JPWO2010050416A1 - Method for dissolving water-soluble polymer - Google Patents

Abstract

A primary aqueous solution 8 in which a water-soluble polymer is dissolved in an amount of 0.3 to 1% by mass is diluted to a secondary aqueous solution having a dilution ratio of 2 to 30 at the time of use to prepare a polymer flocculant, a yield improver for papermaking, and a thickener. A method for dissolving a water-soluble polymer for use as a paper strength enhancer. In order to dilute the primary aqueous solution into the secondary aqueous solution, the in-line mixer 4 is preferably used. By employing the dissolution method, a water-soluble polymer aqueous solution that can withstand long-term use can be provided without reducing the viscosity of the water-soluble polymer aqueous solution.

Description

  The present invention relates to a method for dissolving a water-soluble polymer and an apparatus for producing a water-soluble polymer aqueous solution.

  Conventionally, water-soluble polymers such as polyacrylamide have been used in dilute aqueous solutions for applications such as polymer flocculants, yield improvers for papermaking, thickeners, and paper strength enhancers.

  The water-soluble polymer is usually supplied to the market in the form of a powder or a liquid with a relatively high concentration (usually 25% by mass or more) such as a sol liquid, an emulsion liquid, or a salt water dispersion. ing. Therefore, when these water-soluble polymer powders or liquids are used in the above-mentioned applications, they are usually further diluted to a dilute aqueous solution having a desired concentration.

  However, in order to dissolve the commercially available water-soluble polymer in water to form a dilute aqueous solution, a relatively long time of about 30 minutes to several hours is required, and the operability is poor. Furthermore, a dilute aqueous solution obtained by dissolving a water-soluble polymer has a high volume because the polymer concentration is low. Therefore, the manufacturing apparatus of the dilute aqueous solution of water-soluble polymer, the storage tank of the manufactured dilute aqueous solution, etc. become large. As a result, the installation area of these devices increases.

Patent Document 1 describes a method of dissolving the water-soluble polymer in water by mixing dilution water with a water-in-oil emulsion of the water-soluble polymer. In this method, first, water is mixed into the emulsion to obtain a primary aqueous solution having a relatively high concentration. Thereafter, diluting water is further added to produce a dilute water-soluble polymer aqueous solution having a desired concentration. In the case of Patent Document 1, the water-soluble polymer is more completely diluted relatively easily by the dilution method. However, this method is a method of diluting a water-in-oil emulsion of a water-soluble polymer. For applications where the presence of oil forming the emulsion is a problem, this method cannot be employed.
JP 2001-213968 (Claims, paragraph 0004)

  The present inventors have made various studies on a method for producing a dilute aqueous solution of a water-soluble polymer. That is, the present inventors have used a conventional method for producing an aqueous solution having a target concentration by dissolving a water-soluble polymer in water in one step, or a water-soluble high-concentration supplied in a relatively high concentration liquid state. A conventional method for producing an aqueous solution with a target concentration by further diluting the molecule in one step was examined (hereinafter, a normal dissolution method in which a water-soluble polymer is dissolved in a target concentration in the above one step is abbreviated as a normal dissolution method May be.)

  As a result, the present inventors have noticed that the viscosity of the water-soluble polymer aqueous solution obtained by these conventional methods tends to be lower than the inherent viscosity of the water-soluble polymer aqueous solution. Furthermore, the present inventors have noticed that the water-soluble polymer aqueous solution obtained by the conventional method tends to deteriorate the target performance (practical performance) such as cohesion. Furthermore, the present inventors have also noticed that the water-soluble polymer aqueous solution obtained by the conventional method tends to have poor storage stability. This tendency was particularly remarkable when low-quality water such as mineral water was used for diluting the water-soluble polymer.

  The present inventors have conducted various studies to elucidate the above phenomenon. As a result, first, a medium concentration (0.1 to 1% by mass) water-soluble polymer aqueous solution is prepared as the first step, and then, as the second step, the medium concentration is just before using the water-soluble polymer aqueous solution. A two-stage dissolution method has been conceived in which a water-soluble polymer solution is diluted into a low-concentration water-soluble polymer solution.

  According to the two-stage dissolution method of the present invention, compared to a normal dissolution method (ordinary dissolution method) in which the water-soluble polymer is directly dissolved to the target concentration in one step, the resulting water-soluble polymer aqueous solution has a higher viscosity. It is kept high and the storage stability is also good. As a result, it was confirmed that the water-soluble polymer aqueous solution obtained by this dissolution method was also excellent in practical performance.

  The present invention has been completed based on the above findings. Accordingly, an object of the present invention is to provide a method for producing a water-soluble polymer aqueous solution and an apparatus for producing the same, which can solve the above problems.

  The present invention for achieving the above object is described below.

  [1] A water-soluble polymer in which a primary aqueous solution in which 0.3 to 1% by mass of a water-soluble polymer is dissolved is diluted to a secondary aqueous solution having a dilution ratio of 2 to 30 at the time of use. Dissolution method.

  The method for dissolving a water-soluble polymer as described in [1], wherein the water-soluble polymer is a solid powder.

  [3] The method for dissolving a water-soluble polymer according to [1], wherein the water-soluble polymer is a cationic polymer or an amphoteric polymer.

  [4] The method for dissolving a water-soluble polymer according to [1], wherein the primary aqueous solution is diluted into a secondary aqueous solution using an in-line mixer.

[5] A primary aqueous solution production process for producing a primary aqueous solution in which a water-soluble polymer is dissolved in an amount of 0.3 to 1% by mass and storing it until use;
A secondary aqueous solution production step of diluting the stored temporary aqueous solution into a secondary aqueous solution having a dilution ratio of 2 to 30 times when using the water-soluble polymer aqueous solution;
A method for dissolving a water-soluble polymer, comprising:

  [6] A method for using a secondary aqueous solution in which the secondary aqueous solution dissolved by the dissolution method according to any one of [1] to [5] is used as a polymer flocculant or a papermaking yield improver.

  [7] A primary aqueous solution tank for storing a primary aqueous solution in which 0.3 to 1% by mass of a water-soluble polymer is dissolved, a dilution water supply pipe provided with means A for feeding dilution water at a predetermined flow rate, and the dilution A means B for connecting the in-line mixer interposed in the water supply pipe, the primary aqueous solution tank and the upstream side of the in-line mixer and feeding the primary aqueous solution in the primary aqueous solution tank to the upstream side of the in-line mixer at a predetermined flow rate; An apparatus for producing a water-soluble polymer aqueous solution, comprising a primary aqueous solution supply pipe having a control unit for controlling the flow rates of means A and B.

    The water-soluble polymer dissolution method of the present invention is obtained by dissolving a solid water-soluble polymer with water or diluting a high-concentration water-soluble polymer aqueous solution with water to obtain a medium concentration (0.3 to 1). (Mass%) primary aqueous solution of water-soluble polymer is prepared and stored in advance. Thereafter, when the time for use comes, the stored primary aqueous solution is diluted 2 to 30 times to produce a desired low-concentration secondary aqueous solution for use in various applications.

  In dissolving the water-soluble polymer, it takes a long time to dissolve the solid polymer. However, the time required for further diluting the primary aqueous solution having a medium concentration dissolved in advance to produce the desired secondary aqueous solution is short. Therefore, according to the dissolution method of the present invention, a secondary aqueous solution having a desired concentration can be produced in a short time by diluting the primary aqueous solution. As a result, a dilute aqueous solution having an arbitrary concentration can be produced easily and within a short period of time according to the purpose of the use site or according to fluctuations in operating conditions at the use site. Therefore, this dissolution method can easily cope with fluctuations in the use conditions of the water-soluble polymer aqueous solution.

  According to the two-stage dissolution method of a water-soluble polymer of the present invention, a primary aqueous solution in which a water-soluble polymer is dissolved at a medium concentration (0.3 to 1% by mass) is prepared in advance, and water is used at the time of use. The primary aqueous solution is diluted 2 to 30 times. Therefore, it is not necessary to produce a large amount of a low concentration secondary aqueous solution at a time. As a result, a large storage tank that stores a large amount of the secondary aqueous solution is unnecessary. That is, this melting method can be adopted even in a manufacturing site where the site area is small.

  When the water-soluble polymer is stored in a low-concentration aqueous solution state of less than 0.3% by mass, the solution viscosity decreases. When this water-soluble polymer aqueous solution with reduced viscosity is used as a flocculant or paper yield improver, there is a tendency for the cohesiveness, paper yield improvement and the like to decrease. Further, when the water used as the solvent is low grade water such as mineral water, hard water, river water, etc., the viscosity tends to decrease similarly. However, when storing in a medium concentration solution state of 0.3% by mass or more, the viscosity of the water-soluble polymer aqueous solution is unlikely to decrease. Therefore, according to this dissolution method, a water-soluble polymer aqueous solution that can withstand long-term use can be provided without reducing the viscosity of the water-soluble polymer aqueous solution.

  The apparatus for producing a water-soluble polymer aqueous solution of the present invention can continuously produce a water-soluble polymer aqueous solution having an arbitrary low concentration with a simple configuration. In addition, it is easy to change the concentration of the water-soluble polymer aqueous solution.

FIG. 1 is a flow diagram showing an example of the configuration of the water-soluble polymer aqueous solution production apparatus of the present invention.

DESCRIPTION OF SYMBOLS 100 Manufacturing apparatus of water-soluble polymer aqueous solution 2 Dilution water supply pipe A A means to send dilution water by predetermined flow rate 4 Inline mixer X Flow direction of dilution water 6 Primary aqueous solution tank 8 Primary aqueous solution 10 Bottom wall 12 Primary aqueous solution supply pipe B Means for sending primary aqueous solution 14 Control unit

  In the water-soluble polymer dissolution method of the present invention, the water-soluble polymer used is not particularly limited, and any water-soluble polymer can be used.

  The water-soluble polymer used in the method for dissolving the water-soluble polymer of the present invention includes a water-soluble cationic monomer, an anionic monomer, and a nonionic monomer, which are obtained by singly or copolymerizing. Is preferred. Among these, a cationic polymer having a cationic monomer as an essential component and an amphoteric water-soluble polymer having a cationic monomer and an anionic monomer as essential components are more preferable.

  The cationic monomer is not limited in use as long as it has radical polymerizability. Examples include tertiary salts (hydrochlorides, sulfates, etc.) of dialkylaminoalkyl (meth) acrylates. Specifically, examples of the dialkylaminoalkyl (meth) acrylate include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and diethylamino-2-hydroxypropyl (meth) acrylate.

  Further, examples of the cationic monomer include tertiary salts such as hydrochloride and sulfate of dialkylaminoalkyl (meth) acrylamide. Dialkylaminoalkyl (meth) acrylamide is exemplified by dimethylaminopropyl (meth) acrylamide.

  Furthermore, quaternary salts of dialkylaminoalkyl (meth) acrylates such as halogenated alkyl adducts of dialkylaminoalkyl (meth) acrylates and aryl halide adducts are exemplified. Examples of the halogenated alkyl adduct include methyl chloride adduct. Examples of the halogenated aryl adduct include benzyl chloride adduct.

  Further, quaternary salts such as dialkylaminoalkyl (meth) acrylamide halogenated alkyl adducts and halogenated aryl adducts are exemplified. Examples of the halogenated alkyl adduct include methyl chloride adduct. Examples of the halogenated aryl adduct include a benzyl chloride adduct.

  Among these, tertiary salts or quaternary salts of dialkylaminoalkyl (meth) acrylates are preferable. In this specification, methacrylate and acrylate may be expressed as (meth) acrylate, and methacrylamide and acrylamide may be expressed as (meth) acrylamide.

  Any anionic monomer can be used as long as it has radical polymerizability. As an anionic monomer, unsaturated carboxylic acid and its salt are mentioned. Specific examples include acrylic acid, methacrylic acid, crotonic acid, itaconic acid and maleic acid. Acrylic acid and methacrylic acid are preferred.

  Examples of the salt of the unsaturated carboxylic acid include alkali metal salts such as sodium salt and potassium salt, and ammonium salt.

  Nonionic monomers include (meth) acrylamide, dimethylacrylamide, diethylacrylamide, methyl acrylate, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, methoxyethyl acrylate, butoxyethyl acrylate, ethyl carbitol acrylate, acrylonitrile and vinyl acetate. Is mentioned. Among these, (meth) acrylamide is preferable.

  These cationic monomers, anionic monomers, and nonionic monomers can be used alone or in combination of two or more to produce a water-soluble polymer. As the water-soluble polymer, those having a cationic monomer as an essential component or those having a cationic monomer and an anionic monomer as essential components are preferable as described above.

  When manufacturing a water-soluble polymer, when using a cationic monomer, or when using both monomers of a cationic monomer and an anionic monomer, In addition, it is preferable to use (meth) acrylamide in combination as a nonionic monomer. By using a nonionic monomer in combination, various physical properties of the resulting water-soluble polymer can be adjusted.

When the cationic monomer and (meth) acrylamide are used in combination, the combined ratio of (meth) acrylamide is preferably 1 to 90 mol%, more preferably 10 to 80 mol% of the total water-soluble monomer, 20 to 60 mol% is particularly preferable.
When the cationic monomer and the anionic monomer are used in combination, the combined proportion of (meth) acrylamide is preferably 5 to 80 mol%, more preferably 10 to 70 mol%, and more preferably 20 to 50 mol%. Particularly preferred.

  Yes.

  The weight average molecular weight of the water-soluble polymer is not particularly limited, but when used for a polymer flocculant or the like, 1 million to 20 million is preferable, and 2 million to 10 million is more preferable.

  Water-soluble polymers are usually marketed under the names of polymer flocculants, polymer dehydrators, yield improvers, thickeners, and the like. In the present invention, these commercially available water-soluble polymers can also be used.

  In the present invention, first, the water-soluble polymer is dissolved in water to produce a primary aqueous solution of a water-soluble polymer having a medium concentration of 0.3 to 1% by mass. There is no restriction | limiting in particular as water used in the case of melt | dissolution, Tap water, mineral water, industrial water, distilled water, ion-exchange water, well water, etc. can be used. Among these waters, neutral water having a low metal ion concentration is preferable.

  As a dissolution method, a method in which a calculated amount of a water-soluble polymer is gradually added and dissolved in water while stirring is preferable. Stirring is exemplified by a stirring method using an impeller. The dissolution method itself is known. The dissolution time is usually 30 minutes or more and may be required for about 2 to 3 hours.

  The primary aqueous solution produced by the above method is immediately diluted in that state to prepare a secondary aqueous solution. Alternatively, the primary aqueous solution is stored until the time of use arrives. The storage method is not particularly limited, and may be stored in an air atmosphere by storing in a container or the like in which rainwater or the like is prevented.

  When the concentration of the water-soluble polymer in the primary aqueous solution exceeds 1% by mass, the aqueous solution has high viscosity and poor fluidity. As a result, the load on the stirrer that stirs the aqueous solution tends to be excessive. In addition, it takes a long time to dissolve the water-soluble polymer. Furthermore, since the viscosity of the primary aqueous solution is high, when a secondary aqueous solution is obtained by dilution, a relatively long time is required for dilution. In this case, it becomes difficult to use an in-line mixer or the like which will be described later.

  On the other hand, when the concentration of the water-soluble polymer in the primary aqueous solution is less than 0.3% by mass, the water-soluble polymer aqueous solution tends to decrease in viscosity with time.

  Next, after the primary aqueous solution is produced, the primary aqueous solution is diluted with water immediately after use or when the use time comes after storage. The dilution factor is preferably 2 to 30 times. As dilution water, the water used when manufacturing primary aqueous solution can be used as it is. During the production of the secondary aqueous solution, it is preferable to stir the aqueous polymer solution being diluted. Examples of the stirring method include a method using the above impeller. As a preferable stirring method, there is a stirring method using an in-line mixer. As the in-line mixer, a static mixer having no movable part is preferable.

  Since the water-soluble polymer in the primary aqueous solution is dissolved in water in a uniform state, the time required for dilution of the primary aqueous solution is short. Although depending on the amount of the primary aqueous solution to be handled, when a stirrer equipped with an impeller is used, the primary aqueous solution is normally diluted within 5 minutes, in many cases within 1 minute, and a secondary aqueous solution is obtained. In particular, when using a static mixer, it is diluted in 10 seconds or less. By this dilution, a low concentration secondary aqueous solution is obtained.

  The secondary aqueous solution produced by the dissolution method is a water-soluble polymer aqueous solution obtained by directly dissolving a water-soluble polymer at a desired concentration in one step, as is apparent from the data of the examples described later. In comparison, the viscosity is high, and the decrease in viscosity is small over time. As a result, when this secondary aqueous solution is used as an aggregating agent, a yield improving agent, or the like, beneficial properties such as an improvement in the aggregating effect and an improved yield are exhibited.

  FIG. 1 shows an example of an apparatus for producing a water-soluble polymer aqueous solution that can be suitably used in the method for dissolving the water-soluble polymer.

  In FIG. 1, reference numeral 100 denotes an apparatus for producing a water-soluble polymer aqueous solution. A means A for supplying dilution water at a predetermined flow rate and an in-line mixer 4 are sequentially provided in the dilution water supply pipe 2 along the flow direction X of the dilution water.

  As the in-line mixer, a structure having a stirring blade inside thereof and a structure in which the fluid is stirred by rotating the stirring blade, or a static mixer is preferable. The static mixer has a structure in which a plurality of baffle plates are inserted along a flow direction inside a cylindrical tube. The fluid flowing in the static mixer is repeatedly divided by the baffle plate, and as a result, the fluid is mixed. A commercially available product can be used for the in-line mixer itself.

  Reference numeral 6 denotes a primary aqueous solution tank in which a primary aqueous solution 8 for dissolving 0.3 to 1% by mass of a water-soluble polymer is stored. One end of a primary aqueous solution supply pipe 12 is connected to the bottom wall 10 of the primary aqueous solution tank 6, and the other end is connected to the upstream side of the in-line mixer 4.

  Means B for feeding the primary aqueous solution is interposed in the primary aqueous solution supply pipe 12 to supply the primary aqueous solution 8 to the upstream side of the in-line mixer 4 at a predetermined flow rate.

  Reference numeral 14 denotes a control unit that controls the amount of liquid fed by the means A and B. Under the control of the control unit 14, the means A and B supply in-line diluted water and the primary aqueous solution 8 at an arbitrarily determined flow rate. Supply to mixer 4.

  In this apparatus, by changing the flow rates of the means A and B, the secondary aqueous solution having an arbitrary dilution ratio is taken out from the outlet side of the in-line mixer 4.

  When producing a secondary aqueous solution using this apparatus 100, even if the volume of the primary aqueous solution tank 6 for storing the primary aqueous solution 8 having a medium concentration is small, a large amount of the secondary aqueous solution can be obtained by diluting it. it can. Therefore, according to the method for dissolving a water-soluble polymer of the present invention, the installation area of the apparatus can be reduced. As a result, the method for dissolving a water-soluble polymer of the present invention is suitable for use in a factory or treatment plant that uses a secondary aqueous solution on a small scale.

  In the above description, the means A is provided at the front stage of the in-line mixer 4, but the present invention is not limited to this, and the means A may be provided at the rear stage of the in-line mixer 4. Deformation may be added.

  Hereinafter, the present invention will be described specifically by way of examples. The present invention is not limited to these examples.

Study Example 1 (Study of dissolution time)
In examining the method for dissolving the water-soluble polymer, first, the following preconditions a) and b) were confirmed.

(a) The dissolution time required for dissolving the water-soluble polymer by the two-step dissolution method of the present invention to produce a primary aqueous solution, and dissolving the water-soluble polymer in one step by the normal dissolution method There should be no significant difference between the dissolution time required to produce a water-soluble polymer aqueous solution.
(b) The time for producing the secondary aqueous solution using the primary aqueous solution is short and the production is easy. The confirmation test was performed under the conditions shown in Table 1. That is, a water-soluble polymer aqueous solution having a concentration of 0.1% by mass was prepared by a normal dissolution method using the water-soluble polymers of brands A to G. At this time, the dissolution state of the water-soluble polymer aqueous solution with respect to the elapsed time after the start of dissolution was observed. Meanwhile, primary aqueous solutions of 0.5 mass%, 1.0 mass%, and 1.2 mass% were prepared in the same manner. At that time, the dissolution state of the water-soluble polymer aqueous solution with respect to the elapsed time after the start of dissolution was observed in the same manner as in the normal dissolution method. These results are shown in Table 2.

  From the results in Table 2, the time required for normal dissolution to dissolve the water-soluble polymer to the target concentration of 0.1% by mass in one step, and the concentration of the water-soluble polymer to the primary aqueous solution concentration of 0.3 to 1.0% by mass. It was found that the time required for the primary dissolution to be dissolved is almost the same. It was. Therefore, in the case of the above-mentioned concentration range, it was confirmed that there is no practical difference between the normal dissolution time and the primary dissolution time.

  In addition, when the primary aqueous solution density | concentration is 1.2 mass% density | concentration, it was confirmed that dissolution time becomes long.

Examination example 2 (examination of secondary dissolution time)
The time required for diluting the primary aqueous solution to obtain a uniform secondary aqueous solution (secondary dissolution time) was examined. The examination conditions are shown in Table 4, and the examination results are shown in Table 5.

  As is apparent from the secondary dissolution time in Table 5, the secondary dissolution time required for diluting the primary aqueous solution to prepare the secondary aqueous solution was 10 seconds or less. It was. That is, when the primary aqueous solution was diluted to the secondary aqueous solution, it could be uniformly diluted within 10 seconds. Therefore, an apparatus capable of mixing and diluting in a relatively short time, such as an in-line mixer, can be employed as a dilution apparatus in an apparatus for producing a water-soluble polymer aqueous solution at an actual machine level.

Examples 1-10, Comparative Examples 1-7
A water-soluble polymer aqueous solution was prepared using a normal dissolution method in which the aqueous solution concentration was dissolved in one step and a two-step dissolution method of the present invention in which the primary aqueous solution was further diluted into a secondary aqueous solution. When manufacturing water-soluble polymer aqueous solution, the relationship between these dissolution methods and the viscosity and cation value of the water-soluble polymer aqueous solution obtained by these dissolution methods was examined.

  When employing the normal dissolution method, first, a 0.2% by mass aqueous solution of each brand of water-soluble polymer was prepared, and then the relationship between the elapsed time after preparation of the 0.2% by mass aqueous solution and the viscosity was measured. .

  When adopting the two-step dissolution method, first, a 0.5 or 1.0 mass% aqueous solution (primary aqueous solution) of each brand of water-soluble polymer was prepared. Then, immediately after the preparation, one day later, and two days later, these primary aqueous solutions were diluted into a secondary aqueous solution of 0.2% by mass, and their viscosities were measured. Thereafter, the secondary aqueous solution diluted to 0.2% by mass was allowed to stand, and the relationship between the elapsed time after preparing the secondary aqueous solution and the viscosity was measured.

  Comparing a 0.2% by mass water-soluble polymer aqueous solution prepared by a normal dissolution method with a 0.2% by mass water-soluble polymer aqueous solution prepared by a two-step dissolution method, a highly cationic water-soluble polymer aqueous solution In both cases, and in the case of the amphoteric water-soluble polymer aqueous solution, the physical properties showed more remarkable differences. The viscosity of the water-soluble polymer aqueous solution prepared by the two-step dissolution method was higher than the viscosity of the water-soluble polymer aqueous solution prepared by the normal dissolution method. Furthermore, the rate of decrease in the viscosity of the 0.2% by mass secondary aqueous solution prepared by the two-stage dissolution method is smaller than the rate of decrease in the viscosity of the 0.2% by mass water-soluble polymer aqueous solution usually obtained by the dissolution method. It was.

  Table 6 shows the examination conditions. Table 7 summarizes the results of the study. Furthermore, the cation value was measured. The results are shown in Table 8.

  The present inventors consider the reason why the decrease in viscosity occurs as described below. That is, the pH of the dilute aqueous solution of the water-soluble polymer is close to alkalinity as compared with the high-concentration aqueous solution. As a result, the water-soluble polymer is easily hydrolyzed in the dilute aqueous solution. In the case of an amphoteric water-soluble polymer, an ion complex is easily formed in a dilute aqueous solution. For the above reasons, the physical properties of a dilute aqueous solution of a water-soluble polymer are likely to change greatly over time. In contrast, the medium concentration aqueous solution of the water-soluble polymer keeps the change in physical properties small.

  For the reasons described above, it is obtained by the dissolution method (two-stage dissolution method) of the present invention in which it is stored in the state of a medium-concentration water-soluble polymer aqueous solution, and the medium-concentration water-soluble polymer aqueous solution is stored just before use. The resulting low concentration polymer aqueous solution exhibits better physical properties than a water-soluble polymer aqueous solution usually obtained by a dissolution method.

  This tendency is particularly remarkable in the case of a highly ionic cationic water-soluble polymer and in the case of an amphoteric water-soluble polymer. Specifically, this tendency is remarkable in the case of a medium cationic water-soluble polymer containing 40 mol% or more of cationic monomer units based on the total constituent monomer units, and a high cation of 70 mol% or more. This is particularly remarkable in the case of water-soluble water-soluble polymers.

  Furthermore, in the case of an amphoteric water-soluble polymer in which the cationic monomer unit content (hereinafter referred to as Cv [mol%]) and the anionic monomer unit content (hereinafter referred to as Av [mol%]) are the same, details are given. Is more pronounced when Cv / Av ≦ 10 and Av / Cv ≦ 3.0.

  Furthermore, this tendency is more conspicuous in the case of a highly cationic water-soluble polymer having an acrylate monomer unit than in the case of a highly cationic water-soluble polymer having a methacrylate monomer unit. The reason for this is not clear, but it is presumed that the methacrylate monomer unit has a chemical structure that is relatively less hydrolyzed than the acrylate monomer unit.

  Furthermore, even in the case of a water-soluble polymer aqueous solution having the same concentration, the viscosity of the water-soluble polymer aqueous solution obtained by diluting the primary aqueous solution immediately after preparing the primary aqueous solution is usually obtained by dissolution. It is higher than the viscosity of the aqueous polymer solution. The reason why the difference in viscosity occurs is interpreted by the present inventors according to the reason described below. That is, in the normal dissolution method, it takes 1 hour to dissolve the water-soluble polymer. Furthermore, a dilute water-soluble polymer aqueous solution usually prepared by a dissolution method has a pH that is relatively close to alkalinity, and is stored at this pH until it is used. As a result, the water-soluble polymer usually prepared by the dilution method is hydrolyzed, and an ion complex is formed to lower the viscosity. On the other hand, since the preparation time of the secondary aqueous solution by the two-stage dissolution method is short, it is difficult for the viscosity of the aqueous solution to decrease.

Study example 3
Simulated mineral water containing the salts shown in Table 9 was prepared. In general, the viscosity of a water-soluble polymer aqueous solution prepared using mineral water is lower than that of a water-soluble polymer aqueous solution prepared using water not containing metal ions. Furthermore, the cation value of a water-soluble polymer aqueous solution prepared using mineral water is difficult to measure because salts coexist.

  A water-soluble polymer was dissolved in the simulated mineral water at a concentration shown in Table 10. The water-soluble polymer solution at each concentration was allowed to stand and the presence or absence of precipitates was observed.

  Next, these water-soluble polymer aqueous solutions were diluted with simulated mineral water. The diluted water-soluble polymer aqueous solution was allowed to stand, and the presence or absence of precipitates at that concentration was observed. The results are shown in Table 10.

  The reason for the suspension of the highly cationic water-soluble polymer aqueous solution is thought to be that the water-soluble polymer became amphoteric by hydrolysis, resulting in the formation of precipitates and complexes.

  The amphoteric water-soluble polymer aqueous solution suspends in a short time at a low concentration, but takes a long time to suspend at an intermediate concentration. However, phenomenologically, when diluting a medium concentration aqueous solution of a water-soluble polymer, the diluted low concentration aqueous solution is not suspended immediately after the dilution (suspension is delayed). At present, the reason for this is not fully understood.

Example 18 and Comparative Example 15
Paper factory wastewater sludge dewatering test Paper factory wastewater sludge dewatering test was conducted using water-soluble polymer aqueous solution. The test conditions are listed in Table 11. The test results are shown in Table 12. Regarding the amount of drainage, although it is a slight difference, the two-stage dissolution method of the present invention was advantageous. The moisture content of the cake was higher in the comparative example.

  TS represents evaporation residue, VTS represents ignition loss, SS represents suspended matter, and VSS represents suspended matter ignition loss.

Example 19 and Comparative Example 15
A dewatering test was performed on digested sludge from a sewage treatment plant using a water-soluble polymer aqueous solution. Test conditions are listed in Table 13. The test results are shown in Table 14.

  From Table 14, it can be seen that the two-stage dissolution method of the present invention is advantageous with respect to the floc diameter, filtrate amount, filtrate turbidity, and cake water content. The cake moisture content is lower in Example 19 than in Comparative Example 15. This difference is more conspicuous than the difference between Example 18 and Comparative Example 14 of the DA-based cation.

Example 20, Comparative Example 16
A paper yield test was conducted on a laboratory scale using a water-soluble polymer aqueous solution. The test conditions are shown in Table 15 and the results are shown in Table 16.
The paper yield performance was better when the aqueous polymer solution prepared by the two-stage dissolution method was used than by the normal dilution method. In the case of the normal dilution method, it seems that the performance of the water-soluble polymer is slightly reduced.

Table 15 simulated industrial water as described in the water CaSO ₄ · _2H 2 O (molecular weight _{172.17) 50mg / L, CaCl 2} · 2H 2 O ( molecular weight 147.01) and 40 mg / L, NaHCO ₃ ( It was prepared by adding 60 mg / L of molecular weight 84.02).

Examples 21 and 22, Comparative Examples 17 and 18
Using the water-soluble polymer aqueous solution, an actual machine test using a papermaking machine was performed, and the items shown in Table 18 were evaluated. The results are shown in Table 18. The test conditions are shown in Table 17.

  When the addition amount of the water-soluble polymer was the same, the results obtained in the yield and formation were superior to those using the water-soluble polymer aqueous solution of the two-stage dissolution method than the normal dissolution method. The reason seems to be influenced by the water-soluble polymer dissolution equipment in the actual machine and the water quality conditions of the water used. In other words, in the case of the normal dilution method, it is considered that the viscosity of the water-soluble polymer aqueous solution was drastically decreased and the function of the water-soluble polymer could not be sufficiently exhibited.

Claims (7)

A method for dissolving a water-soluble polymer, comprising diluting a primary aqueous solution in which a water-soluble polymer is dissolved in an amount of 0.3 to 1% by mass into a secondary aqueous solution having a dilution ratio of 2 to 30 at the time of use. . The method for dissolving a water-soluble polymer according to claim 1, wherein the water-soluble polymer is a solid powder. The method for dissolving a water-soluble polymer according to claim 1, wherein the water-soluble polymer is a cationic polymer or an amphoteric polymer. The method for dissolving a water-soluble polymer according to claim 1, wherein the primary aqueous solution is diluted into a secondary aqueous solution using an in-line mixer. Producing a primary aqueous solution in which a water-soluble polymer is dissolved in an amount of 0.3 to 1% by mass and storing the primary aqueous solution until use;
A secondary aqueous solution production step of diluting the stored temporary aqueous solution into a secondary aqueous solution having a dilution ratio of 2 to 30 times when using the water-soluble polymer aqueous solution;
A method for dissolving a water-soluble polymer, comprising: A method for using a secondary aqueous solution in which the secondary aqueous solution dissolved by the dissolution method according to any one of claims 1 to 5 is used as a polymer flocculant or a paper production yield improver. A primary aqueous solution tank for storing a primary aqueous solution in which 0.3 to 1% by mass of a water-soluble polymer is dissolved, a dilution water supply pipe provided with means A for sending dilution water at a predetermined flow rate, and the dilution water supply pipe A primary aqueous solution having means B for connecting the primary aqueous solution tank and the upstream side of the inline mixer to the upstream side of the inline mixer at a predetermined flow rate. An apparatus for producing a water-soluble polymer aqueous solution, comprising a supply pipe and a controller for controlling the flow rates of means A and B.

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