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Process technology comparison of polyacrylamide

Homopolymerization post-hydrolysis polymerization process of Mitsubishi Chemical Corporation of Japanb, After homopolymerization, the hydrolysis polymerization process is to polymerize under the neutral condition of pH=7, and firstly produce non-ionic polyacrylamide.


Then heat and alkali are added for hydrolysis. Some large foreign companies producing polymers such as the United Kingdom, the United States and Japan use this process to produce anionic polyacrylamide with ultra-high molecular weight. The disadvantages of the process are long process, high energy consumption, large investment and long production cycle. The polymerization technology is currently a backward process technology.

The process includes solution preparation, polymerization, granulation, hydrolysis, cutting, drying, grinding, sieving, packaging, and mixing procedures. Process: Dilute the 50% AM aqueous solution with secondary desalinated water to the required concentration, adjust the pH and temperature, enter the polymerizer after measuring, pass high-purity N to remove oxygen, add initiator to start the polymerization reaction, polymerization After the reaction is completed, the non-ionic polyacrylamide colloid is poured out, cut into 3mm particles in the particle chemical section, and enters the hydrolysis reactor.

Spray the NaOH solution onto the polyacrylamide colloidal particles for hydrolysis reaction to prepare anionic HPAM colloid. The colloid is then made into 3 ~ 5rmm granules by a granulator and then enters the first dryer. The water content is reduced from 75% (Wt) to 25% (Wt), then enter the second dryer, the water content is reduced to 10%, after cooling, grinding, sieving, and packaging.


Copolymerization process of French SNF company, Anionic polyacrylamide can be achieved through the copolymerization process of acrylamide and sodium acrylate, but the purity of acrylic acid is the main factor that determines the relative molecular weight of the product. Because the quality of acrylic acid abroad is good, the price is lower than that of acrylamide, but the opposite is true in China. This is why the copolymerization process is widely used abroad to synthesize high molecular weight HPAM, and it is also the main reason why the domestic copolymerization process has not been industrialized.

This is currently the process route that most companies believe can produce high molecular weight HPAM. The biggest feature of this process is the need for the second monomer acrylic acid (AA).

The process is as follows: mix acrylamide, acrylic acid, NaOH and desalinated water solution in a stirring dissolution tank, use NaOH to control the pH of the solution to the set value, and control the final temperature of the solution to be between 0 and 2 ℃ during the mixing process. After the monomer mixture enters the reactor, high purity nitrogen (99.999%) is used to drive oxygen. Initiating agent is added in the process of purging oxygen. The number of people and the order of people are the key to the technology, which is the technical secret of each company. When the polymerization reaction starts, the nitrogen is stopped to drive oxygen. The reaction time per batch is about 3.5~

4h, the colloid temperature after polymerization is about 80-90℃. The colloid is aged in the reactor for about 3 hours, then the reactor is dumped, the colloid is discharged into the pre-cutter, and then cut, granulated, and dried in sequence to make the colloidal HPAM (water content about 62PDG70%) into a dry powdered HPAM (About 10% water content), and finally grinding and packaging.

The hydrolysis polymerization process after homopolymerization of British Union Rubber Company

British Union Gum Company believes that it is impossible to produce HPAM with a relative molecular mass of more than 2000 x 10° by using the pre-alkali homopolymerization and co-hydrolysis process. The company has developed a new process based on the actual situation of tertiary oil recovery in the oil field. That is, the homopolymerization method is used in the central factory

Produce A8000 (a non-ionic intermediate product), and then build peripheral factories at different polymer injection sites, and perform post-hydrolysis in the peripheral factories to produce HPAM aqueous solutions that meet the tertiary oil recovery requirements. The concentration is 2.2%. Injection well. The relative molecular mass of the final product of the process can reach up to 2200×10°, but many factories are to be built in the periphery, and the water used for post-hydrolysis has to be heated to 65-70°C. The production cycle is long, energy consumption is large, and investment is large .

Post-hydrolysis polymerization production process of Daqing Refining and Chemical Company

The whole process consists of 6 processes including grinding oil preparation, reaction liquid preparation, polymerization reaction, post-hydrolysis, drying and crushing packaging. (1) Grinding oil preparation process. It is mainly composed of a grinding oil storage tank and a grinding oil-surfactant preparation tank, and its function is to prepare the surfactants required in the process of making granules. The grinding oil is quantitatively added to the grinding oil-surfactant preparation tank by the grinding oil delivery pump, and a certain amount of surfactant is added at the same time, and the agitator is turned on for stirring. After the stirring is completed, the prepared grinding oil is delivered to each granulation unit with the grinding oil-surfactant feed pump.

(2) The preparation process of the reaction solution.

It is mainly composed of a monomer dissolving tank and a monomer feeding pump. Its function is to prepare an acrylamide solution with a certain concentration and temperature required for the polymerization reaction. A certain amount of acrylamide monomer solution is added to the monomer preparation tank by the refined AM feeding pump, and then the measured demineralized water is added. Start the stirrer to stir, and at the same time pass the chilled brine to cool, and cool the prepared prepolymerization liquid to about 0°C

For aggregation use.

(3) Polymerization reaction process.

It is mainly composed of a polymerization kettle, an intermediate storage tank, a four-screw feeder and a conveying fan. Its function is to polymerize acrylamide by itself under the action of an initiator.

①Deoxygenation of the solution: Oxygen is a polymerization inhibitor for free radical reactions, and the content of oxygen in the reaction solution directly affects the quality of the reaction and the final product. The process uses high-purity nitrogen to remove oxygen in the reaction liquid, and the high-purity nitrogen is blown into the polymerization vessel through a nitrogen nozzle, and the nitrogen blowing time is 1 h.

②Transfer and reaction of reaction liquid: In the process of deoxygenation, different kinds of initiators and functional monomers are added into the polymerization kettle according to the formula, and mixed uniformly under the stirring of high-purity nitrogen. The addition of oxidation-reducing agent initiates the polymerization reaction. During this period, high-purity nitrogen is continuously blown in until the reaction liquid becomes a viscous liquid, and the viscous reaction liquid also prevents the re-dissolution of oxygen.

③Adiabatic reaction and material transfer: With the beginning of the reaction, the temperature in the reactor will gradually increase, and the reaction speed will become faster and faster. The reaction liquid eventually becomes a colloid. During the entire reaction process, the reaction heat is rarely removed, and the entire reaction process can be regarded as an adiabatic process.

④ Cutting and granulation of colloid: The colloid after polymerization is pressed into the intermediate storage box with 0.4MPa compressed air, and then cut and granulated in a four-screw granulator. The particle size can be obtained by the colloid granulator. For 3 ~ 6mm rubber particles. In this process, the grinding oil is continuously added through the pump to prevent the colloids from re-bonding together, and the produced rubber particles are sent to the hydrolysis machine for hydrolysis after passing through the conveying fan.


(4) Post-hydrolysis reaction process.

It is mainly composed of post-hydrolysis reactor, post-hydrolysis material box, regranulator, feed fan and ammonia exhaust fan. Its function is to transform non-ionic polyacrylamide into anionic polyacrylamide through hydrolysis reaction. The material from the polymerization process is driven into the post-hydrolysis reactor by the relay fan. The sensor weighing system is used to measure the transportation volume of the polymer rubber particles, and a certain amount of sodium hydroxide alkali particles is manually added to the upper part of the hydrolysis machine according to a certain proportion. At the same time, it is heated in the jacket of the hydrolysis machine to keep the material at a certain temperature and hydrolyze in the hydrolysis machine.

The hydrolysis machine adopts a horizontal ribbon agitator, which is specially designed for mixing viscous particles. This type of post hydrolysis machine can ensure uniform mixing of materials and uniform heat transfer.

The hydrolysis reaction partially converts the macromolecular nonionic polyacrylamide into anionic polyacrylamide, and the hydrolysis and curing time takes about 2~4h. After the hydrolysis is completed, the material falls from a high position into the post-hydrolysis bin by gravity. The buffer box is composed of 6 pre-grinding screws with the same rotation direction, 1 feeding screw and 1 metering screw. Its main function is to transport materials to the regranulator smoothly and quantitatively. The regranulator is the same as the colloid granulator in structure, the main difference is the sharpness of the cutter. The re-bonded rubber particles are separated by a re-granulator to obtain rubber particles with a particle size of 3-6mm. In this process, grinding oil is continuously added through the pump to prevent the rubber particles from re-bonding together, and the resulting rubber particles are sent in through the conveying fan.

Using this technology, the relative molecular mass of HPAM products in the laboratory reaches 2800×10', and the relative molecular mass of industrially produced HPAM products reaches more than 2200×10°.

The homopolymerization and cohydrolysis with pre-addition of alkali is the most advanced polymerization process in the world today, and it is also a process widely used to obtain polymer polyacrylamide at home and abroad. Due to the homopolymerization process, the relative molecular mass distribution is narrow, and the industrial alkali In the aqueous solution, the mixing is uniform, and the degree of hydrolysis of the product is uniform, which is easy for large-scale industrial production and application. However, it is difficult to obtain ultra-high molecular weight anionic polyacrylamide through the homopolymerization and co-hydrolysis process with pre-alkali, and it is used in other countries such as Britain, France, and Japan.

This process can only produce HPAM with a relative molecular mass below 1500×10". In recent years, my country has made great progress in the research of different reaction types of synthesis technology. Some domestic manufacturers have been able to adopt different types according to user needs. Polyacrylamide of different quality can be produced by the polymerization process. Now the more mature process technologies include copolymerization process, pre-alkali homopolymerization co-hydrolysis process and post-polymerization hydrolysis process.

(1) Copolymerization process. The copolymerization process uses acrylamide and acrylic acid as the main raw materials and water as the solvent. The pH value is adjusted by NaOH before the reaction. The polymerization reaction occurs at a certain initial temperature under the action of the initiator. Carboxylic polyacrylamide products.

Process characteristics: In the copolymerization process, acrylic acid is first neutralized with alkali to generate sodium acrylate, so no ammonia gas is generated during the polymerization process, and the colloidal expansion coefficient is small; the degree of hydrolysis of the product can be adjusted by changing the amount of acrylic acid, which can produce high hydrolysis. (Up to 80%) of polyacrylamide products. The disadvantage of this technology is that the copolymerization process can only be initiated at a lower temperature, and the polymerization reaction is difficult to control due to the narrow adjustment range of the pH value. Acrylic acid has high quality requirements and is difficult to store and transport. The change of temperature causes acrylic acid to produce oligomers, which affects the quality of the polymer. This is mainly manifested in the poor solubility of polymer products and limited molecular chain growth. The relative molecular weight is generally 2000 ×10* or less.

(2) The process of homopolymerization and co-hydrolysis before adding alkali. The pre-alkali homopolymerization co-hydrolysis process uses acrylamide monomer as raw material, water as solvent, and alkalis such as sodium carbonate to adjust the degree of hydrolysis.

The process is characterized by a short process route, and simultaneous polymerization and hydrolysis reactions. The disadvantage is that the initial temperature of the polymerization reaction is relatively high (otherwise the sodium carbonate is easy to crystallize) and the polymerization reaction speed is fast. At the same time, since a large amount of reaction heat is released during polymerization, when the polymerization heat is too late to dissipate, the temperature of the polymerization system rises rapidly, and the hydrolysis reaction releases a large amount of CO. With NHS gas, the colloid expands rapidly, and it is prone to agglomeration, causing equipment damage. Cross-linking of the product leads to poor solubility.

(3) Hydrolysis process after polymerization. After polymerization, the hydrolysis technology first polymerizes into non-ionic polyacrylamide, and then hydrolyzes into HPAM by adding alkali after gelation.

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