JPH0578997A - Method for producting paper - Google Patents

Abstract

PURPOSE:To obtain paper having improved yield and freeness of fine fibers and filler during a papermaking process industrially and advantageously by carrying out papermaking by using an additive comprising an ampholytic polyacrylamide-based copolymer and a specific polymer. CONSTITUTION:Papermaking is carried out by using an additive prepared by blending (A) an ampholytic polyacrylamide-based copolymer containing both a cationic group and an anionic group in the molecule with (B) a polymer (preferably Mannich-modified polyacrylamide-based polymer) containing a cationic group and different from the ampholytic polyacrylamide-based copolymer in a ratio of 99.9:0.1-50:50 (weight ratio) to give the objective paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper manufacturing method,
More specifically, it relates to a method for producing paper using additives that improve the retention and drainage of fine fibers and fillers.

[0002]

2. Description of the Related Art In the paper manufacturing process, in order to increase the productivity, it is strongly required to improve the yield and drainage of fine fibers and fillers in the pulp slurry in the papermaking process. Further, when paper is made into paper, water is circulated in order to reduce the amount of water discharged to the outside of the system, and closed papermaking water is being closed for the purpose of suppressing the amount of fresh water to be replenished newly. Since this closed process treats the used water and reuses it, it is important to minimize the amount of fine fibers and fillers that remain in the white water in the papermaking process without remaining in the paper. The device is designed to increase the yield of fine fibers and fillers.

Conventionally, as means for improving the retention and drainage of such fine fibers and fillers, high molecular weight compounds such as high molecular weight anionic polyacrylamide or high molecular weight cationic polyacrylamide, polyamide epichlorohydrin resin, polyethyleneimine, And a method of adding a highly cationic polymer such as a highly Mannich-modified polyacrylamide is known. More recently, a method of mixing and adding a relatively low molecular weight anionic polyacrylamide and a cationic polyacrylamide (Japanese Patent Application Laid-Open No. Sho 5)
8-60094 and Japanese Patent Laid-Open No. 63-12792) are also known.

[0004]

However, none of the methods has yet been able to achieve satisfactory effects of improving the yield and drainage of fine fibers and fillers, and particularly in the high pH range (pH 6 or more). When papermaking is carried out, these effects are hardly exhibited. Therefore, an object of the present invention is to provide a method for producing paper which can improve the retention and drainage of fine fibers and fillers.

[0005]

In order to solve the above problems, the present invention provides an amphoteric polyacrylamide copolymer having both a cationic group and an anionic group in the molecule,
It is intended to provide a method for producing paper, which comprises making a paper by using an additive having a polymer which has a cationic group and is different from the above-mentioned amphoteric polyacrylamide copolymer.

At this time, it is also preferable that the amphoteric polyacrylamide-based copolymer exhibits a cationic property, and that the polymer having a cationic group is a Mannich-modified polyacrylamide-based polymer.

The present invention will be described in detail below. The amphoteric polyacrylamide-based copolymer having both a cationic group and an anionic group used in the present invention is preferably, but not limited to, ionicity.

As a method of obtaining the amphoteric polyacrylamide copolymer, a method of copolymerizing a cationic monomer, an anionic monomer and acrylamides is also used.
Examples of the cationic monomer used here include compounds represented by the following general formulas [I], (II), and [III]. These can be used alone, but in each general formula and general formula In, two or more kinds can be used in combination.

General formula [I]

[Chemical 1]

(In the formula, A is oxygen or NH, and n is 2
To an integer of 4, R1 is H or a methyl group, R2, R3, R
4, R5 and R6 are the same or different lower alkyl groups, X
-And Y- represent the same or different anionic groups. )

General formula [II]

[Chemical 2]

(In the formula, A is oxygen or NH, and n is 2
To R4, R7 is H or a methyl group, and R8 and R9 are the same or different lower alkyl groups. )

General formula [III]

[Chemical 3]

(In the formula, A is oxygen or NH, and n is 2
To an integer of 4, R10 is H or a methyl group, R11, R12
Are the same or different lower alkyl groups, R13 is a lower alkyl group or a benzyl group, and Z- is an anionic group. )

As the cationic monomer corresponding to the above general formula [I], 2-hydroxy-N, N, N, N ',
N'-pentamethyl-N '-(3- (meth) acryloylaminopropyl) -1,3-propanediammonium dichloride, 2-hydroxy-N-benzyl-N, N
-Diethyl-N ', N'-dimethyl-N'-(2- (meth) acryloyloxyethyl) -1,3-propanediammonium dibromide and the like.

As the cationic monomer belonging to the above general formula [II], N, N-dimethylaminoethyl (meth)
Examples thereof include acrylate and N, N-dimethylaminopropyl (meth) acrylamide.

As the cationic monomer belonging to the above general formula [III], a cationic monomer represented by the above general formula [II] is used as a suitable quaternizing agent such as an alkyl halide or a dialkyl carbonate. Obtained by quaternization with alkyl tosylate, alkyl mesylate, dialkyl sulfuric acid, benzyl halide, etc., for example, N-ethyl-N, N-dimethyl- (2- (meth) acryloyloxyethyl) ammonium bromide, N- Examples thereof include benzyl-N, N-dimethyl- (3- (meth) acryloylaminopropyl) ammonium chloride.

Further, if the cationic monomer belonging to the general formula [II] is quaternized with the above-mentioned quaternizing agent as described above, then a polymerization reaction with acrylamides and anionic monomers is only required. Alternatively, the quaternization agent may be used for quaternization during or after the polymerization reaction of acrylamides, anionic monomers, and cationic monomers belonging to the general formula [II]. In this case all 4
It may be graded, but it goes without saying that a part may be graded.

In the present invention, the above general formula [I],
In addition to the cationic monomers represented by [II] and [III], other cationic monomers can be used.

The anionic monomer used when the amphoteric polyacrylamide copolymer used in the present invention is obtained by the above-mentioned copolymerization method of the monomers is α, β-unsaturated such as acrylic acid or methacrylic acid. Monocarboxylic acid, maleic acid,
Fumaric acid, itaconic acid, α, β-unsaturated dicarboxylic acids such as citraconic acid, unsaturated sulfonic acids such as styrene sulfonic acid, vinyl sulfonic acid and salts thereof, such as sodium salt, potassium salt, ammonium salt and the like. These can be used alone or in combination of two or more.

Acrylamides used when the amphoteric polyacrylamide copolymer used in the present invention is obtained by copolymerizing the above monomers, include N-ethylacrylamide and N-methylacrylamide in addition to acrylamide and methacrylamide. , N-substituted lower alkyl acrylamides such as N, N-dimethyl acrylamide and N-isopropyl acrylamide, etc., and these may be used alone or in combination of two or more. Further, acrylonitrile, (meth) acrylic acid methyl ester, (meth) acrylic acid ethyl ester and the like, which are nonionic monomers, may be used in combination to the extent that water solubility is not impaired.

The above cationic monomer is used in an amount of 0.5 to 20 mol%, preferably 0.5 to 10 based on the total amount of the monomers.
Mol%. If it is less than 0.5 mol%, the adsorptivity to pulp is insufficient, and if it exceeds 20 mol%, the amount of acrylamides supplying the carbamoyl group is reduced, so that hydrogen bonding with pulp fiber is not sufficiently performed. , It may reduce the paper strength.

The above-mentioned anionic monomer is used in an amount of 0.2 to 20 mol% based on the total amount of monomers, preferably 0.2 to 10%.
Mol%. If it is less than 0.2 mol%, it is not sufficient for ionic interaction with the polymer having a cationic group, and if it exceeds 20 mol%, pulp, particularly fine fibers, are excessively dispersed to improve the yield. The effect may not be fully seen.

The molar ratio of the above-mentioned cationic monomer and anionic monomer is preferably such that the copolymer obtained is cationic, but it may be anionic. The cationicity and anionicity can be determined by measuring the cationization degree and the anionization degree by, for example, "colloid titration method" (Ryoichi Sente, 1969, Nanedo Publishing).

Polymers having a cationic group and used in the present invention which are different from the above-mentioned amphoteric polyacrylamide copolymers include polyamide polyamine resins, polyamide polyamine epihalohydrin resins, polyamide polyamine urea formaldehyde resins, amine epihalohydrin resins, Examples thereof include cationized starch, chitosan, polyethyleneimine, polydiallyldimethylammonium halide and highly cationic polyacrylamide.

The above polyamide polyamine epihalohydrin resin can be obtained by reacting epihalohydrin with a dehydrated condensate of polyalkylene polyamine and dibasic carboxylic acid. Examples include Kaimen 557H (manufactured by Dick Hercules Co., Ltd.) and the like.

The above-mentioned polyamide polyamine urea formaldehyde resin can be obtained by reacting formaldehyde with a reaction product of polyalkylene polyamine, dibasic carboxylic acid and urea. For example, Epinox P-
9007Y (manufactured by Dick Hercules Co., Ltd.) and the like.

The amine epihalohydrin resin can be obtained by reacting a primary or secondary monoamine or polyamine with epihalohydrin. For example, Epinox P-700F (manufactured by Dick Hercules Co., Ltd.) and the like can be mentioned.

The above-mentioned highly cationic polyacrylamide can be obtained by copolymerizing a cationic monomer and acrylamides, or by Hoffmann rearrangement or Mannich modification of polyacrylamide.

The Mannich-modified polyacrylamide-based copolymer used in the present invention is characterized in that the polyacrylamide-based copolymer is Mannich-modified with formaldehyde and amines.

Further, as the polyacrylamide-based copolymer component, an anionic polyacrylamide-based copolymer obtained by copolymerizing an anionic monomer may be modified with Mannich using formaldehyde and amines. As the anionic monomer and acrylamides, the same ones as the above-mentioned amphoteric polyacrylamide copolymer can be used. The amount of the anionic monomer is 20 mol% or less, preferably 12 mol% or less, based on the total amount of the monomers. If it exceeds 20 mol%, a sufficient drainage improving effect may not be obtained.

Typical amines used in the above Mannich reaction are aliphatic secondary amines such as dimethylamine and diethylamine, but known primary amines may be used in combination. The Mannich modification rate through the Mannich reaction is appropriately 1 mol% or more, preferably 10 mol% or more. If this is less than 1 mol%, a sufficient drainage improving effect cannot be obtained. Here, the Mannich modification rate indicates the mol% number of formaldehyde and amines used with respect to the amide group in the acrylamide copolymer.

The mixing ratio of the amphoteric polyacrylamide copolymer used in the present invention and the polymer having a cationic group and different from the amphoteric polyacrylamide copolymer is:
Any ratio is possible, preferably 99.9: by weight.
A range of 0.1 to 50:50 is suitable. Further, the mixing of the two may be performed immediately before adding the mixture to the pulp, or may be performed in advance.

The mixture of the amphoteric polyacrylamide copolymer and the polymer having a cationic group and different from the amphoteric polyacrylamide copolymer is 0.01 to 4%, preferably 0.05, based on the pulp. Used by adding ~ 2%.

As a place of addition, a mixing chest,
The machine chest, the head box, the vicinity of the fan pump, the vicinity of the screen, the white water pit, etc. are mentioned, but there is no particular limitation, and generally, the machine chest, the head box, the vicinity of the fan pump, and the vicinity of the screen are suitable.

Regarding the pH of the paper-making system, the above-mentioned conventional techniques (JP-A-58-60094 and JP-A-63-12) are used.
792), the effect of improving the yield and drainage of fine fibers and fillers is insufficient in the acidic region (pH less than 6.0), and the additive is not in the acidic region (pH 6.0 or more).
However, the additive containing the mixture used in the present invention had a pH of 4.0 to 9.0,
Preferably, it can be effectively used in a wide range of pH 4.5 to 7.5.

Further, in the paper-making system using the additive comprising the above mixture according to the present invention, other paper-making additives may be added. Examples of papermaking additives that can be used in combination include solution rosin sizing agents, rosin-based sizing agents such as rosin emulsion sizing agents, alkyl ketene dimers, alkenyl succinic anhydride, neutral sizing agents such as cationic styrene-based polymers, and cationic starch-based agents. Paper strength agents, defoaming agents, dyes, sulfuric acid bands and the like.

The additives according to the present invention can be used in the papermaking of all papers or paperboards. Specifically, they are acidic or neutral printing writing papers, acidic or neutral coated base papers, acidic or neutral papers. Information paper such as PPC paper and thermal paper base paper, acid or neutral pure white roll paper, wrapping paper such as Ranshin kraft paper, acid or neutral liner, packing liner, acid or neutral core core paper, paper core paper, It can be used for making paperboard such as white paperboard and gypsum board base paper.

In the papermaking of the above various papers or paperboards, pulp raw materials are bleached or unbleached chemical pulp such as kraft pulp or sulfite pulp,
Any of bleached or unbleached high-yield pulp such as ground wood pulp, mechanical pulp or thermomechanical pulp, and used paper pulp such as used newspaper, used corrugated paper or used deinked paper can be used.

Additives such as fillers and dyes may also be used as necessary in order to exhibit the physical properties required for each paper type. Examples of the filler include aluminum sulfate, polyaluminum chloride, clay, talc, kaolin, titanium oxide, heavy or light calcium carbonate, and these may be used alone or in combination.

[0040]

[Function] By using the amphoteric polyacrylamide-based copolymer and a polymer having a cationic group and different from the amphoteric polycyclylamide-based copolymer in combination, fine fibers, filler, and Since the mutual relationship with the pulp fiber is strengthened, it is considered that it exerts a remarkable effect on the yield and drainage of the fine fiber and the filler, but the details are not clear. It should be noted that the present invention is not limited by this idea.

[0041]

EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited to these examples. In carrying out the method for producing the paper of this example and the comparative example, an amphoteric polyacrylamide-based copolymer aqueous solution (A series, a series) and a polymer aqueous solution having a cationic group (B series) were prepared as follows. ..

Preparation of Copolymer Aqueous Solution A-1 663.1 g of water in a 1-liter four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube
% Acrylamide aqueous solution 243.2 g, N-benzyl-
80% aqueous solution of N, N-dimethyl- (2-methacryloyloxyethyl) ammonium chloride 19.16
g, 4.68 g of itaconic acid, 12.95 g of a 2% aqueous solution of sodium hypophosphite were charged, then 4.11 g of a 5% aqueous solution of ammonium persulfate was added, and the mixture was introduced at 80 ° C. under nitrogen gas introduction.
The temperature was raised to 0 to complete the polymerization reaction. The polymer thus obtained was a transparent aqueous solution having a non-volatile content of 15.5%, a Brookfield viscosity of 7200 cps at 25 ° C., and a pH of 4.3. When the ionicity was measured by the “colloid titration method” to be described later, it was 0.2 meq / The cationization degree of g was shown. This is designated as copolymer aqueous solution A-1. The measured values are shown in Table 1.

Production of Aqueous Copolymer Aqueous Solutions A-2 to A-4, a-6 and B-5 By mixing the constituent monomer components shown in Table 1, the copolymer A-1 was prepared.
Polymerization reaction similar to that of
A-4, a-6, and B-5 were obtained. Table 1 shows the results of the same measurements as those of the copolymer A-1. In addition,
The amount of the chain transfer agent was appropriately changed in order to obtain the same viscosity. The abbreviations in the table are as follows.

Cationic monomer x1: N-benzyl-N, N-dimethyl- (2-methacryloyloxyethyl) ammonium chloride x2: N, N-dimethylaminopropylacrylamide x3: 2-hydroxy-N, N, N -Triethyl-
N ', N'-dimethyl-N'-3- (acryloylaminopropyl) -1,3-propanediammonium dibromide anionic monomer y1: itaconic acid y2: acrylic acid acrylamides z1: acrylamide z2: methacrylamide

Preparation of Copolymer Aqueous Solution A-5 Copolymer A as in Aqueous Solution A-2 to A-4
-5 was produced and the results of the same measurement as above are shown in Table 1.

[0046]

[Table 1]

Production of Highly Cationic Polymer Aqueous Solution B-1 8.58 g of 30% itaconic acid aqueous solution and 50% acrylamide in a 1 liter four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube. Aqueous solution 137.
93 g, isopropyl alcohol 10.84 g and water 3
45.56 g was sampled and charged, and then the pH was adjusted to 4.0 with 30% sodium hydroxide, and then nitrogen gas was passed through the system to expel oxygen, while the temperature of the reaction solution was adjusted to 65.
The temperature was raised to ° C. Then, while continuing stirring, 2.28 g of a 5% ammonium persulfate aqueous solution as a polymerization initiator was added to proceed the polymerization reaction, and while maintaining the same temperature, 1 hour and 2 hours later, 1.14 g of a 5% ammonium persulfate aqueous solution, respectively. Added one by one. Five hours after the start of polymerization, the nonvolatile content was 14.0%, and the Brookfield viscosity was 5 at 25 ° C.
An aqueous solution of a stable acrylamide copolymer having 100 cps and pH 4.2 was obtained. Thereafter, this polymer aqueous solution was cooled to 40 ° C., and while continuing stirring, 43.65 g of 59% dimethylamine aqueous solution and 36.32 g of 37% formalin aqueous solution were added, and further 30% sodium hydroxide aqueous solution for pH adjustment. 5.29g was added to adjust the pH to 10.7, and the mixture was kept at 40 ° C for 2 hours to have a nonvolatile content of 15.0%.
A stable Mannich reaction product having a viscosity of 6500 cps and a pH of 10.5 was obtained. Hereinafter, this is abbreviated as highly cationic polymer aqueous solution B-1.

Highly cationic polymer aqueous solution B-2 to B-
Production of No. 4 With the blending of the constituent monomer components shown in Table 2, the same polymerization reaction as that of the highly cationic polymer aqueous solution B-1 was performed to obtain highly cationic polymer aqueous solutions B-2 to B-4. Table 1 shows the results of the same measurement as those of the highly cationic polymer aqueous solution B-1. The amount of the chain transfer agent was appropriately changed to obtain the same viscosity.

[0049]

[Table 2]

Measurement of Ionicity It is carried out according to the “colloidal titration method” (Ryoichi Sente, published by Nankodo Publishing in 1969). (Principle) Toluidine blue (TB) is a basic dye and is not adsorbed by the positive colloid having an amino group.
Immediately adsorbed on the negative colloid, it changes to reddish purple (this phenomenon is called meta-chromasy). Utilizing this phenomenon, for example, when TB is added to an aqueous solution of an amphoteric copolymer and a dilute solution of potassium polyvinyl sulfate (PVSK) is dropped, PVSK reacts preferentially with a cationic group, and TB does not discolor. However, beyond the equivalence point, excess PVSK binds to TB and the solution turns from blue to magenta. The degree of cationization can be calculated from the consumption of PVSK by using TB as an indicator.

(Method) (1) Measurement of degree of cationization 100 samples (0.05 to 0.15 g as solid content) were used.
Weigh accurately in a ml measuring flask and add ion-exchanged water up to the marked line. 10 ml of this sample aqueous solution is placed in a 50 ml beaker with a whole pipette. Place the beaker on the magnetic stirrer, put the rotor in and stir gently.
Add a few drops of TB aqueous solution and add blue (sky blue
e) but with N / 500 PVSK in the beaker
When 10 ml of buret is dripped, precipitation occurs near the equivalence point and the liquid becomes cloudy. Further drop PVSK, and when the liquid phase changes from blue to magenta, stop the drop PVSK and read the burette scale.

(2) Measurement of degree of anionization: 10 ml of a sample aqueous solution prepared in the same manner as in the previous section and N /
5 ml of 200 methyl glycol chitosan was placed in a 50 ml beaker with a whole pipette, and the above-described steps 1 to 3 were repeated. N / 200 as a blank test
5 ml of methyl glycol chitosan (or other quaternary cation polymer) is placed in a 50 ml beaker with a whole pipette, and the above-mentioned steps 1 to 3 are repeated in the same manner.

(Calculation) The cationization degree or the anionization degree is calculated by the following formula.

[0054]

[Equation 1]

[0055]

[Equation 2]

In the formula, V: titration amount of N / 500 PVSK aqueous solution (ml) S: sampling amount (g) N: solid content of sample (%) V0: titration amount of blank (N / 200 methyl glycol chitosan only) (Ml)

Example 1 Canadian Standard Freeness (CSF) 400
A sulfuric acid band of 2% per pulp solid content ratio (the same applies below) was added to 1% slurry of corrugated cardboard waste paper pulp of m1. Next, the A series of the amphoteric polyacrylamide copolymer aqueous solution and the B series polymer aqueous solution or existing product which has a cationic group and is different from the A series amphoteric polyacrylamide copolymer aqueous solution are mixed in advance (premix). And added as shown in Table 3. The pulp slurry at this time had a pH of 5.0. The drainage and the retention of this pulp slurry were evaluated. The results are shown in Table 3.

The freeness was evaluated according to JIS P8121. This drainage is expressed in CSF (ml).
Further, the yield was evaluated by the transmittance of white water. The transmittance of this white water was measured by Display as M (%). White water transmittance: TAPPI PAPERMAKERS
Modified Hercules Dynam described in CONFERENCE C171 (1985).
Device similar to ic Drainage Tester (pulp slurry is poured into a container with a diameter of about 7.5 cm, air is sent from the bottom while stirring so as not to form a mat, and stirring and air supply are stopped and the structure is filtered at the same time) Using the above, 500 ml of pulp slurry was poured into a container and 50 ml of the filtrate was collected, and the filtration rate at 620 nm was measured and used as an index of the fast path retention. That is, the higher the filtration rate is, the clearer the filtrate is, and the higher the yield of the fine fibers and the filler is.

[0059]

[Table 3]

In Table 3, K557H is sponge 557H.
(Dick Hercules Co., Ltd.), Chitosan is Kimitsu Kitosan (LLW) (Kimitsu Chemical Co., Ltd.), P-70
0F is Epinox P-700 (manufactured by Dick Hercules Co., Ltd.), and Cato F is cationized starch (manufactured by Oji National Co., Ltd.).

Comparative Example 1 Using the corrugated cardboard waste paper pulp adjusted to pH 5.0 of Example 1, an amphoteric polyacrylamide copolymer aqueous solution A series, an anionic polyacrylamide existing product, and a cationic group were used. Then, a B series polymer aqueous solution different from the A series amphoteric polyacrylamide copolymer aqueous solution and the existing product were added individually, separately (attached), or in premix as shown in Table 4. With respect to this pulp slurry, drainage and retention were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0062]

[Table 4]

In Table 4, PS117 is Polystron 117
(Arakawa Chemical Industry Co., Ltd. anionic polyacrylamide), PS696 is Polystron 696 (Arakawa Chemical Industry Co., Ltd. amphoteric Mannich modified polyacrylamide).

Example 2 To a 450 ml CSF unbleached kraft pulp 1% slurry was added a 0.5% sulfuric acid band per solids to pulp solids ratio. Next, an amphoteric polyacrylamide-based copolymer aqueous solution A-1 and a polymer aqueous solution of B-1 having a cationic group and different from this amphoteric polyacrylamide-based copolymer aqueous solution of A-1 are premixed to prepare a mixture shown in Table 5. Added as above.
The pulp slurry at this time had a pH of 7.0. With respect to this pulp slurry, drainage and retention were evaluated in the same manner as in Example 1. The results are shown in Table 5.

Comparative Example 2 Using the unbleached kraft pulp adjusted to pH 7.0 of Example 2, an amphoteric polyacrylamide-based copolymer aqueous solution A-1, existing anionic polyacrylamide product,
The aqueous solution of the polymer of B-1 having a cationic group and the existing product were added individually, separately (attached), or in premix as shown in Table 6. With respect to this pulp slurry, drainage and retention were evaluated in the same manner as in Example 1. The results are shown in Table 6.

From Tables 3 to 6, a mixture of an amphoteric polyacrylamide copolymer and a polymer having a cationic group and different from this amphoteric polyacrylamide copolymer was compared with those alone or in combination (attachment). It can be seen that the freeness can be remarkably improved.

[0067]

As described above, a cationic group in the molecule,
By papermaking using an additive containing a mixture of an amphoteric polyacrylamide-based copolymer having both anionic groups and a polymer having a cationic group and different from the amphoteric polyacrylamide-based copolymer, , High yield of fine fibers and fillers that have not been obtained conventionally, and excellent drainage can be obtained, and particularly when an amphoteric polyacrylamide-based copolymer having a cationic property is used, these effects become more remarkable, It is extremely significant in the paper manufacturing industry and its industrial effects are enormous.

[Table 5]

[Table 6]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromi Hashimoto 2 Ichihara City, Chiba Prefecture 17 Yawata Kaigan Dori

Claims (3)

[Claims] 1. An amphoteric polyacrylamide copolymer having both a cationic group and an anionic group in the molecule,
A method for producing paper, which comprises making a paper using an additive having a polymer having a cationic group and different from the amphoteric polyacrylamide copolymer. 2. The method for producing paper according to claim 1, wherein the amphoteric polyacrylamide-based copolymer exhibits a cationic property. 3. The method for producing paper according to claim 1, wherein the polymer having a cationic group and different from the amphoteric polyacrylamide copolymer is a Mannich-modified polyacrylamide polymer.