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Process and application of polyacrylamide PAM
Polyacrylamide has good thermal stability. Due to the structure unit with polar groups, amide, easy to form hydrogen bonds, so that it has good water solubility and high chemical activity, easy by grafting and crosslinking are even or reticular structure of various modifying properties. So as to have a series of derivatives and a variety of valuable properties, in the water treatment is of great significance, is the most widely used in the organic polymer net water treatment flocculant.
Polyacrylamide is early in 1893 by moureu with acryloyl chloride and ammonia in low temperature was prepared. From 1954 first commercial production in the United States. Initially, acrylamide (AM) monomer is from acrylonitrile (an) - derived by Hydrate Catalyzed by sulfuric acid, by acrylamide homopolymerization of non ionic polyacrylamide (PAM) and subsequently developed by alkali hydrolysis of anionic polyacrylamide. In the 1970s with the second generation of acrylamide production "water catalyzed legitimate" and the third generation of microbial engineering technology have come out in succession, polyacrylamide series products continuously was developed. As in the 1970s, American Merck company and Halliburton company developed the first successful cationic polyacrylamide, dimethyl diallyl ammonium chloride (PDMDAAC) and dimethyl diallyl ammonium chloride and acrylamide copolymer P (DMDAAC / AM)]; more active in the 1990s foreign of amphoteric polyacrylamide research, development, products have been available.
The study and production of polyacrylamide began in the 1960s, production process mainly uses the traditional aqueous solution polymerization, colloidal mining 8 -- 10%AM aqueous solution and in initiating agent under the action of direct polymerization, dry powder with 20 - polymerization concentration 30%AM aqueous solution, colloid aggregation after granulation, kneading, drying, crushing of polyacrylamide, ratio process is safe, simple, cost low. Inverse emulsion polymerization method -- am aqueous solution with surfactant of AM monomer decomposition in the oil phase formation of emulsion system, in initiating agent of emulsion polymerization to form stable high molecular weight instant Polyacrylamide Latex products, after azeotropic distillation dehydration can be powdered polypropylene products. The process for in the preparation of high molecular weight and narrow distribution of molecular weight of Polyacrylamide Latex or dry powder type products. And inverse suspension polymerization, polymerization of am in aqueous solution with small droplets suspended in the organic solution of system of molecular weight high, instant polyacrylamide beads. Radiation caused method -- calcined amide monomer in the R or ultraviolet ray triggered direct polymerization and a solid product, the process is simple, but the investment is larger, the obtained product molecular weight distribution is very wide. The majority of the application of polyacrylamide requires some kind of ion function. The characteristics of the ion can change the solubility, viscosity and solution properties of polyacrylamide. The manufacture of commodity derivatives is made using the copolymerization method or the use of the subsequent reaction of polyacrylamide.
So far, it has been produced by non ionic polyacrylamide, cationic polyacrylamide, polyacrylamide, and its derivatives. The molecular weight from hundreds of thousands to more than ten million, according to supramolecular and molecular weight can be classified to below low molecular weight (100 million), molecular weight (100 million - 10 million), a high molecular weight (10 million ----1500 million) (15 million above). In the form of goods, there are mainly powder, colloid, emulsion; powder quality is higher, the use of good, easy to dissolve, the use of high cost.
Polyacrylamide itself is non-toxic, because it is in the human body, the vast majority of the in the short term, very few of the digestive tract absorption. Most of the goods do not stimulate the skin, only certain water disintegration may have residual alkali, when repeated, long-term exposure will be irritating. The United States Food and drug administration believes that PAM and its water disintegration is low toxic or non-toxic. The toxicity of PAM is derived from the residual acrylamide monomer and the production process of the toxic metals. Acrylamide nerve caused by agents, damage to the nervous system, after the poisoning table of a weak body, movement disorders and other symptoms. Therefore, all the countries in the world have the provisions of the acrylamide content in the industrial products of polyacrylamide, generally 0.5%~0.05%. The use of water purification treatment, the acrylamide content of 0.2%, for the direct drinking water treatment, the need to 0.05%. International Health Organization was born in 1985 polyacrylamide standard pointed out: am control below 0.05% and control the amount of residual PAM, treated water content will be lower than 0.25ug/L, meet the drinking water standard in most countries. At present, the major countries in Europe and the United States, drinking water treatment and food with PAM AM content in the following 0.05%, and control the amount of PAM.
Recently, the application of polyacrylamide organic product as water treatment agent will be expanded with the increase of water quality and water demand. Such as a water supply company for 97 years and 99 years, the amount has increased by about 8 times, using water from an increase to 6. The use of coagulation, coagulation, drainage. According to reports, in front of the filter investment plus poly propylene amide 0.015~0.05mg/L can increase filter week, enhance the ability to produce 10~16%. But in week increase the filter, the head loss also increases, the recoil time and strength also to a corresponding increase, but in contrast, adding filter aid of Polyacrylamide in economy is cost-effective, dosage of polyacrylamide (PAM) filter, can prevent algae penetrate sand filter, in treatment of sudden accident, to ensure the quality of filtered water, the existing water supply its application filter process, received good results. Polyacrylamide organic products in the water treatment process and its enhanced flocculation, improve the filtration ability, improve water quality, increase the amount of water, saving cost advantage is more and more water supply enterprises willing to accept, polyacrylamide in drinking water treatment field applications are continually being developed, its prospect is optimistic.