JP6770348B2 - Method for producing polymer flocculant powder and method for dehydrating sludge - Google Patents

Description

The present invention relates to a method for producing a polymer flocculant powder and a method for dehydrating sludge. More specifically, the present invention relates to a method for producing a high-performance polymer flocculant powder capable of effectively dehydrating refractory sludge and obtaining a dehydrated cake having a low water content, and sludge using the same. Regarding dehydration method.

Polymer coagulants are used for the purpose of coagulating, sedimenting, and separating suspensions contained in domestic wastewater, industrial wastewater, etc., as yield improvers in the paper industry, admixtures and mud agents in civil engineering and construction, etc. It is used. The polymer flocculant has nonionic, anionic, cationic, and amphoteric ionic properties, but which ionic polymer flocculant is selected depends on the properties of the water to be treated and the treatment method. Of these, the cationic polymer flocculant is used to flocize and dehydrate excess sludge after treating industrial wastewater and domestic wastewater with activated sludge, or as a yield improver in the paper industry. Is often done. In the former, for sludge that is difficult to dehydrate, a polymer having branching or cross-linking is used. In addition, the amphoteric polymer flocculant is used to coarsely floculate suspended particles charged and neutralized with a coagulant, and can be applied to sludge that is difficult to dehydrate or aggregate.

Conventionally, product forms such as powder and water-in-oil emulsion are known as polymer flocculants. Of these, the water-in-oil emulsion has the advantages of excellent solubility and uniform dissolution in a short time, but it is transported because it is more expensive to manufacture than powder and the content of the active ingredient of the polymer flocculant is low. There was a drawback that the cost was high.

Under such circumstances, recently, a cationic or amphoteric water-in-oil emulsion polymer having branching or cross-linking is dried and powdered, and exhibits excellent dehydration performance even for difficult-to-dehydrate sludge, and the transportation cost is reduced. High-performance polymer flocculant powders that eliminate the drawbacks and can be used in existing equipment such as general-purpose automatic melting devices for powders are being developed.

For example, Patent Document 1 states that at least 90% by weight has a particle size of 10 μm or less by reverse phase polymerization of a water-soluble monomer mixture containing a cationic monomer and a cross-linking agent of 5 to 2000 ppm in a non-aqueous liquid. Disclosed is a method for producing spray-dried granules, which comprises preparing a reversed-phase emulsion of subpolymer particles and then spray-drying the reverse-phase emulsion to prepare spray-dried granules having a particle size of at least 90% by weight of 20 μm or more. There is. However, spray drying is not preferable because the drying efficiency is poor and a large amount of energy is required to sufficiently dry and pulverize. In addition, due to the characteristics of the spray dryer, it is necessary to dry little by little in a short time, so it is necessary to dry at a very high temperature, and high molecular weight polymers are susceptible to thermal deterioration, and even if they are manufactured under the same conditions. There was a problem that the quality varied.

Further, in Patent Document 2, an aqueous monomer mixture containing a cationic monomer and a cross-linking agent of 20 to 300 ppm is used as a dispersed phase, and emulsified with a surfactant so that water and an immiscible hydrocarbon are in a continuous phase. A water-in-oil emulsion of a cationic or amphoteric aqueous polymer was obtained, and then the water-in-oil emulsion was emulsion-breaked to agglomerate, and the agglomerate was shredded into 4 to 6 mm using a meat chopper. After that, an example is disclosed in which the mixture is dried at 105 ° C. for 1 hour using a shelf-type ventilation dryer and crushed with a screen having a pore size of 2 mm to obtain a powdery sludge dehydrating agent. However, if the boiling point of the hydrocarbon used is high, the drying time becomes long and the productivity is lowered, and the high molecular weight polymer is susceptible to thermal deterioration due to high temperature drying.

On the other hand, in order to use hydrocarbons with a boiling point of 100 ° C or less, strict care must be taken when handling them because they are highly volatile and flammable. Normally, hydrocarbons are always carbonized in equipment that can completely block the entry of outside air. It is processed under conditions outside the combustion range of hydrogen. However, Patent Document 2 does not have a detailed description of steps other than emulsion break, the type of hydrocarbon is unknown, and it is unclear whether the hydrocarbon can be dried and powdered by a safe method. In particular, when the agglomerated polymer is shredded to 4 to 6 mm with a meat chopper, or when the shredded product is transferred from the meat chopper to a shelf-type ventilation dryer, the equipment that completely shuts off the outside air is the entire equipment. Seems to be extremely complicated. In addition, when using a shelf-type ventilation dryer, it is uneconomical because the hot air used in large quantities must be created with an inert gas such as nitrogen, and hydrocarbons can be recovered and reused. There were problems such as difficulty.

Patent Document 3 describes a step of forming an emulsion of a cationic monomer in a non-aqueous liquid in which the size of the primary particles is less than 20 μm and in the presence of an emulsifier; a step of initiating and completing the polymerization; water from the emulsion. Step of distilling to substantially dry the emulsion; step of separating the non-aqueous liquid and the polymer particles by washing the substantially dried emulsion or the slurry or solid of the dried polymer particles separated from the emulsion with a volatile organic solvent; Separation of the polymer particles as a solid or slurry of the polymer particles wetted with the volatile organic solvent; a dry powder consisting of a primary particle aggregate of the polymer comprising a step of evaporating the solvent from the solid or slurry to obtain a dry powder. The manufacturing method is disclosed.

However, Patent Document 3 is a method for producing a polymer powder for personal care compositions such as cosmetic compositions and topical pharmaceutical compositions for dissolving or swelling in water to form a homogeneous and transparent gel. Therefore, it is different from the technical field of polymer flocculants. Further, in the step of washing the non-aqueous liquid or the emulsifier with the volatile organic solvent, the non-aqueous liquid and the volatile organic solvent are mixed, which hinders the reuse of the non-aqueous liquid and generates a large amount of unnecessary waste liquid. Therefore, it is not preferable. Furthermore, it does not suggest a manufacturing method for improving the performance of the polymer flocculant.

Japanese Patent No. 4043517 Japanese Patent No. 5700534 Japanese Patent No. 4143604

An object of the present invention is to reduce the transportation cost by drying a cationic or amphoteric water-in-oil polymer emulsion having branching or cross-linking into a powder, and to have excellent dehydration performance even for difficult-to-dehydrate sludge. It is an object of the present invention to provide a method for producing a high-performance polymer flocculant powder that can be used by using a general-purpose automatic powder dissolving device or the like.

As a result of diligent studies on the above problems, the present inventors are a method for producing a polymer flocculant containing a crosslinked polymer obtained by polymerizing a specific monomer mixture in a water-in-oil emulsion and then drying it. Therefore, a method for producing a polymer flocculant powder including a specific emulsification step, polymerization step, reflux dehydration step, and drying step has been established. Then, they have found that the polymer flocculant powder obtained by this production method can not only reduce the transportation cost but also exhibit excellent dehydration performance and can be used by using a general-purpose automatic powder dissolving device or the like. completed.

That is, the present invention
[1] A method for producing a polymer flocculant powder, which dries a polymer emulsion obtained by emulsion-polymerizing a monomer mixture containing at least a cationic monomer and a crosslinkable monomer, as follows. (A) to (D)
Step (A): An aqueous phase containing an aqueous solution of the monomer mixture and an oil phase containing a hydrocarbon and a surfactant which are substantially immiscible with water are mixed to reduce the median diameter of the emulsified particles. An emulsification step for producing a water-in-oil monomeric emulsion of 10 μm or less,
Step (B): The monomer mixture in the water-in-oil monomer emulsion is polymerized in the presence of a radical polymerization initiator to prepare a water-in-oil polymer emulsion containing a polymer in the dispersed phase. Polymerization process,
Step (C): Of the condensed liquid consisting of water and hydrocarbons obtained by condensing the vapor separated by evaporating water and hydrocarbons from the water-in-oil polymer emulsion, water is discharged to the outside of the system. By returning the hydrocarbon into the system, a part of water is removed from the water-in-oil polymer emulsion until the dehydration rate represented by the following formula (1) is in the range of 65 to 99%, and the weight is increased. In the reflux dehydration step for producing a coalesced dispersion, the weight of the hydrocarbon used is 0.6 to 2.0 times the mass of the solid content of the water-in-oil polymer emulsion. Process,
Step (D): A drying step of removing hydrocarbons and water from the dispersion to prepare a powder of the polymer.
It is a method for producing a polymer flocculant powder, which comprises.

[2] The method for producing a polymer flocculant powder according to [1], wherein the monomer mixture contains a nonionic monomer.

[3] The polymer flocculant powder according to [1] or [2], wherein the cationic monomer contains one or more of the cationic monomers represented by the following general formula (2). It is a manufacturing method of.

_{^{CH 2 = CR 1 -CO-X}} -Q-N + R 2 R 3 R 4 · Z - ··· of (2)

(However, R ¹ is a hydrogen atom or a methyl group, R ² and R ³ are independent alkyl groups or benzyl groups having 1 to 3 carbon atoms, and R ⁴ is a hydrogen atom or alkyl group or benzyl group having 1 to 3 carbon atoms. X is an oxygen atom or NH, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, and Z ⁻ is a counter anion.)

[4] Any one of [1] to [3], wherein the cationic monomer is at least one of a quaternary salt of methyl chloride of dimethylaminoethyl acrylate and a quaternary salt of methyl chloride of dimethylaminoethyl methacrylate. The method for producing a polymer flocculant powder according to the above.

[5] The method for producing a polymer flocculant powder according to any one of [1] to [4], wherein the hydrocarbon is a hydrocarbon having a boiling point in the normal pressure range of 65 to 180 ° C.

[6] The method for producing a polymer flocculant powder according to any one of [1] to [5], wherein the hydrocarbon is normal heptane.

[7] The method for producing a polymer flocculant powder according to any one of [1] to [6], wherein the HLB value of the surfactant is 3.0 to 9.0.

[8] The method for producing a polymer flocculant powder according to any one of [1] to [7], wherein the reflux dehydration step of the step (C) is performed under reduced pressure conditions of normal pressure to absolute pressure of 4 kPa. ..

[9] The method for producing a polymer flocculant powder according to any one of [1] to [8], wherein the drying step of the step (D) is performed under reduced pressure conditions of an absolute pressure of 2 to 20 kPa.

[10] After the drying step of the step (D), the following step (E)
Step (E): A granulation step of adding a binder while stirring and mixing the polymer powder, wet stirring and granulating, and then drying to granulate the polymer powder.
The method for producing a polymer flocculant powder according to any one of [1] to [9].

[11] The method for producing a polymer flocculant powder according to [10], wherein the binder is a Poval aqueous solution having a saponification degree of 78.0 to 95.0 mol% and an average molecular weight of 1000 to 70000.

[12] A sludge dehydration method in which an aqueous solution of a polymer flocculant powder obtained by the production method according to any one of [1] to [11] is added to the sludge to dehydrate it.

The polymer flocculant powder obtained by the production method of the present invention can not only reduce the transportation cost but also exhibit excellent dewatering performance for difficult-to-dehydrate sludge, and can be used by using a general-purpose automatic powder dissolving device or the like. can do.

The polymer flocculant powder obtained by the production method of the present invention is a sludge coagulant for domestic wastewater and industrial wastewater; a drainage yield improver for papermaking, a drainage improver, a formation aid, and a paper strength enhancer. Paper chemicals such as; coagulants for drilling and muddy water treatment; additives for increasing crude oil production; organic coagulants; thickeners; dispersants; antiscale agents; antistatic agents; and processing agents for textiles, etc. It is possible to do.

The present invention will be described in detail below.
In the present specification, acrylate and / or methacrylate is referred to as (meth) acrylate, acrylamide and / or methacrylamide is referred to as (meth) acrylamide, and acrylic acid and / or methacrylic acid is referred to as (meth) acrylic acid.

The present invention is a method for producing a polymer flocculant powder, which dries a polymer emulsion obtained by emulsion-polymerizing an aqueous solution of a monomer mixture containing at least a cationic monomer and a crosslinkable monomer. It comprises the following steps (A) to (D).
Emulsification step (A): An aqueous phase containing an aqueous solution of the monomer mixture and an oil phase containing a hydrocarbon and a surfactant which are substantially immiscible with water are mixed to obtain a median diameter of the emulsified particles. An emulsification step for producing a water-in-oil monomeric emulsion having a size of 10 μm or less.
Polymerization step (B): The monomer mixture in the water-in-oil monomer emulsion is polymerized in the presence of a radical polymerization initiator to obtain a water-in-oil polymer emulsion containing a polymer in a dispersed phase. Polymerization process to produce,
Recirculation dehydration step (C): Of the condensed liquid consisting of water and hydrocarbons obtained by condensing the vapor separated by evaporating water and hydrocarbons from the water-in-oil polymer emulsion, water is discharged to the outside of the system. At the same time, by returning the hydrocarbon to the system, a part of water is removed from the water-in-oil polymer emulsion until the dehydration rate represented by the formula (1) is in the range of 65 to 99%. In the reflux dehydration step of preparing a dispersion liquid of a polymer, the mass of the hydrocarbon used is 0.6 to 2.0 times the mass of the solid content of the water-in-oil polymer emulsion. Reflux dehydration process,
Drying step (D): A drying step of removing hydrocarbons and water from the dispersion to prepare a powder of the polymer.

(1) Emulsification step (A)
In the emulsification step (A), an aqueous phase consisting of an aqueous solution of a monomer mixture containing at least a cationic monomer and a crosslinkable monomer, and a hydrocarbon and a surfactant substantially immiscible with water. The oil phase containing the above is mixed and emulsified to prepare a water-in-oil monomeric emulsion. The aqueous phase constitutes the dispersed phase of the emulsion and the oil phase constitutes the continuous phase of the emulsion.

The cationic monomer used in the present invention can be any monomer having a radically polymerizable double bond and a cation group capable of radical polymerization. Specifically, in addition to the compound represented by the following general formula (2), diallyldialkylammonium halides such as diallyldimethylammonium chloride can be mentioned. Among these cationic monomers, the following general formula (2) is used because it has excellent radical polymerization reactivity, is easy to increase the molecular weight, and has excellent performance as a polymer flocculant of the obtained polymer. The compound represented by is preferable.

_{^{CH 2 = CR 1 -CO-X}} -Q-N + R 2 R 3 R 4 · Z - ··· of (2)

However, R ¹ is a hydrogen atom or a methyl group, R ² and R ³ are independently alkyl groups or benzyl groups having 1 to 3 carbon atoms, and R ⁴ is a hydrogen atom or an alkyl group or benzyl group having 1 to 3 carbon atoms. Yes, it may be of the same type or different types. X represents an oxygen atom or NH, Q represents an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, Z ⁻ represents a counter anion, and Z ⁻ represents a halide ion such as a chloride ion. And sulfate ion are exemplified.

Specific examples of the cationic monomer represented by the general formula (2) include dialkyls such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and dimethylamino-2-hydroxypropyl (meth) acrylate. Examples thereof include hydrochlorides and sulfates of dialkylaminoalkyl (meth) acrylamide such as aminoalkyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide. Further, it is a halogenated alkyl adduct such as methyl chloride of dialkylaminoalkyl (meth) acrylate or dialkylaminoalkyl (meth) acrylamide, a halogenated benzyl adduct such as benzyl chloride, a dialkyl adduct such as dimethyl sulfate, and the like. A quaternary salt is exemplified.

Among these preferable cationic monomers, a quaternary salt which is a methyl chloride adduct of dimethylaminoethyl acrylate which is particularly easy to increase the molecular weight required for a polymer flocculant and a methyl chloride adduct of dimethylaminoethyl methacrylate. The quaternary salt is most preferable. These cationic monomers may be used alone or in combination of two or more.

In the present invention, a monomer copolymerizable with the above-mentioned cationic monomer can also be used in combination. Among these monomers, nonionic monomers and anionic monomers are exemplified below.

Nonionic monomers include (meth) acrylamide compounds, (meth) methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and hydroxyethyl (meth) acrylate. Examples thereof include alkyl acrylate, styrene, acrylonitrile, vinyl acetate and the like. Among these nonionic monomers, (meth) acrylamide is preferable, water-soluble, and highly high because it is easy to increase the molecular weight required as a polymer flocculant and the performance as a polymer flocculant is excellent. Acrylamide, which has particularly excellent performance as a molecular flocculant, is most preferable. These nonionic monomers may be used alone or in combination of two or more.

Examples of the anionic monomer include (meth) acrylic acid and salts thereof, vinyl sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, maleic acid, and salts thereof. Among these anionic monomers, (meth) acrylic acid and salts thereof are preferable because it is easy to increase the molecular weight required as a polymer flocculant and the performance as a polymer flocculant is excellent. As the salts, alkali metal salts such as ammonium salt, sodium salt and potassium salt are preferable. These anionic monomers may be used alone or in combination of two or more.

In the present invention, the compounding ratio (molar ratio) of each monomer in the monomer mixture is not particularly limited. The compounding ratio (molar ratio) of each monomer in the monomer mixture is cationic monomer: anionic monomer: nonionic monomer = 1 to 100: 0 to 99: 0 to 99. .. When a nonionic monomer is used, the content of the nonionic monomer in the monomer mixture is preferably 3 to 98 mol%, particularly preferably 5 to 95 mol%.

In the present invention, the crosslinkable monomer is used for the purpose of introducing a branch or a crosslinked structure into a polymer chain. As the crosslinkable monomer, methylenebisacrylamide or a di (meth) acrylate represented by the following formula (3) is preferable. In particular, the latter is preferably ethylene oxide having high water solubility and / or propylene glycol-modified di (meth) acrylate. Among these, methylenebisacrylamide having a small molecular weight, being water-soluble and having high reactivity is particularly preferable.

CH ₂ = CR ⁵ -CO-Y-CO-CR ⁶ = CH ₂ ... (3)

However, R ⁵ and R ⁶ are independently H or CH ₃ , Y is O (C ₂ H ₄ O) _n or O (C ₃ H ₆ O) _n , and n is an integer of 1 to 10.

The amount of the crosslinkable monomer is preferably 1 to 1000 ppm, more preferably 1 to 500 ppm, based on the total monomer mass of the monomer mixture. If it is added in excess of 1000 ppm, the degree of cross-linking is too high, and the aggregation performance as a polymer flocculant is significantly reduced.

The hydrocarbons used in the present invention are substantially immiscible with water. In the present invention, substantially immiscible with water means that the solubility in water at 25 ° C. is less than 1000 mg / L. The hydrocarbon used in the present invention preferably has a boiling point in the range of 65 to 180 ° C. at normal pressure, and more preferably in the range of 65 to 130 ° C. Specific examples thereof include hydrocarbons such as n-hexane, cyclohexane, n-heptane, n-octane, and isooctane, as well as paraffins, various mineral oils, and mixtures thereof. Among these, n-heptane has advantages such as azeotropic boiling with water in the reflux dehydration process, drying at a relatively low temperature in the range of 40 to 90 ° C. in the drying process, and easy recovery and reuse. Is the most preferable.
The content of hydrocarbons in the emulsification step (A) and the polymerization step (B) is preferably 15 to 50% by mass with respect to the total amount of the water-in-oil emulsion.

In the present invention, the surfactant is used for the purpose of imparting emulsification stability of the emulsion and dispersion stability of the slurry in the emulsification step (A), the polymerization step (B), and the reflux dehydration step (C). Further, in the production method of the present invention, since it is often dried immediately after polymerization to form a powder, it is not always necessary to improve the separation stability on the premise of long-term storage of the emulsion.
The HLB value of the preferable surfactant in the emulsification step (A) and the polymerization step (B) is 3.0 to 9.0, more preferably 3.0 to 5.0. Further, two or more kinds of surfactants having different HLB values may be used in combination. When two or more kinds of surfactants are used in combination, it is preferable to adjust the weighted average of the HLB values of each surfactant so as to be in the range of 3.0 to 9.0, and 3.0 to 3.0 to 9.0. The range of 5.0 is more preferred.

Here, the HLB value indicates the molecular weight of the hydrophilic group portion in the total molecular weight of the surfactant, and the nonionic surfactant is obtained by the formula of Griffin shown in the following general formula (4). Is something that can be done. The HLB value of the mixed surfactant composed of two or more kinds of nonionic surfactants is obtained as follows. The HLB value of the mixed surfactant is the load average of the HLB values of each nonionic surfactant based on the blending ratio.

Mixing HLB value _{= Σ (HLB S × W S} ) / Σ W S ··· Equation (4)

However, the HLB _S of the general formula (4) indicates the HLB value of the nonionic surfactant S. Further, _{W S} denotes the mass (g) of the nonionic surfactant S has a value of HLB _S.

Examples of surfactants are polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, polyoxyethyl alkylene alkyl ether, sorbitan monooleate, sorbitan sesquiolate, sorbitan monolaure. Rate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan triolate, polyoxyethylene sorbit tetraoleate, polyethylene glycol monooleate, polyethylene glycol dioleate, diethanolamide oleate, monoethanolamide laurate, monostearate Nonionic surfactants such as ethanolamide can be mentioned. The effective addition amount of these surfactants is preferably 0.25 to 15% by mass, more preferably 0.5 to 10% by mass, based on the total amount of the water-in-oil emulsion.

The emulsification conditions are appropriately set according to the composition of the aqueous phase and the oil phase and the emulsification machine used.
In the present invention, the median diameter of the emulsified particles composed of the aqueous solution of the monomer mixture is 10 μm or less. Further, in the present invention, it is preferable that the emulsified particles in the water-in-oil monomer emulsion and the emulsified particles in the water-in-oil polymer emulsion obtained by polymerizing the emulsified particles have substantially the same particle size distribution. .. Therefore, in order to make the particle size distribution of the primary particles of the polymer powder 10 μm or less, the median diameter of the particle size distribution of the emulsified particles in the emulsification step (A) must also be 10 μm or less. The median diameter of the emulsified particles is preferably 0.3 to 10 μm, more preferably 0.5 to 5 μm, and most preferably 0.7 to 3 μm. When the median diameter of the emulsified particles exceeds 10 μm, the aggregation performance of the polymer flocculant is significantly reduced. Even if the median diameter is made smaller than 0.3 μm, the performance of the polymer flocculant is not improved, the amount of the surfactant needs to be increased, and the process of applying higher shear with an emulsifier is required, which is not preferable.
In the present invention, the emulsified particle size means the volume average particle size measured by the laser light scattering method.

(2) Polymerization step (B)
In the polymerization step (B), the above-mentioned monomer mixture in the water-in-oil monomer emulsion is polymerized in the presence of a radical polymerization initiator, and the obtained polymer is contained in the dispersed phase. Make a coalesced emulsion.

The polymerization conditions are appropriately set according to the monomer to be used, the initiator, and the physical properties of the polymer. The polymerization temperature is 0 to 100 ° C., preferably 10 to 80 ° C. The monomer concentration is preferably 20 to 50% by mass, more preferably 25 to 45% by mass. The polymerization time is preferably 1 to 10 hours.

Examples of the polymerization initiator include persulfates such as sodium persulfate and potassium persulfate; organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide, and paramentan hydroperoxide; 2,2'-azobis- ( Amidinopropane) Hydrochloride, azobiscyanovaleric acid, 2,2'-azobisisobutyronitrile and azo compounds such as 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] ; And known ones such as a redox catalyst composed of a combination of hydrogen peroxide, persulfate, sodium bicarbonate and ferrous sulfate. These polymerization initiators may be used alone or in combination of two or more.

As a method for adjusting the molecular weight, a known chain transfer agent can be used. Examples of the chain transfer agent include thiol compounds such as mercaptoethanol and mercaptopropionic acid; reducing inorganic salts such as sodium sulfite, sodium hydrogen sulfite and sodium hypophosphate; alcohols such as ethanol and isopropyl alcohol; sodium methallyl sulfonate. And other allyl compounds.

In addition, additives such as stabilizers, pH adjusters, and antioxidants may be added as long as the effects of the present invention are not impaired.

(3) Reflux dehydration step (C)
In the reflux dehydration step (C), of the condensed liquid consisting of water and hydrocarbons obtained by condensing the vapor separated by evaporating water and hydrocarbons from the water-in-oil polymer emulsion, water is removed from the system. By discharging and returning the hydrocarbon to the system, a part of water is removed from the water-in-oil polymer emulsion to prepare a dispersion of the polymer.

In the production method of the present invention, before the water-in-oil polymer emulsion obtained in the polymerization step (B) is dried under reduced pressure in the drying step (D), the emulsion is not destroyed in the reflux dehydration step (C). Water needs to be removed. If the reflux dehydration step (C) is not carried out or the drying step (D) is carried out with insufficient removal of water, the hydrocarbons are dried before the water, and the water-in-oil polymer emulsion is emulsified. The particles coalesce into a huge hydrogel-like deposit. In that case, the surface area of the gel-like sediment becomes small, so that the remaining water becomes less dry. When the remaining water is subsequently dried under reduced pressure over time, the polymer is deposited on the bottom of the beaker or reactor and solidifies into a glass while adhering. Therefore, it becomes difficult to take it out and pulverize it.

In the reflux dehydration step (C), water is removed from the water-in-oil polymer emulsion until the dehydration rate represented by the following formula (1) is in the range of 65 to 99%, and then in the drying step (D). Dry under reduced pressure. If the drying step (D) is proceeded before the dehydration rate reaches 65%, the emulsified particles of the water-in-oil polymer emulsion may coalesce into a huge hydrogel-like deposit as described above. , There are problems such as poor drying property and difficulty in taking out the solidified product after drying. If reflux dehydration is continued until the dehydration rate exceeds 99%, the polymer may be thermally deteriorated. The more preferred dehydration rate range is 75-97%, and the most preferred dehydration rate range is 80-95%.

The reflux dehydration step (C) is usually carried out under a reduced pressure condition from normal pressure to an absolute pressure of 4 kPa, preferably under a reduced pressure condition from normal pressure to an absolute pressure of 40 kPa. The lower the pressure, the higher the evaporation rate of the heterogeneous azeotropic mixture of hydrocarbons and water, so that the time of the reflux dehydration step (C) can be shortened. However, when reflux dehydration is performed under a pressure lower than the absolute pressure of 40 kPa, the amount of unintended deposits generated may increase, such as the polymer adhering to the gas-liquid interface near the liquid surface on the reactor wall surface and solidifying.

In the reflux dehydration step (C), the amount of hydrocarbons in the step is 0.6 to 0.6 to the mass of the solid content (meaning the total amount of components other than water and solvent) contained in the water-in-oil polymer emulsion. It is 2.0 times. When the content of hydrocarbon is less than 0.6 times the mass of the crosslinked polymer, the crosslinked polymer particles in which the emulsified particles are almost dried before proceeding to the next drying step (D) are intended. It may agglomerate to form huge agglomerates. In the case of mass production equipment, the reflux dehydration step (C) and the drying step (D) may be carried out in separate devices such as a stirring tank type reactor and a vacuum mixing dryer, and a huge agglomerate is produced. If it occurs, it will not be possible to transfer the liquid to the next device, which is not preferable. Further, there is no merit even if the content of the hydrocarbon is more than 2.0 times the mass of the crosslinked polymer, and it is useless because the amount of the target polymer flocculant obtained is reduced. A more preferred hydrocarbon content is 0.7 to 1.5 times the mass of the crosslinked polymer. Further, the polymerization step (B) may be carried out with a smaller content of hydrocarbons, and then additional hydrocarbons may be added before and / or during the reflux dehydration step (C).

The reflux dehydration step (C) is preferably carried out in the state of a slurry in which crosslinked polymer particles are dispersed in a continuous phase in the presence of a surfactant having an HLB value of 3.0 to 9.0. The HLB value of the more preferable surfactant is 3.0 to 5.0. Further, two or more kinds of surfactants having different HLB values may be used in combination. When two or more kinds of surfactants are used in combination, it is preferable to adjust the HLB value so that the weighted average of the HLB values of each surfactant is 3.0 to 9.0. A range of ~ 5.0 is more preferred. When the reflux dehydration step (C) is carried out under the condition of HLB> 9.0, the crosslinked polymer particles formed by almost drying the emulsified particles before moving to the next drying step (D) are formed in the same manner as described above. It is not preferable because it may unintentionally agglomerate to generate huge agglomerates, which makes it impossible to transfer the liquid to the next device.

(4) Drying step (D)
In the drying step (D), hydrocarbons and water are removed from the slurry (dispersion liquid) of the crosslinked polymer particles to prepare a powder of the crosslinked polymer.

The drying step (D) is preferably carried out under a reduced pressure condition of an absolute pressure of 2 to 20 kPa. The lower the pressure, the higher the evaporation rate of hydrocarbons and water, which is preferable because the time of the drying step (D) can be shortened. However, when drying under reduced pressure under a pressure lower than the absolute pressure of 2 kPa from the beginning, depending on the type and content of hydrocarbons and the drying temperature, the amount of hydrocarbons evaporated is too large to be condensed by the condenser, and the hydrocarbons are carbonized in the vacuum pump. Hydrogen may be inhaled. In that case, it is preferable to gradually reduce the pressure and dry according to the temperature difference between the refrigerant temperature and the condensate temperature of the condenser and the state of condensation. Further, it is not preferable to dry at a pressure higher than the absolute pressure of 20 kPa from the beginning to the end of the drying step (D) because the drying time is long.

(5) Granulation process (E)
In the production method of the present invention, it is preferable to carry out the granulation step (E) after the drying step (D). The granulation step (E) is performed in order to further improve the powder properties of the polymer flocculant powdered in the drying step (D). By performing the granulation step (E), the same handleability as a general-purpose powder product can be obtained. In the granulation step (E), the dry powder of the crosslinked polymer obtained in the drying step (D) is stirred and mixed, a binder is added, wet stirring and granulation is performed, and then the powder is dried again. It can be carried out. Examples of the binder include water, an aqueous solution in which another water-soluble polymer is dissolved, and a water-in-oil emulsion in which water-containing gel-like fine particles are dispersed. Two or more of these binders can be used in combination. The binder is preferably added while stirring the powder of the crosslinked polymer. By adding with stirring, the powder and the binder can be mixed more uniformly, and a granulated product having high granulation strength can be obtained.
The addition rate of the binder is preferably 3 to 70% by mass, more preferably 4 to 65% by mass, based on the polymer flocculant powder. The addition rate of water contained in the binder is preferably 3 to 30% by mass, more preferably 4 to 20% by mass, based on the mass of the polymer flocculant powder. If the addition rate of the binder and the water contained in it is too small, it may not be possible to granulate sufficiently, and if it is too large, it may be granulated too much and a large amount of coarse particles may be generated, or the subsequent redrying may take a long time. is there.
In the granulation step (E), if necessary, in order to adjust the particle size of the obtained granulated product, the granulated product after drying is sieved, or the coarse particles generated by the sieving are crushed. You may.

As the other water-soluble polymer used in the granulation step (E), Poval having a saponification degree of 78.0 to 95.0 mol% and an average molecular weight of 10,000 to 70,000 is preferable. By using the Poval, a granulated product having high granulation strength can be obtained.

As a specific example of the granulation step (E), for example, the polymer flocculant powder obtained in the drying step (D) is weighed into a poly cup and stirred with a stirring blade with respect to the mass of the polymer flocculant powder. Add and mix 0.1 to 0.2 times the amount of 8% by mass Poval aqueous solution over several minutes with a syringe pump, vacuum dry at 90 ° C. for 1 hour, and then sieve with a stainless steel test sieve with a mesh size of 2.36 mm. Examples thereof include a method of separating, further crushing the on-product, and passing the entire sample through the same test sieve to obtain a granulated product.

In the sludge dehydration method in which at least one of the polymer flocculants obtained by the production method of the present invention is added to dehydrate the sludge, the sludge to be treated is not particularly limited. In addition to sludge generated in sewage treatment, manure treatment, domestic wastewater treatment, etc., sludge generated in various industrial wastewater treatments such as food factories, meat processing and chemical factories, raw urine generated in livestock farms such as pig farms and its wastewater Various sludges such as sludge generated in the treatment, pulp, and sludge generated in the papermaking industry are treated. There are no restrictions on the type of sludge, and initial sludge, excess sludge, mixed sludge thereof, concentrated sludge, digested sludge treated with anaerobic microorganisms, etc. are all treated.

The sludge dehydration method of the present invention is characterized in that at least one of the polymer flocculants obtained by the production method of the present invention is added to the various sludges to dehydrate them. The following methods are exemplified as specific examples of the dehydration method.
That is, an inorganic flocculant is added to the sludge as needed, and the pH is preferably adjusted to 4 to 7. Then, the polymer flocculant of the present invention is added to the sludge, and the suspension in the sludge and the polymer flocculant are allowed to act by stirring and / or mixing by a known method to form sludge flocs. The formed sludge flocs are mechanically dehydrated by a known means to separate them into treated water and a dehydrated cake. When a crosslinked amphoteric polymer is used as the polymer flocculant of the present invention, it is preferable to use the inorganic flocculant in combination. Further, when the purpose is deodorization, dephosphorification, denitrification, etc., the pH of sludge is preferably less than 5.
The inorganic flocculant is not particularly limited, and examples thereof include a sulfate band, polyaluminum chloride, ferric chloride, ferrous sulfate, and polyferric sulfate.
The dehydrator is not particularly limited, and examples thereof include a screw press type dehydrator, a belt press type dehydrator, a filter press type dehydrator, a screw decanter, and a multiple disk.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. The methods for measuring various physical properties are as follows. The temperature condition for measuring various physical properties is 25 ° C. unless otherwise specified.

[Viscosity of 0.5% aqueous solution]
A sample (powder sample) in an amount of 0.50% by mass was added to 400 mL of pure water and sufficiently dissolved to prepare a sample solution. The viscosity of this sample solution at 25 ° C. and a rotor rotation speed of 12 rpm was measured using a B-type rotary viscometer.

[0.1% salt viscosity]
To a sodium chloride aqueous solution prepared by dissolving 5.84 g of sodium chloride in pure water to a total volume of 80.0 mL, add 20.0 mL of the sample solution after measuring the viscosity of the 0.5% aqueous solution to sufficiently dissolve the sample. A solution was prepared. The viscosity of this sample solution at 25 ° C. and a rotor rotation speed of 60 rpm was measured using a B-type rotary viscometer equipped with a BL adapter and a dedicated BL rotor.

[Bulk specific gravity]
After filling the container with the sample (powder sample) from the funnel set on the cylindrical container with a capacity of 25 mL until it overflows, remove the heaped excess cleanly, and the mass of the sample that fits perfectly in the cylindrical container. The bulk specific gravity was calculated from the volume ratio.

[Granulation strength]
The sample (powder sample) was sieved with a stainless steel test sieve, and particles having a particle size of 1.0 to 1.7 mm were taken out. The granulation strength of these particles was measured by the following method.
First, the first particle whose granulation strength was measured was sandwiched between a laboratory table and a glass plate, and a load was applied from above the glass plate to compress the particles, and the load was gradually increased until the particles were destroyed. Then, the load at the moment when the particles were broken was measured with a hardness tester (trade name "Teklock Durometer GS-720G" manufactured by Teclock Co., Ltd.). Care was taken to keep the laboratory table and the glass plate as parallel as possible. In addition, a load was applied to the particles from directly above the particles via a glass plate with a needle of a hardness tester for measurement.
After measuring the load at the time of compression failure of the first particle, the same operation is repeated to measure the load at the time of compression failure of a total of 10 particles, and the average value of the load is calculated to obtain the average value of the load and the granulation strength (N) And said.

[Flock diameter]
The size of the flocs (flock diameter) in the agglomerated sludge was visually measured.

[Gravity filterability]
Aggregated sludge was poured into a stainless steel test sieve having an inner diameter of 80 mm, a depth of 50 mm, and an opening of 250 μm at once, and gravity filtration was performed. At this time, set the funnel so that the filtrate enters the 200 mL graduated cylinder, measure the volume of the filtrate 5 seconds, 10 seconds, 20 seconds, and 30 seconds after the sludge is added, and perform gravity filtration. Gender was evaluated. Of these, the volume of the filtrate after 10 seconds was defined as the 10-second back liquid volume (mL).

[Appearance of filtrate]
The appearance of the filtrate after the evaluation of the gravity filterability was visually evaluated according to the following criteria.
⊚: No outflow of suspended component (SS) is observed in the filtrate 〇: Almost no outflow of suspended component (SS) is observed in the filtrate △: Outflow of suspended component (SS) is observed in the filtrate A small amount can be seen ×: A large amount of suspended component (SS) flows out from the filtrate.

[Moisture content of dehydrated cake]
A part of the water-containing cake of sludge after gravity filtration remaining on the stainless steel test sieve after evaluating the gravity filterability was taken out in an appropriate amount (about 12 g), and a nylon filter cloth having an opening of 180 μm was set inside for centrifugation. A dehydrated cake was obtained by centrifugation at 2000 rpm for 10 minutes using a settling tube. The obtained dehydrated cake is taken out, weighed in an aluminum pan, dried in a hot air dryer at 105 ° C. for 16 hours, and then the mass after drying is measured, and water content is obtained from the mass ratio of the amount reduced by drying and the mass before drying. I asked for the rate.

<Manufacturing example 1>
17.1 g of sorbitan sesquiolate having an HLB of 3.7 was weighed in a cylindrical separable flask having a capacity of 2 L, and 256.0 g of normal heptane was added and dissolved to prepare an oil phase. On the other hand, 463.8 g of a 79 mass% dimethylaminoethyl acrylate quaternary salt chloride aqueous solution and 67.2 g of a 50 mass% acrylamide aqueous solution were mixed in another beaker, and a 0.1 mass% aqueous solution of methylenebisacrylamide was used as a cross-linking agent. After adding 6 g, 0.8 g of isopropyl alcohol, 4.0 g of a 5 mass% aqueous solution of EDTA / disodium as a chelating agent, and 2.0 g of a 0.35 mass% aqueous solution of t-butyl hydroperoxide as an initiator, ion exchange Water was added and the pH was adjusted to 4.0 with 98% sulfuric acid to prepare 682.6 g of aqueous phase.

Next, the aqueous phase was added while stirring the oil phase in the separable flask, and the mixture was stirred at high speed with a homogenizer to prepare a water-in-oil monomer emulsion having a median diameter of 1.5 μm. A separable cover equipped with a nitrogen gas blowing tube, a reflux condenser, and a thermometer was set in the flask, and degassing was started with nitrogen gas while stirring with a stirring blade. After sufficient degassing, while supplying nitrogen gas, nitrogen gas containing 0.02 vol% of sulfur dioxide is further blown into the water-in-oil monomer emulsion at a supply amount of 11.6 ml / min to start polymerization. I let you. After reaching 50 ° C., after holding at this temperature for 2 hours, the supply amount of nitrogen gas containing sulfur dioxide is increased to 312.2 ml / min, and after further holding at 50 ° C. for 1 hour, nitrogen gas and sulfur dioxide are contained. Nitrogen gas was stopped and polymerization was completed. Then, 4.0 g of a 1% by mass aqueous solution of sodium pyrosulfite and 9.7 g of a 50% by mass aqueous solution of malic acid were added and mixed to obtain a water-in-oil polymer emulsion containing a crosslinked polymer. The composition ratio of the obtained water-in-oil polymer emulsion was 45.4% by mass of solid content, 24.5% by mass of normal heptane, and 30% of water as a result of slight volatilization of normal heptane and water during polymerization. It was 1% by mass.

Next, a separate flask with a capacity of 300 mL equipped with a nitrogen gas inlet, a Dean-Stark apparatus with a reflux condenser on the top, a thermometer, and a vacuum gauge, a pressure control valve, and a vacuum pump on the reflux condenser. In addition, 100.0 g of the aqueous polymer emulsion containing the crosslinked polymer obtained above and 25.4 g of normal heptane were added so that the content of normal heptane was 1.1 times the mass of the solid content. Then, normal heptane was charged up to the branch in the straight pipe part under the reflux condenser, and nitrogen gas was flowed while stirring the inside of the flask with a stirring blade to replace the gas phase in the system with nitrogen.

After that, when the temperature of the oil bath began to rise to 130 ° C., the temperature of the water-in-oil polymer emulsion also increased and reached the co-boiling point at about 84 ° C., and the azeotropic steam containing normal heptane and water was generated. It started to appear. The azeotropic steam rises to the reflux condenser, condenses into a liquid, and falls into the straight pipe section. There, water is phase-separated from normal heptane, and water collects in the lower phase of the straight pipe. On the other hand, since there is normal heptane in the upper phase of the straight pipe portion, the normal heptane overflowing from the straight pipe portion returns to the flask through the branch pipe. When the amount of water accumulated in the straight pipe portion increases in this way, the cock under the straight pipe portion is opened to drain the water, and this operation is repeated until the reflux dehydration step is completed. Then, after the dehydration rate reached 92%, the water-in-oil polymer emulsion was cooled to 40 ° C. or lower to complete the reflux dehydration step.
As the reflux dehydration step progressed and the amount of water contained in the water-in-oil polymer emulsion in the flask decreased, the boiling point increased, and the boiling point of normal heptane gradually approached 98 ° C.

Subsequently, after draining the residual liquid in the straight pipe portion of the Dean-Stark apparatus and the liquid receiving tank installed under it, the pressure is reduced to an absolute pressure of 13 kPa under stirring, and the oil bath is heated from room temperature to 90 ° C to reduce the pressure. It was dried. On the way, the temperature of the water-in-oil polymer emulsion reached the boiling point at about 40 to 43 ° C., and steam containing normal heptane and the remaining water began to be emitted. The degree of vacuum was adjusted while observing the flow rate of the condensate, 90% or more of the total amount of the solvent was evaporated, and after confirming that the product temperature started to rise, finish drying was performed at an absolute pressure of 4 kPa for 30 minutes. The cock under the straight pipe was always opened so that the condensate would not be collected in the straight pipe, and the condensate was collected in the liquid receiving tank under it. When the amount of condensate accumulated in the receiving tank increased, the cock under the straight pipe was closed, the vacuum in the receiving tank was returned with nitrogen, the condensed liquid was discharged, and this operation was repeated until the drying process was completed. .. After 30 minutes, the drying step was completed, and the product temperature was cooled to 40 ° C. or lower to obtain a polymer flocculant powder A1. The state of the slurry after dehydration and the state of the powder after drying were both good. The physical properties of the obtained powder sample were evaluated and shown in Table 1. The solid content of the powder sample was 97.0% by mass.

<Comparative manufacturing example 1>
Emulsification and polymerization were carried out under the same conditions as in Production Example 1 to obtain a water-in-oil polymer emulsion containing a crosslinked polymer. Subsequently, when the vacuum drying in the next step was performed without reflux dehydration, the crosslinked polymer adhered to the bottom surface, the wall surface, the stirring blade, etc. of the separable flask and solidified, and further adhered when the vacuum drying was continued. By the time the solidified product became strong and reached the end point of drying, the deposits were hard and could not be peeled off, and finally the dried product could not be recovered.

<Production Examples 2 to 10, Comparative Production Example 4>
Production Example 1 and Production Example 1 except that the polymerization conditions such as the composition of the monomer, the median diameter, the amount of the cross-linking agent added, the hydrocarbon content, and the reflux dehydration conditions such as the end point of the dehydration rate were changed as shown in Table 1. By the same operation, polymer flocculants powders A2 to A10 and B4 were obtained. The state of the slurry after dehydration and the state of the powder after drying were both good. The physical properties of the obtained powder sample were evaluated and shown in Table 1.

<Manufacturing example 11>
Emulsification and polymerization were carried out under the same conditions as in Production Example 1 to obtain a water-in-oil polymer emulsion containing a crosslinked polymer. After the completion of the polymerization, the load average value of HLB based on the hydrocarbon content and the blending ratio of the surfactant shown in Table 1 is set to 8.0 in a separable flask having a capacity of 300 mL in the same manner as in Production Example 1. Was charged with 100.0 g of a water-in-oil polymer emulsion, 25.4 g of normal heptane, and 1.44 g of a polyethylene glycol oleic acid monoester having an HLB of 13.5, and subjected to reflux dehydration. After that, the same procedure as in Production Example 1 was carried out to obtain a polymer flocculant powder A11. The state of the slurry after dehydration and the state of the powder after drying were both good. In addition, the physical properties of the obtained powder sample were evaluated and shown in Table 1.

<Comparative Manufacturing Examples 2-3>
Emulsification and polymerization were carried out under the same conditions as in Production Example 1 to obtain a water-in-oil polymer emulsion containing a crosslinked polymer. After the completion of the polymerization, the load average value of HLB based on the hydrocarbon content and the blending ratio of the surfactant shown in Table 1 is set to 8.0 in a separable flask having a capacity of 300 mL in the same manner as in Production Example 1. 100.0 g of a water-in-oil polymer emulsion, a predetermined amount of normal heptane, and 1.44 g of a polyethylene glycol oleic acid monoester having an HLB of 13.5 were charged therein and subjected to reflux dehydration. Then, after reaching the end point of the dehydration rate shown in Table 1, the same operation as in Production Example 1 was carried out to obtain polymer flocculant powders B2 to B3.

However, in the separable flask after the completion of reflux dehydration in Comparative Production Example 2, a large amount of slurry aggregates adhered to the wall surface, and the state of the slurry after dehydration was poor.
On the other hand, in Comparative Production Example 3, the separable flask after the completion of reflux dehydration did not adhere to the wall surface as much as in Comparative Production Example 2, but after drying under reduced pressure, a part of the crosslinked polymer was in the separable flask. It adhered to the bottom surface, the wall surface, the stirring blade, etc. and solidified, and a large amount of large lumps requiring crushing were generated, and the state of the powder after drying was poor. However, such coarse particles were also appropriately pulverized into powder samples, and then the physical properties were evaluated and shown in Table 1.

However, the abbreviations in Table 1 represent the following.
"DAC": Dimethylaminoethyl acrylate Methyl chloride quaternary salt "AM": Acrylamide "MBAM": N, N'-methylenebisacrylamide "IPA": Isopropyl alcohol "IsoparG": Hydrocarbon solvent manufactured by Exxon Mobile; trade name "IsoparG"

<Manufacturing example 12>
50 g of the polymer flocculant powder A1 obtained in Production Example 1 was charged into a 300 mL stainless steel separable flask in which stainless steel anchor blades were set so that the clearance between the bottom surface and the wall surface was about 1 mm, and 200 rpm. 9 g of an 8% by mass aqueous solution in which Poval (trade name "Kuraray Poval PVA-203" (trade name "Kuraray Poval PVA-203" manufactured by Kuraray Co., Ltd. (sabling degree = 87 to 89 mol%, average molecular weight = 14,700)) was previously dissolved as a binder while stirring with Was added over about 7 minutes using a syringe pump, and wet stirring granulation was performed. Then, after drying in a vacuum dryer at 90 ° C. for 1 hour, coarse particles were removed by sieving with a stainless steel test sieve having a mesh size of 2.36 mm, and the product passing through was defined as a granulated product 1. The coarse grains were crushed so as to pass through a sieve to obtain a granulated product 2. The granulated product 1 and the granulated product 2 were mixed to obtain a polymer flocculant powder C1. In addition, the powder characteristics and physical properties of the obtained powder sample were evaluated and shown in Table 2.

<Manufacturing Examples 13 to 15>
The same procedure as in Production Example 12 was carried out to obtain polymer flocculant powders C2 to C4, except that the type of poval to prepare the binder, the concentration of the aqueous solution, and the amount of the binder added were changed as shown in Table 2. It was. In addition, the powder characteristics and physical properties of the obtained powder sample were evaluated and shown in Table 2.

<Manufacturing Examples 16 to 17>
Polymer coagulant powders C5 to C6 were obtained in the same manner as in Production Example 12, except that 8 g and 2 g of water were added as the binder instead of the aqueous Poval solution, respectively. In addition, the powder characteristics and physical properties of the obtained powder sample were evaluated and shown in Table 2.

<Comparative manufacturing example 5>
The same procedure as in Production Example 12 was carried out except that no binder was added, to obtain a polymer flocculant powder D1. In addition, the powder characteristics and physical properties of the obtained powder sample were evaluated and shown in Tables 2 and 3.

However, the abbreviations in Table 2 represent the following.
"PVA203": Poval manufactured by Kuraray Co., Ltd .; product name "PVA-203"
"PVA205": Poval manufactured by Kuraray Co., Ltd .; product name "PVA-205"

As is clear from Table 2, the polymer flocculants C1 to C6 to which the binder is added have a larger bulk specific gravity, stronger granulation strength, and powder characteristics than D1 to which no binder is added. outstanding. Further, as the amount of the binder added increased, both the bulk specific gravity and the granulation strength tended to improve. In C4 to which the aqueous Poval solution was added as the binder, the granulation strength was higher than that in C5 to which only water was added, although the amount of the binder added was smaller. It seems to be the effect of Poval.
Furthermore, as a result of the physical property evaluation, the physical properties such as the viscosity of the 0.5% aqueous solution and the viscosity of the 0.1% salt hardly changed regardless of the presence or absence of the binder and the amount of the binder added. Therefore, in the granulation step (E) of the present invention, the powder characteristics can be improved while maintaining the excellent performance of the polymer flocculant.

<Manufacturing example 18>
Similar to Production Example 12 except that 20 g of a water-in-oil polymer emulsion containing the crosslinked polymer obtained in the polymerization step of Production Example 1 was added as a binder over about 15 minutes using a syringe pump. To obtain the polymer flocculant powder E1. At this time, the water content in the binder was 10.5% with respect to the total mass of the polymer flocculant A1 and the solid content of the binder. In addition, the powder characteristics and physical properties of the obtained powder sample were evaluated and shown in Table 3.

<Manufacturing Examples 19-21>
As a binder, the same procedure as in Production Example 18 was carried out except that the amount of the water-in-oil emulsion containing the crosslinked polymer obtained in the polymerization step of Production Example 1 was changed as shown in Table 3. , Polymer flocculant powders E2 to E4 were obtained. In addition, the powder characteristics and physical properties of the obtained powder sample were evaluated and shown in Table 3.

The same tendency as in Table 2 was observed in Table 3. That is, the polymer flocculants E1 to E4 to which the binder was added had a larger bulk specific gravity, stronger granulation strength, and excellent powder properties as compared with D1 to which no binder was added. Further, as the amount of the binder added increased, both the bulk specific gravity and the granulation strength tended to improve.
Furthermore, as a result of the physical property evaluation, the physical properties such as the viscosity of the 0.5% aqueous solution and the viscosity of the 0.1% salt hardly changed regardless of the presence or absence of the binder and the amount of the binder added. Therefore, in the granulation step (E) of the present invention, the powder characteristics can be improved while maintaining the excellent performance of the polymer flocculant.

<Examples 1 to 9, Comparative Examples 1 to 3>
The sludge collected from the public sewage treatment plant 1 was subjected to a tabletop test of floc formation and centrifugal dehydration treatment. The properties of this sludge are pH = 5.0, TS = 30,900 mg / L, VTS / TS = 84.3% by mass, SS = 21,100 mg / L, VSS / SS = 85.8% by mass, The coarse suspended matter / SS = 15.2% by mass and the electric conductivity = 262 mS / m.
First, 100 mL of sludge was collected in a 300 mL beaker, and a 0.2 mass% aqueous solution of the polymer flocculant produced in Production Example 1, Production Example 3, Production Example 12, and Comparative Production Example 4 was added thereto for polymer aggregation. Each agent was added with a syringe so that the amount of the agent added was as shown in Table 4 with respect to the amount of sludge. The sludge was stirred at 1000 rpm for 30 seconds to flock the sludge, and the flock diameter was visually measured. Next, the total amount of the aggregated sludge was poured into a stainless steel test sieve having an inner diameter of 80 mm, a depth of 50 mm, and an opening of 250 μm at once, and gravity filtration was performed. At this time, the funnel was set so that the filtrate would enter the 200 mL graduated cylinder, and the volume of the filtrate was measured every predetermined time to evaluate the gravity filterability. In addition, the appearance of the filtrate was visually evaluated.
Next, an appropriate amount (about 12 g) of the hydrous cake of the sludge after gravity filtration remaining on the stainless steel test sieve after the gravity filterability was evaluated was taken out, and a centrifugal filter cloth having an opening of 180 μm was set inside. Centrifugal dehydration was carried out at 2000 rpm for 10 minutes using a settling tube, and the water content of the obtained dehydrated cake was measured. The results of these tests are shown in Table 4.

From Table 4, the polymer flocculants A1, A3, and C1 obtained in Production Examples 1, 3, and 12 were polymerized with respect to the sludge of the public sewage treatment plant 1 without adding a cross-linking agent. Compared with B4 of Comparative Production Example 4, the amount of the polymer flocculant added was slightly increased, but the floc diameter was large, the gravity filterability was excellent, and no outflow of the suspended component (SS) was observed in the filtrate. The water content of the dehydrated cake was as low as 82% or less, which was excellent.
Further, in A1 in which the median diameter was smaller than that in A3 and in C1 in which A1 was granulated, the water content of the dehydrated cake was less than 80%, which was superior to A3 in dehydration performance.

<Examples 10 to 18, Comparative Examples 4 to 7>
The sludge collected from the public sewage treatment plant 2 was subjected to a tabletop test of floc formation and centrifugal dehydration treatment. The properties of this sludge are pH = 5.1, TS = 41,400 mg / L, VTS / TS = 72.1% by mass, SS = 35,300 mg / L, VSS / SS = 72.4% by mass, The coarse suspended matter / SS = 17.5% by mass and the electric conductivity = 252 mS / m.
100 mL of sludge was collected in a 300 mL beaker, and a 0.2 mass% aqueous solution of the polymer flocculant produced in Production Example 6, Production Example 11, Production Example 18, and Comparative Production Example 4 was added to the sludge. Each was added with a syringe so that the amount added was as shown in Table 5 with respect to the amount of sludge. After that, the same operation as in Example 1 was carried out to measure the floc diameter, gravity filterability, appearance of the filtrate, and water content of the dehydrated cake. The results of these tests are shown in Table 5.

From Table 5, with respect to the sludge of the public sewage treatment plant 2, the polymer flocculant B4 of Comparative Production Example 4 in which the cross-linking agent was not added did not form flocs at all at any amount of 200 to 400 ppm. It was. On the other hand, the polymer flocculants A6, A11, and E1 obtained in Production Example 6, Production Example 11, and Production Example 18 all formed flocs and were extremely effective as polymer flocculants for refractory sludge. ..
In particular, with the polymer flocculant A6 having a high degree of cross-linking, the amount of the polymer flocculant added is slightly larger than that of A11 and E1, but when the appropriate amount is added, the floc diameter is large, the gravity filterability is excellent, and the filtrate is a filtrate. No outflow of the suspended component (SS) was observed, and the water content of the dehydrated cake was as low as about 74%, and the dehydration performance was excellent.
As described above, when the polymer flocculant obtained by the production method of the present invention is used, excellent dehydration performance is exhibited even for difficult-to-dehydrate sludge.

Claims (12)

A method for producing a polymer flocculant powder, which dries a polymer emulsion obtained by emulsion-polymerizing a monomer mixture containing at least a cationic monomer and a crosslinkable monomer, according to the following step (A). To (D)
Step (A): An aqueous phase containing an aqueous solution of the monomer mixture and an oil phase containing a hydrocarbon and a surfactant which are substantially immiscible with water are mixed to reduce the median diameter of the emulsified particles. An emulsification step for producing a water-in-oil monomeric emulsion of 10 μm or less,
Step (B): The monomer mixture in the water-in-oil monomer emulsion is polymerized in the presence of a radical polymerization initiator to prepare a water-in-oil polymer emulsion containing a polymer in the dispersed phase. Polymerization process,
Step (C): Of the condensed liquid consisting of water and hydrocarbons obtained by condensing the vapor separated by co-boiling water and hydrocarbons from the water-in-oil polymer emulsion, water is discharged to the outside of the system. At the same time, by returning the hydrocarbon to the system, a part of water is removed from the water-in-oil polymer emulsion until the dehydration rate represented by the following formula (1) is in the range of 65 to 99%. In the reflux dehydration step of preparing a dispersion liquid of a polymer, the mass of the hydrocarbon in the reflux dehydration step is 0.6 to 2.0 with respect to the mass of the solid content of the water-in-oil polymer emulsion. Double reflux dehydration step,
Step (D): A drying step of removing hydrocarbons and water from the dispersion to prepare a powder of the polymer.
A method for producing a polymer flocculant powder, which comprises.

The method for producing a polymer flocculant powder according to claim 1, wherein the monomer mixture contains a nonionic monomer. The method for producing a polymer flocculant powder according to claim 1 or 2, wherein the cationic monomer contains one or more of the cationic monomers represented by the following general formula (2). ..

^{_{CH 2 = CR 1 -CO-X}} -Q-N + R 2 R 3 R 4 · Z - ··· of (2)

(However, R ¹ is a hydrogen atom or a methyl group, R ² and R ³ are independent alkyl groups or benzyl groups having 1 to 3 carbon atoms, and R ⁴ is a hydrogen atom or alkyl group or benzyl group having 1 to 3 carbon atoms. X is an oxygen atom or NH, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, and Z ⁻ is a counter anion.) The present invention according to any one of claims 1 to 3, wherein the cationic monomer is at least one of a methyl chloride quaternary salt of dimethylaminoethyl acrylate and a methyl chloride quaternary salt of dimethylaminoethyl methacrylate. The method for producing a polymer flocculant powder according to the above. The method for producing a polymer flocculant powder according to any one of claims 1 to 4, wherein the hydrocarbon is a hydrocarbon having a boiling point in the normal pressure range of 65 to 180 ° C. The method for producing a polymer flocculant powder according to any one of claims 1 to 5, wherein the hydrocarbon is normal heptane. The method for producing a polymer flocculant powder according to any one of claims 1 to 6, wherein the HLB value of the surfactant is 3.0 to 9.0. The method for producing a polymer flocculant powder according to any one of claims 1 to 7, wherein the reflux dehydration step of the step (C) is performed under reduced pressure conditions of normal pressure to absolute pressure of 4 kPa. The method for producing a polymer flocculant powder according to any one of claims 1 to 7, wherein the drying step of the step (D) is performed under reduced pressure conditions of an absolute pressure of 2 to 20 kPa. After the drying step of the step (D), the following step (E)
Step (E): A granulation step of adding a binder while stirring and mixing the polymer powder, wet stirring and granulating, and then drying to granulate the polymer powder.
The method for producing a polymer flocculant powder according to any one of claims 1 to 9. The method for producing a polymer flocculant powder according to claim 10, wherein the binder is a Poval aqueous solution having a saponification degree of 78.0 to 95.0 mol% and an average molecular weight of 1000 to 70000. Sludge, claim 1 method of dehydrating sludge dewatering by adding an aqueous solution of the resulting polymeric flocculant powder by the method according to any one of claims 11.