JP2003252911A - Method for producing carboxylic acid based polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of producing a polymer of high quality stably and in good productivity that prevents colorization and contains less impurities, even when reducing widely amounts of an oxygen-containing gas used to initiate a polymerization reaction, in a method for producing a carboxylic acid based polymer by using a redox initiator composed of a hydrogensulfite salt and oxygen. <P>SOLUTION: This method for providing the carboxylic acid based polymer comprises (A) a first polymerization reaction step, in which an aqueous solution of a monomer containing an α-unsaturated carboxylic acid or its salt, an aqueous solution containing a hydrogensulfite salt and a gas containing oxygen are introduced in a flow mixer to polymerize the monomer, and (B) a second polymerization reaction step, in which a reaction product containing an unreacted monomer obtained art the first step is further polymerized. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a carboxylic acid polymer. More specifically, detergent builders,
The present invention relates to a method for producing a carboxylic acid polymer that can be suitably used as a dispersant, a scale inhibitor, and the like.

[0002]

2. Description of the Related Art As a method for producing a carboxylic acid polymer which is polymerized in the presence of a redox initiator of bisulfite and oxygen, a polymerization reaction is carried out by a dropping method in a stirred tank reactor (for example, Patent Document 1 1)) and a method of forming a thin film flow in a reaction tube to carry out a polymerization reaction (see, for example, Patent Document 2).

However, in the former method, it is difficult to control the bubble diameter when increasing the scale, so it is necessary to reduce the solid content concentration, and when obtaining a polymer having a low molecular weight, it is necessary to start. It is necessary to increase the amount of the drug. Therefore, the method has the drawback that the productivity is lowered and the production rate of impurities is increased.

The latter method also has the drawback that a huge amount of gas is required to form a thin film flow in the reaction tube.

As a polymerization method other than the above, static
A method is known in which a monomer and a redox initiator are continuously mixed with a mixer and then fed to an appropriate polymerization vessel (see, for example, Patent Document 3).

However, this method requires that the redox initiator is in a liquid state at the stage of being introduced into the mixer, the initiation reaction rate is high, and the specifications of the mixer and the method of supplying the initiator for preventing clogging. Has the drawback of being limited.

Further, as a method for continuously producing an acrylate-based polymer, a method for producing by using a loop type reactor provided with a static mixer (for example, refer to Patent Document 4) and a static mixer. There is known a method of manufacturing by a loop reactor equipped with a recycling tank (for example, refer to Patent Document 5).

However, the former method has low productivity,
Further, when handling a gas-liquid system, there is a drawback that circulation is not possible due to insufficient gas separation mechanism.

In the latter method, when bisulfite and oxygen are used as redox initiators, these initiators and monomers are directly fed into the loop, and the water-soluble polymer having high viscosity is circulated. The starting reaction is carried out in the state of being present. As a result, the polymerization reaction with high initiator efficiency cannot be performed, and the amount of impurities increases. Therefore,
When the amount of the initiator is increased to reduce the viscosity of the water-soluble polymer in order to increase the efficiency of the initiator and the molecular weight is decreased, the amount of impurities derived from the initiator also increases and the concentration of the water-soluble polymer is increased. If it is lowered, there is a drawback that productivity is lowered.

[0010]

[Patent Document 1] Japanese Patent Publication No. 60-24806

[Patent Document 2] Japanese Patent Publication No. 02-24283

[Patent Document 3] Japanese Patent Publication No. 60-8001

[Patent Document 4] JP-A-60-28409

[Patent Document 5] Japanese Patent Laid-Open No. 2001-98001

[0011]

DISCLOSURE OF THE INVENTION The present invention is directed to a carboxylic acid polymer using bisulfite and oxygen as a redox initiator.
(Hereinafter referred to as "polymer"), even if the amount of oxygen-containing gas used when starting the polymerization reaction is significantly reduced, coloration is suppressed, the amount of impurities is small, and the quality is high. An object of the present invention is to provide a method capable of stably producing a polymer with high productivity.

The term "impurity" as used herein means an addition reaction substance (hereinafter referred to as "addition product") between a hydrogen sulfite salt which is an initiator and an α-unsaturated carboxylic acid or a salt thereof.

[0013]

The present invention provides (A) an aqueous solution of a monomer containing an α-unsaturated carboxylic acid or a salt thereof,
First, an aqueous solution containing bisulfite and a gas containing oxygen are introduced into a flow mixer to polymerize monomers.
Polymerization reaction step, and (B) obtained in the first polymerization reaction step,
The present invention relates to a method for producing a polymer having a second polymerization reaction step of further polymerizing a reaction product containing an unreacted monomer.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In a polymerization reaction of an α-unsaturated carboxylic acid or a salt thereof, a hydrogen sulfite salt and oxygen are used as a redox initiator, an aqueous solution containing a hydrogen sulfite salt, an oxygen-containing gas and an aqueous solution of a monomer. (Hereinafter, referred to as "reaction raw material") is introduced into a flow mixer. By introducing the reaction raw material into the flow-through mixer, fine bubbles are dispersed in the aqueous solution and the oxygen absorption efficiency to the liquid side is enhanced, so that the reaction with high initiator efficiency can be performed.

Further, the reaction product obtained in the above reaction step (hereinafter referred to as "first polymerization reaction step") has at least a gas-liquid mixing mechanism and a temperature control mechanism (hereinafter referred to as "second polymerization reaction step"). In addition, it is possible to finally produce a desired polymer having a high polymerization rate and a small amount of adduct with high productivity.

Further, in the present invention, bisulfite and oxygen are used as a gas-liquid redox initiator. Since gas has a large volume and a large flow velocity in the mixer,
When performing continuous mixing and continuous polymerization, it is possible to prevent clogging of the mixer without using a static mixer.

The first polymerization reaction step is a step of introducing the reaction raw material into a flow mixer to polymerize the monomer.

The α-unsaturated carboxylic acid or its salt is used as a raw material monomer. Among the α-unsaturated carboxylic acids or salts thereof, monomers having acrylic acid or a salt thereof as an essential component are preferable because they are suitable for homopolymerization or copolymerization. Acrylic acid is acrylic acid anhydride or acrylic acid
It can be used as an acrylic acid aqueous solution containing 60% by weight or more. The aqueous solution of acrylic acid may be an aqueous solution of an alkali metal salt of acrylic acid that is partially or wholly neutralized, such as an aqueous solution of sodium acrylate or an aqueous solution of potassium acrylate.

The raw material monomer contains a hydrophilic monomer copolymerizable with α-unsaturated carboxylic acid or a salt thereof, such as maleic acid, acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate. May be. The content of the hydrophilic monomer in the raw material monomer is preferably 0 to 30 mol% from the viewpoint of increasing the polymerization reaction rate and facilitating the control of the molecular weight.

The concentration of the monomer in the aqueous monomer solution (hereinafter referred to as “monomer aqueous solution”) is preferably 10 to 60% by weight, more preferably from the viewpoint of enhancing productivity and facilitating control of reaction and temperature. Is 20 to 50% by weight.

The pH of the aqueous monomer solution is preferably 5 to 9 from the viewpoint of reactivity, and more preferably 6 to 7 from the viewpoint of performing the initiation reaction with high initiator efficiency.

The temperature of the aqueous monomer solution is preferably 5 ° C. or higher from the viewpoint of handling it as an aqueous solution, and 30 ° C. or lower from the viewpoint of suppressing the polymerization of the monomer before the start of the reaction. From these viewpoints, the temperature of the aqueous monomer solution is preferably 5 to 30 ° C. When maleic acid is copolymerized, when the maleate salt is used as an aqueous solution, the temperature of the maleate salt solution is preferably 50 to 90 ° C.

Examples of the bisulfite include sodium bisulfite, potassium bisulfite, magnesium bisulfite and the like. Among these, sodium hydrogen sulfite having a strong reducing action is preferable.

An aqueous solution containing bisulfite (hereinafter,
The concentration of “hydrogen sulfite aqueous solution” is preferably 1 to 40% by weight, more preferably 20 to 40% from the viewpoint of productivity.
40% by weight.

From the viewpoint of facilitating the control of the molecular weight suitable for the intended use and suppressing the formation of adducts, the amount of bisulfite is preferably 0.008 to 0.1 mol per mol of the monomer.

Air is generally used as the oxygen-containing gas (hereinafter, simply referred to as “gas”), but pure oxygen or a gas obtained by diluting pure oxygen with an inert gas may be used. The oxygen concentration in the gas is preferably 10% by volume or more, more preferably 20% by volume or more, from the viewpoint of reactivity with bisulfite. Examples of equipment for supplying gas include compressors and blower equipment. From the viewpoint of stabilizing the reaction, it is preferable to supply the gas at a constant pressure and a constant volume.

The flow mixer is used for gas-liquid mixing. The flow mixer in the present invention includes, for example,
Examples include static mixers such as static mixers and orifice mixers; jet nozzles such as ejectors; pipe mixers such as line mixers. Among these, the static mixer is preferable from the viewpoint that high mixing performance can be exhibited even with a small amount of gas, the durability of equipment, the maintenance, and the like.

As a method of introducing the reaction raw material into the flow type mixer, for example, a method of introducing the aqueous solution of bisulfite and gas into a pipe for introducing the aqueous monomer solution into the flow type mixer, and distributing the reaction raw materials individually The method of directly introducing into the formula mixer and the like can be mentioned. Among these methods, the former method is preferable because the liquid and the gas can be premixed and the gas-liquid dispersibility can be enhanced.

When two or more kinds of monomers are used, an aqueous solution of each monomer can be introduced individually or in a mixture into the flow mixer.

The mixed state of gas and liquid in the flow mixer is an important factor that determines the reactivity of the first polymerization reaction.
In order to stably generate free radicals, it is necessary to improve the contact efficiency of gas-liquid and to create a state of dispersed flow in which fine bubbles are dispersed in the liquid. From this point of view, at the end point of the first polymerization reaction step, the viscosity of the reaction product at 20 ° C. is preferably 700 mPa · s or less, more preferably 400 mPa · s or less. Within such a viscosity range, the gas absorption efficiency to the liquid side becomes high, the molecular weight can be controlled even with a small amount of the initiator, and the formation of an adduct can be suppressed.

When a static mixer is used, the flow rate of the mixed solution of the monomer and the aqueous solution of bisulfite and the flow rate of the gas in the mixer are dispersed within a range that does not cause a pulsating unstable flow state. From the viewpoint of forming a flow state, they are preferably 0.5 m / s or more and 1.0 m / s or more, more preferably 1.0 m / s or more and 3.0 m / s or more.
Such a flow rate can be adjusted, for example, by adjusting the minimum cross-sectional area at the point where the fluid passes in the mixer.

Even when a jet nozzle is used, from the viewpoint of forming a dispersed flow state, the flow rate of the mixed liquid of the monomer and the aqueous solution of bisulfite and the flow rate of the gas in the jet nozzle are preferably 1.0 m / s, respectively. Above and 5m / s
Above, more preferably 3.0 m / s or more and 10 m / s or more. Such a flow velocity can be adjusted, for example, by adjusting the minimum cross-sectional area of the fluid at the location where it passes through the jet nozzle.

When using a pipe stirrer, it is preferable to adjust the rotation speed of the stirring blade and its driving force so that the bubble diameter is 1000 μm or less.

Standard state of gas introduced into the flow mixer
Ratio of volume at (273K, 101.3kPa) and total volume of monomer aqueous solution and bisulfite aqueous solution (value obtained by dividing gas volume by liquid volume; hereinafter referred to as "liquid gas ratio")
Is, depending on the type of the flow mixer, usually, to create a state of dispersion flow, to increase the solubility of the gas in the aqueous solution of the monomer and bisulfite, from the viewpoint of performing a polymerization reaction with high initiator efficiency, preferably Is 1 or more, more preferably 4 or more, and preferably 300 or less, from the viewpoint of reducing the pressure loss in the mixing section and stabilizing the fluidized state and stabilizing the molecular weight of the obtained polymer.
It is more preferably 200 or less. From these viewpoints, the liquid gas ratio is preferably 1 to 300, more preferably 4 to 20.
It is 0.

The residence time of the reaction raw material in the flow-through mixer is preferably 0.05 seconds or more, more preferably 0.1 seconds or more, from the viewpoint of carrying out the initiation reaction with high initiation efficiency, and for very fast redox initiation reaction. Even in such a case, from the viewpoint of being able to suppress the temperature rise due to the heat of polymerization and the pressure loss of the mixer, it is preferably 30 seconds or less, more preferably 10 seconds or less. From these viewpoints, the residence time is preferably within 0.05 to 30 seconds, more preferably within 0.1 to 10 seconds.

The reaction temperature in the first polymerization reaction step is preferably 80 ° C. or lower from the viewpoint of suppressing the branching of the molecular chain of the polymer and the deterioration of hue and suppressing the formation of adducts.
The temperature is more preferably 60 ° C. or lower, and the reaction product obtained is preferably 5 ° C. or higher from the viewpoint of handling as an aqueous polymer solution. From these viewpoints, the reaction temperature is preferably 5 to 80.
C., more preferably 5 to 60.degree.

As the method for controlling the reaction temperature, for example, a method of controlling the polymerization initiation reaction condition in the flow type mixer to control the polymerization rate, a method of removing the heat of polymerization with a cooler or the like can be mentioned. To be

The polymerization rate in the first polymerization reaction step is preferably 30% or more, more preferably 35% or more, from the viewpoint of carrying out the initiation reaction with high initiation efficiency and reducing the production amount of the adduct. It is preferably 90% or less, more preferably 80% or less from the viewpoint of reducing the equipment cost and the amount of gas used and obtaining a polymer of constant quality. From these viewpoints, the polymerization rate is preferably 30 to 90%, more preferably 35 to 80%.

The reaction product, which has passed through the flow-type mixer and started the polymerization reaction, is usually introduced into the second polymerization reaction step by a pipe, but before the introduction into the second polymerization reaction step, heat exchange is performed. It may be passed through a vessel, a storage tank, a gas-liquid separation device, or the like.

Polymerization of the reaction product containing unreacted monomers (hereinafter referred to as "first polymerization reaction product") obtained in the first polymerization reaction step is further carried out in the second polymerization reaction step.

The second polymerization reaction step has at least a gas-liquid mixing mechanism and a temperature control mechanism, and may optionally have a gas supply mechanism, a gas-liquid separation mechanism and a circulation mechanism. Each of these mechanisms is not particularly limited as long as it is one that is usually used in the reaction section for increasing the polymerization rate.

As the gas-liquid mixing mechanism, the same flow-type mixer as that used in the first polymerization reaction step, a stirring tank for performing gas-liquid mixing by an impeller or a nozzle jet, aeration operation, etc.,
Examples thereof include a bubble column in which a gas and a liquid are brought into contact with each other and mixed.
Further, it may be a gas-liquid reaction device capable of performing a gas-liquid mixing operation.

The temperature control mechanism is not particularly limited as long as heat is exchanged, but as a general heat exchanger, a double tube heat exchanger, a multi-tube heat exchanger, a spiral heat exchanger are used. Etc., and the temperature can be adjusted by using a jacket, a coil, or the like attached to the stirring tank.

The gas supply mechanism used as necessary may be the same as that used in the first polymerization reaction step. In addition, in order to compensate for the decrease in gas absorption rate due to the increase in viscosity of the system initiated by the first polymerization reaction, additional supply of gas for increasing the polymerization rate within the range where the pressure loss of the equipment is allowed. Is preferred.

The gas-liquid separation mechanism is not particularly limited, and examples thereof include a cyclone, a falling film gas-liquid separation tower, a gas separation tank having an exhaust valve, and the like. When a gas separation tank is used, it is preferable to install a stirrer in the gas separation tank in order to perform cooling and prevent the monomer concentration from locally increasing. Further, a heat exchanger for condensing water vapor in the gas may be installed in the gas discharge part of the gas-liquid separation mechanism, if necessary.

As for the circulation mechanism, it is sufficient that the circulation system is formed by piping and other devices, and the circulation system may be formed alone or in plural.

As the preferable reaction section used in the second polymerization reaction step, there are provided a reaction section having a flow-through mixer having the above-mentioned mechanism (1) and a stirring tank type reactor having the above-mentioned mechanism (1). Examples of the reaction section, a reaction section in which a loop reactor having the above-mentioned mechanisms (1) to (4) is arranged, and the like.
It is also possible to use a plurality of these reaction parts in combination.

In the second polymerization reaction step, one embodiment in the case of using a reaction section provided with a flow type mixer will be described with reference to FIG.

In FIG. 1, the monomer aqueous solution is supplied from the raw material monomer supply port 1a, the gas is supplied from the gas supply port 2a, and the bisulfite aqueous solution is supplied from the bisulfite aqueous solution supply port 3a.

Each of the supplied components is introduced into the flow-type mixer 4a, and is introduced from the first polymerization reaction product introduction port 5a into the reaction section provided with the flow-type mixer 7a used as the second polymerization reaction step. Be guided. Air is supplied from the gas supply port 6a and transferred to the product receiving tank 9a via the flow-type mixer 7a and the heat exchanger 8a.

First, the reaction raw materials are introduced into the flow mixer 4a to start the first polymerization reaction. Next, the first polymerization reaction product is introduced into the second polymerization reaction step, gas is further supplied from the gas supply port 6a, and the second polymerization reaction is continued while the gas-liquid mixing property is enhanced by the flow mixer 7a. The heat of polymerization generated in the heat exchanger 8a is removed.

From the viewpoint of further increasing the polymerization rate, one or more of the flow type mixers 7a used in the second polymerization reaction step may be arranged. In this case, it is preferable to supplement the gas before each mixer to promote the reaction. Further, from the viewpoint of reducing the pressure loss, a low pressure loss type flow mixer may be sequentially installed as the reaction progresses.

Next, one embodiment in the case of using the reaction section in which the stirring tank type reactor is arranged in the second polymerization reaction step will be described with reference to FIG.

In FIG. 2, the monomer aqueous solution is supplied from the raw material monomer supply port 1b, the gas is supplied from the gas supply port 2b, and the hydrogen sulfite aqueous solution is supplied from the hydrogen sulfite aqueous solution supply port 3b. The supplied components are introduced into the flow-type mixer 4b, and then introduced from the first polymerization reaction step introduction port 5b into the reaction section provided with the stirring tank reactor 8b used in the second polymerization reaction step. . The stirring tank reactor 8b has a gas supply port 9b.
Is provided.

First, the reaction raw materials are introduced into the flow mixer 4b to start the first polymerization reaction. Then, the first polymerization reaction product is introduced into the second polymerization reaction step, degassed through the exhaust port 6b, cooled in the stirred tank reactor 8b equipped with the jacket 7b, and the second polymerization reaction is carried out. . Further, a gas for promoting the reaction is supplied from the gas supply port 9b, and the polymerization rate is increased while performing the aeration and stirring operation.

At this time, the gas supplied from the gas supply port 9b has a bubble diameter of 1000 μm, for example, by a device such as a sintered glass or a perforated plate in order to enhance the gas-liquid contact efficiency.
It is preferable to reduce the size to m or less.

Performing the first polymerization reaction before carrying out the second polymerization reaction greatly improves the control of the molecular weight, which is a drawback thereof, as compared with the conventionally proposed dropping type stirred tank reactor. There is an advantage that can be done.

In the conventional reaction, the monomer, the initiator and the like are dropped directly into the stirred tank type reactor. Therefore, when the monomer concentration is increased to improve the productivity, a high molecular weight product is produced and the molecular weight distribution is also increased. There is a problem of getting bigger.
Therefore, if the amount of the initiator is increased in order to reduce the molecular weight, the problem that the amount of the adduct derived from the initiator increases.

On the other hand, in the present invention, since the first polymerization reaction is carried out before the second polymerization reaction is carried out, the reaction product which has already started the reaction can be introduced into the stirred tank reactor. Therefore, the reaction can be performed in a state where the monomer concentration is substantially low.

As a result, the monomer concentration in the stirring tank can be kept low, and a polymer having a low molecular weight and a narrow molecular weight distribution can be produced with good productivity.

Further, one embodiment in the case of using a reaction section provided with a loop reactor as the second polymerization reaction step in the present invention will be described with reference to FIG.

In FIG. 3, the monomer aqueous solution is supplied from the raw material monomer supply port 1c, the gas is supplied from the gas supply port 2c, the bisulfite aqueous solution is supplied from the bisulfite aqueous solution supply port 3c, and each component is in the flow mixer 4c. And is introduced from the first polymerization reaction product introduction port 5c to the reaction section provided with the loop reactor 6c used as the second polymerization reaction step.

In the loop reactor 6c, a withdrawal port 7c for the reaction product obtained in the second polymerization reaction (hereinafter referred to as "second polymerization reaction product"), a circulation pump 8c, a gas supply port 9c, A flow mixer 10c, a heat exchanger 11c and a gas-liquid separator 12c are arranged.

First, the reaction raw materials are introduced into the flow mixer 4c to start the first polymerization reaction. Next, the first polymerization reaction product is introduced into the second polymerization reaction step, gas for accelerating the reaction is supplied from the gas supply port 9c, and the flow-type mixer 10c further mixes gas and liquid to circulate. The second polymerization reaction is performed by the operation.

The circulating second polymerization reaction product is subjected to removal of the heat of polymerization in the heat exchanger 11c provided in the loop reactor 6c, gas separation in the gas-liquid separator 12c, and recirculation by the circulation pump 8a. To do. Then, from the second polymerization reaction product extraction port 7c provided in a part of the loop reactor 6c, the same amount of the second polymerization reaction product as the first polymerization reaction product introduced into the loop reactor 6c is produced. Polymerization can be continuously performed by extracting the product into the product receiving tank 13c.

In the second polymerization reaction step, examples of the method for increasing the polymerization rate include a method for increasing the mixing performance in the flow-type mixer 10c and a method for increasing the supply amount from the gas supply port 9c. However, increasing the number of passes of the mixing section per average residence time of the second polymerization reaction product in the loop reactor 6c is effective in the circulation operation. The number of passes per average residence time is preferably 5 or more, more preferably 10 or more.

Performing the first polymerization reaction before performing the second polymerization reaction greatly reduces the productivity, which is a drawback thereof, as compared with the case of using a conventionally proposed loop reactor. It has the advantage that it can be improved.

In the conventional reaction, since the monomers, the initiator and the like are directly introduced into the loop reactor, it is difficult to control the molecular weight if the introduction amount is increased to increase the productivity or the concentration thereof is increased. There is also a problem that the amount of unreacted monomer increases. Further, in order to satisfy both the productivity and the quality, it is necessary to lengthen the average residence time in the loop reactor, which causes a problem that the equipment becomes large.

On the other hand, in the present invention, by carrying out the first polymerization reaction before carrying out the second polymerization reaction, it is possible to introduce the reaction product which has already started the reaction into the loop reactor. Therefore, the reaction can be performed in a state where the monomer concentration is substantially low. As a result, the ratio of the amount of the first polymerization reaction product introduced with respect to the circulation flow rate can be increased, so that not only the productivity and quality can be satisfied, but also the equipment can be further downsized. It enables the construction of highly efficient processes. Further, since the average residence time in the loop reactor can be shortened, it is possible to operate with low pressure loss.

The amount of the first polymerization reaction product introduced into the loop reactor in the present invention is preferably 3.3% by weight or more of the circulating flow rate from the viewpoint of productivity, and from the viewpoint of controlling the molecular weight and increasing the polymerization rate. It is preferably 50% by weight or less of the circulation flow rate. From these viewpoints, the introduction amount is preferably 3.3 to 50% by weight of the circulation flow rate. The average residence time in the loop reactor is preferably 1 minute or more from the viewpoint of increasing the polymerization rate, and is preferably 120 minutes or less from the viewpoint of productivity and downsizing of equipment. From these viewpoints, the average residence time is 1 to 120 minutes.

As with the first polymerization reaction step, the reaction temperature in the second polymerization reaction step is from 5 to 5 in the same way as in the first polymerization reaction step from the viewpoint of improving reactivity and quality and facilitating handling as an aqueous polymer solution.
The temperature is preferably 80 ° C, more preferably 5 to 60 ° C. The reaction temperature can be easily adjusted by the temperature control mechanism.

From the viewpoint of improving the quality, it is preferable to continue the reaction until the polymerization rate in the second polymerization reaction step becomes 95% or more. From the viewpoint of further increasing the polymerization rate, the unreacted monomer in the product receiving tank, etc. It is more preferable to perform an aging operation for reducing

The content of unreacted monomers in the aqueous solution of the polymer is preferably 1.0% by weight or less from the viewpoint of improving quality and yield in a 40% by weight aqueous solution of the polymer.
It is more preferably 0.5% by weight or less.

The content of the adduct is preferably 2.0% by weight or less, more preferably 1.0% by weight or less in a 40% by weight aqueous solution of the polymer, from the viewpoint of improving quality and yield.

The weight average molecular weight of the polymer is usually preferably from 100 to 100,000 from the viewpoint of enhancing dispersibility and adsorptivity, and when the polymer is used as a builder for detergents, dispersants, scale inhibitors, etc. Has a weight average molecular weight of 20
It is preferably from 00 to 30,000. The value obtained by dividing the weight average molecular weight by the number average molecular weight (hereinafter referred to as "dispersion index") is preferably 7 or less, more preferably 5 or less.

The solid content in the polymer aqueous solution is preferably 20% by weight or more from the viewpoint of improving productivity.

The polymer may be subjected to post-treatments such as solid content adjustment, pH adjustment, deodorization treatment and decolorization treatment.

[0078]

EXAMPLES Physical properties of the polymers obtained in Examples and Comparative Examples were measured by the following methods.

(1) Measurement of amount of unreacted monomer and adduct and calculation of polymerization rate The amount of unreacted monomer and adduct is measured by HPLC (high performance liquid chromatography), and the amount of unreacted monomer and adduct of known concentration is measured. The concentration in each polymer aqueous solution was calculated from the calibration curve. The polymerization rate is
It was calculated based on the following formula from the amount of unreacted monomer before and after the reaction and the amount of monomer converted to an adduct.

[Polymerization rate] = [(amount of unreacted monomer before reaction)-(amount of unreacted monomer after reaction)-(amount of monomer converted to adduct)] / [amount of unreacted monomer before reaction] ×
100

Regarding the standard adduct (disodium 3-sulfopropionate), Schenck, RTE an
d Danishefski, I., J. Org. Chem., 16, 1683 (1951)
The amount of unreacted monomer was measured by the above-mentioned HPLC and the amount of the polymer was measured by ¹ H-NMR (proton nuclear magnetic resonance method) to determine the purity of the standard adduct.

The HPLC measurement conditions are shown below. Column: Tosoh Corporation, trade name: TSK-GEL ODS-80TS Mobile phase: 0.02 mol / L potassium dihydrogen phosphate with phosphoric acid added
Aqueous solution detector with pH adjusted to 2.5: Ultraviolet detector (wavelength: 210 nm) Column temperature: 30 ° C Flow rate: 1.0 mL / min Sample: Ion-exchanged water was added to the polymer aqueous solution containing 0.8 g of solid content to obtain a total solution. Adjust the volume to 200 mL. Then, 10 μL of this preparation is aliquoted and injected into the column.

(2) Measurement of molecular weight and calculation of dispersion index The molecular weight was measured by GPC (gel permeation chromatography), and the weight average molecular weight and the number average molecular weight were determined by using a conversion standard substance. The dispersion index was calculated from the weight average molecular weight and the number average molecular weight according to the following formula. [Dispersion index] = [weight average molecular weight] / [number average molecular weight]

The GPC measurement conditions are shown below. Mobile phase: 0.1 mol / L potassium dihydrogen phosphate and 0.1 mol / L sodium dihydrogen phosphate aqueous solution / acetonitrile = 90 /
10 (Volume ratio) Detector: Differential refractive index detector Column temperature: 40 ° C Flow rate: 1.0 mL / min Conversion standard substance: Polyacrylic acid [American Standard Corporation (AMERICAN STANDARD CORP)] Sample: Solid content 0.8 Ion-exchanged water is added to the polymer aqueous solution containing g to prepare a total liquid volume of 200 mL. Then, 10 μL of this preparation is aliquoted and injected into the column.

(3) Measurement of Solid Content The aqueous polymer solution was dried in a dryer at 105 ° C. for 2 hours, and the solid content (% by weight) was calculated from the weight before and after the drying.

(4) Measurement of Hue The hue of the polymer aqueous solution is compared with the APHA standard color, and the closest standard color number in the standard color series is the hue of the polymer aqueous solution (AP
HA value).

Example 1 Using the apparatus shown in FIG. 4, 39.0 was used as the first polymerization reaction step.
A weight% sodium acrylate aqueous solution (20 ° C., pH = 6.3, neutralization degree: 95 mol%) and a 35 wt% sodium bisulfite aqueous solution (vs. 5.5 mol% acrylic acid) are supplied by a metering pump and air (air supply) as gas. Compressor with 71.4kg / h [60L / h], 4.89kg / h [3.76L / h], 1.2N
It was introduced into the flow mixer at a flow rate of m ³ / h.

As a flow mixer, a honeycomb plate static mixer (manufactured by Environmental Science Co., Ltd., trade name: Ramond Supermixer, model 03, plate 2 unit), a heat transfer area of 0.3 m as a heat exchanger Liquid gas ratio is 19 (= 1200 [L / h] /63.8 [L / h]) using ² spiral heat exchangers.
And The pressure at the inlet of the flow mixer is 0.45 MPa,
The temperature at the outlet was 60 ° C., and the degree of polymerization at the inlet for the first polymerization reaction product was 68%.

In the second polymerization reaction step, a reaction section (flow mixer) in which 3 / 4B pipe (length: 5.5 m) has two devices arranged in series in order of a flow mixer and a heat exchanger -Heat exchanger-Flow mixer-Heat exchanger) was used. Further, air (air supply and) for accelerating the reaction was supplied in front of each mixer.

Orifice plate type static mixer as a flow type mixer [manufactured by Fujikin Co., Ltd., trade name: Dispersion-kun,
Type: 25D type, number of plates: 15 sets-30 sheets], as a flow type mixer, a lattice plate type static mixer manufactured by the same company (manufactured by Fujikin Co., Ltd., product name: mixed, model: 25M type,
The number of plates: 15 sets-30 plates], and a heat exchanger and a heat transfer area of 0.3 m ² spiral type heat exchanger were used. The flow rate of air was supplied from the front of the mixer, the air supply ^{4.2Nm 3 / h, 3.0Nm 3 /} h of air supplied
And

The reaction product obtained in the first polymerization reaction step is introduced from the first polymerization reaction product introduction port into the flow mixer and the reaction section in which two stages are arranged, and air is supplied and air is generated. Upon receiving the replenishment, the second polymerization reaction was performed, and the obtained second polymerization reaction product was received in the 300 L product receiving tank. After that, the product was aged in the product receiving tank for 0.5 hours.

Sampling was carried out from two points, that is, the outlet of the second polymerization reaction step and the product receiving tank after completion of aging, and the amount of unreacted monomer, the amount of adduct, the molecular weight of the polymer, the solid content and the hue were analyzed, and the polymerization rate and the dispersion index were measured. Was calculated. Sampling at the outlet of the 2nd polymerization step performed 2.0 hours after the start of operation, the amount of unreacted monomer was 1.1% by weight and the amount of adduct was 1.
46% by weight, polymerization rate 95.1%, weight average molecular weight 14700,
The dispersion index was 5.34. The amount of unreacted monomer in the product receiving tank was 0.23% by weight, the amount of adduct was 1.90% by weight, the polymerization rate was 96.7%, the weight average molecular weight was 14980, and the dispersion index was 5.
47, the solid content was 40.2% by weight, and the hue (APHA value) was 20.

Example 2 In Example 1, the number of plate units of the static mixer in the first polymerization reaction step was changed from 2 units to 10 units, and the liquid gas ratio was 19 to 100 (air flow rate 6.38 Nm ³ / h). The same operation as in Example 1 was performed, except that the operation was changed to).

In the first polymerization reaction step, the pressure at the inlet of the flow-type mixer was 1.2 MPa, the temperature at the outlet was 81 ° C., and the polymerization rate was 93%, but the fluid state was unstable and intermittent It became a general flow.

As a result of sampling analysis at the outlet of the second polymerization reaction step, the amount of unreacted monomer was 0.71% by weight, the amount of adduct was 1.52% by weight, the polymerization rate was 95.5%, the weight average molecular weight was 13700, and the dispersion index was It was 7.25. The amount of unreacted monomer in the product receiving tank was 0.39% by weight, the amount of adduct was 1.95% by weight, the polymerization rate was 96.1%, and the weight average molecular weight was 1450.
0, dispersion index 7.68, solid content 39.9% by weight, hue (AP
HA value) was 20.

Example 3 Using the apparatus shown in FIG. 5, 38.6% was used as the first polymerization reaction step.
A weight% sodium acrylate aqueous solution (20 ° C, pH = 6.4, neutralization degree: 97 mol%) and a 35 wt% sodium bisulfite aqueous solution (vs. acrylic acid 5.4 mol%) were used by a metering pump, and air (air supply was used as gas). ) With a compressor of 56.4kg / h [47.4L / h], 3.75kg / h [2.88L / h],
It was introduced into the flow mixer at a flow rate of 0.40 Nm ³ / h.

As the flow-type mixer, the same honeycomb plate static mixer as in Example 1 was used, and the liquid-gas ratio was 8 (= 400 [L
/h]/50.3 [L / h]). The pressure at the inlet of the flow-through mixer was 0.35 MPa, the temperature at the outlet was 52 ° C., and the polymerization rate at the inlet of the first polymerization reaction product was 62%.

In the second polymerization reaction step, the mixture can be cooled by a jacket and an external heat exchanger (heat transfer area: 0.3 m ² spiral type heat exchanger), and a stirring tank type reactor (capacity: 300 L) equipped with an exhaust port is provided. , Turbine blades, 200 r / min) were used, and 64 L of ion-exchanged water was initially charged. Further, aeration and stirring operation for carrying out the second polymerization reaction was carried out while supplying air (air supply: 1.5 Nm ³ / h) for promoting the reaction from the lower part of the stirring tank.

The reaction product obtained in the first polymerization reaction step was dropped into the stirring tank type reactor through the first polymerization reaction product introduction port, and was aerated and stirred, and the second polymerization reaction was carried out. Further, the temperature inside the tank was controlled within the range of 30 ° C ± 5 ° C by the cooling operation. This dropping polymerization operation was continued for 3.0 hours and then aged for 0.5 hours.

After completion of the aging, sampling was carried out from the stirred tank reactor, the amount of unreacted monomer, the amount of adduct, the molecular weight of the polymer, the solid content and the hue were analyzed, and the polymerization rate and the dispersion index were calculated. The amount of unreacted monomer was 0.21% by weight, the amount of adduct was 1.52% by weight, the polymerization rate was 96.3%, the weight average molecular weight was 11020, the dispersion index was 4.85, the solid content was 29.8% by weight, and the hue (APHA value) was 30. .

Example 4 Using the apparatus shown in FIG. 6, 38.6% was used as the first polymerization reaction step.
A weight% sodium acrylate aqueous solution (20 ° C, pH = 6.4, neutralization degree: 97 mol%) and a 35 wt% sodium bisulfite aqueous solution (vs. 3.6 mol% acrylic acid) were used as a gas and air (air supply as air). ) Is 56.4kg / h [47.4L / h], 2.50kg / h [1.92L / h] respectively by the compressor
, 1.0 Nm ³ / h, and introduced into the flow mixer.

As a flow mixer, an orifice plate type static mixer manufactured by Fujikin Co., Ltd. (trade name: dispersion, model: 15D, number of plates: 5 sets-10 plates) was used, and the liquid-gas ratio was 20 ( = 1000 [L / h] /49.1 [L / h]). The pressure at the inlet of the flow-through mixer is 0.25 MPa, the temperature at the outlet is 45 ° C,
The polymerization rate at the inlet of the first polymerization reaction product was 50%.

In the second polymerization reaction step, a loop type reactor (3 / 4B pipe × loop pipe length: 8 m) equipped with a flow type mixer, a heat exchanger, a 50 L gas separation tank having a stirrer and a circulation pump was used. ) Was used to prepare a partially neutralized sodium polyacrylate aqueous solution having a weight average molecular weight of 10,000, a dispersion index of 3.90, and a solid content of 40.0% by weight.
A circulation operation for carrying out the second polymerization reaction was carried out under the conditions of 520 ° C. and 520 L / h.

The reaction product obtained in the first polymerization reaction step was a flow-type mixer installed in a loop-type reactor [orifice plate type static mixer manufactured by Fujikin Co., Ltd. 25D type, number of plates: 3 sets
-6 sheets)], and further mix the gas and liquid with air (air supply: 2.4 Nm ³ / h) to accelerate the reaction, remove the heat of polymerization with a heat exchanger and use a gas separation tank. After deaeration, the second polymerization reaction was carried out by a circulating operation. The circulation pressure was controlled at 0.15 MPa on the discharge side of the circulation pump, the temperature inside the loop reactor was controlled within the range of 40 ° C. ± 3 ° C., and the average residence time inside the loop reactor was 24 minutes. Then, the second polymerization reaction product was received in the 300 L product receiving tank at the same flow rate as the first polymerization reaction product introduced into the loop reactor from the second polymerization reaction product extraction port provided in the gas separation tank.

The above operation was continued for 3.5 hours, and the continuously obtained second polymerization reaction product was received in a 300 L product receiving tank and aged for 0.5 hour. 50L gas separation tank and 30 after aging
Sampling was performed from two locations in the 0 L product receiving tank, and the amount of unreacted monomer, the amount of adduct, the molecular weight of the polymer, the solid content and the hue were analyzed, and the polymerization rate and the dispersion index were calculated.

In sampling of the 50 L gas separation tank at 2.0 hours after the start of operation, the amount of unreacted monomer was 1.
The content was 14% by weight, the amount of adduct was 0.53%, the polymerization rate was 95.3%, the weight average molecular weight was 9800, and the dispersion index was 3.30. The amount of unreacted monomer in the product receiving tank was 0.11% by weight, the amount of adducts was 0.61% by weight, the polymerization rate was 98.8%, and the weight average molecular weight was 1025.
0, dispersion index 3.80, solid content 39.9% by weight, hue (AP
HA value) was 10.

Comparative Example 1 As shown in FIG. 7, in Example 1, the second polymerization reaction of the present invention was not carried out, and 300 L of the first polymerization reaction product was added.
The product was placed in the product receiving tank and aged for 0.5 hours. Sampling in the product receiving tank produced a highly viscous gel, which could not be handled as an aqueous solution.

Comparative Example 2 As shown in FIG. 7, in Example 2, the second polymerization reaction of the present invention was not carried out, and 300 L of the first polymerization reaction product was added.
The product was placed in the product receiving tank and aged for 0.5 hours. In sampling in the product receiving tank, the amount of unreacted monomer was 1.36% by weight, the amount of adduct was 2.05% by weight, the polymerization rate was 92.6%, the weight average molecular weight was 20600, and the dispersion index was 8.56.

Comparative Example 3 As shown in FIG. 8, in Example 3, a 38.6 wt% sodium acrylate aqueous solution and a 35 wt% sodium bisulfite aqueous solution were quantitatively pumped without carrying out the first polymerization reaction of the present invention. By the above, the polymerization reaction was carried out by dropping them directly into the stirred tank reactor for 3.0 hours at flow rates of 56.4 kg / h and 3.75 kg / h, respectively. As for the air required for the reaction, in Example 3, the sum of the air supply used in the first polymerization reaction step (0.40 nm ³ / h) and the supply air supplied from the stirring tank bottom (1.5 Nm ³ / h) Amount of air supply + (1.9Nm ³ /
h) was fed from the bottom of the stirring tank. And after the dropping is completed,
Aged for 0.5 hours.

Sampling was performed from a stirred tank reactor,
When the amount of unreacted monomer, the amount of adduct, the molecular weight of the polymer, the amount of solid content and the hue and the calculation of the polymerization rate and the dispersion index were calculated, the amount of unreacted monomer was 1.05% by weight and the amount of adduct was
4.30% by weight, polymerization rate 87.3%, weight average molecular weight 28100
, Dispersion index 13.56, solid content 29.9% by weight, hue (A
The PHA value) was 50.

Comparative Example 4 As shown in FIG. 9, in Example 4, a 38.6 wt% sodium acrylate aqueous solution, a 35 wt% sodium bisulfite aqueous solution and air were used without carrying out the first polymerization reaction of the present invention. 56.4kg / h, 2.49kg / h and 3.4Nm ^{3 respectively}
It was directly supplied into the loop reactor at a flow rate of / h and the polymerization reaction was carried out by circulating operation. Regarding the air required for the reaction,
In Example 4, the air supply + the total amount of air supply was used (1.0 Nm ³ / h) and the supply to which the air supply to the loop reactor (2.4 Nm ³ / h) in the first polymerization reaction step ( 3.
4 Nm ³ / h) was fed to the loop reactor. Circulation pressure continued to increase immediately after the start of operation, and it became impossible to circulate 1.0 hours after the start of operation. Sampling at the 50L gas separation tank site 0.5 hours after the start of operation, the amount of unreacted monomer was 2.07% by weight, the amount of adduct was 2.53% by weight, the polymerization rate was 89.5%, the weight average molecular weight was 158,000, and the dispersion index was 17.65. there were.

[0112]

According to the production method of the present invention, since the flow mixer is used, even if the amount of the oxygen-containing gas used is greatly reduced, the first polymerization reaction with high initiation efficiency can be performed. It is possible to carry out the reaction, and by introducing the obtained reaction product into the second polymerization reaction step, it is possible to suppress coloring, and to produce a high-quality polymer with a small amount of adducts with high productivity.

Further, by using an aqueous solution containing hydrogen sulfite which is a gas-liquid system and a gas containing oxygen,
It is also possible to prevent blockage in the flow mixer.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing one embodiment of a reaction part provided with a flow-through mixer used in a second polymerization reaction step in the present invention.

FIG. 2 is a schematic explanatory view showing one embodiment of a reaction part provided with a stirring tank type reactor used in the second polymerization reaction step in the present invention.

FIG. 3 is a schematic explanatory view showing one embodiment of a reaction part provided with a loop reactor used in the second polymerization reaction step in the present invention.

FIG. 4 is a schematic explanatory view of an experimental apparatus used in Examples 1 and 2 of the present invention.

5 is a schematic explanatory view of an experimental device used in Example 3. FIG.

FIG. 6 is a schematic explanatory view of an experimental device used in Example 4.

FIG. 7 is a schematic explanatory diagram of an experimental device used in Comparative Examples 1 and 2.

FIG. 8 is a schematic explanatory view of an experimental device used in Comparative Example 3.

FIG. 9 is a schematic explanatory view of an experimental device used in Comparative Example 4.

[Explanation of symbols]

1a Raw material monomer supply port 1b Raw material monomer supply port 1c Raw material monomer supply port 2a Gas supply port 2b Gas supply port 2c gas supply port 3a Hydrogen sulfite aqueous solution supply port 3b Hydrogen sulfite aqueous solution supply port 3c Hydrogen sulfite aqueous solution supply port 4a Flow-through mixer 4b flow mixer 4c flow mixer 5a First polymerization reaction product inlet 5b First polymerization reaction product inlet 5c First polymerization reaction product inlet 6a Gas supply port 6b exhaust port 6c loop reactor 7a Flow mixer 7b jacket 7c 2nd polymerization reaction product extraction port 8a heat exchanger 8b stirred tank reactor 8c circulation pump 9a Product receiving tank 9b Gas supply port 9c gas supply port 10c flow mixer 11c heat exchanger 12c gas-liquid separator 13c Product receiving tank

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazutomo Osaki             1334 Minato Minato, Wakayama Kao Corporation             Within (72) Inventor Kazuki Naito             1334 Minato Minato, Wakayama Kao Corporation             Within F-term (reference) 4J011 DA04 DB03 DB13 DB17                 4J100 AJ02P AJ09Q AK08P AL09Q                       AM15Q CA01 CA04 JA21                       JA57

Claims (4)

[Claims] 1. A monomer is polymerized by introducing (A) an aqueous solution of a monomer containing an α-unsaturated carboxylic acid or a salt thereof, an aqueous solution containing a bisulfite salt, and a gas containing oxygen into a flow mixer. The first polymerization reaction step, and (B)
A method for producing a carboxylic acid-based polymer having a second polymerization reaction step of further polymerizing a reaction product containing an unreacted monomer obtained in the first polymerization reaction step. 2. The polymerization rate in the first polymerization reaction step is 30 to
The production method according to claim 1, which is 90%. 3. In the first polymerization reaction step, the ratio of the volume of the gas containing oxygen in the standard state to the total volume of the aqueous solution of the monomer and the aqueous solution containing bisulfite (liquid gas ratio = volume of gas / volume of gas / The method according to claim 1 or 2, wherein the volume of the liquid) is 1 to 300. 4. In the second polymerization reaction step, from a reaction section in which a flow-type mixer is disposed, a reaction section in which a stirred tank reactor is disposed, and a reaction section in which a loop reactor is disposed. 4. Use of one or more reaction parts selected from the group consisting of
Any one of the production methods.