JPH11255830A - Preparation of acrylamide based polymer composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing acrylamide based polymer compositions excellent in the stability of aqueous solutions thereof. SOLUTION: A crylamide monomer or a mixture of acrylamide with a monomer copolymerizable therewith is polymerized in an aqueous medium in the presence of (a) at least one member selected from salicylic acid, anthranilic acid, 5-sulfosalicylic acid, 5-nitrosalicylic acid, 2,4-dihydroxybenzoic acid, 2,6- dihydroxy-benzoic acid, 4-aminosalicylic acid, 5-methyl-salicylic acid, 2,3-cresotic acid, 2,4-cresotic acid and mixtures thereof and (b) at least one member selected from aminopolycarboxylic acid compounds having at least one group: -N(R1 )R2 or -NH(R3 ) [wherein R1 and R2 are each CH2 COOH or CH2 CH2 COOH; and R3 is CH(CH2 COOH)COOH] and salts thereof with the use of an oxidation- reduction system initiator composed of an organic hydroperoxide and hydrosulfurous acid and/or a salt thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an acrylamide polymer composition having a high molecular weight and excellent stability in an aqueous solution.

[0002]

2. Description of the Related Art Acrylamide polymers are used in many fields such as polymer flocculants, papermaking adhesives, papermaking retention agents, oil recovery agents, drilling mud thickeners, and the like.
In each case, it is usually used as an aqueous solution. An acrylamide polymer is obtained mainly by polymerizing a monomer in an aqueous solution. The resulting polymer is usually
It becomes a powdery polymer by drying and pulverization. From the viewpoints of productivity per polymerization vessel volume, reduction of drying load, and the like, it is preferable that the monomer concentration during the aqueous solution polymerization be higher. However, the viscosity of a high-concentration aqueous monomer solution increases remarkably with the progress of polymerization, making it impossible to stir. For this reason, it becomes difficult to remove the heat of polymerization, so that the removal of the heat of polymerization is often left to the end without removing the heat of polymerization.

[0003] For example, when the concentration of the charged acrylamide monomer is 25% by weight, the temperature rise of the reaction system reaches about 75 ° C. Therefore, the temperature at the time of completion of the polymerization in the aqueous solution polymerization is set at 10
In order to carry out the polymerization at a high monomer concentration while keeping the temperature below 0 ° C., it is necessary to set the polymerization initiation temperature to a low temperature of 25 ° C. or less.

[0004] From this, as a polymerization initiator, peroxides such as potassium persulfate and hydrogen peroxide and ferrous ion,
A redox initiator having a low activation energy using a reducing agent such as sodium hydrogen sulfite in combination, or a combined system of a redox initiator and an azo initiator is preferably used.

However, there is a problem that the acrylamide polymer obtained by using such an initiator system is liable to be deteriorated when used as an aqueous solution. For example, when the acrylamide-based polymer aqueous solution obtained by using such an initiator system is left at room temperature, a phenomenon that the initially indicated value of the aqueous solution viscosity is greatly reduced is observed. This phenomenon is further accelerated under high temperatures, and in severe cases, it may not be possible to use it for the intended application. Although the cause of the decomposition of the polymer has not been clearly elucidated yet, it is considered to be based on a radical reaction involving dissolved oxygen in water.

As one of the solutions, a method of adding a compound having a stabilizing effect to an aqueous polymer solution has been considered, for example, a metal salt of benzotriazole, 2-mercaptobenzothiazole, dimethyldithiocarbamic acid,
Various compounds such as thiourea, 2-mercaptobenzimidazole and methionine have been proposed. As a method of mixing the stabilizer with the polymer, there are a method of mixing into a polymer powder and a method of mixing into a hydrous polymer gel.

[0007]

However, the various stabilizers which have been conventionally studied as described above do not have a sufficient stabilizing effect, and practically no effective stabilizers have been found. It is the current situation. Also, in the method of mixing the stabilizer, it is difficult to uniformly mix the stabilizer and the polymer powder by the method of mixing with the polymer powder, and in some cases, even once mixed, the stabilizer is almost completely separated. . In addition, it is difficult to uniformly mix a stabilizer in a highly viscous gel by a method of mixing the stabilizer in a hydrous polymer gel, and a special mixing device is required. This complicates the manufacturing process and increases the cost.

The method of adding and mixing a stabilizer to an aqueous monomer solution before the monomer is polymerized can most uniformly disperse the stabilizer,
Although the production process is simplified and is an advantageous method, in the case of the stabilizer as described above, the stabilizing effect is low, or when the stabilizer is mixed before polymerization, the effect of the stabilizer on the redox initiator is reduced. As a result, the polymerization rate is reduced, and the productivity of the polymer is deteriorated. In extreme cases, the polymerization may not proceed. Therefore, there has been a strong demand for the emergence of a combination of a stabilizer and an oxidation-reduction initiator that has a more excellent stabilizing effect and does not inhibit polymerization even when added to an aqueous monomer solution and polymerized.

[0009]

Means for Solving the Problems In view of such circumstances, the present inventors have made intensive studies and have found that (a) salicylic acid, anthranilic acid, 5-sulfosalicylic acid, 5-nitrosalicylic acid, and 2,4-dihydroxybenzoic acid. Acid, 2,6-dihydroxybenzoic acid, 4-aminosalicylic acid, 5-methylsalicylic acid, 2,3-
Cresotic acid, one or more selected from 2,4-cresotic acid and salts thereof, and (b) a mixture of one or more selected from the group consisting of specific aminopolycarboxylic acid compounds and salts thereof (hereinafter, referred to as Has been found to exhibit excellent performance as a stabilizer for aqueous polymer solutions.

However, these stabilizers are added to an aqueous monomer solution to add a generally used redox initiator, for example, an organic hydroperoxide / iron redox initiator,
When polymerization was carried out using a potassium persulfate / sodium bisulfite redox initiator, the polymerization rate was reduced, and sometimes the polymerization did not proceed. Therefore, as a result of further study of various redox initiators, only in the case of a specific redox initiator combination, even if the stabilizer is added to the monomer aqueous solution, regardless of the presence or absence of the stabilizer It has been found that the polymerization proceeds and a polymer having excellent physical properties can be obtained, and the present invention has been achieved.

That is, the gist of the present invention is to provide an acrylamide monomer or a monomer mixture composed of at least 25 mol% of acrylamide and at least one monomer copolymerizable therewith with an aqueous medium. Medium, (a) salicylic acid, anthranilic acid, 5-sulfosalicylic acid, 5-nitrosalicylic acid, 2,4-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 4-aminosalicylic acid, 5-methylsalicylic acid, 2,3- (B) at least one —N (R ₁ ) R ₂ group or —NH (R ₃ ) group in a molecule, and at least one selected from cresotic acid, 2,4-cresotic acid and salts thereof; Polymerization using an organic hydroperoxide and a redox initiator comprising dithionous acid and / or a salt thereof in the presence of at least one member selected from the group consisting of aminopolycarboxylic acid compounds and salts thereof. In the preparation of acrylamide-based polymer composition according to symptoms. (However, R ₁ and R
₂ are each independently CH ₂ COOH or CH ₂ CH ₂ COO
H, R ₃ represents CH (CH ₂ COOH) COOH)

The amount of the stabilizer to be added to the acrylamide polymer composition is not particularly limited, and may be appropriately adjusted depending on the degree of the atmosphere to which the aqueous solution of the acrylamide polymer is exposed, the standing period, and the like. It is preferable to add 0.01 to 20% by weight with respect to the coalescence. That is, in order to sufficiently exert the stabilizing effect, it is preferable to add 0.01% by weight or more, and even if it exceeds 20% by weight, the effect of the addition is not so much improved.

In the present invention, an aminopolycarboxylic acid compound means a compound having at least one (substituted) amino group and a plurality of carboxylic acid groups in a molecule, and at least one -N (R) in a molecule. ₁ ) R ₂ group or -NH
An aminopolycarboxylic acid compound having an (R ₃ ) group (provided that R
Specific examples of ₁ , R ₂ and R ₃ have the same meaning as described above) include ethylenediaminetetraacetic acid (hereinafter, referred to as EDTA) and propylenediaminetetraacetic acid (hereinafter, PDT)
A), diethylenetriaminepentaacetic acid (hereinafter, referred to as A)
DTPA), ethylenediaminetetrapropionic acid (hereinafter referred to as EDTP), ethylenediaminedisuccinic acid (hereinafter referred to as EDDS), aspartic aciddiacetic acid
(Hereinafter referred to as ASDA), nitrilotriacetic acid (hereinafter referred to as N
TA).

In the present invention, the component (b) includes E
DTA, PDTA, DTPA, EDDS, ASDA are preferred.

(B) At least one --N (R
₁ ) The ratio of the aminopolycarboxylic acid compound having an R ₂ group or —NH (R ₃ ) group and its salt to the amount of the stabilizer is not particularly limited, but is preferably 50% by weight or less, and is preferably 20% by weight or less. % Is more preferable.
(However, R ₁ , R ₂ , and R ₃ represent the same meaning as described above.)

The carboxylic acid group in the stabilizer may be a free acid or a salt. Examples of the salt include, but are not limited to, sodium salt, potassium salt, ammonium salt, and organic ammonium salts such as trimethylammonium salt and triethylammonium salt. The amino group may be a free amino group or a salt such as a hydrochloride, a nitrate, a carbonate, a sulfate, a phosphate, and an organic acid salt.

In the present invention, as the organic hydroperoxide which is an oxidizing component of the redox initiator, any organic hydroperoxide which is usually used for initiation of polymerization can be used, but t-butyl hydroperoxide, cumene Hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide and 1,1,3,3-tetramethylbutyl hydroperoxide can be exemplified as preferred organic hydroperoxides.

It is necessary to use dithionous acid or a salt thereof as a reducing agent component. However, if the kind and amount thereof do not substantially cause adverse effects such as polymerization inhibition, the reducing agent of the conventional redox initiator may be used. Sodium sulfite, sodium formaldehyde sulfoxylate, ferrous sulfate,
A reducing agent such as ferrous chloride can be used in combination.

In the present invention, only the redox initiator may be used, but an azo initiator may be used in combination. The combined use of an azo initiator has the effect of reducing the amount of residual monomers. As the azo-based initiator, any azo-based initiator can be used as long as it is generally used as a polymerization initiator, and 2,2′-azobis (2-
Amidinopropane) dihydrochloride, 4,4′-azobis (4-cyanovaleric acid) and azobisisobutyronitrile.

The pH of the polymerization solution is determined by considering the temperature at which the redox initiator used becomes active,
An appropriate pH may be selected in the range of pH 2 to 9, preferably pH 4 to 7, in consideration of the molecular weight of the produced polymer and the solubility of the polymer.

The monomer used in the present invention may be acrylamide alone, and a monomer composed of at least 25 mol% of acrylamide and at least one monomer copolymerizable therewith is 100 mol%. It may be a mixture. Examples of monomers copolymerizable with acrylamide include, for example, methacrylamide, acrylic acid, methacrylic acid or salts thereof, acrylamidepropanesulfonic acid such as 2-acrylamide-2-methylpropanesulfonic acid and salts thereof, and N- Vinylpyrrolidone, dialkylaminoalkyl esters and salts thereof and quaternary ammonium salts, acrylonitrile, methacrylonitrile, methyl acrylate, ethyl acrylate, butyl acrylate,
Examples include acrylic acid such as methyl methacrylate and ethyl methacrylate and lower acrylic esters of methacrylic acid.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, parts are by weight unless otherwise specified.

Example 1 0.28 parts of salicylic acid was added to a monomer aqueous solution comprising 72 parts of ion-exchanged water, 20 parts of acrylamide and 8 parts of acrylic acid.
After adding 0.01 part of ethylenediaminetetraacetic acid and adjusting the pH to 6 using sodium hydroxide, the mixture is placed in a Dewar bottle, the inside of the system is replaced with nitrogen, and at 10 ° C., 0.0002 part of t-butyl hydroperoxide is added. Sodium dithionate 0.00
04 parts and 0.06 part of 2,2'-azobis- (2-amidinopropane) dihydrochloride were added. The temperature started to rise 3 minutes after the addition of the initiator, and reached the maximum temperature 40 minutes after the start of the temperature rise. The obtained hydrous polymer gel was extracted from the Dewar bottle, crushed into granules, dried, and crushed to about 2 mm or less to obtain a water-soluble polymer composition.

140p of sodium chloride in ion exchange water
The resulting polymer composition was added to a solution in which pm and calcium chloride were dissolved so as to have a concentration of 160 ppm so as to be 0.05% by weight, and the mixture was stirred and dissolved. A part of the polymer solution thus obtained was filtered through an 80-mesh wire gauze, and the dissolved state was confirmed from the amount of the remaining insoluble gel polymer, and a part was measured for viscosity with a B-type viscometer (25 ° C.). Was measured and then placed in a thermostat adjusted to 70 ° C. One week later, it was taken out of the thermostat, the viscosity was measured, and the viscosity retention was determined by the following equation. Viscosity retention = solution viscosity after holding in thermostat for predetermined time / solution viscosity immediately after dissolution × 100 The results are shown in Table 1.

Examples 2 to 16 Except that salicylic acid was replaced with the same amount of the compound shown in Table 1 (Compound A) and ethylenediaminetetraacetic acid was replaced with the same amount of the compound shown in Table 1 (Compound B). When polymerization was carried out in the same manner as in Example 1, the temperature began to rise 1 to 3 minutes after addition of the initiator, and thereafter,
The maximum temperature was reached after the passage of time in the table. However, Embodiment 1
In No. 6, 0.03 part of compound B was added. The obtained polymer was treated in the same manner as in Example 1 to prepare and evaluate a polymer solution. The results are shown in Table 1 together with the results of Example 1.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that salicylic acid and ethylenediaminetetraacetic acid were not added. The temperature started to rise 3 minutes after the addition of the initiator, and reached the maximum temperature 41 minutes after the addition. did. The obtained water-soluble polymer composition was evaluated in the same manner as in Example 1. Table 1 shows the results together with other results.
Shown in

[0027]

[Table 1] In the column of solubility in Table 1, good means that no undissolved polymer gel can be visually confirmed on the wire mesh. or,
In Tables 1 and 2, θp indicates the time (minute) from the start of temperature rise to the maximum temperature.

Comparative Example 2 0.28 parts of salicylic acid was added to a monomer aqueous solution comprising 72 parts of ion-exchanged water, 23 parts of acrylamide and 5 parts of acrylic acid.
After adding 0.01 parts of ethylenediaminetetraacetic acid and adjusting the pH to 9 using sodium hydroxide, the mixture was placed in a Dewar bottle and replaced with nitrogen. Then, at 10 ° C., 0.003 parts of t-butyl hydroperoxide and tetraethylenepentane were added. Min 0.
003 parts, 0.0002 parts of iron pyrophosphate, and 0.05 parts of 4,4′-azobis- (4-cyanovaleric acid). After the addition for 3 hours, the polymerization did not proceed.

Comparative Example 3 Polymerization was carried out in the same manner as in Comparative Example 2 except that salicylic acid and ethylenediaminetetraacetic acid were not added. One minute after the addition of the initiator, the temperature started to rise, and one minute after the start of the temperature rise.
The maximum temperature was reached after hours. Thereafter, the viscosity retention of the polymer composition obtained in the same manner as in Example 1 was measured and found to be 23%.

Comparative Example 4 0.27 part of salicylic acid was added to an aqueous monomer solution comprising 73 parts of ion-exchanged water, 20 parts of acrylamide and 7 parts of acrylic acid.
After adding 0.01 part of ethylenediaminetetraacetic acid and adjusting the pH to 7 by adding sodium hydroxide, the mixture was placed in a Dewar bottle, and the inside of the system was replaced with nitrogen.
002 parts, 0.002 parts of sodium hydrogen sulfite, and 0.02 parts of 2,2′-azobis- (2-amidinopropane) dihydrochloride were added and polymerized. The temperature started to increase 10 minutes after the addition of the initiator, but the rate of temperature increase at the beginning of polymerization was slow, and it took a long time of 240 minutes to reach the maximum temperature.

Comparative Examples 5 to 19 Instead of salicylic acid, compound A (0.27) shown in Table 2 was used.
Parts) and Compound B (0.01 parts) were added in the same manner as in Comparative Example 4 except that an initiator was added. The polymerization behavior at this time is shown in Table 2 together with the results of Comparative Example 3.

[0032]

[Table 2]

Comparative Example 20 Polymerization was carried out in the same manner as in Comparative Example 4 except that salicylic acid and ethylenediaminetetraacetic acid were not added. The temperature started to rise 5 minutes after the addition of the initiator, and reached the maximum temperature 90 minutes after the addition. did. Thereafter, the viscosity retention of the polymer composition obtained in the same manner as in Example 1 was measured and found to be 24%.

[0034]

According to the method of the present invention, a acrylamide polymer composition having a high molecular weight and good solubility can be obtained with high productivity at a low polymerization initiation temperature of 25 ° C. or less, in a short polymerization time, and In addition, the obtained polymer has higher stability of the aqueous solution than that of the conventional production method, and exhibits excellent stability not only at room temperature but also at a high temperature of 70 ° C.

Claims (4)

[Claims] An acrylamide monomer or a monomer mixture comprising 100 mol% of at least 25 mol% of acrylamide and at least one monomer copolymerizable therewith,
In an aqueous medium, (a) salicylic acid, anthranilic acid, 5-sulfosalicylic acid, 5-nitrosalicylic acid, 2,4-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 4-aminosalicylic acid, 5-methylsalicylic acid, 2, 3-cresotic acid, 2,4-
One or more selected from cresotic acid and salts thereof,
(B) in the presence of one or more selected from the group consisting of aminopolycarboxylic acid compounds having at least one —N (R ₁ ) R ₂ group or —NH (R ₃ ) group in the molecule and salts thereof, A method for producing an acrylamide polymer composition, comprising polymerizing using an organic hydroperoxide and a redox initiator comprising dithionite and / or a salt thereof. (However, R ₁ and R ₂ are each independently CH ₂ COOH or CH ₂ CH ₂ COOH, and R ₃ is CH (CH ₂ COO
H) indicates COOH) 2. The method according to claim 1, wherein (b) is EDTA, PDTA, DTPA,
The method for producing an acrylamide-based polymer composition according to claim 1, wherein the composition is at least one selected from the group consisting of EDDS, ASDA, and salts thereof. 3. An organic hydroperoxide selected from the group consisting of t-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide and 1,1,3,3-tetramethylbutyl hydroperoxide. The method for producing an acrylamide-based polymer composition according to claim 1, wherein the composition is at least one selected from the group consisting of: 4. The method for producing an acrylamide polymer composition according to claim 1, wherein an azo initiator is further used in combination.