JP6411150B2 - Method for producing (meth) acrylic acid polymer aqueous solution - Google Patents

Description

  The present invention relates to a method for producing a (meth) acrylic acid polymer aqueous solution.

  Bisulfite as a chain transfer agent for the purpose of performing a smooth reaction when producing a (meth) acrylic acid polymer by polymerizing a monomer composition containing (meth) acrylic acid (salt). May be selected and used (see, for example, Patent Documents 1 and 2).

  However, in general, when a (meth) acrylic acid polymer is produced using bisulfite as a chain transfer agent, a large amount of residual bisulfite is present in the resulting aqueous solution of (meth) acrylic acid polymer. . Thus, when a large amount of residual bisulfite is present in the (meth) acrylic acid polymer aqueous solution, for example, sulfurous acid gas is generated by decomposition of the residual bisulfite, and the sulfurous acid gas is converted to (meth) acrylic acid. There exists a problem that it melt | dissolves in an aqueous polymer solution and becomes an impurity.

  As a method of reducing the residual bisulfite in the aqueous solution of (meth) acrylic acid polymer obtained when producing a (meth) acrylic acid polymer using bisulfite as a chain transfer agent, conventional polymerization A method of adding hydrogen peroxide after the reaction is known (see, for example, Patent Document 3).

  However, when hydrogen peroxide is added after the polymerization reaction, the sulfurous acid gas present in the gas phase portion of the polymerization reaction vessel reacts with hydrogen peroxide to produce sulfuric acid mist, and the metal used in the polymerization reaction vessel (for example, There is a problem that SUS) is corroded.

JP 7-278206 A JP 2002-338618 A Japanese Patent Laid-Open No. 2002-80502

  An object of the present invention is a method for producing a (meth) acrylic acid polymer using bisulfite, and the concentration of residual bisulfite in the resulting aqueous solution of (meth) acrylic acid polymer is low. An object of the present invention is to provide a method for producing a (meth) acrylic acid polymer aqueous solution capable of suppressing corrosion of a metal by the (meth) acrylic acid polymer aqueous solution.

The production method of the (meth) acrylic acid polymer aqueous solution of the present invention is as follows:
A method for producing a (meth) acrylic acid polymer by adding a monomer composition containing bisulfite and (meth) acrylic acid (salt) to a reaction vessel, and carrying out a polymerization reaction and aging. ,
The addition of sodium hydroxide is started before the end of the addition of the (meth) acrylic acid (salt), and the addition of the sodium hydroxide is completed before the ripening is completed.

  In a preferred embodiment, the addition of the sodium hydroxide is started while 50 mass% to 85 mass% of the total amount of the (meth) acrylic acid (salt) is added.

  In a preferred embodiment, the addition of the sodium hydroxide is completed after 90% by mass of the total amount of the (meth) acrylic acid (salt) has been added until the ripening is completed.

  In a preferred embodiment, the residual bisulfite concentration in the resulting (meth) acrylic acid polymer aqueous solution is less than 1300 ppm.

  In preferable embodiment, APHA of the (meth) acrylic acid type polymer aqueous solution obtained is 50 or less.

  According to the present invention, a method for producing a (meth) acrylic acid polymer using bisulfite, the residual bisulfite concentration in the resulting (meth) acrylic acid polymer aqueous solution is low, and The manufacturing method of the (meth) acrylic acid type polymer aqueous solution which can suppress the corrosion of the metal by the (meth) acrylic acid type polymer aqueous solution produced | generated can be provided.

≪≪Method for producing (meth) acrylic acid polymer aqueous solution≫≫
In the method for producing a (meth) acrylic acid polymer aqueous solution of the present invention, a monomer composition containing bisulfite and (meth) acrylic acid (salt) is added to a reaction vessel, and a polymerization reaction and aging are performed. A method for producing a (meth) acrylic acid-based polymer, wherein the addition of sodium hydroxide is started before the addition of the (meth) acrylic acid (salt), and the water is added until the ripening is completed. The addition of sodium oxide is terminated.

≪Monomer composition≫
A monomer composition is one type of monomer (a monomer having a polymerizable unsaturated double bond) or two or more types of monomers (polymerizable unsaturated) including (meth) acrylic acid (salt). It means a mixture of monomers having a double bond.

  (Meth) acrylic acid (salt) means acrylic acid (salt) and / or methacrylic acid (salt). Acrylic acid (salt) means acrylic acid and / or acrylate, and methacrylic acid (salt) means methacrylic acid and / or methacrylate.

The salt of (meth) acrylic acid (salt) is represented by Z in the —COOZ group. Z is a metal atom, an ammonium group (which constitutes an ammonium salt, ie, COONH ₄ ), or an organic amino group (which constitutes an organic amine salt). Examples of the metal atom include alkali metals such as sodium atom and potassium atom, alkaline earth metals such as calcium atom, and transition metals such as iron atom. Examples of the organic amine salt include primary to quaternary amine salts such as methylamine salt, n-butylamine salt, monoethanolamine salt, dimethylamine salt, diethanolamine salt, morpholine salt, and trimethylamine salt. Among these, in order to fully express the effects of the present invention, M is preferably a sodium atom or a potassium atom.

  In the present specification, the description of “acid (salt)” other than (meth) acrylic acid (salt) has the same meaning as “acid (salt)” in (meth) acrylic acid (salt). Moreover, description of Z of the -COOZ group in (meth) acrylic acid (salt) is also used as it is only for the description of "salt".

  The monomer composition may contain other monomers other than (meth) acrylic acid (salt). Such other monomer may be only one kind or two or more kinds.

  Examples of other monomers include monocarboxylic acid monoethylenically unsaturated monomers other than (meth) acrylic acid such as crotonic acid and α-hydroxyacrylic acid, and salts thereof; itaconic acid, fumaric acid, Unsaturated dicarboxylic acids such as maleic acid, and salts thereof; 3- (meth) allyloxy-2-hydroxy-1-propanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, (meth) allylsulfone Sulfonic acid monomers such as acid, vinyl sulfonic acid, styrene sulfonic acid, 2-sulfoethyl (meth) acrylate, conjugated diene sulfonic acid such as 2-methyl-1,3-butadiene-1-sulfonic acid, and the like Salt; N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylformami N-vinyl monomers such as N-vinyl-N-methylacetamide and N-vinyloxazolidone; Amide monomers such as (meth) acrylamide, N, N-dimethylacrylamide and N-isopropylacrylamide; 3- ( (Meth) allyloxy-1,2-dihydroxypropane, 3-allyloxy-1,2-dihydroxypropane, (meth) allyloxypropane-based compounds such as 3-allyloxy-1,2-dihydroxypropane, and 1 mol of these compounds Compound (3-allyloxy-1,2-di (poly) oxyethylene ether propane, etc.) obtained by adding 1 to 200 mol of ethylene oxide to 1 mol; (meth) allyl alcohol and 1 mol of (meth) allyl alcohol Of 1 to 100 moles of ethylene oxide added to Allyl ether monomers such as compounds; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate ( (Meth) acrylic acid ester monomers; isoprene monomers, and isoprene monomers such as compounds obtained by adding 1 mol to 100 mol of ethylene oxide with respect to 1 mol of isoprenol;

  The content ratio of (meth) acrylic acid (salt) in the monomer composition is a mass ratio, preferably 1% by mass to 100% by mass, more preferably 10% by mass to 100% by mass, Preferably they are 20 mass%-100 mass%, More preferably, they are 40 mass%-100 mass%, More preferably, they are 50 mass%-100 mass%, Most preferably, they are 60 mass%-100 mass%. Most preferably, it is 70 mass%-100 mass%. When the content ratio of (meth) acrylic acid (salt) falls within the above range, for example, when used as a detergent builder, excellent cleaning ability can be exhibited.

  The content ratio of the other monomer in the monomer composition is a mass ratio, preferably 0% by mass to 99% by mass, more preferably 0% by mass to 90% by mass, and still more preferably 0%. % By mass to 80% by mass, more preferably 0% by mass to 60% by mass, further preferably 0% by mass to 50% by mass, particularly preferably 0% by mass to 40% by mass, and most preferably. Is 0% by mass to 30% by mass. When the content ratio of the other monomer in the monomer composition is within the above range, for example, when used as a detergent builder, excellent cleaning ability can be exhibited.

≪Manufacturing method≫
In the method for producing an aqueous (meth) acrylic acid polymer solution of the present invention, a monomer composition containing bisulfite and (meth) acrylic acid (salt) is added to a reaction vessel, and a polymerization reaction and aging are carried out. Do.

<Reaction vessel>
In general, any appropriate reaction vessel can be adopted as long as it is a reaction vessel that can be used for the production of a (meth) acrylic acid polymer aqueous solution. Examples of such a reaction vessel include a metal (eg, SUS) reaction vessel, a glass reaction vessel, and a resin reaction vessel. Typically, a reaction vessel made of metal (for example, SUS) can be mentioned.

<Solvent>
The solvent used in the reaction liquid (polymerization reaction liquid) during the polymerization reaction is preferably an aqueous solvent, and more preferably water. In order to improve the solubility of the monomer composition in the solvent, an organic solvent may be appropriately added as long as it does not adversely affect the polymerization. Examples of the organic solvent to be added include lower alcohols such as methanol and ethanol; amides such as dimethylformaldehyde; ethers such as diethyl ether and dioxane;

<Additives>
In the method for producing a (meth) acrylic acid polymer aqueous solution of the present invention, bisulfite and a monomer composition are added to a reaction vessel. A monomer composition contains (meth) acrylic acid (salt) as mentioned above, and contains another monomer as needed.

  Only one type of bisulfite may be used, or two or more types may be used.

  Examples of the bisulfite include sodium bisulfite, potassium bisulfite, and ammonium bisulfite.

  The amount of bisulfite added is preferably 0.5 g to 20 g as the amount of bisulfite added to 1 mol of the monomer composition used.

  In the method for producing a (meth) acrylic acid polymer aqueous solution of the present invention, it is preferable to use persulfate together with bisulfite.

  Only one persulfate may be used, or two or more persulfates may be used.

  Examples of the persulfate include sodium persulfate, potassium persulfate, and ammonium persulfate.

  The amount of persulfate added is preferably 1 g to 10 g as the amount of persulfate added to 1 mol of the monomer composition used.

  When persulfate is used in combination with bisulfite, the addition ratio of persulfate and bisulfite is, by mass ratio, preferably 0.5 to 10 with respect to persulfate 1. . If the bisulfite is less than 0.5 with respect to persulfate 1 by mass ratio, the effect of bisulfite may not be sufficient, and the weight of the (meth) acrylic acid polymer to be obtained The average molecular weight may be too high. When the bisulfite exceeds 10 with respect to the persulfate 1 by mass ratio, the effect of the bisulfite may not be obtained as much as the addition ratio. However, the blending amount of persulfate and bisulfite is not limited to this range, and the specific blending amount of persulfate and bisulfite can be determined according to the use application and use environment. . For example, when a (meth) acrylic acid copolymer is used as a detergent builder, if the weight average molecular weight is too high, the performance may be deteriorated. Therefore, the blending amount may be determined taking care not to increase the weight average molecular weight more than necessary.

  In addition to persulfate and bisulfite, sulfite and pyrosulfite may be used if necessary.

The polymerization reaction solution preferably contains one or more heavy metal ions. A heavy metal means a metal having a specific gravity of 4 g / cm ³ or more. Specific examples of heavy metals include iron, cobalt, manganese, chromium, molybdenum, tungsten, copper, silver, gold, lead, platinum, iridium, osmium, palladium, rhodium, and ruthenium. The polymerization reaction liquid preferably contains these ions. The polymerization reaction solution more preferably contains iron ions. The ionic value of the heavy metal ion is not particularly limited. For example, when iron is used as the heavy metal, the iron ion dissolved during the polymerization reaction may be Fe ²⁺ , Fe ³⁺ , or a combination thereof.

Heavy metal ions can be added using a solution in which a heavy metal compound is dissolved. The heavy metal compound used in that case is determined according to the heavy metal ion desired to be contained in the polymerization reaction solution. When water is used as the solvent, a water-soluble heavy metal salt is preferable. Examples of the water-soluble heavy metal salt include molle salt (Fe (NH ₄ ) ₂ (SO ₄ ) ₂ .6H ₂ O), ferrous sulfate.7 hydrate, ferrous chloride, ferric chloride, Examples include manganese chloride.

  The content ratio of heavy metal ions is preferably 0.1 ppm to 10 ppm with respect to the total mass of the polymerization reaction solution at the completion of the polymerization reaction. The time when the polymerization reaction is completed means the time when the polymerization reaction is substantially completed in the polymerization reaction solution and a desired polymer is obtained. For example, when the polymer polymerized in the polymerization reaction solution is neutralized with an alkali component, the content of heavy metal ions is calculated based on the total mass of the polymerization reaction solution after neutralization. When two or more kinds of heavy metal ions are included, the total amount of heavy metal ions may be in the above range.

  If the content of heavy metal ions is less than 0.1 ppm, the effect of heavy metal ions may not be sufficiently exhibited. On the other hand, when the content of heavy metal ions exceeds 10 ppm, there is a possibility that the dirt when used as a detergent builder or the scale when used as a scale inhibitor increases.

<Polymerization>
Any appropriate method can be adopted as the polymerization method. One of the preferred embodiments is a method in which the monomer composition, persulfate, and bisulfite are dropped into a reaction vessel charged with a solvent in advance. Of course, other components may be dropped within a range not impairing the effects of the present invention.

  Any appropriate temperature can be adopted as the polymerization temperature. The polymerization temperature is preferably 25 ° C to 99 ° C, more preferably 50 ° C to 97 ° C, still more preferably 60 ° C to 96 ° C, and particularly preferably 70 ° C to 93 ° C. If the polymerization temperature is less than 25 ° C., the weight average molecular weight of the resulting polymer may be excessively increased or the amount of impurities generated may be increased. Moreover, since polymerization time becomes long, there exists a possibility that productivity of a polymer may fall. On the other hand, when the polymerization temperature exceeds 99 ° C., the bisulfite may decompose and a large amount of sulfurous acid gas may be generated. Since sulfurous acid gas dissolved in the liquid phase can be a causative substance of impurities, when a large amount of sulfurous acid gas is generated, the amount of impurities in the resulting polymer may increase. In addition, the recovery cost of sulfurous acid gas in the gas phase may increase. The polymerization temperature refers to the temperature of the polymerization reaction solution. Any appropriate method or apparatus can be used as a method for measuring the polymerization temperature or a control means.

  Arbitrary appropriate pressure can be employ | adopted for the pressure at the time of superposition | polymerization. For example, the pressure may be any of normal pressure, reduced pressure, and increased pressure.

  In the monomer composition, (meth) acrylic acid (salt) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably the total amount, based on the total amount used. Is added to the reaction vessel by dripping substantially continuously. If the ratio of addition is less than 70% by mass (that is, the initial charge is more than 30% by mass), (meth) acrylic acid (salt) may be polymerized in a block manner at the initial stage of polymerization and may have a high molecular weight. . The addition time of (meth) acrylic acid (salt) is preferably 30 minutes to 360 minutes, more preferably 60 minutes to 300 minutes, still more preferably 90 minutes to 240 minutes, and particularly preferably 120 minutes. ~ 200 minutes. When the addition time is shorter than 30 minutes, (meth) acrylic acid (salt) may be polymerized in a block manner and may have a high molecular weight. If the addition time exceeds 360 minutes, not only is the production facility / apparatus limited, but the production cost may increase.

  When the monomer composition contains another monomer, the other monomer is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, based on the total amount used. Particularly preferably, the whole amount is added to the reaction vessel by dripping substantially continuously. If the ratio of addition is less than 70% by mass (that is, the initial charge is more than 30% by mass), (meth) acrylic acid (salt) may be polymerized in a block manner at the initial stage of polymerization and may have a high molecular weight. . The addition time of (meth) acrylic acid (salt) is preferably 30 minutes to 360 minutes, more preferably 60 minutes to 300 minutes, still more preferably 90 minutes to 240 minutes, and particularly preferably 120 minutes. ~ 200 minutes. When the addition time is shorter than 30 minutes, (meth) acrylic acid (salt) may be polymerized in a block manner and may have a high molecular weight. If the addition time exceeds 360 minutes, not only is the production facility / apparatus limited, but the production cost may increase.

  Bisulfite is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and most preferably 90% by mass or more, by dripping the total amount substantially continuously with respect to the total amount used. Add to reaction vessel. By adding the bisulfite as described above, the bisulfite can be efficiently used in the polymerization reaction, and decomposition of the bisulfite at the initial stage of polymerization can be suppressed. The addition time of bisulfite is preferably 30 minutes to 360 minutes, more preferably 60 minutes to 300 minutes, still more preferably 90 minutes to 240 minutes, and particularly preferably 120 minutes to 200 minutes. . Furthermore, bisulfite is preferably added within 60 minutes before and after addition of (meth) acrylic acid (salt), and added within 40 minutes before and after addition of (meth) acrylic acid (salt) in order to efficiently use the bisulfite. Is more preferably completed within 30 minutes before and after, more preferably within 20 minutes before and after, and most preferably within 10 minutes before and after.

  When persulfate is used in combination with bisulfite, the amount of persulfate is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, particularly preferably the total amount, based on the total amount used. Is added to the reaction vessel by dripping substantially continuously. By adding the persulfate as described above, the persulfate is efficiently utilized by the polymerization reaction. The addition time of the persulfate is preferably 30 minutes to 360 minutes, more preferably 60 minutes to 300 minutes, still more preferably 90 minutes to 240 minutes, and particularly preferably 120 minutes to 200 minutes. . Further, in order to efficiently use the persulfate by the polymerization reaction, it is preferable to finish the addition within 60 minutes before and after the end of the addition of (meth) acrylic acid (salt), and within 40 minutes before and after the addition. Is more preferably completed within 30 minutes before and after, more preferably within 20 minutes before and after, and most preferably within 10 minutes before and after.

  In the method for producing a (meth) acrylic acid polymer aqueous solution of the present invention, the addition of sodium hydroxide is started before the completion of the addition of (meth) acrylic acid (salt), and the hydroxylation is completed until the aging is completed. Finish the sodium addition. The addition of sodium hydroxide is started before the end of the addition of (meth) acrylic acid (salt), and the addition of the sodium hydroxide is completed before the ripening is completed. The residual bisulfite concentration in the combined aqueous solution is lowered, and corrosion of the metal by the resulting (meth) acrylic acid polymer aqueous solution can be suppressed.

  In the method for producing the (meth) acrylic acid polymer aqueous solution of the present invention, preferably, sodium hydroxide is added while 50% by mass to 85% by mass of the total amount of (meth) acrylic acid (salt) is added. To start. More preferably, the addition of the sodium hydroxide is started while 56% by mass to 83% by mass of the total amount of (meth) acrylic acid (salt) is added, and more preferably, (meth) acrylic acid (salt) The addition of the sodium hydroxide is started while 67 mass% to 81 mass% of the total amount of is added, and particularly preferably 70 mass% to 79 mass% of the total amount of (meth) acrylic acid (salt) is added The addition of the sodium hydroxide is started while the addition of the sodium hydroxide is most preferably performed while 72% by mass to 78% by mass of the total amount of (meth) acrylic acid (salt) is added. To do. By starting the addition of sodium hydroxide as described above, the concentration of residual bisulfite in the resulting (meth) acrylic acid polymer aqueous solution becomes lower, and the resulting (meth) acrylic acid polymer aqueous solution Metal corrosion can be further suppressed.

  In the method for producing the (meth) acrylic acid polymer aqueous solution of the present invention, preferably, hydroxylation is performed after 90% by mass of the total amount of (meth) acrylic acid (salt) is added until the ripening is completed. Finish the sodium addition. More preferably, the addition of sodium hydroxide is completed after 92% by mass of the total amount of (meth) acrylic acid (salt) has been added until the ripening is completed, and more preferably (meth) acrylic acid ( The addition of sodium hydroxide is completed after the addition of 94% by mass of the total amount of (salt) to the end of ripening, and particularly preferably 96% by mass of the total amount of (meth) acrylic acid (salt) is added The addition of sodium hydroxide is terminated after the ripening is completed, and most preferably, 98% by mass of the total amount of (meth) acrylic acid (salt) is added until the ripening is completed. To complete the addition of sodium hydroxide. By completing the addition of sodium hydroxide as described above, the residual bisulfite concentration in the resulting (meth) acrylic acid polymer aqueous solution becomes lower, and the resulting (meth) acrylic acid polymer aqueous solution Metal corrosion can be further suppressed.

  The term “aging” refers to holding the polymerization temperature for a certain period of time after the addition of the monomer composition, while maintaining the polymerization temperature or changing the polymerization temperature. Aging can be able to reduce the residual monomer. The aging time is preferably 10 minutes to 6 hours, more preferably 20 minutes to 3 hours, and further preferably 30 minutes to 2 hours.

  Further, in the method for producing a (meth) acrylic acid polymer aqueous solution of the present invention, sodium hydroxide is preferably added within 100 minutes before and after the end of the addition of (meth) acrylic acid (salt). More preferably, the addition is completed within 80 minutes before and after, more preferably within 70 minutes before and after, more preferably within 60 minutes before and after, and addition within 50 minutes before and after. Most preferably it is terminated. By completing the addition of sodium hydroxide as described above, the residual bisulfite concentration in the resulting (meth) acrylic acid polymer aqueous solution becomes lower, and the resulting (meth) acrylic acid polymer aqueous solution Metal corrosion can be further suppressed.

  In order to obtain a low molecular weight polymer, the polymerization reaction is preferably carried out under acidic conditions (preferably, the pH is less than 3). Specifically, the degree of neutralization before the start of dropping sodium hydroxide is preferably less than 60 mol%, more preferably less than 50 mol%, still more preferably less than 40 mol%, and most preferably less than 35 mol%. is there. If the degree of neutralization during the polymerization reaction is high, a large amount of impurities may be generated. The lower limit of the degree of neutralization during the polymerization reaction is not particularly limited, but if the degree of neutralization during the polymerization reaction is too low, the amount of sulfurous acid gas generated may increase. Considering these balances, the degree of neutralization during the polymerization reaction is preferably kept at about 30 mol%.

  By performing the polymerization reaction under acidic conditions, the polymerization can be performed at a high concentration and in one stage. Therefore, the concentration process which was necessary in some cases in the conventional manufacturing method can be omitted. Therefore, the productivity of the (meth) acrylic acid polymer is greatly improved, and an increase in manufacturing cost can be suppressed.

  When polymerization is performed under acidic conditions, the degree of neutralization of the resulting (meth) acrylic acid polymer is neutral by adding an alkaline component after the polymerization is completed (preferably pH is 3 to 7). You may control to. Examples of alkali components include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide; ammonia, monoethanolamine, diethanolamine, triethanolamine, etc. Organic amines; and the like. Only 1 type may be sufficient as an alkali component, and 2 or more types may be sufficient as it.

  By the above reaction, the (meth) acrylic acid polymer can be preferably produced in the form of an aqueous solution. That is, preferably, a (meth) acrylic acid polymer aqueous solution is produced.

  The residual bisulfite concentration in the resulting (meth) acrylic acid polymer aqueous solution is preferably less than 1300 ppm, more preferably 1250 ppm or less, still more preferably 1200 ppm or less, and particularly preferably 1100 ppm or less. Most preferably, it is 1050 ppm or less.

  APHA of the obtained (meth) acrylic acid polymer aqueous solution is preferably 50 or less, more preferably 48 or less, further preferably 45 or less, particularly preferably 43 or less, and most preferably 40. It is as follows. The aqueous (meth) acrylic acid polymer solution obtained by the production method of the present invention has such an excellent color tone.

  The aqueous solution of the (meth) acrylic acid polymer thus obtained can obtain, for example, a polymer excellent in scale prevention ability (scale inhibition ability). Specifically, for example, a water treatment agent and a detergent It is particularly suitable for applications such as builder, detergent composition, dispersant, and cleaning agent.

  The weight average molecular weight of the (meth) acrylic acid polymer to be obtained is preferably 1000 to 100,000, more preferably 1000 to 50000, still more preferably 1000 to 10,000, and particularly preferably 1000 to 5000. . If the weight average molecular weight is within this range, the (meth) acrylic acid polymer can most effectively exhibit various performances such as dispersibility, chelating ability, and gel resistance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all. Unless otherwise specified, parts and% in the examples are based on mass.

<Method for measuring weight average molecular weight of polymer>
The weight average molecular weight of the polymer was measured under the following conditions.
Equipment: Tosoh high-speed GPC equipment (HLC-8320GPC)
Detector: RI
Column: SHODEX Asahipak GF-310-HQ, GF-710-HQ, GF-1G 7B manufactured by Showa Denko KK
Column temperature: 40 ° C
Flow rate: 0.5 ml / min
Calibration curve: POLYACRYLIC ACID STANDARD made by Soka Science Co., Ltd.
Eluent: 0.1N sodium acetate aqueous solution

<Metal corrosion test>
In the reaction vessel, a SUS316L metal piece (about 5 g) was suspended so as not to be immersed in the reaction solution, and a (meth) acrylic acid polymer aqueous solution was produced. After completion of the aging, the SUS316L metal piece in the reaction vessel is completely immersed in the reaction solution, stirred for 60 minutes while maintaining the reaction solution at 90 ° C., then the reaction solution is cooled to room temperature, and the SUS316L metal piece is placed in the reaction vessel. It was taken out from.
About the SUS316L metal piece, the mass (A) before putting in a reaction container and the mass (B) after taking out from the inside of a reaction container were measured, and the change of mass was computed.

<Measurement of residual bisulfite concentration>
The residual bisulfite concentration in the aqueous polymer solution was determined by adding redox titration to the aqueous polymer solution and then redox titrating the remaining hydrogen peroxide in the solution with sodium thiosulfate. It was quantified by calculating by. That is, the calculation was performed by (substance amount of hydrogen peroxide added) − (substance amount of residual hydrogen peroxide) = (substance amount of residual sulfite in the aqueous polymer solution).
(Quantification method of hydrogen peroxide concentration)
The hydrogen peroxide concentration in the sample solution was measured according to the following procedure.
In a 100 mL beaker, 1.0 g of potassium iodide was weighed, 70 g of pure water was added, and the mixture was stirred with a magnetic stirrer. To this, 15 mL of 18N sulfuric acid was added with a whole pipette with stirring, and then the sample solution was further changed to brown (Zg) and stirred for 2 minutes.
To this, 1 mL of 1% starch was added with a whole pipette under stirring, and it was confirmed that the solution turned black brown. Immediately after the color change was confirmed, the solution was titrated with a 0.1 M aqueous sodium thiosulfate solution using an automatic titrator (COM-1700 manufactured by Hiranuma Sangyo Co., Ltd.) under stirring, and the point at which the color disappeared was defined as the end point (AmL). Separately, as a blank, a sample to which no sample solution was added was also titrated to obtain an end point (BmL). The hydrogen peroxide concentration was calculated by inputting each measured value into the following equation. However, F shows the factor of 0.1M sodium thiosulfate aqueous solution.
Hydrogen peroxide concentration (%) = (A−B) × 0.17 × F / Z.
(Quantification method of residual bisulfite concentration in polymer aqueous solution)
The residual bisulfite concentration in the aqueous polymer solution was measured according to the following procedure.
A sufficient amount of 0.1% hydrogen peroxide solution was prepared, and an accurate concentration (S%) was calculated according to the above (quantitative method of hydrogen peroxide concentration). In a 20 mL screw tube, 4.0 g of an aqueous polymer solution (with an accurate weight of Xg) and 4.0 g of 0.1% hydrogen peroxide solution (with an accurate weight of Yg) are weighed, and 10% with a magnetic stirrer. Stir for minutes to make Solution C. In a 100 mL beaker, 1.0 g of potassium iodide was weighed, 70 g of pure water was added, and the mixture was stirred with a magnetic stirrer. To this beaker, 15 mL of 18N sulfuric acid was added with a whole pipette under stirring, and then Solution C was changed to brown (Zg) and stirred for 2 minutes. Furthermore, 1 mL of 1% starch was added with a whole pipette under stirring, and it was confirmed that the solution turned black brown. Immediately after the color change was confirmed, the solution was titrated with a 0.1M aqueous sodium thiosulfate solution using an automatic titrator (COM-1700, manufactured by Hiranuma Sangyo Co., Ltd.) with stirring, and the point at which the color disappeared was defined as the end point (AmL). Separately, the end point (BmL) of the sample to which the solution C was not added was obtained as a blank. The residual bisulfite concentration was calculated by inputting each measured value into the following equation. However, F shows the factor of 0.1M sodium thiosulfate aqueous solution.
Residual bisulfite concentration in the aqueous polymer solution (ppm) = 30600 (X + Y) / X (SY / (X + Y) −0.17F (AB) / Z)

<Measurement of iron concentration>
The iron concentration in the aqueous polymer solution was measured by inductively coupled plasma (ICP) emission spectroscopy under the following conditions.
Apparatus: SHIMADZU ICPE-9000
Standard sample: Wako Iron Standard Solution (Fe100)
Measurement wavelength: 259.940 nm

<Measurement conditions of sodium sulfate concentration>
The concentration of sodium sulfate contained in the aqueous polymer solution was measured by ion chromatography analysis under the following conditions.
Device: IC2010 made by TOSOH
Column: Shodex IC SI-90 4E
Column temperature: 25 ° C
Eluent: 1 mM NaCO ₃ 4 mM NaHCO ₃ Acetone 5 wt% Water flow rate: 1.2 mL / min

<Measurement of APHA>
The APHA value of the polymer aqueous solution was measured under the following conditions in accordance with JIS-K3331.
Equipment: Spectral color difference meter “SE6000” manufactured by Nippon Denshoku Industries Co., Ltd.
Measurement mode: Transmittance Measurement wavelength: 380 nm to 780 nm (10 nm interval output)
Light source: Halogen lamp (12V, 50W)
Measurement cell size: 55mm x 40mm x 25mm

[Example 1]
Ion exchange water: 90.4 g was charged into a 1.0 L glass separable flask equipped with a reflux condenser and a stirrer, and SUS316L metal pieces were immersed in the following reaction solution in the flask using Teflon (registered trademark) tape. It was hung so as not to. Thereafter, the ion-exchanged water was heated to 90 ° C. under stirring conditions. After the internal temperature reaches 90 ° C., the internal temperature is maintained at 90 ° C., and 80% acrylic acid aqueous solution (hereinafter also referred to as “80% AAaq”): 150 g, 35% sodium bisulfite aqueous solution (hereinafter “35% SBSaq”) 51.2 g, 15% sodium persulfate aqueous solution (hereinafter also referred to as “15% NaPSaq”): 44.4 g, and 48% sodium hydroxide aqueous solution (hereinafter also referred to as “48% NaOHaq”): 55 .5 g was dropped from different nozzles. The 80% acrylic acid aqueous solution was added dropwise for 180 minutes from the start of the reaction, the 35% sodium bisulfite aqueous solution was added dropwise for 170 minutes from the start of the reaction, and the 48% sodium hydroxide aqueous solution was added dropwise over a period of 60 minutes starting from 140 minutes after the start of the reaction. For the 15% aqueous solution of sodium persulfate, the amount is 1.78 g per mole of acrylic acid for 30 minutes after the start of the reaction, and 0.89 g per mole of acrylic acid from 30 minutes to 60 minutes after the start of the reaction. An amount of 1.33 g per mole of acrylic acid was dropped from 60 to 190 minutes after the start of the reaction.
After completion of the dropwise addition, the reaction solution was kept at 90 ° C. for 60 minutes for further aging. After completion of aging, the SUS316L metal piece in the flask was completely immersed in the reaction solution, stirred for 60 minutes while maintaining the reaction solution at 90 ° C., then the reaction solution was cooled to room temperature, and the SUS316L metal piece was removed from the reaction vessel. I took it out. Thus, a (meth) acrylic acid polymer aqueous solution (1) was obtained.
The results are summarized in Table 1.

[Comparative Example 1]
Ion exchange water: 90.4 g was charged into a 1.0 L glass separable flask equipped with a reflux condenser and a stirrer, and SUS316L metal pieces were immersed in the following reaction solution in the flask using Teflon (registered trademark) tape. It was hung so as not to. Thereafter, the ion-exchanged water was heated to 90 ° C. under stirring conditions. After the internal temperature reaches 90 ° C., the internal temperature is maintained at 90 ° C., and 80% acrylic acid aqueous solution (hereinafter also referred to as “80% AAaq”): 150 g, 35% sodium bisulfite aqueous solution (hereinafter “35% SBSaq”) ): 51.2 g and 15% sodium persulfate aqueous solution (hereinafter also referred to as “15% NaPSaq”): 44.4 g were dropped from different nozzles. The 80% acrylic acid aqueous solution was added dropwise for 180 minutes from the start of the reaction, and the 35% sodium bisulfite aqueous solution was added dropwise for 170 minutes from the start of the reaction. For the 15% aqueous solution of sodium persulfate, the amount is 1.78 g per mole of acrylic acid for 30 minutes after the start of the reaction, and 0.89 g per mole of acrylic acid from 30 minutes to 60 minutes after the start of the reaction. An amount of 1.33 g per mole of acrylic acid was dropped from 60 to 190 minutes after the start of the reaction.
After completion of the dropwise addition, the reaction solution was kept at 90 ° C. for 70 minutes for aging. After completion of aging, 2.02 g of 35% aqueous hydrogen peroxide solution corresponding to 1.3 molar equivalents of residual sodium bisulfite in the solution was added to the reaction solution while maintaining the reaction solution at 90 ° C. Immediately after that, the SUS316L metal piece in the flask was completely immersed in the reaction solution, stirred for 60 minutes while maintaining the reaction solution at 90 ° C., then the reaction solution was cooled to room temperature, and the SUS316L metal piece was removed from the reaction vessel. I took it out. In this way, a (meth) acrylic acid polymer aqueous solution (C1) was obtained.
The results are summarized in Table 1.

The (meth) acrylic acid polymer aqueous solution obtained by the production method of the present invention is used for, for example, scale inhibitors, corrosion inhibitors, water treatment agents, detergent builders, detergent compositions, dispersants, cleaning agents, and the like. This is particularly suitable.

Claims (4)

A method for producing a (meth) acrylic acid polymer by adding a monomer composition containing bisulfite and (meth) acrylic acid (salt) to a reaction vessel, and carrying out a polymerization reaction and aging. ,
Start the addition of sodium hydroxide before the end of the addition of the (meth) acrylic acid (salt), and end the addition of the sodium hydroxide by the end of the aging ,
The addition of the sodium hydroxide is started while 50 mass% to 85 mass% of the total amount of the (meth) acrylic acid (salt) is added .
A method for producing a (meth) acrylic acid polymer aqueous solution. The (meth) terminating the addition of sodium hydroxide during the time between the addition of the 90 wt% of the total amount of acrylic acid (salt) to the ripening is finished, according to claim 1 (meth) acrylic acid For producing an aqueous polymer solution. The manufacturing method of the (meth) acrylic-acid type polymer aqueous solution of Claim 1 or 2 whose residual bisulfite density | concentration in the (meth) acrylic-acid type polymer aqueous solution obtained is less than 1300 ppm. The manufacturing method of the (meth) acrylic acid type polymer aqueous solution in any one of Claim 1 to 3 whose APHA of the (meth) acrylic acid type polymer aqueous solution obtained is 50 or less.