TWI770387B - Methods of manufacturing paper and cardboard - Google Patents

Abstract

A method for producing paper and cardboard, which includes a papermaking step of using a paper stock having a cation requirement of 100 μeq/L or more as a papermaking raw material, and is in the range of 0.005% by mass to 0.1% by mass relative to all the solid content of the paper stock A cationic polyacrylamide 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 was added to the paper stock.

Description

Methods of manufacturing paper and cardboard

The present invention relates to a manufacturing method of paper and cardboard.

Conventionally, papermaking is carried out by going through a papermaking step of making paper a raw material slurry obtained by dispersing a pulp raw material in water. In the papermaking step, a large amount of white water containing fine fibers and fillers is discharged from a paper machine or the like. From the viewpoint of effective use and reuse of water resources, the discharged white water is recycled and used in the papermaking step.

The raw materials for papermaking contain various anionic substances such as resins, sizing agents, fluorescent dyes, and latex. Especially, because of the improvement of the allotment rate of deinking pulp, mechanical pulp, waste paper contained in the papermaking raw material or the reuse of white water, and in the paper manufacturing step, it is easy to accumulate anion waste (anion trash) and the retention rate reduces. , or cause a barrier that fibers, fillers, and other additives, which are raw materials of paper, pass through the wire and flow out to the white water when the paper layer is formed on the wire.

For example, Patent Document 1 describes a method for suppressing the occurrence of defects in paper caused by impeding substances such as anionic waste, micropitch, and turbidity components. A specific water-soluble polymer (A) is added to the paper, the papermaking raw material is diluted with white water, a specific water-soluble polymer (B) is then added, and a retention rate improving agent is appropriately added to perform papermaking. In this method, by adding specific water to the papermaking raw material The soluble polymer neutralizes the charge of the anionic waste, and the fine resin and turbidity components are fixed to the pulp fibers, and as a result, the unfixed fine resin and turbidity components are prevented from agglomerating.

[Prior Art Literature] [Patent Literature]

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

As a water quality index, when 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 anion waste increases. When a large amount of various cationic polymers such as coagulants, retention aids, and paper strength agents are added in order to neutralize the charge of a large amount of anionic waste, a large amount of anionic waste agglomerated in strong cations becomes agglomerated, and is used in papermaking. During the steps, it is easy to adhere to the utensils and equipment, and the problem of deterioration of the condition frequently occurs. In addition, even in the method described in Patent Document 1, when the amount of anion waste increases, sufficient effects cannot be obtained.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a paper and cardboard which can increase the amount of drainage, increase the retention rate, and reduce turbidity even when a large amount of anionic waste is contained in the white water in the papermaking step. manufacturing method.

In order to solve the above-mentioned problem, the present inventors have made diligent studies, and as a result, found that this problem can be solved by adding a specific amount of a specific low-cationic polyacrylamide with respect to all the solid content of the paper stock.

The present invention has been completed based on the above findings.

That is, this application discloses about the following.

[1] A method for producing paper and cardboard, which includes a papermaking step of using a paper stock having a cation requirement of 100 μeq/L or more as a papermaking raw material, and the amount is 0.005% by mass to 0.1% by mass relative to the total solid content of the paper stock The range of adding cationic polyamide amide with cationic charge density of 200μeq/g~1000μeq/g and intrinsic viscosity η of 2.7dL/g~18.3dL/g to paper stock.

[2] The method for producing paper and paperboard according to the above [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 papermaking raw material containing 30% by mass or more of deinked pulp.

[4] The method for producing paper and cardboard according to the above [1], wherein the paper stock is a papermaking raw material containing 30% by mass or more of waste paper pulp.

According to the present invention, it is possible to provide a method for producing paper and cardboard which can increase the amount of drained water, increase the retention rate, and reduce turbidity even when a large amount of anionic waste is contained in the 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: Hybrid Pool

24: Pulp pool

25: Seed box

30: Tuning and papermaking system

31: Whitewater Silo

32, 35: Pump

33: Cleaner

34: Regulator

36: Silkscreen

37: Entrance

38: Net Department

39: White Water

40: Recycling System

41: White water recovery device

42: Recycling Sink

(I)~(X): Addition position of cationic polypropylene amide to paper stock (pulp)

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

The method for producing 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 of using a paper stock having a cation requirement of 100 μeq/L or more as a papermaking raw material, and Add cations 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 in a range of 0.005 mass % to 0.1 mass % with respect to all paper solids. Polypropylene amide.

When a paper stock having a cation requirement of 100 μeq/L or more is used as a papermaking raw material, a large amount of anionic waste is contained in the white water in the papermaking step. In contrast, in the present embodiment, a specific amount of cationic polymer having 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 is added to the total solid content of the paper stock. Acrylamide can inhibit the agglomeration of anionic waste, thereby increasing the amount of water filtration, improving the retention rate and reducing turbidity.

The cationic charge density of the cationic polyacrylamide used in the method for producing the paper and paperboard of the present embodiment is 200 μeq/g to 1000 μeq/g. Here, the cationic charge density refers to the equivalent number (μeq/g) of cationic charges in the monomer units constituting the polymer.

If the cationic charge density is less than 200 μeq/g, the amount of filtered water may decrease, and if the cationic charge density exceeds 1000 μeq/g, the effect of reducing turbidity may not be obtained. From this viewpoint, the cationic charge density is preferably 200 μeq/g to 700 μeq/g, more preferably 200 μeq/g to 300 μeq/g.

The cationic charge density can be determined by the method described in the Examples.

The intrinsic viscosity η of the cationic polyacrylamide is 2.7dL/g~ 18.3dL/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 aggregation reaction can be initiated is narrow, and there is a fear that a sufficient retention effect cannot be obtained. On the other hand, when the intrinsic viscosity η exceeds 18.3 dL/g, the molecular weight of the cationic polyacrylamide is too large, so that the viscosity is high, and there is a fear that the effect of increasing the drainage amount cannot be sufficiently exhibited. From this viewpoint, the intrinsic viscosity η is preferably 9 dL/g to 18 dL/g, more preferably 13 dL/g to 18 dL/g.

Furthermore, the intrinsic viscosity η is measured by using a Cannon-Fenske type viscometer at 30° C. for the flow down time, and based on the measured value, the Huggins formula and the Midforth ( 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 ranges described above, and for example, known polymerization methods such as aqueous polymerization, emulsion polymerization, and suspension polymerization can be used. It is obtained by polymerizing an acrylamide monomer and a cationic monomer. The charge density is adjusted according to the mixing ratio of the monomer to be used, and the intrinsic viscosity is adjusted according to the polymerization temperature, the monomer concentration, and the addition amount of the initiator.

Examples of cationic monomers include (meth)acrylate derivatives such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; dimethylaminoethyl (meth)acrylate and the like; Aminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide and other (meth) acrylamide derivatives; dimethylaminoethyl (meth)acrylate quaternary salts and acid salts; amine monomers such as allylamine, diallylamine, tertiary amine monomers, and their quaternary salts and acid salts. Among them, the quaternary salt of dimethylaminoethyl (meth)acrylate is preferably used.

One or two or more of these cationic monomers can be used.

The blending ratio of the cationic monomer is preferably 0.5 mol % to 9.5 mol %, more preferably 1 mol % to 8 mol %, with respect to the total amount of the monomers serving as the source of all structural units of the cationic polyacrylamide. By making the compounding ratio of a cationic monomer into the said range, the cationic charge density of a cationic polyacrylamide can be made into the said range.

In addition, the blending ratio of the acrylamide monomer is preferably 90.5 mol % to 99.5 mol %, more preferably 92 mol % to 99 mol % with respect to the total amount of the monomers serving as the source of all the structural units of the cationic polyacrylamide. %.

The polymerization initiator used in the production of the cationic polyacrylamide is not particularly limited, and examples thereof include ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, benzyl peroxide, and third Butyl peroxide, etc. One type or two or more types of polymerization initiators can be used.

In addition, in order to adjust the viscosity of the synthesized cationic polyacrylamide, it is preferable to use a chain transfer agent. Although a chain transfer agent is not specifically limited, For example, chlorine tetrachloride, chloroform, carbon tetrachloride, etc. are mentioned. One type or two or more types of chain transfer agents can be used.

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

The papermaking system 10 includes a raw material system 20 , a preparation and papermaking system 30 , and a recovery system 40 .

The raw material system 20 produces pulp from paper raw material. The raw material system 20 of the present embodiment includes a raw material tank ( 1 ) 21 and a raw material tank ( 2 ) 22 . Receiving in the raw material tank (1) (21) Contains: Hardwood Bleached Kraft Pulp (LBKP), Conifer Bleached Kraft Pulp (NBKP), Hardwood Unbleached Kraft Pulp (LUKP) and Conifer Unbleached Kraft Pulp (Needle Unbleached Kraft Pulp, NUKP) and other chemical pulps; mechanical wood pulp (Ground Pulp, GP), thermomechanical pulp (Thermo-Mechanical Pulp, TMP), chemical thermomechanical pulp (Chemi-Thermo-Mechanical Pulp, CTMP) and refined Refiner Mechanical Pulp (RMP) and other mechanical pulp, the raw material tank (2) 22 accommodates: corrugated paper waste paper pulp, liner waste paper pulp, magazine waste paper pulp, newspaper waste paper pulp, land deed waste paper pulp, High-quality paper waste paper pulp and deinking waste paper pulp and other waste paper pulp.

The pulp accommodated 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 is mixed in the mixing chest 23 . The mixed pulp is transferred to a seed box 25 after adding papermaking chemicals such as a binder in a machine chest 24 .

In addition, the raw material tank (1) 21, the raw material tank (2) 22, the mixing tank 23, the pulping tank 24, and the seed tank 25 constitute the raw material system 20 of the present embodiment.

The preparation and papermaking system 30 prepares pulp and performs papermaking. The pulp accommodated in the seed box 25 is supplied to a white water silo 31 and then sequentially supplied to a cleaner 33 by a pump 32 . Furthermore, it is supplied to the screen 36 by the regulator 34 and the pump 35, and it is supplied to the inlet (inlet) 37 after removing the foreign material here. The inlet 37 feeds pulp at an appropriate concentration, speed, and angle to the wire of the wire part 38, whereby floc or flow pattern can be suppressed. Pulp supplied to the web The part 38 is dehydrated in a press part (not shown), then dried in a drying part (not shown), and then appropriately processed to produce paper.

Here, the liquid separated by the net part 38 is the white water 39 . In addition, the white water 39 contains microfibers derived from the raw material pulp normally used in papermaking, other chemicals for papermaking, and the like.

The white water 39 separated by the net part 38 is stored in the white water silo 31 . A 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 .

In addition, the preparation and papermaking system 30 of this embodiment is comprised from the white water silo 31 to the wire part 38.

The recovery system 40 is self-tuned with the papermaking system 30 to recover the white water. 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 content is transferred to the slurry tank 24, and the filtrate is recovered in the recovery tank 42 and stored. A part of the filtrate is further filtered and discharged to the outside, or is used as adjustment water for adjusting the concentration of circulating white water.

In addition, the white water recovery device 41 and the recovery water tank 42 constitute the recovery system 40 of the present embodiment.

White water and conditioning water may contain a small amount of chemicals for papermaking within a range that does not impair the effects of the present invention.

The chemicals for papermaking are not particularly limited, and examples thereof include surfactants, waxes, sizing agents, fillers, rust inhibitors, conductive agents, antifoaming agents, slime control agents, dispersants, viscosity modifiers, and flocculants. , coagulant, paper strength enhancer, retention rate enhancer, Paper powder fall-off prevention agent and accumulation agent, etc.

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

In the method for producing paper and paperboard according to the present embodiment, the addition of cationic polyacrylamide suppresses the agglomeration of anionic wastes. Therefore, as the paper material, a papermaking raw material containing mechanical pulp containing 30% by mass of mechanical pulp can be used. The papermaking raw material of the above deinking pulp, and the papermaking raw material containing 30 mass % or more of waste paper pulp.

The addition amount of the said cationic polyacrylamide is 0.005 mass % - 0.1 mass % with respect to all paper stock solid content. If it is less than 0.005 mass %, the aggregation effect is low, and the retention rate cannot be fully exhibited. Water filter effect. In addition, if it exceeds 0.1 mass %, the aggregation effect is too strong, so there is a possibility of affecting the quality of the product sex. From such a viewpoint, the addition amount of the cationic polyacrylamide is preferably 0.01 to 0.08 mass %, more preferably 0.02 to 0.06 mass % with respect to the total paper stock solid content.

[Example]

Next, the present invention will be described in further detail by way of examples, but the present invention is not limited to these examples at all.

[Cation charge density]

Deionized water was added and dissolved using a graduated cylinder so that the sample concentration was 0.005% (w/v). The pH value was adjusted to 4 with hydrochloric acid (HCl) or sodium hydroxide (NaOH) solution, and polyvinyl potassium sulfate solution was added dropwise until the color of the toluidine blue indicator changed, and the cationic charge density was obtained from the titration amount.

[Intrinsic viscosity η]

The flow time was measured at 30°C using a Cannon-Fenske viscometer (No. 75 manufactured by Kusano Scientific Instruments Co., Ltd.), and based on the measured value, the Huggins formula and Calculated using the Mead-Fuoss formula.

The cationic acrylamide can be synthesized by a known polymerization method, for example, an aqueous polymerization method, an emulsion polymerization method, or a suspension polymerization method. The polymerization example shown below is only one example, and the production method is not limited.

(Synthesis Example 1: Synthesis of Cationic Polyacrylamide A)

Into a 1L separator-type flask with a cooling jacket, put 720 g of water, 71.5 g of acrylamide (AAm) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), dimethylamine 8.5 g of a quaternary salt of ethyl acrylate (DAA) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.008 g of carbon tetrachloride as a chain transfer agent (manufactured by Fujifilm Wako Pure Chemical Industries Ltd.), and When the temperature became 50°C, 0.005 g of an initiator (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred. Then, when the temperature reached 60°C, stirring was stopped, and the temperature was maintained for 4 hours. Then, it cooled, and the cationic polyacrylamide A was obtained.

The cationic charge density and intrinsic viscosity η of the obtained cationic polyacrylamide A were measured by the method. The results are shown in Table 1.

(Synthesis Example 2 to Synthesis Example 8: Production of Cationic Polyacrylamide B to Cationic Polyacrylamide H)

The cationic polyacrylamide B to the cationic polyacrylamide H of Synthesis Example 2 to Synthesis Example 8 were synthesized in the same manner as in Synthesis Example 1, except that the ratio of the monomers described in Table 1 was changed. The cationic charge density and intrinsic viscosity η of the obtained cationic polyacrylamides B to cationic polyacrylamides H were measured by the method. The results are shown in Table 1.

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

[Cation requirement]

The pulp slurry was filtered with a filter cloth having a pass of 150 μm, and the filtrate was collected. The filtrate was put into a flow potentiometer (PCD (Particle Charge Detector)-03 type, manufactured by Mutech Corporation), and the filtrate was titrated according to the titration liquid (Poly-DADMAC, Kishida Chemical Co., Ltd. ) to measure the cation requirement.

[filtered water]

A water filter tester used in a cylindrical tester with an 80-mesh mesh and a water-passing pipe at the bottom was used, and the water in the pulp sample retained in the cylinder was allowed to fall down through the mesh by opening and closing the valve. . The amount of filtered water for 10 seconds at this time was measured with a graduated cylinder.

Furthermore, with the blank group (blank) without adding cationic polyacrylamide The higher the amount of filtered water, the higher the productivity.

〔Retention〕

The filtrate was collected using a filtered water retention rate tester (DFS-03, manufactured by Mutech), the suspended solids concentration (SS concentration) was measured, and the retention rate was calculated by the following formula.

Furthermore, compared with the blank group in which cationic polyacrylamide was not added, the higher the retention rate, the lower the concentration of white water and the lower the load of drainage treatment. In addition, cost reduction can be achieved by saving raw materials.

Retention rate (%)=(1-SS concentration of filtrate/SS concentration of paper stock)×100

[Ash retention rate]

The suspended matter of the filtrate collected by the filtered water retention rate tester was calcined in an electric furnace at 600° C. for 6 hours, the residual ash content was measured, and the ash content retention rate was calculated from the following formula.

Furthermore, compared with the blank group without adding cationic polyacrylamide, the higher the ash content retention rate, the more expected the retention rate effect of fillers such as calcium carbonate, so that cost reduction can be achieved by saving fillers.

Ash retention rate (%)=(1-ash concentration of filtrate/ash concentration of paper stock)×100

[turbidity]

Measurement was performed using a portable turbidimeter (2100Q, manufactured by Donga DKK Co., Ltd.).

Furthermore, the lower the turbidity, the less contamination in the system, and the less the risk of blemishes or paper breakage, compared to the blank group without the addition of cationic polyacrylamide.

[Test 1] Confirmation test at laboratory level

(Example 1)

The paper stock was used in the experiment and was collected from a corrugating medium manufacturing plant (cation requirement (CD): 395 μeq/L). 180 mL of paper stock was taken into a container, 0.005 mass % of a solution obtained by dissolving the cationic polyacrylamide B obtained in Synthesis Example 2 into 0.1 mass % was added, and the sample was stirred at 800 rpm for 20 seconds. liquid.

(Example 2 to Example 15, Comparative Example 1 to Comparative Example 16)

A sample was prepared in the same manner as in Example 1, except that the cationic polyacrylamide B was changed to the cationic polyacrylamide B described in Table 2-1 and added in the amount described in Table 2-1. sample liquid.

(Example 16 to Example 27, Comparative Example 17 to Comparative Example 25)

The cationic polyacrylamide B was changed to the cationic polyacrylamide B described in Table 2-2, and added in the preparation amount described in Table 2-2, and further, as aluminum sulfate and organic coagulant, were added as shown in Table 2-2. A sample liquid was prepared in the same manner as in Example 1, except that Zetaace S701 (manufactured by Kurita Kogyo Co., Ltd.) and PAC (polyaluminum chloride) were added in the preparation amounts described in 2-2.

(Example 28)

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

(Example 29, Comparative Example 26 to Comparative Example 28)

A sample was prepared in the same manner as in Example 28, except that the cationic polyacrylamide E was changed to the cationic polyacrylamide E described in Table 2-2 and added in the amount described in Table 2-2. sample liquid.

It is known that: for the paper stock with high cation requirement (above 100μeq/L), a specific amount of cationic charge density is 200μeq/g~1000μeq/g, and the intrinsic viscosity η is 2.7dL/g~18.3dL/g. Example 1 of Polyacrylamide ~Compared with the blank group without cationic polyacrylamide added in Example 29, the average amount of filtered water is large, the turbidity is low, and the retention rate is improved. In addition, it was found that in Examples 1 to 29, compared with the comparative example in which the cationic polyacrylamide having a cationic charge density of less than 200 μeq/g was added, the average amount of filtered water was increased, and the cationic charge density was more than 1000 μeq added. Compared with the comparative example of the cationic polyacrylamide of /g, the average turbidity was low and the retention rate was improved.

[Experiment 2] Test under the real machine level

(Example 30)

In the manufacturing process of paper and cardboard shown in FIG. 1 , 180 mL of the paper stock (CD=400 μeq/L) before supplying from the pump 35 to the screen 36 (VII) was collected into a container. 0.01 mass % of the cationic polyacrylamide E obtained in Synthesis Example 5 was added thereto, and the mixture was stirred at 800 rpm for 20 seconds to prepare a sample liquid.

(Example 31, Comparative Example 29 to Comparative Example 31)

A sample liquid was prepared in the same manner as in Example 30, except that the cationic polyacrylamide E was changed to the cationic polyacrylamide E described in Table 3 and added in the preparation amount described in Table 3.

It is known that a specific amount of cations with a charge density of 200μeq/g~1000μeq/g and an intrinsic viscosity η of 2.7dL/g~18.3dL/g are added to the paper stock with high cation requirements (above 100μeq/L). Compared with Comparative Example 30 and Comparative Example 31 in which cationic polyacrylamide with a cationic charge density of more than 1000 μeq/g was added, Example 30 and Example 31 of the cationic polyacrylamide had more water permeation, lower turbidity and Increased retention. In addition, the ash retention rate is also improved, and the amount of filler used can be expected to be reduced.

[Industrial Availability]

The method for producing paper and paperboard of the present invention can increase the amount of drained water, improve the retention rate, and reduce turbidity even when anionic waste is contained in a large amount in the 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: Hybrid Pool

24: Pulp pool

25: Seed box

30: Tuning and papermaking system

31: Whitewater Silo

32, 35: Pump

33: Cleaner

34: Regulator

36: Silkscreen

37: Entrance

38: Net Department

39: White Water

40: Recycling System

41: White water recovery device

42: Recycling Sink

(I)~(X): Addition of cationic polypropylene amide to paper stock (pulp)

Claims (4)

A method for producing paper and paperboard, comprising a papermaking step of using a paper stock with a cation requirement of 100 μeq/L or more as a papermaking raw material, and in the range of 0.01% by mass to 0.08% by mass relative to the total solid content of the paper stock. The paper material is added with cationic polypropylene amide with cationic charge density of 200μeq/g~300μeq/g and intrinsic viscosity η of 13dL/g~18.3dL/g. The method for producing paper and paperboard according to claim 1, wherein the paper stock is a papermaking raw material containing mechanical pulp. The method for producing paper and paperboard according to claim 1, wherein the paper stock is a papermaking raw material containing 30% by mass or more of deinked pulp. The method for producing paper and paperboard according to claim 1, wherein the paper stock is a papermaking raw material containing 30% by mass or more of waste paper pulp.

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