Polyacrylamide classification polyacrylamide product introduction: polyacrylamide (PAM) is a water-soluble polymer, insoluble in most organic solvents, has good flocculation, can reduce the friction resistance between the liquid, according to ionic properties can be divided into non-ionic, anionic, cationic and amphoteric type four types. Technical index Item
Model Appearance Molecular Weight (10,000) Solid Content % Ionicity or Hydrolysis % Residual Monomer % Usage Range Anionic White granule or powder 300-2200 ≥88 Hydrolysis degree
10-35 ≤0.2 PH value of water is neutral or alkaline Cationic White Granule 500-1200 ≥88 degree of ionization
5-80 ≤0.2 Belt machine centrifugal filter press non-ionic white particles 200-1500 ≥88 degree of hydrolysis
0-5 ≤0.2 PH value of water is neutral or alkaline amphoteric ionic white particles 500-1200 ≥88 Ionicity
5-50 ≤0.2 Belt machine centrifugal filter press anionic Specific gravity 0.62 Volume 0.5 Principle of action
1) flocculation: PAM is used for flocculation, and the flocculated material type surface properties, especially the kinetic potential, viscosity, turbidity and pH value of the suspension is related to the surface of the particles of the kinetic potential is the cause of particles blocking the joining of the surface charge. The opposite of the PAM, can make the kinetic potential decrease and cohesion.
2) Adsorption and bridging: PAM molecular chain fixed on the surface of different particles, the formation of polymer bridges between the particles, so that the particles form aggregates and settle.
3) surface adsorption: PAM molecules on the polar group particles of various adsorption.
4) enhancement: PAM molecular chain and the dispersed phase through a variety of mechanical, physical, chemical and other roles, the dispersed phase will be implicated in the formation of a network 1, flocculation: PAM can make the suspended material through the electric neutralization, bridge adsorption, flocculation.
2, adhesion: through the mechanical, physical, chemical role, the role of adhesion.
3, resistance reduction: PAM can effectively reduce the friction resistance of the fluid, adding trace amounts of PAM in the water can reduce resistance 50-80%.
4, thickening: PAM in neutral and acid conditions have thickening effect, when the PH value of more than 10 PAM easily hydrolyzed. Semi-network structure, thickening will be more obvious. Polyacrylamide production steps a *** two steps:
1, acrylamide monomer production technology
Acrylamide monomer production of acrylonitrile as raw material, hydration under the action of the catalyst to generate acrylamide monomer crude products, after flash evaporation, refining and refined acrylamide monomer, this monomer that is the raw material for the production of polyacrylamide.
Acrylonitrile + (aqueous catalyst/water) → synthesis → acrylamide crude product → flash → refining → refined acrylamide
By the history of the development of catalysts, the monomer technology has gone through three generations:
The first generation of the sulfuric acid-catalyzed hydration technology, the disadvantage of this technology is that the conversion of acrylonitrile is low, the yield of acrylamide products is low, the by-products are low and the refinement of the great burden. In addition, due to the strong corrosiveness of the catalyst sulfuric acid, the equipment cost is high, which increases the production cost;
The second generation is binary or ternary skeleton copper catalytic production technology, the disadvantage of this technology is that it introduces metal copper ions affecting the polymerization into the final product, which increases the cost of the post-processing and refining;
The third generation is the microbial nitrile hydratation enzyme catalytic production technology, which is mild in reaction conditions, and carried out at room temperature and pressure, and has high selectivity and high pressure. The third generation is microbial nitrile hydration enzyme catalytic production technology, the reaction conditions of this technology is mild, under normal temperature and pressure, with high selectivity, high yield and high activity, the conversion rate of acrylonitrile can reach 100%, the reaction is complete, there are no by-products and magazines, and the product acrylamide does not contain metal copper ions, so there is no need to carry out ion exchange to get rid of the copper ions produced in the process of production, which simplifies the process flow. In addition, the analysis of gas chromatography shows that the product of acrylamide hardly contains free acrylonitrile, which is highly pure. In addition, gas chromatography analysis shows that acrylamide product contains almost no free acrylonitrile and has high purity, which is especially suitable for the preparation of ultra-high relative molecular mass polyacrylamide and non-toxic polyacrylamide required by food industry.
Microbial catalyzed acrylamide monomer production technology, the first by Japan in 1985 to establish a 6000t / a acrylamide device, followed by Russia has mastered the technology, the 1990s Japan and Russia have established a 10,000-ton microbial catalyzed acrylamide device. China is the third country in the world that has this technology after Japan and Russia. The activity of microbial catalyst is 2857 international biochemical units, which has reached the international level. China's microbial catalyzed acrylamide monomer production technology is developed and completed by Shanghai Pesticide Institute through the "7th Five-Year Plan", "8th Five-Year Plan" and "9th Five-Year Plan" and other three five-year plans. The catalyst nitrile hydratase was screened out in 1990, it is the nitrile hydratase obtained by seed culture of strain 163 isolated from the soil at the foot of Taishan Mountain and strain 145 isolated from the soil in Wuxi, codenamed as Norcardia-163. The technology has been put into production in Rugao, Jiangsu, Nanchang, Jiangxi, Shengli Oilfield and Wanquan, Hebei, and it is now in stable operation with high quality and has achieved the standard of ultra-high relative molecular quality polyacrylamide production. Relative molecular mass polyacrylamide quality indicators.
Now is the use of this technology to improve the process of oil two: one is equipped with 2 × 10t / a for the biocatalytic method of acrylamide device Beijing Hengjiu Oilfield Chemical Group Co., Ltd. and the other 1.3 × 10t / a microbial catalytic method of acrylamide device equipped with the Daqing Refining and Chemical Company polymer plant.
2, polyacrylamide polymerization technology
Polyacrylamide production is an aqueous solution of acrylamide as a raw material, under the action of the initiator, the polymerization reaction, in the completion of the reaction generated by the polyacrylamide gelatinous block by cutting, granulation, drying, crushing, and ultimately produce polyacrylamide products. The key process is the polymerization reaction, in the subsequent processing should pay attention to mechanical cooling, thermal degradation and crosslinking, so as to ensure the relative molecular mass of polyacrylamide and water solubility.
Acrylamide + water (initiator/polymerization) → polyacrylamide gel block → granulation → drying → crushing → polyacrylamide products
China's polyacrylamide production technology has gone through three stages:
The first stage is the earliest use of disk polymerization, that is, the polymerization of the mixture of the reaction solution in stainless steel disks, and then these stainless steel disks are pushed to the heat preservation drying room This process is completely handmade workshop type.
The second stage is the use of kneading machine, that is, a good mix of polymerization reaction liquid in the kneading machine heating, polymerization began to start after the beginning of the kneading machine, while the polymerization of kneading, polymerization is completed, the granulation is basically complete, pour out the material by drying, crushed to finished products.
The third stage is, in the late 1980s, the development of a conical kettle polymerization process, by the Ministry of Nuclear Industry in the five Jiangsu Jiangdu Chemical Plant trial success. The process in the conical kettle with the lower part of the material with a rotary knife, the polymer in the press out at the same time, that is, granular, drying by the rotary drum dryer, crushed to the product.
In order to avoid polyacrylamide gel block adhesion in the polymerization kettle kettle wall, some technology using fluorine or silicon polymer compounds coated in the polymerization kettle on the inner wall, but this coating layer in the process of production is easy to fall off and contamination of polyacrylamide products.
The current domestic and foreign polyacrylamide production technology is basically similar to the above third stage, just in the equipment is a little different: polymerization kettle size and type (there are fixed conical kettle, there are also rotating conical kettle, polymerization reaction is completed, the polymerization kettle inverted polyacrylamide gel block pouring out), the way of pelleting (mechanical pelleting, cutting pelleting, and also wet pelleting, that is, dispersed in the pelleting liquid), Drying mode (there are through-flow rotary drying, there are also vibrating fluidized bed drying) and crushing mode. Some of these differences in the quality of equipment, some are used in specific ways on the oil differences, but in general, the polymerization technology tends to be fixed conical kettle polymerization, vibration fluidized bed drying technology.
Polyacrylamide production technology in addition to the above unit operation, there are more obvious differences in the process formulation, such as the current production of ultra-high relative molecular mass polyacrylamide production process, the same low-temperature triggering, there are a former alkali **** hydrolysis process and post-alkali hydrolysis process, the two methods have their own advantages and disadvantages, before the alkali **** hydrolysis process is simple, but there is a hydrolysis of heat transfer The former alkali *** hydrolysis process is simple, but there are hydrolysis heat transfer and cross-linking and relative molecular mass loss of large problems, after the addition of alkali hydrolysis process increases, but the hydrolysis is not easy to produce uniform cross-linking, the relative molecular mass loss of the product is also not large.
Currently, China's polyacrylamide polymerization with the initiator of inorganic initiator, organic initiator and inorganic-organic mixed system in 3 types.
(1) peroxides
Peroxides are roughly divided into inorganic peroxides and organic peroxides. Inorganic peroxides such as potassium perflumate, ammonium persulfate, sodium perbromate and hydrogen peroxide. Organic peroxides such as benzoyl peroxide, lauryl peroxide and tert-butyl hydroxy peroxide. They are formulated with reducing agents such as ferrous sulfate, ferrous chloride, sodium metabisulfite and sodium thiosulfate.
(2) azo compounds
such as azobisisobutyronitrile, azobisdimethylpentanenitrile, azobis(cyano)pentanoic acid sodium salt and a series of azamidine salts developed in 1980's, such as azobis(N-substituted amidine) propane hydrochloride is a class of products developed in the race to join the concentration of 0.005-1 parts per million, the catalytic efficiency is very high, and it can help to produce the products with high molecular mass. products and are soluble in water for ease of use.