TW202012743A - Paper and paperboard production method - Google Patents

Abstract

A paper and paperboard production method: which comprises a papermaking step, which uses a paper stock with a cationic demand of at least 100 [mu]eq/L for the papermaking feedstock; and in which a 200-1000 [mu]eq/g cation charge density, 2.7-18.3 dL/g intrinsic viscosity [eta] cationic polyacrylamide is added to the paper stock in a range of 0.005-0.1 mass% with respect to the total solids of the paper stock.

Description

Paper and cardboard manufacturing method

The invention relates to a method for manufacturing paper and paperboard.

At present, papermaking is carried out by going through a papermaking step of making a raw material slurry prepared by dispersing pulp raw materials in water. In the papermaking step, a large amount of white water containing fine fibers and fillers is discharged from a papermaking machine or the like. From the viewpoint of efficient use and reuse of water resources, the discharged white water is circulated and used in the papermaking step. Papermaking raw materials contain various anionic substances such as resins, sizing agents, fluorescent dyes, and latex. In particular, due to the improvement of the blending rate of deinked pulp, mechanical pulp, and waste paper contained in papermaking raw materials or the reuse of white water, anion trash tends to accumulate and the retention rate decreases during the paper manufacturing process Or, it may cause obstacles such as fibers, fillers, and other additives that are raw materials of paper to form a paper layer on the wire, and then flow out to the white water through the wire.

For example, Patent Document 1 describes a method for suppressing the occurrence of paper defects caused by obstacle substances such as anionic waste, micropitch, and turbidity components, characterized in that the papermaking raw material is diluted before using white water A specific water-soluble polymer (A) is added to it, and then the paper-making raw material is diluted with white water, and then a specific water-soluble polymer (B) is added, and a retention rate improver is suitably added for papermaking. In this method, by adding a specific water-soluble polymer to the papermaking raw material, the charge of the anionic waste is neutralized, and the fine resin and turbidity component are fixed to the pulp fiber. As a result, the unfixed fine resin and turbidity component are prevented Chunking. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2009-249756

[Problems to be solved by the invention] As an indicator of water quality, if the required amount of cations is 100 μeq/L or more (for example, the measured value of a PCD measuring device manufactured by Mutech), the amount of anionic waste increases. If a large amount of various cationic polymers such as coagulant, retention aid, paper strength agent, etc. are added to neutralize the charge of a large amount of anionic waste, a large amount of anionic waste condensed in strong cations will be aggregated, and it will be used in papermaking It is easy to attach to tools and equipment in the process, and the problem of deterioration of the situation occurs frequently. In addition, even in the method described in Patent Document 1, if the amount of anionic waste increases, a sufficient effect cannot be obtained.

The present invention was created in view of this actual situation, and its purpose is to provide a paper and paperboard that can increase the amount of water filtration, increase the retention rate, and reduce the turbidity even when a large amount of anionic waste is contained in white water in the papermaking step Manufacturing method.

[Means to solve the problem] In order to solve the above-mentioned problems, the inventors of the present invention conducted intensive studies and found that the problem can be solved by adding a specific amount of a specific low-cationic polypropylene amide with respect to the solid content of all paper stocks. The present invention has been completed based on these findings.

That is, the disclosure of the present application relates to the following. [1] A method for manufacturing paper and paperboard, which includes a papermaking step using paper stock having a cation requirement of 100 μeq/L or more as a papermaking raw material, and has a content of 0.005 mass% to 0.1 mass relative to the solid content of all paper stocks In the range of %, cationic polypropylene amides with a cationic charge density of 200 μeq/g to 1000 μeq/g and an intrinsic viscosity η of 2.7 dL/g to 18.3 dL/g are added to the paper stock. [2] The method for producing paper and paperboard according to [1], wherein the paper stock is a papermaking raw material containing mechanical pulp. [3] The method for producing paper and paperboard according to the above [1], wherein the paper stock is a paper-making raw material containing 30% by mass or more of deinked pulp. [4] The method for producing paper and paperboard according to [1], wherein the paper stock is a papermaking raw material containing 30% by mass or more of waste paper pulp.

[Effect of invention] According to the present invention, it is possible to provide a method for producing paper and paperboard that can increase the amount of water filtration, increase the retention rate, and reduce turbidity even when a large amount of anionic waste is contained in white water in the papermaking step.

The method of manufacturing paper and paperboard according to an embodiment of the present invention (hereinafter, sometimes referred to as "this embodiment") is characterized by including a papermaking step using paper stock having a cation requirement of 100 μeq/L or more as a papermaking raw material, And the cationic charge density is 200 μeq/g～1000 μeq/g, and the intrinsic viscosity η is 2.7 dL/g～18.3 dL/ in the range of 0.005 mass% to 0.1 mass% relative to the solid content of all paper stocks. g cationic polypropylene amide. In the case of using a paper material with a cation required amount of 100 μeq/L or more as a papermaking raw material, a large amount of anionic waste is contained in white water in the papermaking step. In this regard, in this embodiment, by adding a specific amount of cations with a specific amount of cation to all paper solids, the charge density is 200 μeq/g to 1000 μeq/g, and the intrinsic viscosity η is 2.7 dL/g to 18.3 dL/g. Polyacrylamide can inhibit the aggregation of anionic waste, thereby increasing the amount of filtered water, increasing the retention rate and reducing the turbidity.

The cationic polyacrylamide used in the method for producing paper and paperboard of this embodiment has a cationic charge density of 200 μeq/g to 1000 μeq/g. Here, the cationic charge density refers to the equivalent number (μeq/g) of the cationic charge in the monomer unit constituting the polymer. If the cationic charge density is less than 200 μeq/g, there is a concern that the amount of filtered water may decrease. If the cationic charge density exceeds 1000 μeq/g, there may be a possibility that the effect of reducing turbidity may not be obtained. From such a viewpoint, the cationic charge density is preferably 200 μeq/g to 700 μeq/g, and more preferably 200 μeq/g to 300 μeq/g. The cationic charge density can be obtained by the method described in the examples.

The intrinsic viscosity η of the cationic polypropylene amide is 2.7 dL/g to 18.3 dL/g. If the intrinsic viscosity η is less than 2.7 dL/g, the molecular weight of the cationic polyacrylamide is too small, so the range in which the coagulation reaction can be initiated is narrow, and there is a concern that a sufficient retention effect cannot be obtained. In addition, if the inherent viscosity η exceeds 18.3 dL/g, the molecular weight of the cationic polyacrylamide is too large, so the viscosity is high, and there is a concern that the effect of increasing the amount of water filtration cannot be sufficiently exhibited. From such a viewpoint, the intrinsic viscosity η is preferably 9 dL/g to 18 dL/g, and more preferably 13 dL/g to 18 dL/g. Furthermore, the intrinsic viscosity η is measured using a Cannon-Fenske type viscometer at 30°C, and based on the measured value, the Huggins formula and Midfors ( Mead-Fuoss) formula to calculate.

The cationic polyacrylamide is not particularly limited as long as the cationic charge density and intrinsic viscosity η are within the above ranges, for example, it can be obtained by a known polymerization method such as an aqueous polymerization method, an emulsion polymerization method, a suspension polymerization method, etc. Acrylic amide monomer and cationic monomer were obtained. The charge density is adjusted according to the blending ratio of the monomers used, and the inherent viscosity is adjusted by the polymerization temperature, the monomer concentration, and the amount of the initiator added. Examples of cationic monomers include (meth)acrylate derivatives such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; dimethyl (Meth)acrylamide derivatives such as aminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide; dimethylaminoethyl (meth)acrylate Quaternary salts and acid salts; allylamine, diallylamine and other tertiary amine-based monomers and tertiary amine monomers and their quaternary salts and acid salts. Among them, it is preferable to use a quaternary salt of dimethylaminoethyl (meth)acrylate. One or more of these cationic monomers can be used.

The compounding ratio of the cationic monomer to the total amount of monomers that are the source of all structural units of the cationic polyacrylamide is preferably 0.5 mol% to 9.5 mol%, more preferably 1 mol% to 8 mol% . By setting the blending ratio of the cationic monomer within the above range, the cationic charge density of the cationic polyacrylamide can be within the above range. In addition, the blending ratio of the acrylamide monomer with respect to the total amount of monomers that are the source of all structural units of the cationic polypropylene amide is preferably 90.5 mol% to 99.5 mol%, and more preferably 92 mol% to 99 mol%.

The polymerization initiator used when producing the cationic polypropylene amide is not particularly limited, and examples thereof include ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzophenone peroxide, and third Butyl peroxide, etc. One or two or more polymerization initiators can be used.

In addition, in order to adjust the viscosity of the synthesized cationic polypropylene amide, it is preferable to use a chain transfer agent. The chain transfer agent is not particularly limited, and examples thereof include chlorine tetrachloride, chloroform, and carbon tetrachloride. One or two or more chain transfer agents can be used.

FIG. 1 is a block diagram showing a method of manufacturing paper and paperboard according to an embodiment of the present invention. The papermaking system 10 includes a raw material system 20, a blending and papermaking system 30, and a recycling system 40. The raw material system 20 produces pulp from paper raw materials. The raw material system 20 of this embodiment includes a raw material tank (1) 21 and a raw material tank (2) 22. The raw material tank (1) (21) contains: Leaf Bleached Kraft Pulp (LBKP), Needle Bleached Kraft Pulp (NBKP), Leaf Unbleached Kraft Pulp (LUKP) ) And chemical pulp such as Needle Unbleached Kraft Pulp (NUKP); mechanical wood pulp (Ground Pulp, GP), thermo-mechanical pulp (TMP), chemical thermo-mechanical pulp (Chemi- Thermo-Mechanical Pulp (CTMP) and refined wood pulp (Refiner Mechanical Pulp, RMP) and other mechanical pulps. The raw material tank (2) 22 contains: corrugated waste paper pulp, liner waste paper pulp, magazine waste paper pulp, newspaper Waste paper pulp such as waste paper pulp, land title waste paper pulp, high-quality paper waste paper pulp and deinked waste paper pulp.

The pulp stored in the raw material tank (1) 21 and the raw material tank (2) 22 is supplied to a mixing chest 23 at an appropriate ratio and mixed in the mixing tank 23. The mixed pulp is transferred to the seed box 25 after adding papermaking chemicals such as a binder to the machine chest 24. Furthermore, the raw material tank (1) 21, the raw material tank (2) 22, the mixing tank 23, the slurry tank 24, and the seed tank 25 constitute the raw material system 20 of this embodiment.

The blending and papermaking system 30 converts the pulp to papermaking. The pulp stored in the seed box 25 is supplied to a white water silo 31, and then is sequentially supplied to a cleaner 33 by a pump 32. Furthermore, the pump 35 is supplied to a screen 36, where foreign substances are removed, and then supplied to an inlet 37. The inlet 37 feeds the pulp to the wire of the wire part 38 at an appropriate concentration, speed, and angle, thereby suppressing floc or flow. The supplied pulp is dehydrated in the wire section 38 and a press section (not shown), and then dried in a drying section (not shown), and then subjected to appropriate treatment to produce paper.

Here, the liquid separated by the net portion 38 is white water 39. In addition, the white water 39 contains fine fibers derived from raw material pulp used in papermaking, or other papermaking chemicals. The white water 39 separated by the net part 38 is stored in the white water silo 31. Part of the white water stored in the white water silo 31 is supplied to the pump 32, and the rest is supplied to the white water recovery device 41. Furthermore, the white water silo 31 to the net section 38 constitute the mixing and papermaking system 30 of this embodiment.

The recovery system 40 is self-adjusted to recover white water with the papermaking system 30. The supplied white water is transferred to the white water recovery device 41, filtered by the white water recovery device 41, and subjected to solid-liquid separation. The solid component is transferred to the slurry tank 24, and the filtrate is recovered into the recovery water tank 42 and stored. A part of the filtrate is further filtered and discharged to the outside, or used as adjustment water for adjusting the concentration of the circulating white water. Furthermore, the white water recovery device 41 and the recovery water tank 42 constitute the recovery system 40 of this embodiment.

As long as the effect of the present invention is not impaired, white water and adjusted water may contain a small amount of papermaking chemicals. The papermaking chemicals are not particularly limited, and examples include surfactants, waxes, sizing agents, fillers, rust inhibitors, conductive agents, defoamers, slime control agents, dispersants, viscosity adjusters, and coagulants , Coagulant, paper strength enhancer, retention rate improver, paper powder shedding preventive agent and accumulating agent, etc.

The addition of the cationic polypropylene amide to the paper stock (pulp) can be carried out at the following locations: the supply line of the pulp from the mixing tank 23 to the pulping tank 24 or the pulping tank 24 (I), from the pulping tank 24 Transfer line of seed box 25 or seed box 25 (II), supply line from seed box 25 to white water silo 31 or white water silo 31 (III), supply line from white water silo 31 to pump 32 or pump 32 (IV ), the supply line or cleaner 33 (V) from the pump 32 to the cleaner 33, the supply line or pump 35 (VI) from the cleaner 33 to the pump 35, the supply line or wire mesh from the pump 35 to the wire mesh 36 36 (VII), the supply line or inlet 37 (VIII) from the wire mesh 36 to the inlet 37, the transfer line (IX) of the white water separated by the mesh part 38 to the white water silo 31, the white water from the white water silo 31 to the white water recovery device 41's transfer line or white water recovery device 41(X). Among them, from the viewpoint of suppressing the aggregation of anionic waste, the addition of the cationic polypropylene amide is preferably any of (IV), (V), (VI), (VII), and (VIII) One is more preferably any of (VI), (VII), and (VIII).

In the manufacturing method of paper and paperboard of this embodiment, the addition of cationic polypropylene amide can suppress agglomeration of anionic waste. Therefore, as a paper material, a paper-making raw material containing mechanical pulp, containing 30% by mass, can be used The above papermaking raw materials for deinked pulp and papermaking raw materials containing 30% by mass or more of waste paper pulp.

The added amount of the cationic polyacrylamide is 0.005% to 0.1% by mass relative to the solid content of all paper stocks. If it is less than 0.005 mass%, the aggregation effect is low, and the retention rate and water filtration effect cannot be fully exhibited. In addition, if it exceeds 0.1% by mass, the aggregation effect is too strong, so there is a possibility of affecting the quality of the product. From such a viewpoint, the addition amount of cationic polyacrylamide is preferably 0.01% by mass to 0.08% by mass with respect to all paper solids, and more preferably 0.02% by mass to 0.06% by mass. [Example]

Next, the present invention will be further described in detail by examples, but the present invention is not limited by these examples.

[Cationic charge density] The deionized water was added and dissolved using a measuring cylinder with a sample concentration of 0.005% (w/v). Adjust the pH to 4 using hydrochloric acid (HCl) or sodium hydroxide (NaOH) solution, and dropwise add the polyvinyl potassium sulfate solution until the color of the toluidine blue indicator changes, then determine the cation charge density according to the titration amount.

〔Intrinsic viscosity η〕 A Cannon-Fenske viscometer (No. 75 manufactured by Kusano Scientific Instruments Co., Ltd.) was used to measure the run-down time at 30°C, and based on the measured value, the Huggins formula and Mead-Fuoss formula to calculate.

The cationic acrylamide can be synthesized by a known polymerization method, for example, by an aqueous polymerization method, an emulsion polymerization method, or a suspension polymerization method. The polymerization examples shown below are just one example, and do not limit the manufacturing method. (Synthesis Example 1: Synthesis of cationic polypropylene amide A) In a 1 L separator-type flask with a cooling jacket, put 720 g of water, Acrylamide (AAm) (manufactured by Fuji Film and Koko Pure Chemical Industries, Ltd.) 71.5 g, dimethylaminoethyl acrylate ( DAA) quaternary salt (manufactured by Fuji Film and Kogyo Pure Chemicals Co., Ltd.) 8.5 g, and carbon tetrachloride as a chain transfer agent (manufactured by Fuji Soft Films and Kogyo Pure Chemicals Co., Ltd.) 0.008 g, and at a temperature of 50°C At the time, 0.005 g of an initiator (manufactured by Fuji Film and Koko Pure Chemicals Co., Ltd.) was added and stirred. Then, when the temperature became 60°C, the stirring was stopped, and the temperature was kept for 4 hours. Thereafter, it was cooled to obtain cationic polypropylene amide A. The cationic charge density and intrinsic viscosity η of the obtained cationic polypropylene amide A were measured by the method described above. The results are shown in Table 1.

(Synthesis Example 2 to Synthesis Example 8: Production of cationic polypropylene amide B to cationic polypropylene amide H) The cationic polypropylene amide B to the cationic polypropylene amide H of Synthesis Examples 2 to 8 were synthesized in the same manner as in Synthesis Example 1 except that the monomer ratio described in Table 1 was changed. The cationic charge density and intrinsic viscosity η of the obtained cationic polypropylene amide B to cationic polypropylene amide H were measured by the method described above. The results are shown in Table 1.

[Table 1] Table 1

The sample liquids obtained in Examples and Comparative Examples were subjected to the following measurements. The results are shown in Table 2-1, Table 2-2, and Table 3.

〔Cation requirement amount〕 Filter the pulp slurry with a 150 μm pass filter cloth and take the filtrate. Put the filtrate into a flow potentiometer (PCD (Particle Change Detector)-03 model, manufactured by Mutech)), according to the titration liquid (Poly-DADMAC, Kishida) chemical (share ) The amount of manufacturing) is determined by the cation requirement.

〔Water filtration volume〕 Used in a cylindrical testing machine, a water filter testing machine with an 80 mesh screen and a pipe passing water at the bottom. By opening and closing the valve, the water in the pulp sample retained in the cylinder is dropped through the mesh screen . The amount of filtered water at this time was measured with a graduated cylinder at this time. In addition, compared with a blank group to which no cationic polypropylene amide is added, the more the amount of filtered water, the more the productivity is improved.

〔Retention〕 A filtrate retention tester (DFS-03, manufactured by Mutech) was used to collect the filtrate, the suspended solid content concentration (SS concentration) was measured, and the retention rate was calculated by the following formula. Furthermore, compared with the blank group to which no cationic polyacrylamide is added, the higher the retention rate, the more the white water concentration can be reduced and the load of drainage treatment can be reduced. In addition, cost savings can be achieved by saving raw materials. Retention rate (%) = (1-SS concentration of filtrate/SS concentration of paper)×100

〔Ashes retention rate〕 In an electric furnace, the suspended matter of the filtrate taken by the drainage retention tester was burned at 600°C for 6 hours, the residual ash content was measured, and the ash retention rate was calculated from the following formula. Furthermore, compared with the blank group to which no cationic polyacrylamide is added, the higher the ash retention rate, the more the retention rate effect of fillers such as calcium carbonate can be expected, so cost savings can be achieved by saving fillers. Ash retention rate (%)=(1-ash concentration of filtrate/ash concentration of paper)×100

〔Turbidity〕 The measurement was carried out using a portable turbidity meter (2100Q, manufactured by East Asia DKK Co., Ltd.). Furthermore, compared with the blank group without the addition of cationic polyacrylamide, the lower the turbidity, the lower the stains in the system, and the less the risk of defects or broken paper.

[Test 1] Confirmation test at laboratory level (Example 1) The paper stock was used in the experiment from a corrugating medium (corrugating medium) manufacturing plant (cationic requirement (CD) is 395 μeq/L). Take 180 mL of paper stock in a container, add 0.005 mass% of the solution obtained by dissolving the cationic polypropylene amide B obtained in Synthesis Example 2 to 0.1 mass %, and stir at 800 rpm for 20 seconds to prepare Sample liquid.

(Example 2 to Example 15, Comparative Example 1 to Comparative Example 16) The cationic polyacrylamide B was changed to the cationic polyacrylamide described in Table 2-1, and was added at the blending amount described in Table 2-1, except that the test was prepared in the same manner as in Example 1.样液。 Liquid.

(Example 16 to Example 27, Comparative Example 17 to Comparative Example 25) The cationic polyacrylamide B was changed to the cationic polyacrylamide described in Table 2-2, and was added at the blending amount described in Table 2-2. Furthermore, as the aluminum sulfate and organic coagulant, the table A sample liquid was prepared in the same manner as in Example 1 except that zetaace S701 (manufactured by Kurita Industries) and PAC (polyaluminum chloride) were added at the blending amount described in 2-2.

(Example 28) To LBKP (CD=230 μeq/L) prepared with 25% by mass of coated broken paper, calcium carbonate (manufactured by Shiraishi Industry Co., Ltd.) as a filler was added so as to become 15% by mass to adjust the paper stock. 180 mL of paper was taken in a container, and 0.01 mass% of the cationic polypropylene amide E obtained in Synthesis Example 5 was added thereto, and stirred at 800 rpm for 20 seconds to prepare a sample liquid.

(Example 29, Comparative Example 26 to Comparative Example 28) The cationic polyacrylamide E was changed to the cationic polyacrylamide described in Table 2-2, and it was added in the formulation amount described in Table 2-2, except that the test was prepared in the same manner as in Example 28.样液。 Liquid.

[Table 2-1] Table 2-1

[Table 2-2] Table 2-2

It is learned that a specific amount of cation charge density is 200 μeq/g～1000 μeq/g, and the inherent viscosity η is 2.7 dL/g～18.3 dL/g. Compared with the blank group without the addition of cationic polypropylene amide, the examples 1 to 29 of the cationic polyacrylamide have higher water filtration capacity, lower turbidity, and improved retention rate. In addition, it is understood that the water filtration amount of Examples 1 to 29 is higher than that of the comparative example in which the cationic polypropylene amide having a cationic charge density of less than 200 μeq/g is added, and that the cationic charge density exceeds Compared with the comparative example of 1000 μeq/g cationic polyacrylamide, the average turbidity is low and the retention rate is improved.

[Experiment 2] Experiments at the actual machine level (Example 30) In the manufacturing process of paper and paperboard shown in FIG. 1, the paper stock (CD=400 μeq/L) before (VII) supplied from the pump 35 to the screen 36 is taken into a container of 180 mL. To this was added 0.01% by mass of the cationic polypropylene amide E obtained in Synthesis Example 5, and stirred at 800 rpm for 20 seconds to prepare a sample liquid.

(Example 31, Comparative Example 29 to Comparative Example 31) The sample liquid was prepared in the same manner as in Example 30 except that the cationic polypropylene amide E was changed to the cationic polypropylene amide described in Table 3 and added at the blending amount described in Table 3.

[Table 3] Table 3

It is learned that a certain amount of cation is also added to the water quality with high cation demand (100 μeq/L or more). The charge density is 200 μeq/g～1000 μeq/g, and the intrinsic viscosity η is 2.7 dL/g～18.3 dL/g Examples 30 and 31 of the cationic polyacrylamide of the present invention have much more water and turbidity than Comparative Examples 30 and 31 of the cationic polyacrylamide added with a cationic charge density exceeding 1000 μeq/g. The degree is low and the retention rate is increased. In addition, the ash retention rate is also improved, and it is expected that the amount of filler used will be reduced. [Industry availability]

The method for producing paper and paperboard of the present invention can increase the amount of water filtration, increase the retention rate, and reduce turbidity even when a large amount of anionic waste is contained in white water in the papermaking step.

10: Paper making system 20: Raw material system 21: Raw material tank (1) 22: Raw material tank (2) 23: Mixed pool 24: Slurry tank 25: Seed box 30: Blending and papermaking system 31: White Water Silo 32, 35: pump 33: cleaner 34: Regulator 36: Wire mesh 37: Entrance 38: Network Department 39: White Water 40: Recycling system 41: White water recovery device 42: Recovery sink (I)～(X): Adding part of cationic polypropylene amide to paper (pulp)

FIG. 1 is a block diagram showing a method of manufacturing paper and paperboard according to an embodiment of the present invention.

10: Paper making system

20: Raw material system

21: Raw material tank (1)

22: Raw material tank (2)

23: Mixed pool

24: Slurry tank

25: Seed box

30: Blending and papermaking system

31: White Water Silo

32, 35: pump

33: cleaner

34: Regulator

36: Wire mesh

37: Entrance

38: Network Department

39: White Water

40: Recycling system

41: White water recovery device

42: Recovery sink

(I)~(X): Adding part of cationic polypropylene amide to paper (pulp)

Claims (4)

A method for manufacturing paper and paperboard, which includes a papermaking step using paper stock having a cation requirement of 100 μeq/L or more as a papermaking raw material, and in a range of 0.005% to 0.1% by mass relative to the solid content of all paper stocks Add cationic polyacrylamide with cationic charge density of 200 μeq/g～1000 μeq/g and intrinsic viscosity η of 2.7 dL/g～18.3 dL/g to the paper. The method for manufacturing paper and paperboard as described in item 1 of the patent application, wherein the paper stock is a papermaking raw material containing mechanical pulp. The method for manufacturing paper and paperboard as described in item 1 of the patent application scope, wherein the paper stock is a papermaking raw material containing deinked pulp of 30% by mass or more. The method for manufacturing paper and paperboard as described in item 1 of the patent application scope, wherein the paper stock is a papermaking raw material containing 30% by mass or more of waste paper pulp.

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