JP6839979B2 - A polymer flocculant and a method for producing the same, a method for dehydrating sludge using the polymer flocculant, and a method for evaluating the flocculation performance of the polymer flocculant. - Google Patents

Description

The present invention relates to a polymer flocculant and a method for producing the same, a method for dehydrating sludge using the polymer flocculant, and a method for evaluating the aggregation performance of the polymer flocculant. More specifically, the present invention relates to a polymer flocculant having a predetermined viscoelasticity in an aqueous solution and a method for producing the same, a method for dehydrating sludge using the polymer flocculant, and a method for evaluating the aggregation performance of the polymer flocculant.

Polymer coagulants are used for the purpose of coagulating, sedimenting, and separating sludge contained in domestic wastewater, industrial wastewater, and the like. As the polymer flocculant, a cationic polymer and an amphoteric polymer are often used. Conventionally, the types of monomers, their mole fractions, and their average molecular weights have been the main factors that characterize the types of these polymer flocculants. An appropriate combination of the type of monomer and the mole fraction is selected according to the wastewater properties and sludge properties to be treated.

It is said that the higher the molecular weight, the better the cohesive force of the polymer flocculant. Therefore, in order to increase the cohesive force, one of the means is to increase the molecular weight in a polymerization prescription. Since it is difficult to directly measure the molecular weight, the viscosity of the aqueous solution, which is known to increase as the molecular weight increases, is regarded as one of the alternative indexes. However, even if the polymerization is carried out so that the viscosity of the aqueous solution is increased, the aggregation performance is not always improved.
When preparing an aqueous solution of a polymer flocculant, it is common to fill a stirring tank with water and gradually add the powdered polymer flocculant while rotating the stirrer. At the time of this dissolution, there is a phenomenon that the dissolved liquid crawls up on the shaft of the stirrer, and this phenomenon is called the Weisenberg effect. The Weisenberg effect is derived from the stress generated in the shear plane (horizontal plane perpendicular to the axis of rotation) in the direction perpendicular to the direction of flow and toward the axis of rotation. This stress is generally called the first normal stress. When the first normal stress is large, a viscous resistance may occur during the agglutination reaction with sludge, the agglutination reaction may not proceed, and the agglutination may be insufficient. In other words, even if the formulation simply increases the viscosity of the aqueous solution in order to improve the aggregation performance, the aggregation performance will be improved unless it purely increases the molecular weight of the flocculant without biasing the effect of increasing the first normal stress. hard.

Patent Document 1 discloses a polymer flocculant in which the ratio of the viscosity in an aqueous sodium chloride solution to the viscosity in ion-exchanged water is within a predetermined range. However, there are cases where the aggregation performance is insufficient even if the relationship between these viscosities is simply controlled.
Therefore, in the conventional sludge dewatering method using a polymer flocculant, it may be difficult to sufficiently reduce the water content of the obtained dewatered cake regardless of the salt viscosity value.

Japanese Unexamined Patent Publication No. 2008-104908

The problem to be solved by the present invention is an excellent polymer flocculant and a method for producing the same, a method for dehydrating sludge using the polymer flocculant, and a method for evaluating the flocculation performance of the polymer flocculant. Is to provide.

The present inventors obtained various cationic polymer compounds prepared by changing the type and input amount of the polymerization initiator, the reaction form and the reaction conditions, and examined the viscoelasticity of the aqueous solution of the polymer compound and the dehydration performance with respect to sludge. Various evaluations were made. Specifically, attention was paid to the relationship between the first normal stress NS of the aqueous polymer coagulant solution and the viscosity Vz at the time of low shear. The smaller the value (NS / Vz) obtained by dividing the first normal stress NS by the viscosity Vz at the time of low shear, the narrower the molecular weight distribution of the polymer constituting the polymer flocculant, and as a result, the higher the flocculation performance. It was found that the content ratio of the polymer contained tends to be high. It was also found that the preferred range of NS / Vz values decreases as the mole fraction M of the cationic monomer unit increases. Then, they have found that the aggregation performance of the polymer flocculant can be quantitatively evaluated by multiplying NS / Vz by the molar fraction M (mol%) of the cationic monomer. That is, they have found that a polymer flocculant having a predetermined relationship with the viscoelasticity of an aqueous solution has excellent performance, and have completed the present invention.

The present invention that solves the above problems is described below.

[1] A copolymer obtained by radical polymerization of a monomer mixture containing at least a cationic monomer and a nonionic monomer.
The viscosity Vz (Pa · s) of a 0.1 mass% aqueous solution measured at a ^{shear rate of 0.02 (s -1} ) or less using a dynamic viscoelasticity measuring device at 25 ° C. is the following mathematical formula (1).
1.0 <Vz <30 ... Number (1)
And meet
The mole fraction M (mol%) of the cationic monomer unit with respect to all the monomer units and the first normal stress NS (Pa) at 25 ° C. measured at a ^{shear rate of 10,000 (s -1).} , The viscosity Vz (Pa · s) is the following formula (2).
3,000 ≤ NS / Vz x M ≤ 9,000 ... Number (2)
A polymer flocculant characterized by containing a copolymer satisfying the above conditions.

The polymer flocculant of the above [1] is a polymer flocculant composed of a copolymer containing a cationic monomer and a nonionic monomer. This polymer flocculant is characterized in that the viscoelasticity of its aqueous solution has a predetermined relationship.

The reason why the polymer flocculants satisfying the above formulas (1) and (2) have high flocculation performance is not clear, but the present inventors presume as follows.
Generally, an aqueous solution of a polymer compound is a non-Newtonian fluid exhibiting pseudoplastic viscosity, but when the shear rate is extremely low (when the shear rate is 0.02 (s ^-1 ) or less), it behaves as a Newtonian fluid. Shown. When the viscosities at low shear are the same, it is considered that the polymer compound having a low first normal stress has a narrower molecular weight distribution than the polymer compound having a high first normal stress. A polymer compound having a wide molecular weight distribution contains a large amount of a low molecular weight compound having no aggregation performance. On the other hand, a polymer compound having a narrow molecular weight distribution contains almost no low molecular weight compound. Therefore, when the viscosities at low shear are the same, it is considered that the lower the first normal stress, the higher the aggregation performance.

The invention described in the above [1] includes the inventions described in the following [2] to [7].

[2] The following formula (3)
3,000 ≤ NS / Vz x M ≤ 6,000 ... Number (3)
The polymer flocculant according to [1].

[3] The following formula (4)
5 ≤ M ≤ 40 ... Number (4)
The polymer flocculant according to [1].

[4] The polymer flocculant according to [1], wherein the cationic monomer is a quaternary salt of methyl chloride of dimethylaminoethyl acrylate.

[5] The polymer flocculant according to [1], wherein the nonionic monomer is acrylamide.

[6] The polymer flocculant according to [1], wherein the copolymer is an aqueous gel polymer or a dried product thereof.

[7] The polymer flocculant according to [1], wherein the copolymer is a W / O type emulsion or a dried product thereof.

[8] A monomer mixture containing at least a cationic monomer and a nonionic monomer is subjected to aqueous solution polymerization using a photoinitiator to obtain an aqueous solution gel polymer.
The method for producing a polymer flocculant according to [1], which comprises drying the aqueous gel polymer.

[9] A W / O type emulsion is obtained by emulsion polymerization of a monomer mixture containing at least a cationic monomer and a nonionic monomer.
The method for producing a polymer flocculant according to [1], which comprises drying the W / O type emulsion.

[10] A method for dehydrating sludge, which comprises adding the polymer flocculant according to any one of [1] to [7] to sludge.

[11] The sludge dewatering method according to [10], wherein the sludge is papermaking sludge.

[12] The first normal stress NS (Pa) at 25 ° C. measured at a shear rate of 10,000 (s ^-1 ) is 0.1 mass measured at a ^{shear rate of 0.02 (s -1) or less.} A method for evaluating the aggregation performance of a polymer flocculant, which comprises evaluating the aggregation performance of the polymer flocculant from the value obtained by dividing the% aqueous solution by the viscosity Vz (Pa · s) at 25 ° C.

The polymer flocculant of the present invention has a predetermined relationship with the viscoelasticity of its aqueous solution. That is, since it has a narrow molecular weight distribution and contains a large amount of polymer compounds having high agglutination performance, it exhibits an extremely high agglutination action.
The method for evaluating the agglutination performance of the polymer flocculant of the present invention uses the first normal stress and the viscosity at low shear. This evaluation method is in good agreement with the actual agglutination performance as compared with the conventional evaluation method using various viscosities.

Hereinafter, the present invention will be described in detail.

(1) Polymer flocculant The polymer flocculant of the present invention is a composition containing a copolymer obtained by radical polymerization of a monomer mixture containing a cationic monomer and a nonionic monomer, which will be described later. .. The molar fraction M of the cationic monomer unit with respect to all the monomer units is preferably 5 to 40 (mol%), more preferably 10 to 35 (mol%).

The copolymer contained in the polymer flocculant of the present invention is a 0.1% by mass aqueous solution measured at a ^{shear rate of 0.02 (s -1) or less using a dynamic viscoelasticity measuring device (rheometer).} The viscosity Vz (Pa · s)% at 25 ° C. is the following formula (1).
1.0 <Vz <30 ... Number (1)
Meet.
The lower limit of Vz is preferably 3.0 or more, and more preferably 5.5 or more. The upper limit of Vz is preferably 27 or less, more preferably 25 or less. When the lower limit of Vz is 1.0 or less, the molecular weight of the copolymer is too small and the aggregation performance is insufficient, the floc diameter is not sufficiently large, and the gravity filterability may be lowered. When the upper limit of Vz is 30 or more, the moisture content of the dehydrated cake may not be sufficiently lowered.

At shear rates of 0.02 (s ^-1 ) or less, the aqueous copolymer behaves as a Newtonian fluid. That is, the viscosity Vz may be measured at a shear rate within a range in which the aqueous solution of the copolymer behaves as a Newtonian fluid. The range of the shear rate that can be set differs depending on the measuring device used, but for example, it can be set to ^{0.0147 (s -1) or the like as in the examples described later.}

The copolymer contained in the polymer flocculant of the present invention has a first normal stress NS (Pa) at 25 ° C. measured at a ^{shear fraction of 10,000 (s -1) using a dynamic viscoelasticity measuring device.} The viscosity Vz (Pa · s) and the mole fraction M (mol%) of the cationic monomer unit with respect to all the monomer units are calculated by the following formula (2).
3,000 ≤ NS / Vz x M ≤ 9,000 ... Number (2)
Meet.
The upper limit of NS / Vz × M is preferably 8,500 or less, more preferably 8,000 or less, and more preferably 6,000 or less. When the upper limit of NS / Vz × M exceeds 9,000, the molecular weight distribution of the copolymer is too wide, so that a large amount of low molecular weight copolymer is contained. Therefore, the aggregation performance is insufficient. The normal stress is a force acting in the direction perpendicular to the applied shear stress.

The 0.5% salt viscosity of the copolymer contained in the polymer flocculant of the present invention is 5 to 200 mPa · s, more preferably 10 to 150 mPa · s, and 20 to 100 mPa · s. Is particularly preferable. When the 0.5% salt viscosity is less than 5 mPa · s, the agglutinating performance as a polymer flocculant may be insufficient, the floc diameter may not be sufficiently large, or the gravity filterability may be lowered. If the 0.5% salt viscosity exceeds 200 mPa · s, the water content of the dehydrated cake may not be sufficiently reduced.

The molar fraction M (mol%) of the cationic monomer unit with respect to all the monomer units of the copolymer contained in the polymer flocculant of the present invention is calculated by the following formula (4).
5 ≤ M ≤ 40 ... Number (4)
It is preferable to satisfy the following formula (5).
10 ≤ M ≤ 35 ... Number (5)
It is more preferable to satisfy.

The molar fraction of the nonionic monomer unit to all the monomer units of the copolymer contained in the polymer flocculant of the present invention is preferably 60 to 95 (mol%), preferably 65 to 90 (mol). %) Is more preferable.

(2) Cationic Monomer In the present invention, the cationic monomer is preferably a (meth) acrylate monomer derived from the following chemical formula (1).

In the above chemical formula (1), R ₁ is an alkyl group or benzyl group having 1 to 3 carbon atoms, R ₂ and R ₃ are independently hydrogen atoms or alkyl groups having 1 to 3 carbon atoms, and X is an oxygen atom or NH. Y represents a hydrogen atom or a methyl group, Q represents an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, and Z ⁻ represents a counter anion.

Specific examples of the (meth) acrylate monomer represented by the chemical formula (1) include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and dimethylamino-2-hydroxypropyl (meth) acrylate. Examples thereof include hydrochlorides and sulfates of dialkylaminoalkyl (meth) acrylamide such as dialkylaminoalkyl (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.
These (meth) acrylate monomers may be used alone or in combination of two or more.

Among these preferable (meth) acrylate monomers, dimethylaminoethyl acrylate is quaternary methyl chloride because it is particularly excellent in performance as a polymer flocculant, and is also excellent in quality and storage stability of the acrylate monomer. It is most preferable to use a salt (hereinafter, may be abbreviated as "DAC").

(3) Nonionic Monomer In the present invention, the nonionic monomer is not particularly limited, but for example, in addition to the (meth) acrylamide-based compound represented by the following chemical formula (2), methyl (meth) acrylate, ( Examples thereof include alkyl (meth) acrylates such as ethyl acrylate, butyl (meth) acrylate, and hydroxyethyl (meth) acrylate, styrene, acrylonitrile, and vinyl acetate. Among these nonionic monomers, it has excellent copolymerizability with a cationic monomer, it is easy to increase the molecular weight required as a polymer flocculant, and it has excellent performance as a polymer flocculant. Therefore, a (meth) acrylamide compound represented by the following chemical formula (2) is preferable.

CH ₂ = CR _1- CO-NR ₂ R ₃ ... (2)

However, in the above chemical formula (2), R ₁ is a hydrogen atom or a methyl group, and R ₂ and R ₃ independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, respectively.

Among these (meth) acrylamide compounds, acrylamide (hereinafter, may be abbreviated as "AM") is most preferable because it is water-soluble and has particularly excellent performance as a polymer flocculant.
These nonionic monomers may be used alone or in combination of two or more.

(4) Other Substances The monomer mixture for producing the copolymer contained in the polymer flocculant of the present invention contains the above-mentioned cationic monomer and nonionic monomer as essential components. Other substances may be included as long as the effects of the present invention are not impaired. Examples of other substances include the following anionic monomers and crosslinkable monomers.

Examples of the anionic monomer include (meth) acrylic acid represented by the following chemical formula (3) and salts thereof, vinyl sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, maleic acid and the like, and their salts. Salts can be mentioned. Among these anionic monomers, it is excellent in copolymerizability with the cationic monomer, it is easy to increase the molecular weight required as a polymer flocculant, and it is excellent in performance as a polymer flocculant. , (Meta) acrylic acid represented by the following chemical formula (3) and salts thereof are preferable. As the salts, ammonium salts and alkali metal salts such as sodium salts and potassium salts are preferable.

CH ₂ = CR _1- CO-OM ... (3)

However, in the above chemical formula (3), R ₁ represents a hydrogen atom or a methyl group, and M represents a hydrogen atom, an ammonium group or an alkali metal atom.

Among these (meth) acrylic acids and salts thereof, acrylic acid (hereinafter, may be abbreviated as "AA") and its ammonium salt are particularly preferable because their performance as a polymer flocculant is particularly excellent.
These anionic monomers may be used alone or in combination of two or more.

The blending amount of the anionic monomer in the monomer mixture is preferably 0 to 50 mol%, more preferably 1 to 40 mol%, and even more preferably 1 to 30 mol%. That is, the copolymer contained in the polymer flocculant of the present invention preferably contains an anionic monomer unit in an anionic monomer unit in an amount of 0 to 50 mol%, more preferably in an amount of 1 to 40 mol%, and in an amount of 1 to 30 mol%. It is particularly preferable to include it.

As the crosslinkable monomer, a (meth) acrylate-based crosslinkable monomer having two or more (meth) acryloyl groups represented by the following chemical formula (4) in one molecule (hereinafter, simply “crosslinkable single”). It may be abbreviated as "monomer" or "crosslinking agent").

CH ₂ = CR ₁ -CO -... (4)

However, in the above chemical formula (4), R ₁ is a hydrogen atom or a methyl group, and -CO- represents a carbonyl group.

The number of (meth) acryloyl groups in one molecule of the crosslinkable monomer is two or more. The number is preferably 2 to 5, and more preferably 2 to 3. Even if the number of (meth) acryloyl groups contained in one molecule exceeds 5, the effect of improving the performance as a polymer flocculant corresponding to the number of (meth) acryloyl groups may not be obtained.

Examples of such crosslinkable monomers include methylenebisacrylamide (hereinafter, may be abbreviated as “MBA”), ethylene or polyethylene di (meth) acrylate, polypropylene di (meth) acrylate, and neopentyl glycol di (meth). ) Acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, alkylenebis (meth) acrylamide, mono and polyalkylene glycol di (meth) acrylate, Polymethylolalkampo (meth) acrylate is exemplified. These may be used alone or in combination of two or more.

When the crosslinkable monomer is contained in the monomer mixture, the blending amount thereof is preferably 0.0001 to 0.01 mol%, more preferably 0.0002 to 0.008 mol%. It is particularly preferably 0.0005 to 0.007 mol%. When the amount of the crosslinkable monomer added is 0.0001 to 0.01 mol%, the interaction between the crosslinkable water-soluble polymers is weak, so that the viscosity is low and the handling is excellent. In addition, since the viscosity is low, the reaction with sludge proceeds rapidly, and strong flocs can be formed. Further, if the amount of the crosslinkable monomer added exceeds 0.01 mol%, the crosslinking reaction may proceed too much, which increases the insoluble amount especially in the case of aqueous solution polymerization, and as a polymer flocculant. Since the amount of the active ingredient that acts effectively is reduced, the aggregation effect cannot be sufficiently exerted. Further, in the case of an emulsion, the amount of addition required for the treatment increases, and the treatment cost increases.

(5) Method for Producing Polymer Coagulant The copolymer contained in the polymer flocculant of the present invention is produced by radical polymerization of a monomer mixture containing a cationic monomer and a nonionic monomer. To.

The molar fraction m (mol%) of the cationic monomer with respect to all the monomers of the monomer mixture is calculated by the following formula (6).
5 ≤ m ≤ 40 ... Number (6)
It is preferable to satisfy the following mathematical formula (7).
10 ≤ m ≤ 35 ... Number (7)
It is more preferable to satisfy.

The molar fraction of the nonionic monomer to all the monomers of the monomer mixture is preferably 60 to 95 (mol%), more preferably 65 to 90 (mol%). When the molar fraction of the nonionic monomer is out of the above range, it is difficult to exert the effect on sludge having a wide range of properties.

The method for polymerizing the monomer mixture is not particularly limited except that it is radical polymerization, and specific forms of radical polymerization applicable to the present invention include aqueous solution polymerization, suspension polymerization, emulsion polymerization and the like. Will be done. Among these, aqueous solution polymerization and emulsion polymerization are preferable because the operation method is simple, the raw materials and products are easy to handle, and the production cost in industrial production is also advantageous. Further, after emulsion polymerization, the aqueous layer or oil layer may be volatilized to be powdered.

(5-1) Aqueous Solution Polymerization Aqueous solution polymerization is a method of polymerizing an aqueous solution of the above-mentioned monomer mixture in the presence of a radical polymerization initiator. In the case of aqueous solution polymerization, the concentration of the monomer mixture is preferably 25 to 85% by mass, particularly preferably 30 to 65% by mass. The pH of the aqueous solution of the monomer mixture is preferably adjusted to 2-5.

The radical polymerization initiator used in the polymerization reaction is not particularly limited. In the case of aqueous solution polymerization, persulfates such as potassium persulfate and ammonium persulfate, organic peroxides such as t-butyl hydroperoxide, azo-based initiators such as azobisisobutyronitrile, redox-based initiators and light A polymerization initiator or the like can be appropriately used. These radical polymerization initiators may be used alone or in combination of two or more.

The polymerization start temperature is usually preferably 0 to 35 ° C. The polymerization time is usually preferably 0.1 to 3 hours. Further, the polymerization reaction is preferably carried out in an inert atmosphere in which oxygen does not exist. These polymerization conditions are known. After the completion of the polymerization reaction, post-treatments such as heat treatment, drying, and pulverization are appropriately performed as necessary. Known methods can also be applied to these post-treatments.

Among the above-mentioned production methods by aqueous solution polymerization, there is little variation in the physical properties and quality of the obtained polymer compound, stable production is possible, and the viscoelastic copolymer specified in the present invention can be easily obtained. The photopolymerization method is particularly preferable. As a specific example of the photopolymerization method, a method of irradiating an aqueous solution of the monomer mixture with light in the presence of a photopolymerization initiator and a chain transfer agent to carry out polymerization is exemplified.

The photopolymerization initiator used for photopolymerization is not particularly limited. Examples of preferable photopolymerization initiators include acetophenone-based photopolymerization initiators and azo-based initiators. Among them, a water-soluble azo-based initiator is particularly preferable because of its high solubility in an aqueous solution of the monomer mixture and easy molecular weight increase required as a polymer flocculant.
Specific examples of the water-soluble azo initiator include 2,2'-azobis (2-methylpropionamidine) dihydrochloride, 4,4'-azobis (4-cyanovaleric acid) and the like.
These photopolymerization initiators may be used alone or in combination of two or more.

The amount of the photopolymerization initiator added is not particularly limited. It may be appropriately adjusted according to the type of photopolymerization initiator, the monomer composition and the content of the residual monomer. In the case of a water-soluble azo initiator, it is usually preferably 100 to 3,000 ppm by mass with respect to the total mass of each monomer in the monomer mixture.

Chain transfer agents may be used for the purpose of adjusting the molecular weight. The type is not particularly limited. Examples of the chain transfer agent that can be used in the present invention include alcohols such as methanol, isopropyl alcohol, ethylene glycol and propylene glycol, amines such as methylamine and dimethylamine, thiols such as methanethiol and ethanethiol, and metallic sulfonates. Examples thereof include thiol compounds such as mercaptoethanol and mercaptopropionic acid, reducing inorganic salts such as sodium sulfite, sodium hydrogen sulfite and sodium hypophosphite, and organic sulfonic acid compounds such as metallic sulfonic acid. Among these, sodium bisulfite is preferable because it has high solubility in an aqueous solution of a monomer mixture, is highly effective even with a small amount of addition, and can easily adjust the molecular weight of a crosslinked water-soluble polymer.
These chain transfer agents may be used alone or in combination of two or more.

The amount of the chain transfer agent added is not particularly limited. In the case of sodium bisulfite, usually 5 to 500 ppm is preferable, 10 to 300 ppm is more preferable, and 15 to 200 ppm is most preferable with respect to the total mass of each monomer in the monomer mixture. If the amount of sodium bisulfite added is less than 5 ppm, the generation of insoluble matter may not be suppressed. In that case, the amount of the active ingredient that effectively acts as a polymer flocculant is reduced. In addition, it may cause troubles that block the pump that sends the solution in which the polymer flocculant is dissolved in water. If the amount of sodium bisulfite added exceeds 500 ppm, the molecular weight of the polymer may become too low. In that case, the cohesive force against sludge as a polymer flocculant decreases, and the floc diameter does not increase. In addition, the filtration rate may decrease, or fine solids in the sludge may escape into the filtrate, resulting in deterioration of the transparency of the filtrate.

The light irradiation conditions such as the wavelength of light used for photopolymerization, the irradiation intensity, and the irradiation time are not particularly limited. It may be appropriately adjusted according to the type and amount of the photopolymerization initiator used and the physical properties and performance of the polymer. When the water-soluble azo-based initiator is used as the photopolymerization initiator, light having a wavelength of around 365 nm is preferable, and the irradiation intensity is preferably 0.1 to 10.0 mW / cm ² by a UV irradiance meter for 365 nm. The irradiation time is usually preferably 0.1 to 3 hours.

(5-2) Emulsion polymerization Emulsion polymerization is an oily substance composed of an aqueous phase containing a predetermined monomer, a radical initiator, a chain transfer agent and the like, an immiscible hydrocarbon, and a water droplet type (W) in oil. / O type) This is a method in which a water-in-oil emulsion is formed using an effective amount of a surfactant for forming an emulsion, and a monomer is polymerized in the droplets of the emulsion.

Examples of the oily substance include paraffins, various mineral oils, hydrocarbon-based oils having characteristics equivalent to those of paraffins and various mineral oils, and mixtures thereof. The content of the oily substance is in the range of 15 to 50% by mass, preferably 20 to 40% by mass, based on the total amount of the water-in-oil emulsion.

The surfactant preferably has an HLB of 3 to 11. Examples of such surfactants include nonionic surfactants such as sorbitan monooleate and sorbitan monostearate. The amount of these surfactants added is preferably 0.3 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total amount of the water-in-oil emulsion.

The polymerization conditions for emulsion polymerization are appropriately set according to the monomer used, the initiator, and the physical properties of the polymer. The polymerization temperature is preferably 5 to 90 ° C. The polymerization concentration of the monomer is preferably 20 to 60% by mass, more preferably 20 to 50% by mass. The polymerization time is preferably 1 to 10 hours, more preferably 2 to 6 hours. The polymerization reaction is preferably carried out in an inert atmosphere without oxygen.

The average particle size for emulsion polymerization is preferably 0.03 to 10 μm, more preferably 0.1 to 5 μm, and even more preferably 0.5 to 3 μm. The average particle size refers to the volume average value measured by the laser diffraction method.

After the completion of the polymerization reaction, post-treatments such as heat treatment, drying, and pulverization are appropriately performed as necessary. Known methods can also be applied to these post-treatments.

The polymer flocculant of the present invention may contain components other than the above-mentioned copolymer. Further, if necessary, a pH adjusting agent such as sulfamic acid, malic acid, adipic acid, citric acid and the like; a solubilizing agent such as salt, sodium sulfate, ammonium sulfate, sodium nitrate, calcium chloride and the like may be contained.

(6) Sludge dehydration method In the sludge dehydration method using the polymer flocculant of the present invention, in addition to sludge generated in sewage treatment, urine treatment, domestic wastewater treatment, etc., various types of sludge, meat processing, chemical factories, etc. Various sludges such as sludge generated in industrial wastewater treatment, raw urine generated in livestock farming such as pig farms, sludge generated in the wastewater treatment, and sludge generated in pulp or 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 by adding the polymer flocculant of the present invention to the various wastewaters to dehydrate the sludge. As a specific example of the dehydration method, the polymer flocculant of the present invention is added to various wastewaters, and the suspension in sludge and the polymer flocculant are allowed to act by stirring and / or mixing by a known method. , Form sludge flocs. The formed sludge flocs are mechanically dehydrated by a known means to separate them into treated water and a dehydrated cake.

For the purpose of deodorization, dephosphorification, denitrification, etc., the pH of sludge is preferably less than 5.

The wastewater treatment method of the present invention can sufficiently dehydrate sludge without adding an inorganic flocculant.

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, a multiple disk dehydrator, and a rotary press filter.

(7) Method for evaluating the aggregation performance of the polymer flocculant The method for evaluating the aggregation performance of the polymer flocculant of the present invention is characterized by using the viscoelasticity of an aqueous solution of the polymer flocculant. This evaluation method is
(A) Viscosity Vz of 0.1% by mass aqueous solution measured at a shear rate of 0.02 (s ^{-1) or less at 25 ° C.}
(B) The first normal stress NS at 25 ° C. measured at a shear rate of 10,000 (s ^-1 ) is 25 of a 0.1 mass% aqueous solution measured at a ^{shear rate of 0.02 (s -1) or less.} Product of the value divided by the viscosity Vz at ° C. and the mole fraction M of the cationic monomer unit with respect to all the monomer units (that is, NS / Vz × M).
The aggregation performance is evaluated by. The evaluation method using the two values (a) and (b) is in good agreement with the evaluation result of the aggregation performance actually evaluated.

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. Items not described below were measured according to "JIS K0102 Factory Wastewater Test Method". The temperature condition for measuring various physical properties is 25 ° C. unless otherwise specified.

[Viscosity Vz]
Using a dynamic viscoelasticity measuring device (rheometer) (Rheometer MCR-302 manufactured by Anton Pearl Co., Ltd.), the viscosity of a 0.1 mass% aqueous solution at 25 ° C. was measured at ^{a shear rate of 0.0147 (s -1).} did.

[First normal stress NS]
Using the above dynamic viscoelasticity measuring device, the first normal stress at 25 ° C. of a 0.1 mass% aqueous solution was measured at a ^{shear rate of 10,000 (s -1).}

[0.5% salt viscosity]
To 500 mL of pure water, 20.8 g of sodium chloride and an amount of 0.50% by mass of the sample (polymer) were added and sufficiently dissolved to prepare a sample solution. The liquid temperature was adjusted to 25 ± 1 ° C., and the value after rotation at 30 rpm for 3 minutes was read using a TV-10M type B viscometer manufactured by Toki Sangyo Co., Ltd. equipped with an M1 rotor, and this was read as 0.5% salt. Viscosity was used. When the viscosity exceeded the measurement upper limit of the M1 rotor, the M2 rotor was used.

[Flock diameter]
It was measured visually.

[Filtration rate]
Aggregated sludge was poured into a stainless steel sieve having an inner diameter of 75 mm, a depth of 100 mm, and an opening of 80 mesh 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 amount of liquid (mL) after 10 seconds.

[Appearance of filtrate]
It was measured visually.
◯: There is almost no SS leaking in the filtrate and the filtrate is transparent. Δ: SS leaking in the filtrate can be visually confirmed. ×: SS leaking in the filtrate is visually conspicuous.

[Hand squeezing]
After measuring the filtration rate, the cake was collected and the degree of hand squeezing was evaluated.
Bad: Sludge leaks from between fingers with the first hand squeezing Slightly good: Sludge leaks from between the fingers with the second hand squeezing Excellent: Sludge leaks from between the fingers with the third hand squeezing

<Manufacturing example 1>
A 78% by mass dimethylaminoethyl acrylate methyl chloride aqueous solution (hereinafter abbreviated as "DAC") and a 50% by mass acrylamide aqueous solution (hereinafter abbreviated as "AM") are added to a stainless steel reaction vessel, and distilled water is further added. The total mass was adjusted to 1.0 kg and mixed uniformly. Each monomer had a compounding ratio shown in Table 1, and the total concentration of all the monomers was 40% by mass. This solution was adjusted to pH = 4, and the solution temperature was adjusted to 5 ° C. while blowing nitrogen gas into the solution for 60 minutes. Then, 2,2'-azobis (2-methylpropionamidine) dihydrochloride (hereinafter abbreviated as "V-50") and NaHSO ₃ were added to the total mass of each monomer in terms of solid content. It was added so as to be 1500 ppm and 20 ppm, respectively. Next, this solution was irradiated with light from above the reaction vessel to carry out polymerization, and a hydrogel-like polymer was obtained. A 13W black light was used for light irradiation. The irradiation intensity is 0.4 mW / cm ² , and the irradiation time is 60 minutes. The obtained hydrogel-like polymer was taken out of the container and shredded. This was dried at a temperature of 80 ° C. for 5 hours and then pulverized to obtain a powdery polymer. Various physical properties of this polymer were measured. The results are shown in Table 1.

<Comparative manufacturing example 1>
A polymer was obtained by the same _{procedure as in Production Example 1 except that NaHSO 3 was not used.} Various physical properties of this polymer were measured. The results are shown in Table 1.

<Comparative manufacturing example 2>
88.3 g of 79 mass% DAC aqueous solution and 461 g of 50 mass% AM aqueous solution were added to a metal dewar bottle coated with anti-adhesion coating to set the monomer composition ratio to DAC / AM = 10/90 mol%, and further distilled water was added. 451 g was added to obtain a polymerization solution having a total concentration of 30% by mass and a total mass of 1.0 kg. The pH of this solution was adjusted to 4, and the solution temperature was adjusted to 7 ° C. while blowing nitrogen gas into the solution for 60 minutes. Then, an aqueous solution of V-50 and ammonium persulfate (hereinafter abbreviated as “APS”) was added so as to be 2000 ppm and 20 ppm, respectively, in terms of solid content with respect to the total mass of each monomer. Next, _{an aqueous solution of NaHSO 3} was added so as to be 20 ppm in terms of solid content with respect to the total mass of each monomer, and the mixture was swiftly stirred and then hermetically sealed to allow the polymerization to proceed. After the reaction temperature stopped rising, it was held for 60 minutes to obtain a hydrogel-like polymer. The obtained hydrogel-like polymer was taken out of the container and shredded. This was dried at a temperature of 80 ° C. for 5 hours and then pulverized to obtain a powdery polymer compound (abbreviated as B1; the same applies hereinafter). The 0.5% salt viscosity of B1, the low shear viscosity and the first normal stress were measured. The results are shown in Table 1. In Table 1, "---" means that the chain transfer agent was not added. Further, in Table 1, the description of "20/20" means that ammonium persulfate (APS) and sodium bisulfite (NaHSO ₃ ) are each added in an amount of 20 ppm.

<Manufacturing Examples 2 to 16>
A polymer was obtained in the same manner as in Production Example 1 except that the monomer composition and the composition of the chain transfer agent were changed as shown in Table 1. Various physical properties of this polymer were measured. The results are shown in Table 1.

<Comparative Manufacturing Examples 3 to 11>
A polymer was obtained in the same manner as in Comparative Production Example 2 or Production Example 1 except that the monomer composition and the composition of the chain transfer agent were changed as shown in Table 1. Various physical properties of this polymer were measured. The results are shown in Table 1.

<Manufacturing example 17>
DAC, AM, isopropyl alcohol (2.0% by mass with respect to the monomer) as a chain transfer agent, and distilled water were put into a 1000 ml four-necked separable flask, and the pH was adjusted to 4 with concentrated sulfuric acid. Then, a 20 g aqueous solution containing 0.04 g of V-50 was added, and distilled water was added so that the total amount was 400 g to prepare a monomer aqueous solution. Each monomer had a compounding ratio shown in Table 1, and the total concentration of all the monomers was 56% by mass. Further, this aqueous monomer solution was added to 155 g of paraffin oil in which 10.0 g of a nonionic surfactant of HLB 8.0 was dissolved, and the mixture was emulsified by stirring at high speed for about 1 minute using a homogenizer. Then, a nitrogen gas blowing tube, a reflux condenser, and a thermometer were attached to the flask, and the stirrer was replaced with a stirrer for a normal chemical reaction, and the emulsion was degassed by passing nitrogen gas through the emulsion for 30 minutes while stirring. Then, the temperature was raised to 50 ° C., and polymerization was carried out in a nitrogen gas atmosphere. After completion of the polymerization, 17.2 g of a nonionic surfactant having an HLB of 13.0 was added to obtain an emulsion type polymer compound. Various physical properties of this polymer were measured. The results are shown in Table 1.

<Comparative Manufacturing Example 12>
A polymer was obtained by the same procedure as in Production Example 17 except that isopropyl alcohol as a chain transfer agent was not blended. Various physical properties of these polymers were measured. The results are shown in Table 1.

[Wastewater treatment test 1]
(Examples 1 to 13, Comparative Examples 1 to 10)
Aggregation and dewatering performance were evaluated using paper sludge collected from a paper mill. The sludge used was pH = 6.99, total evaporation residue (TS) = 40,600 (mg / L), ignition loss (VTS) = 40.6 (% TS), suspended solids (SS) = 37. , 400 (mg / L). 200 mL of this sludge was placed in a 300 mL beaker, and each polymer flocculant was added at the ratio shown in Table 2. The addition rate (as the solid content of the flocculant) is shown in Table 2. The sludge was stirred at 200 rpm for 30 seconds using a jar tester to form flocs, and the filtration rate was measured for 10 seconds. These results are shown in Table 2.

In Comparative Examples 1 to 10, the polymer flocculant NS / Vz × M is outside the scope of the present invention. In each of the comparative examples, the floc diameter was not large, the filtration rate was low, and the hand squeezing condition was poor.

[Wastewater treatment test 2]
(Examples 14 to 20, Comparative Examples 11 to 18)
Aggregation and dewatering performance were evaluated using paper sludge collected from a paper mill. The sludge used was pH = 6.6, total evaporation residue (TS) = 28,400 (mg / L), ignition loss (VTS) = 46.9 (% TS), suspended solids (SS) = 31. , 100 (mg / L). 200 mL of this sludge was placed in a 300 mL beaker, and each polymer flocculant was added at the ratio shown in Table 3. The addition rate (as the solid content of the flocculant) is shown in Table 3. The sludge was stirred at 200 rpm for 30 seconds using a jar tester to form flocs, and the filtration rate was measured for 10 seconds. These results are shown in Table 3.

In Comparative Examples 11 to 18, the polymer flocculant NS / Vz × M is outside the scope of the present invention. In each of the comparative examples, the floc diameter was not large, the filtration rate was low, and the hand squeezing condition was poor.

Claims (12)

At least the following chemical formula (1)

(In the chemical formula (1), R ₁ is an alkyl group or a benzyl group having 1 to 3 carbon atoms, R ₂ and R ₃ are independently hydrogen atoms or an alkyl group having 1 to 3 carbon atoms, and X is an oxygen atom or NH. Y represents a hydrogen atom or a methyl group, Q represents an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, and Z ⁻ represents a counter anion.
Cationic monomer unit derived from , and
The following chemical formula (2)
CH ₂ = CR _1- CO-NR ₂ R ₃ ... (2)
(In the chemical formula (2), R ₁ is a hydrogen atom or a methyl group, and R ₂ and R ₃ independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.)
The nonionic monomer units derived from a including copolymers,
The viscosity Vz (Pa · s) of a 0.1 mass% aqueous solution measured at a ^{shear rate of 0.02 (s -1} ) or less using a dynamic viscoelasticity measuring device at 25 ° C. is the following mathematical formula (1).
1.0 <Vz <30 ... Number (1)
And meet
Total monomer mole fraction of the cationic monomer units to monomer units M and (mol%), the first normal stress NS at 25 ° C. as measured at a shear rate 10,000 ^{(s -1) (Pa)} And the viscosity Vz (Pa · s) are the following formula (2).
3,000 ≤ NS / Vz x M ≤ 9,000 ... Number (2)
A polymer flocculant characterized by containing a copolymer satisfying the above conditions. The following formula (3)
3,000 ≤ NS / Vz x M ≤ 6,000 ... Number (3)
The polymer flocculant according to claim 1. The following formula (4)
5 ≤ M ≤ 40 ... Number (4)
The polymer flocculant according to claim 1. The polymer flocculant according to claim 1, wherein the cationic monomer unit is a monomer unit derived from a quaternary salt of methyl chloride of dimethylaminoethyl acrylate. The polymer flocculant according to claim 1, wherein the nonionic monomer unit is a monomer unit derived from acrylamide. The polymer flocculant according to claim 1, wherein the copolymer is an aqueous gel polymer or a dried product thereof. The polymer flocculant according to claim 1, wherein the copolymer is a W / O type emulsion or a dried product thereof. An aqueous gel polymer obtained by polymerizing a monomer mixture containing at least the cationic monomer according to the chemical formula (1) and the nonionic monomer according to the chemical formula (2) into an aqueous solution using a photoinitiator. And
The method for producing a polymer flocculant according to claim 1, wherein the aqueous gel polymer is dried. A W / O type emulsion was obtained by emulsion polymerization of a monomer mixture containing at least the cationic monomer according to the chemical formula (1) and the nonionic monomer according to the chemical formula (2).
The method for producing a polymer flocculant according to claim 1, wherein the W / O type emulsion is dried. A method for dehydrating sludge, which comprises adding the polymer flocculant according to any one of claims 1 to 7 to sludge. The method for dehydrating sludge according to claim 10, wherein the sludge is papermaking sludge. The first normal stress NS (Pa) at 25 ° C. measured at a shear rate of 10,000 (s ^-1 ) is the 0.1 mass% aqueous solution measured at a ^{shear rate of 0.02 (s -1) or less.} A method for evaluating the aggregation performance of a polymer flocculant according to claim 1, wherein the aggregation performance of the polymer flocculant is evaluated from the value divided by the viscosity Vz (Pa · s) at 25 ° C.