RU2373228C1 - Method of preparing aqueous solutions of copolymers - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method is described for preparing aqueous solutions of copolymers, involving a fundamental step for copolymerisation of partially neutralised acrylic and maleic acid in the presence of hydrogen peroxide in amount of 2 to 4% of total mass of monomers at temperature ranging from 85 to 105°C in an aqueous medium, which is realised through gradual addition of an aqueous solution of hydrogen peroxide for 3 to 6 hours into an aqueous solution of partially neutralised maleic acid and simultaneous gradual addition of an aqueous solution of partially neutralised acrylic acid, or an aqueous solution of free acrylic acid, or aqueous solutions of free acrylic acid and a base, and subsequent addition of hydrogen peroxide for 30 to 60 minutes after completion of simultaneous addition of hydrogen peroxide and acrylic acid, and a step for pre-polymerisation by keeping the reaction mixture at polymerisation temperature, distinguished by that, the pre-polymerisation step is realised by keeping the reaction mixture at polymerisation temperature for 35 to 60 minutes, subsequent simultaneous addition of aluminium or potassium persulphate in amount ranging from 0.10 to 0.15% of total mass of monomers and subsequent keeping at polymerisation temperature for 45 to 90 minutes.

EFFECT: increased dispersion capacity of copolymers.

1 cl, 1 tbl, 8 ex

Description

The invention relates to the chemistry of polymers, and in particular to a method for producing aqueous solutions of copolymers of acrylic and maleic acids and their alkaline or ammonium salts, which are widely used as inhibitors of corrosion processes, dispersants in the manufacture of synthetic detergents, paper, in the desalination of sea water, and also in other industries.

A known method of obtaining aqueous solutions of copolymers of partially neutralized acrylic and maleic acids, which includes the main stage of copolymerization of partially neutralized acrylic and maleic acids in the presence of a mixture of hydrogen peroxide and sodium persulfate or sodium perborate in an amount of 1-20% of the total weight of monomers at a temperature of 90-150 ° C (preferably at 105-115 ° C) in an aqueous medium and the stage of copolymerization. The main stage of copolymerization is carried out by gradually simultaneously simultaneously introducing a partially neutralized maleic acid aqueous solution of a mixture of initiators and an aqueous solution of free acrylic acid into an aqueous solution of maleic acid. The stage of additional polymerization is carried out by introducing into the reaction mixture at a polymerization temperature an excess amount (about 3% of the total weight of monomers) of hydrogen peroxide in the form of an aqueous solution. After the process is completed, water or an aqueous solution of sodium hydroxide is usually added (US 5763553, C08F 30/04, 1998).

In this method, aqueous copolymer solutions are obtained with a pH of 7.5-8.5, with a basic substance content of approximately 40%. The average molecular weight of the copolymers is about 20,000. The dispersing ability of the copolymers is estimated by the volume of a 0.25 M solution of calcium acetate, which was titrated until a stable turbidity of 100 ml of a solution containing 10 ml of a 2 M solution of sodium carbonate in the presence of 1 g of copolymer (or approximately 2.5 ml of a 40% copolymer solution). The copolymers obtained by the above technology have a low dispersing ability, since the volume of calcium acetate used for titration is only 14-21 ml, which corresponds to 140-210 mg of Ca / g of copolymer.

The closest in technical essence and the achieved technical result to the proposed method is a known method for producing aqueous solutions of copolymers, which includes the main stage of copolymerization of partially neutralized acrylic and maleic acids in the presence of hydrogen peroxide in an amount of 0.5-5.0% of the total weight of monomers at a temperature of 60-150 ° C (preferably at 100-130 ° C) in an aqueous medium and the stage of copolymerization. The main copolymerization stage is carried out by gradually introducing a partially neutralized maleic acid aqueous solution of hydrogen peroxide into an aqueous solution for 3-8 hours and simultaneously gradually introducing an aqueous solution of partially neutralized acrylic acid or an aqueous solution of free acrylic acid and then continuing to introduce hydrogen peroxide for 1- 3 hours after the end of the joint introduction of hydrogen peroxide and acrylic acid. The prepolymerization step is carried out by holding the reaction mixture at the polymerization temperature for 2 hours (US 5175361, C07C 55/00, 1992).

In this method, copolymer solutions are obtained with a basic substance content of 20-70% (mainly 40-60%) and a degree of neutralization of carboxyl groups in the copolymers 20-80% (mainly 30-70%). The content of residual maleic acid during polymerization at a temperature of 100-120 ° C is 0.1-0.5%.

In the description of the method there is no data on the dispersing ability of the resulting copolymer solutions. To assess their dispersing ability, the known method was reproduced under the conditions of Example 7 from its description: according to the technology described in this patent, a solution of a copolymer of 70% acrylic acid and 30% maleic acid was synthesized and the necessary parameters were determined. The resulting copolymer solution with a viscosity of 20% solution of 44.0 cP contained: the main substance 39.7%, residual monomers: - acrylic acid - 0.05%, maleic acid - 0.34%. The molecular weight distribution of the copolymer is 1.28. The dispersing ability of the copolymer is 2422 mg Ca / g of copolymer.

The copolymer does not have a sufficiently high dispersing ability and a fairly wide molecular weight distribution.

The problem to which the invention is directed, is to increase the efficiency of the use of copolymer solutions.

To solve this problem, a method for producing aqueous solutions of copolymers is proposed, including the main stage of copolymerization of partially neutralized acrylic and maleic acids in the presence of hydrogen peroxide in the amount of 2-4% of the total weight of monomers at a temperature of 85-105 ° C in an aqueous medium, which is carried out by gradual introducing a partially neutralized maleic acid aqueous solution of hydrogen peroxide into the aqueous solution for 3-6 hours and simultaneously gradually partially neutralizing the aqueous solution acrylic acid, or an aqueous solution of free acrylic acid, or aqueous solutions of free acrylic acid and base, and then continuing the introduction of hydrogen peroxide for 30-60 minutes after the completion of the joint introduction of hydrogen peroxide and acrylic acid, and the depolymerization step by holding the reaction mixture at the polymerization temperature, characterized in that the stage of additional polymerization is carried out by holding the reaction mixture at a polymerization temperature for 35-60 minutes, followed by a one-time the introduction of potassium or ammonium persulfate in an amount of 0.10-0.15% of the total weight of monomers and subsequent exposure at the polymerization temperature for 45-90 minutes.

The technical result that can be obtained using the proposed invention is to increase the dispersing ability of the copolymers.

The proposed set of features characterizing the stage of copolymerization of residual monomers allows not only to obtain copolymers with a low content of residual monomers, but also affects the molecular mass distribution of the copolymers towards its narrowing and leads to an unexpected jump (1.5-2 times) dispersing ability of copolymers.

The invention is illustrated by the following examples.

Example 1

7.94 parts by weight are charged into a reactor equipped with a refrigerator, two metering devices, a sleeve for measuring temperature, a jacket for heating and cooling, and a mixing device. maleic acid, 8.35 parts by weight water and 10.95 parts by weight 40% aqueous sodium hydroxide solution (the degree of neutralization of maleic acid is 90%). The main stage of copolymerization is carried out as follows. The contents of the reactor are heated to 95 ° C and 45.35 parts by weight are simultaneously introduced into it simultaneously over the course of 5 hours through the first dosing device. a solution of neutralized to 30% acrylic acid prepared from 18.40 parts by weight acrylic acid, 19.27 parts by weight water and 7.68 parts by weight 40% aqueous solution of sodium hydroxide, and through the second dosing device - 2.19 wt.h. 20% aqueous hydrogen peroxide solution (first portion of initiator). At the end of the joint dosing of hydrogen peroxide and a solution of acrylic acid continue to dose for 60 minutes, 0.44 wt.h. a solution of hydrogen peroxide (the second portion of the initiator), (the total amount of hydrogen peroxide is 2% of the total mass of monomers). To additionally polymerize the residual monomers, the reaction mixture is first allowed to stand for 40 minutes at the polymerization temperature (first exposure), then 0.04 parts by weight are added at a time. potassium persulfate (0.15% of the total weight of the monomers) and again stand the mixture for 60 minutes at the polymerization temperature (second exposure). The resulting copolymer solution is cooled to 25 ° C and additional neutralization is carried out by introducing 15.33 parts by weight of 40% aqueous sodium hydroxide solution (the degree of neutralization of carboxyl groups in the copolymer is 90%).

A copolymer solution is obtained with a basic substance content of 39.9%, a viscosity of a 20% solution of 41.5 cP (Brookfeld LVF viscometer, rotor No. 1, speed 60 s ^-1 ) and a residual monomer content,%: acrylic acid - 0.028, maleic acid - 0.173. The molecular weight distribution of the copolymer (MMP) is 1.13. The dispersing ability of the copolymer is 3912 mg Ca / g of copolymer.

Dispersing ability is determined by the method, the essence of which is the titration of a copolymer solution with a solution of calcium acetate in the presence of sodium carbonate. For this, 10 ml of a 0.1% aqueous solution of the copolymer is placed in a conical flask, 1.0 ml of a 10% aqueous solution of sodium carbonate, 89 ml of water are added thereto and, after thorough mixing, it is titrated with an aqueous solution of calcium acetate with a concentration of 0.25 mol / l until a steady turbidity. The volume of the solution of calcium acetate, which went to the titration, evaluate the dispersing ability of the copolymer, which is measured in mg Ca / g of copolymer.

Example 2

The process is carried out as in example 1, with the following differences. At the main stage of copolymerization, a solution of acrylic acid prepared from 18.40 parts by weight is introduced into the reactor through the first dosing device. acrylic acid and 19.27 parts by weight water, at the stage of additional polymerization, the first exposure of the reaction mass is carried out for 60 minutes and additional neutralization is carried out by the introduction of 23.0 parts by weight 40% aqueous sodium hydroxide solution (the degree of neutralization of carboxyl groups in the copolymer is 90%). The properties of the obtained copolymer are shown in the table.

Example 3

The process is carried out as in example 1, with the following differences. 9.22 parts by weight are charged into the reactor. maleic acid, 13.34 parts by weight water and 8.11 parts by weight 30% aqueous ammonia. The contents of the reactor are heated to 85 ° C and gradually within 3 hours, 41.38 parts by weight are introduced into it simultaneously through the first dosing device. a solution of neutralized to 30% acrylic acid prepared from 17,12 wt.h. acrylic acid, 20.22 parts by weight water and 4.04 parts by weight 30% aqueous ammonia solution, and through the second metering device - 3.95 wt.h. 20% aqueous hydrogen peroxide solution (first portion of initiator). The second portion of the initiator is introduced in an amount of 1.32 wt.h. (the total amount of hydrogen peroxide is 4% of the total mass of monomers). To additionally polymerize the residual monomers, the reaction mixture is first maintained for 45 minutes at the polymerization temperature (first exposure), then 0.026 parts by weight are introduced into it at a time. potassium persulfate (0.10% of the total mass of monomers) and again the mixture is kept for 75 minutes at the polymerization temperature (second exposure). Additional neutralization of the obtained copolymer is carried out by the introduction of 8.08 wt.h. 30% aqueous ammonia solution (the degree of neutralization of carboxyl groups in the copolymer is 90%). The properties of the obtained copolymer are shown in the table.

Example 4

The process is carried out as in example 1, with the following differences. 6.58 parts by weight are charged into the reactor. maleic acid, 1.01 parts by weight water and 34.04 parts by weight 40% aqueous potassium hydroxide solution (the degree of neutralization of maleic acid is 80%). The contents of the reactor are heated to 105 ° C and gradually within 5 hours at the same time through the first dosing device 35.13 wt.h. a solution of neutralized to 40% acrylic acid prepared from 19.76 wt.h. acrylic acid, 1.01 parts by weight water and 15.37 parts by weight 40% aqueous solution of potassium hydroxide, and through the second metering device - 3.29 wt.h. 20% aqueous hydrogen peroxide solution (first portion of initiator). The second portion of the initiator is administered in an amount of 0.66 wt.h. (the total amount of hydrogen peroxide is 3% of the total mass of monomers). Additional neutralization of the obtained copolymer is carried out by the introduction of 15.37 wt.h. 40% aqueous solution of potassium hydroxide (the degree of neutralization of carboxyl groups in the copolymer is 80%). The properties of the obtained copolymer are shown in the table.

Example 5

The process is carried out as in example 1, with the following differences. The contents of the reactor are heated to 90 ° C and 4.86 wt.h. are introduced into the reactor simultaneously with a solution of neutralized acrylic acid through a second metering device over a period of 6 hours. 20% aqueous hydrogen peroxide solution (first portion of initiator). The second portion of the initiator is administered in an amount of 0.41 parts by weight within 30 minutes (the total amount of hydrogen peroxide is 4% of the total mass of monomers). When the residual monomers were copolymerized, the reaction mixture was first incubated for 35 minutes at the polymerization temperature (first exposure), then 0.03 wt.h. ammonium persulfate (0.10% of the total mass of monomers). The properties of the obtained copolymer are shown in the table.

Example 6

The process is carried out as in example 1, with the following differences. 6.58 parts by weight are charged into the reactor. maleic acid, 6.42 parts by weight water and 10.21 parts by weight 40% aqueous sodium hydroxide solution (the degree of neutralization of maleic acid is 90%). The contents of the reactor are heated to 100 ° C and gradually over a period of 5 hours, a solution of acrylic acid prepared from 19.76 parts by weight is introduced through the first dosing device into it. acrylic acid and 18.6 parts by weight water, and through the second dosing device - 3.44 wt.h. 20% aqueous hydrogen peroxide solution (first portion of initiator). The second portion of the initiator is administered in an amount of 0.51 parts by weight within 45 min (the total amount of hydrogen peroxide is 3% of the total mass of monomers). To additionally polymerize the residual monomers, the reaction mixture is first allowed to stand for 45 minutes at the polymerization temperature (first exposure), then 0.045 parts by weight are introduced into it at a time. ammonium persulfate (0.15% of the total weight of the monomers) and again stand the mixture for 45 minutes at the polymerization temperature (second exposure). Additional neutralization of the obtained copolymer is carried out without preliminary cooling by the introduction of 21.96 wt.h. 40% aqueous sodium hydroxide solution (the degree of neutralization of carboxyl groups in the copolymer is 85%). The properties of the obtained copolymer are shown in the table.

Example 7

The process is carried out in a reactor similar to that in Example 1, only equipped with three metering devices. The process is carried out as in example 1, with the following differences. 9.22 parts by weight are charged into the reactor. maleic acid, 9.03 parts by weight water and 14.31 parts by weight 40% aqueous sodium hydroxide solution (the degree of neutralization of maleic acid is 90%). The contents of the reactor are heated to 85 ° C and gradually for 4 hours, 37.34 parts by weight are introduced into it simultaneously through the first dosing device. a solution of acrylic acid prepared from 17.12 wt.h. acrylic acid and 20.22 parts by weight water, through the second dosing device - 4.04 wt.h. 40% aqueous solution of sodium hydroxide and through the third - 3.16 wt.h. 20% aqueous hydrogen peroxide solution (first portion of initiator). The second portion of the initiator is administered in an amount of 0.79 parts by weight. within 60 minutes (the total amount of hydrogen peroxide is 3% of the total mass of monomers). When the residual monomers are copolymerized, the duration of the first exposure of the reaction mixture at the polymerization temperature is 45 minutes, the duration of the second is 90 minutes No additional neutralization of the obtained copolymer is carried out (the degree of neutralization of carboxyl groups in the copolymer is 60%). The properties of the obtained copolymer are shown in the table.

Example 8 (prototype)

The process is carried out in a reactor, as in example 1. 7.94 parts by weight are charged to the reactor. maleic acid, 8.35 parts by weight water and 10.95 parts by weight 40% aqueous sodium hydroxide solution (the degree of neutralization of maleic acid is 90%). The main stage of copolymerization is carried out as follows. The contents of the reactor are heated to 100 ° C and 45.35 parts by weight are simultaneously introduced into it simultaneously over the course of 5 hours through the first dosing device. a solution of neutralized to 30% acrylic acid prepared from 18.40 parts by weight acrylic acid, 19.27 parts by weight water and 7.68 parts by weight 40% aqueous solution of sodium hydroxide, and through the second dosing device - 9.55 wt.h. 4.6% aqueous hydrogen peroxide solution (first portion of initiator). At the end of the joint dosing of a solution of acrylic acid and hydrogen peroxide continue to dose for 60 minutes 1.90 wt.h. a solution of hydrogen peroxide (the second portion of the initiator), (the total amount of hydrogen peroxide is 2% of the total mass of monomers). For the copolymerization of residual monomers, the reaction mixture was held for 120 minutes at the polymerization temperature. The properties of the obtained copolymer are shown in the table.

Table Synthesis conditions and copolymer properties Indicator Synthesis conditions by examples one 2 3 four 5 6 7 According to the prototype The main stage of copolymerization AK: MK ratio 70:30 70:30 65:35 75:25 70:30 75:25 65:35 70:30 Neutralizing agent NaOH NaOH NH ₄ OH Koh NaOH NaOH NaOH NaOH The degree of neutralization,% AK thirty 0 thirty 40 thirty 0 thirty thirty MK 90 90 90 80 90 90 90 90 The copolymerization temperature, ° C 95 95 85 105 90 one hundred 85 one hundred The total amount of H ₂ O ₂ ,% 2 2 four 3 four 3 3 2 Introduction time AK and the first portion of H ₂ O ₂ , h 5 5 3 5 6 5 four 5 the second portion of N ₂ About ₂ min 60 60 60 60 thirty 45 60 60 Stage copolymerization First exposure time, min 40 60 45 40 35 45 45 120 Polymerization initiator,% potassium persulfate 0.15 0.15 0.1 0.15 0.15 ammonium persulfate 0.1 0.15 The second exposure time, min 60 60 75 60 60 45 90

Indicator The properties of the copolymers of the examples one 2 3 four 5 6 7 According to the prototype The degree of neutralization of the copolymer,% 90 90 90 80 90 85 60 60 The content of the main substance in solution,% 39.9 41.2 39.9 41.5 40,0 39.9 38.7 36,2 Viscosity, cP 41.5 40.3 20,0 35.5 30.7 38.8 29.5 44 The content of residual monomers,% AK 0,028 0.010 0,023 0.012 0.010 0.015 0,020 0,050 MK 0.173 0.156 0.210 0,075 0.227 0,073 0.129 0.340 MMP 1.13 1.16 1,08 1.10 1.12 1,11 1.15 1.28 Dispersing ability, mg Ca / g copolymer 3912 3700 4814 4792 4100 4114 4002 2422

Claims (1)

The method of obtaining aqueous solutions of copolymers, including the main stage of copolymerization of partially neutralized acrylic and maleic acids in the presence of hydrogen peroxide in the amount of 2-4% of the total mass of monomers at a temperature of 85-105 ° C in an aqueous medium, which is carried out by gradual introduction for 3- 6 hours in an aqueous solution of partially neutralized maleic acid in an aqueous solution of hydrogen peroxide and the simultaneous gradual introduction of an aqueous solution of partially neutralized acrylic acid, or aqueous a solution of free acrylic acid, or aqueous solutions of free acrylic acid and a base, and then continuing the introduction of hydrogen peroxide for 30-60 minutes after the simultaneous introduction of hydrogen peroxide and acrylic acid, and the stage of additional polymerisation by holding the reaction mixture at the polymerization temperature, characterized in that the stage of additional polymerization is carried out by holding the reaction mixture at a polymerization temperature for 35-60 minutes, subsequent simultaneous administration of potassium persulfate I or ammonium in an amount of 0.10-0.15% of the total mass of monomers and subsequent exposure at the polymerization temperature for 45-90 minutes.