JP6399108B2 - Method for producing acrylic acid polymer aqueous solution - Google Patents

Description

  The present invention relates to a method for producing an aqueous solution containing an acrylic acid polymer suitable as a dispersant for inorganic particles, a water treatment agent and the like.

An acrylic acid polymer having a structural unit derived from acrylic acid or a salt thereof is suitable for a dispersant for inorganic particles, a scale inhibitor in pipes, boilers, heat exchangers, and the like, and a detergent builder. It has been known. In these applications, the weight average molecular weight (Mw) is about 2000 to 10000, and the weight average molecular weight (Mw) divided by the number average molecular weight (Mn) is Mw / Mn, that is, the molecular weight distribution represented by the dispersity is It is said that an acrylic acid polymer mainly composed of a low molecular weight polymer as narrow as possible is suitable.
Furthermore, in the production, it is natural that an efficient production method such as shortening of reaction time or improvement of productivity is desirable. As a production method commensurate with this, continuous production is added in addition to the conventional batch production method. Methods are also being developed.

The following method is known as a method for continuously producing an acrylic acid-based low molecular weight polymer.
In Patent Document 1, a polyacrylate is continuously produced by polymerizing an acrylic monomer mainly composed of an acrylic acid monomer or an acrylate monomer in an aqueous medium. The reactor comprises a reactor, and at least the first reactor is a tank reactor. While continuously charging an acrylic monomer, a polymerization initiator and bisulfite into the first reactor, The monomer is polymerized in an aqueous medium having a pH value maintained at 3.5 or less, the reaction liquid discharged from the first reactor is continuously charged into the second reactor, and the polymerization is performed in the second reactor. A continuous polyacrylate solution having a pH value of 6 to 9, characterized in that the reaction solution is neutralized by adding alkali to the reaction solution in the second reactor or the reactor after the third reactor. A manufacturing method is disclosed.
In Patent Document 2, an acrylic monomer mainly composed of an acrylic acid monomer or an acrylate monomer is polymerized in an aqueous medium, and a water-soluble acrylic heavy polymer is added by adding an alkali if necessary. In the continuous production of the coalescence, a continuous reactor comprising a plurality of reactors, at least the first reactor being a tank reactor, is used, and an acrylic monomer and a polymerization initiator are used in the first reactor. In addition, the acrylic monomer is polymerized while supplying the chain transfer agent, and the polymerization conversion rate of the monomer supplied to the first reactor is maintained at 90% by mass or more in the outlet reaction solution of the first reactor. A continuous process for producing a water-soluble acrylic polymer is disclosed.
In Patent Document 3, a circulating liquid containing a monomer (acrylic acid) having a polymerizable unsaturated bond is circulated in a reactor having a circulation line constituted by a tank and piping that circulates outside the tank. A continuous production method of a water-soluble polymer (polyacrylic acid (salt)) having a step of continuously producing a conductive polymer and a step of removing a part of the circulating liquid from the discharge line, A continuous process for producing a water-soluble polymer is disclosed, wherein a cooler is provided in at least one place.

JP 2003-2909 A JP 2003-40912 A JP 2007-217654 A

  According to the above technique, an acrylic acid polymer having a low degree of dispersion can be produced, but a small amount of a high molecular weight component is contained. For this reason, further improvement is desired, for example, in terms of dispersion performance and lowering the viscosity of the chemical solution. An object of the present invention is to provide an acrylic polymer that is an aqueous solution suitable as a dispersant for inorganic particles, a water treatment agent, etc., having a low degree of dispersion and sufficiently suppressing by-product formation of a high molecular weight polymer. It is providing the method of manufacturing the aqueous solution containing.

The present invention is shown below.
[1] A raw material supply means and a stirring means are provided, and are arranged outside a first reaction tank for polymerizing a monomer containing acrylic acid in the presence of a polymerization initiator and water, and the first reaction tank. And a pipe connecting the discharge port and the introduction port formed in the tank wall of the first reaction tank, and used for the circulation of the first reaction liquid containing the polymer generated in the first reaction tank. In the method of continuously producing an acrylic acid polymer aqueous solution using an apparatus including a first reactor having a circulation pipe, the circulation pipe is cooled to cool the first reaction liquid. Means is provided, and the difference between the temperature of the first reaction liquid at the outlet of the first reaction tank and the temperature of the cooled first reaction liquid at the inlet of the first reaction tank. To 30 ° C. or higher, from the outlet of the first reaction tank to the cooling means An acrylic acid polymer characterized in that the mass ratio of the liquid amount and the liquid amount in the first reaction tank is 0.050 or less, and the polymerization of the monomer and the circulation of the first reaction liquid are performed. A method for producing an aqueous solution.
[2] The method for producing an acrylic acid polymer aqueous solution according to [1], wherein the circulation pipe is connected to a discharge pipe for discharging the first reaction liquid.
[3] The acrylic polymer aqueous solution according to [2], wherein the first reaction liquid obtained from the discharge pipe is neutralized to obtain a second reaction liquid having a pH in the range of 4 to 9. Manufacturing method.
[4] The apparatus further includes a second reactor connected to the discharge pipe, and in the second reactor, the first reaction liquid is neutralized with an alkali agent, The method for producing an aqueous acrylic acid polymer solution as described in [3] above, wherein the second reaction liquid is obtained.
[5] The apparatus further includes a second reactor connected to the discharge pipe, and a third reactor connected to the second reactor, wherein the second reactor includes: In the above [3], the polymerization using the first reaction liquid from the discharge pipe is continued, and in the third reactor, the reaction liquid from the second reactor is neutralized using an alkaline agent. The manufacturing method of acrylic acid polymer aqueous solution of description.
In this 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 the polymer are gel permeation chromatography (hereinafter also referred to as “GPC”). It is a standard sodium polyacrylate conversion value measured by the above. The description of “(meth) acryl” means acryl and methacryl.

  According to the present invention, it is possible to efficiently produce an aqueous solution containing an acrylic acid polymer in which the degree of dispersion (Mw / Mn) is small and the by-product of the high molecular weight polymer is sufficiently suppressed. Therefore, not only a homopolymer or a copolymer containing a structural unit derived from acrylic acid, but a polymer salt obtained by neutralizing a part or all of carboxyl groups derived from acrylic acid with an alkali agent, An aqueous solution containing an acrylic acid polymer having the above-mentioned properties relating to molecular weight can also be produced efficiently. The aqueous acrylic acid polymer solution obtained by the production method of the present invention is suitable as a dispersant for inorganic particles, a water treatment agent and the like.

It is the schematic which shows the structure of the 1st reactor which concerns on this invention. It is the schematic which shows the structure of the manufacturing apparatus used by the Example and the comparative example.

  The present invention includes, for example, a first reactor 10 shown in FIG. 1, that is, a raw material supply means 13 and a stirring means 12, and polymerizes a monomer containing acrylic acid in the presence of a polymerization initiator and water. 1 reaction tank 11 and a pipe that is disposed outside the first reaction tank 11 and communicates the discharge port 15 and the introduction port 17 formed on the tank wall of the first reaction tank 11, Using a device (hereinafter referred to as “manufacturing device”) including a first reactor 10 having a circulation pipe 20 used for circulation of a first reaction liquid containing a polymer produced in the first reaction tank 11. In the method for continuously producing an acrylic acid polymer aqueous solution, the circulation pipe 20 is provided with a cooling means 25 for cooling the first reaction liquid, and is provided at the outlet 15 of the first reaction tank 11. At the temperature of the first reaction liquid and the inlet 17 of the first reaction tank 11 The difference between the temperature of the rejected first reaction liquid and the temperature of the first reaction tank 11 is 30 ° C. or more, and the mass ratio between the liquid volume from the outlet 15 of the first reaction tank 11 to the cooling means 25 and the liquid volume in the first reaction tank 11 is The amount is set to 0.050 or less, and the polymerization of the monomer and the circulation of the first reaction liquid are performed. According to the present invention, an acrylic acid polymer having a dispersity (Mw / Mn) of preferably 1.8 to 2.4, and more preferably 2.0 to 2.2 is included. An aqueous solution having a partial concentration of preferably 25 to 55% by mass, more preferably 35 to 45% by mass is obtained.

The monomer used in the present invention may be only acrylic acid, or may be a combination of acrylic acid and another polymerizable unsaturated compound (hereinafter referred to as “other monomer”). . Examples of other polymerizable unsaturated compounds include salts of acrylic acid, unsaturated monocarboxylic acids having 4 or more carbon atoms or salts thereof, unsaturated dicarboxylic acids or anhydrides or salts thereof, (meth) acrylic acid alkyl esters, Examples include (meth) acrylic acid hydroxyalkyl esters, amide group-containing polymerizable unsaturated compounds, and sulfonic acid group-containing polymerizable unsaturated compounds. These compounds may be used alone or in combination of two or more. The “salt” may be an alkali metal salt such as sodium or potassium, an alkaline earth metal salt such as calcium or magnesium, an organic amine salt such as ammonium salt, monoethanolamine, or triethanolamine. In addition, when combining acrylic acid and another monomer, the ratio of the usage-amount of acrylic acid becomes like this. Preferably it is 50 mass% or more, More preferably, it is 80 mass% or more.
Therefore, the acrylic acid polymer obtained using the above monomer is polyacrylic acid or a salt thereof, a copolymer of acrylic acid and another monomer or a salt thereof, and the like. In the production method of the present invention, a first reaction liquid containing the polymer having the above-mentioned preferable dispersity (Mw / Mn) is obtained by the polymerization step using the first reactor, and is included in the first reaction liquid. Further, when the obtained polymer is further subjected to a conventionally known modification step, the obtained polymer (this polymer is also included in the “acrylic acid polymer” according to the present invention) is preferably the above-described polymer. It has a dispersity (Mw / Mn). That is, when the modification step is, for example, a neutralization step, the polymer contained in the obtained reaction solution (second reaction solution) also has the above preferable dispersity (Mw / Mn).

  The polymerization initiator used in the present invention is not particularly limited, but is preferably a water-soluble compound, and examples thereof include azo compounds, persulfates, hydrogen peroxide, and organic peroxides. The amount of the polymerization initiator used is preferably 0.1 to 3.0 parts by mass, more preferably 0.3 to 2.0 parts by mass, and still more preferably when the monomer is 100 parts by mass. 0.5 to 1.5 parts by mass.

In the production method of the present invention, as described above, a production apparatus including a first reactor having a specific configuration is used.
First, the first reactor will be described with reference to FIG. 1, but the first reactor 10 in FIG. 1 is not limited in the present invention, and can be appropriately provided with equipment not shown. .

The first reaction tank 11 is a container for polymerizing a monomer containing acrylic acid in the presence of a polymerization initiator and water, and includes a raw material supply means 13 and a stirring means 12. The raw material supply means 13 is a means for supplying a monomer, a polymerization initiator, a chain transfer agent, water, an organic solvent and the like to the first reaction tank 11. Generally, when manufacturing an acrylic acid polymer aqueous solution, each raw material is supplied separately, but specific components may be supplied in combination. Moreover, the supply method of each raw material is not specifically limited, It can supply to the 1st reaction tank 11 continuously or intermittently. In addition, a monomer is used so that the density | concentration of the acrylic acid type polymer contained in the target acrylic acid type polymer aqueous solution may be about 30-60 mass%.
Since the monomer is usually polymerized while keeping the temperature constant, the first reaction tank 11 can be provided with a temperature adjusting means, a reflux cooling means, etc. for adjusting the temperature of the raw material or the reaction liquid. The temperature adjusting means preferably includes a structure that covers the side wall and the bottom wall of the first reaction tank 11.

A circulation pipe 20 for circulating the first reaction liquid containing the polymer produced in the tank is disposed outside the first reaction tank 11, and the circulation pipe 20 is connected to the first reaction tank. The discharge port 15 and the introduction port 17 formed in 11 tank walls are connected. The circulation pipe 20 includes a cooling unit 25 that lowers the temperature of the first reaction liquid supplied from the first reaction tank 11, and returns the cooled first reaction liquid from the introduction port 17. In addition, although the circulation of the 1st reaction liquid in the said piping 20 for circulation is performed by the liquid feeding pump which is not shown in FIG. 1, the position of this liquid feeding pump is not specifically limited. The position of the liquid feed pump is any of the piping part 21 from the discharge port 15 of the first reaction tank 11 to the cooling means 25 or the piping part 23 from the cooling means 25 to the introduction port 17 of the first reaction tank 11. Although it is good, it is preferable that it is in the middle of the piping part 21.
As the cooling means 25, a plate heat exchanger, a double tube heat exchanger, a multi-tube heat exchanger, a spiral heat exchanger, or the like can be used.
The piping parts 21 and 23 constituting the circulation pipe 20 may be provided with a temperature holding means for holding the temperature of the first reaction liquid flowing in the pipe on the outside thereof.
Further, the circulation pipe 20 can include a discharge pipe (not shown) for discharging the first reaction liquid (an aqueous solution containing an acrylic acid-based polymer having a preferable Mw / Mn). It is preferable that the pipe portion 21 is branched and disposed.

In FIG. 1, the position of the discharge port 15 for discharging the first reaction liquid is the bottom wall of the first reaction tank 11, but is not limited thereto. For example, the position of the discharge port 15 may be the side wall of the first reaction tank 11, and in this case, it is preferably on the lower side of the first reaction tank 11. Moreover, although the position of the inlet 17 which returns the 1st reaction liquid cooled by the cooling means 25 in the 1st reaction tank 11 is made into the upper side wall of the 1st reaction tank 11, it is not limited to this, It may be a ceiling wall. In addition, in FIG. 1, although the inlet 17 is made into the position higher than the liquid level in the 1st reaction tank 11, it is not limited to this.
The number of circulation pipes 20 formed in the first reactor 10 may be one or two or more.

Next, the manufacturing method using a manufacturing apparatus provided with the 1st reactor 10 is demonstrated.
A monomer, a polymerization initiator, a chain transfer agent, water, an organic solvent, and the like are continuously supplied to the first reaction tank 11 from the raw material supply unit 13 (including intermittent supply), and the stirring unit 12 is driven. The monomer is polymerized while stirring them. In the present invention, it is preferable to supply the raw material, polymerize the monomer, and circulate the first reaction liquid while keeping the amount of the raw material or the reaction liquid in the first reaction tank 11 substantially constant.
Although the polymerization temperature of a monomer is suitably set according to the kind of monomer and polymerization initiator, it is preferably 60 ° C to 100 ° C, more preferably 70 ° C to 90 ° C. In the present invention, in order to continuously produce an aqueous solution containing an acrylic acid polymer having a low degree of dispersion and a by-product of a high molecular weight polymer, the temperature of the first reaction liquid at the outlet 15 is The difference between the temperature of the cooled first reaction liquid at the inlet 17 is 30 ° C. or higher, preferably 30 ° C. to 60 ° C., more preferably 35 ° C. to 55 ° C. The temperature of the liquid (raw material or reaction liquid) in the first reaction tank 11 is likely to change with the polymerization of continuously supplied monomers, and the first reaction liquid flowing through the circulation pipe 20 is cooled and returned. By doing this, the temperature change of the liquid (raw material or reaction liquid) in the first reaction tank 11 is suppressed. Moreover, you may use well-known temperature control apparatuses, such as a jacket and an internal coil. Although the flow rate of the first reaction liquid flowing through the circulation pipe 20 is not particularly limited, the supply speed of the cooled first reaction liquid supplied from the inlet 17 is set from the viewpoint of smooth polymerization. When the total amount of raw materials or reaction liquid in one reaction tank 11 is 100 parts, preferably 0.1 to 20 parts per minute, more preferably 0.2 to 10 parts per minute, still more preferably 0.5 per minute. ~ 5 parts.

  In the present invention, the mass ratio of the liquid amount (amount of the first reaction liquid) in the piping portion 21 from the discharge port 15 to the cooling means 25 and the liquid amount (the amount of the raw material or the reaction liquid) in the first reaction tank 11 is determined. Acrylic acid having a low degree of dispersion and suppression of by-product of a high molecular weight polymer by adjusting to 0.050 or less, preferably 0.001 to 0.040, more preferably 0.005 to 0.020. An aqueous solution containing a polymer can be produced. If the mass ratio exceeds 0.050, the degree of dispersion of the acrylic acid polymer becomes high, and the by-product of the high molecular weight polymer becomes remarkable, which is not preferable.

In the production method of the present invention, the power required for stirring per 1 m ³ of the reaction liquid, that is, the power required for stirring calculated from the power consumption minus the loss inside the motor that drives the stirring means 12 and the amount of the reaction liquid is preferably It is 0.5-3.0 kW / m < ³ >, More preferably, it is 1.0-2.0 kW / m < ³ >. When the power required for stirring is within the above range, an aqueous solution containing an acrylic acid polymer having a low degree of dispersion and a suppressed by-product of a high molecular weight polymer can be produced.
The average residence time of the liquid in the first reaction tank 11 until the polymerization of the monomer supplied from the raw material supply means 13 is completed is appropriately determined depending on the supply speed of the raw material, the internal volume of the first reaction tank 11 and the like. However, it is preferably 0.5 to 4.0 hours, more preferably 1.0 to 3.0 hours.

  According to the present invention, an aqueous solution of an acrylic acid polymer in which the content of the high molecular weight polymer is reduced can be obtained. For example, in applications such as a dispersant for inorganic particles and a water treatment agent, a high molecular weight polymer having a molecular weight of 70,000 or more is not preferable in terms of dispersion performance and low viscosity of a chemical solution. The content ratio of the high molecular weight polymer is preferably 0.2% by mass or less, more preferably 0.1% by mass or less.

As described above, in the first reactor 10, an acrylic acid polymer aqueous solution (first reaction solution) having a low degree of dispersion is produced, and then the first reaction solution (pre-neutralization aqueous solution) is recycled to the circulation pipe. 20 is recovered from the discharge pipe disposed in 20 and subjected to a neutralization step, whereby a part or all of the carboxyl groups contained in the acrylic acid polymer are converted to —COOM ¹ (where M ¹ is Na, A second reaction liquid containing an acrylic acid-based polymer (K, NH _4, etc.) can be obtained. When the first reaction liquid is discharged from the discharge pipe, the first reaction liquid can be supplied to, for example, a second reactor (not shown) and used for the neutralization step.
The method of the neutralization step is not particularly limited, but alkali metal hydroxides or carbonates such as sodium and potassium; alkaline earth metal hydroxides or carbonates such as calcium and magnesium; ammonia; monoethanolamine An aqueous solution in which an alkaline substance such as an organic amine such as diethanolamine or triethanolamine is dissolved as it is or in water is preferably used. The pH of the neutralizing solution is appropriately set according to the purpose of use of the acrylic acid polymer aqueous solution, but is usually 4 to 9.

Hereinafter, a method for producing a particularly preferable acrylic acid polymer aqueous solution as a dispersing agent or a water treatment agent for inorganic particles by the production apparatus shown in FIG. 2 will be described. The acrylic acid polymer contained in this aqueous solution is a neutralized product of a polymer obtained in the presence of a polymerization initiator and a chain transfer agent, and its Mw is preferably 3000 to 10000, more preferably 4000 to 8000 acrylic acid polymer salt.
Examples of the chain transfer agent include hypophosphorous acid and salts thereof, phosphorous acid and salts thereof, sulfurous acid and salts thereof, compounds having a thiol group, and isopropyl alcohol. The amount of the chain transfer agent used is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, and still more preferably 5 to 10 parts by mass when the monomer is 100 parts by mass.

2 is an apparatus in which a first reactor 10, a second reactor 30, and a third reactor 50 are connected in this order. For example, in the first reactor 10 and the second reactor 30, In the third reactor 50, the polymerization of the monomer is completed and neutralization with an alkaline agent is performed.
The first reactor 10 includes, in addition to the configuration of FIG. 1, a discharge pipe 29 that is branched and formed in the middle of a pipe portion 21 that constitutes the circulation pipe 20. A part of the first reaction liquid produced in the first reaction tank 11 is supplied to the cooling means 25 to be cooled and returned to the first reaction tank 11 from the piping part 23, and the other part is discharged. The solution is sent to the second reactor 30 through the piping 29 for use.
The second reactor 30 includes a second reaction tank 31 including a stirring unit 32, and may further include a temperature adjusting unit, a reflux cooling unit, and the like for adjusting the liquid temperature in the second reaction tank 31. The acrylic acid polymer aqueous solution (pre-neutralization aqueous solution) obtained in the second reactor 30 is supplied from the discharge port 35 formed in the tank wall (bottom wall in the drawing) through the discharge pipe 39 to the third reactor. 50.
The third reactor 50 includes a third reaction tank 51 including a stirring unit 52 and an alkaline agent supply unit 53, and further a temperature adjusting unit for adjusting the liquid temperature in the third reaction tank 51, A reflux cooling means or the like can be provided. The neutralized liquid obtained in the third reactor 50 is discharged from a discharge port 55 formed in the tank wall (bottom wall in the drawing).

For the purpose of smooth production, first, an acrylic acid polymer aqueous solution having a solid content concentration close to the target acrylic acid polymer may be stored in the first reaction tank 11 and the second reaction tank 31. preferable.
Next, a monomer containing acrylic acid, a polymerization initiator, and a chain transfer agent are supplied to the first reaction tank 11 to polymerize the monomer. When the polymerization is carried out under the conditions of the present invention using the circulation pipe 20, the monomer polymerization is performed by using the first reactor 10 as described above with reference to FIG. Can be completed. However, in the first reaction liquid sent to the second reactor 30 from the discharge pipe 29 branched in the middle of the pipe portion 21 constituting the circulation pipe 20 in the first reactor 10, there is a trace amount. Therefore, the unreacted monomer is surely polymerized in the second reactor 30. As described above, a part of the first reaction liquid obtained in the first reaction tank 11 is cooled by the cooling means 25 and returned to the first reaction tank 11 to adjust the temperature in the first reaction tank 11. Or used to continue the polymerization. The ratio of the first reaction liquid to be returned to the first reaction liquid discharged from the discharge port 15 is not particularly limited, but the acrylic acid polymer having a low degree of dispersion is smoothly manufactured, and previously stored. Therefore, it is preferably 30 to 90% by mass, and more preferably 55 to 85% by mass, because the other acrylic acid polymer aqueous solution can be smoothly driven out. Thus, the polymerization conversion rate can be improved by carrying out the circulation of the first reaction liquid and the polymerization of the monomer by applying the above average residence time.

  When the polymerization of the monomer starts in the first reaction tank 11, a part of the first reaction liquid is sent from the discharge pipe 29 to the second reaction tank 31 of the second reactor 30. In the second reaction tank 31, since another acrylic acid polymer aqueous solution or the like is stored in advance, it is a mixed liquid with the supplied first reaction liquid at the initial stage of manufacture, and is discharged from the discharge port 35. It is only sent to the third reaction tank 51 of the three reactor 50. In the 1st reaction tank 11, since the aqueous solution of the acrylic acid polymer which has the target solid content concentration is obtained after passing said average residence time, when this aqueous solution is sent to the 2nd reaction tank 31, beforehand, The other acrylic acid polymer aqueous solution contained can be driven out smoothly. Also in the second reaction tank 31, the average residence time of the liquid is appropriately set based on the volume of another acrylic acid polymer aqueous solution accommodated in advance, the supply rate of the first reaction liquid to the second reaction tank 31, and the like. Thus, the polymerization of the unreacted monomer is performed reliably. The Mw of the acrylic acid polymer obtained in the second reactor 30 is preferably 3000 to 10000, more preferably 4000 to 8000, and the dispersity (Mw / Mn) is preferably 1.8 to 2. .4, more preferably 2.0 to 2.2.

  Thereafter, an aqueous solution of an acrylic acid polymer having preferable physical properties is sent to the third reaction tank 51 of the third reactor 50 through the discharge pipe 39. In the 3rd reaction tank 51, an alkali agent is supplied from the alkali agent supply means 53, and a neutralization reaction is advanced with stirring to make an aqueous solution having a desired pH.

  In the above production example, the neutralization step was performed in the third reactor 50. However, the neutralization step may be performed in the second reactor 30 in which the polymerization of the unreacted monomer is continued. It may be performed in both reactors 50. And when the neutralization process is completed only in the second reactor 30, the use of the third reactor 50 can be omitted.

The aqueous acrylic acid polymer solution produced according to the present invention is suitable as a dispersant for inorganic particles, a water treatment agent (an agent that suppresses the formation of scale, precipitation or deposition) and the like.
When used as a dispersant for inorganic particles, the above aqueous solution is usually used as it is, but it may be used in combination with other components such as an antifoaming agent and an antiseptic as necessary. As the inorganic particles, particles made of calcium carbonate, kaolin, talc, clay, silica, aluminum hydroxide, zeolite, titanium dioxide or the like can be used.
In addition, when used as a water treatment agent, the above aqueous solution may be used as it is, and if necessary, other than polymaleic acid or a salt thereof, a (meth) acrylic acid copolymer, a styrene / maleic acid copolymer, You may use in combination with other components, such as a scale inhibitor, a disinfectant, an anticorrosive, a slime inhibitor, and an antifoamer. By using such a water treatment agent, for example, problems such as a decrease in heat exchange efficiency and blockage of piping in a cooling water system, a boiler water system, a seawater desalination apparatus, and the like can be suppressed.

  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. 2. Production apparatus for acrylic acid polymer aqueous solution In the following experimental example, the apparatus 1 shown in FIG. 2, that is, the apparatus 1 in which the first reactor 10, the second reactor 30, and the third reactor 50 are connected in this order. An aqueous acrylic acid polymer solution having a pH of 7 was used.
The first reactor 10 has a bottomed cylindrical container (first reaction tank) 11 that performs polymerization therein, a stirrer 12, and a raw material supply for supplying a monomer, a polymerization initiator, a chain transfer agent, and the like. A temperature adjusting means that is provided so as to cover the outer periphery of the cylindrical container 11, and that uses cooling water. A jacket (not shown) for adjusting the temperature of the liquid and a pipe for circulating a reaction liquid containing an acrylic acid polymer outside the cylindrical container 11, A circulation pipe 20 is provided to connect the discharge port 15 formed on the wall and the introduction port 17 formed on the side wall at a position higher than the liquid level outside the cylindrical container 11. Further, the circulation pipe 20 is provided with a discharge pump 29 and a discharge pipe 29 with a valve for sending the liquid to the second reaction tank 31 of the second reactor 30 from the discharge port 15 to the introduction port 17. The heat exchanger 25 that cools the circulating reaction liquid by using the cheese and the cooling water is sequentially provided. Thermometers for measuring the temperature of the reaction solution are installed at the discharge port 15 and the introduction port 17 of the cylindrical container 11 in which the circulation pipe 20 is disposed (not shown).
The second reactor 30 includes a bottomed cylindrical container (second reaction tank) 31, a stirrer 32, a condenser (not shown), and a jacket (not shown), and further, a cylindrical container. A discharge port 35 for sending a reaction solution containing an acrylic acid polymer to the third reactor 50 is formed on the bottom wall of 31, and is connected to the third reaction tank 51 of the third reactor 50. A liquid feed pump 37 is disposed between the discharge pipe 39 and the discharge pipe 39.
The third reactor 50 includes a bottomed cylindrical container (third reaction tank) 51, a stirrer 52, and a pH adjuster supply for supplying a pH adjuster (alkali agent) into the container 51. A pipe 53, a condenser (not shown), and a jacket (not shown) are provided, and a discharge port 55 for discharging and collecting the acrylic acid polymer aqueous solution to the bottom wall of the cylindrical container 51. Is formed.

2. Production of acrylic acid polymer aqueous solution (1)
Example 1
First, 2200 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 80 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium bisulfite aqueous solution is 3 to the first reaction tank 11. Each was supplied at a rate of 0.5 kg / min, and the polymerization reaction was started while the liquid temperature was kept at 80 ° C. and the rotation speed of the stirrer 12 was 80 rpm. At the same time, the output of the liquid feed pump 27 arranged in the middle of the circulation pipe 20 is adjusted, and the 80 ° C. reaction solution is withdrawn from the discharge port 15 of the first reaction tank 11 at 62 kg / min. Through the pipe 20, 37 kg / min, which is a part of the reaction solution, is cooled by the heat exchanger 25, and the reaction solution at 43 ° C. is supplied from the inlet 17 of the first reaction vessel 11 to the first reaction vessel 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction solution flowing through the circulation pipe 20 from the discharge port 15 to the introduction port 17 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 20 kg. The piping capacity from the heat exchanger 25 to the inlet 17 was 60 kg. Under the above conditions, the polymerization reaction was performed while maintaining the amount of liquid in the first reaction tank 11 at 2200 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 92 minutes. The required power for stirring calculated from the power consumption and the amount of liquid after subtracting the loss inside the motor of the stirrer 12 was 1.1 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 80 ° C. and the amount of liquid in the second reaction tank 31 was maintained at 2200 kg, and the rotation speed of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In order to keep the amount of liquid in the second reaction tank 31 at 2200 kg, the same amount (25 kg / min) of the reaction liquid as that supplied from the first reaction tank 11 is used as the discharge port of the second reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 92 minutes.
Thereafter, in the third reactor 50, water and a 48% sodium hydroxide aqueous solution (hereinafter also referred to as “48% NaOH”) are respectively supplied from the pH adjusting agent supply pipe 53, and the second reactor is supplied. The reaction liquid supplied from No. 30 was neutralized while stirring the mixed liquid and maintaining the liquid temperature at 80 ° C., and the pH of the mixed liquid was set to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 2200 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations were continued for 20 hours, the neutralized solution from the discharge port 55 of the third reaction tank 51 was recovered to obtain an aqueous solution (E1) having a solid content concentration of acrylic acid polymer of 40% (Table). 1).

Subsequently, when the acrylic acid polymer was subjected to gel permeation chromatography (GPC) under the following conditions, Mw was 6000 and Mw / Mn was 2.2. Moreover, the content rate of the polymer of molecular weight 70000 or more calculated | required by molecular weight fraction calculation was 0.01% with respect to the whole acrylic acid polymer.
<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: Sodium polyacrylate manufactured by Soka

Example 2
Except that the power required for stirring was 0.7 kW / m ³ , the same operation as in Example 1 was performed to produce an aqueous solution (E2) having a solid content concentration of acrylic acid polymer of 40%, and GPC measurement was performed. (See Table 1).

Example 3
The same operation as in Example 1 was performed except that the 49 ° C. reaction liquid cooled by the heat exchanger 25 was supplied into the first reaction tank 11, and an aqueous solution (40% solid content concentration of acrylic acid polymer) ( E3) was manufactured and GPC measurement was performed (see Table 1).

Example 4
First, 1800 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration: 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 80 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium bisulfite aqueous solution is 3 to the first reaction tank 11. Each was supplied at a rate of 0.5 kg / min, and the polymerization reaction was started while the liquid temperature was kept at 80 ° C. and the rotation speed of the stirrer 12 was 80 rpm. At the same time, the output of the liquid feed pump 27 arranged in the middle of the circulation pipe 20 is adjusted, and the reaction solution at 80 ° C. is extracted from the discharge port 15 of the first reaction tank 11 at 124 kg / min. Through the pipe 20, 99 kg / min, which is a part of the reaction solution, is cooled by the heat exchanger 25, and the reaction solution at 44 ° C. is supplied from the inlet 17 of the first reaction vessel 11 to the first reaction vessel 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction solution flowing through the circulation pipe 20 from the discharge port 15 to the introduction port 17 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 20 kg. The piping capacity from the heat exchanger 25 to the inlet 17 was 60 kg. Under the above conditions, the polymerization reaction was carried out while maintaining the liquid amount in the first reaction tank 11 at 1800 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 76 minutes. The required power for stirring calculated from the power consumption and the liquid amount after subtracting the loss in the motor of the stirrer 12 was 1.0 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 80 ° C. and the liquid amount in the second reaction tank 31 was maintained at 1800 kg, and the number of revolutions of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In addition, in order to hold | maintain the liquid quantity in the 2nd reaction tank 31 to 1800 kg, the reaction liquid of the same quantity (25 kg / min) as the reaction liquid supplied from the 1st reaction tank 11 is made into the discharge port of the 2nd reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 76 minutes.
Thereafter, in the third reactor 50, water and 48% NaOH are supplied from the pH adjusting agent supply pipe 53, respectively, and neutralization of the reaction solution supplied from the second reactor 30 is performed. Was carried out while maintaining the liquid temperature at 80 ° C., and the pH of the mixed solution was adjusted to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 1800 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations are continued for 20 hours, the neutralized liquid from the outlet 55 of the third reaction tank 51 is recovered, and an aqueous solution (E4) having a solid content concentration of acrylic acid polymer of 40% is produced. Measurements were made (see Table 1).

Example 5
First, 2200 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 80 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium bisulfite aqueous solution is 3 to the first reaction tank 11. Each was supplied at a rate of 0.5 kg / min, and the polymerization reaction was started while the liquid temperature was kept at 80 ° C. and the rotation speed of the stirrer 12 was 80 rpm. At the same time, the output of the liquid feed pump 27 arranged in the middle of the circulation pipe 20 is adjusted, and the 80 ° C. reaction solution is withdrawn from the discharge port 15 of the first reaction tank 11 at 62 kg / min. Through the pipe 20, 37 kg / min, which is a part of the reaction solution, is cooled by the heat exchanger 25, and the reaction solution at 42 ° C. is supplied from the inlet 17 of the first reaction vessel 11 to the first reaction vessel 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction solution flowing through the circulation pipe 20 from the discharge port 15 to the introduction port 17 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 80 kg. The piping capacity from the heat exchanger 25 to the inlet 17 was 60 kg. Under the above conditions, the polymerization reaction was performed while maintaining the amount of liquid in the first reaction tank 11 at 2200 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 95 minutes. The required power for stirring calculated from the power consumption and the amount of liquid after subtracting the loss inside the motor of the stirrer 12 was 1.1 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 80 ° C. and the amount of liquid in the second reaction tank 31 was maintained at 2200 kg, and the rotation speed of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In order to keep the amount of liquid in the second reaction tank 31 at 2200 kg, the same amount (25 kg / min) of the reaction liquid as that supplied from the first reaction tank 11 is used as the discharge port of the second reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 92 minutes.
Thereafter, in the third reactor 50, water and 48% NaOH are supplied from the pH adjusting agent supply pipe 53, respectively, and neutralization of the reaction solution supplied from the second reactor 30 is performed. Was carried out while maintaining the liquid temperature at 80 ° C., and the pH of the mixed solution was adjusted to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 2200 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations are continued for 20 hours, the neutralized solution from the outlet 55 of the third reaction tank 51 is recovered to produce an aqueous solution (E5) having a solid content concentration of acrylic acid polymer of 40%. Measurements were made (see Table 1).

Example 6
First, 2200 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 80 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium bisulfite aqueous solution is 3 to the first reaction tank 11. Each was supplied at a rate of 0.5 kg / min, and the polymerization reaction was started while the liquid temperature was kept at 80 ° C. and the rotation speed of the stirrer 12 was 80 rpm. At the same time, the output of the liquid feed pump 27 arranged in the middle of the circulation pipe 20 is adjusted, and the 80 ° C. reaction solution is withdrawn from the discharge port 15 of the first reaction tank 11 at 62 kg / min. Through the pipe 20, 37 kg / min, which is a part of the reaction solution, is cooled by the heat exchanger 25, and the reaction solution at 43 ° C. is supplied from the inlet 17 of the first reaction vessel 11 to the first reaction vessel 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction solution flowing through the circulation pipe 20 from the discharge port 15 to the introduction port 17 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 20 kg. The piping capacity from the heat exchanger 25 to the introduction port 17 was 180 kg. Under the above conditions, the polymerization reaction was performed while maintaining the amount of liquid in the first reaction tank 11 at 2200 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 97 minutes. The required power for stirring calculated from the power consumption and the amount of liquid after subtracting the loss inside the motor of the stirrer 12 was 1.1 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 80 ° C. and the amount of liquid in the second reaction tank 31 was maintained at 2200 kg, and the rotation speed of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In order to keep the amount of liquid in the second reaction tank 31 at 2200 kg, the same amount (25 kg / min) of the reaction liquid as that supplied from the first reaction tank 11 is used as the discharge port of the second reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 92 minutes.
Thereafter, in the third reactor 50, water and 48% NaOH are supplied from the pH adjusting agent supply pipe 53, respectively, and neutralization of the reaction solution supplied from the second reactor 30 is performed. Was carried out while maintaining the liquid temperature at 80 ° C., and the pH of the mixed solution was adjusted to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 2200 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations are continued for 20 hours, the neutralized liquid from the outlet 55 of the third reaction tank 51 is recovered, and an aqueous solution (E6) having a solid content concentration of acrylic acid polymer of 40% is produced. Measurements were made (see Table 1).

Comparative Example 1
The same operation as in Example 1 was performed except that the 58 ° C. reaction liquid cooled by the heat exchanger 25 was supplied into the first reaction tank 11, and an aqueous solution (40% solid content concentration of acrylic acid polymer) ( C1) was manufactured and GPC measurement was performed (see Table 1).

Comparative Example 2
First, 2200 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 80 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium bisulfite aqueous solution is 3 to the first reaction tank 11. Each was supplied at a rate of 0.5 kg / min, and the polymerization reaction was started while the liquid temperature was kept at 80 ° C. and the rotation speed of the stirrer 12 was 80 rpm. At the same time, the output of the liquid feed pump 27 arranged in the middle of the circulation pipe 20 is adjusted, and the 80 ° C. reaction solution is withdrawn from the discharge port 15 of the first reaction tank 11 at 62 kg / min. Through the pipe 20, 37 kg / min, which is a part of the reaction solution, is cooled by the heat exchanger 25, and the reaction solution at 42 ° C. is supplied from the inlet 17 of the first reaction vessel 11 to the first reaction vessel 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction liquid flowing through the circulation pipe 20 of the introduction port 17 from the discharge port 15 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 160 kg. The piping capacity from the heat exchanger 25 to the inlet 17 was 60 kg. Under the above conditions, the polymerization reaction was performed while maintaining the amount of liquid in the first reaction tank 11 at 2200 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 98 minutes. The required power for stirring calculated from the power consumption and the amount of liquid after subtracting the loss inside the motor of the stirrer 12 was 1.1 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 80 ° C. and the amount of liquid in the second reaction tank 31 was maintained at 2200 kg, and the rotation speed of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In order to keep the amount of liquid in the second reaction tank 31 at 2200 kg, the same amount (25 kg / min) of the reaction liquid as that supplied from the first reaction tank 11 is used as the discharge port of the second reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 92 minutes.
Thereafter, in the third reactor 50, water and 48% NaOH are supplied from the pH adjusting agent supply pipe 53, respectively, and neutralization of the reaction solution supplied from the second reactor 30 is performed. Was carried out while maintaining the liquid temperature at 80 ° C., and the pH of the mixed solution was adjusted to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 2200 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations are continued for 20 hours, the neutralized liquid from the outlet 55 of the third reaction tank 51 is recovered, and an aqueous solution (C2) having a solid content concentration of acrylic acid polymer of 40% is produced. Measurements were made (see Table 1).

3. Manufacture of acrylic acid polymer aqueous solution (2)
Example 7
First, 2900 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 85 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium hypophosphite aqueous solution is supplied to the first reaction tank 11. Was supplied at 3.5 kg / min, and the polymerization reaction was started at a rotational speed of the stirrer 12 of 80 rpm while maintaining the liquid temperature at 85 ° C. At the same time, the output of the liquid feed pump 27 disposed in the middle of the circulation pipe 20 is adjusted, and the 85 ° C. reaction solution is withdrawn from the discharge port 15 of the first reaction tank 11 at 62 kg / min. Through the pipe 20, 37 kg / min, which is a part of the reaction liquid, is cooled by the heat exchanger 25, and the reaction liquid at 46 ° C. is introduced into the first reaction tank 11 from the inlet 17 of the first reaction tank 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction solution flowing through the circulation pipe 20 from the discharge port 15 to the introduction port 17 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 20 kg. The piping capacity from the heat exchanger 25 to the inlet 17 was 60 kg. Under the above conditions, the polymerization reaction was performed while maintaining the liquid amount in the first reaction tank 11 at 2900 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 121 minutes. The power required for stirring was 1.0 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 85 ° C. and the liquid amount in the second reaction tank 31 was maintained at 2900 kg, and the number of revolutions of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In addition, in order to hold | maintain the liquid quantity in the 2nd reaction tank 31 at 2900 kg, the reaction liquid of the same quantity (25 kg / min) as the reaction liquid supplied from the 1st reaction tank 11 is made into the discharge port of the 2nd reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 121 minutes.
Thereafter, in the third reactor 50, water and 48% NaOH are supplied from the pH adjusting agent supply pipe 53, respectively, and neutralization of the reaction solution supplied from the second reactor 30 is performed. Was carried out while maintaining the liquid temperature at 85 ° C., and the pH of the mixed solution was adjusted to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 2900 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations were continued for 24 hours, the neutralized liquid from the discharge port 55 of the third reaction tank 51 was recovered to obtain an aqueous solution (E7) having a solid content concentration of acrylic acid polymer of 40% (Table). 2).
Thereafter, in the same manner as in Example 1, GPC measurement of the acrylic acid polymer contained in the acrylic acid polymer aqueous solution (E7) was performed, and Mw and the like are also shown in Table 2.

Example 8
Except that the power required for stirring was 0.7 kW / m ³ , the same operation as in Example 7 was performed to produce an aqueous solution (E8) having a solid content concentration of acrylic acid polymer of 40%, and GPC measurement was performed. (See Table 2).

Example 9
The same operation as in Example 7 was performed except that the reaction liquid at 54 ° C. cooled by the heat exchanger 25 was supplied into the first reaction tank 11, and an aqueous solution (40% solid content concentration of acrylic acid polymer) ( E9) was manufactured and GPC measurement was performed (see Table 2).

Example 10
First, 2900 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 85 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium hypophosphite aqueous solution is supplied to the first reaction tank 11. Was supplied at 3.5 kg / min, and the polymerization reaction was started at a rotational speed of the stirrer 12 of 80 rpm while maintaining the liquid temperature at 85 ° C. At the same time, the output of the liquid feed pump 27 disposed in the middle of the circulation pipe 20 is adjusted, and the 85 ° C. reaction solution is withdrawn from the discharge port 15 of the first reaction tank 11 at 62 kg / min. Through the pipe 20, 37 kg / min, which is a part of the reaction liquid, is cooled by the heat exchanger 25, and the reaction liquid at 46 ° C. is introduced into the first reaction tank 11 from the inlet 17 of the first reaction tank 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction solution flowing through the circulation pipe 20 from the discharge port 15 to the introduction port 17 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 80 kg. The piping capacity from the heat exchanger 25 to the inlet 17 was 60 kg. Under the above conditions, the polymerization reaction was performed while maintaining the liquid amount in the first reaction tank 11 at 2900 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 123 minutes. The power required for stirring was 1.0 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 85 ° C. and the liquid amount in the second reaction tank 31 was maintained at 2900 kg, and the number of revolutions of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In addition, in order to hold | maintain the liquid quantity in the 2nd reaction tank 31 at 2900 kg, the reaction liquid of the same quantity (25 kg / min) as the reaction liquid supplied from the 1st reaction tank 11 is made into the discharge port of the 2nd reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 121 minutes.
Thereafter, in the third reactor 50, water and 48% NaOH are supplied from the pH adjusting agent supply pipe 53, respectively, and neutralization of the reaction solution supplied from the second reactor 30 is performed. Was carried out while maintaining the liquid temperature at 85 ° C., and the pH of the mixed solution was adjusted to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 2900 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations were continued for 24 hours, the neutralized liquid from the discharge port 55 of the third reaction tank 51 was recovered, and an aqueous solution (E10) having a solid content concentration of acrylic acid polymer of 40% was obtained (Table). 2).
Thereafter, in the same manner as in Example 1, GPC measurement of the acrylic acid polymer contained in the acrylic acid polymer aqueous solution (E10) was performed, and Mw and the like were also shown in Table 2.

Example 11
First, 2900 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 85 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium hypophosphite aqueous solution is supplied to the first reaction tank 11. Was supplied at 3.5 kg / min, and the polymerization reaction was started at a rotational speed of the stirrer 12 of 80 rpm while maintaining the liquid temperature at 85 ° C. At the same time, the output of the liquid feed pump 27 disposed in the middle of the circulation pipe 20 is adjusted, and the 85 ° C. reaction solution is withdrawn from the discharge port 15 of the first reaction tank 11 at 62 kg / min. Through the pipe 20, 37 kg / min, which is a part of the reaction liquid, is cooled by the heat exchanger 25, and the reaction liquid at 46 ° C. is introduced into the first reaction tank 11 from the inlet 17 of the first reaction tank 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction solution flowing through the circulation pipe 20 from the discharge port 15 to the introduction port 17 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 20 kg. The piping capacity from the heat exchanger 25 to the introduction port 17 was 180 kg. Under the above conditions, the polymerization reaction was performed while maintaining the liquid amount in the first reaction tank 11 at 2900 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 126 minutes. The power required for stirring was 1.0 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 85 ° C. and the liquid amount in the second reaction tank 31 was maintained at 2900 kg, and the number of revolutions of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In addition, in order to hold | maintain the liquid quantity in the 2nd reaction tank 31 at 2900 kg, the reaction liquid of the same quantity (25 kg / min) as the reaction liquid supplied from the 1st reaction tank 11 is made into the discharge port of the 2nd reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 121 minutes.
Thereafter, in the third reactor 50, water and 48% NaOH are supplied from the pH adjusting agent supply pipe 53, respectively, and neutralization of the reaction solution supplied from the second reactor 30 is performed. Was carried out while maintaining the liquid temperature at 85 ° C., and the pH of the mixed solution was adjusted to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 2900 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations were continued for 24 hours, the neutralized solution from the discharge port 55 of the third reaction tank 51 was recovered to obtain an aqueous solution (E11) having a solid content concentration of acrylic acid polymer of 40% (Table). 2).
Thereafter, in the same manner as in Example 1, GPC measurement of the acrylic acid polymer contained in the acrylic acid polymer aqueous solution (E11) was performed, and Mw and the like were also shown in Table 2.

Comparative Example 3
The same operation as in Example 7 was performed except that the reaction solution at 63 ° C. cooled by the heat exchanger 25 was supplied into the first reaction tank 11, and an aqueous solution (40% solid content concentration of acrylic acid polymer) ( C3) was manufactured and GPC measurement was performed (see Table 2).

Comparative Example 4
First, 2900 kg of an aqueous solution of polyacrylic acid having a Mw of 6000 (solid content concentration 40%) was accommodated in both the first reaction tank 11 and the second reaction tank 31, and the liquid temperature was maintained at 85 ° C.
Thereafter, using the raw material supply pipe 13, the 60% acrylic acid aqueous solution is 20 kg / min, the 15% sodium persulfate aqueous solution is 1.2 kg / min, and the 30% sodium hypophosphite aqueous solution is supplied to the first reaction tank 11. Was supplied at 3.5 kg / min, and the polymerization reaction was started at a rotational speed of the stirrer 12 of 80 rpm while maintaining the liquid temperature at 85 ° C. At the same time, the output of the liquid feed pump 27 disposed in the middle of the circulation pipe 20 is adjusted, and the 85 ° C. reaction solution is withdrawn from the discharge port 15 of the first reaction tank 11 at 62 kg / min. Through the pipe 20, 37 kg / min, which is a part of the reaction liquid, is cooled by the heat exchanger 25, and the reaction liquid at 46 ° C. is introduced into the first reaction tank 11 from the inlet 17 of the first reaction tank 11. The solution was fed in. The remaining 25 kg / min of the reaction solution from the discharge port 15 was sent to the second reactor 30 by adjusting the valve of the valve disposed in the discharge pipe 29.
Of the reaction solution flowing through the circulation pipe 20 from the discharge port 15 to the introduction port 17 of the first reaction tank 11, the pipe capacity from the discharge port 15 of the first reaction tank 11 to the heat exchanger 25 was 160 kg. The piping capacity from the heat exchanger 25 to the inlet 17 was 60 kg. Under the above conditions, the polymerization reaction was performed while maintaining the liquid amount in the first reaction tank 11 at 2900 kg. The average residence time of the entire reaction solution, combined with the residence time of the reaction solution in the circulation pipe 20, was 126 minutes. The power required for stirring was 1.0 kW / m ³ .
Next, in the second reactor 30, as described above, the reaction liquid supplied at 25 kg / min via the discharge pipe 29 and the polyacrylic acid aqueous solution previously stored are liquid temperature. Was maintained at 85 ° C. and the liquid amount in the second reaction tank 31 was maintained at 2900 kg, and the number of revolutions of the stirrer 32 was mixed at 80 rpm to carry out the polymerization reaction of the remaining acrylic acid. In addition, in order to hold | maintain the liquid quantity in the 2nd reaction tank 31 at 2900 kg, the reaction liquid of the same quantity (25 kg / min) as the reaction liquid supplied from the 1st reaction tank 11 is made into the discharge port of the 2nd reaction tank 31. From 35, the solution was fed to the third reactor 50. The average residence time of the entire reaction solution was 121 minutes.
Thereafter, in the third reactor 50, water and 48% NaOH are supplied from the pH adjusting agent supply pipe 53, respectively, and neutralization of the reaction solution supplied from the second reactor 30 is performed. Was carried out while maintaining the liquid temperature at 85 ° C., and the pH of the mixed solution was adjusted to 7.0. This neutralization reaction was carried out while maintaining the amount of liquid in the third reaction tank 51 at 2900 kg, and when this amount was exceeded, the neutralized liquid (acrylic acid polymer aqueous solution) was discharged from the discharge port 55.
After these operations were continued for 24 hours, the neutralized liquid from the discharge port 55 of the third reaction tank 51 was recovered to obtain an aqueous solution (C4) having a solid content concentration of acrylic acid polymer of 40% (Table). 2).
Thereafter, in the same manner as in Example 1, GPC measurement of the acrylic acid polymer contained in the acrylic acid polymer aqueous solution (C4) was performed, and Mw and the like were also shown in Table 2.

4). Evaluation of Acrylic Acid Polymer Aqueous Solution The acrylic acid polymer aqueous solutions obtained in Examples 1 to 11 and Comparative Examples 1 to 4 were subjected to the following tests. The results are shown in Table 3.

(1) Wet grinding test of heavy calcium carbonate 7.5 g of acrylic acid polymer aqueous solution, 340 g of ion exchange water, and 1000 g of heavy calcium carbonate “No. A heavy coal” (trade name) manufactured by Maruo Calcium Co., Ltd. The mixture was put into a cylindrical container equipped with a stirrer, and lightly stirred to be evenly blended. Next, 2800 g of media (φ1 mm ceramic beads) was put into the cylindrical container and stirred at 1000 rpm for 50 minutes to wet pulverize calcium carbonate. And after passing 150 mesh filter cloth, ion-exchange water was added and the slurry whose solid content concentration is 75% was obtained.
About the obtained slurry, a 2.0 μm under integrated value was measured by a particle size distribution measuring device “Cedigraph 5120” (trade name) manufactured by Micromeritics.
Moreover, about the said slurry, the viscosity immediately after preparing this and the viscosity after leaving still at 25 degreeC for 7 days were measured on the conditions of 25 degreeC and 60 rpm using the B-type viscosity meter.

(2) Stirring dispersion test of heavy calcium carbonate 6.0 g of acrylic acid polymer aqueous solution, 330 g of ion exchange water, and 1000 g of heavy calcium carbonate “Super # 2000” (trade name) manufactured by Maruo Calcium Co., Ltd. Was put into a cylindrical container equipped with a slurry and stirred at 4000 rpm for 10 minutes to obtain a slurry. About this slurry, the viscosity immediately after preparation and the viscosity after standing at 25 degreeC for 7 days were measured on 25 degreeC and 60 rpm conditions using the B-type viscosity meter.

(3) Mud dispersion test 13 mg of an acrylic acid polymer aqueous solution, 1 g of clay “Amazon 88 Non-Predispers” (trade name) manufactured by Mitsubishi Corporation, and 100 g of ion-exchanged water are placed in a 100 mL graduated cylinder, and a magnetic stirrer is used. And stirred for 10 minutes. Then, it left still at 25 degreeC for 18 hours, extract | collected the supernatant liquid, and measured the light absorbency in wavelength 380nm. Higher absorbance means better clay dispersibility.

(4) Calcium carbonate scale inhibition test An acrylic acid polymer aqueous solution was added to 100 mL of 200 mg CaCO ₃ / L calcium chloride aqueous solution so that the content of the acrylic acid polymer was 10 mg. Next, 10 g of 0.2% aqueous sodium hydrogen carbonate solution was added, and the pH of the aqueous solution was adjusted to 8.5 with sodium hydroxide. And this liquid mixture was left to stand at 60 degreeC for 24 hours, the deposit was separated by filtration, the calcium concentration in a filtrate was calculated | required by EDTA titration, and the scale inhibition rate was computed.

As is clear from Table 3, Comparative Examples 1 and 3 both have the temperature of the reaction liquid at the outlet of the outlet of the first reaction tank and the reaction liquid cooled by the heat exchanger in the first reaction tank. This is an example in which the difference from the temperature immediately before the inlet is 22 ° C., the degree of dispersion (Mw / Mn) of the acrylic acid polymer is large, and the content of the high molecular weight polymer is also high. Further, sufficient performance could not be obtained in all of the wet pulverization test, the stirring dispersion test, the mud dispersion test, and the scale inhibition test. In Comparative Examples 2 and 4, the mass ratio of the amount of liquid from the outlet of the first reaction tank to the heat exchanger in the circulation pipe and the amount of liquid in the first reaction tank exceeded 0.050. As an example, the degree of dispersion (Mw / Mn) of the acrylic acid polymer was large, and the content of the high molecular weight polymer was also high. Further, sufficient performance could not be obtained in all of the wet pulverization test, the stirring dispersion test, the mud dispersion test, and the scale inhibition test.
On the other hand, in Examples 1 to 11, acrylic acid-based polymers obtained by the production method of the present invention have a low degree of dispersion (Mw / Mn) of acrylic acid-based polymers and a low content of high-molecular weight polymers. This is an example of a polymer aqueous solution, and excellent results were obtained in any of a wet pulverization test, a stirring dispersion test, a mud dispersion test, and a scale inhibition test.

  The aqueous acrylic acid polymer solution obtained by the present invention is suitable as a dispersant for inorganic particles, a water treatment agent and the like.

1: Production apparatus 10: First reactor 11: First reaction tank 12: Stirrer (stirring means)
13: Raw material supply piping (raw material supply means)
15: Discharge port 17: Inlet port 20: Circulation pipe 21: Pipe part from the discharge port to the heat exchanger (cooling means) 23: Pipe part from the heat exchanger (cooling means) to the inlet 25: Heat exchanger (Cooling means)
27: liquid feed pump 29: discharge pipe 30: second reactor 31: second reaction tank 32: stirrer 35: discharge port 37: liquid feed pump 39: discharge pipe 50: third reactor 51: third Reaction tank 52: Stirrer 53: Pipe for supplying pH adjusting agent (alkali agent supplying means)
55: Discharge port

Claims (5)

A raw material supply means and a stirring means, disposed in the presence of a polymerization initiator and water, a first reaction tank for polymerizing a monomer containing acrylic acid, and disposed outside the first reaction tank; and , A pipe connecting the discharge port and the inlet formed in the tank wall of the first reaction tank, and used for circulation of the first reaction liquid containing the polymer produced in the first reaction tank In a method for continuously producing an aqueous acrylic acid polymer solution using an apparatus comprising a first reactor having a pipe,
The circulation pipe is provided with cooling means for cooling the first reaction liquid,
The difference between the temperature of the first reaction liquid at the outlet of the first reaction tank and the temperature of the cooled first reaction liquid at the inlet of the first reaction tank is 30 ° C. or more,
The mass ratio of the amount of liquid from the outlet of the first reaction tank to the cooling means and the amount of liquid in the first reaction tank is 0.050 or less,
A method for producing an acrylic acid polymer aqueous solution, comprising polymerizing the monomer and circulating the first reaction liquid.   The method for producing an acrylic acid polymer aqueous solution according to claim 1, wherein a discharge pipe for discharging the first reaction liquid is connected to the circulation pipe.   The method for producing an aqueous acrylic acid polymer solution according to claim 2, wherein the first reaction liquid obtained from the discharge pipe is neutralized to obtain a second reaction liquid having a pH in the range of 4-9. The apparatus further comprises a second reactor connected to the discharge pipe;
The method for producing an acrylic acid polymer aqueous solution according to claim 3, wherein the second reaction liquid is obtained by neutralizing the first reaction liquid using an alkali agent in the second reactor. The apparatus further comprises a second reactor connected to the discharge pipe, and a third reactor connected to the second reactor,
In the second reactor, the polymerization using the first reaction liquid from the discharge pipe is continued,
The method for producing an acrylic acid-based polymer aqueous solution according to claim 3, wherein in the third reactor, the reaction solution from the second reactor is neutralized with an alkali agent.

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