JP2003175302A - Composition, amphoteric polymeric flocculant and use of them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition excellent in flocculation and dehydration capacity with respect to various sludges, especially, sludge high in excess ratio, an amphoteric polymeric flocculant, a sludge dehydration method and an yield enhancer excellent in water solubility and yield enhancing capacity. <P>SOLUTION: The composition contains two or more kinds of amphoteric polymers respectively having cationic monomer units and anionic monomer units in a different ratio and having a 0.5% salt viscosity of 10-120 mPa s. As the amphoteric polymers, one of which the mol ratio of the cationic monomer unit to the anionic monomer unit (hereinbelow shown as Ca/An) satisfies Ca/An≥1 and one of which the mol ratio Ca/A satisfies Ca/An<1 are used in combination. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition having excellent coagulation and dehydration properties, a high filtration rate, and excellent flocs capable of obtaining excellent flocs, an amphoteric polymer coagulant, and an amphoteric polymer coagulant. The present invention relates to sludge dewatering applications, retention aids for papermaking, and other applications.

[0002]

2. Description of the Related Art Conventionally, a cationic polymer flocculant has been used alone for the sludge dewatering treatment, but in recent years, a conventional cationic polymer flocculant has been used due to an increase in sludge generation amount and deterioration of sludge properties. With the agent, the treatment condition is not always satisfactory in terms of the sludge treatment amount, the dehydrated cake water content, the SS recovery rate, and the removability of the cake from the filter cloth. Required to do so.

In order to improve these drawbacks of conventional cationic polymer flocculants, various amphoteric polymer flocculants and various dehydration methods using the same have been proposed. For example,
(1) A sludge dewatering method in which a cation-rich amphoteric polymer flocculant having a specific ion equivalent is added to an organic sludge having a pH of 5 to 8 to which an inorganic flocculant containing no inorganic sludge is added (see Patent Document 1), ( 2) A sludge dewatering method in which an acrylate-based cationic polymer flocculant and an amphoteric polymer flocculant are used in combination with an organic sludge having a pH of 5 to 8 (see Patent Document 2), (3).
A dehydration method (Patent Document 3) in which an inorganic coagulant is added to sludge to set the pH to less than 5 and an anion-rich amphoteric polymer coagulant having a specific composition is added, and (4) Inorganic coagulant and anionic polymer in wastewater A method of treating organic wastewater in which a flocculant and a cation-rich amphoteric polymer flocculant are sequentially added (see Patent Document 4) is known.

[0004]

[Patent Document 1] Japanese Patent Publication No. 5-56199 (Claims)

[Patent Document 2] Japanese Patent No. 2933627 (Claims)

[Patent Document 3] Japanese Patent Publication No. 6-239 (Claims)

[Patent Document 4] Japanese Patent Laid-Open No. 6-134213 (Claims)

[0005]

However, although the dehydration methods (1) to (4) described above have their own features, they are not suitable for the recent tendency toward difficult dehydration of wastewater.
It was not always an effective method. That is, since there is a demand for lowering the COD value after wastewater treatment, the ratio of activated sludge treatment to wastewater is higher than before, and the sludge for sludge dewatering treatment contains a large amount of excess sludge, Further, in papermaking wastewater, since the recovery rate of the fiber content in the wastewater is increasing, the fiber content in the sludge becomes low, and the conventional polymer coagulant or sludge dewatering method may not be able to be applied.

On the other hand, in the papermaking process, when diluting a stock containing a filler into a final concentration to be fed into a papermaking machine,
Alternatively, after the dilution, a retention aid is added to suppress outflow of the filler from the paper machine into the white water to improve the retention. As the retention agent, a water-soluble high molecular weight cationic polymer is usually used. More specifically, a cationic acrylamide polymer, a partial hydrolyzate thereof, a Mannich modified product, and the like can be mentioned, and recently, a yield improving method of adding bentonite after adding the cationic polymer to the paper stock. (See Patent Document 5 and the like) and a method in which an acrylamide polymer and an anionic aluminum-containing silica sol are added to the paper material together (see Patent Document 6 and the like) are drawing attention. The acrylamide polymer used for these has a monomer solid content of 10 to 40% by mass.
The polymer produced by aqueous solution polymerization or the like and obtained by the aqueous solution polymerization is usually in the form of a highly viscous paste. Therefore, when used as a retention aid, the paste is diluted with water to 0.1 to 0.5 mass% and used as an aqueous solution. Such a retention improver is used for the purpose of increasing the bond strength between pulp fibers and increasing the strength such as rupture and elongation of the final product paper, and the addition timing in the papermaking process. Also, the polymers used have essentially different molecular weights. That is, as the timing of addition, the paper strength enhancer is added after adding a fixing agent such as a sulfuric acid band to the stock, whereas the retention improver is added immediately before being fed into the paper machine. Should be added to the pulp pulp suspension as much as possible so as not to destroy the floc agglomerates. Regarding the molecular weight of the polymer used, the paper-strengthening agent has a molecular weight of several hundreds of thousands, whereas the retention agent must be a high-molecular weight polymer exceeding 1 million to achieve sufficient retention.
Moreover, since such a high molecular weight substance is added, the amount of the paper-strengthening agent added is 0.1 to 0.5% by mass based on the pulp, while the amount of the retention aid is 0.01 to 0% by mass. 0.05% by mass, and a very small amount is added. As is clear from the above properties, retention aids are required to have properties close to those of flocculants used in wastewater treatment. Since such a retention aid is a high molecular weight compound having a molecular weight of more than 1,000,000, the water-containing paste polymer obtained after the polymerization has very poor solubility in water, and the aqueous solution is used in an actual papermaking process. When used as, it had a problem that it took an extremely long time to be completely diluted. Further, the conventional retention aids have insufficient retention improvement performance, and have a serious drawback in retention performance particularly in the neutral papermaking region. Recently, the papermaking process has been closed, and the reused water and pulp fiber contain a large amount of water-soluble inorganic substances derived from fillers. Performance was inadequate.

The present invention provides a composition, a polymer flocculant and a method for dewatering sludge, which is excellent in coagulation / dewatering performance for various sludges, particularly for sludge having a large surplus ratio. In order to find a retention aid with excellent solubility and excellent retention performance, we have conducted intensive studies.

[0008]

[Patent Document 5] JP-A-4-281095 (Claims)

[Patent Document 6] Japanese Patent No. 2945761 (Claims)

[0009]

Means for Solving the Problems As a result of various studies to solve the above problems, the present inventors have found that the copolymerization ratio of the cationic monomer unit and the anionic monomer unit is different. The present invention has been completed by finding that a composition containing at least one amphoteric polymer is effective. The present invention will be described in detail below. In the present specification, acrylate or methacrylate is referred to as (meth) acrylate, acrylamide or methacrylamide is referred to as (meth) acrylamide, and acrylic acid or methacrylic acid is referred to as (meth) acrylic acid.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION 1. Composition The amphoteric polymer that constitutes the composition of the present invention may be a copolymer having a cationic monomer unit and an anionic monomer unit as essential constituent monomer units.

Examples of the cationic monomer include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, diethylamino-2-hydroxypropyl (meth) acrylate and other dialkylaminoalkyl (meth) acrylate hydrochlorides and sulfuric acid. Tertiary salts such as salts; quaternary salts such as halogenated alkyl adducts such as methyl chloride adducts of dialkylaminoalkyl (meth) acrylate and halogenated aryl adducts such as benzyl chloride adduct; N, N-dimethyl ( Hydrochlorides such as dialkyl (meth) acrylamides such as (meth) acrylamide and tertiary salts such as sulfates; alkyl halide adducts such as methyl chloride adducts of dialkyl (meth) acrylamide and aryl halides such as benzyl chloride adduct Quaternary salts such as adducts That.

Examples of the anionic monomer include (meth) acrylic acid and alkali metal salts or ammonium salts thereof such as sodium salt; maleic acid and the like and alkali metal salts thereof; acrylamide such as acrylamido-2-methylpropanesulfonic acid. Alkyl alkane sulfonic acid and its alkali metal salt or ammonium salt; and vinyl sulfonic acid and its alkali metal salt or ammonium salt.

If desired, the amphoteric polymer may be a combination of monomers other than the above-mentioned monomers, specifically nonionic monomers. As the nonionic monomer,
(Meth) acrylamide, dimethylaminoethyl (meth) acrylate and other dialkylaminoalkyl (meth) acrylates, dialkylaminopropyl (meth)
Dialkylaminoalkyl (meth) such as acrylamide
Examples thereof include acrylamide, styrene, acrylonitrile, vinyl acetate, alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, vinylpyridine, vinylimidazole and allylamine.
Among these, (meth) acrylamide is preferable.

Any of these monomers may be used alone or in combination of two or more.

The preferred combination of monomers in the present invention is a tertiary salt or quaternary salt of dialkylaminoalkyl acrylate as a cationic monomer, an acrylate as an anionic monomer and a nonionic monomer. A copolymer consisting of acrylamide, a tertiary salt or quaternary salt of dialkylaminoalkyl methacrylate as a cationic monomer, a copolymer consisting of acrylate as an anionic monomer and acrylamide as a nonionic monomer, and From a tertiary or quaternary salt of dialkylaminoalkyl methacrylate as a cationic monomer, a tertiary or quaternary salt of dialkylaminoalkyl acrylate, an acrylate as an anionic monomer and acrylamide as a nonionic monomer. There is a copolymer of

With respect to the molecular weight of the amphoteric polymer of the present invention, it has a 0.5% salt viscosity of 10 to 120 mPa · s, which is an index of the molecular weight, and is used as a polymer flocculant described later. In this case, 15 to 90 mPa · s is more preferable in order to achieve a stable dehydration treatment. In the present invention, 0.5% salt viscosity means a sample obtained by dissolving 0.5% of an amphoteric polymer in a 4% sodium chloride aqueous solution.
Rotor No. 5 at 5 ° C with a B-type viscometer. It means the value measured at 60 rpm using 1 or 2.

The method for producing the amphoteric polymer is not particularly limited, and a general polymerization method can be adopted. For example, in the case of aqueous solution polymerization, potassium persulfate, ammonium persulfate, 2,2′-azobis (2-
Amidinopropane) dihydrochloride, a method of performing thermal radical polymerization using a redox-based polymerization initiator or the like, or a photoradical polymerization using UV irradiation using a benzoin or acetophenone type photopolymerization initiator .
Further, in the case of reverse phase emulsion polymerization, a water-insoluble initiator such as azobisisobutyronitrile or benzoyl peroxide may be used in addition to the above-mentioned polymerization initiator.

The gel polymer thus obtained is then cut and chopped by a known method. The shredded polymer is dried at a temperature of about 60 to 150 ° C. using a dryer such as a band dryer, a rotary dryer, a far infrared dryer, and a vibration fluidized dryer, and a roll grinder. And the like to obtain a powdery copolymer, and the particle size is adjusted. The amphoteric polymer used as the raw material for the composition of the present invention is preferably a powdered product.

The composition of the present invention comprises two or more kinds of amphoteric polymers having different ratios of the cationic monomer unit and the anionic monomer unit, and the amphoteric polymer is a cationic monomer unit. A molar ratio of monomer units to anionic monomer units, Ca / An, that satisfies Ca / An ≧ 1 (hereinafter referred to as cation-rich amphoteric polymer) and C
a / An <1 (hereinafter referred to as anion-rich amphoteric polymer)
It is a combination of those satisfying the conditions. As the cation-rich amphoteric polymer, Ca / An is further 1.5 to 1.
0.0 is C as an anion-rich amphoteric polymer.
It is preferable that a / An is 0.5 to 0.9. The cation-rich amphoteric polymer and the anion-rich amphoteric polymer can be obtained by copolymerizing a cationic monomer unit and an anionic monomer unit so as to satisfy the above monomer unit ratio.

The composition of the present invention can be produced by mixing a cation-rich amphoteric polymer and an anion-rich amphoteric polymer. Further, in the sludge dewatering and paper making steps described later, each component may be added separately. As the cation-rich amphoteric polymer and the anion-rich amphoteric polymer, one kind may be used, or two or more kinds may be used in combination. One kind of cation-rich amphoteric polymer and one kind of anion-rich amphoteric polymer are used. It is simple and preferable to do so. The proportion of the amphoteric polymer in the composition may be appropriately set according to the purpose, but is preferably in the range of 20 to 60% by mass of the cation-rich amphoteric polymer and 40 to 80% by mass of the anion-rich amphoteric polymer.

2. Use The composition of the present invention can be applied to various uses. For example, a polymer coagulant and a thickener for paints and the like can be mentioned. Examples of the polymer flocculants include sludge dehydrating agents, retention aids and other papermaking agents in the papermaking process. The composition obtained in the present invention is useful as a polymer flocculant, and is particularly useful as a sludge dehydrating agent and a retention improving agent. Hereinafter, the sludge dehydrating agent and the retention improving agent will be described.

1) Sludge Dewatering Agent and Sludge Dewatering Method When using the sludge dehydrating agent of the present invention (hereinafter sometimes referred to as an amphoteric polymer flocculant), sodium slulfate, sodium sulfate, sulfamic acid, etc. are subjected to dehydration treatment. You may use it, mixing with a well-known additive as long as there is no bad influence.

The sludge dewatering agent of the present invention is applicable to various sludges, and organic sludge and coagulated sedimentation sludge produced in sewage, night soil, and general industrial wastewater such as food industry, chemical industry and pulp or paper industry sludge. Examples thereof include mixed sludge and the like. The sludge dehydrating agent of the present invention can be preferably applied to sludge having a low fiber content, that is, sludge having a high surplus ratio. Specifically, it can be preferably applied to sludge having a surplus ratio of 20 SS% or more, more preferably 20 to 80 S.
Applicable to S% sludge.

The dewatering method using the sludge dewatering agent of the present invention is, specifically, to add the sludge dewatering agent to the sludge and then form the sludge flocs. The method for forming the flock may be a known method.

If necessary, an inorganic flocculant, an organic cationic compound, a cationic polymer flocculant and an anionic polymer flocculant can be used in combination.

As the inorganic coagulant, aluminum sulfate,
Examples include polyaluminum chloride, ferric chloride, ferrous sulfate, and polyiron sulfate.

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

When an inorganic coagulant or an organic cationic compound is added, it is preferable to adjust the pH to 4 to 8 because sludge can be treated more effectively. As a method for adjusting the pH, after adding an inorganic coagulant or an organic cationic compound, if the pH value is satisfied, it is not particularly necessary to adjust the pH, but if the range limited by the present invention is not satisfied, an acid is used. Alternatively, adjust by adding alkali. Examples of the acid include hydrochloric acid, sulfuric acid, acetic acid, sulfamic acid and the like. Examples of the alkali include caustic soda, caustic potash, slaked lime and ammonia.

Examples of the cationic polymer flocculant include homopolymers of the above-mentioned cationic monomers and copolymers of the above-mentioned cationic monomers and nonionic monomers.

Examples of the anionic polymer flocculant include homopolymers of the above-mentioned anionic monomers and copolymers of the above-mentioned anionic monomers and nonionic monomers.

In the present invention, when sludge having a small fiber content, that is, sludge having a high surplus ratio is used, it is preferably used in combination with an anionic polymer flocculant. In this case, the order of adding the coagulant to the sludge is preferably to add the anionic polymer coagulant and then the amphoteric polymer coagulant. As the anionic polymer flocculant, a copolymer having an anionic monomer unit in a copolymerization ratio of 30 mol% or more is preferable, and a copolymer in a copolymerization ratio of 40 mol% or more is more preferable. In this case, the combined ratio of the anionic polymer coagulant and the amphoteric polymer coagulant is, relative to the total amount of all polymer coagulants used,
It is preferable that the anionic polymer coagulant is 1 to 70 mass% and the amphoteric polymer coagulant is 99 to 30 mass%.

The coagulant added to the sludge is added so that the total ratio of the cationic monomer unit and the anionic monomer unit of all the polymer coagulants used satisfies the following formula (1). Preferably.

[0033]

[Formula 2] 0.3 ≤ Caall / Anal ≤ 4.0 (1)

[Note that in the above formula (1), Caall and A
nall is the total amount of the cationic monomer units and the total amount of the cationic monomer units when the total amount of the total anionic monomer units and the total amount of the cationic monomer units of all the polymer flocculants used is converted to 100 mol, respectively. It represents the number of moles of the total amount of anionic monomer units. If it is used outside this range, the granulation property of flocs may become poor, or the total amount of coagulant added may increase abnormally, resulting in an increased water content of the obtained cake.

The addition ratio of the amphoteric polymer coagulant to sludge is preferably 5 to 500 ppm, and the SS is preferably 0.05 to 1% by mass. When the amphoteric polymer flocculant is used in combination with another polymer flocculant, the total amount of all polymer flocculants preferably satisfies the above addition ratio.

The amount of the sludge dehydrating agent and other coagulant added, the stirring speed, the stirring time, etc. may be in accordance with the conventional dehydration conditions.

The flocs thus formed are dehydrated by a known means to obtain a dehydrated cake.

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

The sludge dewatering agent of the present invention can also be applied to a dewatering method using a granulation concentrating tank having a filtering section.
Specifically, after adding an inorganic coagulant to the sludge and further adding a sludge dewatering agent, or together with the sludge dewatering agent, the sludge is introduced into a granulation concentrating tank having a filtering section, and the sludge is filtered from the filtering section. Examples include a method in which the liquid is taken out and granulated, and the granulated product is dehydrated by a dehydrator.

2) Retention Improver and Paper Making Method When the composition of the present invention is used as a retention improver, the amphoteric polymer as a raw material of the composition is preferably in powder form. Also, in actual use, it is preferable to dissolve the amphoteric polymer as a raw material in water and use it as a 0.01 to 0.5 mass% aqueous solution, and more preferably 0.01 to 0.
It is a 1% by mass aqueous solution. The retention aid may be used according to a conventional method, for example, when the stock is diluted to the final concentration to be fed into the paper machine or after the dilution.

The stock material to which the retention agent is applied may be one that is used in a normal paper making process, and usually contains at least pulp and a filler, and if necessary, an additive other than the filler, specifically, Specifically, it includes a sizing agent, a fixing agent, a paper strengthening agent, a coloring agent and the like. As a filler, white clay,
Examples include kaolin, agarite, talc, calcium carbonate, magnesium carbonate, lime sulfate, barium sulfate, zinc oxide and titanium oxide. Examples of the sizing agent include acrylic acid / styrene copolymers and the like, examples of the fixing agent include sulfuric acid band, cationic starch and alkyl ketene dimer, and examples of the paper-strengthening agent include starch and cationic or amphoteric poly (ether). Examples include acrylamide.

As a method of adding the retention aid, an aqueous solution of the composition may be added, or an aqueous solution of the amphoteric polymer as a raw material of the composition may be added and then another aqueous solution of the amphoteric polymer may be added. You can also A preferable addition ratio of the retention aid is 0.05 to 0.05 per mass of dry pulp in the paper stock.
0.8 mass% is preferable, and more preferably 0.05 to
It is 0.5% by mass. PH of stock after addition of retention aid
Is preferably maintained at 5 to 10, and more preferably 5 to 8. After the addition of the retention aid, the stock is immediately fed into the paper machine.

[0043]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. In the following, "parts" means parts by mass. The amphoteric polymer and anionic polymer coagulant used in each example were powdery ones shown in Tables 1 and 2 below. The abbreviations in each table have the following meanings.・ DAC: Quaternary methyl chloride salt of dimethylaminoethyl acrylate ・ AA: acrylic acid ・ AMD: acrylamide

[0044]

[Table 1]

[0045]

[Table 2]

Example 1 25 parts of CR-1 and 75 parts of AR-1 were used as an amphoteric polymer and mixed to prepare a composition, which was used as an amphoteric polymer flocculant. Waste paper pulp wastewater scum wastewater (SS: 33400 mg / l, VSS: 1690
0 mg / l, fiber content: 290 mg / l) and excess sludge (S
S: 10700 mg / l, VSS: 8200 mg / l,
200 ml of 55:45 (SS%) mixed sludge (fiber content: 80 mg / l) was collected in a 300 ml beaker, and after adding an amphoteric polymer coagulant thereto, the mixture was transferred to an empty 300 ml beaker for a total of 5 After the liquid transfer operation was performed, the mixture was stirred 50 times with a spatula to form flocs. The granulation properties of the flocs at this time were evaluated according to the following three grades, and the particle size of the obtained flocs was measured. After that, the sludge floc dispersion was gravity filtered using 80 mesh filter cloth as a filter, and the filtrate volume after 10 seconds was measured, and this was taken as the filtration rate. The self-supporting property of the cake on the filter cloth and the appearance of the obtained filtrate were evaluated according to the following three grades. 4 cakes obtained
It was sandwiched between punching metals of mmφ, a load of 6.5 kg × 3 minutes was applied, the cake weight deviated from the punching holes was weighed, and the peelability to the filter cloth was evaluated according to the following three grades. The evaluation results are shown in Table 4. The sludge dewatering method of Example 1 was excellent in all evaluated coagulation performances.

Granularity excellent; flocs having a large particle size were formed immediately upon stirring. Good; when stirring was continued for a while, flocs having a large particle size were formed. Poor; only flocs having a small particle size were formed even if stirring was continued.・ Excellent filtration appearance; completely transparent. Good; slightly floating matter. Poor; many floating materials are present. -When the floc dispersion was poured into a cylinder during self-supporting gravity filtration, and the cylinder was removed after filtration. Excellent: The cake completely stood by itself. Good: The cake flowed slightly. Bad: The cake has flowed. The condition of the filter cloth when the peelable cake was peeled off from the filter cloth was excellent: no stain was found. Good: Slightly soiled. Bad: It got dirty.

Examples 2 to 5 As the amphoteric polymer flocculant, BL-2 produced in the same manner as in Example 1 using the amphoteric polymers shown in Table 3 below was also used. The sludge was dehydrated in the same manner as in Example 1 except that the anionic polymer flocculant shown in Table 4 was added to the sludge and then the amphoteric polymer flocculant shown in Table 4 was added.
Table 4 shows the results of evaluation performed in the same manner as in Example 1. Example 2
In all cases, the sludge dewatering methods of 5 to 5 were excellent in all coagulation performances evaluated.

[0049]

[Table 3]

[0050]

[Table 4]

Comparative Example 1 The sludge was dehydrated in the same manner as in Example 1 except that the amphoteric polymer coagulant shown in Table 5 was used for the sludge. Table 5 shows the results of evaluation performed in the same manner as in Example 1. The composition monomer ratio of the amphoteric polymer flocculant CO-1 used in Comparative Example 1 was the same as the composition monomer ratio of the amphoteric polymer flocculant BL-1 used in Example 1 after mixing. However, all the aggregation performances were insufficient.

Comparative Examples 2 and 3 Sludge was dehydrated in the same manner as in Examples 2 to 5 except that the anionic polymer coagulant and amphoteric polymer coagulant shown in Table 5 were used for the sludge. It was Table 5 shows the results of evaluation performed in the same manner as in Example 1. The amphoteric polymer flocculants used in Comparative Examples 2 and 3 had a CO-1 and CO-2 constituent monomer ratio of BL-1 and BL- of the amphoteric polymer flocculant, respectively.
The constituent monomer ratios after mixing 2 were the same, but the aggregation performance was insufficient in both cases.

[0053]

[Table 5]

Examples 6 and 7 As a retention agent, 70 parts of CR-1 and 30 parts of AR-1 were used.
An aqueous solution containing 0.05% by mass of the total amount thereof was used in a ratio of parts. Yield improver is manufactured by CR-1 and AR-
1 was added to water with stirring and dissolved 30 minutes after the addition,
It was stirred for another 30 minutes. This is called a yield improving agent BL-3. Similarly, an aqueous solution containing 60 parts of CR-3 and 40 parts of AR-1 in a total amount of 0.05% by mass was produced in the same manner as described above, and this was used as a retention aid BL-4. Say. Disintegrated and beaten LBKP sheet CSF = 450m
1 lwt% pulp slurry is prepared and 1000 rpm
While stirring with, add the following ingredients in this order,
The total retention rate was measured by the dynamic drainage jar method. The results obtained are shown in Table 7. Final of pulp slurry
The pH was 7.2. Light calcium carbonate: 20% by mass (ratio to pulp solids in pulp slurry; hereinafter referred to as pulp) Cationic starch: 0.3% by mass (to pulp) Sulfuric acid band: 1.7% by mass (to pulp) Paper strength enhancement 15 mass% aqueous solution of a copolymer of the agent [DAC / AA / AM = 20/10/70 (molar ratio). Viscosity: 3500 mPa · s]:
0.5% by mass (vs pulp) Yield improver: 250ppm (solid content, vv pulp)

Example 8 In Example 6, the amphoteric polymer AR was used as the retention aid.
-1 of a 0.05 mass% aqueous solution of 70 ppm (solid content,
(Pulp) to 0.0% of amphoteric polymer CR-1
The performance as a retention aid was evaluated by the same method as in Example 6 except that 175 ppm (solid content, relative to pulp) was added as a solid content of a 5 mass% aqueous solution. The results obtained are shown in Table 7.

Comparative Example 4 As a retention aid, a cationic acrylic polymer [DA
C: AM = 10/90 (molar ratio) copolymer, 0.5%
Salt viscosity 70 mPa · s, pasty product] 0.05 mass%
An aqueous solution containing was used. The retention aid was prepared by adding Cation A to water with stirring.
It took 0 minutes. This is called retention aid cation A. In Example 6, 25% of cation A was used as a retention aid.
The performance as a retention aid was evaluated by the same method as in Example 6 except that 0 ppm (solid content, relative to pulp) was used. The results obtained are shown in Table 7.

[0057]

[Table 6]

[0058]

[Table 7]

[0059]

The composition of the present invention, when used as an amphoteric polymer flocculant, has a high filtration rate as a sludge dewatering agent for various sludges, particularly for sludges having a high surplus ratio. The obtained flocs have a large particle size and are excellent in various coagulation / dewatering properties such as excellent self-sustaining property and releasability, and as a retention agent, the retention rate in the papermaking process can be improved.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4D015 BA02 BA09 BB12 BB17 CA11                       DB04 DB12 DC06 DC08                 4D059 AA05 AA06 BE09 BE15 BE16                       BE26 BE56 BE59 DB25 DB26                 4L055 AG71 AG72 AG73 AG89 AH18                       EA25 EA32 FA10

Claims (8)

[Claims] 1. A cationic monomer unit and an anionic monomer unit having a 0.5% salt viscosity of 10 to 120 mPa.
A composition comprising two or more kinds of amphoteric polymers having different ratios of the monomer units, wherein the amphoteric polymer is an anionic monomer of a cationic monomer unit. When the molar ratio (hereinafter referred to as Ca / An) with respect to the monomer unit satisfies Ca / An ≧ 1, Ca / An <1
A composition which is used in combination with those satisfying the above conditions. 2. An amphoteric polymer flocculant containing the composition according to claim 1. 3. A sludge dewatering method, which comprises adding the amphoteric polymer flocculant according to claim 2 to sludge and then dehydrating it. 4. The sludge dewatering method according to claim 3, which further comprises an anionic polymer flocculant. 5. The method for dehydrating sludge according to claim 4, wherein the anionic polymer flocculant has a ratio of anionic monomer units to all constituent monomer units of 30 mol% or more. 6. A polymer flocculant is added to sludge so that the total ratio of cationic monomer units and anionic monomer units of all the polymer flocculants used satisfies the following formula (1). The method for dewatering sludge according to any one of claims 3 to 5, characterized in that. [Formula 1] 0.3 ≦ Caall / Anal ≦ 4.0 (1) [In the above formula (1), Caall and Anall are, respectively, the total amount of anionic monomer units of all the polymer flocculants used. And the number of moles of the total cationic monomer unit amount and the total anionic monomer unit amount when the total amount of all the cationic monomer unit amounts is converted to 100 mol. ] 7. A retention aid for papermaking, which comprises the composition according to claim 1. 8. A papermaking method comprising adding the retention aid according to claim 7 to a paper material and then making the paper.