WO2018003663A1 - Method for producing polymer coagulant powder, and sludge dewatering method - Google Patents

Abstract

Provided is a method for producing a polymer coagulant powder by drying a polymer emulsion obtained by emulsion polymerization of a monomer mixture containing at least a cationic monomer and a crosslinkable monomer, the method including: a step (A) which is an emulsifying step of preparing a water-in-oil type monomer emulsion having an emulsified particle median diameter of 10 µm or less; a step (B) which is a polymerization step of preparing a water-in-oil type polymer emulsion; a step (C) which is a reflux dehydration step of preparing a polymer dispersion by discharging water contained in a condensate, which is obtained by evaporating off water and hydrocarbons from the water-in-oil type polymer emulsion and condensing the water vapor, to outside the system and returning the hydrocarbons to the system, thereby removing water until the dehydration rate is within the range 65-99%, with the mass of the hydrocarbons being 0.6-2.0 times the mass of solid content in the water-in-oil type polymer emulsion; and a step (D) which is a drying step of preparing a polymer powder by removing hydrocarbons and water from the dispersion.

Description

Method for producing polymer flocculant powder and method for dewatering sludge

The present invention relates to a method for producing a polymer flocculant powder and a method for dewatering sludge. More specifically, the present invention provides a method for producing a high-performance polymer flocculant powder capable of effectively dehydrating hardly dewaterable sludge and obtaining a dehydrated cake with a low water content, and sludge using the same. It relates to a dehydration method.

Polymer flocculants are used to agglomerate, settle and separate suspensions contained in domestic wastewater and industrial wastewater, and as a yield improver in the paper industry and as an admixture and a mudifier in civil engineering. It is used. The polymer flocculant has nonionic, anionic, cationic, and amphoteric ionic properties. Which ionic polymer flocculant is selected depends on the properties of the water to be treated and the treatment method. Among these, cationic polymer flocculants are used to flocate and dewater surplus sludge after activated sludge treatment of industrial wastewater and domestic wastewater, or as a yield improver in the paper industry. It is often done. In the former, for sludge that is difficult to dewater, a polymer having branching or crosslinking is used. In addition, the amphoteric polymer flocculant is used to coarsely flocculate suspended particles that have been neutralized with a coagulant, and can be applied to sludge that is difficult to dewater or agglomerate.

Conventional polymer flocculants are known in the form of products such as powders and water-in-oil emulsions. Among them, water-in-oil emulsions have the advantage of being excellent in solubility and being able to dissolve uniformly in a short time, but they are transported due to their higher production costs and lower active ingredient content of polymer flocculants than powders. There was a drawback that the cost was high.

Under these circumstances, recently, cationic or amphoteric water-in-oil emulsion polymers having branching or cross-linking have been dried into powder, exhibiting excellent dewatering performance even for difficult-to-dewater sludge, and reducing transportation costs. Development of high-performance polymer flocculant powder that eliminates the drawbacks and can be used in existing facilities such as a general-purpose powder automatic dissolution apparatus has been carried out.

For example, Patent Document 1 discloses a first particle having a particle size of at least 90% by weight of 10 μm or less by reverse phase polymerization of a water-soluble monomer mixture containing a cationic monomer and 5-2000 ppm of a crosslinking agent in a non-aqueous liquid. Disclosed is a method for producing a spray-dried granule, wherein an inverse emulsion of the next polymer particles is prepared, and then the inverse emulsion is spray-dried to produce a spray-dried granule having a particle size of at least 90% by weight of 20 μm or more. Yes. However, spray drying is not preferable because the drying efficiency is poor and a large amount of energy is required to sufficiently dry and powderize. In addition, because of the characteristics of spray dryers, it is necessary to dry in small portions in a short time, so it is necessary to dry at very high temperatures. High molecular weight polymers are susceptible to thermal degradation and can be manufactured under the same conditions. There was a problem that the quality varied.

In Patent Document 2, an aqueous monomer mixture containing a cationic monomer and 20 to 300 ppm of a crosslinking agent is used as a dispersed phase, and emulsified with a surfactant so that water and an immiscible hydrocarbon become a continuous phase. A water-in-oil emulsion of a cationic or amphoteric aqueous polymer polymerized, and then the emulsion-in-water emulsion is agglomerated and agglomerated, and this agglomerate is chopped to 4-6 mm using a meat chopper After that, an example is disclosed in which a drying sludge dehydrating agent is obtained by drying at 105 ° C. for 1 hour using a shelf-type ventilation dryer and crushing with a screen having a pore diameter of 2 mm. 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 degradation due to high temperature drying.

On the other hand, when using hydrocarbons with a boiling point of 100 ° C or lower, volatile and flammable properties are required, so strict caution is required during handling. Normally, carbonization is always performed in facilities that can completely block outside air. Processed under conditions outside the hydrogen combustion range. However, in Patent Document 2, there is no detailed description of processes other than emulsion break, the type of hydrocarbon is unknown, and it is unknown 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 hot air to be 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 difficulties.

Patent Document 3 discloses a step of forming an emulsion of a cationic monomer in a non-aqueous liquid having a primary particle size of less than 20 μm in the presence of an emulsifier; a step of starting and completing polymerization; and water from the emulsion. A step of substantially drying the emulsion by distillation; a step of separating the non-aqueous liquid and the polymer particles by washing the substantially dried emulsion or a slurry or solid of the dried polymer particles separated therefrom with a volatile organic solvent; Separating the polymer particles as a solid or slurry of polymer particles wetted with the volatile organic solvent; and evaporating the solvent from the solid or slurry to obtain a dry powder. A manufacturing method is disclosed.

However, Patent Document 3 is a method for producing a polymer powder for forming a homogeneous and transparent gel by dissolving or swelling in water for personal care compositions such as cosmetic compositions and topical pharmaceutical compositions. Therefore, it is different from the technical field of polymer flocculants. In addition, the process of washing the non-aqueous liquid and the emulsifier with the volatile organic solvent mixes the non-aqueous liquid and the volatile organic solvent, thus preventing reuse of the non-aqueous liquid and generating a lot of unnecessary waste liquid. Therefore, it is not preferable. Furthermore, it does not suggest a production method for improving the performance of the polymer flocculant.

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

The object of the present invention is to dry a cationic or amphoteric water-in-oil polymer emulsion having branches or crosslinks into a powder, thereby reducing transportation costs and excellent dewatering performance even for hardly dewatered sludge And providing a method for producing a high-performance polymer flocculant powder that can be used using a general-purpose automatic powder-dissolving apparatus.

As a result of diligent investigations on the above problems, the present inventors have found a method for producing a polymer flocculant containing a crosslinked polymer obtained by subjecting a specific monomer mixture to water-in-oil emulsion polymerization and then drying. Thus, a method for producing a polymer flocculant powder including a specific emulsification step, a polymerization step, a reflux dehydration step, and a drying step was established. The polymer flocculant powder obtained by this production method not only reduces the transportation cost, but also exhibits excellent dehydration performance and can be used with a general-purpose powder automatic dissolution apparatus, etc. completed.

That is, the present invention
[1] A method for producing a polymer flocculant powder for drying a polymer emulsion obtained by emulsion polymerization of a monomer mixture containing at least a cationic monomer and a crosslinkable monomer, comprising the following steps: (A) to (D)
Step (A): An aqueous phase containing an aqueous solution of the monomer mixture is mixed with an oil phase containing water and a substantially immiscible hydrocarbon and surfactant, so that the median diameter of the emulsified particles is An emulsification step for producing a water-in-oil monomer 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 produce a water-in-oil polymer emulsion containing a polymer in the dispersed phase. A polymerization process,
Step (C): Among the condensate composed of water and hydrocarbons obtained by condensing vapor separated from the water-in-oil polymer emulsion by evaporating water and hydrocarbons, water is discharged out of the system. Then, 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%. A reflux dehydration step for preparing a dispersion of coalescence, wherein 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. Process,
Step (D): A drying step in which hydrocarbons and water are removed from the dispersion to produce the polymer powder.
It is a manufacturing method of the polymer flocculent powder characterized by including this.

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

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

_{^{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 methyl group, R ² and R ³ are each independently an alkyl group or benzyl group having 1 to 3 carbon atoms, R ⁴ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a benzyl group. , and the good be the same or different .X is oxygen or NH, Q is hydroxy alkylene group of the alkylene group or a C 2-4 1 to 4 carbon atoms, Z ^- represents each pair anion).

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

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

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

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

[8] The method for producing a polymer flocculant powder according to [1], wherein the reflux dehydration step of the step (C) is performed under a reduced pressure condition of normal pressure to absolute pressure of 40 kPa.

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

[10] The method for producing a polymer flocculant granulated powder according to [1], wherein the drying step of the step (D) is performed until the product temperature of the powder reaches 50 ° C. or higher.

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

[12] The method for producing a polymer flocculant powder according to [11], 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 10,000 to 70000.

[13] The period from the end of the step (C) to before the start of the step (D), or in the step (D), includes a granulation step (F). This is a method for producing a polymer flocculant granulated powder.

[14] A sludge dewatering method in which an aqueous solution of the polymer flocculant powder obtained by the production method according to any one of [1] to [13] is added to the sludge for dewatering.

The polymer flocculant powder obtained by the production method of the present invention not only reduces the transportation cost, but also exhibits excellent dewatering performance against difficult-to-dehydrate sludge and is used with a general-purpose powder automatic dissolving device etc. can do.

The polymer flocculant powder obtained by the production method of the present invention is a flocculant for domestic and industrial wastewater sludge; a drainage yield improver for papermaking, a drainage improver, a formation aid, and a paper strength enhancer. Application to a wide range of applications such as agrochemicals for papermaking such as drilling and muddy water treatment, additives for increasing crude oil production, organic coagulants, thickeners, dispersants, scale inhibitors, antistatic agents, and textile treatment agents Is possible.

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

The present invention is a method for producing a polymer flocculant powder for drying a polymer emulsion obtained by emulsion polymerization of 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): The aqueous phase containing an aqueous solution of the monomer mixture and the oil phase containing water and a substantially immiscible hydrocarbon and surfactant are mixed to obtain the median diameter of the emulsified particles. Emulsifying step of producing a water-in-oil monomer emulsion having a thickness of 10 μm or less,
Polymerization step (B): Polymerizing the monomer mixture in the water-in-oil monomer emulsion in the presence of a radical polymerization initiator to produce a water-in-oil polymer emulsion containing a polymer in the dispersed phase. Polymerization process to make,
Reflux dehydration step (C): Out of the condensate composed of water and hydrocarbons obtained by condensing vapor separated from the water-in-oil polymer emulsion by evaporating water and hydrocarbons, water is discharged out of the system. In addition, 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%. A reflux dehydration step for preparing a polymer dispersion, wherein 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 step,
Drying step (D): A drying step of removing the hydrocarbon and water from the dispersion to produce the polymer powder.

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

As the cationic monomer used in the present invention, any monomer having a radical polymerizable double bond and a cationic group capable of radical polymerization can be used. Specifically, in addition to the compound represented by the following general formula (2), diallyldialkylammonium halides such as diallyldimethylammonium chloride can be exemplified. Among these cationic monomers, the radical polymerization reactivity is excellent, the molecular weight is easily increased, and the performance of the resulting polymer as a polymer flocculant is excellent. Therefore, the following general formula (2) The compound represented by these is preferable.

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

Wherein R ¹ is a hydrogen atom or a methyl group, R ² and R ³ are each independently an alkyl group or benzyl group having 1 to 3 carbon atoms, R ⁴ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a benzyl group. Yes, it may be the same or different. 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.

Specific examples of the cationic monomer represented by the general formula (2) include dialkyl such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and dimethylamino-2-hydroxypropyl (meth) acrylate. Examples thereof include hydrochlorides and sulfates of aminoalkyl (meth) acrylates and dialkylaminoalkyl (meth) acrylamides such as dimethylaminopropyl (meth) acrylamide. In addition, dialkylaminoalkyl (meth) acrylates and dialkylaminoalkyl (meth) acrylamides such as methyl halide addition products such as methyl chloride, benzyl halide addition products such as benzyl chloride, dialkyl sulfate addition products such as dimethyl sulfate, etc. Quaternary salts are exemplified.

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

In the present invention, a monomer copolymerizable with the aforementioned cationic monomer may be used in combination. Among these monomers, nonionic monomers and anionic monomers are exemplified below.

Nonionic monomers include (meth) acrylamide compounds, (meth) methacrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and hydroxyethyl (meth) acrylate. Examples include alkyl acrylate, styrene, acrylonitrile, and vinyl acetate. Among these nonionic monomers, (meth) acrylamide is preferred because it is easy to increase the molecular weight required as a polymer flocculant and has excellent performance as a polymer flocculant. Most preferred is acrylamide, which is particularly excellent in performance as a molecular flocculant. 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-acrylamido-2-methylpropane sulfonic acid, maleic acid, and salts thereof. Among these anionic monomers, (meth) acrylic acid and salts thereof are preferable because they can easily achieve a high molecular weight as a polymer flocculant and have excellent performance as a polymer flocculant. 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 mixing ratio (molar ratio) of each monomer in the monomer mixture is not particularly limited. The mixing 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 branched or crosslinked structure into the polymer chain. As the crosslinkable monomer, methylenebisacrylamide or di (meth) acrylate represented by the following formula (3) is preferable. In particular, the latter is preferably di (meth) acrylate modified with ethylene oxide and / or propylene glycol having high water solubility. Among these, methylenebisacrylamide having a low molecular weight, water solubility and high reactivity is particularly preferable.
CH ₂ = CR ⁵ —CO—Y—CO—CR ⁶ = CH ₂ ... (3)
However, R ⁵ and R ⁶ are each 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 crosslinking is too high, and the agglomeration performance as a polymer flocculant is remarkably lowered.

The hydrocarbon used in the present invention is substantially immiscible with water. In the present invention, being 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., more preferably in the range of 65 to 130 ° C. at normal pressure. Specific examples include hydrocarbons such as n-hexane, cyclohexane, n-heptane, n-octane, isooctane, paraffins, various mineral oils, and mixtures thereof. Among these, n-heptane is advantageous in that it is azeotroped with water in the reflux dehydration process, can be dried at a relatively low temperature of 40 to 90 ° C. in the drying process, and is easy to collect and reuse. Is most preferred.
The hydrocarbon content in the emulsification step (A) and the polymerization step (B) is preferably 15 to 50% by mass relative to the total amount of the water-in-oil emulsion.

In the present invention, the surfactant is used for the purpose of imparting emulsion 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 the powder is often dried immediately after polymerization, it is not always necessary to improve the separation stability on the premise of long-term storage of the emulsion.
The preferable HLB value of the surfactant in the emulsification step (A) and the polymerization step (B) is 3.0 to 9.0, and more preferably 3.0 to 5.0. Two or more surfactants having different HLB values may be used in combination. When two or more surfactants are used in combination, it is preferable to use the surfactant so that the weighted average of the HLB values of each surfactant is in the range of 3.0 to 9.0. A 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 Griffin equation shown in the following general formula (4). It is The HLB value of the mixed surfactant composed of two or more kinds of nonionic surfactants can be obtained as follows. The HLB value of the mixed surfactant is a load-averaged HLB value of each nonionic surfactant based on the blending ratio.
Mixed HLB value = Σ (HLB _S × W _S ) / Σ W _S (Formula 4)
However, HLB _S in the general formula (4) indicates the HLB value of the nonionic surfactant S. W _S represents the mass (g) of the nonionic surfactant S having a value of HLB _S.

Examples of surfactants include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkylene alkyl ether, sorbitan monooleate, sorbitan sesquioleate, sorbitan monolaur Rate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitol tetraoleate, polyethylene glycol monooleate, polyethylene glycol dioleate, oleic acid diethanolamide, lauric acid monoethanolamide, stearic acid mono 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 with respect to the total amount of the water-in-oil emulsion.

The emulsification conditions are appropriately set according to the composition of the water phase and the oil phase and the emulsifier to be used.
In the present invention, the median diameter of the emulsified particles made of an aqueous solution of the monomer mixture is 10 μm or less. 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 polymerization thereof have substantially the same particle size distribution. . Therefore, in order to make the median diameter of 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) needs to 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 lowered. Even if the median diameter is smaller than 0.3 μm, the performance of the polymer flocculant is not improved, and an increase in the amount of the surfactant is required, or a process of applying higher shear with an emulsifier is not preferable.
In the present invention, the emulsified particle diameter means a volume average particle diameter measured by a 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 water-in-oil heavy weight containing the resulting polymer in the dispersed phase. Make a coalesced emulsion.

Polymerization conditions are appropriately set according to the monomers and initiators used 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 paramentane hydroperoxide; 2,2′-azobis- ( Amidinopropane) hydrochloride, azobiscyanovaleric acid, 2,2′-azobisisobutyronitrile and 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] And known ones such as a redox catalyst comprising a combination of hydrogen peroxide, persulfate, sodium bisulfite, ferrous sulfate and the like. 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. Chain transfer agents include thiol compounds such as mercaptoethanol and mercaptopropionic acid; reducing inorganic salts such as sodium sulfite, sodium bisulfite and sodium hypophosphite; alcohols such as ethanol and isopropyl alcohol; sodium methallyl sulfonate And allyl compounds.

In addition, additives such as a stabilizer, a pH adjuster, and an antioxidant 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), out of the condensate composed of water and hydrocarbons obtained by condensing vapor separated from the water-in-oil polymer emulsion by evaporating water and hydrocarbons, water is removed from the system. While discharging, returning the hydrocarbon to the system, a part of the water is removed from the water-in-oil polymer emulsion to prepare a polymer dispersion.

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. When the reflux dehydration step (C) is not carried out or the drying step (D) is carried out with insufficient removal of water, the drying of hydrocarbons proceeds before water, and emulsification of the water-in-oil polymer emulsion. The particles merge to form a huge hydrogel deposit. In that case, since the gel deposit has a small surface area, the drying property of the remaining water is deteriorated. Subsequently, when the remaining water is dried under reduced pressure over a period of time, the polymer is deposited on the bottom of the beaker or the reactor and solidified into a glass state while adhering. For this reason, it is difficult to take out the powder 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. When the process proceeds to the drying step (D) before the dehydration rate reaches 65%, as in the case described above, the emulsified particles of the water-in-oil polymer emulsion are united to form a huge hydrogel deposit. There are problems such as poor drying properties 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. A more preferable dehydration rate range is 75 to 97%, and a most preferable dehydration rate range is 80 to 95%.

The reflux dehydration step (C) is usually performed under a reduced pressure condition from normal pressure to an absolute pressure of 4 kPa, and preferably performed 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 azeotrope of hydrocarbons and water, so that the time for the reflux dehydration step (C) can be shortened. However, if reflux dehydration is performed under a pressure lower than an absolute pressure of 40 kPa, the amount of unintended deposits may increase, for example, the polymer may adhere to the gas-liquid interface near the liquid level on the reactor wall and solidify.

In the reflux dehydration step (C), the amount of hydrocarbons in the step is 0.6 to 0.6 of the mass of solid content (referring to the total amount of components other than water and solvent) contained in the water-in-oil polymer emulsion. 2.0 times. If the hydrocarbon content is less than 0.6 times the mass of the cross-linked polymer, the cross-linked polymer particles formed by substantially drying the emulsified particles before moving to the next drying step (D) are intended. They 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 apparatuses such as a stirred tank reactor and a vacuum mixing dryer, for example. If it occurs, it cannot be transferred to the next apparatus, which is not preferable. Further, there is no merit even if the hydrocarbon content is more than 2.0 times the mass of the cross-linked polymer, and the amount of the desired polymer flocculant is reduced, which is useless. A more preferable hydrocarbon content is 0.7 to 1.5 times the mass of the crosslinked polymer. Furthermore, after the polymerization step (B) is carried out with a smaller hydrocarbon content, additional hydrocarbons may be added before and / or during the start of the reflux dehydration step (C).

The reflux dehydration step (C) is preferably performed in the presence of a surfactant having an HLB value of 3.0 to 9.0 in a slurry state in which cross-linked polymer particles are dispersed in a continuous phase. A more preferable surfactant has an HLB value of 3.0 to 5.0. Two or more 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 of each surfactant so that the HLB value is 3.0 to 9.0. A range of ˜5.0 is more preferable. When the reflux dehydration step (C) is performed under the condition of HLB> 9.0, the cross-linked polymer particles formed by substantially drying the emulsified particles before moving to the next drying step (D) are formed as described above. It may unintentionally aggregate to form huge aggregates, which is not preferable because it cannot be transferred to the next apparatus.

(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 produce a crosslinked polymer powder.

The drying step (D) is preferably carried out under a reduced pressure condition of 2 to 20 kPa in absolute pressure. 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 at a pressure lower than 2 kPa from the beginning, although depending on the type, content and drying temperature of the hydrocarbon, the amount of evaporation of the hydrocarbon is too large to condense in the condenser, and the vacuum pump is carbonized. Hydrogen may be inhaled. In that case, it is preferable to reduce the pressure stepwise in accordance with the temperature difference between the refrigerant temperature of the condenser and the condensate temperature and the state of condensation. In addition, drying at a pressure higher than the absolute pressure of 20 kPa from the beginning to the end of the drying step (D) is not preferable because it takes a long time to dry.

In the production method of the present invention, it is preferable to perform the granulation step (E) or (F) described below.

(5) Granulation process (E)
In the manufacturing method of this invention, it is preferable to perform a granulation process (E) after a drying process (D). The granulation step (E) is performed in order to further improve the powder characteristics 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 cross-linked polymer obtained in the drying step (D) is stirred and mixed while adding a binder, wet stirring and granulating, and then drying again. It can be carried out. Examples of the binder include water, an aqueous solution in which other 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 cross-linked polymer powder. 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 with respect to 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 with respect to the mass of the polymer flocculant powder. If the addition rate of the binder and the water contained in the binder is too small, it may not be sufficiently granulated. If it is too much, too much granulation may occur and a lot of coarse particles may be generated, or subsequent re-drying may take a long time. is there.
In the granulation step (E), in order to adjust the particle size of the obtained granulated product as necessary, the granulated product after drying is sieved or the coarse particles generated by sieving are crushed. May be.

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 polycup and stirred with a stirring blade, with respect to the mass of the polymer flocculant powder. Add 0.1 to 0.2 times the 8% by weight aqueous solution of PVA with a syringe pump for several minutes, mix and dry at 90 ° C for 1 hour, and then sieve through a stainless steel test sieve with an aperture of 2.36 mm. And the ON product is crushed, and the whole sample is passed through the same test sieve to obtain a granulated product.

(6) Granulation process (F)
In the production method of the present invention, it is also preferable to perform the granulation step (F) after the completion of the reflux dehydration step (C) and before the start of the drying step (D) or during the drying step (D). . The granulation step (F) is performed in order to further improve the powder characteristics of the polymer flocculant powdered in the drying step (D). In the granulation step (F), a binder is added as necessary between the end of the reflux dehydration step (C) and before the start of the drying step (D) or during the drying step (D). It can carry out by drying with stirring in a drying process (D). At this time, it is preferable to appropriately adjust the stirring conditions and drying conditions so that the powder characteristics of the powdery polymer flocculant are preferably improved. After the addition of the binder, the crosslinked polymer must be dried with stirring. By drying with stirring, the powder and the binder can be mixed more uniformly, and a granulated product having high granulation strength can be obtained. As a result of such granulation, the powder characteristics are improved to the same as those of a general-purpose powder product, and can be handled in the same manner with existing equipment such as an automatic melting device for general-purpose powder.

Examples of the binder include water, an aqueous solution in which a 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. Moreover, the water-in-oil polymer emulsion obtained in the polymerization process can also be used as a binder.
The addition rate of the binder is preferably 3 to 70% by mass, and more preferably 4 to 65% by mass with respect to the total mass of the solid content of the water-in-oil polymer emulsion. The addition rate of water contained in the binder is preferably 3 to 30% by mass, and more preferably 4 to 20% by mass with respect to the total mass of the solid content of the crosslinked polymer. If the addition rate of the binder and the water contained in the binder is too small, it may not be sufficiently granulated. If it is too much, too much granulation may occur and a lot of coarse particles may be generated, or subsequent re-drying may take a long time. is there.
After the drying step (D) including granulation, in order to adjust the particle size of the obtained granulated product, if necessary, the dried granulated product is sieved or coarsely generated by sieving. The grains may be crushed.

As a specific example of the drying step (D) including granulation, for example, in the reflux dehydration step (C), a separable flask equipped with a stirrer, a reflux condenser, a vacuum pump and a liquid receiving tank at the tip of the vacuum line is used. A slurry in which particles of the obtained almost dry cross-linked polymer are dispersed is charged, and a part of the water-in-oil polymer emulsion obtained in the polymerization step (B) is added as a binder at the above-mentioned preferable addition rate. After drying under reduced pressure in a 90 ° C oil bath until no hydrocarbons and the remaining water are distilled off, the mixture is then dried under reduced pressure while stirring until the product temperature reaches 50 ° C or higher. Thereafter, a method of sieving with a stainless steel test sieve having a mesh opening of 2.36 mm, further crushing the ON product, and passing the entire amount of the sample through the test sieve, a granulated product is obtained.

Other water-soluble polymers used in the granulation steps (E) and (F) are preferably poval having a saponification degree of 78.0 to 95.0 mol% and an average molecular weight of 10,000 to 70,000. By using the poval, a granulated product having a high granulation strength can be obtained.

In the sludge dewatering method in which at least one polymer flocculant obtained by the production method of the present invention is added and dehydrated, the sludge to be treated is not particularly limited. In addition to sludge generated in sewage treatment, human waste treatment and domestic wastewater treatment, sludge generated in various industrial wastewater treatment such as food factories, meat processing and chemical factories, manure and wastewater generated in livestock relations such as pig farms Various sludges such as sludge generated in the treatment, pulp or sludge generated in the paper industry are to be treated. There is no restriction | limiting also in the kind of sludge, and all are sludge sludge, excess sludge, and these mixed sludge, concentrated sludge, digested sludge treated by anaerobic microorganisms, etc.

The sludge dewatering method of the present invention is characterized in that at least one polymer flocculant obtained by the production method of the present invention is added to the above-mentioned various sludges for dehydration. The following method is illustrated as a specific example of the dehydration method.
That is, an inorganic flocculant is added to the sludge as necessary, and the pH is preferably adjusted to 4-7. Thereafter, 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 a sludge floc. The formed sludge floc is mechanically dehydrated by known means to separate into treated water and dehydrated cake. In addition, when using a crosslinkable amphoteric polymer as a polymer flocculent of this invention, it is preferable to use the said inorganic flocculant together. Moreover, when aiming at deodorization, dephosphorization, denitrification, etc., it is preferable to make the pH of sludge less than 5.
Although it does not restrict | limit especially as an inorganic flocculant, A sulfuric acid band, polyaluminum chloride, ferric chloride, ferrous sulfate, polyferric sulfate, etc. are illustrated.
Although it does not restrict | limit especially as a dehydration apparatus, A screw press type dehydrator, a belt press type dehydrator, a filter press type dehydrator, a screw decanter, a multiple disk etc. are illustrated.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The measuring method of various physical properties is as follows. The temperature condition for measuring various physical properties is 25 ° C. unless otherwise specified.

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

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

[Bulk specific gravity]
After charging the sample (powder sample) from the funnel set on the cylindrical container with a capacity of 25 mL until the container overflows, remove the piled excess and clean the mass of the sample exactly in the cylindrical container. The bulk specific gravity was determined 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. For these particles, the granulation strength was measured by the following method.
First, the first particle for measuring the granulation strength was sandwiched between an experimental table and a glass plate, a load was applied from above the glass plate to compress the particle, and the load was gradually increased until the particle was broken. Then, the load at the moment when the particles were broken was measured with a hardness meter (trade name “Tecrock Durometer GS-720G” manufactured by Tecrock Co., Ltd.). Care was taken to keep the experimental table and the glass plate as parallel as possible. Further, the load was applied to the particles from directly above the particles with a push pin of a hardness meter through a glass plate.
After measuring the load at the time of compressive fracture of the first particle, the same operation is repeated, the load at the time of compressive fracture of a total of 10 particles is measured, and the average value of the load is obtained and the granulation strength (N) It was.

[Flock diameter]
The size of floc (floc diameter) in the aggregated sludge was measured visually.

(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, and gravity filtered. At this time, set the funnel so that the filtrate enters the 200 mL measuring cylinder, measure the volume of the filtrate after elapse of 5 seconds, 10 seconds, 20 seconds, and 30 seconds after the sludge is charged. Gravity filtration Sex was evaluated. Among these, the volume of the filtrate after 10 seconds was defined as the amount of liquid after 10 seconds (mL).

[Appearance of filtrate]
The appearance of the filtrate after the evaluation of the gravity filterability was visually evaluated according to the following criteria.
◎: Suspension component (SS) outflow is not observed at all in the filtrate 〇: Suspension component (SS) outflow is hardly observed in the filtrate △: Suspension component (SS) outflow is present in the filtrate Slight amount is seen ×: Suspension component (SS) outflow is seen in a large amount in the filtrate

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

<Production Example 1>
17.1 g of sorbitan sesquiolate having an HLB of 3.7 was measured in a cylindrical separable flask having a volume 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% by mass dimethylaminoethyl acrylate methyl chloride quaternary salt solution and 67.2 g of a 50% by mass acrylamide aqueous solution were mixed in another beaker, and a 0.1% by mass aqueous solution of methylene bisacrylamide as a crosslinking agent. 6 g, 0.8 g of isopropyl alcohol, 4.0 g of a 5% by weight aqueous solution of EDTA / disodium as a chelating agent, and 2.0 g of a 0.35% by weight aqueous solution of t-butyl hydroperoxide as an initiator were added, followed by ion exchange Water was added and adjusted to pH 4.0 with 98% sulfuric acid to prepare 682.6 g of aqueous phase.

Next, the water phase was added while stirring the oil phase in a 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 sufficiently degassing, while supplying nitrogen gas, nitrogen gas containing 0.02 vol% of sulfur dioxide was further blown into the water-in-oil monomer emulsion at a supply rate of 11.6 ml / min to start polymerization. I let you. After reaching 50 ° C. and holding at this temperature for 2 hours, the supply amount of nitrogen gas containing sulfur dioxide is increased to 312.2 ml / min, and further holding at 50 ° C. for 1 hour, followed by containing nitrogen gas and sulfur dioxide Nitrogen gas was stopped to complete the polymerization. Thereafter, 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 component ratio of the obtained water-in-oil polymer emulsion was such that normal heptane and water were slightly volatilized during the polymerization, resulting in a solid content of 45.4% by mass, normal heptane of 24.5% by mass and water of 30%. It was 1 mass%.

Next, a 300 mL separable flask equipped with a nitrogen gas inlet, a Dean-Stark device with a reflux condenser attached to the top, a thermometer, and a vacuum gauge, pressure control valve, and vacuum pump on the reflux condenser. In addition, 100.0 g of the water-in-oil polymer emulsion containing the cross-linked polymer obtained above and 25.4 g of normal heptane so that the content of normal heptane is 1.1 times the mass of the solid content. In addition, normal heptane was charged up to the branch in the straight pipe part under the reflux condenser, and the gas phase in the system was replaced with nitrogen by flowing nitrogen gas while stirring the inside of the flask with a stirring blade.

Thereafter, when the temperature of the oil bath started to rise to 130 ° C., the temperature of the water-in-oil polymer emulsion also increased and reached an azeotropic point at about 84 ° C., and azeotropic vapor containing normal heptane and water was generated. I started out. The azeotropic vapor rises to the reflux condenser, condenses into a liquid, and falls to the straight pipe section. Therefore, water is phase-separated from normal heptane, and water accumulates in the lower phase of the straight pipe section. On the other hand, since normal heptane is present in the upper phase of the straight pipe part, normal heptane overflowing and overflowing from the straight pipe part 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 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. The obtained slurry having a dehydration rate of 92% had a solid content of 46.5% by mass, normal heptane of 51.1% by mass, and water of 2.4% by mass.
The boiling point increased as the reflux dehydration process progressed and the amount of water contained in the water-in-oil polymer emulsion in the flask decreased, and gradually approached the normal heptane boiling point of 98 ° C.

Subsequently, after draining the residual liquid from the straight pipe part of the Dean-Stark device and the liquid receiving tank installed thereunder, the pressure is reduced to 13 kPa with stirring and the oil bath is heated from room temperature to 90 ° C. Drying was performed. 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 come out. The degree of vacuum was adjusted while observing the flow rate of the condensate, 90% or more of the total amount of 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. In order to prevent the condensate from accumulating in the straight pipe part, the cock under the straight pipe part was always opened and accumulated in the liquid receiving tank below it. When the condensate accumulated in the liquid receiving tank increased, the cock under the straight pipe part was closed, the vacuum of the liquid receiving tank was returned with nitrogen, the condensate 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 polymer flocculant powder A1. The slurry after dehydration and the powder after drying were both good. The physical properties of the obtained powder sample were evaluated and are shown in Table 1. The solid content of the powder sample was 97.0% by mass.

<Comparative Production 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 drying under reduced pressure in the next step was performed without performing reflux dehydration, the cross-linked polymer adhered and solidified on the bottom surface, wall surface, stirring blade, etc. of the separable flask, and further adhered when continued under reduced pressure drying. When the solidified product became strong and reached the end of drying, the adhered material was hard and did not peel off, and eventually the dried product could not be recovered.

<Production Examples 2 to 10, Comparative Production Example 4>
Except that the polymerization conditions such as monomer composition, median diameter, addition amount of crosslinking agent, and the reflux dehydration conditions such as hydrocarbon content and dehydration rate end point were changed as shown in Table 1, Production Example 1 and The same operation was performed to obtain polymer flocculant powders A2 to A10 and B4. The slurry after dehydration and the powder after drying were both good. The physical properties of the obtained powder sample were evaluated and are shown in Table 1.

<Production 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 completion of the polymerization, in the same manner as in Production Example 1, the load average value of HLB based on the hydrocarbon content and surfactant blending ratio shown in Table 1 is 8.0 in a separable flask having a capacity of 300 mL. Then, 100.0 g of a water-in-oil polymer emulsion, 25.4 g of normal heptane, and 1.44 g of polyethylene glycol oleate monoester having an HLB of 13.5 were charged for dehydration under reflux. Thereafter, the same operation as in Production Example 1 was performed to obtain polymer flocculant powder A11. The slurry after dehydration and the powder after drying were both good. In addition, physical properties of the obtained powder sample were evaluated and are shown in Table 1.

<Comparative Production Examples 2 to 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 completion of the polymerization, in the same manner as in Production Example 1, the load average value of HLB based on the hydrocarbon content and surfactant blending ratio shown in Table 1 is 8.0 in a separable flask having a capacity of 300 mL. The mixture was charged with 100.0 g of a water-in-oil polymer emulsion, 1.44 g of a predetermined amount of normal heptane and 1.44 g of polyethylene glycol oleic acid monoester having an HLB of 13.5, and reflux dehydration was performed. After reaching the dehydration rate end point shown in Table 1, the same operation as in Production Example 1 was performed to obtain polymer flocculant powders B2 to B3.

However, in the separable flask after 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 bad.
On the other hand, in Comparative Production Example 3, the separable flask after completion of reflux dehydration did not adhere to the wall as in Comparative Production Example 2, but after drying under reduced pressure, a part of the crosslinked polymer was separated from the separable flask. While adhering to the bottom surface, wall surface, stirring blade and the like and solidifying, a large amount of large lumps required to be crushed were generated, and the powder state after drying was bad. However, such coarse particles were also appropriately pulverized into powder samples, and then physical properties were evaluated and are 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 “Isopar G”: hydrocarbon solvent manufactured by ExxonMobil; "IsoparG"

<Production Example 12>
50 g of the polymer flocculant powder A1 obtained in Production Example 1 is placed in a 300 mL stainless separable flask in which stainless steel anchor blades are set so that the clearance between the bottom surface and the wall surface is about 1 mm, and 200 rpm 9 g of an 8% by weight aqueous solution in which POVAL (trade name “Kuraray Poval PVA-203” manufactured by Kuraray Co., Ltd. (degree of saponification = 87 to 89 mol%, average molecular weight = 14,700)) as a binder was previously dissolved with stirring. Was added over about 7 minutes using a syringe pump, and granulated by wet stirring. Next, after drying with a 90 ° C. vacuum dryer for 1 hour, coarse particles were removed by sieving with a stainless steel test sieve having an opening of 2.36 mm, and the product passed through was designated as granulated product 1. The coarse particles 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, powder characteristics and physical properties of the obtained powder sample were evaluated and are shown in Table 2.

<Production Examples 13 to 15>
Polymer flocculant powders C2 to C4 were obtained in the same manner as in Production Example 12 except that the type of poval for preparing the binder, the concentration of the aqueous solution, and the addition amount of the binder were changed as shown in Table 2. It was. In addition, powder characteristics and physical properties of the obtained powder sample were evaluated and are shown in Table 2.

<Production Examples 16 to 17>
Polymer flocculant 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 binders in place of the poval aqueous solution, respectively. In addition, powder characteristics and physical properties of the obtained powder sample were evaluated and are shown in Table 2.

<Comparative Production Example 5>
A polymer flocculant powder D1 was obtained in the same manner as in Production Example 12 except that no binder was added. In addition, the powder characteristics and physical properties of the obtained powder samples were evaluated and are shown in Tables 2 and 3.

 

However, the abbreviations in Table 2 represent the following.
“PVA203”: POVAL manufactured by Kuraray Co., Ltd .; trade name “PVA-203”
“PVA205”: POVAL manufactured by Kuraray Co., Ltd .; trade name “PVA-205”

As is apparent from Table 2, the polymer flocculants C1 to C6 with the binder added have a larger bulk specific gravity, stronger granulation strength, and powder characteristics compared to D1 without the binder added. outstanding. Moreover, the tendency for both bulk specific gravity and granulation strength to improve was seen, so that there was much addition amount of binder. And in C4 which added poval aqueous solution as a binder, although the addition amount of the binder was less than C5 which added only water, the granulation strength was high. It seems to be the effect of Poval.
Furthermore, as a result of physical property evaluation, physical properties such as 0.5% aqueous solution viscosity and 0.1% salt viscosity were 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.

<Production Example 18>
As in 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 a period of about 15 minutes using a syringe pump. To obtain a polymer flocculant powder E1. At this time, the moisture contained in the binder was 10.5% with respect to the total mass of the solid content of the polymer flocculant A1 and the binder. In addition, the powder characteristics and physical properties of the obtained powder samples were evaluated and are shown in Table 3.

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

 

In Table 3, the same tendency as in Table 2 was observed. That is, the polymer flocculants E1 to E4 with the binder added have a larger bulk specific gravity, stronger granulation strength, and superior powder characteristics compared to D1 without the binder added. Moreover, the tendency for both bulk specific gravity and granulation strength to improve was seen, so that there was much addition amount of binder.
Furthermore, as a result of physical property evaluation, physical properties such as 0.5% aqueous solution viscosity and 0.1% salt viscosity were 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 desktop tests for floc formation and centrifugal dehydration. 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, Crude suspended matter / SS = 15.2% by mass, and electric conductivity = 262 mS / m.
First, 100 mL of sludge was collected in a 300 mL beaker, and 0.2 mass% aqueous solution of the polymer flocculant manufactured in Production Example 1, Production Example 3, Production Example 12 and Comparative Production Example 4 was polymerized. It added with the syringe so that the agent might become the addition amount shown in Table 4 with respect to the sludge mass. This sludge was stirred at 1000 rpm for 30 seconds to make the sludge floc, and the floc diameter was measured visually. 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, and gravity filtered. At this time, the funnel was set so that the filtrate entered the 200 mL graduated cylinder, and the volume of the filtrate was measured every predetermined time to evaluate the gravity filterability. Further, the appearance of the filtrate was visually evaluated.
Next, an appropriate amount (about 12 g) of the sludge-containing water cake after gravity filtration remaining on the stainless steel test sieve after evaluating gravity filterability was taken out and centrifuged with a nylon filter cloth having an opening of 180 μm inside. Using a settling tube, centrifugal dehydration was performed at 2000 rpm for 10 minutes, and the water content of the obtained dehydrated cake was measured. The test results are shown in Table 4.

From Table 4, the polymer flocculants A1, A3, and C1 obtained in Production Example 1, Production Example 3, and Production Example 12 were polymerized without adding a crosslinking agent to the sludge of the public sewage treatment plant 1. Compared with B4 of Comparative Production Example 4, the amount of the polymer flocculant is slightly increased, but the floc diameter is large, the gravity filterability is excellent, and the suspension component (SS) does not flow out at all in the filtrate. The moisture content of the dehydrated cake was both low and excellent at 82% or less.
Further, in A1 having a median diameter smaller than A3 and C1 obtained by granulating A1, the water content of the dehydrated cake was less than 80%, and the dewatering performance was superior to A3.

<Examples 10 to 18, Comparative Examples 4 to 7>
The sludge collected from the public sewage treatment plant 2 was subjected to desktop tests for floc formation and centrifugal dehydration. In addition, the property of this sludge is pH = 5.1, TS = 41,400 mg / L, VTS / TS = 72.1 mass%, SS = 35,300 mg / L, VSS / SS = 72.4 mass%, Coarse suspended matter / SS = 17.5% by mass, electric conductivity = 252 mS / m.
100 mL of sludge was collected in a 300 mL beaker, and 0.2% by 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 polymer flocculant. It added with the syringe so that it might become the addition amount shown in Table 5 with respect to sludge mass. Thereafter, the same operation as in Example 1 was performed, and the floc diameter, gravity filterability, the appearance of the filtrate, and the moisture content of the dehydrated cake were measured. The test results are shown in Table 5.

From Table 5, the flocs are not formed at any addition amount of 200 to 400 ppm in the sludge of the public sewage treatment plant 2 in the polymer flocculant B4 of Comparative Production Example 4 in which no crosslinking agent was added. It was. On the other hand, the polymer flocculants A6, A11, E1 obtained in Production Example 6, Production Example 11, and Production Example 18 all formed flocs and were extremely effective as polymer flocculants for hardly dewatered sludge. .
In particular, in the polymer flocculant A6 having a high degree of cross-linking, the amount of the polymer flocculant is slightly increased compared to A11 and E1, but the floc diameter is large and the gravity filterability is excellent when the appropriate amount is added. The suspension component (SS) did not flow out, and the moisture content of the dehydrated cake was as low as about 74%, and the dewatering performance was excellent.
As described above, when the polymer flocculant obtained by the production method of the present invention is used, it exhibits excellent dewatering performance even for hardly dewatered sludge.

<Production Example 22>
Almost dry with a dehydration rate of 92% obtained in the reflux dehydration step of Production Example 1 in a 300 mL stainless separable flask with stainless steel anchor blades set so that the clearance between the bottom surface and the wall surface is about 1 mm. 105 g of the slurry in which the particles of the crosslinked polymer dispersed are dispersed, and a water-in-oil polymer emulsion (before the reflux dehydration step) containing the crosslinked polymer obtained in the polymerization step of Production Example 1 as a binder. 18 g was charged as a polymer, and the pressure was reduced to 13 kPa with stirring at 200 rpm, and the oil bath was heated from room temperature to 90 ° C. to start drying under reduced pressure. At this time, the water content in the binder was 9.5% by mass with respect to the total mass of the slurry having a dehydration rate of 92% and the solid content of the binder.
On the way, the temperature of the slurry in which the particles of the cross-linked polymer were dispersed reached the boiling point at about 40 to 43 ° C., and steam containing normal heptane and the remaining water began to come out. The degree of vacuum was adjusted while observing the flow rate of the condensate, 80% by mass or more of the total amount of solvent was evaporated, and after confirming that the product temperature started to rise, finish drying was performed for 30 minutes at an absolute pressure of 4 kPa. .

A white slurry with dispersed polymer particles before drying becomes a highly viscous clay as drying progresses and the normal heptane content decreases. It was dissolved into an aggregate having a distribution of less than mm, and finally changed to a dry granulated product having a high granulation strength. Further, the product temperature reached the maximum range of 55 to 70 ° C.
After finishing the drying step, the product temperature was cooled to 40 ° C. or lower, and then sieved with a stainless steel test sieve having an opening of 2.36 mm to remove coarse particles. The coarse particles 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 granulated powder F1. In addition, the powder characteristics and physical properties of the obtained powder samples were evaluated and are shown in Table 6.

<Production Examples 24 to 25>
The same operation as in Production Example 22 was conducted except that the amount of water-in-oil polymer emulsion containing the crosslinked polymer obtained in the polymerization step of Production Example 1 was changed as shown in Table 6 as the binder. Thus, polymer flocculant granulated powders F3 to F4 were obtained. In addition, the powder characteristics and physical properties of the obtained powder samples were evaluated and are shown in Table 6.

<Production Example 26>
As a binder, the same procedure as in Production Example 1 was performed except that 7 g of water was added instead of the water-in-oil polymer emulsion containing the crosslinked polymer obtained in the polymerization step of Production Example 1. Molecular flocculant granulated powder F5 was obtained. In addition, the powder characteristics and physical properties of the obtained powder samples were evaluated and are shown in Table 6.

<Production Example 23>
First, without adding a binder, only 105 g of the slurry having a dehydration rate of 92% obtained in the reflux dehydration step of Production Example 1 was charged, and the pressure was reduced to 13 kPa with stirring at 200 rpm, as in Production Example 22. The oil bath was heated from room temperature to 90 ° C., and drying under reduced pressure was started.
Next, when about 50% by mass of normal heptane (about 27 g) of the total amount of solvent to be evaporated by drying under reduced pressure is distilled, the crosslinked polymer obtained in the polymerization step of Production Example 1 is used as a binder. 26 g of a water-in-oil polymer emulsion containing as a polymer was charged, followed by drying under reduced pressure in a 90 ° C. oil bath until normal heptane and the remaining water were not distilled while stirring at 200 rpm. And after confirming that the product temperature started to rise, finish drying was performed at an absolute pressure of 4 kPa for 30 minutes.
Thereafter, the same operation as in Production Example 22 was performed to obtain a polymer flocculant granulated powder F2. In addition, the powder characteristics and physical properties of the obtained powder samples were evaluated and are shown in Table 6.

<Production Example 27>
First, without adding a binder, only 105 g of the slurry having a dehydration rate of 92% obtained in the reflux dehydration step of Production Example 1 was charged, and the pressure was reduced to 13 kPa with stirring at 200 rpm, as in Production Example 22. The oil bath was heated from room temperature to 90 ° C., and drying under reduced pressure was started.
Next, when about 50% by mass of normal heptane (about 27 g) of the total amount of solvent to be evaporated by drying under reduced pressure is distilled, 3 g of water is added as a binder, and the mixture is stirred and stirred until the properties of the slurry are stabilized. After that, while stirring at 200 rpm, it was dried under reduced pressure in a 90 ° C. oil bath until normal heptane and the remaining water were not distilled. And after confirming that the product temperature started to rise, finish drying was performed at an absolute pressure of 4 kPa for 30 minutes.
Thereafter, the same operation as in Production Example 22 was performed to obtain a polymer flocculant granulated powder F6. In addition, the powder characteristics and physical properties of the obtained powder samples were evaluated and are shown in Table 6.

<Comparative Production Example 6>
A powdery polymer flocculant G1 was obtained in the same manner as in Production Example 22 except that no binder was added. In addition, the powder characteristics and physical properties of the obtained powder samples were evaluated and are shown in Table 6.

As is apparent from Table 6, the polymer flocculant granulated powders F1 to F6 with the binder added have a larger bulk specific gravity and a stronger granulation strength than the G1 without the binder added. Excellent body characteristics. Moreover, the tendency for both bulk specific gravity and granulation strength to improve was seen, so that there was much addition amount of binder.
Furthermore, as a result of physical property evaluation, physical properties such as 0.5% aqueous solution viscosity and 0.1% salt viscosity were hardly changed regardless of the presence or absence of the binder and the amount of the binder added. Therefore, by adding a binder, drying and granulating while stirring, the powder characteristics can be improved while maintaining the excellent performance of the polymer flocculant.

<Examples 19 to 27, Comparative Examples 8 to 10>
The sludge collected from the public sewage treatment plant 1 was subjected to desktop tests for floc formation and centrifugal dehydration. 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, Crude suspended matter / SS = 15.2% by mass, and electric conductivity = 262 mS / m.
First, 100 mL of sludge was collected in a 300 mL beaker, and a 0.2% by mass aqueous solution of the polymer flocculant produced in Production Example 1, Production Example 3, Production Example 22 and Comparative Production Example 4 was added thereto. Were added with syringes so that the amounts of addition shown in Table 7 with respect to the sludge mass. This sludge was stirred at 1000 rpm for 30 seconds to make the sludge floc, and the floc diameter was measured visually. 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, and gravity filtered. At this time, the funnel was set so that the filtrate entered the 200 mL graduated cylinder, and the volume of the filtrate was measured every predetermined time to evaluate the gravity filterability. Further, the appearance of the filtrate was visually evaluated.
Next, an appropriate amount (about 12 g) of the sludge-containing water cake after gravity filtration remaining on the stainless steel test sieve after evaluating gravity filterability was taken out and centrifuged with a nylon filter cloth having an opening of 180 μm inside. Using a settling tube, centrifugal dehydration was performed at 2000 rpm for 10 minutes, and the water content of the obtained dehydrated cake was measured. The test results are shown in Table 7.

 

From Table 7, the polymer flocculant granulated powders A1, A3, and F1 obtained in Production Example 1, Production Example 3, and Production Example 22 were not added to the sludge of the public sewage treatment plant 1 without adding a crosslinking agent. Compared with B4 of Comparative Production Example 4 polymerized in the same manner, although the amount of the polymer flocculant added is slightly increased, the floc diameter is large, the gravity filterability is excellent, and the suspension component (SS) flows out completely in the filtrate. The moisture content of the dehydrated cake was as low as 82% or less and was excellent.
Further, in F1, which was polymerized and refluxed and dehydrated under the same conditions of Production Example 1 as A1 with a median diameter smaller than A3, and dried and granulated while stirring, the water content of the dehydrated cake was Was less than 80%, and the dehydration performance was superior to A3.

<Examples 28 to 36, Comparative Examples 11 to 14>
The sludge collected from the public sewage treatment plant 2 was subjected to desktop tests for floc formation and centrifugal dehydration. In addition, the property of this sludge is pH = 5.1, TS = 41,400 mg / L, VTS / TS = 72.1 mass%, SS = 35,300 mg / L, VSS / SS = 72.4 mass%, Coarse suspended matter / SS = 17.5% by mass, electric conductivity = 252 mS / m.
100 mL of sludge was collected in a 300 mL beaker, and 0.2 mass% aqueous solution of the polymer flocculant produced in Production Example 6, Production Example 11, Production Example 26, and Comparative Production Example 4 was added to the polymer flocculant. It added with the syringe so that it might become the addition amount shown in Table 8 with respect to sludge mass. Thereafter, the same operation as in Example 19 was performed to measure the floc diameter, gravity filterability, the appearance of the filtrate, and the moisture content of the dehydrated cake. The test results are shown in Table 8.

 

From Table 8, the flocs are not formed at all in the amount of 200 to 400 ppm in the polymer flocculant B4 of Comparative Production Example 4 in which no crosslinking agent was added to the sludge of the public sewage treatment plant 2. It was. On the other hand, the polymer flocculant granulated powders A6, A11, and F5 obtained in Production Example 6, Production Example 11, and Production Example 26 all form flocs and are extremely effective as polymer flocculants for hardly dewatered sludge. Met.
In particular, in the polymer flocculant granulated powder A6 having a high degree of cross-linking, the amount of the polymer flocculant is slightly increased compared to A11 and F5, but the floc diameter is large and the gravity filterability is excellent when the appropriate amount is added. In the 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 dewatering performance was excellent.
As described above, when the polymer flocculant obtained by the production method of the present invention is used, it exhibits excellent dewatering performance even for hardly dewatered sludge.

Claims (14)

1. A method for producing a polymer flocculant powder for drying a polymer emulsion obtained by emulsion polymerization of a monomer mixture containing at least a cationic monomer and a crosslinkable monomer, comprising the following step (A): To (D)
   Step (A): An aqueous phase containing an aqueous solution of the monomer mixture is mixed with an oil phase containing water and a substantially immiscible hydrocarbon and surfactant, so that the median diameter of the emulsified particles is An emulsification step for producing a water-in-oil monomer 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 produce a water-in-oil polymer emulsion containing a polymer in the dispersed phase. A polymerization process,
   Step (C): Among the condensate composed of water and hydrocarbons obtained by condensing vapor separated from the water-in-oil polymer emulsion by evaporating water and hydrocarbons, water is discharged out of the system. Then, 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%. A reflux dehydration step for preparing a dispersion of coalescence, wherein 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. Process,
   Step (D): A drying step in which hydrocarbons and water are removed from the dispersion to produce the polymer powder.
   A method for producing a polymer flocculant powder comprising:
   

   
2. The method for producing a polymer flocculant powder according to claim 1, wherein the monomer mixture contains a nonionic monomer.
3. The manufacturing method of the polymer flocculent powder of Claim 1 in which the said cationic monomer contains the 1 type (s) or 2 or more types of the cationic monomer represented by 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 methyl group, R ² and R ³ are each independently an alkyl group or benzyl group having 1 to 3 carbon atoms, R ⁴ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a benzyl group. , and the good be the same or different .X is oxygen or NH, Q is hydroxy alkylene group of the alkylene group or a C 2-4 1 to 4 carbon atoms, Z ^- represents each pair anion).
4. The polymer flocculant powder according to claim 1, wherein the cationic monomer is at least one of methyl chloride quaternary salt of dimethylaminoethyl acrylate and methyl chloride quaternary salt of dimethylaminoethyl methacrylate. Method.
5. The method for producing a polymer flocculant powder according to claim 1, wherein the hydrocarbon is a hydrocarbon having a boiling point of 65 to 180 ° C at normal pressure.
6. The method for producing a polymer flocculant powder according to claim 1, wherein the hydrocarbon is normal heptane.
7. The method for producing a polymer flocculant powder according to claim 1, wherein the surfactant has an HLB value of 3.0 to 9.0.
8. The method for producing a polymer flocculant powder according to claim 1, wherein the reflux dehydration step of the step (C) is performed under a reduced pressure condition of normal pressure to absolute pressure of 40 kPa.
9. The method for producing a polymer flocculant powder according to claim 1, wherein the drying step (D) is performed under a reduced pressure condition of 2 to 20 kPa in absolute pressure.
10. The method for producing a polymer flocculant granulated powder according to claim 1, wherein the drying step of the step (D) is performed until the product temperature of the powder reaches 50 ° C or higher.
11. After the drying step of the step (D), the following step (E)
    Step (E): A granulating step of adding the binder while stirring and mixing the polymer powder, drying and granulating the polymer powder after wet stirring granulation,
    The manufacturing method of the polymer flocculent powder of Claim 1 containing this.
12. The method for producing a polymer flocculant powder according to claim 11, 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 10,000 to 70000.
13. 2. The polymer according to claim 1, comprising a granulation step (F) from the end of the step (C) to before the start of the step (D), or in the step (D). Method for producing flocculant granulated powder.
14. A method for dewatering sludge, wherein an aqueous solution of the polymer flocculant powder obtained by the production method according to any one of claims 1 to 13 is added to the sludge for dehydration.