JP2017100111A - Cross-linking type polymer coagulant, manufacturing method of the same and waste water treating method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer coagulant, a manufacturing method of the polymer coagulant and a waste water treating method which can exhibit performance in a wide addition rate especially for livestock waste water with regard to the polymer coagulant which is excellent in filtration speed and dehydration property, effectively permits dehydration and can obtain dehydration cake.SOLUTION: In a cross-linking type polymer coagulant, a strain rate y(%) at which a storage modulus G1 and loss modulus G2 in a strain rate dependence measurement at 25°C of 0.1 mass% aqueous solution using a rheometer get to equal to each other satisfies 1≤y<500 and an angle frequency x(rad/s) at which a storage modulus G3 and a loss modulus G4 in an angle frequency dependence measurement at 25°C of 0.1 mass% aqueous solution using a rheometer get to equal to each other satisfies 0.05<x≤15. The coagulant is a water soluble polymer provided by copolymerizing a cationic monomer 5 to 98.9999 mol%, a nonionic monomer 1 to 94.9999 mol% and a cross-linking monomer 0.0001 to 0.01 mol%.SELECTED DRAWING: None

Description

  The present invention relates to a crosslinked polymer flocculant, a method for producing the same, and a wastewater treatment method. Specifically, the present invention relates to a crosslinked polymer flocculant whose aqueous solution has a predetermined viscoelasticity, a method for producing the same, and a wastewater treatment method.

  Polymer flocculants are used for the purpose of coagulating, settling and separating sludge contained in domestic wastewater and industrial wastewater. As the polymer flocculant, a cationic polymer or an amphoteric polymer composed of a linear water-soluble polymer is frequently used. In the treatment of sludge, the moisture content of the dewatered cake is closely related to the addition rate of the polymer flocculant. When the addition rate of the polymer flocculant is low, the water content of the dehydrated cake cannot be lowered sufficiently. In addition, even when the addition rate of the polymer flocculant is high, the water content of the dehydrated cake cannot be sufficiently reduced. That is, the conventional polymer flocculant cannot exhibit good performance even if its addition rate is too low or too high. The optimum addition rate of the conventional polymer flocculant varies depending on the properties of the wastewater. In addition, conventional polymer flocculants have a narrow range of addition rates suitable for wastewater treatment.

  In recent years, the chemical treatment method has come to be used as a treatment method of sludge discharged from livestock facilities due to the trend of large-scale management and environmental consideration. Polymer flocculants are used for the treatment of sludge obtained by separating manure itself with a separator or excess sludge. However, the property of livestock wastewater varies depending on the change of feed for livestock and the season. Moreover, a part of waste water may be in emulsion form. Therefore, efficient treatment of livestock wastewater is difficult with conventional polymer flocculants.

  In order to solve the above problem, there is a method in which 70 to 95% by mass of the total addition amount of the cationic flocculant is added and mixed, and then the remaining flocculant is added (Patent Document 1). However, this method increases the amount of the polymer flocculant used and complicates the process.

  Further, there is a wastewater treatment method using polyamidine, which includes a method of dehydrating using two or more water-soluble polymers having different salt viscosities (Patent Document 2). However, the use of amidine results in increased drug costs. Moreover, since the molecular weight is low, the granulation property is poor. As a result, the amount of flocculant added increases.

JP 2004-202401 A Japanese Patent No. 4823552

  The problem to be solved by the present invention is a polymer flocculant that has excellent cohesiveness to livestock wastewater, has a high filtration rate, can be effectively dehydrated, and can obtain a dehydrated cake with a low water content, and its production It is to provide a method and a wastewater treatment method.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has obtained the following knowledge.
When a conventional polymer flocculant composed of a linear water-soluble polymer is dissolved in water to form an aqueous solution, the linear flocculant is caused by the interaction between flocculant molecules and hydrogen bonding with water molecules. It is thought that the molecule is in a string shape. The polymer flocculant in the form of a string does not easily react with sludge and it is difficult to form a strong sludge floc. Further, the amount of the flocculant composed of the linear water-soluble polymer needs to be increased. In particular, livestock wastewater has a small solid content, and a part thereof is in an emulsion form. Moreover, the property of livestock wastewater changes when the feed of livestock changes. For this reason, conventional polymer flocculants composed of linear water-soluble polymers often have difficulty in efficiently dewatering sludge generated from livestock wastewater.

  On the other hand, a polymer flocculant composed of a crosslinked water-soluble polymer has a rigid molecular structure, and has little interaction between flocculant molecules and water molecules. Therefore, the adsorption speed to sludge is fast and a strong sludge floc can be formed. Moreover, since it has a crosslinked structure, it is more hydrophobic than the linear water-soluble polymer, and the dewaterability of the generated sludge floc is increased.

  In particular, when a cross-linked water-soluble polymer having a predetermined viscoelasticity as an aqueous solution is used as a polymer flocculant, the coagulability with respect to livestock wastewater is excellent, the filtration rate is fast, it can be dehydrated effectively, and the water content is high. The inventors have found that a low dehydrated cake can be obtained, and have completed the present invention.

  The present invention for solving the above problems is described below.

[1] The strain rate y (%) at which the storage elastic modulus G1 and the loss elastic modulus G2 are equal in the measurement of the strain rate dependency of a 0.1% by mass aqueous solution at 25 ° C. using a rheometer is expressed by the following formula (1).
1 ≦ y <500 Formula (1)
While satisfying
The angular frequency x (rad / s) at which the storage elastic modulus G3 and the loss elastic modulus G4 are equal in an angular frequency dependence measurement at 25 ° C. of a 0.1% by mass aqueous solution using a rheometer is expressed by the following formula (2).
0.05 <x ≦ 15 Formula (2)
A crosslinked polymer flocculant characterized by satisfying

[2] The cross-linked polymer flocculant is
5 to 98.9999 mol% of the cationic monomer,
1 to 94.9999 mol% of nonionic monomer,
0.0001 to 0.01 mol% of a crosslinkable monomer,
The crosslinked polymer flocculant according to [1], which is a water-soluble polymer obtained by polymerizing a monomer mixture comprising:

（但し、Ｒ_１は水素原子又はメチル基、Ｒ_２は炭素数１〜３のアルキル基又はベンジル基、Ｒ_３及びＲ_４はそれぞれ独立に水素原子又は炭素数１〜３のアルキル基、Ｘは酸素原子又はＮＨ、Ｑは炭素数１〜４のアルキレン基又は炭素数２〜４のヒドロキシアルキレン基、Ｚ⁻は対アニオンをそれぞれ表す。）
で表されるカチオン性単量体である〔２〕に記載の架橋型高分子凝集剤。 [3] The cationic monomer is
The following general formula (1)

(However, R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkyl group or benzyl group having 1 to 3 carbon atoms, R ₃ and R ₄ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X is (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, and Z ⁻ represents a counter anion.)
The crosslinked polymer flocculant according to [2], which is a cationic monomer represented by the formula:

  [4] The crosslinked polymer flocculant according to any one of [1] to [3], wherein the dosage form of the crosslinked polymer flocculant is an emulsion.

  [5] The crosslinkable polymer flocculant according to any one of [1] to [3], wherein the dosage form of the crosslinkable polymer flocculant is powder.

[6] Cationic monomer 5 to 98.9999 mol%,
1 to 94.9999 mol% of nonionic monomer,
0.0001 to 0.01 mol% of a crosslinkable monomer,
The method for producing a crosslinked polymer flocculant according to [4], wherein a monomer mixture comprising:

[7] Cationic monomer 5 to 98.9999 mol%,
1 to 94.9999 mol% of nonionic monomer,
0.0001 to 0.01 mol% of a crosslinkable monomer,
The method for producing a crosslinkable polymer flocculant as described in [5], wherein a polymer emulsion is obtained by emulsion polymerization of a monomer mixture comprising: and the polymer emulsion is dried.

[8] A wastewater treatment method without adding an inorganic flocculant,
A wastewater treatment method comprising adding the crosslinkable polymer flocculant according to any one of [1] to [5] to wastewater having a total evaporation residue of 2,000 to 50,000 (mg / L) .

  [9] The wastewater treatment method according to [8], wherein the wastewater is livestock wastewater.

  The cross-linked polymer flocculant of the present invention is excellent in cohesiveness with respect to livestock wastewater, has a high filtration rate, can be effectively dehydrated, and a dehydrated cake having a low water content can be obtained. The cross-linked polymer flocculant of the present invention exhibits excellent performance against livestock wastewater having various properties. The cross-linked polymer flocculant of the present invention has a wide range of addition rates that can be taken with respect to wastewater.

Hereinafter, the present invention will be described in detail.
In the present specification, acrylate and / or methacrylate is represented as (meth) acrylate, acryloyl group and / or methacryloyl group is represented as (meth) acryloyl group, and acrylamide and / or methacrylamide is represented as (meth) acrylamide. Acrylic acid and / or methacrylic acid is represented as (meth) acrylic acid.

(1) Crosslinkable polymer flocculant The crosslinkable polymer flocculant of the present invention is characterized by comprising a crosslinkable water-soluble polymer having the parameters described below. The crosslinkable polymer flocculant of the present invention does not substantially contain a linear polymer. Here, being substantially free means that the content of the linear polymer is less than 1% by mass.

(1-1) Crosslinkable water-soluble polymer The polymer flocculant of the present invention is characterized in that the aqueous solution comprises a crosslinked water-soluble polymer having a predetermined viscoelasticity. The physical properties for the crosslinked water-soluble polymer to exhibit excellent performance as a polymer flocculant can be defined by viscoelasticity measured using a rheometer.

In the polymer flocculant of the present invention, the storage modulus G1 and the loss modulus G2 in the strain rate dependency measurement at 25 ° C. of a 0.1% by mass aqueous solution using a rheometer have a strain rate <1%. The time is always in the relationship of G2 <G1, the magnitude relationship between G1 and G2 is reversed in the range of 1% ≦ distortion rate <500%, and the relationship of G2> G1 is always in the case of the strain rate ≧ 500%. With
When the angular frequency ≦ 0.05 rad / s, the storage elastic modulus G3 and the loss elastic modulus G4 in the angular frequency dependency measurement always have a relationship of G3 <G4, and 0.05 rad / s <angular frequency ≦ 15 rad / s. In this range, the magnitude relationship between G3 and G4 is reversed, and when angular frequency> 15 rad / s, the relationship is always G3> G4.

That is, the following formula (2)
tan δ ₁ = G2 / G1 (2)
The tan δ ₁ represented by the formula is 1 in the range where the strain rate is 1% or more and less than 500%. tan δ ₁ = 1 is preferably in the range of 5 to 400%, more preferably in the range of 10 to 300%, and more preferably in the range of 20 to 200%. Particularly preferred. When the point where tan δ ₁ = 1 is a strain rate of 500% or more, the crosslinked water-soluble polymer is not sufficiently crosslinked, and its properties are close to those of the linear water-soluble polymer. As a result, the floc diameter may not increase, the filtration rate may not improve, or the moisture content of the dewatered cake may not decrease. Moreover, it becomes difficult to exhibit the effect with respect to livestock wastewater having various properties. When the point where tan δ ₁ = 1 is less than 1%, the crosslinking reaction of the water-soluble polymer proceeds too much, and the amount added may not increase or the moisture content of the dehydrated cake may not be sufficiently reduced.

Further, the following formula (3)
tan δ ₂ = G4 / G3 (3)
The tan δ ₂ represented by the formula is 1 when the angular frequency x is in the range of 0.05 rad / s <x ≦ 15 rad / s. The tan δ ₂ = 1 is preferably within an angular frequency range of 0.08 to 12 rad / s, more preferably within a range of 0.1 to 10 rad / s, and 0.12 to 1 It is particularly preferable to be within the range of .6 rad / s. When the point at which tan δ ₂ = 1 is an angular frequency of 0.05 rad / s or less, the water-soluble polymer is not sufficiently crosslinked, and its properties are close to those of the linear water-soluble polymer. As a result, the floc diameter may not increase, the filtration rate may not decrease, and the moisture content of the dewatered cake may not decrease. Moreover, it becomes difficult to exhibit an effect with respect to livestock wastewater having various properties. If the point at which tan δ ₂ = 1 exceeds the angular frequency of 15 rad / s, the crosslinking reaction of the water-soluble polymer proceeds too much, and the amount of addition necessary to exhibit high performance increases, or the water content of the dehydrated cake increases. It may not be sufficiently reduced.

The viscoelasticity defined above is an index showing the three-dimensional structure of the crosslinked water-soluble polymer. This value can be adjusted by appropriately changing the addition amount of the crosslinkable monomer, the addition amount of the chain transfer agent, the amount of the polymerization catalyst, and the like. For example, the strain rate at which tan δ ₁ = 1 can be lowered by increasing the addition amount of the crosslinkable monomer. Further, the angular frequency at which tan δ ₂ = 1 can be increased by increasing the addition amount of the crosslinkable monomer. Similarly, by increasing the addition amount of the chain transfer agent, the strain rate at which tan δ ₁ = 1 can be increased. Further, by increasing the addition amount of the chain transfer agent, the angular frequency at which tan δ ₂ = 1 can be lowered.

  The cross-linked water-soluble polymer having a predetermined viscoelasticity is composed of a predetermined cationic monomer, a predetermined nonionic monomer, and a predetermined cross-linkable monomer as essential components, and other copolymerizable monomers. It is produced by polymerizing a monomer mixture having a body as an optional component.

(1-1-1) Cationic monomer The cationic monomer is a monomer having a radical polymerizable double bond and a cationic group capable of radical polymerization, and represented by the following general formula (1): In addition to the compounds represented, diallyldialkylammonium halides such as diallyldimethylammonium chloride can be exemplified. Among these cationic monomers, the radical polymerization reactivity is excellent, the high molecular weight required as a polymer flocculant is easy, and the performance as a polymer flocculant of the obtained cross-linked water-soluble polymer is excellent. A compound represented by the following general formula (1) is preferable because of excellent properties.

However, _{R 1} in the general formula (1) is a hydrogen atom or a methyl group, _{R 2} is an alkyl group or a benzyl group having 1 to 3 carbon atoms, _{R 3} and _{R 4} are a hydrogen atom or a carbon number 1 to independently 3 alkyl groups, which 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, and Z ⁻ represents a counter anion. Examples of Z ⁻ include halide ions such as chloride ions and sulfate ions.

  Specific examples of the cationic monomer represented by the general formula (1) 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, dimethylaminoethyl acrylate is particularly excellent in performance as a polymer flocculant and excellent in quality and storage stability of the cationic monomer and the cross-linked water-soluble polymer. Most preferred are quaternary salts (DAC) which are methyl chloride adducts and quaternary salts (DMC) which are methyl chloride adducts of dimethylaminoethyl methacrylate.
These cationic monomers may be used alone or in combination of two or more.

  The amount of the cationic monomer in the monomer mixture is preferably 5 to 98.9999 mol%, more preferably 20 to 98 mol%, and 50 to 95 mol%. Particularly preferred. That is, the crosslinked water-soluble polymer preferably contains the cationic monomer unit at 5 to 98.9999 mol%, more preferably 20 to 98 mol%, and 50 to 95 mol%. Is particularly preferred.

(1-1-2) Nonionic monomer As a nonionic monomer, (meth) acrylamide compound represented by the following general formula (2), methyl (meth) acrylate, (meth) acrylic Examples thereof include alkyl (meth) acrylates such as ethyl acid, butyl (meth) acrylate, and hydroxyethyl (meth) acrylate, styrene, acrylonitrile, vinyl acetate, and the like. Among these nonionic monomers, it is excellent in copolymerizability with cationic monomers, easily increases in molecular weight required as a polymer flocculant, and has excellent performance as a polymer flocculant. A (meth) acrylamide compound represented by the following general formula (2) is preferable.

CH ₂ = CR ₁ —CO—NR ₂ R ₃ (2)

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

Among these (meth) acrylamide compounds, acrylamide (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.

  The amount of the nonionic monomer in the monomer mixture is preferably 1 to 94.9999 mol%, more preferably 2 to 80 mol%, and 5 to 50 mol%. More preferred. That is, the crosslinked water-soluble polymer preferably contains 1 to 94.9999 mol% of nonionic monomer units, more preferably 2 to 80 mol%, and more preferably 5 to 65 mol%. Is particularly preferred.

(1-1-3) Crosslinkable monomer As a crosslinkable monomer, (meth) acrylate type | system | group which has two or more (meth) acryloyl groups represented by following General formula (3) in 1 molecule. And a crosslinkable monomer (hereinafter sometimes simply referred to as “crosslinkable monomer” or “crosslinking agent”).

CH ₂ = CR ₁ —CO— (3)

However, R < ₁ > in the said General formula (3) 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 2 or more. Those having 2 to 5 are preferred, and those having 2 to 3 are more preferred. Even if the number of (meth) acryloyl groups 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.

  Such crosslinkable monomers include methylene bisacrylamide (MBA), ethylene or polyethylene di (meth) acrylate, polypropylene di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth). Examples include acrylate, tetramethylol methane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, alkylene bis (meth) acrylamide, mono and polyalkylene glycol di (meth) acrylate, and polymethylolalkane poly (meth) acrylate. Is done. These may be used alone or in combination of two or more.

  The amount of the crosslinkable monomer in the monomer mixture is preferably 0.0001 to 0.01 mol%, more preferably 0.0002 to 0.008 mol%, It is especially preferable that it is -0.007 mol%. That is, the cross-linkable water-soluble polymer preferably contains a cross-linkable monomer unit at 0.0001 to 0.01 mol%, more preferably 0.0002 to 0.008 mol%. It is particularly preferable to contain it at 0005 to 0.007 mol%. When the addition amount of the crosslinkable monomer is 0.0001 to 0.01 mol%, since the interaction between the crosslinkable water-soluble polymers is weak, the viscosity is low and the handling is excellent. Moreover, since the viscosity is low, the reaction with the sludge proceeds promptly and a strong floc can be formed. If it is less than 0.0001 mol%, the crosslinking reaction may become insufficient, in that case, the ability to form sludge floc as a polymer flocculant is insufficient, the floc diameter does not become sufficiently large, The water content of the dehydrated cake may not become low. Moreover, when the addition amount of the crosslinkable monomer exceeds 0.01 mol%, the crosslinking reaction may proceed excessively. This increases the insoluble amount particularly 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 exhibited. Moreover, in the case of an emulsion, the addition amount required for a process increases and process cost increases.

(1-1-4) Copolymerizable monomer The polymer flocculant of the present invention is one or two or more types of monomers that can be copolymerized as necessary in addition to the cationic monomer. May be used in combination. Although it does not restrict | limit especially as a monomer which can be copolymerized, The anionic monomer described below is illustrated.

  Examples of the anionic monomer include (meth) acrylic acid represented by the following general formula (4) and salts thereof, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, maleic acid, and the like. Can be mentioned. Among these anionic monomers, it is excellent in copolymerizability with cationic monomers, easily increases the molecular weight required as a polymer flocculant, and has excellent performance as a polymer flocculant. (Meth) acrylic acid represented by the following general formula (4) and salts thereof are preferred. As the salts, ammonium salts and alkali metal salts such as sodium salts and potassium salts are preferable.

CH ₂ = CR ₁ -CO-OM (4)

However, R < ₁ > in the said General formula (4) is a hydrogen atom or a methyl group, M represents a hydrogen atom, an ammonium group, or an alkali metal atom.

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

  The amount of the anionic monomer in the monomer mixture is preferably 1 to 94.9999 mol%, more preferably 2 to 80 mol%, and 5 to 50 mol%. More preferred.

(2) Method for Producing Crosslinked Water-Soluble Polymer The polymerization method for obtaining the crosslinked water-soluble polymer is not particularly limited except that it is radical polymerization. Specific examples of radical polymerization applicable to the present invention Examples of typical forms include aqueous solution polymerization, suspension polymerization, and emulsion polymerization. Among these, aqueous solution polymerization and emulsion polymerization are preferable because they are simple in operation and easy to handle raw materials and products, and are advantageous in terms of production cost in industrial production. Moreover, you may volatilize a water layer or an oil layer after emulsion polymerization, and you may make it powder.

(2-1) Aqueous Polymerization Aqueous polymerization is a method in which an aqueous solution of the monomer mixture is polymerized 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 mass%, particularly preferably 30 to 65 mass%. It is preferable to adjust the pH of the aqueous solution of the monomer mixture 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 initiators such as azobisisobutyronitrile, redox initiators and light A polymerization initiator or the like can be used as appropriate. These radical polymerization initiators may be used alone or in combination of two or more.

  The polymerization initiation temperature is usually preferably 0 to 35 ° C. The polymerization time is usually preferably from 0.1 to 3 hours. In addition, the polymerization reaction is preferably performed in an inert atmosphere in which oxygen is not present. These polymerization conditions are known. After completion of the polymerization reaction, post-treatment such as heat treatment, drying, and pulverization is appropriately performed as necessary. A known method can be applied to these post-treatments.

  Among the production methods by aqueous solution polymerization, there are few variations in physical properties and quality of the obtained cross-linked water-soluble polymer, stable production is possible, and physical properties can be easily adjusted. Particularly preferred. As a specific example of the light irradiation polymerization, there is exemplified a method in which polymerization is carried out by irradiating an aqueous solution of the monomer mixture with light in the presence of a photopolymerization initiator and a chain transfer agent.

The photopolymerization initiator used for light irradiation polymerization is not particularly limited. Examples of preferred photopolymerization initiators include acetophenone photopolymerization initiators and azo initiators. Among them, a water-soluble azo initiator is particularly preferable because the solubility of the monomer mixture in an aqueous solution is high and the high molecular weight necessary as a polymer flocculant is easy.
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 addition amount of the photopolymerization initiator is not particularly limited. What is necessary is just to adjust suitably according to the kind of photoinitiator, the molecular weight of a crosslinkable polymer, a monomer composition, and content of a residual monomer. In the case of a water-soluble azo initiator, usually, 100 to 3000 ppm is preferable on a mass basis with respect to the total mass of each monomer in the monomer mixture.

The chain transfer agent used for photoirradiation polymerization is added mainly for the purpose of adjusting the molecular weight of the crosslinked water-soluble polymer and suppressing the generation of insoluble matter. The type is not particularly limited. Examples of the chain transfer agent that can be used in the present invention include sodium bisulfite, sodium sulfite, sodium hypophosphite, mercaptoethanol, isopropanol and the like. Among these, sodium bisulfite is preferable because the solubility of the monomer mixture in the aqueous solution is high, the effect is high even with a small addition amount, and the molecular weight of the crosslinked water-soluble polymer can be easily adjusted.
These chain transfer agents may be used alone or in combination of two or more.

  The addition amount of the chain transfer agent is not particularly limited. What is necessary is just to adjust suitably according to the kind of chain transfer agent, the molecular weight of a crosslinkable polymer, a monomer composition, the addition amount of a crosslinkable monomer, and an insoluble amount. In the case of sodium hydrogen sulfite, 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. Moreover, it may cause a trouble that blocks a pump that feeds a solution obtained by dissolving a polymer flocculant in water. If the amount of sodium bisulfite added exceeds 500 ppm, the molecular weight of the crosslinked polymer may become too low. In that case, the cohesive force with respect to the sludge as a polymer flocculant falls, and a floc diameter does not become large. Moreover, the filtration rate may fall, or the fine solid substance in sludge may fall out into a filtrate, and the transparency of a filtrate may deteriorate.

Light irradiation conditions such as the wavelength of light used for light irradiation polymerization, irradiation intensity, and irradiation time are not particularly limited. What is necessary is just to adjust suitably according to the kind and addition amount of a photoinitiator to be used, and the physical property and performance of a crosslinking type polymer. When the water-soluble azo 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 measured by a UV illuminometer for 365 nm. The irradiation time is usually preferably from 0.1 to 3 hours.

(2-2) Emulsion polymerization Emulsion polymerization consists of an aqueous phase containing a predetermined monomer, radical initiator, chain transfer agent, etc., an oily substance composed of immiscible hydrocarbons, and a water-in-oil emulsion. In this method, a water-in-oil emulsion is formed using an effective amount of a surfactant to be formed, and the monomer is polymerized in the droplets of the emulsion.

  Examples of oily substances include paraffins, various mineral oils, hydrocarbon oils having characteristics equivalent to 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 3-11. Examples of such surfactants include nonionic surfactants such as sorbitan monooleate and sorbitan monostearate. The addition amount of these surfactants is preferably 0.3 to 10% by mass, and more preferably 0.5 to 5% by mass with respect to the total amount of the water-in-oil emulsion.

  The polymerization conditions for carrying out the emulsion polymerization are appropriately set according to the monomers and initiators used 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, and 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 performed in an inert atmosphere without oxygen.

  The average particle diameter when emulsion polymerization is performed is preferably 0.03 to 10 μm, more preferably 0.1 to 5 μm, and still more preferably 0.5 to 3 μm. The average particle diameter refers to a volume average value measured by a laser diffraction method.

  By using the polymerization method described above, a crosslinked water-soluble polymer having a predetermined viscoelasticity defined in the present invention can be produced. After completion of the polymerization reaction, post-treatment such as heat treatment, drying, and pulverization is appropriately performed as necessary. A known method can be applied to these post-treatments. The viscosity of a 0.1% aqueous solution of a crosslinked water-soluble polymer is 100 to 3000 mPa · s, more preferably 150 to 1500 mPa · s, and particularly preferably 180 to 1000 mPa · s. The viscosity can be adjusted by adjusting the degree of polymerization and the degree of crosslinking. The degree of polymerization can be adjusted by known methods such as polymerization catalyst concentration and use of a chain transfer agent. The degree of crosslinking can be adjusted by adjusting the amount of the crosslinking monomer.

  The weight average molecular weight of the crosslinked water-soluble polymer is preferably 500,000 to 15 million. When the weight average molecular weight is less than 500,000, the ability to form sludge flocs as a polymer flocculant is insufficient, and the floc diameter may not be sufficiently large. On the other hand, when the weight average molecular weight exceeds 5 million, the solubility of the polymer flocculant is deteriorated, which causes troubles that block the pump for feeding the solution.

  The insoluble amount of the crosslinked water-soluble polymer is preferably 50 mL or less, more preferably 20 mL or less, and most preferably 10 mL or less. If the insoluble amount exceeds 50 mL, the amount of active ingredient that effectively acts as a polymer flocculant decreases. Moreover, it may cause a trouble that blocks a pump that feeds a solution obtained by dissolving a polymer flocculant in water.

  The 0.5% salt viscosity of the crosslinked water-soluble polymer is preferably 5 to 50 mPa · s, more preferably 7 to 30 mPa · s, and most preferably 10 to 20 mPa · s. When the 0.5% salt viscosity is less than 5 mPa · s, the aggregation performance as a polymer flocculant may be insufficient, and the floc diameter may not be sufficiently increased, or the gravity filterability may be reduced. If the 0.5% salt viscosity exceeds 50 mPa · s, the water content of the dehydrated cake may not be sufficiently reduced.

(3) Wastewater treatment method In the wastewater treatment method using the polymer flocculant of the present invention, in addition to sludge generated in sewage treatment, human waste treatment and domestic wastewater treatment, various industrial wastewaters such as food factories, meat processing and chemical factories, etc. Various types of sludge such as sludge generated in processing, live urine generated in relation to livestock production such as pig farms and sludge generated in the treatment of waste water, and sludge generated in pulp or paper industry are targeted. 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 processed by anaerobic microorganisms, etc. The polymer flocculant of the present invention has particularly excellent performance for livestock wastewater. In other words, it works particularly effectively on wastewater that is partly in the form of emulsion and wastewater whose components vary.

  The wastewater treatment method of the present invention is characterized by adding the polymer flocculant of the present invention to the above various wastewaters for dehydration. As a specific example of the dehydration method, the polymer flocculant of the present invention is added to various wastewaters, and the suspension in the sludge and the polymer flocculant are allowed to act by stirring and / or mixing by a known method, A sludge floc is formed. The formed sludge floc is mechanically dehydrated by known means to separate into treated water and dehydrated cake.

  For the purpose of deodorization, dephosphorization, denitrification, etc., it is preferable that the sludge has a pH of less than 5.

  The wastewater treatment method of the present invention does not add an inorganic flocculant. Therefore, the processing cost is low and the operation is simple.

  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 dehydrator, a rotary press filter etc. are illustrated.

  EXAMPLES 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.

[Measurement method of strain rate dependence and angular frequency dependence of viscoelasticity]
Using an MCR rheometer manufactured by Anton Paar, the vibration strain rate dependency and the angular frequency dependency of the viscoelasticity of an aqueous solution in which the sample was dissolved at a solid content of 0.1% by mass were measured.
<Viscoelasticity measuring device>
Anton Paar MCR302 rheometer, control software Leoplus 32 (ver. 3.62)
<Measurement conditions>
Jig: 50 mmφ_0.5 ° Cone plate Measurement temperature: 25 ° C.
<Measurement of strain rate dependency>
The storage elastic modulus and loss elastic modulus of the solution when a strain rate of 1% → 1000% was applied at a frequency of 1 Hz were measured.
<Frequency dependence measurement>
The storage elastic modulus and loss elastic modulus of the solution when the angular frequency was applied from 100 to 0.1 rad / s in the linear ascending / descending range of the strain rate of 0.1 to 10% were measured.

[Filtration speed]
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, 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).

[Moisture content of dehydrated cake]
The entire sludge hydrate cake remaining on the stainless steel sieve after the above filtration rate measurement is taken out, sandwiched between belt press filter cloths (made of polyester, Sugaya woven), and using a desktop test belt press machine at 170 kPa for 3 minutes. The dehydrated cake was obtained by pressing. A portion of the center is sampled from the dehydrated cake obtained, weighed in an aluminum pan, dried for 16 hours in a hot air dryer at 105 ° C., and then measured for the weight after drying. The water content was determined from the mass ratio of

<Production Example 1>
A mixture of 313 g of 79% dimethylaminoethyl acrylate methyl chloride quaternary salt solution and 45.4 g of 50% acrylamide aqueous solution, 1.6 g of isopropyl alcohol, 4.0 g of 5% aqueous solution of chelating agent EDTA, t-butyl hydro ter as an initiator After adding 2.0 g of an aqueous solution containing an aqueous solution containing 0.03 g of peroxide and 0.0036 g of methylenebisacrylamide (MBA), ion-exchanged water was added, the pH was adjusted to 3.0 with 98% sulfuric acid, and 704.2 g of An aqueous phase was prepared. While stirring the oil phase, the water phase was added and stirred at high speed with a homogenizer to prepare a water-in-oil emulsion. A nitrogen gas blowing tube, a reflux condenser, and a thermometer were attached to 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 emulsion at a supply rate of 34.9 ml / min to initiate polymerization. After reaching 50 ° C. and holding this temperature for 2 hours, the supply amount of nitrogen gas containing sulfur dioxide is increased to 186.4 ml / min, and further maintained at 50 ° C. for 1 hour, and then containing nitrogen gas and sulfur dioxide. Nitrogen gas was stopped to complete the polymerization. As a hydrophilic surfactant, 14.1 g of polyethylene glycol monooleate having an HLB value of 13.5 is added and mixed so that the weighted average HLB value of the total emulsifier contained in the emulsion is 10.0. After dehydration, drying under reduced pressure was performed to obtain powdered polymer 1. The measurement results of the viscoelasticity of this polymer are shown in Table 1.

<Production Examples 2-7, Comparative Production Examples 1-6>
A polymer was obtained in the same manner as in Production Example 1 except that the monomer composition was changed as shown in Table 1. The measurement results of viscoelasticity of these polymers are shown in Table 1.

[Wastewater treatment test 1]
(Examples 1-4, Comparative Examples 1-6)
Agglomeration and dewatering performance was evaluated using livestock wastewater collected from the farm. The waste water used is pH = 6.69, TS (Total Solid) = 5,000 (mg / L), SS (Suspended Solids) = 3,840 (mg / L). 200 mL of this waste water was put into a 300 mL beaker, and each flocculant was added. The addition rate (as the solid content of the flocculant) is shown in Table 2. The wastewater was stirred at 200 rpm for 30 seconds using a jar tester to form a floc, and the filtration rate for 10 seconds was measured. Sludge on the filter cloth was collected and squeezed at 170 kPa for 3.0 minutes using a test belt press to obtain a dehydrated cake, and the moisture content of the cake was measured. These results are shown in Table 2.

  The polymer flocculant of Example 1 contained a predetermined viscoelastic cross-linked water-soluble polymer, and showed good performance within a range of addition rate of 60 to 100 ppm.

On the other hand, the angular frequency at which tan δ = 1 of the polymer flocculant used in Comparative Example 1 is 0.05 rad / s. The polymer flocculant of Comparative Example 1 had the best filtration rate when the addition amount was 80 ppm, but the filtration rate decreased when the addition amount was further increased. That is, the addition was excessive. Comparative Examples 2 to 3 also had the same results as Comparative Example 1. Comparative Example 4 is a linear polymer having an angular frequency within the range, but a sufficient filtration rate cannot be obtained and the water content is not lowered.
Comparative Examples 5 and 6 were a mixture of a linear polymer and a crosslinked polymer, and the amount added was higher than in Examples 1-4.

[Wastewater treatment test 2]
(Examples 5-8, Comparative Examples 7-9)
Aggregation and dewatering performance were evaluated using livestock wastewater collected from the black pig farm. The waste water used is pH = 7.14, TS (Total Solid) = 13,700 (mg / L), SS (Suspended Solids) = 11,100 (mg / L). 200 mL of this waste water was put into a 300 mL beaker, and each flocculant was added. The addition rate (as the solid content of the flocculant) is shown in Table 2. The wastewater was stirred at 200 rpm for 30 seconds using a jar tester to form a floc, and the filtration rate for 10 seconds was measured. Sludge on the filter cloth was collected and squeezed at 170 kPa for 3.0 minutes using a test belt press to obtain a dehydrated cake, and the moisture content of the cake was measured. These results are shown in Table 3.

  The polymer flocculants of Examples 5 to 8 contained a predetermined viscoelastic cross-linked water-soluble polymer, and showed good performance in a range of addition rate of 60 to 100 ppm. On the other hand, Comparative Examples 7 to 9 could not confirm the improvement of the filtration rate and the reduction of the moisture content as in Examples.

[Wastewater treatment test 3]
(Examples 9-11, Comparative Examples 10-12)
Aggregation and dewatering performance were evaluated using livestock wastewater collected from the black pig farm. The waste water used is pH = 7.52, TS (Total Solid) = 18,100 (mg / L), SS (Suspended Solids) = 14,600 (mg / L). 200 mL of this waste water was put into a 300 mL beaker, and each flocculant was added. The addition rate (as the solid content of the flocculant) is shown in Table 2. The wastewater was stirred at 200 rpm for 30 seconds using a jar tester to form a floc, and the filtration rate for 10 seconds was measured. Sludge on the filter cloth was collected and squeezed at 170 kPa for 3.0 minutes using a test belt press to obtain a dehydrated cake, and the moisture content of the cake was measured.
These results are shown in Table 4.

  The polymer flocculants of Examples 9 to 11 contain a predetermined viscoelastic cross-linked water-soluble polymer, and the addition amount is in the range of 200 to 275 ppm, and the filtration rate of 10 seconds is correlated with the increase in the addition amount. It showed an increase and a decrease in moisture content. On the other hand, in Comparative Examples 10 to 12, the addition rate was 250 ppm, and the filtration rate and the water content reached the peak.

Claims (9)

The strain rate y (%) at which the storage elastic modulus G1 and the loss elastic modulus G2 are equal in the strain rate dependency measurement at 25 ° C. of a 0.1 mass% aqueous solution using a rheometer is expressed by the following formula (1).
1 ≦ y <500 Formula (1)
While satisfying
The angular frequency x (rad / s) at which the storage elastic modulus G3 and the loss elastic modulus G4 are equal in an angular frequency dependence measurement at 25 ° C. of a 0.1% by mass aqueous solution using a rheometer is expressed by the following formula (2).
0.05 <x ≦ 15 Formula (2)
A crosslinked polymer flocculant characterized by satisfying The crosslinkable polymer flocculant is
5 to 98.9999 mol% of the cationic monomer,
1 to 94.9999 mol% of nonionic monomer,
0.0001 to 0.01 mol% of a crosslinkable monomer,
The cross-linked polymer flocculant according to claim 1, which is a water-soluble polymer obtained by polymerizing a monomer mixture comprising: The cationic monomer is
The following general formula (1)

(However, R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkyl group or benzyl group having 1 to 3 carbon atoms, R ₃ and R ₄ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X is (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, and Z ⁻ represents a counter anion.)
The cross-linked polymer flocculant according to claim 2, which is a cationic monomer represented by the formula:   The crosslinkable polymer flocculant according to any one of claims 1 to 3, wherein a dosage form of the crosslinkable polymer flocculant is an emulsion.   The crosslinkable polymer flocculant according to any one of claims 1 to 3, wherein a dosage form of the crosslinkable polymer flocculant is powder. 5 to 98.9999 mol% of the cationic monomer,
1 to 94.9999 mol% of nonionic monomer,
0.0001 to 0.01 mol% of a crosslinkable monomer,
The method for producing a cross-linked polymer flocculant according to claim 4, wherein the monomer mixture comprising the above is emulsion-polymerized. 5 to 98.9999 mol% of the cationic monomer,
1 to 94.9999 mol% of nonionic monomer,
0.0001 to 0.01 mol% of a crosslinkable monomer,
6. The method for producing a cross-linked polymer flocculant according to claim 5, wherein a polymer emulsion is obtained by emulsion polymerization of a monomer mixture comprising: and the polymer emulsion is dried. A wastewater treatment method without adding an inorganic flocculant,
6. A wastewater treatment method comprising adding the cross-linked polymer flocculant according to any one of claims 1 to 5 to wastewater having a total evaporation residue of 2,000 to 50,000 (mg / L). . The wastewater treatment method according to claim 8, wherein the wastewater is livestock wastewater.