JP2000273791A - Production of paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing paper in good operability in the region of pH of acidity to neutrality by adding a cationic polymer containing an amphoteric polyacrylamide in a specific weight average molecular weight range and an amidine ring as recurring units to pulp slurry and making the mixture into paper. SOLUTION: An amphoteric polyacrylamide A having 300,000 to 4,000,000 weight average molecular weight and a cationic polymer B having 0.1-10 dl/g reduced viscosity measured at 25 deg.C as 0.1 g/dl solution in 1 mol/l common salt water and containing 20-90 mol% recurring unit of amidine ring are successively or simultaneously added to pulp slurry at a solid content weight ratio (A/B) of (99.5/0.5) to (50/50) and in a range of a used amount of 0.005-3 wt.% (expressed in terms of solid content) and the mixture is made into paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing paper.

[0002]

2. Description of the Related Art Hitherto, it has been known that polyacrylamide generally has an effect as a papermaking additive, such as better water filtration and paper strength, as its molecular weight is larger.
However, a papermaking additive using a high molecular weight type polyacrylamide has an extremely high viscosity, and thus is inferior in workability as compared with a low molecular weight type polyacrylamide. On the other hand, the low molecular weight type has no problem in terms of work efficiency, but is insufficient in the effect as a papermaking additive as compared with the high molecular weight type.

[0003] In order to solve such problems, there has been proposed a method of adding a cationic polymer having an anionic polyacrylamide and an amidine ring structure as a repeating unit to a pulp slurry. However, even with this method, the fixing of anionic polyacrylamide to pulp is insufficient, and a sufficient paper strength effect cannot be obtained. Furthermore, in recent years, the ratio of used paper has been increasing, and the papermaking pH has tended to increase due to the closure of the paper manufacturing process as part of environmental measures. Large, stable operation was difficult with the above method.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a paper excellent in various effects such as drainage and paper strength is obtained.
It is an object of the present invention to provide a method for producing paper which exhibits a stable effect even with respect to fluctuations of paper and has excellent operability.

[0005]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, (A) amphoteric polyacrylamide and (B) were used as papermaking additives used in the production of paper. The present inventors have found that the above object can be achieved by using a cationic polymer having an amidine ring structure as a repeating unit in combination and adding each of the cationic polymers to a pulp slurry, and have accomplished the present invention.

That is, the present invention relates to a pulp slurry,
(A) an amphoteric polyacrylamide having a weight average molecular weight of 300,000 to 4,000,000, and (B) a solution of 0.1 g / dl in a 1 mol / l saline solution having a reduced viscosity of 0.1 to 0.1 g as measured at 25 ° C. The present invention relates to a method for producing paper, which comprises adding a cationic polymer having an amidine ring structure of 10 dl / g as a repeating unit sequentially or simultaneously and paper-making the paper.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The (A) amphoteric polyacrylamide used in the present invention is, for example, a copolymer of (a) (meth) acrylamide, (b) anionic vinyl monomer and (c) cationic vinyl monomer. Is obtained by

(A) (meth) acrylamide means acrylamide or methacrylamide, which can be used alone or in combination. From the viewpoint of economy, acrylamide is preferably used alone. Hereinafter, in the present invention, (meta) has the same meaning. The amount of the component (a) to be used is generally about 60 mol% or more, preferably 65 mol% or more, based on the total mol of the monomers constituting the polyacrylamide (A) amphoteric. (A) component is 6
If the amount is less than 0 mol%, it is difficult to obtain a sufficient paper strength effect as a papermaking additive. The amount of component (a) used is the balance of components other than component (a).

(B) Examples of the anionic vinyl monomer include α, β-unsaturated monobasic acids such as (meth) acrylic acid, crotonic acid and (meth) allyl carboxylic acid;
Α, β-unsaturated dibasic acids such as maleic acid, fumaric acid, itaconic acid and muconic acid; vinylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, (meth) allylsulfonic acid, etc. Organic sulfonic acids; or alkali metal salts such as sodium salts and potassium salts of these various organic acids, and ammonium salts. One or more of these anionic vinyl monomers can be used without any particular limitation. In particular, it is preferable to use a monomer having a (meth) allyl group, particularly a (meth) allylsulfonic acid or a salt thereof, as one kind of anionic vinyl monomer, since the resulting amphoteric polyacrylamide has a high molecular weight. . In addition, it is preferable to use at least one selected from α, β-unsaturated monobasic acid, α, β-unsaturated dibasic acid and salts thereof.
It is particularly preferred to use itaconic acid. Above all,
It is preferable to combine (meth) acrylic acid and / or itaconic acid with (meth) allylsulfonic acid or a salt thereof.

The amount of the (b) anionic vinyl monomer used is usually about 1 to 40 mol%, preferably 3 to 40 mol%, based on the total mol of the monomers constituting the amphoteric polyacrylamide (A). Preferably it is 3 to 30 mol%.

(C) Examples of the cationic vinyl monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N-dimethylaminopropyl (meth) acrylate.
Vinyl monomers having a tertiary amino group such as acrylamide, N, N-diethylaminopropyl (meth) acrylamide, or salts of inorganic or organic acids such as hydrochloric acid, sulfuric acid, and acetic acid, or vinyl containing the tertiary amino group Examples include vinyl monomers containing a quaternary ammonium salt obtained by reacting the monomer with a quaternizing agent such as methyl chloride, benzyl chloride, dimethyl sulfate, epichlorohydrin and the like.

(C) The amount of the cationic vinyl monomer used is such that the equivalent ratio (cationic group / anionic group) of the ionic functional groups in the (A) amphoteric polyacrylamide is 2 or less. Is preferred. The equivalent ratio (cationic group / anionic group) is as follows: (A) amphoteric polyacrylamide and (B) a cationic polymer having an amidine ring structure described below are added to a pulp slurry.
These are preferred in order to exhibit sufficient effects as a papermaking additive. In particular, it is preferable to use such a ratio that the equivalent ratio (cationic group / anionic group) is in the range of 1.5 or less.

In addition, (A) to amphoteric polyacrylamide,
Means for imparting a cationic group include, as described above, (c) copolymerization of a cationic vinyl monomer, Mannich modification in which anionic polyacrylamide is reacted with formalin and a secondary amine, and hypoxia. A cationic group can also be introduced by a Hoffman reaction in which a halogenate is reacted. When a cationic group is introduced by such modification, the equivalent ratio of the ionic functional group (cationic group / anionic group) in the (A) amphoteric polyacrylamide is adjusted to the same range as described above. Is preferred.

(A) Amphoteric polyacrylamide of the present invention
Is the component (a), the component (b) and the component (c),
General formula (1): CH₂= C (R¹) -CONR
²(R³) (R ¹Is a hydrogen atom or a methyl group, R²Is water
An atom or a linear or branched alkyl having 1 to 4 carbon atoms
Kill group, R³Is a linear or branched alkyl having 1 to 4 carbon atoms
N-substituted (meth) acrylamides represented by
And / or polyfunctional monomers as constituent monomers
Can be included.

N-substituted (meta) represented by the general formula (1)
In acrylamides, a methyl group or a methylene group in the N-alkyl group acts as a chain transfer point, introduces many branched structures into the polymer, and a branched polymer without gelation can be obtained. Examples of the linear or branched alkyl group having 1 to 4 carbon atoms for R ² or R ³ in the general formula (1) include a methyl group, an ethyl group, an isopropyl group, and a t-butyl group. Examples of N, N-substituted (meth) acrylamides include N, N-dimethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, -Isopropyl (meth) acrylamide and Nt-butyl (meth) acrylamide. Among these, copolymerizability,
N, N-dimethylacrylamide is preferred from the viewpoint of chain transfer.

The use of a polyfunctional monomer can also impart a crosslinked structure to (A) the amphoteric polyacrylamide. Examples of the polyfunctional monomer include di (meth) acrylates such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol di (meth) acrylate.
Methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, hexamethylenebis (meth)
Bis (meth) acrylamides such as acrylamide, divinyl esters such as divinyl adipate and divinyl sebacate, allyl methacrylate, diallylamine, diallyldimethylammonium, diallylphthalate, diallylchlorendate, divinylbenzene, N, N-diallylacrylamide and the like A bifunctional vinyl monomer of
Trifunctional vinyl monomers such as 1,3,5-triacryloylhexahydro-S-triazine, triallyl isocyanurate, triallylamine, triallyl trimellitate, tetramethylolmethanetetraacrylate, tetraallyl pyromellitate, N, Tetrafunctional vinyl monomers such as N, N ', N'-tetraallyl-1,4-diaminobutane, tetraallylamine salt, tetraallyloxyethane, and N-methylolacrylamide. Among these polyfunctional monomers, 1,3
5-triacryloylhexahydro-S-triazine,
Triallyl isocyanurate and the like are preferred.

N-substituted (meta) represented by the general formula (1)
The amount of the acrylamides and / or the polyfunctional monomer is usually about 10 mol% or less based on the total mol of the monomers constituting the (A) amphoteric polyacrylamide.
Further, it is at most 5 mol%. In order to exhibit the function of the N-substituted (meth) acrylamides represented by the general formula (1), 0.1 mol% or more, more preferably 0.5 mol% or more is used.

Further, in order to impart hydrophobicity to the (A) amphoteric polyacrylamide, an alkyl ester of the above-mentioned anionic vinyl monomer (having an alkyl group having 1 to 1 carbon atoms).
8) Nonionic vinyl monomers such as acrylonitrile, styrenes, vinyl acetate, and methyl vinyl ether can also be used. When a nonionic vinyl monomer is used, the amount of the nonionic vinyl monomer to be used is usually 3 to the total molar amount of the monomers constituting (A) the amphoteric polyacrylamide.
It is about 0 mol% or less, preferably 20 mol% or less.

(A) The synthesis of amphoteric polyacrylamide can be carried out by various conventionally known methods. For example, it can be obtained by charging the various monomers and water in a predetermined reaction vessel, adding a radical polymerization initiator, and heating under stirring. The reaction temperature is usually about 50-100 ° C, and the reaction time is about 1-5 hours. The reaction concentration (monomer concentration) can be usually performed at about 10 to 40% by weight, and polymerization can be performed even at a high concentration. In addition, the monomer can be charged by various conventionally known methods such as simultaneous polymerization and continuous drop polymerization. As the radical polymerization initiator, a normal radical polymerization initiator such as a persulfate such as potassium persulfate or ammonium persulfate, or a redox polymerization initiator in the form of a combination thereof with a reducing agent such as sodium bisulfite is used. it can. Further, an azo-based initiator may be used as the radical polymerization initiator. The amount of the radical polymerization initiator used is about 0.05 to 2% by weight of the total weight of the monomers, preferably 0.1 to 0.
5% by weight.

(A) The weight average molecular weight of the amphoteric polyacrylamide is from 300,000 to 40,
Adjust to 100,000. Preferably, it is 1,000,000 to 4,000,000. When the weight average molecular weight is less than 300,000, the paper strength effect is insufficient. On the other hand, when the weight average molecular weight exceeds 4,000,000, it is not preferable in terms of workability. In addition, (A) the viscosity of the amphoteric polyacrylamide is preferably about 10,000 cps (25 ° C.) or less in terms of handleability. In addition, the additive for papermaking of the present invention is adjusted to a solid content concentration of 10 to 40% by weight. Normally, the solid content concentration is preferably set to 30% by weight or less.

As the cationic polymer (B) having an amidine ring structure as a repeating unit used in the present invention, various polymers having an amidine ring structure can be used as the polymer repeating unit.

The repeating units of the amidine ring structure include:
For example, the following general formula (2), general formula (3), general formula (4),

[0023]

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[0024]

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[0025]

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(Wherein R ⁴ and R ⁵ each represent a hydrogen atom or a methyl group, and X ⁻ represents an anion, respectively).

The cationic polymer (B) of the present invention comprises the repeating unit having an amidine ring structure represented by the general formula (2), (3) or (4), Those containing about 20 to 90 mol% of the polymer repeating unit are preferred. (B) In order to enhance the effect of the cationic polymer on the pulp agglomerating action, the higher the proportion of the amidine ring structure unit in the molecule, the better the performance. Therefore, the repeating unit of the amidine ring structure is 30 units. It is preferably at least 50 mol%, more preferably at least 50 mol%.
In consideration of ease of production, etc., the repeating unit of the amidine ring structure is preferably at most 85 mol%, more preferably at most 80 mol%.

The method for forming these amidine ring structure repeating units is not particularly limited, but generally, the amidine ring structure repeating unit represented by the general formula (2) or (3) is A copolymer of an ethylenically unsaturated monomer (X) having a substituted amino group capable of forming a primary amino group by a conversion reaction and a nitrile such as (meth) acrylonitrile is produced, and the cyano in the copolymer is further produced. It is formed by reacting a group with a primary amino group to form an amidine.

The ethylenically unsaturated monomer (X) may be, for example, a compound represented by the following general formula (5): CH ₂ ＣＲCR
⁶ NHCOR ⁷ (R ⁶ represents a hydrogen atom or a methyl group;
⁷ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. )). The substituted amino group derived from the ethylenically unsaturated monomer represented by the general formula (5) is easily converted into a primary amino group in the copolymer by hydrolysis or alcoholysis. Examples of the ethylenically unsaturated monomer represented by the general formula (5) include N-vinylformamide (R ⁶ = H, R ⁷ = H) and N-vinyl acetamide (R ⁶ = H, R ⁷ = CH ₃₎ ) Are exemplified.

When the repeating unit having the amidine ring structure represented by the general formula (2) or (3) is formed, the polymerization molar ratio between the ethylenically unsaturated monomer (X) and the nitrile is as follows: Since the performance as an additive for papermaking is better when the ratio of the amidine ring structural unit in the hydrophilic polymer is larger, the ratio is usually 20:80 to 80:20, particularly 40:80.
Preferably, the ratio is 60 to 60:40. If desired, molar ratios outside this range can be employed, for example, polymerization molar ratios with higher proportions of ethylenically unsaturated monomers.

As a method for copolymerizing the ethylenically unsaturated monomer (X) and the nitrile, a usual radical polymerization method is used, and any of bulk polymerization, aqueous solution precipitation polymerization, suspension polymerization, emulsion polymerization and the like are used. be able to. When polymerizing in a solvent, the raw material monomer concentration is usually 5 to 80% by weight,
It is preferably carried out at 20 to 60% by weight. As the polymerization initiator, a general radical polymerization initiator can be used, but an azo compound is preferable, and 2,2'-azobis-2
-Hydrochloride of amidinopropane and the like. The polymerization reaction is generally carried out at 30 to 100 ° C. under an inert gas stream.
Carried out at a temperature of The obtained copolymer can be subjected to the amidination reaction as it is or diluted, that is, in the form of a solution or suspension. In addition, after the solvent is removed and dried by a known method to separate the copolymer as a solid, the copolymer can be subjected to an amidination reaction in a solid state. Incidentally, the obtained polymer is used amount of the radical polymerization initiator,
By adjusting the reaction temperature and the like, one having a desired molecular weight can be appropriately obtained.

The amidination reaction is a two-step reaction in which a substituted amino group of a copolymer is converted into a primary amino group, and then the generated primary amino group is reacted with an adjacent cyano group to form an amidine ring structure, or The copolymer is heated in a water or alcohol solution in the presence of a strong acid or a strong base by a one-step reaction to form an amidine ring structure.
The amidine reaction is preferably a one-step reaction. The one-step reaction is, for example, usually adding a 0.9 to 5 times, preferably 1 to 3 times equivalent of a strong acid, preferably hydrochloric acid, to the substituted amino group of the copolymer, 80-150
° C, preferably at a temperature of 90 to 120 ° C, usually 0.5 to
This is performed by heating for 20 hours. Generally, the higher the equivalent ratio of the strong acid to the substituted amino group and the higher the reaction temperature, the more amidination proceeds. In addition, upon amidine formation, usually 10% by weight based on the copolymer used for the reaction.
At least 20% by weight of water is present in the reaction system.

The cationic polymer (B) thus obtained usually contains 20 to 90 repeating units of the amidine ring structure represented by the general formula (2) and / or (3).
About 0 to 2 mol%, and about 0 to 2 mol% of repeating units derived from the ethylenically unsaturated monomer (X), and 0 to 70 mol% of repeating units derived from the nitriles.
About 0 to 70 mol% of repeating units derived from the converted product (primary amino group) of the ethylenically unsaturated monomer (X).

In the cationic polymer (B), the one having a larger number of repeating units having an amidine ring structure generally has better performance as an additive for papermaking, so that the above formula (2) and / or (3) The repeating unit of the represented amidine ring structure is 0.5 to 10 times the repeating unit of nitriles,
Preferably, the ratio is 2 to 5 times.

The repeating unit derived from the primary amino group is cationic, and is considered to contribute effectively to the performance as a drainage improver like the repeating unit having an amidine ring structure. Therefore, the content of the repeating unit derived from the primary amino group is preferably 5 to 60 mol%. In addition, the total of the cation units including the repeating units having an amidine ring structure represented by the general formulas (2) and / or (3), and further including the repeating units derived from a primary amino group, is generally at least 40 mol%, preferably at least 40 mol%. 60 to 95 mol%. However, the repeating unit having the amidine ring structure represented by the general formula (2) and / or (3) is considered to contribute more effectively to the performance of the papermaking additive than the repeating unit derived from the primary amino group. The repeating unit having an amidine ring structure represented by the general formula (2) and / or (3) is 0.5% of the repeating unit derived from a primary amino group.
It is preferably 10 to 10 times, preferably 2 to 5 times.

Since the cationic polymer (B) generally has poor storage stability as it is, it is necessary to add a strong acid to completely neutralize the cationic unit of the amidine ring structure and the primary amino group. preferable.

The (B) cationic polymer having a repeating unit represented by the general formula (4) as a repeating unit having an amidine ring structure is obtained by polymerizing the ethylenically unsaturated monomer (X). It is formed by converting a part of the substituted amino group of the monomer into a primary amino group and amidating the substituted amino group with a primary amino group generated by a conversion reaction. The amidine treatment is usually carried out in a solvent at about 50 to 110 ° C. for about 1 to 72 hours.
The reaction is usually carried out under stirring, and usually under normal pressure, but may be pressurized if necessary. When the reaction temperature is 5
If the temperature is lower than 0 ° C., the reaction rate is too slow, which is not efficient. On the other hand, if the temperature is higher than 110 ° C., a cross-linking reaction or the like is likely to occur as a side reaction, which is not preferable because it may be insoluble. The repeating unit of the amidine ring structure represented by the general formula (4) is preferably at least 20 mol%.

The cationic polymer (B) of the present invention may contain a repeating unit derived from an anionic vinyl monomer. Generally, when polymerizing the ethylenically unsaturated monomer (X) and the like, an anionic vinyl monomer is copolymerized. Examples of the anionic vinyl monomer include the same ones as those used in (A). The amount of the anionic vinyl monomer to be used is generally preferably about 0 to 20 mol% of all the constituent monomers,
15 mol% is more preferred. In the cationic polymer (B), generally, 0 to 5 mol of a repeating unit derived from (meth) acrylic acid can be generated by hydrolysis of a repeating unit derived from (meth) acrylonitrile.

Further, the cationic polymer (B) of the present invention may further contain a repeating unit derived from (meth) acrylamide in addition to the above-mentioned repeating unit.
Further, a repeating unit derived from (meth) acrylamide and a repeating unit derived from (meth) acrylic acid may form a lactam ring.

The cationic polymer (B) of the present invention is 1 m
ol / l saline solution at 0.1 g / dl, 25
The value of the reduced viscosity measured at 0 ° C is 0.1 to 10 dl / g. Preferably it is 1 to 10 dl / g, more preferably 0.1 to 10 dl / g.
5 to 4 dl / g.

In the present invention, the above-mentioned (A) amphoteric polyacrylamide and (B) the cationic polymer are each added to a pulp slurry as a papermaking additive to form a paper. By adding (A) amphoteric polyacrylamide and (B) a cationic polymer to the pulp slurry, some interaction occurs between the two and the fixation rate to the pulp is improved, and higher drainage and paper strength are achieved. It produces effects and the like.

The method for adding the papermaking additive is as follows:
Addition for papermaking, like adding amphoteric polyacrylamide and then (B) adding cationic polymer, (B) adding cationic polymer and then (A) adding amphoteric polyacrylamide The method may be a method of sequentially adding the agents, or a method of simultaneously adding (A) an amphoteric polyacrylamide and (B) a cationic polymer. As described above, various methods of adding the papermaking additive can be adopted sequentially or simultaneously. However, the method of adding (B) a cationic polymer and then adding (A) an amphoteric polyacrylamide is adopted. However, it is preferable in terms of improving drainage.

Various means can be used for papermaking. The papermaking additive may be added to the pulp slurry before or after the addition of the sulfuric acid band to the pulp slurry. However, it is more preferable that the interval between the addition of the papermaking additive and the addition of the sulfuric acid band is with a certain time interval. Also, since it is desirable to make paper immediately without applying unnecessary share to the generated floc,
It is preferable to add the papermaking additive at a location near the papermaking wire section. In particular, the addition at the fan pump suction port is preferable because the drainage and paper strength are improved. The pH of the pulp slurry can be generally selected from a wide range of 4 to 9. The (A) amphoteric polyacrylamide and / or (B) the cationic polymer in the papermaking additive may be appropriately diluted with water, alcohol, or the like, if necessary.

The amount of the (A) amphoteric polyacrylamide and / or (B) the cationic polymer used as the papermaking additive may be the same as usual, and the total amount thereof is calculated based on the weight of the solid content in the pulp. On the other hand, about 0.005 to 3% by weight,
Preferably, the content is about 0.01 to 1% by weight. The proportion of the (A) amphoteric polyacrylamide and the (B) cationic polymer used is usually the solid content weight ratio of (A)
/ (B) is in the range of 99.5 / 0.5 to 50/50, preferably 99/1 to 70/30. The sulfate band is usually 0.5 to 10% by weight based on the pulp solid content.

[0045]

The paper obtained by the method for producing paper of the present invention is excellent in various effects such as drainage, paper strength and the like.
The range of H is wide and excellent in operability. In particular, the papermaking pH is excellent in the acidic to neutral range.

[0046]

The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In each example, all parts and percentages are by weight unless otherwise specified.

Production Example 1 (Production of amphoteric polyacrylamide) Powdered acrylamide 294.4 was placed in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube.
Parts (89.5 mol% based on the total mol of monomers, the same applies hereinafter), 6.5 parts of 62.5% sulfuric acid, 14.5 parts (2 mol%) of N, N-dimethylaminoethyl methacrylate, 8
0% aqueous solution of acrylic acid 16.7 parts (4 mol%) itaconic acid 12 parts (2 mol%), sodium methallyl sulfonate 11
Parts (1.5 mol%), 4.6 parts (1 mol%) of N, N-dimethylacrylamide and 1300 parts of ion-exchanged water (monomer concentration: 21%), and oxygen in the reaction system was removed through nitrogen gas. The temperature of the system was adjusted to 40 ° C., and 9.8 parts of a 5% aqueous ammonium persulfate solution and 4 parts of a 5% aqueous sodium bisulfite solution were added as a polymerization initiator with stirring.
After the temperature was raised to 90 ° C., the temperature was kept for 2 hours. After polymerization,
105 parts of ion-exchanged water (adjusted to a solid content of 20%) were charged, and the pH was 3.9, the solid content was 20.1%, and the viscosity was 25 ° C.
Was 8500 cps, and a copolymer aqueous solution having a weight average molecular weight of 3,000,000 was obtained. Hereinafter, this aqueous solution is referred to as A-1. The weight-average molecular weight is measured by a low angle light scattering method (GPC).
PH 4.2 by LALLS (manufactured by Tosoh Corporation)
Using an aqueous solution containing acetic acid and sodium acetate as a moving bed,
It was measured at a sample concentration of 0.0125%.

Production Example 2 Powdered acrylamide 288.7 was placed in a four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube.
Parts (89.5 mol% based on the total mol of monomers, the same applies hereinafter), 62.5% sulfuric acid 19.2 parts, N, N-dimethylaminoethyl methacrylate 42.8 parts (6 mol%),
8.2 parts (2 mol%) of 80% aqueous solution of acrylic acid 5.9 parts (1 mol%) of itaconic acid, 3.6 parts (0.5 mol%) of sodium methallylsulfonate, N, N-dimethylacrylamide 2 .2 parts (0.5 mol%) and ion-exchanged water 1
300 parts (monomer concentration: 21%) were charged, and oxygen in the reaction system was removed through nitrogen gas. The temperature of the system was adjusted to 40 ° C., and 9.8 parts of a 5% aqueous ammonium persulfate solution and 4 parts of a 5% aqueous sodium bisulfite solution were added as a polymerization initiator with stirring. After the temperature was raised to 90 ° C., the temperature was kept for 2 hours. After completion of the polymerization, 105 parts of ion-exchanged water (adjusted to a solid content of 20%) were added, and the pH was 3.9, the solid content was 20.1%, the viscosity (25 ° C.) was 7,500 cps, and the weight average molecular weight was 260.
10,000 copolymer aqueous solutions were obtained. Hereinafter, this aqueous solution is referred to as A-2.
And

Comparative Production Example 1 Powdered acrylamide 309.2 was placed in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube.
Parts (92 mol%, based on the total mol of monomers, the same applies hereinafter), 62.5% sulfuric acid 6.7 parts, N, N-dimethylaminoethyl methacrylate 14.9 parts (2 mol%), 80 parts
% Acrylic acid aqueous solution 17 parts (4 mol%), itaconic acid 1
2.3 parts (2 mol%), 1300 parts of ion-exchanged water, and 17.5 parts of isopropyl alcohol were charged, and oxygen in the reaction system was removed with nitrogen gas. Next, 24.5 parts of a 5% aqueous solution of ammonium persulfate and 10 parts of a 5% aqueous solution of sodium hydrogen sulfite were added as a polymerization initiator under stirring, and the temperature was raised from room temperature to 80 ° C., and the temperature was maintained for 3 hours. Thereafter, 650 parts of ion-exchanged water was added, the pH was adjusted to 5 with 48% sodium hydroxide solution, the solid content was 15.2%, and the viscosity (25%).
° C) and an aqueous solution of a copolymer having a weight average molecular weight of 230,000 cps. Hereinafter, this aqueous solution is referred to as C-1.

Comparative Production Example 2 Powdered acrylamide 300.2 was placed in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube.
Parts (88 mol%, based on the total moles of monomers, the same applies hereinafter), 38.9 parts (9 mol%) of an 80% aqueous solution of acrylic acid, 6.2 parts (1 mol%) of itaconic acid, sodium methallylsulfonate 7.6 parts (1 mol%), 4.8 parts (1 mol%) of N, N-dimethylacrylamide and 1300 parts of ion-exchanged water (monomer concentration 21%) were charged, and oxygen in the reaction system was removed through nitrogen gas. . The temperature in the system was adjusted to 40 ° C., and 7 parts of a 5% aqueous ammonium persulfate solution and 3 parts of a 5% aqueous sodium bisulfite solution were charged as a polymerization initiator with stirring. After the temperature was raised to 90 ° C., the temperature was kept for 2 hours. After completion of the polymerization, 70 parts of ion-exchanged water (adjusted to a solid content of 20%) was added, and the pH was 4.0, the solid content was 20.2%, the viscosity (25 ° C.) was 7000 cps, and the weight average molecular weight was 250.
10,000 copolymer aqueous solutions were obtained. Hereinafter, this aqueous solution is referred to as C-2.
And

[0051]

[Table 1]

In the table, AM: acrylamide, DM: N,
N-dimethylethyl methacrylate, AA: acrylic acid, IA: itaconic acid, SMAS: sodium methallylsulfonate, DMAA: N, N-dimethylacrylamide.

Production Examples 3 to 6 (Production of cationic polymer having amidine ring structure) In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, the charged units shown in Table 2 were added. 60 g of the monomer mixture and 340 g of ion-exchanged water were charged. After the temperature was raised to 45 ° C. while stirring in a nitrogen gas stream, 10
% Of an aqueous 2,2'-azobis-2-amidinopropane dihydrochloride solution was added. After stirring and maintaining at 45 ° C. for 4 hours, the temperature was raised to 60 ° C. and further maintained for 3 hours to obtain a suspension in which a polymer was precipitated in water. The suspension contains 200
Then, 2 equivalents of concentrated hydrochloric acid was added to the formyl group in the polymer, and the mixture was kept at 90 ° C. for 4 hours with stirring to amidine the polymer. The obtained polymer solution was added to acetone to cause precipitation, and this was vacuum-dried to obtain polymers B-1 to B-4. Analysis results of polymer composition,
Table 2 shows the reduced viscosities.

[Method of Analyzing Polymer Composition] Each of the polymers B-1 to B-1
B-4 was converted to an absorption peak corresponding to each repeating unit of a ¹³ C-NMR spectrum ( ¹³ C-nuclear magnetic resonance spectrum).
Calculated from the integrated value of

[Measurement of Reduced Viscosity] Each of the polymers B-1 to B-
4 was prepared as a 0.1 g / dl solution in 1 mol / l saline at 25 ° C., and the reduced viscosity was measured with an Ostwald viscometer.

[0056]

[Table 2]

In Table 2, NVF represents N-vinylformamide, AN represents acrylonitrile, and AA represents acrylic acid.

Examples 1 to 19, Comparative Examples 1 to 5 A-1 to A-2 obtained in Production Examples 1 and 2, Comparative Production Example 1
C-1 to C-2 obtained in Preparation Examples 2 to 2, B-1 to B-4 obtained in Production Examples 3 to 6 or PS311 (Hoffman-modified polyacrylamide-based paper strength agent: manufactured by Arakawa Chemical Industries, Ltd.) In Test Example 1 or Test Example 2 in the order and ratio as shown in Table 3.
And added to the pulp slurry.

Test Example 1 L-BKP was beaten with a Niagara beater, and Canadian Standard Freeness (CSF) 42 was used.
The sulfuric acid band (Al) was added to the pulp slurry adjusted to 8 ml.
um) was added to a pulp solid content ratio of 2% to pH 4.7, and then the papermaking additives shown in Table 3 were sequentially added at one-minute intervals (the total amount of the papermaking additives used was The pulp solid content ratio was adjusted to 0.3% or 0.6%). The pulp slurry thus obtained was paper-made using a tappy sheet machine to a basis weight of 100 g / m ^2, and 4 kg
/ Cm ² for 4 minutes. Then, it is dried at 110 ° C. for 3 minutes in a rotary dryer, and is dried at 20 ° C. and 65% R.C.
H. And then subjected to a paper quality test for 24 hours. The drainage was measured according to JIS P-8121.
In addition, the paper quality measuring method is as follows. Compressive strength: JI
SP-8126. Burst strength: JIS P8131. Table 4 shows the results.

Test Example 2 L-BKP was beaten with a Niagara beater, and Canadian Standard Freeness (CSF) 42 was used.
The sulfuric acid band (Al) was added to the pulp slurry adjusted to 8 ml.
um) was added to a pulp solid content ratio of 2% to pH 4.7, and then the papermaking additives shown in Table 3 were added almost simultaneously without an interval (the total amount of papermaking additives used was: Adjusted to a pulp solids ratio of 0.3% or 0.6%).
The pulp slurry thus obtained was paper-made using a tappy sheet machine so as to have a basis weight of 100 g / m ^2, and was press-dewatered at 4 kg / cm ² for 4 minutes. Next, it is dried at 110 ° C. for 3 minutes in a rotary drier,
65% R. H. And then subjected to a paper quality test for 24 hours. The drainage was measured according to JIS P-8121. In addition, the paper quality measuring method is as follows. Compressive strength: JIS P-8126. Burst strength: JIS P81
31. Table 5 shows the results.

Test Example 3 A cardboard waste paper was beaten with a Niagara beater, and Canadian Standard Freeness (CSF) 4 was used.
The sulfuric acid band (A) was added to the pulp slurry adjusted to 50 ml.
lum) is added to the mixture at a pH of 6.
2, and then the papermaking additives shown in Table 3 were sequentially added at one-minute intervals (the total amount of the papermaking additives used was adjusted to a pulp solid content ratio of 0.3% or 0.6%). did). The pulp slurry thus obtained was paper-made using a tappy sheet machine so as to have a basis weight of 150 g / m ^2.
Press dewatering was performed for 4 minutes at kg / cm ² . Then, it is dried at 110 ° C. for 4 minutes in a rotary dryer, and is dried at 20 ° C. and 65%
R. H. For 24 hours. The same operation as in Example 1 was performed to measure drainage, compressive strength and burst strength. Compressive strength: JIS P8126. Burst strength:
According to JIS P8131. Table 6 shows the results.

Test Example 4 Recycled corrugated paper was beaten with a Niagara beater to obtain Canadian Standard Freeness (CSF) 4.
The sulfuric acid band (A) was added to the pulp slurry adjusted to 50 ml.
lum) is added to the mixture at a pH of 6.
2, and then the papermaking additives shown in Table 3 were added at almost the same time without a gap (the total amount of papermaking additives used was 0.3% or 0.6% of the pulp solids ratio. It was adjusted). The pulp slurry thus obtained was paper-made using a tappy sheet machine so as to have a basis weight of 150 g / m ^2, and was press-dewatered at 4 kg / cm ² for 4 minutes. Then, it is dried at 110 ° C. for 4 minutes in a rotary drier,
0 ° C., 65% R.C. H. For 24 hours. The same operation as in Example 1 was performed to measure drainage, compressive strength and burst strength. Compressive strength: JIS P812
6. Burst strength: according to JIS P8131. Table 7 shows the results.

[0063]

[Table 3]

[0064]

[Table 4]

[0065]

[Table 5]

[0066]

[Table 6]

[0067]

[Table 7]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 BG10X BG13W BJ00X GK04 4L055 AG57 AG65 AG70 AG71 AG72 AG73 AG74 AH16 AH18 AH50 BD10 BD13 EA25 EA29 EA30 FA08 FA13

Claims (8)

[Claims] 1. A solution of (A) amphoteric polyacrylamide having a weight-average molecular weight of 300,000 to 4,000,000 and (B) 0.1 g / dl of a 1 mol / l saline solution were measured at 25 ° C. in a pulp slurry. The value of the reduced viscosity is 0.1 to 10
A method for producing paper, comprising adding a cationic polymer having an amidine ring structure of dl / g as a repeating unit sequentially or simultaneously and paper-making. 2. After adding (A) amphoteric polyacrylamide having a weight average molecular weight of 300,000 to 4,000,000 to a pulp slurry, (B) 0.1 g / dl of 1 mol / l saline solution.
Of the reduced viscosity measured at 25 ° C. is 0.1
The method for producing paper according to claim 1, wherein a cationic polymer having an amidine ring structure of 10 to 10 dl / g as a repeating unit is added. 3. A pulp slurry containing (B) 1 mol / l
After adding a cationic polymer having an amidine ring structure having a reduced viscosity value of 0.1 to 10 dl / g as a repeating unit at 25 ° C. as a 0.1 g / dl solution in a saline solution of (A), The method for producing paper according to claim 1, wherein a) amphoteric polyacrylamide having a weight average molecular weight of 300,000 to 4,000,000 is added. (A) An amphoteric polyacrylamide having the general formula (1): CH ₂ ＣC (R ¹ ) -CONR ² (R ³ )
(R ¹ is a hydrogen atom or a methyl group; R ² is a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms;
³ comprises a N-substituted (meth) acrylamide represented by a linear or branched alkyl group having 1 to 4 carbon atoms) and / or a polyfunctional monomer as a constituent monomer. A method for producing paper as described in Crab. 5. The method for producing paper according to claim 1, wherein (A) the amphoteric polyacrylamide contains (meth) allylsulfonic acid or a salt thereof as an anionic component. (A) An amphoteric polyacrylamide comprising, as an anionic component, α, β-unsaturated monobasic acid, α, β-
The method for producing paper according to any one of claims 1 to 5, further comprising at least one of unsaturated dibasic acids and salts thereof. 7. The repeating unit (B) having an amidine ring structure of a cationic polymer has a general formula (2): , General formula (3): General formula (4): (Wherein R ⁴ and R ⁵ each represent a hydrogen atom or a methyl group, and X ⁻ represents an anion, respectively).
The method for producing paper according to any one of the above. 8. The method for producing paper according to claim 1, wherein the repeating unit having an amidine ring structure in the repeating unit (B) is from 20 to 90 mol%.