JP2001089532A - Amphoteric polymer flocculant and method of dehydrating sludge using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-molecular weight amphoteric polymer flocculant capable of providing flocs excellent in balance among strength, filtration rate and moisture content and to provide a method of dehydrating a sludge using the flocculant. SOLUTION: This amphoteric polymer flocculant is obtained by using a copolymer prepared by copolymerizing a reactive monomer having a radically polymerizable group at one end and an anionic group at the other end and 90-10,000 weight-average molecular weight with a cationic monomer as essential monomers. The reactive monomer is a compound represented by the general formula (1) (R1 denotes hydrogen atom or methyl group; R2 denotes a 1-8C linear or a 1-8C branched alkylene group; l denotes a natural number of 1-100; and Y1 denotes hydrogen atom, ammonium ion, an alkali metal ion or an alkaline earth metal ion).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high molecular weight amphoteric polymer flocculant and a method for dewatering sludge using the same.

[0002]

2. Description of the Related Art Conventionally, nonionic, cationic, anionic or amphoteric polymer flocculants have been used for the purpose of flocculating, sedimenting and separating suspended substances contained in domestic wastewater, industrial wastewater and the like. I have. In particular, cationic polymer flocculants are frequently used for dewatering sewage sludge. However, due to an increase in the amount of generated sludge and deterioration of sludge properties, the conventional dehydration method using a cationic polymer flocculant cannot achieve a sufficiently satisfactory dehydration treatment.

In order to solve these problems, it has been proposed to dewater sludge using an amphoteric polymer flocculant, and various amphoteric polymer flocculants used for this purpose have been proposed (for example, JP-A-62-205112, JP-A-53-149292, JP-A-3-18900
No.). However, the conventional amphoteric polymer flocculant needs to be added to sludge in a large amount depending on the sludge to be applied, or the floc particle size becomes small,
Because of insufficient filtration speed, the throughput per unit time could not be increased, and the resulting cake water content could not be further reduced.

[0004] A dehydration method using both an inorganic flocculant and a polymer flocculant has been proposed. JP-A-58-5199
No. 8 describes a method in which polyiron sulfate is used as an inorganic coagulant, a nonionic, anionic, or cationic polymer coagulant is independently added thereto to form a floc and dehydrate. . However, in this method, the diameter of the floc generated is relatively small and the strength is low, so that it is difficult to obtain a dewatered cake having a small water content.

JP-A-59-16599 describes a method for dewatering sludge using an inorganic flocculant and a cationic and anionic amphoteric polymer flocculant. However, in the case of this method, the releasability at the time of peeling the dewatered cake from the filter cloth in the dewatering step is poor, and the water content of the obtained dewatered cake is not sufficiently low.

JP-A-63-158200 discloses a method in which after adding an inorganic coagulant, the pH is adjusted to 5 to 8, and an amphoteric polymer coagulant is added thereto. However, in this method, a sufficient effect may not be obtained depending on the type of sludge to be treated.

[0007] As described above, the properties of sludge vary widely depending on the place where the sludge is generated, and it is actually impossible to dehydrate all sludge with one type of coagulant. Therefore, there has been a demand for a polymer flocculant having various preferable characteristics which can sufficiently cope with various sludge properties.

[0008]

SUMMARY OF THE INVENTION The present inventors have studied various types of polymer flocculants to solve the above-mentioned problems, and have found that a monomer having an anionic functional group having a specific structure is used. An amphoteric polymer flocculant obtained by copolymerizing a cationic monomer and, if necessary, other monomers is used for coagulation and dehydration of various sludges. The inventor has found that the balance between the speed and the water content is excellent, and has completed the present invention. Therefore,
An object of the present invention is to provide an amphoteric polymer flocculant which solves the above-mentioned problems, and a method for dewatering sludge using the amphoteric polymer flocculant.

[0009]

The present invention to achieve the above object is as described below. [1] A reactive monomer having a weight average molecular weight of 90 to 10000 having a radical polymerizable group at one end and an anionic group at the other end, and a cationic monomer as an essential monomer are copolymerized. Amphoteric polymer flocculant comprising a copolymer. [2] The amphoteric polymer flocculant according to [1], wherein the reactive monomer is a compound represented by the following general formula (1).

[0010]

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(Wherein, in the formula (1), R ¹ is a hydrogen atom or a methyl group, R ² is a linear or branched alkylene group having 1 to 8 carbon atoms, and l is a natural number of 1 to 100.) ¹ represents a hydrogen atom, an ammonium ion, an alkali metal ion, or an alkaline earth metal ion.) [3] Dewatering the sludge by adding the amphoteric polymer flocculant described in [1] or [2] above A method for dewatering sludge, characterized in that: [4] A method for dewatering sludge, comprising adding an organic cationic compound or an inorganic coagulant to sludge, and then adding the amphoteric polymer coagulant described in [1] or [2] to dewater the sludge. . [5] An organic cationic compound or an inorganic flocculant is added to the sludge, and then the pH of the sludge is adjusted to 4 to 7, and then the amphoteric polymer flocculant described in the above [1] or [2] is added. A method for dewatering sludge, comprising dewatering.

Hereinafter, the present invention will be described in detail.

In the present specification, an acryloyl group or a methacryloyl group is represented by a (meth) acryloyl group, acrylic acid or methacrylic acid is represented by (meth) acrylic acid, and acrylate or methacrylate is represented by (meth) acrylate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the amphoteric polymer flocculant of the present invention is a reactive monomer having a molecular weight of 90 to 10,000 having a radical polymerizable group at one end and an anionic group at the other end. And a cationic monomer as an essential monomer.

A reactive monomer having a radical polymerizable group at one end and an anionic group at the other end and having a weight average molecular weight of 90 to 10,000 (hereinafter simply referred to as a reactive monomer). As the radical polymerizable group, a (meth) acryloyl group is preferable.
In the present invention, the weight average molecular weight is a value obtained by converting the molecular weight measured by gel permeation chromatography into polystyrene.

Examples of the reactive monomer include a compound having an oxyalkylene unit, a polyester unit, a polyurethane unit, or a polyamide unit.

As the reactive monomer, the following general formula (1)
Compounds represented by-(3) are preferred.

[0018]

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Here, R ¹ , R ³ and R ⁶ represent a hydrogen atom or a methyl group. R ² represents a linear or branched alkylene group having 1 to 8 carbon atoms. R ⁴ is a linear or branched alkylene group having 1 to 6 carbon atoms. R ⁵ and R ^{9 each} represent an alkylene group having 2 to 4 carbon atoms, a cyclic alkylene group, or a divalent aromatic group. As R ⁵ and R ⁹ , an ethylene group,

[0020]

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Is preferred.

A represents an oxygen atom or NH. R ⁷ is an alkylene group having 1 to 6 carbon atoms. R ⁸ has a carbon number of 1 to
8 linear or branched alkylene group, or -COR
^10- is indicated. R ¹⁰ represents a linear or branched alkylene group having 1 to 8 carbon atoms.

L, m and n each represent a natural number of 1 to 100, and a preferable range is 1 to 50. Y ¹ , Y ² and Y
³ represents a hydrogen atom, an ammonium ion, an alkali metal ion, or an alkaline earth metal ion. As the alkali metal, sodium, potassium and the like are preferable. As the alkaline earth metal, calcium, magnesium and the like are preferable.

Preferred examples of the compound represented by the formula (1) include Michael adducts of (meth) acrylic acid such as (meth) acrylic acid dimer, and ring-opening reaction addition of (meth) acrylic acid with a cyclic lactone. Objects and the like. A preferred example of the Michael adduct of (meth) acrylic acid is a compound represented by the following formula (4). In the formula (1), R ¹ is a hydrogen atom, R ² is an ethylene group, and Y ¹ is hydrogen. A compound that is an atom.

In the ring-opening reaction adduct of (meth) acrylic acid and a cyclic lactone, examples of the cyclic lactone include ε-caprolactone, δ-caprolactone, and γ-caprolactone. Among these, ε-caprolactone is preferable, and a preferable example in this case is represented by the following formula (5).
This is a compound represented by the formula (1) wherein R ¹ is a hydrogen atom, R ² is a pentylene group, and Y ¹ is a hydrogen atom.

[0026]

CH ₂ ＣＨCHCOO- (CH ₂ CH ₂ COO) ₁ -H (4) CH ₂ ＣＨCHCOO- (CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ COO) ₁ -H (5) Formula (2) Preferred examples of the compound represented by are acid anhydride adducts of polyalkylene glycol mono (meth) acrylate such as polyethylene glycol mono (meth) acrylate and polypropylene glycol mono (meth) acrylate. In this case, preferred acid anhydrides include succinic anhydride, phthalic anhydride, and hexahydrophthalic anhydride.

Examples of the compound represented by the formula (3) include:
When A is an oxygen atom, an adduct of an alkylene oxide adduct of a hydroxyalkyl (meth) acrylate represented by the following formula (6) and an acid anhydride, and a hydroxyalkyl (meth) represented by the formula (7): ) Acrylic lactone ring-opening reaction adducts and acid anhydride adducts. Note that, in the formula (6), R ′ has 1 carbon atom
To 8 linear or branched alkylene groups.

[0028]

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As the compound represented by the formula (3), when A is NH, an alkylene oxide adduct of N-methylol (meth) acrylamide represented by the following formula (8) and an acid anhydride are used. And adducts. Equation (8)
In the above, R ′ is a linear or branched alkylene group having 1 to 8 carbon atoms.

[0030]

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In this case, preferred acid anhydrides include succinic acid, phthalic acid and hexahydrophthalic acid.

In the present invention, the reactive monomer includes
The compound represented by the formula (1) is preferable because it has excellent polymerizability and a high-molecular-weight linear polymer can be obtained.

Further, two or more reactive monomers may be used in combination.

Cationic Monomer As the cationic monomer used in the present invention, a compound represented by the following formula (9) is preferable.

[0035]

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(In the formula (9), R ¹¹ represents a hydrogen atom or a methyl group. A represents an oxygen atom or NH. R ¹² represents an alkylene group having 2 to 8 carbon atoms. R ¹³ represents a hydrogen atom. Represents an alkyl group or a hydroxyalkyl group having 1 to 8 carbon atoms, and R ¹⁴ and R ¹⁵ represent an alkyl group having 1 to 8 carbon atoms;
Each may be the same or different. (X)
^- represents an anion. ) (X) ^- as a halogen atom ion such as chloride ion, and a sulfate ion.

Specific examples of the cationic monomer represented by the above formula (9) include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and diethylamino-2-hydroxypropyl (meth).
Examples thereof include tertiary amine salts such as dialkylaminoalkyl (meth) acrylate such as acrylate and dialkylaminoalkyl (meth) acrylamide such as dimethylaminopropyl (meth) acrylamide hydrochloride and sulfate. Further, quaternary salts such as the above-mentioned dialkylaminoalkyl (meth) acrylate and methyl chloride adduct of dialkylaminoalkyl (meth) acrylamide can also be exemplified.

Hereinafter, cationic monomers that can be used in the present invention will be more specifically exemplified.

(Meth) acryloyloxyethyl dimethylamine hydrochloride, (meth) acryloyloxyethyl diethylamine hydrochloride, (meth) acryloyloxy-2
-Hydroxypropyldimethylamine hydrochloride or sulfates thereof.

(Meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldiethylmethylammonium chloride,
(Meth) acryloyloxy-2-hydroxypropyltrimethylammonium chloride, or methyl sulfate in place of these chlorides.

These cationic monomers can be used alone or
You may mix and use more than seeds.

Other Copolymerizable Monomer In the present invention, the above-mentioned reactive monomer and cationic monomer are used as monomers constituting the essential constituent units of the amphoteric polymer flocculant of the present invention. It is used. In the present invention, other than the reactive monomer and the cationic monomer constituting the essential structural unit, other monomers that can be appropriately copolymerized can be used in combination. Examples of the other copolymerizable monomers include anionic monomers, for example, (meth) acrylic acid represented by the following formula (10) and salts thereof. As the salts, ammonium salts, alkali metal salts such as sodium and potassium are preferable. These may be used alone or as a mixture of two or more.

[0043]

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(In the formula (10), R ¹⁶ represents a hydrogen atom or a methyl group; M represents a hydrogen atom, an ammonium ion, or an alkali metal ion.) As an anionic monomer, other than vinyl sulfone Examples thereof include acids, 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, and alkali metal salts thereof.

As other copolymerizable monomers, known nonionic monomers can be used. Specific examples include (meth) acrylamide, styrene, acrylonitrile, vinyl acetate, and alkyl (meth) acrylate. These nonionic monomers can be used alone or in combination of two or more.

Particularly preferred nonionic monomers include:
An acrylamide compound represented by the following formula (11) can be given.

[0047]

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(In the formula (11), R ¹⁷ is a hydrogen atom or a methyl group; R ¹⁸ and R ¹⁹ are each independently a hydrogen atom;
To 8 alkyl groups. Of these, acrylamide is particularly preferred.

The proportions of the reactive monomer, the cationic monomer and the monomer copolymerizable with these monomers are preferably as follows on a molar basis.

Reactive monomer: cationic monomer: other copolymerizable monomer = 1 to 35: 1 to 35:39 to 9
8 (mol) The amphoteric polymer flocculant of the present invention comprises a reactive monomer, a cationic monomer, and other monomers copolymerizable with these monomers in the presence of a known polymerization catalyst. And may be produced by copolymerizing

As the polymerization method, aqueous solution polymerization, reverse phase suspension polymerization, reverse phase emulsion polymerization and the like can be adopted, but aqueous solution polymerization is preferred because of easy handling. In the case of aqueous solution polymerization, the total charged concentration of each monomer is 25 to 60% by weight.
It is preferable that

The polymerization initiator is not particularly limited. In the case of aqueous polymerization, potassium persulfate, ammonium persulfate, an azo-based initiator, a redox-based initiator, a photopolymerization initiator and the like can be appropriately used.

The pH of the monomer solution is preferably adjusted to 2-3.

The polymerization initiation temperature is usually preferably from 0 to 35 ° C.

The polymerization time is usually preferably 0.1 to 3 hours. Further, the polymerization reaction is preferably performed in an inert atmosphere in the absence of oxygen. These polymerization conditions are known.

After the completion of the polymerization reaction, an amphoteric polymer flocculant is obtained by appropriately using a known method as necessary.

By polymerizing under the above conditions, a high molecular weight amphoteric polymer flocculant having an average molecular weight of several million can be produced.

In the sludge dewatering method of the present invention, the sludge to be dewatered is not particularly limited. For example, sludge for domestic wastewater treatment, sludge for food factory wastewater treatment, sludge for chemical factory wastewater treatment, sludge for swine farm wastewater treatment, and Various sludges such as pulp or paper industry sludge can be dewatered. The dehydration method specifically includes, for example, adding an inorganic flocculant and / or
Alternatively, an organic cationic compound is added, more preferably p
After adjusting H to 4 to 7, the amphoteric polymer flocculant of the present invention is added to thereby form sludge floc. In addition, for the purpose of deodorization, dephosphorization, and denitrification, pH
Is preferably less than 5. The method of forming the flocks conforms to a known method.

Examples of the inorganic flocculant include a sulfate band, polyaluminum chloride, ferric chloride, ferrous sulfate, and polyiron sulfate.

Examples of the organic cationic compound include polymer polyamines, polyamidines, and cationic surfactants.

The addition amount of the amphoteric polymer flocculant, the inorganic flocculant, and the cationic compound, the stirring speed, the stirring time, and the like substantially follow the conventional dehydration conditions.

The floc thus formed is dehydrated using a known means to obtain a dewatered cake.

Examples of the dehydrator include a screw press dehydrator, a belt press dehydrator, a filter press dehydrator, and a screw decanter.

[0064]

The present invention will be described more specifically with reference to the following examples. Aronix M-56 used in the examples
00 (manufactured by Toagosei Co., Ltd.) is an acrylic acid dimer 57
A mixture of 1% by weight, 26% by weight of the same trimer, 11% by weight of the same tetramer, and 6% by weight of the same pentamer (in the formula (4), l = 1, 2, 3, 4).
In the examples, this was used in a partially neutralized state.

(Example 1) A dimethylaminoethyl acrylate methyl chloride quaternary salt aqueous solution (hereinafter referred to as DAC), an acrylamide aqueous solution (hereinafter referred to as AM) acrylic acid, and Aronix M-5600 were placed in a stainless steel Dewar bottle. 21.0 mol% each, 7
2.0 mol%, 7.0 mol% composition, total weight is 1K
g, distilled water was added so that the total monomer concentration was 28% by weight. The pH of this solution was adjusted to 2.9. The solution temperature was adjusted to 35 ° C. while blowing nitrogen gas into the solution for 60 minutes, whereby an aqueous monomer mixture solution for polymerization was obtained.

Then, based on the total monomer weight, cupric chloride was used as a copper ion at 0.3 ppm and azobisamidinopropane hydrochloride (Wako Pure Chemical Industries, Ltd.) was used as a polymerization initiator.
Polymerization was started by adding 60 ppm of trade name (V-50) and 30 ppm of sodium bisulfite (NaHSO ₃ ).

The polymerization was continued for 3 hours in a stationary state. afterwards,
Take out the obtained hydrogel polymer from the Dewar bottle,
Shredded. This was dried at 80 ° C. for 5 hours and then pulverized to obtain a target amphoteric polymer flocculant.

(Examples 2, 3 and Comparative Examples 1 to 3) Polymerization was carried out in the same manner as in Example 1 except that the amounts of the polymerization initiator and the monomers were changed as shown in Table 1. An amphoteric polymer flocculant was obtained.

The following physical properties were measured using the amphoteric polymer flocculants obtained in Examples and Comparative Examples. Table 1 shows the results.
Shown in

Insoluble content: The amphoteric polymer flocculant was dissolved in pure water to prepare 400 ml of a 0.1% by weight (in terms of solid content) solution. The whole amount of the solution was filtered through a sieve having a diameter of 20 cm and a mesh of 83 mesh, the insoluble matter remaining on the sieve was collected, and the volume was measured.

0.5% Salt Viscosity: The above amphoteric polymer flocculant was dissolved in a 4% by weight aqueous sodium chloride solution to prepare a 0.5% by weight flocculant solution. Using a B-type viscometer, 25
The coagulant solution viscosity after 5 minutes at 60 ° C. and 60 rpm was measured.

[0072]

[Table 1]

(Examples 4 to 6, Comparative Examples 4 to 6) 200 ml of mixed sludge composed of primary sludge, coagulated sludge, and excess sludge from a chemical plant effluent was collected in a 300 ml beaker. To this was added ferric polysulfate until the pH was 5.5. After adding any of the amphoteric polymer flocculants produced in Examples 1 to 3 and Comparative Examples 1 to 3, the sludge was stirred at 150 rpm for 2 minutes using a jar tester to generate sludge flocs. .

Subsequently, the sludge was stirred at 560 rpm for 15 seconds using a handy mixer, and the particle size of the generated floc was measured. As shown in Table 2, the floc diameter of each of the present examples was as large as more than 10 mm.

Then, the sludge floc dispersion was gravity filtered using a 60-mesh net as a filter. 1
The filtration capacity after 0 seconds was measured and indicated as the filtration rate. Using a centrifuge, the sludge after filtration was dehydrated under the conditions of 2000 rpm for 10 minutes, and the water content of the obtained cake was measured. Table 2 shows the measurement results.

[0076]

[Table 2]

(Example 7, Comparative Example 7) Using the amphoteric polymer flocculants A and D of Example 1 and Comparative Example 1, the sludge to be used was converted from surplus sludge and coagulated sludge from the effluent of a chemical plant. A floc was formed in the same manner as in Examples 4 to 6, except that the mixed sludge was changed, and evaluated in the same manner as in Examples 4 to 6. Table 3 shows the results.

As is evident from Table 3, the flocculant of the present invention can obtain excellent floc by adding 150 ppm, whereas the flocculant of the comparative example can be used even when 210 ppm is added. The performance was inferior.

[0079]

[Table 3]

[0080]

The amphoteric polymer flocculant of the present invention has an anionic monomer unit having a specific structure and a cationic monomer unit as essential components in the molecule. When used, a floc exhibiting a flocculant action very efficiently and having an excellent balance of strength, filtration rate and water content can be obtained.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Minoru Atsuchi 1-Funamicho, Minato-ku, Nagoya-shi, Aichi F-term in Nagoya Research Institute, Toagosei Co., Ltd. 4D015 BA06 BA09 CA11 DA04 DA06 DB03 DB13 DB14 DB15 DC06 EA13 FA15 4D059 AA04 AA05 AA06 BE13 BE55 BE57 BE59 DA23 DB24 DB25 DB26 EB05 4J100 AL08P AL08Q AM14P AM14Q BA03P BA03Q BA08P BA16P BA31Q CA04 DA01 JA18

Claims (5)

[Claims] A weight-average molecular weight having a radical polymerizable group at one end and an anionic group at the other end is from 90 to 10,000.
An amphoteric polymer flocculant comprising a copolymer obtained by copolymerizing a reactive monomer of (1) and a cationic monomer as essential monomers. 2. The amphoteric polymer flocculant according to claim 1, wherein the reactive monomer is a compound represented by the following general formula (1). Embedded image (However, in the formula (1), R ¹ is a hydrogen atom or a methyl group, R ²
Represents a linear or branched alkylene group having 1 to 8 carbon atoms, and l represents a natural number of 1 to 100. Y ¹ represents a hydrogen atom, an ammonium ion, an alkali metal ion, or an alkaline earth metal ion. ) 3. A method for dewatering sludge, comprising adding the amphoteric polymer flocculant according to claim 1 or 2 to the sludge and dewatering the sludge. 4. A dewatering method for sludge, comprising adding an organic cationic compound or an inorganic coagulant to the sludge and then adding the amphoteric polymer coagulant according to claim 1 or 2 to dewater the sludge. Method. 5. An organic cationic compound or an inorganic flocculant is added to the sludge, and then the pH of the sludge is adjusted to 4 to 7, and then the amphoteric polymer flocculant according to claim 1 or 2 is added. A method for dewatering sludge, comprising dewatering.