JP6504177B2 - Method for producing acrylic acid copolymer - Google Patents

Description

  The present invention relates to an acrylic acid-based copolymer (hereinafter also referred to as “AA / ATBS-based polymer”) suitable as a main component of a water treatment agent excellent in scale formation suppressing effect on calcium phosphate and a method for producing the same.

Structural units derived from acrylic acid or salts thereof as main components such as dispersants of inorganic particles, agents for suppressing scale formation, precipitation or deposition, and 2-acrylamido-2-methylpropanesulfonic acid ("acrylamido-tert -A copolymer (AA / ATBS polymer) containing a structural unit derived from-butyl sulfonic acid ") or a salt thereof is known.
For example, Patent Document 1 discloses an AA / ATBS polymer neutralized with sodium hydroxide to pH 3.5 to 6.0. Patent Document 2 discloses an AA / ATBS polymer neutralized with sodium hydroxide and calcium hydroxide. Patent Document 3 discloses an AA / ATBS polymer further including a structural unit derived from a poorly water-soluble monomer such as phenoxyethyl acrylate. Patent Document 4 discloses an AA / ATBS polymer further including a structural unit derived from ethoxylated tristyrylphenol methacrylate.

Japanese Patent Publication No. 2000-502394 Japanese Patent Publication No. 6-504939 JP 2000-169508 A Japanese Patent Application Laid-Open No. 11-104479

  However, even with the AA / ATBS polymers disclosed in Patent Documents 1 to 4, their performance may not be satisfied when used as a water treatment agent. In particular, an acrylic copolymer (AA / ATBS polymer) suitable as a main component of a water treatment agent which is not sufficient in the effect of suppressing calcium phosphate scale and is excellent in suppressing the formation of scale also with respect to calcium phosphate Methods of manufacture as well as water treatment agents are desired.

The inventor of the present invention has intensively studied to solve the above-mentioned problems. As a result, when acrylic acid and sodium 2-acrylamido-2-methylpropane sulfonate are polymerized by a conventional method, a high molecular weight polymer is by-produced, although in a small amount, and this high molecular weight polymer has the ability to inhibit scale formation. We have found that it is a factor that lowers In addition, based on such findings, the inventor has found that an AA / ATBS polymer having a high molecular weight polymer content reduced to a specific amount or less exhibits excellent scale inhibition ability even on a calcium phosphate scale. Completed the invention.
Furthermore, regarding the by-production of the above-mentioned high molecular weight polymer, the inventor of the present invention can not continue the polymerization under certain conditions because the concentration of sodium in the reaction liquid changes with the progress of the reaction in the conventional production method. I came to the idea of being a thing. Based on this idea, it is possible to efficiently produce an AA / ATBS polymer having a very low content of the above-mentioned high molecular weight polymer by carrying out the polymerization while maintaining the sodium concentration in the reaction liquid at a constant amount. I found a finding that there is.

The present invention is shown below.
[1] A structural unit (x) derived from acrylic acid or its sodium salt, and a structural unit (y) derived from 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt, comprising the above structural unit (x) The content ratio of the structural unit (y) is 35 to 90 mass% and 10 to 65 mass%, respectively, when the total of the two is 100 mass%,
Weight average molecular weight Mw is 2,000 to 30,000,
The acrylic acid type copolymer whose content rate of an acrylic acid type copolymer whose molecular weight is 70000 or more is 0.30 mass% or less with respect to the total amount of all the polymers.
[2] The acrylic acid copolymer according to the above [1], wherein the polydispersity (Mw / Mn), which is the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, is 3.5 or less.
[3] The structural unit (x) is a structural unit derived from a sodium salt of acrylic acid, and the structural unit (y) is a structural unit derived from a sodium salt of 2-acrylamido-2-methylpropanesulfonic acid The acrylic acid-based copolymer according to the above [1] or [2], which is
[4] A method for producing an acrylic acid-based polymer according to any one of [1] to [3] above,
A step of polymerizing the monomer while continuously supplying a monomer consisting of acrylic acid or its sodium salt and 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt to a reactor Method for producing an acrylic acid copolymer.
[5] A method for producing the acrylic acid copolymer according to any one of [1] to [3] above,
Acrylic acid or its sodium salt and 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt in the presence of a polymerization initiator in the first reactor using a production apparatus in which three reactors are connected The monomer is polymerized while continuously feeding a monomer consisting of the following components, and then the reaction solution is transferred from the first reactor to the second reactor connected to the first reactor. And, in the second reactor, after the polymerization of the monomer contained in the reaction solution is continued, the third reaction in which the reaction solution is connected from the second reactor to the second reactor The manufacturing method of the acrylic acid type copolymer which transfers to a vessel and adjusts pH of a polymer containing liquid to 9 or less in this 3rd reactor.
[6] The process for producing an acrylic acid-based copolymer according to the above [5], wherein the polymerization initiator contains a persulfate.
[7] The method for producing an acrylic acid-based copolymer according to [5] or [6] above, wherein the pH of the polymer-containing liquid is adjusted to 3.0 to 8.0 in the third reactor.
[8] A water treatment agent comprising the acrylic acid copolymer according to any one of the above [1] to [3].
[9] The weight average molecular weight Mw of the acrylic acid copolymer is 4,000 to 20,000.
The content ratio of the acrylic acid copolymer having a molecular weight of 70000 or more is 0.05% by mass or less based on the total amount of all the polymers, and the ratio of the weight average molecular weight Mw to the number average molecular weight Mn The water treatment agent as described in said [8] whose certain polydispersion degree (Mw / Mn) is 3.5 or less.
In the present specification, the weight average molecular weight (hereinafter also referred to as “Mw”) and the number average molecular weight (hereinafter also referred to as “Mn”) of a polymer are gel permeation chromatography (hereinafter also referred to as “GPC”) It is a standard sodium polyacrylate conversion value measured by Moreover, the description of "(meth) acrylic" means acrylic and methacrylic.

Since the acrylic acid copolymer (AA / ATBS polymer) of the present invention has a more uniform composition, it is suitable as a main component such as an agent that suppresses scale formation, precipitation or deposition, a dispersant for inorganic particles, etc. It is. In particular, since the content ratio of the two structural units (x) and (y) is in a specific range, and substantially consists of an acrylic copolymer having an Mw in a specific range, the scale relative to calcium phosphate is obtained. It is suitable as a main component of the water treatment agent which is excellent in the formation inhibitory effect. The acrylic acid copolymer of the present invention can also be used as a component for scale formation inhibitors other than calcium phosphate, dispersants such as inorganic particles, surfactants, antistatic agents, detergent compositions and the like.
According to the method for producing an acrylic acid copolymer (AA / ATBS polymer) of the present invention, the formation of an acrylic acid copolymer having a molecular weight of 70000 or more can be suppressed.
Moreover, the water treatment agent of this invention is excellent in the suppression effect of the scale formation with respect to a calcium phosphate.

It is a schematic diagram which shows the manufacturing apparatus used by this invention.

  The acrylic acid copolymer (AA / ATBS polymer) of the present invention comprises a structural unit (x) derived from acrylic acid or its sodium salt and 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt The structural unit (x) and the structural unit (y) are contained in an amount of 35 to 90% by mass and 10%, respectively, based on the total content of the structural unit (x) and the structural unit (y). The content ratio of an acrylic acid copolymer having an Mw of 2000 to 30,000 and a molecular weight of 70000 or more is 0.30 mass% or less based on the total amount of all the polymers. .

In the AA / ATBS polymer of the present invention, the structural unit (x) contained in the polymer is at least one of a structural unit derived from acrylic acid and a structural unit derived from a sodium salt of acrylic acid; And 2) at least one of a structural unit derived from 2-acrylamido-2-methylpropanesulfonic acid and a structural unit derived from a sodium salt of 2-acrylamido-2-methylpropanesulfonic acid. A particularly preferred embodiment, at least one structural unit (y) is a polymer having a _-SO 3 Na.

  The content ratio of the structural unit (x) and the structural unit (y) constituting the AA / ATBS polymer of the present invention is 100% by mass of the total of the two, from the viewpoint of obtaining high calcium phosphate precipitation preventing ability. 35 to 90% by mass and 10 to 65% by mass, preferably 40 to 80% by mass and 20 to 60% by mass, more preferably 45 to 75% by mass and 25 to 55% by mass.

  When the AA / ATBS polymer of the present invention contains an acrylic acid copolymer having a molecular weight of 70000 or more, the content ratio is 0.30 mass% or less based on the total amount of all the polymers. Preferably it is 0.10 mass% or less, More preferably, it is 0.05 mass% or less.

  The Mw of the AA / ATBS polymer of the present invention is from 2,000 to 30,000, preferably from 4,000 to 20,000, from the viewpoint of obtaining a high ability to prevent precipitation of calcium phosphate. The polydispersity (Mw / Mn), which is the ratio of Mw to number average molecular weight Mn, is 3.8 or less, preferably 3.5 or less, and more preferably 3.1 or less. However, the lower limit is usually 2.0.

The structure of the AA / ATBS polymer of the present invention is not particularly limited, but is preferably a random copolymer.
The AA / ATBS polymer of the present invention is preferably obtained by a continuous polymerization method using a monomer consisting of acrylic acid or its sodium salt and 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt. It can be done.

  In the method for producing the AA / ATBS polymer according to the present invention (hereinafter referred to as “the production method of the present invention”), acrylic acid or its sodium salt, 2-acrylamido-2-methylpropane sulfonic acid or It comprises a step of polymerizing the sodium salt while continuously supplying the monomer comprising the sodium salt.

  In the present invention, the method of producing the AA / ATBS polymer according to the particularly preferred embodiment uses a production apparatus in which three reactors are connected, and acrylic acid or acrylic acid in the presence of a polymerization initiator in the first reactor. A monomer is polymerized while continuously supplying a monomer comprising the sodium salt and 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt, and then a reaction liquid (hereinafter referred to as “reaction liquid” ) Is transferred from the first reactor to the second reactor connected to the first reactor, and in the second reactor, the polymerization of the monomers contained in the reaction liquid (S1) is carried out. The reaction liquid (hereinafter referred to as “reaction liquid (S2)”) is transferred from the second reactor to the third reactor connected to the second reactor, and in the third reactor, By adjusting the pH of the polymer-containing solution to 9 or less That. As described above, according to the present invention, an acrylic acid copolymer which is a high molecular weight polymer by continuously advancing polymerization of a monomer, transfer of a polymer and the like using a continuous tank type polymerization apparatus. In the present invention, it is possible to produce a uniform AA / ATBS-based polymer having a high Mw of 2000 to 30000 and having a high production rate of an acrylic acid-based copolymer, while suppressing the by-product formation. In the production method of the present invention, an acrylic acid copolymer having a Mw of 2,000 to 30,000 or a precursor thereof is substantially obtained by the polymerization of monomers continued in the second and third reactors. Is formed.

  Although the apparatus used by the manufacturing method of this invention is not specifically limited, For example, the schematic of the manufacturing apparatus provided with 3 reactors is shown in FIG. The manufacturing apparatus (100) of FIG. 1 comprises a first reactor (10) including means for supplying the raw material (15), stirring means, temperature control means, reflux cooling means, discharge means, etc., the raw material (25) Second reactor (20) including supply means, stirring means, temperature control means, reflux cooling means, discharge means, etc., means for supplying pH adjuster etc. (35), stirring means, temperature control means, reflux cooling And a third reactor (30) provided with means, discharge means and the like.

In the first reactor (10), monomers consisting of acrylic acid or its sodium salt and 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt are continuously supplied, and the presence of a polymerization initiator It is polymerized down. Preferably, the monomer comprises acrylic acid or 2-acrylamido-2-methylpropane sulfonic acid. In addition, in this reaction system, water is used as a polymerization medium, and a chain transfer agent can be used as needed.
The proportion of acrylic acid constituting the monomer supplied to the first reactor (10) is preferably 35 to 90% by mass, more preferably 40 to 80% by mass, and still more preferably 45 to 75% by mass. is there. The concentration of the monomer in the first reactor (10) is preferably 20 to 200% by mass, more preferably 50 to 150% by mass, based on 100% by mass of the medium for polymerization.
In the production method of the present invention, from the viewpoint of obtaining a polymer having a narrow molecular weight distribution, it is preferable to carry out 90% or more of the polymerization reaction in the first reactor (10). It is suitably adopted to supply the above to the first reactor (10). Furthermore, it is more preferable to supply 95 mass% or more to a 1st reactor (10). Further, in the first reactor (10), it is preferable to carry out the polymerization while selecting the conditions such that the polymerization conversion ratio of the monomer is 90% or more.

Examples of the polymerization initiator include hydrogen peroxide; persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate; dimethyl 2,2'-azobis (2-methylpropionate), 2,2'-azobis Isobutyronitrile), 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2, 4-Dimethylvaleronitrile), 2,2′-azobis (isobutyric acid) dimethyl, 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-methylpropionamidine) dihydrochloride 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] n-hydrate, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride , 2, 2 Azo compounds such as' -azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 1,1'-azobis (cyclohexane-1-carbonitrile); benzoyl peroxide, peroxy Organic peroxides such as lauroyl oxide, peracetic acid, di-t-butyl peroxide, cumene hydroperoxide and the like can be mentioned. These may be used alone or in combination of two or more. In the present invention, persulfates are preferably used.
The amount of the polymerization initiator used is preferably 0.2 to 2.0 parts by mass, more preferably 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the monomer.

As the chain transfer agent, mercaptoethanol, thioglycerol, thioglycollic acid, 2-mercaptopropion, 3-mercaptopropion, thiomalic acid, octyl thioglycolate, octyl 3-mercaptopropionate, 2-mercaptoethanesulfonic acid Thiol-based chain transfer agents such as n-dodecyl mercaptan, octyl mercaptan and butyl thioglycolate; phosphorous acid, hypophosphorous acid and salts thereof (such as sodium hypophosphite and potassium hypophosphite); Sulfuric acid, hydrogen sulfite, dithionite, metabisulfite, and their salts (sodium bisulfite, potassium bisulfite, sodium dithionite, potassium dithionite, sodium metabisulfite, potassium metabisulfite etc.) Can be mentioned. These may be used alone or in combination of two or more.
The amount of the chain transfer agent used is preferably 1 to 20 parts by mass, more preferably 3 to 10 parts by mass, with respect to 100 parts by mass of the monomer.

The polymerization temperature (the temperature of the reaction system) of the monomer in the first reactor (10) is appropriately selected depending on the type of the polymerization initiator and the like, but is preferably 60 because polymerization proceeds smoothly. ° C to 100 ° C, more preferably 70 ° C to 90 ° C.
In the production method of the present invention, the polymerization of the continuously supplied monomers is completed not in the first reactor (10) but in the second reactor (20) or the third reactor (30). Do. Therefore, the reaction solution (S1) obtained in the first reactor (10) and supplied to the second reactor (20) usually contains a polymer, a monomer, a polymerization initiator and the like. Further, in the reaction liquid (S2) obtained in the second reactor (20) and supplied to the third reactor (30), monomers, a polymerization initiator and the like may be contained in addition to the polymer.
The average residence time of the monomers in the first reactor (10) is preferably 30 to 300 minutes, more preferably 50 to 200 minutes.

Next, in the second reactor (20), the polymerization of the monomers remaining in the reaction liquid (S1) fed from the first reactor (10) is advanced. The polymerization carried out in the second reactor (20) may be carried out only on the monomers contained in the reaction liquid (S1), and if necessary, the supplied monomer may be further fed. It may be carried out with the mer. In the second reactor (20), a polymerization initiator, a medium for polymerization, and the like may be stored in advance.
The temperature of the reaction system in the second reactor (20) is preferably 60 ° C. to 100 ° C., more preferably 70 ° C. to 90 ° C. The polymerization temperature may be the same as or different from the temperature in the first reactor (10).
The average residence time of the monomers in the second reactor (20) is preferably 20 to 200 minutes, more preferably 30 to 100 minutes, since polymerization is completed while forming a uniform polymer.

Thereafter, in the third reactor (30), the polymerization of the monomer remaining in the reaction liquid (S2) fed from the second reactor (20), and the acrylic acid contained in the reaction liquid (S2) Neutralization of the precursor of the copolymer is carried out. Since the pH of the reaction solution (S2) is usually in the range of 1.0 to 5.0, for neutralization, usually, hydroxides, chlorides or carbonates of alkali metals such as sodium and potassium; An alkaline aqueous solution in which an alkaline substance such as an organic amine such as monoethanolamine, diethanolamine or triethanolamine is dissolved in water. Be The above-mentioned alkaline substances may be used alone or in combination of two or more.
In the third reactor (30), a polymerization medium or the like may be stored in advance.

The pH of the polymer-containing liquid in the third reactor (30) is adjusted to 9 or less, preferably 3.0 to 8.0, by the alkaline aqueous solution.
To obtain an AA / ATBS polymer-containing liquid substantially comprising an acrylic acid copolymer having a Mw of 2000 to 30,000 and having a solid content concentration of preferably 30 to 50% by the above steps Can. When the polymerization medium is water, an aqueous polymer solution is obtained.

  According to the production method of the present invention, the polymerization reaction can be allowed to proceed under the condition of constant sodium concentration. For this reason, phenomena such as a change in polymerization rate due to a change in sodium concentration hardly occur, and as a result, a homogeneous AA / ATBS system of Mw 2000 to 30,000 while suppressing the formation of a high molecular weight polymer having a molecular weight exceeding 70,000. Polymers can be obtained.

  The acrylic acid-based copolymer of the present invention is a water treatment agent excellent in the scale formation suppressing effect on calcium phosphate, a scale formation inhibitor other than calcium phosphate, a dispersant such as inorganic particles, a surfactant, an antistatic agent, and a detergent composition. Etc. as a component of

  The water treatment agent of the present invention contains the above-mentioned AA / ATBS polymer of the present invention, and is usually a composition further containing water. The type of the AA / ATBS polymer is not particularly limited, and may be only one type or two or more types.

  The content ratio of the AA / ATBS polymer in the water treatment agent of the present invention is preferably 5 to 45% by mass, more preferably 10 to 35% by mass because the effect as the water treatment agent is sufficiently obtained. .

  The water treatment agent of the present invention is, if necessary, other scale suppression such as polyacrylic acid or a salt thereof, polymaleic acid or a salt thereof, a (meth) acrylic acid copolymer, a styrene / maleic acid copolymer, etc. It may contain an agent, a bactericide, an anticorrosive, a slime inhibitor, an antifoamer, and the like.

  The water treatment agent of the present invention is suitable, for example, for calcium phosphate which easily adheres to the heat transfer surface of a heat exchanger, piping of cooling water and the like. Therefore, by using the water treatment agent of the present invention, it is possible to suppress problems such as reduction in heat exchange efficiency, blockage of piping, and the like in, for example, cooling water systems, boiler water systems, seawater desalination apparatuses and the like.

  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, parts and% are based on mass unless otherwise specified.

1. Production of Acrylic Acid-Based Copolymer In the following example, as shown in FIG. 1, three reactors (first reactor 10, second reactor 20 and third reaction) each provided with a stirrer and a condenser The manufacturing apparatus 100 which connected the container 30) in this order was used.

Example 1 (production by continuous polymerization)
In each of the first reactor (10), the second reactor (20) and the third reactor (30), 2100 g of water was charged and maintained at 75 ° C. After that, while stirring the inside of the first reactor (10), 11.0 g / min of a 60% aqueous solution of acrylic acid (hereinafter also referred to as "60% AA"), sodium 2-acrylamido-2-methylpropanesulfonate Of 50% aqueous solution (hereinafter referred to as "50% ATBSNa") at 9.0 g / min, and 15% aqueous solution of sodium persulfate (hereinafter referred to as "15% NPS") at 0.5 g / min, hypophosphorous acid The polymerization was carried out by supplying a 30% aqueous solution of sodium acid (hereinafter also referred to as "30% NHP") at 2.5 g / min. Then, simultaneously with the supply of these raw materials (15), the reaction liquid in the first reactor (10) is transferred to the second reactor (20) at 23.0 g / min, and the first reactor (10) is transferred. The amount of liquid in the solution was 2100 g. The average residence time of the reaction liquid in the first reactor (10) was 90 minutes. In the second reactor (20), at the same time as the supply of the reaction liquid from the first reactor (10) starts, the reaction liquid in the second reactor (20) is added to the third reactor at 23.0 g / min. The liquid was transferred to (30). Thus, the polymerization was continued with stirring in the second reactor (20) while maintaining the liquid amount at 2100 g, and the average residence time of the reaction liquid in the second reactor (20) was 90 minutes. Then, in the third reactor (30), at the same time as the supply of the reaction liquid (pH 4.0) from the second reactor (20) starts, the supply of a 48% aqueous solution of water and NaOH, and the third reactor (30) Discharge and recovery of the reaction solution in the inside were performed. In the third reactor (30) as well, while maintaining the liquid amount at 2100 g, neutralization was continued under stirring so that the pH of the reaction liquid was 7.0. After 24 hours from the start of this production, the reaction solution for 1 hour is collected, and the polymer aqueous solution having pH 7.0 and containing acrylic acid copolymer (E1) having a solid content concentration of 40%. (See Table 1).

Next, the acrylic acid copolymer (E1) was subjected to gel permeation chromatography (GPC) under the conditions shown below, whereby Mw was 8000 and Mw / Mn was 2.8. In addition, the content ratio of the acrylic acid copolymer having a molecular weight of 70000 or more, which was determined by molecular weight fractionation calculation, was 0.02% with respect to the entire acrylic acid copolymer (E1).
<GPC measurement conditions>
Device: Tosoh HLC 8020 system Detection: RI
Column: Tosoh G4000PWxl, G3000PWxl and G2500PWxl connected Eluent: 0.1 M NaCl + phosphate buffer (pH 7)
Standard: Polyaric acid Na made by Sowa Science Co., Ltd.

Example 2 (production by continuous polymerization)
The solid content concentration is 40% by the same operation as in Example 1 except that a 30% aqueous solution of sodium bisulfite (hereinafter also referred to as "30% NaHSO ₃ ") is used instead of 30% NHP. An aqueous polymer solution having a pH of 7.0 was obtained containing the acrylic acid copolymer (E2) (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E2) was analyzed, and the results are shown in Table 1.

Example 3 (production by continuous polymerization)
The same operation as in Example 1 is carried out except that the amounts used of 60% AA and 50% ATBS Na are changed, and an acrylic copolymer (E3) having a solid concentration of 40% is included, and the pH is 7.0 An aqueous polymer solution was obtained (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E3) was analyzed, and the results are shown in Table 1.

Example 4 (production by continuous polymerization)
The same operations as in Example 2 are carried out except that the amounts used of 60% AA and 50% ATBS Na are changed, and an acrylic copolymer (E4) having a solid concentration of 40% is included, and the pH is 7.0 An aqueous polymer solution was obtained (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E4) was analyzed, and the results are shown in Table 1.

Example 5 (production by continuous polymerization)
The same procedures as in Example 1 are carried out except that the amounts used of 60% AA and 50% ATBS Na are changed, and an acrylic copolymer (E5) having a solid concentration of 40% is included, and the pH is 7.0 An aqueous polymer solution was obtained (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E5) was analyzed, and the results are shown in Table 1.

Example 6 (production by continuous polymerization)
The same operation as in Example 2 is carried out except that the amounts used of 60% AA and 50% ATBS Na are changed, and an acrylic acid copolymer (E6) having a solid concentration of 40% is included, and the pH is 7.0 An aqueous polymer solution was obtained (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E6) was analyzed, and the results are shown in Table 1.

Example 7 (Production by continuous polymerization)
The same procedure as in Example 1 is carried out except that the amount used of 30% NHP is changed, and a polymer aqueous solution of pH 7.0 containing an acrylic acid copolymer (E7) having a solid content concentration of 40% is prepared. Obtained (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E7) was analyzed, and the results are shown in Table 1.

Example 8 (production by continuous polymerization)
The same procedure as in Example 2 is carried out except that the amount of 30% NaHSO ₃ used is changed, and an aqueous polymer solution having a pH of 7.0 and containing an acrylic acid copolymer (E8) having a solid content concentration of 40%. (See Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E8) was analyzed, and the results are shown in Table 1.

Example 9 (production by continuous polymerization)
The same procedure as in Example 1 is carried out except that the amount used of 30% NHP is changed, and a polymer aqueous solution of pH 7.0 containing an acrylic acid copolymer (E9) having a solid content concentration of 40% is prepared. Obtained (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E9) was analyzed, and the results are shown in Table 1.

Example 10 (production by continuous polymerization)
The same procedure as in Example 2 is carried out except that the amount of 30% NaHSO ₃ used is changed, and a polymer aqueous solution containing an acrylic acid copolymer (E10) having a solid content concentration of 40% and having a pH of 7.0 (See Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E10) was analyzed, and the results are shown in Table 1.

Example 11 (production by continuous polymerization)
The procedure of Example 1 is repeated except that 50% ATBSNa is used in combination of 5.0 g / min and 50% ATBS in combination instead of using 50% ATBS Na alone, and solid An aqueous polymer solution having a pH of 7.0 was obtained containing an acrylic acid copolymer (E11) having a concentration of 40% (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E11) was analyzed, and the results are shown in Table 1.

Example 12 (production by continuous polymerization)
The procedure of Example 2 is repeated except that 50% ATBSNa is used in combination of 5.0 g / min and 50% ATBS in combination instead of using 50% ATBS Na alone. An aqueous polymer solution having a pH of 7.0 was obtained containing an acrylic acid copolymer (E12) having a concentration of 40% (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E12) was analyzed, and the results are shown in Table 1.

Example 13 (production by continuous polymerization)
The same procedure as in Example 1 was carried out except that 50% ATBS was used instead of 50% ATBS Na, and the supply amount was 8.0 g / min, and an acrylic acid-based co-weight having a solid content concentration of 40%. The polymer aqueous solution of pH 7.0 was obtained including coalescence (E13) (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E13) was analyzed, and the results are shown in Table 1.

Example 14 (production by continuous polymerization)
The same procedure as in Example 2 is carried out except that 50% ATBS is used instead of 50% ATBS Na, and the amount supplied is 8.0 g / min, and an acrylic acid-based coweight having a solid content concentration of 40% The polymer aqueous solution of pH 7.0 was obtained including coalescence (E14) (see Table 1).
Thereafter, in the same manner as in Example 1, the acrylic acid copolymer (E14) was analyzed, and the results are shown in Table 1.

Comparative example 1 (production by semi-batch polymerization)
In a reactor equipped with a stirrer and a condenser, 250 g of water was charged and kept at 75 ° C. Next, a mixture of 470 g of 70% AA and 450 g of 50% ATBS Na, 25 g of 15% NPS, and 100 g of a 30% aqueous solution of sodium hypophosphite were each supplied to the reactor over 3 hours, and polymerization was performed under stirring. . After the feed of the raw materials was completed, the reaction system was aged for 1 hour with stirring while maintaining the reaction system at 75 ° C. Then, a 48% aqueous solution of water and NaOH is supplied to the reaction solution of pH 3.9 to obtain an aqueous polymer solution of pH 7.0 containing an acrylic acid copolymer (C1) having a solid concentration of 40%. The
Thereafter, the acrylic acid copolymer (C1) was analyzed in the same manner as in Example 1. As a result, Mw was 11,000, and Mw / Mn was 3.8. In addition, the content ratio of the acrylic acid copolymer having a molecular weight of 70000 or more, which was determined by the molecular weight fractionation calculation, was 1.0% with respect to the entire acrylic acid copolymer (C1).

Comparative Example 2 (production by batch polymerization)
The same operation as in Comparative Example 1 is carried out except that 30% NaHSO ₃ is used instead of 30% NHP, and it contains an acrylic acid copolymer (C2) having a solid content concentration of 40%, and pH 7.0 The polymer aqueous solution of
Thereafter, the acrylic acid copolymer (C2) was analyzed in the same manner as in Example 1. As a result, Mw was 12000 and Mw / Mn was 3.8. In addition, the content ratio of the acrylic acid copolymer having a molecular weight of 70000 or more, which was determined by molecular weight fractionation calculation, was 1.0% with respect to the entire acrylic acid copolymer (C2).

2. Evaluation of Water Treatment Agent The aqueous solution of the acrylic acid copolymer having a solid content concentration of 40% obtained in the above Examples 1 to 14 and Comparative Examples 1 and 2 is used as it is as a water treatment agent with respect to calcium phosphate. The inhibitory effect of scale formation was confirmed by the method shown below.
<Calcium phosphate scale inhibition test>
Using an aqueous solution of acrylic acid copolymer, disodium phosphate and calcium chloride, the concentration of acrylic acid copolymer is 30 mg / L, the concentration of disodium phosphate is 90 mg / L, the concentration of calcium chloride Prepared a solution of 375 mg / L. Then, while stirring the solution, 20 mL of 0.21% aqueous sodium hydrogen carbonate solution was added, and adjusted to pH 8.5 with sodium hydroxide. Then, after standing at 60 ° C. for 3 hours, the precipitate was separated by filtration, the calcium concentration in the filtrate was determined by EDTA titration, and the scale inhibition rate was calculated.

  The inhibition rate of the water treatment agent containing the acrylic acid copolymer obtained in Comparative Examples 1 and 2 was 81%. On the other hand, according to the water treatment agent containing the acrylic acid-type copolymer obtained in Examples 1-14, it was a high suppression rate as 90 to 99% (refer Table 1).

The acrylic acid-based copolymer of the present invention is a water treatment agent excellent in the scale formation suppressing effect on calcium phosphate, a scale formation inhibitor other than calcium phosphate, a dispersant such as inorganic particles, a surfactant, an antistatic agent, and a detergent composition. Etc. as a component of
The water treatment agent of the present invention is suitable, for example, for calcium phosphate which easily adheres to the heat transfer surface of a heat exchanger, piping of cooling water and the like.

Claims (4)

A method for producing an acrylic acid copolymer, comprising
While continuously supplying a monomer consisting of acrylic acid or its sodium salt and 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt to a reactor, the monomer is polymerized by a continuous polymerization method comprising the step of,
The acrylic polymer includes a structural unit (x) derived from acrylic acid or its sodium salt, and a structural unit (y) derived from 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt, The content ratio of the structural unit (x) and the structural unit (y) is 35 to 90% by mass and 10 to 65% by mass, respectively, when the total of the two is 100% by mass, and the weight average molecular weight Mw is 2,000 to 30,000, the content ratio of acrylic acid-based copolymer molecular weight of 70,000 or more, all of the polymer total weight with respect to 0.30 mass% or less der Ru acrylic copolymer Production method. Acrylic acid or its sodium salt and 2-acrylamido-2-methylpropane sulfonic acid or its sodium salt in the presence of a polymerization initiator in the first reactor using a production apparatus in which three reactors are connected The monomer is polymerized while continuously supplying a monomer consisting of the following components, and then the reaction solution is transferred from the first reactor to the second reactor connected to the first reactor. And, in the second reactor, the polymerization of the monomer contained in the reaction solution is continued, and then the reaction solution is transferred from the second reactor to the third reaction connected to the second reactor. The method for producing an acrylic acid-based copolymer according to claim 1 , wherein the polymer-containing liquid is transferred to a vessel and the pH of the polymer-containing liquid is adjusted to 9 or less in the third reactor. The method for producing an acrylic acid-based copolymer according to claim 2 , wherein the polymerization initiator contains a persulfate. The method for producing an acrylic acid-based copolymer according to claim 2 or 3 , wherein the pH of the polymer-containing liquid is adjusted to 3.0 to 8.0 in the third reactor.

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