JPH11349773A - Stabilization of acrylamide polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize an aqueous solution of acrylamide polymer or its dispersion in an aqueous medium containing a high concentration of an inorganic salt for a long period of time by adding an aminoguanidine and a reducing agent to acrylamide polymer. SOLUTION: (A) One hundred pts.wt. of an acrylamide polymer are mixed with (B) 0.01-10.0 pts.wt., preferably 0.02-8.0 pts.wt. more preferabl-y 0.05-5.0 pts.wt. of an amincguanidine and (C) 0.01-30.0 pts.wt., preferably 0.1-20.0 pts.wt., more preferably 0.5-10.0 pts.wt. of a reducing agent. The component A is an acrylamide polymer or a copolymer thereof with, when necessary, other copolymerizable monomers. The component B is, for example, aminoguanidine hydrochloride, aminoguanidine sulfate, aminoguanidine carbonate or the like. As a component C, is cited sodium (hydrogen) sulfite, ammonium (hydrogen) sulfite or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for stabilizing an acrylamide polymer. More specifically, the present invention relates to a method for stabilizing a dispersion in an aqueous solution of an acrylamide polymer or an aqueous medium containing a high concentration of an inorganic salt.

[0002]

2. Description of the Related Art Acrylamide polymers are used in many fields such as polymer flocculants, thickeners, paper strength agents, retention agents, drainage improvers, and oil recovery agents. Various methods have been proposed for obtaining an acrylamide-based polymer, but are industrially mainly produced by aqueous solution polymerization.

In such aqueous solution polymerization, as the monomer concentration increases, the polymer becomes a gel containing water, and handling such as dissolution becomes difficult as it is. For this reason, they are diluted and used as a low-concentration solution having fluidity, or are dried and powdered for distribution. A method for producing an acrylamide polymer by water-in-oil emulsion polymerization or suspension polymerization in a hydrophobic solvent is also known (JP-A-5-194613).

However, some problems have been pointed out in the method of industrially obtaining such an acrylamide polymer. For example, in the case of aqueous solution polymerization, when pulverizing an acrylamide-based polymer from an acrylamide-based aqueous solution, enormous heat energy is required for drying, and thermal three-dimensional cross-linking due to heating causes insolubilization of the polymer. Occur. In addition, in water-in-oil emulsion polymerization or suspension polymerization in a hydrophobic solvent, there is a problem that equipment needs to be used for the use of a flammable solvent.

As a method for solving the above-mentioned problems, the present inventors filed an application for a method for producing an acrylamide-based polymer dispersion by a precipitation polymerization method in a salt aqueous solution containing a high concentration of inorganic salt (Japanese Patent Application No. 2002-214,878). Hei 9-14670). According to this method, an aqueous dispersion in which fine particles of an acrylamide polymer are dispersed at a high concentration can be obtained, and the polymer is easily swollen / dissolved by diluting the obtained dispersion with water, so that the acrylamide polymer can be obtained. Since a uniform aqueous solution of the polymer is obtained, workability is extremely improved.

In addition, since a flammable organic solvent is not used, it can be manufactured safely and inexpensively, and has many features such as being economically excellent. However, it is difficult to stably store the obtained dispersion for a long time,
Applications were limited in terms of practicality.

In general, when an aqueous solution of an acrylamide polymer is left for a long period of time, the degree of polymerization decreases due to oxidative decomposition of the acrylamide polymer, and the viscosity of the aqueous solution decreases.
There is a problem in terms of stability such that insoluble swelling gel is generated due to intramolecular / intermolecular cross-linking caused by generation of imide bond accompanied by deammonification in the amide side chain, and performance is deteriorated.
In particular, in the acrylamide-based polymer dispersion obtained by the precipitation polymerization method in a salt aqueous solution containing the above-mentioned high-concentration inorganic salt, there is a tendency that the storage stability is more unstable compared to the aqueous solution. .

As a stabilizer for preventing the decomposition and deterioration of the acrylamide-based polymer, urea-based compounds such as diphenylguanidines and / or salts thereof (Japanese Patent Publication No. 5-39978) and guanylurea have been used. Kosho 60-2
No. 3683) is known. These have a certain effect on an aqueous solution of an acrylamide polymer, but have no stabilizing effect on a dispersion of an acrylamide polymer in an aqueous medium containing a high concentration of inorganic salt. .

The present inventors have proposed aminoguanidines as a method of stabilizing a dispersion of an acrylamide polymer in an aqueous medium containing a high concentration of an inorganic salt as well as an aqueous solution of the acrylamide polymer. We filed a method of adding (Japanese Patent Application No. 10-23737).

[0010] These aminoguanidines are more soluble in water than conventionally known diphenylguanidines and the like, and therefore easily dissolved in aqueous solutions containing high concentrations of inorganic salts, and To stabilize the acrylamide polymer by preventing degradation due to intramolecular and intermolecular cross-links caused by the formation of imide bonds accompanied by deammonification in the amide side chain of the acrylamide polymer in an aqueous medium containing It is possible.

However, when the acrylamide polymer is used, it may be stored for a very long time in a storage tank or the like, and further stabilization of the acrylamide polymer has been demanded.

[0012]

SUMMARY OF THE INVENTION In view of the above situation, the present invention is directed to a dispersion of an acrylamide polymer in an aqueous medium containing a high concentration of an inorganic salt as well as an aqueous solution of the acrylamide polymer. It is an object of the present invention to provide a method for stabilizing over a long period of time.

[0013]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, by adding a reducing agent to an acrylamide polymer in addition to aminoguanidines, The present inventors have found that the decomposition and deterioration of the acrylamide polymer can be prevented for a longer period of time, and have reached the present invention.

That is, the method for stabilizing the acrylamide polymer of the present invention is as follows. 1) Aminoguanidines 0.01 to 10 parts by weight and a reducing agent 0.0 with respect to 100 parts by weight of the acrylamide polymer.
A method for stabilizing an acrylamide polymer, comprising adding 1 to 30 parts by weight. 2) a state in which the acrylamide polymer is dispersed in water;
Alternatively, the method for stabilizing an acrylamide polymer according to 1), wherein the acrylamide polymer is present in a state of being dispersed in an aqueous medium containing a high concentration of an inorganic salt.

3) The method for stabilizing an acrylamide polymer according to 2), wherein the concentration of the inorganic salt at a high concentration in the aqueous medium is 5% by weight or more and a saturated concentration or less. 4) The method for stabilizing an acrylamide polymer according to 2), wherein the inorganic salt is an inorganic acid ammonium salt and / or an inorganic acid sodium salt. 5) The method for stabilizing an acrylamide polymer according to 4), wherein the ammonium salt of the inorganic acid is ammonium sulfate. 6) The method for stabilizing an acrylamide polymer according to 4), wherein the sodium salt of the inorganic acid is sodium sulfate.

7) The method for stabilizing an acrylamide polymer according to 1), wherein the aminoguanidine is at least one selected from the group consisting of aminoguanidine hydrochloride, aminoguanidine sulfate, aminoguanidine bicarbonate and diaminoguanidine hydrochloride. . 8) The method for stabilizing an acrylamide polymer according to 1), wherein the reducing agent is at least one selected from the group consisting of sodium bisulfite, sodium sulfite, ammonium bisulfite, and ammonium sulfite.

9) The acrylamide polymer is selected from the group consisting of a homopolymer of acrylamide, a copolymer of acrylamide with another monomer copolymerizable with acrylamide, and a partially modified acrylamide homopolymer. At least one
The method for stabilizing an acrylamide polymer according to 1), which is a seed. 10) The method for stabilizing an acrylamide polymer according to 9), wherein the acrylamide polymer is a copolymer of acrylamide and sodium acrylate. 11) The content of the other monomer copolymerizable with acrylamide is 40 mol% or less based on the total amount of acrylamide and the other monomer copolymerizable with acrylamide.
The method for stabilizing an acrylamide polymer according to the above. 12) A method for stabilizing an acrylamide-based polymer, wherein the other monomer copolymerizable with acrylamide according to 11) is sodium acrylate. Hereinafter, the present invention will be described in detail.

Examples of the acrylamide polymer used in the present invention include acrylamide homopolymers, copolymers with other monomers copolymerizable with acrylamide, partially modified acrylamide homopolymers, and acrylamide homopolymers. And the like.

The other copolymerizable monomers include, for example, nonionic monomers such as methacrylamide and vinylpyridine; (meth) acrylic acid, and (two kinds of compounds of acrylic acid and methacrylic acid; Abbreviated as (meth) acrylic acid, the same applies to the following), 2- (meth) acrylamido-2-methylpropanesulfonic acid, fumaric acid, crotonic acid, maleic acid, styrenesulfonic acid, and alkali metal salts and alkaline earths thereof. Anionic monomers such as metal salts and ammonium salts; and cationic monomers such as ethyl (meth) acrylate trimethylammonium chloride and propyl (meth) acrylate trimethylammonium chloride. Of these, alkali metal (meth) acrylate and alkaline earth metal (meth) acrylate are preferred. These may be used alone or in combination of two or more.

The alkali metal (meth) acrylate,
Examples of the alkaline earth metal (meth) acrylate include lithium (meth) acrylate, sodium (meth) acrylate, potassium (meth) acrylate, magnesium (meth) acrylate, and calcium (meth) acrylate. Is mentioned. Of these, sodium acrylate is most preferably used because it is industrially available and inexpensive.

The content of the other monomer in the above copolymer is 4
0 mol% or less is preferable. If it exceeds 40 mol%, the resulting polymer dissolves in the aqueous solution of the inorganic salt, which is not preferable. As a partially modified acrylamide homopolymer,
40 of the amide groups contained in the acrylamide homopolymer
What converted mol% or less into another functional group by a chemical reaction is mentioned. Specific examples thereof include a hydrolyzate with an alkali, a sulfomethylation reaction product with formaldehyde and sodium bisulfite, a Hoffman reaction product with sodium hypochlorite and an alkali, a Mannich reaction product with formaldehyde and an amine, and the like.

The method for stabilizing an acrylamide polymer of the present invention is particularly effective when the acrylamide polymer is present as an aqueous solution or a dispersion in an aqueous medium containing a high concentration of inorganic salts. The inorganic salt is not particularly limited,
For example, ammonium salts of inorganic acids such as ammonium sulfate, ammonium nitrate, diammonium hydrogen phosphate; potassium sulfate, sodium sulfate, magnesium sulfate, potassium nitrate, sodium nitrate, potassium chloride, sodium chloride, calcium chloride, dipotassium hydrogen phosphate, Examples thereof include alkali metal salts and alkaline earth metal salts of inorganic acids such as monosodium hydrogen phosphate.

These may be used alone or in a suitable mixture. Of these, ammonium salts of inorganic acids and sodium salts of inorganic acids are preferable, and ammonium sulfate and sodium sulfate are more preferable. In the present specification, the concentration of the inorganic salt having a high concentration is preferably 5% by weight or more and a saturated concentration or less. For example, for ammonium sulfate,
43% by weight, 5 to 20% by weight for sodium sulfate
Is preferred.

The aminoguanidine used in the present invention refers to guanidine or a salt thereof substituted with at least one amino group. Specific examples include aminoguanidine, diaminoguanidine, their hydrochlorides, sulfates, bicarbonates, bromates, nitrates, and chloroplatinates. Preferably, aminoguanidine hydrochloride, aminoguanidine sulfate, aminoguanidine bicarbonate, and diaminoguanidine hydrochloride are used. These may be used alone or as a mixture of two or more.

The amount of the aminoguanidine is 0.01 to 10.0 parts by weight based on 100 parts by weight of the acrylamide polymer.
Parts by weight, preferably 0.02 to 8.0 parts by weight, more preferably 0.05 to 5.0 parts by weight. 0.0
If the amount is less than 1 part by weight, the stabilizing effect is small.
Even if it exceeds 0.0 parts by weight, the effect corresponding to the added amount cannot be obtained and it is not economical.

The reducing agent used in the present invention is not particularly limited as long as it has a reducing property. Specific examples of the reducing agent include sulfite compounds such as sodium bisulfite, sodium sulfite, potassium sulfite, ammonium bisulfite, ammonium sulfite, calcium sulfite, barium sulfite, dimethyl sulfite, tetrabutylammonium sulfite; lithium nitrite, Sodium nitrite, potassium nitrite, calcium nitrite, silver nitrite, ethyl nitrite, butyl nitrite, t-butyl nitrite,
Nitrite compounds such as 3-methylbutyl nitrite, isoamyl nitrite and isopentyl nitrite; reducing nitrogen compounds such as hydrazine; aldehydes such as formaldehyde and acetaldehyde; acids such as formic acid and oxalic acid; sugars such as glucose; Ascorbic acid and the like. Preferably,
Sodium bisulfite, sodium sulfite, ammonium bisulfite, and ammonium sulfite are used. These may be used alone or as a mixture of two or more.

The reducing agent is added in an amount of 0.01 to 30.0 parts by weight, preferably 0.1 to 20.0 parts by weight, more preferably 0.1 to 100 parts by weight, based on 100 parts by weight of the acrylamide polymer.
5 to 10.0 parts by weight. If the addition amount is less than 0.01 part by weight, the stabilizing effect is small, and if it exceeds 30.0 parts by weight, the effect corresponding to the addition amount cannot be obtained and it is not economical. It is considered that these reducing agents are dissolved in an aqueous solution containing a high concentration of inorganic salt to remove dissolved oxygen, thereby preventing oxidative decomposition accompanied by a decrease in the degree of polymerization of the acrylamide polymer.

Various methods are available for adding aminoguanidines and reducing agents to the acrylamide polymer. For example, a method in which solid aminoguanidines, a reducing agent, and an acrylamide-based polymer are previously mixed at a predetermined ratio and then dissolved in water, and a powder of the acrylamide-based polymer is dissolved in an aqueous solution in which the aminoguanidines and the reducing agent are dissolved. A method of dissolving, a method of adding a powder of an aminoguanidine and a reducing agent to a dispersion or aqueous solution of an acrylamide-based polymer, respectively, an aminoguanidine previously dissolved in a suitable solvent such as water in a dispersion or aqueous solution of an acrylamide-based polymer And a method of adding a reducing agent.

If the polymerization conditions are selected, it is possible to carry out the polymerization in the presence of aminoguanidines and reducing agents when polymerizing the acrylamide-based monomer. This is effective for improving the stability of the polymer in an aqueous solution state during the production process.

[0030]

EXAMPLES Next, the present invention will be described based on examples.
The present invention is not limited to the following examples unless it exceeds the gist.

Example 1 and Comparative Example 1 A 50 equipped with a stirrer, a nitrogen inlet tube, a thermometer and a reflux cooling tube was used.
After adding 25 g of acrylamide to a 0 mL reaction vessel and dissolving it in 225.0 mL of pure water, oxygen in the reaction system was removed through nitrogen gas, and 42.5 mg of potassium persulfate was added. By polymerizing for an hour, a viscous acrylamide polymer aqueous solution was obtained. The aqueous solution was diluted with pure water to prepare an aqueous solution having a polymer concentration of 0.5% by weight. The viscosity of the obtained aqueous solution at 25 ° C. is 6
It was 75 cps.

Test solutions were prepared by adding aminoguanidine hydrochloride and sodium sulfite to this aqueous solution so that the addition amounts to the polymer were as shown in Table 1. (Examples 1-1, 1-2, 1-3, 1-4, 1-5, 1
-6, Comparative Examples 1-1, 1-2, 1-3). The test liquid was allowed to stand in a thermostat adjusted to 40 ° C., and the viscosity of the aqueous solution was measured after 50 days, 150 days, and 300 days. The viscosity of the aqueous solution was measured using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd. (25 ° C., 12 ° C.).
Rotation). The storage stability of the acrylamide polymer aqueous solution was evaluated by the viscosity retention expressed by the following formula.

Viscosity retention (%) = (viscosity after storage) /
(Viscosity immediately after preparation of test liquid) × 100 The results are shown in Table 1.

[0034]

[Table 1]

Example 2, Comparative Example 2 In Example 1, 18.8 g of acrylamide and 6.2 sodium acrylate were used instead of 25 g of acrylamide.
A viscous acrylamide polymer aqueous solution having a degree of anionization of 20 mol% was obtained in the same manner as in Example 1 except that g was used. Pure water was added to this aqueous solution to dilute it, and the polymer concentration was adjusted to 0.
A 5% by weight aqueous solution was prepared. 25 ° C of the obtained aqueous solution
Was 800 cps.

Test solutions were prepared by adding aminoguanidine hydrochloride and sodium bisulfite to this aqueous solution so that the amounts added to the polymer were as shown in Table 2 (Examples 2-1 and 2-2). , 2-3, 2-4, Comparative Examples 2-1, 2-2, 2-3). This test solution was allowed to stand in a thermostat adjusted to 40 ° C., and the viscosity of the aqueous solution was measured after 50 days, 150 days, and 300 days, and the viscosity retention was determined in the same manner as in Example 1. The results are shown in Table 2.

[0037]

[Table 2]

Example 3 and Comparative Example 3 50 equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a reflux cooling tube.
To a 0 mL reaction vessel, 45.1 g of acrylamide, 14.9 g of sodium acrylate, and 6.5 g of polyvinylpyrrolidone (molecular weight = 10000) were added, and 195.5 mL of pure water was added.
After that, 130.0 g of ammonium sulfate and 8.0 g of sodium sulfate were added. Oxygen was removed by aeration with nitrogen, and potassium persulfate (30 mg) was added.
Polymerization was performed at 8 ° C. for 8 hours to obtain a dispersion of an acrylamide polymer having a degree of anionization of 20 mol%.

A test liquid was prepared by adding aminoguanidine hydrochloride and sodium bisulfite to the obtained dispersion so that the addition amounts to the polymer were as shown in Table 3 (Examples 3-1 and 3-2). 3-2, Comparative Examples 3-1 and 3-
2). The obtained test solution was allowed to stand in a thermostat controlled at 40 ° C., and the solubility and storage stability were evaluated after 50 days, 150 days, and 300 days.

The solubility was evaluated by using 16.7 g of the dispersion liquid in 4 parts.
After dissolving in 83.7 mL of pure water to prepare a 0.5% by weight aqueous solution, the solution was filtered through an 80 mesh wire mesh, washed with water, and the weight of the insoluble swelling gel (insoluble matter) remaining on the wire mesh was measured. When the value was less than 2 g, the solubility was good. When the value was 2 g to 5 g, the solubility was slightly good. The evaluation criteria in Table 3 are:
It was as follows. ：: good solubility Δ: slightly good solubility ×: poor solubility The results are shown in Table 3.

[0041]

[Table 3]

The viscosity of the 0.5% by weight aqueous solution was measured in the same manner as in Example 1, and the storage stability was evaluated based on the viscosity retention. The results are shown in Table 4.

[0043]

[Table 4]

From Tables 3 and 4, the dispersion of the acrylamide-based polymer to which the aminoguanidines and the reducing agents were added was as follows.
It is clear that both the solubility and the stability are excellent after long-term storage, and the results of the test at 40 ° C. show that they are stable even in the summer storage.

Example 4 The acrylamide polymer dispersion obtained in Example 3 was added to
Test solutions were prepared by adding aminoguanidine sulfate and ammonium bisulfite such that the addition amounts to the polymer were as shown in Table 5 (Examples 4-1 and 4-).
2). The test solution was allowed to stand in a thermostat whose temperature was controlled at 40 ° C., and the storage stability was evaluated in the same manner as in Example 1. Table 5 shows the results.

[0046]

[Table 5]

[0047]

According to the present invention, by adding aminoguanidines and a reducing agent to an acrylamide polymer, it is particularly effective for stabilizing the acrylamide polymer in an aqueous solution containing a high concentration of inorganic salt. Not only that, but also in an aqueous solution containing no inorganic salt, a significantly superior stabilizing effect can be obtained as compared with conventionally known stabilizers. The acrylamide-based polymer stabilized by the method of the present invention can be stored for a long period of time, and thus can be used for various uses.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Nobutaka Fujimoto, Inventor No. 1 Irifunecho, Shima-ku, Himeji-shi, Hyogo Sumitomo Seika Co., Ltd. (72) Inventor Takao Okada 64, Nishiwaki, Beppu-cho, Kakogawa-shi, Hyogo Pref.

Claims (12)

[Claims] 1. A method for stabilizing an acrylamide polymer, comprising adding 0.01 to 10 parts by weight of an aminoguanidine and 0.01 to 30 parts by weight of a reducing agent to 100 parts by weight of the acrylamide polymer. Method. 2. The method for stabilizing an acrylamide polymer according to claim 1, wherein the acrylamide polymer exists in a state of being dissolved in water or being dispersed in an aqueous medium containing a high concentration of inorganic salt. 3. The method for stabilizing an acrylamide polymer according to claim 2, wherein the high concentration of the inorganic salt in the aqueous medium is 5% by weight or more and a saturation concentration or less. 4. The method for stabilizing an acrylamide polymer according to claim 2, wherein the inorganic salt is an inorganic acid ammonium salt and / or an inorganic acid sodium salt. 5. The method for stabilizing an acrylamide polymer according to claim 4, wherein the ammonium salt of the inorganic acid is ammonium sulfate. 6. The method for stabilizing an acrylamide polymer according to claim 4, wherein the sodium salt of the inorganic acid is sodium sulfate. 7. The stabilization of an acrylamide polymer according to claim 1, wherein the aminoguanidine is at least one selected from the group consisting of aminoguanidine hydrochloride, aminoguanidine sulfate, aminoguanidine bicarbonate, and diaminoguanidine hydrochloride. Method. 8. The method for stabilizing an acrylamide polymer according to claim 1, wherein the reducing agent is at least one selected from the group consisting of sodium bisulfite, sodium sulfite, ammonium bisulfite, and ammonium sulfite. 9. The acrylamide-based polymer is selected from the group consisting of acrylamide homopolymers, copolymers with other monomers copolymerizable with acrylamide, and partially modified acrylamide homopolymers. 2. The method for stabilizing an acrylamide polymer according to claim 1, wherein the method is at least one of the following. 10. The method for stabilizing an acrylamide polymer according to claim 9, wherein the acrylamide polymer is a copolymer of acrylamide and sodium acrylate. 11. The content of another monomer copolymerizable with acrylamide is 40 mol% or less based on the total amount of acrylamide and another monomer copolymerizable with acrylamide. A method for stabilizing an acrylamide polymer. 12. A method for stabilizing an acrylamide polymer, wherein the other monomer copolymerizable with acrylamide according to claim 11 is sodium acrylate.