JP2009242593A - Preparation of (meth)acrylic acid polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for further improving the clay dispersion ability of a detergent builder. <P>SOLUTION: The preparation of a (meth)acrylic acid polymer comprises the steps of obtaining a first polymer by batch type polymerization of a monomer component including a (meth)acrylic acid in the presence of a persulfate and a bisulfite in the polymerization reactor using a polymerization apparatus having a polymerization reactor and a storage means connected with the polymerization reactor, transporting the first polymer to the storage means, washing the polymerization reactor, and obtaining a second polymer by batch type polymerization of a monomer component including a (meth)acrylic acid in the presence of a persulfate and a bisulfite in the polymerization reactor for transporting the second polymer again to the storage means so as to be mixed with the first polymer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a (meth) acrylic acid polymer. In particular, the present invention relates to a method of producing a (meth) acrylic acid polymer that can exhibit excellent performance when used as a detergent builder.

  Conventionally, for example, when washing clothes, synthetic detergents have been widely used. In general, detergent builders (cleaning aids) are added to such synthetic detergents in order to improve the cleaning ability of surfactants in addition to surfactants that exhibit cleaning ability. It is.

  The detergent builders as described above are roughly classified into inorganic builders, polyvalent carboxylates, and polymer carboxylates because of their structures, but because of their superior performance per unit weight, the current mainstream is polymer carboxylic acids. Salt. In addition, as an index of the cleaning effect of the detergent builder, for example, calcium ion scavenging ability and dispersibility of dirt particles such as mud dirt (clay dispersibility) are used for the polymer carboxylate.

  As polymer carboxylates as detergent builders, for example, water-soluble polymers such as unsaturated carboxylic acid (co) polymers such as acrylic acid and methacrylic acid are known.

  In a conventionally known method for producing a (meth) acrylic acid polymer, for example, in addition to one or two or more water-soluble monomer components, a polymerization initiator (for example, persulfate) or a chain transfer agent ( For example, an additive component such as bisulfite is dropped into a solvent (water) heated to the polymerization temperature over a predetermined time, and then polymerization is completed over a certain period of time (aging time). Thereafter, the reaction solution is allowed to cool after completion of polymerization according to the intended use, and a neutralizing agent is gradually added dropwise to the reaction solution to adjust to a predetermined degree of neutralization or pH, so that the desired polymer is in the form of an aqueous solution. (Patent Document 1 and Patent Document 2). In addition, each component used for reaction may be previously prepared in a reaction container as needed (initial preparation).

  The production of such a (meth) acrylic acid polymer (aqueous solution) may be carried out in a continuous manner or in a batch (batch) manner. The polymer aqueous solution produced in a continuous manner is continuously transferred to a storage means such as a tank and stored until the next process such as shipment or commercialization. On the other hand, a polymer (aqueous solution) produced in a batch system is generally transferred to a storage means every time it is produced, mixed with the previous production, and similarly stored.

  By the way, as described above, the polymers (aqueous solutions) produced in a batch system have the same composition regardless of whether they are produced in any batch, and have the same performance (for example, clay when used as a detergent builder). It is a common technical knowledge for those skilled in the art to show dispersibility). Based on such technical common sense, the composition and performance of the polymer (aqueous solution) finally stored in the storage means are the same as the respective polymer aqueous solutions in each batch.

  In addition, when producing a polymer (aqueous solution) in a batch mode, after extracting the polymer (aqueous solution) from a certain batch, usually 0.1% by mass or more of the polymer (aqueous solution) produced immediately before is reacted. It remains in the device. When manufacturing using an external cooling device as described in Patent Document 1, an aqueous solution of 1% by mass or more may remain in the reaction apparatus.

As described above, when the same aqueous polymer solution is repeatedly produced in a batch system, a washing process is not conventionally performed between the batches even though a part of the aqueous solution produced in the previous batch remains. . This is because the performance of the aqueous polymer solution obtained in each batch is considered to be the same as described above. Other reasons why the cleaning process is not performed include the fact that performing the cleaning process directly leads to a decrease in production efficiency and the additional cost required for the treatment of wastewater generated by the cleaning. It is done.
JP 2003-268037 A JP 2004-75971 A

  In recent years, there has been an increasing demand for detergents that can efficiently remove dirt such as clothing. In order to meet such demands, various detergent builders using (meth) acrylic acid polymers have been reported. However, the performance (particularly, clay dispersibility) of conventionally known detergent builders is still unsatisfactory, and there is still a strong demand for the development of detergent builders that can exhibit excellent clay dispersibility.

  Then, an object of this invention is to provide the means which can improve the clay dispersibility of a detergent builder still more.

  In the situation where technical common sense as described in the background art column exists, the present inventors have intensively studied to achieve the above-described object. As a result, it has been surprisingly found that conventional technical common sense is contrary to the fact. That is, conventionally, it has been considered that the composition and performance of each polymer (aqueous solution) obtained in each batch are the same. In contrast, the present inventors have found that the clay dispersibility of the polymer (aqueous solution) obtained in the first batch is remarkably superior to the polymer (aqueous solution) obtained in the second and subsequent batches. It is. The cause of such a phenomenon is not completely clear, but the polymer (aqueous solution) from the previous batch is already present in the reactor before the start of production of the second and subsequent batches. It is assumed that this residual aqueous solution has some influence on the clay dispersibility of the aqueous solution obtained in the next batch.

  Based on such knowledge, the present inventors once washed the reaction apparatus after the completion of the production of the polymer (aqueous solution) in a certain batch when producing the (meth) acrylic acid-based polymer in a batch system. The polymer (aqueous solution) in the previous batch is removed, then the polymer (aqueous solution) is produced again in batches, and the respective polymers (aqueous solution) obtained in each batch are mixed to finally disperse the clay. The inventors have found that a high-quality polymer (aqueous solution) excellent in performance can be produced, and have completed the present invention.

  That is, the method for producing a (meth) acrylic acid polymer of the present invention uses a polymerization apparatus having a polymerization reactor and storage means connected to the polymerization reactor, and in the polymerization reactor, the persulfate and In the presence of bisulfite, a monomer component containing (meth) acrylic acid is batch-polymerized to obtain a first polymer, and the first polymer is transferred to a storage means and then polymerized. The reactor is washed, and then again in the polymerization reactor, the monomer component containing (meth) acrylic acid is batch-polymerized in the presence of persulfate and bisulfite to form a second polymer. And the second polymer is transferred again to the storage means and mixed with the first polymer.

  According to the present invention, there is little variation in the performance of the (meth) acrylic acid polymer produced for each batch, and the polymer has high performance. An acrylic acid polymer can be produced.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  The present invention relates to a method for producing a (meth) acrylic acid polymer using a polymerization apparatus having a polymerization reactor and a storage means connected to the polymerization reactor. A first polymerization step in which a monomer component containing (meth) acrylic acid is polymerized batchwise in the presence of sulfate and bisulfite to obtain a first polymer; and A transfer step of transferring to the storage means, a cleaning step of cleaning the polymerization reactor after the transfer, and after cleaning, (meth) acrylic acid in the presence of persulfate and bisulfite in the polymerization reactor. A second polymerization step of batch-polymerizing the monomer component to obtain a second polymer, and transferring the second polymer to the storage means and mixing with the first polymer. It is a manufacturing method of a (meth) acrylic-acid type polymer including a mixing process. Hereinafter, although the manufacturing method of this invention is demonstrated in detail, the technical scope of this invention should be defined based on description of a claim, and should not be restrict | limited by the following specific form.

[Reactor]
First, a reaction apparatus suitably used for carrying out the production method of the present invention will be described. The reaction apparatus used in the production method of the present invention has a polymerization reactor and storage means connected thereto. There is no restriction | limiting in particular about another form. Hereinafter, a preferred reaction apparatus that can be used in the present invention will be described in detail with reference to FIG.

  The reaction apparatus shown in FIG. 1 has a polymerization vessel 101 as a polymerization reactor and a tank 123 as storage means. The polymerization vessel 101 is used for a polymerization step (including a neutralization step).

  In the polymerization vessel 101, a stirrer 111 is installed. The stirrer 111 prevents the temperature and concentration in the polymerization vessel 101 from being unevenly distributed in the polymerization step (including the neutralization step), so that the polymerization reaction and the neutralization treatment are performed uniformly. It functions as a stirring means for stirring the solution.

  An outer jacket 113 is provided around the outer periphery of the side surface (and also the bottom surface) of the main body of the superposition kettle 101. The outer jacket 113 functions as a temperature adjusting means for adjusting the temperature of the reaction liquid in the polymerization vessel 101 in the polymerization process (including the neutralization process). In the embodiment shown in FIG. 1, an appropriate switching mechanism (not shown) is provided in the outer jacket 113 so that a heat medium can be passed through during the polymerization reaction and a refrigerant can be passed through during the neutralization step.

  By having such an apparatus configuration, it is possible to remarkably shorten the time required for the neutralization process, and to dramatically improve the productivity, and to greatly reduce the manufacturing cost. Therefore, the product can be provided at a lower cost without impairing its performance as compared with the conventional water-soluble polymer product. As a result, the utility value (product value) can be significantly increased in applications such as aqueous dispersants, scale inhibitors, and detergent builders. In particular, the polymerization reaction and the neutralization step are performed using the same reactor (polymerization kettle 101), which is advantageous in that the production time can be shortened and the apparatus can be downsized by sharing the apparatus.

  In addition, it is preferable that a measuring device such as a temperature, pressure, and flow rate necessary for the polymerization step (including the neutralization step), a control device, and the like are appropriately provided.

  When the reaction apparatus has an external circulation path for the reaction liquid and a heat removal device for removing heat from the reaction liquid circulating in the external circulation path, it is possible to efficiently remove the heat of polymerization. According to such a form, it is possible to perform the polymerization reaction under mild conditions as compared with heat removal using the latent heat of the solvent using a condenser and cooling from the outside using a jacket. In addition, strict temperature control is possible. Due to these reasons, since the clay dispersibility of the resulting polymer is improved, the reactor has an external circulation path for the reaction liquid and a heat removal device for removing heat from the reaction liquid circulating in the external circulation path. Is particularly preferred.

  Further, in the embodiment shown in FIG. 1, in addition to the above-described apparatus configuration, an external circulation path 115 is further connected to the lower part of the polymerization vessel 101 (specifically, below the liquid level in the polymerization vessel). Yes. The external circulation path 115 functions as a circulation means for externally circulating the reaction liquid in the polymerization vessel 101 in the polymerization process or the neutralization process. A heat removal device 117 is provided on the external circulation path 115 for cooling the reaction liquid flowing in the path.

  Further, each component of the polymerization composition and each supply from the storage unit (not shown) of the neutralization agent so that each component of the polymerization composition and the neutralizing agent can be supplied into the polymerization vessel 101. The tip nozzle part of the path is provided so as to be located in a space part above the liquid level of the reaction liquid in the polymerization vessel 101. However, the tip nozzle part 121 may be located in the reaction liquid. In FIG. 1, only one supply path 119 and its tip nozzle part 121 are shown for convenience, but in practice, each component (for example, a single component) used for the polymerization can be added so that each component can be added individually. A supply path 119 and a tip nozzle part 121 corresponding to each of a monomer, a polymerization initiator, a chain transfer agent, a neutralizing agent, and the like are provided. In addition to the above-described supply paths, various pumps and valves may be appropriately provided on the distillate circulation path and the external circulation path as necessary.

  In the reaction apparatus of the embodiment shown in FIG. 1, a tank 123 is provided as a storage means for storing the obtained polymer, separately from the polymerization vessel 101. The tank 123 is connected to the other end of a reaction liquid extraction path 125 connected to the bottom surface of the polymerization tank 101. Various pumps and valves can be appropriately installed on the reaction liquid extraction path as necessary. The reaction liquid extraction path 125 functions as a transfer means for transferring the (meth) acrylic acid polymer produced in the polymerization vessel 101 to the tank 123.

  The tank 123 preferably has an internal temperature adjustment mechanism such as an external jacket or a heater. The tank 123 preferably has a stirring device. Examples of such a stirring device include a device that rotates a stirring blade through a shaft, and a device that mixes by circulating a polymer aqueous solution by a pump installed outside.

  As mentioned above, although the reaction apparatus which can be used for the manufacturing method of this invention was demonstrated easily, the specific form of each component which comprises this apparatus, and the specific structure of a distillate circulation path and an external circulation path | route -There is no restriction | limiting in particular about a usage form, For example, conventionally well-known knowledge, such as Unexamined-Japanese-Patent No. 2003-268037, can be referred suitably.

  For example, the polymerization kettle 101 may be provided with a distillate circulation path for liquefying and condensing a distillate distilled from the polymerization kettle during polymerization and returning it to the polymerization kettle again. In such a form, usually, a condenser for liquefying and condensing gaseous distillate flowing in the distillate circulation path is provided on the path. Moreover, the capacitor | condenser may illustrate the form which each connects the introduction path | route for introducing a cooling fluid, and the discharge path for discharging | emitting the cooling fluid after heat exchange.

[Production method]
The production method of the present invention can be summarized as follows. The polymerization is carried out batchwise in a polymerization reactor (polymerization kettle shown in FIG. 1), and the resulting polymer is transferred to storage means (tank shown in FIG. 1). After washing the reactor (polymerization kettle), the next batch was polymerized, the polymer obtained was transferred again to the storage means (tank), and the polymers obtained in multiple batches were mixed and mixed A (meth) acrylic acid polymer is obtained.

  The production method of the present invention essentially includes two continuous batch polymerization steps. The production method of the present invention is characterized in that the polymerization reactor is washed between the two successive polymerization steps, and the final product is obtained by mixing the polymers obtained in the respective polymerization steps. . Of the two successive polymerization steps described above, the first step is also referred to as a “first polymerization step”, and the subsequent step is also referred to as a “second polymerization step”. Further, the polymer obtained in the first polymerization step is also referred to as “first polymer”, and the polymer obtained in the second polymerization step is also referred to as “second polymer”. In addition, in actual industrial scale production, the batch polymerization process is repeated a great number of times, but the first polymerization process and the second polymerization process are those of many consecutive polymerization processes. It means any two consecutive times, and the words “first” and “second” themselves have no special meaning.

  Hereinafter, the production method of the present invention will be described in detail in the order of steps.

[First polymerization step]
In the first polymerization step, a monomer component containing (meth) acrylic acid is polymerized in a batch manner in the presence of persulfate and bisulfite in a polymerization reactor. Thereby, a (meth) acrylic acid polymer (first polymer) is obtained.

  The monomer component used in this step is not particularly limited as long as it is composed of one or more monomers capable of polymerizing the (meth) acrylic acid polymer. It is sufficient that it contains at least (meth) acrylic acid (hereinafter also referred to as “monomer (I)”), but if necessary, a water-soluble monoethylenic copolymer that can be copolymerized with (meth) acrylic acid. A saturated monomer (hereinafter also referred to as “monomer (II)”) and / or another monomer (hereinafter also referred to as “monomer (III)”) may be contained. A monomer here is comprised by a monomer component, Comprising: The solvent which is other components used in superposition | polymerization, an initiator, and other additives are not included.

  Specific examples of the monomer (I) include acrylic acid and methacrylic acid. These may be used alone or in combination. Preferably, acrylic acid is used alone or in the form of a mixture mixed with methacrylic acid at a predetermined ratio.

  The compounding amount of the monomer (I) in the monomer component is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, and still more preferably based on the total amount of the monomer component. Is 90 to 100 mol%. When the blending amount of the monomer (I) is 50 mol% or more, a polymer excellent in chelating ability and dispersing ability can be obtained. On the other hand, about an upper limit, 100 mol%, ie, the whole quantity (meth) acrylic acid, may be sufficient. Furthermore, when acrylic acid and methacrylic acid are used in combination as the monomer (I), the blending amount of methacrylic acid is preferably 5 mol% or less, more preferably, based on the total amount of the monomer components. It is 0.5-4 mol%, More preferably, it is 1-3 mol%. If the blending amount of methacrylic acid is 5 mol% or less, a decrease in the chelating ability of the polymer can be prevented.

  The monomer (I) can be used in the form of a solution (preferably an aqueous solution) of the monomer (I) after being dissolved in a solvent (preferably water) described later. When the monomer (I) is used as a solution (preferably an aqueous solution), the concentration of the monomer (I) in the solution is preferably 10 to 100% by mass, more preferably 30 to 95% by mass. Yes, more preferably 50 to 90% by mass. Here, if the concentration of the monomer (I) solution is 10% by mass or more, a decrease in the concentration of the product is prevented, and transportation and storage are simplified. On the other hand, the upper limit of the concentration is not particularly limited, and may be 100% by mass (that is, the total amount) of monomer (I), that is, no solvent.

  Monomer (II), ie, a water-soluble monoethylenically unsaturated monomer copolymerizable with (meth) acrylic acid, specifically, (meth) acrylic acid of monomer (I) is sodium Salt partially neutralized with an alkali metal such as potassium or potassium, or salt completely neutralized; salt obtained by partially neutralizing monomer (I) with ammonia or organic amines such as monoethanolamine or triethanolamine, or completely Neutralized salt; monoethylenically unsaturated aliphatic monocarboxylic acid such as crotonic acid and α-hydroxyacrylic acid; salt obtained by partially neutralizing the monoethylenically unsaturated aliphatic monocarboxylic acid with an alkali metal, or completely A monoethylenically unsaturated aliphatic monocarboxylic acid such as ammonia or an organic amine such as monoethanolamine or triethanolamine; A salt partially neutralized or completely neutralized with an amine; a monoethylenically unsaturated aliphatic dicarboxylic acid such as maleic acid, fumaric acid or itaconic acid; the monoethylenically unsaturated aliphatic dicarboxylic acid with an alkali metal Partially neutralized salt or completely neutralized salt; salt obtained by partially neutralizing the monoethylenically unsaturated aliphatic dicarboxylic acid with ammonia or organic amines such as monoethanolamine and triethanolamine, or completely neutralized A monoethylenically unsaturated monomer having a sulfonic acid group such as 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, (meth) allylsulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid; A salt obtained by partially neutralizing the monoethylenically unsaturated monomer with an alkali metal, or completely A salt obtained by partially neutralizing the monoethylenically unsaturated monomer with ammonia or an organic amine such as monoethanolamine or triethanolamine, or a salt completely neutralized; (meth) allyl alcohol, 3- Unsaturated monomers containing a hydroxyl group such as methyl-2-buten-1-ol (prenol) and 3-methyl-3-buten-1-ol (isoprenol), and a monomer obtained by addition polymerization of these with alkylene oxide. And the like. However, it is not limited only to these.

  As the monomer (II), one type or two or more types may be appropriately selected from the above-listed compounds as necessary. Further, among the above-mentioned compounds, since they may be particularly excellent in chelating ability, dispersibility, gel resistance, etc., unsaturated aliphatic dicarboxylic acids, unsaturated hydrocarbons containing sulfonic acid groups, and their One or more compounds selected from partially or completely neutralized salts are preferably used.

  The blending amount of the monomer (II) in the monomer component is preferably 0 to 50 mol%, more preferably 0 to 30 mol%, further preferably based on the total amount of the monomer component. Is 0 to 10 mol%. When the amount of monomer (II) is 50 mol% or less, a sufficient amount of monomer (I) is ensured, and as a result, a polymer excellent in chelating ability and dispersibility is obtained. On the other hand, since the monomer (II) is an optional component, the lower limit of the blending amount is 0 mol%. That is, even if the monomer (II) is not used, if it is a homopolymer (homopolymer) or a copolymer (copolymer) based on the monomer (I) component, the advantageous effects that are preferable for various applications are sufficiently expressed. .

  Monomer (II) can also be used in the form of a solution (preferably an aqueous solution) of monomer (II) dissolved in a solvent (preferably water) described later. When the monomer (II) solution (preferably an aqueous solution) is used, the concentration of the monomer (II) in the solution is preferably 10 to 100% by mass, more preferably 20 to 95% by mass. More preferably, it is 30-90 mass%. Here, if the concentration of the monomer (II) solution is 10% by mass or more, a decrease in the concentration of the product is prevented, and transportation and storage are simplified. On the other hand, the upper limit is not particularly limited, and may be 100% by mass (that is, the total amount) of monomer (II), that is, no solvent.

  The monomer (III) other than the monomers (I) and (II) is not particularly limited. For example, hydrophobic monomers such as vinyl acetate, vinyl pyrrolidone, vinyl ethers, styrene, (meth) acrylic acid esters such as methyl (meth) acrylate and ethyl (meth) acrylate can be used. One or more of these monomers (III) can be appropriately selected and used as necessary. When a hydrophobic monomer is used as the monomer (III), the gel resistance of the resulting (meth) acrylic acid polymer may be deteriorated although it is excellent in the dispersibility of the hydrophobic compound. For this reason, it is necessary to restrict | limit the compounding quantity according to a use application.

  When a hydrophobic monomer is blended as the monomer (III), the blending amount of the monomer (III) is preferably less than 40 mol%, more preferably based on the total amount of the monomer components. It is 0-20 mol%, More preferably, it is 0-10 mol%. In other words, the blending amount of the monomer (I) and the monomer (II) combined with a hydrophilic monomer (that is, a hydrophilic monomer containing (meth) acrylic acid of 50 mol% or more) is: Preferably it is 60 mol% or more with respect to the whole quantity of a monomer component, More preferably, it is 80-100 mol%, More preferably, it is 90-100 mol%. When the amount of the hydrophobic monomer as the monomer (III) is 40 mol% or more (= the amount of the hydrophilic monomer combined with the monomer (I) and the monomer (II)) Is less than 60 mol%), the resulting polymer is not water soluble, as disclosed in US Pat. No. 3,646,099. Moreover, there exists a possibility that the (meth) acrylic-acid type polymer excellent in gel resistance cannot be obtained.

  The monomer (III) can also be used in the form of a solution of the monomer (III) after being dissolved in a solvent (preferably containing an organic solvent) described later. When used as a monomer (III) solution, the concentration of the monomer (III) in the solution is preferably 10 to 100% by mass, more preferably 20 to 95% by mass, and still more preferably 30 It is -90 mass%. When the concentration of the monomer (III) solution is 10% by mass or more, a decrease in the concentration of the product is prevented, and transportation and storage are simplified. On the other hand, the upper limit is not particularly limited, and 100% by mass (that is, the total amount) of monomer (III), that is, no solvent may be used.

  In this step, it is preferable to polymerize the monomer components containing the various monomers described above in an aqueous solution. In one embodiment, the aqueous solution includes a solvent, an initiator, and other additives.

  The solvent used in the polymerization reaction system when the monomer component is polymerized in an aqueous solution is preferably an aqueous solvent such as water, alcohol, glycol, glycerin, or polyethylene glycol, and particularly preferably water. These may be used alone or in combination of two or more. Further, in order to improve the solubility of the monomer component in the solvent, an organic solvent can be appropriately added as long as it does not adversely affect the polymerization of each monomer.

  Specific examples of the organic solvent include lower alcohols such as methanol and ethanol; amides such as dimethylformaldehyde; ethers such as diethyl ether and dioxane; Can be.

  The amount of the solvent used is preferably 40 to 200% by mass, preferably 45 to 180% by mass, and more preferably 50 to 150% by mass with respect to the total amount of the monomer components. When the amount of the solvent used is 10% by mass or more, an increase in molecular weight can be suppressed. On the other hand, if the usage-amount of a solvent is 200 mass% or less, the density | concentration fall of the manufactured (meth) acrylic-acid type polymer will be prevented, and another processes, such as solvent removal, will become unnecessary. Note that most or all of the solvent may be charged into the reaction vessel at the beginning of the polymerization. A part of the solvent may be appropriately added (dropped) to the reaction system alone during the polymerization. Alternatively, a monomer component, an initiator component, and other additives may be dissolved in a solvent in advance, and the solvent may be appropriately added (dropped) to the reaction system together with these components during the polymerization.

  In addition, a superposition | polymerization form is not restrict | limited only to the above-mentioned form. For example, suspension polymerization or emulsion polymerization may be employed in addition to the aqueous solution polymerization. Further, from the viewpoint of the reaction apparatus, stirring polymerization, kneader polymerization, or the like can be employed.

  In this step, the polymerization is carried out in the presence of persulfate and bisulfite. During polymerization, persulfate functions as a polymerization initiator. Bisulfite also functions as a chain transfer agent. By using a polymerization initiator / chain transfer agent of these combinations, a sulfonic acid group is quantitatively introduced at the end of the obtained polymer, and in addition to dispersibility and chelate ability, the gel resistance is excellent (meta ) An acrylic acid polymer is obtained. Such a polymer can effectively express the effects suitable for various uses. Moreover, according to such a form, as will be described later, the polymer obtained can be prevented from having an excessively high molecular weight even when the polymerization concentration is high, and a low molecular weight polymer can be produced efficiently.

  Polymerization in the presence of persulfate and bisulfite in this manner is also preferred from the viewpoint of improving the clay dispersibility of the resulting polymer in high hardness water. Furthermore, such a configuration reduces the viscosity of the aqueous solution when the obtained polymer is in the form of an aqueous solution as compared to a polymer of the same molecular weight obtained using another polymerization initiator system. There is a tendency. Therefore, uniform mixing can be achieved when the aqueous polymer solution produced in a separate batch is mixed in the tank, and there is also an advantage that the product performance is stabilized.

  Specific examples of the persulfate include sodium persulfate, potassium persulfate, and ammonium persulfate. Specific examples of the bisulfite include sodium bisulfite, potassium bisulfite, and ammonium bisulfite. In addition, pyrosulfites such as sodium disulfite capable of forming a bisulfite upon hydration may be used as the bisulfite.

  The addition amount of bisulfite is preferably 0.5 to 20 parts by mass, more preferably 1 to 12 parts by mass, and further preferably 2 to 5 parts by mass with respect to 1 part by mass of persulfate. is there. If bisulfite is 0.5 mass part or more with respect to 1 mass part of persulfate, the effect by bisulfite is fully acquired. That is, a sulfonic acid group is sufficiently introduced at the end of the polymer, and a (meth) acrylic acid polymer excellent in gel resistance in addition to dispersibility and chelate ability is obtained. In addition, an increase in the weight average molecular weight of the (meth) acrylic acid polymer is also prevented. On the other hand, if bisulfite is 20 parts by mass or less with respect to 1 part by mass of persulfate, useless consumption of bisulfite in the polymerization reaction system is prevented. As a result, an increase in the amount of sulfurous acid gas generated due to the decomposition of excess bisulfite is also prevented. In addition, the generation of impurities in the (meth) acrylic acid polymer can be suppressed, and deterioration of the polymer performance and precipitation of impurities during holding at low temperatures can be prevented.

  The added amount of persulfate and bisulfite is preferably 2 to 20 g, more preferably 4 to 15 g, with respect to 1 mol of the monomer component, the total amount of persulfate and bisulfite. More preferably, it is 5-12g, Most preferably, it is 5-9g. If the added amount is a value within the above-described range, the generation of sulfurous acid gas and the generation of impurities during the production process can be reduced. Therefore, a sulfur-containing group such as a sulfonic acid group can be sufficiently introduced into the terminal or side chain of the obtained (meth) acrylic acid polymer. In addition, performance deterioration of the obtained (meth) acrylic acid polymer and precipitation of impurities at low temperature holding are prevented. Moreover, if the total addition amount of a persulfate and a bisulfite is 2 g or more, the increase in the molecular weight of the polymer obtained can be suppressed. On the other hand, if the addition amount is 20 g or less, the effects of persulfate and bisulfite corresponding to the addition amount can be obtained, and adverse effects such as a decrease in the purity of the polymer can be prevented.

  The persulfate can be used in the form of a persulfate solution (preferably an aqueous solution) after being dissolved in the above-described solvent (preferably water). When used as a persulfate solution (preferably an aqueous solution), the concentration of persulfate in the solution is preferably 1 to 35% by mass, more preferably 5 to 35% by mass, and still more preferably 10 to 10%. 30% by mass. Here, when the concentration of the persulfate solution is 1% by mass or more, a decrease in the concentration of the product is prevented, and transportation and storage are simplified. On the other hand, if the concentration of the persulfate solution is 35% by mass or less, precipitation of persulfate can be prevented.

  Bisulfite can also be used in the form of a bisulfite solution (preferably an aqueous solution) dissolved in the above-described solvent (preferably water). When used as a bisulfite solution (preferably an aqueous solution), the concentration of bisulfite in the solution is preferably 10 to 40% by mass, more preferably 20 to 40% by mass, and even more preferably 30 to 30%. 40% by mass. Here, if the concentration of the bisulfite solution is 10% by mass or more, a decrease in the concentration of the product is prevented, and transportation and storage are simplified. On the other hand, if the concentration of the bisulfite solution is 40% by mass or less, precipitation of bisulfite can be prevented.

  In this step, another polymerization initiator or chain transfer agent may be used in combination. If necessary, various compounds can be appropriately used as long as the effects of the present invention are not adversely affected.

  Examples of other polymerization initiators (including chain transfer agents) that can be used in combination include 2,2′-azobis (2-amidinopropane) hydrochloride, 4,4′-azobis-4-cyanoparellic acid, azobisiso Azo compounds such as butyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), benzoyl peroxide, lauroyl peroxide, peracetic acid, di-t-butyl peroxide, cumene hydro Organic peroxides such as peroxides, and hydrogen peroxide may be mentioned.

  These compounds can also be used in the form of a solution (preferably an aqueous solution) dissolved in the above-described solvent (preferably water). The concentration of the compound in the solution when used as a solution (preferably an aqueous solution) may be in a range that does not impair the effects of the present invention, and is usually about the same as the above-described persulfate or bisulfite solution. The concentration is appropriately determined.

As other additives that can be used in this step, an appropriate amount of an appropriate additive can be added as long as the effects of the present invention are not affected. Examples of such additives include heavy metal concentration adjusting agents, organic peroxides, H ₂ O ₂ / metal salts, and the like.

Although it does not restrict | limit especially as a heavy metal concentration regulator, A polyvalent metal compound or a simple substance is mentioned. Specifically, vanadium oxytrichloride, vanadium trichloride, vanadyl oxalate, vanadyl sulfate, vanadic acid anhydride, ammonium metavanadate, ammonium sulfate hypo-nosed Das _{[(NH 4) 2 SO 4} · VSO 4 · 6H 2 O], Ammonium sulfate vanadas [(NH ₄ ) V (SO ₄ ) ₂ · 12H ₂ O], copper (II) acetate, copper (II), copper (II) bromide, copper (II) acetyl acetate, cupric ammonium chloride , Copper ammonium chloride, copper carbonate, copper (II) chloride, copper (II) citrate, copper (II) formate, copper hydroxide (II), copper nitrate, copper naphthenate, copper (II) oleate, maleic acid Copper, copper phosphate, copper (II) sulfate, cuprous chloride, copper (I) cyanide, copper iodide, copper (I) oxide, copper thiocyanate, iron acetylacetonate, iron citrate Monium, ferric ammonium oxalate, ammonium iron sulfate, ammonium ferric sulfate, iron citrate, iron fumarate, iron maleate, ferrous lactate, ferric nitrate, iron pentacarbonyl, ferric phosphate Water-soluble polyvalent metal salts such as ferric pyrophosphate; polyvalent metal oxides such as vanadium pentoxide, copper (II) oxide, ferrous oxide, ferric oxide; iron (III) sulfide, iron sulfide (II), polyvalent metal sulfides such as copper sulfide; copper powder and iron powder.

  Use of the heavy metal concentration adjusting agent described above is preferable because the heavy metal ion concentration in the obtained (meth) acrylic acid polymer can be suppressed to about 0.05 to 10 ppm by mass. In addition, if you use a reaction vessel made of glass lining, etc. with excellent corrosion resistance on the inner wall of an existing reaction vessel made of steel or copper base alloy, a SUS (stainless steel) vessel, a stirrer, etc. Under the production conditions of the invention, it is known that heavy metal ions (especially iron ions) elute into the reaction solution from SUS, which is a material of containers and the like. This is advantageous in terms of cost effectiveness. In the present invention, when using a reaction apparatus such as a SUS reaction vessel or a stirring blade, the same effects can be obtained as in the case of adding the heavy metal concentration adjusting agent. Although there is no problem even if the reaction vessel is made of existing steel or copper base alloy, there is a possibility that a lot of heavy metal ions are eluted. In such a case, since a color due to heavy metal appears, an operation for removing such heavy metal ions is necessary, which is uneconomical. Moreover, there is no problem even if the reaction vessel is subjected to glass lining processing or the like, and a heavy metal concentration adjusting agent may be used if necessary.

  The polymerization temperature in this step is usually 25 to 99 ° C, preferably 50 to 95 ° C, more preferably 60 to 92 ° C, and particularly preferably 70 to 89 ° C. When the polymerization temperature is 25 ° C. or higher, problems such as an increase in molecular weight and an increase in impurities are suppressed. In addition, the extension of the polymerization time can be prevented, and the productivity can be prevented from decreasing. On the other hand, if the polymerization temperature is 99 ° C. or lower, the decomposition of bisulfite is suppressed, and the generation of a large amount of sulfurous acid gas and the accompanying increase in the amount of impurities are prevented. In addition, it is possible to suppress an increase in recovery processing cost due to the discharge of sulfurous acid gas outside the system. In addition, a decrease in the effect due to the bisulfite being released as sulfite gas, that is, an increase in molecular weight can be prevented. The “polymerization temperature” means the temperature of the reaction solution in the reaction system.

  The polymerization temperature does not have to be kept substantially constant during the polymerization, and the profile of the polymerization temperature is not particularly limited as long as the effects of the present invention are not impaired. For example, the polymerization may be started from room temperature (may be less than 25 ° C., that is, even if temporarily out of the above-mentioned polymerization temperature range is not outside the technical scope of the present invention). The temperature of the reaction system may be raised to a preset temperature with a proper temperature rise time (or rate of temperature rise), and then the reaction system may be maintained at the preset temperature. Or you may change dripping time for every dripping components, such as a monomer and an initiator. Depending on the manner of dripping, the temperature may be changed (temperature increase or decrease) over time within the above temperature range during the polymerization.

In particular, in the case of a method of starting polymerization from room temperature (room temperature starting method), for example, if the formulation is 300 minutes, it is preferably within 120 minutes, more preferably 0 to 90 minutes, and even more preferably 0 to 60. Allow to reach set temperature in minutes. When the temperature rise time is within such a range, the resulting polymer can be prevented from increasing in molecular weight. In addition, after the temperature of a reaction system reaches preset temperature, it is preferable to maintain a reaction system at the said preset temperature until the completion | finish of superposition | polymerization. Here, the example of the polymerization time is 300 minutes, but when the polymerization time is different, referring to the example, if the temperature increase time is set so that the ratio of the temperature increase time to the polymerization time is the same In the polymerization of the good monomer component, the pressure in the reaction system is not particularly limited. The pressure may be any of normal pressure (atmospheric pressure), reduced pressure, and increased pressure. Preferably, during polymerization, in order to prevent the release of sulfurous acid gas and to reduce the molecular weight, it is preferable to carry out the reaction under normal pressure or with the inside of the reaction system sealed and under pressure. In addition, when polymerization is performed under normal pressure (atmospheric pressure), it is not necessary to provide a pressurizing device or a decompressing device, and it is not necessary to use a pressure-resistant reaction vessel or pipe. For this reason, normal pressure (atmospheric pressure) is preferable from the viewpoint of production cost. That is, optimal pressure conditions may be set as appropriate depending on the intended use of the resulting (meth) acrylic acid polymer.

  The atmosphere in the reaction system may be an air atmosphere, but is preferably an inert atmosphere. For example, the inside of the system is preferably replaced with an inert gas such as nitrogen before the start of polymerization. Thereby, it is suppressed that atmospheric gas (for example, oxygen gas etc.) in a reaction system melt | dissolves in a liquid phase, and acts as a polymerization inhibitor. As a result, the persulfate as a polymerization initiator is prevented from being deactivated and reduced, and the polymer can be further reduced in molecular weight.

  In this step, the polymerization reaction of the monomer component is preferably performed under acidic conditions. By performing the polymerization under acidic conditions, an increase in the viscosity of the aqueous solution in the polymerization reaction system is suppressed. As a result, a low molecular weight (meth) acrylic acid polymer can be produced satisfactorily. In addition, since the polymerization reaction can proceed under a higher concentration condition than before, the production efficiency can be significantly increased. In particular, by reducing the degree of neutralization during polymerization to 1 to 25 mol%, the effect of reducing impurities can be significantly improved. Specifically, the pH of the reaction solution during polymerization at 25 ° C. is preferably 1 to 6, more preferably 1 to 5, and further preferably 1 to 4. When the pH of the reaction solution is 1 or more, problems such as generation of sulfurous acid gas and corrosion of the apparatus can be suppressed. On the other hand, if pH is 6 or less, the fall of the working efficiency of bisulfite will be suppressed and the increase in molecular weight will be prevented. Moreover, it can superpose | polymerize by a high concentration and one step by performing a polymerization reaction under the acidic conditions as mentioned above. Therefore, the concentration step that was necessary in some cases in the conventional manufacturing method can be omitted. Therefore, the productivity of the (meth) acrylic acid polymer is greatly improved, and an increase in manufacturing cost can be suppressed.

  Examples of the pH adjuster for adjusting the pH of the reaction solution during the polymerization include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metals such as calcium hydroxide and magnesium hydroxide. Examples thereof include organic amine salts such as hydroxide, ammonia, monoethanolamine, and triethanolamine. These may be used alone or in combination of two or more. Among these, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferable, and sodium hydroxide is particularly preferable. In the present specification, these may be simply referred to as “pH adjusting agent” or “neutralizing agent”.

  As described above, the degree of neutralization during the polymerization is preferably 1 to 25 mol%. However, when the monomer component used for the polymerization consists only of the monomer (I), the degree of neutralization during the polymerization. Is preferably 2 to 15 mol%, more preferably 3 to 10 mol%. When the monomer component contains monomer (II) in addition to monomer (I), it is possible to charge a part or all of monomer (II) initially, The degree of neutralization during the polymerization is preferably 1 to 25 mol%, more preferably 3 to 10 mol%. If the degree of neutralization during polymerization is within such a range, the monomer (I) and the monomer (II) can be used even if the monomer component is composed only of the monomer (I). ), The (co) polymerization can be carried out most favorably. Further, the increase in viscosity of the aqueous solution of the polymerization reaction system is suppressed to a minimum, and a low molecular weight polymer can be produced satisfactorily. In addition, since the polymerization reaction can proceed under a higher concentration condition than before, the production efficiency can be significantly increased. If the degree of neutralization during polymerization is 1 mol% or more, an increase in the amount of sulfurous acid gas generated is suppressed, and an increase in molecular weight is prevented. On the other hand, if the degree of neutralization during polymerization is 25 mol% or less, the bisulfite chain transfer efficiency is sufficiently ensured, and the increase in molecular weight is similarly prevented. In addition, an increase in the viscosity of the aqueous solution in the polymerization reaction system accompanying the progress of the polymerization is also suppressed. As a result, a low molecular weight polymer is also obtained. Furthermore, the effect of reducing the degree of neutralization described above is sufficiently exhibited, and the generation of impurities can be greatly reduced.

  The neutralization method is not particularly limited. As the neutralizing agent, for example, an alkaline monomer (II) such as sodium (meth) acrylate may be used. Alternatively, an alkali metal hydroxide such as sodium hydroxide may be used. These may be used in combination. The neutralizing agent may be added in the form of a solid or a solution dissolved in an appropriate solvent (preferably water). The concentration of the neutralizing agent in the solution when the solution is used is preferably 10 to 60% by mass, more preferably 20 to 55% by mass, and further preferably 30 to 50% by mass. If the said density | concentration is 10 mass% or more, the density | concentration fall of a product will be prevented and transportation and storage will become easy. On the other hand, if it is 60 mass% or less, since the possibility of precipitation of the neutralizing agent is reduced and the viscosity can be kept low, liquid feeding is also simple.

  In the polymerization, the monomer, persulfate, bisulfite and other additives are usually dissolved in a suitable solvent (preferably the same type of solvent as the liquid to be dripped) in advance. Solutions, persulfate solutions and bisulfite solutions and other additive solutions. Then, it is preferable to perform polymerization while continuously dropping over a predetermined dropping time with respect to each (aqueous) solvent (one adjusted to a predetermined temperature if necessary) charged in the reaction vessel. . Further, a part of the aqueous solvent may be added dropwise later, separately from the initially charged solvent prepared in advance in a container in the reaction system. However, other forms can be employed. For example, regarding the dropping method, it may be dropped continuously or may be dropped in several portions intermittently. Monomer (II) may be initially charged in part or in whole (in this case, it may be considered that the whole or part of the monomer (II) is dropped at once at the start of polymerization). Further, the dropping rate (dropping amount) of the monomer (II) may also be dropped constantly (constant amount) from the start to the end of dropping, or the dropping rate (dropping rate over time depending on the polymerization temperature etc.) The dripping amount) may be changed. Moreover, even if it does not dripping all the dripping components similarly, you may shift the start time and the end time for every dripping component, or you may shorten or extend dripping time. Thus, the manufacturing method of this invention can be changed suitably in the range which does not impair the effect of this invention. Moreover, when each component is dripped in the form of a solution, you may heat a dripped solution to the same extent as the polymerization temperature in a reaction system. In this way, when the polymerization temperature is kept constant, temperature variation is small and temperature adjustment is easy.

  When the monomers (I), (II) and / or (III) are (co) polymerized, the dropping time may be controlled according to the polymerizability of each monomer. For example, when using a monomer having low polymerizability, the dropping time may be shortened. In addition, a part or the whole amount of the monomer may be charged in a container in the reaction system in advance.

  Furthermore, regarding the molecular weight of the polymer, the molecular weight at the initial stage of polymerization greatly affects the final molecular weight. Therefore, in order to reduce the initial molecular weight of the polymer, 5 to 20% by mass of bisulfite or a solution thereof is added (dropping) within 60 minutes, preferably within 30 minutes, more preferably within 10 minutes from the start of polymerization. It is preferable to do. This form is particularly effective when polymerization is started from room temperature.

  In the polymerization, it is more important to lower the polymerization temperature to suppress the generation of sulfurous acid gas and prevent the formation of impurities. For this reason, the total dropping time in the polymerization is preferably 30 to 360 minutes, more preferably 60 to 300 minutes, and further preferably 90 to 240 minutes. If the total dropping time is 30 minutes or more, the effect of persulfate / bisulfite can be sufficiently exhibited. On the other hand, if the total dropping time is 360 minutes (upper limit) or less, a decrease in productivity can be suppressed. The “total dropping time” refers to the time from the start of dropping the first dropping component (not necessarily one component) to the completion of dropping the last dropping component (not necessarily one component).

  Moreover, about the completion | finish time of dripping of a persulfate (solution) among the dripping components in the case of superposition | polymerization, Preferably it is 1 to 30 minutes from the dripping completion time of monomer (I) (solution), More preferably Delay for 1-20 minutes, more preferably 1-15 minutes. Thereby, the amount of monomer components remaining after the completion of polymerization can be reduced, and impurities caused by the remaining monomers can be significantly reduced.

  Here, if completion | finish of dripping of a persulfate (solution) is 1 minute or more later than completion | finish of dripping of a monomer (I) (solution), the remainder of the monomer component after superposition | polymerization completion can be prevented. As a result, the formation of impurities can be effectively and effectively suppressed. On the other hand, if the dropping of the persulfate (solution) is within 30 minutes from the completion of the dropping of the monomer (I) (solution), the remaining of the persulfate or the decomposition product after the polymerization is suppressed. Occurrence of impurities due to the above can be prevented.

  The solid content concentration in the aqueous solution (that is, the polymerization solid content concentration of the monomer) at the time when the dropping of each component is completed and the polymerization reaction in the polymerization reaction system is completed is preferably 35% by mass or more, more preferably. Is 40-70 mass%, More preferably, it is 45-65 mass%. Thus, if the solid content concentration at the end of the polymerization reaction is 35% by mass or more, the polymerization can be carried out at a high concentration and in one stage. Therefore, a (meth) acrylic acid polymer having a low molecular weight can be obtained efficiently. For example, the concentration step that was necessary in some cases in the conventional manufacturing method can be omitted. Therefore, the manufacturing efficiency can be greatly increased. As a result, the productivity of the (meth) acrylic acid polymer is greatly improved, and an increase in manufacturing cost can be suppressed.

  When the solid content concentration is increased in the polymerization reaction system, the conventional method causes a problem that the viscosity of the reaction solution increases remarkably as the polymerization reaction proceeds, and the weight average molecular weight of the resulting polymer also increases significantly. It was. However, when the polymerization reaction using persulfate / bisulfite as an initiator is carried out on the acidic side (pH at 25 ° C. is 1 to 6 and the degree of neutralization is in the range of 1 to 25 mol%), polymerization is performed. An increase in the viscosity of the reaction solution accompanying the progress of the reaction can be suppressed. Therefore, a polymer having a low molecular weight can be obtained even when the polymerization reaction is carried out under a high concentration condition, and the production efficiency of the polymer can be greatly increased.

  Here, the time point when the polymerization reaction is completed means a time point when a predetermined aging time has elapsed (polymerization is completed) after the completion of dropping of all the dropping components.

  The aging time is usually 1 to 120 minutes, preferably 5 to 60 minutes, and more preferably 10 to 30 minutes. If the aging time is 1 minute or longer, aging is sufficient, and the remaining of the monomer component and the accompanying generation of impurities and performance deterioration can be prevented. On the other hand, if the aging time is within 120 minutes, the risk of coloring the polymer solution can be reduced. In addition, it is uneconomical to extend the aging time after completion of polymerization.

  Moreover, since it is within a polymerization reaction period during aging, the above-described polymerization temperature is applied. Therefore, the temperature here may also be maintained at a constant temperature (preferably the temperature at the end of dropping), or the temperature may be changed over time during aging. Therefore, the polymerization time refers to the above total dropping time + ripening time, and means the time required from the first titration start point to the ripening end point.

[Neutralization process]
As described above, in the polymerization step, the polymerization is performed under acidic conditions (the pH of the reaction solution during the polymerization is 1 to 6 and the degree of neutralization during the polymerization is 1 to 25 mol%). Are preferred. In such a form, after the polymerization is completed, by appropriately adding an appropriate alkali component as a post-treatment, the resulting (meth) acrylic acid polymer is partially or completely neutralized to obtain a polymer. The neutralization degree (final neutralization degree) is set to a predetermined range.

  The final neutralization degree of the polymer is not particularly limited because it varies depending on the intended use, and can be set in a very wide range of 1 to 100 mol%. For example, when used as a detergent builder for a weakly acidic detergent said to be gentle to the skin, it may be used without being neutralized while remaining acidic. Moreover, when using for neutral detergent, an alkaline detergent, etc., you may neutralize with an alkali component as a post-process, and you may use after neutralizing to 90 mol% or more of neutralization degree. In particular, the final neutralization degree of the polymer when used as an acidic polymer is preferably 1 to 75 mol%, more preferably 5 to 70 mol%. Further, the final neutralization degree of the polymer when used as a neutral / alkaline polymer is preferably 75 to 100 mol%, more preferably 85 to 99 mol%. In addition, when the final neutralization degree of the polymer when used as a neutral / alkaline polymer is 99 mol% or less, coloring of the aqueous polymer solution can be prevented.

  Examples of the alkali component that can be used in the neutralization step include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide; ammonia, Examples thereof include those represented by organic amines such as monoethanolamine, diethanolamine, and triethanolamine. As for the said alkali component, only 1 type may be used independently and 2 or more types may be used together.

  Although the supply form of the neutralizing agent is not particularly limited, it is dissolved in an appropriate solvent and supplied in the form of a neutralizing agent solution from the viewpoint of preventing a large amount of heat of neutralization from being generated locally. It is preferable. However, you may supply only with a neutralizing agent (namely, a solvent-free form). The solution concentration when used as a neutralizer solution is appropriately determined according to the purpose of use, and is not particularly limited.

  The method for supplying the neutralizing agent is also not particularly limited, but a method in which the neutralizing agent is supplied into the polymerization reactor through the supply path of the neutralizing agent, preferably dripped continuously from the tip nozzle portion is preferable. When there are two or more neutralizing agent components, it is preferable to supply each neutralizing agent component through separate supply paths. However, separate supply paths may be joined in the middle, and each neutralizer component may be mixed and supplied into the reactor, or each neutralizer component may be mixed in advance in the storage tank of the supply source. Alternatively, the supply may be made through one supply path.

  The supply rate of the neutralizing agent is appropriately determined according to the purpose of use, and is not particularly limited.

  While the neutralization agent is supplied and the neutralization degree of the reaction solution is adjusted, the temperature of the reaction solution in the reactor is not sufficient to remove the generated heat of neutralization, and a large amount of reaction solution is evaporated. The reaction temperature is appropriately determined so that bubbles do not mix with the reaction solution and adhere to the internal circulation or the wall surface of the external circulation path or external heat removal device, resulting in a decrease in heat exchange efficiency. There is no particular limitation.

  In addition, it is also possible to set a final neutralization degree by desalting the (meth) acrylate polymer obtained by the conventional complete neutralization method or the partial neutralization method. However, in this case, the addition of the desalting step complicates the manufacturing process and increases the manufacturing cost. For this reason, a use application may be restrict | limited.

In addition, when the reaction system is used without being neutralized as described above, since the inside of the reaction system is acidic, toxic sulfurous acid gas (SO ₂ gas) remains in the atmosphere in the reaction system. There may be. In such a case, it is preferable to decompose by adding a peroxide such as hydrogen peroxide, or to expel it by introducing (blowing) air or nitrogen gas.

  As described above, the reaction apparatus used for carrying out the production method of the present invention preferably has an external circulation path and a heat removal apparatus. Therefore, it is preferable to perform the polymerization process and a part or all of the neutralization process in the same reaction apparatus because of restrictions on the apparatus. When the polymerization step and the neutralization step are performed in separate reactors, the equipment cost increases, and the product cost may increase accordingly.

[Transfer process]
Next, the (meth) acrylic acid polymer (aqueous solution) produced in the above-described polymerization step (including the neutralization step) is transferred from the polymerization vessel 101 to the tank 123. For the transfer, a reaction liquid extraction path 125 as a transfer means is used. The transferred polymer (aqueous solution) is stored in a tank (possibly mixed with the already stored polymer (aqueous solution)).

  There is no restriction | limiting in particular about the specific form of a transfer process, A conventionally well-known knowledge can be referred suitably. As an example, the temperature of the polymer to be transferred (preferably an aqueous polymer solution) (temperature when flowing into the tank) is preferably 20 to 90 ° C, more preferably 30 to 80 ° C, Preferably it is 40-70 degreeC. If the temperature of the polymer (aqueous solution) to be transferred is 20 ° C. or higher, the viscosity of the aqueous solution can be kept low, and an increase in the burden on transfer means such as a pump can be prevented. On the other hand, if the temperature of the transferred polymer (aqueous solution) is 90 ° C. or lower, coloring of the transferred polymer (aqueous solution) can be prevented. In addition, a transfer process may be performed after adjusting the reaction liquid after a polymerization process (a neutralization process is included) to the temperature within the said range, and you may adjust to the temperature within the said range with transfer.

  In the transfer step, it is usually attempted to extract as much polymer (aqueous solution) as possible from the polymerization vessel 101. However, since the reactor for carrying out the polymerization process using the reactor has a certain size, it is impossible to completely extract all the polymer (aqueous solution) from the polymerization vessel 101. In other words, it is inevitable that a certain amount of polymer (aqueous solution) remains in the reaction apparatus after the transfer step. The polymer (aqueous solution) remains in such a reaction apparatus in the form of the reaction apparatus shown in FIG. 1 having various components (distillate circulation path 103 and external circulation path 115) in addition to the polymerization vessel 101. This is particularly noticeable when used. The amount of the polymer (aqueous solution) remaining in the reaction apparatus after the transfer step may vary depending on the apparatus, but is usually 0.1% by mass or more based on the polymer aqueous solution produced immediately before.

  Here, as explained in the background art section, the polymer (aqueous solution) produced in a batch system has the same composition regardless of whether it is produced in any batch, and thus shows the same performance. This is the common technical knowledge for those skilled in the art. From the viewpoint of such technical common sense and cost, conventionally, a cleaning process between batches has not been performed.

  Despite the conventional situation, the present inventors, contrary to conventional common sense, once washed the reactor after completion of the production of the aqueous polymer solution in a batch, and then again in the batch the aqueous polymer solution. Was tried to mix each polymer aqueous solution obtained in each batch. As a result, as shown in the examples described later, the present invention is completed with the surprising result that a high-quality polymer (aqueous solution) having extremely excellent clay dispersibility can be finally produced. It came to.

  In the present invention, the acrylic acid polymer aqueous solution is most preferably transferred directly to the tank after the polymerization step (including the neutralization step). However, 1) One batch or part of an acrylic acid polymer aqueous solution is temporarily stored in a relay tank (not shown) for the purpose of temperature control, etc., and then transferred to the tank, 2) In the relay tank, a form in which two batches or more are premixed and then transferred to the tank can also be included in the technical scope of the present invention. The relay tank used in such a form may be provided with an internal temperature adjusting mechanism such as an external jacket or a heater, a stirring device, or the like.

[Washing process]
As described above, in the production method of the present invention, the reactor is washed after the transfer of the first polymer obtained in the first polymerization step and before the second polymerization step. There is no particular limitation on the specific form of washing, and the form conventionally used for washing the reactor after completion of all batches can be similarly employed.

  An example of a specific form of washing will be described. First, the washing portion may be at least a part of the reaction apparatus, but at least the polymerization vessel 101 is preferably washed. More preferably, the external circulation path is also cleaned, and even more preferably, the supply path is cleaned. Washing the external circulation path and the supply path is preferable because the clay dispersibility of the obtained polymer is improved.

  Although there is no restriction | limiting in particular about the composition of a washing | cleaning liquid, Preferably water can be used. Moreover, the temperature of a washing | cleaning liquid is about 20-90 degreeC normally. Although the washing time is not limited, it is usually about 10 to 60 minutes. In some cases, the cleaning may be performed using steam.

[Second polymerization step]
The second polymerization step is a polymerization step performed after the above-described first polymerization step / first polymer transfer step / washing step, and its specific form is described for the above-described first polymerization step. The above forms can be similarly adopted. Therefore, detailed description is omitted here. The types and composition of monomer components and persulfate / bisulfite used in the second polymerization step, and various conditions in the polymerization reaction and neutralization step were the same as those in the first polymerization step. Or at least part of them may be different. However, from the viewpoint of stably obtaining a polymer (aqueous solution) product having the same composition, the same raw material composition and reaction conditions as those in the first polymerization step are also employed in the second polymerization step (implementation described later). See Examples 1 and 2.)

[Mixing process]
In this step, the second polymer (aqueous solution) obtained in the second polymerization step is transferred to the tank 123 by the same method as described above, and the first polymer that has already been stored in the tank. It is mixed with coalescence (aqueous solution). The polymer (aqueous solution) mixture obtained by this mixing is the final product produced by the production method of the present invention. Hereinafter, the mixture is also simply referred to as “(meth) acrylic acid polymer (aqueous solution)”.

  Since the specific form of the transfer is as described above, detailed description is omitted here. Moreover, there is no restriction | limiting in particular also about the specific form of mixing, A conventionally well-known knowledge can be referred suitably. After the second polymer (aqueous solution) is transferred to the tank and mixed with the first polymer, it may be left as it is, or in some cases, an appropriate stirring means is installed in the tank and stirred appropriately. Uniform mixing may be achieved.

  As described above, the words “first” and “second” have no special meaning. Thus, for example, when the “second polymerization step” is followed by a transfer step and a washing step, followed by a “further polymerization step”, the “second polymerization step” is another “ The “first polymerization step” can be interpreted, and the “further polymerization step” can be interpreted as another “second polymerization step” corresponding thereto. Therefore, for example, as described in Examples 1 and 2 described later, when 10 batch polymerization steps are performed so as to sandwich the transfer step and the washing step between the respective batch polymerization steps, The two continuous polymerization steps (for example, the first polymerization step and the second polymerization step, the second polymerization step and the third polymerization step, and so on) It corresponds to “the first polymerization step” and “the second polymerization step”.

[(Meth) acrylic acid polymer]
The (meth) acrylic acid polymer obtained by the production method of the present invention may be in the form of a pure polymer except that inevitable impurities can be mixed, or obtained by aqueous solution polymerization as described above. In some cases, it may be in the form of an aqueous solution.

  There is no restriction | limiting in particular about the weight average molecular weight (Mw) of the polymer manufactured by this invention. However, the weight average molecular weight of the polymer is preferably 1000 to 100,000, more preferably 1500 to 50000, still more preferably 2000 to 30000, and particularly preferably 2500 to 10,000. In the production method of the present invention, it is possible to obtain a polymer outside the range of these weight average molecular weights. However, if the weight average molecular weight is a value within such a range, high chelating ability and high dispersibility are compatible. sell. In addition, as a value of a weight average molecular weight (Mw), the value obtained by the measuring method as described in the Example mentioned later shall be employ | adopted.

  The (meth) acrylic acid polymer (aqueous solution) produced by the production method of the present invention exhibits excellent clay dispersibility. Specifically, the clay dispersibility of the obtained polymer (aqueous solution) is preferably 0.63 or more, more preferably 0.65 or more, and further preferably 0.69 or more. In addition, as a value of a clay dispersibility, the value obtained by the measuring method as described in the Example mentioned later shall be employ | adopted.

  In the present invention, as described above, the amount of residual monomer in the resulting polymer is reduced by performing an operation such as delaying the end of dropping of persulfate for a certain time from the end of dropping of monomer. It is possible. Specifically, it can be 5000 mass ppm or less in terms of pure content, and can be 4000 mass ppm or less in a preferred embodiment.

  In the present invention, as described above, it can be obtained by adding an unnecessary component other than a monomer such as an initiator / chain transfer agent or performing an operation such as polymerization at an appropriate polymerization temperature. It is also possible to reduce the amount of impurities (excluding residual monomers) in the polymer. Specifically, depending on the intended use, there are components that may be regarded as impurities or useful components, so it is difficult to define them unambiguously. preferable. In addition, a heavy metal component etc. correspond as a component from which it considers as an impurity or a useful component depending on a use application. For example, when used in a detergent composition containing a bleaching agent, it is an impurity to decompose the bleaching agent even in the presence of a trace amount of heavy metal component, but in a detergent composition not containing a bleaching agent, a trace amount of heavy metal component The amount of peroxide, which is another impurity remaining due to the presence of, can be reduced, and the problem of skin irritation caused by the peroxide can be solved, so that it functions as an active ingredient.

[Usage]
The polymer (aqueous solution) obtained by the production method of the present invention makes use of its characteristics, such as detergent builder, detergent composition, inorganic pigment dispersant, scale inhibitor, chelating agent, fiber treatment agent, wood pulp bleaching aid, etc. It can be used for What is necessary is just to mix | blend another raw material according to each use purpose at the time of use for various uses.

  The detergent builder which is a suitable use of the polymer (aqueous solution) obtained by the manufacturing method of this invention should just contain the said polymer (aqueous solution). Thereby, the water-soluble detergent builder which can express the extremely superior dispersibility, chelate ability, and gel resistance inherent to the (meth) acrylic acid polymer can be provided at a very low cost.

  In addition, with respect to the other blending components and blending ratios other than the polymer (aqueous solution) in the detergent builder of the present invention, there is no particular limitation, based on various components and blending ratios that have been effectively applied to the detergent builder conventionally, As long as the effects of the detergent builder are not impaired, it can be applied (utilized) as appropriate. However, the polymer (aqueous solution) obtained by the production method of the present invention is preferably used as a detergent builder as it is.

  The above-mentioned detergent builder can be mixed with a detergent component such as a surfactant capable of exerting a cleaning ability to constitute a detergent composition. The blending amount of the detergent builder in the detergent composition is preferably 0.1 to 20% by mass with respect to the detergent composition in terms of solid content of the polymer (aqueous solution). If the blending amount of the polymer is 0.1% by mass or more, the effect as a detergent builder can be sufficiently exhibited. On the other hand, when the blending amount of the polymer is 20% by mass or less, an effect corresponding to the addition amount is obtained, which is economically preferable. Moreover, the compounding quantity of surfactant is preferable in it being 1-70 mass% of the whole detergent composition, and an enzyme may be mix | blended in the range of 5 mass% or less depending on the case. If the amount of the surfactant, which is the main component of the detergent composition, is a value within such a range, the balance with other components is excellent, and the cleaning power of the detergent composition can be sufficiently secured. Moreover, about the compounding quantity of an enzyme, the addition effect will fully be acquired if it is 5 mass% or less, and it is economically preferable.

  Specific types of surfactants include anionic surfactants, nonionic surfactants, amphoteric surfactants and cationic surfactants.

  Examples of the anionic surfactant include, but are not limited to, alkylbenzene sulfonate, alkyl or alkenyl ether sulfate, alkyl or alkenyl sulfate, α-olefin sulfonate, α-sulfo fatty acid or ester salt, alkane sulfone. Examples thereof include acid salts, saturated or unsaturated fatty acid salts, alkyl or alkenyl ether carboxylates, amino acid type surfactants, N-acyl amino acid type surfactants, alkyl or alkenyl phosphate esters or salts thereof.

The nonionic surfactant is not particularly limited, and examples thereof include polyoxyalkylene alkyl or alkenyl ether, polyoxyethylene alkylphenyl ether, higher fatty acid alkanolamide or alkylene oxide adduct thereof, sucrose fatty acid ester, alkylglycoxide fatty acid. Examples of amphoteric surfactants include glycerin monoesters and alkylamine oxides, but are not particularly limited, and examples include carboxy-type or sulfobetaine-type amphoteric surfactants, and cationic surfactants include Although not limited, For example, a quaternary ammonium salt etc. are mentioned.

  As an enzyme mix | blended with a detergent composition, protease, lipase, a cellulase etc. are mentioned, for example. In particular, proteases, alkaline lipases and alkaline cellulases that are highly active in the alkaline cleaning solution are preferred.

  Furthermore, for the detergent composition, known alkali builder, chelate builder, anti-redeposition agent, soil release agent, color transfer inhibitor, softener, fluorescent agent, bleaching agent, bleaching aid, fragrance, etc. Ingredients commonly used in other detergent compositions may be blended.

  Examples of the alkali builder include silicate, carbonate, sulfate and the like. As the chelate builder, zeolite, diglycolic acid, oxycarboxylate, EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), citric acid and the like can be used as necessary. Or a well-known water-soluble polycarboxylic acid-type polymer may be used in the range which does not impair the effect of this invention.

  The water treatment agent preferably comprises only the (meth) acrylic acid polymer (aqueous solution) provided by the present invention. However, if necessary, it may be in the form of a composition in which polymerized phosphate, phosphonate, anticorrosive, slime control agent, and chelating agent are blended as other compounding agents. In any case, it is useful for scale prevention in a cooling water circulation system, a boiler water circulation system, a seawater desalination apparatus, a pulp digester, a black liquor concentration tank, and the like. Moreover, you may contain a well-known water-soluble polymer in the range which does not affect performance and an effect.

  The pigment dispersant preferably comprises only the (meth) acrylic acid polymer (aqueous solution) provided by the present invention. However, if necessary, it may be in the form of a composition in which polymerized phosphoric acid and its salt, phosphonic acid and its salt, and polyvinyl alcohol are blended as other compounding agents. In any case, the pigment dispersant exhibits good performance as a dispersant for inorganic pigments such as heavy or light calcium carbonate and clay used for paper coating. For example, by adding a small amount of a pigment dispersant to an inorganic pigment and dispersing it in water, a high-concentration calcium carbonate slurry that has low viscosity and high fluidity and good performance over time. A high concentration inorganic pigment slurry can be produced. The amount of the pigment dispersant used is preferably 0.05 to 2.0 parts by mass with respect to 100 parts by mass of the pigment. If the amount used is 0.05 parts by mass or more, a sufficient dispersion effect can be obtained. On the other hand, if it is 2.0 mass parts or less, the effect corresponding to the addition amount will be acquired and it is economically preferable.

  As the fiber treatment agent, the (meth) acrylic acid polymer (aqueous solution) provided by the present invention may be used alone, but additives such as a dye, a peroxide, and a surfactant are blended. It can also be used as a composition. As said additive, what is normally used for a fiber treatment agent is mentioned. The blending ratio of the polymer and the additive is not particularly limited, but the additive is preferably 0.1 to 100 parts by weight, more preferably 0.2 to 80 parts by weight with respect to 1 part by weight of the polymer. Parts, more preferably 1 to 50 parts by mass. If the compounding amount of the additive is 0.1 parts by mass or more, a sufficient additive effect can be obtained. On the other hand, if it is 100 mass parts or less, the effect by containing a polymer is fully ensured. Moreover, the fiber treatment agent containing the said polymer may also contain other polymers other than the said polymer in the range which does not inhibit performance and an effect. The blending amount of the polymer provided by the present invention in the fiber treatment agent is not particularly limited, but is preferably 1 to 100% by mass, more preferably 5 to 100% by mass with respect to the total amount of the fiber treatment agent. %. Although the woven fabric which can use the woven fabric treatment agent mentioned above is not specifically limited, For example, Cellulosic fibers, such as cotton and hemp; Chemical fibers, such as nylon and polyester; Animal fibers, such as wool and silk; Synthetic fibers and their woven fabrics and blended products are exemplified. When the fiber treatment agent described above is used in the refining process, it is preferable to blend the polymer provided by the present invention with an alkali agent and a surfactant. When applied to the bleaching step, it is preferable to further add a peroxide and a silicic acid-based agent such as sodium silicate as a decomposition inhibitor for the alkaline bleaching agent in addition to the polymer.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

  The physical properties of the polymers obtained in Examples and Comparative Examples were measured by the following methods.

(Solid content measurement)
The solid content was a non-volatile content after 1 g of the (co) polymer solution was dried at 170 ° C. for 1 hour using a hot air dryer. Specifically, 1 g of (co) polymer solution was collected in an aluminum cup (mass is A (g)) weighed in advance and weighed together with the cup (mass is B (g)). And then diluted for 1 hour in a hot air dryer at 170 ° C. Thereafter, the sample was allowed to stand in a desiccator for 5 minutes and then weighed (the mass was C (g)). Solid content was computed according to following Numerical formula 1.

[Weight average molecular weight (Mw)]
It measured under the following conditions by GPC (gel permeation chromatography).

Column: G-3000PWXL (manufactured by Tosoh Corporation)
-Column temperature: 35 ° C
-Mobile phase: 34.5 g of disodium hydrogen phosphate dodecahydrate and 46.2 g of sodium dihydrogen phosphate dihydrate (both reagents were special grades. The reagents used in the following various measurements were All were special grades.) Pure water was added to make a total amount of 5,000 g, and then filtered through a membrane filter with a filter pore size of 0.45 μm. Detector: UV (wavelength: 214 nm)
・ Flow rate: 0.5mL / min
・ Calibration curve: Sodium polyacrylate standard sample
[Clay dispersibility]
1) First, a glycine buffer solution was prepared by adding ion exchange water to 60.56 g of glycine, 52.6 g of sodium chloride, and 60 mL of a 1 mol / L sodium hydroxide aqueous solution to make 600 g.

  2) Further, 0.3268 g of calcium chloride dihydrate and 60 g of the glycine buffer solution prepared in the above 1) were weighed, and ion-exchanged water was further added to make 1000 g to prepare a dispersion.

  3) On the other hand, an aqueous solution of the polymer obtained (adjusted to pH 7) was prepared so as to be 0.1% by mass in terms of solid content.

  4) Into a test tube, put 0.3 g of JIS test powder I, 8 types (Kanto loam, fine particles: manufactured by Japan Powder Industrial Technology Association), 27 g of the dispersion prepared in 2) above, 3 g of the aqueous solution prepared in 3) was added. At this time, the calcium concentration of the test solution was 200 ppm in terms of calcium carbonate.

  5) After sealing the test tube with parafilm, it was shaken lightly so that the clay was dispersed throughout, and then further shaken up and down 20 times.

  6) The test tube was left in a place not exposed to direct sunlight for 20 hours, and then 5 mL of the supernatant of the dispersion was collected with a whole pipette.

  8) Absorbance (ABS) of this liquid was measured with a cell having a wavelength of 380 nm and 1 cm using a UV spectrometer, and this value was defined as clay dispersibility.

<Example 1>
Polymerization kettle (made by SUS, volume 2 m ³ ), thermometer, stirrer (paddle blade), external distillate circulation path, jacket, supply path (for polymerization composition and neutralizing agent) And a reaction device (see FIG. 1) having an external circulation cooling device (external reaction liquid circulation path and heat removal device). In addition, the inside of the reactor was washed.

  Subsequently, 175.0 kg of pure water and 0.0081 kg of Mole salt were poured into the polymerization kettle from the tip nozzle through each supply path. Thereafter, the temperature of the aqueous solution was raised to 85 ° C. with an external jacket under normal pressure while stirring the aqueous solution in the polymerization kettle.

  Next, 80 mass% acrylic acid aqueous solution (hereinafter also referred to as “80% AA”) 450.0 kg, 48 mass% sodium hydroxide aqueous solution (hereinafter also referred to as “48% NaOH”) 20.83 kg, 35 mass% sulfurous acid 67.1 kg of aqueous sodium hydrogen solution (hereinafter also referred to as “35% SBS”) and 60.0 kg of 15 mass% sodium persulfate aqueous solution (hereinafter also referred to as “15% NaPS”) are respectively supplied from the tip nozzle through separate supply paths. 80% AA and 48% NaOH for 180 minutes, 35% SBS starts dropping at the same time as 80% AA for 175 minutes (ie, until 5 minutes before the end of dropping 80% AA), 15 % NaPS starts dropping at the same time as 80% AA and drops over 185 minutes (that is, until 5 minutes after the end of dropping 80% AA). It was. The dropping of each component was continuously performed at a constant dropping rate. After completion of all the dropwise additions, the reaction system was kept at 85 ° C. for another 30 minutes for ripening to complete the polymerization. During the polymerization, the reaction solution was cooled by a heat removal device while always circulating the reaction solution externally. The degree of neutralization of sodium polyacrylate in the reaction solution after polymerization was 5.0%, and the solid content concentration of the reaction solution was 51.5% by mass.

  Thereafter, the reaction solution was cooled to 50 ° C., and 383.3 kg of a 48 mass% sodium hydroxide aqueous solution was gradually dropped from the tip nozzle into the polymerization vessel through the supply path over 60 minutes to neutralize the polymer. During the neutralization of the polymer, the reaction solution was cooled by a heat removal device while always circulating the reaction solution externally.

  Thus, 1156.31 kg of sodium polyacrylate aqueous solution (1-1) was obtained. The degree of neutralization of sodium polyacrylate in the obtained aqueous solution (1-1) was 97.0%, and the solid content concentration (theoretical value) of the aqueous solution (1-1) was 43.17% by mass. . In addition, the method of obtaining the sodium polyacrylate aqueous solution (1-1) using the apparatus and polymerization prescription described above is also referred to as “Synthesis Example 1”. The polymerization formulation of Synthesis Example 1 is shown in Table 1 below.

  The obtained sodium polyacrylate aqueous solution (1-1) was extracted from the polymerization kettle and transferred to a tank connected to the polymerization kettle. By subtracting the amount of the aqueous solution (1-1) extracted from the polymerization kettle from the amount of the aqueous solution (1-1) produced in Synthesis Example 1, the aqueous solution (1-1) remaining in the reaction apparatus after transfer When the amount was calculated, it was 11.6 kg (1.0 mass% with respect to the aqueous solution (1-1) manufactured by the synthesis example 1). Specifically, the amount of the remaining aqueous solution was finely adjusted by introducing the extracted aqueous solution (1-1) into the polymerization kettle in an insufficient amount so that the above-described difference value was 11.6 kg.

  Subsequently, the reactor was washed with water. Specifically, external circulation and agitation were performed while adding water to the extent that the stirring blades were sufficiently applied, and the polymerization kettle and the external circulation path were washed. When the cleaning liquid (water) was extracted and the amount of the cleaning liquid and the solid content were measured, the amount of the cleaning liquid extracted was quantitative.

  Then, the sodium polyacrylate aqueous solution (1-2) was obtained by the polymerization prescription | regulation similar to the said synthesis example 1 using the reactor wash | cleaned above. Next, this was extracted from the polymerization kettle, transferred to a tank connected to the polymerization kettle by the same method as described above, and mixed with the aqueous solution (1-1) already stored. At this time, the inside of the tank was kept at 40 ° C., and the aqueous solution in the tank was constantly circulated to uniformly mix the aqueous solution.

  By repeating the above-described washing-manufacture-transfer operation, sodium polyacrylate aqueous solutions (1-3) to (1-10) are further manufactured, transferred to a tank, and the aqueous solution (1-1) A sodium polyacrylate aqueous solution (1) of this example was obtained in the form of a mixture of an aqueous solution (1-10). The weight average molecular weight (Mw) of sodium polyacrylate contained in the obtained aqueous solution (1) was 5400. Moreover, the clay dispersibility of aqueous solution (1) was 0.72. These results are shown in Table 2 below.

<Example 2>
A reactor similar to that used in Example 1 was prepared. In addition, the inside of the reactor was washed.

  Subsequently, a sodium polyacrylate aqueous solution (2-1) 1150.60 kg was obtained by the same method as in Synthesis Example 1 except that the dripping amount of 35% SBS was changed to 61.4 kg. The degree of neutralization of sodium polyacrylate in the obtained aqueous solution (2-1) was 97.0%, and the solid content concentration (theoretical value) of the aqueous solution (2-1) was 43.21% by mass. . In addition, the method of obtaining the sodium polyacrylate aqueous solution (2-1) using the above-described apparatus / polymerization recipe is also referred to as “synthesis example 2”. The polymerization formulation of Synthesis Example 2 is shown in Table 1 below.

  The obtained sodium polyacrylate aqueous solution (2-1) was extracted from the polymerization kettle and transferred to a tank connected to the polymerization kettle. By subtracting the amount of the aqueous solution (2-1) extracted from the polymerization kettle from the amount of the aqueous solution (2-1) produced in Synthesis Example 1, the aqueous solution (2-1) remaining in the reaction apparatus after transfer The amount calculated was 17.3 kg (1.5% by mass with respect to the aqueous solution (2-1) produced in Synthesis Example 2). Specifically, the amount of the remaining aqueous solution was finely adjusted by introducing the extracted aqueous solution (2-1) into the polymerization kettle so that the difference value described above was 17.3 kg.

  Subsequently, the reactor was washed with water. Specifically, external circulation and agitation were performed while adding water to the extent that the stirring blades were sufficiently applied, and the polymerization kettle and the external circulation path were washed. When the cleaning liquid (water) was extracted and the amount of the cleaning liquid and the solid content were measured, the amount of the cleaning liquid extracted was quantitative.

  Then, the sodium polyacrylate aqueous solution (2-2) was obtained by the polymerization prescription | regulation similar to the said synthesis example 2 using the reactor wash | cleaned above. Subsequently, this was extracted from the polymerization kettle, transferred to a tank connected to the polymerization kettle in the same manner as described above, and mixed with the aqueous solution (2-1) already stored. At this time, the inside of the tank was kept at 40 ° C., and the aqueous solution in the tank was constantly circulated to uniformly mix the aqueous solution.

  By repeating the above-described washing-aqueous solution production-transfer operation, sodium polyacrylate aqueous solutions (2-3) to (2-10) are further produced, transferred to a tank, and an aqueous solution (2-1). -A sodium polyacrylate aqueous solution (2) of this example was obtained in the form of a mixture of an aqueous solution (2-10). The weight average molecular weight (Mw) of the sodium polyacrylate contained in the obtained aqueous solution (2) was 6200. Moreover, the clay dispersibility of aqueous solution (2) was 0.76. These results are shown in Table 2 below.

<Comparative Example 1>
A sodium polyacrylate aqueous solution (C1) was obtained by the same method as in Example 1 described above, except that the cleaning step between batches was not performed. That is, the aqueous solutions in the second batch to the tenth batch were produced in the presence of the remaining aqueous solution (11.6 kg) from the previous batch. In addition, the method of obtaining sodium polyacrylate aqueous solution in the 2nd batch-10th batch of this comparative example is also called "synthesis example 3." The polymerization formulation of Synthesis Example 3 is shown in Table 1 below.
The weight average molecular weight (Mw) of sodium polyacrylate contained in the obtained aqueous solution (C1) was 6200. Moreover, the clay dispersibility of aqueous solution (C1) was 0.61. These results are shown in Table 2 below.

<Comparative Example 2>
Polyacrylic was prepared in the same manner as in Comparative Example 1 except that the prescription of Synthesis Example 1 in which the dripping amount of 35% SBS was changed to 72.9 kg was adopted as the polymerization prescription for the second batch to the tenth batch. A sodium acid aqueous solution (C2) was obtained. Here, the amount of the remaining aqueous solution from the previous batch in the reactor at the start of the second batch to the tenth batch was 11.6 kg. In addition, the method of obtaining sodium polyacrylate aqueous solution in the 2nd batch-10th batch of this comparative example is also called "synthesis example 4." The polymerization formulation of Synthesis Example 4 is shown in Table 1 below. The weight average molecular weight (Mw) of sodium polyacrylate contained in the obtained aqueous solution (C2) was 5400. The clay dispersibility of the aqueous solution (C2) was 0.58. These results are shown in Table 2 below.

<Comparative Example 3>
The formulation of Synthesis Example 2 described above is adopted as the polymerization formulation of the first batch, and the formulation of Synthesis Example 2 in which the dripping amount of 35% SBS is changed to 71.4 kg as the polymerization formulation of the second batch to the 10th batch. A sodium polyacrylate aqueous solution (C3) was obtained in the same manner as in Comparative Example 1 except that it was adopted. Here, the amount of the remaining aqueous solution from the previous batch in the reactor at the start of the second batch to the tenth batch was 17.3 kg. In addition, the method of obtaining the sodium polyacrylate aqueous solution in the second batch to the tenth batch of this comparative example is also referred to as “synthesis example 5”. The polymerization formulation of Synthesis Example 5 is shown in Table 1 below. The weight average molecular weight (Mw) of sodium polyacrylate contained in the obtained aqueous solution (C3) was 6200. Moreover, the clay dispersibility of aqueous solution (C3) was 0.61. These results are shown in Table 2 below.

  Of the results shown in Table 2, comparing the examples and the comparative examples, the clay dispersibility of the finally obtained sodium polyacrylate aqueous solution is dramatically improved by performing the washing step between the batches. Is shown.

  From the above, according to the present invention, it is shown that a means capable of further improving the clay dispersibility of the detergent builder is provided.

It is the schematic which shows one Embodiment of the reaction apparatus used suitably for the manufacturing method of this invention.

Explanation of symbols

101 polymerization kettle,
111 stirrer,
113 External jacket,
115 external circulation path,
117 heat removal device,
119 supply route,
121 tip nozzle,
123 tanks,
125 Reaction liquid extraction route.

Claims (5)

A polymerization reactor;
Storage means connected to the polymerization reactor;
A method for producing a (meth) acrylic acid polymer using a polymerization apparatus having
In the polymerization reactor, in the presence of persulfate and bisulfite, a first polymerization step of obtaining a first polymer by batch polymerization of a monomer component containing (meth) acrylic acid;
A transfer step of transferring the first polymer to the storage means;
A cleaning step of cleaning the polymerization reactor after transfer;
After the washing, in the polymerization reactor, in the presence of persulfate and bisulfite, a monomer component containing (meth) acrylic acid is batch-polymerized to obtain a second polymer. Process,
A mixing step of transferring the second polymer to the storage means and mixing with the first polymer;
A process for producing a (meth) acrylic acid polymer.   The production method according to claim 1, wherein the polymerization step includes a neutralization step of partially or completely neutralizing the polymer by adding a neutralizing agent to the reaction solution.   The polymerization apparatus further comprises an external circulation path for externally circulating the reaction liquid during the polymerization, and a heat removal means for cooling the reaction liquid circulating through the external circulation path. The manufacturing method as described in.   The polymerization apparatus further comprises an external circulation path for externally circulating the reaction liquid after polymerization, and a heat removal means for cooling the reaction liquid circulating in the external circulation path. The manufacturing method of any one of Claims.   The manufacturing method of any one of Claims 1-4 whose temperature of the said 2nd polymer at the time of being transferred to the said storage means is 20-90 degreeC.

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