JP2005054311A - Method for producing paper and paperboard - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing paper and paperboard, corresponding to improvement of utilization ratio of waste paper in recent years, improvement of formulation ratio of broke pulp and closing of the system and suppressing pitch, decreasing defect and further not breaking formation and improving drainage property and yield and enabling improvement of productivity such as decrease of broken paper and production speed-up. <P>SOLUTION: The method for producing paper and paperboard comprises adding a water-soluble cationic high molecular subsidiary polymer to a paper stock, adding a water-soluble cationic high molecular main polymer through at least one shearing step to the paper stock, further adding anionic organic polymer fine particles through at least one shearing step to the paper stock, dehydrating the paper stock having polymers to form a sheet and drying the sheet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing paper and paperboard, and in particular, an anionic organic polymer after adding a water-soluble cationic polymer subpolymer to a paper material and then adding a water-soluble cationic polymer main polymer. By adding fine particles, even with a paper with a lot of anionic trash, while suppressing the deterioration of the texture, drastically improved the drainage and yield, as well as side effects such as poor workability and scale generation. The present invention relates to a paper and paperboard manufacturing method for solving obstacles.

  In recent years, in the manufacture of paper and paperboard, an increase in the utilization rate of waste paper, an improvement in the blending ratio of broke pulp, the closure of the system, etc., and the increase in anionic impurities in the raw material, so-called anion trash, Not only the occurrence of pitch and defects, but also a drop in productivity such as paper breaks and production speed reduction.

  In response to such problems, US Pat. No. 4,388,150 describes a method for improving the yield by adding cationic starch and colloidal silica to the stock before dehydration, which is a registered trademark “Composil”. As commercialized. EP 235893 (corresponding to JP 62-191598 A) also describes a first synthetic cationic polymer prior to a specific shearing step in order to improve drainage, retention, drying and formation properties. And adding a bentonite after the shearing step is disclosed and is commercialized under the registered trademark “Hydrocol”.

  However, the methods of these registered trademarks “Composil” and “Hydrocol” have not yielded a satisfactory effect in terms of yield effect, particularly in the yield of filler. Increasing the amount of filler added improves yield, but in this case there is a problem that the texture of the product decreases. Furthermore, when bentonite is used, it takes time for dissolution, and when using colloidal silica, the concentration of active ingredients is low, which increases transportation costs. There is a problem that the quality deteriorates.

  In Japanese Patent Publication No. 5-29719 (Patent No. 21287702), a cationic polymer having a molecular weight lower than that of the main polymer is added before the main cationic polymer, and finally an anionic inorganic substance is added. A method for improving drainage is described. However, this method has a problem that the yield, in particular, the improvement of the yield effect of the filler is not remarkable.

Furthermore, Japanese Patent No. 2948358 discloses a yield improving method in which a cationic polymer and anionic polymer fine particles are contained in a paper stock. However, this method has a problem that the yield effect is remarkably lowered particularly when there are many anionic impurities in the stock, so-called anion trash.
USP 4,388,150 Publication EP235893 Japanese Patent Publication No. 5-29719 Japanese Patent No. 2948358

  The present invention responds to the recent improvement in the utilization rate of waste paper, the improvement in the blending ratio of broke pulp, and the close-up of the system, etc. Even with a stock with a lot of anionic trash, the pitch can be suppressed and defects can be reduced. It is another object of the present invention to provide a method for producing paper and paperboard that does not break down the texture, improves drainage and yield, and improves productivity such as reducing paper breaks and increasing production speed.

  The method for producing paper and paperboard of the present invention comprises a first step of adding a water-soluble cationic polymer subpolymer to a paper stock, and the water stock of the first step through at least one shearing step. A second step of adding a molecular main polymer, a third step of adding anionic organic polymer fine particles to the stock of the second step via at least one shearing step, and dehydrating the stock of the third step And a fourth step of drying after forming into a sheet shape.

  A problem in the prior art in which a cationic polymer and anionic inorganic fine particles typified by bentonite and colloidal silica are used together is that the cohesive force between the cationic polymer and the anionic inorganic fine particles is not sufficient. This is because when the anionic trash component increases, the cohesive force further decreases, and a sufficient yield effect cannot be obtained.

  In the present invention, a water-soluble cationic polymer subpolymer (hereinafter sometimes referred to as “cationic subpolymer”) is added as a cationic polymer for patch formation, and then a water-soluble cationic polymer main polymer (hereinafter referred to as “cationic subpolymer”). After adding the anionic organic polymer fine particles, the bonding portion between the cationic polymer and the anionic organic polymer fine particles is sufficiently secured, Get strong interaction between cationic polymer and anionic organic polymer fine particles, not only to reduce pitch and reduce defects, but also to improve the drainage and retention, and to reduce paper breakage To improve productivity, such as speeding up production. Here, the formation of the patch means a phenomenon in which the cationic polymer is locally adsorbed on a solid anionic surface such as pulp fiber or filler, and the site becomes cationic.

  As described above, the details of the mechanism of action of the paper and paperboard production method of the present invention in which the cationic subpolymer, the cationic main polymer, and the anionic organic polymer fine particles are sequentially added have not yet been fully elucidated. It is estimated as follows.

The addition of the cationic subpolymer for forming the patch has the following two functions (1) and (2).
(1) By partially neutralizing the anionic trash with the cationic secondary polymer, the cationic main polymer added next is reduced from being consumed by the anionic trash, and the cationic main polymer is more effective. Make it easier.
(2) A cationic secondary polymer for patch formation is added to the stock and includes pulp fibers (in addition to any solids present in the stock such as fillers. Hereinafter, they may be referred to as “fibers”). ) Once agglomerate each other, but after being dispersed by the shearing force in the paper preparation step, a cationic patch is formed on the surface of the fiber and the like, and then the cationic main polymer added is Due to the repulsion between the cationic polymers, it takes a form such as a tail or a loop, and makes it difficult to become flat, thereby improving the binding property with the anionic organic polymer fine particles.

  The operation (2) will be further described with reference to FIGS. When the cationic main polymer 2 is added directly to the fiber 1 or the like as in the prior art, the cationic main polymer 2 adsorbed on the fiber 1 or the like in a tail shape or a loop shape as shown in FIG. With time, it changes into a flat shape as shown in FIG. The flat cationic main polymer 2 ′ cannot sufficiently secure the bonding portion with the anionic fine particles, and as a result, the interaction cannot be sufficiently obtained and the aggregation effect becomes insufficient.

  On the other hand, a cationic subpolymer for patch formation is added according to the present invention, and as shown in FIG. 1 (a), the cationic subpolymer 3 is adsorbed on the surface of the fiber 1 or the like to form a patch. When the cationic main polymer 2 is added, the cationic main polymer 2 is adsorbed to the fiber 1 or the like in the form of tail (2A) or loop (2B) due to repulsion with the cationic subpolymer 3, and becomes flat. hard. As described above, the cationic main polymers 2A and 2B adsorbed to the fiber 1 or the like in a tail shape or a loop shape have many bonding portions with the anionic organic polymer fine particles, and cause a strong interaction with the anionic organic polymer fine particles. Thus, a remarkably high yield effect can be obtained with a remarkably high agglomeration effect as compared with the conventional method.

In the present invention, since anionic organic polymer fine particles are used as the anionic fine particles, the following excellent effects can be obtained as compared with the case of using anionic inorganic fine particles.
(1) The anion degree can be designed freely.
(2) A dissociation sensitive group can be added according to the purpose.
(3) Since the particle swells and reacts more widely, the effect is superior to inorganic particles.

  According to the paper and paperboard production method of the present invention, a strong interaction between the cationic polymer and the anionic organic polymer fine particles provides a good additive effect, and even in the case of a paper with a lot of anionic trash, the pitch can be reduced. In addition to suppressing and reducing defects, it is possible to improve productivity, such as reducing paper breaks and increasing production speed, as well as improving drainage and yield without destroying the texture.

  Embodiments of the paper and board manufacturing method of the present invention will be described in detail below.

  First, the cationic subpolymer, cationic main polymer and anionic organic polymer fine particles used in the present invention will be described.

  There are no particular restrictions on the monomer component of the cationic subpolymer used in the present invention, but in order to form a patch, the intrinsic viscosity in 1 N saline is 15 dl / g or less and the cationic equivalent is 0.5. Those having physical properties of ˜11 meq / g are desirable. When the intrinsic viscosity in 1 N saline exceeds 15 dl / g, the molecular weight is too large and weak against shearing. When the cationic equivalent is less than 0.5 meq / g, it is difficult to form a patch, and when it exceeds 11 meq / g. It reacts strongly and agglomerated foreign matter is formed. The more preferable intrinsic viscosity is 0.1 to 13 dl / g, and the cation equivalent is 1 to 10 meq / g.

  Specific examples of desirable cationic subpolymers include, for example, polyethyleneimine or a condensation product of polyethyleneamine and epichlorohydrin, a homopolymer of dicyandiamide, or a homopolymer of dimethyldiallylammonium, (meth) acryloyloxyethyltrimethylammonium chloride. Or the copolymer of these and acrylamide is mentioned. These cationic subpolymers may be used alone or in combination of two or more. Among these, a polymer of dimethyldiallylammonium or a copolymer with acrylamide, a polymer of (meth) acryloyloxyethyltrimethylammonium chloride or a copolymer with acrylamide is desirable, and the cationic monomer content is 10 to 10. 100 mol% and acrylamide content of 0-90 mol% are preferable.

  Although there is no restriction | limiting in particular in the monomer structural component of the cationic main polymer used by this invention, As a specific example of a desirable cationic main polymer, the copolymer of the cationic monomer and acrylamide shown by following General formula (1) In order to form a large amount of loop-shaped or tail-shaped adsorption on the surface of the patch formed by the cationic subpolymer, the intrinsic viscosity in 1 N saline is 4 dl / g or more, and the cationic equivalent is 0.1 to 0.1. The thing which has a physical property of 11 meq / g is mentioned.

（但し、ＡはＯ又はＮＨを表し、ＢはＣ_２Ｈ_４、Ｃ_３Ｈ_６又はＣＨ_２ＣＨＯＨＣＨ_２を表し、Ｒ^１はＨ、メチル基、エチル基、ベンジル基又は３−クロロ−２−ヒドロキシプロピル基を表し、Ｒ^２，Ｒ^３，Ｒ^４は各々独立に、Ｈ、炭素数１〜３のアルキル基、アルコキシル基、或いはベンジル基を表し、Ｘ⁻はアニオンを表す。）

(However, A represents O or NH, B represents C ₂ H ₄ , C ₃ H ₆ or CH ₂ CHOHCH ₂ , and R ¹ represents H, a methyl group, an ethyl group, a benzyl group, or 3-chloro-2- A hydroxypropyl group, R ² , R ³ , and R ⁴ each independently represent H, an alkyl group having 1 to 3 carbon atoms, an alkoxyl group, or a benzyl group, and X ⁻ represents an anion.)

  If the intrinsic viscosity of the cationic main polymer in 1N saline is less than 4 dl / g, loop or tail-like adsorption cannot be formed on the patch surface, and the cationic equivalent is less than 0.1 meq / g. Adsorption is not obtained, and when it exceeds 11 meq / g, it strongly reacts to form aggregated foreign matters. The more preferable intrinsic viscosity is 5 to 20 dl / g, and the cationic equivalent is 1 to 10 meq / g.

  The cationic main polymer may be a hydrolyzate of N-vinylformamide polymer. In this case, the intrinsic viscosity in 1N saline is 1 to 15 dl / g, and the cationic equivalent is 0.1 meq. / G or more is preferable.

  If the intrinsic viscosity of this cationic main polymer in 1 N saline is less than 1 dl / g, it is difficult to form loop-like or tail-like adsorption on the patch surface, and if it exceeds 15 dl / g, a large flock is formed and the texture is destroyed. End up. Further, if the cationic equivalent is less than 0.1 meq / g, sufficient adsorbing power cannot be obtained. A more preferable intrinsic viscosity is 3 to 15 dl / g, and a cationic equivalent is 0.5 to 8 meq / g.

  The anionic organic polymer fine particles used in the present invention are preferably the fine particles of A described in claim 2 of Japanese Patent No. 2948358, and when cross-bonded, the diameter is less than about 750 nm and non-cross-linked. And is insoluble in water and has a diameter of less than about 60 nm, and the ionicity of the microparticles is at least -0.1 meq / g or more anionic as a cationic equivalent.

  Examples of such anionic organic polymer fine particles include a microemulsion copolymer in which acrylic acid and acrylamide are cross-linked with N, N′-methylbisacrylamide.

  The anionic organic polymer fine particle is a composition comprising a mixture of an ionic polymer fine particle and a high molecular weight ionic polymer or ionic polysaccharide as described in claim 2 of Japanese Patent No. 2948358. It may be.

  In the present invention, a cationic subpolymer is first added to the stock. Since the cationic subpolymer is added for patch formation, it is important that the cationic subpolymer is sufficiently adsorbed on the surface of the fiber or the like. For this purpose, the cationic subpolymer is preferably added before the fan pump in which the white water and the paper are mixed. The addition rate of the cationic subpolymer is preferably 0.002 to 0.5% by weight, more preferably 0.005 to 0.2% by weight, based on the dry paper stock.

  After the cationic subpolymer is added to form the patch, the cationic main polymer is added. The cationic main polymer is added after at least one shearing step after the cationic subpolymer is added. Preferably, the white water and the paper stock are added after being mixed. For example, it is added after the fan pump and the most desirable addition location is just before the machine screen. A preferable addition ratio of the cationic main polymer is 0.002 to 0.5% by weight, and more preferably 0.005 to 0.1% by weight with respect to the dry paper stock.

  After the addition of the cationic main polymer, anionic organic polymer fine particles are added. The anionic organic polymer fine particles are added after at least one shearing step after the cationic main polymer is added. For example, when the cationic main polymer is added before the second fan pump, the anionic organic polymer fine particles are added after the second fan pump, and when the cationic main polymer is added before the machine screen. The anionic organic polymer fine particles are preferably added after the machine screen. The preferred addition rate of the anionic organic polymer fine particles is 0.002 to 0.5% by weight, more preferably 0.005 to 0.1% by weight, based on the dry paper.

  If any of the cationic subpolymer, the cationic main polymer, and the anionic organic polymer fine particles has an addition rate lower than the above range, a sufficient addition effect cannot be obtained, and if the addition rate is large, the texture is destroyed.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

  In addition, the additive used in the following Examples and Comparative Examples is as follows. In the following, “part” means “part by weight”.

(1) Additives used in the examples

(2) Details of Anionic Organic Polymer Fine Particle “C” Used in Examples: Acrylic acid / acrylamide / N, N′-methylenebisacrylamide copolymer: N, N′-methylenebisacrylamide (MBAAm) at 349 ppm A cross-linked microemulsion copolymer of 30 mol% sodium acrylate (AA) and 70 mol% acrylamide (AAm) with a particle size of 130 nm.

  The above-mentioned anionic organic polymer fine particles were produced by the following method.

  Sequentially, 147 parts of acrylic acid, 200 parts of deionized water, 144 parts of 56.5% by weight sodium hydroxide, 343.2 parts of acrylamide crystals, 0.3 part of 10% by weight diethylenetriaminepentaacetic acid pentasodium, and 39. An aqueous phase was prepared by mixing 0 parts and 1.5 parts of 0.52 wt% copper sulfate pentahydrate. To 110 parts of the resulting aqueous phase solution was added 0.25 parts of 1 wt% t-butyl hydroperoxide and 3.50 parts of 0.61 wt% N, N'-methylenebisacrylamide. Next, 120 parts of the aqueous phase was mixed with an oil phase containing 77.8 parts of paraffin oil, 3.6 parts of fatty acid sorbitan (containing oleic acid) and 21.4 parts of polyoxyethylene sorbitol hexaoleate.

The resulting clear microemulsion was degassed with nitrogen for 20 minutes. Polymerization was initiated using gaseous SO ₂ , the exotherm was brought to 40 ° C. and controlled to 40 ° C. using ice water. The ice water was removed when no further cooling was required. Thereafter, nitrogen was passed through for 1 hour to obtain a polymer.

(3) Anionic inorganic fine particles used in comparative examples Colloidal silica: Commercially available colloidal silica having an average particle size of 5 nm stabilized by alkali (trade name “BMA780” manufactured by Eka Chemicals)
Bentonite: a commercially available anionic swelling bentonite made of sepiolite, attapulgite or montmorillonite (Ciba Specialty Chemicals, trade name “Orgaoosorb O”)

Moreover, the following measuring apparatus was used for the yield rate measurement of a filler, and the measurement of a formation index.
Yield rate of filler: Made by Mutech, drainage yield tester “DFS (Dynamic Filtration System)”
Ground index: “3-D Sheet Analyzer” manufactured by M / K System Inc.

Examples 1 to 9, Comparative Examples 1 to 6: Examples of neutral medium paper From a certain paper mill, pulp samples of LBKP (hardwood bleached kraft pulp), NBKP (softwood bleached kraft pulp), DIP (waste paper pulp), After collecting the white water of the actual machine and weighing the above pulp samples so that LBKP 40%, NBKP 20%, DIP 40% (all dry weight%, the same applies hereinafter), the following two (i) and (ii) A cationic subpolymer (patch forming polymer) was added by the method (however, in Comparative Examples 1 to 3, no cationic subpolymer was added).
(i) A cationic subpolymer was added to a DIP sample, and immediately after shearing with a stirrer at 800 rpm for 40 seconds to break the floc, it was mixed with each pulp sample of LBKP and NBKP.
(ii) The cationic subpolymer was added to the stock containing the three kinds of pulp samples at the above ratio, and then immediately sheared with a stirrer at 800 rpm for 40 seconds to break the floc.

  Next, white water is added to the stock obtained by any of the addition methods, and after adjusting so that the concentration per dry weight of the mixed pulp sample is 0.8% by weight, the mixture is again put into the stirrer, Shear was applied at 800 rpm for 40 seconds to break the floc.

  Each stock (A) thus obtained was put into a yield tester “DFS”, and a sulfuric acid band (aluminum sulfate) was added to 1.5% by weight of dry pulp and cationized starch (“Cato-” manufactured by NSC). 3212 ") with respect to dry pulp 0.5% by weight, sizing agent (" NT-87 "manufactured by Arakawa Chemical Industries, Ltd.) 0.25% by weight with respect to dry pulp, calcium carbonate (" TP-12L "manufactured by Okutama Kogyo Co., Ltd.) Were added in the order of 10% by weight of dry pulp and the main cationic polymer, followed by the addition of anionic fine particles, and the filtrate (B) was collected (the DFS setting conditions used the recommended method of Mutek). Shearing by the tester is applied by applying standard agitation).

  Table 2 shows the types and addition amounts of the cationic subpolymer, cationic main polymer and anionic fine particles used in each example.

The concentration of the filler in the collected filtrate (the filler content was according to ash measurement method “ISO1762-1974”) was measured, and the yield rate of the filler was calculated according to the following formula.
Yield rate of filler = [1-ash content of filtrate (B) / ash content of paper material (A)] × 100%

  A handmade sheet was prepared using the paper stock prepared by the same ratio and method as described above, and the texture index was measured.

  Table 2 shows the results of the test using the yield tester and the results of measuring the texture index of the handsheets. As is clear from Table 2, in Examples 1-9, the yield of the filler was improved and the texture was better than in Comparative Examples 1-6.

Examples 10 to 19 and Comparative Examples 7 to 12: Examples of neutral high-quality paper LBKP, NBKP, each pulp sample of coat broke and white water of actual machine were collected from the same paper mill as in Example 1, and LBKP 60%, NBKP 20% The pulp sample was weighed so that the coat broke was 20%, and then a cationic subpolymer (patch-forming polymer) was added by the following two methods (iii) or (iv) (however, Comparative Example 7) No addition of the cationic subpolymer in -9, and addition in both (iii) and (iv) in Examples 18 and 19. That is, after adding to the coating broke in advance, three kinds of pulp samples were blended. Post addition.).
(iii) A cationic subpolymer was added to the coated broke sample, immediately sheared with a stirrer at 800 rpm for 40 seconds to break the floc, and then mixed with each of the LBKP and NBKP pulp samples.
(iv) The cationic subpolymer was added to the stock containing the three types of pulp samples in the above ratio, and immediately sheared with a stirrer at 800 rpm for 40 seconds to break the floc.

  Next, after adding white water to the paper stock of any addition method and adjusting the concentration of the mixed pulp sample per dry weight to 0.8% by weight, the yield tester “DES” And 1.5% by weight of sulfuric acid band with respect to dry pulp and 0.5% by weight of cationized starch (Cato-3212) with respect to dry pulp, and then sizing agent (NT-87) with respect to 0.1% by weight of dry pulp. 25% by weight, calcium carbonate (TP-121) was added in the order of 10% by weight of dry pulp and cationic main polymer, followed by the addition of anionic fine particles, and the filtrate was collected. (Shearing by the tester was applied by applying standard conditions of agitation).

  Table 3 shows the types and addition amounts of the cationic subpolymer, cationic main polymer and anionic fine particles used in each example.

  For the collected filtrate, the yield rate of the filler was determined in the same manner as in Example 1, and the texture index of the handsheet was measured in the same manner as in Example 1. The results are shown in Table 3. As is clear from Table 3, in Examples 10 to 19, the filler yield was improved and the texture was better than Comparative Examples 7 to 12.

Example 20, Comparative Example 13: Example of addition to actual machine (production of neutral high-quality coated base paper)
The results of application to a machine that makes neutral coated high-quality coated paper are shown.

  In this machine, a cationic polymer was added at 100 g / ton per dry weight (both g-effective component / ton-dry raw material) before the screen, and bentonite was added at 100 g / ton per dry weight after the screen to produce paper. It was. The average filler yield rate at this time was 20.2%, and the average texture index was 7.8 (Comparative Example 13).

  In Example 20, the cationic polymer of A-4 in Table 1 as a cationic subpolymer was added to the coat broke chest at 100 g / ton per dry weight of the final product, and the cationic main polymer in Table 1 was added. The cationic polymer of B-1 was added at 100 g / ton per dry weight of the final product, and anionic organic polymer fine particles C were added at 100 g / ton per dry weight of the final product after the screen.

  As a result, the yield rate of the filler increased to 31.7% and the formation index improved to 9.6.

  These results are shown in Table 4.

  According to the paper and paperboard manufacturing method of the present invention, even a paper with a lot of anionic trash not only suppresses the pitch and reduces defects, but also does not break the texture and improves the drainage and yield. At the same time, it is possible to improve productivity by reducing the number of paper breaks and speeding up production. Therefore, the production of paper and paperboard corresponding to the recent improvement in the utilization rate of used paper, the improvement in the blending ratio of broke pulp, the closure of the system, etc. Can be implemented.

It is a schematic diagram explaining the action mechanism of the aggregation effect by this invention. It is a schematic diagram explaining the cause of the cohesion fall in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fiber etc. 2 Cationic main polymer 2 'Flat-shaped cationic main polymer 2A Tail-shaped cationic main polymer 2B Loop-shaped cationic main polymer 3 Cationic subpolymer (patch)

Claims (5)

A first step of adding a water-soluble cationic polymer subpolymer to the stock;
A second step of adding a water-soluble cationic polymer main polymer to the stock of the first step through at least one shearing step;
A third step of adding the anionic organic polymer fine particles to the stock of the second step through at least one shearing step;
A paper and paperboard manufacturing method comprising: a fourth step of dehydrating the paper stock of the third step to form a sheet and then drying.   The water-soluble cationic polymer subpolymer has physical properties such that an intrinsic viscosity in 1 N saline is 15 dl / g or less and a cationic equivalent is 0.5 to 11 meq / g. A method for producing the paper and paperboard described in 1.   When the anionic organic polymer fine particles are smaller than about 750 nm in diameter when cross-linked, and smaller than about 60 nm in diameter when non-cross-linked and water-insoluble, the ionicity of the fine particles is at least as a cationic equivalent. The method for producing paper and paperboard according to claim 1 or 2, wherein the anionic property is -0.1 meq / g or higher. The water-soluble cationic polymer main polymer is a copolymer of a cationic monomer represented by the following general formula (1) and acrylamide, the intrinsic viscosity in 1 N saline is 4 dl / g or more, and the cationic equivalent is The method for producing paper and paperboard according to any one of claims 1 to 3, wherein the method has physical properties of 0.1 to 11 meq / g.

(However, A represents O or NH, B represents C ₂ H ₄ , C ₃ H ₆ or CH ₂ CHOHCH ₂ , and R ¹ represents H, a methyl group, an ethyl group, a benzyl group, or 3-chloro-2- A hydroxypropyl group, R ² , R ³ , and R ⁴ each independently represent H, an alkyl group having 1 to 3 carbon atoms, an alkoxyl group, or a benzyl group, and X ⁻ represents an anion.)   The water-soluble cationic polymer main polymer is a hydrolyzate of N-vinylformamide polymer, the intrinsic viscosity in 1N saline is 1 to 15 dl / g, and the physical equivalent is a cationic equivalent of 0.1 meq / g or more. The method for producing paper and paperboard according to any one of claims 1 to 3, wherein:

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