A method of obtaining a high molecular weight polyacrylamide

 

(57) Abstract:

Usage: obtain high molecular weight polyacrylamide. The inventive creation of highly stable reverse acrylamide emulsions in the presence of salts of metals of group II and III in quantities of 0.001 to 0.05 by weight of the aqueous phase. 1 C.p. f-crystals, 2 tab.

The invention relates to a method for linear polyacrylamide of high molecular weight in the reverse emulsions.

It is known that the polyacrylamide of high molecular weight is used in the processes of wastewater treatment in the pulp and paper industry, and also as a thickener water in the processes of secondary production.

One method of obtaining high molecular weight polyacrylamide is polymerization in inverse emulsion, the dispersed phase which are aqueous solutions of monomers, and a continuous medium nonpolar organic solvents [1] Stabilizers monomer emulsions are sorbitane esters of fatty acids, their polyoxyethylene derivatives and some others, the polymerization is initiated, typically oil-soluble compounds by dinitriles asuitable acid, benzoyl peroxide.

Cons is t to the formation of significant amounts of coagulum on the walls of the reactor and the stirrer. Remove coagulum is a time-consuming process, leading to a significant rise in the cost of the product.

In the known descriptions of polymerization in inverse emulsion process is carried out at relatively low concentrations of monomer in the system 12-25% as the increase of monomer concentration above this limit leads to a sharp increase in the number formed during polymerization of the coagulum. The increase in the content of the emulsifier in the polymerization system, contributing to its stability undesirable because it forces the user to enter additional purification stage latex from the emulsifier, in addition, leads to deterioration of the polymer.

A method of obtaining water-soluble polymers in the reverse emulsion, in which the reduction of the resulting coagulum is achieved by adding alkali metal salts in an amount of from 0.6 to 10% in the aqueous phase of emulsions [2]

The disadvantage of this method is the use of large quantities of salts, electrolytes, which degrades performance and limits the range of applications of the obtained polymer. The quantity of monomer introduced into the aqueous phase does not exceed 40-50% of the total content of polymer clay is th sulfates, chlorides, acetates of sodium, ammonium in the amount of 2-5% to the aqueous phase of emulsions [3]

This reduces the amount of coagulum formed during polymerization, with 50% or more to 2-23% of the content of the monomer in the aqueous phase of the emulsion is 40% of the total content of monomer in the system 28 wt. the content of the emulsifier 2-3 wt.

The disadvantage of this method is the high salt content in the final product (4-12% in terms of dry polymer), which is undesirable, because it makes impossible its use in water treatment processes pulp and paper industry and other industries. In addition, the low polymer content in the finished product forced in some cases to carry out the concentration of the latex to give it consumer qualities.

The purpose of the invention is the creation of highly stable emulsions with a high content of monomer in them, further polymerization which proceeds with the formation of small amounts of coagulum.

This is achieved by the introduction of the dispersed phase Monomeric emulsions, salts of metals of group II and III in quantities of 0.001 to 0.05% of the aqueous phase. The content of monomer in the emulsion is 50-70 wt. to the aqueous phase (up to its limit rastvorimost the s (more than 10 million ), the characteristic viscosity of the polymer is about 25 to 30 DL/g

Slight salt content in the polymers can not limit the scope of their applications. As the dispersion medium Monomeric emulsions used aliphatic hydrocarbons, emulsions stabilized sorbitane esters of fatty acids, the polymerization initiated by azo compounds. The amount of initiator in the oil phase of the emulsions of 0.001-0.05% of the total amount of emulsifier in the emulsion system of 0.5-5% ratio of phases of water:oil varies from 1.5: 2 to 3:1. Monomeric emulsion free from oxygen and polymerized at temperatures of 45-60aboutC. the Content of polymer in the resulting dispersion 20-40% of the amount generated in the water polymerization of coagulum 1-10% as additives are salts of metals of group II and III of the Periodic system and of a number of acids, such as hydrochloric, sulphuric, nitric, boric, and others. All of these salts in the concentration range of 0.001-0.05 to wt. to the aqueous phase can significantly increase the stability of the inverse monomer emulsion.

P R I m e R 1. Prepare a monomer emulsion consisting of 15 g of acrylamide, 15 g of water, 30 g of cyclohexane and 0.7 g of servicemonitoring (span-60) and 0.001 g of dinitrile azotobacteraceae by blowing argon and polimerizuet for 3 h at 55aboutC.

The comparative stability of the Monomeric emulsion during polymerization, characterized by the amount of coagulum formed, are given in table.1.

P R I m e R s 2-7. Prepare emulsions containing 10-20 g of acrylamide, 10-12 g of water, 28-16 g of cyclohexane, 2 g of span-60, 0.001 g of dinitrile asuitable acid and 0.02 to 1 g of salt II-III groups.

Examples are illustrated in the table. 2. The characteristic viscosity of the thus obtained polymers of acrylamide from 24.5 to 28 DL/g

P R I m e R 3 (comparative). As salt additives used sodium acetate (see tab.2).

1. A method of OBTAINING a high MOLECULAR weight POLYACRYLAMIDE, including the formation of a stable inverse monomer emulsion in the presence of inorganic salts and subsequent polymerization, characterized in that use salts of inorganic salts of metals of group II and III in quantities of 0.001 to 0.05% by weight of the aqueous phase.

2. The method according to p. 1, characterized in that the use of sulfates, chlorides, borates, nitrates of the metals of group II and III.

 

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