JP2016108400A - Transparent aqueous solution containing polyacrylic acid salt and potassium hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous solution having excellent transparency even if both polyacrylic acid salt and potassium hydroxide are contained in high concentration.SOLUTION: There is provided an aqueous solution which contains (A) a polyacrylic acid salt composed of a completely neutralized salt of a polyacrylic acid, (B) potassium hydroxide and (C) water, wherein the polyacrylic acid salt (A) is a neutralized product with an alkali agent of a polymer (a) which is obtained by adjusting the use amount of a persulfate as a polymerization initiator to 1.2 pts.mass or less based on 100 pts.mass of a monomer raw material containing an acrylic acid salt or an acrylic acid alkyl ester and the aqueous solution is obtained by using the polyacrylic acid salt (A) or the polymer (a) in an amount corresponding to 1 to 30 mass% and potassium hydroxide (B) in an amount corresponding to 30 to 55 mass% based on the total amount of the aqueous solution.SELECTED DRAWING: None

Description

  The present invention relates to an aqueous solution containing a polyacrylic acid salt composed of a completely neutralized salt of polyacrylic acid and potassium hydroxide (hereinafter referred to as “KOH”) and having excellent transparency.

Conventionally, alkali metal hydroxides and polyacrylates are used in combination in water treatment agents, aqueous detergents, inorganic particle dispersants, etc., that suppress the formation of scales in pipes, boilers, heat exchangers, etc. . The known composition containing these components is as follows.
In Patent Document 1, an aqueous acrylic acid solution neutralized with KOH is polymerized in the presence of sodium persulfate and the like, and then the reaction solution is neutralized with KOH, and then an anionic property comprising an aqueous potassium polyacrylate solution. Dispersant polymers are disclosed.
Patent Document 2 discloses a heavy calcium carbonate wet pulverization step containing polyacrylate obtained by polymerizing acrylic acid in the presence of sodium persulfate and the like and then neutralizing with sodium hydroxide (NaOH) and KOH. Dispersants are disclosed (see Example 7).
Patent Document 3 discloses a light calcium carbonate wet pulverization dispersant containing polyacrylate obtained by polymerizing potassium acrylate in the presence of sodium persulfate or the like and then neutralizing with KOH. (See Example 10).

Special table 2013-502502 gazette International Publication No. 2004/87574 JP 2004-306222 A

In recent years, an aqueous solution containing a polyacrylate having a relatively low molecular weight has been used as a raw material for an aqueous composition that is a water treatment agent, an aqueous cleaning agent, a dispersant for inorganic particles, or the like that suppresses the formation of scale. On the other hand, as an effort to reduce the transportation cost to the workplace where the water treatment agent or aqueous composition is handled, the concentration of the pure component in the raw material has been increased. In particular, in the case of the water treatment agent, an alkali metal hydroxide is used. In addition, a process of transporting an aqueous raw material solution containing both polyacrylate and polyacrylate to a working place to be used, diluting or mixing essential components on the site, and then using the raw material aqueous solution is being introduced. However, when these high-concentration aqueous solutions are prepared by the methods described in Patent Documents 1 to 3, turbidity occurs and transparency may not be obtained. Such a problem is likely to occur under a low temperature condition in a cold region or a climatic season equivalent thereto, and has a problem of causing filter clogging during the manufacturing process.
An object of the present invention is to provide an aqueous solution having excellent transparency even when polyacrylate and KOH are both contained in high concentration.

The present inventor studied the cause of the turbidity of the aqueous solution containing both polyacrylate and KOH at a high concentration under low temperature conditions, and obtained knowledge that the turbidity was caused by precipitation of potassium sulfate. . Based on this finding, the present inventor, for example, produced a partially neutralized or completely neutralized polyacrylate produced by using a polymerization initiator containing a sulfur-containing compound such as a persulfate as a specific amount or less. And when it was made into aqueous solution using KOH, it discovered that transparency was acquired and came to complete this invention. The present invention is shown below.
[1] In an aqueous solution containing (A) a polyacrylic acid salt consisting of a completely neutralized salt of polyacrylic acid, (B) potassium hydroxide, and (C) water, the polyacrylic acid salt (A) is: Polymer (a) obtained by setting the amount of persulfate used as a polymerization initiator to 1.2 parts by mass or less with respect to 100 parts by mass of monomer raw material containing acrylic acid (salt) or alkyl acrylate ester The aqueous solution is 30 to 55% by mass with respect to the total amount of the polyacrylate (A) or the polymer (a) corresponding to 1 to 30% by mass. An aqueous solution containing a polyacrylate, which is obtained using the corresponding potassium hydroxide (B).
[2] The aqueous solution according to [1], wherein the polyacrylate (A) has a weight average molecular weight of 1000 to 30000.
[3] The above [1] or [2], wherein the polymerization initiator for producing the polymer (a) contains at least one selected from an azo compound, hydrogen peroxide and an organic peroxide. Aqueous solution.
[4] The above [1], wherein the polymerization solvent for producing the polymer (a) contains isopropanol, and the amount of the isopropanol used is 40 to 150 parts by mass with respect to 100 parts by mass of the monomer raw material. Thru | or the aqueous solution as described in any one of [3].
[5] The above [1] to [4], wherein the polyacrylate (A) is a polymer obtained by polymerizing an acrylic acid alkyl ester and then saponifying the obtained polyacrylic acid alkyl ester. The aqueous solution as described in any one of these.
[6] The aqueous solution according to any one of [1] to [5], wherein the transmittance at a wavelength of 610 nm is 95% or more.
In this specification, the weight average molecular weight (hereinafter also referred to as “Mw”) of the polymer is a standard sodium polyacrylate conversion value measured by gel permeation chromatography (hereinafter also referred to as “GPC”). . The description of “(meth) acryl” means acrylic and methacrylic. The description of “acrylic acid (salt)” means at least one of acrylic acid and acrylate. The description of “(co) polymer” means a homopolymer and a copolymer.

  The aqueous solution of the present invention is excellent in transparency although the polyacrylate (A) and KOH (B) are both contained in high concentration. Further, the aqueous solution of the present invention is diluted with water, and further, if necessary, other components are blended, and a dilute aqueous solution containing polyacrylate (A) or KOH (B) at a desired concentration. And can be suitably used as a water treatment agent, an aqueous cleaning agent, a dispersant for inorganic particles, or the like that suppresses the formation of scale in pipes, boilers, heat exchangers, and the like. For example, since it contains KOH when used as a water treatment agent, corrosion of piping made of metal or alloy, generation of slime, and the like can be suppressed.

The present invention provides a polyacrylic acid salt (A) comprising a completely neutralized salt obtained by using a polyacrylic acid salt comprising a partially neutralized salt or a completely neutralized salt of polyacrylic acid and KOH, and KOH (B ) And an aqueous solution that may contain other components to be described later depending on the application.
The present invention will be described in detail below.

（式中、Ｍは、Ｎａ、Ｋ、又は、ＮＨ_４である。） The polyacrylate (A) includes one or more structural units derived from the acrylate represented by the following general formula (1), and includes other structural units depending on the application. It may be a water-soluble homopolymer or copolymer. In the polyacrylate (A) according to the present invention, the amount of persulfate used as a polymerization initiator is set to 1. part by mass with respect to 100 parts by mass of a monomer raw material containing acrylic acid (salt) or alkyl acrylate. It is a neutralized product of the polymer (a) obtained with an alkali agent of 2 parts by mass or less, and a neutralized product of the polymer (a) obtained by using a polymerization initiator other than persulfate. There may be. In addition, when the said monomer raw material contains acrylate and does not contain acrylic acid, the obtained polymer (a) can become the said polyacrylate (A) as it is.

(In the formula, M is Na, K, or NH _4. )

The polyacrylate (A) is not only obtained by a method comprising a polymerization step using a specific amount of persulfate as described above, but also uses a polymerization initiator other than persulfate. It may be obtained by a method comprising a conventional polymerization step. Moreover, what was obtained by the method provided with the superposition | polymerization process which used together the specific amount of persulfate and the other polymerization initiator may be used. In the present invention, a polymer obtained by the following methods (P), (Q), (R) and (S) is preferred. In all of the following methods, an aqueous solution of polyacrylate (A) is obtained.
(P) A monomer mainly composed of acrylic acid (salt) (hereinafter referred to as “monomer (m1)”) as a monomer raw material in a polymerization solvent containing water is converted into this monomer (m1). Polymerization was performed in the presence of a persulfate with a use amount of 100 parts by mass or less to 1.2 parts by mass to obtain a polymer (a) composed of an acrylic acid (co) polymer. The monomer (m1) is polymerized in the presence of a polymerization initiator other than persulfate in a polymerization solvent containing polyacrylate (Q) water obtained by reacting a (co) polymer with an alkali agent. A polyacrylate (R) organic solvent obtained by reacting an acrylic acid (co) polymer with an alkali agent after obtaining a polymer (a) comprising an acrylic acid (co) polymer In the polymerization solvent consisting of, as a monomer raw material, a monomer mainly composed of alkyl acrylate (hereinafter referred to as “single” Body (m2) ”) is polymerized in the presence of a persulfate in which the amount used relative to 100 parts by weight of the monomer (m2) is 1.2 parts by weight or less, and an acrylic (co) polymer (heavy) After obtaining a coalescent precursor, this acrylic (co) polymer (polymer precursor) is reacted with an alkaline agent dissolved in water to form a polyacrylate, and then the organic solvent is removed (solvent The monomer (m2) is polymerized in the presence of a polymerization initiator other than persulfate in a polymerization solvent comprising a polyacrylate (S) organic solvent obtained by substitution), and acrylic (co) heavy After obtaining a polymer (polymer precursor), this acrylic (co) polymer (polymer precursor) is reacted with an alkali agent dissolved in water to form a polyacrylate, and then an organic solvent is used. Polyacrylate obtained by removal (solvent replacement)

  The monomer (m1) used in the above methods (P) and (Q) may be only acrylic acid (salt), and carboxyl group-containing polymerizable other than acrylic acid (salt) and acrylic acid (salt). Unsaturated compound, acid anhydride group-containing polymerizable unsaturated compound, (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms, amide group-containing polymerizable unsaturated compound, sulfonic acid group-containing polymerization It may consist of other polymerizable unsaturated compounds such as polymerizable unsaturated compounds. In the latter case, the lower limit of the content ratio of acrylic acid (salt) is preferably 60% by mass and more preferably 80% by mass with respect to the entire monomer (m1).

  Examples of the carboxyl group-containing polymerizable unsaturated compound include methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, cinnamic acid, and salts thereof. These compounds can be used alone or in combination of two or more.

  Examples of the acid anhydride group-containing polymerizable unsaturated compound include maleic anhydride, itaconic anhydride, citraconic anhydride, and the like. These compounds can be used alone or in combination of two or more.

  Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, and (meth) acrylic. Examples include hexyl acid, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like. These compounds can be used alone or in combination of two or more.

  Examples of the amide group-containing polymerizable unsaturated compound include acrylamide. These compounds can be used alone or in combination of two or more. Examples of the sulfone group-containing polymerizable unsaturated compound include acrylamide-2-methylpropanesulfonic acid and salts thereof. These compounds can be used alone or in combination of two or more.

  The monomer (m2) used in the above methods (R) and (S) may be only an acrylic acid alkyl ester, an acrylic acid alkyl ester, a methacrylic acid alkyl ester, or a carboxyl group-containing polymerizable unsaturated. It may be composed of other polymerizable unsaturated compounds such as a compound, an acid anhydride group-containing polymerizable unsaturated compound, an amide group-containing polymerizable unsaturated compound, and a sulfonic acid group-containing polymerizable unsaturated compound. In the latter case, the lower limit of the content of the acrylic acid alkyl ester is preferably 60% by mass, more preferably 80% by mass, based on the entire monomer (m2).

  The acrylic acid alkyl ester is preferably an acrylic acid alkyl ester having a hydrocarbon group having 1 to 20 carbon atoms, and the compounds exemplified above can be used. In the present invention, methyl acrylate is particularly preferably used.

The methacrylic acid alkyl ester is preferably a methacrylic acid alkyl ester having a hydrocarbon group having 1 to 20 carbon atoms, and the exemplified compounds can be used.
Examples of the carboxyl group-containing polymerizable unsaturated compound include (meth) acrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, cinnamic acid, and salts thereof.
As the acid anhydride group-containing polymerizable unsaturated compound, the amide group-containing polymerizable unsaturated compound, the sulfonic acid group-containing polymerizable unsaturated compound, the above-exemplified compounds can be used.

Examples of persulfates that can be used in the above methods (P) and (R) include sodium persulfate, potassium persulfate, and ammonium persulfate. These compounds may be used alone or in combination of two or more.
The amount of persulfate used in the above methods (P) and (R) is the monomer raw material 100 comprising the monomer (m1) or the monomer (m2) because the aqueous solution of the present invention is excellent in transparency. It is 1.2 mass parts or less with respect to a mass part, Preferably it is 1.0 mass part or less, More preferably, it is 0.6 mass part or less. In addition, a lower limit is 0.1 mass part normally.

  In the above methods (P) and (R), only the persulfate may be used as the polymerization initiator, or the persulfate and other polymerization initiators are combined in accordance with the amount of persulfate used. Also good. In the latter case, an azo compound, hydrogen peroxide, an organic peroxide, or the like can be used as another polymerization initiator. In the case of an azo compound, the amount used is preferably 10 to 300 parts by mass, more preferably 50 to 250 parts by mass, and still more preferably 100 to 200 parts by mass with respect to 100 parts by mass of the persulfate. . In the case of hydrogen peroxide, the amount used is preferably 200 to 5000 parts by mass, more preferably 500 to 3000 parts by mass, and still more preferably 1000 to 2000 parts by mass with respect to 100 parts by mass of persulfate. . In the case of an organic peroxide, the amount used is preferably 10 to 300 parts by weight, more preferably 50 to 250 parts by weight, and still more preferably 100 to 200 parts by weight with respect to 100 parts by weight of the persulfate. Part.

  Examples of the azo compound (hereinafter referred to as “azo compound (z1)”) that can be used in the above method (P) include 1-[(1-cyano-1-methylethyl) azo] formamide, 2,2 ′. -Azobis [2- (N-phenylamidino) propane] dihydrochloride, 2,2'-azobis {2- [N- (4-chlorophenyl) amidino] propane} dihydrochloride, 2,2'-azobis {2 -[N- (4-hydroxyphenyl) amidino] propane} dihydrochloride, 2,2'-azobis [2- (N-benzylamidino) propane] dihydrochloride, 2,2'-azobis [2- (N -Allylamidino) propane] dihydrochloride, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis {2- [N- (2-hydroxyethyl) amidino] propane} dihydrochloride salt, , 2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride 2,2′-azobis [2- (5-hydroxy-3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2′-azobis {2- [1- (2 -Hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2'-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2'-azobis [ 2- (2-imidazolin-2-yl) propane], 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2 '-Azobis {2-methyl- -[1,1-bis (hydroxymethyl) ethyl] propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2,2′-azobis (2- Methylpropionamide) dihydrate, 4,4′-azobis-4-cyanovaleric acid, 2,2′-azobis [2- (hydroxymethyl) propionitrile], 2,2′-azobis [2- (2- Imidazolin-2-yl) propane] disulfate, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] tetrahydrate, 2,2′-azobis [2-methyl- N- (2-hydroxyethyl) propionamide] and the like. These compounds may be used alone or in combination of two or more.

  As the azo compound (hereinafter referred to as “azo compound (z2)”) that can be used in the above method (R), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) is used. 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobis (2-methylpropionate), 2,2 ′ -Azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis [N- (2-propenyl) 2-methylpropionamide], 1- [ (1-Cyano-1-methylethyl) azo] formamide, 2,2′-azobis (N-butyl-2-methylpropionamide), dimethyl-1,1′-azobis (1-cyclohe San carboxylate), 2,2'-azobis (N- cyclohexyl-2-methylpropionamide), and the like. These compounds may be used alone or in combination of two or more.

  Examples of the organic peroxide include t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexanoate, di-t-butyl peroxide, benzoyl peroxide, and lauroyl peroxide. , Orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and the like. These compounds may be used alone or in combination of two or more.

In the above methods (Q) and (S), a polymerization initiator other than persulfate, for example, an azo compound, hydrogen peroxide, an organic peroxide, or the like is used. The compound illustrated above can be applied to this organic peroxide.
In the method (Q), the azo compound (z1) is preferably used, and the amount used thereof is 100 parts by mass of the monomer raw material consisting of the monomer (m1) because the aqueous solution of the present invention is excellent in transparency. The amount is preferably 0.1 to 3.0 parts by mass, more preferably 0.5 to 2.5 parts by mass, and still more preferably 1.0 to 2.0 parts by mass.
In the above method (S), the azo compound (z2) is preferably used, and the amount used thereof is a monomer raw material 100 composed of the monomer (m2) because the aqueous solution of the present invention is excellent in transparency. Preferably it is 0.1-3.0 mass parts with respect to a mass part, More preferably, it is 0.5-2.5 mass parts, More preferably, it is 1.0-2.0 mass parts.

  The polymerization solvent used in the above methods (P) and (Q) may be only water, or may be water and other organic solvents such as alcohol and ketone. In the latter case, the other organic solvent is preferably water-soluble, and the lower limit of the content of water is preferably 30% by mass, more preferably 50% by mass, based on the entire polymerization solvent.

Examples of the alcohol include methanol, ethanol, n-propanol, and isopropanol. These compounds can be used alone or in combination of two or more.
Examples of the ketone include acetone and methyl ethyl ketone. These compounds can be used alone or in combination of two or more.

The polymerization solvent used in the above methods (R) and (S) is an organic solvent. Examples of the organic solvent include alcohol, ketone, ester and the like. These may be used alone or in combination of two or more. In the present invention, it is preferable to contain an alcohol, and it is particularly preferable to use an organic solvent composed only of alcohol.
Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-pentanol, and n-hexanol. These compounds can be used alone or in combination of two or more.
Examples of the ketone include acetone and methyl ethyl ketone. These compounds can be used alone or in combination of two or more. Examples of the ester include ethyl acetate and butyl acetate. These compounds can be used alone or in combination of two or more.

The polymerization solvent used in the above methods (P), (Q), (R) and (S) is a polymerization of the monomer raw material in order to obtain a polymer (a) or polymer precursor having a desired molecular weight. It is preferable that isopropanol is contained because it can be smoothly advanced. The amount of isopropanol used is preferably 40 to 150 parts by mass, more preferably 50 to 130 parts by mass, and more preferably 50 to 130 parts by mass with respect to 100 parts by mass of the monomer raw material, regardless of whether isopropanol and other polymerization solvent are used in combination. Preferably it is 60-100 mass parts.
In addition, although the polymerization solvent used by the said method (P) and (Q) contains water, the usage-amount of isopropanol in the case of further containing isopropanol is as above-mentioned, and mass ratio with water at this time is especially It is not limited.

In the above methods (P) and (Q), the polymerization of the monomer (m1) using each polymerization initiator can be carried out by a conventionally known method. And the aqueous solution of the polymer (a) which consists of an acrylic acid type (co) polymer mainly having a structural unit derived from acrylic acid is obtained, and then included in the acrylic acid type (co) polymer by an alkali agent. -COOH is modified to -COOM to obtain polyacrylate (A).
Examples of the alkaline agent include hydroxides or carbonates of alkali metals such as sodium and potassium; hydroxides or carbonates of alkaline earth metals such as calcium and magnesium; ammonia; monoethanolamine, diethanolamine, triethanolamine, etc. The organic amine can be used as it is or in an aqueous solution in which it is dissolved in water.
As described above, when the monomer (m1), which is a monomer raw material, contains acrylate and does not contain acrylic acid, the obtained polymer (a) is directly used as polyacrylate ( Since it can be A), it is not necessary to use an alkali agent for modifying -COOH to -COOM.

  In the above methods (P) and (Q), the Mw of the polymer (a) composed of an acrylic acid (co) polymer obtained by polymerization of the monomer (m1) is preferably 1000 to 30000, more preferably It is 2000-20000, More preferably, it is 3000-10000. The Mw of the polyacrylate (A) obtained by treating this acrylic acid (co) polymer with an alkali agent is also substantially in the above range.

  When the above methods (P) and (Q) are used, an alkali agent is used to form a polyacrylic acid partially neutralized salt in which a part of —COOH contained in the acrylic acid (co) polymer is —COOM. A book containing the polyacrylate (A) using the combined (a) or its aqueous solution and KOH or its aqueous solution constituting the aqueous solution of the present invention, with the remainder of —COOH being —COOK, and KOH (B). The aqueous solution of the invention can be produced.

Next, in the above methods (R) and (S), the polymerization of the monomer (m2) using each polymerization initiator can be carried out by a conventionally known method. Then, an acrylic acid-based (co) polymer (polymer precursor), preferably a polyacrylic acid alkyl ester, mainly having a structural unit derived from an acrylic acid alkyl ester is obtained. ) A polymer (polymer precursor) and an alkali agent dissolved in water are reacted (saponification reaction) to obtain a polyacrylate (A).
The alkaline agent dissolved in the water is usually an aqueous solution of an alkali metal hydroxide such as sodium or potassium, and an organic acrylic (co) polymer (polymer precursor) is used in the saponification reaction. A mixture of solution and alkaline aqueous solution is subjected to heating. The reaction temperature is preferably 30 ° C to 80 ° C, more preferably 50 ° C to 70 ° C. As a result, a reaction liquid containing the polyacrylate (A), the organic solvent as the polymerization solvent, the alcohol produced by the saponification reaction, and water is obtained, and then the alcohol produced by the organic solvent and the saponification reaction. Are removed (solvent substitution) to obtain an aqueous solution of polyacrylate (A).

  Mw of polyacrylate (A) obtained by the said method (R) and (S) becomes like this. Preferably it is 1000-30000, More preferably, it is 2000-20000, More preferably, it is 3000-10000.

  When utilizing the said method (R) and (S), the aqueous solution of this invention can be manufactured using the aqueous solution of polyacrylate (A), KOH, or its aqueous solution.

In the present invention, the polyacrylic acid salt (A) obtained by using the above method (P), (Q), (R) or (S) is contained at a high concentration together with KOH (B). Excellent transparency can be obtained even with an aqueous solution.
When the aqueous solution of the present invention is 100% by mass, the polyacrylate (A) or the polymer (a) corresponding to 1 to 30% by mass is used, preferably 2 to 25% by mass, more preferably 3 to 3% by mass. Polyacrylate (A) or polymer (a) corresponding to 20% by mass, more preferably 5 to 15% by mass is used. KOH is used in an amount corresponding to 30 to 55% by mass, more preferably 32 to 50% by mass, and still more preferably 35 to 45% by mass.

  The aqueous solution of the present invention may contain other components soluble in water, such as an antifoaming agent and a chelating agent, depending on applications.

The pH (25 ° C.) of the aqueous solution of the present invention is usually 13-14. Further, for example, in a wide temperature range of 0 ° C. to 50 ° C., no alteration or the like occurs and is stable, and high transmittance at a wavelength of 610 nm can be maintained. This transmittance is preferably 95% or more, more preferably 98% or more. Then, the aqueous solution of the present invention is diluted with water as it is or in an appropriate ratio, and is applied to alkali treatment in, for example, “boiler water supply and boiler water quality” defined in JIS B 8223. It is suitable for allowing the polyacrylate (A) to act on calcium carbonate that easily adheres to a heat exchanger or the like. When used without being diluted with water, the amount injected into boiler water can be reduced.
The water treatment agent using the aqueous solution of the present invention is suitable for suppressing problems such as a decrease in heat exchange efficiency and blockage of piping in a cooling water system, a seawater desalination apparatus, and the like in addition to a boiler water system.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to this embodiment. In the following, “%” is based on mass unless otherwise specified.

1. Synthesis of acrylic acid polymer salt (polyacrylate precursor) Synthesis Example 1 (Synthesis of acrylic acid polymer salt E1)
A flask equipped with a stirrer and a condenser was charged with 600 g of water and 400 g of isopropanol (hereinafter referred to as “IPA”) and heated to 80 ° C. Next, while maintaining this reaction system at 80 ° C., with stirring, 800 g of 80% aqueous acrylic acid solution (hereinafter also referred to as “80% AA”) and 60 g of 20% 2,2′-azobis (2-amidino) Propane) dihydrochloride aqueous solution (hereinafter also referred to as “20% V-50”) was fed into the flask for 4 hours, respectively, to carry out polymerization. After completion of the supply, the reaction solution was further aged at 80 ° C. for 1 hour.
Next, the pressure of the reaction system was reduced, and while supplying water to the reaction solution, IPA was distilled off until the concentration became 1000 ppm by mass or less. Then, the obtained aqueous solution is set to 80 ° C., and a 48% aqueous solution of water and NaOH (hereinafter also referred to as “48% NaOH”) is further supplied, and the acrylic acid polymer salt (E1) having a solid concentration of 40%. The polymer aqueous solution of pH 7.0 was obtained (refer Table 1).

Next, when the acrylic acid polymer salt (E1) was subjected to gel permeation chromatography (GPC) under the conditions shown below, the Mw was 8,000.
<GPC measurement conditions>
Apparatus: HLC8020 system manufactured by Tosoh Corporation Detection: RI
Column: Tosoh G4000PWxl, G3000PWxl and G2500PWxl are connected. Eluent: 0.1M NaCl + phosphate buffer (pH 7)
Standard: Polyacrylic acid Na manufactured by Soka Science Co., Ltd.

Synthesis Example 2 (Synthesis of acrylic acid polymer salt E2)
A flask equipped with a stirrer and a condenser was charged with 600 g of water and heated to 90 ° C. Next, while maintaining this reaction system at 90 ° C., with stirring, 800 g of 80% AA, 15 g of 15% aqueous sodium persulfate (hereinafter also referred to as “15% NPS”), 100 g of 35% peroxidation. Hydrogen water and 600 g of 48% NaOH were respectively fed into the flask over 10 hours to carry out polymerization. After completion of the feeding, the reaction solution was further aged at 90 ° C. for 1 hour.
Next, the reaction system is set to 80 ° C., and a 48% aqueous solution of water and NaOH is further supplied. A polymer aqueous solution having a pH of 7.0 containing an acrylic acid polymer salt (E2) having a solid content concentration of 40% is obtained. Obtained (see Table 1).
Thereafter, the GPC analysis of the acrylic acid polymer salt (E2) was performed in the same manner as in Synthesis Example 1, and the results are also shown in Table 1.

Synthesis Example 3 (Synthesis of acrylic acid polymer salt E3)
Instead of 60 g of 20% V-50, the same operation as in Synthesis Example 1 was performed except that 32 g of 15% NPS was used, and an acrylic acid polymer salt (E3) having a solid content concentration of 40% was obtained. An aqueous polymer solution having a pH of 7.0 was obtained (see Table 1).
Thereafter, the GPC analysis of the acrylic acid polymer salt (E3) was conducted in the same manner as in Synthesis Example 1, and the results are also shown in Table 1.

Synthesis Example 4 (Synthesis of acrylic acid polymer salt E4)
A flask equipped with a stirrer and a condenser was charged with 650 g of IPA and heated to 80 ° C. Next, while maintaining this reaction system at 80 ° C., 764 g of methyl acrylate and 120 g of 10% 2,2′-azobisisobutyronitrile IPA solution (hereinafter also referred to as “10% AIBN”) Were each fed into the flask over 5 hours for polymerization. After completion of the supply, the reaction solution was further aged at 80 ° C. for 1 hour.
Next, the reaction system was under reduced pressure, and 300 g of IPA was distilled off. Then, after the polymerization solution was brought to 80 ° C., saponification was performed by adding a 32% aqueous solution of NaOH with stirring. Next, the pressure of the reaction system is reduced, and while supplying water to the reaction solution, IPA is distilled off until the concentration reaches 1000 ppm by mass or less, and an acrylic acid polymer salt (E4 having a solid content concentration of 40%) The polymer aqueous solution of pH 7.0 was obtained (refer Table 1).
Thereafter, the acrylic acid polymer salt (E4) was analyzed in the same manner as in Synthesis Example 1, and the results are also shown in Table 1.

Synthesis Example 5 (Synthesis of acrylic acid polymer salt E5)
First, except that the amount of water contained in the flask together with 400 g of IPA was 200 g, the same operation as in Synthesis Example 1 was performed, and the acrylic acid polymer salt (E5) having a solid content concentration of 40% was included. A polymer aqueous solution having a pH of 7.0 was obtained (see Table 1).
Thereafter, the GPC analysis of the acrylic acid polymer salt (E5) was performed in the same manner as in Synthesis Example 1, and the results are also shown in Table 1.

Synthesis Example 6 (Synthesis of acrylic acid polymer salt E6)
A flask equipped with a stirrer and a condenser was charged with 600 g of water and heated to 80 ° C. Next, while maintaining the reaction system at 80 ° C., 800 g of 80% acrylic acid aqueous solution (hereinafter, also referred to as “80% AA”) and 50 g of 20% V-50 were each stirred for 4 hours with stirring. The mixture was fed into the flask and polymerized. After completion of the supply, the reaction solution was further aged at 80 ° C. for 1 hour.
Next, the reaction system is set to 80 ° C., and a 48% aqueous solution of water and NaOH is further supplied. A polymer aqueous solution having a pH of 7.0 containing an acrylic acid polymer salt (E6) having a solid content concentration of 40% is prepared. Obtained (see Table 1).

Synthesis Example 7 (Synthesis of acrylic acid polymer salt C1)
Instead of 60 g of 20% V-50, the same operation as in Synthesis Example 1 was performed except that 70 g of 15% NPS was used, and an acrylic acid polymer salt (C1) having a solid content concentration of 40% was obtained. An aqueous polymer solution having a pH of 7.0 was obtained (see Table 1).
Thereafter, the GPC analysis of the acrylic acid polymer salt (C1) was performed in the same manner as in Synthesis Example 1, and the results are also shown in Table 1.

2. Preparation and Evaluation of Alkaline Aqueous Solution Containing Polyacrylate Examples 1 to 54 and Comparative Examples 1 to 9
Tables 2 to 5 show aqueous solutions of acrylic acid polymer salts (concentration of acrylic acid polymer salt of 40% by mass), KOH, and water obtained in Synthesis Examples 1 to 7, respectively. Using the mass proportions described, the mixture was stirred and mixed at 40 ° C. to prepare a uniform aqueous solution in which polyacrylate and KOH were dissolved. Then, stability was evaluated by the method shown below, and the result was written together in Table 2-Table 5.
<Stability test>
The aqueous solution was placed in a glass container and allowed to stand in a 5 ° C. constant temperature bath. After 24 hours, the sample was placed in a glass cell (cell length: 10 mm), and the transmittance at a wavelength of 610 nm and 5 ° C. was measured with a spectrophotometer.

  As is apparent from Table 5, the aqueous solutions obtained in Comparative Examples 1 to 9 contain polyacrylate prepared by a method outside the scope of the present invention, and thus the transmittance is as low as 93.0% or less. Stability was insufficient. On the other hand, as is clear from Tables 2 to 4, the aqueous solutions obtained in Examples 1 to 54 are less likely to be turbid and have excellent stability even when the polyacrylate and KOH are at high concentrations. It was.

  The aqueous acrylic acid copolymer salt solution of the present invention is widely used in water treatment agents, aqueous cleaning agents, inorganic particle dispersants, etc. that are diluted with water to suppress the formation of scales in pipes, boilers, heat exchangers, etc. Can be used. In particular, since it is excellent in transparency, it is suitable as a raw material for water treatment agents.

Claims (6)

(A) a polyacrylate comprising a completely neutralized salt of polyacrylic acid,
(B) potassium hydroxide,
as well as,
(C) water,
In an aqueous solution containing
In the polyacrylate (A), the amount of persulfate used as a polymerization initiator is 1.2 parts by mass with respect to 100 parts by mass of a monomer raw material containing acrylic acid (salt) or an alkyl acrylate ester. It is a neutralized product of the polymer (a) obtained as follows with an alkali agent,
The aqueous solution comprises the polyacrylate (A) or polymer (a) corresponding to 1 to 30% by mass and the potassium hydroxide (B) corresponding to 30 to 55% by mass with respect to the total amount. An aqueous solution containing a polyacrylate, wherein the aqueous solution is obtained by using the polyacrylic acid salt.   The aqueous solution according to claim 1, wherein the polyacrylate (A) has a weight average molecular weight of 1,000 to 30,000.   The aqueous solution according to claim 1 or 2, wherein the polymerization initiator for producing the polymer (a) contains at least one selected from an azo compound, hydrogen peroxide and an organic peroxide.   The polymerization solvent for producing the polymer (a) contains isopropanol, and the amount of the isopropanol used is 40 to 150 parts by mass with respect to 100 parts by mass of the monomer raw material. An aqueous solution according to claim 1.   5. The polymer according to claim 1, wherein the polyacrylate (A) is a polymer obtained by polymerizing an alkyl acrylate and then saponifying the obtained alkyl acrylate. 6. The aqueous solution described.   The aqueous solution according to any one of claims 1 to 5, wherein the transmittance at a wavelength of 610 nm is 95% or more.