JP3218557B2 - Papermaking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a papermaking method in a papermaking process, and more particularly, to a papermaking pulp in which a specific amphoteric water-soluble polymer is added to a papermaking pulp to improve the yield and / or drainage. It relates to a papermaking method to be improved.

[0002]

2. Description of the Related Art Conventionally, in a papermaking process of papermaking, a retention improver or a drainage improver has been used for the purpose of improving productivity, reducing chemicals used in raw materials, and purifying circulating white water. I have.

[0003] The retention aid or drainage improver is generally a water-soluble high-molecular substance, ie, polyacrylamide and its derivatives, synthetic high-molecular substances such as polyethyleneimine and polyamide polyamine epichlorohydrin resin, or starch and And natural water-soluble polymer substances such as derivatives thereof. Various methods have been proposed for the purpose of further improving the yield and / or drainage.

For example, a method using a cationic starch and an anionic colloidal silica (JP-A-57-51900), a method using an acrylamide-based polymer having a cationic group and colloidal silica (JP-A-62-15)
391), a method of adding colloidal silicic acid and a cationic or amphoteric polyacrylamide derivative and a cationic starch (Japanese Patent Application Laid-Open No. 62-110998), and a method of improving the yield using a cationic polymer and bentonite ( Various proposals have been made, such as JP-A-62-191598.

[0005] These methods are intended to improve the yield or drainage more than the method using a water-soluble polymer alone. Due to the deterioration of pulp conditions and the lowering of the quality of papermaking water, it is not sufficiently satisfactory, and a method for further improving the yield or drainage is strongly desired.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the yield in the papermaking process and the drying process by improving the yield of cellulose fibers and fillers and / or improving the drainage in the papermaking process. To improve it. Another object of the present invention is to establish a stable papermaking method by keeping circulating white water clean. Another object of the present invention is to provide a papermaking method for reducing the load in the white water recovery step and the load in the wastewater treatment step.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve these objects, and as a result, in the papermaking process of papermaking, the amphoteric aqueous solution produced by a specific polymerization method was added to papermaking pulp. The present inventors have found that the above object can be achieved by adding an anionic polymer and anionic colloidal silica and / or bentonite, and have reached the present invention.

That is, in the present invention, an amphoteric water-soluble water-soluble polymer produced by a dispersion polymerization method in an aqueous salt solution is added to papermaking pulp in a papermaking process of papermaking, and then anionic colloidal silica and / or bentonite are added. And improving the yield and / or drainage.

The present invention also relates to a method for preparing a cationic monodisperse in a papermaking pulp in a papermaking process in a papermaking pulp in the presence of an aqueous salt solution which does not dissolve the formed polymer and in the presence of a dispersant of a polymer electrolyte which is soluble in the aqueous salt solution. Addition of an amphoteric water-soluble polymer produced by a dispersion polymerization method in an aqueous salt solution in which a monomer mixture containing a monomer and an anionic monomer as essential components is polymerized while stirring. An object of the present invention is to provide a papermaking method characterized by adding colloidal silica and / or bentonite to improve retention and / or drainage.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The dispersion polymerization method in an aqueous salt solution described above is disclosed in Japanese Patent Application Laid-Open No.
No. 20511 discloses a polymerization method that has recently attracted attention as a method for producing an oil-free high-concentration liquid product of an amphoteric water-soluble polymer.

The present inventors have found that amphoteric water-soluble polymers produced by a dispersion polymerization method in an aqueous salt solution can be produced by a conventional polymerization method having the same monomer composition, for example, an aqueous solution polymerization method, a water-in-oil type emulsion. The present invention was found to significantly improve the yield and / or drainage when used in combination with anionic colloidal silica and / or bentonite as compared with an amphoteric water-soluble polymer produced by a polymerization method.

This is thought to be due to the nature of the dispersion polymerization method in an aqueous salt solution. In this polymerization method, before polymerization, the monomers are uniformly dissolved in a salt aqueous solution as a polymerization solvent, but as the polymerization proceeds, the formed polymer separates and precipitates from the salt aqueous solution, and the dispersant With the help of a dispersion of fine particles is formed. That is, phase separation from a uniform phase to two phases occurs. Although the mechanism of this polymerization is not clearly elucidated, polymers having a steric molecular structure different from those in which polymerization is performed in a homogeneous phase such as aqueous solution polymerization and water-in-oil emulsion polymerization, for example, a polymer having a branched structure. It is expected that many polymers or block polymers are produced. This difference in three-dimensional molecular structure can be expected to be a factor that improves the yield and / or drainage.

One of the cationic monomers constituting the amphoteric water-soluble polymer used in the present invention is preferably represented by the following formula (1).

[0014]

Embedded image

(Where A is O or NH; B is C ₂ H ₄ , C ₃ H ₆ , C ₃ H ₅ OH; R ₁ is H or C
H ₃ ; R ₂ and R _{3 each} represent an alkyl group having 1 to 4 carbon atoms; R ₄ represents H or an alkyl group having 1 to 4 carbon atoms; X ⁻ represents an anionic counter ion. Representative examples of the cationic monomer represented by the above formula (1) include acryloyloxyethyldimethylbenzylammonium chloride, methacryloyloxyethyldimethylbenzylammonium chloride, acrylamidopropyldimethylbenzylammonium chloride, and methacrylamidopropyldimethyl. Benzyl ammonium chloride and the like can be mentioned.

The other cationic monomer used in the present invention is preferably represented by the following formula (2).

[0017]

Embedded image

(Where A is O or NH; B is C ₂ H ₄ , C ₃ H ₆ , C ₃ H ₅ OH; R ₁ is H or C
H ₃ ; R ₂ and R _{3 each} represent an alkyl group having 1 to 4 carbon atoms; R ₄ represents H or an alkyl group having 1 to 4 carbon atoms; X ⁻ represents an anionic counter ion. )

Representative examples of the cationic monomer represented by the above formula (2) include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acrylamidopropyltrimethylammonium chloride,
Examples thereof include hydrochloride and sulfate of dimethylaminoethyl (meth) acrylate or dimethylaminopropyl (meth) acrylamide.

In the cationic monomer of the above formula (1), a strongly hydrophobic benzyl group is bonded to the amino group, and as a result, it is difficult to dissolve in a salt solution despite the water-soluble polymer. . Therefore, when the cationic monomer of the above formula (1) is contained in the components of the cationic water-soluble polymer, the cationic monomer represented by the above formula (1) and the cationic monomer represented by the above formula (2) are used. The molar ratio of the represented cationic monomer can be set in a wide range.

An anionic monomer is used as an essential component together with the amphoteric water-soluble polymer used in the present invention and the above-mentioned cationic monomer. Examples of the anionic monomer include itaconic acid or a salt thereof, maleic acid or a salt thereof, fumaric acid or a salt thereof, a (meth) acrylic anion monomer or a mixture thereof.

Representative examples of the (meth) acrylic anion monomer include (meth) acrylic acid or a salt thereof, 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof, and a mixture thereof. Can be

The plurality of ionic monomers and (meth)
It is also possible to copolymerize acrylamide. The amphoteric water-soluble polymer used in the present invention is obtained by copolymerizing a cationic monomer represented by the above formula (1) and / or the above formula (2), the above anionic monomer and (meth) acrylamide. Is more preferable. The preferred molar ratio of these monomers is not particularly limited, but the molar ratio of the monomers in which the produced polymer does not dissolve in the aqueous salt solution as a polymerization solvent, that is, causes salting out is an essential condition.

However, in order to exhibit the characteristics of the amphoteric water-soluble polymer, the total ionic monomer including cations and anions is preferably contained in the copolymer in an amount of at least 5 mol%, more preferably at least 10 mol%. More preferably, it is performed. When the total ionic monomer content is less than 5 mol% in the copolymer, various properties such as yield and drainage become insufficient.

Further, as for the molar ratio of each ionic monomer, it is preferable that the cationic group in the amphoteric copolymer is larger than the anionic group, so that the gram equivalent value of the cationic monomer is Is preferably larger than the gram equivalent value.

Furthermore, if the copolymer formed with other monomers such as hydrophobic monomers such as acrylonitrile, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate and styrene is water-soluble, It is also possible to polymerize.

Preferred examples of the amphoteric water-soluble polymer are, for example, 3 to 99 mol% of the cationic monomer represented by the above formula (1) or a mixture thereof, represented by the above formula (2). 0 to 50 mol% of a cationic monomer or a mixture thereof, 1 to 30 mol% of the anionic monomer, and a dispersion copolymer of a monomer in which a monomer other than the above-mentioned components in all monomers is acrylamide Coalescence can be mentioned.

Other preferable examples of the amphoteric water-soluble polymer include, for example, 3 to 30 mol% of a cationic monomer represented by the above formula (2) or a mixture thereof, 30 mol%, a monomer-dispersed copolymer in which the monomer other than the above-mentioned components in all the monomers is acrylamide can be exemplified.

The polymerization is carried out while stirring a plurality of monomers in an aqueous salt solution in the presence of a dispersant.
% By weight or more, more preferably 10% by weight or more, and particularly preferably 15 to 40% by weight. Monomer concentration 5
If the amount is less than% by weight, the concentration of the polymer in the dispersion becomes low.

As for the aqueous salt solution which is a polymerization solvent and a dispersion medium, it is an important condition that the polymerization product is not dissolved, that is, salting out occurs. That is, this condition is satisfied,
The combination of the monomer composition of the amphoteric water-soluble polymer, the type of salt, and the salt concentration is important.

Representative examples of the salt include, preferably, salts of polyvalent anions such as sodium sulfate, ammonium sulfate, magnesium sulfate, aluminum sulfate, and sodium dihydrogen phosphate. Any material that does not dissolve the polymerization product can be used.

The salt concentration in the reaction solution at the time of polymerization is determined by the molar ratio of the cationic monomer or anionic monomer represented by the above formulas (1) and (2), and the kind of the salt used. There is no particular limitation because it differs depending on the situation. But usually,
The salt concentration in the reaction solution at the time of polymerization is preferably 15% by weight or more based on the polymerization solvent obtained by subtracting the weight of the monomer from the weight of the polymerization reaction solution, and is preferably in a range up to a saturation concentration or a limit of solubility. The content is more preferably from 30% by weight to 30% by weight, and particularly preferably from 25% by weight to 25% by weight. When the salt concentration is less than 15% by weight, the viscosity of the reaction solution during the reaction increases, and the polymerization becomes difficult.

The salt is added to the solvent at the time of the polymerization to carry out the polymerization, and a part of the salt may be added to the dispersion after the polymerization is completed. The viscosity of the dispersion can be reduced by adding a part of the salt to the dispersion after the completion of the polymerization, rather than by adding the salt to the solvent at the time of polymerization at a time. After a part of the salt has been polymerized, the dispersion obtained by adding the salt to the dispersion has a salt concentration of 1%.
The range is preferably 5% by weight or more, up to the saturation concentration or up to the limit of solubility, more preferably 15 to 25% by weight.
It is.

The composition of a monomer whose polymerization product does not salt out even if the kind and concentration of the salt is changed, and the monomer composition of an amphoteric water-soluble polymer which does not cause salting out of the polymerization product And the combination of salt type and concentration are inappropriate.

It is an essential condition that the polymer electrolyte dispersant coexisting during the polymerization is soluble in an aqueous salt solution.

As the polymer electrolyte, the gram equivalent value of the cationic monomer in the amphoteric copolymer as the product is preferably larger than the gram equivalent value of the anionic monomer. The use of an electrolyte is preferred.

Representative examples of the cationic polymer electrolyte include, for example, 50 to 100 mol% of dimethylaminoethyl (meth) 3acrylate hydrochloride or sulfate, dimethylaminopropyl (meth) acrylamide hydrochloride or sulfate, One kind of a cationic monomer selected from (meth) acryloyloxyethyltrimethylammonium salt, (meth) acryloylaminopropyltrimethylammonium salt, dimethyldiallylammonium salt and a mixture thereof, and 0 to 50 mol% of acrylamide Preference is given to (co) polymerized cationic polymer electrolytes.

The amount of the polyelectrolyte dispersant is about 1 to 15% by weight based on the total amount of the monomers, and about 1 to 15% by weight.
10% by weight is preferred. If the amount is less than 1% by weight, the polymerization product is not obtained in a dispersed state and adheres to each other to form a large mass, which is not preferable. The use of an amount exceeding 15% by weight is not preferred because the viscosity of the finally obtained dispersion itself becomes high and the fluidity may be lost.

The polymerization temperature is not particularly limited because it varies depending on the type of polymerization initiator, and may be any temperature at which the polymerization initiator functions. Further, the polymerization initiator may be any of generally used redox-based and azo-based polymerization initiators, and is not particularly limited.

The concentration of the amphoteric water-soluble polymer in the amphoteric water-soluble polymer dispersion is as high as 5% by weight or more, and usually from 5% by weight to about 40% by weight. The amphoteric water-soluble polymer dispersion contains the above-mentioned salt and the above-mentioned dispersant.

The above-mentioned dispersion contains a high concentration of the amphoteric water-soluble polymer. However, since the amphoteric water-soluble polymer is stably dispersed in the dispersion in the form of fine particles, its viscosity is low.
Since it has a low viscosity of 0 to 3000 cP, it easily flows,
There is a feature that is very easy to handle.

The average particle size of the amphoteric water-soluble polymer particles in the above dispersion is usually 0.1 to 150 μm, preferably 0.1 to 50 μm, more preferably 0.1 to 30 μm.
It is. Average particle size of amphoteric water-soluble polymer particles is 150 μm
When it exceeds, precipitation becomes easy, so it lacks storage stability.
Even when mixed with water when the dispersion is used, the solubility is poor due to the large amphoteric water-soluble polymer particles, and it takes a long time to completely dissolve.

The molecular weight of the amphoteric water-soluble polymer in the above dispersion is not particularly limited. However, when used in the papermaking process of papermaking, the molecular weight is preferably large. The intrinsic viscosity of a solution obtained by dissolving a dispersion in a 2% by weight aqueous solution of ammonium sulfate so that the concentration of the amphoteric water-soluble polymer is 0.5% by weight is generally in the range of about 7 dl / g to 30 dl / g. .

The above dispersion is excellent in storage stability,
Even when stored at room temperature, there is no inconvenience such as the particles adhering to each other and forming a lump.

In the papermaking step, the amount of the amphoteric water-soluble polymer added is from 0.001% by weight to 0.2% by weight based on the stock SS, and the total amount of the anionic colloidal silica and / or bentonite added to the stock is 0.0 per SS
Preferred is from 01% to 0.2% by weight.

Further, the amount of the amphoteric water-soluble polymer added to the stock S
The content is 0.005% by weight to 0.1% by weight per S, and the total amount of the added anionic colloidal silica and / or bentonite is more preferably 0.005% by weight to 0.1% by weight per stock SS.

In the papermaking step, it is preferable that the amphoteric water-soluble polymer is added before the centriscreen in the papermaking step, and that the anionic colloidal silica and / or bentonite is added after the centriscreen.

When the circulating white water is heavily contaminated with an anionic substance or the like, a low molecular weight cationic polymer such as poly-dimethyldiallylammonium chloride, polyamide polyamine epichlorohydrin resin or polyethyleneimine is used in combination. Thereby, the effect of the present invention is further greatly improved.

The anionic colloidal silica used in the present invention is not particularly limited. Anionic colloidal silica is usually silicon dioxide having an OH group on the surface by hydration in water, and its particle surface is porous and generally negatively charged in water. Specifically, for example, a surface area of about 50 described in JP-A-57-51900 is used.
To about 1000 m ² / g, preferably about 300 to about 700
colloidal silica sol having m ² / g silica particles,
Colloidal silica containing about 20 to 90%, preferably about 20 to 90% of the colloidal silica sol can be mentioned. Further, an anionic silica sol in an elongated shape having an almost uniform thickness in the range of about 5 to 20 mμ, having an extension only in one plane, and having a particle diameter by dynamic light scattering of about 40 to 300 mμ is also preferable. Can be used.

[0050]

The amphoteric water-soluble polymer produced by the dispersion polymerization method in an aqueous salt solution has the same monomer composition as the conventional polymerization method,
For example, as compared with an amphoteric water-soluble polymer produced by an aqueous solution polymerization method or a water-in-oil emulsion polymerization method, when used in combination with anionic colloidal silica and / or bentonite, the yield and / or drainage is remarkably improved.

In the dispersion polymerization method in an aqueous salt solution, the monomers are uniformly dissolved in the aqueous salt solution which is a polymerization solvent before the polymerization, but as the polymerization proceeds, the produced polymer is dissolved in the aqueous salt solution. Separates and precipitates from inside. That is, phase separation from a uniform phase to two phases occurs. Although the mechanism of this polymerization is not clearly elucidated, polymers having a steric molecular structure different from those in which polymerization is performed in a homogeneous phase such as aqueous solution polymerization and water-in-oil emulsion polymerization, for example, a polymer having a branched structure. Many polymers and the like are produced, and this difference in the three-dimensional molecular structure can be expected to be a factor that improves the yield and / or drainage.

[0052]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

(Preparation Example of Polymer) (Nos. 1 to 3) Polyacryloyloxy as a dispersant was placed in a 1-liter five-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube. Taking 4.2 g of ethyltrimethylammonium chloride and 84.0 g of ammonium sulfate as a precipitant, ion-exchanged water was used.
0 g was added and dissolved. To this, 100.0 g of a monomer having the composition shown in Table 1 was charged, and the atmosphere was replaced with nitrogen while heating to 50 ° C. To this, a 1% aqueous solution of 2,2′-azobis (2-amidinopropane) hydrochloride was added as a polymerization initiator in an amount of 2.0%.
g and polymerized at 50 ° C. for 10 hours with stirring to obtain a polymer of fine particles dispersed in an aqueous salt solution. To this reaction solution, 21 g of ammonium sulfate was added and dissolved to obtain dispersion polymer samples A to C used in the present invention. Table 1 shows the monomer compositions of the dispersion polymer samples (amphoteric water-soluble polymer dispersions) A to C and the intrinsic viscosities in a 2% by weight aqueous solution of ammonium sulfate.

(Nos. 4 to 6) For comparison, Table 1
Comparative Samples a to c shown in Table 1 were obtained by using an aqueous solution polymerization method and a reverse phase emulsion polymerization method using the monomers having the compositions described. Table 1 shows the monomer compositions and the intrinsic viscosities of the comparative samples a to c in a 2% by weight aqueous ammonium sulfate solution.

[0055]

[Table 1]

(Examples 1 to 7) Tests were conducted in which the amphoteric water-soluble polymer dispersions A to C were added to papermaking pulp to measure the yield. (Softwood Sarashi Kraft Pulp) 15% by weight (based on pulp) of heavy calcium carbonate as a filler was added to softwood bleached kraft pulp (L-BKP) [Canadian Standard Freeness (CSF) = 400 cc], and SS
The concentration was adjusted to 0.5% by weight. Using this slurry, the yield was measured with a brit type dynamic jar tester.

The test was performed according to the following procedure. 0.5% by weight
500 ml of the pulp slurry is charged into a brit type dynamic jar tester. Stirring is started at 1500 rpm, and a 0.1% by weight aqueous solution of the amphoteric water-soluble polymer obtained in Preparation Example is added. Timing starts from this time. After 30 seconds, 0.1% by weight bentonite (trade name: Organozobe-O, manufactured by Allied Colloid Co., Ltd.) and / or 0.1% by weight.
1% by weight anionic colloidal silica (trade name: BMA
-780, manufactured by Nissan Eka Nobel). 3 more
0 seconds later, open the cock for collecting white water, 150 mesh
Drain the white water that has passed through the wire. Discard the white water for the first 10 seconds and then collect the white water for 30 seconds. The amount of white water during this period is defined as Xml. This white water is filtered through a quantitative filter paper (Toyo Roshi Kaisha No. 5C), whose dry weight (W ₀ g) at 105 ° C. has been measured in advance, dried at 105 ° C. and weighed. This weight is defined as w ₁ g. Next, incineration is performed at 600 ° C., and the ash content is measured. This weight is defined as fg. The SS concentration and ash concentration in the white water are determined by the following formula.

[0058]

[0059]

For the 0.5% by weight pulp slurry,
Similarly, the SS concentration and the ash concentration are measured. Respectively, SS
o and Asho. The total yield and the filler yield are determined by the following equations.

[0061]

[0062]

Table 2 summarizes the obtained results.

(Comparative Examples 1 to 7) Instead of the amphoteric water-soluble polymer dispersions A to C used in Example 1, a solution polymerization type amphoteric water-soluble polymer and an emulsion type amphoteric water-soluble polymer a to Using c, the yield was measured in the same manner as in Example 1. Table 2 also shows the obtained results.

[0065]

[Table 2]

(Examples 8 to 14) The amphoteric water-soluble polymer dispersions A to C were added to paper pulp to conduct a drainage test. Cardboard waste paper: Newspaper waste paper = 90: 10 mixed pulp (CSF = 300 cc) was adjusted to a pulp concentration of 1% by weight, and a liquid sulfuric acid band was added at 3% by weight (based on pulp), and the pH was adjusted to 5. And 8. 300 ml of this slurry
Collect it in a 00ml beaker and use a three-one motor to
While stirring at 600 rpm, a 0.1% by weight aqueous solution of the amphoteric water-soluble polymers A to C obtained in Preparation Example 1 is added.
After 30 seconds, 0.1% by weight of anionic colloidal silica and / or 0.1% by weight of bentonite are added.
After another 30 seconds, the stirring is stopped and the slurry is transferred to a 1 liter graduated cylinder. After adjusting the total volume to 1 liter with Shimizu, the mixture is inverted and stirred three times and charged into the Canadian Standard Freeness Tester. C. S. According to the procedure of F measurement, the amount of filtrate flowing out to the side tube is measured. Table 3 shows the obtained results.

Comparative Examples 8 to 14 The same as Examples 8 to 14 except that the amphoteric water-soluble polymer dispersions A to C used in Examples 8 to 14 were replaced by amphoteric water-soluble polymers a to c. The drainage amount was measured by the method. Table 3 also shows the obtained results.

[0068]

[Table 3]

[0069]

According to the papermaking method of the present invention, the yield of cellulose fiber and filler and / or the drainage can be improved in the papermaking process, thereby improving the productivity in the papermaking process and the drying process. Can be improved. Further, the papermaking method of the present invention can keep the circulating white water clean, and can further reduce the load in the white water recovery step and the load in the wastewater treatment step.

Claims (12)

(57) [Claims] 1. A dispersion polymerization method in a salt solution in a paper stock in a papermaking process of papermaking (ie, a polymer soluble in a salt solution in a salt solution in which a monomer is dissolved and a formed polymer is not dissolved). Polymerization is carried out with stirring in the coexistence of a dispersant comprising an electrolyte, a polymerization method for producing a dispersion of fine polymer particles is added and mixed, and then anionic colloidal silica and / or or by admixing the bentonite, a paper making process to improve the yield and / or drainage, as the amphoteric water-soluble polymer is represented by the following formula (1)
3 to 99 mol% of a cationic monomer or a mixture thereof,
Cationic monomer represented by the formula (2) or a mixture thereof
0 to 50 mol%, anionic monomer 1 to 30 mol%
And monomers other than the above components in all the monomers
Addition and mixing of a dispersion copolymer of monomers consisting of
Characteristic papermaking method . Embedded image (Where A is O or NH; B is C ₂ H ₄ , C
₃ H ₆ , C ₃ H ₅ OH; R ₁ is H or CH ₃ ; R ₂ ,
R ₃ is an alkyl group having 1 to 4 carbon atoms; X ⁻ is an anionic pair
Represents an ion. ) (Where A is O or NH; B is C ₂ H ₄ , C
₃ H ₆ , C ₃ H ₅ OH; R ₁ is H or CH ₃ ; R ₂ ,
R ₃ is an alkyl group having 1 to 4 carbon atoms; R ₄ is H or carbon
An alkyl group having 1 to 4; X ^- Table anionic counterion
You. ) 2. A dispersant comprising 50 to 100 mol% of dimethylaminoethyl (meth) 3 acrylate hydrochloride or sulfate, dimethylaminopropyl (meth) acrylamide hydrochloride or sulfate, (meth) acryloyloxyethyl trimethylammonium A cationic monomer selected from a salt, (meth) acryloylaminopropyltrimethylammonium salt, dimethyldiallylammonium salt and a mixture thereof, and a cationic copolymer obtained by (co) polymerizing 0 to 50 mol% of acrylamide. 2. The papermaking method according to claim 1, comprising a molecular electrolyte. 3. The papermaking method according to claim 1, wherein the salt forming the aqueous salt solution used in the dispersion polymerization method is a divalent anion salt. 4. The cationic monomer represented by the above formula (2) or a mixture thereof in an amount of 3 to 30 mol%, an anionic monomer in an amount of 1 to 30 mol%, and a single monomer other than the above components in all the monomers. 4. The papermaking method according to claim 1, wherein a monomer-dispersed copolymer of acrylamide is added and mixed as an amphoteric water-soluble polymer. 5. The papermaking method according to claim 1, wherein the cationic monomer represented by the formula (1) is acryloyloxyethyldimethylbenzylammonium chloride. 6. The papermaking method according to claim 1, wherein the cationic monomer represented by the formula (2) is acryloyloxyethyltrimethylammonium chloride. 7. The anionic monomer which forms the amphoteric water-soluble polymer is (meth) acrylic acid or a salt thereof, itaconic acid or a salt thereof, acrylamido-2-methylpropanesulfonic acid or a salt thereof, and a mixture thereof. claims 1 to 6, characterized in that one selected
Papermaking method according to 1. 8. A paper making process according to claims 1 to 7 anionic monomer forming the amphoteric water-soluble polymer is characterized in that the acrylic acid. 9. The gram equivalent number of the cationic monomer forming the amphoteric water-soluble polymer is larger than the gram equivalent number of the anionic monomer.
9. The papermaking method according to 8 . 10. The inherent viscosity of the amphoteric water-soluble polymer in a 2% by weight aqueous ammonium sulfate solution is from 7 dl / g to 30 dl / g.
dl / g.
10. The papermaking method according to 9 . 11. The amount of the amphoteric water-soluble polymer added to the stock SS
2. The amount of the anionic colloidal silica and / or bentonite is 0.001 to 0.2% by weight, and the total amount of the anionic colloidal silica and / or bentonite is 0.001 to 0.2% by weight based on the stock SS. The papermaking method according to claim 10 . 12. A paper according to claims 1 to 11, characterized in that the addition of added anionic colloidal silica and / or bentonite amphoteric water-soluble polymer of the papermaking process prior centriscreen after centriscreen Method.