SU1763443A1 - Method for preparation of low-molecular (co) polymers of acrylamide - Google Patents

Abstract

The invention relates to the preparation of low molecular weight (co) polymers of acrylamide used as dispersants for aqueous suspensions, emulsion stabilizers. The invention makes it possible to reduce the polymerization time to 1 hour and to obtain a polymer that does not contain traces of initiator. The effect is achieved by conducting (co) polymerization at the boiling point of an aqueous solution of monomers with preliminary barboration through an oxygen-oxygen solution.

Description

The invention relates to the field of polymer chemistry, specifically to a method for producing low molecular weight polymers and copolymers of acrylamide (M 1.5-106), which can be used as dispersants for aqueous suspensions, emulsion stabilizers, etc.

A known method of producing low molecular weight polymers and copolymers of acrylamide 1. The polymerization of 6-28% aqueous solution of acrylamide is carried out at an initial temperature of 20 ° C in the presence of molecular weight regulators.

The disadvantage of this method is that the 6-28% low molecular weight polyacrylamide is a flowable or viscous liquid that is difficult to process into a powder.

The closest to the proposed method is the technical solution for the preparation of low molecular weight water-soluble polymers of acrylamide 2. At 70-100 ° C, 45-55% aqueous solution is polymerized.

acrylamide solution with an initiator content of 0.5-35% of the monomer.

The disadvantages of this method are the following: polymerization is carried out by dosing the monomer into the resulting polymer, so the reaction lasts more than 4 hours; performance of the polymer synthesis device decreases; the amount of initiator is 0.5-35% of the monomer, which leads to contamination of the final product.

The purpose of the invention is to increase the productivity of the polymer synthesis apparatus by reducing the polymerization time and improving the quality of the obtained product.

The expected positive effect from the use of the invention consists of the following: the reaction time is reduced to 1 minute, which leads to an increase in the productivity of the polyacrylamide synthesis unit; the amount of initiator used is significantly lower.

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which increases the quality (purity) of the final product.

This goal is achieved by the fact that in a known method for producing a low molecular weight polymer of acrylamide by radical polymerization according to this invention, the reaction is carried out at the boiling point of an aqueous monomer solution, and the reaction mixture is bubbled with oxygen to prevent the polymerisation at the boiling point.

Qualitative indicators of the finished product are estimated by the molecular weight value.

The invention is illustrated by the following examples.

EXAMPLE 1. A jacketed reactor with a stirrer was charged with 650 ml of a 40% aqueous solution of acrylamide, 0.52 g of potassium persulfate (0.2% of the monomer), 0.75 g of nitryltripropionamide. Air is blown into the liquid through a bubbler at a flow rate of 0.45 l / min and the system is stirred at a speed of 500-600 rpm. The temperature of the reaction mass in the reactor is raised to 90-95 ° C and then poured into the reaction vessel with a layer thickness of liquid not more than 4 cm. The temperature in the jacket of the reaction vessel is maintained 5-7 ° C above the boiling point of the reaction mixture. After 1-2 minutes of boiling and removal of oxygen from the solution, polymerization occurs. The overheating of the reaction mass is removed by evaporation of water from the system. The reaction time is 20-30 seconds. The polymer yield is above 98%.

The rubbery polyacrylamide is removed from the reactor, cut, granulated, dried and ground into a powder with a particle size of not more than 1 mm.

Conducted 3 parallel experiments. The initial temperatures (T °, C) and average mass molecular masses (MCH) are respectively

experience 1020.91 10e

II experience 1020,93 106

III experience 1020,90 106

EXAMPLE 2 As in Example 1, but the oxygen sparging of the system is stopped and the heating of the reaction mass is carried out in the reaction vessel. experience 721.36-106

II experience 861.1-106 III experience 641.43-106

PRI me R 3. As in Example 1, but nitrogen was bubbled through a sparger and the reaction mixture was degassed for 40 minutes at 25 ° C.

Experience 304,6.106 II experience 324.3 106

III experience 294.5-106

EXAMPLE 4 As in Example 1, but a mixture of acrylamide: sodium acrylate is used as a monomer at a weight ratio of 80:20.

experience 1020,

II experience 1020,80.106

III experience 1020,85 106

As can be seen from the data of examples 1 and 4, a low molecular weight polymer and acrylamide copolymer (M 1.5-106) with high reproducibility, without the addition of any molecular weight regulators, is obtained at a constant initial temperature of 100 ° C. Upon termination of the oxygen sparging system (Example 2), although the goal is reached, the reactions start at different temperatures, which leads to a change in molecular weight from 1.1 -106 to 1.43-106. When the initial solution is degassed with nitrogen, the target is not reached.

Claims (1)

Invention Formula The method of obtaining low molecular weight (CO) polymers of acrylamide by polymerizing acrylamide or a mixture of acrylamide and sodium acrylate in an aqueous solution in the presence of a radical initiator, characterized in that the polymerization is carried out at the boiling point of the aqueous solution, and oxygen is bubbled through the aqueous solution until the boiling point is reached.