JPH11209551A - Stabilization of acrylamide-based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stabilizing the objective polymer by which the decomposition and deterioration of an acrylamide-based polymer are prevented and the acrylamide-based polymer is stabilized in an aqueous solution or a dispersion containing a highly concentrated inorganic salt by adding aminoguanidines to the acrylamide-based polymer. SOLUTION: An aqueous solution of (A) an acrylamide-based polymer, or a dispersion of the component A in an aqueous medium containing a highly concentrated inorganic salt are stabilized by adding (B) 0.01-10.0 pts.wt. aminoguanidines to 100 pts.wt. component A in the method for stabilizing the objective polymer. The component A is preferably a copolymer of (i) acrylamide and (ii) sodium acrylate, and the content of the component (ii) is preferably <=40 mol.% based on the total of the components (i) and (ii). The component B is preferably aminoguanidine hydrochloride, aminoguanidine sulfate or the like. The concentration of the highly concentrated salt in the aqueous medium is preferably >=5 wt.% and not more than the saturated concentration, and the inorganic salt is preferably an ammonium salt and/or a sodium salt of an inorganic acid.

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.

The present inventors have filed an application for a method for producing an acrylamide-based polymer dispersion by precipitation polymerization in a salt aqueous solution containing a high concentration of inorganic salt as a method for solving the above-mentioned problems (Japanese Patent Application No. Hei 10-284,837). 9-14670 patent application). 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 it does not use a flammable organic solvent, it has many features such as being safe and inexpensive to manufacture and being economically excellent. However, it is difficult to stably store the obtained dispersion for a long period of time, and its use has been 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 is reduced due to oxidative decomposition of the acrylamide polymer, and the viscosity of the aqueous solution is reduced. There is a problem in terms of stability such as insoluble swelling gel being formed due to intramolecular and intermolecular crosslinks resulting from the formation and the performance being 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. .

[0009]

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.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, by adding aminoguanidines to an acrylamide polymer, the decomposition and decomposition of the acrylamide polymer were carried out. The inventors have found that deterioration can be prevented, and have reached the present invention.

That is, the method for stabilizing an acrylamide polymer of the present invention is as follows. 1) A method for stabilizing an acrylamide polymer, comprising adding 0.01 to 10.0 parts by weight of aminoguanidine to 100 parts by weight of the acrylamide polymer. 2) The method for stabilizing an acrylamide polymer according to 1), wherein the acrylamide polymer is present as an aqueous solution or a dispersion 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 3), 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-based 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 acrylamide-based polymer is at least one selected from the group consisting of acrylamide homopolymers, copolymers of acrylamide with other monomers copolymerizable with acrylamide, and partially modified acrylamide homopolymers. The method for stabilizing an acrylamide-based polymer according to 1). 9) The method for stabilizing an acrylamide polymer according to 8), wherein the acrylamide polymer is a copolymer of acrylamide and sodium acrylate. 10) The content of sodium acrylate is 40 mol% based on the total amount of acrylamide and sodium acrylate.
9) The method for stabilizing an acrylamide polymer according to 9) below. Hereinafter, the present invention will be described in detail.

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

Examples of the other copolymerizable monomers include, for example, nonionic monomers such as methacrylamide and vinylpyridine, (meth) acrylic acid, and (two compounds of acrylic acid and methacrylic acid. ) Abbreviated as acrylic acid.
The same applies to the following), 2- (meth) acrylamide-2
-Methylpropanesulfonic acid, fumaric acid, crotonic acid,
Anionic monomers such as maleic acid, styrene sulfonic acid and their alkali metal salts, alkaline earth metal salts and ammonium salts; ethyltrimethylammonium (meth) acrylate chloride; propyltrimethylammonium (meth) acrylate chloride; And cationic monomers. Of these, alkali metal (meth) acrylate and alkaline earth metal (meth) acrylate are preferred.

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 40
It is preferably at most mol%. If it exceeds 40 mol%, the resulting polymer dissolves in the aqueous solution of the inorganic salt, which is not preferable.
Examples of the partially modified acrylamide homopolymer include those obtained by converting 40 mol% or less of the amide groups contained in the acrylamide homopolymer to another functional group by a chemical reaction. 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 a dispersion in an aqueous solution or an aqueous medium containing a high concentration of an inorganic salt. The inorganic salt is not particularly limited, and examples thereof include ammonium salts of inorganic acids such as ammonium sulfate, ammonium nitrate, and diammonium hydrogen phosphate; potassium sulfate, sodium sulfate, magnesium sulfate, potassium nitrate, sodium nitrate, potassium chloride, sodium chloride; Examples thereof include alkali metal salts and alkaline earth metal salts of inorganic acids such as calcium chloride, dipotassium hydrogen phosphate and monosodium hydrogen phosphate.

These may be used alone or in appropriate mixtures. 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, “high-concentration inorganic salt” cannot be said unconditionally depending on the type of inorganic salt used, but refers to an inorganic salt in a range of 5% by weight or more and a saturated concentration or less. For example, 5 to 43% by weight for ammonium sulfate and 5 to 20% for sodium sulfate.
Shows the concentration range of wt%.

The aminoguanidines used in the present invention refer 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 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.

These aminoguanidines are more soluble in water than conventionally known diphenylguanidines and the like, so that they are easily dissolved in aqueous solutions containing high concentrations of inorganic salts, and It is considered that decomposition and deterioration of the acrylamide-based polymer in an aqueous medium containing carbon dioxide are effectively prevented.

Aminoguanidines are not only particularly effective in stabilizing an acrylamide polymer in an aqueous medium containing such a high concentration of inorganic salts, but also have a stabilizing effect in an aqueous solution containing no inorganic salts. It is remarkably superior to conventionally known stabilizers.

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

Further, if the polymerization conditions are selected, it is possible to carry out the polymerization in the presence of aminoguanidines when polymerizing the acrylamide monomer. This method is used in the process of producing the acrylamide polymer. It is effective for improving the stability of the polymer in an aqueous solution state.

[0025]

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, Comparative Example 1 A 50 equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a reflux cooling tube.
In a 0 mL reaction vessel, add 25 g of acrylamide and add
After dissolving in 25.0 mL, oxygen in the reaction system was removed through nitrogen gas, 42.5 mg of potassium persulfate was added, and the mixture was polymerized at 40 ° C. for 5 hours with stirring to obtain a viscous acrylamide polymer. 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 resulting aqueous solution at 25 ° C. is 67
It was 5 cps.

A test solution in which aminoguanidine hydrochloride was added to the aqueous solution at a ratio of 1.0% by weight based on the acrylamide polymer (Example 1) and a test solution in which aminoguanidine hydrochloride was not added (Comparative Example 1). Prepared. This test solution was allowed to stand in a thermostat controlled at 40 ° C., and the viscosity of the aqueous solution was measured after 25 days, 50 days, and 100 days. The viscosity of the aqueous solution was measured using a B-type viscometer (25 ° C., 12 rotations) manufactured by Tokyo Keiki Co., Ltd. The storage stability of the acrylamide polymer aqueous solution was evaluated by a 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.

[0029]

[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.
Except for using g, a viscous acrylamide polymer aqueous solution having a degree of anionization of 20 mol% was obtained in the same manner as in Example 1. Pure water was added to this aqueous solution to dilute it, and the polymer concentration was 0.5
A weight percent aqueous solution was prepared. The viscosity of the obtained aqueous solution at 25 ° C. was 800 cps.

A test solution in which aminoguanidine hydrochloride was added to the aqueous solution at a ratio of 1.0% by weight based on the acrylamide polymer (Example 2), and a test solution in which aminoguanidine hydrochloride was not added (Comparative Example 2) Was prepared. This test solution was allowed to stand in a thermostat adjusted to 40 ° C., and the viscosity of the aqueous solution was measured after 25 days, 50 days, and 100 days, and the viscosity retention was determined in the same manner as in Example 1. The results are shown in Table 2.

[0032]

[Table 2]

Example 3 and Comparative Example 3 50 equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a reflux cooling tube.
In a 0 mL reaction vessel, 45.1 g of acrylamide, 14.9 g of sodium acrylate, PVP (molecular weight = 1000)
0) 6.5 g was added and dissolved in 195.5 mL of pure water, and then 130.0 g of ammonium sulfate and 8.0 g of sodium sulfate were added. Oxygen was removed by aeration with nitrogen, 30 mg of potassium persulfate was added, and polymerization was carried out at 25 ° C. for 8 hours with stirring to obtain a dispersion of an acrylamide polymer having a degree of anionization of 20 mol%.

[0034] Test liquids were prepared by adding aminoguanidine hydrochloride to the resulting dispersion so that the amount of addition to the polymer was as shown in Table 3 (Examples 3-1 and 3-2;
3-3, Comparative Examples 3-1 and 3-2). The obtained test solution is
Leave in a thermostat controlled at 25 ° C. and 40 ° C., respectively, and store at 25 ° C. for 25 days, 50 days and 100 days.
Days, 10 days, 25 days, and 5 days at 40 ° C storage.
After 0 day, the solubility and storage stability were evaluated respectively.

For the evaluation of solubility, 16.7 g of the dispersion was
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 judged to be good, and when the value was 2 g to 5 g, the solubility was judged to be slightly good.
Table 3 shows the results of storage at 25 ° C, and Table 4 shows the results of storage at 40 ° C.

The evaluation criteria in Table 3 were as follows. ：: Good solubility Δ: Slightly good solubility ×: Poor solubility The evaluation criteria in Table 4 were as follows. ：: Good solubility △: Slightly good solubility ×: Poor solubility

[0037]

[Table 3]

[0038]

[Table 4]

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. Table 5 shows the results of storage at 25 ° C., and Table 6 shows the results of storage at 40 ° C.

[0040]

[Table 5]

[0041]

[Table 6]

Tables 3 to 6 show that the dispersion of the acrylamide-based polymer to which aminoguanidines were added was excellent in both solubility and stability even after long-term storage. It is clear that it is stable on storage.

Example 4 and Comparative Example 4 To the dispersion of the acrylamide polymer obtained in Example 3 were added aminoguanidine sulfate, aminoguanidine bicarbonate, diaminoguanidine hydrochloride or diphenylguanidine in an amount of 1.0 wt. %, To prepare a test solution. The test solution is allowed to stand in a thermostat adjusted to 40 ° C.
The storage stability was evaluated in the same manner as in Example 2. The results are shown in Table 7.

[0044]

[Table 7]

[0045]

The acrylamide polymer stabilized by the method of the present invention is remarkably stable not only in an aqueous solution but also in salt water having a high concentration of inorganic salts and the like, and can be stored for a long time. As a result, it became possible to use it for various applications.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08F 220: 06) (72) Inventor Nobutaka Fujimoto 1st Irifune-cho, Shiima-ku, Himeji-shi, Hyogo Sumitomo Seika Co., Ltd. 72) Inventor Kimihiko Kondo 1st Irifunecho, Shima, Himeji-shi, Hyogo Sumitomo Seika Co., Ltd. 2nd Research Institute (72) Inventor Takao Okada 64-1 Nishiwaki, Beppu-cho, Kakogawa-shi, Hyogo 1st Taki Chemical Co., Ltd.

Claims (10)

[Claims] 1. A method for stabilizing an acrylamide polymer, comprising adding 0.01 to 10.0 parts by weight of aminoguanidine to 100 parts by weight of the acrylamide polymer. 2. The method for stabilizing an acrylamide polymer according to claim 1, wherein the acrylamide polymer is present as an aqueous solution or a dispersion in an aqueous medium containing a high concentration of an 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 3, wherein the inorganic salt is an ammonium salt of an inorganic acid and / or a sodium salt of the inorganic acid. 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 acrylamide polymer is at least 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. The method for stabilizing an acrylamide polymer according to claim 1, which is one kind. 9. The method for stabilizing an acrylamide polymer according to claim 8, wherein the acrylamide polymer is a copolymer of acrylamide and sodium acrylate. 10. The method for stabilizing an acrylamide polymer according to claim 9, wherein the content of sodium acrylate is 40 mol% or less based on the total amount of acrylamide and sodium acrylate.