice, the metal ion chelating agent is trisodium ammonia triacetate (NTA-3Na), which accounts for 0.01% - 0.05% of the total monomer mass fraction.

[0015] As a preferred solvent, urea and sodium chloride were used as the solvents, which accounted for 0.1% - 0.5% and 1% - 5% of the total monomers, respectively.

[0016] As a preferred choice, the step (2) uses phosphoric acid to regulate pH to 4.0-5.5.Initiator at pH 4.0-5.5 had the most moderate initiation efficiency, and phosphate had the least effect on the polymerization. Phosphoric acid was used to regulate PH to reduce the effect of acid on the polymerization.

[0017] As a preferred choice, the reaction liquid is cooled below 5℃in the step (2).Because adiabatic polymerization is exothermic reaction, too high initial temperature will lead to crosslinking of polymer colloids at the later stage of the reaction, so it is necessary to reduce the temperature.

[0018] As a preferred choice, the chain transfer agent is sodium formate or sodium hypophosphite, which accounts for 0.002%-0.02% of the total monomer mass fraction. The chain transfer agent is added with a reaction liquid before the initiator.When initiator is added, the reaction system becomes viscous, so the chain transfer agent is added before the initiator, so that the chain transfer agent is fully dispersed in the reaction liquid before the beginning of the polymerization in the reaction liquid system.

[0019] As a preferred choice, the initiator system is a combination of oxidation-reduction initiator and azo initiator. The oxidant in the oxidation-reduction initiator is potassium persulfate, the reductant is sodium formaldehyde bisulfate and ferrous sulfate, and the azo initiator is azodiisobutyronitrile. The order of the initiator system is azodiisobutyronitrile, potassium persulfate, sodium formaldehyde bisulfate, ferrous sulfate, and the interval time between doses.It's 2-5min.The total mass fractions of azodiisobutyronitrile, potassium persulfate, sodium formaldehyde bisulfate and ferrous sulfate were 0.05%-0.3%, 0.001%-0.008%, 0.002%-0.02%, 0.0015%-0.01%, respectively.The combination initiator system initiated by multi-stage temperature is suitable for adiabatic polymerization from low temperature to high temperature, which makes the copolymerization of MAPTAC, DMDAAC and acrylamide monomers with different polymerization activities more stable and the relative molecular weight of products higher.

[0020] As a preferred choice, the anti-crosslinking agent is sodium hypophosphite, the concentration of solution is 1.0% - 1.5%, and the dosage of solution is 1% of the mass of colloidal particles.

[0021] Beneficial effects of the present invention: By using the method of ternary copolymerization of MAPTAC, DMDAAC and acrylamide, there is no hydrolysis problem in both MAPTAC and DMDAAC, so the ternary copolymerization cationic polyacrylamide has remarkable hydrolysis resistance, flocculation performance has to be maintained and improved, and the product economy is optimized relative to that of the copolymerization of MAPTAC and acrylamide.In the process of polymerization, chelating agents with strong chelating properties were used to enhance the reactivity of the reaction system. Large doses of solvents promoted the dissolution of terpolymer cationic polyacrylamide products. A combination initiator system initiated by multi-stage temperature was used to make the copolymerization of MAPTAC, DMDAAC and acrylamide monomers with different polymerization activities more stable and the relative molecular weight of the products higher.The method is suitable for large kettle production and easy to be industrialized.

[0022] The present invention is further described in detail in connection with specific Examples.

[0023] Example 1

[0024] (1) In an insulated stirred tank with cooling coils, 41.67 kg of 60% dimethyldiallyl ammonium chloride and 50 kg of 50% propyl methacrylamide trimethylammonium chloride, 950 kg of acrylamide crystal, 100 g of trisodium ammonia triacetate, 1 kg of adipic acid, 2 kg of urea, 40 kg of sodium chloride and 2915 kg of industrial pure water were added.

[0025] (2) Stirring at room temperature, adjusting the pH value to 5.5 with phosphoric acid after all the materials are fully dissolved, and cooling the reaction liquid to 5℃.

[0026] (3) Transfer the reaction liquid into the heat preservation reactor, turn on nitrogen to drive oxygen for more than 40 min, add sodium formate 20g, azodiisobutyronitrile 500g, potassium persulfate 10g, formaldehyde sodium bisulfate 20g, ferrous sulfate 15g in turns, addition time interval is 2 minutes, and nitrogen is continue to pass through until the reaction system sticks and the temperature starts to rise, then stop nitrogen and close the heat preservation reactor static reaction.

[0027] (4) Ternary copolymerized cationic polyacrylamide colloidal products with solid content of about 25% and cationicity of 5% were obtained after the reaction system was heated to a constant temperature and then matured for one hour.

[0028] (5) The colloidal products were granulated and mixed evenly by adding 1% colloidal mass fraction of 1% sodium hypophosphite solution into the colloidal particles. After drying, grinding and sieving the colloidal particles, the terpolymer cationic polyacrylamide powder was obtained.

[0065] The application effect of ternary copolymerized cationic polyacrylamide prepared by the preparation method of the present invention in sludge dewatering:

[0066] Ternary copolymer cationic polyacrylamide was used for flocculation and dewatering of municipal sludge in a sewage treatment plant, and compared with two kinds of binary copolymer cationic polyacrylamide.The cationic polyacrylic acyls in comparison were optimized with cationic degree of 40% and molecular weight of 15 dL/g by characteristic viscometer.The water content of municipal sludge is 98.2%, the organic content is 66%, and the supernatant pH is 7.57.The 100 mL fully stirred sludge was measured in a 250 mL beaker. A cationic polyacrylamide solution with 1% mass fraction was added into the syringe. After rapid stirring for 5 seconds and slow stirring for 5 seconds, the sludge was precipitated for 1 minute. The turbidity of the supernatant was measured. The sludge after flocculation and sedimentation was poured into the Brinell funnel. The vacuum was dewatered by vacuum suction and controlled at -0.05 MPa. The moisture content of filter cake after 5 minutes of suction was measured.Dehydration performance of different flocculants.The results are shown in the table.

[0067] Table 1. Water content comparison of mud cake after sludge dewatering (%)

[0068]

Dosage (mg/L)

Ternary copolymerization of cationic polyacrylamide

Binary Copolymerization of cationic polyacrylamide with acryloxyethyl trimethylammonium chloride and acrylamide

Binary copolymerization of methacrylamide, propyl trimethylammonium chloride and acrylamide with cationic polyacrylamide

[0069] Table 2. Supernatant Turbidity Comparison (NTU) after sludge dewatering 

[0070] Binary copolymerization of cationic polyacrylamide with methacrylamide, propyl trimethylammonium chloride and Acrylamide

[0071] It can be seen from Tables 1 and 2 that the moisture content and turbidity of mud cake treated by terpolymer cationic polyacrylamide after dewatering municipal sludge are lower than those of acryloxyethyl trimethyl ammonium chloride-acrylamide copolymer cationic polyacrylamide, which is equivalent to that of methacrylamide propyl trimethyl ammonium chloride-acrylamide copolymer cationic polyacrylamide.Therefore, its flocculation performance is better than that of acryloxyethyl trimethyl ammonium chloride-acrylamide binary copolymerization cationic polyacrylamide, and is equivalent to that of methacrylamide propyl trimethyl ammonium chloride-acrylamide binary copolymerization cationic polyacrylamide.However, considering the monomer preparation process, the price of dimethyl diallyl ammonium chloride is lower than that of methacrylamide propyl trimethyl ammonium chloride, so the preparation cost of the ternary copolymerization cationic polyacrylamide of the present invention is lower and has more cost-effective advantages.

[0072] The above-mentioned Examples are only better Examples of the present invention and are not intended to limit the scope of the present invention. In operation, the above-mentioned Examples can be simplified or changed equivalently according to actual needs.

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